The processing industries require sugar in specific fine crystal sizes. The classification is carried out in screening machines to produce the specified size ranges. Circular screening machines are used, on the one hand, for screening lumps (clumps) that form during the production process and, on the other hand, for refining special types of sugar.
To produce very precise crystal sizes within tight tolerances and special sugar types, the GKM tumbler screening machine (Fig.1) is increasingly finding its way into sugar factories for a wide range of applications (fineness, throughput capacities, etc.). Depending on the requirements, the tumbler screening machines are equipped with up to six screen decks.
During screening, the sugar is fed through the central inlet nozzle. Using the three-dimensional motion of the machine, the sugar is distributed evenly and spirally from the inside to the outside of the screen surface. Finer sugar crystals fall through the screen meshes and the coarser ones are gradually conveyed to the outer edge of the screen, where the sugar is discharged through the lateral machine outlets with the aid of a deflector plate.
Depending on the product to be screened or its fineness, ball tapping, or ultrasonic cleaning is used to clean the screen and constantly avoid plugging, i.e. clogging of the screen insert. For 100% contamination-free screening and to avoid even the slightest ball abrasion despite highly abrasion-resistant balls, ultrasonic cleaning is becoming more and more important.
Self-centring screen insert and pneumatic or manual deck lifters (Fig.2) in combination with quick-release clamps, mean a screen changes are made in the shortest possible time. Typical separation cuts for fractionations are between 2.0mm and 0.20mm. The throughput rates here vary from 10t/h to 50t/h depending on the required crystal size.
In order to ensure the quality of the end product, e.g. when loading lorries or emptying silos, and to be able to comply with the highest food standards, the oversize particles or sugar nodes and impurities must be separated from the sugar. The GKM vibration control screening machine type KTS-VS2 (Fig.3) is perfectly suited for this control screening.
Here, the sugar is dosed-in continuously via the central inlet of the GKM sieving machine. Inside the machine, a cone of bulk material is formed, which is quickly and effectively processed by the two vibration motors located opposite each other. The oversize particles and knots are separated by the screen mesh and are spirally conveyed to the edge by the two-dimensional machine movement and then discharged via the lateral coarse material outlet. The fine sugar, on the other hand, falls through the screen mesh and is discharged directly from the central fines outlet with minimum residence time. Up to now, a separation cut of 4-5mm was typical for control screening and an hourly output of up to 150t. Due to the increased product safety, the cut-off has now been reduced to 2-3mm, at which an hourly output of about 60t can be achieved.
Due to its central inlet and outlet and its very compact design in relation to the output, the machine can be integrated very well into almost any plant. Typical locations are above/below a silo, in front of a packaging plant or a truck loading.