Performance assessment of vortex tube and vertical ground heat exchanger in reducing fuel consumption of conventional pressure drop stations

In natural gas pressure drop stations, before pressure dropping specially in cold seasons, the natural gas is preheated to prevent gas hydrate formation. Indirect water bath heaters employed for preheating. The heaters have low thermal efficiency and consume a large amount of natural gas for preheating. Due to the abundance of natural gas pressure reduction stations, reducing energy consumption is essential in this sector of the gas industry. In this study to reduce the heater energy consumption an innovative system based on using vortex tube and vertical ground heat exchanger is proposed. A vortex tube is used instead of throttle valve to reduce natural gas pressure. Unlike the throttle valve, vortex tube divides the incoming stream into two cold and hot streams. Cold stream enters the shell and tube heat exchanger and receives geothermal heat. Then the warmed cold stream mix with hot steam outgoing from the vortex tube, and goes towards the heater at low pressure. The proposed system can reduce energy consumption up to 88%, and the discounted payback period is always less than 4.5 years.