Application example analysis of wet electrostatic precipitator (WESP) in millions of coal-fired units
2016-02-03 11:38:43
Author: Wang Lei Weng Lingang Xie Gaowang Dai Gangquan
Application Analysis of Wet Electrostatic Precipitator in1,000MW Coal-fired Power Plants
Dai Gangquan, Wang Lei , Wen Lingang,Xie Gaowang
(Zhejiang TUNA Environmental Science & TechnologyCo., Ltd, Shaoxing, Zhejiang, 312000, China)
Abstract: A brief induction of the Wet ElectrostaticPrecipitator (WESP) technology is given in this paper along with itsdevelopments and applications both domestic and international. The focus of thispaper is the application analysis of our WESP in the 1000MW coal-fired powerplants. The fuel gas before/after the implementation of the WESP was sampled, analyzedand compared to show that the WESP is capable to eliminate the super-fineparticles, SO3 aerosol, and the gypsum after the WFGD effectively.
Keywords: Wet Electrostatic Precipitator (WESP), 1000MW, Coal-fired Power Plants,Super-fine Particles.
In recent years, with the rapid development of China's national economy, the disadvantages of some extensive mode of development have gradually emerged, increasingly serious environmental pollution, in the Beijing Tianjin Hebei region, the Yangtze River Delta, the Pearl River Delta as the representative of the economic developed area focus on the outbreak of the severe haze pollution, pose a threat to public health. Flue gas emitted from coal-fired power plants is one of the main sources of air pollution, and it is also the focus of air pollution control.
For implementing the sustainable development concept, state of coal-fired power plant energy-saving emission reduction proposed new requirements, in accordance with the provisions of the thermal power plant emission standard of air pollutants "(gb13223-2011), key areas of sulfur dioxide, nitrogen oxides and dust emission concentration limit of 100, 50, 20mg / Nm3, respectively, due to the pressure of environmental protection, in these areas have been in accordance with the standard gas unit of 50, 35, 5 mg / Nm3 start requirements.
In order to achieve these emissions requirements, a kind of environmental protection equipment is required to remove these fine particles. Wet electrostatic precipitator (WESP) as the terminal depth of atmospheric pollutant control processing system of S03 aerosol, NOx and PM2.5 dust has high removal efficiency, also the mercury removal effect is also very good. Therefore, it has very important significance to study and popularize the application of wet electrostatic dust removal technology in China's coal-fired power plants.
1 wet electrostatic precipitator
1.1. dust removal principle
Wet electrostatic precipitator through the cathode line DC high voltage discharge, ambient air ionization and dust in the flue gas charged by electric field force drives are collected into the dust collecting plate, unlike the dry electric dust cleaning, wet electrostatic precipitator with spray water alternative vibration call to clear the function of grey.
As shown in Figure 1, the wet electrostatic precipitator is generally arranged after wet desulfurization. Most of the dust in flue gas at outlet of wet desulfurization has been dry electric dust cleaning removed and become entrained particulate plaster wet saturated flue gas, through the wet electrostatic precipitator to discharge requirements, from the chimney discharged.
Fig. 1 arrangement position of wet electrostatic precipitator
1.2. application at home and abroad
Wet electrostatic precipitator technology in the United States, Europe, Japan and other developed countries have been more mature, nearly 30 years of experience in coal-fired power plant application, nearly 100 sets of different type of WESP runs successfully in large power plant unit, such as: 2000 put into operation in the Nb power company power plant of Dalhousie 315MW unit; put into operation in 2001 the Chubu Electric Power Hekinan power plant (2 * 1000MW unit [1]; put into operation in 2002 the Xcel Energy Sherburne power plant is 750mW units etc..
In the domestic, wet electrostatic precipitator in metallurgy, sulfuric acid industry has more than 30 years of successful application of [2], has been developed "gas wet electrostatic precipitator" (JB/T6409-2008) industry standards. In recent years with improvement of environmental protection requirements, in the thermal power industry began to applied in a large area, according to incomplete statistics, there are nearly one hundred sets of contract performance, more than 10 units put into operation performance.
1.3. honeycomb tube type WESP industrial test platform
In order to verify the wet electrostatic precipitator, we have set up a conductive glass steel honeycomb tube WESP industrial test platform, as shown in Figure 2, used in the de NOx catalyst kiln flue gas governance in depth, the governance of major pollutants for dust, aerosol and PM2.5, flue gas volume 10000Nm3/h, flue gas temperature 50 to 70 DEG C, inlet dust concentration 55mg/Nm3, design dust removal efficiency was 91%.
As shown in Figure 3, open test platform of cellular WESP, the naked eye can not see the white smoke. The dust measuring instrument, open the WESP concentration of dust emissions reduced to 4.3mg/Nm3, actual dust removal efficiency reaches 92.18% and PM2.5 removal rate reached 85.5%, the droplet removal rate reached 78.7%, the resistance of the device is 185Pa. Measured data shows that the honeycomb tube type WESP can effectively remove catalyst kiln flue gas dust, PM2.5 and droplet, to achieve ultra low emissions.
Fig. 2 3D model of cellular WESP
Figure 3 honeycomb tube WESP test platform is put into operation before and after comparison
2 wet electrostatic precipitator application in one million units of coal-fired power plant ultra low emission projects
Currently coal-fired generating units in China's largest installed capacity of 1000MW, wet electrostatic precipitator application in coal-fired power plant units 1 million is not much, so the application instance of millions of units analysis has a certain practical reference value. This section gives the Guodian Beilun Power Plant Phase III #7 unit (1000MW) adding examples of the application of wet electrostatic precipitator, through before loading the WESP, after the flue gas emission component analysis and comparison of. It is proved that the wet electrostatic precipitator can effectively remove pollutants in flue gas of coal-fired power plant sulfur trioxide aerosols, nitrogen oxides, dust and PM2.5 and meet the requirements of ultra low emissions million coal-fired units.
2.1. application background
In order to reach the new emission standard of National Atmospheric Pollution in coal-fired units, coal-fired units after the completion of the transformation of flue gas emissions to achieve the standard of natural gas units, by the Nanjing State Power Environmental Protection Technology Co., Ltd. and Zhejiang Dechuang environmental protection cooperation EPC general contracting, the Guodian Beilun Power Plant Phase III #6, #7 unit (2 * 1000MW) installation of wet electrostatic dust collection equipment.
2.2. engineering survey
Guodian Beilun Power Plant #6, #7 unit (2 * 1000MW) of wet electrostatic precipitator anode system using modular design, the entire anode system is divided into 48 anode module, module by the production workshop and transported by road, on-site according to drawings assembled into a whole. The conductive glass fiber reinforced plastic has excellent corrosion resistance performance of [2], and it has a strong hydrophobic property, which can effectively prevent the adhesion of dust and gypsum to the anode wall. Conductive glass steel plate with corrosion resistance, light weight, good electrical conductivity, fire resistant, oxidation resistance good with outstanding features, in the technical risk and reliability, operation cost occupies a larger advantage. It represents the development direction of wet electrostatic precipitator technology.
The cathode line is made of 2205 stainless steel tube with high strength and good corrosion resistance. It can be used in the long-term work of the saturated wet flue gas environment. Cathode wire fixed on the upper frame and a lower frame, frame through arranged in the outer casing insulating box support, insulation box boom using ceramic supporting tube, insulating box with electric heating device, maintain the internal temperature of 120 to 140 DEG C, while the insulation box is also equipped with a hot air blowing device to ensure insulation box keep dry insulating state. A fixed anti swing device is arranged at the bottom of the cathode, and the pull rod which is arranged in the device is provided with a ceramic material and is provided with a heating function to ensure the drying and insulation of the pull rod.
Inlet and outlet flue and anode module below the glass flake anticorrosive, the cathode beam, anode module body lining prevulcanized fixed base rubber anticorrosive, cathode frame rest all the 2205 stainless steel production.
At present, the wet electrostatic precipitator of #7 unit has completed the installation, commissioning and trial operation, and put into use. The test data used in this paper are derived from the #7 unit.
2.3. operation condition
#7 units in June 2009 completed and put into production, transformation of the desulfurization system (WFGD) was completed in January 2013, as shown in Figure 4, #7 unit wet electrostatic dust removal device is arranged after the WFGD, taking into account the volume and weight of factors of plant space and wet electrostatic precipitator, in the form of steel bracket of the tower, the independent layout, does not affect the absorption tower safety, support beam to avoid laying underground pipeline. #7 unit of the WESP inlet flue gas flow is about 2950000Nm3/h, wet saturated flue gas flow from WESP to WFGD, smoke flow to the upper and lower".
The honeycomb tube wet electrostatic precipitator in the anode tube upper is provided with a layer of intermittent spray, the spray by flushing water supply by high pressure and a dedicated non clogging rinse nozzle, during normal operation, wet electrostatic precipitator temperature drop is only 2 to 3 degrees Celsius, the intermittent spray, temperature drop 5 to 7 degrees. Spray set collecting electrode surface form a continuous layer of water film, down to collect the dust with water film flow by gravity to the lower part of the sump, online cleaning. When the temperature is above 40, the gypsum is easily soluble in water, the viscosity is decreased, and it is not easy to be bonded on the anode tube, and the whole equipment can not produce dust and gypsum in the process of operation.
Wet electrostatic dust precipitator for #7 unit since March 2015 put into operation has been running for more than two months, the system operation of each index is normal and stable.
Fig. 4 wet electrostatic precipitator of #7 unit (1000MW) of Beilun power plant in Ningbo, China
2.4. application analysis
State power Beilun power plant #7 unit wet electrostatic precipitator normal operation for 2 months, through the various monitoring data sampling and collection, can make a quantitative and qualitative analysis of the effect of wet electrostatic precipitator.
First by the naked eye observation, as shown in Figure 5. #7 unit chimney emissions of flue gas in wet electrostatic precipitator (ESP) operation before and after a comparison of visual contrast, significantly reduced after wet electrostatic precipitator (ESP) operation stack emissions from the white smoke, wet electrostatic precipitator of mist and dust to removing effect is obvious.
Again from the quantitative point of view, the #7 unit complete the "168" hours full load test run after the wet electrostatic dust removal. The unit of real-time environmental data: sulfur dioxide 11.6 mg / Nm3, nitrogen oxides 40.4 mg / Nm3, soot 2.2 mg / Nm3, which marks the coal-fired units after ultra low emission transformation, the pollutant emission targets has reached even better than the gas turbine standard. According to estimates, after the transformation of the #7 unit can be based on the original basis of sulfur dioxide emissions of about 500 tons, about 500 tons of nitrogen oxides, emission reduction of about 27 tons of soot [3].
Figure 5 Guodian Beilun power plant #7 unit WESP was put into operation before and after the chimney emissions comparison chart
3 conclusions and outlook:
Due to its stable and efficient dust removal effect, the wet electrostatic precipitator has been widely used in thermal power plants in developed countries. In this paper, through the analysis of the Guodian Beilun Power Plant #7 unit (MW) coal-fired units wet electrostatic precipitator application examples, it is proved that the wet electrostatic precipitator can effectively remove the main components of flue gas in the aerosol of SO3, nitrogen oxides and dust pollution. With the increasing emphasis on environmental protection of the state and the public, it is believed that the wet electrostatic precipitator will spread to the major coal-fired power plants more quickly, and play an important role in the process of air pollution control in China.
reference
Application analysis of [1] wet electrostatic precipitator in coal fired power plant WFGD, Fifteenth proceedings of the Symposium on electrical dust collection, 2013
[2] Zhu Lianyong, the application of the honeycomb type conductive glass fiber reinforced plastic electric mist sprayer in the production of sulfuric acid, sulfuric acid industry, 2011, 3-14.
[3] China National Power Corporation's official website news, Beilun's first million kilowatts generating units to achieve ultra-low emissions, 2015-3-26.