Source: ash removal and desulfurization circle
Agitator blade is a kind of agitator with two to three pusher stirring parts, the propeller agitator has a high rotation speed when stirring, which can force the material to move along the axial direction, so that the material can be fully circulated and mixed, and the propeller agitator is mostly suitable for mixing liquids, suspensions, emulsions and other materials with low mixing consistency. Its drainage capacity is 30% higher than that of conventional pusher agitators.
1 Blade Introduction
Propeller agitator blades
Propeller agitator blades
It is composed of 2~3 pusher propeller blades (Fig. 2), and the working speed is high, and the circumferential speed of the outer edge of the blade is generally 5~15m/s. The propeller agitator mainly creates axial liquid flow and produces a large circulating volume, which is suitable for stirring low viscosity (<2Pa·s) liquids, emulsions and suspensions with solid particle content of less than 10%. The shaft of the agitator can also be inserted horizontally or diagonally into the tank, where the circulation loop of the liquid flow is asymmetrical, which increases turbulence and prevents the liquid level from sinking.
Turbine agitator blades
It consists of 2~4 straight or curved blades mounted on a horizontal disc. The ratio of the outer diameter, width and height of the blade is generally 20:5:4,
Turbine agitator blades
The circumferential velocity is generally 3~8m/s. The turbine causes a highly turbulent radial flow as it rotates, and is suitable for the dispersion of gases and imparticity fluids and liquid-liquid phase reaction processes. The viscosity of the stirred liquid generally does not exceed 25Pa·s.
Paddle agitator blades
Paddle agitator blades
There are two types: flat paddle type and oblique paddle type. The flat paddle agitator consists of two straight paddle blades. The ratio of the diameter of the blade to the height is 4~10, and the circumferential velocity is 1.5~3m/s, and the radial flow velocity generated is small. The two blades of the slobly paddle agitator are rotated in opposite directions by 45° or 60°, resulting in an axial flow. Paddle agitators are simple in structure and are often used for the mixing of low-viscosity liquids and the dissolution and suspension of solid particles.
Anchor agitator blades
The shape of the outer edge of the paddle should be consistent with the inner wall of the stirring tank, and there is only a small gap between them, which can remove the viscous reaction products attached to the tank wall or the solid matter accumulated at the bottom of the tank, and maintain a good heat transfer effect. The circumferential velocity of the outer edge of the paddle is 0.5~1.5m/s, which can be used to stir Newtonian fluids and plastic-like fluids with viscosities up to 200Pa·s (see Viscous Fluid Flow. However, when stirring high viscosity liquids, there is a large stagnation zone in the liquid layer
Screw belt agitator blades
The outer diameter of the spiral belt is equal to the pitch, and it is specially used for stirring high-viscosity liquids (200~500Pa·s) and plastic-like fluids, and is usually operated in a laminar flow state.
(6) Magnetic stirrer Corning digital heater with a closed-circuit knob to monitor and adjust the stirring speed. The microprocessor automatically adjusts the motor power to suit the water quality, viscous and semi-solid solutions.
Magnetically heats the stirrer blades
Corning digital heat stirrers come with an optional external temperature controller (Cat. No. 6795PR) that can also monitor and control the temperature in the vessel.
Leaf folding agitator blades
According to the physical properties, capacity and stirring purpose of different media, the corresponding stirrer can play a great role in promoting the chemical reaction speed and improving the production efficiency. The rotary blade turbine stirrer is generally suitable for the reaction of gas and liquid phase mixing, and the speed of the agitator should generally be more than 300r/min.
Inverter double-layer agitator blades
The base, strut and motor of the inverter agitator are fixed as one using patented technology. Patented chuck, no loosening, no swinging, no falling off, safe and reliable. Chrome-plated struts, thick at the bottom and fine at the top, strong rigidity and reasonable structure. It has the advantages of easy movement and light weight. Suitable for all types of small containers.
2. Power calculation method
Theoretically, although the stirring power can be divided into two aspects: stirrer power and stirring operation power, in practice, only or mainly consider the agitator power, because the stirring operation power is difficult to be accurately determined, the speed of the agitator is generally set to meet the required stirring operation power. Starting from the concept of stirrer power, the main factors affecting stirring power are as follows.
parameter
The structure and operating parameters of the agitator, such as the type of agitator, the diameter and width of the impeller, the inclination angle of the impeller, the number of impellers, the speed of the agitator, etc.
Width and quantity
The structural parameters of the stirring tank, such as the inner diameter and height of the stirring tank, whether there are baffles or guide cylinders, the width and number of baffles, the diameter of the guide cylinders, etc.
Consistency
The physical properties of the stirring medium, such as the density of each medium, the viscosity of the liquid medium, the size of the solid particles, the aeration rate of the gas medium, etc. From the above analysis, it can be seen that the factors affecting the stirring power are very complex, and it is generally difficult to obtain the calculation equation of the stirring power directly through the theoretical analysis method. Therefore, with the help of experimental methods, combined with theoretical analysis, it is the only way to obtain the formula for calculating stirring power.
Neville-Stokes equations by fluid mechanics
and express it in dimensionless form, and the dimensionless relation (11-14) can be obtained. Np=P/ρN³, dj5=f(Re,Fr) where Np - power standard Fr - Froude number, Fr = N²dj/g, P - stirring power W. In Chinese equation (11-14), the Reynolds number reflects the ratio of the inertial force to the viscous force of the fluid, while the Froude number reflects the ratio of the inertial force of the fluid to the gravitational force. Experiments show that the Fr number has no effect on the stirring power except in the transition flow state of Re>300. Even in the transition flow state of Re>300, the Fr number has little effect on most of the impellers. Therefore, the power factor is directly expressed as a function of the Reynolds number in engineering, without considering the influence of the Froude number. Since only the speed of the agitator, the diameter of the impeller, the density and viscosity of the fluid are included in the Reynolds number, many of the other factors mentioned above must be set in the experiment, and then the relationship between the power standard and the Reynolds number must be determined. It can be seen that all the curves or equations obtained from the experiment as a function of the power standard and the Reynolds number can only be used within certain conditions. The most obvious is that for different propeller types, the relationship curve between the power standard and the Reynolds number is different, and their Np-Re relationship curves will also be different.