Study On Small Scale Expansion Natural Gas Liquefaction Process And Device In Skid-Mounted Package

Natural gas with its efficient and clean properties has become one of the mainenergy in21st century, and the usage is growing larger and larger. The small scaleLNG project has its strategic value in our country due to the small bulk, mobiletransportation, and convenience in open-up and shut-down, as well as the collection ofdisperse gas fields. This paper studies the project and its key technologies, and themain research contents are as follows:1. Surveying research the development of small scale natural gas liquefactioninstallations, selecting the expansion natural gas liquefaction process as this study theobject of this study.2. Surveying research the component and pressure of China’s major natural gasfields, and select a typical gas composition and a purpose natural gas pressure as abasis for the simulation.Through analyzing the natural gas components resource,based on a mixture of material characteristics, selected the PR equation as the accountof state equation in this paper. The software HYSYS was selected to simulate theliquefaction process. Then, the calculation module of the HYSYS major equipmentwas introduced.3. The most important requirements for small LNG installation is simple andeasily for operation. Aimed at this, the expansion liquefaction process was selected asthe object of this study. Based on single-screw compressor and single-screw expanderperformance characteristics which developed in BJUT ministry of education keylaboratory, the three steps compress liquefaction process was proposed. And then, theaccurate calculation and simulation were done for it. Analyzing the proposed threeexpansion liquefaction process, educed that the influence of the gas pressure, storagepressure and compression ratio on the liquefaction process.4. Based on this conclusion，the two steps compress liquefaction process and thetwo steps compress liquefaction process with a regenerator were designed. The mainparameters selection basis of the the new process was provided, and the parameterswere analysed for optimization. The analysis also provides theoretical support for themain parameters determination of the system. From the view that process designsimple and reasonable, those three forms of liquefaction process were analyzed andcompared. And then, the regenerator liquefaction process was considered as the right scheme for small skid-mounted package device. The Global optimization for theregenerator natural gas liquefaction process was made by using of the method ofcomplex, and the best conditions and best optimization results were calculated out.And the results show that the small expansion liquefaction process’s liquefied rate upto84%, and the specific power consuming is9.515kWh/kmol. According to theoptimization results, a comprehensive comparison with several advanced natural gasliquefaction process at home and abroad was made. The comparison demonstrates thatthe small expansion natural gas liquefaction process designed in this study has theadvanced nature.5. The small expansion of liquefaction process was designed into small-skidmounted, modular type. Measurement and separation of the raw gas purificationmodule, natural gas liquefaction module, and refrigeration cycle module, flaring orventing system, LNG storage tank were worked out. Major equipment selectiondesign and its energy matching program were devised, and it can provide a referencefor the device-skid-mounted production.