Dosing corrosive monomers in a pressure reactor

Problem

The monomers to be dosed into the reactor have a high melting point and must be processed at 150°C – 200°C. In addition, the viscosity ranges from 1 to 1,000 mPa·s and both the monomers and the added solvents are chemically aggressive. The materials used must therefore be corrosion resistant. The stirred vessel must be able to be pressurized (max 5 barg) to inertize. The available space in the fume hood is limited to 450 x 600 x 1000 cm.

Requirements for the system designed by Suurmond:

• A stirred vessel of 2 litres that must be able to operate under nitrogen (up to 5 barg) and vacuum to inertize
• Temperature range: >150°C (max. 200°C)
• Viscosity range 1-1000 mPa·s
• Flow: precisely controlled from 1-100ml/min.
• Gravimetric/volumetric control of the volume
• Tracing of the complete system to prevent solidification of the substances
• Corrosion resistant materials
• Maximum back pressure in reactor vessel is 5 barg
• Limited, available space in fume hood (WxDxH) 450 x 600 x 1000 cm

Our solution

Suurmond designed a compact dosing system with heatable pressure vessel on a small platform that can be placed next to the reactor in the fume hood.

Pressure vessel

The system consists of a heatable stainless steel pressure vessel of our own design with a BÜCHI magnetic stirrer type "BMD 075" for keeping the monomers moving and homogeneous. Due to its corrosion resistance, this stable magnetic stirrer is equipped with ceramic ball bearings and a Kalrez O-ring. Stirrer shaft and stirrer are also suitable for corrosive fluids, so that use with chemically aggressive fluids, such as solvents, is no problem. The pressure vessel is equipped with tracing to keep the monomers in the vessel liquid. The complete system is insulated with custom-made thermal insulation mattresses.

Dosing

To dose the monomers, a special execution HNPM micro gear pump type mzr-7255 is used. The pump is therefore executed with an insulation module between pump head and servomotor. This pump is herewith suitable for fluid temperatures up to 200°C (normally, this type of pump is suited up to 60°C)! This micro pump can handle the wide viscosity range just fine. Moreover, the use of this gear pump does not require any pre-pressure. With the mass flow meter, the flow can easily be measured and controlled in closed loop. Both volumetric and gravimetric.

Control

The control is also tailor-made. It is designed in such a way that you can set the dosage yourself and enter the process steps.

Result

This setup allows the customer to dose the monomers both batch-by-batch and continuously in the reactor. The suurDOS® ensures an optimized and extremely accurate polymerization process.