Optimization Of Coupling Processes For Methane Enrichment From Coal Bed Methane And/or Coal Mine Methane

With the increase of natural gas comsuption, the price of it becomes higher and higher.The coal bed methane (CBM) obtains more and more attention as a supplementary energy.The main application of CBM is as a fuel using for power generation. Before the use of CBM,it must be enriched. The common way for CBM separation is using single gases separationprocess. However, it‘s high energy comsuption and investment restricts the recovery andutilization of CBM seviously.Aiming at solving the problems of CBM separation technologies, this study is focused onthe combination of membrane separation, pressure swing adsorption and the cryogenicseparation for CBM separation process. The key point of this study is the design andoptimization of combined process through optimizing energy consumption and the total cost ofthe investment. The optimization method of integration process of CBM separation in thisthesis includes four aspects： the selection of optimization process route, separationcharacteristics of three separation units (membrane separation, pressure swing adsorption andcryogenic separation), energy consumption and investment calculation method of the threeseparation units and the theory of coal bed methane separation optimization process.Based on the theory of CBM concentration, it was built that the process simulationmodel, energy cost model and investment model of membrane, pressure swing adsorption(PSA) and cryogenic separation. Using the combinative method of Aspen plus and separationmodule built the process simulation model of three separation units. Accoding to thesimulation results, three separation unit energy consumption model was built by the weightedaverage method. This method realized the―building block‖calculation of unit plantinvestment, which improved the calculation accuracy.In this study, the three-step method‘is used to achieve the optimal process of the CBM.The first step is to set up models of each gas separation module; the second step is to build theenergy consumption and the investment model of the single separation unit, and the third stepis to solve each variable by using the mathematical programming method. Based on themethod programing, we developed a software used in optimizing CBM concentrated couplingprocess. The configuration of the CBM integration separation can be obtained by inputingbasic parameters. At same time, the software can analysize major variables, which can use inCBM separation process‘s decision-making. The software was applied to optimize the certain CBM separation process. Resultsshowed that the coupling process was more superior to the single-process in terms of totalcost. Four working conditions parameters were analysized by this software and gave theeffects of variable. The strength order of the four main operating parameters of the processis：feed gas pressure> feed gas concentration> product purity> product recovery.Energy Comsumption Index (ECI) can evaluate the energy efficiency of gas separation.Using this standard could reduce computation greatly, which suitable for rapid assessment ofthe CBM concentration process route.