ESTUDO DA VIABILIDADE DO USO DE LAMA DE CAL PROVENIENTE DA INDÚSTRIA DE PAPEL EM MASSA CERÂMICA

Abstract

One of the main solid wastes generated by the paper and cellulose industries is lime sludge. This waste is generated during the production of cellulose and paper made by the process known as alkaline pulping or Kraft. This waste is usually destined for industrial landfills causing a high economic cost and a great environmental impact. Some studies show that it is possible to minimize this impact using this residue in the production of ceramic materials. Therefore, the incorporation of this waste as raw material for the ceramic industry, besides giving a correct destination and recycling to the waste, also reduces the extraction of raw materials from the environment, avoiding the degradation of native areas. Thus, the present study had as objective to verify the feasibility of the use of lime sludge residue in the production of porcelain ceramic bodies. Initially the residue and the raw materials were physically and chemically characterized. The compositions were then prepared with different amounts of added residue (5, 10, 15 and 20%). The specimens formed by uniaxial pressing were sintered at temperatures of 1000oC, 1050oC and 1100oC, with a two hours threshold. The characterization of the sintered bodies was made by measurements of apparent density, apparent porosity, water absorption and flexural strength and by X - ray diffraction analysis and scanning electron microscopy. The results showed that the residue is predominantly composed of calcium carbonate, which is decomposed in CaO and CO2 during the sintering process. In sintering, the presence of CaO changes the reactions and transformations, providing the formation of the crystalline phases anorthite and wollastonite, when more than 10% of lime sludge residue is added. Increasing the amount of residue increases the water absorption, the apparent porosity and decreases the mechanical strength at the sintering temperature of 1100oC. At the sintering temperature of 1000oC, the compositions with residue present higher mechanical strength. Thus, it can be concluded that incorporation of lime sludge residue into the white porcelain ceramic mass is feasible, without significantly altering its properties, in acceptable amounts between 5 and 10% and sintering of 1050°C.