Top 4 Types of Powder Mixers
This article will look at powder mixing, a standard processing step found in many sanitary industries, including food, beverage, personal care, and biopharmaceutical manufacturing.
We’ll focus on:
- An overview of the categories of mixers used in industrial powder mixing and the various mechanisms used in these types of mixers
- The specific issues associated with adding dry powders to wet mixtures, a subject known as powder induction
- The various powder mixers available from CSI
What is a Powder Mixer?
Combining dry ingredients is one of the oldest unit operations in the processing industries. Over the years, many different types of equipment have been developed to homogenize dry materials, including powders. Let’s look first at some common definitions used in describing powder mixers.
As the name suggests, powder mixers are various types of sanitary mixers used to either:
- Combine two flowable dry materials
- Mix a powder into a liquid
While the focus of this article will be primarily on mixing powders into liquids, there are mixing technologies which are common to both applications.
Commonly used in the dairy, food, and beverage industries, powder mixers may be either batch-type or continuous feed. And, they rely on two different mixing technologies, depending on the physical properties of the powder being mixed.
In the case of powders which are relatively incohesive—that is, without particles that easily stick together—a convective mixing process, such as that found in the ribbon mixer described below, may be used to thoroughly combine the dry ingredients.
When materials are cohesive, though—prone to sticking together, as is the case with fine powders, and also with wet materials—then a more intensive mixing process is required using either impact force or shear force to thoroughly combine ingredients. The high shear mixers and liquifiers described in later sections of this article are examples of these intensive-type mixers.
Key issues in powder mixing
There are a couple of operating parameters that impact the productivity of powder mixing. As a general rule, sanitary processing plant operators will seek to achieve as short a mixing time as possible to increase their line productivity. The greater the volume of the powder to be mixed, the longer the time required to blend them together. However, doubling the volume does not necessarily mean doubling the mixing time.
Higher mixing speeds will generally result in shorter mixing times. However, it is essential to note that using excessive mixing speeds with some powders can result in particle breakage and affect product consistency, so processors must consider this factor when mixing.
Types of Powder Mixers
Several different types of mechanisms are used in powder mixers. Some units are batch or continuous mixing only while others can be used for both.
1. Ribbon mixers
Ribbon mixers or blenders consist of a U-shaped horizontal trough and a specially fabricated ribbon agitator.
The agitator is comprised of a set of inner and outer helical blades, pitched in opposite directions. The outer ribbon blades move materials towards the center of the trough, and the inner ribbon moves materials towards the outside of the trough: in this manner. In some models of ribbon blenders, liquid spray bars may be incorporated into the design to coat the dry particles as they are blended in the trough.
2. High Shear Mixers
High Shear mixers use a high speed rotor tip on a rotating shaft to emulsify, homogenize, disperse, and grind mixtures to reduce particle size.
Also called rotor-stator mixers, high shear mixers are also used for powder mixing, and are especially useful when adding liquids to a dry blend. They and are commonly used in sanitary processing applications in the food & beverage industry (preparing sauces, dressings, and pastes) and in pharmaceuticals manufacturing (producing syrups, gels, and creams). High shear mixers are available in both in-line and batch configurations.
3. Liquifiers
Liquifiers are a specialized type of mixer used to blend solids and semi-solids into liquids.
They use the agitation of a liquid to dissolve solid or dry materials into the liquid solution. This type of mixer pumps materials through chambers in the mixer that are fitted with fixed blades or shredders, and the resulting turbulence of the process results in the mixing, blending, or liquification of the dry ingredients.
4. Induction Mixers
Powder induction is the term used for mixing dry powders into liquids.
This mixing technique may be troublesome in production environments, as dust is created when powders are poured directly into liquids. Additionally, dry powder added directly to the surface of liquids tends to agglomerate — clump together — or stick to the wet surfaces of mixing vessels or equipment.
Both problems are solved using specialized equipment designed to introduce the powder directly from its storage container into the liquid with which it will be mixed.
This blending of the two substances either occurs below the surface of the liquid or in the absence of air via some custom mixing apparatus. In either case, no dust is created by the mixing process, and even the finest powders are thoroughly wetted.
CSI offers several products suitable for powder induction applications, as we will describe in the next section.
Powder Mixers and Addition Products from CSI
CSI offers several specialized mixers from suppliers Alfa Laval and Ampco designed specifically for mixing powders used in the sanitary processing industries. Each of these products is described briefly below.
Selecting the right powder mixing equipment for the application can reduce processing times, improve batch to batch consistency, and reduce out of speck product
~ Michael Boyd, Business Development Manager, Ampco
Alfa Laval Hybrid Powder Mixer
The Alfa Laval Hybrid Powder Mixer is a patented hygienic unit that disperses powders into liquids quickly and efficiently.
It pumps the resulting solution at outlet pressures of up to 72 psi, all powered with a single motor. This batch-type mixer is available in both fixed and mobile models.
Ampco Dry-Blend
The AC+ Dry Blender from Ampco Pump is another batch-style powder induction product designed to thoroughly and efficiently blend dry ingredients into liquids.
The unique "tube within a tube" design of the AC+ Blender keeps dry ingredients and liquids separated until they are introduced in the mixing chamber, minimizing excess air so that lumping and foaming does not occur.
Ampco Powder-Max
Ampco’s Powder-Max Powder Mixer is a batch-type or single-pass mixer used for consistent wet/dry ingredients mixing in hygienic and industrial processing applications.
The PM Powder Mixer is designed to be customizable to meet specific applications, further maximizing its efficiency. Various models are available, ranging from 5 to 60 hp.
Ampco ROLEC DH
Ampco Pump’s ROLEC DH is a specialized batch-type brewery mixer used to recirculate a fermenter and simultaneously introduce dry pellets into a stream of beer.
The pellets are held in a pressurized chamber, purged of air with CO2, and introduced into the liquid via the differential pressure created by the ROLEC DH’s shear pump. All components are CIP-able, and the system is fully portable. The use of the ROLEC DH in brewery operations results in an improved aroma and flavor profile in the final product.
Complete Guide to Mixers and Blenders
This guide is designed to provide an overview of the wide range of sanitary mixers and blenders used in hygienic processing applications. It is intended as a primer to aid process engineers and project managers in determining what particular type of mixer or blender to select for a specific application.
Next Steps
As we've shown in this article, mixing powders in sanitary processing applications brings some unique issues to consider in comparison to mixing other materials, including the tendency for powder agglomeration, as well as the specific challenges associated with adding powders to liquids (powder induction). Due to these powder mixing issues, certain types of mixers are better suited to the task than are others, and specialized products have been developed for powder induction applications.
CSI can help you with choosing an appropriate powder mixer for your application. Contact us at (417) 831-1411 to discuss your specific requirements.
ABOUT CSI
Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.