JP2010144969A - Exhaust air circulation type grain dryer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust air circulation type grain dryer enabling stable high-speed drying control without deteriorating drying quality even if moisture values are largely varied during the drying of grains. <P>SOLUTION: The exhaust air circulation type grain dryer includes a burner (5), a drying part (3), an exhaust air fan (6), an exhaust air supply duct (21), a moisture value measuring means (10), a control part (F) for performing exhaust air circulation control to adjust the combustion amount of the burner (5) in accordance with drying speed set separately and adjust the return amount of the exhaust air supply duct (21) corresponding to the moisture values and the like. The control part (F) performs initial drying control to control the exhaust air supply duct (21) according to the return amount determined based on the separately set drying speed for a predetermined initial drying time since drying start. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust air circulation type grain dryer provided with a suction exhaust section for exhaust air circulation that can be adjusted to reflux in a drying section that dries the grain.

Conventionally, as shown in Patent Document 1, a drying unit having a hot-air transmission structure that receives hot air from a hot-air supply unit to dry the grains, and a suction / discharge unit that sucks and discharges exhaust air from the drying unit so as to be recirculated. A wind circulation type grain dryer is known. This exhaust circulation type grain dryer suppresses the evaporation of moisture from the surface by supplying heat and water to the grain simultaneously with high-temperature and high-humidity mixed hot air combined with the reflux exhaust from the suction discharge section. However, by promoting the moisture transfer inside the grain, high-speed drying can be performed while suppressing cracking.
JP 2008-133957 A

  In the above case, it is possible to shorten the drying time without changing the quality by changing the ratio of refluxing the exhaust air according to the moisture content of the grain. , There is a large variation in the moisture value due to differences in the growing conditions and harvesting conditions of the field, and when it is put into a dryer and dried, the moisture value of the grains that are sequentially sent to the drying section and dried is changed. As a result, the rate at which the exhaust air is recirculated changes, which causes a problem that the drying operation becomes unstable.

  The problem to be solved is to provide an exhaust air circulation type grain dryer capable of stable high-speed drying control without deteriorating the drying quality even if the moisture value varies greatly during grain drying. It is in.

The invention according to claim 1 includes a burner (5) that generates hot air so that the amount of combustion can be adjusted, and a drying unit (3) that dries the grain that flows constantly while receiving the hot air from the burner (5). An exhaust fan (6) that sucks hot air from the drying unit (3) and discharges it as exhaust air, and the exhaust air received from the exhaust fan (6) can be diverted to the drying unit (3 Exhaust air supply duct (21) to be returned to), moisture value measuring means (10) for measuring the moisture value of the grain, and the moisture value of this moisture value measuring means (10) so as to follow a separately set drying rate. And a control unit (F) for performing exhaust air circulation control for adjusting the amount of combustion of the burner (5) and adjusting the return amount of the exhaust air supply duct (21) corresponding to the moisture value. In the grain dryer, the control unit (F) sets a predetermined initial drying time from the start of drying. After spent, or by moisture measurement means (10), characterized in that initiating the exhaust circulation control after completion moisture measurement a predetermined number of times.
The control unit of the grain dryer controls the burner (5) so that a predetermined drying speed is obtained during a predetermined initial drying time from the start of drying or until a predetermined number of times of moisture measurement by the moisture value measuring means (10). The grain drying is started by the initial drying control by combustion, and then the grain drying is continued by switching to the exhaust air circulation control by the exhaust air return amount.

  In the first aspect of the present invention, the controller (F) performs the exhaust circulation control after a predetermined initial drying time has elapsed from the start of drying, or after a predetermined number of moisture measurements by the moisture value measuring means (10). Therefore, the drying control operation can be stably performed from the beginning of drying without causing instability control due to variations in moisture value, and drying control by exhaust air recirculation can be performed with high accuracy.

The grain dryer according to the present embodiment will be described.
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 that receive dry hot air generated by the combustion burner 5 on both the left and right sides of the main body 1, and is provided with an exhaust air chamber 12 that communicates with the exhaust fan 6 at the left and right central portions of the main body 1. 11 and the exhaust chamber 12 are provided with a grain flow passage 13, 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. It is the structure which the grain of the storage chamber 2 passes 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 the figure.

  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 located at a forward downward inclination 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 to the left and right. 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.

Further, as shown in the drawing, the fifth exhaust opening e is formed with a large number of slits toward the lower side of the main body.
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 6 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 thus the grains in the downflow passage 13 can be made to act shortly. The 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 of the grain surface, while the heat of the dry wind acting on the grain Mainly promotes the increase in grain temperature, increases the fluidity of moisture in the grain, reduces the moisture gradient between the inside and the surface of the grain unit, reduces the cracking of the body, and allows the drying operation to be performed at high speed. The

  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. Moreover, since the exhaust air is combined 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.

  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. By adjusting to the following, water evaporation from the surface of the grain is suppressed, 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, increasing the grain temperature. The amount of heat used for 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 fluctuates. 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 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 6 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 11 is obtained from the following equation.

Virtual exhaust absolute humidity (U)-absolute humidity (Z) = 12 (g / m3) (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 6 to the hot air chamber 11 to control the θ angle of the first control valve 23, 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 that alternately circulates the grain through the storage unit 2 and the drying unit 3 and alternately performs the drying action and the tempering action (so-called tempering), the grain is dried 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) described above 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 becomes so high that there is much tension | tensile_strength, the quantity 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, but in addition to this, it has been collected from nature such as shiitake mushrooms, timber and marine products, and moisture is applied to the surface part and the inner central part of the object to be dried. 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.

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 and exhausted for a predetermined time (for example, the time during which the cereal grains circulate once or until the moisture meter 10 measures three times at 10 minute intervals). Is discharged to the outside of the machine, and dust generated much immediately after the start of combustion is prevented from being supplied again into the hot air chamber 11 from the return passage (initial drying control A1). During this time, the grain temperature rises by the action of the combustion burner 5.

  When a predetermined time elapses, adjustment is made to return the exhaust air of the exhaust air absolute humidity Ha including the amount of moisture corresponding to the grain moisture value detected by the moisture meter 10 every set time (exhaust air circulation control A2). 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. In addition, since the grain moisture value is still high at the beginning of the exhaust air circulation control, control is performed so that the required exhaust air absolute humidity becomes high as seen in the graph of FIG. That is, in order to control the ratio of returning exhaust air to be high, the grain temperature rises in a relatively short time as shown in FIG. And exhaust air circulation control is performed in the state of a certain high grain temperature.

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 A3).
In this way, the control unit F starts grain drying by normal combustion for a predetermined initial drying time from the start of drying, and then switches to exhaust air circulation control by the exhaust air return amount according to the moisture value. Continue grain drying. Therefore, without causing instability control due to variations in moisture value, the drying control operation is stable from the start of drying, and drying control by high-precision exhaust air recirculation is possible. In addition, the initial drying time is to fully open the first control valve 23, and to discharge large long objects such as dust and sawdust mixed with the grain to the outside of the machine. A clean exhaust can be returned.

  In addition to the above, the initial control can be stabilized by exhausting and circulating the initial predetermined time at the corresponding exhaust air return rate based on the initial moisture measurement, and the predetermined moisture value measurement The initial control can also be stabilized by setting up to the initial drying time.

(At the end of drying)
As for the control at the end of drying, if the moisture value exceeds a predetermined value (for example, + 1.5%) with respect to the finished moisture value, that is, if it approaches the finished moisture value, the exhaust air circulation control is stopped. Alternatively, the grain surface condition can be brought close to that of the conventional hot air drying by controlling the finishing drying by reducing the circulation amount to a small amount. That is, when drying by exhaust air circulation is performed, the grain surface condition is in a high-temperature and high-humidity atmosphere, and the hulling conditions are slightly different. Thus, the hulling can be easily performed. Further, as in the case of conventional hot air drying, the degree of finish can be grasped using a conventional moisture meter.

  The specific control in the vicinity of the finish is performed so that the exhaust air circulation amount is decreased by a few times and is set to a set value. For example, if the exhaust air circulation rate is 60% and the finish control is entered at this time, the exhaust air circulation rate is decreased by 5% every 1 minute, and the exhaust air circulation is stopped in a total of 12 minutes.

  When the circulation is stopped by operating the exhaust air circulation valve all at once without the above control, the steam rises instantly and the temperature of the boiled water drops and moisture evaporation occurs when the pan lid is completely blown down. In addition, since the surface of the grain is dried at once in the dryer and the shell is cracked, the quality of the drying can be ensured by the above-mentioned stepwise reduction of the exhaust air circulation.

  In addition, in the control at the end of drying, once entering the finish control, by configuring the control process to continue the finish control as it is even if the measurement result of the next moisture value is high, It is possible to avoid the situation that causes the body cracking due to the increase and decrease of the exhaust air circulation amount associated with the release of the finish control according to the fluctuation of the moisture value, and to finish the drying stably.

In addition, during exhaust circulation drying, when drying is stopped by a stop switch or automatically stopped due to equipment trouble, the exhaust circulation valve is operated so that the exhaust circulation rate is gradually decreased by a certain amount every predetermined time. The control process is configured as follows. For example, for the post purge (stop control time) of 4 minutes when the stop switch is pressed, the valve is controlled to open 10% every 20 seconds.
As described above, when the exhaust air circulation is performed and the air is dried, the exhaust air circulation valve is gradually opened using the post-purge, so that the exhaust air circulation valve is opened at once and the circulation stop control is performed. It is possible to prevent torso cracking.

(Burner configuration)
Next, the structure of a burner part is demonstrated.
As shown in FIG. 20, the front view of the burner section is a high-speed outside air along the passage 44 that guides the return exhaust air to the positions of the left and right mounting feet 5 c and 5 c of the burner 5 within the burner case 40. The outside air introduction ducts 81, 81 to be introduced straight in are formed in the depth direction.

  As shown in FIG. 21, an exploded perspective view of the hot air supply unit by the burner functions as outside air introduction ducts 81, 81 as a reinforcement for the legs of the burner, and the return exhaust air discharged from the fifth exhaust air opening e. However, since it is guided along the high-speed straight flow line of the outside air that is running in parallel, a good mixed hot air can be obtained without the reflux exhaust air adversely affecting the combustion section.

(Application of exhaust air circulation control)
In the case of hot air drying without current adjustment of exhaust air circulation valve, automatic adjustment by moisture meter is not possible because there is no moisture meter, moisture meter is turned off, and timer is set. This problem is solved because there is a problem that it is not possible to cope with the case where switching from high speed drying by hot air circulation to hot air drying is necessary to avoid quality deterioration such as wrinkles and shell cracks. Therefore, it is configured so that “Yes” or “No” can be set and selected for the exhaust air circulation valve adjustment.

  Specifically, the exhaust air circulation duct is provided with a potentiometer that detects the exhaust air circulation valve and the rotational position of the exhaust air circulation valve, and the exhaust air is exhausted according to the exhaust air circulation valve rotation target value based on the exhaust air circulation rate and the detected value of the potentiometer. The dryer that adjusts the drive of the circulation valve is configured so that it can be set to “ON” or “OFF” for the exhaust air circulation valve adjustment. When the setting is changed from “Yes” to “No”, the exhaust air circulation valve is adjusted to the fully open position (normally hot air drying state). It is configured so that the exhaust air circulation valve can be automatically adjusted “ON” or “NO” by setting “NO”. With such a configuration, it is possible to provide a switching setting selection means for “automatic” and “manual” adjustment of the exhaust air circulation valve, and it becomes possible to prevent deterioration of grain quality and to improve drying performance.

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 Front view showing the internal structure of the burner section The perspective view explaining the inside of a burner case and a heat exhaust air passage case

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Drying part 5 Combustion burner 6 Exhaust fan 7 Elevator 10 Moisture meter (moisture value measuring means)
13 Grain Flow Down Passage 14 Rotary Valve 20 Exhaust Duct 21 Exhaust Supply Duct 22 Second Adjustment Plate 23 First Adjustment Plate 27 Duct 40 Burner Case F Control Unit θ Operating Angle

Claims (1)

A burner (5) that generates hot air so that the amount of combustion can be adjusted, a drying unit (3) that dries the grain that flows constantly while receiving the hot air from the burner (5), and a hot air from the drying unit (3) An exhaust fan (6) that sucks out the exhaust air as exhaust air, and an exhaust air supply duct (6) that returns the exhaust air to the drying section (3) so that the diversion of the exhaust air received from the exhaust fan (6) can be adjusted. 21), the moisture value measuring means (10) for measuring the moisture value of the grain, and the amount of combustion of the burner (5) according to the separately set drying rate by the moisture value of the moisture value measuring means (10) And a control unit (F) that performs exhaust air circulation control that adjusts the return amount of the exhaust air supply duct (21) in accordance with the moisture value.
The controller (F) starts the exhaust air circulation control after a predetermined initial drying time has elapsed from the start of drying or after a predetermined number of times of moisture measurement by the moisture value measuring means (10). A wind circulation type grain dryer.

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