Experimental Study On The Heat Transfer And Product Characteristics Of Wasted Printed Circuit Boards Pyrolyzed In Moving Bed Furnace

With the increasing demand for electronic products and purchasing power,E-waste is rapidly generated in worldwide.As a core component of E-waste,printed circuit boards(PCBs)are produced in large quantities and need to be processed and recycled in a scientific and efficient way.The pyrolysis treatment has low requirements on equipment and low secondary pollution.Currently,many studies have been done on the treatment of waste PCBs by pyrolysis.Most of them are focused on the pyrolysis mechanism of PCBs,and some of pyrolysis experiments are conducted in fixed beds,rotary kiln or other closed containers.There are few studies on waste PCBs pyrolyzed in moving beds furnace.In this paper,the moving bed furnace was used to pyrolyze PCBs under the condition of countercurrent heat transfer between high temperature nitrogen and PCBs particles.The temperature and pressure distribution characteristics in the furnace are studied under different pyrolysis conditions.The pyrolysis oil was tested and analyzed.The results show that the temperature of PCBs particles layer at the bottom of furnace is less affected by feed rate.Increasing the feed rate of PCBs particles reduces the temperature at each position in the furnace,and the main heat exchange position of the PCBs particles and nitrogen migrates down in the furnace.The temperature and temperature gradient of each position in the furnace will increase with the increase of the nitrogen inlet temperature.The main heat exchange position will migrate to the upper part of the furnace as the temperature of the nitrogen flow increases.At a nitrogen temperature of 350°C,a flow rate of 9.5Nm~3/h,and a feed rate of 1.5kg/h,the energy consumption of unit mass PCBs for pyrolysis is 2.75 MJ/kg,which is more than that of pyrolysis in fixed bed furnace by 37.5%.The pressure data indicates that the main heat exchange position in the furnace is located in 1/2-3/4 of the height of PCB particles.The temperature range of this section is 240-350°C.The most ingredients of pyrolysis oil are phenol,4,1-dimethylphenol and 4,4'-(1-methylindenyl)-bisphenol.The content of phenol is significantly negatively correlated with the inlet temperature and feed rate,while the ratio of p-Hydroxybiphenyl and 3,4-dimethyl-benzofuran-propanol are positively correlated with the inlet temperature and feed rate.