Method for purification of carbon dioxide using liquid carbon dioxide

Abstract

The present invention relates to a method for removing at least one contaminant from a gaseous stream substantially comprising carbon dioxide. More specifically said method includes the step of subjecting the gaseous stream to an absorption step in which the absorbent is liquid carbon dioxide.

What is claimed is: 
     
         1 . A method for removing a plurality of contaminants from a gaseous feed stream substantially comprising carbon dioxide, said method comprising:
 subjecting the gaseous feed stream to an absorption step in an absorption column having a top, bottom and an intermediate section, wherein an absorbent is liquid carbon dioxide and wherein the plurality of contaminants are selected from the group consisting of non-polar organic compounds and compounds having a boiling point higher than the boiling point of carbon dioxide; and   obtaining a carbon dioxide enriched gaseous stream and a contaminant rich liquid stream containing at least 95% (w/w) of the plurality of contaminants from the gaseous feed stream,   wherein the temperature of the gaseous feed stream entering the column is higher than a dew point temperature of carbon dioxide at the prevailing absorption condition and the ratio of absorbent to gaseous feed stream is at least 1/11.   
     
     
         2 . The method according to  claim 1 , wherein the plurality of contaminants are selected from the group consisting of NOx's, oxygenates, esters, aromatic compounds, alcohols and combinations thereof. 
     
     
         3 . The method according to  claim 1 , wherein the ratio of absorbent to gaseous feed stream is in the range 1/11 to 1/2, and wherein the plurality of contaminants are selected from the group consisting of NOx's, oxygenates, esters aromatic compounds, alcohols and combinations thereof. 
     
     
         4 . The method according to  claim 1 , wherein the absorbent is an externally supplied source of pure liquid carbon dioxide. 
     
     
         5 . The method according to  claim 1 , wherein the absorption step further comprises an integrated dehydration step. 
     
     
         6 . The method according to  claim 1 , wherein the absorption step further comprises an integrated dehydration step,
 wherein the dehydration step is performed using a water inhibitor, which decreases the water activity in the gaseous feed gas, wherein the water inhibitor is selected from the group consisting of methanol, ethanol, mono ethylene glycol and tri ethylene glycol.   
     
     
         7 . The method according to  claim 6 , wherein the water inhibitor used in the dehydration step is recirculated. 
     
     
         8 . The method according to  claim 6 , further comprising feeding the water inhibitor to the intermediate section of the absorption column at a position higher than a position where the gaseous feed stream is fed to the absorption column. 
     
     
         9 . The method according to  claim 8 , further comprising partially withdrawing the liquid carbon dioxide from the absorption column at a position above the inlet of the water inhibitor. 
     
     
         10 . The method according to  claim 1 , further comprising:
 evaporating the contaminant rich liquid carbon dioxide stream comprising contaminants leaving the bottom section of the column; and   feeding the evaporated contaminant rich liquid carbon dioxide stream to the gaseous stream entering the absorption column.   
     
     
         11 . The method according to  claim 1 , further comprising the steps of:
 optionally heating the carbon dioxide enriched gaseous stream leaving the absorption column,   optionally filtrating the carbon dioxide enriched gaseous stream, and   condensing and/or distilling the carbon dioxide enriched gaseous stream to provide a high purity liquid carbon dioxide stream.   
     
     
         12 . The method according to  claim 1 , wherein the ratio of absorbent to gaseous feed stream is in the range 1/11 to 1/3 and wherein the plurality of contaminants are selected from the group consisting of oxygenates, esters, aromatic compounds and alcohols. 
     
     
         13 . The method according to  claim 4 , wherein the absorbent is a stream from a down stream purification process of the same overall process.