GMF-Gouda has reached an agreement with "Corus Staalfabrieken" in IJmuiden, The Netherlands, for the design and delivery of a complete sludge dehydration installation. The heart of this installation will consist of a GMF-Gouda Paddle Dryer, type 12W120. This model has a drying surface of 120 square meters and a capacity of 12 tons of sludge/hour.
More than six years of preparations and technical meetings between Corus and GMF-Gouda, as well as an extensive number of tests in GMF-Gouda's pilot plant, combined with on-site work with Corus, resulted in the final decision of Corus to choose this sludge dehydration installation. The complete installation will be put into service before the end of 2005.
The process:
After the production of steel, a sludge remains that mainly consists of iron oxide particles. The moisture content of this sludge is very high. By using centrifuges, the sludge is reduced to a moisture level of approximately 30%. Using the paddle dryer, Corus is able to dry this sludge to a final moisture level of approximately 12%. This dried product is less sticky and much easier to transport. Corus will re-use the dried product in their steel production process.
The vapors that are liberated during the drying process will be cleansed through a gas washer to ensure that final vapor emissions will meet strict local environmental demands. The gas washer, as well as the complete electronic control and wiring system of the installation, will be developed and delivered by GMF-Gouda.
The paddle dryer principle:
A horizontal jacketed trough, through which pass two rotating shafts, each arrayed with paddles, is the basic layout of the paddle dryer. Heat transfer medium (steam, thermal oil, or cooling water) cycles continuously through the jacket, hollow shafts, and even the paddles. As product feeds into the dryer, the wedge-shaped paddles ensure perfect localized mixing and mechanical fluidization. Shafts are precisely aligned: the paddles interweave as they turn, creating the ideal surface-to-product contact and plug flow through the dryer. The NPD's dust-tight cover can be adapted for full vacuum or overpressure. Condensation of any vapors evolved during processing can be prevented by heat-tracing of the cover, or by using a small air (or inert gas) flow to a central exhaust port. Cleverly, the whole unit is installed at a slight decline, so particles flow by gravity alone to the opposite end of the trough, for discharge over an adjustable weir.
Various kinds of sludge:
In addition to the sludge processed at Corus, the GMF-Gouda Paddle Dryer is also very suitable for drying other industrial and municipal sludges (sewer sludge). GMF-Gouda has delivered more than 20 paddle dryers in France and England that are being used for the drying of municipal sludge.
