Method for determining reasonable drop strength of green pellets

Abstract

The invention discloses a method for determining reasonable drop strength of green pellets of pellets, which comprises the following steps of: (1) detecting the drop strength of the green pellets before and after transfer, calculating the drop strength loss amount in the transfer process, and recording the drop strength loss amount as N loss transfer; (2) N groups of experiment green pellets are taken and numbered from 1 to N; then carrying out a falling experiment on each group of green pellets, wherein the number of falling times of the xth group of green pellets is x-1; (3) roasting the green pellets subjected to the falling experiment in the step (2), and then respectively carrying out cracked pellet proportion statistics and compressive strength detection on N groups of experiment finished product pellets; and (4) selecting the production line finished product balls which are not subjected to a drop experiment under the same roasting condition in the step (3), and carrying out proportion statistics and compressive strength detection on the cracked balls. According to the method, the drop strength of the green pellets is reasonably controlled, the strength of the green pellets in the operation and roasting process is guaranteed, the strength of the finished pellets is further improved, and support is provided for blast furnace high-proportion pellet smelting.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical raw material detection, in particular to a method for determining the reasonable drop strength of a pelletized ore raw ball. Background Art

[0002] Compared with sintered ore, pellets have a greater carbon reduction advantage. Therefore, the raw materials for blast furnace smelting are gradually changing from sintered ore to pellets. Increasing the proportion of pellets in blast furnaces is the current development trend of environmentally friendly blast furnace ironmaking. With the increase in the proportion of pellets entering the furnace, the quality requirements for pellets are also further improved, especially the strength of pellets has a huge impact on blast furnace smelting. Pellets are subjected to friction, collision and impact during loading and unloading, transportation, storage, furnace loading, and furnace distribution and descent, which produce a certain amount of powder (particle size less than 5mm), affecting the permeability of the material column in the blast furnace and the utilization efficiency of coal gas, and will also increase the amount of furnace dust. Therefore, there are strict requirements for their mechanical strength. The drop strength of green balls is one of the main factors affecting the mechanical strength of finished balls, so ensuring a reasonable drop strength of green balls is an important guarantee for the quality of finished balls. The traditional green ball drop strength index is related to the number of green ball operations, which only ensures that the green balls are neither broken nor deformed during transportation, but ignores its impact on the quality of finished balls. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for determining the reasonable drop strength of a pelletized ore raw ball more accurately and reasonably.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention includes the following steps: (1) Detect the drop strength of the raw balls before and after transportation, and calculate the drop strength loss during transportation, recorded as N 损运 ; (2) Take N groups of experimental raw balls and number them from 1 to N; then perform a drop test on each group of raw balls, and the number of drops for the xth group of raw balls is x-1; (3) The green balls after the drop test in step (2) are roasted, and then the cracked ball ratio and compressive strength of the N groups of finished balls are statistically analyzed; (4) Select finished balls from the production line that have not been subjected to the drop test under the same roasting conditions as step (3) to conduct statistics on the proportion of cracked balls and test their compressive strength; (5) Analyze and compare the cracked ball ratio and compressive strength of the N groups of experimental finished balls and the finished balls of the production line, and calculate the total drop strength loss of the green balls during transportation and roasting, which is recorded as N 损总 The remaining green ball drop strength is N 剩 , determine the reasonable green ball falling strength during the production process.

[0005] Furthermore, in step (1), a number of green balls before transport are selected to test the average drop strength, which is recorded as N 平均 times; select a number of raw balls after transportation to test the average drop strength, recorded as M times; the drop strength loss during the transportation process N 损运 =N 平均 -M.

[0006] Furthermore, in step (2), the green balls that are broken during the falling process are removed.

[0007] Furthermore, in step (5), find the experimental green ball group whose cracked ball ratio of the experimental finished ball is ≤ the cracked ball ratio of the finished ball of the production line and whose compressive strength of the experimental finished ball is ≥ the compressive strength of the finished ball of the production line, and whose cracked ball ratio and compressive strength are closest to the finished ball of the production line. The number of times the experimental green ball group falls is recorded as N. 损总 The remaining raw ball falling strength N 剩 =N 平均 -N 损总 .

[0008] Furthermore, in step (5), the number of reasonable drops of the raw ball N 合理 Meet the following conditions: N 合理 =N 损总 +N 剩 , the N 剩 The corresponding finished ball crack ball ratio and compressive strength must meet the product index requirements and N 剩 ≥1.

[0009] The beneficial effect of adopting the above technical scheme is that: the present invention quantifies the drop strength of green balls into three parts, among which one part is to maintain the strength of green balls during transportation, the second part is to maintain the strength of green balls during roasting, and the third part of the strength is to maintain the reasonable compressive strength and crack ball ratio of finished balls; the finished balls obtained by roasting green balls with different dropping times are tested and analyzed, the influence of the drop strength of green balls on the compressive strength and crack ball ratio of finished balls is summarized, and the three parts of the drop strength of green balls are calculated, and finally the reasonable drop strength of green balls in the production process is obtained.

[0010] This method accurately quantifies the requirements for the drop strength of green balls in each link, analyzes the influence of the drop strength of green balls from two aspects: green balls and finished balls, and makes the requirements for the drop strength of green balls more appropriate and reasonable, providing guarantee for further improving the quality of pellets. This method reasonably controls the drop strength of green balls, ensures the strength of green balls during operation and roasting, further improves the strength of finished balls, and provides support for the smelting of high-proportion pellets in blast furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0012] Figure 1 It is a schematic flow chart of the method of the present invention. DETAILED DESCRIPTION

[0013] The drop strength of the green ball is partly to maintain the strength of the green ball during transportation, partly to maintain the strength of the green ball during roasting, and the remaining part is to support the finished ball to reach a certain strength. Only when the three aspects of strength are met, the quality of the finished ball can be guaranteed. The influence of the drop strength of the green ball on the strength of the finished ball is mainly reflected in the compressive strength and cracked ball ratio of the finished ball. Therefore, the influence of the drop strength of the green ball on the strength of the finished ball can be analyzed by the two indicators of the compressive strength and cracked ball ratio of the finished ball.

[0014] Figure 1 The method for determining the reasonable drop strength of a pelletized ore green ball comprises the following steps: (1) Test the falling strength of green balls before and after transportation: Screen the green balls before transportation from the ball-making plate outlet area. The green balls screened before transportation should be no less than 10 kg and the particle size should be 10-12.5 mm. Take no less than 2 kg to test the average number of times they fall, recorded as N. 平均 At the same time, the green balls after transportation are screened from the head trolley. The green balls after transportation are not less than 2kg and the particle size is 10-12.5mm. The average number of drops is measured and recorded as M times. The drop strength loss during transportation is calculated, which refers to the drop strength deterioration caused by the green balls being dropped and squeezed during transportation. The change is quantified and recorded as N. 损运 , N 损运 =N 平均 -M.

[0015] (2) Selecting experimental raw balls: The raw balls remaining in the raw balls selected from the ball-making plate outlet area in step (1) and not tested for the number of times they fall are used as experimental raw balls. The particle size of the selected experimental raw balls is 10 to 12.5 mm. The experimental raw balls are divided into N groups, each weighing 1 kg, and are numbered from 1 to N, where N is ≥ 6. The N groups of experimental raw balls are subjected to a falling test. The number of times the experimental raw balls in the xth group fall is n. x =x-1, x is the number of each group, that is, the number of times each ball of the first group of experimental balls falls is n1=1-1=0 times, the number of times each ball of the second group of experimental balls falls is n2=2-1=1 times, the number of times each ball of the third group of experimental balls falls is 2 times, and so on. The number of times each ball of the Nth group of experimental balls falls is n N =N-1 times; remove the balls that break during the falling process.

[0016] (3) Roasting the experimental green balls: The N groups of experimental green balls described in step (2) are transferred to the roasting process and roasted in a cage under the same roasting conditions to obtain N groups of experimental finished balls.

[0017] (4) Statistics and testing of finished balls: Statistics on the proportion of cracked balls and tests on the compressive strength of N groups of finished balls are performed to obtain the average proportion of cracked balls and the average compressive strength of each group of finished balls; the cracked balls refer to balls with one or more obvious cracks on the surface of the finished balls.

[0018] (5) Statistics and testing of finished balls of the production line: Select several finished balls of the production line that are produced normally for statistics on the proportion of cracked balls and testing of compressive strength. The particle size of the selected finished balls of the production line is the same as the particle size range of the experimental raw balls, which is 10-12.5 mm. For the compressive strength test, it is best to select at least 50 balls without cracks on the surface, and calculate the arithmetic mean after removing the two maximum values ​​and the two minimum values. Statistic the proportion of cracked balls and test the compressive strength of the selected finished balls of the production line to obtain the average cracked ball proportion and average compressive strength of the finished balls of the production line.

[0019] (6) Comparison of cracked ball ratio and compressive strength analysis: The total drop strength loss during the green ball transportation and roasting process is recorded as N 损总 It refers to the deterioration of the drop strength of the green balls caused by falling and squeezing during transportation during normal production, and squeezing, water evaporation and stress during roasting. The total drop strength loss is quantified as the number of drops of the xth group of experimental green balls when the ratio of the compressive strength of the finished balls of the production line to the cracked balls is close to n. x , find the experimental green ball group x that is closest to the cracked ball ratio and compressive strength of the finished balls of the production line. The cracked ball ratio of the experimental finished balls of this group x is ≤ the cracked ball ratio of the finished balls of the production line, and the compressive strength of the experimental finished balls of this group x is ≥ the compressive strength of the finished balls of the production line. The number of drops of the experimental green balls of this group x is n x N 损总 ; said N 损总 =n x =N 损运 +N 损烧 Since the experimental green balls were roasted in cages, they were protected by iron cages and not squeezed by the material layer during the roasting process. Therefore, there is a certain deviation in the data. This paper can only quantify it approximately as N 损总 =n x .

[0020] The drop strength loss during the green ball roasting process is recorded as N 损烧 It refers to the deterioration of the drop strength of the green balls due to extrusion, water evaporation and stress during the roasting process.

[0021] The remaining drop strength of the green ball after the transfer roasting process is recorded as N 剩 , N 剩 =N 平均 -N 损总 , where N 平均 is the average number of drops, N剩 It refers to the drop strength of the raw ball that supports the finished ball made from it to achieve a certain compressive strength and cracked ball ratio.

[0022] (7) Determine the reasonable number of times the green ball falls N 合理 : The reasonable number of times the ball falls N 合理 The following conditions are met: 1) N 合理 >N 损总 2) N 合理 =N 损总 +N 剩 , the N 剩 The corresponding cracked ball ratio and compressive strength of the finished ball must meet the product index requirements, that is, N 剩 It can be adjusted according to the product index requirements; because too high a drop number will affect other properties of the raw ball, it is best to choose the N that meets the product index requirements 剩 The minimum value among them, and N 剩 ≥1. Example 1

[0023] (1) For the raw balls with a mass ratio of 50%A+20%B+20%C+10%D+4.8% slaked lime+0.6% bentonite, 12 kg of raw balls with a particle size of 10-12.5 mm were sieved from the ball-making plate outlet area, and the average number of drops N was tested. 平均 = 6 times. At the same time, 2 kg of 10-12.5 mm raw balls are sieved from the head trolley, and the average number of drops M is measured, which is recorded as 4 times. The drop strength loss N during operation is calculated. 运损 =N 平均 -M=2 times.

[0024] (2) Take N=6, that is, divide the raw balls taken from the ball-making plate outlet area into 6 groups, each group weighing 1 kg. Perform a drop test on these 6 groups of experimental raw balls. The first group of experimental raw balls each drop 0 times, the second group of experimental raw balls each drop 1 time, the third group of experimental raw balls each drop 2 times, and so on. The sixth group of experimental raw balls each drop 5 times. The balls that break during the falling process are discarded and recorded as 1, 2, 3...6 groups respectively.

[0025] (3) The six groups of experimental raw balls were roasted in cages on the production line under the same roasting conditions to obtain six groups of experimental finished balls.

[0026] (4) The cracked ball ratio and compressive strength test were performed on the six groups of experimental finished balls. The results are shown in Table 1.

[0027] (5) 2 kg of finished balls with a particle size of 10-12.5 mm and the same roasting conditions were screened to count the cracked ball ratio and test the compressive strength. The test results are shown in Table 1 below; Table 1: Cracked ball ratio and compressive strength of the experimental balls and production line balls in Example 1

[0028] (6) The cracked ball ratio and compressive strength of the six groups of experimental finished balls and the finished balls of the production line were analyzed and compared. Among them, the cracked ball ratio and compressive strength of the fourth group of experimental balls were similar to those of the balls of the production line, that is, the finished balls made after the raw balls fell three times had similar strength to the balls of the production line, meeting the requirements that the cracked ball ratio of the experimental finished balls ≤ the cracked ball ratio of the finished balls of the production line, and the compressive strength of the experimental finished balls ≥ the compressive strength of the finished balls of the production line, so N was taken. 损总 =3, that is, the green ball loses three times of drop strength during operation and roasting. 损烧 =N 损总 -N 损运 =3-2=1, so the number of times the green ball falls during the roasting process is N 损烧 1 time; remaining drop strength N 剩 is the average number of drops N 平均 Subtract the number of loss drops N 损总 , that is, N 剩 =N 平均 -N 损总 =3 times, remaining number of drops N 剩 =3 can support the finished pellets with a compressive strength of 2933N and a cracked ball ratio of 6.9%. 平均 If it is 5 times, then the remaining number of drops is N 剩 For 2 times, the finished ball index should be similar to that of the 5th group of balls, with a compressive strength of 2827N and a cracked ball ratio of 6.8%, which also meets the control standard. 平均 If the number of drops is 4, the pellet index will be lower than the control benchmark and will not meet the production conditions. The reasonable average number of drops is equal to N 损总 +N 剩 According to the comparison between the crack ball ratio and compressive strength of the six groups of experimental balls in the table and the production line ball data, N 损总 3 times, and according to the data analysis in the table, N 剩 The value can be 2 or 3 times or more. The finished ball index when it is 2 times can meet the control benchmark, so N 剩 It is more reasonable to take 2 times, so the reasonable average number of drops N 平均 3+2=5 times. After comprehensive analysis, the average number of times the pellets fall is N. 平均 It is most appropriate to control it to 5 times. Example 2

[0029] (1) For the raw balls with a mass ratio of 50%A+20%B+20%C+10%D+4.8% slaked lime+0.6% bentonite, 12 kg of raw balls with a particle size of 10-12.5 mm were sieved from the ball-making plate outlet area, and the average number of drops N was tested. 平均 = 5 times. At the same time, 2 kg of 10-12.5 mm raw balls are sieved from the head trolley, and the average number of drops is measured, which is recorded as 4 times. The drop strength loss during operation is calculated as N 运损 =N 平均 -M=2 times.

[0030] (2) Take N=6, that is, divide the raw balls taken from the ball-making plate outlet area into 6 groups, each group weighing 1 kg. Perform a drop test on these 6 groups of experimental raw balls. The first group of experimental raw balls each drop 0 times, the second group of experimental raw balls each drop 1 time, the third group of experimental raw balls each drop 2 times, and so on. The sixth group of experimental raw balls each drop 5 times. The balls that break during the falling process are discarded and recorded as 1, 2, 3...6 groups respectively.

[0031] (3) The six groups of experimental raw balls were roasted in cages on the production line under the same roasting conditions to obtain six groups of experimental finished balls.

[0032] (4) The cracked ball ratio and compressive strength test were performed on the six groups of experimental finished balls. The results are shown in Table 1.

[0033] (5) 2 kg of finished balls with a particle size of 10-12.5 mm and the same roasting conditions were screened to count the cracked ball ratio and test the compressive strength. The test results are shown in Table 2 below; Table 2: Cracked ball ratio and compressive strength of cage balls and production line balls in Example 2

[0034] (6) The cracked ball ratio and compressive strength of the six groups of finished balls and production line balls were analyzed and compared. Among them, the cracked ball ratio and compressive strength of the third and fourth groups of cage balls were similar to those of the production line balls, but the compressive strength of the fourth group of cage balls was lower than that of the production line balls. Therefore, the data of the third group of cage balls was more appropriate, that is, the finished balls made after the raw balls fell twice had similar strength to the production line balls, so N was taken. 损总 =2, that is, the green ball loses its drop strength twice during operation and roasting. 损烧 =N 损总 -N 损运 =2-1=1, so the number of times the green ball falls during the roasting process is N 损烧 For 1 time, the remaining drop strength N 剩 =N 平均 -N 损总 =3 times, remaining number of drops N 剩=3 can support the finished pellets with a compressive strength of 2831N and a cracked ball ratio of 6.8%. 平均 is 4 times, then the remaining number of drops is N 剩 For 2 times, the finished ball index should be similar to that of the fourth group of balls, with a compressive strength of 2702N and a cracked ball ratio of 5.7%, which also meets the control standard. 平均 For 3 times, the crack ball ratio and the average number of drops N 平均 Similar to the experimental balls in group 5, it also meets the control criteria. However, if the average number of drops N 平均 If it is 2 times, it does not meet the control standard. Comprehensive analysis shows that the average number of pellets falling is N 平均 It is most appropriate to control it to 3 times. Example 3

[0035] (1) For the raw balls with a mass ratio of 50%A+20%B+20%C+10%D+4.8% slaked lime+0.6% bentonite, 12 kg of raw balls with a particle size of 10-12.5 mm were sieved from the ball-making plate outlet area, and the average number of drops N was tested. 平均 = 6 times. At the same time, 2 kg of 10-12.5 mm raw balls are sieved from the head trolley, and the average number of drops is measured, which is recorded as 5 times. The drop strength loss during operation is calculated as N 运损 =N 平均 -M=1 times.

[0036] (2) Take N=6, that is, divide the raw balls taken from the ball-making plate outlet area into 6 groups, each group weighing 1 kg. Perform a drop test on these 6 groups of experimental raw balls. The first group of experimental raw balls each drop 0 times, the second group of experimental raw balls each drop 1 time, the third group of experimental raw balls each drop 2 times, and so on. The sixth group of experimental raw balls each drop 5 times. The balls that break during the falling process are discarded and recorded as 1, 2, 3...6 groups respectively.

[0037] (3) The six groups of experimental raw balls were roasted in cages on the production line under the same roasting conditions to obtain six groups of experimental finished balls.

[0038] (4) The cracked ball ratio and compressive strength test were performed on the six groups of experimental finished balls. The results are shown in Table 1.

[0039] (5) 2 kg of finished balls with a particle size of 10-12.5 mm and the same roasting conditions were screened to measure the cracked ball ratio and compressive strength. The test results are shown in Table 3 below; Table 3: Cracked ball ratio and compressive strength of cage balls and production line balls in Example 3

[0040] (6) The cracked ball ratio and compressive strength of the six groups of finished balls and production line balls were analyzed and compared. Among them, the cracked ball ratio and compressive strength of the fourth and fifth groups of cage balls were similar to those of the production line balls, but the cracked ball ratio of the fifth group of cage balls was higher than that of the production line balls. Therefore, the data of the fourth group of cage balls was more appropriate, that is, the finished balls made after the raw balls fell three times had similar strength to the production line balls, so N was taken. 损总 =3, that is, the green ball loses three times of drop strength during operation and roasting. 损烧 =N 损总 -N 损运 =3-1=2, so the number of times the green ball falls during the roasting process is N 损烧 For 2 times, the remaining drop strength N 剩 =N 平均 -N 损总 =3 times, remaining number of drops N 剩 =3 can support the finished pellets with a compressive strength of 2822N and a cracked ball ratio of 6.7%. 平均 If it is 5 times, then the remaining number of drops is N 剩 The average number of times the raw ball falls is N, and the indicators of the finished ball should be similar to those of the fifth group of balls. The compressive strength is 2877N, and the proportion of cracked balls is 7.9%, which does not meet the control standard. 平均 It is most appropriate to control it within 6 times.

[0041] Comparative Example: For Example 3, the traditional requirement for the drop strength of the green balls is determined according to the number of green ball operations. Generally, the drop strength of the green balls is required to be greater than 3 times to meet the production conditions. However, according to this method, if the average number of green ball drops N 平均 is 4 times, then the remaining number of drops is N 剩 =N 平均 -N 损总 =4-3=1, the finished ball index should be similar to the sixth group of balls, the compressive strength is 2602N, the cracked ball ratio is 9.3%, the cracked ball ratio exceeds the standard and does not meet the control benchmark. Therefore, the number of times the raw ball is dropped according to the traditional method cannot meet the production requirements. According to the method of the present invention, the average number of times the raw ball is dropped N 平均 If it is controlled at 6 times, the crack ball ratio will be reduced and the control benchmark will be reached.

Claims

1. A method for determining the reasonable drop strength of a pelletized ore raw ball, characterized in that: The steps include: (1) Detect the drop strength of the raw balls before and after transportation, and calculate the drop strength loss during transportation, recorded as N 损运 ; (2) Take N groups of experimental raw balls and number them from 1 to N; then perform a drop test on each group of raw balls, and the number of drops for the xth group of raw balls is x-1; (3) The green balls after the drop test in step (2) are roasted, and then the cracked ball ratio and compressive strength of the N groups of finished balls are statistically analyzed; (4) Select finished balls from the production line that have not been subjected to the drop test under the same roasting conditions as step (3) to conduct statistics on the proportion of cracked balls and test their compressive strength; (5) Analyze and compare the cracked ball ratio and compressive strength of the N groups of experimental finished balls and the finished balls of the production line, and calculate the total drop strength loss of the green balls during transportation and roasting, which is recorded as N 损总 The remaining green ball drop strength is N 剩 , determine the reasonable green ball falling strength during the production process.

2. A method for determining the reasonable drop strength of a pelletized ore green ball according to claim 1, characterized in that: In step (1), a number of green balls before transport are selected to test the average drop strength, which is recorded as N 平均 times; select a number of raw balls after transportation to test the average drop strength, recorded as M times; the drop strength loss during the transportation process N 损运 =N 平均 -M.

3. A method for determining the reasonable drop strength of a pelletized ore green ball according to claim 1, characterized in that: In the step (2), the raw balls that are broken during the falling process are removed.

4. A method for determining the reasonable drop strength of a pelletized ore green ball according to claim 1, characterized in that: In step (5), find the experimental green ball group whose cracked ball ratio of the experimental finished ball is ≤ the cracked ball ratio of the finished ball of the production line and whose compressive strength of the experimental finished ball is ≥ the compressive strength of the finished ball of the production line, and whose cracked ball ratio and compressive strength are closest to the finished ball of the production line. The number of times the experimental green ball group falls is recorded as N 损总 The remaining raw ball falling strength N 剩 =N 平均 -N 损总 .

5. A method for determining the reasonable drop strength of a pelletized ore green ball according to any one of claims 1 to 4, characterized in that: The reasonable number of times the raw ball falls in step (5) is N 合理 Meet the following conditions: N 合理 =N 损总 +N 剩 , the N 剩 The corresponding finished ball crack ball ratio and compressive strength must meet the product index requirements and N 剩 ≥1.

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