Part 2 CCT Overview
Coal-fired Power Generation Technologies (Combustion Technologies)

Efficiency Pulverized Coal-fired Power Generation Technology
2A1. High(Ultra Super Critical Steam Condition)
Technology Overview

1. Pulverized coal-fired power generation system
The pulverized coal-fired power generation system (Fig. 1) is widelyused as an established, highly reliable technology. In 2000,
600/610oC USC (Ultra Super Critical Steam Condition) systems wereinstalled at J-POWER’s Tachibanawan Thermal Power Station’s No. 1
and No. 2 plants (1050 MW each). J-POWER’s Isogo New Unit No. 1,fullwhich was put into service in 2002, uses the same system with purevariableregulationpressureatoperation
at the temperature
main steamoftemperatureofvoltage
the main steam
600oC and theo600℃
andthereheatsteam
temperatureof610℃.
Furtherreheat steam temperature of 610 C. Further challenges will be to use
challenges
to usemore typesof coal,efficiency,
increase improve
moretypes willof becoal,increase
generation
generation efficiency, improve environmental measures andenvironmental measures and enhance load operability.
enhance load operability.

Steam

Pulverized
coalAir

Coal pulverizer
Steam conditions

Pressure (kg/cm2)

Temperature (oC)

169
246
325

566
538
596

Subcritical
Supercritical
Ultra-supercritical

566 C

condition of 24.5 MPa x 600 oC/600 oC in 1998. Furthermore,
J-POWER’s Tachibanawan No. 1 and No. 2 plants (1050 MW)
adopted the steam condition of 25.0 MPa x 600oC/610oC in 2000.
Figure 3 shows an example of the relationship between thesteam condition and the efficiency of a supercritical pressure
plant.
Responding to the trend of increasing steam temperatures,
power companies, steel manufacturers, and boiler manufacturers
are promoting the development and practical application of highstrength materials with superior high-temperature corrosion
resistance, steam-oxidation resistance, and workability.
High-temperature materials for use at 650oC have already been
introduced into practical application, with work proceeding todevelop materials for use at 700oC.

610OC
Power generation efficiency (%LHV)

593OC

500

24.5MPa

31.0MPa30

24.1MPa
16.6MPa

400

20
Steam pressure(Right scale)

300

200
1910

Steam pressure MPa

Steam temperature OC600

Steam temperature(Left scale)1001920

1930

1940

1950

1960

1970

CapacitorFig. 1 Pulverized coal-fired power generation system (Rankine cycle)

600OC
538OC

Feed water pump

Coal ash

2. Efficiency increase
Increasing the thermal efficiency of power generation plants is an
important issue not only to decrease the power generation costs
from an economic standpoint, but also for suppressing CO2
emissions. In particular, steam temperatures at coal-fired power
plants, which are currently the most prevalent among large
thermal power plants, have increased. Figure 2 shows the trendof steam condition in recent years.
In 1989, Chubu Electric Power Co., Inc.’s Kawagoe No. 1 plant(700 MW) adopted the steam condition of 316 kg/cm2g (31.0MPa) x 566oC/566oC. In 1993, Chubu’s Hekinan No. 3 plant (700MW) adopted the steam condition of 246 kg/cm2g (24.1 MPa) x538oC/593oC, marking the highest reheated steam temperature in
Japan. Subsequently, The Chugoku Electric Power Co., Inc.’sMisumi No. 1 plant (1000 MW) and Tohoku Electric Power Co.,
Inc.’s Haramachi No. 2 plant (1000 MW) adopted the steamOGSteam turbine

Flue gas

Pulverizedcoal boiler19801990 2000 2005

46045

−144

CO2 reduction rate ー243ー3Efficiency

CO2 reduction rate (%)

CoalGeneratorー442ー541

Main steam temperature (oC) 538

538

Reheat steam temperature (oC) 566（Base）

593

566

600

625

593

600

625

Steam temperature (oC)Fig. 3 Power generation efficiency and CO2 reduction rate
for various steam conditions

Fig. 2 Changes in steam condition over time23

Clean Coal Technologies in Japan

3. Combustion technology
Various combustion techniques have been developed and putclassified according to the suppression of NOx generation at theinto practical application in response to the need to satisfy

burner and the intrafurnace denitration, using all the zones in theJapan’s strict environmental regulations, and to achieve high-furnace.

efficiency combustion. The NOx emission level and the dust

(1) Low NOx pulverized coal burner

generated during the combustion of coal in Japan is at theThe latest burners have both improved ignitability and intraflameworld’s lowest level, even at boiler exit. The ultimate emission

denitration, although the structure varies by boiler manufacturer.

level owes to the flue gas treatment administered at theThese burners basically use the separation of dense and leandownstream side of the boiler. Since NOx and dust emissions

pulverized coal streams and a multilayer charge of combustion

are very closely related, low NOx combustion technology isair. Figures 4 to 7 show the burner structures of several

addressed here. Low NOx combustion technology is roughly

Japanese manufacturers.

Denseflame

Enhancing intraflame denitration combustion through outer-periphery stable ignition
Secondary air Tertiary air
Tertiary air swirling vane

Tertiary air
Secondary air

LeanflameDistributor vane
Oil burner
Reducing flame

Dense flame
Lean flame
Dense flame

Primary air + Pulverized coalPrimary throat
Secondary throat

Dense flame
Lean flame
Dense flame

Rib

Primary flame holding plate
Secondary flame holding plate

Fig. 5 CC-type pulverized coal-fired burner:
Kawasaki Heavy Industries, Ltd.

Fig. 4 Pulverized coal-fired A-PM burner: Mitsubishi Heavy Industries, Ltd.
Burner inner cylinder
Primary air + Pulverized coal

Burner outer cylinder

Secondary air inner vane
Secondary air vane
Flow detectorThroat ring

Tertiary air damper
Oil burnerPrimary air
Inner periphery(Pulverized coal + Air) secondary air

Primary air + Pulverized coal
Tertiary air

Volatile matter combustion zone
Reducing agent generation zone

Furnace walltube
Outer secondary air

Oil burner support
Secondary air vane driver
Secondary air inner vane driver

Outer peripherysecondary air

Secondary air

NOx decomposition zone
Char combustion enhancing zone

Fig. 7 Pulverized coal-fired NR burner: Babcock-Hitachi K.K.

Inner secondary air

Fig. 6 DF inner vane pulverized coal-fired burner:
Ishikawajima-Harima Heavy Industries Co., Ltd.

Furnace exit(2) Intrafurnace denitration

Combustion completion zone

Intrafurnace denitration is conducted by reducing the NOx
generated in the main burner zone, using the residual

Additional airhydrocarbons or the hydrocarbons generated from a small

NOx reducing zone
containing unburned fuelamount of fuel oil fed from the top of the main burner. The
intrafurnace denitration is performed in two stages. Figure 8 is aconceptual drawing of intrafurnace denitration.

Over fire air
Main burner
combustion zone

In the first stage, hydrocarbons reduce NOx levels. In the second
Main burnerstage, the unburned matter is completely combusted by theadditionally injected air.

Intrafurnace denitration
Fig. 8 Conceptual drawing of intrafurnace denitration
24