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Refining Edible Oils

Silverson In-Line mixers are used throughout the world for the refining of edible oils. Degumming and neutralisation is typically a high volume, continuous operation. The reagent additions are a critical stage in the process, requiring the acid to be finely distributed throughout the oil and intensively mixed to accelerate the reaction and maximise yield.

The acid is added to the oil just prior to the inlet of the Silverson In-Line mixer. The materials are drawn into the rotor/stator workhead and intensely mixed in the high shear zone. The fine droplet size obtained ensures the surface area of acid exposed to the oil is maximised, optimising the reaction and obtaining full yield.

Enzymatic degumming is increasingly carried out as an alternative to conventional acid degumming, providing greater yield and a significant reduction in process water required. Silverson High Shear Mixers offer several advantages in this process and are the preferred choice for companies using this method.


Edible Oils

Agitation

Agitators or stirrers come in a vast array of shapes and sizes, including marine propellers, foils, axial and radial flow turbines, gate and anchor stirrer/scrapers, etc. These different types of impeller blades characterise the flow produced and allow agitators to be used for the broadest range of viscosities and batch sizes. If the viscosity is relatively low (for instance, 1 cP or less) these devices can handle batches up to several hundred thousand gallons. As for the viscosity range that can be accommodated, turbine type agitators can operate with fluids of up to 75,000 cP. Slow-speed gate or anchor and gate configurations can handle up to 500,000 cP.

Despite the wide range of capacities and viscosities they can handle, the low shear nature of agitators limits their effectiveness to performing simple tasks such as blending liquids of like viscosities, maintaining in-tank uniformity, and producing flow in a vessel to promote heat transfer from jacketed vessel walls. Where the product has to be processed in some way – liquids of differing viscosities are being blended, powders dispersed and hydrated, an emulsion or suspension formed, solids dissolved or disintegrated and so on, an agitator can take a long time to achieve the required results or, more often than not, is simply not capable. Silverson High Shear Rotor/Stator mixers are ideal for these types of applications and can cut mixing times by up to 90%, offering improved yield and product quality and greater batch-to-batch consistency.

These advantages are further increased by the use of easily interchangeable workheads and screens which allow any one Silverson mixer to perform the duties that in the past may have required several different pieces of process equipment.


Process Improvement
Aeration-Free Mixing

Particle Size Reduction

The high shear action of the Silverson rotor/stator workhead can achieve rapid and uniform milling of both solid and semisolid materials to a low micron size in a single operation.

The degree of particle size reduction will depend on the hardness of the product, but for many applications including the Manufacture of Plant-Based Milk Alternatives, the use of a Silverson mixer will dispense with the need for conventional size-reduction equipment.

Where conventional milling equipment is required, pre-milling the product with a Silverson mixer will create a uniform premix that will pass through the conventional mill at a much faster rate, because media mills work best when fed with a product of a consistent and low particle size. Silverson offers a range of mixers including single and multistage In-Lines designed for processing even the hardest materials such as pigments, dyestuffs, filter cake, titanium dioxide, etc.


Particle Size Reduction
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Reclamation

With today’s environmental and economic pressures, more and more manufacturers want to quickly and efficiently reprocess out-of-spec or waste product. A typical example would be in the confectionery industry where mis-shapen sweets need to be disintegrated and dissolved so that the sugar can be reclaimed and reused.

Silverson mixers are widely used for this application and can efficiently disintegrate and dissolve individual sweets or clumps of sweets that have stuck together.

Other applications include chocolate and gelatin-based confectionery, biscuit filling waste, rubbers, polymers and paper.


Reclamation

Deagglomerating

When adding powders to liquids they have a tendency to form agglomerates which conventional agitators cannot readily break down. The high shear action of the Silverson rotor/stator workhead rapidly disperses agglomerates, exposing increasing areas of the solid to the surrounding liquid. The result is an agglomerate-free solution within minutes.

Adding a high shear Silverson In-Line mixer to the existing process will rapidly produce an agglomerate-free product, improve yield and batch-to-batch consistency. The animation below illustrates how this is achieved.


Deagglomeration
How to Get Rid of Agglomerates

Powder/Liquid Dispersion

Dispersing powders into liquids and creating a consistent, homogeneous product, time after time, is one of the most difficult of all mixing tasks.

Whether the need is to incorporate large volumes of powders or handle small amounts of critical components such as active ingredients, Silverson has a range of products designed to provide the most efficient means of incorporating powders into liquids. The selection of which depends on factors such as the batch size, the type of ingredients and the viscosity of the end product.

The Silverson Ultramix is a hygienic closed-rotor mixer that can rapidly incorporate high percentages of powders and can handle relatively high viscosity mixes. It is particularly suitable for incorporating difficult powders with a tendency to float or “raft.”

For bulk powder dispersion, Silverson offers the Flashblend, a unique powder/liquid mixing system capable of incorporating powders at rates of up to 15,000 kilos per hour.


Powder/Liquid Mixing
2% Aerosil into Water

Dissolving

Silverson High Shear Mixers provide a highly efficient method of solubilising a wide variety of materials from sugars and salts in the food industry to resins, rubbers and polymers in the chemical and petrochemical industries. This is achieved as the high speed rotation of the rotor draws liquid and solid materials upwards into the workhead, where they are subjected to intense but targeted shear in the precision gap between the rotor and stator before being forced out through the stator and projected back into the main body of the mix. With each pass through the workhead, the solids are reduced in size, exposing an increasing surface area to the surrounding liquid and accelerating the solubilisation process.

Silverson offers a range of equipment for this application, including Batch and In-Line mixers and Disintegrator/ Dissolver systems for large-scale manufacture.


Dissolving
66 Brix Sugar Solution

Hydrating

Gums and thickeners are difficult to disperse without forming lumps or “fish eyes” – agglomerations of partially hydrated material with a core of dry powder.

Once these have formed, an agitator will only wash the surface of the agglomerates, slowly hydrating the outside layer, resulting in long mixing times, poor quality and inconsistency between batches. In addition, some ingredients require a degree of shear to activate them and obtain functionality, which cannot be achieved using an agitator.

The high shear action of a Silverson Mixer rapidly disperses the powders, disintegrating any agglomerate and exposing an increasing surface area of the powder to the surrounding liquid. The result is an agglomerate-free solution within minutes.

Silverson offers a range of Batch mixers and In-Line mixers as well as the Flashblend powder/liquid mixing system for this application.


Hydrating
2% Xanthan Gum Solution

Homogenising

Homogenisation requires the ingredients to be processed until a uniform globule or particle size. For most products, including creams, ointments, sauces, flavouring emulsions and pharmaceutical suspensions, this requires a globule or droplet size in the range of 2 – 5 microns.

This can be achieved using a Silverson Mixer Homogeniser. The precision-machined Silverson workhead generates exceptionally high shear rates in a three stage mixing/homogenising process; The high speed rotor draws materials into the workhead where they are intensely mixed. Centrifugal force then drives the materials to the periphery of the workhead and subjects them to mechanical shear in the precision gap between the rotor and stator. This is followed by intense hydraulic shear, as the product is forced through the stator screen at high velocity and circulated back into the mix. Fresh material is continually drawn into the workhead, progressively reducing globule or particle size and quickly resulting in a homogeneous, uniform product.

Silverson offers a range of in-tank and In-Line Mixer Homogenizers for this process. You can test one at your own facility – contact Silverson today.


What Is Homogenisation?
Silverson Mixer/Homogenisers

Emulsifying

The key to creating a stable emulsion is obtaining the finest possible droplet size. The more shear energy introduced into the mix, the smaller the suspended droplets will become, creating a fine stable emulsion.

The high shear rotor/stator design of the Silverson mixer is ideally suited to this application and can easily achieve emulsions with a droplet size of 2 to 5 microns. Finer emulsions down to 0.5 microns can be obtained, depending on the formulation. In many cases, this can eliminate the need for high pressure homogenisers.

Silverson offers a range of in-tank and In-Line mixers widely used for preparation of emulsions, from laboratory scale up to bulk production units.


Emulsifying
Emulsifying In-Line
How to Make an Emulsion

Blending

When blending easily miscible liquids of similar viscosities, an agitator will produce satisfactory results. But where there is a significant difference in viscosity between the two liquids, an agitator tends to move the two liquids around without actually blending them together, and it can take a long time to achieve a uniform blend. For example, when manufacturing honey-based products, which can be extremely difficult to process due to the viscosity and ‘sticky’ characteristics.

With a Silverson high shear mixer, the positive mixing action of the rotor/stator assembly draws the liquids into the workhead where they are rapidly combined before being forced out through the stator and projected back into the vessel; the liquids are blended almost instantaneously.

With some applications, such as continuous dilutions or when the materials react on contact, a Silverson In-Line mixer is most suitable. Typically the secondary liquid would be introduced into the pipeline just upstream of the In-Line mixer so that the liquid streams are subjected to intense high shear on contact, resulting in a homogeneous blend in a single pass.


How to Blend Liquids of Varying Viscosities
Aeration-Free Mixing
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