Understanding of mineral processing and processing of mercury ore

Mercury ore than other non-ferrous metal ores easy to choose, easy smelting, the process is simple, especially single mercury ore. Therefore, mercury ore is usually disposed of in the mine. It is often built in the vicinity of the pit or near the mining or metallurgy-selection-smelting joint venture, but the scale is generally small and the service life is short. High-grade mercury ore can be directly smelted after being crushed, and low-grade ore should be smelted after enrichment by ore dressing .

1. Mercury ore beneficiation method

There are hand selection, re-election and flotation, among which the application of flotation is extensive and most effective. Most of the mercury mining enterprises in China have established mercury mining plants, and most of them are characterized by heavy-floating combined processes, and some medicinal cinnabars are recovered by shaker. In the 1990s, the mercury ore dressing plant in the country had a capacity of 420,000 t/a for ore processing, and the large-scale mercury mining plant in Guizhou had a daily processing capacity of 500 tons. China's mercury ore processing plant has a lower grade of ore. For example, in 1996, the average national mercury content of raw ore was 0.18%, the concentrate grade was usually less than 30%, and the ore recovery rate was 90% to 97%.

2. Production of metallic mercury

Mercury smelting has two methods: fire method and wet method. Pyrophoric smelting is to calcine mercury ore or concentrate at a relatively low temperature (450 ~ 800 ° C), directly reduce the mercury to a gaseous state, and then condense into liquid mercury. The pyrometallurgy process is relatively simple and has high technical and economic indicators. It is a traditional method of mercury refining at home and abroad. Commonly used roasting equipments include rotary kiln, multi-hearth furnace, liquidized roasting and mechanical distillation furnace. Mercury is obtained by leaching mercury concentrate with sodium sulfide or hypochlorite solution, purifying the leaching solution, and obtaining metal mercury by electrolysis or displacement. The wet method can reduce the pollution of mercury, but the process is complicated, and the technical and economic indicators are not as good as the fire method, so it is not widely used. The United States has also developed an electro-oxidation method for extracting mercury from cinnabar ore. The recovery rate of mercury is 90% to 99%, but no production reports have been reported.

China's mercury refining currently uses flotation concentrate-distillation furnace technology. Guizhou mercury mine also has a double-layer single-dilute phase fluidized roaster to treat low-grade crushed ore containing less than 0.1% mercury. Small mines in some areas still use old-fashioned blast furnaces to treat raw ore, which is seriously polluting the environment.

Mercury metal extracted from ore is called primary mercury, which is usually more than 99.9% pure and has a pure and bright appearance and has many uses in industry. For some special applications, such as electronic technology, the purity of mercury is required to be above 99.9999%, which is called high purity mercury. It is obtained by distilling or electrolyzing fine mercury in a vacuum or an atmosphere filled with an inert gas. Mercury produced by mercury mines in China generally contains more than 99.99% mercury. Guizhou mercury, copper and mercury kernel Wuchuan mercury can produce high purity mercury.

3. Production of mercury compounds

There are many compounds of mercury, but there are only three types of industrially known sulfides, oxides and chlorides:

(1) Mercury sulfide Among all mercury compounds, mercury sulfide is the most important one. Almost all of the mercury ore that is sent from the mine to the smelting is in this form and is the main mineral raw material for mercury refining. Natural mercury sulphide is also known as cinnabar or cinnabar. HgS has many isomers, the most important being α-HgS and σ-HgS. σ-HgS is a red powder, commonly referred to as cinnabar. When hydrogen sulfide or various alkali metal sulfides are added to an acidic solution containing mercury, the precipitated HgS is often a black powder, i.e., α-HgS. Cinnabar is a valuable Chinese medicine that can also be used as an industrial raw material and other special purposes. Cinnabar is one of the traditional products in the production of mercury in China, and there are three production methods. One is mined from deposits of mercury-containing high-grade HgS, cinnabar crystals have a significant ore, crushed reselection method by separating the gangue vermilion, and then after high intensity magnetic separation to remove iron dust, fly with water ( It is a process of operation, that is, it is sprayed on cinnabar for washing and drying. The yield of cinnabar is generally 30% to 35%. Most of China's mercury mines use this method to produce cinnabar. The other two methods can also produce cinnabar by artificial synthesis and wet method (ie, chemical precipitation method), but the former is highly polluted by mercury, and the latter is not widely used in industrial production.

(2) Mercury oxide Mercury oxide is often a bright red or orange-yellow powder, and red and yellow oxidized mercury is also included in industrial production. Red oxidized mercury is widely used as a battery depolarizer in various standard mercury cells. Yellow (red) color oxidized mercury is also used in analytical reagents, antiseptic, mildew and pharmaceutical industries. There are three main methods for producing oxidized mercury in the industry. The first is to produce mercury oxide by suspending electrolysis of mercury sulfide concentrate. The mercury concentrate is suspended and electrolyzed in a saline solution to obtain a Na2HgCl4 solution. After purification, sodium hydroxide solution is added to obtain red or yellow oxidized mercury. The second is to dissolve the metal mercury with hydrochloric acid to make mercury chloride, and then react with the alkali solution, or directly dissolve the mercury chloride in water, and react with sodium hydroxide to obtain red or yellow oxidized mercury. The third is to dissolve the mercury in the nitric acid to form Hg(NO3)2, and then heat to decompose to obtain red oxidized mercury or add sodium hydroxide solution to form yellow oxidized mercury.

China's Guizhou mercury mine and Tongren mercury mine have built production workshops to produce oxidized mercury using the above method.

(3) Production of mercuric chloride and its extended products Mercury chloride (HgCl2), also known as mercuric chloride, white rhomboid rhomboid needle crystal, or white crystalline powder, highly toxic, lethal dose is 0.2-0.4g. The analytically pure and chemically pure mercury chloride contents were not less than 99.5% and 99%, respectively, and the ignition residues were 0.02% and 0.04%, respectively. HgCl2 mainly used for chemical industry, but also for zinc-manganese battery, pharmaceutical, analytical reagents, preparation of other antiseptic and mercury salts. In industrial production, the gas phase synthesis method is adopted, that is, the metal is heated to above the boiling point (360 ° C) and the excess pre-heated chlorine gas is gas-phase synthesized in a quartz reactor. Guizhou Mercury Mine, Tongren Mercury Mine and Xinhuang Mercury Mine have established corresponding production workshops. Mercuric chloride is widely used in the plastics industry as a catalyst for the synthesis of vinyl chloride in the form of a mercury chloride catalyst in the production of polyvinyl chloride by the acetylene process.

4. Production of amalgam alloy

Amalgam is a general term for an alloy of mercury and other metals. Titanium amalgam and zinc amalgam are two of the highest value amalgam products in industrial production. Titanium amalgam is mainly used as a mercury releaser instead of liquid mercury for the production of mercury lamps and fluorescent lamps. In the industrial production, the “segment temperature control synthesis method” is adopted to prepare Ti3Hg, and the Guizhou mercury mine has built a production workshop with an annual output of 1~2t titanium amalgam. Zinc amalgam is mainly used in the production of alkaline high-energy batteries, zinc- silver button batteries and zinc-air batteries, and is used as a battery negative active material. There are many methods for zinc amalgamization, and there are two methods, wet and dry. The wet method refers to an amalgamation process carried out in a liquid phase, and there are an electrolysis method, a mercury chloride hydrochloride method, an acetic acid method, and an alkali method. The dry method is based on the formation of amalgam on the surface of gaseous mercury and solid zinc powder, and then continuously penetrates to complete the amalgamation process. The method is easy to industrialize and has less pollution due to its good quality and easy operation. The Huludao Zinc Plant has a corresponding production workshop (the original by-product mercury).

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