Filtration's strange bedfellows
Engineers at Westfalia Separator AG and Seitz-Schenk, both in the German town of Oelde, began informal discussions a decade ago to see if they could design a replacement for DE by combining the benefits of centrifugal force and crossflow filtration. Coincidentally, a major beer industry competitor of Westfalia Separator AG, Pall Corp., acquired Seitz-Schenk in April 2002. Convinced the new system was the wave of the future, Pall and Westfalia put aside their competitive differences and went forward with the partnership.
Jonathan Pratt, vice president of food and beverage with Pall in East Hills, NY, recently discussed the development project and resulting partnership. Pratt is a graduate of the University of Reading in the United Kingdom with an undergraduate degree in chemistry and a graduate of Oxford University with a degree in marketing. He also is a member of the Royal Society of Chemistry. Pratt has been with Pall for nine years, the last four specializing in beer filtration.
FE: How is DE applied in commercial brewing filtration?
Pratt: It's the first clarification step right after beer leaves the fermentation tank. About 95 percent of the world's commercial breweries use it. You have a series of screens in a big filter, and each screen is pre-coated with DE powder. The DE agglomerates with yeast and other haze-forming materials in the beer. You keep adding more powder until you can't get any more into the system, and then the DE is removed. It's a rather cheap way of achieving gross filtration.
Besides the cost of the DE, there is an expense associated with its removal and, more importantly, its disposal. While not so much an issue in the US, disposal costs are significant in other parts of the world. Additionally, if it becomes airborne, the powder is considered a carcinogen. There's a movement to outlaw DE's use in the European Union.
Pratt: Pall developed a process called crossflow filtration to remove yeast. Unlike direct-flow filtration to capture particulates from a stream, crossflow concentrates particulates in the crossflow stream, usually with a ceramic membrane. The hurdle with early-stage yeast removal is that, for a brewery processing 300 barrels of beer an hour or more, the membranes have to be cleaned every hour, so it's not cost effective.
A centrifuge can be used to remove big particulates, but the machine also tends to mash them up. If the yeast is broken up into pieces of 0.2 microns, you aggravate filtration issues downstream. By working with Westfalia Separator, we've engineered a system that combines filtration and a centrifuge in a DE replacement system.
FE: Centrifugal systems and filtration are competing technologies in commercial brewing. How did the DE replacement partnership come about?
Pratt: Going back to 1995, engineers with Westfalia and Seitz-Schenk began discussing this solution. Both companies were based in the same town in Germany. Seitz-Schenk was an engineering firm with a heavy emphasis in the beer industry. The engineers built a pilot plant and began refining the system. Then, three years ago, Pall Corp. acquired Seitz-Schenk. In most of our markets, Pall competes head-to-head with Westfalia. This became a solution that we cooperated on to be able to provide a complete solution to beer companies operating on a global basis. Westfalia and Seitz-Schenk had a solution for small breweries, but today's major breweries want to work with suppliers who can serve them the same in Singapore as in St. Louis. The need to cooperate on a DE replacement system made for some interesting meetings and what Pall and Westfalia could disclose to one another.
Seitz-Schenk was a leader in DE filtration systems, and Pall continues to provide them to breweries and other processors. But DE has its limitations, and I think you'll see large breweries start to move away from it.
FE: How did Westfalia resolve the problem of particulate fragmentation?
Pratt: Typically the bowl of the centrifuge would be rotating at a few thousand RPMs. When the fluid hits the spinning plates, it is pushed to the sides, shattering some of the yeast into sub-micron particles. To avoid that, Westfalia designed a clarifier type SC 35 separator that is prefilled with fluid. Acceleration is gradual, so the yeast doesn't shatter.
FE: Is the crossflow filter different from other Pall crossflows used farther downstream in the brewing process?
Pratt: Membrane type and the particular polymers used were integral to the design process. You must have a specific type of polymer for beer, and you have to engineer the filters for a high-volume process, with a minimum hold time. Beyond that, all crossflows use hollow fibers bundled together-think of spaghetti with a hole in the middle. The combination of the filter design and the special centrifuge pushes the cleaning cycle from one to four hours. It's a batch system, but it's designed for continuous processing because that's where the beer industry is heading. A brewery producing one million barrels a year would probably have three banks of filters with about 20 modules per bank and one centrifuge, while a brewery producing seven million barrels would probably have six or eight banks and work off of two or three centrifuges. Multiple banks would allow the brewery to perform maintenance on one bank while processing continued in the others. The system would be economical for breweries doing 300,000 barrels a year or more.
FE: How space intensive is the system?
Pratt: The centrifuge bowl is no more than three feet in diameter, and the rack of modular filter modules is probably four feet wide and 15 to 18 feet long. The whole system probably has a footprint of 25 by 15 or 20 feet. That's probably half the floor space of a DE system, which requires lots of tanks, valves, pumps and other equipment.
FE: How do the economics compare with DE?
Pratt: The energy costs are higher than DE, but that cost is small compared to the cost of purchasing DE, and there are no disposal issues. We're estimating breweries will see an ROI in two to four years by switching over.
FE: How difficult is it to integrate the system into an existing controls architecture?
Pratt: The centrifuge and the filters only operate when they're being fed, so there isn't much communication needed with the rest of the plant. There's a central PC control for the system, with one control point that is easily wired into the brewery's data system. Allen-Bradley controls were used.
FE: Are there commercial applications?
Pratt: Three breweries are using DE replacement, including Pott's Brewery in Oelde, Germany; that's the showcase for the technology. They make several different beers, all lagers, in a greenfield site built a few years ago.
Wineries began moving away from DE eight years ago. It was easier for them to make the transition. A handful of wineries were using DE replacement eight years ago; now we have 600 systems installed.
FE: DE is used in many beverage filtration processes. Do you see an opportunity beyond brewing for this system?
Pratt: The same concept could be applied, but the system could not be transplanted. High fructose corn sugar is a possibility, but the challenges of viscosity, heat and cleaning would require much different engineering.
Eight of the 10 largest brewers in the world are evaluating DE replacement. I think we'll see an installation in South America within a year. The first North American installation is about 18 months off.