in fixed-bed reactors, selenium porous-media filter, gold-amalgamation filter beds, sodium sulfide injection, and wet scrubbing with mercury-reactive solutions. None of those techniques is used commercially in the United States, but fixed-bed carbon adsorbers used in Europe often produce mercury and dioxin removal efficiencies that are higher than conventional technologies used alone (e.g., scrubber/fabric filter with injection of activated carbon).

SYSTEM OPERATION

Many variables that affect incinerator operation are controlled by operators, so the combustion conditions that control emission rates may be substantially affected by operator decisions. Poor operator control either of the furnace (by permitting temperature or oxygen concentration to decrease) or of the stoking operation can cause reduced combustion efficiency. In most incinerators, mixing and charging of waste into the incinerator, grate speed, over-fire and under-fire air-injection rates, and selection of the temperature setpoint for the auxiliary burner are entirely or partially controlled by plant personnel.

In addition, the extent of emission control achieved by post-combustion APCDs depends on how the devices are operated. Suboptimal operation can be caused by poorly trained or inattentive operators, faulty procedures, and equipment failure. Operators must be attentive to the flow rate of waste into the incinerator and furnace operation so as to allow for effective function of APCDs.

Although some of the most-modern incineration equipment has been automated, there will always be a need for operators to deal with unexpected situations. In addition, automated equipment requires calibration and maintenance, and combustor parts can wear out or malfunction. Examples of what can go wrong include clogged air injection into the incineration chamber, fouled boiler tubes, a hole in the fabric filters, and a clogged scrubber nozzle.

Worker Training

Before the 1980s, there were no uniform national standards for hazardous-waste combustor maintenance or worker-training. The extent and adequacy of maintenance and worker training programs were company-specific and site-specific.

In 1986, the Occupational Safety and Health Administration 1910 regulations were promulgated, requiring worker training in hazardous-material management. Classroom training courses are now required for hazardous-waste workers at remediation sites and plant facilities. Annual refresher courses are required, as is supplemental training for supervisory personnel.

Resource Conservation and Recovery Act (RCRA) regulations impose federal requirements for inspection plans and worker-training plans for all facilities that manage hazardous waste, including combustion facilities. The inspection



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement