| With widely utilizing of fuel gas, desulfurization industry for coal gas under normal temperature developed rapidly. And at present time, the next research must be aimed at improving the properties (physical and chemical) of the desulfurizer to enlarge their application limit. Based on exploitation of high performance BMC iron-based desulfurizer, this dissertation emphasized on the study of the following: mechanism of desulfurizing reaction between the iron-based desulfurizer and H2S, affection factors of the desulfurizing process and the fixed-bed model setting-up for common desulfurization reactor.By our research some properties of iron-based desulfurizer were improved greatly, such as low mechanical intension, waterproof ability and sulfur capacity, showing better performance over other congeneric products: Φ 4-6mm, brown cylindrical particles; radial intension, 450 N/cm2, axis intension, 70 N/cm; pulverization ratio is below 1% with 40% water content under 2Mpa; the most important standout virtue is its high sulfur capacity ( Sw, g S/100g dry desulfurizer), first Sw is above 20% under VSP (h-1, space velocity) 200h-1or 400 h-1, twice accumulative Sw reaches to 40% under the VSP 800 h-1, one time Sw still can reach 15%, and twice accumulative Sw is above 25%. Material utilizing ratio is more than 80%.Affection factor of the desulfurization process, such as temperature, water content both in bed, granularity of particles, H2S content in coal gas and space velocity (VSP ), were all analyzed and the results proved: temperature and water content have a certain value to get the biggest Sw, which is 20 ℃ and 20% respecially. Sw increases a little with H2S content in coal gas because of strengthened physical adsorption. With minimizing of the diameter of the particles, the surface area contacting with coal gas increase doing well to active material utilizing, but meanwhile, the bed resistance increases greatly. With increasing of VSP, Sw decreases greatly. Significance test of all the factors proved their affection ability in turn is: temperature, granularity, water content, space velocity and H2S content in coal gas. So all factors should be considered synthetically in the desulfurization processing.Based on now existing research, XRD, SEM/EPMA and pore character analysis were done to reveal the mechanism of desulfurizing reaction: the active component in BMC is γ -Fe2O3 · H2O. After adding other additives, no any changing of this γ-Fe2O3· H2O occurred but sufficient blending. H2S mostly entered the micro-pore of 15-90A in the particles. This kind of adsorption belongs to weak adsorption, mainly chemical reaction function. In the inner surface of these micro-pores, γ-Fe2O3 · H2O reacted with incoming H2S molecule and turned to Fe2S3. While Fe2S3 met oxygen, it would turn to y -Fe2O3 · H2O again and separated S scattered in the particles. The thermodynamics analysis proved the desulfurization reaction is exothermic reaction. Elevating temperature does not aid the reaction and the quantity of heat released decreases.This dissertation emphasized on model setting-up of fixed-bed desulfurizing reactor.Based on a series of reasonable hypothesis, the reaction velocity was mainly described by two parameters, general mass transferring coefficient Kf and adsorption equilibrium constant Kh. H2S throughout experiments were done under selected temperature 20℃, 40 ℃, 60℃ and 80℃. Each throughout curve can be separated into "three region". Through data regression and optimizing of the parameters, calculated data by computer program were got, which simulates the experimental data very well(R>0.96). After Kf and Kh assured which afford to the Ahrrenius equation perfectly (R>0.99), and the model was set up.In this dissertation focused research in BMC making, factors' analyzing of desulfurizing process, mechanism of desulfurizing and fixed-bed model setting-up. At last, the author gave out some suggestions on next research in this field. |
PDF Full Text Request