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In industrial waste water treatment plants undesired materials such as heavy metals have to be removed from the waste water by means of physical and chemical methods. Usually a thin sludge with a water content of approx. 95% results from this treatment. By using adequate systems for preliminary desiccation such as filter presses, a filter cake with a chunky consistency and a water content of approx. 60% is attained.

With the help of the Hygrex (TM) sludge drying systems the filter cake can be dried up to a remaining water content of approx. 20% - 5%. Thus the weight of the sludge is reduced by 50%.

The overall aim of sludge drying is to reduce the weight of the sludge to be taken to a landfill or to be recycled and thus to gain considerable cost savings.

The Hygrex low-temperature drying principle operates on transporting warm and dry air through a defined volume of filter cake. The dry air now takes up the water stored in the filter cake. In the dehumidifying unit it is then cooled down at a heat exchanger to such an extent that the water can condensate. Right after this process another heat exchanger serves to reheat the air again.

For this reason the air has an enormous water absorbing capacity. Both the heat exchangers, also called air cooler and air heater, are components of a refrigeration cycle. An advantage of this energy balance is that surplus heat arising to supply the air cooler with refrigerant, is used in the air heater to constantly reheat the air. This air is then led through the container filled with sludge. Now you can see another positive effect of the principle. The Hygrex sludge drying process takes place in a closed air cycle. From the system point of view there are no emissions, so no loss of energy occurs.

The drying machines have a simple construction. They are robust and have a long service-life. The experiences of several hundred references has lead to a constant improvement. So nowadays the principle is perfected and field-proven. The system is applicable for standard sludge dryers as well as for customer-tailored solutions. 

• standard cabinet drying
• container drying plants
• ceiling constructiuon
• economy versions

Last Updated on January 31, 2000