Types of Mixers

Chapter 1: Principle of Mixers

This chapter will discuss what industrial mixers are and the considerations in choosing a mixer.

What is a Mixer?

A mixer is a complex and precise tool that is used in combining and mixing of substances and chemicals for manufacturing, production, and industrial use.

There are many types of industrial mixers including the ones that are compact, which are capable of combining plastic polymers quickly for the production of plastics, to ones that are capable of pulverizing and mixing pellets and stones. There are many industries that rely on mixers including pharmaceuticals, food industries, and cosmetics since mixing is an essential part of their production processes. Mixing is associated with food production by most people due to the obvious relationship. There are many mixer applications beyond the production of food. In any industry where there is a requirement of the combining of substances, mixers can be found.

Considerations When Choosing an Industrial Mixer

Some considerations when choosing an industrial mixer include:

Powder Characteristics

The texture and consistency of the powder used for the products must be known. Different characteristics of powders require different types of mixers. Some powders have thin particles that require gentle blending. However, it is a different case when using sticky and cohesive powders.

Powders that are cohesive and sticky can cause problems if they are blended in the wrong mixer. These kinds of powders are capable of sticking to the mixer’s interior walls. To prevent this from happening, high shear mixers are the ideal mixers to choose as they can properly blend particles.

Industrial mixers that exhibit faster torques are able to remove the dislodged particles. The characteristics of the powder are a major factor to consider when opting for the right mixer. If this is overlooked, there can be particle degradation in the mixture and unwanted heat.

Type of Liquid Viscosity

The other important factor to consider is the type of liquid viscosity. There is a need to understand that some liquids exhibit unique characteristics when they are applied to a mixer. Moreover, the type of liquid used is dependent on the product used. The most commonly used types of liquid viscosities are listed below:

• Newtonian liquids
• Thixotropic liquids
• Pseudo plastic liquids
• Dilatant liquids

Vessel Capacity

Industrial mixers may be large vessels. However, the size of the product must be calculated and the capacity of the vessel. A consideration of the capacity of the vessel implies the time that is spent on loading, emptying as well as cleaning, which leads to large downtime. The height of the batch, volume, and the diameter of the vessel must be thought through. These factors help in the identification of a suitable mixer for the products to be mixed.

Mixing Time

The process of blending involves numerous stages, from loading to packing and also to cleaning. Thus, knowing the true time taken by the mixer to blend the products is best. Each mixer has a typical average true mixing time. Some time is estimated for loading while the other is for packing. For the completion of the cycle, it takes longer.

Ease of Cleaning

There are certain types of mixers that consist of many parts which are moving and these cause the dislodging of the product. These products can adhere onto the bearings, walls of the mixer, and the paddle. It might be viewed as a waste because it is a huge amount of product that is being lost. It is also a highly likely carrier, which causes cross contamination.

Therefore, there is a need to take into consideration the total amount of time in drying the parts of the mixer as well as cleaning. However, it takes a long time to both remove the parts and return them. Care and having patience are required in returning the parts. The main goal in selecting the correct or appropriate mixer is to be able to maintain and have a process that is so efficient when manufacturing the product therefore carefulness is always needed.

Risk of Cross–Contamination

It is possible to release allergens when blending and mixing ingredients for products. The mixer machines which are used for different and many recipes are those with a high level of risk for cross contamination. Therefore, research and specialists in these fields suggest that different products should have different mixers. This is because some products have allergens. These are mostly the guidance and what is needed in order to avoid the cross contamination of products.

Chapter 2: Types of Mixers

This chapter will discuss the different types of mixers.

Tumble Blender

Tumble blenders are utilized in dry mixing. It produces a rhythm during its tumbling. Drum tumbler mixer is mostly utilized in the mixing of solids and powders, but in some cases, it also accommodates liquids.

The solids are rotated up and down by the movement of the tumbler. In the mixing of the products, gravity also plays an important role, and there is no need for drum baffles at times of breaking solids into smaller particles. Tumbler blenders have various configurations including octagonal blenders, cone blenders, and V-blenders.

High Shear Mixers

The high shear mixers can be used in solid and liquid materials to yield emulsification, homogenization, dispersion, particle size reduction, and disintegration. They are high speed machines with high powered mixing blades known as shears. They have a shorter mixing time compared to other standard mixers.

High shear mixers can mix liquids and solids that would typically not mix such as oil and water. The high shear mixers can emulsify such immiscible materials. High shear mixers have traditionally been used in the rubber industry but have become applicable in other industries like chemical, food, pharmaceutical, cosmetics, and adhesive industries.

High Speed Mixers

High speed mixers are typically used where a substance needs to be cooled, granulated, or dispersed to move it quickly and prepare it for the next processing step. They can be used in industries like food processing, pharmaceuticals, and paint production. The high speed mixers can be found in sizes and shapes ranging from lab mixers which can be small and high speed to industrial-sized high speed mixers.

Ribbon Blender

This type of mixer is utilized to blend powder and bulk solid blending. It consists of a blender configuration that is capable of totally de-lumping powders through its ribbon-like paddles that are long and intersecting.

Even though it is capable of mixing products effectively and attaining homogeneity, it has a very high cost compared to paddle mixers and its maintenance is much more difficult. However, these types of blenders are utilized in some pharmaceutical industries for achieving the most accurate mixed portions of powders.

Paddle Mixer

These types of mixers are utilized in the mixing of solids, viscous or slurry liquid mixing, and wet-dry mixing. They consist of a central shaft axis for the holding of the blades. They are frequently utilized in dry mixing, but they can also accommodate liquid-solid mixing.

Agitator Mixers

These types of mixers are utilized to mix a liquid and a liquid or mix a liquid and a gas. Top-load washing machines have agitation in the move that can be seen. They consist of an agitating blade in the center that remains stationary while the water is being agitated in the washing machine during its rotation. Agitators that are utilized in the processing of food and beverages industrially have a similar principle and configuration.

The attachment of impellers is done on the shaft of the central axis that is responsible for the rotation of the liquid or at least causes the agitation of the liquids. The blending of substances that are thick by agitators is a sore. These types of mixers are not recommended for products that are too viscous.

There is a range of functions that agitators lend themselves to. These include dissolving gas into a liquid, suspension of solids in liquids, blending miscible liquids, connecting or dispersing liquids that are not able to mix and the transfer of heat in agitated liquid. Agitators are classified into two types that are axial and radial. Their names come from the angle of contact of the impeller blades and the rotation plane.

Axial Flow Impellers

In this type of agitator, there is a creation of an angle that is less than 90 degrees with the rotation plane, by the blade itself. Due to this, the occurrence of the locus of flow happens along the impeller’s axis.

Radial Flow Impellers

In these types of agitators, there are radical flow blades that are parallel to the impeller axis. Because of this, radial flow impeller releases flow beside the radius of the impeller in distinctive designs.

Rotor Mixers

The metal blades of a rotor mixer are installed at the bottom of a container and can spin at variable speeds. This is typically found in blenders.

In some cases, rotor mixers can operate with various attachments which can be detachable. They can thus be applied in industries where there is a need to mix multiple jobs. The rotor mixers can be used in industries such as food production, adhesives, pharmaceuticals, and chemical processing.

Static Mixers

The static mixers use ribbon-like obstructions within a cylinder to mix and blend material. Static mixers have no moving parts and are also known as inline mixers.

They are typically used in production lines that prefer continuous material flow to batch mixing. Thus, static mixers can facilitate smooth operation and faster mixing by mixing constant and steady liquid streams. Static mixers allow a high level of control over the extent of mixing needed. This would depend on the intended outcome where some outcomes are homogenous while others are less precise.

Static mixers are typically used in industries like chemical, cosmetic, automotive, pharmaceutical, and water treatment industries. Static mixers are effective when used with low viscosity liquids and materials.

Disperser Type

A disperser uses concentrated and high speed force to disintegrate, dissolve, and dissipate solids that can be found in powdered materials or liquids. Mixing shafts can have blades that are disc shaped attached to them and make the blades have maximum speed rotation. This yields proper flow, dispersion, and consistency during the blending and mixing process.

Dispersers are typically used in food production as part of solid ingredients liquifying processes or even solidifying materials during storage. Generally, the dispersers are used in processes with substances that are incompatible and would typically require extra force to yield a proper mix and blend. Examples of such substances can be found in adhesives, cosmetics, and pharmaceutical production.

Emulsifier Mixers

These types of mixers are utilized in mixing immiscible liquids. Examples of two substances that are completely not miscible are oil and water. In the cases when there is a requirement of a totally homogenized and emulsified mixture like in making sunscreen, lipstick, lotion, and mixing cosmetics, an emulsifier is utilized.

This mixer is a special type of mixer that not only utilizes pressure for the complete mixing of liquid-liquid substances, but also incorporates isolated vacuum-filled equipment as well as high shear. There is the incorporation of a centrifugal force in vacuum emulsifier homogenizers. The materials are driven by this force into the work head for their breakdown into smaller particles. In the case of cream and milk, cream consists of fat molecules that are large, which separate from milk because of the big difference between the sizes of the molecules; emulsification is responsible for the breaking down of the cream molecules so that they become similar to milk molecules in their size.

Homogenizer Mixers

These types of mixers are utilized in the combination of liquid-liquid mixtures and solid-liquid mixtures. There is an application of extreme force by this mixer. It also applies extreme shear and pressure on the materials or liquid as well, to homogenize the mixture.

Heavy Duty Mixers

These types of mixers are utilized in the mixing of viscous and pasty substances. When a single shaft mixer is run with slurries that are very thick like pasty ingredients, wax compounds, and putty. This would normally cause buckling and failure in mixing equipment. Thankfully, there are heavy-duty mixers designed for mixtures that reach high viscosity above 750,000 centipoises. These heavy-duty mixers include planetary and multi-shaft mixers.

Concrete Mixers

These are machines that combine cement, aggregate like gravel or sand together with water to form concrete. A typical concrete mixer utilizes a drum that revolves for the mixing of the components.

Concrete mixers are utilized for the production of concrete on the construction site to provide the workers with ample time to use the concrete before its hardening. There are various types of concrete mixers mentioned below:

Batch Mixers

This type of concrete mixer is responsible for the production of one batch at a time. It can either have a pan or drum that consists of blades, which prepares the concrete mix when rotated. The rotation speed, blade angle and in some cases the angle at which the drum is inclined can be controlled. These concrete mixers are the most commonly used, and they are highly preferable for use in construction sites that are small and medium-sized. Modern models can fine-tune the system of the mixing process.

There can be a precise adjustment for each batch. Batch mixing is often chosen for products that must be put through strict quality testing. The batch mixing is made ideal for powdery ingredients that are sensitive chemically and are susceptible to change with time through flexibility.

There is a possibility to first blend a portion of the ingredients made by batch mixers before loading additional ingredients. Batch mixers are capable of performing multiple mixing processes in this way. There is a new series that comes with a discharging door with a big radius and also has an additional discharging blade that permits a discharge operation that is faster. The secondary gearbox’s high simplicity and the employ of a primary gearbox that is commercial type allows for easy maintenance operations and operational reliability that is relatively high. Batch mixers have two different categories, which are pan mixers and drum mixers.

Drum Mixers

These types of mixers consist of a double drum that is conical frustum shaped. Depending on its type, the drum can have multiple or a single set of blades which are utilized in the mixing, preparation, and discharging of the concrete mixture. There are a variety of configurations in which drum mixers are found for different applications.

The drum mixer utilizes a paddle with a number of blades that curve in different directions; this is known as a swing-blade paddle. The swing-blade design permits the maximization of liquid movement by the drum mixer within the rotating drum, which reduces the time that is spent on mixing. There are three types of drum mixer types which are:

Tilting Drum Mixer

A tilting drum mixer mixes the ingredients while it is forward rotating, and discharges while it reverses the motion of the concrete mixer drum. This type of mixer is often utilized for the blending of semi dry concrete and plastic. Tilt drums come with many advantages like stable operation, low noise, high working efficiency, convenient movement, high productivity, and high quality.

Tilting drum type concrete mixer is mostly utilized in the construction of bridges, roads, water, and electrical engineering. Tilting drum concrete mixers discharge concrete from the drum by tilting downwards. It is utilized for huge projects, and it is capable of quickly discharging the process. The mixing efficiency of this mixer is primarily dependent on factors like blade size, angle of blades, and the drum’s shape.

These types of drums are well suited for the preparation of concrete with low workability and aggregates of large size. These mixers are preferred highly for construction sites that are large or applications that involve the intensive carrying out of construction work.

Non-Tilting Drum Mixer

This type of concrete mixer mixes the mixture without tilting it, and the rotation of the drum is about the horizontal axis in this methodology. For discharge, the chute is placed in a position that is inclined to get the mixture of the concrete from the drum responsible for the discharge.

These types of drum mixers are available without a tilting drum, which rotates on its horizontal axis for the production of concrete. They consist of openings on both their ends. The ingredients that are required for the production of the mix are fed from one end and the collection of the mix is done on the other end. By attaching a chute to the drum’s opening, the mixing is obtained. The blades of these types of mixers aid in the extraction process. Non-tilting drum mixers are utilized in small construction sites.

Reverse Drum Mixer

Reverse drum mixers are responsible for the production of concrete in single batches. The rotation of the entire drum is about its axis. The loading of the materials is done through a charge chute that is located at the opposite end of the drum. The end-dump models are responsible for the provision of power for the concrete or various blending materials to be manually loaded within the drum, as each facet unloads. In these types of concrete mixers, rotation reversal occurs for different actions. The drum has two openings, one opening is utilized for keeping the ingredients and the other opening is utilized in the mix discharge.

Pan Mixers

This type of concrete mixer consists of a cylindrical pan instead of a drum. Just like drum mixer types, these mixers also consist of blades for the facilitation of the mixing process. The shape of these blades is generally like that of a star to ensure optimum efficiency. In this pan, the mixing of concrete is done by bladed arrangements in series, in a star’s shape inside the pan.

Pan mixers can completely mix complex mixes and keep a momentum that is solid, going through the combining procedure. These types of mixers can have large sizes that can hold up to 1000 gallons (3.79 m³) for large-scale use in the industry.

For the prevention of sticking mortar to the pan surface, they are equipped with scrapers. The pan mixers can vary their types with:

• The one in which the circular type of the pan concrete mixer is uniform while just blades setup in a star manner rotates about the pan’s vertical axis.
• The second type is the one in which there is a rotation of the circular pan and the star blades are stationary. However, the process of mixing is done efficiently and through the hole present in the pan’s center, where the mixture is taken.

Continuous Mixers

These types of mixers have a primary function of mainly mixing, loading and discharging the mix continuously until all the work is done or until the occurrence of the work break. In this mixer, the loading of the materials is done continuously by the screw feeders. These types of mixers are well suited for large projects like dams, high rise buildings, and bridges. Continuous mixers are often the best option for projects of high volume requiring speed and efficiency. Continuous mixers must only be used when mix ratios can differ between the batches.

When more specific ratios are required, batch mixing is a better option, typically. Some manufacturers utilize continuous mixing for the smoothing out of multiple various batch mixes to make the finished product more homogeneous. The batch is removed from the mixing equipment and then the new batch is fed into the continuous mixer.

There are a number of benefits that are offered by a continuous mixer that are found with batch mixing. Continuous mixing requires a smaller number of staff and is much faster. The process of feeding ingredients in this type of mixer is automated and the feeding out of the batches is done automatically with no need for removal or refilling.

Acoustic Mixers

Acoustic mixers use an energy efficient mixing process which is very rapid. The mixing process can be faster than the conventional mixing processes by 10 to 100 times. With this process, less heat is imparted into the mix.

The acoustic mixing process is also repeatable from mix to mix. Thus, it is able to mix any combination of materials. Acoustic mixers can be found in commercial batch systems to continuous operations. They can come with capabilities to be cleaned in place with no rotating hardware that might need cleaning.

Fluidization Mixers

The mechanical fluidization process includes the division of particles and perturbation that is through impingement. To cause turbulence, a rotating element is used. The rotating element causes rapid churning in the tank among the materials. They enter into motion through the solids just like they are a hydrous substance. This process involves double paddle mixers and plow mixers.

Convective Mixers

Convective mixers have a short mixing period. This type of mixer is preferred by some industries because of its faster working rate. Convective mixers are less practical for operations that are diffusive. They are firm physically and contain resolute shelves with an impeller. Ribbon blenders, vertical screw blenders, and paddle blenders are mixers classified under this category.

Dough Mixer

Dough mixers are machines that are utilized in the mixing of different kinds of special bread ingredients. They can also be utilized in the mixing of dumpling skins, noodle ingredients, and others. The main function of dough mixers is the mixing of different ingredients into one for the production of perfect dough. If the dough is mixed better, the resulting dough will be better. The size of the dough mixers is large with a capacity of 50 kg, and they are mostly utilized in the baking industries.

Chapter 3: Applications and Benefits of Mixers

This chapter will discuss the applications and benefits of mixers.

Applications of Mixers

Mixers in the food industry are used to make formulations for foods like cheesecakes. Cheese and butter are mixed together to form a smooth and creamy consistency. This is done without even breaking the butter or even over heating the mixture.

The manufacturing of different types of juices also requires a mixer. Juices and fortified milk are manufactured using very high shear mixtures. In many manufacturing facilities, there is a successful and continuous use of high shear mixtures for dissolving the artificial sweeteners and preservatives into the water. Propeller mixtures were also used but can’t remove the lumps that were made by sweetener and preservative.

Mixers are also used to blend and mix cocktail sauce with fresh shrimp. Vegetables as well as chopped meats are also mixed by use of these high shear mixers. Another significant application is in plant based proteins. Many types of mixers are being used in the production and development of the plant based milks, meats, butter, cheeses, eggs as well as other proteins.

Other applications of mixers in the food industry include in the manufacture of candy and confectionery products, gums, different kinds of soup bases, gums, syrups, pet foods, mayonnaise, ketchup dressings, and dry solid blends to name only a few.

Mixers are also used in the construction industry as concrete mixers, and they play a very important role. They are being used to make concrete in the construction industry. Their main uses are on slabs, dams, walls, foundations, bridges, railroads, and airports.

These mixers greatly minimize the cost of material since the exact amount of material required is the one that is produced. They also eliminate the issue of hot loads. This is because the materials are made exactly on the site. They also cut labor costs by controlling man-hours. The continuous mixer works well without any disturbances, and it produces concrete continuously as long as it is not stopped. The raw materials are fed and the concrete that is discharged is collected at the other end by workers, usually.

These types of mixers mostly consist of a separate feeder unit that takes in the raw materials, in a discharged system as well as a unit for mixing the concrete. These mixers are usually applied if there is a construction of very large structures like tunnels for roads, bridges, or dams.

The use of mixers is also employed in the pharmaceutical industry. To be specific, the mixing equipment that is used in the manufacture of medical devices and pharmaceuticals has a maximum level of complexity since their application is much specialized.

The process of mixing meets various objectives, which are not only the combining of the raw materials. Some of these include the preparation of emulsions and carrying out various chemical reactions. There is also a wide use of mixers in reducing particle sizes, the dissolving of components, the manipulation of rheology, and the facilitation of heat transfer.

As a result of these many and various processes, it is common to introduce different and various kinds of these mixers in order to process the raw materials, to prepare the finished product as well as handle different kinds of intermediates. This is done even within a single product line of pharmaceuticals.

Benefits of Mixers

The use of mixers has various advantages in the different industries in which they are employed. In the food industry, the use of mixers helps in the prevention of variations which are not required from one batch to the other.

Another benefit of using mixers is that they produce finished texture, size, and weight which are very consistent. Another point to note down is that mixers also help to disperse the ingredients consistently. This helps keep the dough evenly hydrated. Mixers also produce large batches of dough that are uniform.

The use of mixers also helps improve the control of recipe as well as repeatability. In the construction industry they also have numerous advantages and these include the reduction or minimization of the human capital cost as well as getting the work done much quicker with very less applied effort.

There is a benefit of mixing the concrete right on the site. The safety and health of the workers is also improved. In the pharmaceutical industry mixers also have numerous benefits and these include improved efficiency, the minimized contamination risk as well as thorough mixing of materials or chemicals.

Drawbacks of Mixers

In the pharmaceutical industry, use of mixers have also drawbacks that are they may deliver insufficient and inefficient agitation. The cleaning of recirculating high mixing systems may be difficult. In the construction industry, there are also drawbacks such as the requirement of a very high initial cost.

Conclusion

The use of mixers has contributed greatly in many of the different sectors they are applied. Over the years they have made work very easy for humanity, and as new technologies evolve there are also many other forms of mixers which come into play. This increases efficiency, reduces the cost, and gets the work done quickly.