Let’s discuss together what the reasons for distillation self-polymerization are, what the principle behind it is, and how to address it; this is just to spark some discussion
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Reasons for self-polymerization: 1. Excess acid; 2. Excessive moisture content; 3. High oxygen level. Solutions: 1. Improve the effectiveness of washing with water and alkali – inspect the packing in the alkali washing tower and turn the Pall ring upside down to ensure sufficient contact area during alkali washing； On the other hand, it is required that the compressor team strengthen the monitoring of the effects of water and alkali cleaning, and immediately notify the conversion unit to make adjustments whenever abnormal pH values are detected. 2. Strictly control the temperature before the machine to ensure effective dehydration. Originally, the dehydration temperature before the machine was set at 25±5°C; it has now been adjusted to 10–15°C, in order to remove as much moisture as possible from the VC gas before it reaches the distillation system, thereby preventing a series of hydrolysis reactions from occurring. 3. Control the negative pressure in the pipeline ahead of the controller and the inlet pipe. The areas where negative pressure is likely to occur mainly include the pipelines in front of the machine and the inlet at the first stage of the compressor. For these areas prone to negative pressure, the workshop and production units regularly arrange personnel to check for leaks, and they also ensure that operations at various stations are carried out under positive pressure conditions. In addition, water collection tanks have been installed at the points in the pipelines in front of the machine where liquid seals may form, thereby preventing negative pressure from arising as a result of such liquid seals. 4. Improve drainage
There are many reasons, but the main ones are the initiators in the polymerized recycled VC and the residual PVC fine powder!
I agree as well; it is mainly the self-polymerization caused by the initiator added to the polymerized and recycled VC, and we add a polymerization inhibitor in the polymerized and recycled condenser.
My opinion: 1. The large VC storage tank should be equipped with a water collection tank and a level gauge for automatic drainage. 2. Adjust the pH before it enters the compressor; the pH should be 8.5. Through the alkali concentration in the alkali scrubber and the amount of ammonia injected. 3. Add the inhibitor uniformly before distillation: 75% solution of tert-butylhydroquinone
Residual initiators can be addressed by adding polymerization inhibitors; I believe the main issues to be dealt with are those related to moisture content and the design of the tower. Using high-efficiency guided sieve trays instead of traditional bubble columns can yield significant improvements. This post was last edited by shizhiyong001 on 2009-3-3 at 08:42
In fact, the self-polymerization of vinyl chloride is determined by its inherent properties; there is a strong attraction between its molecules, and certain external conditions further facilitate this self-polymerization. I think controlling its self-aggregation cannot be avoided through a single action; multiple approaches are necessary. As everyone has already analyzed quite a few reasons above, I will list them briefly again: the main influencing factors are still temperature and moisture control. Special attention should be paid to the control of the temperature and moisture in the compressed syngas; it is recommended to adopt a reasonable post-compressor cooling scheme.