Research On Heat-Resistance Of Filter Materials In Air-Cooled Generator

Resin particles, powdered resin and fiber powder are common filters used in the air-cooling unit. Removing impurities in condensate water is the main function of Condensate Polishing equipment to avoid water quality indicators being worsened in the thermal system. Due to the high water temperature in air-cooled condensate units, heat resistance and leachables of polishing filter are put forward higher requirements.For the resin particles, the national standard is only a screening method for heat resistance, while the maximum value of the resin heat-resistant temperature can not be determined. More over, there is a dispute about the anion resin heat resistance results in domestic and abroad study. It can not directly determine the maximum heat temperature of the anion resin from the study.The main research contents are as follows:Firstly, for the existing problems in thermal stability study, This research improved the thermal stability test methods of various types of resin, and specially studied the thermal degradation law and influencing factors of particle anion resin.Test methods combined with the actual, for different objects, defining the test conditions of the heating temperature, heating time and the water-resin ratio. The results showed that compared with the new resin, heat resistance of the resin treated after heat will increase. And for powdered resin, in a running cycle, degradation rate in high temperature is too low to reach retirement standard. For anion resin particles, It showed that degradation rate increases with the the rising water-resin ratio. When the water-resin ratio is a constant, degradation reaction follows zero-order kinetics well. Anion exchange capacity linearly decreased with time.Secondly, joined the leachable test into evaluation methods of heat resistance. It is important for the high-parameter air-cooled generators demanding water quality. It has been systematically studied that leachables of different type filter materials at high temperatures. A comprehensive index of leachables evaluation system was Initially established including increased leachables comprehensive indicators, the law and factors of leachables, combined with field tests analyzing the leachable effects in detail. The results showed that the new filter materials contained maximum inorganic and organic impurities. Leachables not only affect the quality of water, but also affect the ion exchange capacity. So it needs to focus on leachables cleaning in new filters. Dissolution diminished with the cleaning time exponentially. Rising temperature and water-filter ratio can both increase leaching rate of new resin particles. Through a combination of laboratory and field tests, it can analyze the leachable impact on water quality. According to the relationship of dissolution volume and water-filter ratio, it can be calculated leachable impact under the actual water-filter ratio. Through on-site supervision of water quality can determine releasing and migration of impurities more intuitively and accurately.Thirdly, the external factor and internal factor influencing the heat-degradation rate of resin were analyzed. It found that dissolution of oligomers and degree of crosslinking of resin can significantly affect the heat resistance. The results showed that the affect mechanism is the oligomer can induce breakage of the resin structure and causing degradation of the resin skeleton, and is accompanied by the loss of exchange capacity. The amount of oligomers can be reduced by two removal methods. It showed that the new anion resin should not be directly used in high temperature water. Anion resin should be quitted running as the temperature over60℃; while the degradation rate of the resin removing oligomers is less than4.6%in a year, the condensate filter need not be quitted at high temperatures. Crosslinking index can reflect stability of resin structure. Physicochemical properties of the resin which includes moisture, swelling rate, and glass transition temperatures are all related with the degree of crosslinking. Though these indicators, it can roughly determined resin heat resistance.In this research, it is systematically revealed that the heat-resistance and leachable laws of polishing filters at high temperatures, which provides theoretical guidance and project proposals for the selection of condensate equipment in air-cooled unit.