ZINCEX TM process comprehensively recovers zinc oxide , which guarantees the best process performance: zinc has higher quality, lower power consumption, minimum labor and maintenance requirements, and is worth promoting.
The shortage of zinc sulfide concentrates on the market and the increase in demand for zinc in developed and emerging countries have caused zinc prices to rise, prompting the former zinc industry to consider looking for zinc in more sustainable and competitive conditions. Alternative source. Therefore, the use of recycled zinc oxide in existing smelters has become a consideration for the zinc industry.
First, the advantages of using recycled zinc oxide and the limiting factors of zinc regeneration
In fact, in Europe, Japan and other countries, the proportion of recycled zinc oxide used in zinc refineries is growing, as there are many advantages to regenerating zinc materials for such zinc, such as:
(1) Regenerated zinc materials are cheaper than zinc concentrates;
(2) The recycled zinc material usually does not contain sulfur, so the use of recycled zinc material can increase the processing capacity of the baking furnace without modifying the acid plant;
(iii) Regeneration of zinc oxide not only avoids the formation of expensive, fatal acids (in some places), but also consumes some supplemental acid;
Iron ore containing less than (iv) regeneration of the zinc oxide, their use also reduces the cost of the removal and treatment of iron;
(v) These zinc oxide materials increase the diversity of raw materials, thereby reducing the sensitivity to the concentrate market;
(6) Expanding the processing capacity of a wide range of raw materials, so that the production capacity of existing electrolysis workshops can be utilized;
(7) The energy intensity of the treated regenerated zinc material is less than the energy intensity of the treated sulfide concentrate
The production of galvanized steel accounts for the largest proportion, accounting for almost half of the global zinc demand, mainly used in the construction and automotive industries. Currently, more than 30% of the world's zinc comes from recycled materials. The use of electric arc furnaces (EAF) to regenerate galvanized steel produces a large amount of soot, with more than 6 million tons of filtered soot coming from the electric arc furnace every year worldwide.
The Welz method is the most commonly used process for recovering zinc from arc furnace dust, treating 80% of the total amount of regenerated soot. The second process uses a rotary hearth furnace and another new technology (like the technology that the Primus furnace is being industrialized), which has the advantage of producing iron by-products rather than slag.
In Europe and North America, approximately 1.2 to 1.4 million tons of filtered soot is produced each year. In 1997, the Welz method dealt with 45% of the total amount of soot. After 10 years, in 2007, the amount of soot treated by the Weilz furnace has risen to 80% to 90%, and the zinc content is about 250,000 tons. At present, in the United States, the regeneration rate of soot is about 50% to 55% of the total.
Despite the bright prospects, but there are some factors that limit the use of native zinc refinery zinc regeneration: the complex composition of dust caused by processing difficulties, in addition to metal impurities, the halogen (chloride and fluoride) can also cause problems, because they rich It is concentrated in the electrolyte and is therefore not suitable for direct electrolytic deposition of zinc. Chlorides corrode lead anodes, produces chlorine gas, endangering the health of workers. Therefore, when producing high-quality zinc, the maximum content of chloride should be controlled at 50-100ppm. Typical zinc sulfide concentrates have a chloride content of 5 to 10 ppm, washed Wilz oxides have a chloride content of more than 1000 ppm, and unwashed Welz oxides contain 5% to 8% of chloride.
As a result, in the primary zinc refinery, only the washed Welz oxide can be added to the roaster after mixing with the zinc sulfide concentrate, the ratio of which is not higher than 15% to 20% of the total amount in order to control the heat balance and Impurity content. When using ZINCEX zinc oxide washed or unwashed TM Process, and that there is no limitation. In this way, traditional zinc refineries can also add all the regenerated zinc.
Second, solvent extraction - powerful tools
ZINCEX TM solvent extraction is metal impurities (Cd, Cu, Ni, Co, etc.), halogen (chloro, fluoro), parts of an alkali metal (sodium, potassium), and other components such as calcium, magnesium, manganese, "perfect barrier." In the conventional zinc powder purification process, interference with neutralization and displacement may cause iron, aluminum , arsenic and antimony to enter the zinc electrolysis workshop, which has a very harmful effect. With the ZINCEX TM process, any peaks of iron and aluminum are buffered by the organic phase, while arsenic and antimony are not extracted, and the end result is that the quality of the electrolyte remains unchanged. In addition, chloride ions and fluoride ions are not extracted by the organic phase, avoiding entry into the electrolytic cell.
Figure 1 shows the comparison between the traditional purification process and the ZINCEX TM process.
Figure 1 is a conventional purification process and the comparison process ZINCEX TM. It should be noted, only one step of ZINCEX TM technology equivalent of the traditional six-step process. The solvent extraction process is simpler and fully automated, requiring less labor and minimal solvent consumption.
In short, compared with the conventional zinc purification process, operating costs ZINCEX TM technology reduced about 15%, the investment cost is approximately.
The ZINCEX TM technology developed by Tecnicas Reunidas has been successfully applied to four plants based on solvent extraction of zinc. This is the ideal solution for impure or crude regenerated zinc oxide because it guarantees SHG. Production of zinc. At present, a ZINCEX plant has been built at the Akita Zinc Refinery in Japan (Tonghe Metals and Mining Company) to treat unwashed zinc oxide from several waste sources with an annual processing capacity of 20,000 tons of SHG zinc.
The conceptual processing schematic (see Figure 2) is based on acid leaching of zinc from an acid-containing residual liquid and sulfuric acid from a (washed or unwashed) zinc oxide-containing waste material (such as a Welz oxide). The solution is then neutralized to remove iron and silica. Next, in the solvent extraction stage, zinc is selectively extracted and separated from other impurities in the solution to produce a zinc sulfate solution suitable for electrolytic deposition, which ensures the production of SHG zinc and reduces the energy consumption per ton of zinc.
Figure 2 Schematic diagram of conceptual processing
Another advantage Tecnicas Reunidas regeneration process using zinc PLINT ZINCEX TM technology and techniques suitable combination, can recover all the valuable metals, including zinc, lead and silver.
Third, the conclusion
In summary, ZINCEX TM is a reliable and industrially viable technology for processing all regenerated zinc oxides from existing zinc refineries, ensuring SHG zinc production and reducing energy consumption.
The ZINCEX TM process can handle any type of washed or unwashed zinc oxide with environmental and economic advantages. Therefore, this solvent extraction technology is an ideal solution for smelters that increase production capacity in a sustainable and more economical manner.
It can be said that the ZINCEX TM process guarantees the best process performance: higher quality zinc, lower power consumption, and minimal labor and maintenance requirements - operating costs are reduced by approximately 5% compared to conventional zinc powder purification processes. The investment cost is similar.
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