JP2009109137A - Drying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continually and stably carry out a drying method for carrying out high-speed drying and preventing breaking of grains. <P>SOLUTION: A control part (F1) is provided, outputting a signal reducing exhaust air return amounts with respect to adjusting devices (22, 23) when it is detected that an absolute humidity (HD) of drying air has reached an absolute humidity (HF) in a saturated vapor pressure or it has exceeded an upper limit absolute humidity (β×HF) set in a neighborhood of the absolute humidity (HF), and outputting a signal increasing the exhaust air return amounts with respect to the adjusting devices 22, 23 when it is detected that the absolute humidity (HD) of the drying air is lesser than a lower limit absolute humidity (α×HF) set a predetermined value lower than the absolute humidity (HF) in the saturated vapor pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drying device for agricultural products such as grains and shiitake mushrooms, marine products, or wood.

Patent Document 1 describes a drying apparatus that returns exhaust air and joins it with hot air to dry it.
Further, in Patent Document 2 and Patent Document 3, when the mixing ratio of exhaust hot air at the initial stage of drying is high, the amount of exhaust hot air to be reused is small. It describes the contents that increase the amount of exhaust hot air to be used.
JP 2007-10247 A JP-A 61-195266 Japanese Patent No. 2599270

  Patent Document 1 describes the content of adjusting the amount of exhaust air as much as possible to reach the target exhaust absolute humidity, but does not describe what exhaust air absolute humidity should be used for drying.

Moreover, in patent document 2 and patent document 3, there is no description about the technique which shortens drying time.
It is an object of the present invention to continuously and stably carry out a drying method of drying at high speed and preventing cracking of the grain.

In order to solve the above problems, the present invention has taken the following technical means.
That is, the invention according to claim 1 includes a drying section (3) that dries hot air for drying on an object to be dried, and a return passage (41) that joins exhaust air that has passed through the drying object with the hot air for drying. 44) and an adjustment device (22, 23) for adjusting the return amount of the exhaust air, the drying air in the drying chamber (13) of the drying hot air and the combined air of the exhaust air in the drying chamber (13) A first calculation unit for calculating humidity (HD), a second calculation unit for calculating absolute humidity (HF) at the saturated water vapor pressure of the dry wind, and absolute humidity at the absolute humidity (HD) of the dry air and the saturated water vapor pressure. A comparison unit for comparing (HF), and an absolute humidity (HD) of the drying wind reaches an absolute humidity (HF) at a saturated water vapor pressure or an upper limit absolute humidity (β · HF) is detected A signal for decreasing the exhaust air return amount is output to the adjusting devices (22, 23), and the absolute lower limit absolute value in which the absolute humidity (HD) of the dry air is set lower than the absolute humidity (HF) at the saturated water vapor pressure. When it is detected that the humidity (α · HF) is lower, the drying device is provided with a control unit (F1) that outputs a signal for increasing the exhaust air return amount to the adjusting devices (22, 23). .

  The invention according to claim 2 is a drying section (3) for drying by applying a hot air for drying to an object to be dried, and a return passage (41, 44) for combining the exhaust air after passing through the object to be dried with the hot air for drying. ) And an adjustment device (22, 23) for adjusting the return amount of the exhaust air, the moisture meter (10) for detecting the moisture of the drying object being dried, and the moisture meter (10) A virtual absolute humidity calculating unit that calculates the virtual absolute humidity (U) of the exhaust air based on the detected moisture value of the dry object, and the return path (41, 44) corresponding to the virtual absolute humidity (U). A setting unit that presets an exhaust air return amount for returning exhaust air or an exhaust air return ratio with respect to the total exhaust air amount, and a control unit that operates the adjusting devices (22, 23) to the set exhaust air return amount or exhaust air return ratio. A drying apparatus provided with (F2) is provided.

  According to a third aspect of the present invention, in the second aspect of the present invention, the detection unit for detecting the outside air absolute humidity input to the control unit (F2) is provided, and the exhaust air return amount or the exhaust air return is changed according to the fluctuation of the outside air absolute humidity. The ratio is corrected. According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the dryness of the dry object is calculated based on the moisture detection result of the dry object input to the control unit (F2). A rate calculating unit is provided to correct the exhaust air return amount or exhaust air return ratio in accordance with the fluctuation of the drying rate.

  In the first aspect of the invention, the absolute humidity (HD) of the dry wind reaches the absolute humidity (HF) at the saturated water vapor pressure or exceeds the upper limit absolute humidity (β · HF) set in the vicinity of the absolute humidity (HF). When it is detected, it outputs to the adjusting device (22, 23) so as to reduce the exhaust air return amount, so that it dehydrates beyond the saturated water vapor pressure and dries so that the quality of the dried object is not impaired and dried. When the absolute humidity HA in the section (3) falls below the absolute humidity (α · HF) set lower than the absolute humidity (HF) at the saturated water vapor pressure, the exhaust air return amount is increased to the adjusting device (22, 23). Because it outputs the heat and moisture contained in the exhaust air to the object to be dried, it supplies a large amount of heat to the inside of the object to be dried, and the moisture to be evaporated from the surface of the object to be dried. Absorb from dry object The moisture gradient inside the dried object can be reduced by suppressing the dried object by the moisture in the exhausted air. Therefore, it is possible to make it difficult to cause cracks or the like inside the object to be dried while being dried at high speed.

  In the invention according to claim 2, it is necessary for the surface of the object to be dried by supplying to the drying section (3) the amount of exhaust air containing a large amount of water even in the early stage of drying when the moisture value of the object to be dried is high. Heat can be given while giving proper moisture. Therefore, since the temperature inside the drying object is raised while keeping the moisture gradient inside the drying object small, it is possible to perform high-speed drying with little shell cracking. Moreover, the humidity sensor which detects the humidity of an exhaust wind is not required by adjusting the amount of the exhaust wind returned to a drying part (3) according to the moisture value of the grain detected with a moisture meter (10), and cost is high. In addition, the durability is improved without the humidity sensor being exposed to dust and being consumed.

  In the invention described in claim 3, since the exhaust air return amount or the exhaust air return ratio is increased / decreased according to the change in the outside air absolute humidity (HA), the amount of water return required to follow the change in the outside air It is possible to continue the drying process while correcting to. In the invention of claim 4, since the exhaust air return amount or the exhaust air return ratio is corrected to increase / decrease in accordance with the fluctuation of the drying rate, similarly, even if the drying rate changes, The drying process can be continued while correcting the return amount.

The case where this Embodiment is used for a grain dryer is demonstrated.
1 and 2 are diagrams showing the whole of the grain dryer, and FIG. 3 is a perspective view for explaining the inside of the grain dryer, and a storage unit 2 for storing the grain from above in a rectangular parallelepiped main body 1. The drying unit 3 that dries the grains stored in the storage unit 2 while flowing downward, and the cereal collection unit 4 that collects the dried grains in the drying unit 3 are provided. And the grain stuck in the storage part 2 is dried by the drying part 3 and supplied to the cereal collecting part 4, and the structure of what is called a circulation type grain dryer of the structure supplied to the storage part 2 and tempered again. It is.

In the present embodiment, the longitudinal direction s of the main body 1 is referred to as the front-rear direction, and the short direction t is referred to as the left-right direction.
A burner case 40 having a large number of slit-like outside air intake ports 50 formed on the front side is attached to the front side in the front-rear direction of the main body 1 and in the middle of the left and right sides facing the drying unit 3. Is arranged. The combustion burner 5 is placed so that the combustion disc surface 5d of the combustion burner 5 faces the main body 1 side.

On the rear side in the front-rear direction of the main body 1, a wind exhaust fan 6 is provided at the left and right center position facing the drying unit 3.
Further, an elevator 7 for raising the grain is provided at a position adjacent to the burner case 40 on the front side in the front-rear direction of the main body 1, and a transfer spiral (not shown) is provided on the upper portion of the main body 1. An upper conveying device 8 that conveys the cerealed grains to the storage unit 2 and a dust suction fan 9 that sucks and removes foreign matters such as scum mixed in the grains being conveyed by the upper conveying device 8 are provided.

  10 is a moisture meter that detects the moisture of the grain. The moisture meter is attached to the elevator 7 and calculates the moisture value by taking in the sample grain from the grains being grained and detecting the electrical resistance value for each grain every set time. To do.

  The drying unit 3 is provided with hot air chambers 11 through which dry hot air generated by the combustion burner 5 passes on both left and right sides of the main body 1, and is provided with exhaust air chambers 12 communicating with the exhaust fan 6 at the left and right central portions of the main body 1. A grain flow passage 13 is provided between the chamber 11 and the air discharge chamber 12, and a rotary valve 14 that feeds the grain to the grain collection unit 4 is provided at the lower end of the grain flow passage 13. Therefore, the grains in the storage chamber 2 pass through sequentially.

The cereal collection unit 4 is provided with a lower spiral 15 that conveys the grains to the elevator 7.
The exhaust fan 6 includes an axial flow type fan blade 6b and a fixed plate 6c that applies pressure to the exhaust air generated by the fan blade 6b inside the circular fan body 6a. A discharge duct 20 having a circular cross section is connected to the discharge side.

As shown in FIGS. 6 and 7, a first control valve 23 is provided in the exhaust duct 20 to adjust the ratio of the amount of exhaust air discharged to the outside of the exhaust duct 20 and the exhaust air supply duct 21.
An exhaust air supply duct 21 having a square cross section for supplying exhaust air to the inside of the main body 1 is provided at the upper part of the exhaust air duct 20, and the exhaust air inlet of the exhaust air supply duct 21 is supplied into the exhaust air supply duct 21. A second control valve 22 is provided for adjusting the amount of exhausted air.

  The first control valve 23 and the second control valve 22 are configured to be rotated by a horizontal axis pivot shaft 23a and a pivot shaft 22a, respectively, of which the control valve drive motor 25 is connected to the pivot shaft 23a. Yes. The 1st control valve 23 and the 2nd control valve 22 are connected with the connection rod 24, and it is set as the structure which the rotation operation of the 1st control valve 23 and the 2nd control valve 22 interlock | cooperates. When the second control valve 22 is in the fully closed position ga and exhaust air is not discharged into the exhaust air supply duct 21, the first control valve 23 is in the fully open position fa and all exhaust air is discharged outside the machine.

  On the other hand, when the second control valve 22 is in the fully open position gb and the exhaust air is discharged most into the exhaust air supply duct 21, the first control valve 23 exhausts the most exhaust air. It is located at the closed position fb for discharging the exhaust air to the wind supply duct 21 side. In addition, the 1st control valve 23 and the 2nd control valve 22 are set as the structure which can be opened / closed steplessly, respectively, and the exhaust_gas | exhaustion amount discharged | emitted to the exhaust_gas | exhaustion supply duct 21 is adjusted with the control part F suitably.

  As shown in FIGS. 8 and 9, for example, the control unit F <b> 1 sets the exhaust air return amount by the following calculation. That is, the temperature sensor 30 for detecting the temperature T of the drying air acting on the grains in the passage 13 in the grain flow down passage 13 formed between the hot air chamber 11 and the exhaust air chamber 12, and the drying air The relative humidity sensor 31 for detecting the relative humidity Hs is provided, and these detection results are input to the control unit F1.

  The storage unit ME1 is connected to the control unit F1, and the data corresponding to the wet air diagram, the value of the absolute humidity HF corresponding to the saturated water vapor pressure for each drying air temperature, and whether or not it is near the saturated water vapor pressure The coefficients α and β used as thresholds for the determination, α · HF obtained by multiplying the coefficient α by the absolute humidity HF (for example, α = 0.7), and β · HF obtained by multiplying the coefficient β by the absolute humidity HF (for example, The value of β = 0.1) is stored. The control unit F1 includes a first calculation unit, a second calculation unit, and a comparison unit. Among them, the first calculation unit calculates the absolute humidity HD (= f (T, Hs)) from the detected temperature T and the detected relative humidity Hs. The absolute humidity HF at the saturated water vapor pressure at the detected temperature T is calculated by the second calculation unit. Then, the comparison unit compares the absolute humidity HD and the absolute humidity HF, so that the absolute humidity (HD) of the drying air in the grain flow passage 13 as the drying chamber where the grain exists is the absolute humidity (HD). When it is detected that the upper limit absolute humidity (β · HF) set in the vicinity of the humidity (HF) is exceeded, the exhaust air return amount is controlled to the decreasing side. Further, when it is determined that the absolute humidity HD of the dry wind is equal to or lower than the lower limit absolute humidity α · HF obtained by multiplying the coefficient α by the absolute humidity HF, the comparison unit controls the exhaust air return amount to be increased.

  Therefore, if it is determined that the absolute humidity HD of the dry air is equal to or lower than the upper limit absolute humidity β · HF and the absolute humidity HA of the dry air is greater than the lower limit absolute humidity α · HF, the dry air is close to the saturated water vapor pressure and It is determined that the saturated water vapor pressure is not exceeded, and the exhaust air circulation rate maintains that state.

Among the above controls, the same effect can be obtained by substituting the absolute humidity HF at the saturated water vapor pressure instead of the upper limit absolute humidity and whether or not the absolute humidity HF is reached.
The exhaust air circulation amount can be controlled by performing feedback control to an appropriate exhaust air circulation amount while performing the control as described above. In addition, by the increase / decrease control of the exhaust air return amount, for example, the control valve drive motor 25 is operated for each preset unit step so that the rotation angle θ of the first control valve 23 is interlocked for each unit angle Δθ. .

  As described above, the rotation angle θ of the first control valve 23 is determined by calculating the exhaust air return amount, and the adjustment valve is driven until the rotation angle θ is detected by the angle detection sensor 23b incorporated in the shaft 23a. The motor 25 is configured to be linked in the forward / reverse direction. Since the second control valve 22 is linked to the first control valve 23, the rotation angle of the second control valve 22 is not detected. However, the second control valve 22 is configured to independently rotate and adjust both control valves. In this case, an angle detection sensor and a control valve drive motor are provided.

  Here, referring to FIG. 10, a description will be given of the change in absolute humidity when the hot air for drying is combined with the return exhaust air and acts in the drying chamber and is discharged as exhaust air. The outside air of the predetermined absolute humidity is heated by the burner. After that, it merges with the exhaust. Although the absolute humidity does not change due to heating, the absolute humidity rises due to merging with the exhaust air, and enters the drying room (grain flow passage 13) from the hot air chamber (in this application, the circulation air in the drying chamber is “dried”. In the case of dry wind, the absolute humidity immediately rises upon contact with the grain, and thereafter, the absolute humidity does not increase so much and the air passes through the exhaust chamber. In the present invention, as described above, the amount of return exhaust air is adjusted and controlled so as to be in the range of the upper limit absolute humidity β · HF to the lower limit absolute humidity α · HF in FIG.

  When the first control valve 23 is at the closed position fb for discharging the exhaust air to the exhaust air supply duct 21 side most, the lower inner peripheral surface 20a of the exhaust air duct 20 and the first adjustment plate 23 The length b from the rotating shaft 23a to the outer periphery of the first control valve 23 is shorter than the length from the center of the exhaust duct 20 to the inner peripheral surface 20a so that a gap z with a set interval is formed between the peripheral edge 23a. The area of the first control valve 23 is smaller than the opening area of the exhaust duct 20. j is a turning locus of the first control valve 23;

  The closed position fb where the first control valve 23 discharges the most exhausted air to the exhaust air supply duct 21 side is configured to be located at a downward slope as shown in FIG. 22 is configured to be positioned at a rearward downward inclination, so that the exhausted air can be easily guided into the exhausted air supply duct 21.

  Between the exhaust air supply duct 21 and the main body 1, an exhaust air distribution case 26 serving as an exhaust air distribution passage that distributes the exhaust air that has passed through the exhaust air supply duct 21 to the left and right sides is provided from the top of the exhaust air fan 6 Provided on both sides. The left and right end portions of the exhaust wind dispersion case 26 and the rear end portion of a return duct 27 that forms a hot air chamber through-passage to be described later are configured to communicate with each other through a first exhaust wind opening m.

The return duct 27 is a cylindrical passage provided along the front-rear direction in the left and right hot air chambers 11 and is formed in a trapezoidal shape with a cross-sectional shape and a sharp upper portion in the present embodiment.
Between the main body 1 and the burner case 40, there is formed a first return passage 41 through which exhaust air returned through the main body 1 passes and a hot air passage 42 through which hot air generated by the combustion burner 5 passes. An exhaust passage case 43 is provided. And while setting it as the structure which connects the end of the return duct 27, and the 1st return path 41 with the 2nd ventilation opening part p, the 2nd return path 44 formed in the left-right both sides of the 1st return path 41 and the burner case 40 And the third exhaust opening r. A dust storage case 45 is formed below the burner case 40. A fourth exhaust opening d is formed at the upper left and right ends of the dust storage case 45 so as to communicate with the second return passage 44.

The structure of the heat exhaust air passage case 43 will be described in detail with reference to FIGS.
The hot air passage 42 in the hot exhaust air passage case 43 includes a first hot air passage 46 communicating with the burner case 40 and the first hot air opening c, and hot air that has passed through the first hot air passage 46 from the second hot air opening v. A second hot air passage 47 that supplies the hot air chamber 11 through the third hot air opening w is provided.

  The first return passage 41 and the second hot air passage 47 are formed on the front left and right sides of the main body 1 and are formed in two upper and lower stages, and the first hot air passage 46 is provided at a position facing the burner case 40 on the left and right center side. ing. The first hot air opening c is formed at the center of the first hot air passage 46 and the burner case 40.

In the present embodiment, a path through which the exhaust air from the exhaust air supply duct 21 to the second return passage 44 passes is collectively referred to as a return passage.
The surroundings of the combustion burner 5 will be described.

  A second return passage 44 provided in the burner case 40 and adjacent to the left and right of the combustion burner 5 is provided with a fifth exhaust opening e for exhausting exhaust air. The position of the fifth exhaust air opening e is provided from the combustion disk surface position k of the combustion burner 5 toward the main body 1 and is formed in a number of slit shapes. And the 5th exhaust wind opening e is formed so that the main body 1 side may be opposed like the combustion disk surface 5d of the combustion burner 5.

  Then, the exhaust air discharged from the fifth exhaust air opening e and the hot air generated by the combustion burner 5 are mixed in the heat exhaust air mixing unit 40a located on the combustion flame Q side of the combustion burner 5 and mixed heat. The exhaust air passes through the hot air passage 42, that is, the first hot air passage 46 and the second hot air passage 47 in this order, and is supplied to the hot air chamber 11.

Moreover, as shown in FIG.7 and FIG.8, many slits are formed in the 5th wind exhaust opening e toward the main body lower side.
A burner fan 5a that sucks the primary air of the combustion burner 5 and supplies it to the combustion burner 5 is provided above the combustion burner 5 and on the main body 1 side from the combustion disk surface position k. And the air can be blown to the combustion burner 5 through the air duct 5b.

Reference numeral 70 denotes a wind detection plate that detects the presence or absence of a wind flow. A fuel pump 5 c supplies fuel to the combustion burner 5.
A slit-like combustion flame confirmation opening 43a for confirming the state of the combustion flame Q is provided on the side wall of the heat exhaust air passage case 43 so that not only the state of the combustion flame can be confirmed but also outside air can be introduced, so that heat exhaust through which the hot air passes. The side walls are not easily heated by the heat of the wind passage case 43.

  Next, the hot air generated in the combustion burner 5 receives the suction action of the exhaust fan 6 and acts as dry air on the grains in the downstream passage 13 from the hot air chamber 11, and then becomes exhaust air to become the exhaust air chamber 12 and the return passage. The process until the hot air is mixed with the hot air and supplied to the hot air chamber 11 will be described.

  The hot air generated by the combustion burner 5 passes from the burner case 40 through the first hot air opening c, and from the first hot air passage 46 through the second hot air opening v, the second hot air passage 47, and the third hot air opening w. And supplied to the hot air chamber 11.

  The hot air in the hot air chamber 11 passes through the grain flowing down through the grain flow passage 13 forming a number of slits (not shown) as dry air, acts on the grain, absorbs moisture, and exhausts the wind chamber 12. And is discharged as exhaust air to the exhaust duct 20 by the exhaust fan 6.

  Exhaust air in the exhaust duct 20 is supplied to the exhaust air supply duct 21 so that a necessary exhaust air amount is appropriately circulated to the hot air chamber 11 side through the return passage by controlling the opening degree of the first control valve 23 and the second control valve 22. To be supplied.

  The exhaust air supplied to the exhaust air supply duct 21 is dispersed left and right by the exhaust air distribution case 26 and supplied to the return duct 27 from the first exhaust air opening m. The exhaust air in the return duct 27 passes through the second exhaust passage opening p, the first return passage 41, the third exhaust passage opening r, the second return passage 44, and the fifth exhaust passage opening e to the combustion burner 5. Is discharged from the side of the combustion flame Q in parallel with the direction in which the combustion flame Q is ejected, and mixed with hot air in the hot exhaust air mixing portion 40a located at the position facing the combustion burner board surface, from the first hot air opening c. It is supplied to the first hot air passage 46. The dust contained in the exhaust air from the second return passage 44 falls by its own weight, passes through the fourth exhaust air opening d, and is stored in the dust storage case 45.

Next, operations and effects associated with the configuration of the present embodiment will be described.
By supplying the exhaust air from the exhaust fan 20 to the hot air chamber 11, the heat in the exhaust air is added to the hot air supplied by the combustion burner 5, and the hot air chamber 11, and hence the grains in the flow-down passage 13, can be made short. Grain temperature can be increased over time. And the absolute humidity of the dry hot air which acts on the grain of the grain flow down passage 13 can be increased by controlling the return amount of the exhaust air, and the amount of vaporization from the grain surface can be suppressed.

  That is, when dry hot air mixed with exhaust air is supplied, the dry air suppresses the amount of vaporization to be evaporated from the grain surface by the absolute humidity on the grain surface, while the heat of the dry wind acting on the grain Mainly promotes the increase in grain temperature, improves the fluidity of moisture in the grain, reduces the moisture gradient between the inside and the surface of the grain unit, reduces torso cracking, and can perform drying at high speed .

  Before the exhaust air is supplied from the return duct 27 to the first hot air passage 46, combustion is performed from the fifth exhaust air opening e to the side of the combustion flame Q of the combustion burner 5 through the second return passage 44 adjacent to the burner case 40. By discharging the exhaust air to the heat exhaust air mixing unit 40a in parallel with the jet direction of the flame Q, the combustion flame Q does not flow turbulently and the combustion of the combustion burner 5 can be performed stably. In addition, since the exhaust air is merged on the combustion side of the combustion burner 5, the change in the amount of wind passing around the combustion burner 5 due to the change in the return exhaust air amount can be reduced, and the change in the combustion flame Q can be reduced. it can. And mixing of exhaust air and hot air can be promoted. Further, by not directly exposing the exhaust air to the combustion burner 5, it is possible to prevent the combustion burner 5 from being deteriorated due to the action of dust, moisture, or the like.

  Further, a large amount of dust being exhausted can fall and accumulate in the dust storage case 45, and the amount of dust supplied to the first hot air passage 46 and the hot air chamber 11 can be reduced. By providing the return passage adjacent to the burner case 40, the heat retention of the exhaust air can be improved.

  As in the present embodiment, in a dryer that directly heats the outside air with the combustion burner 5 and supplies the air contained in the combustion gas to the object to be dried, the exhaust air containing dust is discharged from the combustion flame of the combustion burner 5. Dust burns when heated by Q, and the burned dust is supplied to the grain and the quality of the grain has been reduced. According to this embodiment, the quality of the grain is difficult to burn dust. A decrease can be prevented.

Next, the drying control of this embodiment will be described.
FIG. 14 is a graph showing a change in grain temperature and a change in moisture value accompanying a drying operation, L1 shows the drying process of the present embodiment, and L2 shows a conventional drying process. L3 indicates a change in the moisture value of the present embodiment, and L4 indicates a process of the conventional moisture value.

  L2 is a graph in the case where the combustion burner 5 makes the combustion amount constant in the conventional drying process, but the grain temperature gradually rises after the start of combustion, and the grain temperature is approximately until reaching the finish moisture. It shows that it is rising at a certain slope.

On the other hand, the drying process of L1 performs the following processes.
First, after the combustion of the combustion burner 5 is started, the first adjustment plate 23 is fully opened for a predetermined time (for example, the time during which the cereal grains circulate once), and the exhaust air is discharged almost entirely outside the apparatus. A large amount of generated dust is prevented from being supplied again from the return passage into the hot air chamber 11 (dry initial full amount outside-machine discharge step A1).

  When the predetermined time has elapsed, the first adjusting plate 23 and the second adjusting plate 22 are adjusted so that the ratio of the exhausted air to be returned remains constant for a while in a state of a predetermined value or more (for example, 75% or more). Most of the exhaust air is discharged to the return passage side and supplied into the heat exhaust air mixing unit 40a. And it is mixed with the exhaust air and the hot air generated in the combustion burner 5 and supplied from the hot air chamber 11 to the grains in the flow-down passage 13 (dry initial total amount returning step A2).

  For this reason, moisture tends to evaporate from the surface of the grain by the supplied heat, but is suppressed by the moisture supplied together with the heat, and the moisture stays inside the grain. As for the grain temperature, the heat generated by the combustion burner is added to the heat of the exhaust air and applied to the grain, so that a lot of heat is given and the grain temperature rises rapidly.

  In this step, the return amount is corrected by the outside air temperature, and the first adjusting plate 23 and the second adjusting plate 22 are adjusted so that the ratio of the exhaust air to be returned decreases as the outside air temperature increases. Moreover, this process is a process of returning the most exhausted air in the entire drying process.

  Then, the adjustment which returns the exhaust wind of the exhaust wind absolute humidity Ha containing the moisture content according to the grain moisture value detected with the moisture meter 10 for every set time is performed (exhaust wind absolute humidity return process A3). And exhaust air of exhaust air absolute humidity Ha which is below the saturated water vapor pressure and close to the saturated water vapor pressure is supplied to such an extent that the inside of the grain flow passage 13 does not condense beyond the saturated water vapor pressure.

  When close to the finishing moisture value, the first control valve 23 and the second control valve 22 are adjusted and controlled to increase the rate of exhaust air exhaust to the outside of the machine in sequence, thereby decreasing the grain temperature sequentially to the set moisture. The hulling process after arriving and finishing the drying operation can be performed quickly (finishing discharge process A4).

  Here, the drying theory, that is, giving moisture and heat to the grain will be described with reference to FIG. In the conventional drying control, as shown in FIG. 15 (A), when the amount of drying heat generated by the combustion burner 5 and supplied to the grain is 100, the moisture in the grain mainly evaporates at the beginning of drying. Is consumed in the amount of heat to be vaporized (for example, 95), and the rest is used to increase the grain temperature. That is, since the moisture value of the grain is high at the initial stage of drying, most of the supplied heat is used for vaporization of moisture. Therefore, simply increasing the amount of drying heat promotes drying on the grain surface side from the inside of the grain, and on the contrary, the moisture gradient in the grain becomes high and it becomes easy to crack the trunk.

  On the other hand, with respect to the drying control of the present embodiment, as shown in FIG. 15 (B), by returning the exhaust air at the initial stage of drying and generating dry hot air under predetermined conditions, it is possible to perform high-speed drying that is difficult to crack the body. It is to make. That is, assuming that the amount of heat generated in the combustion burner 5 is 100, and the amount of heat of the exhaust air contained in the exhaust air is added to the amount of heat of the dry hot air, the total amount of heat that the exhaust air merges with the dry hot air is 150. . Here, the condition of the new drying air generated when the exhaust air joins the drying hot air is a lower limit in which the absolute humidity is lower than the upper limit absolute humidity near the saturated water vapor pressure and set to a predetermined limit with respect to the saturated water vapor pressure. We know that it is higher than absolute humidity. For example, in the case of drying cocoons, the lower limit from the absolute humidity at the upper limit saturated water vapor pressure is controlled within the range of the lower limit absolute humidity that is about 30% lower than the saturated water vapor pressure state. The upper and lower absolute humidity values are individually set according to the type and environment of the object to be dried.

  And when a new dry wind acts on the grain, the moisture in the grain given the heat is going to vaporize from the grain surface, while the absolute humidity is near the saturated water vapor pressure and the saturated water vapor pressure as described above. Moisture evaporation from the grain surface is suppressed by adjusting to the following, and the amount of heat applied acts on the inside of the grain, for example, the amount of heat used for the heat of vaporization is 60 lower than the conventional 95, which increases the grain temperature. The amount of heat used is 90. Therefore, although the grain temperature rises rapidly, the moisture transfer in the grain is promoted, the moisture gradient does not increase rapidly, and the shell crack is unlikely to occur.

  And since it can adjust according to the moisture value of the grain detected during drying as mentioned below, the amount of exhaust of return exhaust air does not need a humidity sensor etc. which detects the humidity of exhaust air In addition, the cost can be increased, and the drying can be performed while supplying appropriate moisture, that is, moisture enough to keep the grain flow passage 13 below the saturated water vapor pressure and close to the saturated water vapor pressure to the object to be dried.

  It has been found that the new dry air condition described above can be obtained by merging the dry hot air and the exhaust air by the combustion burner 5. That is, the dry wind acting on the grain absorbs moisture and is discharged as exhaust air, but the exhaust air return amount is adjusted by paying attention to the absolute humidity of the exhaust air.

  Here, as shown in the graph of FIG. 16, it has been found by tests that the exhaust wind absolute humidity substantially corresponds to the moisture value of the grain. That is, the higher the moisture value of the grain, the higher the exhaust wind absolute humidity. In addition, as described so far, the dry hot air in the hot air chamber 11 acts on the grain as dry air in the grain flow passage 13 and is exhausted from the exhaust chamber 12. Of these, the dry air and the exhaust air Are substantially equal (in FIG. 10, there is a relationship of “absolute humidity HD≈virtual exhaust wind absolute humidity U”), the detection or estimation of the exhaust wind absolute humidity is the absolute humidity of the dry wind in the grain flow passage 13. Can be virtual.

  The higher the moisture content of the grain, the higher the absolute humidity of the exhaust wind is because the water vapor pressure to be vaporized from the surface of the grain is higher, so that more exhaust air humidity is required to suppress it. This is because, as the drying operation proceeds and the grain moisture value decreases, the amount of moisture vaporized from the grain decreases, and the amount of moisture for suppressing moisture in the grain improves at least. In the present embodiment, a virtual absolute humidity calculating unit that calculates the virtual absolute humidity U is configured by storing the relationship graph of FIG. 16 in the storage unit ME of the control unit F2 or by obtaining a regression equation using the moisture value as a variable. The exhaust air absolute humidity HD required based on the detected moisture value data is virtually assumed.

  If saturated steam is exceeded, condensation may cause the grain to be steamed and quality may be impaired, but to the extent that it does not exceed it, heat and moisture contained in the exhaust air are given to the grain, so much heat inside the grain. In addition, the moisture that is going to evaporate from the surface of the grain is suppressed inside the grain object by the moisture in the exhaust air. When heat is supplied to the inside of the grain, the surface moisture side transition is promoted, so that the moisture gradient inside the grain can be reduced and the inside of the grain is cracked while being dried at high speed. It can be made difficult to wake up.

  And although said virtual exhaust wind absolute humidity U controls the exhaust air return amount in grain drying with knowledge that it substantially corresponds to the moisture value Mn of the grain, the flowchart of FIG. This will be described based on the block diagram.

  In addition to starting the drying operation, the outside air temperature sensor 38 and the outside air humidity sensor 39 detect the outside air temperature TA and the outside air humidity HA, and the grain moisture value Mn, and these detection data are input to the control unit F2. Is done. In the control unit F2, the absolute humidity HA is calculated based on the outside air temperature TA and the outside air humidity HA, and the drying rate calculating unit calculates the drying rate (drying rate) based on the detection result of the moisture value for each predetermined time. Further, the control unit F2 calls the relationship between the detected moisture value Mn and the virtual exhaust wind absolute humidity U in FIG.

  The control unit F2 calculates the exhaust air return amount based on the virtual exhaust air absolute humidity U in addition to the virtual absolute humidity U, the drying rate, and the amount of grain that is input in advance. It should be noted that the relationship between the exhaust air return amount based on these conditions is that the absolute humidity HD of the dry air of the grain is the upper limit absolute humidity near the saturated water vapor pressure as described above, and the lower limit absolute humidity below the predetermined value. These are determined in advance by experiments or the like.

  Based on the calculation of the exhaust air return amount, the angle θ of the first control valve 23 is set, and the first control valve 23 and the second control valve are output to the control valve drive motor 25 so as to become this angle. 22 is activated.

  Also, drying continues, the outside air temperature TA, the outside air humidity HA, and the moisture value Mn are detected periodically, and the absolute humidity Z and the drying rate are calculated each time. When this value fluctuates unlike the previous value, Correct the exhaust air return amount. That is, when the absolute humidity Z decreases, in order to ensure the expected dry wind absolute humidity (approximately equal to the exhausted absolute humidity U), the return amount of exhausted air is corrected to be increased, and conversely when the absolute humidity Z increases, the exhausted air Reduce the return amount.

  Further, by detecting the moisture value Mn, an increase / decrease correction of the exhaust air return amount is performed in the same manner as the drying rate varies. That is, when the drying rate increases, the moisture ratio contained in the return exhaust air increases, so the exhaust air return amount is corrected to decrease, and vice versa.

  In the examples in FIGS. 17 and 18, the exhaust air return amount is set to the operating angle θ of the first control valve 23 based on the absolute humidity Z, the drying rate, the amount of tension, and the virtual exhaust absolute humidity U. Although the configuration is such that the setting control is performed, it may be performed by the control method of FIG. 9 that corrects the deviation of the first control valve 23 from the target value. In this case, since the deviation from the absolute humidity HF corresponding to the saturated water vapor pressure in the vicinity of the saturated water pressure is known at a predetermined time interval, the return amount of the exhaust air can be finely controlled. .

Next, an example of control for adjusting the opening of the control valve will be described using representative numerical values.
The outside air temperature TA detected by the outside air temperature sensor is 20 ° C., the outside air humidity HA detected by the outside air humidity sensor is 70%, and the absolute humidity (Z) calculated by the control unit F2 is 13 g / m ³ . Then, it is assumed that the virtual exhaust wind absolute humidity (U) of the exhaust air as the control target set corresponding to the grain moisture value detected by the moisture meter 10 in FIG. 16 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 the drying rate (it is dried per hour) which shows a drying rate. When the ratio of moisture) is 1.2% / h, how much of the exhaust air is returned to the hot air chamber 13 is obtained from the following equation.

Virtual exhaust absolute humidity (U)-absolute humidity (Z) = 12 (g / m ³ ) (Formula 1)
The maximum amount of water that can be absorbed by outside air is 12 x 1900/1000 ≒ 23 (kg) (Formula 2)
The amount of water removed from the grain per hour is 800 (kg) × 1.2 (% / h) = 9.6 (kg / h) (Formula 3)
From the formula of B2 and the formula of B3 23 / (9.6 + 23) ≒ 0.71 → 71% (Formula 4)
That is, the control valve drive motor 25 is controlled so as to return 71% of the exhaust air amount discharged from the exhaust fan 7 to the hot air chamber 11 to control the θ angle of the first control valve 23, and thereby the second control valve 22. Adjust. That is, the rotation angle θ of the first control valve 23 corresponding to the return rate of the exhaust air is stored in the storage unit ME in advance, and the control valve drive motor 25 corresponds to the exhaust air rate 71% based on the calculation result. Are linked forward and backward.

  More specifically, the above-described arithmetic expression is calculated by calculating the absolute humidity (Z) of the outside air by the control unit F2 from the temperature and humidity of the outside air detected by the outside air temperature sensor TA and the outside air humidity sensor HA, respectively. The difference (increased water volume) between the humidity (Z) and the absolute humidity (U) of the exhaust wind set in advance from the condition of the grain moisture detected by the moisture meter 10 is calculated as the maximum water absorption amount that can be absorbed by the outside air (formula) 1 and equation 2). On the other hand, the amount of water evaporated from the grain by the drying operation (the amount of water removed from the grain per hour in the present embodiment) is obtained (Equation 3), and the amount of increased water is the amount of water evaporated by the drying operation. The ratio to the sum of the values is considered as the ratio for returning the wind.

That is, the above formula 4 is the amount of increased water / (the amount of water evaporated from the grain + the increased amount of water).
Is shown. This formula is particularly effective for a dryer that continuously performs a drying action on an object to be dried.

  However, in this embodiment, in the grain dryer in which the drying operation and the tempering operation (so-called tempering) are alternately performed by circulating the kernel through the storage unit 2 and the drying unit 3, drying is performed as described above. When the grain which supplied heat and moisture in the part is circulated to the storage part 2, when there is too much heat and moisture to be supplied, drying from the grain surface proceeds from the transfer of moisture inside the grain, Grain shell cracking may increase.

Therefore, in the case of a grain dryer, drying control may be performed based on the following formula B5 instead of formula 4.
Increased amount of water / (Amount of water evaporating from grain + Absolute humidity of exhaust air (U)) (Formula 5)
23 / (9.6 + 47.5) ≈0.42 That is, 42% exhaust air is returned.

Note that 47.5 (kg) is calculated from 25 g / m ³ of the absolute humidity (U) and the air volume of the exhaust fan 1900 kg / h.
47.5 = 25 × 1900/1000 (Formula 6)
In a circulation type dryer that performs drying by the tempering method, in order to suppress surface drying while it is stopped in the storage unit 2, the absolute humidity of the exhaust air that is set by the absolute humidity that passes through the storage unit 2 in Equation 5 The total amount of water that the wind passing through the grain per unit time has to be changed and corrected so that it becomes humidity.

  In addition, when the 1st control valve 23 and the 2nd control valve 22 are adjusted so that more than 71% of the amount of exhausted air may be returned to the hot air chamber 11, the more water is returned, the more water is returned. It becomes difficult to remove moisture from the grain. In addition, when the first control valve 23 and the second control valve 22 return an amount smaller than 71% of the exhausted air amount to the hot air chamber 11, the amount of heat returned to the hot air chamber 11 decreases, so that the temperature of the grain rises. It becomes difficult to peel off and the drying speed becomes slow.

  By adjusting the ratio of returning the exhaust air from the equation of the present embodiment, the drying operation with good combustion efficiency can be performed by appropriately using the heat generated by the exhaust air discharged from the exhaust air fan 6, that is, the water absorption force as much as possible. It can be performed.

FIG. 19 is a diagram illustrating correction of the ratio of returning the exhaust air set based on the grain moisture value and the virtual exhaust air absolute humidity based on FIG. 16 described above.
The outside temperature and the amount of grain filling are shown as conditions for correction. That is, it correct | amends so that the ratio which returns exhaust air may be reduced, so that external temperature is high. Curves M1, M2, M3, M4, and M5 indicate correction of the exhaust wind return rate for each amount of tension, and the correction is performed so that the ratio of returning the exhaust wind is reduced as the amount of tension increases.

  Since the drying of the grain is promoted as the outside air temperature becomes higher, it is possible to reduce the amount to return the exhaust air accordingly. Moreover, since the grain temperature which rises most is so high that there is much tension | tensile_strength, the amount which returns exhaust air by that amount can be reduced.

  In the above embodiment, the configuration in which the exhaust air return amount is controlled by the rotation angle θ of the control valve has been described. However, the return amount itself may be detected and controlled, or the exhaust air return ratio with respect to the total exhaust air amount may be set. The form to control may be sufficient.

In this embodiment, the drying rate indicating the drying rate is 1.2%, but the rate of returning the exhaust air is changed depending on the drying rate.
In this embodiment, the absolute humidity of the outside air is obtained from the outside air humidity sensor HA, but instead of the outside air humidity sensor, the absolute humidity of the outside air based on the outside air temperature reference may be determined and used as a substitute value.

  In this embodiment, a grain dryer for straw, wheat, beans, etc. has been described. The present invention can also be used in the case of a dryer that uses an object with a gradient as an object to be dried.

Front view of the whole grain dryer Side view of whole grain dryer The perspective view explaining the inside of the whole grain dryer The perspective view explaining the structure of a drying part and a grain collection part Front view illustrating the configuration of the drying unit and the cereal collecting unit Side view (A) and rear view (B) of exhaust fan for explaining interlocking configuration of first control valve and second control valve A perspective view showing an exhaust air supply duct, an exhaust air distribution case, and an exhaust fan Block Diagram flowchart Schematic diagram showing changes in absolute humidity The perspective view explaining the inside of a burner case and a heat exhaust air passage case Side view explaining the inside of the burner case The perspective view explaining the inside of a burner case Graph showing the relationship between drying process and grain temperature or grain moisture value The figure explaining the heat supplied to a grain (A) (B) Diagram showing the relationship between absolute wind humidity and grain moisture value flowchart Block Diagram The figure which shows changing the ratio which recirculates the exhaust wind with outside air temperature and tension amount

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main body 5 Combustion burner 5a Combustion disc surface 6 of combustion burner Exhaust fan 11 Hot air chamber 13 Grain flow passage 20 Exhaust duct 22 Second adjustment plate 23 First adjustment plate 23a Rotating shaft 24 Rod 44 Second return passage k Combustion Burner surface position e 5th exhaust opening Q Combustion flame

Claims (4)

A drying section (3) for drying by applying a hot air for drying to an object to be dried, a return passage (41, 44) for joining the exhaust air after passing through the object to be dried to the hot air for drying, and a return amount of the exhaust air In the drying apparatus provided with the adjusting device (22, 23) for adjusting
A first calculation unit for calculating an absolute humidity (HD) in a drying chamber (13) of the drying air by the combined air of the hot air for drying and the exhaust air;
A second calculation unit for calculating an absolute humidity (HF) at a saturated water vapor pressure of the dry air;
A comparison unit for comparing the absolute humidity (HD) of the dry wind and the absolute humidity (HF) at the saturated water vapor pressure;
When it is detected that the absolute humidity (HD) of the dry wind reaches the absolute humidity (HF) at the saturated water vapor pressure or exceeds the upper limit absolute humidity (β · HF) set in the vicinity of the absolute humidity (HF), the adjustment is performed. A signal for decreasing the exhaust air return amount is output to the devices (22, 23), and the absolute humidity (HD) of the dry air is lower than the absolute humidity (HF) at the saturated water vapor pressure by a predetermined lower limit absolute humidity ( Control unit (F1) which outputs a signal for increasing the exhaust air return amount to the adjusting device (22, 23) when it is detected that the value is below α · HF)
A drying apparatus characterized by comprising: A drying section (3) for drying by applying a hot air for drying to an object to be dried;
A return passage (41, 44) for joining the exhausted air after passing through the drying object to the hot air for drying;
In the drying apparatus provided with the adjusting device (22, 23) for adjusting the return amount of the exhaust air,
A moisture meter (10) for detecting the moisture of an object to be dried during drying;
A virtual absolute humidity calculating unit that calculates the virtual absolute humidity (U) of the exhaust air based on the moisture value of the dry object detected by the moisture meter (10);
A setting unit that presets an exhaust air return amount that returns exhaust air to the return passage (41, 44) or a total exhaust air amount in correspondence with the virtual absolute humidity (U);
Control unit (F2) for operating the adjusting device (22, 23) to the set exhaust air return amount or exhaust air return ratio
A drying apparatus characterized by comprising: The detection part which detects the outside air absolute humidity input into the control part (F2) is provided, and it was set as the structure which correct | amends an exhaust air return amount or an exhaust air return ratio according to the fluctuation | variation of this outdoor air absolute humidity. Drying equipment. A drying rate calculation unit that calculates the drying rate of the drying object based on the moisture detection result of the drying object input to the control unit (F2) is provided, and the exhaust air return amount or The drying apparatus according to claim 2 or 3, wherein the exhaust air return ratio is corrected.

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