1 October 1997
(2) Some hospitals have co-fired fairly large percentages of relatively dry, noninfectious
paper; plastic products; and paper-product type waste with their infectious waste to successfully
accomplish the job with minimal extra fuel required. The smaller units are usually batch operated
(i.e., waste being fed only when the previous load has been consumed). This only permits a certain
number of loads to be burned per day; furthermore, if there is no provision for an automatic ash-
removal system, the ash must be removed manually following an overnight burndown and cool-off.
c. Environmental Considerations. Current trends are that even the smallest incinerators
(especially medical waste incinerators) will be subject to pollution control regulations.
(1) Air pollution control equipment that may be cost-effective on larger units may be
prohibitively expensive on typical medical waste incinerators. Wet scrubbers have been found to
be very effective and are probably the best pollution control device for these small units since they
capture acid gas and particulates.
(2) High-pressure venturi scrubbers have been used effectively; however, require a great
deal of energy in order to achieve high capture efficiency. If the gases can be cooled by an acid-
gas condenser heat exchanger, a small fabric dust filter may be sufficient and is cost-effective.
(3) The bottom-ash residue must not contain any recognizable medical material (i.e.,
complete burnout). Therefore, sharps may have to be screened from the ash and disposed of
separately as scrap metal. Because of the potential hazards and liability if the unit is poorly
operated, operators will have to be properly trained and certified. A training course has been jointly
established by the American Hospital Association and the American Society of Mechanical
4-9. TECHNOLOGY SELECTION GUIDANCE.
a. Technology Selection. Modular starved-air units have been the most widely selected for the
military services because their capacity includes units below 50 tpd (the size most used at military
installations), without the need for additional air pollution control equipment. Other small-capacity
systems, namely excess-air grate, fluidized-bed, and most rotary kiln incinerator designs, usually
requiresome type of particulate emissions control. A number of states have enacted, or are
enacting, increasingly stringent acid gas and particulate control legislation applicable to small units
(down to 20 tpd have been regulated in New Jersey). It is expected that incinerator plants at
military installations with unit sizes of 20 tpd or greater will most likely be modular unit plants
operating in either the starved-air mode or the excess-air mode and equipped with state-of-the-art
pollution control. Comparative economics will be the ultimate selection factor. For installations not
located in states with highly stringent regulations, or for plants with unit sizes below the Federal
regulatory threshold, the modular starved-air incinerator will probably continue to be the incinerator
of choice. The military procurement guidelines for incinerators will be used to specify this
incineration equipment. It may be modified if it is necessary to allow for excess-air units.
b. Special Needs. Two technologies are expected to have definite, but limited, applications.
The rotary kiln is especially good for difficult-to-burn wastes, such as sludges or other very wet
materials. The fluidized-bed combustor (FBC) should be used for very homogeneous wastes that
may be hazardous because of acidity or possible toxic elements. FBC can also burn liquids and
sludges as well as solids and can burn several fuels simultaneously. Further details on all of these
types of incinerators may be found in the literature listed in the bibliography.