Safety technology of nonferrous metal smelting and

2022-06-05
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Safety technology of nonferrous metal smelting and gold smelting

1. Safety production characteristics of nonferrous metal smelting and gold dressing and smelting

nonferrous metal smelting can adopt a variety of methods for smelting according to the different mineral raw materials and the characteristics of each metal itself, including pyrometallurgy, hydrometallurgy and electrochemical metallurgy. At present, the production of metal is mainly by fire and metallurgical method. The smelting methods of non-ferrous metals can be basically divided into three categories. The first category is the sulfur separation smelting of sulfide mineral raw materials. The metals belonging to this category include copper and nickel; The second category is the production of metals by carbothermal reduction of sulfide mineral raw materials after roasting or sintering. Metals belonging to this category include zinc, lead and antimony; The third type is the solvent leaching of roasted sulfide ore or oxidized mine sulfuric acid, and then the metal is extracted from the solution by electrowinning method. The metals belonging to this kind of smelting method mainly include zinc, cadmium, nickel, cobalt and aluminum. Copper and lead smelters still use pyrometallurgical process to produce gold and silver treatment anode slime. Generally, anode slime treatment includes copper and selenium removal, reduction, smelting and refining of precious lead, silver electrolysis, gold electrolysis and other processes. Lead anode slime is treated by direct smelting, electrolysis or mixed with copper anode slime after copper and selenium removal

the main large-scale non-ferrous smelters in China take pyrometallurgical smelting as the backbone process, and carry out grouping, planning, command, coordination and control management of metallurgical production process. Smelting production is mostly carried out in high temperature, high pressure, toxic, corrosive and other environments. In order to ensure the safety of operators and equipment, special attention must be paid to the implementation of safety protection measures and strive to improve the level of mechanization and automation. Research on metallurgy at home and abroad has confirmed that industry is also the most polluted industry. In the production of non-ferrous metals, it discharges a large amount of waste residue, wastewater and waste gas to the environment directionally and continuously, which is easy to pollute the environment and destroy the ecological balance. There must be perfect "three wastes" treatment projects for treatment and utilization, as well as noise, vibration, odor, radiation and heat pollution, which destroy the ecological balance and cause environmental pollution, Bring harm to people's health and biological growth

(II) main safety technologies in copper smelting, lead smelting, zinc smelting, aluminum smelting and other non-ferrous metal smelting

1. The main safety technology of copper smelting

copper smelting is mainly pyrometallurgical copper smelting, which can be roughly divided into three steps, namely sulfur smelting - blowing - pyrometallurgical refining and electrolytic refining. The main characteristics of safety production in copper smelting are: ① long process flow and many equipment; ② It is known that the process is highly corrosive and the service life of the equipment is short; ③ The discharge of "three wastes" is large and the task of pollution control is heavy. Copper smelting is a chemical reaction process dominated by oxidation and reduction. The equipment is directly or indirectly affected by high temperature or acid-base etching. In order to prolong the service life of the equipment, the following measures should be taken: ① select high-quality, high-temperature and corrosion-resistant equipment; ② Implement major, medium and minor repairs and daily patrol inspection system; ③ Take anti-corrosion measures; ④ Improve the quality of operators and do a good job in equipment maintenance. Copper smelting raw material is mainly copper sulfide refining furnace. Sulfur dioxide is formed in the production process and enters the flue gas. Recovering sulfur dioxide from the flue gas to produce sulfuric acid is one of the important tasks of pollution control. There are many channels for the comprehensive utilization of waste residue, which can be used to produce building materials such as cast stone, cement and slag silicon, and can also be used as pit filler. In addition to heavy metal ions, wastewater also contains harmful impurities such as arsenic and fluorine. Neutralization precipitation method or sulfide precipitation method are commonly used to convert the heavy metal ions into insoluble heavy metal compounds. After purification, the wastewater is recycled and reused. At the same time, the precipitate or concentrated solution is returned to the production system or treated separately to recover the valuable metals. For dusty flue gas, improve dust collection facilities, strictly manage and improve dust collection efficiency; The leaked copper containing solution and copper containing wastewater shall be recycled and treated in a centralized manner

2. Safety technology and accident prevention measures for extracting gold and silver from copper anode slime

the gold and silver smelting in the smelter adopts sulfation roasting wet treatment process. The main safety technical requirements are as follows

(1) treatment of flue gas and smoke. In the process of extracting gold and silver from copper anode, the toxic and harmful gases produced mainly include sulfur dioxide mud, chlorine, nitrogen dioxide and so on. The main treatment measures are as follows: ① set up the rotary kiln tail gas absorption tower to lead the carbon dioxide and selenium dioxide gas generated by the reaction of copper anode mud with concentrated sulfuric acid into the tower through negative pressure, and generate crude selenium products under the action of mercury, so as to achieve the purpose of environmental protection and recovery of valuable elements. The residual gas in the absorption tower shall be washed and neutralized with alkali solution before emptying. In order to ensure the absorption of tail gas, the equipment must be sealed to avoid the leakage of flue gas from rotary kiln and absorption tower. ② The chlorine absorption tower is set, and the chlorine generated in the gold separation production of anode mud is pumped into the tower through the exhaust device, neutralized with alkali solution, or returned to the gold separation operation with perchloride. In order to reduce the excessive production of chlorine and avoid the loss caused by the reaction between sodium chlorate and acid, the gold separation operation of anode slime should not only control the addition speed of sodium chlorate, but also control the acidity and temperature of the solution to prevent chlorine poisoning. ③ A spray dust collector is set to purify the blowing gas of small converter. Because the crude silver powder extracted from anode slime contains a lot of impurities, at present, the smelter uses a small converter and high-temperature air as oxidant to refine the crude silver powder. During the blowing process, a large amount of metal (non-metal) dust enters the furnace gas. Therefore, the dust is absorbed through the spray dust collector and discharged after the furnace gas is purified, so as to reduce air pollution. ④ An exhaust device is set to exhaust the harmful gas generated in the process of gold and silver electrolytic refining, so as to improve the working environment. An exhaust hood is installed above the gold electrolysis cell to pump out the chlorine and hydrogen chloride produced in the process of gold electrolysis and absorb them with alkaline solution. The operation of silver making electrolyte is carried out in the exhaust cabinet. The generated nitrogen dioxide gas is discharged to supplement each other and absorbed with alkali solution. In addition, a ventilator should be installed in the silver electrolysis room to create good ventilation conditions and prevent fog dispersion and waste gas from damaging the health of employees

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