sludge2energy Process Variant Hot Water Boiler

The version “Hot Water Boiler” represents a functional system of a simple design for thermal sewage sludge utilisation.

   1  Sewage sludge acceptance and storage
  2  Sewage sludge drying with belt dryer
  3  Condensation stage
  4  Storage tank for vapour condensate
  5  Sludge logistics and input
  6  Stationary fluidized bed furnace
  7  Waste heat hot water boiler
  8  Pre-separation of ash / fabric filter
  9  Dry sorption / reactor
10  Fabric filter for exhaust air treatment
 11  Optional two-stage scrubber
12  Chimney, emission control
13  Phosphate-containing ash
14  Residue logistics
15  Sorbent dosing

Process description

The sewage sludge produced is fed to an incineration line consisting of sewage sludge reception, drying, combustion, waste heat boiler and downstream flue gas cleaning.

The "hot water boiler" concept uses a belt dryer as the drying unit. To ensure self-sufficient incineration, the partial stream dried to 90 % dry residue (DR) is remixed with the remaining dewatered sewage sludge to 45 % DR before incineration and then thermally utilized in the stationary fluidized bed furnace, the S2E Fluidizer.

The flue gases are cooled in the waste heat boiler, which is connected to the secondary combustion chamber. In this boiler, the heat energy released during the incineration of the sewage sludge is transferred to the hot water system. The heat required to supply the various internal consumers, such as for combustion air preheating, sewage sludge drying and heating, is taken from this hot water circuit. The parameters of the system are selected in such a way that all consumers can be supplied optimally.

Dry flue gas cleaning is used to minimize pollutant gas emissions, which means that no wastewater is produced. The legal requirements with regard to the separation of pollutants from the flue gases of sewage sludge incineration are demonstrably and reliably met.

The phosphorus-containing sewage sludge ashes from the sludge2energy plant are a valuable starting material for future phosphate recovery.

Output range of the "hot water boiler" process:

  • Fuel heat output per line: 0.6 to 3.5 MW
  • Throughput of dewatered sewage sludge: approx. 2,000 to 11,000 t DS/a
  • Input dry residue content: approx. 25 % DR
  • Organic content of dry matter: approx. 60 % oDS