STUDY OF THE EFFECT OF DRYER HYDRAULIC RESISTANCE ON MATERIAL TEMPERATURE

ABSTRACT

In the article, the problem of drying the main raw materials in the cement production processes according to the regulations is studied. As a research object, the scientific research works carried out in the "Turon Eko Cement Group" LLC enterprise in a drum dryer equipped with a υ-shaped nozzle for drying loam used as raw material and loam are presented. In the course of research, the influence of the hydraulic resistance of a drum dryer equipped with a υ-shaped nozzle on the temperature of the material was studied. The lower load of the parameters included in the drying process, i.e., the temperature of the material being dried from the heat agent when the productivity Q_yi =0.073 kg·s, the speed of the heat agent is 5 m/s, the angle of the nozzle pouring the material is 60 degrees, and the number of nozzles is 20 pieces If it is 45 ℃, it is dried when the high load of the parameters, i.e., the productivity Q_yi =0.083 kg·s, the speed of the heat agent is 20 m/s, the angle of the nozzle pouring the material is 30 degrees, and the number of nozzles is 28 pieces. it was determined that the temperature of the material from the heat agent was 75 ℃.

АННОТАЦИЯ

В статье рассматривается вопрос сушки основного сырья в цементных производственных процессах в соответствии с требованиями регламента, объектом исследования является суглинок, используемый в качестве сырья на предприятии ООО “Turon Eko Cement Group”, а также научно-исследовательская работа, проводимая на барабанной сушилке, оснащенной υ-образной насадкой для сушки суглинок. В ходе исследований изучалось влияние гидравлического сопротивления барабанной сушилки, оснащенной П-образной насадкой, на температуру материала. Нижняя нагрузка параметров, вводимых в процесс сушки т. е. производительность труда Q_пр=0,073 кг·с, скорость теплового агента 5 м/с, угол наклона насадки к заливке материала 60 градусов, а температура, получаемая сушильным материалом от теплового агента при количестве насадок 20 штук, составила 45 ℃, тогда как верхняя нагрузка параметров т. е. производительность труда Q_пр=0,083 кг*с, скорость теплового агента 20 м/с, установлено, что при угле наклона сопла к заливке материала 30 градусов и количестве насадок 28 штук температура, получаемая сушильным материалом от теплового агента, составляла 75 ℃.

Keywords: drum dryer, loam, drying kinetics, temperature, lower and upper loading, cement, average temperature of the material.

Ключевые слова: барабанная сушилка, суглинок, Кинетика сушки, температура, нижняя и верхняя нагрузка, цемент, средняя температура материала.

Introduction

In this research work, the issue of drying the main raw materials in the cement production process according to the requirements of the regulation is studied. As a research object, loam (initial moisture content 18%) was used as raw material at "Turon Eco Sement Group" LLC and a drum dryer equipped with a υ -shaped nozzle for drying loam was selected.

As a subject of research, the drying hydrodynamics of the proposed υ-shaped nozzle, assessment of the degree of process acceleration, heat exchange processes between the heating agent and the material being dried, drying time, and material balance were introduced.

Drying of materials is one of the most energy-intensive processes in the technological line. Using this process is important to determine the quality of the finished product. Thermal drying costs account for 10% of the total value of the process [1-3].

In such conditions, it is urgent to create highly efficient, energy-saving drying regimes and regulate and optimize heat exchange processes in drying devices.

It is known from the literature and the research work carried out to date that the drying process depends on the size of the material, moisture content, the method of their movement, the hydrodynamics of the movement of the material with the drying agent, and the parameters of the internal and external environment. The combination of these factors determines the conditions of the drying process. Therefore, according to the physical, chemical, and mechanical properties of the material to be dried, different methods and devices are used in the industry [4-7].

The most common method and equipment mentioned above is the convective drying method, in which drum dryers are used. The simplicity of construction, high performance, and universality have a special place. That's why the tendency to use these drying units in various sectors of the national economy is expanding, but these types of dryers also have disadvantages. For example, some complex processes can be mentioned, such as ensuring the drying intensity, rational use of the heat agent used for drying, optimizing the hydrodynamic parameters, and minimizing the energy consumption. Therefore, the issues of determining and justifying the optimal parameters of this type of device are relevant [8-10].

Research Methodology

It is known from the scientific research works and engineering calculations [8-12] that the technological and technical-economic indicators of the drying apparatus mainly depend on the intensity of heat and mass exchange in the dryer, which in turn depends on the material in the device. depends on the amount of transferred heat and its hydraulic resistance, the number of revolutions of the drum and the angle of inclination of the drum to the plane, the following equation is recommended to theoretically determine the amount of heat absorbed by the material, kcal;

                                                                                 (1)

in which:  - average temperature difference of gas and material, ℃;  - the volume of the drying apparatus, m³.

From equation (1), it can be seen that three directions can be used to increase Q:

1. Increased drum volume ;

2. An increase in the average temperature difference ;

3. Increase in volume ratio .

In addition, the hydraulic resistance of the drum has a significant effect on the moisture content of the material being dried. Therefore, it is necessary to consider the drum resistance when designing the process of intensive drying of the material. Consider this parameter as a value that can be almost ignored in the scientific research works carried out so far. However, the increase in hydraulic resistance allows the material to be kept longer in the drying zone. This, in turn, improves the drying efficiency and improves the heat exchange between the material and the heating agent.

Research results

Based on the above, the influence of the hydraulic resistance of the dryer on the temperature of the material was studied. The following limits of variable factors for conducting research, the number of main nozzles are 20; 24, and 28 (nozzles are arranged in a checkerboard pattern by drying zones), the number of heat exchange zones is 5, the speed of the heat agent (air) coming out of the heater is y= 5÷20 m/s, the efficiency of the device Q_yi =0.073÷0.083 kg·s (the intermediate step increased by 0.005 kg/s). The angle of inclination of the dryer drum relative to the plane is a=13 degrees (according to the technological regulation), and the frequency of rotation of the dryer drum is set to n=15 revolutions/min.

The research was conducted in the following sequence. The material to be dried (initial moisture content of 18%) loaded in the dryer hopper was fed to the dryer with Q_yi =0.073÷0.083 kg·s (the intermediate step increased by 0.005 kg/s). At the same time, the heating agent (air) heated up to 120 ℃ in the colourful was introduced into the dryer simultaneously with the material being dried in the order of 5 m/s in increments of y= 5÷20 m/s in the direction of the material movement.

As the material passes through the 5 zones of the dryer, it is pumped through the nozzles of the dryer. The heating agent and the material to be dried were in the process of mutual heat exchange in step-by-step zone 5. The temperature of the initial dried material leaving the dryer was measured using a thermometer. Experiments were conducted separately for each parameter of variable factors and the obtained results were compared.

The experimental results are presented in Figures 1, 2, and 3, and the general experimental results are presented in Appendix V.

1. The number of υ-shaped nozzles is 20 pieces, with an inclination angle of pouring the dried material α=60 degrees; 2. The number of υ-shaped nozzles is 24 pieces, with an inclination angle of pouring the dried material α=60 degrees; 3. The number of υ-shaped nozzles is 24 pcs., with an inclination angle of pouring the dried material α = 30 degrees;

Figure 1. Variation of material temperature depending on dryer hydraulic resistance. When Q_yi=0.073 kg·s-const.

1. The number of υ-shaped nozzles is 20 pieces, with an inclination angle of pouring the dried material α=60 degrees; 2. The number of υ-shaped nozzles is 24 pieces, with an inclination angle of pouring the dried material α=60 degrees; 3. The number of υ-shaped nozzles is 24 pcs., with an inclination angle of pouring the dried material α = 30 degrees;

Figure 2. Variation of material temperature depending on dryer hydraulic resistance. When Q_yi=0.078 kg·s-const.

1. The number of υ-shaped nozzles is 20 pieces, with an inclination angle of pouring the dried material α=60 degrees; 2. The number of υ-shaped nozzles is 24 pieces, with an inclination angle of pouring the dried material α=60 degrees; 3. The number of υ-shaped nozzles is 24 pcs., with an inclination angle of pouring the dried material α = 30 degrees;

Figure 3. Variation of material temperature depending on dryer hydraulic resistance. When Q_yi=0.083 kg·s-const.

Figures 1, 2 and 3 were processed in the appropriate order and the following empirical equations were obtained using the method of least squares.

1) When n=2.5 rpm-const.

2) When n=3 rpm-const.

3) when n=3.5 rpm-const.

From the graphical relationships in Figures 1; 2 and 3, it can be seen that the decrease in the material discharge angle of the υ-shaped nozzle leads to an increase in the hydraulic resistance in the dryer. This, in turn, increases the intensity of the heat exchange process between the material being dried and the heat agent.

For example, the lower loading of the parameters that are included in the drying process, that is, the productivity Q_yi=0.073 kg·s, the speed of the heating agent is 5 m/s, the material discharge angle of the nozzle is 60 degrees, and the temperature of the material being dried from the heating agent is 45 ℃ when the number of nozzles is 20. High loading of parameters ie performance when the mass=0.083 kg·s, the speed of the heating agent is 20 m/s, the angle of the nozzle pouring material is 30 degrees, and the number of nozzles is 28, the temperature of the material being dried from the heating agent was 75 ℃. It can be seen that the complexity of the design of the dryer, as mentioned above, improves the process of mutual heat exchange. However, the importance of drying zones should also be taken into account during the drying process of granular dispersive materials. The reason is that the aerodynamic movement of the drying agent inside the dryer depends on the organization of zones, which determines the modification of the drying process. Drying modification is closely related to the heat energy used in the process. Drying of solids takes place in five polymorphic modification states. the heat capacity of the substance being dried is also important. That is, when determining the modification interval, the temperature of the heat agent used for drying is determined based on the heat capacity of the substance.

Each modification is stable in its temperature range, and when moving from one modification to another, its structure and the size of the crystal lattice change. This change is a reversible process, accompanied by heat release or heat absorption, and accompanied by a jump in relative volume. As mentioned, the internal structure of the substance and its ability to retain moisture transfer the given energy into a five-step state.

For example, during the drying process of the studied sublink, the absorption of heat from the heat agent of the sublink changes from the first modification to the second, from the second to the third, from the third to the fourth, and from the fourth to the fifth, depending on the drying zone.

At the point of transition from one modification to another, a high-stress deformation occurs in the crystals, which causes the crystals to break, or there is a mutual heat exchange between the surface energy and internal energy of the material being dried. This, in turn, goes in the reverse process.

Therefore, it is important to know the internal structure of the material to be dried, the ability to keep moisture, and the coefficient of exchangeability. Studying these processes allows us to reduce the amount of energy that is lost.

Based on the above, the modification of heat exchange in different parameters of the dryer for the object under study was studied and the energy lost in the process was determined. The results of the experiment are presented in Figure 4.

Figure 4. Graph of change of temperature of material and heat agent along the length of the drum

From the graphical relationships in Figure 4, it can be seen that changes in productivity, agent speed, number of revolutions of the drum, and the angle of inclination lead to a sharp and intensive exchange of temperature along the drum zones. However, the expansion of the sphere of interaction of influencing factors has a dramatic effect on productivity. This, in turn, causes a violation of the drying modification, and as a result, the amount of heat used for drying the material increases. This, in turn, increases the amount of energy lost. Tables 1 and 2 show the determined values of the amount of heat and heat balance used for drying loam for different values of the lower and higher loading parameters.

Table 1 shows the lower load of the parameters included in the drying process, i.e., the experimental results obtained when the work efficiency Q_yi=0.073 kg·s, the speed of the heating agent is 5 m/s, the angle of the nozzle pouring the material is 60 degrees, and the number of nozzles is 20 pieces.

Table 1.

Values of the amount of heat used to dry the loam and the heat balance when the efficiency of the material supplied to the dryer is 0.073 kg·s.

Table 2 shows the lower load of the parameters included in the drying process, i.e., the work efficiency Q_yi=0.083 kg·s, the speed of the heat agent is 20 m/s, the material pouring angle of the nozzle is 30 degrees, and the experimental results obtained when the number of nozzles is 28 pieces.

Table 2.

Values of the amount of heat used to dry the water and the heat balance when the material supplied to the dryer has a productivity of 0.083 kg·s.

The values determined in Tables 1 and 2 showed that the more complicated the internal structure of the material being dried in the dryer, the more the energy spent on the drying process increases. In addition, increasing the resistance of materials and heating agents in drying devices increases the rate of moisture release, but negatively affects the performance of the dryer.

Summary

1. Drying hydrodynamics of the proposed υ-shaped nozzle, evaluation of the level of process acceleration, heat exchange processes between the heating agent and the material being dried, drying time and material balance, as well as the amount of heat used for drying the material was studied.

2. In the conducted experiments, the resistance coefficient of the working volume of the drum dryer is lower load, that is, the speed of the heat agent is 5 m/s, the number of υ-shaped nozzles is 20 pieces, and the productivity of the material being dried is 0.073 kg·s, and z=2.9 It was determined that z=5.9 at high load, i.e. 20 m/s, the number of υ-shaped nozzles is 28 pieces and the productivity of the material being dried is 0.083 kg·s.

3. In the drum dryer, the complexity of the construction leads to an increase in hydraulic resistance, and as a result, the drying time of the material entering the drying process is increased, and as a result, the intensity of heat exchange between the heating agent and the material being dried increases.

4. A photomicrographic analysis of the effect of the internal structure of the dispersed material on the drying process was carried out. The results of the analysis and the results of many studies showed that. That is, the internal structure of the material is of great importance for the interaction of the moisture in the material with the heating agent and for accelerating the rate of transition of moisture to the gas phase (drying rate). For example, an increase in the density of the material being dried causes an increase in the time of evaporation of the moisture contained in its microcapillaries. which in turn increases the energy used for drying.

References:

1. Ахунбаев А. А., Ражабова Н. Р. Высушивание дисперсных материалов в аппарате с быстро вращающимся ротором //Universum: технические науки. – 2021. – №. 7-1 (88). – С. 49-52.
2. Лыков М. В. Сушка в химической промышленности. – 1970.
3. Лыков М.В. Сушка в химической промышленности. Москва – Издательство Строй. 1990.
4. Муштаев В. И., Ульянов В. М. Сушка дисперсных материалов. Москва – Издательство Химия, 1988.
5. Ражабова Н. Р., Халилов И. Л. Современное представление о типах оборудования и технологий сушки //Scientific progress. – 2023. – Т. 4. – №. 1. – С. 158-166.
6. Akhunbayev A. A., Rajabova N. R. Drying of raw materials of cement production in the drum dryer //International Journal of Advance Scientific Research. – 2022. – Т. 2. – №. 11. – С. 50-59.
7. Jumaboevich T. R., Rakhmonalievna R. N. Installation for drying materials in a fluidized bed //Innovative Technologica: Methodical Research Journal. – 2022. – Т. 3. – №. 11. – С. 28-36.
8. Rajabova N. R., Qodirov A. B. Drying of fine materials on a stationary rotary drum machine //International Journal of Advance Scientific Research. – 2022. – Т. 2. – №. 06. – С. 35-39.
9. Rajabova N., Rasuljon T. Impact of dispersed materials internal structure to drying process //Наука И Технологии-2023. – 2023. – С. 10-21.
10. Rasuljon T., Nargizaxon R. Impact on the internal structure of materials to drying process //Universum: технические науки. – 2022. – №. 10-6 (103). – С. 10-18.