Chalk is a soft, brittle organic material representing a form of limestone. It contains at least 98% of mineral calcium (calcium carbonate) with clay and silt as other constituents. It is a sedimentary porous rock extensively used in the production of composite materials, medications and utilized in the food-manufacturing, cosmetic, and other industries. Chalk grinding is a necessary stage in the production of material for its further application in any of the listed fields.
Where and how is fine chalk applied?
Fine chalk is a common constituent in the production of composite materials. It is a versatile, practical, and inexpensive filler distinguished by high performance properties. The use thereof in the production of materials reduces their cost and improves the final product features.
Ground chalk is utilized in a wide range of industries – from construction to food manufacturing. The most common of them include:
- Production of construction materials
This is the main field of use of chalk, because it serves as a filler in the production of grouts, plasters, other construction mixes, paints and varnishes, ceramic tiles, structural sections, PVC pipes, etc.
- Agriculture
A useful feed supplement in livestock farming to maintain the desired level of calcium in the diet of cattle and poultry. In agriculture, chalk is used to adjust the pH level of soils.
- Medicine and pharmaceuticals
It is mainly used as a filler in the production of medications. It is also used as a food supplement if the body is deficient in calcium.
- Cosmetology
Chalk is added to creams, care products, powders, pastes, including toothpastes.
- Food-manufacturing industry
Using the material, the beet juice is purified during sugar preparation.
In addition, fine chalk is used in the production of lime, paper, rubber, glass, and many other items, materials, goods. Fine polishing of surfaces is carried out with the use of fine chalk. The material is also used in household activities, e.g. for chalk painting, whitewashing the surfaces of walls, ceilings, and tree trunks.
Chalk grinding — disadvantages of conventional technologies
The quality and properties of fine chalk largely depend on its grinding fineness. This affects the structure-forming features of the material, the ability to undergo reactions and create strong bonds with other constituents. In the event of high-quality grinding, the chalk grinding fineness should reach only a few micrometers. Depending on the field of use, the size fraction may be tens of microns or even less than 10 microns.
It is quite difficult and energy-consuming to achieve the performance of several micrometers by means of conventional equipment. However, due to a high need for fine chalk milling, it is reasonable to use efficient methods for accomplishing this task.
Traditionally, chalk milling is carried out using mechanical grinding technologies or chemical precipitation methods. Mills and crushers are used in mechanical milling lines:
- Hammer mills
Suitable only for dry grinding wherein it is not always possible to achieve the desired dispersion ability level of the material.
- Ball drums
Efficient, but bulky, noisy, energy-consuming equipment. It is used for wet and dry grinding, however, in both cases, we obtain at the outlet a material with fairly coarse particles admixed.
- Jet mill
Ensures fine milling, but not the best efficiency, requires the use of additional equipment and high energy consumption.
- Disintegrator
It is a mill with two rotors rotating in opposite directions. It is distinguished by problematic scaling and regular wear of working tools.
The method of chemical precipitation in chalk production includes three stages — baking, carbonization, and precipitation. The finished product is synthetic chalk used in the medical and cosmetic fields.
Chalk grinding by means of conventional technologies involves a comprehensive list of processes. First, the material is subjected to coarse crushing; next, magnetic separation, wet pulverization, and grinding by means of jet-type disintegrators take place. Then, the suspension is handled using a dispersant, and upgrading is carried out in hydrocyclones. After that, secondary fine grinding is performed. The suspension is collected, subjected to control sifting, and dried by spraying. At the final stage, washing-off is carried out.
Even this complex and labor-consuming process of chalk grinding does not yield the best results in terms of the quality and purity of finished product.
In order to solve the problems of conventional chalk milling methods, to make the process simpler, faster, and more cost-effective, GlobeCore proposes to use a vortex layer device (AVS). It is a versatile vortex layer device used for fast and efficient dry and wet chalk grinding. The equipment intensifies the processes of obtaining high-quality fine chalk in which case no high costs of operation, maintenance, installation, etc. are required.
Technology for chalk grinding by means of AVS
GlobeCore developed modern chalk milling equipment in the form of vortex layer devices. Two models of the equipment are represented — AVS-100 and AVS-150. They are different in capacity.
Chalk grinding in the vortex layer device occurs according to the principle of processing the material with ferromagnetic particles in an electromagnetic field. The field is created by an inductor comprising a non-magnetic operating chamber.
Driven by an electromagnetic field, the ferromagnetic particles turn into mixers, intensively move about the chamber, rotate, collide with one another, the operating unit walls, and the material processed — a vortex layer is generated. At the same time, chalk particles are mixed, ground, and activated in the chamber.
In order to obtain finer chalk with the particle size of up to a micrometer, it is processed in a liquid medium. The material is exposed to dispersion, mixing, electrolysis, high local pressures, acoustic vibrations, and electromagnetic processing.
The milling fineness can also be adjusted simply by changing the time of processing the material in the chamber. The longer we grind, the finer particles we will obtain at the outlet.
If chalk grinding is carried out by means of the vortex layer device in a dry medium, the process of water electrolysis is excluded, and the particles will be slightly larger due to coarsening. However, in this case, the technological line is simplified, because it is not necessary to extract grains from the liquid and to evaporate the moisture. Thus, if the fineness of particles is not a critical parameter, a simplified dry milling technology could be sufficient.
Chalk grinding by means of AVS also contributes to its activation for better, full interaction with constituents in the preparation of mixtures and materials. There develop active centers on the surface of newly formed grains due to fine milling, splitting of particles. The amount of surface energy increases, and the structure-forming properties of the material become higher.
Advantages of chalk milling by means of a vortex layer device
AVS from GlobeCore is the optimal solution for improving and intensifying the chalk grinding processes due to the following reasons:
- Ease of use
The equipment is distinguished by simple design, low weight — 500 kg without a control section, and the height of just over one and a half meters. It does not require a lot of space to be allocated, and pedestals or additional structures to be installed.
- High milling intensity
AVS is able to efficiently grind chalk to a finely dispersed state, while activating its particles and improving the quality of the final product.
- Cost-effectiveness
The power requirement of AVS, depending on the model, ranges from 4.5 to 9.5 kW which is several times less than that of conventional mills.
- Reduced chalk milling time
In order to obtain fine chalk, it is sufficient to process the material in AVS for several minutes.
Such advantages make AVS a favorable and efficient solution for a chalk grinding production line. The equipment is suitable for construction materials production enterprises, agricultural, mining, medical, and chemical organizations. The vortex layer device can be ordered, and more information about the equipment can be obtained from GlobeCore sales representatives.