POWER October 2014 - 64

MERCURY CONTROL
2. Meeting targets. Test results show the effectiveness of AS-HgX on cumulative stack
mercury in a PRB plant equipped with a circulating dry scrubber. Courtesy: Novinda
● Cumulative average
0.030
0.025
0.020
0.015
0.010
0.005
0.000
5/2
In another trial, shown in Table 2, MATS
compliance was achieved with Amended
Silicates injection, and a concrete-friendly
PAC was evaluated as well. To meet MATS,
the PAC product required concurrent use of a
coal additive for mercury oxidation, as well
as hydrated lime to reduce flue gas SO3
conPlant
target (MATS)
5/4
5/6
5/8
5/10
test for use as a cement replacement in every
sample evaluated to date. The combined financial
impact realized from the sale of fly
ash and avoided disposal costs for that same
fly ash if contaminated by PAC are often
greater than the operating costs for mercury
control in a host unit.
AS-HgX also has been subjected to the
ASTM E1226-10 explosibility test and found
to be not explosible. Therefore, injection systems
for Amended Silicates do not require explosion
suppression or inerting systems, as are
specified for PAC silos in recent procurements.
Some utilities have explored a hybrid approach
for compliance with MATS. One
option is to add an oxidizing agent to the
coal feed coupled with the injection of PAC
or brominated PAC to capture the oxidized
mercury from the flue gas. A concern has
emerged at some plants over evidence of
corrosion associated with the use of halogen
oxidizing agents such as calcium bromide
(CaBr2
). Novinda's Amended Silicates offers
a single-product solution without the use
of corrosive halogen compounds; AS-HgX
serves to both oxidize and capture mercury
from the flue gas.
Amended Silicates has a higher bulk density
compared to PAC and may require minor
modifications to PAC injection systems to
efficiently disperse in the flue gas. Novinda
recommends lance spacing of 30 inches and
discharge locations along the length of the
lance of 30 inches as well. To flow reliably
in PAC silo systems, minor modifications
to the fluidization air pad configuration are
recommended. These changes are typically
implemented in less than one week at a cost
of less than $50,000. The use of higher injection
air velocities at the lance discharge is
recommended as well, which may require an
upgrade to the transport air blower in existing
injection systems.
Economics
Due to its efficient capture of mercury and
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5/20
one-product solution in certain plant configurations,
Amended Silicates generates significant
cost savings for many users. Details for
several cases are presented here.
Comparative economics for a baseload
(90% availability) 110-MW unit burning
PRB coal are shown in Table 1. This unit is
equipped with SCR, a spray dryer absorber,
and a pulse-jet baghouse for particulate control.
In addition to AS-HgX, brominated PAC
was tested in this unit, both as the sole mercury
control sorbent and in combination with
calcium chloride (CaCl2
) added to the coal as
a mercury oxidizer. AS-HgX met the pending
MATS emissions standard with a 20% margin
at an injection rate of 30 lb/hr (1.3 lb/MMacf)
while a higher rate was needed for brominated
PAC. The simultaneous addition of CaCl2
to the coal feed allowed for a reduced brominated
PAC injection rate, but the combined
costs were still higher than AS-HgX. Use of
Novinda's AS-HgX is projected to save the
utility 63% to 70% of the mercury abatement
costs of the brominated PAC alternatives.
tent, which degrades PAC mercury capture
efficiency. In spite of the use of a concretefriendly
PAC, fly ash samples did not meet
specifications for sale as a cement replacement.
In this trial, Novinda's single product
offered a 33% savings over the multiproduct
alternative and preserved the salability of
fly ash, estimated to be worth an additional
$5,000,000 in annual revenue and avoided
disposal costs.
Novinda's Amended Silicates was also
evaluated in a unit burning a moderate sulfur
(~1.7%) eastern bituminous coal. The host
unit was fitted with SCR, which contributed
to a SO3
concentration of about 20 ppm at the
Amended Silicates injection location. This
condition was similar to another unit burning
eastern bituminous coal where a sulfur-tolerant
PAC had been tested with results reported
in the literature. To determine injection rates
of sulfur-tolerant PAC and hydrated lime,
a proportioning factor was calculated as a
simple ratio of plant outputs for the Novinda
host unit and the literature unit. Results of the
economic analysis are presented in Table 3.
The Novinda single-product option of ASHgX
injection to meet MATS showed a 45%
cost savings compared to the combination of
an SO3
-tolerant PAC and hydrated lime.
Carbon Footprint
Amended Silicates products provide a number
of important environmental benefits
when compared to the use of PAC. In light
Table 1. Comparative economics for 110-MW unit burning PRB coal.
Source: Novinda
Product
BrPAC + CaCl2
BrPAC only
AS-HgX
Injection rate
Meets MATS?
50 lb/hr + 400 ppm Yes
100 lb/hr
30 lb/hr
Yes
Yes, plus 20% margin
Cost/hour
$89.50
$110.00
$33.00
Annual
$705,618
$867,240
$260,172
Table 2. Comparative economics for 760-MW unit burning eastern bituminous
coal. Annual costs do not include the effect on revenue from fly ash sales and
avoided disposal costs. Source: Novinda
Case
Multi-product
solution
Product
Concrete-friendly
PAC
Hydrated lime
CaBr2
Novinda
single-product
www.powermag.com
POWER | October 2014
AS-HgX
Injection rate (lb/hr) Product cost Cost/hour Annual cost
$1.10/lb
1,000
3,000 $0.0625/lb
400 $0.90/lb
Total
1,000
$1.10/lb
$1,100.00
$187.50
$360.00
$1,647.50
$1,100.00
$3,069,504
$1,695,936
Stack Hg emissions (lb/GWh)
http://www.powermag.com
POWER October 2014

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