The formation of a given phosphate depends not only on the composition of the melt but also on the rate of cooling. The further cooling of the remanent melt depleted of high-melting oxides results in the formation of more mixed orthophosphates; when cooled rapidly (quenched) a melt containing an adequate proportion of SiO 2 is converted to the glass phase. In long-term firing (over 20 h) at 1600~ or higher the sodium ions are volatilized out of the melt. The complete vaporization of the sodium and the crystallization of the liquid phase are followed by the formation of mixed calcium and magnesium orthophosphates, e.g., Ca3Mg3(PO4) 4. A further increase in the firing temperature and time results in the gradual volatilization of the P205 from the phosphate bond until the latter is completely decomposed.
LITERATURECITED
The service life of refractories in a blast-furnace stack is 3.5-4 years, whereas in the hearth and hearth bottom it is from 10 to 12 years [1]. This means that an increase in the period between stack repairs is an urgent problem which requires a tLmely solution.The durability of the stack lining depends on the composition of the primary slags, the amount of alkalies and zincite in the blast-furnace charge, the composition of the gaseous medium, the abrasive wear by the charge, the thermal stresses, and the conditions under which the furnace is operated, its design, and other factors [2].The specific influence exerted by each of these factors on the durability of the lining differs from one factory to another. This complicates the creation of a universal refractory with all the necessary properties and makes it difficult to establish the most important characteristics governing the stability of artifacts during service. For this reason, there is no agreement concerning the selection of refractories for blastfurnace stacks; however, laboratory and factory investigations have shown that compact kaolin refractories with an A1203 content of 42-45% are promising materials for the lining of the cooled part of the stack.Compact kaolin artifacts with a porosity of less than 12% are being manufactured at the Zaporozhe Refractory Works and the Chasov Yar Refractory Artifact Works, and chamotte artifacts with a porosity of
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.