A method for preparing dense stone material using steel slag

Abstract

The present application relates to a kind of steel slag full utilization method, specifically to a kind of method for preparing high stable compact stone material using steel slag and recycling waste heat.The present application mainly includes the process of melting steel slag densification control, hot crushing, pressure steam carbonation and recovery of part of sensible heat of steel slag.The steel slag product obtained by the present application can replace natural stone for use in traffic infrastructure construction.The present application carries out pretreatment on converter steelmaking final slag by melting steel slag solidification control-pressure steam carbonization, obtains dense steel slag particles by specific air intake system combined with roller crushing, and then uses calcium and magnesium minerals to fix carbon dioxide at high temperature, stabilizes volume expansion element, realizes all stone materialization of steel slag resources, and recovers part of sensible heat of steel slag in full temperature section.After processing by the present application, surface stable and compact steel slag stone material can be obtained.The present application provides an efficient and value-added processing method for large-scale disposal of steel slag, and can be widely applied in high-temperature steel slag treatment in metallurgical industry.

Description

TECHNICAL FIELD

[0001] The application relates to a method for full utilization of steel slag, in particular to a method for preparing high-stability dense stone materials from steel slag and recycling waste heat. BACKGROUND

[0002] According to the data of the National Bureau of Statistics of China, the annual crude steel output in China increased from 813 million tons to 1019 million tons from 2013 to 2023, and 120-140 kg of steel slag was produced per ton of steel. This means that the annual output of steel slag in China has exceeded 100 million tons. However, due to the poor water hardness, low volume stability, serious alkaline pollution, and low added value of steel slag, the large-scale use of steel slag is restricted. Although some steel slag is used in the form of steel slag powder in cement mixtures, most of the steel slag is still stored in the form of stacking, and people have to pay attention to the problems of cement strength reduction and expansion cracking caused by the mixing of steel slag into cement.

[0003] In the national standard GB175-2023 “General Portland Cement” released in 2023, steel slag is not included in the main mixing materials for cement production. Due to the mandatory requirements in the full text, steel slag cannot be used as a mixing material for the production of general Portland cement. Therefore, it is urgent to explore the high-stability and high-value utilization of steel slag other than micro-powder cement, which is also a major challenge for the green, stable and sustainable development of the steel industry.

[0004] The main components of steel slag, silicate and metal oxide, determine its high strength, good wear resistance, and superior stability, which have the ability to replace natural stone as aggregate for road paving, brick making, asphalt mixture or railway ballast. At present, the annual consumption of natural stone for infrastructure construction is as high as several billion tons. Based on the protection of the natural environment, mountain blasting is strictly prohibited. Therefore, the threshold for natural stone mining is becoming higher and higher, and the price is increasing day by day. At present, the proportion of steel slag used in road construction in Japan, Europe and the United States is 32%, 43% and 50% respectively, compared with 3% in China. Therefore, the steel slag stone in China has great market potential and can be used for road construction, which not only can effectively solve the problem of steel slag disposal, but also conforms to the development of circular economy.

[0005] However, in order to ensure the desiliconization and dephosphorization capacity of steel slag during smelting, supersaturated CaO is usually added. During the natural cooling process of steel slag, free calcium oxide (f-CaO) is easily precipitated and wrapped. When f-CaO contacts with water, its volume expands nearly twice, which causes the powdering phenomenon of steel slag. At present, the heat soaking method for treating steel slag also takes advantage of this phenomenon to fully decompose f-CaO and obtain a steel slag product with a powdering rate of 60%-70%. The current steel slag treatment method limits the application range of steel slag products.

[0006] The patent "A steel slag continuous hot stew system and its treatment method" (application number 202111624875.5) passes hot steel slag through pretreatment crushing and continuous hot stew in sequence. The steel slag with particle size less than 20 mm accounts for 75% after treatment, and the f-CaO content is less than 2%. Although this process better digests f-CaO, the obtained steel slag product has high pulverization rate and low strength, which limits its application in infrastructure, road engineering and other fields, also destroys the advantages of high strength and wear resistance of steel slag itself, and a large amount of steel slag waste heat is not utilized. The patent "A test device and test method for recovering steel slag waste heat" (application number 201911248939.9) loads the roller-pressed steel slag into a grate-cooled steel slag heat extraction device, and uses air to exchange heat with the steel slag to extract heat. This process utilizes the steel slag waste heat in the temperature range of 300-800℃, but the steel slag waste heat in the high temperature range of 900-1600℃ has not been utilized, and the treatment time is relatively long. The patent "A treatment device and method for preparing sand and gravel from steel slag tailings" (application number 201910400022.X) uses CO2 and steam at a pressure of 0.2-3 MPa to digest the f-CaO of cold steel slag tailings, and then performs screening, crushing, cleaning and other processes on the digested steel slag, finally obtains steel slag sand and steel slag gravel. This process can only treat cold slag, requires additional steam input, and lacks utilization of steel slag waste heat in the full temperature range. The optimized scheme of the present invention is to accelerate the solidification of molten steel slag during the crushing process by a specific cooling system to obtain relatively dense steel slag particles, then use the steel slag waste heat to produce water vapor and pass in CO2-containing gas for pressure carbonation to solve the problem of poor stability of steel slag, which can more efficiently and energy-savingly stabilize the surface expansion factors of steel slag, and provides a solution to the low utilization rate of steel slag and the shortage of natural stone resources in China. SUMMARY

[0007] The present invention is to develop and utilize domestic steel slag resources, and solve the problem of low utilization rate of steel slag in China. The final product obtained by the existing steel slag pretreatment process has the characteristics of many pores, high pulverization rate, etc., and in the subsequent treatment of steel slag products, finer powder particle size is pursued in order to recover more metal elements from the slag. However, this steel slag treatment method not only consumes a large amount of energy, but also limits the application of steel slag micro-powder after recovering the metal. Therefore, the present invention attempts to control the solidification process of high-temperature steel slag from the source of steel slag production, utilize the competitive precipitation behavior of each mineral phase of steel slag, use large air volume to rapidly solidify the steel slag in the crushing stage, and combine with the composition characteristics of steel slag to stabilize the surface unstable factors by carbonation, reasonably utilize the waste heat of steel slag in the full temperature range, produce steel slag stone with low porosity and good stability without additional modification agent and heat source supply, and break through the core problems of low utilization rate of domestic steel slag and difficulty in replacing natural stone utilization.

[0008] The high-temperature solidification regulation-pressure steam carbonation method designed in the application can obtain steel slag products which can completely or partially replace natural stone materials for aggregate of traffic infrastructure construction, thereby reducing the amount of steel slag stockpiling from the root, relieving the shortage of natural stone materials, and having high research value and application market.

[0009] The optimized design idea of the application is as follows:

[0010] The high-stable and dense stone material prepared from molten steel slag and waste heat recovery method mentioned in the application mainly includes two parts: molten steel slag solidification process regulation and steel slag particle pressure steam carbonation. The reaction process involved in the molten steel slag solidification process regulation is as follows: in the molten steel slag solidification process, RO phase (metal oxide solid solution phase) and 2CaO·SiO2 phase are first precipitated, and the remaining liquid phase adheres to the first precipitated crystal phase. Under ideal conditions, the liquid phase is rapidly solidified by quenching to tightly wrap the generated crystal phase, and the volume and porosity change caused by new phase generation or phase transition can be avoided. However, for a large amount of high-temperature steel slag, quenching is obviously difficult to achieve and is full of danger. Therefore, the regulation of the solidification process is a prerequisite for obtaining dense steel slag. In the initial solidification process of the steel slag, the RO phase and the 2CaO·SiO2 phase gradually grow and continuously absorb Fe, Si and other elements from the liquid phase. At this time, the remaining liquid phase in the slag can still fill the gaps between the existing elements.

[0011] When the temperature of the steel slag decreases to 900-1100℃, the liquid phase in the steel slag is basically solidified. If the steel slag continues to be slowly cooled, solid phase transition and element migration will occur, resulting in the gradual appearance of small pores in the steel slag and their connection with each other, and the original liquid phase gradually forms a flaky and network structure due to element migration, and finally the internal porous and loose phenomenon appears. To avoid this phenomenon, a faster solidification condition needs to be created when the liquid phase in the steel slag is not completely solidified. Therefore, first, a small amount of air is used to preliminarily make the liquid slag crust to improve the efficiency of roller pressure crushing. During the roller pressure crushing process, the air volume is increased to rapidly solidify the steel slag. The roller pressure crushing is performed 1-3 times, and the rapid heat exchange between the gas and the steel slag is used to obtain relatively dense steel slag particles with a particle size of less than 60mm and a temperature of 600-900℃.

[0012] The relatively dense steel slag obtained by solidification regulation is transported to the pressure steam carbonation part. First, water mist is sprayed on the steel slag. The water mist is rapidly gasified when it contacts the surface of the steel slag with a temperature of 600-900℃, and a large amount of water vapor creates a high-pressure and high-humidity environment, accelerating the carbonation process of CaO, 2CaO·SiO2 and MgO and other substances on the surface of the steel slag particles. The reaction process mainly involved in this stage is as follows:

[0013] CaO + H2O → Ca(OH)2 Ca(OH)2 + CO2 → CaCO3+ H2O

[0014] MgO + H2O→ Mg (OH)2 Mg (OH)2 + CO2 + 2H2O → MgCO3+ 3H2O

[0015] 2(2CaO·SiO2) + CO2+ 3H2O → 3CaO·2SiO2·3H2O + CaCO3

[0016] After the solidification regulation, the steel slag lacks sufficient surface area to allow the internal CaO and MgO to fully hydrate and expand, and thus the carbonation reaction only occurs on the surface. The carbonate product generated makes the micro-morphological characteristics of 0.2 ~ 0.4 μm smooth and round, and simultaneously fills the void space less than 0.15 μm. The surface stability of the steel slag particles is improved and the steel slag particles are further densified. In this way, even if there are unstable components in the interior of the steel slag particles, the dense carbonized layer on the surface of the steel slag can isolate water vapor and avoid the hydration reaction, thereby ensuring the long-term stability of the steel slag stone.

[0017] The high-temperature solidification regulation utilizes the medium-high temperature section steel slag waste heat of 900℃~1600℃, and the pressurized steam carbonation utilizes the steel slag waste heat of 200℃~900℃, and the partial sensible heat of the steel slag is recovered in the form of high-temperature gas and water vapor.

[0018] The present application is a method for preparing a dense stone material using steel slag, comprising the following steps:

[0019] Step one

[0020] The molten steel slag is taken as a treatment object, is subjected to air blowing cooling and crushing to obtain steel slag with a surface temperature of 600~900℃, preferably 700~900℃;

[0021] Step two

[0022] The steel slag with a surface temperature of 600~900℃, preferably 700~900℃ obtained in step one is subjected to surface stabilization treatment. The surface stabilization treatment is that the steel slag with a temperature of 600~900℃, preferably 700~900℃ obtained in step one is transferred into a pressurized steam carbonation device for surface stabilization treatment. The pressurized steam carbonation device is a hot steaming tank capable of spraying water mist and introducing CO2-containing flue gas. The water mist is sprayed immediately after the steel slag enters the hot steaming tank, and the water mist is gasified after contacting the hot steel slag, and at the same time, the temperature of the steel slag is reduced. The water vapor increases the pressure of the hot steaming tank, and the pressure in the tank is maintained at 0.1~0.4 MPa by adjusting the pressure reducing valve. In the CO2-containing flue gas, the content of CO2 is 10vol%~30vol% CO2. Under the combined action of pressure, steam and CO2, the unstable factors on the surface of the steel slag are carbonated, and at the same time, the pores are filled.

[0023] In industrial application, in step one, the average temperature of the blown gas is 100-300℃, and the high-temperature gas can be used for cooling the steel slag again after heat exchange. The high-temperature gas realizes the first-stage heat recovery through heat exchange.

[0024] In step one, the molten steel slag includes the following components in percentage by mass: TFe 10-30%, CaO 30-50%, SiO2 10-50%, MgO 5-10%, Al2O3 2-8%, and P2O5 1-3%. In actual application, the molten steel slag also has a small amount of impurities not listed, which can be ignored.

[0025] In step one, the temperature of the molten steel slag is 1400-1600℃.

[0026] In industrial application, the molten steel slag in step one can be the converter steelmaking final slag after multiple recycling. Of course, other components and temperatures that meet the requirements of the present application can also be used in the present application.

[0027] After the steel slag is poured out, air or nitrogen is blown for cooling. In the initial stage, a small air flow ANm 3 / h is used to sweep the high-temperature steel slag for 1-15 min, so that the surface of the steel slag is preliminarily solidified and formed; after the preliminarily solidified steel slag begins to break, a large air flow BNm 3 / h is blown to rapidly cool and solidify the steel slag particles. In this process, the large air flow is blown for 10-50 min, the temperature of the steel slag is reduced to 600-900℃, the average temperature of the gas is 100-300℃, and the recovered steel slag high-temperature sensible heat is 20-40%. Due to the large viscosity of the steel slag, a small air flow is used in the initial stage to rapidly solidify and form a crust on the surface of the steel slag, so that the blocky steel slag is prevented from being re-bonded, and the formation of large closed pores or open pores due to the entrainment of gas is also avoided. In the later stage, a large air flow is used to exchange heat with the steel slag particles in the breaking process, so that the liquid slag phase distributed between the 2CaO·SiO2 mineral phase and the metal oxide mineral phase is rapidly solidified, the gaps of the early-formed mineral phases are filled, and the formation of the network calcium aluminate mineral phase that significantly increases the porosity is avoided. The value of A is 20000-30000, A is less than B, and the value of B is 30000-60000.

[0028] In the method for preparing dense stone material from steel slag, step one can be preferably as follows:

[0029] The molten steel slag is poured into a breaking bed with a closed cover; after the steel slag is poured, the closed cover is closed, 20000Nm 3 / h ~ 30000Nm 3 / h of air and / or nitrogen is blown into the steel slag, and after 1-15 min, a roller pressing breaking device is opened to break the high-temperature steel slag and the air and / or nitrogen flow is changed to 30000Nm 3 / h ~ 60000Nm 3 / h, after 2-4 times of roll crushing, the particle size of the steel slag is less than 60 mm, the temperature of the steel slag is reduced to 600-900 DEG C, and the solidification and granulation time of the steel slag is 10-60 min.

[0030] Preferably, B-A is greater than 10000. Further preferably, B-A is greater than 20000.

[0031] The steel slag obtained in step one is relatively dense steel slag particles, and the cross-sectional porosity is less than 6%.

[0032] In step two of the method for preparing dense stone material by using steel slag, the CO2-containing flue gas is preferably CO2-containing steel plant flue gas.

[0033] The CO2 content in the CO2-containing steel plant flue gas is 10-30%, preferably 10 vol%-20 vol% CO2, and the temperature is 40-150 DEG C.

[0034] In step two of the method for preparing dense stone material by using steel slag, the heat soaking time is preferably 1-3 h, so that the steel slag pile is fully carbonated.

[0035] In step two of the method for preparing dense stone material by using steel slag, the pores inside and outside the steel slag are filled during the heat soaking process, and especially the small pores with a pore size of less than 0.15 μm can be completely filled.

[0036] In step two of the method for preparing dense stone material by using steel slag, 10%-20% of CO2 in the steel plant flue gas can be fixed, and a certain thickness of stable carbonized layer can be formed.

[0037] After the treatment in step two, the temperature of the steel slag is reduced to below 100 DEG C, and the steel slag particles are selected by a magnetic separator to obtain iron-rich components. In industrial applications, the remaining part is transported out of the steel slag treatment workshop by a conveyor belt.

[0038] In the present application, the pressurized steam carbonation device means that a large amount of water vapor is quickly generated by using 600-900 DEG C steel slag waste heat to heat the water mist, and the pressure in the device is maintained at 0.1-0.4 MPa. Carbonation means that CaO, Ca2SiO4, MgO and other substances in the steel slag react with CO2 in the steel plant flue gas under the condition of "pressurized steam" to generate carbonates.

[0039] The fixed CO2 content of the steel slag is 5%-15% by mass.

[0040] In step two of the method for preparing dense stone material by using steel slag, after the completion of step two, the heat soaking is depressurized to normal pressure, and the granular steel slag is transferred to a slag discharge platform. The steel slag is selected by a magnetic separator to obtain iron-rich particles, and the remaining steel slag is selected by a vibrating screen to obtain steel slag stone materials with different particle sizes.

[0041] The iron-rich steel slag particles of the present application are returned to the converter or sintering process for continued use.

[0042] In the present application, the steel slag particles after magnetic separation can effectively improve the stability due to the dense carbonized layer on the surface, which can isolate the unstable factors such as CaO and MgO inside from water.

[0043] In the present application, the recovery rate of heat from molten steel slag is 30% to 50%.

[0044] The present application provides a method for preparing high-stability dense stone materials from molten steel slag and recovering waste heat. The steel slag product obtained by the method can be used in road construction to replace natural stone materials in whole or in part, and the sensible heat of different temperature sections of the steel slag is recovered in the form of hot gas and water vapor.

[0045] Preferably, the method for preparing dense stone materials from steel slag comprises the following steps: pouring the slag into a slag tank after slagging of the converter; lifting the slag tank by a crane and placing it at the inlet of a steel slag crushing bed; automatically tilting the slag tank to pour out the steel slag; closing the slag inlet after the slag pouring is completed; adjusting the air volume to cool the steel slag; starting the roller pressing and crushing device; transferring the granular steel slag to a slag transfer trolley; lifting the slag trolley by a crane and placing it in a pressurized hot steaming tank; starting the pressurized hot steaming by spraying water and introducing CO2 for surface carbonization; lifting the slag trolley by a crane and unloading the slag at an unloading platform; magnetic separation of iron-rich steel slag particles; and preparation of dense and stable steel slag stone materials.

[0046] Preferably, the waste heat recovery method comprises the following steps: cooling the high-temperature steel slag at 1400-1600℃ after gas heat exchange to 600-900℃, and recovering the waste heat of the steel slag in the form of hot gas; using the medium-high temperature section of the steel slag at 600-900℃ to heat water to generate steam to maintain the hot steaming pressure at 0.1-0.4MPa, and integrating the excess steam into the steam pipe network, and recovering the waste heat of the steel slag in the form of steam.

[0047] The steel slag stone material obtained by the present application has a water absorption rate of 0.58-1.02%, a water immersion expansion rate of 0.28-0.52%, a crushing value of 10.5-14.5, and a porosity of 2.5-4.2%. After optimization, the steel slag stone material obtained by the present application has a water absorption rate of 0.58-0.62%, a water immersion expansion rate of 0.28-0.32%, a crushing value of 10.5-11.2, and a porosity of 2.5-3.2%.

[0048] The treated steel slag can be fully utilized, and the steel slag product can replace natural stone materials in whole or in part for use in concrete aggregate and road construction.

[0049] Compared with the prior art, the present application has the following advantages: unlike the traditional steel slag treatment process, the present application performs pretreatment on the converter steelmaking final slag through molten steel slag solidification regulation-pressure steam carbonation, obtains relatively dense steel slag through a specific air inlet system combined with roller crushing, and then uses calcium and magnesium minerals to rapidly fix carbon dioxide at a high temperature, stabilizes the volume expansion element, realizes full stone of steel slag resources, and recovers part of the sensible heat of the steel slag in the whole temperature section.

[0050] 1. The present process proposes a new process of steel slag solidification regulation combined with pressure steam carbonation, and the final product is high-density stable steel slag stone, which reduces the amount of new steel slag stockpiling from the root, and the product can partially or completely replace natural stone for road construction, concrete aggregate, railway ballast and other fields, to alleviate the shortage of natural stone.

[0051] 2. The present process can be improved based on the current steel plant steel slag disposal process of roller crushing-heat sweating method, which has low investment cost, low water consumption, small dust pollution of closed equipment, short treatment period and high product value.

[0052] 3. The waste heat of steel slag in the whole temperature section is effectively utilized, the waste heat of high-temperature steel slag is taken out by room temperature gas, high-temperature steam is produced and enters the steam pipe network of the steel plant or is used for power generation, and the nitrogen or air after heat exchange and cooling can be recycled, which meets the green transformation concept of the steel industry.

[0053] 4. The present application can fix 5-15 kg of CO2 per ton of steel slag, realize the synergistic utilization of waste gas and solid waste, and meet the requirements of steel enterprises for carbon fixation, cost reduction, high value, harmlessness and sustainable development.

[0054] 5. The present application is expected to break through the "technical bottleneck" of the traditional steel slag treatment method, increase the utilization rate of steel slag from 30% to 60%-80%, and realize the metallurgical technology upgrading of effective utilization of metallurgical solid waste steel slag. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 It is a new process diagram for preparing dense stone from steel slag.

[0056] Figure 2 It is a high-temperature molten slag solidification regulation, pressure steam carbonation and whole-temperature-section steel slag waste heat recovery method diagram.

[0057] Figure 3 It is a sampling physical map of steel slag stone obtained in Example 1.

[0058] Figure 4 It is a sampling physical map of steel slag stone obtained in Comparative Example 1.

[0059] Figure 2In the figure, 1 is a slag tank, 2 is a steel slag crust area, 3 is a closed cover, 4 is a steel slag particle, 5 is a roller, 6 is a heat exchange boiler, 7 is a blower, 8 is a slag outlet, 9 is a steel slag transfer tank, 10 is a slag transport vehicle, 11 is a slag tank, 12 is a spraying device, 13 is a hot tank, and 14 is a breathable plate. It can be seen from the figure that the basic process of the present application and the connection relationship of the devices used are shown. Figure 1 The basic process of the present application and the connection relationship of the devices used can be seen from the figure.

[0060] It can be seen from the figure that the product obtained in Example 1 is dense. Figure 3

[0061] It can be seen from the figure that the product obtained in Comparative Example 1 has obvious pores. Figure 4 Specific embodiments

[0062] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0063] Example 1

[0064] The molten steel slag used in this embodiment is converter steel slag, and its composition includes, by mass percent: TFe (total iron) 12%, CaO 36.5%, SiO2 22.5%, MgO 10%, Al2O3 4%, P2O5 2.8%, and the balance is impurities. After converter steelmaking is completed, the steel slag is poured into a slag tank, and each slag tank is connected to 2 converter slags, a total of about 30 t of slag is connected, and after the slag connection is completed, it enters the steel slag treatment workshop, as shown in Figure 1 The specific operation is as follows:

[0065] (1) The trolley carries the slag tank 1 to the roller crushing area, the overhead crane hoists the slag tank to the slag unloading platform, the closed cover 3 of the crushing area is opened, the automatic tilting device of the slag tank is opened, and the slag is poured out until the steel slag is completely poured out; after the steel slag is poured in, the closed cover is closed, and the blower 7 is immediately opened for 5 minutes, with a wind volume of 20000 Nm 3 / h, so that the surface of the liquid steel slag rapidly crusts and solidifies.

[0066] (2) After the steel slag crust is opened, the roller press is opened, and all the blowers are opened, with a system air volume of 40000 Nm 3 ​​ / h, air passes through the air holes and exchanges heat with the steel slag, the roller press machine performs the first crushing, the surface crust steel slag is crushed, and the liquid steel slag is rapidly solidified, the crushing time is 15 min, the particle size of the steel slag is observed, the second crushing is performed by the roller press, and the particle size of the steel slag is less than 60 mm. At this time, the temperature of the steel slag after cooling and crushing is reduced to 800 DEG C, the hot gas is circulated for cooling the steel slag after heat exchange in the boiler 6, and the obtained heat can be used for steam power generation or external steam supply;

[0067] (3) The rotating direction and speed of the roller 5 are adjusted, the granular dense steel slag is pushed to the slag outlet 8, and the steel slag is transported by the slag tank 9 and the slag receiving transfer trolley 10 to a designated position, then the crane hoists the slag tank 9 and transports the steel slag to the slag tank 11, wherein the bottom of the slag tank 11 is provided with air permeable mesh holes. The loading thickness of the steel slag in the slag tank is 400 mm, then the quick opening door of the hot smelting tank is opened, and the steel slag is placed in the hot smelting tank 13. After the steel slag is placed, the quick opening door is closed, the spraying device 12 is started to indirectly spray water mist on the steel slag particles, water vapor is rapidly generated after the water contacts the hot steel slag, and the pressure in the tank gradually increases. The exhaust gas containing CO2 (smelting exhaust gas of a steel plant, wherein the content of carbon dioxide is 20 vol%) is blown into the steel slag from the bottom through the air-permeable steel plate 14, the pressure relief valve is adjusted to maintain the pressure in the hot smelting tank at 0.2 MPa, the hot smelting and carbonization process lasts for 1 h, after the process, the temperature of the steel slag is reduced to below 100 DEG C, and the heat of the steel slag in this stage is recovered in the form of steam.

[0068] (4) The treated steel slag is transported to the slag unloading table by the crane, the iron-rich steel slag particles are selected out by the magnetic separator, the recovery rate of metallic iron is 7%, and the remaining steel slag is selected by the vibrating screen to obtain steel slag stone materials with different particle sizes. The water absorption rate of the steel slag stone material is 0.6%, the water immersion expansion rate is 0.3%, the crushing value is 11, and the porosity is 3%. Then the steel slag stone material is conveyed to the outside of the steel slag treatment workshop by the conveyor belt. The iron-rich steel slag particles can be returned to the converter or added to the sintering for reuse, and the remaining dense and stable steel slag can be used instead of natural stone aggregate. The content of the fixed CO2 in the steel slag is 6% of the mass fraction.

[0069] Example 2:

[0070] The steel slag used in this example is converter steel slag, and the components include, in terms of mass percentage: TFe 19.41%, CaO 44.79%, SiO2 12.31%, MgO 8.09%, Al2O3 3.94%, P2O5 1.02%, and the balance is impurities. After the converter steelmaking is completed, the steel slag is poured into the slag tank, 3 converter slags are connected to each slag tank, a total of about 40 t of slags are connected, and after the slag connection is completed, the steel slag treatment workshop is entered, as shown in FIG. 1, and the difference from example 1 is that the mass of the steel slag connected to the slag tank is different. The specific operation is as follows: Figure 1

[0071] ​(1) The slag ladle 1 is carried by the travelling crane to the roller crushing zone, the overhead crane hoists the slag ladle to the slag unloading platform, the closed cover 3 of the crushing zone is opened, the automatic tilting device of the slag ladle is opened, and the steel slag is completely poured out until the steel slag is completely poured out; after the steel slag is poured in, the closed cover is closed, the air blower 7 is immediately opened to blow for 10 minutes, the air volume is 25000 Nm 3 / h, and the liquid steel slag surface is rapidly crust solidified.

[0072] (2) After the steel slag crust is opened, the roller press is opened, and all the air blowers are opened, the system air volume is 50000 Nm 3 / h, the air passes through the air holes and exchanges heat with the steel slag, the roller press is crushed for the first time, the crust steel slag is crushed and lifted, and the liquid steel slag is rapidly solidified at the same time, the crushing time is 15 minutes, the steel slag particle size is observed, the second roller crushing is carried out, and the steel slag particle size is less than 60 mm. At this time, the temperature of the steel slag after cooling and crushing is reduced to about 700 DEG C, the hot gas is circulated for cooling the steel slag after heat exchange in the boiler 6, and the obtained heat can be used for steam power generation or external steam supply;

[0073] (3) The rotation direction and speed of the roller 5 are adjusted, the granular and dense steel slag is pushed to the slag outlet 8, and the steel slag is transported by the slag chute 9 and the slag receiving trolley 10, the travelling crane hoists the slag chute 9 and transports the steel slag to the slag chute 11, wherein the bottom of the slag chute 11 is provided with air permeable mesh. The steel slag is loaded to a thickness of 550 mm in the slag chute, and then the quick opening door of the hot smelting tank is opened and placed in the hot smelting tank 13. After the steel slag is placed, the quick opening door is closed, the spraying device 12 is started to indirectly spray water mist on the steel slag particles, water vapor is rapidly generated after the water contacts the hot steel slag, and the pressure in the tank gradually increases. The air permeable steel plate 14 is opened, the exhaust gas containing CO2 (steel smelting exhaust gas, wherein the content of carbon dioxide is 20 vol%) is blown into the steel slag from the bottom, the pressure of the hot smelting tank is maintained at 0.3 MPa by adjusting the pressure relief valve, the hot smelting and carbonization process lasts for 1.5 h, and after the process, the temperature of the steel slag is reduced to below 100 DEG C. The heat of the steel slag in this stage is recovered in the form of steam.

[0074] (4) The treated steel slag is transported by the travelling crane to the slag unloading platform, the iron-rich steel slag particles are selected by the magnetic separator, the metal iron recovery rate is 10%, the remaining steel slag is selected by the vibrating screen to obtain steel slag stone materials with different particle sizes, the water absorption rate of the steel slag stone material is 1%, the water immersion expansion rate is 0.5%, the crushing value is 14, and the porosity is 3.5%, and then the steel slag stone material is conveyed to the outside of the steel slag treatment workshop by the conveyor belt. The iron-rich steel slag particles can be returned to the converter or added to the sintering for reuse, and the remaining dense and stable steel slag can replace natural stone. The fixed CO2 content of the steel slag is 10% of the mass fraction.

[0075] Example 3:

[0076] The steel slag used in the present embodiment is converter steel slag, which includes, in mass percentage, TFe 15%, CaO 40.5%, SiO2 16.5%, MgO 7%, Al2O3 7%, P2O5 1.5%, and the balance being impurities. After the converter steelmaking is completed, the steel slag is poured into a slag tank, 4 furnace converter slags are connected to each slag tank, and a total of about 50 t of slag is connected. After the slag connection is completed, it enters the steel slag treatment workshop. The difference from Example 1 is that the mass of the slag tank connected to the steel slag is different. The specific operation is as follows:

[0077] (1) The trolley carries the slag tank 1 to the roller crushing zone, the overhead crane hoists the slag tank to the slag unloading platform, the closed cover 3 of the crushing zone is opened, the automatic tilting device of the slag tank is opened, and the slag is poured out until the steel slag is completely poured out; after the steel slag is poured in, the closed cover is closed, and the air blower 7 is immediately started to blow the steel slag for 15 min, with an air volume of 30000 Nm 3 / h, so that the surface of the liquid steel slag rapidly forms a crust and solidifies.

[0078] (2) After the steel slag crust is opened, the roller press is started, and all the air blowers are started, with a system air volume of 60000 Nm 3 / h, air passes through the air holes and exchanges heat with the steel slag, the roller press performs the first crushing, the surface crust steel slag is crushed, and at the same time the liquid steel slag rapidly solidifies, the crushing time is 25 min, the steel slag particle size is observed, the second roller crushing is performed until the steel slag particle size is less than 60 mm. At this time, the temperature of the steel slag after cooling and crushing is reduced to 600℃, the hot gas is used for cooling the steel slag after heat exchange in the boiler 6, and the obtained heat can be used for steam power generation or external steam supply;

[0079] (3) The rotation direction and speed of the roller 5 are adjusted, the granular and dense steel slag is pushed to the slag outlet 8, and the steel slag is transferred by the slag tank 9 and the slag transfer trolley 10, after reaching the designated position, the trolley hoists the slag tank 9 and transfers the steel slag to the slag tank 11, wherein the bottom of the slag tank 11 is provided with air permeable mesh. The loading thickness of the steel slag in the slag tank is 700 mm, and then the quick opening door of the hot smothering tank is opened and placed in the hot smothering tank 13. After the steel slag is placed, the quick opening door is closed, the spraying device 12 is started to indirectly spray water mist on the steel slag particles, water vapor is rapidly generated after the water contacts the hot steel slag, and the pressure in the tank gradually increases. Open the air inlet device, the waste gas containing CO2 (smelting waste gas of the steel plant, the content of carbon dioxide is 20 vol%) is blown into the steel slag from the bottom through the air permeable steel plate 14, the pressure of the hot smothering tank is maintained at 0.4 MPa by adjusting the pressure relief valve, and the hot smothering and carbonization process lasts for 2 h. After the process, the temperature of the steel slag is reduced to below 100℃, and the heat of the steel slag is recovered in the form of steam in this stage.

[0080] (4) The treated steel slag is transferred by the travelling crane to the slag unloading platform, and the iron-rich steel slag particles are selected by the magnetic separator, and the metal iron recovery rate is 9%, and the remaining steel slag is selected by the vibrating screen to obtain steel slag stone materials with different particle sizes, the water absorption of the steel slag stone material is 1%, the water immersion expansion rate is 0.4%, the crushing value is 13, and the porosity is 4%, and then the steel slag stone material is conveyed to the outside of the steel slag treatment workshop by the conveying belt. Among them, the iron-rich steel slag particles can be returned to the converter or mixed into sintering for reuse, and the remaining dense and stable steel slag can replace natural stone. The CO2 content of the steel slag is 8% of the mass fraction.

[0081] Comparative Example 1: The comparative example is basically the same as Example 1, except that the high-temperature steel slag is not cooled by blowing air, but is cooled and broken by water, and no CO2-containing waste gas is introduced during the heat soaking process. The heat soaking tank pressure is controlled at 0.7 MPa. The final steel slag product has a pulverization rate of about 75%, i.e. most of the steel slag product is small particles or slag powder below 10 mm, and the remaining large particle steel slag product is porous. Since the large particle slag contains unhydrated free calcium oxide, water can still enter the interior of the steel slag through the pores to hydrate slowly, which has a problem of insufficient long-term stability, and it is difficult to meet the size and stability requirements as natural stone aggregate. The water absorption of the product is 2.5%, the water immersion expansion rate is 2.2%, the crushing value is 15, and the porosity is 8.5%.

[0082] Comparative Example 2: The comparative example is basically the same as Example 1, except that no CO2-containing waste gas is introduced during the heat soaking process. Finally, the free calcium oxide and calcium silicate on the surface of the steel slag particles are hydrated, and the steel slag pulverization rate is about 20%. The steel slag particles still contain unreacted free calcium oxide, free magnesium oxide and other substances in the interior of the steel slag particles due to the lack of sufficient surface area for hydration reaction, which has a problem of poor long-term stability and a risk of volume expansion as stone material. The water absorption of the product is 2%, the water immersion expansion rate is 2.8%, the crushing value is 16, and the porosity is 6.5%.

[0083] Comparative Example 3: The comparative example is basically the same as Example 1, except that the steel slag entering the heat soaking tank is naturally cooled steel slag, and water vapor needs to be introduced for pressure heat soaking. The porosity of the naturally cooled steel slag is about 15%, and the average pore size is 60 μm. After pressure heat soaking and carbonation, the free calcium oxide, magnesium oxide and other substances on the surface and in the pores of the steel slag are carbonated, but the generated carbonates cannot fill these pores, and additional water vapor needs to be introduced. The final steel slag product has a water absorption of 2.61%, a water immersion expansion rate of 3.2%, a crushing value of 16, and a porosity of 14%, and has a problem of poor long-term stability.

[0084] Comparative Example 4: The other conditions are the same as Example 1, except that:

[0085] (1) The slag tank 1 is carried to the roller crushing zone by the trolley, the slag tank is hoisted to the slag unloading platform by the overhead travelling crane, the closed cover 3 of the crushing zone is opened, the automatic tilting device of the slag tank is opened, and the steel slag is completely poured out until the steel slag is completely poured out; after the steel slag is poured, the closed cover is closed, the air blower 7 is immediately opened to blow the steel slag for 15 minutes, the air volume is 60000 Nm 3 / h, and the surface of the liquid steel slag is rapidly solidified by forming a crust.

[0086] (2) After the steel slag is crusty, the roller press is opened, and all the air blowers are opened, the system air volume is 20000 Nm 3 / h, air is exchanged with the steel slag through the air holes, the roller press is crushed for the first time, the surface crusty steel slag is crushed, and the liquid steel slag is rapidly solidified, the crushing time is 25 minutes, the steel slag particle size is observed, the second roller crushing is carried out until the steel slag particle size is less than 60 mm. At this time, the temperature of the steel slag after cooling and crushing is reduced to 600 DEG C, the hot air is exchanged with the boiler 6, and then is recycled to cool the steel slag, the obtained heat can be used for steam power generation or external steam supply;

[0087] The water absorption of the obtained product is 1.98%, the water immersion expansion rate is 2.2%, the crushing value is 15, and the porosity is 7%.

Claims

1. A method for preparing dense stone using steel slag, characterized in that, Includes the following steps: Step 1 Molten steel slag is used as the processing target. It is cooled by blowing air and crushed to obtain steel slag with a surface temperature of 600~900℃. Specifically, after the steel slag is poured out, it is cooled by blowing air or nitrogen. Initially, a small air volume ANm is used. 3 Blow high-temperature steel slag for 1-15 minutes per hour to allow the slag surface to initially solidify and take shape; after the initially solidified steel slag begins to break, BNm is blown in. 3 / h high-volume airflow rapidly cools and solidifies steel slag particles; wherein, high-volume airflow for 10~50min reduces the steel slag temperature to 600~900℃, the average gas temperature rises by 100~300℃, and 20~40% of the sensible heat of the high-temperature section of the steel slag is recovered; the value of A is 20000~30000, A is less than B, and the value of B is 30000~60000; In step one, the composition of the molten steel slag, by mass percentage, includes: TFe 10~30%, CaO 30~50%, SiO2 10~50%, MgO 5~10%, Al2O3 2~8%, P2O5 1-3%; Step Two The steel slag with a surface temperature of 600-900℃ obtained in step one is subjected to surface stabilization treatment. The surface stabilization treatment is as follows: the steel slag with a temperature of 600-900℃ obtained in step one is transferred into a pressurized steam carbonation device for surface stabilization treatment. The pressurized steam carbonation device is a hot sump that sprays water mist and introduces CO2 flue gas. After the steel slag enters the hot sump, water mist is immediately sprayed. The water mist is vaporized upon contact with the hot steel slag, and at the same time, the temperature of the steel slag decreases, and the water vapor increases the pressure in the hot sump. The pressure inside the tank is maintained at 0.1~0.4MPa by adjusting the pressure reducing valve; the CO2 content in the CO2 flue gas is 10vol%~30vol%CO2; under the combined action of pressure, steam and CO2, the unstable factors on the surface of the steel slag are carbonized, and the pores are filled at the same time; after the completion of step two, the pressure is released to atmospheric pressure by hot quenching, and the granular steel slag is transferred to the slag discharge platform; the steel slag is separated into iron-rich particles by magnetic separator, and the remaining steel slag is screened by vibration to obtain steel slag stone of different particle sizes; The iron-rich particles can be returned to the converter or sintering process for continued use.

2. The method for preparing dense stone using steel slag according to claim 1, characterized in that: In step one, the average temperature of the blown-in gas is 100~300℃. After heat exchange, the high-temperature gas can be used again to cool the steel slag. The heat exchange of the high-temperature gas realizes the first stage of heat recovery.

3. The method for preparing dense stone using steel slag according to claim 1, characterized in that: In step one, the temperature of the molten steel slag is 1400~1600℃.

4. The method for preparing dense stone using steel slag according to claim 1, characterized in that: BA is greater than 10000.

5. The method for preparing dense stone using steel slag according to claim 4, characterized in that: BA is greater than 20000.

6. The method for preparing dense stone using steel slag according to claim 1, characterized in that: The porosity of the steel slag cross section obtained in step one is less than 6%.

7. The method for preparing dense stone using steel slag according to claim 1, characterized in that: In step two, the CO2-containing flue gas is CO2-containing steel plant flue gas; the CO2 content in the CO2-containing steel plant flue gas is 10~30%, and the temperature is 40~150℃.

8. A method for preparing dense stone using steel slag according to claim 7, characterized in that: The CO2 content in the flue gas from steel plants is 10 vol% to 20 vol%.

9. A method for preparing dense stone using steel slag according to claim 1, characterized in that: In step two, the simmering time is 1-3 hours.

10. A method for preparing dense stone using steel slag according to claim 1, characterized in that: Through the treatment in step two, 10% to 20% of the CO2 in the steel plant flue gas is fixed and a stable carbonization layer of a certain thickness is formed. After step two treatment, the temperature of the steel slag drops below 100℃. The fixed CO2 content of steel slag is 5% to 15% of its mass fraction.

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