Continuous production method of pellet feed

Abstract

The invention discloses a continuous production method of pellet feed, and relates to the technical field of industrial automation control. The method comprises the following steps: creating a modulation control function and a granulation control function based on fixed parameters and process parameters, adjusting inlet steam flow according to the modulation control function so as to adjust the moisture content of an intermediate material, and adjusting the rotating speed of a die roller according to the granulation control function so as to adjust the hardness of a finished product. The hardness of a finished product is monitored in real time, an equipment insensitive area is predicted, when the equipment insensitive area is larger than a preset value, the inertia response process of hardening and tempering equipment or granulation equipment is extracted, and a control pole is calculated according to the inertia response process. If the control pole of the modulation equipment or the granulation equipment is shifted, the insensitive area of the equipment is optimized by adjusting the hardening and tempering process parameters or the granulation process parameters, and it is guaranteed that the system rapidly responds to the characteristic change of the raw materials. Through collaborative optimization of a control mechanism and parameters, the product quality stability under different raw material ratios is effectively improved, and meanwhile production fluctuation caused by equipment inertia is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of industrial automation control, and in particular to a continuous production method of pellet feed. Background Art

[0002] The raw materials of pellet feed include corn flour, wheat bran flour, soybean meal, meat and bone meal, etc. High-temperature steam is added to the raw materials to complete the conditioning, and then the pellet feed is made by ring die extrusion. The raw materials come from agricultural products, the uniformity of the raw materials is poor, and sometimes the pellet hardness does not meet the requirements. In order to ensure the stability of the product during continuous production, the prior art proposes to use a transfer function to adjust the processing parameters. Chinese Patent Publication No. CN118131837A discloses a control method, device, electronic device and storage medium for feed conditioning temperature. The method uses a temperature sensor to collect the actual outlet temperature of the conditioning equipment, and determines the actual set temperature of the pelletizing equipment, and obtains the error value between the actual outlet temperature and the actual set temperature. The error value and the error change rate are fuzzy processed to obtain the control parameters of the PID controller, so as to adjust the current conditioning temperature of the pelletizer in combination with the actual control model. Because there is an insensitive zone (dead zone) in the conditioning and pelletizing equipment, that is, when the control parameter is too small, the mechanical part of the equipment cannot respond in time. The error of the ingredients and physical and chemical properties of the same batch of raw materials is usually within 2%, and the equipment cannot respond in time. When the error accumulates to a qualitative change, the equipment will respond quickly, causing system oscillation and resulting in poor uniformity of finished product quality. Therefore, the existing feed pelleting production method needs to be further improved. Summary of the invention

[0003] In view of the above problems, the present invention provides a continuous production method for pellet feed, which extracts the equipment control function and inertial response process in the tempering and pelleting process, adjusts the tempering process parameters and pelleting process parameters in real time, and ensures that the equipment's process parameters respond in time according to changes in raw materials.

[0004] The invention objectives of this application can be achieved through the following technical means: A continuous production method for pellet feed comprises the following steps: Step 1: Extract the fixed parameters of the quenching and tempering equipment and the quenching and tempering process parameters, generate the quenching and tempering process model, and create the quenching and tempering control function of the quenching and tempering humidity; Step 2: The raw materials and inlet steam enter the conditioning equipment to generate intermediate materials, collect the conditioning humidity and moisture content of the intermediate materials, and adjust the inlet steam flow rate based on the conditioning process model and conditioning control function; Step 3: Extract the fixed parameters of the granulation equipment and the granulation process parameters, generate a granulation process model, and create a granulation control function for the die roller speed; Step 4: The intermediate material enters the granulation equipment to generate finished granules, collects the granulation pressure and the hardness of the finished product, and adjusts the die roller speed based on the granulation process model and the granulation control function; Step 5: Predict the insensitive area of ​​the equipment according to the hardness of the finished product. If the insensitive area of ​​the equipment is greater than the preset value, proceed to step 6, otherwise return to step 1; Step 6: Extract the inertial response process of the moisture content of the intermediate material, calculate the control poles of the quenching and tempering equipment, if the real parts of all control poles are less than or equal to zero, increase the quenching and tempering process parameters and return to step 1; if the real parts of all control poles are greater than or equal to zero, reduce the quenching and tempering process parameters and return to step 1; otherwise, proceed to step 7; Step 7: Extract the inertial response process of the finished product hardness and calculate the control poles of the granulation equipment. If the real parts of all control poles are less than or equal to zero, increase the granulation process parameters and return to step 1. If the real parts of all control poles are greater than or equal to zero, reduce the granulation process parameters and return to step 1. Otherwise, end the task.

[0005] In the present invention, the raw material is one or more of corn flour, wheat bran flour, soybean meal or meat and bone meal, and the intermediate material is starch gelatinized product of corn flour, wheat bran flour, soybean meal or meat and bone meal.

[0006] In the present invention, in step 1, the tempering process model is the relationship between the inlet steam flow rate and the tempering humidity. The material ratio model is generated according to the fixed parameters of the tempering equipment and the energy change equation, and then the tempering process model is generated in combination with the tempering process parameters and the quality change equation.

[0007] In the present invention, in step 2, the tempering process parameter is the raw material humidity W2, the steam flow adjustment rate ΔM1=Q1(W2)G1(s)ΔW1, ΔW1 is the tempering humidity error rate, Q1(W2) is the tempering process model, G1(s) is the tempering control function, and s is a complex frequency variable.

[0008] In the present invention, in step 3, the granulation process model is the relationship between the mold roller speed and the granulation pressure. The mold cavity material model is generated according to the granulation process parameters, the mold cavity dynamics equation is obtained according to the fixed parameters of the granulation equipment, and then the granulation process model is generated in combination with the mold cavity kinematic equation.

[0009] In the present invention, in step 4, the granulation process parameters are the intermediate material feed amount M4, the die roller speed adjustment rate ΔN2=Q2(M4)G2(s)ΔP1, ΔP1 is the granulation pressure error rate, Q2(M4) is the granulation process model, G2(s) is the granulation control function, and s is a complex frequency variable.

[0010] In the present invention, in step 5, the output time interval in which the hardness change rate of the finished product is greater than -0.1% and less than 0.1% is collected, and the input time interval corresponding to the output time interval is extracted. The maximum value of the steam flow adjustment rate or the mold roller speed adjustment rate within the input time interval is the equipment insensitive zone.

[0011] In the present invention, in step 6, the inertial response process of the moisture content of the intermediate material is W3 / W1=K3 / (τ1s+1), wherein W3 is the moisture content of the intermediate material, W1 is the tempering humidity, K3 is the tempering inertia coefficient, and τ1 is the tempering time lag.

[0012] In the present invention, a tempering transfer function is generated by the inertial response process of the moisture content of the intermediate material and the tempering control function. The tempering transfer function is Q1(W2)G1(s)K3 / (τ1s+1). The denominator polynomial D1(s) of the tempering transfer function is extracted, and the solution when D1(s)=0 is the control pole.

[0013] In the present invention, in step 7, the inertial response process of the finished product hardness is H1 / P1=K4 / (τ2s+1), wherein H1 is the finished product hardness, P1 is the granulation pressure, K4 is the granulation inertia coefficient, and τ2 is the granulation time lag.

[0014] The continuous production method of pellet feed implemented in the present invention has the beneficial effect that when the quality of raw materials changes, the inlet steam flow rate and the die roller speed are adjusted according to the tempering control function and the granulation control function to ensure that the moisture content and hardness of the finished pellets remain stable. The insensitive area of ​​the equipment is identified according to the feed production status, and the inertial response process in the tempering and granulation process is extracted. The tempering process parameters and the granulation process parameters are adjusted according to the insensitive area of ​​the equipment and the control pole feedback. The adjusted control function can change the insensitive area of ​​the equipment until the insensitive area of ​​the equipment is less than the preset value, ensuring that the process parameters can respond in time according to the changes in the raw materials. Furthermore, the present invention creates a tempering control function and a granulation control function based on the tempering process model of the inlet steam flow rate and the tempering humidity and the granulation process model of the die roller speed and the granulation pressure, ensuring that the inlet steam flow rate and the die roller speed meet the current production requirements of the raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the production process of pellet feed; Figure 2 This is a schematic diagram of a continuous production line for pellet feed; Figure 3 The present invention is a flow chart of the continuous production method of pellet feed; Figure 4 It is a control process schematic diagram of the tempering control function of the present invention; Figure 5 It is a control process schematic diagram of the granulation control function of the present invention; Figure 6 A schematic diagram of the insensitive area of ​​the device predicted by the present invention; Figure 7 is a curve diagram of the inertial response process of the quenching and tempering equipment of the present invention; Figure 8 It is a schematic diagram of material migration of the quenching and tempering equipment of the present invention; Fig. 9 It is a schematic diagram of the mold cavity of the granulation equipment of the present invention.

[0016] Explanation of some of the reference numerals: conditioning equipment 11, raw material warehouse 12, steam warehouse 13, pressure pump 14, waste gas pool 15, granulation equipment 21, intermediate warehouse 22, finished product warehouse 23. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] Corn, wheat bran and other raw materials are made into intermediate materials with steam through tempering equipment. The intermediate materials are then produced into finished granules through granulation equipment. Due to the poor uniformity of the raw materials, in order to ensure the stability of the finished granules during continuous production, the prior art uses a transfer function to adjust the process parameters. Since the equipment has an insensitive working area, the equipment cannot respond in time to the trace signals of the control parameters. When the error accumulates to a qualitative change (usually 2%), the equipment will respond quickly again, causing adjustment oscillation, resulting in the deterioration of the quality and uniformity of the finished granules. The present invention extracts the control function and inertial response process in the tempering and granulation process, adjusts the tempering process parameters and granulation process parameters in real time, and ensures that the process parameters respond in time according to the changes in the raw materials. Embodiment 1

[0019] Reference Figure 1 and Figure 2 The core equipment of the continuous production line of pellet feed is the tempering equipment 11 and the pelletizing equipment 21, and it also includes a raw material warehouse 12, a steam warehouse 13, an intermediate warehouse 22, and a finished product warehouse 23. The inlet steam enters the tempering equipment 11 from the steam warehouse 13 and the pressure pump 14, the raw material enters the tempering equipment 11 from the raw material warehouse 12, and the remaining outlet steam enters the exhaust gas pool 15. The intermediate material after tempering enters the intermediate warehouse 22, and the intermediate material enters the pelletizing equipment 21, and the finished pellets after pelletizing enter the finished product warehouse 23. The continuous production method of pellet feed of the present invention is used to adjust the processing parameters of each equipment to keep the hardness and moisture content of the finished product stable. Figures 3 to 7 As shown, the continuous production method of pellet feed of the present invention comprises the following steps.

[0020] Step 1: Extract the fixed parameters of the tempering equipment and the tempering process parameters, generate a tempering process model, and create a tempering control function for tempering humidity. The raw material is one or more of corn flour, wheat bran flour, soybean meal or meat and bone meal. The tempering process model is the relationship between the inlet steam flow rate and the tempering humidity. The material ratio model is generated according to the fixed parameters of the tempering equipment and the energy change equation, and then the tempering process model Q1 (W2) is generated in combination with the tempering process parameters and the mass change equation. Please refer to Example 2 for details.

[0021] Step 2: The raw material and the inlet steam enter the tempering equipment to generate the intermediate material, collect the tempering humidity and the moisture content of the intermediate material, and adjust the inlet steam flow rate based on the tempering process model and the tempering control function. The intermediate material is a starch gelatinized product of corn flour, wheat bran flour, soybean meal or meat and bone meal. In this embodiment, the tempering process parameter is the raw material humidity W2, the tempering process model is Q1(W2), the tempering control function is G1(s), s is a complex frequency variable, and the steam flow adjustment rate ΔM1=Q1(W2)G1(s)ΔW1, ΔW1 is the tempering humidity error rate.

[0022] like Figure 4 , a PID controller is used to control the inlet steam flow of the tempering equipment. Specifically, G1(s) is the frequency domain representation of the tempering control function, G1(s)=K p1 +K i1 / s+K d1 s, K p1 K is the tempering ratio coefficient, i1 is the tempering differential coefficient, K d1 is the tempering integral coefficient. Convert G1(s) into time domain representation G1(t), The current tempering humidity at time t is collected, and the tempering humidity error rate ΔW1 between the current tempering humidity and the target tempering humidity is calculated. The inlet steam flow adjustment rate ΔM1 at time t is ΔM1 = Q1(W2)G1(t)ΔW1.

[0023] Step 3: Extract the fixed parameters of the granulation equipment and the granulation process parameters, generate a granulation process model, and create a granulation control function of the die roller speed. The granulation process model is the relationship between the die roller speed and the granulation pressure. The mold cavity material model is generated according to the granulation process parameters, and the mold cavity dynamics equation is obtained according to the fixed parameters of the granulation equipment. The granulation process model Q2 (M4) is generated in combination with the mold cavity kinematics equation. Please refer to Example 2 for details.

[0024] Step 4: The intermediate material enters the granulation equipment to generate finished granules, collects the granulation pressure and the hardness of the finished product, and adjusts the die roller speed based on the granulation process model and the granulation control function. In this embodiment, the granulation process parameter is the intermediate material feed rate, the granulation process model is Q2 (M4), the granulation control function is G2 (s), s is a complex frequency variable, and the die roller speed adjustment rate ΔN2 = Q2 (M4) G2 (s) ΔP1, ΔP1 is the granulation pressure error rate. In this embodiment, in order to ensure the comparability of parameters, the intermediate material feed rate, the inlet steam flow rate and the outlet steam flow rate all refer to the mass per unit time.

[0025] like Figure 5 , a PID controller is used to control the die roller speed of the granulation equipment. Specifically, G2(s) is the frequency domain representation of the granulation control function, G2(s)=K p2 +K i2 / s+K d2 s, K p2 is the granulation ratio coefficient, K i2 is the granulation differential coefficient, K d2 is the granulation integral coefficient. Convert G2(s) into time domain representation G2(t), , substituting G2(t) into the calculation formula of the die roller speed adjustment rate can obtain the die roller speed adjustment rate. Collect the current granulation pressure at time t, and calculate the granulation pressure error rate ΔP1 between the current granulation pressure and the target granulation pressure. The die roller speed adjustment rate ΔN2 at time t = Q2(M4)G2(t)ΔP1.

[0026] Step 5: Predict the equipment insensitive zone based on the hardness of the finished product. If the equipment insensitive zone is greater than the preset value, go to step 6, otherwise return to step 1. Calculate the hardness change rate of the finished product at time t+1 based on the hardness of the finished product at time t and time t+1. The output time interval is iterated forward by one signal cycle as the corresponding input time interval, and the input time interval corresponding to the output time interval is extracted. The hardness change rate of the finished product at time t+1 corresponds to the inlet steam flow adjustment rate and the mold roller speed adjustment rate at time t. Figure 6 , collect the output time interval when the hardness change rate of the finished product is greater than -0.1% and less than 0.1%, collect the inlet steam flow adjustment rate or the die roller speed adjustment rate in the input time interval at this time, and the maximum value of the inlet steam flow adjustment rate or the die roller speed adjustment rate is the equipment insensitive zone. Under ideal conditions, the equipment insensitive zone is less than the preset value of 2%. If the equipment insensitive zone is greater than the preset value, that is, the input signal change less than 2% of the preset value cannot bring about an effective change in the output signal, and the equipment cannot respond in time.

[0027] Step 6: Extract the inertial response process of the moisture content of the intermediate material, calculate the control poles of the conditioning equipment, if the real parts of all control poles are less than or equal to zero, increase the conditioning process parameters and return to step 1; if the real parts of all control poles are greater than or equal to zero, reduce the conditioning process parameters and return to step 1; otherwise, proceed to step 7. In the feed production process, the output signal of the conditioning control function is the conditioning humidity, but the moisture content of the intermediate material does not change proportionally with the conditioning humidity. The change of the moisture content of the intermediate material is an inertial response process (i.e., the first-order inertial link), that is, when the conditioning humidity changes, the moisture content of the intermediate material changes with lag, and finally approaches the conditioning humidity. According to the multiple groups of conditioning humidity and intermediate material moisture content collected in step 2, the parameters of the first-order inertial link are fitted to determine the inertial response process.

[0028] In this embodiment, the inertial response process of the moisture content of the intermediate material is W3 / W1=K3[1-exp(−t / τ1)], where W3 is the moisture content of the intermediate material, W1 is the tempering humidity, K3 is the tempering inertia coefficient, and τ1 is the tempering time lag. Figure 7 As shown. As time increases, W3 / W1 approaches K3, that is, the moisture content of the intermediate material W3 approaches the tempering humidity W1. The inertial response process is converted into the frequency domain and expressed as W3 / W1=K3 / (τ1s+1). The tempering transfer function is generated by the inertial response process and the tempering control function. The tempering transfer function combines the control process of the tempering equipment and the response process of the intermediate material. The tempering transfer function in a stable state can accept the increase of the tempering process parameters and can quickly change the system gain. The tempering transfer function in an unstable state can only reduce the tempering process parameters. Although the system gain changes slowly at this time and the speed of leaving the insensitive area of ​​the equipment is slow, it is beneficial to the stability of the system. Referring to Example 3, the stable state of the tempering transfer function is judged in combination with the control poles of the tempering transfer function.

[0029] Specifically, if the real parts of all control poles are less than or equal to zero, the quenching and tempering transfer function is in a stable state, and the quenching and tempering process parameters can be increased to change the equipment insensitivity zone that may be generated by the current quenching and tempering transfer function, and return to step 1. If the real parts of all control poles are greater than or equal to zero, the quenching and tempering transfer function is in an unstable state, and the quenching and tempering process parameters can be reduced to change the equipment insensitivity zone that may be generated by the current quenching and tempering transfer function, and return to step 1. If the state of the quenching and tempering transfer function is unclear, the quenching and tempering process parameters shall not be adjusted. In this embodiment, the quenching and tempering process parameters are the raw material humidity W2, and the adjustment step size of the raw material humidity is, for example, ±0.05W2. The humidity of the raw material can be increased by spraying water in the raw material. Or the humidity of the raw material can be reduced by drying or drying. In a more preferred embodiment, a deep learning method is used to determine the adjustment step size, and the number of adjustments to the raw material humidity is reduced, so that the raw material humidity is quickly adjusted to the preferred value.

[0030] Step 7: Extract the inertial response process of the finished product hardness, calculate the control poles of the granulation equipment, if the real parts of all control poles are less than or equal to zero, increase the granulation process parameters and return to step 1, if the real parts of all control poles are greater than or equal to zero, reduce the granulation process parameters and return to step 1, otherwise end the task. In the feed production process, the output signal of the granulation control function is the granulation pressure, but the hardness of the finished product does not change proportionally with the granulation pressure. The change in the hardness of the finished product is an inertial response process (i.e., the first-order inertia link), that is, when the granulation pressure changes, the hardness of the finished product changes with lag, and finally approaches the granulation pressure. According to the multiple groups of granulation pressure and finished product hardness collected in step 4, fit the parameters of the first-order inertia link.

[0031] In this embodiment, the inertial response process of the hardness of the finished product is H1 / P1=K4 / (τ2s+1), where H1 is the hardness of the finished product, P1 is the granulation pressure, K4 is the granulation inertia coefficient, and τ2 is the granulation time lag. The granulation transfer function is generated by the inertial response process and the granulation control function, and the granulation transfer function combines the control process of the granulation equipment and the response process of the finished product. The stable state of the granulation transfer function is determined by referring to the preferred method described in Example 3. Similar to step 6, if the real parts of all control poles are less than or equal to zero, the granulation transfer function is in a stable state, and the granulation process parameters are increased to change the equipment insensitivity zone that may be generated by the current granulation transfer function, and return to step 1. If the real parts of all control poles are greater than or equal to zero, the granulation transfer function is in an unstable state, and the granulation process parameters are reduced to change the equipment insensitivity zone that may be generated by the current granulation transfer function, and return to step 1. If the state of the granulation transfer function is unclear, the granulation process parameters shall not be adjusted. In this embodiment, the granulation process parameter is the intermediate material feed amount M4, and the adjustment step of the intermediate material feed amount is, for example, ±0.05M4. The intermediate material feed amount can be changed by the opening and closing size of the intermediate bin. In a more preferred embodiment, a deep learning method is used to determine the adjustment step, reduce the number of adjustments of the intermediate material feed amount, and enable the intermediate material feed amount to be quickly adjusted to the preferred value. Embodiment 2

[0032] This embodiment further discloses a preferred method for generating a conditioning process model and a granulation process model.

[0033] For the quenching and tempering process model.

[0034] First, the material ratio model is generated according to the fixed parameters of the quenching and tempering equipment and the energy change equation. Part of the heat absorbed by the intermediate material comes from the latent heat of high-temperature steam, and part comes from the heat of steam converted into condensed water. That is, the energy change equation: M2c2(T2-T1)=η1[(M1-M3)c1(100-T2)+M1H2], M2 is the raw material feed amount, c2 is the raw material specific heat capacity, T2 is the intermediate material temperature, and T1 is the raw material temperature. η1 is the thermal energy efficiency. M1 is the inlet steam flow rate, M3 is the outlet steam flow rate, c1 is the water specific heat capacity, and H2 is the steam latent heat. The fixed parameters of the quenching and tempering equipment include the thermal energy efficiency, which is usually taken as 60%. For a booster pump of 0.2-0.6Mpa, the steam temperature is usually 120℃-158.8℃, and the steam latent heat is usually taken as 2000kJ / kg-2200kJ / kg. The material ratio model is M2=η1[(M1-M3)c1(100-T2)+M1H2] / [c2(T2-T1)]. The temperature in the energy change equation is expressed in degrees Celsius, and other units are in the International System of Units.

[0035] Then, the tempering process model is generated by combining the tempering process parameters and the quality change equation. During the tempering process, the raw material and the inlet steam enter the tempering chamber, and the outlet steam and the intermediate material are discharged from the tempering chamber. Figure 8 , the raw material and the inlet steam bring in moisture, the outlet steam and the intermediate material bring out moisture, and the intermediate material absorbs condensed water. The mass change of moisture is absorbed by the conditioning chamber, that is, the mass change equation: (W1-W2)M2=η2(M1-M3), W1 is the conditioning humidity, W2 is the raw material humidity, M2 is the raw material feed amount, η2 is the steam dryness, and M1 is the inlet steam flow rate. The steam dryness is usually 70%-90%.

[0036] The material ratio model: M2=η1[(M1-M3)c1(100-T2)+M1H2] / [c2(T2-T1)] and the mass change equation: (W1-W2)M2=η2(M1-M3) can generate the quenching and tempering process model. Taking the raw material humidity W2 as the quenching and tempering process parameter, the quenching and tempering process model is simplified to Q1(W2), M1 / W1∝Q1(W2).

[0037] The conditioning process model can be used to express the functional relationship between the inlet steam flow rate and the conditioning humidity. By measuring the raw material temperature T1, the intermediate material temperature T2, the outlet steam flow rate M3, and inputting the raw material humidity W2, the current conditioning process model can be generated. According to the target conditioning humidity W1, the required inlet steam flow rate M1 can be calculated.

[0038] For the granulation process model.

[0039] First, the cavity material model is generated according to the granulation process parameters. The cavity material volume is M4 / ρ, where ρ is the bulk density of the intermediate material, which is related to the type of intermediate material and is usually 5~12kN / m³. In the continuous production process, the cavity material is the same as the intermediate material feed rate per unit time M4. Cavity material model: M4 / ρ=6×10 -11 πλ1N1N2L2[r1 2 -(r1-L1) 2 ]. λ1 is the ring die opening rate, N1 is the number of ring dies, usually 2, N2 is the die roller speed. r1 is the ring die radius, L1 is the intermediate material thickness, L2 is the ring die width, and M4 is the intermediate material feed amount, i.e., the granulation process parameters.

[0040] Then, the cavity dynamic equation is obtained according to the fixed parameters of the pelletizing equipment. During the pelletizing process, the intermediate material enters the cavity, and the ring die extrude the finished pellets from the die hole. Fig. 9 , the die roller rotates eccentrically, the die roller squeezes the intermediate material, and the hardness of the finished product is related to the granulation pressure. The granulation pressure is the pressure on the intermediate material per unit area. The fixed parameters of the granulation equipment are the rated power P2 of the granulation equipment, the granulation pressure P1=F / S, the total pressure F=9550P2 / (μr1N2), μ is the friction coefficient between the intermediate material and the die cavity, r1 is the radius of the ring die, and N2 is the die roller speed. The cavity dynamics equation: P1=9550P2 / (μr1N2S). S is the area of ​​the extrusion zone.

[0041] Combined with the cavity kinematics equation, the granulation process model is generated. Fig. 9 , the intermediate material is distributed in a ring shape along the side wall of the cavity. The center of the cavity is O1, the center of the ring die is O2, the center angle of the extrusion area is β, and the total pressure F is applied to the extrusion area. The extrusion area S=r1L2β, the center angle β=arccos[(r1-r2) 2 +(r1-L1) 2 -r2 2 ] / [2(r1-r2)(r1-L1)]. The cavity kinematic equation is: S=r1L2arccos[(r1-r2) 2 +(r1-L1) 2 -r2 2 ] / [2(r1-r2)(r1-L1)], r2 is the radius of the mold roller.

[0042] The cavity material model: M4 / ρ=6×10 -11 πλ1N1N2L2[r1 2 -(r1-L1) 2 ] and cavity kinematic equation: S=r1L2arccos[(r1-r2) 2 +(r1-L1) 2 -r22 ] / [2(r1-r2)(r1-L1)] is substituted into the cavity dynamics equation: P1=9550P2 / (μr1N2S), and the granulation process model can be generated. The granulation process model is the relationship between the die roller speed and the granulation pressure. Taking the intermediate material feed amount M4 as the granulation process parameter, the granulation process model is simplified as Q2(M4), N2 / P1∝Q2(M4).

[0043] The pelletizing process model can be used to express the functional relationship between pelletizing pressure and die roller speed. By measuring the rated power P2, ring die opening ratio λ1, ring die radius r1, die roller radius r2, ring die width L2, and inputting the intermediate material feed amount M4, the current pelletizing process model can be generated. According to the target pelletizing pressure P1, the die roller speed N2 can be calculated. Embodiment 3

[0044] This embodiment further discloses a method for determining a stable state of a conditioning transfer function.

[0045] Whether the transfer function of the device is stable can be determined by the Nyquist stability criterion, Routh-Hurwitz criterion, pole position method, etc. This embodiment adopts the pole position method to determine the stable state by calculating the control poles of the quenching and tempering transfer function and the granulation transfer function. If the real parts of all control poles are less than or equal to zero, the quenching and tempering device is in a stable state. If the real parts of all control poles are greater than or equal to zero, the quenching and tempering device is in an unstable state.

[0046] The conditioning transfer function is Q1(W2)G1(s)K3 / (τ1s+1). The denominator polynomial D1(s) of the conditioning transfer function is extracted. The solution when D1(s)=0 is the control pole. The conditioning transfer function combines the control process of the conditioning equipment and the response process of the intermediate material. The granulation transfer function is Q2(M4)G2(s)K4 / (τ2s+1). The denominator polynomial D2(s) of the granulation transfer function is extracted. The solution when D2(s)=0 is the control pole. The control pole s is expressed in complex form: s=σ+jω. When the control pole is expressed in real numbers, ω=0, σ is the real part of the control pole, that is, the solution of the denominator polynomial. Because the constant term of the denominator polynomial is zero and the linear term is not zero, s has at least one non-zero solution. This method is called the pole location method for determining whether the transfer function is stable. The granulation transfer function combines the control process of the granulation equipment and the response process of the finished product.

[0047] For example, in the quenching and tempering equipment, the quenching and tempering process model Q1(W2)=10, the quenching and tempering control function G1(s)=2+1 / s+0.5s, and the inertial response process K3 / (τ1s+1)=0.5 / (0.5s+1) have been calculated and determined. Then the quenching and tempering transfer function of the quenching and tempering equipment is Q1(W2)G1(s)K3 / (τ1s+1)=(2.5s 2+10s+5) / (0.5s 2 +s). Its denominator polynomial D1(s)=(0.5s 2 +s), solve for 0.5s 2 +s=0, the control poles are s=0, s=-2. At this time, the real parts of all control poles are less than or equal to zero, the quenching and tempering process is stable, and increasing the quenching and tempering process parameters will not have a significant impact on the system. The insensitive area of ​​the equipment can be changed by increasing the quenching and tempering process parameters.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for continuous production of pellet feed, characterized in that: The following steps are involved: Step 1: Extract the fixed parameters of the quenching and tempering equipment and the quenching and tempering process parameters, generate the quenching and tempering process model, and create the quenching and tempering control function of the quenching and tempering humidity; Step 2: The raw materials and inlet steam enter the conditioning equipment to generate intermediate materials, collect the conditioning humidity and moisture content of the intermediate materials, and adjust the inlet steam flow rate based on the conditioning process model and conditioning control function; Step 3: Extract the fixed parameters of the granulation equipment and the granulation process parameters, generate a granulation process model, and create a granulation control function for the die roller speed; Step 4: The intermediate material enters the granulation equipment to generate finished granules, collects the granulation pressure and the hardness of the finished product, and adjusts the die roller speed based on the granulation process model and the granulation control function; Step 5: Predict the insensitive area of ​​the equipment according to the hardness of the finished product. If the insensitive area of ​​the equipment is greater than the preset value, proceed to step 6, otherwise return to step 1; Step 6: Extract the inertial response process of the moisture content of the intermediate material, calculate the control poles of the quenching and tempering equipment, if the real parts of all control poles are less than or equal to zero, increase the quenching and tempering process parameters and return to step 1; if the real parts of all control poles are greater than or equal to zero, reduce the quenching and tempering process parameters and return to step 1; otherwise, proceed to step 7; Step 7: Extract the inertial response process of the finished product hardness and calculate the control poles of the granulation equipment. If the real parts of all control poles are less than or equal to zero, increase the granulation process parameters and return to step 1. If the real parts of all control poles are greater than or equal to zero, reduce the granulation process parameters and return to step 1. Otherwise, end the task.

2. The continuous production method of pellet feed according to claim 1, characterized in that: The raw material is one or more of corn flour, wheat bran flour, soybean meal or meat and bone meal, and the intermediate material is starch gelatinized product of corn flour, wheat bran flour, soybean meal or meat and bone meal.

3. The continuous production method of pellet feed according to claim 2, characterized in that: In step 1, the tempering process model is the relationship between the inlet steam flow rate and the tempering humidity. The material ratio model is generated according to the fixed parameters of the tempering equipment and the energy change equation, and then the tempering process model is generated in combination with the tempering process parameters and the quality change equation.

4. The continuous production method of pellet feed according to claim 1, characterized in that: In step 2, the tempering process parameter is the raw material humidity W2, the tempering process model is Q1(W2), the tempering control function is G1(s), s is a complex frequency variable, the steam flow adjustment rate ΔM1=Q1(W2)G1(s)ΔW1, and ΔW1 is the tempering humidity error rate.

5. The continuous production method of pellet feed according to claim 4, characterized in that: In step 3, the granulation process model is the relationship between the mold roller speed and the granulation pressure. The mold cavity material model is generated according to the granulation process parameters, the mold cavity dynamics equation is obtained according to the fixed parameters of the granulation equipment, and then the granulation process model is generated in combination with the mold cavity kinematic equation.

6. The continuous production method of pellet feed according to claim 4, characterized in that: In step 4, the granulation process parameters are the intermediate material feed amount M4, the granulation process model is Q2(M4), the granulation control function is G2(s), s is a complex frequency variable, the die roller speed adjustment rate ΔN2=Q2(M4)G2(s)ΔP1, and ΔP1 is the granulation pressure error rate.

7. The continuous production method of pellet feed according to claim 6, characterized in that: In step 5, the output time interval in which the hardness change rate of the finished product is greater than -0.1% and less than 0.1% is collected, and the input time interval corresponding to the output time interval is extracted. The maximum value of the steam flow adjustment rate or the mold roller speed adjustment rate within the input time interval is the equipment insensitive zone.

8. The continuous production method of pellet feed according to claim 4, characterized in that: In step 6, the inertial response process of the moisture content of the intermediate material is W3 / W1=K3 / (τ1s+1), where W3 is the moisture content of the intermediate material, W1 is the tempering humidity, K3 is the tempering inertia coefficient, and τ1 is the tempering time lag.

9. The continuous production method of pellet feed according to claim 8, characterized in that: The tempering transfer function is generated by the inertial response process of the moisture content of the intermediate material and the tempering control function. The tempering transfer function is Q1(W2)G1(s)K3 / (τ1s+1). The denominator polynomial D1(s) of the tempering transfer function is extracted, and the solution when D1(s)=0 is the control pole.

10. The continuous production method of pellet feed according to claim 6, characterized in that: In step 7, the inertial response process of the finished product hardness is H1 / P1=K4 / (τ2s+1), where H1 is the finished product hardness, P1 is the granulation pressure, K4 is the granulation inertia coefficient, and τ2 is the granulation time lag.

Images