JP5638912B2 - Density distribution estimation method inside reactor using muon - Google Patents

Description

  The present invention relates to a method for estimating a density distribution inside a reactor using cosmic ray muons.

  In general, a chemical reaction proceeds when raw materials put into a reaction furnace are placed under appropriate conditions such as temperature, pressure, and atmosphere. In the chemical industry, it is extremely important to appropriately control and manage a chemical reaction in order to obtain a product of a desired quality, and operating conditions including reaction conditions are strictly controlled. However, it is difficult to grasp the situation inside the reaction furnace, and usually only temperature monitoring is performed by installing a thermocouple on the reaction furnace wall. Therefore, the distribution of raw materials, intermediates, and products in the reactor could not be grasped sufficiently.

Therefore, recently, attempts have been made to use cosmic ray muons to grasp the internal conditions of the reactor. A cosmic ray muon is one of the elementary particles flying from space and has the following characteristics.
・ It has very high permeability that can pass through mountains.
・ The strength of muon is constant depending on the flying angle.
・ The muon attenuates only according to the density of the object.
・ The number of muons flying per hour is almost constant.
Therefore, when the muon passes through the structure, the muon intensity is attenuated according to the density of the structure. The attenuated muon intensity is compared with the muon intensity when there is no structure, and density information of the structure can be obtained from the attenuation width of the muon intensity.

  In Japanese Patent Application Laid-Open No. 2008-145141 (Patent Document 1), “the cosmic ray muon intensity transmitted through the blast furnace through the blast furnace by the measuring device for measuring the cosmic ray muon and the flying direction of the cosmic ray muon transmitted through the blast furnace” Information and non-transparent cosmic ray muon intensity that is not transmitted through the blast furnace are accumulated for a certain period of time, and based on the accumulated data obtained from the actual measurement, the blast furnace state is used as the density, and the cosmic ray muon intensity transmitted through the furnace bottom and the non-transparent universe. Representing the density of the in-furnace filling from the strength ratio of the in-furnace filling that represents the strength ratio of the blast furnace refractory and expressed as a strength ratio to the line muon strength, and estimating the filling A featured blast furnace in-furnace situation estimation method "(Claim 1) is disclosed.

  According to the invention described in Patent Document 1, “the density of the filling in the furnace, the bottom plate, and the furnace wall can be expressed by the intensity ratio between the cosmic ray muon intensity transmitted through the furnace bottom and the non-transparent cosmic ray muon intensity. Therefore, it is possible to estimate from the density the filling in the furnace that forms a boundary with the refractory such as refractory bricks.From the relationship between the refractory in the specific position and the filling in the furnace that forms the boundary, whether or not the state of the furnace is normal is determined. As a result, the situation inside the furnace can be estimated with high accuracy, and the blast furnace can be controlled in accordance with the situation "(paragraph 0034).

  In Japanese Patent Laid-Open No. 2007-121203 (Patent Document 2), “the remaining thickness of the refractory is estimated according to the measured temperature measured by the temperature measuring means arranged in the blast furnace bottom refractory, and the cosmic ray muon is calculated. A blast furnace furnace bottom management method for complementing the remaining thickness by the boundary position determined by a boundary position determining means for determining a boundary position between the refractory and the furnace in which the temperature is measured, wherein the boundary position determining means The measurement unit that measures the cosmic ray muon transmits the cosmic ray muon intensity transmitted through the bottom of the blast furnace furnace, the discrimination information of the flying direction of the cosmic ray muon transmitted through the bottom of the blast furnace, and the blast furnace non-transmitted The non-transparent cosmic ray muon intensity is accumulated for a certain period of time, and the state of the furnace bottom is represented by the intensity ratio between the cosmic ray muon intensity transmitted through the furnace bottom and the non-transparent cosmic ray muon intensity based on the accumulated data. Based on blast furnace Blast furnace bottom management method is characterized by determining the boundary position of the bottom refractory and the furnace. "(Claim 1) is disclosed.

  According to the invention described in Patent Document 2, the estimated value of the remaining thickness of the refractory based on the measured temperature measured by the temperature measuring means such as a thermocouple through the bottom refractory is used to calculate the blast furnace bottom using the cosmic ray muon. Since it is complemented by the determination result of the boundary position between the furnace and the refractory, the remaining thickness of the refractory can be estimated with higher accuracy "(paragraph 0019).

  In Japanese Patent Application Laid-Open No. 2006-284329 (Patent Document 3), position sensitive detection means is arranged as a measurement system at a finite interval position on the side facing a measurement target portion of a large structure, and primary cosmic rays from space. Measures the muon intensity at a predetermined time interval when the elementary particle muon created in the atmosphere and poured on the ground surface penetrates the measurement target part of the large structure and reaches the measurement system constituting the position sensitive detection means, In the method of obtaining the internal structure information of a large structure by knowing the distribution of the muon intensity for each passing route, “If the internal structure of the large structure changes with time, record all the measured data with a computer. In particular, a method characterized by obtaining dynamic internal structure information of a large structure by adding an absolute time with an accuracy of microseconds or less is disclosed (claim) 3).

  According to the invention described in Patent Document 3, “Acquisition of absolute time with an accuracy of sub-microseconds or less to acquire data, thereby tracking a number of real-time changes and synchronizing with time fluctuations of a periodic internal structure. The stroboscopic analysis is possible "(paragraph 0013).

JP 2008-145141 A JP 2007-121203 A JP 2006-284329 A

  The methods described in Patent Document 1 and Patent Document 2 use the data obtained by accumulating the intensity ratio of muons measured by the measuring device for a certain period of time to obtain the density of the filling material in the furnace, It is an invention that tries to determine the boundary position in the furnace. However, since these methods only provide average data for the accumulation period, it is not possible to grasp the situation inside the reactor according to the operation conditions when the operation conditions change during the accumulation period. . Patent Document 3 describes that stroboscopic analysis that is synchronized with temporal fluctuations of the internal structure can be performed by adding data by adding an extremely short absolute time. The counted cosmic ray muon cycle is once every few seconds to several tens of seconds, and such short-time information cannot provide reliable data. Several hundred hours are required to accurately analyze the conditions inside the reactor.

  Then, this invention makes it a subject to provide the method of estimating the density distribution inside the reactor for every operating condition using a cosmic ray muon.

  The operating conditions of the reaction furnace vary depending on the production plan and the like, and vary from one day to half a day. However, it is unlikely that the reactor will be operated at constant operating conditions for hundreds of hours. Therefore, the present inventor considered that the muon data is stratified for each operation condition by associating the data of the muon intensity at a certain time detected by the muon measuring instrument with the operation condition at that time.

  By stratifying muon data for each operating condition, only muon data under a certain operating condition can be extracted later, so if muon data under that specific operating condition is collected for the time required for data analysis, Even if the operating conditions change, the density distribution information inside the reaction furnace under specific operating conditions can be obtained.

Accordingly, the present invention in one aspect,
Step 1 of repeatedly recording the cumulative intensity information for each muon flying direction detected by the muon measuring instrument after passing through the inside of the reactor;
Step 2 for recording the change over time in the operating conditions of the reactor during the execution of Step 1;
Based on the information recorded in step 1 and step 2, step 3 for associating the accumulated intensity information for each direction of muon flight with a certain time with the operating condition;
Based on the information obtained in Step 3, Step 4 for generating a total value of cumulative intensity information for each flight direction detected by the muon measuring instrument under a specific operating condition;
Is a method for estimating the density distribution in the reactor associated with the operating conditions including

  In one embodiment, a measurement method according to the present invention is a muon (hereinafter referred to as “muon”) that is detected by a muon measuring instrument without passing through the inside of the reactor in order to reduce errors caused by the geometric shape of the muon measuring instrument. "Backward muon") is also recorded in step 1, and the muon of the muon detected by the muon measuring instrument through the inside of the reactor obtained in step 4 based on the accumulated intensity information for each backward muon flight direction. The method further includes a step of correcting the total value of the accumulated intensity information for each flying direction.

  In another embodiment of the measurement method according to the present invention, a muon detected by a muon measuring instrument without passing through the inside of the reactor (hereinafter referred to as “rear muon”) is also recorded in step 1 and Elevation angle decreasing according to the muon detector geometry in the horizontal angle direction is selected from the accumulated intensity information for each flying direction of the muon, and the accumulated intensity information at the center of the horizontal angle at the selected elevation angle is represented. The normalization constant for each horizontal angle is determined by dividing the number of events for each horizontal angle at the selected elevation angle by the representative value, passing through the reactor obtained in step 4, and detected by the muon measuring instrument. Step 5 is further included in which the total value of the accumulated intensity information for each flying direction of the muon is divided by the normalization constant for each horizontal angle to calculate the corrected total value of the accumulated intensity information for each flying direction.

  In yet another embodiment of the measurement method according to the present invention, the total value generated in step 4 is a total value when the cumulative measurement time under a specific operation condition is 500 hours or more.

  In still another embodiment of the measurement method according to the present invention, the predetermined time in Step 3 is 5 to 20 minutes.

  In still another embodiment of the measuring method according to the present invention, the reaction furnace is an electric furnace for producing calcium carbide.

  According to the present invention, it is possible to predict the density distribution in the reactor for each operating condition. It is considered that the raw materials, intermediates, and products exist in the reactor with a certain distribution. However, since these reactor materials have different densities, the density distribution in the reactor is clear. Then, the existence area in these reactors can be estimated. As a result, the stabilization of operations and the development of theoretical analysis technology are expected.

It is the schematic which looked at one Embodiment of the muon measuring system which concerns on this invention from the side. An embodiment of the equipment configuration of a muon measuring device is shown. 1 shows a schematic diagram of one embodiment of a scintillation detector. FIG. It is an example which shows the analysis result of the muon detected in the Example. It is a figure which shows the relationship between the detection efficiency by a muon measuring device, and a muon incident angle. This is an example in which the number of muon events for each flight direction is represented in the x and y coordinate systems.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, an electric furnace for producing calcium carbide is used as the reaction furnace. In the present invention, the reaction furnace is an arbitrary furnace for performing a chemical reaction on an industrial scale, and is a concept including an electric furnace, a melting furnace, a roasting furnace, and a firing furnace. The product obtained in the reactor may be a final product or an intermediate product.

  FIG. 1 is a schematic view of a muon measurement system according to this embodiment as viewed from the side, and includes an electric furnace 101, a muon measuring instrument 102, and a data storage PC 103. The muon measuring instrument 102 detects the number of events (intensity information) and the flying direction of cosmic ray muons that have passed through the electric furnace, and stores the cumulative number of events for each flying direction in the memory of the data storage PC 103. In addition, a process computer (not shown) that manages the operating conditions of the electric furnace automatically stores changes in operating conditions over time in a storage unit in the process computer. The operating condition information accumulated in the process computer may be transferred to the data storage PC 103 and stored in the data storage PC 103. The operating conditions may be recorded on a paper medium or an electronic medium together with time information.

  Here, the number of events is the number of muons detected by the muon measuring device 102 (more specifically, the number of muons that have passed through two scintillation detectors 201a and 201b described later). Decreases if the density length (density × length) of the object that has passed through the muon until it reaches the muon measuring device 102, and increases if the density length is small. The more events, the higher the muon strength.

  In the electric furnace 101, a raw material layer mainly composed of a mixture of raw lime (CaO) and coke (C) as a raw material, a molten layer mainly composed of carbide as a product, and a reaction layer in which a raw material and a product are intermingled. It is considered to be divided. Since these layers have different densities, when the density distribution in the electric furnace becomes clear, the distribution state of these layers in the electric furnace also becomes clear.

  As shown in FIG. 2, the muon measuring instrument 102 receives pulse signals from two scintillation detectors 201a and 201b, a power source 202, and a photomultiplier tube arranged at a predetermined interval toward the electric furnace. A discriminator 203 for converting to a digital signal and a data collection / analysis base 204 are housed in an aluminum storage box 205.

  Referring to FIG. 3, each of the scintillation detectors 201a and 201b includes a plurality of modules 301a having a plastic scintillator extending in the horizontal direction and a photomultiplier tube provided at one end thereof in the vertical direction (in FIG. A plurality of modules 301b having a vertical detection module row, a plastic scintillator extending in the vertical direction, and a photomultiplier tube provided at one end thereof in the horizontal direction are arranged in a horizontal direction. In FIG. 3, for the sake of explanation, it is displayed in six rows, but in actuality there are many more).

  The modules 301a and 301b arranged in the vertical direction and the horizontal direction are preferable because the number of units installed per unit length increases as the measurement accuracy in the flying direction of the muon increases. However, if the number is too large, the cost increases. What is necessary is just to set suitably according to a precision or a target object. What is necessary is just to set suitably the area of the measurement surface of the scintillation detectors 201a and 201b according to the size of the reaction furnace to be measured.

  When the muon flies in the direction of the arrow shown in FIG. 3 and passes through the scintillation detectors 201a and 201b, the plastic scintillators in the front and rear modules (301a and 301b) arranged in the muon path emit light and respond. Pulse signals are output from the photomultiplier tubes. This signal conveys information on the direction of muon flight. The pulse signal is converted into a digital signal through the discriminator 203, and processing for determining whether the light emitted from the detector in the data collection and analysis base 204 is derived from muon and determining the path through which the muon has passed is performed. Is called. Thereafter, the information on the number of muon events and the flight direction is stored in the data storage PC 103.

  Here, focusing on the horizontal detection module row, muon passes the second module from the right end on the side close to the electric furnace 101, and passes the third module from the right end on the side far from the electric furnace 101. Yes. From this coordinate information and the distance M between the scintillation detectors arranged forward and backward, the incident angle of the muon in the horizontal direction can be specified. Similarly, paying attention to the vertical detection module row, muon passes the third module from the upper end on the side closer to the electric furnace 101, and passes the third module from the upper end on the side far from the electric furnace 101. Yes. From this coordinate information and the distance between the scintillation detectors arranged forward and backward, the incident angle of the muon in the elevation angle direction can be specified.

  If the muon flight direction is known, the region of the reactor through which the muon has passed can also be known, so that information on the specific region inside the reactor can be indirectly grasped from the data in the specific muon flight direction.

  The center of the muon measuring instrument 102 is at a distance L from the center of the electric furnace 101 in the horizontal direction. Further, the scintillation detectors arranged in front and rear are separated by a distance M. By changing L and M, measurable elevation angle and horizontal angle are determined. Therefore, the distances L and M may be set according to the diameter D and height H of the reactor to be measured.

  In addition to the muon passing through the reaction furnace and sequentially passing through the front scintillation detector 201a and the rear scintillation detector 201b, the muon measuring instrument 102 flies from the opposite side of the reaction furnace and passes through the reaction furnace. The muon (referred to as “rear muon”) that has passed through the rear scintillation detector 201b and the front scintillation detector 201a in sequence is also detected, and the number of events (intensity information) and information on the flying direction are similarly stored in the data storage PC 103. To accumulate. This backward muon is used for data correction (standardization) described later. Whether the detected muon flies from the front or from the rear is determined by which of the scintillation detectors 201a and 201b detects the muon first.

  By the above procedure, the data storage PC 103 passes through the reactor and is detected by the muon measuring instrument, and the muon that is incident from the rear without passing through the reactor and detected by the muon measuring instrument. Information on the number of events and the flight direction is gradually accumulated over time.

  The accumulated number of muon events for each flight direction can be expressed in the x, y coordinate system for each flight direction, for example, with the horizontal angle on the horizontal axis (x) and the elevation angle on the vertical axis (y). FIG. 6 shows an example in which the number of muon events for each flight direction is represented in the x and y coordinate systems. If the muon flying from the electric furnace 101 side comes from the front and rear scintillation detectors (201a, 201b) from an elevation angle of 70 mrad and a horizontal angle +70 mrad, the point A in the coordinates is counted up. . In addition, if the muon flying from the opposite side of the electric furnace 101 is flying from the elevation angle 70 mrad and the horizontal angle +70 mrad by the front and rear scintillation detectors (201a, 201b), the point B in the coordinates is counted. Will be up.

  Here, the data storage PC 103 stores information related to the cumulative number of events for each flight direction from the start of measurement to the present. Therefore, by regularly accessing the information stored in the data storage PC 103 and calculating the difference from the previously obtained information, the number of muon events increased at regular intervals is obtained in association with the flight direction. can do. This operation is conveniently automated by a computer program.

  The muon cumulative flight information obtained at regular intervals thus obtained is correlated with the operation conditions at regular intervals. For example, accumulated flight information of muons every 10 minutes is associated with operating conditions for each 10 minutes. For this reason, it is possible to specify the muon when the reaction furnace is operated under what operating conditions the muon flying in a specific time zone.

  The fixed time only needs to be set according to the time when the operating conditions change, and is not particularly limited. For example, in order to take into account minute fluctuations in the operating conditions, a relatively short time of 5 to 20 minutes is used. Well, when it is sufficient to capture large fluctuations in operating conditions, it may be a day or longer. However, it should be noted that if the operating conditions are divided too finely, the time required to collect the data necessary for analysis becomes longer. The operation conditions are not particularly limited as long as those skilled in the art are considered to affect the density distribution in the reactor. For example, voltage, power, current, temperature, pressure, atmosphere, raw material composition, residence time, etc. Is mentioned.

  Thus, after calculating the number of muon events detected by the muon measuring device per fixed time in association with the flight direction information and the operating conditions, the muon data detected at the target specific operating conditions Is extracted, and the total value of the number of events for each flight direction is calculated. In order to obtain reliable data, it is desirable to measure until a significant intensity distribution occurs in the number of muon events. For example, in order to examine whether there is a significant intensity distribution in the raw material (preheating layer to reaction layer), the average of the number of muon events passing through the raw material (preheating layer to reaction layer) portion in the electric furnace 101 for each elevation angle. If the value and standard deviation are obtained, the standard deviation is subtracted from the average value, and the absolute value is α (excluding the measurement error), it can be said that the greater the α, the higher the reliability. If α deviates from the average value by 1 or more with σ as a unit, it can be said that there is a certainty of 70% and there is a minimum number of events. Further, when α is 3 or more with σ as a unit, the degree of confirmation is 99.8% or more, which is an ideal number of events.

  Since the number of events in each flying direction decreases as the density of the passing material increases, density information is given. As described above, the flying direction corresponds to a specific area inside the reactor. For this reason, it becomes possible to estimate the relative density distribution inside the reactor. It is also possible to make a graph by mapping the flight direction and the number of events.

Although the density distribution in the reactor can be estimated by the above procedure, the muon flying from the azimuth is isotropic in nature but is proportional from the center to the end due to the detection efficiency of the measuring device. (FIG. 5). Therefore, it is necessary to correct the decrease. Therefore, in order to obtain a more reliable result, it is preferable to perform correction to reduce an error caused by the geometry of the muon measuring instrument. Here, since the backward muon does not pass through the electric furnace and the influence of the building is small, the number of events for each flying direction of the backward muon can be used for correction.
The specific procedure is as follows.
Procedure 1) Elevation angle decreasing from the number of events in the flying direction of the rear muon in line with the geometric shape of the muon detector in the horizontal angle direction, that is, the elevation angle having little influence by the geometric shape of the muon measuring instrument Is selected. At this time, it is preferable to select an elevation angle that most closely matches the geometric shape of the muon detector in the horizontal angle direction. The selection of the elevation angle that is less affected by the geometry of the muon measuring instrument can be obtained by the following method.
Focusing on a specific elevation angle, the number of detected backward muon events shows a distribution in the horizontal angle direction according to the number of modules arranged in the horizontal direction. For this specific elevation angle, a set of values divided by each other is obtained for all combinations of the number of events distributed in the horizontal angle direction. At this time, when all of the obtained values are within 3 times, preferably within 2 times the standard deviation when the set of the values is the population, the influence of the geometry of the muon measuring instrument is small. The elevation angle can be recognized, and the elevation angle can be used to calculate the normalization constant.
Further, a difference from the standard deviation is calculated for each divided value, and the elevation angle having the smallest average value can be set as the elevation angle that most decreases with the geometric shape of the muon detector.
Procedure 2) At the selected elevation angle, the number of events at the center of the horizontal angle is used as a representative value, and the number of events for each horizontal angle is divided by the representative value to determine a normalization constant for each horizontal angle.
Procedure 3) Correction by dividing the total number of accumulated events in each muon flight direction detected by the muon measuring instrument after passing through the reactor by the normalization constant determined in step 2 for each horizontal angle. The number of events for each subsequent flight direction is calculated.

  Hereinafter, examples of the present invention will be described. However, this is for illustrative purposes only, and the present invention is not intended to be limited.

  The muon measurement system shown in FIG. 1 was constructed. The muon measuring instrument 102 was installed on the same floor as the electric furnace 101 (inner diameter 7.0 m, height 3.5 m) for producing calcium carbide, at a distance L from the electric furnace center of 9.0 m. The electric furnace 101 has three electrodes (# 1 to # 3). The muon measuring instrument 102 was installed in the direction where the measurement surface faces the electric furnace. Information on the muon detected by the muon measuring instrument 102 is stored in the data storage PC 103. The muon measuring instrument 102 includes a 1 kV high-voltage power source 202, two scintillation detectors 201a and 201b arranged back and forth at an interval M of 120 cm, a discriminator 203 (KAIZU Works, octal coincidence), and data collection analysis. A base 204 (BeBeans Technology, muon readout module) is configured by being stowed in an aluminum storage box 205.

  The individual plastic scintillators constituting the module rows of the scintillation detectors 201a and 201b are 70 cm long × 3.3 cm wide, and are arranged in the vertical direction for vertical detection, and in the horizontal direction for horizontal detection. 12 are arranged in a row. As a result, each module row has a square plate shape of 70 cm × 70 cm. The plastic scintillator uses a product number BC-408 manufactured by Bikeron, and a photomultiplier tube manufactured by Hamamatsu Photonics, product number H 8500 is attached to one end of each plastic scintillator.

  The elevation angle range measurable with this muon measuring device is 47 to 471 mrad, and the horizontal angle range is -470 to 423 mrad as an angle formed with a half line from the center of the muon measuring device to the center of the electric furnace.

  Using the above muon measurement system, data on the number of events and the direction of flight are stored for the muon detected by the muon instrument through the reactor and the backward muon detected by the muon instrument without passing through the reactor. Stored in the PC 103. During this time, the PC 103 for data storage was accessed every 10 minutes, and the difference in the number of muon events every 10 minutes was stored for each flight direction. On the other hand, the average power consumption (MW) of the electric furnace every 10 minutes was stored in the process computer as operating conditions of the electric furnace.

  After the measurement was completed, the difference in the number of muon events every 10 minutes in the flying direction was related to the power consumption of the electric furnace and tabulated. From this data, when the power consumption of the electric furnace is in the range of 4 to 6 MW (low load operation) (cumulative measurement time 522 hours) and when it is 20 MW or more (high load operation) (cumulative measurement time 610 hours) Each data was extracted and the number of each event was summed for each flight direction, and the distribution of the number of muon events for each flight direction was obtained (total accumulated measurement time 1460 hours).

  After that, according to the procedure described above, the elevation angle that decreases most closely in accordance with the geometric shape of the muon detector in the horizontal angle direction is selected from the accumulated intensity information for each direction of arrival of the rear muon, and normalized for each horizontal angle. Constants were determined (Table 1), and the number of vents was corrected based on the constants. As a result, the graph shown in FIG. 4 was obtained. A dotted line is a boundary of contents such as raw materials and products in the electric furnace, and a blank portion is outside the measurement range. This graph corresponds to the relative density distribution in the electric furnace. In the graph, the vicinity described as “low” is a portion having a relatively low density, and is considered to be a raw material layer. The vicinity described as “high” is a portion having a relatively high density, and is considered to be a molten layer of carbide.

101 Electric furnace 102 Muon measuring instrument 103 Data storage PC
201a, 201b Scintillation detector 202 Power supply 203 Discriminator 204 Data collection analysis base 205 Aluminum storage box 301a, 301b Module

Claims (6)

Step 1 of repeatedly recording the cumulative intensity information for each muon flying direction detected by the muon measuring instrument after passing through the inside of the reactor;
Step 2 for recording the change over time in the operating conditions of the reactor during the execution of Step 1;
Based on the information recorded in step 1 and step 2, step 3 for associating the accumulated intensity information for each direction of muon flight with a certain time with the operating condition;
Based on the information obtained in Step 3, Step 4 for generating a total value of cumulative intensity information for each flight direction detected by the muon measuring instrument under a specific operating condition;
A method for estimating density distribution in a reactor associated with operating conditions including   In order to reduce the error caused by the geometry of the muon measuring instrument, the muon detected by the muon measuring instrument without passing through the reactor (hereinafter referred to as “rear muon”) is also included in step 1. Record and correct the total value of the cumulative intensity information for each flying direction of the muon that is detected by the muon measuring instrument through the inside of the reactor obtained in step 4 based on the cumulative intensity information for each flying direction of the backward muon. The method for estimating a density distribution in a reactor according to claim 1, further comprising a step of: The muon detected by the muon measuring instrument without passing through the reactor (hereinafter referred to as “rear muon”) is also recorded in step 1, and the accumulated intensity information for each flight direction of the rear muon is recorded in the horizontal angle direction. Select the elevation angle that decreases according to the geometry of the muon detector, and use the cumulative intensity information at the center of the horizontal angle at the selected elevation angle as a representative value . determine the normalization constant for each horizontal angle the number of in detected muons by dividing each by the representative value, flying of muons detected by the muon instrument through the reactor internal obtained in step 4 2. The method according to claim 1, further comprising a step 5 of calculating a total value of the cumulative intensity information for each flying direction after correction by dividing the total value of the cumulative intensity information for each direction by the normalization constant for each horizontal angle. Reactor density Cloth estimation method.
  The total value generated by step 4 is a total value when the cumulative measurement time under a specific operating condition is 500 hours or more. The density distribution in the reactor according to any one of claims 1 to 3. Estimation method.   The predetermined time in step 3 is 5 to 20 minutes, The method for estimating a density distribution in a reactor according to any one of claims 1 to 4.   The method for estimating density distribution in a reactor according to any one of claims 1 to 5, wherein the reactor is an electric furnace for producing calcium carbide.