Sludge-sludge heat recovery

Spiralex® corrugated tubular heat exchangers for sludge processing

Sludge is produced from the treatment of on-site waste water (eg septic tank) and off-site systems (eg activated sludge). Sludge is viscous, contains small particles and often varies in composition.
Energy can be recovered from sludge by means of methane gas production during anaerobic digestion or by burning of dried sludge, but the revenue of the energy is often insufficient to evaporate the water out of the sludge, or to supply energy to blowers, pumps or centrifuges that are needed for the dewatering.

Nevertheless, the sludge must be treated. Especially the thickening or recovery of energy from sludge is popular. This is not easy, since sludge contains many small particles which precipitate easily. Another “problem” for energy recovery of sludge is the small temperature differences with work is carried out. An extra loop, as protection of the equipment against pollution, is therefore not desirable.

We describe our solution in the appendix with the Spiralex® corrugated tubular heat exchanger. We use this type of heat exchanger as a regenerator, or a sludge-sludge heat exchanger (sludge flows both in the tube and shell). Due to the corrugation of the tubes, the sludge is kept in turbulance and can not precipitate in the heat exchanger, which extends the running time and prevents for fouling.