Correlation of H_2S and COS in the hot coal gas stream and its importance for high temperature desulfurization

Jianglong Yu,Liping Chang,Wei Xie,Dehai Wang 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.4

Thermodynamic analysis of the correlation of H_2S and COS has been carried out at the temperature range of 400-650 ℃ at which high temperature desulfurization of coal gas is usually performed. The correlation of the two sulfur species is mainly through the reaction H_2S+CO→COS+H_2. Simulated coal gas with the following composition CO 32.69%, H_2 39.58%, CO_2 18.27%, N2 8.92% and H_2S 0.47% was used in this study, and the equilibrium concentrations of the two species at different temperatures were calculated. The results of Fe-based sorbents during sulfidation were compared with calculations. It is concluded that the above reaction may reach equilibrium concentration in the presence of the Fe-based sorbents, which means the Fe-based sorbents may effectively catalyze the reaction between H_2S and CO. Because of the correlation of the two sulfur species, both can be effectively removed at high temperatures simultaneously, offering high temperature desulfurization some advantages over low temperature desulfurization processes.

Sulfidation and regeneration of iron-based sorbents supported on activated-chars prepared by pressurized impregnation for coke oven gas desulfurization

Jianglong Yu,Jinxiao Dou,Yongqi Zhao,Arash Tahmasebi 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.10

The sulfidation and regeneration properties of lignite char-supported iron-based sorbent for coke oven gas (COG) desulfurization prepared by mechanical stirring (MS), ultrasonic assisted impregnation (UAI), and high pressure impregnation (HPI) were investigated in a fixed-bed reactor. During desulfurization, the effects of process parameters on sulfidation properties were studied systematically. The physical and chemical properties of the sorbents were analyzed by X-ray diffraction (XRD), scanning electron microscope coupled with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FTIR) and BET surface area analysis. The results of desulfurization experiments showed that high pressure impregnation (HPI) enhanced the sulfidation properties of the sorbents at the breakthrough time for char-supported iron sorbents. HPI method also increased the surface area and pore volume of sorbents. Sulfur capacity of sorbents was enhanced with increasing sulfidation temperatures and reached its maximum value at 400 oC. It was observed that the presence of steam in coke oven gas can inhibit the desulfurization performance of sorbent. SO2 regeneration of sorbent resulted in formation of elemental sulfur. HPIF10 sorbent showed good stability during sulfide-regeneration cycles without changing its performance significantly.

Influence of biomass pretreatment on co-combustion characteristics with coal and biomass blends

김종호,정태용,Jianglong Yu,전충환 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

Fuel blending is one of the most effective ways to use biomass to reduce the use of coal. In this study, co-combustion characteristics including NOx emissions, unburned carbon (UBC), and the char reactivity of coal, biomass, and pretreated biomass blends were investigated by using a lap scale drop tube furnace (DTF) and thermogravimetric analyzer (TGA) to evaluate the availability of pretreated biomass from torrefaction or ashless technology to a pulverized coal boiler. In addition, scanning electron microscopy (SEM) was used to analyze the morphology of biomass and pretreated biomass to observe the physical differences between raw samples and their chars. In the results, NOx showed a linear correlation with the content of inherent fuel-N of biomass except in blending cases with ashless biomass. This indicated that the yields of NOx in these cases were higher than both that of single coal and ashless biomass. In addition, UBC declined with increasing the biomass blending ratio for all blending cases, and this can be explained by examining the fuel ratio and SEM images of the fuel samples. Finally, blends with coal and torrefied biomass showed higher char reactivity and lower activation energy than that with ashless biomass as the blending ratio increased. Overall, this paper indicates that it is better to increase the blending ratio of pretreated biomass than raw biomass up to 30 % for enhanced reactivity and reduced emissions.

The effects of mineral salt catalysts on selectivity of phenolic compounds in bio-oil during microwave pyrolysis of peanut shell

Alisa Mamaeva,Arash Tahmasebi,Jianglong Yu 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.3

Catalytic microwave pyrolysis of peanut shell (PT) using Fe3O4, Na2CO3, NaOH, and KOH for production of phenolic-rich bio-oil was investigated. The effects of catalyst type, pyrolysis temperature, and biomass/catalyst ratio on product distribution and composition were studied. Among four catalysts tested, Na2CO3 significantly increased the selectivity of phenolic compounds in bio-oil during microwave pyrolysis. The highest phenolics concentration of 57.36% (area) was obtained at 500 oC and PT :Na2CO3 ratio of 8 : 1. The catalytic effect to produce phenolic compounds among all the catalysts tested can be summarized in the order Na2CO3>Fe3O4>KOH>NaOH. Using KOH and NaOH as catalyst resulted in formation of bio-oil with enhanced higher heating value (HHV) and lower oxygen content, indicating that these catalysts enhanced the deoxygenation of bio-oil. The scanning-electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis of char particles showed the melting of magnetite and vaporizationcondensation of mineral salt catalysts on char particle, which was attributed to extremely high local temperatures during microwave heating.

Impact of pressure on the carbon structure of char during pyrolysis of bituminous coal in pressurized entrained-flow reactor

Arash Tahmasebi,Kristina Maliutina,Jianglong Yu 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.3

The impact of pressure on the carbon structure of a Chinese bituminous coal was investigated using a pressurized entrained-flow reactor in the temperature and pressure ranges of 700-900 oC and 0.1-4.0MPa, respectively. Pyrolysis pressure had a significant influence on the physiochemical and carbon structure of chars. The specific surface area and the swelling ratio of chars reached their highest values at 1.0MPa. Fourier transform infrared spectroscopy (FTIR) analysis showed that higher pressures enhanced the decomposition of functional groups in chars. Raman spectroscopy analysis results revealed that at elevated pressures, the organic matrix and functional groups were removed from the char structure, leading to higher ordering of the carbon structure. During X-ray diffraction (XRD) analysis, parameters such as the stacking height (Lc), interlayer spacing (d002) and lateral size of the graphite structures (La) were used to evaluate the graphitic structures in chars. The results showed an increase in Lc, La, and the average number of graphene sheets with pyrolysis pressure, indicating a more ordered carbon structure at elevated pressures. The d-spacing of char was in the range of 3.34-3.37 Å, similar to typical graphitic structures.

Desulfurization of coke oven gas using char-supported Fe-Zn-Mo catalysts: Mechanisms and thermodynamics

Jinxiao Dou,Xianchun Li,Arash Tahmasebi,Jing Xu,Jianglong Yu 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.11

Sulfidation properties of char-supported Fe-Zn-Mo sorbents prepared by ultrasonic impregnation method were investigated during simultaneous removal of H2S and COS from coke oven gas (COG) using a fixed-bed quartz reactor. Sorbent samples before and after sulfidation were analyzed using X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The experimental results showed that the addition of Mo significantly improved the desulfurization properties (i.e., breakthrough time, sulfur capacity and desulfurization efficiency) of Fe-Zn sorbents. Desulfurization reactions were exothermic and thermodynamically favorable in the temperature range of 200- 400 oC. Thermodynamic analysis of the sorbents indicated that higher concentration of H2S and lower concentration of H2 favors the reaction of metal oxides with H2S to form metal sulfides.

Low-temperature catalytic hydrogen combustion over Pd-Cu/Al2O3: Catalyst optimization and rate law determination

Kim Jongho,Tahmasebi Arash,Lee Jang Mee,Lee Soonho,전충환,Yu Jianglong 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.6

Catalytic hydrogen combustion (CHC) is a promising technology for clean, efficient, and safe energy generation in hydrogen-fueled systems such as fuel cells and passive autocatalytic recombination. This study investigates catalytic hydrogen combustion over the Pd-Cu/Al2O3 catalysts at low temperatures (<125 °C) to determine the rate law using a differential fixed-bed reactor. The particle size distribution and reducibility of the catalysts were studied to investigate the influence of the catalyst composition on its reactivity. Higher reduction temperatures promoted the formation of metallic Pd, leading to improved catalytic reactivity at the optimized composition of Pd0.75Cu0.25/Al2O3. Furthermore, the rate law of CHC over the optimized catalyst was determined by non-linear regression based on the experimental reaction rates obtained under different partial pressures of H2 and O2. The Langmuir-Hinshelwood single-site mechanism was found to provide the best description of the catalytic combustion of hydrogen at low temperatures.