Mixing Granulators Producing Round Fine-grain Granulate
How to produce round fine-grain granulate at low energy consumption? Mixing granulators offer an alternative.
Thermal processing and mechanical processing are the two options currently available for producing granulate. The high cost of energy consumed in thermal granulation is becoming an increasingly serious problem in many industries, so companies are searching for alternatives such as pressure agglomeration, extrusion and tumble-growth agglomeration. (Roll) pressure agglomeration and extrusion (using perforated roller presses) generally do not produce round fine-grain granulate and an upstream mixing step is needed for both techniques. In contrast, mixing and granulation can take place in a single tumble-growth process using an Eirich mixer.
These mixing granulators with capacities between 1 l and 3,000 l have only one rotor tool. Larger machines have two. There is no need for the high-speed, high-wear choppers which are installed on plough share mixers. Depending on the application, the rotor can run at speed above 30 m/s. This makes it possible to generate high shear forces and quickly distribute the fluids. In a hybrid mixing process, the speed can vary depending on whether wet or drying mixing takes place prior to granulation. By running the process with different tools and at different speeds, grain size can be manipulated over a wide range. Granulate with PSD D50 between 100 μm and 5 mm can be produced depending on the material.