| In recent years, with the development of economic and society, people have realized the seriousness of environmental pollution, thus environmental protection work has been a primary task of the whole society. Application development and popularization of coal gas put forward a higher requirement for desulfurizer industry which is becoming mature, we must address the current various existence shortage of the desulfurizer to develop a new process applicability desulfurizer products.Cerium oxide has been regarded as a new second-generation desulfurizer because of its variable price of oxygen storage and good dispersion characteristics.The purpose of this thesis is try to investigate the effects of the doping of cerium oxide and supports of semi-coke for the desulfurization efficiency, sulfur capacity and pore structure characteristics through the operation of desulfurization and regeneration. 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. Zinc ferrite sorbents are considered to be the novel sorbents, which maintains the high desulfurization efficiency of zinc oxide and the high sulfur capacity and reactivity of iron oxide. The structure of zinc ferrite spinel possesses positive ion-spaces that is favorable to reacting with hydrogen sulfide. Characterization of desulfurizer was carried out by using powder X-ray diffraction, BET methods, X-ray photoelectron spectroscopy and mechanical strength.1. Experiments showed that the desulfurizer which obtained by adding cerium oxide into the carbon-based zinc iron under ultrasonic wave-assisted was feasible. According to the test of particles size of precursor, the optimum preparation conditions were as follows: the concentration of mixed solution of Zn(NO3)2,Fe(NO3)3, and Ce(NO3)3 was 0.5mol/L, the temperature of water bath was 50℃, the time of ultrasonic action was 1h, ammonia was used to precipitation, then dried in the oven, calcined at 700℃for 2 hours.2. The calcination temperature of both active components powder mixed with activated carbon and precursors of desulfurizer had great influence on the grain size of iron zinc, cerium oxide and desulfurization performance. The desulfurizer had the higher desulfurization activity when the former temperature was 700℃, the latter temperature was 500℃.3. Promoter acted as pore-forming, dispersing the active component, increasing the activity of metal oxides and enhance the role of mechanical strength in the desulfurizer. The appropriate addition of cerium oxide would help to reduce the grain size of sorbent, increase the dispersion of oxide, and extend the breakthrough time. Compared with the desulfurizers with different adding amount (0%,4.6%, 8.2%, 11.2%)of cerium oxide, the desulfurizer with 4.6% cerium oxide showed higher desulfurization activity while cerium oxide itself owned desulfurization activity, the large amount of cerium oxide addition was not possible.4. Activated carbon could be used as a carrier for its high surface area and well-developed porous structure. The appropriate mass ratio of activated components to activated carbon could effectively prevent sintering, to improve the desulfurization activity of desulfurizer. Compared with different mass ratio of 8:10, 10:10 and 12:10, the best ratio was 8:10.5. Active component was a major component of sorbent. The content of active component was not as high as possible, it had a certain relationship with mechanical strength which was directly related to the desulfurizer of the re-use. In this study, four content of active component 10%, 20%, 25% and 30% was selected. With the increase of concentration, the breakthrough time and sulfur capacity were significantly increased, but the mechanical strength had declined somewhat. Through the comprehensive consideration, the active component content of 25% was selected for the regeneration of the study focused.6. Due to adding a certain amount of cerium dioxide into the desulfurizer, one purpose of this study is to find out the suitable temperature or temperature zone when the conversion of cerium dioxide could be enhanced on the basis of ensuring the activity of zinc ferrite. In this study, the temperature range of 320℃-520℃was selected to study the activity of desulfurizer, the results show that during the range of 370℃-470℃, the desulfurizers could display the higher activity ; according to the desulfurization accuracy with a comprehensive consideration, the best temperature is 450℃. The compound desulfurizer could be successfully used in medium and high temperature coal gas desulfurization.7. In this study, the selected regeneration conditions are: the temperature is 650℃, the atmosphere is H2O-13%, O2-2%, H2O/O2=6.5, N2 supplement, space velocity is 2000h-1. Active components of 30%, 25% and 20% of the desulfurizer were regenerated under the same conditions, only the content of 25% showed better regeneration performance.8. For the active component content of 25% of the desulfurizer, three consecutive desulfurization—regeneration recycling experiments were operated, the second sulfur capacity increased 2.52% than the first sulfur capacity, while the third sulfur capacity was drastically reduced, just was 36.87% of the first sulfur capacity. Three times of desulfurization time from long to short was: 1st>2nd>3rd; three regeneration time from long to short was: 2nd>1st> 3rd.Finally, through consideration and analysis in the process of experiments, several points on the subject of future research had been proposed. |
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