(A) tin ore beneficiation methods and quality requirements of tin concentrates
In addition to low-concentration tin-rich ore containing more than 40% tin, it can be directly smelted without beneficiation, and other tin ore is generally subjected to beneficiation, and is integrated with tin concentrate containing more than 40% of tin and then smelted.
In order to rationally select the beneficiation method and process, it is necessary to focus on the occurrence of tin in the ore, the size of the tin mineral, the composition and content of the ore material, the structural structure, the mud content and the surrounding rock properties. And the natural type and industrial type of ore are reasonably divided.
The mineral processing methods commonly used in different types of tin ore in China:
1. Easy to choose ore: such as oxidized ore, cassiterite- quartz type ore, tin-containing granite type ore, commonly used for re-election or heavy-floating process.
2. Difficult choice of ore: such as cassiterite-sulphide skarn type ore, cassiterite-sulphide type ore, generally adopts heavy-floating-heavy, magnetic-floating-heavy ore dressing process or combined metallurgical process.
3. extremely refractory ores: The tin-containing iron ore magnetic skarn ore, use magneto - float - weight, fumed or other mineral processing smelt joint process.
In some ore processing plants in China, in the case of fine ore, high iron content, low monomeric cassiterite and many iron and tin, the production of a variety of tin products, that is, maintaining or even improving the final tin concentrate At the same time of the grade, the output of some rich mines (tin 3-10%) and difficult to select mines (tin 1-2%), the tin recovery rate of tin increased by about 10%, increasing the production of tin.
When tin and lead symbiotic ore, tin ore is difficult to pick a qualified, you can elect to send a tin-lead bulk concentrate smelter tin-lead solder or other alloys.
The effects of common impurities:
Arsenic : The entry of crude tin into smelting makes refining difficult. If the arsenic content is too high in refining, it will affect the quality of the tin plate, the non-toxicity of the package and the hardness, brittleness and plasticity of the tin metal. Arsenic volatilizes into soot (formation of cyanogenated cyanogen, etc.), pollutes the environment and seriously harms humans, animals and crops.
é“‹ : High content will affect the tensile strength limit and Brinell hardness of cast tin.
Copper : High content will affect the stability and non-toxicity of tin plating. Affects the hardness, elongation, yield point, etc. of tin.
Iron: high content makes it difficult to separate iron and tin during smelting, affecting the plasticity, corrosion resistance and hardness of tin.
Lead: Partially volatilized into soot during smelting, polluting the environment and causing lead poisoning.
锑 : It is difficult to increase tin refining, and some of it enters the dust to cause pollution. Affects the elongation, hardness, tensile strength, etc. of tin.
(2) Smelting method of tin
The smelting method of tin mainly depends on the material composition and content of the concentrate (or ore). Generally, the fire method is the main method, and the wet method is supplemented.
The production of modern tin generally consists of four main processes: pre-refining treatment, reduction smelting, slag refining and crude tin refining.
Before refining treatment is to remove harmful smelting sulfur, arsenic, antimony, lead, bismuth, iron, tungsten, niobium, tantalum and other impurities, while the purpose of a comprehensive variety of useful metals recovery. The pre-refining treatment methods include selection, roasting, and leaching operations, and a combined process of one or several operations may be employed depending on the type of impurities contained. However, some tin concentrates with high lead, antimony and iron in China can also be processed without refining.
The reduction smelting is mainly to reduce the tin oxide to crude tin, and at the same time reduce the iron oxide to FeO and slag with the gangue component. For this reason, it is impossible to produce metallic iron, so it is necessary to control a weak reducing atmosphere and a suitable temperature, which inevitably restricts the complete reduction of tin oxide, so that the slag contains a high tin (this slag is called slag-rich) and must be further processed. .
The slag is smelted by a smelting furnace, so that the produced slag has a low tin content, a high metal recovery rate, and a large reduction in iron circulation.
The crude tin refining mainly removes impurities such as iron, copper, arsenic, antimony, lead, antimony and silver , and simultaneously recovers useful metals. Generally divided into fire refining and electrolytic refining.
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