A MODEL STUDY OF THE PERFORMANCE
OF A KAZOGNEUPOR SHAFT KILN
B. A. Unaspekov
and L. V. Strekalova
Translated from Ogneupory i Tekhnicheskaya Keramika, Nos.7–8,pp.51–53,July – August, 2002.
Essential requirements placed on the gas heating system of shaft kilns and aimed at the improvement of their
performance characteristics are considered using experimental data.
Shaft kilns are industrial tools commonly used for calci
nation of refractory and building materials.
Many shaft kilns for calcination of granulated refractory
raw materials (magnesite, dolomite, corundum) and lime-
stone are equipped with gas heating systems whose design
fails to provide optimum combustion of gas in the working
(hot) space of thermal power units. This shortcoming results
in decreased quality of the calcined product, reduced produc-
tivity, and uneconomical use of natural gas.
High-temperature shaft kilns with modern gas-heating
systems have not yet gained wide acceptance because of
poor knowledge of their aero- and gas-dynamic performance,
zonal distribution of fuel, and heat- and mass-transfer in the
The main requirements placed on the heating system of
shaft kilns are:
– sufficient access of the gas-air mixture to the interior
of the raw material loaded in the kiln;
– uniform distribution of temperature over cross sec
tions of the shaft;
– uniform mixing of fuel and gas at a minimum excess
of the mixture;
– protection of the kiln lining against overheat.
Allowing for these requirements, an isothermal modeling
study of the performance of a shaft kiln was carried out.
Samples of the gas-air mixture were drawn at different
points and analyzed for methane content. The average me
thane concentration over the cross section Cav was deter
mined by the formula
is the concentration of methane at the ith point of
the cross section, %; n is the number of sampling points.
Next, average concentrations C
were calculated at different
distances from the wall l
, and relationships C
were plotted. The uniformity of cross-sectional distribution
of methane (gas-air mixture penetration) was evaluated
graphically and in terms of the absolute standard deviation
Prior to the experiments, the model was tested for self-
similarity. For that purpose, pressure drops throughout the
height of the shaft kiln were measured as a function of the air
flow rate. It was shown, based on these measurement, that
the Euler criterion was independent of the Reynolds number
for different flow rates. This means that the equality of
Reynolds numbers for the test object and the model in not the
necessary condition, which makes the modeling process a
simpler procedure, in particular, admits similarity of gas-dy
The simulation experiments started under conditions
where the lower array of burners was operating. The static
pressure at the gas-burner level was 2700 Pa, the spacing be
tween the gas nozzle and the air-gas nozzle of the burner (l
was 15 mm, and the corresponding nozzle diameters (d
) were 5 and 20 mm.
Air to the lower section of the shaft model was injected
at a flow rate of 750 m
/h and to the burner — at a flow rate
of 250 m
At these flow rates, the effect of geometrical parameters
of the burner’s channel, the spacing l
, and nozzle diameters
on the penetration of gas jets into the bed of granulated mate
Refractories and Industrial Ceramics Vol. 43, Nos.7–8, 2002
1083-4877/02/0708-0275$27.00 © 2002 Plenum Publishing Corporation
Almatyintergaz Joint-Stock Co., Almaty, Kazakhstan.
VNIIGAZ Research Institute, Russia.