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Preliminary survey of the master's work
Kulikovskaya Olga
Theme of master's work:
Production of heat-isolation materials using resources of Donbass
Leader of work: Professor Nikolai Belomerya
INTRODUCTION
Now the big attention is paid to questions of energy saving. One of such directions is the use of building materials with heat-insulating properties. Claydite is widely used as heat-insulating material for making light concretes and heatfillers.
Claydite is a porous granular material of a cellular structure which was received by bloating of clay raw materials while burning them.
The basic condition of claydite production is bloating of clay raw materials while burning them with formation of the liquor viscous enough for rather wide temperature range during intensive gas emission.
Difficult physical and chemical processes take place in clay material while burning on different temperature range: dehydration, burning-out of organic admixtures, influence of different components of clay on each other; oxidation-reduction reaction and other processes that cause gas emission, formation of liquor, softening of a material. At fast rate of burning the temperature intervals offset and move in the range of high temperature that enables to combine process of gasification with a softening of a material and achievement of the certain viscosity at which bloating of clay occurs. Thus it is important, that by the moment of intensive gas emission there has taken place a sintering of the superficial layer of granules with formation of the closed pores. Otherwise gases easily release through a layer of a material, not bloating it.
Ferric oxides and organic admixtures (carbon) play a great role in the processes of gasification. The most typical reactions:
6Fe2O3 → Fe3O4 + O2↑
2H2O + C → CO2 ↑ + 2 H2↑
V1 – volume of absolutely dry raw product,
V2 – volume of bloating mass.
According to the degree of bloating we can distinguish poorly-, middle-, and well-bloating clay rocks with the coefficient of bloating accordingly not less than 2,5, between 2,5 and 4,5 and above 4,5.
EXPERIMENTAL
The aim of the work is to receive the heat-insulating material called claydite using the technogenic products by recycling the waste of coal output, coal-cleaning, overburden clay rocks, etc.
Materials used in work had been preliminary dried up and crushed before they passed through a sieve 05.
Originally we tested waste rocks and slime of coal-cleaning. From these materials samples in the form of cylinders in diameter 15мм and by height 15мм were formed, which were burnt in electric muffler with cilite heaters up to temperatures (1000, 1100, 1200) оС. We didn’t observe bloating of samples at these temperatures. Therefore we prepared number of mixed materials with introduction of different additions to their composition, such as pyrite drosses and ferric oxides in quantity according to 10,15,20 (mas.%) and 3,5,9 (mas.%). The experiment was repeated at the same temperatures. Bloating of samples was insignificant. This can be explained by the fact than an insufficient quantity glassy phase occurs at burning and gaseous products easily leave a granule, practically not bloating it.
After conducting number of experiments we decided to add clay raw materials (Kramatorsk clay) to the composition. The clay that was added into mixed material, contained waste of coal-cleaning as in the previous experiments this material had given us the best bloating, than the waste rock. The added quantity of clay in mixed material was 20 – 90 (mas. %). Addition of clay increased bloating up to 80 – 90 (mas. %).
Thus a fusible clay is a basis for obtaining of claydite with the use of wastes of coal-cleaning.
On the basis of the received data it has been solved, that the subsequent researches should be conducted on selection of clay material which would provide the best bloating.