Grant Forest Products
Three Fluid Bed Combustors Supplying
Thermal Energy for an Oriented Strand Board Plant 1st Unit - 80MBtu/hr
(Wood Waste, Board Trim) 2nd & 3rd Units - 100 MBtu/hr each

Project Description
The oriented strand board (OSB) plant in Englehart, the largest in the world, produces 1000 tons of various thickness OSB products per day. The thermal energy required for this plant is provided by three independent EPI atmospheric fluid bed (AFB) combustion systems. Fuel for the combustors is generated from the plant waste stream that includes wet bark, log yard cleanup, wafer screenings (wet and dry), board trim, and trash. Each AFB can maintain rated capacity while firing any mix of these fuels ranging from 5 to 60 percent moisture. This latitude of operation is due to the energy storage of the hot sand bed that eliminates the fuel blending required by other combustion technologies. Fuel is metered and conveyed pneumatically to the AFBs for overbed presentation.

The first of these combustion systems, installed in 1981, is rated for 80 MBtu/hr and provides the energy, in the form of hot gas, for two rotary drum dryers. Green wood wafers are processed in the dryers before being oriented in mats for gluing and pressing. Dryer exhaust gases are recycled back to the combustion zone for temperature control of the dryer supply gas. Recycling also reduces the oxygen levels in the dryers as a fire prevention measure. In addition to supplying the dryers, the AFB provides blended flue gas at 1750 F to a thermal oil heater. Hot oil at 25 MBtu/hr is used to heat the board press, the wax and resin tanks, the log pond and the building during the cold season. Cool gas exiting the thermal oil heater is recycled back to the dryer supply to maintain a blend temperature of 1200 F to 1400 F at the dryer inlet.

The other two systems, installed in 1989 as a part of a major plant expansion, are each rated at 100 MBtu/hr. Similar in design to the first system, they provide 70 MBtu/hr each to two 16' by 85' rotary drum dryers. In addition, 25 MBtu/hr is produced by each system as hot thermal oil for the plant thermal heat requirements.

Scope of Supply
EPI provided combustion equipment, thermal oil heaters, ash handling, controls and control logic for installation by the plant. EPI also supplied start-up assistance.

Energy Products of Idaho
4006 Industrial Ave
Coeur d'Alene, Idaho USA 83815-8928
Phone (208) 765-1611 ~ Fax (208) 765-0503
Email: epi2@energyproducts.com

Copyright © 2008 Energy Products of Idaho
Last modified:  November 12, 2008
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