Boiler engineers can select between two main types of fluidized-bed boilers—bubbling fluidized bed (BFB) and circulating fluidized bed (CFB). In BFB boilers the rate from the combustion air is low enough which the fluidized particles be in the fewer furnace; inside a CFB unit the velocity is greater and hot particles are circulated about the same array of the boiler combustion zone. The fuel is exposure to the particles and effective mixing and combustion allows good efficiency and low emissions. Typically 97% to 99% of most burnable carbon within the fuel stream is combusted, even hard-to-burn materials. Boiler thermal efficiencies can be as high as 87% or higher. Although both BFB and CFB systems work with biofuels, CFB is especially suited to large boiler load ranges.

ZG boiler engineer said, "Bed combustion temperature control is fundamental to fluid-bed boilers, Bed temperatures are controlled to limit emissions in order to limit bed material agglomeration." CFB boiler is developed of one kind of horizontal boiler for a wider application in the world.

Agglomeration is usually attributable to alkaline ash, other metals, and phosphates combining with alumina and silica in order to create low-melting-point eutectics that coat the bed particles. If alkali concentrations are too high the coatings melt and bond the particles together; these larger agglomerated particles become fat and affect the fluidization process.

CFB technology supplier provides fuel flexibility as it might burn wood and high Btu fuels. ZG report that CFBs are typical in Europe for sustainable energy projects that burn lower moisture fuels, like clean urban waste wood.

"Making the decision between a BFB or CFB product is not always obvious and should be evaluated over a case-by-case basis," advises by exports from ZG CFB boiler company. "Parasitic power requirements play a vital role in the evaluation process and ultimately system reliability is critical for just about any given project. That evaluation starts off with a comprehensive understanding of fuels, fuel variability, and ash characteristics while being further influenced by emissions requirements."

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