2021年05期目次

  • Dry separator of thin coal seam in Heishan Open-pit Mine

    CHEN Jianqiang;LI Gongmin;XIA Yunkai;ZHANG Bo;CHEN Zengqiang;YAN Guanghui;SHENG Cheng;ZHAO Yuemin;DUAN Chenlong;Xinjiang Energy Co., Ltd.,CHN Energy;Tangshan Shenzhou Machinery Co., Ltd.;Key Laboratory of Coal Processing and Efficient Utilization (China University of Mining & Technology), Ministry of Education;School of Chemical Engineering & Technology, China University of Mining & Technology;

    Based on the climate environment of Heishan Open-pit mine, dry separation process was adopted to achieve coal quality improvement. In order to clarify the raw coal washability of thin coal seams of Heishan Open-pit Mine, the coal quality data were analyzed, the coal type and raw coal quality were determined, and the floating-and-sinking characteristics were analyzed. The separation test of 80-0 mm raw coal was carried out, the particle energy distribution in the bed was studied, and the bed density distribution in the separation process was determined. The response surface analysis was conducted to study the influence of various factors on the ash separation resolution, and the best sorting conditions were determined, and the sorting experiments were carried out, which verified the feasibility of the sorting technology. The results show that the washability of the thin coal seam in Heishan Open-pit Mine is medium.With the increase of frequency, amplitude and gas velocity(factors affecting energy change), the difference in density distribution and ash resolution show a trend of first increasing and then decreasing. Appropriate bed energy input is conducive to the separation and stratification of particles according to density. The response analysis show that ash separation resolution is highly sensitive to changes in various factors. When the frequency is 32 Hz, an amplitude is 2.8 mm, and a gas velocity is 0.6 m/s, the maximum ash resolution is 0.98. Under the optimal separation conditions, the separation density of 80-0 mm raw coal is 1.97 g/cm~3, the E value is 0.22 g/cm~3, the yield of clean coal is 74.92%, and the ash content of clean coal is 21.77%. After re-selection of 13-0 mm clean coal, The ash content is 6.79% lower than that of raw-clean coal, the comprehensive yield of 80-0 mm is 66.99%, and the ash content is 17.91%. The dry process can effectively improve the quality of the product coal of the thin coal seam of Heishan Mine.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 34511K]

  • Fluidization characteristics of multiple dense medium and efficient separation of low-quality coal in dry dense medium fluidized bed

    JIANG Yongning;QI Jian;BA Yulong;WANG Qingfei;ZHANG Zhenxing;GUO Junwei;ZHANG Bo;Xinjiang Energy Co.,Ltd,CHN Energy;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 gas-solid fluidized dry separation is an important and effective way for fine-grained coal separation to improve quality, mineral processing and solid waste recycling in arid and water-scarce regions and alpine regions, and it has great industrial application potential. At present, the fluidized bed used for separation has been studied by many researchers. The basic theory has been studied in depth, including the formation of fluidized bed, fluidized bed aerodynamics, fluidized bed flow model and simulation, etc. However, the low-density separation technology and density adjustment range of dry dense medium fluidized bed still need to be improved. The reasonable selection of dense medium is of great significance to the coal preparation of dry dense medium fluidized bed. It is closely related to the purification and recovery process of the fluidized bed dry coal preparation system, the operation parameters of the separator and the separation effect. A self-made fluidized bed was used to study the fluidization of single component, narrow particle size and wide particle size in two-element dense medium, and the fluidization characteristics of three-element dense medium in a fluidized bed were studied. The fluidization characteristics, expansion rate and particle size of magnetite powder and paigeite powder were compared and analyzed. The results show that both magnetite powder and paigeite powder can reach good fluidized state. With the decrease of dense medium size, the initial fluidized gas velocity decreases significantly, and the expansion property increases gradually. Compared with the mixture of 150-125 μm paigeite powder and 74-45 μm magnetite powder, the bed pressure drop fluctuates more with the mixture of 125-74 μm paigeite powder and 74-45 μm magnetite powder. Under nine different weight ratio conditions, the bed pressure drop of 300-74 μm paigeite powder and 74-45 μm magnetite powder has no obvious fluctuation. With the decrease of the size of dense medium, the expansion property gradually increases. The homogeneity degree of the two-element narrow particle dense medium increases with the increase of the content of paigeite powder. When the two-element wide particle size dense medium is mixed, the approximate horizontal section of the fluidization curve fluctuates more with the increase of fine particles, which is not conducive to form a stable separation environment. With the increase of pulverized coal content, the fluidization effect of ternary dense medium gradually becomes worse. In order to ensure good uniform stability of fluidized bed density, the content of pulverized coal in ternary dense medium should not exceed 15%.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 15126K]

  • Investigation on force characteristics and separation of coal in dry dense medium fluidized bed

    DAI Lin;FANG Shuhai;LI Siwei;LYU Guannan;CHAI Xuesen;DUAN Chenlong;ZHOU Enhui;Xinjiang Energy Co.,Ltd.,CHN Energy;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;

    In recent years, the development of dry separation technology of air dense medium fluidized bed(ADMFB)provides an effective way for clean coal processing in arid and water deficient areas of the world. In the dry heavy medium fluidized bed, the updraft drives the fluidization of dense medium to form a gas-solid two-phase flow bed with pseudo-fluid properties, which creates a uniform and stable fluidization environment suitable for coal separation. The coal particles migrate, float and sink in the bed, and are separated according to density under the comprehensive action of gravity, air drag, medium resistance, bed buoyancy and other forces. The characteristics of coal particles, bed density distribution and operation parameters of fluidized bed are the critical factors affecting the suffering force, settlement characteristics and separation effect of coal particles. Therefore, the migration process of dense particles in the fluidization process and the spatial distribution of bed density were studied. The uniformity and stability of bed density were quantitatively evaluated. The influence of particle size, density, immersion depth and gas velocity on the force properties of coal particles was studied. The response surface method was used to compare the disturbance law and influence degree of different factors. The correlation between the influencing factors and the comprehensive force of coal particles was established. The migration path and stable distribution area of each density component of coal particles with different densities were determined. The results show that the ADMFB with uniform density can be formed by using magnetite powder(0.300-0.074 mm, 2.36 g/cm~3)and glass powder(0.300-0.074 mm, 1.14 g/cm~3)as the binary medium. The binary dense particles are mixed evenly and stably. The bed density fluctuation can be controlled within ±0.01 g/cm~3. The significant degree of the main influencing factors on the force of the selected particles is in the order of particle size, immersion depth and gas velocity. After coal particles are fed into the bed, the density components are rapidly loosened, settled and stratified. The separation time is less than or equal to 8 s. The coal particles with density higher than bed sank rapidly and settled in the area below the bed height of 40 mm. The coal particles with density lower than the bed are loose and migrate laterally along the area near the bed surface, and are distributed in the area above 160 mm. The middle density particles are loose and settled, which are distributed in the bed area above 45 mm.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 12686K]

  • Prediction of minimum fluidization velocity in gas-solid fluidized bed based on machine learning

    BAO Guoqiang;GU Weigen;MU Weiguo;ZHOU Nan;CUI Sen;LI Zhiqiang;LI Yanjiao;ZHOU Enhui;ZHAO Yuemin;DONG Liang;Xinjiang Energy Co.,Ltd.,CHN Energy;Artificial Intelligence Research Institute,China University of Mining & Technology;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;

    Gas-solid fluidized bed is widely used in coal chemical industry, coal combustion, coal separation and other fields due to its high efficiency, flexible operation and other advantages. As one of the most important operating parameters of gas-solid fluidized bed, the minimum fluidization velocity is closely related to the operation design of fluidized bed. Most of the existing models for predicting the minimum fluidization velocity are empirical or semi-empirical formulae, and their accuracy and convenience are still insufficient. In order to accurately predict the minimum fluidization velocity of gas-solid fluidized bed, a prediction model of the minimum fluidization velocity in gas-solid fluidized bed was established based on machine learning, and the internal information behind the model was explored. The minimum fluidization velocity of gas-solid fluidized bed was studied from the aspects of particle properties and equipment conditions. The comprehensive influence on the minimum fluidization velocity was systematically evaluated. The feasibility of predicting the minimum fluidization velocity was verified by using the random forest model, and the relative importance of equipment parameters, particle density and particle size in predicting the minimum fluidization velocity was investigated. The results show that the minimum fluidization velocity is positively correlated with particle size, particle density and bed diameter. The Pearson correlation coefficients are 0.79,0.31 and 0.14,respectively. The particle size has the strongest correlation with the minimum fluidization velocity. Random forest can accurately predict the minimum fluidization velocity according to the particle properties(density, particle size) and the bed diameter, and the determination coefficient of the model is up to 0.875. The characteristic correlation analysis reveals the influence of each characteristic factor on the target variable. The correlation between particle size and minimum fluidization velocity is the strongest, which provides a new idea for predicting the minimum fluidization velocity of gas-solid fluidized bed.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 10238K]

  • Development and challenge of dry coal separation

    LI Siwei;CHANG Bo;LIU Kunlun;ZHOU Chenyang;DONG Liang;DUAN Chenlong;ZHAO Yuemin;Xinjiang Energy Co.,Ltd.,CHN Energy;Key Laboratory of Coal Processing and Efficient Utilization(China University of Mining & Technology),Ministry of Education;School of Chemical Engineering & Technology,China University of Mining & Technology;

    As a non-renewable national strategic resource, coal is still one of the most important basic energy resources in the world. Low quality coal has considerable potential reserves and has become an indispensable energy resource for energy security in China. Coal preparation is the source technology to realize efficient and clean utilization of coal. The traditional wet coal preparation technology strongly depends on water resources. Due to the characteristics of no water, low cost and no pollution, the dry coal preparation technology has provides an effective method for clean and efficient separation and industrial transformation and development of coal resources. The working principle, research status and industrial application progress of air separation, compound dry coal separator, photoelectric separation technology, dry dense medium coal separation technology were analyzed in detail, then the progress of dry coal separation technology at home and abroad was summarized. Based on understanding the progress of the above separation technologies, the limitations of the existing dry separation technologies were pointed out, such as narrow feed size, high water requirement and low intelligence. Then the development trend of coal dry separation technologies was prospected, and the next research focus was pointed out, including breaking through the theoretical bottleneck of fine coal separation and realizing dry separation of whole-grain coal, developing efficient coal separation and drying collaborative technology and solving the problem of water limitation of raw coal, speeding up the research of dry precision separation technology and saving the processing cost of high-quality coal, such as coking coal, carrying out up-scale theoretical research on the separator and realizing the up-grade of the separator, coal-series associated minerals and coal-series solid waste resource utilization, etc.,so as to provide the possible suggestions for the research of dry coal separation technology in future.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 4061K]

  • Development and application of soft-measurement technology for online monitoring of coal quality in power generation

    CHENG Yanting;SONG Lixin;CHI Feng;MA Chao;JING Qiang;WANG Yang;China Datang Corporation Science and Technology Research Institute;Guangdong Datang International Power Generation Co.,Ltd.;Taiji Computer Co.,Ltd.;School of Physics and Optoelectronic Engineering,Shandong University of Technology;

    At present, most industrial online coal analyzers utilize intense energy beam like nuclear radiation scanning, the test utilities are complex, the use and maintenance cost is high, so the on-line detection of incoming coal quality is generally not realized in the field of thermal power in China. Due to the coal quality fluctuation control inefficiency of power generation process caused by coal quality fluctuation, and soft measurement technology for coal quality monitoring begins attracting attention. Utilizing distributed-sensors in the DCS system, soft-measurement of fuel quality of coal fed into the boiler are realized through mechanism analysis and data learning, which meets application requirements for coal-fired power generation with few additional investigation cost. However, coal quality has multiple indexes, identification of different quality index applies different approaches, the soft sensing of incoming coal is lack of systematic technical system demonstration. In this study, the classification and fundamental basis of soft-measurement for coal quality parameters were summarized, and the error analysis of online soft sensing of coal quality was analysed. At last, suggestions of future technological developments of soft-measurement of coal quality were proposed. According to methodological character, soft measurement technologies for coal quality are divided into two types, one type based on mechanism analysis and the other based on machine learning. Soft-measurement of coal quality is more fitted for power generation application. The real-time tracking of the actual coal quality can realize effective regulation of thermal power production process. Coal quality is constructively multiple system, soft-measurement of coal quality based on mechanism analysis builds fundamental models through process analysis of pulverizing, burning, heat and energy transfer, different technical trends are formed. For such technology, explicit models are offered, but the analysis process is easily effected by multiple factors, it is hard to reach accurate results especially for frequent load regulation condition. Coal quality measurement based on machine learning avoids complex mechanism analysis, while on the other hand, sample data set preparing and intelligent modelling facing high requirements for goal of efficient application.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 5388K]

  • Advances on the coal water slurry dispersants

    LI Guo;QIAO Junqiang;LU Haiyun;Shendong Coal Group Co.,Ltd.;National Institute of Clean-and-Low-Carbon Energy;

    Coal-Water Slurry(CWS)gasification and combustion technology is an important part of clean coal technology. High quality CWS has great environmental and economic value for realizing the clean and efficient utilization of coal. The CSW dispersant is one of the main factors affecting the CWS quality. The development of new and efficient CWS dispersant has always been a research hotspot. The conventional dispersants such as lignin based and humic acid sulfonate dispersants have obvious cost advantages with poor stability and high apparent viscosity, which is not suitable for long-time storage or long-distance transportation. Meanwhile, the dispersants such as naphthalene and poly carboxylic acid based are superior to the first two in viscosity reduce of CWS with a high cost. The combination method that mixes the above dispersants together at a certain proportion is effective to make up the shortage caused by one dispersant. However, the attempt to improve the performance of dispersant by chemical modification is uninterrupted, such as adding hydrophilic functional groups as carboxyl, hydroxyl and sulfonic groups and grafting different side chain structure to the main structure of dispersant. In this paper, these achievements were reviewed. The analysis shows that lignin and naphthalene based dispersants are dominated in the CWS market, but the modification of poly carboxylic and nonionic dispersants with low cost modifier is the focus of future research and development, which is expected to achieve a breakthrough in high-performance and low-cost dispersants. In addition, the use of natural products and its waste to prepare CWS dispersants is also a competitive direction in the view of environmental protection and circular economy.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 5313K]

  • Research progress on the properties and applications of direct liquefaction residue of coal

    ZHANG Yajie;XUE Yongbing;LIU Zhenmin;School of Chemical and Biological Engineering,Taiyuan University of Science and Technology;

    In the process of direct coal liquefaction, about 30% of coal liquefaction residues are produced by vacuum distillation. The coal direct liquefaction residues are mainly composed of unseparated heavy oil, unconverted coal, catalysts and other organic and inorganic substances. The development of coal direct liquefaction residues efficient and clean utilization methods are conducive to the rational application of coal resources and the improvement of the integrity and cost of coal liquefaction. This article mainly introduces the composition and structure of coal direct liquefaction residue, and the chemical composition of organic asphaltene, pre-asphaltene, organic macromolecular residue, inorganic ash residue and catalyst in coal direct liquefaction residue are introduced in detail. Through different ways of extraction, high-efficiency extraction and application of coal liquefaction residues can be achieved.The article systemly introduces the contents of coal direct liquefaction residues in gasification hydrogen production, gasification pulping, co-gasification process and gas discharge, etc. The pyrolysis of coal direct liquefaction residues can produce coal tar, and the co-pyrolysis method changes the structure of coal tar and improves the yield of coal tar. The coal direct liquefaction residue as a carbon product can provide a carbon source for it, and the inorganic catalyst in the coal direct liquefaction residue promotes the formation of new carbon materials. The structure of the coal direct liquefaction residue is similar to the structure of natural lake asphalt, and it is a potential asphalt modifier. The modification effect of each component on petroleum asphalt is analyzed by family composition to achieve the modification of petroleum asphalt. Through the compatibility evaluation method, the modification performance of coal direct liquefaction residue is further improved. The application of coal direct liquefaction residue is further prospected. However, a considerable part of the research on the properties and applications of coal direct liquefaction residues is still in the experimental research stage, and there are many problems in the extraction and application stages of coal direct liquefaction residues.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 1350K]

  • Research status and prospect of synthetic applications of 2-methylnaphthalene

    HU Fating;LI Junfang;MAO Xuefeng;CHANG Qiulian;WU Yan;MA Bowen;LIU Min;Beijing Research Institute of Coal Chemistry,CCTEG China Coal Research Institute;State Key Laboratory of Coal Mining and Clean Utilization;

    2-Methylnaphthalene is an important chemical material with high content, wide application and high value in coal-derived oil, petroleum tar and heavy aromatics. In order to extend the processing industrial chain of 2-methylnaphthalene and improve the utilization efficiency, the characteristics, properties and uses of various synthetic compounds of 2-methylnaphthalene were discussed, and the technical characteristics, research status and latest progress of synthesis of these compounds were discussed. Two key technologies for synthesis of 2-methylnaphthoquinone and naphthyl polymer precursors from 2-methylnaphthalene were introduced in this paper and the main synthesis methods were compared and analyzed. The synthesis of 2-methylnaphthoquinone by oxidation of 2-methyl naphthalene can be divided into gas oxidation, peroxide oxidation and other oxidation methods. The gas oxidation method is cheap and easy to obtain from air, and is suitable for large-scale industrial production with continuous operation. However, the reaction conditions are harsh, and the conversion rate of raw materials and the yield of products need to be improved. The peroxide oxidation is green, the reaction conditions are mild, but the cost of peroxide is high and the properties are unstable, which limits its application in industrial production. The oxidation of other oxides mainly uses oxidizing salts as oxidant, which has strong oxidation property, high conversion of raw material and high yield of product. To prevent excessive oxidation, at the same time, the heavy metal wastewater and waste produced in the oxidation process need to be treated thoroughly, which will increase the environmental protection cost of enterprises. 2,6-dimethylnaphthalene and 2-methyl-6-acylnaphthalene are important naphthalene polymer precursors. 2,6-dimethyl naphthalene can be synthesized by disproportionation, methanol alkylation and transfer methylation. The synthesis of 2,6-dimethylnaphthalene by methanol alkylation has the advantages of material, relatively mature technology and simple process, which is a synthesis process of 2,6-dimethylnaphthalene with great application prospect. The synthesis of 2-methyl-6-acyl naphthalene from 2-methylnaphthalene has the advantages of low by-product, high conversion and high yield, which is a research hotspot in the field of synthesizing naphthyl polymer precursors.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 2032K]

  • Governance technology and development trend of NO_x in sintering

    ZHOU Haicheng;GAO Zhifang;LONG Hongmimg;XU Hui;WANG Guangying;GAO Li;School of Metallurgy Engineering,Anhui University of Technology;Key Laboratory of Metallurgical Emission Reduction & Resources Recycling,Ministry of Education,Anhui University of Technology;Anhui Yuanchen Environmental Protection Polytron Technology Co.,Ltd.;

    Sintering flue gas is the largest emission source of pollutants in the iron and steel industry. At this stage, the metallurgical desulfurization and dust removal process is gradually mature, but the removal of NO_x is still in its infancy. Some enterprises have excessive NO_x emissions. With the further improvement of environmental protection indicators, optimizing NO_x treatment process, reducing NO_x emissions in metallurgical flue gas has become the top priority of pollution treatment in the iron and steel industry, which should be paid more attention. The mechanism of N in the sintering process was introduced. Volatile nitrogen participates in the redox reaction. The high temperature and low oxygen conditions promote the reduction reaction to generate N_2 and inhibit the formation of NO_x. At the same time, high temperature promotes the coke nitrogen adsorption capacity and heterogeneous reduction reaction; The characteristics of sintering flue gas were summarized. Its composition is more complex, the content of pollutants is high, the water content and the oxygen content are large, and the lower flue gas temperature leads to lower requirements for the temperature window of the SCR catalyst. These features further restrict the development of sintering flue gas treatment; The existing problems of current several typical denitrification processes and sintering flue gas denitrification technology were compared and analyzed. SCR denitration method is the current mainstream denitration process. The catalytic active components and performance of the catalyst are the core and key of the technology, and it is also a research hotspot in recent years. The new iron-based low-temperature catalyst of γ-Fe_2O_3 containing iron-containing dust is a feasible research direction of denitration catalyst, which has the characteristics of resistance to alkali metal poisoning, good low-temperature catalytic activity, and economical reliability and can further expand the scope of metallurgical resources utilization; The development direction and new technology of denitration were prospected. The research of plasma denitrification and microbial denitrification started relatively late, but due to its smaller effects of flue gas temperature, it can achieve better denitrification effect and has excellent development prospects, but there are several problems that have not been applied in engineering; Improved technology such as the introduction of flue gas recirculation, air staging combustion, low-oxygen combustion and other combustion control technologies can coordinate the flue gas denitration process after sintering by optimizing the structure of the sintering mixture, such as enhanced granulation effect, thick material layer and high basicity sintering, etc. Flue gas NO_x emission concentration; The hierarchical treatment of sintering flue gas has disadvantages such as high investment and operation cost and large area. It is of great significance to develop a reliable, cost-effective and integrated desulfurization and denitrification process. The desulfurization process coupled with SCR denitrification is an important direction for the treatment of sintering flue gas pollutants. By referring to the recent research on some new desulfurization and denitrification technologies and new ideas, the process flow of flue gas recirculation + CO catalytic oxidation + SCR denitrification + CFB/SDA desulfurization is put forward, which can provide some reference for the research and development of denitrification technology in steel works.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 4518K]

  • Research progress on influence mechanism and engineering application of water vapor in nitrogen oxide control technologies

    WANG Jing;ZHANG Ruiping;YANG Fengling;WANG Dongsheng;WU Shaohua;CHENG Fangqin;Institute of Resource and Environment Engineering, Shanxi University;

    During the actual operation of the power plant, it was found that the addition of water vapor can reduce the amount of denitrifying agent used in the SNCR denitration reaction, which has a certain promotion effect on denitrification and also promotes the combustion process. Therefore, studying the influence and mechanism of water vapor on various denitration technologies is of great significance for achieving low-cost and high-efficiency denitration. This paper analyzed and summarized relevant literature reports focusing on the promotion effect and mechanism of water vapor in the denitration reaction. The study found that water vapor indeed can promote the denitration of SNCR, reburning and advanced reburning technologies, but there is no consistent conclusion on the optimal amount of water vapor. The denitration efficiency improvement of adding water vapor in biomass reburning and its advanced reburning were a little smaller than that in pulverized coal reburning, and advanced reburning. The addition of water vapor can effectively promote the generation of OH groups in the SNCR denitration reaction, which can react with the NH_3 reducing agent to generate NH_2 groups, thereby improving its denitration efficiency. The promotion effect of water vapor on reburning is mainly through the formation of OH groups, which increases the volatiles, especially the precipitation of HCN, NH_3, etc., thereby promoting NO reduction. Adding water vapor can increase the denitrification efficiency of advanced reburning technology to more than 80%, it is considered that the denitration mechanism of advanced reburning of biomass by water vapor is similar to the denitration mechanism of reburning, while, the mechanism of advanced reburning of coal powder by water vapor has not been reported. In summary, the influence mechanism of water vapor on advanced reburning should include the both SNCR and the fuel reburning and the interaction between them. However, the current research has not paid attention to the influence on the solid fuel reburning, especially the effects on reduction of NO by coke. Therefore, the influence mechanism and operating conditions of water vapor on advanced reburning and the best reaction conditions should be further studied to provide a strong theoretical support for the application of water vapor in practical.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 6839K]

  • Research progress on collaborative mercury removal of pollution control equipment in ultra-low emission coal-fired power plants

    CAO Xiaoman;LIU Yawen;ZHANG Junmei;JIANG Luxiang;GUO Na;WANG Zuwu;Shandong Power Engineering Consulting Institute Co.,Ltd.;School of Resources and Environmental Science,Wuhan University;

    The treatment of mercury in flue gas of coal-fired power plants mainly relies on the collaborative removal of conventional pollutant purification devices. In order to understand the collaborative mercury removal capacity of pollutant purification facilities in ultra-low emission power plants in China, the field test data of mercury emission from power plants were statistically analyzed. The results reveal that the same type of pollutant purification facilities also have very different mercury removal capabilities. The mercury oxidation efficiency of selective catalytic reduction(SCR)is between 13.2% and 91.1%,and the average mercury oxidation efficiency is 52.7%. Different kinds of dust collectors show different mercury removal efficiency. Among them, LLT-ESP has the best mercury removal efficiency, followed by ESP+FF and ESP. The average mercury removal efficiency of wet limestone gypsum desulfurization system(WFGD)is 54.3%,which is mainly derived from the removal of Hg~(2+). The technical route with LLT-ESP as the core has the highest average mercury removal efficiency in different routes, which is 91.3%. The average mercury removal efficiency of the unit after ultra-low emission transformation is 80.1%,which is about 10% higher than that before transformation.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 4520K]

  • Research progress of the whole process treatment technology for difficult-to-settle slime water

    YANG Yanbin;QU Jinzhou;ZHU Ziqi;ZHOU Anning;School of Chemistry and Chemical Engineering,Xi′an University of Science and Technology;CHN Energy Shendong Coal Preparation Centre;

    In view of the technical problems of difficult-to-settle slime water purification and treatment in wet coal preparation process, such as difficult settling, low treatment efficiency and high cost, this paper discussed the research and application status of new technologies of slime reduction technology, agent system optimization, water quality regulation, electromagnetic field enhancement, microwave treatment, microbial treatment, high efficiency concentration and pressure filtration from the aspects of slime source control, slime water treatment method and slime water terminal treatment equipment, combined with the production practice of difficult settling slime water treatment in Shendong mining area. The problems existing in the industrial application of the whole process treatment technology of difficult-to-settle coal slurry water were analyzed, and the development trend of the technology was prospected. The slime reduction technology is the source of the treatment of difficult-to-settle slime water. The amount of slime entering the slime water system could be reduced by efficient dry screening of feeds using flip-flop screen. For the established and mature coal preparation plants, the yield of secondary slime often could be reduced with measures of the optimization of process flow, the reduction to screen gap of the screen basket, the regulation of operating process parameters. In order to reduce the mixing of fine gangue, the methods for using heavy-medium cyclones with pressureless feed, reducing screen gap of the gangue screen for medium-removing, separately treating unqualified media of gangue, separately settling and treating water of high-frequency sieving under the condition of meeting the production requirements. It could contribute to control the water volume of the slime water system and prevent mixing of coarse-grained materials through strengthening the production organization and water management. The treatment technology of difficult-to-settle slime water is the core of slime water treatment. Inorganic calcium salts and other high-priced metal cations can be added to the slime water to adjust the water quality of the slime water and promote the coalescence of coal slime particles. The yield of slime is effectively reduced by deep classification using electromagnetic vibrating high-frequency screens. The effects of flocculation and sedimentation could be strengthened by improvement of the concentration, filter press process and equipment, using of the electric field, magnetic field, microwave field treatment and microbial flocculation agent. Besides, the side effects of chemical agents on the environment could be reduced. The slime water terminal treatment equipment is the foothold and starting point of the difficult-to-settle slime water treatment. At present, it is mainly developing in the direction of large-scale, localized, high-efficiency, and intelligent.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 1367K]

  • Research and development on deoxidation technology of coal bed methane

    ZHANG Jinhua;LIU Shuxian;QIN Qiang;HE Lixin;National Institute of Clean-and-Low-Carbon Energy;

    Coal bed methane(CBM) is a type of unconventional natural gas resource. The utilizaiton ratio of coal bed methane drained from underground is less than 40% since the low concentration CBM can not be used effectively. The enrichment of this low concentration CBM is an effective way to utilize. However, high content oxygen existing in CBM is an important bottleneck to restrict the utilization of CBM. In view of the existence of oxygen brings certain safety risks and utilization problems in the utilization process, this paper briefly introduces the general situation of CBM resources in china, and the research progress of CBM deoxidation technologies such as combustion, pressure swing adsorption and cryogenic separation was summarized. The principle of deoxidizing technology and the development of deoxidizing materials such as catalyst and adsorbent were introduced. The results show that the catalytic combustion technology is relatively mature, and the development of cheap and highly reactive catalysts is the key to improve deoxidation efficiency. The key of carbon material combustion method is to control the reactive temperature and reduce the methane cracking caused by the relatively high combustion temperature. The key of pressure swing adsorption is the adsorbent with high CH_4/O_2 selectivity. The selectivity directly determines the feasibility and economy of separation. For cryogenic separation, low temperature is required and energy consumption is large, which is suitable for large-scale gas source treatment. Pressure swing adsorption and cryogenic separation have certain basis in industrial demonstration, but there is a risk of crossing the explosion limit in dealing with the low concentration of coal bed methane, process safety assessment and explosion suppression measures are the focus of further improvement. Chemical-looping combustion, nonmetal reduction and membrane separation are all in the early stage of laboratory exploration, which need to be further studied. In the end, it is pointed out that in addition to the continuous improvement of various technologies, the future needs to choose the coal bed methane deoxidization technology according to the advantages and disadvantages of each technology for technical coupling based on the gas source concentration and the enrichment process of deoxidization gas.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 3227K]

  • Feasibility study of direct measurement of raw coal property on conveyor belt by LIBS

    HE Yongchao;YU Ziyu;SHI Libao;QIN Huaiqing;ZHOU Yaning;ZHANG Lifeng;MO Juehui;ZHAO Hang;YAO Shunchun;Hebei Huadian Shijiazhuang Luhua Thermal Power Co.,Ltd.;School of Electric Power,South China University of Technology;Cntest Intelligent Scien-tech Co.,Ltd.;Guangdong Province Engineering Research Center of High Efficiency and Low Pollution Energy Conversion;

    The on-line detection of incoming-coal property is of great significance to optimize the boiler operation and promote the development of intelligent power plant. In recent years, laser induced breakdown spectroscopy has been widely applied in coal property detection, due to its powerful on-line detection. Based on the operation of coal transporting system in the power plant, an on-line detection scheme for LIBS direct measurement of raw coal property on conveyor belt is proposed to meet the basic needs of online detection of incoming-coal property. To validate the feasibility of the detection scheme, the simulation platform for incoming-coal conveyor belt and the LIBS system were set up. 34 actual raw coal samples are placed on the conveyor belt as measurement objects to carry out continuous LIBS measurements and obtain spectral data. According to the spectral characteristics obtained from direct measurement of raw coal, CN388.176 nm is determined as the characteristic peak used in spectra selection and internal standard. Effective spectra selection, spectra averaging and internal standard method are used to reduce the adverse effects of invalid spectra and spectral signal fluctuations. Combined with the partial least squares(PLS)modeling method, the quantitative analysis models of coal property were established, and the good measurements of coal ash, volatiles and calorific value were achieved. The regression coefficient R~2 of the ash, volatile, and calorific value are 0.98,0.97,and 0.97,respectively. The root mean square error of the prediction set are 1.33%,1.03%,and 1.11 MJ/kg, the mean absolute errors are 1.24%,0.97% and 0.88 MJ/kg, respectively. The results validate the feasibility of LIBS directly measuring raw coal quality on the conveyor belt and provide power plants a feasible scheme for online analysis of coal property.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 4837K]

  • Steam pipe rotary-coal slime drying technology for ultra supercritical coal-fired machine

    WANG Linwei;LIU Xianhang;LIU Yunjie;MEI Yuzhu;KONG Guoqiang;Huaibei Shenwan Power Generation Co.,Ltd.;

    In order to explore the comprehensive utilization technology of coal slime and other inferior coal in large coal-fired units and deeply understand the slime drying characteristics and application effect of steam tube rotary dryer slime drying system in ultra supercritical coal-fired units, the laboratory static tests and industrial tests were carried out. Under the static condition of 150-200 ℃,the 50-150 mm large particle size slime was dried at constant temperature. The relationship between slime particle size and drying time was analyzed. The industrial test was carried out by using a new steam rotary tube dryer-coal slime drying system(with a feed rate of 25 t/h)installed firstly in an ultra-supercritical coal-fired unit. The important indexes such as thermal efficiency and energy consumption of the system were analyzed. The results show that in the laboratory static test, it takes more than 50 min for the moisture content of coal slime mass(150 mm)decreasing from 24% to 15%. The coal slime mass drying process experiences two stages: preheating and rapid drying stage(<10 min),stable drying stage. With the increase of drying temperature, the period of preheating and rapid drying stage is shortened. In the industrial test, the drying time of coal slime was slightly shorter than the laboratory results under similar conditions, due to the depolymerization of coal slime in the dryer. With the increase of feed quantity, the moisture content of coal slime products increases. When it exceeds 17%,the system is prone to plugging. When the steam source pressure is 0.35-0.80 MPa, the inlet steam temperature should be reduced to less than 195 ℃,which is beneficial to coal slime drying. In addition, the thermal efficiency of the system can reach 58.6% under the condition of test operation, and it requires 0.112 t of steam and 3.94 kWh of electricity to produce 1 t of coal slime averagely.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 5245K]

  • Characteristics and influencing factors of coal-water slurry pyrolysis

    FENG Fan;YU Juan;ZHANG Yao;LI Boyang;LIN Chen;ZHANG Zhongxiao;School of Mechanical Engineering,Shanghai Jiao Tong University;

    The distribution, composition and yield of pyrolysis products of coal water slurry have an important influence on the effective combustion of coal-water slurry, while H_2,CH_4,CO and other gases produced by pyrolysis of coal-water slurry are conducive to improve the denitration temperature window and the denitration efficiency. In this paper, the coal-water slurry made from Shenmu coal(bituminous coal)was pyrolyzed by a high-frequency heating furnace, and the yield and composition of pyrolysis gas were measured and analyzed. The effects of pyrolysis temperature and heating rate on the pyrolysis characteristics of coal-water slurry were explored. The results show that as the temperature increases, the weight loss rate without water of coal-water slurry continues to increase, increasing by about 10% from 700 ℃ to 1 200 ℃. The yield of volatile matter and pyrolysis gas continue to increase, from 0.50 L/g to 0.73 L/g, which shows that the degree of pyrolysis of coal-water slurry gradually increases. The pyrolysis gas is mainly composed of H_2,CO,CH_4 and CO_2. As the temperature rises, the total volume concentration of H_2,CH_4,CO_(2 )and CO in the total pyrolysis gas decreases in the range of 700-900 ℃,and remains stable in the range of 900-1 100 ℃,and then continues to decline above 1 100 ℃,from initially 90% at 700 ℃ to 78% at 1 200 ℃,in which the volume concentration of H_2,CO_2 and CH_4 decrease in a stepwise manner, while the volume concentration of CO remains almost unchanged. The volume concentration of H_2 decreases most significantly, about 6.1%,while CH_4 decreases by about 4% and CO_2 decreases by about 2.6%. As the temperature increases, the yields of H_2,CO_2 and CH_4 increase first and then decrease, and the peak appears at about 1 100 ℃,while the CO yield continues to increase. The yield of volatiles is affected by the rate of temperature increase. The weight loss rate without water at 667 ℃/min is 6% higher than that at 400 ℃/min. On the whole, the heating rate has not significantly influence on the pyrolysis. The research results provide a reference for understanding the formation characteristics of primary pyrolysis products of coal water slurry.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 5617K]

  • Thermodynamic studies of SNG and power polygeneration system based on coal-steam gasification

    WANG Dan;HE Song;LI Sheng;GAO Lin;Institute of Engineering Thermophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;

    The energy structure is characterized by “more coal, less oil and gas” in China, the Synthetic Natural Gas(SNG)and power polygeneration system with coal gasification technology as the core has wide application prospects in China. However, the coal based polygeneration system based on traditional gasification technology has limitations in further improving energy efficiency. Based on the coal-steam gasification technology, this article integrates an efficient series-parallel SNG and power polygeneration system with a thermochemical recuperation unit. The system model was built in Aspen Plus software. Based on indicators such as thermal efficiency, energy saving ratio and exergy efficiency, the energy utilization characteristics of the system were analyzed. The results show that compared with the SNG and power polygeneration system based on traditional gasification, the thermal efficiency and exergy efficiency of the novel system have been improved by 5.5% and 5.8%,respectively. At the same time, for each set split ratio, there is a best chemical island unreacted syngas recycle ratio to optimize the thermodynamic performance of the system. When the split ratio is 0.5,0.7,0.9,1.0,the corresponding optimal recycle ratio is 4.8,4.4,4.3,4.0 respectively. Also, the series polygeneration system can use energy more reasonably than the series-parallel polygeneration system, and the thermal efficiency, energy saving ratio and exergy efficiency of the series polygeneration system at the optimal recycle ratio can reach 68.06%,20.24%,69.43% respectively. Exergy analysis shows that the two largest parts of the system exergy destruction are mainly distributed in the gasification unit and combined cycle unit, the exergy destruction of the two parts are 17.0% and 6.3% respectively, accounting for 49.4% and 18.3% of the total exergy destruction, respectively. Therefore, polygeneration system based on thermochemical regenerative steam gasification technology has high energy utilization efficiency and carbon emission reduction effect, and can provide an effective energy-saving way for high-efficiency and low-carbon utilization of coal.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 8852K]

  • Effect of chemical modification on adsorption performance of semi-coke

    LI Jun;Yulin Shenhua Energy Co.,Ltd.;

    Semi-coke is a good adsorbent because of its high fixed carbon content, good reactivity and developed pores. Its surface contains a large number of oxygen functional groups, which is easily modified, often used as an adsorbent or catalyst.More pores and better adsorption capacity can be produced by the modified char. In order to study the influence of chemical modification on the adsorption property of semi-coke, the semi-coke produced by Shenmu gas heat carrier vertical pyrolysis furnace was used as raw material and modified by different modification methods such as acid and alkali. The effects of acid and alkali on the pore structure, morphology, specific surface area, deashing rate and adsorption property of semi-coke were studied by FTIR,SEM and nitrogen adsorption methods. The results show that the ash content of semi-coke is reduced after treatment, and the deashing rate of acid-base combined treatment is up to 89.5%. After acid modification, the number of surface acid oxygen-containing groups such as carboxylic acid and phenolic increase, and the specific surface area, pore volume, pore size and adsorption capacity of methylene blue and iodine value decrease. After alkali modification, the specific surface area, pore volume, pore size and adsorption capacity of methylene blue and iodine value increase, and the number of micropores on the surface increase. The specific surface area and pore volume of micropores are 0.009 7 m~2/g and 35.519 4 cm~3/g, respectively. The adsorption capacities of methylene blue and iodine are 1.05 mg/g and 714.11 mg/g, showing good adsorption performance. Under different treatment conditions, the adsorption performance of semi-coke is as follows: alkali treatment semi-coke>primary treatment semi-coke > acid-base combined treatment semi-coke>acid treatment semi-coke.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 5771K]

  • Development of 50 MW CFB coal pyrolysis and combustion multi-generation technology

    LI Chao;LI Guangmin;XIA Zhixiang;TANTAI Zhuxian;FANG Mengxiang;LUO Zhongyang;State Key Laboratory of Clean Energy Utilization,Zhejiang University;Kaifen Dongda Chemical Company,China Pingmei Shenma Group;

    To further promote the industrial application of coal pyrolysis classification conversion polygeneration technology and achieve the clean and efficient resource utilization of coal, the evolution behavior of volatile products and the components distribution of volatile products during coal pyrolysis in a 1 MW demonstration multi-generation facility were investigated.Through the combination of experimental research and theoretical analysis in this paper.The effects of pyrolysis temperature and coal type on the fuel gas yield, tar oil yield, components distribution and heat value of fuel gas were also revealed. The synergistic operation characteristics between pyrolysis reactor and combustion reactor were elucidated during these experimental tests. Based on the data collected from the 1 MW multi-generation system operation a 50 MW CFB multi-generation device which integrated the coal pyrolysis, gasification, combustion, synthesis and other processes into a whole unity was designed to provide theoretic guidance for commercial application of the coal multi-generation technology. The experimental results show that the concentration of main components of CH_4 and H_2 in fuel gas is 41.97% and 28.32% respectively. Under design conditions the yield of tar and fuel gas is 3.16 t/h and 35 262 Nm~3/h. The fuel gas heat value is high to 26.7 MJ/Nm~3. The high tar recovery rate is above 90%,which realizes high gas calorific value and tar recovery, and provides reference guidance for the industrial application of coal pyrolysis classification conversion polygeneration technology.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 5503K]

  • Preparation and electrochemical properties of AC/SWCNTs self-standing thin films by high efficiency combustion

    FENG Yu;LI Shanshan;ZHAO Jiahui;WANG Miao;WANG Jiancheng;MI Jie;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;

    Three kinds of AC(Amorphous Carbon, AC)/SWCNTs(Single-Walled Carbon Nanotubes, SWCNTs)thin films with different component ratios were prepared by low-pressure premixed flame combustion method with anhydrous ethanol as carbon source, ferrocene as catalyst precursor and thiophene as the growth promoter of carbon nanotube, which was used as a self-supporting negative electrode material to assemble sodium ion battery. The crystal structure, micro morphology and composition of the materials were characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and thermogravimetric analysis, and the electrochemical performances of the anode materials for sodium ion batteries were analyzed by charge-discharge performance tests. The results show that with the increase of catalyst content, the layer spacing of carbon materials gradually increases, the crystallization degree of materials decreases, and the amorphous carbon composition increases, which provides space for the reversible storage of Na~+. The composition of the material was analyzed by TG. It is found that when the catalyst content is 0.018 g, the sample(AC/SWCNTs-3)has the largest amorphous carbon content, which is 67.01%. At this time, the carbon layer spacing of the sample is the largest, Na~+ is embedded/stripped, and the cross-linked SWCNTs network structure provides channels for electron transmission. As a carrier attached to amorphous carbon, the decline of capacity is delayed and there is the best electrochemical performance. After 60 cycles of rate performance test, AC/SWCNTs-3 shows good reversibility, and the reversible specific capacity reaches 220.7 mAh/g after 150 cycles at 50 mA/g current density, the electrode can still maintain the specific capacity of 146.7 mAh/g. In addition, the reaction process of sample AC/SWCNTs-3 is a sodium storage mechanism, which is dominated by diffusion control mechanism. At sweep speed of 0.1 mV/s, the capacitive contribution rate is 19.3%. In conclusion, amorphous carbon provides rich active sites in AC/SWCNTs composites, and hollow tubular SWCNTs can be used as channels for rapid electron transmission, ensuring the rapid diffusion and reversible storage of Na~+ in the working process of the battery, so that AC/SWCNTs composites show better electrochemical performance in sodium ion batteries.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 20122K]

  • Depth optimization technology for low NO_x combustion of 300 MW lean coal boiler

    JIANG Ziwei;SU Sheng;REN Qiangqiang;WU Yunkai;YIN Zijun;JIANG Long;HU Song;WANG Yi;XIANG Jun;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

    In the combustion process of lean coal boilers, in order to ensure the ignition, stable combustion and burnout of lean coal, the conditions such as temperature and oxygen content in the combustion process must be fully considered and guaranteed, which is obviously contradictory to the low oxygen and low temperature conditions required for NO_x emission control to a certain extent. Therefore, for the low nitrogen combustion technology of lean coal boiler, how to ensure the low nitrogen combustion without affecting the combustion performance of boiler has always been the difficulty of this technology. Based on the preliminary scheme of low nitrogen combustion technology of boiler, a feasible deep optimization transformation scheme of low nitrogen combustion technology was put forward through system analysis and design. In this paper, for a 300 MW lean coal boiler, the effects of air classification low-nitrogen combustion mode and the area of the bottom secondary air nozzle on NO_x emissions were analyzed through numerical simulation. Based on the preliminary plan of adding three layers of new SOFA wind to the boiler for low-nitrogen combustion reform, through further calculation and analysis, a low NO_x combustion depth optimization for increasing the area of the bottom secondary air nozzle by 1.5 times was proposed. The simulation results show that the NO_x emission is reduced from 473.4 mg/m~3 to 265.3 mg/m~3. The NO_x emission can be reduced by more than 40% after the transformation, and the temperature field and oxygen field of the boiler can be evenly distributed. After the transformation, the actual operation results on site show that the NO_x emission is reduced from 481.6 mg/m~3 before optimization to 269.1 mg/m~3 after optimization, and the emission of nitrogen oxides is reduced by 44.1%,which has realized the safe, high efficient and low pollution operation of lean coal boilers.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 22424K]

  • Design and optimization of local flue guide plate of coal-fired boiler in power plant

    MO Xun;ZHU Dongsheng;YE Zhou;TU Aimin;Guangzhou Institute of Energy Conversion,Chinese Academy of Sciences;CAS Key Laboratory of Renewable Energy;Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development;Yulin University;

    The flow field in the tail flue of coal-fired boiler has a great influence on the service life of its equipment. In order to improve the flow field of the flue at end of the boiler and solve the wear and leakage problem of low-temperature economizer tube bundle due to uneven flow field, and study the influence of guide plates with different design structures on the flow field in the system, the flow field in the original system flue was simulated and analyzed based on ANSYS18.0-FLUENT field simulation software. The results show that the velocity of the flue in front of the low-temperature economizer is uneven due to the change of cross section and the deflection of the direction of the flue. Without the guide plate, the standard deviation(C_v)of the cross section of the heat exchanger at Y=1 700 mm reaches to 70.7%,resulting in the uneven flow field of the heat exchanger, which makes the local flow velocity too high to aggravate the wear of the tube bundle. According to the characteristics of the flue, several guide plates with different structural parameters are set at each key position affecting the flow field. Through a series of detailed analysis and comparison of design schemes, it is found that the plate length, spacing and installation angle of the guide plates set at the position of flue direction deflection or section mutation have a significant impact on the flow field. According to the different characteristics of the positions that affect the flow field of the flue, all the structural parameters of the guide plates were optimized and analyzed. The optimal structural parameters of the guide plates were obtained, and the guide plates with excellent performance was designed. After the corresponding guide plates are added at the corresponding positions, the standard deviation of velocity in the heat exchanger area of scheme 1 is 65.1%,and that in the heat exchanger area of scheme 2 is 55.4%,while scheme 3 greatly improves the flow field in the heat exchanger area, and reduces the standard deviation of velocity in the heat exchanger area to 9.6%.The system resistance only increases by 109.8 Pa, meeting the design requirements. The scheme has high practicability and obvious effect, which provides a good theoretical guidance for practical engineering design.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 29778K]

  • Numerical simulation and optimal design on primary air flow field in medium speed mill of large scale coal-fired units

    ZHANG Jian;XIANG Baixiang;HUANG Jun;LI Yan;WANG Peng;Shenhua Guohua(Beijing)Electric Power Research Institute Co.,Ltd.;CHN Energy Technology& Economics Research Institute;

    In order to reduce the floor area and unit cost, the layout of newly-built coal-fired units in China is mostly very compact in recent 20 years. Among them, changing the front coal bunker to the side coal bunker has become one of the common choices for coal-fired units. The layout of side bunker brings two problems: one is that the pipeline of remote pulverizing system is long, which is easy to lead to uneven distribution of air and powder; Second, the primary air duct is greatly shortened, the air volume measuring device does not have a suitable installation position, and the accuracy of primary air measurement decreases. In order to solve the accidents such as large fluctuation of combustion and air distribution, powder blockage at the outlet of the pulverizer, ignition and excessive NO_x concentration at the outlet of the furnace of 660 MW ultra super-critical side coal bunker coal-fired boiler in a power plant due to the distortion of primary air measurement of the medium speed pulverizer, the flow field of the circular primary air pipe at the inlet of the pulverizer was studied based on the(fluent)numerical simulation software. The primary air flow distribution in the original design and after straightening the air duct were calculated, respectively. The results show that there is an obvious transition point in the primary air velocity distribution at 1 to 3 times the diameter after the pipe turns, with the increase of primary air flow. However, the air volume measurement before and after this point is distorted, resulting in large fluctuation of air volume, when the inlet air velocity is 9.5 m/s. By straightening the inlet pipe, the flow field of the primary air duct is more regular, and the transformation of the flow field tends to be gentle, avoiding the distortion of the primary air measurement. By installing rectifying device, moving the air volume measurement device to the bottom of air powder pipe and appropriately extending the length of straight pipe section, the distortion of air volume measurement can also be avoided to a great extent. If the site space does not meet the conditions, avoiding the components or structures that are easy to cause poor flow stability such as tee, turn, reducer or valve in the short pipeline, and also avoid the impact of distortion of primary air volume measurement on unit disturbance.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 10531K]

  • Cold experiment research of multi-stage air-regulating pre-combustion cyclone burner

    NIU Yanqing;XUE Xufeng;ZHANG Hao;HUI Shien;School of Energy and Power Engineering,Xi′an Jiaotong University;

    Pulverized coal preheating low-nitrogen combustion technology is the research focus of combustion technology. In order to respond to the era development requirements of "energy saving, environmental protection, green and low-carbon economy",and solve the environmental problems of a large number of pollutants produced during the combustion process of coal such as nitrogen oxides and sulfur oxides, a multi-stage air-regulated pre-combustion swirl burner was designed and developed on the basis of a large number of previous studies on preheating combustion technology. The pre-combustion chamber pulverized coal preheating combustion technology is coupled with the air staged combustion technology to generate a highly reducing atmosphere recirculation zone, effectively controlling the generation of NO_x,and improving the ignition performance of refractory coals. In this paper, the influence of different air distribution ratios on the aerodynamic field of the multi-stage air-regulated pre-combustion swirl burner was mainly studied through the cold state model test, and the flow field was tested and analyzed by using the new three-hole probe velocity measurement method to carry out. The results show that under the condition of the constant total air volume, when the primary air rate, the swirl internal secondary air rate and the external secondary air rate are 20.8%,37.5% and 31.2%,the length, width, area and return flow of the recirculation zone reach the maximum, and the the reflux effect is the best, which is conducive to pulverized coal ignition and low NO_x combustion. The existence of the pre-combustion chamber is conducive to the formation of a recirculation zone for stable combustion of pulverized coal, and the swirl internal secondary air is the main factor that affects the airflow characteristics of the recirculation zone, which dominates the formation of the central recirculation zone in the precombustion chamber. The external secondary air affects the temperature of the recirculation zone of the precombustion chamber through the airflow in the suction furnace, which is the fundamental reason for the generation of the peripheral recirculation zone in the precombustion chamber. The primary air with a certain rigidity and the secondary air in the direct current will compress the recirculation zone and affect the combustion stabilization effect of the burner.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 19870K]

  • Compositional analysis of deposits and corrosive layer on water-walls inside a coal-fired boiler under low-NO_x combustion mode

    WANG Yibin;WANG Meng;TAN Houzhang;ZHANG Sicong;ZHANG Xiaodong;YANG Zuwang;School of Energy and Power Engineering,Xi′an Jiaotong University;China Energy Investment Corporation Branch Company of Yuci Power Generation;Xi′an GeRui Power Science and Technology Co.,Ltd.;

    The reducing atmosphere at these regions between the top burner and the SOFA nozzle becomes stronger after the low-NO_x combustion retrofit for a coal-fired boiler. Under this condition, the risk in high-temperature corrosion on water-walls increases sharply. Taking a 330 MW Tangentially Pulverized coal boiler as the object, samples were collected from water-walls surface at different position. The ash and corrosion layer were characterized by elements and minerals, and the causes of slagging on the water-cooled wall in the furnace and the high-temperature corrosion mechanism of pipe wall were analyzed. The results show that Si and Al elements in slags adhered to the water wall at different positions mainly exist as Al_6Si_2O_(13) and Al_2SiO_5,which increase the fusion temperature of ash particles. Fe element mainly exists in Fe_2O_3 and its enrichment is significantly higher than alkali or alkali earth metals. S and Zn elements and a small amount of Pb element are highly enriched in the layered deposits on water-walls which are located at the central height of B and F layer of burner. The content of Zn element is as high as 20%,mainly in the form of PbS,ZnS and ZnAl_(1.04)S_(2.13). The fly ashes deposited on the surface of slags collected at the central height of F layer burner still contains about 7% unburnt carbon, which indicates that swirling flue gas may scour the water-walls. These fly ashes are mainly composed of Si, Al, Fe, C,S and Zn elements, mainly in the form of mullite, hematite and sulfides. The corrosive layer on the water-wall is mainly Fe_(1-x)S,Fe_7S_8,Fe_9S_(10) and Fe_3O_4,and contains a small amount of PbS and PbO_(1.57). The formation of Fe_(1-x)S with varied crystal structure may be attributed to the difference in the local H_2S partial pressure and temperature. Zn and Pb containing species are enriched in layered deposits via vaporization-condensation and the release from unburnt carbon particles adhered on depositing surfaces. While silicoaluminate-rich and iron-rich ash particles stick to the surfaces of water-walls via inertial impaction and thermophoresis deposition.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 19041K]

  • Flowfield optimization of SCR system in large size coal-fired units NO_x ultra-low emission modification

    ZHENG Yan;YAO Xuan;WANG Dongsheng;CHEN Xunqiang;LI Xiaojin;Beijing Engineering Research Center of Power Station Gas Cleaning,Beijing Guodian Longyuan Environmental Engineering Co.,Ltd.;

    Due to the problems of unstable SCR performance and excessive ammonia slip in coal-fired power plants, taking the SCR denitration system of a representative 660 MW supercritical pulverized coal boiler as an example, and combined with the characteristics of ammonia injection grid and stationary vortex ammonia injection mixer, the multi-dimensional optimization and transformation of the stationary vortex denitration ammonia injection mixing device was studied, and the process of flue gas flow, change and mutual mixing at various positions in the flue was analyzed. An optimization based on multi-effect staged mixing, zoning vortex ammonia injection and forced rectification was proposed. According to the CFD calculation results, the optimized design scheme of the SCR reactor system proposed in this paper can fully achieve the requirements of uniform flow field distribution and NH_3/NO_x mixed distribution. At the cross section in the first catalyst layer inlet, the coefficient of variance for flue gas flow velocity is less than 15%,and coefficient of variance for NH_3/NO_x mixing is less than 5%. The incident angle of the flue gas reaching the first catalyst layer is less than 10°. After the modification of the SCR reactor device, the overall distribution of NO_x concentration at the outlet of the denitrification device is uniform, the average concentration is lower than the ultra-low emission limit, and the ammonia escape concentration value is much lower than the design value 3×10~(-6). The practical test results further verify the reliability of optimization method. Therefore, the upgrade idea and theoretical research method are of great significance to guide the ultra-low emission transformation of SCR system of large coal-fired units.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 7984K]

  • Emission characteristics of condensable particulate matter from an ultra-low emission coal-fired power plant

    SUN Hetai;HUANG Zhijun;HUA Wei;SHI Zhipeng;DUAN Lunbo;Jiangsu Frontier Electric Technology Co.,Ltd.;Key Laboratory of Energy Thermal Conversion and Control,Ministry of Education,Southeast University;

    In order to study the influence of air pollution control devices(APCDs)on the condensable particulate matter(CPM)emission characteristics from an ultra-low emission coal-fired power plants in China, the EPA Method 202 A recommended by the U.S. Environmental Protection Agency was used to simultaneously sample the flue gas before and after the wet flue gas desulphurization(WFGD)and after the wet electrostatic precipitator(WESP). Then the migration, transformation and emission characteristics of CPM in the flue gas were obtained based on sample analysis. Through further data analysis, the migration and transformation process of CPM in APCDs and the synergistic removal effect of existing APCDs on CPM in the power plant were studied. The results indicate that CPM dominates the particulate emission in the flue gas after ESP. The mass concentrations of CPM at the WFGD inlet, WFGD outlet and WESP outlet are 24.07,12.71 and 7.72 mg/Nm~3 respectively, while the proportions in TPM are 61.83%,53.34% and 76.06% respectively. With the flue gas flow, the proportion of the inorganic composition of CPM gradually decreases, from 69.38% at the WFGD inlet to 54.40% at the WESP outlet. The inorganic part of CPM is mainly composed of acid radical anions such as SO_4~(2-),NO_3~- and Cl~-,and the mass concentration of SO_4~(2-) is the highest. The removal efficiency of CPM by WFGD and WESP is 47.20% and 39.26%,respectively. The combined removal efficiency of CPM by WFGD and WESP is 67.93%. The results can provide a good reference to the CPM emission and control from an ultra-low emission coal-fired power plant.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 14720K]

  • Effect of acidification evaporation on agglomeration and removal of submicron fine particulate matter

    LI Jinping;XIONG Yingying;SONG Tingting;ZHAO Chaoqun;HU Fei;School of Electric Power and Architecture,Shanxi University;

    In order to further reflect the removal effect of coal dust, through the flue temperture coupling of wet acid ash experimental platform, the dust-containing flue gas dust removal efficiency and particle size of submicron fine particles in simulated flue gas before and after dust removal were tested under the different conditions of cooling, coupling humidification, acidificationan and the changes of the concentration by the acidification evaporation method. The agglomeration and removal performance of submicron fine particles matter were studied. When the temperature of simulated hot dust-containing flue gas is 120 ℃,the absolute humidity is 4.20%,the concentration of ash particles matter is 72.362 μg/m~3,during the process of cooling and condensing to the limit of 80 ℃,the humidity, acidity and the particle concentration of fly ash are adjusted to 8.90%,4.183×10~(-6),385.27 μg/m~3 under the optimum working condition, and the mean diameter of the volume distribution of submicron fine particles agglomerates from 20.370 μm to 51.355 μm; After the dust collector, the efficiency of dust collector reaches 99.63%,the submicron fine particles are effectively removed, the mean diameter of the number distribution is reduced from 1.769 μm to 0.869 μm.The experimental result shows that the adsorption of aerosol droplets by fly ash particles is improved, the mutual adhesion between submicron fine particles is enhanced, the agglomeration of submicron fine particles is intensified, and the agglomerate particle size is effectively captured by the dust collector, and the removal and enhancement of submicron fine particles are promoted after flue gas vaporized by temperature coupling humidity acid ash.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 6692K]

  • Influencing factors of catalytic hydrolysis of carbonyl sulfide in blast furnace gas

    WANG Bin;LIN Yuting;LI Yuran;WANG Jian;ZHU Tingyu;Key Laboratory of Green Process and Engineering,Institute of Process Engineering,Chinese Academy of Sciences;Innovation Academy for Green Manufacture,Chinese Academy of Sciences;

    It is of great significance to implement the source control of FGD for the whole process of ultra-low emission transformation in the iron and steel industry, at present. The difficulty of desulfurization of blast furnace gas is the removal of carbonyl sulfur(COS). Aiming at the emission characteristics of blast furnace gas with frequent temperature fluctuations, high pressure and complex components, alumina catalyst was used to catalyze and hydrolyze COS,and the effects of temperature, chloride ion, dust and oxygen on the conversion rate of carbonyl sulfur were investigated. The influence degree and mechanism of various factors on COS hydrolysis were analyzed. The results indicate that the temperature has the most significant effect on the efficiency of COS hydrolysis. When the temperature is increased from 50 ℃ to 150 ℃,the hydrolysis efficiency increases from 49% to 90%. The higher temperature is conducive to the occurrence of COS hydrolysis reaction. Chloride ion reduces the specific surface area of the catalyst by 20.1%,and the pore volume by 40.0%. The catalyst deactivation caused by chloride ion comes from two aspects, including the reduction of alkaline center on the surface of hydrolysis catalyst, the blockage of catalyst channels and the covering of some active sites. Chloride ion has the most significant inactivation effect. The nano dust in blast furnace gas has a blocking effect on the catalyst pore, reduces the specific surface area of the catalyst by 43.5% and the pore volume by 60.0%. The hydrolysis efficiency decreases significantly with the accumulation of dust. When the oxygen concentration is 0.5%,the hydrolysis efficiency decreases from 85% to 82% with the extension of reaction time and there is no significant decline. Still, when the oxygen concentration increases to 1%,the hydrolysis efficiency decreases from 85% to 66%,the inhibition effect of sulfur deposition is obvious when the oxygen concentration increases. Anti-chlorine, dust resistance and oxygen resistance are the key factors of hydrolysis catalyst. Pre-removal of multiple components in industry can be adopted before hydrolysis to reduce the impact of blast furnace gas impurities on COS hydrolysis efficiency.

    2021 05 v.27;No.135 [Abstract][OnlineView][HTML全文][Download 8516K]



Clean Coal Technology            京ICP备05086979号-19

Website  Copyright © 2019 Clean Coal Technology 
Coal Tower, Hepingli, Chaoyang District, Beijing, China. 100013
Tel:  86-10-87986452 / 010-87986451           E-mail:  jjmjs@263.net