Method for preparing low-boron magnesium-containing pellets by using boron magnesium powder

Abstract

The invention discloses a method for preparing low-boron magnesium-containing pellets by using boron-magnesium powder, which comprises the following steps: step 1, drying and screening boron-magnesium powder, iron ore concentrate and bentonite, and uniformly mixing the screened boron-magnesium powder, iron ore concentrate and bentonite according to a preset mass ratio to obtain a mixed material; step 2, adding a certain amount of water into the mixed material, uniformly mixing, braising to obtain clinker, and pelletizing by using a disc pelletizer to obtain green pellets; 3, oxidizing roasting is conducted on the green pellets through a muffle furnace, and pellets are obtained; the method has the advantages that 1, boron in the boron-magnesium powder effectively reduces the oxidizing roasting temperature in the pellet production process, and energy consumption is reduced; 2, the compressive strength of the pellets is improved, the reducibility of the pellets is improved, the reduction expansion rate of the pellets is reduced, and the soft melting dripping performance of the pellets is improved; and 3, value-added utilization of secondary resources is realized, the operability is high, and the method is an effective way for obtaining pellets with high metallurgical performance.

Description

Technical Field

[0001] The invention belongs to the technical field of pellet preparation, and particularly relates to a method for preparing pellets that meet the requirements of blast furnace ironmaking by using boron magnesium powder produced as a byproduct of a boron chemical plant as an additive. Background Art

[0002] In recent years, with the increasing pressure of environmental protection, sintering production has been restricted. As a high-quality blast furnace raw material, pellets have low energy consumption and low environmental pollution in the production process. Therefore, their use in blast furnace ironmaking processes has continued to increase, and blast furnaces have also achieved good technical and economic indicators. Studies have found that the increase in MgO content in pellets increases the high-temperature soft melting dripping temperature of pellets, which is beneficial to improving the permeability of blast furnaces, but excessive MgO content will reduce the compressive strength of pellets. As a special component of iron concentrate, B2O3 can react with a variety of oxides to form solid solutions to reduce the melting point. During the roasting process of pellets, the amount of liquid phase increases, the fluidity is enhanced, and the strength of pellets is improved. Adding boron-containing magnetite to the pellets can improve the strength of the green balls and reduce the preheating temperature; while reducing the roasting temperature of the pellets, the compressive strength will be significantly improved, and its reduction performance will also be significantly improved. Boron magnesium powder is a by-product of boron chemical industry, and its main minerals include forsterite, serpentine, slaked lime, etc. Among them, the mass fraction of MgO is relatively high, and it contains a small amount of B2O3. The sum of the mass fractions of minerals useful for blast furnace ironmaking, such as CaO, MgO, Fe2O3, etc., can reach more than 60%. Summary of the invention

[0003] In combination with the role of MgO and B2O3 in pellets, the present invention provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The purpose is to address the problem in the prior art that too high MgO will lead to deterioration of the metallurgical properties of pellets. By utilizing the "boron and magnesium complementarity" method, low-boron magnesium-containing pellets with metallurgical properties are prepared, and the value-added utilization of boron-magnesium powder by-products in boron chemical industry is achieved.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing low-boron magnesium-containing pellets using boron-magnesium powder comprises the following steps:

[0006] Step 1:

[0007] The boron magnesium powder, iron ore concentrate and bentonite are dried and sieved, and the sieved boron magnesium powder, iron ore concentrate and bentonite are mixed according to a preset mass ratio to obtain a mixed material;

[0008] Step 2:

[0009] Adding a certain amount of water to the mixed material, mixing, stewing the material to obtain a cooked material, and using a disc ball making machine to make balls to obtain green balls;

[0010] Step 3:

[0011] The green balls are oxidatively roasted in a muffle furnace to obtain pellets;

[0012] The preset mass ratio is: iron concentrate 100: boron magnesium powder 1.0-3.0: bentonite 0-1.3.

[0013] In the step 2, 5 to 10% of water by mass of the mixed material is added to the dry mixed material, and the mixture is mixed while adding water.

[0014] In step 2, the mixture with water is stewed for 5 to 45 minutes.

[0015] In step 2, the diameter of the green balls is 10 to 15 mm.

[0016] In step 2, the drying temperature of the green balls is 105-120° C., and the drying time is 2-12 hours.

[0017] In step 3, the temperature of the muffle furnace is 600-900° C. when the dry balls are placed therein.

[0018] In the step 3, the calcination temperature is 1050-1250° C., the holding time is 5-30 min, and air is continuously introduced into the muffle furnace to maintain an oxidizing atmosphere in the muffle furnace.

[0019] In the step 3, the green balls are taken out from the muffle furnace when they are cooled to 600-900° C. after oxidation roasting, and then cooled in air to obtain the final pellets.

[0020] The obtained pellets have a compressive strength of 1800-3100N / piece, a reducibility of 72%-85%, and a reduction expansion rate of 12.0%-19.0%, so as to meet the use requirements of steel enterprises.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention uses boron magnesium powder to prepare low-boron magnesium pellets. The boron in the boron magnesium powder effectively reduces the temperature of oxidative roasting during the pellet production process and reduces energy consumption;

[0023] 2. The present invention uses boron-magnesium powder to prepare low-boron-magnesium pellets. The boron and magnesium in the boron-magnesium powder improve the compressive strength of the pellets, improve the reducibility of the pellets, reduce the reduction expansion rate of the pellets, and improve the soft melting dripping performance of the pellets;

[0024] 3. The raw material used in the present invention is boron magnesium powder, a by-product of a boron chemical plant, which realizes the value-added utilization of secondary resources, has strong operability, and is an effective way to obtain pellets with high metallurgical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process of the present invention;

[0026] Figure 2-1 This is the macroscopic morphology of boron magnesium powder

[0027] Figure 2-2 XRD pattern of boron magnesium powder

[0028] Figure 3-1 Macroscopic morphology of iron ore concentrate

[0029] Figure 3-2 is the XRD pattern of iron concentrate;

[0030] Figure 4-1 The macroscopic morphology of bentonite

[0031] Figure 4-2 is the XRD pattern of bentonite;

[0032] Figure 5 It is the soft melting dripping performance diagram of implementation 1 to 3 of the present invention;

[0033] Figure 6 The macroscopic morphology of the green ball prepared in embodiment 1 of the present invention;

[0034] Figure 7-1 The macroscopic morphology of the low-boron magnesium-containing pellet prepared in Embodiment 1 of the present invention

[0035] Figure 7-2 This is a microscopic morphology of low-boron magnesium-containing pellets prepared in Embodiment 1 of the present invention;

[0036] Figure 8-1 It is a low-boron magnesium-containing pellet after reduction;

[0037] Figure 8-2 It is a low-boron magnesium-containing pellet after reduction. DETAILED DESCRIPTION

[0038] A method for preparing low-boron magnesium-containing pellets using boron-magnesium powder of the present invention comprises the following steps:

[0039] The boron magnesium powder, iron concentrate and bentonite in the examples are all solid when added.

[0040] The composition of the boron magnesium powder produced as a byproduct of the boron chemical industry is shown in Table 1:

[0041] Table 1 Composition of boron magnesium powder (mass fraction / %)

[0042]

[0043] The composition of the iron ore concentrate is shown in Table 2:

[0044] Table 2 Composition of iron ore concentrate (mass fraction / %)

[0045]

[0046] The composition of the bentonite is shown in Table 3:

[0047] Table 3 Composition of bentonite (mass fraction / %)

[0048]

[0049] In the embodiment of the present invention, the compressive strength detection equipment of the pellet is a pellet compressive strength tester, which is measured according to the standard GB / T 14201-2018 "Method for Determination of Compressive Strength of Iron Ore Pellets".

[0050] In the embodiment of the present invention, the detection equipment of the reducibility of the pelletized ore is a reduction furnace, and the determination is performed according to the standard GB / T13241-2017 "Determination method of reducibility of iron ore".

[0051] In the embodiment of the present invention, the detection equipment for the reduction expansion rate of the pellet is a reduction furnace, and the measurement is performed according to the standard GB / T13240-2018 "Determination of the free expansion index of iron pellets for blast furnaces".

[0052] In the embodiment of the present invention, the detection equipment for the soft melting dripping performance of the pelletized ore is a dripping furnace, and the measurement is performed according to the standard GB / T34211-2017 "Method for Determining the Soft Melting Dripping Performance of Iron Ore under High Temperature Load Reduction".

[0053] The present invention is further described in detail below in conjunction with specific embodiments.

[0054] Example 1

[0055] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0056] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3 kg of iron ore concentrate, 39 g of bentonite and 90 g of boron magnesium powder, mix them, add 7.5 wt% of water, and continue mixing. Cover with plastic film and keep for 40 minutes, then use a disc ball making machine to make balls to obtain green balls, such as Figure 6 shown.

[0057] Step 2: Put the green balls into an oven, set the oven temperature to 120°C, and keep the temperature for 2 hours. After taking out the pellets, put the pellets into a 900°C muffle furnace, heat the muffle furnace to 1200°C at a heating rate of 10°C / min, keep it for 20 minutes, take it out after the muffle furnace cools to 800°C, and cool it to room temperature in air to obtain pellets.

[0058] The performance test results of the pellets are as follows: the compressive strength of the pellets is 2743N / piece, the reducibility is 76%, and the reduction expansion rate is 17.85%. As shown in Figure 7, the macroscopic and microscopic morphologies of the low-boron magnesium-containing pellets prepared in this example are: Figure 7-1 It is the macroscopic morphology of low-boron magnesium-containing pellets; Figure 7-2 Figure 8 shows the microscopic morphology of low-boron magnesium-containing pellets. Figure 8 shows the low-boron magnesium-containing pellets after reduction and reduction expansion: Figure 8-1 It is a low-boron magnesium-containing pellet after reduction; Figure 8-2 It is a low-boron magnesium-containing pellet after reduction and expansion.

[0059] Example 2

[0060] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0061] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate, 19.5g of bentonite and 90g of boron magnesium powder, mix them, add 6.4wt% of water, and continue mixing. Cover with plastic film, keep for 30 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0062] Step 2: Put the green balls into an oven, set the oven temperature to 110°C, and keep the temperature for 6 hours. After taking out the pellets, put the pellets into a muffle furnace at 800°C, heat the muffle furnace to 1050°C at a heating rate of 10°C / min, keep it for 20 minutes, take it out after the muffle furnace cools to 900°C, and cool it to room temperature in air to obtain pellets.

[0063] The performance test results of the pellets are as follows: the compressive strength of the pellets is 2941N / piece, the reducibility is 78.84%, and the reduction expansion rate is 18.29%.

[0064] Example 3

[0065] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0066] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate, 19.5g of bentonite and 60g of boron magnesium powder, mix them, add 6.5wt% of water, and continue mixing. Cover with plastic film, keep for 20 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0067] Step 2: Put the green balls into an oven, set the oven temperature to 115°C, and keep the temperature for 4 hours. After taking out the pellets, put the pellets into a muffle furnace at 850°C, heat the muffle furnace to 1250°C at a heating rate of 10°C / min, keep the temperature for 30 minutes, take them out after the muffle furnace cools to 700°C, and cool them to room temperature in air to obtain pellets.

[0068] The performance test results of the pellets are as follows: the compressive strength of the low-boron magnesium-containing pellets is 2879N / piece, the reducibility is 72.%, and the reduction expansion rate is 17.47%.

[0069] Example 4

[0070] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0071] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate, 19.5g of bentonite and 30g of boron magnesium powder, mix them, add 5wt% of water, and continue mixing. Cover with plastic film, keep for 40 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0072] Step 2: Put the green balls into an oven, set the oven temperature to 120°C, and keep the temperature for 4 hours. After taking out the pellets, put the pellets into a muffle furnace at 700°C, heat the muffle furnace to 1175°C at a heating rate of 10°C / min, keep it for 20 minutes, take it out after the muffle furnace cools to 800°C, and cool it to room temperature in air to obtain pellets.

[0073] The performance test results of the pellets are as follows: the compressive strength of the low-boron magnesium-containing pellets is 3100N / piece, the reducibility is 68.69%, and the reduction expansion rate is 12.91%.

[0074] Example 5

[0075] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0076] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate and 90g of boron magnesium powder, mix them, add 8.4wt% of water, and continue mixing. Cover with plastic film, keep for 10 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0077] Step 2: Put the green pellets into an oven, set the oven temperature to 110°C, and keep the temperature for 3 hours. After taking out the pellets, put the pellets into a muffle furnace at 750°C, heat the muffle furnace to 1200°C at a heating rate of 10°C / min, keep it for 20 minutes, take it out after the muffle furnace cools to 900°C, and cool it to room temperature in air to obtain pellets.

[0078] The performance test results of the pellets are as follows: the compressive strength of the low-boron magnesium-containing pellets is 2139N / piece, the reducibility is 71.57%, and the reduction expansion rate is 18.93%.

[0079] Example 6

[0080] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0081] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate and 60g of boron magnesium powder, mix them, add 9.4wt% of water, and continue mixing. Cover with plastic film, keep for 5 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0082] Step 2: Put the green pellets into an oven, set the oven temperature to 105°C, and keep the temperature for 12 hours. After taking out the pellets, put the pellets into a 900°C muffle furnace, heat the muffle furnace to 1150°C at a heating rate of 10°C / min, keep it for 5 minutes, take it out after the muffle furnace cools to 600°C, and cool it to room temperature in air to obtain pellets.

[0083] The performance test results of the pellets are as follows: the compressive strength of the low-boron magnesium-containing pellets is 1822N / piece, the reducibility is 80.39%, and the reduction expansion rate is 17.10%.

[0084] Example 7

[0085] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0086] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate and 30g of boron magnesium powder, mix them, add 7.3wt% of water, and continue mixing. Cover with plastic film, keep for 35 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0087] Step 2: Put the green pellets into an oven, set the oven temperature to 115°C, and keep the temperature for 10 hours. After taking out the pellets, put the pellets into a muffle furnace at 600°C, heat the muffle furnace to 1175°C at a heating rate of 10°C / min, keep it for 20 minutes, take it out after the muffle furnace cools to 900°C, and cool it to room temperature in air to obtain pellets.

[0088] The performance test results of the pellets are as follows: the compressive strength of the low-boron magnesium-containing pellets is 1800N / piece, the reducibility is 85%, and the reduction expansion rate is 14.16%.

[0089] Example 8

[0090] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0091] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate, 39g of bentonite and 60g of boron magnesium powder, mix them, add 6.8wt% of water, and continue mixing. Cover with plastic film, keep for 45 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0092] Step 2: Put the green balls into an oven, set the oven temperature to 110°C, and keep the temperature for 12 hours. After taking out the pellets, put the pellets into a muffle furnace at 700°C, heat the muffle furnace to 1225°C at a heating rate of 10°C / min, keep it for 20 minutes, take it out after the muffle furnace cools to 800°C, and cool it to room temperature in air to obtain pellets.

[0093] The performance test results of the pellets are as follows: the compressive strength of the low-boron magnesium-containing pellets is 2685N / piece, the reducibility is 74.95%, and the reduction expansion rate is 17.35%.

[0094] Example 9

[0095] like Figure 1 As shown, this embodiment provides a method for preparing low-boron magnesium-containing pellets using boron-magnesium powder. The details are as follows:

[0096] Step 1: Dry the iron ore concentrate, boron magnesium powder and bentonite in an oven and sieve them using a sieve (35 mesh). Weigh 3kg of iron ore concentrate, 39g of bentonite and 30g of boron magnesium powder, mix them, add 10wt% of water, and continue mixing. Cover with plastic film, keep for 25 minutes, and then use a disc ball making machine to make balls to obtain green balls.

[0097] Step 2: Put the green balls into an oven, set the oven temperature to 120°C, and keep the temperature for 4 hours. After taking out the pellets, put the pellets into a muffle furnace at 875°C, heat the muffle furnace to 1200°C at a heating rate of 10°C / min, keep it for 20 minutes, take it out after the muffle furnace cools to 900°C, and cool it to room temperature in air to obtain pellets.

[0098] The performance test results of the pellets are as follows: the compressive strength of the low-boron magnesium-containing pellets is 2192N / piece, the reducibility is 77.49%, and the reduction expansion rate is 15.06%.

Claims

1. A method for preparing low-boron magnesium-containing pellets using boron-magnesium powder, characterized in that: The following steps are involved: Step 1: The boron magnesium powder, iron ore concentrate and bentonite are dried and sieved, and the sieved boron magnesium powder, iron ore concentrate and bentonite are mixed according to a preset mass ratio to obtain a mixed material; Step 2: Adding a certain amount of water to the mixed material, mixing, stewing the material to obtain a cooked material, and using a disc ball making machine to make balls to obtain green balls; Step 3: The green balls are oxidatively roasted in a muffle furnace to obtain pellets; The preset mass ratio is: iron concentrate 100: boron magnesium powder 1.0-3.0: bentonite 0-1.

3.

2. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: In the step 2, 5 to 10% of water by mass of the mixed material is added to the dry mixed material, and the mixture is mixed while adding water.

3. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: In step 2, the mixture with water is stewed for 5 to 45 minutes.

4. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: In step 2, the diameter of the green balls is 10 to 15 mm.

5. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: In step 2, the drying temperature of the green balls is 105-120° C., and the drying time is 2-12 hours.

6. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: In step 3, the temperature of the muffle furnace is 600-900° C. when the dry balls are placed therein.

7. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: In the step 3, the calcination temperature is 1050-1250° C., the holding time is 5-30 min, and air is continuously introduced into the muffle furnace to maintain an oxidizing atmosphere in the muffle furnace.

8. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: In the step 3, the green balls are taken out from the muffle furnace when they are cooled to 600-900° C. after oxidation roasting, and then cooled in air to obtain the final pellets.

9. The method for preparing pellets by using boron magnesium powder instead of bentonite as a binder according to claim 1, characterized in that: The obtained pellets have a compressive strength of 1800-3100N / piece, a reducibility of 72%-85%, and a reduction expansion rate of 12.0%-19.0%, so as to meet the use requirements of steel enterprises.

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