1. Energy Balance across pulverizer is very critical for satisfactory
operation of Steam Generator.

2. Hot air
Heat loss
Puliverizer frictional
dissipation
Dry pulverized coal +
Air + Moisture
Coal
Motor Power Input

3. Prediction of Coal Drying
For predicting the amount of coal drying which is needed from the pulverizers, the following methods were accepted.
For very high rank coals (fixed carbon greater than 93 percent), an outlet temperature of 75 to 80° C appeared most valid.
For low- and medium-volatile bituminous coals, an outlet temperature of ° C appeared most valid.
Bituminous B and C coals appear to have good outlet moisture an outlet temperature of 55 to 60° C is valid.
For low-rank coals, subbituminous through lignite (less than 69 percent fixed carbon, all of the surface moisture and one-third of the equilibrium moisture is driven off in the mills.

5. Fluidized Bed Combustion
A True Appropriate Technology for Effficient Solid Fuel Combustion

8. Liquid Fuel Combustion Systems

9. Oil Fired Furnace

10. Oil Supply System
A typical oil supply system includes an oil tank, oil strainer, oil supply pump, heater and connecting pipelines to the boiler.

11. Design of Oil Supply Systems
General considerations in the design of the oil supply system are safety, cost, convenience and emergency provision.
Heating Loop: Heavy oils are economic but difficult to atomize owing its high viscosity at atmospheric temperatures.
The oil is heated prior to burning.
The heating loop consists of strainer, pump and heater.
Classification of Heating Systems:
Single unit heating loop
Centralized heating loop
Oil pumps are selected as several in number with smaller capacity:

12. Fuel + Air + Ignition ????

13. Flame in Stationary Fuel –Air Chamber
Moving Flames are the Fires!!!

14. On Set of Fire in A Green Forest

15. Forest Fires
Fire is an accident & Dangerous…. Flame is an Engineering Device…

16. Basic Geometry of A Furnace
More Air (Secondary Air)
Primary air + Fuel

17. Furnace Exit
Hot Exhaust gases
Heat Radiation & Convection
Flame
Burner

18. Burners
An unique means to contain & control Fire : Flame.

19. Role of burners Burner Governs: Fuel Ignition
Aerodynamics of Fuel air mixture
Generation of combustion conditions.
The performance of the burner determines whether combustion equipment will operate reliably & economically.
Types of burners:
Swirl types
Direct or Parallel-flow types

20. Simple Burner
Burning Velocity
Flow velocity
Air
Fuel

21. Stability & Flammability Limits
Burning Velocity > Flow Velocity : Flash Back Limit
Burning Velocity < flow Velocity : Blow Off Limit
Burning Velocity = Flow Velocity : Stable Flame.
Rich Mixture
Fuel Flow rate
Flash Back
Stable Flame
Blow off
Lean Mixture
Air Flow rate

22. Burning Velocity & Residence Time
Quality of Fuel & Fuel Chemistry.
Air-fuel ratio
Turbulence level
Time to be spent by fuel particle in the furnace before it burns completely.
Residence time is inversely proportional to burning velocity.
Fuel particle continuously moving.
The distance traveled by the fuel particle should be much larger than furnace height.
Swirl motion will ensure the required residence time.
Internally generated swirl : Swirl Burners.
Externally generated swirl: Direct Burners.

23. Design of Swirl Burners
Proper aerodynamics at the exit of the burner – required to ensure good ignition, stable and efficient combustion.
Good load control
Controlled generation of Nox.
Reliable and safe operation.
Compatibility with the FUEL system and furnace.

24. Types of Swirl Burners for solid fuels
Tangential Swirl Burners

25. Types of Swirl Burners for solid fuels
Axial Swirl Burners

26. Types of Swirl Burners for Liquid Fuels

27. Rotary Cup Oil Burner

28. Draught Systems
Better combustion requires comfortable breathing….

29. Resistance to Air & Gas Flow Through Steam Generator System

30. Draft Required to Establish Air Flow
Flue as out
Air in

31. Natural Draft Hchimney pB = patm + rgas *g *Hchimney
pA = patm + ratm *g *Hchimney
Tgas
Tatm B A

32. Natural Draft Natural draft establishes the furnace breathing by
Natural Draft across the furnace,
Dpnat = pA – pB
Dpnat = patm + ratm *g *Hchimney - (patm + rgas *g *Hchimney)
Dpnat = (ratm - rgas )*g *Hchimney
Natural draft establishes the furnace breathing by
Continuous exhalation of flue gas
Continuous inhalation of fresh air.

33. Pressure Difference Generated in natural draft gas path
The pressure of natural draft is D pnd = (a - g) g H
where D pnd = head of natural draft, Pa
a = ambient air density, kg/m3
g = gas density in the flue, kg/m3
H = height difference between the beginning and the end of the
section, m
The flue gas density, is g is calculated as
Tg = gas temperature 0C
g = gas density in the flue under the standard atmospheric condition
(00C, 1 atm) Nm3/kg

34. Establishment of Flow
The amount of flow is limited by the strength of the draft.
Flow introduces a resistance and weakens the draft.
Resistance to the flow is proportional to the square of velocity.
At steady state flow resistance = Natural draft.

35. Mechanical (Artifical)Draft : Induced Draft
Essential when Natural Draft cannot generate required amount of breathing
Hchimney
pB = pfan,s
pA = patm + ratm *g *Hchimney
Tatm B B A
Tgas

36. Mechanical (Artifical)Draft : Forced Draft
Hchimney
pB = patm + rgas *g *Hchimney
pA = pfan
Tgas
Tatm B A

37. Mechanical (Artifical)Draft : Balanced Draft
Hchimney
pB = pfan,s
pA = pfan.b B
Tatm B
Tgas A

38. Resistance to Air & Gas Flow Through Steam Generator System

39. +ve
-ve

40. Capacity of Fans Forced patm Natural Induced Power Consumed by fan :
Induced Draft Fan
Forced Draft Fan
Forced
patm
Natural
Induced