Vacuum Pyrolysis Mechanism Of Liquid Crystal And Carbon Control For Recycling Indium By Self-reduction From Scrap LCD Panels

This thesis provided a review on recent research progress of the recycling technologies of scrap liquid crystal display panels at home and abroad.Based on the environmental friendliness and large-scale industrialized application,an integrated scrap LCD panels treatment process mainly including mechanical stripping and vacuum pyrolysis self-reduction was proposed.The law of thermal weight loss of stripping product of scrap LCD panels was studied under vacuum and nitrogen environment.By comparing the kinetics of vacuum and nitrogen pyrolysis,vacuum pyrolysis was selected to treat the stripping product.The experiments were conducted under conditions with ultimate temperature ranging from 300 to800℃,system pressure ranging from 20 to 10~5 Pa and holding time ranging from 5 to 30 min in the vacuum pyrolysis equipment designed by ourselves.The optimized parameters were determined as 500℃,20 Pa and 15 min,at which the conversion rate of liquid crystal was 89.10%and the content of indium in residue was 14.18%.By analyzing the composition of vacuum pyrolysis products,the vacuum pyrolysis mechanism of liquid crystal was proposed.By comparing several common adsorbents,13X Molecular sieve was selected to be added into stripping products as an adsorbent before the experiments.The experiments were conducted under conditions with particle size of molecular sieve ranging from<0.3 to>0.8 nm,ultimate temperature ranging from 300 to 700℃,system pressure ranging from 20to 10~5 Pa and additive amount ranging from 10 to 50%.Combining the reaction parameters of vacuum pyrolysis and vacuum carbon reduction,the optimized parameters were determined as 500℃,20 Pa,particle size of<0.3 nm,additive amount of 30%and holding time of 15 min,at which unit quality carbon content was 257.1 mg/g which was increased by nearly20%compared with that of pyrolysis without additive of molecular sieve.According to the characterization of FTIR and SEM,the property and formation of carbon in molecular sieve were deduced.The recovery rate of indium could reach up to 86%by vacuum pyrolysis self-reduction of stripping product.According to the present research,an integrated scrap LCD panel treatment process based on mechanical stripping and vacuum pyrolysis self-reduction was proposed,through which each component of scrap LCD panel could be recovered.Therefore,the process was environmental friendly,efficiency and appropriate for large-scale industrial application,which could realize the reclamation and harmless treatment of scrap LCD panels.