CN105842111B - The detection method of smelter coke gasification activity and post reaction strength - Google Patents

Abstract

The invention provides a method for testing metallurgical coke and carbon dioxide gasification reactivity and post-reaction strength. This method can simulate the macroscopic kinetic behavior of the gasification reaction of coke in a blast furnace. Put coke with a particle size of 23~25mm and a mass of 200±0.5g into a corundum crucible with several holes around and at the bottom. The inner diameter of the crucible is 75~80mm, and the height is 100~150mm. The sample was heated using a large weight thermogravimetric analyzer at a heating rate of 5 °C/min. After the furnace temperature reaches 300°C, 2L/min nitrogen gas is introduced. After the furnace temperature reaches 900°C, the heating rate is changed to 2°C/min to continue the temperature rise, and the gas is changed to 5L/min of carbon dioxide. When the furnace temperature reaches 1050°C. Change the heating rate to 5°C/min and continue to heat up. Stop heating after the weight loss of the sample reaches 25%, and pass in 2L/min of nitrogen until the sample cools below 200°C before performing the strength test. The coke reaction start temperature, low temperature reactivity of coke and high temperature reactivity of coke were calculated from the thermogravimetric curve of coke.

Description

Test method for gasification reactivity and post-reaction strength of metallurgical coke

technical field

The invention belongs to the technical field of coking, and in particular relates to the detection of coke reactivity and post-reaction strength for blast furnaces.

Background technique

Coke provides heat and reducing agent for blast furnace ironmaking, and is also the skeleton of blast furnace material column. Carbon monoxide produced by the gasification reaction of coke and carbon dioxide at a certain temperature is a reducing agent for iron oxides. The gasification reaction also consumes the carbon of the coke while producing the reducing agent, which makes the pore wall of the coke thinner, and the strength of the coke will decrease accordingly.

The reactivity and post-reaction strength of coke have always been the indicators of concern in the ironmaking and coking industries. The currently widely used method for testing coke reactivity and post-reaction strength is GB/T 4000-2008. The method stipulates that 200g of coke with a particle size of 23~25mm is reacted with _CO2 at 1100°C for 120min, and the percentage of coke mass loss is used as the reactivity index (CRI) of coke, and the coke sample after the reaction is put into a type I drum , at a speed of 20r/min for a total of 30min, the total number of revolutions is 600r, and after taking it out, sieve it with a φ10mm round hole sieve, and take the percentage of coke on the sieve in the coke after reaction as the post-reaction strength (CSR). The detection method makes the coke react under constant temperature and constant atmosphere, which is easy to operate, and reflects the gasification reaction ability and the strength of the coke to a certain extent.

However, this method also has some disadvantages. First of all, the temperature range of coke gasification reaction in the blast furnace is about 900~1300℃, and the reaction atmosphere also changes in different regions. In addition, the carbon loss of coke in the blast furnace gasification reaction is almost fixed, about 25%, while the reaction time is fixed in the CSR test, and the carbon loss of coke cannot be fixed.

CN101936979A discloses a method for measuring the post-reaction strength of coke used in a blast furnace. A three-dimensional water-cooled electronic balance is used to detect the weight loss rate of coke in real time. When the temperature of the center of the coke layer reaches 400°C, nitrogen gas is passed; when the coke temperature is 780°C, the preheated carbon dioxide gas is passed through; the coke starts to heat up at a rate of 10°C/min from 800°C, and reaches the set weight loss rate at 1030°C At this time, the heating furnace starts to keep the constant temperature until the cumulative weight loss rate reaches 25%, the carbon dioxide gas is turned off, and the nitrogen gas is passed to cool down. Put the reacted coke sample into a type I drum, and rotate it at a speed of 20r/min for 30min, the total number of revolutions is 600r, take it out and sieve it with a φ10mm round hole sieve, so that the coke on the sieve accounts for the proportion of the coke after the reaction. The percentage is taken as the post-reaction strength.

CN101825548A discloses a method for detecting coke reactivity and post-reaction strength. A corundum reaction tube of Ф80×1000 mm, a reaction tube sealing sleeve and a reaction tube support are placed on an electronic balance, and the coke sample is continuously detected by the electronic balance. Weight change during the reaction. The temperature of coke is raised to 400°C~500°C under the protection of nitrogen, and then _CO2 gas with a flow rate of 5L/min~10L/min is changed, and the heating furnace is raised to 1100°C at a rate of 5°C/min~10°C/min Constant temperature until the weight loss rate is 20% to 30%. Put the reacted coke sample into the type I drum, and rotate it at a speed of 20r/min for 30min, the total number of revolutions is 600r, and then take it out and sieve it with a φ10mm round hole sieve, so that the coke on the sieve accounts for the proportion of the coke after the reaction. The percentage is taken as the post-reaction strength.

The above-mentioned patents do not design test methods for the temperature change law in the blast furnace and the macroscopic kinetic behavior of coke gasification reaction. According to the temperature change characteristics in the blast furnace, it can be divided into three areas: the first heat exchange area, the heat reserve area, and the second heat exchange area, as shown in Figure 1. The temperature of the first heat exchange zone is about 300~900°C. In this temperature range, the temperature gradient is large, but it has not yet reached the active temperature of the reaction between coke and CO ₂ . The temperature in the heat reserve area is about 900~1050°C. The temperature in this area changes slowly, and the gasification reaction of coke has just started. Because the reaction temperature is not high, the reaction rate is slow, and the gas is easy to diffuse into the coke. The temperature of the second heat exchange zone is generally above 1000~1050°C. The temperature gradient in this zone is large. Due to the high temperature, the reaction is fast, and the gas has no time to diffuse into the coke, and it will react within a certain depth from the surface. The higher and higher, the reaction gas will react as soon as it contacts the coke, and almost all the carbon will be consumed on the surface of the coke. The gasification reaction behavior of coke at different temperatures has a significant impact on the post-reaction strength.

Aiming at the above rules, the present invention designs a detection method for coke gasification reactivity and post-reaction cracking properties.

Contents of the invention

The purpose of the present invention is to provide a method for detecting coke reactivity and post-reaction strength, which can simulate the macroscopic kinetic behavior of gasification reaction of coke in a blast furnace, and the detection method comprises the following steps:

(1) Put 200 g of coke with a particle size of 23~25mm into a corundum crucible with a diameter of 75~80mm and a height of 100~150mm with several holes around and at the bottom. (2) Heat the sample with a large weight thermogravimetric analyzer at a heating rate of 5°C/min. After the furnace temperature reached 300°C, 2L/min of nitrogen was introduced to protect the sample. After the furnace temperature reaches 900°C, change the heating rate to 2°C/min to continue heating, and change the gas to 5L/min of carbon dioxide. When the furnace temperature reaches 1050°C. Change the heating rate to 5°C/min and continue to heat up until the weight loss percentage of the sample reaches 25%, then stop heating, change the gas to 2L/min nitrogen until the sample cools below 200°C. (3) The temperature corresponding to the coke gasification reaction rate reaching 0.02%/min was taken as the coke start reaction temperature (T ₀ ), and the weight loss percentage of coke before 1050°C was calculated as the low-temperature reactivity (Reactivity at Low Temperature, RLT), The percentage loss of coke between 1100 and 1200 °C was calculated as the high temperature reactivity (Reactivity at High Temperature, RHT). Put the reacted coke sample into a type I drum, and rotate it at a speed of 20r/min for 30min, the total number of revolutions is 600r, take it out and sieve it with a φ10mm round hole sieve, so that the coke on the sieve accounts for the proportion of the coke after the reaction. Percentage as the post-reaction strength (Post-reaction Strength, PRS).

The beneficial effects produced by the present invention are:

(1) The detection system is set according to the characteristic that the temperature of the heat storage area in the blast furnace changes slowly, while the temperature of the second heat exchange area changes quickly. High mixing control mode and internal diffusion control mode. The coke strength after reaction can better reflect its cracking behavior in blast furnace. (2) The heating rate is slow in the range of 900~1050 °C, and the measured coke starting reaction temperature is more accurate. (3) The low-temperature reactivity and high-temperature reactivity can reflect the gasification reaction capacity of coke more comprehensively.

Description of drawings

Figure 1 is a schematic diagram of the temperature change law in the blast furnace.

Fig. 2 is the thermogravimetric change curve of the coke detected by the present invention.

Detailed ways

(1) Process the coke sample to be tested to a particle size of 23~25mm, and put it into a corundum crucible with an inner diameter of 80 mm and a height of 150 mm with several holes around and at the bottom; (2) Use large-weight thermogravimetric analysis The instrument heats the sample with a heating rate of 5°C/min. After the furnace temperature reaches 300°C, 2L/min of nitrogen gas is introduced to protect the sample. After the furnace temperature reaches 900°C, change the heating rate to 2°C/min to continue heating, and change the gas to 5L/min of carbon dioxide. When the furnace temperature reaches 1050°C. Change the heating rate to 5°C/min and continue to heat up until the weight loss percentage of the sample reaches 25%, then stop heating, change the gas to 2L/min nitrogen until the sample cools below 200°C. (3) According to the thermogravimetric curve of coke, the starting reaction temperature of coke (T ₀ , based on the reaction rate reaching 0.02 %/min), the reaction weight loss rate at low temperature (RILT) and the reaction rate at high temperature (RIHT) were obtained. Put the reacted coke sample into the type I drum, and rotate it at a speed of 20r/min for 30min, the total number of revolutions is 600r, and then take it out and sieve it with a φ10mm round hole sieve, so that the coke on the sieve accounts for the proportion of the coke after the reaction. The percentage is taken as the post-reaction strength. The obtained coke reactivity and post-reaction strength test results are shown in the table below.

Coke samples B, C, D, and E in the table are high-reactivity coke samples prepared after adding catalysts, and sample A is a coke sample prepared from raw blended coal without adding catalysts. The T0 obtained through the test of the present invention reflects the effect of reducing the gasification temperature of the coke after adding the catalyst, and the RLT and RHT respectively reflect the gasification reaction performance of the coke in the low temperature stage and the high temperature stage. PRS reflects the post-reaction intensity of the coke gasification reaction after the chemical reaction control gradually shifts to the mixing control and internal diffusion control. Based on the above results, sample C is the best in both the catalytic effect of the catalyst and the post-reaction strength. However, the above conclusions cannot be obtained by traditional methods.

Samples F and G in the table are two kinds of industrial cokes. From the comparison of the present invention and the national standard test, it can be found that although the CRI of G and F differs only by 2.3, the difference in reaction temperature is 20°C. The RLT index shows that the carbon loss rate of coke F is much higher than that of coke G in the low temperature reaction stage. The chemical reaction is dominant in the low temperature reaction stage, so the matrix (pore wall) reactivity of coke F is significantly higher than that of coke G. Since the low-temperature reaction carbon is lost not only on the surface of the coke but also at a deep distance from the surface of the coke, the post-reaction strength of coke F is slightly lower than that of coke G. The test results of the present invention can not only reflect the properties of the coke, but also explain the reasons more profoundly.

Claims (2)

1. A method for testing the reactivity of metallurgical coke and carbon dioxide gasification and the strength after the reaction: use a large-weight thermogravimetric analyzer to heat the coke sample at a heating rate of 5°C/min, and feed 2L of the furnace after the furnace temperature reaches 300°C /min nitrogen protection sample, after the furnace temperature reaches 900°C, change the heating rate to 2°C/min to continue heating, change the gas to 5L/min carbon dioxide, and when the furnace temperature reaches 1050°C, change the heating rate to Continue to heat up at 5°C/min until the weight loss percentage of the sample reaches 25%, then stop heating, change the gas to nitrogen at 2L/min, and carry out the strength test until the sample cools below 200°C. 2. method as claimed in claim 1 is characterized in that: (1) each test is that particle size is 23～25mm, the coke that quality is 200 ± 0.5g packs in the corundum crucible with some holes around and at the bottom, The inner diameter of the crucible is 75-80 mm, and the height is 100-150 mm; (2) The temperature when the coke reaction rate reaches 0.02%/min is used as the starting reaction temperature of coke, and the weight loss percentage of coke before 1050 °C is calculated as the low-temperature reactivity index of coke , calculate the loss percentage of coke between 1100 ~ 1200 ℃ as the high temperature reactivity index of coke; (3) put the coke sample after the reaction into the type I drum, and rotate at a speed of 20r/min for 30min, The total number of revolutions is 600r, and then it is taken out and sieved with a φ10mm round hole sieve, and the percentage of coke on the sieve in the coke after reaction is used as the strength of coke after reaction.