JP4696940B2 - Grain dryer - Google Patents

Description

  The present invention relates to a grain dryer.

Patent Document 1 describes a technique for reducing a part of exhaust air to a burner part. And the channel | path which reduces exhaust air is provided above the burner part from the upper direction of the exhaust fan.
JP-A 61-195266

  An object of the present invention is to perform a drying operation using exhaust air efficiently.

In order to solve the above problems, the present invention has taken the following technical means.
That is, in the invention according to claim 1, the combustion device (4) for generating hot air for drying the grain, the hot air chamber (13) through which the hot air generated by the combustion device (4) passes, and the grain are dried. A wind exhaust chamber (15) into which hot air that has absorbed moisture in the grain flows, and a wind exhaust fan (7) that sucks the hot air flowing into the wind exhaust chamber (15) and discharges it as exhaust air; Grain dryer provided with a control valve (22) for adjusting the ratio of exhaust air exhausted from the exhaust air fan (7) to the outside of the machine and exhaust air circulating to the hot air chamber (13) side , The ratio of circulating the exhaust air to the hot air chamber (13) is lowered as the outside air temperature is higher , and the ratio of the exhaust air circulating to the hot air chamber (13) is controlled to be lower as the amount of grain is increased. It is set as the grain dryer characterized by providing the control part which performs.

  In the present invention, by simultaneously reducing the heat and moisture contained in the exhaust air to the hot air path, the moisture to be removed from the surface of the grain is suppressed by the moisture contained in the exhaust air, so By making the moisture gradient constant, it becomes difficult to break the grain, and by giving extra heat during exhaust air, the grain temperature is raised in a short time, thereby enabling high-speed drying.

  Further, when the outside air temperature is low, the exhaust air can be efficiently used to raise the grain temperature and the drying operation can be performed, but the rise to the grain temperature to the extent that the grain is damaged can be prevented.

As one of the best modes for carrying out the present invention, a grain dryer will be described in detail.
The grain dryer includes a multi-stage box 1 that contains grains, and the front side of the box 1 is a combustion burner containing chamber 5 that includes an elevator 2 that raises grains and a combustion burner 4 that generates hot air. And an operation panel 6 provided with various switches for operating the drying operation, and the ceiling side of the box 1 is provided with a transport device 3 for conveying the grains cerealed by the elevator 2 to the inside of the box 1, and the box 1 Is provided with an exhaust fan 7 for sucking hot air in the box 1, and an opening / closing door 19 a for opening and closing a slot 19 for feeding grains is provided on the side of the box 1. The elevator 2 is provided with a moisture meter 9 for detecting the moisture of the grain and a grain outlet 18 for discharging the grain in the box 1 to the outside of the machine. 3 is provided with a dust collecting device 50 that collects dust and other foreign matters mixed in the grain conveyed. The operation panel 6 also includes a control unit that controls the drying operation.

In the box 1, a storage chamber 10 is provided in the upper stage, and a drying chamber 11 is provided in the lower stage.
In the upper part of the storage chamber 10, there is provided a diffusion blade 12 that diffuses the grains conveyed by the upper spiral 3 a in the conveying device 3 into the storage chamber 10. The drying chamber 11 includes a hot air chamber 13 through which hot air generated by the combustion burner 4 passes, a downflow passage 14 through which grains flow down from the storage chamber 10, and an exhaust air chamber 15 that receives the suction action of the exhaust air fan 7. Is done. Note that the combustion surface 4 a of the combustion burner 4 is configured to face the hot air chamber 13. A rotary valve 16 is provided at the lower end portion of the flow-down passage 14 to feed the grains that have flowed down the flow-down passage 14 by a predetermined amount. A spiral 17 is provided. The exhaust side of the exhaust fan 7 and the combustion burner storage chamber 5 are connected by a reduction passage 20.

  The reduction passage 20 is attached to the discharge side of the exhaust fan 7, and a control valve 22 that adjusts rotation in the front-rear direction and a first dust storage portion that is formed in a recess at the bottom of the reduction passage 20. 20a is provided. And the reduction | restoration channel | path 20 is made into the structure which penetrates the inside of the hot air chamber 13 in the box 1 from the downward direction of the exhaust fan 7, and is connected to the combustion burner accommodation chamber 5 provided above the terminal part of the reduction | restoration channel | path 20. A second dust storage portion 20b formed in the recess is provided at the bottom of the terminal end of the reduction passage 20. 20c is a cleaning port for the operator to take out the dust stored in the first dust storage unit 20a. Further, the second dust storage portion 20b is configured to be pulled out on the front side. That is, the first dust storage unit 20a and the second dust storage unit 20 are both provided outside the box 1 so that the operator can easily remove the stored dust. Further, the heat of exhaust air can be kept warm by penetrating the inside of the hot air chamber 13 through the reduction passage 20.

An outside air inlet 31 composed of a large number of slits is provided on the front side of the burner housing chamber 5.
A control valve 22 is provided in the reduction passage 20, and a part of the exhaust air is reduced from the state in which all of the exhaust air is reduced to the reduction passage 20 side (solid line in FIG. 1) (the two-dotted line in FIG. 1). ) In such a manner that the degree of opening can be freely adjusted in the front-rear direction, so that the ratio of the exhaust air discharged from the exhaust fan 7 to the outside and the reduction to the hot air chamber 13 can be adjusted. . Further, the control valve 22 is formed in a disc shape, and the lower part rotates toward the rear side and the upper part rotates toward the front side, thereby serving as a guide plate that guides the exhaust air toward the reduction passage 20. And is configured to be rotated by the drive motor 33.

  An exhaust air temperature sensor (not shown) for detecting the temperature of the exhaust air discharged by the exhaust air fan 7 and an exhaust air humidity sensor (not shown) for detecting the relative humidity of the exhaust air are provided in the reduction passage 21. And are provided.

In the grain dryer of the present embodiment, although not shown, an outside air temperature sensor for detecting the outside air temperature and an outside humidity sensor for detecting outside air humidity are provided.
The operation panel 6 will be described. Although not shown, a setting amount setting switch, a finished moisture setting switch, a grain type setting switch, a tension start switch, a ventilation start switch, a drying start switch, a discharge start switch, a stop A switch 67 and various numerical value display boards are provided.

Next, the drying operation will be described.
The operator operates the tension start switch to open the open / close door 19 a and throw grains into the slot 19. The input grain is supplied to the lower spiral 17 and conveyed to the elevator 2, and is supplied from the elevator 2 to the storage chamber 10 through the conveyance device 3. When the drying start switch is operated after the grain has been charged, the combustion burner 4 is activated, a flame is generated on the combustion surface 4a, and hot air is supplied to the hot air chamber 13. On the other hand, the rotary valve 16 also starts to drive, and the grains that flow down the flow-down passage 14 are sequentially fed out to the lower spiral 17. The hot air supplied to the hot air chamber 13 passes through a plurality of slits (not shown) formed in the hot air chamber body 13 a forming the hot air chamber 13 and flows into the downflow passage 14. Then, moisture in the flowing grain is taken away and flows into the exhaust chamber 15. Then, the hot air flowing into the exhaust chamber 15 is sucked by the exhaust fan 7 and discharged to the reduction passage 20 as exhaust air.

  The exhaust air discharged into the reduction passage 20 is blocked by the control valve 22 and flows downward, and is discharged toward the combustion burner housing chamber 5 on the front side of the dryer, and the dust contained in the exhaust air in the middle of the exhaust is on the conveyance start side. Are dropped and stored in the dust storage chamber 20a and the dust storage chamber 20b on the conveyance end side.

Next, a method for controlling the opening degree of the control valve 22 will be described.
The outside air temperature detected by the outside air temperature sensor is 20 ° C., the outside air humidity detected by the outside air humidity sensor is 70%, and the absolute humidity (Z) calculated by the control unit is 13 g / m 3. The exhaust wind (Y) as a control target is, for example, the case where the exhaust air temperature is 30 ° C., the exhaust air humidity is 70%, and the absolute humidity (U) is 25 g / m 3. And the air volume of the exhaust fan 7 of a present Example is 1900 kg / h, the quantity of the grain (rice cake) supplied to the grain dryer is 800 kg, and a drying rate (ratio of the moisture dried per hour) Is 1.2% / h, the rate of exhaust air to be reduced to the hot air chamber 13 is obtained from the following equation.

Absolute humidity (U)-Absolute humidity (Z) = 12 (g / m3) (B)
The maximum amount of water that can be absorbed by outside air is 12 x 1900/1000 ≒ 23 (kg) (B)
The amount of water removed from the dryer per hour is 800 (kg) × 1.2 (% / h) = 9.6 (kg / h) (C)
From the formulas (b) and (c), 23 / (9.6 + 23) ≈0.71 → 71% (2)
In other words, the control valve 22 is adjusted to reduce 71% of the amount of exhaust air discharged from the exhaust fan 7 to the hot air chamber 13.

  In addition, when the control valve 22 is adjusted so as to reduce an amount larger than 71% of the exhausted air amount to the hot air chamber 13, the more water is reduced, the more water is reduced. It becomes difficult to remove. In addition, when the control valve 22 reduces an amount less than 71% of the exhausted air amount to the hot air chamber 13, the amount of heat reduced to the hot air chamber 13 decreases, so that it is difficult to increase the temperature of the grain and the drying speed is increased. Become slow.

  By adjusting the opening ratio of the control valve 22 based on the expression of the present embodiment and adjusting the ratio of reducing the exhaust air to the hot air chamber 13, the heat generated by the exhaust air discharged from the exhaust fan 7, that is, A drying operation with good combustion efficiency can be performed by properly utilizing the water absorption force as much as possible.

The drying control according to the present embodiment will be described in more detail. The outside air temperature sensor and the outside air humidity sensor detect the outside air temperature and humidity, the control unit calculates the outside air absolute humidity, and the outside air absolute humidity and the grain. Comparing the absolute humidity of the exhaust air at the relative humidity and the temperature to compare with the absolute humidity of the exhaust air set in advance from the conditions of moisture and the absolute humidity of the outside air Calculated as water absorption. On the other hand, the amount of water evaporated from the dryer by the drying operation (in this embodiment, the amount of water removed from the dryer per one hour as described above) was obtained, and the increased amount of water was added to the amount of water evaporated by the drying operation. The ratio to the value is considered as the ratio that can reduce the exhaust air. That is, the above formula (d) is the amount of increased water / (the amount of increased water + the amount of evaporated water)
Is shown.

  In conventional hot air drying, every time the moisture on the surface of the grain is removed, the moisture inside the grain is dried by utilizing the property that the water moves using heat conduction to sequentially appear on the surface of the grain. In the exhaust air drying according to the present embodiment, the moisture difference between the grain surface and the inside increases when the drying is rapidly performed at a high temperature in order to perform high-speed drying. By simultaneously reducing the heat and moisture contained in the exhaust air to the hot air path, the moisture to be removed from the grain surface is suppressed by the moisture contained in the exhaust air, and the moisture gradient inside the grain is kept constant. By making it difficult to break the grain, it is possible to dry at high speed by raising the grain temperature in a short time by giving extra heat during exhaust air.

  FIG. 5 is a graph showing the relationship between the outside air temperature and the exhaust air circulation rate, where a to e show curves for different amount of tension, and the amount of tension increases from a to e. As shown in FIG. 5, when the outside air temperature exceeds about 40 ° C., it is not necessary to reduce the exhaust air, and as the outside air temperature decreases, the circulation rate of the exhaust air is increased to increase the grain temperature. And the ratio which exhaust air discharges | emits out of the machine with the adjustment valve 22, and the ratio which returns to the hot air chamber 13 are controlled so that it may change with external temperature. For example, when the outside air temperature is about 10 ° C., the control valve 22 is adjusted so that the ratio of the amount of exhaust air returned to the hot air chamber 13 is about 70%. When the outside air temperature is close to 35 ° C., most of the exhaust air is discharged outside the machine. It is set as the structure discharged | emitted out of the machine from the passage 23. According to this configuration, when the outside air temperature is low, the exhaust air is efficiently used to raise the grain temperature and the drying operation can be performed, but the grain temperature is increased to a grain temperature (for example, 35 ° C. or more) so that the grain is damaged. Can be prevented.

FIG. 6 is a graph showing the relationship between target absolute wind exhaust humidity and grain moisture.
The absolute humidity (U) of the exhaust air (Y), which is the reference for the control target, may be arbitrarily set according to the grain temperature and grain moisture based on the graph of FIG. It is good also as a structure which changes in a control part automatically according to the change of external temperature.

  By the way, the control valve 22 of the reduction passage 20 is set to a position on the side where the exhaust air is discharged to the outside discharge passage 23 side when the drying operation is started. That is, in the case of the combustion burner 4, exhaust air is not circulated until the combustion burner 4 rises and the combustion state is stabilized. Then, after the combustion state is stabilized, the control valve 22 is switched to reduce and circulate the exhaust air to the hot air chamber 13, so that the exhaust air when the combustion in the initial stage of drying is not stable enters the hot air chamber 13. Intrusion can be prevented. In this case, it is the time from when the grain in the storage chamber 10 is dried and returned to the storage chamber 10 again as the timing for starting the reduction / circulation of the exhaust air. For example, the combustion burner 4 starts combustion. The control valve is controlled after a set time has elapsed.

  The exhaust air flowing into the side of the combustion burner storage chamber 5 from the reduction passage 20 and the hot air chamber 13 from the rear side of the combustion burner 4 together with the outside air flowing in from the outside air intake 5 a provided on the front side of the combustion burner storage chamber 5. To be supplied. In the case of the combustion burner 4, if exhaust air is supplied to the side or front of the combustion surface 4 a, fluctuations in the amount of outside air flow will increase and the combustion flame will be disturbed and combustion will become unstable. Since the exhaust air and the outside air are supplied from the rear side of the burner 4, that is, from the direction opposite to the combustion surface 4a, it is possible to prevent the flame of the combustion surface 4a from being disturbed. In addition, it is possible to circulate the exhaust air while introducing a substantially constant amount of outside air without requiring a damper or the like for blocking outside air.

One embodiment of the present invention will be described.
After the operation of the combustion burner 4 is started and the combustion state is stabilized, the control valve 22 is fully closed to reduce the exhaust air in the reduction passage 20 to the combustion burner storage chamber 5. When the exhaust air humidity sensor 25 detects the relative humidity of the exhaust air every predetermined time and detects that the relative humidity of the exhaust air has reached a preset upper limit relative humidity (for example, 90%), the adjustment is performed. When it is detected that the relative humidity detected by the exhaust air humidity sensor 25 has dropped to a lower limit relative humidity (for example, 70%) or less after that, the valve 22 is operated in the opening direction to exhaust the exhaust air to the outside. The control valve 22 is closed and the exhaust air is circulated. With this configuration, the exhaust air is discharged after absorbing a large amount of moisture, the exhaust air having increased humidity is discharged, the control valve 22 is closed again, and the exhaust air is circulated. Good exhaust air circulation.

Next, the control of the control valve 22 at the end of the drying operation will be described.
When it is detected that the grain has reached the set moisture and the drying operation is finished, the control valve 22 is controlled in the direction to open sequentially. By gradually increasing the amount of exhausted air discharged outside the machine, immediately after the drying operation is completed, a large amount of the exhausted air is circulated to cool the reduction passage 20 and the amount of exhausted air exhausted to the outside of the machine sequentially increases. Thus, the hot air chamber 13 can be cooled.

Side view of grain dryer Rear view of grain dryer Front view of grain dryer Cross section of the grain dryer as seen from the front A diagram showing the relationship between the exhaust circulation rate and the outside air temperature Diagram showing the relationship between grain moisture and absolute exhaust humidity

4 Combustion device (combustion burner)
7 Exhaust fan 13 Hot air chamber 15 Exhaust chamber 20 Reduction passage 22 Control valve 20a 20b Dust storage part

Claims (1)

Combustion device (4) for generating hot air for drying the grains, hot air chamber (13) through which the hot air generated by the combustion device (4) passes, and hot air for drying the grains and absorbing moisture in the grains The exhaust air chamber (15) into which the air flows, the exhaust air fan (7) that sucks the hot air flowing into the exhaust air chamber (15) and discharges it as exhaust air, and the exhaust air discharged from the exhaust air fan (7). In the grain dryer provided with the regulating valve (22) for adjusting the ratio of the exhausted air that exhausts the wind to the outside and the exhausted air that circulates to the hot air chamber (13) side,
Control to reduce the rate of exhaust air circulating to the hot air chamber (13) side as the outside air temperature is higher and to reduce the rate of exhaust air circulating to the hot air chamber (13) side as the amount of grain is increased The grain dryer characterized by providing the part.

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