Improvement of the Chrome Electrocorundum Production Process Based on Determination of the Material and Heat Balances of Furnaces at the Yurga Abrasive Plant (YuAZ)
Abstract Generated abstract
This paper analyzes the production of chromium electrocorundum in electric arc furnaces at the Yurga Abrasives Plant through measured material and heat balances. It identifies causes of chemical heterogeneity and material loss, including imperfect charge preparation, segregation during transport and loading, nonuniform furnace temperature, garnisage formation, and dust entrainment to electrostatic precipitators. The heat balance shows that useful heat for heating and melting the charge accounts for about 68 to 70 percent, while major losses occur with exhaust gases, cooling water, and the short electrical network. The authors propose process improvements such as agglomerating the charge, reducing garnisage and dust carryover, controlling air infiltration and cooling water supply, and using exhaust-gas heat for charge preheating.
Full Text
IMPROVING THE PRODUCTION PROCESS OF CHROMIUM ELECTROCORUNDUM BASED ON MEASURING THE MATERIAL AND HEAT BALANCES OF FURNACES AT THE YURGA ABRASIVES PLANT (YuAZ)
A. S. Bogma, I. P. Chashchin, N. A. Tikhonokova,
N. I. Poddubnyak, L. V. Sokolov
(Presented by the scientific-methodological seminar of KhTF)
The process of producing chromium electrocorundum consists in creating conditions for melting the charge, for the phase transition of the γ-form of aluminum oxide into the α-form, and for the processes of crystallization and formation of a solid solution between the main components: aluminum oxide and chromium oxide. At YuAZ, the charge mixture (alumina, chromium oxide, and return dust from electrostatic precipitators) is fed into electric arc furnaces in a finely ground state. The charge is supplied (block melting) in batches until the entire furnace volume is filled with melt.
The measurement and analysis of the material and heat balances of chromium electrocorundum melts at YuAZ made it possible to study the process in greater detail and to identify further ways of intensifying it.
It was established that chromium electrocorundum in the block is noticeably heterogeneous in chemical composition. This is explained primarily by the imperfect method of preparing the charge and by its segregation during transport and loading into the furnace. Another source of compositional heterogeneity in the block is the furnace design, since the temperature distribution over the furnace cross-section is nonuniform. Therefore the charge located near the furnace walls does not melt completely, forming a wall-adjacent layer—garnisage.
The results of the material balance showed that losses (4.5–5.0%) are due mainly to two causes: the formation of garnisage, which crumbles during cooling of the block, and the large entrainment of charge with the gases going to the electrostatic precipitators.
The principal measures for reducing material losses may be: agglomeration of the raw-material mixture before loading into the furnace, reducing the thickness of the garnisage to a minimum, reducing dust carryover by adjusting the operation of the smoke exhausters, and carefully monitoring the operation of the electrostatic precipitators.
The heat balance of the furnace was compiled for the period during which it was under electrical load (23–25 h). The heat balance of the furnace showed that the main item of heat input is the input from electric power. During melting, about 6% of the heat is released by combustion of the carbon of the electrodes and heater, and about 5% of the heat is released during crystallization of chromium electrocorundum.
Useful heat expenditures (heating and melting of the charge) amount to 68–70%. The main items of heat loss are losses with the gases going to the electrostatic precipitator, with the cooling water, and losses
for heating the short electrical network (from the transformer to the furnace).
Reduction of heat losses is possible by decreasing air infiltration into the furnace, using the heat of the exhaust gases to heat the charge before it is loaded into the furnace, regulating the supply of cooling water to the roof and to the furnace shell depending on the extent to which the working volume of the furnace is filled with charge, and establishing the necessary monitoring of the chromium electrocorundum melting process.
The measures outlined on the basis of an analysis of the furnace material and heat balances for improving the production process of chromium electrocorundum at YuAZ have been accepted for implementation.