Moving bed heat exchangers (also moving bed coolers) are stationary heat exchangers for bulk materials for continuous processes in chemical engineering.

Construction

Moving bed heat exchangers essentially exist of a huge number of square tubes which are arranged in heat exchanger packages one above the other. The ends of the tubes are closed with end plates. Behind the plates are reversing chambers for the cooling or heating medium.
The sides of the external tubes are equipped with steel plate strips which hold the product in the shaft. To protect the environments or the product quality, doors that close the side walls can be fitted.
Above and under the heat exchanger are feed respectively discharge hoppers. Different conveyor facilities for bulk materials, as for example conveying screws, bucket conveyors or similar are downstream systems.

Function

The cooling or warming of the bulk materials in the Moving bed Cooler happens indirectly; via water, thermal oil or steam. The heating or cooling medium flows through the square tubes. Medium and product flow in cross countercurrent to each other.
The coolers work according to the Moving Bed Principle. I.e. the product forms a product column which flows continuously down between the cooling pipes. A discharge bottom with variable openings regulates dwell time and flow rate.

Applications

Moving bed heat exchangers can be used for cooling or warming of all free-flowing bulk materials which correspond to the requirements of the apparatus, concerning grain size and angle of repose. The heat exchangers often can be found after rotary kilns and dryers to cool e.g. mineral (quartz sand, Ilmentit etc.) or chemical products (fertilizer, soda etc.). The entry temperatures of the products can reach up to 1200 °C.

Technical specifications

Moving bed heat exchangers have a relatively compact construction. Because of the working principle they need only a small base. However, depending on their application they can build relatively high. Because of having only few moved parts they have low electrical requirements and are low-maintenance. Problems with noise or dust contamination of the environments do not occur.

External links

• Patent: WO9817959 (A1) — 1998-04-30