Title of Invention

METHOD AND APARATUS FOR SEPARATING ACIDIC GASES FROM SYNGAS

Abstract

A method and an apparatus for separating acidic gases from syngas are capable of reducing the necessary power and are capable of obtairiing high-purity CO2 at a high recovery ratio. A purification method and a purification system of coa.i gasification gas using the method and the apparatus are alsq) provided. A apparatus for separating acidic gases from syngas containing acidic gases of CO2 and H2S, in order, converts CO in the syngas into C02, removes H2S contained in the syngas by using a solvent for physical absorption, and removes CO2 from the syngas by using a solvent for chemical absorption.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] METHOD AND APPARATUS FOR SEPARATING ACIDIC GASES FROM SYNGAS; MITSUBISHI HEAVY INDUSTRIES, LTD., A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF JAPAN WHOSE ADDRESS IS 16-5, KONAN 2-CHOME, MINATO-KU, TOKYO, JAPAN THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. 1 METHOD AND APPARATUS FOR SEPARATING ACIDIC GASES FROM SYNGAS Background of the Invention The present invention relates to a method and an apparatus for separating acidic gases from syngas. The composition of the conventional crude gas produced by coal gasif icat ion includes hydrogen (H2) , carbon monoxide (CO) , and carDcn dioxide (C02) as the main components, and also includes nitrogen (N2) , methane (CH4) , hydrogen sulfide (H2S) , and the Like. When C02 is removed from such a syngas co recover CO/ therefrom, first, CO in the crude gas needs to be converted into H2 and C02 by a reaction with steam (shift reaction). In addition, when the gas after purification is used as a raw material for chemicals such as ammonia or as a fuel for powe;i generation, acidic gases such as H2S need to be removed from the crude gas. When CO shift reaction is performed without the removal of H::;S from crude gas, the gas after the shift reaction contci ins both CO?, and H2S, each of which then needs to be separated and recovered individually. Conventionally, in this separation process, a physical absorption process in which H?S is .selectively dissolved in a solvent is employed first to separate C02 and H2S from each other. Fig. 1 shows the configure Li on of an apparatus employing a typical physical absorption process for separating acidic gases from crude syngas. Fig. 1 Is a plan view showing the schematic configuration of H2S removal means and CO2 removal means in one embodiment: of a conventional acidic gas separation apparatus using a physical absorption process. As shown in Pig. 1, shifted gas after the CO shift reaction is introduced into an acidio gas absorption tower 101, and brought into contact with a solvenr. fed by a pump 102d. As a result, H2S is removed. The solvent having absorbed H2S in the crude gas in the acidic gas absorption tower 101 is introduced into an acidic gas stripping tower 106 through an acidic gas concentrat ing tower 104. In the acidic gas stripping tower 106, the absorbed acidic gas is stripped from the solvent by neating with a reboiler 10 9. The stripped acidic gas is exhausted as acidic gas after passing through a condenser .107. On the other hand, the solvent from which the acidic gas has been stripped is introduced into a C02 absorption ::.ower 111 through a pump 102b, a heat exchanger 103, and a cooler 110a. The crude gas from which H2S has been removed in the acidic gas absorption tower 101 is introduced into the C02 absorption tower 111, and again brought into contact with the solvent. As a result, C02 is removed. The purified gas after the C02 removal is used as a fuel for power generation, a raw mater.i al for chemical synthesis, or the like. The solvent having absorbed CO..- is separated into gas components and the solvent in flash drums 112a, 112b, and 112c. The"gas components from the flash drum 112a are returned to the C02 absorption tower 111, whereas the gas components from the flash drums li. 2b and ,12c are exhausted as C02. The solvent from which the gas has been released returns to the CO2 absorption tower ll'l through a pump 112e and a chiller 110c, and is reused in the C02 absorption tower 111, As described above, the conventional acidic gas separation method using physical absorption is a method in which the crude gas after the coal gasification is washed wi t.h a solvent to thereby remove H2S, and the crude gas after the H2S remova 1. is supplied into the CO2 absorption tower, where the solvent again removes CO2. The physical absorption process is characterized that hhS and C02 are separated and recovered by the same solvent; however, the physical absorption process has a problem that the solvent needs to be cooled to a low temperature by a chiller, and hence power required by the chiller is extremely large. Furthermore, the method is advantageous in requiring no heat to strip CO2 from the solvent having absorbed CO2, and in that 90% or more of carbon out of the total carbon (CCHC02+CH4) after coal gasification can be recovered as CO2 by lowering the pressure. On the other hand, the method has a problem that [.he purity of the recovered C02 is low when compared with that obtained in the case of a chemical absorption process to be described later. This is because C02 -is dissolved in proportion to the C02 partial pressure in the crude gas, and CO, H2 and the like dissolved along with CO2 ^re stripped simultaneously in the striping of C02. On the >Lher hand, unlike the physical absorption process, the \'hemi cal absorption process using a solvent containing an organic amine or the like is not capable of separating and recovering H?S and CO2 individually from crude gas after the CO shift reaction. For this reason, it is necessary to fi rst separate H2S before the CO shift reaction, that is, under a condition in which the CO2 partial pressure in the crude gas is low, then to perform the CO shift reaction, and then to remove CO2 by chemical absorption. Fig. 2 is a plan view showing the schematic configuratior. of H2S removal means and C02 removal means in one embodiment of a conventional acidic gas separation apparatus using a chemical absorption process. As shown in Fig. 2, crude gas having been subjected to dust removal with a scrubber is introduced into an acidic gas absorption tower 201, where H;S in the crude gas is separated and removed. The solvent used for the removal of the acidic gas is introduced into an acidic gas stripping tower 204, through a pump 2 02a and a heat exchanger 203a. The acidic gas is stripped from the solvent by heating with a reboiler 207a in an acidic gas stripping tower 204, and is exhausted through a condenser 205.i. On the other hand, the solvent from which the acidic gas has been stripped is supplied into the acidic gas {absorption tower 201, and is reused. The crude gas from which the acidic gas has been removed in the acidic gas absorption tower 201 is introduced into a shift reactor 7, where CO i n tne gas is converted into CO2 by the shift reaction. Next, the crude gas after the shift reaction is introduced into a CO2 absorption tower, where C02 is separated and removed. Thereafter, the gas is exhausted as purified gas. From the solvent having absorbed CO2 in the C02 absorption tower 208, CO, H?, and the like dissolved in the solvent are stripped by flash in a high pressure flash drum 209, and then the solvent is introduced into a C02 stripping tower 210. CO, H2, and the like stripped in the high pressure flash drum 209 join, after passing through a compressor 21$, the crude gas after the shift reaction, and is introduced again into the C02 absorption tower 208. C02 stripped from the solvent in the C02 stripping tower is exhausted through a condenser 205b. Most of the solvent from which CO? has been stripped is returned to the C02 absorption tower 208 through a pump 202d. The rest of the solvent is introduced into a solvent regeneration tower 211 through a pump 202e and a heat exchanger 212a. The solvent regenerated in the so.l vent regeneration tower 211 is returned to the C02 absorption tower 208, and is reused. The C02 stripping tower 210 and the solvent regeneration tower 211 are generally formed as an i ntegrated tower. In such a chemical absorption process, when H2S is removed in th^ acidic gas absorption tower 201, CO2 is also removed and eventually exhausted outside the system. Accordingly, .vhen a low grade coal is used as a raw material, the CO2 partial pressure in the crude gas becomes high, which results in a significant C02 loss in the H2S removal step. Accordingly, there is a problem that, in the CO2 recovery step in the downstream, recovery ratio of carbon does not reach 90% or more of total carbon. However, when compared to the physical absorption process, the chemical absorption process is advantageous in that the necessary power is low, and in that the purity of the recovered C02 is high because CO- is absorbed by a chemical reaction. US Patent Application Publication No. 2006/0156923 disc loses a conf1guration for separating acidic gas by such a chemical absorption process. Summary of the Invention In view of the above problems, the present invention provides a method and an apparatus for separating acidic gases from syngas, both being capable of reducing the necessary powei , and capable of obtaining high-purity C02 at: a high recovery ratio. To achieve the above object, an aspect of the present invention provides an apparatus for separating acidic gases of CO2 and H:,S from syngas containing the acidic gases, the apparatus comprising: shift reaction means for converting CO in the syngas into CO.; physical absorption means for removing, by using a solvent of physical absorption, H2S contained in t: he syngas after the shift reaction; and chemical absorption means for removing, by using a solvent of chemical absorption, CO2 from the syngas from which H2S has been removed by the physical, absorption means. Also, the apparatus of the present invention may further comprise solvent removal means for removing the solvent of physical absorption from the syngas from which H2S is removed by the physical absorption means, the solvent removal means being provided upstream of the chemical absorption means. Also, the apparatus of the present invention may further compiise heat, exchange means for heating the syngas a fter the sol vent removal and before the introduction into the chemical absorption means or circulating water used in the solvent absorbing means, by use of the syngas before the introduction into the physical absorption means and after the shi ft reaction. Also, the apparatus of the present invention may further comprise washing means for washing the syngas after the {shift rea :tion, the washing means being provided upstream of the physical absorption means. Also, in the apparatus of the present invention, the solvent of physical aosorption may be a solvent containing a mixture solution of dimethyl ether and a polyethylene glycols, and i;he solvent of chemical absorption may be a solvent: containing an alkylamine. Also, another aspect of the present invention provides a system for purifying coal gasification gas, the system comprising: a gasifier for producing syngas from coal; a scrubber for removing a hazardous substance in the syngas; and the aforementioned separation apparatus for separating acidic gases ftom the syngas after the removal of the hazardous substance. Also, st;ill another aspect of the present invention provides a method for separating acidic gases from syngas containing acidic gases of CO2, and H2S, the method comprising: a shift reaction step of converting CO in the synqas into CO?; a physical absorption step of removing, by using a solvent of physical absorption, H2S contained in the syngas after the shift reaction; and a chemical absorption step of removing, by using a solvent of chemical absorption, CO2 from the .syngas from which H2S has been removed in the physical absorption st ep. Also, the method of the present invention may further comprise a so;. vent removal step of removing, before the chemical absorption step, the solvent of physical absorption from the syngas from which H2S is removed in the physical absorption stop. Also, tac method of the present invention may further comprise a heating step of heating the syngas after the solvent removal and before the chemical absorption step or circulating Writer used in the solvent removal step, by use of the syngas be t ere the physical absorption step and after the shift reaction. Also, the method of the present invention may further include, before the physical absorption step, a washing step of washing the syngas after the shift reaction. Also, in the method of the present invention, the solvent of physical absorption may be a solvent containing a mixture solut i.on of dimethyl ether and a polyethylene glycols, and the solvent of chemical absorption may be a solvent containing an alkylamine. Also, yet another aspect of the present invention provides a method foi purifying coal gasification gas, the method comprising: a gasification step for producing syngas from coal; a dust removal step for removing a hazardous substance in the synqas in a scrubber; and a separation step by the aforem^ncioned separation method for separating acidic qasefc from the syngas after the removal of the hazardous subs Lance. The present invention makes it possible to remove, by using a solvent of physical absorption, H2S separately from CO2, thereby 1 educes c:02 accompanying the H2S removal, and achieves a carbon recovery ratio of 90%. Also, since CO2 in crude gas after the H:S removal is absorbed by a solvent by chemical absorption, high-purity C02 can be recovered. Also, according to the present invention, a solvent of chemical absorption is used as CO2 removal means, thereby making it possible to eliminate the need for a chiller for cooling the so]vent to a low temperature, and also to reduce the compresscr power to a large extent. Also, according to the present, invention, the use of a sour shift reactor containing suLfur makes it possible to reduce steam supplied f rom the outs ide, when compared with a sweet shift reactor, which is prov ided upstream of the CO2 chemical absorption process, and which contains almost no sulfur. Brief Description of the Drawings Fig. 1 is a plan view showing the schematic configuration of HaS removal means and C02 removal means in one embodiment of a conventional acidic gas separation apparatus using a physical absorption process. Fig. 2 is a plan view showing the schematic configuration ot H2S removal means and C02 removal means in one embodimerr of a conventional acidic gas separation apparatus using a chemical absorption process. Fig. 3 is a block diagram showing an apparatus for separating ac i.dic gases from syngas, according to the present inventi on. Fig. 4 is a schematic plan view showing the configuration of the apparatus for separating acidic gases from syngas in one embodiment of the present invention, and specifically shows a part after a shift reactor. Detailed Description of the Invention An embodiment of the present invention will be described in detail hereinbelow with reference to the drawings. Fig. 3 is a block diagram showing an apparatus for separating aci ciic gases from syngas, according to the present invention. As shown in Fig. 3, the acidic gas separation apparatus of the present invention comprises a gasifier 1, a scrubber 2, a CO shift reactor 3, H2S removal means 4, and CO? removal means 5. As the coal gasifier 1, a general coal gasifier developed by Mitsubishi Heavy Industries, Ltd., Royal Dutch She3.1 pic, Chevron Corporation, or the like can be used. In such a coal qasLfier, crude gas mainly containing carbon monoxide and hydrogen is produced. As the .scrubber 2, any conventionally known scrubber can be employed which can remove dust and hazardous substances in crude gas, such as mercury, heavy metals, and halogens, by oringing the crude gas into contact with a liquid to transfer the hazardous substances to the liquid. Fox example, H spray Lower, a packed tower, a cyclone scrubber, a jet scrubber, a rotary washer, a venturi scrubber, or the like can be used as the scrubber 2. The crude gas from which hazardous substances have been removed in the scrubber 2 is sent to the CO shift reactor 3. In the CO shift reactor 3 used in the present invention, CO in the crude gas is reacted with H2O to cause a shift reaction producing H2 and C02 (H20+CO-^H2+C02) . For example, a CO shift reactor performing the shift reaction at 2 30°C to 480"C is preferable. Also, in the shift reaction, in order to prevent the deposition of carbon from carhon monoxide contained in the gas (2CO—*C+C02) , it is preferable to supply an excess amount of process steam (H20) at an inlet of tihe shift reactor 3. Also, as the CO shift reactor 3 used in the present invention, a sulfur-containing (sour) shift reactor using a catalyst based on Co/Mo or the like can be employed because the crude gas to be subjected to the shift reaction contains H:S of at least TOO ppm or more. In contrast, a catalyst based on Fe os the like is used for a shift reactor (sweet) used.when the conventional chemical absorption process is employed, sinoe the crude gas contains almost no H2S. Shift reaction catalysts containing sulfur, such as Co/Mo-based catalysts, are inore active than shift reaction catalysts containing almost no sulfur, such as Fe-based catalysts. Accordingly, .-ir.eam supplied to the crude gas from the outside can be reduced. Hereinbelow, derailed descriptions will be given of the H2S removal means 4 arid the C02 removal means 5 with reference to Fig. 4. Fig. 4 is a schematic plan view showing the configuration of the apparatus for separating acidic gases from syngas in one embodiment of the present invention, and specifically shows a part after the shift reactor. As shown in Fig. 4, the apparatus for separating acidic gases from syngas of the present invention mainly comprises: a washing tower 3 03 for washing trace amounts of ammonia and hydrocarbons in crude gas after the shift reaction; an acidic gas absorption tower 101 for removing H2S in the crude gas by using a solvent; an acidic gas concentrating tower 104 for concentrating H2S absorbed in the solvent; an acidic gas stripping tower 106 for stripping H2S in the solvent; a solvent absorption tower 306 for removing the solvent contained in i„he purified gas exhausted from the acidic gas absorption tower; 101; a CO- absorption tower 208 for removing CO2 irom gas having passed through the solvent absorption tower 306 by ,ising a solvent; a high pressure flash drum 209 for stripping gases, such as H2 and CO, absorbed in the solvent; a CO. stripping tower 210 for stripping CO2 in the solvent; and a solvent regeneration tower 211 for regenerating the solvent used for the C02 absorption. The CO2 stripping tower 210 and the solvent regeneration tower 211 are generally formed as an integrated tower. According to the embodiment of the present invention, crude gas havLag undergone the shift reaction in the shift reactor is ceo.led by heat exchangers 301a and 301b, and is introduced into a flash drum 302a. The crude gas exhausted from the shilt reactor has a pressure of about 20 atm to 50 atm, and a temperature of about 270°C to 450°C, and is cooled by the heat exchangers 301a and 301b. The temperature of the crude gas after being cooled by the heat exchanger 301a is preferably IIIS^C to 135°C. The temperature of the crude gas after bei.ng cooled by the heat exchanger 301b is preferably 70°C to 100V. Also, since the crude gas exhausted from the shift reactor is humidified by steam, the flash drum 302a removes water in the crude gas cooled by the heat exchangers. The crude gas from which water has been removed by the flash drum 302a is next introduced into the washing tower 303. The wast ing tower 30 3 removes trace amounts of ammonia and hydrocarbons in the crude gas. To the upper part of the washing tower ^03, piping for supplying make-up water as needed is connected. The make-up water is supplied into the washing tower 303 through the piping. Drain water is discharged from the bottom of the washing tower 303, and the drain- water is circulated by a pump 304a to the washing tower "■503 through a cooler 305a. Alternatively, the drain water is not circulated but may be directly subjected to water treatment. The- crude qas from which ammonia and hydrocarbons have been removed is exhausted from the top of the washing tcwer 303, and introduced into the acidic gas absorption rower 101. The acid ic gas absorption tower 101 separates and removes acidic gases, particularly H2S, in the crude gas by a physical absorption process. A solvent is supplied into the acidic gas absorption tower 101, and absorbs acidic gas in the crude gas. The crude gas from which acidic gases have been removed is exhausted from the top of the acidic gas absorption townr 101, and is introduced into the solvent absorption tower 30 6. The solvent after the acidic gas absorption is discharged from the bottom of the acidic gas absorption tower 101, and is heated in a heat exchanger 103 by the solvent regenerated by the acidic gas stripping tower 106. The solvent is then introduced into the acidic gas I concentrating tower 104. As the solvent used in the acidic gas absorption tower 101, a solvent of physical absorption, such as a mixture solution of diethyl ether and a polyethylene glycols, can be used. Also, the temperature of the crude gas in the acidic gas absorption tower 101 is preferably 20°C to 40°C. The aci die gas concentrating tower 104 strips, by f la$h, H?, CC, CO? or the like dissolved in the solvent. H2, CO, -C02 or the like stripped in the acidic gas concentrating towftr 10 4 can be Introduced again into the acidic gas absorption tower 101 through a compressor 105d. The solvent is exhausted from the bottom of the acidic gas concentrating tower 104, arid is next introduced into the acidic gas stripping tower 106. In the acidic gas stripping tower 106, acidic gases, particularly H2S, dissolved in the solvent are stripped by being heated with a reboiler 109. The stripped H2S is exhausted from the top of the acidic gas stripping tower 106, passes through a condenser 107, and is eventually exhausted as acidic gas. In the heat exchanger 103, the solvent regeinerated by the release of acidic gases heats the solvent from the acidic gas absorption tower 101, and supplied, through a pump 102f and a cooler llOd, into the acidic gas absorption tower 101, where the solvent is reused. In the condenser 107, water contained in the acidic gas is condensed .and removed. The condensed liquid is sent back to the acidi.c gas str Lpping tower 106 through a drum 108 and a pump 102c. The solvent absorpti on tower 30 6 removes the solvent contained in crude gas exhausted from the acidic gas absorption tower 101. In the solvent absorption tower 306, the 'solvent is absorbed by water. This prevents the solvent of physical absorption used in the acidic gas absorption tower lOi irom being mixed with a solvent of chemical absorption used in the CO;> absorption tower 208 provided downstream. Drain water discharged from the bottom of the solvent absorption tower 306 is circulated back to the solvent absorption tower 306 through a pump 304b. Additionally, a small amount of feed water is supplied into the solvent absorption tower 306. Also, the drain water can be sent to the acidic gas absorption tower 101 by the pump 304b. The crude gas exhausted from the solvent absorption tower 306 is heated by a heat exchanger 301d, and is introduced into the CO2 absorption tower 208 through a flash dram 302b. The heat exchanger 301d heats gas exhausted from the solvent absorption tower 306 by utilizing heat of the gas aftej-r the shift reaction, in order that the crude gas may havtL- a water saturation temperature that is suitable for the chemical absorption in the CO2 absorption tower 208. In other words, the heat exchanger 301b and the heat exchanger 30Id together represent a single heat exchanger. At this time., the crude gas heated by the heat exchanger 301d has preferably a pressure of 20 atm to 50 atm, and has preferably a temperature of 60°C to 80°C, more preferably a temperature of 6:b°C to 75"C, and most preferably of 70°C. As for conventional heat recovery from the gas cooled to 125°C to 135°C by the heat exchanger 301a, the heat is used, to heat boiler feed water (BFW) or cooled by an air fin cooler and wasted in a case where the heat cannot be used for heat;.i ng BFW, However, as described above, according to the present invention, the heat can be used to heat the crude gas exhausted frcm the solvent absorption tower 306. Also, the heat exchanger may be provided at the position of the heat exchanger 301c in the water circulating line to the solvent absorption tower 306 so as to raise the temperature of circulating water. Also, the heat exchanger 301cl and the heat exchanger 301c may both be provided. The crude gas heated by the heat exchanger is humidified by make¬up water or t.he like. Into the CO2 absorption tower 208, the crude gas from which excess water has been removed in the flash drum 302b is introduced. The CO? absorption tower 208 removes CO2 by the contact of the introduced crude gas with a solvent. Purified gas from which C02 has been removed in the C02 absorption tower 208 is exhausted from the top of the CO2 absorption tower 208. The solvent having absorbed C02 is discharged from; the bottom of the CCb absorption tower 208, and sent to the high pressure flash drum 209. As the solvent used for the CO? absorption, a solvent for chemical absorption, such as an alkylamine, is preferable. Also, the crude gas in the CO2 absorption tower 208 has preferably a pressure of 20 atm to 50 atm, and has preferably a tower top temperature of 40°C to 60°C, which is sui table for C02 absorption, more preferably a temperature of 45°C to 55°C, and most preferably of 5"0°C. The high pressure flash drum 209 strips, by flash, physically scLved gases such as H2 and CO dissolved in the solvent. The gases such as H2 and CO are sent back to the CO2 absorption tower 20 8 through a compressor 213. The solvent from which the physically solved gases have been stripped is discharged from the bottom of the high pressure flash drum 209, and sent to the C02 stripping tower 210. The CO? stripping tower 210 flashes the solvent sent from the high pressuie flash drum 209, and releases C02 from the top of the CO:,. stripping tower 210. The released C02 is exhausted through a condenser 205b. In the condenser 205b, wateur and the Like contained in CO2 are removed. The condensed liquid is sent back to the CO2 stripping tower 210 through a drum 206b and a pump 202c. Most of the solvent from which C02 has been stripped in the ;om the CO2 stripping tower 210 is heated in heat-exchange by the solvent discharged from the solvent regeneration ;ower 21i, and is completely regenerated in the solvent regeneration tower 211. In the .solvent regeneration tower 211, the solvent and the absorbed qas are separated from each other by being heated by a reboiler 207b to regenerate the solvent. The gas stripped in the solvent regeneration tower 211 is sent to the CO2 stripping tower 210 located thereabove. The solvent regenerated in the so Lvent regeneration tower 211 is discharged, as a lean solvent, from the bottom of the solvent regeneration newer 21L. The solvent, after being cooled by a heat exchanger 212b, LS sent by a pump 202f to the C02 absorption tower 208, and is reused. As described above, according to the present invention, sincfc the crude gas is introduced into the CO shift reactor 3 before the H2S removal, highly active catalysts based on Co/M'D and the like can be used Accordingly, CO in the crude gas can be converted into C02 by the shift reaction using a small amount: of: steam. Thereafter, the crude gas is introduced into the H2S removal means 4, where H2S in the crudti gas is removed by the solvent of physical absorption. In this way, the acidic gas separation apparatus of the present invention is capable of separating and removing H2S by the solvent of physical absorption, thereby making it possible to reduce C02 accompanying the H2S removal. The crude gas after the H2S removal is introduced into the solvent absorption tower 306, and the solvent of physical absorption contained in the crude gas is removed. This prevents the solvent of physical absorption from being mixed with the solvent of chemical absorption used in the C02 removal means !) provided downstream of the solvent absorption tower 306. The crude gas from which the solvent has been removed in the solvent absorption tower 306 is next heated by the heat exchanger 301d, and introduced into the C02 removal means- 5. As the heat required by the heat exchanger 301d, heat of the crude gas after: the shift reaction, which is conventionally wasted, is used. In the C02 removal means 5, C02 iili the crude gas is separated and removed by the solvent of chemical absorption, and purified gas is exhausted. In this way, C02 removal from the crude gas is performed by chemical absorption, making it possible to eliminate the need for a chiller for cooling the solvent to a low temperature, and to reduce the compressor power to a large extent. we Claim: 1. An apparatus for separating acidic gases of CO2 and H2S from syngas containing the acidic gases, the apparatus comp rising: shi ft reaction means for converting CO in the syngas into CO2; physica i. absorption means for removing, by using a solvent for physical absorption, H2S contained in the syngas after the shift reaction; and chemical absorption means for removing, by using a solvent for chemical absorption, CO2 from the syngas from which H2S has been removed by the physical absorption means. 2. The apparatus according to claim 1, further comprising solvent removal means for removing the solvent of physical absorption from the syngas from which H2S has been removed by the physical absorption means, the solvent removal means being provided upstream of the chemical absorption means. 3. The apparatus according to claim 2, further comprising heat exchange means for heating the syngas after the solvent removal and before introduction into the chemical absorption meanis and heat; exchange means, by use of the crude syngas heat' before the introduction into the physical absorption I means after the shift, reaction. 4. The apparatus according to any one of claims 1, further comprising washing means for washing the syngas after the shift reaction, the washing means being provided upstream of the .physical absorption means. 5. The apparatus according to claims 1, wherein the solvent for physical absorption is a solvent containing a mixture solution of dimethyl ether and a polyethylene glycols, and wherein the solvent for chemical absorption is a solvent containing an alkylamine. 6. A system for purifying coal gasification gas, comprising: a gasifier for producing syngas from coal; a scrubber for removing a hazardous substance in the syngas; and the separation apparatus according to claim 1, for separating acidic gases from the syngas after the removal of the .hazardous substance. 7. A method for separating acidic gases of CO2, and H2S from syngas containing the acidic gases, the method comprising: a shift reaction step of converting CO in the syngas into C02; a physical absorption step of removing, by using a solvent for physical absorption, H2S contained in the syngas after the shift reaction; and a chemi -a 1 absorption step of removing, by using a solvent tor chemical absorption, CO2 from the syngas from which H2S has been removed in the physical absorption step. 8. The method according to claim 7, further comprising, before the chemical absorption step, a solvent removal step of removing the solvent for physical absorption from the syngas from which H2S has been removed in the physical absorption step. 9. The method according to claim 8 further comprising a heating step of heating the syngas after the solvent removal and before the chemical absorption step and heat exchange step, by use of the crude syngas heat before the physical absorption step and after the shift reaction. 10 The method according to any one of claim 7, further comprising, before the physical absorption step, a washing step of washing the syngas after the shift reaction. 11. The method according to claim 7, wherein the solvent for physical absorption is a solvent containing a mixture solution of dimethyl ether and a polyethylene glycols, and wherein the so]vent for chemical absorption is a solvent containing ar; alkylamine. 12. A method for purifying coal gasification gas, comprising: a gas.it Lcation step for producing syngas from coal; a dust removal step for removing a hazardous substance in t;he syngas in a scrubber; and a separat.ion step by the separation method according to claim 7 for separating acidic gases from the syngas after the removal of the hazardous substance. Dated this 28th day of October, 2009 FOR MITSUBISHI HEAVY INDUSTRIES, LTD. By their Agent (ALIASAGAR DHOLKAWALA) PATENT AGENT NO. IN PA 1391 KRISHNA & SAURASTRI ASSOCIATES

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2504-MUM-2009-POWER OF ATTORNEY(18-11-2009).pdf

2504-MUM-2009-REPLY TO EXAMINATION REPORT(14-2-2012).pdf

2504-MUM-2009-REPLY TO EXAMINATION REPORT(8-8-2012).pdf

2504-MUM-2009-US DOCUMENT(14-2-2012).pdf

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