New development of reuse technology of waste PCB
At present, around the implementation of the EU WWWE directive and all regions of the world, all countries like this regulations (or will begin full implementation), reuse has become a very important work, recycling of waste electronic products. Recycling of waste PCB, enterprises in the use of technology, generally from three aspects should be considered to benefit: (1) access to environmental benefits. To achieve global or regional environmental benefits, that is, air, water, soil and human health are no longer affected. (2) reuse efficiency. To achieve the reuse and commercialization of waste PCB, the principle of minimizing the amount of waste that can be recycled is reduced to the minimum. (3) low cost effectiveness. The cost of reuse of waste PCB should be low. Obtaining this kind of low cost benefit is closely related to what kind of process technology is used in the process.
Recovery of metals from spent PCB
Recovery of metals in waste PCB by 2.1 dry method
Metal smelting in waste PCB is carried out by metal smelting process, and pretreatment shall be carried out before smelting. Its pretreatment uses the method of carbonization or pulverization to separate the metal and the electronic parts which are carried on the PCB. This disassembly, separation and screening project is relatively easy to carry out. The separation and screening of waste PCB components can be separated by their size and relative density. Can also be screened by electrostatic, magnetic, wind, and separation. But the main goal is to increase the recovery rate of metals. It should be noted that the use of dry distillation method will produce a certain amount of gas. There will be bromine flame retardants in these gases, so they need to be completely burned in the 2 burner. In order to prevent bromide from occurring in high combustion, the gas after combustion should be treated with cold water for rapid cooling. In the wastewater treatment facilities, we should pay special attention to the discharge of liquid to achieve the standard of non pollution.
After screening and separating, the metal content in the recovered product is raised and then processed into copper refining. The use of copper smelting method, the extraction process of waste copper component in PCB, is the first to waste PCB into self melting pot, and then through the converter, refining furnace for smelting, and the use of electrolytic copper extraction. The slag obtained in the smelting process contains a large amount of SiO2 in the glass fiber and is recycled as a raw material for adhesives, raw materials (fill materials), paving materials, etc..
For scrap metal recycling, the popular method is dry process. It is the first removal of the battery in the cell phone, and then the whole body of recycling and reuse.
Recovery of metals in waste PCB by 2.2 wet method
The recovery of metals from waste PCB by wet method is mainly applicable to the recovery and reuse of printed circuit boards and parts with high content of precious metals. An American invention patent (US Patent: 2713231) proposed that the acid solution be used to make the metal on PCB become ionized and dissolved, and then add alkali to precipitate silver so as to achieve the purpose of recovery. In the research on this aspect of the patent (Kaiping 9-324222), is proposed. In the waste PCB broken into inorganic acid and hydrogen peroxide in the mixed solution method, to get the soluble metal out of the. Other Japanese companies have recently developed a way to save energy by extracting metals from spent PCB. It uses the complexing agent to select the copper metal to realize its recovery (especially Kaiping 8-85736: thermosetting resin thermal decomposition method and device).
Separation of components in 2.3. waste PCB
In recent years, in addition to the metal recycling in waste PCB, research on the reuse of other components of PCB has also made considerable progress. Technical advances in this area are highlighted in the separation and purification of the recovered components. In the manufacture of PCB substrate material, in order to achieve high reliability and high interlayer adhesion of PCB, the resin binder is usually made of epoxy resin, phenolic resin and other thermosetting resins. In the thermosetting resin after curing, become insoluble polymer melt, which is caused by the separation of its removal and reuse difficult.
Removal of halogen components in 2.4. spent PCB
General electric products, household appliances and so on, in order to safety, and in the PCB resin added halogen, antimony compounds and other flame retardant. It is thought to be harmful to the environment and the human body. Therefore, the removal of halogen components from waste PCB has become an important research and development work in the recycling of waste PCB. The test results of foreign research departments show that in the desktop computer produced in 1990s, the bromine content of PCB is 9% (weight ratio of PCB weight of 100). PCB for television and office electronic products (OE) and so on (usually using phenolic paper based copper clad laminate as substrate), its bromine content accounts for 4.4% - 5.3%, and antimony content accounts for 0.4% - 0.9%.
The removal of waste halogen element PCB, removal is mainly present in the PCB as bromine flame retardant. Since 1960s, the world has begun to study the removal of halogen technology. Today, the removal of halogen is mainly to achieve the "harmless" of waste PCB recovery and reuse". The removal of halogens contained in PCB is the separation of halogen atoms from benzene rings on the benzene ring. In theory, the separation between chlorine atoms and benzene rings requires 916KJ/mol energy.