A method for predicting the reactivity of gasified coal particles

Abstract

The present invention provides a method for predicting the reactivity of gasified coal particles. It includes the following steps: S1: using a visualization device to obtain images of coal char particles at different times in the gasification reaction; S2: calculating the shrinkage rate B of the coal char particles at different times; S3: screening at least two of the coal char particles; S4: calculating the carbon conversion rate x of each coal char particle at different times; making a fitting straight line and calculating the fractal dimension D; S5: determining the fractal dimension of the gasified coal particles and predicting the carbon conversion rate of the gasified coal particles. The present invention uses a visualization device to calculate the fractal dimension of the coal char particles, thereby characterizing the gasification reactivity of the coal char particles, which is of great significance for understanding the real gasification reaction environment and the reaction characteristics of the coal char particles in a complex flow field. According to the prediction results, the operating conditions such as temperature, oxygen content, powder feeding amount and other parameters are adjusted to ensure the gasification effect of the gasified coal particles and improve the gasification reaction efficiency.

Description

Technical Field

[0001] The invention relates to a method for predicting the reactivity of gasified coal particles. Background Art

[0002] Clean and efficient use of coal is the primary task of energy conservation and emission reduction, and coal gasification is an important way to cleanly utilize coal.

[0003] At present, there is no method to calculate or characterize the gasification reaction rate of coal char particles during the gasification reaction; most methods use the fractal dimension of the pore structure of coal char through nitrogen adsorption after the gasification reaction is completed to characterize the changes in the porous structure of the coal char surface during the reaction and the gasification reaction rate. However, the nitrogen adsorption method takes a long time and cannot continuously analyze the fractal dimension of the pore structure in the coal gasification reaction, and there are also restrictions on the types of coal. Summary of the invention

[0004] In order to overcome the problems in the prior art that the analysis time of coal char particles is too long and the analysis method has restrictions on coal types, thus failing to quickly predict the reactivity of gasified coal particles during the gasification reaction, the present invention provides a method for predicting the reactivity of gasified coal particles. The present invention uses a visualization device to calculate the fractal dimension of coal char particles, thereby characterizing the gasification reactivity of coal char particles, which is of great significance for understanding the real gasification reaction environment and the reaction characteristics of coal char particles in a complex flow field. According to the prediction results, the operating conditions such as temperature, oxygen content, powder feeding amount and other parameters are adjusted to ensure the gasification effect of gasified coal particles and improve the gasification reaction efficiency.

[0005] The present invention adopts the following technical solutions to solve the above technical problems.

[0006] The present invention provides a method for predicting the reactivity of gasified coal particles, which comprises the following steps:

[0007] S1: using a visualization device to obtain images of coal char particles at different times during a gasification reaction; the temperature of the gasification reaction is 750° C. to 950° C., the loading amount of the catalyst loaded on the coal char particles is 0 to 10 wt %; the initial equivalent radius of the coal char particles is 100 μm to 150 μm;

[0008] S2: According to the image of the coal char particle in S1, the projected area A and the perimeter P of the coal char particle at different times are measured; according to the projected area A, the shrinkage rate B of the coal char particle at different times is calculated;

[0009] S3: screening at least two of the coal char particles in the image; the screening criteria include that the coal char particles have an approximate shrinkage rate B at the same time, and the same time refers to any time from the start of the reaction to the end of the reaction; wherein the approximate shrinkage rate B means that the difference in shrinkage rate of the coal char particles with different shrinkage rates at the same time is within 20%;

[0010] S4: according to the projected area A of the coal char particles after screening in S3, calculate the carbon conversion rate x of each coal char particle at different times, wherein the carbon conversion rate refers to the average carbon conversion rate of each coal char particle after screening; according to the projected area A and perimeter P of the coal char particles after screening in S3, make a fitting straight line and calculate the fractal dimension D;

[0011] S5: When the gasified coal particles to be analyzed have similar physical parameters and similar reaction conditions as the screened coal char particles, the fractal dimension of the gasified coal particles is determined and the carbon conversion rate of the gasified coal particles is predicted based on the carbon conversion rate x and fractal dimension D of the screened coal char particles at any time from the beginning to the end of the reaction; the similar physical parameters include: the difference between the shrinkage rate of the coal char particles and the shrinkage rate of the gasified coal particles is within 20%, and the difference between the equivalent radius of the coal char particles and the equivalent radius of the gasified coal particles is within 15%; the similar reaction conditions include: the temperature of the gasification reaction is in the range of 750°C to 950°C, and the catalyst loading is in the range of 0 to 10wt%.

[0012] In S1, preferably, the visualization device includes a camera device and / or a display device; more preferably, the visualization device is a high-temperature hot stage microscope.

[0013] In the present invention, the pyrolysis temperature of the coal char particles is conventional in the art, generally around 800°C.

[0014] In S1, preferably, the temperature of the gasification reaction is 800-900°C, for example, 800°C, 850°C or 900°C.

[0015] In S1, preferably, the initial equivalent radius of the coal char particles is 115 μm to 130 μm.

[0016] In S1, preferably, the loading amount of the catalyst is 0wt%, 2.2wt%, 4.4wt%, 6.6wt% or 10wt%.

[0017] In S1, preferably, the catalyst is potassium carbonate.

[0018] In S1, preferably, the loading method is an impregnation method; more preferably, the impregnation method comprises the following steps: adding the coal char particles to an aqueous solution of the catalyst, heating and stirring until viscous, and drying; wherein the heating temperature is preferably 70-80°C, and the drying temperature is preferably 105°C.

[0019] In S1, preferably, the image shooting interval is 20 to 40 seconds, more preferably 20 seconds or 30 seconds. The image shooting interval depends on the equivalent radius of the coal char particles: since the equivalent radius of the coal char particles is small and the gasification time required under the action of the catalyst is short, the image shooting interval should not be too long; if the shooting time is too short, less data on the particle area and perimeter will be obtained, thereby increasing the error of the fitting result.

[0020] In S1, preferably, the image is obtained by processing with ImageJ software.

[0021] Preferably, the ImageJ software processing process includes: ① converting the image into an 8-bit grayscale photo; ② adjusting the grayscale threshold using conventional methods in the art so that the particles are selected completely.

[0022] In S2, preferably, the calculation formula ① of the shrinkage rate B is:

[0023]

[0024] Wherein, A0 is the initial projected area of ​​the coal char particles, A t is the projected area of ​​the coal char particles at time t.

[0025] In S3, preferably, the screening criteria also include: a) the difference in equivalent radius of each of the coal char particles is within 15%; b) each of the coal char particles is not split; c) each of the coal char particles has a clear boundary.

[0026] In S3, preferably, the screening criteria also include: removing coal char particles with extremely poor reactivity, coal char particles that are completely unreactive, or coal char particles that react too quickly; the extremely poor reactivity and complete unreactivity refer to that the shrinkage rate of the coal char particles from the beginning to the end of the gasification reaction is within 10%, and the overly rapid reaction refers to that the rate of change of the shrinkage rate of the coal char particles per unit time in the gasification reaction is more than 30%.

[0027] In S3, preferably, the number of the coal char particles is 3.

[0028] In S4, preferably, the calculation formula ② of the carbon conversion rate x is:

[0029]

[0030] Wherein, A0 is the initial projected area of ​​the coal char particles, A t is the projected area of ​​the coal char particles at time t, A a is the projected area of ​​the coal char particles after the reaction is completed, ρ p is the density of the coal char particles.

[0031] In S4, the carbon conversion rate is based on the assumption that the particle density remains unchanged during the gasification reaction.

[0032] In the present invention, due to the differences in the particles themselves, the carbon conversion rate of a single particle alone cannot represent the gasification reaction conditions in the entire gasifier. Therefore, the average carbon conversion rate of multiple particles is used to reflect the general gasification characteristics, avoiding the influence of particle heterogeneity and the randomness of single particle selection on the experiment. Therefore, in S4, the average carbon conversion rate of each of the coal char particles is selected as the carbon conversion rate.

[0033] In S4, preferably, the fractal dimension D includes calculation formula ③ and formula ④:

[0034]

[0035]

[0036] Wherein, n is the slope of the fitting straight line, and c is the similar fractal shape coefficient;

[0037] According to the logarithm of the projected area and the logarithm of the perimeter of the coal char particles at different times, a straight line fitting is performed as the ordinate and the abscissa, respectively, to obtain the slope n and intercept b of the fitting line. According to formula ③, the relationship of the intercept b is b=-2lgc, thereby calculating the similar fractal shape coefficient c; the slope n is substituted into formula ④ to obtain the fractal dimension D.

[0038] In S5, preferably, when the gasification temperature of the coal char particles is the same as the temperature of the gasification reaction of the gasified coal particles, and the catalyst loading of the coal char particles is the same as the catalyst loading of the gasified coal particles, the fractal dimension of the gasified coal particles is determined to be the fractal dimension D described in S4, and the carbon conversion rate x of the fractal dimension is obtained.

[0039] In S5, preferably, when the gasification temperature of the coal char particles is different from the temperature of the gasification reaction of the gasified coal particles, the fractal dimension D of the gasification temperatures on both sides of the gasified coal particles is taken, and the fractal dimension of the gasified coal particles is calculated by interpolation method, and the carbon conversion rate of the fractal dimension is obtained.

[0040] In S5, preferably, when the catalyst loading of the coal char particles is different from the catalyst loading of the gasified coal particles, the fractal dimension D of the catalyst loading on both sides of the gasified coal particles is taken, and the fractal dimension of the gasified coal particles is calculated by interpolation method, and the carbon conversion rate of the fractal dimension is obtained.

[0041] The interpolation method is a conventional method in the art, specifically taking the middle value between the previous and next points.

[0042] In the present invention, by determining the fractal dimension of the gasified coal particles and predicting the carbon conversion rate of the gasified coal particles, it can be used to guide actual industrial production. When the carbon conversion rate of the gasified coal particles decreases, the oxygen flow rate is increased to increase the temperature in the gasifier; when the carbon conversion rate of the gasified coal particles decreases, the air flow rate is adjusted to increase the particle gasification reactivity; when the carbon conversion rate of the gasified coal particles decreases, the incident angle of the nozzle is adjusted to increase the carbon conversion rate.

[0043] In the present invention, the gasification reaction starts from the outer surface of the coal char particles, gradually forming an ash layer, and then continues to gasify at the interface between the unreacted core and the ash layer. The unreacted core continues to shrink as the gasification reaction proceeds until it disappears completely.

[0044] In the present invention, the surface structure of the coal char in the gasification reaction is analyzed and the gasification reactivity of the coal char particles is characterized by introducing the theory of fractal dimension; fractal geometry uses the concept of fractal dimension D to describe the shape of the particles, and the fractal dimension of the particles is calculated by the area-diameter method. The calculation formula is shown in formula (3), where the area is the projected area of ​​the particle, and the diameter can be calculated by the projected perimeter of the particle. Since a linear relationship is generated between the logarithm of the area LgA and the logarithm of the perimeter LgP, the fractal dimension can be represented by the slope n.

[0045] In the present invention, the fractal dimension D is positively correlated with the carbon conversion rate of the coal char, and can be used to predict the gasification reactivity of gasified coal particles.

[0046] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0047] The reagents and raw materials used in the present invention are commercially available.

[0048] The positive and progressive effects of the present invention are:

[0049] The present invention predicts the reactivity in the coal char gasification reaction according to the fractal dimension value in the coal char particle gasification reaction. The method is simple, fast and can be operated online. It has engineering application value and can be used to guide the adjustment of various parameters in the coal gasification reaction process, which is beneficial to improving the gasification reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 These are images of coal char particles at different times at different gasification temperatures when the catalyst loading is 4.4 wt % in Example 1.

[0051] Figure 2 It is the fitting straight line of the fractal dimension of the coal char particles at different gasification temperatures when the catalyst loading is 4.4wt% in Example 1.

[0052] Figure 3 These are images of coal char at different times at different gasification temperatures in Example 2 with a catalyst loading of 6.6 wt%.

[0053] Figure 4 It is the fitting straight line of the fractal dimension of the coal char particles in Example 2 with a catalyst loading of 6.6wt% at different gasification temperatures.

[0054] Figure 5 It is the fitting straight line of the fractal dimension of the coal char particles in Comparative Example 1 when the catalyst loading is 4.4wt% and the gasification temperature is 800°C.

[0055] Figure 6 It is the fitting straight line of the fractal dimension of the coal char particles in Comparative Example 2 when the catalyst loading is 10wt% and the gasification temperature is 800°C. DETAILED DESCRIPTION

[0056] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0057] In the embodiment of the present invention, the coal char particles are added into an aqueous solution of potassium carbonate by an impregnation method, heated and stirred at 70-80° C. until viscous, and dried at 105° C. to obtain coal char particles loaded with potassium carbonate.

[0058] The calculation formula of shrinkage rate B is:

[0059]

[0060] The calculation formula of carbon conversion rate x is:

[0061]

[0062] Wherein, A0 is the initial projected area of ​​the coal char particles, A t is the projected area of ​​the coal char particles at time t, A a is the projected area of ​​the coal char particles after the reaction is completed, ρ p is the density of the coal char particles.

[0063] The fractal dimension D includes calculation formula ③ and formula ④:

[0064]

[0065]

[0066] Wherein, n is the slope of the fitting straight line, and c is the similar fractal shape coefficient;

[0067] According to the logarithm of the projected area and the logarithm of the perimeter of the coal char particles at different times, the slope n and intercept b of the fitting line are obtained as the ordinate and abscissa respectively. According to formula ③, the relationship of the intercept b is b=-2lgc, so as to calculate the similar fractal shape coefficient c; the slope n is substituted into formula ④ to obtain the fractal dimension D.

[0068] Example 1

[0069] The method for predicting the reactivity of gasified coal particles comprises the following steps:

[0070] S1: A high-temperature hot stage microscope was used as a visualization device to obtain images of coal char particles in the gasification reaction; the image shooting interval was 20s; the images were processed by ImageJ software; the gasification reaction temperature was 800°C, 850°C and 950°C, the loading amount of potassium carbonate as a catalyst in the coal char particles was 4.4wt%, and the initial equivalent radius of the coal char particles was 115μm~130μm.

[0071] Figure 1 The images of coal char particles at different times at different gasification temperatures with a catalyst loading of 4.4 wt% in this embodiment are shown. Figure 1 (a) is the image of coal char particles at 800℃ and 0s; Figure 1 (b) is the image of coal char particles at 800℃ and 120s; Figure 1 (c) is the image of coal char particles at 800℃ and 270s; Figure 1 (d) is the image of coal char particles at 850°C and 0s; Figure 1 (e) is an image of coal char particles at 850°C and 120s; Figure 1 (f) is the image of coal char particles at 850°C and 270s; Figure 1 (g) is the image of coal char particles at 950°C and 0s; Figure 1 (h) is an image of coal char particles at 950°C for 120s; Figure 1 (i) is an image of coal char particles at 950°C and 270s.

[0072] S2: Based on the image of the coal char particles in S1, the projected area A and the perimeter P of the coal char particles at different times are measured; based on the projected area A, the shrinkage rate B of the coal char particles at different times is calculated;

[0073] S3: Filter three char particles in the image, marked as (1), (2) and (3); the screening criteria are: a) the difference in equivalent radius of the three char particles is within 15%; b) the three char particles are not split; c) the boundaries of the three char particles are obvious; d) the three char particles have similar shrinkage rates B at the same time, and the same time refers to any time from the beginning of the reaction to the end of the reaction; wherein, the similar shrinkage rate B means that the difference in shrinkage rates of char particles with different shrinkage rates at the same time is within 20%; e) remove char particles with extremely poor reactivity, completely unreactive char particles or char particles that react too quickly; extremely poor reactivity and completely unreactive mean that the shrinkage rate of char particles in the gasification reaction is within 10%, and too fast reaction means that the rate of change of the shrinkage rate of char particles per unit time in the gasification reaction is more than 30%;

[0074] S4: According to the projection area A of the coal char particles screened by S3, the carbon conversion rate x of each coal char particle at different times is calculated. The carbon conversion rate refers to the average carbon conversion rate of three coal char particles. The carbon conversion rate of the coal char particles after the reaction is completed at 800°C is 0.35, the carbon conversion rate of the coal char particles after the reaction is completed at 850°C is 0.68, and the carbon conversion rate of the coal char particles after the reaction is completed at 900°C is 0.82; according to the projection area A and perimeter P of the coal char particles screened by S3, a fitting straight line is drawn to calculate the fractal dimension D;

[0075] The perimeter P and projected area A of the three coal char particles of this embodiment 1 at different times are shown in Tables 1, 2 and 3. Coal char particles are not regular circles, and their perimeter P and projected area A need to be measured by visualization equipment. Among them, Table 1 shows the perimeter P and projected area A at different times when the catalyst loading is 4.4wt% at 800°C; Table 2 shows the perimeter P and projected area A at different times when the catalyst loading is 4.4wt% at 850°C; Table 3 shows the perimeter P and projected area A at different times when the catalyst loading is 4.4wt% at 900°C.

[0076] Table 1

[0077]

[0078]

[0079] Table 2

[0080]

[0081] Table 3

[0082]

[0083]

[0084] There are some relatively large errors in the data in the table. The reason is that as the gasification reaction proceeds, the coal char particles will produce gasification gas, which will escape from the inside of the coal char particles, causing the coal char particles to expand instantaneously. However, as the reaction proceeds, the size of the coal char particles continues to decrease, reducing the amount of gas escaping from the inside of the coal char particles. During the gasification reaction, the overall change trend of the coal char particle size is relatively fixed.

[0085] Fractal geometry uses the concept of fractal dimension D to describe the shape of particles. The fractal dimension of particles is calculated by the area-diameter method. The relationship between the projected area A and the perimeter P of coal char particles on double logarithmic coordinates is as follows: Figure 2 shown. Figure 2 is the fitting straight line of the fractal dimension of the particles at different gasification temperatures when the catalyst loading is 4.4wt% in this embodiment; wherein, Figure 2 (a) is the fitting straight line of the fractal dimension of coal char particles at 800°C, and its fractal dimension D is 0.80; Figure 2 (b) is the fitting straight line of the fractal dimension of coal char particles at 850°C, and its fractal dimension D is 0.88; Figure 2 (c) is the fitting straight line of the fractal dimension of coal char particles at 900°C, and its fractal dimension D is 0.95.

[0086] S5: Compare the coal char particles and the gasified coal particles to be analyzed to have similar physical parameters and similar reaction conditions, determine the fractal dimension of the gasified coal particles, and predict the carbon conversion rate of the gasified coal particles; similar physical parameters include: the difference between the shrinkage rate of the coal char particles and the shrinkage rate of the gasified coal particles is within 20%, and the difference between the equivalent radius of the coal char particles and the equivalent radius of the gasified coal particles is within 15%; similar reaction conditions include: the temperature of the gasification reaction is in the range of 750°C to 950°C, and the catalyst loading is in the range of 0 to 10wt%.

[0087] Example 2

[0088] The method for predicting the reactivity of gasified coal particles comprises the following steps:

[0089] S1: A high-temperature hot stage microscope was used as a visualization device to obtain images of coal char particles in the gasification reaction; the image shooting interval was 30s; the images were processed by ImageJ software; the gasification reaction temperature was 800°C, 850°C and 950°C, the loading amount of potassium carbonate as a catalyst in the coal char particles was 6.6wt%, and the initial equivalent radius of the coal char particles was 115μm~130μm.

[0090] Figure 3 The images of coal char particles at different times at different gasification temperatures with a catalyst loading of 6.6 wt% in this embodiment are shown in FIG. Figure 3 (a) is the image of coal char particles at 800℃ and 0s; Figure 3 (b) is the image of coal char particles at 800℃ and 120s; Figure 3 (c) is the image of coal char particles at 800℃ and 270s; Figure 3 (d) is the image of coal char particles at 850°C and 0s; Figure 3 (e) is an image of coal char particles at 850°C and 120s; Figure 3 (f) is the image of coal char particles at 850°C and 270s; Figure 3 (g) is the image of coal char particles at 950°C and 0s; Figure 3 (h) is an image of coal char particles at 950°C for 120s; Figure 3 (i) is an image of coal char particles at 950°C and 270s.

[0091] S2: Based on the image of the coal char particles in S1, the projected area A and the perimeter P of the coal char particles at different times are measured; based on the projected area A, the shrinkage rate B of the coal char particles at different times is calculated;

[0092] S3: Filter three char particles in the image, marked as (1), (2) and (3); the screening criteria are: a) the difference in equivalent radius of the three char particles is within 15%; b) the three char particles are not split; c) the boundaries of the three char particles are obvious; d) the three char particles have similar shrinkage rates B at the same time, and the same time refers to any time from the beginning of the reaction to the end of the reaction; wherein, the similar shrinkage rate B means that the difference in shrinkage rates of char particles with different shrinkage rates at the same time is within 20%; e) remove char particles with extremely poor reactivity, completely unreactive char particles or char particles that react too quickly; extremely poor reactivity and completely unreactive mean that the shrinkage rate of char particles in the gasification reaction is within 10%, and too fast reaction means that the rate of change of the shrinkage rate of char particles per unit time in the gasification reaction is more than 30%;

[0093] S4: According to the projection area A of the coal char particles screened by S3, the carbon conversion rate x of each coal char particle at different times is calculated. The carbon conversion rate refers to the average carbon conversion rate of three coal char particles. The carbon conversion rate of the coal char particles after the reaction is completed at 800°C is 0.46, the carbon conversion rate of the coal char particles after the reaction is completed at 850°C is 0.77, and the carbon conversion rate of the coal char particles after the reaction is completed at 900°C is 0.88; According to the projection area A and perimeter P of the coal char particles screened by S3, a fitting straight line is made to calculate the fractal dimension D;

[0094] Fractal geometry uses the concept of fractal dimension D to describe the shape of particles. The fractal dimension of particles is calculated by the area-diameter method. The relationship between the projected area A and the perimeter P of coal char particles on double logarithmic coordinates is as follows: Figure 4 shown. Figure 4 is the fitting straight line of the fractal dimension of the particles at different gasification temperatures when the catalyst loading is 4.4wt% in this embodiment; wherein, Figure 4 (a) is the fitting straight line of the fractal dimension of coal char particles at 800°C, and its fractal dimension D is 0.92; Figure 4 (b) is the fitting straight line of the fractal dimension of coal char particles at 850°C, and its fractal dimension D is 0.95; Figure 4 (c) is the fitting straight line of the fractal dimension of coal char particles at 900°C, and its fractal dimension D is 0.97.

[0095] S5: Compare the coal char particles and the gasified coal particles to be analyzed to have similar physical parameters and similar reaction conditions, determine the fractal dimension of the gasified coal particles, and predict the carbon conversion rate of the gasified coal particles; similar physical parameters include: the difference between the shrinkage rate of the coal char particles and the shrinkage rate of the gasified coal particles is within 20%, and the difference between the equivalent radius of the coal char particles and the equivalent radius of the gasified coal particles is within 15%; similar reaction conditions include: the temperature of the gasification reaction is in the range of 750°C to 950°C, and the catalyst loading is in the range of 0 to 10wt%.

[0096] Example 3

[0097] The catalyst loading of the coal char particles was 2.2%. The method as in Example 1 was used to calculate the fractal dimensions of the coal char particles at different gasification temperatures and the carbon conversion rate after the reaction.

[0098] Example 4

[0099] The catalyst loading of the coal char particles was 10%. The method as in Example 1 was used to calculate the fractal dimensions of the coal char particles at different gasification temperatures and the carbon conversion rate after the reaction.

[0100] Table 4 shows the fractal dimensions of the coal char particles of Examples 1 to 4 at different catalyst dosages and different reaction temperatures.

[0101] Table 4

[0102]

[0103]

[0104] Table 5 shows the carbon conversion rate of the coal char particles in Examples 1 to 4 after the reaction was completed at different catalyst dosages and different reaction temperatures.

[0105] Table 5

[0106]

[0107] Combining Table 4 and Table 5, it can be seen that there is a positive correlation between the fractal dimension of coal char particles and the carbon conversion rate, that is, the larger the fractal dimension, the greater the carbon conversion rate of the coal char particles. Therefore, the fractal dimension of coal char particles can be calculated to predict the gasification reactivity of coal char particles.

[0108] Comparative Example 1

[0109] The catalyst loading of the coal char particles with a particle equivalent radius of 90 μm is 4.4 wt%, and the gasification reaction temperature is 800°C. The method as in Example 1 is used to calculate the fractal dimension of the coal char particles at a gasification reaction temperature of 800°C and a catalyst loading of 4.4 wt% to be 0.83 and the carbon conversion rate after the reaction. Figure 5 This is the fractal dimension of the coal char particles in this comparative example when the catalyst loading is 4.4% and the gasification reaction temperature is 800° C. Compared with the fractal dimension result (0.80) obtained by selecting 115 μm to 130 μm in the experiment, the fractal dimension of this comparative example is larger.

[0110] Comparative Example 2

[0111] The catalyst loading of coal char particles with a particle equivalent radius of 110 to 130 μm is 10 wt%, and the gasification reaction temperature is 800°C. The method as in Example 1 is adopted, but the screening of step S3 is not performed. Three coal char particles are arbitrarily selected, and the fractal dimension of the coal char particles when the catalyst loading is 10 wt% and the gasification temperature is 800°C is calculated. The carbon conversion rates of the three coal char particles after the reaction are calculated to be 37%, 22% and 70%, respectively.

[0112] Figure 6 This is the fitting line of the fractal dimension of the coal char particles in this comparative example with a catalyst loading of 10wt% and a gasification temperature of 800°C. Since the three particles have not been screened in step S3, the points of LgP and LgA are relatively scattered for the particles with large shrinkage rates, and the fitting effect is not good.

[0113] Effect Example 1

[0114] The carbon conversion rate results of coal char particles are reliable. The accuracy of the data is guaranteed by multiple experiments and selecting the average value of particles. Take the catalyst loading of 2.2% and the gasification temperature of 850℃ as an example. As shown in the table, the average carbon conversion rate of the particles in the two experiments is similar. Table 6 shows the average carbon conversion rate of coal char particles at different times when the catalyst loading is 2.2wt% and the gasification temperature is 850℃.

[0115] Table 6

[0116]

Claims

1. A method for predicting the reactivity of gasified coal particles, characterized in that: It includes the following steps: S1: using a visualization device to obtain images of coal char particles at different times during a gasification reaction; the temperature of the gasification reaction is 750° C. to 950° C., the loading amount of the catalyst loaded on the coal char particles is 0 to 10 wt %; the initial equivalent radius of the coal char particles is 100 μm to 150 μm; S2: According to the image of the coal char particle in S1, the projected area A and the perimeter P of the coal char particle at different times are measured; according to the projected area A, the shrinkage rate B of the coal char particle at different times is calculated; S3: screening at least two of the coal char particles in the image; the screening criteria include that the coal char particles have an approximate shrinkage rate B at the same time, and the same time refers to any time from the start of the reaction to the end of the reaction; wherein the approximate shrinkage rate B means that the difference in shrinkage rate of the coal char particles with different shrinkage rates at the same time is within 20%; S4: according to the projected area A of the coal char particles after screening in S3, calculate the carbon conversion rate x of each coal char particle at different times, wherein the carbon conversion rate refers to the average carbon conversion rate of each coal char particle after screening; according to the projected area A and perimeter P of the coal char particles after screening in S3, make a fitting straight line and calculate the fractal dimension D; S5: When the gasified coal particles to be analyzed have similar physical parameters and similar reaction conditions as the screened coal char particles, the fractal dimension of the gasified coal particles is determined and the carbon conversion rate of the gasified coal particles is predicted based on the carbon conversion rate x and fractal dimension D of the screened coal char particles at any time from the beginning to the end of the reaction; the similar physical parameters include: the difference between the shrinkage rate of the coal char particles and the shrinkage rate of the gasified coal particles is within 20%, and the difference between the equivalent radius of the coal char particles and the equivalent radius of the gasified coal particles is within 15%; the similar reaction conditions include: the temperature of the gasification reaction is in the range of 750°C to 950°C, and the catalyst loading is in the range of 0 to 10wt%.

2. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S1, the visualization device includes a camera device and / or a display device; And / or, the temperature of the gasification reaction is 800-900°C; and / or, the initial equivalent radius of the coal char particles is 115 μm to 130 μm; and / or, the loading amount of the catalyst is 0wt%, 2.2wt%, 4.4wt%, 6.6wt% or 10wt%; And / or, the catalyst is potassium carbonate; And / or, the loading method is an impregnation method; And / or, the image shooting interval is 20 to 40 seconds; And / or, the image is obtained by processing with ImageJ software.

3. The method for predicting the reactivity of gasified coal particles according to claim 2, characterized in that: In S1, the visualization device is a high temperature hot stage microscope; and / or, the temperature of the gasification reaction is 800° C., 850° C. or 900° C.; And / or, the impregnation method comprises the following steps: adding the coal char particles into the aqueous solution of the catalyst, heating and stirring until viscous, and drying; And / or, the image shooting interval is 20s or 30s.

4. The method for predicting the reactivity of gasified coal particles according to claim 3, characterized in that: The heating temperature is 70-80°C.

5. The method for predicting the reactivity of gasified coal particles according to claim 3, characterized in that: The drying temperature is 105°C.

6. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S2, the calculation formula ① of the shrinkage rate B is: Wherein, A0 is the initial projected area of ​​the coal char particles, A t is the projected area of ​​the coal char particles at time t.

7. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S3, the screening criteria also include: a) the difference in equivalent radius of each of the coal char particles is within 15%; b) each of the coal char particles is not split; c) each of the coal char particles has a clear boundary.

8. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S3, the screening criteria also include: removing coal char particles with extremely poor reactivity, coal char particles that are completely unreactive, or coal char particles that react too quickly; the extremely poor reactivity and completely unreactive refer to that the shrinkage rate of the coal char particles from the beginning to the end of the gasification reaction is within 10%, and the overly rapid reaction refers to that the rate of change of the shrinkage rate of the coal char particles per unit time in the gasification reaction is more than 30%.

9. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S3, the number of the coal char particles is 3.

10. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S4, the calculation formula ② of the carbon conversion rate x is: Wherein, A0 is the initial projected area of ​​the coal char particles, A t is the projected area of ​​the coal char particles at time t, A a is the projected area of ​​the coal char particles after the reaction is completed, ρ p is the density of the coal char particles.

11. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S4, the fractal dimension D includes calculation formula ③ and formula ④: Wherein, n is the slope of the fitting straight line, and c is the similar fractal shape coefficient; According to the logarithm of the projected area and the logarithm of the perimeter of the coal char particles at different times, a straight line is fitted as the ordinate and the abscissa respectively, and the slope n and intercept b of the fitting line are obtained; according to formula ③, the relationship of the intercept b is b=-2lgc, thereby calculating the similar fractal shape coefficient c; the slope n is substituted into formula ④ to obtain the fractal dimension D.

12. The method for predicting the reactivity of gasified coal particles according to claim 1, characterized in that: In S5, when the gasification temperature of the coal char particles is the same as the temperature of the gasification reaction of the gasified coal particles, and the catalyst loading of the coal char particles is the same as the catalyst loading of the gasified coal particles, the fractal dimension of the gasified coal particles is determined to be the fractal dimension D described in S4, and the carbon conversion rate x of the fractal dimension is obtained; Or, when the gasification temperature of the coal char particles is different from the temperature of the gasification reaction of the gasified coal particles, the fractal dimension D of the gasification temperatures on both sides of the gasified coal particles is taken, and the fractal dimension of the gasified coal particles is calculated by interpolation method, and the carbon conversion rate of the fractal dimension is obtained; Alternatively, when the catalyst loading of the coal char particles is different from the catalyst loading of the gasified coal particles, the fractal dimension D of the catalyst loading on both sides of the gasified coal particles is taken, and the fractal dimension of the gasified coal particles is calculated by interpolation method, and the carbon conversion rate of the fractal dimension is obtained.

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