阅读说明：本技术 含铬污泥与含铬废渣协同利用富集、回收铬资源的方法 (Method for enriching and recovering chromium resource by synergistic utilization of chromium-containing sludge and chromium-containing waste residue ) 是由 汪大亚 华绍广 李书钦 李香梅 裴德健 李刚 于 2021-07-26 设计创作，主要内容包括：本发明公开了一种含铬污泥与含铬废渣协同利用富集、回收铬资源的方法,将含铬污泥和含铬废渣进行细磨、混合制备出混合料,混合料室外碱度((CaO％+MgO％)/(SiO-(2)％+Al-(2)O-(3)％))在0.6～1.5范围、FeO-(x)含量≥15.0％。对混合料进行还原焙烧,焙烧温度控制在1100～1500℃范围。对焙烧产物碎磨处理后,采用强磁选工艺将铁铬尖晶石离出来,获得Cr-(2)O-(3)含量≥20.0％、Cr-(2)O-(3)回收率≥85.0％的铬精矿。本发明将含铬污泥与含铬废渣这两种含铬危废资源进行联用,同时富集这两种资源中的铬,所获得的含铬富集相中铬的品位高,且利用后续分离,具有效率高、污染小且适用范围广等特点,适于应用在含铬资源中铬富集与分离的技术领域。(The invention discloses a method for enriching and recovering chromium resources by utilizing chromium-containing sludge and chromium-containing waste residues cooperatively, which is characterized in that the chromium-containing sludge and the chromium-containing waste residues are finely ground and mixed to prepare a mixture, and the outdoor alkalinity of the mixture ((CaO% + MgO%)/(SiO) 2 ％+Al 2 O 3 %) in the range of 0.6 to 1.5, FeO x The content is more than or equal to 15.0 percent. And carrying out reduction roasting on the mixture, wherein the roasting temperature is controlled within the range of 1100-1500 ℃. After the roasted product is crushed and ground, the ferrochrome spinel is separated out by adopting a strong magnetic separation process to obtain Cr 2 O 3 The content is more than or equal to 20.0 percent and the Cr content 2 O 3 The recovery rate is more than or equal to 85.0 percent. The invention uses the chromium-containing sludge and the chromium-containing waste residueThe two chromium-containing hazardous waste resources are combined for use, chromium in the two resources is enriched simultaneously, the grade of the obtained chromium in the chromium-containing enriched phase is high, the subsequent separation is utilized, and the method has the characteristics of high efficiency, small pollution, wide application range and the like, and is suitable for being applied to the technical field of chromium enrichment and separation in the chromium-containing resources.)

1. A method for enriching and recovering chromium resources by synergistically utilizing chromium-containing sludge and chromium-containing waste residues is characterized by comprising the following steps:

1) raw material treatment: containing CaO, MgO and SiO₂、Al₂O₃、FeO_xThe chromium-containing sludge contains CaO, MgO and SiO₂、Al₂O₃、FeO_xThe chromium-containing waste residue is prepared into alkalinity ((CaO% + MgO%)/(SiO)₂％+Al₂O₃%) in the range of 0.6 to 1.5, FeO_xAdding the mixture with the content of more than or equal to 15.0% into a ball mill for fine grinding and mixing to prepare the mixture, wherein Cr in the chromium-containing sludge₂O₃The content is more than or equal to 8.0 percent, and the Cr in the chromium-containing waste residue₂O₃The content is more than or equal to 3.0 percent;

2) reduction roasting: in a reductive reaction atmosphere, carrying out reductive roasting on the mixture obtained in the step 1) at the temperature of 1100-1500 ℃, so that chromium in the chromium-containing sludge and chromium-containing waste residue is enriched to chromium-containing enriched phase-ferrochrome Fe through a chemical reaction_3-xCr_xO₄Phase (c);

3) magnetic separation and recovery: crushing and grinding the roasted product obtained in the step 2), controlling the grinding granularity to be-0.074 mm and the grain fraction content to be more than or equal to 80.0%, and separating the iron-chromium spinel from the ground product by adopting a strong magnetic separation process to obtain Cr₂O₃The content is more than or equal to 20.0 percent and the Cr content₂O₃The recovery rate is more than or equal to 85.0 percent.

2. A method for enriching and recovering chromium resources by synergistically utilizing chromium-containing sludge and chromium-containing waste residues is characterized by comprising the following steps:

1) raw material treatment: containing CaO, MgO and SiO₂、Al₂O₃、FeO_xThe chromium-containing sludge contains CaO, MgO and SiO₂、Al₂O₃、FeO_xThe chromium-containing waste residue is prepared into alkalinity ((CaO% + MgO%)/(SiO)₂％+Al₂O₃%) in the range of 0.6 to 1.5, FeO_xAdding the mixture with the content of more than or equal to 15.0% into a ball mill for fine grinding and mixing to prepare the mixture, wherein Cr in the chromium-containing sludge₂O₃The content is more than or equal to 8.0 percent, and the Cr in the chromium-containing waste residue₂O₃The content is more than or equal to 3.0 percent;

2) reduction roasting: in a reductive reaction atmosphere, carrying out reductive roasting on the mixture obtained in the step 1) at the temperature of 1100-1500 ℃, so that chromium in the chromium-containing sludge and chromium-containing waste residue is enriched to chromium-containing enriched phase-ferrochrome Fe through a chemical reaction_3-xCr_xO₄Phase (c);

3) and (3) reselection separation and recovery: crushing and grinding the roasted product obtained in the step 2), controlling the grinding granularity to be-0.074 mm, and controlling the grain fraction content to be more than or equal to 80.0%, and respectively adopting a spiral chute, a Nielson (Knelson) concentrator or the combined separation of the spiral chute and the Nielson concentrator to obtain Cr₂O₃The content is more than or equal to 21.0 percent and the Cr content₂O₃The recovery rate is more than or equal to 85.5 percent.

3. The method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue in a synergistic manner as claimed in claim 2, wherein the method comprises the following steps: performing combined reselection on the ground product by adopting a spiral chute-Nielson concentrator to obtain Cr₂O₃The content is more than or equal to 22.0 percent and the Cr content₂O₃The recovery rate is more than or equal to 86.0 percent.

4. The chromium-containing sludge of claim 1, 2 or 3The method for enriching and recovering chromium resources by utilizing the chromium-containing waste residue is characterized by comprising the following steps: the chromium-containing sludge comprises the following main components in percentage by mass: SiO 2₂4.0～8.0％、Al₂O₃2.0～8.0％、FeO_x 3.0～8.0％、CaO 10.0～20.0％、Cr₂O₃10.0-15.0% and the balance of P₂O₅MnO, MgO and other components; the chromium-containing waste residue comprises the following main components in percentage by mass: SiO 2₂15.0～20.0％、Al₂O₃3.0～8.0％、FeO_x20.0～45.0％、CaO2.0～5.0％、Cr₂O₃3.0-10.0%, MgO1.0-5.0%, and the balance of MnO and TiO₂、V₂O₃And other components.

5. The method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue in a synergistic manner according to claim 4, characterized by further comprising the following steps: and (3) preparing pellets with the diameter of 4.0-10.0 mm from the mixture prepared in the step 1), and feeding the pellets into the step 2) for reduction roasting.

6. The method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue in a synergistic manner as claimed in claim 5, wherein the method comprises the following steps: in the step 1), carbon powder is also added into the mixture as a reducing agent to ensure the reducing atmosphere in the step 2).

7. The method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue in a synergistic manner according to claim 6, wherein the method comprises the following steps: the reduction roasting temperature in the step 2) is 1350-1500 ℃.

8. The method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue in a synergistic manner as claimed in claim 7, wherein the method comprises the following steps: the magnetic separation process in the step 3) adopts a vertical ring electromagnetic pulse high gradient magnetic separator for separation, and the magnetic induction intensity is 0.4-1.0 Tesla.

Technical Field

The invention belongs to the field of resource utilization of chromium in dangerous/solid waste, and particularly relates to a method for synergistically utilizing chromium-containing sludge and chromium-containing waste residues in a steel plant and enriching chromium resources in the sludge and the waste residues.

Background

The discharge amount of chromium-containing hazardous/solid waste in China is huge. According to measurement and calculation, the annual emission can reach about 150 ten thousand tons, and the accumulated stock reaches more than ten million tons. Chromium-containing hazardous/solid waste generally contains high contents of elements such as Fe, Cr, V and the like, and is not only toxic hazardous waste and environmental pollutants, but also an important strategic resource. Therefore, the treatment of 'reduction, harmlessness and reclamation' on the waste water has great environmental, economic and social benefits.

At present, the method mainly adopted for separating and recovering the heavy metal element chromium in the chromium-containing dangerous/solid waste mainly comprises hydrometallurgy (acid leaching, alkali leaching, water leaching and salt leaching)) Pyrometallurgy (high-temperature smelting method and roasting-leaching method), biological extraction technology and the like. Chinese patent 'a method for detoxifying and recovering chromium from chromium-containing waste residue' (CN108220604B) proposes a method for resource utilization of chromium in chromium-containing waste residue: oxidizing and roasting the waste residue, separating the solid residue from the chromium-containing solution by means of ultrasonic treatment, hydrothermal reaction and the like, and adding HCl and NaHCO when separating and recovering chromium₃And Na₂CO₃Etc. as surface interface controlling agents to promote the reaction. The method has the disadvantages of complicated process flow, high medicament consumption and new secondary pollution to the environment, and is not widely applied to the industry. Chinese patent 'a method for recovering hexavalent chromium resources from chromium slag'

(CN102191390A) hydrochloric acid and sulfuric acid are adopted to leach hexavalent chromium from the chromium slag at normal temperature, but the chromium recovery rate is only about 60-80%, so that the chromium resource can not be efficiently recovered, and a large amount of generated acid liquor brings serious hidden troubles to the environment. Most of the traditional methods for recovering chromium from chromium-containing resources have the problems of high cost, complex process flow, complex operation, easy generation of secondary pollutants and the like, and have larger improvement space in the process. In view of the above disadvantages, methods for recovering chromium from chromium-containing sludge and chromium-containing slag have been proposed in recent years mainly as follows: reduction precipitation, ion exchange, extraction separation, etc., but these methods all have the following disadvantages: the reduction precipitation method has large acid consumption, and the obtained product has low purity, so the method is not a more suitable method from the aspects of environment and cost; the ion exchange method has longer process period and is not suitable for large-scale production; the extraction separation method has good separation effect only on certain specific ions, but the effect is greatly influenced by impurity ions. These factors limit the industrial application of these methods to some extent.

In conclusion, for the enrichment, separation and recovery of chromium in the chromium-containing hazardous/solid waste, no feasible method exists at present from the viewpoints of economy, environmental protection and process flow simplification, and the efficient and green recycling of the chromium-containing hazardous/solid waste is still a problem to be solved urgently. The invention provides a method for enriching chromium by combining chromium-containing sludge and chromium-containing waste residue. Because chromium in the chromium-containing sludge and the chromium-containing waste residue is difficult to enrich through a conventional physical beneficiation method, the invention provides a high-temperature chemical method, which realizes the pre-enrichment of chromium in the chromium-containing sludge and the chromium-containing waste residue, reduces the dispersion degree of chromium, and obtains a chromium-enriched phase which has high chromium content and is suitable for subsequent separation.

Disclosure of Invention

The invention aims to solve the problems of complex process flow, large medicament consumption, high treatment cost, easy generation of secondary pollution, incapability of large-scale production and the like of the conventional resource utilization of chromium-containing sludge and chromium-containing waste residue, and provides a method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue in a synergistic manner, so that the chromium-containing sludge and the chromium-containing waste residue can be efficiently, environmentally-friendly, low in cost and subjected to synergistic treatment, enrichment and recovery of the chromium resources.

The technical concept of the method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue in a synergistic manner is as follows: by utilizing the self component characteristics and advantages of the chromium-containing sludge and the chromium-containing waste residue, the high-efficiency enrichment of chromium in the chromium-containing sludge and the chromium-containing waste residue is realized by combining the chromium-containing sludge and the chromium-containing waste residue and adjusting the roasting atmosphere and the roasting system, and the obtained chromium-containing enriched phase-ferrochrome spinel Fe_3-xCr_xO₄In the phase, the chromium enrichment degree is high, the chromium-rich phase has a large difference with other mineral phases in the material in physical and chemical properties, and the chromium-rich phase can be separated and recovered in a later stage through a simple ore dressing mode, so that the cost of dressing and metallurgy is reduced, and the pollution to the environment is also reduced.

In order to realize the purpose, the method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue synergistically adopts the following processes and steps:

1) raw material treatment: containing CaO, MgO and SiO₂、Al₂O₃、FeO_xThe chromium-containing sludge contains CaO, MgO and SiO₂、Al₂O₃、FeO_xThe chromium-containing waste residue is prepared into alkalinity ((CaO% + MgO%)/(SiO)₂％+Al₂O₃%) in the range of 0.6 to 1.5, FeO_xAdding the mixture with the content of more than or equal to 15.0% into a ball mill for fine grinding and mixing to prepare the mixture, wherein Cr in the chromium-containing sludge₂O₃The content is more than or equal to 8.0 percent, and the Cr in the chromium-containing waste residue₂O₃The content is more than or equal to 3.0 percent.

The chromium-containing sludge comprises the following main components in percentage by mass: SiO 2₂4.0～8.0％、Al₂O₃2.0～8.0％、FeO_x 3.0～8.0％、CaO 10.0～20.0％、Cr₂O₃10.0-15.0% and the balance of P₂O₅MnO, MgO and other components; the chromium-containing waste residue comprises the following main components in percentage by mass: SiO 2₂15.0～20.0％、Al₂O₃3.0～8.0％、FeO_x20.0～45.0％、CaO2.0～5.0％、Cr₂O₃3.0-10.0%, MgO1.0-5.0%, and the balance of MnO and TiO₂、V₂O₃And other components.

In this step, if FeO is present in the mix_xWhen the content is less than 15 percent, a proper amount of Fe can be added into the mixture₂O₃Powder to act as an enrichment carrier for chromium.

2) Reduction roasting: in a reductive reaction atmosphere, carrying out reductive roasting on the mixture obtained in the step 1) at the temperature of 1100-1500 ℃, so that chromium in the chromium-containing sludge and chromium-containing waste residue is enriched to chromium-containing enriched phase-ferrochrome Fe through a chemical reaction_3-xCr_xO₄Phase (c); the reduction roasting is preferably carried out at 1350-1500 ℃.

3) Magnetic separation and recovery: crushing and grinding the roasted product obtained in the step 2), controlling the grinding granularity to be-0.074 mm and the grain fraction content to be more than or equal to 80.0%, and separating the iron-chromium spinel from the ground product by adopting a strong magnetic separation process to obtain Cr₂O₃The content is more than or equal to 20.0 percent and the Cr content₂O₃The recovery rate is more than or equal to 85.0 percent.

Further, preparing pellets with the diameter of 4.0-10.0 mm from the mixture prepared in the step 1), and feeding the pellets into the step 2) for reduction roasting. The pellet diameter is preferably 4-8 mm.

Further, carbon powder is preferably used as a reducing agent; of course, hydrogen reduction may also be employed to reduce carbon dioxide emissions.

Furthermore, the magnetic separation process in the step 3) adopts a vertical ring electromagnetic pulse high gradient magnetic separator for separation, and the magnetic induction intensity is 0.4-1.0 Tesla. The specific values of the grinding fineness and the magnetic induction intensity can be determined through tests, and the Cr in the chromium concentrate is ensured₂O₃The grade is more than or equal to 20.0 percent, and the Cr is ensured₂O₃The recovery rate is more than or equal to 85.0 percent.

Compared with the prior art, the method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue synergistically has the following advantages:

(1) the method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residue cooperatively utilizes the two different chromium-containing hazardous wastes and effectively controls the components and the roasting system of the mixed raw materials, thereby realizing the simultaneous chromium enrichment of the chromium-containing waste residue and the chromium-containing sludge. In the process flow, the enrichment degree of chromium is as high as more than 90%, and the obtained chromium enrichment phase has larger difference with the physical properties of other mineral phases, so that the difficulty of separating and recovering the chromium enrichment phase at the later stage is greatly reduced, and the Cr in the chromium concentrate separated by magnetic separation₂O₃Grade is not less than 20.0 percent and Cr₂O₃The recovery rate is more than or equal to 85.0 percent.

(2) Compared with the traditional chromium enrichment process flow, the method has higher chromium enrichment efficiency, does not generate substances harmful to the environment in the whole process, creates conditions for efficiently and environmentally recovering chromium, meets the requirements of actual industrial production, and has better application and popularization prospects.

(3) The chromium-containing enriched phase obtained by the method is not easy to form a solid solution with oxysulfide and phosphorus oxide in the slag, and conditions are created for obtaining subsequent high-purity and high-performance chromium products.

(4) By the method, chromium in the chromium-containing waste residue and the chromium-containing sludge can be enriched into the hercynite phase. The tailings obtained after the chromium-rich phase separation can be used as raw materials of microcrystalline glass and cementing materials, so that the secondary pollution of the waste residues is reduced, and the resource utilization of the waste residues is realized.

Drawings

FIG. 1 is a schematic process flow diagram of the method for enriching and recovering chromium resources by utilizing chromium-containing sludge and chromium-containing waste residues in a synergistic manner according to the invention;

FIG. 2 shows FeO(s) and SiO at a temperature of 700-1600K₂(s)、Al₂O₃、Cr₂O₃Delta of reaction_rG^θ-a T-relationship graph;

FIG. 3 is a graph comparing XRD results at 1373K and 1473K firing temperatures, respectively;

FIG. 4 is a scanning electron microscope analysis result of a sample after baking in a reducing baking atmosphere at 1473K.

Detailed Description

In order to describe the invention, the method for the enrichment and recovery of chromium resources by the synergistic utilization of chromium-containing sludge and chromium-containing waste residue according to the invention is further described in detail with reference to the accompanying drawings and examples.

In order to verify the feasibility of the method, the chromium-containing sludge and the chromium-containing waste residue are mixed according to a certain proportion, and the main component of the mixture comprises SiO₂、Al₂O₃、Cr₂O₃And in addition, the magnesium oxide also contains a small amount of MgO. When carbon powder is used as a reducing agent and the reaction is carried out under the reducing roasting condition, because of excessive FeO_xIn the presence of (b), the following reactions occur:

FeO(s)+SiO₂(s)＝FeSiO₃(s) (1)

FeO(s)+Al₂O₃＝FeAl₂O₄(s) (2)

FeO(s)+Cr₂O₃＝FeCr₂O₄(s) (3)

the magnitude of the standard gibbs free energy for each reaction described above can be obtained from the relevant thermodynamic data reviewed in Factsage, and the results are shown in table 1 and fig. 1.

TABLE 1 Standard formation Gibbs free energy changes at different temperatures for reactions (1) - (3)

Table 1 shows FeO and SiO at different temperatures₂、Al₂O₃And Cr₂O₃Reaction to form FeSiO₃、FeAl₂O₄And FeCr₂O₄The magnitude of the standard gibbs free energy. FIG. 1 shows the Δ of reactions (1) to (3) in the temperature range of 700 to 1600K_rG^θ-T contrast plot.

As can be seen from the data in table 1 and fig. 1: FeO and Cr₂O₃Reaction to form FeCr₂O₄Delta of_rG^θAnd minimum. This indicates that: in a temperature range of 700-1600K, in a system formed by the chromium-containing sludge and the chromium-containing waste residue, FeCr₂O₄Is the most easily formed compound, namely, it is completely feasible to enrich chromium in the chromium-containing spinel phase from chromium-containing sludge and chromium-containing waste residue thermodynamically.

The main components of the chromium-containing slag selected in this example are shown in Table 2. As can be seen from Table 2, Cr is contained in the slag₂O₃The content of (A) can reach 9.12%. In addition, the slag also contains a certain amount of metal oxides such as Mn, Ti and the like. Table 3 shows the main components of chromium-containing sludge obtained from a certain plating plant, and Table 2 shows that Cr in the chromium-containing sludge₂O₃The content of (C) is higher and can reach 14.18 percent, and Fe₂O₃The content of (A) is significantly lower.

TABLE 2 Main chemical composition table of chromium-containing vanadium extraction tailings

TABLE 3 Main chemical composition Table of chromium-containing sludge

As shown in a principle process flow chart of the method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residues synergistically, the method for enriching and recovering chromium resources by utilizing the chromium-containing sludge and the chromium-containing waste residues synergistically is implemented by the following steps:

1) raw material treatment: after the chromium-containing sludge and the chromium-containing waste residue are ball-milled and crushed, the chromium-containing sludge and the chromium-containing waste residue are mixed according to a certain proportion to prepare alkalinity ((CaO% + MgO%)/(SiO)₂％+Al₂O₃%) in the range of 0.6 to 1.5, FeO_xThe content is more than or equal to 15.0 percent. It is noted that in order to provide a reducing firing atmosphere, an appropriate amount of carbon powder is added to the mix to act as a reducing agent. In addition, in order to fully enrich and recover Cr in the chromium-containing sludge and chromium-containing waste residues, a slight excess amount of Fe needs to be supplemented to the mixture₂O₃The powder acts as an enrichment carrier for chromium. In addition, Fe₂O₃The adding amount of the powder and the carbon powder is determined according to the chromium content in the chromium-containing sludge and the chromium-containing waste residue.

2) Reduction roasting: preparing the obtained mixture into pellets, controlling the diameter of a pellet sample to be 4-8 mm, drying the sample, and then placing the sample under a reductive roasting condition for reductive roasting, so that chromium in the chromium-containing sludge and chromium-containing waste residue is enriched to a chromium-containing enrichment phase-ferrochrome spinel Fe through a chemical reaction_3-xCr_xO₄Phase (c); the calcination temperature was selected to be 1373K and 1473K, the calcination time was selected to be 3 hours, and an appropriate amount of argon gas was blown in to exhaust the air in the furnace, so that the reduction reaction was sufficiently performed. And after the roasting reaction is finished, cooling the sample at the speed of 5-10K/min. In the process, the chromium in the chromium-containing sludge and the chromium-containing waste residue can enter a pre-designed chromium-containing enrichment phase.

The chromium-containing enriched phase obtained by roasting does not contain impurity elements such as P, Na, S and the like, so that the chromium is beneficial to leaching and extracting in the subsequent process or separating and sorting by adopting other processes.

3) Magnetic separation and recovery: crushing and grinding the roasted product obtained in the step 2), controlling the grinding granularity to be-0.074 mm and the grain fraction content to be more than or equal to 80.0%, and separating the iron-chromium spinel from the ground product by adopting a strong magnetic separation process to obtain Cr₂O₃The content is more than or equal to 20.0 percent and the Cr content₂O₃The recovery rate is more than or equal to 85.0 percent. The magnetic separation process adopts a vertical ring electromagnetic pulse high-gradient magnetic separator for separation, and the magnetic induction intensity is between 0.4 and 1.0 Tesla.

The invention also adopts a spiral chute to reselect the product after ore grinding, thereby obtaining Cr₂O₃21.5% of Cr₂O₃The recovery rate of the chromium concentrate is 86.0 percent, and the product after ore grinding is reselected by a Nielson (Knelson) concentrator to obtain Cr₂O₃22.3% of Cr₂O₃The recovery rate of chromium concentrate is 86.5 percent; the Cr is obtained by adopting the combined reselection of the ground product by a spiral chute-Nielson concentrator₂O₃Content of 24.8% Cr₂O₃The recovery rate of the chromium concentrate is 86.2 percent, and unexpected technical effects are achieved.

In order to verify the feasibility of the scheme provided in the method of the present invention, it is necessary to identify whether the calcined ore has a hercynite phase, XRD analysis is performed on the samples obtained at the calcination temperatures of 1373K and 1473K, respectively, and the comparison result is shown in fig. 3. By comparing XRD results of samples at different roasting temperatures, it can be found that: the ferro-chromium spinel phase is generated in the roasted minerals; furthermore, comparing the samples at 1373K and 1473K roasting temperatures, it can be seen that the content of hercynite phase generated in the roasted minerals gradually increases with the increase of the roasting temperature. FIG. 4 is a graph showing the results of SEM analysis of samples after firing in a reducing firing atmosphere of 1473K, and the results in FIG. 4 show that: in the roasted sample, the enrichment behaviors of Fe and Cr are consistent, and the impurity elements such as P, S and the like are not contained. The combination of the above results can find that: under the reducing roasting atmosphere, FeO is utilized_xAs an enrichment carrier, the chromium-containing sludge and the chromium-containing waste residue are combined, so that abundant Cr resources in the chromium-containing sludge can be enriched into a ferrochrome spinel phase. The enriched phase has high enrichment efficiency and does not contain P, S harmful impurity elements. This shows that the method provided by the patent can indeed achieve better combined enrichment effect on chromium in the chromium-containing sludge and the chromium-containing steel slag.

In addition, the low-chromium tailings discharged by the magnetic separation process can be added with ingredients such as fly ash and the like to prepare building material products such as maintenance bricks and the like, and can also be used for preparing other building materials such as ceramsite and the like, so that no solid waste is discharged.