JPS5974486A - Controller for hot air 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] When drying grains using a dryer, if the drying speed is too fast, the grains will crack, and if the drying speed is too slow, it will take a long time to finish drying, resulting in poor efficiency. will occur.

In order to avoid the negative effects of drying, it is necessary to continue drying at an appropriate constant drying rate throughout.

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 unit time is b, then the drying rate P (%/hour) 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 water removed tQ (Kg
/hour), if the weight of the grain at a certain time is A (Kg), and the weight of the grain a unit time after that is B (Kg), then Q=A-B (equation 2) By the way, excluding water Since the unique weight of grains does not change before and after drying, the following equation holds.

A-A-=B-B - (Equation 3) Calculating b and B from Equation 1 and Equation 3 and substituting them into Equation 2 gives -100 Q = A (1-i) (4 formula).

Generally, the appropriate drying rate P for paddy and wheat is 0.6 to 1.2 (
57 hours), but tentatively P = 0.
8, the amount of water removed that evaporates every hour from the entire grain of 1000 Kg is determined from (Equation 4), A = 1
000Kg, so when a=25 (%), Q=11 (Kg/hour) a=
When 20 (%), Q = 10 (Kg/hour)
When a=15 (%), Q=9.3 (Kg/hour).

Similarly, when P = 0.1, 0.9, and 0.7 are held constant, the water removal amount Q corresponding to the water content is
is calculated using equation (4), and the relationship between the water content and the amount of water removed Q in each case is shown in a graph as shown in Figure 4.

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, it is possible to measure the moisture content a and weight (grain amount) A of the grains during drying, and based on the measured values, calculate the amount of water removed Q that will give the optimum drying speed P. If the hot air from the burner is controlled so that the water removal amount Q matches the actual water removal amount q, the drying speed P can be maintained at a constant optimum value from beginning to end, and grain shell cracking will not occur.

However, when grains are dried by exposing them to hot air, the water evaporated from the grains is included in the exhaust air and discharged outside the machine, so the actual value of the amount of water removed q is determined by the absolute humidity of the hot air and exhaust air. It can be found from the product of the difference between and the amount of hot air per unit time W (Kg).

Since absolute humidity is the number of grams of water contained per kg of air, when this is converted into kilograms, the following equation holds for the actual amount of water removed q.

q = (Absolute humidity of exhaust air - Absolute humidity of hot air) X O, 00
1X W (Kg/hour) (Formula 5) Since the absolute humidity difference between hot air and exhaust air is proportional to the temperature difference between the two, if the ratio is k, then the following equation is obtained.

Therefore, when actually operating the dryer, the normal hot air temperature is between 40°C and 50°C, and now let's assume that the absolute humidity of the hot air is 4 to 8 (g/Kg) and the exhaust air temperature is 21°C. to 27 LC, 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 air diagram in FIG.

From this, it turns out that the value of k within that range is 0.42.

Therefore, from (Equation 5) and (Equation 6), q=(temperature of hot air−temperature of exhaust air) xO, 42mxW. Here, m is the efficiency obtained by subtracting the temperature of the dryer and the temperature of the grain, which is lost due to one row, etc., and is a constant compensation coefficient determined by the model and specifications of the dryer, the type and quality of the grain, etc.

0.42m is a constant, so if we set this to 1 and l~, and the temperature of the hot air is Ta ('C) and the temperature of the exhaust air is Th (0C), then equation (7) can be rewritten as follows. can.

q=(Ta-Tb)
If the wind MW is determined to be between 1 and 1, the temperature can be determined from the measured values by measuring the temperatures Ta and Tb of the hot air and exhaust air.

In this way, the actual water removal amount q obtained from (Equation 8) is
Depending on the moisture content a and grain amount A at that time, (4 formula)
The inventors previously proposed in Japanese Patent Application No. 110817/1983 a control device that keeps the drying rate P constant by drying so as to match the water removal tQ calculated from Since the water removal tfq matches the standard water removal tQ by adjusting and controlling only the hot air temperature Ta while keeping W constant, when the amount of grains to be dried A (Kg) is large and the standard water removal amount Q is large, If the hot air temperature Ta is increased, the temperature difference with the exhaust air temperature Tb in (formula 8) will be increased, and conversely, when the amount of water removed Q is small, the hot air temperature Ta is set low. However, it was necessary to reduce the temperature difference between the exhaust air temperature Tb and the rare exhaust air temperature Tb.

A graph showing the relationship between grain #1 amount A (Kg) and hot air set temperature Ta ('C) in this conventional device shows that
This is shown by the broken line in the figure.

As is clear from this graph, in the conventional device, the difference in hot air temperature TaO is large depending on the amount of grains A to be dried, and the combustion state of the burner must be adjusted to a large extent depending on the amount of grains A. When drying a small amount of grain, the hot air temperature Ta is lowered to reduce the difference with the exhaust air temperature Tb. The disadvantage was that it was uneconomical and the ratio between

By the way, in the first place, when the drying speed P is constant, the amount of energy E required to dry the grains is proportional to the grain iA and is determined by the product of the hot air temperature Ta and the air quality W, so the following equation holds O Energy amount E = 2 x grain amount A (9 equation) Energy amount E = 3 x hot air wetness Ta In order to dry at the same drying speed P regardless of whether A is large or small, if the grain amount A is large, it is necessary to increase the energy amount E in proportion to it, and for this, the hot air temperature Ta must be increased. It is better to increase both the hot air temperature Ta and the air volume W than by increasing the hot air temperature Ta because the amount of increase in the hot air temperature Ta itself is smaller. Similarly, when the grain amount A is small, it is necessary to reduce the energy amount E in proportion to it, but for this purpose, it is better to reduce the amount of air 4w along with the hot air temperature Ta than to reduce the amount of hot air by only the hot air temperature Ta. It is sufficient that the temperature Ta itself does not fall too much.

The present invention focuses on this point and aims to eliminate the above-mentioned conventional drawbacks by increasing/decreasing the amount W of hot air depending on the amount of grains.

That is, in the present invention, as shown by the solid line in FIG. 6, when the amount A of grains to be dried is large, the wind ft
The value of W also increases, and accordingly the hot air temperature Ta is set lower than before.

Moreover, when the grain amount A is small, the air volume W also decreases, so that the hot air temperature Ta is set higher than before.

After setting the hot air temperature Ta according to the grain -tA in this way, burn the burner to reach the set temperature Ta in step 7, and measure the initially set air volume WO and the temperatures Ta and Tb of the hot air and exhaust air. From this value, the actual water removal amount q is measured using (Equation 8), and the air volume W is controlled so that this water removal amount q matches the reference water removal amount Q calculated using (Equation 4).

Next, the present invention will be explained based on embodiments shown in the drawings.

Reference numeral 1 denotes a storage chamber of a dryer, and a chevron-shaped plate 2 having an inverted ■-shaped cross section is provided at the center of the bottom surface of the storage chamber, and guiding swash plates 3, 3 are installed opposite to each other on the left and right sides of the chevron-shaped plate 2. 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 drying chambers 5, 5 are formed by a pair of opposing perforated plates 4.

The discharge port at the lower end of the drying chamber 5.5 is connected to the gutter-like grain flow chamber 7 through the rotary valve 6, and the delivery end of the grain feeding helix 8 suspended horizontally in the concave groove in the center is connected to the grain raising machine 9. Connect to the bottom intake.

A grain feeding helix 10 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 of the soft baking machine, and the burner 12 is connected to the left and right drying chambers 5,
5 into the hot air chamber 14 inside the fan 13.
is connected to the outside of the drying chamber 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 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, the hot air from the burner 12 enters the left and right drying chambers 5 from the central hot air chamber 14, and the drying chamber 5 dries the grains flowing down. Exhaust outside.

The dried grains fall into the flowing grain chamber 7 by the rotation of the rotary pulp 6, and are returned to the storage chamber 1 by the flowing grain helix 8 and the grain elevator 9.
Return to

However, in the present invention, the dryer has a hot air chamber 14 and an exhaust chamber]5.
Temperature sensors Sa and Sb are respectively installed inside the K and measure the actual hot air temperature Ta and exhaust air temperature Tb.

In addition, the support leg 17 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 and is proportional to the weight A (Kg) of grains in the dryer. A grain amount measuring circuit 19 is provided which outputs the voltage.

The grain amount measuring circuit 19 may be constructed by arranging several pressure detection switches and photoelectric switches 18 vertically arranged on the inner wall of the grain storage chamber 1 at equal intervals. In this case, as the drying progresses, the volume of the whole grain decreases and the upper switch 18 is exposed, which is converted into a change in the weight of the grain and a voltage proportional to the weight A (Kg) is output.

Next, the grain amount measuring circuit 19 is connected to the hot air temperature setting circuit 20, and the hot air temperature is set by the circuit 20 according to the output of the circuit 19 so that the grain temperature inside the machine is constant.

21 is a comparison circuit, and a hot air temperature setting circuit 20 is connected to its input side.
A hot air temperature sensor Sa is connected to the hot air temperature sensor Sa, and the actual hot air temperature is set by operating the fuel control device 22 interposed in the fuel system of the burner 12, such as a solenoid valve connected to the output side of the comparison circuit 21. The burner 12 burns by controlling the flow rate of fuel so that it is equal to the temperature.

Next, a well-known moisture content meter G is installed in the storage chamber 1, and connected to the standard water removal amount setting circuit 23 together with the grain amount measuring circuit 19. From the value of the drying rate P, a calculated water removal amount Q to be a reference is calculated based on (Equation 4), and a voltage proportional to the calculated value is output.

On the other hand, the temperature sensors 3a and Sb are connected to the actual water removal amount calculation circuit 24.
This circuit 24 calculates the actual water removal amount q based on the values of the hot air temperature Ta, the exhaust air temperature Tb, and the initially set air volume WO based on (Equation 8), and then calculates a voltage proportional to the value q. Output.

Then, the output sides of the circuit 23 and the circuit 24 are connected to the comparator circuit 25, and the output side of the circuit 25 is connected to the amplifier circuit 26, and the air volume setting circuit 27 is configured as shown in the circuits 23 to 26. is connected to the rotation speed control circuit 28 of the motor 29 of the suction fan 13. Actual amount of water removed q
The rotational speed of the motor 25 of the suction fan 13 is adjusted so that the amount of water removed is equal to the reference amount of water removed Q determined by calculation, and the amount of hot air W is controlled.

The relationship between the air volume W and the rotation speed of the motor 29 is actually measured in advance, and the relationship between the two is stored.

In addition, the air volume W is determined according to the pre-stored relationship like this.
Instead of adjusting the air flow rate, the air flow rate is measured from the air pressure in the heat chamber 14 or the air exhaust chamber 15, and the measured value is compared with the set air flow rate W of the circuit 27, and feedback control is performed to reduce the deviation between the two to zero. It is also possible to control the amount of air.

As the drying progresses, the moisture content a and the total weight A of the grains loaded into the dryer gradually decrease. Accordingly, the hot air temperature Ta also decreases slightly as shown by the solid line in FIG.
Q is also calculated according to the moisture content a and the grain amount A at each time.

On the other hand, the exhaust air temperature Tb increases as the drying progresses, so
The temperature difference between hot air and exhaust air, that is, (Ta-
Tb) decreases as drying progresses. Therefore, in the present invention, the volume W of hot air is controlled so as to increase as the drying progresses, and the value of the water removal amount q in (Equation 8) is made equal to the water removal amount Q.

In short, in the present invention, the amount of water removed Q with a constant drying rate P is calculated according to the measured values of the moisture content a and the grain amount A, which decrease as the drying progresses, and this standard is calculated. Since the amount of hot air from the burner is controlled so that the amount of water removed Q and the actual amount of water removed f4'q always match, the drying speed P is always constant throughout the drying time, and the moisture content a and grain amount A at each time are Since drying can be performed with the amount of water removed that is appropriate for the grain size, it is possible to prevent the occurrence of shell cracking and to dry grains of good quality.Also, since the moisture content and grain amount are actually measured without setting them, troubles due to setting errors can be avoided. The effect is that there is no room for this to occur.

Moreover, in the present invention, the actual amount of water removed q is made to match the standard amount of water removed Q by increasing or decreasing the amount of hot air W.
There is little difference in the hot air temperature Ta when the grain amount A is large and when it is small, so not only is it sufficient to keep the burner 12 small during adjustment, but also the hot air temperature Ta is raised when drying a small amount of grains. Especially since the large air volume W can be reduced,
The speed at which the hot air passes through the drying chamber 5 is slow, so the contact time between the hot air and the grains is long, and as a result, the temperature difference (Ta - Tb) between the hot air and the exhaust air becomes larger than before, and the hot air Energy is efficiently transferred to the heat of evaporation of water from the grains, resulting in efficient drying and fuel cost savings.

Even when the grain amount A is small, the hot air temperature Ta is lower than before.
Since the temperature is low, this has the effect of suppressing the rise in grain temperature and preventing grain shell cracking.

In addition, in the present invention, the actual water removal JLq is determined from the temperature difference rather than from the absolute humidity difference between the hot air and the exhaust air, so an expensive hygrometer is no longer necessary and an inexpensive temperature sensor can be used for highly accurate measurement. It is also effective.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional 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 grain dryer of 1°001 (g). Drying speed P(
57 hours) A graph showing the relationship between the amount of water removed Q and the water content when drying at a constant rate using the drying rate P as a parameter. Figure 5 is a psychrometric diagram showing the relationship between temperature and absolute humidity of hot air and exhaust air. Figure 6 shows the amount of grain A (Kg) to be dried and the hot air set temperature Ta (
In the graph showing the relationship with 'C), the broken line shows that of the conventional device, and the solid line shows that of the device of the present invention. Agent Tetsube Maki (and 2 others) Figure 1 Figure 2

Claims (1)

[Claims] 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 water removal amount q, which is actually measured from the temperature difference between the hot air and exhaust air and the initially set amount of hot air, is calculated based on the moisture content at that time. A grain dryer characterized by controlling the volume of hot air from a burner so as to match a standard amount of water removed Q calculated according to each measurement value of grain amount, thereby keeping the drying speed constant. Burner hot air control device.