Abstract—In this research a mathematical model for direct oxidization of hydrogen sulfide into elemental sulfur in a fluidized bed reactor with external circulation was developed. As the catalyst is deactivated in the fluidized bed, it might be placed in a reduction tank in order to remove sulfur through heating above its dew point. The reactor model demonstrated via MATLAB software. It was shown that variations of H 2 S conversion as well as; products formed were reasonable in comparison with corresponding results of a fixed bed reactor. Through analyzing results of this model, it became possible to propose the main optimized operating conditions for the process considered. These conditions included; the temperature range of 100-130ºC and utilizing the catalyst as much as possible providing the highest bed density respect to dimensions of bed, economical aspects that the bed ever remained in fluidized mode. A high active and stable catalyst under the optimum conditions exhibited 100% conversion in a fluidized bed reactor. Keywords—Direct oxidization, Fluidized bed, H 2 S, Mathematical modeling, Optimum conditions. I. INTRODUCTION HE international restrictions concerning the release of gases containing sulfur compounds into the atmosphere are becoming more and more drastic during recent decades. In this way, it is of interest to find more efficient methods for removing H 2 S and especially SO 2 (i.e.; SO x ) to limit their emissions. A large amount of hydrogen sulfide (H 2 S) is released from crude oil, natural gas refineries and metal smelting process in steel industries. The coal liquefaction process is also considered to be a major source of H 2 S emissions [1-3]. Hydrogen sulfide generated by these processes must be recovered before releasing the gases into the atmosphere, due to the high toxicity of the H 2 S. The general trend is to selectively transform H 2 S into elemental sulfur by the well known equilibrated Claus process [4]. Because of thermodynamic limitations, the maximum F. Golestani is with the Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Avenue, P.O. Box 11365-9465, Tehran, Iran (e-mail: fg1186@gmail.com). M. Kazemeini is with the Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Avenue, P.O. Box 11365-9465, Tehran, Iran (corresponding author to provide phone: +98-21- 6616-5425; fax: +98-21-6602-2853; e-mail: kazemini@sharif.edu). M. Fattahi is with the Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Avenue, P.O. Box 11365-9465, Tehran, Iran (e-mail: moslemfattahi@che.sharif.edu). A. Amjadian is with the Department of Chemical Engineering, Tarbiat Modares University, Tehran, Iran (e-mail: aliamjadian14@gmail.com) efficiency of Claus process cannot be greater than 98%. This means that, for a conventional sulphur plant, the SO 2 emissions may amount up to many thousands of tons per year released into the atmosphere. These limitations led to the development of new processes to deal with the Claus tail-gas, in order to remove as much as possible the H 2 S concentration in the off gas before releasing it to the atmosphere [1]. All these processes to deal with the Claus tail-gas are based upon either oxidation of H 2 S by oxygen or H 2 S absorption/recycling technologies. These processes are based upon catalysts supported on different oxide supports such as α-alumina (α- Al 2 O 3 ), TiO 2 , SiO 2 and to a lesser extent activated charcoal. However, most of the oxide supports used; were rather sensitive to the problem of sulfating during the reaction in the presence of steam, sulfur, SO 2 and oxygen. In recent researches it was observed that SiC based catalyst seemed to be a promising candidate due to its chemical inertness [1-5]. On the other hand, all processes dealing with catalytic oxidization of H 2 S into elemental sulfur were tested in fixed bed reactors and experimental investigations in fluidized bed reactors yet to be realized. Since fluidized bed reactors exhibited elevated conversion factor and selectivity towards the product, it was recommended to study direct catalytic oxidization of H 2 S in a fluidized bed reactor; however certain difficulties encountered especially during extending bench data to industrial scale.The aim of this work was to develop a mathematical model for the catalytic oxidation of H 2 S in a fluidized bed reactor on a NiS 2 /SiC catalyst. Since no experimental data reported for this reaction in fluidized beds, at first results including the variations of H 2 S conversion was compared with those of a fixed bed. However, it was hoped that achieving suitable results involving this reaction in fluidized bed reactors will be realized via more extended investigations utilizing an experimental setup. Next, through analyzing results of the model, parameters influencing this process were determined. Ultimately, studying effects of these parameters, procedures proposed to reach optimum operating conditions for this process. II. FLUIDIZATION Fluidization described the condition when a gas passed up through a bed of solid particles became suspended. Fluidization occurred when superficial velocity of the gas lied in between the minimum fluidization and terminal velocity. If the gas velocity was set to less than the minimum fluidization Optimum Operating Conditions for Direct Oxidation of H 2 S in a Fluidized Bed Reactor Fahimeh Golestani, Mohammad Kazemeini, Moslem Fattahi and Ali Amjadian T World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering Vol:5, No:7, 2011 631 International Scholarly and Scientific Research & Innovation 5(7) 2011 scholar.waset.org/1307-6892/13429 International Science Index, Chemical and Molecular Engineering Vol:5, No:7, 2011 waset.org/Publication/13429