Gasification Reaction Research Articles

Kinetic analysis on reduction process of copper slag with and without CaO

The reduction of copper slag by carbonaceous material is one of the important methods to recovery some valuable elements in copper slag, such as Fe, Zn, Cu, etc. The kinetic reaction mechanism should be mastered in order to promote the recovery rate of metallic elements in copper slag. In this work, isothermal reduction experiments of copper slag with and without CaO were carried out using the anthracite as reducing agent. The reduction behaviour of copper slag with CaO and without CaO was analysed, and the kinetics mechanism was discussed based on traditional gas–solid model and integral method, respectively. The result shows that the reaction temperature significantly affected the reduction degree of copper slag, the copper slag reduction degree can be effectively enhanced by adding a certain amount of CaO in raw materials. Based on the gas–solid model, both the reaction process of copper slag without CaO and with CaO is in accord with interfacial reaction control model before the reaction time of 1200 s and gas diffusion Jander model after 1200 s. Compared with the gas–solid model, it is better to use the integral method to calculate reaction activation energy of the reduction process of copper slag. When CaO is added into copper slag, the basicity goes up and reaction activation energy decreases subsequently. The increase of basicity from 0.06 to 1.20 promotes a decrease by 11.40 kJ/mol in reaction activation energy, illustrating that CaO has a positive effect on the reduction process of copper slag. The control link of the reduction process for each copper slag gradually changes from interfacial chemical reaction to carbon gasification reaction, followed by gas diffusion with the increase of the reduction degree of copper slag.

CALCULATION OF THERMODYNAMIC TEMPERATURES OF CHEMICAL REACTIONS OF STEPWISE MANGANESE REDUCTION PROCESS FROM ITS DIOXIDE BY CO GAS AND GASIFICATION OF SOLID CARBON BY DEGREES OF CHEMICAL AFFINITY OF SUBSTANCES TO OXYGEN

The results of a thermodynamic analysis of the course of chemical reactions of the stepwise reduction of manganese from its dioxide by CO gas and the gasification reaction of solid carbon (Bella-Boudoir) are presented. The goals of the work are to obtain eigenexpressions for calculating the numerical values of the Gibbs free energy depending on temperature using tabulated values of the standard enthalpies of formation and entropies of inorganic substances, as well as to construct graphical dependences of the Gibbs energy on temperature using formulas from literary sources and obtained expressions. Numerical values of the boundary temperatures are obtained above which the chemical reactions of the stepwise reduction of manganese from its dioxide by CO gas and the chemical reaction of gasification of solid carbon (Bella-Boudoir) can or cannot thermodynamically proceed. Considering the complete coincidence of the obtained data on the own (obtained) expressions using two (direct and indirect) methods, it is possible to consider with a significant degree of probability the numerical values of the boundary temperature for the reactions of stepwise reduction of manganese from its dioxide and gasification of solid carbon as reliable, which indicates the possibility of the reduction of Mn2O3 from MnO2, Mn3O4 from Mn2O3 and MnO from Mn3O4 by CO gas, the Bell-Boudoir reaction and the impossibility of the reduction of manganese from MnO by CO gas at the temperatures of the actual process in reduction furnaces. This also confirms that CO gas is not a manganese reducer at the last stage of stepwise reduction of MnO according to scheme (B), refuting any theories and assumptions about the possibility of reducing Mn from MnO by CO gas.

Investigation on steam co-gasification of torrefied biomass and coal: Thermal behavior, reactivity, product characteristic and synergy

The steam gasification of rice straw torrefied at 200–300 °C and its co-gasification with coal were examined in this study. The effect of torrefaction temperature on thermal behavior, reactivity, product characteristic, and synergy were investigated. The results showed that torrefaction temperature influenced the pyrolysis and char gasification stages by shifting them to higher temperature ranges. As torrefaction temperature increased, the H2 content increased while the CO and CH4 contents decreased, with H2/CO molar ratio increasing from 1.8 to 2.4. The total gas yield also increased from 0.95 to 1.30 Nm3/kg, especially with a large increase up to 27.4 %. As for the co-gasification, stages of biomass pyrolysis and coal pyrolysis overlapped at torrefaction temperature of 300 °C. The pyrolysis reactivity decreased while the char gasification reactivity increased with the torrefaction temperature increasing. The H2/CO molar ratio decreased slightly from 3.55 to 3.40, while the total gas yield increased from 1.87 to 1.96 Nm3/kg as well as the cold gas efficiency from 75 % to 77 %. The strongest synergistic effect on the reactivity occurred at torrefaction temperature of 250 °C. The increased torrefaction temperature enhanced the synergistic effect on the total gas yield but weakened it on the H2 yield.

Catalytic gasification of a single coal char particle: An experimental and simulation study

The catalytic coal gasification technology has been widely researched and developed under the background of “Carbon peaking and carbon neutrality goals”. Currently, most of catalytic gasification experiments on coal char particles are analyzed by thermogravimetric analyzer (TGA). However, the gasification agent will be subject to diffusion resistance during the reaction because of the sample stacking, making the inherent reaction kinetics unclear. In this study, we investigated the catalytic gasification behavior of single-particle coal char using high temperature stage microscope (HTSM). With the diffusion resistance ruled out, the reaction conditions when using a HTSM are more similar to those inside a real industrial gasifier. Numerical models of the gasification reaction of single-particle coal char were further developed using the kinetic parameters obtained under HTSM. Three models were investigated, including regular spherical structured, irregular spherical structured and porous spherical structured models, representing different morphologies of coal char particles in the gasifier. The gasification characteristics of coal char particles under different K2CO3 catalyst loadings and gasification temperatures were also studied. Compared with the activation energies data of coal char particles without catalyst, the activation energies of coal char particles loaded with 2.2 %, 4.4 %, 6.6 %, and 10.0 % catalysts were reduced by 110 kJ/mol, 116 kJ/mol, 121 kJ/mol, and 126 kJ/mol, respectively. The reaction surface area affects the temperature distribution. The temperature near the irregular spherical particle is about 20 K higher than the temperature near the regular spherical particle.

Kinetic analysis and model evaluation for steam co-gasification of coal-biomass blended chars using macro-TGA

A macro-thermobalance (macro-TGA) was applied to investigate the steam co-gasification characteristics of the chars produced from Huainan coal (HN), two types of biomasses, sawdust (SD) and wheat straw (WS), and coal-biomass blends at 900–1200 °C under rapid heating conditions. The gasification reaction kinetics were determined by the homogeneous reaction model (VM), shrinking core model (SCM) and random pore model (RPM), and the optimal model was selected by deviation calculation. The results show that the char gasification reactivity increased with the increase of temperature. The promotion effect of biomass semi-coke on coal char mainly occurred in the stage when the carbon conversion rate was greater than 0.5, which is mainly attributed to the migration of active AAEMs to the surface of coal char to catalyze the gasification reaction in the later stage. However, with the increase in temperature, this promoting effect is weakened due to the increasing influence of mass transfer effects over chemical rate control, and increased volatilization of the inorganic species. The RPM model is suitable for describing the coal char gasification process, while the SCM was the model that best fitted the biomass semi-coke and coal/biomass blends, which elucidates the kinetic mechanisms governing the gasification process.

Experimental and kinetic studies on steam gasification of oxidized carbon-rich fraction from coal gasification fine slag

Gasification is an important method to realize the resource utilization of coal gasification fine slag (CGFS). In this work, the carbon-rich fraction (CF) of CGFS was modified by oxidation, and the gasification reactivities, structures, and kinetics of samples were studied. The results demonstrate that compared to CF, the gasification characteristic temperatures of oxidized CF are lower, the weight loss rates are faster, and the gasification reactivities are significantly enhanced. These improvements are attributed to the structural evolutions of oxidized CF. Compared with CF, the specific surface area and pore volume of oxidized CF increase by at least 2.5 and 1.5 times, the proportions of oxygen-containing groups rise, and the carbon microstructure of different oxidized CF varies significantly. CF oxidized by steam exhibits the most developed porosity and the most disordered carbon microstructure, corresponding to the highest gasification reactivity of all the samples. The kinetics results showcase that the diffusion reaction model is suitable for describing the gasification process of samples, so porosity emerged as the primary factor determining the gasification reactivity. However, the influence of carbon microstructure and active groups on the gasification reactivity of oxidized CF is enhanced when the porosity meets the diffusion requirements of the gasification reaction.

Catalytic steam reforming of waste tire pyrolysis volatiles using a tire char catalyst for high yield hydrogen-rich syngas

The production of hydrogen and syngas (H2/CO) from waste tires by pyrolysis catalytic steam reforming was investigated in a two-stage fixed bed reactor. In this study, tire char served as a sacrificial catalyst, facilitating the combination of catalytic steam reforming and char steam gasification reactions. The tire char acted as both a catalyst and a gasification reactant, enhancing the gas product yield. The process parameters investigated were, a reforming temperature range of 700–1000 °C, steam space velocity between 2 and 12 g h−1 g−1char and reaction times of 0.5–2 h. The influence of the parameters on the yield and composition of the product gases and the characteristics of the used catalyst were analyzed in detail. The results indicated that higher temperature and steam space velocity increased H2 and CO yields in the presence of a tire char catalyst. Elemental analysis of the used tire char, surface morphology and pore structure provided insights into the extent of tire char consumption in the reaction. Prolonged reaction time allowed for more thorough reactions between the pyrolysis volatiles and tire char, promoting the production of H2. At a reaction time of 2 h, the H2 yield reached 223 mmol g−1, representing 74 wt% of the maximum hydrogen yield.

Detailed modelling of a double fluidised bed steam gasifier processing woody biomass and solid recovered fuel mixtures

Abstract Double fluidized bed gasification is based on the circulation of an inert bed between two reaction sections: the gasification reactor, where a solid feedstock, generally biomass. is converted into a syngas by steam or air oxidation; the combustor or riser, where residual char from the thermal decomposition of the feedstock is oxidized by air (in some cases with additional fuel) to provide the energy contribution for the gasification reactions and ensure autothermal operation of the system. In this work, detailed modelling of a dual fluidized bed steam gasification reactor is performed in Aspen Plus by incorporating: (1) gas, char and tar production during thermal decomposition of the feedstock according to experimental correlations developed and taken from the literature, (2) heterogeneous and homogeneous reaction kinetics in the gasifier bed and in the freeboard. The model has been validated by comparison with experimental results on different mixtures containing solid recovered fuels and woody biomass. The model is quite accurate in predicting the gas products composition for different feedstocks mixtures (root mean square error of 12% for CO, CO2, H2 and CH4) and enables coupling with different downstream liquid fuels synthesis processes (synthetic natural gas, methanol, dimethyl-ether, Fischer-Tropsch products etc.).

Analytical justification of the thermochemical interaction between blast reagents and carbon-containing products under the influence of magnetic fields

Purpose. To justify and develop a model that describes the effect of magnetic treatment of blast reagents and carbon-containing products on the gasification process for predicting the intensification of gas formation. Methodology. The study involves theoretical modeling based on experimental data to investigate the influence of magnetic fields on the underground coal gasification process and co-gasification of coal and carbon-containing products. The Arrhenius equation was used to estimate the rate constants of gasification reactions in the temperature range of 800–1,000 °C. The effect of the magnetic field was incorporated by adjusting the activation energy (Ea). The results of analytical and experimental studies were processed using methods of computer and mathematical modeling. Findings. The results show that the application of magnetic fields significantly intensifies the gasification process of carbon containing products. Increasing the reactivity of the blast reagents, particularly water and oxygen, leads to a higher overall yield of combustible gases. The use of magnetic fields in the gasification process substantially increases the reaction rate (k) due to the reduction in activation energy (Ea), improving the overall efficiency of gasification. Originality. For the first time, an analytical model has been developed to describe the effect of magnetic treatment of blast reagents and carbon-containing products on the gasification process in the temperature range of 800–1,000 °C. The obtained reaction rates follow an exponential trend. The established and correlation-validated pattern shows the relationship between changes in the approximation coefficient (F ) and the change in the carbon fraction (C, %) during the magnetic treatment of blast components within the specified temperature range. Practical value. The results of this study can be applied to enhance the efficiency of industrial gasification processes, particularly underground coal gasification and co-gasification of coal and carbon-containing productss.

Effects of water injection on reaction temperature and hydrogen production in horizontal co-axial underground coal gasification

Underground coal gasification (UCG) is process of directly recovering energy as combustible gases such as hydrogen and carbon monoxide by combusting unmined coal resources in situ. During UCG process, the temperature in the gasification zone can exceed 1,300 °C, raising concerns about the potential melting of the steel pipe for oxidant injection. To control the temperature in the gasification zone, the use of water injection as an injection agent can be an option. Injecting water during UCG process serves two purposes: it decreases the temperature in the reaction zone by the endothermic effect of water, and it enhances the production of H2 by the reduction reaction of water. However, injecting excessive amounts of water may lead to a significant decrease in the temperature in the reaction zone, consequently cannot maintain the temperature range required for the UCG reaction. This study discusses the effects of water injection on the temperature of the gasification zone and the product gas by developing a chemical reaction model of UCG using COMSOL Multiphysics® software. The model was developed based on the temperature and produced gas results obtained from laboratory-scale artificial coal seam UCG experiments. Our findings reveal that water injection significantly influences the gasification process, controlling temperature in the reaction zone and promoting H2 production through steam gasification and water-gas shift reactions. Moreover, under the experiment and analysis conditions of this study, it is revealed that water injection up to an H2O/O2 molar ratio of 3.9 can effectively control the temperature of the gasification zone with enhancing H2 production.

Catalytic Effects of Potassium Concentration on Steam Gasification of Biofuels Blended from Olive Mill Solid Wastes and Pine Sawdust for a Sustainable Energy of Syngas

The effect of potassium impregnation at different concentrations during gasification, under nitrogen/water steam atmosphere, of char produced via pyrolysis of olive mill residues blended or not with pine sawdust was investigated. Three concentrations (0.1 M, 0.5 M, and 1.5 M) of potassium carbonate solution (K2CO3) were selected to impregnate samples. First, four types of pellets were prepared; one using exhausted olive mill solid waste (G) noted (100G) and three using G blended with pine sawdust (S) in different percentages (50%S–50%G (50S50G); 60%S–40%G (60S40G); 80%S–20%G (80S20G)). Investigations showed that when isothermal temperature increases during the gasification conducted with two water steam percentages of 10% and 30%, the reactivity increases with potassium concentration up to 0.5 M, especially for 100G. Still, higher catalyst concentration (1.5 M) showed adverse effects attributable to silicon release and char pore fouling. Moreover, the effect of the steam concentration on the gasification reactivity was significant with the non-impregnated sample 100G. Finally, a kinetic study was carried out to determine the different kinetic parameters corresponding to the Arrhenius law.

Comprehensive experimental assessment of biomass steam gasification with different types: correlation and multiple linear regression analysis with feedstock characteristics

In order to reveal the correlation between gasification behavior and products with feedstock characteristics, the steam gasification of 13 biomasses was investigated using a thermogravimetric analyzer and a fixed-bed reactor. Meanwhile, a multiple linear regression was used to construct correlation models. The results showed that cellulose content and crystallinity had the greatest influence on pyrolysis reactivity, which was reflected that the cellulose content was strongly positively correlated with the pyrolysis reactivity (Pmax = 0.77), while the lignin content and cellulose crystallinity were opposite. H/C, O/C ratios and SiO2 content had the greatest influence on gasification stage. O/C were strongly negatively correlated with gasification reactivity (Pmax = −0.81). But correlations of K and Ca contents were much less than that of Si. Husk has the best gasification performance than straw and woody with highest H2 and total gas yield of 28.26 and 68.93 mmol·g−1. H2 concentration and yield were significantly affected by the cellulose crystallinity and the fixed carbon content with positively correlation (P = 0.69–0.85). CH4 and CnHm were also influenced by them, but the trend was opposite to that of H2. Cellulose content, followed by SiO2 content mainly affected CO and CO2 and negatively correlated with CO while positively with CO2.

Effect of soaked biomass on gasification temperature performance in an open-downdraft gasifier

Gasification of soaked biomass is a novel approach to saving cost and time of conditioning feedstock. It may have disadvantages on gasification temperature since an open-downdraft gasifier requires a zone with high temperature to maintain endothermic gasification processes. Heat is generated by exothermic reaction in the gasifier. It is supposed to be used by the gasification reactions, and excess water use it too. Ten varieties of biomass with different properties, shapes, and sizes were soaked and utilized as gasification feedstocks. The gasifier was able to maintain a stable temperature above 800 °C when fed soaked hardwoods, unlike soaked softwoods, which made the gasifier unable to maintain a temperature higher than 700 °C. Small, flat-shaped soaked biomasses were able to maintain high temperatures better than that of other-shaped biomasses. Particularly, soaked bamboo and soaked coconut shell made the gasifier able to maintain a high temperature zone of more than 1,000 °C.

Experimental and modeling studies on char combustion under pressurized O2/H2O conditions

The desorption kinetic parameters for pressurized combustion and gasification reactions were determined based on a C++ program coupled with the Langmuir-Hinshelwood (L-H) kinetic model developed and experimental data from pressurized char combustion, and the established L-H kinetic model for pressurized char-O2/H2O combustion was refined in the current paper. The activation energy for desorption in reactions involving pressurized char-O2 and char-H2O was determined to be 250.8 kJ/mol, accompanied by a pre-exponential factor of 5.42 × 1010 g/(m2 s). Using this foundation, the current research conducted simulations to investigate the impacts of temperature, pressure, and H2O concentration on the oxidation adsorption rate (Rads,oxi), desorption rate (Rdes), gasification adsorption rate (Rads,gas), and the competitive influences of kinetics and diffusion processes within the pressurized char-O2/H2O combustion. The simulation results indicate a gradual increase in Rdes and Rads,gas with char conversion to reach a peak, followed by a gradual decline. Conversely, the Rads,oxi varies smoothly throughout the char conversion process. At 1673 K/1.0 MPa, the char-O2/H2O reaction rate is primarily constrained by Rads,oxi and Rads,gas, with the adsorption reaction serving as the rate-controlling step. Moreover, it was noted that a rise in pressure resulted in a linear increase in Rads,oxi, Rdes, and Rads,gas. At elevated temperatures, the impact of pressure on them becomes more noticeable. However, the introduction of H2O mitigates this effect. Elevated temperature and pressure facilitate the competition on the kinetics of char-O2 combustion for O2 diffusion, resulting in the conversion of char being more susceptible to O2 diffusion rate limitation. With the addition of 20 % H2O, the competition effect was weakened. In the case of pressurized combustion involving char and O2/H2O, the char conversion is primarily constrained by the O2 diffusion rate and is scarcely influenced by the H2O diffusion rate.

Recycling of flotation residual carbon from coal gasification fine slag through thermal combustion reaction: Insight into the spatial and temporal multi-scale evolution of typical heavy metals

The necessity for a fundamental comprehension of the migration and transformation patterns of heavy metals in the combustion reaction process is paramount to ensure the effective and targeted prevention and control of heavy metal pollution in the context of large-scale energy utilization of waste coal gasification fine slag. This study aims to reveal the fate of typical heavy metals during the combustion reaction of coal gasification fine slag to provide valuable insight for its clean secondary use. In this work, the thermal combustion reactivity of coal gasification fine slag was initially enhanced through froth flotation, and then the spatial and temporal multi-scale evolution of heavy metals in the flotation carbon-rich fraction was investigated by a series of analytical experiments. The results demonstrate a strong correlation between the volatility of typical heavy metals and the combustion reaction process of the flotation carbon-rich fraction. The volatility of V, Ni, Cu, Zn, and Pb is consistently high, of which the volatility of Zn and Pb is consistently above 50%, while the volatility of Cr, Mn, and Ba exhibits greater temperature sensitivity. As the reaction proceeds, the specific surface area of the solid residue expands, and then the smooth and dense mineral particles dissolve into each other to form a cluster structure simultaneously with the collapse of the pore structure, resulting in the volatility of the heavy metals firstly increasing and then decreasing. Furthermore, alkali metals and alkaline earth metal compounds are effective carriers of Cr, Mn, and Ba in the bottom residual. Additionally, the type and number of crystalline minerals in the bottom residual gradually increase as the reaction progresses. This results in the gradual conversion of the heavy metals bound to unstable carbonate minerals and sulphones into more stable chemical forms. The findings provide novel theoretical support and technical guidance for the environmentally sound and efficient utilization of residual carbon in the waste coal gasification fine slag.

Decoupling study of municipal solid waste gasification: Effect of pelletization on pyrolysis and gasification of pyrolytic char

To explore the influence of pelletization on the thermal conversion of municipal solid waste (MSW), pyrolysis characteristics and gasification reactivity of MSW pellet and powder were investigated in this study. Besides, the physicochemical properties of internal char and external char within the char pellet were separately characterized. Moreover, the relationship between the physicochemical properties of char pellet and its gasification reactivity was clarified. Results showed that the pyrolytic gas yields of MSW pellets were increased by 15.47 % and 11.55 % at 700 °C and 800 °C, respectively, compared to powder MSW. It was mainly attributed that the conversion of monocyclic aromatic hydrocarbons to polycyclic aromatic hydrocarbons was promoted by the longer residence time within the pellets. Meanwhile, the physicochemical properties of pyrolytic char pellets exhibited a significant heterogeneity. Specifically, the number of ordered aromatic rings of char pellet was reduced, while the order degree of carbon structure was enhanced, particularly the internal char. However, the difference magnitude between internal and external char was diminished with temperature. This was due to the higher temperature resulting in a larger surface specific area and pore volume of the char pellet, especially the internal char, thereby enhancing the pyrolysis process. Furthermore, an increase in pore volume within the char pellet improved gasification reactivity when the conversion rate > 0.4. These findings provide a reference for the pyrolysis and gasification process of MSW pellets.

In-situ decomposition of citric acid for eliminating coking in steam reforming of acetic acid through enhanced gasification of coke precursors

H2O and CO2 are two important agents for gasification of precursors of coke in steam reforming (SR). Their in-situ formation from decomposition of reactant might facilitate removal of coke deposit from surface of catalyst. This was investigated in SR of acetic acid (HAc) mixed with presence of citric acid (CA) over Ni/SBA-15 catalyst, as CA could decompose to form simultaneously H2O and CO2 for potentially involving in gasification reactions. The results showed that CA presence could not enhance catalytic activity of Ni/SBA-15 but remarkably promoted the catalytic stability. This was due to effective suppression of coking by CA (42.3 % coke in SR of HAc versus ca. 10 % coke in co-reforming of HAc and CA and 6.7 % coke in SR of CA). The adsorbed *CO2 and *OH species produced in-situ by decomposition of CA effectively gasified the precursors of coke such as *CxHy and O-containing species like *CO and *C-O-C.

Structural analysis and gasification reactivity of chars derived from the slow pyrolysis of extruded coal fines and recycled plastic

The evolution of char resulting from the co-pyrolysis of recycled plastic and discard fine coal, along with the impact of varying plastic additions on the characteristics of the formed char and its subsequent gasification reactivity, remains unexplored. In this study, extrudates were produced using discarded South African Highveld coal fines, combined with either recycled low-density polyethylene (LDPE) or polypropylene (PP), respectively, and charred under a nitrogen atmosphere at three different temperatures (520, 720, and 920 °C). Co-gasification of plastic and coal provides an opportunity to reduce two waste streams simultaneously. The characteristics of the chars produced from the coal fines were compared to those produced from the extrudates formulated at varying plastic content (10, 25 and 50 %wt), using petrographic carbon form analysis, surface area and porosity analysis, as well as XRD carbon crystallite analysis. Thermal fragmentation was observed to degrade the integrity of the extrudates when the plastic content exceeded 10 %, therefore, the chars produced at 920 °C were pulverized (75–150 μm) before undergoing CO2 gasification at 800, 825 and 850 °C in the chemical-controlled regime. Carbon crystalline analyses showed that the chars were more ordered with an increase in plastic content. However, even with the more ordered structure, the gasification reactivity increased similarly with an increase in plastic content for both the extrudate derived chars containing LDPE and PP. Petrographic carbon form analysis showed an increase in crack and pore formation with an increase in plastic addition during all stages of the chars’ evolution as the pyrolysis temperature increased. The VRM time factor showed a positive linear correlation with an increase in BET surface area, especially for the LDPE derived chars (R2 > 0.7720). Therefore, the observed reactivity increase with an increase in plastic content can be correlated to an increase in surface area. Results allude to the possibility of increasing gasification rates in Industrial gasifiers while reducing both coal and plastic waste. Further work should be conducted to minimise the thermal fragmentation propensity of the plastic-containing fine coal bound extrudates to make the extrudates suitable for fixed bed gasification.

Catalytic effects of red mud on coal char gasification and the transformation of active lattice oxygen in iron oxides

Catalytic gasification can obviously accelerate gasification reaction rate. However, recovery of catalysts is currently the main challenge. In this work, a kind of industrial solid waste called red mud was tested as a disposable catalyst for coal gasification and its catalytic behaviors were preferentially investigated. The results show that red mud has well-developed pore structures. A variety of catalytic species were found in it and more active sites were formed, consequently resulting in outstanding catalytic ability. Gasification temperature, O/C ratio, and steam flow rate are suggested to be key points influencing the gasification process. Under the same conditions (950 °C, O/C ratio: 3, and steam flow: 0.05 mL/min), carbon conversion, syngas selectivity, and syngas yield of coal gasification catalyzed by red mud reached up to 83.7 %, 88.6 %, and 119.0 mol/g, respectively, which were enhanced by 21.0 %, 22.5 %, and 2.4 % compared with that using pure Fe2O3. XRD and XPS analyses proved that in the early reduction process, the lattice oxygen gradually dissociated from inside of Fe2O3 crystals and migrated to the outside surface to react with char and reducing gases, leading to the formation of Fe3O4 and Fe. Subsequently, with continuous addition of steam, Fe was oxidized to regenerate Fe3O4 and the oxidation–reduction performance of Fe was hence improved.

The process and mechanism of coke gasification dissolution loss in hydrogen-rich blast furnace

Blast furnace (BF) hydrogen-rich smelting has become an important way for low-carbon ironmaking. The coke gasification dissolution loss will be accelerated by H2O generated through hydrogen reduction, which is the fundamental reason for the limited injection rate of hydrogen-rich gas in BF. The gasification dissolution loss experiments of coke were carried out under different conditions. Experimental results indicate that: The pore size of coke containing H2O is larger under the same gasification time. The quantitative relationship between pore size and gasification time, flow rate of H2O is obtained. The pore wall around the inner hole will gradually be eroded, the pore wall gradually dissolves along the edge of the inner hole. The connectivity between two pores starts from the deep layers of the pores, the pore walls in the deep layers of pores are first connected. The carbon layer spacing slightly decreases with gasification time, which indicates that the microcrystalline cells inside the coke have contracted in the vertical direction. The carbon layer stacking height shows an overall upward trend with the increase of temperature and gasification time, and it will reach a maximum value for a certain temperature. The carbon layer diameter increases with the prolongation of gasification time, the aromatic carbon layers continue to grow as gasification progresses. The dynamic model of H2O diffusion is established, the effective internal diffusion coefficients of H2O under different conditions are calculated, the diffusion ability of H2O is stronger than that of CO2. The mechanism of H2O dissolution loss of coke based on surface active sites is summarized, whether the gasification dissolution loss reaction can occur depends on whether there are active sites on the adsorbed surface. The competitive gasification always occurs vigorously at active sites, the gasification reaction between H2O and C is easier and the reaction rate is higher.