Lng Terminal & Ethylene Processes Integration Technological Study

LNG industry has developed rapidly for several decades. LNG imports to the China will increase significantly. LNG not only contains a mount of cold energy but also more valueable hydrocarbon: ethane, propane, butane etc. Cold energy utilization of LNG have been considered and applied by many international oil companys and governnments. Ethylene industry in China is developing rapidly. The ethylene production is 10278459 ton in 2007 and 9998267 ton in 2008. The light feed material: methane and ethane and propane are the best feed material for ethylene plant, at the same time ethane and propane expands refrigerate compressors are required to separate the ethylene etc, that means plenty and cheap cold energy is also required for ethylene plants. This article is base on the deep analysis and study of cold energy requirement of ethylene facility, LNG terminal, NG pipeline and LNG C2+ facility, integrated use system optimization design concept, traditional optimization theory, data summary and analysis technology, deep study the technology of LNG terminal and ethylene integration, achieves the optimization running proposal of hydrocarbon facility, terminal and NG pipeline. The following aspects are discussed in this paper:Firstly, detail study the process and equipments of LNG terminal, fully analyze the cold energy that LNG contains, study the hydrocarbon extraction facility base on cold energy utilization, expatiate the signification of LNG hydrocarbon extraction. Briefly study the cold quantity and level that ethylene facility required, through the study of LNG, process, material and cold energy consumption of terminal, hydrocarbon facility, ethylene facility, achieve that it has high complementary for LNG terminal, hydrocarbon facility and ethylene, raise the design concept of integration facilities. That is the integration between LNG receiving terminal where C2+ extraction facitity is included and ethylene plant. The advantages of the concept are:The LNG terminal and C2+ extraction facitity could provide a mount of valueable cold energy (from -155℃to -60℃) to ethylene plant.Simultaneously the waste heat energy from the ethylene facilities will be transmissioned to the LNG terminal for LNG revaporization and to C2+ extraction facitity for preheating the LNG feed stream and heating the reboiler at the bottom of distillation column.The LNG terminal and C2+ extraction facitity could provide valueable feed material to ethylene plant which are ethane,propane ,butane,pentane,etc.Fule gas is also provided to ethylene plant from the terminal.Heavier components could be economicly separated by extraction facility in the terminal because of the cold energy utilization.The receiving terminal could handle imported LNG having wide compositional variations.The NG from the terminal could meet the different pipeline specifications and"gas interchangeability"could be easily realized. Secondly, under detail study of process and running characteristics of LNG terminal, take GDLNG terminal as example, study wave of customers gas taking monthly, daily, even hourly during early commissioning and steady commissioning period, under fully study of running situation of C2+ facility and NG pipeline, achieves the proposal of optimization running of terminal and C2+ facility, solves the problems that worried the industry, focuses on the cold energy study during LNG vaporizing, on the base of caparision study of foreign and domestic C2+ extraction technology, takes GDLNG terminal as example, fully study the optimizing operation, current gas taking rule and further increasing gas taking quantity, designs one high effective and energy-saving set of C2+ extraction facility, uses simulation software to make theoretical calculation, optimizes operation parameters.Then, through the study of LNG system vapor-liquid phase balance and model, builds the mathmeticsl model of demethanizer and deethanizer, achieves the parameters of temperature, pressure, flow rate, feed and product for different tray, duty of top condenser and bottom heater.Finally, make economical analysis for LNG C2+ extraction via prices analysis of LNG, propane and butane, gets the result that the economical benefit of C2+ extraction is remarkable.