In the field of steel anticorrosion, hot dip galvanizing process
dominates due to its excellent corrosion resistance, but the
tens of thousands of tons of zinc dregs and waste liquids produced
every year not only cause waste of precious metal resources,
but also bring severe environmental protection pressure. With
the breakthrough of non-ferrous metal automation technology,
the industry pain points of low zinc recovery rate, high energy
consumption and heavy pollution are being systematically
cracked. In this paper, we will analyze the process of hot dip
galvanizing zinc recycling, technological innovation and
industrial value, revealing how automation can reshape the
sustainable development of this field.
First, the need for hot dip galvanizing zinc
recovery and technical challenges
Hot dip galvanizing process, about 8% -15% of the zinc due to oxidation,
splash, residue and other forms of loss, the formation of three
main types of waste:
Zinc ash: floating slag generated by oxidation on the surface of
molten zinc liquid, containing 60%-80% zinc;
Zinc slag: solid waste of iron and zinc alloy settled to the bottom
of the plating tank, with zinc content of 30%-50%;
Waste acid solution: zinc-containing wastewater generated from
pickling process, with zinc ion concentration of 5-20g/L.
The traditional treatment method faces a triple dilemma:
Low recovery rate: the zinc recovery rate of manual slag fishing
+ simple smelting is less than 50%, and a large amount of zinc
resources are lost;
Energy consumption is abnormally high: each ton of zinc slag
treatment consumes more than 800 kWh of electricity, and the
cost accounts for 40% of the total recovery cost;
Secondary pollution: high-temperature smelting releases zinc
vapor and dust, and incomplete treatment of waste acid leads
to soil heavy metal exceeding the standard.
Automated zinc recovery technology
system and core innovation
Modern zinc recovery system through the “intelligent sorting - efficient
purification - closed-loop management” technology chain, to achieve
the zinc resource utilization rate from 50% to 95% of the leapfrog
improvement, the key technologies include:
1. Intelligent sorting and pretreatment of zinc slag
AI visual sorting system: based on spectral analysis (XRF) and machine
vision, real-time identification of Fe, Al, Pb and other impurities
distribution in zinc slag, sorting accuracy of 98%;
Multi-stage crushing and screening line: using jaw crushing + airflow
sorting combination process, the zinc slag particle size control in
0.5-3mm, zinc enrichment up to more than 65%;
Microwave drying device: replace the traditional coal-fired drying,
energy consumption reduced by 70%, to eliminate CO₂ emissions.
2. High-efficiency zinc recovery process innovation
Vacuum distillation technology: under the condition of 10-³Pa vacuum
and 900℃, the zinc evaporation rate reaches 99.2% and the product
purity is over 99.5%, which saves 40% energy compared with the
traditional smelting method;
Electrolysis recovery system: developing pulse electrolysis device for
waste acid solution, zinc deposition efficiency is increased to 85g/(A-h),
and ferrous sulfate by-products are recovered at the same time;
Plasma melting: when dealing with zinc-containing hazardous waste,
the high temperature of 1600℃ thoroughly decomposes dioxin, the
zinc recovery rate is over 90%, and the residue harmless rate is 100%.
3. Full-process automated control platform
Digital twin modeling: builds a three-dimensional mirror image of the zinc
recycling production line, simulates the material flow and thermal field
distribution, and dynamically optimizes the operating parameters of the equipment;
Intelligent feeding system: accurately match the ratio of zinc slag and
melt through weighing sensor + PLC control (e.g. ammonium chloride
addition error ≤ 0.5%);
Synergistic energy management: waste heat boiler recovers flue gas heat
from the distillation furnace, saving over 5000 tons of steam annually;
dust collector and desulfurization tower operate in a linkage, with dust emission ≤10mg/m³.
Third, the industrial value reconstruction
of automated zinc recovery
1. Breakthrough growth in economic benefits
The comprehensive zinc recovery rate jumped from 50% to 92%,
and the annual zinc recovery of a single production line exceeded
3,000 tons, directly increasing income by 60 million yuan;
Vacuum distillation power consumption per ton of zinc has been
reduced to 1,800 kWh, which is 35% lower than the cost of the
traditional process;
The development of by-products (e.g. zinc oxide, zinc sulfate) expands
profit sources and increases added value by 20%.
2. Comprehensively upgraded environmental compliance
Heavy metal wastewater reuse rate reaches 95% after membrane
filtration + electrodialysis treatment, realizing zero discharge;
Dioxin emission concentration <0.1ng TEQ/m³, better than EU standard;
Reduce 42,000 tons of raw ore mining per 10,000 tons of zinc recovery,
and reduce the area of ecological disturbance by 150 mu.
3. Intelligent transformation of production mode
Unmanned workshop: AGV automatically transfers zinc slag, robotic arm
completes unpacking and feeding, reducing manual intervention by 80%;
Predictive maintenance: vibration sensor + voice recognition technology
warns of equipment failure 72 hours in advance, reducing downtime by 90%;
Blockchain traceability: full life cycle tracking of zinc flow to meet the
ESG supply chain audit requirements of automotive, photovoltaic
and other industries.
Industry Trend: Technology Integration Drives
Zinc Recycling Industry Upgrade
Low-carbon process breakthrough
Hydrogen reduction technology replaces coke, cutting carbon emissions by
70% in the zinc recycling process;
Photothermal energy storage system supplies energy for smelting equipment,
with green power utilization rate exceeding 50%.
Micro-scale purification
Supercritical fluid extraction technology accurately separates zinc from trace
impurities (e.g., cadmium, nickel) with a purity of 99.99%;
Nano-bubble flotation device treats low-concentration zinc-containing
wastewater, and the recovery rate is increased to 98%.
Industrial ecological synergy
Constructed a regional recycling network of “galvanizing plant - recycling
enterprise - zinc smelter”, reducing logistics costs by 30%;
The industrial Internet platform accesses national zinc slag trading data,
dynamically optimizing the allocation of recycling capacity.
V. Five evaluation dimensions for selecting
zinc recycling technology
Recovery efficiency: vacuum distillation + electrolysis combination process is
preferred to ensure that the zinc recovery rate is >90%;
Level of energy consumption: the comprehensive power consumption of tons
of zinc treatment should be <2000 kWh, and the utilization rate of waste heat >40%;
Intelligence level: examine the integration capability of modules such as digital
twin, AI sorting and unmanned transportation;
Environmental protection certification: verify whether the equipment meets
GB 31574-2015 and other heavy metal pollution prevention standards;
Return on investment: comprehensively calculate the feasibility of cost
recovery within 3 years, focusing on the percentage of by-product revenue.
Conclusion
The automation revolution of hot dip galvanized zinc recycling is rewriting
the traditional industry label of “high pollution and high energy
consumption”. Through the deep integration of intelligent sorting,
green metallurgy and digital control, this field not only maximizes the
value of resources, but also becomes a model practice of circular economy.
With the deepening of the “dual-carbon” strategy, enterprises with
efficient recycling capacity and zero-emission technology will take the
lead in the new round of industrial upgrading and provide innovative
samples for the sustainable utilization of global metal resources.