Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
  • F26B17/12—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
  • F26B17/12—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft
  • F26B17/14—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft the materials moving through a counter-current of gas
  • F26B17/1408—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft the materials moving through a counter-current of gas the gas being supplied and optionally extracted through ducts extending into the moving stack of material
  • F26B17/1416—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft the materials moving through a counter-current of gas the gas being supplied and optionally extracted through ducts extending into the moving stack of material the ducts being half open or perforated and arranged horizontally
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying good
  • F26B2200/06—Grains, e.g. cereals, wheat, rice, corn

Definitions

• the invention relates to an apparatus for enhancing operational safety and energetic effectiveness of a cross-flow grain dryer.
• the dryer comprises several levels formed from parallel ducts arranged one over the other.
• the dryer is provided with a charging hole at its upper portion and a discharging hole at its lower portion.
• the ducts are provided with inlet opening or outlet opening.
• the dryer is divided vertically into zones comprising several levels, namely a cooling zone arranged above the discharging hole and a drying zone arranged above the cooling zone. Drying medium the temperature and air mass of which are controlled by a control element is introduced through the inlet opening.
• temperature sensors are disposed.
• the invention also relates to a method for operating cross-flow grain dryers.
• cross-flow grain dryers Safe operation, fire protection and efficiency enhancement of cross-flow grain dryers is essential in respect of storing and further processing of grains.
• the known cross- flow grain dryers provide little information about the different rate of travel of the grain moving in the dryer originating from different physical effects (e.g. frictional force along the side walls, at the corners, in the vicinity of guiding elements). However, this information would be important in order to minimize the difference in moisture content observable at the end of the drying process.
• Klixons used in certain types do not .cover the whole drying surface and are used only to stop the operation in case of emergency. When the set temperature is reached it intervenes in the process, stops the operation of the heat generating units and the fans. However, by this tirhe a significant amount of the grain may have been damaged. In most dryers nowadays available on the market neither klixon nor temperature measuring unit is provided or they are used only in a limited number.
• the known solutions try to solve the aforementioned problems by using mechanical interventions. According to these solutions the travel of the grain in the dryer is controlled so as to get the grain mixed in order to make the moisture content of the grain mass homogeneous.
• the method of the present invention provides a different solution.
• Patent application US 4914834 describes a grain column dryer which includes two concentric, cylindrical pervious walls and a pervious cone on the top of the inner pervious wall.
• An impervious heat insulated cylindrical outer wall is spaced outwardly from the pervious walls.
• a heater/blower assembly is supported on a substantially airtight bulkhead in the centre of the dryer to force heated air into an upper heated plenum and out through the concentric pervious walls and the pervious top cone.
• An air recycle collar is attached to the outer pervious wall above the bulkhead baffle. The heated air passes from above the bulkhead baffle down inside of the recycle collar and inside of the impervious outer wall and back through the pervious walls below the baffle to mix with ambient air drawn in through the pervious walls below the impervious outer wall.
• Patent application US 2004154184 teaches a grain dryer control system.
• the system includes moisture and temperature sensors and a means to control the discharge of grain from the dryer. Given a grain discharge temperature, a control temperature and a moisture reduction factor as a function of temperature, the control system calculates an expected moisture reduction in the grain as the grain cools. Grain is discharged from the dryer when the target moisture content after cooling added to the expected moisture reduction in the grain as the grain cools meets the measured grain moisture content in the dryer.
• Patent application US 5992044 describes a grain dryer which has a horizontal plenum connected to a source of heated forced air and has at least one perforated wall.
• An enclosed grain conduit extends along the plenum and has one of its sidewalls being the perforated wall of the plenum.
• the grain conduit has upper and lower ends to receive and discharge the grain to be dried by the heat conveyed to the grain through the perforated wall of the plenum.
• Upper and lower discharge ports are separated by a plate to close the flow of grain therethrough. Horizontal upper and lower feed rolls adjacent the upper and lower ports induce flow of grain out of these ports. With the feed roll adjacent the upper port the discharge of a layer of hotter grain can be accelerated.
• Patent application US 4249891 describes .a continuous grain drying and conditioning apparatus including one or more burners and blowers surrounded by a plenum chamber and air pervious grain holding walls.
• a plenum divider which is selectively adjustable in position divides the grain holding walls into a heating section and a cooling section.
• a multiplicity of grain turning apparatus is disposed in the grain column for separating the grain mass and turning the cooler wetter grain inwardly as it moves downwardly and turning the hotter dryer grain outwardly as it moves downwardly in the grain column.
• Grain is constantly removed from the bottom of the apparatus at a rate governed by the average temperature of the air exiting the grain.
• Grain to be dried and conditioned is constantly introduced into the top of the apparatus at a rate that satisfies the rate of discharge of the dried and conditioned grain. Unsaturated exhaust air is recycled in a controlled manner.
• Patent application RU2338984 describes a grain dryer. Disposal of the sensors is not determined explicitly. Correction of .the different moisture content measured at different points of the tower is not resolved. The difference in the flow rate of the grain is not examined, there are no efforts made for fire protection and sensors are not arranged at every possible discharge point. Difference in the moisture content of the discharged grain is not measured horizontally and there is no effort made to compensate it.
• Patent application GB2121939 describes a horizontal grain drying apparatus the operation of which is different from the cross-flow grain dryers. According to this technology the air is directed on the basis of the measured values, however the homogeneity in the moisture content of the grain mass is not examined and not controlled. The number of the sensors disposed in the apparatus does not ensure control of the entire surface. Especially, the required different flow rate of grain mass having different moisture content is not ensured. Cross-sectional travel control of the grain mass is not resolved.
• Patent application HU192968 describes a method and apparatus for supervision and control of grain dryers at operation.
• the temperature of the drying air is measured and operation of the dryer is controlled on the basis of the measured values.
• the temperature of the drying air and changes of it is constantly measured in the intensive drying zone and separately at each of the exhaust ports and trie measured values are processed. These data represent the current operative conditions.
• the apparatus is provided with temperature sensors and the dryer has an intensive drying zone.
• a temperature measuring element supplying electric signals is arranged in the intensive zone at each of the exhaust ports.
• the temperature measuring elements are connected to a signal processing and/or intervening signal generating electronics.
• the related document employs novel, up-to-date solutions.
• the drying tower is divided into zones but the temperature of the exiting air is only measured in the lower, intensive drying zone.
• the operation of the factory made discharging mechanism is controlled while in the method according to the present invention the size of the discharging hole is adjusted by means of additional discharging elements on the basis of the evaluated signals sent by the individual sensors and the characteristics of smaller sections are considered.
• the discharging elements divide the discharging opening into several sections and these sections are opened or narrowed down to a required extent by means of intervening devices. Otherwise, the discharging mechanism is used in a conventional manner.
• the solution of the present invention makes efforts to simultaneously compensate the positive and negative deviations, the extreme values come closer to the optimal, i.e. to the average moisture content.
• the average moisture content corresponds to the moisture content measured at any point of the discharging mechanism.
• Known devices operating on the basis of monitoring and controlling the average moisture content are not suitable for operating the apparatus according to the present invention.
• 5-6% or even more deviation in moisture content can be observed when the grain is examined horizontally at several points above the discharging mechanism.
• it presents problems in storage e.g. extra tasks and extra costs for treating the grain during storage.
• the degree of deviation in the moisture content determines the quality of the grain.
• this deviation is not considered as there is no feedback about it. Only the average moisture content is measured for selecting the rate of discharge.
• the deviation can be decreased close to zero from cycle to cycle. It is based on the fact that the temperature of the drying medium features the moisture content of the grain being behind it. After equalizing the different values of the exiting temperature of the drying medium the moisture content will also be equalized as an effect of interventions.
• the known methods do not use this solution especially not in the two main - horizontal and vertical - directions.
• the present invention makes use of the data supplied by the sensors positioned vertically and horizontally in order to obtain homogeneous moisture content.
• the solution according to the present invention is based on different principles as compared to the principles of the known solutions; the entire surface of the drying zone is protected against fire. During evaluation of data values of the drying process which deviate from the optimal value are also utilized in order to make correction possible. In addition, the drying apparatus is also diagnosed, uneven temperature of the furnace side and also deviations in the moisture content of the grain discharged through the discharge device can be recognized during the drying process. On occurrence of a possible jam it is displayed on the monitor. In this manner protection against fire is ensured on the entire surface. This means that through the solution of the present invention the apparatus can be operated more safely while the optimal quality of the grain is kept in mind. Controlling on the basis of horizontal measuring is a novel solution.
• the aim of the present invention is to eliminate the danger of damage of the grain mass present in the dryer, to save energy, to prevent the part of grain which is not suitably dry from becoming mouldy and to protect the entire drying surface from fire. It has been realized that if the entire surface of the drying zone of the dryer and at least on the first level of the cooling zone all the air outlet ducts are equipped along their longitudinal axis with temperature , sensors the temperature of the drying medium leaving the grain and the tower can be supervised. The aforementioned problems can be controlled if the temperature of the air exiting the dryer through the grain is constantly supervised. The great number of sensors can be adapted to any type of cross-flow grain dryers.
• the signals of the temperature sensors can be processed by a suitable apparatus and depending on the result of the processing the intervening devices can be operated on the basis of the output signal of the apparatus.
• the dryer comprises several levels formed from parallel ducts arranged one over the other.
• the dryer is provided with a charging hole at its upper portion and a discharging hole at its lower portion.
• the ducts are provided with inlet opening or outlet opening.
• the dryer is divided vertically into zones comprising several levels, namely a cooling zone arranged above the discharging hole and a drying zone arranged above the cooling zone. Drying medium the temperature and air mass of which are controlled by a control element is introduced through the inlet opening.
• heat sensors are disposed at the outflow of the drying medium i.e. at the outlet openings.
• Heat sensors are installed at each of the outlet openings of the drying zone, and in addition at least at the boundary of the drying zone and the cooling zone, at the upper level of the cooling zone, in each of the ducts provided with outlet openings a heat sensing unit is disposed.
• the heat sensing unit comprises a plurality of heat sensors spaced in a determined distance from each other and connected to a common data cable.
• the common data cables are connected to data collector(s). Signals of the data collector(s) and signals of the heat sensors disposed at the outlet openings are transmitted to a central unit.
• the discharging hole comprises discharging elements provided with intervening devices which can be operated independently from each other.
• the present invention also provides a method for operating cross-flow grain dryers in which the dryer comprises several levels formed from parallel ducts arranged one over the other.
• the dryer is provided with a charging hole at its upper portion and a discharging hole at its lower portion.
• the discharging hole comprises discharging elements which can be operated independently from each other, and the ducts are provided with inlet opening or outlet opening.
• the dryer is divided vertically into zones comprising several levels, namely a cooling zone arranged above the discharging hole and a drying zone arranged above the cooling zone. Drying medium the temperature and air mass of which are controlled by a control element is introduced through the inlet opening, and at the outflow of the drying medium, at the outlet openings heat sensors are disposed.
• a heat sensing unit comprising a plurality of heat sensors is disposed for measuring the temperature of the air travelling through the grain.
• the signals of the heat sensors disposed in the ducts and at the outlet openings are transmitted to a central unit advantageously through data collector(s) the position of which is exactly known.
• a graph representing the spatial dispersion of heat is generated from which the physical, thermal features of the dryer is determined and on the basis of it the temperature and the flow rate of the drying medium as well as the rate of discharge is controlled. That is, the flow of the grain is controlled on the basis of the graph of the spatial heat dispersion in order to make the moisture content of the grain homogeneous.
• Figure 1 is perspective front view of a portion of the dryer
• Figure 2 is a perspective view of a level, namely the upper level of the cooling zone provided with heat sensing units installed in the ducts;
• Figure 3 is a perspective view of the dryer in which the central unit controls the process of drying through wired connection;
• Figure 4 is a perspective rear view of a portion of the dryer
• Figure 5 is a perspective view of a channel provided with heat sensing unit; and Figure 6 is a perspective view of the dryer in which the central unit controls the process of drying through wireless connection and the cross-section of the ducts are narrowed down in one direction.
• the present invention provides an apparatus (measuring circuits and communication network) and method for enhancing operational safety of cross-flow grain dryers.
• safe operation of the dryer controlled travel rate and homogeneous moisture content of the grain can be realized by using number of spatially arranged temperature sensors measuring the temperature of the air flowing through the grain and providing data relating to it.
• the solution of the present invention can be used modularly and universally in all types of known grain dryers.
• the problem to be solved by the present invention is to eliminate the danger of quality loss of the grain mass present in the dryer, to save energy, to prevent the grain which is not suitably dry from becoming mouldy and to protect the entire drying surface from fire.
• the apparatus according to the invention comprises several levels 3 formed from parallel ducts 2 arranged one over the other.
• the dryer 1 is provided with a charging hole 4 at its upper portion and a discharging hole 5 at its lower portion.
• the ducts .2 are provided with inlet opening 6 ( Figure 1 ) or outlet opening 7 ( Figure 4).
• the dryer 1 is divided vertically into zones comprising several levels 3, namely a cooling zone 8 arranged above the discharging hole 5 and a drying zone 9 arranged above the cooling zone 8. Drying medium 1 1 the temperature and air mass of which are controlled by a control element 10 is introduced through the inlet opening 6.
• heat sensors 12 are disposed.
• Heat sensors 12 are installed at each of the outlet openings 7 of the drying zone 9.
• the heat sensors 12 are connected to a data collector 15 per level 3.
• a heat sensing unit 13 is disposed ( Figure 2).
• the heat sensing unit 13 comprises a plurality of heat sensors 12 spaced in a determined distance from each other which are connected to a common data cable 14 ( Figure 5).
• Heat sensors 12 are disposed over the entire surface of the drying zone 9, in all of the air exhaust ducts as well as in ducts 2 on the first level 3 of the cooling zone 8 (however, they can be positioned in ducts of other level(s) 3).
• the number of the heat sensors 12 according to the solution of the present invention can be adapted to any type of cross-flow grain dryers, e.g. in Babolna-type towers 260-300, in PETKUS 4000 14-DU 338, in PETKUS 4000 24-DU 536 can be used.
• the common data cables 14 are connected to data collector(s) 15.
• the signals- of the data collector(s) 15 and the signals of the heat sensors 12 positioned at the outlet openings 7 are transmitted through collector cable 19 to central unit 16 by using RS 485 system ( Figure 3).
• Data collector 15 is a communication circuit which is adapted to cooperate with the central unit 16, advantageously with a computer.
• MODBUS protocol or other suitable communication protocol can be used.
• wireless connection is also feasible ( Figure 6).
• Discharging hole 5 comprises discharging elements 18 provided with intervening devices 17 which can be operated independently from each other preferably by a servo motor.
• the connection between central unit 16 and intervening devices 17 may be wired or wireless. In another embodiment intervening devices 17 may be operated mechanically.
• Central unit 16 is connected to intervening devices 17 and control element 10 in order to make intervening in the discharging process of dryer 1 possible as required on the basis of the values obtained relating to the condition of the grain depending on the temperature and moisture content of the drying medium 11. Temperature and moisture content conditions inside the dryer can be measured more correctly if heat sensing units 13 are also disposed lengthwise in ducts 2 of several levels 3.
• the entire drying surface can be controlled, sensors are installed in every outlet opening thereby occurrence of a possible jam at any points of the dryer can be detected and fire cannot break out.
• This is important in respect of operation since it can be well detected even at the uppermost level of the dryer if grain having significantly different moisture content is present in the dryer.
• the rate of travel of the grain can be determined and steps can be taken in due time to change the rate of discharge.
• the method according to the present invention can be used for operating a cross- flow grain dryer 1 realized in the manner as described in the foregoing wherein the dryer comprises several levels 3 formed from parallel ducts 2 arranged one over the other and is provided with a charging hole 4 and a discharging hole 5.
• Discharging hole 5 comprises discharging elements 18 which can be operated independently from each other.
• Ducts 2 are provided with inlet opening 6 or outlet opening 7.
• the dryer is divided into zones: a cooling zone 8 arranged above the discharging hole 5 and a drying zone 9 arranged above the cooling zone 8. Drying medium 1 1 is introduced through the inlet opening 6 and heat sensors 2 are disposed at the outlet opening 7 where the exiting drying medium 22 leaves the dryer.
• a heat sensing unit 13 comprising a plurality of heat sensors is installed 13.
• Heat sensors 12 and heat sensing units 13 are used for measuring the temperature of the air passing through the grain.
• the signals of the heat sensors 12 disposed in the individual ducts 2 and at the outlet opening 7 are transmitted through data collectors 15 to central unit 16.
• the locations of the signal collecting points of data collectors 15 are exactly known. Based on the signals of the data collectors 15 a graph representing the spatial dispersion of heat is generated in the central unit 16.
• thermo features of dryer 1 are determined and on the basis of it the temperature and the flow rate of the drying medium 1 1 as well as the rate of discharge are adjusted by operating/controlling discharging hole 5. That is, the flow of the grain is controlled on the basis of the graph of the spatial heat dispersion in order to make the moisture content of the grain homogeneous.
• the accuracy of the graph of the spatial heat dispersion can be enhanced by positioning number of heat sensing units 13 in each of the ducts 2 on several levels 3 of dryer 1 , .i.e. horizontally, and the signals of the heat sensing units 13 are also processed for generating the graph.
• heat sensors 12 are temperature sensors, e.g. National Semiconductor LM35DZ precision temperature sensors.
• central unit 16 is a computer. To automatize the operation of dryer 1 average value is generated continuously by central unit 16 from the values measured by the number of heat, sensors 12 disposed over the cooling zone 8 and by heat sensing units 13. The average value and the value converted from it are used to supervise the drying process and to control discharging elements 18.
• the average temperature above the cooling zone 8 is determined after each measurement cycle. In this manner the average temperature can be made constant thus the drying process is stabilized in the apparatus according to the invention. Positive/negative deviation from the average value forecasts a change in the moisture content. In this manner there is enough time for correction and discharge of the grain can be controlled at discharging hole 5 by suitably selecting the rate of discharge.
• the average of the values measured (horizontally) in the individual ducts 2 refers to the travel rate of the individual vertical sections.
• Positions of heat sensors 12 must be determined on the basis of the parameters featuring dryer 1. To this the following parameters are needed: the number of the exit windows per levels, the distance between the windows and the number of the levels above the cooling zone.
• heat sensors 12 having a diameter of 6 mm are installed in a 20x15x2 mm aluminium hollow section ( Figure 5), however, more heat sensors may be used if required.
• heat sensors 12 are placed directly in the shielded cable which is protected from external effects by applying insulating synthetic resin and shrinkable tube (not shown in the Figures). Connection to data collector 15 is ensured through data cable 14.
• Data cable 14 is a shielded cable so that external interfering effects - which may be influential in measurements - can be filtered out.
• National Semiconductor LM35DZ TO-92 precision temperature sensors are used, however, other equivalent type may be used.
• the signals of the heat sensors 12 disposed at outlet opening of duct 2 are transmitted directly (the uppermost level 3 in Figure 3) or they can be transmitted collectively (all the outputs of all the sensors in a given level are connected to data collector 15 disposed in each duct 2) to central unit 16.
• the number of the heat sensing units 13 to be installed on a measuring card corresponds to the number of outlet openings .7.
• heat sensing unit 13 may be disposed on several levels 3 of drying zone 9 not only on the upper level 21 of cooling zone 8 if it is required for controlling the drying process (e.g. on twenty levels 3, the number of sensing units 13 provided with respective number of heat sensors 12 may be determined correspondingly to the number of outlet openings per level).
• Each of the data collectors 15 has a unique identifier. On the basis of the unique identifier the central unit 16 obtains its data relating to the currently measured value.
• collector cable 19 five-wire shielded twisted-pair cable
• Collector cable 19 comprises three wires (RS485-A, RS485-B, GND) needed for RS-485 communication and two wires (+12V, GND) needed for power supply.
• Communication devices are connected to collector cable 19 in a chain ( Figure 3).
• data from data collectors 15 to central unit 16 and from central unit 16 to intervening devices 17 and/or to control element 10 are transmitted through a wireless system 20 ( Figure 6).
• Central unit 16 is provided with one (or if required more) USB-RS485 interface (not shown in the Figure) through which communication between data collector 15 and central unit 16 can be ensured.
• Data collector 15 is a communication network using MODBUS protocol. The arrangement can handle and transmit data supplied by hundreds of measuring points since optional number of communication cards i.e. data collector 15 may be coupled (thirty-two per interface).
• the sensing system is adaptable as the number of heat sensors 12 disposed on one level 3 can be increased if required up to eighteen sensors.
• heat sensors 12 are used in the following manner: ten heat sensors 12 per level 3 are disposed on twenty levels 3 and on the upper level 21 of the cooling zone 8 in ten ducts 2 a heat sensing unit 3 comprising six heat sensors 12 are disposed per duct 2.
• heat sensors are used, i.e. on twenty levels 3 thirteen heat sensors 12 per level 3 are disposed and on the upper level 21 of the cooling zone 8 in thirteen ducts 2 a heat sensing unit 13 comprising six heat sensors 12 are disposed per duct 2.
• heat sensors 12 are used, i.e. on thirty-six levels 3 thirteen heat sensors 12 per Level 3 and on the upper level 21 of the cooling zone 8 in thirteen ducts 2 a heat sensing unit 13 comprising six heat sensors 12 are disposed per duct 2.
• a heat sensor 12 is disposed before each- of the outlet openings 7. Further, over the cross-section of the dryer a heat sensing unit 13 comprising six heat sensors 12 is disposed horizontally in each duct 2 on the upper level 21 of the cooling zone 8.
• the operation of the apparatus according to the invention is controlled by software executed in central unit 16.
• the software may be configured in such a manner that the temperature of the air leaving the grain is measured at a determined number of points and the result is displayed.
• Data collectors 15 are polled in determined cycles by central unit 16. Then the temperature data returned by a certain data collector 15 through collector cable 19 are displayed by central unit 16. Measuring is performed continuously, values are displayed on the monitor (not shown in the Figures) of central unit 16. The measured value can be seen until the next measurement.
• the measured values are filtered and averaged by the program. Failure or breakage of the sensor can be detected. Either positive or negative divergence of the temperature from normal is also detected. Values higher than the average are marked in red, lower values are marked in blue and values near the average are marked in green during display. In case of a badly adjusted dryer the following table can be seen.
• the values (displayed in blue) in column 3 show that a certain column of grain travels rather fast (the temperature is lower than the average). As a result of this the moisture content of the grain discharged in this section of the dryer will be higher than the average.
• the values (displayed in red) in column 7 and 8 show that the grain travels rather slow (the temperature is higher than the average) as a result of which the grain will be over dried in this section. (The values diverging from the required are marked in bold in the table).
• the ambient air drawn in by the suction blower is heated, this is the drying medium 11 ( Figures 3 and 6).
• the air should be heated to a maximum degree at which the grain is not damaged but as much moisture as possible is removed. If it is considered during the drying process, the temperature of the drying medium 11 is considered essentially constant. If the temperature of the entering drying medium 11 is constant, the temperature of the exiting drying medium 22 will be characteristic of the moisture content of the grain. This relationship is used to control the drying process, to detect grain masses having different moisture content and to regulate the discharging process.
• Another possible problem may be that the moisture content of the grain entering the dryer is suddenly and significantly becomes different. Taking the above mentioned relation and table, the values in row 1 will be lower than the earlier ones because of the higher moisture content. Then the grain should spend more time in dryer 1 therefore discharge is slowed down and travel of the grain is observed step by step, from level to level.
• the grain having higher moisture content reaches e.g. the ninth level in the dryer (in the table row 9)
• An average value is calculated from the values present in rows 9-16 (the eight levels directly above the cooling zone 8) which is then displayed.
• the temperature of the entering drying medium is constant - for example for corn drying it is usually 100 C° - and the moisture content of the discharged grain is of the required value (e.g. 12.5%).
• the average temperature of the exiting drying medium 22 when leaving the lower portion of the drying zone 9 features the moisture content of the grain therefore this data can be used for controlling the drying process.
• the moisture content of the discharged grain is also constant. This value must be synchronized with the moisture content values measured in the laboratory drying cabinet and if required, the target value must be corrected slightly.
• the moisture content of the grain mass can be made more homogeneous by the present invention.
• the novelty of the method according to the invention as compared to the known solutions is that the average of the measured values in each of the ducts (horizontally) features the travel rate of the vertical sections. These data are crosschecked with the data of the heat sensors arranged in all of the outlet openings in order to obtain a spatial image about divergence of the travel rate, temperature and moisture content of the grain.
• the parameters featuring the grain can be visualized in space.
• a column diagram consisting of 78 columns side by side can be represented. If required, the spatial grid can be further refined by increasing the number of heat sensors.
• the diagram is displayed continuously in this manner information is provided about the sections in which the travel rate of the grain is too high.
• the discharging hole being in its open state for a determined time can be narrowed down by the intervening devices to a required extent so that the grain travelling too fast therefore having too high moisture content can be retained in the active zone for a longer time.
• the same is performed automatically by means of a control algorithm.
• the intervening devices are operated by servo motors or a similar moving mechanism.
• the program On the basis of the continuously measured data the program is able to determine the sections in which the grain travels too fast and narrows the discharging hole down to the extent as programmed.
• the program controls itself and if the obtained data show that the discharging hole must be narrowed down to a larger extent the intervening device further moves to a closing direction. If data measured in the next cycle show that the discharging hole is closed to a larger extent than required, the program performs correction and widens it on the basis of the current values. Correction is done in every cycle continuously until the system becomes in a steady-state condition in which the temperature and the moisture content are homogeneous.
• the advantage of the solution according to the present invention is that it can be used modularly and universally in all types of known grain dryers.
• the entire drying surface is controlled. Heat sensors are disposed in every outlet opening thereby occurrence of a possible jam at any points of the dryer is detected and fire cannot break out. This is important in respect of operation since it can be well detected even at the uppermost levels of the dryer if grain having significantly different moisture content is present in the dryer. By this means the rate of travel of the grain can be determined and steps can be taken to change the rate of discharge.
• the average temperature above the cooling zone is determined after each measurement cycle by the computer of the central unit. By stabilizing the average temperature the drying process is also stabilized.

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