DRYING A HEATING UNIT LINING
L. A. Timoshenko
Translated from Novye Ogneupory, No. 7, pp. 23 – 27, July 2011.
Original article submitted April 21, 2011.
A requirement is demonstrated for drying the lining of a heating unit both during major construction and dur
ing repair. The main principles for carrying out drying and also the dependence of its methods and regimes on
specific engineering and operational characteristics of heat engineering installations are given. An example is
given of drying a lining of heating units for the production of methanol M-450 at OAO Shchekinoazot.
Keywords: drying, heating unit, refractory concrete, UHF energy, infrared thermal energy.
One form of work carried out by the company NK Teplo-
khimmontazh is performance of drying and first warm-up of
heating unit linings after major construction or repair. This is
an important stage and lining life depends significantly on its
correct and technically competent fulfilment. Unfortunately,
this stage is underestimated by many exponents. As is well
known, a heating unit lining contains water, which is present
within it during preparation of materials, or during their stor-
age and assembly. As an example, a ramming refractory mix
has a moisture content of 5 – 9%, traditional dense refractory
concretes (with a cement content of 25 – 30%) during assem
bly have 10 – 12%, and low-cement concretes have 5 – 7%
or lower . A brick lining also contains quite a considerable
amount of water, added with solutions, and also absorbed
from the atmosphere by bricks with pores. Considering this,
it is easy to see how much water is contained in a lining
weighing several hundred tons.
It is well known that drying is removal of free (physical)
and chemically-bonded moisture from refractory material.
This process should be quite slow in order to provide gradual
water removal without a risk of crack development and
breakage of a lining. Establishment of the optimum drying
program and heating becomes a special task, which should
be resolved in cooperation with the producer of the refrac
tory materials used. The duration of drying and first warm-up
of a lining, as also the method for increasing temperature, de
pends on a number of factors: material (type of lining materi
als, their properties, water content), construction (lining
shape and composition, its volume and thickness, density of
furnace metal structures), heat engineering features (heating
systems, gas supply, etc.). In order to achieve favorable re-
sults all of these factors should be taken into account in con-
structing a program for lining heating.
Initially it is recommended to carry out natural drying of
a heating unit with open hatches and manholes, for the best
ventilation, and then to carry out induced drying with air, fed
from a fan. Drying with air normally lasts 48 h . Simulta-
neously with cold drying fan operation is checked and the
hydraulic regime is measured for all air tracts. After drying
with cold air, drying commences with heated flue gases from
fuel combustion, for which natural gas is used. A furnace
with powerful calcining devices is dried by temporary burn
ers based on natural gas. The fuel used may be fuel oil, diesel
oil, coal, and even firewood . However, currently use of
these heat sources is hardly ever encountered in practice.
Drying of a furnace lining with electric heating elements is
carried out by means of these heaters, taking account of all of
the recommendations made for drying with natural gas. In
order to dry heating units of small volume and small lining
layer thickness it is possible to use electric heaters .
Recently new procedures and methods have been devel
oped for carrying out lining drying. There is greater use of
the method of removing moisture by means of microwave
energy (UHF energy) , with successful use in the coun
tries of Western Europe and Japan. Another promising tech
nology in this field is combined use of UHF energy and in
frared thermal energy, i.e., the so-called microwave infrared
method. UHF energy is rapid, volumetric heating, making it
Refractories and Industrial Ceramics Vol. 52, No. 4, November, 2011
1083-4877/11/05204-0253 © 2011 Springer Science+Business Media, Inc.
From materials of the International Conference of Refractory
Specialists and Metallurgists (March 31 – April 1, 2011, Moscow).
ZAO PFK NK, Staryi Oskol, Belgorod Region, Russia.