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

Abstract

The application provides a modeling method, a control method and a system, and equipment for pneumatic conveying. The pneumatic conveying comprises a pneumatic conveying model, and the pneumatic conveying model comprises a minimum pressure drop velocity model. A training process of the minimum pressure drop velocity model comprises the following steps: S1, obtaining at least two groups of fitting data, each group of fitting data comprising a conveying gas velocity in a conveying pipeline and a conveying pipeline pressure drop corresponding to the conveying gas velocity; S2, substituting the fitting data into the minimum pressure drop velocity model; and S3, fitting to obtain fitting coefficients, and training to obtain the minimum pressure drop velocity model. The application can be aimed at a flow pattern of target material, and can calculate a conveying gas velocity, a critical choking gas velocity and a minimum pressure drop velocity in real time, and can measure and control the conveying gas velocity in the pipeline. The system can realize real-time control of a material pneumatic conveying flow pattern.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder particle pneumatic conveying, in particular to a modeling method, a control method and system, and equipment for pneumatic conveying. BACKGROUND

[0002] In the prior art, the conveying of powder particles usually adopts mechanical conveying and pneumatic conveying. Pneumatic conveying has lower mechanical wear and energy consumption than mechanical conveying, and is therefore widely used in many industrial applications. Pneumatic conveying can be divided into 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 velocity (critical gas velocity for dilute phase conveying and dense phase conveying). Dense phase pneumatic conveying moves the powder particles in the form of a deposited layer or group in the pipeline by precisely controlling the gas flow rate in the pipeline. 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 actual applications, the pneumatic conveying flow pattern of powder particles is affected by many factors such as material properties, system structure, and operating parameters. When the material properties of powder particles differ greatly, the applicable flow pattern will also differ, and even plugging (when the conveying gas velocity is lower than the critical plugging gas velocity) can occur. For example, for powdery materials with poor flowability, the conveying efficiency can be improved by optimizing the design of the flow aid fittings and gas distribution components of the sending tank. Therefore, reasonable selection of the conveying flow pattern is crucial to ensure the smooth and efficient operation of the pneumatic conveying system, and also helps to avoid pipeline plugging and the operation of powder particles in the dilute phase interval. In view of the important influence of the flow pattern on the pneumatic conveying of powder particles, the development of a pneumatic conveying system and control method capable of effectively controlling the flow pattern has important theoretical and practical significance for the development and automated operation of the pneumatic conveying system of powder particles in industrial applications. However, the current conveying flow pattern relies on the prediction of the material properties of powder particles, and there is still a lack of specific operation methods for achieving this goal in actual operation. SUMMARY

[0004] In order to overcome the defects of easy plugging or high energy consumption in the prior art when conveying materials by pneumatic conveying, the present application provides a modeling method, a control method and system, and equipment for pneumatic conveying. The control method can calculate the conveying gas velocity, the critical plugging gas velocity and the minimum pressure drop velocity in real time according to the flow pattern of the target material, and measure and control the conveying gas velocity in the pipeline. The system can realize real-time control of the flow pattern of the material in pneumatic conveying. The present application has important significance for guiding the design of the pneumatic conveying device of powder particles in industrial applications and realizing safe and efficient operation.

[0005] The application provides a modeling method of pneumatic conveying, which comprises establishing a pneumatic conveying model, wherein the pneumatic conveying model comprises a minimum pressure drop velocity model;

[0006] The training process of the minimum pressure drop velocity model comprises the following steps:

[0007] S1, acquiring at least two groups of fitting data, wherein each group of the fitting data comprises a conveying gas velocity U g in a conveying pipeline g and a corresponding conveying pipeline pressure drop ΔP;

[0008] S2, substituting the fitting data into the minimum pressure drop velocity model, wherein the minimum pressure drop velocity model is as shown in formula I:

[0009]

[0010] wherein U e is the minimum pressure drop velocity, m / s; U g is the conveying gas velocity, m / s; ΔP is the conveying pipeline pressure drop, Pa; L is the length of the conveying pipeline, m; and ΔP / L represents the unit pipe length pressure drop of the conveying pipeline, Pa / m;

[0011] In formula I, the calculation method of ΔP / L is as shown in formula II:

[0012]

[0013] wherein λ g is the friction coefficient of the conveying gas; μ is the solid-gas ratio, i.e. the ratio of the mass flow of the particles to the mass flow 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 conveying pipeline, m; ρ b is the bulk density, kg / m 3 ; g is the acceleration of gravity, m / s 2 ; and θ is the inclination angle of the conveying pipeline;

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

[0015] λ g = 0.3164Re -0.25

[0016] wherein Re is the Reynolds number;

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

[0018] λ z= aFr b

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

[0020] S3, fitting to obtain fitting coefficients a, b, and training to obtain the minimum pressure drop velocity model.

[0021] In the present application, the material for pneumatic conveying can include powder particles.

[0022] In the present application, the minimum pressure drop velocity refers to the optimal gas flow velocity in the pneumatic conveying device, which can ensure stable and efficient conveying of the material, and can maximize the reduction of energy consumption and pipeline wear, and the point corresponding to the minimum pressure drop per unit pipe length; in the field, it can also be referred to as "economic gas velocity".

[0023] In the present application, d(△P / L) / dU g = 0 represents that the change rate of pressure drop per unit pipe length is zero, corresponding to the lowest point of pressure drop.

[0024] In the present application, by taking the first derivative of U g in formula II, and setting the derivative to 0, U e is obtained. represents "U g at the minimum pressure drop velocity". According to the pneumatic conveying phase diagram, when the conveying capacity is constant, with the increase of the conveying gas velocity, the pressure drop per unit pipe length in the conveying pipeline shows a trend of first decreasing and then increasing. The gas velocity corresponding to the minimum value of the pressure drop per unit pipe length is called economic gas velocity. Therefore, by establishing a pipeline pressure drop model and then taking the derivative of the pipeline pressure drop model, the calculation model of the minimum pressure drop velocity can be obtained.

[0025] In the present application, pipeline pressure drop experimental data under different conveying gas velocities are obtained, and fitting coefficients a, b are obtained by data fitting of λ z ~ Fr.

[0026] In some embodiments, the calculation formula of the minimum pressure drop velocity U e is simplified as:

[0027]

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

[0029] In specific embodiments, the p g is calculated by combining the amount of pipeline gas, temperature and pressure; the p g The calculation formula is:

[0030]

[0031] In specific embodiments, the p g is 1.79 x 10 -5 Pa s.

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

[0033] In specific embodiments, the M s is measured by a weighing system.

[0034] In some embodiments, the pneumatic conveying model further comprises a critical choking gas velocity model; the critical choking gas velocity model is shown as formula III:

[0035]

[0036] wherein, C D is the drag coefficient; U b is the critical choking gas velocity, m / s; θ is the inclination angle of the conveying pipeline; p g is the dynamic viscosity of the conveying gas, Pa s; p g is the density of the conveying gas, kg / m 3 ; d p is the average particle size of the conveying particles, m; g is the acceleration of gravity, m / s 2 ; p p is the density of the conveying particles, kg / m 3 ;

[0037] In specific embodiments, C D is 0.44.

[0038] In the present application, the critical choking gas velocity refers to the minimum conveying gas velocity required for the pneumatic conveying process to occur smoothly. The pneumatic conveying of powder particles is essentially a gas-solid two-phase flow process of interaction between particles and gas flow. When the conveying gas velocity is large enough, the particles are conveyed in the form of suspended flow under the action of the gas flow. As the conveying gas velocity decreases, some particles with small particle size are insufficiently subjected to aerodynamic force to overcome gravity and begin to settle. When the conveying gas velocity decreases to a certain value, the particles settled at the bottom of the pipeline form a stationary sedimentation layer, which eventually causes pipeline blockage. The critical choking gas velocity (U b) can be defined as the lowest conveying gas velocity corresponding to the velocity of the particle group in the conveying direction approaching zero in the pneumatic conveying system. According to the shear law of the powder particles, the driving force of the powder particles in the horizontal direction depends on the force in the vertical direction. When the force in the vertical direction of the particles is in a balanced state, the velocity of the particles in the horizontal direction is 0, and the particles are in a critical jamming state. Therefore, when the sum of the forces in the vertical direction of the particles is 0, the corresponding conveying gas velocity U g is the critical jamming gas velocity U b .

[0039] In a specific embodiment, the critical jamming gas velocity U b is calculated by the gravity F G of the conveying particles, the Saffman lift F L of the conveying particles, the buoyancy F B of the conveying particles, and the drag force F D combined with Newton's second law, and the motion equation of the particles is as follows:

[0040]

[0041] wherein m p is the mass of the conveying particles, kg; F B is the buoyancy of the conveying particles, N; F G is the gravity of the conveying particles, N; F L is the Saffman lift of the conveying particles, N; F D is the drag force of the conveying particles, N; is the change rate of the conveying particle velocity U p with respect to time t, U p is the velocity of the conveying particles, m / s; and θ is the inclination angle of the conveying pipeline.

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

[0043]

[0044] wherein π is the circular constant; d p is the average particle size of the conveying particles, m; g is the acceleration of gravity, m / s 2 ; and ρ p is the density of the conveying particles, kg / m 3 .

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

[0046]

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

[0048] In a preferred embodiment, the buoyancy force F B of the conveying particles is calculated as follows:

[0049]

[0050] wherein π is the circular constant; d p is the average particle size of the conveying particles, m; ρ g is the density of the conveying particles, kg / m 3 ; and g is the acceleration of gravity, m / s 2 .

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

[0052]

[0053] wherein C D is the drag coefficient, which has a value of 0.44; π is the circular constant; d p is the average particle size of the conveying particles, m; ρ p is the density of the conveying particles, kg / m 3 ; U g is the conveying gas velocity, m / s; U p is the velocity of the conveying particles, m / s;

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

[0055] In a preferred embodiment, the equation of motion of the particles takes the boundary condition, U p = 0.

[0056] In a specific embodiment, d p is measured by a particle size instrument.

[0057] In a specific embodiment, ρ p is measured by a particle density instrument.

[0058] In specific embodiments, the ρ g The calculation is based on the pressure and the gas temperature of the conveying pipeline; specifically, the calculation method is as follows:

[0059]

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

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

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

[0063] In specific embodiments, the inner diameter of the conveying pipeline is 0.01 m to 0.2 m.

[0064] The application also provides a control method of pneumatic conveying, comprising the following steps:

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

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

[0067] Step ss3, regulating the conveying gas velocity of the target material based on the conveying gas velocity interval in step ss2.

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

[0069]

[0070] In specific embodiments, the prediction method of the conveying flow pattern is as follows: substituting the average particle size and the particle density of the target material into the flow pattern criterion equation; when the inequality of formula IV is satisfied, the conveying flow pattern of the target material is dilute phase conveying, and when the inequality of formula IV is not satisfied, the conveying flow pattern of the target material is dense phase conveying.

[0071] In the present application, by inputting the particle density p p and the average particle size d p of the target material, the prediction of the applicable flow pattern of the target material can be realized; specifically, according to the interrelation between the particle density and the volume average particle size (the particle size of a sphere having the same volume as the particle) of the target material, the target material can be classified into three types of powder particles, namely, type I, type II and type III. The particle density and the average particle size of the powder particles of type I are relatively small, and the powder particles of type I are suitable for dense phase conveying. The powder particles of type II have a relatively large particle size, and the powder particles of type II can only be conveyed in a dilute phase. The powder particles of type III have a very large particle size, and the powder particles of type III are suitable for plug flow (which belongs to a type of dense phase flow) conveying. Thus, the powder particles of types I and III are both suitable for dense phase conveying, and the powder particles of type II are suitable for dilute phase conveying.

[0072] In some embodiments, the actual flow rate U g of the conveying gas is calculated as follows: collecting pneumatic conveying information, and calculating the actual flow rate U g of the conveying gas according to formula V; 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 of the calculation conveying pipeline under standard state, and P is the gage pressure of the conveying pipeline. Q is obtained by calculation of the indications of the gas mass flow meters; for example, for the first horizontal section, the gas mass flow meters 601 and 602 are arranged in the front section thereof, and the volume flow rate of the conveying gas in the horizontal section is the sum of the indications of the two gas mass flow meters, i.e. Q = Q1 + Q2.

[0075] In step ss2 of the present application, the conveying gas velocity range of the target material is as follows: when the flow pattern 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 conveying, U g >U e .

[0076] In some embodiments, the control method of the pneumatic conveying is performed in a pneumatic conveying device, and the pneumatic conveying device includes an air inlet pipeline, a feeding tank, a conveying pipeline and a plurality of receiving tanks; the lower part and the bottom part of the feeding tank are respectively provided with an air inlet and a discharge outlet, the air outlet of the air inlet pipeline is connected with the air inlet of the feeding tank, and the discharge outlet of the feeding tank is connected with each of the receiving tanks through the conveying pipeline; from the feeding tank to each of the receiving tanks, the conveying pipeline 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 in sequence.

[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 treatment module, the conveying gas pretreatment module comprises a gas compressor, a freeze dryer and an oil remover connected in sequence, and the outlet of the oil remover is connected with the gas inlet of the gas inlet pipeline;

[0080] Preferably, the gas 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 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;

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

[0083] Preferably, from the feeding tank to each receiving tank, 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 arranged between the first throttle and the second throttle;

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

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

[0086] Preferably, the pneumatic conveying device further comprises a dust remover and a booster pump connected with each other; the dust remover is arranged at the top of the feeding tank; and the outlet of the booster pump is connected with the inlet of the freeze dryer;

[0087] Preferably, each of the receiving tanks is provided with a gas phase outlet at the top, and the gas phase outlet is connected to the inlet of the dust collector;

[0088] Preferably, the pneumatic conveying device further 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. The control unit is electrically connected to a gas flow meter and a pressure sensor of the pneumatic conveying device in the pneumatic conveying control method 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, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the pneumatic conveying modeling method as described above, or the pneumatic conveying control method as described above.

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

[0092] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0093] The reagents and raw materials used in this invention are all commercially available.

[0094] The positive and progressive effects of this invention are as follows:

[0095] Based on the flow pattern determined by the particle density and average particle size of the material, this invention can 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. This system can realize real-time control of the flow pattern of pneumatic conveying of powder and granules, effectively improving the efficiency of pneumatic conveying devices for powder and granules. Attached Figure Description

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

[0097] Figure 2Flow pattern prediction map based on material's particle density and average particle size;

[0098] Figure 3 Schematic diagram for force analysis of particles in pipeline;

[0099] Figure 4 Flow pattern control flow chart of example 2.

[0100] Explanation of reference signs:

[0101] Gas compressor 1

[0102] Freeze dryer 2

[0103] Oil remover 3

[0104] First pressure sensor 401

[0105] Second pressure sensor 402

[0106] 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] 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] Discharge valve 9

[0119] First air throttle 1001

[0120] Second air throttle 1002

[0121] Third air throttle 1003

[0122] Fourth air throttle 1004

[0123] First receiving tank 1101

[0124] Second receiving tank 1102

[0125] Third receiving tank 1103

[0126] Dust collector 12

[0127] Booster pump 13. DETAILED DESCRIPTION

[0128] The application will be further described in the following examples without limiting the application to the examples described. The experimental methods in the following examples, if not otherwise specified, are carried out according to the conventional methods and conditions, or according to the instructions of the commercial products.

[0129] Example 1

[0130] The embodiment discloses a pneumatic conveying device. The device comprises an air inlet pipe, a feeding tank 7, a conveying pipe and three receiving tanks; the lower part and the bottom of the feeding tank 7 are respectively provided with an air inlet and an outlet, the air outlet of the air inlet pipe is connected with the air inlet of the feeding tank 7, and the outlet of the feeding tank 7 is connected with the first receiving tank 1101, the second receiving tank 1102 and the third receiving tank 1103 through the conveying pipe; from the feeding tank 7 to each receiving tank, the conveying pipe comprises 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 in sequence.

[0131] The conveying pipe is provided with a first air throttle 1001, a second air throttle 1002, a third air throttle 1003 and a fourth air throttle 1004; the first air throttle 1001, the second air throttle 1002, the third air throttle 1003 and the fourth air throttle 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 air throttle 1001, the second air throttle 1002, the third air throttle 1003 and the fourth air 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 treatment module, and the conveying gas pretreatment module comprises a gas compressor 1, a freeze dryer 2 and an oil remover 3 connected in sequence, and the outlet of the oil remover 3 is connected with the air inlet of the air inlet pipe.

[0134] The air inlet pipe is provided with a first pressure sensor 401, a temperature sensor 5 and a first gas mass flow meter 601, and 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 velocity of the first horizontal section, the conveying gas velocity of the second bending section, the conveying gas velocity of the second vertical section, and the conveying gas velocity of the second horizontal section.

[0136] The feed tank 7 is provided with the second pressure sensor 402.

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

[0138] In the direction from the feed tank 7 to each receiving tank, the second vertical section is sequentially provided with the fifth pressure sensor 405 and the sixth pressure sensor 406.

[0139] The bottom of the feed tank 7 is provided with the weighing system 8, and the first vertical section is provided with the discharging valve 9.

[0140] The pneumatic conveying device further comprises a dust collector 12 and a booster pump 13 connected to each other, the dust collector 12 is arranged at the top of the feed tank 7, and the outlet of the booster pump 13 is connected to the inlet of the freeze dryer 2.

[0141] The upper part of each receiving tank is provided with a gas phase outlet connected to the inlet of the dust collector 12.

[0142] The pneumatic conveying device further comprises a control module, the control module 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; and 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 the embodiment, the target material is continuously conveyed between different tanks along the conveying pipeline under the carrying of the compressed air provided by the gas compressor. The gas flow in the conveying process is measured and controlled by the gas mass flow meters, and the pressure signal is measured by the pressure sensors.

[0144] Embodiment 2

[0145] The embodiment discloses a control method of pneumatic conveying. Figure 4 The flow type control flowchart of the embodiment is shown in FIG. 2.

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

[0147] First, the critical blockage velocity, minimum pressure drop velocity, and conveying velocity are calculated based on signals from the gas flow meter and pressure sensor. Then, the target flow pattern is identified by combining the average particle size and particle density of the conveyed material with the flow pattern criterion equation. Further, the target gas volume is calculated based on the target flow pattern and the relative magnitudes of the conveying velocity with the critical blockage velocity and minimum pressure drop velocity corresponding to different flow patterns. Finally, by feeding back the target gas volume to the gas flow meter, real-time control of the pneumatic conveying flow pattern of powder and granular materials is achieved.

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

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

[0150] Step ss1: Based on the average particle size and particle density of the target material, predict the conveying flow pattern of the target material using the flow pattern criterion equation;

[0151] Based on the particle density and average particle size of the two types of powders mentioned above, and in conjunction with the flow pattern criterion equation, the flow patterns of the two types of powders are determined. The flow pattern criterion equation is as follows:

[0152]

[0153] The prediction method for this conveying flow pattern is as follows: Substitute the average particle size and particle density of the target material into the flow pattern criterion equation; when the inequality of Equation IV is satisfied, the conveying flow pattern of the target material is dilute phase conveying; when the inequality of Equation IV is not satisfied, the conveying flow pattern of the target material is dense phase conveying.

[0154] Figure 2 This is a flow pattern prediction diagram based on particle density and average particle size; this diagram corresponds to the flow pattern criterion equation mentioned above. Figure 2 As shown, powder 1 belongs to Class II powder, and its conveying flow pattern is suitable for dilute phase conveying; 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 velocity model comprises the following steps:

[0157] S1, obtaining at least two groups of fitting data, each group of fitting data comprising a conveying gas velocity U g in a conveying pipeline and a corresponding conveying pipeline pressure drop ΔP; g

[0158] S2, substituting the fitting data into the minimum pressure drop velocity model, the minimum pressure drop velocity model being as shown in Formula I:

[0159]

[0160] wherein U e is the minimum pressure drop velocity, m / s; U g is the conveying gas velocity, m / s; ΔP is the conveying pipeline pressure drop, Pa; L is the length of the conveying pipeline, m; and ΔP / L represents the unit length pressure drop of the conveying pipeline, Pa / m.

[0161] In Formula I, the calculation method of ΔP / L is as shown in Formula II:

[0162]

[0163] wherein λ g is the friction coefficient of the conveying gas; μ is the solid-gas ratio, i.e. the ratio of the mass flow of the particles to the mass flow 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 conveying pipeline, m; ρ b is the bulk density, kg / m 3 ; g is the acceleration of gravity, m / s 2 ; and θ is the inclination angle of the conveying pipeline.

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

[0165] λ g = 0.3164Re -0.25

[0166] wherein Re is the Reynolds number.

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

[0168] λ z = aFr b

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

[0170] S3, fitting to obtain fitting coefficients a, b, training to obtain the minimum pressure drop velocity model.

[0171] Wherein, the minimum pressure drop velocity U e The calculation formula is simplified as:

[0172]

[0173] Wherein, ρ g The density of conveying gas, kg / m 3 ; D is the inner diameter of conveying pipeline, m; μ g The dynamic viscosity of conveying gas, Pa·s; g is the acceleration of gravity, m / s 2 ; M s Solid mass flow, kg / s; a, b are fitting parameters;

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

[0175]

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

[0177] The pneumatic conveying model further comprises a critical choking velocity model; the critical choking velocity model is as shown in formula III:

[0178]

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

[0180] Figure 3 This is a schematic diagram illustrating the force analysis of powder particles inside a pipeline. Critical blockage velocity (U) b The velocity U can be defined as the minimum conveying air velocity in a pneumatic conveying system when the velocity of a particle group in the conveying direction approaches zero. According to the shear law of powder particles, the driving force of a particle in the horizontal direction depends on the force it experiences in the vertical direction. When the forces acting on the particles in the vertical direction are in equilibrium, the velocity of the particles in the horizontal direction is 0, indicating a critical blockage. Therefore, the conveying air velocity U corresponding to the sum of the forces acting on the particles in the vertical direction being 0 is... g That is, the critical clogging velocity U b .like Figure 3 As shown, the critical blockage velocity U b The calculation model uses the gravity F of the transported particles. G Saffman lift F for conveying particles L buoyancy F of the transported particles B , drag force F D The equation of motion for the particle, calculated using Newton's second law, is as follows:

[0181]

[0182] Where, m p The mass of the conveyed particles, expressed in kg; F B For the buoyancy of the transported particles, N; F G For the gravity of the transported particles, N; F L Saffman lift for conveying particles, N; F B For the buoyancy of the transported particles, N; F D The drag force for conveying particles, N; For the conveying particle velocity U p Rate of change of U with time t; p θ represents the velocity of the conveyed particles, in m / s; θ is the inclination angle of the conveying pipe.

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

[0184]

[0185] Where π is the mathematical constant pi; d p The average particle size of the transported particles is given in meters (m); ρ p The density of the conveyed particles, kg / m³ 3 g is the acceleration due to gravity, m / s² 2 ;

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

[0187]

[0188] Where, μ g The dynamic viscosity of the transported gas is given in Pa·s; ρ g The density of the transported gas is kg / m³. 3 ;d p U represents the average particle size of the transported particles, in meters (m). g The gas velocity being transported is in m / s; U p The velocity of the conveyed particles, in m / s; dU g / dy represents the delivery gas velocity U g Velocity gradient perpendicular to the conveying direction;

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

[0190]

[0191] Where π is the mathematical constant pi; d p The average particle size of the transported particles is given in meters (m); ρ g The density of the transported gas is kg / m³. 3 g is the acceleration due to gravity, m / s² 2 ;

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

[0193]

[0194] Among them, C D C is the drag coefficient. D It is 0.44; π is the mathematical constant pi; d p The average particle size of the transported particles is given in meters (m); ρ p The density of the conveyed particles, kg / m³ 3 ;U g The gas velocity being transported is in m / s; U p The velocity of the conveyed particles, in m / s;

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

[0196] The d p The ρ was measured by a particle size analyzer; p The ρ was measured using a particle density meter; g The calculations are based on the pressure and gas temperature of the conveying pipeline; the inner diameter of the conveying pipeline is 0.2m.

[0197] The powder particles 1 and the powder particles 2 are subjected to experiments in the pneumatic conveying device of Embodiment 1. By performing pneumatic conveying experiments at two different conveying gas velocities, the parameters a and b are obtained by power function fitting according to the calculation formula of the minimum pressure drop velocity U e .

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

[0199] Step ss2, according to the conveying flow pattern of the target material, and in combination with the minimum pressure drop velocity and the critical choking gas velocity predicted in step ss1, the conveying gas velocity interval of the target material is determined.

[0200] Specifically, according to the target flow pattern predicted in Embodiment 1, in combination with the conveying gas velocity control method based on the target flow pattern, the corresponding target conveying gas velocity U t can be given. Further, U t is substituted into the following formula, and the target conveying gas flow Q t can be calculated.

[0201]

[0202] Finally, the total gas amount entering the system is controlled by the gas flow meter to be the same as Q t , so as to verify the practicability of the present application.

[0203] Step ss3, based on the conveying gas velocity interval in step ss2, the conveying gas velocity of the target material is regulated.

[0204] By performing pneumatic conveying experiments of different conveying materials and solid mass flow M s , the pneumatic conveying flow pattern control results of the powder particles shown in Tables 1, 2 and 3 are obtained. Table 1 corresponds to the first horizontal section in Table 1, Table 2 corresponds to the second bending section, and Table 3 corresponds to the second vertical section. The conveying flow pattern in the table is based on the conveying solid-gas ratio and the electrical capacitance tomography system. When the solid-gas ratio is less than 50 kg / kg, the conveying flow pattern belongs to the dilute phase, and vice versa. Figure 3

[0205] The electrical capacitance tomography system can obtain the relative concentration of the solid phase of the powder particles in the conveying process. When the relative concentration of the solid phase is greater than 0.5, it can be considered that the conveying flow pattern is dense phase, and vice versa. Table 1 is the flow pattern control result of the powder particles 1 and the powder particles 2.

[0206] Table 1

[0207]

[0208] Table 2​

[0209]

[0210] Table 3

[0211]

[0212] According to Tables 1, 2 and 3, the present application can realize accurate regulation of the flow pattern of the powder and particle pneumatic conveying based on the relative size of the conveying gas velocity, the critical plugging 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, which includes a minimum pressure drop rate model; The training process of the minimum pressure drop velocity model includes the following steps: S1. Obtain at least two sets of fitting data. Each set of fitting data includes the conveying gas velocity U in the conveying pipeline. g and the conveying air velocity U g The corresponding pressure drop ΔP in the delivery pipeline; S2. Substitute the fitted data into the minimum pressure drop rate model, which is shown in Equation I: Formula I; Among them, U e Minimum pressure drop velocity, m / s; U g ΔP is the gas velocity being transported, in m / s; ΔP is the pressure drop across the transport pipeline, in Pa; L is the length of the transport pipeline, in m; ΔP / L represents the pressure drop per unit length of the transport pipeline, in Pa / m. In Equation I, the calculation method for △P / L is as shown in Equation II: Formula II; Where, λ g λ is the friction coefficient of the conveying gas; μ is the solid-to-gas ratio, i.e., the ratio of the mass flow rate of the particles to the mass flow rate of the conveying gas; λ is the solid-to-gas ratio. z For the additional pressure drop coefficient; ρ g The density of the transported gas is kg / m³. 3 D is the inner diameter of the conveying pipe, in meters; ρ b Bulk density, kg / m³ 3 g is the acceleration due to gravity, in m / s². 2 θ is the inclination angle of the delivery pipeline; In Equation II, the friction coefficient λ of the transported gas g The calculation formula is as follows: ； Where Re is the Reynolds number; In Equation II, the additional pressure drop coefficient λ z The calculation formula is as follows: ； Where Fr is a function of the additional pressure drop coefficient; a and b are the fitting coefficients, respectively; S3. Fit the model to obtain fitting coefficients a and b, and train the model to obtain the minimum pressure drop rate.

2. The pneumatic conveying modeling method as described in claim 1, characterized in that, The minimum pressure drop rate U e The simplified calculation formula is as follows: ； Where, ρ g The density of the transported gas is kg / m³. 3 D is the inner diameter of the conveying pipe, in meters (m); μ g The dynamic viscosity of the transported gas is Pa·s; g is the acceleration due to gravity, m / s². 2 M s denoted as solid mass flow rate, kg / s; a and b are fitting parameters.

3. The pneumatic conveying modeling method as described in claim 2, characterized in that, The ρ g The ρ is calculated by combining the gas volume, temperature, and pressure in the pipeline; g The formula for calculation is: ； Where P is the absolute pressure of the pipeline, Pa; M is the molar mass of the gas, g / mol; R is the ideal gas constant, with a value of 8.314 J / (mol·K); and T is the gas temperature, K. And / or, the μ g It is 1.79×10 -5 Pa·s; And / or, the g is 9.79 m / s 2 ; And / or, the M s Obtained by measurement using a weighing system.

4. The pneumatic conveying modeling method as described in 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 Equation III: Formula III; Among them, C D U is the drag coefficient; b θ is the critical clogging velocity, m / s; θ is the inclination angle of the delivery pipeline; μ g The dynamic viscosity of the transported gas is given in Pa·s; ρ g The density of the transported gas is kg / m³. 3 ;d p The average particle size of the transported particles is m; g is the acceleration due to gravity, m / s². 2 ;ρ p The density of the conveyed particles, kg / m³ 3 .

5. The pneumatic conveying modeling method as described in claim 4, characterized in that, C D It is 0.

44.

6. The pneumatic conveying modeling method as described in claim 4, characterized in that, The critical blockage velocity U b The calculation model uses the gravity F of the transported particles. G Saffman lift F for conveying particles L buoyancy F of the transported particles B , drag force F D The equation of motion for the particle, calculated using Newton's second law, is as follows: ； Where, m p The mass of the conveyed particles, expressed in kg; F G For the gravity of the transported particles, N; F B For the buoyancy of the transported particles, N; F L Saffman lift for conveying particles, N; F D The drag force for transporting particles is N; ∂U p / ∂t represents the particle conveying velocity U p rate of change of U with time t p θ represents the velocity of the conveyed particles, in m / s; θ is the inclination angle of the conveying pipe.

7. The pneumatic conveying modeling method as described in claim 6, characterized in that, The gravity F of the conveyed particles G The calculation formula is as follows: ； Where π is the mathematical constant pi; d p The average particle size of the transported particles is given in meters (m); ρ p The density of the conveyed particles, kg / m³ 3 g is the acceleration due to gravity, in m / s². 2 .

8. The pneumatic conveying modeling method as described in claim 6, characterized in that, The Saffman lift F L The calculation formula is as follows: ； Where, μ g The dynamic viscosity of the transported gas is given in Pa·s; ρ g The density of the transported gas is kg / m³. 3 ;d p U represents the average particle size of the transported particles, in meters (m). g The gas velocity being transported is in m / s; U p The velocity of the conveyed particles, in m / s; dU g / dy represents the delivery gas velocity U g Velocity gradient perpendicular to the conveying direction.

9. The pneumatic conveying modeling method as described in claim 6, characterized in that, The buoyancy F of the conveyed particles B The calculation formula is as follows: ； Where π is the mathematical constant pi; d p The average particle size of the transported particles is given in meters (m); ρ g The density of the transported gas is kg / m³. 3 g is the acceleration due to gravity, in m / s². 2 .

10. The pneumatic conveying modeling method as described in claim 6, characterized in that, The drag force F D The calculation formula is as follows: ； Among them, C D d is the drag coefficient, with a value of 0.44; π is pi; d p The average particle size of the transported particles is given in meters (m); ρ p The density of the conveyed particles, kg / m³ 3 ;U g The gas velocity being transported is in m / s; U p The velocity of the conveyed particles is expressed in m / s.

11. The pneumatic conveying modeling method as described in claim 10, characterized in that, The C D It is 0.

44.

12. The pneumatic conveying modeling method as described in claim 6, characterized in that, The motion equation of the particle adopts the boundary condition ∂U p / ∂t = 0, U p = 0.

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

14. A control method for pneumatic conveying, characterized in that, It includes the following steps: Step ss1: Based on the average particle size and particle density of the target material, predict the conveying flow pattern of the target material using the flow pattern criterion equation; and use the minimum pressure drop velocity model and critical blockage velocity model obtained by the pneumatic conveying modeling method as described in any one of claims 4-13 to predict the minimum pressure drop velocity U of the target material. e and critical blockage velocity U b ; Step ss2: Based on the conveying flow pattern of the target material, and in conjunction with the minimum pressure drop velocity and critical blockage velocity predicted in step ss1, determine the conveying gas velocity range of the target material. Step ss3: Based on the conveying air velocity range described in step ss2, adjust the conveying air velocity of the target material.

15. The pneumatic conveying control method as described in claim 14, characterized in that, The flow pattern criterion equation is: Formula IV.

16. The pneumatic conveying control method as described in claim 15, characterized in that, The prediction method for the transport flow pattern is as follows: Substitute the average particle size and particle density of the target material into the flow pattern criterion equation; when the inequality of Equation IV is satisfied, the transport flow pattern of the target material is dilute phase transport; when the inequality of Equation IV is not satisfied, the transport flow pattern of the target material is dense phase transport. And / or, the delivery gas velocity U of the delivery gas g The calculation method is as follows: Collect 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 volumetric flow rate Q of the conveyed gas. Formula V; And / or, the pneumatic conveying control method is performed in a pneumatic conveying device, which includes an air inlet pipe, a feeding tank, a conveying pipe, and several receiving tanks; the feeding tank is provided with an air inlet and a discharge outlet at its lower part and bottom, respectively; the air outlet of the air inlet pipe is connected to the air inlet of the feeding tank; the discharge outlet of the feeding tank is connected to each of the receiving tanks through the conveying pipes; from the feeding tank to each of the receiving tanks, the conveying pipe sequentially includes a first vertical section, a first bend section, a first horizontal section, a second bend section, a second vertical section, a third bend section, and a second horizontal section; The conveying pipeline is equipped 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 located 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 valve, the second throttle valve, the third throttle valve, and the fourth throttle valve are respectively equipped 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.

17. The pneumatic conveying control method as described in claim 16, characterized in that, The pneumatic conveying device further includes a conveying gas treatment module, which includes a gas compressor, a freeze dryer and an oil separator connected in sequence, and the outlet of the oil separator is connected to the inlet of the inlet pipe.

18. The pneumatic conveying control method as described in claim 16, characterized in that, The air intake pipe is equipped with a first pressure sensor, a temperature sensor, and a first gas mass flow meter. The first gas mass flow meter is used to regulate the amount of solid transported during the pneumatic conveying process.

19. The pneumatic conveying control method as described in claim 16, characterized in that, 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 respectively used to adjust the conveying gas velocity of the first horizontal section, the conveying gas velocity of the second bend section, the conveying gas velocity of the second vertical section, and the conveying gas velocity of the second horizontal section.

20. The pneumatic conveying control method as described in claim 18, characterized in that, The feeding tank is equipped with a second pressure sensor; And / or, in the direction from the feeding tank to each of the receiving tanks, the first horizontal section is sequentially provided with a third pressure sensor and a fourth pressure sensor; the third pressure sensor and the fourth pressure sensor are both located between the first throttle and the second throttle; And / or, in the direction from the feeding tank to each of the receiving tanks, the second vertical section is sequentially provided with a fifth pressure sensor and a sixth pressure sensor; And / or, the bottom of the feeding tank is equipped with a weighing system; the first vertical section is equipped with a discharge valve.

21. The pneumatic conveying control method as described in claim 17, characterized in that, The pneumatic conveying device also includes a dust collector and a booster pump connected to each other. The dust collector is located at the top of the feeding tank, and the outlet of the booster pump is connected to the inlet of the freeze dryer. And / or, each of the receiving tanks is provided with a gas phase outlet at the top, and the gas phase outlet is connected to the inlet of the dust collector.

22. The pneumatic conveying control method as described in claim 20, characterized in that, The pneumatic conveying device further 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.

23. A control system for pneumatic conveying, 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 16, and is used to convert the received pressure signal into a gas flow control signal to regulate the gas flow meter.

24. 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, it implements the pneumatic conveying modeling method as described in any one of claims 1-13, or the pneumatic conveying control method as described in any one of claims 14-22.

25. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the pneumatic conveying modeling method as described in any one of claims 1-13, or the pneumatic conveying control method as described in any one of claims 14-22.

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