| With the development of modern industry, the inconsistence between limited reserves of oil resources and increasing demand has become a big issue that attracts more and more attention. But with the transition of focus on high quality oil, the introduction of some conversion processes generated a large amount of refinery gas, such as the process of catalytic cracking, hydrocracking, residuum coking etc. It is a serious waste of petroleum resource if this part of refinery gas cannot be used efficiently. The secondary vent gas was generated in the single separation process while treating rich gas and the poor gas from refinery still contain much light-hydrocarbons and hydrogen. In order to recovery the resource, a couple process, which has high separation efficiency and recovery ratio, is necessary to be developed to reduce the waste of resource and promote economic profit. In this paper, two kinds of secondary vent gases which were remained after single separation process were investigated as raw materials. Based on the traditional shallow condensation process, a modified shallow condensation process enhanced by various membranes was designed for light-hydrocarbons recovery from refinery gases. The designed process was simulated and optimized by the Unisim Design software.In this paper, using the residual gases generated in the process of membrane separation of hydrogen from catalytic cracking gas as raw materials and based on traditional shallow condensation system(SCS), a shallow condensation-vapor membrane (SC-VM) process with back organic vapor membrane was designed to enhance the light-hydrocarbons recovery. Both of the SCS and SC-VM processes were simulated and optimized and finally the optimal parameters were achieved respectively. In comparison to traditional condensation system, SC-VM coupling process was the optimal choice through economic analysis. When the flow rate of residual gas is about 350mol/h, the mass flow of recoveried light-hydrocarbons was 51720t/a and the recovery ratio was improved from 79.7%to as high as 98.8%, the total value of which was about 232.74 million yuan per year. The annual utilities consumption was about 20.72 million yuan, and the specific energy consumption was 0.4006yuan/kg. The economic profit of the couple process was to be 131.70 million yuan per year, which was 40.68 million yuan more than that of the SCS process.Using the desorption gas of PSA purifying H2 from hydrocracking gas as raw materials, a series of modified shallow condensations were designed for light-hydrocarbons recovery from refinery gases with rubbery membranes for light-hydrocarbons enrichment and glassy membranes for hydrogen removal. Based on the traditional shallow condensation system, SC-VM coupling process and HM-SC coupling process were presented for enhancement of the recovery of light-hydrocarbons. At last the respective optimal operation parameters were achieved by simulation and optimization of the two coupling processes.In comparison to other processes, HM-SC coupling process with two stages was the optimal one based on the enconomical analysis. When the flow rate of desorption gas was 400 kmol/h,:the mass flow of the light-hydrocarbons was bout 27333t/a, and the recovery ratio was increased from 55.6%to 75.0%, the value of which was 122.997 million yuan. The yield of byproduct hydrogen with a concentration of 92mol% can be as high as 22.71 million Nm3/h and the total profit of the gas is 24.98 million yuan. The utilities consumption was 12.27million yuan per year, and the specific energy consumption was 0.4500yuan/kg. The economic profit the HM-SC process was about 85.23 million yuan per year, which was 44.45 million yuan more than that of the SCS process and 1.54 million yuan more than that of the SC-VM process.The results showed that the the membrane enhanced shallow condensation process can improve the recovery ratio of light-hydrocarbons and economic profit obviously,. The conclusion gives directions to the future work. |
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