A method for preparing auxiliary cementitious material and concrete products by carbonizing steel slag with industrial kiln exhaust gas

Abstract

The application discloses a method for preparing auxiliary cementitious material and concrete products by carbonizing steel slag with industrial kiln tail gas, and steps are as follows: original steel slag is crushed, iron is removed, and screening is performed, so that a steel slag coarse-fine aggregate mixture and steel slag fine powder are obtained; the steel slag coarse-fine aggregate mixture is carbonized to obtain carbonized coarse aggregate and carbonized fine aggregate; the steel slag fine powder is ground to obtain steel slag micro-powder, the steel slag micro-powder is made into a cake to obtain a steel slag cake; the steel slag cake is subjected to carbonization treatment, and then is dried and ground to obtain a steel slag-based auxiliary cementitious material; the steel slag-based auxiliary cementitious material, silicate cement clinker powder and gypsum powder are mixed to obtain a new low-carbon cementitious material; the carbonized coarse aggregate, the carbonized fine aggregate, the new low-carbon cementitious material and sand are mixed and pressure-formed, and are subjected to carbonization treatment, so that a steel slag multi-stage carbonized product is obtained. The application effectively improves the carbonization rate and carbonization strength through the multi-stage carbonization technology, and avoids the occurrence of uneven carbonization caused by the fact that CO2 carbonization cannot reach the inside of particles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon emission reduction, and particularly relates to a method for preparing auxiliary cementitious material and concrete products by carbonizing steel slag with industrial kiln tail gas. BACKGROUND

[0002] Steel slag is a solid waste with silicate and ferrite as main components formed by adding slagging agent to impurities in molten steel and furnace lining during converter or electric furnace steelmaking. In China, steel slag is mainly produced by converter steelmaking, and is mainly divided into original state steel slag with water content of 2-5% and hot stewed steel slag with water content of 10-15% according to the processing form of steel slag. The hot stewed steel slag is hot steel slag treated by hot stewing with a certain amount of water to convert most of the free calcium and free magnesium into calcium hydroxide and magnesium hydroxide. This treatment process not only wastes waste heat, but also makes the steel slag contain a large amount of water, and at the same time, the hydration of calcium silicate minerals in the steel slag loses activity. In addition, this processing method neither fundamentally eliminates the problem of poor stability nor improves the activity index of steel slag, but only belongs to a simple means of disposing steel slag. The chemical composition and mineral composition of steel slag are complex and variable, and the minerals mainly include C2S, C4AF, f-CaO and magnesium-iron phase solid solution, and also contain a small amount of C3S, f-MgO. Although the chemical composition of steel slag is similar to that of cement, the low content of C3S leads to poor activity, and the high content of f-CaO and f-MgO causes poor volume stability of steel slag, which ultimately affects the resource utilization of steel slag. In addition, the non-active iron-magnesium solid solution contained in the steel slag leads to high energy consumption in the grinding preparation link, and these two reasons limit the building material utilization of steel slag. At present, the annual production of steel slag in China is amazing. According to the calculation of 0.12-0.14 tons of steel slag per ton of steel, the amount of steel slag produced in 2018 has exceeded 100 million tons, and many steel enterprises only simply recycle the metal resources in the steel slag, and the remaining tailings cannot be completely utilized in a harmless way, which has become the No. 1 problem of solid waste treatment in steel smelting plants.

[0003] CN114931853A discloses a method for capturing CO2 in cement kiln flue gas and co-preparing low-carbon cement and the product obtained. The patent uses 150-250 mesh steel slag powder to prepare carbonized steel slag-based low-carbon cementitious material. The steel slag powder with some moisture is suspended in the carbonation reaction equipment for carbonation, and the fine particle steel slag is mixed with more moisture and doped into the flue gas. Even if there is gas-solid separation, due to the absence of a drying process, the flue gas will cause blockage problems for the flue gas dust removal of the cement plant, affecting the carbonation reaction efficiency, and further affecting the activity of the final carbonized steel slag powder. In addition, the patent does not consider that the temperature of the existing cement kiln tail gas flue is generally between 120-180℃, and if the waste heat power generation capacity is to be increased, the temperature will be higher. The flash point of salicylic acid is only 144.5℃, and the boiling point of N,N-dimethylacetamide is 166.1℃, with a flash point of 63.78℃. These activation additives are easy to volatilize into the waste gas and form new pollutants when introduced into the kiln tail gas for carbonization, which can cause safety hazards and affect the subsequent flue gas treatment system.

[0004] CN113072311A discloses a steel slag auxiliary cementitious material, its preparation method and application. The patent mentions that the original steel slag is crushed, the iron is selected, and the steel slag particles with a particle size of 0.02-0.6mm are mixed with an additive solution and then sent to a mill for grinding. CO2 gas is introduced during grinding, and after grinding to 0.05mm, the material is placed in a stirring reaction equipment for secondary carbonation. This indicates that the first grinding in the patent is grinding without drying and without powder selection. If grinding with drying and powder selection, the fine steel slag powder will be quickly dried, and in the absence of moisture and carbonation time, the carbonation efficiency will be difficult to guarantee. Therefore, the patent needs to set up a secondary carbonation process to ensure that the carbonized steel slag auxiliary cementitious material prepared has qualified activity and stability. The patent also does not mention the temperature of the industrial tail gas. High temperature will affect the use effect of the additive, even pollute the flue gas, and the preparation process is complex.

[0005] CN114950119A discloses a method for decarburization of industrial flue gas and co-preparation of steel slag concrete. The patent carbonizes under high liquid-solid ratio (0.5-1.3), i.e. carbonization in water. This needs to solve the problem of the amount of CO2 dissolved in water. Since the solubility of CO2 in water is relatively low, the carbonation effect will be affected. In addition, steel slag powder carbonized in water will become heavy, which can cause sedimentation problems, especially coarse particles that can easily settle. This will result in uneven composition, with the settled particles becoming solid waste with lower activity. In addition, the active minerals in the steel slag powder will undergo hydration reaction and lose part of their activity under high liquid-solid ratio.

[0006] Chinese patent publication CN115196897A discloses a method for preparing low-carbon admixture using cement kiln tail gas, which mentions using steel slag powder and mineralizing agent to mix in proportion, then performing carbonation reaction in the cement kiln tail gas to prepare low-carbon admixture. However, this patent does not consider that the temperature of the cement kiln tail gas is generally > 150℃, and the carbonation reaction is an exothermic reaction, which is not conducive to the chemical stability of the carbonation product. Moreover, the carbonation reaction time is 2-7 days, the efficiency is very low, the steel slag powder is gradually compacted during the carbonation process, and the free calcium carbonation is not too complete.

[0007] In summary, the problems of the prior art are as follows:

[0008] (1) Since the temperature of the existing cement kiln tail gas flue is generally between 120-180℃, the activated additives added in the steel slag will volatilize into the waste gas during carbonization in the kiln tail gas, causing safety hazards and affecting the subsequent flue gas treatment system.

[0009] (2) The existing technology does not set up a drying process under the semi-dry carbonation method, which will cause blockage of the dust collection system. If drying and powder selection are carried out during the grinding process, the fine steel slag powder will be quickly dried, and the carbonation efficiency will be difficult to guarantee under the condition of lack of moisture and carbonation time. Therefore, re-carbonization will be used to solve the problem, and the preparation process is complex. Although carbon sequestration is achieved, the energy consumption is increased.

[0010] (3) Carbonization is carried out under high liquid-solid ratio (0.5-1.3), i.e. carbonization in water, which needs to solve the problem of the amount of CO2 dissolved in water. However, the solubility of CO2 in water is relatively low, which will affect the carbonation effect, and the problems of drying and drying energy consumption also need to be solved.

[0011] (4) The carbonation reaction is an exothermic reaction, which is not conducive to the chemical stability of the carbonation product. Moreover, the carbonation reaction time is 2-7 days, the efficiency is very low, the steel slag powder is gradually compacted during the carbonation process, and the free calcium carbonation is not too complete.

[0012] Therefore, it is necessary to study the above problems and develop a method for effectively carbonizing steel slag using industrial kiln tail gas to prepare auxiliary cementitious materials and concrete products. SUMMARY

[0013] In order to solve the problems existing in the prior art, the present invention provides a method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial kiln tail gas. The auxiliary cementitious materials prepared by the method can directly utilize cement kiln tail gas or steel plant tail gas without separation and purification. The original steel slag can be carbonized in situ, and steel slag particles of different grades can be pre-carbonized to prepare carbonized steel slag aggregate. Finally, the auxiliary cementitious materials prepared from the carbonized steel slag, the carbonized steel slag aggregate, silicate cement, sand and the like are combined to prepare concrete products. The concrete products are carbonized to quickly improve their strength and other properties. Finally, multi-stage carbonization of steel slag is formed to prepare concrete products. The multi-stage carbonization technology effectively improves the carbonization rate and carbonization strength, and avoids the situation where CO2 carbonization cannot penetrate deep into the particles, resulting in uneven carbonization.

[0014] The present invention is achieved by a method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas, comprising the following steps:

[0015] S1. The raw steel slag is first crushed, electromagnetically deironed, and sieved to obtain a mixture of coarse and fine aggregates of 1.0-4.0 mm, fine slag powder less than 1.0 mm, and iron slag;

[0016] S2. Weigh 90-94 parts of the steel slag coarse and fine aggregate mixture in step S1 and 6-10 parts of a carbonization auxiliary agent, mix and stir them evenly; then feed the stirred mixture into a first carbonization device, and then indirectly exchange 150-200° C. flue gas from waste heat power generation into low-temperature flue gas at 80-120° C. to carbonize the steel slag aggregate in the first carbonization device for 0.5-2 h to obtain a carbonized steel slag aggregate mixture; then take out the carbonized steel slag aggregate mixture and feed it into a screening machine for screening to obtain carbonized coarse aggregate and carbonized fine aggregate of different gradations; the carbonized coarse aggregate has a particle diameter of 2.5-4.0 mm and a cylinder pressure strength of 23-45 MPa, and the carbonized fine aggregate has a particle diameter of 1.0-2.5 mm and a cylinder pressure strength of 20-33 MPa.

[0017] The steel slag fine powder in step S1 is sent into a mill, and 0.1-0.2% of a surface active agent for grinding and 0.1-0.5% of a grinding aid agent, each accounting for 0.1-0.2% of the mass of the steel slag fine powder, are added for grinding to obtain steel slag micro-powder; 85-92 parts of the steel slag micro-powder, 8-15 parts of activated water, and 0.1-0.5% of an adsorbent accounting for 0.1-0.5% of the mass of the steel slag micro-powder are weighed and uniformly mixed and stirred to obtain a steel slag mixture with a plasticity index of 12-20%, which is then sent into an extruder for cake making to obtain a steel slag cake with a diameter of 100-150 mm and a thickness of 2-5 mm; the steel slag cake is sent into a second carbonization device, and then 150-200°C flue gas for waste heat power generation is indirectly heat-exchanged into 60-100°C low-temperature tail gas to carbonize the steel slag cake in the second carbonization device for 0.5-2 h, and the carbonized steel slag cake is taken out and sent into a dryer for drying, using 280-350°C waste heat flue gas discharged from the top C1 preheater of the preheating and pre-decomposition system of the cement kiln tail for drying, and then sent into a mill for grinding to obtain a steel slag-based auxiliary cementitious material with an activity index of 90-106% and a specific surface area of 450-600 m 2 / kg; 25-40 parts of the steel slag-based auxiliary cementitious material, 60-70 parts of Portland cement clinker powder, and 0-5 parts of gypsum powder are weighed and uniformly mixed to obtain a new low-carbon cementitious material, and the 28-day compressive strength of the new low-carbon cementitious material is 43.2-57.0 MPa.

[0018] S3, 25-35 parts of the carbonized coarse aggregate in step S2, 24-35 parts of the carbonized fine aggregate, 18-22 parts of the new low-carbon cementitious material, 12-23 parts of sand, and 0.1-0.5% of a polycarboxylate superplasticizer accounting for 0.1-0.5% of the mass of the new low-carbon cementitious material are weighed and uniformly mixed and stirred to obtain a concrete mixture; the concrete mixture is then poured into a product mold, pressure-formed, cured, and then demolded, and the demolded product is sent into a third carbonization device, and then 150-200°C flue gas for waste heat power generation is indirectly heat-exchanged into 65-90°C low-temperature flue gas to carbonize the product in the third carbonization device for 2-6 h, and the carbonized product is taken out to obtain a steel slag multi-stage carbonized product with a compressive strength of 25-48 MPa and a carbonation absorption rate of 18-25%.

[0019] Preferably, in step S2, the carbonization auxiliary agent is a mixed solution composed of 99% of water, 0-0.5% of a carbonization surfactant, and 0-0.5% of a superplasticizer; the superplasticizer is one or a combination of any two of lignosulfonate, polycyclic aromatic salt, and water-soluble resin sulfonate; and the carbonization surfactant is one or a combination of any two of hydrophilic group carboxylate, sulfate, quaternary ammonium salt, PEO derivative, and lactone.

[0020] Preferably, in step S2, the first carbonization device is a 6-8 layer horizontally rolling belt type structure, the shell is stainless steel, and the parameters are as follows: temperature in the device 80-120 DEG C, pressure 0.5-1.0 MPa, humidity ≥80%, CO2 concentration ≥20%.

[0021] Preferably, in step S2, the second carbonization device is a 6-8 layer horizontally rolling porous steel belt type structure, the shell is stainless steel, and the parameters are as follows: temperature in the device 60-100 DEG C, pressure 0.2-0.5 MPa, CO2 concentration ≥20%, humidity ≥85%.

[0022] Preferably, in step S3, the third carbonization device is a tunnel type carbonization reaction device, and the parameters are as follows: temperature in the device 65-90 DEG C, pressure 0.5-1.0 MPa, CO2 concentration ≥20%, humidity ≥70%.

[0023] Preferably, in step S2, the surface active agent for grinding is an anionic surface active agent stearic acid and / or sodium dodecyl benzene sulfonate; the grinding aid is one or a combination of two of polymeric alcohol amine, triethanolamine, triisopropanolamine, ethylene glycol, diethylene glycol.

[0024] Preferably, in step S2, the activated water is one or a combination of two of an amino water reducing agent, a polycarboxylic acid water reducing agent, and latex, and the adsorbent is one or a combination of two of a CO2 pre-adsorbed molecular sieve, active alumina, and silica gel.

[0025] Preferably, in step S2, the steel slag based auxiliary cementitious material contains calcium carbonate products and amorphous silica, the calcium carbonate products are composed of amorphous calcium carbonate, calcite, spar, and vaterite, and the content is 10%-18%; the content of the amorphous silica is 2.5-5%.

[0026] Preferably, in step S2, the 28 day compressive strength of the new low carbon cementitious material is 43.2-57.0 MPa.

[0027] Compared with the prior art, the application has the advantages and positive effects that:

[0028] 1、The present application takes the difference in grindability of each component in the original steel slag as the starting point, since silicate minerals and the like are easy to crush and grind in the original steel slag, and iron-containing minerals and magnesium-containing minerals, or solid solution phases of the two, are relatively difficult to grind. Through crushing, screening and electromagnetic iron removal processes, steel slag particles that are difficult to crush are screened out for separate carbonization to obtain carbonized steel slag aggregate, which can replace ordinary sand and gravel aggregate and save natural resources. In addition, the remaining steel slag powder is separately ground to save power consumption, and the surface free energy of the steel slag powder is increased through mechanical activation, which is beneficial to improving the total amount of CO2 absorption in the subsequent carbonization.

[0029] 2、The steel slag-based auxiliary cementitious material of the present application is obtained by performing a carbonization reaction under the condition of forming a steel slag cake with a certain plasticity, and basically no steel slag dust is generated. The steel slag cake contains sufficient moisture and internally added adsorbent that has previously adsorbed CO2. During the carbonization process of heating and pressurization, CO2 in the adsorbent is slowly released. Since there is pressurization in the external carbonization equipment, it can be ensured that the carbonization reaction is simultaneously performed in the steel slag cake. In addition, a drying process is provided after the carbonization is completed. The dust particles contained in the drying waste gas are much less than in cement production, effectively reducing the operating load of the dust collector in the cement plant.

[0030] 3、The low-temperature waste heat for power generation is effectively utilized in the present application. After indirect heat exchange, the temperature is about 60-120℃. At this temperature, polycarboxylic acid, ethylene glycol and other carbonization aids or activation aids will not be damaged and lose their activation effect. At the same time, it avoids the safety hazards caused by some activation aids reaching the flash point or boiling point due to excessively high temperature.

[0031] 4、The present application makes full use of the 150-200℃ low-temperature waste heat for power generation in cement plants or steel mills (this part of waste heat will be discharged under existing conditions). After indirect heat exchange, the steel slag aggregate, auxiliary cementitious material and concrete products are respectively carbonized. In the process of utilizing low-temperature waste heat, CO2 in the tail gas is captured and permanently stored.

[0032] 5、The present application greatly improves the early activity of the steel slag auxiliary cementitious material and the strength of the carbonized steel slag aggregate through carbonization. The stability of the steel slag aggregate and the auxiliary cementitious material is also eliminated through carbonization. The concrete products are prepared by carbonization of the above-mentioned raw materials. The process technical scheme of multi-stage carbonization of steel slag for preparing building materials is realized. The overall carbonization efficiency and usage of steel slag are improved. The problems of poor strength performance and carbonization only on the surface are solved. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is the process flow chart provided by the embodiment of the present application for preparing auxiliary cementitious material and concrete products by carbonizing steel slag using cement kiln tail gas;

[0034] Figure 2 Schematic diagram of the structure of the first carbonization device and the second carbonization device provided in an embodiment of the present invention;

[0035] Figure 3 This is a front view of a third carbonization device provided by an embodiment of the present invention;

[0036] Figure 4 It is a side view of the third carbonization device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, a method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas includes the following steps:

[0039] S1. The original steel slag is first crushed, electromagnetically deironed, and screened to obtain a mixture of coarse and fine aggregates of 1.0-4.0 mm, fine steel slag powder less than 1.0 mm, and iron slag.

[0040] S2, weighing 90-94 parts of the steel slag coarse and fine aggregate mixture in step S1 and 6-10 parts of the carbonization auxiliary agent, putting them into a stirring device and mixing them evenly for 5-10 minutes; then sending the stirred mixture into the first carbonization device, such as Figure 2 As shown (the mixture is transported inside the equipment in the figure by a belt), the first carbonization equipment is a 6-8 layer horizontally rolling belt structure with a stainless steel shell, and its parameters are as follows: the temperature inside the equipment is 80-120°C, the pressure is 0.5-1.0 MPa, the humidity is ≥80%, and the CO2 concentration is ≥20%; then the 150-200°C flue gas from the waste heat power generation is indirectly heat exchanged into a low-temperature flue gas of 80-120°C to carbonize the steel slag aggregate in the first carbonization equipment for 0.5-2h to obtain a carbonized steel slag aggregate mixture; then the carbonized steel slag aggregate mixture is taken out and sent to a screening machine for screening to obtain carbonized coarse aggregate and carbonized fine aggregate of different gradations; the carbonized coarse aggregate particle diameter is 2.5-4.0mm, the cylinder pressure strength is 23-45MPa, and the carbonized fine aggregate particle diameter is 1.0-2.5mm, and the cylinder pressure strength is 20-33MPa.

[0041] The steel slag fine powder in step S1 is fed into a mill, and a grinding surfactant accounting for 0.1-0.2% of the mass of the steel slag fine powder and a grinding aid accounting for 0.1-0.5% of the mass of the steel slag fine powder are added for grinding to obtain steel slag fine powder; 85-92 parts of steel slag fine powder, 8-15 parts of activated water and an adsorbent accounting for 0.1-0.5% of the mass of the steel slag fine powder are weighed, and the mixture is fed into a high-speed stirring device for mixing and stirring for 5-10 minutes to obtain a steel slag mixture with a plasticity index of 12-20%, which is then fed into an extruder for cake making to obtain a steel slag cake with a diameter of 100-150 mm and a thickness of 2-5 mm; the steel slag cake is fed into a second carbonization device, as shown in FIG. Figure 2 As shown in the figure (the porous steel belt is used to transport the steel slag cake inside the equipment), the second carbonization equipment is a 6-8 layer horizontally rolling porous steel belt structure with a stainless steel shell. Its parameters are as follows: the temperature inside the equipment is 60-100°C, the pressure is 0.2-0.5MPa, the CO2 concentration is ≥20%, and the humidity is ≥85%; then the 150-200°C flue gas from the waste heat power generation is indirectly heat-exchanged into a low-temperature tail gas of 60-100°C to carbonize the steel slag cake in the second carbonization equipment for 0.5-2h, and the carbonized steel slag cake is taken out and sent to the dryer for drying. During the drying process, the 280-350°C waste heat flue gas discharged from the outlet of the C1 preheater at the top of the cement kiln preheating and predecomposition system is used for drying, and then sent to the mill for grinding to obtain a steel slag cake with an activity index of 90-106% and a specific surface area of ​​450-600m 2 / kg of steel slag-based auxiliary cementitious material; the steel slag-based auxiliary cementitious material contains calcium carbonate product and amorphous silicon dioxide, the calcium carbonate product consists of amorphous calcium carbonate, calcite, veneer, and vaterite, with the total content being 10% to 18%; the content of amorphous silicon dioxide is 2.5-5%.

[0042] Weigh 25-40 parts of steel slag-based auxiliary cementitious material, 60-70 parts of silicate cement clinker powder, and 0-5 parts of gypsum powder, mix them evenly, and obtain a new low-carbon cementitious material. The new low-carbon cementitious material has a 28-day compressive strength of 43.2-57.0 MPa.

[0043] In step S2, the carbonization auxiliary agent is a mixture consisting of 99% water, 0-0.5% carbonization surfactant, and 0-0.5% water reducer; the water reducer is one or a combination of any two of lignin sulfonates, polycyclic aromatic salts, and water-soluble resin sulfonates; and the carbonization surfactant is one or a combination of any two of hydrophilic carboxylates, sulfates, quaternary ammonium salts, PEO derivatives, and lactones.

[0044] The surface active agent for grinding is an anionic surfactant sodium stearate and / or sodium dodecyl benzene sulfonate; the grinding aid is one or a combination of polymeric alcohol amine, triethanolamine, triisopropanolamine, ethylene glycol, diethylene glycol.

[0045] The activated water is one or a combination of any two of amino water reducing agent, polycarboxylic acid water reducing agent and latex, and the adsorbent is one or a combination of any two of molecular sieve, activated alumina and silica gel pre-adsorbed with CO2.

[0046] S3, the carbonized coarse aggregate 25-35 parts, the carbonized fine aggregate 24-35 parts, the new low-carbon cementitious material 18-22 parts, the sand 12-23 parts and the polycarboxylic acid water reducing agent accounting for 0.1-0.5% of the mass of the new low-carbon cementitious material in step S2 are weighed and put into a concrete mixer to mix and stir uniformly to obtain a concrete mixture; then the concrete mixture is poured into a product mold, pressure formed, put into a curing chamber for curing for 6-12h, then demolded, and the demolded product is sent into a third carbonization equipment, such as Figure 3 and Figure 4 As shown in the drawings, the third carbonization equipment is a tunnel-like carbonization reaction equipment, and the parameters are as follows: the temperature in the equipment is 65-90℃, the pressure is 0.5-1.0MPa, the CO2 concentration is ≥20%, and the humidity is ≥70%; then the 150-200℃ flue gas for waste heat power generation is indirectly heat-exchanged into 65-90℃ low-temperature flue gas to carbonize the product in the third carbonization equipment for 2-6h to obtain a steel slag multi-stage carbonized product with a compressive strength of 25-48MPa and a carbonation absorption rate of 18-25%.

[0047] In order to better understand the above-mentioned embodiments of the present application, the following further describes them in combination with specific examples.

[0048] Example 1

[0049] Preparation of carbonized coarse aggregate and carbonized fine aggregate, including the following steps:

[0050] S1, the raw state steel slag is first crushed, electromagnetically de-ironed and sieved to obtain a steel slag coarse and fine aggregate mixture of 1.0-4.0mm, a steel slag fine powder less than 1.0mm and iron slag;

[0051] S2, weighing 90 parts of the steel slag coarse and fine aggregate mixture in step S1 and 10 parts of the carbonization auxiliary agent, putting them into a stirring device and mixing them evenly, and the stirring time is 5 minutes; then sending the stirred mixture into the first carbonization device, which is a 6-8 layer belt-type structure that can be horizontally rolled, with a stainless steel shell, and its parameters are as follows: the temperature inside the device is 80°C, the pressure is 0.5MPa, the humidity is 85%, and the CO2 concentration is 20%; then the 15 The 0-200°C flue gas is indirectly heat-exchanged into low-temperature flue gas at 80°C to carbonize the steel slag aggregate in the first carbonization equipment for 0.5h to obtain a carbonized steel slag aggregate mixture; the carbonized steel slag aggregate mixture is then taken out and sent to a screening machine for screening to obtain carbonized coarse aggregate (particle diameter 2.5-4.0mm) and carbonized fine aggregate (particle diameter 1.0-2.5mm) of different gradations; the cylinder compressive strength of the carbonized coarse aggregate is 23.0MPa, and the cylinder compressive strength of the carbonized fine aggregate is 20.0MPa.

[0052] The carbonization auxiliary agent is a mixture consisting of 99% water, 0% carbonization surfactant, and 0.5% water reducer; the water reducer is lignin sulfonate; and the carbonization surfactant is a hydrophilic carboxylate.

[0053] Example 2

[0054] The preparation of carbonized coarse aggregate and carbonized fine aggregate includes the following steps:

[0055] S1. The raw steel slag is first crushed, electromagnetically deironed, and sieved to obtain a mixture of coarse and fine aggregates of 1.0-4.0 mm, fine steel slag powder less than 1.0 mm, and iron slag;

[0056] S2, weighing 94 parts of the steel slag coarse and fine aggregate mixture in step S1 and 6 parts of the carbonization auxiliary agent, putting them into a stirring device and mixing them evenly, and the stirring time is 10 minutes; then sending the stirred mixture into the first carbonization device, which is a 6-8 layer belt-type structure that can be horizontally rolled, with a stainless steel shell, and its parameters are as follows: the temperature inside the device is 120°C, the pressure is 1.0MPa, the humidity is 90%, and the CO2 concentration is 80%; then the 1 The 50-200°C flue gas is indirectly heat-exchanged into low-temperature flue gas at 120°C to carbonize the steel slag aggregate in the first carbonization equipment for 2 hours to obtain a carbonized steel slag aggregate mixture; the carbonized steel slag aggregate mixture is then taken out and sent to a screening machine for screening to obtain carbonized coarse aggregate (particle diameter 2.5-4.0 mm) and carbonized fine aggregate (particle diameter 1.0-2.5 mm) of different gradations; the cylinder compressive strength of the carbonized coarse aggregate is 45.0 MPa, and the cylinder compressive strength of the carbonized fine aggregate is 33.0 MPa.

[0057] The carbonization auxiliary agent is a mixture consisting of 99% water, 0.5% carbonization surfactant, and 0.2% water reducer; the water reducer is a water-soluble resin sulfonate; and the carbonization surfactant is a combination of hydrophilic carboxylate and sulfate.

[0058] Example 3

[0059] The preparation of carbonized coarse aggregate and carbonized fine aggregate includes the following steps:

[0060] S1. The raw steel slag is first crushed, electromagnetically deironed, and sieved to obtain a mixture of coarse and fine aggregates of 1.0-4.0 mm, fine slag powder less than 1.0 mm, and iron slag;

[0061] S2, weighing 93 parts of the steel slag coarse and fine aggregate mixture in step S1 and 7 parts of the carbonization auxiliary agent, putting them into a stirring device and mixing them evenly, and the stirring time is 8 minutes; then sending the stirred mixture into the first carbonization device, which is a 6-8 layer belt-type structure that can be horizontally rolled, with a stainless steel shell, and its parameters are as follows: the temperature inside the device is 80°C, the pressure is 0.7MPa, the humidity is 85%, and the CO2 concentration is 35%; then the 15 The 0-200°C flue gas is indirectly heat-exchanged into low-temperature flue gas at 100°C, which is used to carbonize the steel slag aggregate in the first carbonization equipment for 1 hour to obtain a carbonized steel slag aggregate mixture. The carbonized steel slag aggregate mixture is then taken out and sent to a screening machine for screening to obtain carbonized coarse aggregate (particle diameter 2.5-4.0mm) and carbonized fine aggregate (particle diameter 1.0-2.5mm) of different gradations. The cylinder compressive strength of the carbonized coarse aggregate is 34.3MPa, and the cylinder compressive strength of the carbonized fine aggregate is 28.2MPa.

[0062] The carbonization auxiliary agent is a mixture consisting of 99% water, 0.4% carbonization surfactant, and 0.5% water reducer; the water reducer is a polycyclic aromatic salt; and the carbonization surfactant is a quaternary ammonium salt.

[0063] Example 4

[0064] The preparation of the new low-carbon cementitious material is as follows:

[0065] In this embodiment, the grinding surfactant is an anionic surfactant stearic acid; and the grinding aid is a combination of polymeric alcohol amine and triethanolamine.

[0066] The activated water is an amino water reducer, and the adsorbent is a molecular sieve pre-adsorbed with CO2.

[0067] The steel slag fine powder less than 1.0 mm is sent into a mill, and 0.1% of a surface active agent for grinding and 0.1% of a grinding aid agent accounting for the mass of the steel slag fine powder are added for grinding, to obtain steel slag micro-powder; 85 parts of the steel slag micro-powder, 15 parts of activating water, and 0.1% of an adsorbent accounting for the mass of the steel slag micro-powder are weighed and sent into a high-speed stirring device to be mixed and stirred uniformly for 5 min, to obtain a steel slag mixture with a plasticity index of 12%, which is then sent into an extruder to be made into a cake, to obtain a steel slag cake with a diameter of 100 mm and a thickness of 5 mm; the steel slag cake is sent into a second carbonization device, which is a 6-8 layer porous steel belt type structure that can roll horizontally, and the outer shell is stainless steel, and the parameters are as follows: the temperature in the device is 60°C, the pressure is 0.2 MPa, the CO2 concentration is 20%, and the humidity is 85%. Then, the 150-200°C flue gas for waste heat power generation is indirectly exchanged into 60°C low-temperature tail gas to carbonize the steel slag cake in the second carbonization device for 0.5 h, and the carbonized steel slag cake is taken out and sent into a dryer to be dried, and the 280-350°C waste heat flue gas discharged from the C1 preheater outlet of the top of the preheating and pre-decomposition system of the cement kiln tail is used for drying, and then the steel slag cake is sent into a mill to be ground, to obtain a steel slag-based auxiliary cementitious material with an activity index of 90% and a specific surface area of 450-600 m2 / kg; the steel slag-based auxiliary cementitious material contains calcium carbonate products and amorphous silicon dioxide, the calcium carbonate products are composed of amorphous calcium carbonate, calcite, dolomite, and vaterite, and the content sum is 10%; and the content of the amorphous silicon dioxide is 2.5%. 2 / kg of steel slag-based auxiliary cementitious material; the steel slag-based auxiliary cementitious material contains calcium carbonate products and amorphous silicon dioxide, the calcium carbonate products are composed of amorphous calcium carbonate, calcite, dolomite, and vaterite, and the content sum is 10%; and the content of the amorphous silicon dioxide is 2.5%.

[0068] The steel slag-based auxiliary cementitious material 40 parts, the silicate cement clinker powder 60 parts, and the gypsum powder 0 parts are weighed and uniformly mixed to obtain a new low-carbon cementitious material, and the new low-carbon cementitious material has a 28-day compressive strength of 43.2 MPa.

[0069] Example 5

[0070] The new low-carbon cementitious material is prepared as follows:

[0071] In this embodiment, the surface active agent for grinding is a anionic surface active agent stearic acid; and the grinding aid agent is a combination of polymeric alcohol amine and triethanolamine.

[0072] The activating water is a combination of amino water reducing agent and latex, and the adsorbent is a combination of molecular sieves and active alumina that have adsorbed CO2 in advance.

[0073] The method comprises the following steps: feeding steel slag fine powder having a particle size of less than 1.0 mm into a mill, adding 0.2% by weight of a surfactant for grinding and 0.5% by weight of a grinding aid to grind the steel slag fine powder; weighing 92 parts of the steel slag fine powder, 8 parts of activated water and 0.5% by weight of an adsorbent to mix and stir uniformly in a high-speed stirring device for 10 minutes to obtain a steel slag mixture with a plasticity index of 20%, and then feeding the mixture into an extruder to form a steel slag cake having a diameter of 150 mm and a thickness of 2 mm; feeding the steel slag cake into a second carbonization device, which is a 6-8 layer horizontally rolling porous steel belt structure with a stainless steel shell and the following parameters: a temperature of 100° C., a pressure of 0.5 MPa, a CO2 concentration of 80%, and a humidity of 90%. Then the 150-200℃ flue gas from the waste heat power generation is indirectly heat-exchanged into 100℃ low-temperature tail gas to carbonize the steel slag cake in the second carbonization equipment for 2 hours. The carbonized steel slag cake is taken out and sent to the dryer for drying. During the drying process, the 280-350℃ waste heat flue gas discharged from the outlet of the C1 preheater at the top of the cement kiln preheating and precalcining system is used for drying. Then it is sent to the mill for grinding to obtain a steel slag cake with an activity index of 106% and a specific surface area of ​​450-600m 2 / kg of steel slag-based auxiliary cementitious material; the steel slag-based auxiliary cementitious material contains calcium carbonate product and amorphous silicon dioxide, the calcium carbonate product consists of amorphous calcium carbonate, calcite, veneer, and vaterite, with a total content of 18%; the amorphous silicon dioxide content is 5%.

[0074] Weigh 25 parts of steel slag-based auxiliary cementitious material, 70 parts of silicate cement clinker powder, and 5 parts of gypsum powder, mix them evenly, and obtain a new low-carbon cementitious material. The new low-carbon cementitious material has a 28-day compressive strength of 57.0 MPa.

[0075] Example 6

[0076] The preparation of the new low-carbon cementitious material is as follows:

[0077] In this embodiment, the grinding surfactant is an anionic surfactant stearic acid; and the grinding aid is a combination of polymeric alcohol amine and triethanolamine.

[0078] The activated water is a combination of amino water reducer and latex, and the adsorbent is a combination of molecular sieve pre-adsorbed with CO2 and activated alumina.

[0079] The method comprises the following steps: feeding steel slag fine powder having a particle size less than 1.0 mm into a grinding mill, adding 0.15% by weight of a surfactant for grinding and 0.3% by weight of a grinding aid for grinding to obtain steel slag micropowder; weighing 90 parts of steel slag micropowder, 10 parts of activated water and 0.3% by weight of an adsorbent for the steel slag micropowder, feeding the mixed powder into a high-speed stirring device and stirring the mixture uniformly for 8 minutes to obtain a steel slag mixture having a plasticity index of 16%, and then feeding the mixture into an extruder for cake making to obtain a steel slag cake having a diameter of 130 mm and a thickness of 3 mm; feeding the steel slag cake into a second carbonization device, which is a 6-8 layer horizontally rolling porous steel belt structure with a stainless steel shell and the following parameters: a temperature of 80° C., a pressure of 0.35 MPa, a CO2 concentration of 35%, and a humidity of 85%. Then the 150-200℃ flue gas from the waste heat power generation is indirectly heat-exchanged into 85℃ low-temperature tail gas to carbonize the steel slag cake in the second carbonization equipment for 1.5 hours. The carbonized steel slag cake is taken out and sent to the dryer for drying. During the drying process, the 280-350℃ waste heat flue gas discharged from the outlet of the C1 preheater at the top of the cement kiln preheating and precalcining system is used for drying. Then it is sent to the mill for grinding to obtain a steel slag cake with an activity index of 98.5% and a specific surface area of ​​450-600m 2 / kg of steel slag-based auxiliary cementitious material; the steel slag-based auxiliary cementitious material contains calcium carbonate product and amorphous silicon dioxide, the calcium carbonate product consists of amorphous calcium carbonate, calcite, veneer, and vaterite, with a total content of 15%; the amorphous silicon dioxide content is 3.5%.

[0080] Weigh 30 parts of steel slag-based auxiliary cementitious material, 66 parts of silicate cement clinker powder, and 4 parts of gypsum powder, mix them evenly, and obtain a new low-carbon cementitious material. The new low-carbon cementitious material has a 28-day compressive strength of 52.6 MPa.

[0081] Example 7

[0082] 35 parts of the carbonized coarse aggregate of Example 2, 24 parts of the carbonized fine aggregate, 18 parts of the new low-carbon cementitious material of Example 5, 12 parts of sand, and 0.1% by weight of a polycarboxylic acid-based water-reducing agent were weighed and placed in a concrete mixer for uniform mixing to obtain a concrete mixture. The concrete mixture was then poured into a product mold, pressurized, and placed in a curing room for 6 hours. The mold was then removed, and the product was fed into a third carbonization device, a tunnel-like carbonization reaction device with the following parameters: an internal temperature of 65°C, a pressure of 0.5 MPa, a CO2 concentration of 20%, and a humidity of 70%. The product in the third carbonization device was then carbonized for 2 hours using 150-200°C flue gas from waste heat power generation, which was converted to low-temperature flue gas at 65°C. The product was then removed from the third carbonization device, resulting in a steel slag multi-stage carbonized product with a compressive strength of 25 MPa and a carbonization absorption rate of 18%.

[0083] Example 8

[0084] 30 parts of the carbonized coarse aggregate of Example 2, 32 parts of the carbonized fine aggregate, 20 parts of the new low-carbon cementitious material of Example 5, 16 parts of sand, and 0.2% of the weight of the new low-carbon cementitious material were weighed and placed in a concrete mixer for uniform mixing to obtain a concrete mixture. The concrete mixture was then poured into a product mold, pressurized, and cured in a curing room for 8 hours. The mold was then removed and the product was fed into a third carbonization device, a tunnel-like carbonization reaction device with the following parameters: internal temperature of 90°C, pressure of 1.0 MPa, CO2 concentration of 80%, and humidity of 90%. The product in the third carbonization device was then carbonized for 5 hours using 150-200°C flue gas from waste heat power generation, which was converted to low-temperature flue gas at 75°C. The product was then removed from the third carbonization device, resulting in a steel slag multi-stage carbonized product with a compressive strength of 48 MPa and a carbonization absorption rate of 25%.

[0085] Example 9

[0086] 25 parts of the carbonized coarse aggregate of Example 2, 35 parts of the carbonized fine aggregate, 22 parts of the new low-carbon cementitious material of Example 5, 23 parts of sand, and 0.5% of the weight of the new low-carbon cementitious material were weighed and placed in a concrete mixer for uniform mixing to obtain a concrete mixture. The concrete mixture was then poured into a product mold, pressurized, and placed in a curing room for 12 hours. The mold was then removed and the product was fed into a third carbonization device, a tunnel-like carbonization reaction device with the following parameters: an internal temperature of 75°C, a pressure of 0.7 MPa, a CO2 concentration of 35%, and a humidity of 80%. The product in the third carbonization device was then carbonized for 6 hours using 150-200°C flue gas from waste heat power generation, which was converted to low-temperature flue gas at 90°C. The product was then removed from the third carbonization device, resulting in a steel slag multi-stage carbonized product with a compressive strength of 44 MPa and a carbonization absorption rate of 23%.

[0087] In the present invention, the early activity of the steel slag auxiliary cementitious material and the strength of the carbonized steel slag aggregate are greatly improved through carbonization. The stability of the steel slag aggregate and the auxiliary cementitious material is also eliminated through carbonization. Concrete products are prepared by carbonizing the above raw materials, which embodies the process technology scheme for preparing building materials products by multi-stage carbonization of steel slag, improves the overall carbonization efficiency and usage of steel slag, and solves the problems that the carbonization of products is restricted by porosity, poor strength performance and carbonization only on the surface.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas, characterized in that: The steps include: S1. The raw steel slag is first crushed, electromagnetically deironed, and sieved to obtain a mixture of coarse and fine aggregates of 1.0-4.0 mm, fine slag powder less than 1.0 mm, and iron slag; S2. Weigh 90-94 parts of the steel slag coarse and fine aggregate mixture in step S1 and 6-10 parts of a carbonization auxiliary agent, mix and stir them evenly; then feed the stirred mixture into a first carbonization device, and then indirectly exchange 150-200°C flue gas from waste heat power generation into low-temperature flue gas at 80-120°C to carbonize the steel slag aggregate in the first carbonization device for 0.5-2h to obtain a carbonized steel slag aggregate mixture; then take out the carbonized steel slag aggregate mixture and feed it into a screening machine for screening to obtain carbonized coarse aggregate and carbonized fine aggregate of different gradations; the carbonized coarse aggregate has a particle diameter of 2.5-4.0mm and a cylinder pressure strength of 23-45MPa, and the carbonized fine aggregate has a particle diameter of 1.0-2.5mm and a cylinder pressure strength of 20-33MPa; The steel slag powder in step S1 is fed into a mill, and a grinding surfactant accounting for 0.1-0.2% of the mass of the steel slag powder and a grinding aid accounting for 0.1-0.5% of the mass of the steel slag powder are added for grinding to obtain steel slag powder; 85-92 parts of steel slag powder, 8-15 parts of activated water and an adsorbent accounting for 0.1-0.5% of the mass of the steel slag powder are weighed, mixed and stirred evenly to obtain a steel slag mixture with a plasticity index of 12-20%, which is then fed into an extruder for cake making to obtain a steel slag cake having a diameter of 100-150 mm and a thickness of 2-5 mm; the activated water is one or a combination of any two of an amino water reducer, a polycarboxylate water reducer and a latex; the adsorbent is a mixture of CO2 pre-adsorbed The steel slag cake is sent to the second carbonization equipment, and then the 150-200°C flue gas from the waste heat power generation is indirectly heat-exchanged into a low-temperature tail gas of 60-100°C to carbonize the steel slag cake in the second carbonization equipment for 0.5-2h, and the CO2 in the adsorbent is slowly released to ensure that the carbonization reaction is carried out simultaneously in the steel slag cake; the carbonized steel slag cake is taken out and sent to the dryer for drying. During the drying process, the 280-350°C waste heat flue gas discharged from the outlet of the C1 preheater at the top of the cement kiln preheating and predecomposition system is used for drying, and then sent to the mill for grinding to obtain a steel slag cake with an activity index of 90-106% and a specific surface area of ​​450-600m 2 / kg of steel slag-based auxiliary cementitious material; weigh 25-40 parts of steel slag-based auxiliary cementitious material, 60-70 parts of silicate cement clinker powder, and 0-5 parts of gypsum powder, and mix them evenly to obtain a new low-carbon cementitious material. The new low-carbon cementitious material has a 28-day compressive strength of 43.2-57.0 MPa; S3, weighing 25-35 parts of the carbonized coarse aggregate, 24-35 parts of the carbonized fine aggregate, 18-22 parts of the new low-carbon cementitious material, 12-23 parts of sand, and 0.1-0.5% by weight of a polycarboxylate-based water-reducing agent from step S2, and mixing and stirring uniformly to obtain a concrete mixture; The concrete mixture is then poured into the product mold, pressurized and formed, cured, and then demolded. The demolded product is sent to the third carbonization equipment, and then the 150-200°C flue gas from waste heat power generation is indirectly heat-exchanged into low-temperature flue gas at 65-90°C. The product in the third carbonization equipment is carbonized for 2-6 hours and then taken out to obtain a steel slag multi-stage carbonization product with a compressive strength of 25-48MPa and a carbonization absorption rate of 18-25%.

2. The method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas according to claim 1, characterized in that: In step S2, the carbonization auxiliary agent is a mixture consisting of 99% water, 0-0.5% carbonization surfactant, and 0-0.5% water reducer; the water reducer is one or a combination of any two of lignin sulfonates, polycyclic aromatic salts, and water-soluble resin sulfonates; the carbonization surfactant is one or a combination of any two of hydrophilic carboxylates, sulfates, quaternary ammonium salts, PEO derivatives, and lactones.

3. The method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas according to claim 1, characterized in that: In step S2, the first carbonization equipment is a horizontally rolling belt structure with 6-8 layers, the shell is made of stainless steel, and its parameters are as follows: the temperature inside the equipment is 80-120°C, the pressure is 0.5-1.0 MPa, the humidity is ≥80%, and the CO2 concentration is ≥20%.

4. The method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas according to claim 1, characterized in that: In step S2, the second carbonization equipment is a horizontally rolling porous steel belt structure with 6-8 layers and a stainless steel shell. Its parameters are as follows: temperature inside the equipment is 60-100°C, pressure is 0.2-0.5MPa, CO2 concentration is ≥20%, and humidity is ≥85%.

5. The method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas according to claim 1, characterized in that: In step S3, the third carbonization equipment is a carbonization reaction equipment having a tunnel-like form, and its parameters are as follows: temperature inside the equipment 65-90°C, pressure 0.5-1.0 MPa, CO2 concentration ≥20%, and humidity ≥70%.

6. The method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas according to claim 1, characterized in that: In step S2, the grinding surfactant is an anionic surfactant stearic acid and / or sodium dodecylbenzenesulfonate.

7. The method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas according to claim 1, characterized in that: In step S2, the grinding aid is one or a combination of any two of polyolamine, triethanolamine, triisopropanolamine, ethylene glycol, and diethylene glycol.

8. The method for preparing auxiliary cementitious materials and concrete products by carbonizing steel slag from industrial furnace tail gas according to claim 1, characterized in that: In step S2, the steel slag-based auxiliary cementitious material contains a calcium carbonate product and amorphous silica, wherein the calcium carbonate product consists of amorphous calcium carbonate, calcite, veneer, and vaterite, with a total content of 10% to 18%; and the amorphous silica content is 2.5-5%.

Images