JP2006348302A - Method and apparatus for converting sludge into fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge fuelizing method and apparatus capable of greatly reducing the amount of fossil fuel used in carbonization treatment for converting sludge into fuel.
SOLUTION: A carbonization furnace 30 for carbonizing sludge to generate pyrolysis gas and carbide, a combustion furnace 40 for burning pyrolysis gas, and a line for supplying combustion exhaust gas generated in the combustion furnace to the carbonization furnace as a heat source. 41, a gas engine 70 for generating at least a part of the electric power required to make sludge into fuel, and a heat exchanger 47 for indirectly heating the gas flowing into the combustion furnace with the exhaust gas of the gas engine. Features.
[Selection] Figure 3

Description

  The present invention relates to a method and an apparatus for fueling sludge generated at a sewage treatment plant or the like.

From the standpoint of reducing CO ₂ emissions, carbon neutral biomass has attracted attention as an alternative energy to fossil fuels. Organic sludge, which is one of the biomass, is mostly landfilled or incinerated, and does not use energy. Therefore, in order to suppress the emission of CO ₂ , that is, to suppress the use of fossil fuels, sewage sludge that can be stably collected is converted into a solid fuel by carbonization to be a fuel for coal-fired power generation. The system is considered.

However, when incinerating sludge, the amount of heat generated from the sludge can be used for incineration heat, so the amount of auxiliary fuel used is small. However, when carbonizing sludge, the amount of auxiliary fuel used is used to leave the heat in the carbide. Will increase. Since fossil fuel is used as the auxiliary fuel, if a large amount of fossil fuel is used to produce an alternative fuel for fossil fuel, it is not possible to substantially reduce CO ₂ emissions. Therefore, for example, as described in JP-A-2002-192196, sludge is heated by a carbonization furnace to generate pyrolysis gas together with carbides, and this pyrolysis gas is supplied to a combustion engine such as a gas turbine or a gas engine. A method for supplying energy to save energy has been proposed.
JP 2002-192196 A (FIG. 1)

  However, in the technique described in the above publication, even if the combustion engine is operated only with the pyrolysis gas generated in the carbonization furnace, the energy necessary for carbonizing the sludge cannot be obtained sufficiently. There is a problem that it is necessary to use a large amount of fossil fuel as auxiliary fuel.

  Therefore, in view of the above problems, the present invention has an object to provide a sludge fuelizing method and apparatus capable of significantly reducing the amount of fossil fuel used in carbonization treatment for converting sludge into fuel. To do.

  In order to achieve the above object, the sludge fueling method according to the present invention includes, as one form thereof, a carbonization step in which sludge is carbonized to produce pyrolysis gas and carbide, and sludge is anaerobically digested. A methane fermentation process for generating digestion gas, combusting the pyrolysis gas and digestion gas, and using combustion exhaust gas generated by the combustion as a heat source for the carbonization treatment. Digested sludge generated in the methane fermentation process can be carbonized in the carbonization process.

  In this way, digestion gas obtained by anaerobic digestion of sludge, which is a biomass resource, is combusted together with pyrolysis gas generated by carbonization treatment of sludge, and the combustion exhaust gas generated by this combustion is used as a heat source for carbonization treatment. As a result, sufficient energy can be obtained for the carbonization of the sludge. Therefore, the amount of fossil fuel used can be greatly reduced. In addition, the digestion gas obtained by anaerobically digesting sludge contains hydrogen sulfide and organosilicon compounds such as siloxane. Therefore, when digestion gas is used as gas engine fuel, it is removed. Therefore, there is a problem in that these adsorption removals are expensive. However, in the present invention, digestion gas is burned in a combustion furnace, so that it can be used without removing hydrogen sulfide, siloxane and the like.

  The sludge fueling method according to the present invention includes, as another form, a carbonization step of carbonizing sludge to produce pyrolysis gas and carbide, and adding the woody biomass to the sludge and performing the carbonization treatment. It is characterized by performing.

  Woody biomass, such as thinned wood and pruned branches, has not been used effectively and its utilization rate is low. However, woody biomass has a very low water content and high calorific value compared to sludge, so carbonization of woody biomass with sludge reduces the amount of auxiliary fuel required for carbonization and reduces fossil. The amount of fuel used can be greatly reduced.

  The sludge fueling method according to the present invention is a combination of the above forms as another form, a carbonization step for carbonizing sludge to produce pyrolysis gas and carbide, and anaerobic digestion of the sludge. And a methane fermentation process for generating digestion gas, and using the combustion gas generated by burning the pyrolysis gas and the digestion gas as a heat source for the carbonization treatment, and sludge in the carbonization process The carbonization treatment is performed by adding system biomass. Thereby, the use of fossil fuel can be reduced to a very small amount.

  The sludge fueling method according to the present invention further includes a power generation step of generating power using a gas engine, and at least a part of the power according to the method uses the power generation of the power generation step and is combusted. The exhaust gas of the gas engine can be used as a heat source for indirectly heating the gas flowing into the furnace, and the combustion exhaust gas generated by the combustion furnace can be used as a heat source for the carbonization treatment. As a result, the amount of auxiliary fuel necessary for the combustion of the pyrolysis gas is greatly reduced, so that the amount of fossil fuel used can be greatly reduced.

  Another aspect of the present invention is a sludge fueling apparatus, and as one form thereof, a carbonization furnace for carbonizing sludge to produce pyrolysis gas and carbide, and a combustion furnace for burning the pyrolysis gas A methane fermentation tank for anaerobically digesting sludge to produce digestion gas and digested sludge, a line for supplying the digestion gas from the methane fermentation tank as fuel to the combustion furnace, and combustion exhaust gas generated in the combustion furnace And a line for supplying the carbonization furnace as a heat source. A dehydrator for dewatering sludge, a drying furnace for drying the dehydrated sludge, a line for supplying sludge dried from the drying furnace to the carbonization furnace, and the dewatering machine for removing the digested sludge from the methane fermentation tank And a line for supplying to the device.

  The sludge fueling apparatus according to the present invention includes, as another form, a carbonization furnace that carbonizes sludge to generate pyrolysis gas and carbide, and a woody biomass feeder that supplies woody biomass to the carbonization furnace. It is characterized by including.

  The sludge fueling apparatus according to the present invention is a combination of the above forms as another form, a carbonization furnace for carbonizing sludge to produce pyrolysis gas and carbide, and the pyrolysis gas. A combustion furnace for burning, a methane fermentation tank for anaerobically digesting sludge to produce digestion gas and digested sludge, a line for supplying the digestion gas from the methane fermentation tank as fuel to the combustion furnace, and the combustion furnace It includes a line for supplying generated combustion exhaust gas to the carbonization furnace as a heat source, and a woody biomass feeder for supplying woody biomass to the carbonization furnace.

  The sludge fueling apparatus according to the present invention includes a gas engine for generating at least a part of electric power applied to the apparatus, and heat for indirectly heating the gas flowing into the combustion furnace with the exhaust gas of the gas engine. And an exchanger.

  As described above, according to the present invention, it is possible to provide a sludge fuelizing method and apparatus that can significantly reduce the amount of fossil fuel used in the carbonization treatment for converting sludge into fuel.

(First embodiment)
FIG. 1 is a schematic view showing an embodiment of a sludge carbonization apparatus according to the present invention, in which a methane fermentation tank is provided. As shown in FIG. 1, the sludge carbonization apparatus includes a dehydrator 10 for dewatering the sewage sludge 1, a drying furnace 20 for directly contacting hot water with the dewatered sewage sludge and drying, and carbonizing the dried sewage sludge. It mainly comprises an externally heated rotary kiln type carbonization furnace 30 to be treated, a combustion furnace 40 that combusts pyrolysis gas generated in the carbonization furnace 30, and a methane fermentation tank 60 that anaerobically digests the sewage sludge 2. .

  The drying furnace 20 is not limited to a method in which hot air is directly contacted, and is not particularly limited as long as it can be dried without burning dehydrated sludge. The carbonization furnace 30 is not limited to an externally heated rotary kiln type, and may be an internal combustion type, a fluidized bed type or a screw type. In FIG. 1, the drying furnace 20 and the carbonization furnace 30 are illustrated as separate facilities, but may be an integrated drying carbonization furnace. The methane fermentation tank 60 is not particularly limited as long as it can decompose organic substances under anaerobic conditions using microorganisms such as methane bacteria to generate digestion gas containing methane. As the methane bacterium, for example, the genus Methanobacterium, the genus Methanobacillus, the genus Methanococcus, and the genus Methanosarcina are preferable.

  The dehydrator 10 and the drying furnace 20 are connected by a line 11, and the line 11 is preferably a pipe that can pump sludge by a pump. The drying furnace 20 and the carbonization furnace 30 are connected by a line 21, and the line 21 is preferably a conveyor that can transport dried sludge. The inside of the carbonization furnace 30 and the combustion furnace 40 are connected by a line 31 that is a pipe for pyrolysis gas generated in the carbonization furnace 30. A cyclone 32 for separating and removing carbides from the pyrolysis gas is connected to the line 31. Is provided. A line 33 and a line 34 for discharging carbide are provided at the bottom of the cyclone 32 and the carbide outlet of the carbonization furnace 30, respectively.

  The combustion furnace 40 and the carbonization furnace 30 external heating section are connected by a line 41, and the carbonization furnace 30 external heating section and the drying furnace 20 are connected by a line 42. These lines 41 and 42 are piping for combustion exhaust gas generated in the combustion furnace 40. The line 42 is provided with a line 43 that is a pipe for exhausting a part of the combustion exhaust gas out of the system. In this line 43, an air preheater 44, a heat exchanger 47, an exhaust gas treatment device 48, a fan 49, and a chimney 50 are provided in this order from the carbonization furnace 30 side.

  The drying furnace 20 and the combustion furnace 40 are connected by a line 22 that is a pipe for exhaust gas generated in the drying furnace 20, and a heat exchanger 47 that performs heat exchange with the line 43 is connected to the line 22. Is provided. The fan 45 that sucks air and the combustion furnace 40 are connected by a line 46 that is an air pipe. The line 46 is provided with an air preheater 44 that exchanges heat with the line 43. ing.

  The methane fermentation tank 60 and the combustion furnace 40 are connected by a line 61, and this line 61 is a digestion gas pipe generated in the methane fermentation tank 60. If necessary, the methane fermentation tank 60 and the dehydrator 10 can be connected by a line 62. The line 62 is preferably a pipe that can pump the digested sludge generated in the methane fermentation tank 60 by a pump. The line 62 is provided with a solid-liquid separator 63 that can separate and remove moisture in the digested sludge.

  According to the above configuration, first, the sewage sludge 1 is introduced into the dehydrator 10 and dehydrated until the water content of the sewage sludge 1 is about 80%. The sludge targeted in the present invention is not limited to sewage sludge as long as it is an organic sludge that can be solidified by carbonization. For example, food sludge, papermaking sludge, bill pit sludge, digested sludge, activated sludge Sludge etc. can also be applied. The dewatered sewage sludge is supplied to the drying furnace 20 via the line 11.

  In the drying furnace 20, the sludge is dried until the moisture of the sludge becomes about 30%. The dried sludge is introduced into the carbonization furnace 30 via the line 21. In the carbonization furnace 30, the sludge is heated to about 300 to 600 ° C. in an oxygen-deficient atmosphere to perform carbonization to generate pyrolysis gas and carbide 6 that is a solid fuel. The pyrolysis gas is introduced into the cyclone 32 through the line 31, and the carbide 6 in the pyrolysis gas is separated and removed and then introduced into the combustion furnace 40. The carbide 6 is recovered from a line 34 provided in the carbonization furnace 30 and a line 33 provided in the cyclone 32.

  Moreover, the sewage sludge 2 is also introduced into the methane fermentation tank 60 to perform anaerobic digestion. Similarly to the sewage sludge 1 introduced into the dehydrator 10, the sewage sludge 2 is not particularly limited to sewage sludge as long as it is organic sludge. By anaerobic digestion, methane is generated from the C component and H component in the sewage sludge 2, and digestion gas containing methane is generated. In addition, the temperature, pH, etc. in the methane fermentation tank 60 are set in an environment where methane bacteria can live. Digestion gas generated in the methane fermentation tank 60 is introduced into the combustion furnace 40 via a line 61. Digested sludge generated in the methane fermentation tank 60 is separated and removed by a solid-liquid separator 63, and then introduced into the dehydrator 10 through a line 62, and is converted into fuel by carbonization as in the case of the sewage sludge 1. Can do. Waste water generated in the solid-liquid separator 63 is processed by a waste water treatment facility (not shown).

  In the combustion furnace 40, in addition to the pyrolysis gas generated in the carbonization furnace 30 and the digestion gas generated in the methane fermentation tank 60, combustion air sucked from the fan 45 and preheated by the air preheater 44, The exhaust gas exhausted from the drying furnace 20 and heated by the heat exchanger 47 is introduced. And it burns at the temperature of about 800-1000 degreeC. The combustion exhaust gas generated by this combustion is introduced into the heat generating portion of the carbonization furnace 30 through the line 41 and used as a heat source for carbonization. Thereby, sufficient energy required for carbonization can be obtained, so that the amount of fossil fuel used can be greatly reduced. However, a slight amount of fossil fuel may be supplied to the combustion furnace 40 as auxiliary fuel in order to stabilize the combustion.

  A part of the combustion exhaust gas discharged from the outer heat section of the carbonization furnace 30 is introduced into the drying furnace 20 via the line 42. Further, the remainder of the combustion exhaust gas is discharged from the chimney 50 through the line 43 to the outside of the system.

The carbide 6 which is the solid fuel thus obtained is obtained by carbonizing the sewage sludge 1 and 2 which are carbon-neutral biomass resources as described above, and this carbonization is also performed by fossil fuel. Instead, fuel derived from biomass resources is used. Therefore, by using this carbide 6 as a power generation fuel in a coal-fired power plant (not shown), the amount of fossil fuel used can be essentially reduced, so that CO ₂ emissions can be reduced. it can.

(Second Embodiment)
FIG. 2 is a schematic view showing an embodiment of the sludge carbonization apparatus according to the present invention, in which a woody biomass feeder is provided. In addition, the same code | symbol is attached | subjected about the structure similar to FIG. 1, and detailed description here is abbreviate | omitted. As shown in FIG. 2, the sludge carbonization apparatus mainly includes a dehydrator 10, a drying furnace 20, a carbonization furnace 30, a combustion furnace 40, and a woody biomass supply machine 80.

  The woody biomass feeder 80 is not particularly limited, but is preferably capable of quantitatively and continuously supplying woody biomass. The woody biomass feeder 80 and the carbonization furnace 30 are connected by a line 81, and this line 81 is preferably a conveyor that can carry woody biomass or a pipe that can be pneumatically transported by a pump. The line 81 is provided with a coarse pulverizer 82 for coarsely pulverizing woody biomass. As the coarse pulverizer 82, for example, a shredder, a hammer crusher, a jaw crusher, or the like is preferable.

  According to the above configuration, first, the sewage sludge 1 is introduced into the dehydrator 10 for dehydration. The dewatered sewage sludge is introduced into the drying furnace 20 and dried. The dried sludge is introduced into the carbonization furnace 30. On the other hand, the woody biomass is introduced into the coarse pulverizer 82 from the woody biomass feeder 80 and coarsely pulverized. As the woody biomass, for example, thinned wood, pruned branches, sawmill waste, building waste, etc. are preferable. The coarsely pulverized woody biomass is introduced into the carbonization furnace 30 via a line 81.

  In the carbonization furnace 30, sewage sludge and woody biomass are carbonized to generate pyrolysis gas and carbide 7 as solid fuel. The addition ratio of the woody biomass is preferably 50 to 150%, more preferably 80 to 120% with respect to the dry weight of the sewage sludge. By making the addition ratio 80 to 120%, the amount of fossil fuel used can be made almost zero. Since woody biomass has a lower water content and higher calorific value than sludge, the energy required for carbonization in the carbonization furnace 30 can be reduced by carbonizing the woody biomass together with the sludge. Furthermore, since woody biomass generates more pyrolysis gas than sludge, the pyrolysis gas is burned in the combustion furnace 40, and the combustion exhaust gas is used as a heat source for the carbonization furnace 30. Enough energy can be obtained for the carbonization treatment. Therefore, the amount of fossil fuel used can be greatly reduced. However, a slight amount of fossil fuel may be supplied to the combustion furnace 40 as auxiliary fuel in order to stabilize the combustion.

The carbide 7 is recovered from a line 34 provided at the carbide outlet of the carbonization furnace 30 and a line 33 provided at the bottom of the cyclone 32. Since the carbide 7 is obtained by carbonizing woody biomass together with sludge, the carbon content is higher and the calorie is higher than that obtained by carbonizing only sludge. Therefore, by using this carbide 7 as a power generation fuel in a coal-fired power plant (not shown), the amount of fossil fuel used can be further reduced, and further CO ₂ emission can be reduced. .

(Third embodiment)
FIG. 3 is a schematic view showing an embodiment of the sludge carbonization apparatus according to the present invention, in which a gas engine is provided. In addition, the same code | symbol is attached | subjected about the structure similar to FIG. 1, and detailed description here is abbreviate | omitted. As shown in FIG. 3, the carbonization apparatus for sludge includes a dehydrator 10, a drying furnace 20, a carbonization furnace 30, a combustion furnace 40, and a gas engine 70 that generates power using city gas (natural gas) as fuel. Consists mainly of.

  The gas engine 70 is not particularly limited as long as the gas engine 70 burns a gaseous fuel such as natural gas and thereby generates power. Although omitted in FIG. 3, distribution pipes for supplying electric power generated by the gas engine 70 to each facility of the present apparatus such as the dehydrator 10, the drying furnace 20, the carbonization furnace 30, and the combustion furnace 40 are provided. Is provided.

  Further, the gas engine 70 is provided with a line 71 which is a pipe for introducing exhaust gas generated in the gas engine 70 between the air preheater 44 and the heat exchanger 47 in the line 43.

  According to the above configuration, first, the sewage sludge 1 is introduced into the dehydrator 10 for dehydration. The dewatered sewage sludge is introduced into the drying furnace 20 and dried. The dried sludge is introduced into the carbonization furnace 30. In the carbonization furnace 30, a pyrolysis gas and a carbide 6 that is a solid fuel are generated by carbonization. The pyrolysis gas is introduced into the combustion furnace 40 after the carbide 6 is separated and removed by the cyclone 32. The carbide 6 is recovered from a line 34 provided in the carbonization furnace 30 and a line 33 provided in the cyclone 32.

  On the other hand, city gas is supplied to the gas engine 70 and power is generated by combustion of the city gas. The electric power thus obtained is supplied to each facility of the present apparatus via a distribution pipe (not shown) and used as all or a part of electric power necessary for sludge fuelization by the present apparatus. Further, the gas engine 70 generates exhaust gas of about 400 ° C. along with power generation. The exhaust gas is introduced into the heat exchanger 47 through the line 71 and is used as a heat source for heating the exhaust gas generated in the drying furnace 20 by the heat exchanger 47 and then discharged from the chimney 50.

  In addition to the pyrolysis gas described above, the combustion furnace 40 introduces combustion air sucked from the fan 45 and preheated by the air preheater 44 and exhaust gas exhausted from the drying furnace 20 and heated by the heat exchanger 47. To do. And it burns at the temperature of about 800-1000 degreeC. The combustion exhaust gas generated by this combustion is introduced into the heat generating portion of the carbonization furnace 30 through the line 41 and used as a heat source for carbonization. Thereby, sufficient energy required for carbonization can be obtained.

As described above, by using the high-temperature exhaust gas generated in the gas engine 70 for combustion of the pyrolysis gas in the combustion furnace 40, the amount of auxiliary fuel required in the combustion furnace 40 can be greatly reduced. Therefore, the amount of fossil fuel used can be greatly reduced. By using the carbide 6 obtained in this way as a fuel for power generation in a coal-fired power plant (not shown), the amount of fossil fuel used can be essentially reduced, thus reducing CO ₂ emissions. Can be planned.

(Fourth embodiment)
Each embodiment of FIG. 1 to FIG. 3 can be combined with each other, and carbonization of sludge having a methane fermentation tank and a woody biomass feeder, and carbonization of sludge having a methane fermentation tank and a gas engine. It can also be set as the carbonization apparatus of the sludge provided with the processing apparatus, the woody biomass supply machine, and the gas engine, and the carbonization apparatus of the sludge provided with the methane fermentation tank, the woody biomass supply machine, and the gas engine. Thereby, the use of fossil fuel can be reduced to a very small amount.

It is one Embodiment of the sludge carbonization apparatus which concerns on this invention, Comprising: It is a schematic diagram which shows the case where a methane fermentation tank is provided. It is one Embodiment of the sludge carbonization processing apparatus which concerns on this invention, Comprising: It is a schematic diagram which shows the case where a woody biomass supply machine is provided. It is one Embodiment of the carbonization processing apparatus of the sludge which concerns on this invention, Comprising: It is a schematic diagram which shows the case where a gas engine is provided.

Explanation of symbols

1, 2 Sewage sludge 6, 7 Carbide 10 Dehydrator 20 Drying furnace 30 Carbonization furnace 32 Cyclone 40 Combustion furnace 44 Air preheater 45, 49, 72 Fan 47 Heat exchanger 48 Exhaust gas treatment device 50 Chimney 60 Methane fermentation tank 63 Solid liquid Separator 70 Gas engine 80 Woody biomass feeder 82 Rough crusher

Claims (8)

  A method for converting sludge into fuel, comprising a carbonization step of carbonizing sludge to produce pyrolysis gas and carbide, combusting the pyrolysis gas in a combustion furnace, and using combustion exhaust gas generated by the combustion as a heat source for the carbonization In addition, the method further includes a power generation step of generating power using a gas engine, wherein at least a part of the electric power according to the method uses the power generation of the power generation step and indirectly heats the gas flowing into the combustion furnace As a method for making sludge into fuel, the exhaust gas from the gas engine is used.   The sludge fuel according to claim 1, further comprising a methane fermentation step for anaerobically digesting sludge to generate digestion gas, combusting the digestion gas, and using combustion exhaust gas generated by the combustion as a heat source for the carbonization treatment. Method.   The method for converting sludge into fuel according to claim 2, wherein the digested sludge produced in the methane fermentation step is carbonized in the carbonization step.   The method for converting sludge into fuel according to any one of claims 1 to 3, wherein the carbonization is performed by adding woody biomass to the sludge.   A carbonization furnace for carbonizing sludge to produce pyrolysis gas and carbide; a combustion furnace for burning the pyrolysis gas; and a line for supplying combustion exhaust gas generated in the combustion furnace to the carbonization furnace as a heat source. A sludge fueling apparatus comprising: a gas engine for generating at least part of the power applied to the apparatus; and a heat exchanger for indirectly heating the gas flowing into the combustion furnace with the exhaust gas of the gas engine. Furthermore, the sludge fueling apparatus characterized by including.   The sludge according to claim 5, further comprising: a methane fermentation tank that anaerobically digests sludge to produce digestion gas and digested sludge; and a line that supplies the digestion gas from the methane fermentation tank as fuel to the combustion furnace. Fueling device.   A dehydrator for dewatering sludge, a drying furnace for drying the dewatered sludge, a line for supplying sludge dried from the drying furnace to the carbonization furnace, and supplying the digested sludge to the dehydrator from the methane fermentation tank The sludge fueling apparatus according to claim 6, further comprising:   The sludge fuelizing apparatus according to any one of claims 5 to 7, further comprising a woody biomass feeder for feeding woody biomass to the carbonization furnace.

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