For great demands
Research reactor uses Coriolis technology for charging with hazardous batch ingredients

A new compact Coriolis mass flow meter designed for a pilot plant can be tuned to match the technology and production reaction characteristics of full-scale PVC production units.

Synthomer is a major producer of the polyvinyl alcohols used as suspending agents in the polymerization reactions of Vinyl Chloride Monomer (VCM) to produce PVC. To aid in the development of these additives, the company needed a pilot reactor at its Harlow plant. The plant is designed to be capable of being tuned to match the technology and production reaction characteristics of the full-scale PVC production units. A significant challenge included the containment of the toxic and flammable VCM raw material within a hermetically sealed unit designed to deliver zero emissions of VCM to the environment.
The plant was developed by Strata Technology, a project and design services company based in Sunbury on Thames and specializing in the petrochemical and pharmaceutical industries. At the heart of the plant is a highly automated 10 liter reactor vessel, operating at pressures of up to 18 bar and maximum temperatures of 85 °C. The whole plant is contained within a ventilated enclosure, and effluent gases are treated within a thermal oxidative facility to destroy any VOCs (Volatile Organic Compounds) produced. The automated system will also deliver information on batch calorimetry, reaction profiles, foaming levels and agitator power demands.
In handling the raw material feed into the reactor, Strata Technology placed great emphasis on accurate material delivery, fluid containment and integrity of the pipework. The raw materials, such as VCM, are held in bulk storage tanks. Charging of the reactor is controlled via interlocks and logic within the PLC control system designed by Strata Technology. A Bronkhorst Coriolis flowmeter and control valve are used to provide the critical flow control elements.

The Cori-Flow mass meter
Pivotal to the control system is the precision Cori-Flow mass meter. Two stainless steel tube loops contained within the meter body are fully welded and have no seals or shafts to leak. As a quality assurance check the tubes are helium leak tested in the factory. Integrated within the single, neat Cori-Flow package is all the electronic circuitry required to receive the input command signals from the pilot plant control system: the Cori-Flow provides the drive signals and PID control functions to drive the electromagnetic coil in the flow control valve, as well as establish the mass flow rate requested, whilst also giving an electronic output proportional to actual recorded mass flow.
VCM leak paths are eliminated
The construction of this control valve uses a plunger and orifice combination: flow is controlled using the magnetic force from an electromagnetic coil encapsulated within the valve body. There is no gland packing or external connection to the plunger, eliminating all potential VCM leak paths in this area. The normally closed valve, with a metal-to-metal seal, has good resealing capability. Actual shut-off valves are separate duplicated quarter-turn ball valves further down the line.
The mass flow meter measures the actual mass flow rate of the VCM, and the water flows into the reactor at rates up to 20 kg/h. The monitoring range covers fluid flows from as low as 20 g/h up to 600 kg/h, with a 1 bar maximum pressure drop. The control system monitors these flows to determine when the required batch quantity is complete, and signals to end the batch at the required volume. The operator and the main system can therefore concentrate on adjustment and optimization of the ingredient sequence logic and the timing of the different additions in the polymerization process. The system also monitors and records all process reaction mixture temperatures and pressures for later analysis.
The Cori-Flow units in this reactor system are the primary flow measurement devices on the installation. They control the reactor charge where accurate measurement is very important. The mass flow measurement systems have a repeatability of 0.1% of rate. This measurement is independent of fluid properties such as density, viscosity, conductivity, temperature and pressure.
The microprocessor-based intelligence within the Cori-Flow unit itself can be used for other digital interfaces and communications, as well as computation and control.