Biological fertilizer double granulation is an advanced granulation process for biological fertilizers. The core is to solve the problems of low molding rate, uneven nutrition, and poor particle quality that exist in traditional single step granulation through two granulation processes and supporting screening, drying, and other processes. There are two common core implementation forms, which have distinct characteristics in equipment and application scenarios. The following is a detailed introduction:

Mainstream processes and equipment types

Double drying assisted granulation process: This process is often equipped with a complete production system, and the core is to improve the quality of particle formation through two drying processes combined with screening, suitable for difficult to pelletize biological fertilizers such as silicon calcium potassium magnesium fertilizers. The equipment system includes a mixer, a granulator, a two-stage drying equipment, and a multi-stage screening machine. During operation, the powdered raw materials are first mixed and sent to the granulator for initial ball formation. After wet material screening to remove small particles, they enter the dryer to reduce the moisture content to around 10%; After further drying and screening to remove fine powder, it is sent to the second dryer to reduce the moisture content to about 3%, and qualified particles of 2.5-4.0mm are selected. This process can significantly reduce fertilizer crushing rate and solve the problem of poor granulation quality in traditional equipment.

Dual mode extrusion granulation equipment: This type of equipment belongs to integrated dual granulation equipment, with the main body integrating the ring mold and the flat mold, equivalent to two granulators working together. It can process manure like biological fertilizer raw materials such as chicken manure and sheep manure. During operation, the feeding amount is controlled by a feeder combined with a speed controller, and the material is stirred twice before being squeezed and granulated through dual-mode extrusion. The particles produced by it have uniform composition, smooth surface, moderate hardness, and a temperature rise of less than 30 ℃ during granulation, which can effectively retain the nutrients such as microorganisms in the biological fertilizer. Models such as HP-450 and HP-650 can achieve a yield of 5-8t/h and a granulation rate of over 95%.

Secondary spray granulation process: specifically designed for microbial fertilizer agents, achieving balanced nutrition wrapping through two sprays. Firstly, prepare the bacterial solution in the process. During the initial spraying and granulation, mix and atomize the bacterial solution with auxiliary materials such as polyglutamic acid and chitosan oligosaccharides, evaporate the water and aggregate into small particles. After screening out the unqualified particles, set them aside; Secondary spray granulation involves evenly wrapping the prepared auxiliary slurry containing peptides and other components around the initially formed particles, followed by solidification, drying, powder coating, and other post-treatment processes to achieve a balanced nutritional composition for each fertilizer. For example, Bacillus subtilis and other bacterial strains will be added in the secondary processing to enhance the fertilizers disease resistance and growth promoting effect.