Table of Content

05 July 2018, Volume 51 Issue 7

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Influence of Overhead Line Models on the Secondary Arc Current Research of Double Circuit Overhead Lines on the Same Tower

LI Xutao

2018, 51(7):  1-6.  DOI: 10.11930/j.issn.1004-9649.201701025

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There are many modeling methods for the short double circuit overhead lines on the same tower in the electromagnetic transient analysis. The modelling methods directly influence the simulated results of of the secondary arc current. In this paper, the simulation models of four-generator system including the short double circuit overhead lines are built by the EMTP (Electro-Magnetic Transient Program) software for simulating the secondary arc current. The differences among the three kinds of line models in EMTP are compared in the steady state calculation and transient state research. Based on the theoretical analysis, the explanations for the differences of the three models are discussed. Besides, the suggestions of model selection in secondary arc current research for the short double circuit overhead lines on the same tower are given in the paper.

Research on Impact of TCPST on Receiving-End Power Grid with UHVAC and UHVDC Accessing

WEI Peng, ZHOU Qian, ZHU Xinyao, JI Tuo, ZHANG Ningyu

2018, 51(7):  7-12.  DOI: 10.11930/j.issn.1004-9649.201612033

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With the rapid development and construction of ultra-high voltage (UHV) power grid, the control of power grid turns to be more complex. Using TCPST (controlled phase shifters) and other advanced flow control devices to solve power system planning and operation problems has broad application prospects. In order to study the influence of controlled phase shifter on the security and stability of power grid, basic principles and topologies of TCPST are investigated. The steady and instantaneous models for the controlled phase shifters are also established. The series and parallel transformer parameters are designed. Taking Jiangsu power grid as an example, 500 kV TCPST is applied in the area near Jinsu UHVDC project. The application effect of TCPST is analyzed. Simulation results show that TCPST can solve the problems of DC power reject in small load mode and the DC power output in large load mode, which reduce load losses by 1000 MW after UHVDC bipolar blocking. At the same time the recovery voltage of Suzhou South grid can be improved by 5~10 kV after the failure of power grid. The application of the TCPST can have a positive effect on the protection of security and economy of power grid.

Electric Power Enterprise Offiline Topology Analysis and its Application Based on Terminals Mergence

DU Sanen, RONG Genqi, MA Shiying, WANG Xinyi, LIU Daowei, TUO Youlin

2018, 51(7):  13-20.  DOI: 10.11930/j.issn.1004-9649.201707100

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Power network topology analysis is a process for simplifying complex electrical connection and is the basis for calculation and analysis. According to the characteristics of enterprise power system off-line application, based on the CIM model, the concept of port is introduced, and an electrical connection model is established, which is suitable for electric power enterprise graphical modeling. A link method detailing the actual connection of electrical equipments is proposed. All electrical zero-impedance connected devices (or terminals) are merged for a topological node; then all electrically connected devices (or terminals) are merged for a topological island, using the relationship of topology node and device. Combined with the different access of enterprise internal power system into the external power system, the typical applications of this method in enterprise power system off-line analysis are analyzed. Algorithm analysis and examples show that the method is simple in logic, clear in structure, and rich in information. It is applicable to enterprise power systems off-line application.

Multi-Objective Reactive Power Optimization Based on Opposition-based Learning Cloud Model Adaptive Particle Swarm Optimization

CAO Shengrang, DING Xiaoqun, WANG Qingyan, ZHANG Jing

2018, 51(7):  21-27.  DOI: 10.11930/j.issn.1004-9649.201705051

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An opposition-based cloud model adaptive particle swarm optimization algorithm (OCAPSO) is presented to solve the high-dimensional problems that the conventional PSO algorithm is easy to fall into a locally optimized point. The algorithm convergence speed is accelerated through opposition-based learning, and the cloud model is used to balance the global and local search ability of each particle, and the adaptive mutation mechanism is used to enhance the population diversity. The effectiveness of OCAPSO is verified by high-dimensional generalized Schwarz function. Then single objective and multi-objective reactive power optimization of IEEE30 bus system are tested. The superiority of OCAPSO is confirmed by comparing with the testing results of PSO and EA. Analysis shows that OCAPSO is effective for multi-objective reactive power optimization.

Selection and Optimization of Lightning Overvoltage Gap for 1 000 kV Large Span Line Suspension Tower

ZHANG Sixiang, CHEN Peng, ZHANG Yong, YANG Bo

2018, 51(7):  28-35,135.  DOI: 10.11930/j.issn.1004-9649.201801010

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In order to evaluate the lightning protection performance of 1 000 kV UHV large span line, the value of lightning overvoltage gap is put forward according to the design code, the simulation model is established by ATP-EMTP, and the lightning protection performance is calculated, what's more, the effect of arrester on lightning protection performance is analyzed. The results show that surge arrester can significantly improve the lightning withstand level, decrease the lightning trip-out rate by 66%, reduce tower height and save tower material.

Research and Analysis on the Testing of Ground Impedance of Large Grounding Grid through Straight-Line Method Considering the Influence of Earth

YUAN Pei, HE Zhiqiang, HU Xiaohui, YE Huisheng, HUANG Haibo

2018, 51(7):  36-42.  DOI: 10.11930/j.issn.1004-9649.201708029

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When measuring the ground impedance of a large grounding grid of a substation (or a power plant) using the straight-line method, a measurement error will be included in the result, causing the readings higher than the actual ground impedance. The measurement error is related to two factors. One is the non-uniform distribution of soil resistivity in the vicinity of the large grounding grid, making it difficult to find the zero-potential position. The other is the mutual coupling function through earth between the parallel test leads in long distance, resulting in non-negligible reactance compared to the ground impedance. This paper presents a new method for measuring the ground impedance of a large grounding grid considering the influence of non-uniform soil resistivity and mutual inductance. In the new method, the accurate zero potential position and the corresponding resistance are obtained on the basis of fitting of the measurement curves. Besides, the influence of mutual inductance is removed by the fitting of measured data of inductance under different length of test lines. By comparing the results with CDEGS software simulation, the difference between the measured and simulated results is less than 5%. It is possible to effectively eliminate the influence of non-uniform soil resistivity distribution and mutual coupling between test lines. The new method can effectively improve the accuracy of measurement.

The Electric Field Analysis and Testing Experiments of Split-Type Insulator Detection Robot

CAI Wei, ZHENG Lei, YIN Pengxiang, YAN Biwu, LUO Hao, HONG Xiao, PU Ziheng

2018, 51(7):  43-48,127.  DOI: 10.11930/j.issn.1004-9649.201708162

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The insulator strings of EHV and UHV transmission lines are long, and it is more convenient and effective to detect insulators with robot. The current insulator detection robots are mainly climbing style, large in volume and complex in structure, and needs to be improved. Therefore, a split-type insulator detection robot is designed, which is suitable for detection of the suspended insulator strings. The electric field distribution around the insulator robot is simulated and analyzed. The designed robot is tested for a 220 kV insulator string. The results show that the maximum electric field strength of the split-type robot is 1 753 kV/m and no partial discharge occurs. The voltage measured by the insulator detection robot is less than the original voltage distribution value of the insulator. The actual voltage distribution of insulators can be obtained through compensation and correction. The robot is used to test the low/zero resistance insulators.

Computational Analysis of Passive Interference Protection Distance from Multi-Circuit Power Transmission Lines to Direction-Finding Stations

CHI Xinghe, WEI Dejun, ZHANG Kun, TIAN Lianbo, LI Shipeng, ZHANG Yong

2018, 51(7):  49-53,107.  DOI: 10.11930/j.issn.1004-9649.201711078

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Calculation of the passive interference protection distance from transmission lines to small-bore short-wave radio direction-finding stations is critical for engineering design. Based on the operating frequency of the short-wave direction-finding stations, this paper analyzes the effects of the passive interference of single-base tower's height on the short-wave direction-finding stations when the resonant frequencies are λ/4 and 3λ/4 respectively. Then it further concludes a computing method for calculating the passive interference protection distance from multi-circuit transmission lines to the short-wave direction-finding stations on the condition that the total error of direction-finding equipment is less than 1 degree. This approach not only offers more rational, complete and precise protective measures for the electromagnetic compatible problems between transmission lines and short-wave direction-finding stations, but also provides a reference for future engineering design of transmission lines and a basis for preparation of the new industrial standard-Code for Protective Design of Radio Stations against Effect from DC Overhead Transmissiion Line.

UHV Transmission Loss Allocation Based on Classified Power Flow Tracing Method

CAO Fang, SHU Yali, LI Chengren, GAO Xiao

2018, 51(7):  54-60.  DOI: 10.11930/j.issn.1004-9649.201707094

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In order to choose an appropriate method for network losses allocation, this paper discusses the allocation methods for various network losses in power market, and analyzes their applicability in the UHV power grid. According to the characteristics of the power devices which cause the losses of the network in various parts of the AC/DC power system, this paper proposes a new UHV network loss allocation method, namely classified power flow tracing method, which allocates changing network losses using proportional power flow tracing method based on AC/DC hybrid power apparent flow calculation results, and allocates the fixed network losses using average power flow tracing method based on consumer typical power flow and network usage rate. At last, the rationality and feasibility of the classified power flow tracing method are proved through the AC/DC simulation results of the improved IEEE30 node system and comparison with the traditional power flow tracing method.

Study on ABB UNITROL 6800 Excitation System Field Test and Modeling

JIANG Wei

2018, 51(7):  61-67.  DOI: 10.11930/j.issn.1004-9649.201703046

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An exact mathematic model of generator excitation system is proposed for ABB UNITROL 6800 excitation system transient stability simulation, which considers the gain error caused by thyristor phase-shifting. In addition, a field test method based on small signal step is proposed to measure the open-loop static gains of excitation systems. A formula is also given to calculate this gain. An actual generator excitation field test shows that the gain of the UNITROL 6800 excitation system caused by phase-shifting is related to the set of air gap magnetic field current, and is proportional to the voltage magnitude of the thyristor anode.

MPC Applications in AGC CCS and Steam Temperature Control on Two Ultra-supercritical Coal-fired Power Generation Units

CAI Lijun, ZHU Yucai, LV Xia, WU Zhen, JIANG Pengfei, ZHAO Chao, ZHANG Kangkang, GAO Xing

2018, 51(7):  68-77.  DOI: 10.11930/j.issn.1004-9649.201711202

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In this paper, based on the introduced model predictive control (MPC) technology, the scheme of MPC-based coordinated control system (CCS) and main steam temperature control system is proposed and applied on two ultra-supercritical coal fired power generation units. The comparison between the results of MPC- and PID-based controls shows that the MPC controller can increase the load control accuracy, load variation rate as well as the unit maximum generation, and lower the control error of main steam pressure. The MPC system has been successfully in operation for ten months, which makes the power grid evaluation scores of the two units to be improved considerably, that is, the K_p values have been increased from 1.5 to 2.8 and 3.5 respectively; the rank of the power plant has been increased from medium level to the second (out of 47 power plants) in the local power grid.

Influence of Turbine Droop on the Primary Frequency Control Capacity of Steam Turbine Units

ZHANG Bao, GU Zhenghao, YING Guangyao, DING Yangjun, FAN Yinlong

2018, 51(7):  78-83.  DOI: 10.11930/j.issn.1004-9649.201803125

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The instability of primary frequency modulation of steam turbine units is not rare, and it affects the security of power grid operation seriously. The study on the specific case of East China power grid figures out the root cause of primary frequency control capacity instability of being the large turbine local droop. After analyzing the main factors influencing the turbine local droop, it is concluded that the turbine local droop is closely related to the corresponding power grid frequency deviation. A 600-MW supercritical steam turbine is taken as a case to generate the optimized local droop curve. The results can be used to enhance the capability of the turbine and power grid coordination of steam turbines.

Feasibility Analysis on BEST Technology for Ultra Supercritical Units with Double-Reheat Cycle

DENG Pan, WANG Yajun

2018, 51(7):  84-89.  DOI: 10.11930/j.issn.1004-9649.201804011

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To lower the superheat degree of the extraction steam of the heat regenerative system and improve the economic efficiency of the double-reheat power generating units, an energy-saving plan with the backpressure extraction steam turbine (BEST) allocated is proposed. Through the introduction of the BEST characteristics such as heat recovery steam source, exhaust direction and material selection, the technical issues in the design, manufacturing, operation and control of the double-reheat power generating units adopting BEST are presented, and the feasibility and economic performance of BEST used in high-parameter double-reheat power generating units are also analyzed. The analysis results show that with the BEST technology adopted, the investment of single unit can be reduced by about 24 million RMB while the annual profit can be increased by about 45 million RMB.

Cause Analysis and Improvement on Jammed High Pressure Main Steam Valve of New Type Domestic 1 050 MW Ultra Supercritical Unit

MENG Haiyang

2018, 51(7):  90-94.  DOI: 10.11930/j.issn.1004-9649.201703079

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Upon the completion of 168-hour full load trial operation, the new type of domestic 1050MW unit was then put into operation. Unfortunately, main high pressure valves gradually became sticky and jammed, which caused action failure or in wrong position during operation and full stroke test. Through disassembly analysis, it is found that in addition to the damage and deformation of high pressure main steam valve sleeve seal ring, the narrow gap between valve stem and sleeve or main steam valve disc leads to the main steam valve sticking. In addition to adjusting the oil pressure of the oil pump and the operation of the valve as well as the switching time of the experiment to reduce the impact of the main steam valve stem on the sealing ring of the sleeve, the valve stem is reprocessed to increase the gap between the stem and the sleeve and the main steam valve disc, so as to resolve the problem of the main steam valve jam thoroughly. After the reinstallation, the main steam valve is back to normal place during the daily test and the switch process.

Cause Analysis and Treatment of Abnormal Vibration of the Steam Turbine for Spring-Supported Foundation Table

JIANG Xiaoli, HE Rongyao

2018, 51(7):  95-102.  DOI: 10.11930/j.issn.1004-9649.201802061

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The abnormal vibration of the steam turbine is one of the important factors affecting the operation security. However, the cause analysis of the abnormal vibration is very complicated for the steam turbine with spring-supported foundation table. Through the cause analysis of the abnormal vibration for two ALSTOM ultra-supercritical steam turbines, the fundamental cause of the abnormal vibration is found. Then, a start-up method of reducing the vacuum value of the low pressure casing exhaust is proposed, which has tackled the issue of abnormal vibrations of the spring-supported steam turbines and ensured their operation security.

Configuration and Capacity Calculation of Power-actuated Pressure Relief Valve in Thermal Power Plants

ZHANG Chuanhu, CHEN Xuan, ZHANG Zhongzhou, TIAN Shongfeng, TANG Huifeng, LIU Jianmin, HU Weizu, LU Huancheng

2018, 51(7):  103-107.  DOI: 10.11930/j.issn.1004-9649.201711200

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The power-actuated pressure relief valve (PCV valve) equipped in the thermal power plant boiler is a vital equipment to provide overpressure protection for the boiler. However, in practice, many power plants do not pay enough attention to the configuration of the power drive discharge valve and do not always follow the requirements of ASME and the electric industrial standards which definitely brings hidden dangers to the boiler operation. This paper introduces the relevant standards on the PCV valve configuration, analyzes the existing problems in practice and proposes the solutions. By calculating the adverse effect of manual isolation ball valve with reduced diameter on the discharge capacity, the necessity and importance of properly configuring the PCV valve following the standards are emphasized.

Application of Varnish Potential Rating on Deterioration Analysis of Phosphates Ester Fire Resistant Oil

ZHU Zhiping, WANG Deng, ZHANG Li, LIN Yongping, QIAN Yihua, CHEN Tiansheng, FAN Shengping, SU Wei, FU Qiang

2018, 51(7):  108-112,144.  DOI: 10.11930/j.issn.1004-9649.201711139

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The flash point, volume resistivity and foaming properties of phosphates ester fire resistant oil of unit 5 of a large power plant were found exceeding the standards. To find out the cause of deterioration, many indicators of operating phosphates ester fire resistant oil (operating oil) and new phosphates ester fire resistant oil of unit5 were tested according to DL/T 571-2014 "Guide for operation and maintenance of phosphates ester fire-resistant fluid used in power plant". The results indicated that there was nothing abnormal detected in the chlorine content, elemental analysis or mineral oil, which made it difficult to identify the real cause of deterioration. Then after the varnish potential rating was innovatively applied to the cause analysis of deterioration of phosphates ester fire resistant oil, it was noticed that the varnish potential rating of fire resistant oil of unit 5 was 43.4, while the varnish potential rating of new oil of unit 5 was 0.1. By taking account of the oil color change, it was concluded that the aging of oil was serious and urgent treatment was needed. As a result suggestions to change the oil and strengthen the daily supervision of fire-resistant oil were proposed. Therefore it is of great importance to apply the varnish potential ratings in oil analysis.

Research on Determination of High Temperature Corrosion Tendency of Water Walls and Limiting Concentration Range of H₂S Near Walls

XU Weigang, TAN Houzhang, LIU Yuanyi, WEI Bo, HUI Shi'en

2018, 51(7):  113-119.  DOI: 10.11930/j.issn.1004-9649.201707164

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To prevent the increasingly serious problems of high temperature corrosion of water walls in boilers, the research on the distribution of the near wall atmosphere is carried out in a 300MW boiler. With the test data of high temperature corrosion kinetics of the water wall materials 12Cr1MoV, the corrosion rate under different temperature, atmosphere and cracking period of corrosion layer is forecasted such that the corrosion tendency standard of water walls in boilers at different running time is put forward. The relationship between the corrosion rate and the H₂S concentration, the corrosion time and the cracking period of the corrosion film is established, and the limiting concentration of atmosphere near walls is obtained with the cracking period of 24 h and 48 h as examples. The results show that the concentration of H₂S near walls is proportional to the concentration of CO, but inversely proportional with the concentration of O₂. The high temperature corrosion rate change with time follows the parabolic law, while the change with temperature complies with the Arrhenius law. and the change with H₂S concentration follows the exponential law. As long as the atmosphere near walls is controlled within the limiting concentration range, the serious high temperature corrosion could be prevented.

Bidding Strategies for Gas-Electricity Virtual Power Plants in Multi-energy Market

ZHOU Renjun, LV Jia, ZHANG Wujun, LI Juan, DENG Minghui, XIAO Junwen

2018, 51(7):  120-127.  DOI: 10.11930/j.issn.1004-9649.201802056

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In order to solve the problem of virtual power plant bidding risk caused by uncertainty of wind power and demand response, a gas-electricity virtual power plant with bidirectional conversion function is built by using the new power-to-gas technology and the quick adjusting ability of gas turbine, and a multi-energy market bidding model is proposed for bidding of power market and the natural gas market. By taking the maximum profits of gas-electricity virtual power plant as its optimization objective, the model uses the error probability distribution to express the uncertainty of demand response and wind power output, and determines the scenario description through sampling and filtering. The simulation results show that the gas-electricity virtual power plant of bidirectional conversion can obtain higher bidding profits through flexible bidding in the two markets; and the imbalance penalty cost can be reduced substantially through controlling the gas turbine and power-to-gas output. The gas-electricity virtual power plant can extend the virtual power plant bidding market, which is helpful for virtual power plant to switch the energy form in the future according to different price fluctuations of gas and electricity.

Study on Credit Evaluation of Power Supply Company in Power Market Based on KPCA-MEE

ZHANG Yunlei, DUAN Guang, YU Jing, WANG Haichao, ZHANG Zijun, NIU Dongxiao

2018, 51(7):  128-135.  DOI: 10.11930/j.issn.1004-9649.201711287

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Establishing a complete power supply company credit evaluation system is helpful for regulating power market trade and improving the mechanism construction and management level of power market. In this paper, the kernel principal component analysis method and the matter-element theory are combined together to establish a KPCA-MEE power supply company credit evaluation model. Based on the power supply company credit evaluation index system, the KPCA is applied to realize the dimensionality reduction and to determine the index weight. And then the matter-element extension theory is used to describe the process of credit rank evaluation. Finally, based on the data of four power supply companies, a case study is made to verify the validity of the proposed KPCA-MEE model.

Research on Optimization of TOU Considering Load Development and User Behavior

TAN Xiandong, CHEN Yuchen, LI Yang, JING Jiangbo, JIANG Ning, WANG Zijian, SHEN Yunwei

2018, 51(7):  136-144.  DOI: 10.11930/j.issn.1004-9649.201708165

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As an important economic means of demand-side management, TOU (time of use) is imperative for full implementation in the country. However, the rapid growth of electricity demand lead to TOU ineffective for user's incentive. Aiming at this problem, this paper puts forward a TOU optimization method considering load development, and uses BP neural network prediction and grey prediction to forecast the typical daily load curve of the next two years. The reasonable TOU is obtained through substituting the future load curve into the TOU optimization model as electricity price constraint, and optimizing the typical daily load curve of the year. The optimization results with sole consideration of the typical daily load curve are compared with that with consideration of load development, which verifies the effectiveness of the proposed optimization method for extending the TOU timeliness.

Application of Built-in Gas-to-Gas Heat Exchanger in the Urea Pyrolysis System for SCR Denifrication

SONG Jian, HU Zhangmao, DENG Weili, CHEN Donglin, LIU Lianghua, WEI Mianyuan, WEN Cong

2018, 51(7):  145-151.  DOI: 10.11930/j.issn.1004-9649.201711085

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The urea pyrolysis process adopting the gas-to-gas heat exchanger (GGH) is characterized with simple system and low energy consumption. In this paper, based on the detailed analysis on the characteristics of the GGH, a design of GGH for the use in the process of urea pyrolysis is proposed and applied to the retrofit of the denitration system of a 300-MW unit, in which the original pyrolysis by natural gas heating is changed with GGH. The operation results show that the design of GGH can reduce the natural gas consumption by about 360,000 m³ (standard state) and reduce the operating costs by more than RMB 900,000 yuan each year. The retrofit has obtained good economic benefits.

Flow Field Optimization on the Catalyst Layer Breakage Failure of the SCR-DeNO_x System for a Coal-fired Power Plant

LEI Jianqi

2018, 51(7):  152-156,169.  DOI: 10.11930/j.issn.1004-9649.201708274

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To resolve the problem of serious attrition occurred in the catalyst layer of a domestic 300 MW unit, a static disc mixer is adopted to replace the conventional diversion plate. The distribution of the gas-solid two-phase flow field is measured by the industrial test and the boundary conditions are determined accordingly. The velocity of flue gas and soot, and the distribution of mass concentration of soot in the SCR denitrification system are studied using the computational fluid dynamics method. The optimized scheme is eventually applied to the SCR denitrification retrofit project. The results show that the wear of the catalyst is mainly caused by the uneven mixing of smoke and dust in the flue,and the improper installation of the diversion plate closest to the catalyst.The problem of uneven gas-solid two-phase mixing in the inlet section of the catalyst for SCR denitrification system is resolved under lower pressure resistance,which effectively prolongs the service life of the catalyst.

Improvement of SO₃ Sampling Technology and SO₃ Removal Capability Testing of Flue Gas Treatment Equipment

YANG Ding, CHEN Yongqiang, CHEN Weixiang, ZHENG Fang, LIN Qichao

2018, 51(7):  157-161.  DOI: 10.11930/j.issn.1004-9649.201706037

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Due to its unique chemical properties, SO₃ in coal-fired flue gas has been one of the difficult parts in pollutant testing in coal-fired power plants both at home and abroad. In this article, the SO₃ testing system is developed by utilizing the widely used control-condensation method and taking various factors into consideration during the sampling process. The optimal inner diameter, ring diameter and the number of rings of snake-shaped tube in SO₃ controlled condensation sampling system are determined through experimental simulation as well as the sampling tubes, the temperature control of filter and circulating water bath to improve the capture efficiency of SO₃. This SO₃ sampling system has been used to test the removal capability of the flue gas treatment equipment in the coal-fired boiler. The influencing factors and the trapping mechanism on SO₃ by sampling the flue gas are also analyzed. It is showed that SCR catalyst had some catalytic effects on SO₂, and the conversion rate of SO₂/SO₃ increases with higher flue gas temperature. As for the removal efficiency of SO₃, based on the comparison results of the inlet and outlet concentration between each equipment, the dry dedusting equipment can reach more than 80%, while the wet desulphurization equipment is 35%~40% and the wet electrostatic precipitator is 70%~75%.

An Empirical Study on Environmental Impact of the Integration of the Natural Draft Cooling Tower and the Flue Gas

ZHANG Renfeng, SU Shenshen, MA Jijun, XIE Yongping, SUN Xijin, HAN Jianhua

2018, 51(7):  162-169.  DOI: 10.11930/j.issn.1004-9649.201703098

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In order to track the influences of the natural draft cooling tower (NDCT) with flue gas injection on the regional atmospheric environment and pollutant concentrations in the theoretical plume-downwash area, SO₂ and NO₂ in the area of 400 km² around the Qinling power plant are sampled and analyzed during the heating and non-heating periods, an automatic air quality monitoring station is set to get hourly observations in the theoretical plume downwash area of the NDCT over a year, and combined with meteorological data, an empirical study on the environmental impact of NDCT with flue gas injection is carried out. The results show that the monitoring results of the ambient air quality in both heating period and non-heating period meet the requirements of "the ambient air quality standard" (GB 3095—2012), and the influence of the power plant on the regional environment is acceptable. During the continuous monitoring of the ambient air over time, high concentration of local pollutants resulting from flue gas downwash is not observed. There is no significant difference (P>0.05) between the pollutant concentration in the theoretical washing area when the dominant wind is westward or eastward. The pollutant concentration in the strong wind is significantly lower than that in the low wind (P<0.01) when the wind is westward. The monitoring results show that high concentration of ground pollutants will not happen in the theoretical plume-downwash area of NDCT with flue gas injection.

Analysis of the Ultra-low Emission Transformation and CEMS Acceptance of Coal-fired Power Plant in Anhui Province

HE Jun, MA Dawei, WANG Zhengfeng, XU Yongyi, ZHA Zhiming, ZHANG Qiliang

2018, 51(7):  170-177.  DOI: 10.11930/j.issn.1004-9649.201801151

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The transformation of ultra-low emissions of 67 coal-fired generating units (36 490 MW) has completed in Anhui Province. On this basis, the technical routes of ultra-low emissions of SO₂, NO_x and dust, the economics of the retrofit, the emissions concentrations and emission reductions after retrofit, as well as the problems in the CEMS acceptance of the three types of pollutants were analyzed. The research shows that the ultra-low transformation of coal-fired power plants in Anhui Province mainly follows three typical technical approaches, which are wet electrostatic precipitator, low-temperature electrostatic precipitator and super net electric bag. The 1 000 MW units have the highest economical efficiency, followed by the 600 MW units and 300 MW units. The ultra-low transformation has a remarkable effect on the emissions reduction of the flue gas pollutants in the power plants of the province, and the synergistic removal of the pollutants is effective. However, the current gaseous pollutant monitoring instruments, dust filter materials and testing methods cannot meet the test accuracy requirements of the modified CEMS after transformation. Therefore it is suggested that the low-concentration dust measurement automatic sampling system and blank experiment correction be used for the ultra-low transformation units. In addition, it is recommended to use ultraviolet or infrared smoke analyzer for SO₂ acceptance, and high temperature heating for the sampling pipeline respectively. NO_x acceptance should be based on both the test data of the SCR denitrification outlet and the total discharge NO_x concentration test.

Numerical Simulation on Separation Performance of Tube Mist Eliminator with Holes

YANG Laishun, XU Minghai, CHEN Qiushi

2018, 51(7):  178-184.  DOI: 10.11930/j.issn.1004-9649.201801206

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In this paper, the numerical simulation is carried out to study the effect of the number of the holes, the size of the droplets and the velocity on the separation efficiency and the pressure drop in the tube mist eliminator. The turbulence model and the discrete phase model are used respectively to calculate the movements of the continuous phase and the droplets. The results show that the separation efficiency of the eliminator increases with the increase of the droplet diameter and the velocity. In particular, the eliminator is more effective in removing small droplets. There are approximately 62% of 5 μm and 69% of 10 μm droplets being captured by the tube mist eliminator. In addition, the fins with holes can reduce the pressure drop by 50% in the tube mist eliminator under the studied condition. This study concludes that the tube mist eliminator possesses high separation efficiency on small droplets. Cutting holes on the fins can lower not only the flow resistance, but also the separation efficiency. This conclusion can provide a good basis for theoretical researches and industrial application of the tube mist eliminator.