Ribbon mixers

Here we will introduce the important component of ribbon mixer, and how does work? We refer an active mixer as one in which there are either internal moving parts to randomize the positions of the ingredients, or air jets to create convection currents and turbulence in the powder container.

The first step of the industrial mixer that we will consider is the ribbon mixer.

In a ribbon mixer, a long complicated single paddle is mounted axially and used to disperse the ingredients of the mixture. The ribbon is usually so constructed that the powder near the outside of the container is moved in one direction, whereas in the middle it is moved in the opposite direction. Ribbon mixer are available from several manufacturers and they all have their own type of ribbon. The reader should note that many of the companies mentioned with respect to a particluar type of mixer in the discussion often make other type of mixers, as set out in their catalogs.

Ribbon mixers are widely used in the food industry and the pharmaceutical industry. This type of mixer can have dead pockets, especially near the end of the mixer close to the axis of rotation. Loading and cleaning of a ribbon mixer is asually done from the top of the mixture. The manufacturers usually recommend emptying the system at the end of the mixer. Van den bergh points out that attention must be paid to the design of the mixer, bearings and glands to avoid lubrication contamination. He also states that ribbon mixers are not easy to clean and not recommended for sticky materials. Because the mixing device turns over the whole charge of powder, the powder demands of this type of mixer are relatively high, thus van den Bergh gives an estimate of 12 KW per 1000 kg of charge.(Many of figures on powder demands and of available capacity in industrial mixer are taken from an excellent review article by van den Bergh).

One does not normally fill this type of mixer to more than 50% of the available volume. Normally the capacity of this type of mixer is restricted to anupper limit of 15 m.

Sometimes, to improve the dispersion of ingredients in ribbon mixers, the ribbon blades are built to be close to the cylindrical wall to give high shearing. Sometimes the ribbons are also fitted with rubber wipers to ensure complete intermingling of the ingredients by lifting any packed material near the wall into the middle of the ribbon ensemble. It is difficult to predict the scale-up performance if one attempts to increase mixing captcity by going to a larger mixer of the same type.

In a ribbon mixer the paddles move relatively slowly, as distinct from the movement in another class of mixer which is variously referred to as a paddle or a plowshare mixer.

Ribbon mixer related articls

What is a ribbon mixer?

Basis of ribbon mixer(2)

How to choose a ribbon mixer

Ribbon mixer maintenance