Solid fuel burning systems will usually produce an ash-rich smoke, so dust separation using a multicyclone is necessary.

A multicyclone consists of several cyclones mounted in a steel cabinet.

The mode of action of cyclones is as follows:

• A rotating motion is applied to the air and dust particles are ejected towards the wall of the cyclone due to their high density.
• The dust falls to the bottom of the cyclone and the cleaned smoke goes from the center of the cyclone to the top of the multicyclone, from where it is sucked by the flue gas fan into the chimney.

With an automatic ash system, the ash is transported from the cyclone by an ash auger. The multicyclone is equipped with an ash lock that is in operation when the system is running. The ash lock forms the seal between the cyclone and the ash auger.

The flue gas fan ensures that the evolved flue gas is removed from the boiler regardless of weather conditions.

The flue gas fan is adapted to the pressure loss in the boiler, multicyclone, flue gas pipe, chimney, etc.

The flue gas pipes are steel pipes that are flanged together.

For safety reasons, the flue gas system is equipped with a correct functioning control device so that the system stops when the flue gas is not removed. The control is a differential pressostat.