Study And Analysis On The Utilization Technique Of Liquefied Natural Gas Cryogenic Energy

To overcome the problem of energy supply security and environment protect, China will import a lot of liquefied natural gas (LNG) from other countries. LNG is a cryogenic liquid, and it should be vaporized before supplied to the final consumers. During the vaporized process of LNG, it releases a great deal of cryogenic energy. Using the cryogenic energy of LNG, it could not only save a lot of electric power but also decrease the environmental impacts of LNG vaporization.Since the existing power generation processes with LNG cryogenic energy has small power generating capacity and low energy efficiencies, a direct expansion power generation process with LNG cryogenic is proposed. And its theoretical maximum capacity, power efficiency and exergy efficiency were carried out in this paper. At the same time, five mixtures are compared in the Rankine cycle power generation system. The results show that the system has minimal exergy loss and the high exergy efficiency, when the complex mixture condensation curves are basically the same as LNG gasification curves.Ethane is one of main components of the commercial natural gas in China. As ethane has a higher value than methane, ethane should be recovered from the commercial natural gas. The ethane recovery process from the commercial natural gas with LNG cryogenic energy utilization is proposed. The proposed process has high ethane recovery efficiency. Compared to the power compression refrigeration process, the proposed process can save a lot of electricity. The process was analyzed by the method of exergy analysis and the energy utilization diagram (EUD). The results can be used in the optimization of the process.The current electric refrigeration recovery process of natural gas liquids has high energy consume. A novel process to recovery natural gas liquids from oil field associated gas with LNG cryogenic energy utilization is proposed. The proposed process recovers ethane, liquid petroleum gas (propane and butane) and heavier hydrocarbons, with total recovery rate of natural gas liquids up to 96.8%. Compared to the current electric refrigeration process, the proposed process uses the cryogenic energy of LNG and saves 62.6% of electricity. In this paper, exergy analysis and the energy utilization diagram method (EUD) are used to assess the new process. The results show that exergy efficiency of the new process is 44.3%. Technical and economic analysis showed that, the investment recovery period is 2.25 years, and its internal rate of return is 93.3%, which its capacity is 150×104Nm3/d oil field associated gas.The current process of cold storage with LNG cryogenic energy does not have peaking function, and does not apply to the LNG satellite station. In this paper, a novel process of cold storage with LNG cryogenic energy utilization is proposed, which butane is selected as the refrigerant. Exergy analysis and the energy utilization diagram method (EUD) are used to assess the new process. The results show that the proposed process can saves 96% of electricity, and its exergy efficiency is 27.3%. Technical and economic analysis show shat the new process has a promising economic benefit.Since the current cryogenic grinding processes of waste rubber have high energy consumption, a novel cryogenic grinding process of waste rubber with LNG cryogenic energy utilization is proposed, which air is selected as the refrigerant. The results show that the new process has lower energy consumption, and it consumed 0.1 kWh electricity per kg waste rubber. Compared to the air turbine expansion process, the process can save 67.7% of electricity.According to the actual industrial environment of some LNG receive terminal and LNG satellite station, the integrated utilization programs of their LNG cryogenic energy were dividedly proposed. Their technical and economic analysis was carried out, and the results showed that these two programs have high efficiencies of cryogenic energy, and have a promising future.Based on these results, the software of LNG cryogenic energy utilization is developed in this paper. The software can automatically calculate out the cryogenic energy needs of every customer, and match the needs of every customer. Then, the software can simply analyze the results.