Chemical Company Builds State-of-the-Art Emulsion Plant
Alberdingk Boley selected RHE Händel Engineering GmbH & Co. KG and RHE America to design and supply the equipment. "Our history with this company dates back many years," said Bernard Seguy, president of RHE America. "We've designed and supplied most of the emulsion production trains including raw material and product storage tank farms and buildings to Alberdingk Boley for the last 30 years."
Several factors were given special priority in designing the plant. They included:
- Safety, both operator and equipment;
- Consistent product quality;
- Short batch times;
- Turnaround time minimization.
Safety
Volatile Monomer Storage: Controlling the storage temperature of many of the liquid monomers (such as acrylics, styrene, vinyl acetate, etc.) is a critical safety issue. Alberdingk Boley's storage tanks include equipment to monitor, both automatically and continuously, the liquid monomer temperatures. Also included as part of the monomer storage system is an external heat exchanger loop cooled with chilled water. Any temperature increase in the liquid monomer temperature triggers automatic circulation of the monomer through the heat exchanger loop.Monomer Blending: Preventing runaway reactions in the monomer blending tank is another critical safety issue. The system installed by RHE controls the temperature inside the monomer blending tank by continuously circulating cooling water through half coils on the outside of the vessel. Lastly, if the temperature inside the monomer blending tank increases above the predetermined critical point, reaction inhibitor is automatically injected.
Reaction Start Point: Alberdingk Boley had RHE include a continuous, online enthalpy measurement and temperature gradient system to determine the exact reaction starting point of the polymerization reaction. If the reaction does not start at the expected time, the reactor is automatically shut down. Automatic shutdown means that all raw material feeding is stopped, reactor heating is stopped, reactor cooling is started and alarms are triggered. After shutdown, the operator can sample the mixture in the reactor, determine the reason the reaction did not start as expected, and decide on the correct course of action.
Product Quality
Raw Material Addition: Consistent product quality starts with consistent raw material addition. All tanks of the train are mounted on scales, and the raw materials are added automatically by weight to assure consistent reproducibility.
Full Automatic Process Control: RHE supplied Alberdingk Boley with fully automatic process-control schemes. These control schemes include formula-management programs for the automatic processing of different types of formulations and reports outlining all events for each batch. This user-friendly control system assures consistent product from batch to batch.
Short Batch Times
Agitation: A custom-designed agitator with a variable-speed drive to stir the reactor contents was included. This agitator displays efficient horizontal and vertical mixing. This efficient mixing reduces the batch times because of both better raw material contact and faster heat transfer.
Heating/Cooling Circuit: A controlled heating and cooling circuit was designed to maintain the preset temperature with an accuracy of plus or minus 1 deg C. This tight control of the reactor temperature eliminates hot or cold spots inside the reactor and avoids temperature fluctuations.
Minimize Turnaround Time
Reactor Cleaning: In the production of polymer emulsions, the turnaround time between batches is used to clean the reactor. Polymer emulsions tend to stick to all kinds of surfaces, particularly the inside of the reactor and the reactor agitator. RHE polished all the surfaces in contact with the product to a mirror finish, including the reactor internals and the agitator surfaces.Reactor Design: During the production of polymer emulsions, monomer vapors without inhibitor rise to the top of the reactor vessels. The typical reactor is insulated at the top. As the monomer vapors rise, they tend to polymerize and form a layer of polymer hanging down from the top of the reactor vessel. RHE developed a reactor design for Alberdingk Boley that significantly reduces this problem. Rather than insulating the top of the reactor vessel, a system was designed to cool it with water circulating through half-pipe coils attached to the exterior of the reactor top. Therefore, the monomers rise to the top of the reactor, condense on the reactor surface, and flow back down into the reactants. This virtually eliminates the formation of a polymer layer on the interior of the reactor top, thereby reducing the time and effort needed to clean the reactor between batches.
For more information, contact RHE America at 630/577.0400, ext. 209; e-mail seguyb@amcec.com; or visit www.rhe-america.com.
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