WO2013189125A1

WO2013189125A1 - Method related to determining switching point of a switch-type passive nucleonic level gauge

Info

Publication number: WO2013189125A1
Application number: PCT/CN2012/080198
Authority: WO
Inventors: 郭云昌; 朱敏娟
Original assignee: Guo Yunchang; Zhu Minjuan
Priority date: 2012-06-19
Filing date: 2012-08-16
Publication date: 2013-12-27
Also published as: CN102706416A

Abstract

A method related to determining a switching point of a switch-type passive nucleonic level gauge, comprising the following steps: disposing the switch-type passive nucleonic level gauge in a designated position; determining the material level has reached a preset position, and measuring a gamma ray to obtain a count-rate mean value Nh; determining a level lower than a preset position, and measuring a gamma ray to obtain a count-rate mean value N1; when Nh > N1, once the measurement value is ≥ Nh, issuing a material-full alert; once the measurement value is ≤ N1, dismissing the material-full alert; when Nh < N1, once the measurement value is ≤ Nh, issuing a material-full alert; and when the measurement value is ≥N1, dismissing the material-full alert. The switching-point determination method is suitable for use in a switch-type passive nucleonic level gauge and provides a basis for accurately issuing material-full and material-empty alerts. The three alternative methods, i.e. the direct return difference method, the motion positioning method and the reference positioning method, provide more measurement options for the user depending on actual measurement conditions and, when used as testing methods, improve data reliability.

Description

Method for determining switch point of switch passive nuclear level gauge

[Technical Field] The present invention relates to the field of passive nuclear material level measurement technology, and more particularly to a method for determining a switching point of a switch type passive nuclear material level gauge.

[Background technique]

In the chemical, metallurgical, coal, electric power and other industries, in the process of conveying materials, it is often necessary to measure the material level in the hopper and silo. There are two main methods for measuring the level using gamma ray: one is a conventional nuclear level meter with a radioactive source, such as an automatic level control device disclosed in the domestic patent CN202230393, which essentially utilizes left and right mutual A symmetrical gamma ray column measures the level of the material in the material level bin; the other is a non-radio source nuclear level meter that uses the natural gamma ray to measure the level of the material and the environment without the source. , referred to as the passive nuclear material level meter, the passive nuclear material level meter makes it easy to realize the non-contact measurement level without using the radioactive source but only by using the gamma radioactivity of the measured material itself and the gamma radioactivity in the environment of the tested container. Effective and feasible, the field that originally needs to use the nuclear level gauge is replaced by a passive nuclear level gauge, which greatly reduces the number of radioactive sources used, eliminates the high cost of radioactive source management, and reduces the radiation risk.

According to the alarm mode of the material level measurement, the passive nuclear material level can be divided into two types: switch mode and continuous type. The switch type passive nuclear level gauge is a level meter that can only distinguish whether the material height reaches the set position and outputs a switch signal, that is, the full alarm and the material empty alarm, and the switch type material level alarm refers to the switch type level gauge. The method for determining the alarm point and the alarm release point is different according to the working condition measurement requirements, and some need to be alarmed when the material is full, and some need to be alarmed when the material is empty.

For the switch-type passive nuclear level gauge, the determination of the switch point is the basis for the full and empty alarms, so its accuracy is very critical, but there are few methods for accurately determining the switch point in the prior art. [Summary of the Invention]

The object of the present invention is to make up for the deficiencies of the prior art and to provide a method for accurately determining the switching point of a switching passive nuclear level gauge. In order to achieve the above object, a method for determining a switching point of a switching passive nuclear level gauge is designed, which comprises determining a full alarm switch point and a measuring device for determining a material empty alarm switch point, which is characterized by determining a full alarm switch point. The method uses the direct return method, which includes the following steps:

(a) Install the switch-type passive nuclear level gauge at a selected position so that its installation height meets the height requirements of the alarm. The installation direction is such that the gamma-ray detector can detect the material to be tested and the container to be tested. Gamma ray intensity;

(b) When it is determined that the material level has reached the set position under the minimum allowable confidence level, the gamma ray intensity is measured, and the average count rate Nh is obtained _;

(c) When the material level has been determined to be lower than the set position at the lowest allowable confidence level, the gamma ray intensity is measured to obtain the average count rate N1;

(d) When Nh>Nl, when the ray intensity value is greater than or equal to Nh, the nuclear level meter without the source is full of alarms; when the ray intensity value is less than or equal to N1, the nuclear level meter without the source is discharged. ;

(e) When Nh<Nl, when the measured gamma ray intensity value is less than or equal to Nh, the nuclear level meter without the source is full of alarm; when the measured gamma ray intensity value is greater than or equal to N1, no radiation The source's nuclear level gauge is released from the full alarm.

The method for determining the gap alarm point is to use the direct return method, which includes the following steps: (a) Install the switch-type passive nuclear level gauge at a selected position so that its installation height meets the height requirements of the alarm. The installation direction is such that the gamma-ray detector can detect the material to be tested and the container to be tested. Gamma ray intensity;

(b) When the material level has been determined to be lower than the set position at the minimum allowable confidence level, the gamma ray intensity is measured to obtain the average count rate N1;

(c) When the material level has been determined to be higher than the set position at the lowest allowable confidence level, the gamma ray intensity is measured, and the average count rate Nh is obtained _;

(d) When Nh>Nl, when the measured gamma ray intensity value is less than or equal to N1, the nuclear level meter without radioactive source emits an empty alarm; when the measured gamma ray intensity value is greater than or equal to Nh, no radiation The nuclear level meter of the source cancels the empty alarm;

(e) When Nh<Nl, when the measured gamma ray intensity value is greater than or equal to N1, the nuclear level meter without radioactive source emits an empty alarm; when the measured gamma ray intensity value is less than or equal to Nh, no radiation The source's nuclear level gauge can cancel the material empty alarm. The method of determining the full alarm switch point is replaced by the mobile positioning method instead of the direct return method, which includes the following steps:

(b) keeping the level of the container unchanged, moving the switch passive nuclear level gauge gradually from the top of the container, measuring the intensity of the gamma ray at each position of the same separation distance, and obtaining a gradually changing set of data; (C) The difference between adjacent data is the largest, then the measurement position corresponding to the larger data is the actual material level. According to the direct return method at the measured actual material level, the data of the full alarm and the full material alarm are obtained.

(d) Install the switch-type passive nuclear level gauge back to the selected position, and use the determined data as the basis for the full alarm and the full charge alarm. The method of determining the full alarm switch point is replaced by the reference positioning method instead of the direct return method, which includes the following steps:

(a) In the vicinity of the environmental radiation near the container under test, select a similar container that can be used to determine the material level, and install the switch-type passive nuclear level gauge in a similar position to the measured position of the container under test. Location

(b) Data using the direct return method to obtain the full alarm and the full full alarm;

(c) Install the switch-type passive nuclear level gauge back to the selected position of the tested container, and use the data just determined as the basis for the full alarm and the full charge alarm. The method of determining the material empty alarm switch point uses the mobile positioning method instead of the direct return method, which includes the following steps:

(b) Keep the material level in the container unchanged, and move the switch passive nuclear level gauge gradually from the top of the container, measure the intensity of the gamma ray at each position of the same separation distance, and obtain a gradually changing set of data. ;

(c) The difference between adjacent data is the largest, then the measurement position corresponding to the larger data is the actual material level. At this position, according to the direct return method, the data of the material empty alarm and the material empty alarm are obtained; (d) Install the switch-type passive nuclear level gauge back to the selected position, and use the data just determined as the basis for the material empty alarm and the material empty alarm. The method of determining the material empty alarm switch point adopts the reference positioning method instead of the direct return method, and includes the following steps:

(a) In the vicinity of the environmental radiation near the container under test, select a similar container with the same material that can determine the level, and install the switch passive nuclear level gauge at a position similar to the measurement position of the container under test. ;

(b) The direct return method is used to obtain the data of the material empty alarm and the material empty alarm;

(c) Install the switch-type passive nuclear level gauge back to the selected position of the container to be tested, and use the data just determined as the basis for the material empty alarm and the material empty alarm. The mobile positioning method is suitable for determining that about half of the materials in the container to be tested are determined. The reference positioning method is applicable to all situations, including the inability to determine whether the actual level has reached the installation position, and the fact that it is not possible to determine that there is sufficient material in the container under test. The data refers to the gamma ray intensity value measured by the switched passive nuclear level gauge. Compared with the prior art, the present invention compensates for the blank of the prior art, and provides a switching point determining method suitable for the switch passive nuclear level gauge, which provides a solid foundation for accurately issuing the full and empty alarms, and the present invention The direct return method, the mobile positioning method and the reference positioning method are proposed to replace each other according to the actual measurement situation, which not only increases the selectivity of the user according to the actual measurement situation, but also can be used as a test method to improve the reliability of the data.

[Description of the Drawings] 2 is a schematic diagram of the application of the passive nuclear level gauge according to the present invention; 1. In the material 2. The measured container 3. The passive nuclear level gauge 4. The passive nuclear level gauge bracket [Specific embodiment] The invention is further illustrated by the figures, which can be implemented by those skilled in the art. The invention provides three sets of methods which can be mutually replaced according to actual conditions, and the basic idea is: determining a measuring point, installing a passive nuclear material level meter meeting the sensitivity requirement, measuring gamma rays in a determined response time, respectively determining an alarm The point and alarm release point are different according to the working condition measurement requirements. Some need to alarm when the material is full, and some need to alarm when the material is empty.

The method provided by the invention is applied to a switch type fly ash level gauge, and the level of the ash hopper of the electrostatic precipitator or the bag filter is measured, and the electric hopper or the bag ash hopper of the bag is used as shown in FIG. 2 Pyramid steel plate structure, height 5-8 meters, inclination angle 60 degrees, externally provided with 20-40cm thick insulation material and color steel plate for protection of thermal insulation material, the internal measured material is the temperature formed after pulverized coal combustion is 135-45CTC Fly ash, in view of the temperature, viscosity and ash impact of fly ash and its strong gamma radioactivity, it is highly desirable to employ the method described herein for ash ash monitoring.

The minimum credibility allowed for the material level is determined by the user's standard. For example, the level gauge is installed at 6 meters. When the highest point of the material in the container reaches 10 meters, the material level can be sure that the material level reaches the set position. It is also possible to reach the set position by 9 meters or 8 meters. Similarly, 7 meters, 6.5 meters, and 6.3 meters may reach the set position. If the user believes that if only the highest point is known, it must be at least 6.7 meters, or the user has other methods to confirm that the set position has been reached.

The passive nuclear level gauge used in the embodiment mainly includes: a gamma ray detector, which uses a Nal scintillation detector for measuring the intensity of the gamma ray of the environment in which the material to be tested and the container to be tested are located; The processing module is configured to process the collected gamma ray intensity signal, and combine the software to issue an alarm signal according to a preset switch point, cancel the alarm signal, or according to the pre-acquired gamma ray intensity and the level of the material An electronic circuit that outputs a continuous material level signal; a material level signal output module, an electronic circuit for outputting an alarm signal, an alarm release signal, and a material level signal output by the signal processing module, which may be a light, a sound, an I/O port, Relay, analog output circuit, communication interface, etc.; auxiliary module, including mounting bracket, ray shielding device with improved signal-to-noise ratio, cable connector, antenna, used to set switch point or gamma ray intensity and material level curve parameters Handheld device, communication device for exchanging information between passive nuclear level gauges, etc.; software for controlling gamma detectors, processing gamma signals and outputting alarm signals, canceling alarm signals, or continuous level signals, A collection of all relevant code that implements functions such as communication or human-machine conversations. Example 1

The full positioning alarm switch point of the switch type hopper level gauge is determined by the mobile positioning method. During the system commissioning phase, the safety position is not allowed to be ashed to the installation position of the level gauge. The specific steps are as follows:

(1) Remove the switch type hopper level gauge from the installation position, and monitor the movement of the ash bucket below the installation position;

(2) When there is no fly ash in the hopper, the gamma ray intensity values measured at each height are basically the same;

(3) When the fly ash in the hopper is increased, the gamma ray intensity value measured by the level gauge to the fly ash area or the vicinity of the fly ash area is larger than the gamma ray intensity value of the upper fly ash free area;

(4) As the fly ash increases, the level of the ash bucket rises, and the fly ash area gradually increases. The data measured from the level gauge reacts, that is, the level gauge measures the fly ash area in the lower part or is close to The gamma ray intensity value of the fly ash area becomes larger as the material level increases, but when it increases to a certain extent, the measurement data tends to be stable;

(5) When the area where the gamma ray intensity value is large is close to half of the hopper, that is, when the estimated level reaches half of the hopper, the level gauge is gradually moved downward from the top of the container. The gamma ray intensity is measured at each position of the same interval of 25 cm, and a gradually changing set of gamma ray intensity intensity values is obtained, and the measurement position corresponding to the gamma ray intensity intensity value having the largest difference between adjacent data is the actual material level; When there is a continuous maximum of several adjacent data, the measured position corresponding to the data in the middle position is the actual material level; (6) The data A measured about 50cm below the determined actual material level is the full alarm point; the data B measured around 100cm above the determined actual material level is the full alarm release point;

(6) Then, install the switch type hopper level gauge back to the selected installation position, use the data A just determined as the material full alarm point, and data B is the material full alarm release point.

Example 2

The warehouse pump or pneumatic conveying tank is used to transport the fly ash accumulated in the hopper. When the working condition requires the fly ash to accumulate to 2/3 or 3/4, the alarm will be cancelled and the fly ash will be completely emptied. Considering the southern climate, the outer wall of the steel pump is directly exposed to the outside. The height of the inner ash and the material level can be determined by tapping. The mobile positioning method is another method for determining that the material level is higher than the set position. Method, therefore, the direct return difference method can be used to determine the full alarm point and the full alarm release point of the switch type warehouse pump level gauge, including the following steps:

(1) Install the switch-type tank pump level gauge at the selected position. When the tank pump is ash-free, measure the gamma ray and measure it ten times. After the arithmetic average, the average count rate is N1. When measuring, the switch type will be The source nuclear level gauge is gradually moved downward from the top of the measured container, and the gamma ray intensity is measured at each position of the same separation distance (optimally 25 cm) to obtain a gradually changing set of data;

(2) The ash position in the silo pump is gradually increased. The gray level is judged by the tapping method. When it is determined that the gray level has exceeded the installation position, the gamma ray is measured, measured ten times, and the arithmetic mean is obtained to obtain the average count rate Nh. Among them, the mean value of the count rate Nh is a concept in the random process, and the more the number of measurements, the higher the accuracy. The longer each measurement, the higher the accuracy. In the implementation, the average value can be measured after ten times;

(3) Actual measurement, when the measured value is greater than or equal to Nh, the switch-type warehouse pump level meter is full of alarms; when the measured value is less than or equal to N1, the switch-type warehouse pump level gauge is released from the full alarm.

Example 3

Usually, the amount of ash in the ash bucket in the third and fourth electric fields is very small, and it is difficult to have the opportunity of dust accumulation in a short time. However, these ash buckets are very close to the ash hoppers of the first and second electric fields, and the environmental radiation is very similar. Its size, structure and material are also almost the same. Therefore, the reference point method can be used to refer to the switch point determined on an electric ash hopper as the material full alarm point and the full alarm release point.

Example 4

The coal hopper is a container for supplying coal to the coal pulverizer. When the coal pulverizer is working, empty grinding is not allowed, that is, the coal hopper is not allowed to be empty. Therefore, the material empty alarm is required, and the switch type coal hopper coal is determined by the direct return method. The emptying alarm switch point of the position meter.

When the coal level is lower than the installation position by 100 cm, it is measured ten times, and after arithmetic mean, the average count rate Nl is obtained. When the coal level is higher than the installation position by about 50cm, the measurement is ten times, and after arithmetic arithmetic, the obtained data is Nh. If Nh>Nl, when the measured value is less than or equal to N1, the switch type coal hopper level gauge sends out an empty alarm; when the measured value is greater than or equal to Nh, the switch type coal hopper level gauge cancels the material empty alarm. If Nh < Nl, when the measured value is greater than N1, the switch coal level gauge sends out an empty alarm; when the measured value is less than or equal to Nh, the switch coal level gauge removes the empty alarm.

Claims

A method for determining a switching point of a switching passive nuclear level gauge, comprising determining a full alarm switch point and a measuring device for determining a material empty alarm switch point, wherein the method for determining a full alarm switch point is directly The backlash method consists of the following steps:

(b) When the material level has been reached to the set position with the minimum allowable confidence, the gamma ray intensity is measured to obtain the average count rate Nh;

(d) When Nh>Nl, when the measured m-ray intensity value is greater than or equal to Nh, the nuclear level meter without the source is full of alarms; when the measured m-ray intensity value is less than N1, the nuclear level meter without the source Full alarm;

(1) When Nh<Nl, when the measured m-ray intensity value is less than Nh, the nuclear material level meter without radioactive source is full of alarm; when the measured m-ray intensity value is greater than N1, the nuclear material level meter without radioactive source Release the report

2. A method for determining a switching point of a switched passive nuclear level gauge, characterized in that the method for determining a gap alarm point uses a direct return method comprising the following steps:

(a) Install the switch-type passive nuclear level gauge at a selected position so that its installation height meets the height requirements of the alarm. The installation direction is such that the gamma-ray detector can detect the material to be tested and the container to be tested. Gamma ray intensity; (b) When the material level has been determined to be lower than the set position under the minimum allowable confidence level, the gamma ray intensity is measured, and the average count rate N1 is obtained;

(c) When the material level has been determined to be higher than the set position at the lowest allowable confidence level, the gamma ray intensity is measured to obtain the average count rate Nh;

(d) When Nh>Nl, when the measured gamma ray intensity value is less than N1, the nuclear level meter without radioactive source emits an empty alarm; when the measured gamma ray intensity value is greater than Nh, there is no radioactive source The nuclear level gauge releases the empty alarm;

(e) When Nh<Nl, when the measured gamma ray intensity value is greater than N1, the nuclear level meter without radioactive source emits an empty alarm; when the measured gamma ray intensity value is less than Nh, no radioactive source The nuclear level gauge can cancel the material empty alarm.

3. A method for determining a switching point of a switched passive nuclear level gauge according to claim 1, wherein the method of determining a full alarm switch point is replaced by a direct positioning method by a mobile positioning method, comprising the following steps :

(b) Make the material in the tested container at about half and keep it unchanged. Move the switch passive nuclear level gauge from the top of the measured container gradually downwards, and measure the gamma rays at each position of the same separation distance. Intensity, a set of data that changes gradually;

(c) If the difference between adjacent data is the largest, the measurement position corresponding to the larger data is the actual material level, and the data of the full alarm and the full material alarm are obtained according to the direct return method at the measured actual material level;

(d) Install the gamma ray detector back to the selected position and use the determined data as the basis for the full alarm and the full charge alarm.

4. A method for determining a switching point of a switched passive nuclear level gauge according to claim 1, wherein the method of determining a full alarm switch point is replaced by a reference positioning method instead of a direct return method, comprising the following steps :

(a) in the vicinity of the environmental radiation near the container to be tested, select the material that can determine the material level, a similar container, and the switch passive nuclear level gauge is installed at a position similar to the measurement position of the container to be tested;

(C) Install the switch-type passive nuclear level gauge back to the selected position of the tested container, and use the data just determined as the basis for the full alarm and the full charge alarm.

5. A method for determining a switching point of a switched passive nuclear level gauge according to claim 2, wherein the method for determining a material empty alarm switch point uses a mobile positioning method instead of a direct return method, including the following Steps:

(a) Install the switch-type passive nuclear level gauge at a selected position so that its installation height meets the height requirements of the alarm. The installation direction is such that the gamma-ray detector can detect the material to be tested and the container to be tested. Gamma ray intensity; (b) Keeping the material level in the container unchanged, moving the switch passive nuclear level gauge from the top of the container gradually downward, measuring the intensity of the gamma ray at each position of the same separation distance, will gradually a set of data that changes;

(c) The difference between adjacent data is the largest, then the measurement position corresponding to the larger data is the actual material level. At this position, according to the direct return method, the data of the material empty alarm and the material empty alarm are obtained;

(d) Install the switch-type passive nuclear level gauge back to the selected position, and use the data just determined as the basis for emptying the alarm and releasing the empty alarm.

6. A method for determining a switching point of a switched passive nuclear level gauge according to claim 2, wherein the method for determining a material empty alarm switch point uses a reference positioning method instead of a direct return method, including the following Steps:

(b) The direct return method is used to obtain the data of the emptying alarm and the emptying alarm;

(c) Install the switch-type passive nuclear level gauge back to the selected position of the container to be tested, and use the data just determined as the basis for the material empty alarm and the material empty alarm.

7. A method for determining a switching point of a switched passive nuclear level gauge according to claim 3 or 5, wherein said moving positioning method is adapted to determine about half of the material in the container to be tested. Happening.

8. A method for determining a switching point of a switched passive nuclear level gauge according to claim 4 or 6, wherein said reference positioning method is applicable to all situations, including the inability to determine whether the actual level has been Reaching the installation location also includes the inability to determine that there is enough material in the container under test.

9. A method for determining a switching point of a switched passive nuclear level gauge according to claim 3 or 4 or 5 or 6, wherein said data is measured by a switched passive nuclear level gauge. Gamma ray intensity value.