Special application of inhibiting the bad effect of zinc vapor(2)
.In order to suppress and eliminate the ring effect of front steam, the annealing furnace of hot plating line 5 and 6 adopted four special measures.
(1) the area of the cavity in the elephant trough is large and small. It can be seen that the upper and lower dimensions are the same as those of the lower part. However, the elephant nasal cavity 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 smaller and smaller as it goes down. This makes the area of the inner cavity smaller as it goes down, and the area of the inner cavity at the end of the trunk of the elephant nose groove entering the bath decreases by about half compared with 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 in trunk slot won't.(3) local humidification. The measure includes three interlocking small steps.
Out of the oven most Kong Tong into the protective gas is low dew point (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, and that the road is protecting the gas in a sealed tank water through again after, absorb water vapor into the furnace), its dew point about 25 ℃ or a little higher. The amount of penetration is 65 Nm /h. As the protective gas contains more water vapor, the water vapor will react with the zinc vapor: HO+Zn= h +Zno Zn0 drops back to the surface of the plating solution, as its proportion is larger than that of the aluminum-zinc silicon alloy solution, and will sink to the bottom of the pot and enter the slag.
The protective gas used for humidifying is prepared according to 30% of H2, and the high content of H can suppress the pair of water vapor H0.
The oxidation tendency of the steel belt prevents secondary oxidation on the surface of the steel belt.The high hydrogen content is unnecessary waste for the furnace, and the high dew point is detrimental.
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.
Keep warm in the balance section and the hot tensioning roller room. Despite the above three measures, still there will be a part of not being oxidized zinc steam, steam rises, so will be hot roller chamber and balanced section of the furnace temperature control at about 610 ℃. So the zinc vapor won't be thereThese areas condense into zinc powder, which is released from the top of the furnace to escape out of the furnace.Balanced section and hot roll zhang room at 610 ℃ the prime function of heat preservation, is to achieve the balance of the previous section about effects of the first and second, while doing so had to avoid zinc vapor condenses into the function of zinc powder. Inhibiting the harm of zinc vapor is the third function of equilibrium stage.In addition to the above four measures, another measure has been used in foreign countries: in the middle upper part and middle lower part of the trunk trough, two pairs of partitions can be opened and closed. During normal production, the baffles are in a semi-open and closed state, reducing the area of the inner cavity, thus reducing the amount of zinc vapor passing through.
Clasim also talked about the measure in an initial technical exchange, but canceled it in a later basic design. The Chinese side asked the foreign side why the cancellation was made.-partitions are not necessary.
After the author pecks and grinds this matter, feels because partition board has the side effect that prevents obstruct to wear ribbon, the outside side according to production experience, weigh advantages and disadvantages, just decided to cancel partition board this measure.The production experience shows that the above four measures, only the first three, not the fourth, can effectively inhibit the bad effect of zinc steam.Although hot dip aluminum zinc silicon zinc plated surface evaporation pan out when steam is more than the hot dip galvanized, but because of the workshop space is very big, has good ventilation conditions, concentration of zinc vapor in the air is limited, operation workers close to the plating pot (add alloy bursts, mein slag, cleaning the pot roll surface, clean up the air knife knife lip and remove slag, etc.) of the time is short, zinc steam does not cause significant damage to human body, so, in the developed countries of the hot dip aluminum zinc silicon online, didn't set the pan surface at the top of the zinc vapor smoke discharge set up factories, shi. Therefore, there is no such facility in the foreign design for hengtong line Operators do not have to worry too much about the zinc steam, close to the operation of the pan when wearing a mask to protect it.