Method for improving the balling rate of molybdenum oxide composite pellets

Abstract

The present application relates to the technical field of steelmaking auxiliary materials, in particular to a method for improving the balling rate of molybdenum oxide composite briquetting, in which process, in order to control the material temperature and overcome the problem of reaction heat release in the material, raw dolomite or limestone particles which are not easy to react with water are used to replace the traditional inhibitor lime, and the chemical reaction heat production is effectively controlled; the briquetting process provided by the present application adjusts the conventional one-time stirring and mixing to twice stirring, dry ice is added for cooling during the stirring process, and each time after stirring, standing is carried out, and through the above measures, the problem of material heating caused by the heat generated by material stirring and chemical reaction and then causing the problem of cracked briquetting after briquetting can be effectively solved. The balling rate of the molybdenum oxide composite briquetting for steelmaking produced by the process reaches more than 90%, the breaking strength is greater than 600N, and the falling strength is more than 15 times / (0.5m).

Description

Technical Field

[0001] This invention relates to the field of steelmaking auxiliary materials technology, specifically a method for improving the pelletizing rate of molybdenum oxide composite pellets. Background Technology

[0002] Using molybdenum oxide briquettes instead of ferromolybdenum for direct molybdenum alloying reduces smelting costs, eliminates the alloying step in the smelting process, and significantly saves energy. This has significant practical implications for the comprehensive and efficient utilization of my country's molybdenum resources, improving enterprise economic efficiency, reducing steel production costs, minimizing environmental pollution from steel production, and achieving green and sustainable development in the steel industry.

[0003] Molybdenum trioxide (MoO) has relatively low melting and boiling points, at 795℃ and 1155℃ respectively. It begins to sublimate at 600℃, and the sublimation rate accelerates at 900℃. Due to the volatile nature of molybdenum oxide, its molybdenum recovery rate is low during direct alloying in steelmaking. Using a mixture of multiple components pressed into spheres can solve this problem of low molybdenum recovery.

[0004] However, during the preparation of molybdenum oxide ore briquettes, the chemical and physical effects caused by the mixing and stirring of various raw materials result in significant material heating. Part of this heat comes from the mechanical energy converted into thermal energy during stirring and crushing, and another part comes from the heat released by chemical reactions between materials (such as the heat released by the reaction of calcium oxide in lime with water). Because the temperature is relatively high after stirring, the briquette formation rate is often low, and the resulting briquettes have low strength and are extremely prone to cracking when cooled to room temperature. Figure 1 As shown, the sphere formation rate of the prepared molybdenum oxide spheres is not high.

[0005] Therefore, researching a method to improve the sphericity of molybdenum oxide composite briquettes is crucial for their widespread application. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the sphericity of molybdenum oxide composite briquettes. By improving the composition and preparation process of the composite briquettes, the sphericity and strength of the briquettes are effectively improved.

[0007] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution: A method for improving the sphericity of molybdenum oxide composite spheres includes the following steps: S1. Mix the reducing agent and molybdenum oxide powder evenly. During the mixing process, add some binder and water and dry ice. After mixing evenly, allow the mixture to stand for the first time to obtain the first intermediate material. S2. Stir the first intermediate material, add the remaining binder and water and add dry ice during the stirring process, mix well and let it stand for a second time to obtain the second intermediate material; S3. Press the second intermediate material into balls, dry them to remove moisture, and you will get molybdenum oxide composite briquettes for steelmaking. The reducing agent is selected from at least one of AD powder, silicon carbide and magnesium granules; The inhibitor is selected from at least one of raw dolomite powder and limestone powder; The binder is selected from at least one of caustic soda, white cement, biological starch and hydroxycellulose.

[0008] Existing briquetting methods for mineral materials suffer from poor strength and low briquetting rate during the preparation process, resulting in a high damage rate during transportation. Furthermore, the low briquetting rate during the preparation process leads to a high return rate, which unnecessarily increases production costs. See the journal articles “Xinggang’s Practice in Improving the Quality of Pellets” (Li Xin. Sintering and Pelletizing, 2008, 33(5):53-55), “Experimental Study on Granulation of Fine-Grained Titanium Concentrate” (Han Kexi, Panzhihua Science and Technology Information, 2011, 36(4):52-56), “Analysis of Factors Affecting the Quality of Chengchao Iron Concentrate Pellets” (Yang Dabing, Xu Jiaxin, et al. Journal of Wuhan University of Science and Technology, 2014, 37(1):18-21) and “Hanggang’s Practice in Improving the Quality of Pellets” (Li Nan, Liu Wenbin. Shanxi Metallurgy, 2022, 2:160-161, 164). It can be seen that from at least 2008 to 2022, in the process of improving the above-mentioned pelletizing or pellet quality and pelletizing rate, the research direction of the technicians was mostly to optimize the raw material particle size, moisture content, binder (such as bentonite) and pressing conditions.

[0009] After discovering the problems of low strength and poor pelletizing rate of molybdenum oxide briquettes, this invention improved the process and materials according to existing improvement ideas, but failed to effectively solve the problem. Therefore, it innovatively controlled the material temperature during the stirring process and found that the strength and pelletizing rate of the briquettes were significantly improved.

[0010] In the composite briquetting provided in this invention, the reducing agent accelerates the reduction of molybdenum oxide during the steelmaking process; the raw dolomite or limestone in the inhibitor contains MgCO3 and CaCO3, both of which can inhibit the volatilization of molybdenum oxide, thus effectively ensuring the yield of molybdenum oxide.

[0011] The molybdenum oxide composite briquette provided by this invention has good crushing strength. At the same time, in order to control the material temperature and overcome the problem of exothermic reaction in the material, raw dolomite (MgCO3) or limestone (CaCO3) particles that do not easily react with water are used instead of traditional inhibitor lime (CaO), which effectively controls the heat generated by the chemical reaction.

[0012] In the preparation method provided by this invention, the conventional one-time stirring and mixing is changed to two stirrings. Dry ice is added during the stirring process to cool the material, and the material is allowed to stand after each stirring. These measures can effectively solve the problem of material heating caused by stirring and chemical reaction, which in turn causes the material to crack after briquetting.

[0013] Preferably, the total weight parts of the added reducing agent, inhibitor, molybdenum oxide powder, binder, water, and dry ice are as follows: 5-10 parts reducing agent, 5-10 parts inhibitor, 70-100 parts molybdenum oxide powder, 1-10 parts binder and 1-8 parts water; the weight of the dry ice added is 1-2 times that of the water.

[0014] Further preferably, the total weight parts of the added reducing agent, inhibitor, molybdenum oxide powder, binder, water, and dry ice are as follows: 5-7 parts reducing agent, 5-7 parts inhibitor, 80-90 parts molybdenum oxide powder, 5-7 parts binder, and 5-7 parts water; the weight of the dry ice added is 1-2 times that of the water.

[0015] While ensuring briquetting strength and briquetting rate, good temperature control was achieved by controlling the proportion of each material being fed.

[0016] Preferably, the first settling time is 0.5-1.5 hours; the second settling time is 2-4 hours; more preferably, the first settling time is 1-1.5 hours; the second settling time is 2.5-3 hours.

[0017] Preferably, in step S1, the added adhesive accounts for 40%-50% of the total weight of the adhesive; the added water accounts for 40%-50% of the total weight of the water; and the added dry ice accounts for 40%-60% of the total weight of the dry ice. More preferably, the added adhesive accounts for 45%-50% of the total weight of the adhesive; the added water accounts for 45%-50% of the total weight of the water; and the added dry ice accounts for 50%-55% of the total weight of the dry ice.

[0018] Preferably, in step S1, the stirring time is 5-10 minutes; in step S2, the stirring time is 10-15 minutes. More preferably, in step S1, the stirring time is 6-8 minutes; in step S2, the stirring time is 12-15 minutes.

[0019] Preferably, in step S3, the pressing is performed at a pressure of 15-25 MPa; more preferably, the pressing is specifically performed using a high-pressure roller briquetting machine at a pressure of 18-20 MPa.

[0020] Preferably, in step S3, drying is performed at 150-300℃ for 2-4 hours; more preferably, drying is performed using a mesh belt heating furnace at 200-230℃ for 2-3 hours.

[0021] The beneficial effects of this invention are: 1. The briquetting method provided by this invention greatly improves the briquetting rate of molybdenum oxide briquettes, reaching over 90%, and the briquettes have good crushing strength and significantly improved drop strength.

[0022] 2. In the preparation method provided by the present invention, by using raw dolomite or quicklime, which is not easily reacted with water, instead of traditional lime as an inhibitor, the heat generated by chemical reaction during the material mixing process is effectively controlled. At the same time, the traditional one-time mixing is adjusted to two mixing, and dry ice is added during the mixing process to control the temperature. After each mixing, static cooling is performed, which effectively achieves the temperature control of the material. This not only improves the pelletizing rate of the briquettes but also improves the strength of the briquettes. No obvious cracking is observed in the briquettes. Attached Figure Description

[0023] Figure 1 This is a diagram of molybdenum oxide composite briquettes produced using existing technology; Figure 2 This is a diagram of the molybdenum oxide composite spheres prepared in Example 1. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0025] The raw materials used in the examples and comparative examples are all existing conventional commercial raw materials, and will not be described in detail here.

[0026] Example 1: A molybdenum oxide composite briquette, the raw materials of which, by weight, consist of 5 parts reducing agent, 5 parts inhibitor, 70 parts molybdenum oxide powder, 9 parts binder, and 1 part water. The reducing agent is AD powder, the inhibitor is limestone powder and dolomite powder (in a 1:1 ratio), and the binder is white cement and biological starch (in a 2:1 ratio). The molybdenum oxide powder contains 55% molybdenum by mass and has a particle size of 100 mesh.

[0027] The preparation method of the above molybdenum oxide composite spheres is as follows: S1. Mix 100kg of reducing agent, 100kg of inhibitor and 1400kg of molybdenum oxide powder using a roller mill mixer. During the mixing process, add 90kg of binder and 10kg of water, and 10kg of dry ice. Mix for a total of 6 minutes and let stand for 1 hour to obtain the first intermediate material. S2. Stir the first intermediate material, add 90kg of binder and 10kg of water and 10kg of dry ice during the stirring process, stir for a total of 12 minutes, and let stand for 4 hours to obtain the second intermediate material. The temperature of the second intermediate material is measured to be 32℃. S3. The second intermediate material is pressed into balls using a high-pressure double-roller briquetting machine at 20MPa, and the balls are then sent into a mesh belt heating furnace to dry at 200℃ for 3 hours.

[0028] The temperature measurement method is specifically infrared thermometer detection. In this embodiment, the infrared thermometer is the HT-817 model produced by Dongguan Xintai Instrument Co., Ltd. This selection is only an example, and those skilled in the art can also choose other models of temperature measuring devices according to the situation when measuring.

[0029] like Figure 1 As shown in this embodiment, the pelletizing rate reached 90.6%, and the prepared molybdenum oxide composite pellets for steelmaking did not show any cracking. The average crushing strength was 620N, and the drop strength was 16 times / (0.5m).

[0030] Example 2: A molybdenum oxide composite briquette, by weight, consists of 10 parts reducing agent, 10 parts inhibitor, 90 parts molybdenum oxide powder, 2 parts binder, and 8 parts water. The reducing agent is AD powder, the inhibitor is limestone powder and dolomite powder (in a ratio of 1:2), and the binder is white cement and biological starch (in a ratio of 1:1). The molybdenum oxide powder has a molybdenum mass fraction of 58% and a particle size of 150 mesh.

[0031] The preparation method of the above molybdenum oxide composite spheres is as follows: S1. Mix 300kg of reducing agent, 300kg of inhibitor and 2700kg of molybdenum oxide powder using a roller mill mixer. During the mixing process, add 30kg of binder and 120kg of water, and 240kg of dry ice. Mix for a total of 10 minutes and let stand for 1 hour to obtain the first intermediate material. S2. Stir the first intermediate material, add 30kg of binder and 120kg of water and 240kg of dry ice during the stirring process, stir for a total of 15 minutes, and let stand for 2 hours to obtain the second intermediate material. The temperature of the second intermediate material was measured to be 28℃, and the temperature measurement method was the same as in Example 1. S3. The second intermediate material is pressed into balls using a high-pressure double-roller briquetting machine at 19MPa, and the balls are then sent into a mesh belt heating furnace to dry at 210℃ for 4 hours.

[0032] In this embodiment, the pelletizing rate reached 93.5%, and the resulting molybdenum oxide composite pellets for steelmaking showed no cracking, with an average breaking strength of 625 N. The drop strength was 16 times / (0.5 m).

[0033] Example 3: A molybdenum oxide composite briquette, by weight, consists of 7 parts reducing agent, 7 parts inhibitor, 85 parts molybdenum oxide powder, 6 parts binder, and 7 parts water. The reducing agent is magnesium granules, the inhibitor is limestone powder, and the binder is caustic soda and hydroxycellulose (in a 1:1 ratio).

[0034] The preparation method of the above molybdenum oxide composite spheres is as follows: S1. Mix 140kg of reducing agent, 140kg of inhibitor and 1700kg of molybdenum oxide powder with a particle size of 200 mesh using a roller mill mixer. During the mixing process, add 48kg of binder and 70kg of water, and 100kg of dry ice. Mix for a total of 5 minutes and let stand for 0.5 hours to obtain the first intermediate material. S2. Stir the first intermediate material, add 72kg of binder and 70kg of water and 100kg of dry ice during the stirring process, stir for a total of 10 minutes, and let stand for 3 hours to obtain the second intermediate material. The temperature of the second intermediate material is measured to be 30℃. The temperature measurement method is the same as in Example 1. S3. The second intermediate material is pressed into balls using a high-pressure double-roller briquetting machine at 18MPa, and the balls are then sent into a mesh belt heating furnace to dry at 300℃ for 2 hours.

[0035] In this embodiment, the pelletizing rate reached 94.6%, and the obtained molybdenum oxide composite pellets for steelmaking did not show any cracking. The average crushing strength was 670N, and the drop strength was 18 times / (0.5m).

[0036] A horizontal comparison of Examples 1-3 shows that Example 3 has the best pelleting rate and pelleting strength, which is because Example 3 selected a better feed ratio.

[0037] Comparative Example 1: A molybdenum oxide composite briquette for steelmaking is described. The difference between this comparative example and Example 3 is that dry ice is not added as a coolant during the preparation process; all other aspects are the same.

[0038] The temperature of the second intermediate material was measured to be 49°C, and the temperature measurement method was the same as in Example 3.

[0039] In this comparative example, the pelletizing rate was 75.2%, and 80% of the obtained molybdenum oxide composite pellets for steelmaking cracked. The average breaking strength was 370N, and the drop strength was 1 drop per (0.5m).

[0040] As can be seen from Example 3 and Comparative Example 1, this application effectively controls the heating of materials during the material mixing stage by using dry ice as a process coolant. This is because dry ice is highly volatile, and the volatile process absorbs heat and lowers the temperature of the materials.

[0041] Comparative Example 3: A molybdenum oxide composite briquette for steelmaking has the same composition as in Example 3, but the preparation process is different. The specific preparation process is as follows: All materials were mixed and stirred for 18 minutes. After stirring, the temperature of the material was measured to be 60°C, using the same method as in Example 3. The second intermediate material was then pressed into balls using a high-pressure roller briquetting machine at 20 MPa. The briquettes were then fed into a mesh belt heating furnace and dried at 200°C for 3 hours.

[0042] In this comparative example, the pelletizing rate was 71.8%, and 78% of the obtained molybdenum oxide composite pellets for steelmaking cracked. The average breaking strength was 150N, and the drop strength was 1 drop per (0.5m).

[0043] Comparative Example 4: A molybdenum oxide composite briquette for steelmaking has the same composition as in Example 1, but the preparation process is different. The specific preparation process is as follows: S1. Mix 140kg of reducing agent, 140kg of inhibitor and 1700kg of molybdenum oxide powder using a roller mill mixer. During the mixing process, add 60kg of binder and 70kg of water, and 100kg of dry ice. After mixing for a total of 5 minutes and 6 minutes, the first intermediate material is obtained. S2. Stir the first intermediate material, adding 60 kg of binder and 60 kg of water, and 100 kg of dry ice during the stirring process, and stir for a total of 12 minutes to obtain the second intermediate material; the temperature of the material is measured to be 58°C, and the temperature measurement method is the same as in Example 1.

[0044] S3. The second intermediate material is pressed into balls using a high-pressure double-roller briquetting machine at 20MPa, and the balls are then sent into a mesh belt heating furnace to dry at 200℃ for 3 hours.

[0045] In this comparative example, the pelletizing rate was 75.0%, and 81% of the obtained molybdenum oxide composite pellets for steelmaking cracked. The average breaking strength was 175N, and the drop strength was 1 drop per (0.5m).

[0046] Comparing Example 3 and Comparative Example 3 with Example 1 and Comparative Example 4, it can be seen that the pelletizing rates after one stirring and after two stirrings without resting are 71.8% and 75.0%, respectively. Moreover, the cold-pressing crushing strength is significantly lower than that of Example 1. This is because the present invention changes the conventional one stirring to two stirrings, adds dry ice to cool the mixture during stirring, and allows the mixture to rest after each stirring. These measures can effectively solve the problem of material heating caused by stirring and chemical reaction, which leads to pellet cracking after pressing.

[0047] Comparative Example 5: A molybdenum oxide composite briquette for steelmaking is described. The difference between this comparative example and Example 3 is that the inhibitor is replaced by an equal amount of lime powder, while all other aspects are the same.

[0048] The temperature of the second intermediate material was measured to be 52°C, and the temperature measurement method was the same as in Example 3.

[0049] In this comparative example, the pelletizing rate was 81.1%, and 70% of the obtained molybdenum oxide composite pellets for steelmaking cracked. The average breaking strength was 316N, and the drop strength was 1 drop per (0.5m).

[0050] As can be seen from Example 3 and Comparative Example 5, this application effectively controls the heat generated by chemical reaction during the material mixing stage by using dry dolomite and limestone instead of lime as inhibitors, thereby improving the pelletizing rate and pelletizing strength.

Claims

1. A method for improving the sphericity of molybdenum oxide composite spheres, comprising the following steps: S1. Mix the reducing agent, inhibitor and molybdenum oxide powder evenly. During the mixing process, add some binder and water and dry ice. After mixing evenly, allow the mixture to stand for the first time to obtain the first intermediate material. In step S1, the added adhesive accounts for 40%-50% of the total weight of the adhesive; the added water accounts for 40%-50% of the total weight of the water; and the added dry ice accounts for 40%-60% of the total weight of the dry ice. S2. Stir the first intermediate material, add the remaining binder and water and add dry ice during the stirring process, mix well and let it stand for a second time to obtain the second intermediate material; S3. Press the second intermediate material into balls, dry them to remove moisture, and you will get molybdenum oxide composite balls for steelmaking. The reducing agent is selected from at least one of AD powder, silicon carbide and magnesium granules; The inhibitor is selected from at least one of raw dolomite powder and limestone powder; The binder is selected from at least one of caustic soda, white cement, biological starch and hydroxycellulose; The total weight parts of the added reducing agent, inhibitor, molybdenum oxide powder, binder, water, and dry ice are as follows: 5-10 parts reducing agent, 5-10 parts inhibitor, 70-100 parts molybdenum oxide powder, 1-10 parts binder and 1-8 parts water; the weight of the dry ice added is 1-2 times that of the water. The first settling time is 0.5-1.5 hours; the second settling time is 2-4 hours.

2. The method as described in claim 1, characterized in that, The total weight parts of the added reducing agent, inhibitor, molybdenum oxide powder, binder, water, and dry ice are as follows: 5-7 parts reducing agent, 5-7 parts inhibitor, 80-90 parts molybdenum oxide powder, 5-7 parts binder, and 5-7 parts water; the weight of the dry ice added is 1-2 times that of the water.

3. The method as described in claim 1, characterized in that, The first settling time is 1-1.5 hours; the second settling time is 2.5-3 hours.

4. The method as described in claim 1, characterized in that, In step S1, the added adhesive accounts for 45%-50% of the total weight of the adhesive; the added water accounts for 45%-50% of the total weight of the water; and the added dry ice accounts for 50%-55% of the total weight of the dry ice.

5. The method as described in claim 1, characterized in that, In step S1, the stirring time is 5-10 minutes; in step S2, the stirring time is 10-15 minutes.

6. The method as described in claim 5, characterized in that, In step S1, the stirring time is 6-8 minutes; in step S2, the stirring time is 12-15 minutes.

7. The method as described in claim 1, characterized in that, In step S3, the pressure is increased to 15-25 MPa.

8. The method as described in claim 7, characterized in that, In step S3, pressing is specifically performed using a high-pressure roller briquetting machine at a pressure of 18-20 MPa.

9. The method as described in claim 1, characterized in that, In step S3, drying is performed at 150-300℃ for 2-4 hours.

10. The method as described in claim 9, characterized in that, The drying process involves using a mesh belt heating furnace to dry the product at 200-230℃ for 2-3 hours.

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