A method for carbonation and carbon sealing of steel slag in steelmaking process

Abstract

The present application provides a method for carbonation and carbon sealing of steel slag in a steelmaking process, and relates to the field of metallurgy. The method for carbonation and carbon sealing of steel slag in a steelmaking process comprises: during the process of pouring the steel slag into a slag stewing pool, a convection jet cooling gas intersecting the pouring direction of the steel slag is added to assist the steel slag granulation pretreatment and the sensible heat primary heat exchange process, until the steel slag is cooled to 800-1000°C, and the obtained high-temperature steam is recovered to realize heat recovery; after the slag is poured, the steel slag pouring port is blocked, and the steel slag in the hot stuffy device is covered and sprayed with carbon dioxide-containing gas, hot stuffy powder, and the corresponding coal gas is collected to complete the secondary heat exchange; finally, the jaw crusher is used for primary crushing, rod mill fine grinding and magnetic separation are used to complete the minimization of the particle size and iron content of the tailings. The method provided by the present application realizes the efficient separation and utilization of hot steel slag without the need for high pressure, auxiliary processes for adding grinding aids, etc., and the iron content in the tailings is reduced by less than 2%.

Description

Technical Field

[0001] The present application relates to the field of metallurgy, and in particular to a method for carbonation sealing of steel slag in a steelmaking process. Background Art

[0002] The production of steel is accompanied by the emission of a large amount of steel slag. The storage and disposal of a large amount of waste steel slag will cause problems such as waste of resources, occupation of land and pollution of the environment. With the development of the steel industry, the emission of steel slag is increasing, and the speed of slag disposal is slower than the emission speed. At the same time, as the industry with the largest carbon emissions among the 31 categories of manufacturing, it is very important to effectively control carbon emissions in the steelmaking process.

[0003] As a byproduct of steel production, steel slag is mainly used in road base fillers, cement admixtures and other fields. It is mainly composed of iron oxide, silicate, calcium oxide and magnesium oxide. The calcium component in steel slag can react with CO2 to generate stable calcium carbonate, which plays a role in permanent carbon fixation, reduces CO2 emissions and greenhouse effects, and is currently the most effective, direct and highly executable solution for CO2 capture and storage. Since the spontaneous carbonation of steel slag is an extremely slow process, the current research hotspot is how to increase the reaction rate of steel slag carbonation and achieve industrialization.

[0004] In recent years, wet carbon fixation technology of steel slag has attracted the attention of researchers. The use of this process is conducive to accelerating the reaction rate and improving the leaching effect, but the consumption of leaching solution is large, the equipment requirements are high, and the cost of by-product wastewater treatment is high.

[0005] In the patent of "A method for preparing carbon dioxide capture agent using blast furnace slag", the calcium, aluminum and other oxides in the slag are removed by acid washing to retain silicon dioxide, and the extract powder is mixed with the reagent pure lithium carbonate in a ratio of Li2CO3 to SiO2 greater than 4:1 to finally obtain a lithium-based carbon dioxide capture agent. However, the technical process is relatively complex, the conditions are harsh, the processing cycle is long, it can only be performed under laboratory conditions, and the investment cost is high, making it difficult to achieve. In the patent of "A method for separating carbon dioxide from blast furnace gas from metallurgical slag", the Ca2+ is achieved by adjusting the pH value to 5.5-6.5 using a saturated ammonium chloride solution leaching agent. 2+ The leaching rate of calcium ions reaches 99%, but this technology will produce a lot of wastewater, the environmental cost is high, and the specific carbon fixation effect is not specified. In the patent of "A mineralized material for carbon dioxide storage and its application", a carbonaceous reducing agent is added to blast furnace slag or calcium-magnesium-containing materials to reduce silicon dioxide to ferrosilicon alloy, reducing the consumption of alkali solution in the leaching process. The CO2 storage efficiency of this technology can reach more than 99%. However, the energy consumption and processing costs of this technology are still high.

[0006] In patents such as "A method for preparing ultrafine slag powder using supercritical carbon dioxide" and "Device and method for separating carbon dioxide from blast furnace gas using metallurgical slag", steel slag is granulated, and the carbon fixation efficiency of steel slag is improved with the help of abrasives, high temperature, high pressure and other technical conditions. However, due to the actual equipment conditions, the granulation and stirring effects of steel slag are limited, and the slag sealing capacity is limited under the corresponding technical conditions. In patents such as "A device and method for fixing carbon dioxide and recovering sensible heat using blast furnace slag" and "A method for reducing carbon monoxide synthesis gas with high-temperature molten heat carrier, carbon dioxide and carbon powder", high-temperature slag is crushed into particles, and heat is exchanged with carbon dioxide-containing flue gas in a fluidized bed reactor to achieve carbon dioxide emission reduction and carbon monoxide synthesis. This technology realizes partial utilization of sensible heat, but does not achieve carbon dioxide reserve sealing.

[0007] In summary, indirect leaching treatment effectively avoids the high energy consumption and high pollution caused by high pressure and repeated high temperature operation, but leaching itself is difficult. In order to achieve efficient leaching, it is often necessary to use pressurization, a large amount of additives and other means and produce a large amount of sewage, which is difficult to avoid the dilemma of high cleaning costs. Direct carbonization requires high temperature and high pressure operation, and has a low CO2 storage rate, high process cost, and difficult product separation, resulting in poor economic efficiency. In order to achieve clean and efficient carbon fixation of steel slag, it is necessary to design a more efficient steel slag carbon fixation method.

[0008] At present, in the process of steel slag treatment, the high-temperature steel slag is mainly poured directly into the slag pot, and the steel slag is granulated by water rapid cooling and crushing. The crushed steel slag is poured into a hot stuffy pot. The steel slag contains a certain amount of waste heat. The large pieces of steel slag will crack, powder and self-decompose in the hot stuffy pot, so that the steel slag particle size can be refined. However, in the process of water quenching through water spraying, the uniformity of water spraying on the steel slag is low, the water quenching effect is poor, the steel slag particle size is uneven, the slag and steel are difficult to separate completely, the carbonization uniformity of the slag is poor, and the carbon fixation capacity of the directly used steel slag is insufficient. Summary of the invention

[0009] The purpose of the present application is to provide a method for carbonation and carbon sealing of steel slag in a steelmaking process to solve the above-mentioned problems.

[0010] To achieve the above objectives, this application adopts the following technical solutions:

[0011] A method for carbonation and carbon sealing of steel slag in a steelmaking process, comprising:

[0012] During the process of pouring the steel slag into the slag stewing pool, a convection jet cooling gas is added in a direction intersecting with the pouring direction of the steel slag to perform auxiliary steel slag granulation pretreatment and a sensible heat primary heat exchange process until the steel slag is cooled to 800-1000°C, and the obtained high-temperature steam is recovered to realize heat recovery;

[0013] After the slag is dumped, the slag dumping port is blocked, and the slag in the hot stuffing device is covered and sprayed with carbon dioxide-containing gas to pulverize it, and the corresponding coal gas is collected to complete the secondary heat exchange;

[0014] Finally, the slag is crushed by jaw crusher, finely ground by rod mill and magnetic separation to minimize the particle size and iron content of the tailings.

[0015] The convection jet cooling gas includes water vapor and non-essential compressed air, and the volume proportion of water vapor is not less than 80%; the process of spraying the carbon dioxide-containing gas includes:

[0016] During the hot-stifling pulverization process, when the temperature of the steel slag is less than 800°C and greater than or equal to 200°C, the carbon dioxide-containing gas includes water vapor and optional compressed air, industrial flue gas containing carbon dioxide, and pure carbon dioxide, and the volume proportion of water vapor is not less than 80%, and the volume proportion of carbon dioxide in the industrial flue gas containing carbon dioxide is not less than 30%; when the temperature of the steel slag is less than 200°C, the carbon dioxide-containing gas includes industrial flue gas containing carbon dioxide and / or pure carbon dioxide, water vapor and optional compressed air, and the volume proportion of the industrial flue gas containing carbon dioxide and / or pure carbon dioxide is not less than 80%.

[0017] Preferably, the injection velocity of the convective injection cooling gas satisfies the following formula:

[0018] ;

[0019] Wherein, V is the injection velocity of the convective jet cooling gas, m / s;

[0020] P0—high-pressure gas nozzle inlet pressure, Pa;

[0021] P—high pressure gas nozzle outlet pressure, pa;

[0022] T0—high pressure gas nozzle inlet temperature, K.

[0023] Preferably, the cooling gas is a mixture of compressed air and water vapor, wherein the volume proportion of water vapor is not less than 80%.

[0024] Preferably, the convection jet cooling gas is sprayed by 1-3 high-speed jet guns, each with a pressure of 1.7-13.8MPa and a total flow rate of 10-90Nm 3 / h.

[0025] Preferably, during the process of convectively spraying cooling gas and spraying carbon dioxide-containing gas, the nozzle diameter and the jet flow rate and pressure meet the following relationship:

[0026] ;

[0027] Where: q is the flow rate, in m 3 / s; D is the nozzle diameter, in m; p It is the outlet pressure of high-pressure gas nozzle, in Pa.

[0028] High-pressure and high-speed airflow is used to continuously impact the molten high-temperature slag to break it, granulate it, and solidify it. This process involves multiple changes such as multiphase flow collision, heat transfer, and slag phase change. The greater the mass flow rate of the melt, the greater the required wind speed.

[0029] Preferably, the average particle size of the steel slag satisfies the following relationship:

[0030] ;

[0031] Where: —dimensionless droplet mean diameter; —initial diameter, in m; —Gas-liquid relative motion velocity, in m / s; —Surface tension coefficient of steel slag, unit: N / m; —Surface viscosity coefficient of steel slag, unit: Pa·s; —Steel slag density, unit: kg / m 3 ρ g —Gas density, in kg / m 3 ; —Mass flow rate of molten slag during dumping, in kg / s; —Corresponding proportional constant, according to experience, C=1.157, K 1=-0.303, K 2=0.481, K 3=0.7077.

[0032] Preferably, when the temperature of the steel slag is less than 800° C. and greater than or equal to 200° C., the volume proportion of carbon dioxide in the industrial flue gas containing carbon dioxide is not less than 30%.

[0033] Preferably, when the temperature of the steel slag is less than 200° C., the volume proportion of carbon dioxide in the industrial flue gas containing carbon dioxide is not less than 50%.

[0034] Preferably, the iron content of the tailings is 0.76wt%-1.64wt%.

[0035] Preferably, the industrial flue gas containing carbon dioxide includes one or more of lime kiln tail gas, steel rolling heating furnace tail gas, and sintering tail gas.

[0036] Compared with the prior art, the beneficial effects of this application include:

[0037] The present application provides a method for carbonation and carbon sealing of steel slag in the steelmaking process. During the process of turning over the basin and pouring the slag, the cooling gas jet enters the high-temperature steel slag and reacts with the steel slag to complete the gas heat exchange, which can efficiently cool down the temperature of the steel slag, and can adjust the gas composition according to the different subsequent temperature stages of the steel slag, reduce the excess free CaO in the subsequent hot and stuffy process analysis by means of impact stirring, and preliminarily complete the granulation of the steel slag by jet impacting the steel slag, reducing the condensation of large pieces of steel slag caused by quenching. Different from the existing literature that uses abrasives, high temperature, high pressure and other methods to separate slag and steel, the mixed jet cooling and stirring effect and impact ability are used to homogenize the steel slag composition. Therefore, through the technology provided by this application, there is no need for high pressure, auxiliary processes such as adding grinding aids, etc., to achieve efficient separation and utilization of hot steel slag, and the iron content in the tailings is reduced to less than 2%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0039] Figure 1 It is a schematic diagram of the calculation of the injection velocity of the convective jet cooling gas;

[0040] Figure 2 Schematic diagram of the carbonation and carbon sealing equipment used in the examples. DETAILED DESCRIPTION

[0041] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0042] The calculation formula for the injection velocity of the convective jet cooling gas is obtained through the following process:

[0043] First, according to the energy equation , combined with Figure 1 As shown, the air velocity of the leftmost 0-0 section is approximately 0, and the gas parameters are stagnation parameters. It is represented by P0, T0, ρ0, and the parameters on the flow section after the gas flows into the space are represented by P, T, ρ. Because v0=0 in the container, the energy equation of the 0-0 section and the outlet section can be obtained, that is:

[0044] ,

[0045] Thus we get ;

[0046] Put P0=ρ0RT0 and After substituting, the equation is simplified to:

[0047] ;

[0048] When the jet is ejected through the nozzle, if calculated according to the adiabatic equation, K=1.33 is input into the above formula, the above formula can be easily converted into:

[0049] , , .

[0050] in,

[0051] V—muzzle cooling gas outlet velocity, m / s;

[0052] K—specific heat value, water vapor K is taken as 1.33, CO2K value is taken as 1.28;

[0053] P0—high pressure gas nozzle inlet pressure, Pa

[0054] P—high pressure gas nozzle outlet pressure, pa

[0055] ρ0—density at the inlet of high-pressure gas nozzle, g / cm 3 ;

[0056] R0—universal gas constant, R0=8.314N·m·mol -1 ·K -1

[0057] R—gas constant, N·m / (kg·k)

[0058] M—molecular weight, g / mol

[0059] T0—high pressure gas nozzle inlet temperature, K;

[0060] T—High-pressure gas nozzle outlet temperature, K.

[0061] Compressed air and water vapor (it should be noted that the source of water vapor can be diverse, and it can also be formed by directly spraying water using the high temperature of the slag itself, but the relevant parameters need to be adjusted and will not be expanded in this application) are used as jet media to cut, crush and cool the high-temperature liquid slag flow through atomization. This is the first step to achieve efficient carbon sealing of slag. In this step, the temperature of the slag is reduced to 800-1000°C, and the slag is processed into small-size particles. In this process, the high-speed airflow collides and shears the slag, and the slag is torn, further causing the high-temperature slag above 1000°C to break and generate a large number of small slag particles, so that the free lime and the saturated slag are separated, and the slag temperature is reduced, the thermodynamic and kinetic conditions of the slag crystal reaction in the high-temperature zone are regulated, the physical reaction process of slag pulverization is regulated, the slow conversion of tricalcium silicate to dicalcium silicate at 1250°C to 1100°C is suppressed, the generation of free f-CaO is reduced, and its influence on the performance of slag is reduced.

[0062] .

[0063] After the slag is initially cooled to 800°C, steam with a certain pressure contacts the slag to dissolve free CaO, MgO, etc. in the slag, eliminate free CaO and release heat. At the same time, it cracks under the action of uneven expansion force to help further separate large particles of slag and steel. The chemical reaction formula is as follows:

[0064] ;

[0065] ;

[0066] ;

[0067] .

[0068] In addition, the liquid-solid ratio of slag and water is increased by spraying atomized jet water vapor in the container, and the high-pressure environment is used to stir and statically hydrate the process, which promotes the contact between particles, water and CO2, further improves the degree of reaction, and consumes the free calcium oxide (f-CaO) produced by the decomposition of tricalcium silicate in the slag due to temperature drop, improves the carbonation degree of the production process, promotes the dissolution of CO2 in hot slag, improves the CO2 fixation capacity of slag, and realizes low-carbon and efficient resource utilization of slag. The specific reaction is as follows:

[0069] ;

[0070] ;

[0071] .

[0072] The equipment used in the embodiment is introduced:

[0073] like Figure 2 As shown, the carbonation and carbon sealing equipment includes a slag pouring basin 1, a slag pouring trough 2, a blasting device 3, a spray gun 4, a slag pot 5, a slag cover 6, a slag holding basin 7, a gas-dust separation device 8, a thermoelectric exchange device 9, a gas storage device 10, a dust storage device 11, a slag weighing device 12, a slag particle size classification device 13 and a slag storage device 14.

[0074] The specific usage process is briefly described as follows:

[0075] The converter slag enters the slag pot 5 from the slag pouring basin 1 through the slag pouring chute 2 to control the slag pouring speed and falls into the slag holding basin 7. Under the action of the blast device 3, water vapor, carbon dioxide and other gases are injected into the slag pot 5 by the spray gun 4 to interact with the slag. When all the slag is introduced into the slag pot, the slag cover 6 is covered and water vapor, carbon dioxide and other gases are continued to be sprayed through the blast device 3 and the spray gun 4. The dust and gas enter the gas-dust separation device 8. The gas recovers heat through the thermoelectric exchange device 9 and finally enters the gas storage device 10. The dust enters the dust storage device 11 under the action of gravity. The treated slag is weighed by the slag weighing device 12 and the slag particle size classification device 13 finally enters the slag storage device 14.

[0076] Example 1

[0077] This embodiment provides a method for carbonation and carbon sealing of steel slag in a steelmaking process.

[0078] The steel slag used was the steel slag produced in the production process of a steel plant in Shanxi. The specific composition is shown in Table 1 below:

[0079] Table 1 Component content of steel slag

[0080]

[0081] Take 300kg of steel slag, heat it to 1600℃ in a medium frequency induction furnace, and then cool it naturally to 1450℃. At this time, the density of the steel slag is 2990kg·m -3 The surface tension of steel slag is 0.54N·s, and the surface viscosity coefficient of steel slag is 0.75pa·s.

[0082] After 1450℃, water vapor is used as the main jet medium. By accelerating the water vapor to form a high-speed jet to impact the liquid solute, the molten slag is cooled and crushed. During the experiment, the slag mass flow rate is 3kg / s, the number of high-speed jet guns is 1, the nozzle diameter is 11mm, the pressure of each gun is set to 2.7MPa, and the inlet temperature of the high-pressure gas nozzle is 303K. According to the formula It can be calculated that the jet flow velocity is 500m / s. It can be calculated that the outlet temperature of the compressed gas nozzle is 236K, and then through the formula The average particle size of the steel slag is calculated to be 3.0 mm. At this time, the steel slag is broken into small particles, and a large amount of high-temperature flue gas is recovered at the same time;

[0083] After crushing, the slag is placed in a container, where the temperature is about 1200°C. Maintain the previous conditions and continue to spray water vapor;

[0084] When the temperature drops to 800°C, pressurized water vapor and carbon dioxide gas are sprayed until the temperature reaches 200°C. The flow rate of water vapor is 40 Nm 3 / h, the flow rate of carbon dioxide gas is 10Nm 3 / h, the steel slag continues to break due to stress, and a large amount of high-temperature flue gas is recovered at the same time;

[0085] After the temperature drops to 200°C, continue to spray water and carbon dioxide gas under pressure, with a water vapor flow rate of 10 Nm 3 / h, the flow rate of carbon dioxide gas is 40Nm 3 / h, for 2 hours, for carbonization;

[0086] After magnetic separation, the remaining slag particles were tested for composition. The test results showed that the free calcium oxide content in the remaining slag particles was less than 1%, the iron content was less than 4%, and the average diameter of the slag particles was 3.56 mm. For the carbonation reaction of slag to fix CO2, the carbon fixation rate of the slag was 15.18%, the reaction rate of Ca element in the slag was 62.80%, and the reaction rate of Mg element in the slag was 17.26%.

[0087] Example 2

[0088] This embodiment provides a method for carbonation and carbon sealing of steel slag in a steelmaking process.

[0089] The steel slag used was the steel slag produced in the production process of a steel plant in Shanxi. The specific composition is shown in Table 2 below:

[0090] Table 2 Component content of steel slag

[0091]

[0092] Take 300kg of steel slag, heat it to 1600℃ in a medium frequency induction furnace, and then cool it naturally to 1450℃. At this time, the density of the steel slag is 2190kg·m -3 The surface tension of steel slag is 0.55N·s, and the surface viscosity coefficient of steel slag is 0.75pa·s.

[0093] After 1450℃, water vapor is used as the main jet medium to form a high-speed jet to impact the liquid solute and complete the cooling and crushing of the molten slag. During the experiment, the slag mass flow rate is 5kg / s, the number of high-speed jet guns is 2, the nozzle diameter is 11mm, the pressure of each gun is set to 4.5MPa, and the inlet temperature of the high-pressure gas nozzle is 303K. According to the formula The jet flow velocity is 593 m / s. It can be calculated that the outlet temperature of the compressed gas nozzle is 208K, and then through the formula The average particle size of the steel slag is calculated to be 3.7 mm. At this time, the steel slag is broken into small particles, and a large amount of high-temperature flue gas is recovered at the same time;

[0094] After crushing, place the slag in a container, where the temperature is about 1200°C. Maintain the previous conditions and continue to spray water.

[0095] When the temperature drops to 800°C, pressurized water vapor and carbon dioxide gas are sprayed until the temperature reaches 200°C. The flow rate of water vapor is 40 Nm 3 / h, the flow rate of carbon dioxide gas is 10Nm 3 / h, the steel slag continues to break due to stress, and a large amount of high-temperature flue gas is recovered at the same time;

[0096] After crushing, the slag is placed in a container at a temperature of about 800°C. Pressurized water vapor and industrial waste gas containing carbon dioxide (the carbon dioxide content in industrial waste gas is 56%) are sprayed until the temperature reaches 200°C. The flow rate of water vapor is 80 Nm 3 / h, the flow rate of industrial waste gas is 20Nm 3 / h, the steel slag continues to break due to stress, and a large amount of high-temperature flue gas is recovered at the same time;

[0097] After the temperature drops to 200°C, continue to pressurize and spray water vapor and industrial waste gas containing carbon dioxide (the carbon dioxide content in industrial waste gas is 56%), and the flow rate of water vapor is 10 Nm 3 / h, the flow rate of industrial waste gas is 80Nm 3 / h, for 2 hours, for carbonization;

[0098] After magnetic separation, the remaining slag particles were tested for composition. The test results showed that the free calcium oxide content in the remaining slag particles was less than 1.1%, the average diameter of the slag particles was 4.74 mm, and the carbon fixation rate of the slag was 20.27%.

[0099] Comparative Example 1

[0100] The traditional hot-stemming slag treatment technology using waste heat for self-decomposition has a long treatment cycle. After about 12 to 18 hours of micro-pressure steam and proper temperature control for self-decomposition, large pieces of steel slag are pulverized into slag particles in the hot-stemming tank. The granulated steel slag generally contains 8% to 11% moisture, but the particle size distribution of the treated steel slag is uneven. After the steel slag is hot-stemmed, the particle size greater than 20mm accounts for 30%-35%, and the diameter of some particles can even reach 100mm. During the hot-stemming process, the steel slag needs to be pretreated, and the steel slag needs to be reduced to below 700℃ during the treatment process. The product can be used as a raw material for cement production and manufacturing building materials, but compared with the same silicate, the active silicate and ferroaluminate in the steel slag are lower, the mineral crystals are larger, the steel slag activity is lower, and the hydraulic hardness is poor.

[0101] Comparative Example 2

[0102] The high-pressure slag hot stuffing method can improve the converter slag treatment cycle. The converter slag is treated with steam at a pressure of 0.2~0.3 MPa and 100°C, which shortens the time to 2-3h. The average particle size of the slag treated with high-pressure hot stuffing reaches less than 10mm, and its volume increases by 23%~87%. The pulverization rate of slag less than 0.3 mm reaches 50%~80%, which is lower than that of traditional hot stuffing slag. After high-pressure treatment, the f-CaO of the slag is less than 2%, the water expansion rate is less than 1.5%, and the water consumption per ton of slag is 300kg. However, its particles are still uneven and the slag stuffing effect is not ideal in some processes. During the implementation process, there are slag blocks larger than 30mm that need to be repeatedly rod milled and screened by rod mill. Finally, the slag particle size larger than 10mm accounts for more than 30%, and the comprehensive energy consumption per ton of slag treatment is 1.2kg standard coal.

[0103] Comparative Example 3

[0104] The steel slag used was the steel slag produced in the production process of a steel plant in Jiangsu. The specific composition is shown in Table 3 below:

[0105] Table 3 Component content of steel slag

[0106]

[0107] Take 300kg of steel slag, heat it to 1600℃ in a medium frequency induction furnace, and then cool it naturally to 1450℃. At this time, the density of the steel slag is 3200kg·m -3 The surface tension of steel slag is 0.56N·s, and the surface viscosity coefficient of steel slag is 0.75pa·s.

[0108] After 1450℃, the operation of "using water vapor as the main jet medium to form a high-speed jet to impact the liquid solute to complete the cooling and crushing of the molten slag" in the embodiment of the crushing was not performed. Water vapor was directly used for cooling, and the water vapor flow rate was 50 Nm 3 / h;

[0109] When the temperature drops to 800°C, pressurized water vapor and carbon dioxide gas are sprayed until the temperature reaches 200°C. The flow rate of water vapor is 40 Nm 3 / h, the flow rate of carbon dioxide gas is 10Nm 3 / h, the steel slag continues to break due to stress, and a large amount of high-temperature flue gas is recovered at the same time;

[0110] After crushing, the slag is placed in a container at a temperature of about 800°C. Steam and carbon dioxide gas are sprayed under pressure until the temperature reaches 200°C. The steam flow rate is 40 Nm 3 / h, the flow rate of industrial waste gas is 10Nm 3 / h, the steel slag continues to break due to stress, and a large amount of high-temperature flue gas is recovered at the same time;

[0111] After the temperature drops to 200°C, continue to spray water vapor and carbon dioxide gas under pressure, with a water vapor flow rate of 10 Nm 3 / h, the flow rate of industrial waste gas is 40Nm 3 / h, for 2 hours, for carbonization;

[0112] After magnetic separation, the remaining slag particles were tested for composition. The results showed that the average free calcium oxide content in the remaining slag particles was 3-6%, the average diameter of the slag particles was above 50mm, and the carbon fixation rate of the slag was only 6.38%.

[0113] The method for carbonation and carbon sealing of steel slag in the steelmaking process provided in this application has the following advantages:

[0114] 1. The hot slag is impacted, crushed and cooled by the mixed cooling gas jet, so that the slag is homogenized and granulated, the heat dissipation area of ​​the slag is increased, and the slag is fully contacted with the cooling jet. After the impact, the slag particle size is small and the slag particles are formed;

[0115] 2. The carbon fixation capacity of steel slag is restricted by the particle size, so the steel slag must be effectively ground before it can be used. Due to the difficulty in separating slag from iron, the high iron content of steel slag and the poor grindability, the energy consumption generated by grinding the steel slag is high, and it is very difficult to fully utilize the carbon sealing limit of steel slag. This is an urgent problem to be solved in the existing industrial carbon sealing technology of steel slag. This application introduces engineered high-pressure jet rapid solidification technology into the steel slag treatment process, and comprehensively utilizes subsonic gas atomization, high-pressure water atomization and other methods to achieve efficient separation of steel slag. At the same time, the cooling gas composition is selectively controlled according to the process, and the waste heat of steel slag at different stages is recycled to achieve comprehensive utilization of resources;

[0116] 3. Due to the use of high-pressure jet rapid solidification technology combination, the slag is refined, the slag strength is improved, the gelling activity is improved, and the carbon sealing uniformity of the slag is improved. There is no need for high pressure and other solutions in the existing technology, which is lower in cost and less pollution;

[0117] 4. The cooling gas used in this technology is commonly found in industry or life, with fewer by-products and low pollution. The technology itself is green and environmentally friendly.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, 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 embodiments of the present application.

Claims

1. A method for carbonation sealing of steel slag in a steelmaking process, characterized in that: include: During the process of pouring the steel slag into the slag stewing pool, a convection jet cooling gas is added in a direction intersecting with the pouring direction of the steel slag to perform auxiliary steel slag granulation pretreatment and a sensible heat primary heat exchange process until the steel slag is cooled to 800-1000°C, and the obtained high-temperature steam is recovered to realize heat recovery; After the slag is dumped, the slag dumping port is blocked, and the slag in the hot stuffing device is covered and sprayed with carbon dioxide-containing gas to pulverize it, and the corresponding coal gas is collected to complete the secondary heat exchange; Finally, the slag is crushed by jaw crusher, finely ground by rod mill and magnetic separation to minimize the particle size and iron content of the tailings. The convection jet cooling gas includes water vapor and non-essential compressed air, and the volume proportion of water vapor is not less than 80%; The process of injecting carbon dioxide-containing gas comprises: During the hot-stifling pulverization process, when the temperature of the steel slag is less than 800°C and greater than or equal to 200°C, the carbon dioxide-containing gas includes water vapor and optional compressed air, industrial flue gas containing carbon dioxide, and pure carbon dioxide, and the volume proportion of water vapor is not less than 80%, and the volume proportion of carbon dioxide in the industrial flue gas containing carbon dioxide is not less than 30%; when the temperature of the steel slag is less than 200°C, the carbon dioxide-containing gas includes industrial flue gas containing carbon dioxide and / or pure carbon dioxide, water vapor and optional compressed air, and the volume proportion of the industrial flue gas containing carbon dioxide and / or pure carbon dioxide is not less than 80%.

2. The method for carbonation sealing of steel slag in a steelmaking process according to claim 1, characterized in that: The injection velocity of the convective injection cooling gas satisfies the following formula: ； Wherein, V is the injection velocity of the convective jet cooling gas, m / s; P0—high-pressure gas nozzle inlet pressure, Pa; P—high pressure gas nozzle outlet pressure, Pa; T0—high pressure gas nozzle inlet temperature, K.

3. The method for carbonation sealing of steel slag in a steelmaking process according to claim 1, characterized in that: The cooling gas is a mixture of compressed air and water vapor, wherein the volume proportion of water vapor is not less than 80%.

4. The method for carbonation sealing of steel slag in a steelmaking process according to claim 3, characterized in that: The convection jet cooling gas is sprayed by 1-3 high-speed jet guns, each with a pressure of 1.7-13.8MPa and a total flow rate of 10-90Nm 3 / h.

5. The method for carbonation sealing of steel slag in a steelmaking process according to claim 1, characterized in that: During the process of convectively spraying cooling gas and spraying carbon dioxide-containing gas, the nozzle diameter and the jet flow rate and pressure meet the following relationship: ； Where: q is the jet flow rate, in m 3 / s; D is the nozzle diameter, in m; p It is the outlet pressure of high-pressure gas nozzle, in Pa.

6. The method for carbonation sealing of steel slag in a steelmaking process according to claim 1, characterized in that: The average particle size of the steel slag satisfies the following relationship: ； Where: —dimensionless droplet mean diameter; —initial diameter, in m; —gas-liquid relative motion velocity, in m / s; —Surface tension coefficient of steel slag, unit: N / m; —Surface viscosity coefficient of steel slag, unit: Pa·s; —Steel slag density, unit: kg / m 3 ; ρ g —Gas density, in kg / m 3 ; —Mass flow rate of molten slag during dumping, in kg / s; —Corresponding proportional constant, according to experience, C=1.157, k 1=-0.303, k 2=0.481, k 3=0.7077.

7. The method for carbonation sealing of steel slag in a steelmaking process according to claim 1, characterized in that: When the temperature of the steel slag is less than 200° C., the volume proportion of carbon dioxide in the industrial flue gas containing carbon dioxide is not less than 50%.

8. The method for carbonation sealing of steel slag in a steelmaking process according to claim 1, characterized in that: The tailings have an iron content of 0.76wt%-1.64wt%.

9. The method for carbonation sealing of steel slag in a steelmaking process according to any one of claims 1 to 8, characterized in that: The industrial flue gas containing carbon dioxide includes one or more of lime kiln tail gas, steel rolling heating furnace tail gas and sintering tail gas.

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