25-2 Hazard Analysis

Principal unique hazards associated with off-gas oxidation (thermal/catalytic) include:

a. Physical Hazards

(1) Description: If the BTU value of the waste feed is not controlled and higher than expected BTU value feed is fed into the unit, the temperature of the unit may exceed its design specifications, resulting in damage to the unit and increasing the probability of a release of waste material. Operating off-gas oxidizer systems above the design concentration or temperature may cause auto-ignition and a resulting fire hazard. High BTU value feeds may generate a fire traveling back into the source.

Control: Use experienced operators and supervisors. Audit and apply proper QA/QC to assure work is done as designed. Operate the system within design parameters. Air flow should not exceed the capacity of the system for efficient removal of solids. Temperatures in the primary combustion chamber should never exceed 95% of the ash fusion temperature (as determined by ASTM E953) of the material to be treated. The catalyst bed temperatures should be continuously monitored and controlled. Flame traps and control valves should be incorporated into the design to prevent fires from igniting the source. CONTROL POINT: Design, Operations, Maintenance

25-1 Off-Gas Oxidation (Thermal/Catalytic)

(2) Description: Off-gas oxidation units may cause elevated noise levels in the work area due to the operation of air blowers, pumps, and the ignition of fuels within the combustion chamber.

Control: Baffles and insulation may be designed in and used to control the transmission of noise. Personal protective equipment (PPE) should include hearing protection. Personal electronic communications devices may be used to overcome the noise. Noise-free areas should be established during operations to provide breaks from the noise, which can cause fatigue and inattention. CONTROL POINT: Design, Operations

(3) Description: Off-gas oxidation usually requires storage of flammable fuels (e.g. propane or natural gas). Hazards associated with flammable/combustible fuels include the potential for an on-site spill or release of material. The release may cause worker exposure to the vapors generated, or a fire hazard may exist if the material is ignited.

Control: Consideration should be given to ensure that the type of tanks used are appropriate. They should be located in an appropriate location on the site, equipped with pressure-relief devices, and bermed to help prevent release of material to the work environment. CONTROL POINT: Design, Construction, Maintenance

(4) Description: Since off-gas oxidation units operate electrical systems outdoors, workers may be exposed to electrocution hazards.

Control: Verify that the hazardous area classifications, as defined in NFPA 70-500-1 through 500-10, are indicated on the drawings. All controls, wiring, and equipment should be in conformance with the requirements of EM 385-1-1, Section 11.G and NFPA 70 for the identified hazard areas. Equipment should be grounded and/or provided with ground fault interrupter circuit (GFIC) protection if required by EM 385-1-1, Section 11 or NFPA 70 requirements. CONTROL POINT: Design, Construction, Operations, Maintenance

(5) Description: Thermal oxidizers operate at high temperatures, which may result in thermal burns to workers.

Control: Temperature safety control systems should be included to protect people and equipment. Safety barriers can be included to isolate critical sections of the equipment. Signs should be posted warning of high temperatures and workers may use heat resistant gloves. CONTROL POINT: Design, Operations, Maintenance

(6) Description: Improperly designed systems can corrode or dissolve to a point of failure and cause damage to people or the facilities. Workers may be seriously injured or killed under falling or collapsing equipment.

Control: All transfer equipment (piping, duct work, blowers or fans, process units and instruments) in contact with contaminated materials should be fabricated from materials that are chemically-resistant to that chemical. Hydraulic Institute standards HI 9.1-9.5 discuss appropriate materials for pumping various fluids. Typical chemical resistance charts can be found through the National Association of Corrosion Engineers (NACE). CONTROL POINT: Design, Construction, Maintenance

(7) Description: Liquids can condense and collect in the piping systems, resulting in system over-pressurization and explosion.

Control: In many systems, a knock-out tank or drum is installed to collect condensed liquids before they reach vacuum pumps, blowers, or the treatment unit. Where leaks may occur, containment drip pans or receivers can be included in the design. Spill and/or leak detection instruments can be installed to monitor for leaks or spills and set off alarms when appropriate. CONTROL POINT: Design, Operations, Maintenance

(8) Description: Workers may be exposed via the inhalation exposure route to a VOC, such as toluene, if leaks occur in the pressurized section of the piping system.

Control: Design the system to operate under a negative pressure (e.g. ducts and piping) for the maximum operating pressure expected. Avoid or minimize fugitive emission hazards by designing pressure control mechanisms and appropriate relief systems. Fuel system installation and testing must comply with the applicable requirements of NFPA 30 (Flammable and Combustible Liquids Code), NFPA 31 (Installation of Oil Burning Equipment), NFPA 54 (National Fuel Gas Code), or NFPA 58 (Standard for the Storage and Handling of Liquefied Petroleum Gases), as appropriate to the type of fuel. CONTROL POINT: Design, Operations, Maintenance

b. Chemical Hazards

(1) Description: During maintenance and/or repair, workers entering the unit for cleaning, inspection, or repair of equipment may be exposed to waste materials or incomplete combustion byproducts as part of a confined-space entry. Workers may be exposed to an atmosphere containing toxic materials or to one which is oxygen deficient.

Control: The hazards associated with exposure to these materials should be assessed at the time of confined-space entry, and the appropriate personal protective equipment worn (e.g. air-supplied respirator and disposable protective coveralls). CONTROL POINT: Operations, Maintenance

(2) Description: During operation of the off-gas oxidation unit, workers may be exposed to byproducts of incomplete combustion, such as carbon monoxide, or to airborne toxic materials, including metal acetates, mercury, and chlorine.

Control: Wastes should be classified prior to incineration and only those waste materials compatible with the process should be fed into the unit. The design should set limiting parameters on feed characteristics. The technology selection and design should select the appropriate technology for the known or anticipated wastes to be treated. CONTROL POINT: Design, Operations

(3) Description: Highly chlorinated feed compositions may generate corrosive conditions resulting from HCL gas within the incinerator exhaust stream, causing leaks in the system. The leaks may result in worker exposure via the inhalation/ingestion/dermal exposure routes.

Control: All transfer equipment (conveyors, piping, process units and instruments) in contact with contaminated materials should be fabricated from materials that are chemically-resistant to that chemical. Hydraulic Institute standards HI 9.1-9.5 discuss appropriate materials for pumping various fluids. Typical chemical resistance charts can be found through the National Association of Corrosion Engineers (NACE). CONTROL POINT: Design, Construction, Maintenance

(4) Description: Poisoning/blinding of the catalyst with high metal and/or particulate loadings in the gas stream may decrease the catalytic oxidation efficiency of the system and increase the discharge of toxic wastes into the work and surrounding areas.

Control: The ash content of the waste feed should be monitored and controlled to prevent excessive particulates from that source. Air streams being treated should be adequately pre-treated to remove particulates using filtration, quiescent zone separation, or washing to prevent excessive particulates. The metals content of the air stream needs to be considered in the design to assure that heavy metal poisoning of the catalyst does not occur. CONTROL POINT: Design, Operations, Maintenance

c. Radiological Hazards

Description: NONAPPLICABLE

Control: NONAPPLICABLE

d. Biological Hazards

Description: NONAPPLICABLE

Control: NONAPPLICABLE