A method for selective precipitation separation of chromium from industrial stainless steel slag and its application

Abstract

The present invention relates to the field of metallurgical solid waste resource utilization. Specifically, it relates to a method for selective precipitation and separation of chromium in industrial stainless steel slag and its application. The method for selective precipitation and separation of chromium in industrial stainless steel slag includes: adding the molten chromium-containing stainless steel slag liquid generated during the stainless steel production process into a refining device, where the refining device includes a ladle furnace and / or an induction furnace, adding an alkalinity modifier to the refining device for reaction, so that chromium elements enter the spinel phase and precipitate in a solid state to the bottom of the refining device to form chromium-rich slag; after discharging the liquid chromium-depleted slag above the chromium-rich slag through the slag discharge port of the refining device, performing a first cooling to obtain vitreous silicate; after discharging the chromium-rich slag from the bottom of the refining device, performing a second cooling to obtain chromium-containing spinel. This method can selectively precipitate chromium and separate to obtain chromium-containing spinel and vitreous silicate, realizing high-value utilization of chromium-containing stainless steel slag while fixing chromium.

Description

Technical Field

[0001] The present invention relates to the field of metallurgical solid waste resource utilization, and in particular, to a method for selectively precipitating and separating chromium from industrial stainless steel slag and its application. Background Art

[0002] During the production process of stainless steel, a large amount of stainless steel slag is generated. According to statistics, about 270 - 330 kg of steel slag is produced for every 1 ton of stainless steel produced. Steel slag is a by - product harmful to the environment. For a long time, a large amount of stainless steel slag has been landfilled or stored as hazardous solid waste. Under natural conditions, unstable Cr in stainless steel slag 3+ can be oxidized to Cr 6+ , and the dissolution of chromium will cause damage to the ecological environment. This factor limits the possibility of applying chromium - containing stainless steel slag to other silicate materials (such as glass, ceramics, cement, refractories, etc.). Therefore, one of the bottlenecks in the large - scale utilization of stainless steel slag is the treatment of chromium.

[0003] The existing methods for treating chromium - containing stainless steel slag can be mainly classified into two types. One method is the fixation of chromium, mainly including solidification with cement, glass, and ceramics. Although this method has a large production scale and low cost, it has strict requirements for the chromium content in the slag, especially the poor stability of the later products. Another method is the extraction of chromium, mainly including high - temperature ferrosilicon reduction, wet reduction, and high - temperature melting modification. However, these treatment methods generally have problems such as large environmental impact or low economic benefits.

[0004] Moreover, in the existing technology, the fixation of chromium is generally in the pilot - scale stage of small - scale laboratories. Most of the containers used are crucibles, which need to be heated in an electric furnace, with cumbersome operations and are not suitable for batch processing.

[0005] In addition, in the existing technology, the solid obtained by chromium fixation is at the top of the container, so a diversion plate needs to be added, and the equipment needs to be specially modified for this purpose, which is relatively complex and increases the construction cost.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The first object of the present invention is to provide a method for selectively precipitating and separating chromium from industrial stainless steel slag. This method can selectively precipitate chromium and separate to obtain chromium - containing spinel and vitreous silicate. While fixing chromium, it realizes the high - value utilization of chromium - containing stainless steel slag. At the same time, the present invention adopts a specific refining equipment, which can handle a large amount of steel slag, has a self - heating function and a slag discharge port, is suitable for industrial production, can achieve no operation interval, is convenient for the subsequent separation of liquid - solid products, and does not require modification or addition of shunt equipment.

[0008] The second object of the present invention is to provide the applications of the chromium-containing spinel and vitreous silicate obtained by a method for selective precipitation and separation of chromium in industrial stainless steel slag in the preparation of refractory materials and building materials respectively.

[0009] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0010] The present invention first provides a method for selective precipitation and separation of chromium in industrial stainless steel slag, comprising the following steps:

[0011] Adding the molten chromium-containing stainless steel slag liquid generated in the stainless steel production process into a refining device, the refining device including a ladle furnace and / or an induction furnace, adding an alkalinity modifier to react in the refining device, so that chromium elements enter the spinel phase and precipitate in a solid state to the bottom of the refining device to form chromium-rich slag;

[0012] After discharging the liquid chromium-removed slag above the chromium-rich slag through the slag discharge port of the refining device, performing first cooling to obtain vitreous silicate;

[0013] After discharging the chromium-rich slag from the bottom of the refining device, performing second cooling to obtain chromium-containing spinel.

[0014] The present invention further provides the applications of the chromium-containing spinel and vitreous silicate obtained by the method for selective precipitation and separation of chromium in industrial stainless steel slag in the preparation of refractory materials and building materials respectively.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The method for selective precipitation and separation of chromium in industrial stainless steel slag provided by the present invention can solidify and precipitate chromium in the molten chromium-containing stainless steel slag liquid and selectively separate and recover it, respectively obtaining chromium-containing spinel and vitreous silicate, harmlessly treating the chromium-containing stainless steel slag, and realizing the high-value utilization of the chromium-containing stainless steel slag.

[0017] (2) The method for selective precipitation and separation of chromium in industrial stainless steel slag provided by the present invention, the total chromium leaching concentration in the obtained chromium-containing spinel and vitreous silicate after treatment fully complies with the comprehensive utilization standard of chromium-containing solid waste in the country, and can solve the environmental pollution problem caused by chromium-containing stainless steel solid waste.

[0018] (3) The method for selective precipitation and separation of chromium in industrial stainless steel slag provided by the present invention has a large amount of steel slag to be treated, and the equipment has a self-heating function and a slag discharge port, which is convenient for the subsequent separation of liquid-solid products, and is suitable for large-scale and continuous industrial production.

[0019] (4) The chromium-containing spinel obtained by the method for selective precipitation and separation of chromium in industrial stainless steel slag provided by the present invention is at the bottom of the refining equipment, and solid-liquid separation can be directly carried out through the slag discharge function of the refining equipment. The operation is convenient, the equipment is simple, there is no need to add shunt equipment or transform the equipment, and this method utilizes the waste heat of steel slag, consumes less energy, can use local materials, has a lower production cost, and the prepared product is environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 Schematic process flow diagram of the method for selective precipitation and separation of chromium in industrial stainless steel slag in Example 1 provided by the present invention;

[0022] Figure 2 X-ray diffraction pattern of the vitreous silicate and chromium-containing spinel prepared in Example 1 provided by the present invention;

[0023] Figure 3 Scanning electron microscope pictures of the vitreous silicate and chromium-containing spinel prepared in Example 1 provided by the present invention;

[0024] Figure 4 X-ray diffraction pattern of the vitreous silicate and chromium-containing spinel prepared in Comparative Example 1 provided by the present invention;

[0025] Figure 5 Scanning electron microscope pictures of the vitreous silicate and chromium-containing spinel prepared in Comparative Example 1 provided by the present invention;

[0026] Figure 6 X-ray diffraction pattern of the inseparable product prepared in Comparative Example 2 provided by the present invention;

[0027] Figure 7 Scanning electron microscope pictures of the inseparable product prepared in Comparative Example 2 provided by the present invention;

[0028] Figure 8 Bar chart of the total chromium leaching concentration of the chromium-containing stainless steel slag untreated in Example 1, the vitreous silicate, chromium-containing spinel and inseparable product prepared in each example and comparative example. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0030] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on the quantity.

[0031] If there is no special explanation, the "including" and "comprising" mentioned in the present invention mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or it can only include or comprise the listed components.

[0032] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. Among them, "several" refers to any two or more.

[0033] In the first aspect, the present invention provides a method for selectively precipitating and separating chromium from industrial stainless steel slag, which includes the following steps:

[0034] Add the molten chromium-containing stainless steel slag liquid generated during the stainless steel production process into a refining device, where the refining device includes a ladle furnace and / or an induction furnace. Then, add an alkalinity modifier to the refining device for reaction, so that chromium elements enter the spinel phase and precipitate in a solid state to the bottom of the refining device (the chromium-containing spinel crystals will settle at the bottom of the refining device due to gravity), forming a chromium-rich slag.

[0035] A layered solid layer and a liquid layer are gradually formed in the refining device, where the solid layer is at the bottom of the refining device and the liquid layer is at the top of the refining device, that is, the liquid layer is above the solid layer.

[0036] After the reaction is completed, the liquid dechromium slag above the chromium-rich slag is discharged through the slag discharge port of the refining device and then undergoes a first cooling to obtain a vitreous silicate.

[0037] Among them, the slag discharge port is located at the upper part of the refining equipment.

[0038] After discharging the chromium-rich slag from the bottom of the refining equipment, it is secondarily cooled to obtain chromium-containing spinel.

[0039] It can be understood that the bottom of the refining equipment can be opened / unscrewed and separated.

[0040] The method for selective precipitation and separation of chromium in industrial stainless steel slag provided by the present invention can solidify and precipitate chromium in the molten chromium-containing stainless steel slag liquid and selectively separate and recover it, obtaining chromium-containing spinel and vitreous silicate respectively, harmlessly treating the chromium-containing stainless steel slag and realizing the high-value utilization of the chromium-containing stainless steel slag. The total chromium leaching concentration in the obtained chromium-containing spinel and vitreous silicate after treatment fully complies with the comprehensive utilization standard of chromium-containing solid waste in the country, and can solve the environmental pollution problem caused by chromium-containing stainless steel solid waste.

[0041] Moreover, this method uses a specific refining equipment, which has a large amount of steel slag to be processed, and has a self-heating function and a slag discharge port, is suitable for industrial production, can achieve continuous operation and batch production, and is convenient for subsequent separation of liquid-solid products.

[0042] Meanwhile, the chromium-containing spinel obtained by the method for selective precipitation and separation of chromium in industrial stainless steel slag provided by the present invention is at the bottom of the refining equipment (the density of the spinel phase (chromium-rich slag) (3.6 - 4.6 g / cm 3 ) is greater than the density of the amorphous phase (chromium-depleted slag) (2.3 - 2.7 g / cm 3 ), so when the viscosity is appropriate, the chromium-containing spinel will sink), and solid-liquid separation can be directly carried out through the slag discharge function of the refining equipment without the need for a shunt device. In the prior art, the final heat preservation temperature is relatively low and the viscosity of the slag system is too high, resulting in the inability of spinel crystals to sink and finally accumulating at the top. When the slag viscosity is too high, it is not conducive to subsequent separation, so a shunt device needs to be set up.

[0043] Furthermore, the present invention directly pours the molten chromium-containing stainless steel slag liquid generated in the stainless steel production process into the refining equipment for reaction. Compared with preheating and melting steel slag in the prior art, there is no stacking process, which can reduce the risk of chromium dissolution. At the same time, the molten chromium-containing stainless steel slag liquid has a certain amount of heat, and using its waste heat can reduce the energy consumption of heat preservation. Even an empty refining equipment with waste heat after just reacting in the factory can be used to achieve double waste heat utilization, which is more energy-saving and environmentally friendly.

[0044] In some specific embodiments, the basicity modifier includes at least one of silica, quartz sand, and waste glass.

[0045] Compared with metal-containing modifiers such as iron and aluminum, the silicon-based basicity modifier used in the present invention is more conducive to the enrichment of chromium in the spinel phase because metal ions in metal-containing modifiers such as iron and aluminum will seize the positions of chromium ions in the spinel, which is not conducive to the enrichment of chromium in the spinel phase. Moreover, the chromium-containing spinel obtained by this method does not require magnetic separation, and the operation is simpler.

[0046] In some specific embodiments, in the basicity modifier, by mass percentage, SiO2≥90%, including but not limited to any point value among 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or the range value between any two of them.

[0047] In some specific embodiments, the addition amount of the basicity modifier is such that the mass ratio of CaO to SiO2 in the mixed material is 1 to 1.2, including but not limited to any point value among 1, 1.01, 1.05, 1.1, 1.15, 1.2 or the range value between any two of them.

[0048] In some specific embodiments, during the reaction process, heat preservation is carried out at a temperature of ≥1500°C; including but not limited to any point value among 1500°C, 1530°C, 1550°C, 1580°C, 1600°C, 1630°C or the range value between any two of them.

[0049] In some specific embodiments, the heat preservation time is 30 to 120 min, including but not limited to any point value among 30 min, 40 min, 50 min, 60 min, 80 min, 90 min, 100 min, 120 min or the range value between any two of them. It can be understood that the heat preservation time here is the reaction time.

[0050] By controlling the addition amount of the basicity modifier and the heat preservation conditions within the above ranges, the chromium in the slag obtained after modification can be promoted to enter the spinel phase and precipitate in the form of a solid at the bottom of the refining equipment under the action of gravity.

[0051] In some specific embodiments, the first cooling method includes water quenching and cooling.

[0052] In some specific embodiments, the volume ratio of the water used for water quenching to the liquid dechromized slag is ≥100:1, including but not limited to any point value among 100:1, 110:1, 120:1, 130:1, 150:1, 200:1, 250:1, 300:1 or the range value between any two of them.

[0053] In some specific embodiments, the water used for water quenching is recycled.

[0054] In some specific embodiments, the method of the second cooling includes natural cooling.

[0055] In some specific embodiments, the natural cooling is to open / unscrew the bottom of the refining equipment and then cool naturally to room temperature in an air atmosphere.

[0056] In some specific embodiments, the molten chromium-containing stainless steel slag liquid includes the following components by mass percentage: CaO 40% - 50%, SiO2 30% - 35%, MgO 4% - 5%, Cr2O3 4% - 10%, Al2O3 2% - 4%, Fe2O3 1% - 5% and MnO 1% - 2%.

[0057] In some specific embodiments, the total chromium leaching concentration of the chromium-containing spinel < 0.45 mg / L; including but not limited to the point value of any one of 0.445 mg / L, 0.4 mg / L, 0.3 mg / L, 0.2 mg / L, 0.185 mg / L, 0.18 mg / L, 0.15 mg / L, 0.1 mg / L, 0.05 mg / L or the range value between any two of them.

[0058] In some specific embodiments, the total chromium leaching concentration of the vitreous silicate < 0.12 mg / L, including but not limited to the point value of any one of 0.116 mg / L, 0.11 mg / L, 0.1 mg / L, 0.08 mg / L, 0.07 mg / L, 0.05 mg / L, 0.03 mg / L, 0.01 mg / L or the range value between any two of them.

[0059] In some specific embodiments, the addition of the basicity modifier and the reaction are carried out in a non-oxygen atmosphere, and the non-oxygen atmosphere refers to an atmosphere without oxygen; specifically, the non-oxygen atmosphere can be achieved by blowing argon into the bottom of the refining equipment. The pressure of argon can be, for example, 0.2 - 0.4 MPa, and the flow rate of argon can be, for example, 200 - 400 L / min, but not limited to this.

[0060] In some specific embodiments, during the addition of the basicity modifier and the reaction, the mixed materials are stirred.

[0061] In the second aspect, the present invention provides the applications of the chromium-containing spinel and the vitreous silicate obtained by the method for selectively precipitating and separating chromium in industrial stainless steel slag in the preparation of refractory materials and the preparation of building materials respectively.

[0062] The chromium-containing spinel obtained by the above method can be used to prepare refractory materials, and the vitreous silicate can be used to prepare building materials, reducing the production costs of refractory materials and building materials.

[0063] As an example, the refractory materials include lining bricks for cement rotary kilns, high-temperature resistant materials for ladle refining, etc., but are not limited thereto.

[0064] As an example, the building materials include cement, concrete aggregates, geopolymers, etc., but are not limited thereto.

[0065] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0066] Example 1

[0067] The industrial stainless steel slag provided in this example is composed of the following components by mass percentage: CaO 53.25%, SiO2 30.53%, MgO 4.24%, Cr2O3 4.73%, Al2O3 2.32%, Fe2O3 3.62% and MnO 1.31%.

[0068] For the method for selective precipitation and separation of chromium in the industrial stainless steel slag provided in this example, refer to Figure 1 As shown, it includes the following steps: Pour the molten chromium-containing stainless steel slag liquid into an induction furnace, and add silica (with a SiO2 content of 96 wt.%) as an alkalinity modifier thereto, so that the mass ratio w(CaO) / w(SiO2) = 1.2. Stir and mix by blowing argon into the bottom of the induction furnace. Keep the modified slag at 1550 °C for heat preservation, maintain the molten state of the modified slag, heat preserve and react for 120 min, so that the chromium element in the modified slag enters the spinel phase and precipitates to the bottom of the induction furnace in a solid state to form a chromium-rich slag. Discharge the liquid chromium-depleted slag in the upper part of the induction furnace from the slag discharge port of the induction furnace, and perform water quenching and rapid cooling on it (pour the discharged liquid chromium-depleted slag into a water quenching tank with a fixed volume ratio of normal temperature water). The volume ratio of the water used for water quenching to the liquid chromium-depleted slag is 120:1 to obtain a vitreous silicate. Unscrew the bottom of the induction furnace, and naturally cool the remaining solid chromium-rich slag to room temperature in an air atmosphere to obtain chromium-containing spinel.

[0069] Perform X-ray diffraction and scanning electron microscope analyses on the vitreous silicate and chromium-containing spinel prepared in this example respectively. The results are as Figure 2 and Figure 3 shown. From Figure 2 and Figure 3 it can be seen that the vitreous silicate is an amorphous glassy state, and the main crystal phase of the chromium-containing spinel is spinel.

[0070] Example 2

[0071] The chemical components of the industrial stainless steel slag provided in this example are the same as those in Example 1. The method for selectively precipitating and separating chromium in the industrial stainless steel slag provided in this example includes the following steps: Pour the molten chromium-containing stainless steel slag liquid into a ladle furnace, and add quartz sand with a basicity modifier (where the SiO2 content is 98 wt.%) thereto, so that the mass ratio of CaO to SiO2, w(CaO) / w(SiO2)=1.1. Stir and mix by blowing argon into the bottom of the ladle furnace. Keep the modified slag at 1600°C for heat preservation, maintain the molten state of the modified slag, keep it warm and react for 60 minutes, so that the chromium element in the modified slag enters the spinel phase and precipitates to the bottom of the ladle furnace in a solid state, forming a chromium-rich slag. Discharge the liquid chromium-removed slag in the upper part of the ladle furnace from the slag discharge port of the ladle furnace, and perform water quenching and rapid cooling on it (pour the discharged liquid chromium-removed slag into a water quenching tank with normal temperature water having a fixed volume ratio). The volume ratio of the water used for water quenching to the liquid chromium-removed slag is 100:1 to obtain a vitreous silicate. Open the bottom of the ladle furnace, and naturally cool the remaining solid chromium-rich slag to room temperature in an air atmosphere to obtain chromium-containing spinel.

[0072] Example 3

[0073] The chemical components of the industrial stainless steel slag provided in this example are the same as those in Example 1. The method for selectively precipitating and separating chromium in the industrial stainless steel slag provided in this example includes the following steps: Pour the molten chromium-containing stainless steel slag liquid into an induction furnace, and add waste glass with a basicity modifier (where the SiO2 content is 90 wt.%) thereto, so that the mass ratio of CaO to SiO2, w(CaO) / w(SiO2)=1. Stir and mix by blowing argon into the bottom of the induction furnace. Keep the modified slag at 1500°C for heat preservation, maintain the molten state of the modified slag, keep it warm and react for 90 minutes, so that the chromium element in the modified slag enters the spinel phase and precipitates to the bottom of the induction furnace in a solid state, forming a chromium-rich slag. Discharge the liquid chromium-removed slag in the upper part of the induction furnace from the slag discharge port of the induction furnace, and perform water quenching and rapid cooling on it (pour the discharged liquid chromium-removed slag into a water quenching tank with normal temperature water having a fixed volume ratio). The volume ratio of the water used for water quenching to the liquid chromium-removed slag is 110:1 to obtain a vitreous silicate. Open the bottom of the induction furnace, and naturally cool the remaining solid chromium-rich slag to room temperature in an air atmosphere to obtain chromium-containing spinel.

[0074] Example 4

[0075] The industrial stainless steel slag provided in this example is composed of the following components by mass percentage: CaO 54.03%, SiO2 30.25%, MgO 4.76%, Cr2O3 4.35%, Al2O3 3.39%, Fe2O3 1.27% and MnO 1.95%.

[0076] The method for selective precipitation and separation of chromium in industrial stainless steel slag provided in this embodiment is the same as that in Embodiment 1.

[0077] Embodiment 5

[0078] The industrial stainless steel slag provided in this embodiment is composed of the following components by mass percentage: CaO 53.92%, SiO2 30.03%, MgO 4.75%, Cr2O3 4.34%, Al2O3 3.75%, Fe2O3 1.94%, and MnO 1.27%.

[0079] The method for selective precipitation and separation of chromium in industrial stainless steel slag provided in this embodiment is the same as that in Embodiment 1.

[0080] Comparative Example 1

[0081] The chemical components of the industrial stainless steel slag provided in this comparative example are the same as those in Embodiment 1. The method for selective precipitation and separation of chromium in the industrial stainless steel slag provided in this comparative example is basically the same as that in Embodiment 1, except that the modified slag to be mixed is kept at 1400 °C for 120 min.

[0082] The vitreous silicate and chromium-containing spinel prepared in this comparative example were respectively analyzed by X-ray diffraction and scanning electron microscopy, and the results are as Figure 4 and Figure 5 shown. It can be analyzed that the precipitation product remaining at the bottom of the induction furnace obtained in this comparative example is mainly chromium-containing spinel phase; the liquid slag discharge product mainly presents as a vitreous amorphous phase, and there are some spinel phases, indicating that the holding temperature is too low, and at this temperature, other microcrystalline phases nucleate and precipitate, making the spinel phase unable to settle completely, resulting in some spinel phases still remaining in the glass phase, causing incomplete separation of the obtained product and failing to achieve the purpose of selective separation and recovery of chromium in chromium-containing stainless steel slag.

[0083] Comparative Example 2

[0084] The chemical components of the industrial stainless steel slag provided in this comparative example are the same as those in Embodiment 1. The method for selective precipitation and separation of chromium in the industrial stainless steel slag provided in this comparative example is basically the same as that in Embodiment 1, except that the basicity modifier silica is not added. During the holding process, various crystal phases precipitate in the stainless steel slag, and the spinel crystals formed during holding cannot precipitate, and the melt cannot achieve solid-liquid separation. All the molten slag was naturally cooled to room temperature in the induction furnace to obtain a product that could not be separated.

[0085] The unseparable product prepared in this comparative example was analyzed by X-ray diffraction and scanning electron microscopy, and the results are as Figure 6 and Figure 7 shown. From Figure 6 and Figure 7It can be seen that the product finally generated under this condition is a mixture of spinel phase and (Ca,Mg)2SiO4 phase. The function of the basicity modifier is to regulate the phase equilibrium change of the slag system, making the spinel phase the only high-temperature precipitation phase, so as to promote the entry of chromium elements into the spinel, enabling the spinel crystals to nucleate and precipitate separately in the melt. Therefore, it is impossible to selectively separate and obtain vitreous silicate and chromium-containing spinel without adding the basicity modifier.

[0086] Comparative Example 3

[0087] The chemical components of the industrial stainless steel slag provided in this comparative example are the same as those in Example 1. The method for selective precipitation and separation of chromium in the industrial stainless steel slag provided in this comparative example is basically the same as that in Example 1, except that the basicity modifier silica is replaced with an equal mass of ferric oxide.

[0088] Total chromium leaching concentration test in experimental examples

[0089] The total chromium leaching concentrations of the untreated industrial stainless steel slag in Example 1, the vitreous silicate, chromium-containing spinel and inseparable products prepared in each example and each comparative example were detected respectively, and the results are as Figure 8 shown. Among them, the test method for the total chromium leaching concentration refers to GB 5085.3-2007.

[0090] It can be seen from Figure 8 that the total chromium leaching concentrations of the vitreous silicate and chromium-containing spinel separated and recovered by the method provided by the present invention are significantly lower than those of the chromium-containing stainless steel slag before treatment, which indicates that the method provided by the present invention can effectively fix and precipitate and selectively separate chromium in the chromium-containing stainless steel slag, making it meet the comprehensive utilization standard HJ / T 301-2007 of chromium-containing solid waste, so as to realize the high-value utilization of chromium-containing solid waste.

[0091] Furthermore, by comparing the total chromium leaching concentrations of Example 1 and Comparative Example 1, it can be seen that too low holding temperature will affect the entry of chromium into the spinel phase, and at the same time cause incomplete precipitation of the spinel phase, incomplete solid-liquid separation of the obtained product, and the chromium remaining in the glass phase ultimately leads to an increase in the total chromium leaching concentration.

[0092] By comparing the total chromium leaching concentrations of Example 1 and Comparative Example 2, it can be seen that the stainless steel slag without adding the basicity modifier has more high-temperature precipitation phases, resulting in the spinel phase in the slag not being able to exist alone within the predetermined holding temperature range, so that chromium cannot completely enter the spinel phase, and at the same time, solid-liquid separation cannot be further carried out, ultimately resulting in a higher total chromium leaching concentration.

[0093] By comparing the total chromium leaching concentrations of Example 1 and Comparative Example 3, it can be seen that compared with metal-based modifiers, the silicon-based basicity modifier used in the present invention is more conducive to the enrichment of chromium elements in the spinel phase.

[0094] Although the present invention has been illustrated and described with reference to specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it; those of ordinary skill in the art should understand that without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention; therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for selectively precipitating and separating chromium from industrial stainless steel slag, characterized in that, It includes the following steps: Adding the molten chromium-containing stainless steel slag generated in the stainless steel production process into a refining device, where the refining device includes a ladle furnace and / or an induction furnace, adding an alkalinity modifier to react in the refining device, so that chromium elements enter the spinel phase and precipitate in a solid state to the bottom of the refining device to form chromium-rich slag; After discharging the liquid chromium-removed slag above the chromium-rich slag through the slag discharge port of the refining device, performing a first cooling to obtain vitreous silicate; After discharging the chromium-rich slag from the bottom of the refining device, performing a second cooling to obtain chromium-containing spinel; During the reaction process, heat preservation is carried out at a temperature of ≥1500 °C; The method of the first cooling includes water quenching cooling; In the alkalinity modifier, by mass percentage, SiO2≥90%; The addition amount of the alkalinity modifier is such that the mass ratio of CaO to SiO2 in the mixed materials is 1 to 1.

2.

2. The method for selective precipitation separation of chromium in industrial stainless steel slag according to claim 1, wherein The alkalinity modifier includes at least one of silica, quartz sand, and waste glass.

3. The method for selective precipitation and separation of chromium in industrial stainless steel slag according to claim 1, characterized in that, The heat preservation time is 30 to 120 min.

4. The method for selective precipitation and separation of chromium in industrial stainless steel slag according to claim 1, wherein The method of the second cooling includes natural cooling.

5. The method for selective precipitation and separation of chromium in industrial stainless steel slag according to claim 1, characterized in that The molten chromium-containing stainless steel slag liquid includes the following components by mass percentage: CaO 40% - 50%, SiO2 30% - 35%, MgO 4% - 5%, Cr2O3 4% - 10%, Al2O3 2% - 4%, Fe2O3 1% - 5%, and MnO 1% - 2%.

6. The method for selective precipitation and separation of chromium in industrial stainless steel slag according to claim 1, characterized in that, The total chromium leaching concentration of the chromium-containing spinel < 0.45 mg / L; And / or, the total chromium leaching concentration of the vitreous silicate < 0.12 mg / L.

7. Applications of the chromium-containing spinel and vitreous silicate obtained by the method for selective precipitation and separation of chromium in industrial stainless steel slag according to any one of claims 1 to 6 in the preparation of refractory materials and the preparation of building materials respectively.

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