| CaO has high melting temperature and does not pollute the molten steel.Moreover, the chemical reaction between CaO and S or P is easy to occur. Therefore,CaO is widely used as desulfurating or slagging agent in ferrous metallurgy. As CaOis easy to suck up moisture, the store and transportation of CaO are limited due to itsdeliquescence in the air. Hence, it is very important to research how to improve thehydration resistance of CaO. In this research, the effects of carbonating temperatureand time on microstructure, rate of live weight growth and hydration resistance ofCaO by scanning electron microscope (SEM), X-ray Diffractometer (XRD) andexperiment of hydration resistance. The Carbonating mechanism has been discussedand the reasonable carbonating process of CaO was obtained..CaO powder is carbonated at the temperature of300℃,400℃,500℃,600℃,700℃and800℃for time5min,15min and30min, respectively. The experimentalresults have shown that the CaO powder after carbornated contains a small amount ofCaCO3, which belongs to porous particles material since it is incompact,incondensable and high porosity. At the same carbonating time, the amount of CaCO3rises with the increase of temperature, however, the amount of CaCO3in the CaOpowder carbonated at800℃is almost the same with that of CaO powder withoutcarbonation.At the same carbonation time, the rate of live weight growth of CaO increasesfirstly, and then decreases with temperature heightening. CaO has the largest liveweight growth rate11.499%when it was carbonated at700℃for30min. At the samecarbonation temperature, the rate of live weight growth of CaO rises as the timeprolong. The influence of temperature on carbonation reaction is larger than that oftime.With the temperature increasing, the volume density of CaO powder aftercarbonation enhances firstly, and then decreases, but the change of the porous ratio ofthe above CaO is opposite to that of volume density. CaO has the largest volume density of1.716g/cm3and the lowest porosity ratio of33.358%when CaO powderwas carbonated at700℃for30min.The experimental results of hydration resistance of CaO carbonated under thenormal pressure and temperature (NPT) have shown that the lower the carbonationtemperature is, the earlier the pulverization phenomena is; the shorter the carbonationtime is, the easier the pulverization phenomena is, the hydration resistance effects ofCaO powder carbonated at700℃for15min have no difference from that of betweenfor30min. Small cracks of CaO surface caused by the expansion were observed in theCaO powder. The experimental results of hydration resistance of CaO carbonatedunder the normal pressure and temperature (NPT) have shown that the majorconclusions are drawn as follows: the lower the carbonation temperature is, the earlierthe pulverization phenomena is; the shorter the carbonation time is, the easier thepulverization phenomena is.The experimental results of hydration resistance of CaO carbonated under theconstant temperature and humidity have shown that when the temperature is less than700℃, pulverization degree decreases with the temperature rising. The bigger CaOparticles caused by hydration expansion and slight pulverization were found in theCaO powder carbonated at700℃for15min and30min.In summary, when the carbonation temperature is700℃, hydration resistanceeffect of CaO powder is the best. Considering the economic benefits, the optimizedcarbonation process parametes is700℃for15min.The CaO powder carbonated by the optimized carbonation process was appliedin Helilai limited company and the results have shown that the above CaO powderhas remarkable desulfurization effect and there is no harmful gases produced duringthe use. |
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