Pipeline gas pressure reduction with refrigeration generation

Claim 1

A process for reducing the high pressure of pipeline gas to a predetermined low pressure of a distribution system while generating refrigeration solely with energy derived from the reduction of pressure which comprises compressing said gas in two successive stages to increase the pressure thereof at least about 150 psi, injecting methanol into the thus compressed gas, cooling said compressed gas containing methanol by heat exchange with said gas after expansion as hereinafter set forth, expanding the cooled gas with the performance of work substantially without liquefaction of said gas, said work being utilized in one of said two stages of compression, separating an aqueous methanol condensate from the expanded gas and subjecting said condensate to distillation for the recovery and reuse of said methanol, said distillation receiving reboiler heat from said compressed gas prior to said cooling thereof, recovering low level refrigeration from the thus dehydrated expanded gas and then further expanding said dehydrated expanded gas with the performance of further work substantially without liquefaction of said gas, said further work being utilized in the other of said two stages of compression, recovering low level refrigeration from the further expanded gas and then passing said further expanded gas in countercurrent heat exchange relation with said compressed gas to effect cooling thereof as hereinbefore set forth, utilizing said further expanded gas to provide reflux cooling to said distillation, and thereafter discharging said further expanded gas at said predetermined low pressure into said distribution system.

Claim 9

An apparatus for reducing the high pressure of pipeline gas to a predetermined low pressure of a distribution system and for recovering refrigeration generated solely with energy derived from the reduction of pressure which comprises: a. a first centrifugal compressor coupled to a first turbo-expander, the inlet of said first compressor being connected for the entry of said pipeline gas; b. a second centrifugal compressor coupled to a second turbo-expander, the inlet of said second compressor being connected to the outlet of said first compressor; c. a distillation column with its reboiler connected for passage therethrough of compressed gas from said second compressor; d. means for injecting methanol into said compressed gas; e. a heat exchanger having a first flow path therein connected to the outlet of said second compressor and to the inlet of one of said first and second turbo-expanders; f. a gas-liquid separator connected to the outlet of said one turbo-expander, the liquid outlet of said separator being connected to an intermediate level of said distillation column; g. a first refrigeration recovery exchanger connected to the gas outlet of said separator and to the inlet of the other of said first and second turbo-expanders; and h. a second refrigeration recovery exchanger connected to the outlet of said other turbo-expander and to a second flow path in said heat exchanger, said second flow path being countercurrent to said first flow path and being connected to pass gas leaving said second flow path through the reflux condenser of said distillation column and to discharge gas into said distribution system.

Claim 10

An apparatus for reducing the high pressure of pipeline gas to a predetermined low pressure of a distribution system and for recovering refrigeration generated solely with energy derived from the reduction of pressure which comprises: a. a first centrifugal compressor coupled to a first turbo-expander, the inlet of said first compressor being connected for the entry of said pipeline gas; b. a second centrifugal compressor coupled to a second turbo-expander, the inlet of said second compressor being connected to the outlet of said first compressor; c. a distillation column with its reboiler connected for passage therethrough of compressed gas from said second compressor; d. means for injecting methanol into said compressed gas; e. a heat exchanger having a first flow path therein connected to the outlet of said second compressor and to the inlet of one of said first and second turbo-expanders; f. a gas-liquid separator connected to the outlet of said one turbo-expander, the liquid outlet of said separator being connected to an intermediate level of said distillation column; g. a first refrigeration recovery exchanger connected to the gas outlet of said separator and to the inlet of the other of said first and second turbo-expanders; and h. a second refrigeration recovery exchanger connected to the outlet of said other turbo-expander and to a second flow path in said heat exchanger, said second flow path being countercurrent to said first flow path and being connected to pass gas leaving said second flow path through the reflux condenser of said distillation column and to discharge gas into said distribution system.