High Temperature Pyrolysis Research Of Waste Liquid Crystal Display Panel

With the development of science and technology, more and more electronic productswith LCD glass has been scrapped, and LCD (Liquid Crystal Display) glass has becomethe most representative electronic waste, which is a serious threat to environment safety.So recycling and disposing the waste LCD glass is an urgent task. In the whole process ofrecycling of the LCD glass, removing and recovering the organic parts is the first step withimportant significance. By far, many disposing technologies have been studied anddeveloped：immersed into acetone, thermal shock and combustion.However, some obviousdisadvantages are together with these methods:(a) acetone has very strong toxicity, andeasy to cause the second environmental pollution;(b) the processing efficiency of the firstand second method is very low;(c) the method of combustion will give off a lot ofharmful gases, leading to serious environmental pollution. This study proposed a pyrolysisprocess to recover the organic parts from LCD glass.Firstly, through the thermal gravimetric analysis (TGA), the weight loss situationduring the whole pyrolysis process of the LCD glass was investigated clearly. Then, liquidcrystal, PVA, TAC, TPP and PET, which are the raw materials of the LCD, have beenresearched by the TGA, too. Pyrolysis of the LCD glass reacted violently at thetemperature from570K to650K, and the pyrolysis temperature could be chosen at850K,85.1wt%of the organic parts can be removed by pyrolysis. Through the DTA curves ofthe raw materials, several results can be obtained:(a) the temperature of complete pyrolysis of TPP and liquid crystal is lower, respectively550K and600K.(b) Afterpyrolysis, PVA, TAC and PET would leave some residue while the mass loss rate of liquidcrystal and TPP reached100wt%.Pyrolysis experiment was conducted in the homemade pyrolysis device in850K, andthe pyrolysis products contain liquid oil products, gaseous products and glasses with alittle residue. The oils reached8.99wt%and the gases reached2.83wt%and the removalrate of organic parts reached87.87wt%, which decomposed into66.82wt%oils and21.05wt%gases. The weight of the residue had reached12.13wt%. Then, GC-MS wasused to analyze the pyrolysis products of the LCD glass. The composition of oils was verycomplex and the types up to37. The proportion of acetic acid and triphenyl phosphate washighest in the oils,46.27wt%and32.94wt%respectively. The pyrolysis mechanisms andproducts sources of the liquid crystal glass have been analyzed based on the informationof bonds energy. The pyrolysis mechanism analysis proved that the products mainlyconsisted of acetic acid, triphenyl phosphate and C, which is consistent to the results ofGC-MS analysis.As the estimation result showed, the revenues after accounting for energy costs canbe about$142.48/t according to the market quotation in China.Therefore, pyrolysis process have removed and recovered the liquid crystal and filmsfrom the LCD glass successfully. This recovery technology, featuring simple operation,high removal rate, satisfactory recovery effect, no secondary pollution and good economicbenefits, may be a great choice to solve the problem of removing and recovering theorganic parts of waste LCD glass.