Research And Analysis Of Natural Gas Liquefaction Process With Mixed Refrigerant Refrigeration

Natural gas liquefaction process is a very high energy consumption process.It is necessary to study the influence of key factors of liquefaction process on process performance.This paper aims at optimizing the factors that influence the energy consumption of liquefaction process.Because these influential factors are numerous and highly nonlinear,it is very difficult to find the optimal process conditions.From the thermodynamics,the influences by which the process’s parameters have effects on the performance of the typical liquefied process are exactly and fully analyzed,which consists:the temperature of the nature gas,the procession of high and low pressure refrigerant,the refrigerant components.The aim function is the least for enegy loss of compressor and the energy of the propane pre-refrigeration,establishing the optimization model of the liquefied process,optimizing the Propane-Mixed Refrigerant Cycle by pinch technology.The results show that the energy consumption after optimization can be reduced by 32.6%,and the hot and cold compound curve of the LNG heat exchanger is matched,that is to say,the heat transfer efficiency of the LNG heat exchanger is improved.The variation of methane content in natural gas was studied,the process parameters were optimized,and the results were fitted with MATLAB software.The two-order polynomial fitting equation between mixture refrigerant ratio and specific power consumption is obtained,and the minimum value is solved in the range of the fitted equation.The minimum value in the range of the fitted equation is solved,and the result is verified in the actual production,the results show that the two values are 3.4973 and 3.5148 respectively,the difference is 0.5%,the error is small,and it accords with the engineering requirement.Based on the optimized technological process,the effective performance analysis of the liquefaction device shows that the compressor can lose the most effective energy in the LNG liquefaction process.I propose two kinds of process improvement program,one is changing the mixing stages of the refrigerant compressor from 2 to 3,and the results show that the energy consumption after optimization can be reduced by 6.46%.The other is using the cooling capacity of BOG,and the results show that the energy consumption after optimization can be reduced by 3.78%.