Modeling method, control method, system and equipment for pneumatic conveying

Abstract

The invention provides a pneumatic conveying modeling method, a pneumatic conveying control method, a pneumatic conveying control system and pneumatic conveying equipment. The pneumatic conveying system comprises a pneumatic conveying model, and the pneumatic conveying model comprises a minimum pressure drop speed model; the training process of the minimum pressure drop speed model comprises the following steps that S1, at least two sets of fitting data are obtained, and each set of fitting data comprises the conveying gas speed in the conveying pipeline and the conveying pipeline pressure drop corresponding to the conveying gas speed; s2, fitting data are substituted into a minimum pressure drop velocity model; and S3, fitting to obtain a fitting coefficient, and training to obtain a minimum pressure drop velocity model. According to the system, the conveying gas speed, the critical blocking gas speed and the minimum pressure drop speed can be calculated in real time according to the flow pattern of a target material, the conveying gas speed in the pipeline is measured and controlled, and the system can achieve real-time control over the material pneumatic conveying flow pattern.

Description

Technical Field

[0001] The present invention relates to the technical field of pneumatic conveying of powders and particles, and in particular to a modeling method, a control method, a system and equipment for pneumatic conveying. Background Art

[0002] In the prior art, powders and particles are usually transported by mechanical conveying and pneumatic conveying. Pneumatic conveying has lower mechanical wear and energy consumption than mechanical conveying, so it has been widely used in many industrial applications. Pneumatic conveying can be divided into two types: dense phase conveying and dilute phase conveying according to the movement state of the material in the pipeline, and can be distinguished by the minimum pressure drop rate (critical gas velocity for dilute phase conveying and dense phase conveying). Dense phase pneumatic conveying precisely controls the gas flow rate in the pipeline so that powder particles move in the pipeline in the form of a sedimentary layer or group flow. Compared with dilute phase conveying, dense phase conveying has significant advantages in reducing pipeline and particle wear, reducing energy consumption and improving conveying capacity.

[0003] However, in practical applications, the pneumatic conveying flow pattern of powders and particles is affected by many factors such as differences in material properties, system structure, and operating parameters. When the physical properties of powders and particles differ greatly, the applicable flow pattern will also be different, and even blockage may occur (when the conveying gas velocity is lower than the critical blocking gas velocity). For example, for powdery materials with poor fluidity, the conveying efficiency can be improved by optimizing the design of the flow-aiding accessories and gas distribution components of the sending tank. Therefore, the reasonable selection of the conveying flow pattern is crucial to ensure the smooth and efficient operation of the pneumatic conveying system, and it also helps to avoid pipeline blockage and the occurrence of adverse situations such as the operation of powders and particles in the dilute phase. In view of the important influence of flow pattern on the pneumatic conveying of powders and particles, the development of a pneumatic conveying system and control method for powders and particles that can effectively control the flow pattern has important theoretical and practical significance for the development and automated operation of pneumatic conveying systems for powders and particles in industrial applications. However, the current conveying flow pattern mostly relies on the prediction of the physical properties of powders and particles, and there is still a lack of specific operating methods for how to achieve this goal in actual operation. Summary of the invention

[0004] In order to overcome the defects of the prior art that pneumatic conveying of materials is prone to blockage or high energy consumption, the present invention provides a modeling method, control method, system and equipment for pneumatic conveying. The control method can target the flow pattern of the target material, and calculate the conveying gas velocity, critical blockage gas velocity and minimum pressure drop velocity in real time, and measure and control the conveying gas velocity in the pipeline. The system can achieve real-time control of the pneumatic conveying flow pattern of the material. The present invention is of great significance for guiding the design of pneumatic conveying devices for powders and particles in industrial applications and realizing their safe and efficient operation.

[0005] The present invention provides a modeling method for pneumatic conveying, which includes establishing a pneumatic conveying model, wherein the pneumatic conveying model includes a minimum pressure drop velocity model;

[0006] The training process of the minimum pressure drop rate model includes the following steps:

[0007] S1, obtaining at least two sets of fitting data, each set of fitting data including the conveying gas velocity U in the conveying pipeline g , and the conveying gas velocity U g The corresponding pressure drop of the transmission pipeline △P;

[0008] S2. Substituting the fitting data into a minimum pressure drop rate model, the minimum pressure drop rate model is as shown in Formula I:

[0009]

[0010] Among them, U e is the minimum pressure drop velocity, m / s; U g is the gas delivery velocity, m / s; △P is the pressure drop in the delivery pipeline, Pa; L is the length of the delivery pipeline, m; △P / L represents the pressure drop per unit length of the delivery pipeline, Pa / m;

[0011] In formula I, △P / L is calculated as formula II:

[0012]

[0013] Among them, λ g is the friction coefficient of the conveying gas; μ is the solid-gas ratio, that is, the ratio of the mass flow rate of the particles to the mass flow rate of the conveying gas; λ z is the additional pressure drop coefficient; ρ g is the density of the conveying gas, kg / m 3 ; D is the inner diameter of the delivery pipeline, m; ρ b is the bulk density, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; θ is the inclination angle of the conveying pipeline;

[0014] In formula II, the friction coefficient of the conveying gas λ g The calculation formula is as follows:

[0015] λ g =0.3164Re -0.25

[0016] Where Re is the Reynolds number;

[0017] In formula II, the additional pressure drop coefficient λ z The calculation formula is as follows:

[0018] λ z=aFr b

[0019] Wherein, Fr is the function of the additional pressure drop coefficient; a and b are fitting coefficients respectively;

[0020] S3. Fitting coefficients a and b are obtained by fitting, and the minimum pressure drop rate model is obtained by training.

[0021] In the present invention, the pneumatically conveyed material may include powder or granular material.

[0022] In the present invention, the minimum pressure drop rate refers to the optimal air flow velocity in the pneumatic conveying device, which can not only ensure stable and efficient transportation of materials, but also minimize energy consumption and pipeline wear, corresponding to the point with the minimum pressure drop per unit pipe length; it can also be called "economic air speed" in this field.

[0023] In the present invention, d(ΔP / L) / dU g =0 means the pressure drop change rate per unit pipe length is zero, corresponding to the lowest pressure drop point.

[0024] In the present invention, by treating U in Formula II g Find the first-order derivative and set the derivative to 0 to obtain U e ; Indicates "U at the minimum pressure drop speed g ". According to the pneumatic conveying phase diagram, when the conveying volume is constant, as the conveying gas velocity increases, the pressure drop per unit length in the conveying pipeline shows a trend of first decreasing and then increasing. The gas velocity corresponding to the minimum pressure drop per unit length is called the economic gas velocity. Therefore, by establishing a pipeline pressure drop model and then deriving the pipeline pressure drop model, the calculation model of the minimum pressure drop velocity can be obtained.

[0025] In the present invention, the pipeline pressure drop experimental data under different conveying gas speeds are obtained, and the z ~Fr is used to fit the data to obtain the fitting coefficients a and b.

[0026] In some embodiments, the minimum pressure drop rate U e The calculation formula is simplified to:

[0027]

[0028] Among them, ρ g is the density of the conveying gas, kg / m 3 ; D is the inner diameter of the delivery pipeline, m; μ g is the dynamic viscosity of the transported gas, Pa·s; g is the acceleration due to gravity, m / s 2 ;M s is the solid mass flow rate, kg / s; a and b are fitting parameters;

[0029] In a specific embodiment, the g It is calculated by combining pipeline gas volume, temperature and pressure; the ρ g The calculation formula is:

[0030]

[0031] In a specific embodiment, the μ g 1.79×10 -5 Pa·s.

[0032] In a specific embodiment, the g is 9.79 m / s 2 .

[0033] In a specific embodiment, the M s Measured by a weighing system.

[0034] In some embodiments, the pneumatic transport model further includes a critical blockage velocity model; the critical blockage velocity model is shown in Formula III:

[0035]

[0036] Among them, C D is the drag coefficient; U b is the critical blocking gas velocity, m / s; θ is the inclination angle of the delivery pipeline; μ g is the dynamic viscosity of the transported gas, Pa·s; ρ g is the density of the conveying gas, kg / m 3 ;d p is the average particle size of the transported particles, m; g is the acceleration due to gravity, m / s 2 ρ p is the density of the transported particles, kg / m 3 ;

[0037] In a specific embodiment, C D It is 0.44.

[0038] In the present invention, the critical blockage gas velocity refers to the minimum conveying gas velocity required for the pneumatic conveying process to proceed smoothly. Pneumatic conveying of powders and particles is essentially a gas-solid two-phase flow process in which particles interact with airflow. When the conveying gas velocity is large enough, the particles are transported in the form of suspended flow under the action of the airflow. As the conveying gas velocity decreases, the aerodynamic force on some particles with smaller particle sizes is not enough to overcome gravity and they begin to settle. When the conveying gas velocity is reduced to a certain value, the particles that settle to the bottom of the pipeline form a static sedimentation layer, which will eventually cause pipeline blockage. Critical blockage gas velocity (U b) can be defined as the minimum conveying gas velocity corresponding to the particle group moving in the conveying direction in the pneumatic conveying system when the velocity approaches zero. According to the shear law of powder and granular bodies, the driving force of the powder and granular particles in the horizontal direction depends on the force they are subjected to in the vertical direction. When the force on the particles in the vertical direction is in equilibrium, the velocity of the particles in the horizontal direction is 0, which is in a critical blocking state. Therefore, when the sum of the forces on the particles in the vertical direction is 0, the corresponding conveying gas velocity U g The critical blocking velocity U b .

[0039] In a specific embodiment, the critical blockage gas velocity U b The calculation model uses the gravity F of the transported particles G , Saffman lift force F for transporting particles L , buoyancy F of transported particles B , drag force F D Combined with Newton's second law, the equation of motion of the particle is:

[0040]

[0041] Among them, m p is the mass of the transported particles, kg; F B is the buoyancy of the transported particles, N; F G is the gravity of the transported particles, N; F L is the Saffman lift force for transporting particles, N; F D is the drag force for transporting particles, N; is the particle conveying speed U p The rate of change over time t, U p is the speed of conveying particles, m / s; θ is the inclination angle of the conveying pipeline.

[0042] In a preferred embodiment, the gravity F of the transported particles G The calculation formula is as follows:

[0043]

[0044] Among them, π is the ratio of circumference to diameter; d p is the average particle size of the transported particles, m; g is the acceleration due to gravity, m / s 2 ρ p is the density of the transported particles, kg / m 3 .

[0045] In a preferred embodiment, the Saffman lift force F L The calculation formula is as follows:

[0046]

[0047] Among them, μ g is the dynamic viscosity of the transported gas, Pa·s; ρ g is the density of the conveying gas, kg / m 3 ;d p is the average particle size of the transported particles, m; U g is the conveying gas velocity, m / s; U p is the speed of conveying particles, m / s; dU g / dy is the conveying gas velocity U g Velocity gradient perpendicular to the conveying direction.

[0048] In a preferred embodiment, the buoyancy F of the transported particles B The calculation formula is as follows:

[0049]

[0050] Among them, π is the ratio of circumference to diameter; d p is the average particle size of the transported particles, m; ρ g is the density of the conveying gas, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;

[0051] In a preferred embodiment, the drag force F D The calculation formula is as follows:

[0052]

[0053] Among them, C D is the drag coefficient, which is 0.44; π is the circumference of a circle; d p is the average particle size of the transported particles, m; ρ p is the density of the transported particles, kg / m 3 ; U g is the conveying gas velocity, m / s; U p is the speed of conveying particles, m / s;

[0054] In a preferred embodiment, C D It is 0.44.

[0055] In a preferred embodiment, the equation of motion of the particle uses boundary conditions, U p =0.

[0056] In a specific embodiment, the d p Measured by a particle size analyzer.

[0057] In a specific embodiment, the p Measured by a particle density meter.

[0058] In a specific embodiment, the g The calculation is performed based on the pressure and gas temperature of the transmission pipeline; specifically, the calculation method is as follows:

[0059]

[0060] Where P is the absolute pressure of the delivery pipeline, Pa; M is the molar mass of the gas, g / mol; R is the ideal gas constant, which is 8.314 J / (mol·k); and T is the gas temperature, K.

[0061] In particular embodiments, the particles comprise biomass.

[0062] In a specific embodiment, the particle size of the particles is 0.01 mm to 5 mm.

[0063] In a specific implementation, the inner diameter of the delivery pipeline is 0.01 m to 0.2 m.

[0064] The present invention also provides a method for controlling pneumatic conveying, which comprises the following steps:

[0065] Step ss1, according to the average particle size d of the target material p and particle density ρ p , combining the flow pattern criterion equation to predict the conveying flow pattern of the target material; and using the minimum pressure drop velocity model and critical blockage velocity model obtained by the pneumatic conveying modeling method as described above to predict the minimum pressure drop velocity U of the target material e and critical blockage velocity U b ;

[0066] Step ss2, determining the conveying gas velocity range of the target material according to the conveying flow pattern of the target material and in combination with the minimum pressure drop velocity and critical blocking gas velocity predicted in step ss1;

[0067] Step ss3: Based on the conveying gas speed range in step ss2, the conveying gas speed of the target material is adjusted.

[0068] In some embodiments, the flow pattern criterion equation is:

[0069]

[0070] In a specific implementation, the conveying flow type is predicted as follows: the average particle size and particle density of the target material are substituted into the flow type criterion equation; when the inequality of formula IV is satisfied, the conveying flow type of the target material is dilute phase conveying, and when the inequality of formula IV is not satisfied, the conveying flow type of the target material is dense phase conveying.

[0071] In the present invention, by inputting the particle density ρ of the target material p and average particle size d p The prediction of the applicable flow type of the target material can be realized; specifically, according to the relationship between the particle density and the volume average particle size (the particle size of a sphere with the same volume as the particle) of the target material, the target material can be divided into three types of powders and particles: I, II, and III. The particle density and average particle size of type I powder and particles are relatively small, and they are suitable for dense phase transportation. Type II powder and particles have a larger particle size and can only be transported in a dilute phase. Type III powder and particles have a large particle size and are suitable for embolic flow (a type of dense phase flow) transportation. Therefore, both types I and III powder and particles are suitable for dense phase transportation, and type II powder and particles are suitable for dilute phase transportation.

[0072] In some embodiments, the actual flow rate U of the transport gas is g The calculation method is as follows: Collect the pneumatic conveying information and calculate the actual flow rate U of the conveying gas according to formula V g The pneumatic conveying information includes the inner diameter D of the conveying pipeline, the pressure P of the conveying pipeline, and the volume flow rate Q of the conveying gas;

[0073]

[0074] Wherein, Q is the volume flow rate of the conveying gas entering a certain pipe section in the calculated conveying pipeline under standard conditions, and P is the gauge pressure of the conveying pipeline. Q is calculated by the readings of each gas mass flowmeter; for example, for the first horizontal section, there are gas mass flowmeters 601 and 602 set in the front section, and the volume flow rate of the conveying gas in this horizontal section is the sum of the readings of the two gas mass flowmeters, that is, Q = Q 1 +Q 2 .

[0075] In step ss2 of the present invention, the conveying gas velocity interval of the target material is: when the flow type of the target material is dense phase conveying, U b <U g <U e ; When the flow pattern of the target material is dilute phase transport, U g >U e .

[0076] In some embodiments, the pneumatic conveying control method is performed in a pneumatic conveying device, which includes an air inlet pipe, a material dispensing tank, a conveying pipe and a plurality of material receiving tanks; the lower part and the bottom of the material dispensing tank are respectively provided with an air inlet and a material outlet, the air outlet of the air inlet pipe is connected to the air inlet of the material dispensing tank, and the material outlet of the material dispensing tank is respectively connected to each of the material receiving tanks through a conveying pipe; in the direction from the material dispensing tank to each of the material receiving tanks, the conveying pipe sequentially includes a first vertical section, a first bending section, a first horizontal section, a second bending section, a second vertical section, a third bending section and a second horizontal section;

[0077] The conveying pipeline is provided with a first throttle, a second throttle, a third throttle and a fourth throttle; the first throttle, the second throttle, the third throttle and the fourth throttle are respectively arranged at the starting end of the first horizontal section, the starting end of the second bending section, the starting end of the second vertical section and the starting end of the second horizontal section;

[0078] The first throttle, the second throttle, the third throttle, and the fourth throttle are respectively provided with the second gas mass flow meter, the third gas mass flow meter, the fourth gas mass flow meter, and the fifth gas mass flow meter;

[0079] Preferably, the pneumatic conveying device further comprises a conveying gas processing module, the conveying gas pre-processing module comprises a gas compressor, a freeze dryer and a deoiler connected in sequence, and the outlet of the deoiler is connected to the air inlet of the air inlet pipeline;

[0080] Preferably, the air inlet pipeline is provided with a first pressure sensor, a temperature sensor and a first gas mass flow meter, and the first gas mass flow meter is used to adjust the solid conveying amount in the pneumatic conveying process;

[0081] Preferably, the second gas mass flow meter, the third gas mass flow meter, the fourth gas mass flow meter, and the fifth gas mass flow meter are used to adjust the conveying gas speed of the first horizontal section, the conveying gas speed of the second bending section, the conveying gas speed of the second vertical section, and the conveying gas speed of the second horizontal section respectively;

[0082] Preferably, the material delivery tank is provided with a second pressure sensor;

[0083] Preferably, in the direction from the material sending tank to each of the material receiving tanks, the first horizontal section is provided with a third pressure sensor and a fourth pressure sensor in sequence; the third pressure sensor and the fourth pressure sensor are both provided between the first damper and the second damper;

[0084] Preferably, in the direction from the material sending tank to each of the material receiving tanks, the second vertical section is provided with a fifth pressure sensor and a sixth pressure sensor in sequence;

[0085] Preferably, a weighing system is provided at the bottom of the dispensing tank; and a discharging valve is provided at the first vertical section;

[0086] Preferably, the pneumatic conveying device further comprises a dust collector and a booster pump connected to each other, the dust collector is arranged on the top of the material delivery tank, and the outlet of the booster pump is connected to the inlet of the freeze dryer;

[0087] Preferably, a gas phase outlet is provided at the upper portion of each receiving tank, and the gas phase outlet is connected to the inlet of the dust collector;

[0088] Preferably, the pneumatic conveying device also includes a control module, which is electrically connected to the first gas mass flow meter, the second gas mass flow meter, the third gas mass flow meter, the fourth gas mass flow meter, the fifth gas mass flow meter, the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor, the fifth pressure sensor, the sixth pressure sensor, and the temperature sensor, respectively.

[0089] The present invention also provides a control system for pneumatic conveying, which includes a control unit, which is electrically connected to the gas flow meter and pressure sensor of the pneumatic conveying device in the pneumatic conveying control method as described above, and is used to convert the received pressure signal into a gas flow control signal to regulate the gas flow meter.

[0090] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the modeling method for pneumatic conveying as described above is implemented, or the control method for pneumatic conveying as described above is implemented.

[0091] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the modeling method for pneumatic conveying as described above, or the control method for pneumatic conveying as described above is implemented.

[0092] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0093] The reagents and raw materials used in the present invention are commercially available.

[0094] The positive and progressive effects of the present invention are:

[0095] The present invention is based on the flow pattern determined by the particle density and average particle size of the material, and can calculate the conveying gas velocity, critical blocking gas velocity and minimum pressure drop velocity in real time, and measure and control the conveying gas velocity in the pipeline. The system can realize real-time control of the pneumatic conveying flow pattern of powders and particles, and effectively improve the efficiency of the pneumatic conveying device of powders and particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Figure 1 This is a schematic diagram of the structure of the pneumatic conveying control system of Example 1;

[0097] Figure 2 It is a flow pattern prediction diagram based on the particle density and average particle size of the material;

[0098] Figure 3 It is a schematic diagram of the force analysis of powder particles in the pipeline;

[0099] Figure 4 This is a flow control flow chart of Example 2.

[0100] Description of reference numerals:

[0101] Gas compressor 1

[0102] Freeze Dryer 2

[0103] Degreaser 3

[0104] First pressure sensor 401

[0105] Second pressure sensor 402

[0106] The third pressure sensor 403

[0107] Fourth pressure sensor 404

[0108] Fifth pressure sensor 405

[0109] Sixth pressure sensor 406

[0110] Temperature sensor 5

[0111] First gas mass flow meter 601

[0112] Second gas mass flow meter 602

[0113] The third gas mass flow meter 603

[0114] Fourth gas mass flow meter 604

[0115] Fifth Gas Mass Flow Meter 605

[0116] Feed tank 7

[0117] Weighing system 8

[0118] Feeding valve 9

[0119] The first throttle 1001

[0120] The second throttle 1002

[0121] The third throttle 1003

[0122] Fourth throttle 1004

[0123] The first receiving tank 1101

[0124] The second receiving tank 1102

[0125] The third receiving tank 1103

[0126] Dust collector 12

[0127] Booster pump 13. DETAILED DESCRIPTION

[0128] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0129] Example 1

[0130] This embodiment discloses a pneumatic conveying device. It includes an air inlet pipe, a material dispensing tank 7, a conveying pipe and three material receiving tanks; the lower part and the bottom of the material dispensing tank 7 are respectively provided with an air inlet and a material outlet, the air outlet of the air inlet pipe is connected to the air inlet of the material dispensing tank 7, and the material outlet of the material dispensing tank 7 is respectively connected to the first material receiving tank 1101, the second material receiving tank 1102, and the third material receiving tank 1103 through the conveying pipe; in the direction from the material dispensing tank 7 to each material receiving tank, the conveying pipe includes a first vertical section, a first bending section, a first horizontal section, a second bending section, a second vertical section, a third bending section, and a second horizontal section;

[0131] The conveying pipeline is provided with a first damper 1001, a second damper 1002, a third damper 1003 and a fourth damper 1004; the first damper 1001, the second damper 1002, the third damper 1003 and the fourth damper 1004 are respectively arranged at the starting end of the first horizontal section, the starting end of the second bending section, the starting end of the second vertical section and the starting end of the second horizontal section;

[0132] The first throttle 1001 , the second throttle 1002 , the third throttle 1003 , and the fourth throttle 1004 are respectively provided with a second gas mass flow meter 602 , a third gas mass flow meter 603 , a fourth gas mass flow meter 604 , and a fifth gas mass flow meter 605 .

[0133] The pneumatic conveying device further comprises a conveying gas processing module, and the conveying gas pre-processing module comprises a gas compressor 1, a freeze dryer 2 and a deoiler 3 which are connected in sequence, and the outlet of the deoiler 3 is connected to the air inlet of the air inlet pipe.

[0134] The air inlet pipeline is provided with a first pressure sensor 401, a temperature sensor 5 and a first gas mass flow meter 601. The first gas mass flow meter 601 is used to adjust the solid conveying amount in the pneumatic conveying process.

[0135] The second gas mass flow meter 602, the third gas mass flow meter 603, the fourth gas mass flow meter 604, and the fifth gas mass flow meter 605 are respectively used to adjust the conveying gas speed of the first horizontal section, the conveying gas speed of the second bending section, the conveying gas speed of the second vertical section, and the conveying gas speed of the second horizontal section.

[0136] The material delivery tank 7 is provided with a second pressure sensor 402 .

[0137] In the direction from the material sending tank 7 to each material receiving tank, the first horizontal section is sequentially provided with a third pressure sensor 403 and a fourth pressure sensor 404; the third pressure sensor 403 and the fourth pressure sensor 404 are both provided between the first throttle 1001 and the second throttle 1002.

[0138] In the direction from the material sending tank 7 to each material receiving tank, the second vertical section is provided with a fifth pressure sensor 405 and a sixth pressure sensor 406 in sequence.

[0139] A weighing system 8 is provided at the bottom of the dispensing tank 7; a dispensing valve 9 is provided at the first vertical section.

[0140] The pneumatic conveying device also includes a dust collector 12 and a booster pump 13 which are connected to each other. The dust collector 12 is arranged on the top of the material delivery tank 7 , and the outlet of the booster pump 13 is connected to the inlet of the freeze dryer 2 .

[0141] A gas phase outlet is provided at the top of each receiving tank, and the gas phase outlet is connected to the inlet of the dust collector 12 .

[0142] The pneumatic conveying device also includes a control module, which is electrically connected to the first gas mass flow meter 601, the second gas mass flow meter 602, the third gas mass flow meter 603, the fourth gas mass flow meter 604, and the fifth gas mass flow meter 605 respectively; the control module is also electrically connected to the first pressure sensor 401, the second pressure sensor 402, the third pressure sensor 403, the fourth pressure sensor 404, the fifth pressure sensor 405, the sixth pressure sensor 406, and the temperature sensor 5 respectively.

[0143] By using the pneumatic conveying device of this embodiment, the target material is continuously conveyed between different material tanks along the conveying pipeline under the pressure of compressed air provided by the gas compressor. The gas flow rate during the conveying process is measured and controlled by each gas mass flow meter, and the pressure signal is measured by the pressure sensor.

[0144] Example 2

[0145] This embodiment discloses a control method for pneumatic conveying. Figure 4 This is a flow control flowchart of this embodiment.

[0146] The general process of this control method is as follows:

[0147] First, the critical blockage velocity, minimum pressure drop velocity, and conveying velocity are calculated based on the signals of the gas flow meter and pressure sensor. Then, the target flow pattern is identified based on the average particle size and particle density of the conveyed material combined with the flow pattern criterion equation. The target gas volume is further calculated based on the relative size relationship between the target flow pattern and the conveying gas velocity corresponding to different flow patterns and the critical blockage velocity and minimum pressure drop velocity. Finally, the target gas volume is fed back to the gas flow meter to achieve real-time control of the pneumatic conveying flow pattern of powders and particles.

[0148] Specifically, this embodiment uses two powders and particles, powder 1 and powder 2, with greatly different physical properties as the target materials to be transported. The specific physical property parameters are as follows: the density of the transported particles of powder 1 and the average particle size of the transported particles are ρ p =1586kg / m 3 , d p =313μm; the density of the transported particles of the powder 2 and the average particle size of the transported particles are ρ p =2320kg / m 3 , d p =18μm.

[0149] Specifically, the control method comprises the following steps:

[0150] Step ss1, predicting the conveying flow pattern of the target material according to the average particle size and particle density of the target material in combination with the flow pattern criterion equation;

[0151] Based on the particle density and average particle size of the above two powders and particles, and combined with the flow pattern criterion equation, the flow pattern of the two powders and particles is determined, wherein the flow pattern criterion equation is:

[0152]

[0153] The prediction method of the conveying flow type is as follows: the average particle size and particle density of the target material are substituted into the flow type criterion equation; when the inequality of formula IV is satisfied, the conveying flow type of the target material is dilute phase conveying, and when the inequality of formula IV is not satisfied, the conveying flow type of the target material is dense phase conveying.

[0154] Figure 2 is a flow pattern prediction diagram based on particle density and average particle size; this diagram corresponds to the above flow pattern criterion equation. Figure 2 As shown, powder 1 belongs to Class II powder, and its conveying flow pattern is suitable for dilute phase conveying, while powder 2 belongs to Class I powder, and its conveying flow pattern is suitable for dense phase conveying.

[0155] This embodiment also discloses a modeling method for pneumatic conveying, which includes establishing a pneumatic conveying model, wherein the pneumatic conveying model includes a minimum pressure drop velocity model;

[0156] The training process of the minimum pressure drop rate model includes the following steps:

[0157] S1, obtaining at least two sets of fitting data, each set of fitting data including the conveying gas velocity U in the conveying pipeline g , and the conveying gas velocity U g The corresponding pressure drop of the transmission pipeline △P;

[0158] S2. Substituting the fitting data into a minimum pressure drop rate model, the minimum pressure drop rate model is as shown in Formula I:

[0159]

[0160] Among them, U e is the minimum pressure drop velocity, m / s; U g is the gas delivery velocity, m / s; △P is the pressure drop in the delivery pipeline, Pa; L is the length of the delivery pipeline, m; △P / L represents the pressure drop per unit length of the delivery pipeline, Pa / m;

[0161] In formula I, △P / L is calculated as formula II:

[0162]

[0163] Among them, λ g is the friction coefficient of the conveying gas; μ is the solid-gas ratio, that is, the ratio of the mass flow rate of the particles to the mass flow rate of the conveying gas; λ z is the additional pressure drop coefficient; ρ g is the density of the conveying gas, kg / m 3 ; D is the inner diameter of the delivery pipeline, m; ρ b is the bulk density, kg / m 3 ; g is the acceleration due to gravity, m / s 2; θ is the inclination angle of the conveying pipeline;

[0164] In formula II, the friction coefficient of the conveying gas λ g The calculation formula is as follows:

[0165] λ g =0.3164Re -0.25

[0166] Where Re is the Reynolds number;

[0167] In formula II, the additional pressure drop coefficient λ z The calculation formula is as follows:

[0168] λ z =aFr b

[0169] Wherein, Fr is the function of the additional pressure drop coefficient; a and b are fitting coefficients respectively;

[0170] S3. Fitting coefficients a and b are obtained by fitting, and the minimum pressure drop rate model is obtained by training.

[0171] Among them, the minimum pressure drop rate U e The calculation formula is simplified to:

[0172]

[0173] Among them, ρ g is the density of the conveying gas, kg / m 3 ; D is the inner diameter of the delivery pipeline, m; μ g is the dynamic viscosity of the transported gas, Pa·s; g is the acceleration due to gravity, m / s 2 ;M s is the solid mass flow rate, kg / s; a and b are fitting parameters;

[0174] The g It is calculated by combining pipeline gas volume, temperature and pressure; the ρ g The calculation formula is:

[0175]

[0176] The μ g 1.79×10 -5 Pa·s; g is 9.79m / s 2 ; The M s Measured by a weighing system.

[0177] The pneumatic conveying model also includes a critical blockage velocity model; the critical blockage velocity model is shown in Formula III:

[0178]

[0179] Among them, C D is the drag coefficient, C D The value is 0.44; U b is the critical blocking gas velocity, m / s; θ is the inclination angle of the delivery pipeline; μ g is the dynamic viscosity of the transported gas, Pa·s; ρ g is the density of the conveying gas, kg / m 3 ;d p is the average particle size of the transported particles, m; g is the acceleration due to gravity, m / s 2 ρ p is the density of the transported particles, kg / m 3 ;

[0180] Figure 3 Schematic diagram of the force analysis of powder particles in the pipeline. Critical blocking gas velocity (U b ) can be defined as the minimum conveying gas velocity corresponding to the particle group moving in the conveying direction in the pneumatic conveying system when the velocity approaches zero. According to the shear law of powder and granular bodies, the driving force of the powder and granular particles in the horizontal direction depends on the force they are subjected to in the vertical direction. When the force on the particles in the vertical direction is in equilibrium, the velocity of the particles in the horizontal direction is 0, which is in a critical blocking state. Therefore, when the sum of the forces on the particles in the vertical direction is 0, the corresponding conveying gas velocity U g The critical blocking velocity U b .like Figure 3 As shown, the critical blockage gas velocity U b The calculation model uses the gravity F of the transported particles G , Saffman lift force F for transporting particles L , buoyancy F of transported particles B , drag force F D Combined with Newton's second law, the equation of motion of the particle is:

[0181]

[0182] Among them, m p is the mass of the transported particles, kg; F B is the buoyancy of the transported particles, N; F G is the gravity of the transported particles, N; F L is the Saffman lift force for transporting particles, N; F B is the buoyancy of the transported particles, N; F D is the drag force for transporting particles, N; is the particle conveying speed U p The rate of change over time t; U pis the speed of conveying particles, m / s; θ is the inclination angle of the conveying pipeline;

[0183] Gravity F of the transported particles G The calculation formula is as follows:

[0184]

[0185] Among them, π is the ratio of circumference to diameter; d p is the average particle size of the transported particles, m; ρ p is the density of the transported particles, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;

[0186] Saffman Lift F L The calculation formula is as follows:

[0187]

[0188] Among them, μ g is the dynamic viscosity of the transported gas, Pa·s; ρ g is the density of the conveying gas, kg / m 3 ;d p is the average particle size of the transported particles, m; U g is the conveying gas velocity, m / s; U p is the speed of conveying particles, m / s; dU g / dy is the conveying gas velocity U g The velocity gradient perpendicular to the conveying direction;

[0189] Buoyancy F of transported particles B The calculation formula is as follows:

[0190]

[0191] Among them, π is the ratio of circumference to diameter; d p is the average particle size of the transported particles, m; ρ g is the density of the conveying gas, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ;

[0192] Drag force F D The calculation formula is as follows:

[0193]

[0194] Among them, C D is the drag coefficient, C D is 0.44; π is the ratio of the circumference of a circle; d p is the average particle size of the transported particles, m; ρ pis the density of the transported particles, kg / m 3 ; U g is the conveying gas velocity, m / s; U p is the speed of conveying particles, m / s;

[0195] The equation of motion for the particle uses boundary conditions, U p =0.

[0196] The d p Measured by a particle size analyzer; the ρ p Measured by a particle density meter; the ρ g The calculation is performed based on the pressure and gas temperature of the delivery pipeline; the inner diameter of the delivery pipeline is 0.2 m.

[0197] Powder 1 and powder 2 were tested in the pneumatic conveying device of Example 1. Two groups of pneumatic conveying experiments were carried out at different conveying gas velocities. According to the minimum pressure drop rate U e The calculation formula is used to obtain the parameters a and b through power function fitting.

[0198] According to formula III and the above formula, the critical blockage gas velocity U under different working conditions can be calculated respectively: b and minimum pressure drop rate U e .

[0199] Step ss2, determining the conveying gas velocity range of the target material according to the conveying flow pattern of the target material and in combination with the minimum pressure drop velocity and critical blocking gas velocity predicted in step ss1;

[0200] Specifically, according to the target flow pattern predicted in Example 1, combined with the delivery gas velocity control method based on the target flow pattern, the corresponding target delivery gas velocity U can be given. t . Further, U t Substituting into the following formula, the target gas flow rate Q can be calculated t .

[0201]

[0202] Finally, the total gas volume entering the system and Q are controlled by the gas flow meter. t The same is used to verify the practicability of the present invention.

[0203] Step ss3: Based on the conveying gas speed range in step ss2, the conveying gas speed of the target material is adjusted.

[0204] By carrying out different conveying material and solid mass flow rate M s The pneumatic conveying experiment under the condition of 2000 ℃ was carried out, and the flow pattern control results of pneumatic conveying of powder and granular materials were obtained as shown in Tables 1, 2 and 3. Figure 3 Table 2 corresponds to the first horizontal section, Table 2 corresponds to the second bending section, and Table 3 corresponds to the second vertical section. The transport flow pattern in the table is based on the transport solid-gas ratio and the capacitance tomography system. The transport flow pattern when the solid-gas ratio is less than 50kg / kg belongs to the dilute phase, otherwise it is the dense phase.

[0205] The capacitance tomography system can obtain the relative solid concentration of the powder during the transportation process. When the relative solid concentration is greater than 0.5, the transportation flow pattern can be considered to be dense phase, otherwise it is dilute phase. Table 1 shows the flow pattern control results of powder 1 and powder 2.

[0206] Table 1

[0207]

[0208] Table 2

[0209]

[0210] Table 3

[0211]

[0212] According to Tables 1, 2 and 3, the present invention can realize accurate control of the pneumatic conveying flow pattern of powders and particles based on the relative size adjustment of the conveying gas velocity, the critical blocking gas velocity and the minimum pressure drop velocity.

Claims

1. A modeling method for pneumatic conveying, characterized in that: It includes establishing a pneumatic conveying model, wherein the pneumatic conveying model includes a minimum pressure drop velocity model; The training process of the minimum pressure drop rate model includes the following steps: S1, obtaining at least two sets of fitting data, each set of fitting data including the conveying gas velocity U in the conveying pipeline g , and the conveying gas velocity U g The corresponding pressure drop of the transmission pipeline △P; S2. Substituting the fitting data into a minimum pressure drop rate model, the minimum pressure drop rate model is as shown in Formula I: Among them, U e is the minimum pressure drop velocity, m / s; U g is the gas delivery velocity, m / s; △P is the pressure drop in the delivery pipeline, Pa; L is the length of the delivery pipeline, m; △P / L represents the pressure drop per unit length of the delivery pipeline, Pa / m; In formula I, △P / L is calculated as formula II: Among them, λ g is the friction coefficient of the conveying gas; μ is the solid-gas ratio, that is, the ratio of the mass flow rate of the particles to the mass flow rate of the conveying gas; λ z is the additional pressure drop coefficient; ρ g is the density of the conveying gas, kg / m 3 ; D is the inner diameter of the delivery pipeline, m; ρ b is the bulk density, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; θ is the inclination angle of the conveying pipeline; In formula II, the friction coefficient of the conveying gas λ g The calculation formula is as follows: l g =0.3164Re -0.25 Where Re is the Reynolds number; In formula II, the additional pressure drop coefficient λ z The calculation formula is as follows: λ z =aFr b Wherein, Fr is the function of the additional pressure drop coefficient; a and b are fitting coefficients respectively; S3. Fitting coefficients a and b are obtained by fitting, and the minimum pressure drop rate model is obtained by training.

2. The modeling method of pneumatic conveying according to claim 1, characterized in that: The minimum pressure drop rate U e The calculation formula is simplified to: Among them, ρ g is the density of the conveying gas, kg / m 3 ; D is the inner diameter of the delivery pipeline, m; μ g is the dynamic viscosity of the transported gas, Pa·s; g is the acceleration due to gravity, m / s 2 ;M s is the solid mass flow rate, kg / s; a and b are fitting parameters; Preferably, the g It is calculated by combining pipeline gas volume, temperature and pressure; the ρ g The calculation formula is: Preferably, the μ g 1.79×10 -5 Pa·s; Preferably, the g is 9.79 m / s 2 ; Preferably, the M s Measured by a weighing system.

3. The modeling method of pneumatic conveying according to claim 1, characterized in that: The pneumatic conveying model also includes a critical blockage gas velocity model; The critical blockage velocity model is shown in Formula III: Among them, C D is the drag coefficient; U b is the critical blocking gas velocity, m / s; θ is the inclination angle of the delivery pipeline; μ g is the dynamic viscosity of the transported gas, Pa·s; ρ g is the density of the conveying gas, kg / m 3 ;d p is the average particle size of the transported particles, m; g is the acceleration due to gravity, m / s 2 ρ p is the density of the transported particles, kg / m 3 ; Preferably, C D It is 0.

44.

4. The modeling method of pneumatic conveying as claimed in claim 3, characterized in that: The critical blockage gas velocity U b The calculation model uses the gravity F of the transported particles G , Saffman lift force F for transporting particles L , buoyancy F of transported particles B , drag force F D Combined with Newton's second law, the equation of motion of the particle is: Among them, m p is the mass of the transported particles, kg; F G is the gravity of the transported particles, N; F B is the buoyancy of the transported particles, N; F L is the Saffman lift force for transporting particles, N; F D is the drag force for transporting particles, N; is the particle conveying speed U p The rate of change over time t, U p is the speed of conveying particles, m / s; θ is the inclination angle of the conveying pipeline; Preferably, the gravity F of the transported particles G The calculation formula is as follows: Among them, π is the ratio of the circumference of a circle; d p is the average particle size of the transported particles, m; ρ p is the density of the transported particles, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; Preferably, the Saffman lift F L The calculation formula is as follows: Among them, μ g is the dynamic viscosity of the transported gas, Pa·s; ρ g is the density of the conveying gas, kg / m 3 ;d p is the average particle size of the transported particles, m; U g is the conveying gas velocity, m / s; U p is the speed of conveying particles, m / s; dU g / dy is the conveying gas velocity U g The velocity gradient perpendicular to the conveying direction; Preferably, the buoyancy F of the transported particles B The calculation formula is as follows: Among them, π is the ratio of the circumference of a circle; d p is the average particle size of the transported particles, m; ρ g is the density of the conveying gas, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; Preferably, the drag force F D The calculation formula is as follows: Among them, C D is the drag coefficient, which is 0.44; π is the circumference of a circle; d p is the average particle size of the transported particles, m; ρ p is the density of the transported particles, kg / m 3 ; U g is the conveying gas velocity, m / s; U p is the speed of conveying particles, m / s; Preferably, C D is 0.44; Preferably, the equation of motion of the particle adopts boundary conditions, U p =0.

5. The modeling method of pneumatic conveying as claimed in claim 4, characterized in that: The training method of the pneumatic conveying model satisfies one or more of the following conditions: ①The above p Measured by particle size analyzer; ②The above p Measured by particle density meter; ③The above g Calculation is based on the pressure and gas temperature of the delivery pipeline; ④ The particles include biomass; ⑤ The particle size of the particles is 0.01 mm to 5 mm; ⑥The inner diameter of the conveying pipeline is 0.01m~0.2m.

6. A method for controlling pneumatic conveying, characterized in that: It includes the following steps: Step ss1, predicting the conveying flow pattern of the target material according to the average particle size and particle density of the target material in combination with the flow pattern criterion equation; and using the minimum pressure drop velocity model and the critical blockage gas velocity model obtained by the pneumatic conveying modeling method as described in any one of claims 3 to 5 to predict the minimum pressure drop velocity U of the target material. e and critical blockage velocity U b ; Step ss2, determining the conveying gas velocity range of the target material according to the conveying flow pattern of the target material and in combination with the minimum pressure drop velocity and critical blocking gas velocity predicted in step ss1; Step ss3: Based on the conveying gas speed range in step ss2, the conveying gas speed of the target material is adjusted.

7. The pneumatic conveying control method according to claim 6, characterized in that: The flow pattern criterion equation is: Preferably, the transport flow pattern is predicted as follows: the average particle size and particle density of the target material are substituted into the flow pattern criterion equation; when the inequality of formula IV is satisfied, the transport flow pattern of the target material is dilute phase transport, and when the inequality of formula IV is not satisfied, the transport flow pattern of the target material is dense phase transport; And / or, the conveying gas velocity U of the conveying gas g The calculation method is as follows: Collect the pneumatic conveying information and calculate the conveying gas velocity U according to formula V g The pneumatic conveying information includes the inner diameter D of the conveying pipeline, the pressure P of the conveying pipeline, and the volume flow rate Q of the conveying gas; And / or, the control method of pneumatic conveying is carried out in a pneumatic conveying device, which includes an air inlet pipe, a material dispensing tank, a conveying pipe and a plurality of material receiving tanks; an air inlet and a material outlet are respectively provided at the lower part and the bottom of the material dispensing tank, the air outlet of the air inlet pipe is connected to the air inlet of the material dispensing tank, and the material outlet of the material dispensing tank is respectively connected to each of the material receiving tanks through the conveying pipe; in the direction from the material dispensing tank to each of the material receiving tanks, the conveying pipe sequentially includes a first vertical section, a first bending section, a first horizontal section, a second bending section, a second vertical section, a third bending section and a second horizontal section; The conveying pipeline is provided with a first throttle, a second throttle, a third throttle and a fourth throttle; the first throttle, the second throttle, the third throttle and the fourth throttle are respectively arranged at the starting end of the first horizontal section, the starting end of the second bending section, the starting end of the second vertical section and the starting end of the second horizontal section; The first throttle, the second throttle, the third throttle and the fourth throttle are respectively provided with a second gas mass flow meter, a third gas mass flow meter, a fourth gas mass flow meter and a fifth gas mass flow meter; Preferably, the pneumatic conveying device further comprises a conveying gas processing module, the conveying gas pre-processing module comprises a gas compressor, a freeze dryer and a deoiler connected in sequence, and the outlet of the deoiler is connected to the air inlet of the air inlet pipeline; Preferably, the air inlet pipeline is provided with a first pressure sensor, a temperature sensor and a first gas mass flow meter, and the first gas mass flow meter is used to adjust the solid conveying amount in the pneumatic conveying process; Preferably, the second gas mass flow meter, the third gas mass flow meter, the fourth gas mass flow meter, and the fifth gas mass flow meter are used to adjust the conveying gas speed of the first horizontal section, the conveying gas speed of the second bending section, the conveying gas speed of the second vertical section, and the conveying gas speed of the second horizontal section respectively; Preferably, the material delivery tank is provided with a second pressure sensor; Preferably, in the direction from the material sending tank to each of the material receiving tanks, the first horizontal section is provided with a third pressure sensor and a fourth pressure sensor in sequence; the third pressure sensor and the fourth pressure sensor are both provided between the first damper and the second damper; Preferably, in the direction from the material sending tank to each of the material receiving tanks, the second vertical section is provided with a fifth pressure sensor and a sixth pressure sensor in sequence; Preferably, a weighing system is provided at the bottom of the dispensing tank; and a discharging valve is provided at the first vertical section; Preferably, the pneumatic conveying device further comprises a dust collector and a booster pump connected to each other, the dust collector is arranged on the top of the material delivery tank, and the outlet of the booster pump is connected to the inlet of the freeze dryer; Preferably, a gas phase outlet is provided at the upper portion of each receiving tank, and the gas phase outlet is connected to the inlet of the dust collector; Preferably, the pneumatic conveying device also includes a control module, which is electrically connected to the first gas mass flow meter, the second gas mass flow meter, the third gas mass flow meter, the fourth gas mass flow meter, the fifth gas mass flow meter, the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor, the fifth pressure sensor, the sixth pressure sensor, and the temperature sensor, respectively.

8. A pneumatic conveying control system, characterized in that: It includes a control unit, which is electrically connected to the gas flow meter and pressure sensor of the pneumatic conveying device in the pneumatic conveying control method as described in claim 7, and is used to convert the received pressure signal into a gas flow control signal to regulate the gas flow meter.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the modeling method for pneumatic conveying according to any one of claims 1 to 5, or the control method for pneumatic conveying according to claim 6 or 7 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the modeling method for pneumatic conveying according to any one of claims 1 to 5, or the control method for pneumatic conveying according to claim 6 or 7 is implemented.

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