POWER October 2014 - 63

MERCURY CONTROL
Amended Silicates
The Amended Silicates family of products employs a non-carbon
mercury capture reagent that removes mercury via chemical reaction,
providing economic and environmental advantages unavailable with
carbon-based products.
Amended Silicates employs a bentonite clay substrate amended
with a metal sulfide that acts as the reagent to capture mercury. This
occurs via a chemical reaction that forms mercuric sulfide on the reaction
sites of particle surfaces in flue gas. Mercuric sulfide (cinnabar
in its naturally occurring state) is the most stable form of mercury and
the dominant mercury mineral in Earth's crust.
Amended Silicates directly reacts with elemental and oxidized
mercury to form stable, sequestered mercury compounds on the surface
of the amended clay particles. This means that oxidizing coal
additives or wet scrubber re-emission chemicals are not needed to
maintain compliance with MATS, making Amended Silicates a single-product
solution. Fly ash samples containing collected Amended
Silicates particles have been subjected to the EPA Method 1311 TCLP
test, and leachable mercury has been found to be nondetectable, a further
indication that the mercury is sequestered as an insoluble solid.
Full-Scale Trial Examples
Novinda is supplying Amended Silicates to multiple coal-fired generation
units in the western and midwestern U.S., including four units
at the Gillette Energy Center (GEC) complex operated by Black Hills
Power in Gillette, Wyo.
In a series of trials conducted in each of the four Powder River
Basin (PRB)-fired units at GEC, Novinda demonstrated the superior
performance of Amended Silicates. Trials were completed to optimize
mercury control, as well as to demonstrate extended operations and
assess balance-of-plant impacts. Typical results for one of the units
are shown in Figure 1 for a 30-day trial of AS-HgX. The uncontrolled
mercury emissions from the host unit were between 5 lb/TBtu and 6
lb/TBtu-well above the MATS standard. Once injection was started,
mercury stack emissions quickly dropped below the MATS level; the
injection rate was adjusted over the first week of the trial to minimize
cost while continuing to meet the standard. The optimized injection
rate was determined to be a low 0.26 pounds per million actual cubic
feet (lb/MMacf) of flue gas.
In trials completed in other units at GEC, AS-HgX consistently
out-performed brominated PAC.
" Black Hills continuously makes responsible investments in technology
to help us comply with state and federal environmental policies, "
said Mark Lux, vice president and general manager of power
delivery at Black Hills Corp. " Amended Silicates has proven to be a
consistent performer in achieving our mercury removal objectives,
and Novinda's technology delivers the desired results with less than
half the material required by alternative products, minimizing the
emissions control costs for our customers. "
Another long-term trial was completed at a proprietary plant burning
PRB coal and equipped with an SCR, circulating dry scrubber,
and pulse-jet baghouse. AS-HgX was injected at this site for 18 days,
with results shown in Figure 2. The plant was able to tune the injection
ratio to meet the target mercury emission rate for the entire
period at an average injection ratio of 0.11 lb/MMacf. For this graph,
mercury is plotted as a cumulative average, the required reporting
standard of the EPA MATS rule.
Balance-of-Plant Impact
Other benefits of Amended Silicates' bentonite clay substrate include
compatibility with continued sale of fly ash as a replacement for Portland
cement. (PAC typically contaminates the fly ash, requiring landfill
disposal.) Novinda's Amended Silicates has passed ASTM's C618
October 2014 | POWER
www.powermag.com
We Connect the Dots
Over the past 30
years,
Structural
Integrity has built
a team of over
200 industry experts providing comprehensive
solutions to the energy industry. We connect the
dots from problem to resolution, from regulations
to compliance, from nondestructive examination, to
engineered solutions, even custom equipment.
You can look to us for our:
* Knowledge of power plants, codes, and how
things work.
* Extensive experience and leadership.
* High quality, hard work, and responsiveness.
Call us today and we'll connect
the dots for you.
FROM
ENGINEERING
ANALYSIS TO
ADVANCED NDE,
LOOK TO
STRUCTURAL
INTEGRITY
Scan the QR Code for more information
www.structint.com/power
(877-4S I -POWER)
63
877-474-7693
CIRCLE 22 ON READER SERVICE CARD
http://www.structint.com/power http://www.powermag.com
POWER October 2014

Table of Contents for the Digital Edition of POWER October 2014
