Boiler & Cooling Tower Chemical Treatment: Scaling, Corrosion & Biofouling Prevention

Thermal Efficiency & Asset Protection in Industrial Utilities

Boilers and cooling towers represent the thermal beating heart of industrial processing facilities, processing plants, and food factories across Kenya. Whether producing process steam for food cooking in Thika or rejecting process heat from plastic injection moulding chillers in Industrial Area Nairobi, water is the universal heat transfer medium.

However, untreated water carries dissolved gases (Oxygen, Carbon Dioxide) and mineral ions (Calcium, Magnesium, Silica) that aggressively attack metals and deposit insulating scale on heat transfer surfaces.

Boiler Feed Water Chemistry & Corrosion Prevention

1. Dissolved Oxygen Scavenging

Dissolved oxygen causes severe localized pitting corrosion on boiler internal steel surfaces:

$$2 ext{Na}_2 ext{SO}_3 + ext{O}_2 longrightarrow 2 ext{Na}_2 ext{SO}_4$$

• **Sodium Sulfite ($Na_2SO_3$):** Standard scavenger for low-to-medium pressure boilers (up to 40 bar).
• **DEHA / Carbohydrazide:** Volatile organic scavengers used in high-pressure steam systems where inorganic dissolved solids must be minimized.

2. Alkalinity Builders & pH Elevation

Boiler water pH must be maintained between 10.5 and 11.5 to promote the formation of a protective magnetite ($ ext{Fe}_3 ext{O}_4$) passivation layer on internal steel walls.

• **Sodium Hydroxide (Caustic Soda):** Added to elevate boiler water pH and neutralize carbonic acid corrosion in condensate return lines.

Cooling Tower Water Chemistry: Scale & Biofilm Control

1. Scale & Crystal Modification

As cooling towers evaporate water, dissolved mineral concentration rises. Phosphonates (such as ATMP, HEDP, PBTC) and synthetic acrylic polymers act as threshold inhibitors, distorting crystal lattice growth of Calcium Carbonate ($ ext{CaCO}_3$) so minerals remain suspended rather than adhering to heat exchanger tubes.

2. Biocidal Biofilm Control

Biofilms on cooling tower fill pack reduce cooling efficiency and harbor *Legionella* bacteria.

• **Oxidizing Biocides:** Sodium Hypochlorite, Chlorine Dioxide, Calcium Hypochlorite.
• **Non-Oxidizing Biocides:** Isothiazolinones, Glutaraldehyde, Quaternary Ammonium Compounds (QACs) applied in alternating bi-weekly shock doses.