The use of oxygen in the calcination of limestone was investigated by the authors on rotary kilns at the Krivoi Rog Metallurgical Plant. The length of the kilns is 75 m, the (outside) diameter 3.6 m, and the angle of inclination 3.5 ~ The kiln installation includes a cooler, a waste-heat boiler, cyclones, electrostatic dust precipitators, a flue gas fan, and a 60-m-tall chimney. The kilns are fired by natural gas with a combustion heat of 8390 kcaI/m 3 and a pressure of 2.5-3 arm.*The end wall of the pull-back kiln head contains openings through which single-bore single-type burners with tapered nozzles are introduced into the working space of the kiln. The burners (Fig.

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At the Krivorozhstal' Factory the life,of the brick lining of the 150-ton steel-teeming ladles of the converter shQp is 19.O meltings, ~and that of the 330-ton ladles of the openhearth shop is 22.4~eltings.The specific consumption of ladle brick is fairly high (6.0-6.5 kg/ton of steel).Guniting is a promising and relatively easy way of enhancing the resistance of the ladle lining, reducing the consumption of ladle brick.Work on guniting of the steel-teeming ladle linings has been performed at this factory since 1974.In the open-hearth shop, the ladles are gunited by hand by means of an SB-67 (BM-60) guniter.In 1975, there was put into service in No. 2 converter shop a machine for mechanized guniting of the lining of 150-ton steel-teeming ladles [i], and 1977 saw the introduction of a machine which permitted guniting not only of the lateral surfaces of the ladle but also the bottom.The trend of the work on guniting has been selection of masses exhibiting operational stability, and refinement of the guniting procedure.It was established If] that guniting masses based on Chasov-Yar semiloamy sand, quartzite, and ordinary chamotte (A1203 content less than 32%) exhibit enhanced wear during service.Furthermore, when guniting is performed with quartzite masses, the personnel must be protected from the effect of finely dispersed silica particles.Despite the fact that masses based on Chasov-Yar sand are readily available and cheap, they have not been widely used, for the following reasons.To increase the life of a steelteeming ladle lining by from three to five meltings, we must deposit a gunite layer 110-120 mm thick [i]. However, layers of this thickness often slide during deposition, and their quality is poor.If the layer is thinner, to attain the above increase in the service life we must enhance the guniting frequency; this is not always possible, because it entails a reduction ~in the number of ladles in service. Chasov-Yar sands are nonuniform in both chemical composition and quality; this also reduces the life of gunned layers based on them.Chamotte masses are the most suitable for guniting.The quality of the guniting masses is improved by enhancing their aluminum oxide content [i, 2].