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Newsletter 2006 issue 1 |
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Boiler Efficiency
Inefficient. Underused. Evaluate if your older process equipment matches your facility’s current needs.
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Paul Pagel, MnTAP certified energy manager, and MnTAP intern Ryan Schaefer look over Nordic Ware’s underused boiler. |
Each year, a typical boiler consumes in fuel many times its initial capital investment. An industrial boiler purchased for $75,000 can easily use more than $400,000 in fuel annually.
A one percent increase in efficiency is worth $4,000 in fuel savings. Improved boiler efficiency translates into substantial savings that can pay for a higher efficiency unit many times over.
Schwan Food Company boilers
Dave Bero, senior project engineer at The Schwan Food Company, a producer of frozen food and ice cream in Marshall, took a look at the gas bills of his company’s two Minnesota plants. “One gas bill was twice as high as the other, but demand was less at that plant,” said Bero. To account for the difference, Bero first ruled out the possibility of a bad gas meter. He installed a water flow meter to monitor the volume of water heated per day.
When Bero analyzed where steam was used in the plant, he discovered that demand was intermittent. In summer, demand totalled only a couple hours per day.
By establishing base load on weekends in the summer with zero production and zero hot water flow, Bero discovered that keeping the system at pressure around the clock resulted in a large base load (38 million BTU). He found that most of the wasted energy was from boiler blowdown (purges of hot water that eliminate mineral buildup in the system) and heat loss as steam lines cooled.
Conclusion: using the large central boiler was inefficient.
“We mothballed the large boiler. For heat, we put in two small, 50 horsepower boilers that produce steam at low pressure.” Bero explained, “For winter heating, we’ll run one of the 50s until it can’t handle the load, then we’ll fire up the second. In spring as temperatures warm, we’ll turn off one boiler then the next.”
The new central boiler system is now closed looped, using reverse osmosis (RO). This reduces blowdown purges from 500 to 800 gallons per day (gpd) down to about two gpd— dramatically reducing heat loss. Using RO also reduces the amount of boiler chemicals needed, saving Schwan about $11,000 annually.
For the areas that needed steam in the summer, Bero installed electric steam generators at point of use. A direct contact water heater—99.7 percent efficient—was installed to provide hot water year round.
The changes will reduce Schwan’s fuel use by $160,000 per year. Eliminating the high pressure boiler reduced boiler maintenance burdens and decreased the company’s insurance liability. Bero has implemented several other energy saving projects as well.
Nordic Ware space heaters
Nordic Ware, a cookware and bakeware manufacturer in St. Louis Park, wanted to determine if it was economical to increase use of an underused boiler in its main coating area to heat the building when there was no production. Only one million of the 3.7 million BTUh capacity was being used. As part of a MnTAP intern project, the company investigated how to reduce the energy wasted annually by the underused boiler.
The intern got bids from vendors which indicated that plumbing and insulating new steam lines—to take better advantage of the boiler’s capacity—was cost prohibitive compared to other options. The intern provided energy and cost analysis on the boiler and new equipment options.
“We decided to move ahead and eliminate the boiler. Most of the areas that were heated by the large boiler could be more efficiently heated by going to a smaller, low pressure steam boiler,” said Bette Danielson, Nordic Ware’s safety and environmental affairs manager. Payback on the new boiler is estimated to be only 4.6 months because of the natural gas savings. Plans also include gas unit heaters to minimally heat the building during off-production hours.
“The intern’s investigation and calculations helped us evaluate our options and move ahead—confident of the economic savings down the road,” Danielson commented.
If your facility has been in operation a long time, your system may be due for an update. A MnTAP technical specialist can assist with reducing process-related energy use.
Links
Boiler Efficiency
Boiler system vendor, Cleaver-Brooks, provides background information to help you understand boiler efficiency, and when to replace or repair your system.
Boiler Efficiency Improvement
Many day-to-day actions can substantially impact energy efficiency. The Boiler Burner Consortium offers tips on boiler efficiency improvements. Scroll down to “Boiler Efficiency Improvement Opportunities” for information on optimizing your boiler.
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