CN112834484B - A method and device for online rapid testing of coal quality components in coal-fired power plants - Google Patents

Abstract

The invention relates to a coal quality measurement technology, and aims to provide a method and a device for on-line rapid testing of coal quality components in a coal-fired power plant. Including: extracting pulverized coal from the pulverized coal pipeline of a coal-fired power plant, using a cyclone separator to separate and capture the pulverized coal particles, and dividing them into two parts after mixing; measuring the moisture of a part of the pulverized coal through industrial analysis based on temperature-programmed weighing and measurement , ash, volatile and fixed carbon content; through elemental analysis based on laser-induced breakdown spectroscopy, measure the C, H, O, N, S element concentrations in another part of the pulverized coal; combine the two measurement results, calculate the coal-fired heat value. The invention can simultaneously realize the measurement of coal-fired moisture, ash, volatile matter, fixed carbon content and C, H, O, N, and S element concentrations, which is beneficial to realize real-time monitoring of coal-fired power plants and adjustment of operating parameters; A more accurate and reliable calculation result of coal-fired calorific value can be obtained, so as to realize continuous online coal-fired calorific value analysis of coal-fired power plants.

Description

A method and device for on-line rapid testing of coal quality components in coal-fired power plants

technical field

The invention relates to the technical field of coal quality measurement, in particular to an online fast measurement of coal quality components in a coal-fired smart power plant.

Background technique

In the coal quality evaluation index of coal-fired power plants, coal moisture, ash content, volatile matter, sulfur content, nitrogen content and calorific value are the key indicators. Among them, moisture will affect the calorific value of coal-fired and coal-fired storage and transportation, volatile matter will affect the stable combustion of the boiler, and ash will not only affect the calorific value of coal-fired coal, but also affect the slagging, contamination, and wear of the boiler. The sulfur content in coal-fired power plants is the main source of sulfur dioxide emissions. Nitrogen content affects the emission of nitrogen oxides in flue gas, both of which will cause environmental pollution. Coal-fired calorific value will affect power generation costs and boiler efficiency.

At present, there are two main methods for measuring the calorific value of coal:

One is to directly use the elemental analysis results of coal to calculate the calorific value, and to estimate the calorific value by measuring the content of elements such as C, H, O, S, etc.; The value is not accurate enough. For example, Chinese invention patent application CN 107389608 A discloses an online application of LIBS laser-induced spectral analysis in coal quality detection, and proposes to use LIBS laser-induced spectral analysis to detect coal quality, and to use partial least squares regression based on main elements (PCA-PLS) analyzes and models the obtained spectral data, and obtains coal sample parameters such as carbon content, hydrogen content, sulfur content, volatile matter, and calorific value of coal through calculation. However, this method can only obtain the elemental composition, while the volatile matter and ash content are fitted by the model, which is not directly measured, and the error is large; in addition, the most important moisture cannot be obtained, and the obtained elemental composition cannot be converted to the standard coal quality analysis requirements. Air-dry basis, as-received basis, dry ash-free basis and other standard values.

The other is to directly use the industrial analysis results of coal to calculate the calorific value. Using the industrial analysis results of coal to calculate the calorific value requires the measurement of moisture, ash and volatile matter in the coal, which takes a long time to measure, and the accuracy of the calculation results is affected by the coal. an impact.

In view of the changes and fluctuations of coal quality evaluation indicators directly affecting the operation efficiency, safety and economic benefits of power plants, real-time online measurement and analysis of coal quality plays a crucial role in coal-fired power plants. The fast and accurate measurement of ash content, volatile matter, sulfur content, nitrogen content, calorific value, etc. is of great significance.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art, and to provide a method and device for online rapid testing of coal quality components in a coal-fired power plant.

For solving the technical problem, the solution of the present invention is:

Provided is a method for online rapid testing of coal quality components in a coal-fired power plant, comprising the following steps:

(1) Extract the pulverized coal from the pulverized coal pipeline of the coal-fired power plant, use the cyclone separator to separate and capture the pulverized coal particles, and divide it into two parts after mixing;

(2) Measure the moisture, ash, volatile matter and fixed carbon content of a part of the pulverized coal through industrial analysis based on temperature-programmed weighing and measurement;

(3) Through elemental analysis based on laser-induced breakdown spectroscopy LIBS, the concentration of C, H, O, N, and S elements in another part of the pulverized coal was measured, and expressed as _{Car, LIBS} , _{Har, LIBS} , O _{ar, LIBS,} respectively , N _{ar, LIBS} , _{Sar, LIBS} ;

(4) Combining the industrial analysis result of step (2) and the elemental analysis result of step (3), calculate and obtain the calorific value of coal combustion.

In the present invention, the step (2) specifically includes:

(2.1) Weigh the pulverized coal with the initial mass m and place it in the furnace heating system, control the temperature in the furnace at 105-110 °C, and dry it in a dry nitrogen stream until the mass is constant; obtain the mass m ₁ of the coal sample, and calculate the moisture content The mass fraction of , moisture _Mar = (mm ₁ )/m*100;

(2.2) Maintain a nitrogen atmosphere, raise the temperature in the furnace to 900±10°C, and heat for 7 minutes; obtain the mass m ₂ of the coal sample, and calculate the mass fraction of volatile matter, volatile matter V _ar =(m ₁ -m ₂ )/m *100;

(2.3) Maintain a nitrogen atmosphere, cool to 815±10°C, switch to an air atmosphere, and burn at a temperature of 815±10°C until the mass is constant; calculate the mass fraction of ash according to the mass m ₃ of the remaining coal sample, ash A _ar = _m3 /m*100;

(2.4) Calculate the mass fraction of fixed carbon from the mass fraction of moisture, ash and volatile matter contained in the pulverized coal of initial mass m: fixed carbon FC _ar =100-( _Mar +A _ar +V _ar ).

In the present invention, the step (3) specifically includes:

(3.1) Press the pulverized coal into a coal cake with a smooth surface with a mechanical hydraulic tablet press, and place it on the rotating platform of the elemental analysis measurement system;

(3.2) After the laser beam emitted by the Nd:YAG solid-state laser is focused by the focusing lens, it hits the surface of the briquette in the rotating state to generate plasma; the light receiver collects the optical signal emitted by the plasma during the cooling and attenuation process, It is transmitted to the spectrometer and detector through the optical fiber, and the processed spectral line information is transmitted to the computer;

(3.3) Use the Matlab software to calculate the peak area integral of the spectral line, and use the spectral correction method of local spectral normalization and plasma temperature compensation to calculate the spectral line intensity of the element to be measured; bring the spectral line intensity of the element to be measured into the calibration curve equation , calculate the concentration of the element to be tested.

In the present invention, in the step (3), in the qualitative and quantitative analysis of C, H, O, N, and S elements in pulverized coal, the internal standard method is used for data processing to weaken the matrix effect, and the selected internal standard elements are: Si, elements C, H, O, N, S, Si adopt characteristic spectral lines as follows:

C: 193.09nm, 247.856nm; H: 656.272nm; O: 747.908nm, 729.631nm, 407.7715nm; N: 460.716nm, 742.364nm; .

In the present invention, in the step (4), the calorific value of coal is calculated by using the Mendeleev calorific value calculation formula:

Calorific value Q _{net, ar} = 339C _ar +1030H _ar -109(O _ar -S _ar )-25M _ar

S_ar＝S_ar，LIBS，N_ar＝N_ar，LIBS，O_ar＝100-M_ar-A_ar-C_ar-H_ar-N_ar-S_ar。Among them, Q _{net, ar} is the received base low calorific value of coal, Car _ar = _{Car ar, LIBS} ,

_Sar = _Sar,LIBS , _Nar = _{Nar ,LIBS} , _Oar =100-Mar- _Aar - _Car - _Har - _Nar - _Sar .

The present invention further provides a device for on-line rapid testing of coal quality components in a coal-fired power plant for realizing the foregoing method, including a pulverized coal collection system, an industrial analysis measurement system, and an elemental analysis measurement system; wherein,

The pulverized coal collection system includes a cyclone separator and a suction pump for collecting pulverized coal particles. The cyclone separator is connected to the pulverized coal pipeline and the suction pump of the coal-fired power plant through pipelines. The pipeline enters the cyclone for gas-solid separation;

The industrial analysis and measurement system includes a furnace heating system, a program temperature control system, an atmosphere control system, a weighing measurement system and a data processing system; the program temperature control system is connected to the electric heating device in the furnace heating system through a cable, and the atmosphere control system The cable is connected to the electronically controlled valve on the nitrogen pipeline and the air pipeline; the weighing and measuring system is connected to the computer through the signal line to transmit the weighing data to the data processing system built in the computer;

The elemental analysis measurement system includes a mechanical hydraulic tablet press, solid-state laser, spectrometer, detector, timing controller, focusing lens and a rotating platform; the mechanical hydraulic tablet press is used to press pulverized coal into a smooth-surfaced briquettes; the solid-state laser emits After the laser passes through the focusing lens, it is aimed at the briquettes to be tested on the rotating platform; the light receiver facing the briquettes to be tested is connected to the spectrometer and the detector through the optical fiber, and the latter is connected to the computer through the signal line; the timing controller uses the signal The wires are respectively connected to the detector and the solid-state laser, and are used to control the working sequence of the detector and the solid-state laser.

Description of the principle of the invention:

According to the provisions of GB 212-2008 "Industrial Analysis Method for Coal", the industrial analysis and measurement system based on temperature-programmed weighing and measurement in the present invention controls the temperature and atmosphere in the furnace body through the program temperature control system and the atmosphere control system, The quality of the pulverized coal is monitored in real time by the weighing and measuring system, and the moisture, ash, volatile matter and fixed carbon of the pulverized coal are measured and calculated by adjusting the temperature and atmosphere in the furnace.

Laser-induced breakdown spectroscopy (LIBS) is a kind of atomic emission spectroscopy used for qualitative and quantitative analysis of elements. The sample preprocessing requirements are not high, and the analysis speed is fast. The present invention is based on the elemental analysis and measurement system of laser-induced breakdown spectroscopy, uses laser to interact with the sample to generate plasma, detects the atomic spectrum information emitted in the process of plasma cooling and decay, and realizes the detection of element types and contents in the sample. The obtained spectrum can be analyzed in combination with the internal standard method to realize the qualitative and quantitative analysis of C, H, O, N, and S elements in the coal briquettes.

Using the industrial analysis based on temperature-programmed weighing and measurement combined with the on-line coal quality measurement method based on elemental analysis based on laser-induced breakdown spectroscopy, both the moisture, ash, volatile, fixed carbon content and C, H, O, The online analysis of element concentrations such as N and S can also quickly calculate and obtain the calorific value of coal combustion, providing basic data for the realization of smart power plants, so as to adjust the operating parameters of the power plant in real time, improve the combustion efficiency of boilers, control pollutant emissions, and improve the economy of the power plant. benefit.

In the traditional measurement technology, the thermogravimetric method has no way to directly obtain the calorific value, and can only use the offline measurement method of the calorific value of the cartridge to measure the change of water temperature after burning with oxygen. The general idea is to use spectroscopic methods, but it is difficult to deduct the interference of H and O elements in moisture and ash. Traditional thermogravimetric methods can only obtain industrial analysis, such as moisture, ash, volatiles and other macroscopic quantities. Different from the prior art, the present invention can realize on-line real-time measurement, combining the advantages of both laser spectroscopy and thermogravimetry. The advantage of this is that the thermogravimetric method with small slow macroscopic changes can be coupled with the rapid detection spectroscopy method, and the changes in coal quality and calorific value can be quickly responded.

Compared with the prior art, the beneficial effects of the present invention are:

1. The present invention can simultaneously realize the measurement of coal-fired moisture, ash, volatile matter, fixed carbon content, and C, H, O, N, and S element concentrations, which is beneficial to the realization of real-time monitoring of coal-fired power plants and adjustment of operating parameters ;

2. The industrial analysis of coal combined with elemental analysis based on laser-induced breakdown spectroscopy for coal quality measurement in coal-fired power plants not only takes advantage of the advantages of on-line rapid measurement of laser-induced breakdown spectroscopy, but also makes coal-fired The calculation results of calorific value are more accurate and reliable, so as to realize continuous online calorific value analysis of coal-fired power plants.

Description of drawings

Fig. 1 is the flow chart of the measurement system method of the present invention;

Fig. 2 is the schematic diagram of the online measurement system of the present invention;

3 is a schematic diagram of an elemental analysis measurement system based on laser-induced breakdown spectroscopy of the present invention;

4 is a schematic diagram of an industrial analysis measurement system based on temperature-programmed weighing and measurement of the present invention;

Reference signs: 1-cyclone; 2-air pump; 3-mechanical hydraulic tablet press; 4-elemental analysis measurement system; 5-industrial analysis measurement system; 6-Nd: YAG solid-state laser; 7-focusing lens; 8-coal; 9-rotating platform; 10-receiver; 11-fiber; 12-spectrometer; 13-sequence controller; 14-detector; 15-computer; 16-programmed temperature control system; 17-atmosphere control system; 18-furnace heating system; 19-weighing measurement system; 20-data processing system.

Detailed ways

First of all, it should be noted that the present invention relates to data processing technology, for example, a data processing system is a software function module built into a computer. The program temperature control system and the atmosphere control system in the present invention can be a control device assembled by using hardware components, or can be a software function module built in a computer to replace hardware control. The applicant believes that, after carefully reading the application documents, accurately understanding the realization principle of the present invention and the purpose of the invention, and in combination with the existing known technology, those skilled in the art can use the software programming skills they master to realize the present invention.

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is the measuring system method flow chart of the present invention, comprises the following steps:

Step 101, extracting pulverized coal from the pulverized coal pipeline of the coal-fired power plant, and using a cyclone separator to separate and collect pulverized coal samples;

Step 102, part of the collected pulverized coal samples are sent to an industrial analysis and measurement system based on temperature-programmed weighing and measurement;

Step 103, a part of the collected pulverized coal samples are sent to the elemental analysis measurement system based on laser-induced breakdown spectroscopy;

Step 104, using an industrial analysis and measurement system based on temperature-programmed weighing and measurement, to measure the moisture, ash, volatile matter, and fixed carbon of the pulverized coal;

Step 105, using the elemental analysis measurement system based on the laser-induced breakdown spectroscopy method, combined with the internal standard method, to qualitatively and quantitatively analyze elements such as C, H, O, N, and S in the briquettes;

Step 106, estimating the calorific value of coal combustion in combination with the calorific value calculation empirical formula.

2 is a schematic diagram of an online measurement system of the present invention, which mainly includes a cyclone separator 1 , an air pump 2 , a mechanical hydraulic tablet press 3 , an elemental analysis measurement system 4 , and an industrial analysis measurement system 5 . The pulverized coal flow extracted from the pulverized coal pipeline of the coal-fired power plant passes through the cyclone separator 1 to capture the pulverized coal, and a part of the collected pulverized coal is pressed into a smooth surface coal cake by the mechanical hydraulic tablet press 3, and then sent to the base The elemental analysis and measurement system 4 of laser-induced breakdown spectroscopy conducts qualitative and quantitative analysis of elements in coal; another part of pulverized coal is sent to the industrial analysis and measurement system 5 based on temperature-programmed weighing and measurement for industrial analysis, and the moisture content of pulverized coal is analyzed. , ash, volatile matter, and fixed carbon were measured.

The elemental analysis and measurement system based on laser-induced breakdown spectroscopy of the present invention mainly includes a mechanical hydraulic tablet press 3 and an elemental analysis and measurement system 4 . Figure 3 is an elemental analysis and measurement system based on laser-induced breakdown spectroscopy, which mainly includes Nd:YAG solid-state laser 6, focusing lens 7, briquettes 8, rotating platform 9, light receiver 10, optical fiber 11, spectrometer 12, timing control device 13, detector 14, computer 15. After the laser beam emitted by the Nd:YAG solid-state laser 6 is focused by the focusing lens 7, it hits the surface of the briquettes 8 placed on the rotating platform 9 to generate plasma, and the optical signal emitted during the process of plasma cooling and attenuation passes through the light receiver The collection of 10 is transmitted to the spectrometer 12 and the detector 14 through the optical fiber 11, and the signal is transmitted to the computer 15 for processing.

In the elemental analysis and measurement system 4 based on laser-induced breakdown spectroscopy adopted in the present invention, the mechanical hydraulic sample preparation pressure is controlled at 20-35MPa to ensure the compactness of the sample; the sample quality is controlled at 2-10g, and the hydraulic tablet press mold is a cylinder shape mold; the energy of the solid-state laser 6 is controlled between 30-100mJ/pulse, which not only ensures high-intensity atomic spectral lines, but also avoids the plasma shielding effect as much as possible; the pulse frequency of the solid-state laser 6 is 1-10Hz, and the output The wavelength is 532nm or 355nm. The 532nm and 355nm lasers have both high photon energy and strong ionization; the laser focus point is located 1-3mm below the surface of the briquettes 8 to improve measurement repeatability; the retardation of the spectrometer 12 The time is controlled at 0.5-2μs after the laser pulse, and a better signal-to-noise ratio can be obtained; the measurement range of the spectrometer 12 is 191-950nm, which can realize the simultaneous detection of elements C, H, O, N, and S; in argon gas or helium atmosphere for measurement, which is beneficial to reduce the fluctuation of spectral signal; the rotation speed of the rotating platform 9 is controlled at 1-5rpm to avoid the laser hitting the same point on the sample surface repeatedly.

In the present invention for qualitative and quantitative analysis of C, H, O, N, and S elements in briquettes, the internal standard method is selected for data processing to weaken the matrix effect, and the selected internal standard element is Si, and the elements C, H, O , N, S, Si used characteristic spectral lines are shown in Table 1.

Table 1

element Characteristic line(nm) C 193.09, 247.856 H 656.272 O 747.908, 729.631, 407.7715 N 460.716nm, 742.364nm S 866.649, 868.046, 903.262, 547.8194 Si 288.1579

The invention utilizes the Matlab software to calculate the spectral line peak area integral, adopts the spectral correction method of local spectral normalization and plasma temperature compensation, and calculates the spectral line intensity of the element to be measured. When quantitatively analyzing C, H, O, N, and S elements, first use a sample with a known concentration of the element to be measured, take the concentration of the element to be measured as the abscissa, and the spectral line intensity ratio of the element to be measured and Si element as the ordinate, The calibration curve equation between the concentration of the element to be measured and the spectral line intensity ratio is established. After the calibration curve equation is obtained, the elemental analysis and measurement system 4 is used to detect the unknown concentration of the sample to be measured, and the spectral line intensity of the element to be measured is brought into the calibration curve equation, so that the concentration of the element to be measured can be calculated. The measured concentrations of C, H, O, N, and S elements are expressed as _{Car, LIBS} , _{Har, LIBS} , O _{ar, LIBS} , N _{ar, LIBS} , _{Sar, LIBS} , respectively.

FIG. 4 is a schematic diagram of an industrial analysis and measurement system based on temperature-programmed weighing and measurement of the present invention, which mainly includes a programmable temperature control system 16 , an atmosphere control system 17 , a furnace heating system 18 , a weighing measurement system 19 , and a data processing system 20 . The pulverized coal is placed in the furnace body heating system 18, the temperature of the furnace body is adjusted by the program temperature control system 16, the atmosphere in the furnace is adjusted by the atmosphere control system 17, and the pulverized coal is heated. For measurement, the data is input into the data processing system 20 built in the computer.

In the industrial analysis and measurement system based on temperature-programmed weighing and measurement adopted in the present invention, the industrial analysis method for coal is as follows: weigh the coal powder of mass m and place it in the furnace heating system 18, and pre-feed dry nitrogen through the atmosphere control system 17 , and use the program temperature control system 16 to control the temperature in the furnace at 105-110 ° C, dry it in a dry nitrogen stream to a constant mass m ₁ , and calculate the mass fraction of moisture according to the mass loss mm ₁ of the coal sample; maintain a nitrogen atmosphere, Raise the temperature in the furnace to 900±10°C, and heat for 7 minutes; obtain the mass m ₂ of the coal sample, and calculate the mass fraction of volatile matter according to the mass loss m ₁ -m ₂ ; maintain a nitrogen atmosphere, cool to 815±10° C., switch to In an air atmosphere, calcined to a constant mass m ₃ at a temperature of 815±10 °C, and the mass fraction of ash was calculated; finally, the mass fraction of fixed carbon was calculated based on the mass balance.

Moisture: _Mar = (mm ₁ )/m*100

Volatile matter: V _ar =(m ₁ -m ₂ )/m*100

Ash content: A _ar =m ₃ /m*100

Fixed carbon: FC _ar = 100-(M _ar +A _ar +V _ar )

where _Mar , A _ar , _Var , and FC _ar are the mass fractions of moisture, ash, volatile matter and fixed carbon in the coal sample, respectively, and m is the corresponding initial mass of pulverized coal. The fixed carbon mass fraction FC _ar is calculated from the mass fraction of moisture, ash and volatile matter.

The empirical formula for calculating the calorific value of coal-fired in the present invention is selected from Mendeleev's calorific value calculation empirical formula, and the elemental analysis and measurement system based on laser-induced breakdown spectroscopy is used to obtain the element concentrations of C, H, O, N, and S, and based on The coal moisture content _Mar obtained by the industrial analysis and measurement system of temperature-programmed weighing and measurement is used as the input value of the formula to calculate the calorific value of coal combustion.

Calorific value Q _{net, ar} = 339C _ar +1030H _ar -109(O _ar -S _ar )-25M _ar

S_ar＝S_ar，LIBS，N_ar＝N_ar，LIBS，O_ar＝100-M_ar-A_ar-C_ar-H_ar-N_ar-S_ar。Among them, Q _{net, ar} is the received base low calorific value of coal, Car _ar = _{Car ar, LIBS} ,

_Sar = _Sar,LIBS , _Nar = _{Nar ,LIBS} , _Oar =100-Mar- _Aar - _Car - _Har - _Nar - _Sar .

The advantage of the invention is that the industrial analysis results of coal and the analysis results of C, H, O, N, S and other elements in the coal are combined at the same time, so that the calorific value of the coal can be obtained quickly, and the repeatability of the measurement of the calorific value of the coal can be improved. and accuracy; through the elemental analysis and measurement system based on laser-induced breakdown spectroscopy and the industrial analysis and measurement system based on temperature-programmed weighing and measurement, the moisture, ash, volatile matter, sulfur, nitrogen content, calorific value, etc. It provides basic data for the realization of smart power plants.

Therefore, the present invention proposes a combination of two methods of coal temperature-programmed industrial analysis and LIBS elemental analysis, using elemental analysis to accurately obtain C, H, O, N, S and other element contents in coal, combined with accurate moisture and ash content obtained by industrial analysis After deducting the influence of moisture and ash, the measurement results of the measured elements can be corrected to obtain accurate data of dry ash-free base, and obtain more accurate calorific value. The industrial analysis results are also consistent with the coal quality analysis required by the national standard.

The above description explains the main principles, basic features and advantages of the present invention, and does not limit the scope of implementation of the present invention. What is described in the above specification is only the principles and features of the present invention. Without departing from the spirit and scope of the present invention, the present invention has many changes and improvements, which are all within the scope of protection.

Claims (2)

1. a method for on-line rapid testing of coal quality components in coal-fired power plants, is characterized in that, comprises the following steps: (1) Extract the pulverized coal from the pulverized coal pipeline of the coal-fired power plant, use the cyclone separator to separate and capture the pulverized coal particles, and divide it into two parts after mixing; (2) Measure the moisture, ash, volatile and fixed carbon content of a part of the pulverized coal through industrial analysis based on temperature-programmed weighing and measurement; specifically: (2.1) Weigh the pulverized coal with the initial mass m and place it in the furnace heating system, control the temperature in the furnace at 105-110 °C, and dry it in a dry nitrogen stream until the mass is constant; obtain the mass m ₁ of the coal sample, and calculate the moisture content The mass fraction of , moisture _Mar = ( m - m ₁ )/ m × 100; (2.2) Maintain a nitrogen atmosphere, raise the temperature in the furnace to 900±10°C, and heat for 7 min; obtain the mass m ₂ of the coal sample, and calculate the mass fraction of volatile matter, volatile matter V _ar =( m ₁ - m ₂ )/ m × 100; (2.3) Maintain nitrogen atmosphere, cool to 815±10°C; switch to air atmosphere, and burn to constant mass at 815±10°C _; calculate the mass fraction of ash according to the remaining coal sample mass m3 , ash A _ar = m ₃ / m × 100; (2.4) Calculate the mass fraction of fixed carbon from the mass fraction of moisture, ash and volatile matter contained in the pulverized coal of initial mass m : fixed carbon FC _ar =100 -( _Mar + A _ar + V _ar ); (3) Through elemental analysis based on laser-induced breakdown spectroscopy, measure the C , H , O, N, and S element concentrations in another part of the pulverized coal, which are expressed as _{Car, LIBS} , _{Har, LIBS} , O _{ar, LIBS} , respectively, N _{ar, LIBS} , Sar _{, LIBS} ; specifically include: (3.1) Press the pulverized coal into a smooth-surfaced coal cake with a mechanical hydraulic tablet press, and place it on the rotating platform of the elemental analysis and measurement system; (3.2) After the laser beam emitted by the Nd:YAG solid-state laser is focused by the focusing lens, it hits the surface of the rotating briquettes to generate plasma; the light receiver collects the optical signal emitted by the plasma during the cooling and decay process, It is transmitted to the spectrometer and detector through the optical fiber, and the processed spectral line information is transmitted to the computer; (3.3) Use the Matlab software to calculate the peak area integral of the spectral line, and use the spectral correction method of local spectral normalization and plasma temperature compensation to calculate the spectral line intensity of the element to be measured; bring the spectral line intensity of the element to be measured into the calibration curve equation , calculate the concentration of the element to be tested; (4) Combined with the industrial analysis results of step (2) and the elemental analysis results of step (3), use the Mendeleev calorific value calculation formula to calculate the calorific value of coal combustion: Calorific value Q _{net, ar} = 339 C _ar +1030 H _ar - 109(O _ar - S _ar ) - 25 M _ar Among them, Q _{net, ar is} the low calorific value of coal received base, Car = Car _{, LIBS} , Har = _{Har , LIBS - Mar} ﹒ 2/(2+16), S _ar = S _{ar ,LIBS} , N _ar = N _{ar ,LIBS} , O _ar = 100 - _Mar - A _ar - Car - Har - N _ar - _Sar . 2 . The method according to claim 1 , wherein in the step (3), when qualitative and quantitative analysis of C, H, O, N, and S elements in pulverized coal is performed, data processing is performed by an internal standard method. 3 . In order to weaken the matrix effect, the selected internal standard element is Si, and the characteristic spectral lines of the elements C, H, O, N, S, and Si are as follows: C: 193.09 nm, 247.856 nm; H: 656.272 nm; O: 747.908 nm, 729.631 nm, 407.7715 nm; N: 460.716 nm, 742.364 nm; S: 866.649 nm, 868.046 nm, 903.262 nm, 547.8194 nm; .

Images