Enrichment detection method for low-concentration VOCs (Volatile Organic Compounds) in thermal reaction of solid fuel

Abstract

The invention discloses a method for on-line detection of a solid fuel thermal reaction gas product. The method comprises the following steps: S1, a trace feeder continuously and stably provides dry and loose solid fuel particles into a high-temperature reaction furnace at a rate of 0.5 g / min to 2g / min; s2, mixed gas of nitrogen and oxygen is introduced into the high-temperature reaction furnace through a gas inlet to serve as carrier gas, and solid fuel is combusted; s3, gas generated by combustion in S2 is filtered and introduced into a gas detection unit, gas entering a flue gas analyzer is subjected to synchronous measurement and in-situ sampling detection in the combustion process, waste gas is monitored in real time, and the waste gas comprises one or more of NOx, CO, CO2 and SO2 pollutants; by continuously and stably supplying the coal micro powder, synchronous measurement and in-situ sampling of pollutants such as VOCs, NOx, CO and SO2 in a wide temperature range are realized.

Description

[0001] This application is a divisional application of a patent application with the application date of July 24, 2025, the application number of 2025110278990, and the invention name of a method for online detection of solid fuel thermal reaction gas products. TECHNICAL FIELD

[0002] The present application relates to the technical field of gas detection, in particular to a method for enrichment and detection of low-concentration VOCs in solid fuel thermal reaction. BACKGROUND

[0003] In recent years, China has vigorously promoted the concept of low-carbon and environmentally friendly operation in the industry. Coal is one of the world's main energy sources and an important energy source for power plants in China. Due to its large molecular network structure and complex composition, coal will produce a series of pollution gases such as CO2, VOCs and NO X emissions of these pollutants do not meet the national emission standards, which will seriously pollute the atmospheric environment in China and threaten human health and life. VOCs and NO X are important atmospheric pollutants for monitoring and management in China, and are also important intermediates and products of fuel combustion / pyrolysis. Accurate measurement of VOCs and NO X in a wide temperature range is an important basis for pollution control and improvement of combustion / pyrolysis technology. Current fine measurement of VOCs is common in precise drug delivery in the medical field, environmental monitoring and indoor air quality detection, etc. The measurement is mainly for substances such as acetone, n-pentane, isopentane, benzene, toluene, furan, propylene aldehyde, etc. There is a lack of detection means for C2-C12 multi-type VOCs emitted by fuel combustion, and it cannot meet the measurement requirements of wide temperature range. Chromatography and mass spectrometry are common methods for VOCs measurement, and the time resolution of accurate measurement is generally more than 30 minutes. The accuracy of online measurement and metrology process is poor due to limitations such as technical devices and standard gases. The accurate measurement and metrology of VOCs and NO

[0004] To meet the detection requirements of new environmental protection and deep energy-saving technology development in the field of typical solid combustion equipment, improve the detection accuracy of key pollutants of energy efficiency emissions, this patent focuses on the design of high-accuracy online measurement technology for VOCs and NO X in a wide temperature range, and high-accuracy measurement technology for NO Summary of the Invention

[0005] The purpose of this invention is to provide a method for online detection of gaseous products from the thermal reaction of solid fuels. This invention achieves high-accuracy online measurement by continuously and stably supplying coal powder, enabling simultaneous measurement and in-situ sampling of pollutants such as VOCs, NOx, CO, and SO2 over a wide temperature range, as well as a coordinated method for simultaneous control of carrier gas concentration and flow rate.

[0006] To solve this technical problem, the technical solution of the present invention is: a method for online detection of gaseous products from the thermal reaction of solid fuels, comprising the following steps: S1. A micro feeder for drying solid fuel using microwave heating is installed above the high-temperature reactor. The micro feeder continuously and stably supplies dry and loose solid fuel particles into the high-temperature reactor at a rate Q of 0.5 g / min to 2 g / min. S2. A mixture of nitrogen and oxygen is introduced into the high-temperature reactor through the air inlet as a carrier gas. The high-temperature reactor is heated by a silicon molybdenum rod, and the solid fuel is burned in the high-temperature furnace. S3. The gas produced by the combustion of S2 is introduced into the gas detection unit. During the combustion process, the gas entering the flue gas analyzer is simultaneously measured and sampled in situ for real-time monitoring of the exhaust gas. The exhaust gas includes NO. x One or more of the pollutants: CO, CO2, and SO2.

[0007] The preferred method for continuous feeding using a micro-feeder at a rate of 0.5 g / min to 2 g / min includes the following steps: S11. Micron-sized solid fuel particles are placed in a storage bin. A stirring rod and a screw feeder are arranged from top to bottom in the storage bin. The screw feeder is located in a vertically arranged pipe connected to the lower end of the storage bin. The pipe corresponds to the center position of a rotating horizontal disc. The stirring rod and screw feeder, driven by a drive motor, keep turning and output the coal powder in the storage bin. Meanwhile, the storage silo is also equipped with a microwave heating unit to heat and dry the coal powder inside the storage silo; Water molecules in pulverized coal particles form steam under microwave heating and detach from the micron-sized solid fuel particles. As the micron-sized solid fuel particles are continuously tumbled, the water vapor moves upward and detaches from the storage bin. S12. The micron-sized solid fuel particles located at the center of the disk are evenly dispersed into a thin layer from the center of the disk towards the circumference under the action of centrifugal force as the disk rotates, and then scraped into the feed port of the high-temperature reactor by a scraper. The scraper feeds the micron-sized solid fuel particles from the disk into the feed inlet at a rate of Q. ; in, For effective feeding area; R is the radius of the disc; p is the bulk density of the material; k is the average bulk thickness of the material; L is the actual length of the scraper; n is the rotation speed of the disc; is the effective action width of the scraper; .

[0008] The present application overcomes the mutual adhesion and aggregation of fuel particles into larger lumps due to the electrostatic force and Van der Waals force between the particles by increasing the gap between the particles, reduces the agglomeration of the fuel, and effectively ensures the stability of continuous feeding by the relative fixed position and the fixed area swept between the scraper and the disc through the control of the dryness of the fuel particles and the dispersion of the material by stirring and centrifugal force during the transfer process.

[0009] Preferably, the radius R of the disc is 30 mm, the rotation speed n of the disc is 10 rpm to 180 rpm, and the rotation speed V of the stirring rod and the spiral discharging element in S11 is 0.36 rpm≤V≤5.6 rpm. The present application stabilizes the fuel thickness by the cooperation of the stirring rod and the spiral discharging element with the rotation of the disc, and ensures the stability of feeding.

[0010] Preferably, the micron particle solid fuel in the storage bin in step S11 is heated by microwaves to maintain the temperature in the storage bin at 95℃ to 105℃; and a cover plate is provided on the top of the storage bin; The upper part of the storage bin is further provided with a gas outlet hole for water vapor discharge; The included angle between the scraper and the disc is θ, wherein 30°≤θ≤60°.

[0011] Preferably, the storage bin is made of polypropylene. The material of the discharge bin of the present application is suitable for microwave heating.

[0012] Preferably, when the real-time concentration of the exhaust gas in the flue gas analyzer is stable, the gas chromatography front valve is opened and the gas chromatography sampling six-way valve sampling program is started; The HP-5MS column with a specification of 30mm×25mm×25mm is used in the gas chromatography, the outlet of the chromatographic column is connected with the MSD mass spectrometer detector, the column oven temperature in the gas chromatography is set to 35℃, and lasts for 5 mins, then heated to 180℃ at a rate of 5℃ / min; Maintained at 180℃ for 5 mins; Heated to 250℃ at a rate of 10℃ / min to end; The obtained mass spectrum is searched by INST Pu Ku to determine the generated gas components.

[0013] The present application realizes the determination of the gas components of the solid fuel thermal reaction gas product through the above steps.

[0014] Preferably, for the case that the VOCs concentration is low after the solid fuel combustion, the method for detecting VOCs is as follows: S21, using a temperature controller to control the temperature in the furnace to 500℃ at a heating rate of 5℃ / min, and after the temperature is stable for three minutes, first pass the carrier gas, then open the second valve, the third valve and the fifth valve, close the first valve and the fourth valve, and the gas enters the flue gas analyzer after passing through the adsorption tube, and after stable combustion for 20min, close the feeding, and record the usage of the biomass fuel; S22, close the second valve, the first valve and the fifth valve, open the third valve and the fourth valve, the surface of the adsorption tube is provided with a heating belt to heat the adsorption tube for desorption, after heating, nitrogen is introduced for purging until the infrared spectrum appears stable absorption peak, then open the gas chromatography front valve and start the gas chromatography sampling six-way valve sampling program, and perform gas chromatography detection.

[0015] Preferably, the high-temperature reaction furnace is provided with a cooling system, the cooling system comprises a cooling water pump, a cooling water tank and a cooling water pipeline, cooling water in the cooling water tank is introduced into both ends of the high-temperature reaction furnace through the cooling water supply pipe by the cooling water pump, the cooling water absorbs the heat of both ends of the high-temperature reaction furnace, and then returns to the cooling water tank through the cooling water return circuit to complete the cooling cycle, so that the temperature of both ends of the high-temperature reaction furnace does not exceed 100℃.

[0016] Preferably, the carrier gas in S2 comprises 79% of nitrogen and 21% of oxygen.

[0017] By adopting the above technical scheme, the present application has the following beneficial effects: The present application uses the micro-feeding machine to continuously and stably provide dry and loose solid fuel particles into the high-temperature reaction furnace at a rate Q of 0.5g / min to 2g / min, then controls the carrier gas to ensure stable combustion in the high-temperature furnace, and then filters the gas generated by S2 combustion and introduced into the gas detection unit, and synchronously measures and in-situ samples the gas entering the flue gas analyzer to monitor the exhaust gas in real time during the combustion process, so that the present application can realize in-situ sampling and synchronous measurement of VOCs and NO x , CO, SO2 and other pollutants in a wide temperature range of 273K-1700K; the present application further stably and accurately measures the low-concentration VOCs in the flue gas by controlling the micro-continuous feeding rate of the solid fuel, the concentration and flow of the carrier gas, and the high-accuracy online measurement. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The present application is an apparatus for implementing the method for online monitoring of the solid fuel thermal reaction gas product; Figure 2is a continuous micro-dosing schematic diagram of the micro-dosing machine in the present application; Figure 3 is a perspective view of the micro-dosing machine in the present application; Figure 4 is a feeding stability curve of the micro-dosing machine in the present application; Figure 5 is the online monitoring of the reaction gas concentration by using a flue gas analyzer in Example 4 of the present application; Figure 6 is the gas chromatogram of the solid fuel thermal reaction gas product in Example 5 of the present application; Figure 7 is determined according to Figure 6 the obtained mass spectrum by INST Pu Ku retrieval; Figure 8 is the online monitoring of the reaction gas concentration by using a flue gas analyzer in the comparative example; Reference signs: storage bin 1; pipeline 2; driving motor 3; disc 4; magnetic suspension motor 5; stirring rod 6; spiral feeding part 7; scraper 8; discharge port 9; microwave heating unit 10; exhaust hole 11; cover plate 12. DETAILED DESCRIPTION

[0019] In order to further explain the technical solutions of the present application, the present application will be described in detail below through specific examples.

[0020] Example 1

[0021] The present embodiment discloses a continuous micro-fuel supply method applied to a laboratory reactor, and a device for specifically implementing the method as shown in Figure 1 and Figure 2 includes the following steps: S1, micron particle solid fuel is placed in the storage bin 1, and the stirring rod 6 and the spiral feeding part 7 are sequentially arranged in the storage bin 1 from top to bottom, wherein the spiral feeding part 7 is located in the pipeline 2 communicated with the lower end of the storage bin 1, and the pipeline 2 corresponds to the center position of the rotating disc 4; the stirring rod 6 and the spiral feeding part 7 driven by the driving motor 3 keep turning and output the coal powder in the storage bin 1; At the same time, the storage bin 1 is also provided with a microwave heating unit 10 for heating and drying the coal powder in the storage bin 1; The water molecules in the coal powder particles form steam under the action of microwave heating and are separated from the micron particle solid fuel particles, and with the continuous turning of the micron particle solid fuel, the water vapor moves upward after being separated from the coal powder and is separated from the storage bin; S2, the micron particle solid fuel pile at the center position of the disc 4 is uniformly dispersed into a thin layer in the circumferential direction under the action of centrifugal force with the rotation of the disc 4, and then scraped into the inlet of the laboratory reactor by the scraper 8.

[0022] The rate of the microparticle solid fuel on the disc being sent into the feeding port by the scraper in the embodiment is Q, ; wherein, is the effective feeding area; R is the radius of the disc, in mm; ρ is the bulk density of the material, g / cm 3 ; k is the average bulk thickness of the material in the range of the scraper, mm; L is the actual length of the scraper, mm; n is the rotating speed of the disc, rpm; is the effective action width of the scraper; .

[0023] The feeding amount Q of the present application is introduced as a correction factor, quantifying the influence of the centrifugal force on the material layer; the above process parameters are specifically shown in Table 1.

[0024] The length of the scraper and the inclination angle relative to the rotating disc of the present application are matched with the bulk density and thickness of the material, so as to effectively and accurately control Q, and obtain accurate and continuous micro fuel supply.

[0025] The rate Q of the microparticle solid fuel being sent into the feeding port in the embodiment is shown in Table 1. The present application ensures the stability of the material during the feeding process by synchronously controlling the particle size of the solid fuel particles and the real-time drying degree, so as to stabilize the feeding under the joint action of the disc and the scraper.

[0026] The radius R of the disc in the embodiment is 60 mm, the rotating speed n of the disc is shown in Table 1, and the rotating speed V of the stirring rod and the spiral feeding part in S1 is shown in Table 1. The rotating speed of the spiral feeding part of the present application is mainly to match the rotating speed of the disc and control the stability of Q.

[0027] The microparticle solid fuel in the storage bin in S1 in the embodiment is heated by microwaves to maintain the temperature in the storage bin at 100℃, and the moisture content of the microparticle solid fuel is less than 0.5%. The present application stabilizes the quality drying temperature to ensure effective evaporation of water, and under the premise of uniform particle size of the fuel particles, the viscosity is also effectively controlled, so as to adapt to the dispersion of the disc and the cooperation of the scraper and the disc, and realize continuous supply of micro fuel.

[0028] The top of the storage bin in the embodiment is covered with a cover plate; and the upper part of the storage bin is further provided with a gas outlet hole for water vapor discharge.

[0029] The inner diameter of the pipeline in the embodiment is 1 cm.

[0030] The storage bin is made of polypropylene. The storage bin made of polypropylene is suitable for microwave heating in the present application.

[0031] The whole fixing device is fixed on the pipe furnace or the required feeding port by screws, the feeding port and the storage bin are placed on the fixing device, and the feeding port and the storage bin are fixed on the fixing device by the fixing support. The driving motor is fixed above the storage bin by the L-shaped fixing support, the screw feeder is inserted into the feeding port pipeline, and the height is adjusted to a suitable height.

[0032] In the working process, first, the pulverized coal is added into the storage bin 1, the power is turned on, the driving motor 3 of the screw rod 2 and the magnetic suspension motor 5 for driving the disc 4 to rotate can be controlled respectively, the storage bin 1 is made of high-transmission polypropylene and can transmit microwaves, the fuel particles in the storage bin 1 can be heated by microwaves before formal feeding, the moisture in the sample in the storage bin 1 is removed, the temperature sensor is arranged in the storage bin 1, the temperature change in the bin is fed back in real time, the temperature in the bin is fed back to the microwave heating unit 10, the microwave heating unit 10 adjusts the heating power in real time through the temperature signal of the thermocouple, so that the fuel in the storage bin 1 can be dried at about 100 DEG C, the exhaust hole 11 is arranged in the storage bin 1, and the water vapor during drying flows out through the exhaust hole 11. When formal feeding, the driving motor 3 and the magnetic suspension motor 5 of the stirring rod 6 and the screw feeder 7 are controlled by stepless speed regulation respectively, so that the disc 4 and the screw feeder 7 rotate at a certain rate, the upper half of the screw feeder is provided with the stirring rod 6, and the pulverized coal in the storage bin 1 is stirred. The end of the stirring rod 6 is provided with a thermocouple, the temperature of the material in the bin is monitored in real time, and the pulverized coal in the hopper is continuously stirred in the process of rotation and drying, so that the pulverized coal is prevented from caking or sticking. The screw feeder 7 rotates to continuously transport and guide the pulverized coal downward, and the pulverized coal is transported to the center of the disc 4 through the pipeline 2. The disc is driven to rotate by the magnetic suspension motor, the electromagnetic force is adjusted in real time by using active magnetic suspension control, the speed change of the rotor is accurately controlled, the accurate control of the speed of the rotor can accurately control the feeding speed of the feeder, the rotor is suspended by the electromagnetic force, the friction loss of the mechanical bearing can be completely eliminated, and the long-time work is suitable. The rotation of the disc makes the coal powder falling into the center of the disc by the screw feeder subjected to the action of centrifugal force, the coal powder in the center of the disc moves to the edge continuously, and finally the coal powder is scraped into the feeding port 9 by the scraper 8 at the edge, the feeding is continuous and stable, and it is ensured that the pulverized coal can be evenly dropped into the experimental reactor.

[0033] Example 2

[0034] The main difference between the present example and example 1 is shown in table 1 and table 2.

[0035] Example 3

[0036] The main difference between the present example and example 1 is shown in table 1 and table 2.

[0037] Table 1. Parameters of the solid fuel particles for feeding in Examples 1-3 and Comparative Examples

[0038] Table 2. Parameters of the disc and the scraper and the feeding rate for Examples 1-3 and Comparative Examples

[0039] The present application effectively controls the flowability of the fuel powder particles by drying, and further stabilizes the thickness of the fuel supply by cooperating with the centrifugal action of the fuel powder on the surface of the rotating disc. The most common flow deterioration phenomenon is the adhesion of the fuel particles, which causes unstable feeding, and even pipe blockage when the particle agglomeration is serious. The flow factors of the powder feeding device are very complex, and currently mainly focus on the physical properties of the powder itself, i.e., it is believed that the flow of coal powder is caused by many factors such as coal powder particle size, shape, surface structure, moisture content, etc. Generally, the adhesion and agglomeration phenomenon becomes more and more serious with the gradual decrease of the coal powder particle size. The feeding rate of the present application is designed to be 0.5 g / min-2 g / min, in order to avoid agglomeration in the hopper to form caking and other phenomena, the mechanical dispersion principle is used in the hopper by using spiral stirring and microwave drying technology, to ensure that the sample in the hopper is in a real-time drying state. The coal powder accumulated at the bottom of the storage hopper is continuously turned over and uniformly fed into the feeding chute for feeding. Since the feeding amount is low, in order to reduce the feeding fluctuation caused by the uneven distribution of the coal powder, the actual pipeline channel is very narrow, about 1 cm, and the feeding opening is located near the center of the disc, and the hopper is a leaky type with a volume of 4 liters. This feeding form has small adhesion effect between the contact surfaces of the coal powder, which improves the continuity of the feeding. The coal powder is continuously fed by the present application and flows out from the discharge port, and then is carried into the furnace by the gas.

[0040] Example 4

[0041] The present embodiment discloses a method for on-line detecting the thermal reaction gas product of solid fuel, which comprises the following steps: S1, a micro-feeding machine for drying the solid fuel by using microwave heating is arranged above the high-temperature reaction furnace, and the micro-feeding machine is adjusted according to the method of Example 1 to continuously and stably provide dry and loose solid fuel particles into the high-temperature reaction furnace at a rate of 1 g / min; S2, the temperature controller is used to control the temperature in the furnace to rise at a rate of 5 ℃ / min, and the temperature is raised to 600 ℃, and after the temperature is stable for three minutes, the carrier gas is first passed, and the carrier gas in S2 includes 79% of nitrogen and 21% of oxygen.

[0042] S3, open the second valve, the first valve and the fifth valve of the gas outlet, close the third valve and the fourth valve, the gas path does not pass through the adsorption tube and the infrared spectrum and the gas chromatograph directly to the gas analyzer. Start the feeder, the coal powder falls into the reaction furnace for combustion, the ash after combustion falls into the bottom, the flue gas after filtration enters the flue gas analyzer for detection, the waste gas concentration is shown in Figure 5 .

[0043] Example 5

[0044] The embodiment discloses a method for online detection of solid fuel thermal reaction gas products, comprising the following steps: S1, a micro feeder for drying solid fuel using microwave heating is arranged above the high-temperature reaction furnace, and the micro feeder is adjusted at a rate of 1 g / min to continuously and stably provide dry and loose solid fuel particles into the high-temperature reaction furnace according to the method of example 1; S2, a mixture gas of 79% nitrogen and 21% oxygen is used as a carrier gas. The temperature controller is used to control the temperature in the furnace at a heating rate of 5 ℃ / min, and the temperature is heated to 600 ℃, and after the temperature is stable for three minutes, the carrier gas is first passed; S3, then open the second valve, the first valve, the fourth valve and the fifth valve, close the third valve and the valve before the gas chromatograph sampling port, when the gas concentration in the gas analyzer is relatively stable, open the gas chromatograph front valve and start the gas chromatograph sampling six-way valve sampling program. The column used in the gas chromatograph is HP-5MS (30 mm x 25 mm x 25 mm), the outlet of the chromatographic column is connected with the MSD mass spectrometer detector, the column oven temperature in the gas chromatograph is set to 35 ℃, and the temperature is maintained for 5 mins, then heated to 180 ℃ at a rate of 5 ℃ / min, maintained at 180 ℃ for 5 min, then heated to 250 ℃ at a rate of 10 ℃ / min. The obtained mass spectrum is searched through INST Pu Ku, and the generated gas components are determined, as shown in Figure 6 and Figure 7 .

[0045] Example 6

[0046] The embodiment discloses a method for online detection of solid fuel thermal reaction gas products, comprising the following steps: S1, a micro feeder for drying solid fuel using microwave heating is arranged above the high-temperature reaction furnace, and the micro feeder is adjusted at a rate of 1 g / min to continuously and stably provide dry and loose solid fuel particles into the high-temperature reaction furnace according to the method of example 1; S2, a mixture gas of 79% nitrogen and 21% oxygen is used as a carrier gas. The temperature controller is used to control the temperature in the furnace at a heating rate of 5 ℃ / min, and the temperature is heated to 600 ℃, and after the temperature is stable for three minutes, the carrier gas is first passed; S3, then open the second valve, the third valve, the fifth valve, close the first valve and the fourth valve, the gas enters the flue gas analyzer after passing through the adsorption tube, and the combustion is stable for twenty minutes, then close the feeding, and record the usage of the biomass fuel. Then close the second valve, the first valve and the fifth valve, open the third valve and the fourth valve, the adsorption tube surface is provided with a heating belt to heat the adsorption tube for desorption, after heating, nitrogen is introduced for purging until the infrared spectrum appears stable absorption peak, then open the gas chromatography front valve and start the gas chromatography sampling six-way valve sampling program, and then carry out gas detection.

[0047] The embodiment aims at the VOCs concentration after solid fuel combustion, which is low, the peak value in the gas chromatography is small, and it is difficult to qualitatively and quantitatively determine, so the adsorption tube is needed to enrich, and then desorption is introduced into the chromatography and infrared spectrum.

[0048] Comparative example

[0049] The comparative example discloses a method for on-line detecting solid fuel thermal reaction gas product, comprising the following steps: The main difference between the comparative example and example 4 is that the trace feeder is not provided with microwave drying. According to the process parameters of example 4, the on-line flue gas analyzer is used for detection, and the waste gas concentration is shown in the following table. Figure 8

[0050] Comparing the comparative example with example 4, it can be known that the solid fuel without microwave drying in the comparative example is difficult to realize stable feeding even through centrifugal dispersion, the carrier gas is controlled to ensure stable combustion in the high-temperature furnace, and then the gas produced by combustion is filtered S2 and introduced into the gas detection unit, the pollutants such as VOCs and NO x , CO, SO2 and the like in the gas entering the flue gas analyzer are measured synchronously and sampled in situ during the combustion process, the present application can realize synchronous measurement and in-situ sampling of VOCs and NO x , CO, SO2 and the like in a wide temperature range of 273K-1700K, and synchronous control and cooperation of carrier gas concentration and flow, and high-accuracy on-line measurement.​

Claims

1. A method for enriching and detecting low concentrations of VOCs in the thermal reaction of solid fuels, characterized in that: Includes the following steps: S1. Preheating and Combustion Steps The high-temperature reactor is heated to the target temperature and a carrier gas is introduced. At the same time, dry and loose solid fuel particles are supplied into the furnace at a constant rate so that they are burned to produce flue gas containing VOCs. S2, adsorption and enrichment The flue gas generated in step S1 is guided through the adsorption tube so that the VOCs in the flue gas are adsorbed and enriched, while the remaining waste gas is passed into the flue gas analyzer for routine pollutant monitoring. S3, Desorption and Sample Injection After the predetermined time for adsorption and enrichment is completed, the supply of solid fuel is stopped; then the adsorption tube is heated for desorption, and purge gas is introduced to transport the desorbed high-concentration VOCs components to a gas chromatograph for detection and analysis.

2. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 1, characterized in that: In step S1, a mixture of nitrogen and oxygen is introduced into the high-temperature reactor through the air inlet as a carrier gas, which consists of 79% nitrogen and 21% oxygen.

3. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 1, characterized in that: In step S3, a heating band is provided on the surface of the adsorption tube to heat the adsorption tube for desorption. After heating, nitrogen gas is introduced to purge to the infrared spectrum. When a stable absorption peak appears in the infrared spectrum, the gas chromatograph pre-valve is opened and the gas chromatograph injection six-way valve injection program is started for gas detection.

4. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 1, characterized in that: The duration of the adsorption and enrichment step in step S2 is 10 to 30 minutes.

5. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 1, characterized in that: Above the high-temperature reactor is a micro-feeder that uses microwave heating to dry solid fuel. The micro-feeder continuously and stably supplies dry and loose solid fuel particles into the high-temperature reactor at a rate Q of 0.5 g / min to 2 g / min.

6. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 5, characterized in that: The method for continuous feeding with a micro-feeder at a rate of 0.5 g / min to 2 g / min includes the following steps: S11. Micron-sized solid fuel particles are placed in a storage bin. A stirring rod and a screw feeder are arranged from top to bottom in the storage bin. The screw feeder is located in a vertically arranged pipe connected to the lower end of the storage bin. The pipe corresponds to the center position of a rotating horizontal disc. The stirring rod and screw feeder, driven by a drive motor, keep turning and output the coal powder in the storage bin. Meanwhile, the storage silo is also equipped with a microwave heating unit to heat and dry the coal powder inside the storage silo; Water molecules in pulverized coal particles form steam under microwave heating and detach from the micron-sized solid fuel particles. As the micron-sized solid fuel particles are continuously tumbled, the water vapor moves upward and detaches from the storage bin. S12. The micron-sized solid fuel particles located at the center of the disk are evenly dispersed into a thin layer from the center of the disk towards the circumference under the action of centrifugal force as the disk rotates, and then scraped into the feed port of the high-temperature reactor by a scraper. The scraper feeds the micron-sized solid fuel particles from the disk into the feed inlet at a rate of Q. ； in, For effective feeding area; R is the radius of the disk; ρ is the bulk density of the material; k is the average thickness of the material buildup; L is the actual length of the scraper; n is the rotational speed of the disk; This refers to the effective working width of the scraper; 。 7. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 6, characterized in that: The radius R of the disc is 30mm, the disc rotation speed n is 10rpm to 180rpm, and the rotation speed V of the stirring rod and the spiral feeder in S11 is 0.36rpm≤V≤5.6rpm.

8. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 6, characterized in that: In step S11, the micron-sized solid fuel particles in the storage bin are heated by microwave to maintain the temperature inside the storage bin at 95°C to 105°C; the top of the storage bin is covered with a cover plate. The upper part of the storage silo is also provided with a vent for water vapor to be discharged; The angle between the scraper and the disc is θ, where 30°≤θ≤60°.

9. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 1, characterized in that: The method for controlling the adsorption and enrichment in step S2 is as follows: The temperature controller is used to control the temperature rise inside the furnace. After the temperature stabilizes, the carrier gas is introduced first, followed by opening the second, third, and fifth valves, and closing the first and fourth valves. The gas passes through the adsorption tube and then enters the flue gas analyzer. After stable combustion, the feed is turned off, and the amount of biomass fuel used is recorded.

10. The method for enrichment and detection of low concentration VOCs in the thermal reaction of solid fuels according to claim 1, characterized in that: The control method for desorption and sample injection in step S3 is as follows: Close the second, first, and fifth valves, and open the third and fourth valves. The adsorption tube surface is equipped with a heating band to heat the adsorption tube for desorption. After heating, nitrogen gas is introduced to purge to the infrared spectrum. When a stable absorption peak appears in the infrared spectrum, open the gas chromatography pre-valve and start the gas chromatography injection six-way valve injection program to perform gas chromatography detection.

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