The topic
Polyethylene and polypropylene are among the most frequently used synthetic materials, particularly in the packaging industry, as insulating material for cables and capacitors, in the automobile industry, as raw materials and as coatings for pipelines. Borealis has its own technology to produce these high-quality materials on a large industrial scale. With its motto of “creating added value through innovation”, the company is very keen on increasing the efficiency of its technology for making synthetic materials.
The research question: how can the production of synthetic materials be further optimized?
Polyethylene and polypropylene are produced in fluidized bed reactors from their monomers, which are supplied in the form of pellets about 2 mm in size. The fluidized bed reactors are industrial-scale facilities about the size of a church tower. The raw materials (monomers) are introduced in a gaseous form and converted to solid polymer chains with the help of a catalyst in a process that releases heat. In the ideal case, all of the resulting polymer pellets would have identical sizes and properties but this only happens if the reactors are precisely controlled down to the level of the individual particles. It is important to control and predict the behaviour of all particles as accurately as possible, as each tiny irregularity increases the use of energy and raw materials, produces more rejects and can lead to costly production stops. The technical challenges can be studied empirically on the laboratory scale but the results cannot be simply transferred to the production facilities because of the disparity in scale between the tower-sized reactors and the laboratory equipment. There is a need for new, complex mathematical models and elaborate numerical simulations.
Collaboration in the CD Laboratory
Borealis can only undertake the fundamental research at the necessary level of complexity in collaboration with an external partner with appropriate expertise, which is why the company chose to work with scientists at a university. Prof. Pirker and his team in the CD Laboratory for Particulate Flow Modeling have longstanding experience with mathematical modelling, as well as the necessary resources and computer power. The CD Laboratory has developed and validated a mathematical model based on a description of the problem and using appropriate data sets from Borealis.
Results
The mathematical model developed in the CD Laboratory, the Subgrid Model, can model all key parameters and thereby enables optimization of the process technology. The retention time of the monomers in the reactor, the temperature profile of the reactor and the precise gas flows in the fluidized bed can all be calculated. The results have already been implemented, based on the modelling and on an experimental validation on the laboratory scale – which was also performed in the CD Laboratory. The scientists have used their model to investigate the available facilities in detail and to optimize them, whether they were pilot-scale or production facilities. Borealis has secured patent rights to all relevant technological advances but the model’s methodology has been published and made available to the scientific community via the freely accessible open-source simulation platform CFDEM (www.cfdem.com) for further optimization. The CD Laboratory for Particulate Flow Modeling has also enabled a staff member to qualify as an Associated Professor. The success encouraged Borealis to establish a new CD Laboratory in 2016 to continue its research, again with the University of Linz
