Apparatus and Methods for Natural Gas Transportation and Processing

Abstract

In the transportation and processing of natural gas liquid nitrogen and liquid carbon dioxide is used in a heat exchanger process to liquefy natural gas supplied by a field site. The liquefied natural gas is transported to a regasification plant where cold energy in a part of the liquefied natural gas in an air separation device is used to produce liquid nitrogen and oxygen, natural gas. The oxygen is combusted in a power production plant, which captures the carbon dioxide produced by the combustion. This carbon dioxide is liquefied it using another part of the liquefied natural gas. The liquid nitrogen and liquid carbon dioxide is then transported to be used for further liquefaction of natural gas supplied by the field site.

1 . A method of liquefaction of natural gas supplied by a field site, the method comprising the steps of:
 providing supplies of liquid nitrogen and liquid carbon dioxide, and   performing a heat exchange process between the liquid nitrogen and the liquid carbon dioxide and the natural gas to thereby liquefy the natural gas, wherein the heat exchange process is arranged so that the resultant carbon dioxide is in gaseous or supercritical form at a pressure suited for injection for enhanced oil recovery.   
     
     
         2 . A method as claimed in  claim 1 , wherein no power input is required in the heat exchange process. 
     
     
         3 . A method as claimed in  claim 1 , wherein after the heat exchange process the nitrogen is in gaseous form and is vented to atmosphere. 
     
     
         4 . A method as claimed in  claim 1 , wherein the two phase region is avoided in at least one of the nitrogen, carbon dioxide and natural gas paths in the heat exchange process. 
     
     
         5 . A method as claimed in  claim 1 , wherein a combined carrier is provided, which initially contains the liquid nitrogen and the liquid carbon dioxide, and the method includes loading the liquefied natural gas onto the combined carrier. 
     
     
         6 . A method as claimed in  claim 5 , wherein the liquefied natural gas is stored in the same storage vessels on the combined carrier as the liquid nitrogen and the liquid carbon dioxide. 
     
     
         7 . A method as claimed in  claim 5 , wherein the heat exchange process is carried out on the combined carrier. 
     
     
         8 . A method as claimed in  claim 1 , further comprising the step of using the resultant carbon dioxide for enhanced oil recovery. 
     
     
         9 . A method as claimed in  claim 1 , further comprising the step of sequestration of the resultant carbon dioxide for final storage. 
     
     
         10 . An apparatus for liquefaction of natural gas, the apparatus being arranged to receive liquid nitrogen, liquid carbon dioxide and natural gas, wherein the apparatus comprises:
 a heat exchange device for transferring heat between the natural gas and the liquid nitrogen and the liquid carbon dioxide to thereby liquefy the natural gas, and wherein the heat exchange device is arranged such that the resultant carbon dioxide is in gaseous or supercritical form at a pressure suited for injection for enhanced oil recovery.   
     
     
         11 . An apparatus as claimed in  claim 10 , wherein the heat exchange device is arranged such that no power input is required. 
     
     
         12 . An apparatus as claimed in  claim 10 , wherein the heat exchange device is arranged such that the resultant nitrogen is in gaseous form and the apparatus includes means for venting the nitrogen gas to atmosphere. 
     
     
         13 . An apparatus as claimed in  claim 10 , wherein the heat exchange device is arranged such that the two phase region is avoided in at least one and preferably all of the nitrogen, carbon dioxide and natural gas paths. 
     
     
         14 . An apparatus as claimed in  claim 10 , comprising a combined carrier for containing and transporting the liquid nitrogen and the liquid carbon dioxide for input to the heat exchange device, and for containing and transporting the liquefied natural gas produced by the heat exchange device. 
     
     
         15 . An apparatus as claimed in  claim 14 , wherein the combined carrier comprises storage vessel for containing the liquefied natural gas or the liquid nitrogen and the liquid carbon dioxide. 
     
     
         16 . An apparatus as claimed in  claim 14 , wherein the heat exchange device is on the combined carrier. 
     
     
         17 . A method of producing natural gas, liquefied carbon dioxide and liquefied nitrogen comprising: providing amounts of liquefied natural gas, gaseous carbon dioxide and gaseous nitrogen, and transferring heat from the carbon dioxide and nitrogen to the liquefied natural gas in order to gasify the natural gas and liquefy the carbon dioxide and nitrogen. 
     
     
         18 . A method as claimed in  claim 17 , wherein the carbon dioxide is initially at atmospheric pressure and is compressed to a pressure higher than its triple point before it is liquefied. 
     
     
         19 . A method as claimed in  claim 17 , wherein the output natural gas is at above atmospheric pressure. 
     
     
         20 . A method as claimed in  claim 17 , wherein the liquid natural gas is compressed to a higher pressure than the output pressure of the gasified natural gas before being heated by heat exchange with the carbon dioxide and nitrogen, expanded to the output pressure to produce additional cold duty and work, and then further heated by carbon dioxide and nitrogen. 
     
     
         21 . A method as claimed in  claim 17 , wherein the nitrogen process includes compression followed by cooling by heat exchange with the natural gas to produce liquid nitrogen or cold dense phase nitrogen. 
     
     
         22 . A method as claimed in  claim 17 , wherein a valve or expander is used to reduce the pressure of the liquid or cold dense phase nitrogen to a pressure suitable for transport. 
     
     
         23 . A method as claimed in  claim 17 , wherein liquefaction of the carbon dioxide is achieved by splitting of the stream and compressing the split portions of the carbon dioxide to different pressure levels followed by heat exchange with the natural gas. 
     
     
         24 . A method as claimed in  claim 17 , wherein an air separation unit produces the nitrogen to be liquefied. 
     
     
         25 . A method as claimed in  claim 24 , wherein oxygen produced by the air separation unit is used for an Oxyfuel Power Plant. 
     
     
         26 . An apparatus comprising a heat exchanger, the apparatus arranged to receive liquefied natural gas, gaseous carbon dioxide and gaseous nitrogen and to produce liquid carbon dioxide and liquid nitrogen by gasification of the liquefied natural gas and transfer of heat from the carbon dioxide and nitrogen to the liquefied natural gas. 
     
     
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