Clean Utilization Research Articles

Evolution characteristics of microwave absorbing carbon material on surface of CoFe2O4@biochar during hydrogen production from methane decomposition process

This study proposes a strategy to convert carbon deposits, generated during the catalytic decomposition of methane for hydrogen production, into high-performance microwave-absorbing materials. This approach not only reduces carbon emissions but also achieves carbon fixation and reuse, promoting environmental sustainability. The research demonstrates that cobalt ferrite (CoFe2O4)-loaded biochar catalysts, at different proportions, exhibit highly efficient and selective hydrogen production capabilities in the process of methane decomposition and hydrogen production, with a peak methane conversion rate as high as 83.6 %, which is higher than that of pure biochar catalysts. The improvement was significant, with an increase of 2.2 times. This catalyst not only strengthens the stability of methane decomposition, but also effectively shortens the reaction induction period, showing excellent catalytic performance and stability. Following methane cracking, an ordered, highly crystalline graphitic carbon structure forms within the catalyst, significantly improving its microwave absorption capacity. At a thickness of 1.3 mm, the catalyst’s microwave absorption reaches a peak value of −41.39 dB, with an effective absorption bandwidth of 4.56 GHz. The catalyst’s outstanding microwave absorption performance arises from synergistic mechanisms, such as multi-layer reflection and interface polarization, which effectively convert electromagnetic energy into thermal energy, facilitating efficient electromagnetic wave dissipation. This research presents an efficient catalyst for the clean utilization of methane resources and explores new pathways to convert industrial by-products into high-value materials, particularly with potential applications in microwave-absorbing technologies.

Synergistic regulation of dual thresholds: Hydroxyl occupancy and carbon species in the targeted catalytic hydrocracking of lignite

The preparation of carbon-based catalyst supports from low-grade lignite, followed by its self-catalytic hydrocracking to produce lignite-derived aromatic compounds, is crucial for achieving efficient lignite utilization and expanding aromatic compound sources. During lignite catalytic hydrocracking, the uncontrolled diffusive migration of active hydrogen (H*) and insufficient protection of aromatic rings reduce the yield of aromatic compounds. Using Heishan lignite as the raw material, we employed a relay process of thermal-induced self-assembly and oxidation-mediated carbon distortion for fabricating the Co3O4/AC&GC-S-600 composite material, which features an optimal hydroxyl occupancy ratio and a balanced combination of amorphous carbon/graphite carbon (AC/GC) types. The optimal hydroxyl occupancy threshold balances Co3O4 dispersion and hydrophilicity, facilitating the efficient formation and directional migration of H* through synergistic interaction between Co3O4 and H2O. The adequate threshold of AC/GC ratio regulates substrate adsorption, activation, and inhibition of aromatic hydrogenation, enhancing selective C–O bridge bond cleavage and preserving the unsaturation of aromatic rings. The synergistic regulation of dual thresholds promotes the rapid formation and the directional migration of H*, enabling efficient conversion of Heishan lignite to aromatic compounds (45.8% conversion, 80.8% selectivity) under mild conditions. Characterization techniques, experimental analyses, kinetic studies, and density functional theory calculations confirm that thermally induced self-assembly and oxidation-mediated carbon distortion are crucial for redistributing the carbon framework of the Heishan lignite matrix and regulating the optimal dual thresholds of hydroxyl occupancy and AC/GC types, which are essential for the catalytic hydrocracking of Heishan lignite to aromatic compounds. This strategy provides a scientific basis for selective catalytic production of lignite-based aromatic compounds, thereby supporting its clean and efficient utilization.

Surfactant-modified ZnFe2O4/CaOPS porous acid-base bifunctional catalysts for biodiesel production from waste cooking oil and process optimization

Biodiesel production from waste cooking oil (WCO) with high acid value is useful for clean energy development and utilization. In this work, ZnFe2O4(5)/CaOPS porous bifunctional catalysts were prepared for catalytic production of biodiesel with the help of surfactants such as PVP, SDS and citric acid, using a sol-gel method. The ZnFe2O4(5)/CaOPS catalysts were characterized using XRD, SEM, EDX, NH3-TPD, and BET. The parameters (reaction temperature, catalyst dosage, methanol-oil ratio and reaction time) for the transesterification reaction to produce fatty acid methyl esters (FAMEs) were optimized for the optimal materials using a one-variable method. Experiments were designed using Response Surface Methodology (RSM) and Artificial Neural Network (ANN) for global optimization to obtain the best process parameters. The final average yield of FAMEs was 96.89% under the optimum reaction parameter of catalyst dosage of 5.06wt%, reaction temperature of 63.69°C, reaction time of 212.22min and methanol-oil ratio of 12.96:1. The prepared biodiesel was characterized using FT-IR, 1H NMR as well as 13C NMR and compared with international standard ASTM D6751. The ZnFe2O4(5)/CaOPS catalyst has excellent stability in biodiesel production and has some free fatty acid tolerance. In addition, a cost analysis and sensitivity analysis were done for the production of WCO biodiesel. It is hoped that the research results in this paper can provide a theoretical basis for biodiesel production from WCO with high free fatty acid content.

Unveiling the incorporation of dual hydrogen-bond-donating squaramide moieties into covalent triazine frameworks for promoting low-concentration CO2 fixation

The development of multi-functional materials for low-concentration CO2 fixation into organic carbonates remains a significant challenge. Herein, we constructed several covalent triazine frameworks modified with squaramide moieties (SCTF-R; R = H, F, CF3) using a facile ZnCl2-mediated trimerization approach. The as-prepared SCTFs possess high surface areas (605–833 m2/g) and incorporate high-density hydrogen bond donors as well as CO2-affinity sites. They demonstrate good CO2 adsorption capacity of up to 2.5 mmol/g at 273 K and 1.0 bar CO2 pressure. Notably, the SCTF-CF3 combined with KI exhibits excellent performance in converting low-concentration CO2 into bromopropene carbonate with a yield of 96 % and selectivity of 99 % under mild and metal-/solvent-free conditions. Furthermore, the SCTF-CF3/KI system demonstrates outstanding reusability and versatility. By combining in-situ FT-IR monitoring with DFT calculations, we elucidate the significant contribution of squaramide moieties and reaction mechanism. This work provides an innovative approach for clean and efficient utilization of low-concentration CO2.

Preparation of High-Purity Nano-Iron Phosphate from Titanium-Extraction Tailings by Co-Leaching Synergetic Ultrasonic-Enhanced Precipitation Process.

The preparation of high-performance electrode materials from metallurgical solid waste is an effective strategy to address current energy and environmental challenges. This study utilizes a mixed acid leaching and ultrasound-assisted precipitation process to extract valuable metallic iron from titanium-extraction tailings (TET) to produce high-purity nano-FePO4 electrode material precursors with unique crystal structures. A leaching efficiency of 95.2% for Fe was attained by using the optimized process parameters, which included a mixed acid concentration of 4 mol/L, a liquid-to-solid ratio of 4:1, and a leaching temperature of 70 °C for 1 h. The optimal precipitation conditions were a pH of 2.0, a temperature of 60 °C, an aging time of 30 min, and a stirring speed of 600 rpm, resulting in FePO4 purity up to 99.6% and fine particle size. Thermodynamic calculations, combined with various characterizations, elucidated the leaching and precipitation mechanisms, highlighting the synergistic effect of phosphoric acid and hydrochloric acid in enhancing the leaching reaction. The thermogravimetric analysis indicated that the decomposition of residual ammonium chloride impurities requires calcination above 360 °C. This research not only provides new insights into the high-value, clean utilization of metallurgical solid waste but also supports sustainable resource recovery and environmental protection by transforming waste into valuable products.

Key process of ethanol hydrogen donor promoting the conversion of organic matter in sludge to bio-oil

To develop clean energy utilization of sewage sludge, this study investigated the conversion behavior of organics and energy in supercritical sludge-ethanol system. The influence of liquefied parameters on products distribution, hydrogen supply process of ethanol for sludge liquefaction, migration of organics, and energy transformation were investigated. Results indicated that ethanol acted as both a solvent and a hydrogen donor. It providing H⋅ to promote organics dissociation for bio-oil production through radical reactions. Formation of new products in bio-oil such as C20H38O2 and C20H38O2 may be caused by H⋅ generated from OH and CH in ethanol. The increase in dodecanes and hexadecanes in bio-oil may be formed by recombination of smaller radicals such as HO·, H·, CH3⋅, CH3CH2⋅ from dissociation of ethanol and organics. Additionally, energy migration process indicated that higher temperatures increased carbon content in bio-oil from 40.88 to 48.92 %, decreased oxygen content from 48.6 to 39.56 %, and raised the calorific value of bio-oil from 29.63 to 30.11 MJ/kg. Besides, approximately 74.14 % of sludge energy transferred to bio-oil, while about 71.94 % of oxygen moved to bio-char, reducing the calorific value of bio-char to 0.03 MJ/kg. Notably, about 240.5 kg of bio-oil can be produced from 1t of sludge, reducing net carbon emissions by 43.583 kg, and presenting a sustainable alternative to fossil fuels. This study innovatively investigated the dual role of ethanol for sludge liquefaction, providing an efficient and sustainable method for energy recovery from sludge.

Spray and evaporation characteristics of high-pressure liquid ammonia injection under flash-boiling and evaporating conditions

Ammonia, as an efficient hydrogen carrier, is considered a promising zero-carbon alternative fuel for energy systems. High-pressure liquid ammonia injection enables efficient and clean utilization of ammonia in energy devices. This study systematically investigates the spray and evaporation characteristics of high-pressure liquid ammonia spray with two different nozzle diameters (0.1 mm and 0.3 mm) over wide operating conditions by combining high-speed DBI and shadowgraph techniques. The results indicate that the expansion rate of the small-nozzle spray is greater than that of the large-nozzle spray at low superheat (1.4 ∼ 2). As the superheat exceeds 2, the spray expands significantly radially, with a larger expansion rate for the large-nozzle spray, suggesting the large-nozzle spray is more prone to forming flash-boiling bubbles. Under high temperature and pressure conditions with fixed ambient pressure, the liquid penetration increases and then decreases as the temperature increases, and the inflection point temperature of the large-nozzle spray is higher. Compared with diesel, the axial diffusion of the liquid ammonia is larger while the radial diffusion is smaller. There is a post-supercooling residual region affected by the pilot-evaporated ammonia in the capturing and recirculation regions, where the fuel cannot completely evaporate like the diesel. This characteristic should be considered when designing the liquid ammonia spray system.

AMn2O4 (A = Ni, Co, Cu) oxygen carrier chemical looping reforming of benzene: Migration pathways of reactive oxygen species by experimental and DFT investigations

Chemical looping reforming (CLR) provides a novel solution for clean and efficient utilization of biomass tar. The versatility of oxygen carrier (OC) is essential for improving reforming efficiency. The properties of Mn-based spinel OCs (AMn2O4, A = Ni, Co, Cu) were investigated in the CLR process using benzene as a tar model compound. Detailed characterization and experimental results demonstrate the excellent structural stability of Mn-based spinel. The NiMn2O4 showed the most prominent reforming effect on benzene with the highest conversion of 95.77 % at 850 °C, S/C = 1.0, and WHSV = 3.0 h−1. After 40 cycles, NiMn2O4 and CoMn2O4 maintained significant catalytic activity for benzene reforming, achieving conversions of 92.96 % and 90.07 %, respectively, in the final cycle. Density functional theory (DFT) calculations demonstrate that the addition of H2O increases the activity of NiMn2O4. Compared to benzene adsorption alone, the adsorption energy decreased from −2.20 eV to −2.54 eV after the addition of H2O. The migration path of NiMn2O4 (100) reactive oxygen species in the presence or absence of H2O is directly demonstrated. In the absence of H2O, the activation energy barrier for direct oxidation of C6H5* by NiMn2O4 lattice oxygen is dominant (0.98 eV), but OH* produced by dissociation of H2O exhibits high activity, and oxidation of C6H5* to produce the key intermediate product C6H5O* has an activation energy barrier of only 0.35 eV. In addition, H2O has a predominant role in the replenishment of oxygen vacancies. The elucidation of the oxygen migration mechanism provides new guidance for the design of efficient OCs for catalytic oxidation.

Cold plasma-activated Ni-Co tandem catalysts with CN vacancies for enhancing CH4 electrocatalytic to methyl formate

The direct electrooxidation of methane (CH4OR) into high value-added liquid products has been considered an effective method to efficient and clean utilization of methane. However, this process is mainly limited by CH4 activation and subsequent intermediate regulation. Here, we report the first successful achieve methyl formate from CH4OR on Ni-Co tandem catalysts with CN vacancies prepared by H2 cold plasma. The faradaic efficiency of CH4OR into methyl formate reaches 56.7 % at 2.0 V vs. RHE with remained stability for 160 h. In situ ATR-SEIRAS and DFT calculations suggest that the CN vacancies can shift the d-band center of the active Ni sites upwards to enhance the chemisorption of CH4 over Ni atom near CN vacancy, generating the key intermediates of *CH3 and *CH2. *CH2 further overflows onto the Co atom around the same CN vacancy, providing favorable conditions for esterification reaction to obtain methyl formate. This work opens a new avenue for the development of efficient electrocatalytic systems for the clean utilization of methane and the electrosynthesis of methyl formate under ambient conditions.

Mechanism of microwave-assisted coal desulfurization with urea peroxide

To effectively remove organic sulfur from coal for higher resource efficiency, an innovative microwave-assisted urea peroxide for desulfurization system was designed. The experimental group with different microwave frequencies and the conventional pyrolysis control group were set up to prove the desulfurization effect of microwave in coordination with urea peroxide. The experimental results showed that under 1000 W microwave irradiation and the promotion of urea peroxide, the desulfurization efficiency can reach 67.29 %, with an increase of 38.32 % while the conventional pyrolysis is only 28.97 %. According to the Fourier transform infrared (FTIR) analysis, the effectiveness of microwave coordination with urea peroxide for desulfurization is explained from macroscopic point of view. Benzylidene thiol, dibenzyl sulfide, and dibenzyl disulfide were selected as model compounds for the quantum chemical calculation. The simulation results demonstrated that the changes in the pathway energy barriers for desulfurization align with the experimental material transformations, confirming the accuracy of the simulation. The sulfur-containing bonds of mercaptans will be destroyed to form hydrogen sulfide, and the undestroyed bonds will remain in the organic matter. After being oxidized, the sulfur-containing bond will break to form a water-soluble sulfonic acid free radical. The unoxidized sulfur bonds of thioethers will be destroyed to generate unstable phenyl free radicals and free sulfur radicals. To achieve stability, phenyl free radicals can pair to form diphenylethane or combine with other radicals (such as •H). In contrast, sulfur free radicals can only react with hydrogen radicals to form hydrogen sulfide. However, the limited availability of hydrogen radicals in the system restricts the desulfurization efficiency. After oxidation by urea peroxide, the thioethers will form sulfones. The sulfur-containing bonds will be fractured and directly generate phenyl and sulfur dioxide, which reduces the dependence on hydrogen free radicals. The three-dimensional desulfurization path of microwave collaboration with urea peroxide experiment was simulated and converted to the analytical bond breaking and formation mechanism. This study proved that microwave synergizes with urea peroxide can intensify the desulfurization process. It provides a high-efficiency method for the clean and green utilization of coal, which is conducive to supporting environmentally sustainable development.

Recycling of spent heat pack towards Fe-Fe3O4@NC catalyst for ORR in direct methanol fuel cells and Al-air batteries

The effective repurposing of waste materials is crucial for sustainable development. The widespread use of disposable iron-based chemical warmers (IBCW) generates substantial solid waste annually. In this study, IBCWs were repurposed as raw materials to synthesize different electrocatalyst composites comprising metallic and oxide forms of iron embedded in nitrogen-doped carbon (NC). The composites were evaluated as oxygen reduction reaction (ORR) catalysts. The optimized Fe-Fe3O4@NC demonstrated enhanced ORR kinetics, with an onset potential of 0.92 V and a half-wave potential of 0.86 V vs. RHE. As an air cathode for direct methanol fuel cell (DMFC), Fe-Fe3O4@NC achieved a power density of 33.3 mW cm−2 at 88 mA cm−2, demonstrating its practical applicability. Additionally, a quasi solid-state aluminium-air battery (SAAB) was assembled using this catalyst as the air cathode with a PVA-KOH gel electrolyte and the separator. The quasi SAAB exhibited an open circuit voltage (OCV) of 1.46 V, a power density of 40 mW cm-2, and good rate capability compared to Pt/C. The combined effect of metallic and oxide iron with nitrogen doping enhances the overall catalytic activity. This study demonstrates that IBCWs can be effectively transformed into valuable catalysts for renewable energy applications, enabling clean and sustainable utilization of waste materials.

Solubilization of K and P nutrients from coal gangue by Bacillus velezensis.

Coal gangue piles not only occupy significant amounts of arable land but also cause serious environmental pollution. Therefore, finding sustainable methods for the clean utilization of CG is imperative. Although previous studies have shown that bacteria can promote the solubilization of available phosphorus and available potassium from CG, their impact on promoting plant growth remains understudied. To our knowledge, this study is the first to demonstrate the potential of Bacillus velezensis in enhancing the effectiveness of CG as a mineral fertilizer to support alfalfa growth. The evidence presented in this study provides an ecological strategy for the utilization of CG.

Heavy metal migration and enrichment in desulfurization wastewater during low-temperature triple effect evaporation process

Zero discharge of desulfurization wastewater from coal-fired power plants has become important. Desulfurization wastewater and gypsum from different stages of the low-temperature triple-effect evaporation process of a coal-fired power plant were collected and investigated. The results showed that after low-temperature triple-effect evaporation, the concentrations of Na+, Mg2+, K+, and Cl− in the desulfurization wastewater increased by 7.91, 7.15, 8.49, and 8.35 times, respectively. With the progress of low-temperature triple effect evaporation process, the concentrations of As, Cd, Co, Cr, Cu, Mn, Se, and Zn in the wastewater after the triple effects were 5.85, 75.44, 1.28, 2.34, 13.66, 5.58, 8.59, and 4.35 times higher than those in the raw wastewater. Mn and Se exceeded the emission limits by 40 and 10 times, respectively. After triple-effect evaporation, the concentrations of As, Cd, Co, Cr, Cu, Pb, Se, and Zn in gypsum decreased to 46%, 26%, 66%, 41%, 35%, 97%, 39%, and 51% of the raw gypsum, respectively. Compared with that of other metal sulfates, the solubility of PbSO4 was extremely low under low-temperature conditions, and some PbSO4 precipitated during the triple-effect evaporation process, leading to a gradual decrease in the Pb concentration in the liquid phase. The mercury compounds in gypsum after the first and second effects were the same as those in raw gypsum, both of which were HgS and HgO. After third effect, the mercury compound in gypsum also included HgSO4. In addition, owing to the promoting effect of the pH of desulfurization wastewater approaching 5.50 on the generation of HgS, the proportion of HgS gradually increased, and the proportion of HgO gradually decreased from the raw gypsum to the third effect gypsum. Therefore, the stability of the mercury compounds in gypsum was enhanced. It can provide a good reference for the migration and enrichment of heavy metals in the low-temperature triple-effect evaporation process, which is beneficial for the clean production and efficient utilization of coal.

A new approach to collaborative resource utilization of biological sludge and zinc-bearing dust: Reduction characteristics and mechanisms

This paper proposes an innovative approach for co-processing zinc-bearing dust with biological sludge, using the organic matter in the sludge as a reducing agent to replace traditional fossil fuels (coal/coke). The results show that the reduction process of biological sludge-zinc-bearing dust pellets (BZP) is divided into two stages. In the first stage (25–620 °C), the breakdown of C = C, C-O-C, and C-O bonds present in biological sludge produced carbon oxide (CO) and hydrogen (H2), facilitating the conversion of zinc ferrite (ZnFe2O4) to magnetite (Fe3O4). The second stage (620–1300 ℃), the cleavage of C = C, C–C and C–H bonds and carbon gasification generate more CO and H2, further reducing magnetite (Fe3O4) to metallic iron (Fe) and zinc oxide (ZnO) to zinc monomers (Zn). The activation energy of BZP in the two stages was 32.86 kJ·mol−1 and 73.88 kJ·mol−1, respectively. The metallization rate and the zinc removal rate of BZP achieved 58.47 % and 86.74 %, respectively, indicating the effectiveness and feasibility of the propose of approach. This approach provides a clean and comprehensive utilization way out for zinc-bearing dust and biological sludge.

The contribution of clean energy consumption and production to sustainable economic development: New insights from the PSTR model

Massive consumption of fossil fuels has posed significant threat to sustainable development. Therefore, clean energy is an urgent requirement for sustainable economic development (SED). There is no comprehensive assessment of the relationship between clean energy and the SED, signifying a research gap in understanding the non-linear effects between them. This study fills this gap by calculating the SED index for China and using a panel smoothed transformation regression model. The findings reveal that the impact of clean energy development and utilisation on SED is characterised by non-linearity, which manifests in two key aspects: (1) Clean energy consumption (CEC) positively influences SED, with its impact strengthening alongside improvements in industrial structure optimisation and economic growth. Notably, the threshold values for the industrial optimisation level, industrial structure level, and economic development are 1.0390, 0.4667, and 43730, respectively. (2) The relationship between clean energy production (CEP) and SED follows a U-shaped curve; once economic development surpasses 38,588 units, CEP transitions from a negative to a positive influence on SED. This study provides valuable insights into comprehensive measurement of SED, offering guidance for countries worldwide to formulate context-specific energy policies aligned with their respective industrial structures and stages of economic development to foster SED growth.

Concurrent removal of Fe(II), Cu(II), and Zn(II) cations from acid mine drainage by an industrial solid waste - Steel slag: Behaviors and mechanisms

Acid mine drainage (AMD) contamination poses a severe environmental threat and is a significant risk to human health. There is an urgent need to develop environmentally sustainable and technically viable solutions for water contamination caused by heavy metals. In this study, steel slag (SS) was used as a secondary resource to concurrently remove Fe(II), Cu(II), and Zn(II) from AMD. Because of the loose and porous structure, abundant functional groups, fast sedimentation velocity, and excellent solid-liquid separation, SS showed exceptional removal performance for heavy metal ions. The adsorption kinetic data of Fe(II),Cu(II), and Zn(II) showed good regression with the pseudo-second-order model. Besides, the adsorption of Fe(II) by SS conformed to the Freundlich model, whereas the adsorption of Cu(II) and Zn(II) followed the Langmuir model, with the maximum adsorption amounts of Cu(II) and Zn(II) being 170.69 mg/g and 155.98 mg/g. Furthermore, competitive adsorption was observed among Fe(II), Cu(II), and Zn(II) in a multi-component system, with the adsorption priority being Fe(II)>Cu(II)>Zn(II). The removal mechanism of Fe(II), Cu(II), and Zn(II) in AMD by SS mainly includes electrostatic attraction, chemical precipitation, and surface complexation. Interestingly, the leached concentrations of Fe(II), Cu(II), and Zn(II) from the spent slag after calcination were all within the detection limit of the Chinese emission standard, demonstrating excellent environmental stability. Theoretically, this renders it a viable candidate for use as an additive in construction materials. Meaningfully, the work offers a practical approach for energy-efficient and eco-friendly heavy metal ions adsorption, and the secondary utilization of SS also contributes to the sustainable development of the steel industry. It is beneficial to implement the development concepts of clean production and efficient utilization of industrial solid waste.

Analysis of difficult flotation mechanisms for coarse low-rank coal: Comparing fluidized-bed and mechanical flotation technologies

Efficient flotation of coarse low-rank coal is essential for enhancing energy utilization in the mineral processing industry. As the beneficiation equipment scales up, the precision of particle size classification before flotation decreases, leading to a higher coarse particle content in the feed, which poses significant challenges to traditional flotation processes. Recent advancements in fluidized bed flotation technology have demonstrated considerable advantages in the flotation of coarse-grained metallic minerals; however, its application to coarse low-rank coal remains relatively unexplored. This study investigates the potential of fluidized bed flotation technology for coarse low-rank coal, employing various analytical methods to elucidate difficult flotation mechanisms. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were utilized to comprehensively characterize the surface morphology and chemical composition of coal samples. The influence of increasing particle size on flotation performance was systematically assessed through measurements of induction time and critical detachment amplitude. Comparative flotation experiments were conducted to evaluate the efficacy of traditional mechanical flotation against fluidized bed flotation technologies. Results indicate that the presence of cracks and oxygen-containing functional groups on the coal surface significantly enhances hydrophilicity, hindering flotation recovery rates. With increasing particle size, the induction time between particles and bubbles lengthens, while the critical detachment amplitude decreases, weakening the attachment and increasing detachment likelihood. Although high-efficiency collectors enhance coal particle hydrophobicity, they cannot fully mitigate the turbulence disrupting bubble-particle interactions in mechanical flotation. Conversely, fluidized bed flotation effectively minimizes turbulence interference, leading to an approximate 40 % increase in the recovery rate of coarse low-rank coal (0.25–1.00 mm) compared to traditional mechanical flotation. This study presents a novel technological approach for the efficient recovery of coarse low-rank coal, contributing to the clean utilization of low-rank coal resources.

Corrosion behavior of co-gasification slag of furfural residue and coal on alumina-silica refractories

Gasification of furfural residue with coal can realize its efficient and clean utilization. But the high alkali metal content in furfural slag is easy to cause the corrosion of gasifier refractory. Two gasification coals with different silica alumina ratio and a furfural residue were selected in the study. The effects of furfural residue additions on corrosion of silica brick, corundum brick, high alumina brick and mullite brick were investigated by using XRD, SEM-EDS and Factsage Software, and the corrosion mechanism was analyzed. With increasing furfural residue addition, the permeability of the slags to high-aluminium-bearing refractories first decreases and then increases, while the permeability on silica brick shows a slight decrease trend. Leucite (KAlSi2O6) with high-melting temperature is generated from the reaction of K2O and SiO2 in slag with Al2O3 in refractories after furfural residue is added, which hinders the infiltration of slag in refractories. Kaliophilite (KAlSiO4) of low-melting point is formed when K2O content increases, and this contributes to the infiltration of slag in refractories. The acid-base reaction between slag and silica brick is distinctly occurred, more slag reacts with SiO2 in the silicon brick, resulting in a decrease in the amount of slag infiltrating into the silicon brick as furfural residue is added. The corrosion of silica brick is mainly caused by the acid-base reaction, while the corrosion of three alumina based refractory bricks of corundum, mullite and high alumina brick is determined by slag infiltration. A linear correlation between the percolation rate and slag viscosity is established, the slag permeability increases with decreasing viscosity, resulting in stronger permeability for the high Si/Al ratio slag with lower viscosity.

New Insights on the Understanding of Sulfur-Containing Coal Flotation Desulfurization

The clean and efficient utilization of coal is a promising way to achieve carbon neutrality. Coking coal is a scarce resource and an important raw material in the steel industry. However, the presence of pyrite sulfur affects its clean utilization. Nonetheless, this pyrite could be removed using depressants during flotation. Commonly used organic depressants (sodium lignosulfonate (SL), calcium lignosulfonate (CL), and pyrogallol (PY)) and inorganic depressants (calcium oxide (CaO) and calcium hypochlorite (Ca(ClO)2)) were chosen in this study. Their inhibition mechanism was discussed using FTIR, XPS, and molecular dynamics (MD) methods. The desulfurization ability of organic depressants was shown to be better than inorganic ones. Among the organic depressants, PY proved to be advantageous in terms of low dosage. Physical adsorption was identified as the main interaction form of SL, CL, and PY onto the surface of pyrite, as evidenced from FTIR and XPS analyses. Similarly, MD simulation results showed that hydrogen bonds played a proactive role in the interactions between PY and pyrite. The diffusion coefficient of water molecules on the pyrite surface was also observed to decrease when organic depressants were present, indicating an increase in the hydrophilicity of pyrite. This research is of great significance to utilize sulfur-containing coal and minerals.

Configuration optimization of a biomass chemical looping gasification (CLG) system combined with CO2 absorption

Biomass chemical looping gasification (CLG) combined with CO2 absorption in a dual circulating fluidized bed (DCFB) has emerged as an advanced technology for clean and efficient biomass utilization, yet the reactor design for achieving higher gasification performance and the in-depth understanding of physical-thermal-chemical characteristics is still lacking. This study presents an optimized design aimed at enhancing hydrogen production and carbon reduction in the biomass CLG process with a DCFB reactor by employing the multiphase particle-in-cell (MP-PIC) method integrated with thermochemical sub-models. The proposed reactor is comprehensively compared with the original reactor from the experimental setup in terms of particle mixing, heat transfer, and gasification behaviors. The results indicate that compared to the original setups, the proposed CLG system demonstrates: (i) an improved gas-solid mixing, as evidenced by the particle mixing index rising from 0.23 to 0.34; (ii) an enhanced particle heat transfer coefficient, which boosts heat and mass transfer process; (iii) a 10.11 % increase in H2 concentration alongside a 23.71 % decrease in CO2 concentration; (iv) a particle distribution characterized by higher concentration at the bottom and lower concentration at the top, along with intensified particle back-mixing. The pressure drop inside the combustor is higher than that in the gasifier. A smaller absorbent mean particle diameter and lower-positioned biomass feeding port contribute to the improvement of the CLG performance.