Method and plant for the purification of carbon dioxide using liquid carbon dioxide

Abstract

The present invention relates to an improved method for removing contaminants from a gaseous stream substantially comprising carbon dioxide. More specifically, the method comprises the step of subjecting the gaseous stream to an absorption step in which the absorbent is liquid carbon dioxide wherein the waste of carbon dioxide is minimized by utilizing a compressing means for generating a pressure difference between two streams in a reboiler.

1 - 25 . (canceled) 
     
     
         26 . A method for removing at least one contaminant from a feed stream (f) substantially comprising carbon dioxide, said method comprising the step of subjecting the feed stream (f) to
 a) a purification step in a column having a top, bottom and an intermediate section, the purification step provides a contaminant lean stream (g 2 ) leaving the top section of the column and a contaminant rich liquid stream (l 2 ) leaving, optionally the bottom section of, the column, said contaminant rich liquid stream (l 2 ) being fed to the reboiler (A 3 ) and wherein the contaminant lean stream leaving the top section of the column is further subjected to the steps selected from the two options:   1:   b1) compressing the contaminant lean stream (g 2 ) providing a compressed gaseous stream (g 4 )   c1) cooling the compressed gaseous stream (g 4 ) in the reboiler (A 3 ) providing at least a product stream (p) and a gaseous stream (g 3 ); and   d1) feeding the gaseous stream (g 3 ) to the column at the bottom section of the column; and   2:   b2) cooling the contaminant lean stream (g 2 ) in a reboiler providing at least a product stream (p) and a gaseous stream (g 3 ); and   c2) compressing the gaseous stream (g 3 ) providing a cooled compressed gaseous stream (g 4 ′);   d2) feeding the cooled compressed gaseous stream (g 4 ′) to the column at the bottom section of the column; and depressurising the contaminant rich liquid stream (l 2 ) leaving at the bottom section of the column before entering the reboiler;   wherein the purification step, a, is selected from absorption using an absorbent when the feed stream is gaseous, and rectification having a liquid phase, when the feed stream is liquid, and wherein the absorbent and liquid phase is liquid carbon dioxide.   
     
     
         27 . The method according to  claim 26 , wherein the feed stream (f) is liquid and the further steps are:
 b1) compressing the contaminant lean stream (g 2 ) providing a compressed gaseous stream (g 4 )   c1) cooling the compressed gaseous stream (g 4 ) in a reboiler providing at least a product stream (p) and a gaseous stream (g 3 ); and   d1) feeding the gaseous stream (g 3 ) to the column at the bottom section of the column.   
     
     
         28 . The method according to  claim 26 , wherein the feed stream (f) is gaseous. 
     
     
         29 . The method according to  claim 28 , wherein the further steps are:
 b2) cooling the contaminant lean stream (g 2 ) in a reboiler providing at least a product stream (p) and a gaseous stream (g 3 ); and   c2) compressing the gaseous stream (g 3 ) providing a cooled compressed gaseous stream (g 4 ′);   d2) feeding the cooled compressed gaseous stream (g 4 ′) to the column at the bottom section of the column; and depressurising the contaminant rich liquid stream (l 2 ) leaving at the bottom section of the column before entering the reboiler.   
     
     
         30 . The method to according to  claim 26  wherein the at least one contaminant is selected among compounds having a boiling point higher than the boiling point of carbon dioxide at the prevailing conditions and non-polar compounds. 
     
     
         31 . The method according to  claim 30 , wherein the at least one contaminant is selected from the group consisting of: sulfides, such as hydrogen sulfide, carbonyl sulfides and dimethylsulfide; nitrogen containing compounds, such as N 2 , ammonia and nitrogen dioxide; and hydrocarbons, such as, methane, n-pentane, n-hexane, benzene, toluene and oxygen containing hydrocarbons such as dimethyl ether, acetaldehyde, ethyl acetate, acetone, methanol, ethanol, isobutanol and n-propanol. 
     
     
         32 . The method according to  claim 26 , wherein the ratio of liquid carbon dioxide to the feed stream is 1:3 to 10:1. 
     
     
         33 . The method according to  claim 32 , wherein the ratio of liquid carbon dioxide to the feed stream is 1:3 to 3:1. 
     
     
         34 . The method according to  claim 26 , wherein the purification step further comprises an integrated water inhibitor and/or scavenger step. 
     
     
         35 . The method according to  claim 34 , wherein the water inhibitor and/or scavenger used in the purification step is recirculated in the process. 
     
     
         36 . The method according to  claim 34 , wherein the water inhibitor and/or scavenger is fed to the intermediate section of the purification column. 
     
     
         37 . The method according to  claim 34 , wherein the water inhibitor and/or scavenger is mixed with the feed stream (f) or the absorbent liquid (l 1 ) prior to being fed to the column. 
     
     
         38 . The method according to  claim 34 , wherein a liquid carbon dioxide stream (l 5 ) is partially withdrawn from the purification column at a position above the inlet of the water inhibitor and/or scavenger. 
     
     
         39 . The method according to  claim 34 , wherein the integrated inhibitor step is a dehydration step using a water inhibitor, which decreases the water activity in the feed stream, wherein the water inhibitor is selected from the group consisting of methanol, ethanol, mono ethylene glycol and tri ethylene glycol. 
     
     
         40 . The method according to  claim 26  further comprising at least one of the steps of:
 heating or cooling the product stream leaving the reboiler, and/or 
 purifying the product stream by means of adsorption and/or absorption; and/or 
 condensing and/or distilling the product stream to provide a high purity liquid carbon dioxide stream; and/or 
 feeding a portion of condensed and/or refluxed carbon dioxide to the purification column. 
 
     
     
         41 . The method according to  claim 26 , wherein the purification step is preceded by at least one or more of the steps of:
 compressing,   adsorbing and/or absorbing; and   liquefying by means of for example condensation or distillation.   
     
     
         42 . The method according to  claim 40 , wherein the purification step is preceded by at least one or more of the steps of:
 compressing,   adsorbing and/or absorbing; and   liquefying by means of for example condensation or distillation.   
     
     
         43 . A carbon dioxide purification unit comprising a purification column (A 1 ), a compression means (A 2 ), and a reboiler (A 3 ), said purification column (A 1 ) having a top and a bottom and a section intermediate of the top and the bottom, the purification column having a feeding stream influent (f), a contaminant lean gas effluent (g 2 ) situated at the top part of the column, a liquid carbon dioxide influent (l 1 ) situated at the top part of the column, and a contaminant rich liquid effluent (l 2 ), said contaminant rich liquid effluent (l 2 ) optionally being situated at the bottom part of the purification column,
 wherein the contaminant rich liquid effluent (l 2 ) is connected to the reboiler (A 3 ) additionally having a waste liquid effluent (l 3 ), a product effluent (p), a compressed gaseous influent (g 4 ), and a gas effluent (g 3 ), the gaseous effluent (g 3 ) being connected to the purification column (A 1 ), wherein the compressing means (A 2 ) is inserted between the reboiler (A 3 ) and the purification column (A 1 ) at a position where the contaminant lean gas purification column effluent (g 2 ) is compressed to provide the compressed gaseous influent (g 4 );   or   wherein the contaminant rich liquid effluent (l 2 ) is connected to the reboiler (A 3 ) additionally having a waste liquid effluent (l 3 ), a product effluent (p), a contaminant lean gas purification column effluent (g 2 ), and a gas effluent (g 3 ), the gas effluent (g 3 ) being connected to the compressing means (A 2 ) inserted between the reboiler (A 3 ) and the purification column (A 1 ) at a position between the gas effluent (g 3 ) and a cooled compressed gaseous influent (g 4 ′) connected to the column (A 1 ) and wherein the unit further comprises a depressurising valve (A 4 ), wherein the depressurising valve (A 4 ) is positioned on the contaminant rich liquid effluent (l 2 ).   
     
     
         44 . The unit according to  claim 43 , wherein the feeding influent (f) is situated at the bottom section of the purification column (A 1 ) and the contaminant rich liquid effluent (l 2 ) is connected to the reboiler (A 3 ) additionally having a waste liquid effluent (l 3 ), a product effluent (p), a compressed gaseous influent (g 4 ), and a gas effluent (g 3 ), the gas effluent (g 3 ) being connected to the purification column (A 1 ), wherein a compressing means (A 2 ) is inserted between the reboiler (A 3 ) and the purification column (A 1 ) at a position between the contaminant lean gas purification column effluent (g 2 ) and the compressed gaseous influent (g 4 ) and wherein the purification column is an absorption column. 
     
     
         45 . The unit according to  claim 43 , wherein the feeding influent (f) is situated at the top section of the purification column (A 1 ) and the contaminant rich liquid effluent (l 2 ) is connected to the reboiler (A 3 ) additionally having a waste liquid effluent (l 3 ), a product effluent (p), a contaminant lean gas purification column effluent (g 2 ), and a gas effluent (g 3 ), the gas effluent (g 3 ) being connected to a compressing means (A 2 ) inserted between the reboiler (A 3 ) and the purification column (A 1 ) at a position between the gas effluent (g 3 ) and the cooled compressed gaseous influent (g 4 ′) and wherein a valve (A 4 ) is positioned on the contaminant rich liquid effluent (l 2 ) and wherein the purification column is a rectification column. 
     
     
         46 . The unit according to  claim 43 , wherein the purification column further comprises a water inhibitor and/or scavenger influent (l 0 ) situated at the intermediate section of the column. 
     
     
         47 . The unit according to  claim 43 , wherein the contaminant rich liquid effluent (l 2 ) situated at the bottom section of the column is split in two at a position outside the column and a first liquid effluent (l 2 ′) is connected to the water inhibitor and/or scavenger influent (l 0 ) and a second liquid effluent (l 2 ″) is connected to the reboiler (A 3 ). 
     
     
         48 . The unit according to  claim 46 , wherein the purification column is further provided with a carbon dioxide effluent (l 5 ) situated at a position of the purification column between the water inhibitor and/or scavenger influent (l 0 ) and the liquid carbon dioxide influent (l 1 ). 
     
     
         49 . The unit according to  claim 43 , wherein the unit further comprises a feeding gas source, and wherein the feeding influent (f) is connected to the feeding gas source; and/or
 wherein the unit further comprises a carbon dioxide processing unit such as a heat exchanger and/or a filter and/or a distillation column, and wherein the product effluent (p) is connected to the carbon dioxide processing unit; and/or   wherein the unit further comprises a liquid carbon dioxide reservoir, e.g. a distillation column connected to the product gas outlet and wherein the liquid carbon dioxide influent (l 1 ) is connected to the liquid carbon dioxide reservoir; and/or   wherein the unit further comprises a waste reservoir, and wherein the waste liquid effluent (l 3 ) is connected to the waste reservoir; and/or   wherein the unit further comprises a water inhibitor/scavenger reservoir and wherein the water inhibitor and/or scavenger influent (l 0 ) is connected to the water inhibitor/scavenger reservoir.   
     
     
         50 . The unit according to  claim 43 , further comprising a drying filter, and a compressor wherein the feeding influent (f) up stream is connected to the drying filter, which optional drying filter is connected to the compressor. 
     
     
         51 . The unit according to  claim 46 , wherein the purification column is further provided with a carbon dioxide effluent (l 5 ) situated at a position of the purification column between the water inhibitor and/or scavenger influent (l 0 ) and the liquid carbon dioxide influent (l 1 ) and wherein the carbon dioxide effluent (l 5 ) is connected to the feeding influent (f).