Lng Regasification Configurations and Methods

Abstract

LNG composition of LNG from a storage tank or other source is modified in a process in which the LNG is pumped to a first pressure and split into two portions. One portion of the pressurized LNG is then reduced in pressure and heavier components are separated from the reduced pressure LNG to thereby form a lean LNG. The lean LNG is then pumped to a higher pressure and combined with the other portion to form a leaner LNG. Preferably, separation is performed using a demethanizer, wherein part of the demethanizer overhead product is condensed to form the lean LNG, while another portion is used for column reflux. In further preferred configurations, ethane recovery is variable and in yet other configurations, propane or ethane can be delivered via a batching pipeline.

1 . A LNG processing plant comprising:
 a LNG source that provides a first portion of LNG and a second portion of LNG, both portions having a pressure above a processing pressure;   a pressure reduction device that is coupled to the LNG source and configured to reduce pressure of the first portion to the processing pressure;   a processing unit configured to operate at the processing pressure and to receive the first portion from the pressure reduction device, wherein the processing unit is configured to remove heavier components in the first portion to thereby produce a lean LNG; and   a combination unit in which the lean LNG and the second portion of the LNG are combined to a form a processed LNG.   
     
     
         2 . The LNG processing plant of  claim 1 , further comprising a pump that pumps at least one of the first and second portions to a feed pressure. 
     
     
         3 . The LNG processing plant of  claim 2 , further comprising a demethanizer that receives at least part of the second portion at a pressure lower than the feed pressure. 
     
     
         4 . The LNG processing plant of  claim 1  further comprising a demethanizer that produces an overhead product, wherein a heat exchanger cools at least pan of the overhead product to thereby produce a reflux stream for the demethanizer. 
     
     
         5 . The LNG processing plant of  claim 1  further comprising a demethanizer reflux drum that produces an overhead product, wherein a heat exchanger condenses at least part of the overhead product to thereby produce the lean LNG. 
     
     
         6 . The LNG processing plant of  claim 5  further comprising a second pump that pumps the lean LNG to a delivery pressure. 
     
     
         7 . The LNG processing plant of  claim 1  wherein the combination unit is configured to combine the first portion and the lean LNG at pipeline pressure to thereby form the processed LNG. 
     
     
         8 . The LNG processing plant of  claim 1 , further comprising a deethanizer that receives a demethanizer bottom product and that produces a C2 overhead product and a C3 bottom product. 
     
     
         9 . The LNG processing plant of  claim 8 , further comprising a deethanizer overhead condenser that is configured to provide refrigeration to the C2 overhead product using refrigeration content of the first portion of the LNG. 
     
     
         10 . The LNG processing plant of  claim 1  further comprising a generator that is driven by expansion of a heated and pressurized portion of the first portion of LNG to thereby produce energy. 
     
     
         11 . A LNG processing plant comprising a heat exchanger that is configured such that at least part of a refrigeration content of LNG passing through the exchanger provides refrigeration to a demethanizer reflux stream and further provides condensation cold for a demethanizer reflux drum overhead product in an amount effective to condense the demethanizer reflux drum overhead product, and wherein the reflex stream and the reflux drum overhead product are produced from the LNG passing through the exchanger. 
     
     
         12 . The LNG processing plant of  claim 11  further comprising a demethanizer, wherein the demethanizer is coupled to the exchanger such that at least part of the LNG passing through the exchanger is fed to the demethanizer to thereby form at least one of the demethanizer reflux stream and a condensed demethanizer reflux drum overhead product. 
     
     
         13 . The LNG processing plant of  claim 11  wherein the LNG passing through the exchanger has a pressure of between 300 psig to 600 psig. 
     
     
         14 . The LNG processing plant of  claim 11  further comprising a pump that pumps the condensed demethanizer reflux drum overhead product to a delivery pressure. 
     
     
         15 . The LNG processing plant of  claim 14  further comprising a combination unit in which the condensed demethanizer reflex drum overhead product at delivery pressure is combined with LNG. 
     
     
         16 . A method of processing LNG, comprising:
 providing LNG and pumping the LNG to a feed pressure;   dividing the LNG at feed pressure in a first and second portion;   providing the first portion to a separation pressure and separating heavier components from the first portion at the separation pressure to thereby form a lean LNG;   pumping the lean LNG to a delivery pressure; and   combining the lean LNG and the second portion of the LNG to form a processed LNG.   
     
     
         17 . The method of  claim 16  wherein the feed pressure is between about 700 psig and 1300 psig, the separation pressure is between about 300 psig and 650 psig, and wherein the delivery pressure is between about 700 psig and 1300 psig. 
     
     
         18 . The method of  claim 16  wherein separation of the heavier components from the first portion is performed in a demethanizer reflux drum that produces a demethanizer overhead product. 
     
     
         19 . The method of  claim 18  wherein at least one portion of the demethanizer reflux drum overhead product is condensed to thereby form the lean LNG, and optionally wherein another portion of the demethanizer overhead product is cooled to thereby form a reflux stream for the demethanizer. 
     
     
         20 . The method of  claim 16  wherein separation of the heavier components from the first portion is performed in a demethanizer and in a demethanizer, wherein a demethanizer bottom product is fed to the deethanizer. 
     
     
         21 . The method of  claim 16  wherein ethane rejection or varying levels of ethane recovery is performed by blending a portion of liquid ethane product from a deethanizer overhead with processed LNG from a demethanizer.