Resin load control system and control method

Abstract

The invention belongs to the technical field of new resin materials, and relates to a resin load control system and method, the control system comprises a horizontal reaction kettle, a temperature transmitter, a melt gear pump, a pressure transmitter, a viscometer, a frequency converter, a motor and a distributed control system DCS; the control method comprises the steps that the frequency converter obtains a rotating speed adjusting instruction sent by the DCS, the rotating speed of the motor is adjusted according to the rotating speed adjusting instruction, and then operation of the melt gear pump is controlled; calculating the real-time mass flow rate of the resin; and finally, the rotating speed of the melt gear pump is controlled in real time according to the mass flow set by the daily load of the resin, so that the resin load is stably controlled. According to the resin load control system, the problem that the mass flow and the stable production load of the high-temperature melt cannot be accurately calculated in real time in a wide pressure measuring range is solved; the resin load control method can adapt to online detection and control of the load of the new resin material under various load changes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of resin new materials, and relates to a resin load control system and a control method. BACKGROUND

[0002] At present, in resin new material production, product output is set according to market demand, and resin new material melt real-time quality flow detection and load control are continuously adjusted, only when material of each section reaches balance and stability, the product quality can be ensured. However, this puts forward a high requirement on resin melt real-time quality flow detection accuracy. In actual production, affected by melt pipeline melt pressure fluctuation, especially when melt filter is switched or load is greatly adjusted, melt pressure change will make melt gear pump discharge quantity at the same speed or variable speed more inaccurate, which seriously affects material balance of each section, product quality and resin new material production load control, causing great waste and difficulty.

[0003] Traditional resin new material load control system calculation and control are mainly controlled according to theoretical calculation of the melt gear pump, that is, the volume flow is estimated by the product of the design displacement and the speed of the gear pump, and then the theoretical quality flow is converted. However, this method is only suitable for ideal working conditions with small melt pipeline pressure fluctuation. When the pressure fluctuation range is too large, affected by the technical performance of the gear pump itself and other interference factors, the deviation between the theoretical calculation value and the actual flow is significant, and the greater the working condition changes, the more obvious the error.

[0004] Variable frequency speed regulation is adopted to control the speed of the gear pump, the melt pressure is monitored in real time by the pressure sensor, and the theoretical displacement is corrected by the preset pressure-flow compensation coefficient. However, this scheme only uses a single pressure parameter compensation, and when the pressure suddenly changes (such as ΔP>2MPa) during the switching of the melt filter, since the nonlinear change of the gear pump volumetric efficiency (the measured volumetric efficiency decreases by 12% to 15% under high pressure) is not considered, the mass flow error is still high. And the compensation coefficient is fixed, which cannot adapt to the parameter drift under dynamic working conditions.

[0005] At present, the flow detection and control method in resin industrial production has obvious limitations: the theoretical calculation does not fully consider the influence of pressure wide range change on the actual displacement of the gear pump, resulting in insufficient real-time quality flow calculation accuracy. Especially when the load is greatly adjusted or the melt pressure fluctuates sharply, the error of the traditional method is further enlarged, which is difficult to meet the demand of high-precision production control.

[0006] Therefore, it is of great significance to study a resin load control system and a control method to solve the problems in the prior art. SUMMARY

[0007] The present application aims at solving the problems in the prior art and providing a resin load control system and a control method.

[0008] To achieve the above-mentioned object, the present application adopts the technical scheme as follows:

[0009] The resin load control system comprises a horizontal reaction kettle, a temperature transmitter, a melt gear pump, a pressure transmitter, a viscometer, a frequency converter, a motor and a distributed control system (DCS).

[0010] The temperature transmitter is arranged at the outlet of the horizontal reaction kettle, the outlet of the horizontal reaction kettle is connected with the inlet of the melt gear pump through a melt pipeline I, the outlet of the melt gear pump is connected with the inlet of a melt filter through a melt pipeline II, the pressure transmitter and the viscometer are arranged on the melt pipeline II respectively, the melt gear pump is driven by the motor, the motor is connected with the frequency converter, and the distributed control system (DCS) is in communication connection with the frequency converter, the pressure transmitter, the temperature transmitter and the viscometer respectively.

[0011] The existing resin new material flow detection and control mainly calculate the theoretical mass flow by using the theoretical volume flow of the melt gear pump, and the theoretical volume flow is mainly calculated by multiplying the original design displacement provided by the manufacturer with the gear pump rotating speed. The calculation result of this way is extremely easy to be affected by the load change and the pipeline design. When the melt pipeline pressure fluctuation range is too large, the real-time flow deviation of the theoretical calculation is obvious due to the influence of the technical performance of the gear pump itself and other interference factors. The obtained flow and the actual flow will have a certain degree of deviation, and the error will increase with the change of the working condition. The existing technology only adjusts the process load by using the theoretical flow calculation value. According to the actual working condition, the pressure fluctuation should be within 0.5 MPa, and the influence is small. The greater the pressure range exceeds, the greater the flow deviation calculated.

[0012] The present application fully considers the influence of the gear pump rotating speed, the melt temperature, the dynamic viscosity, the pipeline pressure and the melt density and other parameters. The distributed control system (DCS) calculates the real-time mass flow of the resin new material according to the gear pump rotating speed, the pressure information, the temperature information, the dynamic viscosity, the resin melt density and the rated volume of the melt gear pump, controls the rotating speed of the melt gear pump in real time according to the set mass flow of the resin new material per day, so that the resin new material load control is stable, and the resin new material load can be on-line detected and controlled under various load changes.

[0013] As a preferred technical scheme:

[0014] The resin load control system as described above further comprises a speed reducer, the speed reducer is connected with the motor and connected with the melt gear pump through a universal joint coupling.

[0015] The resin load control system as described above, the melt gear pump comprises melt gear pump I and melt gear pump II, the pressure transmitter comprises pressure transmitter I and pressure transmitter II, the frequency converter comprises frequency converter I and frequency converter II, the motor comprises motor I and motor II, and the reduction gearbox comprises reduction gearbox I and reduction gearbox II;

[0016] A three-way valve is arranged on the melt pipeline I, the inlet of the three-way valve is connected with the horizontal reaction kettle, two outlets of the three-way valve are connected with the melt gear pump I and the melt gear pump II respectively, the melt gear pump I is connected with the motor I through the reduction gearbox I, the melt gear pump II is connected with the motor II through the reduction gearbox II, the frequency converter I is electrically connected with the motor I, and the frequency converter II is electrically connected with the motor II; the melt pipeline II comprises melt pipeline IIa, melt pipeline IIb and melt pipeline IIc, the outlet of the melt gear pump I is connected with the melt pipeline IIa, the outlet of the melt gear pump II is connected with the melt pipeline IIb, the pressure transmitter I is arranged on the melt pipeline IIa, the pressure transmitter II is arranged on the melt pipeline IIb, an electric three-way valve is arranged at the confluence of the melt pipeline IIa and the melt pipeline IIb (by means of electric signal, the opening degree of the electric three-way valve can be adjusted to balance the flow between the two melt gear pumps, so that the overall performance of the system is optimized), two inlets of the electric three-way valve are connected with the melt pipeline IIa and the melt pipeline IIb respectively, and the outlet of the electric three-way valve is connected with the melt pipeline IIc; and a viscometer is embedded on the melt pipeline IIc.

[0017] The distributed control system DCS is in communication connection with the frequency converter I, the frequency converter II, the pressure transmitter I, the pressure transmitter II, the temperature transmitter and the viscometer respectively.

[0018] The resin load control system as described above, the distributed control system DCS comprises a master controller PID1 module, a shunt function control module, a slave controller PID2 module, a slave controller PID3 module and a instantaneous flow calculation module, the master controller PID1 module is connected with the shunt function control module, the shunt function control module is connected with the slave controller PID2 module and the slave controller PID3 module simultaneously, the slave controller PID2 module is connected with the frequency converter I, and is used for realizing control on the rotating speed of the motor I, the slave controller PID3 module is connected with the frequency converter II, and is used for realizing control on the rotating speed of the motor II, and the instantaneous flow calculation module is used for calculating the actual flow of the melt according to the data of the pressure transmitter I, the pressure transmitter II and the temperature transmitter collected in real time, the real-time rotating speed of the melt gear pump I and the melt gear pump II, and the real-time dynamic viscosity measured by the viscometer online.

[0019] The application also provides a resin load control method using the resin load control system, wherein first, the frequency converter I and the frequency converter II respectively obtain the speed adjustment instruction sent by the distributed control system DCS, and the speed of the motor I and the motor II is adjusted according to the speed adjustment instruction, and then the operation of the melt gear pump I and the melt gear pump II is controlled; then, the distributed control system DCS calculates the real-time mass flow of the resin according to the speed of the melt gear pump I and the melt gear pump II, the pressure detected by the pressure transmitter I and the pressure transmitter II, the temperature detected by the temperature transmitter, the dynamic viscosity detected by the viscometer, the resin melt density and the rated volume of the melt gear pump; finally, the speed of the melt gear pump I and the melt gear pump II is controlled in real time according to the set mass flow of the resin per day, so that the resin load control is stable.

[0020] As a preferred technical solution:

[0021] The resin load control method, wherein the real-time mass flow of the resin = MASSFLOW_P01+MASSFLOW_P02, wherein MASSFLOW_P01 represents the real-time mass flow of the melt gear pump I, and MASSFLOW_P02 represents the real-time mass flow of the melt gear pump II.

[0022] When the speed of the melt gear pump I is greater than or equal to 1 RPM:

[0023] MASSFLOW_P01=MPP_THEO_P01-MPP_SLIP_P01;

[0024] MPP_THEO_P01=V·S1·60·D;

[0025]

[0026] When the speed of the melt gear pump I is less than 1 RPM:

[0027] MASSFLOW_P01=0;

[0028] When the speed of the melt gear pump II is greater than or equal to 1 RPM:

[0029] MASSFLOW_P02=MPP_THEO_P02-MPP_SLIP_P02;

[0030] MPP_THEO_P02=V·S2·60·D;

[0031]

[0032] When the speed of the melt gear pump II is less than 1 RPM:

[0033] MASSFLOW_P02=0;

[0034] Wherein, MPP THEO P01 represents the theoretical mass flow of the melt gear pump I, MPP THEO P02 represents the theoretical mass flow of the melt gear pump II; MPP SLIP P01 represents the mass flow loss of the melt gear pump I, MPP SLIP P02 represents the mass flow loss of the melt gear pump II; V is the rated volume of the melt gear pump I or the melt gear pump II (the rated volumes of the two melt gear pumps are equal), S1 is the rotational speed of the melt gear pump I, S2 is the rotational speed of the melt gear pump II, D is the resin melt density, C1 is the mass flow loss correction coefficient of the melt gear pump I, C2 is the mass flow loss correction coefficient of the melt gear pump II, P1 is the outlet pressure of the melt gear pump I, P2 is the outlet pressure of the melt gear pump II, η is the dynamic viscosity measured by a viscometer, a is the pressure influence index coefficient, and b is the rotational speed influence index coefficient.

[0035] The resin load control method as described above introduces the melt density correction under the influence of temperature, that is, the formula D = ρ - c·T (pressure excitation under the coupling of viscosity and temperature), which directly reflects the dynamic influence of temperature change on density; wherein ρ is the density of the resin melt measured in the laboratory at the standard temperature (242℃), c is the density change coefficient with temperature, T is the melt temperature at the outlet in the horizontal reaction kettle, D is kg / m 3 , ρ is kg / m 3 , c is kg / (m 3 ·℃), and T is ℃.

[0036] The resin load control method as described above combines the Poiseuille flow and the Couette flow model, and through theoretical derivation and empirical coefficients, a = 2.15 (gap change item under pressure excitation) and b = 0.25 are obtained for correction of the model, which improves the calculation accuracy in a wide pressure range; c = 0.62, ρ = 1268.0.

[0037] The resin load control method as described above takes the deviation value between the set mass flow of resin per day and the feedback real-time mass flow as the adjustment output value of the main controller PID1 of the distributed control system DCS, calculates the theoretical total rotational speed, and then distributes the rotational speeds of the melt gear pump I and the melt gear pump II according to the theoretical total rotational speed;

[0038] The calculation formula of the theoretical total rotational speed is:

[0039] n total =(Q set / (MASSFLOW_P01+MASSFLOW_P02))×(S1+S2);

[0040] The rotational speed distribution formula is:

[0041] n ref1 =k×n total ;

[0042] n ref2 =(1-k)×n total ;

[0043] Wherein, Q set is the mass flow rate of resin per day load setting, n total is the theoretical total speed, n ref1 is the speed of melt gear pump I distribution, n ref2 is the speed of melt gear pump II distribution, k is the weight coefficient;

[0044] When η>η0, k=0.5+0.1×ln(η / η0), high viscosity is biased to large displacement pump, η is the measured viscosity, η0 is the ideal viscosity;

[0045] When △P>0.5MPa, k=k0-0.5×sin(P1-P2), △P is the pressure difference of melt gear pump inlet and outlet, k0 is the weight coefficient before pressure correction.

[0046] Melt gear pump speed distribution due to the wear of pump gear so that the melt pump pump supply is reduced, or by the pressure before the melt gear pump speed distribution of the melt pump. When the pressure before the melt gear pump is greater than the pressure before the other melt gear pump and the pressure difference △P>0.5MPa, the pump speed will be reduced, and the other melt gear pump will be accelerated to meet the pressure difference before the two pumps within the allowable range.

[0047] High viscosity compensation, high viscosity melt flow resistance is large, need to allocate more speed to the pump with larger displacement to balance the system pressure and reduce the leakage. Logarithmic function design (i.e. the formula above: when η>η0, k=0.5+0.1×ln(η / η0)) makes the adjustment range gradually change with the viscosity deviating from the ideal value, avoiding sudden change.

[0048] Pressure difference compensation, high pressure will lead to uneven load between pumps, and even cause mechanical failure. By dynamically adjusting k, the speed weight of the high pressure side pump is reduced, while the speed of the low pressure side pump is increased, forcing the pressure difference to return to the allowable range.

[0049] The above two conditions are only when the corresponding change condition is met, the system corrects the k value in time, and when it is not met, the k value is not corrected; that is, if neither satisfies η>η0 nor satisfies △P>0.5MPa, the value of k is not corrected, and the original value of k is 0.5, that is, the average distribution of the speed. If the above conditions are not met, it means that there is an abnormality in the production process or the above phenomenon occurs during the load change process, at this time, the process supervisor engineer manually adjusts the load and the rotating speed of the melt gear pump to achieve the basic stability of the production device load, and then the system k value is corrected in time.

[0050] Advantages:

[0051] (1) The resin load control system fully considers the influence of melt temperature, dynamic viscosity, pipeline pressure, melt density change, gear pump rotating speed and other parameters, corrects the instantaneous mass flow detection result through theoretical formula and mathematical modeling, adjusts the rotating speed of the double gear pump through the function strategy of the main controller and the shunt, and controls the stability of the outlet pressure and pump outlet flow, thereby solving the problems of inaccurate calculation of mass flow and stable production load of high-temperature melt in a wide pressure range.

[0052] (2) The resin load control system constructs a gear pump nonlinear transient characteristic model (including a gap change item under pressure excitation and a viscosity-temperature coupling item), innovatively proposes a pressure fluctuation frequency domain compensation algorithm, and real-time corrects the dynamic volume efficiency (compensation deviation ±0.66%) and develops a multi-source disturbance decoupling control strategy (corresponding to the k value weight distribution formula) for independent decoupling control logic of viscosity and pressure difference disturbance. The interactive influence of pressure, rotating speed and viscosity is quantified as a time-varying transfer function, which can adapt to parameter drift under dynamic working conditions.

[0053] (3) The resin load control method using the resin load control system can adapt to various load changes and control the resin new material load online. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is a production process flow chart of polybutylene terephthalate (PBT) resin new material.

[0055] Figure 2 It is a load control flow chart.

[0056] Among them, 1-horizontal reactor, 2-three-way valve, 3-melt pipeline Ⅰa, 4-melt gear pump Ⅰ, 5-reduction gearbox Ⅰ, 6-motor Ⅰ, 7-frequency converter Ⅰ, 8-melt gear pump Ⅱ, 9-reduction gearbox Ⅱ, 10-motor Ⅱ, 11-frequency converter Ⅱ, 12-pressure transmitter Ⅰ, 13-pressure transmitter Ⅱ, 14-electric three-way valve, 15-viscosity meter, 16-temperature transmitter, 17-melt filter inlet. Detailed Implementation

[0057] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0058] A resin load control system, such as Figure 1 As shown, it includes a horizontal reactor 1, a temperature transmitter 16, a melt gear pump, a pressure transmitter, a viscometer 15, a frequency converter, a motor, a distributed control system (DCS), and a gearbox.

[0059] Temperature transmitter 16 is installed at the outlet of horizontal reactor 1. The outlet of horizontal reactor 1 is connected to the inlet of melt gear pump through melt pipe I. The outlet of melt gear pump is connected to melt filter inlet 17 through melt pipe II. Melt gear pump is driven by electric motor. Gearbox is connected to melt gear pump through universal joint coupling.

[0060] The melt gear pump includes melt gear pump I4 and melt gear pump II8; the pressure transmitter includes pressure transmitter I12 and pressure transmitter II13; the frequency converter includes frequency converter I7 and frequency converter II11; the motor includes motor I6 and motor II10; and the gearbox includes gearbox I5 and gearbox II9.

[0061] The three-way valve 2 is arranged on the melt pipeline I, the melt pipeline I includes a melt pipeline Ia 3, a melt pipeline Ib and a melt pipeline Ic, the inlet of the three-way valve 2 is connected with the horizontal reaction kettle 1 through the melt pipeline Ic, the two outlets of the three-way valve 2 are respectively connected with the melt gear pump I 4 and the melt gear pump II through the melt pipeline Ia 3 and the melt pipeline Ib, the melt gear pump I 4 is connected with the motor I 6 through the speed reducer I 5, the melt gear pump II 8 is connected with the motor II 10 through the speed reducer II 9, the frequency converter I 7 is electrically connected with the motor I 6, and the frequency converter II 11 is electrically connected with the motor II 10; the melt pipeline II includes a melt pipeline IIa, a melt pipeline IIb and a melt pipeline IIc, the outlet of the melt gear pump I 4 is connected with the melt pipeline IIa, the outlet of the melt gear pump II 8 is connected with the melt pipeline IIb, the pressure transmitter I 12 is arranged on the melt pipeline IIa, the pressure transmitter II 13 is arranged on the melt pipeline IIb, the electric three-way valve 14 is arranged at the joint of the melt pipeline IIa and the melt pipeline IIb, the two inlets of the electric three-way valve 14 are respectively connected with the melt pipeline IIa and the melt pipeline IIb, the outlet of the electric three-way valve 14 is connected with the melt pipeline IIc, and the viscometer 15 is embedded on the melt pipeline IIc;

[0062] The distributed control system DCS is respectively connected with the frequency converter I 7, the frequency converter II 11, the pressure transmitter I 12, the pressure transmitter II 13, the temperature transmitter 16 and the viscometer 15 in communication;

[0063] As shown in the figure, Figure 2 The distributed control system DCS includes a main controller PID1 module, a shunt function control module, a slave controller PID2 module, a slave controller PID3 module and a instantaneous flow calculation module, the main controller PID1 module is connected with the shunt function control module, the shunt function control module is connected with the slave controller PID2 module and the slave controller PID3 module at the same time, the slave controller PID2 module is connected with the frequency converter I 7, and is used for realizing the control of the rotating speed of the motor I 6, the slave controller PID3 module is connected with the frequency converter II, and is used for realizing the control of the rotating speed of the motor II 10, and the instantaneous flow calculation module is used for calculating the actual flow of the melt according to the data of the pressure transmitter I 12, the pressure transmitter II 13 and the temperature transmitter 16 collected in real time, the real-time rotating speed of the melt gear pump I 4 and the melt gear pump II 8 and the real-time dynamic viscosity measured by the viscometer 15.

[0064] The method for controlling the resin load by using the resin load control system is as follows:

[0065] (1) The frequency converter I and the frequency converter II respectively obtain the rotating speed adjustment instructions sent by the distributed control system DCS, adjust the rotating speeds of the motor I and the motor II according to the rotating speed adjustment instructions, and then control the operation of the melt gear pump I and the melt gear pump II;

[0066] (2) The distributed control system (DCS) calculates the real-time mass flow of resin according to the rotational speed of the melt gear pump I and the melt gear pump II, the pressure detected by the pressure transmitter I and the pressure transmitter II, the temperature detected by the temperature transmitter, the dynamic viscosity detected by the viscometer, the density of the resin melt, and the rated volume of the melt gear pump.

[0067] wherein the real-time mass flow of resin = MASSFLOW_P01 + MASSFLOW_P02, wherein MASSFLOW_P01 represents the real-time mass flow of the melt gear pump I, and MASSFLOW_P02 represents the real-time mass flow of the melt gear pump II;

[0068] when the rotational speed of the melt gear pump I is greater than or equal to 1 RPM:

[0069] MASSFLOW_P01 = MPP THEO P01 - MPP SLIP P01;

[0070] MPP THEO P01 = V·S1·60·D;

[0071]

[0072] when the rotational speed of the melt gear pump I is less than 1 RPM:

[0073] MASSFLOW_P01 = 0;

[0074] when the rotational speed of the melt gear pump II is greater than or equal to 1 RPM:

[0075] MASSFLOW_P02 = MPP THEO P02 - MPP SLIP P02;

[0076] MPP THEO P02 = V·S2·60·D;

[0077]

[0078] when the rotational speed of the melt gear pump II is less than 1 RPM:

[0079] MASSFLOW_P02 = 0;

[0080] D = p - c·T;

[0081] Wherein, MPP THEO P01 represents the theoretical mass flow of the melt gear pump I, MPP THEO P02 represents the theoretical mass flow of the melt gear pump II; MPP SLIP P01 represents the mass flow loss of the melt gear pump I, MPP SLIP P02 represents the mass flow loss of the melt gear pump II; V is the rated volume of the melt gear pump I or the melt gear pump II (the rated volumes of the two melt gear pumps are equal), S1 is the rotating speed of the melt gear pump I, S2 is the rotating speed of the melt gear pump II, D is the resin melt density, C1 and C2 are the mass flow loss correction coefficients of the two melt gear pumps, P1 is the outlet pressure of the melt gear pump I, P2 is the outlet pressure of the melt gear pump II, η is the dynamic viscosity measured by a viscometer, a is the pressure influence index coefficient, b is the rotating speed influence index coefficient; ρ is the density of the resin melt measured in a laboratory at a standard temperature (242 ℃); c is the temperature change influence coefficient of the melt density; T is the melt temperature at the outlet of the horizontal reaction kettle;

[0082] (3) The distributed control system DCS takes the deviation value between the set mass flow of the resin per day and the feedback real-time mass flow as the adjustment output value of the main controller PID1, calculates the theoretical total rotating speed, and then distributes the rotating speeds of the melt gear pump I and the melt gear pump II according to the theoretical total rotating speed, so as to stabilize the resin load control;

[0083] The calculation formula of the theoretical total rotating speed is as follows:

[0084] n total =(Q set / (MASSFLOW_P01+MASSFLOW_P02))×(S1+S2);

[0085] The rotating speed distribution formula is as follows:

[0086] n ref1 =k×n total ;

[0087] n ref2 =(1-k)×n total ;

[0088] Wherein, Q set is the set mass flow of the resin per day, n total is the theoretical total rotating speed, n ref1 is the rotating speed allocated to the melt gear pump I, n ref2 is the rotating speed allocated to the melt gear pump II, and k is the weight coefficient;

[0089] When η>η0, k=0.5+0.1×ln(η / η0), the high viscosity is inclined to the large displacement pump, η is the measured viscosity (dynamic viscosity), and η0 is the ideal viscosity;

[0090] When △P>0.5MPa, k=k0-0.5×sin(P1-P2), △P is the pressure difference between the inlet and outlet of the melt gear pump, k0 is the weight coefficient before pressure correction.

[0091] The specific state of a certain moment in the control process is selected for illustration:

[0092] The produced resin is polybutylene terephthalate (PBT), and in the process control, MPP_THEO_P01=5357.28kg / h, MPP_THEO_P02=5022.45kg / h; V=0.005m 3 , S1=16RPM, S2=15RPM, D=1116.1kg / m 3 , C1=C2=0.85, P1=4.4MPa, P2=4.0MPa, η=250Pa·s; a=2.15, b=0.25, ρ=1268.0kg / m 3 , c=0.62kg / (m 3 ·℃), T=245℃; MASSFLOW_P01=5183.18kg / h and MASSFLOW_P02=4882.85kg / h are calculated based on the above parameters;

[0093] The distributed control system DCS takes the deviation value between the set mass flow of resin per day (which is set according to the design production load range of the production device and the minimum and maximum production capacity of the melt gear pump, and the present invention takes 240 tons / day as an example) and the feedback real-time mass flow as the input of the main controller PID1, calculates the theoretical total speed n total =30.79RPM, and then distributes the speeds of melt gear pump I and melt gear pump II according to the theoretical total speed, and the current η value 250Pa·s is greater than η0 value 200Pa·s (η0 value is determined according to the specification batch number of the process production product), which triggers viscosity correction: k=0.5+0.1×ln(250 / 200)≈0.522; the pressure difference ΔP is 0.4MPa<0.5MPa, and no pressure correction is needed. Speed distribution:

[0094] n ref1 = k×n total =0.522×30.79≈16.07RPM;

[0095] n ref2 =(1-k)×n total =0.478×30.79≈14.72RPM;

[0096] That is, n ref1 =16.07RPM, n ref2 =14.72RPM.

[0097] I. To verify the feasibility of the system control logic, based on the typical operating conditions and assumptions of parameters and step-by-step calculations are as follows:

[0098] Design production load range: Q set = 240 tons / day = 10000 kg / h;

[0099] 1. Melt gear pump parameters:

[0100] Rated volume V = 0.005 m 3 (r Melt gear pump I and melt gear pump II volume is the same);

[0101] Melt gear pump I speed S1 = 16 RPM;

[0102] Melt gear pump II speed S2 = 15 RPM;

[0103] 2. Temperature parameters:

[0104] Outlet temperature T = 245℃ (melt temperature℃);

[0105] Temperature influence coefficient c = 0.62 kg / (m 3 ·℃);

[0106] Laboratory density p = 1268.0 kg / m 3 (standard temperature 242℃);

[0107] Actual melt density D = p - c·T = 1268.0 - 0.62 x 245 = 1116.1 kg / m 3 ;

[0108] 3. Pressure and viscosity parameters:

[0109] P1 (melt gear pump I outlet pressure) = 4.4 MPa;

[0110] P2 (melt gear pump II outlet pressure) = 4.0 MPa;

[0111] Dynamic viscosity η = 250 Pa·s;

[0112] Ideal viscosity η0 = 200 Pa·s;

[0113] Pressure difference ΔP = P1 - P2 = 0.4 MPa;

[0114] 4. Theoretical mass flow calculation:

[0115] Correction coefficient C1 = C2 = 0.85 (assumed empirical value);

[0116] Exponential coefficient a = 2.15, b = 0.25;

[0117] Melt gear pump I (S1 = 16 RPM):

[0118] MPP THEO P01 = V x S1 x 60 x D = 0.005 x 16 x 60 x 1116.1 = 5357.28 kg / h;

[0119]

[0120] MASSFLOW P01 = 5357.28 - 174.1 = 5183.18 kg / h;

[0121] Melt gear pump II (S2 = 15 RPM):

[0122] MPP THEO P02 = V x S2 x 60 x D = 0.005 x 15 x 60 x 1116.1 = 5022.45 kg / h;

[0123]

[0124] MASSFLOW P02 = 5022.45 - 139.6 = 4882.85 kg / h;

[0125] Total real-time mass flow: 5183.18 + 4882.85 = 10066.03 kg / h;

[0126] 5. Control algorithm execution:

[0127] Deviation value = Q set - (MASSFLOW P01 + MASSFLOW P02) = 10000 - 10066.03 = -66.03 kg / h;

[0128] Theoretical total speed calculation:

[0129] n total = (Q set / (MASSFLOW P01 + MASSFLOW P02)) x (S1 + S2) = (10000 / 10066.03) x (16 + 15) ≈

[0130] 30.79 RPM;

[0131] Weight coefficient k correction:

[0132] Current η = 250 Pa s is greater than η0 = 200 Pa s, trigger viscosity correction: k = 0.5 + 0.1 x ln(250 / 200) ≈ 0.522;

[0133] ΔP is 0.4 MPa < 0.5 MPa, no pressure correction is needed.

[0134] Speed distribution:

[0135] n ref1 = k x n total = 0.522 x 30.79 ≈ 16.07 RPM

[0136] n ref2 = (1 - k) x n total = 0.478 x 30.79 ≈ 14.72 RPM

[0137] 6. Supplementary description

[0138] Assuming other conditions are the same, only the pressure P1 is different, P1 = 5.4 MPa, P2 = 4.0 MPa;

[0139] MPP THEO P01 = V x S1 x 60 x D = 0.005 x 16 x 60 x 1116.1 = 5357.28 kg / h;

[0140]

[0141] MASSFLOW P01 = 5357.28 - 270.38 = 5086.9 kg / h

[0142] MPP THEO P02 = V x S2 x 60 x D = 0.005 x 15 x 60 x 1116.1 = 5022.45 kg / h;

[0143]

[0144] MASSFLOW P02 = 5022.45 - 139.6 = 4882.85 kg / h;

[0145] Total real-time mass flow: 5086.9 + 4882.85 = 9969.75 kg / h;

[0146] Control algorithm execution:

[0147] Deviation value = Q set - (MASSFLOW P01 + MASSFLOW P02) = 10000 - 9969.75 = 30.25 kg / h;

[0148] Theoretical total speed calculation:

[0149] n total = (Q set(MASSFLOW_P01+MASSFLOW_P02))x(S1+S2)=(10000 / 9969.75)x(16+15)≈

[0150] 31.09 RPM;

[0151] Weight coefficient k correction:

[0152] Current η = 250 Pa·s is greater than η0= 200 Pa·s, triggering viscosity correction: k = 0.5 + 0.1xln(250 / 200)≈0.522;

[0153] ΔP is 1.4 MPa, which needs pressure correction, that is, when ΔP>0.5 MPa, k = 0.522-0.5xsin(5.4-4) = 0.522-0.5x0.0244 = 0.5098;

[0154] Speed distribution:

[0155] n ref1 =kx n total =0.5098x31.09≈15.85 RPM

[0156] n ref2 =(1-k)x n total =0.4902x31.09≈15.24 RPM;

[0157] The above assumptions show that the application can solve the problem of obvious error of the traditional method when the melt pipeline pressure fluctuation range is too large.

[0158] II. Quantitative stability verification:

[0159] Through 24 hours of continuous production data simulation, the fluctuation of the traditional double-pump control and the double-pump control system of the technology are compared, and the results are shown in Table 1:

[0160] Table 1

[0161]

[0162] In summary, the double-pump control system of the application reduces the flow fluctuation from ±3.79% of the traditional system (the traditional system refers to the control method directly calculated according to the volume formula provided by the gear pump manufacturer) to ±0.66% by dynamically distributing the speed, wherein the set flow is 10000 kg / h. Under high viscosity conditions (η>η0), the weight coefficient k is automatically adjusted, so that the large displacement pump bears more load, avoiding the flow lag caused by viscosity change. The pressure difference correction logic can prevent single pump overload and prolong the service life of the equipment.

Claims

1. A resin loading control system characterized by: The horizontal reaction kettle, temperature transmitter, melt gear pump, pressure transmitter, viscometer, frequency converter, motor and distributed control system DCS are included. The temperature transmitter is arranged at the outlet of the horizontal reaction kettle, the outlet of the horizontal reaction kettle is connected with the inlet of the melt gear pump through melt pipeline I, the outlet of the melt gear pump is connected with the inlet of the melt filter through melt pipeline II, the pressure transmitter and the viscometer are arranged on the melt pipeline II, the melt gear pump is driven by the motor, the motor is connected with the frequency converter, and the distributed control system DCS is in communication connection with the frequency converter, the pressure transmitter, the temperature transmitter and the viscometer.

2. The resin loading control system of claim 1, wherein The speed reducer is connected with the motor and connected with the melt gear pump through the universal joint.

3. The resin loading control system of claim 2, wherein The melt gear pump includes melt gear pump I and melt gear pump II, the pressure transmitter includes pressure transmitter I and pressure transmitter II, the frequency converter includes frequency converter I and frequency converter II, the motor includes motor I and motor II, and the speed reducer includes speed reducer I and speed reducer II. The three-way valve is arranged on the melt pipeline I, the melt pipeline I includes melt pipeline Ia, melt pipeline Ib and melt pipeline Ic, the inlet of the three-way valve is connected with the horizontal reaction kettle through the melt pipeline Ic, the two outlets of the three-way valve are connected with the melt gear pump I and the melt gear pump II through the melt pipeline Ia and the melt pipeline Ib respectively, the melt gear pump I is connected with the motor I through the speed reducer I, the melt gear pump II is connected with the motor II through the speed reducer II, the frequency converter I is electrically connected with the motor I, and the frequency converter II is electrically connected with the motor II; the melt pipeline II includes melt pipeline IIa, melt pipeline IIb and melt pipeline IIc, the outlet of the melt gear pump I is connected with the melt pipeline IIa, the outlet of the melt gear pump II is connected with the melt pipeline IIb, the pressure transmitter I is arranged on the melt pipeline IIa, the pressure transmitter II is arranged on the melt pipeline IIb, the junction of the melt pipeline IIa and the melt pipeline IIb is provided with an electric three-way valve, the two inlets of the electric three-way valve are connected with the melt pipeline IIa and the melt pipeline IIb respectively, the outlet of the electric three-way valve is connected with the melt pipeline IIc, and the viscometer is embedded on the melt pipeline IIc. The distributed control system DCS is in communication connection with the frequency converter I, the frequency converter II, the pressure transmitter I, the pressure transmitter II, the temperature transmitter and the viscometer.

4. The resin loading control system of claim 3, wherein The distributed control system DCS includes a main controller PID1 module, a shunt function control module, a slave controller PID2 module, a slave controller PID3 module and a instantaneous flow calculation module, the main controller PID1 module is connected with the shunt function control module, the shunt function control module is connected with the slave controller PID2 module and the slave controller PID3 module at the same time, the slave controller PID2 module is connected with the frequency converter I and is used for realizing the control of the rotating speed of the motor I, the slave controller PID3 module is connected with the frequency converter II and is used for realizing the control of the rotating speed of the motor II, and the instantaneous flow calculation module is used for calculating the actual flow of the melt according to the data of the pressure transmitter I, the pressure transmitter II and the temperature transmitter, the real-time rotating speed of the melt gear pump I and the melt gear pump II and the real-time dynamic viscosity measured by the viscometer.

5. A method of resin load control using the resin load control system according to claim 4, characterized by: Firstly, the frequency converter I and the frequency converter II respectively obtain the rotating speed adjustment instruction sent by the distributed control system DCS, and adjust the rotating speed of the motor I and the motor II according to the rotating speed adjustment instruction, thereby controlling the operation of the melt gear pump I and the melt gear pump II. Then, the distributed control system DCS calculates the real-time mass flow of the resin according to the rotating speed of the melt gear pump I and the melt gear pump II, the pressure detected by the pressure transmitter I and the pressure transmitter II, the temperature detected by the temperature transmitter, the dynamic viscosity detected by the viscometer, the resin melt density and the rated volume of the melt gear pump.

6. The method of resin loading control according to claim 5, wherein, The real-time mass flow of the resin = MASSFLOW_P01 + MASSFLOW_P02, wherein MASSFLOW_P01 represents the real-time mass flow of the melt gear pump I, and MASSFLOW_P02 represents the real-time mass flow of the melt gear pump II. When the rotating speed of the melt gear pump I is greater than or equal to 1 RPM: MASSFLOW_P01 = MPP_THEO_P01 - MPP_SLIP_P01; MPP_THEO_P01 = V·S1·60·D; When the rotating speed of the melt gear pump I is less than 1 RPM: MASSFLOW_P01 = 0; When the rotating speed of the melt gear pump II is greater than or equal to 1 RPM: MASSFLOW_P02 = MPP_THEO_P02 - MPP_SLIP_P02; MPP_THEO_P02 = V·S2·60·D; When the rotating speed of the melt gear pump II is less than 1 RPM: MASSFLOW_P02 = 0; Wherein MPP_THEO_P01 represents the theoretical mass flow of the melt gear pump I, MPP_THEO_P02 represents the theoretical mass flow of the melt gear pump II, MPP_SLIP_P01 represents the mass flow loss of the melt gear pump I, MPP_SLIP_P02 represents the mass flow loss of the melt gear pump II, V is the rated volume of the melt gear pump I or the melt gear pump II, S1 is the rotating speed of the melt gear pump I, S2 is the rotating speed of the melt gear pump II, D is the resin melt density, C1 is the mass flow loss correction coefficient of the melt gear pump I, C2 is the mass flow loss correction coefficient of the melt gear pump II, P1 is the outlet pressure of the melt gear pump I, P2 is the outlet pressure of the melt gear pump II, η is the dynamic viscosity measured by the viscometer, a is the pressure influence index coefficient, and b is the rotating speed influence index coefficient.

7. The method of resin loading control according to claim 6, wherein, D = ρ - c·T, wherein ρ is the density of the resin melt measured in the laboratory at the standard temperature, c is the temperature change coefficient of the resin melt density, and T is the melt temperature at the outlet of the horizontal reaction kettle.

8. The method of resin loading control according to claim 7, wherein, a = 2.15, b = 0.25, c = 0.62, ρ = 1268.

0.

9. The method of resin loading control according to claim 8, wherein, The distributed control system (DCS) takes the deviation value between the set mass flow of resin per day and the real-time mass flow of feedback as the adjustment output value of the main controller PID1, calculates the theoretical total rotating speed, and then distributes the rotating speeds of the melt gear pump I and the melt gear pump II according to the theoretical total rotating speed; The calculation formula of the theoretical total rotating speed is: n total = (Q set / (MASSFLOW_P01+MASSFLOW_P02)) x (S1+S2); The rotating speed distribution formula is: n ref1 = k x n total ; n ref2 = (1 - k) x n total ; where Q set is the mass flow set for the resin load per day, n total is the theoretical total speed, n ref1 is the speed distributed to the melt gear pump I, n ref2 is the speed distributed to the melt gear pump II, k is the weight coefficient; When η>η0, k=0.5+0.1×ln(η / η0), η0 is the ideal viscosity; When △P>0.5MPa, k=k0-0.5×sin(P1-P2), △P is the pressure difference between the inlet and outlet of the melt gear pump, and k0 is the weight coefficient before pressure correction.

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