A tobacco primary processing drum machine preheating control system and method based on condensation heat metering and waste heat air mixing

Abstract

The application discloses a tobacco primary drying drum machine preheating control system and method based on condensation heat metering and waste heat mixing, which comprises a drying drum machine (1), a hot air circulation system (2), a steam heating branch (3), a hot state detection assembly (4) and a control cabinet (5). The return air is divided and converged by a heating channel (25) and a bypass channel (26), and a complementary air door assembly (29) adjusts the proportion of the two paths. A double-cavity alternating constant-volume metering assembly (39) meters the condensate water of a steam heat exchanger (24). The controller determines the target side effective heat and the releasable waste heat according to the condensation quality, the enthalpy difference and the temperature of the steam and the condensate water, reduces the opening degree of the steam valve and adjusts the bypass proportion when the total heat meets the standard. When the cylinder wall temperature and the return air temperature meet the standard and the temperature difference between the return air and the output air converges, a completion signal is output. The application is suitable for working condition changes, reduces temperature overshoot and preheating time length dispersion, and reduces steam and fan energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of automated control technology for tobacco processing equipment, specifically relating to a preheating control system and method for a tobacco processing roller mill based on condensation heat metering and waste heat mixing air. Background Technology

[0002] In tobacco processing lines, drum-type heating and humidifying equipment such as loosening and rehumidifying machines, leaf moistening machines, feeding machines, and stem feeding machines require the circulating hot air, drum walls, front and rear covers, and steam heat exchangers to reach a suitable thermal state for production before materials are fed in. Insufficient preheating will cause the material to absorb excessive heat upon entering the cold drum, and steam may condense on the cold surface, leading to deviations in temperature, moisture content, and loosening effect from process requirements at the material head stage. Excessive preheating time will increase steam and electricity consumption, as well as wear and tear on drive components under no-load conditions.

[0003] In existing production sites, the hot air temperature is typically monitored using a temperature transmitter in the hot air duct. Preheating is stopped when the measured value reaches the set temperature, or a fixed preheating time is used. The response speed of the hot air temperature is significantly faster than the heat storage rate of the drum wall, shroud, and internal components. When the steam pressure is high, the heat exchanger surface temperature is high, or the temperature probe is subjected to localized hot air impact, the hot air measuring point can reach the set value first, while the drum body remains in a relatively cold state. Conversely, after the steam regulating valve is closed, the heat exchanger metal and retained condensate will continue to release heat to the circulating air, and the hot air temperature may continue to rise, resulting in overshoot.

[0004] Invention patent application CN103315373A discloses a method and apparatus for preheating a tobacco rehumidifier. It involves introducing steam into a heat exchanger at a relatively small, fixed opening, and intermittently opening and closing a heating diaphragm valve and atomizing diaphragm valve until the temperature sensor detects that the preheating is complete. This method can warm the pipes and drain condensate in advance, but its completion criterion still mainly depends on the temperature measuring point reaching the set value, without measuring the actual condensation heat absorbed by the equipment or the releasable residual heat after the valves are closed.

[0005] Invention patent CN109549241B discloses a steam heating control model and method for a tobacco spinning machine, which adopts steam pressure feedback PID in the preheating stage and adjusts the steam valve according to the temperature range of the outlet material in the production stage.

[0006] Invention patent CN102331712B discloses a variable parameter control method for the drum drying process, which improves the control of moisture content at the production outlet through variable parameter PID with dead zone. The above technology focuses on closed-loop control of pressure, temperature or moisture content, but does not use the actual condensation mass before condensation for preheating heat accumulation, nor does it solve how to reduce steam in advance using the waste heat of the heat exchanger before the drum wall reaches a hot state.

[0007] Invention patent CN101904552B discloses a method for measuring the temperature of tobacco material inside a drum using an infrared thermometer, a drum measuring window, and a synchronous control unit.

[0008] Invention patent CN102261962B discloses a method of measuring cylinder wall temperature by installing thermocouples and wireless data loggers inside the drum. The above scheme demonstrates that multi-location thermal state measurement has engineering value, but it is mainly used for temperature measurement and analysis in the production process and does not form a closed-loop relationship with steam condensation heat measurement, advance steam reduction, and waste heat mixing.

[0009] Invention patent CN114886136B discloses a two-stage, temperature threshold and intermittent steam preheating method, but does not perform pre-condensation heat measurement before condensation, nor does it combine waste heat prediction and complementary bypass mixing.

[0010] Utility model patent CN205455999U discloses a device for monitoring the heat exchange capacity and condensation status of thin plates in a tobacco drying machine. It features an open condensate tank downstream of a condensate valve, using a weighing device to measure the condensate entering the tank, and correcting the amount of secondary steam generated by pressure reduction flash evaporation based on the pressure before the condensate valve. However, because the device measures condensate on the open side after condensation, the determination of the condensate quality depends on the estimation of the secondary steam volume. Furthermore, it does not establish a dual-chamber alternating constant-volume measurement system under closed conditions before condensation, nor does it integrate condensation heat measurement with preheating waste heat prediction and air mixing regulation.

[0011] Existing condensate monitoring systems typically involve setting up an open water tank after the steam trap for weighing. The pressure difference before and after condensate collection generates secondary steam, requiring additional correction to the metering values. Furthermore, the inlet and outlet actions of the water tank are not directly relevant to the accumulation of short-term preheating energy. Existing hot air bypasses are generally used for general temperature regulation. If the bypass ratio is not aligned with the remaining heat of the heat exchanger and the heat required by the equipment, early bypassing will prolong the temperature rise, while late bypassing cannot prevent temperature overshoot after valve closure.

[0012] Therefore, a preheating control system and method for a single tobacco spinning roller machine is needed. The actual condensation quality is continuously obtained before the condensate is drained and the pressure is reduced. The enthalpy difference of condensation is used to characterize the heat released by the steam in the heat exchanger. After deducting the heat storage increment and heat dissipation of the heat exchanger, the effective heat on the target side is obtained. The releaseable residual heat of the heat exchanger, the minimum temperature of the cylinder wall, and the uniformity of the supply and return air are combined to determine the steam reduction time and the preheating endpoint, thereby reducing the preheating time dispersion caused by changes in ambient temperature, steam quality, valve characteristics, and condensate status.

[0013] To address the aforementioned technical problems, this invention is proposed. Summary of the Invention

[0014] The purpose of this invention is to provide a preheating control system and method for a tobacco shredding drum machine based on condensation heat metering and waste heat mixing air, so as to solve the problems of existing technology that judge the completion of preheating only based on single-point hot air temperature or fixed time, which cannot reflect the actual heat storage state of the drum wall, and the temperature overshoot caused by waste heat of the heat exchanger after the steam is turned off, and the dispersion of preheating time caused by changes in steam quality and condensate.

[0015] To achieve the above objectives, the present invention adopts the following technical solution:

[0016] The present invention provides a preheating control system for a tobacco shredding drum machine based on condensation heat metering and waste heat mixing air, including a drum machine 1, a hot air circulation system 2, a steam heating branch 3, a thermal state detection component 4, and a control cabinet 5.

[0017] The roller mill 1 includes a roller body 11 mounted on a frame 12, a feed hood 16 and a discharge hood 17 respectively mounted at both ends of the roller body 11, and a drive motor 14 and a transmission mechanism 15 for driving the roller body 11 to rotate.

[0018] The hot air circulation system 2 includes an air supply duct 21, a return air duct 22, a circulating fan 23, a steam heat exchanger 24, a heating channel 25, a bypass channel 26, a distribution box 27, a junction box 28, and a complementary damper assembly 29;

[0019] The return air duct 22 is connected to the distribution box 27 via the discharge hood 17. The heating channel 25 and the bypass channel 26 are connected in parallel between the distribution box 27 and the junction box 28. The steam heat exchanger 24 is disposed in the heating channel 25. The air supply duct 21 is connected to the feed hood 16 via the junction box 28.

[0020] The complementary damper assembly 29 includes a heating damper 291 and a bypass damper 292 respectively disposed in the heating channel 25 and the bypass channel 26. The heating damper 291 and the bypass damper 292 are fixedly connected to the same linkage shaft 293 to reverse the effective flow area of ​​the two channels, so that the total effective flow area of ​​the two channels remains basically unchanged, thereby reducing the sudden change of the operating point of the circulating fan when the mixing ratio is changed.

[0021] The steam heating branch 3 includes a steam pipe 31 connected to the steam inlet of the steam heat exchanger 24, a steam regulating valve 32 installed on the steam pipe 31, and a condensate pipe 38, a dual-chamber alternating constant volume metering component 39, and a steam trap 37 that are sequentially connected to the condensate outlet of the steam heat exchanger 24.

[0022] The dual-chamber alternating constant volume metering assembly 39 includes a first sealed metering chamber 391 and a second sealed metering chamber 392 connected in parallel between the inlet manifold and the outlet manifold. Each sealed metering chamber is equipped with an inlet valve, a drain valve, an upper liquid level switch 397 and a lower liquid level switch 398. The two sealed metering chambers alternately operate in a constant volume filling state from the lower liquid level to the upper liquid level and in a state of draining liquid to the condensate drain 37.

[0023] The dual-chamber alternating constant volume metering component 39 is located between the condensate outlet of the steam heat exchanger 24 and the steam trap 37. The two sealed metering chambers alternately fill and drain liquid. While the steam heat exchanger 24 continuously drains water, the condensate from the lower liquid level to the upper liquid level each time is determined as a calibrated volume, avoiding the difficulty in directly determining the quality of liquid condensate due to flash evaporation after the steam trap.

[0024] The thermal state detection component 4 includes a supply air temperature transmitter 41 located downstream of the manifold 28, a return air temperature transmitter 42 located upstream of the branch box 27, a heating branch outlet temperature transmitter 43 located at the outlet of the heating channel 25, an ambient temperature transmitter 44, a heat exchanger metal temperature sensor 45 thermally connected to the steam heat exchanger 24, a steam pressure transmitter 34 and a steam temperature transmitter 35 located on the steam pipe 31, a condensate temperature sensor 399 located at the inlet of the dual-cavity alternating constant volume metering component 39, and at least three infrared cylinder wall thermometers 19 distributed along the axial direction of the drum body 11 and facing the cylinder wall.

[0025] The PLC controller 51 in the control cabinet 5 is connected to the valve actuator 33 of the dual-chamber alternating constant volume metering component 39, the thermal state detection component 4, the steam regulating valve 32, and the servo actuator 294 of the complementary damper component 29, respectively.

[0026] The PLC controller 51 is configured to: determine the condensation quality based on the number of metering cycles, calibrated volume and condensate temperature output by the dual-cavity alternating constant volume metering component 39; determine the effective heat input increment based on the condensation quality and the enthalpy difference between steam and condensate; accumulate the effective heat on the target side after deducting the heat storage increment and heat dissipation of the heat exchanger; and determine the releasable waste heat based on the difference between the heat exchanger metal temperature and the air supply temperature.

[0027] Before the lowest value detected by the infrared cylinder wall thermometer 19 reaches the cylinder wall temperature threshold, when the sum of the effective heat on the target side and the releasable residual heat reaches the reference heat requirement established by the benchmark preheating data that meets the preheating completion conditions and corrected by the current initial equivalent thermal state, the opening of the steam regulating valve 32 is reduced and the bypass ratio of the complementary damper assembly 29 is increased.

[0028] When the minimum value and return air temperature reach the corresponding threshold, the absolute value of the difference between the supply air temperature and return air temperature is not greater than the heat equalization threshold, and the above conditions are maintained continuously for at least two drum rotation cycles, a preheating completion signal is output.

[0029] Preferably, the heating damper 291 and the bypass ventilation damper 292 are both rectangular butterfly plates adapted to the corresponding channel cross-sections, and are fixed to the linkage shaft 293 with an installation phase difference of 90°.

[0030] The servo actuator 294 is connected to the linkage shaft 293. The diversion box 27 is provided with mechanical limiting members 295 that respectively limit the two extreme positions of the linkage shaft 293, so that the effective flow area of ​​the bypass channel 26 increases when the effective flow area of ​​the heating channel 25 decreases.

[0031] Preferably, the inlet and outlet of the first sealed metering chamber 391 are respectively provided with a first inlet valve 393 and a first outlet valve 394, and the inlet and outlet of the second sealed metering chamber 392 are respectively provided with a second inlet valve 395 and a second outlet valve 396.

[0032] The tops of both sealed metering chambers are connected to the inlet manifold via pressure equalization capillary tubes 390 equipped with one-way throttling devices 3901. The conduction direction of the one-way throttling devices 3901 is from the inlet manifold to the top of the corresponding sealed metering chamber. The PLC controller 51 interlocks the inlet valve and outlet valve of the same sealed metering chamber. After one sealed metering chamber is filled from the lower liquid level to the upper liquid level and the other sealed metering chamber is discharged to the lower liquid level, the already opened inlet valve and outlet valve are closed first. After a preset non-overlapping time, the other two valves are opened to alternate the state of the two sealed metering chambers.

[0033] Preferably, the outer periphery of the roller body 11 is provided with at least three annular temperature measuring bands 18 spaced apart from each other along the axial direction, and each annular temperature measuring band 18 is made of the same material and surface coating to have the same surface emissivity;

[0034] The frame 12 is provided with a mounting guide rail 191 parallel to the axis of the drum body 11. The infrared cylinder wall thermometer 19 is set on the mounting guide rail 191 and corresponds one-to-one with each annular temperature measuring band 18. The detection end of each infrared cylinder wall thermometer 19 is located inside the purge sleeve 192 and faces the corresponding annular temperature measuring band 18. Each purge sleeve 192 is connected to the source of filtered and depressurized compressed air through the purge air manifold 193.

[0035] Preferably, the control cabinet 5 further includes an analog input module 52, a digital input module 53, an analog output module 54, a digital output module 55, a memory 56, and a terminal block 57, and is connected to an alarm 64;

[0036] Steam pressure transmitter 34, steam temperature transmitter 35, condensate temperature sensor 399, supply air temperature transmitter 41, return air temperature transmitter 42, heating branch outlet temperature transmitter 43, ambient temperature transmitter 44, heat exchanger metal temperature sensor 45, and each infrared cylinder wall thermometer 19 are connected to the analog input module 52 via the terminal block 57.

[0037] The level switches, circulating air volume switches 61, drum speed switches 62, and emergency stop contacts 63 of the dual-chamber alternating constant volume metering component 39 are connected to the digital input module 53; the analog output module 54 is connected to the valve actuator 33 and the servo actuator 294 respectively; and the digital output module 55 is connected to the inlet valve and outlet valve, drive motor 14, circulating fan 23, and alarm 64 of the dual-chamber alternating constant volume metering component 39 respectively.

[0038] Preferably, the calibrated volume between the upper liquid level switch 397 and the lower liquid level switch 398 in the first sealed metering chamber 391 and the second sealed metering chamber 392 is ΔV; the PLC controller 51 determines the condensation mass increment Δm in the kth calculation cycle according to the following formula. c (k) Increment of effective heat input ΔQ in (k) Heat exchanger heat storage increment ΔE x (k) and cumulative target-side effective heat E net (k):

[0039] Δm c (k)=N k ·ρ[T c (k)]·ΔV;

[0040] ΔQ in (k)=Δm c (k)·{h s [P s (k),T v (k)]-h c [T c (k)]};

[0041] ΔE x (k)=C x ·[T x (k)-T x (k-1)];

[0042] E net (k)=E net (k-1)+ΔQ in (k)-ΔE x (k)-K loss ·[T eq (k)-T a (k)]·Δt;

[0043] Where, N k ρ[T] represents the number of calibration volume measurements completed within the k-th calculation cycle. c [k] represents the condensate temperature T. c The density corresponding to (k), h s Steam pressure P s (k) and steam temperature T v (k) corresponds to the specific enthalpy of vapor, h c For the specific enthalpy of condensate, C x T represents the equivalent heat capacity of the steam heat exchanger 24 and its retained condensate. x (k) represents the metal temperature of the heat exchanger, K. loss Here, Δt is the heat dissipation correction factor, and T is the calculation period. a (k) represents the ambient temperature, T eq (k) is the equivalent thermal state temperature obtained by weighting the supply air temperature, return air temperature and the detected temperatures of each infrared cylinder wall thermometer 19 according to a preset weight.

[0044] Preferably, the PLC controller 51 is configured according to E res (k)=η x ·C x ·max{T x (k)-T s (k), 0} determines the releaseable waste heat E res (k), where η x T is the utilization coefficient for the transfer of waste heat to the circulating air and the drum body 11. s (k) represents the supply air temperature;

[0045] When E net (k)+E res (k)≥E req Output steam reduction command, where E req This is the reference heat requirement corrected for the initial equivalent thermal state temperature; after reducing steam, at |T b (k)-T r (k)|≥ε T At that time, the PLC controller 51 determines the bypass ratio β(k) according to the following formula:

[0046] β(k)=sat[0,1]{[T b (k)-T cmd (k)] / [T b (k)-T r (k)]};

[0047] Where sat[0,1] indicates that the calculated value is restricted to 0 to 1, T b (k) represents the outlet temperature of the heating branch, Tr (k) represents the return air temperature, T cmd (k) represents the target temperature of the supply air during the waste heat equalization stage, ε T The denominator protection value is greater than 0; in |T b (k)-T r (k)|<ε T At the same time, the bypass ratio of the previous calculation cycle is maintained or a preset bypass ratio is adopted; the complementary damper assembly 29 makes the ratio of the effective flow area of ​​the bypass channel 26 to the total effective flow area of ​​the two channels correspond to β(k).

[0048] Preferably, the control cabinet 5 is connected to an alarm 64; the output conditions of the preheating completion signal include: the lowest value among the detected values ​​of each infrared cylinder wall thermometer 19 is not lower than the cylinder wall temperature threshold minus the cylinder wall allowable deviation, the return air temperature is not lower than the return air temperature threshold minus the return air allowable deviation, the absolute value of the difference between the supply air temperature and the return air temperature is not greater than the heat equalization threshold, and the above conditions are continuously maintained for 2 to 10 drum rotation cycles.

[0049] When the opening of the steam regulating valve 32 is greater than the preset opening and no calibrated volume metering count is generated within the metering timeout period, or when the preheating timer reaches the maximum allowable time but no preheating completion signal is output, the PLC controller 51 closes the steam regulating valve 32, controls the complementary damper assembly 29 to make the bypass channel 26 be in the state of maximum effective flow area, keeps the circulating fan 23 running for a preset circulating cooling time, and drives the alarm 64.

[0050] The PLC controller determines the condensation quality based on the number of meters, the calibrated volume, and the condensate temperature; it determines the effective heat input increment based on the enthalpy difference between steam and condensate; it subtracts the heat storage increment and heat dissipation of the heat exchanger from the effective heat input increment to obtain the target-side effective heat that has been transferred to the drum body, shroud, and circulating air; it determines the residual heat that can continue to be released after the valve is closed based on the degree to which the heat exchanger metal temperature is higher than the supply air temperature; and it adjusts the reference heat requirement of the corresponding formula based on the initial equivalent thermal state.

[0051] When the sum of the accumulated effective heat and the releasable waste heat reaches the corrected reference heat requirement, the PLC controller reduces or closes the steam regulating valve and increases the bypass ratio before the minimum cylinder wall temperature reaches the cylinder wall temperature threshold. During the waste heat equalization stage, the bypass ratio is calculated based on the outlet temperature of the heating branch, the return air temperature, and the target supply air temperature to mix the airflow from the high-temperature heating branch with the return air that has not passed through the heat exchanger. This maintains the circulating air volume while limiting the supply air temperature and gradually transferring the waste heat from the heat exchanger to the drum body.

[0052] When the lowest temperature among multiple axial cylinder wall detection points reaches the cylinder wall threshold, the return air temperature reaches the return air threshold, and the temperature difference between the supply air and return air converges to within the uniform heating threshold and remains within multiple drum rotation cycles, the PLC controller outputs a preheating completion signal. Thus, the determination simultaneously reflects the cold spot of the drum body, the recirculation status of the circulating air, and the internal temperature difference of the system, no longer relying solely on the instantaneous reaching of a set value at a single supply air measurement point.

[0053] Another aspect of the present invention provides a preheating control method for a tobacco processing drum machine, employing a drum machine preheating control system comprising a drum body, a circulating fan, a steam heat exchanger, a steam regulating valve, a heating channel, a bypass channel, and a complementary damper assembly. The heating channel and the bypass channel are connected in parallel between a distribution box and a junction box, and the complementary damper assembly reverses the effective flow area of ​​the two channels. A dual-cavity alternating constant volume metering assembly is provided between the condensate outlet of the steam heat exchanger and the steam trap. The dual-cavity alternating constant volume metering assembly has a first sealed metering cavity and a second sealed metering cavity, each equipped with an upper liquid level switch and a lower liquid level switch.

[0054] The preheating control method includes the following steps:

[0055] S1. Keep the steam regulating valve closed, run the drum body and circulating fan and open the bypass channel to collect the initial temperatures of the supply air, return air, drum wall, heat exchanger metal and the environment to form the initial equivalent thermal state.

[0056] S2. Increase the effective flow area of ​​the heating channel and decrease the effective flow area of ​​the bypass channel, open the steam regulating valve, so that the steam condenses in the steam heat exchanger and heats the circulating air.

[0057] S3. The first and second sealed metering chambers alternately perform constant volume filling and draining from the lower liquid level to the upper liquid level. The condensation mass and effective heat input increment are determined based on the calibrated volume, condensate temperature, steam pressure and steam temperature. The heat storage increment of the heat exchanger determined based on the change of heat exchanger metal temperature and the heat dissipation determined based on the ambient temperature are deducted, and the effective heat on the target side is accumulated.

[0058] S4. Determine the releaseable waste heat based on the difference between the heat exchanger metal temperature and the supply air temperature, and correct the reference heat demand based on the initial equivalent thermal state.

[0059] S5. Before the lowest temperature of the cylinder wall reaches the cylinder wall temperature threshold, when the sum of the effective heat on the target side and the releasable waste heat reaches the corrected reference heat requirement, reduce the opening of the steam regulating valve, and determine the bypass ratio according to the outlet temperature of the heating branch, the return air temperature and the supply air target temperature in the waste heat equilibrium stage, and mix the outlet air of the heating branch and the bypass return air through the complementary damper assembly.

[0060] S6. While the drum body and the circulating fan continue to run, determine the minimum temperature of the drum wall, the return air temperature, and the difference between the supply air temperature and the return air temperature. After the preset conditions are met for at least two consecutive drum rotation cycles, output a preheating completion signal.

[0061] S7. Record the start and end times of preheating, the cumulative condensate mass, the cumulative effective heat on the target side, the time of steam reduction, and the temperature data. When metering timeout, insufficient air volume, drum failure, or preheating timeout occurs, close the steam regulating valve and execute bypass circulation cooling and alarm.

[0062] Preferably, during the commissioning phase, a baseline preheating operation is selected where no alarm is triggered and the preheating completion conditions are met normally. The cumulative effective heat on the target side at the time of completion of the baseline preheating is saved as the initial reference heat demand E. ref,0 And save the corresponding initial equivalent thermal state temperature T. eq,ref0 ;

[0063] The reference heat requirement E for the nth preheating req,n Determined according to the following formula:

[0064] E req,n =E ref,n-1 +C eq ·(T eq,ref0 -T eq,n0 );

[0065] Where n≥1, C eq For the pre-identified equivalent heat capacity of the drum machine and hot air circulation system, T eq,n0 E is the initial equivalent thermal state temperature of the nth preheating. ref,n-1 The reference heat demand is stored before the start of the nth preheating; the updated reference heat demand E is determined according to the following formula only if no alarm occurs during the nth preheating and the preheating completion conditions are met normally. ref,n :

[0066] E ref,n =λ·E ref,n-1 +(1-λ)·[E net,n -C eq ·(T eq,ref0 -T eq,n0 )];

[0067] Where λ is the forgetting coefficient, and 0.7 ≤ λ < 1, E net,n Let E be the cumulative effective heat on the target side when the nth preheating is completed. The amount in square brackets is the converted heat obtained by converting the cumulative effective heat on the target side to the initial equivalent thermal state of the baseline preheating. When an alarm occurs during the nth preheating or the preheating completion conditions are not met normally, let E... ref,n =E ref,n-1 .

[0068] Preferably, the two metering chambers of the dual-chamber alternating constant volume metering assembly have the same calibrated volume and are restored to the inlet main pipe pressure before filling through the pressure equalization capillary tube; the inlet valve and outlet valve of each metering chamber are interlocked, and the switching of the two metering chambers is set to have no overlap time, so as to prevent steam from directly passing through the metering chamber into the condensate trap.

[0069] Preferably, at least three annular temperature measuring bands with the same surface emissivity are arranged along the axial direction on the outer periphery of the drum body. The infrared cylinder wall temperature measuring device on the frame is respectively oriented towards the corresponding annular temperature measuring band, and a clean optical path is formed by the purge sleeve. The PLC controller takes the lowest value among multiple cylinder wall detection values ​​as the completion judgment quantity.

[0070] Preferably, the heating damper and the bypass damper in the complementary damper assembly are fixed on the same linkage shaft and have an installation phase that is 90° apart, so that the total effective flow area of ​​the two channels remains basically stable when the bypass ratio changes.

[0071] The beneficial effects of this invention are:

[0072] Compared with the prior art, the present invention has at least the following beneficial effects:

[0073] (1) In this invention, the dual-chamber alternating constant-volume metering component is set between the condensate outlet of the steam heat exchanger and the steam trap. The two sealed metering chambers are filled and drained alternately, and the liquid condensate is accumulated according to the calibrated constant volume without interrupting the continuous condensation. Compared with estimating based solely on valve opening, nominal steam flow rate, or the weight of the open water tank after condensation, this structure can obtain the condensate mass before flash evaporation and reflect the actual heat released through the heat exchanger by combining the enthalpy difference between steam and condensate. Therefore, it can reduce the influence of steam dryness, pressure, valve flow characteristics, and changes in heat exchanger water accumulation on the judgment of preheating heat.

[0074] (2) This invention uses the cumulative effective heat on the target side, the heat exchanger's releasable waste heat, the lowest axial temperature of the cylinder wall, the return air temperature, and the supply and return air temperature difference together to reduce steam and complete the judgment. The effective heat on the target side is obtained by subtracting the heat storage increment and heat dissipation of the heat exchanger from the condensation enthalpy difference heat, avoiding the heat already stored inside the heat exchanger being included in the cumulative amount and also being repeatedly counted as releasable waste heat; the heat exchanger metal temperature reflects the heat that can still be transferred after the valve is closed, the lowest cylinder wall temperature reflects the latest heating part, and the supply and return air temperature difference reflects whether the circulation loop tends to be uniformly heated. The above quantities physically support each other, which can avoid the "false temperature reaching" caused by the hot air measuring point heating up first, and reduce the risk of premature feeding when the cylinder is still locally cooling.

[0075] (3) In this invention, the PLC controller reduces the steam valve opening in advance when the sum of the accumulated effective heat and the releasable waste heat on the target side reaches the reference required heat, but the lowest temperature of the cylinder wall has not yet reached the cylinder wall temperature threshold. This allows the waste heat in the heat exchanger, pipeline, and stagnant condensate to replace the newly added steam and continue to complete the cylinder heating. This method does not passively close the valve after the temperature exceeds the upper limit, but incorporates the heat migration that will inevitably occur after the valve is closed into the steam reduction time. This can shorten the duration of high-opening steam supply, reduce the continued rise of the air supply temperature, the repeated opening and closing of the valve, and the ineffective steam consumption.

[0076] (4) In this invention, the heating damper and the bypass damper complement each other through the same linkage shaft. When the bypass ratio increases, the opening of the heating channel decreases synchronously, so that the total effective flow area of ​​the two channels remains basically stable. The PLC gives the bypass ratio based on the mixing relationship of the temperatures of the two branches. Thus, during the waste heat equalization stage, some return air can bypass the high-temperature heat exchanger and mix with the air outlet of the heating branch in the manifold box. This not only suppresses the direct impact of instantaneous high-temperature hot air on the measuring point and the drum, but also avoids the large changes in circulation resistance and fan airflow fluctuations caused by ordinary independent damper adjustment.

[0077] (5) In this invention, the reference heat demand is established from a baseline preheating that has not triggered an alarm and whose preheating completion conditions are met normally. The equivalent heat capacity is corrected according to the initial equivalent heat state at each start-up. After each normal preheating is completed, the heat demand increment corresponding to the current initial equivalent heat state relative to the baseline initial equivalent heat state is deducted first. The accumulated effective heat on the target side is converted to the baseline initial equivalent heat state, and then the reference heat demand is updated according to the forgetting factor. This method can avoid the heat difference caused by cold start or warm start being solidified into the reference value and repeatedly compensated during subsequent preheating. At the same time, only the preheating data that has not triggered an alarm and has been completed normally is used for updating, which can prevent abnormal data of steam supply, condensate, air volume or sensors from polluting the reference value. This is beneficial to reduce the dispersion of preheating time between different seasons and different shifts, and improve the stability of the reference heat demand and remaining preheating time estimation.

[0078] (6) In this invention, when the steam valve is in the open state and the dual-chamber metering component does not generate a metering cycle within a specified time, the system can identify "steam supply command but no condensate" as steam supply interruption, valve failure, heat exchanger air resistance or condensate abnormality; combined with circulating air volume, drum speed and emergency stop feedback, the steam can be shut off first when timeout or loss of rotation occurs, and then the bypass channel is placed in the state of maximum effective flow area and the fan is kept circulating for cooling. This protection sequence reduces the risk of continued heat storage in the state of no circulating air or drum stoppage, and retains condensate, temperature and action time, which is convenient for maintenance and traceability. Attached Figure Description

[0079] Figure 1This is a schematic diagram of the overall installation, hot air circulation, and steam connection structure of the preheating control system of the present invention.

[0080] Figure 2 This is a schematic diagram showing the specific structure of the heating channel, bypass channel, complementary damper assembly, and temperature detection location of the present invention.

[0081] Figure 3 This is a schematic diagram of the piping and component structure of the dual-cavity alternating constant volume metering assembly of the present invention.

[0082] Figure 4 This is a schematic diagram showing the installation of the annular temperature measuring belt on the drum body, the infrared drum wall temperature measuring device, and the purging structure of the present invention.

[0083] Figure 5 This is a schematic diagram of the electrical connection between the control cabinet input / output module and the field detection components and actuators of the present invention.

[0084] Figure 6 This is a schematic diagram showing the changes in steam valve opening, bypass ratio, heat criterion, and temperature status over time during the preheating process of this invention.

[0085] Figure 7 This is a flowchart of the preheating control method of the present invention.

[0086] The meanings of the reference numerals in the attached drawings are as follows: 1. Roller conveyor; 11. Roller body; 12. Frame; 13. Support roller; 14. Drive motor; 15. Transmission mechanism; 16. Feed hood; 17. Discharge hood; 18. Annular temperature measuring belt; 19. Infrared cylinder wall thermometer; 191. Mounting guide rail; 192. Purge sleeve; 193. Purge air manifold; 2. Hot air circulation system; 21. Air supply duct; 22. Return air duct; 23. Circulating fan; 24. Steam heat exchanger; 25. Heating channel; 26. Bypass channel; 27. Diverter box 28. Manifold; 29. ​​Complementary damper assembly; 291. Heating damper; 292. Bypass damper; 293. Linkage shaft; 294. Servo actuator; 295. Mechanical limit device; 3. Steam heating branch; 31. Steam pipe; 32. Steam regulating valve; 33. Valve actuator; 34. Steam pressure transmitter; 35. Steam temperature transmitter; 37. Steam trap; 38. Condensate pipe; 39. Dual-chamber alternating constant volume metering assembly; 390. Pressure equalizing capillary tube; 3901. One-way throttling device; 391. First closed metering unit. 392. Second sealed metering chamber; 393. First inlet valve; 394. First drain valve; 395. Second inlet valve; 396. Second drain valve; 397. Upper level switch; 398. Lower level switch; 399. Condensate temperature sensor; 4. Thermal status detection assembly; 41. Supply air temperature transmitter; 42. Return air temperature transmitter; 43. Heating branch outlet temperature transmitter; 44. Ambient temperature transmitter; 45. Heat exchanger metal temperature sensor; 46. Circulating air volume transmitter; 5. Control cabinet; 51. PLC controller; 511. Baseline acquisition program segment; 512. Heat accumulation program segment; 513. Waste heat prediction program segment; 514. Mixed air control program segment; 515. Completion judgment program segment; 52. Analog input module; 53. Digital input module; 54. Analog output module; 55. Digital output module; 56. Memory; 57. Terminal block; 58. Human-machine interface; 59. Industrial communication network; 61. Circulating air volume switch; 62. Drum speed switch; 63. Emergency stop contact; 64. Alarm. Detailed Implementation

[0087] The specific structure and method of a preheating control system for a tobacco processing roller mill based on condensation heat metering and waste heat mixing air, provided by the present invention, will be further described below with reference to the accompanying drawings. This embodiment is only for illustrating the present invention and is not intended to limit the scope of protection of the present invention.

[0088] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product manual. Materials or equipment whose manufacturers are not specified are all conventional products that can be purchased.

[0089] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” to another element, it can be directly connected to the other element, or there may be intermediate elements present.

[0090] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. The terms "inner," "upper," "lower," etc., indicate the orientation or state relationship based on the orientation or state relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0091] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "equipped with" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0092] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0093] Example 1

[0094] like Figure 1 As shown, the preheating control system of this embodiment is configured for one roller mill 1. The roller body 11 is mounted approximately horizontally on the frame 12 and supported by two sets of support rollers 13. The drive motor 14 drives the roller body 11 to rotate around its axis via a reducer and a gear transmission mechanism 15; the feed hood 16 and the discharge hood 17 are fixed on the frame 12 and are rotatably and sealingly connected to both ends of the roller body 11, respectively. When the roller body 11 is preheating, it is in an unloaded state, and its rotational speed can be set to 40% to 100% of the normal production speed, so that the roller wall is repeatedly circulated with hot air in the circumferential direction.

[0095] The return air duct 22 is led out from the return air inlet of the discharge hood 17, and connects to the distribution box 27 in sequence through the circulating fan 23 and the circulating air volume transmitter 46. The heating channel 25 and the bypass channel 26 are separated from the distribution box 27 and rejoin in the junction box 28. The steam heat exchanger 24 is installed in the heating channel 25; the return air absorbs the latent heat of condensation when passing through the fin gaps of the steam heat exchanger 24. The circulating air after confluence enters the feed hood 16 through the air supply duct 21, then passes through the drum body 11 and returns to the discharge hood 17, thus forming a closed loop. The dehumidification branch can be led out from the discharge hood 17 or the return air duct 22 according to the original structure of the equipment; during the preheating stage, only the minimum dehumidification required to prevent condensation is maintained, and its heat loss is included in the heat dissipation correction factor K. loss middle.

[0096] like Figure 2 As shown, the downstream baffle of the diversion box 27 divides the flow channel into a heating channel 25 and a bypass channel 26. Both the heating damper 291 and the bypass damper 292 are rectangular butterfly plates adapted to the cross-section of their respective channels. The two butterfly plates are fixed on the same linkage shaft 293 and have a 90° installation phase. A servo actuator 294 is located outside the diversion box 27 and drives the linkage shaft 293 via a coupling. Two mechanical limiters 295 respectively define the extreme positions of "heating fully open, bypass minimum" and "heating minimum, bypass fully open". The two channels retain 5% to 10% of their minimum effective area to avoid localized stagnation and thermal shock when fully closed.

[0097] The heating branch outlet temperature transmitter 43 is installed between the steam heat exchanger 24 and the manifold 28 to measure the temperature T of the gas flow after passing only through the heat exchanger. b The return air temperature transmitter 42 is located upstream of the distribution box 27 and is used to measure the bypass airflow temperature T. r The supply air temperature transmitter 41 is located downstream of the manifold 28 and is used to measure the mixing temperature T. s The heat exchanger metal temperature sensor 45 is installed on the outer wall of the finned base tube or manifold on the outlet side of the steam heat exchanger 24 and is fixed by a heat-conducting pressure block and an insulation cover, so that it can reflect the sensible heat that can still be released by the heat exchanger after the steam is shut off.

[0098] Steam pipe 31 connects to steam heat exchanger 24 via the equipment's steam interface. Along the steam flow direction, a manual shut-off valve, filter, steam pressure transmitter 34, steam temperature transmitter 35, and steam regulating valve 32 are sequentially installed. Valve actuator 33 is an electric or electro-pneumatic actuator with opening feedback. After condensation in the heat exchanger, steam enters the dual-chamber alternating constant-volume metering assembly 39 via condensate pipe 38, and then is discharged into the recovery pipe via steam trap 37. Because the dual-chamber alternating constant-volume metering assembly 39 is located before the steam trap 37, its operating pressure is close to the condensate side pressure of the heat exchanger, and the condensate has not yet formed a large amount of secondary steam due to pressure reduction.

[0099] like Figure 3 As shown, both the first sealed metering chamber 391 and the second sealed metering chamber 392 are vertically arranged pressure-resistant cylinders, with their upper and lower ends connected to the inlet manifold and outlet manifold, respectively. The two metering chambers can have the same inner diameter, and the upper level switch 397 and the lower level switch 398 have the same installation height difference, ensuring their calibrated volumes are both ΔV. The top of each metering chamber is connected to the inlet manifold via a pressure-equalizing capillary tube 390. The one-way throttling element 3901 directs from the inlet manifold to the top of the metering chamber, allowing steam to slowly enter the top of the metering chamber to maintain pressure balance and suppressing the reverse flow of the medium within the metering chamber to the inlet manifold. Each inlet valve and outlet valve is a normally closed solenoid valve or pneumatic shut-off valve suitable for hot condensate.

[0100] In the first operating phase, the first inlet valve 393 is open and the first outlet valve 394 is closed, filling the first sealed metering chamber 391 from the lower to the upper level. Simultaneously, the second inlet valve 395 is closed and the second outlet valve 396 is open, draining the second sealed metering chamber 392 into the steam trap 37. When the upper level switch 397 of the first sealed metering chamber 391 is activated and the lower level switch 398 of the second metering chamber 392 is activated, the PLC controller 51 first closes the first inlet valve 393 and the second outlet valve 396, waits for a non-overlapping time of 1-3 seconds, and then opens the first outlet valve 394 and the second inlet valve 395, entering the second operating phase. After the second sealed metering chamber 392 is full, the valves are switched in reverse order. The program is configured with hardware and software interlocks to prevent the inlet and outlet valves of the same metering chamber from opening simultaneously.

[0101] Each complete filling from the lower liquid level to the upper liquid level generates a fixed-volume metering pulse. The condensate temperature sensor 399 is installed inside the inlet manifold. For metering chambers with a calibrated volume of 0.5–5 L, the volume can be selected based on the equipment's maximum condensation rate, ensuring a normal filling time of 10–120 seconds for a single chamber. If the filling time is too short, increase the metering chamber volume; if it is too long, decrease the volume or connect multiple metering components in parallel. The design pressure values ​​for both metering chambers should not be lower than the maximum allowable operating pressure of the steam heating branch.

[0102] like Figure 4 As shown, three annular temperature measuring bands 18 are respectively set in the feed end area, middle area, and discharge end area of ​​the drum body 11. The annular temperature measuring bands 18 can be fixed to the outer surface of the drum body by thin metal strips of the same material, and a high-temperature resistant and high-emissivity coating is formed on the outer side; the width of each annular temperature measuring band is more than twice the diameter of the corresponding infrared temperature measuring spot. The mounting guide rail 191 is fixed to the frame 12 and parallel to the drum axis. The three infrared drum wall thermometers 19 can be adjusted and locked along the mounting guide rail 191 so that each detection spot falls on the corresponding annular temperature measuring band 18. This structure directly measures the fixed axial area of ​​the outer drum wall without opening a measuring window on the drum wall for observing the material.

[0103] The detection end of each infrared cylinder wall thermometer 19 is located inside the purge sleeve 192, with the end of the purge sleeve 192 facing the annular temperature measuring band 18 and retaining a measuring opening. The purge air manifold 193 supplies a small amount of filtered and depressurized compressed air to each purge sleeve 192, forming an airflow from the inside out around the optical path to reduce the adhesion of smoke, condensate mist, and oil. The PLC controller 51 takes the minimum value of the three axial temperatures as T. w,min When a temperature sensor signal exceeds its range or the deviation from two adjacent points continuously exceeds the diagnostic threshold, that point is marked as pending inspection, and the automatic output of the preheating completion signal is prohibited.

[0104] like Figure 5 As shown, the PLC controller 51 inside the control cabinet 5 is connected to the analog input module 52, digital input module 53, analog output module 54, digital output module 55, and memory 56 via a backplane bus. Field cables connect to their respective modules via terminal blocks 57. The human-machine interface 58 communicates with the PLC controller 51 via an industrial communication network 59. The memory 56 stores the target temperature, reference heat requirement, equivalent heat capacity, heat dissipation correction factor, waste heat utilization factor, maximum allowable preheating time, and alarm thresholds for different equipment recipes.

[0105] The PLC controller 51 periodically executes the baseline acquisition program segment 511, the heat accumulation program segment 512, the waste heat prediction program segment 513, the air mixing control program segment 514, and the completion judgment program segment 515. These program segments represent control tasks and data interfaces, and can be implemented by function blocks within the same CPU, without requiring multiple independent processors. The analog input module 52 acquires temperature, pressure, airflow, and valve position signals; the digital input module 53 acquires liquid level, airflow, speed, and emergency stop signals; the analog output module 54 drives the steam valve actuator 33 and the damper servo actuator 294; the digital output module 55 drives four metering valves, the drive motor 14, the circulating fan 23, and the alarm 64 via intermediate relays.

[0106] Control calculation:

[0107] 1. Calculation of condensation mass, heat exchanger heat storage increment, and effective heat on the target side.

[0108] Let ΔV be the calibration volume between the upper and lower liquid levels in each metering chamber. In the k-th calculation cycle, the two metering chambers complete a total of N... k The calibration volume was filled with liquid, and the condensate temperature was T. c (k), then the mass increment of condensation is:

[0109] Δm c (k)=N k ·ρ[T c (k)]·ΔV.

[0110] In the formula, ρ[T c [k] represents the density of the condensate at the measured temperature. If the calculation cycle is shorter than one filling time, the time can be allocated to adjacent cycles when the liquid level is triggered; the cumulative mass is still calibrated based on the complete calibration volume.

[0111] According to the steam pressure P s (k), Steam temperature T v (k) Obtain the inlet steam specific enthalpy h from the steam property table in memory 56. s The specific enthalpy of the condensate (h) is obtained based on the condensate temperature. c The heat released by the steam in the heat exchanger during this cycle is:

[0112] ΔQ in (k)=Δm c (k)·{h s [P s (k),T v (k)]-h c [T c (k)]}.

[0113] For saturated steam, it can be determined solely based on P. s (k) Determine h by looking up the table s For steam with a measured temperature higher than the corresponding saturation temperature, then according to P... s (k) and T v (k) Determine the specific enthalpy of the superheated steam. This calculation uses the actual condensate mass and enthalpy difference, and does not directly equate the steam valve opening with heat.

[0114] 2. Equivalent thermal state and heat dissipation correction.

[0115] Equivalent thermal state temperature T eq (k) can be determined according to the following formula:

[0116] T eq (k)=a s ·T s (k)+a r ·T r (k)+Σ (q=1) M a w,q ·T w,q (k).

[0117] In the formula, T s For supply air temperature, T r T represents the return air temperature. w,q Let be the temperature at the q-th cylinder wall detection point, and M be the number of cylinder wall detection points; all weights are greater than or equal to 0, and a s +a r +Σa w,q=1. For the embodiment with three cylinder wall detection points, a can be taken as 1. s =0.20~0.35、a r =0.15~0.30, and the sum of the weights of all cylinder walls is 0.40~0.60. To avoid double counting of heat stored inside the heat exchanger and releasable waste heat, the heat storage increment and the cumulative effective heat on the target side of the heat exchanger are respectively:

[0118] ΔE x (k)=C x ·[T x (k)-T x (k-1)];E net (k)=E net (k-1)+ΔQ in (k)-ΔE x (k)-K loss ·[T eq (k)-T a (k)]·Δt.

[0119] In the formula, C x T represents the equivalent heat capacity of the steam heat exchanger 24 and its retained condensate. x T represents the metal temperature of the heat exchanger. a For ambient temperature, K loss The heat dissipation correction factor combines heat dissipation from the casing and minimum moisture loss, where Δt is the calculation period. E net This represents the cumulative effective heat transferred to the target-side components such as the drum body, shroud, and circulating air; ΔE represents the heat exchanger's temperature rise. x The value is positive and deducted from the enthalpy difference of condensation heat, so ΔE is positive when the heat exchanger cools down. x If the value is negative, the released heat is accordingly included in the target side. K loss During the commissioning phase, the steam can be shut off, a fixed circulating air volume can be maintained, and T can be recorded. eq Identify the attenuation method.

[0120] 3. Criteria for releasing residual heat and reducing steam.

[0121] When the heat exchanger metal temperature Tx is higher than the supply air temperature Ts, the heat exchanger can still release sensible heat to the circulating air after the steam is shut off. In this embodiment, the waste heat that can be released is estimated according to the following formula:

[0122] E res (k)=η x ·C x ·max{T x (k)-T s (k), 0}.

[0123] In the formula, C x η is the equivalent heat capacity of the steam heat exchanger 24 and its retained condensate.x The utilization coefficient of this portion of sensible heat being transferred to the circulating air and drum body 11 during the waste heat equalization stage. C x The initial settings η can be determined by the heat exchanger metal mass, specific heat, and normal condensate retention rate. x The adjustment can be made based on the actual temperature rise after the valve is closed once during commissioning.

[0124] When the lowest temperature of the cylinder wall has not yet reached the cylinder wall temperature threshold and E net (k)+E res (k)≥E req At that time, waste heat prediction program segment 513 outputs a steam reduction command. req It is not a fixed preheating time, but rather a reference heat required for the corresponding equipment to reach a qualified thermal state; it is corrected according to the difference between the current initial equivalent thermal state and the baseline initial state. To prevent malfunctions caused by a single abnormal metering pulse, the steam reduction condition can be required to be met for two consecutive calculation cycles, and the feedback of circulating air volume and drum speed must be normal.

[0125] 4. Waste heat mixing calculation.

[0126] Let the outlet temperature of the heating branch be T. b The return air temperature is T r The desired supply air temperature during the waste heat equilibrium stage is T. cmd The bypass airflow accounts for β of the total airflow in both channels. Assuming the specific heat difference between the two branches is negligible and the total effective area of ​​the two channels remains essentially constant, the mixing temperature satisfies T. cmd =(1-β)T b +βT r Therefore, we can conclude that:

[0127] β(k)=sat[0,1]{[T b (k)-T cmd (k)] / [T b (k)-T r (k)]}.

[0128] Only when |T b -T r |Not less than the denominator protection value ε T The above division is performed at the time, where ε T >0; when |T b -T r |less than ε T At this time, maintain β from the previous calculation cycle or keep the bypass ventilation door in a preset intermediate position. cmd It can be set to a waste heat balance bias of 0-3℃ less than the target supply air temperature to prevent the supply air temperature from continuing to exceed the upper limit after the steam is reduced.

[0129] 5. Criteria for preheating completion.

[0130] Complete the judgment program segment 515, take the lowest temperature Tw,min at each cylinder wall detection point, and simultaneously judge:

[0131] T w,min ≥T w,set -δ w ;T r ≥T r,set -δ r ;|T s -T r |≤δ g The above conditions are maintained continuously for N. rev When the drum completes one rotation cycle and the airflow, speed, and valve position feedback are normal, a preheating completion signal is output. w,set T is the threshold temperature of the cylinder wall. r,set δ is the return air temperature threshold. w and δ r These are the allowable deviations, δ g N is the average heat threshold. rev A value of 2 to 10 can be used. By using the rotation cycle of the drum as the holding measure, each circumferential position can undergo hot air action at least multiple times.

[0132] Working principle:

[0133] like Figure 6 and Figure 7 As shown, after the system is powered on, the emergency stop contact 63, drive motor 14, circulating fan 23, four metering valves, and various sensors are checked first. Initially, steam regulating valve 32 is closed, heating damper 291 is in its minimum position, and bypass ventilation damper 292 is in its maximum position. PLC controller 51 starts the drum body 11 and circulating fan 23, circulating for 30-120 seconds to remove residual heat and obtain the initial temperatures of the supply air, return air, drum wall, heat exchanger metal, and ambient air. If the heat exchanger metal temperature is significantly higher than the ambient temperature, it indicates that the equipment is in a warm-up start-up state, and the required heat should be reduced accordingly in subsequent checks.

[0134] After baseline acquisition, servo actuator 294 rotates heating damper 291 to its maximum opening and bypass damper 292 to its minimum opening, while steam regulating valve 32 ramps up to its rapid heating opening. Steam condenses in heat exchanger 24, and circulating air absorbs heat and enters drum body 11. The two metering chambers begin to work alternately. PLC accumulates the condensate mass by filling liquid with liquid at each calibrated volume, determines the effective heat input increment based on the enthalpy difference between steam and condensate, and then subtracts the heat storage increment and heat dissipation of the heat exchanger to accumulate the effective heat on the target side. The supply air, return air, and drum wall temperatures are used to form an equivalent thermal state and describe the heat distribution, but do not replace the measurement of condensate heat.

[0135] As preheating proceeds, the heat exchanger metal temperature rises first, followed by the supply air temperature, and then the return air and cylinder wall temperatures gradually increase. Waste heat prediction program segment 513 calculates cycle E. res and E net +E res E after initial temperature correction req Comparison. When the criterion is met, the PLC reduces the opening of the steam regulating valve 32 to 0-20%, preferably closing it after the valve position feedback confirms it is in place; simultaneously, the mixing air control program segment 514, based on T... b T r and T cmd Calculate β and drive the complementary damper assembly 29 to gradually increase the bypass ratio.

[0136] During the waste heat equalization phase, a portion of the return air continues to absorb waste heat through the high-temperature heat exchanger, while the other portion bypasses the heat exchanger and mixes with the former in the manifold 28. By changing β, the supply air temperature is limited to near the target, while the total flow area of ​​the circulating fan 23 changes little. The drum body 11 continues to rotate, and the mixed hot air continues to transfer the remaining heat in the heat exchanger and piping to the cold spots on the drum wall; T b With T r As they approach each other, the temperature difference between the supply and return air decreases.

[0137] When the lowest cylinder wall temperature, return air temperature, and supply and return air temperature difference are continuously N rev When the rotation cycle of the roller meets the completion condition, the PLC ends the preheating timer and outputs a material waiting permission. According to the equipment process requirements, the roller body 11 and the circulating fan 23 can continue to operate at the material waiting speed and air volume, or stop after a delay; this material waiting action is set separately from the preheating completion criterion to avoid masking the state of not being evenly heated by immediately stopping the machine.

[0138] For preheating without alarms and where the preheating completion conditions are met, the PLC controller 51, after preheating, deducts the required heat correction amount generated by the difference between the current initial equivalent thermal state and the baseline initial equivalent thermal state from the accumulated effective heat on the target side, to obtain the converted completed heat equivalent to the baseline initial equivalent thermal state, and updates the saved reference required heat according to the forgetting factor. For preheating records with steam supply interruption, condensate abnormality, sensor abnormality, manual intervention, or preheating timeout, the reference required heat is not updated, and the reference required heat saved before the start of preheating continues to be used.

[0139] If the steam regulating valve 32 is open by more than 10%–20%, but neither metering chamber completes one calibrated volume filling within the metering timeout period of 60–300 seconds, the PLC determines that the steam supply or condensation path is abnormal. If the circulating air volume switch 61 is open, the drum speed switch 62 is not confirmed, or the emergency stop contact 63 is activated, the safety logic prioritizes closing the steam regulating valve 32. Subsequently, the complementary damper assembly 29 is controlled to ensure that the bypass channel 26 is in the state of maximum effective flow area. The circulating fan 23 continues to perform bypass circulation cooling for 30–180 seconds when conditions permit, and the specific cause is indicated by the alarm 64 and the human-machine interface 58.

[0140] Example parameters:

[0141] Taking a loosening and rehumidifying machine as an example, the target temperature for the supply air can be set to 60℃, the return air temperature threshold to 55℃, the cylinder wall temperature threshold to 50℃, the allowable deviation for both the cylinder wall and the return air to 2℃, and the heat equalization threshold to 5℃. The three annular temperature measuring bands 18 are located at 20%, 50%, and 80% of the effective length of the feed roller, respectively. These parameters are for illustrative purposes only; the specific values ​​should be determined based on the equipment manufacturer's allowable values ​​and process verification results.

[0142] The single-chamber calibration volume of the dual-chamber alternating constant-volume metering component 39 can be set to 1.5L; the heat calculation cycle is 10s, and the temperature sampling cycle is 1s. During the rapid heating phase, the steam valve opening can increase from 0 to 75% within 30s, and the effective area ratio of the heating channel is 90%; after entering the waste heat equalization phase, T cmd The temperature is set to 58–60℃, and the bypass ratio β is given by the calculation results and is subject to an engineering limit of 0.10–0.90.

[0143] During the commissioning phase, a baseline preheating operation was selected where no alarm was triggered and the preheating completion conditions were met normally. The initial equivalent thermal state temperature T of the baseline preheating was recorded. eq,ref0 The cumulative effective heat on the target side at the time of completion of the baseline preheating is saved as the initial reference heat demand E. ref,0 The reference heat requirement for the nth startup is determined according to the following formula:

[0144] E req,n =E ref,n-1 +C eq ·(T eq,ref0 -T eq,n0 ).

[0145] Among them, C eq For the pre-identified equivalent heat capacity of the drum machine and hot air circulation system, T eq,n0 E is the initial equivalent thermal state temperature for the nth preheating; when n=1, E ref,n-1 For E ref,0If the current equipment is colder than the initial state of the baseline preheating, then T eq,n0 Lower, corrected E req,n Increase; if the equipment is in a warm-up state, then the corrected E req,n Decrease.

[0146] After each preheating cycle, if no alarm occurs and the preheating completion conditions are met normally, the updated reference heat requirement is determined according to the following formula:

[0147] E ref,n =λ·E ref,n-1 +(1-λ)·[E net,n -C eq ·(T eq,ref0 -T eq,n0 )).

[0148] Wherein, λ is the forgetting coefficient, preferably 0.85–0.98; E net,n This represents the cumulative effective heat on the target side upon completion of the nth preheating cycle; the amount within square brackets is the converted effective heat obtained by converting the cumulative effective heat on the target side upon completion of the nth preheating cycle to the initial equivalent thermal state of the baseline preheating. By deducting the increase in heat demand caused by the difference in the initial equivalent thermal state before updating, the heat difference caused by cold start or warm start can be avoided from being repeatedly written into the reference value. Records of steam supply interruption, condensate malfunction, sensor malfunction, manual intervention, or preheating timeout are not included in the update; in this case, let E... ref,n =E ref,n-1 Therefore, the reference heat demand can slowly adapt to long-term changes in the cleanliness of the heat exchanger and the insulation status of the equipment, while avoiding reference value drift caused by initial temperature changes and single failures.

[0149] For leaf-feeding machines, primary feeders, secondary feeders, or stem feeders with higher target temperatures, independent formulas can be created, and the target temperature, reference calorific value, and C20 can be stored separately. eq K loss C x and η x If the equipment does not allow for a bypass channel, the condensate heat metering and pre-steam reduction sections can be retained, and the waste heat transfer rate can be adjusted by frequency conversion of the circulating fan; however, setting a complementary bypass channel can achieve a more direct air mixing capacity with a smaller change in the total circulation resistance.

[0150] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A preheating control system for a tobacco processing roller mill based on condensation heat metering and waste heat mixing air, characterized in that, It includes a drum machine (1), a hot air circulation system (2), a steam heating branch (3), a thermal status detection component (4), and a control cabinet (5); The roller mill (1) includes a roller body (11) mounted on a frame (12), a feed hood (16) and a discharge hood (17) respectively mounted at both ends of the roller body (11), and a drive motor (14) and a transmission mechanism (15) for driving the roller body (11) to rotate. The hot air circulation system (2) includes an air supply duct (21), a return air duct (22), a circulating fan (23), a steam heat exchanger (24), a heating channel (25), a bypass channel (26), a distribution box (27), a junction box (28), and a complementary damper assembly (29). The return air duct (22) is connected to the distribution box (27) by the discharge hood (17), the heating channel (25) and the bypass channel (26) are connected in parallel between the distribution box (27) and the junction box (28), the steam heat exchanger (24) is installed in the heating channel (25), and the air supply duct (21) is connected to the feed hood (16) by the junction box (28). The complementary damper assembly (29) includes a heating damper (291) and a bypass damper (292) respectively disposed in the heating channel (25) and the bypass channel (26). The heating damper (291) and the bypass damper (292) are fixedly connected to the same linkage shaft (293) to reverse the effective flow area of ​​the two channels. The steam heating branch (3) includes a steam pipe (31) connected to the steam inlet of the steam heat exchanger (24), a steam regulating valve (32) installed on the steam pipe (31), and a condensate pipe (38) connected in sequence to the condensate outlet of the steam heat exchanger (24), a dual-chamber alternating constant volume metering component (39), and a steam trap (37). The dual-chamber alternating constant volume metering assembly (39) includes a first closed metering chamber (391) and a second closed metering chamber (392) connected in parallel between the inlet manifold and the outlet manifold. Each closed metering chamber is equipped with an inlet valve, a drain valve, an upper liquid level switch (397) and a lower liquid level switch (398). The two closed metering chambers alternately operate in a constant volume filling state from the lower liquid level to the upper liquid level and in a state of draining liquid into the condensate drain (37). The thermal state detection component (4) includes a supply air temperature transmitter (41) located downstream of the manifold (28), a return air temperature transmitter (42) located upstream of the branch box (27), a heating branch outlet temperature transmitter (43) located at the outlet of the heating channel (25), an ambient temperature transmitter (44), a heat exchanger metal temperature sensor (45) thermally connected to the steam heat exchanger (24), a steam pressure transmitter (34) and a steam temperature transmitter (35) located on the steam pipe (31), a condensate temperature sensor (399) located at the inlet of the dual-cavity alternating constant volume metering component (39), and at least three infrared cylinder wall thermometers (19) distributed axially along the drum body (11) and facing the cylinder wall. The PLC controller (51) in the control cabinet (5) is connected to the valve actuator (33) of the dual-cavity alternating constant volume metering component (39), the thermal state detection component (4), the steam regulating valve (32), and the servo actuator (294) of the complementary damper component (29), respectively. The PLC controller (51) is configured to: determine the condensation quality based on the number of metering cycles, calibrated volume and condensate temperature output by the dual-cavity alternating constant volume metering component (39); determine the effective heat input increment based on the condensation quality and the enthalpy difference between steam and condensate; accumulate the effective heat on the target side after deducting the heat storage increment and heat dissipation of the heat exchanger; and determine the releasable waste heat based on the difference between the metal temperature of the heat exchanger and the air supply temperature. Before the lowest value detected by the infrared cylinder wall thermometer (19) reaches the cylinder wall temperature threshold, when the sum of the effective heat on the target side and the releasable residual heat reaches the reference heat requirement established by the benchmark preheating data that meets the preheating completion conditions and corrected by the current initial equivalent thermal state, the opening of the steam regulating valve (32) is reduced and the bypass ratio of the complementary damper assembly (29) is increased. When the minimum value and return air temperature reach the corresponding threshold, the absolute value of the difference between the supply air temperature and return air temperature is not greater than the heat equalization threshold, and the above conditions are maintained continuously for at least two drum rotation cycles, a preheating completion signal is output.

2. The preheating control system for the tobacco processing roller mill according to claim 1, characterized in that, The heating damper (291) and the bypass damper (292) are both rectangular butterfly plates adapted to the corresponding channel cross sections, and are fixed to the linkage shaft (293) with an installation phase difference of 90°. The servo actuator (294) is connected to the linkage shaft (293) for transmission. The diversion box (27) is provided with mechanical limiting members (295) that respectively limit the two extreme positions of the linkage shaft (293), so that when the effective flow area of ​​the heating channel (25) decreases, the effective flow area of ​​the bypass channel (26) increases.

3. The preheating control system for the tobacco processing roller mill according to claim 1, characterized in that, The first sealed metering chamber (391) is provided with a first liquid inlet valve (393) and a first liquid outlet valve (394) at its inlet and outlet, respectively. The second sealed metering chamber (392) is provided with a second liquid inlet valve (395) and a second liquid outlet valve (396) at its inlet and outlet, respectively. The tops of the two sealed metering chambers are connected to the inlet manifold through equalizing capillary tubes (390) equipped with one-way throttling devices (3901). The conduction direction of the one-way throttling devices (3901) is from the inlet manifold to the top of the corresponding sealed metering chamber. The PLC controller (51) interlocks the inlet valve and outlet valve of the same sealed metering chamber. After one sealed metering chamber is filled from the lower liquid level to the upper liquid level and the other sealed metering chamber is discharged to the lower liquid level, the already opened inlet valve and outlet valve are closed first. After a preset non-overlapping time, the other two valves are opened to alternate the state of the two sealed metering chambers.

4. The preheating control system for the tobacco processing roller mill according to claim 1, characterized in that, The outer periphery of the roller body (11) is provided with at least three annular temperature measuring bands (18) spaced apart from each other along the axial direction. Each annular temperature measuring band (18) is made of the same material and surface coating to have the same surface emissivity. The frame (12) is provided with an installation guide rail (191) parallel to the axis of the drum body (11). The infrared cylinder wall thermometer (19) is set on the installation guide rail (191) and corresponds one-to-one with each annular temperature measuring band (18). The detection end of each infrared cylinder wall thermometer (19) is located inside the purge sleeve (192) and faces the corresponding annular temperature measuring band (18). Each purge sleeve (192) is connected to the source of filtered and depressurized compressed air through the purge air manifold (193).

5. The preheating control system for the tobacco processing roller mill according to claim 3, characterized in that, The control cabinet (5) also includes an analog input module (52), a digital input module (53), an analog output module (54), a digital output module (55), a memory (56), and a terminal block (57), and is connected to an alarm (64). The steam pressure transmitter (34), steam temperature transmitter (35), condensate temperature sensor (399), supply air temperature transmitter (41), return air temperature transmitter (42), heating branch outlet temperature transmitter (43), ambient temperature transmitter (44), heat exchanger metal temperature sensor (45), and each infrared cylinder wall thermometer (19) are connected to the analog input module (52) via the terminal block (57). The level switches, circulating air volume switches (61), drum speed switches (62), and emergency stop contacts (63) of the dual-chamber alternating constant volume metering component (39) are connected to the digital input module (53); the analog output module (54) is connected to the valve actuator (33) and the servo actuator (294) respectively; the digital output module (55) is connected to the inlet valve and outlet valve, drive motor (14), circulating fan (23), and alarm (64) of the dual-chamber alternating constant volume metering component (39) respectively.

6. The preheating control system for the tobacco processing roller mill according to claim 3, characterized in that, The calibrated volume between the upper liquid level switch (397) and the lower liquid level switch (398) in the first sealed metering chamber (391) and the second sealed metering chamber (392) is ΔV; the PLC controller (51) determines the condensation mass increment Δm according to the following formula in the kth calculation cycle. c (k) Increment of effective heat input ΔQ in (k) Heat exchanger heat storage increment ΔE x (k) and cumulative target-side effective heat E net (k): Δm c (k)=N k ·ρ[T c (k)]·ΔV; ΔQ in (k)=Δm c (k)·{h s [P s (k),T v (k)]-h c [T c (k)]}; ΔE x (k)=C x ·[T x (k)-T x (k-1)]; E net (k)=E net (k-1)+ΔQ in (k)-ΔE x (k)-K loss ·[T eq (k)-T a (k)]·Δt; Where, N k ρ[T] represents the number of calibration volume measurements completed within the k-th calculation cycle. c [k] represents the condensate temperature T. c The density corresponding to (k), h s Steam pressure P s (k) and steam temperature T v (k) corresponds to the specific enthalpy of vapor, h c C is the specific enthalpy of condensate. x T represents the equivalent heat capacity of the steam heat exchanger (24) and its retained condensate. x (k) represents the metal temperature of the heat exchanger, K. loss Here, Δt is the heat dissipation correction factor, and T is the calculation period. a (k) represents the ambient temperature, T eq (k) is the equivalent thermal state temperature obtained by weighting the supply air temperature, return air temperature and the detection temperature of each infrared cylinder wall thermometer (19) according to a preset weight.

7. The preheating control system for a tobacco processing roller mill according to claim 6, characterized in that, The PLC controller (51) according to E res (k)=η x ·C x ·max{T x (k)-T s (k), 0} determines the releaseable waste heat E res (k), where η x T is the utilization coefficient for the transfer of waste heat to the circulating air and the drum body (11). s (k) represents the supply air temperature; When E net (k)+E res (k)≥E req Output steam reduction command, where E req This is the reference heat requirement corrected for the initial equivalent thermal state temperature; after reducing steam, at |T b (k)-T r (k)|≥ε T At that time, the PLC controller (51) determines the bypass ratio β(k) according to the following formula: β(k)=sat[0,1]{[T b (k)-T cmd (k)] / [T b (k)-T r (k)]}; Where sat[0,1] indicates that the calculated value is restricted to 0 to 1, T b (k) represents the outlet temperature of the heating branch, T r (k) represents the return air temperature, T cmd (k) represents the target temperature of the supply air during the waste heat equalization stage, ε T The denominator protection value is greater than 0; in |T b (k)-T r (k)|<ε T At the same time, the bypass ratio of the previous calculation cycle is maintained or a preset bypass ratio is adopted; the complementary damper assembly (29) makes the ratio of the effective flow area of ​​the bypass channel (26) to the total effective flow area of ​​the two channels correspond to β(k).

8. The preheating control system for the tobacco processing roller mill according to claim 7, characterized in that, The control cabinet (5) is connected to an alarm (64); the output conditions of the preheating completion signal include: the lowest value detected by each infrared cylinder wall thermometer (19) is not lower than the cylinder wall temperature threshold minus the cylinder wall allowable deviation, the return air temperature is not lower than the return air temperature threshold minus the return air allowable deviation, the absolute value of the difference between the supply air temperature and the return air temperature is not greater than the heat equalization threshold, and the above conditions are maintained continuously for 2 to 10 drum rotation cycles; When the opening of the steam regulating valve (32) is greater than the preset opening and no calibrated volume metering count is generated within the metering timeout period, or when the preheating timer reaches the maximum allowable time but no preheating completion signal is output, the PLC controller (51) closes the steam regulating valve (32), controls the complementary damper assembly (29) to make the bypass channel (26) be in the state of maximum effective flow area, keeps the circulating fan (23) running for the preset circulating cooling time, and drives the alarm (64).

9. A preheating control method for a tobacco processing roller mill, characterized in that, A preheating control system for a drum machine is adopted, comprising a drum body, a circulating fan, a steam heat exchanger, a steam regulating valve, a heating channel, a bypass channel, and a complementary damper assembly. The heating channel and the bypass channel are connected in parallel between the distribution box and the manifold box. The complementary damper assembly reverses the effective flow area of ​​the two channels. A dual-chamber alternating constant volume metering assembly is installed between the condensate outlet of the steam heat exchanger and the steam trap. The dual-chamber alternating constant volume metering assembly has a first sealed metering chamber and a second sealed metering chamber, each equipped with an upper liquid level switch and a lower liquid level switch. The preheating control method includes the following steps: S1. Keep the steam regulating valve closed, run the drum body and circulating fan and open the bypass channel to collect the initial temperatures of the supply air, return air, drum wall, heat exchanger metal and the environment to form the initial equivalent thermal state. S2. Increase the effective flow area of ​​the heating channel and decrease the effective flow area of ​​the bypass channel, open the steam regulating valve, so that the steam condenses in the steam heat exchanger and heats the circulating air. S3. The first and second sealed metering chambers alternately perform constant volume filling and draining from the lower liquid level to the upper liquid level. The condensation mass and effective heat input increment are determined based on the calibrated volume, condensate temperature, steam pressure and steam temperature. The heat storage increment of the heat exchanger determined based on the change of heat exchanger metal temperature and the heat dissipation determined based on the ambient temperature are deducted, and the effective heat on the target side is accumulated. S4. Determine the releaseable waste heat based on the difference between the heat exchanger metal temperature and the supply air temperature, and correct the reference heat demand based on the initial equivalent thermal state. S5. Before the lowest temperature of the cylinder wall reaches the cylinder wall temperature threshold, when the sum of the effective heat on the target side and the releasable waste heat reaches the corrected reference heat requirement, reduce the opening of the steam regulating valve, and determine the bypass ratio according to the outlet temperature of the heating branch, the return air temperature and the supply air target temperature in the waste heat equilibrium stage, and mix the outlet air of the heating branch and the bypass return air through the complementary damper assembly. S6. While the drum body and the circulating fan continue to run, determine the minimum temperature of the drum wall, the return air temperature, and the difference between the supply air temperature and the return air temperature. After the preset conditions are met for at least two consecutive drum rotation cycles, output a preheating completion signal. S7. Record the start and end times of preheating, the cumulative condensate mass, the cumulative effective heat on the target side, the time of steam reduction, and the temperature data. When metering timeout, insufficient air volume, drum failure, or preheating timeout occurs, close the steam regulating valve and execute bypass circulation cooling and alarm.

10. The preheating control method according to claim 9, characterized in that, During the commissioning phase, a baseline preheating operation is selected where no alarm is triggered and the preheating completion conditions are met normally. The cumulative effective heat on the target side at the time of baseline preheating completion is saved as the initial reference heat demand E. ref,0 And save the corresponding initial equivalent thermal state temperature T. eq,ref0 ; The reference heat requirement E for the nth preheating req,n Determined according to the following formula: E req,n =E ref,n-1 +C eq ·(T eq,ref0 -T eq,n0 ); Where n≥1, C eq For the pre-identified equivalent heat capacity of the drum machine and hot air circulation system, T eq,n0 E is the initial equivalent thermal state temperature of the nth preheating. ref,n-1 The reference heat demand is stored before the start of the nth preheating; the updated reference heat demand E is determined according to the following formula only if no alarm occurs during the nth preheating and the preheating completion conditions are met normally. ref,n : AND ref,n =λ·E ref,n-1 +(1−λ)·[E net,n -C eq ·(T eq,ref0 -T eq,n0 )]: Where λ is the forgetting coefficient, and 0.7 ≤ λ < 1, E net,n Let E be the cumulative effective heat on the target side when the nth preheating is completed. The amount in square brackets is the converted heat obtained by converting the cumulative effective heat on the target side to the initial equivalent thermal state of the baseline preheating. When an alarm occurs during the nth preheating or the preheating completion conditions are not met normally, let E... ref,n =E ref,n-1 .

Images