Oilseeds preparation

Introduction

The preparation of seeds plays a very important role in the quality of the oil. This step is intended to facilitate the extraction of oil seeds. The practice shows that a well prepared seed is working much better and gives better yields of oil.

Cleaning

If the seed impurities are not removed, they will be reflected in the cake, bringing with them many agents of alteration. It is not uncommon to find lots of peanuts, for example 1% of Farinet, ie particles smaller than 1 mm. These fragments contain up to 75% oleic acid which negatively influence the refining of oil and the conservation of cake.

Cleaning allows for the removal of metal, earth and stones whose presence may damage the circuit grinding.

The various devices used are:

• the vibrating sieve with seed classification by size and density by size canvases used;
• cyclones with precipitation of dust;
• sieves to sound waves;
• tables densimeter.

Various parameters play an important role on the outcome of the operation:

• speed of seeds.
• dimensions of the canvases used,
• mode of vibration,
• air flow rate insufflation, ...

Shelling and dehulling

Some seeds need to be peeled and dépilliculées before starting the extraction. Since there is a difference between the seeds in terms of thickness, hardness and adhesion of the jacket, special equipment is needed for each category of seed husk.

The operating principle and performance of a knife sheller (Figure 1) make it suitable for mechanical preparation of the different types of oil seeds. Its working principle is a shear between two parallel edges, one of them belonging to a knife, the other a knife resulted in high-speed rotation. Simply multiply the number of knives fixed on the one hand, moving the other and adjust the power required to work for approaching the performances referred. But the gap between two successive blades, whether fixed or mobile, and the game still left in bones and bones rotating factors are also determinants of outcome.

On the same device, number of knives and differences between them are not modifiable. As against the running clearance between rotor bearing knives and mobile bearing stator knives is a fixed parameter on which it is mechanically easier to intervene.

For peanuts for example, the sheller is made of a cylindrical steel drum, on its entire periphery of the plates covered with triangular iron tempered, surrounded at some distance by a casing of perforated sheet metal to heavy long holes rounded . Peanuts in shell are driven by the rotational movement between the plates of the drum and the perforated casing and they are thus in friction against each other, the hull was divided into two and the kernel is released, as soon as the shelling is made, the products pass through perforations of the plate and fall on a screen shaking.

For sunflower, there are two types of aircraft:

• by devices acting Percussion seed: seed projection high-speed (25 to 30 m / s), which shattered the hull and the separation of the kernel.
• acting by friction devices: There are 2 discs striated, the distance between the discs is adjustable depending on the size of the treated seeds.

In both cases, the removal of hulls and seeds unshelled is by sieving and ventilation.

For other seeds (flax, rape and any other small seeds), it does not dehulling.

For oleaginous fruits, such as palm, it is necessary first to a breaking to release the kernel. The principle of the most simple is to project with a rotor nuts in a metal cage. The separation of hulls and kernels are dry or wet.

The dry process uses the principle of classification vibrant inclined treadmill: almonds round and smooth sliding down while the fragments of shells with asperities are back up.

Wet uses the principle of flotation in a salt solution: The fleet while almond hulls settle quickly, but has the drawback to require a subsequent drying.

Can also be used for breaking, hammer mills, but it is desirable to dry the fruit before the operation to facilitate the separation of almonds.

Grinding and sieving

This operation aims to reduce the size of fruit or oilseeds in order to facilitate the work of presses or the action of solvent.

You can use a fluted cylinder mill (Figure 2) for the mechanical preparation of almond oil or seeds. The grooves are made at the periphery of the cylinder to allow the commitment of products and obtaining the proper size. The power is performed by a device adapted to ensure a good distribution of products to grind over the whole length of the cylinders and to control the flow.

Thermal conditioning of the seed

The role of packaging is to promote the separation of oil from the dry matter. The thermal conditioning acts directly on the quality of extraction media, including when to seek a maximum rate of depletion.

Before submitting it to pressing, the crushed seed is heated and may even suffer a moist cooking atmosphere, followed by a drying more or less prolonged pressure before. Heating has the advantage of facilitating the extraction of oil.

Some chauffoir (conditioners) said tube is in the form of one or more horizontal or vertical tubes (Figure 3) heated by a steam jacketed. They are fitted, each with a tree bearing pallets contribute to mixing of seeds introduced and their progress in the device. Openings specially provided help in the evacuation of steam produced in the tubes. There is also Deputy devices possible addition of water or direct steam injection. They include, most often, two tubes: a tube located in the upper, large diameter, which is the heating and a 2^ndtube at the bottom, usually smaller, plays the role of dryer. Feeding is done through a distributor of seeds, adjustable for various flow rates.