Roasting of Mercury Ore
Mercury ore, also known as cinnabar or mercury sulfide, is unique in its use in many industries. Roasting is a process used to pry out the valuable components of mercury ore for a variety of uses.
The roasting process begins by drying out the mercury ore. This is done by heating it to temperatures of 1000 degrees Celsius. During this process, oxide forms and the mercury ore turns from a red to yellowish-gray color. After the ore is cooled, it is crushed by machine to form relatively small chunks, usually about a quarter of an inch in size. The chunks are then placed in a furnace where the roasting and extraction of the mercury from the ore occurs.
The furnace itself is heated to around 700 to 750 degrees Celsius, where the chunks are roasted. At this temperature, the sulfur in the ore bonds with the oxygen in the air to create sulfur dioxide. This bonds with the mercury atoms to extract the mercury and convert it into a vapor form. The mixture is then forced out of the furnace, with the vapors rising and collecting in a chamber fitted with an absorptive material. The absorptive material then extracts the mercury vapor.
The yielded mercury is then placed in an air-tight distillation tank, where it is heated to the boiling point of the mercury. As it boils, the vaporized mercury is collected in a separate chamber by cooling it in a condenser. The outcome is a red liquid that is 99.8% pure mercury.
The leaves from the furnace are then gathered, cooled and compressed into a solid cake-like material for final storage. The cake, which usually weighs about 8 or 9 kilograms, is referred to as “calomel.” The cake is then sent off for heavy metal-finishing processes, or is used to make fluorescent compounds for light bulbs and to serve as a catalyst for hydrogen production for energy utilities.
After the process is done, some of the sulfur dioxide created during the roasting process is recycled and sent back into the furnace. The rest is released as a pollutant, as there is no current method to contain it.
The roasting process of mercury ore serves a purpose in many industries such as metal finishing, fluorescent light bulb manufacturing, and energy production. It allows us to utilize the valuable components inside the ore to create new materials, while also posing some potential ecologic dangers.
