Flow measurement of highly viscous media
Long-term stability and easy cleaning thanks to SAW sensor – The collaboration with Polymaterials AG
The FLOWave flowmeter is suitable in almost every industry, even for polymer production. Polymaterials AG uses them during the scale-up in the pilot plant at Chempark Leverkusen to determine the feed of the highly viscous media upstream of the extruder.
“Since our work often involves innovating and exploring new avenues, we also rely on creativity in terms of technical implementation; and especially when it comes to scaling up, we like to think outside the box to find solutions.”
Small changes have a big impact
During scale-up, the production plant for thermal degassing operates with a planetary roller extruder as a chemical reactor. The interactions during the extrusion process are very diverse. Pressure levels, rotation speed, temperature zones and flow play an important role. Since even the smallest change in one of the parameters can have a major impact on the overall process, it is important to know and maintain constant as many influencing factors as possible. “Depending on the process, there can be as many as 50 parameters,” explains Christian Hauner. To validate the process, the extruder should consistently output a certain amount of polymer granulate at the end. The throughput is therefore an important factor in polymer production. How much polymer flows into the extruder and how much granulate leaves the extruder provides important indicators for assessing product and process quality. Until recently, however, the throughput could only be determined gravimetrically via the granulate obtained. However, collecting and weighing the granulate was very laborious and time-consuming. “There were no other options available for us to begin with. Unfortunately, flowmeters based on the Coriolis principle installed before the extruder have proven to be unsuitable in the past,” said Christian Hauner. If a test did not go as expected, the sensor had to be disposed of because the curved measurement tubes could not be cleaned. In addition, a large amount of resistance had to be overcome during the start. Of course, it is better to simultaneously control what is flowing into the extruder.
“If we know that, for example, 60 litres flow in per hour, we can ultimately evaluate the process quality based on the granulate obtained. With FLOWave, we can easily implement closed-loop control and stationary operation.”
Continuous flow measurement at the inlet of the extruder
The polymer specialists finally found a practical solution for flow measurement in the inlet of the extruder when they paid a visit to Bürkert’s stand at a trade fair. They opted for the FLOWave flowmeter. The flowmeter has now proven itself in the pilot plant and there are plans to utilise more of its functions in the future, such as density determination. The flowmeter works according to the SAW (Surface Acoustic Waves) principle, i.e. it uses the propagation speed of acoustic surface waves in liquids. In extensive testing with highly viscous polymers and temperatures up to 80 °C, the flowmeter proved itself in every aspect of the process. The measuring system does not require any sensor elements in the measurement tube, which has several advantages:
- No leaks
- No material incompatibilities
- No maintenance
- No pressure drop
- Easy cleaning
- Sensor behaves like a pipe (long-term stability, no recalibration)
- Accuracy of 0.4% of the measured value
- Made of high-quality stainless steel
- Significantly lighter than comparable Coriolis systems
The DN 15 variant installed upstream of the extruder weighs approx. 3 kg, i.e. only around a tenth of a comparable Coriolis measuring system. This made handling during installation much easier. The installation position is flexible. The display can be positioned anywhere so that the flowmeter is easily accessible for configuration during commissioning. Various display and control options are available on the process control system. During operation, the SAW flowmeter consumes very little energy and the wear-free measuring principle saves service costs.
“Commissioning was easy. We were able to do it ourselves and if we had any questions we simply gave Bürkert a quick call and they helped us quickly and competently. In Bürkert, we have found a helpful and competent partner with whom we will continue to work together in the future.”
Thanks to the wide range of options and variants, continuous flow measurement based on the SAW principle is also suitable for many other industries, especially since the FLOWave can provide additional measured values such as media temperature and concentration, as well as detect contamination.
“In extensive testing with highly viscous polymers and temperatures up to 80 °C, the flowmeter proved itself in every aspect of the process. In addition, the measuring system does not require any sensor elements in the measurement tube, which makes cleaning easy if an experiment does not go as expected.”