Liquid steel vacuum treatment volatilization arsenic removal

Liquid steel vacuum treatment volatile arsenic removal Liu Shouping Sun Shanchang (Chongqing University, Chongqing 400044) Mass transfer of three links in the gas phase. Strengthen the arsenic mass transfer inside the molten steel. Increasing the molten steel-gas phase contact interface and increasing the vacuum treatment temperature of molten steel can increase the rate of arsenic removal by volatilization.

Arsenic is an element with a lower melting point and sublimation point and a higher vapor pressure. This article starts with the vapor pressure of arsenic in liquid steel and studies the possibility and mechanism of arsenic vacuum volatilization in molten steel.

1 The vapor pressure of arsenic in liquid steel and vacuum arsenic removal from molten steel 1.1 The arsenic vapor pressure in liquid steel There are As, As2 and As4 molecules in the arsenic. The increase in temperature and decrease in pressure can lead to the number of monoatomic arsenic molecules. Due to the high temperature, arsenic in gas can be regarded as a monoatomic molecule. The vapor pressure PAs of pure liquid arsenic have the following relationship with temperature T. The concentration of arsenic in liquid steel is lower than that of pure arsenic, which can be obtained from the definition of activity. The vapor pressure Pa of As: (The aAs and YAsX:As in the test are the activity, activity coefficient and molar concentration of As, respectively; according to: the logarithm of (2) is taken on both sides and substituted into (1), (3) The relation between the arsenic vapor pressure and the arsenic molar concentration Xas and temperature T in molten steel: 1.2. Vacuum removal of arsenic from steel liquid and arsenic and iron separation coefficient For binary alloy solution A-B, A is a solute and B is a solvent. The weight percentages of A and B are a% and b%Ma respectively, and Mb is the molar mass of A and B respectively. When the solution is in equilibrium with the gas phase, the equilibrium gas phase must contain A and B. For Pa and Pb, the arsenic content of the two components A and B in the vapour phase of the gas phase is 0.005%~0.03. This indicates that the initial arsenic content of the liquid steel is very high. Vacuum can still be used to remove arsenic when it is low.

The molar concentration of formula (5) is converted to percent concentration: 001%-~2010P4 and the vapor pressure of arsenic in the gas phase of iron 11 deposited on the container is in the vacuum atmosphere. There is Inet Table 1 pure iron-arsenic II Arsenic removal during vacuum smelting of meta alloys and steels Furnace vacuum degree Ar pressure/kPa Vacuum treatment time/min spindle weight/g Arsenic content in molten steel/% Arsenic removal rate I/% Start of the end of the process G0111.33081790 0750023693 Note: 1G011G019 is a pure iron-arsenic alloy; 2ZllZ14 is a Toms steel, and the ratio (A) to (B) of the gas phase is proportional to the ratio of the A and B components in the gas phase to the left of the (8) equation. The scale factor P is often referred to as the separation factor. Obviously, if the separation factor 卩> f indicates that the component A is present in the gas phase in a larger amount than in the liquid phase, and the component B is just the opposite, it is possible to volatilize A into the gas phase by vacuum; if the separation factor P = B has the same composition in the gas phase and the liquid phase and cannot separate A and B by vacuum; if (K1), the solute A is concentrated in the liquid phase instead.

For general steel liquid, its arsenic content will not be very high, but the solvent iron concentration is usually very high. It can be regarded as H. According to formula (7), the separation coefficient of iron and arsenic in molten steel can be written as: PFe is pure iron liquid vapor The relationship between pressure and temperature T is as follows: (9) Take the logarithm on both sides and substituting (4) and (10), and sort it out: According to formula (11), you can calculate that at 1 o'clock, P=5.4X104. Even if the concentration of arsenic in the molten steel is very low, the separation factor of Fe-As is still very large. Therefore, for the arsenic in molten steel, the separation of Fe and As can be completely achieved by a vacuum method.

1.3 Vacuum liquid steel arsenic removal experiment The steelmaking laboratory of the Steel Research Institute of France conducted a vacuum volatilization and arsenic removal experiment in a vacuum induction furnace (Table 1). The vacuum treatment time was started but the arsenic volatilization rate in Table 2 was calculated theoretically. And experimentally measured arsenic average evaporation rate, calculated by equation (16) arsenic volatilization rate is much larger than the actual measurement. The reason is that the theoretical calculation formula (16) considers the vacuum condition as an absolute vacuum and the volatilization rate of arsenic is completely controlled by the surface evaporation of arsenic. However, these conditions cannot be achieved during the actual vacuum process; the experimental value is within a certain concentration range. The average volatilization rate inside, and the calculated value is the instantaneous volatilization rate per unit area at a certain arsenic concentration, so the two can only be compared relatively. However, the common law between the theoretical value and the experimental value is that the arsenic concentration decreases and the volatilization rate decreases.

3 Conclusions Theoretical calculations and experimental results show that volatilization of arsenic can be achieved during vacuum treatment of liquid steel.

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