Thermal utilization of sewage sludge
EcoDry is a simple, robust, and very efficient process for mono-incineration of sewage sludge, especially suitable for decentralized plants. Depending on the requirements of the customer, the EcoDry process can be implemented with one of the three well proven drying technologies available, namely drum drying (DDS), belt drying (BDS), and fluidized bed drying (FDS).
The EcoDry process is characterized by two essential features
- Full drying before incineration
- Incineration in a cyclone furnace (cycloid combustion chamber)
Full drying before sewage sludge incineration has the advantage of compensating any fluctuations in sludge quality as best possible and thus minimizing the use of auxiliary firing. In addition, the drying process before incineration provides a certain amount of redundancy because it is also possible in most plant concepts to continue drying operations while maintenance work is being performed on the incineration part. This drastically reduces the required sludge storage volume. A further advantage arises, of course, from the substantial reduction in the amount of flue gas as a result of full drying, cutting the investment and operating costs for flue gas cleaning.
The cyclone furnace is a very simple and low-cost solution for incineration of fully dried sludge. In the cyclone (primary) combustion chamber, the fuel, primary and secondary air are blown in at a tangent, as is the recycled flue gas. The sludge particles burn out in the cyclone flow. Most of the ash (> 90%) is discharged through the conical, lower section. In the secondary combustion chamber, the gas phase can be fully oxidized. Due to this two-stage process the combustion can be adapted exactly to the requirements in order to keep the emissions (NOx, CO, organic carbon etc.) well below the permitted limits.
As this technology does not require any mechanical moving parts or complex internals, it provides a subsequent investment cost advantage. Furthermore, cyclone firing requires very little space. In summary, the advantages from technical and ecological viewpoints certainly lie in following aspects:
- Utmost possible reduction in sludge volume
- Energy self-sufficient process
- Safe and full hygienization
- Safe and controlled reduction of emissions (e.g. Hg)
- Low transport costs
The advantages for the customer furthermore include independence from the sludge and disposal market, which ensures stable and low operating costs on a long-term basis.