• Coal grading utilization technologies based on coal pyrolysis:Review and prospect

    SHANG Jianxuan;NIU Ben;NIU Menglong;DU Pengpeng;LIU Qiufang;MA Baoqi;Shaanxi Coal and Chemical Industry Group Co.,Ltd.;National Key Laboratory of Clean Coal Grading Conversion;College of Chemistry & Chemical Engineering,Xi′an Shiyou University;Shaanxi Coal and Chemical Industry Technology Research Institute Co.,Ltd.;

    The development of clean and efficient utilization of coal is of great significance to ensure national energy security, support national economic development and realize the goal of double carbon. Coal grading utilization technologies based on coal pyrolysis with the advantages of high energy conversion efficiency, low carbon emission and low water consumption has become the most promising technical route and industrial practical direction of coal clean and efficient utilization. The development history of coal pyrolysis technology at home and abroad was systematically reviewed. The development and application of coal pyrolysis technology in foreign countries were introduced based on two periods, i.e., the early industrialization in the early to middle of the 20th century and the in-depth research in the 1960s to the end of the 1990s. The typical technologies and industrialization progress of independent research and development in the pyrolysis processes of moving bed, rotary kiln, fluidized bed, belt furnace, rotary furnace and gas bed since 2000 were reviewed. The technology of clean and efficient conversion of coal grading with multiple co-production has undergone more than a decade of development, and a development system for this technology has been established. Based on the characteristics of resources in northern Shaanxi, multi-co-production modes such as coal-oil-electricity-chemical and coal-salt-oil-chemical have been established. The basic research, technical exploration and industrial practice of Shaanxi Coal and Chemical Industry Group in the field of coal grading utilization technology were emphatically introduced. Finally, the future development of coal grading utilization technologies based on coal pyrolysis was prospected from three aspects: the basic research on the application of pulverized coal pyrolysis, development direction of tar grading utilization technology, and the development of system coupling and integration technology. It is an important development direction to establish coal grading utilization technology with more abundant product forms, lower energy consumption, higher project economy and comprehensive resource utilization, low carbon and environmental protection, multi-technology integration and coupling.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 62345K]

  • Future and challenge of coal based ammonia synthesis and clean utilization under the double carbon target

    WU Jin;ZOU Longzhi;CHEN Yang;ZHU Hang;MEI Jian;XIONG Chuhao;WU Ye;LIU Dong;School of Energy and Power Engineering,Nanjing University of Science and Technology;

    Ammonia, as an important chemical raw material, has a history of more than 100 years.Ammonia chemical industry has made great contributions to human′s manufacture and life. However, with the increasingly strict requirements for energy conservation and environmental protection, the new development direction in the new era has brought new challenges to ammonia chemical industry. The development of technologies in ammonia chemical industry was introduced, and the research progress of ammonia synthesis and clean utilization was reviewed from three aspects: ammonia synthesis, ammonia combustion and ammonia utilization. The traditional Haber-Bosch ammonia synthesis process will emit the large amount of CO_2 emissions, and even the most advanced coal gasification or natural gas reforming ammonia production processis difficult to meet the requirements of the dual carbon targe. The renewable energy produce hydrogen-Haber-Bosch process is the most likely green synthetic ammonia technology to be applied on a large scale in the foreseeable stage. With the rapid development of electronic technology and various detection methods, some new ammonia synthesis technologies, such as chemical chain ammonia synthesis technology, electrocatalysis, photocatalysis, plasma technology, has attracted much attention, which can get rid of the high temperature and high pressure in the traditional method, reduce the pollutant emissionand opens up a new way for green ammonia synthesis. Meanwhile, ammonia has also attracted the attention due to the characteristic of high hydrogen storage capacity and combustion products pollution-free in the context of carbon neutralization. The fuels such as hydrogen and methane or catalysts are usually used to promote ammonia combustion.Due to more coal and less gas in China, there are also studies on the co-firing of ammonia and coal, but its stable combustion and the control of nitrogen oxides in products are relatively difficult. The chemical looping technology of ammonia has the advantages of high combustion efficiency, low cost, and almost no NO_x production. In addition, chemical applications such as ammonia hydrogen production, ammonia carbon capture, ammonia desulfurization and denitration have also steadily developed in recent years. Ru-based catalysts for hydrogen production from ammonia have high hydrogen efficiency, and transition metal catalysts are inexpensive. The combination of precious metals and transition metals also provides a good idea for its development. Ammonia carbon capture technology can effectively mitigate the greenhouse effect, and its development is relatively mature, but it still needs to be optimized. Ammonia desulfurization and denitrification can selectively reduce the SO_2 and NO_x in the flue gas. Ammonia/activated carbon method, ammonia/electron beam method and ammonia/pulse corona method all have good development prospects. In a word, the development of the above technologies has further widened the application field of ammonia and opened up a new direction for ammonia chemical industry. The future research of ammonia needs to introduce more sustainable development concepts and scientific and technological innovation on this basis, injecting new impetus into green ammonia chemical industry.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 69900K]

  • Research progress of carbon ash separation technology on coal gasification fine slag

    YANG Jinjin;FAN Panpan;FAN Xiaoting;BAO Weiren;WANG Jiancheng;DONG Lianping;FAN Minqiang;CHANG Liping;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;College of Chemical Engineering & Technology,Taiyuan University of Technology;College of Mining Engineering,Taiyuan University of Technology;

    Coal will be still the most vital fossil energy source in China for a long period of time on the basis of the characteristics of China′s coal-rich, oil-poor and gas-poor energy structure. Coal gasification is the frontier technology for the development of modern coal chemical industry, and an effective way to realize the clean and efficient utilization of coal, which is of strategic meaning to realize the high-quality development of the whole country. Coal gasification fine slag will be produced in the process of coal gasification, which is mainly disposed of by landfilling, and not only occupies the land and pollutes the environment, but also is not conducive to the long-term growth of coal chemical companies. Therefore, the efficient treatment and reuse of coal gasification slag is urgent. Firstly, the physicochemical properties of gasification slag were analyzed and summarized. The residual carbon content of gasification fine slag is related to coal type, gasification process conditions and operating conditions, but the physicochemical properties of gasification fine slag do not vary much, mainly composed of SiO_2, Al_2O_3, CaO, Fe_2O_3 and C. The residual carbon content of gasification fine slag is generally around 20%, and depending on the coal type and gasification operating conditions, the residual carbon content of gasification fine slag can be as high as 50% in some areas, which has some potential utilization value. At present, carbon ash separation methods of gasification slag are mainly sieving, gravity sorting and froth sorting. The sieving classification, gravity separation and flotation technology of gasification slag were systematically summarizes. Through sieving classification and gravity separation technology, low-cost and high-efficiency reuse of gasification fine slag can be achieved in a pollution-free and green way. The adsorption and spreading of the collector on the carbon residue surface of gasification slag can be improved by flotation enhancement, and the hydrophobicity of gasification slag can be improved. Finally, research direction of separation of gasification fine slag was proposed according to the current situation of domestic and foreign research.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 23683K]

  • Research progress of thermal treatment and utilization technology of coal gasification fine ash and slag

    ZHOU Li;LIANG Chen;QI Xiaobin;LI Wei;REN Qiangqiang;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;

    Coal gasification, as the leading technology in coal chemical industry, is an important pathway to achieve clean and efficient utilization of coal. However, the gasification process generates a large amount of gasification ash and slag, which is difficult to achieve resource utilization. Currently, the treatment of gasification ash mainly relies on storage, causing serious environmental and soil pollution issues, which becomes a bottleneck in the development of the coal chemical industry. Therefore, it is urgent to develop large-scale utilization technologies for gasification ash and slag. The thermal treatment technologies for fluidized bed coal gasification fine ash and entrained flow coal gasification fine slag were highlighted, and the disposal principles, disposal capabilities, and research stages of various thermal treatment technologies were summarized. The disposal methods for fluidized bed coal gasification fine ash include steam activation, combustion, gasification, and melting. In order to fully utilize the developed porous structure, abundant amorphous carbon structure, and active sites of gasification ash, a scheme for steam activation to produce activated carbon was determined. The enhanced preheating combustion technology, which prolongs the residence time of gasification ash in the furnace through material leg feeding, achieves a combustion efficiency of over 98% for gasification fine ash. The preheating combustion technology based on circulating fluidized bed can not only achieve stable decarbonization of gasification ash, but also control the emission of NO_x. The coupled regasification of fluidized bed and entrained bed makes up for its poor reactivity by increasing the gasification reaction temperature. The fluidized-melting gasification process utilizes a circulating fluidized bed to fluidize and modify the coal gasification ash, and the modified product and secondary gasifying agent are simultaneously fed into the melting gasification unit to achieve high-temperature melting gasification of the modified fly ash, thereby obtaining synthesis gas from gasification fly ash as a single fuel under atmospheric pressure. The thermal treatment methods for entrained flow gasification fine slag are blending combustion and fluidized-melting combustion. The blending combustion materials mainly consist of raw coal and biomass, but the blending ratio is low, and the large amount of ash in the gasification fine slag presents new challenges to ash conveying systems and other components. The fluidized-melting combustion adopts a technical route of combining thermal modification and high-efficiency incineration of gasification slag, as well as mineral phase reconstruction and high-value utilization of slag, to achieve the separate utilization of organic carbon and inorganic ash components in coal gasification slag. Currently, the thermal treatment technologies for coal gasification ash slag mainly focus on the removal and utilization of organic carbon, while the inorganic ash components, after thermal treatment, still remain as solid waste, without achieving the harmless disposal and resource utilization of coal gasification ash. Therefore, in order to truly achieve large-scale treatment and resource utilization of coal gasification ash and slag, the corresponding high-value utilization technologies must be developed based on the characteristics of inorganic mineral components after thermal treatment, which will be the main research direction in the future.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 12002K]

  • Experiment on high temperature preheating and decarbonization process of coal gasification slag and cement properties of solid phase products

    WANG Xuebin;YU Wei;CHEN Yongqiang;SHI Zhaochen;SHANG Jingpeng;WANG Jianjun;ZHANG Hanlin;School of Energy and Power Engineering,Xi′an Jiaotong University;Zhaoyuan Huichao New Energy Technology Co.,Ltd.;Besino Environment Ltd.;

    Gasification slag is the solid waste produced in the process of coal gasification. At present, it is mainly treated by landfill. It not only occupies a large amount of land, pollutes soil and water, but also causes energy waste. The gasification slag has a certain carbon content, but the volatile content is very low and the water content of the receiving base is very high, which leads to the difficulty of energy utilization of the gasification slag. High temperature preheating decarbonization process is one of the effective technical approaches to realize the resource disposal of ultra-low grade coal-based solid waste developed in recent years. This process can realize the self-stable combustion and burnout process of solid waste with near zero volatile matter and ultra-low calorific value, such as gasification slag and ash sludge mixture. After the gasification slag with the proportion of dry base fixed carbon of 13.1%-16.2% is treated by the integrated equipment of 100 000 tons/year high temperature preheating and decarbonization in the single line of Xinjiang Ganquanpu Industrial Park, the volatilization is basically removed, and the carbon content of exported ash residue is lower than 3%. The stable ignition and efficient burning of input materials can be achieved without adding auxiliary fuel. The flue gas at the outlet of stable operation is converted to 9% O_2 concentration, and the NO_x emission is in the range of 64.5-66.9 mg/m~3. The gasification slag and gasification slag sludge mixture after decarburization of the industrial demonstration production line are ground to replace 30% cement for mortar preparation, and the strength activity index reaches 80% and 91% respectively, meeting the requirements of the strength activity index of fly ash for mortar and concrete mixing and fly ash for cement active mixing materials.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 18981K]

  • Influence mechanism of composition and content of glassy phase on cementitious reactivity of coal gasification slag

    GUO Hanghao;WANG Ji;MA Zhibin;LU Guangjun;GUO Yanxia;State Environmental Protection Key Laboratory on Efficient Resource-utilization Techniques of Coal Waste,Institute of Resources and Environmental Engineering,Shanxi University;School of Chemistry and Chemical Engineering,North University of China;

    The composition and content of glassy phase in coal gasification slag(CGS) change due to the difference in coal species and gasification process. I order to study the effect of glassy phase in CGS on mechanical properties and micromorphology of alkali-excited cementitious material, a CGS of shell gasifier was used as raw material, and the content and composition of glassy phase in CGS was changed by crystallization process at high temperature. The results show that the compressive strength of CGS based cementitious material can reach 30 MPa under the optimal alkali excitation condition. High temperature induced crystallization causes the formation of anorthite in CGS, which not only decreases the content of glassy phase, but also increase the Si/Al of glassy phase. In alkaline environment, anorthite does not take part in dissolution-polymerizationreaction, and less glassy phase in slag leads to decreasing dissolution of Si and Al, which is detrimental to mechanical properties. Besides, the mechanical property of cementitious material is linearly related to content of glassy phase in CGS. Si/Al of glassy phase decides the dissolution ratio of Si and Al under alkaline condition, which is useful for choice of alkali activator to increasethe formation of gel in cementitious material. The micromorphology analysis shows that the surface of coal gasification slag with high glassy phase is smooth, and more gel is generated in alkaline condition. During curing process, the microstructure of cementitious material becomes dense, which lead to increase of mechanical strength.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 23392K]

  • Research progress on the effect of iron on mineral transformation and melting characteristics during coal gasification

    SHEN Zhongjie;DONG Zizheng;LIANG Qinfeng;XU Jianliang;GUO Xiaolei;DAI Zhenghua;LIU Haifeng;National Energy Coal Gasification Technology Research and Development Center,East China University of Science and Technology;Shanghai Engineering Research Center of Coal Gasification,East China University of Science and Technology;College of Chemical Engineering,Xinjiang University;

    Iron is an important element commonly found in coal minerals, and its occurrence parameters such as content and valence are the key factors affecting the physical and chemical properties of coal gasification ash, such as mineral transformation, melting, crystallization, viscosity, rheology, etc. The type of coal used in gasifier and the change of operating conditions(atmosphere and temperature) affect the occurrence form of Fe, and the coal gasification ash containing iron shows different physical and chemical properties, which is of great significance to guide the smooth slagging of gasifier. Research progress on the occurrence form of iron in gasification ash, melting properties of Fe on coal gasification ash, crystallinity and viscosity-temperature properties during cooling process were reviewed. Fe mainly exists in raw coal in the form of FeO, Fe_2O_3, FeS, and FeS_2, and is converted into iron-containing aluminosilicates during coal gasification, which is significantly affected by gas compositions(CO/CO_2/O_2/H_2), chemical compositions and temperature. Due to Fe~(3+) has a strong polarity, it is difficult to react with other minerals, and the melting temperature of ash slag in oxidizing atmosphere is higher. While CO, H_2 and other reducing gases have strong reducibility, Fe_2O_3 in ash slag is reduced to ferrous(Fe~(2+)), its melting temperature is reduced, but reduced to metallic iron(Fe), it has a high melting point characteristic, ash melting temperature increases. The effects of Fe in coal gasification ash on the crystallization properties of molten liquid slag during the cooling process include the types of Fe-containing crystals, crystallization temperature, crystallization conditions, crystal morphology and scale. Among them, the interaction of Fe and Ca in aluminosilicate network structure is significantly affected by atmosphere, temperature and chemical composition. The main effect is the interaction between the transformation of Fe/Fe~(2+)/Fe~(3+) and calcium feldspar minerals, which affects the transformation of iron-containing crystals and the precipitation of iron. The effect of Fe on the viscosity-temperature and viscosity-temperature characteristics of coal gasification slag was discussed, including the variation of viscosity and the critical viscosity temperature, the different valence states and contents of Fe were important parameters in the process of viscosity change and melt structure transformation. Finally, the effect of Fe on the physical and chemical properties of coal gasification ash was summarized. It is expected that the combined physical and chemical effects of iron elemental and ionic state(Fe~(2+)/Fe~(3+)) in complex atmosphere(H_2/CO/CO_2) on mineral conversion, ash melting and crystallization are the key to clarify the role of iron in coal gasification ash. It is necessary to establish a suitable prediction system for the properties of iron coal gasification ash and slag to provide guidance for the operation of industrial gasifier.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 43355K]

  • Research process on ash chemistry of high-sodium coal during gasification

    ZHANG Xianxian;BAI Jin;KONG Lingxue;LI Huaizhu;GUO Zhenxing;BAI Zongqing;LI Wen;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry of Chinese Academy of Sciences;University of Chinese Academy of Sciences;

    Coal gasification is a key technology to develop coal based bulk chemicals and clean fuels, and also an important way to achieve the goal of carbon neutrality. High sodium content and its volatilization of Zhundong coal during gasification lead to serious ash-release problems. Therefore, it is of great significance to clarify the ash deposition and slagging mechanism and ash fluidity during Zhundong coal gasification for the clean and efficient utilization of high-sodium coal. Given this, the research progress on the ash chemistry of high-sodium coal during gasification process was reviewed. The forms and content of sodium in coal were summarized. The migration and transformation mechanisms of sodium in gasification and the ash deposition problem caused by sodium release on the heating surface of the gasifier were clarified. The ashing temperature is set at 500 ℃ because the sodium release in high sodium coal is mainly affected by the gasification temperature. Low melting point sodium-containing minerals are easily generated during the gasification process, reducing the ash melting temperature of high sodium coal ash. When the content of calcium and iron in high sodium coal is high, the formation of low-temperature eutectic of anorthite and gehlenite in coal ash at high temperature, and the formation of low melting point spinel by Fe~(2+) reacting with minerals in coal are important reasons for reducing coal ash melting temperature. Meanwhile, the atmosphere has a certain influence on the minerals evolution of high-sodium coal during thermal conversion. The melting rate of high-sodium coal is fast, and the average melting temperature is low, indicating that the ash has a strong fluidity. The Na_2O can provide O~(2-) and break the bridge oxygen bonds, causing the slag to depolymerize and reducing the viscosity value. The slag grid structure depolymerizes, the viscosity is reduced. The melting mechanism confirms the melting-dissolution mechanism. The precipitation of crystals in the slag during cooling has a crucial impact on the viscosity. The introduction of Na_2O reduces the crystallization temperature of slag and changes the crystal type. At the same time, the viscosity activation energy and crystallization ability of the slag are reduced.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 25915K]

  • Influence of coal blending on fusion characteristics of high alkali coal ash in Xinjiang

    LYU Junxin;LIN Xiongchao;KAWA Omarjiang;YANG Yuanping;BAO Yahan;DING Hua;WANG Yonggang;State Key Laboratory of Coal Mining and Clean Utilization;School of Chemical and Environmental Engineering,China University of Mining & Technology-Beijing;School of Mechanical Engineering,Tsinghua University;Yankuang Xinjiang Coal Chemical Co.,Ltd.;

    In order to study the influence mechanism of coal blending on the ash melting behavior of high-alkali coal in Xinjiang, two typical Xinjiang Zhundong coals with large differences in alkali metal content were used to explore the influence and control mechanism on the melting characteristics of blended coal ash. The ash samples were analyzed by XRD,SEM-EDX,and XRF,and the chemical composition, mineral composition, and microscopic morphology evolution of single coal ash and mixed coal ash were investigated at high temperatures. The phase transformation and mineral composition of were simulated by Factsage to reveal the mechanism of influence of coal blending on the high-temperature melting behavior of high-alkali coal ash in Xinjiang. Studies have shown that high alkali coal ash has high Na_2O content, and feldspar minerals formed at high temperatures are the main reasons for the low melting temperature of ash. Coal blending changes the chemical composition of coal ash and changes the evolution behavior of minerals in coal ash at high temperature, which determines that mixed coal ash have different melting characteristics. However, the ash fusion temperature of blended coal has a nonlinear relationship with the proportion of coal blending. When the ratio of MC coal to BS coal is 1∶4,the blended ash has the lowest ash fusion temperature, and when the ratio is 4∶1,the blended ash fusion temperature is the highest. The low-melting-point minerals labradorite, diopside and bytownite in high-temperature coal ash can undergo low-temperature eutectic with quartz and mullite, resulting in a decrease in ash melting temperature. Thermodynamic calculation results show that feldspar, cordierite, pyroxene and quartz minerals interact to form a low melting temperature eutectic at high temperature, which reduces the formation temperature of liquid phase. The thermodynamic calculation results are similar to the X-ray diffraction results.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 20672K]

  • Fusibility and mineral transformation of Zhundong coal ash with high calcium and magnesium content under high temperature gasification conditions

    LIU Xia;WU Hao;GUO Qinghua;CHEN Xueli;YU Guangsuo;WANG Fuchen;Institute of Clean Coal Technology,East China University of Science and Technology;

    Entrained-flow gasification is an important way for clean and efficient utilization of coal, while Zhundong coal with high content of calcium and magnesium can not be directly applied to industrial gasifiers due to its high ash fusion temperature. The in-depth study of the high-temperature fusion mechanism of Zhundong coal ash has important guiding signification for its gasification application. The fusibility and mineral transformation of high calcium magnesium Zhundong coal ash under high-temperature(1 100-1 500 ℃) gasification conditions were studied using experimental analysis and calculated simulations, and the effect of SiO_2 addition on the fusibility and mineral transformation of raw coal ash was also investigated. The results indicate that when the gasification temperature is below 1 300 ℃, Ca mainly exists in the form of CaS in the high calcium-magnesium Wucaiwan coal ash, while Mg always exists in the form of MgO. When the gasification temperature increases to 1 400 ℃, Ca-based minerals gradually melt in the liquid phase and completely melt at 1 500 ℃, while Mg reacts to form magnesium aluminum spinel of high melting point, resulting in a higher fusion temperature of raw coal ash. An appropriate amount of SiO_2 can combine with Ca and Mg in coal ash to form the akermanite that is prone to low-temperature eutectic, thus significantly reducing the fusion and liquidus temperature of coal ash. Moreover, the combined priority of SiO_2 and CaO is higher than that of MgO. The thermodynamic simulation results show that some Ca and Mg in Wucaiwan coal ash still exist in the form of monoxideat the equilibrium state of 1 600 ℃, leading to a higher liquidus temperature of the raw coal ash. The thermodynamic calculation results can provide a reference for fusibility prediction and high-temperature mineral transformation of coal ash.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 15049K]

  • Slagging tendency and process of coal ashes with high alkali

    SHI Wenju;YAN Jingchong;BAI Jin;CAO Jingpei;Jiangsu Province Engineering Research Center of Fine Utilization of Carbon Resources,China University of Mining & Technology;School of Chemistry & Chemical Engineering,Anhui University of Technology;State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences;

    Slagging is a serious problem limiting the large-scale combustion and utilization of coal ashes with high alkali. Two types of combustion boiler slags with a high alkali metal and high alkaline earth metals respectively were used to investigate the slagging tendency and slagging process by ash fusion temperature tester, thermomechanical analyzer, thermogravimetric-differential scanning calorimeter, XRD, and thermodynamic software FactSage. It is found that the alkali metal in the high alkali ash slag mainly exists in silicoaluminate, while the alkaline earth metal mainly exists in sulfate. The initial sintering temperature of high alkali coal ash slags(SH and PG) is higher than the coal ash slags with high alkaline elements(GJ and CQ), but the ash fusion temperature range of GJ and CQ is larger than SH and PG. Both initial sintering temperature and deposition index can be used to evaluate the slagging tendency of coal ashes with high basic oxides, but there is no direct relationship between the slagging tendency discrimination index and the chemical composition of the ash CaO, K_2O+Na_2O, SiO_2/Al_2O_3, alkali acid ratio B/A, and the content of alkaline earth metal calcium sulfate and alkaline metal silicate Aluminate in the mineral composition. The melting of coal ashes with high basic oxides mainly passed through two stages. The first stage is connected to the melting of low-melting-point alkali metal minerals(albite, nepheline) or the reaction with other minerals in coal ash(quartz, albite) to form the initial liquid phase, the second stage is mainly dominated by low-temperature eutectics which are formed by pyroxene and feldspar.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 26393K]

  • Advances in crystallization behavior of non-Newtonian slags during cooling process

    ZHANG Yongquan;XUAN Weiwei;ZHANG Jiansheng;School of Energy and Environmental Engineering,University of Science and Technology Beijing;Department of Thermal Engineering,Tsinghua University;

    Gasification technology is the leading technology of the coal chemical industry, and the airflow bed gasifier is the direction of large-scale gasification due to the flexible fuel application and high conversion rate. As the raw material components or operating conditions change, the slag may exhibit non-Newtonian fluid properties due to crystal precipitation during the flow process, resulting in poor slag discharge. Therefore, the crystal precipitation behavior of the slag in the furnace has important guiding significance for controlling the rheological properties of the slag and the stable operation of the equipment. Research on the crystallization behavior of non-Newtonian slags was summarized, the influencing factors of the main components and cooling conditions were analyzed. The driving force of crystal growth varies with different undercooling degrees, thereby affecting the crystal growth rate. Increasing the cooling rate leads to insufficient crystal incubation time and thus small crystals. When the cooling rate exceeds the critical cooling rate, the slag takes on a vitreous state. The changes in the main components of the slag lead to changes of the diffusion properties as well as the crystal types. An increase in the alkalinity of the melt leads to an increased crystallization capacity of the slag. In addition, different crystal types, the size and shape of the crystals, the crystallization reaction at the solid-liquid interface, and the crystal growth rate, etc. all undergo changes, resulting in changes in rheological properties. Therefore, the growth characteristics of several common crystals in slag(Anorthite, Melilite and Spinel) were summarized, as well as the influence of the crystals on the rheological properties of the slag. For non-Newtonian slags, the crystal precipitation types and corresponding crystal characteristics are still unclear and need to be further studied. Adjusting the rheological behavior of slag by forecasting and controlling the crystal growth will realize the prediction of the viscosity change of the liquid slag layer, which is significant for optimizing the flow of slag discharge furnace.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 47690K]

  • Effect of the blending between high silicon-aluminum coal and high calcium-iron coal on ash fusion temperature

    ZHAO Wei;LI Fenghai;MA Mingjie;YANG Ziqiang;LI Zhenzhu;College of Chemistry and Chemical Engineering,Henan Polytechnic University;College of Chemistry and Chemical Engineering,Heze University;Shandong Meiyu Engineering Consulting Co.,Ltd.;

    Although new energy technologies are developed rapidly, coal will still be the main energy source in China for a long time to come. High calcium-iron coal is an important coal resource in China, which is widely distributed. Its ash fusion temperature T_(AF) is low and cannot be directly applied to entrained flow gasifier. Therefore, taking high-calcium-iron coal(MO) as the research object, high silicon-aluminum coal(Y4) was selected to regulate its ash fusion characteristics. The regualtion mechanism of ash fusion characteristics was discussed by X-Ray Diffraction(XRD), Fourier Transform Infrared Spectroscopy(FTIR), Raman Spectroscopy(Raman) and FactSage thermodynamic software. The results show that with the increase of Y4 ratio, the T_(AF) of the mixed ash sample increases gradually. When the mixing ratio of Y4 is 40%-50%, the flow temperature of mixed ash sample is 1 354-1 389 ℃, which met the requirements for slag tapping of the entrained-flow gasifier. The XRD and FactSage results show that with the increase of Y4 content, the gradual disappearance of low melting point minerals and the formation of stable aluminosilicate minerals(like anorthite) mainly result in the increase of T_(AF). From the three-phase diagram, it is found that with the increase of Y4 mixing proportion, the minerals in the ash sample change from melilite to anorthite. FT-IR results show that with the increase of Y4 ratio, the Si—O in the ash sample moves to the high frequency region, and forms a broader absorption peak between 900-1 000 cm~(-1). Combined with XRD result, it is judged that the absorption peak is anorthite. From the perspective of silicate melts, the parameter R is introduced to represent Si—O—A. With the increase of Y4 content, the R in the ash sample increases in a "stepped" pattern, leading to an increase in network polymerization degree, which explains the increase in T_(AF).

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 24580K]

  • Migration pattern and solidification treatment technology of heavy metals in coal gasification slag: A review

    CHEN Bowen;XIONG Zhuo;ZHAO Yongchun;ZHANG Junying;School of Energy and Power Engineering,Huazhong University of Science and Technology;State Key Laboratory of Coal Combustion,Huazhang University of Science and Technology;National Environmental Protection Engineering Technology Center for Trace Elements Pollution Control and Low Carbon Utilization of Coal;

    With the continuous development of the coal gasification industry in China, the total amount of coal gasification slag is also increasing, and has become one of the urgent problem. In order to make full use of gasification slag, broaden its application scenario and reflect the potential resource value, a lot of exploration has been carried out in the industries of construction materials, ceramics, molecular sieves, catalysts, etc., and it has been successfully used. However, during the coal gasification process, harmful heavy metal elements(Hg, Cr, Cd, Pb, Zn, Ni) in coal will remain in the gasification slag, which may be released or leached into the environment with precipitation, causing adverse effects on the ecological living environment and human life and health, and affecting the comprehensive utilization of coal gasification slag. In the process of gasification, the release of heavy metals in coal is affected by the gasification temperature, mode and atmosphere, and different kinds of heavy metals are affected by these conditions in different ways and to different degrees. For heavy metals in gasification slag, the leaching rate is influenced by leachate pH, leaching temperature, solid-liquid ratio, particle size and leaching time, among which leachate pH is the main influencing factor. In order to stabilize the heavy metals in slag, reduce the release and leaching of heavy metals and reduce the pollution to the environment, the sequestration treatment technology of heavy metals in coal gasification ash slag is systematically summarized and classified into six ways, such as cement sequestration, heat treatment sequestration, hydrothermal treatment sequestration, additive sequestration, chemical co-precipitation sequestration and co-consolidation of mineralization according to the sequestration method.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 19137K]

  • Viscosity-temperature characteristics and mechanism of co-gasification ash slag with municipal sludge and coal

    WU Hao;LIU Xia;CAO Xi;GUO Qinghua;YU Guangsuo;Institute of Clean Coal Technology,East China University of Science and Technology;

    By blending municipal sewage sludge with coal to prepare sludge slurry, it is expected to achieve resourceful, harmless, and reducing disposal of sludge by using entrained-flow gasification technology. At present, there are few studies on the influence and mechanism of municipal sludge on the viscosity-temperature characteristics of gasification coal ash, which limits the application of sludge-coal water slurry in gasification. Ash of typical coal(YLA) for gasification was selected and mixed with different proportions of sewage sludge ash(SSA) to simulate the co-gasification ash of sludge and coal, and the ash fusion temperatures and viscosity-temperature curves of the raw and mixed ash samples were measured. XRD analysis and phase diagram theory were used to investigate the variation of crystallization tendency in slag during the cooling process, and FTIR was used to characterize the structural distribution of slag silica-oxygen units and to elucidate the mechanism by which municipal sludge ash content changed slag viscosity. The results show that 10% is the ideal SSA addition ratio and the slag discharge performance will be deteriorated if SSA content is above 30%. When SSA content is 10%, the flow temperature is sufficiently reduced and has an operable temperature range of 168 ℃. When the SSA content exceeds 30%, the flow temperature increases due to the significant increase in iron and phosphorus content in the ash, and the operable temperature range is narrowed. And the critical viscosity temperature is close to the lower limit of the operating temperature due to the increased crystallization tendency, which easily causes drastic changes in slag viscosity. FTIR analysis and peak fitting results show that the reduced polymerization of the silica-oxygen structure is the main reason for the decreasing viscosity of the slag with increasing SSA content.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 26741K]

  • Investigationon regulation mechanism of sludge on the ash melting characteristics of coal with high ash fusion temperature (AFT)

    LI Meng;CHEN Xueli;LI Fenghai;XU Jianliang;LIU Xia;Engineering Research Center of Resource Utilization of Carbon-containing Waste with Carbon Neutrality,Ministry of Education,East China University of Science and Technology;School of Chemistry and Chemical Engineering,Heze University;

    The reserve of high ash fusion temperature coal in China is huge, and the content of silicon and aluminum in the ash is high, while the content of basic oxide in some sludge is high. The co-gasification of sludge and high ash fusion temperature coal provides the possibility of regulating the ash melting characteristics of high ash fusion temperature coal. In this study, the effects of municipal sludge(CS) and pharmaceutical sludge(ZY) on the ash melting characteristics of Jiaozuo coal(JZ) with high ash fusion temperature were investigated. The results show that adding CS ash and ZY ash to JZ ash can reduce ash fusion temperature of JZ and adding ZY ash has a more significant effect on reducing the ash fusion temperature of JZ. When the CS and ZY ash ratio is 15% and 10%, respectively, the flow temperature of JZ-CS and JZ-ZY mixtures are reduced to below 1 380 ℃ to meet the slag discharge requirements of entrained flow gasifier CS ash has a high CaO content, and ZY ash has a high Fe_2O_3 content. With the addition of CS ash, the amount of anorthite formed by reaction of CaO in CS ash with Al_2O_3 and SiO_2 increases, and its co-melting with quartz results in the increase of liquid phase content and the decrease of ash melting temperature. Under a weak reducing atmosphere, the Fe~(3+) in JZ-ZY ash is reduced into Fe~(2+), and iron-bearing minerals such as hercynite increases. Hercynite with low melting point can melt at low temperature, and iron-bearing minerals easily form low melting point eutectic with other minerals, which decreases the ash fusion temperature(AFT) of JZ. When the proportion of sludge ash added is the same, compared with JZ-CS ash, JZ-ZY ash has a lower theoretical solid content, lower intensity and quantity of crystal phase diffraction peaks. When the temperature is 1 500 ℃, the mixed ash with 25% ZY ash reaches the full liquid state, while the mixed ash with 25% CS ash still contains some mullite. Mole ionic potential α is positive linearly correlated with the characteristic temperatures of both types of mixed ash. The decrease in α value of JZ-ZY ash is greater, so the melting temperature of JZ-ZY ash decreases more significantly.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 31553K]

  • Composition and structure analysis of the components from low-temperature coal tar pitch

    WU Yuqi;ZHONG Mei;YALKUNJAN Tursun;College of Chemical and Engineering,Xinjiang University;State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources,Xinjiang University;Key Laboratory of Coal Clean Conversion & Chemical Engineering;

    Using low-temperature Coal tar pitch as raw material, it was divided into saturates(Sa), aromatics(Ar), resins(Re) and asphaltenes(As) according to four-component analysis. Their compositions and structures were analyzed by X-ray photoelectron spectrometer(XPS), nuclear magnetic resonance(NMR), Fourier transform infrared spectrometer(FT-IR), elemental analyzer(EA), gel permeation chromatography(GPC) and UV-fluorescence spectrometer(UV) analyzer. The improved Brown-Ladner method was used to calculate the structural parameters of each component. The results show that the molecular weight of components follows the order of As(5 008) > Re(1 042) > Sa(771) > Ar(602). The relative content of ■ in Sa, Ar, Re and As increased sequentially, while the value of C—O shows an opposite change trend. Wherein, C—OH and ■ are the main form of oxygen-containing groups in Sa and As, respectively. All the N in Sa is in the form of amino-N, and the N in Ar and As is embedded in the aromatic layer with pyridine-N type. Three forms of N, i.e. amino-N, pyridine-N and pyrrole-N, are observed in Re. Wherein, the proportion of pyrrole-N is up to 55%. Sulphones and sulphates take the dominant room of S-containing groups in Re and As, being more than 75%. In addition, aromatic rings substitution degree of As(0.42) is higher than that of Re(0.35). The number of naphthenic rings, aromatic rings and the content of heterocyclic atoms in Ar, Re and As all increase successively.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 14008K]

  • Research progress of nanoparticle flotation collector

    SUN Yujin;DONG Xianshu;JIANG Ning;FAN Yuping;MA Xiaomin;XIONG Peng;LIU Jingwen;College of Mining Engineering,Taiyuan University of Technology;Tongling Nonferrous Metals Group holding Co.,Ltd.;Taiyuan Ecological Environment Monitoring Center of Shanxi Province;

    Traditional oil-based collectors have poor performance in recovering difficult-to-float coal slurry such as fine coal, low-rank coal, and oxidized coal. The development of new and efficient flotation reagents and processes is currently a challenging task. Nanotechnology, as a cutting-edge technology, has shown broad application prospects in the field of mineral processing and has received extensive attention and exploration. The progress of research on the use of nanoparticles as mineral flotation collectors is discussed. It highlights the design, synthesis, and application status of novel hydrophobic nanoparticles in flotation. These include anionic and cationic polystyrene nanoparticles, as well as functionalized nanoparticles with better selective adsorption effects. These nanoparticles exhibit excellent flotation performance and can effectively recover difficult-to-float coal and fine mineral resources. In addition, the microscopic interaction mechanism of nanoparticle-mineral interfaces is discussed. The size and surface properties of nanoparticles play an important role in their interaction with minerals. Anionic and cationic polystyrene nanoparticles are hydrophobic and can interact with hydrophobic minerals in coal slurry, enhancing their flotation performance. On the other hand, functionalized nanoparticles can achieve better selective adsorption effects on specific minerals through surface modification. Understanding these micro-interaction mechanisms helps optimize the design and synthesis of nanoparticles and improve their application effectiveness in mineral flotation. Finally, some suggestions were proposed for the research direction of novel nanoparticle collectors. The rapid development of nanotechnology will drive continuous progress and change in the field of mineral flotation, bringing new vitality and opportunities to the mining industry. nanotechnology will play a more important role in mineral flotation.

    2023 07 v.29;No.155 [Abstract][OnlineView][HTML全文][Download 21959K]