Process Design Of Small Skid - Mounted LNG Liquefaction Plant

As one of the three pillars of primary energy, natural gas is cleaner compared to the coal and oil energy sources.Strengthening the development and utilization of natural gas resources not only meet the energy needs of mankind, promote economic development, but also reduce environmental pollution and improve the human environment. China is rich in natural gas resources with a wide range of species and scattering distribution, while the reserves of natural gas are small. So it is hardly to mine the resources by conventional methods from the perspective of economic scale, as the super gas field does. To take advantage of this part of the natural gas resources, we can use a small skid-mounted LNG liquefaction plant transport the liquefied natural gas to the use, which is an effective and feasible way. And it can be used in Vehicle fuel filling station and city gas peaking because of its characteristics. In this thesis, we focus on the comprehensive utilization of natural gas from some well and research the small skid-mounted LNG liquefaction plant.Based on the current process for small scale processing of mixed refrigerant liquefaction process and expander expansion refrigeration technology, the three typical liquefaction processes of C3/MRC liquefaction process, closed mixed refrigerant liquefaction process and N2-CH4liquefaction process are chosen for initial comparison. Under the same temperament of raw material gas conditions and LNG storage conditions, we selects N2-CH4expansion liquefaction process as the research object in this thesis, according to the comparison indicators of power consumption and specific energy consumption and liquefaction ratio and the ease of process. For the cold cryogenic carried out by heavy hydrocarbon and BOG can be used, we make improved the N2-CH4expansion liquefaction process, making heavy hydrocarbon and BOG with the purified natural gas imported into the cold box for the heat exchange. In the meanwhile, we can recycle the expansion work using two stage expansion to achieve the goal of reducing energy consumption. It was be studied for the influence of the main operating parameters of the new process such as refrigerant pressure, swelling quantity, pre-expansion temperature and refrigerant ratio, etc. on process consumption, specific power consumption, liquefaction ratio and refrigerant cooling load. We Optimize the main operating parameters of the improved N2-CH4expansion liquefaction process on the condition of the lowest power consumption. The results are as follows:the liquefaction ration, total power consumption and the power consumption ratio are0.9198,1073.5746kW and46099.9100J/mol respectively, and the maximum and minimal pressures are3.80and0.39MPa. and refrigerant component ratio are0.93:0.07and0.898:0.102. As can be seen from the above results, the total energy consumption was decreased in the improved N2-CH4expansion liquefaction process compared to the original process.at the same time, we made an investigation of the adaptability of the process to fluctuation of the natural gas temperament.Meanwhile.thisthesiscompleted the calculation and selection of main equipment, dividing the whole purification skid liquefaction plant into purification lever block set, liquefied cold box, refrigerant compression-expansion block, LNG storage block and flare stack system. The plant equipment layout and preliminary economic evaluation were also completed in this thesis.