Gas phase method, also known as pyrolysis method, dry method or combustion method. The raw materials are generally silicon tetrachloride, oxygen (or air) and hydrogen, which are reacted at high temperature. The reaction formula is: SiCl4 + 2H2 + O2—> SiO2 + 4HCl. Air and hydrogen are sent to a synthetic hydrolysis furnace after being pressurized, separated, cooled and dehydrated, dried on silica gel, and filtered by dust removal. After the silicon tetrachloride raw material is sent to the rectification column for rectification, it is heated and evaporated in an evaporator, and the dried and filtered air is used as a carrier to be sent to a synthetic hydrolysis furnace. After silicon tetrachloride is gasified at high temperature (flame temperature 1000 ~ 1800 ° C), it is subjected to gas phase hydrolysis with a certain amount of hydrogen and oxygen (or air) at a high temperature of about 1800 ° C; gas phase white carbon black particles generated at this time Very fine, forming an aerosol with the gas, it is not easy to capture, so it is first gathered into larger particles in the concentrator, and then collected by the cyclone separator, then sent to the deacidification furnace, and the gas phase white carbon black is purged with nitrogen-containing air The finished product is PH to 4 ~ 6.