ASH SCREW COOLER

1.1. Bottom Ash Ash is discharge from the bottom of the combustor to maintain the required inventory. Higher bed pressure drop as an indication of accumulation of over size particle-mostly stones, shale, and agglomerated ash. Usually bottom ash draining is periodically operation as the bed ash quantity is generally <10%>

1.2. Ash Screw Cooler Water-cooled ash screw cooler shown in figure.1 below, is a good solution for dry ash discharge that is environtmentally more more acceptable. Ash from the bed is drained into screw whose flights, shaft and casing are all cooled by softened water of high quality.

Figure.1 Ash Screw Cooler

1.3. Holo-Flite dryer / screw cooler
Metso's Holo-Flite® thermal processor is an indirect heat exchanger utilizing a hollow screw for heating, cooling or drying bulk solids, filter cakes, pastes or sludges. It is a proven and efficient thermal processor with over 3000 installations worldwide.(http://www.metso.com)

In the Metso Holo-Flite® processor, individual particles are heated or cooled as they come in contact with the surfaces of the hollow flights, shaft and trough. The product to be processed is continuously conveyed in an axial direction by means of the rotating screw fl ights along a jacketed trough.

Figure.2 Ash Screw Cooler - Hollow Flite

Reference:
1. Boilers for Power and Process By Kumar Rayaprolu
2. Hollow-Flite .(http://www.metso.com)