The Faust automatic straw-fired-boiler type Bio-flow Ⅱ 370 to 2470 producing from 450 to 2500 kW is built in a similar pattern to the Faust bio-Flow Ⅱ for Wood chips and wood pellets. Instead of a step grate, a pushrod system moves to force the fuel and ash inside the boiler through the combustion zone.
The primary air is added at the surface of the fuel bed, in order, to avoid blowing air direct into the fuel, this would create explosive combustion due to the rapid gasifing of the straw, this is also important to avoid high temperatures arising inside the bed of the burning straw, these high temperatures result in melting ash, followed by clinker issues. The pushrod system moves the fuel and ash bed in waves from the stoker auger to the ash auger at the end of the burning chamber. These waves help to crack eventual clinker so it is not settling in zones that cannot be moved.
If the straw is burned on a step grade the step insulates the radiation of heat downwards, resulting in sintering of the ash. In Faust bio-Flow II Straw the ash is capable of radiating its heat to cool surfaces downwards. This gives the minimum of sintering. The mechanical forced flow of the fuel and ash ensure that the retention time in the hot zone does not become too long, this also results in very low sintering.