Research On Several Key Security Technologies In LNG Filling Station

Liquefied natural gas (LNG) as fuel for vehicles compared with gasoline, diesel and compressed natural gas is environmental, economic and safety. LNG car has become a new development trend of natural gas vehicle industry. As the national energy structure adjustment and the environmental protection request, the speed of development of LNG vehicle is faster and faster, with there are a large number of LNG filling stations under construction to meet gas demand of the LNG vehicles.The security issues are the most important issues in LNG filling stations. So the topic of several key security technology for the safety of LNG filling stations were researched and discussed. The main contents are the followings.LKP equation is applied to calculate thermodynamic properties and transport properties of LNG. The property calculation results of several domestic typical LNG source are consistent with the experimental data. Taking the example of Jiangsu Rudong LNG receiving station source, calculate the relationship between LNG saturation property and pressure. The results show the saturation temperature increases and the latent heat of vaporization decreases with the increasing of pressure. In addition, the density of liquid phase and gas phase respectively reduces and increases with the increasing of pressure.For the LNG cryogenic pipelines compensation, the temperature of pre-cooling medium should be as the of the calculated temperature based on comparison of the amount of compensation calculated based on different calculated temperature,which is better for meeting the needs the cold shrinkage of cryogenic pipeline. On the basis of thermal equilibrium one-dimensional steady-state heat transfer in LNG ordinary insulation pipe were analyzed. Thickness of heat insulating layer were calculated under the method of the control pipe per unit length of the cold loss,what meets the requirements for insulation,that recommend thickness is proposed.When the maximum allowed cold loss amount is7W/m, the thickness of the insulating layer100to200mm range for pipeline specifications (DN20, DN25, DN32, DN50) in LNG stations.Taken100to150mm range as insulation thickness, cold loss of pipeline for DN20and DN50can be as low as4to5W/m if temperature difference between air and LNG is larger.Reasons for generating the BOG in LNG filling stations ware concluded based on analysis of the process and characteristics of equipments,which are the pressure difference of the tanker and storage tanks in unloading process, the heat leak of of storage tanks and pipelines, thermal generated by LNG submersible pump running, the aerated volume replacement and atmospheric pressure changes. In view of reasons for BOG,static model for calculating BOG production is put forward. BOG production of combination of different working conditions were calculated to investigate the the treatment process and inhibition of the measures of the BOG.