CN-117660750-B - Method for strengthening gradient separation and resource utilization of calcium-free roasting chromium slag through reducing alkali roasting

Abstract

The invention relates to a method for strengthening the gradient separation and recycling of calcium-free roasting chromium slag through reducing alkali roasting. The method comprises the steps of mixing calcium-free roasting chromium slag, a reducing agent and an alkaline reagent to obtain a chromium slag mixture, placing the chromium slag mixture in an inert atmosphere at a first temperature for a first time to reduce iron oxides in the chromium slag mixture, sodium-treating aluminum and chromium oxides and inhibit reduction of the chromium oxides to obtain a reduced chromium slag mixture, filtering and separating the reduced chromium slag mixture to obtain filter residues and an aluminum enriched filtrate, wherein the aluminum enriched filtrate can be used for producing aluminum oxide and recycling the alkaline reagent, placing the filter residues in an inert atmosphere at a second temperature for a second time, and separating metallic iron through melting and efficiently enriching chromium in the molten residues due to separation of aluminum in the filter residues. The invention can efficiently realize the cascade resource utilization of iron, chromium and aluminum components in the calcium-free roasting chromium slag.

Inventors

• LU CUNFANG
• TIAN CHENG
• LUO HUAZHENG
• ZHANG SHUO
• WANG YELEI
• HE YUANYUAN
• XU RUI
• ZHANG MIN

Assignees

• 重庆理工大学

Dates

Publication Date

20260505

Application Date

20231201

Priority Date

20231125

Claims (6)

1. 1. The method for strengthening the step separation and the recycling of the calcium-free roasting chromium slag through the reduction alkali roasting is characterized by comprising the following steps of: s1, mixing calcium-free roasting chromium slag, a reducing agent and an alkaline reagent to obtain a chromium slag mixture, wherein the reducing agent is selected from coke, the alkaline reagent is selected from sodium carbonate, the mol ratio of reduced carbon to available oxygen in the chromium slag mixture is 1.0-1.2:1, and the mol ratio of the alkaline reagent to aluminum oxide in the chromium slag mixture is 0.9:1; S2, placing the chromium slag mixture in a nitrogen atmosphere, and preserving heat for a first time under a first temperature condition to reduce iron oxides, sodium aluminum oxides and sodium chromium oxides in the chromium slag mixture, and simultaneously inhibiting reduction of chromium oxides in the chromium slag mixture, wherein the heat preservation treatment is followed by cooling and grinding treatment to obtain a pre-reduced chromium slag mixture, the first temperature is 1100-1200 ℃, the first time is 30-60 min, and the flow rate of nitrogen is 100ml/min; s3, placing the pre-reduced chromium slag mixture in water, and filtering to obtain filter residues and aluminum enriched filtrate; and S4, placing the filter residue in an argon atmosphere, preserving heat for a second time under a second temperature condition, and carrying out melt separation to obtain metal iron and chromium enriched residues, wherein the second temperature is 1600-1700 ℃, the second time is 30-60 min, and the flow rate of the argon is 100ml/min.
2. 2. The method for strengthening the step separation and recycling of the calcium-free roasting chromium slag by reducing alkali roasting according to claim 1 is characterized in that in the step S1, before the calcium-free roasting chromium slag, the reducing agent and the alkaline agent are mixed, ball milling and screening treatment are respectively carried out on the calcium-free roasting chromium slag and the reducing agent, the ball milling speed is 20-30 r/min, the ball milling time is 30-180 min, the screening treatment is that the calcium-free roasting chromium slag is sieved by a 50-mesh sieve, and the reducing agent is sieved by a 100-200-mesh sieve.
3. 3. The method for enhancing the step separation and recycling of the calcium-free roasting chromium slag by reducing alkali roasting according to claim 1, wherein in the step S1, after the calcium-free roasting chromium slag, the reducing agent and the alkaline agent are mixed, the method further comprises the step of pressing the mixture into a cake shape to obtain a chromium slag mixture, wherein the pressing pressure is 0.05-0.2 MPa, the diameter of the cake is 20-70 mm, and the thickness of the cake is 5-30 mm.
4. 4. The method for enhancing the step separation and recycling of the calcium-free calcined chromium slag by the reduction alkali roasting according to claim 1, wherein the step S3 comprises the steps of placing the pre-reduced chromium slag mixture in water, stirring for a third time, and filtering to obtain filter residues and an aluminum enriched filtrate; The mass ratio of the pre-reduced chromium slag mixture to water is 1:50-70; and the third time is 10-60 min.
5. 5. The method for strengthening the step separation and recycling of the calcium-free roasting chromium slag by reducing alkali roasting according to claim 1, wherein in the step S3, the aluminum enriched filtrate obtained by filtering is used for the production of aluminum oxide and the recovery of sodium carbonate.
6. 6. The method for strengthening the step separation and recycling of the calcium-free roasting chromium slag by reducing alkali roasting according to claim 1, wherein in the step S4, the separated metallic iron is used as a raw material for steel production, the recycling of iron is realized, and the separated chromium-enriched residue is used in the back-roasting slag for chromium salt production, so that the recycling of chromium is realized.

Description

Method for strengthening gradient separation and resource utilization of calcium-free roasting chromium slag through reducing alkali roasting Technical Field The invention relates to the technical field of chromium slag resource utilization, in particular to a method for strengthening gradient separation and resource utilization of calcium-free roasting chromium slag through reducing alkali roasting. Background Chromium salt (represented by sodium chromate) has a plurality of special performances, is widely applied to the fields of aerospace, military industry, atomic energy industry, steel, ceramics, electroplating, pigment, corrosion resistance, printing and dyeing, printing ink, medicine, catalyst, organic synthesis and the like, and is an indispensable important raw material in national economy and national defense construction. However, in the currently practiced chromium salt production process, a byproduct of "chromium slag" is produced, which contains a certain amount of highly toxic hexavalent chromium component, and a large amount of trivalent chromium in the chromium slag is easily oxidized into hexavalent chromium, and the mass ratio of valuable metal components such as iron, chromium, aluminum and the like in the chromium slag is about 60%, and if the chromium slag is not properly treated, environmental pollution is brought about, and the valuable metal resources are wasted. At present, the main focus of chromium slag treatment is to realize chromium slag harmless detoxication and chromium slag recycling at the same time, and for different chromium salt production processes, the sintering iron-making process treatment has a main chromium slag treatment means that calcium roasting slag and liquid-phase oxidizing slag are directly used as iron-making raw materials and the like. CN 102191390A discloses a method for leaching chromium-containing leaching solution from chromium slag by acid liquor, then reducing and precipitating to extract chromium in the leaching solution, and the whole process consumes a large amount of acid and alkali, so that the problem of secondary environmental pollution is caused, and the economic benefit is low. CN 102978376A discloses a detoxication process for dry reduction of chromium slag, which uses carbon powder as a reducing agent to detoxify the chromium slag in a reducing atmosphere, but the chromium element in the chromium slag is not effectively recovered and the reaction temperature is higher, resulting in higher implementation cost. CN 110330248A discloses a method for preparing porcelain aggregate by innocuous treatment of chromium-containing solid waste, which is to simply detoxify chromium slag, and then use detoxified chromium slag as blank, but the valuable elements in the chromium slag are not recovered. CN114717371 a discloses a method for producing chromium-containing sponge iron by reducing chromium slag in a rotary kiln, and the chromium-containing sponge iron is prepared by reducing mixed pellets of special coal dust and chromium slag in the rotary kiln, but the content of chromium in the sponge iron is lower, chromium element is not effectively recovered, and the energy consumption is higher. The above examples show that the main way of treating the chromium slag is to reduce hexavalent chromium ions with high water solubility and high toxicity into trivalent chromium ions with low toxicity and fix the trivalent chromium ions, for example, the chromium slag is detoxified and then used as raw materials of products such as cement, green bricks, steel and the like, but the chromium slag has the defects of low utilization rate of valuable metals, difficult separation of reduced iron, low utilization value, unstable detoxication and the like. The main idea of chromium slag detoxification is to reduce and solidify hexavalent chromium with high solubility and high toxicity into trivalent chromium, but a great amount of valuable elements are not recycled, and the trivalent chromium is exposed to the environment after the fixing failure of the trivalent chromium, so that the trivalent chromium is oxidized into hexavalent chromium under the action of long-term external complex factors, thereby leading detoxification to fail. The main idea of the recycling of the chromium slag at present is to take the chromium slag as an auxiliary material to participate in the production process of other products after detoxification, but the chromium slag is limited in practical application, such as large energy consumption, limited slag consumption, incomplete extraction of valuable elements and the like. Disclosure of Invention The invention aims to provide a method for strengthening the gradient separation and recycling of calcium-free roasting chromium slag by reducing alkali roasting, so as to effectively realize the gradient separation and recycling treatment of iron, chromium and aluminum components in the calcium-free roasting chromium slag, and utilize the iron, ch