How is foam formed in the distillation feed tank?
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I would like to ask the experienced colleagues: For the PVC that comes out of the polymerization reactor via the VCM process, foam is generated in the feed and discharge tanks due to stirring. What is the composition of this foam? And why does it form? Thank you
Since the polymerization reaction takes place within a sealed container, and according to the principle of thermal expansion and contraction, the temperature inside the reactor is high during the reaction, causing the container to expand and the pressure to increase. However, the pressure inside and outside the PVC particles remains balanced at this point; as a result, the PVC particles in the shape of small footballs do not expand inside the reactor. At the end of the reaction, the gas inside the reactor expands rapidly and is expelled, causing the pressure to drop quickly. This increases the pressure difference inside and outside the PVC particles, which are then pumped to the discharge tank by a centrifugal pump. At this point, the high-temperature and high-pressure water that had been trapped within the PVC particles suddenly lost its restraint; the high-pressure water vapor inside those particles expanded rapidly in an instant, causing the PVC to form. As the pressure increased, foam was generated in the material
I disagree with the view on the second floor. In my opinion, the cause of foam formation is the monomers; when the slurry moves from a high-pressure environment to a lower-pressure one, some of the monomers inevitably release into the gas phase, and this is what leads to foam formation
The formation of foam is due to the presence in the PVC slurry system of surfactants such as hydroxypropyl methylcellulose and polyvinyl alcohol (dispersants). These surfactants, acting under the effect of surface tension, enclose the monomer vinyl chloride; without reduced pressure, this results in a stable system. Once the external pressure decreases, vinyl chloride begins to gradually vaporize and release from the encapsulations, while the encapsulations formed by surfactants are carried into the gas phase along with the vinyl chloride monomer. These encapsulations break apart once they expand to a certain size, thereby forming foam. The formation of foam is detrimental to production; to eliminate this foam, other surfactants must be added to reduce the surface tension of the dispersant, thereby breaking down the encapsulation effect and causing the bubbles to burst before they can enter the gas phase.
Agreed~~Our factory has encountered this issue in actual production; the large amount of foam generated caused serious problems with material carryover in the stripping tower, which hindered production efficiency. This post was last edited by limingshuguang on 2009-4-23 at 14:38.]
It seems to be mainly due to the dispersant, as both dispersants and laundry detergent tend to produce foam.
It’s due to the effect of pressure relief; an antifoaming agent needs to be added
Some defoamer needs to be added during normal production.
Have you drunk cola? It’s the same principle as opening a Coke bottle……