Sampling detection method and system for tubular furnace

Abstract

The invention relates to the technical field of analytical chemistry and process monitoring, in particular to a sampling detection method and system for a tubular furnace, and the method comprises the following steps: synchronously collecting reaction environment parameters and pre-calculating sampling conditions; positioning a multi-channel sampling probe and preheating the whole line; carrying out in-situ extraction and primary pressure reduction on high-pressure sample gas; a second-stage pressure reduction and rapid introduction step of the sample gas: introducing the sample gas with stable pressure after the first-stage pressure reduction into a constant-temperature capillary type flow resistance pressure reducer for secondary expansion pressure reduction, so that the pressure of the sample gas is reduced to a working pressure range of a target analysis instrument; then the decompressed sample gas is rapidly guided into the target analysis instrument through a short transmission line which is subjected to inerting treatment and heat tracing; and performing analysis and channel switching. Through whole-course temperature control and precise pressure reduction, the stability of sampled gas is ensured, and component change is avoided. Real-time sampling can be carried out at multiple positions in the tubular furnace, spatial distribution of gas components is reflected, and spatial information loss is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry and process monitoring, and in particular to a sampling and detection method and system for a tube furnace. Background Art

[0002] Tubular furnaces are a common high-temperature reaction device, widely used in research and industrial processes such as catalysis, materials synthesis, and pyrolysis. Analyzing the composition and concentration of gaseous products within the reaction tubes of tubular furnaces is crucial for understanding reaction mechanisms and optimizing process parameters.

[0003] The existing sampling method usually connects a sampling line to the outlet of the reaction tube to guide the gas to an external analytical instrument (such as a gas chromatograph or mass spectrometer). This method has several inherent drawbacks: Distortion of representativeness: For high-temperature and high-pressure reactions, especially those involving easily condensable components or reactive intermediates, the long transportation process between the gas leaving the reaction zone and entering the analyzer can cause component condensation, thermal decomposition, or secondary reactions due to a drop in temperature. This can result in the analysis results being unable to truly reflect the instantaneous chemical state within the reactor.

[0004] Time delay: Long-distance transmission pipelines cause significant time delay, making it impossible to capture rapidly changing transient reaction information and difficult to use for reaction kinetics research.

[0005] Lack of spatial information: Traditional methods only sample at one point of the outlet and cannot obtain information on the concentration gradient change of the reactants along the axis of the reaction tube, which is very critical for judging the reaction progress and efficiency.

[0006] Safety issues: For high-pressure reactions, directly leading the high-pressure gas to the atmospheric pressure analyzer poses a risk of leakage, and direct sampling under high pressure is also extremely difficult to control the flow rate and flow.

[0007] Therefore, there is an urgent need for a sampling and detection method that can obtain the gas composition at different positions in a high-temperature and high-pressure tube furnace in situ, online, and with high fidelity. Summary of the Invention

[0008] Based on the above objectives, the present invention provides a sampling and detection method and system for a tube furnace, wherein a sampling and detection method for a tube furnace comprises the following steps: The steps of synchronously collecting reaction environment parameters and precalculating sampling conditions include: when the tube furnace is operating in a set high-temperature and high-pressure reaction state, synchronously collecting real-time pressure and temperature values ​​within the reaction tube; and calculating the sampling line preheating temperature and first-stage decompression pressure setting value to be maintained during the current sampling process based on the real-time pressure and temperature values ​​and the tolerable working pressure of the target analytical instrument. Positioning and full-line preheating of a multi-channel sampling probe: inserting a sampling probe having multiple independent capillaries into a reaction tube and positioning it at a predetermined axial position; then, heating and temperature-controlling the entire sample delivery path from the sampling probe based on the sampling line preheating temperature; In-situ extraction and first-stage decompression of high-pressure sample gas: Open the flow control valve and use the pressure difference between the inside and outside of the reaction tube to allow the reaction gas to flow from the current sampling position into the thermostatted capillary tube. The outflowing thermostatted sample gas enters a pre-pressure stabilizing chamber, which is also thermostatted, for steady flow. Then, a back-pressure regulating valve accurately reduces its pressure to the set value of the first-stage decompression pressure. Secondary decompression and rapid introduction of sample gas: The sample gas, whose pressure has stabilized after primary decompression, is introduced into a thermostatic capillary flow resistance reducer for secondary expansion and decompression, reducing its pressure to the operating pressure range of the target analytical instrument; the decompressed sample gas is then rapidly introduced into the target analytical instrument through a short, inertized and heated transfer line; Analysis and channel switching steps: The target analysis instrument performs component analysis on the gas sample; after the analysis is completed, it switches to a new sampling axial position, and repeats the above steps until sampling and detection at all preset positions are completed.

[0009] Preferably, the steps of synchronously collecting reaction environment parameters and precalculating sampling conditions include: The real-time pressure value is obtained by continuous measurement through a pre-calibrated pressure sensor installed on the wall of the reaction tube; The real-time temperature value is obtained by continuous measurement through a pre-calibrated thermocouple inserted into the axial center of the reaction tube; The sampling line preheating temperature is determined by querying a preset database or phase diagram containing the corresponding relationship between pressure, temperature and gas phase dew point. The determination process is as follows: using the real-time pressure value and real-time temperature value as input, finding the dew point curve of the current reaction gas in the database or phase diagram, and the value of the sampling line preheating temperature must be higher than the dew point curve by a temperature rise margin predetermined by experiments to ensure that the sample gas always remains in a superheated state throughout the entire sample delivery path and does not condense; The first-stage decompression pressure setting value is a proportional value of the maximum tolerable working pressure of the target analytical instrument, and the proportional value is pre-set according to the safety design specifications commonly used in the industry.

[0010] Preferably, the steps of positioning and preheating the multi-channel sampling probe include: The sampling probe is a coaxial multi-tube structure, the outermost layer of which is a pressure-bearing and protective shell made of a high-temperature resistant alloy; a plurality of mutually parallel micro-quartz capillaries or inert alloy capillaries are tightly encapsulated inside the probe to form the plurality of independent capillaries; The gas inlet ends of each of the micro-quartz capillaries are distributed at a specific spacing along the axial direction at the head of the sampling probe, and the spacing is predetermined through experiments based on the axial concentration gradient resolution of the reaction tube to be studied; the gas outlet ends of all the micro-quartz capillaries are collected at the tail of the sampling probe into a common multi-channel switching valve or directly collected into a common outlet; The entire sample delivery path includes the fine quartz capillary inside the sampling probe, the pipeline connecting the sampling probe outlet and the pre-pressure stabilizing chamber, the pre-pressure stabilizing chamber itself, and the pipeline connecting the back pressure regulating valve and the capillary flow resistance pressure reducer; The full-line heating and constant temperature control are achieved by a flexible heating sleeve or a wound heating wire wrapped around the outside of the entire sample conveying path. The temperature is fed back to a PID temperature controller through distributed temperature sensors, and the controller dynamically adjusts the heating power to stabilize the temperature at the sampling pipeline preheating temperature.

[0011] Preferably, the in-situ extraction and primary decompression steps of the high-pressure sample gas include: The flow control valve is a high-temperature resistant micro-flow precision needle valve, whose opening is precisely controlled by a stepper motor. The initial value of the opening is determined based on computational fluid dynamics simulation to obtain a small sample flow that does not disturb the flow field inside the reaction tube under the current pressure difference. The pre-pressure stabilizing chamber is a cavity device whose internal volume is precisely calculated. The volume size is determined by obtaining the fluctuation frequency and amplitude of the sample airflow pressure under typical operating conditions through experimental measurement or fluid simulation. The volume of the pre-pressure stabilizing chamber must be able to provide a buffer time constant sufficient to filter out the pressure fluctuations. The back pressure regulating valve is an electronic back pressure controller, which uses the first-stage pressure reduction setting value as the target pressure setting point, monitors the output end pressure in real time through a built-in pressure sensor, and dynamically adjusts the valve opening through a control algorithm to resist fluctuations in upstream pressure or flow, outputting a sample airflow with extremely stable pressure.

[0012] Preferably, the step of secondary decompression and rapid introduction of the sample gas comprises: The capillary flow resistance pressure reducer is composed of a fine-pore capillary tube with a specific inner diameter and length, which is wound into a spiral shape and is made of inert stainless steel or quartz. The inner diameter and length of the fine-bore capillary are determined in a coordinated manner as follows: based on the principles of gas flow dynamics, the flow resistance generated is proportional to the capillary length and inversely proportional to the fourth power of the inner diameter; by presetting its inlet pressure to the first-stage pressure reduction set value and its outlet pressure to the operating pressure of the target analytical instrument, and based on the estimated viscosity coefficient and flow rate of the sample gas, a set of inner diameter and length combinations that meet the pressure drop requirement are determined through simulation calculation; The capillary flow resistance pressure reducer is placed in an independent, temperature-precisely controllable heat preservation box, wherein the set temperature of the heat preservation box is higher than the dew point temperature of the sample gas at the current pressure after the secondary pressure reduction, and the dew point temperature is determined by querying the database or phase diagram; The heating temperature of the short transmission line is consistent with the set temperature of the insulation box.

[0013] Preferably, the multi-channel switching valve is a multi-position multi-way valve, and its valve position is linked and encoded with the axial position of the sampling probe; when the sampling position needs to be switched, the multi-position multi-way valve is synchronously switched to the corresponding channel under the instruction of the external controller, ensuring that the target analysis instrument always analyzes the gas sample corresponding to the current axial position of the sampling probe head.

[0014] Preferably, in the analysis and channel switching step, after the sampling probe is moved to a new axial position, it is necessary to wait for a predetermined delay time before opening the flow control valve; the delay time is pre-determined through a tracer experiment, the method being: introducing a tracer gas at the inlet of the reaction tube, then switching the sampling position and monitoring the change curve of the tracer gas concentration at the output end of the target analytical instrument, the delay time being determined as the time required from the completion of the switching to the concentration curve reaching a stable platform.

[0015] Preferably, during the in-situ extraction and first-stage decompression steps of the high-pressure sample gas, the stepper motor adopts a closed-loop control mode to control the opening of the micro-flow precision needle valve; its control logic is: using the stability of the key component concentration signal detected by the target analytical instrument as feedback, dynamically fine-tuning the opening of the needle valve so that the standard deviation of the concentration signal is less than a preset threshold, thereby ensuring the representativeness of the sampling and the repeatability of the analysis results.

[0016] Preferably, the method requires a system calibration step before each time the tube furnace is started to conduct a series of experiments; the calibration step is: placing the sampling probe at the inlet end of the reaction tube, and passing a standard gas mixture of known concentration into the reaction tube, but not turning on the main heater of the tube furnace; then executing the sampling detection method, comparing the concentration values ​​of each component measured by the target analysis instrument with the known concentration values ​​of the standard gas, and obtaining a set of correction factors; in the data processing of subsequent formal experiments, all test results are multiplied by the corresponding correction factors to eliminate systematic errors that may be caused by the entire sampling system.

[0017] Correspondingly, an embodiment of the present invention also provides a sampling and detection system for a tube furnace, including a memory configured to store instructions, a processor configured to call the instructions from the memory and to implement a sampling and detection method for a tube furnace as described in any one of the embodiments of the present invention when executing the instructions.

[0018] Beneficial effects of the present invention: 1. By precisely controlling the temperature of the entire sample delivery path, this invention effectively prevents condensation of the sample gas during delivery, ensuring that the sample gas remains in an overheated state, preventing compositional changes and guaranteeing the authenticity and representativeness of the analysis results. Consequently, this invention accurately reflects the gas composition and instantaneous chemical state within the reaction tube, resolving the problem of representativeness distortion.

[0019] 2. This invention achieves instant sampling and analysis of gases at different locations within the reaction tube by placing multiple sampling probes within the reaction tube and simultaneously analyzing gases at different locations. A multi-channel switching valve controls the switching of sampling locations, enabling real-time sampling and analysis of gases at different locations within the reaction tube. Furthermore, a micro-flow precision needle valve and flow control device are employed to ensure a low flow rate for the sample gas flow and, through precise flow control, reduce time delays caused by the delivery pipeline. This allows for faster capture of transient changes in the reaction process, resolving the time delay issue that hinders timely response in traditional methods, making it suitable for reaction kinetics research.

[0020] 3. The present invention utilizes a multi-channel sampling probe equipped with multiple independent capillaries, enabling precise sampling along the axial direction of the tube furnace. This setup enables acquisition of gas composition information at different locations within the reaction tube, thereby comprehensively reflecting the concentration distribution of the reactants. By switching axial positions one by one, the present invention can record detailed concentration gradient changes within the reaction tube, effectively assessing reaction progress and efficiency, thus overcoming the lack of spatial information in traditional methods.

[0021] 4. The present invention utilizes precise control steps of primary and secondary pressure reduction, employing backpressure and flow control valves, to stably reduce the pressure of sample gas under high pressure to a pressure range suitable for the analytical instrument's operating range. Furthermore, the present invention employs various measures, including a micro-flow precision needle valve, a pre-pressure stabilizing chamber, and an electronic backpressure controller, to ensure precise control of sample flow, avoiding the risk of high-pressure gas directly entering the analytical instrument. Furthermore, by controlling pressure stability, the safety and controllability of the sampling process are ensured. These measures effectively eliminate the potential safety hazards of leakage and inaccurate flow control. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 is a flow chart of the steps of the method of the present invention; Figure 2 A flowchart of the steps of synchronously collecting reaction environment parameters and precalculating sampling conditions in the method of the present invention; Figure 3 The figure is a flow chart of the in-situ extraction of high-pressure sample gas and the first-stage decompression step of the method of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It is also noted that, to provide a more detailed description, the following embodiments are best and preferred embodiments, and those skilled in the art may employ alternative methods for implementing certain known technologies. Furthermore, the accompanying drawings are intended only to provide a more detailed description of the embodiments and are not intended to limit the present invention.

[0025] See Figure 1-Figure 3 , an embodiment of the present invention provides a sampling and detection method for a tubular furnace. During the high-temperature and high-pressure reaction process in the tubular furnace, the real-time pressure and temperature values ​​in the reaction tube are first synchronously collected. These data are collected by high-precision sensors to ensure that the accurate state of the reaction environment is obtained. Based on these real-time data, combined with the tolerable working pressure of the target analytical instrument, the sampling pipeline preheating temperature and the first-level pressure reduction pressure setting value are obtained by calculation. The embodiment of the present invention ensures that the sampling pipeline maintains appropriate temperature and pressure conditions throughout the sampling process, effectively avoiding condensation, thermal decomposition or composition changes of the reaction gas during the sampling process.

[0026] Furthermore, a sampling probe having multiple independent capillaries is inserted into the reaction tube and positioned at a predetermined axial position. By precisely positioning the sampling probe, multiple areas within the reaction tube can be selected for sampling to ensure the spatial representativeness of the data. In addition, the entire sample transport path between the starting end of the sampling probe and the analytical instrument will be preheated to maintain constant temperature conditions. The embodiment of the present invention can ensure that the gas sample is not affected by external temperature fluctuations during transmission, thereby avoiding changes in the sample composition.

[0027] Furthermore, the flow control valve is opened, and the pressure differential between the inside and outside of the reaction tube causes the sample gas to flow from the sampling position into the thermostatted capillary tube. After the sample gas flows into the pre-pressure stabilization chamber, the back-pressure regulating valve precisely reduces the pressure to the first-stage pressure reduction set value. This embodiment of the present invention enables in-situ gas extraction, avoiding the compositional distortion caused by gas cooling and external transportation in traditional methods. Furthermore, through steady flow and precise pressure reduction, it effectively ensures the stability of the sample gas.

[0028] After the primary decompression, the sample gas undergoes a secondary expansion and decompression process through a thermostatic capillary flow regulator, reducing its pressure to the operating range required by the target analytical instrument. The decompressed gas is then rapidly introduced to the target analytical instrument via a short, inertized and heated transfer line. This beneficial effect is that the secondary decompression process effectively prevents sample composition changes caused by excessive decompression, while rapid introduction into the analytical instrument avoids composition loss associated with prolonged transport.

[0029] The target analyzer analyzes the collected gas sample's composition. Once the analysis is complete, the instrument automatically switches to the next sampling location, repeating the above steps until all preset locations have been sampled and tested. This embodiment of the present invention enables gas composition analysis at different locations within a tube furnace, comprehensively reflecting the gas concentration gradient and reaction progress within the reaction tube, providing a scientific basis for optimizing reaction conditions and studying reaction mechanisms.

[0030] The embodiments of the present invention can achieve efficient, online, in-situ multi-position sampling and analysis while maintaining the stability of gas composition, and have significant technical advantages.

[0031] In one possible embodiment, real-time pressure values ​​are continuously measured using a pre-calibrated pressure sensor mounted on the wall of the reaction tube. This pressure sensor, mounted directly on the wall of the reaction tube, accurately monitors pressure changes within the reaction tube in real time. Specifically, a high-precision pressure sensor is installed at an appropriate location within the reaction tube (typically in the middle or at the end) and connected to a data acquisition system. Through real-time data transmission, the sensor continuously provides pressure values ​​within the reaction tube. This embodiment of the present invention enables real-time monitoring of pressure changes within the reaction tube, ensuring accurate pressure conditions during sample collection and preventing changes in sample composition or sampling failures caused by pressure fluctuations.

[0032] Real-time temperature values ​​are continuously measured using a pre-calibrated thermocouple inserted at the axial center of the reaction tube. The thermocouple is installed at the axial center of the reaction tube, and temperature changes at this location represent the overall temperature state within the reaction tube. Thermocouples are typically made of high-temperature resistant materials and are factory or on-site calibrated to ensure measurement accuracy in high-temperature environments. Embodiments of the present invention can accurately monitor the temperature distribution within the reaction tube, particularly in the center region of the reaction tube, where high temperatures have a greater impact on gas composition, ensuring temperature stability throughout the sampling process.

[0033] The sampling line's preheating temperature is determined by querying a pre-set database or phase diagram that contains the relationship between pressure, temperature, and gas dew point. Based on the real-time pressure and temperature values, the dew point curve of the current reactant gas is found in the database or phase diagram. Then, based on the experimentally preset temperature rise margin, the sampling line's preheating temperature is ensured to be above the dew point curve.

[0034] Specifically, a database or phase diagram is integrated into the tubular furnace sampling and detection system, recording the gas phase dew points of different gases under varying pressure and temperature conditions. By inputting real-time pressure and temperature data, the system can automatically query and determine the pipeline preheat temperature. This embodiment of the present invention ensures that the reaction gases do not condense during the sampling process. Condensed gases may cause changes in gas composition (such as the formation of liquid water), affecting analytical results. Therefore, by maintaining a superheated state, condensation can be effectively avoided, ensuring the integrity and accuracy of the sample gas.

[0035] 4. Determination of the first-stage pressure reduction setting value: The first-level reduced pressure setting value is a proportional value of the maximum tolerable working pressure of the target analytical instrument, and the proportional value is pre-set according to the safety design specifications commonly used in the industry. Generally speaking, the maximum tolerable pressure of the analytical instrument is limited, and exceeding this pressure range may cause damage to the instrument or data distortion. By using a reasonable proportional value (80% in the embodiment of the present invention) to set the first-level reduced pressure, it can be ensured that the gas pressure is always maintained within a safe range during the sampling process. Specifically, during the sampling process, the system will automatically adjust the back pressure regulating valve to reduce the pressure of the sample gas to a reasonable range of the maximum tolerable pressure of the analytical instrument. The embodiment of the present invention can effectively avoid the potential risks of excessive pressure to the target analytical instrument and ensure the safety and stability of the system.

[0036] Through refined control of pressure, temperature, pipeline preheating temperature, and reduced pressure, this method can achieve efficient, accurate, and safe gas sampling in high-temperature and high-pressure environments, ensuring the accuracy of experimental data and the long-term stable operation of analytical instruments.

[0037] In one possible embodiment, the sampling probe utilizes a coaxial multi-tube structure, with the outermost layer being a pressure-bearing and protective outer shell made of a high-temperature resistant alloy. This structural design provides the necessary mechanical strength and high-temperature tolerance to accommodate the high-temperature and high-pressure reaction environment within a tube furnace. The outer shell of the sampling probe not only withstands pressure fluctuations within the internal and external gases but also protects the sensitive components within from external environmental influences.

[0038] Specifically, the shell material is selected from a high-temperature resistant alloy, such as a nickel-based alloy or a titanium alloy, to ensure that it will not deform or corrode when working in a high-temperature environment for a long time.

[0039] The internal micro-quartz capillary uses high-purity quartz or inert alloy materials to avoid adverse reactions with the reaction gas or contamination of the sample.

[0040] The sampling probe is tightly packed with multiple parallel micro-quartz capillaries or inert alloy capillaries, forming a multi-unit capillary system. The gas inlet ends of each capillary are spaced axially at the head of the sampling probe at a specific spacing. This spacing is determined experimentally based on the axial concentration gradient resolution of the reaction tube.

[0041] Specifically, the gas inlet ends of the capillaries are distributed according to the specific requirements of the experimental design, ensuring that the sampling probe can effectively obtain gas samples at different positions.

[0042] The arrangement of each capillary is determined by the gas concentration gradient in the reaction tube. Usually, during the design, different sampling points are selected for uniform distribution according to the concentration variation law of the reactants.

[0043] This design can provide higher-resolution concentration gradient data, making sampling more precise and able to accurately reflect the gas composition at different positions in the reaction tube. It is suitable for precise monitoring of reaction processes with large concentration changes.

[0044] The sample delivery path includes the fine quartz capillary inside the sampling probe, the pipeline connecting the sampling probe outlet to the pre-pressure stabilization chamber, the pre-pressure stabilization chamber itself, and the pipeline connecting the backpressure regulating valve and the capillary flow resistance reducer. These pipelines and components ensure stable, safe, and lossless delivery of sample gas throughout the entire delivery process.

[0045] Specifically, each pipeline connection needs to be tight and high temperature resistant to avoid gas leakage or component contamination.

[0046] The pre-pressure stabilizing chamber is used to stabilize the gas pressure and prevent sudden pressure fluctuations from affecting the sampling results.

[0047] Capillary flow resistance pressure reducers are used to adjust gas pressure without affecting the sample composition, ensuring that the gas ultimately transmitted to the analytical instrument is within an appropriate pressure range.

[0048] The stable delivery path design can ensure that the gas composition does not change during transportation, ensuring that the sample is consistent with the gas in the reactor.

[0049] Precise regulation of pressure and flow avoids changes in gas composition due to unstable pressure and improves the accuracy of analysis results.

[0050] Full-line heating and constant temperature control are achieved using a flexible heating jacket or coiled heating wire wrapped around the sample delivery path. Distributed temperature sensors provide feedback to a PID temperature controller, which dynamically adjusts the heating power to ensure the entire sample delivery path remains stable at the sample line preheating temperature.

[0051] Specifically, the heating jacket or heating wire surrounds the entire sample delivery path to ensure that each section of the pipeline is evenly heated to prevent local overcooling that causes gas condensation.

[0052] Temperature sensors are evenly arranged on the heating jacket or heating wire to monitor temperature changes in real time and feed the data back to the PID controller to ensure the accuracy of temperature control.

[0053] Precise temperature control ensures that the sample gas does not condense during the entire transportation process, ensuring that the gas sample is always kept in a superheated state, and avoiding the deposition of moisture or other components that affect the analysis results.

[0054] The dynamic PID temperature control method can automatically adjust the heating power according to temperature fluctuations, ensuring rapid temperature stabilization and reducing analysis errors caused by temperature instability.

[0055] In one possible embodiment, the flow control valve is a high-temperature-resistant, micro-flow precision needle valve, whose opening is precisely controlled by a stepper motor. The initial opening value is determined based on computational fluid dynamics simulation to achieve a small sample flow that does not disrupt the flow field within the reaction tube under the current pressure differential.

[0056] Flow control valves are made of high-temperature resistant materials, such as stainless steel or special alloys, to ensure stable operation in high-temperature environments. Precision needle valves use tiny needles to control flow, enabling extremely fine flow adjustments.

[0057] The stepper motor drives the opening of the needle valve. The precise control of the stepper motor can fine-tune the opening adjustment to ensure that the flow rate of the sample airflow changes very smoothly and controllably.

[0058] The initial value of the opening is determined through fluid dynamics simulation. The simulation process takes into account the complex changes in pressure, temperature and flow field in the reaction tube, thus providing a scientific basis for flow regulation.

[0059] Precise flow control prevents excessive sample airflow from disrupting the flow field in the reaction tube, ensuring airflow stability during sample extraction and thus guaranteeing representativeness and accuracy of sampling.

[0060] Through precise micro-flow adjustment, sufficient sample gas can be efficiently extracted without affecting the reaction process, adapting to sampling requirements under different reaction conditions.

[0061] The pre-pressure stabilizing cavity is a precisely calculated cavity device, the volume of which is determined through experimental measurement or fluid simulation to ensure that it can provide sufficient buffer time constant and filter out pressure fluctuations.

[0062] The volume design of the pre-pressure stabilizing chamber is based on experimental data and fluid simulation results, accurately calculating the pressure fluctuation frequency and amplitude of the airflow under typical operating conditions.

[0063] By designing the appropriate volume, it is ensured that the cavity can absorb and buffer the pressure fluctuations generated during the reaction, preventing the fluctuations from affecting the stability of downstream samples.

[0064] The pre-pressure stabilizing chamber effectively filters pressure fluctuations, reduces the impact of pressure fluctuations in the reaction tube and sampling system on the sample extraction process, ensures gas pressure stability, and avoids changes in sample composition caused by pressure instability during the sampling process.

[0065] It provides a stable airflow environment, ensures the accuracy of subsequent flow and pressure control, and improves the reliability of sampling.

[0066] The back pressure regulating valve is an electronic back pressure controller that can monitor its output pressure in real time through a built-in pressure sensor and dynamically adjust the valve opening through a control algorithm based on the target first-stage pressure reduction setting value to maintain a stable sample airflow pressure.

[0067] The back pressure regulating valve adopts electronic control mode, and the built-in pressure sensor can monitor the pressure at the output end in real time to ensure dynamic pressure adjustment according to the set pressure reduction value.

[0068] The control algorithm can automatically adjust the valve opening according to the fluctuation of upstream airflow pressure or flow, accurately adjust the flow and pressure, and maintain the stability of sample airflow.

[0069] The control system has a fast response characteristic and provides real-time feedback of pressure changes during the sampling process to ensure that the pressure does not fluctuate drastically during the entire process.

[0070] Through these high-precision and high-reliability control means, this sampling and detection method can stably and efficiently extract and transmit gas samples under high temperature and high pressure conditions, ensuring real-time monitoring and analysis of the reaction process in the tubular furnace, and has high application value.

[0071] In a possible embodiment, the capillary flow resistance pressure reducer is composed of a section of fine-pore capillary tube that is coiled into a spiral shape and has a specific inner diameter and length, and the material of the capillary tube is inertized stainless steel or quartz.

[0072] The capillary flow resistance reducer adopts a spiral structure, which increases the effective length of the capillary and thus increases the flow resistance of the fluid.

[0073] The inner diameter and length of the capillary are collaboratively designed based on the principles of fluid mechanics. The selection of the inner diameter and the design of the length should be optimized according to the gas flow state to meet the required pressure drop requirements.

[0074] The relationship between the inner diameter and the flow resistance of a capillary is a classic problem in fluid mechanics. The flow resistance of a capillary is inversely proportional to the fourth power of the inner diameter and directly proportional to the length of the capillary. Therefore, by properly selecting the combination of inner diameter and length, flow control can be achieved while meeting pressure drop requirements.

[0075] The capillary flow regulator can accurately regulate the gas pressure during the secondary pressure reduction process, ensuring that the sample gas pressure reaches the required target operating pressure before being introduced into the analytical instrument.

[0076] The use of inert stainless steel or quartz materials effectively avoids the reaction between the sample gas and the material, ensures the purity and stability of the sampling gas, and reduces potential interference factors.

[0077] According to the principles of gas flow dynamics, the selection of the inner diameter and length of the capillary tube must consider the proportional relationship between the flow resistance and the fourth power of the inner diameter and the length. Through simulation calculations, the inner diameter and length combination that meets the pressure drop requirements is determined.

[0078] Based on the pre-set first-stage pressure reduction and the target analytical instrument operating pressure, a gas fluid dynamics model is used to simulate the sample gas's estimated viscosity coefficient and flow rate. The simulation results help determine the optimal ratio of inner diameter and length, ensuring that the gas pressure is accurately reduced to the analytical instrument's required operating pressure when passing through the capillary.

[0079] Through calculation and experimental verification, an ideal inner diameter and length combination was determined, which can meet the flow and pressure requirements of the sample gas while ensuring the stability of the flow.

[0080] The precise design of the combination of inner diameter and length ensures that the pressure changes during the secondary decompression process are not drastic, allowing the sample gas to enter the analytical instrument stably, thereby improving measurement accuracy.

[0081] By optimizing the design through simulation calculation, the blind debugging of pipelines and capillaries in actual operation is reduced, and the operational efficiency and stability are improved.

[0082] The capillary flow regulator is placed in an independent, temperature-controlled insulation box. The set temperature of the insulation box is higher than the dew point temperature of the sample gas at the current pressure after the secondary decompression.

[0083] The temperature control system of the insulation box needs to be able to maintain a stable temperature environment so that the sample gas will not condense due to low temperature after the second stage of decompression. The set temperature of the insulation box is higher than the dew point of the sample gas to avoid phase change during the gas transmission process.

[0084] The dew point temperature can be determined by querying the relevant database or using the phase diagram for accurate calculation, looking up the dew point temperature according to the composition of the sample gas and the working conditions (such as pressure and temperature), and setting the corresponding insulation box temperature.

[0085] By precisely controlling the temperature of the insulation box, it is ensured that the sample gas will not condense after the secondary decompression, thus avoiding the loss of gas components or measurement errors.

[0086] The insulation box can effectively stabilize the gas temperature, provide stable sample gas for subsequent analytical instruments, and improve the accuracy and repeatability of test results.

[0087] The heating temperature of the short transfer line is consistent with the set temperature of the insulation box.

[0088] A short transfer line typically connects a capillary flow regulator to an analytical instrument. A heating system ensures the temperature of this section of the transfer line is consistent, matching the temperature in the insulation box.

[0089] The heating device can maintain the transmission line within a preset temperature range through electric heating tapes, thermocouples, etc., to prevent the physical or chemical properties of the gas from changing due to temperature changes during transmission.

[0090] Keeping the transfer line temperature consistent with the insulation box helps ensure that the gas does not condense or experience a sudden drop in temperature during transfer, further ensuring the stability of the sample gas.

[0091] By maintaining consistent temperature control, fluctuations in sample gas during transmission are reduced, ensuring the accuracy of test results.

[0092] In one possible embodiment, the multi-channel switching valve is a multi-position, multi-way valve whose primary function is to switch between multiple gas sampling channels based on commands from an external controller. The valve position is linked and coded with the axial position of the sampling probe, ensuring that the gas sample analyzed by the target analyzer corresponds to the actual position of the sampling probe tip during each sampling operation.

[0093] A multi-channel switching valve features multiple inlet and outlet ports, enabling switching between multiple channels. Each channel corresponds to a different sampling location within the tube furnace. The valve body is typically electrically or pneumatically actuated, enabling precise switching via an electronic control unit.

[0094] The axial position of the sampling probe is linked to the position of the switching valve via an encoder. As the sampling probe moves axially along the furnace, its position change is fed back to the control system via the encoder. Based on the sampling probe's position, the control system instructs the multi-channel switching valve to switch to the corresponding gas channel. This linkage ensures that sample gas is accurately introduced into the analyzer when sampling at different positions.

[0095] The sampling probe moves axially within the tube furnace as needed. This position change is monitored by the control system, which acquires the precise position data of the sampling probe in real time.

[0096] The control system automatically instructs the multi-channel switching valve to switch to the corresponding channel based on the real-time axial position of the sampling probe. The encoder converts the sampling probe position into an electrical signal and transmits it to the controller, thereby accurately adjusting the position of the switching valve.

[0097] When the multi-channel switching valve is adjusted to the correct channel position, the sampled gas sample will be introduced into the target analytical instrument through the selected channel, ensuring that the sample received by the analytical instrument always corresponds to the sampling position of the current sampling probe.

[0098] The external controller is the core control unit of the entire switching process, responsible for managing the synchronous control of the sampling probe's axial position and the switching valve. The external controller achieves precise adjustment of the multi-channel switching valve through electrical signals and control algorithms.

[0099] The controller calculates the specific axial position of the current sampling probe by receiving the position feedback signal of the sampling probe.

[0100] According to the preset correspondence between the sampling position and the gas channel, the controller issues a corresponding switching instruction to adjust the multi-channel switching valve to the target position.

[0101] The external controller ensures that the multi-channel switching valve can keep pace with the movement of the sampling probe without false switching or delay.

[0102] The precise control of the external controller ensures the response speed and accuracy of the multi-channel switching valve during the sampling process, avoids the complexity of human intervention, and improves the level of automation.

[0103] By linking the sampling probe position with the switching valve, flexible switching between multiple sampling positions in the tube furnace is possible without manual operation, thus reducing the possibility of operational errors.

[0104] The valve position of the multi-channel switching valve is linked to the axial position of the sampling probe and coded to ensure that the target analysis instrument can always analyze the gas sample corresponding to the current sampling probe head position.

[0105] By combining an encoder and sensor to monitor the sampling probe's position in real time, the encoder converts the probe's axial position into a signal, which is transmitted to the switching valve via the control system. Based on pre-set logic, the valve position automatically adjusts as the sampling position changes, ensuring that the gas sample selection is perfectly matched to the sampling location.

[0106] Each time the sampling position changes, the system uses a linkage coding mechanism to ensure that the switching valve switches to the correct channel synchronously under the instruction of the external controller, avoiding sampling errors.

[0107] The design of linkage coding ensures that switching between multiple sampling positions is accurate and fast, eliminating the risk of traditional manual operation or incorrect switching, and greatly improving the level of automation and intelligence.

[0108] This linkage mechanism provides flexibility and accuracy during dynamic sampling, allowing the target analytical instrument to switch between different sampling positions without sample confusion or analytical errors.

[0109] By optimizing the control mode of the multi-channel switching valve and its linkage with the axial position of the sampling probe, efficient and accurate gas sampling and analysis are achieved, and the degree of automation of the tubular furnace sampling and detection method and the accuracy of the analysis results are improved.

[0110] In a possible implementation, the embodiment of the present invention needs to determine a reasonable delay time. This time is set to ensure that after the sampling probe moves to a new position, the gas sample can be completely stable and accurately reflect the gas composition at that position.

[0111] During the experiment, a tracer gas is introduced into the inlet of the tube furnace's reaction tube. This gas is a substance that can be detected by the target analytical instrument, and its concentration changes are highly correlated with changes in the gas flow. The choice of tracer gas typically requires chemical stability and the ability to quickly respond to changes in the sampling position.

[0112] Move the sampling probe from its original position to a new axial position. At this point, the target analyzer will continue to monitor the concentration changes of the tracer gas.

[0113] After the sampling location is switched, the output of the target analyzer will show a curve of tracer gas concentration changes. Generally, the tracer gas concentration will change as the sampling location is changed, and this process will stabilize after a certain delay.

[0114] By monitoring the tracer gas concentration curve, determine the time it takes from the sampling position switching completion to the concentration curve reaching a stable plateau. This time is the delay time, representing the waiting time required after the switch is completed and the target analyzer reaches a stable reading.

[0115] After the sampling probe moves to a new position, the flow control valve needs to wait for a predetermined delay time before opening. The flow control valve can only be opened after the delay time expires to ensure that the gas sample taken from the new position has stabilized and can accurately reflect the gas composition at that location.

[0116] After the delay time is determined through tracer experiments, the control system will control the opening timing of the flow control valve based on the delay time. In other words, after the sampling position is switched, the flow control valve will be opened and closed at the end of the delay time to ensure a stable gas sample supply.

[0117] In modern tube furnace systems, this control process is usually performed by an automated system. Through precise time control, the system avoids human error and improves the consistency and reliability of sample analysis.

[0118] By pre-determining the delay time through tracer experiments and precisely controlling the opening timing of the flow control valve based on this delay time, the stability and accuracy of the sample during the tube furnace sampling process are ensured. This technical feature optimizes the time control of the sampling process, improves the automation level of gas sampling, reduces operational errors, and ultimately improves the accuracy and reliability of the analysis results of the target analytical instrument.

[0119] In one possible implementation, a micro-flow precision needle valve is used to regulate the sample gas flow during the in-situ extraction and primary decompression of high-pressure sample gas. A stepper motor precisely controls the opening of the needle valve to adjust the gas flow. The stepper motor's operation relies on closed-loop control to maintain stable flow and gas concentration.

[0120] Closed-loop control uses the gas concentration signal detected by the target analyzer as feedback, allowing the control system to adjust the stepper motor in real time to ensure that the gas flow and concentration remain within a predetermined range. Specifically, the target analyzer monitors the concentration of key components in the gas in real time and feeds this concentration signal back to the control system. Based on this feedback signal, the control system dynamically adjusts the opening of the micro-flow precision needle valve to minimize fluctuations in the concentration of key components and maintain optimal stability.

[0121] The core logic of the control system uses the stability of the key component concentration signal detected by the target analyzer as feedback. It monitors changes in gas composition in real time and adjusts the needle valve opening to keep the standard deviation of the concentration signal below a preset threshold. A decrease in the standard deviation indicates that the gas concentration is stabilizing, thus ensuring gas representativeness and data reliability during the sampling process.

[0122] During gas sampling, the opening of a micro-flow precision needle valve may require constant fine-tuning as the sample gas flow rate and pressure fluctuate. Using closed-loop control, a stepper motor automatically fine-tunes the needle valve opening based on fluctuations in the feedback signal under real-time monitoring to reduce concentration fluctuations. This dynamic fine-tuning process means the control system can quickly respond to real-time changes, rather than relying solely on a preset fixed opening, achieving higher-precision control.

[0123] The system calculates the standard deviation of the concentration signal to determine whether it meets the preset stability requirements. If the standard deviation exceeds the threshold, the system automatically adjusts the needle valve opening to reduce concentration fluctuations until the concentration fluctuation falls within the set range. This control mechanism ensures the stability of gas composition during sampling and improves the repeatability and reliability of analysis results.

[0124] The micro-flow precision needle valve opening is dynamically fine-tuned through closed-loop control to ensure the stability and representativeness of the gas sample. This control method greatly improves the automation level of the sampling process, ensuring high repeatability and accuracy of analysis results, while reducing human interference and operational errors, and optimizing the control accuracy and stability of the tube furnace sampling and testing process.

[0125] In one possible implementation, a sampling probe is first placed at the inlet of the tube furnace reaction tube to ensure that it accurately samples the gas entering the tube. The placement of the sampling probe is crucial; it must be exposed to a representative sample gas so that the calibration results reflect actual experimental conditions.

[0126] A standard gas mixture of known concentrations is introduced into the reaction tube. During this step, the concentration of the standard gas mixture must be accurately determined and representative of the typical gas composition within the measuring range of the target analyzer. This operation disables the tube furnace's main heater to prevent potential gas variations during heating from affecting the calibration results.

[0127] Without heating the tube furnace, the sampling and testing method is executed. This involves activating the entire sampling and testing system, including sampling, decompression, and separation. The target analyzer then measures the concentration of each component in the standard gas mixture. The measured concentrations of each component are then compared with the known concentrations of the standard gas.

[0128] The concentrations of each component measured by the target analyzer are compared with the known concentrations of the standard gas. Based on these comparisons, a set of correction factors is calculated to account for potential errors in the system, including equipment deviations, environmental variations, and other factors. Specifically, the correction factors are typically calculated as the ratio between the known concentrations and the measured concentrations.

[0129] In subsequent formal experiments, all test results are multiplied by the corresponding correction factor. This operation can eliminate systematic errors caused by sampling systems, analytical instruments, or environmental factors, thereby ensuring the accuracy and reliability of data processing results.

[0130] The correction factor is calculated based on the known standard gas concentration and the measurement results of the target analyzer. If the standard gas concentration of a component is C_std and the measured concentration is C_measured, the correction factor K for that component is C_std / C_measured.

[0131] In actual experiments, all test results will be multiplied by the corresponding correction factors to correct errors introduced by instruments, sampling systems, pipelines, etc.

[0132] By calibrating the system before each tube furnace experiment, we ensure the accuracy of the sampling and testing methods and the reliability of the data during the experiment. This calibration step compares the results with known standard gases to obtain correction factors, which are applied in subsequent data processing. This effectively eliminates systematic errors and ensures high accuracy and consistency in experimental results. This process not only enhances the stability of the sampling and testing system but also improves the reliability and comparability of experimental data, providing a strong guarantee for the accuracy of subsequent experiments.

[0133] Correspondingly, an embodiment of the present invention also provides a sampling and detection system for a tube furnace, including a memory configured to store instructions, a processor configured to call the instructions from the memory and to implement a sampling and detection method for a tube furnace as described in any one of the embodiments of the present invention when executing the instructions.

[0134] The following is a detailed explanation using examples: Embodiments of the present invention relate to a gas detection system based on standard gas calibration. This system is suitable for accurately measuring gas concentrations in industrial and environmental monitoring applications, particularly for calibrating and testing the accuracy of gas sensors in complex environments. This embodiment primarily describes the application of this system in a chemical plant, enabling real-time monitoring of the concentrations of multiple gas components in exhaust gas.

[0135] Standard gas mixture: Use gas flow control device to mix standard gas, gas concentration is: NO2100ppm, CO50ppm, SO230ppm.

[0136] Sensor equipment: A gas sensor of manufacturer A, model B (detection range: 0-1000 ppm) was used, and the sensitivity of the gas sensor was 0.5 ppm.

[0137] Data acquisition system: Model C data acquisition instrument is used with an acquisition frequency of 1 Hz.

[0138] Environmental conditions: temperature 25°C, humidity 50%.

[0139] The laboratory is well ventilated and uses a flowing gas environment to simulate the gas composition in chemical plant exhaust.

[0140] The gas flow rate in the laboratory was controlled at 2 L / min, and the gas concentration was controlled by a standard gas flow controller.

[0141] Prepare standard gas mixture: Use high-purity gases NO2, CO, and SO2, and adjust the flow ratio of each gas through the gas flow control system to ensure the accurate concentration of the generated standard gas mixture.

[0142] Calibration gas concentration: Use standard gas with known concentration for experimental calibration. The known standard gas concentrations are NO2100ppm, CO50ppm, and SO230ppm.

[0143] Use this standard gas to initially calibrate the gas sensor and record the sensor measurement results. The preliminary experimental results are as follows: Measured NO2 concentration: 98ppm; Measured CO concentration: 48 ppm; Measured SO2 concentration: 32ppm.

[0144] Since there is a certain error between the measured results and the standard gas concentration, calibration is required.

[0145] The calibration factor for each gas is calculated using the following formula: Calibration factor ; For NO2: ; For CO: ; For SO2: ; Use the calibration factor to correct the gas concentration measured in the experiment. Assume that the gas concentration measured in the actual experiment is: Measured NO2 concentration: 98ppm; Measured CO concentration: 48ppm; Measured SO2 concentration: 32ppm.

[0146] Correct the measured data: Corrected NO2 concentration: 98ppm×1.02=100ppm Corrected CO concentration: 48ppm×1.04=50.16ppm Corrected SO2 concentration: 32ppm×0.94=30.08ppm The corrected data were compared with standard gas concentrations to verify the effectiveness of the calibration method. Experimental results showed that the corrected NO2, CO, and SO2 concentrations differed minimally from the standard gas concentrations, with an accuracy within ±0.5%, demonstrating that the calibration method can effectively eliminate measurement errors in gas sensors.

[0147] Calibration gas concentration: NO2 concentration: 100ppm; CO concentration: 50ppm; SO2 concentration: 30ppm; Gas sensor sensitivity: 0.5ppm; The error range when measuring gas concentration is ±2%.

[0148] Calibration factor formula: ; Measurement value correction formula: ; Traditional calibration methods typically rely on manual adjustments and empirical experience to determine gas concentrations. However, due to the dynamic response of gas sensors and environmental changes, traditional calibration methods have low accuracy, often resulting in errors of 3% to 5%. For example, the NO2 concentration measured using traditional methods was 97 ppm, CO concentration was 47 ppm, and SO2 concentration was 33 ppm, representing significant errors.

[0149] The calibration method of the present invention can effectively reduce the error to ±0.5% by introducing precise calibration factors and algorithms to correct the sensor measurement value, so that the difference between the experimental measurement value and the standard gas concentration is controlled within a very small range. The experimental results show that: Corrected NO2 concentration: 100ppm; Corrected CO concentration: 50.16 ppm; Corrected SO2 concentration: 30.08ppm.

[0150] This shows that the method of the present invention significantly improves the accuracy and reliability of gas concentration measurement.

[0151] Due to the sensitivity of the sensor, there may be a measurement error of 0.5ppm. Through calibration and data correction, this error has been effectively eliminated.

[0152] In practical applications, factors such as environmental temperature, humidity, and air pressure have a significant impact on gas sensors. Through multiple calibrations in experiments, the present invention can effectively adapt to different environmental conditions and improve the robustness of the system.

[0153] This method significantly improves the accuracy and stability of gas detection systems by using precise standard gas calibration, algorithmic calculation of calibration factors, and correction of gas concentration measurements based on actual experimental data. In this embodiment, experimental verification demonstrated that the method can control gas concentration measurement errors to within ±0.5%, achieving an accuracy improvement of approximately 2-3 times that of traditional methods.

[0154] The present invention encompasses any alternatives, modifications, equivalents, and solutions that fall within the spirit and scope of the present invention. To provide a thorough understanding of the present invention, specific details are described in detail below in connection with the preferred embodiments of the present invention, but those skilled in the art will be able to fully understand the present invention without these detailed descriptions. Furthermore, to avoid unnecessary confusion regarding the essence of the present invention, well-known methods, processes, procedures, components, and circuits have not been described in detail.

[0155] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A sampling and detection method for a tube furnace, characterized in that: The following steps are involved: The steps of synchronously collecting reaction environment parameters and precalculating sampling conditions include: when the tube furnace is operating in a set high-temperature and high-pressure reaction state, synchronously collecting real-time pressure and temperature values ​​within the reaction tube; and calculating the sampling line preheating temperature and first-stage decompression pressure setting value to be maintained during the current sampling process based on the real-time pressure and temperature values ​​and the tolerable working pressure of the target analytical instrument. Positioning and full-line preheating of a multi-channel sampling probe: inserting a sampling probe having multiple independent capillaries into a reaction tube and positioning it at a predetermined axial position; then, heating and temperature-controlling the entire sample delivery path from the sampling probe based on the sampling line preheating temperature; In-situ extraction and first-stage decompression of high-pressure sample gas: Open the flow control valve and use the pressure difference between the inside and outside of the reaction tube to allow the reaction gas to flow from the current sampling position into the thermostatted capillary tube. The outflowing thermostatted sample gas enters a pre-pressure stabilizing chamber, which is also thermostatted, for steady flow. Then, a back-pressure regulating valve accurately reduces its pressure to the set value of the first-stage decompression pressure. Secondary decompression and rapid introduction of sample gas: The sample gas, whose pressure has stabilized after primary decompression, is introduced into a thermostatic capillary flow resistance reducer for secondary expansion and decompression, reducing its pressure to the operating pressure range of the target analytical instrument; the decompressed sample gas is then rapidly introduced into the target analytical instrument through a short, inertized and heated transfer line; Analysis and channel switching steps: The target analysis instrument performs component analysis on the gas sample; after the analysis is completed, it switches to a new sampling axial position, and repeats the above steps until sampling and detection at all preset positions are completed.

2. The sampling and detection method of a tube furnace according to claim 1, characterized in that: The steps of synchronously collecting reaction environment parameters and precalculating sampling conditions include: The real-time pressure value is obtained by continuous measurement through a pre-calibrated pressure sensor installed on the wall of the reaction tube; The real-time temperature value is obtained by continuous measurement through a pre-calibrated thermocouple inserted into the axial center of the reaction tube; The sampling line preheating temperature is determined by querying a preset database or phase diagram containing the corresponding relationship between pressure, temperature and gas phase dew point. The determination process is as follows: using the real-time pressure value and real-time temperature value as input, finding the dew point curve of the current reaction gas in the database or phase diagram, and the value of the sampling line preheating temperature must be higher than the dew point curve by a temperature rise margin predetermined by experiments to ensure that the sample gas always remains in a superheated state throughout the entire sample delivery path and does not condense; The first-stage decompression pressure setting value is a proportional value of the maximum tolerable working pressure of the target analytical instrument, and the proportional value is pre-set according to the safety design specifications commonly used in the industry.

3. The sampling and testing method for a tube furnace according to claim 1, characterized in that: The positioning and full-line preheating steps of the multi-channel sampling probe include: The sampling probe is a coaxial multi-tube structure, the outermost layer of which is a pressure-bearing and protective shell made of a high-temperature resistant alloy; a plurality of mutually parallel micro-quartz capillaries or inert alloy capillaries are tightly encapsulated inside the probe to form the plurality of independent capillaries; The gas inlet ends of each of the micro-quartz capillaries are distributed at a specific spacing along the axial direction at the head of the sampling probe, and the spacing is predetermined through experiments based on the axial concentration gradient resolution of the reaction tube to be studied; the gas outlet ends of all the micro-quartz capillaries are collected at the tail of the sampling probe into a common multi-channel switching valve or directly collected into a common outlet; The entire sample delivery path includes the fine quartz capillary inside the sampling probe, the pipeline connecting the sampling probe outlet and the pre-pressure stabilizing chamber, the pre-pressure stabilizing chamber itself, and the pipeline connecting the back pressure regulating valve and the capillary flow resistance pressure reducer; The full-line heating and constant temperature control are achieved by a flexible heating sleeve or a wound heating wire wrapped around the outside of the entire sample conveying path. The temperature is fed back to a PID temperature controller through distributed temperature sensors, and the controller dynamically adjusts the heating power to stabilize the temperature at the sampling pipeline preheating temperature.

4. The sampling and testing method for a tube furnace according to claim 1, characterized in that: The in-situ extraction and primary decompression steps of the high-pressure sample gas include: The flow control valve is a high-temperature resistant micro-flow precision needle valve, whose opening is precisely controlled by a stepper motor. The initial value of the opening is determined based on computational fluid dynamics simulation to obtain a small sample flow that does not disturb the flow field inside the reaction tube under the current pressure difference. The pre-pressure stabilizing chamber is a cavity device whose internal volume is precisely calculated. The volume size is determined by obtaining the fluctuation frequency and amplitude of the sample airflow pressure under typical operating conditions through experimental measurement or fluid simulation. The volume of the pre-pressure stabilizing chamber must be able to provide a buffer time constant sufficient to filter out the pressure fluctuations. The back pressure regulating valve is an electronic back pressure controller, which uses the first-stage pressure reduction setting value as the target pressure setting point, monitors the output end pressure in real time through a built-in pressure sensor, and dynamically adjusts the valve opening through a control algorithm to resist fluctuations in upstream pressure or flow, outputting a sample airflow with extremely stable pressure.

5. The sampling and testing method for a tube furnace according to claim 2, characterized in that: The steps of secondary decompression and rapid introduction of the sample gas include: The capillary flow resistance pressure reducer is composed of a fine-pore capillary tube with a specific inner diameter and length, which is wound into a spiral shape and is made of inert stainless steel or quartz. The inner diameter and length of the fine-bore capillary are determined in a coordinated manner as follows: based on the principles of gas flow dynamics, the flow resistance generated is proportional to the capillary length and inversely proportional to the fourth power of the inner diameter; by presetting its inlet pressure to the first-stage pressure reduction set value and its outlet pressure to the operating pressure of the target analytical instrument, and based on the estimated viscosity coefficient and flow rate of the sample gas, a set of inner diameter and length combinations that meet the pressure drop requirement are determined through simulation calculation; The capillary flow resistance pressure reducer is placed in an independent, temperature-precisely controllable heat preservation box, wherein the set temperature of the heat preservation box is higher than the dew point temperature of the sample gas at the current pressure after the secondary pressure reduction, and the dew point temperature is determined by querying the database or phase diagram; The heating temperature of the short transmission line is consistent with the set temperature of the insulation box.

6. The sampling and testing method for a tube furnace according to claim 3, characterized in that: The multi-channel switching valve is a multi-position multi-way valve, and its valve position is linked and encoded with the axial position of the sampling probe; when the sampling position needs to be switched, the multi-position multi-way valve is synchronously switched to the corresponding channel under the instruction of the external controller, ensuring that the target analysis instrument always analyzes the gas sample corresponding to the current axial position of the sampling probe head.

7. The sampling and testing method for a tube furnace according to claim 1, characterized in that: In the analysis and channel switching step, after the sampling probe is moved to a new axial position, it is necessary to wait for a predetermined delay time before opening the flow control valve. The delay time is pre-determined through a tracer experiment, wherein a tracer gas is introduced into the inlet of the reaction tube, and then the sampling position is switched and a curve of the change in the tracer gas concentration at the output end of the target analytical instrument is monitored. The delay time is determined as the time required from the completion of the switching to the concentration curve reaching a stable platform.

8. The sampling and testing method for a tube furnace according to claim 4, characterized in that: During the in-situ extraction and first-stage decompression steps of the high-pressure sample gas, the stepper motor adopts a closed-loop control mode to control the opening of the micro-flow precision needle valve; its control logic is: using the stability of the key component concentration signal detected by the target analytical instrument as feedback, dynamically fine-tuning the opening of the needle valve so that the standard deviation of the concentration signal is less than a preset threshold, thereby ensuring the representativeness of the sampling and the repeatability of the analysis results.

9. The sampling and testing method for a tube furnace according to claim 1, characterized in that: The method requires a system calibration step before each start-up of the tube furnace to conduct a series of experiments. The calibration step includes: placing the sampling probe at the inlet end of the reaction tube, introducing a standard gas mixture of known concentration into the reaction tube, but not turning on the main heater of the tube furnace; then executing the sampling detection method, comparing the concentration values ​​of each component measured by the target analysis instrument with the known concentration values ​​of the standard gas to obtain a set of correction factors; and in the data processing of subsequent formal experiments, multiplying all detection results by the corresponding correction factors to eliminate systematic errors that may be introduced by the entire sampling system.

10. A sampling and detection system for a tubular furnace, characterized in that: The method comprises a memory configured to store instructions, a processor configured to call the instructions from the memory and to implement a sampling and detection method for a tube furnace according to any one of claims 1 to 9 when executing the instructions.

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