EP2128523B1 - Combustion assembly and method for regulating same - Google Patents

Description

The invention relates to an incinerator with a furnace, means for recirculating combustion residues into the furnace, means for measuring at least one parameter of the combustion and means for influencing the combustion. Moreover, the invention relates to a method for controlling an incinerator.

Such incinerators are widely used and are mainly used as large combustion plants for the incineration of waste and waste. Various combustion parameters are measured and influenced to ensure optimum combustion and to minimize the generation of harmful emissions. It is important that the materials to be burned, in particular the garbage, are burnt out as completely as possible and that little pollutants can be found in the flue gas.

It is also known that incompletely burned out combustion residues back to a grate firing. Especially when recirculating combustion residues, special care must be taken to ensure that the combustion parameters are optimally adjusted during the recirculation in order, on the one hand, to recycle the combustion Materials should not adversely affect and on the other hand to achieve the best possible combustion of the materials to be burned.

document US 2006/081161 discloses an incinerator according to the preamble of claim 1.

The object of the invention is to further develop an incineration plant in such a way that optimum combustion with minimal pollutant emissions is achieved.

This object is achieved with a generic combustion system having a device which acts on the amount of recirculated combustion residues, according to claim 1.

Such a device makes it possible to vary the amount of the recirculated combustion states such that the combustion is acted upon by the variable amount of recirculated combustion residues.

While so far all incompletely burned out combustion residues were returned to the combustion and the supplied combustion air and the other means for influencing the combustion should obtain the best possible combustion, allows the combustion system according to the invention to act selectively by the variation of the amount of recirculated combustion residues on the combustion ,

Thus, for example, in the case of excessive combustion, the size of the flame can be reduced via the amount of recirculated combustion residues. On the other hand, can also be reduced by a reduction of Combustion residue firing intensified to achieve a better burnout.

A particularly advantageous embodiment of the incinerator provides that the furnace is designed as grate firing, in particular with a return grate, and the combustion residues are given up at the beginning of the grate.

In particular, it is also possible to act by means of a device on the location of the return of the combustion residues. Thus, for example, in a grate firing, the recirculation of the combustion residues at the beginning, in the middle or more at the end of the grate take place. In addition, often several juxtaposed gratings are used, on which develops a different firing performance. Here, with a device of the respective grate can be selected with a particularly high firing capacity to introduce here the recirculated combustion residues.

The recirculation of the combustion residues is thus used as an additional means for influencing the combustion.

In order to supply the combustion residues in defined amounts targeted the furnace, it is proposed that the means for recycling the combustion residues has a driven conveyor. Such a conveyor may for example be a screw conveyor. Also pneumatic conveyors are suitable for this purpose.

A special embodiment provides that the combustion residues are recycled at least with a portion of the primary or secondary air. In this case, a pneumatic conveyor supplies combustion residues and combustion air to the furnace.

A particularly advantageous embodiment variant provides that the device for measuring combustion parameters has a camera. With a camera can be accurately determined locally, as the combustion takes place in the supply and in particular at different locations of a combustion grate. This makes it easier to add the combustion residues targeted by location and amount of firing. By means of an image processing system, a targeted recycling of the combustion residues can take place fully automatically. In particular, an automation allows it according to measured parameters to control or regulate the return to Zuführort (place), supplied volume flow (amount) and feed duration (time).

A simple embodiment provides that the recirculation of the combustion residues is controlled. However, it is advantageous if the device acting on the return of the combustion residues has a regulator. Such a controller cooperates with a measuring and an adjusting device to adjust the amount to be returned exactly. The measuring device may in this case have the camera and / or other devices for measuring combustion parameters, while the adjusting device, for example, on the engine a powered conveyor for returning the combustion residues acts.

It is advantageous if several different combustion parameters are calculated in order to supply a calculated value to the controller. For example, increased combustion on a region of the grate may result in increased recirculated flow while an increased level of carbon monoxide measurement in the flue gas reduces the amount and even stops recirculation above a particular threshold.

For example, an increased flue gas temperature may accelerate the engine of recirculated combustion residues, and a decrease in temperature in the flue gas may result in a reduction in the amount of recirculated combustion residue recirculated.

If the combustion system has a regulator, it is proposed that the device for measuring the combustion acts on the regulator.

While a simple embodiment of the combustor provides for linear control or control over a cam between the measured combustion parameter and the recirculated amount, in an optimized combustor, a P-controller, a PI controller, or a PID controller is provided.

If little badly burned combustion residues can be returned to it firing, since the firing parameters do not allow a return, get also badly burned combustion residues to the other combustion residues. On the other hand, an embodiment variant provides that in such a case the badly burned combustion residues are first stored in a buffer storage tank until they can be returned to the combustion plant. In this case, the incinerator has a buffer storage for recirculating combustion residues.

The object underlying the invention is also achieved with a method for controlling an incineration plant, in which combustion residues are returned to the incinerator and parameters of the combustion are measured, wherein the volume flow of recirculated combustion residues is set as a function of at least one measured parameter of the combustion , according to claim 11.

It is advantageous here if the volume flow is regulated.

Particularly good combustion results can be achieved if several combustion parameters are measured and charged for the regulation of the volume flow. A computer can hereby ensure that different combustion parameters act differently on the recirculated volume flow.

A simple procedure provides that the incineration plant is set for a fuel burning value and an increased firing intensity is counteracted by an increased recirculation flow rate. In particular, in refuse incineration plants, the fuel burn value varies and it is therefore very advantageous if time or regional or local excessive combustion intensity can be counteracted with increased recycling of combustion residues.

One embodiment provides that at least one parameter correlating with the burnout is measured, and with reduced burnout the volume flow of the return is increased. This leads to the fact that, in the case of particularly bad combustion of the fuels, a great deal of combustion residues are attributed to the incinerator.

An inventive embodiment is shown in the drawing and will be explained in more detail below.

Figur 1

einen schematischen Aufbau einer Müllverbrennungsanlage mit Rückschubrost und verschiedenen Möglichkeiten einer Primärverbrennungsgasbeeinflussung und einer Sekundärverbrennungsgasbeeinflussung sowie einer Einrichtung, die

auf die Menge der zurückgeführten Verbrennungsrückstände einwirkt.It shows

FIG. 1

a schematic structure of a waste incineration plant with back pressure grate and various possibilities of Primärverbrennungsgasbeeinflussung and a Sekundärverbrennungsgasbeeinflussung and a device that

acting on the amount of recirculated combustion residues.

The firing system 1 shown in the figure has a hopper 2 with subsequent Aufgabeschurre 3 for the task of the fuel 4 on a feed table 5. On the feed table 5 Beschickkolben 6 are provided movable back and forth to the coming of the task chute 3 fuel 4 to a Give up combustion grate 7, on which the combustion of the fuel 4 takes place.

For combustion, it does not matter if it is a sloped or horizontal grate. In the drawing, a push-back grate is shown. However, the method can also be used for example in a fluidized bed combustion plant.

Below the combustion grate 7 there is arranged a device, designated 8 as a whole, for supplying primary combustion gas, which may comprise a plurality of chambers 9 to 13, to which primary combustion gas in the form of ambient air is fed via lines 15 to 19 by means of a blower 14.

The arrangement of the chambers 9 to 13 of the grate is divided into several sub-wind zones, so that the primary combustion gas can be adjusted differently according to the needs on the Feuerungsrost 7. These underwinding zones are also divided in the transverse direction, depending on the width of the firing grate local conditions at different locations regulated primary combustion gas can be supplied.

Above the Feuerungsrost 7 is the furnace 20, which merges in the upper part in a flue 21. At the flue 21 further, not shown aggregates, such as a Abziehkessel and an emission control system on.

The combustion of the fuel 4 takes place mainly on the front part of the Feuerungsrostes 7, above which the flue is 21. In this area, most of the primary combustion gas is supplied through the chambers 9 to 11. On the rear part of the Feuerungsrostes 7 is already burned out fuel, that is, slag, and in this area primary combustion gas is supplied via the chambers 12 and 13 substantially only for cooling the slag 22.

Therefore, the exhaust gas in the rear region 23 of the combustion chamber 20 has an oxygen content which is higher than the front region. The exhaust gas accumulating in the rear region 23 is therefore used as internal recirculation gas for the secondary combustion.

The burned-out parts of the fuel 4 fall as slag 22 into a slag discharge 24 at the end of the combustion grate 7.

From the slag discharge 24, the slag 22, together with the remaining combustion residues, falls into a wet slagger 25, from which it is fed to a separation device 26. The non-sintered or Unmelted residual slag is then added via a line 27 and a conveyor 28 in the task area above the feed table 5 the fuel 4 and thus passes back to the Feuerungsrost. 7

The separation device denoted by 26 only schematically shows the separation of the grate ash into scrap iron, completely sintered inert material granules and non-sintered or molten combustion residues.

In a waste incineration plant, for example, from one ton of garbage with an ash content of 220 kg at the end of the grate 7 320 kg pile ash incurred. These 320 kg of ashes are separated by the separation process indicated by the reference numeral 26 into 30 kg of scrap iron, 190 kg of completely sintered inert granules and 100 kg of non-molten or sintered combustion residues. Part of the boiler ash and filter dust may also be added to the non-sintered or molten combustion residues. This fraction is then re-added via line 27 and conveyor 28 to combustion. In a practical example, 110 kg of the 320 kg of grate ash are returned to the grate firing.

In order not to adversely affect the firing even with a supply of this proportion of slag is worked with a complex control and computer unit 29. This unit 29 calculates measured values of measuring devices and generates control signals to not only blowers control, which act directly on the firing, but also to control the conveyor 28, which varies the recirculated flow rate.

As a rule, the amount of slag 22 accumulating per unit time is no longer equal to the amount of slag added per unit of time. Therefore, a buffer tank 30 is disposed in front of the conveyor 28.

Instead of or in addition to the buffer container 30, the separation process can also be controlled such that, depending on the combustion state, more or less unsintered or molten combustion residues are returned to the grate firing. For example, in a poor combustion, the separation process can be performed so that a higher proportion of non-sintered or molten combustion residues to the fully sintered Inertstoffgranulat, while with particularly good combustion conditions, the qualitative requirements for a fully sintered Inertstoffgranulat be increased, so that a larger amount does not arise sintered or molten combustion residues.

A thermographic camera 31 watches through the flue gases through the surface of the fuel bed 32 and the values recorded thereby are forwarded to the central computer without control unit 29. Designated at 33 and 34 are sensors, several of which are disposed above the surface of the fuel bed layer 32 and which are for measurement of O ₂ , CO and CO ₂ content in the exhaust gas above the fuel bed 32 - ie in the primary combustion zone - are used.

For clarity, all lines that serve to distribute flow media or pass the collected data are shown in solid lines, while lines that carry control commands are shown in phantom.

The control and computer unit receives measured values from the thermographic camera 31, from sensors 33 and 34, and from the conveyor 28 via the current delivery rate to recirculated combustion residues. These data are charged in order to control the conveyor 28 via a line 35, to control the primary air via a line 36 and to control the secondary air via a line 37.

Pure oxygen is conveyed from an air separation plant 38 via a conveying and distributing device 39 on the one hand into a line 40 for admixture with the primary combustion gas and on the other hand into a line 41 for admixing with the secondary combustion gas. Via the line 40 branch lines 42 to 46 are supplied, which are monitored by valves 47 to 51, which in turn are also influenced by the control and computer unit 29.

The supply lines 42 to 46 open into branch lines 15 to 19, which branch off from the line 52 for ambient air and lead to the individual sub-chambers 9 to 13.

The second conduit 41, which emanates from the delivery and distribution device 39, via control valves 53, 54 and lines 56, 57 to the secondary combustion nozzles 58, 59, via which internal recirculation gas is introduced into the combustion chamber. Via branch lines 60, 61, which are monitored via control valves 62, 63, oxygen can be supplied to the secondary combustion gas nozzles 64 and 65, to which secondary combustion gas is supplied via a line 66 from the blower 67. This may comprise either pure ambient air or ambient air mixture with purified exhaust gas.

Via a suction line 68, which leads to the suction fan 69, the recirculation gas is guided to the secondary combustion nozzles 58 and 59, which are arranged at opposite locations of the exhaust train 21.

The Sekundärverbrennungsgasdüsen 64 and 65 are distributed in a larger number on the circumference of the exhaust train 21. Here secondary combustion gas can be fed in the form of ambient air, which is conveyed by means of the blower 67. For this purpose, a suction line 70 is provided, wherein a control element 71 allows the amount of ambient air to be adjusted. Another line 72 connected to the fan 67, which is monitored by a control member 73, serves to draw in purified exhaust gas recirculation gas which is admixed with the ambient air. This purified exhaust gas recirculation gas is sucked through the exhaust gas purification system after flowing through the exhaust gas and has a lower oxygen content compared to the internal recirculation gas. This exhaust gas recirculation gas is primarily for turbulence generation when the amount of exhaust gas in the exhaust train 21 is too low to generate enough turbulence to improve combustion in the secondary region.

The control and computer unit 29 thus controls the entire system and it contains different controllers to act on the individual control devices. For example, while an exceeding of a carbon monoxide limit in the exhaust gas in the control and computer unit 29 leads to a signal to the conveyor 28, with the conveyor 28 is stopped, lead particularly high temperatures, which are detected by the thermographic camera 31, to an increase in performance the conveyor to increase the amount of slag 22 returned to the grate.

In the exemplary embodiment it is shown that the recycled slag is returned to the feed table 6. A variant not shown provides that with a plurality of juxtaposed grates also a special grate for the return can be selected and optionally also during operation of the method between different grates can be selected individually by the return of slag on the combustion controls on different Rusting.

Claims (15)

1. An incineration plant (1) with a firing system, a device for the recirculation of incineration residues (27, 28) into the firing system, a device (33, 34) for measuring at least one parameter of the incineration, a device for influencing the incineration (36, 37) and a device (29) which acts on the quantity of the recirculated incineration residues, characterised in that the device (29) which acts on the quantity of the recirculated incineration residues controls a conveying device (28) which varies the recirculated volume flow.
2. The incineration plant according to claim 1, characterised in that the firing system is constituted as grate firing system and the incineration residues are delivered at the beginning of the grate.
3. The incineration plant according to any one of the preceding claims, characterised in that it comprises a device in order to act on the location of the recirculation of the incineration residues.
4. The incineration plant according to any one of the preceding claims, characterised in that the device for recirculating the incineration residues comprises a driven conveyor.
5. The incineration plant according to any one of the preceding claims, characterised in that the device for measuring parameters of the incineration comprises a camera.
6. The incineration plant according to any one of the preceding claims, characterised in that the device acting on the recirculation of the incineration residues comprises a controller.
7. The incineration plant according to claim 5, characterised in that the device for measuring the incineration acts on the controller.
8. The incineration plant according to claim 5 or 6, characterised in that the controller is a P- controller.
9. The incineration plant according to any one of claims 5 to 7, characterised in that the controller is a PI-, preferably a PID-regulator.
10. The incineration plant according to any one of the preceding claims, characterised in that it comprises a buffer storage for recirculated incineration residues.
11. A method for controlling an incineration plant according to claim 1.
12. The method according to claim 11, characterised in that the volume flow is controlled.
13. The method according to claim 11 or 12, characterised in that a plurality of incineration parameters are measured and are offset for the control of the volume flow.
14. The method according to any one of claims 11 to 13, characterised in that the incineration plant is adjusted for a fuel calorific value and a raised combustion intensity is counteracted with a raised volume flow.
15. The method according to any one of claims 11 to 14, characterised in that at least one parameter correlated with the burnout is measured and the volume flow of the recirculation is increased when there is a reduced burnout.

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