Search

Hydrogen is hailed as a game-changer in global energy systems, offering a sustainable remedy to climate change through its zero waste attributes, beneficial for both power generation and transportation. However, conventional thermochemical methods for hydrogen production, such as steam methane reforming and coal gasification, result in low-quality impure hydrogen, necessitating costly purification processes. Therefore, expediting the advancement of pure hydrogen production methods with minimal to no purification requirements is essential to bolster economic viability and foster widespread adoption across industries. Among these methods, electrolysis and hydrolysis have garnered significant attention in research over the past two decades. However, there is a lack of literature review discussing both electrolysis and hydrolysis for pure hydrogen production within a single article. Hence, this review seeks to fill this gap by providing an overview of pure hydrogen production through electrolysis and hydrolysis. It commences with the classification of different pure hydrogen production methods, followed by a discussion on water electrolysis and other variants of electrolysis, as well as hydrolysis involving light metal-based composites, alloys, and lightweight hydrides. A comparison between electrolysis and hydrolysis for pure hydrogen production is also outlined and discussed, along with an outlook on their future prospects. [Display omitted] • Electrolysis and hydrolysis are the most researched pure H 2 production methods. • Traditional water electrolysis (AWE, PEMWE, AEMWE) are mature but have limitations. • Electrolysis variants with other feedstock are promising but face technical issues. • Hydrolysis yields pure H 2 at mild conditions but needs efficiency-boosting tactics. • Electrolysis is resource-intensive; hydrolysis faces material and technical issues. [ABSTRACT FROM AUTHOR]

• The effect of temperature on plasma gasification of CPMW is explored experimentally. • A temperature of 1800 °C provides the optimum performance for air-CPMW gasification. • The volume fraction of H 2 and CO increases with the increased reactor temperature. Plasma gasification melting (PGM) provides reliable disposal of toxic medical waste with a low heating value, which is capable of converting waste into energy. This study investigates the performance of experiments on plasma gasification for the treatment of chemical-pharmaceutical medical waste (CPMW) with an air medium. A comparative analysis is performed for gasification characteristics at three reactor temperatures (1000, 1400, and 1800 °C). Moreover, a thermodynamic equilibrium model is developed to assess performance features such as syngas yield, high heating value, and cold gas efficiency in the gasification temperature range of 1000–1800 °C. A comparison of the experiment and computational outcomes shows a good agreement. The results show that the quality of syngas and heating value is improved by increasing the temperature of the plasma gasifier so that at 1800 °C, H 2 , CO, and higher heating value (HHV) are obtained as 41 %, 37 %, and 10 MJ/Nm3, respectively. The obtained syngas is a clean fuel with low sulfur-containing and nitrogen-containing. The experimental results provide an extensive comprehension of CPMW gasification in a plasma reactor and consider a possibility for hydrogen and energy production. [ABSTRACT FROM AUTHOR]

Coal gasification coarse slag (CGCS) has become a bulk coal-based solid waste that threatens the ecological environment. The high moisture content of carbon-rich coal coarse gasification slag (CR-CGCS) seriously limits its utilization. In this study, a pore water releasing method was proposed to promote the dewatering of CR-CGCS through size reduction with surface modification. Hexadecyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and kerosene were added during the grinding process, respectively. The results showed that kerosene can significantly improve the dewatering efficiency of CR-CGCS more than CTAB and SDS. The final moisture content of the CR-CGCS could be reduced from 47.50% to 33.01%. The SEM and FTIR results illustrated that kerosene could effectively reduce the content of oxygen-containing functional groups on the surface of CR-CGCS more than CTAB and SDS. Meanwhile, the PVM results showed that CR-CGCS modified by kerosene tended to form hydrophobic agglomerates. The LF-NMR results indicated that only the water in the macropores of CR-CGCS could be released in grinding process, but the water in micropores could be reduced when kerosene, CTAB, or SDS was added in grinding. This study provides new insight into enhancing the dewatering of CR-CGCS and theoretical support for the efficient utilization of CR-CGCS. [ABSTRACT FROM AUTHOR]

Conventional fuel sources, such as fossil fuels, have become unaffordable for the low end of the economy and thus the need for sustainable alternatives. Gasification of coal and biomass is considered as an alternative source for small‐sized engines, such as tricycles in Kenya. Mui basin coal is a low‐quality coal, available in Kenya, and blending with selected biomass (rice husks, Prosopis juliflora, and Hyphaene compressa) presents a new source of alternative transport fuel through cogasification and upgrading. The selected biomass samples were collected, air‐dried, and crushed to 60 μm and subjected to calorific determination, proximate, and ultimate analysis. Blending was done at various ratios weight by weight, while thermochemical determinations were conducted using the American Society for Testing and Materials (ASTM). The fixed carbon content was reported as 29.3 ± 5.51% for Mui basin coal, 21.1 ± 1.55% for rice husk, and 31.0 ± 1.00% for H. compressa. Blending was found to improve the hydrogen:carbon ratio with an average rate of 0.12 and decreased the sulphur and nitrogen content, leading to low emissions. The study revealed that calorific values of the fuel sources were as follows: Mui basin coal, 20.41 ± 0.15 MJ/kg; P. juliflora, 18.68 ± 0.17 MJ/kg; and H. compressa, 18.69 ± 0.00 MJ/kg, while rice husks had 12.95 ± 0.1 MJ/kg. Blending was also found to improve calorific values by average values of 0.4 MJ/kg for P. juliflora, 1.3 MJ/kg for H. compressa, and 2.28 MJ/kg for rice husk. The moisture content was reduced by 1–2% for all fuel sources; ash content was reduced by 33%, while the volatile matter was increased by 11% for P. juliflora, 7% for H compressa, and 0.2% for rice husks. The optimal blend of ratio 1 : 1 when cogasified produced syngas, which was upgraded through cleaning and cooling. The upgraded syngas had a moderate ratio of hydrogen to carbon monoxide with the right modification and retrofitting; it can be applied in internal combustion engines of tricycles‐"tuk tuks." The study reveals that the optimal blending ratio of 1 : 1 for coal:biomass reduces the pollution ash content, increases calorific values, and enhances syngas fuel properties to moderate ratio. [ABSTRACT FROM AUTHOR]

In order to quantitatively calculate the critical depth and critical load of mines affected by rock burst, and to achieve effective prevention and control of rock burst in coal mines, this paper proposes a mechanical model for predicting the occurrence of rock burst in coal mine roadways based on catastrophe theory. Additionally, a theoretical calculation formula for initiating rock burst is derived. The first step was to establish a mechanical analysis model, which directly correlated with the in-situ stress, physical and mechanical characteristics of the coal-rock mass, and engineering structural parameters. Following this, a mechanical instability criterion was derived for the key load-bearing circle within the surrounding rock of the roadway. In the final step, the critical depth and load for rock burst initiation were verified for 25 distinct coal mines in China that were prone to rock burst hazards. The research results demonstrate that the discrepancy between the theoretically calculated critical depth and the actual measured statistical values was less than 35%. In addition, the difference between the theoretically determined critical depth and the value calculated by Pan Yishan was less than 32%. Notably, the ratio of the theoretically calculated critical load to the uniaxial compressive strength of the coal-rock mass ranged from 0.38 to 1.93. This aligns with empirical data on rock burst occurrences, as set out in the engineering classification standards for rock masses. These research outcomes substantiated the practical utility of the proposed theory, thereby laying a robust theoretical groundwork for the quantitative control of rock burst. [ABSTRACT FROM AUTHOR]

Coal is one of the important energy sources; however, the direct combustion of raw coals is discouraged due to their low calorific value and the production of harmful gases. Microbial transformation of coal is an eco-friendly method to convert raw coal into clean and cost-effective valuable products like humic, fulvic acids, and other complex organic compounds. In present study, out of 51 bacterial isolates, 05 isolates, designated as ANK-4, AN-25, ANK-30, BD4, and Mn-250 were selected based on their degradation/solubilization activity for lignite as well as bituminous coal samples. All the isolates showed ligninolytic activity as determined by Azure-B decolorization and Manganese oxidation assays as well as by Guaiacol and α-Naphthol tests. For the bio-treated lignite and bituminous coals, the Z-average size was 434.2 to 187.5 and 587.6 to 280.2 nm and zeta potential was −35.2 to −29.3 and −32.6 to −23.8 mV, respectively. Morphological and molecular studies showed that the isolated bacteria belong to genus Bacillus and Kocuria. The coal solubilization/degradation and ligninolytic activities as well as size and zeta potential studies indicated that the isolated bacteria could be potential candidates for development of green technologies for conversion of coal into valuable products for fuel and non-fuel applications. [ABSTRACT FROM AUTHOR]

The advanced gasification technology of coal is mainly based on oxidation reaction and high temperature but is not suitable for biomass conversion. High tar and CO2 content are the two main issues that affect the efficiency of biomass gasification. In order to deeply convert hydrocarbons/tar and CO2 simultaneously, and enhance syngas yield, the cracking/partial oxidation/reforming reactions and their integrated reaction routes are investigated from an interrelated view. The effects of each reaction on the distribution of C/H elements in hydrocarbons/tar and syngas are illustrated. By cracking and oxidation reaction, the syngas yield can only reach 0.93 Nm3 kg−1, about 58 % of the theoretical maximum value; a large proportion of residual C/H atoms existing in stable hydrocarbons/tar/CO2/H2O are not converted. Based on the concept of lattice O oxidation combined with dry reforming, it realizes syngas yield (CO+H2) 1.56 Nm3 kg−1 with 91.6 % concentration, demonstrating that tar/hydrocarbons and CO2/H2O are converted to syngas efficiently. The effects of [O]/C ratio on gas yield represent a synergistic coordination between lattice Os oxidation and catalytic reforming reaction. Oxidation‐reforming is the optimum route for biomass conversion to high‐quality syngas. [ABSTRACT FROM AUTHOR]

High-pressure black water angle valves are essential equipment of black water flash treatment systems in the coal gasification process, and they usually suffer from a high risk of erosion wear failure. In this study, computational fluid dynamics (CFD), combined with the discrete particle method (DPM) and the volume of fluid (VOF) method, was used to study the flow characteristics and erosion wear phenomenon in high-pressure black water angle valves under different valve cavity radii and opening angles. In particular, a new parameter, the drift index, was introduced to analyze the bias flow phenomenon in the throttling zone. With the increase in valve cavity radius, the drift index first decreases and then increases, and the influence of the valve cavity radius gradually weakens with the increase in the valve opening. It was found that, with the increase in valve cavity radius, the average erosion wear rate of the valve body decreases first and then increases. When the valve cavity radius was 132 mm, the average erosion wear rate of the valve body was the smallest. Therefore, the optimization of the valve cavity radius selection value can reduce the erosion wear damage of the high-pressure black water angle valve and increase its operational dependability. [ABSTRACT FROM AUTHOR]

Coal-based chemical looping gasification (CCLG) has been proposed as an emergent type of coal gasification technology that produces high-quality syngas by using lattice oxygen from oxygen carrier instead of molecular oxygen. In this paper, the Fe–Ni composite oxygen carrier was synthetized using sol-gel method and the gasification performance of the prepared sample was analyzed by a fixed-bed reactor. The results indicated that the Fe–Ni composite oxygen carrier presented a high carbon conversion of fuel and syngas selectivity during the CCLG process. Additionally, the cycle stability test showed that the carbon conversion of fuel and syngas selectivity did not change significantly with the increase of cyclic frequency. To further study the influence of volatiles released from coal on the gasification performance of oxygen carrier, the interactions between the oxygen carrier samples and char obtained at different pyrolysis temperatures were investigated by a fixed-bed reactor and TG-MS, respectively. The results suggested that the gas products (H 2 , CO, CO 2 and CH 4) yields of char-oxygen carrier were significantly lower than those of coal-oxygen carrier. Besides, the pyrolysis temperature for preparing char had a great effect on the carbon conversion of fuel and syngas selectivity due to the distinction of volatiles released from solid fuel. • Efficient Fe–Ni composite oxygen carrier was crafted via sol-gel method. • Fe–Ni composite oxygen carrier showed good performance with desirable reactivity and cyclic stability. • Interaction between oxygen carrier and volatiles released from coal was investigated. • Char gasification was demonstrated to be the rate determining step during the CCLG process. [ABSTRACT FROM AUTHOR]

In this paper, copper slag is used as the heat carrier of coal gasification reaction, and CaO is used as the CO 2 adsorbent of syngas to solve the problem of high cost of heat source and high proportion of CO 2 produced by coal gasification. When copper slag is used as the heat carrier, the adsorption effect of CaO on CO 2 is most pronounced at temperatures of 600 °C and 700 °C, with CO 2 proportion reduced to 8% and H 2 proportion reaching 65%. Additionally, CaO exhibits a significant promotion effect on carbon conversion rate and gasification efficiency at temperatures above 800 °C, with the maximum carbon conversion rate reaching 89% and the highest gasification efficiency reaching 78%. At low temperatures, CaO primarily functions in gas phase reaction, such as WGS reactions, hydrocarbon reforming reactions, tar reforming reactions, and pyrolysis reactions. As the temperature increases, CaO primarily functions in gas-solid reactions such as oxidation reactions and secondary water gas reactions. In high-temperature environments, iron compounds present in copper slag undergo iron reduction reactions, while the Ca 2 Fe 2 O 5 compound formed from the reaction of CaO and Fe significantly promotes reforming reactions. • The copper slag is used as the heat carrier, and the waste heat in the copper slag is utilized. • CaO was selected as the adsorbent, and the synergistic effect with copper slag was found during adsorption. • The proportion of H 2 in syngas can be increased to 89 %. • The reaction mechanism of different temperature stages was analyzed. [ABSTRACT FROM AUTHOR]

Integrating anodic coal gasification fine slag oxidation with cathodic hydrogen evolution reaction presents an environmentally friendly and energy-efficient solution for solid waste recycling and hydrogen production. This innovative approach exhibits higher activity and stability than conventional water electrolysis, while also preventing anode degradation due to its benign reaction conditions. The kinetic investigations have revealed that slag oxidation occurs more rapidly than water oxidation. Specifically, slag undergoes direct and indirect oxidation within the potential regions below and above those of water oxidation, respectively. This study has the potential to shed light on the mechanisms underlying slag electrolysis and offer valuable insights for the simultaneous recycling of solid waste and hydrogen production. [ABSTRACT FROM AUTHOR]

To solve the problem of controlling the stability of small coal pillars under the mining disturbance of the adjacent working face, the fourth panel 403 and 404 working faces of the Gaojiabao coal mine with two mining roadways is taken as the object of this research. The comprehensive research method of combining mechanical theory analysis, coal dynamic disturbance experiments and field engineering practice was adopted. First, the analysis determined the magnitude and frequency of fracture‐related disturbance loading on the overburden roof of the working face; next, the strain and stress threshold indicators of the coal body, sensitive to the external disturbance load of 103 J magnitude (continuous disturbance deformation), were tested and obtained through a self‐developed rock creep disturbance experimental system, and the stress threshold indicators of coal body specimens sensitive to creep disturbance were defined as the long‐term strength. Then, a coal pillar‐roof mechanics structure model was established in the premining and postmining areas of the working face, and the overlying support pressure on the coal pillar body was analysed. Finally, a small coal pillar composite reinforcement support technology with ‘two‐way buttressing anchor cable for pressure reinforcement + steel pipe concrete pier column + overhead roof break’ was designed to ensuring that the coal pillar body would not be destabilised by cumulative disturbance and large deformation under disturbance. According postmining area support capacity calculations, the support loading acting on the coal pillar is approximately 17593 kN, with the stress being 2.93 MPa; and the factor of safety is approximately 1.23. After engineering practice application of this approach, the vertical deformation of the small coal pillar body and side heave disturbance deformation were effectively controlled during the working face mining disturbance, the vertical deformation of the reinforced coal pillar was only 187 mm, and the side heave deformation was finally stabilised at approximately 124 mm, which maintained good stability. [ABSTRACT FROM AUTHOR]

Coal gasification fine slag (CGFS) is rich in unburned residual carbon, silica and alumina, and has a large specific surface area, making it a potential polymer‐reinforcing filler. Tea polyphenol (TP)‐modified coal gasification fine slag (TP‐CGFS‐T) was prepared using flotation and modification methods in this study. The effects of unmodified and modified CGFS‐T on the sulfurization performance, processing properties, thermal stability, fracture morphology, and mechanical properties of natural rubber composite materials were investigated. Results indicated that after TP modification, CGFS‐T exhibited highly uniform dispersion on the surface without the agglomeration of fillers. When the dosage of TP‐CGFS‐T was 20 phr, the comprehensive performance of the natural rubber (NR) composite material was optimal, with a tensile strength of 12.12 MPa, the elongation at break of 1208.83%, the tear strength of 30.94 kN/m, and the shore hardness of 38.7 A. As the amount of TP‐CGFS‐T increased, the scorch time of NR increased, which enhanced the processing safety of rubber. This study provides a strategy for treating CGFS, which can both reduce the pollution caused by CGFS and save costs for NR composite materials. Highlight: The CGFS is separated into concentrate and tailings by flotation.The compatibility between fillers and the matrix is enhanced by TP modification of CGFS‐T.The composite materials show excellent mechanical and processing properties. [ABSTRACT FROM AUTHOR]

Underground coal gasification (UCG) technology can directly convert coal resources to syngas underground, making it important for coal utilization. In this work, the power generation, CO 2 electrolysis, and reversible operation of flat-tube solid oxide cells (SOCs) fueled with UCG syngas were studied. The factors affecting the performances of flat-tube solid oxide cells were investigated. Fueled with syngas (Swan Hills, Canada) at 750 °C, the flat-tube cell achieved a maximum power density of 329.4 mW cm−2 and a current density of 650.8 mA cm−2 at 1.4 V. 100-cycle (250 h) reversible operation of flat-tube SOCs running on syngas (Swan Hills) was accomplished. No carbon deposition on the surfaces of the cell fuel channels was detected. The syngas conversion in flat-tube cells was illuminated based on density functional theory calculations. • The performance of solid oxide cells (SOCs) with syngas was studied. • 100-cycle reversible operation of SOCs with UCG syngas was achieved. • No coking was detected after the long-term reversible test. • DFT calculations illustrated the reaction mechanisms of UCG syngas in SOCs. [ABSTRACT FROM AUTHOR]

To explain the impact of geological and process factors on underground coal gasification in deep coal seam (>2200 m) and promote the efficient and clean extraction and conversion of coal, this study employs the orthogonal experimental design method to investigate the impact of CO 2 coefficient (0–1), moisture content (30–80 wt%), calcite content (0–10 wt%), albite content (0–10 wt%), kaolinite content (0–20 wt%), reaction temperature (550–650 °C), and reaction pressure (23–27 MPa) on the characteristics of coal underground gasification under supercritical H 2 O/CO 2 conditions. Furthermore, range analysis and variance analysis are utilized to determine the degree of influence of each factor and the interaction between factors. Finally, the Gibbs free energy minimization method is used to conduct a thermodynamic equilibrium analysis of coal supercritical H 2 O/CO 2 gasification at high temperatures (750–1000 °C). The results indicate that the three most significant factors affecting the process of coal supercritical H 2 O/CO 2 gasification are the CO 2 coefficient, moisture content, and reaction temperature. The maximum carbon gasification efficiency at 650 °C in experimental cases and 1000 °C in simulation cases is 22.2% and 88.1%, respectively. Although the addition of CO 2 at lower temperatures reduces the carbon gasification efficiency, at high temperatures (>900 °C), a higher initial CO 2 concentration increases the carbon gasification efficiency. The addition of CO 2 under conditions of low moisture content increases the mole fraction of H 2 , but reduces it under conditions of high moisture content (≥70 wt%). Among the three minerals, calcite has the most significant influence on the gasification process. • Analyzed the effects of different factors on underground coal gasification in deep coal seam. • The interaction of CO 2 coefficient with temperature and moisture content is analyzed. • The effect of calcite, albite and kaolinite is limited. • At ≥950 °C, CO 2 can increase the carbon gasification efficiency. • When the moisture content ≤60 wt%, CO 2 can increase the mole fraction of H 2. [ABSTRACT FROM AUTHOR]

Investigating the physicochemical properties and embedding forms of residual carbon (RC) and slag particles (SPs) in coal gasification fine slag (FS) is the basis for achieving its separation and utilization. An in-depth understanding of their compositional characteristics allows for targeted treatment and utilization programs for different components. In this work, the physicochemical properties and embedding forms of RC and SPs in FS were systematically investigated. An innovative calculation method is proposed to determine the mass fraction of dispersed carbon particles, dispersed mineral-rich particles, and carbon–ash combined particles by using a high-temperature heating stage coupled with an optical microscope. The unburned RC with a rough, loose surface and a well-developed pore structure acted as a framework in which the smaller spherical SPs with a smooth surface were embedded. In addition, the sieving pretreatment process facilitated the enrichment of the RC. Moreover, the RC content showed significant dependencies according to the FS particle size. For FS with a particle size of 0.075–0.150 mm, the mass proportions of dispersed carbon, ash particles, and the carbon–ash combination were 15.19%, 38.72%, and 46.09%, respectively. These findings provide basic data and reliable technical support for the subsequent carbon and ash separation process and the comprehensive utilization of coal gasification slag. [ABSTRACT FROM AUTHOR]

In this study, a composite modifier (CMCDL) containing coal gasification residue, dicyandiamide waste slag, and lake sediments was used to modify steel slag at high-temperature. Five kind of raw materials was analyzed in physicochemical properties, mineral composition and microstructure, cementitious properties and soundness, and particle size analysis, the same to steel slag after high-temperature modification (SHTM). The new mineral phases were found that tricalcium aluminate (C 3 A), gehlenite (C 2 AS), magnetite (Fe 3 O 4), spinels (MgFe 2 O 4), quartz (SiO 2), celite (C 6 AF 2) and diopside (CMS 2) formed in the SHTM when the mass fraction increase from 10% to 30% in CMCDL. The HTM with CMCDL increases the glass phase and hydrated mineral (C 3 A, C 3 S, C 2 S) and in raw steel slag, promoting the disassembled of RO phase, turning the phase from FeO into MgFe 2 O 4 and Fe 3 O 4. MgFe 2 O 4 and Fe 3 O 4 have similar crystal structures, and they form mixed spinels. When the content of CMCCL (coal gasification residue: dicyandiamide waste slag: lake sediments =7:9:4) is 20%, the temperature is 1250 °C, result showed that the mass fraction of f-CaO in SHTM using CMCCL decreases from 4.81% to 1.86%, with a decrease of 61.3%, the 28-day activity index of SHTM increases up to 17.6% compared with raw steel slag, reaching 86.2%. Therefore, the CMCDL-blended SHTM can be applied harmlessly in cement and concrete, enabling low-energy fine grinding of steel slag. [ABSTRACT FROM AUTHOR]

Coal gasification to manufacture dihydrogen (H 2) has long been known as a surface process. Recent works have also highlighted the H 2 generating potential of the Organic Matter (OM). The evolution of OM generates H 2 all along the process but this gas is only expected to remain as free H 2 after the maturation and expulsion of the hydrocarbons (HC) which means at a high temperature of above 200 °C. In this paper we studied the potential of three different tertiary coals from Amaga, La Jagua de Ibirico and Barrancas, all located in Colombia. Their H 2 yields were studied using a pyrolyser and the kinetic of the H 2 generation were quantified. All the studied coals are immature to early mature as source rock (SR) with large TOC content, between 66 and 83%, and good H 2 potential. The highest values were found for the Barrancas area where the potential reached 25 mg H 2 /g TOC. The temperature corresponding to the peak of H 2 generation is between 740 and 800 °C depending of the heating rate. This corresponds to the 200–300 °C for the H 2 kitchen, even if the H 2 generation starts before as already observed for continental organic rich source rock. Comparison with the other coals shows that H 2 potential is linear with TOC. In the Colombian coals, the H 2 yield in mg H 2 /g of rock is around 1/4 of the TOC content. In average, these coals have so a H 2 yield about 10 000 mmol H 2 /kg of rock, two orders of magnitude above the "best" olivines. It should nevertheless be kept in mind that the extrapolation of these laboratory data to sedimentary basins remains unconstrained and will need to be refined when well data and modelling tools are available. • The coals have significant H 2 potential in deep sedimentary basins. • High temperature open-system pyrolizer can be used to quantify these H 2 yield. • The reaction kinetic of the H 2 generation from coal is of order 1 and H 2 window generation can extend from 200 to 400 °C. • The Cenozoic Colombian coal's yield of H 2 in mgH 2 /g rock is ca ¼ of its organic carbon content in percentage. • A 80% TOC rich coal has a H 2 yield two orders of magnitude higher than that of olivines at a similar temperature of 250 °C. [ABSTRACT FROM AUTHOR]

The selection of sustainable hydrogen production technologies (HPT) is a paradigm transformation for industrial enterprises to pursue commercial benefits and environmental performance, which has increasingly attracted the attention in academic circles. Therefore, the chief orientation of this research is to construct a novel sustainability-oriented decision-support framework for hydrogen production system. Firstly, an approach is developed to determine expert weights under each criteria in a linguistic environment. Secondly, the Measurement of Alternatives and Ranking according to Composite Solution (MARCOS) method is extended to prioritize sustainable HPT under hybrid information (HMARCOS). Finally, a case study of 5 typical HPT regarding 15 sustainability indicators is conducted. The results display the biomass gasification has the highest sustainability priority for hydrogen production compared with wind turbine electrolysis, photovoltaic electrolysis, steam methane reforming and coal gasification. Furthermore, the reliability and availability of the integrated framework is demonstrated by the comparisons with other approaches. • A complete HPT sustainability criteria system has been established. • A method is presented to determine the DM weights under each criteria. • The HMARCOS model is extended for evaluating the sustainabable potential of HPTs. [ABSTRACT FROM AUTHOR]

South Africa is an energy-intensive developing country in Africa and ranked as the 1st and 14th emitter of greenhouse gas (GHG) in Africa and the world, respectively. The abundance and availability of coal in South Africa make it the mainstay primary source of energy contributing 56% of national total GHG emissions. This paper focused on the duo of energy generation and emission associated with coal processing and utilization in South Africa, and the urgent need to advance coal processing technologies marked by high carbon footprints in consonance with the sustainable development goals. Different gasification techniques and their performances have been compiled and discussed. The economic, environmental impact, energetic, and exergetic characteristics of existing hydrogen production technologies for renewable and non-renewable energy sources have been examined along with hydrogen production from plasma gasification of coal. Hydrogen production via coal or coal/biomass plasma gasification technology (nuclear-, wind-, PV solar-, and concentrated solar power-driven) in addition to carbon capture technology for transforming the captured CO 2 into value-added products appears to be the most viable option to considerably reduce emissions and meet the energy demand of South Africa. This proposed technology can be pivotal to achieving a low-carbon economy (medium-term) and transition to hydrogen economy (long-term) as championed by the global sustainable development agenda. Conclusively, hydrogen (stored in different forms e.g., liquid hydrogen, ammonia, and organic hydride) seems to find more applications (in the space industry, transport, energy storage, defense industry, etc.) than coal owing to its immediate use in distribution/demand centers and remote areas. • Coal is the primary energy source of South Africa and key driver of national CO 2 emissions. • Traditional coal gasification technologies are marked by high CO 2 emissions. • Coal plasma gasification technology is a viable option for low-carbon energy economy. • Hydrogen production via coal or coal/biomass plasma gasification technology leads to zero-carbon economy. • This immensely supports the drive towards attaining the sustainable development goals. [ABSTRACT FROM AUTHOR]

This paper presents a detailed review of the plasma gasification process for waste disposal. Due to Shifting economies and consumerism culture, ample change can be seen across the globe in the form of rapid industrialisation and burgeoning urbanisation, which results in a massive increase in waste generation. Plasma gasification technology is an emerging solution for processing a wide range of waste making it a highly sustainable, efficient, and ecologically sound process. This literature review discusses the feasibility of the plasma gasification method and its superiority over other conventional waste disposal techniques. A comprehensive analysis of different methods of plasma generation for gasification is done in this literature review. The review paper presents a detailed coverup of the entire process of plasma gasification and post-processes. The article discusses the notable advancement, current scenario, and possibilities in plasma gasification methodology in terms of the design of plasma torch, modelling of gasifiers, generation of syngas, and power production. It provides an overview of advanced simulation tools helpful in the analysis of the Waste-to-Energy (WtE) process. This literature review aims to provide an overview of the recent advances in plasma gasification, highlighting the technical aspects, environmental benefits, and economic viability of the technology. It also reviews the latest research and developments in plasma gasification and discusses the challenges and limitations of the technology, as well as the future prospects and potential applications. • Plasma gasification methodology for waste treatment is discussed in detail. • Prominent thermal and non-thermal practices are discussed and compared in this literature review. • Selective use of plasma gas for enhanced efficiency and optimised gas yield/composition. • Hybrid systems offer versatility in processing diverse feedstocks and can achieve higher energy efficiencies. • Plasma-catalysis approach with NTP shows desirable syngas yield. [ABSTRACT FROM AUTHOR]

Hydrogen-rich gas, characterized by high yield and purity, can be effectively generated through the steam gasification of sewage sludge (SS), offering substantial benefits for organic solid waste treatment and resource conservation. This study evaluated the gasification performance in a horizontal moving-bed reactor employing a wet-mixed CaO-red mud (CaO-RM) composite catalyst. The effects of CaO loading rate (CaO/RM), catalyst-to-SS ratio (CaO-RM/SS), and reaction temperature on the syngas yield, lower heating value (LHV), carbon conversion ratio, H 2 to CO (H 2 /CO) ratio, and H 2 yield were investigated. Results indicated that red mud loaded with a calcium-based catalyst significantly enhanced syngas production, particularly for hydrogen generation, during SS gasification. A maximum hydrogen molar fraction of 50.84% and a yield of 7.07 mol/kg were achieved with a CaO/RM of 40% and a CaO-RM/SS of 30% at 750 °C. With the reaction temperature increase from 700 to 900 °C, the catalytic performance for secondary tar cracking and steam reforming was further enhanced. The total syngas yield, H 2 yield, hydrogen molar fraction, LHV of syngas, and carbon conversion rate peaked at 0.79 m³/kg, 19.30 mol/kg, 54.41%, 10,249.48 kJ/kg, and 65.67%, respectively, at 900 °C. • Study boosts energy conversion of sewage sludge with new CaO-RM composite catalyst. • Examines effects of CaO loading rate, catalyst/SS ratio, temperature on gasification. • Prepared CaO-RM catalyst greatly increase syngas, especially hydrogen production. • Temperature rise from 700 to 900 °C boosts catalytic tar cracking and reforming. [ABSTRACT FROM AUTHOR]

Acidic gases such as H2S and CO2 are generated in the refineries during coal gasification. These pollutant gases need to be treated before releasing to the atmosphere. Conventionally, H2S gas is treated by Claus process in which H2S is converted to elemental S and H2O, in presence of O2 at ∼1,200 K. In the present energy scenarios, hydrogen has got importance as a source of clean fuel for industrial application. The H2S generated in the refineries can be a potential precursor of hydrogen. If this hydrogen can be obtained by thermal decomposition of H2S, that can increase the overall economic value of the H2S containing streams and the produced hydrogen can be used for hydrocracking and hydro-treating in refineries, as well as to synthesize value-added products for chemical industries. However, H2S thermal decomposition is an endothermic and equilibrium limited reaction (equilibrium conversion is only ∼15 % at 1,000 K), requiring a very high temperature (∼1,500 K) to achieve even a conversion of greater than 40 %. Packed Bed Catalytic Membrane Reactor (PBCMR) for thermal decomposition of H2S can be a potential technology augmentation and process intensification to increase this equilibrium conversion. In this work, modeling and experimental studies of H2S thermal decomposition using in-house designed & developed PBCMR have been carried out. The modeling studies were validated with experimental data. Clay-alumina ceramic tubular membrane (L: 250 mm; OD: 12 mm; thickness: 2 mm) was fabricated using extrusion process having an average membrane pore size of ∼1 μm and with a porosity of ∼20 %. Pt (2 %) coated alumina extrudes were used as catalyst to accelerate the reaction kinetics. Experimental studies showed that H2S to hydrogen conversion of ∼90 % is achieved using PBCMR at ∼1,523 K, compared to only ∼40 % conversion in a conventional packed bed tubular reactor (without membrane). Modelling studies were carried out to study the influence of operating parameters such as, reactor wall temperature, feed temperature, pressure and feed velocity. Studies showed that reactor wall temperature is having the most dominant effect on H2S conversion, which is confirmed by experimental findings. The studies offer useful insights into the application of PBCMR technology for management of waste gas stream containing H2S and recovery of hydrogen. [ABSTRACT FROM AUTHOR]

The molecular structure of coal is complex, and the existing research methods are limited, so it is difficult to clarify its influence mechanism on the spontaneous-combustion characteristics of coal. In this paper, the previous extraction, FTIR, TPR, TG-DSC and other experimental results are combined to analyze the extraction weakening effect and the correlation analysis of the spontaneous-combustion characteristic parameters of raffinate coal. The results show that extraction can destroy the connection bond of coal molecules, change the content of dominant active groups in the coal spontaneous-combustion reaction, increase the lower limit of the key temperature nodes of coal spontaneous-combustion or extend the temperature range, resulting in an increase in the ignition-point temperature of coal and a decrease in coal quality. This paper will provide a theoretical basis for the study of the microscopic mechanism of coal spontaneous-combustion and then provide new ideas for the development of an active prevention and control technology for coal spontaneous-combustion. [ABSTRACT FROM AUTHOR]

By allowing coal to be converted by microorganisms into products like methane, hydrogen, methanol, ethanol, and other products, current coal deposits can be used effectively, cleanly, and sustainably. The intricacies of in situ microbial coal degradation must be understood in order to develop innovative energy production strategies and economically viable industrial microbial mining. This review covers various forms of conversion (such as the use of MECoM, which converts coal into hydrogen), stresses, and in situ use. There is ongoing discussion regarding the effectiveness of field-scale pilot testing when translated to commercial production. Assessing the applicability and long-term viability of MECoM technology will require addressing these knowledge gaps. Developing suitable nutrition plans and utilizing lab-generated data in the field are examples of this. Also, we recommend directions for future study to maximize methane production from coal. Microbial coal conversion technology needs to be successful in order to be resolved and to be a viable, sustainable energy source. [ABSTRACT FROM AUTHOR]

Coal is the most valuable gasification resource due to its abundance and low cost for commercial applications. But utilization of low-rank Indian coals for gasification is challenging due to difficulty in washing. For utilizing low-grade high ash raw coal, blending is one of the effective methods to control the gasification performances. So, the present study explores the gasification of such a low-rank raw coal blend and compares the results with washed coal blend. The blending effects on raw gas yield (kg/kg of coal) and heating value (Kcal/Nm3) were investigated for coal blends-WH (washed coal with high-rank coal) and RH (raw coal with high-rank coal). In WH, raw gas yield is 1.210 to 1.225 (kg/kg of coal), whereas, in RH is 1.189 to 1.213 (kg/kg of coal), though the fixed carbon content of WH (40.75–41.74%) is lower than RH (44.73–45.25%). In washed coal, raw gas yield is minimum (0.75 kg/kg of coal). The heating value is lower in WH (2730–2871 Kcal/Nm3) than in RH (2884–2978 Kcal/Nm3). Statistical correlation is developed between gaseous components of raw gas and heating value; H2/CO ratio is the most significant parameter. RH gasification is economically viable than WH. [ABSTRACT FROM AUTHOR]

The neutralization of sulfur compounds during the filtration combustion of model mixture compositions containing iron sulfide or copper sulfate by adding marble (CaCO3) is studied. It has been experimentally shown that during burning model charge compositions with additions of both iron sulfide and copper sulfate, replacing chemically inert sapphire with marble leads to a decrease in the combustion temperature by approximately 150–200°C. At the same time, the content of CO2 in gaseous products increases, and the concentrations of CO and H2 decrease. The greatest effect on the absorption of sulfur-containing substances when adding marble is shown in experiments where sulfur is present in the fuel in sulfide form: the addition of 50% marble makes it possible to capture 72% of the initial sulfur content, and for compositions with 90% marble in the charge, 85%. The absorption of the sulfur compounds formed during the combustion of model mixture compositions with copper sulfate is much worse. When the charge contains 50 and 85% marble, sulfur-containing compounds were absorbed by only 19 and 24%, respectively. [ABSTRACT FROM AUTHOR]

It is paramount that solutions to questions of energy security for a developing nation be addressed through its internal resources. India, endowed with 23.8 billion tons of deep un-minable lignite, faces the challenge of economically sustainable extraction. This study presents a comprehensive assessment of lignite's suitability for underground coal gasification (UCG) compared to bituminous coal. Employing a multi-dimensional approach, combining single-step and distributed activation energy model of pyrolysis kinetic modeling with extensive physicochemical analysis (proximate and ultimate analyses, FTIR, SEM–EDX, XRD), revealed that lignite has a lower activation energy making it suitable for UCG. This finding, highlighted by kinetic modeling, is substantiated by the lignite's structural properties as identified in physicochemical analysis. This study leverages machine learning for higher heating value prediction, finding long short-term memory as the most effective model compared to five other models based on the R2 score and error values. Additionally, an XGBoost algorithm-based model predicts syngas heating value and yield while showcasing the application of machine learning in enhancing energy prediction accuracy. The economic analysis, applied for a 50 MW power plant framework, determines the unit costs for syngas and electricity production to be 7.49 and 6.71 $/GJ and 53.68 and 59.93 $/MWh for the samples of lignite and bituminous coal, respectively. The sensitivity analysis revealed that the energy content in syngas is the most significant parameter. These comprehensive findings validate lignite's potential for energy production in India, offering insights for similar resource optimization in other developing countries. [ABSTRACT FROM AUTHOR]

Co-firing zero-carbon fuels as an effective emission reduction strategy in coal combustion processes has garnered widespread attention. This paper proposes utilizing the combustion performance of oxy-hydrogen gas derived from zero-carbon fuels to address issues related to low-concentration coal powder combustion and nitrogen oxide emissions. A test apparatus for coal powder combustion initiated by oxy-hydrogen gas flames was constructed, and experimental and simulation methods were employed to study the impact of oxy-hydrogen gas flame initiation on the temperature inside the combustion chamber, coal powder gasification combustion reactions, and nitrogen oxide emissions. The results indicate that with an excess air coefficient of 0.8, as the oxy-hydrogen gas flow rate increased from 0.022 kg/h to 0.789 kg/h, the average temperature inside the combustion chamber increased from 801 K to 1459 K. The volatile matter release rate and its combustion reaction rate increased, leading to a decrease in volatile matter content. The peak concentration of volatiles was shifted from a position of 68 mm to 7 mm, and the proportion of Cchar–H2O reaction increased from 5% to 34%. NO emissions decreased from 132 ppm to 68 ppm, and the rate of reduction in NO emissions decreased from 15.38% to 5.49%. [ABSTRACT FROM AUTHOR]

Coal seam cavitation is one of the most effective techniques for gas disaster control in low-permeability coal. Due to the difference in cavitation method and process, the damage degree and fracture development range of the coal body around the cavern are greatly different, and the effect of increasing the permeability of the coal body is further changed. In order to further understand the permeability enhancement mechanism of cavitation technology on low-permeability coal and effectively guide engineering applications, this paper conducted experimental research on the unloading damage and permeability evolution characteristics of coal under different cavitation paths using a coal-rock "adsorption-percolation-mechanics" coupling test system. Through the analysis of coal strength and deformation characteristics, coal damage characteristics, and the evolution law of coal permeability combined with the macroscopic damage characteristics of coal, the strength degradation mechanism of unloaded coal and the mechanism of increased permeability and flow were revealed. The results show that unloading can significantly reduce the strength of coal, and the greater the unloading rate, the more obvious the reduction. The essence of this is that unloading reduces the cohesion and internal friction angle of coal—damage and breakage are the most effective ways to improve the permeability of the coal body. Unloading damaged coal bodies not only significantly improves the permeability of the coal body but also improves the diffusion ability of gas, and finally, shows a remarkable strengthening effect of gas extraction. [ABSTRACT FROM AUTHOR]

Gasifying waste represents a sustainable and highly effective approach; however, ensuring rigorous control of hydrogen leakage is paramount to guarantee both safety and long-term sustainability. Due to the distinctive features of these production facilities and the likelihood of their placement in public municipal spaces, it is imperative to prioritize a comprehensive approach to ensuring the safety of these installations. This includes a thorough evaluation of the risks linked to hydrogen and taking proactive measures to prevent accidents, a crucial aspect that has been neglected in prior research endeavors. Therefore, this article introduces an enhanced iteration of the risk management framework based on the failure mode and effects analysis (FMEA) and the evaluation based on distance from average solution (EDAS) methods, implemented in a municipal solid waste gasification system to facilitate hydrogen production. The research employs FMEA to scrutinize potential failure modes, strategically prioritizing them through advancements in the EDAS methodology. Notably, this framework is seamlessly integrated during the conceptual design phase, showcasing its efficacy in bolstering risk-informed design strategies. Through rigorous comparative and sensitivity analyses, the resilience of the framework is underscored. The refined FMEA-EDAS framework holds substantial practical implications for managing hydrogen production facilities by providing a structured approach to resource allocation and ensuring adherence to industry standards. Furthermore, it fosters interdisciplinary collaboration, potentially serving as a knowledge hub to fortify safety measures within the realm of hydrogen production. • We propose a new FMEA-EDAS MCDM for waste-to-hydrogen gasification. • We analyze a real case study with 20 failure modes, revealing root causes. • We validate our framework via comparative and sensitivity analysis. • We provide a comprehensive safety planning solution for the case study. • The proposed mode contributes to global energy transition with cleaner solutions. [ABSTRACT FROM AUTHOR]

Catalytic coal gasification is a promising technology in the field of clean coal utilization. A comprehensive understanding of mechanisms, reaction kinetic, and reactor model is crucial. This article summarizes and analyzes the catalytic mechanisms of key reactions, such as C–O2, C–CO2, C–H2O, and CO–H2. It also compares various kinetic models, including shrinking core model, random pore model, volume model and their respective modifications. Additionally, the article delves into mathematical modellings of catalytic coal gasification, encompassing molecular models or density functional theory, empirical model, computational fluid dynamics, Aspen modeling, and artificial neural network. The aim is to provide a roadmap for the development and scale up of reactors used in catalytic coal gasification. [ABSTRACT FROM AUTHOR]

Co-thermal chemical conversion of coal and biomass is one of the important ways to realize efficient and clean utilization of coal. In this study, a typical Ningdong coal-Yangchangwan bituminous coal and cow manure were used to study the synergistic effect of intrinsic alkali, alkaline earth metals (AAEM) and organic matter on the co-gasification of coal and biomass by thermogravimetry analyzer (TG). The results showed that AAEM had obvious synergistic promotion effect on the gasification of a bituminous coal-cow manure mixture in the isothermal gasification (1000 ℃), whereas the organic matter will show the opposite effect on the process. To further investigate the effect of organic matter on the gasification process, the influence of organic matter on non-isothermal (25-1000 ℃) gasification reaction was investigated with heating rate of 10 ℃ /min, the kinetic parameters of the gasification reaction were obtained by Coats-Redfern method. The increase of biomass mass fraction in the sample facilitates the migration of alkali metals from the material to the solid phase. The possible mechanism of the synergistic effect of intrinsic AAEM/organic matter on the co-gasification process was proposed. [ABSTRACT FROM AUTHOR]

Aiming at the problem that coal gasification fine slag is difficult to float effectively, this paper combines flotation experiments and molecular simulation methods to study the mechanism of composite collectors on the flotation performance of gasification fine slag. In the aspect of molecular simulation, the quantum chemical characteristics of collector molecules and coal molecules in gasification fine slag were studied by density functional theory (DFT) calculation, and the electrostatic potential and frontier orbitals were calculated. Then, the flotation behavior of composite collectors in gasification fine slag was simulated by molecular dynamics. It was found that dodecane and dodecylamine had the best flotation effect as collectors. Finally, the flotation experiment verified that the recovery rate and other related indexes of gasification fine slag were better when dodecane and dodecylamine were used as collectors. [ABSTRACT FROM AUTHOR]

Co-gasification of coal and biomass in a bubbling fluidized bed may offer an effective and economical method to partially replace coal to produce hydrogen, thereby addressing the objectives of achieving a carbon dioxide emissions peak and carbon neutrality. An Artificial neural network (ANN) model was utilized to simulate the hydrogen and other performance of co-gasification in the bubbling fluidized bed. Five types of ANN architectures were tested, including FFBP, CFBP, EFBP, LR, and NARX. Five optimization algorithms were also applied, including L-M, GA, GD, GDX, and PSO, to identify the optimal model to give a more accurate predicate the hydrogen production. The input data were derived from the ultimate analysis of the mixed coal and biomass, the proximate analyzes of mixed coal and biomass, and the operational conditions. The output data consisted of gas composition, carbon conversion, gasification efficiency, total gas yield, syngas yield, low and high heating values of the gas. The LR-PSO with 6 hidden neurons (R2 = 0.9995 and MSE = 0.1357) outperformed other ANN types and optimization algorithms. To further understand the performance of co-gasification, the influences of biomass to coal ratio, equivalence ratio, steam to carbon ratio and temperature on ratio of H 2 to CO and syngas yield were predicted. The highest ratio of H 2 to CO for the work of Li et al. (2010) [26], Song et al. (2013) [27] and Valdés et al. (2015) [28] were 0.7, 1.2 and 0.88, respectively. And those for syngas yield were 0.85, 1.09 and 1.55 m3/kg, respectively. To reveal the important factor on the ratio of H 2 to CO, a detailed analyzed of the contribution ratio was conducted. The most critical factor affecting co-gasification performance in the work of Song et al. (2013) [27] were identified as SC ratio and temperature, which was higher than those of W and ER. The effect of SC exceeded that of T at SC ratio of 0.4, while it came to a reverse at temperature above 700 °C. These findings may serve as a valuable tool for adjusting the various factors to achieve the desired performance in the co-gasification of coal and biomass. [Display omitted] • An ANN model of co-gasification performance was developed in a bubbling fluidized bed. • Layers Recurrent showed better performance than other ANN types. • The Particle Swarm Optimization showed better performance than other optimization algorithms. • A comprehensive analysis was conducted on the H 2 /CO ratio. • The most critical factor affecting co-gasification performance was identified as steam to carbon ratio and temperature. [ABSTRACT FROM AUTHOR]

Lock-in to existing assets and business practices is a major obstacle to the global objective of phasing out coal-fired power to accelerate decarbonization towards Paris Agreement goals. Japan has attracted attention in previous literature, with several studies demonstrating how market and political conditions have propelled investments in new coal-fired power plants while raising barriers to achieving a phase-out. But in addition to market-level conditions, firm-level characteristics – including assets, commitments, investment behaviour and future-oriented innovation activities – are also critical determinants of lock-in vulnerability. To deepen understanding of how such firm-level dynamics might affect the power industry, this empirical study takes the case of ten incumbent utilities in Japan to identify and compare potential sources of coal lock-in. We leverage diverse quantitative and qualitative data to assess the state of: (1) management, assets and operational factors; and (2) the development and deployment of next-generation coal technologies. Through this two-fold approach, we demonstrate how current conditions and future-oriented activities are likely to reinforce tendencies to continue using coal in coming decades, thereby hampering the emergence of phase-out ambitions. These findings harbour important implications for climate policy and the urgent need to end coal burning in the power sector. Japan's major power utilities all intend to maintain coal in power mixes while transitioning to net-zero by 2050, aiming to eliminate carbon emissions rather than coal-fired power per se. Ambitions to reduce dependence on coal are weakened by a multitude of potential lock-in sources across individual utilities. All utilities are attempting to commercialize next-generation technologies such as co-firing with ammonia and biomass, carbon capture and coal gasification. Phasing out coal in Japan thus requires climate policies that incentivize the development and diffusion of non-emitting power sources that offer faster emissions reduction than expensive and unproven technologies. [ABSTRACT FROM AUTHOR]

This document discusses the importance of high-temperature low-emission combustion technology in reducing dependence on fossil fuels and mitigating environmental pollution. The use of catalysts is highlighted as an effective strategy for reducing pollutant emissions, particularly nitrogen oxide (NOx). The document also presents research on various aspects of catalytic combustion, including pyrolysis, synergistic reactions, and ash sintering. The findings emphasize the potential of catalytic combustion in enhancing energy production efficiency and reducing environmental impact. [Extracted from the article]

Context: Coal water slurry (CWS) is a new type of liquid coal product with low pollution, which is mainly used in the chemical industry to produce syngas (CO + H2). It is of great significance to study the microscopic mechanism of CWS gasification reaction for improving the efficiency of coal gasification. In this paper, the method of molecular dynamics based on reaction force fields (ReaxFF-MD) is used to study the gasification process of CWS/O2 system at different temperatures. The results show that, in the range of 1600–2400 K, the macromolecular network structure of lignite is decomposed into a large number of small molecular structures and a small number of light tar free radical fragments, and the types and quantities of reaction products increased rapidly. At 2400–4000 K, the free radical fragments of light tar are further decomposed and reacted with gasification agents, but the types and quantities of reaction products have little change. At 3600 K, a full gasification reaction occurred in the system, and the content of syngas is the highest. Methods: The model was established and optimized by Materials Studio (MS) software. Based on ReaxFF-MD method, Lammps software was used to simulate the gasification process of CWS/O2 system, and the reaction force field files containing C, H, O, N, and S element were used. By calculating the activation energy of gasification reaction, the rationality of the model and calculation method was illustrated. The post-processing of the results was implemented using OVITO, ChemDraw software, and self-programmed Python scripts. [ABSTRACT FROM AUTHOR]

Reductions in greenhouse gas emissions are necessary to slow global warming and decrease the likelihood of irreversible climate scenarios. There is thus an urgent need for low‐emissions fuels. This study conducted a techno‐economic analysis of two different industrial plant concepts for producing hydrogen from woody biomass. One was a large‐scale centralized 60 MWH2 option using dual fluidized bed gasification with CO2 removal. The other was a small‐scale decentralized 1 MWH2 option using fixed‐bed gasification without CO2 removal. Mass and energy balances were calculated by the process simulation software IPSEpro. Key performance indicators, including technical, economic, and environmental parameters, were derived. Overall energy efficiencies of 64.2 and 59.5% and hydrogen yields of 87 and 68 gH2 kg−1BM.db were determined for hydrogen production by dual fluidized bed and fixed‐bed gasification, respectively. The levelized costs of hydrogen amounted to 5.6 and 15.0 €2022 kg−1H2 and agreed quite well with values from the literature. Flexible and decentralized heat, electricity, and hydrogen production based on fixed‐bed gasification within a multiproduct plant were also evaluated. The results show that the multiproduct plant could be economically feasible if at least 63% of the annual operating hours were dedicated to hydrogen production, and assuming a hydrogen selling price of 17.5 €2022 kg−1H2 in Austria. In conclusion, both of the processes that were evaluated are conceivable technologies for the transition of the energy system towards renewable energy sources from a technical and economic point of view, although small‐scale hydrogen production is considerably more expensive. [ABSTRACT FROM AUTHOR]

The separation process is a well‐established method for beneficiation technologies of low‐rank coal, especially in the case of utilization in the thermochemical processes. In this study, three coal samples, including the original low‐rank coal sample and two coal samples (C1 and C2) from the gravity separation process of the original coal sample, were gasified in a multi‐stage gasification process at the gasification temperature of 900°C and the steam‐to‐carbon (S/C) ratio of 1.00 and 1.25. The separation process led to a significant improvement in the quality of coal samples. This improvement is particularly characterized by a higher carbon and volatile fractions and a lower ash content compared with the original coal. This could be the main reason for the higher gasification performance in the case of the experiment of C1 and C2 coal samples. The volume of syngas obtained from gasification experiments of C1 and C2 samples increased between 1.3 and 1.5 times that of the original coal sample. At all S/C ratios and 900°C, the gasification experiment of the C2 sample produced the highest produced gas yield followed by the gasification experiment of the C1 sample. From the chemical point of view, the produced gas had an H2/CO ratio close to the desired ratio of 2.00, which is suitable for chemical synthesis processes. In the case of C1 sample experiments, the H2/CO ratios were 2.11 and 2.18 at S/C ratios of 1.00 and 1.25, respectively. For the experiments of the C2 sample, the H2/CO ratio reached 1.88 and 2.00 at S/C ratios of 1.00 and 1.25, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Underground coal gasification (UCG) is an efficient method for the conversion of deep coal resources into energy. The scope of this work is to model the subsidence of four gasification cavities with a size of 30 m × 30 m × 15 m, separated by 15 m wide pillars. Two scenarios of gasification sequence are modelled, one with the gasification of cavities 1 and 2 followed by 3 and 4, and the other one with the sequence of cavities 1 and 3, followed by 2 and 4. The results show that the final surface subsidence after gasification of four cavities is 9.8 mm and the gasification sequence has an impact only on the subsidence at the intermediate stage but has no impact on the final subsidence after all four cavities are formed, when only the elasticity regime is considered. Additionally, the maximum surface subsidence for the studied cavities of different sizes ranges from 0.016 mm to 7.14 mm, and the relationship between the subsidence and the cavity volume is approximately linear. Finally, a prediction model of surface subsidence deformation is built up using the elastic plate theory, and the formula of surface deformation at a random point is given. The maximum difference between measured and calculated deformation is 4.6%, demonstrating that the proposed method can be used to predict the ground subsidence induced by UCG. [ABSTRACT FROM AUTHOR]

Paddy parboiling in rice industries is an energy-intensive process that requires huge attention for energy conservation, fuel economy, and sustainability. Thus, several research initiatives have been undertaken to adopt a suitable energy conversion system in such industries to improve thermal efficiency and reduce environmental impact. In this study, exergy performance and exergy-based sustainability indicators have been investigated on a reversible bed paddy dryer coupled with a rice husk-fuelled downdraft gasifier. The experiment was conducted at the optimum operating conditions such as an equivalence ratio of 0.2 in the gasifier and a drying air temperature of 80℃ in the dryer. The exergy efficiency of the reversible bed dryer and the gasifier were 65.53% and 70.92% respectively. The lowest exergy efficiency of 35.29% was seen in the combustion chamber since a huge exergy destruction of 2.75 kW occurred. Therefore, the combustion chamber has a high potential improvement of about 1.66 kW. Due to less exergy destruction, the gas cooler and air duct showed high exergy efficiency of 62.36% and 76.2% respectively and the lowest values in exergy-based sustainability indicators. The assessment of environmental and sustainability factors on each component showed that the combustion chamber has a high waste exergy ratio of 0.688, environment effect factor of 1.95, exergy destruction coefficient of 0.69, and exergy sustainability index of 0.51. [ABSTRACT FROM AUTHOR]

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/%. [ABSTRACT FROM AUTHOR]

[Display omitted] The orientation-guidance coupled with in-situ activation methodology is developed to synthesize the N -doped porous carbon (NPC) with well-developed porosity and high specific surface area, using coal pitch as a carbon precursor. The orientation-guidance and activation are dedicated to generating microporous and mesoporous channels, respectively. The in-situ N incorporation into the carbon skeleton is realized along with the formation of porous carbon (PC), ensuring the uniformity of N doping. As an electrode material of supercapacitor, benefiting from the robust hexagon-like building block decorated with micro-mesoporous channels and N doping, NPC electrode affords a significant improvement in capacitive energy-storage performance, achieving a specific capacitance of up to 333F g−1 at 1 A/g, which far exceeds those of PC and activated carbon. Notably, even under high mass loading of 10 mg cm−2, the NPC maintains a satisfactory capacitance of 258F g−1 at 1 A/g. When employed as the anode in Li-ion capacitor (LIC), apart from exhibiting enhanced anode behavior compared to graphite anode, NPC also delivers exceptional cyclability. Furthermore, density functional theory calculations have validated the enhanced electrical conductivity and Li storage ability contributed by N doping, providing a theoretical foundation for the observed improvements in electrochemical performance. A full LIC configured with NPC anode delivers extraordinary Ragone performance and outstanding cyclability. This work also proposes a feasible way to realize the oriented conversion of coal pitch into high-performance electrode materials for electrochemical energy-storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coal ash is an important source of germanium, a crucial resource in modern society. • A coal gasification ash can be used both as germanium source and as building material. • An integrated valorization process for a real coal gasification fly ash is shown. • A more circular and sustainable recycling alternative for this waste is presented. • Better waste management option for coal gasification plants and old ash deposits. A Circular Waste Management alternative is considered in this paper in which a complete ash valorization process is proposed for an Integrated Gasification with Combined Cycle fly ash, trying to extract maximum value from this waste before it is discarded. In the paper, germanium, a scarce resource vital in our modern society, is first extracted from fly ash using water, with an extraction yield of 85%, and subsequently, the leached fly ash is used in the manufacture of fire-resistant boards containing 60% ash, thereby avoiding its disposal in a landfill. The potential environmental impact caused by the two stages of the process was analyzed, and the final effluent was considered to achieve a zero-discharge objective. This paper contributes to the development of a more sustainable management alternative for an industrial waste produced in increased amounts and provides the basis for a symbiotic coupling relationship among various industrial sectors. [ABSTRACT FROM AUTHOR]

Abstract Coal catalytic hydrogasification (CCHG) is a straightforward approach for producing CH4, which shows advantages over the mature coal-to-CH4 technologies from the perspectives of CH4 yield, thermal efficiency, and CO2 emission. The core of CCHG is to make carbon in coal convert into CH4 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 CH4 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 CO2 into CCHG. Preliminary investigations from our laboratories demonstrated that the integrated CCHG and biomass/CO2 hydrogenation process could perform as an emerging pathway for boosting CH4 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, CO2, and coal-derived wastes.