Document ID: EPA-HQ-OAR-2002-0051-1898
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-12-20T05:00Z

October 24, 2006

									

MEMORANDUM

											

To:		Portland Cement Docket OAR-2002-0051

From:		Jeffrey Cole, RTI

Subject:	Estimated Portland Cement Mercury Removal Based on Utility Data

INTRODUCTION

	The Portland Cement NESHAP effort can be aided by the use of the EMF
database developed from stack test reports of the Electric
Utility/Information Collection Effort (EU/ICE).  The EU/ICE was a
multiyear data collection effort led by the EPA/OAQPS/ESD/CG.

	

	The EMF database was based on data from 80 speciated Hg stack test
reports of which the FGD portion was a subset.  There were 16 test
reports in this subset analyzing EU plants equipped with FGDs after some
form of PM device (ESP or FF).  The units and their EMFs were
categorized into similar fuel type/boiler type/emission control system
categories (which we called “stack-tested bins”). Typically, each
emissions test report contained data from three emission stack test
runs, which included speciated Hg information.  The 16 test reports had
3 sample run each for a total of 48 speciated Hg sample runs.  The data
can be found at:   HYPERLINK
"http://www.epa.gov/ttn/atw/combust/utiltox/control2.zip" 
http://www.epa.gov/ttn/atw/combust/utiltox/control2.zip 

	Because stack testing did not analyze every configuration of fuel
type/emission control/boiler type system, the units that did not match
perfectly had to be assigned to a stack-tested bin in order for their
emissions to be quantified.  The hierarchy of unit characteristics
chosen for making the assignments was fuel type, boiler type, and,
finally, emission control system.  Some engineering judgment was also
used to assign bins to those units that did not perfectly fit into a
stack-tested bin.

	It should be noted that not all EMF averages showed removal of Hg. 
Some EMF averages showed a generation of Hg by the tested unit.  This
discrepancy could be accounted for by a number of factors, such as an
inaccurate mercury-in-coal analysis or an inaccurate flue-gas Hg test
before or after the last control device.  None of the stack tests used
in these computations was found to have any documentation as to errors
or problems found during or after the stack testing.  EPA decided that
if no errors or problems were presented in the stack test reports, the
data would be used.  EPA’s main purpose in this model was to determine
the total nationwide 1999 Hg emissions from all coal-fired electric
utility power plants in the U.S.  Because of the combination of test
inaccuracies and bin assignments, it was inevitable that some units
would be modeled as emitting less Hg than they actually emitted and some
would be modeled as emitting more.  In some cases, the computed emission
rate was greater than the inlet amount.  Although physically improbable,
these cases were used as computed to balance cases that were modeled as
emitting too little mercury.

	In the EU/ICE effort, a different method was used to average fuel
type/boiler type/emission control system(s) from all dual-controlled
units (units having both a PM and an SO2 control device).  Since stack
test flue-gas speciated Hg was analyzed at the inlet and outlet of the
last control device, the effect of the PM control on Hg removal on these
dual-controlled units was not clear.  Thus:

●	EPA decided that it would be more realistic to add the PM control
device removal of Hg to the SO2 control device removal of Hg for
dual-controlled units.  

●	The PM control device average EMF was taken from the bin of a unit
with a similar fuel type/boiler type/PM emission control system to the
dual-controlled bin it was modifying.

●	The average EMF of a tested unit with a single PM control device was
multiplied by each individual run EMF from a similarly configured
dual-controlled unit.

●	These modified EMFs were averaged.  This average was used to compute
the Hg removal of a dual-controlled unit in the national emissions
model.

Note: Since this Portland Cement data collection effort may wish to look
at FGD Hg removal data without the effect of the PM control we have
included 2 sets of data (one with the APCD contribution and one
without). Also note that these 48 sample run data were obtained from
plants that burned bituminous coal, subbituminous coal, lignite coal,
and one unit that burned a combination of bituminous coal and petroleum
coke.

	The majority coal burned in electric utility units in the U.S. is
bituminous coal.  It is reasonable to assume that cement kilns use
bituminous coal as their major source of fuel. If this is assumed then
the data set would be reduced to 8 test reports had 3 sample run each
for a total of 24 speciated Hg sample runs.

	 There was an effect noted during Ontario Hydro Hg speciation testing
where the inlet filter apparatus was masked and did not record the inlet
Hg species accurately.  This effect was observed before APCDs, however
since these data look before and after FGDs (were the PM has already be
removed) this concern is mute.

CONCLUSION

	As shown in the attached spreadsheet (see “Results” tab) and in
Table 1, for all FGD data (all coals) the average APCD/FGD Hg EMF was
0.5278 (or 47.22 percent removal). The average FGD only Hg EMF was
0.5773 (or 42.27 percent removal). For FGD data (bituminous coal only)
the average APCD/FGD Hg EMF was 0.5338 (or 66.20 percent removal). The
average FGD only Hg EMF was 0.4403 (or 55.97 percent removal).  As
shown in and in Table 2, the average FGD speciated Hg emission split (in
either case [APCD/FGD or FGD]) for all coal types is 1.4 percent
particulate-bound mercury (Hgp), 12.7 percent ionic mercury (Hg2+), and
85.9 percent elemental mercury (Hg0).  The average FGD speciated Hg
emission split (in either case [APCD/FGD or FGD]) for all bituminous
coal only is 1.9 percent particulate-bound mercury (Hgp), 19.4 percent
ionic mercury (Hg2+), and 78.7 percent elemental mercury (Hg0).

Table 1. Mercury Removal from FGDs (from EU/ICE)

R

R

R

R

R

                            All Coal Types

Particulate-bound mercury (Hgp)	1.4

Ionic mercury (Hg2+)	12.7

Elemental mercury (Hg0)	85.9

                                                               
Bituminous Coal Only

Particulate-bound mercury (Hgp)	1.9

Ionic mercury (Hg2+)	19.4

Elemental mercury (Hg0)	78.7

 Emission Modification Factor - An EMF is a fraction obtained from the
amount of Hg exiting an air pollution control device (APCD) divided by
the amount of the Hg entering that device. The total EMF can also be
defined as one minus the total Hg removal fraction.  For example, a
total EMF of 0.68 is equal to a Hg removal of 0.32 (or 32 percent).