JPH0536713B2 - - Google Patents

Description

[Detailed description of the invention]

In conventional dryers, the volume of hot air is constant from the start to the end of drying, so as the grains dry, the humidity of the exhaust air decreases, allowing dry exhaust air to be released into the atmosphere while still retaining sufficient drying capacity. However, it had the disadvantage of poor thermal efficiency. In the present invention, when the humidity of the exhaust air drops to a certain value, the flow rate of the hot air is reduced, thereby allowing the hot air to contact the grains for a long time to fully demonstrate its drying ability, thereby preventing a decrease in the humidity of the exhaust air, The purpose is to improve the thermal efficiency of Motsutsu dryers. The present invention will be described based on an embodiment shown in the drawings. Reference numeral 1 denotes a storage chamber of a dryer, and a chevron plate 2 having an inverted V-shaped cross section is provided at the center of the bottom of the storage chamber 1. Direction swash plates 3, Install 3. Perforated plates 4 are connected to both side edges of the chevron-shaped plate 2 and the lower edges of the guiding swash plates 3, 3, respectively, and a pair of opposing perforated plates 4 form a drying chamber 5, 5. The discharge ports at the lower ends of the drying chambers 5 and 5 are connected to a gutter-like grain flow chamber 7 through a rotary valve 6, and the output end of a grain feeding helix 8 suspended horizontally in a groove in the center is connected to a grain hoist 9.
Connect to the bottom intake of the A grain feeding helix 10 is connected to the upper part of the grain raising machine 9,
Its terminal end is opened above the diffusion plate 11 suspended from the center of the ceiling plate of the storage chamber 1. Then burner 1 is placed opposite the front and back of the dryer.
2 and a suction fan 13 are installed, and the burner 12 is exposed to the hot air chamber 14 inside the left and right drying chambers 5, 5, and the fan 13 is attached to the outside of the drying chambers 5, 5 and the exhaust area surrounded by the outer wall of the dryer. Connect to the wind chamber 15.
16 is a shield plate that closes off the side of the hot air chamber 14 opposite to the burner 12. The grains pass through a grain hoist 9 and a grain feeding helix 10, are spread evenly into a storage chamber 1 by a diffusion plate 11, and flow down a drying chamber 5. At this time, hot air from the burner 12 enters the left and right drying chambers 5 from the central hot air chamber 14, dries the grains flowing down, and the exhausted air containing moisture is released into the exhaust chamber 15.
The air is then exhausted to the outside of the machine by a fan 13. The dried grains fall into the flow grain chamber 7 by rotation of the rotary valve 6, and are returned to the storage chamber 1 by the grain feeding helix 8 and the grain raising machine 9. However, in this embodiment, temperature sensors Sa and Sb are installed inside the hot air chamber 14 and exhaust air chamber 15 of the dryer, respectively, to measure the actual hot air temperature Ta and exhaust air temperature Tb. A grain amount setting circuit 17 is provided to set the grain amount A loaded into the dryer, and this is connected to the hot air temperature setting circuit 18, so that the hot air temperature is adjusted according to the grain amount A so that the grain temperature inside the dryer is constant. Set. Reference numeral 19 denotes a comparison circuit, to which a hot air temperature setting circuit 18 and a hot air temperature sensor Sa are connected to the input side, and a fuel pipe of the burner 12, such as a solenoid valve, is connected to the output side of the comparison circuit 19. The fuel control device 20 is operated to control the flow rate of fuel so that the actual hot air temperature becomes equal to the set temperature, and the burner 12 is burned. Next, a humidity sensor that measures the absolute humidity Ma of the hot air.
Ha is installed inside the hot air chamber 14, and this is used as a temperature sensor.
It is connected to the exhaust air humidity determination circuit 21 along with Sa and Sb. Therefore, the absolute humidity difference between hot air and exhaust air is proportional to the temperature difference between the two, so if the ratio is k and the absolute humidity of exhaust air is Mb, k = absolute humidity difference between hot air and exhaust air/hot air and exhaust air. Temperature difference = Mb-Ma/Ta-Tb (1 equation). Since the normal hot air temperature Ta is 40℃ to 50℃, let us assume that the absolute humidity Ma of the hot air is 4 to 8 (g/Kg).
So, assuming that the exhaust air temperature Tb is between 21℃ and 27℃,
As shown by the broken line in the psychrometric diagram of FIG. 4, the absolute humidity Mb of the exhaust air at the exhaust air temperature Tb at that time is determined as shown in Table 1.

[Table] From this, it turns out that the value of k within that range is 0.42. Therefore, if k = 0.42 in (Equation 1), the absolute humidity Mb of the exhaust air will be Mb = Ma + (Ta - Tb) x 0.42 x K (Equation 2). Here, K is the ratio of the total heat amount of the hot air to the heat amount used for drying, and is a constant. According to equation (2), the exhaust air humidity determination circuit 21 determines the absolute humidity Mb of the exhaust air from the absolute humidity Ma of the hot air detected by the humidity sensor Ha, the hot air temperature Ta detected by the temperature sensors Sa and Sb, and the exhaust air temperature Tb. Calculate. Next, the output side of this circuit 21 is connected to the grain amount setting device 1.
7 is connected to the air volume setting circuit 22, and in the circuit 22, the initial value Wp and lower limit value Wq of the set air volume W are determined according to the grain amount A as shown in FIG.
After the start of drying, when the absolute humidity Ma of the exhaust air decreases to a predetermined value, the circuit 21 detects this and decreases the value of the set air volume W (Kg). The output side of the air volume setting circuit 22 is connected to the rotation speed control circuit 23 of the motor 24 of the suction fan 13, thereby controlling the rotation speed of the motor 24 so that the set air volume W output by the circuit 22 is achieved. The relationship between the set air volume W and the rotation speed of the motor 24 is actually measured in advance, and the relationship between the two is stored in the circuit 23. In the embodiment of the drawing, the humidity sensor Ha is installed in the hot air chamber 14.
However, since the absolute humidity of the hot air and the outside air are the same, the humidity sensor Ha may be installed outside the dryer to measure the humidity of the outside air. If the humidity sensor Ha is installed inside the hot air chamber, it can be integrated with the hot air temperature sensor Sa, so it can be manufactured at low cost, and if the humidity sensor Ha is installed outside the dryer, it will not be affected by heat and the accuracy will be improved. It has the advantage of being high. In either case, the hot exhaust air always flows inside and outside the dryer, does not stagnate, and has an even distribution of temperature and humidity, so the exhaust air humidity detected based on this is also consistent. Note that the gist of the present invention does not change even if relative humidity is used instead of absolute humidity. In short, the present invention controls the combustion of the burner 12 so that the hot air temperature is set according to the amount of grain to be dried, and also determines the initial value Wp and lower limit value Wq of the amount of hot air according to the amount of grain. Alternatively, when the humidity Mb of the exhaust air determined from the humidity of the outside air and the temperatures Ta and Tb of the hot air and exhaust air decreases to a predetermined value, the volume W of the hot air is reduced. Therefore, in the present invention, as the moisture content of the grain decreases as the drying time passes and the humidity of the exhaust air drops to a predetermined value, the volume of hot air decreases, and the time required for the hot air to cross the drying chamber 5 increases. Since the hot air is in contact with the grains for a long period of time, the drying ability of the hot air is fully utilized, reducing the amount of fuel consumed by the burner and allowing for highly efficient drying. In this way, the present invention reduces the amount of hot air when drying has progressed to a certain extent, but since the timing is based on the humidity of the exhaust air that is detected evenly, the amount of air may be reduced too early or too late. control at the correct timing. In addition, since the volume of hot air does not fall below the lower limit, the grains can be dried in a short time without unnecessarily reducing the drying speed of the grains.
Since this is not provided in the exhaust air chamber 15, the dust contained in the exhaust air does not adhere to the humidity sensor Ha, and the humidity of the exhaust air can be accurately measured.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal front view of a grain dryer embodying the present invention, Fig. 2 is a cross-sectional plan view thereof, Fig. 3 is a block diagram of its control system, and Fig. 4 is a hygrodynamic diagram showing hot air and exhaust. Shows the relationship between wind temperature and humidity. FIG. 5 is a graph showing the relationship between the initial value Wp and lower limit value Wq of the set air volume W of hot air and the grain amount A.

Claims (1)

[Claims] 1 The combustion of the burner is controlled so that the hot air temperature is set according to the amount of grain to be dried, and the initial value and lower limit of the amount of hot air are determined according to the amount of grain, and the humidity of the hot air or outside air, the hot air, and the exhaust air are controlled. A hot air control device for a burner in a grain dryer, characterized in that the volume of hot air is reduced when the humidity of the exhaust air determined from the temperature of and the humidity of the exhaust air decreases to a predetermined value.