Fluidized Bed Combustors

Fluidized bed combustion systems use a heated bed of sand-like material suspended (fluidized) within a rising column of air to burn many types and classes of fuel. This technique results in a vast improvement in combustion efficiency of high moisture content fuels, and is adaptable to a variety of "waste type fuels. The scrubbing action of the bed material on the fuel particle enhances the combustion process by stripping away the carbon dioxide and char layers that normally form around the fuel particle. This allows oxygen to reach the combustible material much more readily and increases the rate and efficiency of the combustion process.

Bed Recycle System

The key to EPI's dominance of the difficult waste fuel combustion market is our patented bed recycle system. EPI is the only company that offers uniform bed drawdown, integrated air cooling and automatic cleaning and reinjection of the bed material. This innovative feature enables EPI systems to operate on fuels with significant quantities of 4-inch minus noncombustible tramp material (contaminants such as rocks, metal. etc.). In grate style systems, tramp materials and ash slag can cause significant problems requiring a shutdown to correct. In other fluidized bed systems, tramp materials can build to the point that fluidization is no longer possible allowing clinkers to form. In these systems, a shutdown is usually also required to clean out the accumulation.

Complete and Efficient Combustion.

The turbulence in the combustor vapor space combined with the tumultuous scouring effect and thermal inertia of the bed material provide for complete, controlled and uniform combustion. These factors are key to maximizing the thermal efficiency, minimizing char, and controlling emissions. The high efficiency of a fluid bed combustor makes it particularly well suited to problem fuels with low BTU value and high moisture characteristics. EPI's systems have consistently achieved high combustion efficiencies. In typical units, the carbon burnout percentages within the combustor are well in excess of 99 percent.

Waste Fuel Diversity

EPI systems have operated on fuels as diverse as agricultural waste, municipal solid waste, wood wastes, industrial and municipal sludges, plastic, tires and coal. Fluidized bed systems are also capable of efficiently combusting fuels of varying consistency. EPI units have demonstrated the ability to handle a variety of wastes within a single combustor. EPI's San Joaquin Valley Energy Project units have logged operating time over 68 varieties of agricultural and urban wood waste. EPI's patented bed cleaning system, which removes large non-combustible material from the bottom of the bed, allows EPI units to burn otherwise problematic fuels with a minimal amount of processing.

Low Emissions

Emissions from a fluidized bed unit are inherently lower than conventional technologies for the following reasons:

	Low combustion temperatures and low excess air within the bed reduces the formation of certain emissions such as NO_x.
	High combustion efficiency results in flue gases that contain low amounts of CO.
	Emissions such as SO_x and NO_x may be abated within the fluidized bed system by injecting limestone into the bed and ammonia into the vapor space.

These features of fluidized bed combustion, combined with EPI's vast experience with a variety of fuels have allowed EPI units to comply with some of the most stringent air quality regulations in the country, including six operating plants in California. EPI units have consistently been accepted as the Best Available Control Technology "BACT" by env9ironmental regulatory agencies.

Favorable Ash Properties

The high combustion efficiency of a fluid bed results in a reduced amount of inorganic material as fine ash. The remaining larger material consists mainly of non-combustibles, such as rocks, and wire brought in with the fuel, and coarse sand-like neutral particles. Low combustion temperatures in the fluidized bed minimize the formation of toxic materials that might go into the ash. Ash samples from EPI systems have consistently tested nontoxic, and in many instances the ash is being sold as input for other products such as cement.

Operating Flexibility

EPI's fluidized bed systems have demonstrated the ability to operate under a wide range of load conditions. The thermal "flywheel" effect of the bed material allows swings in moisture and heating content of the fuel to be absorbed by the system without negative impact. Conversely, the low fuel inventory present in the unit makes it very responsive to varying loads. The fluidized bed also maintains efficiency during system turn-down. The operating flexibility demonstrated by existing EPI units has proven quite valuable for some of EPI's customers allowing them to take advantage of utility incentive programs for generation that follows electric demand.

Low Operating Costs

The lack of moving parts in a fluid bed reduces maintenance costs and down time. EPI units have achieved operating availabilities above 98% and have kept operating costs relatively low given the difficult fuels they are burning.

Environmentally Sound Energy Production from Waste

Fluidized bed combustion is an environmentally favorable, proven technology for disposal of solid wastes and generation of energy. The combination of EPI's vast experience in developing solutions for a wide variety of applications, with the favorable characteristics of fluidized bed combustion make EPI the leader in providing environmentally sound waste disposal solutions.

Energy Products of Idaho
3568 W Industrial Loop
Coeur d'Alene, Idaho USA 83815-6016
Phone (208) 765-1611 ~ Fax (208) 765-0503
Email: epi2@energyproducts.com