THE ENERGY INDUSTRY TIMES - AUGUST 2018
US and Russian coals. The plant’s full
fuel flexibility potential will be realised
over time as the KOSPO team
gets more experience and masters
plant operation. Stay tuned.”
According to SFW, environmental
performance on these low rank coals
has also been “excellent”, meeting the
design limits. NOx and SOx emissions
are each guaranteed at 50 ppm (at 6
per cent O2). Dust emissions are controlled
by an electrostatic precipitator,
so that particulates do not exceed 20
mg/Nm3. Carbon dioxide emissions
are around 800 g/kWh, which is about
25 per cent below a typical operating
coal plant in Korea today.
Good environmental performance
compared to pulverised coal plant is a
characteristic of CFB combustion.
This is because fuel particles, recycled
coal with high moisture, low ash, and
low sulphur with a heating value of
around 4200 kcal/kg. High quality
coals typically have a calorific value
above 5500 kcal/kg.
Giglio commented: “In these first
years of operation, the Samcheok
CFB plant has been firing mainly
Indonesian coals and domestic biomass.
KOSPO has now begun exploring
other fuels sources by test firing
back to the lower furnace from solids
separators, have a longer residence
time in the combustion zone. A high
rate of solid circulation and excellent
mixing inside the furnace keeps the
combustion temperature even and at a
moderate level over the whole load
range. It also allows the use of low
excess air. These two things are the
main contributors to low NOx emissions
and reduced ammonia consumption
in the SCR.
The plant’s environmental performance
will be further improved as
more biomass is introduced to the mix.
The boilers are expected to burn about
5 per cent biomass in terms of heat
input, depending on availability. This
is likely to be in the form of recycled
wood waste from the local lumber industry
and imported wood pellets.
“At the moment they are targeting
local biomass,” said Giglio. “But to
get to 5 per cent, they will have to
look to the international market.”
The successful operation of Samcheok
Green Power project serves to
further the argument that CFBs can
play an important role in reducing
emissions while providing fuel flexibility.
And as environmental pressures
grow, CFB technology offers an elegant
solution at many levels for
countries like South Korea.
Giglio concluded: “It’s proving out
the solution that KOSPO wanted;
they wanted a reliable, fuel flexible
plant; they wanted a clean plant
without big expensive flue gas cleaning
systems to lower South Korea’s
power cost; and it’s working as
expected.”
Special Project Supplement
The CFB boiler in-line arrangement incorporates supercritical
steam parameters accompanied by Benson vertical-tube
technology
Measured process parameters at different load levels
50% load 75% load 100% load
Unit gross output (MWe) 500 750 978
Main steam flow (kg/s) 195 296 393
Main steam pressure (bar) 158 214 50
Main steam temperature (°C) 603 603 603
Reheat steam temperature (°C) 604 597 604
Bed temperature (°C) 812 812 833
Flue gas exit temperature (°C) 120 132 137
SO2 emissions (ppm)* 28 0 0
NO2 emissions after SCR (ppm)* <50 <50 <50
CO emissions (mg/m3n)* 35 8 7
* @ 6% O2, dry
3D cutaway of a single boiler