Desulfurization Performance Of Iron Oxide Medium High Temperature Coal Gas Desuifurizer And Kinetics Study Of Thermal Process Of The Precursor

Medium and high temperature desulfurization is the key technology for theclean and high efficient development and sustainable utilization of coalresources, which is of great significance to promote the green industrialdevelopment, reduce the generation of atmospheric pollutants and emissions,and improve the atmospheric environment quality. At present, iron oxide sorbentis the most widely used in medium and high temperature coal gas desulfurizer,which always is the hot topic of research.In this paper, the thermally induced decomposition of FeC2O4·2H2O, whichwas synthesized by solid-state method using FeCl2·4H2O and H2C2O4·2H2O asraw materials, was investigated in the dynamic air atmosphere usingTG-DTG/DSC. The kinetic model and kinetic parameters of the seconddecomposition stage of the precursor were determined by the comparison of theintegral methods of Ozawa and Coats-Redfern. Iron oxide sorbent was preparedwith the active component Fe2O3, carrier and binder arenaceous clay by twodifferent heating way and the desulfurization evaluations were carried out using a homemade fixed-bed reactor with a gas mixture simulating the Texaco coal gas. The effects of the content of active component and microwave calcination temperature and time on the properties of sorbents were investigated. At the same time, X-ray diffraction, X-Ray Photoelectron Spectroscopy, Scanning Electron Microscopy and N2adsorption were applied to investigate physical and morphology properties of the sorbents. The main conclusions are summarized as follows:1.The formation of γ-Fe2O3which is the final product of the decomposition was further confirmed by the XRD patterns and DSC curves. The chemical equations corresponded can be described as: FeC2O4·2H2Oâ†'FeC2O4+2H2O FeC2O4+O2â†'Fe2O3+CO22.The activation energy Eβ is113.90kJ/mol ensured by Ozawa and Coats-Redfern Integral method. the decomposition conversion function can be described as following. G(α)=-ln(1-α)2/3ln[G(α)/T2]=15.10-13760.60/T3.The decomposition conformed to the model of random nucleation and subsequent growth, corresponding to the An (n=3/2) model.4.The optimal prepared conditions of microwave heating are showed as follows:the content of active component, calcining temperature and time is30%,500℃, and30min, respectively. Under this optimal conditions, the breakthrough time and sulfur capacity of microwave heating are14.5h and9.88%, respectively. However, the breakthrough time and sulfur capacity ofconvention heating are11h and7.35%, respectively. Obviously, the resultsindicate that the sulfidation performance of sorbent prepared by the microwavemethod is much better.5.Nitrogen adsorption and SEM results showed that the sulfidation is apadding pores process because of pore volume and pore size were declined assame as surface area.6.Under the optimal conditions, significant differences encountered whencomparing the sorbents prepared by two methods. In the case of microwave, amuch smaller particle size has also been marked from the XRD patterns. XPSanalysis shows that Fe2p and O1s binding energy are lower which is moreconducive to hydrogen sulfide adsorption and reaction. Surface characteristicsuch as higher surface element content (Fe and O) has been noticed, which isparticularly relevant with the targeted promising desulfurization performance.Furthermore, sorbents calcinated by microwave heating show an enrichedporous characteristic (surface area, pore volume and pore size) characterisedby relatively high specific surface area compared with that of conventionalheating, in which a dramatic collapse of the structure was observed, leading tonon-porous materials with very low values of the specific surface area, asevidenced by N2absorption and SEM. These remarkable differencesmentioned above in both inner structure and surface of the sorbents result in a better desulfurization performance.