| Coal is one of the most important energy in our country, the realization of effective clean use of coal, become a strategic task for the sustainable development of energy in our country. Hot coal gas desulfurization as one of the key technologies, which can not only rise the utilization of coal, but also is of great significance to air environment protection. At present, iron-based, zincbased and their composite metal oxides have been widely used, among these sorbents, ZnO sorbent attracted more attention due to its high precision. Considering that the blocking of pore inside after desulfurizing would lead to the desulfurization activity reduced and thus cannot recycle, ZnO sorbent in this paper was prepared by the regeneration of ZnS precursor so as to obtain a porous microstructure.In this paper, the nano-sized ZnS was synthesized by solid-phase reaction of Zn(CH3COO)2 and NaS at home temperature, and the effect of dispersant, ratio of reactant, grinding time and calcination time on the ZnS particles were studied by the characteristic mean of XRD. The Zn O sorbent was prepared with the Zn S precursor binder red earth by regenerated using a homemade fixed-bed reactor at an oxygen-containing atmosphere. The influence of the content of active component, regeneration temperature, space velocity and oxygen concentration on the regeneration of the sorbents were tested. The regeneration kinetics were studied by thermogravimetry analyzer(TGA) at oxygen-containing atmosphere, and an equitable model was established to calculate the order of reaction and apparent activation energy, which lay a theoretical foundation for the subsequent studies. At last, the prepared ZnO sorbents were taken for desulfurization evaluation and the XRD, SEM and BET characterization methods were used to explain the change of sulfur capacity from the microscopic perspective. The main conclusions were summarized as follows:1. The optimal condition for preparation nano-sized ZnS particles by solidphase method at home temperature is: dispersant isopropyl alcohol, the ratio of reactant 1:1, grinding time 60 min, calcination time 120 min. The ZnS particles prepared in this condition are on proper size and uniformly distributed.2. ZnO sorbents are synthesized with Zn S precursor by regeneration reaction in fixed-bed reactor at oxygen-containing atmosphere. Considering with the regeneration rate and mechanical strength, the best conditions are obtained: regeneration temperature 650 ℃, content of O2 6 vol.%, space velocity 4000 h-1, content of active component(ZnO) 35 wt.%. In this condition, the regeneration production shows a higher regeneration rate and a better mechanical strength.3. The regeneration behavior of the ZnO sorbents at oxygen-containing atmosphere were tested in thermgravimetric analyzer. According to the TG curves, the regeneration reaction can be assumed as first-order reaction by Uniform Conversion Model.4. The Equivalent Grain Model was used in the kinetics studies of ZnO regeneration at oxygen-containing atmosphere, and the kinetics parameters were calculated by Arrhenius equation, the chemical reaction activation energy is 43.12 kJ/mol, the corresponding frequency factor is 4.450 m/s. And 38.38 kJ/mol and 5.42×10-2 m2/s for diffusion inside, respectively.5. The desulfurization tests of ZnO sorbents prepared under the best conditions were carried out in a homemade fixed-bed reactor. The breakthrough time and sulfur capacity were reduced with the increase of regenerationsulfurization cycle.6. The sorbents before and after regeneration were characterized by XRD, SEM and BET. The results indicates that the regeneration is a pore-making process, because the specific surface areas, pore volume and pore size were increased after regeneration. Contrary to the regeneration, the sulfidation is a pore-blocking process, the specific surface areas, pore volume and pore size were declined. |
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