Improve the cleaning effect of screen changer
The cleaning of the screen changer is divided into three steps: TEG cleaning, high pressure water gun cleaning and ultrasonic cleaning.
TEG is a colorless transparent neutral oily liquid with a boiling point of 276 C. It can alcoholyze and dissolve polyester under heating condition [2]. TEG cleaning is to dissolve the polyester melt on the screen changer by heating and cooking under the action of TEG solvent. The newly removed melt filter core, wrapped by polyester melt, must be cooked in TEG cooking tank and removed at 285 C for 4 hours at constant temperature. Removing the filter core, it is found that some melt still can not be completely dissolved. Therefore, the constant temperature time is increased from 4 hours to more than 6 hours to dissolve all the melt adhering to the filter core. At the same time, the secondary TEG cooking method is adopted, that is, the removed filter core is loaded into a hoisting basket for secondary cooking, so as to further increase the effect of cooking and cleaning.
Strengthen high-pressure water gun to wash TEG cooking filter element, because it is dirty, it must be washed with high-pressure water gun. And the use of external filter screen changer, impurities left in the outer layer of the screen changer filter. To this end, a special high-pressure water gun is used to wash out the impurities from inside to outside. At the same time, the outer protective cover of the filter element is removed to enhance the cleaning effect. In order to wash the filter core to a large extent, 10 filters were randomly removed from a set of screen changer filters, and 5 of them were removed at random. Then the filter core was cleaned by high-pressure water gun, and then cleaned by ultrasonic wave for 2 hours. Bubble point test was done. The comparison results are shown in Table 2. It can be seen that in the stage of high-pressure water gun washing and ultrasonic cleaning, the iron cover outside the screen changer filter core is removed, which makes it easier to clean the filter core.
Strengthening ultrasonic cleaning is necessary because small molecular impurities are easy to squeeze into the filter element under high pressure, and it is difficult to wash them out with high-pressure water gun. In order to find out the cleaning time, a group of experiments were done. The results are shown in Table 3. Increasing the time of ultrasonic cleaning alone is not the way. Therefore, the ultrasonic cleaning time should be set at 2-3 hours.
After the steam back-blown screen changer filter element was cleaned by ultrasonic wave, some impurities were removed, but some remained in the filter mesh. In order to remove these impurities, a 1.6 MPa steam back-blowing production line was built to remove the internal impurities to the greatest extent. Practice has proved that the effect is remarkable.