JP2004217834A - Method for recovering gas in treatment of biomass in cdq - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering a combustible gas which is useable for other application as a fuel replacing petroleum or LNG and a chemical raw material without utilization by combustion of a combustible gas which can carry out only low-efficiency heat recovery when thermally decomposing biomass such as wood or sewage sludge cake and effectively utilizing the combustible gas produced by the thermal decomposition in CDQ (a coke dry quencher). <P>SOLUTION: The method for recovering the gas in treatment of biomass in CDQ comprises introducing air for partial combustion for burning a part of the combustible gas produced by thermal decomposition of biomass into a pre-chamber 4 in order to keep the temperature of the pre-chamber to a temperature suitable for thermal decomposition of biomass, when charging biomass such as wood or sewage sludge cake into the pre-chamber 4 in the upper part of a cooling chamber 5 in CDQ and carrying out thermal decomposition of the biomass by utilizing sensible heat of red heat coke 1 and using the combustible gas produced by thermal decomposition as a cooling gas and recovering excess combustible gas as a fuel gas. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for recovering combustible gas at the time of treating biomass of wood, sewage sludge cake, and the like in a coke dry quencher (hereinafter, referred to as CDQ) in a coke dry quencher.
[0002]
[Prior art]
In the CDQ, red hot coke is charged into the pre-chamber of the CDQ main body, lowered into the cooling chamber, and the inert gas, which is a cooling gas introduced from the lower part of the cooling chamber, exchanges heat with the red hot coke to recover the heat of the red hot coke. After introducing the inert gas into the boiler through the annular duct and the flue to exchange heat, the inert gas is again pumped to the cooling chamber by the circulation blower and circulated. The steam obtained by heat exchange in the boiler is sent to a generator and collected as electric energy.
[0003]
As a method of treating biomass using CDQ, a method of loading biomass (sewage sludge cake) into a pre-chamber of a CDQ main body and performing a thermal decomposition treatment is disclosed in Patent Document 1, for example.
[0004]
The thermal decomposition treatment method disclosed in Patent Document 1 uses the sensible heat of red hot coke to thermally decompose organic components of sewage sludge cake in a pre-chamber, and converts water and red hot coke in sewage sludge cake to aqueous. by gasification reaction, CO, leads to the flue as a combustible gas such as H _2, is intended for introducing combustion air in the flue combustion.
[0005]
However, ash contained in biomass such as wood and sewage sludge cake contains more alkali metal components such as Na and K than ash of coal, and has a low melting point and high adhesion. Therefore, when combustible gas containing biomass ash generated from biomass such as wood and sewage sludge cake is burned, the combustion temperature is restricted (usually 900 ° C.) in order to avoid melting of biomass ash. In other words, when combustible gas containing biomass ash is burned at high temperatures, the biomass ash melts, causing stickiness and adverse effects on bricks due to adhesion to the furnace wall and troubles that lower thermal efficiency by adhering to the surface of the heat transfer tube of the boiler. Occurs. Therefore, combustion must be performed at a combustion temperature of about 900 ° C., and as a result, only low-efficiency heat recovery can be performed.
[0006]
On the other hand, biomass such as wood and sewage sludge cake containing a large amount of flammable volatiles is thermally decomposed by CDQ, and as a method of using the flammable gas generated by the pyrolysis, a large amount of flammable gas generated by the pyrolysis is used. If it can be recovered as a fuel gas, it can be considered to be used for other purposes as a fuel or chemical raw material to replace petroleum and LNG. Furthermore, if the biomass ash is removed after recovering the combustible gas, high-temperature combustion can be performed without causing the ash melting problem, and highly efficient heat recovery can be performed.
[0007]
A method of recovering a surplus of cooling gas containing combustible gas in CDQ is described in Patent Document 2, for example, but the CDQ described in Patent Document 2 does not process biomass. Since biomass contains ash as described above, special management such as thermal decomposition temperature is required.
[0008]
[Patent Document 1]
Japanese Patent No. 2789988
[Patent Document 2]
JP 2001-200257 A
[Problems to be solved by the invention]
The problem to be solved by the present invention is to thermally decompose biomass such as wood and sewage sludge cake in CDQ, and to effectively use the combustible gas generated by the pyrolysis. It is an object of the present invention to provide a method for recovering combustible gas that can be used for other purposes as a fuel or chemical raw material that substitutes for petroleum or LNG, instead of using it.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method for recovering combustible gas during biomass treatment in a CDQ according to the present invention comprises charging a red hot coke into a cooling chamber of a CDQ main body, introducing a cooling gas from a lower part of the cooling chamber, And the red hot coke are brought into contact in the cooling chamber to raise the temperature of the cooling gas, and the heated gas is transported from the cooling chamber to the boiler via the annular duct and the flue to recover the heat of the heated gas and cool it. In the CDQ, which is converted into a gas and circulated again and reused as a cooling gas introduced into the lower part of the cooling chamber, biomass such as wood and sewage sludge cake is charged into a pre-chamber at the upper part of the cooling chamber, and the biomass is converted into red hot coke. Thermal decomposition using sensible heat, while using the combustible gas generated by the pyrolysis as the cooling gas, and recovering excess combustible gas as a fuel gas, Les chamber to a temperature suitable for the pyrolysis of biomass, and introducing a partial combustion air for burning a portion of the combustible gas produced by the pyrolysis of biomass in the pre-chamber.
[0012]
The amount of partial combustion air introduced into the pre-chamber is controlled by the pre-chamber temperature.
[0013]
Further, water and / or steam may be introduced into the pre-chamber. The water and / or steam is used for controlling the pre-chamber temperature, and also has a function of causing a water gasification reaction with biomass-fixed carbon and red-hot coke to increase the amount of combustible gas generated.
[0014]
Further, air for adjusting the gas calories of the recovered fuel gas may be introduced into the annular duct and / or the flue.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples shown in the drawings.
[0016]
Example 1
FIG. 1 is a configuration diagram of a CDQ that implements the combustible gas recovery method according to the present invention. In the CDQ, the red hot coke 1 is introduced into the prechamber 4 after opening the lid 3a from the coke charging inlet 3 on the upper part of the CDQ main body 2, lowered into the cooling chamber 5, and supplied from the cooling gas pipe 14 below the cooling chamber 5. The inert gas as a cooling gas to be exchanged with the red hot coke 1 is heat-exchanged, and the high-temperature inert gas recovered from the heat of the red hot coke 1 is introduced into the boiler 13 from the annular duct 6 via the flue 10 to perform heat exchange. After that, the circulating blower 15 feeds and circulates the pressure to the lower part of the cooling chamber 5. The cooled coke is discharged from the coke discharge port 7 at the bottom of the CDQ main body 2.
[0017]
The pre-chamber 4 is provided with a biomass loading inlet 8 for wood, sewage sludge cake and the like, and an air inlet 9 for partial combustion. Among the biomass, the wood is roughly pulverized to about 10 to 50 mm by a hammer crusher or the like (not shown) and is continuously charged from the biomass inlet 8. The flue 10 is provided with a collision wall 11 and a dust catcher 12 for collecting dust separated by the collision wall 11. A cyclone 16 for dust separation is provided in a pipe between the boiler 13 and the circulation blower 15. Further, a gas recovery pipe 17 for recovering excess combustible gas (cooling gas) is provided on the outlet side of the circulation blower 15.
[0018]
In CDQ having the above configuration, the biomass charged into the pre-chamber 4 is thermally decomposed by the sensible heat of the red hot coke 1, CO, combustible gases such as H ₂ is generated. However, latent heat of evaporation of water contained in biomass, heat absorption in the water gasification reaction of evaporated water with red hot coke 1, sensible heat of generated gas, etc. are deprived from sensible heat of red hot coke 1, resulting in The temperature of the pre-chamber 4 decreases.
[0019]
On the other hand, the composition of the gas generated by pyrolysis of biomass such as wood and sewage sludge is determined by its pyrolysis temperature. When thermally decomposed at a low temperature of about 700 to 800 ° C., liquid components such as tar are generated. The liquid component such as tar is a gas at a high temperature, but condenses as a liquid when the temperature is lowered to about 400 ° C. For this reason, when a liquid component such as tar is generated, it is condensed and adheres to the heat transfer tube of the boiler 13 or the like, which is a factor of deteriorating thermal efficiency. Further, when pyrolysis is performed at a lower temperature, the amount of flammable gas originally generated is reduced, and the solid is discharged together with coke from the coke outlet 7 as a solid, or collected as dust in the dust catcher 12 or the cyclone 16. And cannot be used effectively.
[0020]
Therefore, in order to charge a large amount of biomass into the pre-chamber 4 of the CDQ main body 2 and thermally decompose it at high efficiency without causing any trouble, it is necessary to keep the temperature of the pre-chamber 4 constant. Further, a decrease in the temperature of the pre-chamber 4 also leads to a decrease in the amount of heat recovered in the boiler 13 and reduces the amount of main steam. A decrease in the amount of main steam also leads to a decrease in power generation efficiency.
[0021]
Therefore, in the present invention, air is introduced into the pre-chamber 4 from the air inlet 9 for partial combustion. The introduced partial combustion air reacts with and burns a part of the combustible gas generated from the biomass, prevents the temperature of the pre-chamber 4 from dropping, and efficiently converts the biomass without generating liquid components such as tar. Maintain the temperature at which pyrolysis can be performed (about 900 ° C). In addition, since the temperature of the pre-chamber 4 is not decreased, it is possible to avoid a decrease in the amount of heat recovered by the boiler 13, and does not cause a decrease in power generation efficiency.
[0022]
The combustible gas generated in the pre-chamber 4 is mixed with the high-temperature coke cooling gas that has been introduced from the lower part of the cooling chamber 5 and exchanged heat with the red-hot coke 1, is guided from the annular duct 6 to the flue 10, and is passed through the boiler 13. Heat exchange and cooling. The mixed gas of the coke cooling gas and the combustible gas cooled by the boiler 13 is pressurized by the circulation blower 15 and re-introduced into the cooling chamber 5 as the cooling gas of the red hot coke 1. By this circulation, the coke cooling gas becomes combustible gas, and surplus combustible gas unnecessary for cooling red hot coke is recovered as a fuel gas from the gas recovery pipe 17, and is used as a fuel or chemical raw material for replacing petroleum and LNG. Effectively used for applications.
[0023]
Example 2
FIG. 2 is a configuration diagram of a CDQ that implements another flammable gas recovery method according to the present invention. The same components as those of the CDQ shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0024]
In this embodiment, in order to keep the temperature of the pre-chamber 4 constant, the amount of the partial combustion air introduced into the pre-chamber 4 is controlled by the temperature of the pre-chamber 4. Specifically, the controller 19 controls the introduction pipe of the partial combustion air so that the temperature of the pre-chamber 4 measured by the temperature sensor 18 provided in the pre-chamber 4 becomes a predetermined temperature (about 900 ° C.). The opening / closing degree of the flow control valve 20 provided in the above is adjusted.
[0025]
Example 3
FIG. 3 is a configuration diagram of a CDQ that implements another flammable gas recovery method according to the present invention. The same components as those of the CDQ shown in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted.
[0026]
In the previous embodiment 2, the amount of the partial combustion air introduced into the pre-chamber 4 is controlled in order to keep the temperature of the pre-chamber 4 constant. However, in the present embodiment, the amount of the partial combustion air varies. Instead, water and / or steam is introduced from the water and / or steam inlet 21 provided in the pre-chamber 4 to control the temperature of the pre-chamber 4. Specifically, the controller 22 introduces water and / or steam so that the temperature of the pre-chamber 4 measured by the temperature sensor 18 provided in the pre-chamber 4 becomes a predetermined temperature (about 900 ° C.). The degree of opening and closing of the flow control valve 23 provided in the pipe is adjusted.
[0027]
According to the present embodiment, a combustible gas (H ₂ , CO) is generated by a water gasification reaction between the water and / or steam introduced into the pre-chamber 4 and the biomass-fixed carbon or the red-hot coke 1, and the combustible gas is generated. Can be increased.
[0028]
Example 4
FIG. 4 is a configuration diagram of a CDQ that implements another flammable gas recovery method according to the present invention. The same components as those of the CDQ shown in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted.
[0029]
In the present embodiment, an air inlet 24 is provided in the flue 10 and air for adjusting gas calories is introduced therefrom.
[0030]
When biomass is thermally decomposed in the pre-chamber 4 to generate a combustible gas, the amount and composition of the gas generated by the pyrolysis fluctuate depending on the temperature conditions of the pre-chamber 4 and the input of the red-hot coke 1. Controlling the gas to be recovered as fuel gas to a constant calorie is easier to use effectively, so by burning the fluctuating calorie with the air introduced into the flue 10, the calorie of the gas to be recovered as fuel gas is kept constant. I try to keep it. The amount of heat of the fluctuating calories burned by the air is converted into heat by the combustion, recovered by the boiler 13, and used effectively.
[0031]
The air amount is controlled by opening and closing a flow control valve 27 provided on an air introduction pipe by a controller 26 so that the gas calorie measured by a gas calorie meter 25 provided on the outlet side of the cyclone 16 becomes a predetermined calorie. This is done by adjusting the degree.
[0032]
In this embodiment, the air for adjusting the gas calorie is introduced into the flue 10, but may be introduced from the annular duct 6, or may be introduced from both the flue 10 and the annular duct 6. good.
[0033]
【The invention's effect】
According to the present invention, the temperature of the pre-chamber becomes a temperature suitable for the thermal decomposition of biomass, so that the thermal decomposition of the biomass is performed efficiently, without causing equipment troubles and a decrease in the heat recovery efficiency, without causing the combustion of the flammable gas. Recovery can be performed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a CDQ for implementing a combustible gas recovery method according to the present invention.
FIG. 2 is a configuration diagram of a CDQ that implements another flammable gas recovery method according to the present invention.
FIG. 3 is a configuration diagram of a CDQ that implements another flammable gas recovery method according to the present invention.
FIG. 4 is a configuration diagram of a CDQ that implements another flammable gas recovery method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Red hot coke 2 CDQ main body 3 Coke inlet 3a Coke inlet lid 4 Pre-chamber 5 Cooling room 6 Annular duct 7 Coke outlet 8 Biomass inlet 9 Partial combustion air inlet 9 Combustion air inlet 10 Flue 11 Collision wall 12 Dust catcher 13 Boiler 14 Cooling gas pipe 15 Circulation blower 16 Cyclone 17 Gas recovery pipe 18 Temperature sensor 19 Controller 20 Flow control valve 21 Water and / or steam inlet 22 Controller 23 Flow control valve 24 Air inlet 25 Gas calorie meter 26 Controller 27 Flow control valve

Claims (4)

The red hot coke is charged into the cooling chamber of the main body of the CDQ, a cooling gas is introduced from the lower part of the cooling chamber, and the cooling gas is brought into contact with the red hot coke in the cooling chamber to raise the temperature of the cooling gas. In the CDQ which is conveyed from the cooling chamber to the boiler via the annular duct and the flue to recover the heat of the heat-raising gas to form a cooling gas, and is circulated again and reused as the cooling gas introduced into the lower part of the cooling chamber, Wood, biomass such as sewage sludge cake is charged into the pre-chamber above the cooling chamber, and this biomass is thermally decomposed using the sensible heat of red-hot coke, and the combustible gas generated by the pyrolysis is used as the cooling gas. And recovering excess combustible gas as fuel gas,
A biomass in a CDQ, wherein partial combustion air for burning a part of combustible gas generated by biomass pyrolysis is introduced into the prechamber in order to bring the prechamber to a temperature suitable for biomass pyrolysis. Combustible gas recovery method during treatment. The method according to claim 1, wherein the amount of the partial combustion air introduced into the pre-chamber is controlled by a pre-chamber temperature. 3. The method of claim 1, wherein water and / or steam is introduced into the pre-chamber. The flammable fuel for treating biomass in the CDQ according to any one of claims 1 to 3, wherein air for adjusting gas calories of the fuel gas to be recovered is introduced into the annular duct and / or the flue. Gas recovery method.

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