One production method for the production of fumed silica involved a continuous flame hydrolysis technique. It involves the conversion of silicon tetra chloride (SiCl4) to the gas phase using an oxy hydrogen flame. It then reacts with water to yield silica (SiO2) and hydrochloric acid thus:
The HCl is easily separated as it remains in the gas phase, while the fumed silica is solid.
Treated gradescan be produced by reacting the silica fume with organosilicons. This can convert the natural hydrophilic fumed into a hydrophobic material.
Here introduces the Gas-Phase manufacturing technique, which includes seven courses: Pretreatment of raw material, Aggregate, Mixing, Gas-Solids Separation, Deacidify, Packing, Waste gas treatment.
By hydrolyzing SiCl4 , a byproduct in the procedure in production of polysilicon, in oxyhydrogen flame at high temperature, we get the Primary particles, a particle of 7-40nm. The Primary particles forms agglomerate measured by micron, after being accumulated and collided, and then, the agglomerate and the waste gas produced in the production of Primary particles at high temperature, go into the high efficiency separator, which is called the gas-solid separation.Then, SiO2 from the bottom of the High Efficiency Separator goes into the Deacidiy Tower to deacidify, after that, the products go into Storage Bin to be packaged. The waste gas from the top of the high efficiency separator once again goes into the tail gas treatment system. The non-polluting gas emits directly/goes into the air.
The chemical equation as follows：2H2 + O2 + SiCl4 → SiO2 + 4HCl