Coal quality multi-element nondestructive analysis method based on compact D-D neutron source

Abstract

The invention discloses a coal quality multi-element nondestructive analysis method based on a compact D-D neutron source, relates to the technical field of nondestructive detection, and solves the technical problem that the existing neutron activation analysis technology based on a nuclear reactor cannot quickly and accurately detect the content of each element in a coal sample due to high equipment cost, large volume and complex operation. The method comprises the following steps: preparing a simple substance sample of each element, acquiring a pure gamma-ray energy spectrum of the simple substance sample by using a gamma-ray detector, and constructing a single element spectrum matrix; preparing a simulated coal sample, and obtaining a pure gamma-ray energy spectrum of the simulated coal sample; based on the single-element spectrum matrix and the pure gamma-ray energy spectrum of the simulated coal sample, analyzing the element content of the simulated coal sample; comparing the element content of the simulated coal sample during preparation with the element content of the simulated coal sample obtained by analysis, and determining a test method of coal element information in reality; according to the method, the content of various elements in the coal sample can be rapidly and accurately detected, and the method is crucial to development and utilization of coal resources.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing, and in particular is a multi-element nondestructive analysis method of coal quality based on a compact DD neutron source. Background Art

[0002] Neutron Activation Analysis (NAA) is a high-precision nondestructive testing technology based on nuclear reactions, which has been widely used in the field of elemental quantitative detection. As a complex organic-inorganic mixture, the elemental composition of coal has an important influence on combustion efficiency, pollutant emissions and the quality of coal chemical products. Therefore, rapid and accurate detection of the content of multiple elements in coal samples is crucial to the development and utilization of coal resources. The existing neutron activation analysis technology based on nuclear reactors has some limitations; first, the cost of such equipment is very high, including construction, maintenance and operation costs; second, due to the involvement of radioactive materials and the need for a large space to house the reactor, this technology is difficult to popularize; third, the operation is complicated and requires professional technicians to manage and monitor, etc. These problems limit the promotion and use of NAA technology in a wider range of application scenarios. Therefore, the present invention provides a multi-element nondestructive analysis method for coal quality based on a compact DD neutron source. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes a multi-element nondestructive analysis method of coal quality based on a compact DD neutron source, which is used to solve the technical problem that the existing neutron activation analysis technology based on nuclear reactors cannot quickly and accurately detect the content of each element in the coal sample due to high equipment cost, large size and complex operation.

[0004] To achieve the above object, the first aspect of the present invention provides a method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source, comprising the following steps:

[0005] According to the element information in the actual coal quality, samples of each element are prepared to obtain samples of each element, which are marked as single-element samples; wherein the element information includes the element type and element content;

[0006] Obtain the gamma energy spectrum and neutron number of the single-element sample, perform denoising on the obtained gamma energy spectrum to obtain a pure gamma energy spectrum; construct a single-element spectrum matrix based on the gamma energy spectrum of the single-element sample;

[0007] Prepare simulated coal samples according to the element information in the actual coal quality, and obtain the pure gamma energy spectrum of the simulated coal samples;

[0008] Based on the single element spectrum matrix and the pure gamma spectrum of the simulated coal sample, the element content of the simulated coal sample is analyzed;

[0009] The element content of the simulated coal sample when it is prepared is compared with the element content of the simulated coal sample obtained by analysis to determine the testing method for the element information of coal quality in reality.

[0010] Preferably, the single substance sample is obtained by:

[0011] Based on the element information in the actual coal quality, single-element samples of different types and masses of each element are configured.

[0012] Among them, common elements in coal include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), etc.

[0013] Preferably, the step of obtaining the gamma spectrum and neutron number of the single substance sample comprises:

[0014] A fixed high voltage is applied by a compact DD neutron source to irradiate single-element samples of each element; wherein the fixed high voltage is within a preset high-voltage threshold range; and a gamma detector is used to collect gamma rays excited and neutron rays reflected in the single-element sample to obtain a gamma energy spectrum and a neutron number.

[0015] Preferably, the method for obtaining the pure gamma spectrum comprises the following steps:

[0016] Obtaining the intensity of the gamma energy spectrum from the gamma energy spectrum;

[0017] The intensity Y0 of the pure gamma energy spectrum is calculated by the formula Y0=Yi-Ybg, and the pure gamma energy spectrum is subjected to neutron normalization and gamma normalization; wherein Yi is the intensity of the gamma energy spectrum; Ybg is the intensity of the background gamma energy spectrum, and the intensity of the background gamma energy spectrum is the gamma energy spectrum collected without placing any gamma detectors.

[0018] Preferably, the neutron normalization and gamma normalization processing of the pure gamma energy spectrum comprises:

[0019] The gamma normalized value Y01 is calculated by the formula Y1=Y0 / ZS; wherein ZS is the actual measured neutron number;

[0020] The neutron normalization value Z0 is calculated by the formula Z0=ZS / ZB; wherein ZB is the known standardized neutron number.

[0021] Preferably, the analyzing the element content of the simulated coal sample comprises:

[0022] By the formula X=(A T ωA) -1 A TωY1 calculates the content X of each element in the simulated coal sample; where A is the single element spectrum matrix; w is the weight matrix.

[0023] Preferably, the single element spectrum matrix includes the gamma energy spectrum characteristics of each element, and the corresponding relationship between the gamma energy spectrum characteristics and the element content; the weight matrix is ​​a diagonal matrix, and the elements on the diagonal represent the weights of each detection channel of the gamma detector.

[0024] Preferably, the actual testing method of coal quality element information is determined by the following method, including:

[0025] The pure gamma energy spectrum of the simulated coal sample and the single-element spectrum matrix are inversely solved by the least squares method. By continuously adjusting the inverse parameters, the error between the inverse result and the element content when the simulated coal sample is prepared is made less than the preset error value. The element information of the actual coal quality is then tested based on the single-element spectrum matrix and the pure gamma energy spectrum of the simulated coal sample.

[0026] Preferably, analyzing the error between the inverse solution result and the element content when the simulated coal sample is prepared includes:

[0027] By calculating the residual sum of squares R and chi-square test value χ 2 The specific calculation formula is as follows:

[0028]

[0029] Where i is the detection channel number of the gamma detector, i = 0, 1, ..., n, n is a positive integer; k is the element type number of the coal quality, k = 0, 1, ..., P, P is a positive integer; y i is the count of the ith channel; a ik is the count of the single element spectrum of element k in the i-th channel; x k is the content of element k in the simulated coal sample; nP is the degree of freedom used.

[0030] Preferably, the chi-square test value χ 2 Used to test the rationality of the inverse solution; to judge χ 2 Is the value less than the preset test value? If yes, the error between the inverse solution result and the element content when the simulated coal sample is prepared is less than the preset error value; if no, the error between the inverse solution result and the element content when the simulated coal sample is prepared is not less than the preset error value, and it is necessary to optimize the single element spectrum matrix or check the data of the simulated coal quality.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The neutron activation analysis realized by the compact DD neutron source in the present invention can effectively reduce the dependence of the equipment on the experimental site and operating conditions, while ensuring the neutron yield and gamma detection efficiency. Especially in coal sample detection, combined with high-efficiency detectors (such as BGO, SiC, etc.), the gamma energy spectrum and neutron counts can be accurately collected to provide high-quality data for spectral library construction. By designing a reasonable single-element sample irradiation experimental process and combining it with advanced data processing methods such as neutron number normalization and gamma energy spectrum normalization, the influence of the matrix effect can be significantly reduced, and a single-element spectrum matrix with high adaptability can be generated; and, by introducing a mixed sample verification link, the present invention further ensures the reliability and applicability of the single-element spectrum matrix, and provides strong technical support for the non-destructive analysis of complex components of coal samples; in addition, the compact DD neutron source has the advantages of small size, low cost, and convenient operation, and is particularly suitable for coal quality testing in laboratories and field environments; in summary, the present invention successfully solves the limitations of traditional neutron activation analysis technology in coal sample testing through the combination of a compact DD neutron source, single-element spectrum matrix construction and mixed sample verification, and provides an efficient, economical and reliable solution for the non-destructive testing of multi-element complex samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 is a flow chart of the method of the present invention;

[0035] Figure 2 This is a system structure block diagram of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] See also Figure 1-Figure 2 The first embodiment of the present invention provides a method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source, comprising the following steps:

[0038] Step 1: Prepare samples of each element according to the element information in the actual coal quality, obtain samples of each element, and mark them as single-element samples; wherein the element information includes the element type and element content;

[0039] Specifically, the element information contained in the coal quality is obtained from coal quality research data, such as relevant literature at home and abroad; based on the element information in the coal quality, samples of each element of different types and masses are configured.

[0040] Among them, common elements in coal include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), etc.

[0041] Step 2: Obtain the gamma spectrum and neutron number of the single-element sample;

[0042] Specifically, a fixed high voltage is applied by a compact DD neutron source to irradiate single-substance samples of each element; wherein the fixed high voltage is within a preset high-voltage threshold range; and a gamma detector is used to collect gamma rays excited and neutron rays reflected in the single-substance sample to obtain a gamma energy spectrum and a neutron number.

[0043] Among them, the irradiation time and intensity are determined according to the sample properties, detector efficiency, neutron source intensity and experimental accuracy requirements. The compact DD neutron source currently used has a continuous and stable high neutron yield at 75kV (75kV is a high voltage set by continuous attempts in experiments, such as eliminating various factors such as high-voltage sparks and unstable yields). We generally set the irradiation time to 5 minutes per group. The resolution of the gamma spectrum collected in 5 minutes can meet the requirements of spectrum interpretation, and the time consumed is also within a reasonable range, which can achieve fast and accurate spectrum acquisition in real experiments; the neutron count N recorded by the neutron detector (SiC) and the intensity of the gamma energy spectrum recorded by the gamma detector (BGO, NaI).

[0044] Step 3: De-noise the obtained gamma energy spectrum to obtain a pure gamma energy spectrum; construct a single-element spectrum matrix based on the gamma energy spectrum of the single-element sample;

[0045] Obtaining the intensity of the gamma energy spectrum from the gamma energy spectrum;

[0046] The intensity Y0 of the pure gamma energy spectrum is calculated by the formula Y0=Yi-Ybg, and the pure gamma energy spectrum is subjected to neutron normalization and gamma normalization;

[0047] Among them, Yi is the intensity of the gamma energy spectrum; Ybg is the intensity of the background gamma energy spectrum. The intensity of the background gamma energy spectrum is the gamma energy spectrum collected without placing any gamma detectors. It reflects the sum of various gamma-ray signals received by the detector under specific environment and conditions. The background gamma spectrum generally includes cosmic rays, environmental radioactivity, detector inherent background, electronic noise, etc.

[0048] The gamma normalized value Y01 is calculated by the formula Y1=Y0 / ZS; wherein ZS is the actual measured neutron number;

[0049] The neutron normalization value Z0 is calculated by the formula Z0=ZS / ZB; wherein ZB is the known standardized neutron number.

[0050] It should be noted that gamma spectrum normalization is to correct for neutron count fluctuations, experimental conditions, and detector efficiency, so that gamma spectra measured at different times and under different conditions can be compared and analyzed on the same basis, thereby improving the accuracy and reliability of the data; neutron normalization refers to comparing the collected neutron counts with the preset neutron counts to correct for the impact of experimental conditions on neutron counts;

[0051] The single element spectrum matrix includes the gamma spectrum characteristics of each element and the corresponding relationship between the gamma spectrum characteristics and the element content.

[0052] Step 4: Prepare a simulated coal sample according to the element information in the actual coal quality, and obtain a pure gamma energy spectrum of the simulated coal sample;

[0053] The simulated coal sample is subjected to the same irradiation experiment as in step two, and a pure gamma spectrum of the simulated coal sample is obtained by the method in step three.

[0054] Step 5: Analyze the element content of the simulated coal sample based on the single element spectrum matrix and the pure gamma spectrum of the simulated coal sample;

[0055] By the formula X=(A T ωA) -1 A T ωY1 calculates the content X of each element in the simulated coal sample; where A is the single element spectrum matrix; w is the weight matrix.

[0056] Among them, the weight matrix is ​​a diagonal matrix, and the elements on the diagonal represent the weights of each detection channel of the gamma detector. When the detection channel count is less than or equal to 1, its weight value is set to 1 to avoid the influence of the low-count channel on the final result. The pure gamma energy spectrum is fitted with the known element content to construct a single-element spectrum matrix.

[0057] Step 6: Compare the element content of the simulated coal sample when it is prepared with the element content of the simulated coal sample obtained by analysis to determine the testing method for the element information of coal quality in reality.

[0058] The pure gamma energy spectrum of the simulated coal sample and the single-element spectrum matrix are inversely solved by the least squares method. By continuously adjusting the inverse parameters, the error between the inverse result and the element content when the simulated coal sample is prepared is made less than the preset error value. The element information of the actual coal quality is then tested based on the single-element spectrum matrix and the pure gamma energy spectrum of the simulated coal sample.

[0059] Specifically, by calculating the residual sum of squares R and the chi-square test value χ 2 The specific calculation formula is as follows:

[0060]

[0061] Judgment 2 Is the value less than the preset test value? If yes, the error between the inverse solution result and the element content when the simulated coal sample is prepared is less than the preset error value; if no, the error between the inverse solution result and the element content when the simulated coal sample is prepared is not less than the preset error value, and the single element spectrum matrix needs to be optimized or the simulated coal quality data needs to be checked. 2 If the value is close to 1, it means that the error between the actual measured value of each element in the simulated coal sample and the calculated value of the model is small; otherwise, the error between the actual measured value of each element in the simulated coal sample and the calculated value of the model is large, and it is necessary to optimize the single element spectrum matrix or check the quality of the experimental data.

[0062] Where i is the detection channel number of the gamma detector, i = 0, 1, ..., n, n is a positive integer; k is the element type number of the coal quality, k = 0, 1, ..., P, P is a positive integer; y i is the count of the ith channel; a ik is the count of the single element spectrum of element k in the i-th channel; x k is the content of element k in the simulated coal sample; nP is the degree of freedom used.

[0063] It should be noted that the residual sum of squares R is used to measure the error between the actual measured value of the element content of the coal sample and the model calculated value. In the least squares method, the goal is to minimize R so that the gap between the predicted value and the actual value is as small as possible, thereby improving the accuracy of model fitting; the chi-square test value χ 2 Used to check the rationality of the inverse solution;

[0064] Residual sum of squares R and chi-square value χ 2 The significance of the comprehensive verification results is that R reflects the absolute fitting error of the model, while χ 2It reflects the relative fitting error and statistical significance of the model. Avoid using R alone and ignoring the effect of degrees of freedom.

[0065] Part of the data in the above formula is calculated by removing the dimension and taking its numerical value. The formula is a formula closest to the actual situation obtained by software simulation of a large amount of collected data; the preset parameters and preset thresholds in the formula are set by technical personnel in this field according to actual conditions or obtained through simulation of a large amount of data.

[0066] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source, characterized in that: include: According to the element information in the actual coal quality, samples of each element are prepared to obtain samples of each element, which are marked as single-element samples; wherein the element information includes the type of element and the content of the element; Obtain the gamma energy spectrum and neutron number of the single-element sample, perform denoising on the obtained gamma energy spectrum to obtain a pure gamma energy spectrum; construct a single-element spectrum matrix based on the gamma energy spectrum of the single-element sample; Prepare simulated coal samples according to the element information in the actual coal quality, and obtain the pure gamma energy spectrum of the simulated coal samples; Based on the single element spectrum matrix and the pure gamma spectrum of the simulated coal sample, the element content of the simulated coal sample is analyzed; The element content of the simulated coal sample when it is prepared is compared with the element content of the simulated coal sample obtained by analysis to determine the testing method for the element information of coal quality in reality.

2. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 1, characterized in that: The method for obtaining the single substance sample is as follows: Based on the element information in the actual coal quality, single-element samples of different types and masses of each element are configured.

3. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 2, characterized in that: The step of obtaining the gamma energy spectrum and neutron number of the single substance sample comprises: A fixed high voltage is applied by a compact DD neutron source to irradiate single-element samples of each element; wherein the fixed high voltage is within a preset high-voltage threshold range; and a gamma detector is used to collect gamma rays excited and neutron rays reflected in the single-element sample to obtain a gamma energy spectrum and a neutron number.

4. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 3, characterized in that: The method for obtaining the pure gamma spectrum comprises the following steps: Obtaining the intensity of the gamma energy spectrum from the gamma energy spectrum; The intensity Y0 of the pure gamma energy spectrum is calculated by the formula Y0=Yi-Ybg, and the pure gamma energy spectrum is subjected to neutron normalization and gamma normalization; wherein Yi is the intensity of the gamma energy spectrum; Ybg is the intensity of the background gamma energy spectrum, and the intensity of the background gamma energy spectrum is the gamma energy spectrum collected without placing any gamma detectors.

5. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 4, characterized in that: The neutron normalization and gamma normalization processing of the pure gamma energy spectrum includes: The gamma normalized value Y01 is calculated by the formula Y1=Y0 / ZS; wherein ZS is the actual measured neutron number; The neutron normalization value Z0 is calculated by the formula Z0=ZS / ZB; wherein ZB is the known standardized neutron number.

6. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 5, characterized in that: The element content of the simulated coal sample is analyzed, including: By the formula X=(A T ωA) -1 A T ωY1 calculates the content X of each element in the simulated coal sample; where A is the single element spectrum matrix; w is the weight matrix.

7. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 6, characterized in that: The single element spectrum matrix includes the gamma spectrum characteristics of each element and the corresponding relationship between the gamma spectrum characteristics and the element content; the weight matrix is ​​a diagonal matrix, and the elements on the diagonal represent the weights of each detection channel of the gamma detector.

8. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 6, characterized in that: The actual testing method of coal quality element information is determined by the following methods, including: The pure gamma energy spectrum of the simulated coal sample and the single-element spectrum matrix are inversely solved by the least squares method. By continuously adjusting the inverse parameters, the error between the inverse result and the element content when the simulated coal sample is prepared is made less than the preset error value. The element information of the actual coal quality is then tested based on the single-element spectrum matrix and the pure gamma energy spectrum of the simulated coal sample.

9. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 8, characterized in that: Analyze the error between the inverse solution result and the element content when the simulated coal sample is prepared, including: By calculating the residual sum of squares R and chi-square test value χ 2 The error analysis is performed on the value, and the calculation formula is as follows: Where i is the detection channel number of the gamma detector, i = 0, 1, ..., n, n is a positive integer; k is the element type number of the coal quality, k = 0, 1, ..., P, P is a positive integer; y i is the count of the ith channel; a ik is the count of the single element spectrum of element k in the i-th channel; x k is the content of element k in the simulated coal sample; nP is the degree of freedom used.

10. The method for nondestructive analysis of coal quality multi-elements based on a compact DD neutron source according to claim 9, characterized in that: The chi-square test value χ 2 Used to test the rationality of the inverse solution; to judge χ 2 Whether the value is less than the preset test value; If yes, the error between the inverse solution result and the element content when the simulated coal sample is prepared is less than the preset error value; If not, the error between the inverse solution result and the element content when the simulated coal sample is prepared shall not be less than the preset error value, and it is necessary to optimize the single element spectrum matrix or check the data of the simulated coal quality.

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