Research On Components Analysis And Treatment Methods Of Exhaust Gas During Heating And Dismantling Waste Printed Circuit Boards

With the high-speed development of electronic industry and continuous application of high and new technology, increasing numbers of electrical and electronic equipments are wasted which produce large numbers of waste PCB. When recovering waste PCB, the first process needed to be done is to heat and remove electronic elements which would produce a lot exhaust gases. These gases are harmful, toxic and cancerogenic and will cause secondary pollution without proper treatment before discharge.In order to determine the emission components in the process of heating and dismantling wasted printed circuit boards (PCB), the discharging gases were collected and analyzed by means of Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography-Mass Spectroscopy (GC-MS), Ion Chromatography (IC), Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) and X-ray Photoelectron Spectroscopy (XPS). The results showed that the wasted PCB produced phenol and other kinds of organic compounds following the breaking of O-C, C-C, C-Br bonds in brominated epoxy resins when being heated, and released large numbers of acid gases containing chemical elements such as S, N, Cl. It also released smoke dusts containing heavy metals such as Sn, Pb, Sb, Hg, Cd and Cr.A kind of exhaust gas treatment system was proposed for the process of heating and dismantling PCB. Heavy metal dusts, inorganic acid gases and organic gases were removed separately by adsorption, absorption and high temperature combustion. Using Aspen Plus to model the chemical process of exhaust gas treatment platform of recovering waste PCB. The results showed that absorption liquid flow should be linear with exhaust gas flow. To ensure the absorption tower’s treatment efficiency, absorption liquid flow should keep at least300mol/h, NaOH should keep at least8kg/h, the appropriate pressure of combustion equipment is1atm, the appropriate temperature is850℃, the appropriate excess air coefficient a is1.2.Using FLUENT to simulate the gas flow field of absorption tower, influencing factors including exhaust gas entrance velocity v, entrance inclination angle β and entrance eccentric distance P were studied. The result showed that when v=10m/s,β=0°, P=8cm, the velocity field of absorption tower was evenly distributed and it would be beneficial for the purification of exhaust gas.