Sorbent injection into a slipstream baghouse for mercury control: Project summary
Jeffrey S. Thompson
a,
⁎
, John H. Pavlish
a
, Lucinda L. Hamre
a
, Melanie D. Jensen
a
, David Smith
b
,
Steve Podwin
b
, Lynn A. Brickett
c
a
Energy and Environmental Research Center, 15 North 23rd Street, Stop 9018, Grand Forks, ND 58202-9018, USA
b
SaskPower, 2901 Power House Drive, Regina, Saskatchewan, Canada S4P 0S1
c
National Energy Technology Laboratory, Department of Energy, 626 Cochrans Mill Road, P.O. Box 10940, MS 922-273C, Pittsburgh, PA 15236-0940, USA
abstractarticle info
Article history:
Received 16 June 2008
Received in revised form 1 June 2009
Accepted 18 June 2009
Keywords:
Electrostatic precipitator–fabric filter
Trace elements
Continuous mercury monitor
Sorbent injection
Mercury
Mercury control
A project led by the Energy and Environmental Research Center to test and demonstrate sorbent injection as
a cost-effective mercury control technology for utilities burning lignites has shown effective mercury capture
under a range of operating conditions. Screening, parametric, and long-term tests were carried out at a
slipstream facility representing an electrostatic precipitator–activated carbon injection–fabric filter
configuration (called a TOXECON™ in the United States). Screening tests of sorbent injection evaluated
nine different sorbents, including both treated and standard activated carbon, to compare mercury capture as
a function of sorbent injection rate. Parametric tests evaluated several variables including air-to-cloth (A/C)
ratio, flue gas temperature, cleaning frequency, and dust loading to determine the effect on mercury control
and systems operation. Long-term tests (approximately 2 months in duration) evaluated the sustainability of
systems operation.
The screening tests identified four sorbents that achieved greater than 90% mercury capture. Longer-term
tests demonstrated mercury capture of 82% at sorbent injection rates of about 2–2.5 lb/Macf. Ash loading and
A/C ratio affected the operation of the fabric filter. At lower ash loadings, A/C ratios as high as 6 ft/min could
be sustained while operating with conventional bags, but higher ash loadings required the use of high-
permeability bags to overcome pressure drop issues.
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
The U.S. Environmental Protection Agency's (EPA's) Clean Air
Mercury Rule, which was issued on March 15, 2005, established
“standards of performance” for both new and existing coal-fired power
plants that limit their mercury emissions [1]. This has more serious
implications for facilities burning lignite than other coals because the
mercury emissions from lignite may be more difficult to control.
Lignite mercury levels are comparable to those of other coals, but they
contain significantly less chlorine and more calcium than bituminous
coals. These compositional differences have been shown to affect the
quantity and form of mercury emitted from a boiler as well as the
ability of control devices to capture the mercury. Higher coal chlorine
content tends to correlate with an increase in the fraction of oxidized
mercury (Hg
2+
) present in the total mercury emission. The pre-
dominant form of mercury emitted from lignite is the elemental form
(Hg
0
). Because oxidized mercury tends to be more easily captured than
elemental mercury, new approaches are needed for lignite-fired
utilities to cost-effectively meet future mercury regulations.
Halogen addition has shown promise for mercury control in
western fuels because it enhances the reactivity of both fly ash and
injected sorbents. The lack of reactive halogens (e.g., chlorine)
typically results in the higher Hg
0
fraction in the emissions of western
fuels. Unfortunately, capture of the mercury by a sorbent that is
subsequently removed with the fly ash can significantly impact the
disposition of the fly ash. One emission control method that offers an
alternative is an electrostatic precipitator (ESP)–activated carbon
injection (ACI)–fabric filter (FF) system, an Electric Power Research
Institute (EPRI)-patented system known as TOXECON™ in the United
States. The TOXECON configuration enables separate treatment or
disposal of the ash that is collected in the secondary FF, leaving the ash
collected in the primary particulate control device unaffected [2].
A multiphase project was undertaken by the Energy and Environ-
mental Research Center (EERC), SaskPower, the U.S. Department of
Energy (DOE), the North Dakota Industrial Commission, North Dakota
utilities, and EPRI to identify cost-effective mercury control options for
lignite-fired power plants. The main goal of Phase II was to test and
demonstrate sorbent-based mercury control for electric utilities that burn
lignite. A secondary goal was to increase the scientificunderstandingof
Fuel Processing Technology 90 (2009) 1392–1399
⁎ Corresponding author. Tel.: +1 701 777 5245; fax: +1 701 777 5181.
E-mail address: jthompson@undeerc.org (J.S. Thompson).
0378-3820/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.fuproc.2009.06.016
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