Recycle Of Waste Unglazed Porcelain Tile

Waste ceramic is a kind of common ceramic waster sintered at high temperature, whichis generated during production of ceramics and also a precious resource that can be reused. Itis beneficial for cost saving, environmental protection and sustainable development ofceramic industry if the waste ceramic can be recycled into porcelain tile productions.In this thesis, physical and chemical properties of waste unglazed porcelain powder wereanalyzed, and basic formula of slurry that no waste porcelain powder was prepared throughorthogonal experiment, on this basis, different content, fineness and chemical composition ofwaste porcelain powder were used to replace sand and gravel raw material in basic formula,the effects of waste porcelain powder on slurry properties and sintering behavior, mechanicalproperties, and microstructures of porcelain tile specimens were investigated. In addition, bigsize porcelain specimens were conducted on line for preliminary test of feasibility ofproduction.The XRD, SEM, and DTA-TG analysis indicate that the main phases of waste porcelainpowder include mullite, quartz and glass phase, and the waste porcelain powder has anirregular and sharp-edged microstructure, and besides, it has a good thermal stability that nonoticeable chemical changes during calcination.The effect of solid concentration, deflocculant content, CMC content and pH value onthe fluidity and stability of basic formula of slurry were investigated through orthogonalexperiment. Combined with the actual production, the suitable parameters for the slurrypreparation was determined as follows: solid concentration was68%, deflocculant contentwas0.2%, and CMC content was0.03%.0wt%，10wt%,20wt%,30wt%,40wt%,50wt%, and60wt%of waste porcelainpowder was substituted for the sand and gravel raw material in basic formula, respectively.The effect of waste porcelain powder content on slurry properties was studied, and the resultsshowed that sieve residue and fluidity of the slurry increased with increasing content of thewaste porcelain powder, whereas the thixotropy of the slurry decreased. The slurry withdifferent content of waste porcelain powder showed shear thinning behaviour as thepseudoplastic fluid. Green specimens were prepared from the slurry above, and tests on the green propertiesshowed that the bending strength and density of green compacts both decreased graduallywith increasing content of the waste porcelain powder, which resulting in the lower sinteringproperties.The result of bending strength of sintered specimens and capacity of resistance to hightemperature deformation testing indicated that the strength of specimens sintered at differenttemperature was an increasing trend as a whole, and the capacity of specimens to resistdeformation at high temperature increased with increasing content of waste porcelain powder.The optimum sintering temperature of1180℃was selected based on all kinds ofproperties above. The SEM observation of specimens sintered at1180℃showed that theamounts of mullite crystal increased with the increasing content of waste porcelain powder inraw materials, and the mullite grains had grown in size during densification.Two kinds of green specimens, one preparated with “bottom material” that contained thewaste porcelain powder and the other preparated with “bottom material” and “surfacematerial” gained from factory that without waste porcelain powder, were sintered in roller kiln,and the results showed that the former specimens sintered at high temperature had a darkcolor, and the shrinkage increased from8.0%to10.7%while the content of waste porcelainpowder in “bottom material” increased from0%to60%, the color of the latter specimenssintered at high temperature depended on “surface material”, and the shrinkage increasedfrom8.0%to9.1%while the content of waste porcelain powder in “bottom material”increased from0%to60%. Other various indexes of the porcelain tile specimens were goodand met the requirements of porcelain tile quality tests.Finally, considering the complexity of waste porcelain sources and its powered process,we analysed the effects of different fineness and chemical composition of waste porcelainpowder on the properties of procelain specimens. The results indicated that the fineness ofwaste porcelain powder had a greater influence on properties of porcelain specimens than thechemical composition, and the smaller waste porcelain powder would accelerate thedensification of green compacts.