The Alaskan Brewing Co. is going green, but instead of looking to solar or wind energy, it has turned to a very familiar source: beer. The Juneau-based beer maker has installed a unique boiler system, designed to utilize brewery waste and cut fuel costs at the same time. A high-pressure, firebox biomass boiler furnace now burns the company’s spent grain—the waste accumulated from the brewing process—into steam. This steam powers the majority of the brewery’s day-to-day operations.

“We had to be a little more innovative just so that we could do what we love to do—and do it where we’re located,” explained Alaskan Brewing co-founder Geoff Larson.

Alaskan Brewing Company is the first brewery opened in Juneau since Prohibition, and from its beginning 1986, owners Marcy and Geoff Larson sought to establish a process for making high-quality, craft-brewed beer—one that wasn’t only cost-efficient, but also environmentally responsible.

“Supplies and fuel are expensive here, due to the distances involved,” added Geoff Larson. “Brewing in Alaska is a challenge because everything other than labor and water has to be imported, so we’re always looking for ways to be creative in obtaining and using our resources.”

Last call
For years, the Alaskan Brewing Co. was barely turning a profit by selling its spent grain. The company gets $60 for every ton of it sent to farms in the Lower 48, but it costs them $30 to ship each ton. So, the owners started looking at alternatives, including whether they could use spent grain in-house.

Though many breweries around the world use spent grain as a co-fuel in energy recovery systems, it isn’t normally done with a steam boiler. “Nobody was burning spent grain as a sole fuel source for an energy recovery system…for a steam boiler,” said maintenance supervisor Suki Patterson.

Other brewers sometimes add spent grain as supplemental fuel in their processes, but the system at the Alaskan Brewing Company is thought to be the only one in the United States that uses it as the sole source of boiler fuel. Any excess grain is shipped out as cattle feed.

“During our production cycle, we would have to burn hundreds of gallons of diesel fuel per day to fire the boiler,” Patterson explained. “With this system, we can use by-products from the brewing process, but that presents some unique issues. Conventional hog-fuel boilers typically burn feedstocks that produce about 0.5% ash, while the spent grain that we use produces more than five percent.”

The key element in the company’s successful boiler operation is an acoustic cleaner. As a matter of course, ash accumulation issues had been forcing the company to shutdown its equipment to cool and manually clean the swirlers and collectors of its ash handler on a weekly basis. The process required an outage of three to four days, including as much as 12 hours of maintenance time with bottle brushes and bead blasting.

Developing an ash handling process that not only cut this time, but also met the brewery’s goals for efficiency and environmental stewardship was significant. And now, instead of shutting down the equipment after just 25 hours of operation, company officials report that the system can complete an entire brewing cycle—with little or no performance loss—in 94 hours of boiler runtime.

Equipment breakdown
The high-pressure firebox boiler installed at The Alaskan Brewing Co, with left-side breeching, operates at 125 PSI during the brewing process, achieving 6,600 pounds of steam per hour from a furnace volume of 519 cubic feet. To manage the ash and minimize emissions, a dust collector imparts a whirling motion to the ash-laden exhaust gas as it enters the multiple-tube cyclonic collector. This action generates centrifugal force that concentrates particles of entrained dust at the interior walls of the collecting tubes. The particles then fall and are discharged from the bottom of the tube, with clean gas exiting through the outlet at the collecting tube’s vertical centerline. The boiler also uses soot blowers on a timer to clear the fire tubes.

“Unlike other fuels typically used in the brewing process, dried grain also produces an extremely fine ash that readily absorbs moisture from the atmosphere,” Patterson continued. “It tends to develop a gummy texture, so it can collect on the interior surfaces and become difficult to remove.”

Intent on resolving the problem, Patterson researched the issue online, finding information on how brewers and other industries were successfully managing fine ash, aerosols, and smoke particles. She even developed detailed engineering drawings of the system to help explain the situation and outline the operating conditions.

The conditions resembled issues seen every day in coal-fired power plants, biomass-fueled boilers, and other applications. As a result, it appeared to be an environment in which a sonic horn could provide some significant benefit (see Image 4). Patterson saw immediate improvement after installation.

“We’re still fine-tuning the process, and we may add a second horn in another location,” she said. “But our plant manager and engineering technician agree that this is an important first step in completely resolving our ash problems.”

Martin Engineering provides technologies to make bulk materials handling cleaner, safer, and more productive. Since 1944, Martin Engineering products (such as vibrators, air cannons, and sonic horns) have enhanced the movement of solids through industrial processes, and improved conveyor performance by cleaning belts and controlling dust and spillage at transfer points.

Hurst Boiler specializes in the manufacturing of modular biomass boiler systems with outputs ranging from 28 kW to 52 MW thermal, and offers seven different types of biomass stoker/gasifiers—which have used almost 2,000 different types of biomass fuels over the last 40 years.

Martin Engineering
www.martin-eng.com
www.martin-eng.com/products/flow-aid-solutions/sonic-horns/martin-sonic-horn

Hurst Boiler & Welding Company, Inc.
www.hurstboiler.com