Fireball configuration in coal fired boilers can be wall-fired, tangentially fired (corner-fired), or roof-fired depending on the location of the burners. Tangentially fired furnaces have burners located in the corners which allows for self-stabilizing flames and staged combustion. Wall-fired furnaces have burners located on the furnace walls and allow for stable flames from individual swirl burners. Recent improvements to firing systems using jet burners have demonstrated better temperature control and flexibility in fuel use without spray attemperation.

1. FIRE BALL CONFIGURATION IN COAL FIRED BOILER
KUMARASWAMY HIREMATH
Senior Research Fellow, MTD
CPRI- Bangalore
PRESENTATION
ON

2. INTRODUCTION
What is Coal fired Thermal power plant?
Working principle & cycles of thermal power plant
Design of Burners for optimized combustion.

3. •The most important task of the boiler furnace is to provide conditions for
proper combustion of fuel which is achieved by:
Fuel supply of the boiler furnace at the required rate and keeping it in the
furnace by the time sufficient for burnt out.
Air supply of the boiler furnace at the required rate and proper mixing with
the fuel.
•TYPES OF BOILER FURNACES
Coal-fired boilers can be classified regarding the type of a furnace:
Grate boilers (stoker)
Pulverized fuel-fired boilers (PF)
Fluidized-bed boilers.

4. Zones of combustion on grate
Burning on the travelling grate

5. Coal burning on Grate
Flame
Ignition vault of the grate furnace

6. PULVERIZED COAL FURNACES
Modern pulverized coal-fired boilers in modern power plants
pulverized coal-fired boilers have mainly furnaces with membrane
walls and major heat transfer is due to radiation.
PHASES OF PULVERIZED COAL BURNING
The time of pulverized coal-air mixture in a furnace can be divided
into three periods:
 drying, devolatilization and ignition of coal particles, which requires
0.2–0.3 s,
 Intensive mixing and burning of pulverized coal-air jet during 0.5–
1.5 s on a distance of 1–5 m with formation of flame kernel of the
temperature 1500–1600 °C,
 Burnout of larger coal particles and cooling of flue gas during 1–3 s
on a distance 2/3 of the furnace.

7. TYPES OF PULVERIZED COAL-FIRED
FURNACES
The main criteria is location of burners:
Wall-fired furnaces
Roof-fired furnaces
Corner-fired furnaces (Tangentially fired)

8. RIGHTWALL
LEFTWALL
REAR WALL
FRONT WALL
BURNER Pulverized coal supply of
corner-fired boilers
Contd.

9. BURNER BOX/ CORNER FIRED
FURNACE

10. ADVANTAGES OF TANGENTIALLY-FIRED
FURNACES
Self-stabilization of pulverized coal flames,
Delayed ignition of pulverized-coal/air mixture,
Staged mixing of pulverized coal/primary air
mixture and secondary air,
Efficient heat transfer to the boiler walls,
Tolerance of the fuel variation.

11. WALL-FIRED FURNACES
Swirl Burner
Coal mills

12. Pulverized coal swirl
burner
Swirl burners on the wall of a furnace

13. ADVANTAGES OF WALL-FIRED FURNACES
Stable flame in a single swirl burner
Easy ignition of pulverized-coal/air mixture
Fast mixing of pulverized coal/primary air mixture
and secondary air
Considerable burn-out of coal near the burner
Possibility of boiler operation with low load.

14. ROOF-FIRED FURNACES

15. ROOF FIRED FURNACES

16. Conclusion
 Improvements of firing systems with jet burners during modifications and for newly built
power plants in recent times have shown some positive experience. Tilting burners could
demonstrate the control of the RH temperature without any spray attemperators in daily
operation
 Additionally the flexibility in the fuel input could also be improved for modified plants
by means of target-oriented measures such as an adaptation of the grinding plant in order
to enable a change of the fuel calorific values.
 By a proper adjustment of the mill and firing systems as well as a consistent
implementation of process engineering requirements in the design phase, minimum steam
generator loads can now be achieved in a stable and safe manner.
 Additional measures allow to use biomass in the power plant in a high efficient way. It
can be considered as an additional contribution to the protection of the environment and
reduction of the CO2 output.