What's wrong with zinc vapor?
Like the hot dip aluminum zinc silicon, nasal groove from the zinc plating solution surface evaporation steam upward movement, the trunk tank room, hot roller, cooling segment (if not balanced section), encounter cold can produce sublimation, condenses into solid zinc powder, stick to the roll surface, air cooling air outlet surface and roof, furnace wall surface, whenever boiler stop, open the lid of the stove, air into the furnace, zinc powder oxidizing reaction, into Zno Zno, this is known as zinc ash.Zinc dust accumulated over time, more and more.In this way, loose accumulation of the zinc ash particles can drop in the furnace roller surface, and then stick to surface of steel strip, result in the leakage after plating plating surface defects such as: zinc ash accumulation particles surrounded by roller compaction GeWo will bring pressure on steel.That's the downside of zinc vapor.
In order to suppress and eliminate the bad effect of zinc steam, the annealing furnace of hot-plating line no.5 and no.6 took four special measures.
(1) the lumen area in the trunk of elephant is large and small.It can be seen that the dimensions of the upper and lower parts are the same as those of the lower part.However, the elephant suspension slot of line 5 and line 6 is different from this one. Its width is the same as that of the top and bottom, but its thickness is lower and lower as it goes down, which makes the area of the inner cavity smaller as it goes down, and the area of the inner cavity at the end of the image groove that enters the plating solution is about half smaller than that of the upper part.As a result, the surface area of the coating in the trunk was reduced by half, and the amount of zinc vapor entering the trunk was reduced by half.
(2) elephant trunk is insulated.On the trunk tank appearance package dedicated electrical heating body and thermal insulation layer, and automatic temperature control, keep the elephant nose groove cavity temperature at about 610 ℃, and zinc steam condenses into zinc powder as the groove will not.
(3) local humidification.The measure includes three interlocking small steps.
Most out of the oven into Kong Tong into the low dew point of shielding gas (55 ℃), but from the hot roll zhang chamber and trunk groove adjacent Kong Tong into the shielding gas is after a moderate humidifying in advance (in the distribution room, road protection gas from in a sealed tank water through again after, absorb water vapor into the furnace), its dew point about 25 ℃ or a little higher.The pass-through volume is 65 Nm /h. As the protective gas contains more water vapor, the water vapor will react with the zinc vapor: H0+Zn= h +Zno
The Zn0 drops back to the surface of the plating solution, because its specific gravity is larger than that of the aluminum-zinc silicon alloy solution, which will sink into the bottom of the pot and enter the bottom slag.2. The protective gas used for humidifying is prepared according to 30% of H2, and the high content of H2 can suppress the oxidation tendency of water vapor H0 on the steel belt and prevent secondary oxidation on the surface of the steel belt.
High hydrogen content is unnecessary waste for the whole furnace, and high dew point is harmful.For this reason, in the lower part of the equilibrium section, an inlet hole and the middle and upper part of the four inlet holes, a pure N with low dew point, (fine nitrogen) 335 Nm/h, are mixed and diluted with the protective gas with 30% h content and high dew point, and then become the protective gas with about 5% h content and low dew point.