Biomass - Through the Looking Glass
December 1, 2009
A window and door manufacturer that used up to 100,000 lb/hr of steam was informed that its steam source was being eliminated. No problem! Working with a design firm forged a clear vision: overhauls of its steam and biomass systems, plus a warm-water recovery plan that took advantage of (and protected) the local environment. See how the company’s HVAC emerged renewed and renewable.
Engineers who offer clients ‘outside the box’ thinking not only solve the issue of the day but also provide solutions that meet their clients’ needs well into the future.
Such was the case with a recent engineering project for Andersen Corporation, where TKDA met the initial need of finding a new source of steam for the company but also designed a warm-water recovery system that went beyond the initial scope of the project and met Andersen’s long-range goals.
The SituationAndersen Corporation (Bayport, MN) is the largest window and door manufacturer in North America. The company’s campus is located on the St. Croix River - a national scenic river way that flows into the Mississippi River.
In 2005, Andersen Corporation was notified that they would need to find a new source of steam for their facility. They had been generating a portion of their steam in-house and purchasing additional steam from a nearby thermal facility, which was changing its offerings and could no longer meet Andersen’s needs.
With less than 24 months to have the new system designed, developed, and installed, the company hoped to find an innovative solution that not only replaced their old system that included an antiquated wood-fed boiler system, but also lessened the environmental impact of their facility on the nearby community while adhering to extensive regulatory requirements.
TKDA, an engineering, architecture, and planning firm headquartered in Saint Paul, MN, offered an innovative solution that went beyond Andersen’s initial needs and designed a facility that eliminated Andersen’s reliance on coal-based steam, decreased its landfill waste and emissions, and enabled the company to control its current and future energy requirements by using new, state-of-the-art equipment.
The SolutionAfter many discussions and a thorough feasibility study, TKDA designed a $22 million facility that gives Andersen the flexibility to produce virtually 100% of its required steam and heat from renewable energy.
The project included three distinct parts: a warm-water recovery system, a steam-generating facility, and a wood-handling system.
The steam-generating facility consists of a 15,000-sq-ft building that is sized for the peak production of 120,000 lb/hr of saturated high pressure steam, which meets Andersen Corporation’s peak steam requirement of 100,000 lb/hr (or equivalent heat load). This was accomplished by using two 40,000 lb/hr wood/gas-fired boilers, one gas/oil-fired 40,000-lb/hr back-up boiler and four 100,000 cfm makeup AHUs.
TKDA’s design incorporated a warm-water recovery system to heat outside air brought into the facility, thus reducing the wood fuel needed to heat the building. The system takes warm wastewater from a nearby energy plant and pulls heat from it for heating fresh air in the three million sq-ft-facility.
Specifically, the warm-water recovery system pumps 60°F condenser cooling water from a discharge canal located one-quarter mile away through a reused 10-in. steam piping system to the makeup AHUs. This water is then distributed to the four makeup AHUs used to temper the 400,000 cfm of outside air that is introduced into the manufacturing area.
The outside air is brought into the facility through wall louvers. The makeup AHUs also have a redundant energy source of steam and natural gas that can be used if needed. Once the water passes through the makeup AHUs, it is routed to an outfall and discharged into the St. Croix River National Scenic Waterway.
The warm-water recovery system eliminated Andersen’s need for a fourth boiler because using the heat from the warm water reduces the steam load to the point where the third gas/oil dual-fuel boiler operates as the back-up boiler. After a year and a half of operation, it has proven to be a real cost benefit as it reduced the steam load by 30,000 lb/hr. It also reduced the amount that flows into the nearby St. Croix River from the adjacent power plant. The warm-water AHUs provide the equivalent thermal load of one wood-fired boiler unit. Installation of four large AHUs offset the need for an additional boiler through reuse of heat recovered from the condenser water. These units also reduced fugitive air infiltration by approximately 80%.
Special low nitrogen oxide (NOx) burners were also installed as a backup heat source to the warm water. This was the first time low NOx burners have been used in this manner outside of California. The design provides reduced energy consumption and improved performance. If needed, flue gas may be recirculated to further reduce nitrogen oxide emissions. Flue gases pass through an electrostatic precipitator to remove particulate matter emissions.
A third component of the design involved a system of wood-fired boilers that actually recycle the facility’s waste products, so the excess wood from manufacturing doors and windows becomes fuel for the boilers.
Specifically, wood waste from the manufacturing process is run through a hammer mill, making it into wood ‘flour’ that can be fed into three boilers through a pneumatic system and metered into the boilers, which use low NOx burners. The boilers were designed to accept the wood flour, ensuring complete combustion and minimal ash generation. (A positive byproduct of the new process - an ash utilization program for soil enhancement by local crop farmers is being planned to replace a previous waste landfill program.)
Andersen is one of the first companies in the nation to install new boilers that meet the Industrial Boiler National Emissions Standards for Hazardous Air Pollutants. The new facility reduces permitted emission limits of criteria pollutants by 53%. Building a new plant on site also enabled Andersen to decommission all six existing wood or fuel oil-fired boilers.
The ResultThe new steam-generating facility, which was fully functional in May of 2007, adheres to Andersen’s environmental performance guidelines for both manufacturing products and process. In addition, it requires less energy and offers superior performance.
The facility was constructed by the design/build team assembled by TKDA that included Pioneer Power, Siegfried Construction, and Hunt Electric. TKDA has earned several awards for this project including a national honor from the American Council of Engineering Companies.
While finding and developing new technologies that work is important, it is paramount that engineering firms look for ways to bring these new ideas together for the good of the client.
For instance, starting from the ground up, the team minimized regulatory interaction on the site’s flood plain and scenic St. Croix River by utilizing the footprint of an existing storage building. In addition, existing steam pipeline was used for water transfer, vs. being replaced, which eliminated the need for installation of a new water transfer pipe.
As more and more companies seek to reduce their consumption of natural resources due to federal mandates, engineering firms need to offer creative solutions. TKDA recently dedicated a team to focus solely on providing energy saving designs and plans that provide energy efficient alternatives for facility heating, power and cooling for a variety of building types and infrastructure.
TKDA’s engineers successfully brought an innovative solution to Andersen by designing a system that produces efficient, renewable energy while allowing Andersen’s manufacturing operations to remain environmentally sensitive to the nearby St. Croix River. ES