Application of Waste Heat Utilization Technology in Reconstruction of Electrostatic Precipitator in Thermal Power PlantElectrostatic precipitator is the mainstream of the thermal power plant dust pollution control equipment, but it is more sensitive to the use of coal dust than the resistance in China's coal in the case of change, especially for high specific resistance dust conditions, the ESP There is anti-corona, so that the efficiency of dust reduction, which is a major drawback of traditional electrostatic precipitator.
Dust emission standards (≤ 30mg / Nm3), the new emission standards become a huge driving force for the development of ESP technology. ESP industry to meet the new emission standards quickly introduced a number of large units for the application of new technology, waste heat utilization technology is one of them. Electrostatic precipitator is the mainstream of the thermal power plant dust pollution control equipment, but it is more sensitive to the use of coal dust than the resistance in China's coal in the case of change, especially for high specific resistance dust conditions, the ESP There is anti-corona, so that the efficiency of dust reduction, which is a major drawback of traditional electrostatic precipitator. In recent years, engineering and technical personnel from the boiler tail process system to consider the boiler exhaust gas temperature further reduced (from 120 ~ 170 ℃ down to 90 ~ 110 ℃), making the majority of coal dust ratio can be reduced to Electrostatic precipitator the best working range, which fundamentally solve the electrostatic precipitator in the high specific resistance dust conditions, prone to anti-corona dust removal efficiency problems.
Figure 1 is a typical coal than the dust than the resistance and temperature curve, when the temperature at about 150 ℃ when the maximum resistance of dust, with the temperature rise and fall, the specific resistance of dust will be reduced. Flue gas temperature increase will affect the thermal efficiency of the boiler is clearly unrealistic, the temperature is reduced to reduce the specific resistance of dust, dust from the regulation of the beginning of the dust to start to reduce the dust than the resistance. Take the waste heat utilization technology to achieve the flue gas thermostat, to reduce the dust than the resistance to adapt to the efficient operation of dust, to achieve dust emission reduction, but also to achieve coal saving, energy saving multiple effects.
1 waste heat utilization process
Coal-fired power plant commonly used waste heat utilization process is generally the use of waste heat to heat the system of low water condensate, so as to achieve the purpose of flue gas cooling and condensate heating. The heating system of the waste heat utilization system can be divided into two modes. Figure 2 shows the parallel arrangement mode, take a single water back to the water return process, with the booster pump and pipeline valve system, through the P I D automatic adjustment, to achieve automatic control of waste heat utilization system. The advantage of parallel arrangement is that the mode can be solved separately without affecting the normal operation of the power generation system.
Figure 3 for the waste heat using the series arrangement mode, in the low-plus loop on the appropriate location to set the cut-off valve, and before and after the valve in the water and backwater, set the hot water recirculation system and bypass system, through the PID automatic adjustment, Automatic control. Compared with the parallel mode, the mode cooling effect is more obvious.
2 waste heat in the use of a thermal power plant
2.1 Waste heat utilization process description
(Figure 4), from the shaft seal heater outlet to take a condensate, through the booster pump to improve the pressure in the pipeline system, the condensate will be sent to the electrostatic precipitator front heat exchanger Gas-water heat transfer, heat transfer after the condensate back to the 7th low outlet, due to the shaft seal heater outlet temperature is low (about 4 5 ℃), by setting the recirculation pipeline and booster pump, the heat transfer After the high temperature of the water back to the inlet, to improve the water temperature into the heat exchanger to ensure that the heat exchanger pipe water temperature is higher than the wall corrosion temperature; in the electrostatic precipitator four inlet flue layout of a heat exchanger for the system In the gas - water heat transfer.
2.2 Waste heat utilization control system
The control system of waste heat utilization mainly includes smoke temperature adaptive control, water temperature adaptive control and soot blowing control. Smoke temperature adaptive control: each heat exchanger outlet set up two temperature measuring points, by adjusting the valve opening or pump speed, control of condensate into the heat exchanger and the heat exchange of flue gas to achieve the smoke The temperature is kept within a constant range. Smoke temperature adaptive control logic diagram shown in Figure 5.
Water temperature adaptive control: heat exchanger inlet water temperature (three take two) for the feedback parameters, by adjusting the valve opening and pump speed, control the amount of water into the heat exchanger to achieve the heat exchanger inlet water temperature remained constant Of the range, to avoid the low temperature corrosion of the metal wall of the heat exchanger. Water temperature adaptive control logic diagram shown in Figure 6.
Soot control: waste heat utilization system using sound wave soot, the control method is divided into manual injection and automatic sequence injection, at the same time with the operation of the solution function. The role of the soot control system is to remove the fouling of the heat transfer module, so that the heat exchanger to maintain good heat transfer performance.
2.3 operating conditions
From the actual operation point of view, in the case of boiler load becomes larger, increase the return pipe electric control valve opening and booster pump frequency, water supply pipe flow increases, the use of heat exchanger heat exchanger outlet flue gas temperature and booster pump The outlet pipe water temperature is reduced; in the case of boiler load becomes smaller, reduce the return pipe electric control valve opening and booster pump frequency, water supply pipe flow, waste heat using the heat exchanger outlet flue gas temperature and booster pump The outlet pipe water temperature is rising. Which through the smoke temperature adjustment and water temperature regulation, so that the heat exchanger outlet flue gas temperature and heat exchanger inlet temperature to maintain a constant temperature range. Table 1 is in the unit under different load, waste heat utilization system operating parameters.
After the test of Jiangxi Electric Power Research Institute, in the case of waste heat utilization technology put into operation, a power plant in Jiangxi Province, a dust concentration of 16mg / m3, dust removal efficiency of 9.9.91%, unit heat consumption decreased by an average of 54.69kJ / kWh , The plant power consumption is reduced by 0.15%, the average coal consumption is reduced by 2.57g / kWh, considering the environmental and other factors, the average annual coal saving 2.18g / kWh, to achieve a good energy saving effect. Waste heat utilization technology in the successful application of electrostatic precipitator, indicating that the technology has a good way to reduce emissions, recycling energy efficiency, it is worth further application.
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