, first of all, the purpose of granulation and the problems to be solved must be clarified, and then compared with the following factors, the inappropriate methods are excluded, and a suitable and simple method is determined.
(1) Material characteristics. Whether the material is powder or molten, whether the slurry and paste materials can be pumped and atomized, and whether the materials have heat sensitivity, etc., must be considered when selecting.
(2) Requirements for production capacity. If the required production capacity is large, many methods cannot be applied.
(3) Requirements for particle size and particle size distribution. Some methods, such as spray-drying granulation, can only obtain very fine particles, and the powder can be agglomerated to obtain smaller particles, while other methods, such as pressing, can obtain large agglomerates.
(4) The shape of the pellets. Rolling, stirring and granulating, spraying and granulating can obtain approximately spherical particles; shot cooling and solidifying granulation can obtain completely spherical particles; extrusion granulation can produce column particles. The possible impact of different shapes of particles on subsequent work should be estimated.
(5) The strength of the pellets. The granules obtained from powder agglomeration and shot peening have weak mechanical strength. If high-strength particles are required, it is necessary to use a compression method or sintering and baking to strengthen them. For extrusion molding, a high-strength binder is selected.
(6) The porosity and density of the pellets are empty. The void ratio and density are closely related to the strength. Some extrusion granulation processes can better control the void ratio and density to meet the needs of a certain application.
(7) Is it possible to carry out several processes (such as granulation and drying, chemical reactions) simultaneously? Certain methods and equipment (such as cylindrical fertilizer machine granulator
) are well suited for granulation processes with simultaneous chemical reactions.
(8) Space restrictions. For example, the extrusion method can obtain higher production capacity with a smaller device, while other methods, such as shot peening, require a higher vertical space to install tower equipment.
Through the above analysis and comparison, at least two different granulation methods can be initially selected, and these original choices can be further considered by experiments or pilot plant experiments. Then make the final choice based on the reliability, flexibility, and ease of manufacture and maintenance of the equipment.