Method for determining reactivity of coke for vanadium-titanium smelting blast furnace

Abstract

The invention provides a reactivity determination method of coke for a vanadium-titanium smelting blast furnace, and belongs to the technical field of blast furnaces. The reactivity determination method of the coke for the vanadium-titanium smelting blast furnace comprises the following steps: S1, preparing experimental samples, wherein the experimental samples comprise a vanadium-titanium iron ore sample and a coke sample; s2, the experimental sample is put into a reactor, and the coke sample is located above the vanadium-titanium-iron ore sample; s3, simulating conditions of a blast furnace for reducing a soft melting zone, and carrying out heating reduction and solution loss reaction on the experimental sample in the reactor; s4, after the reaction is completed, cooling and preserving the sample; and S5, weighing the weight of the coke after cooling and sample preservation, and calculating the reactivity CRI (Ti). According to the method, the reduction condition of the system of the coke for the vanadium-titanium smelting blast furnace is more consistent with the actual condition of blast furnace production, so that the coke quality is improved, the blast furnace shaft efficiency is pre-judged in advance for a vanadium-titanium blast furnace operator, operation countermeasures are taken, and the ironmaking cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of blast furnace technology, and in particular to a method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces. Background Technology

[0002] Vanadium-titanium iron ore is a co-existing mineral composed mainly of iron, vanadium, and titanium, along with various valuable elements (such as chromium, cobalt, nickel, copper, and scandium). It is an important strategic resource for the iron and steel and non-ferrous metals industries. Compared with ordinary iron ore smelting, vanadium-titanium iron ore blast furnace smelting exhibits a unique behavior between coke and titanium oxides in the slag. When the coke reaches the softening zone (>1000℃), a soft melt comes into contact with the coke, reacting strongly to form a high-melting-point Ti(C,N) solid solution. This causes problems such as slag viscosity, difficulty in separating slag and iron, and difficulty in dripping. Coke reactivity, as a core indicator measuring its efficiency in chemically reacting with oxidizing gases (such as CO2) under high-temperature conditions, directly relates to the skeletal support role and thermal stability played by coke during blast furnace smelting. In my country, the assessment of coke reactivity for blast furnaces is mainly based on the Coke Reactivity Index (CRI) for quantitative characterization (GB / T4000-2017 standard).

[0003] To improve CO utilization and reduce energy consumption in the upper part of the blast furnace, the coke needs to have low reactivity and strong resistance to CO2 dissolution. After entering the lower part of the blast furnace, the coke needs to have high post-reaction strength and minimal breakage to reduce the contact area with the molten material and slag, thus reducing slag intrusion and the formation of TiC, TiN, and Ti(C,N). The process of titanium oxides reacting with coke to form a high-melting-point Ti(C,N) solid solution is generally considered to involve the reduction of high-valence titanium oxides by carbon at high temperatures. The resulting TiC and TiN exist as solid solutions in the slag. The TiC / TiN ratio in the Ti(C,N) solid solution is related to the formation temperature and nitrogen partial pressure. The special characteristics of vanadium-titanium iron ore smelting result in higher requirements for coke reactivity in blast furnaces compared to smelting ordinary ores. The national standard CRI for coke reactivity only tests the percentage of mass loss of coke samples after reacting in CO2 gas at 5 L / min for 2 hours under constant temperature conditions of 1100℃. However, the actual temperature of coke dissolution reaction in vanadium-titanium iron ore blast furnaces is 900~1300℃, and the reducing gas in the reaction only comes from the reduction of vanadium-titanium iron ore.

[0004] Therefore, it is unreasonable to use the national standard CRI index for coke reactivity to evaluate the reactivity of coke used in vanadium-titanium smelting blast furnaces for enterprises that use vanadium-titanium iron ore for smelting. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces. This method addresses the limitation of existing national standard coke reactivity indicators, which are constrained by the interaction between vanadium-titanium magnetite and coke within the blast furnace, thus failing to provide an objective and reasonable evaluation of the reactivity of coke used in vanadium-titanium smelting blast furnaces. To solve this technical problem, the method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces of this invention is beneficial for improving the quality of coke used in vanadium-titanium steel enterprises, and for reducing the blast furnace coke ratio and improving smooth operation.

[0006] To achieve the above objectives, the present invention provides a method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces, comprising the following steps: Step S1. Preparing experimental samples, including vanadium-titanium iron ore samples and coke samples; Step S2. Placing the experimental samples into a reactor, wherein the coke sample is positioned above the vanadium-titanium iron ore sample; Step S3. Simulating the conditions of the blast furnace reduction softening zone, causing the experimental samples in the reactor to undergo heating reduction and dissolution reactions; Step S4. After the reaction is completed, cooling and preserving the sample; Step S5. Weighing the coke after cooling and preserving the sample and calculating the reactivity CRI(Ti).

[0007] Preferably, step S1 includes: crushing the sinter and pellets of iron-containing raw materials to obtain iron-containing raw materials with a particle size of 10~12.5mm as vanadium-titanium iron ore samples; crushing the coke to obtain coke with a particle size of 18~22mm as coke samples; and drying the vanadium-titanium iron ore samples and coke samples.

[0008] Preferably, step S2 includes: placing 200±1g of high-alumina spheres at the bottom of the reactor; placing 500±1g of vanadium-titanium iron ore sample into the reactor and positioning it above the high-alumina spheres; placing 125±1g of coke sample above the vanadium-titanium iron ore sample; and applying 1~2kg / cm² of pressure. 2 The pressure is applied downwards above the coke sample.

[0009] Preferably, step S3 includes: starting heating from room temperature, and after the temperature reaches 200°C, introducing nitrogen gas at a flow rate of 2~5 L / min; when the temperature reaches 850°C, switching the gas from nitrogen to a mixed gas at a flow rate of 15 L / min, the mixed gas including 30% CO and 70% N2; and after the temperature reaches 1350°C, the reaction is completed, and the heating system is turned off; wherein, the heating rate from room temperature to 850°C is 10°C / min, the heating rate from 850°C to 1100°C is 2°C / min, and the heating rate from 1100°C to 1350°C is 5°C / min.

[0010] Preferably, step S4 includes: after the reaction is completed, switching the reducing gas to nitrogen with a flow rate of 2~5L / min, venting the reducing mixed gas in the pipeline, closing the gas path when the temperature is naturally cooled to 200℃, and taking out the sample after it is cooled to room temperature.

[0011] Preferably, the formula for calculating the reactivity CRI(Ti) in step S5 is: CRI(Ti) = (mm 1350 ) / m, where m 1350 is the weight of the coke after the reaction is complete, in g; m is the weight of the coke before the reaction, in g.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The reduction conditions of the system of coke used in vanadium-titanium smelting blast furnace of the present invention are more in line with the actual situation of blast furnace production, which is conducive to improving the quality of coke and enabling vanadium-titanium blast furnace operators to predict the efficiency of the blast furnace body in advance, take operational countermeasures, and reduce ironmaking costs. (2) The properties and furnace charge structure of vanadium-titanium iron ore are very different from those of ordinary iron ore. The developed method for evaluating the reactivity of coke used in vanadium-titanium smelting blast furnaces simulates the combined effects of coke dissolution reaction on the reduction, heat exchange and coke deterioration of vanadium-titanium blast furnaces. The furnace charge system and reaction conditions of coke are more consistent with the actual production situation of vanadium-titanium blast furnaces, which is conducive to promoting the rational matching of ore and coke furnace charge, saving high-quality coking coal from Shanxi or Australia, and making reasonable, scientific and effective use of regional coking coal. Attached Figure Description

[0013] Figure 1 A schematic flowchart of the method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces provided by the present invention. Figure 2 This is a schematic diagram of the loading inside the reactor provided by the present invention.

[0014] Icon labels: 1. Vanadium-titanium iron ore sample; 2. Coke sample; 3. Reactor; 4. High-alumina ball; 5. Pressure rod. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be arbitrarily combined with each other.

[0016] See Figure 1 and Figure 2 As shown, the present invention provides a method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces, comprising the following steps: Step S1. Prepare experimental samples, including vanadium-titanium iron ore sample 1 and coke sample 2, comprising: After crushing the sinter and pellets containing iron, the iron-containing raw materials were obtained by passing them through a square-hole sieve with a particle size of 10~12.5mm as vanadium-titanium iron ore sample 1. After the coke was crushed, coke with a particle size of 18~22mm was obtained through a square hole sieve as coke sample 2. After drying an appropriate amount of experimental samples (vanadium-titanium iron ore sample 1 and coke sample 2), weigh 500±1g of vanadium-titanium iron ore sample 1 and 125±1g of coke sample 2 for later use. In vanadium-titanium iron ore sample 1, sinter and pellets are uniformly mixed according to the on-site usage ratio of the vanadium-titanium smelting blast furnace.

[0017] Step S2. Place the experimental sample into reactor 3, following the order of upper layer coke and lower layer iron-containing raw material. This includes the following steps: Place 200±1g of high-temperature resistant high-alumina balls 4 at the bottom of reactor 3; Place 500±1g of vanadium-titanium iron ore sample 1 into reactor 3 and place it above high-alumina sphere 4; Place 125±1g of coke sample 2 on top of vanadium-titanium iron ore sample 1; Apply 1~2 kg / cm 2 The pressure is applied downwards above the coke sample 2 via the pressure rod 5.

[0018] Step S3. Simulate the conditions of the blast furnace reduction softening zone, causing the experimental sample in the reactor to undergo heating reduction and dissolution reactions, including: Heating begins at room temperature. Once the temperature reaches 200℃, nitrogen gas is introduced at a flow rate of 2-5 L / min. When the temperature reaches 850℃, the gas is switched from nitrogen to a mixed gas with a flow rate of 15 L / min, consisting of 30% CO and 70% N2. The reaction is completed when the temperature reaches 1350℃, at which point the heating system is turned off. The heating rate is 10℃ / min from room temperature to 850℃, 2℃ / min from 850℃ to 1100℃, and 5℃ / min from 1100℃ to 1350℃.

[0019] Step S4. After the reaction is complete, cool the sample to preserve its quality, including: After the reaction is completed at 1350℃, switch the reducing gas to nitrogen with a flow rate of 2~5L / min, and purge the reducing mixture in the pipeline. When the temperature is naturally cooled to 200℃, close the gas line and take out the sample after it has cooled to room temperature.

[0020] Step S5. Weigh the coke after cooling and preserving the sample and calculate the reactivity CRI (Ti).

[0021] The formula for calculating reactivity CRI(Ti) is: CRI(Ti) = (mm) 1350 ) / m; In the formula, m 1350 is the weight of the coke after the reaction is complete, in g; m is the weight of the coke before the reaction, in g.

[0022] The reactor in step S2 above is the reactor used in the national standard GB / T13241-2017. Example 1

[0023] 1) Prepare samples of iron ore A and coke A to be tested. Their composition is shown in Table 1. After crushing coke A, obtain a sample of 20±1mm. After crushing block iron ore A, obtain a sample of 10~12.5mm. Dry all samples and weigh 125±1g of coke A and 500±1g of iron ore A for later use.

[0024] 2) Place the experimental samples into the reactor in the order of coke on top and iron-containing raw materials below. Place 200g of high-alumina spheres at the bottom of the reactor, then place 500g of weighed iron ore A on top of the high-alumina spheres. Next, place 125g ± 1g of weighed coke A on top of the iron ore A. Finally, apply a 2kg / cm² pressure to the entire experimental material. 2 Pressure, such as Figure 2 As shown.

[0025] 3) Simulate the reduction and melting zone conditions in a blast furnace to carry out the heating reduction and dissolution reaction. Start heating from room temperature to 1350℃, with the heating rate as follows: room temperature to 850℃: 10℃ / min; 850℃ to 1100℃: 2℃ / min; 1100℃ to 1350℃: 5℃ / min. After the temperature reaches 200℃, nitrogen gas is introduced at a flow rate of 2-5 L / min. When the temperature reaches 850℃, the gas is switched to a mixed gas (30% CO + 70% N2) at a flow rate of 15 L / min. After the temperature reaches 1350℃, the reaction is complete and the heating system is turned off.

[0026] 4) Allow the sample to cool naturally after the reaction is complete, and then preserve it with nitrogen gas. Once the temperature reaches 1350℃, the reaction is complete. Then, switch the reducing gas to nitrogen gas at a rate of 2L / min to purge the reducing mixture in the pipeline. Allow the sample to cool naturally to 200℃, then close the gas line. Remove the sample after it has cooled to room temperature.

[0027] 5) Weigh the coke after the reaction and calculate the reactivity CRI (Ti) as 17.63%.

[0028] CRI (Ti) = (125-102.96) / 125=17.63%

[0029] Example 2 The method is the same as in Example 1, except that: 1) Samples of iron ore B and coke B to be tested were prepared, and their compositions are shown in Table 1. 2) After loading, apply a 1 kg / cm² pressure to the entire experimental material. 2 The pressure; 3) Nitrogen gas is introduced at a flow rate of 5 L / min after the temperature reaches 200℃; 4) Once the temperature reaches 1350℃, switch the reducing gas to nitrogen at a rate of 5L / min to purge the gas from the pipeline. 5) Weigh the coke after the reaction and calculate the reactivity CRI (Ti) as 19.10%.

[0030] Example 3 The method is the same as in Example 1, except that: 1) Samples of iron ore C and coke C to be tested were prepared, and their compositions are shown in Table 1; 2) After loading, apply 1.5 kg / cm² to the entire experimental material. 2 The pressure; 3) After heating begins, nitrogen gas is introduced at a flow rate of 3 L / min; 4) Once the temperature reaches 1350℃, switch the reducing gas to nitrogen at a rate of 5L / min to purge the gas from the pipeline. 5) Weigh the coke after the reaction and calculate the reactivity CRI (Ti) as 20.21%.

[0031] Example 4 The method is the same as in Example 1, except that: 1) Samples of iron ore D and coke D to be tested were prepared, and their compositions are shown in Table 1; 2) After loading, apply 1.8 kg / cm² to the entire experimental material. 2 The pressure; 3) Nitrogen gas is introduced at a flow rate of 4 L / min after the temperature reaches 200℃; 4) Once the temperature reaches 1350℃, switch the reducing gas to nitrogen at a rate of 3L / min to purge the gas from the pipeline. 5) Weigh the coke after the reaction and calculate the reactivity CRI (Ti) as 21.54%.

[0032] As can be seen from the above embodiments, the present invention applies appropriate pressure to the experimental sample and adopts a layered structure of upper coke and lower ore. During the heating process, a mixed reducing gas is introduced to first react with the oxygen atoms of iron, titanium and other metal oxides in the lower vanadium-titanium iron ore through CO to generate CO2 gas. The generated CO2 gas then reacts with the coke to undergo a dissolution reaction, "truly" simulating the dissolution reaction of coke in the vanadium-titanium blast furnace. This avoids the deviation caused by excessive reaction due to directly introducing CO2, which would exaggerate the reactivity of coke. It overcomes the defect of the national standard coke reactivity test method being insufficiently representative of the true reactivity of coke in the blast furnace. It effectively solves the problem that the coke reactivity test only tests the properties of the coke itself and has no correlation with the properties of vanadium-titanium iron ore, thus leading to the inability of the coke CRI index to truly reflect the efficiency of the blast furnace.

[0033] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces, characterized in that, Includes the following steps: Step S1. Prepare experimental samples, including vanadium-titanium iron ore samples and coke samples; Step S2. Place the experimental sample into the reactor, wherein the coke sample is located above the vanadium-titanium iron ore sample; Step S3. Simulate the conditions of the blast furnace reduction softening zone, and subject the experimental sample in the reactor to heating reduction and dissolution reaction; Step S4. After the reaction is complete, cool the sample to preserve its quality. Step S5. Weigh the coke after cooling and preserving the sample and calculate the reactivity CRI (Ti).

2. The method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces according to claim 1, characterized in that, Step S1 includes: The sintered ore and pellets containing iron were crushed to obtain iron-containing raw materials with a particle size of 10~12.5mm as vanadium-titanium iron ore samples. The coke was crushed to obtain coke samples with a particle size of 18-22 mm. Dry vanadium-titanium iron ore samples and coke samples.

3. The method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces according to claim 1, characterized in that, Step S2 includes: Place 200±1g of high-alumina balls at the bottom of the reactor; Place a 500±1g sample of vanadium-titanium iron ore into the reactor and position it above the high-alumina sphere. Place a 125±1g coke sample on top of the vanadium-titanium iron ore sample; Apply 1~2 kg / cm 2 The pressure is applied downwards above the coke sample.

4. The method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces according to claim 1, characterized in that, Step S3 includes: Heating begins at room temperature. Once the temperature reaches 200°C, nitrogen gas is introduced at a flow rate of 2-5 L / min. When the temperature reaches 850°C, the gas is switched from nitrogen to a mixed gas with a flow rate of 15 L / min, consisting of 30% CO and 70% N2. The reaction is completed when the temperature reaches 1350°C, at which point the heating system is turned off. The heating rate is 10℃ / min for room temperature to 850℃, 2℃ / min for 850℃ to 1100℃, and 5℃ / min for 1100℃ to 1350℃.

5. The method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces according to claim 1, characterized in that, Step S4 includes: After the reaction is complete, switch the reducing gas to nitrogen with a flow rate of 2~5L / min, purge the reducing mixture in the pipeline, and close the gas line when the temperature naturally cools to 200℃. Remove the sample after it cools to room temperature.

6. The method for determining the reactivity of coke used in vanadium-titanium smelting blast furnaces according to claim 1, characterized in that, The formula for calculating the reactivity CRI(Ti) in step S5 is: CRI(Ti) = (mm 1350 ) / m, where m 1350 is the weight of the coke after the reaction is complete, in g; m is the weight of the coke before the reaction, in g.

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