Page 81 - Wastewater Solids Incineration Systems

50 Wastewater Solids Incineration Systems

FIGURE 5.2 Liquid behavior of gas fluidized beds.

varies proportionally to height, like a liquid column. The pressure difference between
any two points in a bed is approximately equal to the static head of the bed between
the two points. The bed also has liquid-like flow properties. Solids will gush in a jet
from a hole in the side of the container and can be made to flow like a liquid from
vessel to vessel.
When applied to incineration, the liquid-like behavior of the fluidized bed offers
the following advantages:

• Smooth, liquid-like flow of particles allows continuous, automatically con-
trolled operations with ease of handling.
• Rapid mixing of solids leads to nearly isothermal conditions throughout the
reactor; hence, the operation can be controlled simply and reliably.
• Circulation of solids between two fluidized beds makes it possible to transport
vast quantities of heat produced or needed in large reactors.
• Fluidized beds are suited to large-scale operations.
• Heat- and mass-transfer rates between gas and particles are high when com-
pared with other modes of contacting.
• Rate of heat transfer between a fluidized bed and an immersed object is
high; hence, heat exchangers within fluidized beds require relatively small
surface areas.
The advantages and economy of fluidized contacting have led to its successful
use at WWTPs and in industrial operations such as calcining, ore roasting, drying