EP4058727A1

EP4058727A1 - Method and device for controlling the combustion in furnace systems

Info

Publication number: EP4058727A1
Application number: EP20804255.6A
Authority: EP
Inventors: Mohammadshayesh Aleysa
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2019-11-13
Filing date: 2020-11-10
Publication date: 2022-09-21
Also published as: CA3158466A1; KR20220092978A; US20220404017A1; DE102019217537A1; WO2021094291A1

Abstract

The application relates to a method for controlling the combustion in furnace systems, wherein an oxygen coefficient is determined from the temperature in a combustion chamber area and/or in the waste-gas flues of the furnace system and also on the basis of an energy balance of the combustion process in the single-chamber furnace system, the combustion air and the waste gas, and said oxygen coefficient is used to control the primary and secondary combustion material flows and therefore the thermal output and also the combustion quality. The invention also relates to a device for feeding combustion air in the furnace chamber of a furnace system, which device has a chamber (1), which on a first side has a main duct (2) for feeding ambient air and/or air from the chimney system and on a second side has a pane-washing air duct (3) and a secondary-air duct (4), both the pane-washing air duct (3) and the secondary-air duct (4) being provided with a motor-controlled valve (5) so that the pane-washing air duct (3) and the secondary-air duct (4) are closable independently of one another, the valves (5) being connected to a stepless motor (6, 7) so that the valves (5) can be moved steplessly.

Description

Method and device for controlling combustion in

Combustion systems

The invention relates to a method and a device, which can be used in particular in this method, for regulating the combustion of fuels, such as solid fuels, in combustion systems, for example in individual combustion systems, such as hand-loaded individual combustion systems

Various measures are known to improve the combustion and emission behavior in single room combustion systems. In order to improve the combustion and emission behavior in single-room combustion systems, combustion, design and control measures as well as integrated technologies based on catalytic and thermal effects can be used.

The combustion principle in single-room firing systems plays a major role in the combustion and emissions behavior. The optimization of the combustion and emission behavior can be achieved through automatic loading in which the fuel throughput and the appropriate amount of combustion air can be set precisely and precisely. Automatic loading of logs is technically possible, but cannot be implemented due to the general, usage and operating conditions of the individual room firing systems. Manual loading through a lock system without opening the combustion chamber door and thus suddenly cooling the combustion chamber is technically possible and can also be used in single-room firing systems. The lock system not only keeps the combustion chamber warm, but also stabilizes the pressure conditions there in such a way that no flue gas or pollution can occur in the installation room regardless of the pressure and flow conditions in the combustion system. In addition, the sluice system enables uniform loading (support regime) to be implemented, which results in a significant reduction in emissions.

The combustion process (drying, degassing, gasification, combustion of the fuel gas) takes place differently depending on the type of combustion air supply into the furnace and its flow direction and shape to the fuel. A combustion process can be described as favorable if it produces a fuel gas with favorable combustion properties and sufficient heat for the oxidation. Both high-energy (strong) and low-energy (weak) fuel gases lead to unfavorable combustion with numerous pollutants. For example, the supply of combustion air into the lower area of the bed of embers leads to uncontrolled gasification, which requires a regulated, precise supply of the secondary air. Without an appropriately regulated secondary air supply, incomplete combustion occurs. A better design of the combustion process also includes the grading of the combustion air, so that not only controlled gasification, but also a rapid cooling of the active reaction zone can be avoided.

The constructive and fluidic measures are measures with which favorable flow conditions with optimal oxidation conditions in the active reaction zone can be ensured over a longer period of time during the burn-up. The shape, volume and geometry of the combustion chamber and the afterburning chamber with the downstream exhaust flues play a major role in the oxidation process. In addition, correct positioning and distribution of the primary and secondary air openings makes a massive contribution to stabilization and consequently to improving the combustion quality. An optimal construction can be calculated and determined with a flow simulation.

The combustion can also be controlled by technical control measures.

The regulation of the combustion process in single-room firing systems takes place exclusively by regulating the combustion air, whereby a controlled thermal conversion of the fuel with proper combustion must be guaranteed. The regulation is intended to prevent the combustion process from falling into either a lack of oxygen or an excess of oxygen. In addition, the release of heat should take place in a more controlled manner, so that a high degree of heat utilization efficiency can be achieved with a high level of thermal comfort.

So-called integrated technologies are also known. These are usually installed in the combustion system before the heat exchanger or the heat dissipation. Their main task is to support the oxidation process. In the case of integrated technologies, a distinction must be made between thermal and catalytic processes:

With the catalytic oxidation process, the exhaust gas is fed into the catalytically coated structure (granulate fill, foam structure made of oxide and non-oxide ceramics, honeycomb, wire mesh or wire mesh). The flammable pollutants contained in the exhaust gas such. B. carbon monoxide (CO) and hydrocarbons (C _n H _m , VOCs, PAHs) come into contact with the catalytically active surface of the catalyst. In the presence of oxygen, the oxidation reactions through the catalyst can take place at a temperature greater than 300 ° C. These pollutants are converted into substances such as water and carbon dioxide through oxidation and are thus toxicologically reduced. The catalyst is not used up in the course of the oxidation. It only ensures that the reactions take place at a lower temperature level (already at 300 ° C instead of 500 ° C).

When used in biomass furnaces, catalytic oxidation processes have the disadvantage that catalytic poisoning occurs during the combustion of unfavorable fuels due to high exposure to undesirable pollutants (such as halogens, sulfur, polymers, tar, soot and other aerosols). As a result, the catalytic effect is steadily reduced and completely eliminated over time. In addition, the catalytic coating (also the washcoat) is exposed to high thermal and mechanical (erosion by the dust or high exhaust gas velocities) stress as well as strong temperature changes (from approx. 250 ° C to approx. 900 ° C) during operation or after several Operating hours damaged. It is essential that part of the catalytic coating and heavy metals such as platinum, rhodium and Palladium is removed over time and can get into the environment via the exhaust gas and cause health and environmental problems [according to Beebe et al. Heterogeneous Catalysis I, Heidelberg 1943, Janbozorgi et al. Handbook of Combustion,

Vol. 1, Weinheim, 2010].

The built-in technology (for thermal oxidation processes) is a technology that was developed by the Fraunhofer Institute for Building Physics IBP as part of a project funded by FNR. The operating principle of the built-in technology is based on the provision of favorable oxidation conditions during combustion within a defined built-in module. This module stores enough energy in the form of heat during combustion and automatically makes it available for thermal oxidation if the temperatures during combustion drop below certain limits (exhaust gas temperature <module temperature). Due to its special architecture, the built-in module ensures an intensive mixing of the combustible exhaust gas components with the combustion air as well as an extension of the active dwell time through multiple deflections or swirling of the exhaust gases. The stored energy (heat) is intended to prevent the oxidation of unburned components in the exhaust gas in unfavorable operating phases such as B. enable when placing wood and lead to a stable combustion process regardless of the dynamics of the combustion process. The built-in technology has a number of technical and conceptual advantages compared to the technologies currently used to reduce pollutants in small combustion systems, which can ensure that it can be implemented in practice. These advantages include, above all, the guarantee of safe operation without the need for intensive maintenance (once every two years), longevity (at least 5 years), low specific costs (less than 1.5 € per kilowatt system output), high technical integration capability and technical flexibility in terms of construction and operation and no need for operating energy. The built-in technology has shown a particularly stable function both in the area of single room firing systems and in the area of biomass boilers. Detailed results on this technique can be found in: in Aleysa, M .; Weclas, M .; Leistner, Ph .: Correlation of the filter-reactor architecture with thermophysical functional conditions for the research and development of a non-catalytic 3D-porous filter-reactor system for biomass-operated small combustion systems, final report of a project funded by the German Federal Foundation (DBU), AZ 30550, Stuttgart 2015, 59 pp;

Aleysa, M .; Leistner, Ph .: Improvement of the combustion and emission behavior in biomass-powered single room combustion systems through the use of special fittings, final report of a project funded by the Agency for Renewable Raw Materials (FNR), FKZ: 13NR104, Stuttgart 2016, 162 S;

Aleysa, M., Leistner, Ph .: Low-Emission-Combustion System (LEVS) for the combustion of solid fuels in gasification boilers, final report on a research project funded by the Federal Ministry for Economic Affairs and Energy,

FKZ: 03KB093A, Stuttgart 2017, 168 S; and Aleysa, M .: Conceptual, constructive and control measures for reducing pollutants and increasing the efficiency of log firing in practice, lecture in the 7th specialist colloquium Measures and technologies for reducing fine dust from biomass firing, Stuttgart,

18th May 2017.

Combustion control of hand-fed single room firing systems is a topical issue that requires research. The control of the combustion process in such firing systems is due to the primitive construction and the non-automatable fuel loading very difficult and requires the development of new control philosophies.

The initial situation for the use of controllers in single-room firing systems is presented here from a normative, technical and sales perspective, which are of great importance for the successful development and implementation of controllers in practice.

So far there are no normative regulations for the testing of hand-loaded single-room firing systems with controllers according to DIN EN 13240, DIN EN 13229, DIN EN 15250 etc. For the development of the regulation, the parent method or the EC Machinery Directive 2006/42 / EC should first be used. The approval of single room firing systems with controllers can be done in test laboratories such as B. the test laboratory for fireplaces and exhaust systems of the Fraunhofer Institute for Building Physics IBP, which have a flexible accreditation in the field of fireplaces. As part of the flexible accreditation (Category II), the test laboratories are entitled to develop new test methods and offer them to the manufacturers without any further coordination with the German Accreditation Service (DAkkS). It should be mentioned that the basis for the normative regulation of the use of controllers in single-room heating systems is being worked on and should be taken into account in the new series of the DIN EN 16510 standard.

From a technical point of view, it is possible to implement the regulation in individual room heating systems. The safety-related application and framework conditions have yet to be determined. In order to achieve a high feasibility in practice, concepts for the uniform combustion air supply should be developed, which can be used regardless of the construction and design of the individual room heating systems. Individual developments of controllers are not economical and cannot be financed by many medium-sized and small companies.

The integration of controllers in hand-loaded single-room firing systems leads to a corresponding increase in acquisition costs and requires a new concept for the warranty guarantees. With a large number of individual room firing systems, controllers that are prone to defects lead to unfavorable economic consequences. The use of sensitive sensors such as B. Lambda probes should therefore be avoided.

An important point with the regulators is the need for the power supply. The dependency of the hand-fed single room firing systems on the electricity has so far not been desired by either the manufacturers or the users. For marketing reasons, such fireplaces should therefore be independent of electricity or supply themselves with the necessary electricity. According to the state of the art, there are two technical possibilities. With the first option, the electricity (up to 250 watts) is generated by the thermal (thermoelectrics), with the second option using solar panels. A storage unit is required for both options. When using lambda probes or similar sensors with a high power consumption, the use of domestic electricity is unavoidable.

Proceeding from the prior art, the invention is therefore based on the object of a method for regulating the combustion in a single-room combustion system and a device for this purpose to provide that does not have the disadvantage of the prior art and with which, in particular, a safe and sustainable reduction in pollutant emissions, heat production suitable for mining and an increase in efficiency can be achieved.

The object is achieved according to the invention by a method according to claim 1 and a device according to claim 10. Advantageous further developments of the invention can be found in the subclaims.

According to the invention, a method for regulating the combustion in combustion systems, for example individual combustion systems, such as hand-loaded individual combustion systems, is proposed, which is characterized by the fact that the temperature in a combustion chamber area and / or in the exhaust flues of the combustion system and possibly in the exhaust gas as well as an energy balance of the During the combustion process in the combustion system, the combustion air and the exhaust gas, an oxygen coefficient is determined with which the primary and secondary combustion air flows and thus the thermal output as well as the combustion quality are regulated. This regulation can be done quickly.

In this context, an oxygen coefficient is to be defined as a value which gives direct conclusions about the oxygen content in the active oxidation zone or the oxygen requirement for proper combustion.

For the measurement of the temperature, the earlier and the further away from the radiation area the temperature is measured, the more precise and reproducible the calculation of the oxygen value is. The optimal range for measuring the temperature for the control is the first flue gas draft after the flue gas baffle plate in the combustion chamber. This will reduce the influence of the Ember bed heat radiation on the temperature measurement is reduced and the temperature sensors are protected from thermal stress, especially when using unfavorable fuels.

The control concept is technically structured in such a way that it can serve as a manufacturer-independent standard application or as a universal standard solution. It can therefore not only be used for new, but also for existing old single-room heating systems with a reasonable amount of effort.

The control principle and function of the method according to the invention can be illustrated as follows: For a successful development of a universally applicable control, the combustion process has a standardized combustion air supply (primary (SSL-PL + RL_PL) +)

Secondary air SL).

In particular, the method according to the invention achieves a safe, sustainable reduction in pollutant emissions as well as an increase in the efficiency of the thermal conversion of the fuel and an improvement in the degree of utilization through needs-based heat production through the permanent detection of the ambient temperature: By regulating the combustion process, low-pollutant and efficient combustion is achieved guaranteed by a more precise supply of the combustion air. Furthermore, by demonstrating and monitoring the operation for the operators, optimal operation of the combustion system can be digitally explained in an intuitive, simple manner and the quality of the combustion can be recognized and assessed. The optimal operation of the combustion system results from the evaluation of the combustion quality thanks to the intelligence of the control. It is possible to collect statistical data and evaluate the functionality of the fireplace in practice. The method according to the invention is based on an energy balance method. This compares the energies of the components before and after combustion. A detailed description is given below. In contrast to the controllers according to the state of the art (see above), robust temperature sensors can be used in the combustion chamber area and, if necessary, in the exhaust system, with which an oxygen signal and thus an oxygen coefficient can be generated with the help of parameterizable algorithms via an energy balance in the combustion chamber can be used for fast / immediate control of the combustion process. For the method according to the invention, it is favorable for the temperatures in the combustion chamber area and / or in the first exhaust gas flue of the first exhaust gas baffle plate to be recorded at at least one point for the energy balance and in the installation room for needs-based heat production for the purpose of increasing utilization efficiency and used for the control.

In addition, the signals generated by the temperature sensor can be used to generate a virtual signal (so-called emission reference value: ERW signal) using other intelligent algorithms, which is used to evaluate the operation. The integral and differential development of the ERW value over time describes a process behavior with which conclusions can be drawn about the combustion quality and the causes in the negative and positive case.

In one embodiment, the temperature in the furnace can be measured at at least one, for example two different points. In a further embodiment, the temperature in the combustion chamber can be at two points and possibly also at the Temperature in the exhaust gas can be measured. The temperature sensors mentioned above can be used for these measurements. In this way it is possible to determine the temperatures in a particularly reliable manner.

In one embodiment, the combustion is controlled via the supply of primary air (which may include or consist of primary air from the grate air and primary air from the windshield rinsing air (PL = RL-PL + SSL-PL)) and / or via the supply of secondary air.

The regulation of the primary air, such as grate air and / or windshield scavenging air, can take place in relation to the desired combustion output or the setting of favorable temperatures in the combustion chamber area for efficient and low-emission combustion. The amount of primary air supplied to the combustion process determines the intensity of the thermal conversion of the fuel and thus the thermal output of the combustion system. When setting the primary air, the heat demand of the installation room can also be taken into account and the primary air can be set accordingly, which means that heat can be produced as required and consequently the heat can not only be efficiently produced but also used efficiently. Grate air can be supplied in addition to the windshield rinsing air if this is not sufficient for combustion, as is the case when burning damp or very thick logs or when burning coal.

In one embodiment, the secondary air can be supplied in such a way that the oxygen content in the combustion chamber area is as favorable as possible, such as about 7% by volume to about 10% by volume, for example about 8% by volume to about 9% by volume for an optimal post-oxidation is. For the regulation, that can virtual oxygen signal is used, which can be generated every second by the algorithms on the basis of the measured temperatures.

The advantages of temperature-based control consist not only in the low production costs and durability, but also in the parameterizable algorithms, which enable simple handling when adapting the programming and universal use of the controller without any software changes. All relevant process specifications are taken into account in the parameterization factors.

The following is a detailed description of the energy balance method for determining the excess oxygen in the combustion chamber area and the parameterizable algorithm:

A combustion can be represented schematically as follows:

C + 0 ₂ -> C0 ₂ + heat

This creates exhaust gases. Furthermore, heat losses can occur. Under adiabatic conditions these are zero.

The fuel can be described as follows:

The combustion air can be represented as follows:

The exhaust gas can be represented by the following formula: A simplified energy balance for a combustion process is given above. The energy supplied to the combustion process via the fuel is equal to the energy generated during the thermal conversion and carried as heat via the exhaust gas. Adiabatic means that the thermal conversion takes place without any heat loss. Formula 1 results from this assumption: Formula

Where:: fuel mass flow [kg / s], H _u: calorific value of the Fuel: specific amount of combustion air [Nm ³ / kg fuel],: temperature of the combustion air,: specific amount of exhaust gas [Nm ³ / kg], _{P, L c:} specific heat capacity of air at constant pressure, c _{P, R:} specific heat capacity of the exhaust gas at a constant _pressure: exhaust or Combustion chamber temperature after completion of combustion, c _B: specific heat capacity of the fuel,: fuel temperature during charging.

The combustion chamber or exhaust gas temperature described in Formula 1 represents the maximum temperature that can be achieved in the combustion chamber area during the thermal conversion or combustion of the fuel, which can be achieved under adiabatic conditions or without any heat losses and with a stoichiometric amount of combustion air (lambda : 1) is produced.

The energy transferred with the combustion air as well as with the fuel is very small compared to the energy produced during the combustion and can be neglected. This means that Formula 1 can be shortened to the following form:

Formula 2 or for one kilogram of fuel:

The specific exhaust gas quantity V _R [Nm ³ / kg fuel] is calculated from Formula 3: Formula 3

Using formula 3 in formula 21 results in formula 4: Formula 4

The specific minimum amount of flue gas V _{R, min} and the minimum specific stoichiometric amount of combustion air L _min can be calculated approximately according to formula 5 and formula 6 or according to the approximations according to Rosin-Fehling:

L _min = 0.241 XH _u / 1,000 + 0.5 [Nm ³ / kg] Formula 5

V _{R, min} = 0.217 XH _u / 1,000 + 1.67 [Nm ³ / kg] Formula 6

The calculation in formula 5 can also be carried out using the elemental composition of the fuel.

Using formula 5 and formula 6 in formula 3 results in formula 7 for calculating the specific exhaust gas quantity [Nm ³ / kg fuel):

V _R = 0.217 * H _u / 1,000 + 1.67 + (λ-1) X [(10.241 * H _u /1,000 + 0.5] Formula 7 When describing formula 4 in terms of lambda, formula 8 results for the determination of lambda or the excess air ratio: Formula 8

The specific heat capacity c _{P, R of} the exhaust gas depends on the exhaust gas temperature and results approximately from Formula 9: Formula 9

Using Formula 5, Formula 6 and Formula 9 in Formula 8 results in Formula 10 for determining lambda or the excess air ratio:

The supply of combustion air can be controlled directly by the oxygen coefficient. The determination or calculation of the excess oxygen or the oxygen coefficient is not mandatory here.

Lambda is a function of, among others, H _u , K _B , K _F and K _s: λ = f (H _u , K _B , K _F and K _S , L _min and V _r, min) where:

L _min: the minimum amount of air required for stoichiometric combustion and:

V _{r, min} ; the minimum amount of flue gas or exhaust gas that is produced with stoichiometric combustion or with lambda = 1. L _min and V _{r, min} depend on the fuel properties, above all on the elemental composition, and are calculated directly from them.

Lambda (after the integration of the correction factors K _B , K _F and K _s , lambda can be referred to as the lambda coefficient n) is a function of three correction factors k _B , k _F and k _s:

K _B: correction factor of the fuel. This factor takes into account the deviation of the fuel used from the ideal fuel. k _F: Correction factor for extrapolating the non-adiabatic energy conversion operations that existed during combustion to adiabatic energy conversion operations. The factor k _F therefore takes into account the thermal losses through the fireplace up to the temperature measuring point in the combustion chamber area. k _s takes into account the ratio: primary air (SSL- PL) / secondary air (SSL-SL), which results from the windshield rinsing air and generally depends on the height of the window Hs. Here, the higher the viewing window of the fireplace or Hs is, the more the washing air can act as primary air. As a rule, k _{s takes} a value between 0.93 and 1.07 and is used in the calculation equation for oxygen and not for lambda in the equation as follows: or oxygen coefficient = (21 * λ * ks 21) / λ * ks

It should be mentioned that the calculation shown above can be switched to the C0 ₂ value. The combustion-related dependency between C0 ₂ and 0 ₂ results from the following formula:

CO ₂ CO _2max 0 ₂

CO _2max : 19 vol .-% to 21 vol .-% (it depends on the carbon content of the fuel)

The correction factors k _f , k _b and k _s are explained in more detail below. The concrete values are not fixed, they can be calculated using the following mathematical functions: k _b : y = f (x) [X _min = 500, X _max = 1000, Y _min = 0.75, Y _max = 1.2 ] kf: y = f (x) [x = 50 _min / _max x = 1000, Y _min = _1/0, Y _max = 2.5] _s k: y = f (x) [x _min = <20 x _max => 60, Y _min <0.93, Y _max = 1.07]

The calculations or the factors for the mathematical function are specified by the system limits (maximum temperature that can be achieved during real, proper combustion, temperature trends and changes during operation)

These correction factors are explained further below. Non-adiabatic conditions during combustion in the fireplace can be taken into account using _{the correction factor k F:}

When burning in fireplaces, heat losses occur due to the heat given off by the fireplace into the installation room and there are therefore no adiabatic conditions. To adapt the non-adiabatic to adiabatic conditions, the correction factor k _{F is} defined, which takes into account the heat emission (undesired heat losses) through the fireplace during the thermal conversion of fuel. It can have a value from one to four, depending on the type of individual room combustion system and the operating status.

This value is determined by a function. The following applies here: the greater the heat release or heat loss in the combustion chamber area (from the flame zone to the end of the post-oxidation chamber) before the oxidation is complete, the higher the value of this factor.

The functional parameters of the factor k _F can, for example, be set automatically in a software of a control element by entering technical data of the type of fireplace once. The size (area and height) of the combustion chamber, the lining of the fireplace, the size and type of glazing of the combustion chamber door, etc. play a decisive role here.

Furthermore, the type and properties of the fuel and the quality of the condition can be taken into account _{by the correction factor k B as follows:}

Correction factor k _B takes into account the variation in the fuel properties. The value of this factor varies and is determined during the combustion by an integrated function in Calculated analogously to the factor k _F , for example in an appropriately programmed control device, and changed in the control algorithms. The function of the correction factor k _F is based on the combustion behavior or the changes in temperatures over time in the combustion chamber area.

In general, the faster the rise in the combustion chamber temperature, the higher the value of the factor k _B. In addition, the slower the rise in the furnace temperature, the _{lower the value of the factor k B.} _{Here, k B can have} values from 0.80 to 1.2.

The factors k _F and k _{B also} depend on one another. The dependency is also determined and taken into account, for example by being appropriately integrated into the software of a control device.

Furthermore, the quality of the operating quality of the fireplace can be _{taken into account by the correction factor k q} as described below:

The factor k _q plays a role in the regulation of the

Combustion air supply only plays a subordinate role and is not relevant for the calculation of the excess oxygen in the combustion chamber area. The values of this factor can be varied and result from an integral calculation or change in the combustion chamber temperature over time with regard to a certain operating point of the combustion, whereby a point in time or a time range describes from which or in which the evaluation of the furnace temperature change takes place. In contrast to the factor k _B , which If only the energy content of the fuel is taken into account, the factor k _q gives direct conclusions about the loading regime (fuel quantity, number of logs loaded, fineness of the fuel, etc.). According to the consideration introduced above and when using the correction factors defined above or an average value of the lower calorific value of 17,000 [kJ / kg], formula 11 results, with which the excess air number can be parameterized by the factors k _F and k _B or by the Temperature measurement in the combustion chamber area can be calculated.

formula

11

The excess oxygen in the firebox area results from formula 12:

Oxygen in the combustion chamber area: Formula 12

Equation 12 can be supplemented by the correction factor k _s .

It takes into account the ratio of primary air (SSL-PL) to secondary air (SSL-SL), which arises from the window rinsing air and usually depends on _{the height of the window H s.} The following applies here: the higher the viewing _{window of the fireplace (H s} ), the more the window rinsing air can act as primary air. k _s can have a value from 0.93 to 1.07 and it can be used in equation 12 as follows: 0 ₂ = (21 * λ * k _s -21) / λ * k _s :

Formula 11 and Formula 12 provide the basis for controlling combustion systems with the help of temperature measurement in the furnace area or on the basis of the energy balance method according to the method according to the invention. The parameters specified above (temperature measurement,

Energy balance method) is used to determine the oxygen demand or to supply it to the process as well as to set the optimal oxidation temperatures in the active reaction zone in such a way that proper combustion and consequently operation of the fireplace can be guaranteed.

The calculation of the oxygen coefficient using the energy balance method can not only be carried out for the secondary air supply, but is also beneficial in order to recognize the limits of the primary air actuator and the primary air (gasifying air regardless of how the fireplace is supplied or through the grate, laterally, or via the fuel)) accordingly or in good time, thereby avoiding the combustion getting into a lack of oxygen.

The normative

Incineration calculations are taken into account or used.

In one embodiment, the method according to the invention can be carried out automatically. The control interventions can therefore take place automatically. This can be done, for example, by means of a control unit in which the above formulas are stored in appropriate software, including the correction parameters that may have to be entered. The temperature values from the combustion chamber area and / or the exhaust gas are then also transmitted to this control unit. After calculating the oxygen in the combustion chamber, the supply of primary air and / or secondary air can be regulated automatically by a controller. Subject of the present The invention is also a device with which this control of the supply of primary and / or secondary air can be carried out in a particularly favorable manner, in particular with which the advantages described above can be achieved particularly favorably.

The device according to the invention for supplying combustion air in the combustion chamber of a single-room combustion system is characterized in that it has a chamber that has a main channel on a first side for supplying ambient air and / or air from the chimney system and a disc scavenging air channel on a second side and has a secondary air duct through which the primary and / or secondary air can be fed into the combustion chamber, both the washer scavenging air duct and the secondary air duct being provided with a flap so that the washer scavenging air duct and the secondary air duct can be closed independently of one another, the flaps with are connected to a stepless motor so that the flaps can be moved steplessly.

The window rinsing air functions as primary (SSL-PL) and secondary air (SSL-SL) depending on the height of the viewing window of the combustion system.

For example, the first side of the chamber can be located opposite the second side of the chamber. Other configurations are also possible.

In one embodiment, the flaps can be designed as disks which are mounted on the air inlet of the primary duct and / or the secondary air duct. In a further embodiment, the flaps can both the windshield washing air via the windshield washing air duct and the Regulate the grate air via the grate air duct. The window rinsing air can be regulated for an opening of 0% to x% and the grate air can be regulated from 100% - x%, where x denotes the percentage opening width of the flaps and is generally 70% to 90% for an adequate design of the air supply ducts .

In a further embodiment, the device can have at least one solar panel and / or a device for thermoelectric power generation and / or a regular power supply via the domestic socket Regulation can be provided. In this way, the required power requirement of the device can be made available without great effort

In one embodiment, the device can furthermore have a control or regulating unit which is adapted to automatically control or regulate the air supply.

The device is shown in detail below:

Air flaps with stepless motors can be used to regulate the combustion air supply. The flaps regulate defined opening widths via two flaps that can be designed, for example, as panes which are built at the air inlet of the air chambers or ducts that are separated from one another. The two flaps are installed in a box or pipe system, which draws all of the combustion air from the environment via a main duct or from the chimney system in the case of room air-independent operation. The negative pressure and the boiler temperature for single-room firing with water-bearing components as Safety-relevant variables can be recorded using a built-in pressure monitor or temperature sensor and integrated accordingly into the software.

No domestic energy supply is required to operate the control system due to the very low energy consumption of the hardware and the control actors (control flaps). In contrast to other systems, the power consumption is very low and is in the watt range. This power requirement can be provided by a solar panel, thermoelectrically during the combustion, or with a domestic power socket, in each case possibly with a corresponding simple power storage unit (cf. also above).

In the event of a power failure or a technical defect, the primary air flap rotates to the zero position for technical reasons, at which the primary air opening is 100% closed. To avoid dangerous conditions such as B. heavy smoke in the living room or deflagrations due to the lack of oxygen in the furnace such. B. to avoid loading in the presence of a bed of embers, a mechanism for regulating the combustion air is provided. With this mechanism, when the primary air flap is retracted from a 40% level to 0% level, a mechanically locked safety air flap is simultaneously actuated mechanically, which provides a correspondingly large opening and thus a sufficient amount of combustion air is supplied to the combustion process for safe combustion. This is only an exemplary description of a technical possibility. It can also be implemented with other technical possibilities.

The regulation of the primary air flap in normal operation can be over 60% (between 40% to 100%) of the total opening width of the Primary air take place, whereby the secondary air can be regulated from 0% to 100% of the opening width.

With the method according to the invention and the device according to the invention, a number of advantages are achieved: The regulation can be carried out with inexpensive, robust and long-lasting sensors which deliver stable signals or require no maintenance and calibration in practice. Resistant temperature sensors that require simple electronics for processing the signals can be used here. The automatic control, which can be adjusted with the setting of parameters, enables the control to be quickly adapted to all types of combustion systems, regardless of their design, without the need to change the software. · The software and hardware with the combustion air distribution system can be used universally and take into account all normative requirements and approval regulations of the DIBt (Deutsches Institut für Bautechnik) for technical approval and safe operation in practice. · The hardware components with the sensors and the control actors can be selected in such a way that the control system can be operated without any heavy current or domestic power supply. The total power consumption is in the watt range. A simple solar module can supply the control system with the necessary electricity. · The technical combination of the air distribution system with the method according to the invention enables universal use in new firing systems as well as safe retrofitting of many individual room firing systems that exist in practice. · Thanks to the intelligent control, the heat is not only produced efficiently, but also used efficiently, which means that not only resources but also significant C0 ₂ savings can be achieved.

The invention is to be explained in more detail below with reference to figures without restricting the general inventive concept. It is

1 shows a representation of a hand-loaded single-room firing system.

Fig. 2 shows a plan view of the device according to the invention.

Fig. 3 shows the paramagnetically measured and calculated with the model equation oxygen concentration in a single room combustion system.

Fig. 4 shows oxygen, furnace temperature and carbon monoxide when operating a single-room combustion system.

1 shows a hand-loaded single-room combustion system 10. It has a combustion chamber area 11 in which a fuel is burned. For example, window scavenging air (SSL) and / or grate air (RL) can be introduced into the combustion chamber area 11 via a window scavenging air duct 3 and secondary air (SL) can be introduced into the combustion chamber area 11 via a secondary air duct 4. The air flows are shown in Fig. 1 with arrows. Rust air can be introduced if the oxygen content of the windshield rinsing air is insufficient to set the combustion in motion with sufficient intensity to achieve favorable temperatures for carrying out the oxidation reactions, as is the case with the Burning damp and / or thick logs or coal. The grate air can reach the combustion chamber area 11 from below through the grate. The path of the grate air is shown in Fig.

1 shown with an arrow. Both the window scavenging air duct 3 and the secondary air duct 4 can be closed independently of one another via flaps 5, whereby these flaps can be continuously adjusted by motors 6, 7 in order to ensure precise control of the air admission. In the combustion chamber area 11 there are two temperature sensors T ₁ , T ₂ , which can be provided on the baffle plate, for example. In addition or as an alternative, temperature sensors can be installed in the first exhaust flue after the exhaust baffle plate. However, this is only one example of a location at which the temperature sensors T ₁ , T ₂ can be provided. Of course, they can also be located in other places in the combustion chamber area, such as in the exhaust flue. Furthermore, a further temperature sensor T _Ab , with which the temperature in the exhaust gas is measured, can be located in the exhaust gas area. Furthermore, the ambient temperature T _u in the installation room can be measured and taken into account for the regulation. The measurement of the temperature of the exhaust gas provides more information, but it is not mandatory, but optional. The measured temperature values are transmitted to the control unit 12 (control unit / microcontroller) (see dashed lines). The oxygen is calculated there using the above formulas and parameters. Depending on the result obtained, the supply of primary air and / or secondary air can then be regulated by issuing appropriate commands to the motors 6, 7. The flows of the combustion air are as follows: SSL-SL: windshield rinsing air as secondary air; SSL-PL:

Windshield rinsing air as primary air; RL-PL: grate air as primary air; SL: secondary air. In Fig. 2, the device according to the invention is shown in plan view, with which the supply of primary and / or secondary air can be controlled in the combustion chamber area.

The device has a chamber 1, which on a first side has a main channel 2 for the supply of air and / or air from the chimney system (combustion air) (shown as an arrow) and on a second side a disc scavenging air channel 3 (SSL: disc scavenging air) and a secondary air channel 4 (SL: secondary air, like 0 ₂₎ , whereby both the washer-scavenging air channel 3 and the secondary air channel 4 are provided with a flap 5 (only indicated schematically in FIG. 2), so that the scavenging air channel 3 and the secondary air channel 4 can be closed independently of one another are, wherein the flaps 5 are each connected to a stepless motor 6, 7, so that the flaps 5 can be moved continuously. Furthermore, a grate air duct 13 is provided, the grate air being regulated via the flap 5, which is connected to the motor 6 for the disc rinsing air duct 3.

The device also has a solar panel 8, with which the electricity required to operate the device can be generated.

In FIG. 3, the oxygen concentrations calculated according to the model equation and measured with a paramagnetic oxygen analysis are shown during the combustion of beech logs in a prototype of a single-room combustion system from the Hase company. In FIG. 3 it can be seen that the concentrations of oxygen in the exhaust gas calculated and measured on the basis of the model equation correlate and the model equation is therefore very well suited for determining the oxygen content in the exhaust gas. Using a simple test system, the control concept based on the energy balance method of the Fraunhofer Institute for Building Physics IBP was implemented on the basis of a PLC control (programmable logic controller). The pollutant emissions such. B. carbon monoxide reduced by 62% and fine dust by approx. 43% compared to operation without control (see. Fig. 4). In addition, the efficiency was increased by approx. 16% based on practical operation. A further improvement can be achieved through further development of the software.

It can be seen from the diagram in FIG. 4 that when the controller is used, the combustion chamber temperature is above a favorable or average combustion chamber temperature of greater than 550 ° C. over a longer period of combustion. The same applies to the oxygen content in the exhaust gas, which means that clear conclusions can be drawn about the controlled combustion.

According to the invention, the targeted regulation of the secondary air (SSL-SL + SL) takes place by means of an oxygen coefficient calculated using the energy balance method

Furthermore, with the oxygen coefficient, the primary air actuator can also be operated within its favorable limits, which can prevent the combustion from falling into oxygen deficiency. This means when the secondary air actuator reaches its maximum limit (flap 5 of the stepper motor 6 (or secondary air actuator) 90% open; here 10% as a reserve) and the calculated oxygen coefficient is still below the oxygen setpoint stored in the program the primary air (RL-PL + SSL-PL) is reduced in good time to avoid a lack of oxygen and thus incomplete combustion avoid. As an alternative to the stepper motor 6, a servomotor can also be used.

The targeted regulation of the primary air (SSL-PL + RL-PL) takes place for the setting of a favorable temperature in the active reaction zone (combustion chamber + post-oxidation chamber) for an effective implementation of the oxidation reactions or a complete combustion.

The description and evaluation of the combustion quality (completeness of the combustion) as well as the operational quality of the fireplace is carried out through a differential and integral evaluation of the recorded temperatures, the calculated oxygen coefficient and the behavior of the control actuators or the stepper motors or servomotors (6 and 7) to control the Combustion air supply. The following knowledge is gained and the users are informed accordingly or digitally trained to better operate the fireplace:

- Use of moist fuels

- Use of dry fuel in large quantities

- Loading large quantities of fuel

- Illegal incineration of waste such as B. Plastic, waste oil, etc.

- Detection of unfavorable or very high or very low chimney drafts.

Of course, the invention is not limited to the embodiments shown in the figures. The above description is therefore not to be regarded as restrictive but rather as explanatory. The following claims are to be understood in such a way that a named feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Provided If the description or the claims define “first” and “second” features, this is used to distinguish between features of the same type without establishing a ranking.

Claims

λ claims

1. A method for regulating the combustion in combustion systems, characterized in that from the temperature in a combustion chamber area and / or in the exhaust flues of the combustion system and an energy balance of the

During the combustion process in the individual room combustion system, the combustion air and the exhaust gas, an oxygen coefficient is determined with which the primary and secondary combustion air flows and thus the thermal output and the combustion quality are regulated.

2. The method according to claim 1, characterized in that the

The supply of combustion air is regulated by the oxygen coefficient.

3. The method according to claim 1 or 2, characterized in that an oxygen requirement for the combustion is calculated according to the following formula

, where λ is determined as follows

, where k _{B has} a value of 0.80 to 1.2, for which Exhaust gas and / or furnace temperature is, k _{F has} a value of 1 to 4 and H _u indicates the calorific value of the fuel.

4. The method according to any one of the preceding claims, characterized in that the temperature in the furnace area and / or in the flue gas is measured at at least one point.

5. The method according to any one of the preceding claims, characterized in that the temperature in the installation room of the furnace is measured for a needs-based heat production.

6. The method according to any one of the preceding claims, characterized in that the regulation of the combustion takes place via the supply of primary air and / or via the supply of secondary air.

7. The method according to claim 6, characterized in that the primary air is disc rinsing air and / or grate air.

8. The method according to claim 6, characterized in that the supply of the secondary air takes place so that the

Oxygen content in the furnace area is about 7% by volume to about 10% by volume, for example about 8% by volume to about 9% by volume.

9. The method according to any one of the preceding claims, characterized in that the regulation of the combustion takes place automatically.

10. Device for supplying combustion air in the furnace of a combustion system, characterized in that it has a chamber (1) which on a first side has a main channel (2) for supplying ambient air and / or air from the chimney system and on a second side a window scavenging air channel (3) and a secondary air channel (4), both the window scavenging air channel (3) and the secondary air channel (4) being provided with a motor-controlled flap (5) so that the window scavenging air channel (3) and the Secondary air duct (4) can be closed independently of one another, the flaps (5) being connected to a stepless motor (6, 7) so that the flaps (5) can be moved continuously.

11.Vorrichtung according to claim 10, characterized in that the first side of the chamber (1) is opposite the second side of the chamber (1).

12.Vorrichtung according to any one of claims 10 or 11, characterized in that the flaps (5) are designed as discs which are mounted on the air inlet of the Scheibenspülluftkanal (3) and / or the secondary air channel (4).

13.Vorrichtung according to any one of claims 9 to 12, characterized in that one of the flaps (5) regulates both the disk rinsing air via the Scheibenspülluftkanal (3) and the grate air via the grate air channel (13).

14.Vorrichtung according to any one of claims 10 to 13, characterized in that the device has at least one solar panel (8) or a device for thermoelectric power generation or a regular power supply via the domestic power socket.

15.Vorrichtung according to any one of claims 10 to 14, characterized in that it further comprises a control or regulating unit (12) which is adapted to automatically control or regulate the air supply.

16.Use of the method according to one of claims 1 to 9 or the device according to one of claims 10 to 14 for monitoring the operation of a combustion system for their optimal operation and to ensure the quality of combustion.