STUDY OF HEAT AND MASS TRANSFER DURING FIRING
OF HEAT INSULATION OBJECTS BASED ON BURNT ROCKS
AND BEIDELLITE CLAY
V. Z. Abdrakhimov,
E. S. Abdrakhimova,
and V. K. Semenychev
Translated from Novye Ogneupory, No. 4, pp. 31 – 34, April 2011.
Original article submitted December 12, 2010.
Heat and mass transfer is studied during firing of ceramic heat insulation objects making it possible to monitor
firing taking account of a change in the effective thermal properties of an object, manufactured using burnt
rocks, in the temperature range of physicochemical transformations, and also to determine rational firing re
gimes. It is revealed that the least value for the coefficient of effective thermal conductivity for the material
corresponds to a temperature range within which the intensity of physicochemical processes is more signifi
Keywords: heat insulation objects, heat and mass transfer, coal ash slag, beidellite clay, firing, coefficient,
thermal conductivity, thermal diffusivity.
For the outer lining of a furnace it is desirable to use heat
insulation objects NK-23 (ShL-0.45) with an application
temperature of 1200°C (TU 15441-037-22298789–2007).
The size of objects is 250 ´ 120 ´ 65 mm, and the grade is
not lower than M150. Results are provided in this article for
a study of heat and mass transfer processes during firing if
heat insulation objects based on beidellite clay and burnt
rocks. Burnt rocks form in areas of shale recovery. Shales,
which during recovery are impossible to separate from
gangue are sent to a dump. In waste piles that combine stor
age of gangue and shales as a result of an increased amount
in dump mixes of organic compounds there is self-ignition,
which leads to formation of a considerable amount of waste,
i.e. burnt rock. Consequently, burnt rocks are a product of
low-temperature firing with self-burning of rock (mixture of
clay and shale) in spoil heaps in an oxidizing medium. The
amount of burnt rock in spoil heaps is from 75 to 90% of the
dump volume. The chemical composition of burnt rocks is
presented in Table 1.
Although they are a waste product burnt rocks are identi-
cal with respect to the chemical composition of aluminosili-
cate natural raw material, which makes it possible to use
them as a basic charge component in producing objects. In
contrast to clay components burnt rocks do not exhibit plas
ticity and binding capacity, and therefore materials based on
them require use of plastic components.
Burnt oxides have a high calcium and iron oxide content,
which gives rise to a relatively sintering temperature
(1050 – 1100°C) and also aluminum oxide, which leads to an
increase strength and frost resistance of objects. Consider
able losses during calcining promotes of objects of it from
within, since organics contained within the burning rocks
start to ignite.
The clay material used was beidellite clay of the
Obraztsov deposit of the Samara region. In refractoriness
Refractories and Industrial Ceramics Vol. 52, No. 2, July, 2011
1083-4877/11/05202-0133 © 2011 Springer Science+Business Media, Inc.
Samara Academy of State and Municipal Management, Samara,
TABLE 1. Component Chemical Composition
Oxide content, wt.%
CaO MgO R
Beidellite clay 54.38 19.46 8.52 1.75 1.82 2.73 1.82 8.42
Burnt rocks 39–40 12 – 13 7 – 8 19.0 – 19.5 0.5 – 1.0 0.5 – 1.0 6 – 7 14 – 15