Study On The Collection And Utilization Of Cold Energy In The Process Of Natural Gas Gasification Of L-CNG Filling Station

With the gas vehicle constant promotion and popularization, various regions build a lot of L-CNG refueling stations, but the use of gas station’s cold energy of LNG gasification has not been carried out.The temperature of the LNG is about -162.0 degrees Celsius, the cooling energy produced by gasification is about 830～860kJ/kg, which is huge available.This paper first analyzes the advantages and disadvantages of the existing LNG cold energy utilization, in view of the engineering practice of this project, use power generation and cooling system for the combination of the cold energy of the gas station LNG cold energy. In terms of power generation, considering the actual cost of construction and power generation efficiency, this paper adopts low-temperature Organic Rankine cycle power generation and selects refrigerant mixtures in mass ratio 1:1 R290/R600 composition as the Rankine circulation working medium, and chooses 50% of water and ethylene glycol solution with low freezing point as cooling working fluid. In the design of the whole process system, the article has selected the air temperature type gasified as process system gasified, used the U type pipe structure of heat exchanger and adopts the scroll expander. And then the paper use Aspen Plus software to simulate the process of the system, and calculate the exergy efficiency of all the equipment. The exergy efficiency of the LNG heat exchanger is 28.56%,the exergy efficiency of Rankine cycle heat exchanger is 38.83%, the exergy efficiency of LNG reheater is 40.04%,the exergy efficiency of fan coil is 57.99%. And the exergy efficiency of expansion machine is 70.75%, the exergy efficiency of Rankine cycle refrigerant pump is 95.25%, the exergy efficiency of cooling refrigerant pump is 96.54% and the energy efficiency of system is 42.25%.Through the analysiswe can conclude that the exergy efficiency of the syetem is depending on the exergy efficiency of heat exchanger. The exergy efficiency of the heat exchanger is mainly affected by the temperature difference between hot and cold fluid, the greater the temperature difference between hot and cold fluid, the more of energy loss, the lower ofexergy efficiency.Finally, choosing Nanning Xin Yang CNG filling station as the research object, selecting the gasification of 10 cubic meters a day in filling station as a benchmark, the paper designed process system engineering, and calculated technical parameters of all the equipment. Results show that the daily cooling energy is 148.104kW, the expansion of external power output is 154.549kW, process system working fluid and pump consumption of electrical energy is 15.656 kW. The total investment of the project is 303 thousand yuan, annual revenue is 27 thousand yuan. The investment cost will recover in about 12 years. The designer of the process is simple, which just covers an small area, has the safely operation, has higher elasticity, and has high practicability.