The vacuum system plays a key role in the devolatilization process.
High efficiency devolatilization
The vacuum system plays a key role in the devolatilization process. Not only is it important to create a vacuum — the separation of solid particles from the volatiles which are extracted from the melt presents a particular challenge. Many extruders require an absolute pressure of < 5 mbar, using dry vane vacuum pumps. During the devolatilization of polymers, it is inevitable that monomers, oligomers and other solid particles or sublimates are sucked out. If these enter the pump, they will drastically reduce its operating life and for this reason, separating systems are needed which under tough industrial operating conditions are extremely maintenance intensive.
Thanks to its extremely high surface area exchange rate, the MRS extruder can in most cases provide excellent devolatilization with a vacuum of only 30 mbar. This permits the use of much simpler and less sensitive water ring pumps which create a vacuum using a rotating impeller, mounted eccentrically to the liquid ring. The liquid in circulation can be passed over a belt filter under atmospheric conditions. In this way, the maintenance of the system can be reduced to an absolute minimum.
The circulating fluid is heated through the process. In order to avoid an increase in the steam pressure, the liquid is pumped through a heat exchanger where it is kept at a steady temperature of around 10°C. The intelligent design permits simple cleaning of the heat exchanger while the system is operating.
While normally the MRS extruder operates on standard applications with its low maintenance 25 mbar liquid ring vacuum system, special effects can be achieved using its intensive surface area exchange in combination with deeper vacuums (e.g. 0,5 – 2 mbar). Gneuss has also standard solutions available for such applications.
Advantages of the MRS vacuum system:
- Handles liquids, vapor and solid particles
- Isothermic compression (no contamination during condensation)
- Oil free compression (no contamination during condensation)
- Simple design with water ring pump and belt filter
- Robust and not sensitive to blocking of suction and pressure pipes
- Standard vacuum level of 25 mbar