Process optimization of helium extraction and co-production of LNG from natural gas based on exergy analysis
Exergy analysis is an effective means of evaluating energy grade and energy utilization efficiency.Based on exergy analysis results,the location and causes of irreversible losses in the process flow can be accurately identified,thus providing the direction of process optimization.In order to improve the exergy efficiency of the key equipment in a NGL recovery unit for helium extraction and co-production of LNG and reduce the overall energy consumption of the unit,on the basis of adopting the improved exergy analysis method,the Aspen HYSYS software is used to analyze in detail the efficiency of the key equipment in the unit,and then a process optimization plan is proposed.The results show that the exergy losses can be divided into four types,the improved exergy analysis method can be used to obtain the proportion of various types of exergy losses of the equipment,and then evaluate the improvement potential of the equipment.In most equipment,endogenous exergy losses are greater than exogenous exergy losses,compressors and air coolers primarily have avoidable endogenous exergy losses,the main types of exergy losses of cold boxes are various,and towers mainly experience unavoidable exergy losses.When the multi-flash concentration is used to replace the dual-tower concentration,i.e.,the overhead gas of demehtanizer firstly enters helium gas concentration tower for pre-concentration,and then enters the liquefaction unit for further concentration,the total compression work is 11 575 kW lower than that in the original sheme,and the effective energy utilization ratio is higher.It is concluded that the exergy loss of the improved process is reduced by about 21 648.4 kW from the original level,and the system's exergy efficiency is increased by about 14.75%.The optimization results verify the feasibility of the improved exergy analysis in the process for helium extraction and co-production of LNG from natural gas,providing a reference for the optimization of helium extraction process in practical engineering.
万方数据
维普
