US3787985A - Dryer control system and method - Google Patents

Dryer control system and method Download PDF

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US3787985A
US3787985A US00280114A US3787985DA US3787985A US 3787985 A US3787985 A US 3787985A US 00280114 A US00280114 A US 00280114A US 3787985D A US3787985D A US 3787985DA US 3787985 A US3787985 A US 3787985A
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dryer
trajectory
during
indication
transitional period
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R Fowler
E Freeh
D Koenig
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Industrial Nucleonics Corp
ABB Automation Inc
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Industrial Nucleonics Corp
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Assigned to ACCURAY CORPORATION reassignment ACCURAY CORPORATION CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE: 07/02/79 Assignors: ACCURAY LEASING CORPORATION
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    • A—HUMAN NECESSITIES
    • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
    • A24B—MANUFACTURE OR PREPARATION OF TOBACCO FOR SMOKING OR CHEWING; TOBACCO; SNUFF
    • A24B3/00—Preparing tobacco in the factory
    • A24B3/04—Humidifying or drying tobacco bunches or cut tobacco
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements for supplying or controlling air or other gases for drying solid materials or objects
    • F26B21/30—Controlling, e.g. regulating, parameters of gas supply
    • F26B21/35—Temperature; Pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/22—Controlling the drying process in dependence on liquid content of solid materials or objects

Definitions

  • Moisture in tobacco flowing through a dryer is controlled so that it is maintained substantially at a desired amount during start up and shut down trasitional periods of the tobacco flow through the dryer. Trajectories for the dryer drying rate during the start up and shut down periods are provided in a computer memory. During start up, an indication of the moisture and flow rate of the tobacco flowing into the dryer is derived to enable the amount of moisture expected to be removed by the dryer (dryer duty) to be calculated. When shut down commences the temperature of the dryer is derived and stored in the memory.
  • the trajectory and dryer duty are time weighted so that a weighting factor for the trajectory decreases as the transitional period progresses and a weighting factor for the dryer duty increases as the period progresses and the two time weighted indications are combined to control the dryer drying rate.
  • the shut down trajectory and stored drying rate indication are time weighted so that a weighting factor for the trajectory increases as the period progresses and a weighting factor for the drying rate indication decreases as the period progresses and the two time weighted indications are combined to control the drying rate of the dryer.
  • the present invention relates generally to dryer con trol and more particularly to a controller wherein moisture of a material flowing through a dryer is maintained substantially at a set point value even though there is a substantial change in the dryer load.
  • moisture of a material emerging from a dryer of the above mentioned type is maintained approximately at a desired value even if there is a substantial change in the dryer load, as during start up orshut down.
  • the result is achieved by providing a trajectory for the dryer drying rate during the transitional period of the substantial change.
  • the trajectory is determined by factors such as the drying characteristics of the dryer and the dryer load, which in turn is a function of the flow rate and moisture of material through the dryer, and the type of material.
  • the trajectory provides for a gradual change in the dryerdrying rate during the transit na Pe iod. While the ns p of gradually h n ng the drying rate of a dryer during the transitional period is disclosed in the prior art, we are unaware of any device actually utilizing the concept.
  • the dryer is smoothly controlled during the transitional period and the moisture of the material emerging from th dryer remains close to the set point value throughout the transitional period.
  • a trajectory is provided for the dryer dyring rate, from an initial relatively low value to a final, relatively high value.
  • the dryer duty associated with the material being fed to the dryer is monitored to derive an indication of what the dryer drying rate should be to enable the material which subsequently emerges from the dryer to be a specified set point moisture.
  • the process operation is most likely to be erratic, but toward the end of the start up or transitional period the computed dryer duty provides a relatively accurate indication of the desired dryer drying rate.
  • the trajectory at the beginning of the start up transitional period has a relatively high probability of accurately controlling the dryer drying rate because the dryer load due to the material is not substantial.
  • the material in thedryer has a greater effect on determining what the dryer drying rate should be.
  • time weighting functions are'assigned to the trajectory and the dryer duty indication so that the weighting factor assigned to the trajectory decreasesas the start up period progresses, while the weighting factor assigned to the dryer duty indication increases as the length of the period increases.
  • the two time weighted indications are combined to derive a control signal for the dryer.
  • a characteristic of the dryer such as its temperature
  • a time-weighted shut down trajectory is such that the effect of the dryercharacteristic decreases as the shut down period progresses, while the trajectory effect increases as the period length increases.
  • the weighted trajectory and dryer characteristics are combined toderive a control signal for the dryer drying rate.
  • the actual drying rate at the beginning of the shut down period may be less than the initial trajectory drying rate. If the drying rate trajectory were utilized underthe'se circumstances, without time weighting, additional drying would occur to prothe temperature effect at the beginning of the shut down period, the dryer temperature is brought smoothly to a predetermined temperature without being influenced substantially by the dryer performance during normal running conditions.
  • feedback is provided during start up by storing the error signal which subsisted during the immediately preceeding processing interval. Since the dryer performance generally does not deviate materially from one shut down period to the following start up period, the prior error signal can usually be considered as an accurate measure of the amount of correction which should be applied during the next start up.
  • the dryer is utilized for enabling tobacco fed through it to have a predetermined moisture.
  • the principles of the invention are applicable to other types of material drying systems wherein material flows through the dryer and substantial changes occur in the load on the dryer.
  • an object of the present invention to provide a new and improved system for and method of controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained even though there is a relatively large change in the dryer load, e.g., as caused by a substantial change in the amount, type, or moisture of the material in the dryer.
  • Another object of the invention is to provide a new and improved system for controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained during start up and shut down transitional periods of material flow through the dryer.
  • An additional object of the invention is to provide a new and improved system for and method of controlling a dryer for new material that flows through the dryer so that a desired moisture content of the material is approximately maintained during a start up transitional period of material flow through the dryer.
  • a further object of the invention is to provide a new and improved system for and method of controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained during a shut down transitional period of material through the dryer.
  • An additional object of the invention is to provide a new and improved system for and method of controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained even though there is a substantial change in the dryer load, wherein a predetermined characteristic of the dryer and an actual indication of the dryer duty during the period are combined to provide a Smooth transition.
  • Another object of the invention is to provide a new and improved system for and method of controlling a dryer for material that flows through the dryer wherein prior indications of moisture error are utilized to assist in control during start up when no actual mositure error indications can be derived.
  • FIG. 1 is a schematic, block diagram of one embodiment of the invention.
  • FIGS. 2A-2D are graphic representations of start up trajectories and weighting factors utilized for the trajectories and for characteristics of the material in the dryer.
  • FIG I of the drawing wherein there is illustrated a'source ll of relatively moist tobacco, typically having a moisture of 20 percent by weight, which is fed via a conveying system, including belt weigher 12, to a controlled dryer l3.
  • Dryer 13 is of the type wherein tobacco flows into and out of it, and the tobacco flows through the dryer so that it is resident therein for a substantial time period; during normal (run) operation, material continuously flows through dryer 13 so that the rate of flow into the dryer approximately equals the flow rate of material out of the dryer.
  • dryer 13 is of the rotary drum type. Material flowing from dryer 13 is conveyed to cooler 14, from which material flows to storage bin 15 via conveyor 16.
  • dryer 13 The drying rate of dryer 13 is influenced by the temperature thereof. To this end, dryer 13 is supplied with dry steam from source 17 via valve 18, the position (i.e.', opening) of which is controlled by actuator 19.
  • the position of valve 18 is controlled by a local analog controller 52 which responds to a temperature transducer 25.
  • the set point of controller 25 is furnished by computer control unit 21 in response to indications of various parameters indicative of the tobacco flowing into and out of dryer 13, as well as the dryer operating characteristics.
  • the weight and moisture of tobacco supplied to dryer 13 are respectively monitored by belt weigher transducer 22, which functions in conjunction with belt weigher l2, and moisture transducer 23 which responds to the moisture of the tobacco on conveyor 12.
  • Moisture of the conditioned tobacco flowing out of cooler 14 is monitored with a moisture transducer 24 that measures that tobacco on conveyor 16.
  • Moisture transducers 23 and 24 can be of any well known type, such as infrared photoelectric transducers or dielectric transducers.
  • the drying rate of dryer 13 is related to dryer temperature as measured by temperature transducer 25, located within dryer 13.
  • Computer control unit 2 1' is preferably a general purpose, cyclically operating digital computer that includes the usual input-output devices, memory, arithmetic unit and transfer buses.
  • the computer is preferably programmed to perform a number of operations in sequence.
  • the operations important to the calculation of the dryer control signal are indicated in FIG. 1 as boxes indicative of computer elements. Each of these. operations is well known and can be performed by many existing general purpose computers. In the alternative, it is to be understood that a special purpose computer including each of the elements illustrated incomputer control unit 21 can be employed.
  • the computer includes a number of alternative operational modes. Its particular mode of operation is responsive to the status of dryer l3, i.e., whether the dryer is in a start up, run, shut down, or precondition period. During start up and shut down, the dryer load changes since the amount of material in dryer 13 varies. During run, dryer 13 is completely filled, but during precondition there is no material in the dryer, and it is maintained at predetermined temperature awaiting the flow of tobacco through it.
  • the different operating modes of the system are represented in the diagram for computer Control unit 21 as switches to simplify the presentation. It is to be understood, however, that in an actual general purpose computer there are no physical switches and that the switching functions are performed by conventional logic included in 'the computer.
  • Analog-to-digital converters 2629 respond for a predetermined time interval to average their input signals over the interval so that the signals derived from them can be considered as representativeof the monitored quantity per unit length of time. The output signals of converters 2629 are periodically sampled and supplied to the remainder of computer control unit 21.
  • the output signals of converters 27 and 28 are monitored to determine the dryer system operating mode since these converters respond to the presence or absence of tobacco flowing into and out of dryer 13.
  • Zero output signals are derived by converters 27 and 28 only when there is no material flowing into and out of dryer 13; some finite signal value is derived from converters 27 and 28 in response to the flow of material into and out of the dryer.
  • the dryer In response to both of converters 27 and 28 indicating that there is no material flowing into or out of dryer 13, the dryer is set to the precondition mode. In response to material flowing only into dryer 13 and no material emerging from the dryer, the dryer is in the start up mode. If material is flowing into dryer l3 and out of dryer 13, the dryer system is activated to the run mode; the system is activated to the shut down mode in response to material flowing out of dryer 13, to the exclusion of material flowing into the dryer.
  • logic element 33 includes four AND elements 34-37 which respectively derive binary one outputsall during the precondition, start up, run, and shut down modes.
  • AND element 34 has a pair of inputs respectively responsive to the A and B outputs of zero detectors 31 and 32;
  • AND element 36 has a pair of inputs respectively responsive to the A and T3 outputs of detectors 31 and 32; and
  • AND element 37 has a pair of inputs respectively responsive to the A and D outputs of zero detectors 31 and 32.
  • a delay of one sample period is providedfor the mode indicating signal which'the system is leaving and the delayed signal is compared in an AND gate with a mode indicating signal for the dryer mode being entered.
  • the output signal of AND gate 34 is delayed by one cycle time in delay element 38, the output of which is combined in AND element 39 with the start up indicating output of AND gate 35.
  • AND element 39 derives a binary one signal for one sample period to enable certain elements in the remainder of computer control unit 21 to be properly activated.
  • the output signal of AND element 36 is delayed by one sample period in delay element 41, the output of which is combined with the shut down indicating signal derived from element 37 in AND element'42.
  • AND element 42 derives a binary one signal during the cycle time beginning with the shut down interval.
  • the system is characterized by a feed forward loop responsive to the moisture and flow rate of tobacco supplied by belt 12 to dryer 13 and a feedback loop responsive to the percent moisture in the tobacco on conveyor 16.
  • the feed forward signal which is indicative of the dryer duty (the amount of drying which must be performed by the dryer to provide tobacco having a predetermined moisture) is derived by computing the moisture weight of the tobacco fed to the dryer and subtracting that weight from the desired moisture weight of the tobacco when it emerges from the dryer in accordance with:
  • M 1 the percentage moisture of the tobacco fed into dryer 13, as monitored by transducer 23;
  • W1 is the weight of the tobacco fed into dryer 13, as monitored by gauge 22;
  • OMR M3/ 1 M3 a set point of the desired fraction of the moisture weight (M3) in the total weight of the dried tobacco on conveyor 16.
  • the signal derived from converter 26 is delayed by the transport time between transducers 22 and 23 in delay element 55 so that the output of delay element 55 is time synchronized with the output of converter 27 and signals simultaneously derived by elements 27 and 55 are for the same mass of material flowing into dryer 13.
  • the weight and moisture percentage signals are multiplied together in multiplier element 56.
  • the expected weight of the moisture for this mass of material is derived by determining the percentage of solid materials, exclusive of water, in the tobacco by subtracting the output of converter 27 from unity in subtraction element 56, the output of which is represented by (l M1).
  • the (l Ml) output of subtraction element 57 is multiplied in multiplier element 58 by a stored OMR set point signal in the computer memory and by the output of delay element 55; multiplier element 58 thereby derives an output signal commensurate with (OMR) (W1) (l-Ml).
  • the output of multiplier element 58 is indicative of the expected moisture weight of the considered mass of tobacco after it has emerged from dryer 13.
  • the expected moisture weight indicating signal derived from multiplier 58 is subtracted from the input moisture weight indicating signal derived from multiplier element 56 in subtraction element 59.
  • the JDY indicating output signal of subtraction element 59 is processed to derive a dryer control signal indicative of dryer load.
  • the difference indication derived by element 59 is averaged in averaging element 61 over a number of sample periods, i.e.,over a number of samples derived from the analog-to-digital converters, to remove relativelyhigh frequency transients by a process which is somewhat similar to a low pass filter operation
  • the time averaged output signal of element 61, JDY is modified by a predetermined coefficient, B1, in multiplier element 62 which derives a signal that is combined with a predetermined constant, B0, indicative of the desired moisture of the conditioned tobacco on conveyor 16; the combining operation is performed by adder element 63 which derives an output signal in accordance with the linear, polvnomial expression B B1 (J YD).
  • the signal derived by element 63 is a linear polynomial of the quantity m the output signal could be a higher order polynomial, of any other suitable function.
  • the signal derived by element 63 is indicative of a feed forward component of the set point temperature required to achieve the desired moisture of the conditioned tobacco on conveyor 16.
  • the feed forward component derived from adder element 63 reflecting the required drying rate of dryer l3, i. e. the dryer load, due to the moisture weight of tobacco fed to the dryer, is combined, after suitable delay in element 64, with an error indicating feedback component derived by a proportional-integral feedback loop which is responsive to the output signal of moisture gauge 24, as derived from analog-to-digital converter 28.
  • the delay provided by delay element tuned in accordance with the dryer response characteristics.
  • the output of digital-to-analog converter 28, responsive to moisture gauge 24, is fed to proportional-integral element 65 of a well known type, which is also responsive to a digital moisture set point signal, which indicates the desired moisture of the tobacco on conveyor 16.
  • Proportionalintegral element 64 derives an error signal indicative of the difference between the moisture set point signal and the output of converter 28 during each sample cycle of the converter, integrates the error signal, and adds the integrated error signal to the original error signal to derive the feedback component for the set point temperature of dryer 13.
  • the output signal of adder 66 is connected via switch 50 to digital to analog computer element 53 which in turn provides an analog set point signal controller 52.
  • dryer 13 is controlled so that tobacco emerging from it is maintained approximately at a set point moisture during the transitional periods between the end of the precondition mode and the beginning of the run mode, i.e., the start up mode, and between the end of the run mode and the beginning of the precondition mode, i.e., the shut down mode.
  • computer 21 includes in its memory start up and shut down trajectories which are stored in memory elements 71 and have dryer temperature versus time relationships as respectively indicated in FIGS. 2A and 2B.
  • the trajectories of FIGS, 2A and 2B are-mirror images of each other tosimplify the presentation herein.” However, the trajectories need not be mirror images of each other, but are synthesized to model the response of dryer 13 to expected dryer load variations during start up and shut down to achieve a predetermined moisture in the tobacco emerging from p the dryer.
  • the shapes of the start up and shut down trajectories are determined by the dryer characteristics, assumed moisture of the tobacco in the dryer, the flow rate of tobacco through the dryer, the amount of tobacco in the dryer at the beginning or end of the transition, and the drying properties of the tobacco being treated.
  • the trajectory has a relatively small temperature versus time slope and a higher slope in the -center portion of the transitional period.
  • the initial temperature value of the start up trajectory and final temperature value of-the shut down trajectory are equal to each other and the temperature at which the dryer 13 is maintained during the precondition mode, which subsists during the time interval between the end of the shut down mode and beginning of the start up mode.
  • the maximum values of the two trajectories, at the end of the start up trajectory and beginning of the shut down trajectory, are average temperatures at which it is expected the dryer will-be operating during the normal run mode.
  • the time duration of the start up and shut down trajectories can be considered as constant because the-time for material to be transported through the dryer is relatively constant.
  • the trajectories of FIGS. 2A and 2B are nominal trajectories.
  • the trajectories illustrated in FIGS. 2A and 2B are constructed assuming identical changes in the-volume of material flowing through dryer 13 during each start up and shut down period. The principles of the invention, however, are equally applicable to systems wherein there is a smaller change in the volume of the material.
  • the trajectory can be appropriately scaled as a function of time. If the material moisture or type of material changes,-trajectories for these variables can be determined and stored. Working trajectories must be devel oped for each application considering the various factors described supra.
  • Each of the trajectories includes a number of discrete steps at which temperature remains constant during each scan period.
  • an index counter which controls readout of the trajectories is stepped and the temperature value associated with the trajectory may be changed; in the illustrated trajectories, it is assumed that a finite change occurs after each scan period.
  • the tobacco moisture is controlled to the approximate set point since the trajectories of FIGS. 2A and 28 have the greatest effect on dryer 13 when a minimum amount of tobacco is in the dryer, at the beginning of start up and the end of shut down; the trajectories have a minimum effect on dryer 13 when the dryer is almost fully loaded with tobacco, at the beginning of shut down and end of start up. Characteristics of the dryer operation respectively have the greatest and least effects when maximum and minimum amounts of tobacco are in the dryer.
  • time weighting functions (FIGS. 2C and 2D) are applied to the start up and shut down trajectories as well as to an indicated dryer characteristic. Each of the time weighting functions is similar to a straight line that varies from zero to one during the start up and shut down periods.
  • the two time weighting factors include a number of discrete, equal amplitude levels, the number of which is equal to the number of scan periods in the transition period.
  • the time weighting factor of FIG. 2C which varies from. a maximum value of one to a minimum value of zero during the transitional period, is applied to the start up temperature trajectory of FIG. 2A such that the time weighting factor is multiplied by the temperature trajectory and the temperature trajectory thereby has a maximum effect at the beginning of the start up cycle, a minimum effect at the end of the start up cycle and is fifty percent effective in thecenter of the start up cycle.
  • the weighting factors of FIGS. 2C and 2D are also utilized to control the effect of the measured characteristics of the dryer operation during the transitional periods.
  • the time weighting factor of FIG. 2C is appliedto an indication of the temperature of dryer 13 at the beginning of the shut down transition period and the weighting factor of FIG. 2D is applied to the moisture indication derived by adding element 63 during the start up mode.
  • the temperature magnitudes associated with the start up and shut down trajectories are stored in trajectory memory 71 and are derived from the memory during the appropriate start up or shut down mode.
  • the memory locations are read out during the transitional periods in response to different locations in the memory being indexed by index counter 72, which is advanced once each sample period during the transitional periods by oscillator 73, which derives an output pulse at the beginning of each sample period.
  • Index counter 72 includes a maximum count (N 1) equal to the number of steps (N) minus one in the transitional periods; in the illustrated system and FIGS. 2AD, N is assumed to be 25.
  • Index counter 72 is reset to a count of zero at the beginning of the startv up and shut down periods.
  • the counter includes a reset to zero input terminal which causes the counter to be reset to a zero count in response .to, a binary one input signalbeing applied thereto.
  • Binary onesign'als are applied to the reset to zero terminal of counter 72 in response to the dryer mode shifting from precondition to start up, as indicated by a binary one output of AND element 39, or in response to the dryer shifting from a run to shut down mode, as indicated by a binary one output being derived by AND element 42.
  • the step indicating signal derived from counter 72 is applied selectively to start up and shut down inputs of trajectory memory 71 under the control of switching element 74, which is selectively connected between the output of the counter and the start up and shut down inputs of the trajectory memory.
  • the temperature values of the start up and shut down trajectories are selectively read from the memory in response to closure of start up and shut down switching elements and 76,
  • Elements 74-76 are responsive to the mode indicating signals derived by AND elements 35 and 37. As the count of index counter 72 is advanced, the magnitudes of the signals fed through switching element 75 or 76 are varied in a predetermined manner, as illustrated for example, in FIGS. 2A and 2B.
  • the signals fed through switching elements 75 and 76 are respectively fed to multiplication elements 77 and 78.
  • Second inputs supplied to multiplication elements 77 and 78 are indicative of the actual time position within the transitional period and the complement of the time position, as respectively illusthrough switching elemen't 75 is modified so that it is multiplied by a maximum amount toward the beginning of the start up cycle, but is multiplied by a minimum, almost zero value, toward the end of the cycle.
  • the shut down trajectory is modified in multiplication element 78 so that it is only slightly modified toward the beginning of the shut down period, but is decreased significantly toward the end of the shutdown cycle.
  • the weighting factor signals applied to multiplication elements 77 and 78 are applied in parallel to modify the monitored characteristics of dryer 13 which are indicative of dryer loading.
  • the expected dryer loading factor as represented by Equation (1) and derived from addition element 63, is modified in multiplicationelement 81 by the weighting factor variation indicated by FIG. 2C, as expressed by the output of index counter 72.
  • the comple mentary weighting factor signal as indicated by FIG. 2D and derived from subtraction element 79, is multiplied in multiplier element 82 by asignal indicative of the dryer temperature at the beginning of the shut downperiod.
  • the output of analog-to-digital converter 29 which reflects the temperature monitored by probe 25, is fed to memory element 83 via switching element 84.
  • Switching element 84 is normally maintained in a closed condition so that memory 83 is updated after each sample period.
  • the output of AND element 36 causes switching element 84 to open, whereby during the duration of the shut down period memory 83 stores the temperature value of dryer 13 at the beginning of the shut down period.
  • switching element 50 is controlled by the output of AND element 37 so that the shut down temperature set point signal is fed to digital to analog converter element 53.
  • the set point signal derived by addition element 85 is responsive to the time weighted shut down trajectory and the time weighted temperature indication respectively derived from ultiplication elenents 78 and 82.
  • switching element 50 is activated in response to the output of AND element 34 to feed the stored precondition temperature signal from memory element 51 to the digital to analog converter 53.
  • a binary one signal is derived from AND element 35, whereby switching element 50 activated so that the output of addition element 86 is fed to element 53.
  • AND element 86 responds to the time weighted start up trajectory derived from multiplication element 77 and the time weighted signal indicative of the dryer duty or load, as derived from multiplication element 81'.
  • Addition element 86 also responds to a residual feedback signal. An actual indication of the error cannot be divided during the start up interval because no material passes the moisture transducer 24 at any time during the start up interval.
  • the residual error indication is fed to addition element 86 by memory element 87 which is selectively responsive to the output of proportional-integral controller 65, as fedthrough switch 88.
  • Switch 88 is maintained in a closed condition during the run mode in response to output signals of AND gates 36 and 37 being supplied thereto.
  • switch element 88 is open, whereby the signal stored in memory 87 is indicative of the error signal derived by proportional-integral control element 65 during the last step of the run mode. Since it is'expected that the dryer error during the start up mode is generally similar to the dryer error during the immediately preceding operating period, the error signal stored in memory 87 provides a relatively accurate indication of the amount by which the time weighted trajectory and moisture removal computation must be corrected during the start up mode.
  • a system for controlling a dryer for material that flows through the dryer so that adesired moisture content of the material is approximately maintained even though there is a significant change in the dryer load during a transitional period means for providing a predetermined trajectory for the dryer drying rate during the transitional period, means for deriving an indication of the dryer performance during at leasta portion of said transitional period, means for time weighting said trajectory and indication in opposite directions during said transitional period, and means for combining the time weighted trajectory and time weighted indication to derive a control signal for the dryer.
  • a method for controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained even though there is a significant change in the dryer load during a transitional period comprising the steps of in a computer: storing a predetermined trajectory for the dryer drying rate during the transitional period, deriving an indication of said transitional dryer performance during at least a portion of the period, time weighting said trajectory and indication in opposite directions during the period; and controlling the dryer in response to concomitantly derived time weighted values of the trajectory and indication.
  • a method of controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained even though there is a signficant change in the dryer load during a transitional period including the steps of providing a predetermined trajectory for the dryer drying rate during the transitional period, said trajectory being determined by the dryer characteristics and the expected dryer load change during said transitional period, deriving an indication of the dryer performance during at least a portion of said transitional period, time weighting said trajectory and indication in opposite directions during said transitional period, and combining the time weighted trajectory and time weighted indication to derive a control signal for the dryer.
  • means for providing a time weight trajectory for the dryer drying rate during the transitional period said trajectory being determined by the drying characteristics of the dryer, the change of the material flow rate during the period and the change in the amount of material during said transitional period, means for deriving a time. indication of the dryer performance during at least a portion of said transitional period, said trajectory and indication being time weighted in opposite directions during the period, and
  • a method of controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained during a start up or shut down transitional period of flow of the material through the dryer comprising in a computer storing a predetermined trajectory for the dryer drying rate during the transitional period, said trajectory being determined by the drying characteristics of the dryer, the change of the material flow rate during said transitional period and the change in the amount of material during said transitional period, deriving an indication of the dryer performance during at least a portion of said transitional period, time weighting said trajectory and indication in opposite directions during said transitional period so that as the period progresses the effects of the weighting factors on said indication and said trajectory change in opposite directions; and concomitantly controlling the dryer in response to the time weighted trajectory and time weighted indication.
  • means for providing a time weighted trajectory for the dryer drying rate during the transitional period said trajectory being determined by the drying characteristics of the dryer, the change of the material flow rate during said transitional period and the change in the amount of material during said transitional period
  • means for deriving a time weighted indication of the moisture of the material flowing into the dryer during said transitional the period said trajectory and indication being time weighted during said transitional period so that a weighting factor for the trajectory decreases as said transitional the period progresses and a weighting factor for the indication increases as said transitional period progresses
  • means for deriving a control signal for the dryer in response to the time weighted trajectory and indication means for providing a time weighted trajectory for the dryer drying rate during the transitional period, said trajectory being determined by the drying characteristics of the dryer, the change of the material flow rate during said transitional period and the change in the amount of material during said transitional period
  • means for deriving a time weighted indication of the moisture of the material flowing into the dryer during said transitional the period said
  • the system of claim 6 further including means for storing a prior indication of a moisture feedback error, and wherein the control signal deriving means is responsive to the stored indication of a moisture feedback error.
  • said moisture indicating deriving means includes means for deriving the indication as a function of the amount of water to be removed from the material while-the material is resident in the dryer.
  • means for providing a time weighted trajectory for the dryer drying rate during the transitional period said trajectory being determined by the drying characteristics of the dryer,"the change of the material flow rate during said transitional period and the change in the amount of material during said transitional period
  • means for deriving a time weighted indication of a drying characteristic of the dryer at the beginning of said transitional period said trajectory and indication being time weighted during said transitional period so that a weighting factor given to the trajectory increases as said transitional period progresses and a weighting factor given to the indication decreases as the said transitional the period progresses
  • means for combining the time weighted trajectory and indication to derive a control signal for the dryer.
  • drying characteristic deriving means includes means for deriving the indication in response to the temperature of the dryer.
  • a system for controlling a dryer for material that flows through the dryer so that a desired moisture content of the material is approximately maintained even though there is a'significant change in the dryer load during a transitional period means for providing a time weighted trajectory for the dryer drying rate during the transitional period, means for deriving a time 7 dryer.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Drying Of Solid Materials (AREA)
US00280114A 1972-08-14 1972-08-14 Dryer control system and method Expired - Lifetime US3787985A (en)

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AU (1) AU5921473A (fa)
CA (1) CA986211A (fa)
DE (1) DE2341094A1 (fa)
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Cited By (30)

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US3892045A (en) * 1974-05-10 1975-07-01 Mechtron Int Corp Fuel allocation system and method for industrial dryers and the like
US3905123A (en) * 1973-10-15 1975-09-16 Industrial Nucleonics Corp Method and apparatus for controlling a tobacco dryer
US3942262A (en) * 1973-12-05 1976-03-09 Phillips Petroleum Company Dryer temperature control
FR2386794A1 (fr) * 1977-04-07 1978-11-03 Jouin Claude Procede et dispositif de regulation d'un sechoir a tambour tournant
US4286391A (en) * 1980-02-11 1981-09-01 General Electric Company Control system for an automatic clothes dryer
EP0146759A1 (en) * 1983-11-15 1985-07-03 Japan Tobacco Inc. Tobacco drying machine
EP0165578A3 (en) * 1984-06-21 1987-07-29 Japan Tobacco Inc. Process for the temperature control of a drying apparatus for tabacco leaves
GB2238105A (en) * 1989-10-28 1991-05-22 Motan Plast Automation Ag Method for drying material and apparatus for operating such a method
EP0481110A1 (en) * 1990-10-17 1992-04-22 GARBUIO S.p.A. Rotary conditioning drum, particularly for drying tobacco
DE4204771A1 (de) * 1992-02-18 1993-08-19 Hauni Werke Koerber & Co Kg Verfahren und anordnung zum betrieb eines dampfbeheizten trockners
US5570521A (en) * 1990-11-26 1996-11-05 Ffi Corporation Control system for a grain dryer and probe mounting apparatus therefor
US6502581B2 (en) * 1997-11-20 2003-01-07 Brown & Williamson Tobacco Corporation Method and device for regulating the output humidity of tobacco
US20040143992A1 (en) * 2002-11-26 2004-07-29 Do Gi Hyeong Laundry drier control method
CN102499429A (zh) * 2011-12-13 2012-06-20 卧龙电气集团股份有限公司 用于密集烤房控制器的实时时钟判断装置及其方法
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CN103315383A (zh) * 2013-06-19 2013-09-25 浙江中烟工业有限责任公司 一种烟草制丝加料水分控制方法
WO2014085168A1 (en) * 2012-11-27 2014-06-05 Corning Incorporated Systems and methods for adaptive microwave drying of ceramic articles
CN104062989A (zh) * 2014-05-22 2014-09-24 云南昆船设计研究院 一种烤片机温度快速调节计算方法
CN104522872A (zh) * 2014-11-05 2015-04-22 上海烟草集团有限责任公司 多模式薄片烘烤设备的工作方法及其水分控制系统
CN103704875B (zh) * 2012-10-09 2016-01-20 北京精密机电控制设备研究所 一种高精度烟丝水分控制方法及其控制系统
CN106249788A (zh) * 2016-08-31 2016-12-21 王小兰 一种基于自组织的大棚种植监控专家系统
CN106360801A (zh) * 2016-08-31 2017-02-01 王小兰 一种烤烟叶加工实时监控系统
CN109549241A (zh) * 2018-12-29 2019-04-02 浙江中烟工业有限责任公司 一种应用于制丝筒式烟机的蒸汽加热控制模型、蒸汽加热控制方法
CN111248481A (zh) * 2020-04-01 2020-06-09 贵州中烟工业有限责任公司 一种六干燥区的网带直接干燥复烤工艺
CN111657541A (zh) * 2020-07-20 2020-09-15 四川中烟工业有限责任公司 一种启动块的调节装置及系统
CN112401288A (zh) * 2020-12-04 2021-02-26 贵州省烟草科学研究院 一种双排湿结构的烟叶控湿烤箱及其控制方法
CN114831330A (zh) * 2022-05-23 2022-08-02 红云红河烟草(集团)有限责任公司 一种制丝车间松散回潮工序智能加水模型的建立方法
CN117099993A (zh) * 2023-09-14 2023-11-24 杭州安脉盛智能技术有限公司 一种物料水分控制方法、装置、电子设备及存储介质

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CN113876008B (zh) * 2021-11-17 2023-11-21 河南中烟工业有限责任公司 一种控制松散回潮烟片含水率稳定性的方法
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DE1532065A1 (de) * 1966-04-30 1970-01-15 Hauni Werke Koerber & Co Kg Tabakvorbereitungsanlage
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US2188528A (en) * 1936-12-09 1940-01-30 George M Clark Method of and machine for conditioning stereotype matrices
US2360838A (en) * 1941-04-05 1944-10-24 Atti Raphael Apparatus for roasting coffee
US2768629A (en) * 1953-09-24 1956-10-30 American Mach & Foundry Moisture measuring method and apparatus
US3039201A (en) * 1956-09-26 1962-06-19 Koerber & Co Kg Apparatus for treating tobacco products
US3429317A (en) * 1963-11-18 1969-02-25 Hans Koch Method of conditioning tobacco
US3386448A (en) * 1965-09-09 1968-06-04 Hauni Werke Koerber & Co Kg Method and apparatus for conditioning tobacco
DE1532065A1 (de) * 1966-04-30 1970-01-15 Hauni Werke Koerber & Co Kg Tabakvorbereitungsanlage
GB1196163A (en) * 1966-05-04 1970-06-24 Hauni Werke Koerber & Co Kg Device for Combining Tobacco Streams in Correctly Proportioned Amounts

Cited By (42)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3905123A (en) * 1973-10-15 1975-09-16 Industrial Nucleonics Corp Method and apparatus for controlling a tobacco dryer
US3942262A (en) * 1973-12-05 1976-03-09 Phillips Petroleum Company Dryer temperature control
US3892045A (en) * 1974-05-10 1975-07-01 Mechtron Int Corp Fuel allocation system and method for industrial dryers and the like
FR2386794A1 (fr) * 1977-04-07 1978-11-03 Jouin Claude Procede et dispositif de regulation d'un sechoir a tambour tournant
US4286391A (en) * 1980-02-11 1981-09-01 General Electric Company Control system for an automatic clothes dryer
EP0146759A1 (en) * 1983-11-15 1985-07-03 Japan Tobacco Inc. Tobacco drying machine
EP0165578A3 (en) * 1984-06-21 1987-07-29 Japan Tobacco Inc. Process for the temperature control of a drying apparatus for tabacco leaves
GB2238105B (en) * 1989-10-28 1994-03-09 Motan Plast Automation Ag Method for drying material and apparatus for operating such a method
GB2238105A (en) * 1989-10-28 1991-05-22 Motan Plast Automation Ag Method for drying material and apparatus for operating such a method
EP0481110A1 (en) * 1990-10-17 1992-04-22 GARBUIO S.p.A. Rotary conditioning drum, particularly for drying tobacco
US5570521A (en) * 1990-11-26 1996-11-05 Ffi Corporation Control system for a grain dryer and probe mounting apparatus therefor
DE4204771A1 (de) * 1992-02-18 1993-08-19 Hauni Werke Koerber & Co Kg Verfahren und anordnung zum betrieb eines dampfbeheizten trockners
DE4204771B4 (de) * 1992-02-18 2006-01-12 Hauni Maschinenbau Ag Verfahren und Anordnung zum Betrieb eines dampfbeheizten Trockners
US6502581B2 (en) * 1997-11-20 2003-01-07 Brown & Williamson Tobacco Corporation Method and device for regulating the output humidity of tobacco
US20040143992A1 (en) * 2002-11-26 2004-07-29 Do Gi Hyeong Laundry drier control method
US7941937B2 (en) * 2002-11-26 2011-05-17 Lg Electronics Inc. Laundry dryer control method
CN102499429A (zh) * 2011-12-13 2012-06-20 卧龙电气集团股份有限公司 用于密集烤房控制器的实时时钟判断装置及其方法
CN102499429B (zh) * 2011-12-13 2013-09-18 卧龙电气集团股份有限公司 用于密集烤房控制器的实时时钟判断装置及其方法
CN103704875B (zh) * 2012-10-09 2016-01-20 北京精密机电控制设备研究所 一种高精度烟丝水分控制方法及其控制系统
US9429361B2 (en) 2012-11-27 2016-08-30 Corning Incorporated Systems and methods for adaptive microwave drying of ceramic articles
WO2014085168A1 (en) * 2012-11-27 2014-06-05 Corning Incorporated Systems and methods for adaptive microwave drying of ceramic articles
CN103217010B (zh) * 2013-04-08 2015-05-20 上海烟草集团有限责任公司 物料烘缸设备的控制系统
CN103217010A (zh) * 2013-04-08 2013-07-24 上海烟草集团有限责任公司 物料烘缸设备的控制系统
CN103211295A (zh) * 2013-04-19 2013-07-24 湖南中烟工业有限责任公司 烟草回潮机出口水分控制方法及其装置
CN103315383A (zh) * 2013-06-19 2013-09-25 浙江中烟工业有限责任公司 一种烟草制丝加料水分控制方法
CN103315382B (zh) * 2013-06-19 2015-04-15 浙江中烟工业有限责任公司 一种烟草制丝工艺中基于级联型pid的加料水分控制装置
CN103315382A (zh) * 2013-06-19 2013-09-25 浙江中烟工业有限责任公司 一种烟草制丝工艺中基于级联型pid的加料水分控制装置
CN103315383B (zh) * 2013-06-19 2015-10-14 浙江中烟工业有限责任公司 一种烟草制丝加料水分控制方法
CN104062989A (zh) * 2014-05-22 2014-09-24 云南昆船设计研究院 一种烤片机温度快速调节计算方法
CN104522872A (zh) * 2014-11-05 2015-04-22 上海烟草集团有限责任公司 多模式薄片烘烤设备的工作方法及其水分控制系统
CN104522872B (zh) * 2014-11-05 2016-03-16 上海烟草集团有限责任公司 多模式薄片烘烤设备的工作方法及其水分控制系统
CN106249788A (zh) * 2016-08-31 2016-12-21 王小兰 一种基于自组织的大棚种植监控专家系统
CN106360801A (zh) * 2016-08-31 2017-02-01 王小兰 一种烤烟叶加工实时监控系统
CN106360801B (zh) * 2016-08-31 2018-03-20 贵州派腾科技服务有限公司 一种烤烟叶加工实时监控系统
CN109549241A (zh) * 2018-12-29 2019-04-02 浙江中烟工业有限责任公司 一种应用于制丝筒式烟机的蒸汽加热控制模型、蒸汽加热控制方法
CN109549241B (zh) * 2018-12-29 2021-04-20 浙江中烟工业有限责任公司 一种应用于制丝筒式烟机的蒸汽加热控制模型、蒸汽加热控制方法
CN111248481A (zh) * 2020-04-01 2020-06-09 贵州中烟工业有限责任公司 一种六干燥区的网带直接干燥复烤工艺
CN111657541A (zh) * 2020-07-20 2020-09-15 四川中烟工业有限责任公司 一种启动块的调节装置及系统
CN112401288A (zh) * 2020-12-04 2021-02-26 贵州省烟草科学研究院 一种双排湿结构的烟叶控湿烤箱及其控制方法
CN114831330A (zh) * 2022-05-23 2022-08-02 红云红河烟草(集团)有限责任公司 一种制丝车间松散回潮工序智能加水模型的建立方法
CN114831330B (zh) * 2022-05-23 2023-07-25 红云红河烟草(集团)有限责任公司 一种制丝车间松散回潮工序智能加水模型的建立方法
CN117099993A (zh) * 2023-09-14 2023-11-24 杭州安脉盛智能技术有限公司 一种物料水分控制方法、装置、电子设备及存储介质

Also Published As

Publication number Publication date
ZA735237B (en) 1974-07-31
GB1445200A (en) 1976-08-04
CA986211A (en) 1976-03-23
JPS4985652A (fa) 1974-08-16
DE2341094A1 (de) 1974-02-28
AU5921473A (en) 1975-02-20

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