The collection of waste gas from electroplating production lines is the key first step in waste gas treatment.
Author: Marisa
The collection of waste gas from electroplating production lines is the first key step in waste gas treatment, which directly affects the subsequent treatment effect. The following are common collection methods and technical points:
1. Capture Hoods
Applicable scenarios: tanks (such as pickling, chrome plating, cyanide plating tanks, etc.) or local gas production points.
Type:
Lateral Hoods: Applicable to open tanks, exhaust gas is sucked from the side.
Canopy Hoods: Installed above the tank, relying on natural rising airflow to collect exhaust gas.
Enclosing Hoods: Semi-enclosed/fully enclosed design, with the highest collection efficiency (up to 90% or more).
Design points:
Control wind speed: generally need to reach 0.5~1.5 m/s (adjusted according to the toxicity of pollutants).
Avoid air flow interference: stay away from workshop vents or areas where people walk.
2. Closed System
Applicable scenarios: continuous electroplating lines with high degree of automation (such as roll-to-roll electroplating and rack plating automatic lines).
Method:
The plating tank, washing tank, etc. are sealed as a whole, leaving only the workpiece inlet and outlet.
Prevent exhaust gas from escaping through negative pressure suction (-50~-100 Pa).
Advantages: Collection efficiency>95%, reducing workshop pollution.
3. Exhaust duct design (Ductwork)
Key parameters:
Wind speed: 8~12 m/s is recommended for the main duct and 6~8 m/s for the branch duct (to prevent dust deposition).
Material:
Corrosion resistance: PP (polypropylene), FRP (glass fiber reinforced plastic) or PVC (for acidic exhaust gas).
Explosion-proof: stainless steel (when containing organic solvents or hydrogen).
Layout: Reduce right-angle elbows and use inclined tees to reduce resistance.
4. Fan selection (Exhaust Fan)
Air volume calculation: based on the opening area of the hood or enclosed space × control wind speed.
Air pressure requirements: need to overcome pipeline resistance, purification equipment resistance and residual pressure (usually ≥1200 Pa).
Anti-corrosion type:
PP fan (acidic exhaust gas)
Fiberglass fan (mixed exhaust gas)
Explosion-proof fan (when containing organic solvents or hydrogen).
5. Special gas treatment (targeted collection)
Hydrogen cyanide (HCN): needs to be collected separately to avoid mixing with acidic exhaust gas (to prevent the generation of highly toxic HCN gas).
Chromic acid mist (CrO₃): install a high-efficiency mesh collector (Mesh Pad Mist Eliminator) above the tank.
Organic solvents (VOCs): enclosed collection + explosion-proof design.
6. Intelligent control and energy saving
Variable frequency fan: adjust the air volume according to the production rhythm (such as frequency reduction when the automatic line is in standby).
VAV variable air volume system (Variable Air Volume): Real-time adjustment of suction volume through sensors.
Precautions
Safety regulations: Flammable exhaust gases (such as hydrogen and organic solvents) must comply with explosion-proof standards (such as ATEX or NFPA).
Maintenance convenience: The pipeline has a reserved cleaning port and the gas collection hood is removable.
Co-processing: If the exhaust gas contains particulate matter (such as sandblasting process), a pre-cyclone dust removal or filter is required.
By properly designing the collection system, the subsequent purification efficiency can be significantly improved and the operating cost can be reduced. Is it necessary to further explain the collection plan for a specific exhaust gas (such as chromic acid mist or cyanide)?