WHAT DO I NEED TO DO TO COMPLY?
TABLE 4-1. EMISSION LIMITS
| Only subject to recordkeeping and reporting | ||
a mg/dscm = milligrams per dry standard cubic meter of exhaust air;
gr/dscf = grains per dry standard cubic feet of exhaust air;
dynes/cm = dynes per centimeter;
lbf/ft = pound-force
per foot.
bSmall
means a facility having a maximum potential rectifier capacity
of less than 60 million ampere-hours per year (assuming an operating
schedule of 8,400 hours per year and a 70 percent tank utilization)
or an actual rectifier capacity of less than 60 million ampere-hours
per year demonstrated through the use of nonresettable meters.
Existing means installed before 12/16/93 (proposal date of regulation).11234
| Control technique | ||
| Packed-bed scrubber (PBS) | Visually inspect device to ensure there is proper drainage, no chromic acid buildup on the packed beds, and no evidence of chemical attack on the structural integrity of the device. | 1/quarter |
| Visually inspect back portion of the chevron-blade mist eliminator to ensure that it is dry and there is no breakthrough of chromic acid mist. | 1/quarter | |
| Visually inspect ductwork from tank or tanks to the control device to ensure there are no leaks. | 1/quarter | |
| Add fresh makeup water to the top of the packed bed.a,b | Whenever makeup is added | |
| Composite mesh-pad (CMP) system | Visually inspect device to ensure there is proper drainage, no chromic acid buildup on the pads, and no evidence of chemical attack on the structural integrity of the device. | 1/quarter |
| Visually inspect back portion of the mesh pad closest to the fan to ensure there is no breakthrough of chromic acid mist. | 1/quarter | |
| Visually inspect ductwork from tank or tanks to the control device to ensure there are no leaks. | 1/quarter | |
| Perform washdown of the composite mesh-pads in accordance with manufacturer's recommendations. | Per manufacturer | |
| PBS/CMP system | Same as for CMP system. | Same as for CMP system |
| Fiber-bed mist eliminatorc | Visually inspect fiber-bed unit and prefiltering device to ensure there is proper drainage, no chromic acid buildup in the units, and no evidence of chemical attack on the structural integrity of the devices. | 1/quarter |
| Visually inspect ductwork from the tank(s) to the control device to ensure there are no leaks. | 1/quarter | |
| Perform washdown of fiber elements in accordance with manufacturer's recommendations. | Per manufacturer | |
| Other air pollution control device (APCD) | To be proposed by the source for approval by the Administrator. | Proposed by the source for approval by the Administrator |
| Monitoring equipment | ||
| Pitot tube | Backflush with water, or remove from the duct and rinse with fresh water. Replace in the duct and rotate 180 degrees to ensure that the same zero reading is obtained. Check pitot tube ends for damage. Replace pitot tube if cracked or fatigued. | 1/quarter |
| Stalagmometerd | Follow manufacturer's recommendations. | Per manufacturer |
aIf greater than 50 percent of the scrubber water is drained (e.g., for maintenance purposes), makeup water may be added to the scrubber basin.
bFor horizontal-flow scrubbers, top is defined as the section of the unit directly above the packing media such that the makeup water would flow perpendicular to the air flow through the packing. For vertical-flow units, the top is defined as the area downstream of the packing material such that the makeup water would flow countercurrent to the air flow through the unit.
cWork practice standards for the control device installed upstream of the fiber-bed mist eliminator to prevent plugging do not apply as long as the work practice standards for the fiber-bed unit are followed.
dDevice
used to measure the surface tension of the bath.3
SUMMARY OF THE REQUIREMENTS
The major requirements of the
regulation can be categorized as follows:
Decorative chromium electroplaters
must be in compliance with the regulation by January 25,
1996. Hard chromium electroplaters and chromium anodizers must
be in compliance with the regulation by January 25, 1997.
Emission limits and work practice
requirements are discussed in this chapter. Testing and monitoring
requirements are covered in Chapter 5, and recordkeeping
and reporting requirements are discussed in Chapter 6.
In addition, a detailed "table
of contents" of the regulation is included in Appendix D
of this guidebook. It lists the requirements of the regulation
and gives the section of the regulation where these requirements
are found.
EMISSION LIMITS
The regulation specifies emission
limits (expressed as concentration of chromium) that can typically
be achieved by the use of a certain technique to reduce emissions
(such as a control device or fume suppressant). The emission limits
are presented in Table 41. The emission reduction technique
that corresponds to the emission limit is shown in parentheses
in Table 41.
What is meant by "small"?
As shown in Table 4-1, small, existing hard chromium electroplating
tanks have a less stringent emission limit to meet than large
hard chromium electroplating tanks. A source is considered small
by definition if the maximum cumulative potential rectifier capacity
of all hard chromium electroplating tanks within the facility
is less than 60 million ampere-hours per year.
For example...
A facility having both hard chromium electroplating and chromium
anodizing tanks ducted to the same control device would only consider
the rectifier capacity associated with the hard plating tanks
in determining the size. However, a facility having a series of
hard plating tanks ducted to a control device in one building
and another series of hard plating tanks ducted to a control device
in a different building must consider the total capacity of all
tanks in determining size because size must be determined for
all hard plating tanks within the facility boundaries.
If the maximum rectifier capacity
is 60 million ampere-hours per year, a source may demonstrate
that it should be considered small instead of large by using either
of the following procedures:
How do I calculate the maximum cumulative potential rectifier capacity? The maximum cumulative potential rectifier capacity is based on a maximum potential operating schedule of 8,400 hours per year for the facility and assumes that each tank is in operation for 70 percent of the total operating hours.
For example... To calculate the maximum cumulative potential rectifier capacity for a facility, sum the total installed rectifier capacities associated with all hard plating tanks (SCR in amperes) and multiply this sum by 8,400 hours/year and 0.7, as shown below:
What is meant by "existing"? A tank qualifies as "existing" if it was installed before December 16, 1993, which was the date this regulation was proposed in the Federal Register.
Which control technique
should I use to meet the emission limit?
As mentioned above, the emission limits are based on the level
of control that can be maintained using a certain control technique.
However, you may choose to use another control technique, as long
as you can meet the emission limit for your type of facility.
The following paragraphs discuss the control techniques in Table 41.
Typical control efficiencies
are also given in the following paragraphs. But, beware that actual
performance levels may vary from these typical values, depending
on such factors as the inlet conditions and how well the control
devices are operated and maintained. For more information on how
these typical control efficiencies were derived, see Chapters
4 and 5 of EPA's Chromium Emissions from Chromium Electroplating
and Chromic Acid Anodizing Operations--Background Information
for Proposed Standards (Volume I) (EPA453/R93030a).
For information on the availability of this document, see
Chapter 10 of this guidebook.
Packed-bed scrubbers
are typically used to reduce emissions of chromic acid mist from
electroplating and anodizing tanks. Both single and double packed-bed
designs are used. Chromic acid mist is removed from the gas stream
primarily by droplets impacting on packing media. First, the gas
stream is wetted by spraying water countercurrent to the gas flow
to enlarge the droplet size. The gas stream then passes through
the packed bed(s) where the droplets impinge on the packing media.
The regulation requires periodic washing of packing material using
an overhead weir.
In most cases, the packed-bed
section of the scrubber is followed by a mist eliminator section
comprised of a single chevron-blade mist eliminator. The mist
eliminator removes any water entrained from the packed-bed section.
Treated gases then pass through an induced draft fan and out a
stack or exhaust vent. The scrubber water is usually recirculated
and periodically tapped and discharged to the electroplating tanks
as makeup solution.
Typical efficiencies of packed-bed
scrubbers are 97 percent for decorative chromium electroplating
and anodizing tanks and 99 percent for hard chromium electroplating
tanks. Schematics of a single packedbed scrubber and a double
packedbed scrubber are provided in Figures 41
and 42, respectively. Figure 43 is a schematic
of a chevronblade mist eliminator.
Composite mesh pads
consist of layers of interlocked fibers densely packed between
two supporting grids. The composite mesh pad was developed to
remove small particles (< 5mm
or 0.2 mils) that were not effectively controlled by conventional
technologies. The layers of material in composite pads are arranged
with the smallest diameter fiber layer located in the center of
the pad and progressively larger diameter layers located on both
sides of the center. Particles collide with the fibers in the
pad and adhere to their surfaces. These captured particles coalesce
into larger droplets as they travel through the small-diameter
fiber layers in the center of the pad. These enlarged particles
either drain to the bottom of the unit or are reentrained in the
gas stream. The reentrained particles are then captured by the
large-diameter fiber layers in the back of the pad. A schematic
of a typical composite meshpad is provided in Figure 44.
Composite mesh-pad systems incorporate
a larger particle removal system prior to the composite mesh pad
to reduce the plugging potential of the pad. The large particle
removal system can either be a series of larger diameter mesh
pads or a packed-bed scrubber section.
Typical removal efficiencies
associated with this control device are greater than 99 percent.
Fume suppressants
are compounds that are added directly to the bath to reduce or
inhibit misting. Fume suppressants include: wetting agents, foam
blankets, and combinations that include both a wetting agent and
a foam blanket. An important distinction between wetting agents
and foam blankets is how they reduce emissions. Wetting agents
reduce or inhibit misting by lowering the surface tension of the
bath. When the surface tension of the solution is reduced, gases
escape at the surface of the solution with less of a "bursting"
effect, forming less mist. Foam blankets do not preclude the formation
of chromic acid mist, but rather trap the mist formed under a
blanket of foam. The foam blanket is formed by agitation produced
by the hydrogen and oxygen gas bubbles generated during electroplating.
Once formed, the foam blanket is usually maintained at a thickness
of 1.3 to 2.5 cm (0.5 to 1.0 in.) and covers the entire surface
of the bath.
Fume suppressants typically reduce
chromium emissions by more than 99 percent.
What if I want to use a
different control technique?
You may use another control technique, as long as you meet the
emission limit for your type of facility. You do not need EPA
approval to choose another technique; however, you must get EPA
approval on the monitoring parameters and test methods that you
will use. An example of another control technique that may be
used is the fiber-bed mist eliminator, which is described below.
Fiber-bed mist eliminators
mostly have been used to reduce acid mists from sulfuric, phosphoric,
and nitric acid plants. These systems remove contaminants from
a gas stream through the mechanisms of inertial impaction and
Brownian diffusion. Fiber-bed units are designed for horizontal,
concurrent gas-liquid flow through the bed. The contaminated gas
stream flows toward the downstream face of the bed. The acid mist
in the gas stream impacts on the surface of the fibers and drains
down the outer face of the bed to the sump while the cleaned gas
flows up and out the top of the unit. A schematic of a typical
fiber-bed mist eliminator is presented in Figure 45.
Fiber-bed mist eliminators are
typically installed downstream of an existing control system.
The upstream device removes the majority of the emissions and
thus prevents plugging of the fiber bed.
Adequate test data are not available
to accurately quantify the control efficiency of fiber-bed mist
eliminators. However, EPA believes that these systems can achieve
the emission limits that were based on the use of composite mesh-pad
systems and fume suppressants based on qualitative data available.
WORK PRACTICES
Besides complying with the emission
limits discussed above, you will also be required to perform work
practice standards. Work practice standards are required to ensure
that the control technique you use to comply with the regulation
is properly maintained. Poor maintenance could result in system
degradation over time, and eventually lead to an increase in emissions.
Work practice standards must be performed quarterly in most cases.
The requirements vary slightly depending on which control device
you use, as shown in Table 42.
In addition to these work practices,
you will also be required to write an operation and maintenance
(O&M) plan for your facility. (Decorative chromium electroplating
operations that use a trivalent chromium bath do not have to prepare
an O&M plan.) The O&M plan must be developed and implemented
by the compliance date for your facility. However,you do not have
to submit your plan to EPA. The O&M plan will include:
You may use any standard operating
procedure (SOP) manuals, vendor O&M manuals, Occupational
Safety and Health Administration (OSHA) plans, or other existing
plans as part of your O&M plan, as long as they meet the criteria
in the regulation.