Polymerization of vinyl chloride monomer
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During maintenance, the vinyl chloride monomer storage tanks in our plant have a thick layer of self-polymer at the bottom of the tank. How can this be resolved?
Is there water accumulated in the single-tank reservoir? Pay attention to draining the monomer storage tank. This post was last edited by edc1233 on 2008-7-5 18:15]
The main goal is to reduce moisture content. In the fresh monomer tank: 1. It is required that the vinyl chloride plant reduce the moisture content of vinyl chloride, ideally to ppm levels; a solid alkali dryer can be used for this purpose； 2. Reduce tank temperature ； 3. Increase the frequency of drainage, with operators carrying out drainage operations effectively ； 4. The monomer filter in the feed pipeline of the fresh monomer tank must be in good condition. Monomer recovery tank: 1. Lower the tank temperature ； 2. Increase the frequency of drainage, with operators carrying out drainage operations effectively ； 3. Increase cyclic filtration ； 4. The recovered gaseous monomer must be filtered, and a polymerization inhibitor must be added ； 5. After an abnormal recovery occurs in the reactor, the monomer in the recovery monomer tank must be processed promptly to prevent excessive self-polymerization caused by residual initiators. This post was last edited by edc1233 on 2008-7-5 18:17.]
Specific measures: 1. Require the vinyl chloride plant to reduce the water content in vinyl chloride to less than 100 ppm; liquid or solid alkali drying processes can be used for this purpose. 2. Strictly control the iron content and pH level in the monomer. 3. Increase the frequency of drainage, with operators ensuring proper drainage procedures are followed. 4. A filter should be installed before fresh monomer is introduced into the tank. 5. In the event of abnormal recovery, the monomer in the recovery tank must be processed promptly to prevent excessive self-polymerization caused by residual initiators. 6. A polymerization inhibitor can be added in appropriate proportions to the monomer tank.
Fresh monomer is used for enhanced water discharge; an inhibitor such as nonylphenol can be added to the recovery pipeline to prevent self-polymerization of the recovered monomer
There are roughly two possible reasons: 1: The water content in the monomer is above the limit. 2: The polymerization off-gases are returned directly to the gas holder, carrying the initiator with them.
The most important things are to keep the drainage and tank temperatures low, and to add a polymerization inhibitor when recovering the reacted VCM gas. This post was last edited by edc1233 on 2008-6-26 19:20]
What is the typical temperature of the monomer storage tank? Could someone please explain in detail how to reduce the concentration of water in the monomer to below 100PPM?
The temperature of the monomer tank is generally at room temperature. The approach we are using at present is to employ an alkaline solid dryer to remove water from both the gaseous and liquid vinyl chloride streams, resulting in a final monomer moisture content of around 100 ppm.
The self-polymerization of the recycled monomer may also be due to an insufficient amount of terminator; increasing the amount of terminator appropriately should help. This post was last edited by limingshuguang on 2008-6-27 11:49.]
Using high-pressure water to clean the tank today is giving me a headache. Overtime.
It is required that the water content of the monomers leaving the VCM synthesis workshop and entering the storage tanks be less than 50 ppm; polymerization inhibitors can also be added regularly to the monomer storage tanks. The key is still to keep the water content in the monomers under control.