Abstract:As a carbon-neutral renewable energy source,biomass gasification technology represents one of the core pathways for its large-scale utilization.Catalytic upgrading of biomass producer gas achieves high-value conversion through targeted component transformation and efficient impurity removal,offering advantages such as a wide operating temperature range,high product purity,and easy integration with renewable energy systems.Based on the composition characteristics of biomass producer gas,the components are separated into H2,synthesis gas(CO+H2),hydrocarbons,CO2,pollutants.This systematic review summarizes the current research status of catalytic technologies across five pathways for upgrading biomass producer gas:hydrogen purification and production,synthesis gas component conversion,hydrocarbon reforming,CO2 capture and conversion,and synergistic pollutant removal.Research reveals that all pathways highly depend on the synergistic mechanism among the active phase,support,and additives of catalysts.In hydrogen production pathways,CeO2/Fe2O3-modified Ni-based catalysts significantly enhance coking resistance.For syngas conversion,Fe-based catalysts favoring low-carbon olefins and Co-based catalysts favoring long-chain alkanes are respectively adapted based on differences in n(H2)/n(CO)ratios.Hydrocarbon reforming focuses on CH4 and tar conversion,enhancing stability through bimetallic synergy and mesoporous confinement effects.Although CO2 capture has established three material systems:Ca-based,amine-based,and MOFs-integration of capture and conversion processes remains relatively low.Pollutant removal demonstrates high efficiency in treating single sulfur or nitrogen compounds but lacks effective solutions for synergistic removal of multiple pollutants.Future research may focus on innovative technical approaches such as rational design of multifunctional catalysts and regulation of oxygen vacancy and interfacial effects to address bottlenecks including insufficient processing capacity,low process integration,and poor catalyst stability.

Abstract:The sulfur and nitrogen elements in low-rank coal significantly impactits processing,conversion,and utilization.A clear understanding of the occurrence forms,structure,and migration patterns of sulfur and nitrogen during thermal conversion not only mitigates their potential environmental hazards but also enables the targeted conversion of these elements intosulfur-ornitrogen-containing chemicals and the development of sulfur-/nitrogen-doped novel carbon materials for high-value applications.To this end,this paper systematically summarizes the occurrence forms of sulfur and nitrogen in low-rank coal;analyzes the effects of pyrolysis atmosphere,pyrolysis temperature,catalysts,and other factors on the distribution characteristics and migration pathways of sulfur-and nitrogen-containing compounds in coal pyrolysis products;and explores the application of machine learning methods such as Random Forest and LightGBM in predicting pyrolysis products.Sulfur in low-rank coal primarily exists as organic sulfur,while nitrogen is predominantly present as four types of organic nitrogen:pyrrolic nitrogen,pyridinic nitrogen,quaternary nitrogen,andoxidized pyridinic nitrogen.Specifically,within vitrinite,the predominant sulfur-containing functional groups are thiophene,thiol,and thioether,while the nitrogen-containing functional groups are primarily pyridinic and benzonitrile derivatives.In contrast,within inertinite,the forms of sulfur-containing functional groups are similar to those in vitrinite,but the nitrogen is predominantly present as amine and pyrrolic structures.Increasing pyrolysis temperature promotes the decomposition of sulfur and nitrogen elements.Slower heating rates favor the removal of organic sulfur,whilefaster heating rates are more conducive to the migration of nitrogen to gaseous products.H2,water vapor,and CO2 atmospheres all promote the decomposition of sulfur-and nitrogen-containing compounds.Specifically,H2 and water vapor provide hydrogen radicals that attack sulfur and nitrogen atoms in heterocyclic aromatics,thereby accelerating their decomposition.The CO2 atmosphere promotes C—S,C—C,and C-N bond cleavage,accelerating the formation of gaseous sulfur-and nitrogen-containing compounds.Both calcium-based and iron-based catalysts exhibit sulfur fixationcapabilities while also influencing the conversion of nitrogen,typically promoting its release as gaseous species such as HCN and NH3.During pyrolysis,inorganic sulfur(primarily pyrite)is transformed into pyrrhotite,which further reacts with active hydrogen and CO to form gaseous products like H2S and COS;the undecomposed fraction remains in the char.Organic sulfur decomposition primarily occurs through C-S bond cleavage.The resulting sulfur-containing radicals react with hydrogen atoms or other hydrogen donors to form gaseous products like H2S and SO2.Other sulfur-containing groups polymerize or combine with aromatic rings to form polycyclic sulfur-containing aromatics,migrating into tar and char.Nitrogen in pyrolysis gas originates from the ring-opening reactions of nitrogen-containing heterocycles like pyridine and quinoline.Nitrogen in tar derives from the elimination and reorganization of heterocyclic compounds such as pyridines and pyrroles,while highly stable organic nitrogen remains in the char.Using out-of-bag estimation for hyperparameter optimization of the random forest algorithm reduced the prediction deviation for naphthobenzothiopheneto 0.11％.The LightGBM model built on raw coal physical parameters achieved a prediction accuracy with a coefficient of determination(R2)of 0.91 for morphological forms of sulfur.Further hyperparameter optimization using Hyperopt not only reduced the computation time by 60％but alsoincreased model's R2 to 0.96.In summary,elucidating the migration and transformation characteristics and mechanisms of sulfur and nitrogen during the pyrolysis of low-rank coal,and constructing machine learning prediction models with multi-source feature parameter inputs,provide significant theoretical and practical guidancefor the targeted transformation of sulfur-and nitrogen-containing structural units in coal,their high-value utilization,and the development of technologies for reducing pollutant emissions.

Abstract:To elucidate the critical ignition mechanisms and governing principles of ammonia-coal co-firing under industrially relevant turbulent swirling conditions,and to address the ignition stability challenges in coal-fired boilers,a systematic investigation of pulverized coal flame ignition characteristics is conducted on a custom-built tubular dual-swirl burner platform.Optical diagnostics and image processing techniques are utilized to quantitatively analyze the effects of the ammonia injection strategy(premixed with primary air vs.staged with secondary air),ammonia energy share(ENH3,0-50％),and global equivalence ratio(Φtotal,0.59-0.95)on the ignition delay time.It is revealed that the ammonia injection strategy is identified as the dominant factor controlling coal ignition performance.Compared to the premixed mode,coal ignition is significantly enhanced by staged injection(ammonia supplied with secondary air).At a constant ammonia share(ENH3=30％),the ignition delay time of the downstream coal flame is observed to decrease remarkably from 9.8 ms(premixed)to 4.4 ms,representing a reduction exceeding 55％.This phenomenon is attributed to the formation of an independent high-temperature ammonia flame within the secondary air stream,which provides a high-enthalpy environment for pulverized coal particles in the primary air.Consequently,the competitive consumption of oxygen between the two fuels within the oxygen-lean primary air is effectively mitigated,thereby achieving rapid ignition.Under the staged mode,the ignition delay is effectively reduced by increasing the ammonia share,with a monotonic shortening trend observed in the upstream coal ignition delay as ENH3 increases from 10％to 50％.Conversely,coal ignition is inhibited by a decrease in the global equivalence ratio;specifically,as Φtotal decreases from 0.95 to 0.59(at ENH3=50％),the downstream ignition delay time is prolonged from 6.1 ms to 8.3 ms.In the premixed mode,a distinct spatial dependence of the ammonia share impact is exhibited:Ignition in the upstream near-field region is delayed with increasing ENH3,whereas it is accelerated in the downstream region.It is concluded that implementing spatially staged injection of ammonia and coal is established as a fundamental approach to ensuring stable ignition in high-share ammonia-coal co-firing systems.The control strategies and mechanisms revealed herein provide a crucial scientific basis for the design and optimization of industrial-grade ammonia-coal co-firing burners.

Abstract:Under the concept of"waste to waste",coal-fired fly ash and waste incineration fly ash were used as curing agents to evaluate the curing stability of Cu,Zn,Ni,Cr,Cd,Hg,Pb and As in desulfurization sludge,and to optimize their modification.Sludge and fly ash from three different power plants were selected and screened out by TCLP leaching experiment,and the curing experiment was carried out under the condition of 6％curing agent addition and solid-liquid ratio 1∶3.The results showed that both types of fly ash could significantly reduce the leaching concentration of heavy metals,and the overall curing effect of waste incineration fly ash was better.Characterization showed that the hydration products generated during the curing process could fill pores and improve structural compactness,thereby achieving physical coating and chemical adsorption of heavy metals.After further modification of fly ash by ball milling method and alkali excitation method,the curing rate of various heavy metals can be increased to 85％-95％.The results of BCR step-by-step extraction showed that the heavy metals were significantly transformed from easy migration to stable form after curing,which verified the feasibility of fly ash curing technology in heavy metal curing treatment of desulfurization sludge.

Abstract:Bio-Energy Carbon Capture Utilization and Storage(BECCUS)has been proposed as a negative carbon technology,which combines the biomass combustion with CCUS techniques to achieve rapid,large-scale,and sustainable CO2 reduction.Biomass oxy-fuel combustion technology replaces the fuel in oxy-fuel combustion with a mixture of biomass and coal or pure biomass,and adopts high-purity oxygen and recirculated flue gas as the oxidizer,so that it can achieve high CO2 concentration in the flue gas.Compared with conventional pulverized coal oxy-fuel combustion and biomass air combustion,due to significant changes in fuel and combustion atmosphere,the furnace temperature and heat flux,pollutant emissions,heating surface issues,CO2 capture efficiency,and power plant efficiency in biomass oxy-fuel combustion also undergo noticeable changes.In this regard,based on previous research,this article systematically reviews the latest research progress in biomass oxy-fuel combustion technology,summarizes the combustion characteristics and pollutant formation mechanisms of biomass oxy-fuel combustion:the reaction kinetics parameters of biomass oxy-fuel combustion remain largely consistent under both air-and oxy-fuel atmospheres;the gasification reactions of biomass char with CO2 and H2O help reduce NOx formation and promote coal char burnout,generating more fine particulate matter;the initial oxygen concentration required for biomass oxy-fuel combustion to match air combustion exceeds 30％.The article also points out the challenges faced by biomass oxy-fuel combustion,such as fuel instability,high costs,heating surface corrosion,and pollutant formation.To address these issues,it proposes researching the synergistic effects of co-firing multiple biomass types on combustion characteristics(i.e.,ignition,burnout)and pollutants formation(i.e.,NOx,SO2,HCl),forming new insights to enhance combustion and suppress pollutant generation;optimizing operational parameters of biomass oxy-fuel combustion and regulating furnace temperature to mitigate ash deposition,slagging,and corrosion;adopting emerging technologies such as pressurized oxy-fuel combustion and pressurized circulating fluidized bed oxy-fuel combustion to improve combustion efficiency and reduce pollutant emissions;and designing new multi-generation processes for electricity-heat-gas production based on biomass oxy-fuel combustion to achieve autonomous regulation of multi-objective products and adapt to diverse application scenarios.Ultimately,this provides a theoretical basis and important reference for achieving low-carbon and clean combustion of biomass.

Abstract:The process route for producing ethanol via carbon-containing resources(coal-derived)syngas through dimethyl ether(DME)carbonylation to methyl acetate(MA),followed by MA hydrogenation,offers advantages such as mild reaction conditions and the use of cost-effective,easily prepared catalysts.This pathway represents a significant approach for achieving clean and efficient coal utilization,as well as promoting the transformation of coal into high-value chemicals.The DME carbonylation reaction serves as the core step of this process,and the application of zeolite catalysts in DME carbonylation has attracted widespread attention.This review summarizes recent advances in the understanding of the reaction pathways and deactivation mechanisms of zeolite catalysts in DME carbonylation.It discusses the application of various zeolites,particularly mordenite,in DME carbonylation and clarifies the nature of the active sites in zeolite catalysts.Building on the understanding of reaction pathways,deactivation mechanisms,and active sites,the review further outlines modification strategies for zeolite catalysts.These strategies primarily aim to precisely regulate the number and spatial distribution of active centers,effectively inhibit the acid sites responsible for coke formation,and enhance the mass transfer efficiency by optimizing the crystal size or pore structure.Specific discussions cover three main aspects:acid site regulation,microstructural modulation,along with summaries of research findings related to catalyst regeneration,optimization of preparation conditions,and industrial molding technologies.Finally,based on a summary of existing research,the review identifies current challenges and outlines future research directions for zeolite catalysts in DME carbonylation.

Abstract:As the only scalable low-carbon alternative fuel for aviation,the technical maturity,economic viability,policy adaptability,and environmental impacts of sustainable aviation fuel(SAF)have become core factors for industrial implementation.Based on the current development status and publicly available industry data,the authors systematically sort out the characteristics of SAF feedstocks,the principles and maturity differences of production technology routes,comprehensively interpret the global policy framework(international CORSIA mechanism,EU ReFuelEU,US inflation reduction act(IRA),and China's pilot policies),analyze the core factors restricting economic viability,and quantify its carbon footprint(emission reduction rate of 50％-92％)combined with well-to-wake(WtW)life cycle assessment.In terms of technical routes,the hydroprocessed esters and fatty acids(HEFA)technology,featuring high technical maturity and relatively stable feedstock supply,currently accounts for approximately 80％of the global sustainable aviation fuel(SAF)production volume,making it the most feasible industrialization pathway in the short term.In contrast,the fischer-tropsch process(FT)and power-to-liquid(PtL)technologies,despite their high current costs and lack of large-scale commercialization,are widely recognized as key development directions in the medium to long term due to their superior feedstock adaptability and greater emission reduction potential.at the policy level,the global primary saf incentive framework is jointly constituted by the carbon offsetting and reduction scheme for international aviation(CORSIA)launched by the international civil aviation organization(ICAO),the ReFuelEU Aviation regulation implemented by the European Union,the tax incentive provisions under the U.S.Inflation reduction act(IRA),and regional pilot policies in China.Among these,the EU's mandatory blending mandate and the U.S.tax credit policy have demonstrated remarkable effectiveness in driving capacity construction and downstream application of SAF.Economic analysis indicates that policy subsidies can reduce the production cost of the HEFA route by 30％-40％,with its price projected to drop to within 1.5 times that of conventional jet fuel by 2030.For China,it is imperative to strengthen the supply chain construction of sustainable feedstocks such as waste oils and biomass,and establish a multi-tiered incentive mechanism based on carbon pricing,fiscal subsidies,and green finance,thereby systematically promoting the healthy,orderly,and large-scale development of the domestic SAF industry.

Abstract:Achieving highly-efficient and clean utilization of coal has long been a primary concern in coal-fired power generation.Continuously improving power generation efficiency and reducing carbon emissions are paramount to the green-oriented and low-carbon transition.As an emerging power cycle technology,supercritical carbon dioxide(Sc-CO2)power generation offers higher theoretical efficiency than conventional steam cycles and is expected to play a crucial role in enhancing future coal-fired unit efficiency and optimizing thermal systems.Compared to conventional steam boilers,Sc-CO2 boilers exhibit a significant lack of engineering design experience.The validation of whether flue gas achieves efficient heat transfer across the entire temperature range and whether the working fluid attains the targeted thermodynamic parameters under a given design scheme has emerged as a pivotal research challenge for technological breakthroughs in the field of Sc-CO2 boiler engineering.Therefore,establishing a complete Sc-CO2 boiler thermal calculation system to obtain the temperature distributions of flue gas and working fluid at each heating surface is particularly important.Based on the domestically developed world's first 50 MW,29.2 MPa/602 ℃/602 ℃ Sc-CO2 boiler with a box-type configuration,a Sc-CO2 boiler thermal calculation model is established.A thermal calculation platform for supercritical carbon dioxide has been developed using Fortran 90 and Python 3.11,enabling thermal calculations to obtain flue gas and CO2 temperature distributions at each heating surface inlet and outlet.Based on the thermodynamic performance analysis,the current design successfully enables the superheated and reheated CO2 to achieve the targeted thermodynamic parameters,and the flue gas duct arrangement is considered sound.However,an issue of excessive temperature differential between the inlet and outlet of the economizer has been identified.A comparative analysis of the design characteristics between the Sc-CO2 boiler and conventional steam boilers is also provided.

Abstract:Hydrogen,as a clean energy carrier with high energy density and zero carbon emissions from combustion products,has an irreplaceable central position in the future energy system.In the strategic context of global energy structure transformation and dual carbon goals,the development of sustainable renewable energy hydrogen production technology is a key path to cope with the energy crisis and climate change.However,current mainstream hydrogen production processes(such as steam methane reforming)are highly dependent on fossil fuels,accompanied by significant carbon dioxide emissions,which restrict their environmental benefits.Therefore,green hydrogen preparation technologies driven by renewable energy sources(such as green electrical energy and light energy)have become a research focus.Three types of renewable energy hydrogen production technologies are systematically reviewed from the perspectives of principles,challenges,and scale-up potentials:① A s the most mature"green hydrogen"production technology currently available,water electrolysis for hydrogen production features both rapid start-stop capability and flexible load response.It is compatible with hydrogen production using renewable energy sources with strong volatility,such as wind power and photovoltaic power,and can effectively absorb and store renewable energy.Water electrolysis for hydrogen production encompasses alkaline water electrolyzers,proton exchange membrane electrolyzers,anion exchange membrane electrolyzers,and solid oxide electrolyzers,with their respective technical characteristics.The core bottleneck is the cost problem caused by high power consumption,coupling with renewable energy is regarded as a core pathway to reduce electricity costs.With the continuous decrease in the costs of renewable energy power generation and electrolyzers,the cost of green hydrogen is expected to achieve parity.② Photocatalytic decomposition of water to produce hydrogen can be directly driven by solar energy to decompose water,which is theoretically advantageous.It faces the challenge of low conversion efficiency of solar to hydrogen,so the development of high-efficiency and stable photocatalysts is the key to the breakthrough.③Photoelectricity chemical decomposition of water to hydrogen combines the advantages of photochemical decomposition and electrochemical decomposition,with great potential.However,the conversion efficiency still needs to be greatly improved,the development of larege-scale,efficient,stable and low-cost photoelectrode materials is the core task of the current research.In addition,the large-scale application of the three hydrogen production technologies plays an important role in energy reform,and then elaborates on the large-scale pathways of these three hydrogen production technologies.Finally,the direction of technological innovation is discussed from the three dimensions of efficient activation and utilization of raw materials(water),optimal control of process energy consumption,and enhancement of output per unit of energy consumption,and the focus of future research is also looked forward to.Currently,water splitting for hydrogen production technology imposes relatively high requirements on the purity of feedwater,necessitating pre-treatment of water quality prior to hydrogen production,which incurs additional cost input.Furthermore,the global shortage of freshwater resources and uneven geographical distribution further restrict the large-scale application of hydrogen production technology based on pure water.Distributed hydrogen production technology using atmospheric water harvesting and direct seawater electrolysis for hydrogen production can fundamentally address this issue.On the other hand,reducing the cost of hydrogen production and improving the energy utilization efficiency of hydrogen production systems are also of crucial importance.These discussions aim to provide references for promoting the development of efficient,economical,and sustainable"green hydrogen"technology.

Abstract:To meet the urgent demand for efficient and low-carbon power generation in distributed energy systems under the"dual carbon"goals,The overall performance and core component technologies of micro gas turbines(MGTs)are comprehensively reviewed.Based on an extensive literature survey and comparative analysis of representative commercial products,key performance indicators of MGT systems are evaluated,and the technological gaps between domestic and international developments are identified.Particular attention is given to the design challenges and optimization strategies with four critical components:the compressor,turbine,combustor,and recuperator.Significant disparities remain in core component technologies and system integration levels between domestic and advanced international MGTs.In compressors,passive flow control techniques have been shown to effectively alleviate low-Reynolds-number flow losses and enhance aerodynamic performance.Turbine temperature capability and service life are primarily constrained by material limits,relying on advances in high-temperature alloys and thermal protection technologies.For combustors,advanced combustion combustion concepts-including rich-burn/quick-quench/lean-burn(RQL),flameless oxidation,and micro mix combustion-demonstrate strong potential for achieving high efficiency,ultra-low NOx emissions,and broad fuel adaptability.With respect to recuperators,most existing MGT systems employ metallic primary surface designs,whereas ceramic recuperators are considered a promising pathway to further improve heat recovery and raise overall system efficiency toward the 40％level.Micro gas turbines are therefore regarded as a key enabling technology for future distributed energy networks.Continued progress is expected to depend on sustained innovations in materials,aerodynamic and thermal design,and control strategies of core components,as well as deeper integration with renewable energy systems.

Abstract:Potassium-based solid adsorbents show important application potential in the field of post-combustion carbon dioxide capture and direct air capture due to their advantages of low cost,environmental friendliness and good matching with low-temperature flue gas.However,the low mechanical strength,large bed pressure drop,and poor mass transfer performance of powdered adsorbents in practical engineering applications have seriously restricted their large-scale applications.For this reason,this paper systematically reviews the research progress on materials and processes of potassium-based adsorbents from powder to structured molding,focusing on the types and properties of carrier materials,the principles,advantages and limitations of molding technologies,and the key challenges faced in the scale-up application of potassium-based adsorbents.In terms of carriers,traditional porous materials,structured honeycomb carriers and new materials all show different performance characteristics,and the adsorption capacity and cycling stability can be effectively enhanced by regulating the pore structure and surface properties.In the molding process,extrusion,extrusion rounding,graphite casting,coating,hydrophobic surface-assisted synthesis,spray pelletizing and the emerging 3D printing and other technologies have their own advantages,which can significantly improve the mechanical properties of adsorbents,mass transfer efficiency and engineering applicability.However,in the face of the poisoning of adsorbents caused by complex components in real industrial flue gas,microstructural degradation due to deliquescence,and high energy consumption for regeneration,potassium-based adsorbents still need to make further breakthroughs in material design and process integration.Future research should focus on the development of multifunctional composite adsorption systems with antitoxicity,hydrophobicity,catalysis,etc.,and promote the scale-up and commercial application of potassium-based adsorbents by combining intelligent structural design and system energy-efficiency optimization,with a view to providing theoretical support and technical references for the development of potassium-based adsorbents from laboratory research to industrial application.

Abstract:Ammonia cofiring in coal-fired boilers is one of the promising technical routes for the decarbonization of coal-fired power plants.However,ammonia cofiring could potentially result in drastic increase of NOx emissions due to its high nitrogen content.Effective control of NOx emissions is thus one of the key factors that affect the technical feasibility of ammonia cofiring in coal-fired boilers.Therefore,the divergent trends of NOx emissions with respect to NH3 cofiring ratio(RNH3)observed in experimental studies were systematically reviewed.A unified mechanism underlying these divergent trends was proposed-the net NO formation is determined by the competition between the NO formation and reduction reactions of NH3 in the varying O2 environment of the furnace.In a boiler environment,NOx emissions are jointly determined by the NO formation during the initial stage of combustion in the main combustion zone,NO reduction by NH3 in the reduction zone,and NO formation by the oxidation reaction of residual NH3 with staging air in the burnout zone.The NO formation-reduction-formation processes can add up to generate a variety of NOx emission trends.Therefore,the divergent NOx trends observed in the experiments should not be simply attributed to the effects of NH3 cofiring mode or ratio but should comprehensively take into consideration the resultant changes of NH3 combustion environment brought about those different NH3 cofiring conditions.Based on the above NO formation mechanism of NH3-coal cofiring,the key factors that should be considered in engineering NOx prediction model of NH3 cofiring were further elucidated,with particular emphasis on the necessity of converting the key boiler design and operating parameters,which directly affect the furnace flow and O2 distributions,to the boundary conditions of the model.By simulating NH3 cofiring in a 40 MW boiler and a 600 MW boiler,respectively,the results by different NO models were compared and validated.Results indicated that the modified Østberg mechanism showed good qualitative and quantitative agreement with the testing results.Furthermore,the results revealed a distinctive NOx formation characteristic of NH3 cofiring.Although NH3 combustion may generate a large amount of NO,due to the rapid combustion consumption of O2 by NH3,an O2-deficient NO reduction zone is formed adjacent to the high NO formation zone in which the initially formed NO is going to be immediately reduced by the residual NH3.This characteristic contributes to a substantial reduction in the net NO production of NH3 cofiring.

Abstract:Under the context of China's"Dual Carbon"strategic goals,coal-fired power plants,as one of the primary sources of carbon emissions,are crucial targets for carbon reduction.Chemical absorption is the most mature among various carbon capture technologies and has been implemented in numerous demonstration projects in China.This paper aims to systematically review the development of carbon capture technologies in coal-fired power plants,focusing on two major technical pathways:the chemical side and the thermal side.Optimizations on the chemical side cover the evolutionary development from first-generation benchmark absorbents to second-generation mixed amine absorbents,and further to third-generation phase-change absorbents and ionic liquids,highlighting the mechanisms and potential of novel absorbents in reducing regeneration energy consumption.It also summarizes how innovations in industrial equipment and optimizations in absorption/desorption processes enhance system energy efficiency.On the thermal side,optimizations aim to mitigate the coupling conflicts between carbon capture systems and coal-fired units,with a focus on thermal integration technologies.These include optimizing steam extraction schemes for the water-steam system,integrating feedwater regenerative heating,employing absorption heat pumps,and incorporating renewable energy sources such as solar,geothermal,and biomass to provide auxiliary energy-thereby fundamentally reducing the system's"energy penalty".The study further indicates that by implementing flexible operational strategies such as solvent storage and flue gas bypass,carbon capture power plants can achieve both carbon reduction and deep peak-shaving capabilities.On this basis,this paper points out future development directions for chemical absorption-based carbon capture technology from multiple perspectives including economy,stability,and flexibility.

Abstract:Impelled by the"dual-carbon"targets,the transition toward a new power system dominated by renewable energy is accelerating.Nevertheless,conventional coal-fired power units encounter critical bottlenecks under deep peak-shaving operating conditions,characterized by insufficient operational flexibility and constraints on renewable energy accommodation.The latest research progress of Molten Salt Thermal Energy Storage(MSTES)technology coupled with coal-fired units is reviewed in this paper.The whole chain analysis is made from the dimensions of materials,equipments,system integration and operation control,in order to provide theoretical basis and technical support for related engineering applications.Initially,the thermophysical properties of four mainstream molten salt systems are synthesized,with particular emphasis on the compatibility between various molten salts and coal-fired units across different temperature ranges,alongside advancements in salt synthesis optimization.Subsequently,structural evolution and heat transfer enhancement mechanisms in key equipment-specifically molten salt tanks and heat exchangers—are examined.Then,the multi-source heat integration mode and control strategy of the coupled molten salt heat storage system in coal-fired units are presented in steady-state and dynamic operation models.The flexibility evaluation indexes such as peak load regulation depth,ramping rate,round-trip efficiency and exergy efficiency are analyzed.Economic and environmental evaluations of existing demonstration projects reveal that MSTES integration significantly mitigates wind and solar curtailment.Despite high capital costs,the technology exhibits a short payback period and robust life-cycle economic viability.Looking toward large-scale deployment,future research should prioritize high-performance low-cost materials,whole-system dynamic optimization,and multi-energy complementary integration.Moreover,establishing sound capacity pricing mechanisms and carbon trading markets is essential to fully realize the regulatory value of flexible resources,fostering a virtuous cycle between technological advancement and market returns.

Abstract:The control of particulate matter from combustion sources has always been a key issue in the field of air pollution prevention and control.Particulate matter includes filterable particulate matter(FPM)and condensable particulate matter(CPM).FPM refers to soot.Its control technology has become relatively mature and its treatment effect has reached the level of ultra-low emissions.CPM refers to substances that exist in a gaseous state in the flue and are converted into particles by cooling and condensation after discharge.Although CPM has not yet been included in the scope of mandatory governance,its environmental impact and potential hazards have been increasingly valued,and related research has gradually become a new hotspot.This paper systematically reviews the latest research progress of CPM in recent years:In terms of environmental impact,the latest quantitative analysis shows that CPM makes important contributions to organic aerosols and PM2.5 in the atmosphere,and should be given sufficient attention;In terms of CPM measurement,although the existing impinger cooling method and dilution cooling method have undergone improvements,their equipment and operation are complex,the real-time data is poor,and there are many error factors,which seriously affect the convenience and accuracy;CPM online measurement technology has made breakthroughs,but further optimization is needed;The latest CPM emission data shows that the CPM emission concentration of some emission sources has exceeded FPM.CPM contains complex organic and inorganic components,and after condensation,it forms ultrafine particles;Research on the formation mechanism of CPM has made progress:elements such as sulfur,chlorine,and nitrogen in the fuel,as well as substances such as water vapor,sulfur oxides,and nitrogen oxides in the flue gas,affect the content of inorganic components in CPM,while the organic components of CPM are influenced by factors such as fuel characteristics,combustion conditions,and combustion adequacy;In terms of CPM control,a large amount of research has focused on the collaborative removal of CPM by existing air pollutant treatment equipment,and three CPM control methods have also been developed:flue gas cooling,adsorption,and fuel mixing.However,the efficiency of these methods needs to be improved.In the future,we should further explore the environmental impact of CPM,develop reliable CPM online detection technology,reveal the formation mechanism of CPM,develop efficient control technology for CPM,and comprehensively promote the theoretical research and engineering practice of CPM pollution prevention and control.

Abstract:Precise regulation of the hydrogen-to-carbon ratio(n(H2)/n(CO))in syngas is a key factor for the efficient preparation of high-value-added chemicals and represents one of the core technologies for the low-carbon transition of the coal chemical industry and related processes.It directly determines the production efficiency,energy consumption,and carbon emissions of downstream synthesis processes.Although the conventional Water-Gas Shift(WGS)reaction is the most commonly used method for n(H2)/n(CO)adjustment,it is constrained by thermodynamic equilibrium and catalyst stability,and inevitably generates additional CO2 during the reaction process.To break through the limitations of traditional n(H2)/n(CO)regulation processes,this review elaborates on regulation strategies from a diversified perspective:the introduction of exogenous hydrogen enables rapid and precise n(H2)/n(CO)adjustment,but its large-scale application is still limited by hydrogen production costs and infrastructure construction;emerging short-process catalytic technologies(such as CO2 electrocatalysis and photocatalysis)can directly generate syngas with customized n(H2)/n(CO)during the reaction,yet their current production yields do not match industrial-scale demand;process intensification and system coupling(including multi-reforming coupling,Sorption-Enhanced Water-Gas Shift,membrane reactor coupling,biomass gasification integrated with SEWGS and the reverse Boudouard reaction,and co-gasification)achieve synergy between syngas production,n(H2)/n(CO)regulation,energy efficiency enhancement,and carbon emission reduction through multi-reaction synergy,in-situ product removal,reaction path integration,and feedstock complementarity.Overall analysis reveals that syngas n(H2)/n(CO)regulation technology is shifting from"unit optimization"toward"systematic integrated coordination and optimization,"providing support for building a low-carbon,short-process,and highly flexible green syngas production and utilization platform,which is of great significance for achieving China's carbon peaking and carbon neutrality goals.

Abstract:Chromium and its compounds are important chemical raw materials used in various industrial fields such as electroplating,leather tanning,and catalysis.However,with the rapid development of industry,chromium pollution has become one of the important environmental issues.Chromium(Ⅵ)has strong toxicity and can be absorbed by the human body through respiratory,digestive,and skin pathways,posing a health hazard.Therefore,it is urgent to effectively control and restoration chromium pollution.At present,the treatment methods for chromium containing wastewater mainly include physical,chemical,and biological methods,aiming to effectively remove or transform chromium ions in the system,thereby reducing their potential harm to the environment and human health.Although Cr(Ⅲ)is a relatively stable form,it may transform into more toxic Cr(Ⅵ)under specific conditions,so its control and restore have important environmental significance.For the treatment of chromium containing sludge,stabilization,heat treatment,and resource utilization are mainly used,and the treatment effect is influenced by multiple factors such as the valence state of chromium and so on,in recent years,research has found that the use of layered double metal hydroxides(LDHs)materials can fix heavy metal chromium ions through eutectic substitution,forming a more stable ultra stable mineralization structure,significantly reducing their mobility and bioavailability in the environment,providing a new approach for the remediation of water bodies and soils.In addition,the development of low toxicity or chromium free alternative materials is also considered an important direction,and some transition metals have shown certain substitution potential in fields such as electroplating,leather tanning,and catalysis.It is worth noting that LDHs demonstrate application advantages in chromium resource substitution,such as showing good development prospects in corrosion-resistant coatings and catalysts.This article systematically reviews the main treatment technologies and their advantages and disadvantages for chromium containing wastewater and sludge,and introduces the research progress on chromium resource recovery and substitution strategies,providing theoretical support and technical reference for future chromium pollution control.

Abstract:Fluorinated gases(F-gases),primarily consisting of chlorofluorocarbons,hydrochlorofluorocarbons,hydro fluorocarbons,perfluorinated compounds,sulfur hexafluoride,and nitrogen trifluoride,are widely used in the industrial sectors such as refrigeration,semiconductor manufacturing,and electrical insulation for power equipment due to their excellent chemical stability,thermodynamic properties,and electrical insulation capabilities.However,these characteristics also result in their long atmospheric lifetime and strong infrared radiation absorption capacity,leading to a high global warming potential and posing a continuous and severe threat to the global climate system.Although international legal instruments such as The Montreal Protocol on Substances that Deplete the Ozone Layer(hereinafter referred to as the Montreal Protocol)and its Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer(hereinafter referred to as the Kigali Amendment),along with relevant national laws and regulations,have imposed strict controls on the production and use of F-gases,their irreplaceability in many industrial fields has led to a continuous increase in their atmospheric concentrations worldwide.Therefore,the development of efficient and feasible F-gases treatment and disposal technologies is particularly urgent.This review systematically summarizes the emission sources,environmental impacts,and control policies of F-gases;based on literature metrics analysis,it reveals the research progress in F-gases treatment and disposal technologies,with a focus on the current research hotspot—adsorption technology.It summarizes strategies for enhancing the adsorption performance and selectivity of F-gases through structural regulation and surface modification,clarifies the adsorption mechanisms and cycle stability of various materials for different types of F-gases,and further analyzes the challenges faced in scaling up adsorption technology under complex operating conditions such as high humidity and multi-component competitive adsorption.This review aims to provide references for the development of efficient adsorbent materials and the optimization of F-gases adsorption processes,thus offering theoretical support for achieving deep reduction of F-gases and contributing to the realization of the"dual carbon"strategic goals.

Abstract:China's energy resource endowment characterized by"abundant coal,scarce oil and gas"determines the dominant role of coal in the energy structure.As the energy transition strategy continues to advance,the traditional coal industry faces dual pressures of declining economic returns and low-carbon transformation,making technological innovation imperative.This work focuses on the green,low-carbon and high-value transformation of the modern coal industry.Firstly,it highlights key directions in clean coal utilization,and reviews the current development of related technologies from the perspectives of energy-oriented and resource-oriented utilization,providing insights for the low-carbon upgrading of the industry.Secondly,considering the future shift of coal from a"dominant energy source"to a"safety-net energy source,"this paper explores technological pathways aimed at the synthesis of high-quality solar fuels through the coupled utilization of solar energy and coal for energy and resource purposes,with the goal of opening up a high-value model for the synergistic development of coal and renewable energy.Based on the proposed innovative pathway"from clean coal utilization to solar fuel synthesis,"the existing coal industry should focus on advancing low-carbon production technologies such as supercritical/ultra-supercritical power generation and circulating fluidized bed low-nitrogen combustion/oxyfuel combustion;concurrently,circular economy technologies,including the preparation of high-value carbon-based materials and the reuse of coal-based solid waste,should be prioritized to enhance the clean utilization of coal in both public welfare and advanced materials sectors.Furthermore,integrating green fuel synthesis technologies such as solar thermochemical processes into coal industry upgrades will gradually deepen the coupled utilization of renewable energy and coal resources,providing fresh impetus for building a sustainable energy system.Facing the future demand for zero-carbon energy development,the coal industry is advancing breakthroughs in key directions:clean energy utilization,high-value resource utilization,and systematic integration of new energy sources.Through the full-chain industrial upgrade encompassing"carbon reduction,carbon fixation,and negative carbon emissions,"a key technological system supporting energy transformation will eventually be formed.

Abstract:Thermoacoustic instability is a self-excited oscillatory phenomenon triggered by the mutual coupling between heat release rate fluctuations and acoustic oscillations in combustion systems.It is widely observed in energy and power equipment including gas turbines,aeroengines,industrial burners,and gas water heaters.Against the backdrop of low-carbon energy transition,the rapid growth in natural gas consumption and increasingly stringent nitrogen oxide emission standards have led combustion systems to frequently operate under low-emission conditions,for instance lean combustion and premixed modes,deviating from the stoichiometric ratio.This has resulted in frequent occurrences of thermoacoustic instability,manifesting as intense pressure oscillations,flame fluctuations,and increased noise,which severely compromise operational safety and equipment lifespan.This review systematically outlines recent research progress in oscillation mechanisms,triggering factors,nonlinear dynamic behaviors,current research status,and control strategies related to thermoacoustic instability in gas combustion.Starting from the classical Rayleigh criterion,the energy-positive-feedback mechanism of thermoacoustic coupling is explained.Typical oscillation types,among them Helmholtz-type,longitudinal modes,circumferential modes,and intrinsic thermoacoustic modes,are categorized and discussed in terms of their characteristics and causes.Regarding nonlinear behaviors,the physical mechanisms underlying dynamic phenomena like limit cycle oscillations,beating oscillations,and intermittent oscillations are further analyzed.Modeling approaches based on flame transfer functions and flame describing functions,together with their applications in predicting nonlinear oscillations,are also introduced.The review systematically summarizes current experimental diagnostic techniques in the field of gas thermoacoustic instability,encompassing high-frequency pressure measurements,particle image velocimetry,planer laser induced fluorescence,and chemiluminescence imaging,as well as numerical simulation methods including large eddy simulation,low-order network models,and Helmholtz solvers.Active and passive control strategies,for example acoustic dampers,fuel modulation,and plasma actuators,are also covered.Finally,challenges in current research and future development directions are discussed.It is emphasized that further breakthroughs are needed in areas such as combustion mechanisms of low-carbon fuels,multi-scale intelligent modeling,high-precision experimental diagnostics,and intelligent control to advance the design and optimization of low-emission,high-stability combustion systems.