阅读说明：本技术 一种基于低场核磁共振快速检测煤炭全水分的方法 (Method for rapidly detecting total moisture of coal based on low-field nuclear magnetic resonance ) 是由 毛玉强 谢广元 夏文成 彭耀丽 沙杰 梁龙 李懿江 郑康豪 于 2019-12-27 设计创作，主要内容包括：一种基于低场核磁共振快速检测煤炭全水分的方法,适用于煤质的全水分的检测。取待测全水分煤炭进行核磁测试条件下进行测试,由核磁测试软件和T<Sub>2</Sub>图谱获得首峰点值,将首峰点值带入核磁信号首峰点值与煤炭全水分之间的关系式中即可获得全水分。其检测速度快,精度高,大大降低了煤炭全水分测试的时间、人力成本,为实现全水分在线检测提供了重要借鉴与指导意义；所用的低场核磁共振设备具有安全、小型化、低成本、易于操作和测试速度快等诸多优点,可以满足选煤厂的各种需求,具有很好的适应性。(A method for rapidly detecting the total moisture of coal based on low-field nuclear magnetic resonance is suitable for detecting the total moisture of the coal. Taking the to-be-tested full-moisture coal to perform testing under the condition of nuclear magnetic testing, and performing testing by using nuclear magnetic testing software and T 2 And obtaining a first peak value by the atlas, and substituting the first peak value into a relational expression between the first peak value of the nuclear magnetic signal and the total moisture of the coal to obtain the total moisture. The method has high detection speed and high precision, greatly reduces the time and labor cost of the coal total moisture test, and provides important reference and guiding significance for realizing the online detection of the total moisture; the low-field nuclear magnetic resonance equipment has the advantages of safety, miniaturization, low cost, easiness in operation, high testing speed and the like, can meet various requirements of a coal preparation plant, and has good adaptability.)

1. A method for rapidly detecting the total moisture of coal based on low-field nuclear magnetic resonance is characterized by comprising the following steps:

a, preparing coal with known different total moisture as a sample, putting the sample into a nuclear magnetic testing measuring cylinder, and generating low-field nuclear magnetism for the nuclear magnetic testing measuring cylinder by using a nuclear magnetic generator, wherein the low-field nuclear magnetism testing is completed according to set parameter conditions and time;

b, in the low-field nuclear magnetic test process, collecting T of coal with different total moisture contents by using a low-field nuclear magnetic nanopore analyzer₂The relaxation map is used for generating initial peak values of hydrogen protons in water in coal with different total moisture contents by means of nuclear magnetic analysis software, comparing the initial peak values of the coal with different total moisture contents with coal total moisture content by means of drawing analysis software Origin 9.0 and confirming that the initial peak values and the coal total moisture content are in positive correlation relation, so that a model is established by means of nuclear magnetic test results, namely the initial peak values and the coal total moisture content;

c, performing second-order linear model fitting by using the initial peak value and a model established by the coal total moisture to obtain a relational expression between the initial peak value of the nuclear magnetic signal and the coal total moisture: y ═ a × x²+ b x + c, wherein: y is the initial peak value in the nuclear magnetic test result, x is the total moisture percentage of coal, a, b and c are coefficients of the fitting model, the coefficients of a, b and c can be directly obtained by fitting and are respectively 17.54, 521.71 and 52.17, and the fitting degree R of the model is²0.9996, which indicates that the first peak value has a good second-order linear relationship with the total moisture of the coal;

d, putting the to-be-tested full-moisture coal into a nuclear magnetic testing measuring cylinder, testing under the nuclear magnetic testing conditions specified by the invention, and testing by using nuclear magnetic testing software and T₂The relaxation map obtains the initial peak value, and the value is substituted into the second-order linear equation established by the invention to obtain the total moisture.

e, selecting any full-moisture coal, crushing, then obtaining the initial peak value of the hydrogen protons in the water in the currently tested coal by utilizing the steps a and b, and substituting the obtained initial peak value into a second-order linear equation model to predict the full-moisture value of the selected coal.

2. The method for rapidly detecting the total moisture of the coal based on the low-field nuclear magnetic resonance according to claim 1, which is characterized in that: the particle size of the used coal is less than 24mm, and if the coal is not crushed as required, the total moisture content of the coal is in the range of 0-50.04%.

3. The method for rapidly detecting the total moisture of the coal based on the low-field nuclear magnetic resonance as claimed in claim 1, wherein the nuclear magnetic parameter conditions of the total moisture test comprise:

the nuclear magnetism type is a permanent magnet, the generation frequency of the nuclear magnetism generator is 12MHz, the magnetic field intensity of the nuclear magnetism generator is 0.3 +/-0.05T, the diameter of a nuclear magnetism probe coil is 25mm, the temperature of the magnet is controlled to be 32 +/-0.1 ℃ in the nuclear magnetism test process, the pulse sequence is CPMG, the echo time is 0.1ms, the sampling frequency is 32, the repeated sampling waiting time is 6000ms, and the echo number is 16000.

4. The method for rapidly detecting the total moisture of the coal based on the low-field nuclear magnetic resonance according to claim 1, which is characterized in that: the test time for the nuclear magnetic test was 4 min.

5. The method for rapidly detecting the total moisture of the coal based on the low-field nuclear magnetic resonance according to claim 1, which is characterized in that: the model of the low-field nuclear magnetic nano-pore analyzer is NMRC12-010V of Nymei technologies, Inc. of Suzhou, and the drawing analysis software is Origin 9.0.

Technical Field

The invention relates to a method for detecting total moisture in coal, in particular to a method for quickly detecting the total moisture in the coal based on low-field nuclear magnetic resonance, which is suitable for detecting the total moisture of the coal with small particle size in the coal industry.

Background

Coal is a fossil energy source and has a very abundant reserve in the world. It has been widely used in steel, chemical industry, thermal power generation and other industries. The total moisture content of coal produced by a coal preparation plant is a very important parameter in determining the subsequent use of the coal product. In the production process of a coal preparation plant, if the total moisture contained in the clean coal is too high, the calorific value of the clean coal is seriously reduced, and the coal product cannot be unloaded. It is likely that these clean coals with too high a moisture content will be returned by customers, which affects not only the reputation and economic efficiency of the coal preparation plant, but also its normal production. Therefore, the total moisture of coal must be detected quickly and accurately before the refined coal is sold.

At present, the oven drying method is usually adopted to detect the total moisture of coal, and the method comprises the following steps: putting coal to be tested in

Drying at c until the weight remains constant, and then the weight loss before and after drying can be calculated to derive its total moisture from the ratio of the weight loss to the weight of the coal without drying. Although the detection method can obtain accurate moisture content, the detection method needs a long time and is difficult to realize on-line detection, which obviously is not beneficial to the realization of the automation link of the coal preparation plant in the future. Therefore, it is very urgent to develop a method for rapidly and accurately detecting the moisture content of coal products.

Nuclear magnetic resonance is a physical process in which nuclei with non-zero magnetic moments undergo zeeman splitting at a spin energy level under the action of an external magnetic field, and resonate to absorb radio-frequency radiation of a certain frequency. Nuclear magnetic resonance spectroscopy is a branch of spectroscopy in which the resonance frequency is in the radio frequency band and the corresponding transition is the transition of the nuclear spins at the nuclear zeeman energy level. Depending on the function and application of nuclear magnetic resonance, it can be classified into nuclear Magnetic Resonance Spectroscopy (MRS), Magnetic Resonance Imaging (MRI), and nuclear magnetic resonance relaxation spectroscopy. Intermolecular interaction (physical information) and relaxation time spectra can be obtained by nuclear magnetic resonance relaxation spectroscopy. The NMR relaxation spectrum is dominated by low field strength (<1T), i.e. low field NMR (LF-NMR). The low-field nuclear magnetic resonance has the advantages of safety, miniaturization, low cost, easy operation and the like.

At present, the number of the current day,¹h and¹³c NMR has been studied extensively, and¹h NMR is also known as Proton Magnetic Resonance (PMR).¹The H nucleus can be converted from a high energy state to a low energy state by non-radiative means, which is called relaxation. Currently, there are two relaxation modes, spin lattice relaxation and spin-spin relaxation. The nuclei of high energy states transfer energy to surrounding molecules by alternating magnetic fields, i.e. the system releases energy into the environment and returns to the low energy state itself, which is called spin lattice relaxation. Spin lattice relaxation reduces the total energy of the magnetic nuclei, also referred to as longitudinal relaxation. The rate is 1/T₁Denotes, T₁Referred to as longitudinal relaxation time. Two nuclei having a certain distance, different precession frequencies and precession directions exchange energy and change the precession direction, which is called spin-spin relaxation. Spin-spin relaxation is also referred to as transverse relaxation because it does not change the total energy of the magnetic nuclei. The rate is 1/T₂Denotes, T₂Referred to as transverse relaxation time. At a lower frequency and a shorter pulse interval, T₂Can provide the function of T₁The same measurement information. But T₂Measured speed ratio T of₁And (4) the method is quick. Thus, the transverse relaxation time T₂Testing is widely used.

Based on¹H LF-NMR is a principle of obtaining coal porosity by detecting hydrogen nuclei in water, a certain relation necessarily exists between a nuclear magnetic test signal and coal moisture, and the exploration of the relation between the nuclear magnetic test signal and the coal moisture is beneficial to obtaining a method for detecting the total moisture of the coal based on low-field nuclear magnetic resonance, so that the H LF-NMR has great significance for realizing the on-line detection of the total moisture of the coal in a coal preparation plant.

Disclosure of Invention

The technical problem is as follows: the invention aims to provide a method for rapidly detecting the total moisture of coal, which aims at overcoming the defects of the prior art and has high detection precision.

The technical scheme is as follows: in order to realize the technical purpose, the method for rapidly detecting the total moisture in the coal based on the low-field nuclear magnetic resonance comprises the following steps:

a, preparing coal with known different total moisture as a sample, putting the sample into a nuclear magnetic testing measuring cylinder, and generating low-field nuclear magnetism for the nuclear magnetic testing measuring cylinder by using a nuclear magnetic generator, wherein the low-field nuclear magnetism testing is completed according to set parameter conditions and time;

b, in the low-field nuclear magnetic test process, collecting T of coal with different total moisture contents by using a low-field nuclear magnetic nanopore analyzer₂The relaxation map is used for generating initial peak values of hydrogen protons in water in coal with different total moisture contents by means of nuclear magnetic analysis software, comparing the initial peak values of the coal with different total moisture contents with coal total moisture content by means of drawing analysis software Origin 9.0 and confirming that the initial peak values and the coal total moisture content are in positive correlation relation, so that a model is established by means of nuclear magnetic test results, namely the initial peak values and the coal total moisture content;

c, performing second-order linear model fitting by using the initial peak value and a model established by the coal total moisture to obtain a relational expression between the initial peak value of the nuclear magnetic signal and the coal total moisture: y ═ a × x²+ b x + c, wherein: y is the initial peak value in the nuclear magnetic test result, x is the total moisture percentage of coal, a, b and c are coefficients of the fitting model, the coefficients of a, b and c can be directly obtained by fitting and are respectively 17.54, 521.71 and 52.17, and the fitting degree R of the model is²0.9996, which indicates that the first peak value has a good second-order linear relationship with the total moisture of the coal;

d, putting the to-be-tested full-moisture coal into a nuclear magnetic testing measuring cylinder, testing under the nuclear magnetic testing conditions specified by the invention, and testing by using nuclear magnetic testing software and T₂The relaxation map obtains the initial peak value, and the value is substituted into the second-order linear equation established by the invention to obtain the total moisture.

e, selecting any full-moisture coal, crushing, then obtaining the initial peak value of the hydrogen protons in the water in the currently tested coal by utilizing the steps a and b, and substituting the obtained initial peak value into a second-order linear equation model to predict the full-moisture value of the selected coal.

The particle size of the used coal is less than 24mm, and if the coal is not crushed as required, the total moisture content of the coal is in the range of 0-50.04%.

The nuclear magnetic parameter conditions of the total moisture test include:

the nuclear magnetism type is a permanent magnet, the generation frequency of the nuclear magnetism generator is 12MHz, the magnetic field intensity of the nuclear magnetism generator is 0.3 +/-0.05T, the diameter of a nuclear magnetism probe coil is 25mm, the temperature of the magnet is controlled to be 32 +/-0.1 ℃ in the nuclear magnetism test process, the pulse sequence is CPMG, the echo time is 0.1ms, the sampling frequency is 32, the repeated sampling waiting time is 6000ms, and the echo number is 16000.

The test time for the nuclear magnetic test was 4 min.

The model of the low-field nuclear magnetic nano-pore analyzer is NMRC12-010V of Nymei technologies, Inc. of Suzhou, and the drawing analysis software is Origin 9.0.

Has the advantages that: due to the adoption of the technical scheme, the method has the advantages that:

1) the model established by the invention can be used for quickly predicting the total moisture of coal, only 4min is needed, meanwhile, the maximum error between the total moisture predicted by the model and the actual moisture is small and is only 0.4%, and the detection precision is high.

2) Compared with the traditional oven method for testing the total moisture of the coal, the method disclosed by the invention is beneficial to obviously improving the efficiency of the coal preparation plant for detecting the moisture of the product coal, greatly reduces the waste of manpower and material resources of the coal preparation plant and reduces the production cost; meanwhile, due to the accuracy of the prediction result, the risk that the client returns the product coal is avoided, the normal production of the coal preparation plant is ensured, and important reference and guidance are provided for realizing the automatic production and detection of the coal preparation plant.

3) Compared with high-field nuclear magnetic resonance, the low-field nuclear magnetic resonance device has the advantages of safety, miniaturization, low cost, easiness in operation, high testing speed and the like, can meet various requirements of a coal preparation plant, and has good adaptability.

Drawings

FIG. 1 shows that the method for rapidly detecting total moisture in coal based on low-field nuclear magnetic resonance of the invention detects T of coal with different actual total moisture₂A relaxation map schematic;

FIG. 2 is a schematic diagram of the initial peak values of coal with different actual total moisture detected by the method for rapidly detecting total moisture in coal based on low-field nuclear magnetic resonance;

FIG. 3 is a schematic diagram of fitting between the initial peak value and the actual total moisture of coal in the method for rapidly detecting the total moisture of coal based on low-field nuclear magnetic resonance.

The specific implementation mode is as follows:

embodiments of the present application are further described below with reference to the accompanying drawings:

the method for rapidly detecting the total moisture of the coal based on the low-field nuclear magnetic resonance comprises the following steps:

a, preparing coal with known different total moisture as a sample, putting the sample into a nuclear magnetic testing measuring cylinder, and generating low-field nuclear magnetism for the nuclear magnetic testing measuring cylinder by using a nuclear magnetic generator, wherein the low-field nuclear magnetism testing is completed according to set parameter conditions and time; the particle size of the used coal is less than 24mm, if the used coal is not crushed as required, the total moisture content of the coal is in the range of 0-50.04%;

b, in the low-field nuclear magnetic test process, collecting T of coal with different total moisture contents by using a low-field nuclear magnetic nanopore analyzer₂The relaxation map is used for generating initial peak values of hydrogen protons in water in coal with different total moisture contents by means of nuclear magnetic analysis software, comparing the initial peak values of the coal with different total moisture contents with coal total moisture content by means of drawing analysis software Origin 9.0 and confirming that the initial peak values and the coal total moisture content are in positive correlation relation, so that a model is established by means of nuclear magnetic test results, namely the initial peak values and the coal total moisture content;

c, performing second-order linear model fitting by using the initial peak value and a model established by the coal total moisture to obtain a relational expression between the initial peak value of the nuclear magnetic signal and the coal total moisture: y ═ a × x²+ b x + c, wherein: y is the initial peak value in the nuclear magnetic test result, x is the total moisture percentage of coal, a, b and c are the coefficients of the fitting model, a, b and c,The c coefficient can be directly obtained by fitting, namely 17.54, 521.71 and 52.17, and the fitting degree R of the model is²0.9996, which indicates that the first peak value has a good second-order linear relationship with the total moisture of the coal;

d, putting the to-be-tested full-moisture coal into a nuclear magnetic testing measuring cylinder, testing under the nuclear magnetic testing condition specified by the invention for 4min, and testing by using nuclear magnetic testing software and T₂The relaxation map obtains the initial peak value, and the value is substituted into the second-order linear equation established by the invention to obtain the total moisture.

e, selecting any full-moisture coal, crushing, then obtaining the initial peak value of the hydrogen protons in the water in the currently tested coal by utilizing the steps a and b, and substituting the obtained initial peak value into a second-order linear equation model to predict the full-moisture value of the selected coal.

The nuclear magnetic parameter conditions of the total moisture test include:

the nuclear magnetism type is a permanent magnet, the generation frequency of the nuclear magnetism generator is 12MHz, the magnetic field intensity of the nuclear magnetism generator is 0.3 +/-0.05T, the diameter of a nuclear magnetism probe coil is 25mm, the temperature of the magnet is controlled to be 32 +/-0.1 ℃ in the nuclear magnetism test process, the pulse sequence is CPMG, the echo time is 0.1ms, the sampling frequency is 32, the repeated sampling waiting time is 6000ms, and the echo number is 16000.

The model of the low-field nuclear magnetic nano-pore analyzer is NMRC12-010V of Nymei technologies, Inc. of Suzhou, and the drawing analysis software is Origin 9.0.