Preparation of titanium-rich material from titanium-containing blast furnace slag low-temperature acid-base method

Panxi vanadium-titanium magnetic iron ore is the world's leading multi-metal total (with) deposits, which accounted for titanium reserves in the world. But so far, the utilization rate of titanium resources in ore is very low, about 15%. The main reason is that about 50% of the titanium in the ore is converted into iron-containing blast furnace slag with iron concentrate after smelting through the blast furnace. The content of TiO _{2 in the} titanium-containing blast furnace slag is as high as 20% to 26%. During the production period of Panzhihua Iron and Steel Co., Ltd., the slag slag of the West Slag Field stacked on the Jinsha River during the production period of 1970-1992 reached more than 30 million tons. If the TiO ₂ content is 20%, only the content of TiO ₂ in the blast furnace slag of the West Slag Field is It is more than 6 million tons, and at least 600,000 tTiO _{2 is} added every year thereafter. According to this estimation, so far, the total amount of TiO ₂ in Panzhihua blast furnace slag has been nearly 20 million tons, which is undoubtedly a huge treasure of titanium resources. However, it is accumulated as industrial solid waste together with blast furnace slag, which is not only not used, but also causes great environmental problems and economic burden for the local area. How to develop high-titanium blast furnace slag using this artificial secondary resource, especially the titanium resource among them has become an important urgent issue.

For decades, the comprehensive utilization of high-titanium blast furnace slag, especially for the extraction of Ti0 _2, has been extensively studied. However, due to various reasons such as technical infeasibility, complicated process, high temperature working conditions, complicated equipment, high economic cost or environmental protection requirements, effective breakthroughs have not yet been achieved.

Based on the analysis of the chemical composition, phase composition and fabric characteristics of titanium-containing blast furnace slag, this paper adopts a two-step low-temperature acid-base method with simple experimental conditions and mild conditions, that is, the method of alkali dissolution after acid dissolution. The acid-soluble impurities such as Ca, Mg, Al, Fe, etc. in the blast furnace slag are removed, and Ti and Si enter the slag in the form of H ₄ Si0 ₄ and H ₂ Ti0 ₃ ; and the Ti 2 ₂ is removed by alkali dissolution to obtain a titanium-rich material. .

  First, the experiment

(1) Equipment and equipment

The experimental equipment is a self-assembly reaction device: ZDHW type thermostat electric heating sleeve, JJ-1 type timing electric mixer, DRZ-9 adjustable temperature controller, 6-13 box type resistance furnace, DL-10,000 electric furnace, BS-2245 electronic balance, 202-OOAB desktop drying oven, 2XZ-1 rotary vane vacuum pump, thermometer, condenser, four-necked flask, etc.

(2) Raw materials

The experimental raw materials are air-cooled high-titanium blast furnace slag supplied by Panzhihua Iron and Steel Research Institute. After crushing, sieving treatment, magnetic separation and iron removal, screening and taking a sieve sample of -120 mesh (-0.125mm) as a reaction The sample was tested and the main chemical analysis results are shown in Table 1.

Table 1 Chemical composition (mass fraction)/% of titanium-containing blast furnace slag

Note: The data was tested and analyzed by the Huayang Testing Center of the Sichuan Provincial Geological Survey Bureau of the Ministry of Land and Resources.

(three) experimental principle

1, acid hydrolysis separation

It can be seen from Table 1 that the main components in the titanium-containing blast furnace slag are TiO ₂ , SiO ₂ , Ca 0 , Mg 0 , Al ₂ 0 ₃ and Fe ₂ 0 _{3 ,} etc., in the process of removing impurities by using titanium chloride type blast furnace slag. By chemical reaction, among which Ca0, Mg0, A1 ₂ 0 ₃ and Fe ₂   0 ₃ and the like easily dissolve with hydrochloric acid to form a strong electrolyte chloride, and the silicon component forms a solid precipitate to achieve separation.

Since Ti0 ₂ is an amphoteric oxide, its acidity and basicity are weak, and the corresponding titanate and titanium salt are prone to hydrolysis under certain conditions. Therefore, the main chemical reactions that occur during the reaction of Ti0 ₂ are:

Ti0 ₂ +4HC1=TiC1 ₄ +2H ₂ 0(1)

TiC1 ₄ +4H ₂ 0=H ₄ Ti0 ₄ ↓+4HCl(2)

H ₄ Ti0 ₄ =H ₂ Ti0 ₃ ↓+H ₂ 0 (3)

Therefore, titanium eventually enters the filter residue in the form of white metatitanic acid (H ₂ TiO ₃ ) precipitate during the reaction.

It is known from the formulas (1) to (3) that in order to stably store titanium in the form of titanium ions in the filtrate, it is necessary to consume a large amount of acid under acidic conditions, thereby causing waste of acid and increasing cost. The total reaction formula of the formulas (1) to (3) can be abbreviated as:

Ti0 ₂ +H ₂ 0=H ₂ Ti0 ₃ ↓ (4)

It can be seen from the formula (4) that Ti0 ₂ can be regarded as not consuming dilute hydrochloric acid throughout the reaction process. If titanium is enriched in the filter residue, the purpose of enriching titanium can be achieved while saving a large amount of acid. This is one of the ideas in this paper.

2, alkaline separation

The main components of the filter residue obtained by the above acid hydrolysis separation process are titanium and silicon, wherein Si mainly exists in the form of H ₄ Si0 ₄ , which easily reacts with NaOH to form Na ₂ SiO ₃ . Therefore, the slag obtained after the acid hydrolysis is reacted with NaOH, and the reaction formula is:

H ₄ SiO ₄ +2NaOH = Na ₂ SiO ₃ +3H ₂ O (5)

The reaction can be carried out without high temperature conditions, thereby achieving the separation of silicon from titanium which remains in the form of slag after the reaction.

(four) experimental process

A certain volume, a specified concentration of hydrochloric acid is added to a four-necked flask, the condensed water is turned on, stirring is started, and the mixture is heated to a specified temperature, and the weighed reaction sample is added to a four-necked flask to perform a timed reaction. After a certain period of time, The reaction solution was filtered, and the filtrate was weighed to collect a cake. A certain volume of the filtrate was weighed, and the contents of Ca, Mg, Al, and Ti were measured by titration. The acid hydrolysis residue and the NaOH solution are added to the four-necked flask in a certain ratio, the condensed water is turned on, the stirring is started, and the mixture is heated to the specified temperature. After the reaction for a certain period of time, the reaction liquid is filtered to determine the silicon content in the filtrate, and the filter residue is rich. Titanium material, the process flow is shown in Figure 1.

  Second, the results and discussion

(1) Main factors affecting the acid hydrolysis reaction process

During the acid hydrolysis reaction, the factors affecting the element leaching rate in the titanium-containing blast furnace slag mainly include reaction time, temperature, acid concentration and acid-slag ratio.

Figure 2 is a graph showing the relationship between the leaching rate of the components and the reaction time at a starting concentration of 6 mol/L of acid at 100 °C. It can be seen from Fig. 2 that the influence of reaction time on the leaching rate of each element in the titanium-containing blast furnace slag is not the same. The leaching rate of Ti0 ₂ decreases with the increase of reaction time. This is because the initial concentration of acid is higher at the beginning of the reaction, and the rate of formation of TiC1 ₄ is faster, but as the reaction time increases, the acid consumption increases, and the acid in the solution The concentration is lowered, resulting in hydrolysis of TiCl _{4 and} a decrease in Ti ⁴⁺ content in the solution. After 4 h of reaction, the leaching rate of Ti0 ₂ was already low, only about 2.79%; while the leaching rate of Ca0, Mg0 and A1 ₂ 0 ₃ increased with time, and the leaching rate reached the maximum when the reaction reached 4 h. After that, the leaching rate of Mg0 was significantly less than that of Mg0, and the leaching rate of A1 ₂ 0 ₃ and CaO did not change significantly.

Figure 3 is an experimental result of the effect of reaction temperature on the element leaching rate in titanium-containing blast furnace slag. It can be seen from Fig. 3 that the temperature has a great influence on the reaction of blast furnace slag. With the increase of temperature, the leaching rates of CaO, Mg0 and A1 _{2 3} increase, while the leaching rate of titanium with temperature The rise first rises and then falls, and the leaching rate is less than 2% at 100 °C. This is because when the temperature is high, the TiCl ₄ formed by the reaction is largely hydrolyzed to form a precipitate and enters the slag, so that the Ti ⁴⁺ content in the filtrate is lowered. After more than 100 ° C, the temperature has little effect on the reaction.

Figure 4 is an experimental result of the effect of acid concentration on element leaching rate. As can be seen from Fig. 4, when the acid concentration is low, the reaction is insufficient, and the acid concentration is increased, so that the Ti ⁴⁺ content in the solution is too high, which is disadvantageous for the separation of Ti0 ₂ from other impurity components. Therefore, the concentration of hydrochloric acid is preferably 5-6 mol/L. At this time, the leaching rate of Ti0 ₂ is lower, less than 3%, and the leaching rate of CaO, MgO, and A1 _{2 3} is high.

According to the analysis of the content of each component in the blast furnace slag, it is assumed that the oxides such as CaO, MgO, Al ₂ 0 ₃ and hydrochloric acid can completely react, and the mass of hydrochloric acid required to consume 100 g of blast furnace slag can be calculated as 110 g, that is, the theoretical acid slag ratio Is 1.1..1. In fact, the acid slag ratio will be lower than this value. However, if the acid slag ratio is too small, the leaching rates of CaO, MgO, and Al ₂ 0 ₃ are not high. Figure 5 shows the effect of the acid slag ratio on the leaching rate of each element. As can be seen from Fig. 5, the acid slag ratio is between 0.9 and 1.0, and the leaching rates of CaO, MgO, and Al ₂ 0 ₃ are high, and the leaching rate of Ti0 ₂ is increased as the acid slag ratio is increased.

(2) Factors affecting the alkali dissolution reaction process

After the treatment by the aforementioned acid hydrolysis process, the residue and the filtrate were respectively obtained. Ca0, Mg0, and Al ₂ 0 ₃ mainly enter the filtrate, and Ti0 ₂ and Si0 ₂ enter the filter residue, thereby realizing the separation of the main impurity components in the titanium-containing blast furnace slag from Ti0 ₂ and Si0 ₂ . The alkali residue reaction of the filter residue with NaOH is carried out to separate the Ti0 ₂ from the SiO ₂ . Alkali-soluble in the reaction separation test investigated the relationship between the reaction time, temperature, and ratio of alkali slag separation component extraction rate and the filtrate extraction rate of Si0 ₂ was measured, and the percentage of the residue of Ti0 ₂ was measured, the results were obtained as Figures 6-8 show.

It can be seen from Fig. 6 to Fig. 8 that the separation and extraction rates of Ti0 ₂ and SiO ₂ in the filter residue increase with the increase of the reaction time, the increase of the reaction temperature and the increase of the alkali slag ratio. The reaction conditions were comprehensively analyzed with a reaction time of 2 h, an alkali slag ratio of 0.5, and a temperature of 100 ° C. Under these conditions, the separation of Ti0 ₂ and Si0 _{2 results} in a rich state containing more than 73% of Ti0 ₂ and a leaching rate of SiO ₂ of about 85%.

  Third, the conclusion

(1) The two-step low-temperature acid-base method can effectively separate and extract the main components in the titanium-containing blast furnace slag, and the Ti0 ₂ content can be more than 73%, which can be used as titanium dioxide production and other titanium materials for production. Titanium-rich material.

(2) In the acid hydrolysis process, the leaching rate suitable for obtaining Ti0 ₂ is low, and the preferred reaction conditions for the high leaching rate of Ca0, Mg0, and Al ₂ 0 ₃ are hydrochloric acid concentration 5-6 mol/L, reaction time 4 h, The acid slag ratio is 0.9 to 1.0, and the temperature is 100 °C. Under these conditions, the leaching rates of Ca, Mg, and Al were 20%, 64%, and 70%, respectively, while the leaching rate of Ti0 ₂ did not exceed 3%.

(3) In the alkaline solution reaction, the preferred conditions for the effective separation of TiO ₂ and SiO ₂ are reaction time 2 h, alkali slag ratio 0.5, reaction temperature 100 ° C, and Ti0 ₂ 73% or more can be obtained. Titanium-rich material.