Formulation of Hydrochloric Acid Pickling Process System for Packaging Steel Strip

Formulation of Hydrochloric Acid Pickling Process System for Packaging Steel Strip
　　 When pickling with hydrochloric acid, the pickling speed increases with the increase of acid concentration and temperature, but the volatility of hydrochloric acid limits the increase of acid concentration and temperature. In the pickling tank, the evaporation of hydrogen chloride gas increases sharply with the increase in temperature, also increases with the increase in the concentration of hydrochloric acid, and also increases with the increase in the content of ferrous chloride in the acid solution, but the impact is the greatest Is the temperature.
　　 When the content of hydrochloric acid is not large, ferrous chloride has good solubility. Figure 2-9 shows the solubility curves of ferrous chloride in hydrochloric acid and ferrous sulfate in sulfuric acid. It can be seen that its solubility decreases as the concentration of hydrochloric acid increases. Figure 2-10 shows the relationship between the pickling time and ferrous chloride when the temperature is 20, 40, and 60°C. In acid solutions of different concentrations, with the increase of ferrous chloride, the pickling time decreases. The shortest pickling time is obtained when its content is lower than the saturation value by about 4-8%. After the minimum value is exceeded, the pickling time is reduced. Liters, so the pickling time is the longest when the content of ferrous chloride is close to the saturation value. Therefore, the acid solution with the concentration of ferrous chloride close to the saturated state is not used in the production to avoid prolonging the pickling time. When the concentration of hydrochloric acid is high, the ferrous chloride can easily reach the saturated state, so the acid concentration should not be too high. In the pickling process, although the concentration of the acid solution decreases, the content of ferrous chloride rises. Because these two factors have opposite effects and cancel each other out in a certain period of time, the pickling speed is nearly maintained during the longer period of pickling. constant.
　　According to the above, in order to avoid the saturation of ferrous chloride to affect the pickling time, and to avoid excessive volatilization of hydrochloric acid due to too high temperature, the hydrochloric acid pickling process system is generally acid concentration 20-130g/L, temperature 70 -90℃, Fe++ ion concentration 45-145g/L.