- SONG Shulei;YAN Shanwen;XU Xuan;CHEN Zengqiang;LIU Hongqi;Key Laboratory of Coal Processing & Efficient Utilization,Ministry of Education;School of Chemical Engineering,China University of Mining and Technology;Shandong Ruifu Lithium Industry Co.,Ltd.;
In order to study the electroconductivity of anthracite and improve its conductivity, and make anthracite become a part of filler and electrode materials, ultra-pure anthracite with ash content of 0.13% was prepared by acid solution method. The effects of moisture, ash content, pressure, particle size and mineral composition on the electroconductivity of ultra-pure anthracite were investigated by powder resistivity tester. The results show that the electrical conductivity of anthracite increases with the increase of moisture and pressure. The electrical conductivity increases gradually with the decrease of ash content. The electrical conductivity increases sharply with the ash content decreasing when the ash content is less than 1.0%. When the pressure is 4.00 MPa, the moisture is 6.21%, the particle size is 0.2-0.1 mm, and the ash content is reduced to 0.13%, the electrical conductivity of anthracite is the best, and its electrical conductivity is 1.44×10~(-7) S/cm. In the study range, the influence of particle size on the conductivity of anthracite is small. The order of electrical conductivity of common minerals in coal is: pyrite > kaolinite > silica > calcium carbonate > calcium sulfate, pyrite has the highest conductivity value, which reaches 1.32×10~(-2) S/cm. The electrical conductivity of anthracite increases with the increase of pyrite content, but decreases with the increase of other mineral content. The response surface model is used to optimize the orthogonal experimental results, and the quadratic regression equation between the electrical conductivity of anthracite and moisture, ash content and particle size is obtained. The influence of moisture and ash content on the conductivity testing results of anthracite is significant, in which ash has the greatest influence on conductivity, followed by moisture and particle size.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 902K] - ZHAO Yunpeng;WU Fapeng;QIU Lele;XIAO Jian;CAO Jingpei;WEI Xianyong;Key Laboratory of Coal Processing and Efficient Utilization,Ministry of Education,China University of Mining & Technology;Jiangsu Province Engineering Research Center of Fine Utilization of Carbon Resources,China University of Mining & Technology;
Thermal dissolution(TD) under mild conditions is an effective way to obtain organic species from lignite. However, the conventional TD affords low yield of soluble portions(SPs). Herein, a series of Al_2O_3-loaded metal catalysts prepared by co-precipitation method were used to investigate the catalytic thermal dissolution(CTD) behavior of Zhaotong lignite in isopropanol. For comparison, TD of Zhaotong lignite was conducted under the same conditions. The physicochemical properties of the catalysts were investigated by XRD, H_2-TPR, TEM and XPS, and the compositions as well as structural features of SPs obtained from TD and CTD were analyzed by GC/MS, FTIR and MALDI-TOF-MS. The results show that NiCu/Al_2O_3 exhibites superior performance to other catalysts on CTD of Zhaotong lignite, in which the active components exist in the form of NiCu alloy with interaction between Ni and Cu. The yields of SPs obtained by TD and CTD first increases and then decreases with the elevation of temperature, and the highest yields of SPs from TD and CTD at 320 ℃ are 27.69% and 50.54%, respectively. The introduction of the catalyst can increase the yields of asphaltene(AS), preasphaltene(PAS) and oil in SPs, in which the enhancement of the latter two components is more obvious than that of AS. Phenols are the main group components in the TD derived oil with a relative content of 64.44%, while the CTD derived oil mainly consists of arenes, phenols, alcohols and ketones, indicating that the catalyst promotes the cleavage of covalent bond in the soluble organic fragments and the hydrogenation of phenols. Compared with the AS and PAS obtained from TD, those acquired from CTD possess a narrower molecular weight distribution range, and the intensity of adsorption peaks assigned to the hydroxyl group and ether bonds in the FTIR spectra become weaker or disappeared, suggesting that CTD facilitates the hydrogenolysis of C—O bonds. CTD can directly get soluble organic species with high yield from lignite under relatively mild conditions, and the results of the study may provide a reference to develope process for directly acquiring chemicals from lignite.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 982K] - ZHU Xueshuai;SUN Tao;SONG Zhao;YAN Shumai;RUAN Leyi;BAI Sihang;XU Huiyuan;WEI Lubin;School of Chemical & Environmental Engineering,China University of Mining and Technology-Beijing;Yibin Tianyuan Kechuang Design Co.,Ltd.;
Against the backdrop of "carbon peak and carbon neutrality", airflow separation has garnered attention across various industries due to its advantages of environment friendly, low cost, water-free, low investment, and facile process. To upgrade the airflow separation adaptability on multiple fields, regions and working conditions, it is urgent to solve challenges such as narrow sorting range of materials, inefficient fine-grained separation and equipment scaling up difficulties. A systematic review on the research progress of airflow separation around separation theory, technical application and technology improvement was conducted. The principle of airflow separation was first introduced, the force on particles during pneumatic separation process and the progress of separation theory was analyzed. Secondly, the application progress of airflow separation in solid waste, mining, agriculture was reviewed, the technical advantages and shortcomings were analyzed. Subsequently, the technical improvement progress of air supply mode optimization and equipment structure optimization in airflow separation were systematically analyzed. Finally, the solution paths of existing challenges were given, including improving the processing capacity of the equipment through the monomer parallel and similar amplification criteria, improving the adaptability and dispersion of wet materials through integrated pre-drying, separation and drying, and upgraded feeding method, and improving the separation efficiency of fine and thin materials through narrow particle separation and the pretreatment process that maintaining the shape consistency of materials. The future development direction of airflow separation in intelligent detection and control, large-scaling separation equipment, separation efficiency refinement and separation association were prospected, providing important basis for further research and promotion of airflow separation.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 354K] - ZHANG Bo;YAO Shaoyu;SUN Zongsheng;CUI Fengyuan;Key Laboratory of Coal Processing and Efficient Utilization Ministry of Education,China University of Mining and Technology;
Coal is the ballast and stabilizer for ensuring China′s energy security. With the depletion of high-quality coal resources, the utilization of low-quality coal has gradually taken the lead. Low-rank coal reserves are large and have high moisture content, which reduces its subsequent utilization efficiency. Coal drying can effectively reduce coal moisture, improve coal quality, and promote the clean and efficient utilization of high water content low quality coal. The moisture in coal was summarized and classified according to the location and nature of the storage. The classification of the pore structure and oxygen-containing functional groups in coal and the influence of the drying process on the physicochemical structure of coal were reviewed, and the influence of the physicochemical structure of coal on the removal and reabsorption of moisture was then analyzed. The results show that the moisture in small pores and the moisture bonded in the form of hydrogen bonding are more difficult to remove, and the reduction of pore volume and oxygen-containing functional groups after drying can effectively inhibit the moisture reabsorption, and the ignition point of coal is affected by the type of coal and the moisture content, and the upper limit of the drying temperature should be reasonably controlled to prevent overheating and combustion of the coal during drying. The current application status of evaporation drying and dehydration technology was summarized, including drum drying, low-temperature steam drying, fluidized bed drying, vibration mixed-flow drying, microwave drying and other drying methods, and different drying methods were compared and evaluated, and the research direction of future drying technology was explored. The structure of the hot flue gas drying equipment is simple, the processing capacity is large, but the drying process needs to strictly control the oxygen content, and the safety is relatively low. Microwave drying has the advantages of selective heating and fast drying rate, but it may have thermal runaway in the late stage of drying, and it is mainly in the laboratory/pilot research stage at present. The drying technology using steam as the heat medium has high safety and no waste water and exhaust gas discharge, with low energy consumption and high safety features, and can be further researched on steam transient drying technology, to solve the safety and high efficiency dewatering and quality improvement of coal with wide grain size.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 606K] - ZHOU Changchun;WEN Zhiping;ZHOU Maiqiang;XU Ge;School of Chemical and Technology Engineering,China University of Mining and Technology;
With the continuous traction of Chinese government policies and the new artificial intelligence technology, the research of mine intelligence has continued to make breakthroughs in recent years. The intelligent construction of coal preparation plant as a part of intelligent mine has received great attention, among which, the intelligent control technology of coal flotation has been one of the key bottlenecks hindering the intelligent construction of coal preparation plant. In this paper, the life cycle of coal slime flotation data was taken as the main research line, the research progress of coal flotation intelligent control technology was reviewed from three perspectives: online prediction of coal flotation concentrate/tailings ash content, intelligent addition of the flotation regents and intelligent decision-making of coal flotation system, and the research tendency of coal flotation intelligent control was looked forward to the future. The online prediction of concentrate ash content is still difficult, and the single computer visual feature information of froth image is not reliable, the prediction technology of tailings ash content is relatively more reliable. The addition of flotation regents is limited by multiple flotation condition variables at the same time, and the adaptability and generalization ability of model performance in the entire working condition interval need to be further improved. The current research on flotation intelligent control technology is limited by the prediction accuracy of coal flotation concentrate/tailings ash content, sensor detection accuracy, and agent addition accuracy. The flotation process dataset is more dimensional, making it difficult to establish a reliable knowledge base. The new generation of artificial intelligence technology represented by deep learning can adapt to this kind of data structure. In addition, the existing flotation monitoring system only targets specific minerals, with high uniqueness. In the future, the coal flotation intelligent control system should focus on overcoming the limitations of index prediction and sensor detection accuracy, and establish a large dataset and large model of multi-coal and templated intelligent control data.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1257K] - TANG Ying;WU Xiaodan;SUN Jingyao;SU Zhan;CHANG Zhibing;WANG Chuchu;KUANG Wenhao;Research & Development Center,CNOOC Gas & Power Group;Key Laboratory of Liquefied Natural Gas and Low Carbon Technology,China National Offshore Oil Corporation;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
The softening and melting of cohesive tar-rich coal caused by heating may lead to wellbore blockage and formation disturbance, which is an important factor to be considered for in-situ pyrolysis. In this paper, the pyrolysis of cohesive tar-rich coal at 300-700 ℃ was conducted to investigate the oil and gas precipitation rules and their composition properties, and the evolution characteristics of physical properties of semi-coke and its indicative significance for in-situ pyrolysis were analyzed. The results shows that the tar yield reaches the maximum value of 7.75% at 500 ℃, and the content of light components(boiling point lower than 300 ℃) of the derived tar is the highest(32.2%). The tar components chang significantly at 400-500 ℃, and the content of phenols increases while that of aromatics decreases. The softening temperature and curing temperature of the coal sample are 389 and 455 ℃ respectively. Consequently, the macro-porosity of semi-coke increases from less than 10% to about 50% at ≥400 ℃, while the micro-pore structure is more developed only at the high temperature stage of 600-700 ℃. The thermal conductivity of semi-coke decreases first and then increases with temperature, and reaches a minimum value of 0.06 W/(m·℃) at 400 ℃. In-situ pyrolysis of cohesive tar-rich coal may be confronted with potential problems such as channel blockage, volatile precipitation obstruction and slow thermal conductivity of coal seam. These problems are expected to be solved by using fracturing proppant with viscosity breaking effect or applying near critical water in-situ conversion technology.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 805K] - LI Ning;CHU Ruizhi;WU Jiaxin;MENG Xianliang;WU Guoguang;LI Xiao;LI Weisong;JIANG Xiaofeng;YU Shi;School of Chemical Engineering & Technology,China University of Mining and Technology;
SAPO-34 molecular sieve has the problems of low olefin selectivity and easy carbon deposition of acidic sites in MTO reaction. In this article, Metal Co was introduced into the pores of SAPO-34 through equal volume impregnation method, and the effect of Co addition on the catalytic performance and carbon deposition behavior of Co/SAPO-34 catalyst in the MTO reaction was systematically investigated. The results indicate that metal Co can serve as a central site for dehydrogenation reactions, weaken hydrogen ion transfer, inhibit the generation of alkanes, and effectively improve the selectivity of olefins in the reaction. At the same time, the introduction of Co metal can also precisely regulate the strength of acid centers on the surface of SAPO-34, increase the ratio of weak acid to strong acid, thereby weakening the carbon deposition effect of strong acid centers and inhibiting the deactivation of catalyst. By combining characterization methods such as NH_3-TPD, H_2-TPD, BET, TG, XPS, GC-MS, etc., this paper deeply explored the carbon deposition behavior of Co/SAPO-34 catalyst in MTO reaction. It is found that key carbon deposition precursors like polymethyl-substituted benzene are preferentially deposited on micropores and strong acid sites, and significantly promote the generation of polycyclic aromatic hydrocarbons. The relatively large pore volume and appropriate weak acid concentration can synergistically promote the decomposition and transformation of carbon deposition precursors, inhibiting the formation of hard coke. The calculation of carbon deposition rate shows that Co_(0.5)/SAPO-34 with appropriate acidity and pore structure has the highest methanol conversion rate, low-carbon olefin selectivity and the longest catalytic life.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1250K] - REN Guohang;GU Bo;YANG Xiaoqin;PENG Xiaoxue;WEI Jinyu;JIA Jia;LIN Zhe;QIN Zhihong;School of Chemical Engineering and Technology,China University of Mining and Technology;
Supercapacitors are a type of high-performance electrochemical energy storage device with high power density, strong cycling stability, and fast charge-discharge rates, which play a crucial role in the storage of renewable energy. To enhance the performance of supercapacitors and meet the growing demands for energy storage, NiCo-MOF@CNTs composite electrode materials were prepared using a hydrothermal method. By varying the amount of carbon nanotubes(CNTs), the energy storage properties of the composite material were optimized. CNTs not only increase the material′s specific surface area and conductivity, but also form a unique vine-like structure with NiCo-MOF. NiCo-MOF constitutes the leaves of the vine in this structure, providing active sites for charge storage, while CNTs form the stems connecting to the leaves, continuously transferring electrons to the active centers, thereby improving electrochemical performance. In comparison to the case without the addition of CNTs, the specific surface area of the most effective NiCo-MOF@CNTs5 increases from 25.65 m~2/g to 44.27 m~2/g and the average pore size decreases from 37.86 nm to 18.99 nm. The pore distribution is more favorable for the diffusion and transport of electrolyte ions. The specific capacitance reaches up to 1 569 F/g at a current density of 1 A/g, and the rate performance reaches 74% at an increased current density of 20 A/g, which is higher than that of the NiCo-MOF electrode material without CNTs(42.6%). After assembling into an asymmetric supercapacitor, the specific capacitance remains at 194 F/g at a current density of 1 A/g and still maintains 147 F/g at a higher current density of 20 A/g. After 5 000 charge-discharge cycles at 5 A/g current density, the capacitance retention rate is 91.2%. The energy density at a power density of 759 W/kg reaches 50.63 Wh/kg, and a high energy density of 41.94 Wh/kg is achieved even at an increased power density of 17.3 kW/kg.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1212K] - HU Yancheng;ZHANG Wenjing;CAO Jingpei;School of Chemical Engineering and Technology,China University of Mining and Technology;
Aromatic polycarboxylic acids, such as terephthalic acid, phthalic acid, trimellitic acid, trimesic acid and pyromellitic acid, are important bulk chemicals in modern industry. They can be used to prepare diverse polymers that have been widely applied in various aspects of our daily life. Industrially, these compounds are obtained by catalytic oxidation of petroleum-derived aromatic hydrocarbons at elevated temperature and pressure. In the context of dual carbon strategy, using renewable biomass to replace traditional fossil energy to produce chemicals is of great significance. The process for biomass conversion included catalytic degradation of biomass into a series of C1-C6 platform molecules, and subsequent carbon-carbon couplings of these compounds. This review carefully summarized the advances in catalytic conversion of biomass-based compounds into aromatic polycarboxylic acids. The novelty of these works is the establishment of new biomass-based synthetic process towards aromatic polycarboxylic acids, and the key challenging step is the construction of aromatic rings. To address this issue, two strategies have been developed:(1) Diels-Alder reaction of furans with olefins and subsequent aromatization via dehydration.(2) Alcohol dehydration to dienes and subsequent Diels-Alder reaction, followed by aromatization via dehydrogenation. This review is categorized by the types of aromatic polycarboxylic acids, including terephthalic acid, phthalic anhydride/acid, benzenetricarboxylic acid, and pyromellitic acid. This review provides important guidance for the development of new biomass conversion system and process optimization.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1683K] - YUE Xiaoming;LIU Tianlong;ZHAO Zihan;AN Zhaoyang;LUO Peng;Jiangsu Province Engineering Research Center of Fine Utilization of Carbon Resources (Ministry of Education),China University of Mining and Technology;Zhaoqing Shunxin Coal Chemical Technology Co.,Ltd.;
As main material for supercapacitor electrodes, porous carbon has the advantages of good electrical conductivity, high chemical stability and wide range of operating temperature. In this paper, porous carbon materials were prepared by chemical activation using Inner Mongolia coal tar pitch(CTP) as raw material, K_2CO_3 and KOH as the activators respectively. The preparation process conditions were optimized, and the differences in structure and electrochemical performance of the porous carbon prepared by the two activators were compared. The results show that the optimal preparation conditions for K_2CO_3 and KOH activation are both activation temperature of 700 ℃ activation time of 60 min, and mass ratio of activator to CTP of 2∶1. There are significant differences in the microstructure of porous carbon prepared by the two activators. The surface of porous carbon(PH-T700) prepared by KOH activation is flat and smooth, with a large number of regular circular pores distributed, but the porous carbon(PC-T700) obtained by K_2CO_3 activation shows a coral structure. Compared with PH-T700, PC-T700 has more mesopores and less ionic diffusion resistance. At a current density of 1 A/g, the specific capacitance of PC-T700 and PH-T700 are 252.90 and 261.02 F/g, respectively. PC-T700 and PH-T700 are assembled into button type symmetrical capacitors, with specific capacitance of 226.01 and 225.51 F/g at 0.5 A/g, respectively. PC-T700 shows better rate capability and cycling stability. After 5 000 times of charging and discharging, the specific capacitance of PC-T700 and PH-T700 are 103.77% and 98.20% of the initial values, respectively. When power density reaches 1 038.46 W/kg, the energy density of PC-T700 still maintains 7.5 Wh/kg, which is higher than that of PH-T700.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1082K] - LIU Jinchang;YAN Zuoxian;WANG Xinyu;XIE Qiang;LIANG Dingcheng;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
Pitch-based carbon fiber is a crucial engineering material extensively utilized in aerospace, national defense, and military industries, etc. However, the lengthy preparation process and numerous influencing factors hinder the production of pitch-based carbon fiber with exceptional mechanical performance. This work delved into the current state, methods, mechanisms, and regulation of raw material pretreatment, pitch precursor preparation and control, melt-spinning, stabilization, carbonization, and graphitization to address these challenges comprehensively. It emphasized that the breakthrough direction for pitch-based carbon fiber lies in its molecular-level directional and controllable preparation. The raw materials for pitch-based carbon fiber include coal-based, petroleum-based, biomass-based, and polymer-based materials as well as pure compounds. Distillation and extraction are the common methods for the pretreatment of raw materials. The preparation of pitch precursor is essentially a liquid-phase carbonization reaction that involves parallel hydrogen transfer reactions and free radical reactions, including complex reaction processes such as cyclization, aromatization, oligomerization, and condensation. Aromatic oligomers condense at high temperatures to form the basic structural units of polycyclic aromatic hydrocarbon flakes, which continuously aggregate through thermal effect to form aggregates. The basic structural units stack together with the force of van der Waals, forming parallel stacking bodies to convert to basic building unit aggregates. The basic building unit aggregates can transform into long-range disordered and short-range ordered non-graphitization structures under different reaction conditions, as well as into long-range ordered and short-range ordered graphitization structures. When the pitch precursors derive from coal-based, petroleum-based, and biomass-based materials, the thermal condensation method with simple equipment, easy operation, and low cost is usually selected owing to their high reaction activity. In contrast, higher temperatures are required to initiate free radical reactions when pure compounds with low reactivity such as naphthalene and methyl naphthalene are used as raw materials. Therefore, catalytic synthesis is usually used. Melt-spinning plays a role in shaping, and the diameter and shape of carbon fibers can be adjusted by changing the spinning parameters and the shape of the spinneret. Moreover, the molecular rearrangement effect of melt-spinning on the precursor of mesophase pitch is particularly significant, making it easier for graphite microcrystals to form ordered graphite crystal structures along the axial one-dimensional arrangement. To prevent the melting of pitch fibers during the carbonization process, it is necessary to transform the pitch fibers from thermoplastic to thermosetting, that is, through a slight oxidation reaction, the polycyclic aromatic hydrocarbon molecules in the pitch undergo oxidation, condensation, decomposition, and dehydration, forming a specific cross-linked structure, and ultimately generating a certain amount of oxygen-containing functional groups in the fiber structure. Carbonization is the formation of carbon fibers with molecular structural characteristics of carbon materials through complex chemical reactions and structural transformations of stabilized fibers. During the carbonization process, graphite microcrystals undergo rearrangement, non-carbon atoms are removed, and the carbon element content further increases. After graphitization, the graphite crystal structure becomes more complete and highly oriented, which transforms carbon fibers into graphite fibers and enhances their strength performance. In addition, it provides clear guidance for optimizing and improving time-consuming and energy-intensive stabilization steps in carbon fiber production.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1248K] - ZHAO Jinke;GUO Ziyi;DUAN Chenlong;HUANG Dongyan;DONG Tingyu;WANG Haoxue;ZHOU Enhui;Sun Yueqi Honors College,China University of Mining & Technology;School of Chemical Engineering & Technology,China University of Mining & Technology;School of Economics and Management,China University of Mining & Technology;
high-sulfur anthracite generates a large amount of sulfur oxides during combustion, causing serious damage to the atmospheric environment. It is necessary to seek a path for its development from traditional fuel to high-end materials with increasingly strict environmental requirements. Due to the lack of technical indicators for the preparation and application of activated carbon in specific fields, the preparation goals are unclear, and the targeted preparation of activated carbon is an urgent issue to be addressed. In this study, two types of activated carbon with specific surface areas of 1 066.42 m~2/g(AC-1)and 1 568.79 m~2/g(AC-2)were obtained by using high-sulfur smokeless coal from Jincheng area, prepared by physical activation and phosphoric acid impregnation. Characterization was performed using FTIR, XPS, SEM, and other methods. The results show that the mesopore volume of AC-1 is 1.688 nm, while that of AC-2 is 0.718 nm, indicating that the former has a more developed mesoporous structure. The adsorption performance of two activated carbons using Cu~(2+) as the adsorbate was studied. The results indicate that the adsorption performance of AC-1 is significantly superior to that of AC-2, and the adsorption behavior is jointly determined by pore size distribution and surface functional group content. The optimal adsorption conditions are found to be pH=4, temperature at 35 ℃, activated carbon dosage of 0.30 g, and adsorption time of 2 hours. Kinetic studies reveal that the adsorption process of both activated carbons for Cu~(2+) is chemisorption rather than intraparticle diffusion-controlled. The fitting results of the adsorption isotherms indicate that the Langmuir isotherm model is not applicable to AC-2, possibly due to its predominance of physical adsorption. In this study, the influence of pore distribution and surface functional group content on the adsorption performance was discussed, providing guidance for the targeted preparation of activated carbon with good water-phase heavy metal ion removal capability from high-sulfur smokeless coal.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 916K] - XIE Weiwei;MU Wushuang;YAN Yongji;YU Yifan;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
Extraction residue of coal liquefaction residue(ER) refers to the substance remaining after obtaining heavy oil and asphalt through extraction from coal direct liquefaction residue, accounting for about 15% of the original coal amount. By using scanning electron microscopy(SEM) to observe the loose and porous structure on the surface of the ER, the ash content can be reduced by flotation, and it can be used to produce activated carbon. Due to the adhesion of heavy oil and asphalt to the surface of unreacted coal in the extract, various substances in the ER have indistinguishable hydrophobicity, making flotation difficult. Therefore, heat treatment was used to remove heavy oil and asphalt, reducing the overall hydrophobicity of the ER and increasing the difference between unreacted coal with hydrophobicity and hydrophilic silicate minerals and catalysts(Fe_7S_8). After heat treatment to remove heavy oil and asphalt, the remaining silicate minerals and catalysts remain hydrophilic and remain in the pores and surface of unreacted coal. Therefore, ultrasonic treatment was used to remove these hydrophilic substances, exposing the hydrophobic surface of unreacted coal. At this time, the hydrophobicity of the ER increases, and the difference between coal and hydrophilic impurities increases, which is beneficial for flotation. Flotation tests were conducted on the EER before and after treatment. The results shows that it is difficult to perform flotation on the original sample of the ER. The ER after calcination at 260 ℃ for 1 hour in a muffle furnace can be subjected to flotation. On the basis of heat treatment, ultrasonic treatment was carried out. With the increase of ultrasonic treatment time, the clean coal yield shows an upward trend and the ash content shows a downward trend. The flotation clean coal yield and ash content of the ER treated with ultrasound for 10 minutes are 58.20% and 23.63%, respectively. Compared with the ER treated only with heat, the flotation clean coal yield increases by 17.80% and the ash content decreases by 2.88%. Both heat treatment and ultrasonic treatment have a promoting effect on flotation. Scanning electron microscopy and DSA100 contact angle analyzer were used to detect and analyze the surface characteristics of the ER before and after ultrasonic treatment. Through scanning electron microscopy, it is observed that there are a large number of impurities adhered to the surface of the ER. As the ultrasonic treatment time increases, the surface impurities gradually decreases, the contact angle gradually increases, and the hydrophobicity increases. Scanning electron microscopy and contact angle analysis both support the flotation results.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 573K] - YANG Zhe;HUANG Gen;ZHAO Yujia;WANG Luyang;SUN Xiaoli;LIAO Yinfei;CUI Xiaoke;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;National Engineering Research Center of Coal Preparation and Purification,China University of Mining and Technology;
Efficient separation of residual carbon and minerals in the gasification fine slag is the premise of its high-value utilization, but the poor floatability of the gasification fine slag has become one of the major issues on its flotation separation. In this paper, the flotation effect and mechanism of the oil collector, dodecane, were studied by using the gasification fine slag from the opposed multi-burner(OMB) coal-water slurry gasifier. Measurements including X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FITR) were applied. It is found that the aromatic structure and side chains on the surface of the gasification fine slag are in poor content compared to coal samples, and the existence of rich oxygen-containing groups is found. The pore structures of the gasification fine slag are characterized by low-temperature nitrogen adsorption and mercury intrusion porosimetry measurements. The specific surface area of the sample is 62.03 m~2/g, and the pores are widely distributed on nano to micron scale. The liquid-powder wetting measurement and modified Lucas-Washburn equation are applied and wetting processes of gasification fine slag powder by water and dodecane are characterized. It is found that the residual carbon of gasification fine slag is more easily wetted by dodecane than that of water, while the minerals of tailings in gasification fine slag are more easily wetted by water. However, the water wettability of residual carbon and tailings are not in much difference. The adsorption behavior of oil collector in pores is justified by the T_2 inversion spectrum of low-field H~1 NMR. The adsorption behavior of the oil collector in pores increases with the increase of oil dosage and the decrease of oil droplet size. In fine gasification slag flotation, the oil collector is trapped in the pores in large quantities, which makes it difficult to adsorb on the surface of residue carbon, resulting in poor flotation indexes.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1285K] - SUN Fengshuai;DAI Shiqi;WANG Lei;XING Yaowen;GUI Xiahui;State key Laboratory of Coking Coal Resources Green Exploitation,China University of Mining and Technology;Chinese National Engineering Research Center of Coal Preparation and Purification,China University of Mining and Technology;School of Chemical Engineering and Technology,China University of Mining and Technology;
Lithium, gallium and other strategic key metals are endowed in the coal gangue in some mining areas of Shanxi and Inner Mongolia, and the enrichment of lithium and gallium elements has gradually become a research hotspot. However, the content of lithium and gallium in coal gangue is very low, and direct leaching needs to consume a lot of chemicals, so it is still a big challenge to enrich lithium and gallium efficiently and economically. In order to improve the enrichment efficiency of lithium and gallium in the coal gangue, research was carried out on the state of lithium and gallium in the coal gangue in Shuozhou, Shanxi Province, and the pre-enrichment method. Using step-by-step chemical extraction method, mineral phase composition, mineral dissociation analysis, inductively coupled plasma mass spectrometry, scanning electron microscopy and energy dispersive spectroscopy, the Li and Ga elements in the coal gangue were studied, and the feasibility of the pre-enrichment of Li and Ga in the coal gangue by removing pyrite was investigated by using high-gradient magnetic separation. The results show that the gangue is mainly composed of kaolin, pyrite, quartz, calcite, mica and other minerals, and the elements of lithium and gallium are mainly in silicate minerals, with less pyrite content. The lithium content in the original ore is 146.37 μg/g, and gallium content is 25.04 μg/g. Lithium and gallium elements can be pre-enriched in the gangue through pyrite threw off by magnetic separation. In 1 000 mT, pre-enrichment effect is the best, and the lithium in the magnetically selected tailings is 210.63 μg/g which is 1.45 times of lithium content, the lithium recovery rate is 88.00%. Gallium recovery rate is 31.88 μg/g which is higher than the gallium element in the original ore, and gallium recovery rate is 80.07%.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1570K] - LIANG Dingcheng;YANG Lulu;XIE Qiang;XIE Zhucan;DENG Qingwen;GUO Binshuo;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
One of the primary sources of carbon emissions is CO_2, which may be separated from flue gas in power plants using zeolite membranes with different pore sizes. This technique is crucial for achieving carbon neutralization and lowering carbon emissions. The connection between the zeolite and the carrier is not strong when zeolite membranes are used to segregate flue gas in high-temperature and high-pressure gas conditions. It can easily cause the membrane layer to rupture or peel off the carrier during the flue gas separation, making large-scale zeolite membrane separation difficult. The binding modes between zeolites and carriers and the characteristics of the binding force were reviewed, and the methods for quantitatively characterizing the binding force were summarized. The results show that the all-silica Decadodecasil 3R(DD3R) zeolite, which has pore diameters between CO_2/N_2 molecules, may form strong covalent solid connections with the ceramic carrier that has been treated with acid, producing a zeolite membrane that is tightly attached. Even in the presence of steam, the membrane efficiently separates CO_2/N_2 from flue gas. Traditional experimental methods(such as ultrasonication, scratching, and indentation) cannot provide detailed data when examining the bonding at the interface between the carrier, zeolite, and modifier. However, molecular simulation can compensate for these shortcomings by simulating and quantifying the bonding at the material′s interface at the atomic scale, offering a robust theoretical foundation for selecting the best carrier modification technique.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 316K] - ZHOU Wei;ZHAO Shixi;XIE Xinyu;LU Shijian;NI Zhonghai;YANG Feifei;School of Chemical Engineering and Technology,China University of Mining and Technology;China Nuclear Power Engineering Co.,Ltd.;
Catalytic hydrogenation of CO_2 to valuable chemicals is one of the key technologies to relieve global warming and promote the sustainable development of human society. Two-dimensional MoS_2 materials have emerged as promising catalysts for CO_2 activation and conversion due to their unique layered structure and adjustable S vacancies sites, which is the key active center for CO_2 hydrogenation. In order to develop an efficient process for S vacancy creation, building S vacancies on MoS_2 nanosheet were used as the basis for introducing S vacancies on the surface using H_2O_2 etching method, and the reaction properties of CO_2 at atmosphere and high pressure before and after H_2O_2 etching were compared. The results show that H_2O_2 etching can significantly enhance the content of S vacancies without changing the crystal structure of MoS_2 or affecting the chemical properties of S vacancy sites, which significantly enhances the conversion rate of CO_2 catalytic hydrogenation without affecting the product distribution. Specifically, the S vacancies catalyze CO_2 dissociation to produce CO at atmosphere pressure with selectivity higher than 96%, whereas they are able to catalyze the hydrogenation of CO_2 to the methanol at high pressure of 5 MPa and 180 ℃ with high selectivity(79%). Increasing the reaction temperature improves the CO_2 conversion, but the selectivity of methanol will be signifi-cantly reduced, accompanied by the generation of methane. Briefly, this work demonstrates a simple and effective method to create S vacancies on MoS_2, providing theoretical and technical support for the industrial application of MoS_2 catalysts.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 780K] - ZHAO Minnan;ZHANG Jiayin;ZHANG Xinmiao;XU Heng;LUAN Jinyi;LU Dingxiang;ZHAO Pengyu;CHEN Xiangze;WU Zhenkang;School of Chemical and Environmental Engineering,China University of Mining & Technology-Beijing;Sinopec(Beijing) Research Institute of Chemical Industry Co.,Ltd.;
It is expected that integrated carbon capture and conversion(iCCC) will reduce the overall cost of carbon capture & conversion by leveraging the CO_2 conversion process to simultaneously regenerate CO_2-rich solutions. To assess the feasibility of coupling biomethanation and carbon capture, the absorption performance of a slightly alkaline absorbent(pH=10) prepared with 4.2 g/L NaHCO_3, 6 g/L Na_2CO_3 and a microbial nutrient solution for CO_2 in simulated flue gas in a packed column was investigated. Second, the CO_2-rich solution was subjected to a five-cycle regeneration experiment using the biomethanation process in anaerobic bottles. The results show that in the flow-through mode, when the gas flow rate of packed column is ≤1.0 L/min, with the increase of liquid flow rate, CO_2 removal rates of all experimental groups gradually increase and can be stabilized above 80%, and the liquid flow rate of this packed column is suitable to be ≤ 0.9 L/min. Overall volumetric mass transfer coefficients of the packed column at different gas flow rates(0.4-1.2 L/min) are generally stable between 17-19 mol/(h·kPa·m~3). As a result of CO_2 absorption, NaHCO_3 in the absorption solution increases and Na_2CO_3 decreases, with a ratio between 1.2 and 1.9. Under the condition that the CO_2 removal rate is greater than 80%, the slightly alkaline absorbent can be recycled 6 times at a gas flow rate of 0.6 L/min and liquid flow rate of 0.7 L/min. The utilization rate of the active component CO_3~(2-) reaches 89.5%, and the total inorganic carbon(TIC) of the formed CO_2-rich solution is 0.127 mol/L at a pH of 8.82, creating an environment conducive to the growth of biomethanation microorganisms. The results of the cyclic experiments on the bio-regeneration of the CO_2-rich solution reveal that the absorbed CO_2 of the absorbent is basically stable in the range of 69.6-78.6 mmol/L after each regeneration and the CH_4 production is reproducible during the regeneration process. As a result of the regeneration experiment, alkali-resistant bacteria at the phylum level, such as Firmicutes and Actinobacteriota, are somewhat enriched. Approximately 99% of archaeal genera are dominated by hydrogenotrophic methanogens before and after regeneration, but the slightly alkaline environment during regeneration results in a 19.5% decrease in the relative abundance of Methanobrevibacter and a 18.7% increase in the relative abundance of unclassified＿ f＿Methanobacteriaceae, respectively. In conclusion, the above experimental results indicate the feasibility of biomethanation combined with carbon capture.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 866K] - ZHANG Chunhui;ZHANG Zhao;CHEN Leyi;LI Weixian;Institute of Whole Process Pollution Control and Circular Economy,China University of Mining and Technology-Beijing;Hebei Leache Chemistry Co.,Ltd.;
Coal will still be an important part of the China′s energy structure in the future. The acid coal mine drainage(ACMD)containing high concentrations of sulfates produced during the coal mining process is the key to restricting its realization of high-quality, green and sustainable development. ACMD is an important industrial pollution source of SO_4~(2-), primarily generated by the oxidation of sulfur containing ores after exposure. The formation mechanism and hazards of ACMD were reviewed and the technologies that could be used for source prevention and subsequent treatment were analyzed. Adhering to the principle of "prevention is better than cure", the comprehensive analysis was conducted on the technical characteristics of preventing sulfate production such as biocides, oxygen isolation and surface passivation. Many technologies are currently used in the subsequent treatment stage, including active remediation technologies such as chemical precipitation, adsorption, ion exchange and membrane technology, and passive remediation technologies based on biological treatment and constructed wetlands. Active remediation technology has problems such as the risk of secondary pollution and higher costs, while the widespread application of passive remediation technology is restricted due to the processing time and system stability. Due to the considerable market of sulfuric acid in the chemical and metallurgical industries, recycling sulfuric acid from ACMD is a good resource prospect. Current potential technologies for recovering sulfuric acid from ACMD include distillation, diffusion dialysis, electrodialysis, solvent extraction and crystallization. The technical and economic feasibility of each process for application in ACMD was evaluated. Finally, the future development prospects of sulfate prevention and resource recovery technologies in ACMD were emphasized, including conducting in-depth research on prevention technologies, reducing treatment costs, and developing new and stable treatment and recovery processes, providing new control strategies and broader research ideas for pollution control and waste recycling in the coal industry.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 504K] - JIA Jianli;GAO Xiaolong;ZHANG Ben;ZHAO Shenwei;HAN Yuxin;YUAN Haokun;WANG Yequan;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
In view of the prominent problems of chromium(Cr), arsenic(As) heavy(class) metals and polycyclic aromatic hydrocarbons(PAHs) such as phenanthrene(Phe) and Benzo[a]pyrene(BaP) in soils such as coking plants, and the lack of green and low-carbon remediation technologies, rye grass-maize-Rhodococcus aetherivorans(BW2) was utilized for plant-microbe co-remediation. The results show that Cr, As, Phe, and BaP concentrations in the soil of the combined remediation group decrease by 9.63%, 5.28%, 45.14%, and 26.87%, where the removal of heavy metals is largely dependent on plants, the removal of PAHs is largely dependent on microorganisms and their interactions with plants. Plants mainly absorb extractable heavy metals, and the exchangeable Cr in soil of different restoration groups decreases by 2.19% on average after 63 d, while the exchangeable As increases during the restoration process due to degradation. The exchangeable Cr and carbonate-bound Cr are strongly positively correlated with actinomycetes in soil, while the two As forms are positively correlated with Bacteroidetes, Armatimonadetes, FBP and Planctomycetes. There is an obvious interaction between pollutant removal efficiency, and it is also affected by the dynamic abundance of enzyme activities and different functional microorganisms. In turn, soil microbial community structure and function also change under the comprehensive effect of soil pollutant types, concentrations and physical and chemical properties.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1767K] - ZHANG Liping;YAO Ruihan;ZHAO Xiaoxi;LEI Wenbo;LI Huitong;ZHAN Yongqi;SUN Huaran;GAO Yiqing;School of Chemical & Environmental Engineering,China University of Mining & Technology-Beijing;
In China, the wastewater produced by electronics, photovoltaic, inorganic fluorine chemical industry, coal mining, coal-based chemical industry generally has the problem of exceeding fluoride. As a new method of wastewater fluoride removal, there are problems such as large dosage and sludge production. Preparation conditions of the defluoridation agent were designed and optimized by response surface BBD method, and the defluoridation performance was compared with that of common coagulants. Scanning electron microscopy(SEM) and X-ray powder diffraction(XRD) were used to characterize and analyze the defluorination agents at different preparation stages. The mechanism of defluorination was explored in combination with the residual element level and the utilization rate of each element in the supernatant after treatment. The results show that the optimal preparation conditions for defluorination agents are n(M)/n(Si)(M refers to the total amount of metal) is 44.91, n(Al)/n(Mg) is 40.64, and n(Al)/n(Fe) is 34.92. Under these conditions, when the dosage of defluorination agents prepared is 1.35 g/L, the fluoride concentration can be reduced from 20 mg/L to 0.71 mg/L, which is below the limit of 1.0 mg/L of GB 3838—2022 Water Environmental Quality Standard Class Ⅲ standard of Surface. The fluoride removal rate reaches 96.45%, and the correlation coefficient R~2 of the model established by response surface method is 0.969 0. For the fluorine-containing water samples with initial fluorine concentration of 10-200 mg/L, the fluoride removal agent is added proportioned, and the residual fluorine concentration in the supernatant is all less than 1.0 mg/L. The order of defluorination performance with common coagulants is: defluorination agent >PAC>PAFC>PFS. SEM and XRD analysis show that the morphology and structure of the occuridation agents are changed, and a variety of polyhydroxyl polymers are formed through reactive polymerization. The ion exchange occur between these polyhydroxyl polymers and fluoride ions, thus the fluoride ions are removed. Based on the analysis of the residual elements in the supernatant and the concentration of metal elements in the defluorination reagent, the element utilization rates of aluminum, silicon, iron and magnesium are 99.98%, 97.16%, 92.22% and 18.39%, respectively. The defluorination reagent is effective and suitable for many kinds of industrial wastewater containing fluorine.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 1201K] - WANG Qibao;AO Lixin;ZHANG Kai;YANG Kang;TANG Yuwei;TAN Xuying;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;
Spontaneous combustion phenomenon of coal gangue as an associated product of coal is frequent in the process of long-term stockpiling, which directly or indirectly produces ecological pollution, water pollution, geological disasters and many other problems, resulting in huge economic losses and human casualties. Coal gangue is a complex physical and chemical reaction process that is influenced by many factors, including its own properties, self ignition conditions, and external environment, from the initial stage of accumulation to the combustion state. In order to improve the prevention and control of spontaneous combustion of gangue in mining areas, the research status of the spontaneous combustion theory of coal gangue was analyzed. The research progress of scholars at home and abroad on the mechanism of spontaneous combustion of coal gangue and governance methods at this stage was systematically summarized. The main key influencing factors and process mechanisms that trigger spontaneous combustion were presented focusing on three necessary factors affecting the spontaneous combustion of gangue, combustibles, oxygen, and temperature. A more comprehensive introduction was given to the main methods of prevention and control of spontaneous combustion in existing gangue mountains. The advantages and disadvantages of self ignition fire extinguishing methods of various conventional coal gangue and treatment technologies were compared and analyzed. The limitations of the effectiveness of conventional techniques for treatment were pointed out. The land remediation and ecological restoration are disposed of in response to coal gangue replacing sand and stone materials for backfilling areas such as open pits and coal mining subsidence areas. It is proposed to identify the control targets for spontaneous combustion management in the prevention and treatment process, enhancement of specific properties of fire protection materials, intelligent equipment to improve the accuracy of identification of fine monitoring, and the use of a variety of monitoring and early warning technology synergistic spontaneous combustion prevention and control materials. The future development of coal gangue spontaneous combustion prevention and control technology, the research direction of mining fireproofing materials were proposed, providing reference and theoretical support for the subsequent research on the mechanism of spontaneous combustion of coal gangue and the application of spontaneous combustion control engineering.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 799K] - ZHANG Wei;WEI Jialu;JOSé Antonio Alonso;SUN Chunwen;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;Instituto de Ciencia de los Materiales de Madrid,CSIC;
With the growing demand for green energy and environmentally friendly society, there is an urgent need to accelerate the development of advanced energy conversion devices or systems, and fuel cells are considered future efficient power generationen systems. Among different types of fuel cells, solid oxide fuel cells(SOFCs)are a kind of clean power generation devices with broad prospects due to their unique multi-fuel operation capability and high energy conversion efficiency. However, due to incomplete oxidation of the hydrocarbon fuels, the traditional nickel-cermet anodes used in SOFCs operating under hydrocarbon fuels results in carbon deposition on the anode, leading to a decrease in the cell performance. In this review, the carbon deposition mechanism and strategies to solve carburization in anode of hydrocarbon-fueled SOFC were discussed, mainly focusing on the widely studied various types and the research progress of bimetallic-cermet materials with mixed ion-electron conductors. The carbon resistance mechanism of bimetallic-cermet materials were summarized, mainly manifest in reducing the carbon deposition rate on the anode surface and accelerating the removal of carbon deposition. The principle of in situ exsolution of nanoparticles in perovskite materials under reducing atmosphere were introduced as well, the application of nanoparticles formed by in situ exsolution and metal oxide heterostructures formed with perovskite bodies in carbon-resistant anodes were discussed. In addition, the application of multilayer anodes and single-atom catalyst anodes in intermediate temperature SOFCs were explored. Driven by the tremendous progress of fuel cell technology, there has been a new interest in pursuing integrated coal gasification fuel cells(IGFCs)power generation systems that can be used as stationary power generation. This system is of great significance for achieving clean and efficient utilization of coal, and the key to this technology lies in the maturity of SOFCs. Finally, some future research directions in hydrocarbon-fueled SOFCs were proposed.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 2556K] - ZHANG Leiqi;LIN Qin;LIU Min;WU Qiliang;ZHANG Xuesong;ZHAO Bo;HU Liang;YANG Zhibin;State Grid Zhejiang Electric Power Company Research Institute;Research Center of Solid Oxide Fuel Cell,China University of Mining & Technology-Beijing;
Remaining useful life prediction is an effective solution to solve the problem of short life and high cost of PEMFC system. In this paper, the degradation mechanism of PEMFC system, including proton exchange membrane, catalytic layer, diffusion layer and other components, was reviewed. The factors influencing the aging of PEMFC system were summarized from intrinsic factors and external factors, especially improper operation in operation and management would accelerate the aging of PEMFC system. The commonly used degradation performance indexes to characterize the aging degree of PEMFC were summarized. The selection of degradation performance indexes is of great significance to the research of life prediction. The advantages, disadvantages and applicability of different indexes were introduced. Common faults and life prediction were introduced from three aspects: model-driven, data-driven and hybrid-driven. Model-driven and data-driven have their own advantages and disadvantages. Hybrid can combine their advantages and improve the precision and accuracy of prediction. Finally, the future direction of prediction research was prospected.
2024 01 v.30;No.161 [Abstract][OnlineView][HTML全文][Download 474K] 下载本期数据