Gas phase residence time distribution determination system and method

Abstract

The invention relates to the technical field of chemical engineering, in particular to a gas phase residence time distribution measuring system and a gas phase residence time distribution measuring method. The gas source unit is used for conveying compressed gas into the fixed bed reactor; the tracer agent supply unit is used for conveying a tracer agent into the fixed bed reactor; the tracer concentration measuring part is arranged at the gas outlet end of the fixed bed reactor and is used for measuring the concentration of the tracer at the gas outlet end of the fixed bed reactor in real time; and the curve generation unit is used for generating a gas phase retention time distribution characteristic curve corresponding to fluid in the fixed bed reactor according to the tracer concentration, measured by the tracer concentration measurement part in real time, of the gas outlet end of the fixed bed reactor. By applying the measuring system, the gas phase residence time distribution characteristic curve can be rapidly and accurately measured, and reliable data support is provided for gas flow characteristic analysis in the fixed bed reactor.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, and in particular to a system and method for measuring gas phase residence time distribution. Background Art

[0002] Fixed-bed reactors are widely used in chemical catalysis due to their simple structure, stable operation, and easy catalyst loading and unloading. Their reaction efficiency depends crucially on the gas residence time distribution (RTD). Accurately measuring RTD is crucial for understanding reactor flow characteristics, optimizing conversion and product selectivity, developing kinetic models, and achieving reactor scale-up.

[0003] At present, RTD experimental determination mainly relies on pulse tracer method and step tracer method, but the related technologies and applications are mostly concentrated in liquid phase systems. This is because liquid phase tracers are easy to implement, have high detection sensitivity and little interference with the flow state. In contrast, there is a significant lack of accurate RTD measurement methods suitable for gas phase systems, and there are obvious limitations: on the one hand, the injection control of gas phase tracers is difficult, and the traditional pulse tracer method has high requirements for the accuracy of valves and control systems, which is prone to errors due to injection technology; on the other hand, the gas phase detection method is not sensitive enough, and it is difficult to capture the changes in tracer concentration in real time and accurately, resulting in low reliability of measurement results. In addition, the existing gas phase RTD measurement system has a complex structure and high cost, which makes it difficult to meet the needs of rapid and accurate measurement of reactor flow characteristics in engineering applications.

[0004] Therefore, there is an urgent need for a gas phase residence time distribution measurement system and method to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the above-mentioned background technology and to provide a gas phase residence time distribution measurement system and method.

[0006] In order to achieve the above object, the first aspect of the present invention provides a gas phase residence time distribution measurement system, the gas phase residence time distribution measurement system comprising: Fixed bed reactor; a gas source unit, for delivering compressed gas to the interior of the fixed bed reactor; a tracer supply unit, configured to deliver the tracer into the interior of the fixed bed reactor; a tracer concentration measuring element, disposed at the gas outlet of the fixed bed reactor, for measuring the tracer concentration at the gas outlet of the fixed bed reactor in real time; A curve generating unit is used to generate a gas phase residence time distribution characteristic curve corresponding to the fluid in the fixed bed reactor according to the tracer concentration at the gas outlet end of the fixed bed reactor measured in real time by the tracer concentration measuring element.

[0007] Preferably, the gas source unit comprises: a buffer tank, a gas delivery end of which is connected to a gas inlet end of the fixed bed reactor; a gas compressor, configured to deliver compressed gas to the buffer tank; A mass flow meter is used to measure the compressed gas flow at the gas delivery end of the buffer tank in real time, and to adjust the compressed gas flow at the gas delivery end of the buffer tank by adjusting the compressed gas flow output by the gas compressor; The tracer supply unit comprises: Tracer tank; A mass flow controller, whose air inlet end is connected to the tracer tank and whose air delivery end is connected to the fixed bed reactor, is used to control the flow rate of the tracer delivered to the fixed bed reactor.

[0008] Preferably, a gas mixing device is further included, wherein the gas supply ends of the buffer tank and the mass flow controller are both connected to the gas mixing device, and the gas supply end of the gas mixing device is connected to the gas inlet end of the fixed bed reactor, for mixing the compressed gas and the tracer and then delivering them to the fixed bed reactor; A flow sensor is provided on the gas delivery pipeline between the gas delivery end of the gas mixing device and the gas inlet end of the fixed bed reactor, for measuring the flow rate of the mixed gas delivered to the fixed bed reactor in real time.

[0009] Preferably, the gas mixing device comprises: a shell, wherein a mixing chamber is formed inside the shell, and a bottom outlet of the mixing chamber is connected to an air inlet end of the fixed bed reactor; A Y-shaped flow divider is provided at the compressed gas inlet at the top of the mixing chamber, and is used to evenly disperse the compressed gas into multiple streams before injecting them into the mixing chamber; An annular injection pipe is horizontally arranged in the middle of the mixing chamber, and a plurality of injection holes are evenly distributed along the circumference of the annular injection pipe. The axes of the injection holes form an angle of 30-60 degrees with the axis of the mixing chamber, and the extended lines of the axes of all the injection holes intersect at the same point on the axis of the mixing chamber, forming a converging injection layout for injecting the tracer into the mixing chamber; The porous mixing plate is horizontally arranged in the mixing chamber and located below the annular injection pipe, and is used for secondary mixing of the compressed gas and the tracer and generating vortex.

[0010] Preferably, it also includes: a pressure detection unit, the pressure detection unit being used to detect the gas pressure at the gas outlet end of the buffer tank and the gas pressure at the gas outlet end of the gas mixing device; A control unit is electrically connected to the pressure detection unit and the gas compressor, and is used to dynamically adjust the power of the gas compressor according to the detection result of the pressure detection unit so that the flow rate of the mixed gas introduced into the air inlet end of the fixed bed reactor is the same as the flow rate of the compressed gas introduced alone.

[0011] A second aspect of the present invention provides a method for measuring gas phase residence time distribution, which is applied to the above-mentioned gas phase residence time distribution measurement system. The gas phase residence time distribution measurement method includes: The compressed gas output by the gas compressor of the gas source unit is transported to the fixed bed reactor through the buffer tank and the gas mixing device in sequence, and the flow rate of the compressed gas is adjusted by a mass flow meter; When the compressed gas flow rate at the gas inlet end of the fixed bed reactor meets a first set condition, the tracer in the tracer tank of the tracer supply unit is delivered to the gas mixing device through the mass flow controller at a second set flow rate, and is mixed with the compressed gas in the gas mixing device before being delivered to the fixed bed reactor, wherein the first set condition is the first set flow rate and lasts for a first preset time period; The tracer concentration at the gas outlet of the fixed bed reactor is measured in real time using a tracer concentration measuring device, and a gas phase residence time distribution characteristic curve corresponding to the fluid in the fixed bed reactor is generated based on the tracer concentration at the gas outlet of the fixed bed reactor measured in real time by the tracer concentration measuring device.

[0012] Preferably, it also includes: Obtaining a first pressure and a second pressure, and calculating a first pressure difference based on the first pressure and the second pressure; the first pressure is the gas pressure at the gas outlet end of the buffer tank when the first set condition is met, and the second pressure is the gas pressure at the gas inlet end of the fixed bed reactor when the first set condition is met; calculating a first resistance within the gas mixing device based on the first pressure difference and the density of the compressed gas; calculating a second resistance according to the first resistance and a density of a mixed gas of compressed gas and tracer; The adjustment pressure is calculated based on the first resistance, the second resistance and the first pressure difference, and the power of the gas compressor is adjusted based on the adjustment pressure so that the flow rate of the mixed gas introduced into the air inlet end of the fixed bed reactor is the same as the flow rate of the compressed gas introduced alone.

[0013] Preferably, calculating the first resistance in the gas mixing device according to the first pressure difference and the density of the compressed gas specifically includes: ; ; ; in, R 1 is the first resistance, P 1 is the first pressure, P 2 is the second pressure, is the difference between the first pressure and the second pressure, is the density of the compressed gas, is the first flow rate, Set the flow rate for the first time. is the diameter of the mixing chamber; The calculating of the second resistance according to the first resistance and the density of the mixed gas of the compressed gas and the tracer specifically includes: ; ; in, R 2 is the second resistance, is the resistance index obtained from the resistance index mapping database according to the flow rate of the tracer, is the density of the mixed gas, is the density of the tracer, Set the flow rate for the second; The calculating and adjusting the pressure according to the first resistance, the second resistance, and the first pressure difference specifically includes: ; ; in, To regulate pressure, is the pressure of the mixed gas at the inlet end of the fixed bed reactor, is the target pressure difference.

[0014] Preferably, the construction of the resistance index mapping database includes: Various operating conditions were set according to the ratio of tracer flow rate to compressed gas flow rate, and the flow rate at the inlet end of the fixed bed reactor was maintained constant under each operating condition; Repeat the experiment at least three times for each working condition, and collect data pairs corresponding to each working condition, wherein the data pairs include the density of the mixed gas and the corresponding resistance; Iteratively fitting the data pairs of each working condition to obtain a corresponding resistance index, and constructing a resistance index mapping database according to the tracer flow rate and the corresponding resistance index; The calculation formula of the corresponding resistance is: ; The target formula of the iterative fitting is: ; in, For the corresponding resistance, is the measured pressure difference, is the measured flow velocity, k is the coefficient.

[0015] Preferably, the construction of the resistance index mapping database further includes: dynamically revising the resistance index mapping database, and the dynamic revising of the resistance index mapping database specifically includes: After completing the set number of measurement experiments, randomly select a set number of working conditions to re-measure the density and resistance coefficient of the mixed gas; If the deviation between the measured drag coefficient and the calculated value in the drag index mapping database is greater than a set threshold, the data under the working condition is refitted to update the drag index in the resistance index mapping database.

[0016] According to the above technical solution, based on the gas phase residence time distribution measurement system, through the cooperation of the gas compressor, buffer tank and mass flowmeter of the gas source unit, the gas flow rate can be first stabilized and compressed, and then the tracer can be constantly injected through the tracer tank and mass flow controller of the tracer supply unit. During operation, no complex pulse injection device is required, the requirements for valves and control systems are low, and the injection error can be effectively reduced. The tracer concentration at the gas outlet end of the fixed bed reactor can be measured in real time through the tracer concentration measuring device, and the gas phase residence time distribution characteristic curve is then generated by the curve generation unit based on the tracer concentration data. This can achieve rapid and accurate measurement of the gas phase residence time distribution characteristic curve and provide reliable data support for the analysis of gas flow characteristics in the fixed bed reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic structural diagram of a gas phase residence time distribution measurement system in a specific embodiment; Figure 2 1. It is a schematic diagram of the structure of the gas mixing device of the gas phase residence time distribution measurement system; Figure 3 is a schematic diagram of the curve of CO2 tracer concentration changing with time; Figure 4 It is a schematic diagram of the gas phase residence time distribution characteristic curve corresponding to the change of CO2 tracer concentration over time; Figure 5 This is a flow chart of the method for determining gas phase residence time distribution.

[0018] Description of Reference Numerals 1. Fixed bed reactor; 2. Gas compressor; 3. Buffer tank; 4. Mass flow meter; 5. Tracer tank; 6. Mass flow controller; 7. Tracer concentration sensor; 8. Gas mixing device; 9. Flow sensor; 10. Shell; 11. Mixing chamber; 12. Y-type splitter; 13. Annular injection pipe; 14. Injection hole; 15. Porous mixing plate; 16. Control unit; 17. First pressure sensor; 18. Second pressure sensor; 19. Branch pipe. DETAILED DESCRIPTION

[0019] The following describes in detail the specific implementation of the embodiment of the present invention. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0020] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate relative importance or implicitly specify the quantity of the technical features indicated. Therefore, unless otherwise specified, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features; "plurality" means two or more. The term "comprising" and any variations thereof are intended to imply the non-exclusive inclusion, possible presence, or addition of one or more other features, units, components, and / or combinations thereof.

[0021] Furthermore, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly, and may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0022] The first aspect of the present invention provides a gas phase residence time distribution measurement system, such as Figure 1-4 As shown, the gas phase residence time distribution measurement system includes: Fixed bed reactor 1; A gas source unit, used for delivering compressed gas to the interior of the fixed bed reactor 1; a tracer supply unit, configured to deliver the tracer into the interior of the fixed bed reactor; a tracer concentration measuring device, provided at the gas outlet end of the fixed bed reactor 1, for measuring the tracer concentration at the gas outlet end of the fixed bed reactor 1 in real time; specifically, the tracer concentration measuring device is a tracer concentration sensor 7; The curve generating unit is used to generate a gas phase residence time distribution characteristic curve corresponding to the fluid in the fixed bed reactor 1 according to the tracer concentration at the gas outlet end of the fixed bed reactor 1 measured in real time by the tracer concentration measuring unit.

[0023] In a preferred embodiment, the gas source unit includes: A buffer tank 3, a gas transmission end of which is connected to an air inlet end of the fixed bed reactor 1; A gas compressor 2, used for delivering compressed gas to the buffer tank 3; The mass flow meter 4 is used to measure the compressed gas flow at the gas delivery end of the buffer tank 3 in real time, and to adjust the compressed gas flow at the gas delivery end of the buffer tank 3 by adjusting the compressed gas flow output by the gas compressor 2; The tracer supply unit comprises: Tracer tank 5; The mass flow controller 6 has an air inlet end connected to the tracer tank 5 and a gas delivery end connected to the fixed bed reactor 1 , and is used to control the flow rate of the tracer delivered to the fixed bed reactor 1 .

[0024] Specifically, the experimental process for determining the gas phase residence time distribution characteristic curve in the fixed bed reactor 1 is as follows: at the beginning of the experiment, the gas compressor 2 is turned on to generate compressed air, and the compressed air is introduced into the air inlet end at the top of the fixed bed reactor 1 through the air pipe. After confirming that the air path is unobstructed and there is no leakage, the main air flow compressed air flow at the air inlet end of the fixed bed reactor 1 is adjusted by the mass flow meter 4; after the mainstream flow is stable, the tracer tank 5 is opened, and the mass flow controller 6 is used to accurately control and continuously output a constant flow of CO2 tracer, and introduce it into the fixed bed reactor 1 through the air pipe; at the same time, the tracer concentration sensor 7 is used to measure the CO2 tracer concentration at the air outlet end of the fixed bed reactor 1 in real time, and its concentration data changing with time is recorded, such as Figure 3 As shown; then, the curve generating unit performs normalization processing on the concentration data of the CO2 tracer concentration measured in real time by the tracer concentration sensor 7, that is, the CO2 tracer concentration value at the outlet of the fixed bed reactor 1 is divided by the CO2 tracer concentration value at the inlet of the fixed bed reactor 1, and finally generates a gas phase residence time distribution characteristic curve corresponding to the fluid in the fixed bed reactor 1. ,like Figure 4 shown.

[0025] ; in, is the gas phase residence time distribution characteristic curve, is the CO2 tracer concentration at the outlet of the fixed bed reactor, is the CO2 tracer concentration at the inlet end of the fixed bed reactor.

[0026] In an embodiment of the present invention, the gas flow rate can be stabilized by first compressing the gas flow rate through the coordination of the gas compressor, buffer tank, and mass flow meter of the gas source unit, and then the tracer can be constantly injected through the tracer tank and mass flow controller of the tracer supply unit. During operation, no complex pulse injection device is required, the requirements for valves and control systems are low, and the injection error can be effectively reduced. The tracer concentration measuring device can measure the tracer concentration at the outlet of the fixed bed reactor in real time, and then the curve generation unit generates a gas phase residence time distribution characteristic curve based on the tracer concentration data, which can achieve rapid and accurate determination of the gas phase residence time distribution characteristic curve and provide reliable data support for the analysis of gas flow characteristics in the fixed bed reactor. Among them, there are many types of gas tracers. The reason why CO2 is preferred as a tracer in the present invention is that it is low in cost, safe and easy to obtain.

[0027] Further preferably, the gas phase residence time distribution measurement system further includes a gas mixing device 8, the gas delivery ends of the buffer tank 3 and the mass flow controller 6 are both connected to the gas mixing device 8, and the gas delivery end of the gas mixing device 8 is connected to the gas inlet end of the fixed bed reactor 1, for mixing the compressed gas and the tracer and then delivering them to the fixed bed reactor 1. By further providing the gas mixing device 8, the CO2 tracer and the compressed air can be fully mixed before the CO2 tracer is introduced into the fixed bed reactor 1, thereby improving the uniformity of the CO2 tracer concentration in the mixed gas at the gas inlet end of the fixed bed reactor 1, eliminating local tracer concentration fluctuations, and avoiding characteristic curve distortion caused by uneven mixing, thereby further improving the accuracy of the gas phase residence time distribution characteristic curve measurement.

[0028] Further preferably, a flow sensor 9 is provided on the gas delivery pipeline between the gas delivery end of the gas mixing device 8 and the gas inlet end of the fixed-bed reactor 1 for real-time measurement of the flow rate of the mixed gas delivered to the fixed-bed reactor 1. Since the flow rate after the introduction of the CO2 tracer must be the same as the flow rate when compressed air alone is introduced during the measurement process, monitoring by the flow sensor 9 allows for timely feedback adjustment of the system, thereby ensuring a constant flow rate before and after the introduction of the CO2 tracer, providing a stable flow rate reference for RTD measurement and ensuring test continuity.

[0029] In a specific embodiment, the gas mixing device 8 includes: A housing 10, wherein a mixing chamber 11 is formed inside the housing 10, and a bottom outlet of the mixing chamber 11 is connected to an air inlet end of the fixed bed reactor 1; A Y-shaped flow divider 12 is provided at the compressed gas inlet at the top of the mixing chamber 11 and is used to evenly disperse the compressed gas into multiple streams before injecting them into the mixing chamber 11; An annular injection pipe 13 is horizontally disposed in the middle of the mixing chamber 11. A plurality of injection holes 14 are evenly distributed along the circumference of the annular injection pipe 13. The axes of the injection holes 14 form an angle of 30-60° with the axis of the mixing chamber 11. The extended lines of the axes of all the injection holes 14 intersect at the same point on the axis of the mixing chamber 11, forming a converging injection layout for injecting the tracer into the mixing chamber 11. The porous mixing plate 15 is horizontally arranged in the mixing chamber 11 and located below the annular injection pipe 13, and is used to mix the compressed gas and the tracer for the second time and generate a vortex.

[0030] In the embodiment of the present invention, specifically, the shell 10 is cylindrical, and a cylindrical mixing chamber 11 is formed inside the shell 10. The outlet of the mixing chamber 11 is connected to the air inlet end of the fixed bed reactor 1. A Y-shaped splitter 12 is provided at the inlet of the mixing chamber 11, and an annular injection pipe 13 and a porous mixing plate 15 are provided in the mixing chamber 11. The Y-type splitter 12 is arranged at the inlet end of the mixing chamber 11 and is coaxially arranged with the shell 10. The inlet of the Y-type splitter 12 serves as the compressed air inlet of the gas mixing device 8, and the outlet of the Y-type splitter 12 is connected to the mixing chamber 11; the Y-type splitter 12 includes a plurality of branch pipes 19, and the plurality of branch pipes 19 are arranged along the circumference of the Y-type splitter 12. The plurality of branch pipes 19 are used to divert the compressed air so that the compressed air is evenly divided into multiple branches at the initial stage of entering the mixing chamber; this layout utilizes the momentum distribution principle of the fluid in the bifurcated pipe to convert the high-speed flow of a single airflow into the low-speed uniform flow of multiple thin-layer airflows, laying the foundation for the subsequent uniform mixing of the CO2 tracer. The annular injection pipe 13 is arc-shaped and is arranged in the middle of the mixing chamber 11. The annular injection pipe 13 is coaxially arranged with the mixing chamber 11 and is fixed to the inner wall of the mixing chamber 11. The inlet of the annular injection pipe 13 is connected to the tracer tank 5. A plurality of injection holes 14 are evenly distributed along the circumference of the annular injection pipe 13. The axis of the injection hole 14 and the axis of the mixing chamber 11 preferably form an angle of 45°, and the extended lines of the axes of all the injection holes 14 converge at the same point on the axis of the mixing chamber 11, forming a convergent injection layout, so that the CO2 tracer is injected into the main fluid with oblique momentum, and then the CO2 tracer jet and the compressed air form spiral turbulence in the central area of ​​the mixing chamber 11, thereby enhancing the radial diffusion capacity. The porous mixing plate 15 is arranged perpendicular to the axis of the mixing chamber 11 and is fixed to the side wall of the mixing chamber 11. A plurality of pores are provided on the porous mixing plate 15. A gasket is installed between the edge of the porous mixing plate 15 and the side wall of the mixing chamber 11 to ensure that the airflow flows only through the pores of the plate. The porous mixing plate 15 is located downstream of the annular injection pipe 13, and the axial distance between the porous mixing plate 15 and the annular injection pipe 13 needs to ensure that the CO2 tracer and the compressed air are initially mixed before being subjected to vortex stirring.

[0031] In another preferred embodiment, the gas phase residence time distribution measurement system further comprises: A pressure detection unit, which is used to detect the gas pressure at the gas outlet of the buffer tank 3 and the gas pressure at the gas outlet of the gas mixing device 8; A control unit 16 is electrically connected to the pressure detection unit and the gas compressor 2, and is used to dynamically adjust the power of the gas compressor 2 according to the detection result of the pressure detection unit so that the flow rate of the mixed gas introduced into the air inlet end of the fixed bed reactor 1 is the same as the flow rate of the compressed gas introduced alone.

[0032] In the embodiment of the present invention, specifically, Figure 1As shown, the pressure detection unit includes a first pressure sensor 17 and a second pressure sensor 18. The first pressure sensor 17 is provided in the gas path between the buffer tank 3 and the gas mixing device 8, and is used to detect the gas pressure at the gas outlet of the buffer tank 3. The second pressure sensor 18 is provided in the gas path between the gas mixing device 8 and the fixed bed reactor 1, and is used to detect the gas pressure at the gas inlet of the fixed bed reactor 1. The control unit 16 is preferably a PLC control unit. By collecting real-time pressure data at the gas outlet of the buffer tank 3 and the gas inlet of the fixed bed reactor 1, it dynamically adjusts the power of the gas compressor 2, compensates for the effect of density changes caused by CO2 tracer injection on the flow rate, and further improves the accuracy of the gas phase residence time distribution characteristic curve measurement.

[0033] The second aspect of the present invention provides a method for measuring gas phase residence time distribution, which is applied to the above-mentioned gas phase residence time distribution measurement system, such as Figure 1 、 Figure 2 and Figure 5 As shown, the gas phase residence time distribution determination method comprises the following steps: S1, the compressed gas output by the gas compressor 2 of the gas source unit is transported to the fixed bed reactor 1 through the buffer tank 3 and the gas mixing device 8 in sequence, and the flow rate of the compressed gas is adjusted by the mass flow meter 4; Specifically, step S1 is the preparation stage for the formal measurement experiment. First, the gas compressor 2 is turned on, and compressed air is introduced into the fixed-bed reactor 1 through the buffer tank 3 and gas mixing device 8. Compressed air serves as the carrier gas, and its flow stability is the benchmark for RTD testing. Establishing a stable and smooth flow is essential to eliminate the effects of initial fluctuations. The mass flowmeter 4 then adjusts the compressed air flow at the outlet of the buffer tank 3 so that the flow at the inlet of the fixed-bed reactor 1 meets the first set flow rate required for the test. The mass flowmeter 4 also displays the flow at the outlet of the buffer tank 3.

[0034] S2. When the compressed gas flow rate at the gas inlet end of the fixed bed reactor 1 meets the first set condition, the tracer in the tracer tank 5 of the tracer supply unit is delivered to the gas mixing device 8 through the mass flow controller 6 at a second set flow rate, and is mixed with the compressed gas in the gas mixing device 8 before being delivered to the fixed bed reactor 1, wherein the first set condition is the first set flow rate and lasts for a first preset time period; Specifically, when the compressed air flow rate at the air inlet end of the fixed bed reactor 1 meets the first set flow rate and the duration reaches the first preset time, it indicates that the system has stabilized. Then the tracer tank 5 is opened, and the CO2 tracer flow rate is adjusted to the second set flow rate required for the test through the mass flow controller 6. The CO2 tracer is introduced into the gas mixing device 8 to mix with the compressed air, and finally the mixed gas is introduced through the air inlet end of the fixed bed reactor 1.

[0035] S3. Using a tracer concentration measuring device to measure the tracer concentration at the gas outlet of the fixed bed reactor 1 in real time, and generating a gas phase residence time distribution characteristic curve corresponding to the fluid in the fixed bed reactor 1 based on the tracer concentration at the gas outlet of the fixed bed reactor 1 measured in real time by the tracer concentration measuring device.

[0036] Specifically, the tracer concentration sensor 7 is used to detect the CO2 tracer concentration at the outlet of the fixed bed reactor 1 in real time, and the following is obtained: Figure 3 The concentration change data shown in FIG is then normalized by the curve generation unit to obtain the concentration change data as shown in FIG. Figure 4 The gas phase residence time distribution characteristic curve is shown.

[0037] Based on the above embodiment, in practical applications, a rapid and accurate determination of the gas phase residence time distribution characteristic curve can be achieved, and reliable data support can be provided for the analysis of gas flow characteristics in a fixed bed reactor.

[0038] In a preferred embodiment, the gas phase residence time distribution determination method further comprises: Obtaining a first pressure and a second pressure, and calculating a first pressure difference based on the first pressure and the second pressure; the first pressure is the gas pressure at the gas outlet end of the buffer tank 3 when the first set condition is met, and the second pressure is the gas pressure at the gas inlet end of the fixed bed reactor 1 when the first set condition is met; Calculating a first resistance in the gas mixing device 8 according to the first pressure difference and the density of the compressed gas; calculating a second resistance according to the first resistance and a density of a mixed gas of compressed gas and tracer; The adjustment pressure is calculated based on the first resistance, the second resistance and the first pressure difference, and the power of the gas compressor 2 is adjusted based on the adjustment pressure so that the flow rate of the mixed gas introduced into the air inlet end of the fixed bed reactor 1 is the same as the flow rate of the compressed gas introduced alone.

[0039] In an embodiment of the present invention, the adjustment pressure is further calculated based on the first resistance, the second resistance and the first pressure difference, and the power of the gas compressor 2 is adjusted according to the adjustment pressure, so that the flow rate of the mixed gas introduced into the air inlet end of the fixed bed reactor 1 is the same as the flow rate of the compressed gas introduced alone. In practical applications, the accuracy of the measurement of the gas phase residence time distribution characteristic curve can be further effectively improved.

[0040] In a specific embodiment, the calculating the first resistance in the gas mixing device 8 according to the first pressure difference and the density of the compressed gas specifically includes: ; ; ; in, R 1 is the first resistance, P 1 is the first pressure, P 2 is the second pressure, is the difference between the first pressure and the second pressure, is the density of the compressed gas, is the first flow rate, Set the flow rate for the first time. is the diameter of the mixing chamber; The calculating of the second resistance according to the first resistance and the density of the mixed gas of the compressed gas and the tracer specifically includes: ; ; in, R 2 is the second resistance, is the resistance index obtained from the resistance index mapping database according to the flow rate of the tracer, is the density of the mixed gas, is the density of the tracer, is the second set flow rate, i.e. the flow rate of CO2 tracer; The resistance index mapping database includes multiple CO2 tracer flow ratios and the resistance index corresponding to the flow ratio of each CO2 tracer. The specific resistance mapping database is shown in Table 1 below: Table 1:

[0041] The calculating and adjusting the pressure according to the first resistance, the second resistance, and the first pressure difference specifically includes: ; ; in, To regulate pressure, is the pressure of the mixed gas at the inlet end of the fixed bed reactor, measured by the second pressure sensor 18, The target pressure difference is obtained. Afterwards, the PLC control unit adjusts the power of the gas compressor 2 through PID to keep the reading of the first pressure sensor 17 at At this time, it can be ensured that the flow rate of the mixed gas remains unchanged after the CO2 tracer is introduced.

[0042] Further preferably, the present invention provides a method for constructing the resistance index mapping database, and the construction of the resistance index mapping database includes: A variety of operating conditions are set according to the ratio of the tracer flow rate to the compressed gas flow rate, and the flow rate at the inlet end of the fixed bed reactor 1 is maintained constant under each operating condition; Repeat the experiment at least three times for each working condition, and collect data pairs corresponding to each working condition, wherein the data pairs include the density of the mixed gas and the corresponding resistance; Iteratively fitting the data pairs of each working condition to obtain a corresponding resistance index, and constructing a resistance index mapping database according to the tracer flow rate and the corresponding resistance index; The calculation formula of the corresponding resistance is: ; The target formula of the iterative fitting is: ; in, For the corresponding resistance, is the measured pressure difference, is the measured flow velocity, k is the coefficient.

[0043] Specifically, the method for establishing the resistance index mapping database is as follows: first, four operating conditions are set according to the CO2 tracer flow rate of 5%, 10%, 15% and 20%. Under each operating condition, the inlet flow of the fixed bed reactor 1 is maintained at the first set flow rate, and the air compressor power is adjusted by the PLC control unit to compensate for the density change; then, the experiment is repeated three times for each operating condition, and data pairs consisting of the mixed gas density and the corresponding resistance are collected. After obtaining the three sets of data pairs corresponding to each operating condition, the average value is obtained by averaging; finally, the Levenberg-Marquardt algorithm is used for fitting , coefficient of determination k and resistance index The initial value of the parameter is set, and the convergence condition is that the parameter update amount is less than 0.01% or the number of iterations is greater than or equal to 200 times. After obtaining the resistance index corresponding to each working condition, the resistance index mapping database shown in Table 1 above can be established.

[0044] Further preferably, the construction of the resistance index mapping database further includes: dynamically revising the resistance index mapping database, and the dynamic revising of the resistance index mapping database specifically includes: After completing the set number of measurement experiments, randomly select a set number of working conditions to re-measure the density and resistance coefficient of the mixed gas; If the deviation between the measured drag coefficient and the calculated value in the drag index mapping database is greater than a set threshold, the data under the working condition is refitted to update the drag index in the resistance index mapping database.

[0045] Specifically, the dynamic correction of the resistance index mapping database is as follows: for example, after completing 50 measurement experiments, three working conditions are randomly selected for re-measurement, and the threshold is set to a deviation of >3% between the measured resistance coefficient and the calculated value in the resistance index mapping database. At this time, it is considered that the resistance index mapping database needs to be corrected, and the correction operation is triggered. The correction process is to recalculate the resistance index under the error condition according to the above-mentioned process of establishing the resistance index mapping database, and update the resistance index mapping database.

[0046] The gas phase residence time distribution measurement system and method provided by the present invention can first stabilize the compressed gas flow rate through the cooperation of the gas compressor, buffer tank and mass flowmeter of the gas source unit, and then constantly inject the tracer through the tracer tank and mass flow controller of the tracer supply unit. During operation, no complex pulse injection device is required, the requirements for valves and control systems are low, and the injection error can be effectively reduced. The tracer concentration at the gas outlet end of the fixed bed reactor can be measured in real time through the tracer concentration measuring element. The gas phase residence time distribution characteristic curve is then generated by the curve generation unit based on the tracer concentration data. This can achieve rapid and accurate measurement of the gas phase residence time distribution characteristic curve and provide reliable data support for the analysis of gas flow characteristics in the fixed bed reactor.

[0047] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical scope of the present invention, various simple variations of the technical solution of the present invention may be made. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple variations and combinations should also be considered as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A gas phase residence time distribution measurement system, characterized in that: The gas phase residence time distribution measurement system comprises: Fixed bed reactor (1); A gas source unit, used for delivering compressed gas to the interior of the fixed bed reactor (1); a tracer supply unit, used for delivering the tracer into the interior of the fixed bed reactor (1); A tracer concentration measuring element is provided at the gas outlet of the fixed bed reactor (1) and is used to measure the tracer concentration at the gas outlet of the fixed bed reactor (1) in real time; A curve generating unit is used to generate a gas phase residence time distribution characteristic curve corresponding to the fluid in the fixed bed reactor (1) based on the tracer concentration at the gas outlet of the fixed bed reactor (1) measured in real time by the tracer concentration measuring element.

2. The gas phase residence time distribution measurement system according to claim 1, characterized in that: The gas source unit comprises: A buffer tank (3), a gas delivery end of which is connected to an air inlet end of the fixed bed reactor (1); A gas compressor (2) for delivering compressed gas to the buffer tank (3); A mass flow meter (4) is used to measure the compressed gas flow at the gas transmission end of the buffer tank (3) in real time, and to adjust the compressed gas flow at the gas transmission end of the buffer tank (3) by adjusting the compressed gas flow output by the gas compressor (2); The tracer supply unit comprises: Tracer tank (5); A mass flow controller (6) has an air inlet end connected to the tracer tank (5) and a gas delivery end connected to the fixed bed reactor (1), and is used to control the flow rate of the tracer delivered to the fixed bed reactor (1).

3. The gas phase residence time distribution measurement system according to claim 2, characterized in that: It also includes a gas mixing device (8), the gas delivery ends of the buffer tank (3) and the mass flow controller (6) are both connected to the gas mixing device (8), and the gas delivery end of the gas mixing device (8) is connected to the gas inlet end of the fixed bed reactor (1), for mixing the compressed gas and the tracer and then delivering them to the fixed bed reactor (1); A flow sensor (9) is provided on the gas delivery pipeline between the gas delivery end of the gas mixing device (8) and the gas inlet end of the fixed bed reactor (1) for real-time measurement of the flow rate of the mixed gas delivered to the fixed bed reactor (1).

4. The gas phase residence time distribution measurement system according to claim 3, characterized in that: The gas mixing device (8) comprises: A shell (10), wherein a mixing chamber (11) is formed inside the shell (10), and a bottom outlet of the mixing chamber (11) is communicated with an air inlet end of the fixed bed reactor (1); A Y-shaped flow divider (12) is provided at the compressed gas inlet at the top of the mixing chamber (11) and is used to evenly disperse the compressed gas into multiple streams before injecting them into the mixing chamber (11); An annular injection pipe (13) is horizontally arranged in the middle of the mixing chamber (11), and a plurality of injection holes (14) are evenly distributed along the circumference of the annular injection pipe (13), wherein the axis of the injection hole (14) forms an angle of 30-60° with the axis of the mixing chamber (11), and the extended lines of the axes of all the injection holes (14) intersect at the same point on the axis of the mixing chamber (11), forming a convergent injection layout for injecting the tracer into the mixing chamber (11); A porous mixing plate (15) is horizontally arranged in the mixing chamber (11) and located below the annular injection pipe (13), and is used to cause secondary mixing of the compressed gas and the tracer and generate vortexes.

5. The gas phase residence time distribution measurement system according to claim 3 or 4, characterized in that: Also includes: A pressure detection unit, the pressure detection unit is used to detect the gas pressure at the gas outlet end of the buffer tank (3) and the gas pressure at the gas outlet end of the gas mixing device (8); A control unit (16) is electrically connected to the pressure detection unit and the gas compressor (2), and is used to dynamically adjust the power of the gas compressor (2) according to the detection result of the pressure detection unit, so that the flow rate of the mixed gas introduced into the air inlet of the fixed bed reactor (1) is the same as the flow rate of the compressed gas introduced alone.

6. A method for measuring gas phase residence time distribution, characterized in that: The gas phase residence time distribution measurement system according to any one of claims 1 to 5, wherein the measurement method comprises: The compressed gas outputted by the gas compressor (2) of the gas source unit is sequentially transported to the fixed bed reactor (1) through the buffer tank (3) and the gas mixing device (8), and the flow rate of the compressed gas is adjusted by the mass flow meter (4); When the compressed gas flow rate at the air inlet end of the fixed bed reactor (1) satisfies a first set condition, the tracer in the tracer tank (5) of the tracer supply unit is delivered to the gas mixing device (8) through the mass flow controller (6) at a second set flow rate, and is mixed with the compressed gas in the gas mixing device (8) and then delivered to the fixed bed reactor (1), wherein the first set condition is the first set flow rate and lasts for a first preset time period; The tracer concentration at the gas outlet of the fixed bed reactor (1) is measured in real time using a tracer concentration measuring device, and a gas phase residence time distribution characteristic curve corresponding to the fluid in the fixed bed reactor (1) is generated based on the tracer concentration at the gas outlet of the fixed bed reactor (1) measured in real time by the tracer concentration measuring device.

7. The method for measuring gas phase residence time distribution according to claim 6, wherein: Also includes: Acquiring a first pressure and a second pressure, and calculating a first pressure difference according to the first pressure and the second pressure; The first pressure is the gas pressure at the gas outlet of the buffer tank (3) when the first set condition is met, and the second pressure is the gas pressure at the gas inlet of the fixed bed reactor (1) when the first set condition is met; Calculating a first resistance in the gas mixing device (8) based on the first pressure difference and the density of the compressed gas; calculating a second resistance according to the first resistance and a density of a mixed gas of compressed gas and tracer; The regulating pressure is calculated based on the first resistance, the second resistance and the first pressure difference, and the power of the gas compressor (2) is adjusted based on the regulating pressure so that the flow rate of the mixed gas introduced into the air inlet end of the fixed bed reactor (1) is the same as the flow rate of the compressed gas introduced alone.

8. The method for measuring gas phase residence time distribution according to claim 7, wherein: The calculating of the first resistance in the gas mixing device (8) according to the first pressure difference and the density of the compressed gas specifically includes: ； ； ； in, R 1 is the first resistance, P 1 is the first pressure, P 2 is the second pressure, is the difference between the first pressure and the second pressure, is the density of the compressed gas, is the first flow rate, Set the flow rate for the first time. is the diameter of the mixing chamber; The calculating of the second resistance according to the first resistance and the density of the mixed gas of the compressed gas and the tracer specifically includes: ； ； in, R 2 is the second resistance, is the resistance index obtained from the resistance index mapping database according to the flow rate of the tracer, is the density of the mixed gas, is the density of the tracer, Set the flow rate for the second; The calculating and adjusting the pressure according to the first resistance, the second resistance, and the first pressure difference specifically includes: ； ； in, To regulate pressure, is the pressure of the mixed gas at the inlet end of the fixed bed reactor, is the target pressure difference.

9. The method for measuring gas phase residence time distribution according to claim 8, wherein: The construction of the resistance index mapping database includes: A plurality of operating conditions are set according to the ratio of the tracer flow rate to the compressed gas flow rate, and the flow rate at the inlet end of the fixed bed reactor (1) is maintained constant under each operating condition; Repeat the experiment at least three times for each working condition, and collect data pairs corresponding to each working condition, wherein the data pairs include the density of the mixed gas and the corresponding resistance; Iteratively fitting the data pairs of each working condition to obtain a corresponding resistance index, and constructing a resistance index mapping database according to the tracer flow rate and the corresponding resistance index; The calculation formula of the corresponding resistance is: ； The target formula of the iterative fitting is: ； in, For the corresponding resistance, is the measured pressure difference, is the measured flow velocity, k is the coefficient.

10. The method for measuring gas phase residence time distribution according to claim 9, wherein: The construction of the resistance index mapping database further includes: dynamically revising the resistance index mapping database, wherein the dynamic revising of the resistance index mapping database specifically includes: After completing the set number of measurement experiments, randomly select a set number of working conditions to re-measure the density and resistance coefficient of the mixed gas; If the deviation between the measured drag coefficient and the calculated value in the drag index mapping database is greater than a set threshold, the data under the working condition is refitted to update the drag index in the resistance index mapping database.

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