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Abstract:
The comprehensive recovery of wet process zinc refining technology is very important for environmental protection and resource conservation. This article summarizes the current situation and difficulties of comprehensive recovery in wet process zinc refining technology, and introduces the latest research progress and application cases. At present, the comprehensive recovery in wet process zinc refining technology mainly includes comprehensive recovery of sulfur dioxide, comprehensive recovery of zinc, and comprehensive recovery of iron. The comprehensive recovery of sulfur dioxide mainly includes the treatment of sulfur dioxide in zinc electrolysis acid mist, the treatment of exhaust gas from roasting sulfuric acid leaching residue, and the treatment of tail gas from acid regeneration. The comprehensive recovery of zinc mainly includes the recovery of zinc from gypsum, cadmium, and liquid ammonia. The comprehensive recovery of iron mainly includes the recovery of iron from hematite, iron chloride slag, and lead blast furnace slag. In addition, the research and application of comprehensive recovery of other by-products such as germanium, copper, and nickel have also been carried out. Through the analysis of the above-mentioned aspects of comprehensive recovery, some suggestions are put forward to promote the development of comprehensive recovery in wet process zinc refining technology.
Keywords: Wet process zinc refining; comprehensive recovery; sulfur dioxide; zinc; iron
Introduction:
Zinc is an important non-ferrous metal, widely used in various fields. With the development of society, the demand for zinc is increasing year by year. However, the traditional pyrometallurgical process for producing zinc is not only energy-intensive but also generates a large amount of SO2 and dust pollution. To reduce the pollution and improve the recovery of valuable metals, the wet process zinc refining technology has been developed rapidly in recent years. Compared with the traditional pyrometallurgical process, the wet process zinc refining technology has the advantages of low energy consumption, less pollution, and high recovery rate. However, due to the complexity of the process, there are still many challenges to be faced in the comprehensive recovery of by-products.
Comprehensive recovery of sulfur dioxide:
Sulfur dioxide is the main pollutant generated in the process of wet process zinc refining. As a strong corrosive and toxic gas, it not only pollutes the environment but also corrodes equipment and affects the life of the equipment. Therefore, the comprehensive recovery of sulfur dioxide in the wet process zinc refining process is of great importance.
(1) Treatment of sulfur dioxide in zinc electrolysis acid mist:
During the electrolysis of zinc, a large amount of acid mist containing sulfur dioxide is generated. If not treated in time, it will cause serious pollution to the environment. The current treatment methods mainly include sodium hydroxide absorption method, soda lime absorption method, and magnesium oxide absorption method. Among them, the sodium hydroxide absorption method is the most widely used. The reaction equation is as follows:
2NaOH+SO2→ Na2SO3+H2O
(2) Treatment of exhaust gas from roasting sulfuric acid leaching residue:
In the process of roasting sulfuric acid leaching residue, a large amount of sulfur dioxide is generated. The current treatment methods mainly include desulfurization by CaO, NH3 cooling and absorption, and membrane separation technology. However, these methods have their shortcomings, such as high energy consumption, high investment, and low efficiency.
(3) Treatment of tail gas from acid regeneration:
In the process of acid regeneration, a large amount of tail gas containing sulfur dioxide is generated, and it is also accompanied by the discharge of residual liquid. The current treatment methods mainly include absorption and desulfurization with sodium hydroxide solution, absorption and desulfurization with sodium carbonate, and absorption and desulfurization with magnesium oxide.
Comprehensive recovery of zinc:
In addition to sulfur dioxide, the comprehensive recovery of zinc is also an important issue in wet process zinc refining technology. Zinc is a valuable metal, and its recovery rate directly affects the economic benefits of the enterprise.
(1) Recovery of zinc from gypsum:
After the precipitation of zinc oxide, a large amount of sulfate ions are left in the solution, and gypsum is generated by adding sulfuric acid. The recovery of zinc from gypsum mainly includes the methods of acid leaching, pressure leaching, oxidation roasting, and ammonia-cyanide complexation. Among them, the utilization of ammonia-cyanide complexation is the most promising.
(2) Recovery of zinc from cadmium:
In the process of zinc refining, a small amount of cadmium will inevitably be mixed into the zinc sulfate solution, which will greatly affect the quality of high-purity zinc. The current recovery methods mainly include ion exchange, selective precipitation, and solvent extraction.
(3) Zinc recovery from liquid ammonia:
In the process of zinc refining, liquid ammonia is used as an organic solvent to extract zinc ions. The recovery of zinc from liquid ammonia mainly includes the methods of stripping and scrubbing. Among them, the ammonia-carbonate method has the advantages of low cost and high efficiency.
Comprehensive recovery of iron:
Iron is one of the impurities in the zinc sulfate solution. If not removed in time, it will not only affect the quality of high-purity zinc but also cause the precipitation of zinc oxide to be incomplete. Therefore, the comprehensive recovery of iron is also an important issue in wet process zinc refining technology.
(1) Recovery of iron from hematite:
Hematite is one of the main raw materials for the production of hematite iron. In the process of wet process zinc refining, hematite is added to absorb iron ions. After absorption, it can be used for the production of hematite iron.
(2) Recovery of iron from iron chloride slag:
Iron chloride slag is a by-product generated in the process of zinc refining. It contains a certain amount of iron and other valuable metals, such as copper, nickel, cobalt, and zinc. The recovery of iron from iron chloride slag mainly includes the methods of reduction roasting, flash smelting, and electric furnace smelting.
(3) Recovery of iron from lead blast furnace slag:
Lead blast furnace slag is a by-product generated in the process of lead smelting. It contains a certain amount of iron and other valuable metals, such as zinc, copper, and silver. The recovery of iron from lead blast furnace slag mainly includes the methods of magnetic separation and flotation.
Conclusion:
The comprehensive recovery of wet process zinc refining technology is very important for environmental protection and resource conservation. Through the analysis of the comprehensive recovery of sulfur dioxide, zinc, and iron in the wet process zinc refining process, it can be seen that there are still many difficulties to be solved. In order to promote the development of comprehensive recovery technology, it is necessary to carry out more in-depth research on the technological principles and key technologies of comprehensive recovery, and continuously improve the comprehensive recovery technology to achieve the goal of high recovery rate and low pollution.