PERFORMANCE RESULTS OF 10 YEARS OF INDUSTRIAL EXPERIENCE OF SLUDGE DRYING WITH AN INNODRY 2E SYSTEM
P. Knoer, A. Poisson, Degrémont Technologies, INNOPLANA
(free)
It is now 10 years since the first sewage sludge drying plant, built according to the innovative INNODRY
system was commissioned. In the meantime the experience gathered has proven the fundamental features
of the process. The main focus of this paper is to demonstrate validated results of conservation of energy.
The patented system referred to consists of two process steps. The first process step is to dry the
dewatered sludge to a paste containing 45% DS by a horizontal thin film evaporator. This paste is then
pressed through a die screen to produce sludge strings. In the second process step these strings are dried
with a belt dryer using the condensation heat from the first process step for its own heating.
A heat balance of the system is shown to explain the process-integrated heat recovery. This features heat
consumption figures as low as 650 kWh/t of evaporated water. Additionally, the system used to export
waste heat from the INNODRY 2E to existing digesters is described, thus enabling self-sufficiency of the
available biogas for digestion and drying. This is possible thanks to the low heat consumption rate of the
drying plant. Furthermore, an integration of the INNODRY 2E into an energy loop with a gas turbine CPH is
outlined, which is feasible again thanks to the low energy consumption of the drying plant.
The paper further presents and discusses experienced process performance achievements, such as dried
sludge properties, particle size distribution and dust formation, pathogen removal as well as safety aspects.
Experience of plant operation, gained from some of the 15 plants built in Europe will be presented as well
as the environmental impact of vent air and condensate effluent return.
KEYWORDS
Thermal drying, sewage sludge, sludge drying, dry sludge properties, energy conservation, anaerobic
digestion.
