JP5793934B2 - Grain dryer - Google Patents

Description

  The present invention relates to a drying control device in a grain dryer.

In the circulation type grain dryer, the exhaust air circulation type grain dryer which supplies the exhaust air after drying the grain to the hot air chamber again and reuses the heat and moisture of the exhaust air is known (patent) Reference 1).
In the circulation type grain dryer, when the grain drying is performed in a small amount of state where the whole of the drying net part of the grain flow passage in the drying room is not filled with grain, the burner is burned in a small amount and hot air dried. It is publicly known that alternately performs hot air drying and ventilation drying in which hot air drying is stopped (Patent Document 2).

JP 2009-109137 A JP 2009-210184 A

  In the exhaust air circulation type grain dryer, the present invention provides an exhaust fan that passes through the drying chamber in a small amount of state where all the drying net portions of the grain flow passage of the drying chamber are not filled with the grain. There is a problem that the grain resistance to exhaust air is small, the amount of air passing through the burner and the wind speed increase, and the combustion flame of the burner tends to disappear.

  The present invention is intended to solve such problems and facilitate burner combustion.

The invention of claim 1
A drying chamber (3) provided with a grain flow passage (9) through which the grain flows down;
Dry hot air generated by mixing the hot air generated by the burner (5) and the outside air is sent to the drying chamber (3) by the exhaust fan (7) to dry the grain, and the hot hot air is passed through the exhaust chamber (8). In the grain dryer which is discharged to the outside through the machine, the burner (5) is provided with a burner fan (38) for adjusting the combustion air whose rotation speed can be adjusted by a burner fan motor (38m). 2) A tension amount setting means (SW8, SE6) for setting or detecting a grain tension amount in the drying chamber (3) is provided, and a grain tension amount of the tension amount setting means (SW8, SE6) If the amount of the grain flow passage (9) is small enough not to be filled with the grain , the rotational speed of the burner fan motor (38m) is adjusted to decrease so that the rotational speed of the burner fan (38) is less than the standard rotational speed. Controller (41) for adjusting the predetermined rotational speed reduction Provided,
Exhaust air return amount adjusting means (22, 23) for adjusting the exhaust air circulation amount for returning the exhaust air discharged from the exhaust air chamber (8) by the exhaust fan (7) to the drying chamber (3) is provided,
In the case where the amount of grain in the tension setting means (SW8, SE6) is the quantity that the grain is filled in all of the grain flow down passages (9), the exhaust air return adjustment means (22, 23) Performs exhaust air circulation drying to adjust the exhaust air return amount to the final moisture value,
In the case where the amount of grain tension of the tension amount setting means (SW8, SE6) is a small amount in which all the grain flow passages (9) are not filled with grain, the predetermined moisture value is determined from the final moisture value from the initial stage of the drying operation. The exhaust air return amount adjusting means (22, 23) adjusts the exhaust air return amount to a high intermediate moisture value, and performs hot air drying that does not circulate the exhaust air from the intermediate moisture value to the finished moisture value. It is characterized by.

  According to the first aspect of the present invention, when the amount of grain inserted by the amount-of-insertion detecting means (SW8, SE6) is equal to or less than the predetermined amount, the rotational speed of the burner fan motor (38 m) is adjusted to be reduced and the burner fan ( 38) is adjusted to decrease the predetermined number of rotations below the standard number of rotations, so that in a small amount of dry drying operation, blow-off of dry air occurs in the drying chamber (3), and the amount of air passing through the burner (5) increases. In the small quantity combustion state of (5), there is a possibility that the combustion flame becomes lifted and the flame blows out, but the combustion flame is stabilized by lowering the rotational speed of the burner fan (38) than in the normal combustion state. be able to.

In addition, when the amount of grain squeezed by the amount setting means (SW8, SE6) is such that the grain is filled in all the grain flow passages (9), the exhaust air return amount adjusting means (22, 23) performs exhaust air circulation drying to adjust the exhaust air return amount to the finished moisture value,
In the case where the amount of grain tension of the tension amount setting means (SW8, SE6) is a small amount in which all the grain flow passages (9) are not filled with grain, the predetermined moisture value is determined from the final moisture value from the initial stage of the drying operation. The exhaust air return amount adjusting means (22, 23) adjusts the exhaust air return amount to a high intermediate moisture value, and performs hot air drying that does not circulate the exhaust air from the intermediate moisture value to the finished moisture value. When the grain moisture value of the initial drying operation is high, exhaust air circulation drying that considers energy saving is executed, and when there is a possibility that the moisture value decreases and the grain value is absorbed by approaching the finished moisture value, By stopping circulation drying and switching to hot air drying, the drying efficiency can be increased .

The external appearance perspective view of a grain dryer. The cutting front view of a grain dryer. The side view of a burner, a cutting | disconnection side view, and a rear view. The external appearance perspective view of the lower part of a grain dryer. The perspective view which shows the inside seen from the front of the grain dryer. The perspective view which shows the inside seen from the back surface of the grain dryer. The cutaway side view of an exhaust fan and an exhaust duct. The front view of an operation panel. Control block diagram. flowchart.

Embodiments of the present invention will be described below with reference to the drawings.
First, based on FIG.1 and FIG.2, the whole structure of the circulation type grain dryer which comprises this invention is demonstrated.

  Reference numeral 1 denotes a machine frame of a dryer. In the machine frame 1, a storage chamber 2, a drying chamber 3, and a grain collection chamber 4 are sequentially arranged from the upper side to the lower side. The drying chamber 3 is formed with a plurality of left and right grain flow passages 9, 9, and hot air leading to the burner wind tunnel 25 of the burner 5 on one side of the left and right grain flow passages 9, 9 (S direction in FIG. 1). A chamber 6 is disposed, and a wind exhaust chamber 8 leading to the fan body 7a of the exhaust fan 7 is disposed on the other side in the front-rear direction of the left and right grain flow passages 9, 9, and the lower ends of the left and right grain flow passages 9, 9 The parts are inclined down toward the center and merged to provide a feeding valve 10.

  Further, a far-infrared radiator 17 is disposed on the front side of the wind exhaust chamber 8 located in the middle part of the left and right grain flow passages 9 and 9. The far-infrared radiator 17 is formed in a square shape in front view and coated with a far-infrared radiation paint. The far-infrared radiator 17 faces the burner 5 with the front side facing the burner 5, passes through the exhaust chamber 8, and passes through the left and right grain flow passages 9 and 9. The grain is exposed to far-infrared radiant heat to promote grain drying. And by the reciprocating rotation of the said delivery valve | bulb 10, a grain is made to flow down, delivering a predetermined amount at a time, and a hot air is bathed and dried to a grain.

  On the outer side of the machine frame 1, an elevator 11 is erected to reduce the grains collected on the front and rear sides of the cereal collection chamber 4 to the storage chamber 2. Although not shown in the elevator 11, a bucket belt is wound around the upper and lower drive pulleys and driven pulleys, and the dried grain is transferred to the front and rear sides by the lower conveying device 14 provided at the bottom of the cereal collection chamber 4. 11 is configured to cereal. A rotary diffusion plate (the grain diffused by the elevator 11 is supplied from the elevator 11 to the starting end side of the upper transfer device 16 and is further fed laterally by the upper transfer device 16 and disposed in the upper central portion of the storage chamber 2. (Not shown) and diffused and dropped into the storage chamber 2 so as to be evenly stuck.

  The grain circulation system composed of the elevator 11, the lower transfer device 14, and the upper transfer device 16 is driven by an elevator motor (not shown) disposed on the upper frame of the elevator 11. In addition, a moisture meter 24 is provided on the wall surface of the elevator 11 in the middle of the upper and lower parts, and sample particles are taken in from intakes (not shown) provided at intervals between the ascending and descending strokes of the bucket belt of the elevator 11 to obtain the moisture value. It is configured to measure. The moisture meter 24 is a known device that compresses and pulverizes sample grains one by one between a pair of electrode rolls, and electrically converts the resistance value to convert the moisture value of each grain.

  Further, as shown in FIG. 3, the burner 5 is provided with a fuel supply electromagnetic pump 36, a burner vaporizing cylinder motor 37, a burner fan motor 38m, an igniter 39 and the like, and an ON / OFF signal of the fuel supply electromagnetic pump 36 and There are large and small supply signals, burner vaporizing cylinder motor 37 rotational speed command signal, burner fan motor 38m rotational speed command signal, igniter 39 energization signal, etc., and the fuel supply amount, combustion air supply amount, and vaporizing cylinder rotational speed are controlled synchronously. However, liquid fuel is vaporized and burned.

Next, a mixed circulation configuration of the dried exhaust air and hot air will be described with reference to FIGS.
The exhaust air supply duct 21 is branched from the exhaust duct 20 on the lower exhaust side of the exhaust fan 7, and the exhaust duct 20 is provided with a first circulation control valve 22 for adjusting the circulation air volume. It is configured to be adjustable. The exhaust air supply duct 21 is provided with a second circulation control valve 23 that can be adjusted by a second circulation control motor M7. The first circulation control valve 22 and the second circulation control valve 23 are opened and closed in a related manner so that the amount of circulating air flowing from the exhaust air duct 20 to the exhaust air supply duct 21 can be adjusted. In this embodiment, the generic name of the first circulation control valve 22 and the second circulation control valve 22 is referred to as an exhaust air amount regulator.

  Further, an exhaust air distribution case 26 is connected to the lower side of the exhaust air supply duct 21, and the returned exhaust air is dispersed in the left and right direction (t direction in FIG. 1) in the left and right exhaust air distribution cases 26, and the left and right hot air chambers 6. , 6 are supplied to the left and right return ducts 27, 27 arranged so as to penetrate through the inside, and the returned exhaust air is generated in the burner 5 in the mixing chamber K in the front duct 43 as shown by the arrows in FIG. The hot air is mixed and supplied to the hot air chamber 6 to dry the flowing grain in the left and right grain flowing passages 9 and 9.

Next, the drying action of the grain dryer will be described.
A predetermined amount of grain is put into the storage chamber 2 by using the elevator 11 from a holding hopper (not shown). Next, the drying operation is started by controlling the combustion with the combustion amount corresponding to the grain type, the dry finishing moisture value, the drying speed, the automatic detection or the manually set grain embedding amount. The grains in the storage chamber 2 are dried while being subjected to hot air while flowing down the left and right grain flow passages 9 and 9 of the drying chamber 3, and flow down to the collecting chamber 4. Further, when a part or almost all of the exhaust air is returned to the exhaust air supply duct 21 from the exhaust air duct 20 on the lower exhaust side of the exhaust fan 7, the returned exhaust air flows from the exhaust air distribution case 26. It flows into the left and right return ducts 27, 27, the moisture and heat quantity of the exhaust air are mixed with the hot air, and the grains flowing down the left and right grain flow passages 9, 9 are dried.

  The dried grain is transferred to one side in the front-rear direction by the lower transport device 14, then cerealed by the elevator 11, taken over by the upper transport device 16, and circulated again to the storage chamber 2, and has a tempering action for a while. receive. When the moisture value measured by the moisture meter 24 reaches the final moisture value while repeating such a process, the drying operation is finished.

Next, the operation panel 31 of the dryer will be described with reference to FIG.
On the lower side of the operation panel 31, a tension switch SW1, a ventilation drying switch SW2, a combustion switch of the burner 5 that starts the grain loading, and a drying switch SW3 that starts the drying operation by driving the feeding valve 10, A discharge switch SW4 for discharging the grains in the storage chamber 2 to the outside of the machine, a stop switch SW5 for stopping various driving of the machine body, and an emergency stop switch SW6 for stopping the driving of the dryer in an emergency are provided.

  In addition, on the upper left side of the board surface, a grain type setting switch SW7 for selecting the type of dry grain, a manual setting for the amount of extension or an amount setting switch SW8 for selecting automatic detection, and moisture for setting the finishing moisture value Various operation switches such as a value setting switch SW9, a drying speed switch SW10 for setting a drying speed, and a drying mode switch SW11 for setting a drying mode are provided, and a display unit 32 for digitally displaying various display items is provided on the right side of these switches. A display monitor 33 for displaying display items on the left side of the unit 32 is provided.

  As shown in FIG. 5, a controller (CPU) 41 is provided in a control box 45 (shown in FIG. 1) provided above the burner wind tunnel 25. As shown in FIG. 9, the switches SW1 to SW11 are connected to the input side of the controller 41, and the outside air temperature sensor SE1, hot air temperature sensor SE2, exhaust air temperature sensor SE3, moisture meter electrode temperature sensor SE4, moisture sensor SE5. , An extension amount detection device SE6, a load current sensor SE7 for detecting the load current value of the elevator motor, and the like are connected.

  Further, on the output side of the controller 41, an exhaust fan motor M1, an elevator motor M2, a feed valve motor M3, a burner drive means M4, a moisture meter drive means M5, a first circulation control motor M6, and a second circulation are provided via an output circuit. An adjustment motor M7 is connected, and a display unit 32 for displaying various display items digitally, a display monitor 33, an abnormality display monitor 33 for displaying various abnormalities of the dryer, and the like are connected via an output circuit.

  The burner drive signal of the controller 41 includes an ON / OFF signal and a large / small supply signal of the fuel supply electromagnetic pump 36, a rotation speed command signal of the burner vaporizing cylinder motor 37, a rotation speed command signal of the burner fan motor 38m, and an igniter 39 signal. There is an energization signal and the like, and the fuel supply amount, the combustion air supply amount, and the vaporization cylinder rotation speed are controlled synchronously to vaporize and burn the liquid fuel.

  Further, during the drying operation, the hot-air set temperature preset and stored is compared with the hot-air temperature detected by the hot-air temperature sensor SE2, and the electromagnetic pump for fuel supply that is periodically turned on so that the difference becomes small The drying operation is performed while changing and controlling the on-time signal of 36, and when the grain moisture reaches the target moisture value, the drying operation is stopped.

Next, the drying operation control will be described with reference to FIG.
The operation of inserting the grain into the storage chamber 2 is completed, and the amount of cultivated grain is manually set by the equipping amount setting switch SW8 (or the amount of cultivating grain is automatically detected by the equipping amount detection sensor SE6 and automatically set). When the drying switch SW3 is turned on (step S1), the drying operation is started (step S2). When the drying operation is started, driving of the elevator 11, the upper transfer device 16, the diffusing device, and the feeding valve 10 is started, and the combustion amount of the burner 5 is controlled based on the set drying rate and the amount of tension. The grains flowing down the grain flow passages 9 and 9 are fed to the cereal collection chamber 4 while being heated and supplied to the lower transfer device 14. The dried kernel is circulated and supplied to the storage chamber 2 and the drying chamber 3 via the lower transfer device 14, the elevator 11 and the upper conveyance device 16, and is predetermined from the kernel being crushed by the elevator 11 at predetermined intervals during the circulation. The sample number of grains is taken into the moisture meter 24 and the moisture value is measured (step S2).

  Next, a determination is made as to whether or not the amount of tension is equal to or less than the set amount (step S3). If Yes, the exhaust air regulator, that is, the first circulation controller, is determined based on a predetermined small amount of tension adjustment standard according to a command from the controller 41. The valve 22 and the second circulation control valve 23 are adjusted so that the amount of exhaust air is appropriately returned from the exhaust air duct 20 to the hot air chamber 6 via the exhaust air supply duct 21 to supply a fuel of a predetermined amount or less to the burner 5. Then, exhaust air circulation drying is executed (step S4).

  Next, the combustion drying operation in which the burner 5 is burned at every set time and the ventilation drying in which the combustion of the burner 5 is stopped are alternately executed (step S5), and then a set intermediate moisture value (for example, a predetermined amount higher than the finished moisture value) It is determined whether or not the measured moisture value of the moisture meter 24 has reached 18%) (step S6). If No, the process returns to step S5, and if Yes, the first circulation control valve 22 is fully opened and the second circulation control valve 23 is substantially fully closed so that there is almost no exhaust air return amount. Switching to drying (step S7). Next, it is determined whether or not the finish moisture value has been reached (Step S8). If No, the process returns to Step S7. If Yes, the combustion of the burner 5 is stopped, and the burner 5 for a predetermined time is stopped. When a predetermined time has passed and the burner 5 is cooled (step S11), the entire drive unit of the grain dryer is stopped and the drying operation is finished (step S12).

  Further, it is determined whether or not the tension amount is equal to or less than the set amount (step S3). If No, the first circulation control valve 22 and the second circulation control valve 23 are discharged based on a predetermined tension amount adjustment criterion. The air volume is returned from the exhaust duct 20 to the hot air chamber 6 via the exhaust air supply duct 21, and a large amount of fuel is supplied to the burner 5 to supply a predetermined amount of fuel, and exhaust air circulation drying is executed (step S9). Next, it is determined whether or not the finish moisture value has been reached (Step S10). If No, the process returns to Step S10. If Yes, the combustion of the burner 5 is stopped and the burner cooling process for a predetermined time is performed. Is executed (step S11), and when the predetermined process is completed, the entire drive unit of the grain dryer is stopped and the drying operation is completed (step S12).

The technical concept of the drying operation in the flowchart of FIG. 10 will be described.
In the case of performing a small amount of dry drying in which all of the drying net portions of the left and right grain flow passages 9 and 9 of the drying chamber 3 are not filled with grains, the vicinity of the finish is higher than the finish moisture value from the initial stage of the drying operation. Between the moisture value (for example, 18%), exhaust air circulation drying is performed by circulating the exhaust air and mixing the exhaust air and hot air, and the moisture value near the finish (18%) to the finished moisture value (for example, 15%). In the meantime, exhaust air circulation drying is stopped and finish drying is performed by hot air drying.

  When a drying test was performed, in a small amount of dry drying in which all of the drying net portions of the left and right grain flow passages 9 and 9 of the drying chamber 3 are not filled with grains, the moisture value is discharged until the moisture value is close to the finished moisture value. When wind circulation drying was continued, it was found that the grains absorb moisture instead of drying and the drying efficiency decreases. According to the above configuration, when the grain moisture value of the initial drying operation is high, exhaust air circulation drying that considers energy saving is performed, and when the moisture value decreases as the moisture value approaches the final moisture value, the grain may absorb moisture. By stopping the exhaust air circulation drying and switching to the hot air drying, it is possible to avoid the above problems and increase the drying efficiency while performing the energy saving operation.

Next, one example will be described.
When performing a small amount of dry drying in which all the drying net portions of the left and right grain flow passages 9 and 9 of the drying chamber 3 are not filled with grains, the combustion drying operation in which the burner 5 is burned and the combustion of the burner 5 are performed. Stopped ventilation drying is executed alternately every set time. Then, at the end of the drying operation, when the combustion of the burner 5 is stopped and the cooling process of the burner for a predetermined time is executed, the adjustment states of the first circulation control valve 22 and the second circulation control valve 23 at the time of the drying operation are kept as they are. Maintaining and maintaining the exhaust air circulation state, the opening adjustment of the first circulation control valve 22 and the second circulation control valve 23 is stopped, and the exhaust air circulation state is not stopped.

  If it is dry with a small amount, the whole grain circulates in a short time, and the first circulation control valve 22 and the second circulation control valve 23 that have been closed so far are opened at once in the cooling process of the burner. If adjusted, the humidity of the dry wind may decrease and the grain may crack. However, according to the said structure, such a malfunction can be prevented.

  Next, a control example of the burner 5 of this embodiment will be described. When performing a small amount of dry drying in which all the drying net portions of the right and left grain flow passages 9, 9 of the drying chamber 3 are not filled with grain, a rotation speed reduction command is output to the burner fan motor 38m, and the burner 5 The rotation speed of the burner fan 38 that sends the combustion air to the engine is reduced by a predetermined rotation speed (for example, 50 rpm) with respect to the standard rotation speed.

  In the drying operation with a small amount of filling, dry air blows out from the left and right grain flow passages 9, 9, so that the amount of air passing through the burner 5 increases, and in the minimum combustion state of the burner 5, the combustion flame becomes lifted, and the flame Blowout and backfire may occur. However, the combustion flame can be stabilized by lowering the rotational speed of the burner fan 38 than in the normal combustion state.

  In the case of performing a small amount of dry drying in which all of the drying net portions of the left and right grain flow passages 9 and 9 of the drying chamber 3 are not filled with grains, if non-ignition occurs when the burner 5 is ignited, the burner fan motor 38m When the rotational speed is decreased and the rotational speed of the burner fan 38 is lowered by a predetermined rotational speed (for example, 50 rpm) from the standard rotational speed, and the ignition of the burner 5 is confirmed, the predetermined time (for example, 5 minutes) remains unchanged. The rotation speed may be continued, and the rotation speed of the burner fan 38 may be returned to the normal rotation speed after a predetermined time has elapsed.

  In a small amount of dry drying, dry air blows out from the left and right grain flow passages 9, 9, so that the amount of air passing through the burner 5 increases and ignition is difficult. In addition, it is difficult to determine from the outside of the machine whether there is blow-through. According to the above-described configuration, when the ignition is not performed when the burner 5 is ignited, it is assumed that the drying air in the drying chamber 4 is blown off, and the rotational speed of the burner fan 38 is automatically reduced below the normal combustion state. Problems with poor ignition can be avoided.

  When the outside air temperature sensor SE1 detects a reference low temperature (for example, 10 degrees C) or less, the rotation speed of the burner fan 38 is decreased by a predetermined number of rotations (for example, 50 rpm) from the standard rotation speed, and the flame detection sensor detects When the ignition is confirmed by the information, the burner fan 38 is rotated at the low rotation speed as it is for a predetermined time (for example, 10 minutes), and is returned to the high standard rotation speed after the predetermined time has elapsed.

  When the temperature is low, it is difficult for the fuel to vaporize, resulting in poor ignition of the burner 5. However, according to the above configuration, the ignitability of the burner 5 can be improved, and the burner fan 38 is rotated at a low rotation speed for a predetermined time after the burner 5 is ignited. Smooth combustion can be continued while avoiding the adhesion of.

  Next, another control example will be described. When performing a small amount of dry drying in which all of the drying net portions of the left and right grain flow passages 9 and 9 of the drying chamber 3 are not filled with grains, the exhaust air circulation is used until a predetermined time has elapsed from the initial stage of the drying operation. Exhaust air circulation drying in which exhaust air and hot air are mixed is executed, and when a predetermined time has elapsed, exhaust air circulation drying is stopped, and hot air drying is switched to finish drying. The predetermined time can be set to be longer or shorter depending on the difference between the initial moisture value and the finished moisture value.

  When the exhaust air circulation drying is continued in a state where the drying net is not filled in all the drying net portions of the left and right grain flow passages 9 and 9 of the drying chamber 3, the grains in the drying chamber 3 and the storage chamber 2 are removed. It becomes highly humid and the grain below the left and right grain flow passage 9.9 in the drying chamber 3 becomes difficult to dry, and at some point the grain temperature falls below the grain temperature in the storage chamber 2 and absorbs moisture. Condensation may occur. However, according to the said structure, a drying efficiency can be improved, avoiding such a malfunction and carrying out an energy-saving operation.

  Alternatively, when performing a small amount of dry drying in which all the drying net portions of the left and right grain flow passages 9, 9 of the drying chamber 3 are not filled with kernels, the exhaust air is not returned to the hot air chamber from the beginning of the drying operation. It is good also as a structure of the drying control which controls an exhaust air quantity regulator and performs the drying operation and ventilation operation which are shown in FIG. 10 alternately to a finishing moisture value.

DESCRIPTION OF SYMBOLS 1 Grain dryer 2 Storage room 3 Drying room 4 Grain collection room 5 Burner 6 Hot air room 7 Exhaust fan 8 Exhaust room 9 Grain flow lowering path 22 Exhaust air return amount adjustment means 23 Exhaust air return amount adjustment means 38 Burner fan 38m Burner fan motor 39 Igniter 41 Controller SW8 Tension amount setting means (Tension amount setting switch)
SE6 Stretching amount setting means (stretching amount detection device)

Claims (1)

A drying chamber (3) provided with a grain flow passage (9) through which the grain flows down;
Dry hot air generated by mixing the hot air generated by the burner (5) and the outside air is sent to the drying chamber (3) by the exhaust fan (7) to dry the grain, and the hot hot air is passed through the exhaust chamber (8). In the grain dryer which is discharged to the outside through the machine, the burner (5) is provided with a burner fan (38) for adjusting the combustion air whose rotation speed can be adjusted by a burner fan motor (38m). 2) A tension amount setting means (SW8, SE6) for setting or detecting a grain tension amount in the drying chamber (3) is provided, and a grain tension amount of the tension amount setting means (SW8, SE6) If the amount of the grain flow passage (9) is small enough not to be filled with the grain , the rotational speed of the burner fan motor (38m) is adjusted to decrease so that the rotational speed of the burner fan (38) is less than the standard rotational speed. Controller (41) for adjusting the predetermined rotational speed reduction Provided,
Exhaust air return amount adjusting means (22, 23) for adjusting the exhaust air circulation amount for returning the exhaust air discharged from the exhaust air chamber (8) by the exhaust fan (7) to the drying chamber (3) is provided,
In the case where the amount of grain in the tension setting means (SW8, SE6) is the quantity that the grain is filled in all of the grain flow down passages (9), the exhaust air return adjustment means (22, 23) Performs exhaust air circulation drying to adjust the exhaust air return amount to the final moisture value,
In the case where the amount of grain tension of the tension amount setting means (SW8, SE6) is a small amount in which all the grain flow passages (9) are not filled with grain, the predetermined moisture value is determined from the final moisture value from the initial stage of the drying operation. The exhaust air return amount adjusting means (22, 23) adjusts the exhaust air return amount to a high intermediate moisture value, and performs hot air drying that does not circulate the exhaust air from the intermediate moisture value to the finished moisture value. grain dryer and said.

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