When there are Emerson Exchange sessions about brewing beer, each is usually very well attended, even without free samples. There were at least two at the 2017 exchange, at opposite ends of the spectrum, a small craft brewery (Badger Hill) and a mega-brewer, MillerCoors. As different as the two companies are, both presentations talked about measuring level, and how much process information can be captured from a very basic differential pressure (DP) level measurement.
Andrew Klosinski, optimization engineer for MillerCoors discussed how the brewery made some major advances in its fermentation process by changing the way they measure level in the fermenters. His presentation has been turned into an article in the March issue of Control: MillerCoors Optimizes Fermentation. As sophisticated as the brewing process is, there are still inconsistencies caused by the ingredients and other factors.
Beer is a food product, and no matter how much the process is instrumented and automated, it's still subject to the variability of agricultural feedstocks (barley, hops, etc.) and biological processes (fermentation using a living organism—yeast). The recipes and procedures do not work the same way every time, and even small changes in feedstock or process conditions can have a significant impact on the characteristics of the final product. There are ways to quantify and measure some critical attributes, but ultimately the human element plays a major role in regulating the process to ensure the consistency consumers expect.
These inconsistencies do indeed call for the human element, but if humans don’t know what’s happening inside those huge tanks, they can’t perform to their utmost. Upgrading instrumentation to capture some critical attributes makes process improvements possible and practical. Andrew discussed two specific situations where adopting a new level measuring technique made a significant difference. The first had to do with capturing an important byproduct, carbon dioxide, and by deploying the Rosemount™ 3051S Electronic Remote Sensor (ERS™) system from Emerson, operators were able to get a better picture of CO2 production.
When a new batch of wort is pumped into a fermenter, CO2 production does not begin immediately. Some time is required for the yeast to start working, and enough CO2 has to be produced to drive all the air out of the headspace before collection begins. The standard procedure in the brewery was to wait a specific number of hours before collecting CO2 because there was no useful indication of when the yeast had hit its stride. Since the ERS system allows access to the individual measurements from both sensors, we were able to read the pressure in the headspace. Having that reading helped us realize that CO2 production was beginning earlier than we thought, so we changed the procedure to begin collection when the pressure reached a tipping point, which was often many hours ahead of the normally scheduled time.
So, having a direct pressure measurement from the fermenter headspace helped operators maximize CO2 capture. Being able to recognize when the fermentation cycle is complete also helps maximize throughput for the fleet of fermenters, a huge benefit.
When wort is first pumped into a fermenter, its specific gravity (SG) is high, raised by its glucose content. Throughout the fermentation cycle, the SG of the beer drops. Similarly, CO2 production slows and stops as fermentation reaches its end. The ERS system can recognize both events, and send corresponding data to the control room. By watching the output from the ERS system, operators can tell when fermentation is complete, and the product can be moved from the fermenter into the aging tanks. Prior to installing the ERS system, fermentation was declared finished by the calendar. Watching the actual fermentation performance of batches using the ERS system data suggested that CO2 production ceased and the SG stopped declining long before the schedule said it was done, often as many as 40 to 50 hours early.
Andrew and his colleagues determined that the beer could indeed be moved to the aging tanks sooner than previously believed, shortening the time spent in the fermenters. With less time, more batches could be put through the process without changing any quality attributes of the final product, and without adding new equipment. They found free capacity, thanks to information gleaned from their Rosemount level instrument. There’s more detail in the article, so give it a thorough reading. It’s always interesting to see how clever engineers figure these things out.
You can find more information like this and meet with other people looking at the same kinds of situations in the Emerson Exchange365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the Level Group and other specialty areas for suggestions and answers.