A coal quality multi-element nondestructive analysis method based on a compact D-D neutron source

Abstract

The application discloses a coal quality multi-element nondestructive analysis method based on a compact D-D neutron source, relates to the technical field of nondestructive testing, 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 size and complicated operation; the application prepares elemental samples of each element, collects pure gamma energy spectrum of the elemental samples by using a gamma detector, and constructs a single-element spectrum matrix; a simulated coal sample is prepared, and its pure gamma energy spectrum is obtained; based on the single-element spectrum matrix and the pure gamma energy spectrum of the simulated coal sample, the content of elements in the simulated coal sample is analyzed; the content of elements when the simulated coal sample is prepared is compared with the content of elements in the simulated coal sample obtained through analysis, and a test method for coal quality element information in reality is determined; and the application realizes quick and accurate detection of the content of multiple elements in a coal sample, which is crucial for the development and utilization of coal resources.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nondestructive testing, and particularly relates to a coal quality multi-element nondestructive analysis method based on a compact D-D neutron source. BACKGROUND

[0002] Neutron Activation Analysis (NAA) is a high-precision nondestructive testing technology based on nuclear reactions, which has been widely used in element quantitative detection. Coal is a complex organic-inorganic mixture, and its element composition has an important influence on combustion efficiency, pollutant emission and coal chemical product quality. Therefore, it is crucial to quickly and accurately detect the content of various elements in coal samples for 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 substances and the need for a large space to accommodate the reactor, this technology is difficult to popularize. Third, the operation is complex and requires professional technical personnel to manage and monitor, which limits the promotion and use of NAA technology in more extensive application scenarios. Therefore, the application provides a coal quality multi-element nondestructive analysis method based on a compact D-D neutron source. SUMMARY

[0003] The application aims to at least solve one of the technical problems existing in the prior art. To this end, the application provides a coal quality multi-element nondestructive analysis method based on a compact D-D 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 various elements in coal samples due to high equipment cost, large size and complex operation.

[0004] To achieve the above-mentioned purpose, the first aspect of the application provides a coal quality multi-element nondestructive analysis method based on a compact D-D neutron source, comprising the following steps:

[0005] Prepare samples of each element according to the element information in the actual coal quality to obtain samples of each element, which are marked as single-element samples; wherein the element information includes element types and element contents;

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

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

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

[0009] Compare the element content when the simulated coal sample is prepared with the element content of the simulated coal sample obtained by analysis to determine the testing method of the element information of the actual coal quality.

[0010] Preferably, the single-element sample is obtained in the following manner:

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

[0012] Among them, the common elements in coal quality are, for example, 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 gamma spectrum and neutron number of the single-element sample are obtained in the following manner:

[0014] The single-element sample of each element is irradiated by a compact D-D neutron source with a fixed high voltage; wherein the fixed high voltage is within a preset high voltage threshold; and the gamma detector is used to collect the excited gamma rays and reflected neutron rays in the single-element sample to obtain the gamma spectrum and neutron number.

[0015] Preferably, the pure gamma spectrum is obtained in the following manner:

[0016] The intensity of the gamma spectrum is obtained from the gamma spectrum;

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

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

[0019] The gamma normalization value Y1 is calculated by the formula Y1=Y0 / ZS; wherein ZS is the actually 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 analysis of the element content of the simulated coal sample comprises:

[0022] The content X of each element in the simulated coal sample is calculated by the formula ; wherein A is a single-element spectrum matrix; and w is a weight matrix.

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

[0024] Preferably, the testing method of the element information of the real coal quality comprises the following steps of:

[0025] The pure gamma spectrum of the simulated coal sample is inversely solved by the least square method based on the single element spectrum matrix, and the inverse solution result is continuously adjusted until the error between the inverse solution result and the element content when the simulated coal sample is prepared is less than a preset error value, and then the element information of the real coal quality is tested based on the single element spectrum matrix and the pure gamma spectrum of the simulated coal sample.

[0026] Preferably, the error between the inverse solution result and the element content when the simulated coal sample is prepared is analyzed, and the analysis comprises the following steps of:

[0027] The error is analyzed by calculating a residual sum of squares R and a chi-square test value The specific calculation formula is as follows:

[0028] ;

[0029] ;

[0030] Wherein, i is a detection channel number of the gamma detector, i=0, 1, …, n, n is a positive integer; k is an element type number of the coal quality, k=0, 1, …, P, P is a positive integer; is a count of the i-th channel; is a count of the i-th channel of the single element spectrum of the element k; is a content of the element k in the simulated coal sample; and n-P is a degree of freedom.

[0031] Preferably, the chi-square test value is used to test the rationality of the inverse solution result; and it is judged whether the value is less than a 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; and 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 data of the simulated coal quality needs to be checked.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] The neutron activation analysis realized by the compact D-D neutron source can effectively reduce the dependence of the equipment on the experimental site and the operating conditions, and ensure the neutron yield and the gamma detection efficiency, especially in the coal sample detection, in combination with the high-efficiency detector (such as BGO, SiC, etc.), the gamma energy spectrum and the neutron count can be accurately collected, and high-quality data are provided for the spectral library construction. Through the design of a reasonable single-element sample irradiation experiment process, and in combination with advanced data processing methods such as neutron number normalization and gamma spectrum normalization, the influence of the matrix effect can be significantly reduced, and a single-element spectrum matrix with high adaptability is generated. In addition, the compact D-D neutron source has the advantages of small size, low cost and convenient operation, and is especially suitable for coal quality detection in the laboratory and on-site environment. In summary, the combination of the compact D-D neutron source, the single-element spectrum matrix construction and the mixed sample verification can successfully solve the limitations of the traditional neutron activation analysis technology in the coal sample detection, and provide an efficient, economical and reliable solution for the nondestructive detection of multi-element complex samples. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0035] Fig. 1 The method flowchart of the present application is shown in the figure.

[0036] Fig. 2 The system structure block diagram of the present application is shown in the figure. DETAILED DESCRIPTION

[0037] The technical solutions of the present application will be described clearly and completely in combination with the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0038] Please refer to Figs. 1-2 The first aspect embodiment of the present application provides a coal multi-element nondestructive analysis method based on a compact D-D neutron source, including the following steps:

[0039] Step one: according to the actual coal quality element information to prepare each element sample, get each element sample, marked as single element sample; wherein, the element information includes element type and element content;

[0040] Specifically, from the coal quality research data, such as relevant literature at home and abroad, the element information contained in the coal quality is obtained; based on the element information in the coal quality, different types and different qualities of each element sample are configured.

[0041] Among them, the common element types in coal quality are, such as 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.

[0042] Step two: obtain the gamma spectrum and neutron number of the single element sample;

[0043] Specifically, the single element sample of each element is irradiated by a compact D-D neutron source with fixed high voltage; wherein, the fixed high voltage is within a preset high voltage threshold; and the gamma detector is used to collect the excited gamma rays and reflected neutron rays in the single element sample, to obtain the gamma spectrum and neutron number.

[0044] Among them, the irradiation time and intensity are determined according to the sample properties, detector efficiency, neutron source intensity and experimental accuracy requirements. The existing compact D-D neutron source has a stable high neutron yield at 75kV (75kV is obtained in the experiment, such as excluding high voltage sparking, unstable yield and other factors). We generally set 5 minutes as a group, and the gamma spectrum resolution collected in 5 minutes can meet the spectrum resolution requirements, and the time length 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 gamma spectrum intensity recorded by the gamma detector (BGO, NaI).

[0045] Step three: denoising the obtained gamma spectrum to obtain a pure gamma spectrum; based on the gamma spectrum of the single element sample, a single element spectrum matrix is constructed;

[0046] The intensity of the gamma spectrum is obtained from the gamma spectrum;

[0047] Through the formula Y0=Yi YbgCalculate the intensity Y0of the pure gamma spectrum, and perform neutron normalization and gamma normalization on the pure gamma spectrum;

[0048] Wherein, Yi is the intensity of the gamma spectrum; Ybg is the intensity of the background gamma spectrum, the intensity of the background gamma spectrum is the gamma spectrum collected without placing any gamma detector, which reflects the sum of various gamma ray signals received by the detector in a specific environment and conditions, and the background gamma spectrum generally includes cosmic rays, environmental radioactivity, detector intrinsic background, electronic noise, etc.

[0049] The gamma normalization value Y1 is calculated by the formula Y1=Y0 / ZS; wherein ZS is the actually measured number of neutrons;

[0050] The neutron normalization value Z0 is calculated by the formula Z0=ZS / ZB; wherein ZB is the known standardized number of neutrons.

[0051] It should be noted that the gamma spectrum normalization is to correct the neutron counting fluctuation, correct the influence of experimental conditions and detector efficiency, so as to ensure that the gamma spectra measured at different times and under different conditions are compared and analyzed under the same reference, and the accuracy and reliability of the data are improved; the neutron normalization refers to comparing the collected neutron count with the preset number of neutrons to correct the influence of experimental conditions on the neutron count;

[0052] 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.

[0053] Step four: prepare a simulated coal sample according to the element information in the actual coal quality, and obtain the pure gamma spectrum of the simulated coal sample;

[0054] Wherein, the simulated coal sample is subjected to the same irradiation experiment as step two, and the pure gamma spectrum of the simulated coal sample is obtained by the method of step three.

[0055] Step five: based on the single-element spectrum matrix and the pure gamma spectrum of the simulated coal sample, analyze the element content of the simulated coal sample;

[0056] The content X of each element in the simulated coal sample is calculated by the formula

[0057] Wherein, the weight matrix is a diagonal matrix, and the elements on the diagonal line represent the weights of each detection channel of the gamma detector; for the case where the detection channel count is less than or equal to 1, the weight value is set to 1 to avoid the influence of low count channels on the final result, and the pure gamma spectrum is operated and fitted with the known element content to construct the single-element spectrum matrix.

[0058] Step six: compare the element content when the simulated coal sample is prepared with the analyzed element content of the simulated coal sample to determine the test method of the coal quality element information in reality. ​

[0059] The pure gamma spectrum of the simulated coal sample and the single-element spectrum matrix are inversely solved using the least squares method. By continuously adjusting the inverse solution parameters, the error between the inverse solution result and the element content when the simulated coal sample is prepared is made less than the preset error value. Then, the element information of the coal quality in reality can be tested based on the single-element spectrum matrix and the pure gamma spectrum of the simulated coal sample.

[0060] Specifically, this is achieved by calculating the residual sum of squares R and the chi-square test value. Error analysis is performed on the values, and the specific calculation formula is as follows:

[0061] ;

[0062] ;

[0063] judge If the value is less than the preset test value, then the error between the inverse solution result and the elemental content when the simulated coal sample was prepared is less than the preset error value; otherwise, the error between the inverse solution result and the elemental content when the simulated coal sample was prepared is not less than the preset error value, and the single-element spectral matrix needs to be optimized or the simulated coal quality data needs to be checked. A value close to 1 indicates that the error between the actual measured value and the model calculated value of each element in the simulated coal sample is small; otherwise, the error between the actual measured value and the model calculated value of each element in the simulated coal sample is large, and the single-element spectral matrix needs to be optimized or the quality of the experimental data needs to be checked.

[0064] Where i is the detection channel number of the gamma detector, i=0,1,…,n, where n is a positive integer; k is the element type number of the coal, k=0,1,…,P, where P is a positive integer; Let i be the count of the i-th channel; Let be the count of the single-element spectrum of element k in the i-th channel; nP represents the content of element k in the simulated coal sample; nP represents the degrees of freedom.

[0065] It should be noted that the residual sum of squares (R) is used to measure the error between the actual measured values ​​and the model calculated values ​​of elemental content in coal samples. In the least squares method, the goal is to minimize R, so that the difference between the predicted and actual values ​​is as small as possible, thereby improving the accuracy of the model fit; the chi-square test value... Used to verify the reasonableness of the inverse solution results;

[0066] Sum of Squares R and Chi-square value The significance of the comprehensive validation results lies in the fact that R reflects the absolute fitting error of the model, while This reflects the model's relative fitting error and statistical significance. Avoid using R alone and neglecting the influence of degrees of freedom.

[0067] Part of data in the above formula is calculated by removing dimension, and the formula is obtained by software simulation of a large amount of collected data to be closest to the real situation; the preset parameters and the preset threshold in the formula are set by the person skilled in the art according to the actual situation or obtained by a large amount of data simulation.

[0068] The above examples are only used to illustrate the technical method of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical method of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical method of the present application.

Claims

1. A method for multi-element non-destructive analysis of coal quality based on a compact D-D neutron source, characterized in that, The method comprises the following steps: According to the element information in the actual coal quality, prepare samples of each element to obtain samples of each element, marked as elemental samples; wherein, the element information includes element type and element content; Obtain the gamma spectrum and neutron number of the elemental sample, and perform denoising processing on the obtained gamma spectrum to obtain a pure gamma spectrum; based on the gamma spectrum of the elemental sample, construct a single-element spectrum matrix; According to the element information in the actual coal quality, prepare a simulated coal sample, and obtain the pure gamma spectrum of the simulated coal sample, comprising: Obtain the intensity of the gamma spectrum from the gamma spectrum; Calculate the intensity Y0 of the pure gamma spectrum by the formula Y0=Yi-Ybg; wherein, Yi is the intensity of the gamma spectrum; Ybg is the intensity of the background gamma spectrum, which is the gamma spectrum collected without placing any gamma detector; Perform neutron normalization and gamma normalization processing on the pure gamma spectrum, comprising: Calculate the gamma normalization value Y1 by the formula Y1=Y0 / ZS; wherein, ZS is the actually measured neutron number; Calculate the neutron normalization value Z0 by the formula Z0=ZS / ZB; wherein, ZB is the known standardized neutron number; Based on the single-element spectrum matrix and the pure gamma spectrum of the simulated coal sample, analyze the element content of the simulated coal sample, comprising: The content X of each element in the simulated coal sample is calculated by the formula ​ Wherein, w is the weight matrix; A is the single-element spectrum matrix, which 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 line represent the weights of each detection channel of the gamma detector; Compare the element content when the simulated coal sample is prepared with the analyzed element content of the simulated coal sample to determine the test method of the coal quality element information in reality.

2. The coal quality multi-element non-destructive analysis method based on a compact D-D neutron source according to claim 1, characterized in that, The acquisition method of the elemental sample is: Based on the element information in the actual coal quality, configure elemental samples of different types and different qualities of each element.

3. The coal quality multi-element non-destructive analysis method based on a compact D-D neutron source according to claim 2, characterized in that, The method for obtaining the gamma spectrum and neutron number of the elemental sample comprises: Irradiate the elemental sample of each element by a compact D-D neutron source with a fixed high voltage; wherein, the fixed high voltage is within a preset high voltage threshold; and collect the excited gamma rays and reflected neutron rays of the elemental sample by a gamma detector to obtain the gamma spectrum and neutron number.

4. The coal quality multi-element non-destructive analysis method based on a compact D-D neutron source according to claim 1, characterized in that, The test method of the coal quality element information in reality is determined by the following method, comprising: Perform least squares inverse solution on the pure gamma spectrum of the simulated coal sample and the single-element spectrum matrix, and continuously adjust the inverse solution parameters until the error between the inverse solution result and the element content when the simulated coal sample is prepared is less than a preset error value, and then test the element information of the coal quality in reality based on the single-element spectrum matrix and the pure gamma spectrum of the simulated coal sample.

5. The coal quality multi-element non-destructive analysis method based on a compact D-D neutron source according to claim 4, characterized in that, Analyze the error between the inverse solution result and the element content when the simulated coal sample is prepared, comprising: By calculating the residual sum of squares R and the chi-square test value Error analysis is performed on the values, and the calculation formula is as follows: ； ； Wherein, 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; is the count of the i-th channel; is the count of the i-th channel of the single element spectrum of element k; is the content of element k in the simulated coal sample; n-P is the degree of freedom used.

6. The coal quality multi-element non-destructive analysis method based on a compact D-D neutron source according to claim 5, characterized in that, The chi-square test value For checking the rationality of the inverse solution result; determining Whether the value is less than the preset test value; 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; 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 data of the simulated coal quality needs to be checked.

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