Clean Coal Technology

2024年02期目次

Research progress on predictive models for slag flow in gasifiers
ZHAO Yijun;BAI Menglong;ZHANG Linyao;School of Energy Science and Engineering,Harbin Institute of Technology;
Under the "dual carbon" strategic goal, coal gasification technology will be an important development path in China′s future coal industry. In the promotion and application of coal gasification technology, the flow behavior of slag seriously affects the stable operation time of gasifiers, indirectly affecting the quality of synthesis gas and the heat loss of furnace walls. The effective prediction model for slag flow characteristics to solve flow parameters has attracted much attention. This study discussed the existing predictive models for the flow characteristics of slag in gasifiers and looks forward to the future research directions of predictive models. At present, prediction models can be divided into one-dimensional prediction models and two-dimensional prediction models based on the dimension of slag flow. Both one-dimensional steady-state and non-stationary prediction models have gone through the stages of construction and improvement. The two-dimensional prediction model is still in the construction stage due to the lack of relevant mathematical formula descriptions and flow concept assumptions. The calculation accuracy of the model can be improved by considering the temperature distribution of liquid slag, the selection of additional stress, the selection of critical viscosity, and the treatment of slag viscosity. Looking ahead to the future, the application scenarios of one-dimensional prediction models require more comprehensive regulations and more detailed analysis is needed for the parameters solved by steady-state and non-stationary prediction models. The construction theory of two-dimensional prediction models requires a more detailed breakthrough, clarifying the priority of slag flow in the axial and circumferential directions under nonsteady state conditions. The calculation accuracy of slag flow prediction models needs to be comprehensively improved, with a focus on factors such as the non-constancy of slag properties, non-uniformity of melting, fluctuation of flue gas flow rate, and diversity of coal ash types.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 13254K]

Multistable-flexible ammonia process adapted to renewable energy
JI Xu;LIN Jin;NIE Lihong;ZHOU Li;YUAN Shaojun;ZHANG Huan;HE Ge;DAI Yiyang;School of Chemical Engineering,Sichuan University;Department of Electrical Engineering,Tsinghua University;Tsinghua Sichuan Energy Internet Research Institute;China Chengda Engineering Co.,Ltd.;Tsingyun (Chengdu) Technology Co.,Ltd.;
Given the imperative shift towards achieving carbon peaking and carbon neutrality objectives, the pivotal role of wind and solar renewable energy generation in energy development becomes evident. "Green hydrogen", with its ability for long-term storage and zero-carbon attributes, is anticipated to play a foundational role alongside electricity in the future energy system. This integration is crucial for addressing challenges associated with the incorporation of wind and solar power into the energy matrix. However, the development of "green hydrogen" is facing challenges particularly in terms of safety and economic feasibility throughout various stages of production, storage, and transportation. These challenges are primarily attributed to the intrinsic properties of hydrogen and material limitations induced by hydrogen embrittlement. Addressing the economic challenges related to both "green electricity" and "green hydrogen" within the context of dual carbon goals, the approach of "electrically producing green ammonia" is deemed essential. Recent studies have studied multiple solutions based on the well-established "Haber-Bosch" ammonia process to mitigate uncertainties associated with wind and solar resources. In this paper, a renewable power to ammonia multistable-flexible process(RePtAmMuFlP) was proposed to tackle the design, equipment, and operational challenges associated with the intricate coupling of "source-grid-hydrogen-ammonia" technical characteristics. This research explored the systemic technical architecture of RePtAmMuFlP. In addition, an optimization model was developed to adjust the economic operating loads and periods, while a digital simulation model was also constructed to integrate renewable power, hydrogen, and ammonia, considering factors like power constraints, renewable power fluctuations, hydrogen-ammonia demand, system operating efficiency, and equipment reliability. This integrated model facilitates the coordinated optimization of "renewable power to green ammonia" operations in different scenarios, offering a dynamic design approach for industrial systems. Furthermore, the macroscopic kinetic models of catalysts under complex operating conditions were investigated, which led to improvements in catalyst structural performance, internal structure of synthesis towers, and the integration of power-hydrogen-ammonia with collaborative scheduling and intelligent control technologies. This RePtAmMuFlP has achieved economic operation loads ranging from 30% to 110%, with a load adjustment rate of 0.5% to 1.0% per minute. It also supports adjustments in daily, shift, and intra-shift loads, with the overall energy consumption per unit of ammonia surpassing the benchmark value set by GB 21344—2015 Energy consumption limit of unit product of ammonia.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 8097K]

Application of quantum chemical calculations to the mechanism of clean and efficient coal conversion
MA Xuelu;ZHANG Zihan;XIE Qiang;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
In the pursuit of carbon peak and neutrality targets, China′s significant reliance on coal as a primary energy source requires ongoing focus on its clean and efficient utilization. Quantum chemistry, a theoretical method used to analyze microstructure and mechanisms, has played a crucial role in coal chemistry research. By providing microscopic information, quantum chemistry has facilitated the development of clean and efficient coal utilization technology. This review aimed to summarize the application of quantum chemistry in optimizing the molecular structure of coal models, studying reaction mechanisms, and analyzing factors affecting reactions. It also highlighted the microscopic challenges encountered in coal pyrolysis, combustion, gasification, and liquefaction, includingthe migration and transformation mechanism of nitrogen during coal pyrolysis and combustion, the gasification characteristics between functional groups and CO_2, the hydrogen transfer mechanism of coal liquefaction, and the mechanism of influencing factors, such as atmosphere and catalyst. Lastly, it provided an overview of scientific challenges faced by quantum chemistry in the field of clean and efficient coal transformation, which involved in the evolution model of coal metamorphism, the mechanism of multi-factor effect in coal reaction, the complete transformation mechanism, catalyst optimization, and innovative integration process, offering insights for the advancement and application of clean coal technology.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 4204K]

Molecular insights into the microscopic interaction between lignite and water: A multiscale molecular modelling study
WU Yuhua;LI Ronghua;ZHANG Xi;GAO Hongfeng;ZHU Meilin;LIU Caizhu;WU Jianbo;ZHANG Hui;BAI Hongcun;State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University;College of Chemistry and Chemical Engineering,Ningxia University;College of Basic Medical Sciences,Ningxia Medical University;
Coal-water interfacial interactions are one of the key scientific issues in clean coal technology. However, the microscopic mechanism of lignite-water interaction is still unclear in terms of atomic scale structure and electronic properties. There is a lack of systematic investigation on the interaction energy, stable structural features, and interaction nature of different functional groups in lignite with water molecules. Herein, the molecular mechanism of lignite-water microscopic interaction based on multi-scale molecular simulations was investigated. The interaction between representative model structures of lignite and a single water molecule was investigated by quantum chemical calculations. The localized minima configurations of different adsorption sites on lignite and corresponding stable adsorption configurations are obtained. The interaction forms between lignite and water molecules were intuitively illustrated by independent gradient model(IGM), which mainly included van der Waals interactions and hydrogen bonds. The electrostatic interaction was quantitatively described and identified as the dominant factor stabilizing the lignite-water interaction by energy decomposition analysis. Furthermore, the assembly behaviors and evolution characteristics of different numbers of lignite molecules interacting with a large number of water molecules were revealed based on molecular dynamics simulations. The aggregation phenomena of lignite molecules in bulk water were elucidated. The molecular dynamics simulation results also confirm that lignite bind to H_2O mainly through electrostatic interaction.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 4587K]

Gasification reactivity of coal gasification fine slag and its separated carbon-rich residues
WU Yajuan;REN Liang;GONG Yan;GUO Qinghua;YU Guangsuo;WANG Fuchen;Institute of Clean Coal Technology,East China University of Science and Technology;
With the widely application of entrained-flow coal gasification technology in China′s coal chemical industry, the production of coal gasification fine slag is increasing year by year. At present, the resource utilization of gasification fine slag has become one of the difficult problems in the treatment of solid waste in coal chemical industry. In this paper, gasification fine slag with different carbon contents and its separated carbon-rich residues were selected as the research objects. The structural parameters such as composition, pore structure and microstructure were analyzed. The gasification reactivity of coal gasification fine slag under CO_2 atmosphere was investigated based on thermogravimetric analyzer. The gasification reaction kinetics was analyzed by iso-conversional method, and the internal relationship between the structural characteristics of coal gasification fine slags and its carbon-rich residues and their gasification reactivity was revealed. The results show that the pore structure is the key factor affecting the gasification reactivity of gasification fine slag and its separated carbon-rich residues, and the samples with developed pore structure have higher gasification reactivity. With the increase of heating rate in gasification process, the gasification reaction range of gasification fine slag and its carbon-rich residues shiftes to high temperature. In addition, the gasification reaction activation energy of gasification fine slag and carbon-rich residues with relatively high fixed carbon content decreases with the increase of conversion rate, while the gasification reaction activation energy of gasification fine slag and carbon-rich residues with high ash content of the sample itself increases with the increase of conversion rate. The research results provide theoretical guidance for the resource utilization of gasification fine slag and its separated carbon-rich residues.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 6830K]

Effect of biomass ash on coal char gasification
DING Liang;ZHANG Xu;WEI Jiale;LI Wenyuan;LI Weipeng;WANG Zhiqing;FANG Yitian;College of Chemistry and Chemical Engineering,Xi′an Shiyou University;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences;
Biomass ash, rich in alkali and alkaline earth metals(AAEM), can be served as a natural catalyst in coal catalytic gasification. The promoting effect of biomass ash on coal gasification is a fundamental reason for the synergistic effect during co-gasification of biomass and coal. However, the AAEM in biomass ash may undergo deactivation during gasification, leading to the loss of catalytic activity. The effects of factors such as biomass ash type, content and temperature on coal char gasification through fixed-bed pyrolysis and gasification experiments were analyzed, combined with the analysis of XRD, Raman, XRF, and BET. The results indicate that the catalytic effect of biomass ash is related to the content and existing form of AAEM. The gasification reactivity of coal char increases with the increasing addition of wheat straw ash. However, when the addition of wheat straw ash reaches 40%, the reactivity of the coal char tends to change smoothly. Wheat straw ash has an inhibitory effect on the gasification of coal char in the early stage of gasification reaction. As the carbon conversion increases, the catalytic effect of wheat straw ash decreases with the increasing temperature at the same conversion level. In order to inhibit the deactivation of potassium in wheat straw ash, eggshell was used as an additive to investigate the effects of mixing wheat straw ash with eggshell on the gasification of coal char. The results indicate that the catalytic effect of wheat straw ash on the gasification of coal char can be further enhanced by adding 25% wheat straw ash and 5% eggshell. The addition of wheat straw ash results in a large specific surface area, an enriched pore structure, a more disordered carbon structure, a decrease in the gasification reaction activation energy and an increase in the gasification rate of the coal char. Random pore model is the most appropriate model to simulate the gasification behavior of coal char and the coal char with wheat straw ash. The findings provide a reference for the application of biomass ash in catalytic coal gasification.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 6340K]

Influence of heavy oil composition structure on the rheological properties of coal-oil slurry
LIU Lei;JIN Lijun;ZHONG Mei;DAI Zhenghua;LIU Yang;State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources,Xinjiang University;School of Chemical Engineering and Technology,Xinjiang University;Xinjiang Key Laboratory of Coal Clean conversion & Chemical Engineering Process,Xinjiang University;School of Chemical Engineering,Dalian University of Technology;State Key Laboratory of Fine Chemicals,Dalian University of Technology;Institute of Coal Chemical Engineering,Dalian U
Xinjiang, with abundant low-rank coal and heavy oil resources, holds significant potential for the coal-oil co-liquefaction industry. However, poor fluidity of heavy oil considerably hinders its development. To examine the impact of the compositional structure of heavy oil on the rheological properties of coal-oil slurry, in this work, five types of heavy oils with distinct properties and two types of industrial circulating solvent oils were selected, and the variation in the rheological properties of the Shangwan coal-oil slurry was investigated. In addition, the compositional structure of the vacuum residue heavy oil was regulated via pre-hydrogenation. Based on the analysis of the composition, structure, and rheological properties of heavy oil, the influence of the compositional structure of heavy oil on the rheological properties of coal-oil slurry was revealed. The results indicate that heavy oil in its original state belongs to the Newtonian fluid. However, the addition of coal powder promotes the transform into a pseudoplastic fluid, displaying shear-thinning characteristics. High content of resin and asphaltene components in heavy oil leads to high viscosity of the formed coal-oil slurry. In addition, the rich thixotropic structure within the system makes the non-Newtonian fluid characteristics more pronounced. The pre-hydrogenation of vacuum residue heavy oil significantly decreases the viscosity of the resultant coal-oil slurry. Notably, the viscosity of the coal-oil slurry by using pre-hydrogenation heavy oil at 380 ℃ for 2 h decreases to 451 mPa·s at 135 ℃. Pre-hydrogenation facilitates the breakdown of long chains in vacuum residue oil into short-chain hydrocarbons, the resin and asphaltene components in vacuum residue oil are transformed into saturated and aromatic components, thereby inhibiting the formation of micelles and reducing the viscosity of the coal-oil slurry. In particular, after pre-hydrogenation at 380 ℃ for 2 h, the resin content was decreased by about 21% compared to the untreated sample, the weight average molecular weight declines to 1 594 Da, and the H content at β position of the aromatic ring increases by about 20%.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 4006K]

Influence of cross-linking modification of coal tar pitch on carbon structure
CHENG Junxia;MAN Mengyao;CHU Hongyu;WU Qiuping;SONG Shuaichao;WEN Xiliang;ZHU Yaming;ZHAO Xuefei;College of Chemical Engineering,University of Science and Technology;
The microstructure of pitch-based carbon products is highly dependent on the properties of precursor pitch. While using chemical cross-linking to modify asphalt, although all the reaction mechanism of chemical cross-linking operates via electrophilic substitution reaction, the degree of such modification fluctuates based on the type of cross-linking agent and catalyst utilized, which in turn impacts the structure of resulting carbon products. Using medium and low temperature coal tar pitch as raw materials, the effects of three cross-linking agents: terephthalyl alcohol(PXG), benzaldehyde(BA), p-phenylenediamine chloride(TPC), coupled with five catalysts: p-toluenesulfonic acid, concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid, and boric acid on the structure of carbon products after asphalt crosslinking modification were explored. The thermal stability and functional group changes of cross-linking modified pitch through TG-DTG and FT-IR were studied. XRD and Raman were used to characterizethe microstructural differences of modified pitch carbon products. The results show that the presence of cross-linking agents and catalysts facilitate occurrence of molecular crosslinking in pitch, effectively curbing the volatilization of light components during thermal conversion, and substantially enhancing pitch′s coking value, softening point, and thermal stability among other metrics. When PXG serves as a cross-linking agent, the methylene H on the branched chain within the cross-linked product is not easily replaced. Conversely, when boric acid functions as the catalyst, the methyl H at the branch chain′s end is more prone to replacement. Utilizing BA as cross-linking agent, the position of hydrogen substitution predominantly occurs on the aromatic ring. When TPC is used as the cross-linking agent and concentrated sulfuric acid is used asthe catalyst, the content of ■ functional groups in the cross-linked product increases, indicating that TPC participates more in the reaction under this combination. Irrespective of the cross-linking agent used, when concentrated hydrochloric acid is employed as a catalyst, the crosslinking reaction substantially promotes the substitution of C—H bonds on the benzene ring and branch chains. After cross-linking modification, the strong π-π interactions among molecules in pitch′s carbonization process are weakened, effectively hindering the formation of ordered carbon structures, thereby increasing I_D/I_G values. Simultaneously, the interlayer spacing d_(002) of carbon microcrystals significantly expands, while the L_c value demonstrates a declining trend and the number of aromatic layers reduces, indicating that chemical cross-linking not only disrupts the arrangement of ordered carbon structures, but also restrains the development of carbon microcrystals. When boric acid isused as a catalyst, the catalytic effect is more ideal. The resultant carbon product′s d_(002) exhibits the highest performance amongst its group. When PXG and boric acid collectively cross-link with pitch, the d_(002) of the achieved carbon material extends to 0.377 nm. In conclusion, this study lays a robust practical basis for the further targeted regulation and construction of pitch-based carbon materials.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 5236K]

Optimization of active metal Ni d charge density for efficient phenanthrene hydrogenation over Ni₂P/Al₂O₃ catalyst
JING Jieying;LI Ze;ZHAO Zemin;ZHANG Yu;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;
The content of phenanthrene in high temperature coal tar is relatively high. The hydrogenation saturation of phenanthrene through catalytic not only expands the utilization of phenanthrene, but also obtains perhydrophenanthrene, which is an ideal component for jet fuel due to its high density and calorific value. However, the competitive adsorption between phenanthrene and intermediate hydrogenation products in the process of phenanthrene hydrogenation is not conducive to the adsorption and activation of phenanthrene on the catalyst, and the further hydrogenation of symmetric octahydrophenanthrene is the speed control step in the hydrogenation saturation process of phenanthrene. Due to the difficulty in adsorption and activation of symmetric octahydrophenanthrene on the catalyst, the catalyst activity is often difficult to meet the hydrogenation demand. According to the π-complex adsorption mechanism between polycyclic aromatic hydrocarbon and transition metals, polycyclic aromatic hydrocarbon and active metals act as electron donors and electron accepters respectively in the process of reactant adsorption and activation. Therefore, when the active metal Ni in the Ni-based catalyst is in the electron-deficient state, it is conducive to the formation of perhydrophenanthrene. However, the reason why the amount of Ni electron deficiency and its electronic structure affect the performance of the catalyst for hydrogenation of phenanthrene and symmetric octahydrophenanthrene needs to be further explored. In addition, considering the advantages of the supported Ni_2P catalysts, such as high stability, strong sulfur resistance and nitrogen resistance, Ni_2P/Al_2O_3 catalysts with different d charge densities were prepared by adjusting the P/Ni amount-of-substance ratios using hypophosphite disproportionation method, to investigate the influence of Ni d charge density on the adsorption and reaction performance of phenanthrene and symmetric octahydrophenanthrene. The results show that under reaction conditions of 320 ℃, 5 MPa, and Weight Hourly Space Velocity(WHSV) of 1 309 h~(-1), the Ni-2.5P/Al_2O_3 catalyst obtains the highest turnover-frequency(f_(TO)) of 44.64×10~(-3) s~(-1). By describing the interaction strength between phenanthrene, symmetric octahydrophene, and catalyst surfaces through adsorption activation entropy, it was found that the adsorption strength of phenanthrene and symmetric octahydrophenanthrene on the surface of Ni-xP/Al_2O_3 catalysts with different P/Ni molar ratios are different. Further, by quantitatively calculating the Ni d charge density, it was identified that the suitable Ni d charge density for the hydrogenation of phenanthrene over Ni-xP/Al_2O_3 catalyst is about-0.24 e, and the suitable Ni d charge density for the hydrogenation of symmetric octahydrophenanthrene is about-0.05 e.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 6355K]

Simulation study on the reaction mechanisms of Fe-based oxygenc arrier supported by CeO₂ with CO
MU Lin;SUN Meng;ZHANG Bin;SHANG Yan;DONG Ming;CHEN Jianbiao;HUO Zhaoyi;Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education,School of Energy and Power Engineering,Dalian University of Technology;School of Energy Science and Engineering,Nanjing Tech University;School of Materials and Metallurgy,University of Science and Technology Liaoning;
Chemical looping combustion technology is a new type of combustion technology with near zero carbon emission. Oxygen carrier plays the dual role of oxygen carrying and heat transfer in chemical looping combustion reaction. Improving the reaction performance of Fe-based oxygen carrier by tuning microstructure has been one of research focuses in the field of chemical looping technology. In this study, CeO_2 was used as the active catalytic support to catalyze and tune of Fe-based oxygen carrier based on density functional theory. The electronic structural characteristic parameters of CO adsorption, such as state density, adsorption energy, differential charge density, and activation energy at the different sites of Fe_2O_3 clusters, were systematically analyzed by optimizing the constructed composite model. The results show that the electrons of Fe_2O_3 clusters are transferred to CeO_2(111) surface, and the binding energy is-3.92 eV, and Fe_2O_3 clusters can be bonded on the CeO_2(111) surface stably. Density of states(DOS) analysis show that the p and d orbitals of Fe_2O_3 clusters after loading migrate to the Fermi level at-8-0 eV, indicating that the adsorption is enhanced. The electrons in the p and d orbitals of Fe_2O_3 clusters decrease, the existing electrons transition to higher energy levels, and the electronic activity of Fe_2O_3 clusters increases. Therefore, the activation energies of CO molecules at three adsorption sites of Fe_2O_3 clusters in Fe_2O_3/CeO_2 complex oxygen carrier decrease. Furthermore, CeO_2(111) enhances the adsorption of CO at the Fe top of Fe_2O_3 clusters, increasing the adsorption energy from-0.33 eV to-1.78 eV. Then the over-strong adsorption at the O top is weakened, and the adsorption energy is reduced from-2.69 eV to-2.32 eV, this also facilitates the subsequent release of CO_2 molecules from the surface of Fe_2O_3 clusters, thus effectively tuning the overall adsorption effect of Fe_2O_3 clusters on CO. It provides theoretical guidance for the design, preparation, and optimal tuning of Fe-based oxygen carrier.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 3196K]

Development and research progress of catalytic system of high-value derivatives of dimethyl oxalate
GUO Fengqin;ZHAO Liyan;WANG Liguo;CAO Yan;HE Peng;LI Huiquan;School of Rare Earths,University of Science and Technology of China;Ganjiang Innovation Academy,Chinese Academy of Sciences;National Engineering Research Center of Green Recycling for Strategic Metal Resources,CAS Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Sciences;
China′s energy resource structure can be characterized as coal-rich but oil-lean and gas-lean, resulting in a high dependence on coal resources. Therefore, how to give full play to the advantages of China′s large coal reserves and realize the cleaner, low-carbon, and diversified utilization of coal resources is an urgent problem to be solved. Converting non-renewable coal to diversified chemicals and reducing the consumption and external dependence on the use of oil and natural gas has been the key direction of China′s coal resource utilization research. After the gasification of coal into CO and H_2 at high temperatures, the conversion of dimethyl oxalate(DMO) synthesized from CO and H_2 synthesis gas into a variety of oxygen-containing chemicals by catalytic hydrogenation reaction is a proven feasible technical route. With the gradual development of the technology for the conversion of DMO to a variety of high-value chemicals, such as methyl glycolate(MG), ethylene glycol(EG), ethanol, dimethyl carbonate(DMC), and oxalamide, through indirect and continuous hydrogenation reactions, it has enabled China′s abundant coal resources to be utilized more efficiently and promoted the balance of China′s energy structure. This work centered on the conversion of DMO to downstream products in detail and discussion. According to the research on DMO in recent years, the preliminary hydrogenation of DMO can obtain MG, the secondary hydrogenation of MG can obtain EG, the dehydration of EG can obtain ethanol, C_3-C_4 alcohol, and the ammoniation of DMO can prepare oxalamide, which is a "new type of nitrogen fertilizer". The research progress of catalysts used in the conversion of downstream products, the catalytic mechanism of different catalysts, and the adsorption-activation mechanism of active species were summarized. The current methods to improve catalyst performance by introducing other additives, regulating surface acidity and alkalinity, and introducing the second and third metals were summarized in detail. The high selectivity and limitations of the current loaded copper-based catalysts, iron-based catalysts, and silver-based catalysts in the DMO hydrogenation process were discussed in detail. The problems of high-temperature sliding and toxic deactivation of copper-based catalysts, poor intermediate product hydrogenation of iron-based catalysts, and weak C-O bond activation process of silver-based catalysts with the continuous expansion of production capacity were pointed out, and the reasons for the deactivation of the catalysts and the solutions were further discussed and analyzed in detail. The problems and challenges of the current DMO hydrogenation process route are pointed out in detail, and the future research direction and development trend of DMO hydrogenation catalysts were given.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 8549K]

Research advances on solvothermal conversion of levoglucosan into value-added chemicals
TANG Guangchuan;HUANG Xin;QIN Hui;YU Feifan;LIU Tianlong;WEI Fu;RAN Jingyu;Key Laboratory of Low-Grade Energy Utilization Technology and Systems of Ministry of Education,Chongqing University;Jiangsu Province Engineering Research Center of Fine Utilization of Carbon Resources,China University of Mining & Technology;Carbon Neutrality Institute,China University of Mining and Technology;
Pyrolysis of lignocellulose is an efficient way to utilize biomass. The primary product of cellulose pyrolysis is levoglucosan(LGA), with a yield of up to 80%. Consequently, the high-value utilisation of LGA can be achieved through efficient conversion into other platform chemicals. The latest research progress on the pyrolysis of cellulose to LGA was presented, the influence of reactor types and reaction conditions on LGA yield were summarized, and biomass pretreatment could enhance the industrial scale production of LGA. Then LGA conversion to levoglucosenone, glucose, and furan compounds under different conditions were concluded. It is found that Br?nsted acid sites and in-situ removal of generated water during reaction improve levoglucosenone yield, with the maximum yield close to 60%, developing suitable catalysts and solvents can further improve levoglucosenone yield. Additionally, LGA can be effectively converted to glucose by acid hydrolysis, attaining both yield and selectivity nearing 100%, and the catalyst with long-term stability, providing an indirect method for producing glucose from cellulose. Furthermore, the effects of catalysts and solvents on the formation of furanic compounds, acids and esters were summarized, indicating that these chemicals were formed via glucose as the intermediate.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 2830K]

Research progress of biomass-derived porous carbon materials for supercapacitors
CAO Junya;CHEN Tianyue;LUO Chenhui;ZHANG Lixin;SANG An;School of Chemistry and Environmental Engineering,China University of Mining and Technology-Beijing;
The increase in energy consumption has promoted the development of green energy, while promoting the rapid development of energy storage systems. Supercapacitors have been widely concerned with the advantages of high-power density and long cycle life, among which capacitive carbon materials have gradually become research hotspots. The preparation of porous carbon material for supercapacitors using biomass, which is widely sourced, renewable, inexpensive and environmentally friendly, has solved the problem of energy storage while developing green energy. The structure control and performance improvement of porous carbon materials are important ways to improve the performance of supercapacitors. Biomass-derived porous carbon materials and its applications in the field of supercapacitors were reviewed. The preparation methods and technical status of porous carbon materials were summarized according to the classification system of raw material sources(plants, animals and microorganisms) and material dimensions(zero, one, two and three dimensions). The preparation process of porous carbon was divided into carbonization and activation. The mechanism of carbonization and activation, the selection of activation methods and the characteristics of common activators were briefly described. However, there are many influencing factors in the preparation process of bio-derived porous carbon materials, and the performance is still inferior compared with traditional coal-based carbon materials. It is necessary to carry out various design optimization, including selection of biomass precursors, rational use of carbonization technology, regulation of various influencing factors in the activation process and selection of doping substances in the modification process. Based on the application requirements in the field of supercapacitors, the optimization methods of biomass porous carbon materials were discussed, including pore structure regulation, surface element doping and the formation of new carbon materials by composite with graphene. The difficulties and key points of the application of porous carbon materials in supercapacitors were reviewed. By finding the optimal combination of porous carbon materials with high specific surface area, uniform pore distribution and high conductivity, the charge storage capacity of electrode materials can be improved to overcome the problem of low energy density of supercapacitors, ensuring that the voltage resistance of supercapacitors can meet the requirements at the same time. On this basis, the research direction of improving the electrochemical performance and cycle stability of materials, ensuring the stability and consistency of raw material sources, and gradually realizing the commercialization needs of mass production were proposed.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 9577K]

Composition and structural evolution of graphene oxide prepared from Shenfu coal and its macerals
LIU Guoyang;YAN Xin′e;LI Keke;LI Jun;ZHANG Yating;JIA Jia;ZHU Youyu;DANG Yongqiang;DUAN Yingfeng;School of Chemistry and Chemical Engineering,Xi′an University of Science and Technology;School of Civil Engineering,Xi′an Traffic Enginering Institute;National Institute of Clean-and-Low-Carbon Energy;
The preparation of graphene from coal as raw material is a very promising approach for coal material and high-value utilization. Exploring the evolution law of coal and its macerals in the preparation of graphene oxide based on their composition and structural differences is the theoretical basis for developing coal based graphene preparation technology. The vitrinite and inertite groups in Shenfu coal were enriched by gravity separation, and graphitized carbon with different coal composition was obtained by high-temperature graphitization method, and the graphitized carbon was used as the precursor through modified Hummer oxidation method to prepare coal-based graphene oxide. Elemental analysis, FT-IR, XRD, Raman spectroscopy, SEM,TEM and AFM were used to study the composition and structure evolution of Shenfu coal and its macerals, during the preparation of graphene oxide. The results show that carbonization treatment transforms the coal structure into an amorphous carbon structure, while high-temperature graphitization transforms the coal structure into a graphitized carbon structure. The rich-inertinite has a larger graphitized carbon microcrystalline structure due to the presence of layered structures with many aromatic structures units. After high-temperature graphitization treatment, for the graphitized carbon from rich-inertinite, Raman spectrum value(A_(D1)/A_G) is 0.382, and the value(A_(D1)/A_G) from rich-vitrinite is 0.686, and the value(A_(D1)/A_G) is 0.864 from the raw coal. The thickness of graphene oxide from graphitized carbon obtained from rich-inertinite is approximately 5 nm. The graphitized carbon prepared from rich-vitrinite mainly presents a block structure, and the graphite microcrystalline structure is small, resulting in a smaller size of graphene oxide with a thickness of approximately 10 nm. Due to the formation of rod like structures during graphitization in raw coal, it is difficult to form an ordered lamellar structure in raw coal due to the formation of rod structure during graphitization, and it is also difficult to obtain graphene oxide by oxidative stripping.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 5554K]

Pore structure reformation of tar-derived templated carbons with high volumetric capacitive properties
WU Dongyang;SUN Fei;FAN Wei;WANG Kunfang;ZHANG Boran;ZHAO Guangbo;School of Energy Science and Engineering,Harbin Institute of Technology;
Among all kinds of energy storage devices, supercapacitors have attracted wide attention because of outstanding characteristics such as high power density, ultra-fast charge and discharge speed, and long cycle life. Porous carbon materials are widely used in electrical doubl layer capacitor(EDLC) electrode materials because of their adjustable multi-scale structure, high specific surface area and abundant pore structure. However, the high porosity results in loose carbon skeleton structures, which reduces the material density and further limits the volumetric performance of the double-layer capacitor. Therefore, the key to enhance the volumetric performance of double-layer capacitors lies in carbon electrode materials with a rational pore structure and a dense skeleton. In this study, low-cost coal tar was utilized as the carbon source, and a template method was used to carbonize the different template materials prepared by the phase transformation process after coated by tar, resulting in carbon nanosheets(PCS) with dense porous structure. The optimized hierarchical pore structure in the material reduced the proportion of surplus meso-/macropores, resulting in a high packing density of 0.64 g/cm~3 and enabling both excellent gravimetric and volumetric capacitance properties. With an aqueous EDLC as demonstration, the fabricated PCS electrode can achieve a high-level volumetric capacitance of 277 F/cm~3 at a low mass loading of 2 mg/cm~2 and 243 F/cm~3 at a high mass loading of 8 mg/cm~2, with maximum volumetric energy density and power density reaching 8.46 Wh/L and 10.9 kW/L, respectively. In addition, double-layer symmetric capacitors also exhibited excellent cyclic stability, demonstrating the potential of PCS in high-density energy storage in double-layer capacitors.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 6871K]

Construction of Ni-MOF derived NiS₂@CNTs and its electrochemical properties
WANG Shuang;ZHAO Jiahui;WANG Miao;QU Weiqiang;WANG Jiancheng;MI Jie;PEI Jinping;FENG Yu;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;Key Laboratory of Coal Science and Technology,Ministry of Education,Taiyuan University of Technology;Shanxi Installation Group Co.,Ltd.;
It is crucial to enhance the electrical conductivity and cycling stability of transition metal sulfides for high performance of supercapacitors. Herein, Nickel disulfide nanoparticles composite carbon nanotubes(NiS_2@CNTs) were fabricated from Ni-MOF precursor after carbonizing and vulcanizing processes. It is found that the NiS_2 nanoparticles and CNTs of NiS_2@CNTs composites, which are synthesized under the mass ratio of 1∶6 between Ni@CNTs and sublimated sulfur, presenting uniform dispersion and large specific surface area, providing abundant reactive sites, rapid ionic diffusion and strong electron transport efficiency for the electrochemical reaction. The tests show that the specific capacitance at NiS_2@CNTs reached 568.0 F/g(0.5 A/g). By using NiS_2@CNTs and activated carbon(AC) as positive and negative electrodes, NiS_2@CNTs//AC device exhibites the maximum output energy density and power density of 15.6 Wh/kg and 3 207 W/kg, and displays as high as 98.1% of capacitance retention and 99.7% of coulombic efficiency after 5 000 cycles, showing that the electrode is expected to achieve long-term recycling and has a good practical application potential.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 6364K]

Zinc storage properties of MnO₂ recovered from spent lithium-ion batteries
PENG Xue;LIU Peiyan;XIA Ming;LIU Yuanyuan;School of Chemistry and Chemical Engineering,Yantai University;College of Chemical Engineering,Nanjing Tech University;
With the rapid growth of the lithium-ion batteries, searching effective strategies for recycling decommissioned LIBs has become a hot topic in the fields of industry and academia. Previous studies have extensively investigated the recovery of valuable resources from waste lithium-ion batteries, but the study on directly converting waste lithium-ion battery materials into electrode materials of new energy storage system is relatively few. To achieve the resource reuse of retired batteries, a simple H_2SO_4 impregnation method could be used to convert lithium manganese oxide(LiMn_2O_4) material from waste lithium-ion batteries into MnO_2. Then the prepared MnO_2 was used as the cathode material for aqueous zinc ion batteries. The effects of acid impregnation temperature and time on the morphology, structure, and electrochemical performance of the prepared MnO_2 were investigated through the characterization technologies of XRD, XPS, BET, SEM, CV, TEM, EIS, and electrochemical performance test.The results indicate that LiMn_2O_4 material could undergo dismutation reaction during acid impregnation process, and the Li~+ and some Mn~(2+) would dissolve from LiMn_2O_4 lattice. It is found that the impregnation temperature has a significant impact on the ion dissolution rate. At room temperature, the dissolution rate of ions in LiMn_2O_4 lattice is slow, and λ-MnO_2 material with similar crystal structure with that of LiMn_2O_4 is obtained. While under hydrothermal condition, the relatively high reaction temperature would intensify the vibration of atoms in lattice, and accelerate the rate of ion dissolution. Then more compact and thermodynamically stable crystal structures of γ-MnO_2 and β-MnO_2 are obtained. The electrochemical performance test results show that γ-MnO_2 material with a nanorod-like morphology and a large specific surface area exhibits high discharge capacities of 273.3 and 127.2 mAh/g at the current densities of 0.3 and 3.0 A/g, respectively. It also displays the optimal cyclic stability and the corresponding capacity retentions are 77.1%, 65.7%, and 43.9% after 200, 500, and 1 000 cycles at the current density of 3.0 A/g. In addition, the electrochemical mechanism study by ex-XRD technology shows that the energy storage mechanism of this Zn//MnO_2 cell follows a H~+/Zn~(2+) co-insertion/extraction mechanism.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 6341K]

Effect of CO₂ concentration and ratio on the dissolution loss characteristics of coke
CAI Xiaoqing;GE Dong;SONG Xianfeng;ZHANG Dailin;GAO Zhifang;School of Metallurgy Engineering,Anhui University of Technology;Coking Plant of Laiwu Branch,Shandong Iron and Steel Co.,Ltd.;School of Chemistry and Chemical Engineering,Anhui University of Technology;
The reaction properties of coke mixed with lump coke or powder coke in a CO_2 environment could successfully lower the rate of dissolving loss and enhance the quality of dry quenched coke. In order to investigate the dissolution loss mechanism of dry quenched coke mixed with different particle sizes, a homemade high-temperature coke reaction measurement device was used to study the dissolution loss reaction of carbon under various particle size ratios and different concentrations of CO_2. The optical microscope analysis combined with the Coats-Redfern method were used to investigate the dissolution mechanism of dry-quenching coke with different particle sizes. The results indicate that the proportion of powder coke increases at various concentrations, that the powder coke dissolution loss rate is roughly 0.7-0.9 times that of the mixed coke, and that more CO_2 reacts with the powder coke to produce a reactive carbon-solvation reaction, which increases the mixed coke dissolution loss rate of lump coke-powder coke as the proportion of powder coke increases. However, the isotropy of lump coke and powder coke decreases while the amount of anisotropic tissue increases significantly at different concentrations. In particular, the anisotropic tissue value of powder coke is on average 4% higher than that of lump coke, and it is more reactive. The activation energy of the reaction also decreases as the concentration of CO_2 and the proportion of powder coke increase. The more powder coke there is in the coke at a given concentration, the more likely it is that the carbon-solvation reaction will occur. The amount of powder coke has a major impact on the rate at which mixed coke dissolves at low concentrations. The highest reduction in activation energy that occurs as the amount of powder coke increases is 30%. The research findings may offer a theoretical foundation for further reducing the dissolution loss rate of dry quenched coke.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 5379K]

Current situation and prospect of machine learning-driven boiler combustion optimization technology
YAO Shunchun;LI Longqian;LU Zhimin;LI Zhenghui;School of Electric Power,South China University of Technology;Key Laboratory of Energy Efficiency and Clean Utilization in Guangdong Province;
With the rapid increase of installed capacity of renewable energy power generation, unstable conditions such as variable load and unstable combustion during deep peak regulation put forward higher requirements for combustion optimization control of thermal power units. The rapidly developing artificial intelligence technology and deep learning algorithm provides an important means for boiler parameter prediction modeling and optimization. In terms of machine learning algorithms, this paper summarized the research status of feature screening and modeling algorithms, and pointed out that traditional statistical methods and linear dimensionality reduction methods had poor scientific interpretation and can not identify high-dimensional data well, and feature screening methods combined with deep learning algorithms had more obvious advantages in processing complex thermal power unit data. The advantages and disadvantages of various neural networks in NO_x emission concentration modeling were compared. Among them, long short-term memory neural network and convolutional neural network have better effects in processing time series data, and the integrated model can improve the generalization ability and robustness of the whole model by combining the advantages of different learners. In the application of prediction model, the establishment of prediction model for SCR denitration system can facilitate operators to simulate and modify adjustable parameters, and at the same time, it can be used as a soft measurement method to monitor the operating state of the combustion system. Advanced control methods, such as feedforward control and model predictive control, which introduce NO_x emission concentration prediction model, can effectively improve the poor effect of traditional PID control for thermal power units. In multi-objective optimization, NO_x removal efficiency and boiler efficiency or denitrification cost are usually used as optimization objectives, in order to achieve the harmonious unity of economic and social benefits.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 2482K]

Combustion characteristics of coke oven gas chemical looping of copper-based oxygen carrier
FAN Xinyu;LU Chunqiang;ZUO Huicong;LI Zhiqiang;JIANG Lei;LI Kongzhai;Faculty of Metallurgical and Energy Engineering,Kunming University of Science and Technology;Engineering Research Center of Metallurgical Energy Conservation and Emission Reduction,Ministry of Education;
Coke oven gas(COG) is a major byproduct generated during the coking process, containing complex gas components such as CO, H_2, CH_4, and CO_2. Chemical looping combustion is a technology that efficiently converts COG and captures high-purity carbon dioxide. A series of x(%)CuO/Ce-Zr-O(x=30, 50, 70, 90) oxygen carriers were prepared using the sol-gel method for the study of chemical looping combustion characteristics of COG. XRD analysis indicates that the phases of x(%)CuO/Ce-Zr-O oxygen carriers consist of a solid solution of CuO and Ce_(0.67)Zr_(0.33)O_2. Due to the incorporation of Zr~(4+) ions into the CeO_2 lattice, a distinct oxygen vacancy Raman characteristic peak appears at 617 cm~(-1). H_2-TPR, CO-TPR, CH_4-TPR, and COG-TPR results suggest that the addition of Ce-Zr-O solid solution enhances the low-temperature oxygen release capacity of copper species. Under conditions of 800 ℃, the CO_2 capture rate of the CuO sample is 34%, which increases to 100% with the addition of 10% Ce_(0.67)Zr_(0.33)O_2. After 50 cycles of oxidation-reduction, the performance of the CuO sample significantly deteriorates, while the reactivity and phase structure of the 90CuO/Ce-Zr-O sample remain largely unchanges. This indicates that the interaction between CuO and Ce_(0.67)Zr_(0.33)O_2 enhances the oxygen release capacity and cycling stability of copper species. This research contributes to expanding the utilization pathways of COG.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 9755K]

Effect of preheating air equivalent ratio on preheating combustion of coal slime mixed in a circulating fluidized bed
YANG Sufeng;ZHU Jianguo;University of Chinese Academy of Sciences;State Key Laboratory of Coal Conversion,Institute of Engineering Thermophysics Chinese Academy of Sciences;
The high-efficient and clean combustion of coal slime is one of the most important ways for solid waste resource utilization as coal slime has the characteristics of high ash content, fine particle, and low heating value. Using a novel technology with the coupling of circulating fluidized bed combustion and fluidizing preheating for pulverized coal, and some experiments were performed in a comprehensive evaluation test bench for 30 kW. The preheating combustion experiment of circulating fluidized bed bituminous coal blended with coal slime was carried out by keeping some parameters unchanged, including mixing ratio, feed rate, equivalence ratio, the ratio of secondary air to tertiary air, and excess air ratio, and using measurement instruments such as gas analyzer and flue gas analyzer. The results show that this new process is in a quite stable running, and with a preheating temperature above 800 ℃, and the preheating fuel can be continuously and stably transported to the circulating fluidized bed. The temperature profile in the circulating fluidized bed is uniform with an extremely small temperature difference, as mixing bituminous coal with high ash content coal slime increases the amount of circulating ash. With the increasing of equivalence ratio for preheating air from 0.36 to 0.51, there is a rise of preheating temperature, the volume fraction of CO_2 and HCN in the preheated gas increase, and the volume fractions of CO, H_2, CH_4 and NH_3 decrease, with the heating value of coal gas from 2.02 MJ/m~3 to 1.49 MJ/m~3. Also, with the increasing of the preheating air equivalence ratio, the volume fraction of NO along the height of circulating fluidized bed gradually increases, and the volume fraction of CO shows the atmosphere with higher at the bottom and lower at the upper part. The NO_x emission increases from 172 mg/m~3 to 242 mg/m~3(6% O_2). It can be concluded that the lower equivalence ratio for preheating air benefits to achieve high-efficient and clean combustion with coal slime mixed into bituminous coal, which provides a new technical route and data support for the development and application with coal slime utilization.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 3579K]

Effect of characteristic parameters on the fuel-air mixing uniformity inside the micromix nozzle
CHEN Xuanren;WANG Hui;WANG Chao;ZHANG Xu;CHEN Dong;TANG Jiancheng;School of Energy Science and Engineering,Harbin Institute of Technology;
Due to the small size, large number and non-swirl structure of the micromix nozzle, the micromix combustor structure may form a new design criterion. In order to explore the optimization method of the mixing characteristics inside the micromix nozzle, the characteristic parameters such as Reynolds number inside the nozzle, the relative premixed length and the jet momentum ratio were extracted and the effect of the characteristic parameters on the fuel/air mixing characteristics were studied by Large-eddy simulation model. The results show that, with the increase of premixed distance, the mixing space is expanded, and the mixing characteristics obviously improves. Moreover, the fuel-air mixture is more intense under the large jet momentum ratio, and the mixing quality also show an upward trend. However, fuel inlet velocity has little impact on the mixing performance of the nozzle, and when the Reynolds number is above 1×10~5, the flow state reaches the second self-modeling region in the nozzle, and the mixing uniformity is no longer related to Reynolds number. Further, the mixing uniformity of the nozzle is fitted by these characteristic parameters, the fitting formula could accurately predict the mixing uniformity while the equivalence ratio is in the range of 0.5—1.0, the Reynolds number is above 1×10~5 and the inlet air temperature is in the range of 18—818 ℃. The fitting formula can be used to preliminarily calculate the mixing characteristics of the micromix nozzle and provide reference experience for the nozzle structural design.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 4279K]

Pilot-test of coal-fired boiler coupling with waste incineration technology
ZHANG Rui;CAO Jun;LEI Ling;CAO Yufei;Zibo Chenyue Baoshan Environmental Protection Technology Co.,Ltd.;School of Energy and Power Engineering,Nanjing University of Science and Technology;
The production of municipal solid waste increases year with year as the development of urban modernization. The demand for waste incineration is strong. However, the traditional waste incineration power plant has the disadvantages of low thermal efficiency, high environmental protection costs, and worse economic performance, which make it rely on financial subsidies from the government. The coal-fired power plant coupling with waste incineration technology can co-process municipal solid waste, reduce the cost of waste incineration, and reduce the coal consumption and CO_2 emission of coal-fired power plants. However, the waste incineration process will generate a lot of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans(PCDD/Fs), which may increase the toxicity of the flue gas of coal-fired boiler. To investigate the influences of coupling technology on coal-fired boilers, the experiments were conducted on a 100 kW pilot-test bench. The combustion characteristics and pollutant emission characteristics were analyzed in the experiments. The results indicate that the temperature distribution of the coal-fired boiler become more even after coupling with waste incineration, and the temperature of the combustion zone and lower zone of the boiler decreases about 30 ℃, while the temperature of the upper zone increases about 35 ℃. The decomposition effects of coal-fired boiler on PCDD/Fs are very obvious. When the red mud is blended with the waste, the PCDD/Fs concentration of the flue gas of a coal-fired boiler decreases to 0.003 4 ng/m~3, which can meet the standard for pollution control on the municipal solid waste incineration of China.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 2369K]

Synergistic effects of co-combustion of coal and biomass
ZHOU Wei;WANG Haofan;XIONG Shengxi;JIANG Silei;HE Xiaoyan;MA Xiaochun;LOU Chun;YAO Bin;Jiangxi Ganneng Co.,Ltd.;School of Energy and Power Engineering,Huazhong University of Science and Technology;Xinjiang Uygur Autonomous Region Research Institute of Measurement & Testing;
Biomass fuel is a promising alternative of fossil fuels. Co-combustion biomass in coal-fired power plants is currently a primary method of utilizing biomass energy. Due to the synergistic effect in the coupled combustion process of coal and biomass, the difference between the combustion characteristics of co-combustion of biomass with coal and those of two alone cannot be determined through the arithmetic average of chemical composition or related properties. The high potassium content in biomass exacerbates the slagging tendency on the heating surface. To investigate the synergistic effects during the co-combustion of coal and biomass, Shenfu bituminous coal and chestnut shell were selected as experimental samples. These materials were prepared into shaped pellets by mixing, grinding, and pressing for combustion experiments conducted on a Hencken flat-flame burner. The ignition delay time was determined via using high-speed cameras combined with image processing technology. The flame temperature and gaseous K concentration during the combustion process were measured using a spectrometer based on flame emission spectrum theory. Then, the synergistic effects and reasons of ignition, combustion, and gaseous alkali metal release characteristics during co-combustion were investigated. Finally, the slagging index for various conditions was obtained using the results of ash analysis and the correlation between the release of gas-phase alkali metals and the slagging index was established. The results show that the ignition delay time under the co-combustion condition is lower than the theoretical value, confirming the existence of synergistic effects during ignition, which is characterized by the promotion of the ignition through the influence of cellulose pyrolysis and alkali metal catalysis. The difference between ignition delay time and theoretical value reaches the maximum value of 1.91 s under 50% biomass mass fraction, indicating the maximum synergistic effect. The release of gaseous alkali metals during co-combustion is lower than the theoretical value, indicating that the synergistic effect in gaseous alkali metal release during co-combustion acts as an inhibitory factor. This inhibition effect is attributed to the volatile-coke interaction and the inorganic reactions in which the reactions of Si, Al with K dominates the synergistic effect. As the release of gaseous K increases, the values of base-acid ratio and silica ratio increase, the tendency of slagging also increases. The correlation coefficients between the slagging indices and the release of gaseous K are both more than 95%, indicating that the release amount of gaseous K is highly correlated with the slagging index. It can be seen that the release of gaseous K obtained by online monitoring has the potential to predict the slagging tendency.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 3325K]

A novel low-carbon distributed energy system with complementation between natural gas and medium-temperature solar energy
WANG Bin;HAO Yong;GUO Ke;SHAO Yu;JIANG Qiongqiong;HONG Hui;JIN Hongguang;School of Energy,Power and Mechanical Engineering,North China Electric Power University;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;Department of Thermal Science and Energy Engineering,University of Science and Technology of China;
Complementation between natural gas and solar energy based on chemical looping exhibit advantages in low carbon emissions, energy storage, and high energy efficiency. Currently, typical reduction temperature of methane-based chemical looping is 800 ℃. The conversion rate of methane is comparatively low at a medium temperature of 450 ℃, resulting in reduced efficiency in both thermochemical energy storage and distributed energy systems. A novel thermochemical energy storage method was proposed to address the low methane conversion rate under medium temperature conditions. The method involves the consumption of hydrogen by an oxygen carrier, leading to a decrease in hydrogen partial pressure, thereby shifting the reaction of methane reforming forward and subsequently enhancing methane conversion rates. Mechanistic experimental results show that the new thermochemical energy storage method of methane reforming coupled with chemical looping achieves a higher conversion rate than that of the traditional methane-based chemical looping. Methane is completely converted through multiple cycles at 450 ℃. A multi-energy complementary distributed energy system model was established based on the new thermochemical energy storage method. Natural gas-solar thermochemical energy storage method elevates low-grade solar energy to high-grade chemical energy while simultaneously achieving low-energy decarbonization. The solid fuel generated from the natural gas-medium-temperature solar energy thermochemical method produces high-temperature thermal energy during the oxidation step. The high-temperature thermal energy is harnessed to generate electricity through a turbine, and subsequently, an excess heat recovery system enables absorption refrigeration and heating, thereby achieving efficient complementary utilization of solar energy and fossil fuels. The operational performance of the system under typical conditions was investigated, showing that the distributed energy system based on the new method achieved a net solar electricity generation efficiency of 24.90% and a fuel saving rate of 43.24%, demonstrating significant advantages in energy savings and emission reduction.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 4732K]

Research progress of coal fly ash for CO₂ mineralization process
ZHANG Chujie;WANG Yugao;YAO Zhenchao;YANG Jiangfeng;College of Chemical Engineering and Technology,Taiyuan University of Technology;
CO_2 mineralization is one of the key technologies to meet the challenge of global warming and other ecological problems caused by the massive emission of greenhouse gases such as CO_2, which has become a major challenge to the survival of all mankind. The energy resource endowment pattern of "relatively coal-rich, oil-poor and gas-poor" has led to the fact that China′s main energy source is still dominated by coal, which has a high CO_2 emission intensity, and the industrial solid waste generated from the combustion of coal fly ash also faces a huge problem of disposal. Compared with traditional mineralized raw materials, coal fly ash has received widespread attention due to its abundant reserves, easy accessibility and low transportation costs. Coal fly ash can achieve CO_2 mineralization and sequestration through direct and indirect mineralization, and reduce the environmental risks associated with the accumulation or disposal of coal fly ash while CO_2 mineralization and sequestration is taking place. Under the goal of carbon peaking and carbon neutrality, the use of coal fly ash to mineralize and sequester CO_2 is an efficient strategy with great potential to combat global warming. The current status of coal fly ash emissions and utilization in China were described. The research progress of direct and indirect coal fly ash mineralization was reviewed, the advantages and disadvantages of different mineralization processes were compared and analyzed, the regulation mechanism of the process parameters on the efficiency of coal fly ash mineralization in the process of CO_2 mineralization was clarified. In order to address the lack of mechanistic explanation of CO_2 mineralization from coal fly ash, the mechanisms of gas-liquid diffusion and other mechanisms controlling the mineralization rate during the mineralization process were clarified through the introduction of the shrinking nucleus model and the surface coverage model, which were commonly used to describe the CO_2 mineralization reaction. Finally, the existing problems and future research directions of the coal fly ash mineralization process were analyzed, aiming to provide a reference for the use of coal fly ash solid waste to mineralize CO_2.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 5331K]

Research progress and application of cementing materials prepared from coal based solid waste
CHANG Ruiqi;ZHANG Jianbo;LI Huiquan;QU Jiangshan;LI Shaopeng;LI Zhanbing;WU Wenfen;National Engineering Research Center of Green Recycling for Strategic Metal Resources,CAS Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Sciences;School of Chemical Engineering,University of Chinese Academy of Sciences;
Coal gangue, fly ash, and gasification slag are solid wastes generated from coal mining, chemical conversion, and coal-fired power generation processes. These wastes have an annual emission of over 1.5 billion tons with a comprehensive utilization rate of about 60%. However, their current utilization mainly focuses on low-end construction materials consumption, leading to market saturation. In light of impending environmental protection policies, there is an urgent need to develop new methods for resource utilization of coal-based solid waste. Due to the cementing properties of coal-based solid waste such as aluminosilicate composition, potential pozzolanic activity, and unique microstructure characteristics, low-cost and high-performance low-carbon cementitious materials have emerged as a promising avenue for large-scale and high-value utilization.The activation technology and application fields of coal-based solid waste cementitious materials were reviewed and prospected. The impact of physical excitation, alkali excitation, and acid excitation on the mineral phase transformation of gelled materials and their influence on product properties were elucidated. Furthermore, an overview was provided regarding the merits of existing technologies as well as the challenges that need to be addressed. In terms of application fields analysis includes building materials production road repair environmental remediation among others where coal-based solid waste cementitious materials can be utilized effectively. Based on the above situation, the future development direction of coal-based solid waste cementitious materials such as excitation mechanism research, component ratio optimization, material environmental protection performance, engineering application and promotion were prospected. It has important reference significance for the preparation of cementitious materials from coal-based solid waste, and provides a new way for large-scale utilization of coal-based solid waste.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 5309K]

Changes of pollutant emission from co-combustion of coal and paper mill sludge in pulverized coal boiler
LYU Pu;ZHAI Hongguang;HAO Yingzhi;MENG Xiandong;YANG Fangxiong;TIAN Yongjing;TAN Quanyin;School of Environment,Tsinghua University;Research Institute for Environmental Innovation(Suzhou);School of Environmental Science and Engineering,Suzhou University of Science and Technology;Qingzi Waste Environmental;Hebei Provincial Solid Waste Pollution Control Center;
The co-combustion of paper mill sludge in coal-fired boilers presents an economically viable sludge disposal method. The paper mill sludge contains a lot of organic matter. Based on the reason, the coal-fired heating boiler that built in the paper mill to burn the paper sludge was used in the experiment. The co-combustion can reduce sludge treatment costs and utilize the thermal energy present in the sludge.Co-firing paper mill sludge in the boiler has the potential to alter the composition of pollutants in solid wastes like flue gas, furnace slag, fly ash. A co-firing test was conducted using a 2×300 MW unit boiler in a paper mill. A total of 755 tons of paper mill sludge was blended with a coal-to-sludge ratio of 22∶1. The calorific value of the mixed fuel showed a slight reduction compared to coal. The blending test lasted for 3 d. Samples of flue gas, dried sludge, slag and fly ash were collected. 3 flue gas samples and 3 dried sludge samples were collected before blending, 1 blank sample of slag and fly ash was collected, and 6 flue gas samples, 16 slag samples and 50 fly ash samples were collected after blending. The results indicate that conventional gaseous pollutants in the flue gas such as NO_x increases by 1.5 times, SO_2 concentration increases slightly, and heavy metals Ni, Zn, Ba, Se, Cr, Mn, Sb, Pb, Cu are detected. The most prevalent heavy metals are Ba and Zn. PCDD/Fs are not detected in the blank flue gas samples, with an average concentration of 1.2 pg/m~3(in TEQ) in the co-firing group. Following co-firing, the furnace slag exhibits a notable increase in Pb concentration by 2.5 times, while concentrations of Cu, Ni, Co, Ba, and Mn decreases by 1.5 to 2.5 times. PCDD/Fs concentrations remain within permissible limits in both groups. The concentration of heavy metal elements in fly ash shows significant variations, with elements such as Ba, Mn, and As increasing by 1.5 to 2.0 times, while others decreases compared to the blank group. PCDD/Fs are not detected in the coal fly ash of the blank group, and the concentration of dioxins in the fly ash of the mixed-burning group is 2 pg/g. All pollutants generated during this co-firing test remains within the prescribed limits set by Chinese national standards.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 3456K]

Self-reactivation of spent limestone to enhance its CO₂ capture capacity in multiple cycles
SUN Rongyue;HU Tianjiao;YIN Pengxiang;SHEN Hao;TAO Chengfei;LYU Xun;School of Energy and Power Engineering,Nanjing Institute of Technology;Xizi Clean Energy Equipment Manufacturing Co.,Ltd.;
Calcium looping process is a kind of cost-effective and high-efficiency CO_2 capture technology. A certain amount of fresh calcium based sorbent should be supplemented to the process and corresponding amount of spent sorbent is discharged. It is of significant to realize in situ reutilization of such a quantity of spent calcium based sorbent. A dual-fixed bed reactor was employed to prepare the spent limestone and investigate the cyclic carbonation conversions of spent limestone after self-reactivation. XRD, SEM and N_2 adsorption analysis were employed to discuss the mechanism that self-reactivation improves the CO_2 capture capacity of spent limestone. The results show that when placed in a constant humidity environment, spent limestone can absorb the H_2O in the air to form Ca(OH)_2 and go on to form calcium hydroxide hydrate when the value of water absorption φ is 100%. The limit value for φ is 130%. CO_2 capture capacity of the spent limestone is dramatically enhanced after self-reactivation, which is proportional to φ. Compared with CaCO_3, the CO_2 capture capacity of spent limestone is much more sensitive to φ. When φ is 130%, the CO_2 capture capacity of the spent limestone after self-reactivation is even higher than that of the fresh limestone. The microstructure analysis results show that due to the sintering occurred under high temperature calcination, the CaO grain size in calcined limestone increases from 41.9 nm to 72.2 nm. The micro-pores are blocked. The pore volume and BET surface area decrease dramatically. After self-reactivation, the CaO grain size in the calcined limestone obviously decreases, and plenty of pores are regenerated on the surface. When φ is 130%, the CaO grain size decreases to 35.1 nm, the pore volume and BET surface area are recovered to 70.5% and 107.6% those of the calcined fresh limestone, especially the pore volume that distributed in 10-100 nm is regenerated dramatically. Therefore, the CO_2 capture capacity of spent limestone can be enhanced by self-reactivation. The self-reactivation process can accelerate the attrition rate of spent limestone. However, even when φ is 100%, the diameter of the sorbent particle only decreases by 0.55% per hour. To sum up, the spent limestone after self-reactivation can sufficiently be used as supplementary sorbent instead of fresh limestone in calcium looping process for CO_2 capture.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 3230K]

Mechanism of pulverized coal preheating-combustion low-NO_x reduction and synergistic control of particulate matter
ZHU Guangqing;HU Runjie;HUI Shi′en;NIU Yanqing;Key Laboratory of Thermo-Fluid Science and Engineering of MOE,School of Energy and Power Engineering,Xi′an Jiaotong University;
Combustion optimal is expected to realize efficient low-NO_x combustion of pulverized coal with synergistic control of particulate matter(PM), and is also a crucial clean combustion method to accomplish low-carbon goals. To clarify the formation and reduction mechanisms of NO and particulate matter(PM), the release of coal nitrogen, the conversion of volatile nitrogen, the NO formation and reduction mechanism, and the PM formation have been investigated during the preheating-combustion. The main gas components and PM were measured by a flue gas analyzer and an electrical low pressure impactor(ELPI+), respectively. The results indicate that the gas-phase excess air coefficient(α_(gas)) serves as an effective criterion for the reactivity(oxidative or reductive) of the preheating zone, which predominantly involves gas-phase reactions. An increase in excess air coefficient(α_p) slightly impairs the operation of the preheating zone, yet significantly enhances the reduction of NO during the entire preheating-combustion process. A higher preheating temperature notably decreases NO formation, with NO reduction efficiency increasing from 42.25% to 51.44% as preheating temperature rises from 1 200 K to 1 600 K. However, this effect diminishes with an increase in α_p. Raising the temperature has a promoting effect on both char oxidation for NO formation and char reduction of NO, but the effect on NO formation is more pronounced. Concurrently, the preheating-combustion process reduces the of PM, particularly 27.57% reduction in PM_(0.3). The preheating-combustion technology can achieve the synergistic source control of PM and NO formation, which is important for the clean combustion of coal.
2024 02 v.30;No.162 [Abstract][OnlineView][HTML全文][Download 5495K]

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2024年02期目次

Research progress on predictive models for slag flow in gasifiers

Multistable-flexible ammonia process adapted to renewable energy

Application of quantum chemical calculations to the mechanism of clean and efficient coal conversion

Molecular insights into the microscopic interaction between lignite and water: A multiscale molecular modelling study

Gasification reactivity of coal gasification fine slag and its separated carbon-rich residues

Effect of biomass ash on coal char gasification

Influence of heavy oil composition structure on the rheological properties of coal-oil slurry

Influence of cross-linking modification of coal tar pitch on carbon structure

Optimization of active metal Ni d charge density for efficient phenanthrene hydrogenation over Ni₂P/Al₂O₃ catalyst

Simulation study on the reaction mechanisms of Fe-based oxygenc arrier supported by CeO₂ with CO

Development and research progress of catalytic system of high-value derivatives of dimethyl oxalate

Research advances on solvothermal conversion of levoglucosan into value-added chemicals

Research progress of biomass-derived porous carbon materials for supercapacitors

Composition and structural evolution of graphene oxide prepared from Shenfu coal and its macerals

Pore structure reformation of tar-derived templated carbons with high volumetric capacitive properties

Construction of Ni-MOF derived NiS₂@CNTs and its electrochemical properties

Zinc storage properties of MnO₂ recovered from spent lithium-ion batteries

Effect of CO₂ concentration and ratio on the dissolution loss characteristics of coke

Current situation and prospect of machine learning-driven boiler combustion optimization technology

Combustion characteristics of coke oven gas chemical looping of copper-based oxygen carrier

Effect of preheating air equivalent ratio on preheating combustion of coal slime mixed in a circulating fluidized bed

Effect of characteristic parameters on the fuel-air mixing uniformity inside the micromix nozzle

Pilot-test of coal-fired boiler coupling with waste incineration technology

Synergistic effects of co-combustion of coal and biomass

A novel low-carbon distributed energy system with complementation between natural gas and medium-temperature solar energy

Research progress of coal fly ash for CO₂ mineralization process

Research progress and application of cementing materials prepared from coal based solid waste

Changes of pollutant emission from co-combustion of coal and paper mill sludge in pulverized coal boiler

Self-reactivation of spent limestone to enhance its CO₂ capture capacity in multiple cycles

Mechanism of pulverized coal preheating-combustion low-NO_x reduction and synergistic control of particulate matter