- CHEN Lijuan;WANG Shihai;WEI Bo;LIU Xiaotian;LIU Kunpeng;WANG Jianjiang;LI Xian;CHENG Zening;School of Chemical Engineering and Technology,Xinjiang University;State Key Laboratory of Coal Combustion and Low Carbon Utilization,Huazhong University of Science and Technology;Zhundong Energy Research Institute,Xinjiang Yianchi Energy Co.,Ltd.;
Melting characteristics of different densities of Zhundong high-iron coal were studied and the uneven melting law of Zhundong high-iron coal was explored. The organic heavy liquid floatation sedimentation method was used to separate components of different densities from Zhundong high-iron coal. The mineral composition of each coal sample after low-temperature ashing, as well as the chemical composition and melting temperature of coal ash were measured. The ash structure, element distribution and mineral composition were also analyzed using XRD and SEM-EDS. The results show that Zhundong high-iron coal and its density components mainly distributes between 1.40-1.50 g/cm~3,accounting for 51.79%, and the occurrence forms of iron in coal are mainly pyrite and a small amount of siderite. The change of elements in the coal ash leads to the change of the density of the separated components. With the increase of the elemental content of Fe, the density of the coal sample components increases, and in the prepared coal ash. With the density component exceeding 1.50 g/cm~3, the elemental content of Fe reaches 67.50%. The ash composition of each density component varies greatly and Fe in the coal is one of the main factors affecting the melting point, which can significantly reduce the melting temperature of the overall coal ash. Combining XRD and SEM-EDS analysis of high-temperature ash samples, the increase of Gehlenite content in different density components is the reason for the increase of ash melting point. Fe and Mg are mainly enriched in block shaped ash particles with clear contours, while Si and Ca are mainly enriched in the melting zone, and the content of block shaped particles increases with increasing density. It is speculated that the minerals of block shaped ash particles are mainly magnesium iron oxides and Hematite, and the minerals in the melting zone are mainly Gehlenite. At 1 300 ℃, the melting zone of coal ash does not melt together with the massive particles, indicating that Fe in high iron coal mainly exists in foreign minerals in the coal. Sodium containing minerals will undergo low-temperature co melting reactions with Gehlenite, reducing the melting temperature of the melting zone.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 442K]
2024 06 v.30;No.166 [Abstract][OnlineView][Download 1089K] - MA Daoyang;LI Rui;ZHANG Lan;JIAN Yongxin;WANG Yibin;CUI Weidong;TAN Houzhang;WANG Xuebin;School of Energy and Engineering,Xi′an Jiaotong University;The Boiler & Pressure Vessel Safety Inspection Institute of Henan Province;School of Materials Science and Engineering,Xi′an Jiaotong University;
With the proposal of the national dual carbon strategy, power station boilers tend to develop towards high parameters. In order to investigate the chlorine corrosion that may exist during the combustion of typical high-chlorine coal in Xinjiang in high-parameter boilers and to investigate its protective measures, the chlorine corrosion resistance of Super 304, T92, C-HRA-5, TP347H, and 12Cr1MoV were compared and the effect of corrosive temperatures(600, 650, and 700 ℃) on the chlorine corrosion characteristics were investigated in the atmosphere of simulating burning high-chlorine coal in high-parameter boilers. The chlorine corrosion resistance of Inconel 625 coatings with different yttrium oxide contents(0%, 0.2%, 0.4%, 0.6% and 0.8%) were also studied. The results show that the corrosion temperature has a great influence on the chlorine corrosion resistance of the material, and when the temperature is higher than 700 ℃, some of the materials will have great deformation, and Super 304, T92, C-HRA-5, TP347H and 12Cr1MoV are unable to meet the actual production use. At 650 ℃, C-HRA-5 and TP347H perform better with fitted corrosion weight gain curves of y~2=312.371x,R~2=0.96 and y=1.927x,R~2=0.94. Inconel 625 coating significantly improves the 12Cr1MoV substrate resistance to chloride corrosion. With the increase of yttrium oxide content in the coating, the anti-chlorine corrosion effect shows a trend of first increase and then decrease, adding 0.4% yttrium oxide has the best effect.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 984K] - YALKUNJANG Tursun;GAO Zhiwei;DAI Zhenghua;ZHONG Mei;JIN Lijun;LI Jian;LIU Yang;WEI Bo;State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources,School of Chemical Engineering and Technology,Xinjiang University;Xinjiang Key Laboratory of Coal Clean Conversion & Chemical Engineering,School of Chemical Engineering and Technology,Xinjiang University;School of Chemical Engineering,Dalian University of Technology;
Chemical looping combustion is recognized as an efficient technology for low-carbon emissions, offering distinct advantages in enhancing fuel utilization and decreasing CO_2 emissions. In this study, Fe_2O_3/Al_2O_3 oxygen carrier was employed in a two-stage fixed-bed reactor to conduct direct and staged chemical looping combustion experiments of Zhundong coal. The physicochemical properties of the fresh and spent oxygen carrier has been investigated. Results indicate that the carbon conversion and CO_2 selectivity of the chemical looping combustion of Zhundong coal pyrolysis volatiles increase with increasing temperature and OC/C ratio. The enhanced OC/C ratio and temperature contribute to an improves carbon conversion during the chemical looping combustion of Zhundong coal char, but with a decrease in CO_2 selectivity. Compared to direct chemical looping combustion of coal, staged chemical looping combustion significantly improves the CO_2 selectivity and slightly reduced the carbon conversion under the same condition. At a reaction temperature of 800 ℃, the CO_2 selectivity of staged chemical looping combustion reaches to 89.51%, representing a 29.18% increase compared to direct chemical looping combustion. At a reaction temperature of 950 ℃, the carbon conversion of staged chemical looping combustion is 60.40%, which is 6.78% lower than that of direct chemical looping combustion. The reduction of degree the oxygen carrier with char is higher than with coal pyrolysis volatiles, suggesting that the reaction between char and the oxygen carrier is one of the limiting factors in the chemical looping combustion of coal. This study provides a crucial theoretical foundation and technical support for achieving low-carbon clean combustion of Zhundong coal.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 1167K] - WU Qiwei;HU Shihao;LIU Jingwen;ZHANG Yize;LI Hui;ZHOU Hao;State Key Laboratory of Clean Energy Utilization,Zhejiang University;
The clean and efficient conversion and resource utilization of high-alkali coal have significant strategic importance for achieving the "dual carbon" targets. Liquid slag boilers have considerable advantages in burning high-alkali coal, but there is still a lack of research on the ash deposition and elemental migration characteristics of coal that is entirely burned with high alkali. This study investigated the ash deposition and slagging characteristics and the elemental migration patterns of Zhundong coal during combustion in a 20 MW horizontal liquid slag boiler. Ash deposition probes 1 and 2 were set up before and after the slag trap to study the effect of ash deposition on the heat transfer surface on thermal efficiency. The results indicate that during the initial layer formation stage, the heat flux density across the probe surface rapidly decreases, and as the deposit grew, the heat flux density gradually decreases, and when the deposit growth becomes stable, the heat flux density will fluctuate within a certain range. The formation process of ash deposition can be divided into three stages according to the rate of change of heat flux density on the probe surface: a rapid decline phase, a slow decline phase, and a stable phase. The final stable relative heat flux densities of probes 1 and 2 are 0.75 and 0.83, respectively. In addition, by analyzing the appearance, mineral composition, and chemical composition of the ash and deposits at different positions in the furnace, the impact of elemental migration on ash deposition and slagging was explored. The micro-characterization of ash deposition shows that oxides such as Al_2O_3, Fe_2O_3, and SiO_2 are enriched in the high-temperature slag samples, while CaO, MgO, Na_2O, and SO_3 are mainly found in the deposits of the low-temperature area. The formation of the initial layer on the heat transfer surface is closely related to the condensation of alkali metals and their sulfates, with the average mass fractions of Na_2O in the high-and low-temperature area samples being 1.38% and 4.70%, respectively. The iron element is enriched in the slag and acts as a flux, forming a low-temperature eutectic with the silicon-calcium-magnesium-aluminum system, which leads to a reduction in the ash melting temperature.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 732K] - GUO Huina;WU Yuxin;FENG Lele;LIU Jie;Department of Energy and Power Engineering,Tsinghua University;School of Safety Engineering,China University of Mining and Technology;
Biomass co-firing in coal-fired power plants represents a viable technology for efficient and low-cost CO_2 reduction. The high energy consumption for crushing biomass fuel results in relatively large particle sizes entering the furnace. The burnout of these large particles in the high-temperature turbulent environment within the furnace is a matter of concern. A four-fan opposed high-temperature turbulent experimental apparatus was employed to create a nearly homogeneous and isotropic turbulent flow field. Woody biomass particles of two sizes(d_(p, 0) = 2.5 and 6.0 mm) were used as the research subjects, the effect of turbulent fluctuation velocity u_(rms) on the combustion characteristics of millimeter-sized biomass particles were examined by varying the furnace temperature(T_(gas) = 500, 700, 900 ℃) and turbulent fluctuation velocity(u_(rms)=0-1.8 m/s). The particle temperature using a particle surface-center temperature measurement system was used and the entire combustion process using a color image capture system was captured. The biomass particle′s combustion time, ignition mode, flame shape, and particle size change under different conditions could be determined. The results indicate that biomass particles tend to undergo homogeneous ignition, with the mode of ignition shifting to heterogeneous only at T_(gas)=500 ℃ when u_(rms) increases. The particle heating rate before ignition rises by nearly 30%, and the particle surface temperature during the volatile combustion stage increases by approximately 300 ℃, when u_(rms) increases to 1.8 m/s. The increase in u_(rms) causes the volatile flame front to wrinkle and deform, intensifying homogeneous combustion and slightly shortening the volatile combustion time. The porosity development of biomass char becomes more rapid, allowing a large amount of oxygen diffuse into the particles and react with carbon matrix, significantly shortening the char burnout time by over 40% and increasing the char combustion temperature. The larger the particle turbulent Reynolds number, the more significant the impact of turbulent fluctuation. Raising the furnace temperature weakens the effect of increasing u_(rms) on particle temperature but strengthens its effect on shortening the combustion time.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 1489K] - LU Hao;BAI Jin;KONG Lingxue;GUO Zhenxing;LI Huaizhu;LI Wen;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences;University of Chinese Academy of Sciences;
Gasification is one of the important technologies to realize the transformation of coal from fuel to raw material and to promote the clean and efficient utilization of coal. Entrained-flow gasification is currently the predominate gasification technology, and the stable operation of gasifiers requires that the liquid slag must have good fluidity. The crystallization behavior of the slag can lead to decreased flowability, resulting in abnormal shutdown of the gasifier, which is a major cause of abnormal shutdowns of gasifiers. The main crystallization characteristics were summarized and discussed that affected the fluidity of slag and the key to studying crystallization behavior: crystallization kinetics. Firstly, the methods of judging the crystallization mechanism based on crystallization behavior and selecting appropriate crystallization kinetics models were summarized. The principles and characteristics of different crystallization detection methods were compared to obtain more accurate crystallization behavior data by selecting the appropriate crystallization behavior detection method according to the research focus, facility characteristics and slag properties. Finally, the effects of chemical composition and operating conditions on crystallization behavior were summarized. Significant differences in the crystallization mechanisms between different crystals cause that the same chemical composition has different effects on the crystallization behavior of different crystals. When the chemical composition of the designated slag is within a specific phase region, the influence of chemical composition and operating conditions on crystallization behavior of the primary phase mineral becomes more regular, and the conclusions obtained can provide more accurate guidance for the regulation of crystallization behavior. Combining research results with phase diagrams or establishing simple and accessible predictive models can better guide the control of slag crystallization behavior. Currently, the study of crystallization behavior mainly relies on experimental methods. Future research could integrate phase-field simulation and molecular dynamics simulation, among other methods, to further explore the mechanisms of crystallization and examine the effects of factors such as temperature fields and flow fields within gasifiers on crystallization characteristics.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 2410K] - LIU Xiaotian;WANG Shan;WEN Rongrong;XU Yanfeng;GAO Haoyang;WEI Bo;Key Laboratory of Coal Clean Conversion & Chemical Engineering Process, School of Chemical Engineering and Technology,Xinjiang University;
The Zhundong Heishan mining area, particularly the Jiangjunmiao No.2 mine, is abundant in high iron coal reserves, a source of high-quality power coal. The impact of primary associated minerals in coal on the performance of coal water slurry was focused on, using these coal samples. The samples, varying by mineral content, type, and distribution rule, were divided into different density grades via the coal flotation and sedimentation separation method, facilitating an evaluation of their influence on slurryability. Energy dispersive spectrometer(EDS), X-ray diffraction(XRD), and X-ray fluorescence(XRF) were utilized to pinpoint the elemental content and mineral composition in the samples. Correlations between different mineral element content and pulping performance were calculated using SPSS software. It was observed that the density of Zhundong high iron coal primarily concentrated in the 1.40-1.50 g/cm~3 range, representing 55.88% of the total. Coal samples exceeding 1.50 g/cm~3 in density accountes for roughly 4.88%.Pyrite, ferric sulfate, kaolin, and quartz content increased proportionally to the coal sample density. Coal samples exceeding 1.50 g/cm~3 in density contained high levels of associated minerals, with Al, Si, S, and Fe reaching their peak. In this case, the Fe mass fraction increases from below 0.5% to 5.97%. Coal water slurry samples displayes a decrease in viscosity and stability as coal sample density increases. The coal water slurry viscosity generated by the ZD1 coal sample, with less than 1.40 g/cm~3 density, stand at 960 mPa·s, with a water precipitation rate of 1.37%. Meanwhile, the slurry sample generated by coal samples exceeding 1.50 g/cm~3 in density is too thin, reducing slurry viscosity to 320 mPa·s and elevating the water precipitation rate to 9.09%. The correlation analysis reveales that the associated Na, Mg, and Ca elements in coal are relatively evenly distributed across coal samples at all density grades, and showes no clear correlation with the slurry forming performance. Conversely, the contents of Al, Si, S, and Fe elements are significantly and extremely significantly negatively correlated with the slurry viscosity and stability, respectively. In other words, the higher the pyrite, ferric sulfate, kaolin, and quartz mass fractions are, the more pronounced the downward trend in the viscosity and stability of the coal water slurry are.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 525K] - REN Yuan;MO Wenlong;MA Yaya;GUO Jia;WEI Xianyong;AKRAM Naeem;State Key Laboratory of Corbon Based Energy Resource Chemistry and Utilization,College of Chemical Engineering,Xinjiang University;Xinjiang Key Laboratory of Clean Coal Transformation and Chemical Process,College of Chemical Engineering,Xinjiang University;Xinjiang Energy Co.,Ltd.;Key Laboratory of Coal Processing and High Efficiency Utilization,Ministry of Education,China University of Mining and Technology;School of Chemical Engineer
Taking Balochistan lignite(BL) in Pakistan as the research object, the chemical formula of BL is C_(167)H_(130)O_(53)N_2S according to element analysis. The existing forms of oxygen, nitrogen and sulfur in BL organic structure were analyzed by X-ray photoelectron spectroscopy(XPS). The characteristics of the main functional groups in the organic structure of BL were studied by Fourier transform infrared spectroscopy(FT-IR). The main functional groups in the aliphatic structure of BL are —CH and —CH_2. The main substituted forms of benzene ring in BL are trisubstituted and tetra substituted. The carbon skeleton structure of BL organic structure was explored by ~(13)C-NMR. In the molecular structure of BL, the ratio of aromatic bridge carbon to pericarbon X_(BP) is 0.21, and the carbon is mainly composed of aromatic carbon and fatty carbon, of which the mass fraction of fatty carbon is 53.23%, and the proportion of aromatic carbon is 41.93%. The aromatic structure is mainly benzene ring and naphthalene ring, oxygen is mainly in the form of carboxyl, carbonyl, ether oxygen and phenolic hydroxyl, while nitrogen is mainly in the form of pyrrole nitrogen, and sulfur is mainly thiophene. A two-dimensional molecular structure model of BL was established. The three-dimensional structure of BL molecular model was constructed by hydrogenation saturation through materials studio, and the molecular model was further optimized. The space effect is significant, and the BL three-dimensional structure model with the lowest energy is obtained. It is found that van der Waals energy is the key factor for the stability of BL molecular structure. The calculated ~(13)C-NMR spectra of BL model structure are basically consistent with the experimental spectra, which verifies the rationality of the BL structure model.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 808K] - HU Mengqi;LUO Jie;LIU Yang;ZHONG Mei;DAI Zhenghua;JIN Lijun;YALKUNJANG Tursun;LI Jian;State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources,School of Chemical Engineering and Technology,Xinjiang University;Xinjiang Key Laboratory of Coal Clean Conversion & Chemical Engineering,Xinjiang University;State Key Laboratory of Fine Chemicals,Institute of Coal Chemical Engineering,School of Chemical Engineering,Dalian University of Technology;
In the co-pyrolysis process of coal and biomass, the mixing mode significantly affects the interaction between volatile components, which in turn affects the distribution of products. In this study, the co-pyrolysis products distribution, composition, and properties of Naomaohu coal(NMH) and cotton stalks(CS) under four mixing modes, which is separated placement(Case 1), mechanical mixing(Case 2), coal in the upper layer of cotton stalks(Case 3), and coal in the lower layer of cotton stalks(Case 4). Combined with the fractal theory, the pore characteristics of co-pyrolysis char were studied, and the synergistic effect of co-pyrolysis was explored. The results show that the synergistic effect of NMH and CS varies with different mixing modes, and the mixing mode has a significant impact on the distribution and properties of co-pyrolysis products. In Case 4 method, the co-pyrolysis tar yield is the highest, 15.94%, which is 3.89% higher than the theoretical calculation value, and the positive synergistic effect is the most significant. At this point, the hydrogen rich components generated by CS pyrolysis interact with the volatiles of NMH pyrolysis in a timely manner, which result in a decrease in the yields of H_2, CH_4, and C_2-C_4 compared to the theoretical values, and an increase in the co-pyrolysis tar yield. Different mixing modes have a negative synergistic effect on the light oil in co-pyrolysis tar. The decrease in the oxygen-containing compounds may be due to the co-pyrolysis process promoting deoxygenation reactions(such as decarboxylation and decarboxylation), further generating fatty hydrocarbons, and reducing the occurrence of cross-linking reactions of oxygen-containing functional groups. During the co-pyrolysis process, ·H radicals and active oxygen-containing groups have a positive synergistic effect, promoting the transfer of O, N, and S atoms in tar to solid or gas products. From the fractal dimension of char, the fractal dimensions D_1 and D_2 of the char are between 2-3, indicating that the roughness and pore structure of the char meet the basic characteristics of the fractal structure. For Case 3 and Case 4 methods, the surface of the sample char located in the lower layer is rougher. The CS-C obtained by Case 3 method has smaller pores; while the pores of NMH-C obtained by Case 4 method are more uneven and the pore structure is more complex.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 846K] - LI Dongsheng;LU Zhishuai;GUO Yue;LYU Zhongbin;ZHANG Hong;ZHANG Yuhui;JIA Xin;XU Guangwen;Institute of Energy and Chemical Industry Technology,Shenyang University of Chemical Technology;
The kinetics of tar cracking is essential to an accurate pyrolysis model and reactor design. Previous studies have predominantly focused on the overall cracking behavior of tar. However, it is evident that the cracking behavior differs significantly between light and heavy tar fractions. In order to gain a more precise understanding of the cracking behavior at different temperatures and establish a secondary reaction model, the cracking behavior and reaction kinetics of two distinct tar fractions were investigated using a micro fluidized bed reaction analyzer(MFBRA) under Ar atmosphere conditions at 550,600,650,700 ℃. The results demonstrate that higher temperatures result in increased yields of cracking-formed gases. Specifically, light tar cracking primarily produces CO and CH_4, while heavy tar generates CO, CH_4, and H_2 as its main products. Moreover, heavy tar exhibits more readily occurring cracking with shorter reaction times compared to light tar. By employing an isothermal method in MFBRA analysis, it is found that the average activation energy for light oil cracking was 49.49 kJ/mol, which is higher than that for heavy oil cracking(33.47 kJ/mol). Furthermore, by comparing activation energies obtained from isothermal methods with mechanism models, suitable mechanism functions are identified: a chemical reaction(n=2) model for CO during heavy oil cracking, three-dimensional diffusion models(spherical symmetry) for CH_4 during both types of oil cracking, and a contraction geometry model(cylindrical symmetry) for H_2 specifically during heavy oil cracking but not present in light oil cracking scenarios. These results provide valuable insights into developing reasonable secondary reaction models for simulating selective oil cracking.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 758K] - LEI Ming;TIAN Xi;HONG Dikun;ZHANG Qian;ZHANG Lei;Department of Power Engineering,North China Electric Power University;Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology;
Oxy-combustion technology, as a promising CO_2 reduction method for coal-fired power plants, holds significant importance for achieving sustainable energy goals. Due to the physical properties and gasification reactions of CO_2 and H_2O, the coal conversion process in an oxy-fuel atmosphere may differ significantly from that in an air atmosphere. Through a review of existing literature, it is found that CO_2 impacted the release rate of volatiles and the physical structure and chemical properties of char during coal pyrolysis process. However, few researchers have focused on the role of the physical properties of the mixed gas of CO_2 and H_2O. During the combustion of coal or char, the high specific heat of CO_2 and its low oxygen diffusion rate have a noticeable inhibitory effect on the burning process. However, possibly due to differences in H_2O concentration, there is still debate over the mechanism by which the properties of mixed gases affected the combustion process, especially under pressurized conditions. Regarding gasification reactions, current studies indicate that single CO_2 gasification and CO_2/H_2O co-gasification increase the yield of volatiles during coal pyrolysis, but reduce the yield of char, and the gasification effect is enhanced at elevated pressure. Furthermore, the reactivity of char increase due to the large surface area from gasification, and its surface functional groups may also change. It is widely accepted that during the combustion of coal or char, CO_2 gasification can promote carbon consumption at high temperatures and low oxygen concentrations, and the addition of H_2O further accelerate this process. With rising environmental pressure, the proportion of carbon consumption attributed to CO_2 gasification gradually increase, but there is currently limited research on the effects of CO_2/H_2O co-gasification under pressurized conditions. The pyrolysis and combustion behaviors of coal under CO_2 and H_2O gasification in the oxy-fuel atmosphere were summarized which provided some theoretical reference for the future development of oxy-combustion technology.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 401K] - WANG Xinggang;JIAO Lixin;CAO Zhixiong;LI Bin;HAN Bo;HUANG Diefang;FU Yonghong;LI Xin;Exploration and Development Research Institution,China Petroleum Tuha Oilfield Branch;Institute of Geology,China Petroleum Logging Co.,Ltd.;College of Geology and Mining Engineering,Xinjiang University;
The gasification reaction efficiency of coal in the gasification channel is a key issue affecting the gas composition and calorific value of underground coal gasification. To reveal the effects of reaction temperature and pressure on the gasification behavior and product distribution characteristics of lignite in water vapor using the coal deposited in the Santanghu Basin, pyrolysis experiments were carried out using lignite collected from the Xishanyao Formation of the Santanghu Basin based on a fixed-bed pyrolysis furnace under different reaction temperatures and pressures. With the increase of reaction temperature(300-900 ℃), the gas mass fraction increased from 3.84% to 24.29%, and the mass fractions of water and tar increased first and then decreased. The volume of H_2 and CH_4 increased significantly with the increase of reaction temperature, with the maximum volume of 100.89 and 106.09 mL/g at 900 ℃, respectively. The total mass of pollutants decreases, and the mass is relatively small at 900 ℃, 17.72 mg/g. Increasing the reaction pressure(1.5-3.0 MPa) is beneficial to improve the conversion of semi-coke and increase the gas mass fraction. The increase of reaction pressure aggravates the secondary reaction, which is conducive to the occurrence of hydrogasification reaction and methanation reaction, resulting in a significant increase in the volume of CH_4. At 700 ℃, the volume of CH_4 increases by up to 26.89 mL/g. However at 700 ℃, the free radical hydrogenation saturation reaction is promoted, resulting in an increase in the total mass of pollutants. It is suggested that in the actual production, the reaction temperature and pressure should be increased by controlling the moving speed of steam injection, and the temperature of gasification reaction zone should be controlled away from 700 ℃,which is beneficial to the formation of H_2 and CH_4, so as to improve the efficiency and clean development of underground coal gasification process. The research results can provide guidance for the underground coal gasification process of lignite in Xishanyao Formation of the Santanghu Basin.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 1453K] - LIAO Mingyue;LEI Zhiping;JIA Tongxin;LI Yazhou;LI Zhanku;YAN Jingchong;SHUI Hengfu;YAN Honglei;REN Shibiao;WANG Zhicai;KANG Shigang;Anhui Province Key Laboratory of Coal Clean Conversion and High Value-added Utilization,School of Chemistry &Chemical Engineering,Anhui University of Technology;
Porous carbon materials with superior performance and low-cost have emerged as the preferred sulfur host materials in lithium-sulfur batteries, however, utilizing cheap raw materials to achieve large-scale preparation still faces great challenge. In this study, porous carbon materials were synthesized using abundant high sulfur coal as the feedstock and magnesium oxide and potassium hydroxide both as templates and activators. The study delved into the investigation of structure-activity relationship of these materials when employed as sulfur host materials in lithium sulfur batteries. It is observed that mesoporous(constituting 74%) are predominantly generated due to the templating action of MgO. KOH serves as an active agent primarily responsible for the formation of micropores(constituting 72%). The combined use of MgO and KOH leads to the creation of carbon material, PC_(MgO+KOH), characterized by large specific surface area(1 616 m~2/g),high pore volume(1.02 m~3/g),and rich pore structure(54% mesoporous and 46% microporous). The results of electrochemical performance test show that the S@PC_(MgO+KOH) has good rate performance and excellent cycle stability. After 500 cycles of charging ang discharging at 1 C, it can still retain 553.2 mAh/g, with a capacity retention rate of 65.5% and a decay rate of only 0.075% per cycle, demonstrating good rate performance and excellent cycling stability. The excellent electrochemical properties of PC_(MgO+KOH) can be attributed mainly to its low ohmic resistance and charge transfer resistance, rapid polysulfide redox reaction kinetics, and exceptional capability in binding lithium polysulfide. This study provides an alternative route for the preparation of low-cost and high-performance host materials for lithium-sulfur batteries.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 2290K] - YANG Hailong;WANG Lu;YAN Haijun;SI Jianxin;WU Ronglan;LI Xiaofei;WANG Jide;GUAN Qingqing;SUN Hui;LIANG Changhai;State Key Laboratory of Oil and Gas Fine Chemicals,Ministry of Education and Xinjiang Uyghur Autonomous Region,School of Chemical Engineering and Technology,Xinjiang University;State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources,Xinjiang University;Xinjiang Uygur Autonomous Region Product Quality Supervision and Inspection Institute;State Key Laboratory o
Developing of environmental friendly, high-efficiency, stable and low-cost non-mercury catalyst is the key to PVC production using coal-route-based acetylene hydrochlorination. To improve the current problems of low catalytic activity and poor stability of copper(Cu)-based catalysts applied in the acetylene hydrochlorination reactions, a series of Cu/Urea-CAC catalysts were prepared by urea modification strategies and the effects of the urea addition and Cu loading on the catalytic performances of catalysts for acetylene hydrochlorination were investigated. When the urea content is 15% and the Cu loading is 20%,the Cu/Urea-CAC catalyst reveal the optimal catalytic performance with the 92.6% C_2H_2 conversion and 98.2% vinyl chloride selectivity under the reaction conditions of 160 ℃,a C_2H_2 gas hourly space velocity of 120 h~(-1) and molar ratio of hydrogen chloride to acetylene is 1.25. Combination with the characterization results of XPS,XRD,SEM,N_2 adsorption and desorption, ICP-OES and TG techniques, it is suggested that the enhanced catalytic performance is mainly related to the appropriate urea addition, which can effectively inhibit Cu species reduction and loss, and decrease the carbon deposition, thereby improving the catalytic performance activity of Cu-supported on Xinjiang coal-based carbon catalysts for acetylene hydrochlorination. The results will expand the application of Xinjiang coal-based carbon and provide theoretical support for the design, synthesis and catalysis of a new catalytic system for acetylene hydrochlorination.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 884K] - CHEN Dong;WANG Hui;WANG Ming;WANG Dengyuan;WU Xuehua;School of Energy Science and Engineering,Harbin Institute of Technology;
Supercapacitors are high-performance energy storage devices with high power density, excellent cycling performance and high safety. However, their low energy density limits their development. In order to further improve the energy density of supercapacitors and meet the growing demand for energy storage, improving the electrochemical performance of electrode materials is the key. In order to improve the electrochemical performance of fly ash-based manganese silicate/manganese oxide, graphene oxide and fly ash-based manganese silicate/manganese oxide composites were synthesized by electrostatic assembly method, and their electrochemical performance was optimized by adjusting the amount of graphene oxide added. The mechanism of the effect of graphene oxide on the electrochemical performance of fly ash-based manganese silicate/manganese oxide was also studied. The morphology and structure of the materials were characterized by XRD, SEM, XPS and FTIR, and the properties of the materials and devices were tested by Cyclic Voltammetry, Galvanostatic Charge-Discharge and Electrochemical Impedance Spectroscopy. The results show that the charge transfer rate of FA@MS/MO/GO-2 is greatly improved after optimization, and FA@MS/MO/GO-2 has a specific capacitance of 737.4 F/g at a current density of 0.5 A/g, which is higher than that of FA@MS/MO not compounded with graphene oxide(293.4 F/g). FA@MS/MO/GO-2 has the best capacity retention rate(67%) when the current density increases from 0.5 A/g to 8.0 A/g, which is higher than that of FA@MS/MO(44%). After FA@MS/MO/GO-2 and commercial activated carbon are respectively assembled as positive and negative electrodes for asymmetric supercapacitors, the energy density of the device can reach 15.75 Wh/kg(power density is 375 W/kg), and the capacity retention rate and coulombic efficiency can reach 100% at 10 000 cycles at 5 A/g, which shows that the electrode material has the potential of long-term recycling and has a good practical application prospect.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 978K] - HU Yanlong;WANG Qiang;HU Dingkai;ZHANG Yingshuang;CHEN Yali;LU Shijian;School of Chemical Engineering,Xinjiang University;School of Chemical Engineering,China University of Mining and Technology;
To achieve the purpose of rapid screening of phase change absorbent, a new phase change absorbent-MDEA/polyethylene glycol dimethyl ether(NHD)/H_2O was quickly screened with N-methyl diethanolamine(MDEA) as the main absorbent, organic solvent as the phase separation accelerator and water as the solvent, guided by the theory of Hansen solubility parameter. The thermal stability of the phase change absorbent was tested by thermogravimetric analysis(TGA), and the CO_2 absorption and desorption performance of the phase change absorbent was investigated by CO_2 absorption and desorption experiments, as well as the recycling ability.~1HNMR was used to test the distribution of the substances before and after the phase change. The results show that MDEA/NHD/H_2O phase change absorbent has the highest thermal stability compared with 30% ethanolamine(MEA) absorbent and MDEA/n-butanol/H_2O phase change absorbent reported in the literature. NHD as a phase separation accelerator can promote the dissolution of CO_2 in the phase transition absorbent, MDEA/NHD/H_2O phase transition absorbent liquid-liquid phase separation requires the coexistence of NHD and H_2O. At the absorption temperature of 25 ℃, the MDEA/NHD/H_2O phase change absorbent with a mass ratio of 3∶5∶2 has the highest CO_2 absorption capacity of 1.069 5 mol/L. The phase change absorbent developed in this paper can reduce the volume of desorption liquid sent to the desorption unit to 42%. The CO_2 desorption efficiency reached 98.96% at a desorption temperature of 90 ℃. The total CO_2 cycling capacity of MDEA/NHD/H_2O phase change absorbent with a mass ratio of 3∶5∶2 was 9.260 4 mol/L after 10 cycles of absorption at 25 ℃ and thermal desorption at 90 ℃. Compared with 30% MEA absorbent, 30% MDEA absorbent and MDEA/n-butanol/H_2O phase change absorbent, it has the highest CO_2 cycling capacity. The ~1HNMR test results showed that the upper liquid phase of the phase change absorbent was mainly composed of NHD, which was a CO_2-lean phase. The lower liquid phase is mainly composed of MDEA and MDEAH~+, which is a CO_2-rich phase.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 1177K] - CEN Zhoutao;WANG Jingyu;ZHAO Dongqiang;LI Min;WU Yuxin;Department of Energy and Power Engineering,Tsinghua University;Yan′an Thermal Power Plant,Datang Shaanxi Power Generation Co.,Ltd.;
The particle rebound behaviors of particle-wall collisions have significant impacts on the particle motion and the separation efficiency in the gas-solid separation process. Previous studies have focused on the collision behavior of the spherical particles. However, in actual industrial processes, particles such as coal powder, biomass, and ore are all non-spherical particles. There are significant differences in the rebound behavior between the non-spherical particles colliding with the wall and the spherical particles. To explore the rebound behavior of the non-spherical particles colliding with the wall, an experimental device for particle-wall collisions was established. High-speed photography and image processing methods were used to obtain basic data of particle-wall collisions of the non-spherical particles. The influence of the key parameters such as particle material, sphericity, wall roughness, impact angle, and impact speed on particle-wall rebound behavior was analyzed. Based on the established four-parameter model of particle-wall collisions and neural network models, the rebound behavior between non-spherical particles and the wall was predicted. The results indicate that there is consistency in the rebound behavior of non-spherical particles colliding with the wall. Sphericity plays an important role in particle-wall collisions. The four-parameter model can predict collision results and random distribution characteristics well, while neural network models trained based on experimental data can achieve better prediction results.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 1034K] - LI Mingyang;BIE Yiran;HE Yong;WANG Bo;WANG Xiaoding;WANG Zhihua;State Key Laboratory of Clean Energy Utilization,Zhejiang University;Dongfang Electric Co., Ltd.;
The sulfuric acid decomposition reactor is an important equipment in the thermochemical sulfur iodine hydrogen production system, its heat transfer needs to match the hydrogen production capacity of the system. In order to study the effect of different structures of sulfuric acid decomposition reactors on heat transfer, and to ensure that the heat transfer of the reactor meets the system requirements while also meeting the limitations of manufacturing processes. Through experiment, the reaction kinetics parameters of sulfuric acid decomposition reaction were calibrated and a reaction kinetics model was established. The reactor was simulated by gPROMS to obtain parameters such as pressure, temperature, flow rate, and component concentrations within the reactor. Results show that the total conversion rate can not be improved by adjusting the length ratio of the preheating section and the reaction section or increasing the thermal conductivity of the packed particles, while the total length of the reactor remains unchanged. Increasing the length of the preheating section in the reactor can significantly increase the total conversion rate. The key reason is that the length of the preheating section determines whether the temperature inside the reactor can reach the optimal temperature of 850 ℃ required for the SO_3 decomposition reaction. Reducing the reactor diameter does not increase the total conversion rate, although reducing the diameter of the reactor is beneficial for heat transfer, due to the unchanged inlet flow rate, the fluid flow rate increases significantly, reducing the residence time of the reactants and significantly increasing the reactor flow resistance. Using a sleeve annulus internal and external heating structure as the preheating section of the reactor can effectively improve the total conversion rate. When both internal and external heating are used, increasing the heat transfer area is beneficial for shortening the length of the preheating section. The length of the preheating section requires about 900 mm to achieve a reactor outlet temperature of 850 ℃. A reactor structure design that meets the requirements has been found.
2024 06 v.30;No.166 [Abstract][OnlineView][HTML全文][Download 657K] 下载本期数据