Since 2005, MU’s college of agriculture, food, and natural resources (CAFNR) and the MU extension have been dedicated to helping the school’s power plant find the most cost-effective biomass fuel sources. Viable alternatives have included burning corn cobs, switch grass, woody biomass from mill waste, and discarded pallets blended with coal.
MU has co-fired biomass in its existing stokers under this program since 2006. With support from MU’s forestry department, MU has developed comprehensive sustainability standards for forest-derived biomass, which are incorporated in the biomass-supply contract for the power plant.
The new boiler will be fueled annually by more than 100,000 tons of regionally supplied and sustainably sourced biomass. This new biomass boiler, along with the co-firing of biomass in the plant’s stoker boilers, is expected to significantly reduce MU’s use of coal.
MU’s combined heat and power (CHP) plant supplies electricity, heating, and cooling for more than 15 million gross square feet of buildings, including three hospitals, a research reactor, several research facilities and laboratories, academic and administrative buildings, residential halls, and athletic facilities. The plant is a 2010 U.S. Environmental Protection Agency (EPA) Energy Star CHP award recipient and is much more efficient than a conventional power plant because it produces simultaneously thermal energy (steam for heating and cooling) and electricity for the campus.
Realizing the growing importance of sustainability to students, faculty, and staff, Brady Deaton, MU chancellor, signed the American College and University Presidents’ Climate Commitment in 2009 and established the MU sustainability office. The current climate action plan sets a goal of reducing greenhouse gas emissions by 30 percent by 2016, and the new biomass boiler will bolster MU’s ability to reach this goal.
How Does it Work?
Fluidized sand at the bottom of the furnace is heated with gas start-up burners. This hot, fluidized sand ignites the biomass when it enters the furnace. Hot flue gas is created from the combustion of the biomass. The hot flue gas from the combusted biomass travels from the furnace area through the boiler to transfer heat to the water flowing through the boiler.
Steam from the boiler water is captured in the steam drum and flows through the super heater which further heats the steam. The steam leaves the boiler and goes to the plant’s steam turbine generators, which produce electricity and extracted thermal energy for the MU campus.
Construction on the massive project began in May 2010 and was completed in December 2012. The project included installing the new biomass boiler and a horizontal and vertical expansion of the existing boiler house, as well as structural restoration of two existing 325-foot-tall, cast-in-place concrete chimneys. Also included in the project was the complete replacement of the plant’s existing fuel unloading, handling, and storage system.
Work to implement the new fuel systems included construction of a new fuel unloading and processing building, construction of five fuel-storage silos, and extensive conveyor systems to permit the handling of coal and biomass on the same footprint. The first phase of the fuel project included the replacement of the coal system, which included constructing two under-silo coal conveyors which travel from the fuel-receiving building to bucket elevators adjacent to the existing boiler house. Each conveyor system is approximately 250-feet in length. The project also included the replacement of two over-bunker coal conveyors that are approximately 200-feet long within the existing boiler house, as well as two vertical bucket elevators which are 80-feet tall.
Temporary fuel-handling and conveying systems were put in place to feed the remaining boilers while the existing systems were being replaced. The temporary systems provided MU with an uninterrupted supply of fuel, and therefore steam and electrical power for approximately eight months of the project.
The construction sequence required that the conveying equipment be put in place following foundation construction of the new fuel-unloading and processing building. Plant operations required that the coal system be put into operation as soon as it was in place, so the fuel building was built from the foundation up, around, and over the operating systems.
McCarthy Building Cos. Inc., St. Louis, acted as the project’s construction manager, in partnership with CB&E Construction Group, Chesterfield, Mo. Sega Engineering and Technical Services, Overland Park, Kan., served as the design engineer.
AZCO Inc., Menasha, Wis., was the subcontractor for the installation of the new boiler and all of the conveying systems. Kaiser Electric, Fenton, Mo., was the electrical contractor.
“We knew going into the coal system work that multiple shifts would be required in order to succeed. AZCO and Kaiser Electric brought the manpower and resources to the project team that were required to execute an extremely difficult project in a very short period of time and keep the plant running without interruption,” said Mark Smith, project director, McCarthy Building Cos. Inc.
Publication date: 2/18/2013