Cleening the Way to Energy Savings

Using a dry ice blasting process, Freez-it-Cleen has saved ethanol plants an estimated $3 million in natural gas costs since 2008.
By Holly Jessen | April 15, 2010
In an effort to save energy, an ethanol plant could install new, more efficient equipment. One company in Cedar, Minn., has a different idea. By cleaning the equipment ethanol plants have already, Alternative Methods Inc.'s Freez-it-Cleen service offers substantial energy savings without a big price tag.

Bushmills ethanol plant in Atwater, Minn., schedules a cleaning with Freez-it-Cleen during every six-month maintenance shutdown. Freez-it-Cleen uses its patent-pending cryogenic processing to scour the built up gunk off the ethanol plant's economizer and boiler tubeshelping the plant run more efficiently with less energy. "Basically the payback is just about instant," says Art Lange, maintenance manager at Bushmills.

Over time, a plant's boiler tubes become fouled with corn distiller's grains, dried ash and refractory, explains Kelly Brannick, president of Alternative Methods. This, in effect, insulates the tubes and reduces the efficiency of steam generation. "What happens is they have to turn up the natural gas so they can create steam," he says. And, as the energy used goes up, so does the emission output. Besides cleaning boilers at ethanol plants, the process can also be used on centrifuge bowls, oil separators and even grain receiving and load-out buildings, he says.

By the Numbers
A 2008 study at a 50 MMgy Minnesota ethanol plant shows what the company can do in terms of saving energy. Minnesota Technical Assistance Program part of the University of Minnesota, analyzed boiler efficiency at Granite Falls Energy after two separate cleanings in April and October. The study concluded that had the cleaning not been done, the ethanol plant would have paid out, in total, approximately $150,750 in additional fuel costs due to decreased efficiency of its boilers. "We recommend that Granite Falls Energy clean the boiler tubes and economizer every six months," said Shaina Brown, MnTAP engineer, in a letter to the Granite Falls maintenance manager. The study also suggested that, besides saving energy, a cleaning every six months could reduce the load on the boilers. At the beginning of the study, Granite Fall's boiler efficiency was calculated at 83.4 percent which increased 0.8 percent to 84.6 percent after the first cleaning. If the cleaning had not been completed at that time, the study said, boiler efficiency would have dropped 1 percent over the next six months. Instead, before the October cleaning, boiler efficiency had only dropped 0.4 percent. After the second cleaning, boiler efficiency was at 84.3 percent, nearly a percent higher than one year earlier, when the study started.

For the study, MnTAP estimated natural gas costs a $1 per therm, based on the average cost at that time. Even with today's lower natural gas prices, ethanol plants will see a return, Brannick says. Cleaning a thermal oxidizer at a 50 MMgy plant typically costs around $20,000 or less, depending on whether the equipment has been cleaned before. According to the study, Granite Falls, a 50 MMgy plant, saved an estimated $70,762 in natural gas costs after just one cleaning, showing an obvious payback. For larger, 100 MMgy plants, some upfront costs can be avoided with the second thermal oxidizer, Brannick adds, bringing the Freez-it-Cleen charges to about $36,000 for cleaning two units at one plant.

Besides saving natural gas, the Freez-it-Cleen treatment can also help drop stack temperature, which, in turn, decreases the emission of pollutants, Brannick says. At the Granite Falls plant, stack temperature was decreased by 32 degrees during the study. While the average decrease is about 40 degrees, one ethanol plant saw a dramatic degree decrease following cleaning to 300 degrees, down from the 480 degree stack temperature it had been recording for about a month. "Stack temperature is a real good indicator that they have a problem," he says.

Another benefit of clean equipment is extended lifespan. As the tubes are fouled they can overheat and start to warp or crack, which of course, generally happens in the middle, where the broken part has to be cut out and welded to fix. Some of Brannick's customers have had to replace broken equipment in the past but hope never to do so again, Brannick says. MnTAP saw that potential as well. "The scope of this project did not include the costs and savings associated with long term improved performance and longer equipment life," Brown commented, "but it is worth considering as another benefit of the cleaning."

Getting Started
Brannick hasn't always worked with dry ice. For 17 years he was in the aluminum die cast industry, which he described as brutal and dirty. Part of his job was purchasing needed equipment. Eventually, he started researching ways for the company to keep it clean. "It bothered me that all this nice equipment that I'd buy for 50, 60, $70,000 would get so dirty," he tells EPM.

At first, he used high pressure steam and water, but that damaged electrical components. Eventually he hit upon using dry ice, which leaves no residue and doesn't result in a waste stream. However, the company didn't want to buy the needed equipment or pay employees to do the cleaning, so Brannick started his own side business. By 2004 he quit his job to pursue it full time. "I got a lot of inquiries," he says.

"At the time I started [the company], ethanol was not even on my radar screen," Brannick says. Although Freez-it-Clean has other customers, ethanol jobs now make up 80 percent of the workload. In the spring of 2008, the company cleaned three thermal oxidizers. By last fall that number had jumped to 32.

He first noticed ethanol plants during trips from Minnesota to Sioux Falls, S.D. Brannick often traveled that route on the way to and from jobs, visiting family or on pheasant hunting trips. Along the way, over and over, he saw at least three ethanol plants. "I always thought, They've got to have something I can clean,'" he told EPM.

It wasn't until 2006 when Brannick started visiting ethanol plants and doing small cleaning jobs. A year later he was asked by Bushmill ethanol to clean its clean boiler tubes and thermal oxidizer and its stack economizer coils. "Like any good salesman, I said I could do it," he says.

Once he looked a little closer, he realized it was going to be a tough job. The issue is, he says, boilers are made up of a tight bundle of tubes, about 8 feet by 10 feet and 12 feet tall. Brannick worked with some of his associates to come up with a "funky tool" that could clean around all those tubes. It's a time consuming process that Freez-it-Cleen has perfected though trial and error.

The first tools were made out of aluminum and were basically destroyed by the end of the third job. So, four new tools were designed, this time formed out of stainless steel and not welded. The next step will be to make the tools out of titanium. The company has also worked to decrease the time it takes to complete each job. Today, Brannick says, a single thermal oxidizer can be cleaned in about 10 to 12 hours14 if it has never been cleaned before. "That first job we worked 14 hours the first day and 10 hours the second day," he says with a laugh.

More to Clean
Just this spring, Freez-it-Cleen began a new project often requested by ethanol plants to clean the pits used in handling grain and distillers grains. With the EPA cracking down on the allowable amount of dust and the threat of fines for companies that don't comply, this is a concern. "It's a high risk explosion area and they become very moldy," he tells EPM.

Until now, the company hasn't been able to tackle this type of cleaning project due to safety concerns. The CO2, or dry ice, pushes out air, leaving crews without breathing air, he explains. So, Brannick partnered with Glacier Technology of Plymouth, Minn., to build a ventilation system. In late February, Freez-it-Cleen tested the new system at the Hawkeye Renewables plant in Iowa Falls, Iowa. The new venting system was used to clean the pits and tunnels under the grain receiving area with dry ice. "It worked as expected or even better than expected," he told EPM. "The outcome was very good." Dry ice will kill existing mold but it will eventually grow back because of the conditions of those areas, Brannick cautions. He recommends a yearly cleaning, while maintaining basic housekeeping throughout the year. EP

Holly Jessen is associate editor of Ethanol Producer Magazine. Reach her at (701) 738-4946 or hjessen@bbiinternational.com.