Comparatively Analysis of the Technologies to Recovery Pressure Enegy at Natural Gas Pressure Reduction Station

Natural gas transmission pipelines usually operate at a considerable high pressure, which need to be reduced to a relative low pressure before it enters the local distribution system. During this process, a large amount of exergy is wasted when has passing through the throttle valves. This paper investigates a several of technologies used to recovery this part of energy based on the theoretical and practical consideration. These technologies includes: 1) Electricity generation. The throttle valve will be replaced by a turbo-expander, which powers generator to produce electrical energy. 2) LNG production. When the natural gas passes through an expander instead of a throttle valve, the temperature of the natural gas will drop dramatically. In this case, part of the gas will be condensed. 3) Application for refrigeration and air-conditioning. The cold exergy produced by the natural gas passing through the expander can drive a refrigerating system or directly utilized for cooling load. 4) Rubber comminuting. The cold exergy produced along the natural gas passing through the expander can be transferred to the non-flammable working medium gas, which can directly contact and froze the recycling materials such as rubber. The quickly frozen rubber will be easily crushed into powders. Current researches and applications of the above technologies will be studied. The energy recovery efficiency and potential development will be analyzed according to different kinds of natural gas transmission stations. The influence factors on the recovery efficiency will be investigated, such as the high to low transmission pressure, distribution pipelines category, gas flow rate and its fluctuation, gas supply and environment temperature. Form this research it is found that the directly application of the cold exergy is more economical and efficient than LNG production, electricity generation and rubber comminuting.