Role of iron ore in enhancing gasification of iron coke:Structural evolution,influence mechanism and kinetic analysis

The utilization of iron coke provides a green pathway for low-carbon ironmaking.To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification,the effect of iron ore on the microstructure of iron coke was investigated.Furthermore,a comparative study of the gasification reactions between iron coke and coke was conducted through non-isothermal thermogravimetric method.The findings indicate that compared to coke,iron coke exhibits an augmentation in micropores and specific surface area,and the micropores further extend and interconnect.This provides more adsorption sites for CO_(2) molecules during the gasification process,resulting in a reduction in the initial gasification temperature of iron coke.Accelerating the heating rate in non-isothermal gasification can enhance the reactivity of iron coke.The metallic iron reduced from iron ore is embedded in the carbon matrix,reducing the orderliness of the carbon structure,which is primarily responsible for the heightened reactivity of the carbon atoms.The kinetic study indicates that the random pore model can effectively represent the gasification process of iron coke due to its rich pore structure.Moreover,as the proportion of iron ore increases,the activation energy for the carbon gasification gradually decreases,from 246.2 kJ/mol for coke to 192.5 kJ/mol for iron coke 15wt%.

Structural properties of residual carbon in coal gasification fine slag and their influence on flotation separation and resource utilization:A review

Coal gasification fine slag(FS)is a typical solid waste generated in coal gasification.Its current disposal methods of stockpil-ing and landfilling have caused serious soil and ecological hazards.Separation recovery and the high-value utilization of residual carbon(RC)in FS are the keys to realizing the win-win situation of the coal chemical industry in terms of economic and environmental benefits.The structural properties,such as pore,surface functional group,and microcrystalline structures,of RC in FS(FS-RC)not only affect the flotation recovery efficiency of FS-RC but also form the basis for the high-value utilization of FS-RC.In this paper,the characteristics of FS-RC in terms of pore structure,surface functional groups,and microcrystalline structure are sorted out in accordance with gasification type and FS particle size.The reasons for the formation of the special structural properties of FS-RC are analyzed,and their influence on the flotation separation and high-value utilization of FS-RC is summarized.Separation methods based on the pore structural characterist-ics of FS-RC,such as ultrasonic pretreatment-pore-blocking flotation and pore breaking-flocculation flotation,are proposed to be the key development technologies for improving FS-RC recovery in the future.The design of low-cost,low-dose collectors containing polar bonds based on the surface and microcrystalline structures of FS-RC is proposed to be an important breakthrough point for strengthening the flotation efficiency of FS-RC in the future.The high-value utilization of FS should be based on the physicochemical structural proper-ties of FS-RC and should focus on the environmental impact of hazardous elements and the recyclability of chemical waste liquid to es-tablish an environmentally friendly utilization method.This review is of great theoretical importance for the comprehensive understand-ing of the unique structural properties of FS-RC,the breakthrough of the technological bottleneck in the efficient flotation separation of FS,and the expansion of the field of the high value-added utilization of FS-RC.

Agglomeration of coal and polyethylene mixtures during fixed‑bed co‑gasification

The article presents the results of experimental studies on the gasification of mixtures of brown coal and polyethylene(up to 20 wt%fraction)in a laboratory reactor.The work aims to study the agglomeration process during the heating and oxidation of the mixtures.The measurement results(gas composition,pressure drop)provide indirect information on the dynamics of thermal decomposition and structural changes in the fuel bed.We have shown that the interaction between polyethylene and a coal surface leads to the formation of dense agglomerates,in which the molten polymer acts as a binder.Clinkers form as a result of interfacial interactions between components and filtration flow rearranging.The hydrogen/carbon ratio in the solid residue of coal-polyethylene co-gasification increases from 0.07–0.2 to 1.11,indicating the formation of stable hydrocarbon compounds on the carbon surface.The conducted research makes it possible to identify possible interactions between chemical reactions and transfer processes that lead to agglomeration in mixtures of coal with polyethylene.

Upcycling municipal solid waste to sustainable hydrogen via two-stage gasification-reforming

As global municipal solid waste(MSW)quantities continue to escalate,serious socio-environmental challenges arise,necessitating innovative solutions.Waste-to-hydrogen(WTH)via two-stage gasification-reforming(TSGR)presents an emergent technology for MSW upcycling,offering to ease waste management burdens and bolster the burgeoning hydrogen economy.Despite early initiatives to advance TSGR technology,a cohesive and critical analysis of cutting-edge knowledge and strategies to enhance hydrogen production remains lacking.This review aggregates literature on MSW upcycling to hydrogen via TSGR,with a focus on optimizing process control and catalytic efficiency.It underscores technological avenues to augment hydrogen output,curtail catalyst costs,and refine system performance.Particularly,the review illuminates the potential for integrating chemical and calcium looping into TSGR processes,identifying opportunities,and pinpointing challenges.The review concludes with a summary of the current state of techno-economic analysis for this technology,presenting outstanding challenges and future research directions,with the ultimate goal of transitioning WTH from theoretical to practical application.

Multiscale analysis of fine slag from pulverized coal gasification in entrained-flow bed

Fine slag(FS)is an unavoidable by-product of coal gasification.FS,which is a simple heap of solid waste left in the open air,easily causes environmental pollution and has a low resource utilization rate,thereby restricting the development of energy-saving coal gasification technologies.The multiscale analysis of FS performed in this study indicates typical grain size distribution,composition,crystalline structure,and chemical bonding characteristics.The FS primarily contained inorganic and carbon components(dry bases)and exhibited a"three-peak distribution"of the grain size and regular spheroidal as well as irregular shapes.The irregular particles were mainly adsorbed onto the structure and had a dense distribution and multiple pores and folds.The carbon constituents were primarily amorphous in structure,with a certain degree of order and active sites.C 1s XPS spectrum indicated the presence of C–C and C–H bonds and numerous aromatic structures.The inorganic components,constituting 90%of the total sample,were primarily silicon,aluminum,iron,and calcium.The inorganic components contained Si–O-Si,Si–O–Al,Si–O,SO_(4)^(2−),and Fe–O bonds.Fe 2p XPS spectrum could be deconvoluted into Fe 2p_(1/2) and Fe 2p_(3/2) peaks and satellite peaks,while Fe existed mainly in the form of Fe(III).The findings of this study will be beneficial in resource utilization and formation mechanism of fine slag in future.

A critical review on direct catalytic hydrogasification of coal into CH_(4):catalysis process configurations,evaluations,and prospects

Coal catalytic hydrogasification(CCHG)is a straightforward approach for producing CH_(4),which shows advantages over the mature coal-to-CH_(4) technologies from the perspectives of CH_(4) yield,thermal efficiency,and CO_(2) emission.The core of CCHG is to make carbon in coal convert into CH_(4) efficiently with a catalyst.In the past decades,intensive research has been devoted to catalytic hydrogasification of model carbon(pitch coke,activated carbon,coal char).However,the chemical process of CCHG is still not well understood because the coal structure is more complicated,and CCHG is a combination of coal catalytic hydropyrolysis and coal char catalytic hydrogasification.This review seeks to shed light on the catalytic process of raw coal during CCHG.The configuration of suitable catalysts,operating conditions,and feedstocks for tailoring CH_(4) formation were identified,and the underlying mechanisms were elucidated.Based on these results,the CCHG process was evaluated,emphasizing pollutant emissions,energy efficiency,and reactor design.Furthermore,the opportunities and strategic approaches for CCHG under the restraint of carbon neutrality were highlighted by considering the penetration of“green”H2,biomass,and CO_(2) into CCHG.Preliminary investigations from our laboratories demonstrated that the integrated CCHG and biomass/CO_(2) hydrogenation process could perform as an emerging pathway for boosting CH_(4) production by consuming fewer fossil fuels,fulfilling the context of green manufacturing.This work not only provides systematic knowledge of CCHG but also helps to guide the efficient hydrogenation of other carbonaceous resources such as biomass,CO_(2),and coal-derived wastes.

A Gasification Technology to Combine Oil Sludge with Coal-Water Slurry:CFD Analysis and Performance Determination

The development of more environment-friendly ways to dispose of oil sludge is currently regarded as a hot topic.In this context,gasification technologies are generally seen as a promising way to combine oil sludge with coal–water slurry(CWS)and generate resourceful fuel.In this study,a novel five-nozzle gasifier reactor was analyzed by means of a CFD(Computational fluid dynamic)method.Among several influential factors,special attention was paid to the height-to-diameter ratio of the gasifier and the mixing ratio of oil sludge,which are known to have a significant impact on the flow field,temperature distribution and gasifier performances.According to the numerical results,the optimal height-to-diameter ratio and oil mixing ratio are about 2.4:1 and 20%,respectively.Furthermore,the carbon conversion rate can become as high as 98.55%with the hydrolysis rate reaching a value of 53.88%.The consumption of raw coal and oxygen is generally reduced,while the effective gas production is increased to 50.93 mol/%.

Effective separation of coal gasification fine slag: Role of classification and ultrasonication in enhancing flotation

Effective separation of residual carbon and ash is the basis for the resource utilization of coal gasification fine slag(CGFS).The conventional flotation process of CGFS has the bottlenecks of low carbon recovery and high collector dosage.In order to address these issues,CGFS sample taken from Shaanxi,China was used as the study object in this paper.A new process of size classification-fine grain ultrasonic pretreatment flotation(SC-FGUF)was proposed and its separation effect was compared with that of wholegrain flotation(WGF)as well as size classification-fine grain flotation(SC-FGF).The mechanism of its enhanced separation effect was revealed through flotation kinetic fitting,flotation flow foam layer stability,particle size composition,surface morphology,pore structure,and surface chemical property analysis.The results showed that compared with WGF,pre-classification could reduce the collector dosage by 84.09%and the combination of pre-classification and ultrasonic pretreatment could increase the combustible recovery by 17.29%and up to 93.46%.The SC-FGUF process allows the ineffective adsorption of coarse residual carbon to collector during flotation stage to be reduced by pre-classification,and the tightly embedded state of fine CGFS particles is disrupted and surface oxidizing functional group occupancy was reduced by ultrasonic pretreatment,thus carbon and ash is easier to be separated in the flotation process.In addition,some of the residual carbon particles were broken down to smaller sizes in the ultrasonic pretreatment,which led to an increase in the stability of flotation flow foam layer and a decrease in the probability of detachment of residual carbon particles from the bubbles.Therefore,SCFGUF could increase the residual carbon recovery and reduce the flotation collector dosage,which is an innovative method for carbon-ash separation of CGFS with good application prospect.

Experimental study on the activation of coal gasification fly ash from industrial CFB gasifiers

Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environment.To realize the application of CGFA as a precursor of porous carbon materials,the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed.Then,the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor.Finally,the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig,and its advantages are highlighted.The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%,an ultrafine particle size(d50:16.3–26.1 μm),and a relatively developed pore structure(specific surface area SSA:139.29–551.97 m^(2)·g^(-1)).The proportion of micropores in CGFA increases gradually with the coal rank.Steam activation experiments show that the pore development of CGFA mainly includes three stages:initial pore development,dynamic equilibrium between micropores and mesopores and pore collapse.The SSA of lignite fly ash(LFA),subbituminous fly ash(SBFA)and anthracite fly ash(AFA)is maximally increased by 105%,13%and 72%after steam activation;the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA>LFA>AFA.As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19,the carbon conversion ratio increases from 14.4%to 26.8%and the cold gas efficiency increases from 6.8%to 10.2%.The SSA of LFA increases by up to 53.9%during the fluidization activation process,which is mainly due to the mesoporous development.Relative to steam activation in a tube furnace reactor,fluidization activation takes an extremely short time(seconds)to achieve the same activation effect.It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35%to create pores in the initial development stage.

Advancements in biomass gasification research utilizing iron-based oxygen carriers in chemical looping:A review

Biomass,recognized as renewable green coal,is pivotal for energy conservation,emission reduction,and dualcarbon objectives.Chemical looping gasification,an innovative technology,aims to enhance biomass utilization efficiency.Using metal oxides as oxygen carriers regulates the oxygen-to-fuel ratio to optimize synthesis product yields.This review examines various oxygen carriers and their roles in chemical looping biomass gasification,including natural iron ore types,industrial by-products,cerium oxide-based carriers,and core-shell structures.The catalytic,kinetic,and phase transfer properties of iron-based oxygen carriers are analyzed,and their catalytic cracking capabilities are explored.Molecular interactions are elucidated and system performance is optimized by providing insights into chemical looping reaction mechanisms and strategies to improve carrier efficiency,along with discussing advanced techniques such as density functional theory(DFT)and reactive force field(ReaxFF)molecular dynamics(MD).This paper serves as a roadmap for advancing chemical looping gasification towards sustainable energy goals.

Mechanism of K/Ni Etching for Biochar-H_(2)O Gasification

Biomass-H_(2)O gasification is a complex thermochemical reaction,including three processes of volatile removal:homogeneous/heterogeneous reforming,biochar gasification and etching.The rate-determining step is biochar-H_(2)O gasification and etching so the DFT is carried out to see the catalytic role of different metal elements(K/Ni)in the zigzag biochar model.The calculation results show that the gasification of biochar-H_(2)O needs to go through four processes:dissociative adsorption of water,hydrogen transfer(hydrogen desorption,hydrogen atom transfer),carbon dissolution and CO desorption.The energy barrier indicated that the most significant step in reducing the activation energy of K is reflected in the hydrogen transfer step,which is reduced from 374.14 kJ/mol to 152.41 kJ/mol;the catalytic effect of Ni is mainly reflected in the carbon dissolution step,which is reduced from 122.34 kJ/mol to 84.8 kJ/mol.The existence of K causes the edge to have a stronger attraction to H and does not destroy theπbonds of biochar molecules.The destruction ofπbonds is mainly due to the role of H free radicals,while the destruction ofπbonds will lead to easier C-C bond rupture.Ni shows a strong attraction to O in OH,which forms strong Ni-O chemical bonds.Ni can also destroy the aromatic structure directly,making the gasification easier to happen.This study explored the catalytic mechanism of K/Ni on the biochar-H_(2)O gasification at the molecular level and looked forward to the potential synergy of K/Ni,laying a foundation for experimental research and catalyst design.

Numerical Simulation of Pressurized Spouted Fluidized Bed for Coal Semi-Gasification

Numerical simulation study is conducted for a pressurized spouted fluidized bed coal carbonizer, in which hydrodynamics of pressurized spouted fluidized bed, chemical reactions and energy balance are taken into account. The effect of operating conditions such as bed pressure, air and steam mass flow ratio, temperature on product compositions in the bed is investigated. According to the calculated results, bed pressure and bed temperature have the key effects on coal semi gasification.

Numerical simulation on the fluidized bed gasification and CaO dechlorination of refuse derived fuel

A three-dimensional numerical model verified by previous experimental data is developed to simulate the fluidized bed gasification of refuse derived fuel （RDF）. The CaO dechlorination model obtained by the thermal gravity analysis （TGA） is coupled to investigate the process of CaO dechlorination. An Eulerian-Eulerian method is adopted to simulate the gas-solid flow and self-developed chemical reaction modules are used to simulate chemical reactions. Flow patterns, gasification results and dechlorination efficiency are obtained by numerical simulation. Meanwhile, simulations are performed to evaluate the effects of Ca/Cl molar ratio and temperature on dechlorination efficiency. The simulation results show that the presence of bubbles in the gasifier lowers the CaO dechlorination efficiency. Increasing the Ca/Cl molar ratio can enhance the dechlorination efficiency. However, with the temperature increasing, the dechlorination efficiency increases initially and then decreases. The optimal Ca/Cl molar ratio is in the range of 3. 0 to 3. 5 and the optimal temperature is 923K.

Thermal performance analysis of advanced partial gasification combined cycle

This paper presents the thermodynamic performance analysis and comparison of four kinds of advanced pressurized fluidized bed combustion combined cycle (APFBC-CC) system schemes, two based on pressurized fluidized bed (PFB) combustion and the other two based on atmospheric circulating fluidized bed (CFB) combustion. The results show that the first scheme avoids high temperature gas filter, but has the lower cycle efficiency and syngas heating value. The second scheme can gain the highest cycle efficiency, however it is better to now lower the filter operating temperature. The third and fourth schemes, based on CFB, have lower efficiencies than the second one. But the fourth one, with preheating air/steam for gasification, can obtain the highest heating value of syngas and gain higher efficiency than the third one.

Gasification kinetics of bulk coke in the CO2/CO/H2/H2O/N2 system simulating the atmosphere in the industrial blast furnace

The gasification characteristics and gasification kinetics of coke in complex CO2/CO/H2/H2O/N2 systems similar to the gas system of industrial blast furnace (BF) were studied by the method of isothermal thermogravimetric analysis. The experimental gas compositions and the corresponding temperature were chosen according to data reported for industrial BFs. The gasification behavior of coke was described by the Random Pore Model (RPM), Volumetric Model (VM), and Grain Model (GM). Results showed that the gas composition of the coke gasification zone in BF changes slightly and that the temperature is the most important factor affecting coke gasification. The lower activation energy of coke samples (Coke Reaction Index (CRI)>50) is due to the high Fe2O3 in the ash, lower degree of graphitization, and larger pore structure. In addition, the choice of kinetic model does not differ substantially in describing the gasification mechanism of coke in a BF.

Hydrogen generation from polyvinyl alcohol-contaminated wastewater by a process of supercritical water gasification

Gasification of polyvinyl alcohol （PVA）-contaminated wastewater in supercritical water （SCW） was investigated in a continuous flow reactor at 723-873 K, 20-36 MPa and residence time of 20-450 s. The gas and liquid products were analyzed by GC/TCD, and TOC analyzer. The main gas products were H2, CH4, CO and CO2. Pressure change had no significant influence on gasification efficiency. Higher temperature and longer residence time enhanced gasification efficiency, and lower temperature favored the production of H2. The effects of KOH catalyst on gas product composition were studied, and gasification efficiency were analyzed. The TOC removal efficiency （RTOC）, carbon gasification ratio （RCG） and hydrogen gasification ratio （RHG） were up to 96.00%, 95.92% and 126.40% at 873 K and 60 s, respectively, which suggests PVA can be completely gasified in SCW. The results indicate supercritical water gasification for hydrogen generation is a promising process for the treatment ofPVA wastewater.

Effect of CO_2 and H_2O on gasification dissolution and deep reaction of coke

To more comprehensively analyze the effect of CO_2 and H_2O on the gasification dissolution reaction and deep reaction of coke, the reactions of coke with CO_2 and H_2O using high temperature gas–solid reaction apparatus over the range of 950–1250°C were studied, and the thermodynamic and kinetic analyses were also performed. The results show that the average reaction rate of coke with H_2O is about 1.3–6.5 times that with CO_2 in the experimental temperature range. At the same temperature, the endothermic effect of coke with H_2O is less than that with CO_2. As the pressure increases, the gasification dissolution reaction of coke shifts to the high-temperature zone. The use of hydrogen-rich fuels is conducive to decreasing the energy consumed inside the blast furnace, and a corresponding high-pressure operation will help to suppress the gasification dissolution reaction of coke and reduce its deterioration. The interfacial chemical reaction is the main rate-limiting step over the experimental temperature range. The activation energies of the reaction of coke with CO_2 and H_2O are 169.23 kJ ·mol-1 and 87.13 kJ·mol^(-1), respectively. Additionally, water vapor is more likely to diffuse into the coke interior at a lower temperature and thus aggravates the deterioration of coke in the middle upper part of blast furnace.

Biomass gasification technology:The state of the art overview

In the last decades the interest in the biomass gasification process has increased due to the growing attention to the use of sustainable energy. Biomass is a renewable energy source and represents a valid alternative to fossil fuels. Gasification is the thermochemical conversion of an organic material into a valuable gaseous product, called syngas, and a solid product, called char. The biomass gasification represents an efficient process for the production of power and heat and the production of hydrogen and second-generation biofuels.This paper deals with the state of the art biomass gasification technologies, evaluating advantages and disadvantages, the potential use of the syngas and the application of the biomass gasification. Syngas cleaning though fundamental to evaluate any gasification technology is not included in this paper since; in the authors＇ opinion, a dedicated review is necessary.

Comparison of kinetic models for isothermal CO_2 gasification of coal char–biomass char blended char

This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, and 1000℃ under CO2. With an increase in BC blending ra- tio, there were an increase in gasification rate and a shortening of gasification time. This could be attributed to the high specific surface area of BC and the high uniformity of carbon structures in CC when compared to those in BC. Three representative gas-solid kinetic models, namely, the volumetric model （VM）, grain model （GM）, and random pore model （RPM）, were applied to describe the reaction behavior of the char. Among them, the RPM model was considered the best model to describe the reactivity of the char gasification reaction. The activa- tion energy of BC and CC isothermal gasification as determined using the RPM model was found to be 126.7 kJ/mol and 210.2 kJ/mol, re- spectively. The activation energy was minimum （123.1 kJ/mol） for the BC blending ratio of 75%. Synergistic effect manifested at all mass ratios of the blended char, which increased with the gasification temperature.

Environmental benefits of underground coal gasification

Environmental benefits of underground coal gasification are evaluated. The results showed that through underground coal gasification, gangue discharge is eliminated, sulfur emission is reduced, and the amount of ash, mercury, and tar discharge are decreased. Moreover, effect of underground gasification on underground water is analyzed and CO 2 disposal method is put forward.