Abstract:

According to the characteristics of the cold energy of liquefied natural gas (LNG) , a new recovery process of light hydrocarbons from liquefied natural gas was presented based on the gradient utilization of cold energy.The proposed recovery process was performed without using any gas compressor , and the cold energy of LNG was used to re-liquefy the methane-rich residual gas and to re-condense and store the methane in tanks in low-pressure liquid phase , the process was of the function of peak shaving , and the recovered light hydrocarbons in low-pressure liquid phase were easy to store and sell. Then , a case study of applying the process was carried out for the imported3.7 X 10⁶ t/a LNG from Australia by Shenzhen. The results indicate that , as compared with the conventional technologies, the proposed process can reduce the power consumption by 47.3% and decrease the heat load by 27.3% ,that approximately 20% of the methane-rich residual gas is re-condensed and stored in tanks in low-pressure liquid phase for the peak shaving of natural gas downstream system by vaporizing it ， that the C₂^＋ hydrocarbons recovered from LNG can be used as a substitution for naphtha and the feed of ethylene unit , with the advantages in decreasing the investment and saving the energy consumption and the cost.

Key words: liquefied natural gas, cold energy, C₂^＋ light hydrocarbon recovery, process optimization, process deslgn