TWO PROBLEMS IN REFRACTORY HEAT TREATMENT
N. A. Tyutin
Translated from Novye Ogneupory, No. 4, pp. 106 – 108, April, 2009.
Original article submitted February 5, 2009.
The various forms of refractory heat treatment are considered: drying, initial firing, and heat treatment proper.
It is possible to mechanize the treatment completely starting with the molded refractories in ring tunnel ovens
with single-row shrinkers. There is a discussion of stages and causes for unsatisfactory working in Russian
ultrahigh-temperature shaft ovens for making superdense products from magnesium oxide.
Keywords: heat treatment, drying, initial firing, heat treatment proper, ring tunnel furnace, shaft furnace.
There are three distinct heat-treatment processes in the
current production of refractories: drying, initial heating, and
heat treatment proper. The first two are traditional aspects,
while the last has appeared relatively recently in the produc-
tion of refractories with special properties, in particular ones
Drying is the removal of water, while initial firing pro-
duces the required properties and stabilizes the geometry,
while the heat treatment proper produces the final properties
of the product. All the processes are conducted in the temper-
ature pattern of a circulating working body, which consists of
the combustion products from hydrocarbon fuel, as mixed
with air, or gas mixtures of special composition, and air.
The heat treatment is given by changing the thermal state
(enthalpy) in the temperature pattern of the working body.
The decisive processes in the heat treatment are the heat and
mass exchange between the product and the working body,
whose roles vary in the different stages. In drying, the deci
sive process is mass exchange, while on preliminary firing it
is heat exchange, and in heat treatment proper both heat and
mass exchange are involved. In these processes, the proper
ties of the finished product are generated or else those of a
semifinished product for subsequent processing.
The three processes are characterized by individual
modes of treatment which are based on the dependence of
the temperature and concentration patterns in the product or
working body on time and the specifications for the compo
sition of the latter. The modes of treatment are determined by
the physicochemical nature of the product, but the heat-treat
ment method, the geometrical parameters of the product, and
the design of the oven have substantial effects on the inten
sity, energy consumption, and product quality.
The three processes are conducted in heat-technology
plant (HTP) termed dryers and ovens. Current HTP are fairly
complicated systems consisting of reactors in the form of
drying or oven chambers; transport facilities; energy supply
systems; facilities ensuring industrial and ecological safety
and process control. The main element in any HTP is the re-
actor, where the process is conducted with heat and mass ex-
change between the product and the working body.
At this organization in the half-century of its existence
we have dealt with a wide range of HTP for treating powder
and molded refractories. The HTP developments have taken
two lines for traditional and new forms of heat treatment. In
the development of HTP for traditional forms, much use has
been made of experience in operating existing plant with the
improvement of individual components and the plant as a
whole. In the development of HTP for new forms of product
treatment, a vigorous search has been made for solutions for
the reactors in drafts and design developments.
Out of all the treatment problems that institute has han
dled, two have not been resolved. The first is to obtain com
plete mechanization of the treatment, and the second is to de
velop an ultrahigh-temperature shaft furnace for making
superdense products from magnesium oxide.
Complete mechanization has been achieved without par
ticular difficulty in the technology of handling powder prod
ucts. In the technology of making molded products (items),
complete mechanization has been possible only in the pro
duction of components of simple shape using saggers of one
particular style of standard dimensions. For items of compli
cated shape, complete mechanization is possible only with
single-row saggers. The saggers should be of geometrically
simple form and technologically effective for the complete
mechanism of loading and unloading the product.
Refractories and Industrial Ceramics Vol. 50, No. 2, 2009
1083-4877/09/5002-0118 © 2009 Springer Science+Business Media, Inc.
VOSTIO JSC, Ekaterinburg, Russia.