Bright and clean tin surface is a necessary condition for manufacturing float glass with excellent performance. Tin is easily oxidized at high temperatures, which will contaminate the glass surface and cause quality defects, so consider using inert or reducing gases. N2+H2 (N2 92%-96%, H2 4%-8%) is used at home and abroad as the protective gas for the tin bath to prevent oxidation of tin.

1. Main technical parameters of shielding gas: As far as domestic float glass companies are concerned, most of them currently use N2+H2 as shielding gas. The pressure of the gas supply equipment is generally maintained at about 0.03MPa, and the flow rate (standard state) is maintained at 1400～1500m /h, where nitrogen (standard state) is 1300～1400m/h; hydrogen (standard state) is 90～110m/h (about 5%-8% of the mixed gas). The distribution in the tin bath mostly uses 5% to 6% in the head; 2% to 4% in the middle; and 4% to 6% in the tail. Quality control index of shielding gas: Nitrogen ≤10ppm, dew point ≤-60℃.

2. The influence of the pressure fluctuation of the protective gas on the working conditions of the tin bath: In the normal production process of float glass, the atmosphere in the tin bath is relatively stable. Tin is very volatile in the temperature region of the tin bath and will not affect glass production. However, when the pressure of the protective gas fluctuates, oxygen and sulfur components are often mixed into the tin bath, resulting in a large change in the atmosphere in the tin bath. In the tin bath, SnS and SnO are extremely volatile substances. Due to their existence, the volatility of the tin liquid is greatly increased. At this time, SnO is quickly oxidized to SnO2, which causes the pollution of pure tin and the space of the tin bath. At the same time, the precipitation of SnS and the supersaturated precipitation of SnS in the tin liquid adhere to the upper and lower surfaces of the molten glass ribbon, causing "spots" in the glass, forming pits after cooling, causing light distortion points. SnO will make the glass "frost".