Method for monitoring abnormal condition of wet return rate in pelletizing process

Abstract

The invention discloses a method for monitoring the wet return rate in a pelletizing process, and the normal operation range of the wet return rate in the pelletizing process is obtained by collecting the operation data of the wet return rate in a normal pelletizing process. In daily production, by making a scatter diagram and combining the operation areas of the SF6 rate and the SF6-3 rate, whether the current pelletizing process is normal or not and the main problems can be obtained. Therefore, measures can be taken in time to stabilize the yield of green pellets according to abnormal conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of steel, and in particular relates to a monitoring method for abnormal wet return rate in a pelletizing process. Background Art

[0002] At present, the main raw material structure used in the blast furnace ironmaking process is sintered ore plus pellets. As an important component of blast furnace ironmaking raw materials, pellets have irreplaceable advantages such as uniform particle size and high total iron content. The iron concentrate used in the pellet production process is pelletized and screened, and the green balls that meet the particle size requirements enter the roasting process, and those that do not meet the particle size requirements become wet return ore and return to the batching and pelletizing process. The proportion of wet return ore to the amount of material entering the pelletizing machine is the wet return rate. Because the pelletizing process of the pelletizing machine is mainly monitored manually and the work intensity is high, and the main factors affecting the wet return rate are the ballability of the incoming material and moisture. The above factors are constantly changing, but the manual sampling and monitoring of the pelletizing process is discontinuous, which will cause the wet return rate to change greatly in the daily production process, resulting in fluctuations in the weight of the green balls entering the roasting process, affecting the quality of the finished pellets. At present, the main means of monitoring the ball making effect is that the operators of each shift regularly screen the raw balls produced by the ball making machine to determine the quality of the raw balls and make corresponding adjustments. This monitoring status is non-continuous monitoring and is only adjusted when the raw ball data exceeds the qualified range. There is a "monitoring vacuum" between two samplings, and it is impossible to make advance predictions and adjustments in advance. In response to the above problems, this method is specially proposed to use the proportion and trend of large and small particle size return ore to derive the measures that need to be adjusted, thereby accelerating the reaction speed and strengthening the level of raw ball quality process control. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a method for collecting wet return production data in the pelletizing process, establishing an abnormal operation model, and thus issuing an early warning for abnormal conditions of the continuous operation data of the wet return rate, and providing adjustment measures after judgment.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for monitoring abnormal wet return rate in a pelletizing process, comprising the following steps:

[0006] A. Collect the hourly average data of the belt scale after each screen in the screening system and the total amount of material entering the pelletizing machine at the same time;

[0007] B. The weight of the returned balls on the receiving belt after the first sieve under the pelletizer (number: SF6-3, which removes the powder <8mm after the pelletizer) is divided by the proportion of all the materials entering the pelletizer at the same time, which is defined as the SF6-3 rate, which mainly reflects the powder proportion;

[0008] C. The weight of the returned balls screened out by the second double-layer roller screen numbered SF3 is divided by the proportion of all materials entering the pelletizing machine at the same time, which is defined as the SF3 rate. It mainly reflects the proportion of particles with a size greater than 16 mm and the proportion of particles with a size less than 8 mm that are broken due to insufficient strength after being screened by SF6-3.

[0009] D. Total wet return rate SF6 rate plus SF3 rate plus SF6-3 rate;

[0010] E. Collect the hourly average data of SF6 rate and SF6-3 rate in the pelletizing process;

[0011] F. Perform descriptive statistics and normal distribution verification on the operating data;

[0012] G. Determine the abnormal distribution judgment standard based on the distribution law of the operating data; if the distribution is normal, the probability density function of the normal distribution is used to calculate the values ​​when the two tails have a probability of 5% as the normal state operation range; if the distribution is non-normal, the 5th quantile and the 95th quantile are used as the upper and lower limits of normal operation;

[0013] H. Draw an operation monitoring diagram of the wet return rate of the ball making process according to the judgment standard determined in step H;

[0014] I. Make corresponding adjustments based on the abnormal conditions reported in the graph: SF6 exceeds the upper limit and SF6-3 exceeds the upper limit, indicating that the green ball particle size is too small and there is a lot of powder; the SF6 rate is within the normal range but the continuous increase trend for more than 5 hours indicates that the wet return rate is constantly increasing. It is necessary to judge whether the green ball particle size is too large or too small by the corresponding SF6-3 rate and SF3 rate at the corresponding time:

[0015] If the SF6-3 rate is rising continuously, it means that the particle size of the raw balls is gradually getting smaller, and the proportion of raw balls smaller than 8 mm is increasing; if the SF3 rate is gradually rising and SF6-3 has no obvious change or is gradually decreasing, it means that the overall particle size of the raw balls is getting larger, and it is necessary to reduce water on the ball making machine;

[0016] If the SF3 rate is gradually rising and SF6-3 is increasing, it means that the overall raw ball particle size is gradually getting smaller, and water needs to be added to the ball making machine; if SF6 exceeds the lower limit, it means that the ball making effect is good and no adjustment is needed.

[0017] Furthermore, in the step E, the collection period is 80-120 hours.

[0018] Furthermore, in the step E, the collection is performed for 100 hours.

[0019] Furthermore, abnormal production data during startup and shutdown are not included in the statistics.

[0020] Furthermore, the method can take timely measures to stabilize the output of green balls in response to abnormal situations.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] The present invention obtains the normal operating range of the wet return rate in the pelletizing process by collecting the operating data of the wet return rate in the normal pelletizing process. In daily production, by making a scatter plot, combined with the operating area of ​​the SF6 rate and the SF6-3 rate, it can be obtained whether the current pelletizing process is normal and the main existing problems. Therefore, measures can be taken in time to stabilize the output of raw balls in response to abnormal situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] Figure 1 is a normal distribution graph;

[0025] Figure 2 is a scatter plot of SF6 rate;

[0026] Figure 3 It is a scatter plot of SF6-3 rate. DETAILED DESCRIPTION

[0027] A method for monitoring abnormal wet return rate in a pelletizing process, comprising:

[0028] A. Descriptive statistics and Anderson-darling normality test were performed on the SF6 rate after eliminating the impact of start-up and shutdown, and the P value was 0.176>0.05. The descriptive statistics results and the P value of the normality test showed that the SF6 rate was normally distributed with a mean of 0.30153 and a standard deviation of 0.04284.

[0029] B. According to the probability density function of the normal distribution, the SF6 rate under normal conditions is calculated to be between 0.2311 (23.11%) and 0.3720 (37.20%). Figure 1 As shown), the operating range is a symmetrical distribution area with the mean as the symmetry axis, and the above area (23.11%-37.20%) is defined as the normal operating area of ​​SF6 rate.

[0030] C. Descriptive statistics and Anderson-darling normality test were performed on the SF6-3 rate after eliminating the impact of start-up and shutdown, and the P value was 0.308>0.05. The descriptive statistics results and the P value of the normality test showed that SF6-3 was normally distributed with a mean of 0.066417 and a standard deviation of 0.030236.

[0031] D. According to the probability density function of the normal distribution, it is calculated that the SF6-3 rate under normal conditions is distributed between 0.01668 and 0.1162 in 90% of the cases, and the operating range is a symmetrical distribution area with a symmetrical mean. The above area is defined as the normal operating area of ​​the SF6-3 rate.

[0032] E. Plot the SF6 rate and SF6-3 rate during normal production operation on the graph with the normal operating limit.

[0033] F. Abnormal warning:

[0034] from Figure 2 and Figure 3 The scatter plot of the two runs shows:

[0035] From 8:00 to 13:00, the SF6 rate continued to rise for 5 consecutive hours, and the corresponding SF6-3 rate also continued to rise. This shows that although the total wet return rate is within the normal range, it has continued to rise for 5 consecutive hours, mainly because the SF6-3 rate of <8mm is rising, indicating that the moisture content of the raw materials is constantly drying up and the pelletizing particle size is too small, and water needs to be added.

[0036] It can be seen from the operating time at 16:00 that the SF6 rate at that hour exceeded the upper limit of the operating area of ​​90%, but the SF6-3 rate screened out <8mm was between the mean and the upper limit, indicating that both SF6-3 and SF3 were high. This was mainly because there were more powders <8mm, resulting in more SF6-3 returns and more SF3 screened out <8mm. Attention should be paid to the moisture content of the raw materials and the strength of the green balls.

[0037] At 20 o'clock, the SF6-3 rate exceeded the upper control limit and the total wet return rate SF6 was close to the upper limit, indicating that there were too many small-sized raw balls. Attention should be paid to the moisture content and the thickness of the bottom of the plate. It may be that the moisture content is low or the bottom of the plate collapses, resulting in a large number of small-sized balls less than 8mm coming out of the ball making machine. Water needs to be added to the ball plate of the ball making machine.

[0038] The 26-point SF6-3 rate exceeds the lower control limit, which means that fewer small-sized raw balls are screened out, and it is possible that the raw balls are overall too large. However, combined with the 26-point total wet return rate (SF6 rate) being within the normal range, the possibility of the raw balls being too large is ruled out, indicating that the ball making situation is good and no adjustment is needed.

[0039] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for monitoring abnormal wet return rate in a pelletizing process, characterized in that: The steps include: A. Collect the hourly average data of the belt scale after each screen in the screening system and the total amount of material entering the pelletizing machine at the same time; B. The weight of the returned balls on the receiving belt after the first sieve under the pelletizer is divided by the proportion of all the materials entering the pelletizer at the same time, which is defined as the SF6-3 rate, which mainly reflects the proportion of powder; C. The weight of the returned balls screened out by the second double-layer roller screen numbered SF3 is divided by the proportion of all materials entering the pelletizing machine at the same time, which is defined as the SF3 rate. It mainly reflects the proportion of particles with a size greater than 16 mm and the proportion of particles with a size less than 8 mm that are broken due to insufficient strength after being screened by SF6-3. D. Total wet return rate SF6 rate plus SF3 rate plus SF6-3 rate; E. Collect the hourly average data of SF6 rate and SF6-3 rate in the pelletizing process; F. Perform descriptive statistics and normal distribution verification on the operating data; G. Determine the abnormal distribution judgment standard based on the distribution law of the operating data; if the distribution is normal, the probability density function of the normal distribution is used to calculate the values ​​when the two tails have a probability of 5% as the normal state operation range; if the distribution is non-normal, the 5th quantile and the 95th quantile are used as the upper and lower limits of normal operation; H. Draw an operation monitoring diagram of the wet return rate of the ball making process according to the judgment standard determined in step H; I. Make corresponding adjustments based on the abnormal conditions reported in the graph: SF6 exceeds the upper limit and SF6-3 exceeds the upper limit, indicating that the green ball particle size is too small and there is a lot of powder; the SF6 rate is within the normal range but the continuous increase trend for more than 5 hours indicates that the wet return rate is constantly increasing. It is necessary to judge whether the green ball particle size is too large or too small by the corresponding SF6-3 rate and SF3 rate at the corresponding time: If the SF6-3 rate is rising continuously, it means that the particle size of the raw balls is gradually getting smaller, and the proportion of raw balls smaller than 8 mm is increasing; if the SF3 rate is gradually rising and SF6-3 has no obvious change or is gradually decreasing, it means that the overall particle size of the raw balls is getting larger, and it is necessary to reduce water on the ball making machine; If the SF3 rate is gradually rising and SF6-3 is increasing, it means that the overall raw ball particle size is gradually getting smaller, and water needs to be added to the ball making machine; if SF6 exceeds the lower limit, it means that the ball making effect is good and no adjustment is needed.

2. The method for monitoring abnormal wet return rate in the pelletizing process according to claim 1, characterized in that: In the step E, the collection period is 80-120 hours.

3. The method for monitoring abnormal wet return rate in the pelletizing process according to claim 1, characterized in that: In the step E, the collection period is 100 hours.

4. The method for monitoring abnormal wet return rate in the pelletizing process according to claim 1, characterized in that: Abnormal production data during startup and shutdown are not included in the statistics.

5. The method for monitoring abnormal wet return rate in the pelletizing process according to claim 1, characterized in that: This method can take timely measures to stabilize the output of green balls in response to abnormal situations.

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