Development of a method of accelerated drying of casting ladle linings

Abstract

Drying of the working layer of a lining is the final preparation operation and to a large extent if determines the service life and quality of a ladle lining [i-4]. About 80% of existing preparation operations are based on use of the combustion products of liquid or gaseous fuels as the energy carrier. This is related primarily to the accessibility of fuel sources and the relatively simple and reliable design of the equipment [i-4].Practical experience and service of drying equipment with fuel burners has revealed its primary disadvantages [2]: low efficiency in use of energy, which does not exceed 30% even with use of recuperator~ contamination of the atmosphere and working areas with the combustion products of fuel containing oxides of sulfur, nitrogen, and carbon and unfavorable working conditions in the zone of operation of the equipment as the result of increased temperatures.Preparation operations being developed and equipment being designed must be distinguished by high economy and ecological cleanliness. Therefore development of effective operations and equipment for drying the working layer of a lining requires more thorough study of the physicochemical processes occurring in removal of moisture from refractories. The overwhelming majority of present methods of drying linings are based on delivery of heat to the outer surface of the working layer. In this case the flow of heat and the flow of moisture being removed are directed opposite to one another. The temperature gradient causes high resistance to removal of water vapor, directing most of the moisture into the depth of the lining toward the ladle shell.This creates unfavorable conditions for removal of moisture and requires a greater consumption of energy for final drying of the lining. Intense supply of heat leads to development of thermal defects both on the surface and in the depth of the lining (crumbling, cracks). Defects occur as the result of the increasing steam pressure caused by intense supply of heat. In addition, the heat flow prevents removal of moisture through the surface of the working layer lining. In the final analysis this leads to a reduction of lining life.For the purpose of reducing thermal defects a number of investigators have developed less severe methods for drying of linings with controlled fuel supply [i, 3, 4]. The addition of elements promoting heat exchange between the gas flow and the lining also improves the thermal energy characteristics of the process somewhat.The elements include inserts in the cavity of the ladle distributing the flow of combustion products and increasing the length of contact of the heat carrier and the lining [3,4]. The measures adopted made it possible to reduce fuel consumption and increase the efficiency of energy utilization.However, the basic discrepancy, countermovement of the heat flow and the energy flow, is not eliminated by these measures, in addition, the elements inserted complicate the design of the drying equipment.In [2] the use of electric heating elements of current-conducting ...