Method of recovery of natural gas liquids from natural gas at ngls recovery plants

Abstract

A method to recover natural gas liquids from natural gas streams at NGL recovery plants. The present invention relates to methods using liquid natural gas (LNG) as an external source of stored cold energy to reduce the energy and improve the operation of NGL distillation columns. More particularly, the present invention provides methods to efficiently and economically achieve higher recoveries of natural gas liquids at NGL recovery plants.

What is claimed is: 
     
         1 . A method for recovery of natural gas liquids from natural gas using the cold energy stored in LNG comprising the step of:
 The storage and supply of LNG as an external cooling source to control the operation and recovery of NGLs in a distillation column.   
     
     
         2 . The method as defined in  claim 1 , providing LNG as a reflux stream by a temperature control of the overhead gas stream by mixing of LNG with the rising gas stream in the distillation column. 
     
     
         3 . The method as defined in  claim 1 , providing LNG to directly mix with un-distilled expanded, feed gas to allow distillation column to operate at higher pressures without loss of recovery. 
     
     
         4 . The method as defined in  claim 1 , providing LNG as a stripping gas for carbon dioxide concentration in NGL product stream. 
     
     
         5 . method described in  claim 1 , providing LNG to cool an overhead stream to generate a second reflux stream for a dual reflux distillation column operation. 
     
     
         6 . A method for recovery of natural gas liquids from a natural gas comprising the steps of:
 positioning a storage vessel for liquid natural gas (LNG) at a NGL recovery plant facility that has at least one distillation column for recovering natural gas liquids (NGLs);   adding LNG from the storage vessel by direct mixing to control the temperature profile in a NGL distillation column, the temperature in the overhead product of the distillation column being controlled by controlling addition of LNG as a reflux stream, the temperature in the expanded feed gas to the distillation column being controlled by controlling addition of LNG as a tempering gas, the stripping of carbon dioxide from the NGL product stream being controlled by controlling the addition of LNG as stripping gas.   
     
     
         7 . The NGL recovery plant as defined in  claim 6 , wherein LNG provides additional cooling energy to the inlet plant gas feed. 
     
     
         8 . NGL recovery plant as defined in  claim 6 , wherein the use of LNG as an external cold energy source is used to increase the overall energy efficiency and recovery of NGLs.