Method for preparing high-sulfur iron aluminate cement by using steel slag iron extraction tailings

Abstract

The invention relates to the technical field of cement materials, in particular to a method for preparing high-sulfur iron aluminate cement by using steel slag iron extraction tailings, which comprises the following steps: taking the steel slag iron extraction tailings as a main raw material, adjusting the composition of the raw material by using carbide slag, aluminum ash and desulfurized gypsum as auxiliary materials, and adding a small amount of lithium slag to adjust the composition of clinker minerals. The high-sulfur iron aluminate cement clinker is prepared by a staged calcining process, and the anhydrite is added to prepare the cement, so that the dependence of the traditional iron aluminate cement production on natural mineral resources and carbon emission are effectively reduced, and the prepared cement has excellent compressive strength and is suitable for industrial production. And a systematic solution is provided for high-added-value utilization of the steel slag iron extraction tailings.

Description

Technical Field

[0001] This invention relates to the field of cement materials technology, and in particular to a method for preparing high-sulfur ferroaluminate cement using iron extraction tailings from steel slag. Background Technology

[0002] Ferroaluminate cement is a special type of cement mainly composed of anhydrous calcium sulfoaluminate (C4A3), dicalcium silicate (C2S), and iron phase. It is characterized by rapid hardening, early strength, excellent corrosion resistance, and frost resistance. Traditional ferroaluminate cement production methods use limestone, bauxite / iron bauxite, and gypsum as main raw materials, which are then batched and calcined. This method heavily relies on natural mineral resources, and the bauxite / iron bauxite resources are becoming increasingly scarce and their prices are rising. Furthermore, the raw material mining and calcination processes are energy-intensive and generate high carbon emissions, thus hindering the development of this type of cement.

[0003] Steelmaking processes generate a large amount of steel slag, accounting for about 15%-20% of crude steel production. Due to problems such as large fluctuations in composition and phase composition, poor stability (e.g., free CaO and free MgO causing volume instability) and low cementitious activity, the comprehensive utilization rate of steel slag is less than 30%. Apart from being used for low-value-added applications such as roadbeds and backfilling, or modified for use as concrete admixtures, most steel slag is stockpiled for a long time, which not only occupies a large amount of land, but also pollutes the environment and causes a huge waste of resources.

[0004] To reduce costs and resource consumption, using industrial solid waste to replace natural raw materials has become an industry trend. Some existing technologies attempt to use industrial solid waste to produce aluminoferrite cement clinker. CN117700134A discloses a red mud-based aluminoferrite cement, which uses high-calcium solid waste, high-silicon solid waste, high-alumina solid waste and Bayer process red mud as raw materials. After grinding, homogenization, sample preparation, calcination and cooling, red mud-based aluminoferrite cement clinker is produced. The red mud-based aluminoferrite cement clinker is mixed with the remaining high-calcium solid waste, high-alumina solid waste and high-sulfur solid waste and ground together to obtain red mud-based aluminoferrite cement. However, the cement prepared by it has low mechanical strength. CN118529953A discloses an aluminoferrite cement clinker, which uses steel slag powder, bauxite, limestone, anhydrite and lithium carbonate as raw materials for firing. It still uses a large amount of natural raw materials.

[0005] The total iron content in steel slag ranges from 10% to 40%. Recovering iron resources from steel slag can not only create significant economic benefits but also reduce dependence on primary iron ore. Industrially, processes such as magnetic separation and carbon reduction are commonly used to extract iron resources from steel slag. However, the tailings after iron extraction also face problems of stockpiling and low utilization. Compared to the original steel slag, the iron content of the iron-extracting tailings is significantly reduced, while the calcium content is increased. However, existing technologies lack a systematic method based on the chemical composition of this type of tailings to transform steel slag iron-extracting tailings from "difficult-to-use solid waste" into "ferroaluminate cement raw materials" through clinker design and calcination control. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing high-sulfur ferroaluminate cement using steel slag iron extraction tailings. Specifically, this invention uses steel slag iron extraction tailings as the main raw material, supplemented with carbide slag, aluminum ash, and desulfurized gypsum to adjust the raw meal composition, and adds a small amount of lithium slag to regulate the clinker mineral composition. High-sulfur ferroaluminate cement clinker is prepared through a staged calcination process, and anhydrite is added to prepare cement. This not only effectively reduces the dependence of traditional ferroaluminate cement production on natural mineral resources and carbon emissions, but also produces cement with excellent compressive strength, providing a systematic solution for the high-value-added utilization of steel slag iron extraction tailings.

[0007] Specifically, the present invention provides a method for preparing high-sulfur ferroaluminate cement using steel slag tailings, comprising the following steps: 1) Weigh out 29-33 parts by weight of steel slag tailings, 17-24 parts of calcium carbide slag, 21-27 parts of aluminum ash, 18-27 parts of desulfurization gypsum, and 5-9 parts of lithium slag. Dry, crush, grind, and mix the raw materials evenly to obtain raw meal. 2) The raw materials are calcined in stages and then cooled to obtain clinker. 3) Weigh out 85-89 parts of clinker and 11-15 parts of anhydrite by weight, mix them evenly, and grind them finely to obtain the final product.

[0008] This invention uses steel slag tailings as the core raw material, supplemented with carbide slag, alumina ash, desulfurized gypsum, and lithium slag, to regulate the clinker phase composition. Research shows that, considering the calcination characteristics of steel slag tailings, introducing excess SO3 into the clinker chemical composition can prevent insufficient C4A3 formation due to SO3 decomposition during calcination. It also introduces a certain amount of free calcined anhydrite into the clinker. This calcined anhydrite mineral phase, formed through high-temperature calcination, synergistically interacts with the externally added anhydrite, regulating the hydration process and optimizing the composition and microstructure of the hydration products—ettringite, alumina gel, ferric gel, and hydrated calcium silicate—thereby improving the mechanical properties of the cement.

[0009] This invention, due to the high SO3 content and the staged calcination process involving the addition of lithium slag, generates C5S2$, which is not commonly found in conventional aluminoferrite clinker. Research in this invention indicates that as C4A3$ continuously hydrates, Al(OH)4 in the pore solution... - Reaching a supersaturated state can significantly stimulate the hydration activity of C5S2, exhibiting higher hydration activity than C2S, which is more beneficial to the development of cement strength in the later stages.

[0010] Preferably, the main chemical composition and content of the steel slag iron extraction tailings are: CaO: 45-60%, total iron calculated as Fe2O3: 8-12%, Al2O3: 3-7%, SiO2: 10-18%, MgO: 6-9%.

[0011] Preferably, the drying temperature in step 1) is 100-110℃ and the drying time is 1-3h.

[0012] Preferably, in step 1), the powder is ground to a fineness of 200 mesh or less.

[0013] Preferably, the calcination in step 2) is carried out at 1100-1200℃ for 30-40 min, and then at 1320-1350℃ for 20-30 min.

[0014] Preferably, step 2) cooling is achieved by using forced air cooling.

[0015] Preferably, the main chemical components and contents of the clinker in step 2) are: CaO: 40-49%, Fe2O3: 3-6%, Al2O3: 20-23%, SiO2: 5-9%, SO3: 12-16%.

[0016] Preferably, the main chemical components and contents of the anhydrite in step 3) are: CaO: 38-41%, SO3: 50-54%, SiO2: 1-2%, MgO: 1-4%.

[0017] Preferably, step 3) involves fine grinding to a particle size ≤ 75 μm.

[0018] The present invention also relates to cement prepared by the above-mentioned method of preparing high-sulfur ferroaluminate cement using iron extraction tailings from steel slag.

[0019] The present invention also relates to the application of the above-mentioned cement in the manufacture of building materials and engineering construction.

[0020] This invention has the following technical advantages: 1. This invention uses steel slag tailings as the core raw material. By adding solid waste raw materials such as carbide slag, alumina ash, desulfurization gypsum, and lithium slag, and optimizing the calcination process, it transforms these materials into high-sulfur ferroaluminate cement clinker. This not only reduces reliance on traditional mineral resources such as natural limestone and bauxite, but also transforms previously difficult-to-treat and low-value-utilize industrial solid waste into high-value-added building materials. This achieves efficient resource utilization of solid waste, resulting in significant economic benefits and resource conservation advantages. 2. This invention effectively promotes the formation of C4A3, C2S, and iron phases by regulating the composition of raw materials and calcination process, and also generates C5S2. Excessive free anhydrite in clinker and external anhydrite can fully promote cement hydration and improve the mechanical properties of cement.

[0021] 3. This invention uses steel slag tailings and carbide slag to replace limestone, thereby reducing carbon emissions during cement production. Detailed Implementation

[0022] To characterize the technical effect of this invention, cement was prepared and its performance was tested. During the testing process, the clinker was ground and the XRD pattern was quantitatively analyzed using Topas full-spectrum analysis software. During the mechanical property testing, cement was prepared and neat cement paste specimens were prepared under the condition of a fixed water-cement ratio of 0.4. After curing in a standard curing chamber at a temperature of 20±1℃ and a relative humidity of not less than 90% for 24 hours, the specimens were demolded and then placed in water at 20℃ for curing. The compressive strength of the specimens was tested using a universal pressure testing machine at different ages.

[0023] Example 1 Cement preparation steps:

[0024] 1) Weigh out 31 parts by weight of steel slag tailings, 23 parts by weight of calcium carbide slag, 23 parts by weight of aluminum ash, 22 parts by weight of desulfurization gypsum, and 9 parts by weight of lithium slag. Dry, crush, grind, and mix the raw materials evenly to obtain raw meal.

[0025] 2) Calcine the raw material at 1150℃ for 30 minutes, then at 1350℃ for 30 minutes, and cool to obtain clinker.

[0026] 3) Weigh out 88 parts of clinker and 13 parts of anhydrite by weight, mix them evenly, and grind them finely to obtain the final product.

[0027] Tests revealed that the clinker mineral phases included 36.43% C4A3, 20.08% C2S, 15.06% iron phase, 8.25% C5S2, 11.76% f-CaSO4, and 8.42% amorphous phase. The 3-day compressive strength was 58.9 MPa, the 7-day compressive strength was 63.4 MPa, and the 28-day compressive strength was 66.1 MPa.

[0028] Example 2 1) Weigh out 33 parts by weight of steel slag tailings, 19 parts by weight of calcium carbide slag, 26 parts by weight of aluminum ash, 24 parts by weight of desulfurization gypsum, and 7 parts by weight of lithium slag. Dry, crush, grind, and mix the raw materials evenly to obtain raw meal. 2) Calcine the raw material at 1200℃ for 40 minutes, then at 1350℃ for 20 minutes, and cool to obtain clinker. 3) Weigh out 88 parts of clinker and 13 parts of anhydrite by weight, mix them evenly, and grind them finely to obtain the final product.

[0029] Tests revealed that the clinker mineral phases included 34.71% C4A3, 17.92% C2S, 14.34% iron phase, 9.47% C5S2, 12.08% f-CaSO4, and 11.50% amorphous phase. The 3-day compressive strength was 49.3 MPa, the 7-day compressive strength was 52.6 MPa, and the 28-day compressive strength was 62.0 MPa.

[0030] Comparative Example 1

[0031] Cement preparation steps: 1) Weigh out 35 parts by weight of steel slag tailings, 28 parts by weight of calcium carbide slag, 26 parts by weight of aluminum ash, 10 parts by weight of desulfurization gypsum, and 9 parts by weight of lithium slag. Dry, crush, grind, and mix the raw materials evenly to obtain raw meal. 2) Calcine the raw material at 1150℃ for 30 minutes, then at 1350℃ for 30 minutes, and cool to obtain clinker. 3) Weigh out 88 parts of clinker and 13 parts of anhydrite by weight, mix them evenly, and grind them finely to obtain the final product.

[0032] Tests revealed that the clinker mineral phases included 26.22% C4A3, 18.76% C2S, 15.21% iron phase, 6.24% C5S2, 7.68% f-CaSO4, and 25.89% amorphous phase. The 3-day compressive strength was 35.6 MPa, the 7-day compressive strength was 45.7 MPa, and the 28-day compressive strength was 47.3 MPa.

[0033] Comparative Example 2 Cement preparation steps: 1) Weigh out 31 parts by weight of steel slag tailings, 23 parts by weight of high-calcium fly ash, 23 parts by weight of red mud, 22 parts by weight of desulfurized gypsum, and 9 parts by weight of lithium slag. Dry, crush, grind, and mix the raw materials evenly to obtain raw meal. 2) Calcine the raw material at 1150℃ for 30 minutes, then at 1350℃ for 30 minutes, and cool to obtain clinker. 3) Weigh out 88 parts of clinker and 13 parts of anhydrite by weight, mix them evenly, and grind them finely to obtain the final product.

[0034] Tests revealed that the clinker mineral phases included 29.47% C4A3, 14.50% C2S, 15.61% iron phase, 10.39% C5S2, 11.76% f-CaSO4, and 18.27% amorphous phase. The 3-day compressive strength was 45.5 MPa, the 7-day compressive strength was 49.6 MPa, and the 28-day compressive strength was 51.4 MPa.

[0035] Comparative Example 3 Cement preparation steps: 1) Weigh out 36 parts by weight of steel slag tailings, 25 parts by weight of calcium carbide slag, 24 parts by weight of aluminum ash, and 23 parts by weight of desulfurization gypsum. Dry, crush, grind, and mix the raw materials evenly to obtain raw feed. 2) Calcine the raw material at 1350℃ for 60 minutes, then cool to obtain clinker. 3) Weigh out 88 parts of clinker and 13 parts of anhydrite by weight, mix them evenly, and grind them finely to obtain the final product.

[0036] Tests showed that the clinker mineral phases included 38.34% C4A3, 21.17% C2S, 12.55% iron phase, 10.26% f-CaSO4, and 17.68% amorphous phase. The 3-day compressive strength was 37.0 MPa, the 7-day compressive strength was 50.8 MPa, and the 28-day compressive strength was 52.9 MPa.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention 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 or all of the technical features therein. Such modifications or substitutions 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 high-sulfur ferroaluminate cement using iron extraction tailings from steel slag, characterized in that, Includes the following steps: 1) Weigh out 29-33 parts by weight of steel slag tailings, 17-24 parts of calcium carbide slag, 21-27 parts of aluminum ash, 18-27 parts of desulfurization gypsum, and 5-9 parts of lithium slag. Dry, crush, grind, and mix the raw materials evenly to obtain raw meal. 2) The raw materials are calcined in stages and then cooled to obtain clinker. 3) Weigh out 85-89 parts of clinker and 11-15 parts of anhydrite by weight, mix them evenly, and grind them finely to obtain the final product.

2. The method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to claim 1, characterized in that, The main chemical composition and content of the steel slag iron extraction tailings are as follows: CaO: 45-60%, total iron calculated as Fe2O3: 8-12%, Al2O3: 3-7%, SiO2: 10-18%, MgO: 6-9%.

3. The method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to claim 1, characterized in that, In step 1), the drying temperature is 100-110℃ and the drying time is 1-3 hours.

4. The method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to claim 1, characterized in that, In step 1), grind the powder to a finer mesh than 200 mesh.

5. The method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to claim 1, characterized in that, Step 2) The calcination stage is carried out at 1100-1200℃ for 30-40 minutes, and then at 1320-1350℃ for 20-30 minutes.

6. The method for preparing high-sulfur ferroaluminate cement using iron extraction tailings from steel slag according to claim 1, characterized in that, Step 2) Cooling is achieved by using forced air cooling.

7. The method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to claim 1, characterized in that, Step 2) The main chemical components and contents of the clinker are: CaO: 40-49%, Fe2O3: 3-6%, Al2O3: 20-23%, SiO2: 5-9%, SO3: 12-16%.

8. The method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to claim 1, characterized in that, Step 3) The main chemical components and contents of anhydrite are: CaO: 38-41%, SO3: 50-54%, SiO2: 1-2%, MgO: 1-4%.

9. The method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to claim 1, characterized in that, Step 3) Grind finely until the particle size is ≤75μm.

10. Cement prepared by the method for preparing high-sulfur ferroaluminate cement using steel slag tailings according to any one of claims 1-9.