Transitions - Sustainable Design: The Science of Sustainability and Green Engineering - page 128

Thermal Destruction Systems

The green engineer must carefully match the control technologies in a project to
the problems at hand. If these technologies are to treat hazardous wastes thermals,
this decision can be the difference between success and failure of the life cycle.
The types of thermal systems vary considerably. Five general categories are
available to destroy contaminants: (1) rotary kiln, (2) multiple hearth, (3) liquid
injection, (4) fluidized bed, and (5) multiple chamber.

Rotary Kiln
The combustion chamber in a rotary kiln incinerator such as the one illus-
trated in Figure 3.7 is a heated rotating cylinder that is mounted at an angle
with possible baffles added to the inner face to provide the turbulence necessary
for the target three T's for the contaminant destruction process to take place.
Engineering design decisions, based on the results of laboratory testing of a spe-
cific contaminant, include (1) angle of the drum, (2) diameter and length of
the drum, (3) presence and location of the baffles, (4) rotational speed of the
drum, and (5) use of added fuel to increase the temperature of the combustion
chamber as the specific contaminant requires. The liquid, sludge, or solid haz-
ardous waste is input into the upper end of the rotating cylinder, rotates with the

Figure 3.7 Rotary kiln system.
Adapted from J. Lee, D. Fournier, Jr., C.
King, S. Venkatesh, and C. Goldman,
Project Summary: Evaluation of Rotary
Kiln Incinerator Operation at
Low-to-Moderate Temperature
Conditions , U.S. EPA, Washington, DC,
1997.