| As the most impotant resource in modern industry, the reserve of petroleum is very limited. Using petroleum resouce efficiently and fully is the requirement of sustainable development, and attracts more and more attention. In the petroleum refining process, great amount of refinery vent gas made up of hydrogen and light hydrocarbon such as methane, ethane, and propane etc.is produced. For a long time, single seperation technology is applied in China, only hydrogen or only part of light hydrocarbon is recoveried, others are used as fuel gas, which is a serious waste of petroleum resource. For example, refinery with production scale up to 10 million tons may lose hydrogen costing 80 million yuan, light hydrocarbon up to several hundred million yuan. In view of this, developing new vent gas recovery process to recover refinery vent gas to the maximum is a target that every petrochemical company and research institute pursues. This paper designed a multi-technology coupling process combining with the traditioanl separation and the advantages of membrane separation technology to synchro recover multi-objective products from refinery vent gas, simulated and optimize the process by HYSYS software.According to hydrogen concentration of vent gas, the paper divides refinery vent gas into lean-H2 vent gas and rich-H2 vent gas. Processes are designed and analysed respectively. For lean-H2 vent gas, on the basis of analyzing the traditional compression/condensation -distillation process, comprehensive recovery process coupling with VOC membrane /hydrogen membrane system was designed. For 400kmol/h isomerization recycle tower vent gas, main operation parameters were determined: condensation temperature, stage cut of each membrane, etc and economic analysis was investigated. Compared with traditional process, the coupling process can recover 92% H2 2058 Nm3/h, H2 recovery ratio reaches 86%; and 788kg/h more LPG is recoverd, LPG recovery ratio increases from 82.8% to 96.6%; economic profit increases 24 million yuan per year, improved by 17%.For rich-H2 vent gas, process composing of hydrogen seperation system, compression/condensation system, distillation system and VOC membrane/hydrogen membrane system was designed. For 290kmol/h reforming PSA desorbed vent gas, main operation parameters were investigated, and economic analysis were discussed. Compare with traditional H2 membrane recovery process, the process designed recovers 94% H2 463 Nm3/h, recovery ratio increases from 77.7% to 96.6%; and 3911kg/h more LPG is recoverd, the recovery ratio reaches to 94.3%; economic profit improves 96 million yuan per year.As H2 concentration distribution range of vent gas is wide in modern large scale refineries, based on the comprehensive recovery process designed before aiming at treating two kinds of refinery vent gas, the paper designed comprehensive recover integration process which can simultaneously deal with multi feed stockes of different H2 concentration. As to the current short supply situation of raw material for large scale ethene project in China, ethane co-production process was designed, despite the products H2, LPG and C5 light oil, ethane——high-quality raw material for ethene production was also recovered. For the two vent gas stocks previous memtioned, after optimization, H2 production achieves 5201 Nm3·h-1, recovery ratio 93.2%; LPG 10.7t·h-1, recovery ratio 96.5%; ethane 4.28 t·h-1, recovery ratio 83.8%. Economic profit of the process reaches 409 million yuan per year, compared with the process without ethane production, the profit increases nearly 50%. |
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