JPS594876A - Controller for combustion of burner in cereal drier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] In conventional grain dryers, the hot air temperature of the burner is set appropriately depending on the amount of grain, so there is a difference in the water removal ability of the hot air due to differences in outside air humidity, and there is a difference depending on the type and quality of grain. Differences in whether or not it dries easily were not taken into consideration, and the drying speed varied widely, resulting in long drying times and drying being too fast, which sometimes resulted in shell cracking.

To overcome this drawback, it is necessary to control the combustion of the burner so as to keep the drying rate of the grain constant.

Since the drying rate is the decrease in the moisture content (%) of the grain per unit time, the moisture content at a certain time is a.

If the moisture content after many units of time is b, then the drying rate P (57 hours) at that point is p = a - b
(Equation 1) When the drying speed is P, the weight of water evaporated from the grain per unit time, that is, the amount of water removed Q (Kg
/time), if the weight of the grain at a certain time is A (Kg), and the weight of the grain after many units of time is B (Kg), then Q=A-B (equation 2) By the way, excluding water Since the weight of each grain does not change before and after drying, the following formula holds.

If b and B are determined from (Formula 1) and (Formula 3) and substituted into (Formula 2), the following is obtained.

Generally, the appropriate drying rate P for paddy and wheat is 0.6 to 1.2 (
57 hours), but if we assume that P = 0.8 and keep it constant, the amount of water removed Q that evaporates every hour from the entire 1000 kg grain is determined from (Equation 4), A = 1000 kg.
Therefore, when a=25 (%), Q=11 (Kg/hour) a=
When 20 (%), Q = 10 (Kg/hour) a =
When it is 15 (%), Q = 9.3 (Kg/hour)
becomes. When the relationship between the moisture content a and the amount of water removed Q is plotted, the graph shown in FIG. 4 is obtained.

When the drying rate P is set to a certain value in this way, the amount of water removed Q can be determined from the moisture content a and the weight A of the grains by calculating (Equation 4).

Therefore, the moisture content a and weight A of the grains being dried are measured, and based on the measured values, the amount of water removed Q that will give the optimum drying speed P is calculated sequentially. Water amount q
By controlling the combustion of the burner so that the values match, the drying rate P can be maintained at a constant optimum value from beginning to end.

However, the weight A of the grains does not decrease significantly before and after drying, so the weight A is set to an appropriate constant value in advance, and water removal tQ is performed based on the weight A at that constant value and the measured value of the moisture content a. may be calculated.

Or, as is clear from the graph in Figure 4, the amount of water removed Q
Even when drying from the beginning to the end with a constant value of Q = 10 (Kg/hour), the drying rate P remains constant at approximately 0.8 (57 hours), and in general, even if the moisture content a varies, the amount of water removed Q Since this changes only by a slight difference that can be ignored in practical terms, it is practical to set the value of the water removal amount Q to a constant value in advance.

In any case, if we calculate the amount of water removed Q that will give the optimum drying rate P, and then control the combustion of the burner so that the actual amount of water removed q matches this, the drying rate can be maintained at the optimum value from beginning to end. No cracking of the finished grain occurs.

Based on this knowledge, the present invention aims to make the drying rate P constant by matching the calculated water removal iQ with the actually measured water removal amount q.

An embodiment of the present invention will be described based on the drawings. Reference numeral 1 denotes a storage chamber of a dryer. A chevron-shaped 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, 3 are arranged opposite to each other on the left and right sides of the chevron-shaped plate 2. Install. Perforated plates 4 are connected to both side edges of the chevron plate 20 and the lower edges of the guiding swash plates 3, 3, respectively, and a set of two opposing perforated plates 4 are connected to each other.
drying chambers 5, 5 are formed.

The discharge ports at the lower ends of the drying chambers 5 and 5 are exposed through the rotary pulp 6 into a gutter-like grain flow chamber 7, and the delivery end of the shell helix 8 suspended horizontally in the groove in the center is connected to the grain raising machine 9. Connect to the bottom intake.

A grain feeding helix 1o is connected to the upper part of the grain elevating machine 9, and its terminal end is opened above a diffusion plate 11 suspended from the center of the ceiling plate of the storage chamber 1.

Then, a burner 12 and a suction fan 13 are installed opposite to each other on the front and back sides of the dryer, and the burner 12 is connected to the left and right drying chambers 5 and 5.
The fan 13 is connected to the outside of the drying chambers 5, 5 and to the exhaust chamber 15 surrounded by the outer wall of the dryer. 16 is a shield plate that closes off the side of the hot air chamber 14 opposite to the burner 12.

The grains are spread evenly into the storage chamber 1 by the diffusion plate 11 through the grain raising machine 9 and the grain feeding helix 10, and flow down the drying chamber 5.

At this time, the 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 passes through the exhaust chamber 15 and is sent to the 7-an 13. Exhaust outside.

After drying, the grains flow into the grain chamber 7 through the rotation of the rotary valve 6.
The grain is returned to the storage chamber 1 by the grain feeding helix 8 and the grain raising machine 9.

Since all of the water evaporated from the grains is included in the exhaust air, the actual amount of water removed q is the product of the difference in absolute humidity between the hot air and the exhaust air and the air volume F (Kg) that passes through the drying chamber 5 during unit time. be equivalent to. Absolute humidity is the number of grams of water contained per kilogram of air, so when this is converted into kilograms, the following formula holds true.

q = (absolute humidity of exhaust air - absolute humidity of hot air) x O, 00
1x F (Kg/hour) (Formula 5) The absolute humidity difference between hot air and exhaust air is proportional to the temperature difference between the two, so the ratio is e.
Then, it becomes .

Therefore, when actually operating the dryer, the normal hot air temperature is between 40°C and 50°C, and now assume that the absolute humidity of the hot air is 4 to 8 (g7Kg) and the exhaust air temperature is 27°C.
If the temperature is between 296C and 296C, the absolute humidity at the exhaust air temperature at that time is determined as shown in Table 1, as shown by the broken line in the humidity diagram in FIG.

Table 1 From this, it turns out that the value of e within that range is 0.42.

Therefore, from (Equation 5) and (Equation 6), q = (Heat JtoFm degrees - Exhaust air temperature I X 0.42m
XF (Type 7) Totoru. Here, m is the efficiency obtained by subtracting the amount lost due to temperature rise between the dryer and the grain, and is a constant compensation coefficient determined by the model and specifications of the dryer, the type and quality of the grain, etc.

Therefore, in the present invention, temperature sensors Sa and Sb are installed inside the hot air chamber 14 and exhaust air chamber 15 of the dryer, respectively, and a pressure sensor 17 such as a diaphragm pressure gauge is installed inside the hot air chamber 14. Sa, Sb
and 17, and the actual water removal 44. according to (7). Connect to the arithmetic circuit E that calculates q.

Here, the absolute value K (mmHg) of the atmospheric pressure in the hot air chamber 14 and the air volume F (Kg) passing through the drying chamber 5 are approximately proportional to the same as shown in FIG. This is converted into F and then converted into voltage and output.

In place of the pressure sensor 17, a magazine chamber 1 as shown in FIG.
It is also possible to use a device that blows wind onto the resistance plate 18 rotatably hanging down from the ceiling of No. 5, tilts it, and detects the angle of inclination and the amount of air F.

Generally, in the early stage of drying, the grain has low ventilation resistance and the wind-stripes, F is large, but as drying progresses, the grain shrinks, the ventilation resistance increases, and the air flow rate F decreases.

Normally, at the end of the drying period, the air volume at the beginning of the drying is IO or 1
It will be reduced by 5%. The air volume F also differs depending on the variety of grains to be dried.

The actual value of the airflow F, which changes under various conditions, is measured by the pressure sensor 17, and its output is sent to the temperature sensor j9.
a, is input to the arithmetic circuit E together with the output of Sb, and (-7
Water removal amount according to formula).

Calculate the actual value of q.

On the other hand, the support leg 19 at the bottom of the dryer has a built-in sensor such as a resistance wire strain meter that converts weight into electrical quantity, and receives the sensor signal to determine the weight of grain in the dryer fi: A (Kg )
A grain amount measuring circuit W that outputs a voltage proportional to is provided.

Then, the well-known moisture content meter W attached to the grain storage device 1 and the grain amount measuring circuit W are connected to the reference water removal amount calculation circuit NK, and this circuit N
The amount of water removed Q is subtracted according to equation (4).

Next, the output sides of the circuits N and E are connected to a comparator C, and the output sides thereof are further connected to the fuel valve V of the burner 12.

Then, the actual amount of water removed q is compared with the calculated amount of water removed Q that should be the standard. If q is larger than Q, the pulp V is squeezed, and if it is smaller, the valve ■ is opened and the burner 12 is combusted. control automatically.

As mentioned above, without measuring the weight A of the grains,
When calculating the amount of water removed, Q, based on the measured values of weight A and moisture content a, which are set to an appropriate constant value in advance, a variable resistor is used in place of the grain amount measuring circuit W. A grain amount setting circuit for setting the weight A is connected.

If you still want to set the water removal amount Q instead of calculating it from the measured values of grain moisture content a and weight A, discontinue the grain amount measurement circuit W and moisture content meter G and use the standard water removal amount. In place of the calculation circuit N, a reference water removal amount setting circuit for setting the water removal amount Q using a variable resistor may be connected.

In short, in the present invention, not only the temperature of the hot air and exhaust air blowing inside the dryer, but also the air volume F (Kg) is actually measured using an air volume measuring device such as a pressure sensor 17 or a resistance plate 18. Since the actual water removal - J&Q is calculated from the measured value, even if the high air volume F changes depending on whether the degree of drying is early or late, the type of grain, the rate of contamination, etc. By controlling the combustion so that the actual amount of water removed q can be calculated correctly, and the amount of water removed Q calculated separately from the grain amount and moisture content always matches, the drying rate is always kept at a constant and optimal drying rate. It has the effect of being able to dry stably and producing grains of good quality without shell cracking.

Furthermore, in the present invention, the actual amount of water removed q is determined from the temperature difference rather than the absolute humidity difference between the hot air and the exhaust air, so an expensive hygrometer is not necessary and high-precision measurement can be performed using an inexpensive temperature sensor.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a grain dryer embodying the present invention;
Figure 2 is a cross-sectional plan view, Figure 3 is a block diagram of its control system, and Figure 4 is the drying speed P = 1000 kg of grain.
0.8 (37 hours) Water removal amount Q when drying constant
Figure 5 is a graph showing the relationship between the air flow rate F (Kg) passing through the drying chamber and the air pressure K (mmHg) in the hot air chamber, and Figure 6 is a graph showing the relationship between The cross-sectional view of the embodiment, FIG. 7, is a humidity diagram showing the relationship between the temperature of hot air and exhaust air and the absolute humidity with broken lines. Agent: Tetsu Maki (2 people) Funeral map 2

Claims (1)

[Claims] The amount of water removed, Q, calculated according to the amount of grain to be dried, is compared with the amount of water removed, q, measured from the temperature difference between the hot air and exhaust air of the dryer and the air volume, and the drying speed is determined by burning the burner so that both agree. A combustion control device for a burner in a grain dryer, which is characterized by keeping the temperature constant.