Acid mist (HCl, HNO₃, H₂SO₄, etc.) from pickling and plating baths. Alkaline mist (NaOH, NH₃) from cleaning and stripping processes. Cyanide gases (if cyanide plating is used). Chrome mist (CrO₃, hexavalent chromium) from chrome plating. Organic vapors (degreasing solvents, additives). Each source may require different capture and treatment methods.
Author: Robby
Calculating the required air volume (Q) for an electroplating plant's waste gas treatment tower (e.g., scrubber or activated carbon adsorber) depends on several factors, including the type of exhaust source, the contaminants being treated, and the design of the system. Below is a step-by-step method to determine the air volume.
Electroplating exhaust gases mainly come from:
Acid mist (HCl, HNO₃, H₂SO₄, etc.) from pickling and plating baths.
Alkaline mist (NaOH, NH₃) from cleaning and stripping processes.
Cyanide gases (if cyanide plating is used).
Chrome mist (CrO₃, hexavalent chromium) from chrome plating.
Organic vapors (degreasing solvents, additives).
Each source may require different capture and treatment methods.
The air volume is typically calculated in cubic meters per hour (m³/h) and depends on:
Hood/capture system design (lateral draft, push-pull, enclosed hood).
Plating tank dimensions (for tank exhaust).
Minimum capture velocity (to ensure fumes are contained).
Q=A×V×3600Q=A×V×3600
Q = Air volume (m³/h)
A = Cross-sectional area of the tank or hood opening (m²)
V = Required capture velocity (m/s)
3600 = Conversion factor (seconds to hours)
| Type of Emission | Capture Velocity (m/s) |
|---|---|
| Acid/alkali mist (low toxicity) | 0.25 – 0.5 |
| Chromic acid mist (chrome plating) | 0.5 – 1.0 |
| Cyanide gases | 0.5 – 1.0 |
| High-volatility solvents | 0.5 – 1.5 |
Tank dimensions: 1.5 m (L) × 0.8 m (W)
Open surface area (A): 1.5 × 0.8 = 1.2 m²
Capture velocity (V): 0.5 m/s (for acid mist)
Required air volume (Q):
Q=1.2 m2×0.5 m/s×3600=2160 m3/hQ=1.2m2×0.5m/s×3600=2160m3/hIf multiple tanks are connected to the same scrubber, sum their individual air volumes:
Qtotal=Q1+Q2+Q3+…Qtotal=Q1+Q2+Q3+…
Example:
Tank 1 (acid): 2160 m³/h
Tank 2 (chrome): 3000 m³/h
Total Q: 2160 + 3000 = 5160 m³/h
Add 10–20% extra air volume to account for leaks and resistance.
If ductwork is long or has many bends, increase fan capacity accordingly.
Revised Q:
Qfinal=Qtotal×1.2=5160×1.2=6192 m3/hQfinal=Qtotal×1.2=5160×1.2=6192m3/h
The scrubber capacity must match or exceed the calculated Q.
Fan selection should consider static pressure (resistance from scrubber, ductwork, filters).
| Contaminant | Recommended Treatment |
|---|---|
| Acid mist | Wet scrubber (packed bed, venturi) |
| Chromic acid | Redox scrubber (NaHSO₃ reduction) |
| Organic vapors | Activated carbon adsorber |
| Alkali mist | Acid-wash scrubber |
Check local emission standards (e.g., EPA, EU Industrial Emissions Directive).
Measure face velocity at hood openings (should be ≥0.5 m/s for most cases).
Conduct stack testing to ensure scrubber efficiency.
Calculate open tank area (A).
Select capture velocity (V) based on contaminant type.
Compute air volume (Q = A × V × 3600).
Sum air volumes for multiple tanks.
Add 10–20% for system losses.
Choose a scrubber & fan with sufficient capacity.
Verify compliance with emission regulations.
Example Final Requirement:
For a chrome plating tank (1.2 m², V=0.8 m/s):
Q=1.2×0.8×3600=3456 m3/hQ=1.2×0.8×3600=3456m3/h
With 20% safety margin: 4147 m³/h → Select a 4500 m³/h scrubber.