Together with the Wastewater Disposal Department of the City of Pirmasens, PFI Biotechnology has built a pilot plant for Thermal Pressure Hydrolysis (TPH) of activated sludge with the following specifications:
- Treatment of 10,000 t/a of activated sludge (6 to 7 % dry matter)
- Treatment temperature 140 to 160 °C (maximum 200 °C) attained by utilisation of waste heat from a cogeneration plant by way of heat transfer oil (180 to 220 °C)
- 70 % heat recovery through combination of sludge input heating with heat from sludge recooling
- Reaction section to guarantee a residence time of 0.5 to 2 h (depending upon the delivery rate of sludge) at the set treatment temperature
- Use of dynamic heat exchangers (scraped surface heat exchangers) to prevent fouling on the heat exchanger surfaces (ΔT up to 100 °C)
- Disintegration of the sludge by pressure release through a special pressure control valve (pressure drop from 24 bar to atmospheric pressure is possible)
The experience gained from operation of the pilot plant can be applied to other locations and sludges.