Method and system for the small-scale production of liquified natural gas (lng) and cold compressed natural gas (ccng) from low-pressure natural gas

Abstract

A system for the production of LNG from low-pressure feed gas sources, at small production scales and at lower energy input costs. A system for the small-scale production of cold compressed natural gas (CCNG). A method of dispensing natural gas from stored CCNG, comprising: dispensing CCNG from a CCNG storage tank; pumping the CCNG by a cryogenic liquid pump to a pressure suitable for compressed natural gas dispensing and storage in on-vehicle compressed natural gas storage tanks; recovering cold from the CCNG by heat exchange with natural gas feeding the natural gas production plant to replace dispensed product. A system for the storage, transport, and dispensing of natural gas, comprising: means for handling natural gas in a CCNG state where the natural gas is a non-liquid, but is dense-enough to allow for pumping to pressure by a cryogenic liquid pump.

What is claimed is: 
     
         1 . A method of producing cold compressed natural gas, comprising:
 providing a stream of feed gas;   compressing the stream of feed gas so the feed gas reaches a pressure of about 700 psia or higher;   directing the stream of feed gas through a heat exchanger in a first direction and directing a refrigerant through the heat exchanger in a second direction substantially opposite to the first direction such that the feed gas is cooled to between about −150° F. and about −170° F., thereby converting a first portion of the stream of feed gas to cold compressed natural gas.   
     
     
         2 . The method of  claim 1  further comprising directing a second portion of the stream of feed gas through a refrigeration production device such that the second portion of the stream of feed gas substantially drops in pressure and forms a low-pressure outflow stream of vapor and liquid. 
     
     
         3 . The method of  claim 2  further comprising directing the low-pressure outflow stream of vapor and liquid from the refrigeration production device for use as refrigerant in subsequent production of cold compressed natural gas; 
     
     
         4 . The method of  claim 2  wherein the refrigerant comprises the low-pressure outflow stream of vapor and liquid. 
     
     
         5 . The method of  claim 1  wherein the cold compressed natural gas has a pressure higher than its critical pressure and a temperature colder than its critical temperature and is capable of being pumped with a cryogenic liquid pump. 
     
     
         6 . The method of  claim 2  wherein the refrigeration production device is a multi-phase expander. 
     
     
         7 . The method of  claim 2  wherein the refrigeration production device is a Joule Thomson valve. 
     
     
         8 . The method of  claim 1  further comprising storing the cold compressed natural gas. 
     
     
         9 . The method of  claim 8  further comprising dispensing the stored cold compressed natural gas. 
     
     
         10 . The method of  claim 9  wherein the dispensing comprises:
 pumping the cold compressed natural gas with a cryogenic liquid pump; and 
 directing the cold compressed natural gas through a heat exchanger in a first direction and directing a stream of feed gas in a second direction substantially opposite the first direction such that the cold compressed natural gas cools the feed gas and the feed gas warms the cold compressed natural gas, thereby converting the cold compressed natural gas to compressed natural gas. 
 
     
     
         11 . The method of  claim 10  further comprising storing the compressed natural gas in one or more on-vehicle fuel tanks. 
     
     
         12 . A method of dispensing compressed natural gas, comprising:
 directing a stream of cold compressed natural gas out of a storage vessel;   pumping the cold compressed natural gas with a cryogenic liquid pump; and   directing the cold compressed natural gas through a heat exchanger in a first direction and directing the stream of feed gas in a second direction substantially opposite the first direction such that the cold compressed natural gas cools the feed gas and the feed gas warms the cold compressed natural gas, thereby converting the cold compressed natural gas to compressed natural gas.   
     
     
         13 . The method of  claim 12  further comprising storing the compressed natural gas in one or more on-vehicle fuel tanks.