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The integrated gasification combined cycle (IGCC) technology is renowned for its high energy utilization efficiency. However, the exhaust emissions from an IGCC power plant still contain a significant amount of carbon dioxide (CO 2), which has a detrimental impact on the environment. Therefore, it is necessary to capture CO 2 and reduce its emissions in IGCC systems. This study develops an integrated model for the process simulation of a 250 MW IGCC system with an advanced CO 2 capture technology. After establishing the model, sensitivity analysis is conducted to obtain the optimal parameters for methyldiethanolamine (MDEA) absorption. The operational parameters of the coal gasification unit are optimized to mitigate the elevated energy consumption. The results indicate that the original gasification system has an energy consumption rate of 57.6 %, whereas the optimized system achieves a significant reduction to 42.8 %, resulting in a notable improvement in the energy efficiency of the gasification unit by 10.2 %. The exergy efficiency of the gasification process is improved by 6.4 %. This research paradigm showcases the opportunity to significantly enhance the sustainability and economic feasibility of IGCC technology. [Display omitted] • An integrated model for CO 2 capturing using MDEA absorption technology was developed. • Sensitivity analysis was conducted to determine the optimal parameters for CO 2 capture. • The main operating parameters of the gasification unit in the IGCC system were optimized. • A notable improvement in energy efficiency of gasification unit by 10.2 % after optimization. • The exergy efficiency of gasification process is improved by 6.4 % after optimization. [ABSTRACT FROM AUTHOR]

The Allam cycle is a novel oxy-fuel power system that has the potential to achieve efficient negative carbon emissions. Compressed carbon energy storage (CCES) technology could improve the stability of power plants. A biomass gasification Allam cycle combined with the CCES system is proposed and evaluated in this research. The energy efficiency of the Allam-CCES cycle during the charge and discharge time is 36.43 % and 39.45 %, respectively. The round trip efficiency (RTE) of the CCES system is 62.04 %. The exergy destruction of the Allam-CCES system is 317.02 MW. Economic analysis shows that the proposed system has a net present value of 447347.97 k$, implying benefits in economic performance. The total cost rate of the Allam-CCES system is 6959.63 $/h. The influence of the storage pressure on the CCES system is evaluated. The RTE drops from 64.55 % to 61.12 % as the high storage pressure rises. The variation of RTE has a crest when the low storage pressure is near critical pressure. The highest RTE is 90.71 % in the research range of low storage pressure. This paper could provide information on biomass gasification Allam cycle integrated with CCES technology, and offer insights to realize efficient and economic carbon emissions reduction. • Compressed CO 2 energy storage is integrated with biomass gasification Allam cycle. • Thermodynamic and economic performance of the system is assessed. • The effects of energy storage pressure on the system performance are discussed. • The power efficiency during the charge and discharge time is 36.43 % and 39.45 %. • The net present value of the system is 447347.97 k$. [ABSTRACT FROM AUTHOR]

Based on the compositional properties of the syngas produced by supercritical water gasification (SCWG) of coal, a CO 2 near-zero-emission power generation system with integrated supercritical water gasification of coal and solid oxide fuel cell (SOFC) is proposed. The chemical energy of the syngas is cascade utilized by the SOFC and gas turbine to generate electricity. The exhaust gas from the anode of SOFC is combusted with pure oxygen in the combustor of the gas turbine to produce high-temperature flue gas which is consisted of CO 2 and H 2 O. The CO 2 can be easily separated and captured from the flue gas. The heat for preheating the feed water of the gasifier and driving the gasification reactions is provided by the exhausts of the combustor, SOFC cathode, and the exothermic heat produced through electrochemical reaction in the SOFC. The influences of key parameters such as the temperature of the SOFC and fuel utilization rate on the system performance are investigated, and the distribution law and transfer conversion mechanism of the energy and exergy are revealed. When the temperature of the SOFC is 1000 °C, and the fuel utilization rate is 83 %, the power efficiency of the system is 43.65 % and the exergy efficiency is 42.61 %. In addition, the CO 2 capture rate is close to 100 %. Economic analysis is also performed. The levelized cost of electricity (LCOE) of the proposed power system is 0.272¥/kWh. CO 2 near-zero-emission is realized through combining the electrochemical reaction within the SOFC and the oxy-combustion in the combustor of the gas turbine, which is of great significance to achieve the carbon peak and carbon neutrality goals. • A novel CO 2 near-zero-emission power system with integrated SCWG of coal and SOFC is proposed. • Energy, exergy and economic analyses are conducted out. • Maximum power generation efficiency of 43.65 % is obtained. • The levelized cost of electricity of the novel power system is 0.272 ¥/kWh. [ABSTRACT FROM AUTHOR]

Bedding structures are commonly present in the underground coal mine pillar rock mass, posing a certain threat to its stability. In order to gain a deeper understanding of the damage, destruction, and energy conversion of bedding coal, uniaxial compression experiments were conducted on bedding coal samples. The research results reveal that the compressive strength of coal is highest when the bedding dip angle is 0° (28.74 MPa), followed by 30° and 90° (15.03 and 14.02 MPa), and lowest at 60° (10.03 MPa). The damage evolution curve of coal at a bedding dip angle of 60° exhibits an early sharp increase, indicating that macroscopic damage is easily induced along the bedding planes under this condition. As the bedding dip angle increases from 0° to 90°, the degree of damage to coal under energy drive exhibits a pattern of difficulty-ease-difficulty. When the bedding dip angle is 0°, the coal sample fractures steadily as cracks expand. At 30°, the failure process involves a gradual and steady expansion of cracks followed by an unstable extension. At 60° and 90°, the fractures result in sudden and unstable damage. Furthermore, this study explores the inherent mechanisms of anisotropy and the evolution models of damage in bedding coal. [Display omitted] • The inherent mechanisms of the anisotropy of damage in bedding coal was discussed. • The applicability of the uniaxial damage evolution model was discussed. • The mechanism of the effect of laminations on mechanical properties was studied. [ABSTRACT FROM AUTHOR]

China generates substantial quantities of gasified fine ash (GFA) annually through entrained flow bed coal gasification processes. These GFAs are laden with significant amounts of poorly reactive carbon and abundant ash resources, including silica, aluminum. Typically GFA represent not only a gross squandering of resources but also a potential source of environmental contamination. In order to use both ash and carbon of GFA, our team has developed the thermal modification -melting combustion method. The study conducted thermal modification-melting combustion experiments of GFA with auxiliary heating fuel and varying moisture content on a pilot-scale experimental platform. The aim was to ascertain the influence of operating conditions on the physical and chemical properties of GFA fuel, as well as the carbon conversion rate of GFA and the potential for reusing ash after melting combustion in the entire system. The results indicate that an increase in the moisture content of GFA allows the thermally modified fine ash (MFA) to possess smaller particle sizes and more reactive sites in carbon structures, along with higher combustible gas yield and calorific value. Post-melting combustion, the residual carbon conversion rate in GFA surpassed 96.88 %, indicative of a high recovery potential. Moreover, the ash slag, rich in inorganic non-metallic glassy phases, emerged as a promising candidate for material reuse and application. • Thermal modification and melting combustion of GFA on a pilot scale. • Auxiliary fuel and moisture's impact on melting combustion were studied. • The physical and chemical properties of MFA under different conditions. • Carbon conversion and ash utilization potential were analyzed. [ABSTRACT FROM AUTHOR]

Petroleum coke, a byproduct of petroleum refining, is considered a potential alternative fuel owing to its low ash content and high calorific value. This study aims to enhance our understanding of the pyrolysis process and its potential applications by investigating the effect of pressure on the pyrolysis of petroleum coke, focusing on changes in its syngas composition and char structure. High-pressure pyrolysis was employed to explore structural changes, decomposition pathways, and gas production. High pressures increase the residence time and promote secondary pyrolysis, leading to the increased production of hydrogen. Also, high pressure can promote gasification reactions such as methanation. The influence of pressure on the chemical and physical structures of the produced char was also observed. Higher pressures resulted in more active secondary pyrolysis, causing a decrease in the aromatic groups and an increase in the aliphatic and oxygen-containing groups in the char. The surface area and porosity of char increased at higher pressures, enhancing its reactivity and gasification rate. Overall, this study provides valuable insights into the effects of pressure on petroleum coke pyrolysis, shedding light on its potential as an alternative energy resource and highlighting changes in gas composition and char structure under various pressure conditions. • High-pressure pyrolysis was employed to better understand the pyrolysis process. • High pressures suppressed primary pyrolysis and promoted secondary pyrolysis. • H 2 was converted to CH 4 through promoted methanation reactions at high pressure. • Pressurized char can be advantageous for ironmaking and gasification reactivity. [ABSTRACT FROM AUTHOR]

The in situ transformation of the carbohydrate substances is presented in the context of methane (CH 4) formation by methanogens. In situ coal conversion methods have been characterized due to the beneficial effect of unconventional coal mining. The research was carried out on less mature coals, with a lower carbonisation degree of organic matter, because they are more effective in conversion to bioenergy gas, which can be used for all pro-ecological activities. The original concept of experimental research was presented by combining the properties of a polydisperse substrate, which is pig slurry, and used for brown coal biogasification (anaerobic digestion) in two brown coal bed systems. For this purpose, a laboratory monosubstrate reactor for the fermentation of pig slurry in a lignite bed was developed. The mainaim of the research presented in the article is to assess the amount of agricultural biogas produced in the process of mesophilic methane fermentation with the use of a polydisperse substrate using a brown coal bed placed in a fermentor. The partial goals are: - presentation of analogies of techniques and methods of underground coal gasification (UCG) to biogasification of brown coal; - a set of correlation equations for calculating flow resistance coefficients through granular porous structures; - comparison of experimental values of flow resistance with calculations according to various models. The justification of the main goal and partial goals refers to the development of a new technique and method of obtaining biogas, taking into account the Reynolds number and the own model of the gas flow resistance coefficient. The novelty of the article are: developed own model for determining the correlation dependence of the flow resistance coefficient as a function of the Reynolds number, - the results of research that indicate the practical use of pig slurry in a lignite bed for which intensive biogas production takes place at lignite. - minor deposit in relation to lignite - flat fragments of a deposit. The inhibition phenomenon and the dynamics of the process during the production of biogas in the brown coal bed were also observed in the research. An additional advantage of the innovation in the article is the combination of a polydisperse substrate with a porous bed - the simplicity of the research is the production of biogas on a lignite bed, which is a medium for biogas-producing bacteria. It has been shown that: - the developed lignite biogasification system with the participation of a polydisperse substrate in the fermenter (laboratory vessel) ensures the production of biogas in the absence of thermal insulation of the fermenter; - for a lignite deposit, the biogas stream is stable with increasing temperature; while above the temperature of 38 °C–42 °C, the biogas stream is characterized by a downward trend. Comparing the flows of the biogas stream, the following can be observed: - the intensity of biogas production for lignite (smaller bed), there is a greater phase exchange, because the bed layout provides more space for the adhesion of methanogenic microorganisms, - in turn, in the case of lignite (flat fragments of the deposit), there is less phase exchange, i.e. less biogas production. The performed rheological tests of pig slurry proved the foaming properties of the sub-strate at 25 °C and 500 rpm for a kinematic viscosity of 27.5 mPa. Characteristic foaming properties are manifested by the polydisperse system, which is pig slurry. • Experimental research on the use of polydisperse substrate (pig slurry) for biogas production using a lignite seam. • Immobilization of brown coal - a fine deposit, compared to brown coal - flat fragments of the deposit. • Biogas production intensity for brown coal. • Flow resistance coefficient model – taking into account the experimental constant of 142. • Monosubstrate reactor for fermentation of pig slurry in a lignite bed. [ABSTRACT FROM AUTHOR]

Underground coal gasification (UCG) is a process that produces combustible gas by the in-situ gasification of coal seams. For a steady and efficient gasification project, the ignition of coal seam is a prerequisite. The heating method and reacting process of coal seam play an essential role to the ignition. A coal seam ignition model coupled with heptane combustion was created to simulate the deep UCG ignition stage employing the chemical ignition method. A 1700 K heptane jet flame and a U-shaped pyrolysis gas flame formed the heat source. The flame temperature of pyrolysis gas was around 1300 K. The effective heating length of the flame increased with the heating time, which reached 600 mm at 400 s. The coal seam reaction process was divided into four stages: (1) heptane flame stabilization, (2) coal seam heating, (3) pyrolysis gas release, and (4) pyrolysis gas flame stabilization. It was the third stage when the coal seam ignited. The coal seam would ignite faster with a lower excess air coefficient, and the ignition time ranged from 225 to 275 s when the excess air coefficient was 1.39. The outlet carbon dioxide concentration increased by about 5 %–17 % when the coal seam ignited. • A coal seam ignition model coupled with heptane combustion was created. • The ignition process of a deep Underground coal gasification was simulated. • Coal seam reaction characteristics in four stages were explored. • The increase in outlet CO 2 can be used as an indication of coal seam ignition. [ABSTRACT FROM AUTHOR]

Generating clean, efficient, and low-carbon electricity from coal is imperative for limiting the global temperature rise to 1.5 °C. This study presents a near-zero-carbon-emission power generation system that utilizes staged coal gasification. The innovation of this system is the division of coal gasification into two stages: intermediate-temperature pyrolysis, followed by high-temperature gasification. This process begins with utilizing waste heat from the exhaust of a gas turbine to drive the partial gasification of coal during pyrolysis. The nongaseous products from this stage are then completely gasified in the gasifier, and chemical recuperation is performed, in which heat from the syngas at the gasifier's outlet preheats the reactants at the inlet and aids in reforming pyrolysis gas. For CO 2 capture, an oxyfuel combustion strategy is used. Our system produced net electricity and exergy efficiencies of 43.01 and 47.57 %, respectively, surpassing both pre-combustion CO 2 capture systems based on staged coal gasification (improvements of 3.04 and 5.37 %, respectively) and coal-water slurry gasification (improvements of 3.55 and 5.8 %, respectively). Moreover, the carbon emissions from our system are approximately 90 g/kWh lower than those from these systems. Thus, this study offers an environmentally sustainable approach to utilizing coal that may facilitate achieving global environmental goals. • Proposes a near-zero carbon emission coal-based power generation system. • Bifurcates coal gasification into intermediate-temp pyrolysis and high-temp gasification. • Employs oxyfuel combustion strategy for CO 2 capture. • Utilizes high-temperature sensible heat in syngas through chemical recuperation. • Achieves energy and exergy efficiencies of 43.01 and 47.57 %, both superior to the baseline systems. [ABSTRACT FROM AUTHOR]

To establish a sustainable energy system, it is essential to achieve low-carbon and clean utilization of coal. In this study, a novel hydrogen and power cogeneration system with full CO 2 capture that based on coal supercritical water gasification (SCWG) is proposed. Hydrogen is separated from syngas produced by coal SCWG, and the remaining combustible gas is burned to generate power. Moreover, supercritical CO 2 cycle is integrated within the cogeneration system to recover the waste heat with high exergy efficiency. Thermodynamic performances, effects of key operation parameters and off-design performances under part-load conditions of the cogeneration system are analyzed. Under the design condition, the cogeneration system produces 20.26 mol kg−1 hydrogen and generates 8746 kJ kg−1 net power, achieving the high energy efficiency and exergy efficiency of 54.77 % and 52.54 %. The exergy efficiency of cogeneration system can be enhanced by optimizing the operation parameters, which is increased by 0.42 %, 4.03 % and 1.10 % with the optimal coal water slurry concentration (17.5 %), higher gasification temperature (750 °C) and higher gas turbine inlet parameters (1500 °C/3 MPa), respectively. The cogeneration system performance decreases with the power load, and the exergy efficiency decreases by 9.61 % when the system power load reduces from 100 % to 30 %. • A novel hydrogen and power cogeneration system based on coal SCWG is proposed. • Exergy efficiency of the cogeneration system achieves 52.54 % with full CO 2 capture. • Effects of key operation parameters on the system performance are evaluated. • The system off-design performance under part-load conditions is analyzed. [ABSTRACT FROM AUTHOR]

With the development of polymer flooding technology, polymer-containing oily sludge (PCOS) has become a major pollutant on offshore oil platforms. Supercritical water gasification system is an efficient and pollution-free technology compared to conventional PCOS treatment. However, the system model for PCOS has not yet been established and the theoretical model for system optimization is insufficient. In this work, a novel auto-thermal system is established based on supercritical water gasification technology for the treatment of PCOS. Through the thermodynamic analysis, an optimization plan is concluded and used for the establishment of a modified system with Organic Rankine Cycle. Results show that the two-stage reactor reduces the gasification reaction temperature from 652 °C to 502 °C, and the Organic Rankine Cycle system using Isopropanol recover 9.1 % chemical exergy of feedstock with the optimal parameters (superheat, evaporation temperature and circulating pressure). The energy and exergy efficiency of the modified system has increased by 52.4 % and 42.4 % compared to the original system. Besides, a life cycle assessment is adopted for the environment analysis. The results show that the increasing gasification temperature and PCOS slurry concentration can reduce system unit exergy loss. Global Warming Potential reaching the minimum value of 26.1 at 65 wt%. • Two-stage gasification system of polymer-containing oily sludge was proposed. • Waste heat utilization system was simulated based on Organic Rankine Cycle. • Optimal parameters on exergy efficiency was obtained. • Life cycle assessment of sludge gasification was conducted. • Modified system reduced the gasification temperature of sludge. [ABSTRACT FROM AUTHOR]

Blast furnace slag, a main by-product of ironmaking process, contained high-quality sensible heat, accounting for almost 30 % of total energy consumption in iron and steel industry. This paper proposed CO 2 coal gasification method aimed at recovering waste heat from blast furnace slag. Based on Gibbs free energy minimization, influence of temperature, CO 2 /C, pressure and steam were investigated. Under optimal operating conditions at 1023–1198 K, CO 2 /C of 1.5–2.0 and atmospheric pressure, total amount of syngas was 2.78 kmol, with 67.1 % CO and 8.79 % H 2. Addition of steam could adjust compositions of syngas. H 2 /CO of syngas reached 1.0, 1.5 and 2.0 when H 2 O(g)/CO 2 were 1.45/0.55, 1.73/0.27 and 1.95/0.05, which could be used as organic raw materials for chemical industry. Meanwhile, energy and exergy efficiencies of coal gasification were found to be 63.84 % and 62.58 %, respectively, under optimal operating conditions. For different syngas products, when H 2 O(g)/CO 2 was 1.95/0.05, exergy loss was the lowest, with internal and external exergy loss amounting to 31.80 % and 2.16 % respectively. These works provided theoretical guidance on use of the coal gasification reaction for recovering waste heat from blast furnace slag and contributed to the achievement of the strategic goal of CO 2 energy saving and emission reduction. [Display omitted] • A novel resource utilization method of the blast furnace slag was proposed. • The optimal operation conditions for gasification reactions were determined. • The energy and exergy destruction and distribution of the technology were analyzed. • The energy and exergy efficiencies were 63.84 % and 62.58 %, respectively. • By adjusting the addition of steam, different synthesis gas products could be obtained. [ABSTRACT FROM AUTHOR]

Underground coal gasification (UCG) is a promising technology, which can convert deep coal seams into high calorific value gas products through in-situ controllable combustion, for the traditional coal mining technology. However, the structure of raw coal is dense, and it is difficult for the injected gasification agent to penetrate from the coal surface to the inside of coal in the gasification channel, which leads to worse gasification performance. Different from conventional straight flow injection, swirl flow injection is proposed to improve the effective contact between the gas and the coal surface to enhance the gasification reaction efficiency. In this work, various types of novel swirl nozzles were independently designed. The characteristics of gas production, temperature distribution and tar pollutant are studied with different swirl angles. As the swirl number increases from 0 to 1.41, there is a significant enhancement in the residence time of oxygen in the axial direction and a reduction of the mass transfer between oxygen and the coal wall in the radial direction. As the oxygen flow rate increases from 0.5 to 2 L/min, swirl flow injection exhibits stronger gasification performance than traditional straight flow injection, such as maximum gas calorific value and tar generation control capability. [Display omitted] • The swirl nozzles with different swirl numbers were independently designed. • The gasification performances under different swirl angles were studied. • Effect of oxygen flow rate on the optimum swirl angle was analyzed. [ABSTRACT FROM AUTHOR]

Disposal of coal gasification fine slag (CGFS) has caused environmental pollution and resource waste. Its decarbonization is the bottleneck of aluminum and silicon resource utilization. A fluidization-melting combustion system is proposed in this study to realize the decarbonization. The fluidized thermal modification and burnout characters of residual carbon in CGFS were investigated experimentally on a bench-scale test rig. A two-stage decarburization path of CGFS was concluded and verified. The fluidized modification of CGFS is first conducted to decrease the particle size and improve the specific surface area and combustion reactivity. So, the modified exposed carbon in CGFS rapidly burns in the melting furnace to generate the condition above the fluid temperature of minerals. Then the mineral shell of the amorphous mineral covered carbon in CGFS is molten and damaged, and the carbon appears and burns out. The decrease in the thermal modification temperature induced deceases in melting combustion temperature and decarbonization efficiency. Efficient decarbonization of CGFS produced by three different entrained bed gasifiers was realized by the fluidization-melting combustion, the decarburization efficiencies are all above 95% and the comprehensive carbon contents of ash and slag are all below 5%. • Treatment of gasification fine slag by a fluidization-melting combustion system. • A two-stage decarburization path of gasification fine slag is concluded. • The combustion reactivity is improved through the fluidized thermal modification. • Mineral shell is damaged and residual carbon burns out during melting combustion. • Efficient decarbonization of three kinds of gasification fine slag is verified. [ABSTRACT FROM AUTHOR]

Hydrogen metallurgy is an effective way to decarbonize the steel industry. In this study, a new system integrating biomass supercritical water gasification (SCWG) with hydrogen generation-shaft furnace-electric arc furnace (HSE) was proposed. The thermodynamic performance of SCWG-HSE system were analyzed and optimized. The results show that the gasification and energy efficiency of SCWG system increase with an increase in the gasification temperature. The carbon emission of the SCWG-HSE system are effectively reduced, and the product yield and energy efficiency of the system are improved by increasing gasification temperature and recovering furnace top gas. The energy and exergy efficiency of the SCWG-HSE system are 46.66% and 40.17%, respectively. The exergy destruction of SCWG gasifier and electric arc furnace are the major exergy damage sources of the SCWG-HSE system. The exergy efficiency of the ironmaking system reaches 51.60%, and the energy consumption and carbon emission per unit product are 18.49 GJ/t and 902.40 kg/t, respectively. Compared with the traditional Coking-Blast furnace ironmaking process, the energy consumption and carbon emission of this system are reduced by 7.32% and 40.84% respectively. This work is expected to open a new way for the application of biomass in the low-carbon steel industry. [Display omitted] • A steel making system of biomass SCWG coupled with DRI was proposed. • The energy and exergy efficiency of SCWG-HSE process is 46.66% and 40.17%. • The effect of gasification temperature on SCWG-ironmaking process was analyzed. • The CO 2 emission of the SCWG-Ironmaking route with CCS is 902.40 kg/t-iron. [ABSTRACT FROM AUTHOR]

The scale of pig breeding in China is the largest in the world, and the pollution problem of breeding wastewater is serious. Supercritical water gasification (SCWG) process is a clean and efficient treatment technology for breeding wastewater. This paper involved constructing the molecular model of the primary organic components in pig breeding wastewater. The effects of time, temperature and mass concentration, and the interactions of different components on the SCWG characteristics of pig breeding wastewater were studied by molecular dynamics (MD) simulation, and the decomposition process of lignin and lipid molecules in the SCWG process were analyzed, and the possible intermediates were explored. The results showed that the effect of parameters on carbon gasification efficiency (CE) and H 2 production follows the order of temperature > time > mass concentration. During the gasification of lignin and lipid molecules, the C–O–C bond was broken first, and the gasification rate of lignin molecules was slow due to the benzene ring. Interactions among different organic decompositions hindered the gasification process. This paper will provide theoretical guidance for the selection of operation parameters and the control of products in the actual pig breeding wastewater treatment process. • The MD model of wastewater containing complex organics was established. • The effects of key parameters on SCWG of pig breeding wastewater were studied. • The detailed SCWG mechanisms of pig breeding wastewater were analyzed. • The intermediate products from SCWG of pig breeding wastewater were explored. • The interaction mechanisms of different organics during SCWG were analyzed. [ABSTRACT FROM AUTHOR]

Utilizing renewable reservoirs as a primary source of energy in power systems significantly mitigates environmental concerns. This approach, coupled with the integration of various subsystems, yields multiple products, thereby enhancing economic benefits. This paper introduces an innovative multi-generation system based on a gasifier-fed solid oxide fuel cell. In this system, waste heat recovery is achieved through a bespoke transcritical CO 2 cycle, combined with a Kalina cycle and an organic Rankine cycle subsystem. Additionally, a proton membrane electrolyzer is employed to supply a reactor for ammonia production. A comprehensive analysis of this configuration is performed, employing thermodynamic, economic, and environmental assessment methodologies. Moreover, two multi-objective optimization strategies are implemented to determine the system's optimal operating conditions. The results demonstrate that the proposed system generates a net power output of 293.1 kW, provides cooling of 40.8 kW, produces hydrogen at a rate of 2.689 kg/h, and ammonia at a rate of 15.14 kg/h. The environmental and economic impacts of these products are quantified as an exergoenvironmental impact rate of 111.89 Pt/h and a cost rate of 11.77 $/h, resulting in an exergy efficiency of 27.59%. Furthermore, the system's financial feasibility is evident from its payback period of approximately 3.42 years and a net present value of 1.64 M$. The study also identifies that variations in the fuel cell's current density significantly influence the system's exergy performance and environmental footprint. • Design of a novel multi-generation based on the gasifier-SOFC integration. • Application of exergoenvironmental approach. • Producing 2.689 kg/h of hydrogen and 15.14 kg/h ammonia. • Assessing 27.59% exergy efficiency and 111.89 Pt/h exergoenvironmental impact rate. • Achieving a payback period of 3.42 years and 1.64 M$ net profit. [ABSTRACT FROM AUTHOR]

The storage of supercritical carbon dioxide in the coal underground gasification combustion cavity can not only reduce greenhouse gas emissions, help control global climate change, but also avoid potential geological hazards caused by the long-term existence of coal-burning holes. It is an important innovative development direction for the global coal industry. However, currently, there is insufficient examination of the practicality and hazards of UCG-CCS through industrial trials, which considerably restricts the spread and use of UCG-CCS. This study employs theoretical analysis and numerical simulation to examine the geological feasibility of UCG-CCS. It finds that the risk of carbon dioxide leakage in UCG-CCS is predominantly due to overlying rock fractures being diffused by the integrity of the cover layer and the parameters of the gasification furnace. It has also been found that the development height of cap rock fractures is closely related to CO 2 injection pressure and gasification furnace width. As CO 2 injection pressure increases, the capping fracture exhibits a descending trend resembling a stair-step; as gasification furnace width decreases, the development height of cap rock fractures decreases. On this basis, the technical approach and design method of preventing carbon dioxide leakage in UCG-CCS are proposed. The research findings have significant theoretical and practical implications for site selection and risk assessment in UCG-CCS process engineering. • This paper verifies the feasibility of UCG-CCS from the geological perspective. • The study confirmed that caprock fractures are the most significant potential pathway for leakage in UCG-CCS projects. • Measures the impact of CO 2 injection pressure and gasifier parameters on the development of overburden fractures in UCG-CCS. • Optimal storage parameters for UCG-CCS were designed to ensure both the best security and economic benefits. [ABSTRACT FROM AUTHOR]

In this study, gasifier-dual fuelled engine (G-DFE) performance was conducted and compared together with gasification of individual feedstock (i.e., mahua wood, coconut shell, sawdust briquette) and their blends with low-grade coal. Additionally, the performance of different sets of feedstock gasification and engine utilization were compared with optimal input and output response using response surface methodology (RSM). The inputs of G-DFE include gasification equivalence ratio (GER) and engine load percentage. The G-DFE performance includes engine brake thermal efficiency (BTE), diesel saving (DS), and CO, CO 2 , HC, and NO X emissions. Results depict biomass co-gasification blends presented higher engine performance than single feedstock gasification. The (briquette + mahua) producer gas (PG) based dual fuel (DF) engine offers a maximum BTE of 27.6% at input condition of GER 0.12 and 100% load. The maximum DS of 63.44% was obtained for coconut shell G-DFE. Regarding optimum emission, the maximum CO and HC, belong to the setting of GER 0.10 for briquette and (briquette + mahua) G-DFE. The maximum CO 2 and NO X belong to the setting of GER 0.10, 100% load for (briquette + mahua), and GER 0.43, 100% load for mahua G-DFE, respectively. Further, the study's experimental results and optimizations can guide G-DFE management for improved operation and reduced environmental footprint. [Display omitted] • Feasibility study of gasification/co-gasification integrated CI engine was executed. • Co-gasification decreases cold gasification and carbon conversion efficiency. • Biomass co-gasification operated dual fuel engine yields highest BTE of 27.6%. • Coconut shell-PG operated dual fuel engine shows maximum diesel saving of 63.44%. • Composite desirability of RSM-model lies in the range of 0.67–0.96. • Maximum engine NO X in dual fuel mode was 22.63% less than neat diesel run. [ABSTRACT FROM AUTHOR]

Coal-based Allam cycle is an advanced low-carbon and efficient power cycle that uses syngas produced by coal gasification to drive the semi-closed supercritical CO 2 cycle for electric power generation. To improve the thermodynamic and economic performance, a novel coal-based Allam cycle coupled to CO 2 gasification is proposed. Compared to the reference system, the steam for gasification is eliminated and the mole fraction of H 2 within the raw syngas is reduced, which could effectively decrease the moisture fraction of the combustion flue gas and give enough margin to intensify heat integration. Thereby, more process heat has been saved to drive the efficient supercritical CO 2 cycle and the raw syngas cooling heat is further recovered by the main recuperator. Results show that the net efficiency of the novel system soars to 43.99%, which is enhanced by 0.67% points. Moreover, the exergy efficiency increases by 0.65% points with the total exergy destruction and loss reduced by 1.23%. In addition, the total plant investment (TPI) and the cost of electricity (COE) are reduced by 1.42% and 1.39%, respectively, which proves that the novel system is also superior for commercial application. • CO 2 gasification of coal is coupled to a semi-closed supercritical CO 2 cycle. • Heat integration is improved with the elimination of steam for gasification. • Energy/exergy efficiency is enhanced by 0.67/0.65% points. • Superior economic performance is obtained with COE decreased by 1.39%. [ABSTRACT FROM AUTHOR]

Underground coal gasification is an essential means of meeting the growing energy needs of some countries. In this paper, a new numerical simulation method of thermal-force-chemical-displacement multi-field coupling is developed, and in order to better adapt to the actual working conditions, taking Shanjiaoshu Coal Mine as the geological background, the first gasification working face of No. 12 coal seam is simulated based on the controlled retraction injection point technology. This method is used to simulate the heating of coal body by the ignition device at the initial stage of UCG, the chemical-thermal changes triggered by spontaneous combustion of the coal body under the continuous backward movement of the injection point, and the simulation of the formation of the cavity after the coal gasification reaction. Finally, the evolution of temperature and displacement fields in No.12 coal seam after gasification reaction is analyzed. Therefore, this study aims to simulate the actual working conditions more realistically, optimize the UCG technology, and produce more clean energy syngas to improve the energy situation in China. • A coupled thermal-force-chemical-displacement multi-field calculation of coal and surrounding rock strata. • Simulating of continuous movement of the gasification point to fit the actual process of CRIP. • The heat flowing into the model is calculated based on the chemical change. [ABSTRACT FROM AUTHOR]

Hydrogen is a clean energy source, and its use helps to mitigate climate change. Underground coal gasification for hydrogen production is a promising method for countries with abundant coal resources and high hydrogen demand. However, the existing coal-to-hydrogen process underground exhibit low production efficiency. This work proposes the use of swirl flow injection to improve hydrogen production efficiency, and also explores the influence of other injection conditions (oxygen flow rate, steam mass flow and steam temperature) on hydrogen production. For straight flow injection, the effect of steam addition on gasification performance depends on the oxygen flow rate, and the highest H 2 production is 14.6 L under 1 L/min oxygen and 1 g/L steam. With a swirl flow injection, H 2 production increases with steam addition for both 1 L/min and 2 L/min oxygen, which shows a larger H 2 production than straight flow injection. The highest H 2 production for swirl flow injection is 19 L under 2 L/min oxygen and 1 g/L steam. An increase in steam temperature barely affects the composition of products but apparently increases the amount of products. The fracture effect of high temperature steam might cause a sudden increase of H 2 and CH 4 at the late stage. [Display omitted] • Hydrogen production behavior with swirl flow injection was studied. • Effects of oxygen flow rate and steam mass flow were analyzed. • Temperature field and gas products at different steam temperature were discussed. [ABSTRACT FROM AUTHOR]

The non-renewable nature of conventional power plants and the challenges associated with fuel costs and environmental impact highlight the need for innovative solutions. This research proposes a biomass-based combined system designed to produce multiple products, including electric power, coolant, and heat, addressing the drawbacks associated with conventional power generation. The proposed system integrates a biomass gasification unit with a helium gas turbine and a Kalina power unit. Additionally, a domestic water heater is incorporated into the Kalina cycle for heat generation, and the heat loss from the helium gas turbine is utilized in a modified Kalina cycle with a refrigeration unit. To further enhance efficiency, a dual-loop organic flash cycle is employed to recycle waste heat from the modified Kalina cycle. The analysis of this framework encompasses technical aspects, including energy, exergy, and economic considerations. The system is optimized using the multiple-objective particle swarm optimization method. Two scenarios are explored based on the desired product capacities: heat-electric power and coolant-electric power. In the first scenario, the system demonstrates an optimal electric power generation capacity of 6239.56 kW, along with favorable exergetic and economic outcomes. The optimal exergetic efficiency, net present value, and payback period are determined as 35.57 %, 15.07 M$, and 3.97 years, respectively. This research presents a comprehensive approach to biomass-based power generation, considering both technical and economic aspects, and provides valuable insights for sustainable energy solutions. • Renewable CCHP system using biomass feedstock and suitable waste management. • Use of helium gas turbine, Kalina cycles, and organic flash cycle for a CCHP model. • Technical energetic, exergetic, and economic analyses and multi-criteria optimization. • Heat-electric power scenario leads to the highest optimal electric power at 6239.56 kW. • Optimal exergetic efficiency and payback period are found at 35.57 % and 3.97 years. [ABSTRACT FROM AUTHOR]

As deep coal mining continues to expand, the problem of coal spontaneous combustion (CSC) becomes increasingly severe, posing a significant threat to the safe extraction of energy resources. For preventing CSC, it is of great significance to determine the relationship between the content changes of major elements in the constituent coals and CSC, and it is a necessary study to reveal the mechanism of CSC. By utilizing elemental analyzers, it was found the coal experienced dominant changes in O/C ratios up to 120 °C, H/C ratios between 120 and 270 °C, and O/C ratios beyond 270 °C; By employing a correlation approach, it was determined that the key elements influencing heat release during CSC, i.e., C, H, and O. Additionally, with the key elements as monomers, the migration and transformation process of its mutual composition and structure was investigated, and mastered the influence of elemental migration on the thermal reaction properties in the CSC, as well as uncovering migration and transformation pathways in the CSC. Meanwhile, both the critical groups and temperatures that promote CSC generation were obtained, i.e., –CH 2 , –C O, and 150 °C, It is expected that the study results may provide theoretical support for the development of fire extinguishing materials. [Display omitted] • Coal contains an inverse relationship between C and O, independent of temperature. • Revealed microscopic mechanisms which O can contribute to the occurrence of CSC. • Explained the elemental migration transformation pathways in the CSC. • Identified key groups and temperatures that promote the occurrence of CSC. [ABSTRACT FROM AUTHOR]

This study investigated the co-gasification of agricultural and plastic wastes, which is a potential method for waste disposal. Waste shiitake substrate (WSS) and polyethylene (PE) were selected and their properties were investigated. The thermal degradation behavior and gases produced were explored using thermogravimetric analysis coupled with Fourier-transform infrared spectrometry (TG-FTIR). In addition, the activation energy was determined by the FWO method, and the synergistic effect and gas yield were estimated. The co-gasification of WSS and PE assisted by CO 2 and steam was conducted using a bubbling fluidized bed gasifier. Results indicate that BR60 % had the maximum C–O band, C–C bond, C–H band, and CO yields. Blending WSS and PE resulted in an evident synergistic effect. The activation energies of BR20 % had the lowest value. The Taguchi method was used to determine the optimal parameters, maximum normalized H 2 concentration, H 2 /CO ratio, CGE, and exergy efficiency. The H 2 yield and H 2 /CO ratio were predominantly affected by the CO 2 /(CO 2 +H 2 O) ratio, and the best concentration and ratio were 28.6 % and 1.34. The CGE and exergy efficiencies were predominantly affected by gasification temperature, and the best results were 71.6 % and 72.4 %, respectively. Finally, the collected tars were analyzed using gas chromatography-mass spectrometry (GC/MS). • Gasification of waste shiitake substrate (WSS) and Polyethylene (PE) were studied. • Positive synergy exists and the blended fuels can reduce the activation energy. • A bubbling fluidized-bed gasifier is performed with Taguchi method. • The maximum syngas properties (H 2 /CO, H2, CGE, and exergy efficiency) were obtained. • Olivine enhances the decomposition of naphthalene and increases the heavy PAH. [ABSTRACT FROM AUTHOR]

Underground coal gasification (UCG) in deep coal seam was attracting more and more attentions all over the world due to its characteristics of safety, clean and low carbon. In the study, the ignition of UCG in deep coal seam was simulated by employing computational fluid dynamics (CFD). A new method setting gas diffusion in coal seam as transitional diffusion (TD) was put forward, and the TD and Fickian diffusion (FD) mechanism were compared. It was elucidated that TD mechanism was more accurate for UCG model. The default FD mechanism in coal seam overestimated the reaction rate of coal seam. With TD mechanism, coal seam in turn went through external heating controlled (EHC) region and hybrid heating controlled (HHC) region during the ignition of UCG. The demarcation temperature between EHC and HHC regions was 720 K. Then, various inlet temperatures and mass fractions of O 2 were attempted during the simulation of UCG ignition. The time spent by the ignition was shortest with 1100 K inlet temperature and it was ∼180 s. The less the inlet mass fraction of O 2 was used, the slower combustion rate was. CO 2 was the most potential indicator to get access to the underground condition. • Appropriate courant number was 0.83 for UCG ignition simulation. • Coal seam in turn went through EHC region and HHC region during ignition. • FD mechanism overestimated the reaction rate of coal seam. • The optimum inlet temperature and mass fraction of O 2 were 1100 K and 18.4 %. • The increase of CO 2 concentration on outlet is an indicator of UCG ignition. [ABSTRACT FROM AUTHOR]

Supercritical water gasification (SCWG) technology, a clean and efficient method for organic waste treatment, has considerable application prospects in the background of carbon emission reduction. In this study, an auto-thermal SCWG system of chicken manure for NH 3 and power production was proposed for recycling waste resources. Thermodynamic analysis and environmental impact assessment were conducted under different operational conditions. The system exhibited optimal energy, exergy, and cold gas efficiencies of 62.34 %, 53.75 %, and 57.75 %, while simultaneously generating 3372.11 kg/h of NH 3 and 1677.1 kW of net power, all within processing 10 t/h of dry chicken manure. The global warming potential of this system was only 3.31 kg CO 2 -eq/kg NH 3 with carbon capture and storage. The sensitivity analysis indicated that the moderate increase in gasification temperature, higher feedstock concentration, appropriate preheated water flow, and suitable feedstock distribution ratio collectively enhanced system performance by mitigating exergy destruction in the partial oxidation and heat exchange process. By converting waste heat into electrical energy rather than industrial steam, the Organic Rankine Cycle system enhances the practical viability of waste heat recovery. This work expects to provide essential theoretical guidance for the scale-up and design of the biomass waste SCWG system. • The effect of key parameter fluctuations on system performance was investigated. • Exergy destruction mainly occurred in oxidation reactor and medium heat exchanger. • Optimal energy, exergy, and cold gas efficiencies are attained at 62.34 %, 53.75 %, and 57.75 %, respectively. • The ORC units converted waste heat into electricity for local consumption. • The GWP of this system under typical conditions was 3.31 kg CO 2 -eq/kg NH 3 with CCS. [ABSTRACT FROM AUTHOR]

The co-gasification of coal and dried sewage sludge (DSS) was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor. In this study, the effect of the blending ratio of coal and DSS was investigated. Producer gases that were obtained from the tar-cracking reactor filled with active carbon contained high levels of hydrogen (maximum H 2 : 27.7 vol%) and low tar contents (minimum tar: 0 mg/Nm3). Upon gasification of the coal/DSS blends, the hydrogen content decreased and tar content increased with increasing DSS. Blends with coal/DSS ratios of 70/30 and 50/50 showed a synergetic effect on tar reduction, which could be attributed to the high ash content of the DSS. The gasification of the 70% DSS blend increased the condensed tar yield by only 0.1 wt%, compared to coal gasification. Lastly, a hot filter filled with Fe-impregnated active carbon was applied to completely remove tar from producer gas, which led to the production of a tar-free and hydrogen-rich gas (30 vol%). Furthermore, the Fe-impregnated active carbon reduced the H 2 S content to 229 ppmv. In summary, it was possible to produce a clean gas from coal and DSS blends in the UOS gasification process. • The co-gasification was performed using a two-stage gasifier with active carbon. • Coal gasification produced a tar-free gas having 27.7 vol% H 2. • Tar-free gas could be obtained from the co-gasification of 30% DSS blend. • Gasification of 70% DSS blend increased condensed tar yield only by 0.1 wt%. • Fe-impregnated active carbon produced a tar-free gas having 30 vol% H 2. [ABSTRACT FROM AUTHOR]

The methanol and electricity poly-generation system based on coal partial gasification is proposed. Techno-economic analysis of the system is conducted by using Aspen Plus and the effects of methanol synthesis temperature and cyclic gas reflux ratio on the system performance are studied. The detailed economic data are obtained. The IGCC system is established simultaneously and compared with the poly-generation system. The results show that both methanol production and system efficiency decrease with the increase of methanol synthesis temperature. Methanol production increases while system efficiency decreases with increase of the recycle gas ratio. System efficiency would reach as high as 56.8%, while the system efficiency of IGCC is 53.11%. By the calculation of the economic data, the IRR and the payback period of the poly-generation system are 24.1% and 4.14 years, respectively. While IRR and payback period of IGCC system are 3.4% and 18.06 years, respectively. The results show that methanol and electricity poly-generation system based on coal partial gasification has a promising prospect. • The proposed system is based on coal partial gasification and CFB technology. • The power generation efficiency of the PGCC is more than 3% higher than that of IGCC. • The IRR and payback period of PGCC is ∼21% higher and 14 years shorter than that of IGCC. [ABSTRACT FROM AUTHOR]

In recent decades, rising energy consumption, population growth, and material production have contributed to environmental degradation. Harnessing the chemical energy in these materials in a circular economy can mitigate these issues. While recycling processes recover valuable constituents, significant post-recycling fractions remain viable for energy recovery. This study investigates the energy recovery potential from biomass materials via combustion, gasification, and anaerobic treatment, and from polymers and coal through combustion and gasification. Some materials not typically considered for combustion, such as food and green waste, are included due to their potential processing in combustion plants. Using thermodynamic principles, we assess the limits and opportunities for sustainable energy recovery across 200 materials, identifying correlations between the heating value and compositional analyses. The study also estimates the potential products and environmental impacts of energy production from these materials. Despite their lower heating value, biomass materials offer considerable net carbon reductions, but land use, water consumption, public health issues, and feedstock supply risks warrant consideration. Biomass combustion yields lower carbon emissions than polymer or coal combustion. Biomass and polymer gasification show high potential due to their higher H 2 /CO ratios. Anaerobic treatment of biomass materials generates significant methane, offering modest energy output. Synthetic polymers possess high heating values, comparable to fossil fuels, and provide net CO 2 emission benefits, although substantially lower than those of biomass materials. Biomass combustion or gasification results in significantly lower NO x and SO x emissions compared to polymers and coal. Accounting for energy output, biomass gasification generates the lowest emissions per MJ. • Devised generalized formula for 200+ material impacts. • First study to systematically compare biomass, polymers, and coal. • Revealed higher energy yield in gasification of select biomass types. • Identified lower GHG in gasification vs. combustion. • Found non-linear relations between compositions and HHV. [ABSTRACT FROM AUTHOR]

To achieve sustainable energy supply and carbon neutral, it is essential to enhance the efficiency and reduce carbon emissions for coal power. In this study, a coal power generation system based on supercritical water gasification (SCWG) with full CO 2 capture is proposed. The system achieves autothermal gasification by partial oxidation of coal in the SCWG gasifier. Gasification water is preheated by turbine exhaust, and organic Rankine cycle (ORC) is integrated to recover the waste heat of turbine exhaust. Simulation and thermodynamic analysis models of the system are developed. Results show the energy efficiency and exergy efficiency of system with benchmark parameters reach 52.95 % and 54.11 %, respectively. The largest exergy destruction occurs in gasifier and accounts for 41.36 % of the total exergy loss. Irreversibility of heat transfer mainly occurs in water heat exchanger and ORC, accounting for 4.81 % and 5.59 % of the total loss. Effects of key operating parameters on the system performance are investigated. Results show the optimal turbine exhaust pressure is 0.1 MPa, and higher turbine inlet temperature can enhance the system efficiency. System with reheat configuration shows potential in thermodynamic and economic aspects, and the exergy efficiency of double reheat system is improved from 37.25 % to 45.08 %. • Novel coal power generation system with supercritical water gasification is proposed. • System simulation, thermodynamic and economic analysis models are developed. • Exergy efficiency of the proposed system achieves 54.11 % with full CO 2 capture. • Effects of key operating parameters on the system performance are investigated. • SCWG system with reheat shows potential in thermodynamic and economic aspects. [ABSTRACT FROM AUTHOR]

In this study, the impact of oxygen flow rate on the cavity of the gasification zone was analyzed through two experiments using a coaxial hole model. The oxygen flow rate was controlled between 3 L/min and 5 L/min for experiment one and between 7.5 L/min and 15 L/min for experiment two. For the estimation of the cavity volume of the gasification zone in UCG, the stoichiometric method, the Delaunay triangulation approach, and the voxelization method were used. The actual gasification zone cavity volume change was obtained by dividing the coal consumption monitored by electronic mass balance by the apparent density of the coal. After analyzing and comparing the cavity volumes of the gasification zone obtained by the three estimation methods with the actual cavity volume of the gasification zone, the results showed that the stoichiometric method had an estimation error of less than 6.5 %. The Delaunay triangulation approach could reduce the estimation error for the convex cavity volume of the gasification zone to within 10 %. The voxelization method could reduce the estimation error for the cavity volume of the gasification zone to below 8 % and accurately describe the shape of the cavity. • The relationship between differential coal consumption rate and differential average temperature was analyzed. • The volume of the cavity in the gasification zone at different oxygen flow rates was estimated using the injected oxygen volume. • The Delaunay triangulation approach is proposed to estimate the cavity volume and shape at different oxygen flow stages based on acoustic emission localization information. • The Voxelization method is proposed to estimate the cavity volume and shape at different oxygen flow stages based on acoustic emission localization information. [ABSTRACT FROM AUTHOR]

In this study, an underground coal gasification-based integrated multigenerational system is developed to generate multiple useful outputs, including electricity, heating, cooling, hydrogen, ethanol and sulfuric acid, for achieving cleaner applications and meeting the community needs. An application of this conceptually developed system is considered for a community as identified in Kutahya, Turkey. The proposed system is developed, modelled, and analyzed using thermodynamic-based, sensitive modeling tools and software packages. The effects of operating conditions such as oxygen, steam, as well as lignite feed rate, reference temperature, and gasifier temperature are investigated to evaluate the performance of the integrated underground coal gasification system. This research further aims to analyze the influence of varying system parameters and operational conditions on ethanol and hydrogen generation and increase energetic and exergetic efficiencies while reducing harmful product gas emissions. In this regard, many parametric studies of the underground coal-powered multigeneration system are conducted. According to the results, the integrated underground lignite gasification combined system's overall system energetic and exergetic efficiencies are found to be 68.8% and 66.56%, respectively. • A novel energy system is designed and analyzed for a sustainable community in Kutahya, Turkey. • Many parametric studies are performed to investigate underground coal gasification parameters. • The energy and exergy efficiencies, as well as the rate of exergy destruction, are examined. • The impact of various operational circumstances is investigated on the performance of subsystems and the overall system. [ABSTRACT FROM AUTHOR]

In the paper the results of the systematic study on oxygen/steam co-gasification of sewage sludge blends with biomass waste such as olive pomace or energy crops such as Sida Hermaphrodita to hydrogen rich gas were presented. In the first part of the experimental campaign the oxygen/steam gasification of sewage sludge, Sida Hermaphrodita and olive pomace, respectively, at 700, 800 and 900 °C were gasified. Only small amount of the total gas was produced in the oxygen/steam gasification of analyzed sewage sludge in all studied temperatures. The carbon conversion rate varied between 64% at 700 °C to 66% at 900 °C. The hydrogen amount in the total gas produced in the sewage sludge gasification was 28%vol. at all studied temperatures. The main conclusion from this part of experiments was that gasification of sewage sludge is ineffective. Different conclusions were drawn on the basis of Sida Hermaphrodita and olive pomace gasification tests at all studied temperatures. Therefore in the second part of the experimental campaign the co-gasification experiments of Sida Hermaphrodita /olive pomace blends with 10%w/w and 20%w/w of sewage sludge. The co-gasification experimental campaign covered series of tests at temperatures of 700, 800 and 900 °C, respectively. The comprehensive analysis of the experimental results of co-gasification and the physical and chemical parameters important for the co-gasification process performance were also conducted with the application of chemometric methods, such as hierarchical clustering analysis and principal component analysis. Based on the experimental results the optimal fuel blends as well as the optimal conditions of co-gasification were determined. It was proven that steam co-gasification of sewage sludge with selected biomass is beneficial in terms of the total gas produced and its composition. • Energy technologies development in H 2 production and waste valorization were proposed • The optimal conditions of co-gasification were determined • The highest H 2 gas content in co-gasification process of olive pomace blends with 20%w/w of sewage sludge [ABSTRACT FROM AUTHOR]

As the main pollutant of paper mills, black liquor has brought great pressure to the wastewater treatment process of paper mills. Based on the coal-water slurry gasification (GS-CWS) technology, this paper designed the gasification system of black liquid coal-water slurry (GS-BLCWS) by utilizing weak black liquor of pulp mills, investigated and modeled the energy requirements of the GS-BLCWS. Feasibility assessment of the GS-BLCWS and the traditional alkali recovery systems (TARS) were carried out, including energy efficiency, economic feasibility and environmental impacts. The comparison results showed that the steam demands of two technologies can be self-sufficient. But the total energy efficiency of GS-BLCWS (69.78%) is higher than that of the TARS integrating GS-CWS (63.07%), and the energy output ratio of black liquor increased from 9.9% to 69.78%. From an economic point of view, GS-BLCWS can generate syngas, which can be used for drying in the papermaking workshop and shows better economic efficiency. Meanwhile, GS-BLCWS has lower environmental impacts that there is no emission of sulfur oxides and particulate matter. Considering the short payback period (5.81 years) of GS-BLCWS, the small environmental impact, and the self-sufficiency of steam and electricity, it has broad application prospects. [Display omitted] • A gasification system for preparing coal-water slurry syngas from weak black liquor. • The feasibility of GS-BLCWS in energy, economy and environment is evaluated. • GS-BLCWS improves the energy utilization efficiency of weak black liquor. • Sensitivity analysis shows that the price of syngas has the greatest impact on PBP. [ABSTRACT FROM AUTHOR]

Coal-based power generation systems combined with CO 2 capture can generate clean, efficient, decarbonized electricity and have recently received significant attention. This study proposes a high-efficiency power generation system with CO 2 capture using cascading coal gasification coupled with chemical recuperation. The proposed system involves using waste heat from the gas turbine exhaust to start coal pyrolysis, achieving the first stage of chemical recuperative pyrolysis. Pyrolysis products, excluding coal gas (CG), are fed into the gasifier for the second stage of coal gasification. Furthermore, the sensible heat of syngas at the gasifier outlet is sequentially used to preheat the gasification agent and tar, supply heat for CG reforming, and generate steam. The cascading coal gasification and stepwise utilization of thermal energy decrease oxygen consumption during gasification and reduce the proportion of partially oxidized coal. The results indicate that, at a 90% carbon capture rate, the net power generation efficiencies of the proposed and reference systems are 40.26 and 37.58%, with exergy efficiencies of 39.22 and 36.55%, respectively. The improvements in the proposed system primarily stem from its highly efficient coal utilization, which decreased exergy destruction for the gasification process by 43%. These results imply the system may enhance efficient, low-carbon coal use. • A proposed power generation system uses cascading coal gasification and CO 2 capture. • Coal pyrolysis is heated with waste heat from gas turbine exhaust, improving coal's chemical energy use. • The system offers 40.26% power generation and 39.22% exergy efficiency with 90% carbon capture. • The system reduces CO 2 emissions to 84.64 g/kWh, a 6.63% drop from the reference system. [ABSTRACT FROM AUTHOR]

Supercritical water gasification (SCWG) is a potential clean technology for utilizing solid fuel or waste without producing gaseous pollution. Efficient energy integration and recovery strategies play an essential role in the endothermal gasification process. Previous approaches have only focused on the heat source or heat transfer with very little attention to the utilization of the abundant supercritical water in the product gas. This paper proposes an innovative series design for heat integration in the SCWG system while taking the gasification process into account. Notably, the first-stage oxidized hot fluid containing abundant water is directly utilized as the gasification agent for the second-stage gasification reactor. The thermodynamic analysis shows that the cold gas and exergy efficiency in the two-stage series system is 17.4% and 15.0% higher than in the previous single-stage gasification reactor. The sensitivity analysis illustrates that increasing series stages and feedstock concentration while decreasing oxidation proportion and the agent-slurry ratio can improve the overall system efficiency by decreasing the demand for oxygen, power consumption, and heat transfer rate. The series design should offer an innovative and practical approach for the heat supply in the industrial SCWG plant. • Series design for supercritical water gasification of coal-water slurry was simulated. • The optimized cold gas and exergy efficiency is improved by 17.4% and 15.0%. • The Sankey diagram shows that the series design reduces reaction and heat recovery exergy loss. • Higher series stages facilitate methane production, less oxygen demand, and higher efficiency. • The critical parameters were studied by sensitivity analysis for optimization. [ABSTRACT FROM AUTHOR]

Currently, the severe fluctuation of steam temperature in double-reheat (DR) ultra-supercritical (USC) units has become a major problem that constrains their efficient and flexible operation, wherein the deviation of coal calorific value from the design value is one of the major reasons for this issue. However, the effect of coal calorific value variation on the steam temperature characteristics during the flexible operation of DR USC units remains unclear. A dynamic model of a 1000 MW DR USC unit is developed with primary principles and validated with real operation data. The effect of the coal calorific value variation on the steam temperature characteristics is revealed. Results show that as the calorific value of the coal increases, the main steam temperature can always maintain at the design value with attempering water adjustments, while the two reheat steam temperatures decrease. The steady-state deviations of the reheat steam temperatures are positively correlated with the magnitude of the coal calorific value variation, where the deviation of the secondary reheat steam temperature is larger. Meanwhile, as the load increases, the steady-state deviations of reheat steam temperatures increase, but the response time decreases. Finally, the effect of calorific value variation on the boiler efficiency is studied. As the coal calorific value increases, the boiler efficiency firstly rises caused by the decrease in the loss of the flue gas and then falls caused by the limited furnace temperature increase. This study provides guidance on the DR USC boiler operation under coal variation. • A dynamic model of a 1000 MW double-reheat ultra-supercritical unit is developed. • The effect of the coal calorific value variation on the steam temperature characteristics is revealed. • The effect of calorific value variation on the boiler efficiency is revealed. • This study provides guidance on the double-reheat ultra-supercritical boiler operation under coal variation. [ABSTRACT FROM AUTHOR]

In this study, a clean and efficient hydrogen production system with synergistic conversion of coal and solar energy is proposed, and the energetic and exergetic evaluation are carried out. The main feature is that the syngas produced by supercritical water coal gasification contains a large amount of steam and some methane, which is very suitable for steam methane reforming reaction to generate high-purity hydrogen. Through thermochemical complementary and chemical recuperative methods, concentrated solar energy and high-temperature flue gas are used to supply reaction heat for the supercritical water coal gasification and steam methane reforming processes, respectively. The results showed that the energy and exergy efficiencies reach approximately 50.15% and 50.81%, respectively, which is an increase of 10.42% and 10.78%. The key reason for the improvement in system performance is that the exergy destruction during gasification and reforming is reduced by 7.81% points. As a result, the hydrogen-rich syngas chemical exergy is approximately 54.27% higher than that of the reference system. In addition, sensitivity analysis is employed to disclose the effect of key parameters on the hydrogen yield, syngas composition and methane conversion rate. This study presents a promising solution for large-scale hydrogen production processes. • A hydrogen production system with synergistic conversion of coal and solar energy. • Thermochemical complementary and chemical recuperative methods are adopted. • Hydrogen yield for the proposed hydrogen production system reaches 9361 kmol/h. • Energy and exergy efficiencies increased by 10.42% and 10.78%–50.15% and 50.81%. • Sensitivity analysis reveals the effect of key parameters on the proposed system. [ABSTRACT FROM AUTHOR]

Regenerative cooling technology plays an important role for development of scramjet engine. In order to further improve thermal performance of regenerative cooling system with hydrocarbon fuel, a distributed regenerative cooling system using catalytic steam reforming of supercritical aviation kerosene and distributed supply of water is evaluated in the present study. Thermal performances of distributed catalytic steam reforming system (DCSR) and conventional catalytic steam reforming system (CSR) are compared. The effects of pressure and secondary injection ratio of water on DCSR are numerically analyzed. The results show that DCSR renders higher heat transfer coefficient and larger heat absorption capacity than CSR. Coke content of DCSR decreases by up to 20% while heat transfer coefficient increases by 12.02% compared with CSR. With secondary injection ratio increasing from 30.98% to 71.60%, coke content decreases by up to 37.53% while heat transfer coefficient increases by up to 44.45%. As coke deposition is significantly removed by in situ steam gasification reaction, no heat transfer deterioration is found near the outlet of the cooling mini-channel. Moreover, the cumulative heat absorption capacity of DCSR increases by 24.3% than CSR. This study provides preliminary insight into thermal performance of DCSR for scramjet engines. Schematic diagram and thermal performance evaluation of distributed regenerative cooling system. [Display omitted] • Proposed a distributed regenerative cooling system using hydrocarbon fuel • Identified different performance of distributed and conventional cooling system • Revealed effects of pressure and secondary injection ratio on thermal performance • The distributed cooling system enhances heat transfer and heat absorption • Realized in situ coke deposition removal by catalytic steam gasification reaction [ABSTRACT FROM AUTHOR]

This work addresses clean utilization of coal through thermo-chemical processes (i.e., gasification & methanation) that convert solid carbonaceous feedstock to gaseous fuel for power generation, which features potential advantages for environmental benignity and energy security. It would be beneficial to convert coal to synthetic natural gas (SNG) that can feed the combined cycle units in the regions like Taiwan where natural gas (NG) is imported, which would help stabilize the price of electricity and alleviate the energy security concern. The objective of this study is to investigate the performance as well as the pros and cons between integrated and non-integrated SNG plants. The characteristics of power and chemical plants differs in various aspects, thus the concept of non-integrated approach to produce SNG and power offers better system resilience, availability and market flexibility at the expense of reduced efficiency. Fuel switch strategy would be one of the key pillars for the pathway toward Net-Zero Emissions (NZE) by 2050. Alternative energy carriers (AECs), generally synthesized from conversion of other energy sources, may provide solutions to decarbonization and low-emission environment. In summary, the thermo-chemical conversion processes studied in the present work address the core issues in clean and efficient utilization of carbonaceous resources. Integrated configuration: Heat integration among various processes exhibits higher system efficiency. Non-integrated version: Separated Syngas/SNG/Power plants offer improved system resilience and availability. [Display omitted] • Gasification can convert coal to syngas using for clean power and derived chemicals. • Methanation produces synthetic natural gas for electricity to better energy security. • Novelty on comparing the integrated-with non-integrated configuration is presented. • Non-integrated configuration offers improved system resilience and availability. • Non-integrated plants exhibit a bit lower efficiency but produce extra process steam. [ABSTRACT FROM AUTHOR]

The white cement industry is facing the challenge of alternative fuel utilization replacing conventional fuel due to the impact of alternative fuel ash on the whiteness of clinker. On the other hand, municipal solid waste (MSW) disposal is a huge waste management problem worldwide. The present article focuses on utilizing MSW-based refuse derived fuel (RDF) as an alternative fuel in white cement. The ash-free producer gas derived via RDF gasification is proposed to overcome the challenge of direct RDF utilization. Aspen plus-based producer gas co-processing model for a calciner has been developed, considering 100% petcoke firing as the baseline scenario. The co-processing of producer gas further augmented the model to achieve a 15–20% thermal substitution rate (TSR). The developed model is validated using the actual plant data. The model results at 15% TSR predicted that the calciner outlet temperature will get reduced by 19 °C, with a 5.3% rise in calciner exit gas volume, which is manageable. CO 2 mitigation potential at 15% TSR is estimated to be 11.33% of the baseline scenario. The TSR contribution of producer gas sensible heat at 593 °C is 2.7%, whereas the petcoke enters the system at 60 °C with negligible sensible heat. [Display omitted] • Producer gas from RDF gasification as an alternative fuel for a white cement plant • Aspen Plus modelling for producer gas co-processing in calciner at 8, 15 & 20% TSR • Prediction of calciner outlet temperature and CO 2 emissions with an increase in TSR • Impact of RDF moisture and producer gas temperature on calciner performance [ABSTRACT FROM AUTHOR]

SOFC poly-generation system exhibits the potential for clean and efficient conversion, but few studies have been conducted on the comparative analysis of the combined cooling, heating and power considering CO 2 capture and condensate recovery. This study investigates a novel near-zero emission poly-generation system based on biomass gasification and SOFC employing different biomass fuels. This combined system adopting oxy-fuel combustion instead of traditional pre-combustion makes the flue gas easier to achieve a concentrated CO 2 stream, thereby the system structure is simplified and the purity of captured CO 2 is improved. The results reveal that the larch wood is the preferred fuel for the proposed system and the corresponding overall efficiency, exergy efficiency and unit cost of products achieve 80.17%, 29.12% and 20.49 $/GJ, respectively. The exergy analysis demonstrates that the exergy destruction mainly occurs in gasifier and turbine. The exergoeconomic analysis indicates that SOFC possesses a greater exergoeconomic factor of 85.12%. The parametric analysis shows that increasing gasifier temperature (T gas), SOFC temperature difference (ΔT) and current density (j) decreases overall efficiency. The higher T gas results in a higher unit cost (c t), whereas c t is more economic as ΔT increases. Besides, as j changing, c t of various biomass-based systems exists an optimal value. • Proposing a novel near-zero emission poly-generation system. • Examining the system performance when using typical biomasses. • Conducting thermodynamic and exergoeconomic analysis for the proposed system. • Finding the optimal unit cost of the products for different biomass systems. [ABSTRACT FROM AUTHOR]

Coal to ethylene glycol (CtEG) process is criticized for its high energy consumption and poor thermodynamic performance. This process is detailed modeled by dividing it into coal gasification, water gas shift, acid gas removal, dimethyl oxalate synthesis, ethylene glycol synthesis, and ethylene glycol refining units. After comparing and verifying with literature and industrial data, this work conducts a detailed advanced exergy analysis and optimization of the CtEG process. Results show that the exergy efficiency of the CtEG process is only 33.56%, and the coal gasification, dimethyl oxalate synthesis, and ethylene glycol synthesis units have the largest exergy destruction. Furthermore, the exergy destruction of all components in the CtEG process is dominantly endogenous (76.03%) and avoidable (64.62%). The real improvement potential of the CtEG process is 64.62%. A parametric study was then performed to investigate the effect of key parameters on the thermodynamic performance of the CtEG process to reduce its avoidable endogenous and exogenous exergy destruction. After optimization, the exergy efficiency of the improved CtEG process is increased by 12.34%, and the avoidable exergy destruction is reduced by 160.48 MW compared with the reference system. Therefore, the improved CtEG process has better thermodynamic performance than the reference process. [Display omitted] • A detailed advanced exergy analysis and optimization of the CtEG process was conducted. • Exergy destruction of the CtEG process is dominantly endogenous (76.03%). • Real improvement potential of the CtEG process is 64.62%. • Exergy efficiency of the improved CtEG process is increased by 12.34% after optimization. [ABSTRACT FROM AUTHOR]

The current study demonstrates the synergistic effect of co-gasification of high-ash Indian coal and biomass (press mud and sawdust) blends in varying proportions in a pilot-scale bubbling fluidized bed gasifier (BFBG) with a capacity of 20 kg/h. The effect of blending on product gas yield, composition and heating value, carbon conversion, and cold gas efficiency was critically analyzed. Mineralogical transformations and catalytic effects were investigated during co-gasification, wherein minerals in ash residue, such as hematite, sylvite, chlorite, K-feldspar, CaO, and MgO, showed a catalytic role in co-gasification, increasing the product gas compositions, and reverse the trend for kaolinite and phosphate minerals. Blending coal with biomass enhances the porosity and reactivity of blends, surface morphology, gasification performance, and product gas yield. So, high ash coal and biomass are suitable for gasification. The high ash coal gasification comprises the volumetric product gas composition (%) of CO (9.79), CO 2 (8.75), H 2 (13.6), and CH 4 (1.12) with the maximum blends (40%) of biomass, the volumetric composition (%) is enhanced comprising CO (17.71), CO 2 (14.8), H 2 (19.9) and CH 4 (2.05) for press mud blend, and CO(15.84), CO 2 (14.2), H 2 (18.3) and CH 4 (2.29) for sawdust blend, respectively, and HHV increases from 3.42 (MJ/Nm3) to 5.59(MJ/Nm3). • Co-gasification of high ash coal and biomass in fluidized bed gasification. • Effect of Organic and inorganic elements on product gas composition. • Catalytic effect of Minerals oxides as CaO, MgO and Fe 2 O 3 on product gas. • The 60:40, Coal to sawdust ratio, is suitable for better gasification performance. • Coal-press-mud blends provide better carbon conversion, HHV and gas compositions. [ABSTRACT FROM AUTHOR]

The safe and steady running of coal chemical looping gasification system (CCLGS) is directly related to the whole production benefit. CCLGS is composed of dryer, pyrolyzer, decomposer, fuel reactor (FR), and air reactor (AR), which reflects the complexity of the entire production process. In this paper, a novel dynamic safety control strategy based on process modeling and complex risk computation is put forward to ensure the stable operation of CCLGS. First, the process modeling of CCLGS is carried out by Aspen Plus, and the obtained simulation results are in agreement with experimental results. Then, the CCLGS complex network is formed by constructing the adjacency matrix and calculating comprehensive indicator (C i) value to evaluate the importance of the variables and support risk computation. Subsequently, the risk values of five units are computed based on the unit maximum material coefficient (UMMC), unit general risk coefficient (UGRC), and unit special risk coefficient (USRC). The results prove that FR and AR have higher risk grades than other units. Finally, dynamic control study for FR and AR processes is conducted with the aim of evaluating pressure controllers by safety integrity level. The research will provide beneficial approaches for the safety control of actual plant. [Display omitted] • Process modeling provides accurate basic data for complex risk computation. • Key variables selection improves the efficiency of the risk calculation. • The risk value calculation of each CCLGS unit is put forward for the first time. • Dynamic safety analysis strategy is proposed to ensure the smooth running of CCLGS. [ABSTRACT FROM AUTHOR]

Coal catalytic pyrolysis has been applied in the clean and efficient utilization of low-rank coal to obtain combustible gases and high value-added chemicals. Herein, Ni–Co–Ca catalysts were added into coal through impregnation for catalytic pyrolysis of Yunnan lignite and the char steam gasification. The H 2 production reached 3.24 mmol/g of coal and the gas conversion was 27.84% of the coal pyrolysis under 5Ni–5Co–1Ca. The char conversion reached 98.21% and the H 2 production was 90.68 mmol/g of char steam gasification. Ni and Co could promote coal catalytic pyrolysis by cracking the C–H and C–C bonds. The formation of Ni–Co alloy could prevent catalysts inactivation due to the metal oxidation, lattice distortion and carbon deposition. Density functional theory (DFT) calculations indicated that the electron transfer from Co to Ni has been improved due to the Ca promoting effect, enhancing Ni catalytic activity and promoting coal pyrolysis for more small gaseous molecules. Ca could endow char with abundant pore structure, improving the irregular degree of char crystallite structure, which was attributed to the char gasification at high temperature to obtain H 2. This study provided guidance to modulate pyrolysis products distribution by regulating catalysts properties. Ni–Co–Ca catalysts were added into coal through impregnation for catalytic pyrolysis of Yunnan lignite and the char steam gasification for high H 2 yield and efficient char conversion. Ni and Co could promote coal catalytic pyrolysis by cracking the C–H and C–C bonds. Ca promoted the electron transfer from Co to Ni, enhancing Ni catalytic activity and promoting coal pyrolysis for more small gaseous molecules. [Display omitted] • Ni–Co–Ca in catalytic pyrolysis and char gasification were investigated. • The formation of Ni–Co alloy prevented catalysts inactivation. • Ca improved the electron transfer from Co to Ni. • The H 2 yield were 3.24 mmol/g of coal pyrolysis and 90.68 mmol/g of char gasification, respectively. [ABSTRACT FROM AUTHOR]

The present work deals with CFD simulation for coal gasification in a fluidized bed gasifier. Different design parameters were checked to validate the stability of the reactor. 8 reactions were taken into consideration for the simulation of gasification. A mixture of pure oxygen, water vapor, and nitrogen entering through the bottom of the distributor was used as the gasifying agent. The coal sample was fed from the side wall of the reactor 20 cm above the gas distributor. Three Australian coal samples having different compositions were simulated using CFD simulation and results were validated to justify the modeling of the reactor. The effect of the oxygen-to-carbon ratio on coal gasification was studied to get the maximum yield of synthesis gas. The cold gas efficiency of the reactor was found to be within 45–60% which was agreeing well with the literature data. The carbon conversion was also found to be between 40 and 50%. The yield of synthesis gas was measured and the mass fraction of outlet gases was calculated through simulation. These results imply that the gasifier modeling is satisfactory. Thus, it can be concluded that the CFD-modeled reactor can be used as a base design for an industrial gasifier. • CFD simulation for three coal samples was conducted using a fluidized bed gasifier. • Eight numbers of reactions are considered for the simulation of gasification. • The effect of the oxygen-to-carbon ratio on the yield of synthesis gas was studied. • The cold gas efficiency, carbon conversion, and volatile yields were determined. • The yield of synthesis gas through simulation is validated against the literature. [ABSTRACT FROM AUTHOR]

The high quality waste heat recovery of the molten blast furnace slag was necessary and urgent. In this paper, the flow characteristic of the molten slag reactor was investigated by numerical simulation. Firstly, the three-dimensional model was established for investigating the gas-liquid two-phase flow. The gas-liquid flow was modeled to be turbulent, which was described by the RNG k-ε model, and the interface of gas and liquid was conducted by the VOF model. Secondly, the top-submerged cold experiment system was constructed to validate the accuracy of the simulation model. Thirdly, the bubble behavior, gas phase distribution and molten slag motion were investigated. The bubble in the reactor would go through five stages and the maximum gas fraction reached about 4.87% at 0.75s. Meanwhile, the gas phase distribution and molten slag motion were closely related to the bubble behavior. Ultimately, the matrix analysis method was applied to obtain the optimal parameters of the reactor. The optimal condition improved the flow behavior in the molten BFS reactor significantly. The present results of the simulation provided an insight for the gas-liquid two-phase flow in molten slag reactor, which would provide the theoretical guidance for industrial applications. • Gas-liquid interaction characteristic in molten slag was investigated in detail. • Bubble behavior was grasped by simulation and validated by cold experiment. • The changing of gas phase distribution and liquid motion with bubble were obtained. • Optimal structure and operation parameters were obtained by matrix analysis method. [ABSTRACT FROM AUTHOR]

For a fixed bed gasifier, coal gas is mainly derived from dry distillation zone and gasification zone. The upstream gas from gasification zone will inevitably affect the composition and production of dry distillation gas. Therefore, the composition of upstream gas and the reaction conditions of dry distillation zone were simulated to perform experiments of Yining coal pyrolysis under a series of atmospheres. Some new discoveries are obtained. H 2 O and the hydrogen-containing gas have a significant impact on the release of dry distillation gas. H 2 O inhibits the release of CO, CO 2 and CH 4 , but promotes the release of H 2 which is not from char−H 2 O gasification. When the hydrogen-containing gas passes through dry distillation zone, the path of stabilizing radicals is completely changed, resulting in that coal pyrolysis changes from a process of generating H 2 under inert atmosphere to a process of consuming a large amount of H 2. In addition, water gas shift reaction is the only homogeneous reaction observed obviously in dry distillation zone, which can promote the production increase of CO 2 , but can not prevent the production decrease of H 2 in coal gas. • Coal pyrolysis in dry distillation zone of fixed bed gasifier is simulated. • H 2 O inhibits the release of CO, CO 2 , CH 4 and C n H m , but promotes the release of H 2. • Upstream gas promotes the release of CO 2 , CO and CH 4 , except H 2. • The consumption of H 2 in dry distillation zone reduces H 2 production in coal gas. • WGS is the only homogeneous reaction occurred obviously in dry distillation zone. [ABSTRACT FROM AUTHOR]