In the field of non-ferrous metal smelting and resource recovery, metal distillation separation
technology, with its unique thermodynamic principle, has become a key means of processing
complex metal mixtures. By utilizing the boiling point difference between the metals, distillation
separation can realize the extraction of high purity metals under high temperature environment,
especially suitable for the recovery of rare and precious metals, alloy composition separation and
industrial waste regeneration. This paper will systematically analyze the core principle of metal
distillation separation, process and its application value in modern industry.
The basic principle of metal distillation separation
Metal distillation separation is a physical purification method based on thermodynamic properties, the
core of which lies in the use of volatile differences in different metals for graded purification. The
specific process is divided into three steps:
Heating and evaporation: the metal mixture is heated to a high temperature in a closed distillation furnace,
and the low-boiling point metals (such as zinc, lead, cadmium) take the lead in vaporization, while the
high-boiling point metals (such as copper, iron, nickel) remain in liquid or solid state;
Gradient condensation: by adjusting the temperature gradient in the condensation zone, the different metals
in the vapor are sequentially condensed and precipitated at specific temperature intervals;
Layered collection: The separation and purification is accomplished by collecting the condensed metal liquids
separately using physical isolation devices.
For example, in the separation of zinc and lead, the boiling point of zinc (907 ° C) is significantly lower than
lead (1749 ° C), by controlling the furnace temperature in the 900-1000 ° C interval, can be prioritized to distill
the zinc into a gaseous state, condensed to obtain the purity of more than 99.9% of the zinc ingot, while
the lead is retained as residue.
Core advantages of metal distillation separation
Compared with traditional hydrometallurgy or mechanical separation, distillation separation technology has three
significant advantages:
Highly selective separation
By precisely controlling the temperature and pressure parameters, the stepwise separation of metals can be realized.
For example, in the separation of tin and antimony, the boiling point of tin (2602℃) is higher than that of antimony
(1635℃), and the two metals can be recovered separately through two-stage distillation, avoiding the secondary
pollution of materials by chemical reagents.
Outstanding environmental benefits
The distillation process does not require corrosive agents such as acid and alkali, which reduces the emission of
waste water and exhaust gas. Data from a smelter shows that when vacuum distillation is used to treat
cadmium-containing waste, the emission of harmful substances is reduced by 70% compared with the traditional
process, while the recovery rate is increased to 92%.
Adaptation to complex raw materials
Ores, waste alloys or electronic scrap with high impurities can be processed. For example, when separating tin,
lead and copper from waste circuit boards, distillation technology can directly remove non-metallic components
such as plastics and resins, simplifying the recovery process.
Typical application scenarios and process flow
1. Recovery of rare and precious metals
In gold smelting, the boiling point difference between silver and gold is more than 500℃. Through high-temperature
distillation, silver can be prioritized to evaporate and separate, so that the purity of gold from 85% to 99.5%. Vacuum
distillation technology can also avoid gold oxidation loss and reduce refining cost.
2. Industrial waste regeneration
A metal processing plant uses a multi-stage distillation system to treat zinc-containing scrap:
First-stage distillation (850 ℃): zinc vapor condensation into ingots, the residue in the lead content down to less than 5%;
Secondary distillation: further separation of lead and trace cadmium, cadmium recovery rate of up to 80%;
Residue utilization: the remaining high boiling point metal residue is used to manufacture corrosion-resistant alloys,
realizing the goal of zero-waste.
3. Special alloy preparation
In the production of titanium alloys, distillation technology is used to remove the separation of magnesium (boiling point
1090 ℃) and titanium (boiling point 3260 ℃). Through high-temperature distillation under the protection of inert gas,
the magnesium residue in titanium ingot can be completely removed to meet the requirements of aerospace-grade
materials.
Technical difficulties and innovation direction
1. Control of energy consumption at high temperature
Distillation separation requires continuous high temperature (1000-3000 ℃), the traditional process energy consumption
accounts for up to 40% of the production cost. Innovative solutions include:
Waste heat recovery system: Utilizing the waste heat of the condensation section to preheat the raw materials and reduce
the overall energy consumption;
Plasma heating technology: replacing the traditional electric furnace to increase heating efficiency by 30%;
Vacuum distillation optimization: lowering the boiling point of metals by 200-500°C by lowering the system pressure, reducing
energy consumption.
2. Metal oxidation and pollution
Metals are easy to react with oxygen to generate oxides under high temperature environment, which affects the purity of r
ecovery. Industrial practice shows:
Inert gas protection (such as argon, nitrogen) can reduce the oxidation loss rate from 15% to less than 3%;
The inner wall of the reactor is coated with corrosion-resistant ceramic materials to reduce the risk of impurity mixing.
3. Trace metal capture
For the recovery of indium, gallium and other dilute metals, it is necessary to solve the problem of capturing low concentration
components in the vapor. The application of new porous adsorbent materials and laser-induced condensation technology
increases the indium recovery rate from 60% to 85% and reduces the risk of equipment fouling.
Dual value of environmental protection and economy
The promotion of metal distillation and separation technology is driving the industry to green transformation:
Resource utilization enhancement: a lead-zinc mine separates germanium (boiling point 2833°C) and lead (1749°C) from
tailings by distillation, reducing germanium recovery cost by 60%;
Circular economy boost: an e-waste treatment plant uses distillation technology to separate tin, copper and precious metals,
reducing landfill waste by 2,000 tons per year;
Carbon emission optimization: compared with the traditional pyrometallurgical smelting, the vacuum distillation process
reduces carbon dioxide emissions by 45%, in line with the EU carbon tariff standards.
Future Development Trends
Intelligent temperature control system: real-time adjustment of furnace temperature profile through AI algorithm, reducing
errors of manual intervention;
Compound process integration: distillation linked with electrolysis and flotation processes, e.g. distillation to separate
low-boiling point metals first, then purify high-boiling point metals by electrolysis;
Nano-condensation materials: development of nano-coatings with directional adsorption capacity to enhance the trapping
efficiency of trace metals;
Modular equipment design: miniaturized distillation device to adapt to the needs of small and medium-sized processing
plants, reducing the threshold of technology application.
Conclusion
Metal distillation and separation technology is moving from traditional smelting to a new stage of intelligence and refinement.
Whether it is to cope with the challenge of resource shortage or to respond to environmental protection policies, this technology
has shown irreplaceable advantages. With the breakthroughs in material science and automation control, the application
scenarios of distillation separation will be further expanded to provide cleaner and more efficient solutions for the
non-ferrous metal industry.