Abstract:
The invention involves a process for maintaining a low level of carbon monoxide in a carbon dioxide product stream and also for keeping the carbon monoxide out of the fully shifted synthesis gas. The overall process is a process for treating both fully shifted and partially shifted or unshifted synthesis gas. The carbon monoxide is separately removed by a carbon monoxide stripping column and returned to the partially shifted or unshifted synthesis gas which can then undergo a shift reaction to convert the carbon monoxide to carbon dioxide.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention generally relates to a process for a gas removal zone, such as an acid gas removal zone. More specifically, this invention relates to improvements in efficiency of such processes in which the level of carbon monoxide is reduced from the carbon dioxide that is being removed. 
         [0002]    In gasification applications in which the final product is liquid fuels or chemicals, typically both a fully shifted and a partially shifted or unshifted feed must be treated in a process that removes the sulfur compounds (including H 2 S and COS) and CO 2 . Among the processes that can provide such treatment are the Selexol® process—using a mixture of dimethyl ethers of polyethylene glycol (UOP LLC, Des Plaines, Ill.), the Rectisol® process—using a methanol solvent (licensed by both Linde A G, Polach, Germany and Lurgi A G, Frankfurt Am Main Germany), the Sulfinol® process—using a mixture of sulfolane and an aqueous solution of either di-isopropanol amine or methyl-diethanol amine (Jacobs, Pasadena, Calif.), the Flexsorb® process—using a proprietary solvent (ExxonMobil Research and Engineering, Fairfax, Va.), the Morphysorb® process—using a mixture of n-formylmorpholine and n-acetylmorpholine (Uhde GmbH, Dortmund, Germany) and the Purisol® process using N-Methyl-2-Pyrrolidone (NMP) (Lurgi A G, Frankfurt Am Main Germany). Each of these processes employs a solvent that absorbs the sulfur compounds and/or carbon dioxide from an acid gas. 
         [0003]    The most straightforward set-up for these types of processes is a separate train for both feeds. From a capital cost stand-point it is advantageous to have separate H 2 S and CO 2  absorbers for the 2 feeds and common equipment for the remainder of the process. These set-ups are typically able to meet the sulfur specs for the treated gases and product CO 2  without problems. However, the electricity requirements for a CO 2  recycle compressor within the process can become excessive as the CO specification in the product CO 2  is reduced below 1 mol-%. In current applications 1000 ppmv CO specifications for the product CO 2  are becoming the industry norm. The difficulty in keeping CO out of the product CO 2  is due to the high levels in the partially shifted or unshifted feed and the relatively large absorption of CO in the H 2 S and CO 2  absorbers for this feed. The large quantities of recycle gas from the CO 2  recycle compressor ultimately increase the semi-lean and lean solvent requirements and associated utilities such as refrigeration and reboiler duty to undesirable levels as well. An additional restriction on the treated fully shifted syngas that makes some options for limiting the CO in the product CO 2  unusable due to a limit on the CO contamination that is allowable from the partially shifted or unshifted gas. Other designs were disclosed in U.S. application Ser. No. 12/566,822 filed Sep. 25, 2009 in which the 1000 ppmv CO specification for the product CO 2  is maintained while minimizing utility requirements by transferring the absorbed CO from the partially treated or untreated syngas to the fully shifted syngas. However, these designs are sometimes unacceptable because despite reductions in CO in the CO 2  stream, they can increase the CO in the treated fully shifted syngas by 20 to 30%. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides a process for separation, recovery and utilization of gas streams comprising sulfur compounds, carbon dioxide and carbon monoxide from a synthesis gas (also referred to herein as “syngas”) comprising an unshifted synthesis gas or a partially shifted synthesis gas produced from high pressure partial oxidation of a hydrocarbonaceous reactant while removing carbon monoxide from these gas streams and concentrating CO in a partially shifted or unshifted synthesis gas stream. The process comprises first contacting the synthesis gas with a first liquid solvent in a first acidic gas removal unit to selectively absorb and remove at least a portion of carbon dioxide from the synthesis gas and to produce a purified synthesis gas; and then sending a portion of the first liquid solvent to a second acidic gas removal unit wherein at least a portion of carbon dioxide is contacted with the first liquid solvent mixed with a second liquid solvent to remove CO 2  from a shifted synthesis gas to produce a purified shifted synthesis gas. The process further comprises two options for maintaining the CO level at an acceptable level through the use of one or more CO stripping columns. The CO levels in the product CO 2  are kept at acceptable levels without increasing the CO in the treated fully shifted syngas via a CO stripping column. The solvent from the CO 2  absorber for the partially shifted or unshifted syngas is routed to the CO stripping column where it is counter currently contacted with treated fully shifted syngas. The fully shifted syngas effectively removes the CO that is absorbed from the partially shifted or unshifted syngas from the solvent and prevents it from entering the product CO 2 . The overhead vapor stream from the CO stripping column that contains the desorbed CO is compressed, cooled, and then returned to the CO 2  absorber for the partially shifted or unshifted syngas. 
         [0005]    A second option for minimizing the amount of CO from the partially shifted or unshifted syngas that contaminates the fully shifted syngas is to return the overhead from the H 2 S concentrator and rich solution flash to the H 2 S absorber for the partially shifted or unshifted syngas rather than the H 2 S absorber for the fully shifted syngas. This option is a lower priority alternative than the CO stripping column as the amount of CO in the H 2 S concentrator and rich solution flash overhead streams is much less than the CO that is removed in the CO stripping column. Also, sending these overhead streams to the H 2 S absorber for the partially shifted or unshifted syngas noticeably increases the solvent requirement for this absorber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  shows the carbon dioxide removal section for an absorbent process for treating a single synthesis gas stream. 
           [0007]      FIG. 2  shows the carbon dioxide removal sections of an absorbent process for processing both a fully shifted and an unshifted or partially shifted feed using separate absorbers for two feed gases but equipment in common for other parts of the process. 
           [0008]      FIG. 3  shows carbon dioxide removal sections for an absorbent process for processing both shifted and unshifted or partially shifted feeds that minimize the carbon monoxide in a product carbon dioxide stream. 
           [0009]      FIG. 4  shows a process for process both shifted and unshifted or partially shifted feeds that minimize carbon monoxide in product carbon dioxide by use of a carbon monoxide stripping column. 
           [0010]      FIG. 5  shows a sulfur removal section for an absorbent process for processing both shifted and unshifted or partially shifted feeds using separate absorbers for two feed gases but common equipment elsewhere in the process. 
           [0011]      FIG. 6  shows a modification of the sulfur removal section for an absorbent process for processing both shifted and unshifted or partially shifted feeds using separate absorbers for two feed gases but common equipment elsewhere. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    As used herein, the term “stream” can be a stream including various hydrocarbon molecules, such as straight-chain, branched, or cyclic alkanes, alkenes, alkadienes, and alkynes, and optionally other substances, such as gases, e.g., hydrogen, or impurities, such as heavy metals, and sulfur and nitrogen compounds. The stream can also include aromatic and non-aromatic hydrocarbons. Moreover, the hydrocarbon molecules may be abbreviated C 1 , C 2 , C 3  . . . C n  where “n” represents the number of carbon atoms in the one or more hydrocarbon molecules. Additionally, characterizing a stream as, e.g., a “partially-lean solvent stream” or a “lean solvent stream” can mean a stream including or rich in, respectively, at least one partially-lean solvent or lean solvent. 
         [0013]    As used herein, the term “zone” can refer to an area including one or more equipment items and/or one or more sub-zones. Equipment items can include one or more reactors or reactor vessels, heaters, exchangers, pipes, pumps, compressors, and controllers. Additionally, an equipment item, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones. 
         [0014]    As used herein, the term “vapor” can mean a gas or a dispersion that may include or consist of one or more hydrocarbons. 
         [0015]    As used herein, the term “cooler” can mean a device cooling a fluid with water. 
         [0016]    As used herein, the term “chiller” can mean a device cooling a fluid to a temperature below that obtainable by only using water. Typically, a chiller may use a refrigerant such as ammonia, a hydrocarbon or a hydrofluorocarbon. 
         [0017]    As used herein, the term “rich” can mean an amount of generally at least about 30%, or about 30% to about 70%, by mole, of a compound or class of compounds in a stream. 
         [0018]    As used herein, the term “absorber” can include an adsorber, and relates, but is not limited to, absorption and/or adsorption. 
         [0019]    As depicted herein, process flow lines in the drawings can be referred to as lines, effluents, streams, or portions. A line can contain one or more effluents, streams or portions. 
         [0020]    Often, a sour gas, such as a syngas, from a gasifier is treated with a solvent in at least one absorber to selectively remove one or more sulfur compounds, such as a hydrogen sulfide or a carbonyl sulfide, and carbon dioxide. It is sometimes desired to produce large quantities of hydrogen along with power from a gasification unit. In such instances a portion of the syngas from the gasifier is shifted to hydrogen in a reactor according to the reaction CO+H 2 O→CO 2 +H 2 . See for example U.S. Pat. No. 5,152,975 to Fong et al., incorporated herein by reference. The remainder of the syngas is cooled without shifting and, after further processing, sent to a combustion turbine. In addition, in gasification applications in which the final product is liquid fuels or chemicals, typically both a fully shifted and a partially shifted or unshifted feed must be treated in a process that removes the sulfur compounds (H 2 S and COS) and CO 2 . There are several commercial processes for this application that are currently being marketed, including the Selexol® process—using a mixture of dimethyl ethers of polyethylene glycol (UOP LLC, Des Plaines, Ill.), the Rectisol® process—using a methanol solvent (licensed by both Linde A G, Polach, Germany and Lurgi A G, Frankfurt Am Main Germany), the Sulfinol® process—using a mixture of sulfolane and an aqueous solution of either di-isopropanol amine or methyl-diethanol amine (Jacobs, Pasadena, Calif.), the Flexsorb® process—using a proprietary solvent (ExxonMobil Research and Engineering, Fairfax, Va.), the Morphysorb® process—using a mixture of n-formylmorpholine and n-acetylmorpholine (Uhde GmbH, Dortmund, Germany) and the Purisol® process using N-Methyl-2-Pyrrolidone (NMP) (Lurgi A G, Frankfurt Am Main Germany). Each of these processes employs a solvent that absorbs the sulfur compounds and/or carbon dioxide from an acid gas. The most straightforward set-up for these types of processes is a separate train for both feeds similar to what is pictured in  FIG. 1 . From a capital cost stand-point, it is advantageous to have separate H 2 S and CO 2  absorbers for the two feeds and common equipment for the remainder of the process similar to what is pictured in  FIG. 2 . The set-up in  FIG. 2  is typically able to meet the sulfur specifications for the treated gases and product CO 2  (using a medium pressure vent CO 2  and CO 2  from a vacuum compressor in  FIGS. 1 and 2 ) without problems. However, the electricity requirements for the CO 2  recycle compressor become excessive as the CO spec in the product CO 2  is reduced below 1 mol-%. The difficulty in keeping CO out of the product CO 2  is due to the high levels of CO in the partially shifted or unshifted feed and the relatively large absorption of CO in the H 2 S and CO 2  Absorbers for this feed. In current applications 1000 ppmv CO limits in the product CO 2  are becoming the normal specification. The large quantities of recycle gas from the CO 2  recycle compressor ultimately increase the semi-lean and lean solvent requirements and associated utilities such as refrigeration and reboiler duty to undesirable levels as well. 
         [0021]    The CO levels in the product CO 2  are kept at manageable levels by transferring the CO that is absorbed in the H 2 S and CO 2  absorbers for the partially shifted or unshifted syngas to the treated fully shifted syngas. This transfer is acceptable as long as the additional CO in the treated fully shifted syngas does not adversely affect its properties, which is the case for most applications. The absorbed CO is transferred to the fully shifted syngas by combining the solvent from the bottom of the CO 2  absorber for the partially shifted or unshifted syngas with sidedraw solvent from the CO 2  absorber for the fully shifted syngas and returning the combined solvent to the CO 2  absorber for the fully shifted syngas ( FIG. 3 ). Prior to returning the solvent to the CO 2  absorber for the fully shifted syngas it is chilled and contacted with overhead vapor from the H 2 S absorber for the fully shifted syngas to increase the CO 2  loading. The increased CO 2  loading combined with the relatively low level of CO in the fully shifted syngas provides a driving force that causes desorption of much of the CO in the CO 2  absorber into the fully shifted syngas. This desorption effectively removes the CO that is absorbed from the partially shifted or unshifted syngas from the solvent and prevents it from entering the product CO 2 . One design based on the  FIG. 3  configuration had electricity requirements of slightly less than 12 mW. Designs based on separating the 2 feeds into separate trains (as in  FIG. 1 ), having separate absorbers for the 2 feeds without the transfer of CO into the fully shifted gas (as in  FIG. 2 ), or a variation of the separate absorbers case in which the partially shifted or unshifted syngas has its own recycle flash and compressor, require a minimum of 10 mW more electricity to operate even when the 1000 ppmv CO spec in the product CO 2  is met. 
         [0022]    The invention is best implemented via the configuration presented in  FIG. 4 . Since the invention requires modifications in only the CO 2  removal section, it is possible to implement via the CO 2  removal section configurations appearing in  FIG. 4  combined with an H 2 S removal section that is configured at the discretion of the engineer, such as shown in  FIG. 5  or  6 . 
         [0023]    In order to understand the present invention, it is useful to first consider a simplified explanation of a system to treat a single synthesis gas stream.  FIG. 1  shows a carbon dioxide removal section for an absorbent process for treating a single synthesis gas stream. A solvent or mixture of solvents is used in the process. Among the solvents that can be used are a dimethyl ether of polyethylene glycol, a N-methylpyrrolidone, a tetrahydro-1,4-oxazine, a methanol, and a mixture comprising diisopropanolamine, tetrahydrothiophene-1,1-dioxide and mixtures thereof  FIG. 1  shows a feed stream  2  of syngas which may be a feed syngas or a syngas feed from a sulfur removal section that is not shown in the figure. The stream  2  is shown entering a lower portion of a carbon dioxide absorber  4  in which the syngas travels in an upward direction while contacting the solvent to remove carbon dioxide and producing a treated syngas  62  that is shown exiting a top portion of carbon dioxide absorber  4 . A lean stream  8  of solvent is shown being cooled by chiller  10  and then continuing as stream  12  to enter an upper portion of carbon dioxide absorber  4 . Lean stream  8  of solvent is either a fresh stream that has not been employed in the carbon dioxide removal section of the present invention or the lean stream has been regenerated through removal of impurities including carbon dioxide and sulfur compounds. The loaded solvent  14  is shown exiting the bottom of carbon dioxide absorber  4  and pass through a loaded solvent chiller  16  to continue as cooled loaded solvent stream  18  that is either sent to a carbon dioxide removal section that has a series of flash drums and compressors or it may be pumped to a sulfur removal section (not shown) or otherwise disposed of. The portion of the cooled loaded solvent stream  18  that is sent to the carbon dioxide removal section first is shown going to a carbon dioxide recycle flash drum  20  in which a portion of the solvent stream  22  is flashed to a carbon dioxide recycle compressor  24  to continue as compressed stream  26  that is sent to carbon dioxide recycle cooler  28  to return the compressed stream to about the temperature of stream  2  and finally to return to a bottom portion of carbon dioxide absorber  4 . A solvent stream  32  is sent from carbon dioxide recycle flash drum  20  to carbon dioxide vent flash drum  34  from which vents purified carbon dioxide stream  36 . The solvent stream then continues in line  38  to carbon dioxide vacuum flash drum  40  with carbon dioxide leaving at line  42  to vacuum compressor  44  and to purified carbon dioxide stream  46 . A stream of semi-lean solvent that now has a reduced concentration of carbon dioxide is shown in line  48  to be pumped by semi-lean solvent pump  50  to return to a middle portion of carbon dioxide absorber  4  through line  52 . The portion of the loaded solvent that exits the carbon dioxide removal section shown in  FIG. 1 , is sent through line  60  to pump  62  where it is pumped as exiting the system shown at  64 . 
         [0024]      FIG. 2  is also shown to provide a comparison between the prior art process of  FIG. 2  with the process of the invention shown in  FIG. 4 .  FIG. 2  shows the carbon dioxide removal section for an absorbent process for processing both fully shifted and unshifted or partially shifted feeds using separate absorbers for two feed gases but common equipment for other aspects of the process. More specifically, there are shown a first feed  102  and a second feed  124  that are being sent to a first carbon dioxide absorber  104  and a second carbon dioxide absorber  116 , respectively. The first feed  102  may be an unshifted or a partially shifted syngas feed or a syngas feed from a sulfur removal section of the process. The second feed  124  may be a fully shifted syngas feed or may be a syngas feed from a sulfur removal section of the process. First feed  102  contacts a solvent as explained in  FIG. 1  above in which carbon dioxide is removed from first feed  102  to be dissolved or otherwise contained within the solvent until the solvent is regenerated. A treated unshifted or partially shifted syngas  162  exits the top of carbon dioxide absorber  104 . Second feed  124  contacts a solvent in carbon dioxide absorber  116  and a treated fully shifted syngas exits at  118 . A lean solvent  108  is cooled by lean solvent chiller  110  and passes through line  112  to lines  114  and  115  to enter a top portion of carbon dioxide absorbers  104  and  116 , respectively. Regarding carbon dioxide absorber  104 , a loaded solvent stream  168  exits a bottom portion of carbon dioxide absorber  104  and then passes through line  126  to loaded solvent pump  128 , to line  130  to loaded solvent chiller  132  and line  134 . The loaded solvent stream in line  134  is then either sent in line  136  to be regenerated or to the sulfur removal sections of the process to be used in sulfur removal absorbers. Similar to loaded solvent stream  168  that exits carbon dioxide absorber  104  is shown a second loaded solvent stream  120  that exits carbon dioxide absorber  116 . Loaded solvent stream  168  and second loaded solvent stream  120  are combined in line  126 . Also shown in  FIG. 2  is a portion of the solvent being sent through a series of flash drums to remove a carbon dioxide product. More specifically, a portion of the loaded solvent stream continues through line  138  to carbon dioxide recycle flash drum with an overhead vapor passing through line  142  to carbon dioxide recycle compressor  144  to line  146  to carbon dioxide recycle cooler  148  to line  150  and then to return to bottom portion of carbon dioxide absorber  116 . The solvent having a higher proportion of carbon dioxide relative to the overhead vapor in line  142  is sent through line  152  to carbon dioxide medium pressure vent flash drum  154  with a medium pressure flow of carbon dioxide exiting through line  156  and the solvent stream continuing to line  158  to carbon dioxide vacuum flash drum  160 . The carbon dioxide exits through line  162  to vacuum compressor  164  and then exits the process in line  166 . The solvent which now is considered to be semi-lean is returned to the carbon dioxide absorbers through line  168  to semi-lean solvent pump  170  to line  172 . One portion of the semi-lean solvent in line  172  is returned to the first carbon dioxide absorber through line  176  and a second portion of the semi-lean solvent is returned to the second carbon dioxide absorber through line  174 . 
         [0025]      FIG. 3  generally shows carbon dioxide removal sections of an absorbent process for purifying a gas stream that contains two different feeds such as a shifted and an unshifted or partially shifted feed that minimizes the carbon monoxide content in a carbon dioxide stream that is removed from the feeds. More specifically, there are shown a first feed  102  and a second feed  124  that are being sent to a first carbon dioxide absorber  104  and a second carbon dioxide absorber  116 , respectively. The second feed  124  is shown first passing through line  125  prior to entering second carbon dioxide absorber  116 . The first feed  102  may be an unshifted or a partially shifted syngas feed or a syngas feed from a sulfur removal section of the process. The second feed  124  may be a fully shifted syngas feed or a syngas feed from a sulfur removal section of the process. In this embodiment of the invention, a portion of a loaded solvent in line  134  from first carbon dioxide absorber  104  is combined with the second feed  124 . 
         [0026]    First feed  102  contacts a solvent as explained in  FIG. 1  above in which carbon dioxide is removed from first feed  102  and then a treated unshifted or partially shifted syngas  162  exits the top of carbon dioxide absorber  104 . Second feed  124  contacts a solvent which removes carbon dioxide in carbon dioxide absorber  116  and a treated fully shifted syngas exits at  118 . The solvent that is used in the two carbon dioxide absorbers are shown as a lean solvent  108  that is cooled by lean solvent chiller  110  and then passes through line  112  to lines  114  and  115  to enter a top portion of carbon dioxide absorbers  104  and  116  respectively. Regarding carbon dioxide absorber  104 , a loaded solvent stream  168  exits a bottom portion of carbon dioxide absorber  104  and then passes through line  126  to loaded solvent pump  128 , then to line  130  to loaded solvent chiller  132  and then line  134 . The loaded solvent stream is then either sent in line  136  to be regenerated or to the sulfur removal sections of the process to be used in sulfur removal absorbers or a portion from line  134  is combined with second feed  124  in line  125 . Similar to loaded solvent stream  168  that exits carbon dioxide absorber  104  is shown a loaded solvent stream  180  that exits carbon dioxide absorber  116 . Loaded solvent stream  168  and loaded solvent stream  180  are combined in line  126 . Also shown in  FIG. 3  is the solvent being sent through a series of flash drums to remove a carbon dioxide product. More specifically a loaded solvent stream  120  exits a bottom portion of carbon dioxide absorber  116  to carbon dioxide recycle flash drum with an overhead vapor passing through line  142  to carbon dioxide recycle compressor  144  to line  146  to carbon dioxide recycle cooler  148  to line  150  and then to return to a bottom portion of carbon dioxide absorber  116 . The solvent having a higher proportion of carbon dioxide relative to the overhead vapor in line  142  is sent through line  152  to carbon dioxide medium pressure vent flash drum  154  with a medium pressure flow of carbon dioxide exiting through line  156  and the solvent stream continuing to line  158  to carbon dioxide vacuum flash drum  160 . The carbon dioxide stream which contains less than 10% carbon monoxide exits through line  162  to vacuum compressor  164  and then exits the process in line  166 . The solvent which now is considered to be semi-lean is returned to the carbon dioxide absorbers through line  168  to semi-lean solvent pump  170  to line  172 . One portion of the semi-lean solvent is returned to the first carbon dioxide absorber through line  176  and a second portion of the semi-lean solvent is returned to the second carbon dioxide absorber through line  174 . 
         [0027]      FIG. 4  shows a carbon dioxide removal section of an absorbent process for processing both shifted and an unshifted or partially shifted feeds that minimize the amount of carbon monoxide in the product carbon dioxide using a carbon monoxide stripping column. A feed  202  that is an unshifted or partially shifted feed or a feed from a sulfur removal section of the process is shown entering a lower portion of carbon dioxide absorber  204 . A treated unshifted or partially shifted gas flow  262  exits the upper part of carbon dioxide absorber  204 . A flow of solvent containing carbon monoxide exits in line  268  and then is shown entering an upper portion of carbon monoxide stripping column  282 . A gas flow containing carbon monoxide then exits carbon monoxide stripping column  282  in line  286  and is shown entering carbon monoxide recycle compressor  288  with a compressed gas passing to line  290  to carbon monoxide recycle cooler  292  to line  294  and then to enter a bottom portion of carbon dioxide absorber  204 . A slip stream  298  from a treated fully shifted synthesis gas is shown entering a lower portion of carbon monoxide stripping column  282  and a solvent stream  284  exits a lower portion of carbon monoxide stripping column  282  and then is shown passing to a carbon dioxide medium pressure vent flash drum  254 . A stream  256  of product carbon dioxide exits carbon dioxide medium pressure vent flash drum  254 . The remaining solvent then passes in line  258  to carbon dioxide vacuum flash drum with carbon dioxide exiting in line  262  to a vacuum compressor  264  with product carbon dioxide shown in line  266  leaving the vacuum compressor  264 . The solvent which is now semi-lean following removal of the carbon dioxide then is shown passing in line  268  to a semi-lean solvent pump  270  and then through line  272  with a portion of the solvent going to each of the two carbon dioxide absorbers shown in  FIG. 4 . More specifically, one portion of semi-lean solvent passes in line  274  to a middle portion of carbon dioxide absorber  216  and a second portion of semi-lean solvent passes in line  276  to a middle portion of carbon dioxide absorber  204 . Also shown is a supply of lean solvent  208  that is cooled by chiller  210  to line  212  with one portion of lean solvent  214  entering carbon dioxide absorber  204  and a second portion of lean solvent  215  entering carbon dioxide absorber  216 . In regards to carbon dioxide absorber  216 , a solvent stream  220  exits as shown at the bottom of carbon dioxide absorber  216  and then either ends up being cooled and returned to carbon dioxide absorber  216 , sent to be regenerated or sent to sulfur removal sections of the process that are not shown in  FIG. 4 . More particularly, the solvent stream  220  is shown going to loaded solvent pump  226  to line  230  to loaded solvent chiller to line  234  and then either to line  236  to either be regenerated or to enter the sulfur removal portions of the process, or a portion of solvent stream  220  may enter the carbon dioxide flash drum section of the process by being sent through line  227  to carbon dioxide recycle flash drum  240 . Carbon dioxide gas stream  242  is flashed from carbon dioxide recycle flash drum  240  and then is compressed by carbon dioxide recycle compressor  244  with compressed carbon dioxide stream  246  to be cooled by carbon dioxide recycle cooler  248  and passing through line  250  to carbon dioxide absorber  216 . Also shown is a loaded solvent stream  225  that passes through line  225  to carbon dioxide absorber  216  with a stream  224  containing a fully shifted synthesis gas feed or a synthesis gas feed from a sulfur removal section of the process being combined with loaded solvent stream  225 . 
         [0028]      FIG. 5  shows a sulfur removal section for an absorbent process for processing both a shifted and an unshifted or partially shifted feed using separate absorbers for the two feed gases but common equipment elsewhere. The loaded solvent that is used in the carbon dioxide removal sections of the process can be used in the sulfur removal section of the process.  FIG. 5  shows loaded solvent stream  502  from the carbon dioxide removal sections of the process entering an upper portion of a first sulfur absorber  504  that is for sour unshifted or partially shifted syngas. A second sulfur absorber  506  is shown that treats sour fully shifted syngas stream  512 . A feed  514  of sour unshifted or partially shifted syngas enters a lower portion of sulfur absorber  504 . An unshifted or partially shifted syngas exits in a gas stream  510  from an upper portion of sulfur absorber  504  to be treated in the carbon dioxide removal section of the process such as shown in  FIG. 4 . A loaded solvent stream  516  exits from a bottom portion of sulfur absorber  504 , then combines with a loaded solvent stream  518  exiting sulfur absorber  506  with the combined loaded solvent stream  520  passing through a lean/rich heat exchanger  524  and then passing through line  532  to hydrogen sulfide concentrator  534 . A gas exits in line  536  to be cooled by cooler  537  through line  539  to stripping gas compressor  541  through line  543  to another stripping gas cooler  545  to line  547  to stripping gas knockout drum  556 . A vapor stream exits stripping gas knockout drum  556  in line  558  to be sent to sulfur absorber  506 . A liquid stream  560  exits the bottom of the stripping gas knockout drum  556  to be sent to hydrogen sulfide stripper  566 . In connection with hydrogen sulfide stripper  566  is shown a stripper reboiler  592  which takes a stream  596  of solvent from a bottom portion of the hydrogen sulfide stripper  566  with steam entering in line  595  and a condensed liquid exiting in line  597 . After being heated in stripper reboiler  592 , a stream is returned to hydrogen sulfide stripper  566  though lines  594  and  598 . A vapor stream  576  exits hydrogen sulfide stripper  566  to pass through line  576  to reflux condenser  578  through line  580  to reflux drum  584 . Acid gas  582  exits and is sent to a sulfur recovery unit. A liquid stream returned through line  585  to reflux pump  584  plus makeup/purge water  586  to reflux pump  588  to line  590  to hydrogen sulfide stripper  566 . 
         [0029]    A liquid stream  538  exits hydrogen sulfide concentrator  534  and is sent to a rich flash drum  540 . Vapors exit through line  542  to cooler  544  to rich flash gas knock out drum  548 . Gas exits in line  550  to be compressed by rich flash gas compressor  552  and then to be sent through line  554  to stripping gas knockout drum  556 . Liquid exits rich flash drum  540  through line  564  to be sent to hydrogen stripper  566 . 
         [0030]    A lean solvent stream  568  exits at the lower end of hydrogen sulfide stripper  566  and is pumped by low pressure lean solvent pump  570  to line  572  through lean/rich heat exchanger  524  to line  526  to high pressure lean solvent pump  528  to be pumped to be used in the carbon dioxide removal section of the process such as shown in  FIG. 4 . 
         [0031]      FIG. 6  shows a sulfur removal section for an absorbent process for processing both shifted and unshifted or partially shifted feeds using separate absorbers for two feed gases but common equipment elsewhere in the process. In this embodiment of the invention, the return flow from the hydrogen sulfide concentrator and rich flash drum overhead are sent to the hydrogen sulfide absorber for partially shifted or unshifted syngas instead of being returned to the absorber for fully shifted syngas as shown in  FIG. 5 .  FIG. 6  shows a sulfur removal section for an absorbent process for processing both a shifted and an unshifted or partially shifted feed using separate absorbers for the two feed gases but common equipment elsewhere. The loaded solvent that is used in the carbon dioxide removal sections of the process can be used in the sulfur removal section of the process.  FIG. 6  shows a loaded solvent stream  502  from the carbon dioxide removal sections of the process entering an upper portion of a first sulfur absorber  504  that is for sour unshifted or partially shifted syngas. A second sulfur absorber  506  is shown that treats sour fully shifted syngas stream  512 . A feed  514  of sour unshifted or partially shifted syngas enters a lower portion of sulfur absorber  504 . An unshifted or partially shifted syngas exits in a gas stream  510  from an upper portion of sulfur absorber  504  to be treated in the carbon dioxide removal section of the process such as shown in  FIG. 4 . A loaded solvent stream  516  exits from a bottom portion of sulfur absorber  504 , then combines with a loaded solvent stream  518  exiting sulfur absorber  506  with the combined loaded solvent stream  520  passing through a lean/rich heat exchanger  524  and then passing through line  532  to hydrogen sulfide concentrator  534 . A gas exits in line  536  to be cooled by cooler  537  through line  539  to stripping gas compressor  541  through line  543  to another stripping gas cooler  545  to line  547  to stripping gas knockout drum  556 . A vapor stream exits stripping gas knockout drum  556  in line  599  to be sent to sulfur absorber  504 . A liquid stream  560  exits the bottom of the stripping gas knockout drum  556  to be sent to hydrogen sulfide stripper  566 . In connection with hydrogen sulfide stripper  566  is shown a stripper reboiler  592  which takes a stream  596  of solvent from a bottom portion of the hydrogen sulfide stripper  566  with steam entering in line  595  and a condensed liquid exiting in line  597 . After being heated in stripper reboiler  592 , a stream is returned to hydrogen sulfide stripper  566  though lines  594  and  598 . A vapor stream  576  exits hydrogen sulfide stripper  566  to pass through line  576  to reflux condenser  578  through line  580  to reflux drum  584 . Acid gas  582  exits and is sent to a sulfur recovery unit. A liquid stream returned through line  585  to reflux pump  584  plus makeup/purge water  586  to reflux pump  588  to line  590  to hydrogen sulfide stripper  566 . 
         [0032]    A liquid stream  538  exits hydrogen sulfide concentrator  534  and is sent to a rich flash drum  540 . Vapors exit through line  542  to cooler  544  to rich flash gas knock out drum  548 . Gas exits in line  550  to be compressed by rich flash gas compressor  552  and then to be sent through line  554  to stripping gas knockout drum  556 . Liquid exits rich flash drum  540  through line  564  to be sent to hydrogen stripper  566 . 
         [0033]    A lean solvent stream  568  exits at the lower end of hydrogen sulfide stripper  566  and is pumped by low pressure lean solvent pump  570  to line  572  through lean/rich heat exchanger  524  to line  526  to high pressure lean solvent pump  528  to be pumped to be used in the carbon dioxide removal section of the process such as shown in  FIG. 4 . 
         [0034]    Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. 
         [0035]    In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated. 
         [0036]    From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.