• Advances in coal macerals separation and quality-based utilization of low-rank bituminous coal

    ZHOU Anning;ZHANG Huaiqing;LI Zhen;QU Jinzhou;ZHAO Wei;YANG Zhiyuan;ZHAO Shiyong;School of Chemistry and Chemical Engineering,Xi′an University of Science and Technology;Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Natural Resources;

    The processing and utilization of coal resources in the context of "Dual Carbon" target is facing fundamental changes. The traditional utilization methods no longer meet the current ecological and environmental protection requirements, and coal, as the cornerstone of national energy security, will continue to be played an important role. More than 40% of the coals in China are high-quality low-rank bituminous coals. During the process of conversion and utilization, they are faced with the problem of high inertinite(>35%), which limits the high-value transformation of this part of the resource. Due to the similarity between macerals and the complexity of occurrence characteristics, the separation of coal macerals is difficult and challenging, which greatly restricts the high-quality conversion and utilization of these resources. In order to fully understand the progress of development and utilization of coal macerals, and to promote the clean, efficient and low-carbon utilization of coal resources, three aspects, the determination, separation methods and clean utilization of coal macerals, were focused on. And the ideas and directions for future development were put forward. The determination methods of macerals faced the problem of difficulty in identifying fine-grained materials or low test accuracy. Therefore, there is an urgent need to develop a high-efficiency determination method based on the structural parameters of coal macerals, which is not limited by particle size. In terms of separation methods of macerals, new separation methods such as electroflotation-electrocoagulation separation, oily bubble flotation and jet milling-fineness grading system can effectively improve the traditional separation methods with poor selectivity and low enrichment rate, and have the advantages of process control and strong adaptability. The coal differential processing and clean utilization technology centered on the separation of coal macerals breaks the conventional coal-use standard and coal type restrictions. After the coal macerals are effectively separated, the vitrinite-rich coal can be widely used in coal blending, coking, pyrolysis, liquefaction and other fields. Inertinite-rich coal can be used as fuel or raw material for preparing carbon materials. Coal quality-based utilization based on macerals can fundamentally improve the energy efficiency of coal conversion and utilization, and reduce carbon and pollutant emissions.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 41483K]

  • Research on the low carbon transformation path of power generation under the goal of carbon neutralization

    HU Daocheng;ZHANG Shuai;HAN Tao;ZHENG Xufan;GU Yongzheng;XU Dong;China Energy Investment Group Co.,Ltd.;New Energy Technology Research Institute,CHN Energy;Guodian Power Development Co.,Ltd.;

    The goal of "carbon peak and carbon neutral" points out the direction and path for the low-carbon transformation and scientific and technological innovation in China′s power generation field. Under the background of the innovative development of the global energy and power industry, the development of power generation towards low-carbon, clean, intelligent, electrification, marketization and internationalization will become an inevitable trend. The current situation, existing problems and future technological development path of low-carbon transformation scientific and technological innovation in the field of power generation in China were analyzed in the direction of clean and efficient coal power generation, renewable energy power generation, nuclear energy, advanced energy storage and hydrogen energy. In order to adapt to the new power system based on new energy, the traditional main power supply gradually changes to the basic power supply in China′s coal-fired power units. However, most of the domestic units are designed according to the basic load, and the key indicators such as load regulation range and load change rate are far behind those of abroad. In addition, there are still the problems of low efficiency and high carbon emission of old units. In the future, it is necessary to strengthen the research on flexible and intelligent power generation, ultra-high parameter coal-fired power generation, new and efficient coal-fired power generation, and carbon capture, utilization and storage(CCUS) technologies. The hydropower technology in China has been improved in an all-round way and formed the integration capacity of whole industrial chain. However, it also needs to make efforts in high head, large capacity and ultra-low head generator units, safe and efficient operation and smart power stations. The wind power technology in China has made comprehensive research, deployment and breakthroughs in wind turbine design and manufacturing, wind farm development and operation and maintenance, equipment testing and certification, and standard system construction, and it also needs to tackle the key problems in the direction of large-scale, lightweight and low-cost wind power generation, promote the application of next-generation information and communication technology, and improve the localization rate of key components. The photovoltaic power generation technology in China is basically synchronized with the world. High efficiency and low cost are its main technical direction. The solar thermal power generation technology in China lags behind foreign countries with respect to systematic design and integrated operation, and it is necessary to develop solar thermal power generation technology with large capacity, high parameters, long-time heat storage and low cost. The geothermal power generation and marine power generation technologies in China are in the stage of basic research or technology research and verification, technical research and engineering demonstration still need to be strengthened in the future. In terms of nuclear filed, China already has a complete nuclear fuel cycle and nuclear industry system, and nuclear power technology is in the forefront of the world, however, problems still exist in basic technology, process, materials, software and other aspects. It is also necessary to strengthen the research in advanced nuclear energy systems and comprehensive utilization of nuclear energy, adhere to the technical route of closed nuclear fuel cycle, and continuously improve the safety of nuclear energy utilization. In terms of energy storage technology, At present, China′s energy storage filed is moving towards large-scale development, but there is still a gap between the energy storage industry and the overall healthy development, and the energy storage technology still needs to be developed in the direction of safety, long life, low cost and large-scale. In terms of hydrogen energy technology, China has formed a complete industrial chain, but hydrogen mainly comes from gray hydrogen. In the future, the development of electrolytic water to produce green hydrogen technology supported by large-scale photovoltaic power generation or wind power generation will become the focus.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 1312K]

  • Binary catalytic pyrolysis of lignite for light aromatics under single mode microwave

    CAI Wenxuan;WANG Qingdong;LI Tuo;CHEN Yu;LI Xiaoyuan;School of Chemistry and Chemical Engineering,Wuhan University of Science and Technology;

    Light aromatic hydrocarbons including benzene, toluene and xylene, as important chemical raw materials, have important applications in the fields of dyes, pesticides and medicine. Petroleum resources is scarce but lignite resources is rich in China. Using the selectivity, high efficiency and heating uniformity of microwave heating technology, it is expected that tar rich in light aromatics is obtained by microwave pyrolysis of lignite. In this study, Yunnan lignite was used as raw material, and a single-mode microwave reactor with higher control accuracy of microwave electric field distribution was adopted, to explore the effects of binary catalysis NiFe_2O_4,NiMoO_4 and Fe_2(MoO_4)_3 on electric field distribution, light aromatics content in tar and pyrolysis behavior during microwave pyrolysis from the perspective of microwave electric field distribution. The dielectric parameters of the coal samples were measured by vector network analyzer, and the electric field distribution was simulated. The results show that the addition of binary metal oxides changes the electric field distribution, reduces electric field intensity and effectively increases the coal samples′ ability of absorbing microwaves energy and converting it into thermal energy, which improves the heating rate and final temperature during pyrolysis. The chemical composition of tar and char was analyzed by GC-MS,FT-IR. The results show that the addition of binary metal oxides increases the content of small molecular alkyl groups and · H in the decomposed system effectively by promoting the cracking of macromolecular alkyl and macromolecular aromatic structures and effectively improves the content of light aromatics in tar. After the adding of NiFe_2O_4,Fe_2(MoO_4)_3 and NiMoO_4,the content of light aromatics increases from 21.21% to 44.28% and 37.46% and 43.21%respectively, but the tar yield decreases from 10.28% to 9.76%,6.51% and 9.20% due to the increase of the cracking reaction, and the gas yield increases; in addition, there are d orbital holes in the active center of the transition metal, and by combining with oxygen-containing groups, an R_2-OX-R_1(X is a metal active component) structure is formed, which promotes the cracking of the oxygen-containing structure and has a positive effect on reducing the content of oxygen-containing substances in tar.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 22937K]

  • Research progress on adsorption materials for coal based cyanide compounds

    FENG Yu;ZHOU Chuang;ZHANG Li;Shanxi Xinhua Chemical Defense Equipment Research Institute Co.,Ltd.;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;Key Laboratory of Coal Science and Technology of Ministry of Education,Taiyuan University of Technology;

    The occurrence characteristics of energy resources in China determine that coal is the main energy in China for a long time in the future. It is of great significance to the sustainable development of China′s economy and society and the protection of ecological environment by the clean conversion and utilization of coal and the treatment of pollutants in the process of coal conversion. Due to the special reaction conditions of coal chemical industry and many coal conversion processes as well as the unique element composition of coal, cyanide exists in coal gasification gas, pyrolysis tail gas and coke oven gas. The wastewater and washing water produced by coal gasification and coking also contain a certain amount of cyanide, such as hydrocyanic acid(HCN) and cyanogen chloride(CNCl). Hydrocyanic acid(HCN) is a colorless gas with a slight bitter almond flavor and highly toxic compound, which is easy to disperse in the air. Inhalation of high concentration hydrogen cyanide gas in a short time will cause asphyxia and acute poisoning. Cyanogen chloride(CNCl), soluble in water, is also a highly toxic chemical gas. After being inhaled by the human body, it will cause strong irritation to the eyes and respiratory tract and do strong harm to the human body. Due to its chemical properties and high toxicity, the generation of cyanide containing waste gas has brought many hazards to human body and environment. It is urgent to study the adsorption and purification of cyanide containing gas. The methods of purifying gaseous cyano compounds were introduced. At present, the treatment methods of gas pollution sources containing cyanide mainly include absorption method, combustion method, catalytic hydrolysis method, adsorption method and so on. Taking hydrocyanic acid and cyanuric chloride as examples, the sources, treatment methods and common adsorption materials were summarized. The preparation methods and material characteristics of activated carbon, carbon fiber, molecular sieve, metal organic framework and other materials were analyzed. At present, the research on porous material adsorbents mainly focuses on surface modification, so as to increase the contribution of chemical adsorption on the basis of simple physical adsorption, improve the loading and dispersion of active components, and adjust the active sites of surface reaction, which can not only improve the adsorption capacity and performance of activated carbon based adsorbent, but also avoid the desorption of adsorbate caused by weak physical adsorption force. The development trend of cyanide adsorption materials was prospected. The research and development of various materials focus on: Large-scale and low-cost continuous preparation of adsorption materials with uniformity and uniformity, improve the surface reaction activity and structural efficiency of the material, improve the loading capacity and adsorption capacity of active components, and prevent the desorption of gaseous pollutants after adsorption, efficient regeneration of adsorption materials, efficient recycling, avoiding the generation of harmful solid waste, so as to improve the comprehensive performance of adsorption materials.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 8435K]

  • Influence law of physical and chemical properties of the recycled hardened cement powder by mineral carbonation with low concentration of CO_2

    LIU Qi;WU Shengkun;LI Linkun;HUANG Tianyong;JIAO Zekun;The Unconventional Petroleum Research Institute,China University of Petroleum-Beijing;Beijing Building Materials Academy of Sciences Research;School of Chemical and Environmental Engineering,China University of Mining and Technology-Beijing;

    In order to mitigate the negative impact of CO_2 emitted by the cement industry on climate change, low concentration CO_2 was used to mineralize the recycled fine powder produced in the process of recycling aggregates from construction waste, so as to partially replace the traditional cement with high carbon emission. In this work, the effects of different mineralization processes on the activity, water absorption and admixture adaptability of recycled hardened cement powder were studied, and the mineralization mechanism of recycled hardened cement powder with low concentration of CO_2 was investigated. The results show that the performance of recycled hardened cement powder by direct aqueous mineral carbonation is much better than those of gas-solid carbonation. Compared with untreated regenerated micropowder, the water requirement of recycled hardened cement powder is reduced by 33%,and the hydration activity and additive adaptability are increased by 14% and 39% respectively. Property improvement of the recycled hardened cement powder by CO_2 mineral carbonation is mainly due to the reaction of CO_2 reacted with calcium hydroxide, calcium silica hydrate, ettringite and unhydrated cement clinker tricalcium silicate, dicalcium silicate to generate relatively dense calcite calcium carbonate(CaCO_3, CC) and amorphous silica gel(SiO_2·nH_2O), refine the pores or microcracks, so as to reduce the water demand of recycled micro powder, and enhance the properties of the hydration activity and additive adaptability finally. The recycled micro powder after CO_2 mineralization treatment can meet the requirements of JG/T 573-2020 Recycled Micro Powder for Concrete and Mortar to replace cement as a mineral admixture in a high proportion. While realizing the resource utilization of solid waste, CO_2 is permanently fixed in the recycled micro powder, providing a new way for the deep decarbonization of the cement industry.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 34871K]

  • Simulation study on flue gas temperature deviation of 700 ℃ tangentially fired boiler with multi-factor optimization

    ZHOU Changxin;LIU Jianquan;WU Zhenxin;SU Tong;HU Weichen;KONG Zheng;College of Energy and Mechanical Engineering,Shanghai University of Electric Power;Shanghai Boiler Works Co.,Ltd.;

    700 ℃ tangential firing boiler has serious flue gas temperature deviation problem. A 660 MW tangential firing boiler with 700 ℃ corners was numerically simulated by commercial Fluent software. Using the method of simulated orthogonal test, five factors, such as the anti-tangential angle of the over-fire air(factor A),the velocity offset of the over-fire air(factor B),the possible interaction between the anti-tangential angle of the over-fire air and the velocity offset of the over-fire air(factor A×B),the upward swing angle of the burner(factor C) and the deflection angle of the secondary air(factor D),were set at two levels for each factor, and the flue gas temperature deviation at furnace outlet was used as the test index for optimization. Three analytical methods, such as range, variance and weight matrix, were used to analyze the simulated data. The results show that the order of importance of each factor to the test index is: factor D > factor A > factor B > factor A×B> factor C,among which, the influence of factor D is very significant, that of factor A is significant, and that of the other three factors is not significant. The weight ratio of each factor is: factor A(0.184),factor B(0.068),factor A×B(0.033),factor C(0.024)and factor D(0.544);the numerical simulation shows that the best combination of factors and levels is A_2B_2C_2D_1. Under this combination, the flue gas temperature deviation on the left and right sides of the outlet section of the boiler furnace is 6.6 K,and the flue gas temperature deviation on the left and right sides of the outlet section of the boiler furnace can be controlled.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 29566K]

  • Behavior characteristics and NO_x emission analysis of new flue gas recirculation in fluidized bed

    LI Yanmin;YAN Jin;SUN Rongyue;WANG Taiqi;WANG Peng;LU Xiaofeng;School of Energy and Power Engineering,Nanjing Institute of Technology;Key Laboratory of Low Grade Energy Utilization Technology and System,Ministry of Education,Chongqing University;

    As an important technical means of low-NO_x combustion, flue gas recirculation(FGR) technology has been widely adopted in pulverized coal boilers and chain boilers. However, in circulating fluidized bed(CFB) boilers, the stable combustion capacity under low load is seriously limited due to the conventional injection mode. In order to reduce NO_x emission under the premise of ensuring bed temperature, a new FGR method based on the synergistic effect of FGR in dilute phase zone and supplementary combustion air was proposed. The thermal experiments were carried out on a 0.2 t/h CFB combustor, and the effects of operating parameters and injection positions on combustion characteristics and NO_x emission in the furnace were analyzed in detail. The key results show that the flue gas temperature in this area will decrease by 40-60 ℃, and the furnace temperature profiles will first decrease and then increase, resulting in a temperature drop of about 10 ℃ at the furnace outlet. The supplementary combustion air from the upper part of the furnace can effectively improve the gas temperature at furnace outlet. With the increase of FGR ratio, the middle FGR injection can gradually reduce the NO_x emission. When the FGR ratio reaches 16%, the NO_x emission can be reduced by 32% and the bed temperature is kept unchanged. With the increase of top FGR ratio, the NO_x emission will decrease first and then increase. When different FGR/supplementary combustion air is sent into the top of the furnace, the mass concentration of NO_x increases from 249 to 304 mg/m~3 and the conversion rate of NO_x increases from 17% to 33% gradually with the increase of supplementary combustion air volume and the decrease of FGR ratio. The mode of middle FGR + top supplementary combustion air could reduce the NO_x emission by 38% and maintain the combustion efficiency over 98.7%. Eventually, a NO_x emission prediction model under FGR mode was proposed based on FGR injection position, excess air coefficient and FGR ratio, which could provide technical basis for better low-NO_x combustion during low-load operation of CFB boilers.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 19517K]

  • Research on alkali metal measurement during the cyclone combustion process of Zhundong coal based on flame spectrum

    PU Yang;LIU Yang;FU Peifang;LOU Chun;School of Energy and Power Engineering,Huazhong University of Science and Technology;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    The reserves of high alkali coal are abundant in the Zhundong area of Xinjiang, but in the process of its combustion and utilization, the release of alkali metals such as Na and K into the flue gas in the form of gaseous phase will cause ash deposition, slagging, and corrosion, etc. on the heat exchange surface of the boiler. The on-line detection of the alkali metal release in the gas phase has certain guiding significance for solving the above problems. A portable system for detecting the concentration of gaseous alkali metals in the flame was developed based on flame spontaneous emission spectrum. Using this system, the on-line detection of high alkali coal combustion flame in liquid slag removal cyclone boiler was carried out. The flame temperature, gas phase Na concentration and band thermal radiation energy at different measuring points were obtained, and X-Ray Fluorescence Spectrometer(XRF) was used to analyze the ash and liquid slag samples, simultaneously. The results show that the gas phase Na mass concentration in the furnace is unevenly distributed. The average flame temperatures of the two slag chambers burning Hami coal and Shenhua coal are 1 415 and 1 436 ℃, respectively, and the gas phase Na mass concentrations are 40.0 mg/m~3 and 25.3 mg/m~3, respectively. The gas-phase Na concentration and band thermal radiation energy can reflect the combustion state in the furnace, and the measurement results have a certain correlation with the composition analysis results of fly ash and liquid slag. The Na mass concentration in fly ash and liquid slag increases, but more migrated to the fly ash.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 15120K]

  • Emission reduction effect and economic analysis of civil square honeycomb briquettes combustion heating

    LI Zhimin;JIAO Mingze;PRABIN Shrestha;LIU Cheng;XUE Chunyu;LIU Guangqing;College of Chemical Engineering,Beijing University of Chemical Technology;Inner Mongolia Xinhongqing Energy Technology Development Co.,Ltd.;

    The adoption of clean briquette heating technology with low-emission and low-cost technology path is one of the effective measures to achieve clean heating in underdeveloped rural areas of China, which can effectively solve the environmental pollution problems brought about by the burning of raw coal for heating. The emission reduction potential and economy of the two new types of civil square honeycomb briquettes when used with stoves specifically designed for them were evaluated. The results show that the emission factors of PM_(2.5) based on unit fuel mass of anthracite square honeycomb briquette and bituminous square honeycomb briquette are 0.09 and 0.43 g/kg, CO emission factors are 51.61 and 38.35 g/kg, NO_x emission factors are 0.72 and 0.63 g/kg, respectively. Compared with raw coal, the anthracite square honeycomb briquette and the bituminous square honeycomb briquette reduce 96.16% and 81.64% of PM_(2.5), 85.15% and 88.97% of CO, and 53.25% and 59.09% of NO_x, respectively. The sulfur fixation rate of anthracite square honeycomb briquette, bituminous square honeycomb briquette and raw coal are 61.55%, 70.76% and 20.93%, respectively. The square honeycomb briquettes produces lower PM_(2.5), CO and NO_x emissions than raw coal, and has better sulfur fixation effect, which can effectively reduce SO_2 emission. The emission reduction potential of the honeycomb briquettes is not only affected by the fuel properties, but also by the stove parameters such as feed mode, combustion mode, and air supply system. From an economic standpoint, the heating costs of using these honeycomb briquettes are comparable to that of using raw coal, primarily due to the wide range of raw materials available for their production bringing down their costs considerably. The combination of square honeycomb briquette and its special stoves has the advantages of stable combustion, high combustion efficiency and good emission reduction effect, which greatly reduces the cost pressure of users′ heating in winter, and provides an effective solution for the coal-fired clean heating work in the northern rural areas of China that do not have other clean heating forms due to economic conditions.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 15592K]

  • Effects of extraction methods on molecular structure characteristics of Huangling coal

    XUE Wenhai;DU Meili;LIU Zhongcheng;WANG Hanjiao;LIU Lei;College of Chemistry and Chemical Engineering,Xi′an University of Science and Technology;

    Huangling coal is an important oil-rich coal resource in China. The rational and efficient utilization of oil-rich coal resources can not only promote China to reduce its dependence on coal and increase the use of clean energy, but also help China to achieve the goal of carbon peak and carbon neutrality. Therefore, ultrasonic-assisted extraction method was used to study the extraction of oil-rich Huangling coal by different extraction methods, and the molecular structure characteristics before and after extraction were analyzed by scanning electron microscopy, low-temperature liquid nitrogen adsorption method and Fourier transform infrared spectroscopy. The extraction effects of petroleum ether(PE), carbon disulfide(CS_2), methanol(MeOH), acetone(DMK), carbon disulfide/acetone(CS_2/DMK), carbon disulfide/nitromethyl pyrrolidone(CS_2/NMP) under ultrasonic assisted conditions were investigated. The results show that the extraction rates of single-stage extraction are CS_2/NMP, CS_2/DMK, PE, DMK, MeOH and CS_2 in descending order. The total extraction rate of PE, CS_2, MeOH, DMK and CS_2/DMK is 16.91%. The study on the structure of CS_2/NMP extract and the fifth grade CS_2/DMK extract show that the particle size of CS_2/NMP extract decreases significantly, and the surface of the fifth grade CS_2/NMP extract is loose and porous. The pore size and pore size of the fifth grade CS_2/NMP extract at the pore size of less than 6 nm are higher than those of the fifth grade CS_2/NMP extract. The aroma of CS_2/NMP extract is higher than that of grade 5 extract. Compared with raw coal, the absorption peaks corresponding to fat structure and benzene ring 4 substitution of the two kinds of raffinate are obviously weakened, and the characteristic absorption peaks of minerals are significantly strengthened and the aliphatic chain is longer and branched chain was reduced, indicating that these two extracts are more conducive to oil formation.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 16265K]

  • Pyrolysis characteristics of oil shale in CO_2/N_2 atmosphere

    BAI Jingru;HAO Tiantian;YANG Le;WANG Bo;WANG Jiaqi;Engineering Research Centre of Oil Shale Comprehensive Utilization,Ministry of Education,Northeast Electric Power University;Beijing Power Equipment Group Co.,Ltd.;

    At present, with the continuous consumption of primary energy, oil shale has come into people′s sight with its rich reserves. At the same time, the use of primary energy has aggravated the emission of CO_2, resulting in different degrees of environmental problems, and researches have shown that CO_2 can be used to produce gas. Therefore, in order to explore the effect of CO_2 atmosphere on oil shale pyrolysis, thermogravimetric infrared spectroscopy(TGA-FTIR) was used in this paper to explore the pyrolysis weight loss of oil shale under five different mixing atmospheres(CO_2 and N_2 mixed in different proportions) and different heating rates. Solid-phase Fourier infrared spectrometer was used to detect the solid-phase products. Peakfit software was used to perform peak fitting analysis of gas/solid phase Fourier infrared spectra. The results show that the total weight loss rate of oil shale pyrolysis shows a weak trend of first increasing and then decreasing with the increase of CO_2 concentration, which makes the peak of weight loss rate move to the high temperature region, and increases the weight loss rate of oil shale pyrolysis in the third stage. Excessive CO_2 inhibits the pyrolysis of oil shale. With the increase of heating rate, the total weight loss rate of oil shale pyrolysis decreases. Under the same conditions, moderate CO_2 concentration increases the production of C_nH_m and CH_4, while excessive CO_2 inhibits their production. For semi-coke, the vibration intensity of carbonates in CO_2 atmosphere decreases, and the pyrolysis temperature of some functional groups changes. Under the same pyrolysis conditions, there are more kinds of functional groups and higher intensity in the char under CO_2 atmosphere, and the pyrolysis reaction moves to the high temperature region.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 29262K]

  • Research on chromaticity analysis and decolorization of high melting point Fisher-Tropsch wax

    JIANG Chenguang;LI Hu;ZHANG Shengzhen;ZHANG Wei;KANG Shanjiao;ZHANG Cuiqing;National Institute of Clean and-Low-Carbon Energy;Coal to Oil Branch Office of Ningxia Coal Industry Co.,Ltd.,CHN Energy;

    A series of high melting point Fischer-Tropsch wax products with a melting point of 70-110 ℃ were obtained by solvent extraction, using the Fischer-Tropsch crude wax obtained from the indirect liquefaction demonstration device of Ningxia coal as the raw material. In order to improve the chromaticity of the high melting point Fischer-Tropsch wax, the relationship between the chromaticity and the drop melting point of wax with high melting point was studied. Two types of adsorbents including activated clay and activated carbon, were used to adsorb and decolorize the No.110 wax samples with poor color, and the best decolorization process conditions were selected. Then, the material composition and physical and chemical properties of the wax-like products and adsorbents before and after decolorization were compared through a series of characterization tests such as high temperature simulation distillation, N_2 absorption and desorption, flourier transform infrared spectrometer(FTIR),diffraction of X-rays(XRD),thermogravimetric analysis, element analysis, inductively coupled plasma atomic emission spectrometer(ICP-AES),nuclear magnetic resonance(~(13)C-NMR and ~1H-NMR),etc. It can be found that the decolorization effect of activated clay is better than that of activated carbon, and the Saybolt color number of the No.110 wax product with high color value is +16. The reasons for the poor chromaticity of high melting point wax are not only the inorganic components mainly composed of residual ultrafine catalyst particles, but also the organic components of unsaturated carbon-carbon double bonds, heteroatomic compounds containing oxygen, nitrogen, and sulfur. The oxidative deterioration of the unsaturated carbon-carbon double bond and the broken bond of hydrocarbons with low bond energy, and the oxidation of sulfur and nitrogen heteroatom compounds may be the main reasons for the color reversion of the products after decolorization.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 17046K]

  • Research progress on catalytic hydrogen production based on steam reforming of light bio-oil

    SHAN Mingxuan;WANG Kun;YANG Meiling;ZHAO Rongyang;LIANG Wenzheng;WANG Fengyin;WANG Cuiping;Clean Energy Laboratory,College of Civil Engineering and Architecture,Shandong University of Science and Technology;School of Mechanical and Electrical Engineering,Qingdao University;

    Hydrogen, as a high energy density and environment-friendly energy, has attracted much attention. At present, the main sources of hydrogen production include fossil fuels, water, biomass, etc. Biomass is a carbon neutral resource, which can promote the realization of China′s "Dual Carbon" goal. The bio-oil produced by biomass pyrolysis or hydrolysis has the disadvantages of low calorific value, strong acidity and high viscosity. The light and heavy components in bio-oil should be reformed separately to produce high value-added products. The components in light bio-oil are relatively simple, cheap and the conversion route is economical and feasible, the catalytical steam reforming of bio-oil is generally considered to be a promising hydrogen production way and the selection of catalyst is the most key factor affecting the efficiency and stability of hydrogen production. In this paper, the recent researches on hydrogen production from catalytic with steam reforming of light bio-oil were reviewed. The process principles of traditional steam reforming, adsorption enhanced steam reforming, autothermal steam reforming, chemical looping steam reforming and sorption-enhanced chemical looping steam reforming were emphatically introduced, and the effects of catalysts and CO_2 adsorbents on hydrogen production performance were summarized and compared. Compared with expensive noble metal catalysts in the traditional steam reforming technology, the Ni-based catalyst has been widely recognized because of its low cost and high hydrogen production performance. However, the defects of easy sintering and carbon deposition still need to be improved by composite active metal modification. The adsorption-enhanced steam reforming technology can improve the yield and purity of hydrogen production through CO_2 in-situ adsorption to a certain extent. The hydrotalcite like compound CO_2 adsorbent has strong alkalinity and large specific surface area, but it needs to be modified to increase the CO_2 adsorption temperature to meet the temperature needs of light bio oil steam reforming. Alkali metal CO_2 adsorbent has strong stability but high cost. And CaO has become one of the most promising adsorbent due to its low cost and excellent CO_2 adsorption characteristics at medium and high temperature. The autothermal reforming process combines the advantages of traditional and partial oxidation steam reforming to produce hydrogen, but it consumes O_2 and easily leads to catalyst deactivation. The sorption-enhanced chemical looping steam reforming technology is the route of applying the oxygen carrying, heat carrying and catalytic multifunctional particles coupling CO_2 adsorption, which combines the self-thermal advantages of chemical looping and enhanced adsorption advantages for high H_2 purity, and has the potential of wide application. However, the mismatch of heat and mass flow rate in the catalytic and adsorption process, and the influence of carbonation process on catalysis need to be further studied.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 12282K]

  • Effect of catalysts and solvents on production in coal hydrolyzing reaction

    YANG Qing;WANG Xingbao;LI Wenying;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;

    Direct coal liquefaction(DCL) is one of the effective ways for coal-hydro conversion and directional production of high-quality fuels and high value-added chemicals. The direct coal liquefaction process is a complex reaction system composed of coal, hydrogen, solvent and catalyst, involving the material transfer and reaction of gas phase, liquid phase and solid phase. While the solvent acts as hydrogen source during DCL,the catalyst promotes the hydrogenation of macromolecules and thermal cracked fragments of coal. How to effectively coordinate and play the role of catalyst and solvent in coal hydrogenolysis reaction will determine the structure composition and yield of liquid products of coal hydrogenolysis reaction. The pyrolysis of typical model compounds in coal, such as aromatics, alkylaromatics, and hydrocarbons having sulfur/oxygen/nitrogen/halogen, etc. was summarized, and the changes observed on the physicochemical properties of these compounds in common solvents, heavy oil solvents and organic waste solvents were discussed, which might affect the subsequent hydrogen-assisted liquefaction. The mechanism of solvent swelling, hydrogen transfer and hydrogen supply to coal was analyzed. A brief introduction was given on the free radical reaction and catalytic liquefaction mechanism occurring during the DCL. The role and status of various DCL catalysts such as metals, metal oxides, metal sulfides, and solid acids(e. g. metal halides and others) were described with a special emphasis on iron-based catalysts. Then, the possible synergistic effect of solvent and catalyst in the hydrogen transfer process of direct coal liquefaction process was discussed. This effect can not only promote the coal hydrogenolysis reaction, improve the yield of direct coal liquefaction oil, but also adjust the structure of liquid products. Finally, in order to further improve the yield of coal liquefaction, the specific research contents and methods in strengthening the synergistic effect of solvent and catalyst were put forward.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 2788K]

  • Comparison of thermo-electric decoupling modes of 300 MW subcritical unit

    ZHU Xudong;MA Honghe;HAN Yang;School of Electrical and Power Engineering,Taiyuan University of Technology;

    In order to solve the increasingly serious thermo-electric coupling problem of heating units, thermo-electrolytic coupling modes such as extraction steam condensing steam heating, low-pressure cylinder no-load heating, and high-low bypass combined heating were proposed. At present, there are few comparative studies on the electric heating characteristics and heating capacity of different thermoelectric coupling modes. Taking a 300 MW subcritical heating unit as an example, the extraction steam condensing steam heating(back pressure 14 kPa), low-pressure cylinder no-load heating(back pressure 3 kPa) and the high-low bypass system combining with heating mode were modeled by using Aspen Plus V11 software. The electric heating characteristics, thermodynamic properties of the unit were compared and analyzed by using the method of variable working condition calculation. The results show that under the condition of the same main steam flow, the maximum heating and steam extraction capacity of low-pressure cylinder no-load heating mode is about 185 t/h higher than that in extraction steam condensing steam heating mode. The ratio of steam intake from the high-parameter expander to the steam turbine intake(abbreviated as steam intake ratio) has a greater impact on the maximum heat-to-electricity ratio of the high-low bypass heating mode. When the main steam flow remains constant, the maximum heat-to-electricity ratio of the high-low bypass heating mode increases with the increase of the inlet steam ratio. Compared with the extraction steam condensing heating mode and the low-pressure cylinder no-load heating mode, the maximum heat-to-electricity ratio increased by 1.981 and 1.227 times respectively. When the main steam flow is the rated value, the standard coal consumption of generating unit calculated by the equivalent electricity method for the three heating modes is 311.64, 262.32 and 258.22 g/kWh respectively.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 13835K]

  • Optimal design of high temperature bypass flue for wide-load SCR-DeNO_x device under limited space

    ZHANG Chucheng;YE Xinglian;LIU Dongdong;SU Yinbiao;YANG Ding;LUO Kun;College of Energy Engineering,Zhejiang University;Fujian Longking Co.,Ltd.;

    With the transformation and upgrading of China′s energy structure, more and more coal-fired power plants have been operating in the medium-low load range for a long time, which exposes the problem that the inlet flue gas temperature of SCR-DeNO_x can not meet catalyst requirement at low-load operation. And the flue gas bypass modification is a flexible and efficient method to improve the gas temperature. Taking the wide load denitrification gas bypass reconstruction project of a 600 MW unit as an example, the design difficulties and flow field problems of bypass flue under limited construction space were discussed by using the numerical simulation method, and a kind of optimal design ideas were put forward. The results show that: After program analysis, the main difficulties caused by space limitation mainly include two aspects: short mixing distance between main flue gas and by-pass flue gas, and the unfavorable uniformity of NH_3/NO_x distribution. After program optimization, the flow field distribution in the SCR denitration system is greatly improved, and the relevant flow field technical indexes can be satisfied whether the bypass flue is put into operation or not. Especially when the bypass flue is put into operation, the relative standard deviation of NH_3/NO_x distribution at inlet of the 1 st layer catalyst is decreased from 20.5% under initial plan to 3.7%, and the temperature deviation is reduced from-21.6-51.5 ℃ under initial plan to-13.8-9.5 ℃. A series of measures such as separating a part of the main flue as the bypass flue, adopting the form of smoke return with small passage and guide plate, and placing the AIG and mixer downstream of the bypass smoke return can significantly improve the flow field distribution uniformity, which is an important reference significance to wide-load SCR-DeNO_x project.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 18433K]

  • Sodium capture mechanism of Zhundong coal blended with coal gangue

    XU Tianyao;FU Peifang;LIU Yang;XIE Zihan;XIONG Zhe;School of Energy and Power Engineering,Huazhong University of Science & Technology;State Key Laboratory of Coal Combustion,Huazhong University of Science & Technology;

    The coal resources in Zhundong area of Xinjiang is rich and easy to exploit. However, the high content of alkali metal(sodium) in Zhundong coal leads to serious fouling and slagging during combustion, which seriously restricts the large-scale utilization of zhundong coal. A large number of coal gangue will be produced in the mining and utilization of Zhundong coal. If it can be combined with Zhundong coal, it can not only solve the problems of coal gangue accumulation, occupation and pollution, but also make new contributions to the clean and safe utilization of Zhundong coal. Aiming at the fouling and slagging problems of Zhundong high-alkali coal, the effects of temperature and coal type on sodium release characteristics and the sodium capture effect of coal gangue additives were studied by comprehensively using TGA-DSC, XRD, XRF and other analytical methods. The results show that the amount of sodium released from ashed Zhundong coal at 500 ℃ increases with the rise of temperature. The two largest temperature ranges are 500-850 ℃(HSQ:24.62%,XHS:22.30%) and 1 200-1 400 ℃(HSQ:20.37%,XHS:49.09%). The sodium retention rate of HSQ blended sample at 850 ℃and 1 000 ℃ are increased by 22.60% and 19.23%, respectively, and sodium is immobilized in the ash in the form of K(Na, K)_3Al_4Si_4O_(16) and NaAlSi_3O_8. The sodium retention rate of XHS blended sample at 850 ℃ and 975 ℃ is increased by about 15% relative to the original, and NaAlSiO_4 and Na_6(AlSiO_4)_6 are the main forms of sodium. Above 1 200 ℃, the Na in the two groups of samples is present as amorphous substances. The capture and release of sodium are carried out simultaneously, and the sodium content captured by coal gangue additives decreases with the increase of temperature, but at a high temperature of 1 400 ℃, the sodium content of the two Zhundong coal blended samples is more than twice that of the original sample, and still has a good sodium capture effect.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 29470K]

  • Chemical composition and structural characteristics of amorphous components in circulating fluidized bed-derived coal fly ash

    WANG Wenhan;MA Zhibin;LU Guangjun;ZHANG Yuanyuan;LI Zhen;LI Lifeng;Institute of Resources and Environmental Engineering,Shanxi University;Shanxi Hepo Power Generation Co., Ltd.;

    Due to the lower ash formation temperature of circulating fluidized bed fly ash(CFB-FA), its amorphous fractions are significantly different from conventional pulverized coal furnace fly ash(PC-FA). At present, the chemical composition and structure of the amorphous components in CFB-FA are not well understood. Taking four kinds of CFB fly ash as the research object, the Retiveld full spectrum fitting method and the acid-alkali-based alternate method were used to calculate the content of amorphous components in fly ash.Combining the chemical composition and mineral quantitative results, the main chemical composition of the amorphous components in the CFB-FA was obtained. Based on the ~(27)Al and ~(29)Si magic-angle rotating nuclear magnetic resonance(NMR) spectrum, the coordination structure of silicon and aluminum in the amorphous component was revealed using the rewind integral peak fitting method. The results show that the main phase of the four CFB ashes is amorphous aluminosilicate, the mass fraction of which is more than 65%, and the main chemical compositions of amorphous components are SiO_2 and Al_2O_3. The Si/Al(molar ratio) of amorphous component is lower than the total Si/Al of the raw fly ash. The contents of amorphous components in the CFB-FA obtained by acid-alkali alternate method are slightly lower than those calculated by Retiveld full spectrum fitting. NMR results reveal that the Si-O-Si and Si-O-Al structures of amorphous components in the CFB-FA are highly disordered and unstable. The aluminum in the amorphous component of CFB-FA ash mainly exists in four-coordinated([AlO_4]) and six-coordinated([AlO_6]) aluminum oxide structures. The silicon in the amorphous component is mainly Q_4(0 Al) structure. [SiO_4] structures are connected by bridging oxygen to form Si-O-Si structure with high degree of polymerization; and [AlO_4] or [AlO_6] combines with [SiO_4] to form Si-O-Al structures of Q_3(1 Al) or Q_4(1~2 Al). The HCl solution destroys [AlO_4] structure and causes Al to dissolve, and the NaOH solution destroys [SiO_4] structure and causes Si to dissolve. The Si and Al in amorphous composition of CFB ash can be separated by the acid-alkali-based alternate method.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 35198K]

  • Development of optimization and evaluation methods of flue gas desulfurization technology for coal-fired power plants under carbon emission reduction scenarios

    GAO Mingkai;YANG Pu;WU Haibin;CHENG Fangqin;YANG Fengling;Institute of Resources and Environment Engineering,Shanxi University;State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources;

    A large amount of pollutants is emitted into the air in coal-fired power plants. Among them, SO_2 can cause various diseases to the human respiratory system. At the same time, it will react with rain to form acid rain during the precipitation process, which will cause serious harm to the ecological environment of our country. It is very important to control SO_2 emission. Flue Gas Desulfurization(FGD) technology is one of the important means to control SO_2 emissions in industry. The characteristics, principles, process flow and influencing factors of desulfurization efficiency of the two commonly used FGD technologies in coal-fired power plants: The circulating fluidized bed furnace desulfurization technology and the limestone-gypsum wet FGD technology were introduced. And the research status of optimization methods of FGD technology in coal-fired power plants was summarized. The methods of technology optimization include process modeling optimization, automatic control system optimization and system operating conditions optimization. In view of the complexity of FGD working conditions and the lack of overall optimization research, it is proposed that artificial intelligence technology can be applied to the optimization of the complexity of flue gas desulfurization technology. In addition, the traditional technical evaluation method focuses on the evaluation of technical and economic performance, and the impact of a large number of greenhouse gases released by FGD technology on the environment can′t be comprehensively analyzed. Under the background of national energy conservation and emission reduction, in view of the limitations of traditional technology evaluation methods, it is proposed that the method of Life Cycle Assessment(LCA) can be adopted for FGD system to realize the measurement control of carbon emissions and other harmful substances emissions during its entire life cycle, and conduct a comprehensive environmental impact assessment. The application of Life Cycle Assessment in flue gas desulfurization of coal-fired power plants is summarized. LCA combined with process simulation is put forward to quickly obtain the evaluation results of different processes and improve ability to select, optimize and make decisions on different technologies.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 11369K]

  • Research progress on the treatment technology of municipal solid waste incineration fly ash

    ZHU Tao;CHONG Xuyang;WANG Ruonan;XUE Zeyu;CHEN Miaomiao;YE Zefu;ZHU Zhujun;Institute of Atmospheric Environmental Management and Pollution Control,China University of Mining & Technology-Beijing;Shanxi Gemeng Sino US Clean Energy R & D Center Co.Ltd.;

    Municipal solid waste incineration(MSWI) fly ash has high leaching toxicity of heavy metal and contains dioxins, which is extremely harmful to the environment. It is designated as hazardous waste. Therefore, fly ash must be stabilized before landfill treatment. By introducing the leaching toxicity of heavy metals and the pollution characteristics of dioxins in fly ash, the research progress of the treatment technology of MSWI fly ash was systematically elaborated for the treatment of dioxins and heavy metals. According to the process principle, it is divided into three types of technologies: physical and chemical treatment, thermal treatment, and stabilization and solidification. The high-temperature treatment process was emphasized. Especially, the plasma melting technology can achieve high-efficiency degradation of dioxins, and the solidification effect of heavy metals is great. In addition, the product of the plasma melting technology has high leaching resistance and environmental stability, which makes it show a better performance in the subsequent use of building materials. Therefore, the plasma melting technology is considered as an effective technology for MSWI fly ash treatment with great development potential and industrial application prospects. The current treatment of MSIW fly ash with development potential was summarized, the disposal principle, research status and industrial prospects of each process were analyzed. Finally, the future improvements and development directions for existing problems were suggested.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 5870K]

  • Water occurrence characteristics and dehydration of low quality coal and slime

    ZHANG Jinlong;FAN Youlin;CHANG Ting;YANG Fan;YAN Guanghui;ZHANG Bo;Shenhua Baotou Energy Co.,Ltd.;School of Chemical Engineering & Technology,China University of Mining & Technology;Key Laboratory of Coal Processing and Efficient Utilization (China University of Mining & Technology),Ministry of Education;

    Coal is the main energy in China, which has greatly promoted the development of national economy. With the exploitation of high-quality coal, the content of fine coal and the difficulty of coal washing increase gradually. For the problem of low-quality coal(fine coal and slime) with high water content and low calorific value in coal preparation plant, the drying research was conducted by moisture meter, thermogravimetric-gas chromatograph-mass spectrometer instrument. The moisture occurrence characteristics and pyrolysis characteristics were examined, the temperature ranges for moisture removal were studied, and the best condition of low-quality coal drying was revealed. The decomposition temperature of coal was studied, and the pyrolysis process at different stages was revealed. The influence of vibration frequency on the separation effect of 6-0.5 mm coal was investigated by compound dry separator. The results show that for the fine coal and slime, the external water content are 17.84% and 39.20%,and the internal water content are 10.97% and 9.54%,respectively. The external water content of slime is higher than that of fine coal, and the internal water content is similar. The pyrolysis process can be divided into three stages. Water escapes before 101.9 ℃,and the critical temperature for the decomposition of macromolecules in coal is 305.7 ℃. For the 6-0.5 mm coal, when the vibration frequency of compound sparator is 36 Hz, the clean coal yield is 45.48% and the ash content is 10.36%, which effectively realizes the quality improvement and ash reduction of low-quality coal.

    2022 07 v.28;No.143 [PaperDigest][OnlineView][HTML全文][Download 21599K]
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