A method to improve the activity of stainless steel slag

Abstract

The present application discloses a method for improving the activity of stainless steel slag, which relates to the technical field of comprehensive utilization of resources. The method for improving the activity of stainless steel slag includes the following steps: placing hot stainless steel slag in a hot soaking pit or a slag pot, and hot soaking and spraying water for cooling to 100°C - 1000°C; introducing carbon dioxide in the first stage (pressure 0.1 - 0.5 Mpa, time 0.5 - 2 hours) into the container, and spraying water synchronously (the amount of sprayed water is 0.3 - 0.7 times the mass of the slag); then introducing air (pressure 10 - 15 Mpa, time 0.5 - 1 hour); then introducing carbon dioxide in the second stage (pressure 0.2 - 0.6 Mpa, time 1 - 2 hours), and spraying a small amount of water synchronously (the amount of sprayed water is 0.03 - 0.08 times the mass of the slag); after cooling, highly active stainless steel slag is obtained. With the collaborative design of staged gas introduction and spraying water for cooling, the content of free calcium oxide in the stainless steel slag is less than 2%, and the activity index reaches the standard of primary steel slag powder, greatly improving the resource utilization rate. At the same time, the fixed emission reduction of carbon dioxide is achieved, which helps with resource recycling and low-carbon development.

Description

Technical Field

[0001] This application belongs to the field of resource comprehensive utilization technology, and in particular relates to a method for improving the activity of stainless steel slag. Background Technology

[0002] Stainless steel slag is a solid waste generated during the stainless steel smelting process. Its main chemical components are CaO, SiO2, Al2O3, MgO, etc., and its phase composition includes dicalcium silicate and tricalcium silicate, which are similar to the mineral composition of cement clinker, and it has hydration and cementing properties.

[0003] However, stainless steel slag is formed at a high temperature of 1600℃. The silicate minerals in it are perfectly crystallized, with large grains and high chemical stability, making them difficult to hydrate. This results in low activity of stainless steel slag, which in turn leads to its low utilization rate in the building materials field.

[0004] Therefore, there is an urgent need to conduct research on technologies to improve the activity of stainless steel slag, so as to improve the performance of stainless steel slag and increase its resource utilization rate. Summary of the Invention

[0005] To address some or all of the technical problems existing in the prior art, this application provides a method for improving the activity of stainless steel slag.

[0006] This application provides a method for improving the activity of stainless steel slag, comprising the following steps performed sequentially: Step S1: Place the hot stainless steel slag in a hot braising container and perform hot braising and water cooling to cool the stainless steel slag to a specified temperature range of 100℃-1000℃. Step S2: Introduce carbon dioxide into the hot curing container, control the carbon dioxide pressure to be 0.1-0.5 MPa, and introduce it for 0.5-2 hours. During the carbon dioxide introduction process, continuously perform hot curing and water cooling on the stainless steel slag. The total amount of water added during this stage is 0.3-0.7 times the mass of the stainless steel slag. Step S3: After the carbon dioxide is introduced, air is introduced into the hot-pressed container, and the air pressure is controlled at 10-15 MPa for 0.5-1 hour. Step S4: After the air is introduced, carbon dioxide is introduced into the hot curing container, and the carbon dioxide pressure is controlled at 0.2-0.6 MPa. The introduction time is 1-2 hours. During the carbon dioxide introduction process, the stainless steel slag is continuously cooled by water. The amount of water introduced at this stage is 0.03-0.08 times the mass of the stainless steel slag. Step S5: After the stainless steel slag cools, highly active stainless steel slag is obtained.

[0007] Preferably, the hot braising container is a hot braising tank or a slag tank.

[0008] Preferably, the water cooling in steps S1 and S2 is achieved by spraying water evenly onto the surface of the stainless steel slag through a nozzle set on the top of the hot braising container.

[0009] Preferably, in step S5, the free calcium oxide content of the highly active stainless steel slag is <2%.

[0010] Preferably, in step S5, the 7-day activity index of the high-activity stainless steel slag is >65%, and the 28-day activity index is >80%, meeting the first-grade steel slag powder standard.

[0011] The method for improving the activity of stainless steel slag in this application has the following advantages and positive effects: (1) By adopting a process design that involves introducing carbon dioxide and air in stages during the hot curing process, and coordinating with water cooling, the coarse silicate mineral crystal structure inside the stainless steel slag can be effectively destroyed, significantly reducing the content of free calcium oxide and significantly improving its hydration and gelling properties. This enables the stainless steel slag to achieve a 7-day activity index ≥65% and a 28-day activity index ≥80%, successfully reaching the first-grade steel slag powder standard, breaking through the bottleneck that traditional processes can only reach the second-grade standard. In addition, by utilizing the temperature and environmental conditions during the hot curing process of stainless steel slag, carbon dioxide can fully react with and be fixed in the slag minerals. In this way, industrial carbon fixation is achieved while optimizing material performance, effectively reducing carbon emissions, and without generating secondary pollution, thus achieving the dual goals of "waste treatment" and "low-carbon development".

[0012] (2) It solves the problem of low utilization rate of stainless steel slag in the building materials field due to its low activity, achieves the resource recycling of solid waste, and reduces the environmental pressure caused by land occupation and soil and water pollution due to stockpiling. The reduction of free calcium oxide content avoids the problem of volume instability caused by hydration expansion during subsequent use, improves the safety and reliability of the product in the fields of building materials and road construction, and expands the application scenarios of stainless steel slag. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only for further understanding of the embodiments of this application and constitute a part of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a comparison table of process parameters and effects of various embodiments of the stainless steel slag activity enhancement method of this application. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0015] The method for improving the activity of stainless steel slag according to this application includes the following steps performed in sequence: Step S1: Place the hot stainless steel slag in a hot braising container and perform hot braising and water cooling to cool the stainless steel slag to a specified temperature range of 100℃-1000℃; the hot braising container is a hot braising pool or slag pot. Step S2: Introduce carbon dioxide into the hot curing container, control the carbon dioxide pressure to be 0.1-0.5 MPa, and introduce it for 0.5-2 hours. During the carbon dioxide introduction process, continuously perform hot curing and water cooling on the stainless steel slag. The total amount of water added during this stage is 0.3-0.7 times the mass of the stainless steel slag. Step S3: After the carbon dioxide is introduced, air is introduced into the hot-pressed container, and the air pressure is controlled at 10-15 MPa for 0.5-1 hour. Step S4: After the air is introduced, carbon dioxide is introduced into the hot curing container, and the carbon dioxide pressure is controlled at 0.2-0.6 MPa. The introduction time is 1-2 hours. During the carbon dioxide introduction process, the stainless steel slag is continuously cooled by water. The amount of water introduced at this stage is 0.03-0.08 times the mass of the stainless steel slag. Step S5: After the stainless steel slag cools, high-activity stainless steel slag is obtained. The activity index is tested according to the national standard GB / T17671-1999 Cement Mortar Strength Test Method (ISO Method). The free calcium oxide content of the high-activity stainless steel slag is <2%, the 7-day activity index is >65%, and the 28-day activity index is >80%, which meets the first-class steel slag powder standard.

[0016] Preferably, the water cooling in steps S1 and S2 is achieved by spraying water evenly onto the surface of the stainless steel slag through a nozzle set on the top of the hot braising container.

[0017] This application provides four specific comparative embodiments to clearly verify the significant effects of the technical solution, as follows: Example 1: (1) 90 tons of hot stainless steel slag were poured into the hot brine tank and water was sprayed onto the stainless steel slag through the nozzles on the hot brine tank cover to cool it down. The total amount of water sprayed was 45 tons.

[0018] (2) After the steel slag cooled to room temperature, the free calcium oxide content in the slag was measured to be 5.67%.

[0019] (3) The activity index of steel slag was tested according to the national standard GB / T17671-1999. The activity index was 62% after 7 days and 75% after 28 days, which met the standard requirements of secondary steel slag powder.

[0020] Example 2: (1) Pour 90 tons of hot stainless steel slag into the hot brine tank and cool the stainless steel slag with water through the nozzles on the hot brine tank cover.

[0021] (2) When the slag temperature in the hot simmering tank is cooled to 600℃, carbon dioxide is introduced at a pressure of 0.5 MPa for 1.5 hours.

[0022] (3) While passing carbon dioxide, the steel slag is still cooled with water, and the amount of water is 45 tons.

[0023] (4) Then, air is introduced at a pressure of 10 MPa for 1 hour; then carbon dioxide is introduced at a pressure of 0.6 MPa for 2 hours, and 3 tons of water are pumped.

[0024] (5) After cooling, the free calcium oxide content in the slag was 1.59%. Compared with the free calcium oxide content of 5.67% in Example 1, it was significantly reduced.

[0025] (6) The activity index of the steel slag was tested according to the national standard GB / T17671-1999. The activity index was 75% after 7 days and 84% after 28 days, which met the standard requirements of Grade I steel slag powder. Compared with Example 1, the activity index was significantly improved.

[0026] Example 3: (1) There are 30 tons of hot stainless steel slag in the slag pot. Water is sprayed onto the stainless steel slag through the nozzle on the slag pot lid to cool it. The total amount of water sprayed is 16 tons.

[0027] (2) After the slag cooled to room temperature, the free calcium oxide content in the slag was measured to be 6.23%.

[0028] (3) The activity index of steel slag was tested according to the national standard GB / T17671-1999. The activity index was 60% after 7 days and 73% after 28 days, which met the standard requirements of secondary steel slag powder.

[0029] Example 4: (1) There are 30 tons of hot stainless steel slag in the slag pot. Water is sprayed onto the stainless steel slag through the nozzle on the slag pot cover to cool it.

[0030] (2) When the slag temperature in the slag pot is cooled to 200°C, carbon dioxide is introduced into the slag pot at a pressure of 0.3 MPa for 1 hour.

[0031] (3) While carbon dioxide is being introduced, water is still being pumped to cool the steel slag, with a total water volume of 17 tons.

[0032] (4) Then, air is introduced at a pressure of 11 MPa for 0.5 hours; then carbon dioxide is introduced at a pressure of 0.35 MPa for 1 hour, and 1 ton of water is pumped.

[0033] (5) After cooling, the free calcium oxide content in the slag was 0.69%. In Example 4, carbon dioxide was introduced during the water pumping process, and the free calcium oxide content was 0.69%, which was significantly lower than the 6.23% free calcium oxide content in Example 3.

[0034] (6) The activity index of the steel slag was tested according to the national standard GB / T17671-1999. The activity index was 76% after 7 days and 88% after 28 days, which met the standard requirements of Grade I steel slag powder. Compared with Example 3, the activity index was significantly improved.

[0035] Through append Figure 1 The comparison table of process parameters and effects of various embodiments of the method for enhancing the activity of stainless steel slag clearly verifies the significant effect of the technical solution, as detailed below: 1. Comparison between Example 1 (Standard Example of Hot Curing Tank) and Example 2 (Invention Example of Hot Curing Tank) Example 1 only used water cooling, resulting in a high content of free calcium oxide in the stainless steel slag. The activity index failed to reach the first-level standard and only met the requirements of the second-level steel slag powder.

[0036] In Example 2, by adding a step of introducing CO2 and air in stages during the hot curing process, the free calcium oxide content decreased significantly and the activity index increased significantly, successfully meeting the first-grade steel slag powder standard and achieving key optimization of stainless steel slag performance.

[0037] 2. Comparison between Example 3 (Standard Example of Slag Pot) and Example 4 (Invention Example of Slag Pot) Example 3 relied solely on water cooling, resulting in a significantly excessive free calcium oxide content and a low activity index, only meeting the secondary steel slag powder standard.

[0038] Example 4 uses the same process as Example 2, but the free calcium oxide content is reduced to an even lower level and the activity index is further improved. It also meets the first-grade steel slag powder standard, and the effect is better than the invention example in the hot quenching tank scenario, which verifies the adaptability of the technical solution to different hot quenching equipment.

[0039] In summary, compared with the corresponding benchmark examples, the free calcium oxide content in the invention examples using the method of this application is significantly reduced, eventually stabilizing below 2%, effectively solving the problem of volume instability in stainless steel slag caused by excessively high free calcium oxide content. The 7-day and 28-day activity indices of the invention examples are significantly higher than those of the benchmark examples, breaking through the bottleneck of secondary steel slag powder and reaching the standard of primary steel slag powder, greatly improving the hydration and cementation performance of stainless steel slag, laying the foundation for its efficient utilization in the building materials field. Regardless of whether a hot curing tank or a slag pot is used as the hot curing equipment, this technical solution can stably exert its effect, verifying the versatility and reliability of the process. The invention examples achieve industrial carbon sequestration by introducing CO2, achieving the goal of reducing carbon emissions while optimizing the performance of stainless steel slag, thus balancing resource utilization and low-carbon development.

[0040] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. At the same time, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. In addition, the terms "front," "rear," "left," "right," "upper," and "lower" in this document refer to the placement states shown in the accompanying drawings.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for improving the activity of stainless steel slag, characterized in that, The following steps are performed sequentially: Step S1: Place the hot stainless steel slag in a hot braising container and perform hot braising and water cooling to cool the stainless steel slag to a specified temperature range of 100℃-1000℃. Step S2: Introduce carbon dioxide into the hot curing container, control the carbon dioxide pressure to be 0.1-0.5 MPa, and introduce it for 0.5-2 hours. During the carbon dioxide introduction process, continuously perform hot curing and water cooling on the stainless steel slag. The total amount of water added during this stage is 0.3-0.7 times the mass of the stainless steel slag. Step S3: After the carbon dioxide is introduced, air is introduced into the hot-pressed container, and the air pressure is controlled at 10-15 MPa for 0.5-1 hour. Step S4: After the air is introduced, carbon dioxide is introduced into the hot curing container, and the carbon dioxide pressure is controlled at 0.2-0.6 MPa. The introduction time is 1-2 hours. During the carbon dioxide introduction process, the stainless steel slag is continuously cooled by water. The amount of water introduced at this stage is 0.03-0.08 times the mass of the stainless steel slag. Step S5: After the stainless steel slag cools, highly active stainless steel slag is obtained.

2. The method for improving the activity of stainless steel slag according to claim 1, characterized in that, The hot braising container is a hot braising tank or a slag pot.

3. The method for improving the activity of stainless steel slag according to claim 1, characterized in that, The water cooling in steps S1 and S2 is achieved by spraying water evenly onto the surface of the stainless steel slag through nozzles set on the top of the hot braising container.

4. The method for improving the activity of stainless steel slag according to claim 1, characterized in that, In step S5, the free calcium oxide content of the highly active stainless steel slag is <2%.

5. The method for improving the activity of stainless steel slag according to claim 1, characterized in that, In step S5, the 7-day activity index of the high-activity stainless steel slag is >65%, and the 28-day activity index is >80%, reaching the first-grade steel slag powder standard.

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