An ordinary medical thermometer contains mercury, and a fluorescent lamp contains mercury. It is used in various fields of technology, metallurgy, agriculture. To become useful to people, this metal goes through a difficult path from the bowels of the earth to industrial producers.
Mercury ore, cinnabar, is mined in mines by drilling or blasting. In this case, electrical equipment or explosives are used. The extracted material is transported from the mines on conveyor belts, trucks or trains to further processing sites. There the ore is crushed in one or more cone crushers. The crushed ore is placed in special mills for further grinding. The mill can be filled with short steel rods or steel balls for a better effect.
The finely ground substance enters the oven for heating. Heat is provided by burning natural gas or other fuels at the bottom of the kiln. Heated cinnabar reacts with oxygen in the air. The result is sulfur dioxide, which allows the mercury to rise as a vapor. This process is called roasting. Mercury vapor rises and leaves the furnace along with sulfur dioxide, water vapor and other combustion products. A significant amount of fine dust from the powdered ore is also transferred, which is separated and collected.
From the oven, hot vapors enter a water-cooled condenser. When the vapors are cooled, mercury, which has a boiling point of 357 ° C, is the first to condense into a liquid. The remaining gases and vapors are vented or further processed to reduce air pollution.
Liquid mercury is collected. Since it has a very high specific gravity, any impurities tend to rise to the surface and form a dark film or foam. These impurities are removed by filtration, and the content of pure mercury in the resulting substance is 99.9%. The impurities are further processed to collect mercury, which may have formed compounds.
The resulting mercury is usable, but for some purposes a substance with a higher pure mercury content is required. For this, additional methods of cleansing are used. Among them are mechanical filtration, electrolytic process, and the use of chemicals. The most common method is triple distillation. The temperature of the liquid mercury is gently raised until the impurities are separated or the mercury itself evaporates. This process is carried out three times, each time increasing the purity of the substance.