Automatic on-line descaling and anti scaling of th

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Automatic descaling and anti scaling technology of steam turbine condenser rotating plastic tie

automatic descaling and anti scaling technology of steam turbine condenser rotating plastic tie Yu Tianlan Peng Deqi Liu Guiying Jiang Shaoqing branch Heng Yu Xiumin Yang Xianghong (Institute of mechanical cleaning, Zhuzhou Institute of technology, Zhuzhou 412008) 25mm thick scale will reduce the heat transfer coefficient by 31 This paper introduces the principle and test results of automatic descaling, anti scaling and heat transfer enhancement of self rotating plastic ties, and further calculates and analyzes the economic benefits that can be brought to power plant steam turbines by using this technology. Fund Project: the key scientific and technological research project (00208) funded by the Ministry of education generally has different degrees of scaling in heat transfer equipment. The increase of thermal resistance after scaling will seriously reduce the heat transfer efficiency of the equipment. The average reduction of the operating efficiency of heat exchangers in China caused by dirt is 50% For example, Hunan Dacheng zinitrogen group company is a unit with relatively good management level and benefits in the same industry. The author's investigation on the fouling and cleaning of the condenser of the electromagnetic directional valve 1 of the self-contained power plant in the energized state is: 1 2kW unit, the inner diameter of the condensing pipe is 18mm, and the dosing Zijiang water is used as the circulating cooling water, and the flow rate is 2 0m/s (because the rubber ball cleaning device is not easy to use, it has been removed) the cooling water pressure difference is 0.16~0.26mpa The vacuum degree before and after cleaning differs by 10%, and it drops seriously after one month of cleaning. When the outlet temperature of circulating water is 31~39 ° c.9000kw (i.e. 75% load), the vacuum is only 8KPa, and the dirt on the visible heat transfer surface may make any attempt to improve the performance unsuccessful. Therefore, in terms of energy-saving measures, the evaluation of dirt and prevention of scaling is one of the major focuses of * and the thermal conductivity found is 1 163~0.175w/(m2. °), the thermal conductivity of soft scale is 1 163~3.49w "m2.c) in the calculation of fouling influence in this paper, 1.75w" M2 ° C is taken. The influence amplitude of scale with different thickness on K value is calculated in table 1 Table 1 Influence amplitude of dirt with different thickness on K value: dirt thickness in the pipe/mm, corresponding foot value/Suwa. (2. ° 0 scale's influence amplitude on K value/Note: the dirt composition is mainly silicate. It can be seen that even if the dirt thickness is small, its influence is quite significant, and it is very necessary to adopt energy-saving technology that can realize automatic continuous cleaning and anti scaling. 2. The automatic cleaning of the rotation link and the edge of the heat transfer enhancement zone collide and squeeze the dirt layer. Under the joint action of circumferential scraping and shearing and radial collision, the automatic connection of dirt can be achieved The continuous cleaning function has a good automatic anti scaling effect on the irregular heat transfer surface that originally had no scale. 2.2 test of automatic cleaning ability in the simulation test of automatic cleaning ability of self rotating plastic ties, three kinds of ties with different plastic components are installed in three copper tubes in series, so as to compare under the condition of exactly the same flow rate. About 1.0mm thick artificial dirt is prefabricated in the pipe. The artificial scale is made of 20% cement and 80% calcium carbonate and latex, and its hardness is much higher than the actual scale. After the tie is installed, turn on the pump and water to conduct the dirt cleaning ability test. After a week, disassemble it to observe the cleaning effect, as shown in Table 2. The automatic cleaning effect of the rotating plastic tie. The tie number, copper tube size/cleaning conditions, flow rate in the tube/m, 1 cleaning time, 1 cleaning effect is not clean and very dry). It can be seen that the plastic tie made of 23 materials can effectively realize automatic continuous cleaning and anti scaling. 2.3 heat transfer enhancement: a self rotating plastic tie with a certain gap with the inner wall of the tube is set in each condensing tube of the condenser (for example), which generates self rotation and vibration oscillation driven by the kinetic energy of the cooling water flow. The results of the side edge test of the self rotating tie show that when re=5.0104, the installation of the self rotating plastic tie can increase the heat transfer coefficient K by about 16% 3. Production increase benefit of automatic cleaning tie under the condition that the inlet steam temperature of the steam turbine remains unchanged, the efficiency of the device can be increased by about 35% for every 10% reduction in the exhaust steam temperature; For every 1% change in condenser pressure, the power of intermediate pressure turbine will change by 1%, and that of high pressure turbine will change by 0.8% Next, calculate the increase of vacuum degree and steam turbine output according to this. The prerequisite for comparison is whether plastic ties are installed in the condensing pipe and the load of the condenser remains unchanged. According to the equation, q= = constant, after the heat transfer coefficient K value is increased, the required heat transfer temperature difference is reduced, the condensation temperature and pressure of steam are reduced, the vacuum degree is increased, and the output of steam turbine is increased. After the self rotating plastic tie is installed in the tube, it not only keeps the condensation tube clean and free of scale, but also has 16% heat transfer enhancement. The inlet temperature of condenser cooling water is 18 ° C, the outlet temperature is 30 ° C, the corresponding vacuum degree is 7kpa, and the corresponding steam condensation temperature is about 39. Calculate the vacuum degree and the corresponding steam condensation temperature of the original (neither cleaned nor heat transfer enhanced) condenser with different dirt thickness, and then calculate the percentage of vacuum degree increase and the amplitude of steam turbine output increase. According to the above calculation method, the economic benefits generated by the use of cleaning ties are shown in table 3 Table 3 Calculation benefits of condensers with different thicknesses of dirt after using the self rotating tie technology dirt thickness/mm heat transfer temperature difference without tie/condensation temperature without tie/vacuum degree without tie/kpa scale removal heat transfer enhancement amplitude/% vacuum degree with tie/kpa output increase amplitude of tie/% 3.1 benefit calculation take 12MW units as an example, if the original dirt thickness is 20 and 0.25mm respectively, after using the self rotating plastic tie automatic cleaning technology, heat transfer 2 The coefficient of precautions for the use of impact testing machine can be increased by 000h, and the benefit per kilowatt hour is 0.20 yuan, so the economic benefit can reach 4 per year. Conclusion even if the dirt thickness on the inner wall of the pipe is small, only 0.25mm, the influence on the value of heat transfer coefficient K has been quite significant, up to 31.2% As a new mechanical cleaning method, self rotating plastic ties have good cleaning and anti scaling functions. The self rotating plastic cleaning link also has a certain heat transfer enhancement effect, which is a function that the rubber ball cleaning, reciprocating brush cleaning and other currently used technologies at home and abroad do not have. About 6.1 billion kw, with an annual installed capacity of more than 11million kW, so the application market of this technology is very broad. If the technology popularization rate is 50% and the vacuum degree is increased by 2% on average, the annual average operation time of the unit is 6000 hours, and the yield increase benefit per kilowatt hour is 0.20 yuan, the annual yield increase benefit can reach 2.4 billion yuan

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