System, method and apparatus

Abstract

The present invention relates to an apparatus, system or method for reducing pressure in a gas flow for a gas let-down system. The present invention further relates to an apparatus, system or method for drying gas. A system ( 10 ) for reducing pressure in a gas flow for a gas let-down system comprises an expander ( 102 ) driven by gas at a first pressure expanding to a second pressure, and a compressor ( 104 ) for compressing the gas from the second pressure to a third pressure, whereby the third pressure is lower than the first pressure and the third pressure is higher than the second pressure. By first expanding the gas and then compressing the gas the intermediate temperature of the gas at the second pressure is lower than if the gas is expanded directly to the third pressure. Further, a drying system for drying a gaseous fluid supplying heat to a heat exchanger comprises a liquid separator, a heat exchanger downstream of the liquid separator and a cooler for extracting heat from the gaseous fluid upstream of the liquid separator using the cold gas downstream of the heat exchanger. By extracting heat from the gaseous fluid the temperature of the gaseous fluid at the inlet to the separator can be reduced causing liquid in the gaseous fluid to condense and be separated in the separator.

1 . A system for reducing pressure in a gas flow for a gas let-down system comprising an expander driven by gas at a first pressure expanding to a second pressure, and a compressor for compressing the gas from the second pressure to a third pressure, whereby the third pressure is lower than the first pressure and the third pressure is higher than the second pressure. 
     
     
         2 - 40 . (canceled) 
     
     
         41 . A system according to  claim 1 , wherein the expander drives the compressor, preferably directly. 
     
     
         42 . A system according to  claim 41  wherein the expander drives the compressor by way of a common shaft. 
     
     
         43 . A system according to  claim 1 , further comprising a heat exchanger for heating the gas at the second pressure. 
     
     
         44 . A system according to  claim 43 , wherein the heat exchanger is arranged to provide heat exchange to at least one of: ambient air, to ground, or water, or an ambient heat source, and a waste heat source. 
     
     
         45 . A system according to  claim 43 , wherein the heat exchanger is arranged to provide cooling to a refrigeration load. 
     
     
         46 . A system according to  claim 43 , wherein a secondary circuit is arranged to transfer heat from a heat source to a heat exchanger. 
     
     
         47 . A system according to  claim 1 , wherein the expander further drives an electric generator. 
     
     
         48 . A system according to  claim 1 , wherein the system is arranged to conduct a portion of gas to the inlet of the expander, and to conduct a further portion of gas to the outlet of the compressor, the further portion of gas bypassing the expander and the compressor. 
     
     
         49 . A system according to  claim 48 , wherein the further portion of gas drives a further expander that optionally further drives an electric generator. 
     
     
         50 . A system according to  claim 1 , wherein the system is arranged to conduct a portion of gas to the inlet of the expander, and to conduct a further portion to the compressor, the further portion bypassing the expander. 
     
     
         51 . A system according to  claim 50 , wherein the further portion drives the compressor. 
     
     
         52 . A system according to  claim 51 , wherein the further portion drives the compressor by means of a tip turbine. 
     
     
         53 . A system according to  claim 1 , wherein the system is arranged to conduct a portion of gas to the inlet of the expander, and to conduct a further portion of gas to an inlet of a further expander. 
     
     
         54 . A system according to  claim 53 , wherein the further expander and the expander both drive the compressor. 
     
     
         55 . A system according to  claim 53 , wherein the system is arranged to conduct the further portion of gas from the outlet of the further expander to the outlet of the compressor. 
     
     
         56 . A system according to  claim 1 , further comprising a recuperator for transferring heat from one portion of the gas to another. 
     
     
         57 . A system according to  claim 43 , further comprising a recuperator for transferring heat from one portion of the gas to another and, optionally, wherein the recuperator is arranged to transfer heat from gas upstream of the expander to gas downstream of the heat exchanger. 
     
     
         58 . A system according to  claim 56 , wherein the recuperator is arranged to transfer heat from gas downstream of the compressor to gas upstream of the expander. 
     
     
         59 . A system according to  claim 1 , wherein the system is arranged to conduct a portion of gas from the outlet of the compressor to the inlet of the heat exchanger. 
     
     
         60 . A system according to  claim 59 , wherein the system is arranged to conduct a portion of gas from the outlet of the compressor to the inlet of the compressor. 
     
     
         61 . A system according to  claim 1 , further comprising a sealable vessel containing system rotative components. 
     
     
         62 . A system according to  claim 61 , wherein the system rotative components include an output drive shaft of the expander and an input drive shaft of the compressor. 
     
     
         63 . A system according to  claim 62 , further comprising a gas bearing supporting the output drive shaft of the expander or the input drive shaft of the compressor. 
     
     
         64 . A system according to  claim 62 , further comprising a magnetic bearing supporting the output drive shaft of the expander or the input drive shaft of the compressor. 
     
     
         65 . A system according to  claim 1 , further comprising a controller for activating the system when a system inlet gas temperature is below a pre-defined threshold. 
     
     
         66 . A system according to  claim 1 , wherein the expander comprises a turbine. 
     
     
         67 . A gas let-down station comprising a system according to  claim 1 . 
     
     
         68 . A gas distribution network comprising a system according to  claim 1 .