Fluidized Bed Firing

Stationary / Circulating / Two Stages with Gasification

Tailored solution, high flexibility of the fed material; combustibles with the most varied properties, such as variable content of ashes, water and volatile matter, variable calorific value and level of harmful substances. The use of solid, liquid, muddy, pasty or gaseous combustibles provides the fluidized bed firing with the properties of a multi-fuel firing:

  • Simultaneous combustion of different fuels
  • High energetic efficiency by optimal fuel and heat transition
  • Homogeneous combustion
  • Reduced formation of harmful gases (CO, NOx)
  • Observance of very reduced nitrogen oxide emissions as relatively low combustion temperatures without temperature peaks occur
  • No moving parts in the combustion area
  • Very balanced air distribution over the whole fluidized bed. During the combustion this results in comparable low emissions
  • Combustion temperatures and the associated NOx emissions keep a relatively low level
  • Compact, rugged furnace with low maintenance expenditure
  • Economic, efficient and particularly environmentally friendly combustion

Contrary to a grid firing, blending of the above fuels is simple. A big advantage is the thermal recovery or elimination of problematic matter, such as very humid fuels, with high sulphur content, with a low density etc.

Special Evolution of the Technology

The fuel is used in a gasificator with stationary fluidized bed and pushed via a duct hydraulically into the gasificator chamber. The gasificator chamber is equipped with ceramic plates and coated bed heating surfaces. The effective bed heating surface, the air index and the bed temperature can be controlled. From the second stage of the stationary fluidized bed system hot bed ashes can be returned to the gasificator stage.

The gas generated in the first stage / gasificator stage will be purified by hearth furnace coke and converted into electricity by a gas motor/gas turbine. The heat of the gas motor/gas turbine is used for the regenerative heating of the water/steam circuit and in part for the air heating. The gasificator stage can be used with a variable air index, temperature and power. In the second stage the post-combustion of the exceeding gas takes place. The heat is used for steam generation and will be converted into electricity by the turbine.

The two-stage process yields the following advantages:

  • Robust operating behaviour
  • Wide fuel range
  • Process gas with high calorific value
  • Constant gas quality
  • Electric plant efficiency > 40%
  • Smaller boiler heating surfaces by higher heat transition coefficients
  • Smaller measuring and control expenditure for the heat input control

This plant technology reaches the goal of a high electric efficiency at affordable prices and one significant increase of the efficiency of this new plant system.