Valorization of High-Carbon Fly Ash and Spent Sand as Raw Materials in the Portland Cement Clinker Manufacture

摘要

Subject of this paper is to investigate the effect of two types of alternative raw materials on Portland clinker formation: high-carbon fly ash and spent sand. The alternative raw materials had several peculiarities such as, the glass content of fly ash was 46.5% with high amounts of unburnt carbon( ca.13%) while the spent sand was characterized by fine grains, the volume of particles smaller than 45 microns being 60%. The typical raw mixture (containing limestone, marl and pyrite cinder) and that containing 12.94% fly ash and 7.17% spent sand as marl replacement material were burnt in a muffle furnace and then analyzed by X-ray diffraction to observe the obtained phases. The effect of alternative raw materials was studied by means of optical microscopy, X-ray diffraction and mercury intrusion porosimetry. Besides these analyses the rate of free lime consumption during the sintering of raw meals were measured. The chemical composition of the two clinkers was performed, too. The presence of high-carbon fly ash as raw material promotes the binding of free lime, especially in the temperature range 1300 and 1370 oC. It also favors formation of alite and belite at lower temperatures.Physical and mechanical properties of cement obtained by grinding clinkers with gypsum up to fineness about 3600 cm2/g were determined and evaluated in according with EN 197-1 specification. The both cements complied with all requirements established by EN 197-1.By using the fly ash with 13% C content and fine spent sand into clinker manufacture is possible to reduce the sinterig temperature of the raw meal by 80oC. The unburned carbon from fly ash could be save nearly 16% of total fuel energy.