ICHEM

• Boiler feed water


  The water supplied to a boiler for the purpose of generating steam
• Boiler feed water


  • It plays a crucial role in the overall operation and efficiency of a steam boiler system
  • The quality and properties of boiler feed water are essential factors in ensuring the reliable and safe operation of the boiler
• Boiler feed water is crucial for the safe and efficient operation of boilers
• It is essential that the feed water meets certain properties to prevent scale formation, corrosion, and other issues within the boiler system
• Purity


  Feed water should be free from impurities such as suspended solids, dissolved gases, and organic matter
• High levels of impurities

  Can lead to scale formation on boiler surfaces, reducing heat transfer efficiency and causing overheating
• Alkalinity


  Adequate alkalinity helps to control pH levels and prevents acidic corrosion in the boiler
• Low alkalinity


  Can lead to acidic conditions, resulting in corrosion of boiler internals
• Ideal boiler water pH

  Maintained between 10.5-11.5 (alkaline)
• Controlling the pH of water is one of the important treatments in boiler water treatment
• pH value of water

  • 1 to 6 is considered acidic water (not good for boiler water)
  • 7 is median
  • 8 to 14 is considered alkaline water (10.5 - 11.5 ideal for boiler water)
• If either pH or alkalinity increases, water will accordingly become acidic or alkaline, leading to detrimental effects caused due to acidic attack or caustic embrittlement
• Hardness


  Hardness in water is mainly due to the presence of calcium and magnesium ions
• Excessive hardness


  Can lead to scale formation on boiler surfaces, reducing heat transfer efficiency
• Purpose of controlling hardness

  To prevent scale formation building on the interior surface
• Scale buildup inside the boiler

  Reduces insulation, preventing the heating of water and generation of steam, leading to overheating and damage to the internal parts of the boiler, reducing the overall efficiency
• Dissolved Oxygen


  Oxygen should be removed from feed water to prevent corrosion in the boiler
• Corrosion due to dissolved oxygen


  Can lead to damage to boiler tubes and other components
• pH Level


  pH levels should be maintained within a specified range to prevent corrosion and scale formation
• Low pH


  Can lead to acidic corrosion
• High pH


  Can cause caustic corrosion
• Chloride ion


  • Standard value of chloride ion is less than 300 mg Cl/l
  • The more the chloride ions, the more the scale formation
• Formation of chloride ions can be done by controlling the amount and time of boiler blowdown
• Total Solids and electrical conductivity

  • Conductivity (25°C) <2000 micromhos
  • Increase of total solids promotes deposition of scales in the boiler as well as in the equipment consuming steam due to carry over
  • More amount of dissolved solids also leads to more scale formation and carrying over
• Phosphate


  • Standard value of Phosphate is 20-40 mg PO4/l
  • Phosphates reacts with calcium and forms calcium phosphates, which is a major scale forming component
  • Phosphates also contributes to the prevention of alkali corrosion and caustic embrittlement
• Oil


  • For an Ideal boiler water, oil content should be nil
  • Lubricating oil may contaminate the feed system and it finally reaches on boiler tubes
  • This is done in order to prevent carbonization of oil and formation of scales due to boiler heat
• Proper care should be taken to minimize the oil-in-water emulsion


  • Effect is Corrosion and carbonization
  • If it sticks on the boiler tubes, it reduces the heat transfer thereby reducing the boiler efficiency
• Summary of ideal boiler water properties

  • Appearance - clear and free of mud
  • Chloride content - <100 ppm Cl
  • "P" alkalinity - 100-150 ppm CaCO3
  • Total alkalinity - <2 x "P" alkalinity
  • pH at 25°C - 10.5-11.5
  • Hydrazine excess - 0.2-0.5 ppm N2H4
  • Phosphate excess - 20-50 ppm PO4
  • Specific gravity (20°C) - <1.003 kg/m3
  • Conductivity (25°C) - <2000 micromhos
  • Oil content - nil
• Scale is the most significant contributor to efficiency loss in your steam boiler system
• Scale buildup


  Can reduce the effectiveness of heat exchangers and prevent hot water in the boiler from reaching the needed temperature
• By removing and preventing scale buildup, your boiler will restore its efficient operation
• Sludge


  • Similar to the more solid deposits of scale but has a softer texture
  • When sludge reaches the boiler tank, it has exposure to high temperatures
  • If the level of boiler water dissolved solids is too high, these can be removed on a regular basis using the scum valve on each boiler, whereas dissolved solids can be minimized by blowing some of the water out of the boiler and replacing it with fresh distilled feed water
• The blowdown procedure


  1. Check with the bridge that it is safe to blow down the boiler if the ship is in port

  2. Open the ship's side blowdown valve

  3. Ensure that the boiler is filled to the high water level

  4. Slowly open the boiler scum valve and reduce the water level to the normal position, then close the scum valve

  5. Refill the boiler to the high water level position and blow down the boiler using the blowdown valve

  6. After the blowdown of the boiler, close the boiler blowdown valve and then close the line and ship's side valves

  7. Test the boiler chemical concentrations and adjust as necessary
• Foaming in the boiler tank

  • Occurs when solids in the water float to the top
  • When the water heats, these solids foam from the steam
  • Some rise through the steam to the turbines or superheaters
  • When the solids deposit on these, the system loses efficiency
  • Eventually, the solids will work their way throughout the rest of the boiler, causing more damage
• Corrosion within the boiler system

  • Can transpire anywhere in the boiler
  • Often happens starting on the inside and eventually works its way out
  • Signs of corrosion may not be evident until a pipe or tank leaks
• Preventing corrosion is essential to preserving the integrity of the system
• By preventing corrosion, you also avoid leaks caused by chemical damage to your boiler system
• Boiler feed water treatment processes

  • Mechanical Filtration - Removes suspended solids from the water, preventing them from entering the boiler
  • Deaeration - Removes dissolved gases, especially oxygen, from the water to prevent corrosion
  • Water Softening - Reduces hardness by exchanging calcium and magnesium ions with sodium ions using ion exchange resins
  • Reverse Osmosis (RO) - Removes dissolved impurities through a semi-permeable membrane, providing highly purified water
  • Chemical Treatment - Chemical additives such as oxygen scavengers, corrosion inhibitors, and pH adjusters are added to the water to control various water properties
• Boiler water treatment can prevent many issues with the system, ranging from minor to severe
• The initial treatment of the water is important, in addition to filtering, monitoring water quality and adding chemicals as needed to maintain balance