Germany
September 15, 2016

Throwing away valuable seed is a costly undertaking – even in the single-digit percent range. The medium fraction in the gravity separator is the grey area in which the proceeds are eliminated. Up until now, the medium fraction was sorted out on a second table, or sorting had to take place again on the same table. Each repeated feeding through the machine causes additional stress to the grain – all the way to reduced germination and breakage. Furthermore, the implementation of additional machines, more time and higher effort are needed. The German technology developer PETKUS has constructed a gravity separator for seed sorting as well as for the food industry that is equipped with an innovative surface. The novel construction precisely separates the heavy goods from the light. Thanks to the zig-zag shaped “mid-ex” (middlings excluded) rib construction, the lifting force is increased and, depending on the specific weight, the grains are separated and move upwards or downwards, as if they were on a staircase. Sorting processes are therefore pared down and made more efficient and the product is processed more carefully.

“Recirculating the medium fraction would mean adding an extra process and would take significantly longer”, explains Dr. Khaled Raed, Innovation Manager at the ROEBER Institute GmbH, a subsidiary of the PETKUS group, which places its know-how in many innovations. “If products are frequently changed, it offers the possibility to shape the process more efficiently and also pare it down. With the special table lining on the Gmid-ex, a ribbed construction that divides the flow of goods into a normal and a premium quality, a significantly higher sorting efficiency can be guaranteed – completely without having a medium fraction,” says Raed, who developed the new gravity separator.

After special blades that are already very close to the product inlet have carried out an initial mechanical selection of the grain, the actual sorting takes place in accordance with physical principles: on the table, a fluidised bed is created with air and the surface of the table begins to vibrate. Through this combination, layering of the goods takes place. Grains with a higher specific weight remain in the lower layer of material and are moved upwards; in contrast, lighter grains swim on top of the layer of material and flow in the direction of the incline. In the event that the table is being used in its entirety, the table’s inclination and airflow must be increased. That is coupled with a relatively high percentage of heavy grains that are separated imprecisely and are therefore lost. “If the airflow is increased, heavy grains are also lifted up and collects less in the layer of material. It leads to inadequate separation and ultimately leads to the loss of grains,” Raed explains the problem. “Therefore, we thought about how the strength of the airflow and the inclination of the tables is increased and how losses can be optimised at the same time.”

Strengthening the lifting force with zig-zag shaped ribbed constructions

As a result, there was the modification of the deck in the form of a zig-zag shaped outer surface on the last third of the table. Through the ribbed construction, a mechanical hurdle is created and the grains can move upwards or downwards above this, like on a staircase. But in particular, the airflow is diverted and no longer streams vertically above the deck. Heavy particles are transported upwards by the closed ribbed flanks; lighter particles are moved downwards out of the perforated ribbed flanks by the airflow, which is directed to the right and above. The ribbed construction strengthens the lifting force during the sieving motion and diverts the airflow, similar to the lamella sieves in a combine harvester. Because of that, light products and heavy products are separated better. Grains that make it over the separating edge are light products and treated as a consumer good. All of the rest is considered as heavy product and is treated as high-quality seed. The height of the separating edge can also be individually set. For lower performance, one uses a lower edge; for higher performance, a correspondingly higher.

Implementation in the seed and food industries

Up to 500 different configuration options, so-called “recipes”, simplify operation for the users. Therefore, batches are reproducible and documentable. Especially during the frequent change of types of crops during the season, the memory function is helpful and saves time. In addition, the machine can be controlled by a tablet or smartphone from any location via WLAN. The remote service allows for remote maintenance. With its distinctive deck, the gravity separator can be used for the seed processing of cereals, corn, fine seeds, pulses, oil seeds and grass seeds, as well as for the separation of impurities from lentils, peas, beans, coffee, peanuts, hazelnuts or almonds in the food industry. In addition, metals, plastic, rubber, wood and materials are easily separated from each other.

The customer profits from a new table lining

With the Gmid-ex, an approximately 20% lower output is to be expected in comparison with the standard version. But it is only at first glance that quality comes at the cost of quantity. Because with the mid-ex technology, the exactness and efficiency in separation is significantly improved, even after just one pass through the machine, the quantity of high-quality seeds increases. Neither a second table nor a re-sorting of the grains is necessary. “The Gmid-ex gravity separator is offered for all areas in which there is more of a focus on quality than performance and precise as well as thorough sorting is important,” says Dr. Raed.

Website: http://www.petkus.de

Published: September 15, 2016