WO2008089842A1

WO2008089842A1 - Method and device for burning refuse

Info

Publication number: WO2008089842A1
Application number: PCT/EP2007/050609
Authority: WO
Inventors: Theodor Koch; Franco Cairella
Original assignee: Seko-Patent Gmbh
Priority date: 2007-01-22
Filing date: 2007-01-22
Publication date: 2008-07-31
Also published as: EP2122250A1

Abstract

With the present method for burning refuse (2) in a burner (1), wherein the refuse (2) is ignited on a grate (4) and burned, and the resulting combustion gases are discharged to a combustion chamber (5) via one or more flue gas flue (7) to a waste gas flue (8), a liquid is injected in the head region (5a) of the combustion chamber (5) of the burner (1). In this manner, the temperature of the flue gas can advantageously be adjusted in this region (5a) and maintained in a certain range. In particular, a rising flue gas temperature is lowered by means of evaporating a liquid, in that heat is accordingly withdrawn from the flue gas by evaporating the liquid.

Description

Method and device for burning garbage

The present invention relates to a method for incinerating waste according to the preamble of claim 1 and to such a device according to the preamble of claim 11.

Waste incineration plants resp. Refuse incinerators are known, for example, in the form of so-called grate firing systems. They are suitable for burning solid fuels such as household waste,

Industrial waste, coal, etc. These fuels are burned on a grate. In a first phase, the fuel is dried and degassed. This is partly already done in the feed zone of the plant. This process is triggered by the radiation of the combustion chamber and the addition of preheated air. Also here takes place the ignition of the fuel on its surface due to the flame radiation of the combustion chamber. In a second phase, the main combustion takes place with the dried fuel completely igniting (not just at the surface). In this phase, more air is supplied than in the first phase. Here, the conversion of solid carbon to gaseous products takes place, which pass through the combustion chamber into the afterburner chamber of the steam boiler and finally into the flue gas outlet. Firebox prevail high temperatures. Depending on the calorific value of the fuel, the supply of the amount of air is controlled in this phase. customized. However, there are limits to this adaptation, since the additionally supplied air is also used for Cooling of the grate is used and just for high-calorific fuel usually with excess air for precisely these reasons mentioned must be worked. The last phase then takes place the residual combustion. The not yet completely burnt out fuel, ie the

Combustion residue, such as pressed paper, coarse substances and residual solid carbon, passes here for combustion respectively. for burnout. Since the lowest possible heat loss should occur so that the residual combustion can be carried out as completely as possible, only a correspondingly small amount of air should be supplied here (due to the risk of cooling the combustion residue).

The phases shown here typically take place separately in the incinerator, by applying the fuel to a mobile grate which slowly transports the fuel forward in the combustor. Depending on the type of fuel, the transitions of the phases are fluid or not recognizable, especially at high fuel calorific values.

Thus, for example, EP 0 815 394 discloses a waste incineration plant in which solid or pasty material is burned on a furnace grate with a closed combustion chamber arranged above the grate region. The afterburning chamber is only then arranged on the entire grate area. Thus, the hot flue gases from the first grate area, in which the actual combustion of the burning material takes place, are guided over the rear area of the grate. This makes it possible for the combustion residues to be melted in this rear area. As a result, even when domestic or commercial waste is incinerated, the remaining combustion residues can be minimized. However, in such a system, the

Combustion performance can not be easily increased, otherwise the temperatures in the combustion chamber are too high.

The object of the present invention was to increase the combustion performance of an incinerator mentioned above. This object is achieved according to the invention by a method according to the features of claim 1. Further, inventive embodiments are shown in the features of further claims 2 to 10. In the inventive method for burning garbage in a firing boiler, the garbage is ignited on a grid and burned and the resulting combustion gases in a furnace over one or more flues be led to a flue gas outlet, is in the head area of the firebox of the firing boiler

Liquid injected. Thus, the temperature of the flue gas can be advantageously adjusted in this area and kept in a certain range. In particular, an increasing flue gas temperature is lowered by evaporation of a liquid by the flue gas through

Evaporation of the liquid is removed according to heat.

As the upper area, the boiler area above the actual firebox or fire area becomes direct above the grate. The flue gas rises here directly above the fire area of the grate and gives off some of its heat to the wall of the steam train. So that a complete combustion process can be ensured, a combustion air temperature of about 85O ⁰ C at a residence time to be obtained of about 2 'in the combustion gases when passing through this area. A much higher temperature is not desirable, as this can lead to the formation of unwanted NOx (thermal NOx), which later has to be laboriously reduced again in the area of the flue gas outlet. Next, at higher temperatures slagging of the side walls of the steam train, which in turn leads to a deterioration of the heat output arranged in this area

Heat exchangers leads and thus to a further undesirable increase in temperature. The slagging of the sidewalls of the steam train can only take place at an interruption of the combustion process, i. the operation of the system must be interrupted for this purpose.

Advantageously, an increase in the combustion capacity can now be achieved by the injection of liquid according to the invention by supplying a higher amount of fuel to the combustion grate and thus increasing the temperature of the combustion gases. In the upper part of the steam train, the required temperature can nevertheless be maintained by injecting a liquid which reduces the temperature of the combustion gas by removing heat of vaporization in this area. Also, it will change the temperature of the combustion gas in the uppermost region of the steam train and in particular in the subsequent steam train, for example, reduced to below 650 ⁰ C to 600 ⁰ C. Thus, a possible corrosion of arranged in these subsequent Dampfzugbereichen superheater is reduced resp. reduced. Otherwise, the chlorine constituents occurring in the combustion gas could be at high temperatures, typically of more than 600 ⁰ C resp. 650 ⁰ C lead to chlorine corrosion. For example, liquid is additionally injected in the central region of the combustion chamber of the boiler. Thus, the temperature is held there at a desired level and avoided that the fly ash located in the combustion gas melts and thereby it comes to a slagging on the walls of the steam train.

For example, in addition to the lower part of the combustion chamber directly above the grate, ie in the transition region between the combustion chamber above the grate and the flue above, liquid is injected. Also in this area can thus be set and regulated the combustion gas temperature. The local arrangement of the injection points in this area can take into account the fact that the combustion temperature in the central core zone of the grate is hottest and in the edge regions, at the transition to the wall of the firebox, lower temperatures occur. This means that the combustion process does not run homogeneously over the entire width of the grate, but that Temperature differences of up to 200 ⁰ C may occur. By appropriate arrangement and dimensioning of the injection quantity of the liquid, the combustion temperature over the entire width of the combustion grate can now advantageously also be set to a specific, constant value over the entire width of the combustion grate and thus also a constant composition of the combustion gas can be achieved.

This effect occurs not only due to the geometric conditions of the incinerator, i. the dimensions of the grate and the geometric arrangement of the firebox, but also by the inhomogeneous composition of the fuel, ie the garbage.

For example, the liquid is injected under pressure, preferably under an adjustable, constant pressure, continuously or pulsating. Thus, the bodies resp. Be targeted area cooled with high temperatures and thus a homogenization of the combustion process and the temperature profile of the combustion gas can be achieved. The greater the pressure of the liquid is set in the supply lines, the finer the atomization of the liquid can be done and thus a rapid mixing and evaporation of the liquid can be achieved. This allows the influence on the temperature to be very finely adjusted and possibly regulated. For example, the liquid is injected via one or more nozzles. For smaller systems with a mean boiler width of up to 4 meters, one nozzle per injection point can be provided, with larger ones Boilers can also be arranged several nozzles per injection point, preferably distributed over the width.

For example, the amount of injected liquid via valves, preferably set over several valves, controlled, taking into account the temperature conditions in the boiler and / or in the furnace. Of course, the nozzles can be fed via manually operated valves with a common supply line. The use of controlled valves, for example, controlled by a central computer, but allows a more accurate and temporally virtually without delay control of the temperatures. The computer can advantageously the current, measured temperatures in the individual areas of the combustion chamber, respectively. of the steam train to control the valves to reach the target values. For this purpose, temperature sensors are attached to the appropriate points, which are connected directly to the computer.

For example, the control of the valves is such that the temperature is maintained in certain areas of the boiler and / or the firebox in a predetermined temperature range by more or less liquid is supplied to the associated nozzles. Advantageously, the corresponding temperature value or temperature range can be predefined and by appropriate opening respectively. Closing the valves to the nozzles, this temperature value can also be achieved resp. being held. For example, water is used as the liquid or water provided with additives such as urea and / or additives.

For example, the liquid is provided in a liquid reservoir and is injected under a pressure of at least 40 bar in a line system. The pressure is by means of a resp. set several pressure pumps and the nozzles via controllable valves connected to this line system. As already stated above, a particularly fine atomization of the liquid can be achieved with a high pressure and thus a good mixing and rapid evaporation can be achieved.

For example, the separated from the flue gas resp. recovered liquid returned to the liquid reservoir. Thus, only a small proportion of new resp. fresh liquid needed for the combustion process, which has a positive effect on the overall energy balance. Overall, a higher uniformity of the combustion process is achieved with the inventive method and the formation of NOx can be reduced despite increased fuel supply. Also, the potential risk of corrosion is reduced as well as the formation of slag due to the melting of fly ash parts at high combustion temperatures. Overall, the injection of liquid fuel throughput compared to conventional operation by at least 10% resp. increase up to 25%. Another advantage is that by the homogenization and lowering of the combustion temperature, the deposition of fly ash by bonding to the tubes of the heat exchanger resp. Boiler pipes prevented or at least reduced, with which an extension of the operating time between the cleaning intervals of over 100% can be achieved.

Another advantage is the fact that this method can be used with only a small structural complexity of existing systems and thus their throughput (fuel quantity) can be increased without exceeding the permissible values, in particular the vapor pressure in the superheater of the boiler , The object is further achieved according to the invention by the features of a combustion system according to claim 11. Further embodiments according to the invention result from the features of the further claims 12 to 16.

Embodiments of the present invention will be explained in more detail below with reference to figures. Show it

Fig. 1 shows schematically the longitudinal section through a waste incineration plant;

2 shows the diagram of an inventive liquid injection for waste incineration plants.

3 is a schematic longitudinal section through a waste incineration plant with liquid injection according to the invention; 4 shows the plan view of a cross section of the system according to FIG. 3; and

5 shows the plan view of a cross section of an alternative system according to FIG. 3.

In FIG. 1, the longitudinal section through the boiler 1 of a typical waste incineration plant is shown purely schematically. The fuel 2 in the form of waste is collected outside the boiler 1 and stored and for the combustion process via a feed shaft 3 the

Combustion grate 4 supplied. Above the combustion grate, the firebox 5 is arranged, which, for example in the case of a medium-flow firing, tapers in a funnel shape approximately above the middle of the combustion grate 4 and subsequently widens again.

As a result of the combustion process of the refuse on the combustion grate 4, the combustion gases pass upwards into the combustion chamber 5 and develop the highest temperatures in the uppermost region. For the operation of such a plant is a series of

Demands made. So in the furnace to a temperature of at least 85O ⁰ C with a residence time of at least 2 sec has demanded so odor nuisance around can be largely excluded. In addition, the laws for the purification of the air demand in the rule

Compliance with maximum emission of pollutants as well as a low exhaust gas temperature. The resulting within the plant temperature gradient is therefore in usually used thermally in the combustion boiler by heat exchangers.

A higher temperature in the combustion chamber must be prevented, so that it does not form too much NOx, which again reduced before discharging into the environment resp. must be excreted and thus the fly ash in the combustion air does not melt and settles as slag on the walls of the furnace or flues. Further, these parts can stick at too high a temperature, the tubes of the heat exchanger in the flue and thus reduce their efficiency as well as increase the corrosion, for example by chlorine gas, which is the case especially at high temperatures of about 600 ⁰ C.

Thus, the combustion performance of such systems can not be increased arbitrarily, since this at elevated

Fuel supply, i. Increased supply of waste, leading to higher temperatures with the disadvantages described.

In order to still achieve a higher combustion performance when needed, such as in the need for processing of increased amounts of waste, according to the invention, according to the invention, liquid can be injected at different points in the combustion chamber, resp. be dusted.

FIG. 2 shows the functional diagram of such a device according to the invention for the injection of liquid into the boiler 1 of a waste incineration plant.

The liquid, for example water, is provided in a liquid tank 10. From this liquid tank 10, the liquid by means of a High pressure pump 11 is fed into a manifold 12.

By means of pressure regulating valves 13, the pressure in

Manifold tube 12 kept constant at an adjustable, defined pressure level. Several nozzles 14, 15, 16 and 17 are each connected via their own supply lines to the manifold 12. For example, by means of solenoid valves 18, the nozzles 14, 15, 16 and 17 can be controlled individually, i. be opened or closed. The solenoid valves 18 can be controlled either manually or advantageously automatically via a controller.

To an optimal temperature setting of the boiler 1 resp. To reach the temperature in the combustion chamber 5 of the boiler 1, the nozzles 14, 15, 16 and 17 at the following locations of the combustion chamber 5 are arranged.

The nozzles 14 are arranged in the uppermost region of the combustion chamber 5, where the highest temperatures of the combustion process occur. Up to this range, the flue gases usually must have exhibited a minimum temperature of over 850 ⁰ C for a period of 2 seconds. Now, if the burning power is increased by increasing the supply of fuel, the temperature in this range exceeds this value, which is not desirable for the reasons described above. By opening the solenoid valves 18 of the nozzles 14, the temperature in this area can be lowered to the desired value.

If the temperature is kept below 650 ⁰ C - 600 ⁰ C in this area, corrosion of the subsequent superheater can be prevented or at least reduced. This occurs, for example, by the chlorine constituents contained in the flue gas, when the temperature of the flue gas is above 600 ⁰ C.

To be able to limit the temperature in a further increase in the fuel supply and an associated increase in the flue gas temperature in the lower area of the combustion chamber, nozzles 15 are arranged in the central region of the combustion chamber.

Finally, 5 more nozzles 16 can be arranged in the area immediately above the grate 4 of the combustion chamber to already regulate there the firing temperature when needed, ie. lower by injecting liquid. This can be prevented, in particular, that in these areas, the fly ash contained in the flue gas melts and thus slagging of the wall area of the combustion chamber can be prevented.

Furthermore, further nozzles 17 can be arranged in the uppermost area of the combustion chamber, which, like the nozzles 14, reduces the risk of corrosion of subsequent heat exchanger elements by reducing the temperature of the flue gas in this area.

Another advantage of being able to

Flue gas temperature to be controlled exactly resp. to adjust is that so that the amount of steam of the boiler 1 of the incinerator can be kept constant and thus the incinerator can deliver a constant amount of heat.

In Figure 3, such a system set up is shown schematically in longitudinal section. In the upper region of the combustion chamber 5, the nozzles 14 are arranged. By injecting liquid evaporation heat is removed from the firing gases during their evaporation, whereby the temperature drops. According to the amount of injected liquid can thus the

Temperature in the corresponding range can be set to a specific value.

Further nozzles 15 and 16 are arranged in the central region and lower region of the combustion chamber 5, whereby an influence of the temperature can be made in these areas.

Further nozzles 17 are arranged in the upper region of the boiler 1 immediately adjacent to the upper region of the combustion chamber 5 in order to influence the temperature of the flue gas before the flow through the following heat exchangers resp. to reduce.

The nozzles 14, 15, 16 respectively. 17 may be embodied in known forms. Thus, they may be formed, for example, in a lance shape, the tips of which can be arranged far protruding into the combustion chamber.

Thus, the combustion chamber temperature can be reduced to the desired values even with increased supply of fuel.

In FIG. 4, the plan view of a cross section of the incinerator according to FIG. 3 in the region above the grate 4 is shown purely schematically. It is a relatively small incinerator with a width of the grate resp. the combustion chamber 5 of up to about 4 m. In each case a single nozzle 14, 15, 16 resp. 17 arranged approximately in the middle of the respective cross-sectional area.

For larger systems, from a width of more than 4m wide, two or more nozzles per location can be arranged, as shown in Figure 5. Advantageously, the nozzles are transverse to a line across the width of the grate 4, respectively. arranged in the combustion chamber or in any other suitable pattern.

Thus, the injection quantity of liquid can be metered individually and thus over the width of a homogeneous temperature distribution can be achieved. Advantageously, a homogenous combustion can thus be achieved even with an inhomogeneous calorific value of the fuel. Achieve a temperature of incineration. If necessary, the evaporated liquid can be used before the

Chimney area of the incinerator are also recovered via steam and fed back into the liquid tank, so that even with continuous operation, only small amounts of fresh liquid are needed.

The inventive arrangement of nozzles for the injection of liquid, the combustion performance of existing systems can be increased by more than 20%, without thereby exceeding the limits of the steam generating plant. Also, the operating time between cleaning intervals for cleaning the combustion chamber and / or the heat exchanger by extending the slag deposit can be extended, so that the overall efficiency of such a system increases can be. This allows the rising waste mountain to be managed with existing plants or new plants with increased combustion performance can be designed and constructed.

Claims

claims

A method of burning garbage (2) in a firing boiler (1), wherein the garbage (2) is ignited and burned on a grate (4) and the resulting combustion gases in a firebox (5) via one or more flues ( 7) to a flue gas outlet (8), characterized in that in the head region (5a) of the combustion chamber (5) of the firing boiler (1) liquid is injected.

2. The method according to claim 1, characterized in that in addition in the central region (5b) of the combustion chamber (5) of the firing boiler (1) liquid is injected.

3. The method according to claim 1 or 2, characterized in that in addition in the lower region (5c) of the combustion chamber (5) directly above the grate (4) liquid is injected.

4. The method according to any one of claims 1 to 3, characterized in that the liquid is injected under pressure, preferably at an adjustable, constant pressure, continuously or pulsating.

5. The method according to claim 4, characterized in that the liquid via one or more nozzles

(14; 15; 16; 17).

6. The method according to claim 4 or 5, characterized in that the amount of the injected liquid via valves (18), preferably via a plurality of valves (18), is controlled, under Consideration of the temperature conditions in the firing boiler (1) and / or in the firebox (5).

7. The method according to claim 6, characterized in that the control of the valves (18) takes place such that the temperature in certain areas of the firing boiler (1) and / or the firebox (5) is set in a predetermined temperature range by the associated Nozzles (14; 15; 16; 17) more or less liquid is supplied.

8. The method according to any one of claims 1 to 7, characterized in that water is used as the liquid or water provided with additives such as urea and / or additives.

9. The method according to any one of claims 1 to 8, characterized in that the liquid in one

Liquid reservoir (10) is provided and is fed under a pressure of at least 40 bar in a conduit system (12).

10. The method according to claim 9, characterized in that the separated from the flue gas resp. recovered liquid is returned to the liquid reservoir (10).

11. An apparatus for burning garbage in a Feuerungskessel (1), with a grate (4) and arranged above the firebox (5), at least one with the

Combustion chamber (5) connected flue gas duct (7) which is connected to a flue gas outlet (8), characterized in that at least in the head region of the combustion chamber (5) at least one nozzle (14) is arranged for the injection of liquid.

12. The device according to claim 11, characterized in that further in the central region of the combustion chamber (5) at least one nozzle (15) is arranged for the injection of liquid.

13. The apparatus of claim 11 or 12, characterized in that further in the lower region of the combustion chamber (5) above the grate (4) at least one nozzle (16) is arranged for the injection of liquid.

14. Device according to one of claims 11 to 13, characterized in that all the nozzles (14; 15; 16; 17) are connected to a common pipe system (12), wherein preferably each nozzle (14; 15; 16; a separate valve (18) is connected to the pipe system (12).

15. The apparatus according to claim 14, characterized in that the pipe system (12) via a pressure pump (11) with a liquid tank (10) is connected.

16. Device according to one of claims 14 to 15, characterized in that the valves (18) are designed as automatically controllable valves which are connected to a common control unit.