阅读说明：本技术 一种无钙焙烧铬酸钠碱性液低温除杂生产低硅高纯金属铬的方法 (Method for producing low-silicon high-purity metal chromium by calcium-free roasting of sodium chromate alkaline solution through low-temperature impurity removal ) 是由 郭树志 金绍祥 贾伟 刘亚凤 王丽 康春生 孙萍 赵秀媛 高金 李昆朋 陈悦 于 2020-07-22 设计创作，主要内容包括：一种无钙焙烧铬酸钠碱性液低温除杂生产低硅高纯金属铬的方法,取无钙焙烧铬酸钠碱性液投入反应釜中加入,进料温度40℃～60℃；反应釜进料完成后,调整反应釜搅拌速度75r/min～130r/min,向反应釜内加入硫酸,原料加完后,停止搅拌,将反应后的物料打入隔膜压滤机进行压滤操作,待物料充满压滤机后用水进行在线洗涤,得到低硅铬酸钠溶液；利用低硅铬酸钠溶液生产低硅氧化铬,低硅氧化铬采用炉外法冶炼,获得低硅高纯金属铬。优点是：该方法使得铬铁矿无钙焙烧生产过程中,中和温度降低、蒸汽消耗下降、省略熟化过程、铝泥过滤性能提高、缩短压滤周期、设备使用寿命延长、生产周期缩短。(A method for producing low-silicon high-purity metal chromium by removing impurities from calcium-free roasting sodium chromate alkaline solution at low temperature comprises the steps of adding the calcium-free roasting sodium chromate alkaline solution into a reaction kettle, and feeding at 40-60 ℃; after the feeding of the reaction kettle is finished, adjusting the stirring speed of the reaction kettle to 75-130 r/min, adding sulfuric acid into the reaction kettle, stopping stirring after the raw materials are added, pumping the reacted materials into a membrane filter press for filter pressing, and washing the materials with water on line after the filter press is filled with the materials to obtain a low-silicon sodium chromate solution; the low-silicon chromium oxide is produced by using the low-silicon sodium chromate solution, and is smelted by adopting an external furnace method to obtain low-silicon high-purity metal chromium. The advantages are that: the method has the advantages of reducing the neutralization temperature, reducing the steam consumption, omitting the curing process, improving the aluminum mud filtering performance, shortening the filter pressing period, prolonging the service life of equipment and shortening the production period in the calcium-free roasting production process of the chromite.)

1. A method for producing low-silicon high-purity metal chromium by calcium-free roasting of sodium chromate alkali solution at low temperature and impurity removal is characterized by comprising the following steps:

the method comprises the following specific steps:

(1) feeding of reaction kettle

Adding the calcium-free roasting sodium chromate alkaline solution into a reaction kettle, wherein the concentration of the calcium-free roasting sodium chromate alkaline solution is 180-200 g/L, Al₂O₃The content is more than or equal to 3.7g/L, the feeding volume accounts for 80 percent of the total volume of the reaction kettle, and the feeding temperature is 40-60 ℃;

(2) adjusting the stirring speed

After the feeding of the reaction kettle is finished, adjusting the stirring speed of the reaction kettle to 75 r/min-130 r/min;

(3) adjusting the rate of addition of sulfuric acid

At 0.5m³/h～0.9m³Adding sulfuric acid into the reaction kettle at a speed of/h, and controlling the end point pH value to be 6-9;

(4) aging

After the raw materials are added, stopping stirring, and directly performing filter pressing without curing;

(5) filter pressing and washing

Pumping the reacted materials into a membrane filter press for filter pressing operation, and after the filter press is filled with the materials, performing online washing by using water to obtain a low-silicon sodium chromate solution;

(6) adding the low-silicon sodium chromate solution into a reaction tank, adding lime and flake caustic soda, heating to a temperature of more than 80 ℃, carrying out vanadium removal reaction, and filtering by a filter press to obtain a low-silicon low-vanadium chromate acid-base solution;

(7) adding sulfur and caustic soda flakes into the low-silicon low-vanadium chromic acid alkaline solution, and fully reacting under a boiling condition to obtain chromium hydroxide;

(8) the low-silicon chromium oxide is generated by calcining the low-silicon chromium oxide at a high temperature of more than 1200 ℃ in a kiln after being filtered and washed by a diaphragm filter press, and the low-silicon chromium oxide is smelted by adopting an external furnace method to obtain the low-silicon high-purity metal chromium.

2. The calcium-free calcined sodium chromate base of claim 1The method for producing low-silicon high-purity metal chromium by removing impurities from a neutral solution at low temperature is characterized by comprising the following steps of: in on-line washing, per 100m³The water consumption of the materials is 20m³。

3. The method for producing low-silicon high-purity metallic chromium by removing impurities from a calcium-free roasted sodium chromate alkaline solution at low temperature according to claim 1, which is characterized by comprising the following steps of: the stirring speed of the step (2) is 90 r/min-100 r/min.

4. The method for producing low-silicon high-purity metallic chromium by removing impurities from a calcium-free roasted sodium chromate alkaline solution at low temperature according to claim 1, which is characterized by comprising the following steps of: the calcium-free roasting sodium chromate alkaline solution is 17m³The adding time of the sulfuric acid is 20 to 40 minutes.

Technical Field

The invention relates to a method for producing low-silicon high-purity metal chromium by removing impurities from a calcium-free roasting sodium chromate alkaline solution at a low temperature.

Background

In the industrial production of domestic chromium salt, the sodium chromate alkali solution contains a small amount of impurities such as sodium aluminate, free alkali and trace sodium silicate, and sulfuric acid is added in the neutralization process to adjust the sodium chromate alkali solution to be neutral, so that the sodium aluminate can be hydrolyzed to separate out aluminum hydroxide precipitate, commonly called aluminum mud, and the main reaction principle is as follows: 2NaAlO₂+H₂SO₄+2H₂O＝2Al(OH)₃+Na₂SO₄Meanwhile, in the process of removing aluminum, part of silicon is separated out along with aluminum hydroxide, but aluminum mud is colloid and is difficult to filter, so that the temperature needs to be increased in the traditional production to convert the aluminum mud into larger compact particles so as to reduce the viscosity of the solution and improve the filterability of an aluminum hydroxide filter cake, and meanwhile, the aluminum hydroxide filter cake is subjected to heat preservation and curing for more than half an hour so as to further improve the filterability of the filter cake. The temperature of the neutralization process for removing silicon and aluminum from the traditional sodium chromate alkali solution is higher than 80 ℃, a large amount of steam is consumed, and the requirement on equipment is high.

Disclosure of Invention

The invention solves the technical problem of providing the method for producing the low-silicon high-purity metal chromium by removing impurities from the sodium chromate alkaline solution without calcium roasting at low temperature, and the method ensures that the neutralization temperature is reduced, the steam consumption is reduced, the curing process is omitted, the filtering performance of aluminum mud is improved, the filter pressing period is shortened, the service life of equipment is prolonged, and the production period is shortened in the production process of the chromite without calcium roasting.

The technical solution of the invention is as follows:

a method for producing low-silicon high-purity metal chromium by calcium-free roasting of sodium chromate alkali solution through low-temperature impurity removal comprises the following specific steps:

(1) feeding of reaction kettle

Adding the calcium-free roasting sodium chromate alkaline solution into a reaction kettle, wherein the concentration of the calcium-free roasting sodium chromate alkaline solution is 180-200 g/L, Al₂O₃The content is more than or equal to 3.7g/L, the feeding volume accounts for 80 percent of the total volume of the reaction kettle, and the feeding temperature is 40-60 ℃;

(2) adjusting the stirring speed

After the feeding of the reaction kettle is finished, adjusting the stirring speed of the reaction kettle to 75 r/min-130 r/min;

(3) adjusting the rate of addition of sulfuric acid

At 0.5m³/h～0.9m³Adding sulfuric acid into the reaction kettle at a speed of/h, and controlling the end point pH value to be 6-9;

(4) aging

After the raw materials are added, stopping stirring, and directly performing filter pressing without curing;

(5) filter pressing and washing

Pumping the reacted materials into a membrane filter press for filter pressing operation, and after the filter press is filled with the materials, performing online washing by using water to obtain a low-silicon sodium chromate solution;

(6) adding the low-silicon sodium chromate solution into a reaction tank, adding lime and flake caustic soda, heating to a temperature of more than 80 ℃, carrying out vanadium removal reaction, and filtering by a filter press to obtain a low-silicon low-vanadium chromate acid-base solution;

(7) adding sulfur and caustic soda flakes into the low-silicon low-vanadium chromic acid alkaline solution, and fully reacting under a boiling condition to obtain chromium hydroxide;

(8) the low-silicon chromium oxide is generated by calcining the low-silicon chromium oxide at a high temperature of more than 1200 ℃ in a kiln after being filtered and washed by a diaphragm filter press, and the low-silicon chromium oxide is smelted and produced by an external furnace method to obtain the low-silicon high-purity metal chromium.

Further, in the case of on-line washing, per 100m³The water consumption of the materials is 20m³。

Furthermore, the stirring speed of the step (2) is 90 r/min-100 r/min, the silicon removal effect is good, and the silicon content in the produced chromium metal is less than or equal to 0.04 percent.

Further, the calcium-free roasting sodium chromate alkaline solution is 17m³The adding time of the sulfuric acid is 20 to 40 minutes.

The process of the invention does not need to add any impurity element, greatly enlarges the temperature range of the reaction, has lower temperature compared with the traditional process, thereby reducing the steam consumption, simultaneously, the temperature of the feed liquid is kept between 40 and 60 ℃ during the filter pressing, the temperature is lower, the service life of the filter plate is effectively prolonged, the granularity and the filtering performance of the aluminum mud are relatively stable, and the service life of the filter cloth of the filter press is effectively prolonged at low temperature. Compared with the traditional neutralization process, the method can omit the steam heating and curing process, shorten the filter pressing time, improve the utilization rate of equipment and shorten the production period under the same quality requirement.

Compared with the traditional process, the method has the advantages of wide operation conditions, reduced operation steps and further plasticity on product quality. The silicon content in the metal chromium produced by the solution is less than or equal to 0.04 percent, and is reduced by 0.16 percent compared with the calcium-roasted silicon content of 0.2 percent, thereby meeting the product requirement of the market on low-silicon metal chromium.

Detailed Description