Coal Gasification Experiments Research Articles

Influences of removable gas injection methods on the temperature field and gas composition of the underground coal gasification process

In this paper, the effects of changing the injection position of a gasification agent on temperature fields and gas compositions are investigated through an experimental model of the underground gasification of coaxial coal. A 3D model of the temperature field is constructed based on the experimental temperature parameters using kriging interpolation; the 900 °C isothermal surface is used as the reference plane to define the oxidation zone, and its plane and volume expansion rate are analyzed. The underground coal gasification experiment is divided into five stages according to the injection location. The average expansion rates of the oxidation zone in each stage are 2.04 cm/h, 1.93 cm/h, 3.44 cm/h, 3.68 cm/h, and 3 cm/h along the X-direction and 0.69 cm/h, 0.09 cm/h, 0.56 cm/h, 1.69 cm/h, and 1.01 cm/h along the Z-direction; the expansion rate along the X-direction is greater than that along the Z-direction. The expansion volumes of the oxidation zone after the five stages increase from 0.0097 m3 to 0.0168 m3, 0.0321 m3, 0.0521 m3 and 0.0657 m3. An analysis of the expanded volume of the oxidation zone compared with the volume of the cavity shows that both features are similar in shape and that the final volume of the cavity is smaller than the final expanded volume of the oxidation zone; the volume of the cavity is approximately 77.3 % of the expanded volume of the oxidation zone. The formation of a cavity requires the temperature to reach the conditions for the oxidation reaction of the coal and the rupture and flaking of the ash layer that accumulates after the reaction by the actions of certain stresses, such as thermal. The composition of the product gas and the strength of the chemical reactions involved are evaluated based on stoichiometric conservation. A short period after a shift in the injection position of the gasifier greatly impacts the chemical equilibrium of the UCG process with a large change in the strength of the chemical reaction, followed by a relatively small change when the gasification process stabilizes.

Modification of extended chemical percolation devolatilization model for application to low-rank coals

For understanding coal gasification reactions, primary pyrolysis reaction is important as the first stage of the gasification reactions. Recently, the authors developed a primary pyrolysis model to predict tar formation behavior by extending the chemical percolation devolatilization (CPD) model which is often used to predict pyrolysis behavior. The extended CPD (Ex-CPD) model predicts gas and tar components as respective chemical species. Consequently, the secondary tar decomposition behavior can be calculated by elementary step-like reaction models. However, some of the coal structure parameters used in the model contradict the 13C NMR data. That is, the molecular weight of the aromatic ring clusters calculated by the original Ex-CPD decreases with the aromatic index obtained by 13C NMR. In this study, this problem was resolved by modifying the calculation procedure to determine the coal structure parameters. The recalculated aromaticity index agreed with that calculated from the 13C NMR data. The modified Ex-CPD model was validated through comparison with coal gasification experiments using a pressurized drop tube furnace. The calculation results successfully described the trend of light gases, soot, and char yield in the experiments.

Large-Scale Experimental Simulations of In Situ Coal Gasification in Terms of Process Efficiency and Physicochemical Properties of Process By-Products

This paper presents a series of surface experiments simulating underground coal gasification (UCG). The main goal of the experiments was to investigate the influence of the gasification medium and the coal rank on the gasification process. Four multi-day trials were carried out using a laboratory gasification facility designed for the large-scale experimental simulations of UCG and located in the Experimental Mine “Barbara”, located at Mikołów, Poland. Two Polish bituminous coals were investigated: coal sourced from “Piast-Ziemowit” mine and coal sourced from “Wesoła” mine. Each of the two coals was gasified in two separate experiments using oxygen-enriched air (OEA) and pure oxygen as the respective gasifying agents. Gasification with oxygen resulted in significantly higher gas quality and higher process efficiency than gasification with OEA. Higher concentrations of hydrogen (23.2% and 25.5%) and carbon monoxide (31.8% and 33.4%) were obtained when oxygen was used as a gasifying reagent, while lower concentrations were obtained in the case of gasification with OEA (7.1% and 9.5% of hydrogen; 6.4% and 19.7% of carbon monoxide). Average gas calorific values were 7.96 MJ/Nm3 and 9.14 MJ/Nm3 for the oxygen experiments, compared to 2.25 MJ/Nm3 and 3.44 MJ/Nm3 for the OEA experiments (“Piast-Ziemowit” coal and “Wesoła” coal, respectively). The higher coalification degree of “Wesoła” coal (82.01% of carbon) compared to the “Piast-Ziemowit” coal (68.62% of carbon) definitely improves the gas quality and energy efficiency of the process. The rate of water condensate production was higher for the oxygen gasification process (5.01 kg/h and 3.63 kg/h) compared to the OEA gasification process (4.18 kg/h and 2.63 kg/h, respectively), regardless of the type of gasified coal. Additionally, the textural characteristics (porosity development) of the chars remaining after coal gasification experiments were analyzed. A noticeable development of pores larger than 0.7 nm was only observed for the less coalified “Piast-Ziemowit” coal when analyzed under the more reactive atmosphere of oxygen.

Optical Properties of Coal after Ex-Situ Experimental Simulation of Underground Gasification at Pressures of 10 and 40 bar

Coal gasification experiments were carried out in a reactor used to simulate underground coal gasification (UCG) processes under ex situ conditions at pressures of 10 and 40 bar. Changes in the optical properties of the organic matter were analyzed and the influence of temperature on coal during the UGC process was subsequently determined. The values of the true maximum reflectance determined for the gasification residue at pressures of 10 and 40 bar, and at distances of 0.75 and 1.75 m, reached a level corresponding to semi-graphite. Furthermore, it was found that the values of the true maximum reflectance and bireflectance decrease with increasing distance from the reactor chamber inlet. In addition, the results show that, regardless of the pressure used during the experiment, the temperature influence on the coal decreased with increasing distance from the reactor chamber inlet. The true temperatures operating during the experiment were higher than those recorded by the thermocouples, regardless of the pressure used. However, it was found that the distance at which the influence of temperature on the coal is still marked during the gasification process depends on the pressure used in the experiment. For example, in the case of the experiment at a pressure of 10 bar, the estimated distance is approximately 60 m, while for a pressure of 40 bar, it is approximately 35 m. These results can, and should, be taken into account for the planning of an UGC process.

Comparison of Tar Samples from Reaction Zone and Outlet in Ex-Situ Underground Coal Gasification Experiment

Tar remaining in the gasification cavity during underground coal gasification (UCG) is an important pollution source, while the reported studies only focus on the tar behavior at the outlet. The present work aims to compare the tar properties from the reaction zone and the outlet, analyze the tar evolution during gasification, and discuss possible measures to control tar pollution. Tar was sampled with a self-developed equipment from an ex-situ underground coal gasification experimental system and analyzed by GC-MS. The gas composition, temperature, and PM10 were also compared for the reaction zone and the outlet. Compared with the tar from reaction zone, the tar from outlet has a smaller percentage of high boiling point content, PAHs, C, O, N, S, Cl, Si, and a larger percentage of H. The PAHs percentage in tar at the outlet in this work is closer to the field data than the lab data from literature, indicating the experimental system gives a good simulation of tar behavior in underground coal gasification. Condensation due to a fast temperature drop is one of the main reasons for PAHs decreasing. Tar cracking and soot formation also cause the decrease of heavy tar, proven by the light gas and particulate matter results.

Migration of Co, Cd, Cu, Pb to the groundwater in the area of underground coal gasification experiment in a shallow coal seam in the experimental mine ‘Barbara’ in Poland

A numerical model of inorganic pollutants migration in the area of ​​ underground coal gasification (UCG) reactor in the post-operational phase was constructed in this study. Also the deceleration of migration and the shape of the contaminant plume in individual geological formations of the reactor surroundings, resulting from different values ​​of sorption affinity, were compared. The simulations were carried out for four selected metals (Co, Cd, Cu, Pb), which in relation to the raw coal and post-process char showed different sorption properties. The sorption parameters of the tested systems were determined experimentally on the basis of the Freundlich isotherm equation. The retardation coefficients were calculated and the degree of sorption intensity in hydrogeological media was classified from II (in the cobalt-char and metals-coal systems) to the IV class of sorption intensity (in the copper-char system).The modeling was carried out using the finite element method (FEM) in the COMSOL Multiphysics computing environment in a two-dimensional plane. The simulation of pollutant migration was carried out for the transient state, with the assumed time horizon up to 20 years after the termination of the UCG experiment. The bottom of the cavity formed due to the coal gasification in situ (10 m × 20 m ellipse) was assumed as the source of contamination and the spread of metals in a horizontal plane 200 m long and 200 m wide was analyzed.To compare the extent to which sorption phenomena affect the spread of pollutants, an additional model was constructed, taking into account only the advection–dispersion movement of the contaminant plume. The consequence of sorption interactions for the tested systems was the delay of the contaminant plume migration depending on time since the termination of the gasification process and depending on the distance from the source of pollution. Due to high sorption affinities, the post-process char acts as an effective buffer for inorganic pollutants and slows down the migration of analyzed metals even 20 years after UCG experiment. The greatest slowdown in migration in relation to the velocity of groundwater flow as a result of sorption occurred for copper transport in the char layer.

Study of Electrochemical Catalytic Coal Gasification: Gasification Characteristics and Char Structure Evolution.

Electrochemical catalytic coal gasification experiments with Fuxin (FX) coal under a CO2 atmosphere were conducted to evaluate the effects of power and temperature on coal gasification and char structure evolution during electrochemical catalytic gasification (ECG). When the power was 400 W, with temperature increasing from 800 to 1000 °C, the CO content in the gas products increased by 8.16%, the H2 content increased by 8.39%, and the CH4 concentration in the gas products initially increased and then decreased. When the temperature is 900 °C, with power increasing from 0 to 400 W, the CO content in the gas products increased by 58.27%, the H2 content increased by 81.33%, and the CH4 concentration in the gas products increased from 1.31 to 2.37%. The gasification reactivity and the concentration of combustible gas generated during ECG were higher than those during common coal gasification. Thermal electrons play important roles in ECG. These electrons could promote ring opening reactions and aromatic compound cracking and inhibit aromatization reactions while increasing the number of oxygen-containing functional groups in char, consequently enhancing the char gasification reactivity.

Screening of UCG chemical reactions and numerical simulation up-scaling of coal seam from laboratory models

Underground coal gasification (UCG) is a promising option for utilising deep-seated coal for the in-situ production of syngas. In this study, we modelled and screened the chemical reactions using the previous laboratory UCG experiments to investigate the complicated chemical reaction processes to apply them to field scale UCG operations. First, we constructed 1D and 3D numerical models by matching simulation with the laboratory coal combustion and gasification experiments involving a combustion tube test and then physically scaled the 3D experiments reported by Thorsness et al. and Stańczyk et al., respectively. We considered 5 chemical reactions from 12 chemical reactions by matching simulation to the experimental results. We adjusted the chemical reaction parameters used in our numerical simulations to match those of the experimental data. The numerical simulation results show that the proposed model can be applied in the laboratory as well as in the field-scale UCG operations to predict gasification behaviours, especially the temperature distribution, gas production rate, and gas composition.

An exsitu underground coal gasification experiment with a siderite interlayer: course of the process, production gas, temperatures and energy efficiency

A 72-h ex situ hard coal gasification test in one large block of coal was carried out. The gasifying agent was oxygen with a constant flow rate of 4.5 m3/h. The surroundings of coal were simulated with wet sand with 11% moisture content. A 2-cm interlayer of siderite was placed in the horizontal cut of the coal block. As a result of this process, gas with an average flow rate of 12.46 m3/h was produced. No direct influence of siderite on the gasification process was observed; however, measurements of CO2 content in the siderite interlayer before and after the process allow to determine the location of high-temperature zones in the reactor. The greatest influence on the efficiency of the gasification process was exerted by water contained in wet sand. At the high temperature that prevailed in the reactor, this water evaporated and reacted with the incandescent coal, producing hydrogen and carbon monoxide. This reaction contributes to the relatively high calorific value of the resulting process gas, averaging 9.41 MJ/kmol, and to the high energy efficiency of the whole gasification process, which amounts to approximately 70%.

CFD Simulations of Allothermal Steam Gasification Process for Hydrogen Production

The article presents an experimental laboratory setup used for the empirical determination of the gasification of coal samples in the form of solid rock, cut out in the form of a cylinder. An experimental laboratory set enabled a series of experiments carried out at 700 °C with steam as the gasification agent. The samples were prepared from the coal seam, the use of which can be planned in future underground and ground gasification experiments. The result of the conducted coal gasification process, using steam as the gasification agent, was the syngas, including hydrogen (H2) with a concentration between 46% and 58%, carbon dioxide (CO2) with a concentration between 13% and 17%, carbon monoxide (CO) with a concentration between 7% and 11.5%, and methane(CH4) with a concentration between 9.6% and 20.1%.The results from the ex-situ experiments were compared with the results of numerical simulations using computational fluid dynamics (CFD) methods. A three-dimensional numerical model for the coal gasification process was developed using Ansys-Fluent software to simulate an ex-situ allothermal coal gasification experiment using low-moisture content hard coal under atmospheric conditions. In the numerical model, the mass exchange (flow of the gasification agent), the turbulence description model, heat exchange, the method of simulating the chemical reactions, and the method of mapping the porosity medium were included. Using the construction data of an experimental laboratory set, a numerical model was developed and its discretization (development of a numerical grid, based on which calculations are made) was carried out. Tip on the reactor, supply method, and parameters maintained during the gasification process were used to define the numerical model in the Ansys-Fluent code. A part of the data were supplemented on the basis of literature sources. Where necessary, the literature parameters were converted to the conditions corresponding to the experiment, which were carried out. After performing the calculations, the obtained results were compared with the available experimental data. The experimental and the simulated results were in good agreement, showing a similar tendency.

Removal of pollutants from aqueous solutions by coals and residual cokes obtained from simulated underground coal gasification experiments

Groundwater pollution caused by underground coal gasification (UCG) as well as its remediation has attracted significant public attention. In this paper, model gasification experiments on three types of coals with different coalification degrees were carried out using a UCG model test system. The residual coal and coke samples were characterized via SEM, low temperature N2 adsorption, and FT-IR. Thereafter, their adsorption of phenol and Cr(VI) from simulated wastewater as well as the purification of gas washing water were investigated. Compared with the raw coals, the UCG residual cokes presented a higher specific surface area (SBET) of 44.99–381.51 m2/g and total pore volume (Vt) of 0.040–0.228 cm3/g; Cokes obtained from brown coal gasification had the highest SBET and Vt values. Parts of O-containing groups were preserved after the gasification. Phenol and Cr(VI) were removed by all types of coals and residual cokes. The removal rate of phenol increased with SBET and Vt, and cokes presented higher phenol adsorption capacities than those of raw coals. The O-containing groups significantly influenced and favored the removal of Cr(VI). Brown coal and its UCG coke had the highest adsorption capacities, with phenol removal rates of 17.71% and 72.44%, and presented the highest adsorption capacities, with Cr(VI) removal rates of 29.02% and 21.77%, respectively. When UCG residual cokes were used, the removal rates of total organic carbon (TOC) in both types of gas washing water exceeded 82%. Almost all the Cr and Se and some of the Ni were removed from gas washing water.

Aquatic risk assessment based on the results of research on mine waters as a part of a pilot underground coal gasification process

One of the possible applications of available hard coal resources is their underground gasification directly in the deposit. The gas obtained in this way is discharged to the surface for use in chemical synthesis or energy purposes. The environmental risk of the technology is mainly related to the potential negative impact of the process on groundwater and surface water, due to the need to remove process condensates and the drainage of the exploitation area. The risk occurs both during the process and after its completion. This article presents the results of a pilot study carried out in the Wieczorek Mine. The coal gasification experiment was carried out over 6 months (with 2 months of gas extraction) in real conditions in a georeactor located 450 m below the surface and on the surface of the object (cooling and cleaning system for gasification products). Water monitoring was carried out before the experiment, during the experiment and 5 years after the end of the process. The analysis includes the results of underground and surface water monitoring within the range of the potential impact of the pilot plant. The paper also presents the analysis of water-tar condensate collected from the gas cleaning system.

Characterisation of the Contaminants Generated from a Large-Scale Ex-Situ Underground Coal Gasification Study Using High-Rank Coal from the South Wales Coalfield

This paper presents an analysis of contaminants generated from large-scale, laboratory-based, underground coal gasification (UCG) experiments using a high-rank coal from the South Wales Coalfield. The experiments were performed at atmospheric and elevated pressures (30 bar) by varying the oxidants’ composition. The experiments were designed to predict the amount of produced water and contaminants generated at each stage of the operating conditions. The mass balance of water supplied and produced in the experiments was accounted for. Chemical analyses of produced water, char and ash contents were performed to quantify the inorganic and organic chemical parameters. Most of the contaminant concentrations in the produced water from the 30-bar pressure experiment were lower than the concentrations generated from the atmospheric pressure experiment. The measured concentrations of the inorganic chemical species and the inorganic parameters of the coal seam water from the South Wales Coalfield were used in theoretical calculations to predict the dominant equilibrium species concentrations in a hypothetical scenario of effluent contaminated groundwater. The biodegradation of organic contaminants such as phenol, benzene and sorbed fractions of inorganic contaminants from the produced water on iron oxide in the ash residue was predicted using existing biotransformation kinetics and surface complexation models, respectively. The biodegradation of phenol and benzene would be a slow process even at optimum conditions and the iron oxide left in the cavity can act as a sorbent for a few inorganic species. The evidence from the present study suggests future work towards (i) developing an appropriate water treatment process during gas cleaning, (ii) operational procedure (pressure and proportions of oxidant) and (iii) developing UCG-specific experimental prediction of contaminant transportation and transformation kinetics.Graphical abstract

Coal char characteristics variation in the gasification process and its influencing factors

Underground coal gasification is a burgeoning coal exploitation technique that coal is directly converted into gaseous fuel by controlled combustion. In this paper, the gasification experiments of Inner Mongolia lignite, Xinjiang subbituminous coal, and Hancheng medium volatile bitumite were conducted respectively by using the tube furnace coal gasification experiment system. The gasification process was conducted under 3°C/min increment within the range of 600–900°C. The gas composition was analyzed by gas chromatography and the pore structure of the coal char was detected by low-temperature N2 adsorption. The results show that the gasification temperature, gasification agent, and coal type have an important influence on the gasification reaction. With the increase of gasification temperature, the effective component, gas calorific value, and gas production rate increase. When CO2 is used as the gasifying agent, the effective components in the gas are mainly CO. When H2O(g) is used as the gasifying agent, the effective component of gas is H2. The coal gasification performance with low thermal maturity is obvious better than the high rank coal with higher coalification. N2 adsorption–desorption experiments show that the pore is mainly composed by transition pore and the micropores, the specific surface area is chiefly controlled by a pore size of 2–3 nm. With the increase of coalification degree, the adsorption amount, specific surface area, and total pore volume show a decreasing trend. The gasifying agent has a great influence on the pore structure of the coal char. The gasification effect of H2O (g) is significantly better than that of CO2. Analyzing the gasification characteristics and pore changes of different coal rank coals under different gasification agents, we found that Inner Mongolia lignite is more conducive to the transport of gasification agents and gaseous products in coal.

Improvement of resource recovery rate for underground coal gasification through the gasifier size management

Underground coal gasification is one of the most vital technical directions for the future development of the coal industry. Currently, numerous small-scale underground coal gasification industrial tests of different processes have been successively conducted, which has laid a solid foundation for further large-scale experiment and production. However, with the expansion of underground coal gasification experiment scale and promoting application, the surrounding rock stability and surface subsidence must be considered. Moreover, there exists a bottleneck problem, which should be solved urgently, that how to design underground gasification production for different geological conditions to improve resource recovery rate. To solve this issue, this paper analyzed the existing situation of resource recovery rate of industrial experiment for underground coal gasification without shaft. Also, the improvement method for resource recovery rate of underground coal gasification with considering of the gasifier safety and surface subsidence was proposed in combination with the technology characteristics of underground coal gasification. Meanwhile, the influence rule of gasifier parameters on the coal pillars stability and surface subsidence was revealed. From the findings in this research, it can be expected that the resource recovery rate of underground coal gasification without shaft can be increased from about 40% to more than 60% under the both conditions of the safe production of underground gasifiers and surface subsidence control. These research results are of great significance for enhancing the economic benefits of underground coal gasification and promoting its industrialization and large-scale production.

Analysis of syngas production and reaction zones in hydrogen oriented underground coal gasification

Underground Coal Gasification (UCG) is an emerging technology that utilizes unmined coals. In UCG process, coal is burned and gasified underground. Produced syngas is collected through drilled wells to be processed or used directly. Syngas comprises mainly CO2, CO, H2 and CH4 and its hydrogen content majorly depends on gasification agents and properties of coal gasified. It is assumed that the combustible components of syngas, such as CO and H2, are products of heterogeneous gasification reactions and oxygen is almost solely consumed by homogeneous combustion reactions of these combustible components. These assumptions are widely used to simplify dynamic UCG models. Here, a lab-scale hydrogen oriented underground coal gasification experiment was performed for Turkish lignite. Using the experimental data, a two-dimensional underground coal gasification computational fluid dynamics (CFD) model was built to investigate cavity formation, reaction zones, reaction rates and the syngas properties. By developing the CFD model, valuable insights regarding which reactions are dominant in which region are gained and UCG process is better understood. Two-stage gasification method was employed in the experiment. Experiments were performed using lignite having high volatile, high ash and moderate moisture contents in a prism-shaped ex-situ reactor. Oxygen and steam were successfully supplied as gasification agents. In the steam-gasification stage with a supply rate of 5 m3/h, hydrogen content and calorific value of syngas were measured up to 40 (vol.) % and 8 MJ/Nm3, respectively. Experimental and CFD model results were compared to validate the mathematical model and assumptions used in UCG syngas production process.

Characteristics of coal partial gasification experiments on a circulating fluidized bed reactor under CO2[sbnd]O2 atmosphere

Coal partial gasification experiments are carried out on a self-designed circulating fluidized bed (CFB) gasifier under CO2O2 atmosphere. The CFB gasifier system is mainly composed of a ceramic furnace, auger screw conveyor, gas supplier, gas-solid separation unit, temperature and pressure measuring system, and Distributed Control System (DCS). The experiments are conducted at temperatures between 800 and 930 °C. The coal with particle size of 0.45–0.9 mm is selected for experiments. Mixture of CO2 and O2 is adopted as reactant gas. The oxygen-coal ratio varies from 0.38 to 0.8. The results show that as oxygen-coal ratio increases, the concentration of CO + H2 first goes up and then declines. When the oxygen-coal ratio is 0.57, the concentration of CO + H2 reaches the maximum value. To a certain extent, the higher oxygen-coal ratio results in better gas composition. The volume fraction of combustible gas and the lower calorific value reach ∼40% and 5.58 MJ/Nm3. To explore the variety of char structure features, the Scanning Electron Microscope (SEM) and Raman Spectrometer are adopted. The results show that the pores of char are getting opened as the reactant gas enters the inside of char and new O-containing functional group and more aromatic rings are generated. It makes the chars become more disordered.

Laboratory scale studies on CO2 oxy-fuel combustion in the context of underground coal gasification

Oxidizing/gasifying agents play an essential role in the economy of underground coal gasification (UCG). The selection of feed gases to UCG depends on the prevailing conditions and inherent properties of a coal seam. Steam based UCG operation would lead to transportation and operational difficulty for efficient gasification. Alternatively, CO2 gas is a potential gasifying medium for coal gasification and this option would ensure the reutilization of waste CO2 gas in a UCG operation. Thus, in the present study, borehole coal combustion and gasification experiments are carried out to simulate CO2 enhanced UCG system using a low ash coal originating from the Northeast region of India. UCG experiments are simulated in a laboratory scale using CO2/O2 gases and the results are compared with pure oxygen and oxygen enriched air based UCG operation. The composition and calorific value of syngas are analysed for various gasifying agents. The CO2/O2 borehole experimental studies show that a CO enriched product gas (∼40 vol.%) can be generated under dried coal seam conditions. Thermo-gravimetric analysis (TGA) studies show that the rate of pyrolysis is higher under a CO2 atmosphere as compared to N2 atmosphere. Further, the TGA results show that the generated CO2 pyrolysis products led to substantial char gasification even at low temperatures. The reactivity of tar with CO2 enhanced the calorific value of the product gas due to dry reforming reactions. Also, the presence of suitable inorganic species in the coal progressed the CO2 gasification through ash catalysis.

Pilot-scale underground coal gasification (UCG) experiment in an operating Mine “Wieczorek” in Poland

In this article, the results from a pilot-scale, underground coal gasification (UCG) experiment conducted in an operating coal mine “Wieczorek” were presented. The 60-day gasification trial demonstrated that through the appropriate selection of the test site and by applying all safety standards essential for the coal mining industry, UCG in an active mine can be conducted safely and efficiently. The idea of the technical realization of the UCG process, as well as selected gasification results, such as the primary mass balance parameters, gas production rate, coal consumption rate, coal gasification efficiency and the changes in gas composition, were presented.

Investigate the Adsorption Behavior of CO2on Char–Inorganic Compound Model for Coal Gasification

The effect of inorganic compounds (e.g., Na2CO3, CaCl2, FeCl3, and H3BO3) on the gasification reactivity was investigated. On the one hand, coal and CO2 gasification experiments were performed using a thermogravimetric analyzer. On the other hand, five models (Na2CO3-char, CaCl2-char, FeCl3-char, char, and H3BO3-char) were established in Materials Studio software due to the fact that the char gasification is the rate-determining section. Then the adsorption mechanism of gasification agent (CO2) in the above five models was simulated using the grand canonical Monte Carlo method. After that, diffusion coefficient and adsorption activation energy were estimated. From the results of experiments, the catalytic ability followed the sequence of Na2CO3-coal > CaCl2-coal > FeCl3-coal > coal > H3BO3-coal. By comparing the activation energy of CO2 adsorption in simulation, it may be noted that the sequence of CO2 adsorption ability is the same as the inorganic compound catalytic ability. Therefore, it is inferred th...