Guizhou Zunyi Titanium Factory is China's largest large-scale smelting plant for sponge titanium. It is the leading sponge titanium production plant in China. In the smelting process, a large amount of chlorine gas is generated. In order to reduce environmental pollution, water is used to remove chlorine. This produces a large amount of waste hydrochloric acid. The concentration of this waste acid is about 20%, which is difficult to handle, and because the waste acid contains a large amount of impurities. Therefore, there are certain difficulties in recycling it. It is imperative to solve the problem of waste hydrochloric acid in titanium plants. As one of China's Guizhou province's mineral resources, its reserves of manganese ore of living in a third country. The manganese ore resources in Guizhou Province are mainly distributed in Zunyi and Songtao. With the serious disorderly mining in recent years, the grade of manganese ore resources has gradually decreased. In this low-grade rhodochrosite as metallurgy, chemical industry raw materials, difficult to be exploited. Because most of the manganese ore resources in Guizhou Province are characterized by poverty, fineness and miscellaneous, there is certain difficulty in mineral processing . The comprehensive utilization of low-grade manganese ore resources in Zunyi and Songtao has always been a concern of researchers in metallurgical and chemical industries. The problem.

Therefore, the authors propose an experimental scheme for the preparation of manganese chloride tetrahydrate from low-grade rhodochrosite in Zunyi by using hydrochloric acid waste hydrochloric acid. The single factor method is used to investigate the leaching temperature, leaching time, liquid-solid ratio and acid excess coefficient. The effect on manganese leaching rate.

First, the experiment

(a) principle

The leaching reaction of rhodochrosite and hydrochloric acid is mainly the reaction process of manganese carbonate and hydrochloric acid in rhodochrosite, and the components of Fe ₂ O ₃ , FeO, CaO and MgO in rhodochrosite can also be reacted with hydrochloric acid to dissolve into solution. The main reaction equation is as follows:

MnCO ₃ +2HCl=MnCl ₂ +H ₂ O+CO ₂

(â–³G ^@ =-100.661KJ/mol)

The Gibbs free energy ΔG < O of the above reaction was calculated, and the reaction proceeded spontaneously. Since the temperature used in the experiment is not high, the influence of temperature on the reaction direction is not too obvious and can be basically applied. Thermodynamic analysis The above reactions were completely spontaneous.

(2) Raw material composition

1. Industrial hydrochloric acid: from Zunyi Titanium Industry Group, the concentration is about 22% to 25%.

2, rhodochrosite: from the Zunyi area.

3. Hard manganese ore: from Zunyi area.

4. Pyrolusite: a small amount of rich ore from the old areas of Yunnan.

The raw material ingredients are listed in Table 1.

Table 1 Raw material ingredients

(3) Method and process flow

By stirring and leaching, the hydrochloric acid and sulfuric acid slag are prepared into a leaching solution according to a certain liquid-solid ratio under heating conditions, and then filtered and purified to obtain a manganese chloride tetrahydrate product, and the process flow is shown in FIG.

Fig.1 Process flow of extracting waste manganese from ore manganese ore to prepare manganese chloride tetrahydrate

Second, the results and analysis

Select leaching temperatures of 70, 80, 90 and 95 ° C; leaching time 40, 60, 80 and 100 min; reaction liquid to solid ratio of 2:1, 2.5:1, 3:1; low concentration hydrochloric acid excess coefficient of 1, 1.3, 1.5 Several groups of experiments were performed separately for single factor experiments.

(2) Effect of leaching temperature on iron leaching rate

The reaction temperature was set at 70, 80, 90 and 95 °C. The leaching conditions were 200 g of rhodochrosite, 60 g of hard manganese ore, 240 mL of hydrochloric acid, the ratio of liquid to solid was 2.5:1, the leaching time was 60 min, and the pH of the reaction was 0.5~. 1.0, the reaction end point pH value 4.0 to 5.0.

Figure 2 Effect of leaching reaction temperature on manganese leaching rate

Figure 2 shows the effect of the leaching reaction temperature on the manganese leaching rate. It can be seen from Fig. 2 that as the leaching temperature increases, the leaching rate of manganese increases accordingly. However, the excessive temperature is not obvious for improving the leaching effect of manganese, but also increases the input cost. Therefore, it is preferable to select 80 ° C as the experimental leaching temperature.

(2) Effect of leaching reaction time on manganese leaching rate

The reaction time was 40, 60, 80 and 100 min. The leaching conditions were 200 g of rhodochrosite, 60 g of hard manganese ore, 250 mL of hydrochloric acid, liquid-solid ratio of 2.5:1, leaching reaction temperature of 80 ° C, and pH of the reaction process of 0.5 °. 1.0, the reaction end point pH value 4.0 to 5.0.

Figure 3 Effect of leaching reaction time on manganese leaching rate

Figure 3 shows the effect of leaching reaction time on manganese leaching rate. It can be seen from Fig. 3 that as the leaching time increases, the leaching rate of manganese increases accordingly. The leaching time increased from 40 min to 60 min, the leaching rate increased by 6%, and then increased to 80 min, and the leaching rate increased by 0.5%. Therefore, the longer the leaching time of the acid immersed manganese ore, the better the leaching effect of manganese. However, after the leaching time reaches 60 min, the increase of the leaching rate is obviously small. Considering that the leaching time after 60 min will increase the cost and the effect is not obvious, so the leaching time is preferably 60 min.

(III) Effect of solid ratio of leaching reaction on manganese leaching rate

Three groups of experiments were prepared with liquid-solid ratio of 2:1, 2.5:1, and 3:1. The leaching conditions were 200 g of rhodochrosite, 60 g of hard manganese ore, 250 mL of hydrochloric acid, leaching reaction time of 60 min, and leaching reaction temperature of 80 ° C. The pH of the process is 0.5 to 1.0, and the pH of the reaction end is 4.0 to 5.0.

Fig. 4 Effect of liquid-solid ratio of leaching reaction on manganese leaching rate

Figure 4 shows the effect of the solid ratio of the leaching reaction solution on the manganese leaching rate. As can be seen from Fig. 4, the leaching rate of the reaction is optimal when the reaction liquid to solid ratio is 2.5:1. Therefore, the reaction liquid to solid ratio in the reaction system is preferably 2.5:1.

(V) Effect of waste acid excess coefficient on manganese leaching rate

Three groups of experiments with acid excess coefficient of 1, 1.3, 1.5 were arranged. The leaching experimental conditions were 100 g of rhodochrosite, 40 g of hard manganese ore, 130 mL of hydrochloric acid, leaching reaction time of 60 min, leaching reaction temperature of 80 ° C, liquid-solid ratio of 2.5:1, reaction. The process pH is 0.5 to 1.0, and the reaction end point pH is 4.0 to 5.0.

Figure 5 Effect of waste acid excess coefficient on manganese leaching rate

Figure 5 shows the effect of the excess acid excess coefficient on the manganese leaching rate. As can be seen from Fig. 5, when the excess coefficient of hydrochloric acid is 1.3 (the amount of hydrochloric acid used is 170 mL), the primary leaching rate of manganese is the best and is superior to other experimental conditions. Therefore, the excess coefficient of the selected acid is preferably 1.3. However, it can also be seen that the amount of spent acid used has little effect on the manganese leaching rate, so a small excess coefficient can be appropriately selected if necessary in combination with actual needs.

(5) Analysis of results

Through the single factor analysis of the four main factors, it can be seen that for the first two factors, with the extension of the reaction time, increasing the reaction temperature can improve the leaching rate of the product well, but when the reaction time reaches 60 min, the reaction temperature reaches After 80 ° C, the leaching rate of manganese no longer has obvious changes. In order to reduce the production cost, these two parameters are selected as the optimal reaction conditions. It can be seen from the two parameters of liquid-solid ratio and waste acid excess coefficient that when the liquid-solid ratio is 2.5:1 and the waste acid excess coefficient is 1.3 times, the manganese leaching rate reaches a maximum value, so the two parameters are selected as the most Good reaction conditions.

Based on the optimal process conditions obtained by exploratory experiments and single factor experiments, we conducted a three-factor and three-level orthogonal experiment with a fixed acid excess coefficient of 1.3, and obtained the best process conditions similar to the single factor experiment: The leaching reaction time was 60 min, the leaching reaction temperature was 80 ° C, and the reaction liquid-solid ratio was 2.5:1. According to the single factor analysis, the liquid-solid ratio has the greatest influence on the manganese leaching rate, the reaction temperature is second, and the reaction time has the least influence on the manganese leaching rate.

(6) Best process conditions experiment

After determining the optimum process conditions for the leaching reaction, experiments with this process parameter were arranged under the condition that the fixed waste acid excess coefficient was 1.3. The results are shown in Table 2.

Table 2 Experimental results of optimal process conditions

It can be seen from Table 2 that the primary leaching rate of manganese obtained from the optimum process conditions under the same experimental conditions is significantly better than that obtained by each single factor experiment.

(VII) Analysis of product manganese chloride tetrahydrate

The manganese chloride leaching solution obtained by the experiment is concentrated, and then the cleaning agent is added in two steps to remove the calcium and magnesium from the various heavy metal ions, and then the leaching solution after the impurity removal is filtered, concentrated and crystallized, and the crystallized product is obtained. After analysis, the quality can reach the industrial standard HG/T 3816-2006 of industrial grade manganese chloride tetrahydrate, and the product quality is qualified.

Third, the conclusion

(1) Through the single factor experiment of leaching reaction, the optimal reaction conditions of the process were determined. The quality of the obtained leachate after purification, impurity removal, concentration and crystallization can reach the current industry standard of industrial grade manganese chloride tetrahydrate.

(2) The process has solved the problem of waste acid treatment in Zunyi Titanium industry and the resource utilization of medium and low grade manganese ore in Zunyi area, and realized the problem of resource recycling and utilization, which has high economic value.

(3) The process is simple, easy to operate, low in investment, high in efficiency, easy to realize industrialization, and has great practical value.

Brief Introduction & Working Principle