Cooling Tower Chemical Treatment: Antiscalant, Biocide & Corrosion Control
How to calculate blowdown rates and dose antiscalants, biocides, and corrosion inhibitors in industrial cooling towers.
Cooling towers are the lungs of an industrial plant. Without proper chemical treatment, they quickly succumb to scale, corrosion, and biological fouling (like Legionella).
Engineering Calculation: Cooling Tower Blowdown
Scenario: Circulation rate 1,000 m³/hr, Temp drop 10°C
Evaporation ≈ 1% of circulation for every 5.5°C drop
Evaporation % = (10 / 5.5) × 1% = 1.82%
Evaporation flow = 1,000 × 1.82% = 18.2 m³/hr
Operating at 5 cycles of concentration:
Blowdown = Evaporation / (Cycles - 1)
Blowdown = 18.2 / (5 - 1) = 4.55 m³/hr
Make-up water = Evaporation + Blowdown = 22.75 m³/hr (22,750 L/hr)
Chemical Dosing (e.g., 30 ppm into make-up):
30 ppm = 30 mg/L
Chemical mass = 22,750 × 30 = 682,500 mg/hr = 0.6825 kg/hr
Daily chemical requirement = 16.38 kg/day
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