Boiler Feedwater Treatment Equipment

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Boiler Feedwater Treatment Equipment

Boiler feedwater treatment equipment refers to equipment that processes water used for boiler replenishment through a series of technologies and devices. Its purpose is to remove harmful substances such as impurities, salts, and microorganisms from the water, ensuring the water quality meets the operational requirements of boilers.

The water quality of boiler feedwater is directly related to the safety, economy, and stability of boiler operation. If the feedwater quality fails to meet standards:

  • Hardness ions such as calcium (Ca²⁺) and magnesium (Mg²⁺) in the water tend to form scale, which reduces thermal efficiency and increases energy consumption;
  • Gases such as dissolved oxygen and carbon dioxide accelerate the corrosion of metal components, shortening the service life of equipment;
  • Excessively high concentrations of suspended solids or soluble salts in the water can cause carryover of water in steam, affecting steam quality.

Treatment Processes and Technologies

1. Pretreatment

  • Mechanical Filter: Removes large-particle impurities using filter media such as quartz sand and anthracite.
  • Activated Carbon Filter: Adsorbs residual chlorine, organic substances, and odorous compounds to protect subsequent membrane systems.
  • Softener: Uses sodium ion exchange resin to remove Ca²⁺ and Mg²⁺ from water, reducing water hardness.

Softening Treatment

For low-pressure boilers (≤1.6MPa), sodium ion exchange softening is commonly used to remove hardness. The principle is that Na⁺ in the resin undergoes an exchange reaction with Ca²⁺ and Mg²⁺ in the water, thereby achieving water softening.

2. Reverse Osmosis (RO) System

For medium and high-pressure boilers (>1.6MPa), simple softening cannot meet water quality requirements, so an RO system must be introduced for preliminary desalination. RO membranes can effectively remove over 98% of dissolved salts, colloids, bacteria, and most organic substances.

3. Ion Exchange Desalination System

The ion exchange system is divided into three types: Cation Exchange Bed, Anion Exchange Bed, and Mixed Bed (MB). It is mainly used to remove anions and cations from water to obtain high-purity desalinated water:

  • The cation exchange bed removes cations such as Ca²⁺, Mg²⁺, and Na⁺;
  • The anion exchange bed removes anions such as Cl⁻, SO₄²⁻, and HCO₃⁻;
  • The mixed bed is filled with a mixture of anion and cation resins in a certain ratio, enabling deep desalination in one step. The conductivity of the produced water can be as low as below 0.1μS/cm.

4. Electrodeionization (EDI)

EDI is a new type of continuous desalination technology that combines the advantages of ion exchange and electrodialysis. It requires no acid-alkali regeneration, making it environmentally friendly. Suitable for feedwater treatment of medium and high-pressure boilers, it produces water with stable quality (resistivity up to 10~18MΩ・cm) and features high operational automation, making it ideal for continuous operation.

5. Post-treatment and Deaeration

To further improve water quality and prevent internal corrosion of boilers, additional treatments are required, including ultraviolet sterilization, ozone/chlorine disinfection, and deaeration by deaerators.