Thermal Treatment

Blending and Homogenisation Plant for the Conditioning of Basin Sludges for Thermal Diposal

The polluted sewage sludge is pre-sieved and then crushed in a planetary-gear extruder to enable trouble-free incineration in a stationary fluidized bed combustion system.

 

Summary

Basin sludges often contain solid matters (e.g. stones, wood, metal), which may endanger dosing and conveyance aggregates of stationary fluidised bed incineration facilities. Special conditioning steps are neccessary to make this material suitable for thermal waste disposal.

The conditioning of basin sludges is performed with a specially adapted planetary roller extruder technique. First, multi-level sieving removes coarse and abrasive material (e.g. stones, metals and wood). Then the remaining smaller solids are crushed in a planetary roller extruder, so that the material receives a defined grit size.

By this continuous preparation process a homogeneous material is generated, which matches the mechanical requirements of a downstream disposal plant, especially with a stationary fluidised bed incineration. The excavation of basins with this new technique leads to a reduction of soil, surface and ground water pollution and makes as well a contribution to climate protection.

In the past, sewage sludge has been stored in open basins in many places in Germany, but as the sludge is still microbiologically active, this type of disposal results in permanent emissions of the climate gas methane. BETREM Emscherbrennstoffe GmbH, which is responsible for the management of two sewage tanks in Bottrop, requested subsidies for a blending and homogenization plant for the conditioning of basin sludges. The aim of this process is the incineration of the sludge in an industrial power plant which uses stationary fluidized bed combustion.

The subsidized blending and homogenization plant was set up to process the basin sludge, which is full of stones and other foreign matter, for trouble-free use in a stationary fluidized bed combustion system. The aim is to empty the basins on a continuous basin in the years to come and to dispose of the sludge thermally together with the newly occurring sewage sludge.

For this process, BETRAM chose a two-phase plant configuration. In the first phase, the basin sludge is roughly sieved to remove any stones with a diameter of more than 8mm. In the second phase, the basin sludge is crushed in a planetary-gear extruder to achieve a grain size which is smaller than 2mm. This grain size is necessary for trouble-free incineration of the sludge in a stationary fluidized bed system.

First analyses of the material produced in the processing plants have shown that this is very suitable for use in the intended power plant. This means that energy can continue to be recovered from the sludge contained in the basins in the years to come. The methane emissions from the sewage sludge basins will be reduced to zero in the medium term, while at the same time the prepared basin sludge will contribute to the energy produced in the power plant.

The first experiences made with the demonstration plant would indicate that the process being used is also suitable for the conditioning of basin sludge for thermal disposal at other sites.

Project Participants

Implementing Institution

Betrem Emscherbrennstoffe GmbH

More Project Informations

Project title: Errichtung und Inbetriebnahme einer Misch- und Homogenisierungsanlage zur Aufbereitung von Beckenschlämmen für die thermische Entsorgung

Project number: 1338

Project period: 2005 - 2008

Project region: Germany (North Rhine-Westphalia)

Project contact:

Frau Fischer
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+49 (340) 2103 3067
+49 (340) 2104 3067

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Source: Environmental library of the Federal Environment Agency (UBA)