A method for analyzing activation energy during isothermal fluidity testing of coking coal

Abstract

The present invention relates to an activation energy analysis method during an isothermal fluidity test of coking coal, comprising the following steps: 1) a Gibbsian fluidity test; 2) an isothermal fluidity test; 3) isothermal fluidity curve processing; 4) determining a variation pattern of an isothermal fluidity characteristic parameter with temperature; and 5) activation energy calculation during the isothermal fluidity test. The method analyzes the isothermal fluidity curve of the coking coal, establishes a reaction kinetics equation within a key temperature range of 400-440°C for the coking coal, determines the reaction activation energy corresponding to different stages of the coking coal fluidity, thereby evaluating the quality of the coking coal and predicting the coking characteristics of the coking coal.

Description

Technical Field

[0001] The present invention relates to the technical field of coking coal evaluation, and in particular to a method for accurately evaluating the activation energy of coking coal reaction by utilizing isothermal fluidity reaction kinetics. Background Art

[0002] Coal fluidity characterizes the viscosity of the colloids formed during coal pyrolysis and is one of the indicators of coal's plasticity. Coal's Gieseler fluidity reflects both the quantity and quality of the colloids. Fluidity is an effective means of studying coal rheology and thermal decomposition kinetics, and can be used to guide coal blending and predict coke strength. A commonly used method for measuring fluidity is the Gieseler plasticometer method, proposed by German engineer K. Gieseler in 1934. Gieseler fluidity reflects the properties of the colloids formed upon heating coal, such as the quantity, thermal stability, viscosity, fluidity, and volatile analysis of the colloids.

[0003] The Gibbs-type fluidity test primarily measures the fluidity and temperature range of the colloid. It simultaneously reflects both the quantity and properties of the colloid and can accurately reflect the thermoplastic behavior of the colloids in different types of coking coal during the coking process. Its strong ability to differentiate and its sensitivity to oxidation make it a key indicator of coking coal quality. Gibbs-type fluidity provides a scientific basis for the rational use of coking coal, the optimization of coal blending, and the accurate prediction of coke quality.

[0004] The plastic temperature range of coking coal is relatively concentrated, generally between 380 and 450°C. Within this temperature range, the reaction activation energy of coking coal is of great significance for accurately evaluating its quality, predicting its coking behavior, and controlling the quality of coke. Summary of the Invention

[0005] The present invention provides an activation energy analysis method during the isothermal fluidity test of coking coal, establishes the reaction activation energy within the key temperature range of coking coal, can scientifically evaluate the quality of coking coal, and provide a basis for predicting the coking characteristics of coking coal.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for analyzing activation energy during isothermal fluidity testing of coking coal is proposed. By analyzing the isothermal fluidity curve of coking coal, a reaction kinetic equation within the critical temperature range of 400-440°C is established for coking coal. The reaction activation energy corresponding to different fluidity stages of the coking coal is determined, and the quality of the coking coal is evaluated, and the coking characteristics of the coking coal are predicted.

[0008] A method for analyzing activation energy during isothermal fluidity testing of coking coal specifically comprises the following steps:

[0009] 1) Gillespie flow test;

[0010] 2) Isothermal flow test;

[0011] 3) Isothermal flow curve processing;

[0012] The fluidity of coking coal changes with time and is divided into three stages, namely the melting stage, the maximum fluidity stage and the coking stage. The isothermal fluidity data of the melting stage and the coking stage are linearly fitted to determine the melting slope and the coking slope.

[0013] 4) Determine the variation of characteristic parameters of isothermal fluidity with temperature;

[0014] Based on the isothermal fluidity test data of coal samples in the temperature range of 400-440℃, the fluidity characteristic parameters at different temperatures are calculated respectively. The isothermal fluidity characteristic parameters, including the relationship between melting slope, coking slope, maximum fluidity, and extrapolated maximum fluidity and temperature, are fitted using a single-variable linear equation.

[0015] 5) Calculation of activation energy during isothermal flow testing;

[0016] The reaction activation energy of different coal samples at different stages of isothermal fluidity test was calculated based on the intercepts of the linear regression equations between melting slope, coking slope, maximum fluidity and extrapolated maximum fluidity and temperature.

[0017] Furthermore, in step 1), the process of the Gillespie flow test is as follows:

[0018] The coking coal is crushed to a particle size of less than 0.85 mm, and then divided into coal samples using a bisection device. The coal samples are crushed to a particle size of less than 0.425 mm using a step-by-step crushing method, and it is ensured that the portion of the coal sample with a particle size less than 0.2 mm does not exceed 50%. After the coal samples are fully mixed, coal samples are taken from different parts and placed into the crucible of the Gillespie plastic tester.

[0019] A static load is applied to the coal sample, and a dynamic load is used to drop the coal sample from a height multiple times to change the coal sample from a loose state to a formed state. A stirring paddle is provided in the crucible, and a constant torque is applied to the stirring paddle shaft. The plasticity meter head is lowered to the bottom of the crucible and immersed in a molten solder bath at a temperature of 280-320°C. The crucible is immersed in the molten solder bath for 10±2 minutes to allow the molten solder bath to return to its initial temperature, and then heated at a rate of 3.0±0.1°C / min.

[0020] When the drum speed or electronic sensor reading is 1.0 ddpm, read the temperature and dial reading at 1 minute intervals until the stirring paddle stops rotating; record the maximum rotation index (i.e., fluidity) and the corresponding time and temperature.

[0021] Furthermore, in step 2), the process of isothermal fluidity test is as follows:

[0022] The preparation and analysis of coal samples are the same as those in the Gibbs flow test. The experimental temperature is 400-440°C. The coal sample is quickly heated to the set temperature and kept constant to perform an isothermal flow test. A curve showing the relationship between isothermal flow and time is established. During the test, the temperature fluctuation is controlled to be ≤0.1°C / min. The crucible is immersed in a molten solder bath for 10±2 minutes to restore the temperature of the molten solder bath to its initial temperature.

[0023] Furthermore, in step 3), the isothermal fluidity curve processing process is as follows:

[0024] The isothermal fluidity curve is used to obtain the softening start time ts, the time to reach the maximum fluidity tmax, the solidification time tr, the plastic time interval (i.e., the time interval in the plastic state ΔT=tr-ts), and the maximum fluidity MF;

[0025] The extrapolated maximum fluidity [ln(MFc)] is calculated based on the extrapolated intersection point of the melting equation and the coking equation.

[0026] Furthermore, in step 5), the reaction rate k of the coal sample in the isothermal fluidity test conforms to the Arrhenius equation, that is: k = A × exp(-Ea / RT); where: R is the ideal gas constant; T is the temperature, K; A is the pre-exponential factor; and Ea is the activation energy, kcal / mol.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) By analyzing the isothermal fluidity curve of coking coal, establishing the reaction kinetic equation within the key temperature range of coking coal, and determining the reaction activation energy at different stages of coking coal fluidity development, the quality of coking coal can be scientifically evaluated and the basis for predicting the coking characteristics of coking coal can be provided;

[0029] 2) The analytical method of the present invention is simple to operate and easy to implement, and is of great significance for coking enterprises to scientifically evaluate coking coal and reduce raw material procurement costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a typical isothermal fluidity curve;

[0031] Figure 2 It is a schematic diagram of isothermal fluidity curve processing;

[0032] Figure 3 is the isothermal fluidity curve of coal sample 1 (420℃);

[0033] Figure 4 Isothermal fluidity curve processing for coal sample 1 (420°C);

[0034] Figure 5 is the isothermal fluidity curve of coal sample 2 (420℃);

[0035] Figure 6 Isothermal fluidity curve processing for coal sample 2 (420°C);

[0036] Figure 7 isothermal fluidity curve of coal sample 3 (420°C);

[0037] Figure 8 Isothermal fluidity curve processing for coal sample 3 (420°C);

[0038] Figure 9 isothermal fluidity curve of coal sample 4 (420°C);

[0039] Figure 10 Isothermal fluidity curve processing for coal sample 4 (420°C);

[0040] Figure 11 isothermal fluidity curve of coal sample 5 (420°C);

[0041] Figure 12 Isothermal fluidity curve processing for coal sample 5 (420°C);

[0042] Figure 13 isothermal fluidity curve of coal sample 6 (420℃);

[0043] Figure 14 Isothermal fluidity curve processing for coal sample 6 (420°C);

[0044] Figure 15 is the isothermal fluidity curve of coal sample 7 (420℃);

[0045] Figure 16 Isothermal fluidity curve processing for coal sample 7 (420°C);

[0046] Figure 17 is the isothermal fluidity curve of coal sample 8 (420℃);

[0047] Figure 18 Isothermal fluidity curve processing for coal sample 8 (420°C);

[0048] Figure 19 is the isothermal fluidity curve of coal sample 9 (420℃);

[0049] Figure 20 Isothermal fluidity curve processing for coal sample 9 (420°C);

[0050] Figure 21 is the isothermal fluidity curve of coal sample 10 (420°C);

[0051] Figure 22 Isothermal fluidity curve processing (420°C) for coal sample 10;

[0052] Figure 23 is the isothermal fluidity curve of coal sample 11 (420℃);

[0053] Figure 24 Isothermal fluidity curve processing for coal sample 11 (420°C);

[0054] Figure 25 is the isothermal fluidity curve of coal sample 12 (420°C);

[0055] Figure 26 Isothermal fluidity curve processing for coal sample 12 (420°C);

[0056] Figure 27 isothermal fluidity curve of coal sample 13 (420°C);

[0057] Figure 28 Isothermal fluidity curve processing for coal sample 13 (420°C);

[0058] Figure 29 is the isothermal fluidity curve of coal sample 14 (420°C);

[0059] Figure 30 Isothermal fluidity curve processing for coal sample 14 (420°C);

[0060] Figure 31 is the isothermal fluidity curve of coal sample 15 (420℃);

[0061] Figure 32 Isothermal fluidity curve processing for coal sample 15 (420°C);

[0062] Figure 33a is the relationship between the melting slope of the coal sample [ln(km)] and the temperature (1 / T);

[0063] Figure 33b is the relationship between the melting slope of the coal sample [ln(km)] and the temperature (1 / T);

[0064] Figure 34 is the relationship between the coking slope [ln(kc)] and temperature (1 / T) of the coal sample;

[0065] Figure 35 is the relationship between the maximum fluidity of the coal sample [ln(lnMF)] and the temperature (1 / T);

[0066] Figure 36is the relationship between the extrapolated maximum fluidity [ln(lnMFc)] of the coal sample and the temperature (1 / T);

[0067] Figure 37 is the relationship between the activation energy (Ea) in the melting range and the standard Gibbs maximum fluidity;

[0068] Figure 38 is the relationship between the activation energy of the coking zone and the maximum fluidity of the standard Gibbs formula;

[0069] Figure 39 the relationship between the activation energy calculated for maximum mobility and the activation energy calculated for extrapolated maximum mobility;

[0070] Figure 40 the relationship between the activation energy calculated for maximum mobility and the standard maximum mobility;

[0071] Figure 41 Relationship between the activation energy calculated for the extrapolated maximum fluidity and the standard maximum fluidity. DETAILED DESCRIPTION

[0072] The present invention discloses an activation energy analysis method for the isothermal fluidity test of coking coal. By analyzing the isothermal fluidity curve of the coking coal, a reaction kinetic equation is established in the critical temperature range of 400-440°C for the coking coal. The reaction activation energy corresponding to different fluidity stages of the coking coal is determined, and the quality of the coking coal is evaluated, and the coking characteristics of the coking coal are predicted.

[0073] The activation energy analysis method in the isothermal fluidity test process of coking coal described in the present invention specifically comprises the following steps:

[0074] 1) Gillespie flow test;

[0075] 2) Isothermal flow test;

[0076] 3) Isothermal flow curve processing;

[0077] The fluidity of coking coal changes with time and is divided into three stages, namely the melting stage, the maximum fluidity stage and the coking stage. The isothermal fluidity data of the melting stage and the coking stage are linearly fitted to determine the melting slope and the coking slope.

[0078] 4) Determine the variation of characteristic parameters of isothermal fluidity with temperature;

[0079] Based on the isothermal fluidity test data of coal samples in the temperature range of 400-440℃, the fluidity characteristic parameters at different temperatures are calculated respectively. The isothermal fluidity characteristic parameters, including the relationship between melting slope, coking slope, maximum fluidity, and extrapolated maximum fluidity and temperature, are fitted using a single-variable linear equation.

[0080] 5) Calculation of activation energy during isothermal flow testing;

[0081] The reaction activation energy of different coal samples at different stages of isothermal fluidity test was calculated based on the intercepts of the linear regression equations between melting slope, coking slope, maximum fluidity and extrapolated maximum fluidity and temperature.

[0082] Furthermore, in step 1), the process of the Gillespie flow test is as follows:

[0083] The coking coal is crushed to a particle size of less than 0.85 mm, and then divided into coal samples using a bisection device. The coal samples are crushed to a particle size of less than 0.425 mm using a step-by-step crushing method, and it is ensured that the portion of the coal sample with a particle size less than 0.2 mm does not exceed 50%. After the coal samples are fully mixed, coal samples are taken from different parts and placed into the crucible of the Gillespie plastic tester.

[0084] A static load is applied to the coal sample, and a dynamic load is used to drop the coal sample from a height multiple times to change the coal sample from a loose state to a formed state. A stirring paddle is provided in the crucible, and a constant torque is applied to the stirring paddle shaft. The plasticity meter head is lowered to the bottom of the crucible and immersed in a molten solder bath at a temperature of 280-320°C. The crucible is immersed in the molten solder bath for 10±2 minutes to allow the molten solder bath to return to its initial temperature, and then heated at a rate of 3.0±0.1°C / min.

[0085] When the drum speed or electronic sensor reading is 1.0 ddpm, read the temperature and dial reading at 1 minute intervals until the stirring paddle stops rotating; record the maximum rotation index (i.e., fluidity) and the corresponding time and temperature.

[0086] Furthermore, in step 2), the process of isothermal fluidity test is as follows:

[0087] The preparation and analysis of coal samples are the same as those in the Gibbs flow test. The experimental temperature is 400-440°C. The coal sample is quickly heated to the set temperature and kept constant to perform an isothermal flow test. A curve showing the relationship between isothermal flow and time is established. During the test, the temperature fluctuation is controlled to be ≤0.1°C / min. The crucible is immersed in a molten solder bath for 10±2 minutes to restore the temperature of the molten solder bath to its initial temperature.

[0088] Furthermore, in step 3), the isothermal fluidity curve processing process is as follows:

[0089] The isothermal fluidity curve is used to obtain the softening start time ts, the time to reach the maximum fluidity tmax, the solidification time tr, the plastic time interval (i.e., the time interval in the plastic state ΔT=tr-ts), and the maximum fluidity MF;

[0090] The extrapolated maximum fluidity [ln(MFc)] is calculated based on the extrapolated intersection point of the melting equation and the coking equation.

[0091] Furthermore, in step 5), the reaction rate k of the coal sample in the isothermal fluidity test conforms to the Arrhenius equation, that is: k = A × exp(-Ea / RT); where: R is the ideal gas constant; T is the temperature, K; A is the pre-exponential factor; and Ea is the activation energy, kcal / mol.

[0092] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0093] The plastic temperature range of coking coal is relatively concentrated, generally between 380 and 450°C. Within this temperature range, the reaction activation energy of coking coal is of great significance for accurately evaluating its quality, predicting its coking behavior, and controlling the quality of coke.

[0094] The purpose of the present invention is to propose a method for analyzing the activation energy during the isothermal fluidity test of coking coal and to establish the reaction activation energy within the key temperature range of coking coal, so as to scientifically evaluate the quality of coking coal and provide a basis for predicting the coking characteristics of coking coal.

[0095] For the above-mentioned purpose, the present invention is achieved through the following technical solutions:

[0096] 1. Gillespie flow test;

[0097] Crush a coking coal sample (hereinafter referred to as the coal sample) to a particle size of less than 0.85 mm, then reduce it using a bisection device (e.g., 500 g). Divide the reduced coal sample into multiple portions (e.g., 4 portions). Take one portion and crush it using a step-by-step crushing method to a particle size of less than 0.425 mm, ensuring that no more than 50% of the sample is less than 0.2 mm. Thoroughly mix the coal sample, and take coal samples (e.g., 5 g) from different locations and load them into the crucible of the Gillespie plastometer. During sample loading, rotate the stirring paddle to ensure that the coal sample fills the gap below the stirring arm.

[0098] Use a static load (such as 9 kg) to press on the coal sample, and use a dynamic load (such as 1 kg) to drop freely from a high place (such as 115 mm height) for multiple times (such as 12 times) to hit the coal sample, so as to change the coal sample from a loose state to a formed state.

[0099] A stirring paddle is vertically installed in the center of the crucible, and a constant torque is applied to the stirring paddle shaft, such as 101.6±5.lg·cm[(9.96±0.05)×10 -3 Constant torque of N·m.

[0100] Lower the plastic meter head to the bottom of the crucible and immerse it in a molten solder bath (e.g., 75 mm deep) at a temperature of 280-320°C (e.g., 300°C). Insert a thermocouple into the molten solder bath and control the heating so that the temperature of the molten solder bath returns to its initial temperature within 10±2 minutes of immersing the crucible in the molten solder bath. Then heat it at a rate of 3.0±0.1°C / min.

[0101] When the drum speed or electronic sensor reading reaches 1.0 dd / min, read the temperature and dial reading at 1-minute intervals until the stirring paddle stops. Record the instrument's maximum rotational index (i.e., fluidity dd / min) and the corresponding time (min) and temperature (°C).

[0102] 2. Isothermal fluidity test;

[0103] The preparation and analysis of coal samples are the same as the Gillespie fluidity test process and will not be described in detail here.

[0104] The experimental temperature is a temperature between 400 and 440 ° C. The coal sample is quickly heated to the set temperature and kept constant to perform an isothermal fluidity test and establish a curve showing the relationship between fluidity and time.

[0105] Ensure that the temperature fluctuation during the test is ≤0.1℃ / min. Control the heating so that the temperature of the molten solder bath returns to the initial temperature within 10±2min after the crucible is immersed in the molten solder bath.

[0106] 3. Isothermal fluidity curve processing;

[0107] During the plastic change stage of coking coal, there are two opposite reactions: cracking reaction and condensation reaction. A typical isothermal fluidity curve is as follows: Figure 1 As shown. Figure 1 It can be seen that during the isothermal fluidity test, the fluidity increases slowly at the beginning, then accelerates in an inverted U-shape, reaches a maximum value, and then decreases rapidly; then, as time goes on, the fluidity slowly decreases to 1 ddpm, and the test ends.

[0108] The isothermal flow curve can be used to obtain parameters such as the softening start time (ts), the time to reach maximum fluidity (tmax), the solidification time (tr), the plastic time interval (the time interval in the plastic state ΔT = tr-ts) and the maximum fluidity (MF).

[0109] During the isothermal fluidity test, the change of coal sample fluidity over time can be divided into three stages, such as Figure 2 As shown. That is:

[0110] (1) Melting stage: The fluidity increases with time. This is the melting stage of coking coal.

[0111] (2) Maximum mobility stage: Within a certain time range, the fluidity of high-volatile coking coal is high and remains basically stable. This stage varies depending on the type of coal. For some coking coals with a maximum fluidity of less than 10,000 ddpm, this stage may not exist.

[0112] (3) Coking stage: The fluidity of coking coal decreases with time. This stage is the coking stage of coking coal.

[0113] During the isothermal fluidity test, the fluidity (lnMF) of the isothermal fluidity curve of most coking coals in the melting stage and the coking stage is basically linear with time. However, at the beginning of the isothermal fluidity test, the test data is relatively volatile, so it is necessary to remove the fluctuating data points and perform linear fitting on the isothermal fluidity data in the melting stage and the coking stage respectively to determine the melting slope (km) and the coking slope (kc). The units of the melting slope and the coking slope are both min. -1 .

[0114] for Figure 2 The isothermal fluidity curve shown in the figure fits the melting range equation within 5 to 12 minutes as follows:

[0115] ln(MF)=1.315t-5.956R2=0.9912……Formula (1)

[0116] The fitting equation for the coking interval within 17 to 25 minutes is:

[0117] ln(MF)=-1.071t+27.194R2=0.9943……Formula (2)

[0118] Where: ln(MF) is the isothermal fluidity, ddpm; t is the reaction time, min; R2 is the correlation coefficient.

[0119] The maximum fluidity reached 19,030 ddpm at 13 minutes. However, between 12 and 17 minutes, the fluidity was excessive, and the measured value fluctuated due to gas evolution. The extrapolated maximum fluidity [ln(MFc)] can be calculated based on the extrapolated intersection of the melting equation and the coking equation. The extrapolated maximum fluidity (MFc) at 13.89 minutes was 10,431 ddpm.

[0120] For high-volatile, high-flow coking coal, the release of volatiles during pyrolysis can interfere with the maximum fluidity measurement, affecting the accuracy and repeatability of the test results. The present invention uses a curve extrapolation method to obtain an extrapolated maximum fluidity, which is unaffected by the release of volatiles. Compared with the maximum fluidity measured by test, the test has strong repeatability and is a more stable measurement indicator.

[0121] 4. Variation of characteristic parameters of isothermal fluidity with temperature;

[0122] According to the isothermal fluidity test data of coal samples in the range of 400-440℃, the fluidity characteristic parameters at different temperatures were calculated respectively. The relationships between the isothermal fluidity characteristic parameters, melting slope [ln(km)], coking slope [ln(kc)], maximum fluidity [ln(lnMF)], extrapolated maximum fluidity [ln(lnMFc)] and temperature (1 / T) were fitted using a single-variable linear equation.

[0123] 5. Calculation of activation energy during isothermal flow test;

[0124] In isothermal fluidity tests, the reaction rate (k) of coking coal conforms to the Arrhenius equation:

[0125] k=A×exp(-Ea / RT)……Formula (3)

[0126] Where: R is the gas constant, T is the temperature (K), A is the pre-exponential constant, and Ea is the activation energy (kcal / mol).

[0127] Based on the intercept (Ea / R) of each univariate linear regression equation between the melting slope [ln(km)], coking slope [ln(kc)], maximum fluidity [ln(lnMF)] and extrapolated maximum fluidity [ln(lnMFc)] and temperature (1 / T), the reaction activation energy of different coal samples at different stages of the isothermal fluidity test (melting stage, maximum fluidity stage and coking stage) was calculated.

[0128] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the protection scope of the present invention is not limited to the following examples.

[0129] [Example]

[0130] In this embodiment, 15 kinds of experimental coal samples were tested for isothermal fluidity at 420℃. The isothermal fluidity curves and treatment results are shown in Figure 2. Figure 3-32 shown.

[0131] The isothermal fluidity curve of coking coal varies with the constant temperature, but has similar changing rules.

[0132] The reaction temperatures were fixed at 400℃, 420℃ and 440℃, and isothermal fluidity tests were carried out on 15 coal samples at these temperatures to obtain the maximum fluidity data, fit the melting slope and coking slope, and calculate the extrapolated maximum fluidity.

[0133] The melting slope of coal sample [ln(k m The relationship between )] and temperature (1 / T) is as follows Figure 33a 、 Figure 33b As shown in the two figures, the melting slope of the coal sample [ln(k m )] has a good linear relationship with temperature (1 / T).

[0134] Coking slope of coal sample [ln(k c The relationship between )] and temperature (1 / T) is as follows Figure 34 As shown. Figure 34 It can be seen that the coking slope of the coal sample [ln(k c )] has a good linear relationship with temperature (1 / T).

[0135] The relationship between the maximum fluidity of coal sample [ln(lnMF)] and temperature (1 / T) is as follows: Figure 35 As shown. The extrapolated maximum fluidity of the coal sample [ln(lnMF c The relationship between )] and temperature (1 / T) is as follows Figure 36 As shown. Figure 35 and Figure 36 It can be seen that the variation of the slope of the extrapolated maximum mobility and the slope of the maximum mobility with temperature is similar. The maximum mobility of the coal sample [ln(lnMF)] and the extrapolated maximum mobility [ln(lnMF c )] has a good linear relationship with temperature (1 / T).

[0136] According to the intercept (Ea / R) of each univariate linear regression equation, the reaction activation energy of different coal samples at different stages of the isothermal fluidity test (melting stage, maximum flow stage and coking stage) can be calculated, as shown in Table 1.

[0137] Table 1 Activation energy of coal samples during isothermal fluidity test (Ea, kJ / mol)

[0138]

[0139]

[0140] The standard maximum fluidity test results of the coal samples are shown in Table 2.

[0141] Table 2 Standard maximum fluidity test results of coal samples

[0142]

[0143] (1) Melting stage

[0144] The relationship between the activation energy (Ea) in the melting stage and the standard maximum fluidity is as follows: Figure 37 As shown. Figure 37 It can be seen that the activation energy within the melting range fluctuates within a wide range, showing significant differences among coal types. The activation energy (Ea) calculated based on the melting slope increases with the increase of the standard maximum fluidity. Generally, the activation energy (Ea) of low-fluidity coal (lnMF < 3.55) is 77 to 172 kcal / mol, the activation energy of medium-fluidity coal (3.55 ≤ lnMF < 10) is about 150 to 230 kJ / mol, and the activation energy of high-fluidity coal (lnMF > 10) fluctuates over a wider range, generally exceeding 200 kJ / mol.

[0145] (2) Coking stage

[0146] The relationship between the activation energy (Ea) in the coking stage and the standard maximum fluidity is as follows: Figure 38 As shown. Figure 38 It can be seen that in the coking stage, except for one test point, the activation energy of the remaining coal samples is relatively concentrated (concentrated in the range of 200 ± 30 kJ / mol) and does not change significantly with fluidity, indicating that the trend and behavior of low fluidity of each coal sample are similar.

[0147] (3) Maximum flow stage

[0148] The relationship between the activation energy calculated from the maximum fluidity and the activation energy calculated from the extrapolated maximum fluidity is as follows: Figure 39 As shown in the figure, the activation energy calculated from the two maximum fluidities has a positive correlation.

[0149] Under isothermal conditions, the relationship between the activation energy calculated from the maximum fluidity and the Gibbs maximum fluidity measured by the standard fluidity test is as follows: Figure 40 shown.

[0150] Under isothermal conditions, the relationship between the activation energy calculated from the extrapolated maximum fluidity and the Gibbs maximum fluidity measured by the standard fluidity test is as follows: Figure 41 shown.

[0151] Depend on Figure 40 and Figure 41It can be seen that the maximum fluidity measured by the Gibbs-type flowability test is generally negatively correlated with the activation energy measured under isothermal conditions. The activation energy calculated based on the maximum fluidity (lnMF) decreases with the increase of the standard Gibbs-type maximum fluidity. The activation energy of low-fluidity coal (lnMF < 3.55) is approximately 137-173 kJ / mol, the activation energy of medium-fluidity coal (3.55 ≤ lnMF < 10) is approximately 90-110 kJ / mol, and the activation energy of high-fluidity coal (lnMF > 10) fluctuates widely, generally less than 90 kJ / mol.

[0152] The activation energy calculated based on the extrapolated maximum fluidity (lnMF) also decreases with increasing standard Gibbs maximum fluidity, and is lower than the activation energy calculated from the maximum fluidity. The activation energy of low-fluidity coal (lnMF < 3.55) is approximately 100 to 172 kJ / mol, while that of medium-fluidity coal (3.55 ≤ lnMF < 10) fluctuates between 60 and 100 kJ / mol. High-fluidity coal (lnMF > 10) is generally less than 60 kJ / mol.

[0153] 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 analyzing activation energy during isothermal fluidity testing of coking coal, characterized in that: By analyzing the isothermal fluidity curve of coking coal, a reaction kinetic equation for the critical temperature range of 400-440°C is established to determine the reaction activation energy corresponding to different stages of coking coal fluidity. This allows the quality of the coking coal to be evaluated and its coking characteristics to be predicted. The specific steps include: 1) Gillespie flow test; 2) Isothermal flow test; the process of isothermal flow test is as follows: The preparation and analysis of coal samples are the same as those for the Gibbs flow test. The experimental temperature is 400-440°C. The coal sample is rapidly heated to the set temperature and maintained constant to perform an isothermal flow test. A curve of the change in isothermal flow over time is established. During the test, the temperature fluctuation is controlled to ≤0.1°C / min. The crucible is immersed in a molten solder bath for 10±2 minutes to allow the temperature of the molten solder bath to return to its initial temperature. 3) Isothermal flow curve processing; The fluidity of coking coal changes with time and is divided into three stages, namely the melting stage, the maximum fluidity stage and the coking stage. The isothermal fluidity data of the melting stage and the coking stage are linearly fitted to determine the melting slope and the coking slope. 4) Determine the variation of characteristic parameters of isothermal fluidity with temperature; Based on the isothermal fluidity test data of coal samples in the temperature range of 400-440℃, the fluidity characteristic parameters at different temperatures are calculated respectively. The isothermal fluidity characteristic parameters, including the relationship between melting slope, coking slope, maximum fluidity, and extrapolated maximum fluidity and temperature, are fitted using a single-variable linear equation. 5) Calculation of activation energy during isothermal flow testing; The reaction activation energy of different coal samples at different stages of isothermal fluidity test was calculated based on the intercepts of the linear regression equations between melting slope, coking slope, maximum fluidity and extrapolated maximum fluidity and temperature.

2. The method for analyzing activation energy during isothermal fluidity testing of coking coal according to claim 1, wherein: In step 1), the process of the Gillespie flow test is as follows: The coking coal is crushed to a particle size of less than 0.85 mm, and then divided into coal samples using a bisection device. The coal samples are crushed to a particle size of less than 0.425 mm using a step-by-step crushing method, and the portion of the coal sample with a particle size less than 0.2 mm is ensured to not exceed 50%. After the coal samples are fully mixed, coal samples are taken from different locations and placed into the crucible of the Gillespie plastic tester. A static load is applied to the coal sample, and a dynamic load is used to drop the coal sample from a height multiple times to change the coal sample from a loose state to a formed state. A stirring paddle is provided in the crucible, and a constant torque is applied to the stirring paddle shaft. The plasticity meter head is lowered to the bottom of the crucible and immersed in a molten solder bath at a temperature of 280-320°C. The crucible is immersed in the molten solder bath for 10±2 minutes to allow the molten solder bath to return to its initial temperature, and then heated at a rate of 3.0±0.1°C / min. When the drum speed or electronic sensor reading is 1.0 ddpm, read the temperature and dial reading at 1 minute intervals until the stirring paddle stops rotating; record the maximum rotation index (i.e., fluidity) and the corresponding time and temperature.

3. The method for analyzing activation energy during isothermal fluidity testing of coking coal according to claim 1, wherein: In step 3), the isothermal fluidity curve processing process is as follows: The isothermal fluidity curve is used to obtain the softening start time ts, the time to reach the maximum fluidity tmax, the solidification time tr, the plastic time interval (i.e., the time interval in the plastic state ΔT=tr-ts), and the maximum fluidity MF; The extrapolated maximum fluidity [ln(MFc)] is calculated based on the extrapolated intersection point of the melting equation and the coking equation.

4. The method for analyzing activation energy during isothermal fluidity testing of coking coal according to claim 1, wherein: In step 5), the reaction rate k of the coal sample in the isothermal fluidity test conforms to the Arrhenius equation, that is, k = A × exp(-Ea / RT); where: R is the ideal gas constant; T is the temperature, K; A is the pre-exponential factor; and Ea is the activation energy, kcal / mol.

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