1. Distinguish from the ore itself

Calcite cleavage is very clear, transparent, the surface of the ore is a very clear plane, no matter how to break, can see the plane. Calcite is also divided into large calcite and small calcite, the more regular cleavage for large calcite, large calcite transparency is very high, cleavage disorder for small solution. There are three colors of calcite ore, milky white phase, yellow phase, red phase, the color of each origin in China is different.

Marble is divided into coarse concentrate and fine crystal ore, the same tone is bluish white phase, this ore domestic reserves are very much, make powder dosage is also very large. Basically distributed in Sichuan, Guangxi, Zhejiang, Anhui, Shandong and other places, ore quality is not the same in each area. From the microscopic crystal structure, calcite belongs to hexagonal crystal system. Marble crystals are generally cubic in shape.


2.Distinguish from the calcium carbonate content and the appearance of the powder

The main components of calcite and marble are calcium carbonate, the calcium content of good calcite can reach more than 99%, and the calcium content of good marble is about 96-98%. Calcite pink is soft, yellow and red. Marble powder slightly feel blue, blue phase, the feeling of whiteness difference will be dark.

3.distinguish from the application performance of powder
Due to the calcite ore quality crystal cleavage is very good, made of powder powder dispersion, liquidity, particle size distribution and the oil absorption value of the powder, covering rate is better than marble. Good calcite powder whiteness can do more than 95-97 (400 mesh powder), marble whiteness is lower, better about 93-95 (400 mesh), two kinds of powder in the downstream customers play their respective roles. The price of calcite powder will be slightly higher than that of marble powder. Therefore, downstream customers will choose their own powder according to their own cost and quality requirements. The purity of calcite is very high, so the powder can be used in various fields of food grade, such as toothpaste, food additives, edible calcium tablets, feed additives and so on. And can pass the EU's environmental indicators. For some enterprises with high requirements, calcite powder must be the first choice. Because the hue, whiteness, dispersion and temperature resistance of calcite powder and marble powder are not the same, the downstream customers who have requirements on the hue of the product can also choose the use of powder.

4. Analysis of industrial application examples
Plastic industry: marble powder and calcite powder are used, according to customer requirements choose to use.
Under the condition of the same formula, the same or similar particle size distribution of calcite calcium carbide and marble calcium carbide filling plastic products will show different differences, mainly showing the color and physical mechanics (tensile force and impact resistance) differences.


Color difference
Due to the different metal elements contained in calcite and marble, the color of the powder is different. The product made of calcite powder filled in plastic will show milky yellow or milky red (that is, the magnetic white and milky white that the industry says), soft color and good covering power.

Physical and mechanical differences
Due to the different crystal structure of calcite and marble, the tensile strength and impact resistance will be different after filling plastic products. Calcite belongs to hexagonal crystal system, the crystal is generally jujube nucleus shape, the length and diameter is relatively large; Marble crystals are generally cubic in shape and small in diameter. The powder with large diameter and length ratio has a certain reinforcing effect in plastics, and the mechanical properties of plastic products such as tensile force and impact resistance are better. Such as calcite calcium and marble calcium with the same particle size distribution in the same formula to fill PVC pipe profiles and other products, marble powder than calcite powder to make products are easier to brittle, poor toughness.

With limestone as raw material by the calcine, digestion, carbonic acid, the dry separation and classification of the product is called light calcium carbonate, is one of the most widely use inorganic filler, widely used in rubber, plastic, papermaking, coating, paint, printing ink, printing, cable, food, medicine, cosmetics, daily necessities, feed, oil and other industries.
Ultrafine calcium carbonate, especially nanometer calcium carbonate particles, not only retains the properties of original calcium carbonate, but also has the properties of nanometer particles. By controlling the preparation conditions, calcium carbonate nanoparticles with different particle sizes and crystal shapes can be obtained. Therefore, there are many differences between nano calcium and light calcium in production process, quality control, appearance, particle size and application. Understanding the differences between them helps us to identify and develop non-functional calcium carbonate products according to different needs.

1. Differences in production process and quality control
Although there are many production methods of light calcium carbonate, carbonization is almost the only method to achieve industrial production in China. Calcination of limestone and other raw materials to produce quick lime is mainly composed of calcium oxide and carbon dioxide, and then water digestion of lime to generate lime milk is mainly composed of calcium hydroxide, and then carbon dioxide carbonization of lime milk to generate calcium carbonate precipitation, and finally calcium carbonate precipitation through dehydration, drying and grinding will produce light calcium carbonate. This method is characterized by low energy consumption, simple process and abundant raw materials, which can meet the requirements of different industries.
China began to develop and produce nano calcium carbonate in the early 1980s, and realized industrial production at the end of 1980s. The research and development units in China mainly include Beijing University of Chemical Technology, East China University of Science and Technology, School of Chemical Engineering, Harbin Engineering University, Hefei Institute of Solid State Physics, Chinese Academy of Sciences, Tianjin Research Institute of Chemical Industry, etc.

The production process of nano calcium carbonate is mainly divided into four steps: calcination purification, digestion, carbonization, dry packaging. Production to a selection of limestone ore calcine, calcium oxide and kiln gas and calcium oxide digestion, and will generate suspended calcium hydroxide crushed under high shear force, the multi-stage spiral liquid separation to remove particles and impurities, have a certain concentration of refined bubbled into calcium hydroxide slurry, add the appropriate surface modification agent, the carbide to the finish line, The calcium carbonate slurry is then dehydrated, dried and surface treated to obtain the desired nano calcium carbonate product.

1) digestion
The preparation process of light calcium has low requirements on digestion temperature and quality of digestion water. The recycled filtrate of centrifugal dehydration can be used as hot water for digestion, which can make full use of heat energy to improve digestion reaction temperature and reduce the consumption of water in production. It is generally required that the lime is medium-burned or over-burned, and the viscosity of the raw slurry after digestion is low, which is conducive to improving the carbonization efficiency.

The preparation of nano calcium carbonate should use light burned lime with high activity, high digestion temperature and stable viscosity of raw slurry. Available raw slurry in the process of refining slag washing liquid as absorb water, but cannot use the ripe slurry filtrate digestion, because of the filtrate contained large amounts of calcium carbonate crystal, added to the raw slurry will be involved in the seed carbonation reaction, affect the uniformity of the carbide crystal, easy to produce larger particles in the process of crystal crystal, affect the product particle size distribution.

2) carbide
The preparation of light calcium does not control the initial temperature of carbonization reaction, and almost does not control the concentration and viscosity of raw pulp and concentration. Sometimes in order to improve the carbonization speed, under the condition that the sedimentation volume reaches the requirement, adding a part of cooked pulp in the initial carbonization raw pulp can obviously improve the carbonization reaction speed, and can be used as a means to adjust the sedimentation volume of products.

Nano calcium carbonate is prepared by carbonization reactor different from ordinary light calcium, equipped with cold water jacket to control the reaction temperature, agitator to improve the mixture of gas and liquid and refrigeration equipment. Control the initial temperature of raw pulp carbonization, lime emulsion concentration, concentration, temperature, flow rate and stirring speed and other process parameters, but also can use multi-stage carbonization to control the crystal size and crystal shape. Since many seeds cannot be brought in at the initial stage of the carbonization reaction, the carbonization reactor should be easy to clean so that the necessary cleaning of the system can be carried out after each batch of carbonization. A certain amount of crystal shape control agent can also be added in the process of raw pulp or carbonization reaction to adjust the reaction speed, improve the crystal dispersion performance and control the role of crystallization, the carbonization process control is much more complex than ordinary light calcium or fine calcium.

3) dry
Light calcium is generally controlled as long as the whiteness, moisture, screen residue and value of the product to meet the requirements, so in the product after drying, after a simple screening packaging products. The drying temperature is not high, as long as it does not exceed the decomposition temperature of calcium carbonate, so ordinary light calcium is generally dried at 600-750℃, with high efficiency.

Nano calcium carbonate is mostly after surface treatment, so when the product is dry, the temperature should not be controlled too high, otherwise it will cause the surface active agent coking, the product seriously yellow, affecting the quality of the product. At present, the drying temperature of nano calcium carbonate is generally 200-300℃, and the process control temperature is slightly different depending on the residence time of materials in different drying systems. After drying, crushing, depolymerization and grading are the key methods for quality control of nano calcium carbonate products. For products with different particle distribution and different surfactant treatment, there are different emphases in selecting drying and grinding grading equipment.


2. Different appearance quality

1) the appearance
When rubbing nano calcium carbonate powder with fingers, the particles feel fine and smooth, and the adhesion is strong. It is difficult to wash the powder on fingers. The dust formed by the powder in the air is difficult to settle, and the paste formed by the miscible nano calcium carbonate with small particle size and water is not high in whiteness and has a slightly transparent feeling.

2) white degree
Because ordinary nano calcium carbonate products pay great attention to the control of impurities such as "black and yellow spots" in the product in the production process, the whiteness of the product is relatively high, generally 94%96%, slightly higher than that of ordinary light calcium, but some ordinary light calcium inactive products have high whiteness, which can reach 96% to 97%.

3) Packing density
In general, the bulk density of nano calcium carbonate products is small, mostly 0.4-0.6g/cm3, while the bulk density of light calcium carbonate products is 0.6-0.7g/cm3. However, with the continuous improvement of the application performance of nano calcium carbonate products, the bulk density of some products is gradually increasing, and the bulk density of products produced by different drying equipment varies greatly. At present, it is difficult to distinguish nano calcium carbonate products from ordinary light calcium products in terms of bulk density.

3. Different particle size and crystal shape

1) Different particle sizes
The essential difference between nano calcium carbonate and ordinary light calcium is that the original particle size is also called the primary particle size is different, through transmission electron microscopy analysis and detection can accurately identify the two products.

2) Different crystal shapes
Because of nanometer calcium carbonate with a greater difference between ordinary light calcium carbide process, the nano calcium carbonate crystal microtek shape change crystallization process, the shape of the crystal is given priority to with the cube, the shape of the crystal with the technological conditions and the influence of the shape control agent and diversified, and ordinary light calcium crystal shape is relatively single, give priority to with spindle, chrysanthemum shape crystals formed or reunion together.

4.different application process performance and role
Due to its small particle size, nano calcium carbonate has some special properties in the application materials, such as rubber and plastic has strong reinforcement and modification, can greatly improve part of the mechanical properties and optical properties of the material. Therefore, nano calcium carbonate can be used as both functional filler and volume filler. Ordinary light calcium is obviously inferior to nano calcium carbonate in terms of strengthening performance, so it generally only has volume filling effect.

Nano-sized calcium carbonate has achieved industrialization in China, different carbonization method arises at the historic moment, the increasing scale and increasing production, application domain expands unceasingly, from rubber, printing ink and other industries to plastics, paper, paint, adhesives and other industries rapidly expand, demand is increasing at an annual rate of 20%, high-end products on the market, To meet the growing demand of the two major markets at home and abroad.

Today, functional calcium carbonate has become a big demand point in the calcium carbonate application market. In the face of market demand, different users have different requirements for products. In addition to the particle size of calcium carbonate products, they also look at product performance and quality. Only in this way can various functional calcium products have stronger market competitiveness. Therefore, more efforts can be made on the application performance of nano-sized calcium carbonate, and more functional and special nano-sized calcium carbonate can be developed. The same is true of other inorganic powder materials.

1. Different packing densities
The most obvious difference between heavy calcium and light calcium lies in the different bulk density of the products. Generally, the bulk density of heavy calcium products is larger, ranging from 0.8 to 1.3g/cm3, while that of light calcium products is smaller, mostly ranging from 0.5 to 0.7g/cm3. The bulk density of some nano calcium carbonate products can reach about 0.28g/cm3. Heavy calcium and light calcium products can also be roughly distinguished by the packaging volume of the products. Generally, heavy calcium products are mostly 25kg/ package and the packaging volume is small, while the packaging volume of light calcium products of the same quality is obviously larger. Some nano calcium carbonate products are also packaged in 15kg/ package or 20kg/ package.


2.whiteness
Because heavy calcium products have more relative impurities and larger particles, the whiteness of the products is generally 89%~93%, and a few products can reach 95%, while the whiteness of light calcium products is 92%~95%, and some products can reach 96% ~ 97%, which is the main reason why light calcium products are mostly used for high-grade or light-colored products.

3.water
Heavy calcium product moisture is low, but also more stable, generally 0.2%~0.3%, some high-grade heavy calcium product moisture can reach about 0.1%. The water content of ordinary light calcium products is 0.3%~0.8%, and sometimes there are certain fluctuations. Nano calcium carbonate products also vary in moisture content depending on the type of application, with some products having a moisture content of less than 0.1 and some products having a moisture content of about 1.5%.


4. Different particle sizes
The particle size of heavy calcium products ranges from 0.5 to 45um, and the smaller the particle size, the higher the price. Currently, there is no industrial production of nano-sized heavy calcium, but some ultrafine calcium products contain a very small amount of particles with a particle size of about 100nm. The particle size of ordinary light calcium products is generally 0.5~15um, and the particle size of nano calcium carbonate is generally 20~200nm. Identification methods can be adopted by transmission or scanning electron microscopy analysis and detection, more intuitive and accurate, can also be used to determine specific surface area or particle size analyzer analysis and detection methods to judge.


5. Different crystal types
Due to mechanical crushing and grading of heavy calcium products, the particle shape is irregular, also known as amorphous. The particle size of precipitated calcium carbonate products is generally more regular, for example, ordinary light calcium is mainly in spindle shape, and nano calcium carbonate is mainly in cubic crystal type.


6. different performance in the application process
In the application process, heavy calcium products are mainly used in papermaking, rubber and plastic industries, filling volume is generally large, mainly as a volume filler, reduce the manufacturing cost of applied products. Light calcium products are widely applied in a wide range of fields, mainly volume filling, while nano calcium carbonate products are often used as functional fillers such as modification or reinforcement in the application process, and the filling amount is generally small. Lightweight calcium carbonate products are mainly used in plastics, rubber, coatings, adhesives and inks.

1, hydrophobic
The surface of active calcium carbonate coated with organic active agent has strong hydrophobic performance, which is the most significant difference between active calcium and inactive products. The identification method is also relatively simple: take a few products placed in clean water, after a certain period of stirring the majority of the products suspended on the water, the water is clear and not turbid, it is activated calcium; If all or most of the product is submerged in water and the water becomes cloudy, it is an inactive product.


2. Liquidity
Because the surface of activated calcium products is covered by organic surfactant molecules with lower surface tension, its specific surface energy is lower than that of non-activated products, the viscosity resistance between particles is reduced, and the flow performance of particles is improved, so the powder has similar to the fluidity of liquid, and the flow performance of inactive products is obviously poor. Attention should be paid to the comparison under the same conditions such as temperature, humidity and product moisture.

3. Dispersion
The difference of dispersion can be seen from the good fluidity of the active products. The active calcium products have good solubility and dispersion with the base materials in the application process due to their good dispersion. The penetration capacity of particles is also strong, but also easy to form dust, ordinary woven bag urgent packaging products in the process of loading and unloading and use of large dust.


4. different particle size
As the surfactant of active calcium products reduces the surface energy of particles, the agglomeration strength of particles is weakened, and the particle size will be significantly reduced. Through scanning electron microscopy, active calcium and non-active calcium products can be clearly distinguished.


5. Different oil absorption values
The particle size of activated calcium products decreases, so that the void rate between particles decreases, and the microscopic surface of particles becomes smooth and smooth. Therefore, when detecting the oil absorption value of products, activated calcium products are lower than inactive products.


6, calcium carbonate content is different
Active calcium products generally contain 1.0%-5.0% organic active agent, so the calcium carbonate content is 1%-5% lower than that of inactive products. The smaller the particle size of active calcium products (such as nano calcium carbonate), the higher the surfactant content, the lower the calcium carbonate content.