Volume 02 Issue 06-2022
35
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
06
Pages:
35-39
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
A
BSTRACT
In the article ecologically clean drying of fine dispersed materials chemical and allied industries are
considered. The equipment design and technology of drying fine-dispersed materials had been prepared.
K
EYWORDS
Contact drying, finely dispersed materials, rotary-drum apparatus.
I
NTRODUCTION
Drying of wet particulate materials is usually
carried out in convective bed dryers. If it is
necessary to dry wet fine materials having a
particle size of 5-50 microns. This drying method
is not always effective. The reason for this is that
part of the product is carried away by the exhaust
gases and pollutes the environment. As a result, it
becomes necessary to clean the secondary air [1-
Journal
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Research Article
DRYING TONKODISPERSE MATERIALS IN AN UNSUCCESSED
ROTARY-DRUMING MACHINE
Submission Date:
June 05, 2022,
Accepted Date:
June 15, 2022,
Published Date:
June 27, 2022
Crossref doi:
https://doi.org/10.37547/ijasr-02-06-05
N.R. Rajabova
Assistant, Fergana Polytechnic Institute, Fergana, Republic of Uzbekistan
A.B. Qodirov
Assistant, Fergana Polytechnic Institute, Fergana, Republic of Uzbekistan
Volume 02 Issue 06-2022
36
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
06
Pages:
35-39
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
3]. This method requires rather bulky equipment
for dust collection, since several stages of cleaning
are required. Convective drying is especially
undesirable for small-tonnage industries with a
wide range of products, in some cases having
environmentally harmful components, the loss of
which affects the environmental situation,
especially when drying toxic materials [4-7].
In such cases, it is necessary to use contactless
dryers of the contact type, for example, rotary
drum dryers. This type of dryer has been
developed in a number of countries, but as far as
we know, they are not widely used in industry [6-
9].
Based on the above conclusions, it is advisable to
investigate the process of drying aggressive,
environmentally harmful finely dispersed
materials in apparatuses of this type, since it
became necessary to use them in production.
Studies were carried out with a number of finely
dispersed materials (less than 20 μm) - for deep
drying (up to 0.01%) of phenyl C2 (powder
press), for drying highly moist activated carbon
paste and other finely dispersed materials. The
device is a fixed horizontal heated drum (D=180
mm, L=300 mm), inside which is a rotating rotor
with blades. When the rotor rotates with blades,
the material is thrown to the periphery, where a
moving mixed layer is formed, which is in contact
with the heated wall. Drying of the material takes
place in a layer, the maximum thickness of which,
and hence the residence time of the particles in
the apparatus, is determined by the size of the gap
between the div and the blades (the layer
thickness may be less).¬
The required heat flux was maintained constant
or regulated, if necessary, to maintain a constant
wall temperature by a voltage regulator.
Secondary steam with a small amount of non-
condensable gases was removed from the
apparatus along its axis and condensed in the heat
exchanger, therefore, product losses and
environmental pollution were excluded [5-8].
The drying kinetics was studied in batch and
continuous processes (material samples were
taken periodically). The temperature of the
material in the layer was measured, as well as the
temperature of the inner surface of the drum wall.
On the basis of experiments, kinetic curves of
changes in humidity and temperature of the dried
material in a batch process at different numbers
of rotor revolutions were obtained. Analysis of
the data showed that with an increase in the
speed of rotation of the rotor, the intensity of
drying increases, and the temperature of the
material by the end of the process approaches the
temperature of the heating surface. The influence
of the number of revolutions on the heat transfer
coefficient was also studied at different initial
moisture content of the material. With an
increase in the initial humidity, the heat transfer
coefficient increases significantly and reaches
high values - about 500W/m2K, but decreases
significantly with decreasing humidity (less than
200 W/m2K). It seemed interesting to reveal the
change in the heat transfer coefficient along the
perimeter of the drum. The experiments were
Volume 02 Issue 06-2022
37
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
06
Pages:
35-39
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
carried out with dry material and the local values
of the heat transfer coefficient were measured
with a thermistor sensor. The heat transfer
coefficient was measured at 8 points along the
inner perimeter of the drum. Experimental data
showed that at low rotor speeds, the heat transfer
coefficient is low, which is explained by poor
mixing of the layer, and in the upper part of the
drum particles are separated, since at these rotor
speeds the centrifugal forces are small compared
to gravitational forces. Because of this, the profile
of the heat transfer coefficient is uneven around
the perimeter of the drum. With a further increase
in the angular velocity of the rotor, the heat
transfer coefficient increases, as the mixing of
particles improves and the number of their
contacts with the hot surface increases, the
centrifugal forces also increase. With an increase
in the angular velocity of the rotor, the ratio of
centrifugal force to gravity increases rapidly. This
leads to a uniform distribution of the material in
the gap along its perimeter and, as a result, an
increase in the contact heat exchange surface due
to the use of the upper part of the drum with an
increase in the angular velocity of the rotor and to
equalize the local heat transfer coefficients.
An analysis of studies on heat and mass transfer
processes occurring during drying in rotary
dryers shows that, based on existing studies of the
drying process, it is impossible to take into
account all the characteristic features and
changes in the kinetics of such a process.
A more complete model would be that would take
into account the change in the material
temperature in each of the stages of drying, the
equilibrium between the wet material, the
additional heat input from energy dissipation due
to the rapid movement of the dispersed material
and the heated structural elements of the drum,
as well as the effect of longitudinal mixing of the
dispersed material.
On the basis of general ideas about drying and its
laws, the physical picture of the process by stages
occurring in the drying plant is considered, the
developed mathematical models are described
and their solution is given. The development of a
mathematical model is based on the known laws
of conservation of energy and mass of matter,
provisions from the theory of drying and the laws
of equilibrium between the material and the
drying agent.
The period of removal of free moisture is
characterized by the fact that evaporation
proceeds according to the laws of the
transformation of free liquid into vapor. During
this period, the drying process is determined
mainly by the rate of heat supply from the heated
wall to the material being dried.
One of the most important parameters that
determine the drying mode is the wall
temperature. In a continuous drying process, the
wall temperature along the length of the dryer
changes due to heat transfer to the evaporation of
the liquid, to heating the material and rotor
blades.
The calculation of the period of removal of bound
moisture differs from the calculation of the period
Volume 02 Issue 06-2022
38
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
06
Pages:
35-39
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
of removal of free moisture in that the surface
temperature of the material rises, it is necessary
to calculate using the modified relationship
between the wall and the material being dried.
As a result of thermal contact of the material with
hot walls and rotor blades, a layer of dried
material appears, the thickness of which
gradually increases. And in the dried state, the
dispersed material in terms of heat-conducting
properties is not so far from the properties of
heat-insulating materials. This is due to the fact
that the main resistance to heat transfer is
concentrated in the zone of the material in contact
with the heat-releasing surface. The processes
taking place in this zone essentially depend on the
Lykov criterion. With its small values, the liquid
will not have time to be supplied from the inner
layers of the material to the contact surface, a
layer of dry material will appear separating the
contact surface and the evaporation surface. The
temperature of this layer on the contact surface is
the same as the temperature of the heated wall,
C
ONCLUSION
The results of the research were used by us in the
design and testing of a pilot plant, in particular for
fine material with a capacity of 100 kg of moisture
per hour. The dimensions of the pilot plant were
450 mm in diameter and 1500 mm in length. For
phenylone C2, the overall dimensions of the pilot
plant are identical to those of the laboratory plant.
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39
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
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Pages:
35-39
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5.636
)
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