Acid wet refining process technology

First, the acid wet refining process

Acid wet antimony began in 1870, its research and development experienced three stages. A first stage is ferric chloride as chloride leaching agent, antimony metal leaching solution obtained by electrolysis or substitution of stop 1985, industrial application yet. The second stage is only a few years. Its main feature is the use of antimony pentachloride or chlorine as a chlorinating agent to directly obtain antimony from strontium sulfide or concentrate to obtain small-scale industrial applications. At present, it is the third stage. Its main features are high- lead complex antimony concentrate and multi-metal complex niobium-containing materials to prepare a variety of high-grade antimony products, combined with plasma ultra-fine powder technology to produce high-purity ultra-fine antimony oxide. The production line was put into industrial application in 1998.

Due to the low concentration of sulfur dioxide fumes and the market pattern of adapting to sputum, acid wet refining has obvious advantages over traditional fire methods in developing and utilizing China's extremely rich high-lead complex antimony resources.

The method has been the main industrial applications of wet acidic antimony is based chlorinating agent A ^# - an aqueous solution of antimony pentoxide as the leaching agent "oxidation - hydrolysis" and "New chloride - hydrolysis method", which are It was developed by Zhongnan University of Technology under the guidance of Professor Zhao Tian. The former is only applicable to single sulfide ore, while the latter can handle complex antimony or concentrate and produce high purity products. In addition, the acid wet smelting method which has been industrially applied also includes "chlorine leaching-hydrolysis method" which was successfully developed by Guangdong Institute of Technology Zengda. Chlorine gas instead of ferric chloride as a chlorination-leaching agent is a major advancement in acid wet refining technology. The biggest advantage of this method is that it avoids the interference of a large amount of iron on the separation process and does not require regeneration of the leaching agent, but it also exists. Problems such as low elemental sulfur yield, high chlorine consumption, low leachate concentration, high acid consumption and difficult process control. In response to these problems, Zhongnan University of Technology has successfully developed A ^# chlorinating agent. A ^# chlorinating agent has the advantages of ferric chloride and chlorine chlorinating agent, but it has abandoned their shortcomings. Its discovery and use will be acid wet method.锑 Push to a new stage. The principle process of acid wet refining is shown in Figure 1. It mainly includes chlorination-leaching, reduction, hydrolysis, neutralization and replacement. The process used can be simple and versatile for different processing objects. For single sulphide ore, there is no need to remove lead, arsenic removal and recovery of valuable elements. For the brittle sulphur bismuth concentrate and lead anode mud, the steps are the longest. The high-lead or high-arsenic antimony sulfide ore should be added to the lead-free and arsenic removal steps on the basis of a single antimony sulfide ore.

Figure 1 Process of acid wet refining principle

Second, the acid leaching of bismuth sulfide concentrate

(1) Leaching method and technical conditions

The chlorination-leaching process of strontium sulfide concentrate and brittle sulphide concentrate is divided into cyclic leaching and non-circulating leaching. A ^# is the leaching cycle ^- as a chlorinating agent is necessary leaching embodiment leaching agent: A ^# as chlorinating agent must be prepared by the leaching agent is regenerated and returned. Chlorine leaching is a non-circulating leaching, the leaching conditions are: (1) to ensure the free acidity of 2.5 ~ 3.0mol ∕ L, can also use NaCl to replace part of the free acid; (2) reaction temperature of 80 ~ 85 ° C; (3) reaction time 2.0 ~ 4.0 h; (4) the amount of chlorine gas, the leaching end of the leaching solution containing Sb ^{5 +} 10g ∕ L; (5) must be washed with 2.0 ~ 2.5mol · dm ^-3 acid leaching slag 3 to 5 times, then washed 3 ~ 5 times. The circulating leaching conditions are: (1) the excess coefficient of the chlorinating agent is 0.1 to 0.15; (2) the number of fractions of the leaching solution, calculated according to the relevant formula, for a single strontium sulfide ore, generally about 60%, and for the brittle sulphur bismuth ore concentrate Mines are as high as 72% to 75%: (3) leaching agent acidity: HCl 1.5 ~ 2.0mol ∕ L; H ₂ SO ₄ 0.75 ~ 1.0mol ∕ L, H ₂ SO _{4 is} mainly used to inhibit lead into the leachate; 4) The temperature and time are the same as the general leaching; (5) The leaching end point is judged: the leaching solution is reddish brown, and Sb ^{5 +} 5 to 10 g/L is taken as the standard. (6) using mixed acid washing slag, acid acidity is the same as leaching agent, the amount is equal to the amount of leaching liquid in the open circuit; (7) after pickling, the leaching slag is washed 3 to 5 times, and the washing water is 50% of the concentrate. The acid washing is prepared from the returned hydrolyzate or leaching water washing solution and concentrated hydrochloric acid and concentrated sulfuric acid (used in the treatment of high lead bismuth concentrate). According to their acidity and the volume of acid to be mixed, a binary or ternary triplet is established. The group, the solution can be used to find their respective usage. In this way, acid is used, and complex antimony ore can save more than 40% of acid, and a single antimony ore can save more than 30% of acid, and reduce wastewater discharge.

(2) Leaching process practice and equipment

Leaching Leaching cyclic operation as an example: the leaching process, including configuration and A ^# regeneration of the chlorinating agent, plus mineral, heat, stirring, filtering and washing step forty. A ^# chlorinating agent prepared by the regeneration liquid before the leachate and returned all the acid wash, to check its main component, the acidity and volume to meet the requirements, i.e., chlorine gas, and the regeneration rate ^{([Sb 5 +] / [} Sb] T) When ≥95%, regeneration is completed. The leaching and regeneration are carried out in the same reactor. After the regeneration is completed, the ore leaching can be carried out, and a large amount of heat is released by leaching and regeneration, so that the speed of chlorine and ore is accelerated. Cooling measures must be taken to remove excess heat. Generally, an enamel reaction kettle (with a jacket) is used as the leaching and regeneration tank, and a reaction tank made of other corrosion-resistant materials can also be used, but a cooling and heat-discharging device must be attached. The leaching tank cover is provided with four uniformly distributed chlorine pipes made of steel pipes with polytetraethylene inside, and the exhaust pipes are exhausted by the exhaust fan. During the leaching process, maintain a temperature of about 80-85 ° C, check whether it reaches the end point, if the leaching solution is grayish white, the oxidant is not enough, need to supplement the oxygen, make the leaching solution turn brown red, and Sb ^{5 +} is 5 ~ 10g ∕L It can be filtered, and the filtration can be carried out on a vacuum suction tank or a belt filter; since it is pickled and washed, it is not filtered by a filter press. If it is a filter belt, it is necessary to set a filter section, a pickling section and a water washing section, and the filter residue is automatically removed after washing, and the labor intensity is small. When the filter is filtered by the suction filter, the leaching solution is just filtered, but the filter residue is pickled before it is cracked, so that it is washed 3 to 5 times; after the acid wash is completed, it is washed with water. Of course, filtration with a suction filter tank is much more labor intensive.

(III) Technical data and indicators of the leaching process

The actual production data of the cyclic chlorination-leaching of the brittle bismuth lead ore is taken as an example. The composition of concentrate, leaching residue, immersion liquid, pickling liquid and water washing liquid is shown in Table 1.

Table 1 Raw materials and chemical constituents of the leaching process

Continued on the table

According to the slag calculation, the leaching rate of bismuth and silver is 97.97% and 78.98%; the slag content of lead is ≥99%; the conversion rate of sulfur is 99.74%. The main chemical materials consumption: chlorine 1.236t∕t (Sb ₂ O ₃ ); industrial hydrochloric acid 0.350L∕t (Sb ₂ O ₃ ); industrial sulfuric acid 0.250t∕t (Sb ₂ O ₃ ).

Third, the reduction of leachate

The leachate contains high-valent ions such as Sb ^{5 +} and Fe ^{3 +} , which must be reduced before hydrolysis, and the reducing agent can be made of tantalum powder or iron powder. Generally, the active cerium powder which is replaced by the hydrolyzate is optimally treated, and the active cerium powder is protected by water to prevent oxidation and reduction reactions:

The reduction process is carried out at room temperature, with the reducing solution being white or light green as the reduction end point. If the silver content in the leachate is high, the silver will be replaced by the replacement during the reduction, that is, after the reduction reaches the end point. The precipitated silver is added in batches with 5 to 20 mesh fine iron powder. When the immersion liquid contains Ag ≥ 0.5 g ∕ L, the recovery rate of silver is greater than 90%, and the silver content of the reducing slag is ≥ 7%. The reducing solution is easily oxidized and hydrolyzed in time.

4. Hydrolysis of bismuth sulfide concentrate leaching reduction solution

(1) Hydrolysis methods and technical conditions and indicators

Hydrolysis includes both dilute hydrolysis and neutralization hydrolysis. Neutralization hydrolysis should not be used in the case of good dilute hydrolysis and dehydration. Neutralization hydrolysis is only suitable for the reduction solution of anode mud and extremely complex brittle bismuth concentrate ore concentrate.

The dilute hydrolysis is carried out at a normal temperature, and the hydrolyzate is controlled to contain Sb ^{3 +} 1 to 2 g ∕ L, and the amount of water added is calculated by the formula (1). After dehydration, the mixture was stirred for 10 to 20 minutes; the chlorinated filter cake was washed with pure water for 8 times or more. The numerically controlled hydrolysis rate of the neutralization hydrolysis process is 45% to 50% when the lead anode mud is used. For the long slope brittle sulphur concentrate ore concentrate, take 85%, use ammonia or soda as the neutralizer, calculate the addition amount according to formula (2), the washing requirements are the same as the dilute hydrolysis process. If necessary, some compounding agents are added during the hydrolysis to improve product quality. The hydrolysis rate is very high (≥95%). The hydrolyzate contains ∕1g∕L.

(1)

(2)

(2) Hydrolysis process operation

When the reducing solution is added to the clarified water, SbCl ₃ begins to hydrolyze, producing some unstable intermediates:

The slurry is very viscous and requires agitation, followed by an obvious dehydration process:

Sb ₄ O ₅ Cl ₂ with good filtration performance is produced. After dehydration for 10-20 min, the agitation was stopped, and then the supernatant was extracted, and then the chlorination of the bottom was filtered. For medium-sized and above factories, it is better to filter with a filter. The filter is equipped with a filter section and a washing section. It is washed with pure water to ensure clean chlorination, continuous filtration, and low labor intensity. Small-scale plants are filtered using a vacuum suction tank. After the hydrolyzate is filtered, the filter cake is washed with pure water for 8 times or more to ensure the cleaning of the impurity elements.

5. Neutralization of bismuth oxychloride leaching from bismuth sulfide concentrate

The purpose of neutralization is to remove chlorine from Sb ₄ O ₅ Cl ₂ and convert it to Sb ₂ O ₃ , generally using ammonia as a neutralizer:

In addition, adding appropriate amount of compounding agent and transition agent at the same time of neutralization can greatly reduce the content of impurity elements such as lead and iron in cerium oxide (≤ 0.001%), and convert the crystal form of cerium oxide from the orthorhombic transformation, which is greatly reduced. The photosensitivity of Otaru is very beneficial for maintaining whiteness. In the neutralization process, the neutralization washing liquid is used to adjust the slurry, and it is neutralized under normal temperature conditions. The pH of the neutralization end point is about 7.5, and it is stable for 10 to 20 minutes. Then, filter and wash, medium-sized and above factories should use filter belts, filter belts should be equipped with filter section and washing section, small-scale factory vacuum pumping filter, washing with pure water, washing to the end point (more than 8 times) When the solution was checked with AgNO ₃ , there was no white precipitate.

The quality of high-purity yttrium oxide products directly prepared from brittle sulphide lead ore concentrate and sorghum lead anode slime is shown in Table 2.

Table 2 Contents of main components and impurity elements of high-purity cerium oxide directly prepared by new chlorination-hydrolysis method and AC method (%)

Note: The new chlorination-hydrolysis method does not take the arsenic removal method; the AC method performs the dry distillation process of one more reducing solution than the new chlorination-hydrolysis method, and then produces pure SbCl ₃ and then hydrolyzes.

6. Drying of wet cerium oxide

The wet cerium oxide has a water content of about 30% and must be dried to reduce the water content to less than 0.1%. Medium-sized and above should be dried by continuous drying equipment, and small-scale drying trays should be dried in tunnel kiln. It should be noted that the generated water vapor contains a trace amount of HCl, and the material of the drying device is preferably steel-lined fluoroplastic or heat-resistant rubber.

7. Displacement of hydrolyzate

The hydrolyzate contains about Sb ^{3 +} 1 g ∕ L and contains H ⁺ 1.0 to 1.4 mol ∕L. A small portion returned to the wash acid, and most of the way. In order to recover the hydrazine therein and provide active strontium powder for the reduction process, the hydrolyzate must be replaced with iron filings. The replacement process is carried out at room temperature, and the amount of iron is 1.2 times the theoretical amount ([Sb ^{3 +} ]>0.5g∕L) or 2.0 times ([Sb ^{3 +} ]≤0.5g∕L), and the replacement time is about 30min. After the water method, the liquid without the white precipitate was removed to the end of the replacement. At this time, it must be filtered immediately. If stirring is continued, the active niobium powder is oxidized by air to be dissolved.

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