ADVANTAGE OF HEAT INSULATION MADE OF MATERIALS
WITH NATURAL POROSITY
A. V. Belyakov
and S. É. Ivanov
Translated from Novye Ogneupory, No. 7, pp. 41 – 44, July 2008.
Original article submitted April 21, 2008.
Various heat insulation materials produced at home and abroad are compared. The advantage of using natural
nano-structured materials is substantiated.
Under contemporary economic conditions in order to
provide competitiveness domestic metallurgical enterprises
need to increase the production efficiency by reducing
energy consumption, increasing the service life of heating
units, and reducing specific consumption for output of
finished product. Here the main effect is achieved as a result
of improving lining operating conditions, both as a result of
creating new forms of heat insulation and refractory
materials, and expansion of their characteristics and standard
Use of natural porous materials undoubtedly has a
number of advantages: the preparation process of manu-
facturing the final objects is simplified due to the absence of
complex preparatory operations for pore formation; the
strength of the objects obtained is higher due to higher
strength of the matrix material, uniform pore distribution and
correspondingly uniform distribution of mechanical loads.
From many publications on heat transfer it is well known
that at high temperature the heat insulation effect depends
not only and (not so much) on the number of pores, but also
on their size, structure and distribution throughout the
volume of a material. Results of research carried out by
specialists of OOO MMK and OOO RTPK and the work of
O. M. Gladkov (MGOU) have shown that at above 900°C it
is best to use heat insulating materials having pores with a
size of 10 mm (Fig. 1) . Depending on the aggregate state
of a substance and features of thermal energy transferred by
it a conditional series of bodies for their value of thermal
conductivity (as it increases) has the following form: gases –
polymers – liquids – amorphous substances – crystalline
substances – metals.
Since all heat insulation objects, or material comprising
them, are as a rule heterogeneous porous bodies, then the
effect of thermal conductivity of these systems is determined
by the thermal conductivity of the solid and gas phases. It is
undoubted that with an increase in gas phase or porosity the
thermal conductivity of the system decreases. This feature is
explained by the fact that pores, forming new surfaces in a
dense structure, become dissipation centers. Here there is a
reduction in the average of free travel of particles and the
phonon thermal conductivity of the system decreases [2, 3].
Due to presence of a considerable number of pores with a
size of less than 1 mm in the mass of a shell of amorphous
character (Fig. 2) use of such a natural material as diatomite
makes it possible to prepare highly efficient heat insulation
materials. In thermal conductivity parameter it wins consi-
derably compared with other traditional heat insulation
materials. The small size of diatomite pores and the greater
number of them with equal density provides better heat
insulation. Objects made of diatomite are distinguished by
low thermal conductivity, high strength and chemical resis
tance. Results are given below for testing objects grade
KPD-5000 in the SINTEF laboratory (Norway). The mate
rials, used in electrolyzers for melting primary aluminum,
during operation are subject to different corrosive agents.
Therefore for all materials there was testing simulating
Refractories and Industrial Ceramics Vol. 49, No. 4, 2008
1083-4877/08/4904-0300 © 2008 Springer Science+Business Media, Inc.
D. I. Mendeleev RKhTU, OOO Diatomovyi Kombinat, Russia.
Fig. 1. Thermal conductivity of gases in relation to pore diameter.