[lead and Zinc Summit] Development and Industrial Application of Zinc smelting Technology

SMM May 18: at the 16th lead and Zinc Summit held by Shanghai Futures Exchange and SMM in 2021, Song Yan, an engineer of China Enfei Engineering and Technology Co., Ltd., introduced the development and industrial application of zinc smelting technology. He said that in view of the low degree of resource guarantee, serious dependence on imports of ores, lagging development of zinc recovery industry, and outstanding environmental problems in the domestic zinc industry, it has become a development trend in the field of zinc smelting in China to improve the existing zinc smelting process and innovate zinc smelting technology. the development of zinc-containing secondary resources recovery and utilization technology has become the development trend in the field of zinc smelting in China.

Overview of Zinc Resources

According to the (USGS) statistics of the US Geological Survey, in 2020, the global zinc resources (metal zinc) reserves were about 250 million tons, with China ranking second, about 44 million tons, accounting for 17.6% of the total reserves. In 2020, the output of zinc in China is as high as 642.5t. With less than 20% of the world's zinc reserves, China has provided more than 40% of the global zinc production capacity, and zinc resources are overexploited.

It is worth mentioning that affected by the novel coronavirus epidemic, the zinc production capacity of other major zinc-producing countries in the world has generally decreased except China, and China's zinc production capacity has exceeded 40% of the global zinc production capacity. At present, the global zinc demand is increasing year by year, zinc production and demand is upside down, supply exceeds demand; China is not only a large zinc producer in the world, but also a large zinc consumer in the world, with consumption exceeding 45% of the world's total output. But at present, there are some problems in the domestic zinc industry, such as low degree of resource security, serious dependence on ore imports, lagging development of zinc recovery industry, and outstanding environmental problems. Therefore, we should improve the existing zinc smelting process, innovate zinc smelting technology, and develop the recovery and utilization technology of secondary resources containing zinc. It has become the development trend in the field of zinc smelting in China.

Development and Industrial Application of Mineral Zinc smelting Technology

Brief introduction:

At present, zinc smelting is mainly divided into two processes: fire process and wet process. The zinc production capacity of the pyrometallurgical zinc process is less than 20% of the total zinc production capacity, and more than 80% of the other zinc production capacity is wet process.

There are three kinds of zinc smelting processes in China, namely, vertical pot zinc smelting, ISP zinc smelting and electric furnace zinc smelting. The original manger furnace, saddle furnace, square furnace or slightly regular flat pot furnace used in remote areas a few years ago has been banned from production and construction by the state because of its high energy consumption, low recovery rate, waste of resources and environmental pollution. Now it has been basically shut down or transformed.

The typical representative of vertical pot zinc smelting is Huludao Zinc Plant, but because the single series production capacity is difficult to be large-scale, and the energy consumption and environmental protection are difficult to compare with the wet process, this process has not been popularized and applied on a large scale. As for the ISP process, a total of 19 ISP production lines have been built all over the world, but all of them have been closed abroad because of environmental protection. At present, there are still 4 ISP blast furnace zinc smelting production lines in China (Shaoguan, Huludao, Baiyin, Baoji Dongling).

Because of relatively low investment, short process, easy operation and no outstanding problems in environmental protection, electric furnace zinc smelting has been developing continuously in remote provinces such as Yunnan, Guizhou, Sichuan, Shaanxi, Gansu, Ningxia, Qinghai and other remote provinces and regions with sufficient zinc resources and low cost in the past decade.

At present, 98 electric furnaces have been built and put into operation in more than 40 factories in China, and the total installed power of electric furnaces is 232 MW,. The total annual output of zinc is 30-350000 tons. The unit power of the electric furnace that has been put into production is between 1000~6300kVA, and the unit consumption of crude zinc electricity fluctuates between 3500 ~ 4300kW h / t depending on the concentrate grade.

However, at present, the wet process is still the most widely used in the market. The wet process is divided into direct leaching and indirect leaching. The details are as follows:

Wet process-direct leaching

Direct leaching of zinc sulphide concentrate is one of the important technical advances in zinc smelting in China in recent years, which mainly includes the pressure leaching developed after 1980s and the atmospheric oxygen leaching process developed at the beginning of this century. Among them, the pressurized oxygen-enriched leaching process has been applied in foreign Kemingco Company, Yingqiao Company and Ruhr Zinc Company, and in China Zhongjin Lingnan, Yunye, Western Mining and other companies. the atmospheric pressure oxygen-enriched leaching process has been applied in Korea Zinc Union Company, New Politon Company and Zhuye Group.

Wet process-indirect leaching

The wet zinc smelting-indirect leaching process is definitely the most widely used production method in the world, and the output of electric zinc produced by this method accounts for more than 90%. In the wet zinc smelting industry, the main production process is roasting of zinc sulphide concentrate in fluidized bed roasting-roasting leaching-purification of leaching solution-electrodeposition of clean solution-electric zinc ingot. Among them, according to the different leaching process, it can be divided into conventional method and hot acid leaching method. In foreign countries, it is still mainly conventional hair, and its production capacity accounts for about 60% of the total production capacity of zinc. At present, China has mainly hydrometallurgical zinc, accounting for more than 80% of the total output of zinc. The conventional leaching residue contains about 20% zinc.

Industrial application

1. Direct leaching-improvement of pressurized oxygen-enriched direct leaching of zinc concentrate

A smelter adopts pressurized oxygen-rich direct leaching process, the production scale is 100000 t a zinc ingot, the zinc leaching rate is more than 98%, there is no need to build flue gas sulphuric acid and tail gas desulfurization system, and the sulfur in the zinc concentrate is recovered to sulfur. The process is suitable for remote areas where there is no market for sulfuric acid.

two。 Indirect leaching-conventional leaching

As the slag produced by the hot acid leaching process is a kind of dangerous waste, the later pyrometallurgical treatment can not be avoided. Therefore, the existing zinc smelting technology is returning to the conventional leaching process and is developing in the direction of large-scale equipment and harmless treatment of leaching residue.

1 large-scale equipment-a new 300000-ton zinc project in a certain group

The new scale of the project is 300000 tons of zinc per year, supporting the construction of two sets of sulfuric acid systems with a by-product of 600000 tons of sulfuric acid, as well as a large smelting base for comprehensive recovery of various valuable metals. Two 152m2 fluidization roasters were selected for this process.

2 harmless slag-comprehensive utilization of zinc smelting resources in a lead-zinc smelter in Gansu

The project is designed to deal with 14 × 104t/a lead-silver slag per year. The existing production process produces about 10.4 × 104t/a lead-silver slag, which is filtered and dried, then smelted by side-blowing melting furnace and fuming furnace fuming slag treatment process, and the insufficient part is used to deal with the lead-silver slag stored in the existing slag yard. A 13m2 side-blown immersion combustion melting furnace and a 10m2 fuming furnace are selected in this process.

3. New wet process of indirect leaching-hot acid leaching-key technologies of carbon-free green wet zinc smelting and hematite process.

Key technological innovations:

The key technologies and equipment for zinc concentrate zinc-iron separation-iron resource utilization with independent intellectual property rights have been developed, and the key technologies and equipment for efficient recovery of zinc leaching slag with independent intellectual property rights have been developed. the key technology of removing arsenic from copper by replacement of acid solution iron powder, pre-neutralization and limestone indium precipitation was invented, and a new carbon-free green wet zinc smelting technology for roasting waste heat supply in the whole system was developed.

1 Hot acid leaching-the key technology of iron resource utilization in the hematite process of a factory in Yunnan Province.

The project breaks through the technological bottleneck of iron removal by hematite process and solves the worldwide problem of smelting and utilization of high-iron sphalerite alone.

4. Research and development technology-direct smelting process for oxidative desulphurization of lead-zinc mixed concentrate

In view of polymetallic dense symbiotic refractory lead-zinc sulphide ores, China Enfei Design and Northeastern University have jointly developed a direct smelting technology for oxidation and desulphurization of lead-zinc mixed concentrates. This technology can replace ISP method and save energy and protect environment.

Recovery and Resource Utilization of Secondary Materials containing Zinc

I. technological innovation:

1. Aiming at low-grade carbonate lead-zinc oxide ore, the technology of volatilization and recovery of zinc from rotary kiln was developed.

(2) the technology of treating zinc leaching residue and zinc-bearing oxide ore by side-blowing immersion melting pool furnace;

3. The technology of direct reduction and recovery of lead and zinc from copper smelting slag by rotary hearth furnace;

4. New technology of recovering valuable metal elements such as lead and zinc by treating copper smelting slag in CR furnace.

Second, specific applications:

1. Volatilization Technology of Rotary Kiln-600000 t / a lead and Zinc smelting Project in Xinjiang

According to the characteristics of Huoyun carbonate lead-zinc oxide ore, the project uses a rotary kiln to volatilize, and the enriched lead-zinc oxide dust is extracted by wet leaching-solution purification-electrolysis-melting and casting to produce zinc ingots. The design scale is to produce 500000 tons of electric zinc and 100000 tons of electric lead per year. A total of 4 φ 6.2m × 85m rotary kilns and their matching waste heat boilers and dust collection systems are set up in this process.

2. Side blowing immersion combustion molten pool smelting technology-Environmental Protection and Energy Saving Technical Reform Project for the treatment of Zinc leaching Slag in a Plant in Yunnan Province

The project adopts side-blown furnace melting + fuming furnace fuming process, the designed treatment scale is 350 t / d for zinc leaching slag and 250 t / d for lead-zinc symbiotic oxide ore, which has been successfully put into production in July 2019. A 16m2 side-blown melting furnace is selected for this process.

3. Direct reduction technology of rotary hearth furnace-comprehensive utilization project of copper tailings from a factory in Gansu Province.

The project uses copper slag tailings as raw materials and adopts the process of "rotary hearth furnace direct reduction + grinding magnetic separation + iron powder compaction". It is designed to deal with 800000 tons of copper tailings, 276000 tons of reduced iron powder, 34000 tons of zinc oxide powder and 449000 tons of steam. The construction of the project began in mid-April 2015, and by the end of December 2016, the main construction of the project was completed and the rotary hearth furnace system was put into trial production. In June 2017, the commissioning of the rotary hearth furnace system was completed.

4. Recovery of lead and zinc from copper smelting slag by CR furnace

The "short process copper smelting technology" is a further upgrade on the basis of the second generation of bottom blowing copper smelting technology. Through the organic connection of one smelting furnace, two copper smelting furnaces and one CR furnace (ComprehensiveRecovery-- comprehensive recovery furnace), the short process of copper smelting and lead and zinc recovery is formed.

Technological process:

Summary of New and efficient Green Zinc smelting Technology

Pyrometallurgical zinc smelting-Bref furnace short-flow pyrometallurgical zinc smelting process

In order to solve the problems of high energy consumption, process plant and low direct yield of traditional pyrometallurgical zinc smelting process, combined with the advantages of side blowing furnace and electric furnace, Enfei invented a Bref furnace (smelting-reduction volatilization furnace) short-flow zinc smelting process.

Technical advantages: short process, low energy consumption and low carbon emissions.

Summary

There are some problems in China's zinc industry, such as over-exploitation of resources, low degree of resource protection, serious dependence on imports of ores, high energy consumption of lead and zinc industry, prominent environmental pollution problems, large carbon emissions and so on.

The existing zinc smelting technology is mainly based on the conventional wet leaching process, and the slag treatment technology is developing rapidly, and it is developing in the direction of large-scale equipment and innovative smelting process of secondary materials containing zinc oxide. The cost of direct leaching process is further reduced, but it is still unable to compete with the traditional process. Hematite law has realized industrialization in our country.

In view of the resources of refractory lead-zinc symbiotic ores, the innovative oxidative desulphurization direct smelting process of lead-zinc mixed concentrate combined with bottom blowing, ISP and electric furnace is considered, and a new and efficient green zinc smelting process is considered for zinc sulphide concentrate.