Syngas production via coal char-CO2 fluidized bed gasification and the effect on the performance of LSCFN//LSGM//LSCFN solid oxide fuel cell

Fluidized bed reactor is widely used in coal char-CO_2 gasification. In this work, the production of syngas by using a fluidized bed gasification technique was first investigated and then the effect of the produced syngas on the performance of the solid oxide fuel cell with a configuration of La_(0.4)Sr_(0.6) Co_(0.2)Fe_(0.7)Nb_(0.1)O_(3-δ)//La_(0.8)Sr_(0.2)Ga_(0.83)Mg_(0.17)O_(3-δ)//La_(0.4)Sr_(0.6) Co_(0.2)Fe_(0.7)Nb_(0.1)O_(3-δ)(LSCFN//LSGM//LSCFN)was studied. During the syngas production, we found that the volume fraction of CO increased with the increment of gasification temperature, and it reached a maximum value of 88.8%, corresponding to a composition of 0.76% H_2, 88.8% CO, and 10.44% CO_2, when the ratio of oxygen mass flow rate to that of coal char(MO2/Mchar) increased to 0.29. In the following utilization of the produced syngas in solid oxide fuel cells, it was found that the increasing CO volume fraction in the syngas results in a gradual increase of the peak power density of the LSCFN//LSGM//LSCFN cell. The maximum peak power density of 410 m W/cm~2 was achieved for the syngas produced at 0.29 of M_(O2)/M_(char). In the stability test, the cell voltage decreased by 4% at a constant current density of 0.475 A/cm~2 after 54 h when fueled with the syngas with the composition of 0.76% H2, 88.8% CO, and 10.44% CO_2.It reveals that a carbon deposition with the content of 13.66% in the anode is attributed to the cell performance degradation.     

Hydrogen for oil refining via biomass indirect steam gasification: energy and environmental targets

The energy and CO₂ consequences of substitution of a fossil-fuel-based hydrogen production unit with a biomass-based process in a large European refinery are studied in this study. In the base case, the biomass-based process consists in atmospheric, steam–blown indirect gasification of air-dried woody biomass followed by necessary upgrading steps. The effect of gradually substituting the current refinery hydrogen production unit with this process on global energy and CO₂ targets is estimated first. Few process concepts are studied in further detail by looking at different degrees of heat integration with the remaining refinery units and possible polygeneration opportunities. The proposed process concepts are compared in terms of energy and exergy performances and potential reduction in refinery CO₂ emission also taking into account the effect of marginal electricity. Compared to the base case, an increase by up to 8 % points in energy efficiency and 9 % points in exergy efficiency can be obtained by exploiting process integration opportunities. According to energy efficiency, steam production appears the best way to use excess heat available in the process while electricity generation through a heat recovery steam cycle appears the best option according to exergy efficiency results. All investigated cases yield to significant reduction in CO₂ emissions at the refinery. It appears in particular that maximal emission reduction is obtained by producing extra steam to cover the demand of other refinery units if high efficiency marginal electricity scenarios are considered.     

Numerical study of hydrogen production by the sorption-enhanced steam methane reforming process with online CO<Subscript>2</Subscript> capture as operated in fluidized bed reactors

A three-dimensional (3D) Eulerian two-fluid model with an in-house code was developed to simulate the gas-particle two-phase flow in the fluidized bed reactors. The CO₂ capture with Ca-based sorbents in the steam methane reforming (SMR) process was studied with such model combined with the reaction kinetics. The sorption-enhanced steam methane reforming (SE-SMR) process, i.e., the integration of the process of SMR and the adsorption of CO₂, was carried out in a bubbling fluidized bed reactor. The very high production of hydrogen in SE-SMR was obtained compared with the standard SMR process. The hydrogen molar fraction in gas phase was near the equilibrium. The breakthrough of the sorbent and the variation of the composition in the breakthrough period were studied. The effects of inlet gas superficial velocity and steam-to-carbon ratio (mass ratio of steam to methane in the inlet gas phase) on the reactions were studied. The simulated results are in agreement with the experimental results presented by Johnsen et al. (2006a, Chem Eng Sci 61:1195–1202).     

Economic and environmental evaluation of coal-and-biomass-to-liquids-and-electricity plants equipped with carbon capture and storage

Among various clean energy technologies, one innovative option for reducing the emission of greenhouse gases (GHGs) and criteria pollutants involves pairing carbon capture and storage (CCS) with the production of synthetic fuels and electricity from a combination of coal and sustainably sourced biomass. With a relatively pure CO₂ stream as an inherent byproduct of the process, most of the resulting GHG emissions can be eliminated by simply compressing the CO₂ for pipeline transport. Subsequent storage of the CO₂ output in underground reservoirs can result in very low—perhaps even near-zero—net GHG emissions, depending on the fraction of biomass as input and its CO₂ signature. To examine the potential market penetration and environmental impact of coal-and-biomass-to-liquids-and-electricity (CBtLE), a system-wide sensitivity analysis was performed using the MARKet ALlocation energy model. CBtLE was found to be most competitive in scenarios with a combination of high oil prices, low CCS costs, and, unexpectedly, non-stringent carbon policies. In the scheme considered here (30 % biomass input on an energy basis and 85 % carbon capture), CBtLE fails to achieve significant market share in deep decarbonization scenarios, regardless of oil prices and CCS costs. Such facilities would likely require higher fractions of biomass feedstock and captured CO₂ to successfully compete in a carbon-constrained energy system.     

Biofiltration of H<Subscript>2</Subscript>S-rich biogas using <Emphasis Type="Italic">Acidithiobacillus thiooxidans</Emphasis>

Biogas has limited use in energy generation mainly due to the presence of hydrogen sulfide (H₂S). Currently, most of the techniques employed in the removal of H₂S from biogas have a chemical base, with high material costs and generating secondary pollutants. Biological processes for H₂S removal have become effective and economical alternative techniques to traditional gas-treatment systems based on physicochemical techniques. Therefore, the aim of this work was to investigate the performance of a bench-scale biofilter for the removal of H₂S present in synthetic biogas. In addition, CO₂ and CH₄ concentrations in the outlet biogas were evaluated. The inoculum used in the experiment was composed of Acidithiobacillus thiooxidans fixed on a packing of wood chips. Synthetic biogas was supplied to the system with a composition of 60 % CH₄, 39 % CO₂ and 1 % H₂S. The biofilter operated continuously for 37 days with an average H₂S removal efficiency of 75 ± 13 % and maximum of 97 %. The elimination capacity of the system reached an average of 130 ± 23 g m^?3 h^?1 and a maximum of 169 g m³ h^?1. The biofiltration system showed an average reduction of only 6 % in CH₄ concentration from biogas. Thus, besides being efficient in the removal of H₂S, the system was able to maintain the biogas energy value.     

Co-production of power and urea from coal with CO<Subscript>2</Subscript> capture: performance assessment

Coal-based power plants are largest emitter of CO₂ as a single sector. To use fossil fuels (including coal), CO₂ capture and storage is a visible option. But large energy requirement for this process and risk associated with storage of CO₂ demand alternative solutions including recycling of captured CO₂. In this paper, a co-production of power and urea is proposed using coal with captured CO₂. Detailed ASPEN Plus^® model is developed for this plant. As shift reaction for producing H₂ has significant effect on output parameters, analysis is done for two different values of shift reaction, i.e., 90 and 95 % conversion. Plant consumes substantial auxiliary power (~19 % for the base case). Auxiliary power becomes a minimum for about 25 % captured CO₂ utilization for 95 % shift conversion. An economy factor is also defined to estimate the economic advantage of utilizing captured CO₂. Results show that economic advantage is obtained for CO₂ utilization beyond ~5 % for 95 % water gas shift reaction and it is beyond ~10 % for a 90 % shift reaction.     

Greenhouse gases mitigation by CO<Subscript>2</Subscript> reforming of methane to hydrogen-rich syngas using praseodymium oxide supported cobalt catalyst

This study focuses on the potential of hydrogen-rich syngas production by CO₂ reforming of methane over Co/Pr₂O₃ catalyst. The Co/Pr₂O₃ catalyst was synthesized via wet-impregnation method and characterized for physicochemical properties by TGA, XRD, BET, H₂-TPR, FESEM, EDX, and FTIR. The CO₂ reforming of methane over the as-synthesized catalyst was studied in a tubular stainless steel fixed-bed reactor at feed ratio ranged 0.1–1.0, temperature ranged 923–1023 K, and gas hourly space velocity (GHSV) of 30,000 h^?1 under atmospheric pressure condition. The catalyst activity studies showed that the increase in the reaction temperature from 923 to 1023 K and feed ratio from 0.1 to 1.0 resulted in a corresponding increase in the reactant’s conversion and the product’s yields. At 1023 K and feed ratio of 1.0, the activity of the Co/Pr₂O₃ catalyst climaxed with CH₄ and CO₂ conversions of 41.49 and 42.36 %. Moreover, the catalyst activity at 1023 K and feed ratio of 1.0 resulted in the production of H₂ and CO yields of 40.7 and 40.90 %, respectively. The syngas produced was estimated to have H₂:CO ratio of 0.995, making it suitable as chemical building blocks for the production of oxygenated fuel and other value-added chemicals. The used Co/Pr₂O₃ catalyst which was characterized by TPO, XRD, and SEM-EDX show some evidence of carbon formation and deposition on its surface.     

Production of methanol and organic carbonates for chemical sequestration of CO2 from an NGCC power plant

Global economic development anticipates a growth in demand of the energy sector whose supply in the coming decades will remain achieved by burning fossil fuels. The need to stabilize the CO₂ atmospheric concentration requires technologies for capturing and reutilization of this greenhouse gas. Such scenario motivates feasibility analysis of power generation with post-combustion capture of CO₂ from the flue gas associated with its transformation into chemical commodities. Specifically, the economic performance of an integrated NGCC with post-combustion capture and utilization is evaluated to balance aggregated revenues with energy penalty. The proposed CO₂ reutilization is the production of methanol (MeOH), organic carbonates—dimethyl carbonate (DMC) and ethylene carbonate (EC), and ethylene glycol (EG). The study uses CO₂ capture with MEA (monoethanolamine), including compression of the captured gas followed by its conversion to methanol and organic carbonates, and separation of products with recycle of reactants. Three scenarios were evaluated corresponding to the capture of 30, 50, and 80 % of the CO₂ present in the flue gas. The comparative analysis includes definition of design premises followed by synthesis of process flowsheet, process simulation in the three scenarios, with sizing of the main pieces of process equipments for economic analysis—capital and operational expenditures (CAPEX and OPEX). Results indicated economic feasibility for the three scenarios. Furthermore, energy and mass balances showed that the emissions from energy demand to drive reactions and separations surpasses the proposed sequestration of CO₂ by chemical utilization in the scenarios of 30 and 50 % of CO₂ capture from NGCC emissions. In reality, CO₂ accounting for cases 1 and 2 reveals a “carbon debt” while for case 3 a net positive abatement of CO₂ occurs which increases process revenue by 1.7 % and reduces ROI in 1 year.     

A study of gas and solid mixing behaviors in a three partitioned fluidized bed

A previously unknown partitioned fluidized bed gasifier (PtFBG) has been developed for improving coal gasification performance. The basic concept of the PtFBG is a fluidized bed divided into two parts, a gasifier and a combustor, by a partitioned wall. Char is burnt in the combustor and the generated heat is supplied to the gasifier along with the bed materials. During that time, highly concentrated CO₂ is inevitably generated in the combustor. Therefore, vigorous solid mixing is an essential precondition as well as minimizing horizontal gas mixing. In this study, gas and solid mixing behaviors were verified in a cold model three partitioned fluidized bed (3-PtFB). Glass beads with an average diameter of 150 μm and a particle density of 2500 kg/m³ were used as bed materials. For the gas mixing experiments, CO₂ and N₂ were introduced into the beds through each distributor. Then, outlet gas flow rates and concentrations were measured by gas flow meters and an IR gas analyzer respectively. The calculated gas exchange ratios ranged from 3% to 10% with varying gas flow rates. For the solid mixing experiments, 1000 μm polypropylene particles with a density of 883 kg/m³ were continuously fed into the reactor. Then, the polypropylene particles were distributed to the entire beds evenly. Solid mixing behaviors were very analogous to liquid mixing behaviors in a continuous stirred tank reactor (CSTR).     

Pretreatment methods for gasification of biomass and Fischer–Tropsch crude production integrated with a pulp and paper mill

In this paper, the influence on the system performance and greenhouse gas (GHG) emissions of different biomass pretreatment methods before gasification and Fischer–Tropsch (FT) crude production was evaluated. Entrained flow gasification has the benefit of producing a practically tar-free synthesis gas with nearly complete carbon conversion. This gasifier type requires a relatively dry fuel, with small particle size, at high pressure. The size can be acquired by milling, which is energy intensive and feeding is challenging. Torrefaction of biomass facilitates milling; it thus requires less electricity, however, the torrefaction process requires heat. Pyrolysis decomposes the biomass into gaseous, liquid, and solid parts, respectively. This further makes feeding easier, but comes with a greater heat demand than torrefaction. The impact of the different pretreatment methods on the overall energy system has been evaluated using process integration methodology. The results show that the excess heat from an FT process with a biomass input of 300 MW_HHV can replace the bark boiler in a large chemical pulp and paper mill, producing 350,000 tonnes of bleached paperboard annually. With the preconditions given for this study, thermal pretreatment of biomass may be beneficial in terms of wood-to-FT crude efficiency, with efficiencies up to 68 %, assuming 40 % electrical efficiency. Pretreatment using pyrolysis performed the best in regards to GHG emissions, if CO₂ from acid gas removal was vented, while milling, with an annual reduction of around 700,000 tonnes of CO₂,_eq, had the best results if the CO₂ was captured and sequestrated.     

Biohydrogen production from agroindustrial wastes via Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564)

The anaerobic production of biohydrogen from different pretreated agroindustrial wastes, including rice bran (RB), de-oiled RB (DRB), sago starch (SS), and palm oil mill effluent (POME) via Clostridium saccharoperbutylacetonicum N1-4 was investigated in a batch culture system at 30 °C and a pH of 6.2. A yield of 7627, 6995, and 6,363 mL H₂/L was obtained from H₂SO₄ (1 %)-treated DRB (10 %), enzymatically hydrolyzed DRB (10 %) and HCl (1 %)-treated DRB (10 %), respectively; however, untreated DRB (10 %) was able to produce only 3,286 mL H₂/L. A strategic treatment of RB (10 %) with HCl (1 %) followed by enzymatic hydrolysis could produce 3,172 mL H₂/L. An enzymatically hydrolyzed mixture of each POME and SS (5 %) produced 3,474 mL H₂/L, and a remarkable enhancement of H₂ production (7,020 mL H₂/L) was achieved when the same mixture was subjected to XAD-4 resin treatment. In contrast, the enzymatically hydrolyzed SS (5 %) could produce only 4,628 mL H₂/L. Conclusively, it can be stated that agricultural wastes have a potential as substrates for biohydrogen production and that pretreatment with C. saccharoperbutylacetonicum N1-4 can contribute positively to enhancing the production.     

Gas desulphurization by sorption of SO2 on CuO/Al2O3 solid sorbent in a counterflow multistage fluidized bed reactor: Experimental analysis and modelling of the reactor

This paper gives a review of several works performed in the Laboratory of Chemical Engineering of Toulouse (France) on the desulphurization of gas mixtures by chemical sorption of sulphur dioxide on cupric oxide deposited on porous alumina particles in a counterflow multistage fluidized bed reactor. The first part of the paper presents experimental results concerning effects of gas and solids flow rates, hold up of solids in the reactor, temperature and concentrations of SO₂ and other gases (CO₂, H₂O and NO _x ). Desulphurization yields exceeding 90% were obtained using a four-stage reactor and sulphur dioxide content could be reduced from 3000 ppm to less than 300 ppm with a small gas pressure drop. The presence of other components in the flue gas led to slight changes in the desulphurization yield. This could be corrected by a better choice of the operating conditions. The second part of the article presents the modelling of the reactor by taking into account the residence time distribution of the solid particles through it. Comparison between the model predictions and experimental results showed that the assumptions of Davidson and Harrison are sophisticated enough to describe reactor operation under steady state conditions. This paper is dedicated to Dr L K Doraiswamy on his sixtieth birthday.     

Temporary feeding shocks increase the productivity in a continuous biohydrogen-producing reactor

Continuous hydrogen production stability and robustness by dark fermentation were comprehensively studied at laboratory scale. Continuous bioreactors were operated at two different hydraulic retention times (HRT) of 6 and 10 h. The reactors were subjected to feeding shocks given by decreases in the HRT, and therefore the organic loading increases, during 6 and 24 h. Results indicated that the H₂ productivity was significantly improved by the temporary organic shock loads, increasing the hydrogen production rate up to 40%, compared to the rate obtained at the steady-state condition. Besides, it was observed that after the shock load, the stability of the reactor (measured as the hydrogen production rate) was recovered attaining the values observed before the feeding shocks. The bioreactor operated at shorter HRT (6 h) showed better H₂ productivity (17.3?±?1.1 L H₂/L-d) in comparison with the other one operated at 10-h HRT (12.4?±?1.6 L H₂/L-d).     

Application of BICOVOX catalyst for hydrogen production from ethanol

Catalytic activity of cobalt-doped bismuth vanadate [Bi₄(V_0.90Co_0.10)₂O_11?δ ; BICOVOX] powder, prepared by a solution combustion synthesis and calcined at 800 °C (BICOVOX-800), for hydrogen production using low-temperature steam reforming of ethanol, has been reported in this paper. The effects of reaction temperature (250–400 °C) and feed concentration (H₂O/EtOH = 2.5:1 and 23:1 mol ratio) on the steady-state ethanol conversion and selectivity of H₂, CO₂, CO, and CH₄ have been investigated (up to 30 h). It is observed that with an increase in reaction temperature and H₂O/EtOH mole ratio, H₂ and CO₂ selectivity increases and CO and CH₄ selectivity decreases. The maximum H₂ selectivity and ethanol conversion are observed to be 63 and 88%, respectively, for H₂O/EtOH = 23:1 mol ratio at 400 °C. The XRD results show that the fresh BICOVOX-800 has pure γ-phase and is highly crystalline. The used catalyst (more than 150 h total) is detected to have less crystallinity and to partially decompose into Bi₂O₃ and BiVO₄ phases.     

Cement and carbon emissions

Because of its low cost, its ease of use and relative robustness to misuse, its versatility, and its local availability, concrete is by far the most widely used building material in the world today. Intrinsically, concrete has a very low energy and carbon footprint compared to most other materials. However, the volume of Portland cement required for concrete construction makes the cement industry a large emitter of CO₂. The International Energy Agency recently proposed a global CO₂ reduction plan. This plan has three main elements: long term CO₂ targets, a sectorial approach based on the lowest cost to society, and technology roadmaps that demonstrate the means to achieve the CO₂ reductions. For the cement industry, this plan calls for a reduction in CO₂ emissions from 2 Gt in 2007 to 1.55 Gt in 2050, while over the same period cement production is projected to increase by about 50 %. The authors of the cement industry roadmap point out that the extrapolation of existing technologies (fuel efficiency, alternative fuels and biomass, and clinker substitution) will only take us half the way towards these goals. According to the roadmap, the industry will have to rely on costly and unproven carbon capture and storage technologies for the other half of the required reduction. This will result in significant additional costs for society. Most of the CO₂ footprint of cement is due to the decarbonation of limestone during the clinkering process. Designing new clinkers that require less limestone is one means to significantly reduce the CO₂ footprint of cement and concrete. A new class of clinkers described in this paper can reduce CO₂ emissions by 20 to 30 % when compared to the manufacture of traditional PC Clinker.     

3D simulation on pressurized oxy-fuel combustion of coal in fluidized bed

Pressurized oxy-fuel combustion technology is considered as a perspective carbon capture technology in industrial process. A computational fluid dynamics (CFD) model based on Multi-Phase Particle-In-Cell (MP–PIC) method was developed to predict pressurized oxy-coal combustion process in fluidized bed. The heterogeneous and homogeneous combustion reactions of coal were considered in this model. The predicted results were validated the accuracy of this model with experimental data from a 15 kW_th pressurized fluidized bed combustor in terms of the gas component and temperature characteristics. The characteristics of gas–solid flow and combustion under different pressure (0.1–2 MPa) and oxygen atmosphere were studied in this work. The predicted results show that the intensity of particle motion and the expansion degree in the fluidized bed was gradually decreased with an increase in pressure. A correlation was proposed based on the simulation results to maintain suitable fluidization conditions in pressurized circulating fluidized bed at different pressures. The temperature of particle phase region gradually increased with combustion pressure and inlet O₂ concentration increased. In addition, the CO₂ concentration in outlet increased while the emission of CO and NO_x decreased as the combustion pressure increased.     

Carbon dioxide absorption by ammonia intensified with membrane contactors

Membrane gas absorption technology is a promising alternative for CO₂ removal from post-combustion coal-fired flue gases. This study examines an alternative which consists in absorbing carbon dioxide by ammonia aqueous solution in a membrane contactor to improve the capture processes and to intensify the gas–liquid transfer. Absorption measurements through a membrane contactor have been made. The influence of the material nature constituting the membrane and operating parameters on the capture efficiency has been studied. The potentialities of dense skin membrane contactors are discussed with regard to both increased CO₂ mass transfer performances and mitigation of ammonia volatilization. The results have shown that it is possible to capture CO₂ from ammonia through a membrane with capture efficiency greater than 90 %. The membrane limits ammonia losses but does not eliminate it. The experimental results are used to calculate an intensification factor of 5, which represents the comparison between the membrane overall absorption rate to that of the column.     

Photocatalytic CO<Subscript>2</Subscript> conversion over Au/TiO<Subscript>2</Subscript> nanostructures for dynamic production of clean fuels in a monolith photoreactor

Global economic development intensifies the consumption of fossil fuels which results in increase of carbon dioxide (CO₂) concentration in the atmosphere. The technologies for carbon capture and utilization to produce cleaner fuels are of great significance. However, phototechnology provides one perspective for economical CO₂ conversion to cleaner fuels. In this study, CO₂ conversion with H₂ to selective fuels over Au/TiO₂ nanostructures using environment friendly continuous monolith photoreactor has been investigated. Crystalline nanoparticles of anatase TiO₂ were obtained in the Au-doped TiO₂ samples. The Au deposited over TiO₂ in metal state produced plasmonic resonance. CO₂ was efficiently converted to CO as the main product over Au/TiO₂ with a maximum yield rate of 4144 µmol g-catal.^?1 h^?1, 345 fold-higher than using un-doped TiO₂ catalyst. The significantly enhanced photoactivity of Au/TiO₂ catalyst was due to hindered charges recombination rate and Au metallic-interband transition. The photon energy in the UV range was high enough to excite the d-band electronic transition in the Au to produce CO, CH₄, and C₂H₆. The quantum efficiency over Au/TiO₂ catalyst for CO was considerably improved in the continuous monolith photoreactor. At higher space velocity, the yield rates of CO gradually reduced, but the initial rates of hydrocarbon yields increased. The stability of the recycled Au/TiO₂ catalyst was sustained in cyclic runs. Thus, Au-doped TiO₂ supported over monolith channels is promising for enhanced CO₂ photoreduction to high energy products. This provides pathway that phototechnology to be explored further for cleaner and economical fuels production.     

A Highly Active Star Decahedron Cu Nanocatalyst for Hydrocarbon Production at Low Overpotentials

The electrochemical carbon dioxide reduction reaction (CO₂RR) presents a viable approach to recycle CO₂ gas into low carbon fuels. Thus, the development of highly active catalysts at low overpotential is desired for this reaction. Herein, a high‐yield synthesis of unique star decahedron Cu nanoparticles (SD‐Cu NPs) electrocatalysts, displaying twin boundaries (TBs) and multiple stacking faults, which lead to low overpotentials for methane (CH₄) and high efficiency for ethylene (C₂H₄) production, is reported. Particularly, SD‐Cu NPs show an onset potential for CH₄ production lower by 0.149 V than commercial Cu NPs. More impressively, SD‐Cu NPs demonstrate a faradaic efficiency of 52.43% ± 2.72% for C₂H₄ production at ?0.993 ± 0.0129 V. The results demonstrate that the surface stacking faults and twin defects increase CO binding energy, leading to the enhanced CO₂RR performance on SD‐Cu NPs.     

A model on desulfurization characteristics of an entrained bed-bubbling bed hot gas cleanup system for IGCC

A mathematical model has been developed to predict performance of a continuous entrained-bed and bubbling fluidized-bed hot gas desulfurization system in IGCC. The model combines the particle residence time with the kinetic rate in each reactor. The model has been applied to the KIER’s laboratory scale fluidized bed process. The present model provided a reasonable fit in predicting experimental results that the outlet concentration of H₂S from the desulfurizer and SO₂ from the regenerator increased nearly proportionally to the inlet concentration of H₂S to the desulfurizer. The model also could predict well the outlet concentration of O₂ from the regenerator to decrease as the inlet concentration of H₂S to the desulfurizer increased. The present model predicted with reasonable accuracy mean diameter of bed particles and sulfur content of particles in desulfurizer and regenerator.