Basics of Steam Engineering which is used in a fabricated line in a .ppsx.ppt

It is about energy conservation which is used in fabrication line

1. 7/16/2018 Cheema Boilers Limited 1

2. INTRODUCTION TO BOILERS 7/16/2018 Cheema Boilers Limited 2

3. Boiler is a vessel which produces steam at more than 1 Kgcm² and temperature 100° C. Boiler designs are governed by Indian Boiler Regulations 1923 laws. Inspection agencies control & implement this law to ensure safety to the public. Vessel upto 25 Ltr capacity and below 1Kgcm² is not covered under IBR Act. 7/16/2018 Cheema Boilers Limited 3 What is a Boiler?

4. Use of steam : Utility for Power Or Process Assembly :Shop assembled/Site assembled Nature of support : Bottom /Top supported Steam condition: Saturated/Superheated Firing system : Oil/ Gas fired Solid fuel fired fixed grate, Dumping grate, Reciprocating grate, Traveling grate Pulverized fuel fired, Fluidized bed, AFBC and CFBC 7/16/2018 Cheema Boilers Limited 4 Classification of Boilers

5. Fire tube boilers Water tube boilers Fire cum Water tube boilers Heat source : Coal, Oil, Gas, Bio-Mass, Waste heat Construction : Bi-drum, Single drum, Multi-drum, Shell & Tube Installation : Out door / In door Circulation : Natural / Forced/Once throw Draft: natural/forced/induced/balanced 7/16/2018 Cheema Boilers Limited 5 Further classification of Boilers

6. 7/16/2018 Cheema Boilers Limited 6 Types of Water Tubes Super Heater Coil Membrane Membrane Bank Tubes

7. Boiler parameters Capacity, Steam outlet pressure , Steam outlet temperature , Feed water inlet temperature Fuel characteristics Boiler efficiency Ambient conditions Other statutory and auxiliary stipulations 7/16/2018 Cheema Boilers Limited 7 Design Inputs

8. Ambient temperature Relative humidity Site elevation Seismic zone 7/16/2018 Cheema Boilers Limited 8 Ambient Conditions

9. Boiler efficiency = Heat Output / Heat Input i.e. Steam Enthalpy x Steam Output Fuel Input x Fuel Enthalpy 7/16/2018 Cheema Boilers Limited 9 Boiler Efficiency

10. Dry flue gas loss : Enthalpy difference between flue gas leaving boiler and ambient air multiplied by dry flue gas quantity Fuel moisture loss : Heat taken by the fuel moisture to become water vapour Moisture due to combustion of hydrogen loss : Every unit of hydrogen in fuel produces 9 units of moisture. Heat taken by this moisture to become water vapour 7/16/2018 Cheema Boilers Limited 10 Losses in Boilers Contd…..

11. Air moisture loss : enthalpy difference in moisture brought in by combustion air between flue gas temperature and ambient temperature Unburnt carbon loss : heat lost due to incomplete combustion of carbon in fuel Unaccounted losses : small losses which can not be accurately calculated like heat loss in blow down water , heat going with ash , heat loss by radiation from boiler openings etc. Radiation loss : heat loss from boiler external surface to atmosphere 7/16/2018 Cheema Boilers Limited 11 Contd…..

12. Considerations Initial cost vs. Running fuel cost Energy conservation Waste fuel utilization Governing factors Excess air Flue gas outlet temp. Moisture and hydrogen content in fuel Ambient temperature and moisture Completeness of combustion Effectiveness of insulation 7/16/2018 Cheema Boilers Limited 12 Efficiency Matters

13. NCV means Net Calorific Value GCV means Gross Calorific Value Boiler efficiency on NCV is equals to Boiler efficiency on GCV x GCV/NCV The difference in efficiency is the heat loss due moisture in fuel 7/16/2018 Cheema Boilers Limited 13 What is NCV & GCV?

14. Three types of heat is added to feed water in the boiler to convert the same to steam. Sensible heat up to boiling point. Latent heat to convert liquid phase water to vapour phase steam. Sensible heat addition to raise the steam temperature from saturation to the desired super heat temperature. 7/16/2018 Cheema Boilers Limited 14 Heat Addition In Boiler

15. Water boils at its saturation temperature. Boiling temperature of water at ambient condition in sea level is 100°C. Boiling temperature increases with pressure. Latent heat decreases with pressure. From & At 100°C means only latent heat of evaporation of water to be calculated i.e. 540KCal/Kg of water. 7/16/2018 Cheema Boilers Limited 15 Water Boiling

16. Furnace – In this fuel is burnt and heat is released. The absorption of heat by radiation & convention is done here. Super heater – The steam is super heated above saturation temperature in this part. Boiler banks or Evaporator – Part of sensible heat & latent heat is added in this zone. Economizer – Sensible heat is added to water to take it close to saturation temperature. Air heater – Heat from hot flue gases is observed by incoming combustion air in this part to increase the efficiency & combustion. Steam drum : Steam from steam-water mixture from furnace & evaporator is separated here. Water drum : Holds enough water volume to protect boiler furnace tubes in the event of boiler trip. 7/16/2018 Cheema Boilers Limited 16 Components of Boiler

17. By the major type of heat receipt - Radiant super heater - Convective super heater By orientation - Horizontal , fully drainable - Vertical , non- drainable By arrangement - In-line - staggered By flow of gas and steam - Parallal flow - Counter flow 7/16/2018 Cheema Boilers Limited 17 Types of Super Heater

18. By orientation - Horizontal - Vertical By arrangement - In-line - staggered Type of tube - Plain tube - Finned tube 7/16/2018 Cheema Boilers Limited 18 Types of Economizer Steaming economizers will cause hammering hence it is recommended to keep the temperature 20°C below saturation temperature of particular boiler.

19. Tubular air heaters - Heat exchange across tubes from gas to air - Air heater is stationary - Used for industrial boilers Rotating air heaters - Elements heated and cooled by the gas and air respectively as it moves through them - Continuously rotating - More compact for large size boilers 7/16/2018 Cheema Boilers Limited 19 Types of Air Heaters

20. Boiler feed pumps : Sustains boiler pressure by pumping against operating pressure. Failure of feed pump results in boiler trip & hence standby essential. Multi-stage centrifugal pumps are generally used. Normally driven by electric motor. Steam turbine drive can be used. Flow control is by outlet control valve. To save power variable speed drives are also used. 7/16/2018 Cheema Boilers Limited 20 Boiler Auxiliaries Contd…..

21. Fans : Provides combustion air. Evacuates flue gas to chimney. Generally centrifugal fans are used. Axial fans may be used in large boilers for FD fan. Normally driven by electric motor. Steam turbine drive can be used. Normally controlled by inlet guide vane/ damper. To save power variable speed drives are used. 7/16/2018 Cheema Boilers Limited 21 Contd…..

22. Mechanical Dust Collector. - Can be single or multi-cyclone. - Dust collection efficiency between 90% to 95%. - Dust separates due to centrifugal action. - Good for large particle sizes. - Draft loss around 75-100 mmwc . Wet Scrubbers : - Uses moisture to capture dust. - Used in boilers using low ash fuels like bagasse. - Water is an essential pre-requisite. - Draft loss 75 to 100 mmwc. - Converts air pollution to water pollution. 7/16/2018 Cheema Boilers Limited 22 Dust Collectors Contd…..

23. Electro-static precipitators: Ionizes the gases and dust captured on the cathodes Efficiency as high as 99.9% Can capture finer dust Draft loss only 25 mmwc High voltage used as elements to be electrically charged Used for large solid fuel fired boilers and cement plants Bag filters : Uses cloth as filters Generally used in low erosive dust Efficiency above 99.9% High draft loss 75 to 150 mmwc and hence high ID fan power consumption Bags needs frequent maintenance and replacement 7/16/2018 Cheema Boilers Limited 23 Contd…..

24. Natural circulation Forced circulation Assisted forced circulation Once through boilers What does good circulation do ? Essential to protect the furnace tubes from over heating failure. To keep the evaporation in the nucleate boiling range. 7/16/2018 Cheema Boilers Limited 24 Boiler Water Circulation

25. Nucleate boiling : Lower heat flux. Ensures that always water is in touch with heating surface and thus ensures good cooling. Boundary layer heat transfer co-efficient higher and temperature drop across boundary layer larger. Film boiling : Very high heat flux. Steam in touch with heating surface & hence cooling is poor. Boundary layer heat transfer co-efficient lower and lower temperature drop across the boundary layer. 7/16/2018 Cheema Boilers Limited 25 Types of Boiling

26. Motive force for natural circulation is the density difference between the water and water steam mixture. This is high at low pressures and low in high pressure boilers due to the behavior of steam and water densities with pressure. 7/16/2018 Cheema Boilers Limited 26 Natural Circulation

27. C + O 2 CO 2 + Heat 2H 2 + O 2 2H 2 O + Heat S +O 2 SO 2 + Heat I kg of C requires 2.667 kg of Oxygen 1 kg of H 2 requires 8 kgs of Oxygen 1 kg of Sulphur requires 1 kg of Oxygen 7/16/2018 Cheema Boilers Limited 27 Combustion Calculations

28. Stoichiometric air is the quantity of air theoretically required to complete the combustion of fuel. Practically stoichiometric air quantity is not sufficient to complete the combustion due to fuel particle size and homogeneity of fuel and air is not good. 7/16/2018 Cheema Boilers Limited 28 Air Combustion

29. Excess air is the quantum of air that is required over and above stoichiometric air quantity to have satisfactory completion of combustion. Solid fuels require more excess air than liquid fuels. Liquid fuels require more excess air than gaseous fuels. 7/16/2018 Cheema Boilers Limited 29 Excess Air

30. Fixed grate / Reciprocating grate: 40-50 % Dumping grate : 35-40 % Traveling grate : 35% Traveling grate with spreader stoker : 30-35 % Fluidized bed : 20-25 % Pulverized fuel firing : 20% 7/16/2018 Cheema Boilers Limited 30 Excess Air Levels at Solid Fuel Firing

31. Pressure jet burners : 15 - 20% Steam/air atomized burners : 10 - 15% Rotary cup burners : 10 - 15% Gas burners – natural gas : 5 - 10% Gas burners – low calorie gases : 10 - 15% 7/16/2018 Cheema Boilers Limited 31 Excess Air Levels at Liquid & Gaseous Fuel Firing

32. Hope you have understood the basics of steam engineering. THANKS FOR YOUR CONCENTRATION 7/16/2018 Cheema Boilers Limited 32