A calcium-magnesium-based composite organic binder for pellets and its preparation and use method

Abstract

The present invention relates to a calcium-magnesium-based composite organic binder for pellets and its preparation and use methods. The calcium-magnesium-based composite organic binder for pellets is composed of the following components, measured by dry weight percentage: 97% to 99% converter slag, 0.5% to 2.2% polyethylene oxide, and 0.5% to 2.3% instant carboxymethyl starch. The present invention utilizes converter slag as a calcium-magnesium-containing raw material, adds a polyethylene oxide solution that has not been dehydrated or dried, and an instant carboxymethyl starch solution, and then undergoes microwave heating, stirring, and deep fusion reaction to obtain the calcium-magnesium-based composite organic binder for pellets. This not only achieves efficient and resource-recycling utilization of converter slag, but also helps improve the quality of pellets and reduce production costs for steel enterprises.

Description

Technical Field

[0001] The present invention relates to the technical field of sintered pellet preparation, and in particular to a calcium-magnesium-based composite organic binder for pellets and a preparation and use method thereof. Background Art

[0002] Pellets are one of the main feedstocks for blast furnace ironmaking and are categorized into acidic and basic pellets. Basic pellets are typically blended with limestone and slaked lime to increase the CaO content and alkalinity (between 0.5 and 1.15). Basic pellets exhibit excellent reducibility and remelting properties, enabling a lower fuel ratio in blast furnaces, thereby improving productivity. With the country's increasing emphasis on environmental protection, more steel companies are increasing the use of basic pellets to reduce the proportion of sintered ore used in ironmaking. Consequently, demand for basic pellets, and even low-basicity pellets, is increasing.

[0003] Currently, alkaline pellet production mostly uses a mixture of limestone powder, iron ore concentrate, and bentonite as raw materials. Since bentonite's primary chemical component is SiO2, increasing the amount of limestone added also reduces the iron grade of the pellets. If the concentrate has a high SiO2 content and coarse particle size, not only will the amount of limestone required be large, but a large amount of binder will also be required. Furthermore, the increased SiO2 content in the pellets and the decomposition of the limestone increase the porosity and reduce the compressive strength. The large amount of slaked lime used as a flux causes the pellets to crack and pulverize, leading to severe sticking. Existing solutions to these problems primarily involve replacing bentonite with calcium-based binders.

[0004] Chinese patent application number CN201710742740.6 discloses a "method for preparing iron-carbon composite briquettes for blast furnaces using hot converter slag." The method utilizes the waste heat of hot converter slag to heat the iron-carbon composite briquettes, causing them to undergo a reduction reaction to produce metallic iron. The calcium and magnesium resources in the converter slag serve as a binder to bind carbon, metallic iron, and their oxides, producing iron-carbon composite briquettes with a certain basicity. This reduces environmental pollution from steel slag and lowers ironmaking production costs. While this technical solution mentions using the calcium and magnesium resources in converter slag as a binder to bind carbon, metallic iron, and their oxides, converter slag is not used as a binder for pellet production. The present invention, however, combines converter slag with polyethylene oxide and instant carboxymethyl starch to produce a composite organic binder required for flux pellet production. The flux pellets produced using the calcium-magnesium-based composite organic binder described in this invention not only increase green pellet strength but also improve their metallurgical properties, achieving a two-pronged advantage, achieving a technical effect of "1+1>2."

[0005] Qian Qiang's article, "Experimental Research on Modified Converter Slag Micropowder as a Substitute for Bentonite" (Fujian Metallurgy, 2018, Issue 2), argues that converter micropowder has a certain degree of hydraulic activity. To fully utilize the unique gelling properties of converter micropowder, a feasibility study was conducted on using converter micropowder as a substitute for bentonite in pelletizing. This study completed the research on converter slag micropowder as a substitute for bentonite. The binder used is converter slag or a mixture of converter slag and bentonite. The calcium-magnesium-based composite organic binder described in the present invention is composed of converter slag and organic matter. When added to iron ore powder to prepare pellets, it is much more effective than using converter slag directly as a binder. Furthermore, the organic matter volatilizes during the pellet roasting process, increasing the iron content of the pellets entering the blast furnace, which helps reduce the coke ratio and increase blast furnace production. Summary of the Invention

[0006] The present invention provides a calcium-magnesium-based composite organic binder for pellets and a preparation and use method thereof. Converter slag is used as a calcium-magnesium-containing raw material, and a polyethylene oxide solution and a quick-dissolved carboxymethyl starch solution that have not been dehydrated or dried are added. The calcium-magnesium-based composite organic binder for pellets is obtained after a deep fusion reaction by microwave heating, stirring, and so on. This not only realizes the efficient and resource-recycling utilization of converter slag, but also is beneficial to improving the quality of pellets and reducing the production costs of steel enterprises.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The invention discloses an organic binder for a calcium-magnesium-based composite machine of pellets, which is composed of the following components in terms of dry basis weight percentage: 97% to 99% of converter slag, 0.5% to 2.2% of polyethylene oxide, and 0.5% to 2.3% of instant carboxymethyl starch.

[0009] A method for preparing an organic binder for a calcium-magnesium-based composite pellet machine comprises the following steps:

[0010] 1) Crushing and grinding the converter slag into powder, weighing it and placing it into a reaction vessel;

[0011] 2) adding the polyethylene oxide solution into the reaction vessel containing the converter slag powder according to the dry basis ratio;

[0012] 3) adding the instant carboxymethyl starch solution to the reaction vessel containing the converter slag powder according to the dry basis ratio;

[0013] 4) placing the reaction vessel in a microwave generator and performing a radiant heating heap leaching reaction for 10 to 20 minutes; the temperature after heating is 100 to 110° C., grinding and sieving the dried product to obtain a pelletized calcium-based composite machine organic binder, wherein the particle size composition is that particles less than 0.044 mm account for more than 95%.

[0014] Furthermore, the converter slag has a CaO content of 40% to 50%, an Al2O3 content of 5% to 10%, a SiO2 content of 10% to 18%, a MgO content of 6 to 10%, a MnO content of less than 1.0%, and the rest being impurities, calculated by weight percentage.

[0015] Furthermore, the converter slag powder has a particle size composition in which particles smaller than 0.074 mm account for more than 95%.

[0016] Furthermore, the polyethylene oxide solution is a 2% polyethylene oxide aqueous solution with a viscosity greater than 2000 Pa.s.

[0017] Furthermore, the instant carboxymethyl starch is a 2% aqueous solution of instant carboxymethyl starch with a viscosity greater than 1000 Pa.s.

[0018] A method for using an organic binder for a pelletizing calcium-magnesium-based composite machine, wherein the binder is added during the pelletizing of iron ore powder in a ratio of Wherein: W1 is the dry basis mass percentage of the calcium-magnesium-based composite organic binder, W2 is the dry basis mass percentage of the iron concentrate, R is the target binary alkalinity of the pellets, which is 0.2-1.5, X1(CaO) is the mass fraction of calcium oxide in the calcium-magnesium-based composite organic binder, X1(SiO2) is the mass fraction of silicon dioxide in the calcium-magnesium-based composite organic binder, and X2(SiO2) is the mass fraction of silicon dioxide in the iron concentrate.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) Using converter slag as a raw material containing calcium and magnesium achieves efficient and resourceful utilization of converter slag, reducing its harm to the environment;

[0021] 2) Using converter slag as a calcium-containing raw material instead of limestone and slaked lime used in conventional binders is beneficial to saving heat consumption in pellet production. It also avoids the problem of reduced pellet strength caused by CO2 emission due to limestone decomposition during pellet roasting, thereby improving the compressive strength of the pellets.

[0022] 3) Compared with the method of using bentonite as a binder or a component of a binder, the present invention reduces the SiO2 and Al2O3 content brought into the pellets, can effectively reduce the amount of blast furnace ironmaking slag, and ultimately reduce the production costs of steel enterprises;

[0023] 4) Using converter slag as the binder raw material can introduce a certain amount of MgO into the pellets, which is beneficial to improving the metallurgical properties of the pellets.

[0024] 5) The composite organic binder of the present invention is added to iron ore powder to prepare pellets, which is much better than directly using converter slag as a binder. In addition, the organic matter will volatilize during the pellet roasting process, increasing the iron content of the pellets when entering the blast furnace, which is beneficial to reducing the blast furnace coke ratio and increasing the output. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart for the preparation and use of an organic binder for a calcium-magnesium-based composite machine for pelletizing ore according to the present invention. DETAILED DESCRIPTION

[0026] The organic binder for a calcium-magnesium-based composite machine of pellets of the present invention is composed of the following components in terms of dry basis weight percentage: 97% to 99% of converter slag, 0.5% to 2.2% of polyethylene oxide, and 0.5% to 2.3% of instant carboxymethyl starch.

[0027] like Figure 1 As shown, the method for preparing an organic binder for a calcium-magnesium-based composite machine of pelletized ore according to the present invention comprises the following steps:

[0028] 1) Crushing and grinding the converter slag into powder, weighing it and placing it into a reaction vessel;

[0029] 2) adding the polyethylene oxide solution into the reaction vessel containing the converter slag powder according to the dry basis ratio;

[0030] 3) adding the instant carboxymethyl starch solution to the reaction vessel containing the converter slag powder according to the dry basis ratio;

[0031] 4) placing the reaction vessel in a microwave generator and performing a radiant heating heap leaching reaction for 10 to 20 minutes; the temperature after heating is 100 to 110° C., grinding and sieving the dried product to obtain a pelletized calcium-based composite machine organic binder, wherein the particle size composition is that particles less than 0.044 mm account for more than 95%.

[0032] Furthermore, the converter slag has a CaO content of 40% to 50%, an Al2O3 content of 5% to 10%, a SiO2 content of 10% to 18%, a MgO content of 6 to 10%, a MnO content of less than 1.0%, and the rest being impurities, calculated by weight percentage.

[0033] Furthermore, the converter slag powder has a particle size composition in which particles smaller than 0.074 mm account for more than 95%.

[0034] Furthermore, the polyethylene oxide solution is a 2% polyethylene oxide aqueous solution with a viscosity greater than 2000 Pa.s.

[0035] Furthermore, the instant carboxymethyl starch is a 2% aqueous solution of instant carboxymethyl starch with a viscosity greater than 1000 Pa.s.

[0036] like Figure 1 As shown, the method of using the organic binder of calcium-magnesium-based composite machine for pelletizing ore of the present invention is to add the organic binder when making iron ore pellets, and the addition ratio is Wherein: W1 is the dry basis mass percentage of the calcium-magnesium-based composite organic binder, W2 is the dry basis mass percentage of the iron concentrate, R is the target binary alkalinity of the pellets, which is 0.2-1.5, X1(CaO) is the mass fraction of calcium oxide in the calcium-magnesium-based composite organic binder, X1(SiO2) is the mass fraction of silicon dioxide in the calcium-magnesium-based composite organic binder, and X2(SiO2) is the mass fraction of silicon dioxide in the iron concentrate.

[0037] To make the purpose, technical solutions, and technical effects of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are now clearly and completely described. The embodiments described below are part of the embodiments of the present invention, not all of them. In combination with the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] [Example]

[0039] In this embodiment, the proportions of the various components of the pelletized calcium-magnesium-based composite organic binder are shown in Table 1. The chemical composition of the converter slag is shown in Table 2, and the chemical composition of the iron ore concentrate is shown in Table 3.

[0040] Table 1 Distribution ratio of each group (dry basis weight percentage %)

[0041] serial number converter slag Polyethylene oxide Soluble carboxymethyl starch Example 1 98.6 0.8 0.8 Example 2 97.2 0.5 2.3 Example 3 97.6 2.0 0.4 Example 4 97.9 1.2 0.9 Example 5 97.2 2.2 0.6

[0042] Table 2 Chemical composition of converter slag (weight percentage %)

[0043] MgO <![CDATA[SiO2]]> CaO <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> FeO <![CDATA[P2O5]]> 7.78 15.34 43.22 9.18 5.16 8.12 1.8

[0044] Table 3 Chemical composition of iron ore concentrate (weight percentage)

[0045] TFe FeO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> CaO 68.28 29.82 0.89 2.12 0.74 <0.1

[0046] In this embodiment, the preparation process of the pelletized calcium-magnesium-based composite organic binder is as follows:

[0047] (1) Crushing and grinding the converter slag into a powder, wherein the particle size composition is 96.8% of the particles are less than 0.074 mm, and the weighed converter slag is placed in a reaction vessel;

[0048] (2) Adding the polyethylene oxide solution according to the dry basis ratio directly into the reaction vessel containing the converter slag powder;

[0049] (3) adding the instant carboxymethyl starch solution to a reaction vessel containing converter slag powder according to the dry basis ratio;

[0050] (4) placing the reaction vessel in a microwave generator and subjecting it to radiation heating for heap leaching reaction for 15 minutes; the temperature after heating is 100° C., grinding the dried product, and passing it through a 200-mesh sieve to obtain a pelletized calcium-magnesium-based composite organic binder, wherein the finished product has a particle size composition of more than 95% of particles less than 0.044 mm.

[0051] The prepared calcium-magnesium-based composite organic binder of pellets was added to the iron ore concentrate powder. The proportion of the calcium-magnesium-based composite organic binder of pellets added to the pellets is shown in Table 4. The performance indicators of the prepared green balls are shown in Table 5.

[0052] Table 4 Calcium-magnesium based composite organic binder ratio (weight percentage %)

[0053] serial number Alkalinity R target value Iron concentrate Binder ratio Example 1 0.2 98.94 1.06 Example 2 0.6 96.30 3.70 Example 3 1.2 89.75 10.25 Example 4 0.8 94.52 4.48 Example 5 0.4 97.71 2.29

[0054] Table 5: Comparison table of raw ball indicators

[0055]

[0056] The case where converter slag alone is used as a binder is taken as comparative example 1, and the case where converter slag and bentonite (1:1) are used as raw materials to prepare a binder is taken as comparative document 2. The chemical composition and metallurgical indicators of the finished pellets of each embodiment and comparative example are compared in Tables 6 and 7.

[0057] Table 6: Chemical composition comparison table of finished pellets (weight percentage)

[0058] serial number TFe FeO <![CDATA[SiO2]]> CaO MgO <![CDATA[Al2O3]]> Example 1 64.04 0.19 5.98 0.21 1.04 ＜0.1 Example 2 63.50 0.19 5.78 0.22 1.54 ＜0.1 Example 3 62.89 0.18 5.96 0.23 2.04 ＜0.1 Example 4 63.02 0.19 5.82 0.22 1.82 ＜0.1 Example 5 63.56 0.18 5.85 0.21 1.23 ＜0.1 Comparative Example 1 64.04 0.19 5.98 0.21 1.04 ＜0.1 Comparative Example 2 63.82 0.22 6.12 0.23 1.03 ＜0.1

[0059] Table 7: Metallurgical index comparison table of finished balls

[0060]

[0061] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing an organic binder for a calcium-magnesium-based composite pellet machine, characterized in that: The organic binder for a calcium-magnesium-based composite machine for pelletizing ore is composed of the following components, calculated by dry weight percentage: 97% to 99% of converter slag, 0.5% to 2.2% of polyethylene oxide, and 0.5% to 2.3% of instant carboxymethyl starch; the converter slag has a CaO content of 40% to 50%, an Al2O3 content of 5% to 10%, a SiO2 content of 10% to 18%, and a MgO content of 6% to 10%, with the remainder being impurities; and a method for preparing the organic binder for a calcium-magnesium-based composite machine for pelletizing ore comprises the following steps: 1) Crushing and grinding the converter slag into powder, weighing it and placing it into a reaction vessel; 2) adding the polyethylene oxide solution into the reaction vessel containing the converter slag powder according to the dry basis ratio; 3) adding the instant carboxymethyl starch solution to the reaction vessel containing the converter slag powder according to the dry basis ratio; 4) placing the reaction vessel in a microwave generator and performing a radiant heating heap leaching reaction for 10 to 20 minutes; the temperature after heating is 100 to 110° C., grinding and sieving the dried product to obtain a pelletized calcium-based composite machine organic binder, wherein the particle size composition is that particles less than 0.044 mm account for more than 95%.

2. The method for preparing an organic binder for a pelletized calcium-magnesium-based composite machine according to claim 1, characterized in that: The converter slag powder has a particle size composition of particles smaller than 0.074 mm accounting for more than 95%.

3. The method for preparing an organic binder for a pelletized calcium-magnesium-based composite machine according to claim 1, characterized in that: The polyethylene oxide solution is a 2% polyethylene oxide aqueous solution with a viscosity greater than 2000 Pa.s.

4. The method for preparing an organic binder for a pelletized calcium-magnesium-based composite machine according to claim 1, characterized in that: The instant carboxymethyl starch is a 2% aqueous solution of instant carboxymethyl starch with a viscosity greater than 1000 Pa.s.

5. A method for using the organic binder for calcium-magnesium-based composite pellets prepared by the method for preparing the organic binder for calcium-magnesium-based composite pellets according to claim 1, characterized in that: Iron ore powder is added during pelletizing, and the addition ratio is Wherein: W1 is the dry basis mass percentage of the calcium-magnesium-based composite organic binder, W2 is the dry basis mass percentage of the iron concentrate, R is the target binary alkalinity of the pellets, which is 0.2-1.5, X1(CaO) is the mass fraction of calcium oxide in the calcium-magnesium-based composite organic binder, X1(SiO2) is the mass fraction of silicon dioxide in the calcium-magnesium-based composite organic binder, and X2(SiO2) is the mass fraction of silicon dioxide in the iron concentrate.

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