WO2019148901A1 - Method for treating chromium slag by chlorinating calcination in combination with hydrothermal mineralization - Google Patents

Abstract

A method for treating chromium slag by chlorinating calcination in combination with hydrothermal mineralization, comprising: adding chloride salt into chromium slag and mixing the chloride salt and the chromium slag to be uniform, raising the temperature to 400-1000 °C to perform high-temperature calcination treatment for 0.5-12 h, and grinding and sieving after cooling; adding the obtained fine powder to a hydrothermal reactor, adding an mineralizer aqueous solution, and performing hydrothermal mineralization reaction at a temperature of 30-250 °C for 2-24 h; and cooling the mixture and leaving it to stand to obtain a chromium-containing supernatant and solid slag, washing the solid slag with water and drying the solid slag to obtain detoxified chromium slag, and reusing the chromium-containing supernatant for production or performing chromium recovery treatment. Chromium slag is treated by chlorinating calcination technology in industrial metallurgy in combination with hydrothermal mineralization, solving the problem of separating hexavalent chromium from internal solid particles in chromium slag, improving separation efficiency and recovery efficiency of chromium, providing high social and economic benefits.

Description

Method for treating chrome slag by chlorination roasting combined with hydrothermal mineralization Technical field

The invention belongs to the technical field of chromium slag treatment, and particularly relates to a method for treating chromium residue by chlorination roasting combined with hydrothermal mineralization.

Background technique

The chromium pollution is mainly derived from the chromium salt production and use industry, and is mainly based on the pollution of chromium-containing waste residue. Calcium roasting and calcium-free roasting processes used in the production of chromium salts produce chromium-containing waste residues. Among them, the calcium roasting process will produce 2-3 tons of chromium slag per ton of product produced. Although calcium-free roasting significantly reduces the chromium slag emissions and the hexavalent chromium content, the risk remains. In view of this, in order to get rid of the pollution caused by chromium slag, some developed countries continue to compress chromium salt production capacity and import chromium salt products from developing countries. At present, China has become a large country in the production and use of chromium salts, with the world's largest output and consumption, and the country with the largest amount of chromium slag production and reserves. Therefore, the treatment idea of detoxifying and recovering chromium resources has become an important idea for treating chromium slag.

The harmlessness of chromium slag is mainly the in-situ reduction/fixation of chromium slag to reduce its toxicity, and chromium is still in the slag. We know that even the low-toxic trivalent chromium, in the presence of a large amount of the environment, will lead to the enrichment of chromium in the soil and into the human food chain, which will endanger human health for a long time. Moreover, the trivalent chromium in the chromium residue after detoxification may still be reoxidized to hexavalent chromium under the action of long-term oxidation conditions in the environment or by the action of manganese oxidizing bacteria, and has secondary toxicity. Therefore, a more ideal solution is to extract and reuse chromium from chromium slag (or industrial chrome-containing solid waste) into the industry – radically reducing toxic and hazardous substances while recycling and recycling rare strategic metal resources. In this sense, the combination of harmlessness and resource utilization of chromium slag is an important development direction of chromium slag treatment research.

The chlorination roasting method is mainly used in the metallurgical industry. The chlorine element is chemically active and has a wide range of applications. Under certain conditions, it is easier to react with most metals or compounds such as metal oxides to form metal chlorides. Other metal compounds (such as oxides, sulfides, etc.), metal chlorides are easily soluble in water, ethanol and other solvents, relatively low melting point, easy to volatilize, etc., and for different metals, the degree of oxidation is different and There are significant differences in the physicochemical properties of the resulting metal-vaporized. The chlorination roasting method is to convert the target metal component in the mineral raw material into a corresponding chloride by using a chlorinating agent such as chlorine gas, hydrogen chloride or solid chloride salt in the roasting process, and to achieve the target metal according to the characteristics of the above metal chloride The process of component separation and refining. According to the nature of the metal chloride, the high-temperature chlorination roasting method can be used to directly separate the metal from the gangue in the form of a gas phase or a molten phase, and the refining mineral raw material can be purified by other extraction methods such as infiltration. Secondly, the chlorination roasting method has lower operating temperature than other pyrometallurgical methods and saves energy; finally, the chlorination roasting method is beneficial to the comprehensive utilization of ore, and the metal separation efficiency is high; according to the difficulty of chlorination for different metals, The physicochemical properties of the produced metal chlorides are significantly different. Therefore, for the comprehensive utilization of low-grade components complex ore and waste tailings, the chlorination roasting method can be used to effectively separate the enriched metals, and the comprehensive utilization effect is obvious. However, the current chlorination roasting method is mainly used for the separation and enrichment of metals in industrial metallurgical mineral raw materials. There has not been any report on the combined treatment of chlorination roasting with hydrothermal mineralization.

The Chinese patent "Recycling Process for Treatment of Chromium Slag and Wastewater" (CN102699006A) takes into account the recovery of chromium and the reuse of solid slag. Under normal temperature conditions, the chromium slag is almost completely dissolved with acid, and then different precipitants are added separately. The mixed ions in the solution are precipitated and separated, but this method requires a large amount of chemical reagents such as an acid and a precipitant, and the process is complicated and the treatment cost is high.

Summary of the invention

In view of the shortcomings and deficiencies of the above prior art, it is an object of the present invention to provide a method for chlorination roasting combined with hydrothermal mineralization to treat chromium slag.

The object of the invention is achieved by the following technical solutions:

A method for treating chrome slag by chlorination roasting combined with hydrothermal mineralization comprises the following steps:

(1) adding chlorinated salt to the chromium slag and mixing uniformly, then heating to 400-1000 ° C, performing high-temperature baking treatment for 0.5 to 12 h, cooling and sieving;

(2) adding the fine powder after the step (1) is added to the hydrothermal reactor, adding a mineralizer aqueous solution, hydrothermal mineralization reaction at a temperature of 30 to 250 ° C for 2 to 24 hours;

(3) The mixed liquid obtained in the step (2) is cooled and allowed to stand to obtain a chromium-containing supernatant liquid and solid residue, and the solid residue is washed with water and dried to obtain detoxified chromium residue, and the chromium-containing supernatant is used for production. Or recycle chrome.

Preferably, the chloride salt in step (1) is sodium chloride or calcium chloride.

Preferably, the mass ratio of the chromium slag to the chloride salt is 1: (0.5 to 1.5).

Preferably, the mineralizer described in the step (2) is at least one of sodium carbonate and sodium hydrogencarbonate; and the concentration of the mineralizer aqueous solution is 0.5 to 1.5 mol/L.

Preferably, the solid-liquid ratio of the sieved fine powder and the mineralizer aqueous solution in the step (2) is 1: (0.5 to 10) (w/w).

Preferably, the step of recovering the chromium treatment in the step (3) is: adding a reducing agent to reduce the hexavalent chromium of the solution to trivalent chromium, and then adding a precipitating agent NaOH to produce a Cr(OH) ₃ precipitate for recovery. The reducing agent includes sodium sulfide, sodium hydrogen sulfite, and the like.

The principle of the invention is as follows:

Due to the complex composition and phase of the chromium slag, the leaching of hexavalent chromium includes not only the surface free state and the leaching of the adsorbed hexavalent chromium, but also the slow diffusion and dissolution of the soluble hexavalent chromium trapped inside the solid particles. The package leads to a large mass transfer resistance, and the hexavalent chromium in the sandwich state is difficult to leaching in a short time. Therefore, the chlorination roasting method can be selected to react with most metals or metal compounds including chromium at high temperature to form corresponding chlorides, which have the characteristics of lower melting point and can be released inside the microscopic solid particles to reach the metal materials including chromium and The purpose of separation of other solid phase impurities is to improve chromium separation and refining efficiency, and ultimately increase the recovery rate of chromium. In addition, the subsequent mineralizer hydrothermal treatment causes a small amount of trivalent chromium in the chromium slag to be oxidized to hexavalent chromium, and it is easier to enter the solution with the presence of dichromate.

The method of the invention has the following advantages and benefits:

The invention combines the chlorination roasting technology in industrial metallurgy to treat the chromium slag, solves the problem that the hexavalent chromium in the chromium slag is difficult to separate from the internal solid particles (including aluminosilicate, iron oxide, etc.), and improves the separation of chromium. Efficiency and recycling efficiency. The treated slag leaching hexavalent chromium content is lower than the national standard (HJ/T301-2007) general industrial solid waste residue, and the process is simple, suitable for large-scale industrial production processes, large processing capacity, high recovery rate, detoxification The effect is good, with high social and economic benefits.

DRAWINGS

1 is a schematic flow chart of a chlorination roasting combined with hydrothermal mineralization treatment of chromium slag according to an embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

Example 1

A method for chlorination roasting combined with hydrothermal mineralization to treat chromium slag according to the embodiment is shown in FIG. 1 . Specific steps are as follows:

(1) 5 kg of chromium slag and 2.5 kg of sodium chloride are mixed uniformly, and then placed in a high-temperature roasting furnace for 400 h at 400 ° C for 3 h, the heating is stopped, and naturally cooled to room temperature and then ground and sieved;

(2) adding the fine powder after the step (1) to the hydrothermal kettle, and adding 1.0 mol/L sodium carbonate solution according to a solid-liquid ratio of 1:5 (w/w), stirring well and heating to Hydrothermal mineralization reaction at 120 ° C for 3 h;

(3) The mixture obtained in the step (2) is naturally cooled to room temperature and allowed to stand for 12 hours to obtain a chromium-containing supernatant liquid and solid residue, and the solid residue is separated from the chromium-containing supernatant by filtration, and the solid residue is washed with water, dried and dried. After the detoxification of the chromium residue, the chromium-containing supernatant is reused in the production, or collected in a wastewater treatment station for reduction, recovery, purification treatment (adding a reducing agent (such as sodium sulfide, sodium hydrogen sulfite), the solution The hexavalent chromium is reduced to trivalent chromium, and the precipitated NaOH is added to produce Cr(OH) ₃ precipitate for recovery. After treatment, the water can reach the national drainage standard). Water can be recycled in the system throughout the process.

The original chromium residue of the present embodiment has a hexavalent chromium concentration of 740 mg/L, and the treated residue has a hexavalent chromium concentration of 0.975 mg/L.

Example 2

A method for chlorination roasting combined with hydrothermal mineralization to treat chromium slag according to the embodiment is shown in FIG. 1 . Specific steps are as follows:

(1) 10 kg of chromium slag and 10 kg of sodium chloride are mixed uniformly, and then placed in a high-temperature roasting furnace and calcined at 400 ° C for 6 h, the heating is stopped, and naturally cooled to room temperature and then ground and sieved;

(2) adding the fine powder after the step (1) to the hydrothermal kettle, and adding 1.5 mol/L sodium carbonate solution according to a solid-liquid ratio of 1:5 (w/w), stirring well and heating to Hydrothermal mineralization reaction at 150 ° C for 2 h;

(3) The mixture obtained in the step (2) is naturally cooled to room temperature and allowed to stand for 0.5 h to obtain a chromium-containing supernatant liquid and solid residue, and the solid residue is separated from the chromium-containing supernatant by filtration, and the solid residue is washed with water and dried. After detoxification of the chromium residue, the chromium-containing supernatant is reused in production, or collected in a wastewater treatment station for reduction, recovery, and purification treatment (adding a reducing agent (such as sodium sulfide, sodium hydrogen sulfite), The solution of hexavalent chromium is reduced to trivalent chromium, and the precipitated NaOH is added to produce Cr(OH) ₃ precipitate for recovery. After treatment, the water can reach the national drainage standard). Water can be recycled in the system throughout the process.

The original chromium residue of the present embodiment has a hexavalent chromium concentration of 763 mg/L, and the treated residue has a hexavalent chromium concentration of 1.025 mg/L.

Example 3

A method for chlorination roasting combined with hydrothermal mineralization to treat chromium slag according to the embodiment is shown in FIG. 1 . Specific steps are as follows:

(1) 10 kg of chromium slag and 15 kg of sodium chloride are mixed uniformly, and then placed in a high-temperature roasting furnace at 800 ° C high temperature roasting for 1.5 h, the heating is stopped, naturally cooled to room temperature and then ground and sieved;

(2) adding the fine powder after the step (1) to the hydrothermal kettle, and adding 1.0 mol/L sodium carbonate solution according to a solid-liquid ratio of 1:10 (w/w), stirring well and heating to Hydrothermal mineralization reaction at 180 ° C for 12 h;

(3) The mixture obtained in the step (2) is naturally cooled to room temperature and allowed to stand for 0.5 h to obtain a chromium-containing supernatant liquid and solid residue, and the solid residue is separated from the chromium-containing supernatant by filtration, and the solid residue is washed with water and dried. After detoxification of the chromium residue, the chromium-containing supernatant is reused in production, or collected in a wastewater treatment station for reduction, recovery, and purification treatment (adding a reducing agent (such as sodium sulfide, sodium hydrogen sulfite), The solution of hexavalent chromium is reduced to trivalent chromium, and the precipitated NaOH is added to produce Cr(OH) ₃ precipitate for recovery. After treatment, the water can reach the national drainage standard). Water can be recycled in the system throughout the process.

The original chromium residue of the present embodiment has a hexavalent chromium concentration of 752 mg/L, and the treated residue has a hexavalent chromium concentration of 0.850 mg/L.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and modifications may be made without departing from the spirit and scope of the invention. Simplifications should all be equivalent replacements and are included in the scope of the present invention.

Claims (7)

A method for treating chrome slag by chlorination roasting combined with hydrothermal mineralization, comprising the steps of: (1) adding chlorinated salt to the chromium slag and mixing uniformly, then raising the temperature to 400-1000 ° C, performing high-temperature roasting treatment for 0.5 to 12 h, cooling and sieving; (2) adding the fine powder after the step (1) is added to the hydrothermal reactor, adding a mineralizer aqueous solution, hydrothermal mineralization reaction at a temperature of 30 to 250 ° C for 2 to 24 hours; (3) The mixed liquid obtained in the step (2) is cooled and allowed to stand to obtain a chromium-containing supernatant liquid and solid residue, and the solid residue is washed with water and dried to obtain detoxified chromium residue, and the chromium-containing supernatant is used for production. Or recycle chrome. A method for treating chromium residue by chlorination roasting combined with hydrothermal mineralization according to claim 1, wherein the chloride salt in the step (1) is sodium chloride or calcium chloride. The method according to claim 1, wherein the chromium slag and the chlorinated salt are added in a mass ratio of 1: (0.5 to 1.5). A method for treating chromium residue by chlorination roasting combined with hydrothermal mineralization according to claim 1, wherein the mineralizer in the step (2) is at least one of sodium carbonate and sodium hydrogencarbonate. The concentration of the mineralizer aqueous solution is 0.5 to 1.5 mol/L. The method for treating chromium residue by chlorination roasting combined with hydrothermal mineralization according to claim 1, wherein the solid-liquid ratio of the sieved fine powder and the mineralizer aqueous solution in the step (2) is 1: (0.5 ~ 10). The method for treating chromium residue by chlorination roasting combined with hydrothermal mineralization according to claim 1, wherein the step of recovering chromium in the step (3) is: adding a reducing agent to reduce the hexavalent chromium of the solution to Trivalent chromium is added to the precipitant NaOH to produce Cr(OH) ₃ precipitate recovery. The method of claim 6, wherein the reducing agent is sodium sulfide or sodium hydrogen sulfite.

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