The blow tank shown in Figure 4.2 is a top discharge type. It is shown with a discharge valve so that it can be isolated from the conveying line. It also has a vent line and valve so that it can be de-pressurized independently of the conveying line. Discharge is arranged through an off-take pipe which is positioned above the fluidizing membrane. The material is discharged vertically up and the discharge pipe exits the blow tank through the top of the vessel, and hence the term ‘top discharge’ in this case.