JPH09318256A - Method for drying grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the consumption of fuel by heating a drying chamber at a prescribed supply air temperature during an initial drying period and at a prescribed constant temperature corresponding to an amount of grain feed thereafter, and adjustably controlling and drying the drying chamber to a reduced pressure lower by a prescribed pressure than an atmospheric pressure to dry the drying chamber at a preset drying rate. SOLUTION: A reduced pressure type grain dryer is used. The amount of fuel feed of a petroleum combustion burner 7 is controlled so that drying hot air temperature becomes about 35 deg.C during an initial drying period and becomes substantially constant temperature near 40 deg.C predetermined depending on the type or the amount of feed of grain when the water content of the grain to be dried reaches a water content value or smaller predetermined depending on the kind of the grain. Then, a drying chamber is adjustably controlled to a reduced pressure lower by approximately -40 to -200mmAq than atmospheric pressure and dried so that the drying rate of the grain reaches a preset drying rate depending on the type and the amount of feed of grain. Namely, the value of the drying supply air temperature detected by a supply air temperature detector 2 is compared with a preset reference temperature so that it is controlled by a control circuit 6.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for drying grains such as paddy and wheat.

[0002]

2. Description of the Related Art Conventionally, for drying grains such as paddy and wheat, the hot air for drying is discharged from the storage chamber at the top of the dryer to the drying chamber at the bottom and allowed to flow down. Dried by passing between the flowing grains in a drying chamber,
So-called circulating hot air dryers are commonly used.

The temperature of the hot air for drying is, for example, the type of dried grain, the amount of air, the ambient temperature, the grain temperature, the moisture content of the grain, and the drying speed (moisture drying rate per hour). It is controlled by various conditions.

In addition, the air in the closed hollow chamber is forcibly sucked by the rotation of the rotator to be exhausted to the outside, and the pressure in the room is reduced to maintain a substantially constant equilibrium state of the pressure difference between the inside and the outside. A so-called reduced-pressure equilibrium heating / drying method is also known in which outside air heated to a desired temperature is fed into the hollow chamber while the equilibrium state is maintained to dry the object to be dried in the hollow chamber. See JP-B-59-52753).

However, although the drying apparatus utilizing the reduced pressure equilibrium heating drying method is suitable for drying paste or tea,
It is not suitable for drying a large amount of paddy and wheat grains at the drying rate required for the current agricultural work schedule.

[0006]

By the way, various research institutes have studied the effect of the drying condition of paddy on the eating quality of rice. According to a published report, the blast temperature of the circulating hot air dryer is 50 ° C. It is said that when the temperature is -60 ° C or higher, the taste is deteriorated.

Further, the higher the initial moisture content and the blast temperature, the lower the taste of the dry-finished rice, and the initial moisture content is 22, 26, 30% as a drying condition with a taste reduction value of 0.1 as an allowable limit.
It can be estimated that the critical blast temperature in the case of is 55, 48, and 35 ° C., respectively (see FIG. 3). Furthermore, the relationship between the drying conditions and the germination reduction rate of paddy when dried by a conventional circulation dryer. Fig. 4 shows that the germination of heat-dried paddy is significantly affected by the initial water content at the start of drying and the air temperature, and the higher the respective, the greater the germination damage. And
The limit line of 0.1 in taste deterioration in Fig. 3 is the germination reduction rate of 5% in Fig. 4.
There is also a report that it is estimated that there is a deep correlation between the germination of paddy and the taste of the rice, which is almost in line with the limit line (see FIG. 5). (Toyama Prefectural Agricultural Technology Center Research Report No. 5 reprint, issued in May 1989)

Further, cooked rice having a high mixed ratio of broken rice has a bad appearance, is not sticky, is soft, and deteriorates the taste and overall evaluation, and the long-term high temperature storage in intermittent drying makes the rice steamy and tasty. It is widely known that it affects.

From the above, it can be said that it is a necessary condition for maintaining the taste that the drying blast temperature is made as low as possible and the drying is performed so fast that the cracking of the barrel, which is the cause of crushed rice, does not occur.

However, in the above-described conventional circulating hot air drying method, even when the grain has a high moisture content in the initial stage of drying or the moisture variation between the grain grains is large, the preset drying rate is set. In order to obtain it, the blast temperature for drying may be controlled to a high temperature, and there is a problem in that the germination rate, germination force and taste of grain may be impaired.

Further, in order to dry a large amount of grains at the time of harvesting grains, it is necessary to dry at a drying rate that does not hinder the schedule of agricultural work, and the conventional circulation system that requires a large amount of high temperature air. In the hot air dryer, the fuel consumption of the oil burning burner for heating is large and there is a problem that the cost increases.

[0012] The present invention provides a series of agricultural work to produce a good-quality dry product, which has a high moisture content and a large variation in moisture content, without spoiling the germination rate and germination force and having no cracks in the barrel. It is an object of the present invention to provide a grain drying method that can be obtained economically and efficiently at a drying rate that is as fast as possible so as not to hinder the operation.

[0013]

The grain dryer used in the present invention for achieving the above object is based on a conventional circulating hot air dryer, and is improved by adding various parts to a reduced pressure equilibrium heat drying method. It is a part of it. However,
To increase the temperature in the drying chamber, a frictional heat generating portion is not provided in the rotating region of the rotating body for forced exhaust as described in Japanese Patent Publication No. 59-52753, and an air supply port opened to the minimum necessary. The air sucked in more is heated by burning an appropriate amount of fuel with an oil burning burner.

In addition to improving the pressure performance of the suction / exhaust fan, the exhaust fan motor is a variable rotation speed motor, and the rotation speed is controlled to increase / decrease so that the inside of the drying chamber is kept above atmospheric pressure. Increase / decrease is controlled to a reduced pressure state (static pressure value) of about -40 to -200 mmAq.

The grain drying method of the present invention uses the above-mentioned vacuum type grain dryer, and the hot air temperature for drying is about 35 ° C. at the initial stage of drying.
In addition, when the moisture content of the dried grain becomes equal to or lower than the moisture value predetermined by the type of grain, the temperature becomes approximately 40 ° C. which is approximately predetermined by the type of grain and the amount of swelling. Thus, the fuel supply amount of the oil burning burner is controlled. And, the drying speed of the grain (rate of moisture loss per hour) is the type of grain,
It is characterized in that drying is performed while increasing / decreasing a depressurized state (static pressure value) in the drying chamber so that a drying rate (water loss rate per hour) set in advance by the amount of swelling is obtained.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a control block circuit diagram for carrying out the drying method according to the present invention, in which 1 is a time-dependent detection of a drying rate of dried grains, that is, an hourly drying rate, and the detection signals are compared. A drying loss rate detector for sending to the circuit 5, wherein 2 detects the temperature of hot air blown on the grains in the drying chamber,
It is a blast temperature detector for sending the detection signal to the comparison circuit 5.

Reference numeral 3 is a static pressure value detector for detecting the reduced pressure state (static pressure value) in the drying chamber and sending it to the comparison circuit 5.

Reference numeral 4 denotes a reference setting circuit for setting the drying rate of the grain, the temperature of the drying blast and the static pressure value in the drying chamber.
This circuit 4 includes a drying blast temperature reference value that is preset according to the moisture content of the dried grain, an hourly drying rate reference value that is preset according to the moisture content of the dried grain, and It has a role of sending a signal of a static pressure value reference value preset in the drying chamber according to the hourly drying rate reference value to the comparison circuit 5.

Therefore, as shown in FIG. 2, in the reference setting circuit 4, for example, hot air having a substantially constant temperature of about 35 ° C. in the initial stage of drying and about 40 ° C. thereafter is used to dry the dried grains to a predetermined moisture content. Blast temperature reference table for drying up to 30% to 25% of the moisture content of the dried grain is about 0.7% per hour drying rate, and between 25% and 20% moisture is the drying rate reduction per hour. According to the hourly drying rate reference table and the hourly drying rate reference table set so that the hourly drying rate is around 0.8% between about 0.9% and the water content of 20% to 13%. It incorporates a static pressure reference table that is set to maintain the hourly drying rate.

The reference numeral 5 compares the signals sent from the drying loss rate detector 1, the blast temperature detector 2 and the static pressure value detector 3 with the signals sent from the reference setting circuit 4 to heat them. Device (oil fuel combustion burner) 7 and decompression device (suction / exhaust fan) 8
Is a comparison circuit for sending a signal to the control circuit, and the numerical value of the drying blast temperature detected by the blast temperature detector 2 during drying and the numerical value determined by the drying temperature reference table shown in FIG. In comparison, a signal is promptly sent to the control circuit 6 to increase / decrease the fuel supply amount to the heating device (oil combustion burner) 7.

Also, the hourly drying loss rate value of the grain detected by the drying loss rate detector 1 is larger or smaller than the value determined by the hourly drying loss rate standard table shown in FIG. At times, the correction value is added to or subtracted from the value determined by the static pressure value reference table shown in FIG. 2, the value is compared with the value detected by the static pressure value detector 3, and a signal is promptly sent to the control circuit 6, The number of rotations of the motor of the decompression device (suction / exhaust fan) 8 is increased / decreased so that the static pressure value in the drying chamber is adjusted to the reference static pressure value.

Thus, it is possible to efficiently produce a dry grain having a high germination rate, a high germination tendency, and no cracks in the body and a good taste.

[0024]

As described above, in the grain drying method according to the present invention, even if the moisture content is high at the initial stage of drying or there is a large variation in moisture content between grains, about 35% is obtained at the initial stage of drying.
In order to heat at a blast temperature of ℃, and then to a substantially constant blast temperature of around 40 ℃, depending on the amount of infiltration, and to dry at a preset drying rate (drying rate per hour), Since it is controlled to increase or decrease from atmospheric pressure to a reduced pressure state (static pressure value) of about -40 to -200 mmAq and dried, fuel consumption is low and economically impairs the germination rate of paddy, wheat, and germination of beer wheat. In addition, it is possible to obtain a dry product of good quality and good taste at a drying speed as high as possible so that cracking of the body does not occur.

[Brief description of drawings]

FIG. 1 is a control block circuit diagram for carrying out a drying method according to the present invention.

FIG. 2 is an example of a drying blast temperature reference table preset according to grain moisture, an hourly drying loss rate criterion table of grain moisture, and a static pressure value reference table in a drying chamber.

FIG. 3 shows the relationship between the drying conditions and the deterioration in the taste of finished rice in a conventional circulation dryer.

FIG. 4 shows the relationship between the drying conditions and the rate of germination reduction of paddy when dried by a conventional circulation dryer.

FIG. 5 is a diagram showing the relationship between the germination reduction rate of rice and the taste when dried by a conventional circulation dryer.

[Explanation of symbols]

 1 Drying rate detector 2 Blower temperature detector 3 Static pressure value detector 4 Standard setting circuit 5 Comparison circuit 6 Control circuit 7 Heating device (petroleum combustion burner) 8 Pressure reducing device (suction blower)

Claims (1)

[Claims] 1. The drying blast temperature is about 35 ° C. at the initial stage of drying.
In addition, when the moisture content of the dried grain becomes equal to or lower than the moisture value predetermined by the type of grain, the temperature becomes approximately 40 ° C. which is approximately predetermined by the type of grain and the amount of swelling. As described above, the fuel supply amount of the heating device (oil burning burner) is controlled to be increased or decreased, and the drying rate of the grain (moisture drying rate per hour) is set in advance according to the type of grain and the amount of swelling ( (Heat moisture loss rate per hour)
A method for drying grains, which comprises drying while controlling the number of rotations of a decompression device (suction / exhaust fan) motor so that the decompression state (static pressure value) is about 40 to -200 mmAq.