METHOD TO PRODUCE NATURAL GAS LIQUIDS (NGL'S) AT GAS PRESSURE REDUCTION STATIONS

• US 20090282863A1
• Filed: 05/15/2008
• Published: 11/19/2009
• Est. Priority Date: 05/15/2008
• Status: Active Grant

• Current Assignee: 1304338 Alberta, Ltd., 1304342 Alberta, Ltd.
• Original Assignee: 1304338 Alberta, Ltd.
• Inventors: Lourenco, Jose, Millar, MacKenzie
• Granted Patent: US 8,640,494 B2
• Time in Patent Office: Days
• US Class Current: 62/619
• CPC Class Codes: C10L 3/10 Working-up natural gas or synthetic natural gas
• CPC Class Codes: F25J 2240/02 Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• CPC Class Codes: F25J 2260/02 Integration in an installation for exchanging heat, e.g. for waste heat recovery
• CPC Class Codes: F25J 2260/10 Integration in a gas transmission system at a pressure reduction, e.g. "let down" station
• CPC Class Codes: F25J 3/061 Natural gas or substitute natural gas
• CPC Class Codes: F25J 3/0635 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/064 separation of CnHm with 2 carbon atoms or more

Abstract

A method to recover NGL'"'"'s at gas Pressure Reducing Stations. A first step involve providing at least one heat exchanger having a flow path for passage of high pressure natural gas with a counter current depressurized lean cold gas. A second step involves passing the high pressure natural gas stream in a counter current flow with the lean cold gas and cooling it before de-pressurization. A third step involves the expansion of the high pressure cooled gas in a gas expander. The expansion of the gas generates shaft work which is converted into electrical power by the power generator and the expanded low pressure and cold gas enters a separator where NGL'"'"'s are recovered. This process results in the recovery NGL'"'"'s, electricity and the displacement of a slipstream of natural that is presently used to pre-heat gas at Pressure Reduction Stations.

Claims

1. A method to recover Natural Gas Liquids (NGL'"'"'s) at Pressure Reduction Stations, comprising the steps of:

providing at least one heat exchanger, each heat exchanger having a flow path for passage of a high pressure natural gas stream and a counter current passage for a depressurised cold lean gas stream;

passing the high pressure natural gas stream along the heat exchanger in order to cool the high pressure natural gas stream through a heat exchange with the depressurized cold lean gas stream before pressure reduction, such that hydrates are condensed out of the high pressure natural gas stream;

removing hydrates from the high pressure natural gas stream;

passing the high pressure natural gas stream, which has had hydrates removed, through a gas expander to reduce pressure of the natural gas stream;

passing the natural gas stream, which has been reduced in pressure through a separator to produce a first stream of depressurized cold lean natural gas and a second stream of NGL'"'"'s.

2. The method of claim 1, including a step of heating a portion of the first stream and then blending selected quantities of the heated portion of the first stream with selected quantities of an unheated portion of the first stream.

3. The method of claim 1, including a step of heating at least a portion of the first stream by passing the portion of the first stream through a heat exchanger.

4. The method of claim 3, including a step of heating at least a portion of the first stream by passing the portion of the first stream through a heat exchanger adapted to dissipate excess cold to atmosphere.

5. The method of claim 3, including a step of heating at least a portion of the first stream by passing the portion of the first stream through a heat exchanger having a counter current waste heat stream.

6. The method of claim 1, including a step of connecting the gas expander to a power generator and using the power generated to run heaters and heating at least a portion of the first stream with the heaters.