Study On High Intensity Methanation Catalyst And Process Under High Steam To Gas Ratio

The huge amount of recycling gas leads to high energy consumption in the traditional adiabatic methanation process.The non-recycle methanation process controls temperature by steam instead of recycling process gas,which can save recycling gas compression energy consumption.In this paper,relevant technological conditions of methanation process without circulation is investigated by thermodynamic analysis,and the formulation of catalyst used under high steam to gas ratio(S/G),including the carrier,active component,additives and preparation methods,is also investigated.Thermodynamic simulation results show that the oulet temperature of the high intensity period can be controlled at about 650? when S/G is 1.0,which is suitable for this process.For the catalyst,steam added or not,a certain degree of nickel oxidation and alumina hydration will happen,because the methanation reaction produces a large amount of steam.Higher calcination temperature of the carrier and impregnation method can inhibit the carrier hydration.Experiment results showed that LZ2 carrier calcined at T?,?-Al2O3,had excellent methanation activity;the activity increased with the NiO loadings amount,till 20%.High NiO loadings caused the aggregtation of Ni crystallite size,which was more prone to carbon deposition.The activity was much better when the catalyst was calcined at t+100?.The effects of Mg,Mn,M and X promoters on the catalytic activity,stability and resistance to carbon deposition were also investigated.There are four kinds of NiO: ?-NiO,?1-NiO,?2-NiO and NiAl2O4,?1-NiO and ?2-NiO are good for the activity.?2-NiO contents increasing can improve the catalyst stability.Promoter X can improve not only the methanation activity,but also the stability at high temperature.The catalyst PX-2 with Ni:X=5,has the best activity,can meet the needs of the high S/G and high temperature methanation,the high S/G supplementary methanation and steam free supplementary methanation.The catalyst can be reduced at low temperature(550?).After 100 h stability test,the activity was stable and carbon deposition was rare.The catalyst has bright prospect in industrial application.