Method for preparing compact stone by using steel slag

Abstract

The invention relates to a method for full utilization of steel slag, in particular to a method for preparing high-stability compact stone by using steel slag and recovering waste heat. The method mainly comprises the processes of molten steel slag compactness regulation and control, thermal crushing, pressure steam carbonation and recovery of part of sensible heat of the steel slag. The obtained steel slag product can replace natural stones to be used for traffic infrastructure construction. Converter steelmaking final slag is pretreated through molten steel slag solidification regulation and pressure steam carbonation, compact steel slag particles are obtained through combination of a specific air inlet system and rolling crushing, then calcium and magnesium minerals are utilized to rapidly fix carbon dioxide and stabilize volume expansion elements at a high temperature, all steel slag resources are made into stone, and the steel slag resource utilization rate is increased. Meanwhile, part of sensible heat of the full-temperature-section steel slag is recovered. The steel slag stone with a stable and compact surface can be obtained after the treatment of the method. An efficient and value-added treatment mode is provided for large-scale absorption of the steel slag, and the method can be widely applied to high-temperature steel slag treatment in the metallurgical industry.

Description

Technical Field

[0001] The invention relates to a method for fully utilizing steel slag, and in particular to a method for preparing highly stable and dense stone by utilizing steel slag and recovering waste heat. Background Art

[0002] The large-scale use of steel slag is restricted by its poor hydraulic properties, low volume stability, serious alkaline pollution, and low added value. Although some steel slag is used in cement mixtures in the form of steel slag powder, most of the steel slag is still stored in a stockpile, and people have to pay attention to the problems of reduced cement strength, expansion and cracking caused by the addition of steel slag to cement.

[0003] Therefore, it is urgent to explore high-stability and high-value-added utilization methods of steel slag other than micro-powder cement. This 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, excellent stability and other properties. It has the ability to replace natural stone as aggregate for paving, brick making, asphalt mixture or railway ballast. At present, the annual consumption of natural stone used in infrastructure construction is as high as billions of tons. Based on the protection of the natural environment, blasting is expressly prohibited. Therefore, the threshold for natural stone mining is getting higher and higher, and the price is increasing. Therefore, my country's steel slag stone has great market potential and can be used in road construction. It can not only absorb steel slag on a large scale and effectively solve the problem of steel slag disposal, but also conform to the development of circular economy construction.

[0005] However, in order to ensure the desiliconization and dephosphorization capabilities of steel slag, supersaturated CaO is usually added during the smelting process. As a result, free calcium oxide (f-CaO) is easily precipitated and wrapped in the natural cooling process of steel slag. After f-CaO comes into contact with water, its volume expands nearly twice, causing the steel slag to pulverize. The current hot stuffing method for treating steel slag also uses this phenomenon to fully dissolve f-CaO and obtain steel slag products with a pulverization rate of 60% to 70%. The current steel slag treatment method limits the application scope of steel slag products.

[0006] The patent "A continuous hot stewing system for steel slag and its treatment method" (application number 202111624875.5) pre-processes the hot steel slag, crushes it, and continuously hot stews it. After treatment, the steel slag with a particle size of less than 20 mm accounts for 75%, and the f-CaO content is less than 2%. Although this process can effectively eliminate f-CaO, the obtained steel slag product has a high powdering rate and low strength, which limits its application in infrastructure, road engineering and other fields. It also destroys the advantages of high strength and wear resistance of the 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-crushed steel slag into a grate-cooled steel slag heat extraction device, and uses heat exchange between air and steel slag to extract heat. This process utilizes the waste heat of steel slag in the temperature range of 300~800℃, but the waste heat of steel slag in the high temperature range of 900~1600℃ has not been utilized, and the processing time is relatively long. The patent "A processing device and method for preparing sand and gravel from steel slag tailings" (application number 201910400022.X) uses CO2 and steam to digest the f-CaO of cold steel slag tailings at a pressure of 0.2 to 3MPa, and then screens, crushes, cleans and other processes on the digested steel slag to finally obtain steel slag sand and steel slag stone. This process can only process cold slag, requires additional steam input, and lacks the use of waste heat from the full temperature range of steel slag. The optimized solution of the present invention is to accelerate the solidification of molten steel slag through a specific cooling system during the crushing process to obtain denser steel slag particles, and then use the waste heat of steel slag to produce water vapor and introduce gas containing CO2 for pressurized carbonation to solve the problem of poor stability of steel slag. It can stabilize the surface expansion factor of steel slag more efficiently and energy-savingly, and provide a solution to the low utilization rate of steel slag and the shortage of natural stone resources in my country. Summary of the invention

[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 my country. The final product obtained by the existing steel slag pretreatment process has the characteristics of many pores and high pulverization rate, and pursues finer powder particle size in the subsequent treatment of steel slag products, so as to recover more metal elements in the slag. However, this steel slag treatment method not only consumes a large amount of energy, but also the application of the steel slag micropowder remaining after metal recovery is very limited. Therefore, the present invention attempts to regulate the high-temperature steel slag solidification process from the source of steel slag production, utilizes the competitive precipitation behavior of various mineral phases of steel slag, uses a large air volume to quickly solidify the steel slag in the crushing stage, and combines the composition characteristics of steel slag to use carbonation to stabilize the surface instability factors, and reasonably utilizes the waste heat of the full temperature section of steel slag. Under the condition of no additional modifier and heat source supply, it produces steel slag stone with low porosity and good stability, breaking through the core problems such as low utilization rate of domestic steel slag and difficulty in replacing natural stone utilization.

[0008] The steel slag product obtained by the high-temperature solidification regulation-pressurized steam carbonation method designed by the present invention can fully or partially replace natural stone for use as aggregate in transportation infrastructure construction, thereby reducing the amount of steel slag stockpiles from the source and alleviating the tense situation in the use of natural stone. It has high research value and application market.

[0009] The optimized design idea of ​​the present invention is:

[0010] The method for preparing highly stable and dense stone and waste heat recovery from molten steel slag mentioned in the present invention can be mainly divided into two parts: regulation of the solidification process of molten steel slag and carbonation of steel slag particles with pressurized steam. The reaction process involved in the regulation of the solidification process of molten steel slag is as follows: RO phase (metal oxide solid solution phase) and 2CaO·SiO2 phase are first precipitated during the solidification process of molten steel slag, and the remaining liquid phase grows dependent on the first precipitated crystal phase. Under ideal conditions, the liquid phase can be quickly solidified by quenching to tightly wrap the generated crystal phase to obtain dense steel slag, and the volume and porosity changes caused by the formation or phase change of new phases can be avoided. However, for large-volume high-temperature steel slag, quenching is obviously difficult to achieve and full of dangers. Therefore, regulating the solidification process is a prerequisite for obtaining dense steel slag. During the initial solidification process of steel slag, RO phase and 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 slag drops to 900~1100℃, the liquid phase in the slag is basically solidified. If the slag is cooled slowly, solid phase change and element migration will occur, resulting in the gradual appearance of tiny pores inside the slag and interconnection. The original liquid phase gradually forms a flaky and mesh structure due to element migration, and finally the internal porous and loose phenomenon appears. To avoid this phenomenon, it is necessary to create a faster solidification condition when the liquid phase in the slag is not completely solidified. Therefore, first use a small air volume to initially crust the liquid slag to improve the efficiency of roller crushing. Increase the blast air volume during the roller crushing process to quickly solidify the slag. Roll crushing is performed 1~3 times, and the rapid heat exchange between gas and slag is used to obtain denser slag particles with a particle size of less than 60mm and a temperature of 600~900℃.

[0012] The denser slag obtained by solidification control is transferred to the pressurized steam carbonation part. First, water mist is sprayed on the slag. The water mist quickly vaporizes when it contacts the surface of the slag at 600-900℃. A large amount of water vapor creates a pressurized and high-humidity environment, which accelerates the carbonation process of CaO, 2CaO·SiO2 and MgO on the surface of the slag particles. The main reaction processes involved in this stage are:

[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 solidification and regulation, the steel slag lacks sufficient surface area for the internal CaO and MgO to fully hydrate and expand. Therefore, the carbonization reaction only occurs on the surface, and the generated carbonate products make the microscopic morphological features of 0.2 ~ 0.4μm smooth and round, while filling the void space less than 0.15μm. 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 still unstable components inside the steel slag particles, the dense carbonized layer on the surface of the steel slag can isolate water vapor and avoid hydration reactions, thus ensuring the long-term stability of the steel slag stone.

[0017] In the high-temperature solidification control, the waste heat of steel slag in the medium and high temperature range of 900℃~1600℃ is utilized, and the pressurized steam carbonation utilizes the waste heat of steel slag in the range of 200℃~900℃, and part of the sensible heat of the steel slag is recovered in the form of high-temperature gas and water vapor respectively.

[0018] The present invention provides a method for preparing dense stone by using steel slag, comprising the following steps:

[0019] Step 1

[0020] Taking molten steel slag as the processing object, blowing and cooling it and crushing it to obtain steel slag with a surface temperature of 600-900°C, preferably 700-900°C;

[0021] Step 2

[0022] The steel slag obtained in step 1 with a surface temperature of 600-900°C, preferably 700-900°C, is subjected to surface stabilization treatment, and the surface stabilization treatment is as follows: the steel slag obtained in step 1 with a temperature of 600-900°C, preferably 700-900°C, is transferred into a pressurized steam carbonation device for surface stabilization treatment, wherein the pressurized steam carbonation device is a hot stuffy tank capable of spraying water mist and passing flue gas containing CO2; water mist is sprayed immediately after the steel slag enters the hot stuffy tank, and the water mist is vaporized after contacting the hot steel slag, while the temperature of the steel slag is reduced, and the water vapor increases the pressure of the hot stuffy tank, and the pressure in the tank is maintained at 0.1-0.4MPa by adjusting the pressure reducing valve; the content of CO2 in the CO2-containing flue gas is 10vol%-30vol%CO2; under the combined action of pressure, steam and CO2, unstable factors on the surface of the steel slag are carbonated, and the pores are filled.

[0023] In industrial applications, in step 1, the gas blown in is heated up by an average of 100-300°C, and the high-temperature gas can be used again to cool the slag after heat exchange. The high-temperature gas realizes the first stage of heat recovery through heat exchange.

[0024] In step 1, the composition of the molten steel slag includes, by mass percentage, TFe 10-30%, CaO 30-50%, SiO2 10-50%, MgO 5-10%, Al2O3 2-8%, and P2O5 1-3%. In practical applications, the molten steel slag also contains a small amount of impurities not listed, which can be ignored.

[0025] In step 1, the temperature of the molten slag is 1400~1600℃.

[0026] When used in industry, the molten steel slag in step 1 can be the final slag of converter steelmaking after multiple recycling. Of course, steel slags with other components and temperatures that meet the requirements of the present invention can also be used in the present invention.

[0027] After the slag is poured out, blow air or nitrogen to cool it. In the initial stage, a small air volume of ANm is used. 3 / h to purge the high-temperature slag for 1~15min to make the surface of the slag initially solidify and form; after the initial solidified slag begins to break, BNm 3 / h large air volume to quickly cool and solidify the slag particles. Among them, the large air volume is blown for 10~50min, the slag temperature is reduced to 600~900℃, the gas temperature rises by 100~300℃ on average, and the sensible heat of the high temperature section of the slag is recovered by 20~40%. Due to the high viscosity of the slag, a small air volume is used in the early stage to quickly solidify and crust the surface of the slag, avoiding the blocky slag from bonding again, and avoiding the formation of large closed or open pores due to the involvement of gas. In the later stage, a large air volume is used to exchange heat with the crushed slag particles, so that the liquid slag phase distributed between the 2CaO·SiO2 mineral phase and the metal oxide mineral phase is quickly solidified, filling the gap of the early generated mineral phase, and avoiding the formation of a network calcium aluminate mineral phase that causes a significant increase in pores. The value of A is 20000~30000, and A is less than B. The value of B is 30000~60000.

[0028] In the method for preparing dense stone using steel slag of the present invention, step 1 may preferably be:

[0029] Pour the molten slag into the crushing bed with a closed cover; after the slag is poured in, close the closed cover and blow 20000Nm 3 / h ~ 30000Nm 3 / h air and / or nitrogen for 1~15min, then turn on the roller crushing device to crush the high-temperature slag and change the air and / or nitrogen flow rate to 30000Nm 3 / h~60000Nm 3 / h, after roller crushing 2 to 4 times, the slag particle size is less than 60mm, the slag temperature is reduced to 600~900℃, and the slag solidification and granulation time is 10~60min.

[0030] Preferably, BA is greater than 10,000. More preferably, BA is greater than 20,000.

[0031] The steel slag obtained in step 1 is relatively dense steel slag particles, and its cross-sectional porosity is less than 6%.

[0032] The present invention provides a method for preparing dense stone by using steel slag. In step 2, the CO2-containing flue gas is preferably steel plant flue gas containing CO2.

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

[0034] The present invention provides a method for preparing dense stone by using steel slag. In step 2, the hot stuffing time is preferably 1-3 hours to allow the steel slag pile to be fully carbonated.

[0035] The present invention discloses a method for preparing dense stone by using steel slag. In step 2, during the hot stuffing process, pores inside and outside the steel slag are filled, especially micro pores with a pore size less than 0.15 μm can be completely filled.

[0036] The present invention discloses a method for preparing dense stone by using steel slag. Through the treatment in step 2, 10% to 20% of CO2 in the flue gas of the steel plant can be fixed and a stable carbonized layer of a certain thickness can be formed.

[0037] After the treatment in step 2, the temperature of the slag is reduced to below 100°C, and the iron-rich components are selected from the slag particles by a magnetic separator. When used in industry, the remaining part is transported out of the slag treatment workshop by a conveyor belt.

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

[0039] The fixed CO2 content of steel slag is 5%~15% of its mass fraction.

[0040] The present invention discloses a method for preparing dense stone using steel slag. After the second step is completed, the granular steel slag is transferred to a slag discharge platform after the pressure is released to normal pressure. The steel slag is passed through a magnetic separator to select iron-rich particles, and the remaining steel slag is vibrated and screened to obtain steel slag stones of different particle sizes.

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

[0042] In the present invention, the dense carbonized layer on the surface of the steel slag particles after magnetic separation can isolate the unstable factors CaO, MgO, etc. that have not been carbonized inside from water, thereby effectively improving the stability thereof.

[0043] In the present invention, the recovery rate of heat brought by the molten slag is 30% to 50%.

[0044] The present invention discloses a method for preparing highly stable and dense stone from molten steel slag and recovering waste heat. The steel slag product obtained after treatment by the method can completely or partially replace natural stone for road construction, and part of the sensible heat of the steel slag in different temperature ranges can be recovered in the form of hot gas and water vapor.

[0045] Preferably, the method for preparing dense stone with steel slag: pour the slag into the slag pot after the converter is discharged - the slag pot is hoisted by a crane and placed at the entrance of the steel slag crushing bed - the slag pot is automatically tilted to pour out the steel slag - the slag inlet is closed after the slag discharge is completed - the air volume is adjusted to cool the steel slag, and the roller crushing device is started - the granular steel slag is transferred to the slag trough of the steel slag transfer trolley - the slag trough is hoisted by a crane and placed in a pressurized hot stuffy pot - water is pumped and CO2 is introduced to start pressurized hot stuffiness and surface carbonation - the slag trough is hoisted by a crane to the slag unloading platform to unload the slag - the iron-rich steel slag particles are magnetically separated to obtain dense and stable steel slag stone;

[0046] Preferably, the waste heat recovery method is as follows: the high-temperature steel slag at 1400-1600°C in the roller crushing stage is cooled to 600-900°C after gas heat exchange, and the waste heat of the steel slag is recovered in the form of hot gas in this stage. The medium-high temperature steel slag at 600-900°C in the pressure-heating stage is used to heat water to generate steam to maintain a heat-stuffing pressure of 0.1-0.4MPa, and the excess steam can be incorporated into the steam network, and the waste heat of the steel slag is recovered in the form of steam in this stage.

[0047] The steel slag stone obtained by the present invention has a water absorption rate of 0.58-1.02%, a water 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 obtained by the present invention has a water absorption rate of 0.58-0.62%, a water 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 processed steel slag can be fully utilized, and the steel slag products can fully or partially replace natural stone for use in concrete aggregate and road construction.

[0049] Compared with the prior art, the present invention has the following advantages: Different from the traditional slag treatment process, the present invention pre-treats the final slag of converter steelmaking through the solidification control of molten slag - pressurized steam carbonation, obtains denser slag through a specific air intake system combined with roller crushing, and then uses calcium and magnesium minerals to quickly fix carbon dioxide at a higher temperature, stabilize the volume expansion elements, realize the full stoneization of slag resources, and at the same time recover part of the sensible heat of slag in the whole temperature range.

[0050] 1. This process proposes a new process of steel slag solidification control combined with pressurized steam carbonation. The final product is a highly dense and stable steel slag stone, which reduces the stockpile of new steel slag from the source. Its products can partially or completely replace natural stone for road construction, concrete aggregate, railway ballast and other fields, alleviating the shortage of natural stone.

[0051] 2. This process can be improved based on the current steel slag disposal process of steel plants, roller crushing-hot stuffing method, with low investment cost, low water consumption, small dust pollution from closed equipment, short processing cycle and high product value.

[0052] 3. Effectively utilize the waste heat of the slag in all temperature sections. The waste heat of the high-temperature section of the slag is carried out through room-temperature gas, and the high-temperature steam produced enters the steam pipeline of the steel plant or is used for power generation. The nitrogen or air after heat exchange and cooling can be recycled, which is in line with the concept of green transformation of the steel industry.

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

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

[0055] Figure 1 This is a schematic diagram of a new process for preparing dense stone using steel slag according to the present invention.

[0056] Figure 2 It is a schematic diagram of a method for high-temperature slag solidification control, pressurized steam carbonation and full-temperature section steel slag waste heat recovery according to the present invention;

[0057] Figure 3 This is a physical picture of the steel slag stone sample obtained in Example 1;

[0058] Figure 4 This is a physical picture of the sampling of steel slag stone obtained in Comparative Example 1.

[0059] Figure 2In the figure, 1 is a slag pot, 2 is a slag crusting area, 3 is a closed cover, 4 is slag particles, 5 is a roller, 6 is a heat exchange boiler, 7 is a blower, 8 is a slag outlet, 9 is a slag transfer trough, 10 is a slag transport vehicle, 11 is a slag trough, 12 is a spray device, 13 is a hot stuffy pot, and 14 is a breathable plate. Figure 1 The basic process of the present invention and the connection relationship of each device used can be seen in the figure.

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

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

[0062] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] Embodiment 1:

[0064] The molten steel slag used in this embodiment is converter steel slag, and its composition by mass percentage includes: TFe (full iron) 12%, CaO 36.5%, SiO2 22.5%, MgO 10%, Al2O3 4%, P2O5 2.8%, and the remainder is impurities. After the converter steelmaking is completed, the steel slag is poured into the slag pot. Each slag pot receives 2 furnaces of converter slag, and the total slag is about 30t. After the slag is received, it enters the steel slag processing workshop, such as Figure 1 As shown, the specific operations are as follows:

[0065] (1) The crane carries the slag pot 1 to the roller crushing area, and the overhead crane lifts the slag pot to the slag unloading platform. The crushing area sealed cover 3 is opened, and the automatic tipping device of the slag pot is turned on to pour the slag until the steel slag is completely poured out; after pouring the steel slag, the sealed cover is closed, and the fan 7 is immediately turned on to blow the steel slag for 5 minutes, with an air volume of 20000Nm 3 / h, so that the surface of liquid slag can quickly form a crust and solidify.

[0066] (2) After the slag crusts, start roller press 5 and all fans at the same time, with the air volume of 40000Nm 3 / h, the air exchanges heat with the slag through the air holes, the roller press performs the first crushing, the surface crusted slag is crushed, and the liquid slag solidifies quickly. The crushing time is 15 minutes. The slag particle size is observed, and the second roller crushing is performed until the slag particle size is less than 60mm. At this time, the temperature of the slag after cooling and crushing is reduced to 800℃, and the hot gas is circulated after heat exchange in the boiler 6 to cool the slag. The heat obtained can be used for steam power generation or external steam supply;

[0067] (3) Adjust the rotation direction and speed of the roller 5 to push the granular dense slag to the slag outlet 8, and transfer the slag by the slag trough 9 and the slag transfer trolley 10. After arriving at the designated position, the slag trough 9 is hoisted by the crane and the slag is transferred to the slag trough 11, wherein the bottom of the slag trough 11 has a breathable mesh. The slag in the slag trough is loaded to a thickness of 400 mm, and then the hot stuffy tank quick-opening door is opened and placed in the hot stuffy tank 12. After the slag is placed, the quick-opening door is closed, and the spraying device 12 is started to indirectly spray water mist on the slag particles. After the water contacts the hot slag, water vapor is quickly generated, and the pressure in the tank gradually increases. The ventilation device is turned on, and the waste gas containing CO2 (steel plant smelting waste gas, in which the carbon dioxide content is 20 vol%) is blown into the slag from the bottom through the breathable steel plate 14. The pressure relief valve is adjusted to maintain the pressure of the hot stuffing tank at 0.2 MPa. The hot stuffing and carbonization process lasts for 1 hour. After this process, the temperature of the slag is reduced to below 100°C. At this stage, the heat of the slag is recovered in the form of steam.

[0068] (4) The treated slag is transported to the slag unloading platform by a crane, and the iron-rich slag particles are selected by a magnetic separator, with a metal iron recovery rate of 7%. The remaining slag is vibrated and screened to obtain slag stones of different particle sizes. The water absorption rate of the slag stone is 0.6%, the water expansion rate is 0.3%, the crushing value is 11, and the porosity is 3%. Then it is transported to the outside of the slag processing workshop by a conveyor belt. Among them, the iron-rich slag particles can be returned to the converter or added to the sintering for reuse, and the remaining dense and stable slag can be used instead of natural stone aggregate. The fixed CO2 content of the slag is 6% of its mass fraction.

[0069] Embodiment 2:

[0070] The steel slag used in this embodiment is converter steel slag, and its composition by mass percentage includes: TFe 19.41%, CaO 44.79%, SiO2 12.31%, MgO 8.09%, Al2O3 3.94%, P2O5 1.02%, and the remainder is impurities. After the converter steelmaking is completed, the steel slag is poured into the slag pot. Each slag pot receives 3 furnaces of converter slag, and a total of about 40 tons of slag is received. After the slag is received, it enters the steel slag processing workshop, such as Figure 1 As shown, the difference from Example 1 is that the quality of the steel slag received by the slag pot is different. The specific operation is as follows:

[0071] (1) The crane carries the slag pot 1 to the roller crushing area, and the overhead crane lifts the slag pot to the slag unloading platform. The crushing area closed cover 3 is opened, and the automatic tipping device of the slag pot is turned on until the slag is completely poured out; after pouring the slag, the closed cover is closed, and the fan 7 is immediately turned on to blow the slag for 10 minutes, with an air volume of 25000Nm 3 / h, so that the surface of the liquid slag can quickly form a crust and solidify.

[0072] (2) After the slag crusts, start roller press 5 and all fans at the same time, with the air volume of 50000Nm 3 / h, the air exchanges heat with the slag through the air holes, the roller press performs the first crushing, the crusted slag is crushed and lifted, and the liquid slag solidifies quickly. The crushing time is 15 minutes. The slag particle size is observed, and the second roller crushing is performed until the slag particle size is less than 60mm. At this time, the temperature of the slag after cooling and crushing is reduced to about 700℃, and the hot gas is circulated after heat exchange in the boiler 6 to cool the slag. The heat obtained can be used for steam power generation or external steam supply;

[0073] (3) Adjust the rotation direction and speed of the roller 5 to push the granular dense slag to the slag outlet 8, and transfer the slag by the slag trough 9 and the slag transfer trolley 10. After arriving at the designated position, the slag trough 9 is hoisted by the crane and the slag is transferred to the slag trough 11, wherein the bottom of the slag trough 11 has a breathable mesh. The slag in the slag trough is loaded to a thickness of 550mm, and then the hot stuffy tank quick-opening door is opened and placed in the hot stuffy tank 12. After the slag is placed, the quick-opening door is closed, and the spray device 12 is started to indirectly spray water mist on the slag particles. After the water contacts the hot slag, water vapor is quickly generated, and the pressure in the tank gradually increases. The ventilation device is turned on, and the waste gas containing CO2 (steel plant smelting waste gas, in which the carbon dioxide content is 20 vol%) is blown into the slag from the bottom through the breathable steel plate 14. The pressure relief valve is adjusted to maintain the pressure of the hot stuffing tank at 0.3 MPa. The hot stuffing and carbonization process lasts for 1.5 hours. After this process, the temperature of the slag is reduced to below 100°C. At this stage, the heat of the slag is recovered in the form of steam.

[0074] (4) The treated slag is transported to the slag unloading platform by a crane, and the iron-rich slag particles are selected by a magnetic separator. The recovery rate of metallic iron is 10%. The remaining slag is vibrated and screened to obtain slag stones of different particle sizes. The water absorption rate of the slag stone is 1%, the water expansion rate is 0.5%, the crushing value is 14, and the porosity is 3.5%. Then it is transported to the outside of the slag processing workshop by a conveyor belt. Among them, the iron-rich slag particles can be returned to the converter or added to the sintering for reuse, and the remaining dense and stable slag can replace natural stone. The fixed CO2 content of the slag is 10% of its mass fraction.

[0075] Embodiment 3:

[0076] The steel slag used in this embodiment is converter steel slag, and its composition by mass percentage includes: TFe 15%, CaO40.5%, SiO2 16.5%, MgO 7%, Al2O3 7%, P2O5 1.5%, and the remainder is impurities. After the converter steelmaking is completed, the steel slag is poured into the slag pot. Each slag pot receives 4 furnaces of converter slag, and the total slag is about 50t. After the slag is received, it enters the steel slag processing workshop. The difference from Example 1 is that the quality of the steel slag received by the slag pot is different. The specific operation is as follows:

[0077] (1) The crane carries the slag pot 1 to the roller crushing area, and the overhead crane lifts the slag pot to the slag unloading platform. The crushing area closed cover 3 is opened, and the automatic tipping device of the slag pot is turned on to pour the slag until the steel slag is completely poured out; after pouring the steel slag, the closed cover is closed, and the fan 7 is immediately turned on to blow the steel slag for 15 minutes, with an air volume of 30000Nm 3 / h, so that the surface of liquid slag can quickly form a crust and solidify.

[0078] (2) After the slag crusts, start roller press 5 and all fans at the same time, with the air volume of 60000Nm 3 / h, the air exchanges heat with the slag through the air holes, the roller press performs the first crushing, the surface crusted slag is crushed, and the liquid slag solidifies quickly. The crushing time is 25 minutes. The slag particle size is observed, and the second roller crushing is performed until the slag particle size is less than 60mm. At this time, the temperature of the slag after cooling and crushing is reduced to 600℃, and the hot gas is circulated after heat exchange in the boiler 6 to cool the slag. The heat obtained can be used for steam power generation or external steam supply;

[0079] (3) Adjust the rotation direction and speed of the roller 5 to push the granular dense slag to the slag outlet 8, and transfer the slag by the slag trough 9 and the slag transfer trolley 10. After arriving at the designated position, the slag trough 9 is hoisted by the crane and the slag is transferred to the slag trough 11, wherein the bottom of the slag trough 11 has a breathable mesh. The slag in the slag trough is loaded to a thickness of 700 mm, and then the hot stuffy tank quick-opening door is opened and placed in the hot stuffy tank 12. After the slag is placed, the quick-opening door is closed, and the spraying device 12 is started to indirectly spray water mist on the slag particles. After the water contacts the hot slag, water vapor is quickly generated, and the pressure in the tank gradually increases. The ventilation device is turned on, and the waste gas containing CO2 (steel plant smelting waste gas, in which the carbon dioxide content is 20 vol%) is blown into the slag from the bottom through the breathable steel plate 14. The pressure relief valve is adjusted to maintain the pressure of the hot stuffing tank at 0.4 MPa. The hot stuffing and carbonization process lasts for 2 hours. After this process, the temperature of the slag is reduced to below 100°C. At this stage, the heat of the slag is recovered in the form of steam.

[0080] (4) The treated slag is transported to the slag unloading platform by a crane, and the iron-rich slag particles are selected by a magnetic separator. The recovery rate of metallic iron is 9%. The remaining slag is vibrated and screened to obtain slag stones of different particle sizes. The water absorption rate of the slag stone is 1%, the water expansion rate is 0.4%, the crushing value is 13, and the porosity is 4%. Then it is transported to the outside of the slag processing workshop by a conveyor belt. Among them, the iron-rich slag particles can be returned to the converter or added to the sintering for reuse, and the remaining dense and stable slag can replace natural stone. The fixed CO2 content of the slag is 8% of its mass fraction.

[0081] Comparative Example 1: This comparative example is basically the same as Example 1, except that the high-temperature steel slag is not cooled by air blowing, but is cooled and crushed by water, and no CO2-containing waste gas is introduced during the hot stuffing process. The hot stuffing tank pressure is controlled to be 0.7MPa during the hot stuffing process. The final steel slag product has a pulverization rate of about 75%, that is, the steel slag products are mostly small particles or slag powders less than 10mm, and the remaining large-particle steel slag products are porous. Since the large-particle slag contains incompletely hydrated free calcium oxide, water can still enter the steel slag through the pores and slowly hydrate, resulting in the problem of insufficient long-term stability, and it is difficult to meet the size requirements and stability requirements as natural stone aggregates. The obtained product has a water absorption rate of 2.5%, a water expansion rate of 2.2%, a crushing value of 15, and a porosity of 8.5%.

[0082] Comparative Example 2: This comparative example is basically the same as Example 1, except that no CO2-containing waste gas is introduced during the hot stuffing 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 densely regulated steel slag does not have sufficient surface area for hydration reaction, and there are still unreacted free calcium oxide, free magnesium oxide and other substances inside the steel slag particles, which has poor long-term stability and the risk of volume expansion when used as stone. The obtained product has a water absorption rate of 2%, a water expansion rate of 2.8%, a crushing value of 16, and a porosity of 6.5%.

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

[0084] Comparative Example 4: Other conditions are the same as those in Example 1, except that:

[0085] (1) The crane carries the slag pot 1 to the roller crushing area, and the overhead crane lifts the slag pot to the slag unloading platform. The crushing area sealed cover 3 is opened, and the automatic tipping device of the slag pot is turned on until the slag is completely poured out; after pouring the slag, the sealed cover is closed, and the fan 7 is immediately turned on to blow the slag for 15 minutes, with an air volume of 60000Nm 3 / h, so that the surface of liquid slag can quickly form a crust and solidify.

[0086] (2) After the slag crusts, start roller press 5 and all fans at the same time, with the air volume of 20000Nm2 blown into the system. 3 / h, the air exchanges heat with the slag through the air holes, the roller press performs the first crushing, the surface crusted slag is crushed, and the liquid slag solidifies quickly. The crushing time is 25 minutes. The slag particle size is observed, and the second roller crushing is performed until the slag particle size is less than 60mm. At this time, the temperature of the slag after cooling and crushing is reduced to 600℃, and the hot gas is circulated after heat exchange in the boiler 6 to cool the slag. The heat obtained can be used for steam power generation or external steam supply;

[0087] The obtained product has a water absorption rate of 1.98%, a water swelling rate of 2.2%, a crushing value of 15, and a porosity of 7%.

Claims

1. A method for preparing dense stone using steel slag, characterized in that: The steps include: Step 1 The molten steel slag is treated as the object, and is cooled by air blowing and crushed to obtain the steel slag with a surface temperature of 600-900° C., preferably 700-900° C.; Step 2 The steel slag obtained in step 1 with a surface temperature of 600-900°C, preferably 700-900°C, is subjected to surface stabilization treatment, and the surface stabilization treatment is as follows: the steel slag obtained in step 1 with a temperature of 600-900°C, preferably 700-900°C, is transferred into a pressurized steam carbonation device for surface stabilization treatment, wherein the pressurized steam carbonation device is a hot stuffy tank capable of spraying water mist and passing flue gas containing CO2; water mist is sprayed immediately after the steel slag enters the hot stuffy tank, and the water mist is vaporized after contacting the hot steel slag, while the temperature of the steel slag is reduced, and the water vapor increases the pressure of the hot stuffy tank, and the pressure in the tank is maintained at 0.1-0.4MPa by adjusting the pressure reducing valve; the content of CO2 in the CO2-containing flue gas is 10vol%-30vol%CO2; under the combined action of pressure, steam and CO2, unstable factors on the surface of the steel slag are carbonated, and the pores are filled.

2. The method for preparing dense stone using steel slag according to claim 1, characterized in that: In step one, the temperature of the blown gas rises by an average of 100-300°C, and the high-temperature gas can be used again to cool the slag after heat exchange; the high-temperature gas realizes the first stage of heat recovery through heat exchange.

3. The method for preparing dense stone using steel slag according to claim 1, characterized in that: In step 1, the molten steel slag comprises, by mass percentage, TFe 10-30%, CaO 30-50%, SiO2 10-50%, MgO 5-10%, Al2O3 2-8%, and P2O5 1-3%.

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

5. The method for preparing dense stone using steel slag according to claim 1, characterized in that: After the slag is poured out, blow air or nitrogen to cool it. In the initial stage, a small air volume of ANm is used. 3 / h Blow the high-temperature slag for 1~15min to make the surface of the slag initially solidify and form; after the initial solidification of the slag begins to break, blow into the BNm 3 / h large air volume to quickly cool and solidify the slag particles; wherein, the large air volume is blown for 10~50min, the slag temperature is reduced to 600~900℃, the gas temperature rises by 100~300℃ on average, and the sensible heat of the high temperature section of the slag is recovered by 20~40%. Due to the high viscosity of the slag, a small air volume is used in the early stage to quickly solidify and crust the surface of the slag, thereby avoiding the blocky slag from bonding again and avoiding the formation of large closed or open pores due to the inclusion of gas. In the later stage, a large air volume is used to exchange heat with the crushed slag particles, so that the liquid slag phase distributed between the 2CaO·SiO2 mineral phase and the metal oxide mineral phase is quickly solidified, filling the gap of the early generated mineral phase, and avoiding the formation of a network calcium aluminate mineral phase that causes a significant increase in pores. The value of A is 20000~30000, and A is less than B. The value of B is 30000~60000.

6. The method for preparing dense stone using steel slag according to claim 5, characterized in that: Preferably, BA is greater than 10,000; more preferably, BA is greater than 20,000.

7. The method for preparing dense stone using steel slag according to claim 5, characterized in that: The cross-sectional porosity of the steel slag obtained in step 1 is less than 6%.

8. The method for preparing dense stone using steel slag according to claim 1, characterized in that: In step 2, the CO2-containing flue gas is preferably steel mill flue gas containing CO2; the CO2 content in the steel mill flue gas containing CO2 is 10-30%, preferably 10vol%-20vol% CO2, and the temperature is 40-150°C.

9. The method for preparing dense stone using steel slag according to claim 1, characterized in that: In step 2, the hot and stuffy time is preferably 1-3 hours.

10. The method for preparing dense stone using steel slag according to claim 1, characterized in that: Through the treatment in step 2, 10% to 20% of CO2 in the flue gas of the steel plant can be fixed and a stable carbonized layer of a certain thickness can be formed; After the treatment in step 2, the temperature of the steel slag is reduced to below 100°C, and the iron-rich components of the steel slag particles are selected by a magnetic separator; The fixed CO2 content of steel slag is 5%~15% of its mass fraction.

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