JPS5920625Y2 - Hot air temperature control device for circulating grain dryer - Google Patents

Description

[Detailed description of the invention] This invention relates to a hot air temperature control device for a circulating grain dryer, and specifically regulates the temperature of the grain to be dried so that it does not exceed a certain temperature during drying, thereby impairing the quality of the grain to be dried. This is an attempt to reduce the loss of drying energy in the final stage of drying.

Conventionally, this type of dryer blows hot air at a substantially constant temperature from the beginning.

In this case, grain temperature increased as drying progressed.

It was pointed out that an excessive rise in grain temperature would lead to quality deterioration, and an improvement was made to detect the grain temperature and control the hot air temperature to prevent the grain from exceeding a certain temperature. .

However, the reason why a device that performs the control described in (2) above has not been put into practical use is because of the following problems.

a. How to accurately grasp the grain temperature, b. Comparing only the hot air temperature and grain temperature creates a range that cannot be controlled due to the capacity of the hot air generator, and more complex upper and lower limit regulations are required. etc. must be done.

Taking these circumstances into consideration, the inventor conducted a detailed study on the rise in grain temperature during the drying process, and found that, for example, during drying of paddy, until the moisture content falls below 20%, the grain temperature rises due to the latent heat of vaporization. It was found that while the increase in grain temperature was small, the increase in grain temperature became significantly larger from around 17%.

Therefore, hot air temperature control in consideration of the grain temperature during the drying process can be simplified by performing the control separately until the grain temperature increases and afterward.

In addition, it is known that at the time when the grain temperature rises significantly, quality changes such as side splitting due to drying are likely to occur at the same time, and from another perspective, the hot waste air that has passed through the drying section still shows a high temperature. It is known that the drying effect is not sufficient.

This idea was devised with these points in mind.

The contents will be explained below based on an illustrated example.

Reference numeral 1 designates a known circulating grain dryer, in which a storage section 3 is provided above the drying section 2, feed valves 4, 4 provided at the lower end of the drying section 2, and a transverse conveyor 5 provided below the storage section 3. , an elevator 6, a two-part conveyor 7, and a circulation mechanism.

The drying section 2 has a grain flow path 21 formed of a perforated plate 8.
．． 21 and ventilation passages 23.2 formed alternately on both sides thereof.
3 and a hot air path 22 are provided, and a hot air generator (not shown) is provided in series to supply hot air to the hot air path 22.

The hot air generator is a well-known device that includes a furnace, an electromagnetic pump that supplies fuel to the furnace, and a blower (or exhaust fan).

Furthermore, a hot air temperature sensor 9 made of a thermistor Th or the like is provided in the hot air path 22.

On the other hand, directly below the feed valve 4, a grain barrel 11 with a rotary valve 10 inside is disposed above the cross conveyor 5 and slightly inward from the side wall. While interlocking with the feed-out valve 4, the grain fed out by the feed-out valve 4 is stored in the flow grain cylinder 11 while the feed-out valve 4 is stopped.

Then, the flowing grain cylinder 11 is placed so as to be buried in this stored grain.
A grain temperature sensor 13 consisting of a thermostat (TH) or the like is installed inside the grain temperature sensor.

The hot air temperature control device for this grain dryer will be explained with reference to FIGS. 2 and 3. The hot air generator E mainly controls the amount of fuel supplied by changing the driving frequency of the coil L of the electromagnetic pump P. A variable resistance VR that can control the hot air temperature.

etc. as a hot air temperature setting device A, a thermistor Th etc. as a hot air temperature sensor 9, a bridge circuit including these as a comparison circuit B, an oscillation circuit C that changes the oscillation frequency according to the output of the comparison circuit B, and an oscillation circuit C. The hot air temperature is controlled to be maintained at a set hot air temperature by a drive circuit that drives the electromagnetic pump P according to the oscillation frequency of the hot air.

This compositional action, etc. is explained in Utility Application No. 53-89108
5-6675).

The feature of this device is that when a grain temperature sensor 13 consisting of a thermostat (TH) or the like detects a predetermined temperature (36 to 39 degrees Celsius in the case of paddy), a relay RY is connected between the comparison circuit B and the oscillation circuit C. A hot air temperature regulating circuit F is provided in which the normally open contact RY, is closed and a resistor R1 is interposed, and the normally closed contact RY, ' of the relay RY is opened.

With the above configuration, when this dryer is operated,
The grain stored in the grain flow path 21, 21 of the drying section 2 and the storage section 3 above it is fed out and discharged downward in sequence by the feeding valves 4, 4, and is sent from the cross conveyor 5, elevator 6, upper conveyor 7, etc. It is circulated by a circulation mechanism.

During the circulation process, when passing through the drying section 2, the material comes into contact with hot air and is dried, and this process is repeated to dry it to a desired moisture content.

A part of the grain fed out by the feeding valve 4 is transferred to the grain barrel 1.
1 and is temporarily held in a stationary state by the action of a rotary valve 10 that interlocks with a delivery valve 4 that rotates intermittently (the rotary valve 10 can be replaced with another shutter that opens and closes intermittently sell.

) and a grain temperature sensor 13 provided inside the flow grain cylinder 11.
However, the temperature of the grains immediately after being discharged from the drying section 2 is detected without being affected by the hot air temperature or the outside air.

Furthermore, the hot air generator E is controlled based on a command from a comparison circuit B that compares the temperature set by the hot air temperature setting device A with the temperature detected by the hot air temperature sensor 9 and issues a signal, so that the hot air is always maintained at the set temperature. As drying progresses, the grain temperature rises, and when it reaches a predetermined value, the grain temperature sensor 13
(thermistor Th) operates, turning on relay RY,
A resistor R1 is interposed between the comparison circuit B and the oscillation circuit C, and this state is self-maintained so that it continues even if the grain temperature returns to a predetermined value or less due to a change in outside temperature.

By appropriately selecting the resistor R1, the temperature To-Tx, which is lower than the set value To set by the hot air temperature setting device A by a predetermined temperature Tx, can be set as the new set temperature.

At this time, it is practically convenient to set Tx to around 4°C.

This invention has the following effects due to the above-described configuration and operation.

■ Grain temperature can always be maintained within a constant value (for example, 40°C) without being affected by changes in outside temperature.

■ The temperature of the grain is measured immediately after passing through the drying section, when the temperature of the grain itself has risen the most, while the grain is stopped, and in a position where there is little influence from other hot air or outside air. The impact on quality was minimized.

◎ In the normal feedback format, the set temperature rises again as the grain temperature itself falls, causing the hot air temperature to fluctuate up and down, but this problem is eliminated.

■ Reduce heat loss at the end of drying.

Note that the grain temperature sensor 13 is
Not limited to TH, another bridge circuit may be used, and a combination of a memory and an arithmetic device may be used instead of a relay.

[Brief explanation of the drawing]

The drawings show one embodiment of this invention; Fig. 1 is a longitudinal cross-sectional view of the dryer, Fig. 2 is an explanatory diagram of hot air temperature control, and Fig. 3 is a diagram illustrating hot air temperature control.
The figure also shows a circuit diagram, in which 2 is a drying section, 21 is a grain flow path, 22 is a hot air path, 3 is a storage section, 4 is a delivery valve, 9 is a hot air temperature sensor, 10 is a rotary valve, and 11 is a grain flow path. Cylinder 13 is a grain temperature sensor.

Claims (1)

[Scope of utility model registration request] In a device where grain is stored in a drying section and a storage section, and the grain is circulated by a circulation mechanism and brought into contact with hot air in the drying section, the position where the temperature of the dried grain increases the most during circulation and where it is not exposed to hot air. a grain temperature sensor provided in the drying section; a hot air generator for blowing hot air into the drying section; a hot air temperature sensor provided in the hot air to detect the temperature of the hot air obtained by the hot air generator; a hot air temperature setting device for setting the temperature; a comparison circuit for comparing the temperature set by the hot air temperature setting device with the temperature detected by the hot air temperature sensor; 1. A hot air temperature control device for a circulating grain dryer, comprising a hot air temperature regulation circuit that lowers the hot air temperature set by a temperature setting device by a predetermined temperature.