Calcium carbonate, as an inorganic filler, is widely used in industries of plastics, rubber, coatings and paper-making. بياض is one of the important indicators to measure its quality. Whiteness not only affects the appearance of the product, but also directly affects the market value and application performance of the product. This article will discuss the main factors affecting the whiteness of carbonate and propose corresponding solutions.
The main factors affecting the whiteness
1. Quality of raw material
Limestone is the most important factor affecting the whiteness of calcium carbonate. The impurities, such as: iron, manganese and hydrochloric acid insoluble matter, will significantly reduce the whiteness of the product. Only when the iron conten ≤0.12%, the manganese content≤0.006%, and the hydrochloric acid insoluble content≤0.30%, can calcium carbonate with acceptable whiteness be produced. Experienced raw material screeners can give preliminary judgment on the purity of limestone based on its appearance. Usually limestone with cyan or light gray colors has higher purity, while limestone that contains more impurities, such as iron and manganese, is patterned or spotted with yellow, brown or pink colors.
2. Fuel selection
In the production of calcium carbonate, the selection of fuel is also crucial. The content of impurities such as sulfur and ash in anthracite will directly affect the whiteness of calcium carbonate. The sulfur content of anthracite for production should be ≤1.5%, the ash content should be ≤25%, and the content of other impurities should be ≤2.0%, then it can meet the requirements of producing calcium carbonate with qualified whiteness.
3. Production technology
❊ Calcination condition
The calcination condition of quicklime has an important influence on the whiteness of calcium carbonate. Strictly controlling the calcination temperature and time to avoid over-burning of quicklime as well as removing impurities such as coke slag and coke nuclei can improve the whiteness of calcium carbonate
❊ Carbonization process
During carbonization process, the reaction between Ca(OH)2 and CO2 must be complete to ensure no alkali return and no agglomeration, thereby improving the dispersibility, particle fineness and distribution uniformity of crystal particles. This is also one of the key ways to improve the whiteness of the product.
4. Particle size and water content of ore
The finer the particle size of the ore, the higher the whiteness. However, mineral products with different uses have different requirements for particle size, so it needs comprehensive consideration. In addition, the water content of the ore is also an important factor affecting whiteness. Reducing the water content of the ore can effectively improve the whiteness of calcium carbonate.
In response to above problems, we can adopt following solutions
1. Select high-quality raw material
Select limestone with low impurity content of iron and manganese as raw material, and ensure the purity through strict screening and classification. At the same time, through chemical analysis to ensure that all indicators meet production requirements.
2. Optimize fuel selection
Select low-sulfur, low-ash anthracite as fuel to reduce negative impact on whiteness. Moreover, regularly test the fuel quality to ensure stability of fuel quality.
3. Improve production technology
✬ Calcination process
Optimize calcination temperature and time to ensure the quality of quicklime. At the same time, improve calcination efficiency and reduce occurrence of over-burning by improving calcination equipment.
✬ Carbonization process
Improve the purity of kiln gas CO2 to ensure complete reaction between Ca(OH)2 and CO2. Meanwhile, strengthen monitoring of carbonization process to ensure no alkali return and no agglomeration.
4. Fine grinding and classifying
Fine grinding and classifying of calcium carbonate can improve the uniformity and fineness of particles. Improving the whiteness of calcium carbonate by physical methods is an effective way to improve product quality.
5. Chemical treatment
Through appropriate chemical treatment, such as acid washing and alkali washing, to remove impurities in calcium carbonate and improve its purity. Chemical treatment can significantly improve the whiteness, but attention must be paid to safety and environmental issues during treatment process.
6. Add additives
Add appropriate amount of whitening agent like titanium dioxide during production can improve the whiteness. However, in order to avoid adverse effects on product performance, the dosage should be controlled.
Overview
The whiteness of calcium carbonate is an important indicator to measure its quality, to some extent, it affects the application and market share of calcium carbonate.
As mentioned above, physical method can improve the whiteness of calcium carbonate, that is, through grinding and classifying, using grinder and classifier to finely process calcium carbonate. Qingdao Epic Powder Machinery Co., Ltd. has a variety of deep processing equipment for powders, including: jet mill, impact mill, ball mill, roller mill, various classifiers and a variety of surface coating modification equipment. Among them, the ball mill and classifier are suitable for fine grinding and grading of calcium carbonate, thereby improving the whiteness.
If you have any related demands or questions, please feel free to contact Qingdao Epic, they are always available.
