Effect of calcium based catalyst on production of synthesis gas in gasification of waste bamboo chopsticks

This study investigated the effects of calcium based catalyst (calcium oxide) on variation of gas composition in catalytic gasification reaction stages by controlling the gasification temperature between 600 °C and 900 °C whilst varying a catalyst/biomass ratio from 0 to 0.2 w/w. The tested biomass generated from used bamboo chopsticks were used as the feedstock. To assess the gas composition variation, the ratio of H₂/CO, H₂/CO₂, CO/CO₂, and 3H₂/CH₄ are four important factors that affect the performance of catalytic gasification process. The maximum ratio of H₂/CO increased from 0.23 to 0.72 in the gasification temperature range between 600 °C and 900 °C and 0%–20% calcium based catalyst addition ratio. This is due to enhanced H₂ production as a result of the facilitated water–gas shift reaction. The ratios of CO/CO₂ and 3H₂/CH₄ increased significantly from 0.9 to 2.1 and from 2.6 to 4.1, respectively, when the gasification temperature increased from 600 °C to 900 °C and 20% catalyst addition ratio. Obviously, the high temperature and catalyst addition are favorable for production of CO and H₂ during gasification of tested biomass. In conclusion, the tested mineral calcium based catalyst (CaO) can help facilitating the reaction rate of partial oxidation and water–gas shift reaction, enhancing the quality of synthesis gas, and reduction of the gasification reaction time. This catalyst has potential application in gasification of waste bamboo chopsticks in the future.     

Syngas production by gasification of aquatic biomass with CO2/O2 and simultaneous removal of H2S and COS using char obtained in the gasification

Applicability of gulfweed as feedstock for a biomass-to-liquid (BTL) process was studied for both production of gas with high syngas (CO + H₂) content via gasification of gulfweed and removal of gaseous impurities using char obtained in the gasification. Gulfweed as aqueous biomass was gasified with He/CO₂/O₂ using a downdraft fixed-bed gasifier at ambient pressure and 900 °C at equivalence ratios (ER) of 0.1–0.3. The syngas content increased while the conversion to gas on a carbon basis decreased with decreasing ER. At an ER of 0.1 and He/CO₂/O₂ = 0/85/15%, the syngas content was maximized at 67.6% and conversion to gas on a carbon basis was 94.2%. The behavior of the desulfurization using char obtained during the gasification process at ER = 0.1 and He/CO₂/O₂ = 0/85/15% was investigated using a downdraft fixed-bed reactor at 250–550 °C under 3 atmospheres (H₂S/N₂, COS/N₂, and a mixture of gases composed of CO, CO₂, H₂, N₂, CH₄, H₂S, COS, and steam). The char had a higher COS removal capacity at 350 °C than commercial activated carbon because (Ca,Mg)S crystals were formed during desulfurization. The char simultaneously removed H₂S and COS from the mixture of gases at 450 °C more efficiently than did activated carbon. These results support this novel BTL process consisting of gasification of gulfweed with CO₂/O₂ and dry gas cleaning using self-supplied bed material.     

Effect of temperature on the gasification of olive bagasse particles

A semi-batch fluidized-bed gasifier was used to investigate the experimental gasification process of olive bagasse particles, an olive oil industry residue. The effect of bed temperature was studied, in the range of 750 to 900 °C. The oxidant agent was air, fed at constant flowrate, and sand particles were used as bed material. The bagasse particles used had diameters within 1.25–2 mm and the biomass was characterized in terms of its higher heating value and ultimate analysis. During each run, several gaseous samples were collected to be further analysed by gas chromatography allowing the quantification of CO, CO₂, H₂, CH₄, O₂ and N₂. The reaction mechanism of the gasification process is determinant on the composition of the producer gas. Experimental results showed that higher bed temperatures favoured gas production as well as other gasification performance parameters. Best results were obtained for a bed temperature of 850 °C.     

Modelling and experimental investigations on gasification of coarse sized coal char particle with steam

The steam gasification characteristics of coal char produced two sub-bituminous coals of different origin have been investigated through modelling and experiments. The gasification experiments are carried out in an Isothermal mass loss apparatus over the temperature range of 800–900 °C using a gas mixture of 65% steam and 35% N₂. A fully transient single particle gasification model, based on the random pore model, is developed incorporating reaction kinetics, heat and mass transport inside the porous char particle and the gas film. Stefan-Maxwell equation and Knudson diffusion are incorporated in the multi-component diffusion of species and pore diffusion. The model is validated with the experimental data of the present authors as well as that reported in the literature. The particle centre temperature is found to increase, then decrease and increase again to reach the reactor temperature finally, and the trend is more prominent for the larger particles. The pore opening phenomenon is more evident in SBC2 char, leading to a final char porosity of 0.65 vis-à-vis 0.52 in SBC1 and making it more reactive. Temporal evolution of contours of carbon conversion and concentration of other gaseous species like steam, H₂O, H₂, CO and CO₂ in the particle are computed to investigate the gasification process. A higher temperature is found to favour both the rate peak and the total production of H₂ for both the chars. The total H₂ production from SBC2 char is found to be 0.0189 mol and 0.0236 mol at 800 and 850 °C, while the same for SBC1 char is0.0232 mol and 0.0290 mol respectively. The reaction follows the shrinking core model at the outset, shifting to the shrinking reactive core model subsequently.     

Solar-driven steam-based gasification of sugarcane bagasse in a combined drop-tube and fixed-bed reactor – Thermodynamic,kinetic, and experimental analyses

Syngas production via steam-based thermochemical gasification of Brazilian sugarcane bagasse, using concentrated solar energy for process heat, was thermodynamically and experimentally investigated. Energy and exergy analyses revealed the potential benefits of solar-driven over conventional autothermal gasification that included superior quality of syngas composition and higher yield per unit of feedstock. Reaction rates for the gasification of fast pyrolyzed bagasse char were measured by thermogravimetric analysis and a rate law based on the oxygen exchange mechanism was formulated. In order to provide residence times long enough for adequate char conversion, a laboratory-scale entrained flow reactor that combines drop-tube and fixed-bed concepts was developed. Testing was performed in an electric furnace with the final aim to supply heat by concentrated solar radiation. Experimental runs at reactor temperatures of 1073–1573 K and a biomass feed rate of 0.48 g/min yielded high-quality syngas of molar ratios H₂/CO = 1.6 and CO₂/CO = 0.31, and with heating values of 15.3–16.9 MJ/kg, resulting in an upgrade factor (ratio of heating value of syngas produced over that of the feedstock) of 112%. Theoretical upgrade factors of up to 126%, along with the treatment of wet feedstock and elimination of the air separation unit, support the potential benefits of solar-driven over autothermal gasification.     

Hydrogen-rich syngas production from municipal solid waste gasification through the application of central composite design: An optimization study

This study aims to investigate the influence and interaction of experimental parameters on the production of optimum H₂ and other gases (CO, CO₂, and CH₄) from gasification of municipal solid waste (MSW). Response surface method in assistance with the central composite design was employed to design the fifteen experiments to find the effect of three independent variables (i.e., temperature, equivalence ratio and residence time) on the yields of gases, char and tar. The optimum H₂ production of 41.36 mol % (15.963 mol kg-MSW⁻¹) was achieved at the conditions of 757.65 °C, 0.241, and 22.26 min for temperature, ER, and residence time respectively. In terms of syngas properties, the lower heating value and molar ratio (H₂/CO) ranged between 9.33 and 12.48 MJ/Nm³ and 0.45–0.93. The predicted model of statistical analysis indicated a good fit with experimental data. The gasification of MSW utilizing air as a gasifying agent was found to be an effective approach to recover the qualitative and quantitate products (H₂ and total gas yield) from the MSW.     

Potassium catalytic hydrogen production in sorption enhanced gasification of biomass with steam

Sorption enhanced gasification (SEG) of biomass with steam was investigated in a fixed-bed reactor to elucidate the effects of temperature, catalyst type and loading on hydrogen production. K₂CO₃, CH₃COOK and KCl were chosen as potassium catalyst precursors to improve carbon conversion efficiency in gasification process. It was indicated that from 600 °C to 700 °C, the addition of K₂CO₃ or CH₃COOK catalyzed the gasification for hydrogen production, and hydrogen yield and carbon conversion increased with increasing catalyst loadings of K₂CO₃ or CH₃COOK. However, the hydrogen yield and carbon conversion decreased as the amount of KCl was increased due to inhibition of KCl on gasification. The maximum carbon conversion efficiency (88.0%) was obtained at 700 °C corresponding to hydrogen yield of 73.0 vol.% when K₂CO₃ of 20 wt.% K loading was used. In particular, discrepant catalytic performance was observed between K₂CO₃ and CH₃COOK at different temperatures and the corresponding mechanism was also discussed.     

Process simulation and optimization of groundnut shell biomass air gasification for hydrogen-enriched syngas production

In this study, a detailed steady-state equilibrium simulation model was designed using ASPEN Plus software to analyze and assess the efficiency of the groundnut shell biomass air gasification process. The developed model includes three general stages: biomass drying, pyrolysis, and gasification. The predicted results are quite similar to those found in the literature, which is consistent with simulation results being validated against experimental data. The effect of different operating parameters, like the gasification temperature, gasification pressure, and the equivalence ratio (ER), on the syngas composition and H₂/CO ratio is investigated using sensitivity analysis. The findings of the sensitivity analysis revealed that raising the temperature preferred H₂ and CO production, whereas increasing the pressure has favored CO₂ and CH₄ production. Increasing the ER value also boosted CO and CO₂ yield. Moreover, in an effort to optimize the amount of H₂ generated within the process, the sensitivity analysis was used to evaluate the simultaneous effect of operational parameters on the molar fraction of H₂. To maximize H₂ as a desired product, the following operating parameters were achieved: gasification temperature of 894 °C, gasification pressure of 1 bar, and ER of 0.05, resulting in an H₂ molar fraction of 0.64.     

Assessment of sugarcane bagasse gasification in supercritical water for hydrogen production

Sugarcane bagasse is one of the major resources of agricultural biomass waste in the world. In this work, supercritical water gasification characteristics of sugarcane bagasse were investigated. The effect of temperature (600–750 °C), concentration (3–12 wt%), residence time (5–20 min) and catalysts (Raney-Ni, K₂CO₃ and Na₂CO₃) on bagasse gasification were studied. A kinetic study on the non-catalytic and Na₂CO₃ catalytic bagasse gasification was conducted to describe the kinetic information of the bagasse gasification reaction. The results showed that a higher reaction temperature, a lower bagasse concentration and a longer residence time could favor the gasification of bagasse, leading to a higher hydrogen yield. Bagasse was nearly completely gasified at 750 °C without using any catalyst and the carbon gasification efficiency could reach up to 96.28%. The addition of employed catalysts remarkably promoted the bagasse gasification reactivity. The maximum hydrogen yield (35.3 mol/kg) was achieved at 650 °C with the Na₂CO₃ loading of 20 wt%. The experimental data fitted well with a homogeneous model based on a Pseudo-first-order reaction hypothesis. The kinetic study showed that Na₂CO₃ catalyst could lower the activation energy E_a of bagasse gasification from 117.88 kJ/mol to 78.25 kJ/mol.     

Characteristics of cardboard and paper gasification with CO2

Evolutionary behavior of syngas chemical composition and yield have been examined for paper and cardboard at three different temperatures of 800, 900 and 1000 °C using CO₂ as the gasifying agent at constant flow rate. Specifically the evolution of syngas chemical composition with time has been investigated. Pyrolysis of the sample was dominant at the beginning of the gasification process as observed from the high initial devolatilization of the sample followed by char gasification of material to form syngas for a long period of time. Results provided the role of gasification temperature on kinetics of the CO₂ gasification process. Increase in gasification temperature provided increased conversion of the sample material to syngas. Thus the sample conversion to syngas was low at the low temperature of 800 °C while at elevated temperatures of 900 and 1000 °C substantial enhancement of the kinetics process occurred. The evolution of extensive reaction rate of carbon-monoxide was calculated. Results show that increase in temperature increased the extensive reaction rate of carbon-monoxide. The global behavior of syngas chemical composition examined at three different temperatures revealed a peak in concentration of H₂ to exhibit after few minutes into the gasification that changed with gasification temperature. At 800 °C gasification temperature peak in H₂ was displayed at 3 min into gasification while it decreased to only 2 min, approximately, at gasification temperatures of 900 and 1000 °C. The effect of reactor temperature on CO mole fraction has also been examined. Increase in the gasification temperature enhances the mole fraction of CO yields. This is attributed to the increase in forward reaction rate of the Boudouard reaction (C+CO₂2CO). The results show important role of CO₂ gas for the gasification of wastes and low grade fuels to clean syngas.     

Hydrogen production by catalytic gasification of coal in supercritical water with alkaline catalysts: Explore the way to complete gasification of coal

Supercritical water gasification (SCWG) of coal is a promising technology for clean coal utilization. In this paper, hydrogen production by catalytic gasification of coal in supercritical water (SCW) was carried out in a micro batch reactor with various alkaline catalysts: Na₂CO₃, K₂CO₃, Ca(OH)₂, NaOH and KOH. H₂ yield in relation to the alkaline catalyst was in the following order: K₂CO₃ ≈ KOH ≈ NaOH > Na₂CO₃ > Ca(OH)₂. Then, hydrogen production by catalytic gasification of coal with K₂CO₃ was systematically investigated in supercritical water. The influences of the main operating parameters including feed concentration, catalyst loading and reaction temperature on the gasification characteristics of coal were investigated. The experimental results showed that carbon gasification efficiency (CE, mass of carbon in gaseous product/mass of carbon in coal × 100%) and H₂ yield increased with increasing catalyst loading, increasing temperature, and decreasing coal concentration. In particular, coal was completely gasified at 700 °C when the weight ratio of K₂CO₃ to coal was 1, and it was encouraging that raw coal was converted into white residual. At last, a reaction mechanism based on oxygen transfer and intermediate hybrid mechanism was proposed to understand coal gasification in supercritical water.     

Effect of Ce on 5 wt% Ni/ZSM-5 catalysts in the CO2 reforming of CH4 reaction

The aim of this study is to investigate the promotional effect of Ce on Ni/ZSM-5 catalysts in the CO₂ reforming of CH₄ reaction. The evaluation of the catalytic performances of the composite catalysts was conducted in a fixed-bed reactor at atmospheric pressure. The influencing factors, including temperature, Ni and Ce loadings, molar feed ratio of CO₂/CH₄, and time-on-stream (TOS), were investigated. The characteristics of the catalysts were checked with Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The reduction and the basic properties of the composite catalysts were elucidated by temperature-programmed reduction by H₂ (H₂-TPR) and temperature-programmed desorption of CO₂ (CO₂-TPD), respectively. The reactivity of deposited carbon was studied by sequential temperature-programmed surface reaction of CH₄ (CH₄-TPSR) and temperature-programmed oxidation using CO₂ and O₂ (CO₂-TPO and O₂-TPO). Results indicate that higher CH₄ conversion, H₂ selectivity, and desired H₂/CO ratio for 5 wt% Ni & 5 wt% Ce/ZSM-5 could be achieved with CO₂/CH₄ feed ratio close to unity over the temperature range of 500–900 °C. Moreover, the addition of Ce could not only promote CH₄ decomposition for H₂ production but also the gasification of deposited carbon with CO₂. The dispersion of Ni particles could be improved with Ce presence as well. A partial reduction of CeO₂ to CeAlO₃ was observed from XPS spectra over 5 wt% Ni & 5 wt% Ce/ZSM-5 after H₂ reduction and 24 h CO₂–CH₄ reforming reaction. Benefiting from the introduction of 5 wt% Ce, the calculated apparent activation energies of CH₄ and CO₂ over the temperature range of 700–900 °C could be reduced by 30% and 40%, respectively.     

Syngas production by chemical looping gasification of rice husk using Fe-based oxygen carrier

The chemical looping gasification (CLG) of rice husk was conducted in a fixed bed reactor to analyze the effects of the ratio of oxygen carrier to rice husk (O/C), temperature, residence time and preparation methods of Fe-based oxygen carriers. The yield of gas, H₂/CO, lower heating value of syngas (LHV), conversion efficiency and performance parameters were analyzed to obtain CLG reaction characterization and optimal reaction conditions. Results showed that when O/C increased from 0.5 to 3.0, the gas production, H₂/CO, CO₂ yield and carbon conversion efficiency gradually increased, while the yield of H₂, CO and CH₄ and LHV gradually decreased. At the same time, a highest gasification efficiency was obtained when O/C was 1.5. As increasing temperature, the gas production, CO yield, carbon conversion efficiency and gasification efficiency gradually increased, while the yield of H₂, CH₄ and CO₂, H₂/CO and LHV gradually decreased. Sintering and agglomeration was obvious when the temperature was higher than 850 °C. When the reaction time increased from 10 min to 60 min, the gas production, CO yield, carbon conversion efficiency and gasification efficiency gradually increased, but the yield of H₂, H₂/CO and LHV decreased, among which 30 min was the best reaction residence time. In addition, coprecipitation was the best preparation method among several preparation methods of oxygen carrier. Finally, O/C of 1.5, 800 °C, 30 min and coprecipitation preparation method of oxygen carrier were the optimal parameters to obtain a gasification efficiency of 26.88%, H₂ content of 35.64%, syngas content of 56.40%, H₂/CO ratio of 1.72 and LHV of 12.25 MJ/Nm³.     

Production of hydrogen enriched syngas from municipal solid waste gasification with waste marble powder as a catalyst

Marble processing leads to the production of high amount of waste marble powder (WMP) as a byproduct, which can be a potential health risk and has hazardous impacts on the surrounding environment. However, marble is composed of calcite making it suitable for the calcium-based catalyst. Moreover, no study has been carried out to utilize this WMP in municipal solid waste (MSW) gasification process. Therefore, there is a need to address its utilization as a potential catalyst/sorbent in the gasification of municipal solid waste (MSW). A laboratory scale batch-type fixed bed reactor was used to study the effect of WMP addition on the CO₂ adsorption, steam reforming capability and char gasification in the presence of steam. Produced gas composition, gas yield, carbon conversion efficiency and tar yield were examined at different WMP to MSW ratios. Effect of temperature and steam rate varying from 700 to 900 °C and 2.5–10 ml/min respectively were also considered in this study. WMP showed a good capacity towards hydrogen enriched syngas production as well as CO₂ adsorption and tar reforming. The H₂ concentration increased significantly with an increase in the WMP to MSW mass ratio, while CO₂ decreased. A significant effect of temperature and steam rate was also observed on the produced gas composition, gas yield, and tar content. This study helps us to understand the effect of WMP addition in MSW gasification process and thus assists in the industrial application.     

Syngas production by integrating CO2 partial gasification of pine sawdust and methane pyrolysis over the gasification residue

The aim of this work was to study syngas production by integrating CO₂ partial gasification (for CO production) of pine sawdust (PS) and methane pyrolysis (for H₂ production) over the gasification residue. Effect of the gasification conditions (including CO₂ flow rate, reaction temperature, mass ratio of PS:Ni and reaction time) was investigated on properties of the gasification residue. Besides CO-rich gas released from the gasification process with CO₂ conversion up to about 92%, the gasification residue could serve as robust catalyst for H₂ production by methane pyrolysis. Thanks to the nickel crystallites formed with high reduction degree and high dispersion on the surface after the gasification process, the gasification residue was competent for high and stable methane conversion (about 91%) at 850 °C. In addition to the flexible syngas output (in theory, with an arbitrary ratio of H₂/CO), valuable filamentous carbons can be achieved by regulating the process parameters.     

Hydrogen production from steam gasification of tableted biomass in molten eutectic carbonates

The steam gasification of tableted biomass for H₂ production in molten salts was investigated under different conditions. The results showed that the ternary molten carbonates (32 wt% Li₂CO₃, 33 wt% Na₂CO₃ and 35 wt% K₂CO₃) acted as heat medium and catalyst in the gasification process. The use of molten salts could significantly increase total gas and H₂ production and simultaneously decrease the concentrations of CO and CH₄ in the product gas, and also decrease the yield of condensable tar. The increase in gasification temperature and mass ratio of steam to biomass (S/B) was beneficial for H₂ production process. However, excessive steam contributed slightly to the increase in H₂ production and largely increased the energy consumption. The optimal S/B ratio was found to be 1.0. The feedstock after tabletting could completely immersed in molten salts, which improved the contact between biomass and molten salts and thus favored the biomass gasification for H₂ production. When biomass particle size was 0.25 g/piece, the yield of H₂ reached 807.53 mL/g biomass.     

Enhanced hydrogen production by the catalytic alkaline thermal gasification of cellulose with Ni/Fe dual-functional CaO based catalysts

A two-stage system involving alkaline thermal gasification of cellulose with Ca(OH)₂ sorbent and catalytic reforming with Ni/Fe dual-functional CaO based catalysts is proposed and applied to enhance H₂ production and in-situ CO₂ capture. The results show that the H₂ concentration is maximized at a considerably lower temperature (500 °C) than commercialized biomass gasification processes, reducing energy consumption. Sol-gel method is deemed better than impregnation method for its lower cost and higher-concentration H₂ production. Among the prepared catalysts, sol-NiCa catalyst exhibits the best performance in CO₂ absorption, resistance to carbon deposition, and cyclic stability, creating maximum H₂ concentration (79.22 vol%), H₂ yield (27.36 mmol g⁻¹ cellulose), and H₂ conversion (57.61%). Introduction of Ni rather than Fe on the CaO based catalyst promotes steam methane reforming at moderate temperature range of 400–600 °C, generating low contents of CH₄ (5.38 vol%), CO₂ (4.82 vol%), and CO (10.58 vol%).     

Gasification of biomass to hydrogen-rich gas in fluidized beds using porous medium as bed material

Experiments were carried out to study the characteristics of biomass gasification in a fluidized bed using industrial sand and porous medium as bed materials. Analysis was conducted to investigate the effects of different operation parameters, including bed material, gasification temperature (600 °C–900 °C), oxygen enrichment in the gasifying agent (21 vol.% to 50 vol.%), and steam flow rate (1.08 kg/h to 2.10 kg/h), on product yields and gas composition. The results of gas chromatography show that the main generated gas species were H₂, CO, CO₂, CH₄, and C₂H₄. Compared with industrial sand as bed material, porous medium as bed material was more suitable for gasifying biomass to hydrogen-rich gas. The physical characteristics of porous structure are more favorable to heat transfer, producing the secondary crack of heavy hydrocarbons and generating more hydrogen and other permanent gases. The product yields of hydrogen-rich gas increased with increasing gasification temperature. The hydrogen concentration improved from 22.52 vol.% to 36.06 vol.%, but the CO concentration decreased from 37.53 vol.% to 28.37 vol.% with increasing temperature from 600 °C to 900 °C under the operation parameters of porous bed material at a steam flow rate of 1.56 kg/h. With increasing oxygen concentration, H₂ concentration increased from 12.36% to 20.21%. Over the ranges of the examined experimental conditions, the actual steam flux value (e.g., 1.56 kg/h) was found to be the optimum value for gasification.     

Comprehensive experimental study on supercritical water gasification of oilfield sludge: Effect of operation parameters,and catalysts on the products

Supercritical water gasification (SCWG) was adopted to treat oilfield sludge and produce syngas. The effect of temperature (400–450 °C), reaction time (30–90 min) and catalyst addition on syngas production and residual products during SCWG of oilfield sludge was studied. When increasing SCWG temperature from 400 to 450 °C with reaction time of 60 min, the H₂ yield and the selectivity of H₂ increased significantly from 0.53 mol/kg and 75.53% to 0.98 mol/kg and 78.09%, respectively. It is noteworthy that when the reaction time was too long, CO₂ and CO were converted to CH₄ with the consumption of H₂ via methanation reaction. The addition of Ni/Al₂O₃ catalyst can substantially promote the production of high-quality syngas from SCWG of oilfield sludge. The H₂ yield and its selectivity at 450 °C and 60 min were as high as 1.37 mol/kg and 84.05% with 10Ni/Al catalyst. Moreover, the catalysts with bimetal loading (Fe–Ni, Rb–Ni or Ce–Ni) were found to be beneficial for improving gasification efficiency, H₂ yield, and the degradation of organic compounds. Among them, 5 wt% Rb on 10Ni/Al catalyst performed the best catalytic activity for SCWG at 450 °C and 60 min, which had the highest H₂ yield of 1.67 mol/kg and selectivity of 86.09%. More than 90% of total organic carbon in sludge was decomposed after the SCWG with all the catalysts. These findings indicated that catalytic SCWG is a promising alternative for efficiently dealing with oilfield sludge.     

Gasification of landfill leachate in supercritical water: Effects on hydrogen yield and tar formation

Landfill leachate was gasified in supercritical water (SCW) in a batch reactor made of 316 SS. The effects of temperature, pressure, reaction time and oxidation coefficient (OC) on the pollutant removal efficiencies and gasification characteristics were investigated. To observe the formation of tar and char visually, a capillary quartz reactor was also used. Results indicated that CO₂, H₂ and CH₄ were the most abundant gaseous products. Temperature has an appreciable effect on the gasification process. Increasing temperature enhanced the H₂ yield (GY_H2) and TOC removal efficiency (TRE) significantly. Although the influence of reaction time on the fractions of gaseous products was negligible at time above 300 s, the yields of H₂, CH₄, and CO₂ increased with reaction time whereas the CO, C₂H₄ and C₂H₆ yields decreased. Tar and char formation was evident on the interior surface of capillary quartz reactor. Adding a little oxidant could increase H₂ and CH₄ yields and decrease tar and char formation. GY_H2 reached up to the maximum of 231.3 mmol L^?1 leachate at 500 °C, 25 MPa, 600 s and 0.2 OC, which was 2.4 times of that without oxidant.