Combined Mass Flow - Pressure Control for safe and automated reactor pressure control.
Thermal measurement principle
The proposed set-up may slightly vary per application, since the concept can be applied to both analog or digital systems. Furthermore the instruments used may be in ‘laboratory style’ or with rugged industrial housing, IP65 protected and optionally with ATEX Zone 2 approval. To illustrate the solution, uniquely offered by Bronkhorst, please see the adjacent schematic.
At the inlet of the reactor, a mass flow controller (MFC) takes care of the process gas delivery, whilst an electronic pressure transmitter (EPT) measures the reactor pressure. At the outlet of the system there is a flow restriction which could simply be a (needle) valve or, as shown in the illustration, a mass flow regulator (MFR) with local display. The reactor pressure is controlled by giving a setpoint to the pressure transmitter. In the illustration this is done via RS232 by a script programmed into a PC. The integrated PID-controller of this pressure meter (Master) controls the valve position of the mass flow controller's control valve (Slave). When building up the pressure in the reactor, the maximum inlet flow is restricted by the mass flow controller, thus preventing a flow peak. By using the ‘slave factor’ option, the maximum flow can be adjusted.