Energy Consumption Analysis Of Biogas Decarbonization Coupling Process Based On Hydrate Separation Technology

As a green and renewable energy,biogas is difficult to be widely used because of its high CO2 content,resulting in resource waste and environmental pollution.Gas separation of hydrate technology has the characteristics of simple operation and no pollution.It can be applied to remove CO₂ from biogas.It is very important for the development and utilization of biogas to study the decarbonization of biogas by hydrate technology.This paper discussed the energy consumption of biogas decarbonization by hydrate,absorption and membrane separation technology,coupled the process according to the advantages and disadvantages of different technologies,and optimized the energy consumption index（ECI）as the evaluation index.In this paper,the landfill gas（67mol%CH₄/33mol%CO₂）of a landfill plant in Guangzhou was selected as the research object,and the scale of biogas was 1100×10⁴ Nm³/year.Aspen was used to simulate the process of methane decarbonization by hydrate method.The results show that the energy consumption of compression unit accounts for 83.37%of the total energy consumption of the process.The process can reduced the overall energy consumption by recovering the energy of the product gas.In the energy recovery process,the recovery process of cold energy followed by pressure energy had a higher energy recovery efficiency.After energy recovery,the overall process energy consumption is reduced to 281.98k W,the CH₄recovery energy consumption is reduced to 0.31 kwh/kg CH₄,and the ECI value was 11.08.In the gas separation of absorption technology,the results showed that the energy consumption of reboiler of regeneration tower and gas compression unit accounted for 74.05%and 24.90%of the total energy consumption respectively.The compressed high temperature biogas can be used to preheat the methyldiethanolamine（MDEA）rich liquid.After energy recovery optimization,the overall energy consumption of the absorption process reduced to820.51 k W.The energy consumption of CH₄ recovery reduced to 0.77 k Wh/kg CH₄,and the ECI value was 22.06.The membrane separation technology was used to decarbonize biogas.The optimal membrane area of the first,second and third stage under the treatment capacity is12000 m²,2000 m² and 4000 m²respectively.The energy consumption of gas compression unit accounted for 98.76%of the total energy consumption of the process,and the total energy consumption of the process was 253.21 k W.The energy consumption of CH₄ recovery was 0.24k Wh/kg CH₄,and the ECI value was 7.16.On the basis of the above research,hydrate-absorption coupling and hydrate-membrane separation coupling processes were constructed,and the energy consumption of the coupling processes was analyzed.The results showed that the coupling process can effectively improve the gas recovery and product concentration.Compared with the absorption process,the hydration unit in the coupled process reduced the gas amount of absorption unit,and the regeneration energy consumption of the absorption liquid reduced by 88.91%.Compared with the membrane separation,the hydrate-membrane separation coupling processes reduced the gas load of the membrane unit,and the membrane area decreased from 18000 to 6900 m².After optimization,the energy consumption of hydrate-absorption coupling process was 346.88 k W,the energy consumption of CH₄ recovery was 0.37 k Wh/kg CH₄,and the ECI value was 10.76.The energy consumption of hydrate-membrane separation coupling process is 309.56 k W,the energy consumption of unit CH₄recovery is 0.34 k Wh/kg CH₄,and the ECI value was 10.65.The results of this study showed that the coupling of hydrate separation process with other separation processes can achieve more efficient,low consumption and low cost of biogas decarbonization.