THE MONOLITHIC REFRACTORY LINING
FOR FURNACES FIRED BY WOOD FUEL
and V. Antonovich
Translated from Novye Ogneupory, No. 9, pp. 13 – 15, September, 2003.
Service conditions of the refractory lining of the furnaces of drying drums fired by wood fuel (polishing dust
for wood fiber boards) are analyzed. Combustion of this fuel produces 9% of solid-state ash containing
low-melting compounds capable of infiltrating into the chamotte refractory. Because of the frequent thermal
shocks associated with heat-cool operating regimes and the attack by molten ash slag, the chamotte lining un
dergoes degradation. To improve the operating conditions and extend the service life of the lining, the use of a
castable monolithic material with superior resistance to high temperature and corrosion is proposed.
For countries or regions that that lack natural fuel re-
sources, the use of renewable sources of energy has always
been an issue of intense concern. Viewed in this light, vari-
ous types of biological energy, that is, the energy produced
from wood (firewood, sawdust, branches, bark, waste from
wood-working industry), straw, etc.
In recent years, in Lithuania under the PHARE program,
a number of thermal power plants have been converted to
wood fuel. In 2001, these power plants consumed about
1 million m
of firewood to generate 7 ´ 10
W × hofen
ergy . Furthermore, firewood has been used to feed indus
trial drying units, steam boilers, and even a tunnel brick kiln.
A survey of power plants fired by wood has revealed
that, in spite of the relatively low calorific value
(18.9 MJ/kg), the refractory lining of the furnace is prone to
wear and requires frequent restoring repair. This comes from
several factors. First, in combustion of wood, a temperature
from 900 to 1600°C (depending on the moisture content) can
be attained. Second, in using wood fuel, maintaining the
heat-release rate at a constant level poses a problem, unlike
with the use of readily controlled gas and oil burners. For this
reason, thermal stability of the lining in wood-fired plants
must be sufficiently high. Third, the firewood leaves about
1% of ash that contains much (10 – 15%) low-melting alkali
oxides with a high fluxing ability. The molten material infil
trates into the lining and causes corrosive damage to it. All
these factors indicate that the development of a highly
wear-resistant refractory lining for wood-fired power units is
a challenging problem.
In what follows we consider, as an example, the service
conditions of the lining in a power plant which uses the pol-
ishing dust for wood fiber boards (WFB).
SERVICE CONDITIONS FOR THE LINING
MADE UP FROM REFRACTORY BRICKS
At present, two drying drums (G. Mšller, Germany) are
in service at the Girju Bizonas (Lithuania) plant for produc
tion of wood fiber boards that are equipped with horizontal
cylindrical furnaces 2.15 m in diameter and 5.8 m in length.
The furnaces have burners installed in them that can use the
polishing dust for wood fiber boards as a fuel. The normal
working temperature is 1200 – 1300°C; in heavy-duty re
gimes, it may reach 1400°C.
The lining of the furnace is composed of two brick lay
ers: an insulating layer of lime silica bricks 32 mm thick and
a layer of chamotte bricks (ShA-grade) 124 mm thick. On
the outer side, the casing of the furnace is enclosed within an
air-cooled “jacket” (at the air temperature of 110 – 130°C).
The five-year experience gained in the use of the fur
naces shows that complete replacement of the lining should
be done every year, along with partial repair every
2 – 3 months. An analysis of the WFB dust used as a fuel
showed that, at 1200°C, some 9% of unburned material
(solid glassy particles) remained. With time, a hard glassy
film became deposited on the surface of the lining and in the
bottom of the furnace. After two-three weeks of service, the
power unit had to be shut down for cleaning the furnace bot
tom of the accumulated waste.
Refractories and Industrial Ceramics Vol. 44, No. 5, 2003
1083-4877/03/4405-0295$25.00 © 2003 Plenum Publishing Corporation
Gediminas Vilnius Technical University; Research Institute for
Thermal Insulation, Vilnius, Lithuania.