Kaolin, especially ultra-fine calcined kaolin, as a very important inorganic non-metallic material, has always played a very important role in the paper industry with its excellent physical properties. Calcined kaolin used in paper industry is a porous and high whiteness structural functional material, which is mainly used to replace expensive titanium dioxide and other high-grade pigments. As a manufacturer of grinding equipment, the calcined kaolin ultra-fine vertical roller mill produced by HCMilling(Guilin Hongcheng) has been widely used and recognized in the production of calcined kaolin. The following is an introduction to the production method of calcined kaolin:

The quality requirements of the paper industry for calcined kaolin are mainly shown in the requirements for the particle size, whiteness, hiding power, oil absorption, viscosity concentration, pH value, wear value and other indicators of calcined kaolin. Under the circumstances that the market of ordinary washed kaolin has been shrinking year after year due to the impact of heavy calcium carbonate, the market sales have been booming, which has made many manufacturers follow suit. Since the 1980s, a large number of coal series kaolin has been discovered (it is said that the prospective reserves exceed 10 billion tons). Because of its high quality and few harmful impurities, coal series kaolin has become an ideal raw material for the production of paper coating grade calcined kaolin. The market prospect of calcined kaolin produced from coal series kaolin is broad.

The production process of calcined kaolin mainly includes two parts: crushing superfine process and calcining whitening process.

1. Grinding superfine process of calcined kaolin production method: grinding superfine process is an important link to determine the quality of kaolin. Crushing of coal series kaolin superfine is hard kaolin (from 5~20mm to 40~80 μ m) Ultrafine (from 40 to 80 μ M to – 10 μ M or – 2 μ m)。 calcined kaolin Raymond mill and calcined kaolin vertical roller mill produced by HCMilling(Guilin Hongcheng) are coarse crushing equipment, which can be used for the preliminary coarse crushing of calcined kaolin production method, and can process 80-600 mesh coal series kaolin; HLMX series calcined kaolin ultra-fine vertical roller mill, ring roller mill and other ultra-fine crushing equipment are suitable for ultra-fine crushing in the production method of calcined kaolin, which can process 3-45 μ M superfine kaolin powder is an ideal calcined kaolin superfine powder mill.

2. The calcination and whitening process of calcined kaolin production method: In view of the diagenetic characteristics of coal series kaolin, that is, it contains some organic matter, so that its raw ore whiteness is only 6~40%, which is far from meeting the quality requirements of paper industry for coated kaolin, so the calcination decarburization and whitening process must be adopted. According to the different requirements for the quality of kaolin, it can also be divided into two products: medium temperature calcined kaolin and high temperature calcined kaolin.

Process comparison of calcined kaolin production methods: according to whether the superfine process is wet process or dry process and the sequence of superfine process and calcination process, four production processes can be combined, namely

(1) wet superfine process followed by calcination process (2) dry superfine process followed by calcination process (3) calcination followed by wet superfine process (4) calcination followed by dry superfine process. Because people have different understanding of ultra-fine materials, the process routes used in different enterprises are different:

(1) The wet superfine calcination process is relatively long, but it has strong adaptability to raw materials, and the product quality can meet the needs of the paper industry;

(2) The calcination and rewetting superfine process generally requires special drying equipment and dispersion equipment. This process has weak adaptability to raw materials, but can produce products required by the paper industry;

(3) The dry superfine calcination process and the first calcination and then dry superfine process can not produce kaolin for paper industry (due to the reason of superfine equipment), which requires high quality of raw materials.

Overall, the process of dry superfine before calcination has strong practical applicability, and the process flow diagram is: raw ore → crushing → crushing → dry superfine → calcination → product. The advantages of this process are: (1) the process is short, and the whole process requires only three to four main equipment. If Hongcheng HLMX calcined kaolin ultrafine powder mill is selected, only three equipment are needed, namely, crusher, calcined kaolin ultrafine powder mill,       calciner, which is convenient for overall management and reasonable scheduling; (2) The energy utilization is reasonable. In this process, the superfine process of materials is placed before the calcination process to avoid the problem of consuming more energy due to crushing and burning materials. If the powder calcination process is adopted, it can be regarded as a full dry production process. As far as technology is concerned, energy utilization is more reasonable.

Using coal series kaolin to produce coating grade calcined kaolin for paper industry is undoubtedly an effective way to rationally utilize coal gangue. It should be noted that appropriate process routes should be selected according to local resources and capital. If you want to know more about the production methods and equipment selection of calcined kaolin, please call us for details.