Method and device for the liquefaction of a gaseous co2 stream

Abstract

The invention relates to a device for the liquefaction of a gas flow containing at least 95 mol-% carbon dioxide, comprising at least a first compression stage in which the feed gas flow is compressed; means for condensing the compressed flow, formed by two in-series phase separators, in order to partially condense the flow and produce a liquid flow; a first heat exchanger; a second heat exchanger; a means for conveying at least part of the liquid flow into the tubes of the first heat exchanger; a means for discharging a first part of the liquid cooled in the second heat exchanger, a valve, a means for conveying as second part of the liquid cooled in the second exchanger, and a means for compressing at least part of the vaporized flow and mixing this with the fed gas flow.

1 .- 13 . (canceled) 
     
     
         14 . A process for the liquefaction of a gas flow containing at least 95 mol % of carbon dioxide, comprising:
 a) compressing the feed gas flow in at least a first compression stage,   b) cooling the compressed flow in order to at least partially condense the compressed flow, thereby producing a liquid flow, the cooling being performed in a first heat exchanger in order to partially condense it, reducing the partially condensed flow in pressure thereby producing a first reduced pressure flow and sending the first reduced pressure flow to a first phase separator, reducing a liquid from the first phase separator in pressure thereby producing a second reduced pressure flow and then sending the second reduced pressure flow to a second phase separator and withdrawing the liquid flow from the second phase separator,   c) cooling at least a portion of the liquid flow removed from the second phase separator in the tubes of a second heat exchanger which is a shell and tube heat exchanger,   d) cooling a first part of the liquid cooled in the second exchanger, subsequently reducing the cooled first part in pressure, thereby producing a liquid product,   e) cooling a second part of the liquid cooled in the second exchanger or of a liquid produced by reducing in pressure and partially vaporizing the cooled second part by reducing the pressure in a valve and is evaporating the cooled second part in the shell of the first exchanger in order to form a vaporized flow, and   f) compressing at least a part of the vaporized flow and mixing the compressed vaporized flow with the feed gas flow.   
     
     
         15 . The process of  claim 14 , in which a gas from the first phase separator is mixed with the feed gas flow at a first pressure. 
     
     
         16 . The process of  claim 14 , wherein a gas from the second phase separator is mixed with the feed gas flow. 
     
     
         17 . The process of  claim 16 , wherein the gas from the second phase separator is mixed with the feed gas flow at a second pressure lower than the first pressure. 
     
     
         18 . The process of  claim 17 , wherein the gas from the second phase separator is mixed with the feed gas flow upstream of the first compression stage. 
     
     
         19 . The process of  claim 14 , wherein the liquid from the first phase separator is not cooled upstream of the reduction in pressure. 
     
     
         20 . The process of  claim 14 , wherein the second heat exchanger is a final subcooler. 
     
     
         21 . The process of  claim 20 , wherein the final product is not cooled downstream of the second exchanger. 
     
     
         22 . A device for the liquefaction of a gas flow containing at least 95 mol % of carbon dioxide, comprising at least a first compression stage in which the feed gas flow is compressed, a means for condensing the compressed flow, in order to partially condense it in order to produce a liquid flow, a first heat exchanger, in which the compressed flow is cooled in order to partially condense it, a means for reducing in pressure the partially condensed flow, a first phase separator into which the pressure-reduced flow is sent, a means for reducing in pressure a liquid from a first phase separator, a second phase separator, a means for sending the pressure-reduced liquid to the second phase separator and a means for withdrawing the liquid flow from the second phase separator, a second heat exchanger which is a shell and tube heat exchanger, a means for sending at least a part of the liquid flow into the tubes of the second heat exchanger, a means for taking out, as liquid product, a first part of the liquid cooled in the second exchanger, which is subsequently reduced in pressure, a valve, a means for sending a second part of the liquid cooled in the second exchanger to be reduced in pressure in the valve and to be vaporized in the shell of the second exchanger, in order to form a vaporized flow, and a means for compressing at least a part of the vaporized flow and mixing it with the feed gas flow. 
     
     
         23 . The device of  claim 22 , further comprising a means for sending a gas from a first phase separator downstream of the first compression stage. 
     
     
         24 . The device of  claim 22 , further comprising means for sending a gas from the second phase separator upstream of the first compression stage. 
     
     
         25 . The device of  claim 22 , not comprising cooling means between the first phase separator and the valve. 
     
     
         26 . The device of  claim 22 , wherein the second heat exchanger is the final subcooler of the device.