(1) Smashing method
In the process of feed processing, for feeds such as cereals and cakes, it is crushed, crushed, crushed and chopped.
a. Crushing and crushing—The material is crushed by external impact in an instant. It is most beneficial for crushing brittle materials. Because of its wide adaptability and high productivity, it is widely used in feed mills.
b. Grinding—The material is subjected to a certain amount of pressure and shear between the moving surface and the material is broken when the shear stress reaches the shear strength limit of the material.
c. Crushing—The material is placed between two comminuting surfaces. After the pressure is applied, the powder is crushed due to the compressive stress reaching its compressive strength limit, so the pulverizing effect is better.
De sawing - When squeezing a material with a flat surface and a sharp-edged working surface, the material splits in the direction of the pressure line of action, when the tensile stress on the splitting plane reaches or exceeds the material's tensile strength limit broken.
(2) Mechanical properties of materials
The mechanical properties of the material have a great relationship with the pulverization method to be selected. According to the relationship between material strain and stress, and the ultimate stress, the mechanical properties include the following five types:
a. Strength - The strength of a material is its resistance to external forces. It is usually expressed by the force per unit area when the material is broken, that is, Pa, and can be classified into compressive strength, tensile strength, torsional strength, bending strength, shear strength, and the like depending on the manner in which the force is broken.
b. Hardness—Hardness is the ability of a material to resist the marking or pressing of other materials into its surface. It is also understood to be the energy required to produce local deformation on a solid surface.
c. Brittleness—brittleness is a property opposite to plasticity. From the aspect of deformation, when the brittle material is damaged by force, only minimal elastic deformation occurs before fracture, and plastic deformation does not occur, so its ultimate strength generally does not exceed Elastic limit.
d. Resilience—The toughness of a material is the ability to absorb energy during plastic deformation under the influence of external forces. The greater the absorbed energy, the better the toughness and vice versa.
e. Easy to grind (broken) - the strength and hardness alone are not sufficient to fully and accurately indicate the difficulty of material comminution, because the pulverization process is determined by the physical properties of the material, as well as the particle size, particle shape, and pulverization method. And many other factors. The so-called friability is the power consumption ratio required to pulverize a material from a certain particle size to a specified particle size under certain pulverization conditions.
For a specific material, there is an intrinsic connection between the above five mechanical properties, which leads to the complication of the comprehensive properties of the materials, which have an effect on the deformation force required for pulverization. In general, the stronger the strength, the smaller the hardness, the smaller the brittleness and the greater the toughness, the more deformation energy is required. An important basis for selecting the comminution method is the physical properties of the pulverized material. Among them, the strength and rupture of the material to be pulverized are two main indicators. For hard and tough materials, impact and extrusion are more effective; for tough materials, shearing is better, and brittle materials are suitable for impact crushing. In feed processing, the crushing of grain raw materials is generally carried out by a hammer mill, which is mainly caused by impact pulverization, and the raw materials such as enamel containing more fibers are mainly sheared and ground. In short, according to the physical and mechanical characteristics of the material, the correct selection of the pulverization method is of great significance for improving the pulverization efficiency and saving energy.
(3) Crushing model
Rosin-Rammler et al. believe that the particle size distribution of the pulverized product has two components, namely acceptable fine powder and unqualified coarse powder. According to this double formation analysis, it can be inferred that the destruction and pulverization of the particles are not caused by one type of damage, but are composed of two or more kinds of destruction effects.
a. Volume pulverization model - the entire particle is destroyed, and the pulverized product is mostly intermediate particles with large particle size. As the pulverization process progresses, these intermediate particles are gradually pulverized into fine powder components, and impact pulverization and extrusion pulverization are relatively close to this model.
b. Surface pulverization model - At a certain moment of pulverization, only the surface of the granules is destroyed, and the micropowder component is ground, and this destructive effect does not substantially involve the inside of the granule. This situation is typical of grinding and grinding.
a. Uniform comminution model—The force applied to the granules causes the particles to produce uniform dispersive damage and is directly pulverized into fine powder. The uniform comminution model only conforms to particle comminution where the structure is extremely tight.
The actual pulverization process is often the synthesis of the smashing models of the previous work types. The former constitutes an excessive component and the latter forms a stable component. The particle size distribution of the pulverized product obtained by volume pulverization and surface area pulverization is different. The particle size after volume pulverization is narrower and concentrated, but the proportion of fine particles is smaller. After surface pulverization, there are more fine particles, but the particle size distribution range is wider, that is, There are also more coarse particles.
English Name: carbonate iron (cFe)
Chemical formula: Fe2 (CO3) 3
Category: mineral
Nature: similar to aluminum carbonate, it is difficult to exist at room temperature for a long time.
Because the combination of the carbonate ion and the iron ion is very unstable, it happens instantaneously, and it hydrolyzes in an instant, so it's not easy to get this material in general.
But it doesn't rule out certain conditions.
Iron Carbonate,Iron Dust Cupric Carbonate,Ferrous Carbonate,Professional Ferrous Carbonate
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