An agitator is a device used to mix various types of materials uniformly and homogeneously by transferring a motion. A shaft and impeller are the main parts of this equipment which are driven by the motors using electricity. This device has great importance in mixing solids and gases, promoting chemical reactions, promoting heat transfer, etc.
This device is used at present in chemical processing industries, cement industries, sugar industries, paint industries, adhesive industries, toiletries industries, agricultural, biotechnology, pharmaceutical industries, cosmetics, metal extractions, ink, etc. It is used to carry out a proper chemical reaction, homogeneous mixing operations, filtration purposes, drying, heat exchange, chemical transfer purposes, etc.
Agitator Definition
It is an important device used to transfer motion to liquids or semi-solid materials. The motion which is transferred by this device is in the form of stirring. It has a shaft and an impeller/propeller. The shaft part connects to the gearbox. This part is driven by motors using electricity. The liquids, solids, slurries, and pastes can be mixed well by using this device. It is also used to mix liquids and gases, mix solids and gases, promote chemical reactions, promote heat transfer, etc.
The materials in the chemical reactors become uniform and homogeneous and remain in a proper mixed state for use in this device. At present, this device is used worldwide in various types of industries like food, pharmaceuticals, chemicals, processes, cosmetics, agriculture, biotechnology, metal extractions, ink, paint, adhesives, metal processing, polymer processing, etc.
This device is mostly used in industrial sectors for running industrial processes such as for carrying out a chemical reaction, homogeneous mixing operations, filtration purposes, drying, heat exchange, chemical transfer purposes, etc. This device has a wide range of applications for having a variety of impellers that come in different sizes and shapes.
Agitator Working Principle
This device creates a laminar flow of materials by importing a motion inside the tank. A good homogenized media can be generated by rotating immersed impellers in this equipment at a controlled speed, also called revolutions per minute (RPM). The impeller pushes the materials in radial and tangential directions for homogeneous mixing.
A single or multi-component material is induced easily by the rotating impeller to flow and shear the media inside the tank at a uniform rate and homogeneous pattern. This device creates homogeneous solutions and suspensions to achieve a uniform consistency as well as transfer various types of solutions in a mixed state and prevent concentration gradient.
The blades of this device possess a large surface area, so they are able to come in close contact with the various materials to mix and enhance chemical reactions inside a reactor as well as increase heat transfer to a jacket. As a result, a consistent temperature of the solution inside a vessel can be achieved easily. The liquid, suspensions, highly viscous liquids, gaseous, and solid materials are handled properly by using this device.
It is a very important matter to select the right type of agitator, sizing, and design for the specific works. It must be remembered about the properties of viscosity and sensitivity to shear stress during the selecting matter of an agitator.
Agitator Parts
There are three main components in an agitator. These are the motor component, shaft component, and impeller component.
Motor component
This part helps to drive this tool assembly properly. It generates the right amount of torque to induce flow and shear to the media at a controlled degree. The power factor of an agitator generally depends on various matters like specific gravity, viscosity, solid properties of materials, numbers of the impeller, speed of the impeller, diameter of the impeller, and power number of the impeller.
Shaft Component
This part is generally attached to the motor’s driveshaft and transfers the torque to the impeller part. This part is constructed by various types of materials like couplings, end caps, and other devices. The various types of materials are built up by using various seals in this part.
Impeller Component
It is a very important part of an agitator to calculate the flow pattern, efficiency of the homogenizing process, and mixing parameters. It exerts energy to actually mix the materials homogeneously. It is constructed by a hub and blades. The hub part is attached to the shaft by a shaft key and a grub screw.
The blades are attached to the hub by screwing or welding. A welding connection is preferable to a screwing connection because it prevents the material build on the fasteners and fittings. The number of impellers in an agitator generally depends on the impeller properties, the working vessel characteristics, and specific media gravity.
Agitator Types
There are five types of agitators namely turbine agitators, paddle agitators, anchor agitators, propeller agitators, and helical agitators. The descriptions of these agitators are given below:
Turbine Agitator
This type of tool has great importance in industrial sectors for having versatility and proper mixing ability. A turbulent movement of fluid can be created by this device due to the combination of rotational as well as centrifugal motion. The input of this equipment has an axial flow but the output is radial. This device is very much used in metal industries, pharmaceuticals, grease, cosmetics industries, and chemical processing industries to perform various types of chemical reactions and for having a very high blending efficiency.
Paddle Agitator
This basic type of equipment consists of blades that are paddle-shaped. The blades of this device stretch throughout the reactor and reach the walls of the reactor. It creates a uniform laminar flow for the liquids. Paddle agitator is generally used for the handling of viscous materials in chemical processing industries, pharmaceuticals, food industries, etc.
Anchor Agitator
The shape of this device is like an anchor. This equipment can extend and spread throughout the vessel area in such a way that there are very less clearance areas between the blades and the walls of the vessel. A laminar flow condition can be generated easily by using this tool. It sweeps easily the whole batch of materials because the blades in this device are almost in physical contact with the walls of the vessels. This equipment is widely used in ink, paint, and adhesive industries for creating laminar flow conditions.
Propeller Agitator
The shape of this equipment is like a marine-type propeller. The blades of this agitator help to minimize the centrifugal force and to increase the axial flow. The inlet flow of the materials in this device is parallel to the shaft and the outlet flow is also parallel to the shaft, the ideal flow is axial type. This device is used to stir the viscosity liquids in pharmaceutical industries and also various types of industries that use suspensions as the agitators don’t let the solid particles settle.
Helical Agitator
The blades of this equipment are arranged in a structure of helix similar to the threaded screw looks. The materials moved in this equipment are axial in nature because of the way the blades or the ribbons move while the helical agitator is in operation. A vigorous motion is created in the fluid materials during the operation of this equipment. It is mostly used in polymer processing industries and other chemical industries for handling viscous-type materials.
Agitator Flow Patterns based on Impeller characteristics
There are four types of flow patterns in an agitator impeller depending on its characteristics which discussions are given below:
Axial Flow Impeller
It has angled blades that make less than 1000 to the plane of rotation in such a way that a “top-to-bottom cyclic” flow pattern can be easily achieved. The various types of materials at the upper portion of the vessel can be forced to flow downstate until it is deflected at the tank bottom. Then the materials spread over the tank bottom and flow up along the vessel wall before being drawn by the impeller to prevent the solids and solutes from settling at the tank bottom.
It is used to handle solid suspensions, lower-viscosity fluids, and heat transfer applications. This type of impeller is generally installed in tanks where large vertical currents are desired.
Radial Flow Impeller
This impeller creates a media for making a perpendicular flow of the media to the impeller’s axis of rotation. A side-to-side flow pattern is generated by the radial flow impeller. The fluid exits from the impeller and flows towards the tank’s walls to move in an upward or downward direction until it is drawn again to the impeller’s center.
It generates a high degree of shear and less flow but it is perfect for blending the viscous liquids and for gas-liquid and liquid-liquid dispersions. This impeller is mostly used for low-level mixing inside elongated tanks.
Tangential Flow Impeller
This impeller creates a circular path around the shaft to flow the materials. The materials rotate around the vessel together with the impeller blades with a very low vertical flow. This impeller is very much used to blend the highly viscous media and stratification.
Close Clearance Impeller
The diameter of this impeller is about 70% of the vessel diameter which produces a small clearance between the vessel wall and the outer edges of the impeller. It helps to prevent any type of fouling and reduce the rate of heat transfer. This impeller is used widely for low-speed laminar blending of highly viscous liquids in paints, inks, adhesives, grease, and polymer processing industries.
Frequently Asked Questions (FAQs)
What is an agitator mixer?
It is equipment to generate the homogenized media among the various types of materials by following the shaking or stirring mechanisms with rotating immersed impellers at a controlled speed.
What are the types of agitator machines?
There are five types of agitators namely turbine agitators, paddle agitators, anchor agitators, propeller agitators, and helical agitators.
What are the parts of an agitator?
There are three parts in an agitator namely motor component, shaft component, and impeller component.
What are the uses of an agitator?
This device is widely used in the sugar industry; paint industry, adhesive industry, toiletries industry, agricultural, biotechnology, pharmaceutical industries, chemical processing industries, cement industries, cosmetics, metal extractions, ink, etc. to carry out chemical reactions, homogeneous mixing operations, filtration purposes, for drying, for heat exchange, for chemical transfer purposes, etc.
