Table of Contents
Convection Oven: Regulatory Requirements
The Clean Air Act
regulates the emission of volatile
organic compounds (VOCs) (40 CFR Part 60)
and hazardous air
pollutants (HAPs) (40 CFR Part 61 and 40
CFR Part 63), and provides specific standards of performance to control
emissions from various types of coating operations (40
CFR Part 60). Depending on the solvent content of the coating
material applied, sufficient VOC and HAP emissions could develop in convection
ovens to subject an operator to major
source requirements and Title
V permitting requirements. The Act also regulates the formation
of nitrogen oxides (NOx) from combustion
sources; however, emissions of NOx are often well below compliance levels
for small operations.
Controlling VOC emissions can be accomplished in two ways. A coating
material with a lower VOC content can be used. Otherwise, air
pollution control equipment is required on curing oven exhaust systems
to recover or incinerate the VOCs and HAPs before they are released from
the facility. Controlling NOx emissions can be achieved by adding
oxidation systems, scrubbers or adsorbers to the exhaust system if necessary.
Do exhaust air streams have air pollution control equipment attached? Is that air pollution control equipment working properly? Does the
final exhaust air have concentrations of pollutants below required levels?
Convection Oven: Common Causes of Violation
Emission of volatile organic compounds or hazardous air pollutants from
convection oven structures may occur and exceed limits allowed by Clean
Air Act Title V permits. The quantity of VOCs or HAPs released from
the curing coating material depends on the amount of organic solvent in
the coating formulation. These emissions in the exhaust air stream
can be captured and treated to prevent their release to the atmosphere. Common air pollution control tactics include solvent recovery, solvent
incineration, and solvent concentration.
Emission of nitrogen oxides (NOx) may occur and exceed limits allowed by
Title V permits. The quantity of NOx formed depends on the amount
of combustion products and evaporated diluent that combine and come in
contact with a direct flame.
Convection Oven: Sources of Pollution
Emissions of nitrogen oxides (NOx), when products of combustion and curing
contact a direct flame (dependent on the coating material formulation).
Heat loss through oven doors, heated work pieces, poorly insulated walls,
and improperly sealed panels.
Emissions of volatile organic compounds and hazardous air pollutants (dependent
on the coating material formulation).
Parts which have been improperly cured (overcured or undercured), resulting
in the need to strip and recoat.
Convection Oven: Pollution Prevention Alternatives
Nitrogen oxide (NOx) emissions can be reduced by introducing fresh air
into the combustion chamber. Fresh air will lower the flame temperature
and prevent NOx formation.
Heat loss can be reduced by improving insulation of the structure, and
sealing panel joints.
Proper curing can be achieved consistently by monitoring air flow circulation
systems for accurate operation.
Volatile organic compound and hazardous air pollutant emissions can be
reduced by using powder coating or waterborne coating formulations, rather
than solvent-based coating materials.