1 October 1997
INSTRUMENTATION AND CONTROLS
a. Instrumentation and control systems for incinerator plants are critical to the successful
operation of the plant. As many individual systems are involved, the controls are nearly always
distributed type using multi-loop PLC's networked to a central computer based system.
b. Individual systems requiring control include; fuel feed system for refuse, overfire and
under-fire combustion air, auxiliary fuel burners, boilers and other heat recovery devices,
material handling systems for refuse, fly ash, bottom ash, dry powders, slurries, compressed
air systems, water systems, boiler feed controls, scrubber controls, carbon injection systems,
urea or ammonia injection, continuous emission monitoring equipment (CEM), fly ash
stabilization facilities, etc.
c. Incinerators in the size range of 100 tpd may include the following control and monitoring
(1) Process Instrumentation. This instrumentation monitors the conditions under which the
basic processes in the incinerator are proceeding (e.g., chamber temperatures, gas concentrations
of CO and CO2, gas flow rate).
(2) Data Acquisition and Recording. This equipment provides data that will assist in
determining operating costs and help determine areas where potential improvement in operations
are cost effective (e.g., auxiliary fuel consumed, steam produced).
d. Larger incinerators have more sophisticated instrumentation and control systems.
6-2 . BASIC DESIGN GUIDELINES. Guidance for typical incinerator instrumentation is listed in
table 6-1. Basic control areas and their relationships to this instrumentation are shown in table 6-2.
6-3. BASIC DESIGN CONCEPTS. Fundamental concepts for incinerator control design are
a. Combustion Air Control.
(1) To obtain complete combustion of refuse, the proper amount of air must be introduced
above and underneath the grate/hearth commensurate with the mode of operation (i.e., starved air
or excess air).
(2) Because of the nonhomogeneous nature of raw refuse, the actual under-fire air
requirement varies considerably. (Note: pretreatment of the waste in the MRF can significantly
reduce the heterogeneity problem). The largest and most sophisticated incinerators have under-fire
air control systems involving motor-operated dampers and sensors to adjust the air flow relative to
the quality and quantity of waste being fed (as determined by temperature sensors in the furnace).
Most smaller units, use manual control of dampers to partition air to the various stages. The