EXPERIMENTAL INVESTIGATION OF PRESSURE LOSSES IN WET DUST CLEANING CONE MESH DEVICE

ABSTRACT

The article presents the results of an experimental study conducted in different gas and liquid flow regimes when cone-shaped meshes with 3 different square hole sizes were installed in the experimental device of the wet dust cleaning cone-meet apparatus. The experimental values of the lost total pressures were determined depending on the local and general hydraulic resistance coefficients of each mesh installed on the working bodies of the device. As a result, it is possible to determine the optimal values of the dust gas cleaning efficiency of the apparatus depending on the determined total pressures in these conical grids.

АННОТАЦИЯ

В статье представлены результаты экспериментального исследования, проведенного в различных режимах течения газа и жидкости при установке в экспериментальное конусно-сетчатого устройство мокрой пылеочистки конусных сеток с тремя различными размерами квадратных отверстий. Экспериментальные значения потерь полного давления определялись в зависимости от коэффициентов местного и общего гидравлического сопротивления каждой сетки, установленной на рабочих органах устройства. В результате создана возможность определения оптимальных значений эффективности пылегазоочистки аппарата в зависимости от определенных суммарных давлений в этих конических сетках.

Keywords: dusty gas, wet method, fluid, conical mesh, resistance coefficient, pressure, gas velocity, fluid consumption.

Ключевые слова: запыленный газ, мокрый метод, жидкость, коническая сетка, коэффициент сопротивления, давление, скорость газа, расход жидкости.

Introduction

Currently, as a result of the development of industry in the conditions of Uzbekistan, as in other countries, the level of atmospheric air pollution is increasing. The amount of emissions released into the atmosphere from chemical, building materials, hydrometallurgy, and cotton industry enterprises is especially high [1,3,7]. In order to solve these problems, dust and gas cleaning devices with different structural structures are being created and scientific research is being carried out worldwide [4,5,6]. The main requirements for the devices being created are the simplicity of the construction structure, high cleaning efficiency and low energy consumption.

Research object

Based on the above requirements, we have developed a new structure of the wet cone contact apparatus and are conducting scientific research [1,4,7]. The advantage of this device is that in order to increase the contact surface between dusty gases and the liquid supplied to the device, the contact element of the device is made of conical grids (Figures 1 and 2) [1,4,7].

As a result of theoretical studies, a formula for calculating the total lost pressure in the device was derived.

The appearance of this derived formula is as follows [1,4,7].

                                                 (1)

Experimental studies were conducted on the device, and the local resistance coefficient ξ_l=0,6 in the dusty air inlet and outlet pipe to the device was made to simplify calculations. The formula for calculating the total resistance of the device is presented in the following form [2].

                       (2)

At the next stage of the experimental research, the resistance coefficients of 3 different sizes of а=1,1; а=1,3; а=1,6 mm square hole conical grids installed on the device and the total resistance coefficients of the device were determined [2]. The task before us was focused on the experimental determination of the total lost pressure in the case of fluid injection into the device, depending on the determined resistance coefficients.

The results obtained

When calculating the total lost pressure, if we put formula 2, which calculates the total resistance coefficient of the above-mentioned device, into formula 1, the following simple form will appear.

                        (3)

where ∆k is the correction factor, determined by experiments [2]. R- is the radius of the base of the conical grid, m; r-radius of the cut part of the conical mesh, m; The average value of the length of the circumference of the base of the l_c -grid and the length of the circumference of the cut part, m; d- mesh wire diameter, m; a - mesh square hole dimensions m; ω_m - the speed of movement of the dusty air mixture on the surface of the drum grid, m/s; ρ_m – is the density of the mixture of dust and air, which is determined according to the following equation [5], kg/m³

                                           (4)

where ρ_a -air density, kg/m³; ρ_d - dust density, kg/m³; γ- the percentage of dust in the air, %.

To determine the total lost pressure in the device, experimental studies were carried out in the following order.

The size of the square hole in the working zone of the device is a=1,1; 1,3; 1,6 mm conical grids were installed and fixed gas consumption of Q=170÷850 m³/h (with a step of 170 m³/h) was given for each of them. At each gas consumption, water was sprinkled on the device’s cone nets from 12 S32-412 brand nozzles Q_w=0,3÷1,2 m³/h (in steps of 0,3 m³/h).

At each step of water sprinkled on the selected cone grids, gas velocities and flow rates were determined. The total resistance coefficients in the case of the device being sprayed with water were determined by the differences in gas consumption. Total pressures lost as a function of gas velocities and total drag coefficients determined for each mode were determined. The results obtained from the experiments are presented in Table 1.

Table 1.

Results of experiments on determining the pressures lost in the apparatus

Conditional symbols in the table.

When the gas comes out of the ventilator: ω_gas- gas velocity, m/s; Q_gas- gas consumption, m³/hour;

When the device is sprayed with water, the gas is released from the device: Q_w- water consumption, m³/hour; ω_gas^а- gas velocity, m/s; Q^a_w- gas consumption, m³/hour; ξ_w- coefficient of resistance in the case of splashing water; ξ_gen- total resistance coefficient; Р_gen- total lost pressure, Pa.

From the experimental results presented in Table 1 above, it can be seen that the total pressure increases with the increase in liquid consumption at constant gas velocity. The total pressure increases even when the gas velocity is changed at a constant value of liquid consumption. But the difference between the pressure losses generated by changing the gas velocity at constant fluid consumption given the 3 different mesh sizes is small. When graphs of dependence on modes were constructed, the separation of lines became awkward. Therefore, graphs of the relationship between the lower and upper limit values ​​of the lost total pressures were constructed (Figures 3, 4, 5).

The mesh square hole size a=1,1 mm const.

When gas consumption Q_gas=170÷850 m³/hour.; 1-Upper limit, when liquid consumption Q_w =1,2 m³/h.; 2- Lower limit, when liquid consumption Q_w =0.3 m³/h.

Figure 3. Graph of change of pressure depending on gas velocity

When the results of the experimental research are processed by the least squares method on the basis of the computer program, the form of the regression equations is as follows:

а=1,1 mm when const;

For the upper limit;

y = 2,9432x² - 40,734x + 192,61     R² = 0,9976                                                     (5)

For the lower limit;

y = 2,9949x² - 37,545x + 174,09     R² = 0,992                                                       (6)

Mesh square hole size a=1.3 mm const.

When gas consumption Q_gas= 170÷850 m³/hour.; 1-Upper limit, when liquid consumption Q_w =1,2 m³/h.; 2- Lower limit, when liquid consumption Q_w =0.3 m³/h.

Figure 4. Graph of pressure change depending on gas velocity

The resulting regression equations look like this:

when а=1,3 mm const;

For the upper limit;

                                y = 2,5806x² - 27,911x + 121,87     R² = 0,9517                     (7)

For the lower limit;

                                y = 2,5942x² - 32,563x + 150,52     R² = 0,9632                     (8)

The mesh square hole size a=1,6 mm const.

When gas consumption Q_gas= 170÷850 m³/hour.; 1-Upper limit, when liquid consumption Q_w =1.2 m³/h.; 2- Lower limit, when liquid consumption Q_w =0.3 m³/h.

Figure 5. Graph of pressure change depending on gas velocity

The resulting regression equations look like this:

when а=1,6 mm const;

For the upper limit;

y = 2,4704x² - 31,788x + 149,91      R² = 0,9668                                                    (9)

For the lower limit;

y = 2,2597x² - 28,672x + 137,13      R² = 0,9656                                                  (10)

As can be seen from the above table 1 and the graphs depicted in figures 3, 4, 5, when a conical screen with a mesh square hole size a=1,1 mm is installed, the liquid consumption is lost at the upper limit of Q_w=1,2 m³/h with the change of the gas velocity. the total pressure changed to P_gen=67÷1712 Pa according to the gas velocity. At the lower limit of liquid consumption Q_w=0,3 m³/h, it changed to P_gen=62÷1596 Pa in accordance with the gas velocity. At the next stage, when a conical mesh with mesh square hole size a=1,3 mm was installed, the total pressure lost at the upper limit of liquid consumption Q_w=1,2 m³/h changed to P_gen=63÷1560 Pa according to the gas velocity. At the lower limit of liquid consumption Q_w=0,3 m³/h, it changed to P_gen=58÷1294 Pa in accordance with the gas velocity. When a conical grid with a square hole size a=1,6 mm was installed, the total pressure loss at the upper limit of liquid consumption Q_w=1,2 m³/h changed to P_gen=63÷1560 Pa according to the gas velocity. At the lower limit of liquid consumption Q_w=0.3 m³/hour, the total pressure loss was observed to change to P_gen=58÷1294 Pa, in accordance with the gas velocity. The lower and upper lines of the total lost pressures in the graphs described above are the upper and lower points of the experiments conducted on the modes, and the dust gas cleaning efficiency of the device is determined according to these limit points and lines and the modes between them (on the hatched surface), and the optimal values ​​​​of the total lost pressures at a high value of the cleaning efficiency is selected.

Summary

In this scientific research work, the square hole size of the experimental device of the wet dust cleaning cone-type apparatus is a=1,1; 1,3; 1,6 mm conical tubes were installed and the results of an experimental study in different gas and liquid flow regimes were presented. The experimental values ​​of the lost total pressures were determined depending on the local and general hydraulic resistance coefficients of each mesh installed on the working bodies of the device. As a result, it was possible to determine the optimal values ​​of the dust gas cleaning efficiency of the device depending on the determined total pressures in these conical grids.

References:

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