Synergistic modification treatment method for metallurgical slag

Abstract

The invention discloses a metallurgical slag synergistic modification treatment method, which belongs to the field of solid waste treatment, and comprises the following steps: mixing liquid blast furnace slag and liquid steel slag according to a ratio of (1.5-2.5): 1, carrying out an oxidation-reduction reaction on carbon and sulfide reducing substances in the blast furnace slag and iron oxide in the steel slag, and carrying out natural sinking and floating separation, the mixed slag tends to be layered from top to bottom according to different densities, and sequentially comprises calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium ferrite and molten iron from top to bottom; part of dicalcium silicate and slag above are poured into a slag tank to be subjected to slag flushing treatment, the rest dicalcium silicate, tricalcium silicate, calcium ferrite and molten iron are conveyed to a converter to be smelted, dicalcium silicate, tricalcium silicate and calcium ferrite serve as slag formers for dephosphorization and desiliconization of the converter, and dephosphorization and desiliconization in the earlier stage of converter smelting are promoted. The two kinds of slag are subjected to cooperative treatment, the reduction characteristic of the blast furnace slag is utilized, steel slag metal elements are fully recycled, and all slag components are recycled and reasonably utilized in a high-value mode.

Description

Technical Field

[0001] The invention belongs to the field of solid waste treatment, and in particular relates to a method for synergistic modification of steel slag and blast furnace slag. Background Art

[0002] my country is the largest steel producer, with an annual steel output of over 1 billion tons, and nearly 100 million tons of steel slag. Steel slag has high basicity and high viscosity, and contains a large amount of free iron and divalent and trivalent iron oxides, which are very difficult to crush and separate, resulting in a waste of valuable resources and difficulties in the utilization of tailings. In addition, blast furnace slag contains a large amount of reducing substances such as free carbon and sulfides. At the same time, the calcium content of blast furnace slag is very low, which affects the quality of cement when used for cement clinker, and is not a mineral phase favored by the cement industry. In order to solve the above problems, the present invention discloses a synergistic modification treatment method of two slags. Summary of the invention

[0003] According to Archimedes' principle, in a molten liquid, when the gravity of a substance is greater than the buoyancy of the surrounding substances, the substance will sink as long as it overcomes the adhesion of the surrounding substances; conversely, if the gravity of a substance is less than the buoyancy of the surrounding substances, the substance will float as long as it overcomes the adhesion of the surrounding substances. It can be seen that the viscosity of the mixed slag is the determining factor for the sinking and floating separation of various substances.

[0004] Liquid blast furnace slag is mixed with liquid steel slag, and the reducing substances such as carbon and sulfide in the blast furnace slag undergo redox reactions with the iron oxides in the steel slag, reducing part of the iron oxides in the steel slag to a high-density metallic state. As long as the viscosity of the slag is reduced to an appropriate level, the metallic iron will gradually sink to the bottom of the slag. The free metal particles carried in the steel slag also sink to the bottom of the furnace. At the same time, the basicity of blast furnace slag is relatively low, generally around 1.1, while the basicity of steel slag is relatively high. Depending on the phosphorus and sulfur content of the molten iron and the type of steel being smelted, the basicity of the final steel slag will vary, usually in the range of 2.5 to 6; the temperature of blast furnace slag is usually between 1400℃ and 1530℃, and the temperature of steel slag is between 1550℃ and 1680℃. The temperature of steel slag with high basicity must be high, and the iron oxides in the slag must also be high. Usually, the amount of blast furnace slag in steel joint enterprises is about twice that of steel slag. If blast furnace slag and steel slag are mixed at a ratio of 2:1, the basicity of the mixed slag is between 1.5 and 2.7, which is moderate. The iron oxide in the steel slag is relatively high. The increase in the phase of molten slag after mixing will reduce the melting point of the molten slag. In addition, the reaction exothermic temperature rise will make the viscosity of the mixed slag lower than that of steel slag, and the fluidity will be better. The mixing ratio of blast furnace slag and steel slag depends on the output ratio of the two slags of the enterprise. When low-grade ore is used for blast furnace smelting, the output of blast furnace slag will be large. When fine materials are used for smelting, the output of blast furnace slag will be less. The output of converter slag is related to the quality of molten iron and the type of steel smelted. The mixing ratio of the two slags is based on the actual output ratio of the two slags. Generally, the ratio of blast furnace slag to steel slag is (1.5-2.5):1. Practice has shown that the viscosity of the mixed slag will be significantly lower than that of steel slag, and is close to the viscosity of blast furnace slag. After mixing, the slag is kept warm and placed still. Under the action of gravity and buoyancy, the material with low density floats upward under the action of buoyancy, and the material with high density sinks downward, gradually forming a natural stratification. The stratification speed mainly depends on the slag viscosity. If the melt vibration is increased, the sinking and floating separation speed will be promoted. Therefore, the present invention adds a micro-vibration scheme for the slag pot. However, this scheme increases the difficulty of equipment manufacturing and the life of the slag pot will be affected to some extent.

[0005] After a certain period of natural sinking and floating separation, the high-density substances sink to the bottom, and the low-density substances float to the top. After mixing, the slag will tend to be layered from top to bottom according to different densities, from top to bottom, calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium ferrite, and molten iron. The lower layer is more obvious, and the molten iron and iron compounds basically sink to the lower part. The upper layer is relatively poor, and the calcium phosphate and calcium silicate layers are not very obvious, but the overall trend is that there is basically no calcium phosphate in the lower part, and there is basically no iron compound in the upper part, and the middle part is basically dicalcium silicate and tricalcium silicate.

[0006] Since the amount of dicalcium silicate in the mixed slag is relatively large, it can be used as both water slag flushing and slag-making agent for smelting. According to the production needs of the enterprise, part of the dicalcium silicate and above slag can be poured into the slag pot for slag flushing treatment, and the remaining dicalcium silicate, tricalcium silicate, calcium ferrite and molten iron can be sent to the converter for smelting. Dicalcium silicate, tricalcium silicate and calcium ferrite are all slag-making agents for converter dephosphorization and desiliconization. Adding these liquid slags to the converter can promote dephosphorization and desiliconization in the early stage of converter smelting.

[0007] In order to ensure that the temperature and viscosity of the mixed slag can meet the conditions for slag sinking and floating separation, the following should be noted in the slag discharge process and related equipment preparation of the two slags:

[0008] After the converter taps out steel, except for some slag left as slag splashing and furnace protection, the rest of the slag and residual molten steel are all poured into the insulation slag pot, covered and insulated, and sent to the mixed slag treatment site. Do not pour the slag splashing and furnace protection slag into the insulation slag pot.

[0009] At the blast furnace iron-tapping site, the slag ditch insulation is started from the slag retainer. The length of the iron-tapping ditch can be shortened as much as possible to reduce the cooling of blast furnace slag. The blast furnace slag is discharged into the insulation slag pot. After the slag is discharged, it is covered and insulated and sent to the mixed slag treatment site.

[0010] A tilting slag mixing tank is set up at the slag mixing site. Generally, the design volume of the slag mixing tank is relatively large. For example, the volume of the slag mixing tank is more than 4 times that of the blast furnace slag tank. The blast furnace slag of a general steel joint enterprise is twice the steel slag. For ease of operation, two tanks of blast furnace slag are first poured into the tilting slag mixing tank each time, and then one tank of blast furnace slag is poured into the steel slag. Since blast furnace slag contains reducing substances such as carbon powder and sulfide, and steel slag contains a large amount of oxidizing substances, when the two slags are mixed together, an oxidation-reduction reaction will occur, gas will be generated, and splashing is easy to occur. Therefore, when pouring steel slag, it needs to be poured slowly, which is also the reason why the slag mixing tank is designed to be larger. After the slag mixing is completed, the slag mixing tank is covered with a cover for insulation.

[0011] If the slag temperature is low after mixing, the slag fluidity becomes worse, that is, the slag viscosity increases, which is not conducive to sinking and floating separation. Therefore, a medium frequency furnace heating method is used, or an oxygen-burning gun is used to heat the slag to appropriately supplement heat, reduce the slag viscosity, and improve the fluidity of the mixed slag.

[0012] After mixing the slag, let it stand for 25 to 50 minutes. Further, the vibration facilities of the slag mixing tank can be added to speed up the sinking and floating speed and shorten the sinking and floating time. The sinking and floating speed will also be faster if the slag viscosity is low. The specific time needs to be determined by practical exploration. After natural sinking and floating, the slag will be naturally layered according to different densities. According to the composition and needs, it is dumped and separated. The upper calcium phosphate, calcium silicate, and part of the dicalcium silicate slag are sent to the slag flushing place for treatment. The lower part of the dicalcium silicate, tricalcium silicate, calcium ferrite slag and molten iron are poured into the molten iron tank. After the iron is tapped, it is sent to steelmaking with the molten iron for use. This treatment not only reduces the logistics cost, but also avoids the low temperature of the treated slag and iron, which causes sticking to the tank. At the same time, during the iron tapping process, the molten iron reacts with the treated mixed slag, and the calcium ferrite in the slag reacts with the phosphorus and silicon in the molten iron, which plays a role in pre-dephosphorization and pre-desiliconization. When adding molten iron to the converter, the slag and iron are mixed and flushed, and pre-dephosphorization and pre-desiliconization reactions occur again. When adding auxiliary materials and smelting, the influence of slag on smelting should be considered to reduce the amount of slag-making agent added and shorten the smelting time. Information feedback should be provided during the transportation of molten iron. Dicalcium silicate can be used for water slag flushing or as a slag-making agent. The destination depends on the smelting needs and is determined by the operator.

[0013] The blast furnace slag of the present invention is a silicate and aluminate composed of CaO, MgO, Al2O3, SiO2, MnO, FeO and the like. CaO, SiO2, Al2O3 and MgO are the main components of blast furnace slag, which account for more than 95% of the blast furnace slag. Since the blast furnace slag comes from a strong reducing environment, it contains a variety of reducing substances, such as sulfide, unburned carbon powder from coal injection, and a small amount of coke particles. Due to the different ore grades and the types of smelting pig iron, the chemical composition of blast furnace slag varies greatly. The main component contents are: CaO 31-50%, SiO2 31-44%, Al2O3 5-18%, MgO 2-16%, FeO 1.2-2%, and MnO 0.3-1.2%.

[0014] The main chemical components of the converter slag described in the present invention are: T.Fe 12-30%, CaO 30-60%, SiO 8-20%, MgO 5-12%, and the basicity is between 2.5 and 6. Due to the different molten iron components, different amounts of scrap steel added, different smelting steel types, different furnace service life and different slag making materials, the slag components fluctuate greatly and the slag temperature also varies greatly. Usually the slag temperature is between 1550°C and 1680°C. The main mineral phases are tricalcium silicate (C3S), dicalcium silicate (C2S), calcium iron olivine, free calcium oxide (f-CaO), free magnesium oxide, etc. Due to the high content of harmful components such as free calcium oxide (f-CaO) and free MgO, the steel slag after cooling treatment contains a large amount of f-CaO and free MgO with coarse crystals and dense structure. These f-CaO and free MgO will continue to hydrate and expand in volume for a long time after coming into contact with water, resulting in extremely poor long-term stability of the steel slag during utilization, which seriously restricts the safe utilization of steel slag.

[0015] Liquid blast furnace slag and steel slag are mixed in a ratio of (1.5-2.5):1. The reducing substance reacts with the oxidizing substance to release heat and produce micro-stirring. Free calcium oxide, free magnesium oxide and metastable tricalcium silicate react with calcium silicate to generate stable dicalcium silicate and magnesium silicate, thereby eliminating free calcium oxide and free magnesium oxide that cause high viscosity of the steel slag, reducing the viscosity of the mixed slag, improving fluidity, and facilitating the sinking and floating separation of phases in the slag.

[0016] The viscosity of the mixed slag is the most important factor that determines the effect of slag sinking and floating separation. Therefore, blast furnace slag and steel slag must be well insulated and dispatched during the slag discharge, transportation and treatment process to avoid the slag waiting for a long time, reduce the process cooling, and ensure low viscosity during the slag sedimentation process. If the slag viscosity is high, it needs to be heated.

[0017] In order to promote the separation of sinking and floating, the slag mixing tank can be slightly vibrated. A vibration table is added to the bottom of the slag mixing tank. The vibration table is equipped with a hydraulic lifting device. The vibration table first lifts the slag mixing tank to a state where it is separated from the driving device to avoid damage to the driving equipment when the slag mixing tank vibrates.

[0018] Beneficial effects of the present invention:

[0019] (1) The energy consumption of the synergistic modification process of steel slag and blast furnace slag is low;

[0020] (2) The two slags are processed in a coordinated manner, the reducing properties of blast furnace slag are utilized, and the metal elements of steel slag are fully recovered and utilized;

[0021] (3) Through collaborative treatment, the performance of water slag is improved, and hydrogen sulfide is no longer emitted during the slag flushing process;

[0022] (4) The discharge of wastewater and waste gas during the slag treatment process is avoided, and no tailings are generated. All slag components are fully resourced and reasonably utilized with high value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Process flow chart of the collaborative modification treatment method of steel slag and blast furnace slag of the present invention. DETAILED DESCRIPTION

[0024] A slag treatment workshop is set up near the blast furnace of the iron plant. According to the amount of slag to be treated and the treatment cycle, several tiltable slag mixing tanks are set up. The tiltable slag mixing tank body is insulated and equipped with an insulation cover. The insulation cover is equipped with an oxygen-fueled lance or a stirring lance blowing hole and a smoke exhaust port. A high-flow oxygen-fueled top lance or a stirring lance is set on the top. A mechanical stirrer can also be used. Stirring with a stirrer needs to be stirred before covering. An induced draft hood is set above the smoke exhaust port to cool the flue gas by letting in a certain amount of cold air. A dust collector is set behind the induced draft hood, and a frequency-modulated induced draft fan is set at the rear of the dust collector. The oxygen-fueled lance can heat the mixed slag with oxygen gas and stir it at the same time, or it can spray nitrogen or compressed air to stir the slag. The oxygen-fueled lance has both heating and stirring functions. A bottom medium-frequency heating device can also be set up to heat the upper slag by heating the bottom molten iron, and to supplement the slag with heat when the slag temperature is low. When medium-frequency heating is required, some molten iron should be left at the bottom of the tiltable slag mixing tank. The medium-frequency heating process also has a certain stirring effect. By stirring, the steel slag and blast furnace slag can be fully mixed and reacted, which promotes the subsequent sinking and floating separation. Choose between oxygen-burning gun heating and medium-frequency heating.

[0025] Process flow such as Figure 1 As shown, after the slag is loaded into the steel slag tank and the blast furnace slag tank, they are transported to the tiltable mixing slag tank respectively. Both the steel slag tank and the blast furnace slag tank are insulated and covered. Blast furnace slag is added first, and then steel slag is added. There will be a reaction when the steel slag is added, and it is added gradually to avoid splashing. Therefore, the tiltable mixing slag tank needs to be made larger to avoid slag overflow. In the present invention, the volume of the tiltable mixing slag tank is 2 to 4 times the volume of the blast furnace slag tank. After adding the steel slag, determine whether heat needs to be supplemented based on the fluidity of the slag after mixing. If the fluidity is very good and no heat is needed, an oxygen-combustion gun can be used to spray nitrogen or compressed air for a short time of stirring. If the fluidity is poor, the oxygen-combustion gun can be started to supplement heat. Bottom medium-frequency induction heating can also be used. The top oxygen-combustion gun has a stirring function when spraying to supplement heat, and the stirring procedure can be omitted.

[0026] The number of tiltable slag mixing tanks needs to be determined based on the amount of slag to be processed and the processing cycle, and spare equipment should be reserved.

[0027] After the tilting slag mixing tank is temperature-controlled and stirred, it is left to sink and float for 25 to 50 minutes, and then the slag is dumped. If the top high-phosphorus slag is used as a phosphate fertilizer base material, the top calcium phosphate slag is poured out first. The slag amount needs to be actually tested or calculated based on theory. The slag amount can be calculated after accumulating certain data. If it is not used as a phosphate fertilizer base material, it can be discharged together with the calcium silicate and part of the dicalcium silicate in the middle, and sent to the slag flushing equipment for water quenching. The remaining dicalcium silicate, tricalcium silicate, calcium ferrite and molten iron in the lower part are poured into the molten iron tank together, and after the iron is discharged, it is sent to the converter for smelting together with the molten iron. Dicalcium silicate, tricalcium silicate and calcium ferrite all have the effect of promoting slag formation in the early stage of the converter, and have both the effect of promoting dephosphorization and the effect of promoting desiliconization. The amount of slag discharged in the early stage needs to be tested according to actual conditions. After data accumulation, the amount of slag discharged from the upper part can be calculated based on experience. Dicalcium silicate can be sent to slag flushing or poured into the molten iron tank to be smelted in the converter with the molten iron. Its amount is also relatively large. It is relatively easy to operate with it as the boundary. The on-site staff controls the proportion of slag discharged based on experience and smelting needs.

[0028] The temperature of blast furnace slag is generally between 1400℃ and 1530℃. When discharging the slag, the shortest process is used and the slag ditch is covered and insulated, and then it flows into the insulated slag pot. After the slag is discharged, the slag pot is covered and insulated, and then sent to the mixed slag processing workshop to wait for mixed slag processing.

[0029] The tapping temperature of converter smelting is generally between 1550℃ and 1680℃. After tapping, the remaining molten steel and slag are discharged into the insulation slag pot, leaving part of the slag as splashing slag to protect the furnace. Do not pour the splashing slag into the slag pot.

[0030] After covering, it is sent to the slag treatment workshop.

[0031] It is recommended to set up a slag mixing workshop in the iron and steel plant. First, the amount of blast furnace slag is large, which can reduce transportation costs; second, the slag iron sent to the converter for smelting after slag mixing treatment can be added to the molten iron tank and returned to the converter steelmaking workshop with the molten iron, which not only reduces transportation costs, but also avoids the low slag temperature and stickiness to the tank after treatment.

[0032] Example 1

[0033] A certain steel company produces 2,500 tons of blast furnace slag and 1,250 tons of steel slag every day. The method of the present invention is used for steel slag treatment and blast furnace slag modification. The tilting slag mixing tank is set next to the blast furnace of the ironmaking plant. There are 6 tilting slag mixing tanks, 5 for use and 1 for standby. Each tilting slag mixing tank can hold 100 tons of slag. It is equipped with a high-speed oxygen-burning gun for heating and connected to a compressed air pipe for stirring with compressed air. A lifting and lowering vibration platform is set at the bottom of the tilting slag mixing tank. Before the vibration platform works, the tilting slag mixing tank is lifted up and separated from the drive system. The slight vibration of the vibration platform promotes the separation of slag from sinking and floating. The blast furnace slag tank and the steel slag tank are designed to hold 25 tons. The blast furnace slag ditch has been modified, and the slag ditch has been covered and insulated, and it flows directly into the insulated slag tank. The slag tank has been covered and insulated; after the converter smelts steel, the steel slag and residual steel are directly discharged into the insulated steel slag tank, and part of the steel slag is reserved for slag splashing to protect the furnace. After the slag splashing to protect the furnace, no slag is discharged. After the slag is discharged, the slag tank is covered and sent to the slag mixing treatment area to wait for slag mixing.

[0034] First, add blast furnace slag into the tiltable slag mixing pot, and then gradually add steel slag. The ratio of blast furnace slag to steel slag is 2:1 (50 tons: 25 tons). A liftable guide plate is set above the tiltable slag mixing pot. When adding steel slag, the slag is impacted in the tangential direction of the steel slag to make the lower slag rotate and flow, promoting slag mixing. After adding slag, determine whether to heat it according to the slag temperature and fluidity. If the slag viscosity is large, use an oxygen-burning gun to heat and stir. If the slag fluidity is very good, use compressed air to stir. When stirring, the cooling factor should be considered, which is generally controlled within 1 minute. After stirring, it will naturally sink and float and separate. Let it stand for 25 to 35 minutes. According to the slag temperature, if the standing time is too long, the slag will cool too much, which will affect the fluidity during water quenching. After a period of testing and exploration, the slag pouring ratio was determined. Each time, about two-thirds of the slag is poured out for water flushing, and the remaining one-third is poured into the molten iron tank. After the iron is tapped, it is sent to the converter for smelting with the molten iron. The use of calcium phosphate alone was not considered. The consumption of converter smelting lime is reduced by 15 kg / ton iron, and the dephosphorization effect in the early stage is significantly improved. After two months of operation, about 400 tons of molten iron can be recovered every day, about 1,000 tons of calcium ferrite and dicalcium silicate slag-making agents can be recovered, and about 2,300 tons of water-quenched slag can be delivered every day. The economic benefits are significant.

[0035] Example 2

[0036] A steel company produces 3,700 tons of blast furnace slag and 1,800 tons of steel slag every day. The steel slag was originally heated and then crushed and magnetically separated. After the magnetic separation, the tailings were ultra-finely ground and powdered and sold to cement plants. After the new building materials standards were introduced, the ultra-fine powder could not be sold directly, and the method of the present invention was used to carry out the coordinated modification of steel slag and blast furnace slag. The mixed slag treatment workshop is located next to the blast furnace of the ironmaking plant. There are 8 tiltable mixed slag tanks, 7 for use and 1 for standby. Each tiltable mixed slag tank can hold 100 tons of slag. The blast furnace slag tank and the steel slag tank can hold 25 tons of slag. The bottom of the tiltable mixed slag tank is equipped with medium-frequency induction heating, and the upper part of the tiltable mixed slag tank is equipped with a liftable guide inclined plate. When adding steel slag, the liftable guide inclined plate is used for diversion, and the lower slag is impacted in the tangential direction, so that the steel slag and blast furnace slag are fully mixed to promote reaction and homogenization. The top of the tiltable slag mixing tank is equipped with a heat preservation cover, and a compressed air stirring gun hole is provided in the middle. A compressed air stirring gun is provided on the top of the tiltable slag mixing tank. After adding the steel slag, the heat preservation cover is added, and then the compressed air stirring gun is lowered to stir the slag to promote slag mixing. The stirring time is controlled within 1 minute.

[0037] The blast furnace slag ditch has been modified, and it flows directly into the slag pot 2 meters after flowing out of the slag retainer. The slag ditch has been covered for insulation, and the slag pot has been covered for insulation. After the slag is discharged, it is sent to the mixed slag processing workshop.

[0038] After the converter smelts steel, the slag is directly discharged into the heat-insulating slag tank, and part of the slag is reserved for slag splashing to protect the furnace. After the slag splashing to protect the furnace, no slag is discharged, and the slag tank is covered for heat preservation. The slag tank is transported to the mixed slag processing workshop.

[0039] First, add blast furnace slag into the tiltable slag mixing tank, and then add steel slag. The ratio of blast furnace slag to steel slag is 2:1 (50 tons: 25 tons), that is, add 2 cans of blast furnace slag into the tiltable slag mixing tank each time, and then add 1 can of steel slag. When adding steel slag, a lifting and lowering guide inclined plate is set. The steel slag is guided by the inclined plate, impacting the tangential direction of the lower slag, so that the lower slag produces a swirl flow, which promotes the full mixing of steel slag and blast furnace slag. Usually, the slag fluidity is very good after mixing. Occasionally, when the production organization of the iron or steel plant is not smooth, the slag temperature is low, and the bottom medium frequency induction heating is required. After adding steel slag, it is generally stirred with compressed air for about 1 minute. After stirring, the slag mixing tank is left to stand for 35 to 50 minutes, and then the upper slag is poured into the blast furnace slag tank and sent to the original slag flushing place for water quenching and slag flushing. In the early stage, we took samples while pouring and discharging slag to determine the slag composition. After a month of statistical exploration, we determined the proportion of slag pouring and discharging. Basically, two-thirds of the slag was poured out for water slag flushing, and one-third was added to the molten iron tank. After the iron was tapped, it was sent to the converter with the molten iron for smelting. After two months of operation, about 480 tons of molten iron can be recycled every day, about 1,300 tons of slag-making agent can be recycled, and about 3,700 tons of slag can be sent for water quenching every day. The consumption of lime-based slag-making agent for converter steelmaking was reduced by about 18 kg / ton of steel, and the consumption of steel materials was reduced by about 27 kg / ton of steel. The dephosphorization effect of molten steel was significantly improved. The economic benefits are significant.

Claims

1. A method for collaborative modification of metallurgical slag, characterized in that: The following steps are involved: Liquid blast furnace slag and liquid steel slag are mixed in a ratio of (1.5-2.5):1, and the carbon and sulfide reducing substances in the blast furnace slag are used to undergo redox reactions with the iron oxides in the steel slag. After natural sinking and floating separation, the mixed slag tends to be layered from top to bottom according to different densities, and from top to bottom they are calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium ferrite, and molten iron; part of the dicalcium silicate and above slag is poured into a slag pot for slag flushing treatment, and the remaining dicalcium silicate, tricalcium silicate, calcium ferrite and molten iron are sent to a converter for smelting. The dicalcium silicate, tricalcium silicate and calcium ferrite are used as slag-making agents for converter dephosphorization and desiliconization, and promote dephosphorization and desiliconization in the early stage of converter smelting.

2. The method for synergistic modification of metallurgical slag according to claim 1, characterized in that: After the converter taps out steel, some slag is retained as splashing slag to protect the furnace, and the rest of the slag and residual molten steel are all poured into the insulated slag pot, covered and insulated, and sent to the mixed slag treatment site; the blast furnace slag is tapped into the insulated slag pot, covered and insulated after the slag is tapped, and sent to the mixed slag treatment site.

3. The method for synergistic modification of metallurgical slag according to claim 1, characterized in that: A tiltable slag mixing tank is set up at the slag mixing site. The volume of the slag mixing tank is 2 to 4 times that of the blast furnace slag tank. During each processing, blast furnace slag is first poured into the tiltable slag mixing tank, and then half the amount of steel slag of the blast furnace slag is poured into it.

4. The method for synergistic modification of metallurgical slag according to claim 1, characterized in that: The temperature of the blast furnace slag is between 1400°C and 1530°C, the temperature of the steel slag is between 1550°C and 1680°C, and the slags are left to stand for 25 to 50 minutes after mixing.

5. The method for collaborative modification of metallurgical slag according to claim 1, characterized in that: The blast furnace slag is a silicate and aluminate composed of CaO, MgO, Al2O3, SiO2, MnO and FeO, and the main components are: CaO 31-50%, SiO2 31-44%, Al2O3 5-18%, MgO 2-16%, FeO 1.2-2%, and MnO 0.3-1.2%; the main chemical components of the converter slag are: T.Fe 12-30%, CaO 30-60%, SiO 8-20%, MgO 5-12%, and the basicity is between 2.5 and 6.

6. The method for synergistic modification of metallurgical slag according to claim 1, characterized in that: In order to promote the separation of sinking and floating, the slag mixing tank is slightly vibrated. A vibration table is added to the bottom of the slag mixing tank. The vibration table is equipped with a hydraulic lifting device. The vibration table first lifts the slag mixing tank to a state where it is separated from the driving device to avoid damage to the driving equipment when the slag mixing tank vibrates.

7. The method for synergistic modification of metallurgical slag according to claim 1, characterized in that: The slag mixing tank is a tiltable slag mixing tank. The tiltable slag mixing tank body is insulated and equipped with an insulation cover. The insulation cover is provided with an oxygen combustion gun or a stirring gun blowing hole and a smoke exhaust port. A high-flow rate oxygen combustion top gun or a stirring spray gun, or a mechanical stirrer is provided on the top. Stirring with a stirrer requires stirring before covering. The oxygen combustion gun can use oxygen fuel gas to heat the mixed slag and stir it at the same time, and can also spray nitrogen or compressed air to stir the slag. An induced draft hood is provided above the smoke exhaust port to cool the flue gas by letting in cold air. A dust collector is provided behind the induced draft hood, and a frequency-modulated induced draft fan is provided at the rear of the dust collector.

8. The method for synergistic modification of metallurgical slag according to claim 7, characterized in that: A medium frequency heating device is arranged at the bottom of the tiltable slag mixing pot, which heats the upper slag by heating the molten iron at the bottom, and supplements heat to the slag when the slag temperature is low; when medium frequency heating is required, some molten iron is left at the bottom of the tiltable slag mixing pot.

9. The method for collaborative modification of metallurgical slag according to claim 1, characterized in that: After mixing the slag, let it stand for 25 to 50 minutes, first pour out the upper calcium phosphate, calcium silicate and part of the dicalcium silicate slag for water flushing slag, pour the remaining dicalcium silicate and the slag iron under it into the molten iron tank, and after the iron is tapped, send it to the converter for smelting with the molten iron.

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