Control of Ethylene and Propylene Polymerisation Processes

Abstract

Many polymerisation processes can be accurately controlled by the regulation of chain growth through rheological measurement of average molecular weight. This article looks at the new developments in rheological analysers that can reintroduce closed-loop control into a variety of polyethylene and polypropylene manufacturing processes. Through the study of the exact flow patterns in Melt Flow Index test, computer fluid dynamics has enabled this industry standard test method to be faithfully replicated in the some of the more advanced instruments. These instruments can now be classed as analysers and serve the intended purpose of better control of the polymerisation processes. The whole of the polymer industry can benefit from this combined system of measurement and control technology. Closed-loop control of the primary polymer manufacture can ensure that the product is made to close tolerances instead of the present permitted ±10% passband. The manufacturer can benefit from improved plant efficiency by making the desired product as well as being able to guarantee a highly consistent product. The downstream processor can benefit from reduced material usage and elimination of process set-up wastage. A large variety of recyclers and the raw material manufacturers can benefit from the new technology by introducing reaction grades of polymer into the existing processes or by improving the measurement and control of those processes that are already producing reaction grades.