Desulfurization Sorbents Research Articles

Retracted] Manganese-based Regenerable Sorbents for Flue Gas Desulfurization and Recovery of H2S

Mn2O3/SiC regenerable sorbents with various manganese contents are prepared by the sol-gel method. For the sorbent with a manganese content of 50%, the best desulfurization and regeneration perform...

Ni-Zn-based nanocomposite loaded on cordierite mullite ceramic for syngas desulfurization: Performance evaluation and regeneration studies

A series of Ni-Zn-based nanocomposites with various Ni:Zn mol ratios was prepared using a facile hydrothermal-calcination method. The Ni-Zn-based nanocomposites were characterized using XRD, FESEM, EDX and N2 adsorption, indicating that all the Ni-Zn-based nanocomposites consisted of hierarchical nanostructure. The Ni-Zn-based nanocomposites were used as sorbents for desulfurization of simulated syngas. It was found that the optimum Ni:Zn mol ratio for preparing highly-regenerable sorbent was 2:5 and hence, this ratio was used to prepare the Ni-Zn-based nanocomposite loaded on cordierite mullite honeycomb (NiZn-28-HC). The characterization study revealed that the immobilized Ni-Zn-based nanostructure consisted of seaweed-like morphology with 10 µm thickness. After 5 desulfurization-regeneration cycles, the NiZn-28-HC demonstrated only a minor loss in the desulfurization performance. Investigation of the surface chemical states using XPS revealed that the marginal sorbent deactivation during repeated desulfurization-regeneration cycles was mainly due to the formation of sulfate. The influence of HCl on the desulfurization-regeneration cycle was also studied, showing that the presence of HCl can inhibit the desulfurization process due to competition reaction with sulfur compounds for sorption onto the sorbent active sites. However, it was found that HCl up to 50 ppmv has no significant influence on the performance and regenerability of the sorbent. The results indicated that the NiZn-28-HC is a promising sorbent with high reactivity and stability for syngas desulfurization.

A kinetic study of CFB boiler separated bottom ashes during the steam hydration reaction

Abstract Although petcokes/coals can be efficiently combusted in a circulating fluidized bed (CFB) boiler with in-situ limestone desulfurization, only 20%–40% calcium of limestone particles is typically sulfated. Here, the CFB boiler separated bottom ashes are activated by 200 °C steam in a 15 rpm rotary drum to be recycled as the secondary desulfurization sorbent. Calcium oxide hydration reaction effectively cracks the ash calcium sulfate shell by the formation of calcium hydroxide from ash calcium oxide core and steam. The maximum conversion reaches 76% after ca. 5 min hydration time for 260 µm BA particles with an initial loading of 2 kg. The reaction kinetic study shows that the reaction has an apparent reaction order of 3.4 ± 0.5 to the concentration of core calcium oxide. The water vapor diffusion through the calcium sulfate layer is the likely to be the reaction rate-limiting step as predicted by the shrinking core model.

The dissolution kinetics of industrial brine sludge wastes from a chlor-alkali industry as a sorbent for wet flue gas desulfurization (FGD)

ABSTRACTThe disposal of industrial brine sludge waste (IBSW) in chlor-alkali plants can be avoided by utilization of IBSW as a sorbent in wet flue gas desulfurization (FGD). The shrinking core model was used to determine the dissolution kinetics of IBSW, which is a vital step in wet FGD. The effects of solid-to-liquid ratio (m/v), temperature, pH, particle size, and stirring speed on the conversion and dissolution rate constant are determined. The conversion and dissolution rate constant decreases as the pH, particle size, and solid-to-liquid ratio are increased and increases as the temperature, concentration of acid, and stirring speed are increased. The sorbents before and after dissolution were characterized using x-ray fluorescence (XRF), x-ray diffraction (XRD), and scanning electron microscopy (SEM). An activation energy of 7.195 kJ/mol was obtained and the product layer diffusion model was found to be the rate-controlling step.Implications: The use of industrial brine sludge waste as an alternative sorbent in wet flue gas desulfurization can reduce the amounts of industrial wastes disposed of in landfills. This study has proved that the sorbent can contain up to 91% calcium carbonate and trace amounts of sulfate, magnesium, and so on. This can be used as new sorbent to reduce the amount of sulfur dioxide in the atmosphere and the by-product gypsum can be used in construction, as a plaster ingredient, as a fertilizer, and for soil conditioning. Therefore, the sorbent has both economic and environmental benefits.

Role of silanol groups on silica gel on adsorption of benzothiophene and naphthalene

The adsorptive removal of sulfur-containing compounds such as thiophene derivatives from transportation fuels has received extensive attention because of its economic and environmental advantages compared to the hydrodesulfurization process. In our previous study, we suggested that the adsorption sites for benzothiophene and naphthalene on the silica surface consist of different types of silanol groups, and the removal of vicinal silanols from the silica surface should enable silica materials to adsorb benzothiophene selectively. In this study, an attempt is made to prove this hypothesis for the development of novel desulfurization sorbents. Heat treatment of silica gel was performed at different temperatures to remove vicinal silanol groups, and the adsorption capacities of benzothiophene and naphthalene were evaluated. The amount of naphthalene adsorbed on heat-treated silica gel decreased with increasing heat-treatment temperature, whereas the amount of benzothiophene adsorbed on silica gel treated at 873 and 1073 K showed only a slight decrease. Considering the heat treatment might lead to the removal of vicinal silanols due to dehydration of surface silanols, the results indicate that vicinal silanol groups were selective adsorption sites for naphthalene. Moreover, for binary-component systems, the adsorption capacities of benzothiophene and naphthalene were almost identical because of multilayer adsorption of naphthalene on adsorbed benzothiophene, and the adsorption capacities of benzothiophene for single- and binary-component systems were also identical. This suggests that the heat treatment of silica enables the selective removal of benzothiophene.

Carbonate Minerals with Magnesium in Triassic Terebratula Limestone in the Term of Limestone with Magnesium Application as a Sorbent in Desulfurization of Flue Gases

AbstractThis article presents the results of studies of Triassic (Muschelkalk) carbonate rock samples of the Terebratula Beds taken from the area of the Polish part of the Germanic Basin. It is the area of Opole Silesia. The rocks were studied in the term of possibility of limestone with magnesium application in desulfurization of flue gases executed in power plants. Characteristic features of especially carbonate phases including magnesium-low-Mg calcite, high-Mg calcite, dolomite and huntite were presented in the article. They were studied to show that the presence of carbonate phases with magnesium, especially high-Mg calcite makes the desulfurization process more effective. Selected rock samples were examined using a microscope with polarized, transmitted light, X-ray diffraction, microprobe measurements and FTIR spectroscopy. The results of studies show a domination of low magnesium calcite in the limestones of the Terebratula Beds. In some samples dolomite and lower amounts of high-Mg calcite occurred. Moreover, huntite was identified. The studies were very important, because carbonate phases like high-Mg calcite and huntite which occurred in rocks of the Triassic Terebratula Beds were not investigated in details by other scientists but they presence in limestone sorbent could influence the effectiveness of desulfurization process.

Effects of Microwave Irradiation on the Structure of Zinc Oxide Sorbents for High Temperature Coal Gas Desulfurization

To investigate the effects of microwave irradiation on the structure properties of ZnO sorbents, fractal dimensions and desulfurization kinetics of sorbents prepared by microwave and conventional heating respectively have been studied in the present paper. The performances for desulfurization were tested in a fixed-bed reactor, and the sorbents were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Fractal dimensions were calculated based on the Frenkel-Halsey-Hill theory, and desulfurization kinetics of sorbents was acquired by the equivalent grain model. The analysis date revealed that the fractal dimensions and sulfur capacity of sorbents prepared by microwave heating are 2.744 and 10.77%, while those of the sorbents prepared by conventional heating are 2.719 and 8.633%. Desulfurization kinetics studies presented that the apparent chemical reaction activation energy and the diffusion activation energy of sorbents heated by the microwave method are 6...

Study on the Desulfurization Performance of N-Type and P-Type Semiconductor Pyrolysis Char Composite Catalyst

Ordos coal pyrolysis product roasted under 750oC was used as desulfurization sorbents to investigate the effect of flue gas desulfurization performance of supported metal catalyst. There were 14 kinds of metal oxides from groups IA, IIA, VIB, VIIB, VIII, IB and IIIB chosen as active components to prepare metal oxide supported catalysts by equivalent volume impregnation method. And the mechanism of pyrolysis was studied. The similarities of desulfurization performance among the same group of metal oxides were related to the structure of their outer electrons. In addtion, the influence of transition metal oxides on the desulfurization performance was related to metal oxide semiconductor type. Finally, the influence of the VIII group oxide catalyst of iron (Fe), Cobalt (Co), Nickel (Ni) on the desulfurization performance showed the characteristics of diversity related to their d percentage (%).

Evaluation of the cycling performance of a sorbent for H2S removal and simulation of desulfurization-regeneration processes

High temperature gas desulfurization is an efficient and environmentally-friendly process for syngas purification. This paper investigated the cycling behaviors of iron oxide/red clay desulfurization sorbents within 12 desulfurization-regeneration cycles in a fixed-bed quartz reactor. The results showed that the sulfur capacities of the regenerated sorbents reduced to less than 50% with all the regeneration rates of the sorbents exceeded 70.15%. The surface and structural properties of the sorbents in the desulfurization-regeneration cycles were characterized by XRD, XPS, SEM, BET and elemental mapping analyses. According to XRD analyses, the particle size of the sorbents gradually increased with the number of desulfurization-regeneration cycles. These cycles reduced the surface area and blocked the pore structure, which have a contribution on the degenerated desulfurization performances of regenerated sorbents. The XPS and EDS spectra indicated the existence of the sulfur-containing compounds in the cycled sorbents, contributing to the lowered regeneration rate of the sorbents. The concentrations of iron and oxygen on the surface decreased over the repeated cycles, which are adverse to the adsorption of acidic H2S. A simulation model was created using COMSOL Multiphysics software to predict the performance and characteristics of the desulfurization-regeneration processes and elucidate its specific mechanism in the desulfurization and regeneration reactions. The comparison between predictions using COMSOL and experimental results were also conducted. Although there are deviations observed in the comparison, the simulated results match the experimental data to a large degree and show the feasibility of the COMSOL Multiphysics in the study of desulfurization and regeneration.

Dry syngas purification process for coal gas produced in oxy-fuel type integrated gasification combined cycle power generation with carbon dioxide capturing feature

Electricity production from coal fuel with minimizing efficiency penalty for the carbon dioxide abatement will bring us sustainable and compatible energy utilization. One of the promising options is oxy-fuel type Integrated Gasification Combined Cycle (oxy-fuel IGCC) power generation that is estimated to achieve thermal efficiency of 44% at lower heating value (LHV) base and provide compressed carbon dioxide (CO2) with concentration of 93 vol%. The proper operation of the plant is established by introducing dry syngas cleaning processes to control halide and sulfur compounds satisfying tolerate contaminants level of gas turbine. To realize the dry process, the bench scale test facility was planned to demonstrate the first-ever halide and sulfur removal with fixed bed reactor using actual syngas from O2–CO2 blown gasifier for the oxy-fuel IGCC power generation. Design parameter for the test facility was required for the candidate sorbents for halide removal and sulfur removal. Breakthrough test was performed on two kinds of halide sorbents at accelerated condition and on honeycomb desulfurization sorbent at varied space velocity condition. The results for the both sorbents for halide and sulfur exhibited sufficient removal within the satisfactory short depth of sorbent bed, as well as superior bed conversion of the impurity removal reaction. These performance evaluation of the candidate sorbents of halide and sulfur removal provided rational and affordable design parameters for the bench scale test facility to demonstrate the dry syngas cleaning process for oxy-fuel IGCC system as the scaled up step of process development.

Insights to the microwave effect in the preparation of sorbent for H2S removal: Desulfurization kinetics and characterization

High temperature coal gas desulfurization is an efficient and environmental-friendly process for clean coal technologies such as the integrated coal gasification combined cycle. This study adopted microwaves as the energy source to prepare iron oxide desulfurization sorbents and investigated the effect of microwave heating on the properties of the sorbents. The desulfurization kinetics of H2S removal by the two kinds of sorbents heated using both microwave and conventional method were studied and the sorbents were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N2-adsorption and energy dispersive spectrometry (EDS). The shrinking core model was used to describe the desulfurization reaction. The calculated activation energies of microwave-heated sorbent in the regions of chemical reaction and diffusion control were both smaller than those of the conventional-heated sorbent. The characterization data indicate that the sorbents prepared by microwave heating have higher contents of active metal elements on the surface, which improve the adsorption efficiency. Fractal dimensions were calculated based on Frenkel-Halsey-Hill theory and the results revealed that the fractal dimension of microwave-heated sorbent is 2.850 and that of conventional-heated sorbent is 2.832. The results indicate that microwave irradiation provides a more porous internal structure and irregular surface which facilitates gas transfer during the desulfurization process. Overall, the microwave heating method produced sorbents with better H2S removal performance, suggesting the potential of using this method to prepare improved industrial sorbents.

Dynamics of Bed for Regeneration of Cerium Oxide High-Temperature Coal Gas Desulfurization Sorbent

The dynamic behavior of bed for regeneration of cerium oxide high temperature gas desulfurization sorbent under the atmosphere of O2 was investigated in the fixed bed micro-reactor. O2 concentration during the regeneration can be detected by an oxygen analyzer, and the sulfur content of sorbent in the bed was test using sulfur analyzer. The effects of O2 concentration, regeneration temperature on the dynamic behavior of bed for regeneration of CeO2 desulfurization sorbent were discussed. According to the experimental results, the length and movement speed of regeneration zone are calculated. The results showed that the increase of O2 concentration in inlet gas obviously improves the movement speed of regeneration zone in bed for CeO2 desulfurization sorbent, and the increase of regeneration temperature can decreased the length of the regeneration zone and improved the movement speed of the regeneration zone. The increase of regeneration temperature had a better effect on the improvement of bed utilization of sorbent than that of O2 concentration.

The Properties of Iron Oxide Desulfurization Sorbents Regenerated under the Synergy of SO<sub>2</sub>-O<sub>2 </sub>Atmosphere

Iron oxide (Fe2O3) desulfurization sorbent was prepared from FeSO4 and NH4HCO3 by precipitation method, and its regeneration behavior under different atmosphere was studied by using Thermos gravimetric analyzer. It is found that the regeneration of Fe2O3 desulfurization sorbent is the best in the synergy of SO2-O2 atmosphere. When the concentration of O2 or SO2 in the synergy of SO2-O2 atmosphere was increased, the regeneration time can be reduced, which is beneficial to the regeneration of iron oxide desulfurization sorbent. The regeneration of Fe2O3 desulfurization sorbent in the synergy of SO2-O2 atmosphere can not only prevent sorbent sintering in single O2 atmosphere but also improve the rate of regeneration in single SO2 atmosphere.

The Effect of Regeneration Conditions on the Properties of CeO<sub>2</sub> Desulfurization Sorbent in SO<sub>2</sub> Atmosphere

CeO2 desulfurization sorbent was prepared by calcination of Ce(NO3)3 ● 6H2O and the effect of regeneration conditions on its properties in SO2 atmosphere was investigated in a fixed bed reactor. The regeneration conversion and the yield of elemental sulfur for CeO2 desulfurization sorbent were tested and calculated. And the composition and the morphology of CeO2 desulfurization sorbent before and after regeneration were obtained by X-ray diffraction and scanning electron microscope. It was found that the main components of the regeneration products of Ce2O desulfurization sorbent were solid CeO2 and gaseous elemental S in SO2 atmosphere. The optimum regeneration condition of CeO2 desulfurization sorbent is that the regeneration temperature of 750 °C and the SO2 concentration of 4.25 %, under which the CeO2 desulfurization sorbent shows the higher regeneration conversion of 96 % and the yield of elemental sulfur of 68.95 wt. %.

Thermodynamic aspects of gasification derived syngas desulfurization, removal of hydrogen halides and regeneration of spent sorbents based on La2O3/La2O2CO3 and cerium oxides

The thermodynamic analyses are focused on the determination of theoretical equilibrium concentrations of H2S, HCl and HF for La2O3, La2O2CO3 and CexOy-based sulfur compounds sorbents, on possible interferences of hydrogen halides in H2S removal in the temperature range 600–1100K and on upstream selective deep removal of HCl and HF in producer gas. Minimization of Gibbs energy for the system was used in more complicated situations. The lowest H2S concentration (<0.1ppm-v) can be attained by Ce2O3-based sorbents at temperatures below 800K. Oxidation of the Ce2O3-based sorbents to less efficient higher Ce-oxides (with limit of CeO2) is thermodynamically preferred in real producer gas. Presence of CO2 in gas phase leads to formation of lanthanum oxy-carbonate (La2O2CO3) with lower efficiency in H2S removal than La2O3. The thermodynamic analyses are also focused on suitable ways and conditions for regeneration of spent desulfurization sorbents (Ce2O2S and La2O2S) to the corresponding oxides or oxy-carbonates at temperatures 600K–1100K. The Ce2O2S-based spent cerium sorbents are advantageously regenerated by reaction with SO2 at temperatures over 700K. In this way CeO2, elemental sulfur and small concentrations of S2O are theoretically produced. If the cerium halides are formed, their decomposition and full Ce-sorbent regeneration is thermodynamically possible rather by reaction with steam. The La-based spent sulfur sorbents are restored by reaction with CO2 and H2O vapor leading to formation of La2O2CO3 and H2S. The suitable operating conditions involve temperatures between 700 and 800K and higher operating pressures. Potential small contents of La-oxy-halides (LaOF and LaOCl) in the spent sorbent are converted into La2O2CO3 in such a regeneration process.

Effect of Cu-Doped ZnO Sorbents for Desulfurization

The purpose of this work is to synthesize undoped and Cu-doped ZnO sorbents by citrate-gel method and compare desulfurization efficiency, particularly H2S, at 150°C and 300°C. The undoped ZnO result shows a single phase of hexagonal zincite while the CuO monoclinic phase appeared with ZnO hexagonal phase in Cu-doped compositions (denoted by ZCx where x = mol% of Cu). The microstructure and surface area have been investigated by SEM and BET, respectively. The surface area decreases with the amount of Cu and all of them have a porous structure with small grains. The desulfurization performance of all specimens have been investigated by fixed-bed reactor. The results from breakthrough time indicate ZC20 sorbent has highest sulfur sorption capacity at 300°C. The XRD results show ZnO and CuO in ZC20 can absorb sulfur and completely transform to ZnS, cubic CuS and hexagonal CuS at 300°C.

In Situ Preparation and Regeneration Behaviors of Zinc Oxide/Red Clay Desulfurization Sorbents

High-temperature gas desulfurization is an efficient and environmentally friendly process for syngas cleanup. The present study investigated the in situ preparation of a zinc oxide/red clay desulfurization sorbent and its desulfurization–regeneration behavior in O2/N2 atmospheres. The effects of regeneration temperature, space velocity, and O2 concentration on the regeneration behaviors of ZnO/red clay sorbents were also investigated. The surface and structural properties of the sorbents before and after regeneration were characterized by thermogravimetric–differential scanning calorimetry, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, elemental mapping, and N2 adsorption–desorption analyses. According to the results, the highest regeneration rate was achieved under the conditions of 6 vol % O2 and a space velocity of 3000 h–1 at 650 °C. After four cycles of desulfurization–regeneration experiments, the breakthrough time of the regenerated sorbents reduced by 18.7% and...

H2S 제거를 위한 고온건식 탈황제의 연구 및 기술개발동향

청정석탄기술 중 하나인 석탄가스화 복합발전기술의 이론적 고찰 및 주요단위공정에 사용되는 고온건식 탈황제의 연구 및 기술개발 동향을 조사하였다. 고온건식 탈황제 개발의 중요한 요소는 반응성, 내구성 및 내마모성에 있으며, 탈황제 종류는 칼슘계, 아연계, 망간계, 철계, 구리계 등이 있다. 현재 고온건식 탈황제의 경우 선진국을 중심으로 아연계 탈황제 제조기술이 가장 상용화 단계에 있으며, 국내에서도 다양한 지지체를 사용하여 가격이 저렴하고 성능이 우수한 아연계 및 비아연계 고온건식 탈황제의 상용화를 위한 연구개발이 진행 중에 있다. Theoretical reviews of integrated gasification combined cycle one of the clean coal technologies and trends in the study and technology development for high temperature desulfurization sorbents were investigated. Reactivity, durability and abrasion resistance is an important key for development of high temperature desulfurization sorbents, the kind of things include calcium, zinc, manganese, iron and copper-based sorbents. Current status of high temperature desulfurization sorbents, manufacturing techniques of zinc-based sorbent in advanced countries has commercialized. In case of Korea, various research studies are underway to commercialize the Zn and non Zn-based high temperature desulfurization sorbents to cheaper and superior capability using various supports.

High H2O-resistance CaO-MnOx/MSU-H sorbents for hot coal gas desulfurization

A series of xMnyCa/MSU-H sorbents with various Mn/Ca molar ratio were first designed and synthesized with a sol-gel method. The desulfurization performance of the new sorbent was investigated at 600–800°C in hot coal gas. 90Mn10Ca/MSU-H exhibited better desulfurization performance at 750°C with a breakthrough sulfur capacity (BSC) of 18.69g S/100g sorbent compared to other supported Mn-based sorbents (13.2g S/100g sorbent) in similar desulfurization condition, and strong durability in multiple sulfidation-regeneration cycles using oxidation/reduction regeneration method which resolved the scientific issue of that CaSO4 is hardly decomposed to CaO. The introduction of Ca species effectively promoted the dispersion of active constituents, which improved the desulfurization activity. More importantly, 90Mn10Ca/MSU-H showed excellent H2O-resistance ability due to the fact that CaO enhanced the sorption of H2O. Moreover, the utilization of MSU-H with large pore size and excellent thermal stability effectively assured fast mass-transfer and confined the migration of active particles, which led to long lifetime stability of sorbents.

Analysis of Vitrification Processes and Characteristics of Geochang Granite Stone Sludge for Desulfurization Sorbent of MCFC

The vitrification processes and characteristics of Geochang granite stone sludge were investigated for the application of desulfurization sorbent of Molten Carbonate Fuel Cell (MCFC). From the X-ray fluorescence analysis (XRF) results using Geochang granite stone sludge, it was confirmed that the network formers (SiO₂ and Al₂O3) in granite stone sludge were present between 83.2 and 87.2 wt% and the rest was comprised of network modifiers (K₂O, Na₂O, CaO, Fe₂O3 and MgO). When Borax (Na₂B₄OSUB7/SUB-10H₂O) was added in the granite stone sludge system for promoting the decomposition and reducing the melting viscosity of refractory SiO₂ and Al2O3 comprising of stone sludge, it was observed that the melting point of the granite stone sludge system was reduced by more than 400°C and the optimized melting temperature for granite stone and borax systems was around 1400°C when comparing X-ray diffraction analysis (XRD) results. Phase transitions and thermal reactions of granite stone sludge systems were also investigated from thermal analysis using Thermogravimetric Analysis (TGA)/ Differential Scanning Calorimeter (DSC).