Research Of Integrated Technology Of A Novel LNG Cold Energy Separation With Oxy-fuel Power System

As the contradiction between China's energy supply and demand becomes tighter,and the import volume of LNG increases year by year,the rational use of LNG cold energy becomes more and more important.Due to the time and space difference between production and utilization,a great deal of cold energy is released into the sea at present,which not only wastes energy,but also affects the living environment in the surrounding sea areas.This paper presents a new integrated process of LNG cold energy air separation and oxygen-enriched combustion power system based on the process data in the actual work,and in the actual production where the LNG terminal and natural-gas power plant are geographically close.The feature of this process is that the air separation unit utilizes a single column to conduct air separation at a lower pressure and utilizes the heat exchange of the air separation system itself instead of the conventional condenser and reboiler,and the pressure of the material can be fully recovered to expand work,thereby reducing the energy consumption of the air separation system;Meanwhile,the process also integrates a set of oxygen-enriched combustion gas power system,the use of oxygen in the air separation unit and gasification of natural gas for oxy-combustion power generation,as well as the use of low-temperature oxygen cold energy and LNG low-grade cold energy CO₂ capture to improve the exergy efficiency of LNG cold energy utilization.The paper uses Aspen Plus chemical process simulation software to model the LNG cold energy air separation unit,oxygen-enriched combustion gas power system and CO₂ capture system of the process,and analyzes some key operating parameters in the designed process through simulation.Based on the analysis of the main factors of the process,in order to reduce the energy consumption of LNG cold energy air separation units,increase the output power of the oxygen-enriched combustion gas-powered power cycle,and improve the utilization of LNG cold energy and the exergy efficiency of the process system,the integrated process of the LNG cold energy air separation and oxygen-enriched combustion power system is optimized.The optimized process results show that the production energy consumption of liquid nitrogen,liquid oxygen,nitrogen and oxygen is 268.2KW·h/t,320.9 KW·h/t,18.7 KW·h/t and 80.2 KW·h/t,respectively.The total output power of the gas-powered power cycle is119.54MW,the net output power is 104.16MW,the total efficiency of the oxygen-enriched combustion gas-powered cycle is 64.76%,and the net efficiency of the gas-fired power cycle is 55.48%.Compared with the existing similar technologies,not only the energy consumption of the product is reduced,but also CO₂ can be completely captured.Finally,the thermodynamic analysis of the entire system and the utilization of LNG cold energy was performed.The results show that the exergy efficiencies of the LNG cold energy air separation unit,the oxygen-enriched combustion gas power unit and the CO₂ capture unit are 50.85%and 37.46%,respectively.The overall system exergy efficiency is 48.11%,and the LNG cold energy exergy efficiency is 65.08%,which is 8.3%higher than that of other direct air separation of LNG cold energy?56.8%?and 4.2%higher than that of LNG cold energy air separation oxygen enriched combustion process?60.9%?.