RU2781076C1 - Biomass heating plant with optimized flue gas treatment - Google Patents

Abstract

FIELD: energy.

SUBSTANCE: invention relates to the field of energy. A biomass heating plant for burning fuel in the form of pellets and/or wood chips comprises a boiler with a combustion device, a heat exchanger with inlet and outlet, the combustion device having a combustion chamber with a primary combustion zone and a secondary combustion zone provided downstream of it, the secondary zone combustion chamber is hydrodynamically connected to the inlet of the heat exchanger, the primary combustion zone is limited from the side by several bricks of the combustion chamber, and the biomass heating plant also has a recirculation device for recirculating the flue gas formed during the combustion of fuel in the combustion device. The recirculating device has a recirculation inlet, which is provided downstream of the heat exchanger outlet and is hydrodynamically connected to it, and a primary air channel for supplying primary air, a primary mixing unit with a primary mixing chamber and a primary mixing channel, the primary mixing chamber being provided downstream relative to of the recirculation inlet and the primary air duct and is hydrodynamically connected to them, and at least two air valves, which are provided on the inlet side of the primary mixing chamber, and a primary passage to the primary combustion zone, which is provided downstream of the primary mixing duct and is hydrodynamically connected to it, and the primary mixing unit is designed so that it can mix the flue gas from the recirculation inlet with primary air from the primary air channel through at least two air valves of the primary mixing chamber.

EFFECT: invention allows to reduce the amount of harmful emissions into the atmosphere.

6 cl, 31 dwg

Description

Technical field

The invention relates to a biomass heating plant with optimized flue gas treatment.

First of all, the invention relates to a recirculation device for a biomass heating plant with at least one mixing chamber, as well as a flue gas condenser and a transfer screw.

State of the art

Biomass heating systems, especially biomass boilers, are known in the power range from 20 to 500 kW. Biomass can be considered as an inexpensive, local, crisis-free and environmentally friendly fuel. As combustible biomass or as solid fuels, for example, wood chips or pellets are available.

Most often, pellets consist of wood shavings, sawdust, biomass or other materials that are compressed into small discs or cylinders with a diameter of about 3 to 15 mm and a length of 5 to 30 mm. Chips (also called wood chips, wood shavings or shavings) are wood shredded with cutting tools.

Biomass heating installations for fuel in the form of pellets or chips essentially have a boiler with a combustion chamber (combustion chamber) and a heat exchanger adjacent to it. Due to stricter statutory regulations in many countries, biomass heating systems also have a fine dust filter. As a rule, there are also various other equipment, such as fuel feeders, adjustment devices, sensors, safety thermostats, pushbutton switches, flue gas or exhaust gas return system, boiler cleaning device and a separate fuel tank.

The combustion chamber is usually provided with a device for supplying fuel, a device for supplying air and a device for igniting fuel. The air supply device, in turn, usually has a low-pressure blower in order to preferably influence the thermodynamic factors during combustion in the combustion chamber. The fuel supply device can, for example, be equipped with a side valve (so-called cross-feed combustion). In this case, fuel is supplied to the chamber from the side by means of a screw or piston.

The fixed bed combustor also typically includes a grate into which fuel is substantially continuously supplied and burned. This grate supports the combustion fuel and has openings, such as slots, which allow a portion of the combustion air to pass to the fuel as primary air. In addition, the grate can be made fixed or movable. In addition, there are fireboxes with a grate, in which the combustion air is supplied not through the grate, but only from the side.

When the primary air passes through the grate, the grate is in particular also cooled, whereby the material is protected. In addition, with insufficient air supply, slag formation can occur on the grate. First of all, furnaces that are to be fed with different fuels, as the present disclosure is primarily concerned with, have the inherent problem that different fuels have different ash melting points, water content and different fuel behavior. As a result, it is problematic to design a heating system that is equally well suited to different fuels. In addition, the combustion chamber can usually be divided into a primary combustion zone (direct combustion of fuel on the grate, as well as in the gas space above it to supply additional air for combustion) and a secondary combustion zone (the zone of flue gas after additional air supply). Drying, pyrolytic decomposition, as well as gasification of fuel and burning out of charcoal take place in the combustion chamber. In addition, for complete combustion of the resulting combustible gases in one or more stages (secondary air or tertiary air), additional combustion air is supplied to the beginning of the secondary combustion zone.

The combustion of pellets or wood chips after drying has essentially two phases. In the first phase, the fuel is at least partially pyrolytically decomposed and converted into gas due to high temperatures and air that can be blown into the combustion chamber. In the second phase, the combustion of the gasified fractions takes place, as well as the combustion of any residual fuel (eg charcoal) that may be present. In this respect, the fuel is gasified and the resulting gas, as well as the charcoal it contains, are co-burned.

Pyrolysis is the thermal decomposition of solids in the absence of oxygen. Pyrolysis can be divided into primary and secondary pyrolysis. The products of primary pyrolysis are pyrolysis coke and pyrolysis gases, and pyrolysis gases can be divided into condensable at room temperature and non-condensable gases. Primary pyrolysis occurs at about 250-450°C and secondary pyrolysis at about 450-600°C. The subsequent secondary pyrolysis is based on the further reaction of the initially formed pyrolysis products. Drying and pyrolysis take place, at least to a large extent, without the participation of air, since volatile CH compounds are released from the particles, and therefore air cannot reach the surface of the particles. Gasification can be considered as part of the oxidation, the solid, liquid and gaseous products formed during the pyrolytic decomposition are reacted by further thermal action. This occurs when a gasifying agent such as air, oxygen, water vapor or carbon dioxide is added. The lambda value during gasification is greater than zero and less than one. Gasification occurs at about 300 to 850°C or even up to 1200°C. Complete oxidation with excess air (lambda greater than 1) then occurs due to additional air supply to this process. The reaction products are essentially carbon dioxide, water vapor and ash. For all phases, the boundaries are not rigidly established, but blurred. By means of a lambda sensor provided at the exhaust gas outlet of the boiler, the combustion process can advantageously be controlled.

In general terms, the efficiency of combustion due to the conversion of pellets to gas is increased, since the gaseous fuel mixes better with the combustion air and thus undergoes a more complete transformation and less emissions of harmful substances, less unburned particles and ash (fly ash or dust particles).

When biomass is burned, gaseous or airborne combustion products are formed, the main constituents of which are carbon, hydrogen and oxygen. These can be subdivided into emissions from full oxidation, from partial oxidation, and substances from trace elements or contaminants. With respect to full oxidation emissions, these are essentially carbon dioxide (CO ₂ ) and water vapor (H ₂ O). The purpose of combustion is to generate carbon dioxide from the carbon of the biomass, since the released energy can be more fully utilized in this way. The release of carbon dioxide (CO ₂ ) is largely proportional to the carbon content of the amount of fuel burned, so carbon dioxide is also dependent on the useful energy produced. The reduction can essentially only be achieved by improving the efficiency. Incineration residues are also formed, such as ash or also slag.

However, the complex combustion processes described above are not so easy to manage. For example, more generally, there is a need for improvement with respect to combustion processes in biomass heating plants.

Furthermore, in addition to supplying air to the combustion chamber, flue gas or exhaust gas return devices are known which return exhaust gas from the boiler for cooling and re-combustion in the combustion chamber. In this case, according to the prior art, there are usually openings in the combustion chamber for supplying primary air through an air duct supplying the combustion chamber, and, in addition, there are openings located around the perimeter of the combustion chamber for supplying secondary air from the secondary air duct. Flue gas recirculation can take place under or above the grate. In addition, flue gas recirculation can take place either mixed with the combustion air or separately.

The flue gas or combustion exhaust gas in the combustion chamber is led to a heat exchanger so that hot combustion gases flow through the heat exchanger to transfer heat to the heat exchange medium, which is usually water at about 80°C (typically between 70°C and 110°C). In addition, the boiler usually has a radiation part, which is built into the combustion chamber, and a convective part (the heat exchanger adjacent to it).

With regard to the ignition device, it is mostly a hot air device or an incandescent device. In the first case, combustion is started by supplying hot air to the combustion chamber, the hot air being heated by electrical resistance. In the second case, the glow device has a glow plug / ignition rod or several glow plugs to heat the pellets or wood chips through direct contact until the combustion process starts. Glow plugs can also be motorized so that during the ignition phase they remain in contact with pellets or wood chips and then move back so as not to remain exposed to the flame. This solution is wear-prone and costly.

In principle, conventional biomass heating systems have the problem that the gaseous or solid emissions are too high, that the efficiency is too low and that the dust emissions are too high. In addition, variable quality due to varying water content and lumpiness of the fuel is problematic, making it difficult to burn the fuel more evenly with lower emissions. First of all, with biomass heating systems, which must be suitable for different types of biological or biogenic fuels, the changing quality and consistency of the fuel makes it difficult to maintain a consistently high efficiency of the biomass heating system. There is a significant need for optimization in this regard.

A disadvantage of conventional biomass pellet heating systems may be that pellets that fall into the combustion chamber may roll out or slip off the grate or grate, or fall near the grate and enter an area of the combustion chamber where the temperature is lower or where poor air supply, or they may even fall into the lowest chamber of the boiler or the ash shaft. Pellets that do not remain on the grate or grate do not burn completely and thus cause poor efficiency, excessive ash and a certain amount of unburned harmful particles. This is true for pellets as well as wood chips.

For this reason, known biomass pellet heating systems have near the grate or grate and/or at the outlet of the combustion gases, for example, a baffle sheet to keep the fuel cells in place. Some boilers have ledges on the inside of the combustion chamber to prevent pellets from falling into the ash handling system and/or into the lowest chamber of the boiler. However, these baffle sheets or protrusions can in turn accumulate combustion residues, making cleaning difficult and can obstruct airflow in the combustion chamber, which in turn reduces efficiency. In addition, this reflective sheet requires its own manufacturing and installation costs. This is true for pellets as well as wood chips.

Biomass heating plants for pellets or wood chips have the following additional disadvantages or problems.

One problem is that incomplete combustion due to uneven distribution of fuel on the grate and due to suboptimal mixing of air and fuel contributes to the accumulation and shedding of unburned ash through the air inlets that lead directly to the grate, or from the end of the grate into the air channels or air supply area.

This is particularly annoying and causes frequent interruptions to perform maintenance such as cleaning. For these reasons, a large excess of air is usually maintained in the combustion chamber, however, as a result, the flame temperature and combustion efficiency are reduced, and this leads to high emissions of unburned gases (for example, CO, CyHy), NOx and dust (for example, due to increased vortex formation).

The use of a low head blower does not provide a suitable swirl of air in the combustion chamber and does not allow optimum mixing of air and fuel. It is usually difficult to form an optimal vortex flow in conventional combustion chambers.

Another problem with known burners without air staging is that both phases, the conversion of pellets into gas and combustion, occur with the same amount of air simultaneously in the entire combustion chamber, as a result of which the efficiency is reduced.

In addition, there is a need for optimization, especially also for the heat exchangers of biomass heating devices according to the prior art, that is, their efficiency could be increased. There is also a need for improvement with respect to the often difficult and inefficient cleaning of conventional heat exchangers.

The same is true for conventional electrostatic precipitators in biomass heating systems. Their discharge and collection electrodes are systematically clogged with combustion residues, which impairs the formation of an electric field for filtering and filtering efficiency.

It may be an object of the invention to develop a biomass heating system with hybrid technology which has low emissions (primarily with respect to fine dust, CO, hydrocarbons, NOx), which can be operated with wood chips and pellets in an adaptable manner in terms of fuel and which has a high efficiency factor. action and which, under certain conditions, has an optimized flue gas treatment.

In this case, according to the invention and additionally, the following considerations play a role:

The hybrid technology should make it possible to use both pellets and wood chips with water contents between 8 and 55 percent by weight.

Low gaseous emissions (less than 50 or 100 mg/Nm ³ ) on a dry flue gas basis and 13 percent O ₂ vol.) must be achieved.

Low dust emissions of less than 15 mg/Nm ³ should be aimed at when operating without ESPs and below 5 mg/Nm ³ with ESPs.

A high efficiency of up to 98% based on the energy input of the fuel (calorific value) must be achieved.

In addition, it can be envisaged that the operation of the plant is to be optimized. For example, simple ash removal, simple cleaning or simple maintenance should be possible.

In addition, there must be a high availability of the plants.

In this case, the task set above or the potential statements of individual problems can relate to individual partial aspects of the entire installation, for example to the combustion chamber, heat exchanger or electric filter installation or flue gas condenser.

Optimized flue gas treatment is to be understood as meaning all those measures by which flue gas or combustion can be improved. This may, for example, include measures that make the biomass heating plant less emitting, more energy efficient or more economical and that maintain hydrodynamic and/or physical treatment of the flue gas. The general concept of flue gas treatment includes, for example, flue gas condensation, which is also explained below, or flue gas recirculation, which is also explained below.

These aforementioned problem(s) are solved by means of the subject matter of the independent claims. Other aspects and preferred improvements are the subject of dependent claims.

According to one aspect of the present disclosure, a biomass heating plant for burning fuel in the form of pellets and/or wood chips is provided, the plant having the following: downstream of it, a secondary combustion zone, wherein the combustion device has a rotary grate on which fuel can be burned, and the secondary combustion zone of the combustion chamber is hydrodynamically connected to the inlet of the heat exchanger, and the primary combustion zone is limited on the side by several bricks of the combustion chamber.

The advantages of this configuration and also the following aspects are obtained from the following description of the respective embodiments.

According to one development of the above aspect, a biomass heating plant is provided, which furthermore has: a recirculation device for recirculating the flue gas formed during combustion in the combustion device, the recirculation device having the following: a recirculation inlet which is provided downstream of the heat exchanger outlet and hydrodynamically connected to it, and a primary air channel for supplying primary air, a primary mixing unit with a primary mixing chamber and a primary mixing channel, wherein the primary mixing chamber is provided downstream relative to the recirculation inlet and the primary air channel and is hydrodynamically connected to them, and at least at least two air valves, which are provided on the primary mixing chamber on the inlet side, and a primary passage to the primary combustion zone, which is provided downstream of the primary mixing channel and hydro is physically connected to it, wherein the primary passage is provided upstream of the rotary grate, the primary mixing unit being configured to mix flue gas from the recirculation inlet with primary air from the primary air duct by means of at least two primary mixing chamber air valves .

According to one improvement of the above aspect, a biomass heating plant is provided, wherein the primary mixing passage is directly connected to the outlet of the primary mixing chamber of the primary mixing chamber, and the primary mixing passage is provided downstream of the primary mixing chamber.

According to one development of the above aspect, a biomass heating plant is provided, wherein the primary mixing channel extends in a straight line and has a minimum length of 700 mm from beginning to end.

According to one improvement of the above aspect, a biomass heating plant is provided, wherein the air valves of the primary mixing chamber are spool valves.

According to one improvement of the above aspect, a biomass heating plant is provided, which, in addition, has the following: the primary mixing chamber on the outlet side has a primary mixing chamber outlet, and the primary mixing chamber on the inlet side has at least two valve openings, and the primary mixing chamber the chamber is configured so that at least two valve passages and the outlet of the primary mixing chamber are not located opposite each other through the primary mixing chamber, so that the flows entering the primary mixing chamber through at least two valve passages into the primary mixing chamber change direction or are rejected.

According to one improvement of the above aspect, a biomass heating plant is provided, the recirculating device furthermore having: a secondary air duct for supplying secondary air, a secondary mixing unit with a secondary mixing chamber and a secondary mixing duct, the secondary mixing chamber being provided downstream of the recirculation inlet and a secondary air duct and hydrodynamically connected thereto, and at least two air valves, which are provided on the inlet side of the secondary mixing chamber, and secondary air nozzles, which are provided in the bricks of the flow chamber and which are oriented sideways into the primary combustion zone and which are provided downstream of the secondary mixing chamber and are hydrodynamically connected to it, the second mixing unit being configured to mix flue gas from the recirculation inlet with secondary air from the secondary air duct by means of at least two air valves of the secondary mixing chamber.

According to one improvement of the above aspect, a biomass heating plant is provided, the recirculating device furthermore having the following: a secondary air duct for supplying secondary air, a secondary thermostating duct, the secondary thermostating duct being provided downstream of the secondary air duct and being hydrodynamically connected to it , and at least one air valve, which is provided on the inlet side on the secondary temperature control channel between the secondary temperature control channel and the secondary air channel, and secondary air nozzles, which are provided in the bricks of the combustion chamber and which are directed laterally into the combustion chamber and which are provided below flow relative to the secondary temperature control channel and are hydrodynamically connected to it, and the secondary temperature control channel is designed so that it can heat the flue gas before it enters the combustion chamber.

According to one improvement of the above aspect, a biomass heating plant is provided, which, in addition, has the following: an electrostatic filter device for filtering flue gas, a flue gas condenser, which is provided downstream of the electrostatic filter device and is hydrodynamically connected to it, wherein: a flue gas condenser gas has a first hydrodynamic connection and a second hydrodynamic connection for the flow of the heat exchange medium through the flue gas condenser, and the flue gas condenser has several U-shaped heat exchanger tubes, and several U-shaped heat exchanger tubes are arranged in groups in the first direction parallel to each other, and the groups of heat exchanger tubes arranged parallel to each other in the second direction, wherein the groups of heat exchanger tubes are hydrodynamically connected in series between the first hydrodynamic connection and the second hydrodynamic connection In addition, the plurality of U-shaped heat exchanger tubes are arranged so that they form a cross-shaped countercurrent configuration with respect to the flow of flue gas through the plurality of heat exchanger tubes.

According to one improvement of the above aspect, a biomass heating plant is provided, wherein a plurality of U-shaped heat exchanger tubes are arranged so that they form, in the second direction, hydrodynamically flow passages for the flow of flue gas, the passages having a minimum width SP2 (in the first direction) of 6.0 mm ±2 mm.

According to one improvement of the above aspect, a biomass heating plant is provided, wherein the ends of all U-shaped heat exchanger tubes are disposed in a plate-like tube base member, and a plurality of 7 to 12, preferably 8 to 10, heat exchanger tubes 493 are arranged as a group in the first direction, several, from 8 to 14, preferably from 10 to 12, groups of pipes 493 of the heat exchanger are located in the second direction.

According to one development of the above aspect, a biomass heating plant is provided, wherein the U-tubes of the heat exchanger have a maximum length of 421 mm ± 50 mm, and/or consist of material 1.4462 (as of the date of filing of the application, the revision of the definition of this material).

According to one improvement of the above aspect, a biomass heating plant is provided, which furthermore has the following: an ash discharge screw for transporting combustion residues from the boiler, the ash discharge screw having a transfer screw which is rotatably located in the transfer screw housing and has countermovement

According to one improvement of the above aspect, a biomass heating plant is provided, wherein the combustion residues in the transfer screw housing are pressed together by the rotation of the ash discharge screw so that they at least substantially separate or seal the combustion residues in relation to flue gas between the combustion chamber and outlet of the heat exchanger.

According to one improvement of the above aspect, a biomass heating plant is provided, wherein the body of the intermediate auger has an upwardly open opening, which is surrounded by a funnel-shaped element, and the counterflow of the auger is designed so that the combustion residues are discharged from the opening upwards when the ash discharge screw rotates.

According to one improvement of the above aspect, a biomass heating plant is provided, wherein the ash discharge auger on one side of the transfer auger has a larger diameter than on the other side of the transfer auger.

"Horizontal" in the present case may indicate the orientation of the axis or cross-section, assuming that the boiler is also installed horizontally, in connection with which, for example, the reference point may be ground level. Optionally, "horizontally" in the present case may mean "parallel" to the main plane of the boiler 11, as it is usually defined. In addition, optionally, especially in the absence of a reference plane, "horizontal" can be understood as "parallel" to the combustion plane of the grate.

While all of the above individual features and details of an aspect of the invention and improvements to that aspect have been described in connection with a biomass heating plant, all of these individual features and details are also disclosed as being independent of a biomass heating installation.

First of all, the flue gas recirculation device, the transfer auger, the primary mixing unit, the secondary mixing unit and the flue gas condenser are described independently of the biomass heating plant and can therefore be claimed independently of it.

In this regard, further disclosed is a recirculation device for recirculating flue gas formed during combustion of fuel in a combustion device, the recirculation device having the following: a recirculation inlet, which is designed to be provided downstream of the heat exchanger outlet and be fluidly connected to it, and a channel primary air for supplying primary air, a primary mixing unit with a primary mixing chamber and a primary mixing channel, wherein the primary mixing chamber is provided downstream of the recirculation inlet and the primary air channel and is hydrodynamically connected to them, and at least two air valves, which are provided on the inlet side of the primary mixing chamber, and a primary passage to the primary combustion zone, which is provided downstream of the primary mixing channel and is fluidly connected to it, wherein the primary mixing unit is so that it can mix flue gas from the recirculation inlet with primary air from the primary air duct by means of at least two primary mixing chamber air valves.

This recirculating device may be combined with other aspects disclosed herein as the skilled person recognizes it is technically feasible.

The flue gas recirculation option can take place either only as flue gas recirculation under the grate with primary air or also as flue gas recirculation under and above the grate (i.e. with primary and secondary air). Flue gas recirculation above the grate serves to improve mixing and temperature control in the combustion chamber and the combustion chamber bricks. Recirculation of the flue gas under the grate also serves to regulate the temperature (however, here to regulate the temperature of the fuel layer) and can influence the duration of the burning of the fuel layer, whereby differences between, for example, wood chips and pellets can be equalized or reduced.

In addition, a flue gas condenser is disclosed that can be connected to a flue gas outlet of a boiler, wherein: the flue gas condenser has a first fluid connection and a second fluid connection for flowing a heat exchange medium through the flue gas condenser, and the flue gas condenser has several U- shaped tubes of the heat exchanger, moreover, several U-shaped tubes of the heat exchanger are arranged in groups parallel to each other in the first direction, and the groups of heat exchanger tubes are parallel to each other in the second direction, and the groups of heat exchanger tubes are hydrodynamically connected in series between the first hydrodynamic connection and the second hydrodynamic connection, several U -shaped tubes of the heat exchanger are arranged so that they form a cruciform countercurrent configuration with respect to the flow of flue gas through several tubes of the heat exchanger.

This flue gas condenser may be combined with the other aspects disclosed herein as the skilled person will recognize as technically feasible. First of all, a preferred combination of a flue gas condenser and an electrical filter device is disclosed.

In addition, an ash unloading auger for transporting combustion residues from a boiler of a biomass heating plant is disclosed, the ash unloading auger having a transfer auger, which is rotatably located in the transfer auger body and has a counter-thread.

This ash auger can be combined with other aspects and individual features disclosed herein, as the person skilled in the art finds it technically feasible.

The biomass heating plant according to the invention will be explained in more detail below in the exemplary embodiments and individual aspects with reference to the figures of the drawings.

Fig. 1 shows a three-dimensional overview of a biomass heating plant according to one embodiment of the invention,

Fig. 2 shows a cross-sectional view through the biomass heating plant according to FIG. 1, which is taken along the section line SL1 and which is shown when viewed from the side view S,

Fig. 3 also shows a cross-sectional view through the biomass heating plant according to FIG. 1 showing the flow paths, the cross-sectional view taken along the section line SL1, and which is shown when viewed from the side view S,

Fig. 4 shows a partial view according to FIG. 2 which represents the geometry of the combustion chamber of the boiler according to FIG. 2 and FIG. 3,

Fig. 5 shows a sectional view through the boiler or boiler combustion chamber along the vertical section line A2 according to FIG. four,

Fig. 6 shows a three-dimensional sectional view of the primary combustion zone of the rotary grate combustion chamber according to FIG. four,

Fig. 7 respectively shows FIG. 6 exploded view of the bricks of the combustion chamber,

Fig. 8 shows a view of the rotary grate with the elements of the rotary grate from above, from the sectional line A1 according to FIG. 2,

Fig. 9 shows the rotary grate according to FIG. 2 in the closed position, with all three elements of the rotary grate oriented horizontally or closed,

Fig. 10 shows the rotary grate according to FIG. 9 in the state of partial cleaning of the rotary grate in the flame maintenance mode,

Fig. 11 shows the rotary grate according to FIG. 9 in a state of complete cleaning, which is carried out preferably during plant downtime,

Fig. 12 shows a highlighted angled view of an exemplary recirculation device with firebox bricks that surround the primary combustion zone,

Fig. 13 shows a highlighted translucent angled view of the recycling device of FIG. 12,

Fig. 14 shows a side view of the recycling device 5 according to FIG. 12 and FIG. 13,

Fig. 15 shows a schematic block diagram which shows the flow paths in the respective individual components of the biomass heating plant and the recirculation device according to FIG. 12-14,

Fig. 16 shows according to the appearances according to FIG. 12 and FIG. 13 is an oblique sectional view of an exemplary primary mixing chamber as well as two inlet side (primary) air valves 52 with their (primary) valve prechambers 525,

Fig. 17 shows according to the appearances according to FIG. 12 and FIG. 13 with respect to the optional secondary recirculation, a sectional view, from a different oblique angle, of an exemplary secondary mixing chamber, as well as two inlet side (secondary) air valves with their (secondary) valve prechambers,

Fig. 18 shows a three-dimensional overview of the biomass heating plant according to FIG. 1 with additional outer lining and additional flue gas condenser,

Fig. 19A shows the flue gas condenser 49 of FIG. 18 in a side view from the direction of the arrow H of FIG. eighteen,

Fig. 19B shows the flue gas condenser 49 of FIG. 18 in a side view from the direction of the arrow Y of FIG. eighteen,

Fig. 20 shows an internal view of the flue gas condenser according to FIG. 18 and FIG. 19,

Fig. 21 shows the flue gas condenser from a top view looking into the flue gas inlet of the flue gas condenser,

Fig. 22 shows the flue gas condenser according to FIG. 18 from a horizontal sectional view from above,

Fig. 23 shows a three-dimensional view of several tubes of a heat exchanger with a tube base element and a tube holder,

Fig. 24 shows a side view of several tubes of the heat exchanger according to FIG. 23,

Fig. 25 shows a top view of several tubes of the heat exchanger of FIG. 23,

Fig. 26 shows a top view of several tubes of the heat exchanger of FIG. 23,

Fig. 27A shows a selected from FIG. 2 and FIG. 3 cross-sectional view of the ash discharge auger with transition auger,

Fig. 27B shows a 3D angled view of the ash discharge screw of FIG. 27A,

Fig. 28 - shows a three-dimensional view at an angle of the body of the adapter auger,

Fig. 29 shows a detailed sectional view of an ash discharge screw with a transfer screw according to FIG. 27A,

Fig. 30 shows a highlighted translucent angled view of a recirculation device according to another embodiment,

Fig. 31 shows a schematic block diagram which discloses the flow paths in the respective individual components of the biomass heating plant and the recirculation device of FIG. 30 according to another embodiment.

Description of exemplary embodiments

Hereinafter, by way of example only, various embodiments of the present disclosure are disclosed with reference to the accompanying drawings. However, the embodiments and the terms used therein are not to be used as a limitation of the present disclosure to certain embodiments, and they are to be interpreted to include various modifications, equivalents, and/or alternatives according to the embodiments of the present disclosure.

If the description were to use a general concept for the features or elements shown in the figures, then it is assumed that for a person skilled in the figures, not only special features or elements are disclosed, but also general technical solutions.

With regard to the description of the figures, the same reference signs may be used in the individual figures to refer to similar or technically related elements. In addition, for clarity, individual detailed or sectional views may show more elements or features with reference symbols than general views. It should be assumed that these elements or features are also respectively disclosed in the general views, even if they are not explicitly shown there.

It should be understood that the only form of a noun that corresponds to a subject may include one or more subjects, unless the appropriate context clearly indicates something else.

In the present disclosure, an expression such as "A or B", "at least one of A and/or B", or "one or more of A and/or B" may include all possible combinations of the features listed together. Expressions such as "first", "second", "primary", or "secondary" as used herein may represent different elements regardless of their sequence and/or value, and do not limit the respective elements. If an element (e.g., the first element) is described as being "operably" or "communicatively" connected to or connected to another element (e.g., the second element), then the element may be directly related to the other element, or connected to the other element via the other element (e.g., third element).

As used in this disclosure, the expression "configured to" (or "performed") can be, for example, replaced by "suitable for", "fit for", "adapted for", "made for", "capable of" depending from technical possibilities. Optionally, in a particular situation, the phrase "the device is configured to" or "done to" may mean that the device may work in conjunction with another device or component, or may perform a corresponding function.

All dimensional data given in "mm" should be understood as a dimensional range of ±1 mm around the indicated value, unless other tolerances or other ranges are explicitly stated.

It should be noted that the present individual aspects, such as a rotary grate, a combustion chamber or a filter device separately or separately from a biomass heating plant, are disclosed here as separate parts or separate devices. Therefore, the specialist will understand that here also individual aspects or parts of the installations are disclosed in themselves. In this case, individual aspects or parts of the installation, first of all, are disclosed in the subsections indicated in brackets. It is envisaged that these individual aspects may also be the subject of claims.

In addition, for clarity, the figures do not always separately indicate all the features and elements, especially if they are repeated. Moreover, elements and features, depending on the circumstances, are indicated by way of example. Similar or identical elements are then to be understood as such.

(Biomass heating plant)

In FIG. 1 shows a three-dimensional perspective view of a biomass heating plant 1 according to an exemplary embodiment of the invention.

The arrow V in the figures indicates the front view of the apparatus 1, and the arrow S in the figures indicates the side view of the apparatus 1.

The biomass heating plant 1 has a boiler 11 which rests on a boiler base 12 . The boiler 11 has a boiler body 13 made of, for example, sheet steel.

At the front of the boiler 11 there is a combustion device 2 (not shown), which can be accessed through the first maintenance hole with a cover 21. On the holder 22 of the turning mechanism for the turning grate 25 (not shown), the turning mechanism 23 is fixed, by means of which the moving forces can be transmitted to the bearing axle 81 of the rotary grate 25.

In the center of the boiler 11 is a heat exchanger 3 (not shown), which can be accessed from above through a second maintenance opening 31 with a lock.

At the rear of the boiler 11 is an optional filter device 4 (not shown) with an electrode 44 (not shown) which is suspended by an insulated electrode holder 43 and which is energized through the electrode supply line 42. The exhaust gas of the biomass heating plant 1 is discharged through the flue gas outlet 41, which is fluidly positioned downstream of the filter device 4. A fan can be provided here.

A recirculation device 5 is provided downstream of the boiler 11, which recirculates part of the flue gases or exhaust gases through channels 51, 53 and 54 and dampers 52 to cool the combustion process and reuse it in the combustion process. This recirculating device 5 will be explained in detail later with reference to FIG. 12-17.

In addition, the biomass heating plant 1 has a fuel supply device 6, with which fuel is transported in a controlled manner to the combustion device 2 in the primary combustion zone 26 from the side onto the rotary grate 25. The fuel supply device 6 has a paddle feeder 61 with a fuel supply pipe 65, moreover, the paddle dispenser 61 has a drive motor 66 with control electronics. Driven by the drive motor 66, the axle 62 drives the transfer mechanism 63, which can drive the (not shown) fuel screw conveyor 67 so that the fuel is supplied in the fuel supply channel 64 to the combustion device 2.

At the bottom of the biomass heating plant 1, an ash removal device 7 is provided, which has an ash removal screw conveyor 71 in the ash removal channel, which is driven by a motor 72.

In FIG. 2 shows a sectional view through the biomass heating plant 1 according to FIG. 1, which is taken along the line SL1 and which is shown in side view S. In the corresponding FIG. 3, which shows the same cross section as FIG. 2, the flue gas flows and hydrodynamic cross sections are schematically shown for clarity. With respect to FIG. 3, it should be noted that the individual areas compared to FIG. 2 are shown shaded. This is only for illustrative purposes of FIG. 3 and the visibility of the arrows S5, S6 and S7 flows.

From left to right in Fig. 2, a combustion device 2, a heat exchanger 3 and an (optional) filter device 4 of the boiler 11 are provided. The boiler 11 rests on the boiler base 12 and has a multi-walled boiler body 13 in which water or other heat exchange fluid can circulate. For the supply and removal of the heat exchange medium, a water circulation device 14 with a pump, valves, pipelines, etc. is provided.

The combustion device 2 has a combustion chamber 24 in which the fuel combustion process essentially takes place. The combustion chamber 24 has a multi-element rotary grate 25 described later in more detail, on which fuel 28 is located.

In addition, referring to FIG. 2, the primary combustion zone 26 of the combustion chamber 24 is surrounded by (multiple) combustion chamber bricks 29, the combustion chamber bricks 29 defining the geometry of the primary combustion zone 26 . The cross section of the primary combustion zone 26 (for example) along the horizontal section line A1 is substantially oval (for example, 380 mm ± 60 mm × 320 mm ± 60 mm, it should be noted that some of the above combinations of values \u200b\u200bmay also give an oval cross section ). The arrow S1 schematically shows the flow from the secondary air nozzle 291, this flow (shown purely schematically) having swirling induced by the secondary air nozzles 291 in order to improve the mixing of the flue gases.

In this case, the secondary air nozzles 291 are designed in such a way that they introduce (preheated by means of the combustion chamber bricks 29) secondary air tangentially into the combustion chamber 24 with its oval cross-section at this point. This results in a swirling or swirling flow S1 which flows upwards in an approximately helical manner. In other words, a spiral flow flowing upward and rotating around a vertical axis is formed.

The secondary air nozzles 291 are thus oriented so that they introduce secondary air - when viewed in a horizontal plane - into the combustion chamber 24 tangentially. In other words, the secondary air nozzles 291 are provided for a secondary air inlet not oriented towards the center of the combustion chamber. In addition, such a tangential inlet can also be used in the case of a circular combustion chamber geometry.

Here, all the secondary air nozzles 291 are oriented so that they result in either a right-handed or a left-handed flow. In this regard, each secondary air nozzle 291 can contribute to the formation of swirl flows, with each secondary air nozzle 291 having the same orientation. With regard to the above, it should be noted that in exceptional cases, the individual secondary air nozzles 291 may be located neutral (centered) or opposite (oppositely oriented), although this may degrade the hydrodynamic efficiency of the device.

The combustion chamber bricks 29 form the inner lining of the primary combustion zone 26, store heat and are directly exposed to the fire. In this way, the combustion chamber bricks 29 also protect other materials of the combustion chamber 24, such as cast iron, from direct exposure to the combustion chamber flame. The combustion chamber bricks 29 are preferably aligned with the shape of the grate 25. In addition, the combustion chamber bricks 29 have secondary air or recirculation nozzles 291 which recirculate the flue gas to the primary combustion zone 26 for re-participation in the combustion process and, above all, for cooling as needed. In this case, the secondary air nozzles 291 are directed not at the center of the primary combustion zone, but acentrically to cause swirling of the flow in the primary combustion zone 26 (ie swirling and swirling flow, which will be explained in more detail below). The combustion chamber bricks 29 will be described in more detail below. Insulation 311 is provided at the inlet of the boiler tubes. The oval shape of the primary combustion zone 26 (and nozzle) and the length and position of the secondary air nozzles 291 preferably contribute to the formation and maintenance of a swirl flow, preferably until the combustion chamber 24 is closed off.

The secondary combustion zone 27 adjoins either at the height of the combustion chamber nozzles 291 (when considered functionally or thermally) or at the height of the combustion chamber nozzle 203 (when considered purely structurally or constructively) to the primary combustion zone 26 of the combustion chamber 26 and defines the radiation part of the combustion chamber 26. In the radiation part, the flue gas formed during combustion gives off its thermal energy mainly through thermal radiation, primarily to the heat exchange medium, which is located in both left chambers 38.

The corresponding flue gas flows are shown in FIG. 3 by means of arrows S2 and S3 purely by way of example. These eddy currents, as the case may be, include small reverse flows or other turbulences, which are represented by the purely schematic arrows S2 and S3. However, the basic principle of the manifestation of flows in the combustion chamber 24, based on the arrows S2 and S3, is understandable or calculable for a person skilled in the art.

Pronounced swirling, rotational or eddy currents are formed in the isolated or limited combustion chamber 24 by means of supplying secondary air through nozzles. In this case, above all, the oval geometry of the combustion chamber 24 contributes to the fact that the vortex flows can develop without interference or optimally.

After exiting the nozzle 203, which again bundles these vortex flows, candle flame-shaped rotational flows S2 appear (cf. also FIG. 21), which can preferably reach the combustion chamber overlap 204, whereby the the space of the combustion chamber 24 is available. In this case, the vortex flows are concentrated in the middle A2 of the precise chamber and ideally use the volume of the secondary combustion zone 27 . In addition, the constriction created by the swirl nozzle 203 reduces rotational flows, thereby creating turbulences to improve air-flue gas mixing. So, due to the narrowing or reduction by means of the nozzle 203 of the combustion chamber, transverse mixing occurs. However, the rotational momentum of the flows is also at least partially retained above the combustion chamber nozzle 203, which supports the propagation of the flows up to the combustion chamber overlap 204 .

Consequently, the secondary air nozzles 291 are integrated into the elliptical or oval cross section of the combustion chamber 24 so that, due to their length and their orientation, they induce eddy currents which rotate the flue gas-secondary air mixture and thereby make it possible (improved again by the combination with the combustion chamber nozzle 203 located above them) complete combustion with a minimum excess of air and therefore maximum efficiency. This is also shown in FIG. 19-21.

At the same time, the secondary air supply is designed in such a way that it cools the hot bricks 29 of the combustion chamber by flowing around them, and the secondary air, in turn, is itself heated, as a result of which the rate of combustion of flue gases increases and the completeness of combustion is ensured even at extremely low load (for example, 30% of rated load).

The first maintenance hole 21 is insulated with an insulating material such as vermiculite. This secondary combustion zone 27 is designed to ensure that the flue gas is burnt off. The specific geometry of the secondary combustion zone 27 will be described in more detail later.

After the secondary combustion zone 27, the flue gas flows into the heat exchange device 3, which has a bundle of boiler tubes 32 provided parallel to each other. In the boiler tubes 32, the flue gas flows downward, as in FIG. 3 is shown by arrow S4. This part of the flow can also be referred to as the convective part, since the heat transfer from the flue gas takes place essentially on the walls of the boiler pipes by means of forced convection. Due to the temperature gradients induced in the boiler 11 in the heat exchange medium, for example in water, a natural water convection is established, which contributes to the mixing of the boiler water.

Boiler tubes 32 are provided with spring swirlers 36 and helical or band swirlers 37 to improve the efficiency of the heat exchange device 4. This will be explained in more detail later.

The outlet of the boiler tubes 32 terminates through the inlet 34 or the inlet of the reversing chamber in the reversing chamber 35. In this case, the reversing chamber 35 is sealed against the combustion chamber 24 so that the flue gas from the reversing chamber 35 cannot flow back into the combustion chamber 24. However, despite this , a common transport path is provided for incineration residues that may end up in the common flow area of the boiler 11. In the event that a filter device 4 is not provided, the flue gas is led upward again into the boiler 11. Another case of an optional filter device 4 is shown in Fig. 2 and Fig.3. In this case, the flue gas after the reversing chamber 35 is again introduced upwards into the filter device 4 (cf. arrows S5), which in this case is, for example, an electrostatic filter device 4. In this case, flow flaps can be provided at the inlet 44 of the filter device 4, which equalize flue gas inflow into the filter.

Electrostatic dust filters, also called electrostatic purifiers, are devices for precipitating particles from gases that are based on the electrostatic principle. These filter devices are primarily used for electrical exhaust gas cleaning. In electrostatic precipitators, dust particles are electrically charged by the corona discharge of the corona electrode and are attracted to the oppositely charged electrode (collecting electrode). The corona discharge occurs at a suitably charged high voltage electrode (also called corona electrode) inside the electrostatic precipitator. Preferably, the (corona) electrode is covered with protruding points and possibly made with sharp ribs, since there the density of the force fields and thus the electric field strength is greatest and, therefore, contributing to the corona discharge. The opposite electrode (collecting electrode) usually consists of a grounded section of the chimney that is placed around the electrode. The degree of purification of the electrostatic precipitator depends, first of all, on the residence time of the exhaust gas in the filter system and the voltage between the corona and collecting electrodes. The rectified high voltage required for this is provided by a high voltage generation device (not shown). The high voltage generation plant and the electrode holder should be protected from dust and damaging use in order to avoid unwanted leakage currents and prolong the life of the plant 1.

As shown in FIG. 2, a rod-shaped electrode 45 (which is preferably made in the form of an elongated, lamellar steel spring, cf. FIG. 15) is held approximately in the center of the approximately chimney-shaped interior of the filter device 4. The electrode 45 consists of at least substantially of high quality spring steel or chrome steel and is held by the electrode holder 43 through a high voltage insulator, ie the electrode insulation 46 .

The (corona) electrode 45 oscillates downwardly into the interior of the filter device 4. In this case, the electrode 45 can, for example, oscillate back and forth across the longitudinal axis of the electrode 45.

Cage 48 simultaneously serves as a counter electrode and as a cleaning mechanism for filter unit 4. Cage 48 is connected to ground potential or ground potential. Due to the existing potential difference, the flue gas flowing through the flue gas filter device 4 (cf. arrows S6) is filtered as described above. When the filter device 4 is cleaned, the electrode 45 is de-energized. Preferably, cage 48 has an octagonal, constant cross-sectional profile, which, for example, makes it possible to understand the view of FIG. 13. Preferably, cage 48 may be cut with a laser during manufacture.

The flue gas after leaving the heat exchanger 3 (from its outlet) flows through the rotary chamber 35 into the inlet 44 of the filter device 4.

In this case, the (optional) filter device 4 is optionally fully integrated integrated into the boiler 11, whereby the wall surface facing the heat exchanger 3 and washed by the heat exchange medium is also used for heat exchange in the direction from the filter device 4 to the heat exchanger, due to which the efficiency of the installation 1 is still once it improves. In this way, at least part of the wall of the filter device 4 can be washed by the heat exchange medium, whereby at least part of this wall is cooled by boiler water.

At the filter outlet 47, exhaust gas flows out of the filter unit 4 as indicated by the arrows S7. After leaving the filter, part of the exhaust gases through the recirculation device 5 is again supplied to the primary combustion zone 26. And this will be explained in more detail below. This recycled exhaust gas or flue gas can be abbreviated as "Rezi" or "ReziGas".

The remaining part of the exhaust gas through the exhaust gas outlet 41 is removed from the boiler 11.

The ash removal device 7 is located in the lower part of the boiler 11. Through the ash removal screw conveyor 71, the ash deposited and precipitated, for example, from the combustion chamber 24, the boiler pipes 32 and the filter device, is transported from the boiler 11 on the side.

The combustion chamber 24 and the boiler 11 of this embodiment were calculated by CFD simulation. In addition, practical experiments were carried out to validate the CFD simulation. The starting point of the discussion was the calculations for a 100 kW boiler, however, a power range of 20 to 500 kW was foreseen.

CFD simulation (digital flow mechanics) is a spatially and temporally separated simulation of flows and heat conduction processes. In this case, the flow processes can be laminar and/or turbulent, occur accompanied by chemical processes, or we can talk about multi-phase systems. Therefore, CFD simulations are well suited as a design and optimization tool. In relation to the present invention, CFD simulations have been used to optimize the hydrodynamic parameters so that the above objectives of the invention are solved. First of all, as a result, the mechanical design and dimensions of the boiler 11, the combustion chamber 24, the secondary air nozzles 291 and the combustion chamber nozzles 203 were decisively determined by means of CFD simulations and also by appropriate practical experiments. The simulation results are based on the flow simulation taking into account heat transfer.

The above components of the biomass heating plant 1 and the boiler 11, which are the results of CFD simulations, will be described in more detail below.

(Combustion chamber)

The execution of the form of the combustion chamber is important in order to be able to comply with the requirements according to the tasks. Due to the shape or geometry of the combustion chamber, the best possible turbulent mixing and homogenization of flows along the cross section of the flue gas channel, minimization of combustion volume, as well as reduction of excess air and recirculation ratio (economical, operating costs), reduction of CO and CxHx emissions, NOx emissions, dust emissions, reduction of local temperature peaks (scale formation and slagging) and reduction of flue gas velocity local peaks (material impact and erosion).

Fig. 4 which is a partial view of FIG. 2 and FIG. 5, which is a sectional view through the boiler 11 along the vertical section line A2, represents a combustion chamber geometry that satisfies the aforementioned requirements for a biomass heating plant over a wide power range, for example from 20 to 500 kW. The vertical section line A2 can also be understood as the middle or central axis of the oval combustion chamber 24.

Indicated in Fig. 3 and FIG. 4 and the dimensions obtained by CFD calculations and practical experiments with an example boiler with a power of approximately 100 kW, in particular the following: BK1 = 172 mm ± 40 mm, preferably ± 17 mm,

VK2=300 mm±50 mm, preferably ±30 mm,

VK3=430 mm±80 mm, preferably ±40 mm,

ВК4=538 mm±80 mm, preferably ±50 mm,

VK5=(VK3-VK2)/2=e.g. 65 mm±30 mm, preferably ±20 mm,

VK6=307 mm±50 mm, preferably ±20 mm,

ВК7=82 mm±20 mm, preferably ±20 mm,

VK8=379 mm±40 mm, preferably ±20 mm,

ВК9=470 mm±50 mm, preferably ±20 mm,

VK10=232 mm±40 mm, preferably ±20 mm,

VK11=380 mm±60 mm, preferably ±30 mm,

VK12=460 mm±80 mm, preferably ±30 mm.

However, all data on sizes and values should be understood as given by way of example only.

With these values, both the geometries of the primary combustion zone 26 and the secondary combustion zone 27 of the combustion chamber are optimized in this case. The size ranges given are ranges by which the requirements are met (approximately) as well as the exact values given.

Preferably, the geometry of the chamber of the primary combustion zone 26 and the combustion chamber 24 (or the internal volume of the primary combustion zone 26 of the combustion chamber 24) are determined using the main parameters: Volume with an oval horizontal main surface with dimensions of 380 mm ± 60 mm (preferably ± 30 mm ) × 320 mm ± 60 mm (preferably ± 30), as well as a height of 538 mm ± 80 mm (preferably ± 50 mm).

The above dimensional data can be scaled in relation to each other and can be applied to other power boilers (eg 50kW or 200kW).

As a development of this, the volume defined above may have an upper opening in the form of a combustion chamber nozzle 203, which is provided in the secondary combustion zone 27 of the combustion chamber 24, which has a combustion chamber bevel 202 protruding into the secondary combustion zone 27, which preferably contains a heat exchange medium. 38. The bevel 202 of the combustion chamber reduces the cross section of the secondary combustion zone 27 . In this case, the bevel 202 of the combustion chamber is provided at an angle k of at least 5%, preferably at an angle k of at least 15%, and even more preferably at an angle k of at least 19% relative to the imaginary provided horizontal or direct overlap H of the combustion chamber (cf. dashed horizontal line H in Fig. 4).

In addition, the combustion chamber cover 204 is also provided to be inclined upwards in the direction of the inlet 33. Thus, the combustion chamber 24 in the secondary combustion zone 27 has a combustion chamber ceiling 204 which is provided to be inclined upwards in the direction of the inlet 33 of the heat exchanger 3. This combustion chamber ceiling 204 extends in the section according to figure 2, at least essentially straight or straight and oblique. The angle of inclination of the straight or even overlap 204 of the combustion chamber may be relative to the (imaginary) horizontal, preferably from 4 to 15 degrees.

By means of the combustion chamber cover 204, another chamfer(s) is provided in the combustion chamber 24 in front of the inlet 33, which, with the combustion chamber chamfer 202, forms a funnel. This funnel turns the upward swirling or swirling flow to the side and diverts this flow approximately horizontally. Due to the already turbulent upward flow and the funnel shape in front of the inlet 33, it is ensured that all heat exchanger tubes 32 or boiler tubes 32 flow around evenly, which ensures an equally distributed flue gas flow in all boiler tubes 32. This greatly optimizes the heat transfer in the heat exchanger 3.

Here, above all, the combination of vertical and horizontal bevels 202, 204 in the secondary combustion zone in combination as an inflow geometry can achieve a uniform flue gas distribution on the convective boiler tubes.

The combustion chamber bevel 202 serves to homogenize the flow S3 in the direction of the heat exchanger 3 and thus flow around the boiler tubes 32. This results in a most even distribution of the flue gas to the individual boiler tubes in order to optimize the heat transfer there. In detail, the combination of bevels with the cross section of the boiler inlet turns the flue gas flow so that the most even distribution of the flue gas flow or volumetric flow to the respective boiler tubes 32 occurs.

According to the prior art, there are often combustion chambers with a rectangular or polygonal combustion chamber and nozzle, however, the irregular shape of the combustion chamber and nozzle, as well as their combined action, represent an additional obstacle to uniform air distribution and good mixing of air and fuel and, thus, good burnout, as understood in this case. First of all, the angular geometry of the combustion chamber results in flow lines or preferred flows which unfavorably lead to uneven flow around the heat exchanger tubes 32 .

Therefore, in this case, the combustion chamber 24 is provided without dead corners or without dead edges. Thus, in this case, it has been found that the geometry of the combustion chamber (and the entire flow in the boiler) plays a decisive role in considerations regarding the optimization of a biomass heating installation. Therefore (refusing to give the usual rectangular or polygonal or purely cylindrical shapes) the oval or round basic geometry described here without dead corners was chosen. In addition, this basic geometry of the combustion chamber and its design have also been optimized with the above dimensions/size ranges for a 100 kW boiler. In doing so, these sizes / size ranges are chosen so that, above all, different fuels (pellets and wood chips) with different qualities (eg different water content) can also be burned with a very high efficiency. This was revealed by practical tests and CFD simulations.

First of all, the primary combustion zone 26 of the combustion chamber 24 may include a volume that preferably has an oval or approximately circular horizontal cross section around the outer perimeter (such an example cross section is indicated by A1). In addition, this horizontal cross-section may preferably represent the basic surface of the primary combustion zone 26 of the combustion chamber 24. Above the height indicated by the double arrow BK4, the combustion chamber 24 may have an approximately constant cross-section. Thus, primary combustion zone 24 may have an approximately oval-cylindrical volume. Preferably, the side walls and base surface (grate) of the primary combustion zone 26 are perpendicular to each other. In this case, the bevels 202, 204 described above can be provided together as the walls of the combustion chamber 24, the bevels 202, 204 forming a funnel that terminates at the inlet 33 of the heat exchanger 3 and has a minimum cross section there.

Above, the term "approximately" is used, since, of course, there may be individual cuts, structurally determined deviations or slight asymmetries, for example when individual bricks 29 of the combustion chamber transition into each other. However, these minor deviations play only a secondary role hydrodynamically.

The horizontal cross-section of the combustion chamber 24 and above all the primary combustion zone 26 of the combustion chamber 24 can preferably also be correct. In addition, the horizontal cross section of the combustion chamber 24 and, above all, the primary combustion zone 26 of the combustion chamber 24 may preferably be a regular (and/or symmetrical) ellipse.

In addition, the horizontal cross section (outer perimeter) of the primary combustion zone 26 can be made constant above a certain height (eg 20 cm).

In this case, an oval-cylindrical primary zone 26 of the combustion chamber 24 is provided, which, according to CFD simulations, allows a noticeably more uniform and better air distribution in the combustion chamber 24 than with the rectangular combustion chambers according to the prior art. In addition, the absence of dead spaces prevents the existence of areas in the combustion chamber with poor air flow, which increases efficiency and reduces slag formation.

Also, the nozzle 203 in the combustion chamber 24 is designed as an oval or substantially circular constriction to further optimize flow conditions. The above-described swirl of flow in the primary zone 26, which is due to the secondary air nozzles 291 specially designed according to the invention, results in an upward, approximately swirling or helical flow movement, which flow movement is also favored by oval or approximately circular nozzles, and not hindered by conventional rectangular nozzles. . This optimized nozzle 203 beams the upward rotating flue gas-air mixture and provides better mixing, keeping the swirling flow in the secondary combustion zone 27 and thus complete combustion. This also minimizes the necessary excess air. This improves the combustion process and increases efficiency.

In this way, above all, the combination of the secondary air nozzles 291 described above and the swirl flows thus induced with the optimized nozzle 203 serve to bundle the upwardly rising rotating flue gas-air mixture. This ensures at least approximately complete combustion in the secondary combustion zone 27 .

Due to this, the swirling or swirling flow is bundled by the nozzle 203 and directed upwards, whereby this flow propagates further upwards than usual in the prior art. This, as the specialist understands from the laws of physics regarding the rotational momentum, has its reason in the forced decrease in the distance of the swirling air flow from the axis of rotation or the central axis of the swirl (cf. similar to the physics of the pirouette effect).

In addition, in the present case, the flow movement in the secondary combustion zone 27 and from the secondary combustion zone 27 to the boiler tubes 32 is optimized, as will be explained in more detail below.

The bevel 202 of the combustion chamber in FIG. 4, which can also be seen without reference symbols in FIG. 2 and FIG. 3 and at which the combustion chamber 25 (or its cross-section) tapers from bottom to top, at least approximately linearly, provides, according to CFD calculations, an averaging of the flue gas flow in the direction of the heat exchanger 4, whereby its efficiency can be improved. When this horizontal cross-sectional area of the combustion chamber 25 from the beginning to the end of the bevel 202 of the combustion chamber is narrowed, preferably at least 5%. In this case, the bevel 202 is provided on the side of the combustion chamber 25 towards the heat exchange device 4 and is rounded in the place of maximum narrowing. According to the prior art, the parallel or straight walls of the combustion chamber are not constricted (so as not to impede the flow of flue gas). To this is added, singly or in combination, a combustion chamber cover 204 extending obliquely horizontally upwards in the direction of the inlet 33, which diverts the swirling flow in the secondary combustion zone 27 to the side and evens out its distribution of flow velocities.

The inflow or diversion of the flue gas flow upstream of the tube bundle heat exchanger is designed in such a way that uneven inflow into the tubes is best prevented, whereby the temperature peaks in the individual boiler tubes 32 can be kept low and thus the heat transfer in the heat exchanger 4 can be improved (better use of surfaces heat exchanger). As a result, the efficiency of the heat exchange device 4 is improved.

In detail, the gaseous volume flow of flue gas through the sloped wall 202 of the combustion chamber at a constant speed (also in the case of different combustion states) is directed to the heat exchange tubes or boiler tubes 32. Due to the sloped ceiling 204 of the combustion chamber, this effect is further enhanced, and the effect is caused funnels. The result is a uniform heat distribution of the individual boiler tubes 32 with respect to the heat exchange surfaces and thus an improved utilization of the heat exchange surfaces. Thus, the temperature of the exhaust gas is reduced and the efficiency is increased. In this case, the distribution of the flow, especially in the one shown in FIG. 3 indicator line WT1 is noticeably more uniform than according to the prior art. The indicator line WT1 represents the inlet surface for the heat exchanger 3. The indicator line WT3 indicates an exemplary cross-sectional line through the filter device 4 in which the flow is set to be most homogeneous or more or less evenly distributed across the cross-section of the boiler tubes 32 (particularly due to flow dampers at the inlet of the filter device 4 and due to the geometry of the reversing chamber 35). The uniform flow through the filter device 3 or the last chimney of the boiler minimizes the formation of separate jets and thereby also optimizes the deposition efficiency of the filter device 4 as well as the heat transfer in the biomass heating system 1.

In addition, an ignition device 201 is provided on the bottom of the combustion chamber 24 on the fuel bed 28 . It can cause initial ignition or re-ignition of the fuel. The ignition device 201 may be a filament igniter. Preferably, the ignition device is stationary or moves sideways horizontally to the fuel injection site.

In addition, after the exit of the flue gas from the filter device, a lambda sensor (not shown) can be (optionally) installed. By means of a lambda sensor, a control device (not shown) can recognize the corresponding calorific value. Thus, the lambda sensor can provide an ideal mixture ratio between fuel and oxygen supply. Despite varying fuel qualities, high efficiency and higher efficiency are achievable as a result.

Shown in FIG. 5, the fuel layer 28 shows a coarse fuel distribution due to fuel supply from the right side in FIG. A flue gas-fresh air mixture flows from below through this layer 28 of fuel, which is provided by the recirculation device 5. This flue gas-fresh air mixture is preferably preheated/cooled and has an ideal quantity (mass flow) and ideal mixing ratio. mixture, as regulated by a control system not shown, based on various measured data recorded by the sensors and the corresponding air valves 52.

In addition, in FIG. 4 and FIG. 5 shows a combustion chamber nozzle 203 in which a secondary combustion zone 27 is provided and which accelerates and bundles the flue gas flow. As a result, the flue gas stream is better mixed and can be burned more efficiently in the post-combustion zone 27 or the secondary combustion zone 27 . The area ratio of the combustion chamber nozzle 203 is in the range of 25% to 45%, however, it is preferably 30% to 40% and, for example, for a 100 kW biomass heating plant 1, ideally is 36%±1% (ratio measured inlet area to the measured outlet area of the nozzle 203).

Therefore, the above data regarding the geometry of the combustion chamber of the primary combustion zone 26 together with the geometry of the secondary air nozzles 291 and the nozzle 203 represent a preferred improvement of the present disclosure.

(Bricks of the combustion chamber)

In FIG. 6 shows a three-dimensional cross-sectional view (obliquely from above) of the primary combustion zone 26 as well as an isolated part of the secondary combustion zone 27 of the combustion chamber 24 with rotary grate 25 and, above all, of the particular design of the combustion chamber bricks 29. Fig. 7 shows, respectively, Figs. 6 is an exploded view of the bricks 29 of the combustion chamber. Views according to Fig. 6 and FIG. 7 can preferably be made with the above dimensions according to FIG. 4 and FIG. 5. However, this is not mandatory.

The chamber wall of the primary combustion zone 26 of the combustion chamber 24 is provided with several combustion chamber bricks 29 in a modular design, which, among other things, facilitates manufacturing and maintenance. Maintenance is facilitated primarily by the possibility of extracting the individual bricks 29 of the combustion chamber.

On the supporting surfaces 260 of the bricks 29 of the combustion chamber, grooves 261 and protrusions 262 are provided for positive locking (only a few of them are shown in Fig. 6 to prevent redundancy in the figures as an example) to create a mechanical and essentially tight connection, so that in turn , to prevent the entry of disturbing foreign air. Preferably, two at least substantially symmetrical bricks of the combustion chamber (with the possible exception of openings for secondary air or recirculated flue gas) form a complete ring. In addition, the three rings are preferably stacked on top of each other to form an oval-cylindrical or optionally also at least approximately circular (the latter not shown) primary combustion zone 26 of the combustion chamber 24.

Three combustion chamber bricks 29 are provided as top termination, the annular nozzle 203 being supported by two fixing bricks 264 which are fitted in a positive manner on the top ring 263. suitable sealing material.

The anchor bricks 264, which are preferably symmetrical, may preferably have an inwardly inclined bevel 265 to facilitate sweeping the fly ash onto the rotary grate 25.

The lower ring 263 of bricks 29 of the combustion chamber lies on the support plate 251 of the rotary grate 25. On the lower edge between this lower ring 263 of bricks 29 of the combustion chamber, ash is deposited in an increasing amount, which independently and preferably seals this transition when operating the heating installation 1 on biomass.

In the middle ring of bricks 29 of the combustion chamber, (optional) openings are provided for recirculation nozzles 291 or secondary air nozzles 291. In this case, the secondary air nozzles 291 are provided in the bricks 29 of the combustion chamber at least approximately at the same (horizontal) height of the combustion chamber 24.

In the present case, three rings of combustion chamber bricks 29 are provided, as this represents the most efficient way of manufacturing and also maintenance. Optionally, 2, 4 or 5 such rings may also be provided.

The combustion chamber bricks 29 preferably consist of high temperature silicon carbide and are therefore very wear resistant.

Bricks 29 of the combustion chamber are provided in the form of shaped bricks. The combustion chamber bricks 29 are molded such that the interior volume of the primary combustion zone 26 of the combustion chamber 24 has an oval horizontal cross-section, whereby dead corners or dead spaces through which the flue gas-air mixture normally does not normally flow optimally are prevented by ergonomic shaping, whereby the fuel available there does not burn optimally. Due to the proposed shaping of the combustion chamber bricks 29, the flow through the grate 25 of primary air, which passes through the grate 25 also for fuel distribution, and the unhindered flow of swirl flows are improved, and hence the combustion efficiency is improved.

The oval horizontal cross-section of the primary combustion zone 26 is preferably a point-symmetrical and/or regular oval with a minimum internal diameter of BK3 and a maximum internal diameter of BK11. These dimensions were the result of optimizing the primary combustion zone 26 of the combustion chamber 24 through CFD modeling and practical testing.

(Rotary grate)

In FIG. 8 shows a top view of the grate 25 from the sectional line A1 in FIG. 2.

Preferably, the view according to FIG. 8 can be made with the above dimensions. However, this is not mandatory.

The rotary grate 25 has a base plate 251 as a base element. In the approximately oval opening of the base plate 251, an adapter 255 is provided that bridges the intermediate space between the first rotary grate element 252, the second rotary grate element 253, and the third rotary grate element 254, which are rotatably mounted in bearings. As a result, the rotary grate 25 is provided in the form of a grate with three individual elements, i.e. it can be called a triple grate. The elements 252, 253 and 254 of the rotary grate are provided with air holes for the flow of primary air.

The rotary grate elements 252, 253 and 254 are flat and heat-resistant metal plates, for example of metal casting, which on their upper side have at least a substantially shaped flat surface and on their lower side are connected to bearing axles 81, for example, through intermediate carriers. When viewed from above, the elements 252, 253 and 254 of the rotary grate have curved and complementary sides or contours relative to each other.

First of all, the rotary grate elements 252, 253 and 254 have complementary and curved sides relative to each other, and preferably the second rotary grate element 253 has concave sides in the direction of the first and third adjacent rotary grate element 252, 254 respectively and, preferably, the first and third rotary grate members 252, 254 each have a convex side in the direction of the second rotary grate member 253. As a result, the breaking action of the rotary grate elements is improved, since the breaking length is increased and the breaking forces (similar to scissors) act purposefully.

The grate elements 252, 253 and 254 (as well as their framing in the form of a transition element 255) have, when viewed together from above, an approximately oval outer shape, thereby again preventing dead corners or dead spaces in which suboptimal combustion or ash could undesirably accumulate. The optimal dimensions of this outer shape of the rotary grate elements 252, 253 and 254 are indicated in FIG. 8 double arrows DR1 and DR2. Preferably, but not exclusively, DR1 and DR2 are defined as follows:

DR1=288mm±40mm, preferably ±20mm

DR2=350mm±60mm, preferably ±20mm

These values turned out to be optimal values (ranges) in CFD simulations and the following practical experiments. These dimensions correspond to the dimensions according to Fig.4 and Fig.5. These dimensions are preferred especially for the combustion of different fuels or wood chips and pellets (hybrid heating) in the power range from 20 to 200 kW.

At the same time, the rotary grate 25 has an oval combustion surface, which is more favorable for fuel distribution, air flow through the fuel and fuel burnout than a conventional rectangular combustion surface. The combustion surface 258 is formed in the center by the surfaces of the rotary grate members 252, 253 and 254 (in a horizontal position). The combustion surface is thus the upwardly oriented surface of the grate elements 252, 253 and 254. Preferably, this oval combustion surface corresponds to the loading surface of the fuel when it is introduced or pushed laterally onto the rotary grate (cf. arrow E in FIGS. 9, 10 and 11). First of all, fuel can be supplied from a direction that is parallel to the longer central axis (major axis) of the oval combustion surface of the rotary grate 25.

Preferably, the first rotary grate element 252 and the third rotary grate element 254 can be made identical with respect to their surface. In addition, the first rotary grate element 252 and the third rotary grate element 254 may be identical or structurally identical to each other. This can be seen in FIG. 9, for example, where the first rotary grate element 252 and the third rotary grate element 254 have the same shape.

In addition, the second rotary grate element 253 is disposed between the first rotary grate element 252 and the third rotary grate element 254.

Preferably, the rotary grate 25 is provided with an approximately point-symmetric oval combustion surface 258.

Also, the rotary grate 25 may form an approximately elliptical combustion surface 258, with DR2 being the dimension of its major axis and DR1 being the dimension of its minor axis.

In addition, the rotary grate 25 has an approximately oval combustion surface 258 that is axisymmetric about the central axis of the combustion surface 258.

In addition, the rotary grate 25 has an approximately round combustion surface 258, and this entails minor disadvantages in fuel supply and distribution.

In addition, two rotation motors or drives 231 are provided, with which the rotary grate elements 252, 253 and 254 can be rotated accordingly. Details regarding the operation and advantages of the present rotary grate 25 will be described later with reference to FIGS. 9, 10 and 11.

First of all, for heating systems with pellets or wood chips (and, above all, for hybrid biomass heating systems), downtimes can often occur due to the formation of slag in the combustion chamber 24, especially on the rotary grate 25. Slag occurs during the combustion process always when the flame reaches temperatures above the melting point of the ash. Then the ash becomes soft, sticky and, after cooling, forms a hard and often dark-colored slag. This process, also known as sintering, is undesirable in a biomass heating system 1, since the combustion chamber 24 can malfunction due to the accumulation of slag: it is switched off. Typically, the combustion chamber 24 must be opened and the slag must be removed.

The melting range of ash (it extends from the sintering temperature to the pour point) is very much dependent on the combustible material used. Spruce wood has, for example, a critical temperature of about 1200°C. However, the melting range of fuel ash can also be subject to strong fluctuations. Depending on the amount and composition of the minerals contained in the wood, the behavior of the ash during the combustion process changes.

Another factor that can influence the formation of slag is the transport and storage of wood pellets or chips. Namely, they must enter the combustion chamber 24 as undamaged as possible. If wood pellets are already crushed when they enter the combustion process, this increases the density of the burning layer. The result is stronger slag formation. First of all, in this case, the transport from the storage room to the combustion chamber 24 is important. Particularly long paths, as well as bends and corners, lead to damage or abrasion of wood pellets.

Another factor relates to the management of the incineration process. Until now, the goal has been to keep the temperature as high as possible in order to achieve the best possible burn-in and low emissions. Due to the optimized geometry of the combustion chamber and the geometry of the combustion zone 258 of the rotary grate 25, the combustion temperature on the grate can be kept low and high in the area of the secondary air nozzles 291 and, consequently, the formation of slag on the grate can be reduced.

In addition, the resulting slag (and also ash) is preferably removed by the specific shape and functionality of the present grate 25. This will be explained in more detail with reference to FIG. 9, 10 and 11.

In FIG. 9, 10, and 11 show a three-dimensional view of the rotary grate 25 with a base plate 251, a first rotary grate element 252, a second rotary grate element 253, and a third rotary grate element 254. The views in Fig. 9, 10 and 11 may preferably correspond to the above dimensions. However, this is not mandatory.

This view shows the rotary grate 25 as a free-standing retractable part with the rotary grate mechanism 23 and the drive(s) 231. The rotary grate 25 is provided mechanically so that it can be separately pre-fabricated in a standard module system, and is introduced and integrated as a sliding part into the provided elongated opening of the boiler 11. In addition, this facilitates the maintenance of this wear-prone part. As a result, the rotary grate can be made modular, and it can be quickly and efficiently removed and reinserted as a complete part with the rotary grate mechanism 23 and the drive 231. As a result, the modular rotary grate 25 can also be assembled and dismantled by means of a quick locking. In contrast, prior art rotary grates are usually mounted rigidly and thus can be operated or mounted with difficulty.

Drive 231 may have two separately controlled motors. Preferably, they are provided on the side of the grate mechanism 23 . Electric motors may have reduction gears. In addition, limit switches can be provided which provide end stops for the end positions of the grate elements 252, 253 and 254, respectively.

The individual components of the grate mechanism 23 are provided as interchangeable. For example, the gears are provided for insertion. This facilitates maintenance and, if necessary, replacement on the side of the mechanism during installation.

The elements 252, 253 and 254 of the rotary grate 25 are provided with the holes 256 already mentioned. motors 231 rotate respectively at least 90 degrees, preferably at least 120 degrees, and even more preferably 170 degrees, around the respective bearing or pivot axis 81. The maximum angle of rotation may be 180 degrees or slightly less than 180 degrees. , as the edges of the grate 257 allow. Meanwhile, the rotation mechanism 23 is configured such that the third rotary grate element 254 can be rotated independently of the first rotary grate element 252 and the second rotary grate element 253, and that the first grate element 252 and the second grate element 253 can be rotated together. and independently of the third element 254 rotary grate. The pivoting mechanism 23 can suitably be provided, for example, by means of impellers, toothed or driving belts and/or toothed wheels.

The rotary grate elements 252, 253, and 254 may preferably be laser-cut cast grate to ensure accurate shape maintenance. This is done primarily to direct the air through the fuel bed 28 as precisely as possible and to avoid interfering air currents, such as jets of air at the edges of the grate elements 252, 253 and 254.

The openings 256 in the rotary grate members 252, 253 and 254 are made so that they are small enough for conventional pellet material and/or conventional wood chips that they do not fall through, or that they are large enough that air can flow well through the fuel. In addition, holes 256 are chosen to be large enough so that they cannot be blocked by ash particles or impurities (eg, any stones in the fuel).

In FIG. 9 shows the rotary grate in a closed position with all of the rotary grate members 252, 253 and 254 oriented horizontally or closed. This is the position in normal use. By uniformly distributing the plurality of holes 256, uniform flow through the bed 28 of the fuel (this is not shown in FIG. 9) on the rotary grate 25 is ensured. In this regard, an optimum combustion state can be created here. Fuel is applied to the rotary grate 25 from the direction of the arrow E, in this respect the fuel is pushed onto the rotary grate 25 on the right side of FIG. 9.

During operation, ash or slag accumulates on the rotary grate 25 and especially on the rotary grate elements 252, 253 and 254. In the case of the present rotary grate, the rotary grate 25 can be effectively cleaned.

In FIG. 10 shows the rotary grate in a state of partial cleaning of the rotary grate 25 in the bed-burning mode. To do this, only the third element 254 of the rotary grate is rotated. Due to the fact that only one of the three rotary grate elements is rotated, the burning layer on the first and second rotary grate elements 252, 253 is preserved, while ash and slag can fall down from the combustion chamber 24 at the same time. As a result, external ignition is not required to resume operation (this saves up to 90% of ignition energy). Another result is reduced wear on the ignition device (eg ignition rod) and energy savings. In addition, ash removal can advantageously take place during the operation of the biomass heating plant 1.

In FIG. 10 also shows the state of maintaining the burning layer during the (often already sufficient) partial cleaning, thus, in contrast to the usual complete cleaning of a conventional grate, there should not be a prolonged ignition, which may require several tens of minutes.

In addition, potential slag formation or accumulation of slag on both outer edges of the third rotary grate element 254 when it is rotated is stopped, and due to the curved outer edge of the third rotary grate element 254, shearing occurs not only over a greater overall length than conventional rectangular elements according to state of the art, but also with an uneven distribution of movement relative to the outer edge (in the middle there is more movement than at the bottom or top edges). Due to this, the cutting function of the rotary grate 25 is noticeably enhanced.

In FIG. 11, the (two-sided) grate edges 257 of the second rotary grate element 253 can be seen. These grate edges 257 are designed such that the first rotary grate element 252 and the third rotary grate element 254 in its closed state lie on the upper side of the grate edges 257 and hence the rotary grate elements 252, 253 and 254 are provided without play. and thus provided with sealing. This prevents air jets and undesirable uneven primary air flows through the burning bed. Preferably, the combustion efficiency is thereby improved.

In FIG. 11 shows the rotary grate 25 in a state of complete cleaning, which is preferably carried out during plant downtime. At the same time, all three rotary grate elements 252, 253 and 254 rotate, with the first and second rotary grate elements 252, 253 preferably rotating in the opposite direction than the third rotary grate element 254. Due to this, on the one hand, the complete emptying of the rotary grate 25 is realized, and on the other hand, ash and slag are now destroyed on four indirect outer edges. In other words, the preferred 4-fold function is implemented. As explained above with respect to FIG. 9 regarding the geometry of the outer edges is also true for FIG. ten.

In general, the present rotary grate 25, in addition to normal operation (cf. Fig. 9), preferably implements two different types of cleaning (cf. Fig. 10 and 11), and partial cleaning makes cleaning possible during operation of the installation 1 .

In comparison, the rotary grate systems available on the market are not ergonomic and, due to the rectangular geometry, have undesirable dead corners in which the primary air cannot optimally pass through the fuel, whereby the formation of air jets can occur. Slag formation often occurs in these corners. These points provide the worst burning with the worst efficiency.

The real simple mechanical design of the 25 rotary grate makes it strong, reliable and durable. (Recirculating device)

In order to optimize the recirculation device 5 briefly mentioned above, again CFD simulations, additional reflections and practical tests were carried out. The flue gas recirculation for the biomass heating system described below was provided for.

During the calculations, a boiler with a power of 100 kW was simulated in the case of a rated load with a load range from 20 to 500 kW with different fuels (for example, wood chips with a water content of 30%). In addition, in the present case, for all surfaces in contact with the flue gas, a slight disturbance during use (so-called 1 mm thick fouling) was taken into account. The emissivity of such a pollution layer is set to 0.6.

The result of this optimization and related considerations is shown in FIG. 12-17. In FIG. 12-17 show different views of the recirculation device 5 as seen in FIG. 1-3.

In FIG. 12 shows a highlighted angled view of the recirculation device 5 with the combustion chamber bricks 29 which surround the primary combustion zone 26 . In FIG. 13 is an exposed translucent angled view of the recycling device of FIG. 12. In FIG. 14 shows a side view of the recycling device 5 according to FIG. 12 and 13. Arrow S in FIG. 12-14 corresponds to arrow S in FIG. 1 which shows the direction of the side view of the biomass heating plant 1.

The recycling device 5 will be described below with reference to FIG. 12, 13, 14 and 15.

The recirculation device 5 has a recirculation inlet 53 with an inlet recirculation channel 531 and a divider 532 inlet recirculation channel. A recirculation inlet 53 and an inlet recirculation channel 531 are provided downstream of the blower 15 (cf. FIG. 3) at the flue gas outlet of the biomass heating plant 1 after the heat exchanger 3 or after the (optional) filter device 4. The inlet recirculation channel divider 532 can branch flue gas to be recirculated or recirculated gas into a primary recirculation channel 56 and an optional secondary recirculation channel 57. If there is no secondary recirculation, then the inlet recirculation channel divider 532 is also not required.

The primary recirculation passage 56 terminates through an air valve 52, in this case for example a butterfly valve 52, in the primary mixing chamber 542. In addition, in the primary mixing chamber 542 it terminates through another air valve 52, in this case for rotary damper, the primary air channel 58, which in turn has a primary air inlet 581 for, for example, room or fresh air, respectively called primary air. The primary air channel 58 may have a primary air sensor 582 (for example, to detect the temperature and/or oxygen content of the primary air).

Via the primary air inlet 581 and the primary air duct 58 and the air valve 52, the still unmixed primary air, i.e. fresh air or ambient air, enters the primary mixing chamber 542, in which the ambient air is mixed with the recirculated air according to the setting of the air valve 52. flue gas from the primary recirculation channel 56. Downstream of the primary mixing chamber 542, a primary mixing channel 54 is provided, in which the mixture of primary (fresh) air and flue gas is further mixed. The primary mixing chamber 542 with the valves 52 and the primary mixing channel together form the primary mixing unit 5a.

The secondary recirculation passage 57 terminates through an air valve 52, in this case for example a butterfly valve 52, in a secondary mixing chamber 552. damper, ends the secondary air channel 59, which, in turn, has a secondary air inlet 591 for secondary fresh air. The secondary air channel 59 may have a secondary air sensor 592 (for example, to detect the temperature and/or oxygen content of the secondary air).

Through the secondary air inlet 591 and the secondary air duct 59 and the air valve 52, the secondary fresh air, i.e. ambient air, enters the second mixing chamber 552, in which the ambient air is mixed with the recirculated flue gas from the secondary recirculation duct according to the setting of the air valve 52 57. Downstream of the secondary mixing chamber 552, a secondary mixing duct 55 is provided in which the mixture of secondary fresh air and flue gas is further mixed. Secondary mixing chamber 552 with its valves 52 and secondary mixing channel 55 form a secondary mixing unit 5b.

The setting of the four air valves 52 is adjusted accordingly by the valve setting actuator 521, which may be an electric motor, for example. 12, for reasons of clarity, only one of the four valve actuators 521 is indicated.

The primary mixing channel 54 has a minimum length L1. The minimum length L1 is, for example, at least 700 mm from the beginning of the primary mixing channel 54 at the outlet of the primary mixing chamber 542 to the end of the primary mixing channel 54. It has been found that the length L1 of the primary mixing channel 54 must also be longer for good mixing and be preferably at least 800 mm, ideally 1200 mm. In addition, the length L1, preferably for structural and pneumatic reasons, should not exceed, for example, 2000 mm. The primary mixing channel 54 at its upstream end may have an inlet funnel that tapers towards the end of the primary mixing channel 54. As a result, the flow at the upstream start of the channel 54 gathers in the center into a bundle and is again better mixed, so how, due to temperature differences, jet formation can occur primarily on the upper side of the channel 54. This jet formation is preferably counteracted by the narrowing of the primary mixing channel 54 at its beginning.

The (optional) secondary mixing passage 55 has a minimum length L2. The minimum length L2 is, for example, at least 500 mm from the beginning of the secondary mixing channel 55 at the outlet of the secondary mixing chamber 552 to the end of the secondary mixing channel 55. It has been found that the length L2 of the secondary mixing channel 55 for good mixing must also be longer and be preferably at least 600 mm, ideally 1200 mm. In addition, the length L2, preferably for structural and pneumatic reasons, should not exceed, for example, 2000 mm. The secondary mixing channel 55 at its upstream start may also have an inlet funnel that tapers towards the downstream end of the secondary mixing channel 55.

Primary mixing channel 54 and (optional) secondary mixing channel 55 can be made with a rectangular cross-section with an appropriate internal width of 160 mm±30 mm (vertical) / 120 mm±30 mm (vertical) and an internal thickness (horizontal) of 50 mm±15 mm. Due to this design of the primary mixing channel 54 and the secondary mixing channel 55, respectively, in the form of a long, flat channel adjacent to the heat exchanger 3 and the combustion device, many advantageous effects are achieved. On the one hand, the mixture of flue gas and primary (fresh) air/secondary (fresh) air is preferably preheated before it enters the combustion zone. For example, a mixture that, after primary mixing chamber 542, has a temperature of +25 degrees Celsius at the downstream end of the primary mixing channel 54, in the case of rated load, has a temperature higher than 15 degrees Celsius. On the other hand, the cross section and the longitudinal extent are chosen such that mixing continues after the mixing chambers 542, 552, thereby improving the homogenization of the flow. In this case, the flow is provided with a sufficient path for further mixing of the turbulent flow already at the beginning of the path.

In other words, an elongated primary mixing channel 54 provides a path for further mixing after the primary mixing chamber 542, with the primary mixing chamber 542 purposefully provided to generate significant turbulence towards the start of the path leg. This can also be facilitated by the optional inlet funnel channels 54, 55.

Preferably, both lengths L1 and L2 can be matched within a certain tolerance (±10 mm).

Through the primary passage 541, the recirculated flue gas, which has previously been well mixed with the "fresh" primary air, is fed from below to the grate 25. Through its openings 256, the mixture of recirculated flue gas and primary fresh air (i.e., primary air for the combustion chamber 24) enters the primary combustion zone 26 of the combustion chamber 24. In this respect, the primary recirculation for recirculation of the flue gas-primary fresh air mixture is provided such that it enters the primary combustion zone 26 from below.

Through the (optional) secondary passage 551 and the adjacent annular channel 50 (cf. Fig. 13) around the bricks 29 of the combustion chamber, recirculated flue gas, which has previously been well mixed with "fresh" secondary air, i.e. secondary fresh air (or in the absence of secondary recirculation with primary (fresh) air) is supplied to the (also optional) nozzles 291 recirculation or secondary air. In this case, the secondary air nozzles 291, as described, are not oriented towards the center of the primary combustion zone 26, but are oriented acentrically in order to cause the upward flow from the primary combustion zone 26 to the secondary combustion zone 27 to swirl (i.e., an upward swirling flow with a vertical axis spins). In this regard, secondary recirculation can be provided to recirculate the flue gas-secondary fresh air mixture at least partially to the secondary combustion zone 27 .

In FIG. 13 and FIG. 14 respectively shows FIG. 12 flow paths of air, recirculated flue gas and flue gas-air mixture in the recirculation device 5 by means of (schematic) flow arrows S8-S16. Arrows S1-S16 show the hydrodynamic configuration, ie the flow paths of individual gases or moving masses in the biomass heating plant 1. At the same time, many of the available components or features are hydrodynamically connected, and this can happen indirectly (that is, through other components) or directly.

As is clear from FIG. 13 and FIG. 14, the flue gas that flows out after heat exchange from the heat exchanger 3 and from the optional filter device 4 enters through the recirculation inlet 5 into the recirculation inlet 531 of the recirculation device 5 (see arrow S8). After the (optional) splitting of the flue gas stream by the (optional) inlet recirculation channel divider 532, the primary recirculation flue gas flows through the primary recirculation channel 56 (see arrow S10), depending on the installation of one of the adjustable air valves 52 in the primary mixing chamber 541, in which the flue gas is mixed with primary fresh air, which flows through the primary air duct 58, depending on the installation of another of the adjustable air valves 52, also into the primary mixing chamber 541 (see arrow S12).

As a result, a mixed flow (see arrow S14) of flue gas and primary fresh air occurs in the primary mixing duct 54, in which both of these components are preferably mixed due to the turbulence and the length of the primary mixing duct 54. At the end of the primary mixing duct 54, a homogeneous mixture of flue gas and primary fresh air occurs, which flows through the primary passage 541 to the primary combustion zone 26 (see arrow S16). If there is a (hydrodynamically similar primary recirculation) secondary recirculation, then the flue gas, after separation in the inlet recirculation channel separator 532, flows through the secondary recirculation channel 57 through another adjustable air valve 52 into the secondary air chamber 552 (see arrow S9), in which the flue the gas is mixed with the secondary fresh air also flowing in through the secondary air duct 59 and another adjustable valve 52 into the secondary mixing chamber 552 (see arrow S11). This mixing of flue gas and secondary fresh air continues in the secondary mixing duct (see arrow S13), thus improving the mixing of both components. The resulting, preferably homogeneous mixture is transferred through the secondary passage 551 into the annular channel 50 around the bricks 29 of the combustion chamber and through the recirculation nozzles 291 into the combustion chamber (see arrow S15).

The schematic block diagram according to FIG. 15 shows previously explained with reference to FIG. 12-14 flow paths in the respective individual components of the recirculation device 5 as well as the flows of the biomass heating plant 1. In the block diagram of FIG. 15 shows both primary recycling and optional secondary recycling as a complete circuit. The recirculation device 5 may also have only primary recirculation.

By means of flue gas recirculation, it is, in principle, mixed with fresh air after combustion, in particular the oxygen content is increased, and fed to a new combustion. As a result, combustible residues in the flue gas, which would otherwise be discharged unused via the chimney, can now contribute to combustion.

The respective valves 52 with primary mixing chamber 541 and (extending, preferably approximately horizontally) primary mixing channel 54 form the primary mixing unit 5a. The respective valves 52 with the secondary mixing chamber 552 and the secondary mixing channel 55 may form a secondary mixing unit 5b. With respect to those hidden in FIG. 14 parts of the flow directions, it is recommended to refer to FIG. 3 and related explanations.

In addition, in FIG. 15 additionally takes into account the so-called false clearance (air sucked through leaks), which in this case is considered as an interfering factor. In this case, the false plume enters from the environment through leaks and, above all, through the fuel supply system into the combustion chamber 24, and it represents an additional source of air for combustion, which should be taken into account when establishing the ratio of the components of the mixture or mixtures. Therefore, the biomass heating system 1 is in this case preferably designed such that the false connection in the case of a rated load is less than 6%, preferably less than 4% of the air quantity of the mixture of primary fresh air and recirculated flue gas (and in the case of an existing secondary recirculation air quantity of a mixture of secondary fresh air and recirculated flue gas and a mixture of primary air and recirculated flue gas).

In addition, the flue could unfavorably flow back into the combustion chamber 24 from other flue gas flow paths after combustion, for example via a conventional ash removal system. The solution to this problem is provided by the adapter screw 73 described in detail below, whereby the flue gas recirculation 5 and thus the flue gas treatment can be improved.

(Primary mixing chamber and secondary mixing chamber with valves)

In FIG. 16 shows a cross-sectional view of the primary mixing chamber 542 as well as the two inlet side (primary) air valves 52 with their (primary) valve prechambers 525 at an oblique angle of view (cf. the appearance of FIG. 12 and FIG. 13).

The recirculated flue gas flows through the tubular primary recirculation duct 56 through the primary recirculation valve inlet 544 into an optionally provided, and in this case only by way of example, overhead (primary) valve prechamber 525, which is surrounded by a valve housing 524 of the upper (primary) air valve 52. Instead 525, the primary recirculation channel 56 can, for example, also be designed such that its cross-section continuously expands in the direction of the air valve 52, whereby its own prechamber could be eliminated.

Through the primary air passage 58, the primary fresh air flows through the primary air inlet 545 into an optionally provided, and in this case only by way of example, lower (primary) valve prechamber 525, which is surrounded by another valve housing 524 of the lower (primary) air valve 52.

Optionally, recirculated flue gas may also be supplied to the lower valve chamber 525, while primary fresh air may be supplied to the upper valve chamber.

The (primary) valve prechambers 525 of the (primary) air valves 52 are approximately in the shape of a frustocone or cylinder and expand the cross-sectional area in this case for the example of the upper flue gas flow valve 52 compared to the cross-sectional area of the primary recirculation channel 56. Thus, on the one hand, material and space can be saved since the primary recirculation passage 56 can be provided with a smaller cross-section, and on the other hand, a large effective valve surface can be provided to control (or regulate) the flow through the air valve 52. Such an enlarged valve surface has, above all, the advantage that it is less sensitive to contamination (among other things to the formation of soot) and, due to the larger cross section, has a lower pressure loss in the open state.

The air valves 52 in this case, for example, are butterfly valves 52.

The top and bottom (primary) air valves 52 may be identical.

Both air valves 52 in the form of butterfly valves 52 respectively include a valve setting actuator 521, for example, an electric motor that can rotate a valve setting shaft 522 mounted in bearings with the possibility of rotation, as well as a valve body 527 placed on the valve setting shaft 522 with a fastening element of the mounting axis and at least one valve flap 523. At least one valve flap 523 of the valve body 527 of the respective air valve 52 is provided downstream of the end of the valve chamber 525. primary mixing chamber 542, and a valve body 527 is provided on the opposite side of the valve setting actuator 521 of the primary mixing chamber 542.

At least one valve flap 523 is positioned so that it can be moved or rotated to at least two different positions to set the capacity of the air valve 52.

For example, in one of the first positions, at least a partial region of the valve passage 526 is hydrodynamically closed by means of a shut-off plane, which is provided by the valve flap 523, so that flue gas cannot flow through the partial region of at least one valve passage 526 into the primary mixing chamber. In the second of the positions, the closure plane at least partially vacates the partial region so that flue gas can flow through the partial region.

In the first position, the air valve 52 may preferably be fully closed, with the closing plane of the at least one valve flap 523 completely covering the passage surface of the respective at least one valve passage 526. In FIG. 16, this closed position of the valve is shown by way of the lower air valve 52, by way of example.

In addition, in the second position, the air valve 52 is preferably fully open, with the closing surface of the at least one valve flap 523 completely clearing the passage surface of the corresponding at least one valve passage 526. In FIG. 17, this open position of the valve is shown by way of an example of the upper air valve 52. In the fully open state, the air valve passage surface may, for example, be 5300 mm ² ±500 mm ² . Preferably, the air valve 52 can be freely set between a fully open state and a fully closed state.

In this case, respectively, one air valve 52 in the primary mixing chamber 542, for example, is provided with two valve flaps 523 with respectively two valve passages 526 (that is, the valve body forms a fan valve). However, only one or also several valve flaps and a corresponding number of valve openings 526 may also be provided.

In addition, in FIG. 16, valve surface 528 can be seen in which valve passages 526 are provided and which is formed by primary mixing chamber housing 546. Preferably, the valve flaps 523 at any position of the valve body 527 may lie on the valve surface 528 or against the valve surface 528. Preferably, the air valve 52 is configured such that the orifice area of the valve port 526 is larger than the cross-sectional area of the primary recirculation valve inlet 544 (and the primary air inlet 545) to optimize pressure loss by the valve.

Both valve blades 523 are provided to be mirror symmetrical (point symmetrical) with respect to the central axis of the mounting axis 522. Further, both valve blades 523 are crescent-shaped. Accordingly, both respective valve passages 526 can also be crescent-shaped. In this case, the crescent shape can, for example, be provided in such a way that it sharpens at the outer end of the crescent.

This crescent shape of the at least one valve blade 523 causes the flow that flows through the at least one valve port 526 to still flow unevenly in cross section, but without a large increase in pressure loss. This improves mixing in the primary mixing chamber 542.

In addition, the aforementioned design of the air valve 52 in the form of a butterfly valve is also significant in so-called low-load operation or also when the biomass heating plant 1 is switched on, i.e. when it is only operated at low temperatures. Due to the low temperatures, conventional flap valves will be especially contaminated with soot in the flue gas. As a result of this contamination, conventional valves are actuated with great difficulty, which unfavorably increases their load and hence wear. The present embodiment of the air valve 52 reduces this problem.

By means of the (example upper) air valve 52, in this case the example valve 52 with rotary damper, it is possible to set the amount of recirculated flue gas before it is mixed with (fresh) primary air. The other air valve 52 for primary fresh air accordingly makes it possible to regulate the supplied primary fresh air. In this way, the mixture ratio of the primary fresh air and the recirculated flue gas can advantageously be determined. In this way, the mixture ratio can be adapted to different operating points or optimal combustion operating points.

The top butterfly valve 52 may also be referred to as a primary flue gas return valve.

The bottom rotary damper valve 52 may also be referred to as a primary fresh air valve.

Instead of butterfly valves 52, other types of valves may be used, such as sliding flapper valves, linear flapper valves, or ball valves.

Positioned hydrodynamically downstream of both air valves 52, a primary mixing chamber 542 serves to bring the recirculated flue gas with the primary fresh air, which are provided for the primary combustion zone 26 of the combustion chamber 24. The primary mixing chamber 542 and both (primary) valves 52 are part of the primary mixing unit 5a and are used for controlled mixing of flue gas with primary fresh air.

The primary mixing chamber 542 is formed by the primary mixing chamber housing 546. The body 546 of the primary mixing chamber is provided approximately rectangular or box-shaped and has an outlet 543 of the primary mixing chamber. The outlet 543 of the primary mixing chamber is provided downstream of both valve ports 526. An outlet 543 of the primary mixing chamber is provided on the opposite side of both valve passages 526 to the side of the body 546 of the primary mixing chamber.

The primary mixing chamber housing 546 with its valve ports 526 and the primary mixing chamber outlet 543 may be configured such that they do not lie directly opposite each other through the volume of the chamber. In other words, the inlets 542 of the primary mixing chamber 542 and the outlet 543 from the primary mixing chamber 542 are provided such that the combined flue gas and primary fresh air streams can better mix as the streams are combined.

For example, at the primary mixing chamber 542 according to FIG. 16, the (total) flue gas flow is forcibly deflected downwards by means of the top air valve 52 immediately before the primary fresh air enters the primary mixing chamber 542. Due to this, the two flows are advantageously combined and can better mix up.

In addition, both the flue gas flow through the upper air valve 52 and the primary fresh air flow through the lower air valve 52 (which, for example, in Fig. 16 are directed to the left) hit the wall of the primary mixing chamber housing 546, due to which they even at low flow rates, they forcibly form air turbulences. This promotes uniform mixing of the flue gas with the primary fresh air.

In addition, the inlet flows of primary fresh air and flue gas in the primary mixing chamber 542 are crescent-shaped, which is an additional element that creates turbulence already at the entrance to the primary mixing chamber 542.

A good or homogeneous mixing of the recirculated flue gas with the primary fresh air is important, as this could otherwise lead to streaks (i.e. too long irregularities) in the combustion air, which would have a negative effect on the combustion process. For example, in the case of an inhomogeneous mixture of primary (fresh) air and recirculated flue gas, the emission of harmful substances from the biomass heating installation 1 increases.

As a result, the above configuration advantageously improves the mixing of the flue gas with the primary fresh air with a simple structure.

In FIG. 17 shows, with respect to secondary recirculation, a cross-sectional view of the secondary mixing chamber 552, as well as the two inlet side (secondary) air valves 52 with their (secondary) valve prechambers 525, at an oblique angle of view (cf. the external view, respectively, of Fig. 12 and Fig. . 13). The same or similar features according to FIG. 17 correspond structurally and functionally to the features of FIG. 16, wherefore, in order to avoid repetitions, it is recommended to refer to the above descriptions with respect to the substantially similar FIG. 16.

The recirculated flue gas flows through the tubular secondary recirculation duct 57 through the secondary recirculation valve inlet 554 into an optionally provided and in this case for example lower (secondary) valve prechamber 525, which is surrounded by a valve housing 524 of the upper (secondary) air valve 52. Through the secondary air passage 58 secondary fresh air (fresh air) flows through the secondary air valve inlet 555 into an optionally provided and in this case for example located at the top (secondary) valve prechamber 525, which is surrounded by another valve body 524 of the lower (secondary) air valve 52.

In this case, the position of the inlets of the recirculation channels 56, 57 into the valve prechambers 525 (and thus the position of the valve 52 provided for the flue gas) is such that the recirculation channels 56, 57 can be drawn in parallel over the longest possible distances. As a result, the recirculation channels 56, 57 can be jointly insulated and, preferably, heat losses through the sections of the recirculation channels 56, 57 can be reduced.

Optionally, recirculated flue gas may also be supplied to the upper (secondary) valve chamber 525, while secondary fresh air is supplied to the lower (secondary) valve chamber 525.

The secondary mixing chamber 552 has a secondary mixing chamber body 556 with a mixing chamber volume and a secondary mixing chamber outlet 553 similar to the primary mixing chamber 542.

Both air valves 52 of FIG. 17, as in the case of FIG. 16 are made in the form of butterfly valves. The upper and lower (secondary) air valves 52 may be identical. The bottom butterfly valve 52 may also be referred to as a secondary flue gas return valve. The bottom butterfly valve 52 of FIG. 17 is shown in the fully open state.

The top butterfly valve 52 may also be referred to as a secondary fresh air valve. The top butterfly valve 52 of FIG. 17 is shown in only a partially open state.

Both secondary rotary valves 52 are provided to be approximately identical with respect to both primary rotary valves 52 of FIG. 16. This applies primarily to the crescent shape of the valve flap 523.

The secondary mixing chamber 552 located after both air valves 52 serves to combine the recirculated flue gas with the primary fresh air which is provided for the primary combustion zone 26 of the combustion chamber 24. The primary mixing chamber 542 and both (primary) valves 52 are part of the primary mixing unit 5a and serve controlled mixing of flue gas with primary fresh air.

The secondary mixing chamber 552 is formed by the secondary mixing chamber housing 556. The secondary mixing chamber body 556 is provided as being approximately rectangular or box-shaped and has a secondary mixing chamber outlet 553 . The outlet 553 of the secondary mixing chamber is provided downstream of both valve ports 526. An outlet 553 of the primary mixing chamber is provided on the opposite side of both valve passages 526 to the side of the body 556 of the primary mixing chamber.

In addition, the secondary mixing chamber body 556 with its valve ports 526 and the secondary mixing chamber outlet 553 may be configured such that they do not lie directly opposite each other through the volume of the chamber. In other words, the inlets 526 of the secondary mixing chamber 552 and the outlet 553 from the secondary mixing chamber 552 are provided such that the combined flue gas and primary fresh air streams can better mix as the streams are combined.

In contrast to the primary mixing chamber 542 configuration of FIG. 16, secondary mixing chamber 552 has an optional configuration of secondary mixing chamber inlets 526 and outlet 553 from secondary mixing chamber 552. With outlet 553 located between both inlets 526 (or valve ports 526). As a result, the flow of secondary fresh air from the upper inlet 526 and the flow of flue gas and the lower inlet 526 are deflected so that they meet approximately in the center of the secondary mixing chamber 552, mix there with the formation of a swirl and exit as a common stream from the outlet 553 By repeatedly reversing the direction and combining the two flows in this way, as in the case of the primary mixing chamber 542, mixing of the secondary fresh air and the primary fresh air can advantageously take place.

Thus, the configuration effects of the secondary mixing chamber 552 of FIG. 17 are similar to the effects of the primary mixing chamber 542 of FIG. 16, which is recommended to refer to.

A good (homogeneous) mixing of the primary fresh air or secondary fresh air with the recirculated flue gas makes an important contribution to optimizing the combustion processes in the biomass heating plant 1. For example, primary fresh air and secondary fresh air typically have an oxygen content of about 21%, while the recirculated flue gas in normal load operation has, for example, only about 4 to 5% oxygen content. If non-homogeneous mixing were to occur during recirculation, then the fuel bed 28 would be supplied with oxygen from below and also the primary combustion zone 26 would be non-homogeneous. In the worst case, in the case of strong jet formation during recirculation, air would be supplied to a part of the combustion fuel with a very low oxygen content. The combustion process of this part would be noticeably worse.

However, by means of the primary mixing unit 5a and the (optional) secondary mixing unit 5b, homogeneous mixing of the primary fresh air or secondary fresh air with the recirculated flue gas is ensured. Other benefits of homogeneous mixing are the reduction of temperature peaks (which can cause fouling and slagging) as well as the reduction of flue gas velocity peaks (which increase material stress and plant erosion).

The implementation of the secondary air or recirculation nozzles 291 for secondary recirculation is here presented from the same point of view as above.

Nozzles 291 secondary air or recirculation are located so that the cross section of the combustion chamber 24 is turbulent mixing and homogenization of the flow. First of all, the secondary air or recirculation nozzles 291 are located and oriented so that they can lead to a swirling flow in the combustion chamber 24.

First of all, the implementation of the secondary air nozzles 291 as explained above leads to a minimization of the combustion volume as well as to a reduction in emissions.

If only primary recirculation is provided, then by means of both (primary) air valves 52 both the mass flow (kg/h) and the mixture ratio of recirculated flue gas and primary fresh air can advantageously be controlled so that at least approximately the optimum operating point of combustion in the biomass heating system 1 is reached.

If secondary recirculation and primary recirculation are to be provided, they can advantageously be controlled independently of each other. That is, the mass flow (kg/h) and the ratio of the primary recirculation mixture and the mass flow (kg/h) the ratio of the secondary recirculation mixture can be respectively adjusted independently of each other.

As a result, the combustion can advantageously be set flexibly and optimized at the operating point, also taking into account the known inflow of false clearance. In other words, the use of primarily two (primary recirculation only) or four (primary and secondary recirculation) independently adjustable air valves 52 results in a wider control range for the recirculation device 5 than is normally provided.

In the case of operation, the primary air flow range, or optionally also the secondary air flow range, can be fully automatically controlled by means of a control device. This achieves optimized performance optimization and combustion optimization, reduces slagging by not exceeding the ash melting temperature in the combustion chamber and ensures high efficiency, very low fine dust values with low NOx emissions, and this with different fuels and different fuel qualities, since, therefore, the recycling device 5 is particularly suitable for hybrid combustion with different fuels.

Therefore, the recirculation device 4 provides improved flue gas treatment.

(flue gas condenser)

In addition, a flue gas condenser can be provided in the biomass combustion plant 1. The flue gas condenser is a special kind of heat exchanger.

Depending on the composition of the fuel and the air supply, both their moisture content and the content of chemically bound hydrogen atoms in the fuel, different amounts of water vapor and other condensables are formed in the flue gas during combustion. If it is cooled in the flue gas condenser below the dew point, the water vapor and accompanying substances can condense and the released heat of condensation can be transferred to the heat transfer medium. Since the latent heat content of the flue gas is used as a result, fuel consumption and CO2 emissions can be reduced as a result.

During the most often incomplete combustion of biological materials (especially when heating with wood chips and pellets), when the flue gas is cooled, glossy soot, fly ash, fly dust, tree resin or tar and, in some cases, unburned carbohydrates are deposited. They heavily contaminate the surfaces of the heat exchanger and usually lead to deposits that interfere with the extraction of exhaust gases or draft in the chimney. Therefore, for example, fireplaces and tiled stoves without a flue gas condensation unit are operated at flue gas temperatures above 120° C., which is disadvantageous as it is energy inefficient. Pollutants and water vapor not separated by this (heat of condensation and residual energy content can be up to 70% of the calorific value) can be released into the environment in a negative way.

As a result, the flue gas condenser for biomass heating systems 1 with hybrid technology aims to provide an optimized flue gas condenser with high efficiency, which is nevertheless insensitive to fouling.

In FIG. 18 shows a three-dimensional overview of the biomass heating plant according to FIG. 1 with an additional outer lining 16 (eg insulation 16) and an additional flue gas condenser 49. The flue gas condenser 49 is installed next to the boiler 11 by means of a fastening device 499 and is connected via a flue gas or flue gas inlet 411 to the flue gas or flue gas outlet 41 of the boiler 11. The flue gas flows through the flue gas condenser 49 and flows out of it through the outlet pipe 412 flue gas. The flue gas condenser has a side surface 498 with a maintenance hole closed in this case.

In addition, an orifice flange 497 is provided to hold a spray pipe protruding into the flue gas condenser 49 (not shown). This spray pipe projecting horizontally from the flange has downward (spray) nozzles and is connected to the water supply line. By activating the water supply, the interior of the flue gas condenser 49 can be cleaned.

In addition, in the flue gas condenser 49 of FIG. 18, a first fluid duct 491 and a second fluid duct 492 for the heat exchange medium are provided on the head member 495 of the flue gas condenser 49. In this case, one of the pipes is an inlet pipe, and the other is an outlet pipe. Typically, the heat exchange medium circulates in a closed circuit, which makes the heat absorbed by the heat exchange medium useful.

A condensate outlet 496 is provided on the underside of the flue gas condenser 49, through which the condensate formed inside the flue gas condenser 49 can drain.

FIG. 19A shows the flue gas condenser 49 according to FIG. 18 in a side view from the direction of the arrow H of FIG. 18. In FIG. 19B shows the flue gas condenser 49 of FIG. 18 in a side view from the direction of the arrow V of FIG.

Arrow OS1 shows schematically the flow or flow of flue gas within the flue gas condenser 49 from top to bottom, ie from the flue gas inlet 411 to the flue gas outlet 412. In this case, the flue gas flow is essentially directed downwards and, after entering the condenser 49, the flue gas is distributed in its internal volume.

FIG. 20 shows an internal view of the flue gas condenser 49 of FIG. 19A and FIG. eighteen.

Inside the flue gas condenser 49, several heat exchanger tubes 493 are arranged across the main flow direction. The heat exchange medium flows through these U-tubes 493 of the heat exchanger and the flue gas flows around them. In this case, heat transfer takes place. First of all, condensation of the flue gas can occur on the heat exchanger tubes, with which the components of the flue gas (primarily water) are separated. Multiple heat exchanger tubes 493 may also be referred to as a heat exchanger tube bundle 493.

For condensate, a condensate collection funnel 4961 is provided at the bottom of the flue gas condenser 49, which catches the condensate and discharges it to the condensate outlet 496. From there, the condensate can be disposed of. In addition, the condensate collection funnel 4961 is configured to divert the flue gas flow at the bottom of the flue gas condenser 49 sideways or horizontally towards the flue gas outlet 412.

Due to the directed flow of flue gas in the direction of the condensate outlet 496, the discharge of the condensate is advantageously accelerated.

Several U-shaped tubes 493 of the heat exchanger are held on one side by a tube holder 4931. In addition, both ends of several U-shaped pipes 493 of the heat exchanger are fixed on the base element 4932 pipes, for example, welded. The base element 4932 pipes is a plate element with multiple holes for pipes 493 of the heat exchanger. The tube base member 4932 forms the inwardly facing portion of the head member 495. The head member 495 includes a chamber-like flow duct between the first fluid tube 491 and the second fluid tube 492 such that a plurality of heat exchanger U-tubes 493 are connected in series with each other. other groups. For example, a predetermined number of heat exchanger U-tubes 493 are hydraulically connected in parallel to form a heat exchanger U-tube group, and the groups in turn can be hydraulically connected in series with each other. This guiding channel may further be provided by a head element flow guide 4951 having dividing plates 4951 which subdivide the cavity in the head element 495 into separate hydraulic compartments. This is primarily seen from a joint examination of Fig. 20 and 23.

The pipes 493 of the heat exchanger are made grouped in one chimney. This single-flue design can be easily cleaned, since only one set of cleaning nozzles is required, and preferably provides for a homogeneous inflow and flow of the flue gas.

The heat exchange medium flows through one of the hydrodynamic pipes 491, 492 into the flue gas condenser 49 and then, due to the dividing plates, flows out through the head element 495 and the U-tubes 493 of the heat exchanger and again through another hydrodynamic pipe. In this case, the heat exchange medium flowing through the flue gas condenser 49 absorbs heat from the flue gas.

The flue gas condenser 49 with the heat exchanger tubes 493 form a smooth tube heat exchanger. In this case, the heat exchange medium is located in the pipes 49 of the heat exchanger 3, and the flue gas flows around the pipes 493 of the heat exchanger. The heat exchanger tubes 493 may, for example, consist of material 1.4462 or 1.4571. The stainless steel material 1.4462 (preferably X2CrNiMoN22-5-3) proved to be more stable and better than material 1.4462 (V4A) in this case. In detail, 1.4462 has a particularly high corrosion resistance (primarily against stress corrosion cracking and chemical corrosion) and very good mechanical properties (e.g. strength), suitable for use at temperatures from 100°C to 250°C, good weldability and polishability. The reduced nickel content, in contrast to conventional austenite, makes the use of steel 1.4462 also preferable from an economic point of view, since it, despite the best material properties, is not significantly expensive.

An important factor in optimizing the efficiency of the heat exchange process is the optimization of the surfaces and flow around the multiple U-tubes 493 of the heat exchanger. This will be explained in more detail with reference to FIGS. 21-26.

In FIG. 21 shows the flue gas condenser 49 from a top view looking into the flue gas inlet 411 of the flue gas condenser. It can be understood that a plurality of heat exchanger tubes 493 form a flue gas flow-crossing structure in which the heat exchanger tubes 493 are arranged vertically in line with each other. Due to this, the present flue gas condenser 49 has a cross flow with respect to the flow of the heat exchange medium (eg water) with respect to the flow direction of the flue gas (OS1). Intermediate spaces (slots) of constant width are provided between the heat exchanger tubes 493.

In FIG. 22 shows the flue gas condenser 49 of FIG. 18 from a horizontal sectional view from above. In this case, the heat exchanger pipes are located over the entire cross-sectional area of the flue gas condenser 49 so that the first (horizontal) intermediate spaces 4934 relative to each other between the heat exchanger pipes 493 and the second (horizontal) intermediate spaces 4935 between the heat exchanger pipes 493 and the outer walls of the flue gas condenser 49 have essentially constant width. Minor exceptions to this may occur at the pivot points 4933 formed by the loops of the tubes 493 of the heat exchanger, as variable and partly large intermediate spaces are inevitably present. Thus, the heat exchanger U-tube 493 has two straight separate tubes with a pivot point 4933 between them.

The first intermediate spaces 4934 form, when viewed in the view of FIG. 22, a sort of vertical and rectilinear "narrow passage" between heat exchanger tubes 493 through which flue gas can flow vertically. This reduces the pressure loss, while with the above-described smooth tube structure, efficient heat exchange can be achieved.

In addition, the intermediate spaces 4934 between the heat exchanger tubes 493 and the second intermediate spaces 493 5 between the heat exchanger tubes 493 and the outer walls of the flue gas condenser 49 may be provided such that the first intermediate spaces 4934 have a greater horizontal width than the second intermediate spaces 4935.

The arrangement of the intermediate spaces 4934, 4935 described above preferably results in a uniform distribution of the flue gas flow and thus a more homogeneous and more efficient heat exchange.

In FIG. 23 shows a three-dimensional view of several heat exchanger tubes 493 with a tube base member 4932 and a tube holder 4931. The tube holder 4931 may be made of sheet metal with punched holes for the U-tubes 493 of the heat exchanger. The tube holder 4931 serves to secure the heat exchanger tubes 493 and reduces the mechanical load on the ends of the heat exchanger tubes 493. The plate tube holder 4932 is connected to the heat exchanger tubes 493 so that the tube base member 4932 is provided with passage holes 4936 corresponding to the heat exchanger tubes 493 and the heat exchange medium can appropriately flow through the tube base member 4932.

The outer dimensions of the multiple heat exchanger tubes 493 (tube bundle) and the tube base member 4932 can be, for example, 42×⋅187×421 mm, resulting in a very compact structure.

The heat exchanger pipes 493 with their U-shape are arranged vertically, whereby two separate pipes (or pipe sections) are provided vertically one above the other for each U-shaped heat exchanger pipe 493.

In FIG. 24 shows a side view of several heat exchanger tubes 493 of FIG. 23. Preferably, there may be a second fluid port 492 for the inlet of the heat exchange medium, and there may be a first fluid port 491 for the outlet of the heat exchange medium. For this case, in Fig. 24, the arrows show the flow of the heat exchange medium out of the heat exchanger tubes 493 and into the heat exchanger tubes. The three arrows labeled OS1 show schematically the flue gas flow. The flow of the heat exchange medium moves alternately from left to right and vice versa, and at the same time meanders in the form of a meander from bottom to top against the direction of flow. In this regard, the present flue gas condenser 49 has a cross-countercurrent configuration. This configuration proved to be ideal for heat recovery. In addition, the flue gas condenser 49 can advantageously be easily cleaned.

In FIG. 25 is a plan view of a plurality of heat exchanger tubes 493 of FIG. 213 to illustrate the overall geometry of the multiple heat exchanger tubes 493 of FIG. 23.

The flue gas also enters between the heat exchanger tubes 493 from above, that is, from the view of FIG. 25 you can see the flue gas passages. These passages are elongated slots or narrow passages through which the flue gas is distributed and must pass in contact with the large surfaces of the pipes 493.

Here, the first intermediate spaces 4934 may have a (eg, horizontal) width SP2 (width of the flue gas slot or narrow passage in the first direction), which may preferably be 6.0 mm ± 2 mm. As a result, this width SP2 is noticeably smaller than usual, which improves efficiency.

The width SP2 can be, for example, equal to or smaller than the width SP1 (minimum distance).

The outer diameter of the heat exchanger tubes 493 may, for example, be 12.0 mm ± 1 mm. Thus, the pitching distance of the flue gas condenser 49 may, for example, be 12.0 mm+6 mm=18 mm±1.55 mm.

The dimensions of the overall structure and above all the widths SP2 are advantageously chosen so that in this case high heat transfer rates and hence high efficiencies (>107%) can be achieved with a small required volume. Preferably, the width SP2 in the form of a narrow gap can be provided for the entire number of tubes 493 of the heat exchanger to coincide.

Several heat exchanger tubes 493 in FIG. 23 have eleven (11) vertical tube bundles and nine (9) horizontal tube bundles, which has proved to be a good compromise between compact design, heat exchanger efficiency, flue gas pressure loss, heat exchange medium pressure loss, and mechanical complexity. . Thus, a total of 99 heat exchanger U-tubes 493 can be provided, for example.

Due to this, the horizontal tube bundles 493 of the heat exchanger are arranged in groups in the first direction (in this case, for example, in the horizontal direction) and parallel to each other. Such a group is shown in Fig. 25.

In addition, the groups of horizontal tube bundles are arranged parallel to each other in the second direction (in this case, for example, vertically above each other), as shown by way of example in FIG. 24. Preferably, the first and second directions may be orthogonal to each other.

After calculations and practical tests, it has proven to be advantageous that the following ranges of the number of tubes can lead vertically and horizontally to a heat exchanger optimized in the sense described above:

- 8 to 14, preferably 10 to 12, vertical U-tubes 493 of the heat exchanger, and

- 7 to 12, preferably 8 to 10, horizontal U-tubes 493 of the heat exchanger.

For individual pipes, the following quantity ranges can (for example) be provided:

- from 16 to 28, preferably from 20 to 24, vertical (separate) pipes,

and

7 to 12, preferably 8 to 10, horizontal (individual) pipes.

One U-tube 493 of the heat exchanger in this case comprises 2 separate pipes from the vertical view and 1 single pipe from the horizontal view.

In FIG. 26 shows a single (highlighted) exemplary heat exchanger tube 493 of FIG. 23 and its dimensions. However, the dimensions of the tube 493 of the heat exchanger may also differ from them. For example, also with other dimensions of the heat exchanger tube 493, the passage width SP2 can be maintained at 6 mm±2 mm.

Shown on the left side of Fig.26 the middle line represents the middle axis of the U-shaped pipe 493 of the heat exchanger. Preferably, all the middle lines of several U-shaped tubes 493 of the heat exchanger are parallel to each other.

Another advantage of the design is that multiple identical or identical heat exchanger U-tubes 493 can be mass-produced. The separately manufactured heat exchanger tubes 493 are then welded to the base member before or after they are inserted into the tube holder 4931.

The rather small narrow passage width SP2 is made possible primarily because the above-described biomass heating system 1, due to its efficiency and "clean" combustion, results in only very slight fouling of the heat exchanger tubes 493 . This can primarily be facilitated by an upstream electrostatic filter device 4. In addition, automatic cleaning can be provided in the flue gas condenser 49, for example by means of water-spraying nozzles. These water-spraying nozzles can be automatically activated by means of a control device, for example at regular intervals, in order to wash away or spray precipitation. The flush water can then be drained through the condensate outlet 496 from the flue gas condenser 49, whereby the condensate outlet 496 can perform a dual function. As a result, the flue gas condenser 49 can be actively decontaminated, whereby the width of the narrow passage can become small.

In this way, the flue gas condenser 49 can be combined with a hydrodynamically upstream electrostatic filter device 4. In this way, very low dust contents in the flue gas can be achieved and, in turn, an energy-efficient concept with a slot width of 6 ± 2 mm is advantageously 5±1 mm, between heat exchanger bundles in cross-counterflow design as tube bundle heat exchanger.

With the above configuration, it is also calculated that the pressure loss in the flue gas can be kept below 100 Pa (rather about 60 Pa), while a difference of 14 K between the temperature of the flue gas and the outlet fluid is calculated to be achievable. The heat exchange power with the above exemplary dimensions is approximately 19.1 kW. In this case, the present flue gas condenser 49 is, above all and in contrast to the prior art for biomass heating systems, designed and therefore also suitable for a wide power range from 20 to 500 kW.

However, the flue gas condenser 49 provides improved flue gas treatment.

A real flue gas condenser 49 with a small passage width SP2 returns all sensible and additionally, in particular, latent heat back from the flue gas. Due to this, the efficiency of the entire installation can be significantly increased - in the case of pellets as fuel (M7) up to 105% and in the case of wood chips as fuel (M30) up to more than 110% (respectively based on the energy input of the fuel (calorific value ).(Transition auger)

In the lower part of the biomass heating plant 1 according to FIG. 2 and 3 show an ash removal device 7 which has an ash discharge screw 71 (transport screw) with a transfer screw 73 in the ash removal channel, which is driven, i.e. rotated, by a motor 72.

The ash discharge screw 71 of the ash removal device 7 serves to effectively remove the combustion residues from the bottom of the boiler 11 into an ash container 74, which is shown in FIG. 18. In addition, the transition screw 73 of the ash discharge screw 71 serves to separate the individual flow areas of the boiler 11 (see arrows S1 and S5), so it separates the combustion chamber 24 from the reversing chamber 35. In this case, the flue gas after passing through the heat exchanger 3 must not fall uncontrollably to incineration.

An exemplary object is to provide an ash discharge screw 71 that provides efficient separation for the flue gas in the boiler and is durable and cheap.

In FIG. 27A shows, extracted from FIG. 2 and 3 are cross-sectional views of the ash discharge screw 71 with the transfer screw 73. FIG. 27B shows an angled 3D view of the ash discharge screw 71 of FIG. 27A. In FIG. 28 is an angled 3D view of the body 75 of the transfer screw 73. FIG. 29 shows a detailed view of the ash discharge screw 71 with the transfer screw 73 of FIG. 27A.

The auger 71 for unloading the ash through its axis 711 at its right end (or the rear end of the boiler 11) is rotatably driven by a motor 72 (not shown in FIGS. 27A, 27B, 28 and 29) and serves to convey to the left in the ash container 74 the residues of incineration, such as ash. This common transport device is shown in FIG. 27A, 27B and 29 by arrow AS.

In addition, the ash discharge screw 71 according to FIG. 27A, 27B, 28, and 29 has a transfer auger section 73. The transfer auger 73 designates a portion of the ash discharge auger 71 that is located in the transfer auger body 75.

In detail, the screw 71 for unloading ash has three sections:

1) the furnace section 714 or part 714 of the ash discharge screw 71 located in the furnace region (in Fig. 27A, 27B and 29 it is shown on the left),

2) the heat exchange section 713 or the portion 713 of the ash discharge screw 71 located in the heat exchange section (shown on the right in FIGS. 27A, 27B and 29), and

3) section of the transition screw 73 between these two sections or the transition screw 73 in the body 75 of the transition screw.

The direction of rise or the course of the turns of the heat exchange section 713 and the fuel section 714 are consistent with each other, that is, both sections are provided for dextrorotatory or levorotatory. Therefore, if (not shown in FIGS. 27A, 27B, 28 and 29) the motor 72 rotates the screw 71 to discharge the ash, the transport direction for the combustion residues in the heat exchange section 713 and the combustion section 714 are respectively the same. However, the transfer screw 73 is provided differently on its part. This will be explained in more detail later with reference to FIG. 28 and 29.

The ash discharge screw 71 according to FIG. 27A, 27B, 28 and 29, the left side of the transfer screw 73 has a larger diameter than the right side of the transfer screw. For this purpose, a screw shaft with a larger diameter, for example, can be provided or fitted on a common or integral or multi-part screw shaft 711 provided for all three sections of the ash discharge screw 71 . By means of differences in diameter, the discharge of incineration residues is optimized, since more incineration residues are obtained in the combustion chamber 24.

The body of the transfer screw 75 according to FIG. 27A, 27B, 28, and 29 has an opening 751 on its upper side. Further, the transfer auger body 75 has a restrictive plate 752, a main body cylindrical section 75, a fastening and separating element 754, and a funnel-shaped element 755.

The fastening and separating member 754 supports the main body section 753 and simultaneously separates both flow areas of the boiler 11 on the outer area of the body 75. Both areas in FIG. 29 are labeled "burner" and "heat exchanger" and the dashed line between them should represent the separation of both areas. Optionally, the fastening element and the separating element may be provided respectively separated from each other. Also, optionally, a separating element may be omitted, for example, when the main body section 753 is provided completely integrated into the dividing wall of the boiler 11. In any case, the main body section 753 is designed in the boiler 11 so that although it separates the two flow areas for flue gas and /or fresh air, however creates a connection in relation to the unloading of ash.

Cylindrical main section 753 of the body accommodates the transition screw 73. While the transition screw 73 can rotate freely in the main section 753 of the body. Accordingly, the inner diameter of the main body portion 753 is configured to match the (maximum) outer diameter of the transfer screw 73 with respect to the gap size. The dimension of the distance is designed such that it allows free rotation of the transfer screw 73, but at the same time, too much free space is prevented.

In addition, a centering washer 712 is provided on the screw shaft 711, which centers the shaft 711 in the main housing portion 753 and optionally also acts as a bearing. In addition, the centering washer 712 is a shutter for the internal volume of the main section 753 of the housing.

The funnel 755 is provided to surround the overlying opening 751. The funnel 755 narrows its horizontal cross-sectional area downwards towards the opening 751. In other words, the funnel 755 is provided to open upwards around the opening 751.

In addition, the screw 73 has two sub-sections, which respectively have an opposite direction of rise or flight. In other words, the transfer screw 73 has two sub-sections 731, 732, one of which has a left-hand rotation screw and the other a right-hand rotation screw.

In detail, the rise of the heat exchange section 713 of the ash discharge screw 71 in the transition to the transfer screw 73 in the lower right section 732 continues unchanged. In this case, subsection 732 is provided with a right-handed screw. In contrast, left subsection 731 is provided with a left hand screw.

In a more general sense, the transition screw has two subsections with screws 731, 732 with mutually opposite strokes. Due to this, the transition screw 73 has a built-in counter 731.

The above construction affects the following: The combustion residues are transported from the space below the heat exchanger 3 or from the rotary chamber 35 and possibly from the optional filter device 4 by rotating the screw of the heat exchange section 713 into the main 753 section of the housing formed by the housing 73. In FIG. 29 this is shown schematically by the arrow AS1.

These combustion residues AS1 and also the combustion residues falling into the funnel from the combustion chamber 24, which in FIG. 29 is shown schematically by arrow AS2, thus reaching approximately the middle of the transfer auger 73 and from there into the left subsection 731 of the transfer auger (see arrow AS3). However, due to the opposite strokes of the screw of the subsection 731, the combustion residues are again driven in the opposite direction, which is shown schematically by the arrow AS4.

Due to this, the combustion residues are brought together between both sub-sections 731, 732 of the transition screw 73. Thus, the sub-sections with screws 731, 732 are designed so that the combustion residues move along it towards each other when the axis 711 rotates.

In other words, the counter 731 of the transfer auger 73 brings together (and seals) the combustion residues within the body 75 of the transfer auger.

Due to the limited volume, the combustion residues are compacted under the opening 751 and form a movable in relation to the individual components (for example, with its ash particles), but no less sealing plug. Over time and increasing volume, combustion residues are forced or forced upward and outward towards opening 751. In this regard, a plug of mobile solids is formed in the transfer screw body 75, which seals against gases. However, this plug makes it possible to transport the material.

The restrictor plate 752 deflects these combustion residues to the side, as shown schematically by arrow AS5. These incineration residues squeezed out of the housing 75 then fall from the left side into the furnace section or into the furnace section of the ash auger 71 and are thus finally discharged from the boiler 11 (see arrow AS).

As a result, the flow areas "burner" and "heat exchanger" are separated from each other with respect to flue gas flows and fresh air flows, while communication is provided with respect to combustion residues and discharge of combustion residues can take place.

According to the state of the art, it is usually provided either that, at a negative additional cost, two separate ash discharge screws are provided in the boiler for separate flow regions, or that the ash of the ash discharge screw is guided through the transition piece and by means of a plain bearing through the sealing intermediate wall of the boiler. In this case, the plain bearing must be designed in such a way that it at least partially substantially seals. The sleeve bearing is negatively subjected to wear as it is exposed to foreign bodies in the fuel, slag, flames, water and high temperatures. Therefore, such a plain bearing causes significant costs in production, installation in the boiler and also in maintenance.

The construction described above completely avoids the use of such a plain bearing and, in addition, is simple (hence economical) and efficient.

In addition, flue gas treatment is improved, since incorrect air flows during flue gas recirculation are prevented, since good sealing against flue gas against possible backflow into the combustion chamber 24 is provided.

To ensure the initial filling of the intermediate screw housing 75, the initial commissioning of the biomass heating plant 1 at the plant can take place. In this case, a first combustion process takes place, in which a sufficient volume of combustion residues is generated for filling, and in this case it is still insignificant that the sealing function is not yet guaranteed.

(Flue gas recirculation of another embodiment)

In FIG. 30 shows a highlighted translucent angled view of a recirculation device of another embodiment.

In this other embodiment, the secondary air supply is not provided with recirculation, as in the embodiment according to FIG. 13, a simple controlled or adjustable supply of fresh air. In this regard, another embodiment can be manufactured more simply and economically, and yet still provide many of the above advantages of the embodiment of FIG. 13. First of all, also with this embodiment, as shown by practical tests, the set goals in terms of efficiency can be achieved.

Matching reference symbols in FIG. 30 disclose essentially the same ideas as shown in FIG. 13, therefore, in order to prevent repetition, only the differences between both embodiments are essentially described.

Butterfly valves of the embodiment of FIG. 13 in another embodiment according to FIG. 13 have been replaced with sliding flap valves. In addition, in another embodiment according to FIG. 30 there is no secondary mixing of the recirculated exhaust gas and fresh air, but only a controlled or controlled supply of fresh air to the recirculation nozzles 291 . Here, the secondary mixing passage 55 is retained as the secondary temperature control passage 5 5b, and the fresh air temperature control function is performed. In this case, a secondary temperature control channel 55b is provided along the wall of the boiler 11, whereby the fresh air that is supplied from the secondary air channel 59 is preheated (see arrow S13a) by the heat of the boiler 11 before the secondary air is introduced into the combustion chamber 24. Correspondingly, the channel 5 The secondary temperature control 5b is provided with a rectangular cross-section which has a greater (vertical) height than a (horizontal) thickness, whereby the secondary temperature control channel 55b "adheres" to the boiler wall and maintains a large heat exchange surface. The preheated secondary air increases the combustion efficiency. For details regarding the implementation of the channel 55b secondary temperature control, it is recommended to refer further to the description of the secondary mixing channel 55.

The arrow S15 shows that the secondary air flows through the secondary passage 551 into the annular channel 50 around the bricks 29 of the combustion chamber and through the recirculation nozzles 291 into the combustion chamber 24. As a result, not only is the secondary air preferably additionally heated, but also the bricks 29 of the combustion chamber are preferably cooled. chamber, which, for example, reduces the formation of slag on the bricks of the combustion chamber (cf. the above descriptions regarding the minimum temperature of slag formation).

Arrows S8 and S10 show only the flow of flue gas downstream of the heat exchanger 3 (or optional filter device 4) to the primary mixing unit 5a which in this embodiment is designed more simply and economically.

In FIG. 31 is a schematic block diagram which discloses the flow paths in the respective individual components of the biomass heating plant and the recirculation device of FIG. 30 according to another embodiment.

Like reference numerals disclose essentially the same ideas of FIG. 15, therefore, in order to prevent repetition, only the differences between both embodiments are essentially described.

There is no mixing of secondary air from fresh air and recirculated exhaust gas. In this regard, the secondary mixing chamber 552 and the valve 52 for the recirculated exhaust gas are not provided. The divider 532 of the input recirculation channel is also excluded. The secondary mixing passage 55, although it may be mechanically identical to the embodiment of FIG. 15, but is not functionally part of a channel for mixing fresh air and recirculated exhaust gas, but rather serves only (this is further the same as the embodiment according to Fig. 15) to pre-thermostat the fresh air before entering the combustion chamber 24.

In addition, in another embodiment, it is possible to completely dispense with the supply of secondary air, and the biomass heating system 1 can be provided only with primary recirculation.

(Other embodiments)

The invention, along with the elucidated embodiments and aspects, allows for other implementation principles. Thus, for example, individual features of different embodiments can be arbitrarily combined with each other, as long as it seems feasible to a person skilled in the art.

In this case, the recirculation device 5 with primary recirculation and secondary recirculation is described. However, the recirculation device 5 in its basic configuration may have only primary recirculation and no secondary recirculation. With this basic configuration of the recirculation device, respectively, components necessary for recirculation can be completely eliminated, for example, the inlet recirculation channel divider 532, the secondary recirculation channel 57 and the corresponding secondary mixing unit 5b, which will be explained later, as well as the recirculation nozzles 291 can be eliminated.

In turn, optionally, only one primary recirculation can be provided so that the secondary mixing unit 5b and the corresponding channels are eliminated, and the secondary recirculation mixture is supplied not only under the rotary grate 25, but it is also supplied (for example, through another channel) to those provided in this option nozzles 291 recirculation.

This option is mechanically simpler and therefore economical, however, despite this, it has recirculation nozzles 291 for the formation of flow swirl in the combustion chamber 24.

An air quantity sensor, a vacuum regulator membrane mechanism, a temperature sensor, an exhaust gas sensor and/or a lambda sensor may be provided at the inlet of the flue gas recirculation device 5.

In addition, instead of only three rotary grate elements 252, 253 and 254, two, four or more rotary grate elements may also be provided. In the case of, for example, five rotary grate elements, they can be arranged with the same symmetry and functionality as the present three rotary grate elements. In addition, the elements of the rotary grate can also be molded or made differently relative to each other. More rotary grate elements have the advantage that the breaking function is enhanced.

With regard to the given dimensions, it should be noted that, deviating from them, other dimensions or combinations of dimensions may be envisaged.

Instead of the convex sides of the elements 252 and 254 of the rotary grate, their concave sides can be provided, and the sides of the element 253 can be made additionally convex. Functionally, it's almost the same.

Fuels other than wood chips or pellets can be used as fuel for a biomass heating plant.

The biomass heating plant disclosed here can be heated exclusively with one type of fuel, for example only with pellets.

The combustion chamber bricks 29 can also be provided without recirculation nozzles 291 . This, above all, may be applicable in the case where secondary recycling is not provided.

The rotating flow or swirling flow in the combustion chamber 24 may be right-handed or left-handed.

The overlap 204 of the combustion chamber can also be provided in sections, for example, stepped, inclined.

Secondary (re)circulation can also be carried out only with secondary air or fresh air flows, and in this respect no flue gas can be recirculated, but only fresh air supplied.

Nozzles 291 secondary air is not limited to purely cylindrical holes in the bricks 219 of the combustion chamber. They can also be made in the form of holes having the shape of a truncated cone or made with a narrowing in the middle part.

Dimensions and dimensions given are to be understood as exemplary only and may vary.

In this case, the recirculation device 5 in the embodiment according to FIG. 12 is described with primary recirculation and secondary recirculation. However, the recirculation device 5 in its basic configuration may have only primary recirculation and no secondary recirculation. In this basic configuration of the recirculation device, the components required for recirculation can be completely eliminated, for example, the recirculation inlet divider 532, the recirculation channel 57 and the corresponding secondary recirculation unit 5b, which is described, as well as the recirculation nozzles 291, can be eliminated.

In turn, only the primary recirculation can optionally be provided so that the secondary mixing unit 5b and the corresponding channels are eliminated, and the primary recirculation mixture is supplied not only under the rotary grate 25, but it is also supplied (for example, through another channel) to the provided in this embodiment, the recirculation nozzles 291. This variant is mechanically simpler and therefore more economical, and yet has recirculation nozzles 291 to form a swirling flow or swirling flow in the combustion chamber 24.

An air quantity sensor, a vacuum regulator membrane mechanism, a temperature sensor, an exhaust gas sensor and/or a lambda sensor may be provided at the inlet of the flue gas recirculation device 5.

In the case of the transfer auger 73, a counter-flow can also be provided on the other side of the auger 71 for unloading ash (mirror-symmetrical).

The embodiments disclosed herein are provided for the purpose of describing and understanding the disclosed technical aspects only and should not limit the scope of the present disclosure. Therefore, it should be understood that the scope of the present disclosure includes every variation or other miscellaneous embodiments that are based on the technical idea of the present disclosure.

LIST OF REFERENCES

1 biomass heating plant

11 boiler

12 boiler base

13 boiler body

14 water recycling device

15 blower

16 outer lining

2 combustion device

21 first maintenance hole for the burner

22 swivel holder

23 turning mechanism

24 heating chamber

25 rotary grate

26 primary combustion zone of the combustion chamber

27 secondary combustion zone or radiation part

28 fuel layer

29 bricks of the combustion chamber

A1 first horizontal section line

A2 first vertical section line

201 ignition device

202 bevel of the combustion chamber

203 combustion chamber nozzle

204 overlap of the combustion chamber

211 insulating material, e.g. vermiculite

231 swing drive or motor(s)

251 rotary grate base plate

252 first element of the rotary grate

253 second element of the rotary grate

254 third element of the rotary grate

255 adapter

256 holes

257 grate edges

258 burning surface

260 supporting surfaces of bricks of the combustion chamber

261 groove

262 ledge

263 ring

264 fixing bricks

265 bevel of fixing bricks

291 secondary air or secondary air nozzles

3 heat exchanger

31 holes for heat exchanger maintenance

32 boiler pipes

33 boiler pipe inlet

34 PTZ camera input

35 PTZ camera

36 spring swirler

37 band or spiral swirler

38 heat exchange medium

331 insulation at the inlet of boiler pipes

4 filter device

41 exhaust outlets

42 electrode power line

43 electrode holder

44 filter input

45 electrode

46 electrode insulation

47 filter output

48 cage

49 flue gas condenser

411 flue gas supply line to flue gas condenser

412 flue gas outlet from flue gas condenser 481 cage holder

491 first hydrodynamic nozzle

492 second hydrodynamic nozzle

493 heat exchange tube

4931 pipe holder element

4932 pipe base element

4933 hinges/pivots

4934 first intermediate space between heat exchange tubes

4935 second intermediate space from heat exchange tubes to outer wall of flue gas condenser

4936 through holes

495 head element

4951 head element flow guide

496 condensate outlet

4961 condensate collection funnel

497 flange

498 side face with maintenance hole

499 Fixing device for flue gas condenser

5 recycling device

50 annular channel around the bricks of the combustion chamber

52 air valve

52s slide valve

53 recirculation input

54 primary mixing channel

55 secondary mixing channel

55b secondary thermostat channel

56 primary recirculation channel

57 secondary recirculation channel

58 primary air channel

59 secondary air channel

5a primary mixing unit

5b secondary mixing block

521 valve setting actuator

522 valve stem

523 flap valve

524 valve body

525 valve prechamber

526 valve bore

527 valve body

528 valve face

531 inlet recirculation channel

532 input recirculation channel divider

541 primary pass

542 primary mixing chamber

543 primary mixing chamber outlet

544 primary flue gas recirculation valve input

545 primary air valve inlet

546 primary mixing chamber housing

551 secondary pass

552 secondary mixing chamber

553 primary mixing chamber outlet

554 secondary flue gas recirculation valve input

555 secondary air valve inlet

556 secondary mixing chamber housing

581 primary air inlet

582 primary air sensor 591 secondary air inlet

592 secondary air sensor

6 fuel supply

61 paddles

62 fuel supply axis

63 transmission mechanism

64 fuel supply channel

65 fuel supply holes

66 drive motor

67 propeller propeller

7 ash removal device

71 ash unloading augers

711 auger axle

712 centering washer

713 heat exchanger screw

714 furnace area

72 ash removal motor with mechanism

73 transition auger

731 right subsection - left hand auger

732 left sub-section - right-handed screw

74 ash container

75 auger body

751 housing hole

752 limit plate

753 main section of the building

754 fixing and separating element

755 funnel element

81 bearing axle

82 rotary axis of the tongue of the fuel level

83 fuel level tab

831 main surface

832 central axle

833 parallel to surface

834 holes

84 support groove

85 sensor flange

86 mechanism for measuring the height of the burning layer

9 cleaning device

91 cleaning drive

92 cleaning shafts

93 shaft holder

94 ledge

95 swirler holders

951 bearing elements

952 vertical lugs

953 flue gas openings

954 notches

955 rotation bearing rods

96 double-arm percussion lever

97 impact head

E fuel injection direction

S* flow arrows.

Claims (24)

1. Heating plant (1) on biomass for burning fuel in the form of pellets and/or wood chips, having boiler (11) with combustion device (2), heat exchanger (3) with inlet (33) and outlet, moreover, the combustion device (2) has a combustion chamber (24) with a primary combustion zone (26) and a secondary combustion zone (27) provided downstream of it, wherein the secondary combustion zone (27) of the combustion chamber (24) is hydrodynamically connected to the inlet (33) of the heat exchanger (3), moreover, the primary combustion zone (26) is limited from the side by means of several bricks (29) of the combustion chamber, and The biomass heating system (1) also has the following: a recirculating device (5) for recirculating the flue gas formed during the combustion of fuel in the combustion device (2), characterized in that the recirculating device (5) has the following: inlet (53) recirculation, which is provided downstream relative to the outlet of the heat exchanger (3) and hydrodynamically connected to it, and primary air channel (58) for primary air supply, a primary mixing unit (5a) with a primary mixing chamber (542) and a primary mixing channel (54), wherein the primary mixing chamber (542) is provided downstream of the recirculation inlet (53) and the primary air channel (58) and is hydrodynamically connected to them , and at least two air valves (52) which are provided on the inlet side of the primary mixing chamber (542), and a primary passage (541) to the primary combustion zone (26), which is provided downstream of the primary mixing channel (54) and is hydrodynamically connected to it, moreover, the primary mixing unit (5a) is designed so that it can mix the flue gas from the recirculation inlet (53) with primary air from the primary air channel (58) through at least two air valves (52) of the primary mixing chamber (542). 2. Heating plant (1) on biomass according to claim 1, wherein the primary mixing channel (54) is directly connected to the outlet (543) of the primary mixing chamber (542) and the primary mixing channel (54) is provided downstream of the primary mixing chamber ( 542). 3. A biomass heating plant (1) according to one of the preceding claims, wherein the primary mixing channel (54) extends in a straight line and has a minimum length of 700 mm from beginning to end. 4. Heating plant (1) on biomass according to one of the preceding claims, wherein the air valves (52) of the primary mixing chamber (542) are valves (52) with a rotary damper, which respectively have a valve body (547) with at least one sickle-shaped valve flap (523) and at least one corresponding crescent valve passage (526) into the primary mixing chamber (542). 5. Heating plant (1) on biomass according to one of the preceding claims, wherein the primary mixing chamber (542) on the outlet side has an outlet (543) of the primary mixing chamber, the primary mixing chamber (542) on the inlet side has at least two valve passages (526) and the primary mixing chamber (542) is designed so that at least two through holes (526) of the valve and the outlet (543) of the primary mixing chamber are not located opposite each other through the primary mixing chamber (542), so that entering through at least two through passages openings (526) of the valve into the primary mixing chamber (542), the flows change direction or are deflected. 6. Heating plant (1) on biomass according to one of paragraphs. 1-5, and the recirculating device (5), in addition, has the following: a secondary air channel (59) for supplying secondary air, a secondary mixing unit (5b) with a secondary mixing chamber (552) and a secondary mixing channel (55), moreover the secondary mixing chamber (552) is provided downstream of the recirculation inlet (53) and the secondary air channel (59) and is hydrodynamically connected to them, and at least two air valves (52) which are provided on the secondary mixing chamber (552) on the inlet side, and nozzles (291) of the secondary air, which are provided in the bricks (29) of the combustion chamber and are directed sideways to the primary combustion zone (26) and which are provided downstream of the secondary mixing channel (55) and are hydrodynamically connected to it, moreover, the secondary mixing unit (5b) is designed so that it can mix the flue gas from the recirculation inlet (53) with the secondary air from the secondary air channel (59) through at least two air valves (52) of the secondary mixing chamber (552).

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