On the characteristics of slurry cross-flow airlift towers and microplate airlift towers

Thread Content

Currently, the slurry gas lift towers used by PVC manufacturers in China can be divided into two main categories: one is the slurry cross-flow gas lift tower, and the other is the microplate gas lift tower with an overflow weir. Most manufacturers still use cross-flow stripping towers, while a smaller number of them, such as Qilu, Taihua, Daguhua, and Canghua, use microporous plate gas towers. Features of cross-flow gas towers: 1. Low cost 2. Relatively simple to manufacture 3. Easy to operate 4. High processing capacity 5. Operated at positive pressure, making them safer 6. Few control points, resulting in less reliance on DCS 7. Strong ability to adapt to fluctuations in various process parameters 8. Not prone to tower blockage 9. Easy to clean with short cleaning time 10. Can basically meet the requirements regarding resin residue levels 11. Require high installation skills 12. Higher steam consumption compared to overflow weir air lift towers. 　Characteristics of the overflow weir air lift tower: 1. High cost; 2. Complex manufacturing process; 3. High requirements for the skills of operators; 4. Operation under negative pressure; 5. Numerous instruments and control valves, with a high dependence on DCS control; 6. High requirements for the stability of various process parameters; 7. Prone to tower clogging; 8. Long cleaning time; 9. The residual amount of resin after air lifting meets the standards without the need for drying; 10. Lower requirements for installation techniques compared to cross-flow air lift towers; 11. Lower steam consumption. 　The following are my personal views on operating an overflow weir air lift tower well. 1. The steam pressure and flow rate must remain stable, with each adjustment amount not exceeding 0.1 tons per 5 minutes. If necessary, a dual-valve system can be installed to maintain steam stability through simultaneous regulation of pressure and flow. 2. The temperature of the slurry entering the tower should be at least 96.5 degrees Celsius; if the slurry heat exchanger is an original imported model from Nitto, achieving 96.5 degrees Celsius is not a problem. In the case of domestically produced heat exchangers, it may be possible to use the waste heat generated during PVC conversion to raise the temperature appropriately. It is known that similar heat exchangers can also be manufactured in China using imported technologies. 3. The control of the tower top pressure is based on the residual amount of resin; the vacuum level should not be too high to ensure safety. 4. When producing high-grade resins, it is essential to add an adequate amount of high-quality defoamer. 5. The capacity of the spray tank should be 50% greater than the static liquid volume in the air lift tower, with the water temperature set at 98 degrees Celsius, so that there is sufficient water available for flushing and replacement in case of any abnormalities in the air lift tower. 6. The layout of the air lift pipeline requires careful consideration, and it needs to be adjusted continuously through practice.