Optimum Design Of Membrane-based Hybrid Processes For Biogas Comprehensive Utilization

As the potential alternative to conventional natural gas, biogas is very important in the system of renewable energy resource. After proper purification, it can be utilized as urban fuel gas and compressed natural gas, etc. However, the current biogas treatment technologies are usually lacking in some aspects, e.g., simple product structure, environmental pollution, and waste in resource. Accordingly, biogas comprehensive utilization based on novel purification technologies are urgently demanded, with the target to improving resource usage, reducing separation cost, and avoiding environmental impact. On the basis of the single-stage two-step membrane process, a classical design in our previous work, it is to develop separation for effectively solving the key problems facing in the manufacturing process of biogas and promoting the development of biomethane industry in China, which is from the way of step-by-step purification/utilization, exhaust gas of catalytic combustion harmlesss and rich carbon dioxide production.First of all, the quality of two kind of biomethane were determined in meeting the needs of injecting into the rural town fuel gas grid and substitute vehicle gas (CNG), respectively. And scale of production was put forward to treat 1000 m3/h raw biogas to produce 2000 m3 civil pipe gas and 1000 cars annually 36500 km of 3.55×106 m3 vehicle biomethane. Meanwhile, Membrane-catalytic combustion integrated process and membrane-rectification integrated process were designed, respectively. It could be based upon three directions which were the purifying products diversification, the innocent treatment and the transition of exhaust gas. Subsequently, synchronous continuity production process and intermittent production process were simulated and optimized by the HYSYS design software, which economic benefits was as the main evaluation criterion in the two hybrid processes with the analysis of the influence of pressure.In membrane-catalytic combustion integrated process, intermittent production process was better for tank volume of civil biomethane and economic benefits. Based on comprehensive energy utilization analysis, heat exchanger network of catalytic combustion was designed in the process simulation with medium pressure steam (5.0 MPa) and softened water (70℃), which economic benefits increased from 5.5 million RMB to 5.84 million RMB in each year.In membrane-rectification integrated process, synchronous continuity production process was better process for economic benefits with the analysis of the influence of pressure. Subsequently, through heat exchanger network of carbon dioxide liquefaction process was designed, energy was compared with the traditional process, which was saved 15% by residue cold energy and step-by-step liquid carbon dioxide, which economic benefits increased from 13.28 million RMB to 13.34 million RMB in each year.The simulation results indicate that the two schemes of membrane hybrid processes for multivariate utilization of biogas can obtain huge economic profits, good environment and social benefits. In this paper, the development of the process can improve the problem of product of a single, high energy consumption, high separation cost, methane resource usage and meet the needs of natural gas rural market characteristics, which promotes the biogas industry develop towards business scale direction of the low-cost green and diversified products.