A method for preparing a silicate cement using iron ore tailings and desulfurization gypsum

Abstract

The application provides a method for preparing Portland cement by using iron ore tailings and desulfurization gypsum, which comprises the following raw materials: cement clinker, iron ore tailings powder, nanocrystal nucleus suspension and desulfurization gypsum, wherein the Ca / Si in the nanocrystal nucleus suspension is 0.6-0.9, and the Mg / Si is 0.04-0.06. 3。 The iron ore tailings are heated, crushed and screened, and then ground with the cement clinker and the desulfurization gypsum, and the nanocrystal nucleus suspension is added, so that the Portland cement is obtained, and the specific surface area of the Portland cement is 300-400 m 2 / kg. The raw materials, the proportioning and the method for preparing the Portland cement have the advantages that the raw material iron ore tailings are reused to solid waste resources, the product is safe and reliable, the bending strength and the compressive strength of the cement are improved, and the Portland cement is a good green building material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Portland cement, in particular to a method for preparing Portland cement by using iron ore tailings and desulfurization gypsum. BACKGROUND

[0002] The stockpiling of iron ore tailings not only has low resource utilization rate, but also has great harm to the surrounding environment, so the comprehensive utilization of iron ore tailings is of great significance to improve resource utilization and environmental protection. At present, the most simple and feasible methods for tailings treatment and utilization are: first, covering soil to make fields. In the area with sufficient soil, 10-20 cm of soil can be pressed and then planted, and the soil is covered to expand the cultivated land area. This method is suitable for tailings in valley shape. This method can cause secondary dust harm due to the thin soil layer. Secondly, making full use of organic organisms to absorb the substances in the degradable solidified waste materials in the tailings, which overcomes the disadvantages of using a large amount of soil layer and being limited by the shape of the tailings, but has the problem of low degradation rate. The preparation of Portland cement by using iron ore tailings is a good method for the reuse of iron ore tailings, but it has the following problems: (1) the existing technology uses iron ore tailings to make Portland cement mixed materials, which has unstable cement folding and compression resistance; (2) the setting time of Portland cement prepared by using iron ore tailings is long, which reduces the preparation efficiency; (3) the Portland cement is easy to produce floating powder, and long-term use can cause a large amount of heavy metals to be dissolved, which can easily damage the surrounding environment. Therefore, the present application provides a method for preparing Portland cement by using iron ore tailings and desulfurization gypsum. SUMMARY

[0003] In view of this, the present application provides a method for preparing Portland cement by using iron ore tailings and desulfurization gypsum.

[0004] The technical scheme of the present application is as follows:

[0005] A method for preparing Portland cement by using iron ore tailings and desulfurization gypsum, comprising the following raw materials by weight: cement clinker 30-50 parts, iron ore tailings powder 30-40 parts, nano crystal nucleus suspension 10-15 parts, and desulfurization gypsum 5-8 parts.

[0006] The preparation of the nano crystal nucleus suspension comprises the following steps:

[0007] S1. Mix raw materials Ca(NO3)2 and Mg(NO3)2, add potassium nitrate solution, stir, mix, and drop poly carboxylic acid water reducing agent to obtain mixture I;

[0008] S2. Add raw material Na2SiO3 to the potassium nitrate solution, stir, mix, and drop poly carboxylic acid water reducing agent to obtain mixture II;

[0009] S3. Mixing and stirring mixture I and mixture II, adjusting pH value, to obtain nanocrystalline core suspension.

[0010] Further, the volume concentration of the potassium nitrate solution is 10-15%, and the mass ratio of Ca(NO3)2, Mg(NO3)2 and Na2SiO3 is (8-10):(3-5):(6-8).

[0011] Further, the content of the polymer HOOC-CH2-CH(COOH)-(CH2-COONa)-CH2-COOH in the polycarboxylate superplasticizer is 75-90%.

[0012] Further, the stirring is magnetic stirring, the stirring speed is 200-230 rpm, the temperature is 15-25 DEG C, and the time is 25-35 min; and the pH value is adjusted to 11.5-11.8.

[0013] Further, the nanocrystalline core suspension has Ca / Si of 0.6-0.9 and Mg / Si of 0.04-0.06.

[0014] Further, the cement clinker is composed of CaO, SiO2, Al2O3 and Fe2O3 with a mass ratio of (60-65):(15-20):(3-6):(2-5).

[0015] Further, the iron ore tailings are stirred, heated and ground, the heating is to heat the iron ore tailings to 780-810 DEG C at a rate of 10-15 DEG C / min, the holding time is 3-3.5 h, and then the grinding is performed after the temperature is decreased to room temperature, the particle size after the grinding is <80 mu m, and the residual amount after passing through a 200 mesh sieve is <3%.

[0016] Further, the cement clinker, the iron ore tailings powder and the desulfurization gypsum are mixed and ground, and the grinding time is 15-20 min.

[0017] A method for preparing a silicate cement by using iron ore tailings and desulfurization gypsum, comprising the following manufacturing steps: mixing a cement clinker, an iron ore tailings powder, desulfurization gypsum and a nanocrystalline core suspension, to obtain a silicate cement with a specific surface area of 300-400 m 2 / kg.

[0018] Compared with the prior art, the method has the following beneficial effects:

[0019] The silicate cement prepared by the raw material, the proportioning and the method of the present application, added with the nanocrystalline core suspension raw material, is safe and reliable, can simultaneously improve the flexural strength and the compressive strength of the cement, and obtains high-strength silicate cement, which is better applied to concrete engineering. The nanocrystalline core suspension material prepared by the raw material and the proportioning in a certain proportion is compounded with the cement clinker, the iron ore tailing powder and the desulfurization gypsum to form a better space network microstructure, the initial setting time and the final setting time are shortened, the cement setting efficiency is improved, and the application effect of the flexural and compressive strength of the silicate cement is realized. DETAILED DESCRIPTION

[0020] In order to better understand the technical content of the present application, the following specific examples are provided to further illustrate the present application.

[0021] The experimental methods used in the embodiments of the present application are all conventional methods unless otherwise specified.

[0022] The materials, reagents and the like used in the embodiments of the present application can be obtained from commercial channels unless otherwise specified.

[0023] The polycarboxylic acid water reducing agent is purchased from Guizhou Wanqian Building Material Co., Ltd. The iron ore tailing powder is derived from the iron ore tailings of Shilu Iron Mine in Changjiang, Hainan.

[0024] Example 1

[0025] A method for preparing silicate cement by using iron ore tailings and desulfurization gypsum, comprising the following raw materials by weight: cement clinker 35 parts, wherein the cement clinker is composed of CaO, SiO2, Al2O3 and Fe2O3 in a mass ratio of 60:15:3:2, iron ore tailing powder 30 parts, nanocrystalline core suspension 15 parts, and desulfurization gypsum 5 parts. The silicate cement comprises the following manufacturing steps: heating the iron ore tailings to 780 ℃ at 10 ℃ / min, holding for 3 h, then reducing to room temperature for grinding, and the particle size after grinding is 70 μm, and passing through a 200 mesh screen. The cement clinker, the ground iron ore tailing powder and the desulfurization gypsum are mixed and ground, and the grinding time is 15 min. The sieved cement clinker, iron ore tailing powder, desulfurization gypsum and nanocrystalline core suspension are mixed, and the specific surface area of the mixture is 350 m 2 / kg, to obtain the silicate cement.

[0026] The preparation of the nanocrystalline core suspension comprises the following steps:

[0027] Step (1): The raw materials Ca(NO3)2, Na2SiO3 and Mg(NO3)2 are weighed according to the mass ratio of 9:7:4, a potassium nitrate solution with a volume concentration of 12% is prepared, and the content of the polymer HOOC-CH2-CH(COOH)-(CH2-COONa)-CH2-COOH in the polycarboxylic acid water reducing agent is 80%.

[0028] Step (2): Ca(NO3)2 and Mg(NO3)2 were mixed and added into the potassium nitrate solution, stirred and mixed, and polycarboxylic acid water reducing agent was added dropwise to obtain mixture I.

[0029] Step (3): Na2SiO3 was added into the potassium nitrate solution, stirred and mixed, and polycarboxylic acid water reducing agent was added dropwise to obtain mixture II.

[0030] Step (4): mixture I and mixture II were mixed and stirred, and after mixing, magnetic stirring was carried out at a stirring speed of 200 rpm, a temperature of 20°C and a time of 30 min. After stirring, the pH value was adjusted to 11.7, and continuous stirring was carried out to obtain a nanocrystalline core suspension, wherein Ca / Si was 0.8 and Mg / Si was 0.05.

[0031] Example 2

[0032] A method for preparing a silicate cement by using iron ore tailings and desulfurization gypsum comprises the following raw materials by weight: cement clinker 50 parts, wherein the cement clinker is composed of CaO, SiO2, Al2O3 and Fe2O3 in a mass ratio of 65:20:6:5, iron ore tailings powder 40 parts, nanocrystalline core suspension 10 parts, and desulfurization gypsum 8 parts. The silicate cement comprises the following preparation steps: the iron ore tailings are heated at 12°C / min to 810°C, and the holding time is 3.2 h, and then the temperature is reduced to room temperature for grinding. After grinding, the particle size is 75 μm, and the ground material is sieved through a 200 mesh screen. The cement clinker, the ground iron ore tailings powder and the desulfurization gypsum are mixed and ground for 20 min. The sieved cement clinker, the iron ore tailings powder, the desulfurization gypsum and the nanocrystalline core suspension are mixed, and the specific surface area of the mixture is 350 m2 / g to obtain the silicate cement. 2 / kg, to obtain the silicate cement.

[0033] The preparation of the nanocrystalline core suspension comprises the following steps:

[0034] Step (1): Ca(NO3)2, Na2SiO3 and Mg(NO3)2 were weighed according to a mass ratio of 10:6:3, a potassium nitrate solution with a volume concentration of 12% was prepared, and the content of the polymer HOOC-CH2-CH(COOH)-(CH2-COONa)-CH2-COOH in the polycarboxylic acid water reducing agent was 80%.

[0035] Step (2): Ca(NO3)2 and Mg(NO3)2 were mixed and added into the potassium nitrate solution, stirred and mixed, and polycarboxylic acid water reducing agent was added dropwise to obtain mixture I.

[0036] Step (3): Na2SiO3 was added into the potassium nitrate solution, stirred and mixed, and polycarboxylic acid water reducing agent was added dropwise to obtain mixture II.

[0037] Step (4): mixing and stirring mixture I and mixture II, after mixing, magnetic stirring is carried out, stirring speed is 220 rpm, temperature is 25℃, time is 25 min, after stirring, pH value is adjusted to 11.6, continue stirring, to obtain nanocrystalline core suspension, wherein Ca / Si is 0.6, Mg / Si is 0.04.

[0038] Example 3

[0039] A method for preparing Portland cement by using iron ore tailings and desulfurization gypsum, including the following raw materials by weight: cement clinker 40 parts, wherein the cement clinker is composed of CaO, SiO2, Al2O3 and Fe2O3 with a mass ratio of 62:17:4:5, iron ore tailings powder 35 parts, nanocrystalline core suspension 14 parts, desulfurization gypsum 6 parts. The Portland cement includes the following manufacturing steps: heating the iron ore tailings to 800℃ at a rate of 12℃ / min, holding for 3.5h, then cooling to room temperature and grinding, after grinding, the particle size is 70μm, and passing through a 200 mesh screen. Mixing and grinding the cement clinker, the ground iron ore tailings powder and the desulfurization gypsum, the grinding time is 20 min. Mixing the screened cement clinker, the iron ore tailings powder, the desulfurization gypsum and the nanocrystalline core suspension, the specific surface area of the mixture is 350 m 2 / kg, to obtain the Portland cement.

[0040] The preparation of the nanocrystalline core suspension includes the following steps:

[0041] Step (1): weighing raw materials Ca(NO3)2, Na2SiO3 and Mg(NO3)2 according to a mass ratio of 9:6:3, preparing a 14% potassium nitrate solution, and preparing a polycarboxylate superplasticizer with a polymer HOOC-CH2-CH(COOH)-(CH2-COONa)-CH2-COOH content of 80%.

[0042] Step (2): mixing raw materials Ca(NO3)2 and Mg(NO3)2 into the potassium nitrate solution, stirring and mixing, and adding the polycarboxylate superplasticizer dropwise to obtain mixture I;

[0043] Step (3): adding raw material Na2SiO3 into the potassium nitrate solution, stirring and mixing, and adding the polycarboxylate superplasticizer dropwise to obtain mixture II;

[0044] Step (4): mixing and stirring mixture I and mixture II, after mixing, magnetic stirring is carried out, stirring speed is 230 rpm, temperature is 15-25℃, time is 35 min, after stirring, pH value is adjusted to 11.8, continue stirring, to obtain nanocrystalline core suspension, wherein Ca / Si is 0.9, Mg / Si is 0.06.

[0045] Comparative Example 1

[0046] The difference between Comparative Example 1 and Example 1 is that the nanocrystal core suspension raw material is removed from the raw material of the Portland cement, and other raw materials and preparation methods remain unchanged.

[0047] Comparative Example 2

[0048] The difference between Comparative Example 2 and Example 1 is that the preparation raw material potassium nitrate solution of the nanocrystal core suspension is replaced by an equal amount of potassium silicate solution, and other raw materials and preparation methods remain unchanged.

[0049] Comparative Example 3

[0050] The difference between Comparative Example 3 and Example 1 is that the content of the polymer HOOC-CH2-CH(COOH)-(CH2-COONa)-CH2-COOH in the polycarboxylic acid water reducing agent is replaced by 50%, and other raw materials and preparation methods remain unchanged.

[0051] Comparative Example 4

[0052] The difference between Comparative Example 3 and Example 1 is that the pH adjustment step is removed, and the volume concentration of the potassium nitrate solution is replaced by 7%, and other raw materials and preparation methods remain unchanged.

[0053] Control Example:

[0054] A commercially available Portland cement is used as a control example, which is purchased from Hainan Xinda Cement Products Co., Ltd.

[0055] Test

[0056] According to the requirements of GB / T 17671-2021 “Cement Mortar Strength Test Method (ISO Method)”, GB / T 1346-2011 “Cement Standard Consistency Water Consumption, Setting Time, and Stability Test Method”, and GBT 176-2017 “Cement Chemical Analysis Method”, the flexural strength (MPa) and compressive strength (MPa) of the Portland cement prepared by the methods of Examples 1-3 and Comparative Examples 1-4 are measured at 5 days and 25 days, respectively, and the setting time, including initial setting time and final setting time, is recorded (Table 1). The test results show that the flexural strength and compressive strength of the Portland cement prepared by the methods of Examples 1-3 at 5 days and 25 days are higher than those of Comparative Examples 1-4, and at the same time, the initial setting time and final setting time of the Portland cement prepared by the methods of Examples 1-3 are shortened, and the setting efficiency of the cement is improved.

[0057] According to the Solid Waste Leaching Toxicity Test Method (HJ / T 299-2007), the leaching toxicity experiment of the product is carried out, and the ICP method is used to detect the heavy metal dissolution, and the results are shown in Table 2. The heavy metal ion leaching concentration meets the requirements of GB5085.3-2007 “Hazardous Waste Identification Standard-Leaching Toxicity Identification”.

[0058] Table 1

[0059]

[0060] Table 2

[0061]

[0062] Test results: the present application uses cement clinker, iron ore tailings powder, nanocrystal core suspension desulfurization gypsum to prepare portland cement, wherein the content of polymer HOOC-CH2-CH(COOH)-(CH2-COONa)-CH2-COOH in polycarboxylate superplasticizer, which is the raw material of nanocrystal core suspension, is 75-90%, the pH value is adjusted to 11.5-11.8, the Ca / Si in the prepared nanocrystal core suspension is 0.6-0.9, and the Mg / Si is 0.04-0.06. The portland cement prepared by the method of examples 1-3 of the present application effectively improves the flexural strength, and the flexural strength test of the 5th day and the 25th day shows that the flexural strength of the portland cement prepared by examples 1-3 is higher than that of comparative examples 1-4 and higher than that of the positive control. At the same time, the 5th day and 25th day compressive strength of the portland cement is also improved. When the raw material ratio or the preparation method of comparative examples 1-4 is changed, the quality of the portland cement is reduced when the nanocrystal core suspension is removed or the composition of the polymer in the polycarboxylate superplasticizer is changed. Therefore, the portland cement prepared by the raw material, raw material ratio and preparation method of the present application is safe to use, has high setting efficiency, and has the application effect of flexural and compressive strength.

[0063] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing Portland cement using iron ore tailings and desulfurization gypsum, characterized by, The cement clinker, the iron ore tailing powder, the nano-crystal core suspension and the desulfurization gypsum are mixed and ground, and the grinding time is 15-20 min. The preparation method of the iron ore tailing powder comprises the following steps: stirring, heating and grinding the iron ore tailing, the heating is to heat the iron ore tailing to 780-810 ℃ at a heating rate of 10-15 ℃ / min, the holding time is 3-3.5 h, and then the iron ore tailing is cooled to room temperature and ground, the particle size of the ground iron ore tailing is less than 80 μm, and the residual amount after passing through a 200 mesh sieve is less than 3%; The preparation of the nano-crystal core suspension comprises the following steps: S1. mixing raw materials Ca(NO3)2 and Mg(NO3)2, adding a potassium nitrate solution, stirring, mixing, and dropping a polycarboxylic acid water reducing agent to obtain a mixture I; S2. adding raw material Na2SiO3 to a potassium nitrate solution, stirring, mixing, and dropping a polycarboxylic acid water reducing agent to obtain a mixture II; S3. mixing and stirring the mixture I and the mixture II, adjusting the pH value, and obtaining the nano-crystal core suspension; The Ca / Si of the nano-crystal core suspension is 0.6-0.9, and the Mg / Si is 0.04-0.

06. The volume concentration of the potassium nitrate solution is 10-15%, and the mass ratio of Ca(NO3)2, Mg(NO3)2 and Na2SiO3 is (8-10):(3-5):(6-8). In the preparation of the nano-crystal core suspension, the stirring is magnetic stirring, the stirring speed is 200-230 rpm, the temperature is 15-25 ℃, and the time is 25-35 min; and the adjusting of the pH value is 11.5-11.

8. The method for preparing the silicate cement by using the iron mine tailings and the desulfurization gypsum comprises the following manufacturing steps: mixing the cement clinker, the iron mine tailings powder, the desulfurization gypsum and the nanocrystal nucleus suspension, the specific surface area is 300-400 m 2 / kg, and the silicate cement is obtained.

2. The method for preparing a Portland cement using iron ore tailings and desulfurization gypsum according to claim 1, characterized by, The cement clinker is composed of CaO, SiO2, Al2O3 and Fe2O3 with a mass ratio of (60-65):(15-20):(3-6):(2-5).

3. The method of manufacturing Portland cement using iron ore tailings and desulfurization gypsum according to claim 1, characterized by, The cement clinker, the iron ore tailing powder and the desulfurization gypsum are mixed and ground, and the grinding time is 15-20 min.

4. The method of manufacturing Portland cement using iron ore tailings and desulfurization gypsum according to claim 1, characterized by, ​

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