Page 189 - Wastewater Solids Incineration Systems

156 Wastewater Solids Incineration Systems

FIGURE 7.9 Venturi particle collection efficiency graph.

2.4.3 Operation and Maintenance

A Venturi scrubber must be separated from the incinerator breeching by either a
water seal or a metallic expansion joint. This separation is required to allow differen-
tial movement between the incinerator and the relatively stable APC equipment. The
incinerator will increase in height as it goes from a cold to hot operating condition. A
cross-section of a Venturi scrubber with a water seal is shown in Figure 7.10. As
shown in the figure, at the top of the Venturi throat is a collar with a water seal. Water
is continuously supplied to allow for evaporation. The depth of the seal must be
greater than the negative pressure that can be expected at the inlet to the Venturi. For
fluid bed incinerators (without an induced draft fan) the pressure at the Venturi inlet
is approximately 10 to 12 kPa (40 to 50 in w.c.), which precludes the use of a water
seal. Thus, for fluid bed incinerators a metallic expansion joint is typically used.
On some Venturi scrubbers quench water (or throat water) is added directly
above the throat to cool the gases to the adiabatic saturation temperature before the