Carbon black production process

The raw materials for the production of pigmented carbon black are petroleum products and bituminous coal tar products. It is formed by incomplete combustion or pyrolysis of hydrocarbons at high temperatures.

1) Lamp black production process

The earliest carbon black production method in history is the lamp black production process. In this process, the raw materials are burned on a flat burning iron plate with a diameter of up to 1.5 m. The gas hood is collected, and then reaches the deposition device through the elbow (bend 1/4) and the fire tube. In order to control the characteristics of the carbon black produced, it should be ensured that the raw materials are mainly incompletely burned near the gap between the combustion plate and the exhaust hood. But in the pipe slightly into the pipeline, the combustion will be thermally decomposed under the lack of oxygen, thus forming larger carbon black particles. For these reasons, the composition has a wide range of particle size distribution, and the main feature is coarse particles. Since only a small part of the particles formed between the combustion disk and the exhaust hood can contact the oxygen in the air, these carbon blacks have only a small amount of surface oxides, the corresponding pH value is neutral, and the volatile matter is very small.

2) Gas black production process

The name of gas black comes from its production process: when the raw material hydrocarbon is heated, it is firstly gasified, and then the spontaneous combustion gas (for energy) is carried into the burner as a carrier. The large amount of carbon black emitted by these bat-shaped burners Generated in a fan-shaped flame. Since each flame is small and burns in the air, the formation of carbon black is very different from the production process of lamp black (incomplete combustion). Here, the carbon black particles are very fine. According to different types, the average particle size is between 10 and 30 nm, and the average particle size of gas black is 13 nm. On the burning flame, there is a slowly rotating water-filled drum. Carbon black is deposited on the drum. When it is scraped, the carbon black is scraped away. When the temperature is still high, the newly formed carbon black comes into contact with oxygen in the air. As a result, partial oxidation occurs, forming a large number of acidic groups, and the corresponding gas black pH value is in the acidic range. And can get about 6% of volatile matter, which represents its surface oxide content.

3) The production process of channel black

This production process uses natural gas as the raw material. The channel black process is similar to the gas combustion process of the gas black production process. The natural gas burns and emits many fan-shaped flames. The product obtained is similar to gas black, but the difference is that flat water cooling is used here. The U-shaped groove is used as a deposition groove for carbon black. Due to ecological and economic reasons, the use of this method was discontinued many years ago. The production of gas black will not affect the ecological environment, and the gas black process is still in use.

4) Furnace black production process

Gas black is produced in the open atmosphere, but the furnace black production process is carried out in a closed furnace under oxygen-deficient conditions. Instead of many small fires, a large flame is used. Oil is used as the raw material and combustible gas is added to make it reach the required temperature in the furnace. By changing the furnace black production process conditions, the required pigment black can be obtained. For example: under different conditions, carbon black can reach a wide range of average particle size, from 80 nm to as small as 15 nm, and even as small as gas black. But for the same particle size, there is still a difference between gas black and furnace black, mainly due to the difference in surface chemistry. Furnace black products are relatively rough, with an average particle size of 40nm. In addition, when the furnace black production process is used, a small amount of basic compounds or other additives can be added to change the degree and type of aggregates, thereby obtaining high-structure or low-structure carbon black.

Because furnace black is produced under conditions of almost below atmospheric pressure and insufficient air. Therefore, most of them lack acidic surface oxides, but found the pyrone structure mentioned above which is alkaline reaction. Regarding the alkaline pH value of furnace black, it is because of the addition of alkaline earth in the spray quenching cold water when the carbon black formation is terminated, and the addition of alkaline salt to reduce the structure. In addition, if this furnace black is no longer subjected to post-oxidation treatment, its volatile content will be lower.