A gas-liquid fixed bed liquid distributor and design method thereof

Abstract

The present invention discloses a gas-liquid fixed bed liquid distributor and a design method thereof, and relates to the field of liquid distributors. The technical solution thereof includes a liquid storage tank and a drip assembly; the drip assembly includes a first drip tube, a second drip tube and at least one gasket clamped between the first drip tube and the second drip tube, and the gasket is provided with a through hole; a plurality of liquid outlets are provided on the bottom surface of the liquid storage tank, and each liquid outlet is connected to a drip assembly. The liquid flows downward in the drip assembly by gravity. The present invention splits a single long tube for controlling the liquid flow rate into a first drip tube, a second drip tube and a gasket, which significantly reduces the processing difficulty and processing cost, and at the same time reduces the possibility of the capillary effect, and can achieve lower flow rate control. In addition, by changing the number of gaskets, the outflow velocity of the drip assembly can be fine-tuned, and the control accuracy of the outflow velocity of the drip assembly can be improved.

Description

Technical Field

[0001] The present invention relates to the field of liquid distributors, and more particularly to a gas-liquid fixed bed liquid distributor and a design method thereof. Background Art

[0002] The shell-and-tube fixed bed reactor is a commonly used chemical reactor, mostly used for highly exothermic reactions. The reactor structure is similar to the fixed tube sheet heat exchanger. The tube side is the reaction zone, and the catalyst is loaded in the reaction tube. The material reacts when passing through the catalyst bed in the reaction tube. The shell side space is filled with heat exchange medium to form a reaction heat exchange system. Common applications of the shell-and-tube fixed bed reactor include methanol synthesis tower, ethylene oxide reactor, acrylic acid reactor and coal-to-ethanol reactor.

[0003] When using a tube-in-tube fixed bed reactor for chemical reactions, it is particularly important to evenly distribute the reactants to each reaction tube. Chinese patent CN205269603U provides a multiphase liquid distributor for a tube-in-tube reactor, wherein the liquid distribution system includes a liquid distribution layer and a liquid redistribution layer, the liquid distribution layer includes a circular bottom plate, a cofferdam is provided on the periphery of the circular bottom plate, a plurality of liquid separation sleeves are evenly embedded on the circular bottom plate, the top of the liquid separation sleeve is flush with the upper surface of the circular bottom plate, and the lower end thereof extends out of the lower surface of the circular bottom plate by a certain length. The liquid redistribution layer includes a circular bottom plate, a cofferdam is provided on the periphery of the circular bottom plate, a plurality of liquid redistribution sleeves are evenly embedded on the circular bottom plate, the top of the liquid redistribution sleeve extends out of the upper surface of the circular bottom plate by a certain distance, and at least one overflow hole is provided on the side wall of the part of the liquid redistribution sleeve located above the circular bottom plate, the lower end of the liquid redistribution sleeve extends out of the lower surface of the circular bottom plate by a certain length, and the lower end of the liquid redistribution sleeve of the liquid redistribution layer is inserted into the tubes of the reactor tube bundle.

[0004] In the patent, the liquid distribution layer controls the flow rate in the liquid distribution sleeve by the inner diameter of the liquid distribution sleeve. Without the liquid redistribution layer, the liquid distribution layer cannot distribute liquid at extremely low flow rates, because extremely low flow rates mean that the inner diameter of the liquid distribution sleeve is only a few millimeters or even less than one millimeter, and it is difficult to accurately control the inner diameter during the production of the liquid distribution sleeve. Moreover, due to the extremely small inner diameter, the capillary phenomenon in the liquid distribution sleeve will also be very serious, making it difficult for the liquid to flow out of the liquid distribution sleeve continuously.

[0005] The liquid redistribution layer in the patent controls the liquid flow in the redistribution sleeve by the liquid flow entering the liquid redistribution layer, which requires that all overflow holes be arranged at the same height, which is difficult to arrange. Moreover, when the patent is used, even slight vibration will affect the overflow of liquid at the overflow hole. Summary of the invention

[0006] With respect to the existing liquid distributor, when the flow rate in the tube is controlled by the inner diameter of the tube, it is impossible to distribute the liquid at an extremely low flow rate due to the capillary phenomenon in the tube, and the problem that the inner diameter of the extremely small tube is difficult to accurately control during the production process, and when the liquid is distributed based on the overflow principle, it is difficult to arrange all the overflow holes at the same height. The present invention provides a gas-liquid fixed bed liquid distributor, which includes a liquid storage tank and a drip assembly. The drip assembly includes a first drip tube, a second drip tube and at least one gasket, and the gasket is provided with a through hole. In a drip assembly, all gaskets are clamped between the first drip tube and the second drip tube, and a connected fluid channel is provided in the first drip tube, all gaskets and the second drip tube, and the flow area of ​​the through hole is smaller than the flow area of ​​the first drip tube and the flow area of ​​the second drip tube, and no capillary effect occurs in the first drip tube and the second drip tube. A plurality of liquid outlets are arranged on the bottom surface of the liquid storage tank, and each liquid outlet corresponds to a drip assembly. The top end of each first drip tube is communicated with the corresponding liquid outlet, and the bottom end of each second drip tube is inserted into the array tube of the fixed bed reactor.

[0007] The present invention is further configured as follows: a groove is provided at the top of the second drip tube, the first drip tube and the second drip tube are detachably connected, and all gaskets are located in the groove.

[0008] The present invention is further configured that: the first drip tube and the second drip tube are threadedly connected.

[0009] The present invention is further configured such that the total thickness of the gaskets in a drip assembly is less than or equal to 3 mm.

[0010] The present invention is further configured as follows: a gasket has a thickness of 1-2 mm.

[0011] The present invention is further configured as follows: the through hole is a circular hole with a hole diameter of 0.1-1.0 mm.

[0012] The present invention is further configured such that the liquid level in the liquid storage tank is 0.1-0.5 m.

[0013] The present invention also provides a design method for a gas-liquid fixed bed liquid distributor: the structure of the gas-liquid fixed bed liquid distributor is designed by: the inner diameters of the first drip tube and the second drip tube, and the lengths of the first drip tube and the second drip tube are given; the outflow rate per unit time of a drip assembly is given; ; Under the condition that the liquid flows only by gravity in the gas-liquid fixed bed liquid distributor, the CFD fluid simulation software is used to calculate the liquid flow in the gas-liquid fixed bed liquid distributor, and the outflow rate of a trickle flow component is calculated. At least one design scheme within the range of +Δ, Δ is a given value, and the design scheme includes the flow area of ​​the through hole, the total thickness of the gasket of a drip assembly and the liquid level height in the liquid storage tank.

[0014] The present invention is further configured as follows: when calculating the design scheme, the inner diameters of the first drip tube and the second drip tube, and the length of the first drip tube are given as conditions, and the calculation using CFD fluid simulation software is performed. The design scheme calculation process is:

[0015] S1. Obtain the liquid flow coefficient in the liquid distributor of the gas-liquid fixed bed according to the drip experiment or CFD fluid simulation software ;

[0016] S2. and Substitute this into the calculation formula for the small hole outflow:

[0017] The small hole outflow formula is as follows:

[0018]

[0019] Where A is the flow area of ​​the through hole, g is the acceleration of gravity, and h is the height of the liquid level in the liquid storage tank;

[0020] Based on the small hole outflow formula, we can calculate Under these conditions, the corresponding relationship between A and h is obtained, and the corresponding A and h are regarded as a set of data;

[0021] S3. Based on the corresponding relationship between A and h in S2, the liquid flow in the gas-liquid fixed bed liquid distributor is calculated by CFD fluid simulation software, and the outflow rate of a trickle flow component is calculated. +Δ range, each set of data in S2 corresponds to the total thickness of the gasket of a drip assembly.

[0022] The present invention is further configured as follows: before S1, the liquid level in the liquid storage tank 1 is 0.1-0.5m, and As a condition, the flow area range of the through hole is limited based on the empirical formula of small hole outflow; the empirical formula of small hole outflow is:

[0023]

[0024] Where A is the flow area of ​​the through hole, g is the acceleration of gravity, h is the height of the liquid level in the liquid storage tank, and h is 0.1-0.5m; when L / d≤2 is set, is 0.6; when L / d>2 is set, is 0.8; d is the inner diameter of the through hole, and L is the total thickness of a drip assembly gasket.

[0025] In summary, the present invention has the following beneficial effects compared with the prior art: In the present invention, the liquid flows downward in the drip assembly by gravity, and the outflow velocity of the drip assembly is controlled by the flow area in the gasket. The present invention splits a single long tube for controlling the flow velocity of the liquid into a first drip tube, a second drip tube and at least one gasket, wherein the first drip tube can reduce the influence of different distances between different liquid outlets and the side wall of the liquid storage tank on the outflow velocity of the drip assembly. In the present invention, the inner diameters of the first drip tube and the second drip tube are not limited by the requirements of the outflow velocity of the drip assembly, which significantly reduces the processing difficulty and processing cost of the first drip tube and the second drip tube, and eliminates the possibility of capillary effect in the first drip tube and the second drip tube. Secondly, the gasket is a sheet body, the drilling accuracy is easier to ensure, the processing cost is low, and because the length of the through hole in the gasket is difficult to meet the requirements of the capillary effect, the gasket can achieve lower flow rate control compared with a single long tube for controlling the flow velocity of the liquid. In addition, the present invention can also adjust the length of the area used to control the flow rate in the drip assembly by changing the number of gaskets, and achieve fine-tuning of the outflow speed of the drip assembly by increasing or decreasing the friction between the gasket and the liquid, thereby further improving the control accuracy of the outflow speed of the drip assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of the gas-liquid fixed bed liquid distributor in Example 1;

[0027] Figure 2 It is a schematic diagram of the structure of the experimental device in Example 2;

[0028] Figure 3 Schematic diagram of the relationship between the CFD simulated flow rate and the actual flow rate of a single tube, the through-hole flow area, and the liquid level height of the liquid storage tank in Example 2;

[0029] Figure 4 The gas-liquid distribution in the trickle assembly in Example 2;

[0030] Figure 5 This is a schematic diagram of the structure of the liquid distributor A in Comparative Example 1.

[0031] In the figure: 1, liquid storage tank; 2, first drip tube; 3, second drip tube; 4, gasket; 5, valve; 6, measuring cup; 7, total liquid tank; 8, downcomer; 9, connecting pipe. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the invention.

[0033] It should be noted that the directions or positional relationships indicated by terms such as “center”, “up”, “down”, “horizontal”, “left”, “right”, “front”, “back”, “lateral” and “longitudinal” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, it is a schematic diagram of the structure of a gas-liquid fixed bed liquid distributor in Example 1 of the present invention. In this embodiment, a gas-liquid fixed bed liquid distributor includes a liquid storage tank 1 and a drip assembly. The drip assembly includes a first drip tube 2, a second drip tube 3 and at least one gasket 4, and a through hole is opened on the gasket 4. In a drip assembly, all gaskets 4 are clamped between the first drip tube 2 and the second drip tube 3, and a connected fluid channel is provided in the first drip tube 2, all gaskets 4 and the second drip tube 3. The flow area of ​​the through hole is smaller than the flow area of ​​the first drip tube 2 and the flow area of ​​the second drip tube 3, and no capillary effect occurs in the first drip tube 2 and the second drip tube 3. A plurality of liquid outlets are arranged on the bottom surface of the liquid storage tank 1, and each liquid outlet corresponds to a drip assembly. The top end of each first drip tube 2 is connected to the corresponding liquid outlet, and the bottom end of each second drip tube 3 is inserted into the tube array of the fixed bed reactor.

[0036] In this embodiment, the liquid flows downward in the drip assembly by gravity, and the outflow velocity of the drip assembly is controlled by the flow area in the gasket 4. In this embodiment, a single long tube for controlling the flow velocity of the liquid is split into a first drip tube 2, a second drip tube 3 and at least one gasket 4, wherein the first drip tube 2 can reduce the influence of different distances between different liquid outlets and the side wall of the liquid storage tank 1 on the outflow velocity of the drip assembly. In this embodiment, the inner diameters of the first drip tube 2 and the second drip tube 3 are not limited by the requirements of the outflow velocity of the drip assembly, which significantly reduces the processing difficulty and processing cost of the first drip tube 2 and the second drip tube 3, and eliminates the possibility of capillary effect in the first drip tube 2 and the second drip tube 3. Secondly, the gasket 4 is a sheet body, the drilling accuracy is easier to ensure, the processing cost is low, and because the length of the through hole in the gasket 4 is difficult to meet the requirements of the capillary effect, the gasket 4 can achieve lower flow rate control compared with a single long tube for controlling the flow velocity of the liquid. In addition, in this embodiment, the length of the area used to control the flow rate in the drip assembly can be adjusted by changing the number of gaskets 4, and the friction between the gaskets 4 and the liquid can be increased or decreased to achieve fine-tuning of the outflow speed of the drip assembly, thereby further improving the control accuracy of the outflow speed of the drip assembly.

[0037] Specifically, a groove is formed at the top of the second drip tube 3, the first drip tube 2 and the second drip tube 3 are detachably connected, and all the gaskets 4 are located in the groove to facilitate adjustment of the number of gaskets 4. In this embodiment, the first drip tube 2 and the second drip tube 3 are threadedly connected.

[0038] Specifically, the first drip tube 2 is threadedly connected to the liquid storage tank 1 to facilitate disassembly and assembly of the drip assembly.

[0039] Specifically, the total thickness of the gasket 4 in a drip assembly is less than or equal to 3 mm. At this time, when the CFD fluid simulation software is used to predict the flow rate of the drip assembly, the flow coefficient calculated based on the calculation results of the CFD fluid simulation software is less than the flow coefficient calculated based on the actual drip data of the drip assembly, which helps to use the CFD fluid simulation software to infer the actual outflow of the drip assembly. At the same time, the total thickness of the gasket 4 less than or equal to 3 mm also helps to reduce the possibility of capillary effect in the gasket 4. In this embodiment, the total thickness of the gasket 4 in a drip assembly is 1-3 mm.

[0040] Specifically, the thickness of a gasket 4 is 1-2 mm. When the thickness of a gasket 4 is less than 1 mm, the gasket 4 is easily deformed when processing the through hole. When the thickness of a gasket 4 is greater than 2 mm, the difficulty of processing the through hole will increase significantly, thereby significantly increasing the cost of processing the through hole.

[0041] Specifically, the through hole is a circular hole with a pore diameter of 0.1-1.0 mm, which is equivalent to the inner diameter of a capillary, so as to control the outflow rate of a drip assembly at an extremely low flow rate, such as 0.5 L / h-1.5 L / h.

[0042] The liquid level in the liquid storage tank 1 is maintained at 0.1-0.5m to reduce the influence of the liquid level in the liquid storage tank 1 on the flow coefficient in the drip assembly, so as to facilitate the prediction and calculation of the outflow of a drip assembly through CFD fluid simulation software, and then accurately design the flow area of ​​the through hole, the total thickness of the gasket 4 in a drip assembly and the liquid level in the liquid storage tank 1.

[0043] This embodiment also provides a design method for a gas-liquid fixed bed liquid distributor, which is used to perform structural design on the above-mentioned gas-liquid fixed bed liquid distributor. The design method is as follows: given the inner diameters of the first drip tube 2 and the second drip tube 3, and the lengths of the first drip tube 2 and the second drip tube 3; given the outflow rate per unit time of a drip assembly ; Under the condition that the liquid flows only by gravity in the gas-liquid fixed bed liquid distributor, the CFD fluid simulation software is used to calculate the liquid flow in the gas-liquid fixed bed liquid distributor, and the outflow rate of a trickle flow component is calculated. At least one design scheme within the range of +Δ, Δ is a given value, and the design scheme includes the flow area of ​​the through hole, the total thickness of the gasket 4 of a drip assembly and the liquid level height in the liquid storage tank 1.

[0044] Specifically, when calculating the design scheme, the inner diameters of the first drip tube 2 and the second drip tube 3, as well as the length of the first drip tube 2 are given as conditions, and the calculation using CFD fluid simulation software is performed. The design scheme calculation process is:

[0045] S1. Obtain the liquid flow coefficient in the liquid distributor of the gas-liquid fixed bed according to the drip experiment or CFD fluid simulation software ;

[0046] S2. and Substitute this into the calculation formula for the small hole outflow:

[0047] The small hole outflow formula is as follows:

[0048]

[0049] Wherein, A is the flow area of ​​the through hole, g is the acceleration of gravity, and h is the height of the liquid level in the liquid storage tank 1;

[0050] Based on the small hole outflow formula, we can calculate Under these conditions, the corresponding relationship between A and h is obtained, and the corresponding A and h are regarded as a set of data;

[0051] S3. Based on the corresponding relationship between A and h in S2, the liquid flow in the gas-liquid fixed bed liquid distributor is calculated by CFD fluid simulation software, and the outflow rate of a trickle flow component is calculated. +Δ range, each set of data in S2 corresponds to the total thickness of the gasket 4 of a drip assembly.

[0052] In this embodiment, S1 is used to obtain the liquid flow coefficient in the gas-liquid fixed bed liquid distributor according to the CFD fluid simulation software. Specifically, the total thickness of the gasket of a drip assembly is set, and at least one of the flow area of ​​the through hole and the liquid level in the liquid storage tank is used as a variable. The liquid flow in the gas-liquid fixed bed liquid distributor is calculated multiple times by using CFD fluid simulation software. The calculation results are brought into the small hole outflow formula to calculate multiple liquid flow coefficients, and the average of all liquid flow coefficients is taken as the value used by S2. .

[0053] The small hole outflow formula is as follows:

[0054]

[0055] in, The outflow rate per unit time of a drip flow component calculated by CFD fluid simulation software; is the liquid flow coefficient calculated by the CFD fluid simulation software, A1 is the flow area of ​​the through hole, g is the gravity acceleration, and h1 is the liquid level height in the liquid storage tank 1; A1 and h1 are given values.

[0056] Specifically, the CFD fluid simulation software meshes all fluid channels before calculation. The CFD fluid simulation software performs transient solution to the flow state of the liquid in the gas-liquid fixed bed liquid distributor based on the implicit format of the VOF model. The solution method is the Simple algorithm, and the momentum equation, turbulent kinetic energy and turbulent kinetic energy dissipation rate are solved using the second-order upwind format.

[0057] Specifically, CFD fluid simulation software calculations are based on physical assumptions, which include:

[0058] 1. Assume that when liquid is dripped into the liquid reservoir 1, the liquid level height of the liquid reservoir 1 remains basically unchanged after 10 seconds of outflow time. During the dripping process, the pressure velocity fluctuation range at the gas-liquid interface in the liquid reservoir 1 is extremely small, and the influence of the pressure velocity fluctuation at the gas-liquid interface in the liquid reservoir 1 on the fluid flow rate is negligible.

[0059] 2. Assume that the effect of the length of the air calculation domain outside the bottom end of the second drip tube 3 on the flow coefficient at the bottom end of the second drip tube 3 is negligible.

[0060] 3. Assume that the distance from the liquid outlet to the side wall of the liquid storage tank 1 has negligible effect on the flow coefficient in the drip assembly.

[0061] Specifically, before S1, the liquid level in the liquid storage tank 1 is 0.1-0.5m, and As a condition, the flow area range of the through hole is limited based on the empirical formula of small hole outflow; the empirical formula of small hole outflow is:

[0062]

[0063] Where A is the flow area of ​​the through hole, g is the acceleration of gravity, h is the height of the liquid level in the reservoir 1, and h is 0.1-0.5m; Based on Hu Renqiang's 2022 paper "Numerical Study on the Flow Coefficient of Aircraft Engine Nacelle Drainage Holes", when L / d≤2 is set, is 0.6; when L / d>2 is set, is 0.8; d is the inner diameter of the through hole, and L is the total thickness of a drip assembly gasket 4.

[0064] Specifically, the design schemes are further screened based on two factors. The first factor is the total thickness of the gasket 4 in a drip assembly. The smaller this factor is, the closer the calculation result of the CFD fluid simulation software is to the actual drip result, the less likely the capillary effect is, and the gasket 4 is easier to install. The second factor is the liquid level in the liquid reservoir 1. The larger this factor is, the smaller the impact of the liquid inlet in the liquid reservoir 1 is, and the smaller the impact on the liquid flow rate in the drip assembly is.

[0065] Specifically, the real-time flow rates at the top of the first drip tube 2, the bottom of the first drip tube 2, the top of the second drip tube 3 and the bottom of the second drip tube 3 are respectively monitored during calculation by the CFD fluid simulation software; based on the degree of real-time flow rate fluctuation at the top of the first drip tube 2, the bottom of the first drip tube 2, the top of the second drip tube 3 and the bottom of the second drip tube 3, the design scheme is further screened, and the gas-liquid fixed bed liquid distributor is designed based on a design scheme with a small degree of real-time flow rate fluctuation at the top of the first drip tube 2, the bottom of the first drip tube 2, the top of the second drip tube 3 and the bottom of the second drip tube 3.

[0066] In summary, in this embodiment, the liquid flows downward in the drip assembly by gravity, and the outflow velocity of the drip assembly is controlled by the flow area in the gasket 4. In this embodiment, a single long tube for controlling the flow velocity of the liquid is split into a first drip tube 2, a second drip tube 3 and at least one gasket 4, wherein the first drip tube 2 can reduce the influence of different distances between different liquid outlets and the side wall of the liquid storage tank 1 on the outflow velocity of the drip assembly. In this embodiment, the inner diameters of the first drip tube 2 and the second drip tube 3 are not limited by the requirements of the outflow velocity of the drip assembly, which significantly reduces the processing difficulty and processing cost of the first drip tube 2 and the second drip tube 3, and eliminates the possibility of capillary effect in the first drip tube 2 and the second drip tube 3. Secondly, the gasket 4 is a sheet body, the drilling accuracy is easier to ensure, the processing cost is low, and because the length of the through hole in the gasket 4 is difficult to meet the requirements of the capillary effect, the gasket 4 can achieve lower flow rate control compared with a single long tube for controlling the flow velocity of the liquid. In addition, in this embodiment, the length of the area used to control the flow rate in the drip assembly can be adjusted by changing the number of gaskets 4, and the friction between the gaskets 4 and the liquid can be increased or decreased to achieve fine-tuning of the outflow speed of the drip assembly, thereby further improving the control accuracy of the outflow speed of the drip assembly.

[0067] Example 2

[0068] The experiment was conducted using a low-flow gas-liquid fixed bed reactor, and its main parameters are shown in Table 1:

[0069]

[0070] It should be noted that the distance H1 between the bottom of the liquid storage tank 1 and the tube sheet is based on the velocity uniformity index γ in the upper head of the fixed bed reactor.v to confirm.

[0071] It is necessary to design the gas-liquid distribution structure according to the process plan, and set the gas phase to be evenly distributed in the tubes of each fixed bed reactor. Under this condition, the gas-liquid fixed bed liquid distributor is designed with the goal of evenly distributing the liquid phase outflow from the liquid storage tank 1 to the tubes of each fixed bed reactor.

[0072] The experimental liquid parameters are shown in Table 2:

[0073]

[0074] Taking water as an example, based on the empirical formula for small hole outflow in Example 1, the empirical outflow rate of a drip assembly with different parameters is calculated.

[0075] The outflow rate of a trickle flow component is shown in Table 3:

[0076]

[0077] Design single pipe outflow With the liquid level in the liquid storage tank being 0.1-0.5m as the condition, a design scheme of a gas-liquid fixed bed liquid distributor based on the empirical formula of small hole outflow is constructed, as shown in Table 4:

[0078]

[0079] Based on Table 4, the inner diameter of the through hole in the design of the gas-liquid fixed bed liquid distributor is limited to 0.4-0.6 mm to reduce the calculation amount of the design. At the same time, Table 4 also proves that there are multiple combinations of structural parameters that meet the design flow requirements at the same time.

[0080] like Figure 2As shown, this embodiment constructs an experimental device based on the gas-liquid fixed bed liquid distributor recorded in Example 1, and the experimental device includes a liquid storage tank 1, a drip assembly, a connecting pipe 9, a valve 5 and a measuring cup 6, wherein there is only one drip assembly. The liquid storage tank 1 and the first drip tube 2 are connected by a connecting pipe 9, and the two ends of the connecting pipe 9 are respectively threadedly connected to the liquid storage tank 1 and the first drip tube 2. The valve 5 is threadedly connected to the bottom end of the second drip tube 3, and a measuring cup 6 is arranged below the valve 5. In this embodiment, the diameter of the liquid flow channel of the liquid storage tank 1, the connecting pipe 9 and the valve 5 at the narrowest point is greater than 5mm. The dimensions of each part of the experimental device are: the distance h11 from the bottom surface of the liquid storage tank 1 to the bottom surface of the liquid storage tank 1 is 35mm, the length h12 of the liquid flow channel in the connecting pipe 9 is 29mm, the length h13 of the first drip tube 2 is 30mm, the total length h14 of the liquid flow channel in the second drip tube 3 and the valve 5 is 51mm, and the liquid level height in the liquid storage tank 1 is h15. The inner diameter of the first drip tube 2 is 5 mm, the diameter of the liquid flow channel in the second drip tube 3 is 5 mm, and the thickness of a gasket 4 is 1 mm.

[0081] Before the experiment, close valve 5 to release water into the liquid storage tank 1 until the liquid level height h15 in the liquid storage tank 1 reaches the specified height.

[0082] During the experiment, the timing starts when the valve 5 is opened, and the water in the liquid storage tank 1 falls into the measuring cup through the drip assembly. When the liquid in the measuring cup 6 reaches the specified scale line, the valve is closed and the timing stops. The actual single-tube flow rate is calculated by dividing the volume of the liquid in the measuring cup 6 by the time required for the liquid in the measuring cup 6 to reach the specified scale line.

[0083] The experimental device is simulated by CFD, and the CFD simulated flow rate at the outlet of valve 5 when valve 5 is opened is calculated.

[0084] Based on the above-mentioned empirical formula for small hole outflow, the empirical flow rate of the valve 5 in the experimental device is calculated according to the liquid level height h15 in the liquid storage tank 1 in the experimental device, the total thickness of the gasket 4 (through hole length) and the through hole diameter.

[0085] The error percentage between the CFD simulation flow rate and the actual single-tube flow rate is calculated as the CFD and experimental error percentage, and the error percentage between the empirical flow rate and the actual single-tube flow rate is calculated as the empirical and experimental error percentage.

[0086]

[0087]

[0088] The actual single-tube flow rate, CFD simulation flow rate, empirical flow rate, CFD and experimental error percentage, and empirical and experimental error percentage are shown in Table 5.

[0089]

[0090] In the present embodiment, when performing S1 of the design method of the gas-liquid fixed bed liquid distributor, the total thickness of the gasket 4 of the drip assembly is set to 1 mm, the aperture of the through hole of the gasket 4 is set to 0.4 mm, and the liquid level in the liquid storage tank 1 is used as a variable to calculate the CFD simulation flow rate and the actual single-tube flow rate, and the CFD simulation flow rate and the actual single-tube flow rate are substituted into the small hole outflow formula in S1, see Figure 3 .

[0091] Liquid flow coefficient C in the experimental device d for Figure 3 The slope of the curve in Table 5 and Figure 3 It can be found that the actual drip data of the experimental device is in good agreement with the CFD simulation data. On this basis, since the acquisition of actual drip data is more cumbersome, time-consuming, and the data is more discrete, it is recommended to use Figure 3 The slope of the curve corresponding to the CFD simulation data is used as the C used by S2 d .

[0092] Figure 3 The slope of the curve corresponding to the CFD simulation data, that is, the flow coefficient of water in the experimental device is 0.80-0.85, which is different from 0.6 or 0.8 in the empirical formula of small hole outflow. Therefore, when designing the gas-liquid fixed bed liquid distributor, the liquid flow coefficient C in the gas-liquid fixed bed liquid distributor obtained based on the drip experiment or CFD fluid simulation software is used. d The design calculation is more realistic. Comparing the flow data of a liquid mixture and water calculated by CFD under the same working conditions, the outflow of the liquid mixture is slightly larger than the outflow of water, and the flow coefficient of the liquid mixture calculated by CFD is also around 0.8~0.85. d When affected by viscosity, density, interfacial tension, etc., the liquid flow coefficient C in the gas-liquid fixed bed liquid distributor obtained by the drip test should be used. d , C used as S2 d To reduce errors, the drip experiment can be carried out by the experimental device described in this embodiment, wherein the dimensions of each part can be adjusted based on actual conditions, and this embodiment is only for illustration.

[0093] The outlet flow rate of the bottom gasket 4 of a drip assembly is significantly affected by the inner diameter of the gasket 4 itself and the number of gaskets 4. Gas will be discharged from the outlet of the bottom gasket 4 of the drip assembly within the first 2 seconds of dripping, resulting in fluctuations in the outlet flow rate of the bottom gasket 4 of the drip assembly within the first 2 seconds of dripping. After 2 seconds of dripping, stable and continuous flow can be achieved at the outlet of the bottom gasket 4 of the drip assembly.

[0094] Using the two liquids in Table 2, the flow rate of a drip assembly under different gasket 4 inner diameters, different gasket 4 numbers, and different liquid level heights of the liquid storage tank 1 in Example 1 is calculated by using the small hole outflow empirical formula and CFD fluid simulation software. During the calculation, the inner diameter of the first drip tube 2 is set to 5mm, the diameter of the liquid flow channel in the second drip tube 3 is set to 3mm, the thickness of a gasket 4 is 1mm, and the length of the liquid flow channel in the second drip tube 3 is 119mm. Based on the calculation results, the difference rate between the CFD calculated flow rate of the liquid phase mixture and the flow rate calculated by the empirical formula is calculated as the difference rate (mixed), and the difference rate between the CFD calculated flow rate of water and the flow rate calculated by the empirical formula is calculated as the difference rate (water). The difference rate calculation formula is as follows:

[0095]

[0096] The calculation results are shown in Table 6.

[0097]

[0098] Based on Tables 5 and 6, it can be found that the empirical formula for small-hole outflow cannot reflect the subtle differences in outflow rate caused by the physical properties of different materials. Therefore, the actual outflow rate of a drip flow component of the gas-liquid fixed bed liquid distributor designed using the empirical formula for small-hole outflow is often significantly different from the calculated value of the empirical formula for small-hole outflow.

[0099] Based on the gas-liquid fixed bed liquid distributor in Example 1, the gas-liquid distribution is analyzed with the structural parameters that the inner diameter of the first drip tube 2 is 5 mm, the inner diameter of the second drip tube 3 is 5 mm, the through hole diameter of the gasket 4 is 0.4 mm, and the thickness of the gasket 4 is 1 mm, 2 mm, and 3 mm respectively. The liquid of the gas-liquid fixed bed liquid distributor is water. The analysis results are shown in Figure 4 , Figure 4 The thickness of the gaskets 4 of the three drip assembly from left to right is 3mm, 2mm, and 1mm respectively. Figure 4 From the gas-liquid distribution in the drip assembly, it can be found that the diameter of the fluid channel below the gasket in the drip assembly suddenly increases, and the second drip tube continuously flows out in a drip-like state, which means that capillary effect is basically not formed in the drip assembly, which is conducive to the uniform outflow of the liquid.

[0100] Based on the above experimental analysis results, the design method of the gas-liquid fixed bed liquid distributor described in Example 1 was adopted, and the design scheme was calculated by CFD fluid simulation software. The thickness of a gasket 4 was set to 1 mm. The design scheme is shown in Table 7.

[0101]

[0102] Based on Table 7, it can be seen that the outflow rate of a trickle component satisfies There are 5 design schemes. Further analysis of these 5 design schemes shows that the liquid level of schemes C3 to C5 is low, and it is easy to produce a large feed impact at the liquid surface of the liquid storage tank 1. In addition, the more gaskets 4 there are, the higher the requirements for the processing of the through holes and the installation accuracy of multiple gaskets 4 are, and one gasket 4 is more convenient to install. Therefore, it is more appropriate to adopt scheme C1, which has a small number of gaskets 4, is easy to install, and has uniform gas-liquid two-phase outflow distribution.

[0103] Example 2

[0104] Randomly design several water , using Example 2 Figure 3 The slope of the curve corresponding to the CFD simulation data is 0.8, which is the liquid flow coefficient C of the liquid in the gas-liquid fixed bed liquid distributor recorded in Example 1. d Based on the design method of the gas-liquid fixed bed liquid distributor described in Example 1, the design scheme of the gas-liquid fixed bed liquid distributor is calculated, see Table 8.

[0105]

[0106] Based on Table 8, various design flow values ​​and their corresponding gas-liquid fixed bed liquid distributor parameters can be quickly calculated, and the liquid level height in the storage tank can be adjusted.

[0107] Comparative Example 1

[0108] like Figure 5 As shown, Comparative Example 1 provides a common liquid distributor A, which includes a main liquid tank 7 and at least one downcomer 8 ( Figure 5 The number of downcomers 8 in the figure is for illustration only, and the text description shall prevail). All downcomers 8 pass through the bottom surface of the main liquid tank 7 and are fixedly connected to the main liquid tank 7. When there are multiple downcomers 8, the top heights of all downcomers 8 are consistent. The liquid in the main liquid tank 7 overflows into the downcomers 8. The inner diameter d of the downcomers 8 is A is 10 mm, and the length L of the downcomer 8 is A It is 350mm.

[0109] A three-dimensional model of a liquid distributor A with 12 downcomers 8 was constructed. The liquid in the main liquid tank 7 was the liquid phase mixture recorded in Table 2 of Example 2, and the liquid level in the main liquid tank 7 was maintained at 0.3 m. The CFD simulation of the liquid distributor was performed, and the instantaneous outflow rate Q of each downcomer 8 when overflowing for 2.5 s was calculated. A , see Table 9.

[0110]

[0111] From Table 9, it can be seen that even if all downcomers 8 have the same size, the flow rate allocated to each downcomer 8 is not uniform, and the flow rate deviation between different downcomers 8 is very obvious. It is difficult to maintain a uniform flow rate in all downcomers 8 by adjusting the liquid level height in the total liquid tank 7.

[0112] A liquid distributor A with only one downcomer 8 was constructed, water was filled into the main liquid tank 7, and the liquid level in the main liquid tank 7 was kept at 0.3m, and a single-tube outflow experiment was conducted. The total weight of water discharged from a downcomer 8 within the set overflow time was repeatedly measured, and the total weight of water discharged was divided by the overflow time to calculate the experimental single-tube flow rate corresponding to each total weight of water discharged. In this comparative example, the overflow time was set to 10min, and the experimental results are shown in Table 10.

[0113]

[0114] It can be found from Table 10 that the experimental repeatability of the same downcomer 8 is poor, and the outflow rate of the liquid distributor A is easily affected by liquid level fluctuations.

[0115] Comparative Example 2

[0116] Comparative Example 2 provides a common liquid distributor B, which differs from Comparative Example 1 in that when there are multiple downcomers 8, the tops of all downcomers 8 do not need to maintain the same height. All downcomers 8 are completely submerged below the liquid surface in the main liquid tank 7, and the flow rate of the downcomers 8 is controlled by their own inner diameters.

[0117] In this comparative example, the liquid distributor B has only one downcomer 8. A dripping experiment of a downcomer 8 is performed on the liquid distributor B to obtain an experimental outflow rate of the downcomer 8. A CFD simulation of a downcomer 8 is performed on the liquid distributor B to obtain a CFD predicted outflow rate of the downcomer 8. The error percentage between the experimental outflow rate and the CFD predicted outflow rate is calculated, and the results are shown in Table 11.

[0118] The calculation formula of the error percentage in this comparative example is as follows:

[0119]

[0120]

[0121] Based on Table 11, it can be seen that the actual outflow rate of the downcomer 8 in the liquid distributor B is quite different from the outflow rate predicted by CFD, so it is difficult to perform the structural design of the liquid distributor B based on the outflow rate predicted by CFD.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A design method for a gas-liquid fixed bed liquid distributor, characterized in that: The design method is as follows: given the inner diameters of the first drip tube and the second drip tube, and the lengths of the first drip tube and the second drip tube; given the outflow rate per unit time of a drip assembly ; The liquid flow in the gas-liquid fixed bed liquid distributor is simulated and calculated using CFD fluid simulation software, with the condition that the liquid only flows by its own gravity in the gas-liquid fixed bed liquid distributor. The outflow rate of a trickle flow component is calculated. + at least one design solution within the range of Δ, Δ being a given value, the design solution including the flow area of ​​the through hole, the total thickness of the gasket of a drip assembly and the height of the liquid level in the liquid storage tank; When calculating the design scheme, the inner diameters of the first drip tube and the second drip tube, as well as the length of the first drip tube are given as conditions, and the calculation using CFD fluid simulation software is performed. The design scheme calculation process is as follows: S1. Obtain the liquid flow coefficient in the liquid distributor of the gas-liquid fixed bed according to the drip experiment or CFD fluid simulation software ; S2. and Substitute this into the calculation formula for the small hole outflow: The calculation formula for the small hole outflow is as follows: Where A is the flow area of ​​the through hole, g is the acceleration of gravity, and h is the height of the liquid level in the liquid storage tank; Based on the small hole outflow formula, we can calculate Under these conditions, the corresponding relationship between A and h is obtained, and the corresponding A and h are regarded as a set of data; S3. Based on the corresponding relationship between A and h in S2, the liquid flow in the gas-liquid fixed bed liquid distributor is calculated by CFD fluid simulation software, and the outflow rate of a trickle flow component is calculated. +Δ range, each set of data in S2 corresponds to the total thickness of the gasket of a drip assembly.

2. The design method of a gas-liquid fixed bed liquid distributor according to claim 1, characterized in that: Before S1, the liquid level in the storage tank is 0.1-0.5m, and As a condition, the flow area range of the through hole is limited based on the empirical formula of small hole outflow; the empirical formula of small hole outflow is: Where A is the flow area of ​​the through hole, g is the acceleration of gravity, h is the height of the liquid level in the liquid storage tank, and h is 0.1-0.5m; when L / d≤2 is set, is 0.6; when L / d>2 is set, is 0.8; d is the inner diameter of the through hole, and L is the total thickness of a drip assembly gasket.

3. A gas-liquid fixed bed liquid distributor, characterized in that: A gas-liquid fixed bed liquid distributor is designed using the design method described in claim 1 or 2, comprising a liquid storage tank and a drip assembly; the drip assembly comprises a first drip tube, a second drip tube and at least one gasket, and the gasket is provided with a through hole; in a drip assembly, all gaskets are clamped between the first drip tube and the second drip tube, and a connected fluid channel is provided in the first drip tube, all gaskets and the second drip tube, the flow area of ​​the through hole is smaller than the flow area of ​​the first drip tube and the flow area of ​​the second drip tube, and no capillary effect occurs in the first drip tube and the second drip tube; a plurality of liquid outlets are arranged on the bottom surface of the liquid storage tank, and each liquid outlet corresponds to a drip assembly; the top end of each first drip tube is connected to the corresponding liquid outlet, and the bottom end of each second drip tube is inserted into the tube array of the fixed bed reactor.

4. A gas-liquid fixed bed liquid distributor according to claim 3, characterized in that: A groove is provided at the top of the second drip tube, the first drip tube and the second drip tube are detachably connected, and all gaskets are located in the groove.

5. A gas-liquid fixed bed liquid distributor according to claim 4, characterized in that: The first drip tube and the second drip tube are threadedly connected.

6. A gas-liquid fixed bed liquid distributor according to any one of claims 3 to 5, characterized in that: The total thickness of the gaskets in a drip assembly is less than or equal to 3 mm.

7. A gas-liquid fixed bed liquid distributor according to claim 6, characterized in that: The thickness of one gasket is 1-2 mm.

8. The gas-liquid fixed bed liquid distributor according to claim 6, characterized in that: The through hole is a circular hole with a hole diameter of 0.1-1.0 mm.

9. A gas-liquid fixed bed liquid distributor according to claim 8, characterized in that: The liquid level in the liquid storage tank is 0.1-0.5m.

Images