• Dynamic cost analysis of hydrogen production from wind power and photovoltaic power

    SUN Xudong;CHENG Xuelei;WANG Shumeng;WANG Jiawei;ZHAO Yuying;ZHANG Bo;School of Management,China University of Mining & Technology-Beijing;Beijing Sino Hytec Co.,Ltd.;School of Management,Xiamen University;

    With the gradual maturity of hydrogen production from new energy generation, the cost of hydrogen production directly affects the commercialization and application of hydrogen energy industry. Based on the changes of input and operating cost of water electrolysis hydrogen production technology, a dynamic cost calculation model was constructed for four combined schemes of electrolytic water hydrogen production, including alkaline water electrolysis cell(ALK) + wind power, proton exchange membrane water electrolysis cell(PEM) + wind power, alkaline water electrolysis cell(ALK) + photovoltaic(PV) power and proton exchange membrane water electrolysis cell(PEM) + photovoltaic(PV) power, from the respective of new energy generation cost. And the impact of relevant factors on the cost of hydrogen production was studied through sensitivity analysis. The results show that the cost of hydrogen production of four combination schemes reduces by 13.95%, 29.22%, 19.55% and 31.03%, respectively, during the research period(2017—2020), and the cost of hydrogen production in 2020 is 17.90, 28.27, 21.54 and 32.23 yuan/kg, respectively. Power consumption and power generation cost are the most potential factors to reduce the cost of hydrogen production in the four schemes. Through the comparative analysis of the economy of different hydrogen production technologies such as other power sources and traditional petrochemical energy, it is found that in different hydrogen production scenarios, the hydrogen production technologies from low to high cost are hydrogen production from coal, industrial by-product, natural gas, coal + Carbon Capture and Storage(CCS), ALK wind power, methanol, ALK PV, ALK valley electricity, PEM PV and PEM valley electricity.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 18142K]

  • Status and development trend of rapid load regulation technology for circulating fluidized bed boiler

    HU Xiannan;DENG Boyu;LIU Huanpeng;YANG Dong;YANG Hairui;Department of Energy and Power Engineering,Tsinghua University;State Key Laboratory of Low-carbon Thermal Power Generation Technology and Equipment,Harbin Institute of Technology;State Key Laboratory of Multiphase Flow in Power Engineering,Xi′an Jiaotong University;

    In the background of the carbon peaking and carbon neutrality goals, China is accelerating the construction of a new power system in which the proportion of new energy sources is gradually increasing, and coal-fired power plants are currently the most economical regulating power sources for the large-scale grid connection of renewable energy. Due to their inherent advantages, circulating fluidized bed boiler units are crucial for the deep and flexible peaking of coal-fired power plants. However, because of their peculiar design and mode of operation, these units have a low load change rate, making it necessary to increase their capacity to absorb large amounts of new energy for the grid. The influencing factors that governed the load change rate of circulating fluidized bed boilers were analyzed including the inertia of gas-solid two-phase flow, combustion of solid particles, heat transfer between the water side and the furnace side, hydrodynamic safety, dynamic matching problem of the turbine and boiler, and the physical mechanism of inertia generation was also explained. The key technologies to improve the rapid load change capability of the circulating fluidized bed unit were summarized. By accelerating the flow parameters, improving the heat transfer coefficient, reducing the heat capacity of the furnace side, enhancing the heat transfer between the furnace and the water side, strengthening the combustion reaction, optimizing the control strategy, and considering the feasibility of industrial size boilers, a comprehensive optimization technology solution was proposed, namely the concept of an "intelligent take in/out" system, which was validated in a 135 MW circulating fluidized bed boiler. The results indicate that it is possible to enhance the boiler′s average load change rate by 16% and sustain a short-term maximum load variation rate of up to 4%/min. According to this, using a data-driven dynamic model of the thermal system, a multi-temporal matching operation technology of the thermal system incorporating innovative technologies, an advanced collaborative control system with "three self-integrated", and a reference to the established energy storage and utilization technology of pulverized coal-fired power plants, the design idea of a circulating fluidized bed unit with flexible operation at a wide range of load was provided, which offered theoretical guidance for future practical industrial applications in China.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 29215K]

  • Modeling of nitrogen oxide emission in circulating fluidized bed for deep peak regulation

    GAO Mingming;GUO Jiongnan;YU Haoyang;WANG Yake;YUE Guangxi;School of Control and Computer Engineering,North China Electric Power University;Huaneng Renewables Co.,Ltd.;Department of Energy and Power Engineering,Tsinghua University;

    In order to respond to the green environmental protection spirit of the 19th National Congress of the Communist Party of China and meet the ultra-low emission requirements of circulating fluidized bed units, it is of great significance to establish an accurate NO_x emission concentration mechanism control model for the design of denitrification automatic control method of circulating fluidized bed units. Based on the combustion mechanism of circulating fluidized bed boiler, the model of immediate combustion carbon was established, and the fuel nitrogen was divided into volatile nitrogen and immediate combustion carbon nitrogen to construct the self-generation model of NO_x in the furnace. The NO_x self-reduction model was derived by considering the reduction effect of CO and immediate combustion carbon on NO_x. A selective non-catalytic reduction denitrification model was constructed, and a circulating fluidized bed nitrogen oxide emission model suitable for deep peak shaving was established based on the above models. The relationship between operating parameters and NO_x emission concentration under deep peak regulation and the influencing factors of selective non-catalytic reduction denitrification efficiency were explored. The simulation verification test shows that the established circulating fluidized bed NO_x model has achieved good simulation results. The average prediction time of the model calculation value under steady-state conditions is 114 s, and the average relative error with the measured value is 2.50%. The average prediction time of the model under deep peak shaving is 126 s, and the average relative error between the calculated value and the measured value is 5.42%. The calculation of the model is 2-3 minutes earlier than the actual measurement, which has a certain prediction effect.The designed NO_x emission concentration model in this paper can provide a reference for the future research of circulating fluidized bed units to adapt to deep peak regulation, rapid load change and ultra-low emission.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 11250K]

  • Stability characteristics of reheat steam temperature of large-scale CFB boilers at low load

    YANG Zhongzhi;LU Xiaofeng;JUE Jiayi;MENG Baosheng;WANG Pengcheng;School of Energy and Power Engineering,Chongqing University;Geely Baikuang Group Co.,Ltd.;Shanxi Hepo Power Plant Co.,Ltd.;

    As one of the key process of flexible power generation, long-term stable low load operation technology plays an important role in the continuous expansion of renewable energy grid connection. It is very common to adopt the operation mode of uneven coal feeding in order to reduce pollutant emissions or adjust bed temperature in the process of load regulation of circulating fluidized bed(CFB) boiler, and this mode put forward higher requirements for the design and operation of CFB boilers. At the same time, the flue gas temperature at the outlet of CFB boiler is low at low load. How to ensure that the steam parameters reach the rated value is one of the urgent problems to be solved to realize the flexible operation of CFB boiler. The parameters of two 350 MW supercritical CFB boilers under coal cut-off and low load operation conditions were deeply calculated and analyzed, and the methods to stabilize the reheat steam temperature at low load were studied. The results show that when the boiler operates under coal cut-off conditions with partial coal feeding ports interrupted, the bed temperature, furnace outlet flue gas temperature, furnace outlet oxygen content and high-temperature reheated steam temperature are basically positively correlated with the coal feeding rate at each coal feeding port. However, the coal feeding deviation and bed temperature deviation have little effect on the outlet steam temperature deviation of water-wall because of the positive flow response characteristics of the water-wall of supercritical CFB boilers. Based on the above research, a boiler transformation and operation optimization technical scheme for stabilizing the outlet steam temperature of high-temperature reheater in supercritical CFB boiler under long-term peak shaving and low load operation was proposed, which could ensure the basic stability of steam temperature at the outlet of high-temperature reheater at low load.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 28708K]

  • Experiment and theoretical calculation of flow instability in deep peak-shaving of supercritical units

    YANG Dong;NIE Chao;ZHOU Ke;HE Gaoxiang;ZHANG Xirong;State Key Laboratory of Multiphase Flow in Power Engineering,Xi′an Jiaotong University;Xi′an Thermal Power Research Institute Co.,Ltd.;Yuhuan Branch,Huaneng (Zhejiang) Energy Development Co.,Ltd.;

    In order to study the flow instability in the tube during the deep peak shaving and low load state of supercritical units, the flow instability in the inclined smooth tube with 20° inclination angle was experimentally studied and analyzed. The typical oscillation characteristics of nucleate boiling starting point oscillation, pressure drop oscillation and density wave oscillation were summarized, and the effects of mass flow rate, inlet subcooling and upstream compressible volume on nucleate boiling strarting point oscillation and density wave oscillation under low pressure parameters were emphatically analyzed. The results show that the flow pulsation in the tube can be weaken and the flow stability of the working fluid in the heating tube can be improved due to the increase of mass flow rate. The influence of inlet subcooling and compressible volume on the oscillation is dual and the law is relatively complex. In addition, a typical one-dimensional single channel vertical tube instability calculation loop was established, and the variation of heat flux and mass flow were calculated and analyzed. According to the results, the inlet and outlet flows oscillate inversely with time, and the critical heat flux and critical mass flow rate of loop instability are obtained. In the low load operation condition of the unit, the heat flux of the heating tube is much lower than the critical heat flux, and the mass flow rate is much higher than the critical mass flow rate, so as to ensure the stability of the working fluid flow in the heating tube. The flow instability of the working fluid in the inclined tube and the vertical upward heating tube can be determined by dimensionless parameters.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 33547K]

  • Research progress of fast variable load method on steam working medium side of thermal power unit

    ZHANG Yuanyuan;ZHANG Pusen;NIE Hao;YANG Fengling;CHENG Fangqin;Institute of Resources and Environment Engineering,Shanxi University;State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources,Shanxi University;Shanxi Guojin Coal and Electricity Co.,Ltd.;

    As the rapid development of renewable energy puts forward higher requirements for deep peak regulation of thermal power units, the variable load regulation performance of thermal power units has become one of the important factors affecting the economic benefits of thermal power plants. Based on the review of the development of rapid variable load methods, various fast variable load methods on the working medium side were systematically summarized, including condensate throttling technology, feed water bypass regulation technology, heating extraction regulation technology, regenerative steam extraction regulation technology, back pressure regulation technology, advance energy balance strategy(AEB) technology, etc.,and the principles of these methods were introduced in detail. The development status of each method was summarized, and the applicable scope, variable load performance, advantages and disadvantages of each method were analyzed and compared. It is found that at present, condensate throttling technology and heating extraction steam regulation technology are relatively studied and applied, and play an obvious role in responding to load change instructions and improving variable load capacity at the initial stage of variable load. The research on variable load rate of pulverized coal fired boiler is more mature than that of circulating fluidized bed boiler, and the variable load rate is generally higher. Finally, the development trend of rapid load change rate promotion of thermal power units in the future was put forward, and on the basis of continuing to develop the existing fast load change methods, a new coordinated control strategy was designed and applied, which combined various regulation methods with traditional coordinated control. The application of the coupling of energy storage technology and thermal power units and the search for a wider range of peak regulation and more economical means on the basis of existing units will further improve the climbing speed of thermal power units, reduce the minimum stable output and increase the peak regulation and frequency regulation capacity of the power plant.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 12826K]

  • Feedback characteristics of steam parameters during load variation in thermal power units in the context of deep peaking

    FENG Fuyuan;ZHENG Qiwei;CHEN Heng;PAN Peiyuan;XU Gang;LIU Tong;School of Energy,Power and Mechanical Engineering,North China Electric Power University;

    With the introduction of the "double carbon" strategy in China, the installed capacity of renewable energy generation increases constantly, and thermal power units play an increasingly important role in grid peaking. In order to study the feedback characteristics of steam parameters during load variation in thermal power units, a dynamic model of a 300 MW thermal power unit was established on the Dymola platform, and the common plant control configuration was embedded in the model to study the dynamic characteristics of the unit with different magnitude load changes and different rate load changes. The results show that during the same rate of load variation, the main steam temperature varies in a smaller range due to the embedded main steam temperature control system, and the range of reheat steam temperature is relatively large due to the absence of reheat steam temperature adjustment strategy, with a minimum of 529.0 ℃. During the same magnitude of load variation, the slower the rate of load variation is, the smaller the deviation of the main steam temperature from the rated value is, and the reheat steam temperature has the same trend at different variable load rates, and eventually reaches the same stable value.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 19881K]

  • Experiment on ignition distance of pulverized coal stream with rich oxygen in one-dimensional furnace

    YAN Gaocheng;ZHAO Hujun;ZHANG Jianhua;AN Lisheng;School of Electric Power, Civil Engineering and Architecture,Shanxi University;CHN Energy Long Yuan Blue Sky Energy Conservation Technology Co.,Ltd.;Datang Shanxi Renewable Power Company;

    In order to cope with the problems of combustion instability of pulverized coal during deep peak shaving in thermal power boilers, an oxygen-rich stable combustion method was proposed, and coal powder airflow ignition tests were conducted in a one-dimensional furnace.The influence of oxygen concentration, primary air velocity and pulverized coal concentration on ignition distance of pulverized coal was studied.Four oxygen concentrations were selected for study, i.e. 21%(air), 25%, 30% and 35% in thd progress of experiments, the primary air speed was designed as 18, 23, 28 and 33 m/s respectively, and there werefive working conditions for coal powder concentration, namely 0.2, 0.3, 0.4, 0.5, and 0.6 kg/kg(calculated by the mass of coal powder carried by each kilogram of air). The data from on the ignition distance of coal powder airflow were given under different working conditions, with detailed analysis on the experimental data and its variation rule. The results show that the ignition distance will be shortened by 82.5 mm along with the increase of 1% in oxygen concentration, but the values of the shorten of ignition distance decrease gradually with the continuous increase of oxygen concentration. The variation rate in ignition distance shows an increasing trend with the increase of primary air velocity, especially when the wind speed is greater than 28 m/s, the primary air velocity has a significant effect on ignition distance. The influence of pulverized coal concentration on ignition distance appears to be complex, as the optimum pulverized coal concentration increases with the increase of oxygen concentration. By comparing the experimental results, it is concluded that the influence of oxygen concentration and primary air speed on ignition distance is greater than that of pulverized coal concentration. Finally, the mathematical model with specific reference to oxygen concentration and ignition distance of pulverized coal was fitted by experimental data, which revealed that there is an exponential function relationship between ignition distance and oxygen concentration.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 12725K]

  • Preparation and catalytic performance of hierarchical porous silica-supported copper catalysts for dehydrogenation of methanol to methyl formate

    QUAN Yanhong;JIN Yuting;WANG Na;ZHAO Jinxian;REN Jun;State Key Laboratory of Clean and Efficient Coal Utilization,Taiyuan University of Technology;College of Chemical Engineering and Technology,Taiyuan University of Technology;

    Methyl formate is an important downstream product in coal chemical industry, which is mainly produced employing copper catalyst for methanol dehydrogenation. However, the agglomeration and sintering of copper are the key factors limiting the catalyst performance. A series of ordered hierarchical porous silica(HPS) presenting both mesopores and micropores were fabricated at different hydrothermal temperatures and used for preparing supported copper catalysts with ammonia evaporation and impregnation methods. Dehydrogenation of methanol to methyl formate(MF) over Cu/HPS catalysts was investigated and found that the catalyst activity decreased in the order of Cu/HPS-130> Cu/HPS-160> Cu/HPS-100> Cu/HPS-130-W. The characterization results show that the texture properties of HPS is heavily affected by the hydrothermal temperatures. The HPS-130 support shows more ordered hierarchical structure with appropriate pore size distribution compared with HPS-100 and HPS-160, which can promote the dispersion of Cu particles and prevent agglomeration and sintering of active copper species during the reaction. Moreover, the Cu/HPS-130 catalyst by the ammonia evaporation method exhibites the optimal catalytic performance with methanol conversion of 38.7% and MF selectivity of 79.8% under 0.2 MPa with 300 ℃, significantly superior to Cu/HPS-130-W prepared through impregnation method. The excellent catalytic performance of Cu/HPS-130 can be attributed to the formation of Cu-O-Si species, derived from the strong interaction between surface silica and copper precursor in the process of ammonia evaporation approach, which greatly inhibiteds the stripping of copper particles on the Cu/HPS catalysts.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 39236K]

  • Pretreatment and oxygen-depolymerization of coal tar pitch to prepare benzene polycarboxylic acids

    GU Bao;WANG Yugao;LIU Gang;SUN Yuqin;NIU Zeshi;SHEN Jun;College of Chemistry and Chemical Engineering,Taiyuan University of Technology;Shanxi Intellectual Property Protection Center;

    Coal tar pitch(CTP) is abundant in aromatic ring structures, which would facilitate preparing high added value benzene polycarboxylic acids(BCAs) by oxygen-depolymerization of CTP. However, during the preparation of BCAs by alkal-O_2 oxidation of CTP, part of CTP is bonded to the inner wall and bottom of the reactor, which hinders CTP further oxidation. Extraction with CH_3OH and air oxidation were used in CTP pretreatment, and the influence of pretreatment methods was explored on the preparation of BCAs by alkali-O_2 oxidation of CTP. Some light components of CTP could be removed after extraction, reducing adhesion between CTP and the reactor. Then, the extraction residue of CTP with CH_3OH was further pre-oxidized by air, which introduced the oxygen-containing functional groups, thus increasing the collision between extraction residue and aqueous alkali. In the resulting water soluble acids from oxidation of the pre-treated CTP, the selectivity of BCAs can reach 80%. Furthermore, the relative content of benzenepentacarboxylic acid and mellitic acid in BCAs could increase up to 24%.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 14096K]

  • Composition, structure and properties of low melting Fischer-Tropsch waxes

    YU Yanan;CI Donghui;ZHANG Shengzhen;CHEN Shengli;ZHANG Wei;LI Hu;JIANG Chenguang;National Institute of Clean-and-Low-Carbon Energy,Beijing;College of Chemical Engineering and Environment,China University of Petroleum,Beijing;CTL Company,China Energy NingXia Coal Industry Company;

    The composition, structure and properties of No.52 F-T wax and four kinds of No.52 petroleum wax were investigated by the use of Gas Chromatography(GC), X-ray diffraction(XRD), Differential Scanning Calorimetry(DSC)and other characterization methods. The results show that the five waxes are mainly composed of long-chain alkanes, and in compared with petroleum waxes, the F-T wax has narrow carbon number distribution, highn-alkane component content, high saybolt color value, low iso-alkane component content,low needle penetrationvalue, and low oil content. At room temperature, both F-T and the petroleumwaxeshave the orthorhombic crystal structure. F-T wax has similar DSC as petroleum wax with respect to a weak solid-solid phase transition peak and a strong solid-liquid phase transition peak. According to the results of the polarized microscope, the oblique square sheet-shaped crystals are arranged closely. In the process of cooling, the radial size of the sheet wax crystal gradually increases, and the wax crystal will continue to form a large solid crystal group, thus forming a three-dimensional spatial network structure. It indicates the high content of n-alkanes in the wax of No.52, which is consistent with the GC results.The No.52 F-T wax is better than petroleum wax in terms of physical pr-operties and chemical composition, and is similar to petroleum wax with respect to crystal structure and thermal properties.The No.52 F-T wax can be used as petroleum wax. The low-toxicity special extraction agent developed by NICE can realize the production of No.48-54 fully refined paraffin wax in the aromatics-free system, which is expected to replace the traditional solvent.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 18244K]

  • Effect of acid and alkali pretreatment on methane production from peat

    WANG Ying;HAO Siwen;MA Litong;WANG Zaiyao;School of Chemistry and Chemical Engineering,Inner Mongolia University of Science and Technology;Inner Mongolia Engineering Research Center of Comprehensive Utilization of Bio-coal Chemical Industry;

    Peat methane conversion has the status of low methaneproduction. It is necessary to explore the effect of acid and alkali pretreatment on peat methane production, to promote peat biomethane conversion. Using herbaceous peat as raw material, biomethane fermentation was carried out after acid and alkali pretreatment, the effects of acid and alkali pretreatment on peat methane fermentation daily gas production, total gas production, humic acid concentration, acetic acid concentration, glucose concentration, pH value were analyzed. The results show that the highest daily gas production value on the 5th day of the acid pretreatment group is 8.71 mL/g, which is 193.27% higher than that of the acid pretreatment control group, and the peak daily gas production of the alkali pretreatment group is 3.67 mL/g on the 5th day, which increases by 83.5% than the alkali pretreatment control group. The total gas production of the acid pretreatment group is 41.95 mL/g, which is an increase of 90.68% compared with the acid pretreatment control group, and the total gas production of the alkali pretreatment group is 44.27 mL/g, which is 61.28% higher than the alkali pretreatment control group. Acid and alkali pretreatment are beneficial to promote the degradation of organic matter in the peat methane fermentation system, and alkali pretreatment has better effect on the production of biomethane from peat, significantly increase the biomethane production from peat.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 15101K]

  • Combustion performance of desulfurized slag-CuFe_2O_4 mixed oxygen carrier in coal chemical chain

    LI Xugang;WANG Wei;LI Jun;GUO Chaofan;XU Binghui;LIU Tongqing;ZHANG Gang;School of Electric Power,North China University of Water Resources and Electric;Zhuhai Shenzhen Energy Hongwan Power Co.,Ltd.;

    The waste CaSO_4 from desulfurized gypsum is used as resource to prepare calcium-based oxygen carrier for chemical looping combustion, which has the characteristics of easy access to raw materials, low cost and high oxygen loading rate. The desulfurized slag was used as raw material, CaSO_4-CuO, CaSO_4-Fe_2O_3 and CaSO_4-CuFe_2O_4 mixed oxygen carriers were prepared according to the template-sol-gel combustion synthesis method adopted by the research group. Five reduction and oxidation cycles of the four oxygen carriers and coal were carried out in a high temperature fixed bed reactor. Discovery of the reaction mechanism and sulfur release rule of coal chemical chain were studied in detail. The results show that the mixed oxygen carriers of desulfurized slag-CuO reaction activity is obviously improved, and the loaded CuO reduces the release of sulfur-containing gas. Desulfurized slag-Fe_2O_3 improves the reaction activity of the oxygen carrier. Desulfurized slag-CuFe_2O_4 mixed oxygen carriers increases the carbon conversion efficiency, has good reaction activity and circulation characteristics, and it is completely feasible to be used in coal chemical looping combustion. The activity of oxygen carrier of desulfurized slag mixed with Cu and Fe increases obviously, but the mixed oxygen carrier has partially sintered and deactivated during multiple cycles. In the side reaction of desulfurization slag mixed oxygen carrier and coal, Cu and Fe show good sulfur fixation effect, in the side reaction of desulfurized slag-CuFe_2O_4 mixed oxygen carrier and coal, the peak concentration of SO_2 gas is only 37×10~(-6).

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 28218K]

  • Research progress on synergistic removal of multi-pollutants from municipal solid waste incineration flue gas in China

    QUE Zhengbin;LI Debo;XIAO Xianbin;LIU Pengyu;CHEN Zhaoli;CHEN Zhihao;FENG Yongxin;National Engineering Laboratory of Biomass Power Generation Equipment,North China Electric Power University;China Southern Grid Power Technology Co.,Ltd.;College of Power Engineering,North China Electric Power University;

    The technology of pollutant removal from municipal solid waste incineration flue gas in China are becoming more and more mature, but there are some problems with complex system and high cost. If the collaborative removal technology of multi-pollutants in flue gas can be adopted to replace two or more removal technologies in the existing process, the process system can be effectively simplified, the occupation area can be reduced, and even the cost of pollutant removal can be reduced. The cooperative removal technology of multi-pollutants from municipal solid waste incineration flue gas in China was summarized and discussed from the perspectives of removal principle, research progress, technological process, industrial application and application effect. The main advantages and disadvantages are as follows: the low temperature plasma cooperative removal technology has strong adaptability to flue gas, which can remove many kinds of flue gas pollutants such as NO_x, SO_2, HCl, Hg~0, dioxin and so on, with high efficiency, but the equipment cost and the operation power consumption are high. The synergistic removal technology of carbon-based materials can also remove a variety of flue gas pollutants, and can recover resources by desorption and regeneration, but the removal efficiency is low and there is a risk of secondary pollution. The synergistic oxidation removal technology is mainly aimed at NO_x, SO_2 and HCl pollutants, which requires the process to be set up after dust removal, and mainly has the problems of low denitrification efficiency and difficulty in treating wastewater products. The synergistic removal technology of SCR denitrification is an improvement of SCR catalyst, which requires a high cost of catalyst, but the removal efficiency of Hg~0 and dioxin is not high, and affects the denitrification process and the treatment of scrapped catalyst. the synergistic denitrification technology with composite catalytic media has better removal effect on dust and dioxin, but the cost of filter bag is relatively high. Other technologies, such as the synergistic removal of metal compounds by adsorption/oxidation, currently have relatively few research applications. Based on the current development of collaborative removal technology, it can be concluded that cost and removal efficiency are still the main factors limiting the application of technology, and it is still necessary to promote technology to reduce cost and increase efficiency, and further develop and mature. In addition, due to the differences in physical and chemical properties of different pollutants, there is a phenomenon of mutual influence in the process of collaborative removal, but the current research is less involved, and further research is needed to avoid the phenomenon of competition and suppression, as far as possible to achieve mutual promotion and collaborative removal.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 9090K]

  • Experiment on the NO_x reduction by the selective non-catalytic reduction inside the air-flow bed pulverized coal industrial boiler

    DUAN Lu;CUI Yuhong;MENG Changfang;LI Hui;ZHANG Chao;Beijing Tiandi Rongchuang Technology Co.,Ltd.;

    Selective Non Catalytic Reduction(SNCR) denitrification technology is one of the most important technology for denitration from coal-fired industrial boilers. The NO_x removal efficiency of SNCR in the utility boiler is generally low. And few work has been done to study on the SNCR from industrial boilers. In the study, the temperature inside the chamber of the furnace and the NO_x emission concentration with different spray gun positions, the hydraulic pressure and the gas pressure were measured for a 20 t/h entrained-flow boiler, and the denitrification performance of SNCR in an entrained flow bed coal powder industrial boiler was studied. The results show that the temperature window of SNCR using urea is range of 790-850 ℃, which is located around the central region of the furnace. The better NO_x removal efficiency can be achieved with the spray gun on the centre of the side wall in comparison with that on the top of the furnace. The depth and angel of the spray gun inside the furnace have less influence on the NO_x removal efficiency. When the spray gun is located the best position, the NO_x emission concentrion is 38 mg/m~(3 )with NO_x removal efficiency of 87.2%, satisfying the ultra-low emission standard. The flow rate of the spray gun increases with the increase of the hydraulic pressure or the decrease of the gas pressure. When the hydraulic pressure is larger than the gas pressure, the excellent atomization can be obtained and the small liquid droplet can be uniform distributed like a fan. When the ammonia-nitrogen molar ratio is larger than 2.38 and less than 3.00, the lower the hydraulic pressure is, the higher the denitrification efficiency is. The SNCR denitrification efficiency is higher and ammonia escape is less with hydraulic pressure larger than 0.30 MPa and less than 0.35 MPa, as well as gas pressure greater than 0.29 MPa and lower than 0.40 MPa. The homogeneous droplet size distribution and the uniform spatial distribution have more important impact on the NO_x removal efficiency than that of the sector angle.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 16547K]

  • Occurrence and emission characteristics of polycyclic aromatic hydrocarbons in CFB boiler

    LIU Xiaoxu;WANG Lusong;ZHANG Xiaoguang;FAN Xiaohua;Hebei Jiantou Shahe Power Generation Co.,Ltd.;Hebei Ji-Yan Energy Science and Technology Rsearch Institute Co., Ltd.;

    In order to understand the distribution and emission of polycyclic aromatic hydrocarbons(PAHs) in flue gas of circulating fluidized bed(CFB) boiler, the gaseous and granular PAHs in flue gas of a 200 MW CFB boiler were collected and analyzed, and the occurrence and distribution characteristics of PAHs in gas and solid of flue gas were studied. The content of PAHs in three solid samples ofcoal, fly ash and slag was analyzed. The results show that the final PAHs emission concentration of CFB boiler unit is 4.03 μg/m~3, with the gas phase and solid phase PAHs concentration of 1.88 μg/m~3 and 1.66 μg/m~3, respectively. The gas phase PAHs in the flue gas are dominated by 2-5 rings, while the solid PAHs are dominated by 4 and 5 rings at the beginning of boiler emission. After a series of ultra-low emission control facilities treatment, the final emission of PAHs are mainly 2 and 3 rings. The total amount of PAHs in coal sample is 26.20 μg/g, with the content of 3-5 rings. The total amount of PAHs in slag and fly ash is 3.12 μg/g and 3.85 μg/g, respectively, mainly consisting of 3-4 rings. The overall collaborative removal efficiency of PAHs by all ultra-low emission control facilities can reach 97.46%. The results show that the synergistic removal effect of existing flue gas treatment facilities can meet the corresponding emission requirements.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 12158K]

  • Dynamic prediction of the NO_x concentration at SCR system outlet based on MIC-CFS-LSTM model

    WU Kangluo;HUANG Jun;LI Zhenghui;RUAN Bin;LUO Sheng;LU Zhimin;YAO Shunchun;School of Power,South China University of Technology;Guangzhou Zhujiang Electric Power Co.,Ltd.;School of Automation Science and Engineering,South China University of Technology;

    Aiming to improve the prediction accuracy of the concentration of nitrogen oxides(NO_x) in the flue gas at the outlet of selective catalytic reduction(SCR) system for coal-fired power plants, a prediction model method based on the maximum information coefficient(MIC) and long-short term memory(LSTM) neural network was proposed. Firstly, MIC was used to estimate the delay time between various input parameters and the recorded NO_x concentration, and the data were reconstructed according to the estimated delay time. Then the MIC value of the reconstructed data was used as an index to evaluate the correlation between input variables and output variables, and the correlation-based feature selection(CFS) algorithm was used to select the input variables. Finally, based on the data after time delay reconstruction and variable selection, the dynamic prediction model of NO_x concentration at SCR outlet was established using LSTM neural network. The model was used to analyze the recorded operation data of a 320 MW coal-fired unit in Guangdong. The results show that the LSTM prediction model established after time delay reconstruction and variable selection has high accuracy, superior to deep neural networks(DNN) model and radial basis function(RBF) model, with the mean absolute percentage error of 2.58% and the root mean square error of 2.02, which can meet the requirements of field application.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 24077K]

  • Air membrane protection technology for water wall of opposed combustion boiler

    PENG Zonggui;SUN Jun;LIAN Lingxian;SU Fangwei;LIU Yongsheng;DU Zhihua;MENG Xinyu;SHAN Hengjie;GUO Wenhai;PENG Longfei;Huaneng Qinbei Power Generation Co.,Ltd.;Xi′an Thermal Power Research Institute Co.,Ltd.;

    After the ultra-low emission transformation of domestic coal-fired unit boilers, there are varying degrees of high-temperature sulfur corrosion problems in the boiler water wall, especially the opposed combustion boiler, which seriously threaten the safe and stable operation of the boiler.In order to fundamentally solve the problem of high temperature sulfur corrosion of water wall, an air membrane protection technology was proposed to prevent high temperature sulfur corrosion of opposed combustion boiler water wall. The numerical calculation software was used to simulate and calculate the flue gas composition near the water wall during boiler operation. Taking the volume fraction of O_2, CO and H_2S components in the flue gas as the main research object, the position, number of layers, vertical inclination and air volume ratio of the air membrane protection nozzle were optimized, and the research results were compared and verified through the on-site verification test.The numerical calculation research and field test results show that after the application of air membrane protection technology, the changes of boiler thermal efficiency and NO_x volume concentration at the inlet of SCR denitration reactor are insignificant, and the boiler operation parameters are normal, which will not have an adverse impact on the normal operation of the boiler.After the application of air membrane protection technology, the average volume fraction of O_2 near the water wall can reach more than 5.0%, which is more than 5 times higher than that before application, and the average volume fraction of H_2S can be reduced by more than 85% compared with that before application, which can be controlled below 100 μL/L.The reducing atmosphere in the area near the water wall is eliminated and the concentration of corrosive gas H_2S is significantly reduced.The high-temperature sulfur corrosion ofwater wall can be fundamentally treated and the safety of boiler operation is significantly improved.The air membrane protection technology of water wall has a good demonstration effect on the prevention and treatment of high temperature sulfur corrosion of boiler water wall of the same type of unit.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 42845K]

  • Review on the preparation of fracturing proppant from coal-based solid waste

    ZHAO Xuesong;LIU Qi;The Unconventional Petroleum Research Institute,Beijing Key Laboratory for Greenhouse Gas Storage and CO2-EOR,China University of Petroleum-Beijing;

    In recent years, the unconventional oil and gas exploration and development has made important progress in China. Hydraulic fracturing technology has become an important measure to increase oil and gas production. As an important part of fracturing technology, proppants have attracted attention in terms of the types, parameters, fracturing fluid carrying and self-migration. Fracturing proppant is an important material for supporting fractures to keep open during hydraulic fracturing, which is the key to improve unconventional oil and gas recovery. However, fracturing proppants are faced with the problems of resource depletion and high production costs caused by over-exploitation of raw materials. In order to solve these problems, the preparation of fracturing proppants from coal-based solid wastes that are consistent with the composition of fracturing proppant raw materials has attracted much attention. The production, properties and comprehensive utilization of coal-based solid wastes were summarized. The research progress of fracturing proppants prepared from coal-based solid wastes at home and abroad was mainly discussed. Coal gangue and fly ash are the most common and polluted coal-based solid wastes, and their chemical compositions are mainly composed of SiO_2 and Al_2O_3. Pore can be produced by CO_2, water vapor and organic matter in the residual carbon and the decomposition of organic matter in coal gangue and fly ash during the sintering process, which are wrapped by the liquid phase to form closed pores, playing a similar role as pore-forming agent, to effectively reduce the apparent density and volume density of fracturing proppant and improve the conductivity of proppant. The use of coal-based solid waste to prepare fracturing proppants cannot only effectively reduce the consumption of natural minerals, reduce production costs and alleviate environmental pollution, but also obtain fracturing proppants that meet industry standards, realizing the resource utilization of coal-based solid waste. Finally, the development and application trends of fracturing proppants prepared from coal-based solid wastes were prospected. Proppant materials will develop towards low-cost, low density, high-strength and multi-functional development direction in the future.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 16477K]

  • Investigation on the fragmentation behavior of coal and corresponding semicoke particles of different ranks at different residence time

    QIAO Kai;ZHONG Shan;TANG Siyang;MA Kui;SONG Lei;YUE Hairong;LIANG Bin;School of Chemical Engineering,Sichuan University;Institute of New Energy and Low-carbon Technology,Sichuan University;

    During the processes of coal combustion and gasification, the fragmentation of coal particle occurs throughout the whole reaction process. Coal particles fragment due to different reasons at different residence times, and the fragmentation behavior and particle size distribution variations caused by different mechanisms are also different. However, the fragmentation mechanisms and applicable models at different residence times are yet not clear. In order to investigate the fragmentation behavior of different coals and semi-cokes at different residence times, coals ofdifferent ranks including anthracite, bituminous coal, lignite and the corresponding semicokes were used as test samples for the high-temperature fragmentation experiments carried out in a horizontal-chamber furnace at 1 473 K under nitrogen atmosphere. In addition, a particle thermal stress model was developed with ANSYS finite element analysis software, and the fragmentation mechanism of different coals and their semicokes were analyzed based on the experimental and numerical simulation results. The simulation results show that the thermal stress induced primary fragmentation should occur in less than 2 s after heating for anthracite and different semicokes with low volatile matter content. As expected, the high-temperature fragmentation experiment also shows that these samples indeed only suffer thermal stress fragmentation in the initial 2 s. Bituminous coal and lignite continuously release volatiles during the residence time of 10 s, and the primary fragmentation occurs mainly due to the devolatilization. For the bituminous semicoke and lignite semicoke, numerous weak connections are produced during the pretreatment pyrolysis process, and obvious secondary fragmentation is observed in 6-10 s, and in the later period of the experiment, the fragmentation severity of the two semicoke samples is greater than that of the raw coal samples.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 15661K]

  • Effect of lipophilic groups of PSS dispersant on the slurry formation characteristics and surface adsorption behavior of non-stick coal

    YE Zefu;MENG Xianliang;WU Guoguang;Shanxi Gemeng US-China Clean Energy R&D Center Co.,Ltd.;School of Chemical Engineering & Technology,China University of Mining & Technology;

    To improve the status quo of low slurry formation concentration and poor slurry performance of non-stick coal, Herein, Shenhua non-stick coal(SNC) was used as the object of study, and five kinds of sodium polystyrene sulfonate(PSS) dispersants with different lipophilic strengths were selected. The mechanism of the effect of the dispersant lipophilic groups on the slurry formation of SNC was investigated by examining the constitutive relationships between the strength of PSS lipophilic groups and the rheological properties, stability performance, wetting performance and adsorption behavior of SNC coal-water slurry. The results show that the strength of the lipophilic groups of PSS dispersants significantly affects the stability, rheology and apparent viscosity of the non-stick coal slurry. The longer lipophilic chain segments, the increases cross-linking between molecules and the larger spatial potential resistance formed make the slurry more stable. However, the apparent viscosity and rheology of coal-water slurry will be extremely high when the polymerization degree of PSS is 187 because the adsorption amount of dispersant molecules on the coal surface and its adsorption constant KL value increase and then decrease with the increase of PSS polymerization degree. SNC particle surface, which in turn forms uniform water molecule adsorption sites on the coal particle surface and promotes the formation of a uniformly textured hydration film.The SNC coal water slurry prepares with the dispersant content of 0.6% of dry coal powder and the slurry concentration of more than 61% has better slurry performance.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 23627K]

  • Analysis and suggestion of carbon emission in thermal power plants under the background of carbon peak and carbon neutrality

    LIU Gaojun;Jibei Electric Power Research Institute,State Grid Jibei Electric Power Co.Ltd.,North China Electric Power Research Institute Co.Ltd.;

    The mainstream methods of calculation and verificationfor carbon emission was introduced, and calculation of carbon emission for a typical 660 MW coal-fired unit, 365 MW gas-fired unit and 660 MW oil-fired unit was introduced. Under given conditions, the total carbon emissions of the three types of thermal power plants are 2 303 751 t, 573 945 t and 1 988 626 t/a respectively, and the ratios of carbon emissions to electricity generation are 0.827 9,0.373 0 and 0.714 7 t/a respectively. Gas units emit the lowest carbon emissions per unit of electricity generation, only 45 percent of that of coal-fired units. Accordingly, oil-fired units emit 86% of the carbon emissions of coal-fired units. The burning of fossil fuels commonly accounts for more than 99% of the total carbon emissions from coal-fired power plants. The proportion of carbon emission from desulfurization process is related to the sulfur content in coal. The smallest proportion of carbon emissions is generated by net electricity purchases. In order to effectively regulate and reduce carbon emissions, it is suggested to comply with the development trend of high parameter and large capacity of coal-fired units, and actively deploy low-carbon and zero-carbon energy such as photovoltaic, wind power, nuclear power and hydropower.It is necessary to promote carbon sequestration methods such as technological and ecological carbon sequestration, develop green financial products, and standardize carbon emission trading markets.

    2023 06 v.29;No.154 [Abstract][OnlineView][HTML全文][Download 2118K]