Wood boiler scales Durability and maintenance

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The boiler offers many environmental benefits, but it also presents operational challenges.



By Dan Hounsell, Editor-in-Chief

HVAC

City Hall in Battle Creek, Michigan is one of two facilities served by a wood-fired boiler. Jessica Vanderkolk, Communications Manager

Institutional and commercial facilities have undertaken a series of efforts over the past two decades to minimize the impact of their operations on the environment. From water conservation and recycling to reflective roofing and solar power, updated technology and processes have enabled organizations to reduce waste, minimize costs and benefit the environment.

The role of maintenance and engineering managers in these organizations is to try to ensure that new and upgraded systems deliver the expected durability and benefits while continuing to operate their services efficiently and profitably. . Achieving these two objectives is often difficult.

Spotlight on the boiler

For Katie Norton, facilities manager for the town of Battle Creek, Michigan, the challenge is a wood-fired boiler. The boiler serves Battle Creek City Hall with 76,625 square feet and Police Headquarters with 48,649 square feet, and has been in operation for 13 years. Two natural gas boilers were installed at the same time.

The installation of the biomass boiler was one of the city’s efforts to meet its sustainability goals.

“The previous system was steam heating, and they used a lot of energy to heat the water until it reached boiling point,” says Norton. “The current system required less chemical treatment because it was a closed-loop system and didn’t waste as much energy boiling large amounts of water.

“The city’s climate protection policy goal at the time was to establish 15% renewable energy in city facilities by 2015. (The manufacturer) predicted that the biomass boiler would take 90% of the thermal load, and therefore more than 40% of the energy consumed by the buildings would come from a renewable energy source, thus meeting the objective of the climate protection policy of the city of 15% renewable energy source and reduction in carbon dioxide emissions.

A unique aspect of boiler operation is the system that feeds wood chips to the system.

“There is a wood bunker that houses the wood chips and has an auger and conveyor belt system,” she says. “This system automatically distributes and delivers the appropriate amount of chips to the boiler located in the basement of City Hall. The biomass boiler had to cover 80 to 90% of the heating load of the two buildings. During the coldest temperatures, natural gas boilers kick in to provide second-stage heating and back up the biomass. »

During the first performance of the boiler, it provided the expected benefits.

“The advantage of the system is that we don’t use as much natural gas, which is better for the environment, and the wood chips are much cheaper than using natural gas,” Norton says, adding, ” According to the (manufacturer’s) annual energy savings report and my experience, I believe the system was accurate in its energy efficiency predictions for the first 10 years.

Interview questions

The operational challenges of the wood boiler increased after its first life.

“There has never been a perfect solution for removing ash from the system,” says Norton. “The boiler is housed in the basement, two flights of stairs down and in the center of the building. The guys should empty the ashes at least once a week and put them in trash bags and haul them up. to the dumpsters across the parking lot.

Another challenge is finding a fuel source.

“The system is very picky about the type of wood we use,” says Norton. It was increasingly difficult to find someone locally who could deliver this type of wood chips to us in a timely manner. The only qualified company we could find to work on the boiler is a refractory company in the Detroit area, and it was difficult to schedule them because they are very busy. »

Norton says the weather can also create additional maintenance issues.

“We can’t run the system if outside air temperatures are consistently above 50 degrees because condensation builds up inside the boiler,” Norton explains. “It requires a lot of maintenance and monitoring.”

Boiler challenges are not only unique. They have an impact on the bottom line.

“They are there to monitor and tweak the system daily. What we save in energy costs is likely consumed by labor costs. Ensure grates are clear, ashes are emptied, remove stick jams for auger system, regularly sweep chimney inside, monitor oxygen level, adjust auger inlet by depending on the wood we can obtain and maintain the wood supply. My two maintenance technicians have to clean the system, remove the ashes and unload the wood from the semi-trailer. »

The system also developed an air leak due to the breakdown of the brick interior and as a result the facilities have been running on gas for most of this season, Norton says.

“The wood boiler depends on a controlled supply of oxygen to the chamber,” she says. “If that power goes out, we have trouble controlling the temperature inside the chamber. After 13 years of running the boiler there have been areas of wear in the seams, brick lining and gaskets causing a leak in the controlled air chamber allowing uncontrolled oxygen to enter inside . It took some time to locate the leak. With an abundance of oxygen, the boiler would burn too much and distort the ash auger arm inside the unit. »

Despite these challenges, Norton says public funding constraints make it unlikely the department will be able to replace the boiler anytime soon.

“We have no immediate plans at this time.” she says. “It is difficult for government entities to be proactive due to funding issues. The majority of taxpayers’ money immediately returns to the community to help citizens, so government facilities have been forced to be very responsive. We are taking steps to be more proactive in the future, but it will be a complete culture change that will take time.”

Dan Hounsell is editor for the Installs Market. He has over 25 years of experience in the fields of engineering, maintenance and grounds management in institutional and commercial facilities.




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