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REACTOR FOULING

Scale deposition (fouling) on reactor's internal surfaces has caused severe problems since the beginning of S-PVC industry such as:
- Long polymerization times due to fouling's low heat transfer
- High down times due to discharge clogging with broken-off fragments
- Loss of materials due to scale scrap
- Poor Quality due to morphological problems derived from changes in mixing patterns.
All of these resulted in lower Plant's Productivity and Efficiency.
As commented, vinyl chloride polymerization is a very complex process that involves time-evolving, concurrent, simultaneous interacting chemical and physical phenomena.
Some internal-surface phenomena that influence fouling are…
Adsorption/precipitation of Suspending agents (SA) on metal surfaces
Adsorption/condensation of VCM on metal surfaces
Reaction of growing macroradicals with metal active sites
Reaction of growing macroradicals with adsorbed suspending agents
Swelling of PVA/PVC deposits with VCM
Polymerization on VCM-swelled SA/PVC deposits
Fouling on clean-metal surfaces inside S-PVC reactors starts when Suspending Agents and VCM adsorb on metal surfaces at the beginning of the reaction.
Fast (co)polymerization initiated by metal active sites or initiator decomposition anchor some polymer chains and form a thin PVC/suspending agent copolymer film layer firmly stick to metal surface by interlocking with surface wall roughness.
Any PVC or PVC/SA (co)polymer, either just formed or from previous batch, swells with VCM and undergoes further polymerization, growing quickly by precipitation of macroradicals and accretion of sticky polymerizing droplets creating an irregular thick layer that eventually would break out but leaving a thin film layer that repeats the growing phenomena next batch.


Development and proper application of Highly-efficient Antifouling Agents has lowered drastically most problems associated with fouling, allowing reactor use for extended periods.
Highly-efficient Antifouling Agents forms a thin solid layer of insoluble phenol-based polycondensation material that adhere by interlocking with surface roughness and cover internal metal surface, effectively hindering free-radical surface reaction.
This layer has lower hydrophilicity compared to metal surface so that adsorption of Suspending Agents is discouraged, minimizing accretion of polymerizing droplets.
For all of the above, it is very important to understand all phenomena involved to properly select both application and curing conditions that maximize the efficiency of the specific Antifouling Agent you are using on all reactor's internal surfaces.

Do you have excessive fouling in your reactors or cooling devices?
Do you want to reduce Fish Eyes caused by fouling?
Do you want to get rid of fouling scraps produced in your reactor?
Do you want to change your Antifouling Agent for a more cost-efficient one?
Do you want to extend the occupation period of your reactor between cleanings?
Let me help you understand and safely control fouling phenomena
in your polymerization reactors to optimize
the performance of your S-PVC resins and Production Plant.
View my PROFILE and visit my CONSULTING SERVICES page.
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