Power Generation and Boiler Classification

Power Sector Growth

• India's power generation capacity grew from 1,362 MWe in 1947 to 1,43,542 MWe by November 30, 2008.
• Coal accounts for 55% of India's power generation
• The projected total capacity by 2012 is 215,800 MWe.

Boiler Classification

• Boilers are classified as either package or field erected.
• Types of boiler include fire tube and water tube.
• Boilers are also classified by their purpose: power boilers and utility boilers.

Fire Tube Boilers

• Combustion gases in a fire tube boiler pass through tubes submerged in water.
• The furnace in a fire tube boiler can be either separate or built into the boiler shell.
• Fire Tube boilers can be:
  • Dry back or Wet back
  • Oil fired or coal fired
  • Externally fired or internally fired
  • Through tube or Return tube
  • Horizontal, Vertical, or Inclined.
• Other designs include:
  • Simple Vertical Boiler
  • Two Pass Boiler
  • Scotch Marine Boiler
  • Locomotives type Boilers.

Water Tube Boilers

• Boilers are divided into Natural Circulation, Forced Circulation, and Assisted Circulation Types.
• Water tube boilers can be classified by the number of drums:
  • Drumless (Once Through Type)
  • Single Drum
  • Two (Bi-) Drum
  • Three (Tri-) Drum
  • Multi-Drum

Fuels Used in Boilers

• Solid Fuels:
  • Coal (Most Common)
  • Bagasse, Straw, Firewood, Other Bio-fuels
  • Coke breeze
  • Pet-coke
  • Washery Rejects/Middling
  • Municipal Garbage/Manure
• Liquid Fuels:
  • Fuel Oil: L.D.O./H.F.O./L.S.H.S./H.S.D.
  • Black Liquor (Pulp Industry Waste)
  • Naphtha
• Gaseous Fuels
  • Coke-oven Gas
  • Blast Furnace Gas
  • Corex Gas
  • Bio-Gas
  • Natural Gas

Solid Fuel Firing Systems

• For Coal Firing:

  • Fuel Bed Firing:
    • Chain Grate/Renfrew & Oldbury Stoker
    • Traveling Grate Stoker (Style 28X Stoker, Rotograte Spreader Stoker)
  • Suspension Firing:
    • Fluidizing Bed Firing:
      • Bubbling Fluidizing Bed Firing
      • Atmospheric Fluidizing Bed Firing
      • Circulating Fluidizing Bed Firing
      • Pressurized Fluidizing Bed Firing
    • Pulverized Coal Firing:
      • Direct Firing:
        • Front Fired
        • Opposed Fired
        • Downshot Fired (U-Type / W- Type )
        • Corner Fired
      • Indirect Firing:
        • Bin System
        • Burners: Laminar / Turbulent / Low-NOx

• For Bagasse Firing

  • Horse Shoe Furnace
  • Dumping Grate Furnace
  • Rotograte Furnace.

Liquid Fuel Firing Arrangement

• For Oil Firing:
  • Steam Atomized
  • Air Atomized
  • Pressure Atomized
• For Black Liquor
  • Black Liquor Guns Spraying on the Furnace Walls
  • Burning of Char at the Furnace Hearth.

Gaseous Fuel Firing Equipment

• For High C.V. Gases:
  • Spud Burners
• For Low C.V. Gases (such as Blast Furnace Gas):
  • Scroll Type Burners

Function of Steam Generators

• Generate steam at a specific rate, quantity, temperature, pressure, and superheat.
• Separates, washes, and dries the steam.
• Controls combustion or balances the rate of heat generation and absorption.
• Minimizes heat losses through incombustibles or ash.