POWER July 2010 - 43

AIR QUALITY MANAGEMENT
emissions intensity, with emissions comparable
to those from natural gas firing.
Isogo typically operates in the single-digit
ppm concentration range for SO2
and NOx
(against Unit 2 permit levels of 10 ppm and
13 ppm), at less than 5 mg/Nm3
(0.005 lb/
mmBtu) for particulates, and with well over
90% control of both elemental and oxidized
forms of mercury (Figure 2).
Development History
The basic process concept originated with
Bergbau Forschung in the 1950s in Germany.
Additional development was provided
by Foster Wheeler in the late 1960s in
conjunction with its Resox process. Commercialization
with activated coke was
achieved by Mitsui Mining in the 1980s.
Full commercialization by EPDC as an advanced
generation multipollutant control
technology for coal-fired boilers followed
in the 1990s.
Process development efforts in the late
1970s focused on high-efficiency (98%) SO2
removal efficiency, but researchers quickly
recognized that ReACT also provided NOx
removal. The ReACT process design for SO2
control routinely removes 20% to 40% NOx
as a co-benefit, and the process can be configured
to achieve 50% to 70% NOx
removal
or higher by adding secondary injection of
ammonia into the regenerator.
EPDC, which had faced serious difficulties
in obtaining water from local government
water agencies when siting earlier
projects, began developing ReACT as an
alternative to wFGD because the process
used a fraction of the water required by a
wFGD system. Reducing the water demand
of the Isogo site post-repowering was a
key project requirement, making ReACT a
natural selection for that project. J-POWER
subsequently acquired the rights to the technology
from Mitsui in 2005 and has since
provided units for refinery, incineration, and
sinter plant applications through its subsidiary
J-POWER EnTech.
The ReACT process has been successfully
demonstrated in the U.S. over a period
of five months as part of an Electric
Power Research Institute project hosted
by Sierra Pacific Power at its North Valmy
Station. Valmy reported the following outstanding
removal rates: 97.6% to 99.9% for
SO2
, 25.7% to 48% for NOx
, and 97.1% to
99.6% for Hg removal. (The data were reported
in " ReACT Process Demonstration
at Valmy Generating Station, " C. Dene, et
al., MEGA Symposium, Paper 123, 2008.)
The expected high levels of SO2
, NOx, and
Hg removal were entirely consistent with
commercial results at the full-scale units
in Japan.
July 2010 | POWER
www.powermag.com
Activated coke
Shape/diameter
Specific surface area
SO2 adsorption capacity
Pore size (Angstrom)
Pore volume
Raw material
Application
Tablet/almond ~10 mm
150-300 m2/g
60-120 mg/g
10-1,000 A
0.05-0.1 cc/g
Roga-Index (abrasion resistance) 95%
Coal
SOx, NOx, Hg removal
Activated carbon
Powdered
>1,000 m2/g
NA
10-100 A
0.5-0.6 cc/g
70%-85% (for tablet forms)
Coal
Hg removal
3. Three-step process. ReACT multipollutant removal is accomplished in three steps:
The adsorption stage, where pollutants are captured on activated coke; the regeneration stage,
where the activated coke is regenerated; and the by-product recovery stage, where a marketable
sulfuric acid by-product is available. Source: Hamon Research-Cottrell Inc.
Adsorption stage
AC
Regeneration stage
AC
*1 *2
Flue gas
Booster fan
AC
NH3
Adsorber
Clean gas
Stack
AC hopper
Hot air
*3
Air
Lock
hopper
AC Dust
Regenerator
By-product recovery stage
Lock hopper
SO2 rich gas
Hot gas
*2
Separator
Furnace Fuel
*3
43
2. Small environmental footprint. ReACT is a regenerative activated coke-based
technology that produces saleable by-products (sulfuric acid or gypsum) and, as a dry process,
does not require water. The technology should be of special interest to U.S. utilities burning
lower-sulfur western fuels, especially at locations where there are significant water supply concerns.
J-POWER reports that SO2 and NOx emissions at the Isogo plant are both at single-digit
ppm concentration levels-emissions that are on par with a natural gas-fired plant. Data for
Japan represent combined data for Japan's 10 regional electric utilities and J-POWER. Figures
for Isogo represent actual performance for fiscal 2008. Country figures represent combined
emissions intensity for coal-, oil-, and gas-fired thermal power plants. Source: Federation of
Electric Power Companies of Japan
Sulfur oxides
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Nitrogen oxides
3.3
3.4
3.4 3.5
1.6
1.2
1.4 1.4
ISOGO
0.7 0.8
USA
(2005)
Canada
(2005)
UK
(2005)
France
(2005)
Germany
(2005)
0.8
0.6
0.2 0.2
Italy
(2005)
Japan
(2007)
New No.1
0.3 0.7
Isogo
(2008)
Table 1. Comparison of the properties of activated coke and activated
carbon. Source: Hamon Research-Cottrell Inc.
By-product
recovery unit
Vent
By-product
*1
g/kWh

http://www.powermag.com

POWER July 2010

Table of Contents for the Digital Edition of POWER July 2010