Incineration plant and method for operating an incineration plant

Abstract

The invention relates to a method for combusting solid fuels in an incineration plant (1), wherein the solid fuel is combusted on a combustion surface (2), wherein the combustion surface (2) is cooled with a coolant, characterized in that the heat energy obtained from the combustion surface (2) is used to operate a heat energy conversion unit (5), which is connected to a heat energy distribution network (6).

Description

[0001] The present invention relates to an incineration plant and a method for operating an incineration plant. The incineration plant comprises a combustion chamber, in which a fuel, in particular a fuel of solid material (also referred to as solid fuel) is combusted. For example, waste or biomass as solid material may be combusted in the combustion chamber.

[0002] A combustion grate may be arranged within the combustion chamber for transporting the solid material and the residues of the combusted solid material (i.e. ash and slag) through the combustion chamber. The solid material and the residues of the combusted solid material form a so-called combustion bed during combustion on top of the combustion grate. The top of the combustion grate forms a combustion surface. The combustion grate is usually arranged within a lower section of the combustion chamber, wherein the combustion grate conveys the combustion bed from an end of a combustion material inlet shaft to a slag container downstream of the combustion grate. The solid fuel is usually supplied to the combustion material inlet shaft by a crane as supply device, wherein the preferably vertically aligned material inlet shaft is arranged above the front of the combustion grate.

[0003] The combustion grate is preferably embodied as reciprocating grate, but it is also possible that the combustion grate is embodied in a different way, for example as vibrating grate, traveling grate or roller grate. The combustion grate may comprise multiple grate bars. Primary air as oxidant gas may be supplied from below the combustion grate to the combustion bed arranged on top of the combustion grate, so that the solid material arranged on the combustion grate is combusted with the primary air. For example, a wind box for supplying oxidant gas may be arranged below the combustion grate for embodying the device, with which the oxidant gas is supplied to the combustion grate. The oxidant gas advances from the wind box through or along elements forming the combustion grate to the combustion bed on top of the combustion grate.

[0004] The main process steps on the grate (in the direction of travel of the solid waste) are: drying of the waste or biomass, devolatilization, combustion, afterburning of the solid residues (mainly ash and slags). Additionally, nozzles may be arranged above the combustion grate within the combustion chamber and / or within at least one path, with which nozzle(s) secondary oxidant gas, tertiary oxidant gas for afterburning or an oxygen-poor carrier gas can be provided to the combustion gases.

[0005] It is known to cool the combustion grate and therefore the combustion surface during the combustion process. For example, each grate bar of the combustion grate may have a channel which is flown through by a coolant, such as water or cooling air. The coolant is supplied by a cooling device, which comprises a pump for circulating the water through the combustion grate and through a heat exchanger for cooling the coolant outside the combustion grate.

[0006] It is an object of the present invention to provide a more energy efficient incineration plant and a method for operating an incineration plant more energy efficient.

[0007] A possible solution for this object is given with the incineration plant and the method for operating an incineration plant with the features of the respective independent claim. Further solutions and preferred embodiments are described in the preceding and following description as well as in the subclaims, wherein single features of the preferred embodiments can be combined in a technically meaningful manner. In particular, features disclosed with regard to the incineration plant can be applied to the method, and vice versa.

[0008] The object is in particular solved by an incineration plant which comprises a combustion surface, a cooling device for cooling the combustion surface with a coolant and a heat energy conversion unit, which is operated with the heat energy obtained from the combustion surface.

[0009] The object is also solved by a method for combusting solid fuels in an incineration plant, wherein the solid fuel is burned on a combustion surface, which combustion surface is preferably embodied by the top of a combustion grate, wherein the combustion surface is cooled with a coolant, wherein the heat energy obtained from the combustion surface is used to operate a heat energy conversion unit.

[0010] For example, the heat energy conversion unit is a heat pump, which comprises a condenser, an evaporator, an expansion valve and a compressor, wherein the evaporator is connected to the cooling device for cooling the combustion surface, so that the evaporator is operated with the coolant which is heated by the combustion bed on top of the combustion grate. The condenser of the heat pump is in turn connected to a heat drain, i.e. a (internal) process medium of the incineration plant, such as feedwater, combustion gas, flue gas or recirculation gas or an (external) user, such as heating installation, drinking water treatment or a heat energy distribution network, which might be embodied as a district heating network.

[0011] With other words: The present invention suggests to use a heat energy conversion unit in order to transfer the temperature level of the coolant used for cooling the combustion surface within the combustion chamber to a temperature level of a heat drain, such as a heat distribution network, boiler feedwater or a combustion gas supply, flue gas line, recirculation gas line, heating installation or drinking water installation. This way, the heat energy derived from cooling the combustion grate can be used most efficiently.

[0012] The combustion surface is in particular a horizontally arranged surface, on which the solid fuel and the residues of the solid fuel rest during the combustion process. The combustion surface is in particular formed by the top surface of a combustion grate.

[0013] The elements of the combustion grate, such as grate bars or rolls, are cooled by a coolant. The coolant is preferably circulated by the cooling device. The cooling device preferably comprises a feed line, a return line, a pump and / or a heat exchanger.

[0014] In particular, the combustion grate is connected to the feed line, with which the coolant is provided to the combustion grate. The combustion grate is also connected to the return line, through which the coolant heated up by the combustion process on top of the combustion surface is returned. The feed line and the return line are embodied to a circuit, in which circuit also a heat exchanger for cooling the coolant is arranged. The heat exchanger within the so formed cooling device is preferably embodying part of the condenser of the heat pump.

[0015] Each element of the combustion grate (i.e. grate bar(s) or roll(s), drum(s)) may have a cooling channel through which the coolant flows during operation. The cooling channels of the elements of the combustion grate may be connected in series and / or parallel to the feed line and the return line of the cooling device.

[0016] The combustion grate may have drums in order to embody a roller grate. In this case, the drums of the roller grate are cooled by the coolant.

[0017] Preferably, the grate is a reciprocating grate, which comprises multiple grate bars which are arranged in rows behind each other and which rows reciprocate against each other. Preferably, the grate bars are cooled by the coolant and most preferably by water as coolant.

[0018] At least one further / auxiliary heat source may be connected to the heat energy conversion unit and in particular to the heat pump, wherein the medium supplied from the further / auxiliary heat source to the heat energy conversion unit has a temperature which is below the temperature of the medium supplied to the heat energy distribution network. This way the same heat pump may be used with multiple heat sources to supply energy to the heat energy distribution network.

[0019] The district heating network as heat drain is connected to multiple buildings which use the heat energy provided by the district heating network for heating and / or providing hot water. Alternatively or additionally, the heat energy conversion unit may be connected directly to a heating installation or drinking water installation.

[0020] The heat energy conversion unit may be connected to the boiler feedwater supply, so that the heat energy derived from the combustion surface can be used to preheat the boiler feedwater.

[0021] In a further embodiment the heat energy conversion unit may be connected to the combustion gas supply, so that the primary oxidant gas and / or the secondary oxidant gas can be preheated with the heat energy derived from the combustion surface.

[0022] In a further embodiment the heat energy conversion unit may be connected to the flue gas line, so that the flue gases produced by the combustion process can be heated with the heat energy derived from the combustion surface.

[0023] In a further embodiment the heat energy conversion unit may be connected to the recirculation line, so that recirculation gases (withdrawn flue gases to be recirculated to the combustion process) can be heated with the heat energy derived from the combustion surface.

[0024] The invention and the technical background will now be described with regard to the figure, which exemplary shows an embodiment of the present invention.

[0025] The figure shows an incineration plant 1, which has a combustion chamber 15. A combustion grate 3 is arranged in the lower section of the combustion chamber 15.

[0026] The combustion grate 3 is embodied as reciprocating grate, which comprises multiple grate bars 4. The top of the grate bars 4 forms a combustion surface 2.

[0027] The to be combusted solid material is supplied by a supply device 7 embodied as crane through a combustion material inlet shaft 16 to the front of the combustion grate 3. The to be combusted material and the solid residues of the combusted material are advanced by the combustion grate 3 to a slag container 8.

[0028] A wind box 20 is arranged below the combustion grate 3, wherein a primary air supply 13 embodied as a blower provides primary air to the wind box 20. The primary air advances through or along the grate bars 4 to the solid material arranged on the combustion surface 2.

[0029] The combustion grate 3 is connected to a cooling device 14. The cooling device 14 comprises a feed line 18 and a return line 19, which are to form a circuit, in which circuit a pump 17 is arranged. The circuit of the cooling device 14 also comprises a heat exchanger, which is part of an evaporator 10 of a heat energy conversion unit 5 embodied as heat pump.

[0030] The heat conversion unit 5 further comprises a compressor 12, a condenser 9 and an expansion valve 11 which are connected to form a circuit, which is flown through by a refrigerant.

[0031] The condenser 9 of the heat conversion unit 5 is further connected to a heat energy distribution network 6 which is in particular embodied as a district heating network connected to multiple buildings.

[0032] The heat conversion unit 5 works as a known heat pump, wherein the heat energy derived from the combustion grate 3 is used to evaporate the refrigerant of the heat conversion unit 5 within the evaporator 10. The refrigerant is then compressed by compressor 12 and provided to the condenser 9, which is connected to the heat energy distribution network 6, so that heat energy is provided to the heat energy distribution network 6. The refrigerant is then provided to the expansion valve 11.

[0033] By using the heat energy conversion unit 5, the temperature level of the coolant (i.e. about 80°C within the return line 19 can indirectly be transferred to a temperature level (i.e. more than 100°C or even more than 120°C) of the coolant medium of the heat energy distribution network 6.Reference Signs

[0034] 1Incineration plant 2Combustion surface 3Combustion grate 4Grate bars 5Heat energy conversion unit 6Heat energy distribution network 7Supply device 8Slag container 9Condenser 10Evaporator 11Expansion valve 12Compressor 13Primary air supply 14Cooling device 15Combustion chamber 16Combustion material inlet shaft 17Pump 18Feed line 19Return line 20Wind box

Claims

1. Method for combusting solid fuels in an incineration plant (1), wherein the solid fuel is combusted on a combustion surface (2), wherein the combustion surface (2) is cooled with a coolant, characterized in that the heat energy obtained from the combustion surface (2) is used to operate a heat energy conversion unit (5).

2. Method according to claim 1, wherein the heat from the heat energy conversion unit (5) is supplied at least to one of the following: - a heat energy distribution network (6), - boiler feedwater, - combustion gas, - flue gas, - recirculation gas, - heating installation, - drinking water.

3. The method of claim 1 or 2, wherein the solid fuel advances on top of the combustion surface (2) through a combustion chamber (15).

4. The method according to any one of claims 1 to 3, wherein the combustion surface (2) consists of a plurality of combustion elements and oxidant gas is supplied from below through the combustion surface (2) to the solid fuel.

5. The method according to any one of claims 1 to 4, wherein the solid fuel is waste or biomass.

6. The method according to any one of claims 1 to 5, wherein the coolant is water.

7. Incineration plant (1), comprising a combustion surface (2), a cooling device (14) for cooling the combustion surface (2) with a coolant, and a heat energy conversion unit (5), which is operated with the heat energy obtained from the combustion surface (2).

8. Incineration plant (1) according to claim 7, wherein the heat energy conversion unit (5) is connected at least to one of the following: - to a heat energy distribution network (6), - a feedwater supply, - a combustion gas supply, - a flue gas line, - a recirculation gas line, - a heating installation, - a drinking water installation.

9. Incineration plant (1) according to claim 7 or 8, wherein the combustion surface is formed by a combustion grate (3).

10. Incineration plant (1) according to claim 9, wherein the combustion grate (3) comprises a plurality of grate bars (4).

11. Incineration plant (1) according to any one of claims 7 to 10, wherein the heat energy conversion unit (5) is a heat pump.

12. Incineration plant (1) according to any one of claims 7 to 11, further comprising a supply device (7) for supplying solid fuel to the combustion surface.

13. Incineration plant (1) according to any one of claims 7 to 12, wherein the heat energy distribution network (6) is a district heating network.

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