The global calcite resources are abundant, and the high-quality calcite resources with CaCO3 content ≥97% are also large. Therefore, at present, the industry does not generally perform mechanical beneficiation processing on the other stones, and only simple washing and hand selection are carried out. At present, the processing of calcite is mainly pulverization, classification and surface modification.
Crushing, grading
The purpose of the pulverization classification is to process a heavy calcium carbonate product that meets the fineness requirements of the application field. The process and equipment are determined according to the product fineness requirements. For products below 400 mesh, the general principle process is: raw ore → crushing → grinding (powder) → (grading). The main equipments include Raymond mill (suspension roller mill), rotary barrel ball mill , vertical mill (press roller mill), centrifugal self-grinding or rotary mill, hammer mill, vibration mill, and turbine mill. Most dry-type pulverization processes are used. The feed size and product fineness of these equipment are listed in the table below.
| Equipment type | Raymond Mill | Ball mill | Vertical mill | Rotary mill | Vibration mill | Hammer mill | Turbine crusher |
| Feeding size, mm | ≤30 | ≤30 | ≤30 | ≤35 | ≤5 | ≤10 | ≤10 |
| Product fineness, μm | 40～125 | 40~150 | 30~150 | 20~150 | 15~150 | 15~150 | 40～350 |
Superfine pulverization and fine grading
The ultrafine pulverization process of calcite at home and abroad mainly includes dry and wet methods. The dry process is generally used to produce products with d97 ≥ 3 ~ 5 μm, and the wet process generally uses products with d97 ≤ 3 ~ 5 μm (d90 ≤ 2 μm).
The dry superfine pulverizing equipment used in the industry mainly includes a high-speed mechanical impact mill, a rotary cylinder ball mill, a stirring ball mill, a vibrating ball mill, a high-pressure roller mill, a grading mill, a cyclone self-grinding mill, and a jet mill. In addition to the airflow mill with self-grading function, in order to ensure the product fineness and particle size distribution requirements, fine grading equipment is generally arranged on the actual production line. The configuration methods are built-in and external, and the built-in type is closed-circuit production. In the external mode, there are two types of production methods: open circuit and closed circuit. The open circuit type is classified into two different fineness products by the classifier, and the closed circuit type only produces one ultrafine powder. The classifiers commonly used in dry production lines are centrifugal or vortex air or air classifiers, such as MS, MSS, ATP, LHB, QF and other models.
Surface modification
The heavy calcium carbonate processed by calcite is the most abundant inorganic filler in the current organic polymer based materials. However, the surface-treated heavy calcium carbonate has poor compatibility with the polymer, which tends to cause uneven dispersion in the polymer matrix, thereby causing interface defects of the composite material and reducing the mechanical strength of the material. These disadvantages become more pronounced as the amount is increased. Therefore, in order to improve the application properties of the heavy calcium carbonate filler, it must be surface-modified to improve its compatibility or affinity with the polymer binder.
The surface modification of heavy calcium carbonate is mainly by surface chemical treatment by adding a surface modifier. Surface modifiers employed are: stearic acid (salt), titanate coupling agent, aluminate coupling agent, a zirconium aluminate coupling agent, atactic polypropylene, polyethylene wax and the like. Surface modification is carried out by means of equipment. Chang Ying's surface modification equipment is SLG type continuous powder surface modification machine, high-speed heating mixer, eddy current grinding and fluidization modification machine.
After the calcium carbonate is dried (the dry powder with low moisture content can also be dried), it is added to the surface modification machine, and a certain amount of surface modifier is added, and the active heavy carbonic acid after surface modification is obtained after a certain period of time. calcium.
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