Shaft heat exchanger

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Shaft heat exchangers , also known as shaft coolers, are fixed bulk material heat exchangers for continuous processes in process engineering .

construction

Shaft heat exchangers essentially consist of a large number of square tubes which are arranged one above the other in heat exchanger packages. The ends of the tubes are closed with head plates. Behind it there are deflection chambers for the cooling or heating medium. The long sides of the outer tubes have metal strips that hold the product in the shaft. In addition, to protect the environment or the product quality, doors are often found with which the side walls can be closed. Inlet and discharge funnels are located above and below the cooler . Various conveyors for bulk goods, such as B. screw conveyors , bucket elevators , etc. are downstream of the cooling system.

functionality

The bulk material in the shaft heat exchanger is cooled or heated indirectly; using water, thermal oil or steam. The heating or cooling medium flows through the square tubes. The medium and product are guided to one another in a cross-countercurrent. The coolers work on the moving bed principle. I.e. a column of product is created which flows continuously downwards between the cooling tubes. A discharge base with variable opening cross-sections is used to regulate the dwell time and flow speed.

Applications

Chute heat exchangers can be used for cooling or heating all free-flowing bulk materials that meet the requirements of the apparatus in terms of grain size and angle of repose. The heat exchangers are often found behind rotary kilns and dryers for cooling z. B. mineral (quartz sand, ilmentite etc.) or chemical products (fertilizer, soda etc.). The inlet temperatures of the products can be up to 1200 ° C.

Process engineering peculiarities

The use of square tubes results in an optimal use of the exchange area (high heat transfer coefficient ), which results in a very compact design. Because of this and the way they work, shaft heat exchangers only require a small footprint, but can be relatively high depending on the application. Since they have hardly any moving parts, they are usually low-maintenance and have low energy consumption. Problems with noise or dust pollution in the environment hardly arise.

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