ISSN: 0975-766X CODEN: IJPTFI Available Online through ... · 2−65,2708∙(x 2) 2+28,229∙(x 3)...

Liliya Hasanovna Zagorodnjuk* et al. International Journal of Pharmacy & Technology

IJPT| Sep-2016 | Vol. 8 | Issue No.3 | 15146-15155 5146

ISSN: 0975-766X

CODEN: IJPTFI

Available Online through Research Article

www.ijptonline.com

OPTIMIZATION OF MIXING PROCESS FOR HEAT-INSULATING MIXTURES IN A

SPIRAL BLADE MIXER 1Liliya Hasanovna Zagorodnjuk*,

2Valery Stanislavovich Lesovik,

3Aleksandr Anatolevich Volodchenko,

4Vladimir Trofimovich Yerofeyev

1,2,3Belgorod State Technological University named after V.G. Shoukhov, 46, Kostyukov str.,

Belgorod, 308012, Russia. 4Mordovia State University named after N.P. Ogarev, Russia, 430005, Saransk, Bolshevistskaya str., 68.

Received on 14-07-2016 Accepted on 11-08-2016

Abstract.

Currently the mortars based on dry mixtures are operated in the variety of conditions. They must meet a set of

requirements for physical-mechanical and operational parameters and have a sufficient durability. The mixing of

mixture raw components is one of the most important process steps for the preparation of dry mixtures, which makes

a significant impact on the processes of structure development and the properties of the resulting composite. The

article describes the regularities of individual structure development and general polystructure in the cement

composite, prepared on the basis of dry thermal insulation mixtures during the stage of its preparation in mixing

devices. The results of mixing process study in a spiral-blade mixer are provided. It was shown that the mixing of the

dry thermal insulation mixtures in a spiral blade mixer provides a sufficient uniform mixing of the mixture with

different average density of the constituent components and fully meets the technical requirements of dry mixtures

preparation of this functional purpose. This mixing unit is recommended for the preparation of thermal insulation dry

mixtures, which provides a high quality of mixing, which does not result in the overgrinding of ready mixture

components, thus, providing the obtaining of high physical, mechanical and performance properties of a thermal

insulation solution on the basis on the dry mixture preparation.

Keywords: The mixing of components, dry heat-insulating mixtures, spiral-blade mixer, mixing quality.

Introduction:

The final property of any material is developed by a complex of its constituent components and the efficiency of its

technological process obtaining. Dry construction mixtures have a very complex multimineral composition consisting

of a large number of components, and the physical and chemical processes in them are conditioned by the interaction

within the system "a mineral binder - a polymeric binder - a filler - modifying additives - water". A highly efficient


IJPT| Sep-2016 | Vol. 8 | Issue No.3 | 15146-15155 Page 15147

mixing of dry compound ingredients will provide a high reactivity of the mixture components and will create the best

conditions for the implementation of structure relation law and ensures the obtaining of composites with desired

properties [1-16]. The rational choice of a mixer for the ingredients of a mixed highly filled disperse system,

guarantees the required performance of an obtained material as it was shown by numerous studies.

Main part: The evaluation of equipment use effectiveness in relation to a particular technological process, and

studied materials requires the performance of experimental studies in order to determine the main technological and

operational characteristics of devices. A special equipment was used during the conduct of the experimental research

concerning the mixing process study for dry thermal insulation mixtures in a spiral blade mixer: an experimental

device for the study of mixing processes with the ability to change test parameters and operating modes within the

limits set by the statement of objectives; measuring devices (pressure gauges, flowmeter, etc.) corresponding to the

research of the process under study and providing the necessary measurement accuracy. Taking into account the

abovementioned requirements and the plan of experiments, an experimentally-industrial sample of a spiral blade

mixer was used to determine the variable parameters and the study process of dry building compound mixing.

The principle of a mixer operation for the mixing of bulk materials is as follows. Mixing components are loaded

through a feed opening and fall into a drum. An electric motor is turned on along with a load, making a vertical shaft

rotate through a V-belt transmission. During the rotation of blades in a drum a vortex begins to form, which pulls

material from the top to the bottom of the drum. The material starts to circulate. After a certain time (15-25 seconds),

an electric drive of the drum is turned on. This electric drive consists of an electric motor, a worm gear and a V-belt

belt transmission.

The drum starts to rotate. The drum rotates in the opposite direction of the blade rotation and the direction of the

drum rotation is selected according to the direction of the screw turns. The material is loaded by the blades on the

screws. Screw augers raise blending components in vertical and horizontal direction. Moving along a screw surface, a

mixture reaches the second row of blades and enters the middle portion of the screw and moves up after the

movement both in vertical and in horizontal direction. The mixture reaches the top part of the drum there, where

reinstalled blades cut the moving mixture off the screw and is direct it down towards the main stream of the mixture.

After stirring, the mixture is discharged through a discharge opening. The process is repeated after a mixer unloading.

They studied the effects of main parameter changes in an experimentally-blade mixing device (load factor, mixing

time, the number of vertical shaft revolutions) on the physical and mechanical properties of the insulating mixture.



The influence of investigated factors on the properties of thermal insulation dry mixtures was studied by three-factor

experiment obtaining full quadratic relationships. The following elements were taken as variation factors: load

coefficient (40-60%), mixing time (30-70 seconds) and the number of vertical shaft turns (250-750 min-1). An

experiment planning conditions and a design matrix are shown in Table 1.

Table 1 – Experiment planning terms.

Factors Variation levels Variation

interval Natural view Coded view -1 0 +1

Load coefficient х1 0,4 0,5 0,6 0,1

Mixing period х2 30 50 70 20

The number of

vertical shaft turns

x3 250 500 750 250

In accordance with the planning matrix 17 options of mixing were carried out in which load factor, mixing time and

the number of vertical shaft revolutions varied, as was indicated previously. The ratio of components remained

unchanged.

In order to perform tests the mixtures were prepared as follows. Weighed dry ingredients, cement and sand were

placed in a mixing drum in which the mixing of the mixture occurred during the scheduled time, and then the

prepared mixtures were placed in dry polyethylene packages and tied tightly. Then the investigated and preliminary

prepared dry mixture composition was placed into a spherical bowl made of stainless steel, preliminary wiped with a

damp cloth. Then water was poured in a mixture groove according to V/T ratio of 0.2. After the mixing with water

the groove was filled with a mixture, and after 30 seconds of the first pouring of water they were stirring it gently and

then rubbed the mixture vigorously with a spatula until a smooth consistence. The duration of mixing and grinding

made 4 minutes after water pouring. In order to determine the average density and the compression strength of the

hardened mortar 70 × 70 × 70 mm cubes were molded, two samples per composition. Prior to the production of

samples and forms the inner surface of the pan and walls was lightly greased with lubricating oil. The prepared mass

was laid into a mold and compacted by rodding. The samples were hardened at the room temperature of (20 ± 2) °C

and the relative humidity of (65 ± 10)% in accordance with GOST 5802-86 for 28 days. Then the samples were

weighed, measured and tested by the caliper on compression. The equation of the solution average density regression.

The regression equation for the average density of a hardened mortar has the following form:



y=376,32+27∙x1+2,5∙x2+19∙x3+43,2292∙(x1)2−65,2708∙(x2)

2+28,229∙(x3)

2--6,25∙x1∙x2+7,5∙x1∙x3+0,75∙x2∙x3

Using the obtained regression equation one may analyze the influence of the studied factors on the solution average

density. The comprehensive understanding concerning the loading factor influence, mixing time and the number of

the vertical shaft turns at the average density of a solution can be obtained by a nomogram development using the

regression equation (Fig. 1-4). The nomogram allows to optimize the technological process and manage it effectively.

Using the nomogram one may keep an output parameter at a given level, changing the factors included in the

regression equation by an appropriate way.

Figure 1. The nomogram of the average density dependence on load factor and mixing time.

Figure 2. The nomogram of the average density dependence on a vertical shaft speed and mixing time.

Figure 3. The nomogram of the average density dependence on the load factor and the number of vertical

shaft revolutions.

a)

b)



c)

Figure 4. The nomograms of the average density dependence on the number of vertical shaft revolutions and

shift time at various load factors: a) Кз=0,6; b)Кз=0,5; c)Кз=0,4

The regression equation concerning solution compressive strength. The result of experimental data statistical

processing is the obtaining of the regression equation for compressive strength:

y=0,9403+0,0682∙х1+0,0218∙х2+0,0637∙х3+0,0264(х1)2-

0,0486∙(х2)2+0,0589∙(х3)

2+0,0690∙х1∙х2+0,000∙х1∙х3+0,0503∙х2∙х3

Using the obtained regression equation one can analyze the influence of studied factors on the compressive strength.

The total picture about the load factor impact, the mixing time and the vertical shaft speed on the compressive

strength of a solution at compression can be obtained by developing a nomogram using the regression equation (Fig.

5-8). The nomogram allows to optimize the technological process and manage it effectively manage. Using the

nomogram an output parameter can be maintained at a given level, changing the factors included in the regression

equation by an appropriate way.

Figure 5. The nomogram of average compressive strength dependence on the load factor and mixing time.

Figure 6. The nomogram of average compressive strength dependence on the number of vertical shaft

revolutions and mixing time.



Figure 7. The nomogram of the average compressive strength dependence on the speed of a vertical shaft and

the load factor of a mixer drum.

Figure 8. The nomogram of the average compressive strength dependence on the speed of a vertical shaft and

mixing time.

During tests the mixture sieving was performed after each stage of mixing using an experimental spiral blade mixer.

The results are shown in Table 2.

Table 2 - The results of dry mortar sieving after mixing.

Experiment № Residues on sieves, % by weight Pass through a sieve,

0,125 % by weight 1,2 0,63 0,315 0,125

1 1 13,15 25 40 15

2 1 14 10 31 40

3 0,5 14,5 30 30 25

4 1 20 29 35 15

5 1 18 26 30 25

6 1 13,15 25 40 15

7 1 15 15 26 43

8 1 16 20 33 30



9 1,5 13,5 20 35 30

10 1 14 15 30 40

11 1 14 15 40 30

12 1 20 29 35 15

13 1 18 26 30 25

14 1,5 18,5 30 25 25

15 1 15 15 26 43

16 1 14 25 25 35

17 0,5 14,5 30 30 25

During the test performance the screening was conducted after each experiment using a mechanical sieve according

to the following fractions: 1,2; 063; 0,315; 0,125 and the passing through the sieve 0,125, the sieving results are given

in Table 2.

Based on the fact that the perlite sand in its natural commodity state has the predominant fractions on the sieve №

0,63 sieve at the amount of 46%, and the sieve № 0,315 - 43%, and by the end of mixing the amount of these

fractions is reduced on these sieves to 13.15 ... 20% and to 10 ... 30% respectively, and the amount of a fine fraction

(sieve № 0,125 and fine fraction (dust) increases from 45.0 ... 71.0%. These results suggests that the mixing in a

mixer does not result in the overgrinding of a raw material mixture, which is reflected on the final physical,

mechanical and operational characteristics of a thermal insulation solution.

The feature of a spiral blade mixer is that this mixer produces a dry heat insulation mixture with the desired qualities

of mixing without the breakdown of a raw mixture. The additional grinding of raw mixture components is absent.

Thus, the use of a spiral-blade mixer for the mixing of raw material components with different density may fully meet

the technical requirements of a mixing device for the mixing of components with different densities. This mixing

device is recommended for the preparation of dry thermal insulation mixtures providing the high quality of mixing,

and consequently high physical, mechanical and performance properties of a final product.

Figure 9. The nomogram of the average density dependence on the speed of a vertical shaft, the load factor

and the mixing time.



Figure 10. The nomogram of the average density dependence on the speed of a vertical shaft, the load factor

and the mixing time.

Fig. 9 and 10 show the nomograms of optimum parameter influence such as mixing time (30 ... 70 seconds), the load

factor (0.4 ... 0.6), and the number of a vertical shaft turns (300 ... 700 min-1

), on the average density and the average

strength of the thermal insulation solution.

The best performance of physical and mechanical properties for thermal insulation solutions prepared from mixtures

of dry ingredients in a spiral-blade mixer were set after performed studies. According to the results of the processed

data, we can conclude that the following technological parameters are the optimal values to obtain the mixtures with

desired properties:

- The load factor of a mixing drum - 0.55 ... 0.60%;

- Mixing time - 50 ... 70 seconds.

- A vertical shaft speed - 500 ... 750 min-1

.

The obtained results indicate that the use of this mixer allows to get dry thermal insulation mixtures with desired

properties which allow to use them according to a given functional purpose.

Summary. In order to create high-quality and durable thermal insulation solutions on the basis of dry mixes it is

necessary to provide a high homogeneity, the stability of properties and a constant composition for them. Besides,

given that dry mixes are applied generally in the solutions with a standardized small thickness, the demands are put

forward to ensure the maximum safety of filler grains, without the violations of the mass granulometric ratio

concerning filler fractions.

This preparation of dry building mixtures in industrial environment allows to achieve a high homogeneity and a high

quality and durability. Highly efficient mixing of the dry components in production environment will ensure a high

reactivity of a mixture at the use on a construction site. Thus, in order to provide the abovementioned requirements

the use of effective mixing methods for mixture components and a rational choice of the mixing equipment is

necessary.



Conclusions

It was found that the mixing of dry thermal insulation mixtures in a spiral blade mixer provides a rather uniform

mixing of a mixture with different average density of the components and fully meets the technical requirements of

dry mix preparation. This mixing unit is recommended for preparation of dry thermal insulation mixtures, which

provides a high quality of mixing, and does not lead to the overgrinding of mixed components and as a result,

ensuring high mechanical and performance properties of a thermal insulation solution on the basis of dry mixture

preparation.

References

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Corresponding Author:

Liliya Hasanovna Zagorodnjuk*,

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