A method and system for sampling and testing a tube furnace

Abstract

This invention relates to the fields of analytical chemistry and process monitoring technology, and particularly to a sampling and detection method and system for a tubular furnace. The method includes: synchronous acquisition of reaction environment parameters and pre-calculation of sampling conditions; positioning and preheating of multi-channel sampling probes; in-situ extraction of high-pressure sample gas and a first-stage depressurization step; a second-stage depressurization and rapid introduction step: the pressure-stabilized sample gas after the first-stage depressurization is introduced into a temperature-controlled capillary flow resistance pressure reducer for secondary expansion and depressurization, reducing its pressure to the operating pressure range of the target analytical instrument; then, the depressurized sample gas is rapidly introduced into the target analytical instrument through a short, inertized, and heated transfer line; analysis and channel switching. Through full-process temperature control and precise depressurization, the stability of the sampled gas is ensured, avoiding compositional changes. Real-time sampling can be performed at multiple locations within the tubular furnace, reflecting the spatial distribution of gas components and avoiding spatial information loss.

Description

Technical Field

[0001] This invention relates to the fields of analytical chemistry and process monitoring technology, and in particular to a sampling and detection method and system for a tubular furnace. Background Technology

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

[0003] Existing sampling methods typically involve connecting a sampling line to the outlet of the reaction tube to guide the gas to external analytical instruments (such as gas chromatographs or mass spectrometers). This method has several inherent drawbacks:

[0004] Representative distortion: For high-temperature and high-pressure reactions, especially those involving easily condensable components or reactive intermediates, the gas may undergo condensation, thermal decomposition, or secondary reactions due to temperature drop during its long transport process after leaving the reaction zone and before entering the analyzer. This results in the analysis results failing to accurately reflect the instantaneous chemical state within the reactor.

[0005] Time delay: Long-distance delivery pipelines cause significant time delays, making it impossible to capture rapidly changing transient reaction information and making it difficult to use for reaction kinetic studies.

[0006] Spatial information is missing: Traditional methods only sample at the outlet point, which cannot obtain information on the concentration gradient changes of reactants along the axial direction of the reaction tube, which is crucial for judging the reaction progress and efficiency.

[0007] 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 volume.

[0008] Therefore, there is an urgent need for a sampling and detection method that can obtain gas components at different locations inside a high-temperature and high-pressure tubular furnace in situ, online, and with high fidelity. Summary of the Invention

[0009] To achieve the above objectives, the present invention provides a sampling and testing method and system for a tubular furnace, wherein the sampling and testing method for a tubular furnace includes the following steps:

[0010] Synchronous acquisition of reaction environment parameters and pre-calculation of sampling conditions: When the tubular furnace is operating in the set high temperature and high pressure reaction state, the real-time pressure value and real-time temperature value in the reaction tube are collected synchronously; based on the real-time pressure value and real-time temperature value, as well as the working pressure that the target analytical instrument can withstand, the preheating temperature of the sampling pipeline and the set value of the first-stage decompression pressure that need to be maintained during this sampling process are calculated.

[0011] Positioning and preheating of the multi-channel sampling probe: Insert a sampling probe with multiple independent capillaries inside into the reaction tube and position it at a predetermined axial position; then, based on the preheating temperature of the sampling pipeline, perform full-line heating and constant temperature control on the entire sample delivery path starting from the sampling probe.

[0012] In-situ extraction and first-stage pressure reduction of high-pressure sample gas: Open the flow regulating valve and use the pressure difference inside and outside the reaction tube to make the reaction gas flow from the current sampling position into the temperature-controlled capillary tube; the outflowing temperature-controlled sample gas enters a similarly temperature-controlled pre-pressure stabilizing chamber for flow stabilization, and then its pressure is precisely reduced to the first-stage pressure reduction set value through a back pressure regulating valve.

[0013] The sample gas undergoes a two-stage decompression and rapid introduction process: The sample gas, after undergoing a first-stage decompression and achieving stable pressure, is introduced into a constant-temperature capillary flow resistance pressure reducer for a second expansion and decompression, reducing its pressure to the operating pressure range of the target analytical instrument; then, the decompressed sample gas is rapidly introduced into the target analytical instrument through a short, inertized, and heated transmission line.

[0014] Analysis and channel switching steps: The target analysis instrument performs component analysis on the gas sample; after the analysis is completed, switch to the new sampling axis position, and repeat the above steps until sampling and detection at all preset positions are completed.

[0015] Preferably, the steps for synchronous acquisition of reaction environment parameters and pre-calculation of sampling conditions include:

[0016] The real-time pressure value is obtained by continuous measurement using a pre-calibrated pressure sensor installed on the reaction tube wall;

[0017] The real-time temperature value is obtained by continuous measurement using a pre-calibrated thermocouple inserted at the axial center of the reaction tube.

[0018] The preheating temperature of the sampling pipeline is determined by querying a preset database or phase diagram containing the correspondence between pressure, temperature and gas phase dew point. The determination process is as follows: with the real-time pressure value and real-time temperature value as input, the dew point curve of the current reaction gas is found in the database or phase diagram. The value of the preheating temperature of the sampling pipeline must be higher than the dew point curve by a temperature rise margin determined in advance through experiments, so as to ensure that the sample gas remains in a superheated state throughout the entire sample delivery path and does not condense.

[0019] The first-level pressure reduction setting value is a percentage of the maximum operating pressure that the target analytical instrument can withstand, and this percentage is preset according to industry-standard safety design specifications.

[0020] Preferably, the positioning and preheating steps of the multi-channel sampling probe include:

[0021] The sampling probe has a coaxial multi-tube structure. Its outermost layer is a pressure-bearing and protective shell made of high-temperature resistant alloy. Its interior is tightly encapsulated with multiple parallel micro-fine quartz capillaries or inert alloy capillaries, forming the multiple independent capillaries.

[0022] The inlet of each of the micro-quartz capillaries is distributed along the axial direction at a specific interval at the head of the sampling probe. This interval is determined experimentally in advance based on the axial concentration gradient resolution of the reaction tube to be studied. The outlets of all the micro-quartz capillaries converge at the tail of the sampling probe to a common multi-channel switching valve or directly to a common outlet.

[0023] The entire sample delivery path includes the micro-quartz capillary inside the sampling probe, the pipeline connecting the sampling probe outlet to the pre-pressure stabilizing chamber, the pre-pressure stabilizing chamber itself, and the pipeline connecting the back pressure regulating valve to the capillary flow resistance pressure reducer.

[0024] The entire heating and constant temperature control is achieved by a flexible heating sleeve or wound heating wire wrapped around the outside of the entire sample delivery path. Its temperature is fed back to a PID temperature controller through distributed temperature sensors, which dynamically adjusts the heating power to stabilize the temperature at the preheating temperature of the sampling pipeline.

[0025] Preferably, the in-situ extraction and first-stage depressurization step of the high-pressure sample gas includes:

[0026] The flow regulating valve is a high-temperature resistant micro-flow precision needle valve. Its 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 gas flow that does not disturb the internal flow field of the reaction tube under the current pressure difference.

[0027] The pre-stabilizing chamber is a cavity device whose internal volume has been precisely calculated. The method for determining its volume is as follows: by experimental measurement or fluid simulation, the fluctuation frequency and amplitude of the sample gas flow pressure under typical operating conditions are obtained. The volume of the pre-stabilizing chamber needs to provide a buffer time constant sufficient to filter out the pressure fluctuation.

[0028] The back pressure regulating valve is an electronic back pressure controller. It uses the first-level pressure reduction setpoint as the target pressure setpoint, monitors its output 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, and outputs a sample gas flow with extremely stable pressure.

[0029] Preferably, the two-stage depressurization and rapid introduction step of the sample gas includes:

[0030] The capillary flow resistance pressure reducer consists of a spiral-shaped capillary tube with a specific inner diameter and length, and its material is inert stainless steel or quartz.

[0031] The method for determining the inner diameter and length of the fine-aperture capillary is as follows: According to the principle of gas flow dynamics, the flow resistance generated is directly proportional to the capillary length and inversely proportional to the fourth power of the inner diameter; by pre-setting its inlet pressure to the first-stage pressure reduction set value and the outlet pressure to the working pressure of the target analyzer, and based on the estimated viscosity coefficient and flow rate of the sample gas, a combination of inner diameter and length that can meet the pressure drop requirements is determined through simulation calculation.

[0032] The capillary flow resistance pressure reducer is placed in a separate, precisely temperature-controlled insulated box. The set temperature of the insulated box is higher than the dew point temperature of the sample gas at the current pressure after the two-stage pressure reduction. The dew point temperature is determined by querying the database or phase diagram.

[0033] The heat tracing temperature of the short transmission line is consistent with the set temperature of the insulation box.

[0034] Preferably, the multi-channel switching valve is a multi-position multi-way valve, whose valve position is linked to the axial position of the sampling probe; when it is necessary to switch the sampling position, the multi-position multi-way valve synchronously switches to the corresponding channel under the instruction of the external controller, ensuring that the target analyzer always analyzes the gas sample corresponding to the current axial position of the sampling probe head.

[0035] Preferably, in the analysis and channel switching step, after the sampling probe is moved to a new axial position, a predetermined delay time is required before the flow regulating valve is opened; the delay time is determined in advance by a tracer experiment, the method of which is to introduce a tracer gas into the inlet of the reaction tube, then switch the sampling position and monitor the change curve of the tracer gas concentration at the output of the target analyzer, and the delay time is determined as the time required from the completion of the switching to the concentration curve reaching a stable plateau.

[0036] Preferably, in the in-situ extraction and first-stage decompression step of the high-pressure sample gas, the stepper motor controls the opening of the micro-flow precision needle valve in a closed-loop control mode. The control logic is as follows: using the stability of the concentration signal of the key component detected by the target analyzer as the feedback quantity, the opening of the needle valve is dynamically fine-tuned 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.

[0037] Preferably, the method requires a system calibration step before each series of experiments is started with the tubular furnace. The calibration step is as follows: the sampling probe is placed at the inlet of the reaction tube, and a standard gas mixture of known concentration is introduced into the reaction tube, but the main heater of the tubular furnace is not turned on; then the sampling and detection method is executed, and the concentration values ​​of each component measured by the target analyzer are compared with the known concentration values ​​of the standard gas to obtain a set of correction factors; in the data processing of subsequent formal experiments, all detection results are multiplied by the corresponding correction factors to eliminate systematic errors that may be caused by the entire sampling system.

[0038] Accordingly, embodiments of the present invention also provide a sampling and detection system for a tube furnace, including a memory configured to store instructions, a processor configured to retrieve the instructions from the memory, and capable of implementing a sampling and detection method for a tube furnace as described in any embodiment of the present invention when executing the instructions.

[0039] The beneficial effects of this invention are:

[0040] 1. This invention effectively avoids condensation of the sample gas during transport by precisely controlling the temperature throughout the sample delivery path, ensuring that the sample gas remains in a superheated state and preventing changes in its composition, thus guaranteeing the authenticity and representativeness of the analytical results. Therefore, this invention can accurately reflect the gas composition and instantaneous chemical state within the reaction tube, solving the problem of representativeness distortion.

[0041] 2. This invention achieves real-time sampling and analysis of gas at different locations within the reaction tube by setting multiple sampling probes within the tube and simultaneously analyzing the gas at different positions. A multi-channel switching valve controls the switching of sampling positions. Simultaneously, a micro-flow precision needle valve and flow regulation device ensure a small flow rate for the sample gas and reduce time delays caused by the delivery pipeline through precise flow rate adjustment. This allows for faster capture of transient changes during the reaction process, solving the time delay problem that traditional methods cannot respond to in a timely manner, and is suitable for reaction kinetic studies.

[0042] 3. This invention employs a multi-channel sampling probe, which contains multiple independent capillaries, enabling precise sampling along the axial direction of the tube furnace. This configuration allows for the acquisition of gas composition information at different locations within the reaction tube, thus comprehensively reflecting the concentration distribution of reactants. By switching the axial position sequentially, this invention can record detailed changes in the concentration gradient within the reaction tube, thereby effectively determining the reaction progress and efficiency, overcoming the spatial information deficiency of traditional methods.

[0043] 4. This invention employs precise control steps of primary and secondary pressure reduction, using back pressure regulating valves and flow regulating valves to stably reduce the pressure of the sample gas under high pressure to a level suitable for the operating pressure range of the analytical instrument. Furthermore, this invention utilizes multiple methods, including a micro-flow precision needle valve, a pre-positioned pressure regulating chamber, and an electronic back pressure controller, to ensure precise control of the sample flow rate, avoiding the risk of high-pressure gas directly entering the analytical instrument. By controlling pressure stability, the safety and controllability of the sampling process are ensured. These measures effectively eliminate the safety hazards of leakage and inaccurate flow control. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart of the steps of the method of the present invention;

[0046] Figure 2 This is a flowchart illustrating the steps of synchronous acquisition of environmental parameters and pre-calculation of sampling conditions in the method of the present invention.

[0047] Figure 3 This is a flowchart illustrating the in-situ extraction and first-stage decompression steps of the high-pressure sample gas in the method of this invention. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0049] Please see Figures 1-3 This invention provides a sampling and detection method for a tubular furnace. During the high-temperature and high-pressure reaction process in the tubular furnace, real-time pressure and temperature values ​​within the reaction tube are first collected synchronously. These data are acquired using high-precision sensors to ensure accurate understanding of the reaction environment. Based on this real-time data, combined with the operating pressure tolerance of the target analytical instrument, the preheating temperature of the sampling pipeline and the setpoint for the first-stage pressure reduction are calculated. This invention ensures that the sampling pipeline maintains suitable temperature and pressure conditions throughout the sampling process, effectively preventing condensation, thermal decomposition, or compositional changes of the reaction gases during sampling.

[0050] Furthermore, a sampling probe with multiple independent capillaries is inserted into the reaction tube and positioned at a predetermined axial location. By precisely positioning the sampling probe, multiple areas within the reaction tube can be sampled, ensuring spatial representativeness of the data. In addition, the entire sample transport path from the sampling probe's initiation point to the analytical instrument is preheated to maintain constant temperature conditions. This embodiment of the invention ensures that gas samples are unaffected by external temperature fluctuations during transport, thereby preventing changes in sample composition.

[0051] Furthermore, the flow regulating valve is opened, and the sample gas flows from the sampling position into the temperature-controlled capillary tube through the pressure difference inside and outside the reaction tube. After the outflowing sample gas enters the pre-pressure regulating chamber, the pressure is precisely reduced to the first-stage pressure reduction set value by the back pressure regulating valve. This embodiment of the invention can extract gas in situ, avoiding the compositional distortion caused by gas cooling and external transportation in traditional methods. At the same time, through flow stabilization and precise pressure reduction, the stability of the sample gas is effectively guaranteed.

[0052] After the first-stage decompression, the sample gas undergoes a second expansion and decompression process using a temperature-controlled capillary flow resistance pressure reducer, lowering its pressure to the operating pressure range required by the target analytical instrument. Then, the decompressed gas is rapidly introduced into the target analytical instrument via a short, inertized, and heated transfer line. The advantages of this step are that the second-stage decompression process effectively avoids changes in sample composition due to excessive decompression, and the rapid introduction into the analytical instrument avoids component loss caused by prolonged transport.

[0053] The collected gas samples are analyzed using a target analysis instrument. After analysis, the system automatically switches to the next sampling location, repeating the above steps until all preset locations have been sampled and tested. This invention enables gas composition analysis at different locations within a tubular furnace, comprehensively reflecting the gas concentration gradient and reaction process within the reaction tube, providing a scientific basis for optimizing reaction conditions and studying reaction mechanisms.

[0054] The embodiments of the present invention can achieve efficient, online, in-situ multi-location sampling and analysis while maintaining the stability of gas composition, which has significant technical advantages.

[0055] In one possible implementation, the real-time pressure value is continuously measured using a pre-calibrated pressure sensor mounted on the reaction tube wall. This pressure sensor, directly mounted on the reaction tube wall, enables real-time and accurate monitoring of pressure changes within the reaction tube. Specifically, a high-precision pressure sensor is installed at an appropriate location within the reaction tube (typically the middle or end) and connected to a data acquisition system. Through real-time data transmission, the sensor continuously provides the pressure value within the reaction tube. This embodiment of the 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 failure due to pressure fluctuations.

[0056] Real-time temperature values ​​are continuously measured using a pre-calibrated thermocouple inserted at the axial center of the reaction tube. The thermocouple, installed at the axial center of the reaction tube, reflects the overall temperature state within the tube. Thermocouples are typically made of high-temperature resistant materials and are factory-calibrated or field-calibrated to ensure measurement accuracy under high-temperature conditions. This invention accurately monitors the temperature distribution within the reaction tube, especially in the central region where high temperatures significantly affect gas composition, ensuring temperature stability throughout the sampling process.

[0057] The preheating temperature of the sampling pipeline is determined by querying a preset database or phase diagram containing the correspondence between pressure, temperature, and gas phase dew point. Based on the real-time pressure and temperature values, the dew point curve of the current reacting gas is found in the database or phase diagram. Then, according to the preset temperature rise margin, the preheating temperature of the sampling pipeline is ensured to be higher than the dew point curve.

[0058] Specifically, a database or phase diagram is integrated into the tubular furnace sampling and testing system to record the vapor dew points of different gases under various pressure and temperature conditions. By inputting real-time pressure and temperature data, the system can automatically query and determine the pipeline preheating temperature. This embodiment of the invention ensures that the reaction gas does not condense during sampling. Condensation can lead to changes in gas composition (such as the formation of liquid water), affecting the analytical results. Therefore, by maintaining a superheated state, condensation can be effectively avoided, ensuring the integrity and accuracy of the sample gas.

[0059] 4. Determination of the first-stage pressure reduction setpoint:

[0060] The primary pressure reduction setting is a percentage of the target analytical instrument's maximum withstand operating pressure, pre-set according to industry-standard safety design specifications. Generally, the maximum withstand pressure of an analytical instrument is limited; exceeding this pressure range may cause instrument damage or data distortion. By setting the primary pressure reduction using a reasonable percentage (80% in this embodiment), the gas pressure can be ensured to remain within a safe range during sampling. Specifically, during sampling, the system automatically adjusts the back pressure regulating valve to reduce the sample gas pressure to a reasonable range within the analyzer's maximum withstand pressure. This embodiment effectively avoids the potential risks of excessive pressure to the target analytical instrument and ensures the system's safety and stability.

[0061] By refining the control of pressure, temperature, pipeline preheating temperature, and depressurization pressure, this method can achieve efficient, accurate, and safe gas sampling under high temperature and high pressure environments, ensuring the accuracy of experimental data and the long-term stable operation of analytical instruments.

[0062] In one possible implementation, the sampling probe employs a coaxial multi-tube structure, with the outermost layer being a pressure-bearing and protective shell made of a high-temperature resistant alloy. This structure is designed to provide the necessary mechanical strength and high-temperature resistance to adapt to the high-temperature, high-pressure reaction environment inside the tubular furnace. The outer shell of the sampling probe not only withstands pressure changes between the internal and external gases but also protects the internal sensitive elements from external environmental influences.

[0063] Specifically, the outer shell is made of high-temperature resistant alloys, such as nickel-based alloys or titanium alloys, to ensure that it will not deform or corrode when working in high-temperature environments for a long time.

[0064] 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.

[0065] The sampling probe is internally encapsulated with multiple parallel micro-fine quartz capillaries or inert alloy capillaries, forming multiple independent capillaries. The gas inlet end of each capillary is distributed along the axial direction at a specific interval at the head of the sampling probe. This interval is set in advance through experiments based on the axial concentration gradient resolution of the reaction tube.

[0066] Specifically, the gas inlet end of the capillary is distributed according to the specific requirements of the experimental design to ensure that the sampling probe can effectively acquire gas samples from different locations.

[0067] The arrangement of each capillary is determined based on the gas concentration gradient inside the reaction tube. Typically, during the design phase, different sampling points are selected and evenly distributed according to the concentration variation pattern of the reactants.

[0068] This design provides higher resolution concentration gradient data, enabling finer sampling and accurate reflection of gas composition at different locations within the reaction tube. It is suitable for precise monitoring of reaction processes with large concentration variations.

[0069] The sample delivery path includes a micro-quartz capillary tube inside the sampling probe, a pipeline connecting the sampling probe outlet to the pre-pressure regulating chamber, the pre-pressure regulating chamber itself, and a pipeline connecting the back pressure regulating valve and the capillary flow resistance pressure reducer. These pipes and components ensure that the sample gas is delivered stably, safely, and without damage throughout the entire delivery process.

[0070] Specifically, all pipe connections need to be tight and heat-resistant to prevent gas leaks or contamination.

[0071] The pre-pressure stabilizing chamber is used to stabilize the gas pressure and prevent sudden pressure fluctuations from affecting the sampling results.

[0072] Capillary flow resistance regulators are used to regulate gas pressure without affecting the sample composition, ensuring that the gas ultimately delivered to the analyzer is within the appropriate pressure range.

[0073] A stable delivery path design ensures that the gas composition does not change during transportation, guaranteeing that the sampled gas is consistent with the gas inside the reactor.

[0074] Precise control of pressure and flow rate prevents changes in gas composition due to pressure instability, thus improving the accuracy of analytical results.

[0075] The entire heating and temperature control is achieved through a flexible heating jacket or wound heating wire wrapped around the sample delivery path. The temperature of the heating jacket or heating wire is fed back to a PID temperature controller via distributed temperature sensors. The controller dynamically adjusts the heating power to ensure that the temperature of the entire sample delivery path remains stable at the preheating temperature of the sampling pipeline.

[0076] Specifically, a heating jacket or heating wire surrounds the entire sample delivery path to ensure that each section of the pipe is heated evenly and to prevent localized overcooling that could lead to gas condensation.

[0077] Temperature sensors are evenly distributed 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.

[0078] Precise temperature control ensures that the sample gas does not condense during the entire transport process, keeping the gas sample in a superheated state and preventing the deposition of moisture or other components from affecting the analysis results.

[0079] 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.

[0080] In one possible implementation, 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 simulations to obtain a small sample gas flow that does not disturb the flow field inside the reaction tube under the current pressure differential.

[0081] The flow control valve is made of high-temperature resistant materials, such as stainless steel or special alloys, to ensure stable operation in high-temperature environments. The precision needle valve uses a tiny needle to control the flow, enabling extremely fine flow adjustment.

[0082] The stepper motor drives the opening of the needle valve. The precise control of the stepper motor can refine the opening adjustment, ensuring that the flow rate of the sample gas is extremely stable and controllable.

[0083] The initial value of the opening was determined through fluid dynamics simulation. The simulation process took into account the complex changes in pressure, temperature and flow field inside the reaction tube, thus providing a scientific basis for flow regulation.

[0084] Precise flow control prevents excessive sample gas flow from disrupting the flow field within the reaction tube, ensuring gas flow stability during sample extraction and thus guaranteeing the representativeness and accuracy of the sampling.

[0085] By precisely adjusting the micro-flow rate, sufficient sample gas can be extracted efficiently without affecting the reaction process, adapting to sampling needs under different reaction conditions.

[0086] The pre-stabilizing chamber is a precisely calculated cavity device whose volume is determined through experimental measurement or fluid simulation to ensure that it can provide a sufficient buffer time constant to filter out pressure fluctuations.

[0087] The volume design of the pre-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.

[0088] By designing an appropriate volume, the chamber can absorb and buffer pressure fluctuations generated during the reaction process, preventing these fluctuations from affecting the stability of downstream samples.

[0089] The pre-pressure stabilizing chamber effectively filters pressure fluctuations, reducing the impact of pressure fluctuations in the reaction tube and sampling system on the sample extraction process, ensuring stable gas pressure, and avoiding changes in sample composition caused by pressure instability during sampling.

[0090] It provides a stable airflow environment, ensuring the accuracy of subsequent flow and pressure control and improving the reliability of sampling.

[0091] 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 according to the target primary pressure reduction setting value through a control algorithm to maintain a stable sample gas flow pressure.

[0092] The back pressure regulating valve adopts electronic control, 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.

[0093] The control algorithm can automatically adjust the valve opening based on fluctuations in upstream airflow pressure or flow rate, precisely regulate flow and pressure, and maintain stable sample airflow.

[0094] The control system has a fast response capability, providing real-time feedback on pressure changes during the sampling process to ensure that the pressure does not fluctuate drastically throughout the process.

[0095] Through these high-precision and high-reliability control methods, this sampling and detection method can stably and efficiently extract and transport gas samples under high temperature and high pressure conditions, ensuring real-time monitoring and analysis of the reaction process inside the tubular furnace, and has high application value.

[0096] In one possible implementation, the capillary flow resistance pressure reducer consists of a spirally coiled capillary tube with a specific inner diameter and length, made of inert stainless steel or quartz.

[0097] The capillary flow resistance pressure reducer uses a spiral structure, which increases the effective length of the capillary, thereby improving the flow resistance of the fluid.

[0098] The inner diameter and length of the capillary are designed in conjunction with fluid dynamics principles. 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.

[0099] The relationship between inner diameter and capillary flow resistance is a classic problem in fluid mechanics. The flow resistance of a capillary is inversely proportional to the fourth power of its inner diameter and directly proportional to its length. Therefore, by appropriately selecting the combination of inner diameter and length, flow control can be achieved while meeting pressure drop requirements.

[0100] Capillary flow resistance pressure reducers can precisely regulate gas pressure during the two-stage pressure reduction process, ensuring that the sample gas reaches the required target operating pressure before being introduced into the analyzer.

[0101] Using inert stainless steel or quartz materials effectively prevents the sample gas from reacting with the material, ensuring the purity and stability of the sampled gas and reducing potential interference factors.

[0102] Based on the principles of gas flow dynamics, the selection of the capillary's inner diameter and length must consider the proportional relationship between flow resistance and the fourth power of the inner diameter and the length. Simulation calculations are used to determine the optimal combination of inner diameter and length that meets the pressure drop requirements.

[0103] Based on the pre-set primary decompression pressure and the target analytical instrument operating pressure, a gas hydrodynamic model is used for simulation calculations according to the estimated viscosity coefficient and flow rate of the sample gas. The simulation results help determine the optimal ratio of inner diameter and length, ensuring that the gas pressure is accurately reduced to the operating pressure required by the analytical instrument when passing through the capillary.

[0104] Through calculation and experimental verification, an ideal combination of inner diameter and length was determined that can meet the flow rate and pressure requirements of the sample gas while ensuring the stability of the flow rate.

[0105] The precise design of the inner diameter and length combination ensures that the pressure change during the two-stage decompression process is not drastic, allowing the sample gas to enter the analyzer stably, thereby improving measurement accuracy.

[0106] By optimizing the design through simulation calculations, the need for blind adjustments to pipes and capillaries during actual operation is reduced, thereby improving operational efficiency and stability.

[0107] The capillary flow resistance pressure reducer is placed in a separate, temperature-controlled insulated box, the set temperature of which is higher than the dew point temperature of the sample gas at the current pressure after two-stage pressure reduction.

[0108] The temperature control system of the insulated box needs to maintain a stable temperature environment so that the sample gas does not condense due to excessively low temperatures after undergoing two-stage decompression. The set temperature of the insulated box is higher than the dew point temperature of the sample gas to prevent phase change during gas transport.

[0109] The dew point temperature can be determined by consulting relevant databases or by using phase diagrams for precise calculation. The dew point temperature can be found based on the composition of the sample gas and the working conditions (such as pressure and temperature), and the corresponding temperature of the insulation box can be set.

[0110] By precisely controlling the temperature of the insulated box, it is ensured that the sample gas will not condense after the second-stage decompression, thus avoiding the loss of gas components or measurement errors.

[0111] The insulated box can effectively stabilize the gas temperature, providing a stable sample gas for subsequent analytical instruments and improving the accuracy and repeatability of the test results.

[0112] The heat tracing temperature of the short transmission line is consistent with the set temperature of the insulation box.

[0113] Short transmission lines typically connect capillary flow resistance regulators to analytical instruments, and a heat tracing system ensures the temperature consistency of this transmission line, matching the temperature within the insulation box.

[0114] Heat tracing devices can maintain the transmission line within a preset temperature range using electric heating belts, thermocouples, or other methods, preventing changes in the physical or chemical properties of the gas during transmission due to temperature variations.

[0115] Maintaining the temperature of the transfer line consistent with that of the insulation box helps ensure that the gas does not condense or experience a sudden drop in temperature during transfer, further guaranteeing the stability of the sample gas.

[0116] By maintaining consistent temperature control, fluctuations in sample gas during transmission were reduced, ensuring the accuracy of the test results.

[0117] In one possible implementation, the multi-channel switching valve is a multi-position multi-way valve whose main function is to switch between multiple gas sampling channels according to instructions from an external controller. The valve position is linked to 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 head during each sampling.

[0118] The multi-channel switching valve has multiple inlets and outlets, allowing switching between multiple channels. Each channel corresponds to a different sampling location within the tube furnace. The valve body is typically electrically or pneumatically controlled, with precise switching achieved through an electronic control device.

[0119] The axial position of the sampling probe is linked to the valve position of the switching valve via an encoder. As the sampling probe moves axially along the furnace body, its position change is fed back to the control system via the encoder. The control system then switches the multi-channel switching valve to the corresponding gas channel based on the sampling probe's position command. This linkage method ensures that sample gas is accurately introduced into the analytical instrument when sampling at different positions.

[0120] The axial position of the sampling probe within the tube furnace is moved as needed. The positional changes of the sampling probe are monitored by the control system, which acquires precise positional data of the sampling probe in real time.

[0121] The control system automatically commands 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.

[0122] When the multi-channel switching valve is adjusted to the correct channel position, the sampled gas sample will be introduced into the target analyzer through the selected channel, ensuring that the sample received by the analyzer always corresponds to the sampling position of the current sampling probe.

[0123] 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.

[0124] The controller calculates the current axial position of the sampling probe by receiving the position feedback signal of the sampling probe.

[0125] Based on the preset correspondence between sampling locations and gas channels, the controller issues corresponding switching commands to adjust the multi-channel switching valve to the target position.

[0126] An external controller ensures that the multi-channel switching valve can be synchronized with the movement of the sampling probe, preventing erroneous switching or delays.

[0127] The precise control of the external controller ensures the response speed and accuracy of the multi-channel switching valve during the sampling process, avoiding the complexity of human intervention and improving the level of automation.

[0128] By linking the sampling probe position with the switching valve through coding, multiple sampling positions within the tubular furnace can be flexibly switched without manual operation, thus reducing the possibility of operational errors.

[0129] The valve position of the multi-channel switching valve is linked to the axial position of the sampling probe, ensuring that the target analyzer can always analyze the gas sample corresponding to the current sampling probe head position.

[0130] By employing an encoder and sensor in conjunction, the encoder converts the axial position of the sampling probe into a signal through real-time monitoring of the probe's position. This signal is then transmitted to the switching valve via the control system. Based on pre-defined logic, the valve position automatically adjusts according to changes in the sampling position, ensuring a perfect match between the gas sample selection and the sampling location.

[0131] 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 command of the external controller, thus avoiding sampling errors.

[0132] The linked coding design ensures accurate and rapid switching between multiple sampling locations, eliminating the risks of traditional manual operation or incorrect switching, and greatly improving the level of automation and intelligence.

[0133] This linkage mechanism provides flexibility and accuracy during the dynamic sampling process, ensuring that the target analytical instrument can switch between different sampling locations without sample confusion or analytical errors.

[0134] By optimizing the control method of the multi-channel switching valve and its linkage with the axial position of the sampling probe, efficient and accurate gas sampling and analysis were achieved, improving the automation level and accuracy of the tubular furnace sampling and detection method.

[0135] In one possible implementation, embodiments of the present invention require determining a reasonable delay time, which is set to ensure that after the sampling probe moves to a new position, the gas sample can be fully stable and accurately reflect the gas composition at that position.

[0136] During the experiment, a tracer gas was introduced at the inlet of the reaction tube in the tube furnace. A tracer gas is a substance detectable by a target analysis instrument, and its concentration changes are highly correlated with changes in gas flow. The selection of a tracer gas typically requires it to be chemically stable and capable of rapidly responding to changes in the sampling location.

[0137] The sampling probe is moved from its original position to a new axial position. At this time, the target analyzer continues to monitor the concentration change of the tracer gas.

[0138] After the sampling location is changed, the output of the target analyzer will show a curve of the tracer gas concentration change. Typically, the tracer gas concentration will change as the sample is taken from the new location, and this process will stabilize after a certain delay.

[0139] By monitoring the tracer gas concentration curve, the time required from the completion of the sampling location switch to the point where the concentration curve reaches a stable plateau is determined. This time is the delay time, representing the waiting time required for the target analyzer to achieve stable readings after the switch is completed.

[0140] After the sampling probe moves to the new position, the flow control valve will only open after a predetermined delay. The flow control valve will only open after this delay to ensure that the gas sample taken from the new position has stabilized and accurately reflects the gas composition at that location.

[0141] Once the delay time is determined through tracer experiments, the control system will control the opening timing of the flow regulating valve based on the delay time. That is, after the sampling position is switched, the opening and closing operation of the flow regulating valve will be performed at the end of the delay time to ensure a stable gas sample supply.

[0142] In modern tube furnace systems, this control process is usually performed by an automated system. Through precise time control, the system avoids errors caused by human operation and improves the consistency and reliability of sample analysis.

[0143] By pre-determining the delay time through tracer experiments and precisely controlling the opening timing of the flow regulating valve based on this time, the stability and accuracy of samples during tubular furnace sampling 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 enhances the accuracy and reliability of the analytical results from the target analytical instrument.

[0144] In one possible implementation, during the in-situ extraction and primary depressurization of the high-pressure sample gas, a micro-flow precision needle valve is used to regulate the flow rate of the sample gas. A stepper motor adjusts the gas flow rate by precisely controlling the opening of the needle valve, and the operation of the stepper motor relies on a closed-loop control mode to maintain stable flow rate and gas concentration.

[0145] Closed-loop control mode refers to using the gas concentration signal detected by the target analyzer as feedback, and then adjusting the stepper motor in real time through the control system to ensure that the gas flow rate 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 the 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 concentration fluctuations of key components and stabilize them at an ideal state.

[0146] The core logic of the control system uses the stability of the concentration signal of the key component detected by the target analyzer as feedback to monitor changes in gas composition in real time. By adjusting the opening of the needle valve, the standard deviation of the concentration signal is kept below a preset threshold. A decrease in the standard deviation indicates that the gas concentration is stabilizing, thus ensuring the representativeness of the gas and the reliability of the data during the sampling process.

[0147] During gas sampling, the opening of the micro-flow precision needle valve may require continuous fine-tuning as the sample gas flow rate and pressure change. Through closed-loop control, the stepper motor can automatically fine-tune the needle valve opening based on fluctuations in the feedback signal under real-time monitoring, thereby reducing concentration fluctuations. This fine-tuning process is dynamic, meaning the control system can respond quickly to real-time changes rather than simply relying on a preset fixed opening, thus achieving higher precision control.

[0148] The system calculates the standard deviation of the concentration signal to determine whether it meets preset stability requirements. If the standard deviation exceeds a threshold, the system automatically adjusts the needle valve opening to reduce concentration fluctuations until the fluctuations are within the set range. This control mechanism ensures the stability of the gas composition during sampling, improving the repeatability and reliability of the analytical results.

[0149] The opening of the micro-flow precision needle valve is dynamically fine-tuned using a closed-loop control mode to ensure the stability and representativeness of the gas samples. This control method significantly improves the automation level of the sampling process, ensures high repeatability and accuracy of analytical results, while reducing human interference and operational errors, and optimizing the control precision and stability of the tubular furnace sampling and detection process.

[0150] In one possible implementation, the sampling probe is first placed at the inlet of the tubular furnace reaction tube to ensure accurate collection of the gas sample entering the reaction tube. The position of the sampling probe is crucial; it must be ensured that it contacts a representative sample gas so that the calibration results reflect the actual experimental conditions.

[0151] A standard gas mixture of known concentration is introduced into the reaction tube. In this step, the concentration of the standard gas mixture must be accurately determined beforehand and representative of typical gas components within the measurement range of the target analytical instrument. The main heater of the tube furnace is not activated during this operation to avoid potential gas changes during heating that could affect the calibration results.

[0152] Under conditions where the tubular furnace is not heated, the sampling and detection method is performed. This involves starting the entire sampling and detection system, including sampling, depressurization, and separation processes, and then using a target analytical instrument to detect the concentration of each component in the standard gas mixture. At this point, the measured concentration values ​​of each component should be compared with the known concentration values ​​of the standard gas.

[0153] The concentration values ​​of each component measured by the target analytical instrument are compared with the known concentration values ​​of the standard gas. Based on the comparison results, a set of correction factors are calculated. These factors can correct for possible errors in the system, including equipment deviations, environmental changes, and other factors. Specifically, the correction factors are usually calculated as the ratio between the known concentration value and the measured concentration value.

[0154] In subsequent formal experiments, all test results are multiplied by the corresponding correction factor. This operation eliminates systematic errors caused by sampling systems, analytical instruments, or environmental factors, thereby ensuring the accuracy and reliability of the data processing results.

[0155] 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, then the correction factor for that component is K = C_std / C_measured.

[0156] In actual experiments, all test results are multiplied by a corresponding correction factor to correct for errors introduced by instruments, sampling systems, pipelines, etc.

[0157] By calibrating the system before each experiment using the tube furnace, the accuracy of the sampling and detection methods and the reliability of the data during the experiment can be ensured. The calibration process, through comparison with known standard gases, yields a correction factor, which is then applied in subsequent data processing. This effectively eliminates systematic errors and guarantees high precision and consistency of the experimental results. This process not only enhances the stability of the sampling and detection system but also improves the reliability and comparability of the experimental data, providing strong support for the accuracy of subsequent experiments.

[0158] Accordingly, embodiments of the present invention also provide a sampling and detection system for a tube furnace, including a memory configured to store instructions, a processor configured to retrieve the instructions from the memory, and capable of implementing a sampling and detection method for a tube furnace as described in any embodiment of the present invention when executing the instructions.

[0159] The following examples will illustrate this in detail:

[0160] This invention relates to a gas detection system based on standard gas calibration, suitable for accurate measurement of gas concentration in industrial and environmental monitoring fields, particularly for calibrating and testing the accuracy of gas sensors in complex environments. This embodiment mainly describes the application of this system in a chemical plant for real-time monitoring of the concentration of multiple components in exhaust gas.

[0161] Standard gas mixture: The standard gas is prepared using a gas flow control device, and the gas concentrations are: NO2 100ppm, CO 50ppm, SO2 30ppm.

[0162] Sensor equipment: Gas sensor from manufacturer A, model B (detection range: 0-1000ppm), with a sensitivity of 0.5ppm.

[0163] Data acquisition system: Uses a model C data acquisition instrument with an acquisition frequency of 1Hz.

[0164] Environmental conditions: Temperature 25°C, humidity 50%.

[0165] The laboratory is well-ventilated and uses a flowing gas environment to simulate the gas composition of chemical plant exhaust gases.

[0166] The gas flow rate in the laboratory is controlled at 2L / min, and the gas concentration is controlled by a standard gas flow controller.

[0167] Preparation of standard gas mixtures: High-purity gases NO2, CO, and SO2 are used. The flow ratio of each gas is adjusted through a gas flow control system to ensure the accuracy of the concentration of the generated standard gas mixture.

[0168] Calibration of gas concentrations: Experimental calibration was performed using standard gases of known concentrations, namely NO2 100ppm, CO 50ppm, and SO2 30ppm.

[0169] The gas sensor was initially calibrated using the standard gas, and the sensor measurement results were recorded. Preliminary experimental results are as follows:

[0170] Measured NO2 concentration: 98 ppm;

[0171] Measured CO concentration: 48 ppm;

[0172] The measured SO2 concentration was 32 ppm.

[0173] Because the measured results have a certain error compared to the standard gas concentration, calibration is required.

[0174] The calibration factor for each gas is calculated using the following formula:

[0175] Calibration factor ;

[0176] Regarding NO2:

[0177] ;

[0178] For CO:

[0179] ;

[0180] For SO2:

[0181] ;

[0182] The gas concentration measured in the experiment is corrected using a calibration factor. Assume the gas concentration measured in the actual experiment is:

[0183] The measured NO2 concentration was 98 ppm.

[0184] CO concentration measured: 48 ppm;

[0185] The measured SO2 concentration was 32 ppm.

[0186] Correct the measured data:

[0187] Corrected NO2 concentration: 98ppm × 1.02 = 100ppm

[0188] Corrected CO concentration: 48ppm × 1.04 = 50.16ppm

[0189] Corrected SO2 concentration: 32ppm × 0.94 = 30.08ppm

[0190] The corrected data were compared with standard gas concentrations to verify the effectiveness of the calibration method. Experimental results show that the corrected NO2, CO, and SO2 concentrations are very close to the standard gas concentrations, with an accuracy within ±0.5%, indicating that the calibration method can effectively eliminate the measurement error of the gas sensor.

[0191] Calibrate gas concentration:

[0192] NO2 concentration: 100 ppm;

[0193] CO concentration: 50 ppm;

[0194] SO2 concentration: 30 ppm;

[0195] Gas sensor sensitivity: 0.5 ppm;

[0196] Error range for measuring gas concentration: ±2%.

[0197] Calibration factor formula:

[0198] ;

[0199] Correction formula for measured values:

[0200] ;

[0201] In traditional calibration methods, the calibration process typically relies on manual adjustments and experience to determine gas concentrations. However, due to the dynamic response of gas sensors and environmental changes, the calibration accuracy of traditional methods is relatively low, often resulting in errors of 3% to 5%. For example, using traditional methods, the measured NO2 concentration is 97 ppm, CO concentration is 47 ppm, and SO2 concentration is 33 ppm, which are relatively large errors.

[0202] The calibration method of this invention, by introducing a precise calibration factor and algorithm to correct the sensor measurements, can effectively reduce the error to ±0.5%, keeping the difference between the experimental measurements and the standard gas concentration within a very small range. Experimental results show that:

[0203] Corrected NO2 concentration: 100 ppm;

[0204] Corrected CO concentration: 50.16 ppm;

[0205] Corrected SO2 concentration: 30.08 ppm.

[0206] This demonstrates that the method of the present invention significantly improves the accuracy and reliability of gas concentration measurement.

[0207] Due to sensor sensitivity limitations, a measurement error of 0.5 ppm may exist. This error has been effectively eliminated through calibration and data correction.

[0208] In practical applications, environmental factors such as temperature, humidity, and air pressure have a significant impact on gas sensors. Through multiple calibrations in experiments, this invention can effectively adapt to different environmental conditions and improve the robustness of the system.

[0209] This invention 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 shows that the method of this invention can control the gas concentration measurement error within ±0.5%, which is approximately 2-3 times more accurate than traditional methods.

[0210] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0211] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A sampling and testing method for a tubular furnace, characterized in that, Includes the following steps: Synchronous acquisition of reaction environment parameters and pre-calculation of sampling conditions: When the tubular furnace is operating in the set high temperature and high pressure reaction state, the real-time pressure value and real-time temperature value in the reaction tube are collected synchronously; based on the real-time pressure value and real-time temperature value, as well as the working pressure that the target analytical instrument can withstand, the preheating temperature of the sampling pipeline and the set value of the first-stage decompression pressure that need to be maintained during this sampling process are calculated. Positioning and preheating of the multi-channel sampling probe: Insert a sampling probe with multiple independent capillaries inside into the reaction tube and position it at a predetermined axial position; then, based on the preheating temperature of the sampling pipeline, perform full-line heating and constant temperature control on the entire sample delivery path starting from the sampling probe. In-situ extraction and first-stage pressure reduction of high-pressure sample gas: Open the flow regulating valve and use the pressure difference inside and outside the reaction tube to make the reaction gas flow from the current sampling position into the temperature-controlled capillary tube; the outflowing temperature-controlled sample gas enters a similarly temperature-controlled pre-pressure stabilizing chamber for flow stabilization, and then its pressure is precisely reduced to the first-stage pressure reduction set value through a back pressure regulating valve. The sample gas undergoes a two-stage decompression and rapid introduction process: The sample gas, after undergoing a first-stage decompression and achieving stable pressure, is introduced into a constant-temperature capillary flow resistance pressure reducer for a second expansion and decompression, reducing its pressure to the operating pressure range of the target analytical instrument; then, the decompressed sample gas is rapidly introduced into the target analytical instrument through a short, inertized, and heated transmission line. Analysis and channel switching steps: The target analysis instrument performs component analysis on the gas sample; after the analysis is completed, switch to the new sampling axis position, and repeat the above steps until sampling and detection at all preset positions are completed.

2. The sampling and testing method for a tubular furnace according to claim 1, characterized in that, The steps for synchronous acquisition of reaction environment parameters and pre-calculation of sampling conditions include: The real-time pressure value is obtained by continuous measurement using a pre-calibrated pressure sensor installed on the reaction tube wall; The real-time temperature value is obtained by continuous measurement using a pre-calibrated thermocouple inserted at the axial center of the reaction tube. The preheating temperature of the sampling pipeline is determined by querying a preset database or phase diagram containing the correspondence between pressure, temperature and gas phase dew point. The determination process is as follows: with the real-time pressure value and real-time temperature value as input, the dew point curve of the current reaction gas is found in the database or phase diagram. The value of the preheating temperature of the sampling pipeline must be higher than the dew point curve by a temperature rise margin determined in advance through experiments, so as to ensure that the sample gas remains in a superheated state throughout the entire sample delivery path and does not condense. The first-level pressure reduction setting value is a percentage of the maximum operating pressure that the target analytical instrument can withstand, and this percentage is preset according to industry-standard safety design specifications.

3. The sampling and testing method for a tubular 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 has a coaxial multi-tube structure. Its outermost layer is a pressure-bearing and protective shell made of high-temperature resistant alloy. Its interior is tightly encapsulated with multiple parallel micro-fine quartz capillaries or inert alloy capillaries, forming the multiple independent capillaries. The inlet of each of the micro-quartz capillaries is distributed along the axial direction at a specific interval at the head of the sampling probe. This interval is determined experimentally in advance based on the axial concentration gradient resolution of the reaction tube to be studied. The outlets of all the micro-quartz capillaries converge at the tail of the sampling probe to a common multi-channel switching valve or directly to a common outlet. The entire sample delivery path includes the micro-quartz capillary inside the sampling probe, the pipeline connecting the sampling probe outlet to the pre-pressure stabilizing chamber, the pre-pressure stabilizing chamber itself, and the pipeline connecting the back pressure regulating valve to the capillary flow resistance pressure reducer. The entire heating and constant temperature control is achieved by a flexible heating sleeve or wound heating wire wrapped around the outside of the entire sample delivery path. Its temperature is fed back to a PID temperature controller through distributed temperature sensors, which dynamically adjusts the heating power to stabilize the temperature at the preheating temperature of the sampling pipeline.

4. The sampling and testing method for a tubular furnace according to claim 1, characterized in that, The in-situ extraction and first-stage depressurization steps of the high-pressure sample gas include: The flow regulating valve is a high-temperature resistant micro-flow precision needle valve. Its 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 gas flow that does not disturb the internal flow field of the reaction tube under the current pressure difference. The pre-stabilizing chamber is a cavity device whose internal volume has been precisely calculated. The method for determining its volume is as follows: by experimental measurement or fluid simulation, the fluctuation frequency and amplitude of the sample gas flow pressure under typical operating conditions are obtained. The volume of the pre-stabilizing chamber needs to provide a buffer time constant sufficient to filter out the pressure fluctuation. The back pressure regulating valve is an electronic back pressure controller. It uses the first-level pressure reduction setpoint as the target pressure setpoint, monitors its output 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, and outputs a sample gas flow with extremely stable pressure.

5. The sampling and testing method for a tubular furnace according to claim 2, characterized in that, The two-stage depressurization and rapid introduction steps for the sample gas include: The capillary flow resistance pressure reducer consists of a spiral-shaped capillary tube with a specific inner diameter and length, and its material is inert stainless steel or quartz. The method for determining the inner diameter and length of the fine-aperture capillary is as follows: According to the principle of gas flow dynamics, the flow resistance generated is directly proportional to the capillary length and inversely proportional to the fourth power of the inner diameter; by pre-setting its inlet pressure to the first-stage pressure reduction set value and the outlet pressure to the working pressure of the target analyzer, and based on the estimated viscosity coefficient and flow rate of the sample gas, a combination of inner diameter and length that can meet the pressure drop requirements is determined through simulation calculation. The capillary flow resistance pressure reducer is placed in a separate, precisely temperature-controlled insulated box. The set temperature of the insulated box is higher than the dew point temperature of the sample gas at the current pressure after the two-stage pressure reduction. The dew point temperature is determined by querying the database or phase diagram. The heat tracing temperature of the short transmission line is consistent with the set temperature of the insulation box.

6. The sampling and testing method for a tubular furnace according to claim 3, characterized in that, The multi-channel switching valve is a multi-position multi-way valve, whose valve position is linked to the axial position of the sampling probe. When it is necessary to switch the sampling position, the multi-position multi-way valve synchronously switches to the corresponding channel under the instruction of the external controller, ensuring that the target analyzer always analyzes the gas sample corresponding to the current axial position of the sampling probe head.

7. The sampling and testing method for a tubular 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, a predetermined delay time must be waited before the flow regulating valve is opened. The delay time is determined in advance by a tracer experiment. The method is as follows: a tracer gas is introduced into the inlet of the reaction tube, and then the sampling position is switched and the change curve of the tracer gas concentration at the output of the target analyzer is monitored. The delay time is determined to be the time required from the completion of the switching to the concentration curve reaching a stable plateau.

8. The sampling and testing method for a tubular furnace according to claim 4, characterized in that, In the in-situ extraction and first-stage decompression of the high-pressure sample gas, the stepper motor controls the opening of the micro-flow precision needle valve in a closed-loop control mode. The control logic is as follows: using the stability of the concentration signal of the key component detected by the target analyzer as the feedback quantity, the opening of the needle valve is dynamically fine-tuned 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 tubular furnace according to claim 1, characterized in that, Before each series of experiments is started using the tubular furnace, a system calibration step is required. This calibration step involves placing the sampling probe at the inlet of the reaction tube and introducing a standard gas mixture of known concentration into the reaction tube without turning on the main heater of the tubular furnace. Then, the sampling and detection method is executed, and the concentration values ​​of each component measured by the target analyzer are compared with the known concentration values ​​of the standard gas to obtain a set of correction factors. In the subsequent data processing of formal experiments, all detection results are multiplied by the corresponding correction factors to eliminate systematic errors that may be caused by the entire sampling system.

10. A sampling and detection system for a tubular furnace, characterized in that, Includes a memory configured to store instructions, a processor configured to retrieve the instructions from the memory, and, when executing the instructions, to implement a sampling and detection method for a tubular furnace as described in any one of claims 1-9.

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