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Surface Properties of Carbon Black

Jul 23, 2022

The pH value, volatile matter and diphenylguanidine sorption rate of carbon black are the quality indicators reflecting the chemical properties of carbon black surface. When there are few alkali metal salts in carbon black, the pH value of furnace carbon black has a certain relationship with volatile matter. Generally speaking, controlling the pH value of carbon black also controls the volatile content of carbon black.

Oil furnace carbon black is usually alkaline (except for grooved furnace black), and the pH value is generally 7-10. There are several methods for controlling and adjusting the pH value of oil furnace black.

1. In the case of certain equipment and using the same raw material, it is beneficial to reduce the pH value of oil furnace black by reducing the processing amount of raw oil.

2. When using a bag filter to collect carbon black, appropriately extend the time interval between two times of rapping in the bag filter, and the pH value will drop. When the processing volume of the raw oil is the same, the bag filter with a larger collection area has a lower pH value than the bag filter with a smaller collection area.

3. In process operation, increasing the ratio of tangential air to axial air will promote the decrease of pH value.

Diphenylguanidine adsorption rate is also called DPG adsorption rate. The adsorption amount of carbon black to diphenylguanidine depends on the volatile content and specific area of carbon black. When the surface area is roughly the same, the adsorption rate of diphenylguanidine mainly reflects the acid and basicity of the carbon black surface.

The adsorption rate of diphenylguanidine is also affected by the salts (strong acid and weak base salt or strong base and weak acid salt) in the volatile ash of carbon black. In technology, the following methods can be used to control the sorption rate of diphenylguanidine:

1. The diphenylguanidine adsorption rate of oil furnace carbon black increases or decreases with the increase or decrease of the air-oil ratio. Therefore, the adsorption rate of diphenylguanidine can be controlled by increasing or decreasing the air-oil ratio.

2. When the air-oil ratio is not changed, the temperature of feed oil and air into the furnace can be increased to increase the adsorption rate of diphenylguanidine.

3. When the process conditions remain unchanged, the reaction furnace body is well insulated, which reduces the heat loss on the surface of the furnace body, increases the furnace temperature relatively, and also increases the diphenylguanidine adsorption rate.