JP2006335956A - Method of recovering surplus offgas in coke dry quenching equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of recovering a surplus off-gas in coke dry quenching equipment capable of effectively recovering energy (sensible heat and combustion heat) of the surplus off-gas in a simple process. <P>SOLUTION: The surplus off-gas containing combustible components such as hydrogen discharged from the coke dry quenching equipment is introduced into a hot air generator 23 in coal drying/preheating equipment without being passed through a dust collector, and is combusted in the hot air generator. The combusted gas is then used as a heating gas for drying and preheating coking coal 21 in a drying/preheating device 20. The off-gas can be used without being passed through a dust collector, because dust in the off-gas is removed finally in a cyclone dust collector 27 and a bug filter dust collecter 28 in the coal drying/preheating equipment. Further, the off-gas can be used without any concern about corrosion of a gas conduit or the like caused by a small amount of hydrogen chloride contained in the off-gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for recovering a gas containing a combustible component such as hydrogen extracted as surplus gas from a circulating cooling gas of a coke dry fire extinguishing facility (hereinafter referred to as “excess offgas” or simply “offgas”).

  The red hot coke extruded from the coke oven was conventionally sprinkled and cooled (wet fire extinguishing). However, in recent years, dry fire extinguishing that can recover the sensible heat of red hot coke and that does not generate dust during fire extinguishing has been adopted. Often done.

  FIG. 2 is a diagram illustrating a schematic configuration of a commonly used coke dry fire extinguishing facility and a cooling gas circulation system. As shown in the figure, the cooling tower 1 of the coke dry fire extinguishing equipment has an upper pre-chamber 2 and a lower cooling chamber 3, and a red hot coke 7 charged into the pre-chamber 2 from the coke charging inlet 4. Is gradually lowered and cooled in the cooling chamber 3 while exchanging heat with a circulating cooling gas mainly composed of an inert gas such as nitrogen, and discharged from the coke discharge port 6 as cooling coke 8.

  The circulating cooling gas is supplied from the lower part of the cooling chamber 3 and rises in a countercurrent contact with the descending coke to become a high-temperature gas of about 800 ° C. It is led out to an annular flue 5 formed in an annular shape on the outer periphery of the chamber 2, passes through the flue 5, dust such as coke powder is removed by a dust remover 9, and then guided to the heat recovery boiler 10. The high-temperature gas generates steam in the heat recovery boiler 10 and the sensible heat is recovered. The temperature is usually lowered to 150 to 200 ° C., and dust is removed by the cyclone 11, and then circulation cooling is performed by the circulation blower 12. The gas is again fed into the cooling chamber 3 as a gas.

  In the cooling chamber 3, the red hot coke is cooled by the circulating cooling gas, and in the process, the amount of the circulating cooling gas is gradually increased by the gas mainly containing hydrogen and carbon monoxide released from the red hot coke. Therefore, one of the following two methods (first and second methods), which are roughly classified as follows, is employed, the amount of the circulating cooling gas is kept substantially constant, and the operation stability is maintained.

  The first method is a method in which an amount corresponding to the increasing gas amount is taken out as a surplus off-gas from the cooling gas circulation system and mixed with blast furnace gas or the like to be used as fuel gas.

  Further, the second method is the method illustrated in FIG. 2, in which air or the like is supplied by the air blowing blower 14 through the air blowing conduit 13 in the annular flue 5 or the like, and the combustible component in the circulating cooling gas is burned. In this method, the temperature of the gas is increased to increase production of steam generated in the heat recovery boiler 10. In this case, the surplus off-gas extracted from the off-gas extraction pipe 15 branched from the circulation gas system contains almost no flammable components such as hydrogen and carbon monoxide. Therefore, after the dust is removed by the dust collector 16, it is diffused into the atmosphere. Is done.

  The first method will be described in detail. The surplus off-gas is a combustible gas containing hydrogen and carbon monoxide and can be used as a fuel for a heating device or the like. Technical development has been made for efficient operation. For example, in Patent Document 1, when semi-coke is introduced into a pre-chamber of a coke dry fire extinguisher and air is baked to produce a product coke, the emitted gas (excess gas) taken out from the circulation gas line of the dry fire extinguisher A method is disclosed in which off-gas) is used as a fuel for a combustion water preheating furnace for the equipment, or is recovered as a fuel gas when the emitted gas has a high calorie.

  In Patent Document 2, when the coke charging inlet of the coke dry fire extinguishing equipment is closed (when not charged) for the purpose of reducing fluctuations in the amount of recovered combustible gas, air or A method is disclosed in which oxygen-containing combustion exhaust gas is injected and the combustion exhaust gas is injected into the lower portion of the coke layer of the pre-chamber when the coke charging inlet is open (at the time of charging).

  In Patent Document 3, in addition to the circulating gas flowing in the cooling chamber and the gas generated in the cooling chamber, gas is taken out from the pre-chamber of the coke dry fire extinguishing equipment, thereby reducing the amount of steam recovered in the boiler of the dry fire extinguishing equipment. A method for obtaining a high-calorie gas with a high hydrogen concentration is disclosed.

  Further, in Patent Document 4, for the purpose of easily removing excess offgas, a discharge means for continuously extracting dust is provided below the bag filter that collects excess offgas, and the boiler and dust removal of the coke dry fire extinguishing equipment are provided. An apparatus is disclosed in which a dust transport pipe is connected to a pipe connecting the container.

  However, in the methods described in Patent Documents 1 to 4, since the recovered gas is widely used as a fuel gas in various heating furnaces and the like, fine dust such as coke powder contained in off-gas is removed. It is necessary, and a dust collector such as a bag filter is required. Also, when using the recovered off-gas as a general-purpose fuel gas, especially when transporting long-distance conduits, it is inevitable that the gas temperature will drop to near the atmospheric temperature along the way. There is also a problem that a trace amount of hydrogen chloride contained in the gas is combined with moisture in the gas and condensed as hydrochloric acid to accelerate corrosion of the gas conduit and combustion equipment. Therefore, these methods are not necessarily advantageous as a method for recovering and using surplus off gas.

  In addition, the installation of a dust collector such as a bag filter that can remove fine dust is intended to increase the production of steam generated in the heat recovery boiler, and then, in the second method in which excess off-gas is released into the atmosphere, the environmental protection Indispensable from the viewpoint.

Japanese Patent Laid-Open No. 7-109459 JP-A-7-242879 JP-A-8-218074 JP-A-10-36850

  The present invention solves the problems in the prior art as described above, and simplifies the energy of surplus off gas discharged from the coke dry fire extinguishing equipment (that is, sensible heat of surplus off gas and combustion heat when it is burned). It is an object of the present invention to provide a method for recovering and utilizing the gas pipe and combustion equipment without causing corrosion of the gas conduit and combustion equipment due to a small amount of hydrogen chloride in the off-gas.

  In order to recover the above-described problem, that is, to collect surplus off gas and use it as a fuel gas, the present inventors need a dust collector such as a bag filter, and use conditions of the recovered gas (for example, over a long distance). In order to solve the problem that corrosion of gas conduits and the like is promoted due to a small amount of hydrogen chloride in the offgas depending on the pipe transport), the energy of surplus offgas, ie, sensible heat and combustion heat, is directly applied. In addition, the study was repeated with the aim of developing a method that can be used effectively.

  As a result, surplus off gas is directly introduced into the hot air generator of the coal drying preheating facility directly through the conduit without passing through the dust collector, and after burning, the combustion gas is heated to dry and preheat the coking coal. As a result, it is found that the energy held by the surplus off-gas can be efficiently recovered without causing the above-mentioned problem (that is, a simple process without requiring a large facility). It came to an eggplant.

The gist of the present invention resides in the surplus off gas recovery method for the coke dry fire extinguishing facility described below.
That is, surplus off gas containing flammable components such as hydrogen discharged from the coke dry fire extinguishing equipment is led to the hot air generator of the coal drying preheating equipment without passing through the dust collector, and after burning, the combustion gas is This is a method for recovering surplus off-gas from a coke dry fire extinguishing facility used as a heating gas for drying and preheating coke raw coal.

  Here, the “surplus off gas” is a gas withdrawn out of the system as surplus gas in order to keep the amount of gas circulating in the cooling gas circulation system of the coke dry fire extinguishing equipment substantially constant. In addition, “contains a combustible component such as hydrogen” means that this surplus off gas includes not only nitrogen for cooling coke but also combustible components such as hydrogen and carbon monoxide generated from red hot coke. .

  In addition, the “coal drying preheating equipment” is used to preheat and dry coke raw coal that has been used in the past in order to increase and equalize the bulk density of coal in the carbonization chamber of the coke oven and reduce the heat of dry distillation. It is a facility for carrying out and generally comprises a dry preheater of the heated gas direct contact type.

  In this surplus off-gas recovery method of the present invention, the surplus off-gas contains 5 to 35% hydrogen and 5 to 20% carbon monoxide in volume% (hereinafter, “%” in the gas composition is “volume%”. Meaning that the amount of heat generated is large and a large amount of heated gas can be obtained.

  According to the method for recovering surplus off gas from a coke dry fire extinguishing facility according to the present invention, the energy (sensible heat and combustion heat) held by the circulating cooling gas discharged from the heat recovery boiler of the coke dry fire extinguishing facility can be obtained by a simple process. It can be recovered and used as a heating gas in a coal drying preheating facility. Since the off gas is directly introduced into the hot air generator of the coal drying preheating facility, it is not necessary to pass through a dust collector, which is required in the conventional off gas recovery method, and a gas conduit or the like caused by a small amount of hydrogen chloride in the off gas. It does not cause corrosion.

  As described above, the method for recovering surplus off-gas from a coke dry fire extinguishing system according to the present invention includes a coal dry preheating system that does not pass surplus off gas containing a combustible component such as hydrogen discharged from the coke dry fire extinguishing system through a dust collector. This is a method of using the combustion gas as a heating gas for drying and preheating coke raw coal after being led to a hot air generator and burning.

  Excess off-gas discharged out of the system contains hydrogen as a combustible component, so it is burned with a hot air generator of a coal drying preheating facility, and the resulting high-temperature combustion gas is used as a heating gas (heating gas) It is used for drying and preheating coking coal.

  FIG. 3 is a diagram illustrating a schematic configuration of a commonly used coal drying preheating facility and a flow of heated gas.

  As shown in FIG. 3, the coal drying preheating facility includes a continuous horizontal fluidized bed type drying preheater 20, a cyclone dust collector 27, a bag filter dust collector 28, an exhaust blower 29, and a hot air generator 23. The raw material coal 21 continuously supplied onto the fluidized bed 20a (eye plate) of the drying preheater 20 forms a fluidized bed on the fluidized bed 20a by the heated gas introduced from the lower part of the drying preheater 20. And dried and preheated in contact with the heated gas and discharged as dry preheated coal 22.

  The heated gas is a gas obtained by diluting a high-temperature combustion gas obtained by burning a fuel gas 24 such as a coke oven gas with combustion air 25 with a hot air generator 23 to a predetermined temperature with dilution air 26. Then, it is supplied from the lower part of the drying preheater 20 toward the fluidized bed 20a.

  The heated gas, which has passed through the fluidized bed 20a and whose temperature has decreased due to heat exchange with the raw material coal 21 in the fluidized state immediately above, is removed from dust such as coal dust by the cyclone dust collector 27 and the bag filter dust collector 28. The air is sucked by the exhaust blower 29, passes through the exhaust pipe 30, and is diffused into the atmosphere.

  When the heating gas having the predetermined temperature is generated by dilution with air, it is inevitable that the oxygen concentration in the heating gas becomes high. Therefore, when it is necessary to avoid alteration such as oxidation of coal due to oxygen contained in the heated gas, a part of the heated gas discharged from the drying preheater 20 is circulated through the exhaust gas circulation pipe 31 to replace air. A method of reducing the oxygen concentration in the heated gas is used as a gas for dilution.

  As shown in FIG. 3, the coal drying preheating equipment includes a cyclone dust collector 27 and a bag filter dust collector 28 for removing dust such as coal powder. Therefore, after surplus off gas is directly introduced into the hot air generator of the coal drying preheating facility, that is, without passing through the dust collector, and burned, the combustion gas can be used as a heating gas.

  In the methods described in Patent Documents 1 to 4 described above, since the range of utilization of recovered gas as fuel gas is various such as various heating furnaces, fine dust such as coke powder contained in off-gas is preliminarily removed from the bag filter. It is necessary to remove with a dust collector such as. However, in the method of the present invention, a facility that uses the collected off-gas is specified, and dust is also removed there. Therefore, it is not necessary to pass the dust collector, which is one of the great advantages of the method of the present invention. .

  In the surplus off-gas recovery method of the present invention, when the temperature of the heated gas to be obtained is too high, dilution air may be mixed so as to reach a predetermined temperature, the temperature of the heated gas is too low, and the amount of gas is If not enough, the amount of heat may be supplemented with a fuel gas such as coke oven gas. An embodiment in which a heating gas obtained by combustion of a fuel gas such as the coke oven gas is mainly used, and a heating gas obtained by combustion of the off-gas is used as appropriate.

  In the surplus off gas recovery method of the present invention, if the surplus off gas contains 5 to 35% hydrogen and 5 to 20% carbon monoxide, the calorific value is large and a high temperature gas is obtained. It is desirable because a large amount of heated gas can be obtained by dilution.

  As described above, the surplus offgas recovery method of the present invention is obtained by introducing surplus offgas extracted from the circulating cooling gas of the coke dry fire extinguishing equipment into the hot air generator of the coal drying preheating equipment for the coke oven and burning it. This method uses a high-temperature combustion gas as a heating gas, and can be applied to an apparatus that uses a hot air generator for generating a heating gas. Therefore, the method of the present invention is not limited to the fluidized bed type coal drying preheating facility illustrated in FIG. 3, and can be applied to, for example, an airflow column type coal drying preheating facility. Further, the off-gas extracted from the circulating cooling gas still has sensible heat after passing through the heat recovery boiler of the coke dry fire extinguishing equipment, and this sensible heat can be used at the same time.

  As described above, according to the surplus off gas recovery method of the present invention, fine dust such as coke powder in the surplus off gas is transferred to the generated heated gas, and finally the cyclone dust collector 27 of the coal drying preheating facility and Since it is removed by the bag filter dust collector 28, the surplus off gas can be directly used as fuel gas in the hot air generator of the coal drying preheating facility without passing through the dust collector.

  Moreover, since the excess off gas extracted out of the system is immediately introduced into the hot air generator of the drying preheating facility by the conduit, the temperature drop is small. Therefore, corrosion of gas conduits and combustion equipment due to a small amount of hydrogen chloride in the off-gas can be normally suppressed without taking special measures. Even when countermeasures are required, it is possible to prevent hydrochloric acid from being condensed and prevent corrosion of gas conduits and the like by taking simple heat retention measures.

  Thus, according to the surplus off gas recovery method of the present invention, the energy (combustion heat and sensible heat) possessed by the off gas can be directly and effectively used by a simple process.

  Below, an example of embodiment of the surplus off gas recovery method of the coke dry fire extinguishing equipment of the present invention is described based on a drawing.

  FIG. 1 is a diagram illustrating a schematic configuration and a gas flow of a coke dry fire extinguishing equipment and a coal dry preheating equipment for coke used when implementing the method for recovering surplus off gas according to the present invention.

  As shown in FIG. 1, the coke dry fire extinguishing equipment has the same configuration as the dry fire extinguishing equipment shown in FIG. 2, and the coal dry preheating equipment for coke has almost the same configuration as the dry preheating equipment shown in FIG. A blower blower 35 is attached instead of the dust collector 16 in FIG. 2, and is different in that it is connected to the hot air generator 23 of the coal drying preheating facility in FIG. 3 through an off-gas conduit 36.

  In order to carry out the surplus off-gas recovery method of the present invention using this apparatus, the surplus off-gas extracted from the circulating cooling gas of the coke dry fire extinguishing equipment through the off-gas extraction pipe 15 is boosted by the blower blower 35 and the off-gas conduit 36 is used. It introduce | transduces into the hot air generator 23 of a coal drying preheating equipment.

  The introduced off gas reacts with the combustion air 25 in the hot air generator 23 and burns, is mixed with the dilution air 26, adjusted to a predetermined temperature, and then sent to the drying preheater 20 as a heating gas. .

  When it is necessary to avoid alteration such as oxidation of coal due to oxygen contained in the heated gas, a circulating exhaust gas (discharged from the drying preheater 20) guided by the exhaust gas circulation pipe 31 instead of the dilution air 26 is used. Part of the heated gas) can be used.

  The heated gas sent to the drying preheater 20 comes into contact with the fluidized coal particles immediately above the fluidized bed 20a to dry and preheat it, and the temperature of the heated gas itself decreases and is discharged from the drying preheater 20. Is done. The discharged heated gas is diffused from the exhaust tube 30 to the atmosphere after the dust is removed by the cyclone dust collector 27 and the bag filter dust collector 28.

  Through this process, it becomes possible to use the combustion heat and sensible heat of the offgas for the dry drying of coal, and compared with the case where no offgas is introduced, the hot air generator 23 of the coal drying preheating facility. Therefore, the amount of fuel gas 24 required can be reduced.

  On the other hand, the off gas is composed of a combustible component such as hydrogen or carbon monoxide and an inert gas such as nitrogen. By introducing the off gas, a part of the dilution air 26 is replaced by the inert gas. No dilution air is required. Therefore, the amount of heated gas does not increase due to the introduction of off-gas. Even when a part of the heated gas discharged from the drying preheater 20 is circulated by the exhaust gas circulation pipe 31 instead of the dilution air 26, the part of the circulating gas is replaced by the inert gas such as nitrogen. There is no change in the amount balance of the heated gas.

  Accordingly, only the blower blower 35 and the offgas conduit 36 must be additionally installed in order to carry out the surplus offgas recovery method of the present invention. Conversely, a bag filter or the like required for conventional offgas recovery is used. There is no need to provide a dust collector, and off-gas can be recovered and used effectively by a simple process. In addition, since the excess offgas extracted through the offgas extraction pipe 15 is immediately introduced into the hot air generator 23 of the drying preheating facility, the temperature drop is small, and corrosion of gas conduits and the like due to a small amount of hydrogen chloride in the offgas is caused. It is not promoted.

  Further, in the example shown in FIG. 1, an air blowing conduit 13 is attached to the annular flue 5, and when this is used, when steam is necessary, air or the like is blown by a blower 14 to circulate cooling gas. It is possible to burn the combustible components therein and increase the production of steam generated in the heat recovery boiler 10 (however, in this case, the offgas contains almost no combustible components). Since the surplus off-gas recovery method of the present invention can be implemented by the simple process as described above, the method of the present invention can be applied, or steam recovery can be prioritized depending on the situation at that time. This is one of the advantages of the method of the present invention.

  According to the method for recovering surplus off gas from a coke dry fire extinguishing system according to the present invention, the energy (combustion heat and sensible heat) possessed by the off gas can be preheated with a simple process without using a dust collector, which has been conventionally required. It can be recovered and used as heated gas in the facility. There is no concern about corrosion of gas pipes and the like caused by a small amount of hydrogen chloride in off-gas. Therefore, it can utilize suitably for the excess offgas collection | recovery of a coke dry fire extinguishing equipment.

It is a figure which illustrates the schematic structure and gas flow of the coke dry-type fire extinguishing equipment and the coal dry preheating equipment for coke used when implementing the surplus off gas recovery method of this invention. It is a figure which illustrates the schematic structure of the coke dry-type fire extinguishing equipment used normally, and the circulation system of a cooling gas. It is a figure which illustrates the schematic structure of the coal drying preheating equipment currently used, and the flow of heating gas.

Explanation of symbols

1: Cooling tower 2: Pre-chamber 3: Cooling chamber 4: Coke charging inlet 5: Circular flue 6: Coke discharge port 7: Red hot coke 8: Cooling coke 9: Dust remover 10: Heat recovery boiler 11: Cyclone 12: Circulating blower 13: Air blowing conduit 14: Air blowing blower 15: Off-gas extraction pipe 16: Dust collector 20: Dry preheater 20a: Fluidized bed 21: Raw coal 22: Dry preheated coal 23: Hot air generator 24: Fuel gas 25: Combustion Air 26: Dilution air 27: Cyclone dust collector 28: Bag filter dust collector 29: Exhaust blower 30: Exhaust tube 31: Exhaust gas circulation line 35: Blower blower 36: Off-gas conduit

Claims (2)

  Excess off gas containing flammable components such as hydrogen discharged from the coke dry fire extinguishing equipment is guided to the hot air generator of the coal drying preheating equipment without passing through the dust collector and burned, and then the combustion gas is used for coke. A surplus off-gas recovery method for coke dry fire extinguishing equipment, characterized in that it is used as a heating gas for drying and preheating raw coal. The method for recovering surplus offgas of coke dry fire extinguishing equipment according to claim 1, wherein the surplus offgas contains 5 to 35% hydrogen and 5 to 20% carbon monoxide by volume.

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