Granulation is a dry process of converting powder into granules of various shapes and sizes
- Chemicals (sodium carbonate, sodium chloride, sodium sulphate, sodium nitrate, ammonium chloride, iron sulphate, calcium chloride, foundry additives)
- Fertilizers (PK, NPK, potassium chloride, potassium sulphate, ammonium sulphate, potassium nitrate, phosphate, potash slag)
- Coal or charcoal for production of activated carbon
- Oxides (uranium oxide, chromium oxide, iron oxide, zinc oxide)
- Minerals (lime, dolomite, magnesia)
- Paint pigments
- Nickel ore dust
- Dried sewage sludge
Depending on the properties of the raw materials and the requirements for the final product, granulation processes may vary. Nevertheless, a number of main stages can be distinguished:
- The supply process of raw materials from a hopper with a separator for removing foreign particles with the function of destruction of packed particles and a magnet
- Grinding raw materials, if you want to increase the uniformity of the final product and the quality of mixing
- Storage of raw materials in a bunker
- Weighing and dosing of components
- Mixing of components
- Component pressing
- Compressed product grinding
- Component refinement (polishing, hardening…)
SAHUT-CONREUR offers complete turnkey systems that include all the units needed for a proper granulation process, as well as automated process monitoring and control systems.
- A preparation unit for powders (screening-crushing, drying, sieving)
- A weighing and mixing unit of the components
- A compaction unit transforming the powders into flakes
- A granulation-screening unit converting the flakes into granules of the required size
- And for some plants and in particular for the production of compacted fertilizers, a finishing unit with polishing and coating of granules for improved appearance, reduced number of residual fines and easier storage
Principle of operation
During the dry compaction, there is no liquid and no binder. Instead, small particles of fertilizer are subjected to high pressure, compressed together so that the surface of the particles are close enough for the intermolecular and electrostatic forces to cause adhesion.
The material goes to granulation after pressing. This section includes the necessary equipment for producing granules from plates: it is divided into smaller fragments - the primary crusher-granulator is located downstream of the roller compactor. Particles in the required size range (for example, from 2 to 4 mm) pass through a sieve and then they are removed as a finished product. Contemporaneously, larger particles (more than 4 mm) are fed to a secondary granulator crusher, and smaller ones (less than 2 mm) - on the roller compactor. This stage of the compact granulation process has a significant effect on plant performance. By changing the type of crusher-granulator or their parameters (rotor speed, mesh size), you can change the yield of the finished product twice.
The final treatment comprises a dry polishing unit and a coating unit. The dry polishing unit consists of a polishing drum and a finishing screen. Drum polishing improves the quality of the final product by rounding the sharp edges of the granules and destroys poor-quality granules. The final sieve then removes dust from abrasion of the granules in the polishing drum. This removes dust from the finished product. The coating of the granules serves to eliminate the sticking effect of the material and, in some cases, to protect the outer surface of the granules (it is necessary for a slower release of fertilizers). The coating device consists of a drum into which material is supplied together with solid or liquid materials for coating and a rough protective screen for breaking lumps formed in this drum.
- This is a dry process that does not require water or a binder (in some cases, 1-2% of the water is added to the product before compaction: the water is then removed naturally due to a slight temperature increase (about 20 ° C) when the product passes between the rollers)
- No energy costs for drying; 30% less power consumption than wet granulation
- Operating costs are lower since there are no problems with corrosion
- Low emissions because of the absence of water or gas during the process. The compacting process is environmentally friendly
- Less investments in equipment, as there is no dryer and cooler. The process technology adapts well to local conditions
- In the process, finely dispersed powder materials (KCl, (NH4) 2SO4, phosphates, etc.) can be used. That powder materials are difficult to bulk mix
- The process has better adaptability to local conditions for the supply of raw materials. Raw material purchases can be optimized continuously depending on local conditions
- Fertilizers produced by compaction are less likely to stick together (as dry components are used). Moreover, they are more durable
- Switching to different recipes is quick and effective
- Plant productivity can be in a wide range: from small (2 t / h) to a fully automated production of 60 t / h and above
The process of increasing the particle size of a material in a dry process, in which dust and powders take shape and bulk structure. Product compaction is achieved by mechanical compression through a two-roll roller press.
Special Roller Press specifically adapted for grinding can crush materials of variable size range