50-Ton Zinc Capacity | Natural Gas-Heated Environment-Friendly Hot-Dip Galvanizing Production Line | Batch Galvanizing & Surface Treatment System for Steel Structural Parts

1. Product Overview

This straight-line environment-friendly hot-dip galvanizing production line features a zinc kettle with internal dimensions of 4.7m×1.0m×1.8m, 50-ton zinc capacity, and maximum hourly capacity of 2 tons/hour. The line covers the full process of pre-treatment (pickling, rinsing, fluxing), galvanizing, cooling, passivation, and exhaust gas treatment. It uses natural gas micro-positive pressure heating and incorporates a cascade flue gas waste heat utilization system (including five patented technologies: combustion air heating, fluxing liquid heating, workpiece drying, sludge drying, and kettle edge waste heat recovery). It is suitable for high-volume, environmentally compliant hot-dip galvanizing of steel structural parts.

2. Industry Challenges & Root Cause Analysis

High natural gas consumption and operating costs:Natural gas accounts for the largest portion of galvanizing line operating costs. Root cause: flue gas waste heat directly discharged without cascade recovery.

Acid mist and zinc fume pollution:Pickling and galvanizing generate acid mist and zinc-containing dust – environmental compliance pressure. Root cause: lack of enclosed negative-pressure pickling rooms and efficient bag filter + water curtain deodorization systems.

Difficult fluxing liquid iron content control:Iron ion accumulation in fluxing liquid affects coating quality and increases zinc consumption. Root cause: lack of online iron removal and automatic pH balance systems.

Galvanizing process relies on manual operation:Immersion time and temperature controlled manually – inconsistent coating thickness and higher costs. Root cause: lack of PLC automatic program control for galvanizing timing management.

3. Solution

3.1 High-Efficiency Natural Gas Heating System:High-speed pulse burners (TJ100×4 sets) – instantaneous gas consumption 112m³/h – dual main intake control (one active, one standby). Three-stage PLC temperature control – zinc bath temperature 438-450℃ automatically controlled – gas consumption approximately 12.5m³ per ton of parts at full load.

3.2 Cascade Flue Gas Waste Heat Utilization System (5 Patents):500℃ flue gas → stainless steel heat exchanger heats water to 90℃ → titanium alloy heat exchanger heats fluxing liquid to 50-70℃. 300℃ flue gas → drying tank heats workpieces. 200℃ flue gas → combustion air heat exchanger heats air to 50-150℃ – saves 3m³ gas per ton of parts. Kettle edge waste heat (~200℃) → stainless steel double-layer coil heats water for acid heating / space heating. Final flue gas → workshop heating. Comprehensive annual savings of ~180,000m³ natural gas (based on 60,000-ton capacity) and ~RMB 114,000 in sludge treatment costs.

3.3 Enclosed Acid Mist Treatment System:Pickling tanks with enclosed acid mist treatment rooms – ground rail carts for material loading/unloading – negative pressure maintained inside – no acid mist escape. Acid mist passes through pre-treatment + absorption neutralization tower (automatic dosing, 22kW variable frequency fan, inlet/outlet pH probes) for compliant discharge. Rinse water reused for new acid preparation – reduces alkali usage.

3.4 Zinc Fume Collection & Purification System:Double-sided suction capture of zinc fume at kettle edges – smoke suction + bag filter + induced draft fan + water curtain deodorization (chimney, ducts, etc.) – 37kW variable frequency – starts 2-3 minutes before kettle immersion – saves 300% power.

3.5 Automatic Iron Removal & pH Balance System:Fluxing liquid equipped with automatic iron removal equipment – ensures iron content ≤1mg/L, pH controlled around 5 – effectively reduces zinc consumption and improves coating quality.

3.6 Automated Galvanizing Control System:PLC automatic program design – crane automatically enters set zinc immersion time after lifting parts – zinc temperature automatically controlled – prevents manual over-immersion adding unnecessary zinc layers and costs.

4. Technical Specifications

5. Selection Guide

5.1 Recommended Scenarios

• High-volume hot-dip galvanizing of steel structural parts

• New construction or upgrade of galvanizing lines requiring environmental compliance

• Energy-saving galvanizing plants seeking natural gas consumption reduction and waste heat utilization

5.2 Key Selection Considerations

1. Kettle size and capacity: Verify 4.7×1.0×1.8m kettle and 2 tons/hour capacity meet production needs

2. Fuel conditions: User to supply natural gas with calorific value ≥8400×4.18kJ/m³, pressure 100-200kPa

3. Power supply: User to supply 220V/60Hz 3-phase power, total capacity ~205kW

4. Facility conditions: User responsible for building, foundations, water/electricity/gas lines to equipment interface

5. Lifting equipment: User to supply hoists and cranes (3-ton + 3-ton units)

6. Environmental requirements: Acid mist and zinc fume treatment systems meet local emission standards

6. FAQ

Q1: How much natural gas can the waste heat utilization system save?

A: Combustion air heating system heats air to 50-150℃ – saves approximately 3m³ gas per ton of parts. At 60,000-ton annual capacity, annual gas savings ~180,000m³. Combined with fluxing heating, workpiece drying, kettle edge heat recovery, and workshop heating – significant comprehensive energy savings.

Q2: How is acid mist emission compliance ensured?

A: Enclosed negative-pressure pickling room with ground rail cart operation – prevents acid mist escape. Acid mist passes through pre-treatment then absorption neutralization tower with automatic dosing – inlet/outlet pH probes – 22kW variable frequency fan adjusts extraction volume – ensures compliant discharge.

Q3: How does the zinc fume treatment system work?

A: Double-sided suction captures zinc fume at kettle edges – smoke passes through bag filter for dust removal – then water curtain deodorization tower – finally discharged via chimney through induced draft fan. 37kW variable frequency fan starts 2-3 minutes before kettle immersion – significant power savings.

Q4: How is fluxing liquid iron content controlled?

A: Automatic iron removal equipment continuously circulates and removes iron – ensures iron content ≤1mg/L – pH automatically regulated to ~5. Low iron content effectively reduces zinc consumption, minimizes zinc dross generation, and improves coating surface quality.

Q5: Can the line achieve automatic operation?

A: PLC automatic program control – crane automatically enters set zinc immersion time after lifting parts – zinc temperature auto-controlled – prevents manual over-immersion and zinc layer thickening. Pickling room crane with wireless remote control – convenient and safe.