Biomass gets famous window-maker out of a logjam

Wood-fired steam, warm water recovery replace coal-fired predecessor

By Kate Bachman

December 17, 2011

Andersen Corporation, the nation’s largest window manufacturer, built Minnesota’s first combined warm-water recovery and bio-mass steam plant that uses sawdust and wood waste to produce power.

As you cross the bridge over the St. Croix River on I-94 from Hudson, Wis., to Minnesota and head north on Route 95 along the river at night, you will see an imposing smokestack with red lights looming eerily in the distance.

The smokestack belongs to an Xcel Energy coal-fired electricity plant in Bayport, Minn. Until a few years ago, the Xcel plant was the source of steam for the heating and cooling needs of the 65-acre headquarters and main manufacturing plant of Andersen Corp. In fact, piping runs directly from the energy facility to the adjacent window manufacturer's plant.

Then, in February 2005, Xcel notified Andersen that it could no longer supply the steam and that the manufacturer would need to find a new power source by April 2007.

That put the company in a bit of a jam.

Logjam

The relatively abrupt halt of the company's steam source did not promote panic among the company's leadership. After all, Andersen is a 108-year-old company. It has been in jams before. In fact, America's largest window manufacturer was borne of a logjam. Literally.

In 1903 a mileslong logjam occurred on the St. Croix River that deadlocked all movement of the thousands of logs felled from the forests nearby that were on their way to lumber mills to become the building materials of future homes and businesses. An enterprising young man named Hans Andersen saw this as an opportunity and he seized it.

A mathematician, Andersen calculated how many and which logs needed to be removed to unwedge the jam. He offered to purchase the troublesome logs and remove them a few miles upstream from their original sawmill destinations. With the newly acquired wood, he opened his own sawmill, which was the precursor to today's window and door manufacturing plant—which still houses its own lumber milling operation.

Just as Hans Andersen viewed the logjam as an opportunity, his successors viewed the steam source loss as an opportunity to find a more energy-efficient alternative and to eliminate reliance on coal-based steam.

As a result, the company built a new wood-fired boiler steam-generating plant and heat recovery system that provides all of the company's steam and thermal demand for the 2.5-million-square-foot facility and powers some of its manufacturing equipment (see Figure 1).

With both the steam plant and the heat recovery systems, the manufacturer is using already-available resources.

The feedstock for the biomass steam plant is Andersen's own sawdust and wood waste byproducts, reclaimed from its on-site milling operations.

The warm water recovery system accesses warm discharge water from the Xcel power plant.

The new steam plant became fully operational in April 2007 and has been hugely successful, garnering the company a number of awards along the way. But getting to that point was no log ride.

Evaluating Options

"When we received notice, we stepped back and said, 'All right, this is inevitable; what are we going to do?' said Chuck LeRoux, director, corporate safety, security, and environmental management for Andersen.

One option the company could have acted on was to relocate, but Andersen Windows is not a cut-and-run company. As the area's largest employer of about 3,000 people (9,000 in North America), it is firmly established in the St. Croix River Valley. The average employee tenure is 15 years. Some of them are third-, even fourth-generation, said Susan Roeder, corporate affairs manager. "Grandpa worked here. Mom and dad worked here. Mom and dad still work here."

"Our dedication to the valley and to this location here hasn't changed," LeRoux said. This is still a strategic part of the business. We need to stay here."

Installing all natural gas-fired boilers was the next consideration.

"Putting all your money into one fuel is really risky in this day and age," offered Dan Hinrichs, manager of corporate technical services. If you commit to having natural gas as your primary fuel source, you're beholden to the natural gas market, which is volatile."

LeRoux added, "That would have been the easy thing to do. But this created an opportunity for us.

"We've been an environmental partner in the community," he continued. "We've got a national scenic waterway on one side that we have to protect from an environmental standpoint—air, water, emissions, stormwater, all of that. We've got two railroads crossing our property, and we've got roads that dissect the property to have access to the river. We're embedded in a residential neighborhood. We just have to be very careful about what we do here in the valley.

"So we asked, what are the opportunities?" The company has a significant amount of wood waste from its sizable milling operation and has historically used its sawdust to help heat the plant.

"We had six old boilers at the facility, pre-1986. One dated back to 1947. A number of our boilers had no control equipment on them. We couldn't modify them, and so we couldn't use them," LeRoux said.

LeRoux and the group dispatched a request for proposals (RFP) to engineering firms for the design/build of a new steam power system.

Airtight Time Frame

LeRoux and his team had to move quickly and nimbly, LeRoux said. He made calls to large engineering firms throughout the country and tried to get them to submit plans almost immediately. "They asked, 'Can't I do this in three months?' We had to say, 'No. You need to get it here next week!'"

The group relayed the technical data, such as the steam demand, and that the submitted plans had to adhere to four guiding principles, LeRoux said. "The solution had to meet our environmental guidelines. It had to be fuel-flexible. Cost is always a concern, and it had to be reliable. And then we left it really open-ended."

About 20 proposals and quotes came in from firms all over the country, some of them as high as $31 million.

Available Resources

A decision on the design/build firm and contractual agreements had to be made by early 2006. The selection committee included representatives from all parts of the company, including the executives. The group gave a lot of consideration to all of the proposals, weighing the options and measuring their effectiveness and fit with the guiding principles.

"What will that do to our environmental emissions? Is it reliable? It is cost-effective? Is it flexible? So we evaluated all the different combinations of ideas, but the one that used available resources was the one we kept coming back to," LeRoux said.

Andersen Corp. selected TKDA, St. Paul, as the design firm, whose proposal was two-part: first, build two cogenerational, 40,000-pounds-per-hour (PPH) wood-fired/natural gas boilers on-site, plus a 40,000-PPH gas/oil boiler as backup. Second, take advantage of the proximity to the power plant and existing steam piping system; install a warm water recovery system, accessing the power plant's warm water discharge to supply 400,000 cubic feet per minute (CFM) to new makeup air units.

"That was the idea that ultimately tipped the scales into working with that firm," LeRoux said. "An engineer at TKDA actually sketched it on a napkin. He said, 'You've got that massive power plant there. What do they do? How do they operate?'

"We knew that they extract water from the river as sort of a giant radiator to cool off the turbines in the plant, and then they discharge clean, noncontact warm water back to the river.

"The warm water recovery is such a unique opportunity, so we thought we would leverage that as best we can," he said.

Contracts were signed. Subcontractors and suppliers were chosen.

"That was when it became a reality that there was no turning back," LeRoux said.

Beyond the Napkin

A lot of the concepts had to be constructed and details unwedged, LeRoux said. It's not as though they had another company that had installed a warm water recovery system involving a power plant to model after.

Would Xcel be warm to the idea? And how would it work? Who would pay for what?

"So we looked at the existing 10-inch-diameter steam line. Can that supply the warm water instead of the steam? And we were able to work that out. We had to rework some connections," LeRoux said.

Planning for the build cycle of the boiler installation was complicated by time constraints. "If we did this all off-site and put in three packaged boilers, they could do that in six months. If they were to go in on-site using an existing slab on the property, reclaiming all the metal from the deconstructed building, nine months," LeRoux said.

LeRoux called the permitting stage "the real hinge point. You can't really do anything until you have a permit in hand."

At one point LeRoux and Roeder had to appeal to the Minnesota Pollution Control Agency to move forward with some of the permits. "Chuck and I had to go sit in the governor's office and say, 'If we don't get this paperwork … We've got 12 months to build or we won't be making windows in Bayport in 12 months. That's not a threat. That's a reality,'" Roeder said.

As with any construction project, weather was a factor. Everything had to be online before the next heating season. "If you miss that, now you can't do some of the construction and you can't meet the demands of the production," LeRoux said.

Other challenges included some long-buried debris, including asbestos that was uncovered when they removed the old storage building, that resulted in a remediation project.

"We said, 'OK, that's not going to slow us down. Let's figure it out and get through it,'" LeRoux said.

There were internal pressures too. "And all this time, the operations people who were making windows were kind of giving us the look and saying, 'You'd better get that working. Don't mess with our production schedule!'" Roeder said.

The system was commissioned (fired up) in January 2007 and online by April.

What It Feeds, How It Works

Hinrichs managed the technical aspects of the project from start to finish. "A lot of different facets of the organization were involved in it. It was a fun project. It was pretty much all I did for three years.

Hinrichs explained in detail what the steam demand is applied to and how the system works.

There are three areas of steam consumption:

1. Building heat. Hot water is used for baseboard heaters and coils and reheat coils. All of the painting, drying, and wood handling operations draw exhaust air to outside, creating negative air pressure. The steam is needed to heat the makeup air to offset that.
   
   
2. Production processes, primarily flashing off of paint coatings, and for drying parts that have been treated with wood preservatives.

   The steam power is also used in solvent recovery. "On all of our paint processes and wood dipping processes where solvents are involved, we run that through a solvent recovery unit," Hinrichs said. "We use steam to liberate it out of the carbon bed, and then we condense that mixture, separate it through gravity separation, capture the solvent, and then reuse it."
   
   

3. Production of chilled water. "We have steam absorbers, about 2,800 tons of capacity. There's a lithium bromide within the chillers, and we use the characteristics of the lithium bromide to cool the water, and then the steam and pressure reverses the change of state in the lithium bromide. And through all that you make chilled water."

The chillers are used for comfort cooling. They are also used to cool lube heat exchangers on the actual extrusion and sheet line equipment, as well as profiles, and water tanks. The chilled water cools some of the gearboxes and lubrication systems on the large air compressors, he relayed.

"That's our largest baseload in the summer—chilled water. Our steam load in summer is 30,000 to 35,000 lbs. an hour," Hinrichs said.

The water chilling is a closed-loop process. The chilled water runs through heat exchangers that extract the cold temperatures. This prevents production parts from contaminating the water. "It's all recycled," he added.

Warm Water Recovery. Andersen contracted with Xcel to pay for the turbines, and Xcel supplies Andersen with the warm water discharge using the same pipe formerly used to supply steam.

"So we basically tapped into their turbines, and the new makeup air units just extract the heat out of the water they discharge—we're only taking about 3 percent of it—and we discharge it back into the river," Hinrichs said.

The water at the Xcel plant is about 60 degrees, and then as the winter progresses it gets a little cooler, Hinrichs explained. "We get the greatest amount of heat recovery on the coldest days because we've got a larger approach. So on a -20-degree day, we can heat that -20-degree air with that warm water up to about 50 degrees, so we're getting a 70-degree rise on 400,000 CFM of air."

Boiler Steam. The boiler plant houses the three boilers. The two cogeneration boilers typically burn wood, but they also can burn natural gas. A third is a gas/oil boiler for backup. Natural gas is used primarily during the winter months when the window- and door-maker is not producing as much for the building industry.

The white pine that the windows are constructed from because of its insulating properties works very well in the boilers too, Hinrichs said. "After we collect our shavings and sawdust, we run it through grinders and we turn it into almost like a wood flour and store that in the north brown silo (see Figure 2)."

The boiler control system is very sophisticated (see Figure 3). "So depending on load and which boilers are running, that controls the speed of the augers in delivering wood waste over to the boiler," he said.

Level controllers energize the unloaders in the north brown silo. "That's just a start/stop and it conveys the wood flour to keep the bins full. The rate of wood to the boilers is controlled by the pressure controllers within the boiler control system, he explained. Four augers rotate, drop, and pull wood out of the bin onto a shaker table, which shakes the wood to prevent it from compacting.

"Then you've got a conveying fan, which maintains about 5,000 FPM as the wood drops in and shoots it up this 8-in. pipe overhead. That shoots the wood flour down and it goes into a corkscrew in the wind box, the forced-draft fan.

"So you're mixing the forced draft; you're mixing the wood; it goes through a tangential corkscrew; and it shoots it into the furnace. Inside the furnace we have a gas bud, and that ignites the wood once we shoot it into the furnace.

"So we're burning the wood in suspension," Hinrichs said.

The flue gas goes out the front of the boiler, and both boilers connect to a common breaching. A flue gas economizer extracts more heat out of the flue gas, used to preheat the feedwater. "So that's additional heat recovery," he said.

Results

Heat Recovery. Hinrichs said that, on average, the warm water recovery reduces the steam consumption load of 360,000 MMBtu by about 20 percent.

The warm water recovery system provided enough temperature elevation to eliminate the need for an additional boiler and associated emissions. "So you have no emissions, everything's a closed pipe system," Hinrichs said.

The system lowers the temperature of the water discharged into the St. Croix River by about 7 to 10 degrees, which benefits the ecological balance of the river system.

Boilers. The boiler system was designed to be flexible so the company would not have to rely on only one energy source, Hinrichs said. "Steam is generated from the plant from wood waste heat or from natural gas or fuel oil depending on whether or not we're curtailing our usage, and what combination of boilers we have running," Hinrichs explained. "We're conditioned here to always look at redundancy, because in a manufacturing operation, you just don't want to start and stop based on having steam some of the time."

Since the system went online on April 30, 2007, the company has never had an unscheduled outage or an instance when it couldn't meet production needs. "That's a big deal," Hinrichs said.

"Here we're using the byproduct of a manufacturing process, so we know the availability of that. It's somewhat dependent on business conditions, but then we also have natural gas as well. So we've got a couple fuel choices. It gives us some flexibility in selecting the most economical fuel.

"We've literally got miles of dust collection, ductwork, and wood-conveying lines and storage vessels located around the plant," he continued. "We had all that infrastructure in-house, so the investment in that part of the system to support this plant was minimal. I think we probably put less than $200,000 in improvements into that system to support this new plant," Hinrichs said.

Environmental Benefits,Upgrades

The company seized the opportunity to facilitate additional environmental benefits with the installation:

• The wood-fired boilers are equipped with low nitrogen oxide (0.22-lb.-MMBtu) burners.
• Advanced control equipment on the boilers helps significantly reduce PM10 (particulate matter 10 microns).
• The plant was built on the footprint of an old storage building using some of the steel recycled from that building.
• The company installed a new stormwater management system that reduces sedimentation and runoff into the river.
• All of the energy-efficiency efforts have reduced greenhouse gas emissions.

Hinrichs said the entire new energy system, in addition to other energy consumption reduction efforts, has removed $3.5 million out of the facility energy demand costs over the past five years. "That's compounded savings.

"With the boilers, you might pay a little bit more for some of these things, but look at the return on investment five, 10, 15 years from now. We're spending, but we know the long-term ROI is there—and the ROI from an environmental standpoint. Emissions are down for the long haul."

$18 Million Investment Equals Commitment

Roeder stressed that the capital expenditure was symbolically significant. "This was a major investment. From a cost perspective, it was one of the largest capital projects we've ever undertaken. Being privately held, we're able to look long-term in terms of investments in our products and people.

"This obstacle might have been a bit more difficult to resolve in a different culture. Because Andersen is a private company, it can make long-term decisions that aren't impacted by the quarterly performance of the company. We were given a lot of latitude to be able to say, 'This is the right thing to do.'"

Roeder added, "Our employees are the shareholders. We've been here a long time, and the community wants to know you're going to be here for another century to come. This was an $18 million investment for us that clearly demonstrated that this business is in it for the long haul."

Andersen Corp., 100 Fourth Ave. N., Bayport,
MN 55003, 651-264-5150, www.andersencorp.com