New sludge spiral heat exchanger for heating cooling duties

The latest version of Alfa Laval’s Spiral Heat Exchanger(ALSHE) for sludge /water duties, the ALSHE  STW, has been developed specifically for cooling industrial waste and for a number of duties involved in the treatment of domestic sewage sludge including:

• Heating sewage sludge in the digester
• Heating during pasteurisation
• Preheating sludge to enhance dewatering
• Cooling industrial sludges and other waste streams

Used for heating, cooling and heat recovery duties, the ALSHE STW includes a number of design features that enhance thermal performance and simplify service and maintenance. It has one free-flow channel 25mm in width; enabling it to handle sludges with minimal risk of fouling. This capability is enhanced by the high shear which provides a self-cleaning capability. Allied to the exchanger’s direct counter-current flow, the net effect is a very high level of thermal efficiency. As a consequence, the ALSHE STW incorporates a large heat transfer capability in a very compact body; reducing capital and installation costs. As an indication of its compact size, the largest model would fit comfortably into a 1.5 metre cube. In fact, it packs so much thermal efficiency into its compact shape that its installed footprint is up too three times smaller than that of an equivalent Shell&Tube heat exchanger.
There are five exchangers in the range. The smallest, the ALSHE STW 200, provides a performance range of 100-300 KW in a typical sludge digester heating application, while the largest model, the 1000, has a performance range of 500-1200 KW for the same duty.