Calomel Tower

The calomel process for mercury removal

Widely used in non-ferrous metal production and metallurgical applications, the process converts mercury vapor into stable, solid calomel (mercurous chloride), enabling both environmental protection and potential mercury recovery.

The process is based on the reaction of elemental mercury vapor with a circulating solution of mercuric chloride (HgCl₂), converting the mercury into insoluble mercurous chloride, commonly known as calomel.

Mercury-containing process gas is introduced into a packed absorption Calomel tower, where it comes into contact with the recirculating mercuric chloride solution. Within the Calomel tower, mercury reacts with the absorbent and forms mercurous chloride, which precipitates from the liquid phase as a stable solid.

A side stream of the circulating solution is continuously directed to a primary settler, where the calomel solids are separated by gravity. The clarified liquid is returned to the absorption system, while the concentrated solids are transferred to a secondary settler for further thickening. If required, zinc dust can be added to enhance mercury precipitation and maximize recovery efficiency.

The concentrated calomel solids are then discharged for storage, recovery, sale, or further processing. Through this continuous scrubbing and separation process, mercury is effectively removed from the gas stream, enabling reliable compliance with stringent environmental regulations while supporting the recovery of valuable mercury-containing by-products.