Steel slag oxygen-enriched coal gangue injection quenching and tempering and solid waste treatment synergistic method

Abstract

The invention discloses a steel slag oxygen-enriched coal gangue injection quenching and tempering and solid waste treatment synergistic method, and belongs to the field of solid waste treatment. Through cooperative treatment, different combustion-oxygen ratios are controlled in different stages, and the processes of further temperature regulation, tempering, standing self-settling separation, pouring out of low-density high-phosphorus slag and low-calcium slag at the upper part, and water feeding and slag flushing by using a heat preservation slag tank are carried out for water quenching treatment to obtain building material production raw materials, and high-density high-calcium slag and molten metal at the lower part are left; sending to a smelting furnace as a slag former and a smelting raw material. According to the method, two kinds of solid waste are solved at the same time, slag-metal separation is promoted, secondary oxidation loss of metal is avoided, and resource utilization of coal gangue components is achieved.

Description

Technical Field

[0001] The invention belongs to the field of solid waste treatment, and relates to a steel slag oxygen-enriched injection coal gangue tempering and coordinated solid waste treatment method, and particularly relates to a steel slag and coal gangue coordinated treatment method. 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, high content of free CaO and MgO, complex composition, unstable performance and other factors, making it difficult to recycle it. In particular, the new building materials standards have greatly reduced the use of steel slag, making it the most troublesome solid waste in the steel process. Every year, landfilling steel slag occupies a large amount of land and causes great environmental pollution problems. It is urgent to find a green and environmentally friendly treatment process to ensure the green and sustainable development of the steel industry and promote the construction of waste-free cities.

[0003] my country is the country with the largest coal reserves and mining volume. The coal mining process produces a large amount of coal gangue, which contains a large amount of organic matter, many of which have a calorific value of 7000-10000kJ and contain a high volatile matter. It spontaneously combusts in hot weather seasons. This incomplete combustion produces a large amount of pollutants, many of which are VOCs and CO, which are all air pollutants. At present, many treatment processes for coal gangue have problems such as VOCs escape. For example, when coal gangue is used to burn bricks, the volatile matter in the coal gangue is evaporated and escaped at low temperature before the ignition point, and it cannot be treated and utilized at all. Almost all of it is discharged into the atmosphere, causing air pollution. Therefore, it is urgent to find a green and environmentally friendly treatment process to promote the construction of more waste-free cities. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for tempering coal gangue by oxygen-enriched injection of steel slag and coordinated solid waste treatment, which can simultaneously solve two solid wastes, promote slag-metal separation, avoid secondary oxidation loss of metals, and realize resource utilization of coal gangue components.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for steel slag oxygen-enriched injection of coal gangue for tempering and coordinated solid waste treatment comprises the following steps:

[0007] Step 1. Add liquid slag into the slag treatment furnace using an insulated slag tank;

[0008] Step 2. Low oxygen-fuel ratio injection: According to the composition of the added steel slag, the slag basicity of the final slag is set, the oxygen-fuel ratio is controlled, the atmosphere in the slag is guaranteed to be a reducing atmosphere, the metal oxides are fully reduced, and the slag temperature is controlled at the same time. The vibration generated by the injection promotes the agglomeration and growth of the reduced metal substances, which gradually sink to the bottom of the furnace to achieve slag-metal separation; when the gas is ready for recovery, it is recycled in the gas cabinet, and when the calorific value or oxygen concentration exceeds the standard, the secondary combustion is started. For secondary combustion, a secondary combustion gun is set at the upper part of the furnace, or a secondary combustion chamber is set outside the furnace.

[0009] Step 3. High oxygen-fuel ratio injection: adjust the oxygen-fuel ratio and add cooling materials to adjust the temperature; the oxidizing atmosphere causes the residual carbon in the slag to burn, and the residual iron and ferrous iron are oxidized into the stable phase of Fe2O3; the cooling material can be the original cold steel slag after magnetic separation treatment, or other cold quenched and tempered materials. The quenched and tempered slag temperature is 1430℃-1530℃, and the composition meets the target customer's composition requirements, and the homogeneity and fluidity meet the slag flushing requirements;

[0010] Step 4. Adjust the slag temperature and homogenize it, then stop the furnace and prepare for slag tapping; when tapping, the slag and iron are mixed and poured into an insulation sedimentation tank and covered for insulation;

[0011] Step 5. The slag iron is placed in the insulation sedimentation tank for 35min-50min. The materials in the tank are self-separated according to their different specific gravities. The specific gravities of the materials in the tank are as follows from small to large from top to bottom: calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrite, and molten iron. The upper calcium phosphate, calcium silicate and part of the dicalcium silicate are poured out and sent to the slag flushing area for slag flushing treatment. Part of the dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrite and molten iron are sent to the converter or electric arc furnace for smelting.

[0012] Step 6. Pour the calcium phosphate, calcium silicate and part of the dicalcium silicate in the upper part into the insulated slag tank for water quenching. After the water quenching, the composition and phase structure of the steel slag meet the requirements of the target customers.

[0013] In step 2, when the gas meets the recovery conditions, it enters the gas cabinet for recovery, and when the calorific value is low or the oxygen concentration exceeds the standard, the secondary combustion is started;

[0014] In step 2, the slag basicity of the final slag is 0.9-1.3; the oxygen-fuel ratio is (0.5-0.7):1; the slag temperature is controlled to be 1500°C-1550°C;

[0015] In step 3, the oxygen-fuel ratio is adjusted to be greater than 1.2:1;

[0016] After the reaction in step 3, flue gas is generated, and the generated flue gas is used for waste heat recovery, preheating scrap steel or recovering steam;

[0017] In step 3, when adjusting the temperature by adding coolant, the effect of spraying cold slag on the final slag composition should also be considered.

[0018] In step 5, the slag flushing and smelting ratio of dicalcium silicate is determined in combination with smelting requirements, modeling and theoretical calculations; dicalcium silicate, tricalcium silicate, calcium manganate and calcium ferrite are used as slag-forming agents for smelting and smelting with molten iron.

[0019] Compared with the prior art, the present invention is beneficial in that:

[0020] 1. Through coordinated processing, the combustion of coal gangue provides heat for the tempering of steel slag, and the silicon-aluminum compounds in the coal gangue provide acidic components for the tempering of high-alkalinity steel slag, thus solving two types of solid waste at the same time and turning them all into valuable resources.

[0021] 2. By controlling the oxygen-fuel ratio, the early slag is placed in a reducing atmosphere, which not only recovers metal substances but also recovers part of the coal gas.

[0022] 3. By controlling the oxygen-fuel ratio and injecting overoxygen in the later stage, the steel slag is oxidized, eliminating FeO that affects the quality of cement, and turning the steel slag into ordinary cement clinker.

[0023] 4. By adjusting the temperature and tempering, the viscosity of the steel slag is reduced, which is conducive to the self-sedimentation separation and recovery of valuable slag and metal, eliminating the need for crushing and magnetic separation, and avoiding the generation of tailings.

[0024] 5. The recovered metal is high-temperature liquid iron, which can be directly used for steelmaking. The physical heat is fully utilized, avoiding the secondary heating melting energy consumption and burning.

[0025] 6. This process treats coal gangue, and all components of the coal gangue are utilized as resources without any pollutant emissions. It is a green and environmentally friendly treatment process.

[0026] 7. The dicalcium silicate, tricalcium silicate, calcium manganate and calcium ferrite in the heat-insulating settling tank of the present invention are all dephosphorization and desiliconization slag-making materials. The liquid slag is beneficial to the low-temperature dephosphorization of the converter or the electric arc furnace. All the iron-manganese-containing metal elements are returned to the smelting furnace for smelting, thereby avoiding the loss of metal materials. The high-calcium material can reduce the consumption of steelmaking slag-making agents. The calcium phosphate has a light specific gravity and can be poured out completely, thereby avoiding the phosphorus enrichment of the steel slag reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A process device diagram of an embodiment of the present invention;

[0028] Among them, 1-furnace body, 2-compound spray gun, 3-smoke collecting hood, 4-smoke duct, 5-smoke annular duct, 6-intake bronchial pipe, 7-charge preheating vertical furnace, 8-dust collector, 9-induced draft fan, 10-air inlet valve, 11-chimney, 12-gas holder, 13-chimney valve, 14-gas holder valve, 15-smoke composition analysis and detection instrument, 16-unloading valve, 17-unloading closed chamber, 18-unloading chute, 19-side closed door, 20-first layer manipulator, 21-second layer manipulator, 22-feeding closed valve, 23-lower storage chamber, 24-upper storage chamber, 25-closed cover plate, 26-closed discharge valve, 27-secondary combustion gas nozzle, 28-secondary combustion chamber. DETAILED DESCRIPTION

[0029] The present invention provides a steel slag oxygen-enriched injection coal gangue tempering and coordinated solid waste treatment method, comprising the following steps:

[0030] Step 1. Add liquid slag into the slag treatment furnace using an insulated slag tank;

[0031] Step 2. Low oxygen-fuel ratio injection: According to the composition of the added steel slag, the final slag basicity is set at 0.9-1.3, and the oxygen-fuel ratio is controlled to 0.5-0.7:1 to ensure that the atmosphere in the slag is a reducing atmosphere and the metal oxides are fully reduced. At the same time, the slag temperature is controlled to 1500℃-1550℃. The vibration generated by the injection promotes the aggregation and growth of the reduced metal substances, which gradually sink to the bottom of the furnace to achieve slag-metal separation. During the injection process, if the gas meets the recovery conditions, it will be recycled in the gas cabinet. If the calorific value or oxygen concentration exceeds the standard, secondary combustion will be started.

[0032] Step 3. High oxygen-fuel ratio injection: Adjust the oxygen-fuel ratio to be greater than 1.2:1, burn the residual carbon in the slag, and oxidize the residual iron and ferrous iron into the stable phase of Fe2O3; the slag temperature will continue to rise during high oxygen-fuel ratio injection, and it is necessary to add cooling materials to cool it down, such as the original cold slag after magnetic separation treatment, or other quenching and tempering materials. The flue gas at this stage is only used for waste heat recovery.

[0033] Step 4. Adjust the slag temperature to 1430℃-1530℃. Stop spraying after the slag homogeneity composition is qualified, and pour all the slag iron into the insulation sedimentation tank.

[0034] Step 5. The slag iron is placed in the insulation sedimentation tank for 35-50 minutes. The materials in the tank are separated according to their specific gravity. The specific gravity of the materials in the tank is from small to large and from top to bottom: calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrite, and molten iron. The upper calcium phosphate, calcium silicate and part of the dicalcium silicate are poured out and sent to the slag flushing area for slag flushing treatment. Part of the dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrite and molten iron are sent to the converter or electric arc furnace for smelting. The slag flushing and smelting ratio of dicalcium silicate is determined in combination with smelting requirements, modeling and theoretical calculations; dicalcium silicate, tricalcium silicate, calcium manganate and calcium ferrite are used as slag-making agents for smelting with molten iron.

[0035] Step 6. Pour the calcium phosphate, calcium silicate and part of the dicalcium silicate in the upper part into the insulated slag tank for water quenching. After the water quenching, the composition and phase structure of the steel slag meet the requirements of the target customers.

[0036] The process system adopted by the present invention is as follows Figure 1 As shown, it includes a rotary slag treatment furnace body 1, an oxygen or oxygen-enriched air and coal gangue powder composite spray gun 2 is arranged in the furnace body, a flue gas collecting hood 3 is arranged on the furnace body 1 and connected to a flue gas duct 4, the flue gas duct 4 is connected to a flue gas annular duct 5, the flue gas annular duct 5 is connected to a charge preheating vertical furnace 7 by a bronchial pipe 6, a dust collector 8 is arranged behind the exhaust port of the vertical furnace 7 and connected with a pipeline, an induced draft fan 9 is arranged behind the dust collector 8, an adjustable air inlet valve 10 is arranged on the intermediate pipeline between the dust collector and the induced draft fan, a smoke exhaust chimney 11 and a gas tank 12 are arranged behind the induced draft fan, a chimney valve 13 is arranged in front of the chimney 11, and a gas tank valve 14 and a flue gas composition analysis and detection instrument 15 are arranged in front of the gas tank.

[0037] If the calorific value of the gangue is low or if you do not want to recover the coal gas, you can set a secondary combustion-supporting gas nozzle 27 on the upper part of the oxygen-burning gun, or set a secondary combustion chamber 28 between the converter gas collecting hood and the annular flue to perform secondary combustion on the flue gas. The lower part of the slag is a reducing atmosphere, and secondary combustion is performed in the upper space of the furnace or behind the furnace to ensure that the exhaust CO and VOCs emissions meet the standards.

[0038] The bottom of the charge preheating vertical furnace 7 is provided with a discharge valve 16, and a discharge closed chamber 17 is provided below the discharge valve 16, in which a discharge chute 18 is placed. The discharge closed chamber 17 is provided with a side closed door 19, which is opened when the discharge chute is taken and delivered, and is usually in a closed state;

[0039] The air intake branch pipe 6 connecting the flue gas annular flue 5 and the preheating charge vertical furnace 7 should be set at a sufficient height from the bottom of the vertical furnace to prevent the discharge valve and the discharge system at the bottom of the vertical furnace from being damaged by high temperature. The specific distance depends on the temperature of the flue gas entering the furnace and the material selection of the discharge system. It is based on not affecting the life of the equipment. Because the hot flue gas goes up and a certain distance is reserved, the heating temperature of the steel tapping system at the bottom of the vertical furnace is the temperature of the bottom of the second layer of scrap steel. The scrap steel temperature here generally does not exceed 700°C. Therefore, the heat-resistant material of the bottom of the vertical furnace only needs to be heat-resistant to 700°C. The material is easy to choose.

[0040] The charge preheating vertical furnace 7 is provided with two layers of manipulators in the middle for supporting the preheated materials, namely the first layer manipulator 20 and the second layer manipulator 21. If the flue gas temperature is high and there is value in further recycling, the preheating material layer can be increased to increase the preheating recovery. In this preheating method, the temperature of the first layer manipulator 20 will not exceed 700°C, and the temperature of the second layer manipulator 21 will not exceed 500°C. Neither of them can withstand high temperatures, and the materials are easier to select, which reduces the equipment maintenance cost and makes the equipment operation more stable. The furnace bottom also cannot withstand high temperatures, and the selection of furnace bottom equipment materials is more economical.

[0041] The top of the charge preheating vertical furnace 7 is provided with a charging closed valve 22, a lower storage chamber 23, an upper storage chamber 24 and a closed cover plate 25, and a closed discharge valve 26 is provided between the upper and lower storage chambers. When charging from the lower storage chamber to the vertical furnace, the charging closed valve 22 is opened, the material in the lower storage chamber is added to the vertical furnace, and then the charging closed valve 22 is closed; then the closed discharge valve 26 is opened, and the material in the upper storage chamber 24 is placed in the lower storage chamber 23; then the closed discharge valve 26 is closed, and then the closed cover plate 25 is opened, and then the material to be preheated is added to the upper storage chamber, and the closed cover plate 25 is closed after the material is added. Such multi-layer sealing can reduce the air entering the system when the induced draft fan induces air, causing safety accidents and unnecessary combustion. The time for charging into the vertical furnace and discharging from the upper and lower storage chambers should be controlled as much as possible during the slag and iron-discharging time period of the slag treatment furnace, at which time the induced draft system is in a non-working state. The feeding time of the upper storage chamber should also be as short as possible. After the feeding is completed, the sealing cover plate 25 is quickly closed.

[0042] The time for discharging the preheated charge is also selected during the slag treatment furnace slag tapping time period. First, open the discharge valve 16, discharge the preheated charge at the bottom layer into the discharge chute 18 of the discharge closed chamber 17, close the discharge valve 16, open the side closed door 19, take out the discharge chute 18 with the preheated charge, put the empty discharge chute 18 back, and then close the side closed door 19.

[0043] After closing the discharge valve 16, the first layer manipulator 20 discharges the material, and after discharging the material, the first layer manipulator 20 returns to the material receiving state, and then the second layer manipulator 21 discharges the material, and after discharging the material, the second layer manipulator 21 returns to the material receiving state, and then the upper feeding system feeds the material;

[0044] Gas recovery: According to the calorific value of coal gangue, if the calorific value is high, the calorific value of the gas is adjusted by adjusting the oxygen-fuel ratio, and gas recovery is performed at the rear. The oxygen concentration in the flue gas is detected by the gas analysis detector 15. When the oxygen concentration reaches the safe recovery value, the gas tank valve 14 is opened and the chimney valve 13 is closed at the same time; when the oxygen concentration in the flue gas exceeds the safe value, the gas tank valve 14 is closed and the chimney valve 13 is opened at the same time.

[0045] If gas recovery is not performed, a secondary combustion-supporting gas nozzle 27 must be provided above the oxygen-fuel lance nozzle. The number of combustion-supporting gas nozzles must not be less than four to avoid incomplete combustion. A certain rotation angle is provided at the nozzle outlet to allow the combustion-supporting gas to form a rotating flow in the furnace, which is conducive to complete combustion.

[0046] Set up CO and O2 rapid analysis instruments at appropriate locations behind the furnace, and control the injection volume of combustion-supporting gas through the feedback data from the analyzers. It is necessary to avoid exceeding the CO emission standard and to control the O2 concentration not to be too high, otherwise it will cause oxidation loss of the preheated metal material in the rear.

[0047] If the foaming and overflow of steel slag is considered, the solution will cause the secondary combustion gas nozzle to be blocked, affecting the secondary combustion effect. A secondary combustion chamber can be set up behind the furnace. Combustion in the secondary combustion chamber makes it easier to control the exhaust gas composition. The secondary combustion chamber also has the function of removing large dust particles.

[0048] The content of the present invention will be further described below in conjunction with specific embodiments.

[0049] Example 1

[0050] A steel plant used the abandoned original 60-ton steelmaking converter for transformation, dismantled the original flue gas treatment system, and only retained a small amount of gasification flue cooling system. A secondary combustion chamber was set up at the rear of the gasification flue cooler. The secondary combustion chamber also has the function of settling and removing large particles of dust. A scrap steel preheating vertical furnace was set up at the rear. Since the local coal gangue has a high calorific value, generally 9000-10000kJ / kg, and the content of inorganic substances such as silicon, aluminum, calcium, and magnesium is low, a gas recovery system was set up to recover part of the gas during the reduction period, and the calorific value of the gas can reach 3300-5000kJ / Nm 3 , can participate in the balanced use of gas within the factory.

[0051] The steel plant adopts a new slag-making process, a low-slag smelting process, and a converter slag-retaining operation. All the steel slag is retained after steelmaking. No slag-making material is needed in the early stage of the converter. All the retained slag is used as the early slag. The slag is removed after dephosphorization and desiliconization, and the early desiliconization and dephosphorization slag is removed. Then, the appropriate alkalinity slag is made according to the amount of remaining slag, and the amount of early slag will be very small. Therefore, this process does not produce high-alkalinity terminal smelting slag. The alkalinity of the early dephosphorization and desiliconization slag is 0.9-1.3. According to the composition of coal gangue, the oxygen-fuel ratio is controlled at 0.5-0.7:1 to ensure that the atmosphere in the slag is reducing, so that the metal oxides are fully reduced. The slag temperature is controlled at 1500℃-1550℃, and the slag has good fluidity. The vibration generated by the injection promotes the agglomeration and growth of the reduced metal substances and accelerates the separation of slag and iron. After injection, adjust the oxygen-fuel ratio to greater than 1.2:1, add the original magnetic separation steel slag as cold material, continue to inject, burn the residual carbon in the slag, and oxidize the residual iron and ferrous iron into Fe2O3 stable phase. Finally, the slag temperature drops to 1430℃-1500℃, stop injecting, remove the slag with a gun, pour it into the slag tank for water quenching. The composition and phase structure of the steel slag after water quenching are basically similar to those of blast furnace slag, which fully meets the new building materials standards.

[0052] During the reduction period, the gas can be recycled if the calorific value is sufficient and the oxygen content meets the standard. If the calorific value is insufficient or the oxygen content exceeds the standard, secondary combustion is adopted. The average gas recovery per ton of steel slag is 30Nm 3 , recovery steam 500Nm 3 , 125 kg of molten iron was recovered. The magnetic separation recovery process was omitted, greatly reducing the consumption of steel materials per ton of steel. The new slag making process greatly saved the consumption of slag making materials.

[0053] The steel slag produced by converters and electric arc furnaces is a high-temperature liquid slag above 1550℃, with a relatively high basicity, containing a large amount of iron oxide and free metallic iron. If it is loaded into a metallurgical furnace similar to a converter, and coal gangue powder is sprayed with full oxygen or oxygen-enriched oxygen, the organic matter and carbon in the coal gangue will add heat to the slag during the combustion process, offsetting part of the melting of the coal gangue and the reaction cooling. The coal gangue also contains a large amount of silicon dioxide and aluminum oxide, which will react with the high calcium and magnesium substances in the steel slag, reduce the basicity and melting point of the slag, and generate a stable phase. By controlling the oxygen-fuel ratio, the steel slag is controlled to be reducing, and the carbon and hydrocarbons in the unburned coal gangue and the CO produced by incomplete combustion react with easily reducible substances such as iron oxide and manganese oxide in the steel slag to reduce it into alloy metals. When the basicity of the slag is reduced and the fluidity is improved, the newly reduced iron-manganese-silicon alloy and free metallic iron will sink to the bottom of the furnace, realizing the separation of slag and gold. After the slag and metal are separated, the oxygen-fuel ratio is changed, and the amount of oxygen injected is increased to turn the slag into oxidizing slag, so that the unburned carbon is burned off, and the tiny iron particles and FeO that have not sunk to the bottom of the furnace are oxidized into the stable phase of Fe2O3. Due to the high oxygen-fuel ratio injection slag temperature will continue to rise, the melting point of the slag after treatment is low, and the fluidity will be very good at 1450℃-1500℃. If the slag temperature is too high, it will affect the life of the furnace lining, so it is necessary to add cooling materials to cool it down. The cooling materials can be sprayed in or directly put in. The cooling materials can be the cold steel slag after the original magnetic separation treatment, the waste heat treatment of the stock steel slag, or other quenching and tempering materials. Finally, according to the residual heat and composition of the slag, the final slag adjustment is made. After the temperature and composition reach the design standard, the slag and iron are mixed out and poured into the insulation sedimentation tank with a cover for insulation. The slag iron is placed in the insulation sedimentation tank for 35-50 minutes. The materials in the tank are separated according to their specific gravity. The specific gravity of the materials in the tank is from small to large: calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrate, and molten iron. The specific gravity of the materials in the tank is from small to large from top to bottom: calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrate, and molten iron. The upper calcium phosphate, calcium silicate and part of the dicalcium silicate are poured out and sent to the slag flushing area for slag flushing treatment. Part of the dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrate and molten iron are sent to the converter or electric arc furnace for smelting. The slag flushing and smelting ratio of dicalcium silicate is determined in combination with smelting requirements, modeling and theoretical calculations; dicalcium silicate, tricalcium silicate, calcium manganate and calcium ferrate are used as slag-making agents for smelting with molten iron. . Pour the upper calcium phosphate, calcium silicate and part of dicalcium silicate into the insulated slag tank for water flushing treatment, so that the slag after water flushing treatment meets the cement standard requirements.

[0054] The amount of coal gangue injected is determined according to the alkalinity of the slag and the contents of silicon, aluminum, calcium, magnesium, potassium, sodium, etc. in the coal gangue. The final composition should minimize the melting point and viscosity of the new organism while meeting the requirements of cement clinker to facilitate the separation of slag and gold.

[0055] The steel slag with better fluidity after tempering and temperature adjustment can be sent to the blast furnace slag flushing area for treatment, or a new water slag flushing system can be built, or other slag treatment processes can be used.

[0056] After slag discharge, molten metal is recovered at the bottom of the furnace. Since the amount is not large, it can be recovered after several furnaces are processed. The amount of molten iron in the furnace can be seen in the later stage of slag discharge.

[0057] During the process of injecting coal gangue powder, the oxygen-fuel ratio is controlled to make the slag in a reducing atmosphere state. A large amount of carbon monoxide gas will be generated in the flue gas. Whether to recycle the coal gas is determined based on the content of organic matter, carbon, silicon and aluminum in the coal gangue. According to the heat balance calculation, if the calorific value of the coal gas exceeds 2800kJ, it has recycling value. It can also be determined based on the gas balance needs of the enterprise and the utilization of flue gas waste heat. If the coal gas is recycled, both the calorific value and the oxygen concentration value must be controlled within a safe range. In order to solve the problem of excessive CO and combustible gas released by the coal gas when the coal gas is not recycled, a secondary combustion combustion-supporting gas injection port is set at the upper part of the spray gun, or a secondary combustion chamber is set behind the furnace to ensure that the flue gas emissions meet the standards.

[0058] The secondary combustion chamber should have sufficient heat storage capacity to ensure that the generated radiation intensity can fully burn the low calorific value gas. If the waste heat of the flue gas is used for scrap preheating, the excess oxygen content of the flue gas after the secondary combustion should be controlled to reduce the burning loss of scrap.

[0059] When the inorganic components of coal gangue such as silicon and aluminum are low, and the carbon and organic components are high, the oxygen supply intensity can be adjusted to reduce, no secondary combustion is performed, the concentration of combustibles in the flue gas is increased, and a gas cabinet is installed at the rear for gas recovery. When recovering gas, the O2 concentration is strictly controlled within the safe value. When gas recovery is not performed, the secondary combustion is continued.

[0060] Since the flue gas temperature is relatively high, a waste heat recovery flue can be used to recover steam in the high-temperature section at the front end, and then a charge preheating device can be built after the waste heat boiler to cool the flue gas using the preheated charge. A vertical furnace can also be built directly behind the flue gas hood to preheat the incoming charge, such as scrap steel, ferroalloys, limestone, dolomite, etc. The flue gas temperature is reduced to a dust removal temperature after preheating the charge. If there is no gas recovery, it can be discharged directly; if there is gas recovery, if the flue gas temperature is higher than the gas recovery temperature, a heat exchanger can be installed after dust removal to cool the gas down to an acceptable state for the gasholder to enter the gasholder for recovery. If the gas temperature is not high, it can directly enter the gasholder.

[0061] The slag treatment metallurgical furnace is in hot state, and the temperature in the furnace is always guaranteed to be above 1000℃. The gangue powder sprayed into the furnace burns with oxygen, and the combustion temperature is also above 1000℃. The volatile matter of the gangue will be cracked into short-chain hydrocarbons after dry distillation and evaporation, so it will not cause scaling and blockage in the flue gas treatment system.

[0062] The furnace wall structure and cooling of the slag treatment metallurgical furnace adopt the refractory and water cooling mode similar to that of the steelmaking converter. The basicity of steel slag is relatively high, and the concentration of magnesium oxide is also relatively high, so the melting point is relatively high, and a solid shell will be formed near the refractory. During the slag treatment process, the refractory temperature of the furnace wall is below 1450℃, and the slag shell formed by the cooling wall will not be completely melted and destroyed. Therefore, as long as a certain amount of magnesium material is sprayed regularly for repair, the life of the furnace body is guaranteed.

[0063] The composition of the tempered slag is designed according to the standard requirements of building materials. The melting point of the slag after the injection of coal gangue powder will be lower than the steel slag after converter smelting, so that the treated steel slag has good fluidity, which is conducive to the sedimentation and self-separation in the insulation sedimentation tank after it is discharged from the furnace.

[0064] The dicalcium silicate, tricalcium silicate, calcium manganate and calcium ferrite in the insulated sedimentation tank are all dephosphorization and desiliconization slag-making materials. The liquid slag is conducive to low-temperature dephosphorization in the converter or electric arc furnace. All the iron and manganese metal elements are returned to the smelting furnace for smelting, avoiding the loss of metal materials. The high-calcium material will reduce the consumption of steelmaking slag-making agents. The calcium phosphate has a light specific gravity and is all poured out, avoiding phosphorus enrichment in the reuse of steel slag.

Claims

1. A method for steel slag oxygen-enriched injection of coal gangue for tempering and coordinated solid waste treatment, characterized in that: The following steps are involved: Step 1. Add liquid slag into the slag treatment furnace using an insulated slag tank; Step 2. Low oxygen-fuel ratio injection: according to the added steel slag composition, the slag basicity of the final slag is set, the oxygen-fuel ratio is controlled, the atmosphere in the slag is ensured to be a reducing atmosphere, the metal oxides are fully reduced, and the slag temperature is controlled at the same time. The vibration generated by the injection promotes the aggregation and growth of the reduced metal substances, realizes the separation of slag and gold, and sinks to the bottom of the furnace; Step 3. High oxygen-fuel ratio injection: adjust the oxygen-fuel ratio and add cooling materials to adjust the temperature; the oxidizing atmosphere causes the residual carbon in the slag to burn, and the residual iron and ferrous iron are oxidized into the stable phase of Fe2O3; the cooling material can be the original cold steel slag after magnetic separation treatment, or other cold quenched and tempered materials. The quenched and tempered slag temperature is 1430℃-1530℃, and the composition meets the target customer's composition requirements, and the homogeneity and fluidity meet the slag flushing requirements; Step 4. After the slag temperature and composition are adjusted to meet the requirements, the furnace is stopped after homogenization, and the slag and iron are poured into the insulation sedimentation tank at the same time; Step 5. The slag iron is placed in the insulation sedimentation tank for 35-50 minutes. The materials in the tank are separated according to their specific gravity. The specific gravity of the materials in the tank is from small to large and from top to bottom: calcium phosphate, calcium silicate, dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrite, and molten iron. The upper calcium phosphate, calcium silicate and part of the dicalcium silicate are poured out and sent to the slag flushing place for slag flushing treatment. Part of the dicalcium silicate, tricalcium silicate, calcium manganate, calcium ferrite and molten iron are sent to the converter or electric arc furnace for smelting; Step 6. Pour the calcium phosphate, calcium silicate and part of the dicalcium silicate in the upper part into the insulated slag tank for water quenching. After the water quenching, the composition and phase structure of the steel slag meet the requirements of the target customers.

2. The method for steel slag oxygen-enriched injection of coal gangue for tempering and coordinated solid waste treatment according to claim 1, characterized in that: In step 2, when the gas meets the recovery conditions, it enters the gas tank for recovery. When the calorific value is low or the oxygen concentration exceeds the standard, the secondary combustion is started.

3. The method for steel slag oxygen-enriched injection of coal gangue for tempering and coordinated solid waste treatment according to claim 1, characterized in that: In step 2, the slag basicity of the final slag is 0.9-1.3; the oxygen-fuel ratio is (0.5-0.7):1; and the slag temperature is controlled to be 1500°C-1550°C.

4. The method for steel slag oxygen-enriched injection of coal gangue for tempering and coordinated solid waste treatment according to claim 1, characterized in that: In step 3, adjust the fuel-oxygen ratio to greater than 1.2:

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5. The method for steel slag oxygen-enriched injection of coal gangue for tempering and coordinated solid waste treatment according to claim 1, characterized in that: In step 3, flue gas is generated after the reaction, and the flue gas is used for waste heat recovery, preheating scrap steel or recovering steam.

6. The method for steel slag oxygen-enriched injection of coal gangue for tempering and coordinated solid waste treatment according to claim 1, characterized in that: In step 5, the slag flushing and smelting ratio of dicalcium silicate is determined in combination with smelting requirements, modeling and theoretical calculations; dicalcium silicate, tricalcium silicate, calcium manganate and calcium ferrite are used as slag-forming agents for smelting and smelting with molten iron.

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