MEMORANDUM

May 28, 2002

TO: Environmental Caucus of MACT WG

Bill O' Sullivan

John Paul

FROM: Martha Keating

Re: Non-Hg HAPs Analysis

Using the data provided to the Utility MACT subgroup, I have compiled
and sorted the data for the metals (other than mercury) from the utility
boiler stack tests. I have also compiled the limited data for the acid
gases. The conclusions I drew from the data are presented below. In
addition, I have included a number of suggestions concerning surrogate
measures, and the rationale for these suggestions, provided to me by
Bill O' Sullivan. I hope this information will further the WG's
discussion of these pollutants.

# Metals

I looked at the metals data 2 different ways. First, I compiled the
percent removal data for each tested boiler (see file
metals_by_site.xcl). Then I sorted the data by metal across sites (see
file metals_by_pollutant.xcl) and looked at the range of percent
removal. (Note that I deleted data points where there was not both inlet
and outlet data.) Several things immediately jump out:

1.  Removal efficiencies for all of the metals *except* selenium are, in
    most cases, in excess of 90% and typically 95% or higher.

2.  There is a range of removal efficiency for some of the metals,
    however when the data are grouped by boiler, you can clearly see
    that the poor removal efficiencies are limited to certain test
    sites. In other words, certain sites clearly stand out as having
    lower removal efficiencies regardless of the metal. Adding the fuel
    type and control device to the data set revealed that the boilers
    with the poor removal efficiencies were more likely to burn either
    lignite or subbituminous coal (except 3 fired bituminous coal and
    had either an FGD (2) or a CS-ESP (1)).

3.  Selenium removal efficiencies vary across the tested sites. These
    date were looked at separately (see file selenium removal.xcl).

4.  There are 34 tests. Therefore, calculating a MACT floor would mean
    taking the average removal efficiency of the top 12% or 4 sites.

5.  [For every metal, including selenium, the average of the top 12% is
    99 percent removal.]{.underline} (Note that even though there is a
    range of removal efficiencies for selenium, the top 12% still
    achieve 99% removal.)

I conclude from these data that grouping the metals is appropriate,
because their removal efficiencies are so similar, and further that
separate categories for some metals are not needed. It is also apparent
that if EPA subcategorizes by fuel type, the floor for metals would not
be 99%. In fact the data are far more variable for different metals when
lignite and subbituminous coal are burned. In the event of fuel
subcategories, we may need to look again at grouping the metals
differently.

# Acid Gases

I also compiled just the data for the acid gases (see file HCL_HF
rmoval.xcl). There are just a few data points with both inlet and outlet
data, and in my opinion they are inadequate for a floor calculation.
Most have outlet concentrations higher than the inlet.

# Surrogate Measures

The following suggestions (and supporting rationale) are put forth by
Bill O'Sullivan and get to the heart of the next question: how to we
measure the removal of the metals and other pollutants? Bill makes
specific suggestions for surrogate pollutants and what their levels
could be. A couple of issues that remain in my mind is first, for the
metals, does the surrogate measure represent 99% removal which would be
the MACT floor? Second, for the other pollutants, how do we justify
stringent levels, even with a surrogate measure, if the emissions test
data are not adequate to set a floor?

From Bill O' Sullivan:

Following up on the 5/13/2002 utility MACT workgroup meeting, here is a
state air regulator (who is also a mechanical engineer) common sense
proposal for dealing with other HAPs from coal fired power plants. This
proposal uses surrogates for all HAPs (other than Hg) and recognizes
that existing air pollution control technology and methods in common use
for the criteria air pollutants also reduce HAP emissions from coal
boilers.\
\
1. Particulate HAPs - Use particulate NSPS as MACT surrogate.\
\
Particulate HAP emissions from coal firing are primarily metals, and
also include polycyclic organic matter (POM). Coal combustion is the
largest, or amongst the largest, source category for emission of many
heavy metal HAPs in the USA. Coal combustion is generally not a large
emitter of POMs, provided good combustion is maintained. (See 3 below.)\
\
The existing NSPS for particulates can be applied to all coal plants as
a minimum MACT requirement for particulate HAPs. The NSPS is 0.030 lbs.
per million Btu. Actual particulate levels with large ESPs or baghouses
are typically under 0.010 lbs. per million Btu. Older non-NSPS units
emit near 0.100 lb./million Btu or higher particulate levels. Hence,
applying the NSPS can get 90% or greater particulate reduction and
similar particulate HAP reductions for non-NSPS units. To the extent
that certain particulate HAPs are concentrated in the finest
particulates (i.e. lead, arsenic and cadmium), increasing the
effectiveness of total particulate control could provide a
proportionally higher level of particulate HAP control.\
\
Applying the existing particulate NSPS would likely result in emissions
of significant amounts of heavy metals being reduced by 90% or greater
from non-NSPS coal units. Better particulate control would also reduce
mercury emissions and POM emissions.\
\
2. Acid Gas HAPs - Use SO2 NSPS as MACT surrogate.\
\
Hydrochloric acid (HCl) and hydroflouric acid (HF) are the primary HAP
acid gases emitted by coal fired power plants. Hydrochloric acid is the
HAP emitted in highest amount in the USA, and coal combustion emits more
hydrochloric acid than any other source category in the USA.\
\
Hydrochloric acid is readily controlled by scrubber technology for
sulfur dioxide control. It is usually controlled at higher removal
efficiency than SO2. Greater than 95% reduction of HCl can be expected
with either a wet or wet/dry scrubber.\
\
Hence, NSPS control of SO2 is an appropriate baseline for MACT control
of HCl. In addition to use of SO2 control as an initial surrogate for
acid gas HAPs (especially HCl), periodic testing of HCl and HF should be
required to ensure that low levels result from SO2 scrubbing. Based on
this information, more specific HCl or HF MACT limits can be set in the
future if significant levels of these remain after scrubbing for acid
gases.\
\
3. Organic HAPs - Use Carbon Monoxide as MACT surrogate.\
\
Organic HAPs include polycyclic organic matter (POM), polyaromatic
hydrocarbons (PAH), and dioxin. With good combustion these should be
emitted at insignificant levels. However, there are currently little or
no requirements for good combustion from coal burning utility boilers.
Furthermore, NOx control requirements have sometimes encouraged the
modification of combustion processes in ways that have increased CO and
other products of incomplete combustion.\
\
Good combustion practice is to use carbon monoxide as the principle
indicator of incomplete combustion since it is emitted in relatively
high amounts when combustion is poor and can be accurately and
inexpensively measured. Continuous monitoring of carbon monoxide is used
to trim the air to fuel ratio to ensure maximum combustion of fuel,
which in turn ensures minimum organic emissions, including organic HAPs.
Carbon monoxide monitoring is also a good indicator of other combustion
problems, such as poor fuel atomization (oil) or coal distribution in
the boiler.\
\
There is already precedent in state reasonably available control
technology (RACT) rules for using carbon monoxide as a surrogate for VOC
emissions from boilers. NJ requires CO continuous monitors and has a
limit of 100 ppmv at 7% oxygen, daily average for VOC RACT for utility
boilers. Typical actual CO levels for well-controlled coal boilers are
less than 10 ppmv. Similarly, CO can be used as a surrogate for
minimization of organic HAP emissions.\
\
Given that there is sparse data correlating organic HAP emissions to CO,
a prudent first step would be to set a fairly liberal MACT limit of
between 10 and 100 ppmv CO at 7% oxygen, require periodic HAP testing as
part of the MACT, and update the MACT limit in the future to reflect
best combustion control methods.\
\
OIL NOTE: The above recommendations for particulate and organic HAPs can
also be applied to heavy oil combustion which emits significant amounts
of certain heavy metals (nickel) and can emit significant amounts of
organic HAPs if the combustion control is poor. The recommendations for
organic HAPs can apply to light oil combustion as well.