• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.604-610
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• 2007

Characteristics of steam gasification and combustion of naphtha tar pitch, which is the bottom product of naphtha cracking process, were investigated by using the thermo gravimetric analyzer to develop the technology for obtaining syngas by using the naphtha tar pitch as a carbon source. Friedman's and Ozawa-Flynn-Wall method were used to calculate activation energy, reaction order and frequency factor of reaction rate constant for both of steam gasification and combustion. The activation energy of combustion of naphtha tar pitch based on the fractional conversion by Friedman's method was in the range of 41.58 ~ 68.14 kJ/g-mol when the fractional conversion level was in the range of 0.2~0.6, but 183.07~191.17 kJ/g-mol when the conversion level was 0.9~1.0, respectively. In case of steam gasification of naphtha tar pitch, the activation energy was in the range of 31.87~44.87 kJ/g-mol in the relatively lower conversion level (0.2~0.6), but 70.63~87.79 kJ/g-mol in the relatively higher conversion level (0.8~0.95), respectively. Those results exhibited that the steam gasification as well as combustion would occur by means of two steps such as devolitilization followed by combustion or gasification.

• Resources Recycling
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• v.30 no.6
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• pp.12-18
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• 2021

The water-gas shift reaction is the subsequent step using steam for hydrogen enrichment and H₂/CO ratio-controlled syngas from gasification. In this study, a water-gas shift reaction was performed using syngas from an RPF gasification system. The water-gas shift using a catalyst was performed in a laboratory-scale tube reactor with a high temperature shift (HTS) and a low temperature shift (LTS). The effects of the reaction temperature, steam/carbon ratio, and flow rate on H₂ production and CO conversion were investigated. The operating temperature was 250-400℃ for the HTS system and 190-220℃ for the LTS system. Steam/carbon ratios were between 1.5 and 3.5, and the composition of reactant was CO : 40 vol%, H₂ : 25 vol%, and CO₂ : 25 vol%. The CO conversion and H₂ production increased as the reaction temperature and steam/carbon ratio increased. The CO conversion and H₂ production decreased as the flow rate increased due to reduced retention time in the catalyst bed.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.62-66
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• 2009

Utilization and interest of unconventional fuel and process residue such as oil sand and its residue, oil sand coke, have been increased because of the continuous rise of fuel price and conventional fuel availability. In this study, the gasification of oil sand coke produced from coking process of oil sand was performed to utilize as an energy resource using lab-scale fixed bed gasification system. The combustion characteristics of oil sand bitumen and oil sand coke were investigated by using TGA and lab-scale gasification system was applied to reveal the characteristics of produced syngas composition with oxygen/fuel ratio, temperature and steam injection rate. Oil sand coke shows a high carbon content, heating value and sulfur content and low ash content and reactivity. In case of oil sand coke gasification, generally with increasing temperature, the amount of steam introduced and decreasing oxygen injection rate, $H_2$ content in product gas increased while the $CO_2$ content decreased. The calorific value of syngas shows about $2100kcal/Nm^3$ and this result indicates that the oil sand coke can be used as a resource of hydrogen and fuel.

• Journal of Hydrogen and New Energy
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• v.22 no.3
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• pp.386-401
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• 2011

Mathematical models for various steps in coal gasification reactions were developed and applied to investigate the effects of operation parameters on dynamic behavior of gasification process. Chemical reactions considered in these models were pyrolysis, volatile combustion, water shift reaction, steam-methane reformation, and char gasification. Kinetics of heterogeneous reactions between char and gaseous agents was based on Random pore model. Momentum balance and Stokes' law were used to estimate the residence time of solid particles (char) in an up-flow reactor. The effects of operation parameters on syngas composition, reaction temperature, carbon conversion were verified. Parameters considered here for this purpose were $O_2$-to-coal mass ratio, pressure of reactor, composition of coal, diameter of char particle. On the basis of these parametric studies some quantitative parameter-response relationships were established from both dynamic and steady-state point of view. Without depending on steady state approximation, the present model can describe both transient and long-time limit behavior of the gasification system and accordingly serve as a proto-type dynamic simulator of coal gasification process. Incorporation of heat transfer through heterogenous boundaries, slag formation and steam generation is under progress and additional refinement of mathematical models to reflect the actual design of commercial gasifiers will be made in the near futureK.

• Journal of Hydrogen and New Energy
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• v.23 no.6
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• pp.647-653
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• 2012

We have investigated the kinetics and activity of waste catalysts for steam-lignite gasification. Waste catalysts I, II, III and reference $K_2CO_3$ were used and physical mixed with a coal. The gasification experiments were carried out with the low rank coal loaded with 1 wt% and 5 wt% catalyst at the temperature range from 700 to $900^{\circ}C$ using thermobalance reactor. It was observed that the carbon conversion reached almost 100% regardless of the kinds of catalysts at $900^{\circ}C$. The shortest time to reach the designated conversion was obtained for 1 wt% waste catalyst II and 5 wt% $K_2CO_3$ at $900^{\circ}C$. The gasification reaction rate constant increased with increasing the temperature. Highest rate constant was obtained with $K_2CO_3$ at $900^{\circ}C$. The lowest activation energy was 69.42 kJ/mol for 5 wt% waste catalyst II. The waste catalyst had an influence on the reduction of activation energy.

• Environmental Engineering Research
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• v.10 no.3
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• pp.122-130
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• 2005

Gasification of carbonaceous wastes such as shredded tire, waste lubricating oil, plastics, and powdered coal initiates a single-stage reforming reactor(reformer) Without catalyst and a syngas burner. Syngas is combusted with $O_2$ gas in the syngas burner to produce $H_2O\;{and}\;CO_2$ gas with exothermic heat. Reaction products are introduced into the reforming reactor, reaction heat from syngas burner elevates the temperature of reactor above $1,200^{\circ}C$, and hydrogen gas fraction reaches 65% of the product gas output. Reactants and heat necessary for the reaction are provided through the syngas burner only. Neither $O_2$ gas nor steam is injected into the reforming reactor. Multiple syngas burners may be connected to the reforming reactor in order to increase the syngas output, and the product syngas is recycled into syngas burner.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.417-423
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• 2007

Oxy-gasification or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization, mixture fraction model and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The influence of turbulence on the gas properties was taken into account by the PDF (Probability Density Function) model. A numerical simulation with the coal gasification model is performed on the Conoco-Philips type gasifier for IGCC plant. Gas temperature distribution and product gas composition are also presented. Numerical computations were performed to assess the effect of variation in oxygen to coal ratio and steam to coal ratio on reactive flow field. The concentration of major products, CO and H2 were calculated with varying oxygen to coal ratio (0.2-1.5) and steam to coal ratio(0.3-0.7). To verify the validity of predictions, predicted values of CO and H2 concentrations at the exit of the gasifier were compared with previous work of the same geometry and operating points. Predictions showed that the CO and H2 concentration increased gradually to its maximum value with increasing oxygen-coal and hydrogen-coal ratio and decreased. When the oxygen-coal ratio was between 0.8 and 1.2, and the steam-coal ratio was between 0.4 and 0.5, high values of CO and H2 were obtained. This study also deals with the comparison of CFD (Computational Flow Dynamics) and STATNJAN results which consider the objective gasifier as chemical equilibrium to know the effect of flow on objective gasifier compared to equilibrium. This study makes objective gasifier divided into a few ranges to study the evolution of the gasification locally. By this method, we can find that there are characteristics in the each scope divided.

• Environmental Engineering Research
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• v.17 no.2
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• pp.89-94
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• 2012

Pyrolysis/gasification technology utilizes an energy conversion technique from various waste resources, such as biomass, solid waste, sewage sludge, and etc. to generating a syngas (synthesis gas). However, one of the major problems for the pyrolysis gasification is the presence of tar in the product gas. The tar produced might cause damages and operating problems on the facility. In this study, a gliding arc plasma reformer was developed to solve the previously acknowledged issues. An experiment was conducted using surrogate benzene and naphthalene, which are generated during the pyrolysis and/or gasification, as the representative tar substance. To identify the characteristics of the influential parameters of tar decomposition, tests were performed on the steam feed amount (steam/carbon ratio), input discharge power (specific energy input, SEI), total feed gas amount and the input tar concentration. In benzene, the optimal operating conditions of the gliding arc plasma 2 in steam to carbon (S/C) ratio, 0.98 $kWh/m^3$ in SEI, 14 L/min in total gas feed rate and 3.6% in benzene concentration. In naphthalene, 2.5 in S/C ratio, 1 $kWh/m^3$ in SEI, 18.4 L/min in total gas feed rate and 1% in naphthalene concentration. The benzene decomposition efficiency was 95%, and the energy efficiency was 120 g/kWh. The naphthalene decomposition efficiency was 79%, and the energy yield was 68 g/kWh.

• Journal of the Korean Society of Combustion
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• v.15 no.1
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• pp.22-29
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• 2010

In this study, carbon conversion was measured using an electronic mass balance. In a lab scale furnace, each coal sample was pyrolyzed in a nitrogen environment and became coal char, which was then gasified with steam under isothermal conditions. The reactivity of coal char was investigated at various temperatures and steam concentrations. The VRM(volume reaction model), SCM(shrinking core model), and RPM(random pore model) were used to interpret experimental data. For each model the activation energy(Ea), pre-exponential factor (A), and reaction order(n) of the coal char-steam reaction were determined by applying the Arrhenius equation into the data obtained with thermo-gravimetric analysis(TGA). According to this study, it was found that experimental data agreed better with the VRM and SCM for 1,000 and $1,100^{\circ}C$, and the RPM for 1,200 and $1,300^{\circ}C$. The reactivity of chars increased with the increase of gasification temperature. The structure parameter(${\psi}$) of the surface area for the RPM was obtained.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.528-532
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• 2009

Integrated Gasification Combined Cycle (IGCC) power plant converts coal to syngas, which is mainly composed with hydrogen and carbon monoxide, by the gasification process and produces electric power by the gas and steam turbine combined cycle power plant. The purpose of this study is to investigate the influence of gasification process to type and structure of gasifier. For this purpose, the performance characteristics of gasification reaction are analyzed with the operation characteristic of pilot-scale 2-stage coal gasifier. It is found that gasification reaction, floating characteristic of melted slag, particle stick of inside of the gasifier, particle stick and deposit of Syngas cooler are the causes in the different performance characteristics.