EPC Project for Sanmenxia Gold and Silver Refining: Process, Emissions Control, and SGE Certification

This EPC project established a gold and silver refining plant for Sanmenxia Gold & Silver Refining Co., Ltd. Specifically, its scope covered the complete process from workshop design and equipment production to installation, commissioning, and staff training.

The plant refines two primary materials: crude gold and crude silver. In the gold refining process, operators first use nitric acid to remove impurities. Next, they dissolve the material with chloride and then reduce it with sodium sulfite. This series of steps ultimately produces 99.99% pure gold powder. Finally, the facility granulates and casts this powder into standard 1kg gold ingots that meet all Shanghai Gold Exchange requirements. For silver refining, the plant employs a smelting and electrolysis method. This process yields silver powder with a purity exceeding 99.99%, which workers then melt and cast into 15kg ingots.

To manage emissions, the project installed dedicated treatment systems for different waste streams:

• For instance, the team treats high-concentration nitrogen oxides (from nitric acid use and electrolyte preparation) with a multi-stage system: two-stage bubble absorption, four-stage jet absorption, and a final two-stage alkaline spray.

• Similarly, they handle smelting exhaust gas by first using baghouse dust removal, followed by a two-stage alkaline spray.

• For other acidic and unorganized workshop gases, a two-stage alkaline spray process suffices.

The project successfully started operations in February 2019. Consequently, by December 2020, Sanmenxia Gold & Silver Refining had earned approval from the Shanghai Gold Exchange as its 36th certified supplier of standard gold ingots.