FLUID BED COMBUSTION SYSTEMS

FLUID BED
COMBUSTION SYSTEMS

After 50 years of development Fluidised Bed Combustion is internationally recognised as the definitive firing technology for a wide range of fuels. The reason is simply that the technology allows the combustion process to be controlled accurately, ensuring high combustion efficiencies and low emissions. It also has the ability to burn a wide range of fuels, either individually fired or mixed, allowing total fuel flexibility.

A fluidised bed consists of finely sieved sand, limestone or ash, which is fluidised by a stream of high pressure air producing a 'grate' with many unique characteristics. The behaviour of the bed is similar to that of a boiling liquid, with vigorous movement and mixing. Air, fuel and hot bed material mix intimately creating rapid heat transfer and efficient combustion.

Combustion takes place partially in the bed and also in a zone above the bed where secondary air is introduced to complete the combustion process. We utilise the 'STABB' (Sparge Tube Atomised Bubbling Bed) fluidised bed combustion system which has many unique features, making it the best technology available today.
In comparison other designs are more expensive, complicated and less reliable.

The 'STABB' fluid bed is a simple, low cost design, offering multi-fuel capability with unbeatable reliability, efficiency and clean combustion. Our fluid bed products provide significant advantages over other designs, at a price which is lower than a conventional 'grate'.

UNIQUE FEATURES

The unique fuel feeding device delivers all of the fuel exactly where it is needed - in the middle of the bed, allowing it to be thoroughly mixed with the hot sand and primary air. A high velocity air curtain surrounding the fuel, ensures the fines are not blown from the end of the feeder and out of the furnace partially burnt.

Uniform bed temperatures are maintained across the whole bed area regardless of the fuel selected, the result being low unburnt loss and high efficiency.

The design allows bed temperatures to be automatically controlled, independent of load, without the need for large amounts of excess air, or in-bed cooling tubes with their inherent circulation, scaling and erosion problems. Two stage combustion is achieved safely without the fear of escalating bed temperatures.

Fuel contaminants such as hard ash, tramp metals, stones etc, do not have to be screened from the fuel before feeding to the bed. They are simply drawn down through the sparge tube air distributor and removed from as few as one underbed extraction point. Using a water cooled screw bed material is extracted and classified in an air blown separator. This feature ensures the bed always fluidises evenly over the whole of its area, and it may even be used to separate and recover high value metals from certain feedstocks.

Low heat release from the bed when slumped ensures a boiler's drum level is maintained following an unplanned shutdown. The large amount of heat retained in the bed means instantaneous start-ups.

Preheated primary air, up to 800 deg C can be used to maintain bed temperatures, allowing sludges, certain liquid waste streams or wet wood to be burnt without the need for expensive support fuel.

These features combine to make our design the most effective to date, and one that cannot be beaten for price or performance.

The ‘STABB' fluid bed is the result of research and development spanning more than 50 years.