76.What is SCAH? And how many types of them in the market?

As explained above the air will be pre-heated before admitting to rotary air heater using steam. This heat exchanger is known as Steam Coil Air Heater (SCAH).

Coil type and vertical tube are the two types used in the market. Coil type is using simple instruments and control. But efficiency is low. The Trap used at the outlet of steam can only extract the latent heat from the steam. The steam pressure will be 10 to 14 bar. The exit temperature will be around 200 Deg.C.  In a vertical tubular type the water is maintained in the tubes and the heat can be extracted as low as 70 to 100 Deg.C.