THE MACHINES OF THE MILL: THE PURIFIER

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The article describes the machines that make up the mill, in particular the purifier.

In the previous articles, we explained the grinding process (you can read about grinding here). We already talked about the rollermill (you can read about the rollermill here) and the plansichter (you can read about the plansichter here).

We have not discussed, however, about the products of grinding that need further processing. Purifiers process some intermediate fractions selected by the plansichters, which carry out a further selection on a particle size basis. The result is a flour particularly suitable for fresh pasta.

The history of the purifier

Cylindrical mills have adopted the purifiers since the second half of the nineteenth century. Those of that time were known as “semolina cleaners” and they worked in different ways.

Principles which will be developed in modern machines were defined only with the “marseillaise cleaner”. The machine was equipped with a fan, which invested the product, driving away lighter fractions, such as bran.

But it needed to work with the surface of the detachments exposed to the environment. The poor hygienic level led to the design of machines closed by a box above the trabatto, equipped with fan.

Therefore, we can trace back to the end of the 800 the birth of machines for the cleaning of the semolina based on the principles still of reference:

• Grain size selection by stacking frames;
• Selection based on specific weight and fluid bed functioning.

The characteristics of the purifier

The purifiers receive the intermediate particle size fractions selected by plansichter. Therefore they are able to make a very accurate selection. The machines also select the flour according to their specific weight. This distinguishes between “clean” groats (the finished product), “dressed” groats (the product to be remilled) and bran.

Let’s see the main characteristics of the purifier:

• They are binate machines and each side has detaching bodies that vibrate, thanks to the vibrators;
• The detaching bodies, consisting of stacks superimposed, are surmounted by self-cleaning closed chambers, put in depression by the suction; The air flow invests the frames from the bottom to the top;
• A self-adjustable feeding system allows a uniform distribution of the product on the sieve;
• Collecting channels house the heavy flours and send them to further grinding stages, or to silos. The discharges, instead, send the light flours to further grinding stages;
• Valves of the air control guarantee a constant flow of air on the stacks.

The process carried out by the purifier in the mill can be summarized in 3 steps:

• Flour is loaded on the stacks of the first level, which vibrate and arrange meshes with increasing lights;
• Simultaneously a flow of air crosses the breaks from the bottom to the top;
• Action of vibration and aspiration causes the flour to become stratified. Machine sucks in the bran fragments and sends the clothed“”semolina to the drains. Pure semolina passes to the levels below, to be purified and sent to the collecting channels.

The first Molitecnica Sud purifier

As for the company reality of Molitecnica Sud, the first purifier built in our factory dates back to 1990. Today we are able to design and build not only high-quality purifier entirely produced in Italy, but also complete mill suitable for every need.