Quantitative regulation method of compressive strength and co2 absorption rate of carbonated steel slag product

Abstract

The application provides a quantitative regulation method for compressive strength and CO2 absorption rate of carbonated steel slag products, and belongs to the technical field of steel slag resource utilization. By adding calcium and silicon raw materials with a certain molar ratio into hot-melt steel slag, one or more of the following carbonated active minerals: beta-C2S, gamma-C2S, C3S2, CS and CaO are synthesized by using the residual heat of the hot-melt steel slag. The water-quenched steel slag is ground and pressed into a blank, and then the carbonated steel slag product is prepared through carbonation. The low-calcium silicate mineral is synthesized through solid-phase reaction, the carbonation efficiency of the steel slag is improved, the residual heat of the steel slag is fully utilized, the heat is recycled, and the development of the building material industry is conducive to energy saving and carbon reduction. By adjusting the component ratio of the calcium raw material and the silicon raw material in the steel slag, the strength growth rate and the CO2 absorption rate of the carbonated steel slag are quantitatively regulated, the strength and the carbon sequestration rate of the carbonated steel slag building material product are optimized, the consumption of the steel slag is accelerated, the amount of CO2 is stably increased, and the resource and environmental pressure is fully relieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of comprehensive utilization of resources, and relates to a method for quantitatively regulating the compressive strength and CO2 absorption rate of carbonated steel slag products. BACKGROUND

[0002] As a by-product of the steelmaking process, the large accumulation of steel slag has caused serious environmental pollution and waste of resources. According to different smelting processes, the components of steel slag have great differences, and the main active mineral component is β-C2S mineral. However, due to the slow hydration activity of β-C2S, the early hydration strength of C2S is hindered, thus limiting the early hydration activity of steel slag, resulting in slow early strength growth of steel slag, and further affecting the compressive strength of steel slag products. In addition, the steel slag contains overburned free calcium oxide (f-CaO) and free magnesium oxide (f-MgO), which will cause serious stability problems in the later hydration process of steel slag.

[0003] Carbonation curing can improve the stability of steel slag products. As the main hydration active mineral component of steel slag, the 2h carbonation compressive strength of β-C2S can be as high as 70MPa or more, and at the same time, the carbonation curing process can stably store a certain amount of CO2. However, due to the limited content of active components in steel slag and the large fluctuation of different types of steel slag components, the strength of steel slag products obtained by curing under certain carbonation conditions is limited, which limits the application range of steel slag products and the further increase of CO2 absorption.

[0004] The cooling process of steel slag usually adopts heat pouring method, heat steaming method, or air quenching method, etc. processing technology, resulting in a large amount of heat loss. The high temperature waste heat generated by hot melt state steel slag can be used to generate low carbon silicate minerals (such as γ-C2S, C3S2 and CS) with high carbonation activity and no hydration activity, thereby increasing the content of carbonation active mineral components in steel slag, which is beneficial to the improvement of the compressive strength of steel slag products. In addition, the hydration products of steel slag, such as Ca(OH)2, have high carbonation activity and can be used to increase the CO2 absorption rate in the carbonation process. Figure 1 For the experimental data obtained in the doctoral thesis of the research group "Relationship between calcium carbonate growth and performance in steel slag carbonation process", the carbonation compressive strength and CO2 absorption of each mineral phase in steel slag obtained under certain carbonation conditions (99.9% CO2 concentration, constant CO2 partial pressure 0.2MPa, curing for 168h) are as follows. SUMMARY

[0005] In view of the problems of low compressive strength and CO2 absorption amount of carbonated steel slag products and poor stability in the prior art, the present application provides a quantitative regulation method for the compressive strength and CO2 absorption rate of carbonated steel slag products, which uses calcium-rich industrial raw materials (one or more of carbide slag, limestone, marble slag) and silicon-rich industrial raw materials (one or more of fly ash, fly ash, zeolite, silica ash) to generate calcium silicate minerals (such as β-C2S, γ-C2S, C3S2, CS) by using the residual heat of hot molten steel slag, and when there is excess calcium material, free calcium oxide is generated, and after water quenching and cooling, steel slag rich in calcium silicate mineral components is generated, and after carbonation curing, steel slag building material products with good volume stability and quantitatively regulated compressive strength and CO2 absorption amount are obtained, the compressive strength of the carbonated steel slag building material products reaches 20-100MPa, and the CO2 carbon sequestration rate reaches 5.0%-30.0%.

[0006] The raw materials used in the preparation of the steel slag product of the present application are mainly industrial solid waste and industrial flue gas, and the residual heat of hot molten steel slag is recycled and utilized, thereby expanding the strength growth rate and CO2 absorption rate of the carbonated steel slag building material product, providing a way for expanding the utilization of steel slag resources, and providing a way for reducing industrial carbon emissions and expanding the utilization of solid waste resources.

[0007] To achieve the above object, the technical scheme adopted by the present application is:

[0008] A quantitative regulation method for the compressive strength and CO2 absorption rate of carbonated steel slag products, comprising the following steps:

[0009] S1. Mix the calcium-rich industrial raw material and the silicon-rich industrial raw material uniformly, mix and stir the mixture uniformly using an industrial mixer to obtain a calcium-silicon material powder.

[0010] S2. When the hot molten steel slag is discharged, the calcium-silicon powder obtained in step S1 is uniformly poured into the hot molten steel slag according to the design proportion of high carbon sequestration and high carbonation strength contribution minerals (mixing the calcium-silicon powder material with the hot molten steel slag), and the calcium-silicon powder material reacts with the hot molten steel slag by utilizing the residual heat of the hot molten steel slag, and after water quenching and cooling, a steel slag rich in calcium silicate minerals is generated. When the calcium material is excessive, CaO is contained in the product, and Ca(OH)2 is generated after water quenching and cooling.

[0011] S3. The steel slag powder obtained in step S2 is crushed and ground to obtain a steel slag powder with a fineness of 300m 2 / kg or more.

[0012] S4. After stirring the steel slag powder obtained in step S3 with water uniformly, different building material products are formed by pressing.

[0013] S5. The green body of step S4 is placed in a sealed carbonation reactor, industrial flue gas is introduced, and carbonation curing is carried out under the condition of carbon dioxide gas partial pressure to obtain a carbonated steel slag product with adjustable compressive strength and CO2 absorption rate, which is prepared by adjusting the calcareous component and siliceous component in the steel slag.

[0014] Further, in step S1, the molar ratio of the calcium-rich industrial raw material to the silicon-rich industrial raw material is 1:(0-0.6).

[0015] Further, the calcium-rich industrial raw material is one or more of carbide slag, limestone, and marble slag, and the silicon-rich industrial raw material is one or more of fly ash, fly ash, zeolite, and silica fume.

[0016] Further, in step S2, the calcium-siliceous powdery material accounts for 5%-30% of the mass of the hot-melt steel slag.

[0017] Further, the calcium-silicate minerals in the steel slag include one or more of β-C2S, γ-C2S, C3S2, and CS.

[0018] Further, in step S2, after water quenching, cooling, and crushing and grinding, the calcium-silicate mineral content in the obtained steel slag is not less than 20%, the RO phase is not higher than 10%, the free calcium oxide content is not higher than 10%, and the fineness is not less than 300m 2 / kg.

[0019] Further, in step S2, the temperature for the solid phase reaction caused by the waste heat of the hot-melt steel slag is 1200-1400℃, and the holding time is 1-4h. That is, the waste heat of the hot-melt steel slag mixed with calcium-siliceous powdery material is 1200-1400℃, and the holding time is 1-4h.

[0020] Further, in step S4, the steel slag powder is mixed with water at a liquid-solid ratio of 0.11-0.15.

[0021] Further, in step S5, the concentration of CO2 in the industrial flue gas is 20-90%, and the reaction is carried out at 0.1-0.4MPa for 2-24h. More preferably, the industrial flue gas is introduced at 0.15-0.30MPa.

[0022] Further, in step S4, the pressure loading rate for pressing the green body into a plate shape is 0.5-1.0mm / min, the holding time is not more than 2min, and the mold size for pressing the steel slag plate product is selected according to the actual application. More preferably, the forming pressure of the pressure for pressing the green body into a plate shape is 8MPa, the holding time is 0min, and the mold size for pressing the green body is 100mm×100mm×20mm.

[0023] The carbonated steel slag product with quantitatively controlled compressive strength and CO2 absorption rate prepared by the manufacturing method is obtained by adjusting the mass ratio of calcareous and siliceous raw materials in the steel slag to quantitatively control the compressive strength and CO2 absorption rate, and the steel slag product with good volume stability is obtained.

[0024] The present application can adjust the strength of the same kind of steel slag product according to different actual application conditions, and achieve the absorption of different CO2 contents at the same time, which is used for producing steel slag products with different strength requirements by the same kind of steel slag, including steel slag aggregate, steel slag plate and steel slag brick.

[0025] The beneficial effects of the present application are:

[0026] (1) The present application fully utilizes the waste heat of the hot-melt steel slag, and synthesizes one or more of low-calcium silicate minerals beta-C2S, gamma-C2S, C3S2 and CS through solid-phase reaction in the hot-melt steel slag. When there is excess CaO content, CaO generates Ca(OH)2 material through water quenching cooling process, which improves the carbonation active mineral components of the steel slag, effectively improves the carbonation efficiency of the steel slag on one hand, and fully utilizes the waste heat of the steel slag, achieving the recycling of heat.

[0027] (2) The present application takes bulk solid waste steel slag as the main raw material, adjusts the carbonation active mineral components, expands the strength growth range of the steel slag, and accelerates the absorption of CO2, which provides a solution to the problem of large fluctuation of different kinds of steel slag components and limited utilization of the same kind of steel slag. The present application can further accelerate the consumption of the steel slag while improving the stable absorption of CO2, and fully relieves the resource and environmental pressure.

[0028] (3) The present application synthesizes calcium silicate minerals with carbonation activity through the waste heat of the steel slag, adjusts the mass ratio of calcareous components and siliceous components in the steel slag, and obtains steel slag products with quantitatively controlled compressive strength and CO2 absorption, which realizes negative carbon emission and has important significance for promoting the development of energy saving and carbon reduction in the building material industry in China. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The carbonation compressive strength and CO2 absorption of each mineral phase in the steel slag obtained under certain carbonation conditions (99.9% CO2 concentration, constant CO2 partial pressure 0.2 MPa, curing for 168 h) are shown.

[0030] Figure 2 The quantitative growth results of carbonation compressive strength and CO2 absorption rate obtained when the molar ratio of calcareous and siliceous raw materials CaO:SiO2 is 1:0.5. DETAILED DESCRIPTION

[0031] The specific embodiments of the present application are further explained in connection with the following examples. The examples described herein are intended to be illustrative of the application and are not intended to limit the application.

[0032] In the following examples, the steel slag powder used is from a converter steel slag treated by rapid water cooling from the Anshan Iron and Steel Group, and its mineral composition is shown in Table 1; the calcium-rich industrial raw material used for synthesizing silicate minerals with a certain calcium-silicon ratio is limestone from the Guizhou Wengfu Group, and its chemical composition is shown in Table 2; the silicon-rich industrial raw material used is silica fume.

[0033] Table 1 Mineral composition of steel slag powder (wt%)

[0034] Mineral composition [Alpha]-C2S [C4AF] [C3S] CaCO3 RO phase a f-CaO f-MgO ACn b ]] Mass percentage (wt%) 22.01 5.85 4.36 5.67 15.12 4.10 5.67 37.22

[0035] ( a RO phase: Fe3O4 and FeO; b ACn: amorphous phase and a small amount of other mineral phases.

[0036] Table 2 Chemical composition of limestone

[0037] Chemical composition CaO SiO2 Al2O3 Fe2O3 MgO SO3 Mass percentage (wt%) 88.71 3.48 0.90 0.64 4.28 1.96

[0038] As can be seen from Table 1, the content of the main active mineral β-C2S in the steel slag in the examples is 22.01%, and other mineral components include C4AF 5.85%, C3S 4.36%, CaCO3 5.67%, RO phase 15.12%, f-CaO 4.10%, f-MgO 5.67%, ACn 37.22%; as can be seen from Table 2, the content of CaO in limestone is 88.71%, SiO2 is 3.48%, Al2O3 is 0.90%, Fe2O3 is 0.64%, MgO is 4.28%, SO3 is 1.96%; the content of SiO2 in silica fume is 97.00%.

[0039] Example 1

[0040] A quantitative control method for the compressive strength and CO2 absorption rate of a carbonated steel slag product, the control method comprising the following steps:

[0041] (1) uniformly mixing calcium-rich industrial raw materials and silicon-rich industrial raw materials in a molar ratio of 1:0.5 to obtain a calcium-silicon powder material.

[0042] (2) pouring 10% of the calcium-silicon powder material (1.0 t) into 10 t of hot molten steel slag, maintaining the internal temperature of the hot molten steel slag at 1200°C for 4 h, and obtaining a steel slag containing β-C2S and γ-C2S as the main carbonation active mineral components after water quenching.

[0043] (3) The steel slag obtained in step (2) is crushed and ground to obtain steel slag powder containing 25.2% β-C2S and 4.6% γ-C2S, and the steel slag powder is sieved through a 200-mesh screen.

[0044] (4) The steel slag powder and water are stirred for several minutes at a liquid-solid ratio of 0.11 until they are uniformly mixed, and the obtained mixture is placed in a stainless steel mold and pressed into a 100 mm x 100 mm x 20 mm body at a pressure of 8 MPa, a loading rate of 0.5 mm / min, and a holding time of 30 s.

[0045] (5) The body is placed in a sealed carbonation reactor, and industrial flue gas with a CO2 concentration of 90% is introduced to perform carbonation curing at a constant industrial gas CO2 partial pressure of 0.2 MPa for 2 h. The 3h stability pressure and steam experiment is performed on the batch of test pieces. The experimental results are shown in Table 3.

[0046] Example 2

[0047] Different from Example 1, in step (2), 5% of calcium-silicon powder material (0.5 t) is poured into 10 t of hot molten steel slag. In step (3), steel slag powder containing 28.9% β-C2S and 2.0% γ-C2S is obtained. In step (5), the CO2 concentration of the industrial gas is 50%, the partial pressure is 0.3 MPa, and the carbonation curing time is 10 h, and the rest is the same as Example 1.

[0048] Example 3

[0049] Different from Example 1, in step (2), 20% of calcium-silicon powder material (2.0 t) is poured into 10 t of hot molten steel slag. In step (3), steel slag powder containing 30.3% β-C2S and 7.3% γ-C2S is obtained. In step (4), clean water is added at a liquid-solid ratio of 0.13, and the body is formed by pressing at a pressure of 10 MPa, a loading rate of 1.0 mm / min, and a holding time of 0. In step (5), the CO2 partial pressure of the industrial gas is 0.3 MPa, and the carbonation curing time is 6 h, and the rest is the same as Example 1.

[0050] Example 4

[0051] Different from Example 1, in step (2), 30% of calcium-silicon powder material (3.0 t) is poured into 10 t of hot molten steel slag. In step (3), steel slag containing 35.1% β-C2S and 10.3% γ-C2S is obtained. In step (5), the CO2 partial pressure of the industrial gas is 0.15 MPa, and the carbonation curing time is 24 h, and the rest is the same as Example 1.

[0052] Example 5

[0053] The difference between Example 1 is that the calcium-rich industrial raw material and silicon-rich industrial raw material are mixed in a ratio of 1:0.6 in step (1) to obtain a raw material, which is heated to 1300°C in the hot molten steel slag for 2h, and then cooled by water quenching to obtain a steel slag containing β-C2S, C3S2and CS as the main carbonation active mineral components. In step (3), 25.0% β-C2S, 8.6% C3S2and 10.0% CS are obtained. In step (5), the CO2concentration of the industrial gas is 20%, the gas partial pressure is 0.15 MPa, and the carbonation curing time is 12h, and the rest is the same as Example 1.

[0054] Example 6

[0055] The difference between Example 1 is that the calcium-rich industrial raw material and silicon-rich industrial raw material are mixed in a ratio of 1:0 in step (1) to obtain a raw material, which is heated to 1300°C for 3h, and then cooled by water quenching to obtain a steel slag containing CaO as the main carbonation active mineral. In step (3), 19.8% β-C2S and 10.0% Ca(OH)2are obtained. In step (4), clean water is added at a liquid-solid ratio of 0.15, and pressed into a 100mm×100mm×20mm body at a pressure of 6MPa, with a loading rate of 1.0mm / min and a holding time of 2min. In step (5), the carbonation time is 12h, and the rest is the same as Example 1.

[0056] Comparative group

[0057] The sample of the comparative group is a steel slag powder containing 22.0% β-C2S as the main carbonation active mineral, which is obtained by cooling without adding spherical raw material particles. The obtained mixture is stirred with water for several minutes to obtain a uniform mixture, and then placed in a stainless steel mold to press into a 100mm×100mm×20mm body at a pressure of 8MPa, with a loading rate of 0.5mm / min and a holding time of 0. The test pieces are subjected to 3h stability autoclaving experiment, and the experimental results are shown in Table 3.

[0058] Carbonated steel slag sample

[0059] The difference between the sample of the comparative group is that the body obtained by pressing in the comparative group is placed in a sealed carbonation reactor, and industrial flue gas with a CO2concentration of 90% is introduced, and carbonated at a constant CO2partial pressure of 0.2MPa for 2h, and the test pieces are subjected to 3h stability autoclaving experiment, and the experimental results are shown in Table 3.

[0060] Table 3 Performance results of each example

[0061]

[0062] As shown in Table 3, by adjusting the molar ratio of calcareous raw material and siliceous raw material in hot-melt steel slag and the mixing mass ratio with hot-melt steel slag, the compressive strength and CO2 absorption rate of the steel slag product can be proportionally controlled within a certain range. When the CaO:SiO2 molar ratio of the calcareous raw material and the siliceous raw material is 1:(0-0.6),

[0063] When the calcareous raw material and the siliceous raw material are 5%-30% of the mass of the steel slag, the compressive strength of the carbonated steel slag product can reach 20-100 MPa, and the CO2 absorption rate can reach 5.0%-30.0%.

[0064] The above-described embodiments only express the implementation manners of the present application, and cannot be understood as the limitation of the scope of the patent of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application.

Claims

1. A method for quantitatively controlling the compressive strength and CO2 absorption rate of carbonated steel slag products, characterized in that, Calcium-rich and silicon-rich industrial raw materials are used to generate calcium silicate minerals from the residual heat of hot-melted steel slag. When there is excess calcium material, free calcium oxide is generated. After water quenching and cooling, steel slag rich in calcium silicate minerals is generated. After carbonation curing, steel slag products with good volume stability and quantitatively controllable compressive strength and CO2 absorption are obtained. The specific steps include: S1. Mix calcium-rich industrial raw materials and silicon-rich industrial raw materials at a molar ratio of 1:(0-0.6) evenly, and use an industrial mixer to mix and stir the mixture evenly to obtain calcium-silicon material powder; In step S1, the calcium-rich industrial raw material is one or more of carbide slag, limestone, and marble slag, and the silicon-rich industrial raw material is one or more of fly ash and zeolite. S2. During the discharge of hot-melt steel slag, calcium silicate powder is mixed with the hot-melt steel slag according to the designed ratio of high carbon fixation and high carbonation strength contributing minerals, wherein the calcium silicate powder accounts for 5%-30% of the mass of the hot-melt steel slag; utilizing the residual heat of the hot-melt steel slag, the calcium silicate powder reacts with the hot-melt steel slag in a solid-phase reaction, and after water quenching and cooling, steel slag rich in calcium silicate minerals is generated. The calcium silicate minerals in the steel slag include one or more of β-C2S, γ-C2S, C3S2, and CS; wherein the solid-phase reaction temperature is 1200℃-1400℃, and the holding time is 1h-4h; when the calcium material is in excess, the product contains CaO, which is converted into Ca(OH)2 after water quenching and cooling; S3. The steel slag rich in low-calcium silicate minerals obtained in step S2 is crushed and ground to obtain a fineness of 300 μm. 2 Steel slag powder of / kg or above; S4. After mixing the steel slag powder obtained in step S3 with water at a liquid-to-solid ratio of 0.11-0.15, press it into different building material products. S5. Place the preform pressed in step S4 into a closed carbonation reactor, introduce industrial flue gas, and perform carbonation curing under carbon dioxide gas partial pressure conditions to obtain a carbonated steel slag product with adjustable compressive strength and CO2 absorption rate, which is made by adjusting the calcium and silicon components in the steel slag.

2. The method for quantitatively controlling the compressive strength and CO2 absorption rate of carbonated steel slag products according to claim 1, characterized in that, In step S5, the compressive strength of the carbonated steel slag product reaches 20-100 MPa, and the CO2 carbon fixation rate reaches 5.0%-30.0%.

3. The method for quantitatively controlling the compressive strength and CO2 absorption rate of carbonated steel slag products according to claim 1, characterized in that, In step S2, after water quenching, cooling, crushing, and grinding, the resulting steel slag contains no less than 20% calcium silicate minerals, no more than 10% RO phase, no more than 10% free calcium oxide, and has a fineness of no less than 300 μm. 2 / kg.

4. The method for quantitatively controlling the compressive strength and CO2 absorption rate of carbonated steel slag products according to claim 1, characterized in that, In step S5, the concentration of CO2 in the industrial flue gas is 20-90%, and the reaction time is 2h-24h at 0.1MPa-0.4MPa.

5. The method for quantitatively controlling the compressive strength and CO2 absorption rate of carbonated steel slag products according to claim 1, characterized in that, In step S5, the pressure is 0.15MPa-0.30MPa.

6. The method for quantitatively controlling the compressive strength and CO2 absorption rate of carbonated steel slag products according to claim 1, characterized in that, In step S4, the pressure loading rate for pressing the plate-shaped blank is 0.5-1.0 mm / min, the holding time is no more than 2 min, and the mold size used for pressing the steel slag plate product is selected according to the actual application.

7. The method for quantitatively controlling the compressive strength and CO2 absorption rate of carbonated steel slag products according to claim 1, characterized in that, By adjusting the mass ratio of calcium and silicon raw materials in steel slag, its compressive strength and CO2 absorption rate can be quantitatively controlled, resulting in steel slag products with good volume stability. Steel slag products with various strength requirements can be produced from the same type of steel slag.

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