| Coal bed methane (CMB) is a kind of unconventional natural gas stored in coal bed, which mainly consists of CH4, N2 and a small amount of CO2.It is also a new type of highly efficient clean energy.If emissioned into the air directly,it is not only waste of resources, but also caused a serious green gas.So it is significant to mine and utilizethe coalbed methane reasonably. The reserves of CMB is 37 trillion cubic meters in China, which is the third highest in the world. If it can be mined and utilizethed largly, it will change the situation of shortage of fuel gas in our country. The physical and chemical properties of CH4 and N2arevery similar, so it is difficult to separate CH4 and N2 from each other.It is also the biggest difficulty for utilization of CMB. Pressure swing adsorption (PSA) is the most appropriate technology for utilization of CMB, but which needs a high efficient adsorbent.The main research and experimental conclusions of this paper are as follows:1. Take the sample AC as carbon matrix, CH4 is cracked at 1123-1173K for carbon deposition on AC, which can adjust the aperture.The X/AC is prepared by aging and crystallization. The crystalline, pore structure and surface properties of the samples were investigated by X-ray diffraction (XRD), adsorption isotherms of N2 at 77K.The adsorption isotherms of CH4 and N2 were tested at 298K and 100KPa.The experiment showed that when the cracking temperature is 1173K for 2h, aperture distribution of composites concentrate on 0.45-0.55 nm and equilibrium separation ratio of CH4/N2 reached 2.8.2. Inorder to simplify the experimental steps and enhance the operability of experiment, glucose and sucrose solution was impregnated into thechannel of the X/AC. Take X/AC as the raw material, according to solid:liquid=5g:25 ml to charge, then cured at453K and roasted at 823K in N2 atmosphere.The influence of different impregnation concentration and times in experiment were studied.The experimental results showed that the 0.2g/ml glucose solution impregnated 3 times is the best impregnation condition that the equilibrium separation ratio of CH4/N2 reached 2.8 and the adsorption quantity of CH4 kept at 11.8cm/g. The experiment also showed that reduction of microporous pore volume is not entirely decided the adsorption performance of X/AC, the properties of the surface also played a crucial role. The increase of the C=O functional groups on surface can also help improve the selectivity of CH4/N2.3. The X/AC was treated with NH4Cl, NH4NO3 and HNO3 solution with solid-liquid ratio of lg:25ml at 348K.The experiments showed the frame structure of X/AC wasdamaged and the micropore volume lost seriously after treatment.The equilibrium and kinetics selectivity of X/AC treated with NH4Clreached 3.1 and 9.7.4. X zeolite/activated carbon composite material was treated with KC1, CaCl2 and MgCl2 solution for ion exchange, got K-X/AC, Mg-X/AC and Ca-X/AC composite materials.It was found that after exchanged with K+the micropore volume of X/AC had a little loss, but the micropore size distribution was relatively concentrated in the 0.45-0.55nm. The selectivity of CH4/N2reached 3.1 and adsorption quantity of GH4/kept atl4.6 cm3/g, which is mainly attributed to the increase of the electric intensity of X/AC and the micropore volume of 0.45-0.55nm. |
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