Disposing of sewage sludge is expensive. In addition to the energy costs, it generates the largest portion of operating costs. As a result, the goal must be to reduce the amount of sludge to the greatest extend possible. In addition sludge represents a major energy resource. Digestion alone only makes use of this potential to a certain extent.
A PYREG® plant mineralises even wet biomass like sewage sludge. This dramatically reduces the amount of sludge to be disposed of. The intelligent integration of the plant into the overall system uses the energy remaining in the digested and dried sewage sludge for the mineralisation process.
What remains is mineralised sewage sludge ash. The phosphorus contained in this end product is to a large extent benefitial to organic plants life. This sewage sludge ash can therefore be processed directly into plant fertiliser using the PYREG process.
How the innovative PYREG® process works
- The sludge is fed to the PYREG® reactor by means of a rotary wheel sluice. The rotary wheel sluice prevents the entry of air into the reactor and serves as back-burn protection.
- In the PYREG® reactor, two inter-meshing augers provide transportation through the reactor and allow the uniform heating of the fuel up to 650°C. The exhaust gases from the connected combustion chamber provide the heat.
- During the heating of the fuel, burning gases escape into the combustion chamber with a flameless burner and are cleanly burnt at around 1,250°C. The system operates under negative pressure, which prevents the release of flammable gases and emissions.
- The mineralisation product – sewage sludge ash – is discharged via a rotary wheel sluice.
In the PYREG® reactor the phosphorus contained in the sewage sludge is not vitrified – this distinguishes the process from monoincineration. Consequently no complex and energy intensive processing is necessary. The sewage sludge ash can be marketed directly as raw material for the fertiliser industry. It is highly valued because of its purity and the very high plant availability of the recycled phosphorus.
Other biomasses can be converted to high-quality biochar in the PYREG® reactor. In this case the structure of the carbon contained in the mineralised material is similar to charcoal. Bound in the biochar, the carbon is no longer released as climate hazardous and flammable carbon dioxide, and – used as a fertiliser – it remains in the soil and serves as a soil improver and reservoir for micronutrients and water.