1. Project Background

A steel structure manufacturer planned to build a natural gas heated linear hot dip galvanizing line for processing steel components up to 8.6 meters in length, including transmission towers, highway guardrails, and building embedments.

Customer requirements:

• Zinc pot size: 8.6m × 1.0m × 1.6m

• Zinc capacity: 75 tons

• Hourly output: 3 tons

• Must meet emission standards for acid mist and zinc fumes

WUXI WONDERY INDUSTRY EQUIPMENT CO., LTD. was responsible for process design and equipment integration.

2. Technical Challenges and Solutions

H2: Acid Mist Treatment – Sealed Negative Pressure + Two-Stage Spray Neutralization

Operating conditions:

• Three pickling tanks, each 8.6m × 1.0m × 1.6m

• Immersion time: 6 minutes per tank (adjustable)

• High acid mist generation requiring complete containment

Design solution:

1. Fully enclosed acid mist chamber: 11m × 10.6m × 4.0m, flame-retardant fiberglass panels

2. Negative pressure maintenance: 11kW variable frequency fan

3. Two-stage scrubber tower:

   • Tower size: φ1800mm × 6500mm, PP material (10mm thickness)

   • Filler: PP wreath (3.5 inches diameter), two layers

   • Defogging layer: PP spheres (2.0 inches diameter), one layer

   • Spray layer: PP-1/2 spiral nozzles, two layers

   • Circulating pump: 5.5kW vertical acid/alkali resistant pump

4. Automatic pH control: Dual pH probes (inlet/outlet) with automatic dosing

Technical conclusion:
The combination of enclosed structure + negative pressure exhaust + two-stage spray neutralization effectively controls acid mist escape. Online pH monitoring ensures accurate chemical dosing, suitable for continuous pickling of 8.6-meter long tanks.

H2: Zinc Fume Treatment – Double-Sided Suction + Bag Filter + Water Curtain Deodorization

Operating conditions:

• Zinc pot size: 8.6m × 1.0m × 1.6m

• Zinc bath temperature: 438–450℃ (PLC controlled)

• High volume of zinc particulate fume during immersion

Design solution:

1. Double-sided suction ducts:

   • Side ducts: 8600mm × 2500mm × 250mm, two sets

   • End duct: 6000mm × 3000mm × 250mm, one set

   • With deflectors, flanges, and sealing strips

2. Bag filter system:

   • Main unit size: 5540mm × 3000mm × 6500mm

   • Filtration area: 640m²

   • Filter bags: φ133mm × L3500mm, 426 sets

   • Filter material: waxed nylon needle-punched (service life ≥2 years)

3. Fan: 55kW double-sided suction variable frequency fan

4. Water curtain deodorization tower:

   • Tower size: φ2800mm × 6500mm, PP material (12mm thickness)

   • Circulating pump: 7.5kW vertical acid/alkali resistant pump

Operation strategy:

• Variable frequency fan runs only 2–3 minutes per zinc pot loading

• Bag filter collects zinc particles; water curtain removes odors

Technical conclusion:
For an 8.6-meter long zinc pot, double-sided suction covers the entire fume generation area. The 640m² filtration area meets the 3 tons/hour production requirement. The VFD control strategy reduces continuous power consumption.

3. Waste Heat Recovery Options (Selected by Customer)

4. Engineering Interface

Responsibilities in this case:

• Supplier: Equipment supply, internal piping, control cabinet & internal cables, installation guidance, commissioning guidance, training materials

• Buyer: Civil work, plant building, external utilities (water/electricity/gas), compressed air, hoisting equipment, scaffolding, meals/accommodation for technicians, fire protection, lightning protection

5. Case Summary

For this 8.6m hot dip galvanizing line, the following fume treatment solutions were implemented:

• Acid mist: Sealed negative pressure chamber + two-stage spray neutralization

• Zinc fume: Double-sided suction + bag filter + water curtain deodorization

All equipment parameters match the 8.6m × 1.0m × 1.6m tank dimensions and 3 tons/hour capacity. The waste heat recovery modules further reduce operating energy costs.