Hydrometallurgical and pyrometallurgical technologies for waste circuit boards

Driven by domestic and foreign researchers, the comprehensive treatment technology of electronic waste has made rapid progress in recent years, and some of them have been applied in actual industrial production. At present, the most widely used are mechanical treatment technology, biometallurgical technology, hydrometallurgical technology, low-temperature alkaline smelting technology and pyrometallurgical technology.

1. Hydrometallurgical technology

The characteristics of hydrometallurgical technology are flexibility and efficiency. The process of using this technology to treat electronic waste is: first, the pre-treated electronic waste is placed in an acidic or alkaline solution medium for reaction. The solution after the reaction is separated and deeply purified to remove impurities, and then the solvent is used for extraction, adsorption or ion exchange, etc., and the metal is recovered by concentration, and finally the metal is recovered by electrolysis, chemical reduction or crystallization.

Hydrometallurgical technology basically does not produce waste gas, the residual treatment after metal extraction is relatively convenient, can produce greater economic benefits, the process is relatively simple, and it has a great advantage over pyrometallurgy in the field of precious metal extraction. However, this technology also has great shortcomings: 1) It can only process relatively simple electronic waste; 2) Metals wrapped by debris on the surface cannot be leached; 3) The leachate and residue are toxic, and secondary pollution is easy to occur if not properly treated; 4) The recycled metal is single. Currently, only precious metals and copper can be recycled, and other metals and non-metals cannot be recycled.

2. Pyrometallurgical Technology

The purpose of the NRTS furnace production process is to use low-grade scrap copper, electronic waste, industrial waste slag and other copper-containing materials, with lump coal as auxiliary fuel and reducing agent, limestone and quartz as flux, through DCS control of the spray gun to introduce natural gas, oxygen and process wind, so as to control the oxidation reaction, reduction reaction and slag reaction in the furnace to produce crude copper, slag and flue gas.

The NRTS furnace production process system is mainly composed of raw material batching system, NRTS furnace smelting system, waste heat recovery system and flue gas treatment system. The raw material batching system is mainly responsible for the feeding of raw materials such as electronic waste, industrial waste slag, low-grade copper, slag-making flux and reducing agent. The raw materials are transported into the furnace through belts. The NRTS furnace smelting system is mainly responsible for the smelting of raw materials and the output of products. Its operation process is divided into four stages: smelting operation, reduction operation, sedimentation separation operation and discharge casting operation.

The flue gas treatment system is mainly responsible for curbing the generation of dioxins, collecting dust from flue gas and treating flue gas components, and finally meeting environmental emission requirements.