Integrated Intelligent Energy

Configuration of electrode and plate in ESP and numerical simulation of particle migration in the electric field

CHEN Bing, GUO Yongheng, LI Hongjiao, LIU Baiqian, ZHANG Ganyang, ZHAO Haibao

2020, 42(9): 1-8.

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Electrostatic precipitators（ESP） are widely used in power plants，waste incineration，glass production and many other industries.Studying the configuration of discharge electrode and dust collecting plate（hereinafter referred to as electrode-plate） systematically is important for ESP in improving its efficiency.The discharge characteristics，flow field characteristics，particle trajectories and dust collection efficiency of the electrode-plate with six different configurations are studied by simulation.It is found out that the current density distribution near the plate surface is significantly affected by the shapes of electrodes，and the electrode-plate configured needle electrode is of the greatest current density.Due to the concave and convex structure of the dust collecting plate，the peak current density is always generated at the corner of the plate.And the sharp electrode tip will create an electric field intensity with high peak values on the surface of the electrode wire.Because of the prominent influence of electrodes' shape on the air flow distribution，needle shaped discharge electrode can speed up the maximum velocity of ionic wind.Particle trajectories and relative dust collection efficiency of six different electrode-plate configurations are calculated，and the one configured needle electrode and 480C pressed plate is of the highest dust collection efficiency.

Numerical simulation for synergistic control on denitration in the pulverized coal boiler with air staging and flue gas circulation

BAI Hao, ZHANG Jian, GUO Xinwei, LIU Yicheng, MA Qianhui, ZHANG Zhongxiao

2020, 42(9): 9-15.

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Numerical simulation was taken on a 75 t/h pulverized coal boiler in a power plant，to study the effect of its synergistic control on air staging and flue gas circulation on its combustion characteristics in furnace and NOx emission.The modeling results show that the temperature and CO volume fraction at the furnace outlet rise with the increase of SOFA rate，while the NOx mass concentration drops.And with the increase of flue gas circulation rate，the oxygen volume fraction in the secondary air to furnace declines，yet the denitration efficiency goes up.When the flue gas circulation rate exceeds 15%，the combustion stability will be affected.Synergistic control on air staging and flue gas circulation can make the furnace temperature distribute evenly along furnace height.Having taken the optimized scheme（SOFA rate=25%，flue gas circulation rate=15%），the efficiency of synergistic denitration reaches 61% without prominent effect on the CO volume fraction at furnace outlet.It shows that this optimized scheme can lead to a better low-nitrogen combustion with a decent burn-out rate.The research results have certain theoretical guiding significance for the precise control on denitration of pulverized coal boilers.

Numerical simulation of spraying effects and impacts on the desulphurization tower shell with two types of nozzles

LIN Yu

2020, 42(9): 16-25.

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Numerical simulation for spraying effects of desulphurization towers with solid and hollow cone nozzles were investigated respectively by computational fluid dynamics (CFD) method, through which the diffusion and distribution characteristics of slurries were obtained, and the erosion on the tower shell made by impingement of near-wall slurries was also explored. The main results are as follow. No matter what types of nozzles are used in four-layer spray, the profiles of gaseous velocity magnitude, pressure, turbulent kinetic energy and temperature fields are alike, and the liquid phase contributes to the similar rectification effect of flue gas. For the spray layers with solid cone nozzles, the mass concentration of droplets and the thickness of the liquid film on the tower shell increase gradually from the top to the bottom. Sprayed from hollow cone nozzles, intensive slurries near the tower shell jet out in umbrella-shape film and impinge severely on the wall，generating high-concentration arc one by one on the wall，while the droplets rebounding from the wall create low mass concentration areas beneath the arcs. The higher the liquid mass concentration on the wall is, the higher the local erosion rate is.Corresponding to the four-layer spray taking hollow cone nozzles, four waved belts of high erosion rate appear on the shell. Taking the hollow ones as near-wall nozzles, the maximum wall erosion rate in spraying zone is 5 times as much as that taking solid cone nozzles. Thus, solid cone nozzles is the best choice for near-wall nozzles in spray towers.

Selection and design of SCR catalyst for a high-temperature dedusting and denitration integrated device

WANG Wei, WANG Lele, KONG Fanhai, CHEN Mu, YAO Yan, LEI Siyuan

2020, 42(9): 26-31.

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A demonstration project of a high-temperature dedusting and denitration integrated device for a 350 MW coal-fired power generation unit was taken as the research object，and the device's high-temperature low-dust layout was compared with the regular high-temperature high-dust layout. The impact of the two layouts on the selection and design of SCR catalyst was analyzed from technical and economic aspects.Through the lateral comparison and analysis on related data， it is concluded that integrated arrangement can alleviate the risk of wear， ash blockage and chemical poisoning of the catalyst. Selecting small aperture honeycomb-shaped catalyst with 35 holes can reduce the total volume of the catalyst. The chemical life of SCR catalyst can be extended from 3 years （24 000 h） under conventional high-temperature high-dust arrangement to five to six years in a relatively clean environment. At the same time， this integrated arrangement contributes to reducing the investment and operation cost of the device. Studying the integrated arrangement is of great significance for the scientific design of SCR denitration device and its technology development.

Prediction model for the pH value of absorption tower slurry based on LSTM neural networks

CUI Boyang, WANG Yonglin, WANG Yun, SUN Daping, WANG Hua

2020, 42(9): 32-36.

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In the limestone-gypsum wet desulfurization systems of thermal power plants， the pH value of circulating slurry in absorption towers is an important parameter that affects the performance of desulfurization systems. Therefore， establishing an effective pH value prediction model is fundamental for improving the desulfurization efficiency. The absorption tower system has the characteristics of massive data volume and variable parameters which have strong correlations. Thus，feature extraction and Pearson's r correlation analysis were performed on the data from a plant-level SIS （Supervisory Information System） database.Then， the extracted features were taken as the input of the Long Short-Term Memory （LSTM） neural network to obtain a prediction model for the pH value of desulfurization slurry. The model was applied to a supercritical 330 MW unit coal-fired unit desulfurization system in predicting the pH value of the absorption tower. The root mean square error （RMSE） of the pH values predicted by LSTM neural network model is 0.004， and the mean absolute error （MAE） is 0.003； The test shows that the data tracking results made by LSTM neural network model is of little fluctuations， small errors and high stability.

Application of intelligent model in denitration control system optimization

SUN Zhe, LIU Zhenbo

2020, 42(9): 37-44.

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Current denitration systems of thermal power plants has some problems such as delayed measurement at denitration inlets and outlets， distorted values at some NOx measuring points， and inconsistency between values measured at denitration reactor outlets and denitration environmental protection devices. To deal with these problems， a 300 MW power plant is taken as an example for the intellectualization and optimization of its denitration control system. The optimized denitration system can meet the requirements of ultra-low emission， and prevent ammonia escape led by excessive ammonia. Artificial intelligence technology is used in building the SCR denitration system model which can be continuously improved by powerful self-taught learning and intelligence development of the technical optimization control system（TOCS）.Then，the operation state can be predicted and the control quantity can be accurately calculated.After the running of TOCS， quality control of denitration systems can be largely improved with reduced ammonia spraying volume and mitigated ammonia escape on the premise of NOx emission conforming to standards.

Review and prospect of researches on boilers´ flue gas acid dew point

LIU Xiuru, LI Peipei, WANG Xianpeng, LU Xuge, WANG Zhiqiang

2020, 42(9): 45-55.

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Flue gas acid dew point is an important parameter in setting boilers´ exhaust temperature and preventing low-temperature corrosion.After considering the influencing factors of acid dew temperature（ADT） comprehensively， the volume fractions and partial pressures of SO3 and water vapor were considered to be the most direct influencing ones.After introducting empirical formulas for ADT， application conditions and calculation errors of modifier formulas for empirical formulas from the Soviet Union and other commonly-used empirical formulas were summarized. The pros and cons of each empirical formula were compared.The Soviet Union empirical formula that has considered the influence of ash is not suitable for low-sulfur fuels. The measurement of volume fractions and partial pressures of SO3 and H2SO4 in flue gas brings difficulties to other empirical formulas which have a wider application range，though. In conclusion， the prospect for ADT measurement and calculation is given based on the status quo and shortages of current researches.And considering different combustion conditions ，the empirical formulas with better accuracy， reproducibility and applicability are deduced .

Effect of ultra-low emission transformation on emission reduction of thermal power plants in Anhui Province

WANG Runfang, MA Dawei, HUANG Qishun, CHEN Jian, YU Jing, CHENG Jing, ZHANG Qiliang

2020, 42(9): 56-62.

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Ultra-low emissions transformation for coal-fired power plants in Anhui Province was made from 2014 and basically completed in 2019. Comparing the emission of SO2， NOx and particulate matter before and after the transformation， the discharge performance and emission reduction of the three pollutants above was calculated and taken as the basis for quantitative study on ultra-low emissions transformation for coal-fired power plants. Taking WRF-Chem model， air quality improvement made by ultra-low emissions transformation was assessed. The results show that the SO2， NOx and particulate matter discharged from coal-fired power plants in Anhui decreased from 40 174.1， 65 947.2 and 14 683.6 t in 2014 to 12 579.5， 23 709.3 and 1 817.6 t in 2019， with reduction ratios of 68.7%，64.1% and 87.6%， respectively. WRF-Chem stimulated the pollutant distribution under two different scenarios， whose results showed that after the ultra-low emission transformation in Anhui Province， the average mass concentrations of SO2， NOx， PM2.5 and PM10 in the atmosphere decreased by around 0.41， 1.49， 1.28 and 2.07 μg/m3， being down by 4.0%， 4.1%， 2.7% and 2.8% roughly. The results show that ultra-low emission transformation has a significant effect on the air pollutant reduction， while PM2.5 and PM10 show a limited reduction affected by non-thermal power sources. The study providing ideas for the further pollutant control.

Economic analysis on white plume treatment for coal-fired units

ZHOU Nan, LIANG Xiujin, LI Zhuang

2020, 42(9): 63-68.

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White plume from coal-fired power plants exerts certain effect on surrounding environment as apparent visual pollution. The condensable particles contained in wet plume can also cause pollution to local environment. Analyzing the white plume treatment of 2 × 300 MW coal-fired units in a power plant， three comprehensive transformation schemes were proposed and the advantages and disadvantages of each technical route were compared. The economic analysis on schemes was made by minimum cost method considering both capital expenditure and consumption. It provides a reference for white plume treatment scheme selection .

Study on form distribution and emission of mercury from ultra-low emission coal-fired power plants

YU Jing, HOU Bo, HUANG Qishun, MA Dawei, CHEN Qian, CHENG Jing

2020, 42(9): 69-75.

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In order to study the effects of flue gas pollutants purification facilities on mercury emission and migration characteristics， content and form distribution of mercury discharged from four ultra-low emission coal-fired units were measured. Experimental results show that selective catalytic reduction （SCR） devices only remove an insignificant amount of mercury directly， but the denitration catalyst can facilitate the mercury removal in rear devices by catalytic oxidizing Hg0.ESP would remove the majority of Hg0 ，and WFGD could effectively eliminate Hg2+ .Mercury in fire coal would transport into fly ash， by-product of WFDG and flue gas，while mercury discharged in flue gas is mainly in form of Hg0 .Mercury emission factor （EFe） was between 15.20～30.00 μg/（kW·h）.The results show that the ultra-low emission transformation has a certain effect on mercury emission reduction， and the reduction is affected by technical routes of the transformation.

Trial operation performance of the flue gas treatment system for a Shidongkou sludge treatment upgrading project

ZHANG Pengfei

2020, 42(9): 76-81.

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A sludge treatment upgrading project was built on the original sludge treatment facilities in Shidongkou， one of the three wastewater treatment districts in central city of Shanghai. Shidonkou sludge treatment upgrading project takes drying and incineration technology to deal with the sludge from local wastewater treatment plant（WWTP）.The flue gas processed by cyclone dust separating + semi-dry spraying+ activated carbon injection and absorption+ filter dedusting+ wet de-acidification +flue gas reheating techniques can meet the requirement of national standards and the newest local standards of Shanghai. The practical data show that the flue gas procedure is feasible and effective.And with fluid-bed-incinerators， it is competent in municipal sludge incineration and flue gas treatment.Although the current emission standards for flue gas implemented by this project is advanced in China，and some have even reached the EU level， upper limits of a few pollutant are still far higher than that required by the ultra-low emission in power industry， which means that further upgrading for the flue gas treatment system is promising.

Theoretical study and practice of desulfurization wastewater vaporization by mechanical atomization

WANG Tao, XING Haoruo, LIU Daokua, ZHANG Feng, GUO Shaoyuan, WU Kai, MA Shuangchen

2020, 42(9): 82-87.

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Taking the desulfurization wastewater produced from the operation of coal-fired power plants as the research object， the mechanical atomization evaporation technology applied for treating desulfurization wastewater is discussed.To make theoretical study， the main factors affecting evaporation are found out， which includes droplet diameter， temperature and wind speed. Then，based on the shortcomings of the existing natural evaporation technology，this technology is improved by installing atomization devices， increasing the heat of water body， and accelerating the wind velocity during the evaporation process， which integrates and turns out to be the mechanical atomization evaporation technology.At present，the mechanical atomization evaporation technology can effectively treat the desulfurization wastewater in coal-fired power plants and the wastewater from coal chemical industry， and has achieved favorable outcomes. However， application of this technology might lead to environmental pollution.To overcome these shortcomings， the mechanical atomization evaporation technology can be improved by adopting multi-energy coupling，which can realize its low-cost zero-emission operation.

Study on wastewater zero discharge technical scheme for coal-fired power plants

CHEN Haijie, LI Fei, SUN Ying, GU Xiaobing, GAO Fei, YANG Linjun

2020, 42(9): 88-92.

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Wastewater zero discharge from thermal power plants is key to environmental protection at present.How to realize the zero discharge of wastewater from coal-fired power plants is analyzed considering existing wastewater treatment facilities and processes. The results show that all kinds of wastewater can be classified and utilized step by step by optimizing the wastewater treatment system. Reverse osmosis concentrated water can be used as supplementary water of desulfurization system so as to reduce the wastewater discharge and improve its reuse rate. Desulfurization wastewater that cannot be reused is processed by evaporative crystallization and flue gas evaporation， which achieves overall wastewater zero discharge.This scheme is of social and environmental benefits.

Treatment process upgrade of wastewater from denitration catalyst production

WANG Jianguo, QIN Yiming, GAO Chunyu, MENG Fanqiang, WANG Zhengshang, WANG Song, CHEN Hua

2020, 42(9): 93-96.

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Taking a domestic denitration catalyst manufacturer as an example， the design and upgrade scheme of a wastewater treatment process is introduced. By analyzing the conventional wastewater treatment process and its shortcomings， a new wastewater treatment process is designed based on the actual requirements of the industry. This process creatively reuses the wastewater from the production process， which saves the cost of wastewater treatment and the cost of raw materials， and realizes zero discharge of wastewater and resource utilization in the production process. The process saves a lot of chemicals （such as sodium hypochlorite， sulfuric acid， etc.） that were used in denitration catalyst wastewater treatment. This updated process is effective and environmental protective.It points out the direction for the domestic wastewater treatment process in this industry.

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