Polyvinyl chloride (PVC) is one of the most common types of plastics. Production of PVC fi rst began in Germany in the early 1930’s. Since then, global PVC manufacturing has grown to over 35 million tons annually.
VCM is a fl ammable, toxic gas that is the main feedstock of PVC production. The raw materials of VCM are ethylene and chlorine. These two materials combine to form ethylene dichloride which is thermally cracked to
create VCM. Ethylene is a byproduct of steam cracking in the refi nery. The chlorine typically comes from a chloralkali facility located close by.
pH Measurement Challenges
The VCM / PVC processes are highly water intensive thus the need for reliable on-line pH and ORP measurements is a primary requirement.
Barben Performance Series pH sensors are specifi cally designed for harsh chemical processes thus are well suited for the measurement challenges in the VCM / PVC processes. The patented Axial Ion Path® reference half cell uses multiple fi ltering chambers to greatly slow the ingress of process chemicals from poisoning the sensor internals. The large annular Teflon junction provides a much greater surface area then conventional
pH sensors. The increased area is effective in reducing the plugging due to particulate matter and simplifies cleaning. Because of these design advantages the Barben sensor can be installed directly into the process instead of on a sample line.