Most of the concrete used in the construction of

Chapter 5, Problem 5.44

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Most of the concrete used in the construction of buildings, roads, dams, and bridges is made from portland cement, a substance obtained by pulverizing the hard, granular residue (clinker) from the roasting of a mixture of clay and limestone and adding other materials to modify the setting properties of the cement and the mechanical properties of the concrete. The charge to a portland cement rotary kiln contains 17% of a dried building clay (72 wt% SiOz, 16% Ah03, 7% Fe203, 1.7% K20, 3.3% NazO) and 83% limestone (95 wt% CaC03, 5% impurities). When the solid temperature reaches about 900C, calcination of the limestone to lime (CaO) and carbon dioxide occurs. As the temperature continues to rise to about 1450C, the lime reacts with the minerals in the clay to form such compounds as 3 CaOSiOz, 3 CaOAh03, and 4 CaO . Ah03 . Fe203. The flow rate of COz from the kiln is 1350 mJ/h at 1000C and 1 atm. Calculate the feed rates of clay and limestone (kg/h) and the weight percent of Fe203 in the final cement.