Study On Coal-bed Methane Deoxidation With Chemical-Looping Combustion

The content of CH4 in the coal-bed methane (CBM) varies from 20% to 75%, for the mixing of air, meanwhile, the oxygen content changes between 5% and 15%. CBM is always discharged into air since it is easy to explode during exploiting. It is not only a great waste to resource, but also does great harm to gas pollution. Because the greenhouse effect caused by methane is as 21 times as carbon dioxide at same volume. Removal oxygen from CBM is a key step for utilized this resource. The chemical-looping combustion (CLC) is adopted in this paper to remove oxygen in the CBM.The Cu-based oxygen carrier was screen out from four kinds oxygen carrier commonly used in CLC. In order to improve its anti-sintering ability, the active component CuO was loaded on Al2O3 by co-precipitation method. The effect of the preparation process on performance of oxygen carrier was studied by themogravimetric analysis and screening out the most suitable condition for preparation:the CuO loading:80%, pH:8.0 calcination temperature:600 degress, calcination time:2hours. The oxygen carrier was characterized by XRD, BET, and SEM. Results showed that Cu mainly existed in the form of CuO in the oxygen carrier prepared by co-precipitation, the surface area was 39.6928 m2g-1 and sintering was not found in the SEM after 20 cyclesThe effect of concentration of CH4 and reduction temperature on reaction kinetics of CH4-GuO and the effect of concentration of oxygen and oxidation temperature on reaction kinetics of O2-CU were respectively studied. The kinetics equations of the oxidation and reduction were established.The reduction kinetics of oxygen carrier: (-RA)=1.53×107exp(-Ea/RT)CCH40.8439The oxidation kinetics of oxygen carrier: (-RA)=e60337CO20.4031The effect of imported gas flow, the CH4 or O2 concentration in the gas and reaction temperature on the oxygen removal of CBM and regenerating of oxygen carrier was studied in the tube furnace. Results showed the imported gas flow and oxygen concentration had influence on the oxygen removal and oxided conversion of oxygen carrier. The reaction temperature had little effect on reaction. But keeping the oxidation temperature around 250 degree could prevent CuO being reduced by CH4 during oxidation. On the condition that the imported gas flow was 274.8ml/min, the reaction temperature was 250 degree, and the volume concentration of O2 in the imported was 10 percent. Oxygen concentration in the outlet gas could decease below 2%. The gas handing capacity of unit mass oxygen carrier was 1.1L/g.In the reduction, the imported gas flow, the CH4 concentration and reaction temperature would affect the conversion of CuO. On the condition that the imported flow is 91.6ml/min, the gas per mass oxygen carrier needed and time were compared at different imported gas concentration in order to achieve 90% of CuO reduction conversion. Results showed the higher concentration of CH4, faster the oxygen carrier was reduced and less gas demanded When the concentration of CH4 is 50%, the gas needed to reduce unit mass oxygen carrier is 0.15L.It only took 5min to reach the conversion of 90% of CuO. In the outlet gas methane concentration had no obvious tail phenomenon, can be directly recycled.