JP2007063539A - System and method for purifying gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system and a method for purifying a gas, wherein such a gasified gas formed from an organic waste and a biomass fuel, or the like can surely be cleaned with the use of an easy processing system. <P>SOLUTION: The gas purifying system comprises low-temperature dust-collecting equipment 20 which removes a dust in the gasified gas generated from a gasification apparatus 18, and gas-cleaning equipment A which cleans the gasified gas removed of the dust with the low-temperature dust-collecting equipment 20. At the upstream side of the low-temperature dust-collecting equipment 20, there is provided a mechanism to throw therein an adsorbent adsorbable harmful materials in the gasified gas flowing into the equipment 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas purification system and a gas purification method, and more particularly, a low-temperature dust collection facility that removes gasification gas generated from a gasification facility, and a gas cleaning system that cleans the gasification gas removed by the low-temperature dust collection facility. The present invention relates to a gas purification system having a facility and a gas purification method.

  Gasification technology has attracted attention as a technology for converting energy efficiently from waste (organic waste) containing organic matter such as wood chips and sewage sludge and biomass fuel. It is possible to generate power by burning the gas generated by gasification in an internal combustion engine such as a gas engine or a gas turbine, and the power generation efficiency is to directly burn fuel to generate steam. It has a feature of higher efficiency by a boiler power generation system that generates power by using a power source (Patent Document 1).

  However, the gas generated from the gasifier contains harmful corrosive substances and pollutants such as dust, tar, ammonia, dioxins, heavy metals, and hydrogen chloride. Problems such as clogging and corrosion occur.

  Therefore, the gasification gas generated from the gasification furnace is detoxified as shown in FIG. That is, the generated gasification gas is collected by a low-temperature dust collection facility such as a bag filter, and after dust in the gasification gas is removed, the gasification gas is introduced into the gas cleaning facility A0, Wet cleaning is performed to remove acidic components. The gas cleaning equipment A0 includes a temperature reducing tower 1, an acid cleaning tower 2, an alkali cleaning tower 3, and the like. The gasified gas is first exposed to a temperature reducing tower 1 having a cooling water shower device, and then sent to an acid cleaning tower 2 where it is neutralized with an acid to remove ammonia, tar and the like in the gasified gas. Further, acid components such as hydrogen chloride remaining in the gasification gas sent to the alkali cleaning tower 3 are neutralized and removed, and the purified gasification gas is used as a gas engine or gas turbine gas. It is sent to equipment and used. Here, P is a circulation pump, T is a cooling tower for generating cooling water, and secondary treatment water is appropriately supplied to the acid cleaning tower 2 and the alkali cleaning tower 3.

  Cleaning equipment wastewater generated from the temperature reducing tower 1, acid cleaning tower 2, and alkali cleaning tower 3 constituting the gas cleaning equipment A0 is temporarily stored in the storage tank 4, and then sent to the pH adjustment tank 6 by the transfer pump 5. Here, an acid or alkaline agent is administered to adjust the pH. Thereafter, the waste water is sent to a coagulation tank 7 where a coagulant is added, and coagulation sedimentation processing is performed to remove suspended substances and the like.

  The waste water from which suspended substances have been removed is sent to a sedimentation tank 8 for further solid-liquid separation, and then sent to an activated sludge treatment facility or a biological denitrification facility, where organic matter and nitrogen compounds (ammonia) ) And are decomposed. Here again, the pH is adjusted again in the pH adjusting tank 9, sent to the precipitation tank 10 and separated into solid and liquid, and then decomposed in the activated sludge treatment equipment B.

  The activated sludge treatment facility B includes an anaerobic tank and an aerobic tank and a membrane separation tank, and has a mechanism for appropriately adding methanol as an organic carbon source for denitrifying bacteria. Here, MP is a main circulation pump, R is a blower for supplying air to an aerobic tank, P1 is a sludge return pump for returning sludge to be treated again, and P2 is a part of sludge for pH. This is a surplus sludge return pump that returns to the adjustment tank 9.

  The wastewater biologically treated by the activated sludge treatment facility B is sent to the activated carbon adsorption raw water tank 11 by the transfer pump P3, and then fed to the activated carbon adsorption tower 12 by the activated carbon adsorption raw water pump P4 to be biologically treated. Depending on the type, dioxins and heavy metals remaining without being removed are adsorbed and removed. The cleaned wastewater is once stored in the treatment tank 17 and then discharged by the treated water pump P5.

  The sludge generated in the settling tanks 8 and 10 is appropriately extracted and stored in the sludge storage tank 13, and then fed to the dehydrator 14 by the sludge transfer pump P6. The solid portion is conveyed by the screw conveyor 15 or the like. After being discharged out of the field, the liquid portion is once stored in the drainage tank 16, and then sent to the pH adjustment tank 6 by the drainage return pump P7 and reused.

JP 2003-65084 A

  However, the above-mentioned prior art has a complicated process, a wide variety of processes, a large amount of necessary equipment, a small equipment cost and processing cost, and there is a strong demand for the emergence of a processing system that can be reliably processed by a simpler processing system. Yes.

  Therefore, in view of the above-described problems of the prior art, an object of the present invention is to provide a gas purification system that can reliably purify gasified gas generated from organic waste or biomass fuel by a simpler processing system. And providing a gas purification method.

  The above-mentioned subject is achieved by the invention described in each claim. That is, the characteristic configuration of the gas purification system according to the present invention includes a low-temperature dust collection facility that removes gasification gas generated from the gasification facility, and a gas cleaning facility that cleans the gasification gas removed by the low-temperature dust collection facility. And a mechanism for introducing an adsorbent capable of adsorbing harmful substances in the gasified gas introduced into the low-temperature dust collection equipment is provided upstream of the low-temperature dust collection equipment. It is in.

  According to this configuration, before the gasified gas is introduced into the low-temperature dust collection facility, an adsorbent capable of adsorbing the harmful substances in the gasified gas is introduced in advance, so that most of the harmful substances are removed. (Substantially the only harmful substance remaining is ammonia), the load on the gas cleaning equipment on the downstream side can be significantly reduced, and the scale of the gas cleaning equipment can be remarkably simplified compared to the processing system of the prior art.

  As a result, it was possible to provide a gas purification system and a gas purification method that can reliably purify gasified gas generated from organic waste or biomass fuel by a simpler processing system.

  A pH adjusting tank for adjusting pH of waste water generated from the gas cleaning equipment is provided, and a distillation tower for distilling the waste water adjusted by the pH adjusting tank is provided, and the can liquid of the distillation tower is neutralized. It is preferable to provide a mixed neutralization tank that can be discharged.

  According to this configuration, it is possible to reliably generate harmless wastewater from which harmful substances are removed by separating residual harmful substances in the wastewater with a simple configuration.

  The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. It is preferable that waste water is distilled by the distillation tower, and the can liquid of the distillation tower is used as circulating water for the alkali washing tower, and then neutralized and discharged by the mixed neutralization tank. .

  According to this configuration, the circulating water used in the temperature-decreasing tower and the acid washing tower can be combined into waste water, and harmful substances can be effectively removed in the downstream distillation tower and discharged as harmless waste water.

  In addition to a pH adjustment tank that adjusts the pH of the wastewater generated from the gas cleaning equipment, a diffusion tower that supplies the carrier gas to disperse the wastewater adjusted by the pH adjustment tank is provided. It is preferable to provide a mixed neutralization tank that can neutralize and discharge the can liquid.

  According to this configuration, since the diffusion tower is used instead of the distillation tower, the purification system can be made inexpensive and the can liquid of the diffusion tower can be cleaned and discharged.

  The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. The waste water may be diffused by the stripping tower, and the can liquid of the stripping tower may be used as circulating water for the alkali cleaning tower, and then neutralized and discharged by the mixing neutralization tank. .

  It is preferable to provide a diffusion tower for supplying a carrier gas to dissipate waste water generated from the gas cleaning equipment, and to allow the can liquid of the diffusion tower to be discharged.

  According to this configuration, since the diffusion tower is used instead of the distillation tower, the refining system can be made inexpensive equipment, and the can liquid of the diffusion tower does not contain the pollutant, so it can be discharged without any trouble. it can.

  The gas cleaning equipment has a temperature reduction tower and an absorption tower, and the mixed waste water generated from the temperature reduction tower and the absorption tower is supplied to the diffusion tower to be diffused, and the diffusion It is preferable that part of the can liquid in the tower is discharged and used as an absorbent in the absorption tower.

  According to this configuration, since no chemicals are used in the gas cleaning facility, the pH adjustment process and the like can be reduced, and no supplemental water is required, so only the moisture condensate in the gasification gas is out of the system. As a result, the equipment configuration can be simplified.

  It is preferable that the adsorbent is any one of activated carbon, slaked lime, sodium-based chemicals, or a mixture thereof.

  According to this configuration, these adsorbents can effectively adsorb and remove harmful substances such as dioxins, heavy metals, and tar that may be contained in the gasification gas. The load can be reliably reduced.

  It is preferable that the ammonia gas distilled or diffused by the distillation tower or the stripping tower and concentrated to be supplied to a denitration facility disposed at a subsequent stage of the gasification facility or the gas utilization facility.

  According to this configuration, since the ammonia gas taken out from the distillation tower or the stripping tower has a high concentration, it can be effectively used for denitration equipment and the like, and the overall processing cost can be reduced.

  Further, the characteristic configuration of the gas purification method according to the present invention is that the gasification gas generated from the gasification facility is removed by a low-temperature dust collection facility, and the gasification gas removed by the low-temperature dust collection facility is cleaned by the gas cleaning facility. In this method, an adsorbent capable of adsorbing harmful substances in the gasified gas introduced into the low-temperature dust collection equipment is introduced upstream of the low-temperature dust collection equipment.

  According to this configuration, it is possible to provide a gas purification method that can reliably purify gasified gas generated from organic waste or biomass fuel by a simpler processing system.

  It is preferable to adjust the waste water generated from the gas cleaning equipment to a pH of 9 or more in a pH adjusting tank, distill the waste water adjusted to pH with a distillation tower, and neutralize and discharge the can liquid of the distillation tower. .

  According to this configuration, residual harmful substances in the wastewater can be separated and removed with a simple configuration.

  The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. It is preferable that the waste water is distilled by the distillation tower, and the can liquid of the distillation tower is used as circulating water for the alkali washing tower, and then neutralized and discharged.

  According to this configuration, the circulating water used in the temperature-decreasing tower and the acid washing tower can be combined into waste water, which can be discharged as harmless waste water.

  The waste water generated from the gas cleaning equipment is pH adjusted in a pH adjustment tank, and the waste water adjusted by the pH adjustment tank is supplied to a diffusion tower together with a carrier gas to be diffused, and the can liquid of the diffusion tower is mixed. It is preferable to neutralize and discharge in a neutralization tank.

  According to this configuration, the refining system can be an inexpensive facility, and the can liquid in the diffusion tower can be cleaned and discharged.

  The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. Waste water is diffused by the stripping tower, and the can liquid of the stripping tower is used as circulating water for the alkali washing tower, and then neutralized and discharged by the mixing neutralization tank. Good.

  It is preferable that waste water generated from the gas cleaning equipment is supplied to a diffusion tower together with a carrier gas to be diffused, and the can liquid of the diffusion tower is discharged.

  According to this configuration, in addition to making the purification system inexpensive, the can liquid of the stripping tower can be discharged without any trouble because it does not contain contaminants.

  The gas cleaning equipment has a temperature-decreasing tower and an absorption tower, and the mixed waste water generated from the temperature-decreasing tower and the absorption tower is supplied to the stripping tower to perform stripping treatment. In addition, it is preferable to use a part of the absorbent as an absorption liquid for the absorption tower.

  According to this configuration, the pH adjustment process and the like can be reduced, and no makeup water is required. Therefore, only the water condensation in the gasification gas can be discharged out of the system, thereby simplifying the manufacturing process. .

  As the adsorbent, it is preferable to use activated carbon, slaked lime, or a sodium-based agent or a mixture thereof.

  According to this configuration, these adsorbents can effectively adsorb and remove dioxins, heavy metals, and tars that may be contained in the gasification gas.

  It is preferable that the ammonia gas distilled and concentrated by the distillation tower is supplied to a denitration facility disposed at a subsequent stage of the gasification facility or the gas utilization facility.

  According to this configuration, high-concentration ammonia gas taken out from the distillation tower can be effectively used for denitration equipment and the like, and the overall processing cost can be reduced.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic flow of a gas purification system according to an embodiment of the present invention.

  This gas purification system uses a gas cooling facility 19 to process gasified gas generated from a gasification facility 18 such as a fluidized bed gasification furnace or a circulating fluidized bed gasification furnace with a low temperature dust collector such as a bag filter. The water is sprayed and heat exchanged here, and cooled to about 200 ° C. or less.

  The gasified gas cooled by the gas cooling equipment 19 is adsorbed such as slaked lime or activated carbon powder in the vicinity of the inlet of the low temperature dust collection equipment 20 while being fed to the low temperature dust collection equipment 20 through the pipe 25. It is characterized by being blown by a feeding device (not shown). Therefore, harmful substances such as dioxins, tars, and heavy metals that may be contained in the gasification gas are adsorbed by the adsorbent that is blown in, collected by the low-temperature dust collection facility 20, and collected. . The dust collected by the low temperature dust collection equipment 20 is sent to the ash treatment equipment or carried out of the field and detoxified.

  The gasification gas discharged from the low-temperature dust collection facility 20 is sent to the gas cleaning facility A and cleaned in a state where harmful substances such as dioxins, tars, and heavy metals are removed. The gas cleaning equipment A is basically composed of a temperature reducing tower 21, an acid cleaning tower 22, an alkali cleaning tower 23, etc., as in the prior art. By these gas cleaning equipment A, corrosive substances in gasified gas, Pollutants and the like are removed, cleaned, and sent to a gas utilization facility such as a gas engine or a gas turbine for use.

  The temperature-decreasing tower circulating water W1 circulated in the temperature-decreasing tower 21 is circulated by the circulation pump P, and is effectively cooled by the cooling tower T via the heat exchanger.

  The circulating water W2 in the acid cleaning tower 22 is appropriately supplied with a chemical C1 such as sulfuric acid for pH adjustment, so that the cleaning effect can always be sufficiently exhibited. Further, the temperature-decreasing tower circulating water W1 and the acid cleaning tower circulating water W2 are partly extracted as appropriate, once sent to the mixing tank 32 and mixed, and then fed to the pH adjustment tank 26 by the transfer pump P8. The Here, the chemical C2 (alkaline agent such as sodium hydroxide) is charged and adjusted to pH 9 or higher, and then sent to the distillation tower 27 by the transfer pump P9. In the distillation tower 27, the steam S supplied from the outside is supplied. Distilled as a heat source.

  A heat exchanger 29 is disposed in the piping around the distillation column 27 and exhibits a function of increasing thermal efficiency. In the heat exchanger 28 disposed at the outlet of the distillation tower 27, water is condensed by the cooling water fed from the cooling tower C, and ammonia contained in the water is separated as ammonia gas. The ammonia gas can be used by being supplied to a denitration facility (not shown) disposed downstream of the gasification facility 18 or the gas utilization facility, or can be used for other purposes. That is, the circulating water sent to the distillation column 27 is heated to, for example, 100 ° C. or more by the steam S and discharged, and after the ammonia gas is separated through the heat exchanger 28, the circulating water is cooled to about 80 ° C. Then, it returns to the bottom from the upper part of the distillation column 27 again. By repeating this circulation process, the ammonia in the circulating water is concentrated and separated and used as a highly concentrated ammonia gas.

  Moreover, the water (can liquid) collected at the bottom of the distillation column 27 is alkaline water that does not contain contaminants, and is supplied to the alkali cleaning column 23 by the transfer pump P10. At this time, the alkaline water is heat-exchanged with a heat exchanger 29 arranged in the middle of being sent from the pH adjusting tank 26 to the distillation tower 27, and at the downstream side by the cooling water fed from the cooling tower C. Heat is exchanged in the heat exchanger 30 and cooled to about 60 ° C.

  On the other hand, in the alkali cleaning tower 23, the circulating water W 3 is circulated by the circulation pump P in the same manner as the temperature-decreasing tower 21 and the acid cleaning tower 22, and a part thereof is drawn out and sent to the mixing neutralization tank 31. Here, after the chemical C1 such as sulfuric acid is added and the pH is adjusted, it is discharged by the drainage pump P11 or sent to the gas cooling facility 19 for use.

  As described above, according to the present embodiment, the process of adsorbing and removing the harmful pollutants that may be contained in the gasification gas with the adsorbent in advance before the processing is performed in the gas cleaning equipment. Therefore, the remaining gasification gas can be substantially limited to only ammonia, so the load for processing can be reduced, and the scale of the gas cleaning equipment is significantly simplified compared to the processing system of the prior art. it can. Moreover, since the ammonia gas taken out from the distillation tower has a high concentration, it can be effectively used for denitration equipment and the like, and the overall processing cost can be reduced.

[Another embodiment]
(1) As another embodiment of the present invention, a gas purification system configured as shown in FIG. 2 may be used. That is, this gas purification system uses a stripping tower 33 in place of the distillation tower 27 of the gas purification system of the embodiment shown in FIG. The waste water is diffused and the steam S is fed and heated. As the carrier gas Ga1, air is usually used, but is not limited to this. From the outlet of the stripping tower 33, the water heat-exchanged by the heat exchanger 28 is condensed by the cooling water fed from the cooling tower C, and the gas Ga2 containing ammonia is separated as a gas. As in the case of the above-described embodiment, this ammonia gas is supplied to a denitration facility (not shown) disposed downstream of the gasification facility 18 or the gas utilization facility and is used for other purposes. be able to. The point that the can liquid of the stripping tower 33 is fed to the alkali cleaning tower and then neutralized and discharged in the mixed neutralization tank 31 is the same as in the above embodiment. In this embodiment, since the stripping tower 33 is used in place of the distillation tower 27, the purification system can be made inexpensive.

  (2) Further, a gas purification system configured as shown in FIG. 3 may be used. That is, in this gas purification system, the gas cleaning equipment A is different from the above-described embodiment, and includes a temperature reducing tower 21, an absorption tower 34, and the like. By these gas cleaning equipment A, corrosive substances and pollutants in the gasification gas are obtained. Are absorbed and removed. Thereafter, the gasified gas is used in gas utilization facilities such as a gas engine and a gas turbine in the subsequent stage, as in the above embodiment. Circulating water W4 circulating through the temperature reducing tower 21 is circulated between the absorption tower 34 while releasing heat in the heat exchanger 35. A portion of this dewarming tower circulating water W4 is withdrawn as discharged water W5 from the absorption tower 34 and supplied to the diffusion tower 33 through a heat exchanger 29 for increasing the thermal efficiency, and a carrier gas such as air. While Ga1 is being supplied, the vapor S is used as a heat source to be dissipated. From the outlet of the diffusion tower 33, the water exchanged by the heat exchanger 28 is condensed by the cooling water fed from the cooling tower C, and the ammonia-containing gas Ga2 is separated as a gas. As in the case of the above-described embodiment, this ammonia gas is supplied to a denitration facility (not shown) disposed downstream of the gasification facility 18 or the gas utilization facility and is used for other purposes. be able to. Since the water W6 at the bottom of the stripping tower 33 does not contain a pollutant, it is supplied again to the absorption tower 34 by the pump P, and a part thereof is withdrawn and discharged outside the system. The amount corresponds to the condensed water in the exhaust gas discharged from the low temperature dust collection facility 20.

  According to this embodiment, since no chemical is used in the gas cleaning facility A, the pH adjustment process and the like can be reduced, and no makeup water is required. Only the system will be discharged, and the equipment configuration can be simplified.

  (3) In the above embodiment, examples using slaked lime and activated carbon as the adsorbent were given, but the adsorbent is not limited to these, and sodium bicarbonate and other sodium-based adsorbents can be used. Furthermore, these may be used alone or in combination.

  (4) In the above embodiment, as the gas cleaning equipment A, the temperature reduction tower 21, the acid cleaning tower 22, and the alkali cleaning tower 23 have been described as examples. However, these are not necessarily all provided, For example, the structure which has only the temperature reduction tower 21 may be sufficient. In this case, a part of the temperature-decreasing tower circulating water W1 is withdrawn and fed to the distillation tower 27 and distilled by the process shown in FIG. It can supply and neutralize.

  (5) Examples of gas utilization equipment applicable to the present invention include power generation equipment such as a gas engine and a gas turbine, and liquid fuel production equipment such as methanol production equipment.

  (6) Examples of the fuel applicable to the present invention include various solid fuels and industrial wastes in addition to various organic wastes.

Schematic flowchart showing a gas purification system according to an embodiment of the present invention. Schematic flowchart showing a gas purification system according to another embodiment of the present invention. Schematic flowchart showing a gas purification system according to still another embodiment of the present invention. Schematic flow diagram showing a gas purification system according to the prior art

Explanation of symbols

18 Gasification gas equipment 20 Low-temperature dust collection equipment 21 Temperature reduction tower 22 Acid washing tower 23 Alkaline washing tower 26 pH adjustment tank 27 Distillation tower 31 Mixing neutralization tank 33 Stripping tower 34 Absorption tower A Gas washing equipment Ga1 Carrier gas

Claims (18)

A gas purification system having a low-temperature dust collection facility for removing gasification gas generated from a gasification facility and a gas cleaning facility for cleaning the gasification gas removed by the low-temperature dust collection facility. A gas refining system characterized in that a mechanism for introducing an adsorbent capable of adsorbing harmful substances in the gasified gas introduced into the low-temperature dust collection facility is provided upstream. A pH adjusting tank for adjusting pH of waste water generated from the gas cleaning equipment is provided, and a distillation tower for distilling the waste water adjusted by the pH adjusting tank is provided, and the can liquid of the distillation tower is neutralized. The gas purification system according to claim 1, further comprising a mixing neutralization tank that enables discharge. The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. The waste water is distilled by the distillation tower, and the can of the distillation tower is used as circulating water for the alkali washing tower, and then neutralized and discharged by the mixed neutralization tank. The gas purification system as described. In addition to a pH adjustment tank that adjusts the pH of the wastewater generated from the gas cleaning equipment, a diffusion tower that supplies the carrier gas to disperse the wastewater adjusted by the pH adjustment tank is provided. The gas refining system according to claim 1, further comprising a mixed neutralization tank that neutralizes the can liquid and enables discharge. The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. The gas purification according to claim 4, wherein waste water is diffused by the stripping tower, and the can liquid of the stripping tower is used as circulating water for the alkali washing tower, and then neutralized and discharged by the mixed neutralization tank. system. The gas purification system according to claim 1, further comprising a diffusion tower that supplies a carrier gas to disperse wastewater generated from the gas cleaning equipment, and enables the can liquid of the diffusion tower to be discharged. The gas cleaning equipment has a temperature reduction tower and an absorption tower, and the mixed waste water generated from the temperature reduction tower and the absorption tower is supplied to the diffusion tower to be diffused, and the diffusion 7. The gas purification system according to claim 6, wherein a part of the tower can is discharged and used as an absorbing liquid for the absorption tower. The gas purification system according to any one of claims 1 to 7, wherein the adsorbent is activated carbon, slaked lime, or a sodium-based drug, or a mixture thereof. 9. The ammonia gas distilled or diffused by the distillation tower or the stripping tower and concentrated to be supplied to a denitration facility disposed downstream of the gasification facility or the gas utilization facility. Gas purification system. In a gas purification method of removing gasified gas generated from a gasification facility with a low-temperature dust collection facility and cleaning the gasification gas removed by the low-temperature dust collection facility with a gas cleaning facility, the upstream side of the low-temperature dust collection facility In addition, an adsorbent capable of adsorbing harmful substances in the gasification gas introduced into the low-temperature dust collection facility is introduced into the gas purification method. The waste water generated from the gas cleaning equipment is adjusted to a pH of 9 or more in a pH adjusting tank, and the pH-adjusted waste water is distilled by a distillation tower, and the can liquid of the distillation tower is neutralized and discharged. The gas purification method as described. The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. The gas purification method according to claim 11, wherein the waste water is distilled by the distillation tower, and the can liquid of the distillation tower is used as circulating water for the alkali washing tower, and then neutralized and discharged. The waste water generated from the gas cleaning equipment is pH adjusted in a pH adjustment tank, and the waste water adjusted by the pH adjustment tank is supplied to a diffusion tower together with a carrier gas to be diffused, and the can liquid of the diffusion tower is mixed. The gas purification method according to claim 10, wherein the gas is neutralized and discharged in a neutralization tank. The gas cleaning equipment has a temperature-decreasing tower, an acid cleaning tower, and an alkali cleaning tower, and the mixed waste water generated from the temperature-decreasing tower and the acid cleaning tower is supplied to the pH adjustment tank, and the pH is adjusted. The waste water is diffused by the stripping tower, and the can liquid of the stripping tower is used as circulating water for the alkali washing tower, and then neutralized and discharged by the mixed neutralization tank. Gas purification method. The gas purification method according to claim 10, wherein waste water generated from the gas cleaning equipment is supplied to a diffusion tower together with a carrier gas to be diffused, and the can liquid of the diffusion tower is discharged. The gas cleaning equipment has a temperature-decreasing tower and an absorption tower, and the mixed waste water generated from the temperature-decreasing tower and the absorption tower is supplied to the stripping tower to perform stripping treatment. The gas purification method according to claim 15, wherein a part of the gas is discharged and used as an absorption liquid of the absorption tower. The gas purification method according to any one of claims 10 to 16, wherein as the adsorbent, activated carbon, slaked lime, or a sodium-based drug or a mixture thereof is used. The gas purification method according to any one of claims 11 to 17, wherein the ammonia gas distilled and concentrated by the distillation tower is supplied to a denitration facility disposed at a subsequent stage of the gasification facility or the gas utilization facility.

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