Mixing It Up with Industrial Mixers and Agitators: Function Over Form

In part 1 of “mixing it up with industrial mixers and agitators”, we discussed the difference between mixers and agitators and four key functions of industrial tanks mixers.

Many industrial mixers and agitators are designed to be multi-functional or meet specific functions. So, function is usually more important than form because the intended result of the mixing process (function) will determine the design (form).

As your supplier of industrial mixers in Ontario, we’ve put together another four functions that testify to the fact that function is more important than form, at least where industrial tank mixers and industrial tank agitators are concerned.

4 additional functions of an industrial mixer and agitator

1. Crystallization

The reverse of dissolving, crystallization is achieved by either cooling or heating a solution to remove crystals. Some crystals must be gently agitated at low speeds to prevent fracture, while others form on the surface when cooled and must be scraped off with the impeller. Crystals can also concentrate at the bottom of the vessel or be maintained in suspension. The type of crystallization required will influence the type of agitation, while the handling of crystals dictates the choice of an impeller system.

2. Heat transfer

Heat transfer is the transfer of heat between the contents of the vessel and a heating or cooling surface (such as coils, plates, or even the wall of the vessel itself). Without getting too scientific, heat is usually transferred by conduction from the wall of the vessel (in most industrial processes this would be a tank) or the surface of the internal heating elements to the contents of the vessel.

As these contents are mixed or agitated, heat is carried through the mass through convection. The mixing process speeds up this conduction and can promote heat transfer through forced convection. Heat transfer applications are similar to liquid blending. The difference is that with heat transfer, the heat source is installed in the vessel.

For viscous liquids, you can use conventional propeller and turbine mixers. But to maintain flow where liquids are highly viscous, you must use larger diameter low-speed impellers that allow increased horsepower. Other factors like the presence of solids, temperature, conductivity, and whether the materials decompose or solidify at the temperature of the heating or cooling medium will influence the type of agitator required.

3. Extraction

In the world of mixing and agitation, the term extraction defines the separation of one or more components of a mixture by using a solvent. At least one of the components must not be immiscible – not forming a homogenous mixture when combined with another – or be partly soluble in the extractive liquid, which allows two phases to occur during and after extraction.

There are several types of extraction processes:

• Liquid-liquid extraction, in which the treated mixture is liquid, and the two phases formed are both liquids
• Leaching, in which one or more components of a solid mixture are separated/removed through a liquid treatment
• Washing, where the solids removed through a liquid treatment (in a process similar to leaching) are present on the solid surface (instead of throughout the solid phase)
• Precipitive extraction, in which a homogeneous liquid of two or more components is split into two phases by adding a third component

In all these processes, agitation is used to improve extraction. High shear and high turnover are generally required to disperse the phases in both liquid-liquid extraction and leaching, which means mixers or agitators need higher horsepower. However, washing and precipitive extraction usually require only mild agitation, similar to blending.

4.Gas dispersion

Dispersion of gas generally refers to any operation in which a gas is distributed throughout a liquid, with a chemical reaction occurring as a result. In order to ensure effective gas dispersion, the correct equipment is required, such as multiple impellers, sufficient horsepower and space for expansion during gassing.

Generally speaking, any increase in gas input increases horsepower requirements to ensure equal dispersion of gas, whereas increasing the operating pressure of the vessel tends to decrease the horsepower required. However, increasing the operating temperature also increases reaction rates, which increases gas volume by vapor expansion. This means that the horsepower required to produce an equivalent gas dispersion at lower temperatures may increase.

Clearly, every mixing system has a range of benefits and limitations, with some featuring complex designs to enable them to carry out their required function.

Depending on what products you need to mix, their density and viscosity, and the size of the mixing container or tank, it’s crucial to choose the right type of industrial mixer or agitator for the function required. The Visser Sales Corp. team have the experience and industry knowledge to solve your industrial tank mixer and industrial agitator tank requirements, tailored to your process. Call us (toll-free) on 1-800- 367-4180 to learn more about our range.

As your supplier of industrial mixers in Ontario, we’re here to help you choose, install, maintain, and monitor a variety of equipment. And to answer questions about things you’ve previously tried gone wrong.