Use Process Control Valves as Rheometers to Predict and Control Polyethylene Molecular Weight and Molecular Weight Distribution, 2005 PLACE Conference
In polyethylene production, having fast reliable feedback on molecular weight (MW) and molecular weight distribution (MWD) is critical for producing high quality resins. Historically this feedback comes from the quality control (QC) lab, but feedback times are at least 30 minutes, if not longer. One-third of a railcar can be produced in a large commercial plant in 30 minutes. One alternative is to install an online melt indexer or rheometer for these measurements. The downside of these online instruments is that they are expensive and can require frequent maintenance. This article describes how pressure drops across process control valves and die plates can be used as a measure of viscosity at different shear rates, which can be used to predict MW and MWD. These predicted values are then used to control the process.
Use Process Control Valves as Rheometers to Predict and Control Polyethylene Molecular Weight and Mo