POWER October 2011 - 74

MERCURY REMOVAL
Table 4. Economics of TRAC catalyst for a typical 680-MW unit. Source: Hitachi
Power Systems America Ltd.
Coal type
Eastern bituminous
Hg oxidation @ air preheater outlet (APH; %)
Rate of activated carbon injection (ACI; lb/MACF)
Cost of ACI ($/yr)
Powder River Basin
Hg oxidation at APH outlet (%)
Rate of ACI (lb/MACF)
ACI cost ($/yr)
90
10
7,600,000
30
1.5
1,140,000
92
6
4,600,000
63
1.0
760,000
Notes: Assumes $0.75/lb for untreated activated carbon. MACF = million actual cubic feet.
activity of the TRAC catalyst was significantly
higher than that of the conventional
catalyst with low-chlorine coal. Figure 11
presents the Hg CEM results before and after
TRAC replacement.
The superior performance benefits of
TRAC have been demonstrated, but what
about the costs? The economics of adding
TRAC catalyst are illustrated in Table 4. For
most eastern bituminous coal applications,
the existing catalyst is sufficient to oxidize
the mercury. However, some units can benefit
from an extra boost of mercury oxidation
with one or two layers of TRAC. For PRB
applications, TRAC can help to minimize the
amount of ACI required and thereby save the
cost of mercury oxidation.
The most cost-effective mercury control
strategy is to use existing equipment in order
to comply with new standards. In particular,
Southern Company has evaluated mercury
oxidation across catalysts with enhanced
95
80
0.5
380,000
3 regular
layers
1 TRAC plus 2
regular layers 3 TRAC layers
mercury oxidation, such as TRAC. This strategy
requires that the oxidation be maintained
across a range of temperatures, fuel halogen
contents, and NOx
a catalyst would allow utilities to reduce or
eliminate the need for halogen injection and
simultaneously comply with stringent NOx
emission standards.
Based on pilot-test results, Southern
Company moved forward with full-scale
applications of TRAC catalyst at several
generating facilities burning PRB and bituminous
fuels. ■
-Anthony C. Favale, PE (anthony.
favale@hal.hitachi.com) is the director
of SCR products; Stephen Guglielmo
(stephen.guglielmo@hal.hitachi.com)
is the northeast sales manager; and
Dr. Peter Jin, PE (peter.jin@hal.hitachi.
com) is SCR engineering manager for
Hitachi Power Systems America Ltd.
Yoshinori Nagai (yoshinori.nagai.kw@
hitachi.com) is the general manager of
reserch and development for Babcock
Hitachi, K.K., Japan. Dr. Corey A. Tyree
(catyree@southernco.com) is a project
manager in Southern Company's Research
& Environmental Affairs Group
in Birmingham, Ala.
control levels. Such
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