JPS5950916B2 - Hot air circulation continuous dryer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a hot air circulation type continuous dryer.

Conventionally, the hot air circulation type continuous dryer shown in FIG. 1 (longitudinal sectional view) has been used, and has an inlet opening 3 as an inlet for the material to be dried 81 at one end and an inlet for the material to be dried 82 at the other end. It has a drying chamber 2 provided with an outlet opening 19 as an outlet and circulates hot air 46. 47. 48 is the inlet opening 3 and the outlet opening 1
Exhaust fan 1
5, the internal pressure of the drying chamber 2 is maintained at a reduced pressure with respect to the outside air at the inlet opening 3 and the outlet opening 19.

The circulating hot air 46 is blown into the drying chamber 2 through the hot air circulation duct 17, mixed with the flowing outside air 32 which enters the drying chamber 2 through the outlet opening 19, and becomes circulating hot air 47, which flows through the drying chamber 2 and is dried. The material to be dried 81 that continuously passes through the chamber 2 and the inner wall of the drying chamber 2 are heated, and the solvent vapor of the coating film of the material to be dried 81 that evaporates from the material to be dried 81 and the gas of the decomposition products generated from the coating film. The mixture becomes circulating hot air 48, which flows from the drying chamber 2 into the hot air circulation duct 6.

Flowing outside air 3 flows into the drying chamber 2 from this opening 3.
The organic solvent and the decomposed product gas in the hot air generate oxidation heat,
The hot air temperature rises, is sucked in by the hot air circulation fan 10, and is discharged as circulating hot air 41, a part of which is transferred to the exhaust air 4.
2, it is discharged to the outside of the dryer via the exhaust duct 11 by the exhaust fan 15.

The remainder of the circulating hot air 41 is sent to the circulation duct 1 as circulating hot air 44.
6, the heated air is heated by the heat source 18 as circulating hot air 45, and is blown out into the drying chamber 2 as circulating hot air 46 through the circulation duct 17, continuing the hot air circulation cycle to perform continuous drying.

In this process, the feeding speed of the material to be dried 81 and the temperature and flow rate of the circulating hot air 47 are selected so that the drying conditions for the material to be dried 81 are optimal and the best dried material 82 is obtained, and these conditions are satisfied. The volume of the exhaust duct 11 is controlled by the rotational speed of the exhaust fan 15 so that the flow of outside air 31 and outside air 32 is
, the flow rate of the circulating hot air 47 according to the rotation speed of the hot air circulation fan 10, and the temperature of the circulating hot air 47 according to the heating amount of the heat source 8 and the heat source 18, but by reducing the load on the heat source 8 and the heat source 18, In order to save the amount of heat required for drying the material to be dried 81, it is important to reduce the amount of heat carried away by the exhaust gas 42. Therefore, the organic solvent and decomposed gas generated from the material to be dried 81 can cause a gas explosion. The total amount of the outside air 31 and the outside air 32 must be reduced within the limit, but the amount of the exhaust 42 is related to the amount of outside air 31 and the outside air 32, and the samurai heat value of the exhaust 42 is reduced. Is a drifter outside air 31°32
Since there is a close relationship between the temperature of the outside air 3 and the temperature of the exhaust air 42, there is a limit to how much heat can be saved for drying.
1 and the amount of outside air 32 cannot be adjusted independently.

In order to improve these drawbacks, the present invention preheats the main amount of air required for drying using the exhaust air of the dryer, and then forces the air into the dryer, allowing the air to flow into the dryer from the opening of the dryer. The amount of outside air flowing into the dryer 1 can be adjusted and reduced to save the amount of heat required for drying, and as shown in FIG. and an outlet opening 19 as an outlet for the dried material 82, and the outlet opening 19 communicates with the outside air via the pressure equalization box 4.

When circulating hot air 46 flows into the drying chamber 2 from the hot air circulation duct 17, outside air 32 flows into the drying chamber 2 from the pressure equalization box 4 through the outlet opening 19, mixes with the circulating hot air 46, and becomes the circulating hot air 47. and moves inside the drying chamber 2 in the direction of the inlet opening 3.

At this time, the temperature 64 of the circulating hot air 46 and the temperature 6 of the circulating hot air 47 are
5 is detected and the difference temperature of (64-65) is compared with the preset temperature difference △66, and the difference between (64-65) and △66 is detected by the comparison calculation circuit 66, and (66-65) - △66=
0, the comparison calculation circuit 66 sends a signal to increase or decrease the rotation speed of the motor of the pressurizing fan 5, and changes the rotation speed of the pressurizing fan to control the internal pressure of the pressurizing and equalizing box 4. Adjust the amount of 32.

The circulating hot air 47 heats the object to be dried 81 and the inner wall of the drying chamber 2, and mixes the solvent vapor of the paint of the object to be dried 81 generated from the object to be dried 81 and the gas of the decomposition product of the coating of the object to be dried 81. This becomes circulating hot air 48, mixes with the outside air 31 flowing in from the inlet opening, and flows into the circulation duct 6 as circulating hot air 49.

At this time, the temperature 61 of the circulating hot air 48 and the temperature 6 of the circulating hot air 49
2 is detected, the temperature difference (61-62) is compared with a preset temperature difference △63, the difference between (61-62) and △63 is detected by the comparison calculation circuit 63, and (61-62) - △ 63=
The comparison calculation circuit 63 sends a signal to increase or decrease the rotation speed of the motor of the exhaust fan 15 so that the internal pressure at the inlet opening 3 of the drying chamber 2 is 0.
The amount of outside air 31 flowing in is controlled.

By setting △63°866 to the minimum within these controllable ranges, the amounts of outside air 31 and 32 can be respectively minimized.

The circulating hot air 49 is preheated by a heat source 8 provided in the oxidation chamber 7 , passes through the catalyst layer 9 , solvent vapor, decomposed product gas, etc. oxidizes and generates heat, increasing the temperature of the circulating hot air, which is then sucked into the circulation fan 10 . After being discharged, it becomes circulating hot air 41, and a part of it reaches the heat exchanger 13 as exhaust air 42, where the temperature is lowered by heat radiation.
Exhaust fan 15 through exhaust duct 14 as exhaust 43
is discharged outside the dryer.

Prevents gas explosions such as organic solvents generated during the drying process,
Also, for its oxidation, and as air as the main part of the circulating hot air, the air 3 is injected by the outside air by the air supply fan 12.
3 is inhaled and preheated by the heat exchanger 13, and the preheated air 3
4. Supply air into the dryer.

The remaining circulating hot air 44 that has flown as exhaust 42 from the circulating hot air 41 mixes with the preheated air 34 to become circulating hot air 45 and reaches the heat source 18 via the circulation duct 16, where it is heated and circulated as circulating hot air 46 via the circulation duct 17 to the drying room. 2 and continues continuous drying.

In this way, a part of the heat carried away by the exhaust gas is recovered by heating the supply air required for drying, and is returned to the dryer.
By minimizing the amount of air flowing into the dryer through the opening, the amount of heat required for drying can be saved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a conventional hot air circulation type continuous dryer, and FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a hot air circulation type continuous dryer according to the present invention. 31... Outgoing outside air, 3゛2... Outgoing outside air, 33... Incoming outside air, 34... Preheating air, 1... ...Dryer, 2...Drying room,
3...Inlet opening, 4...Pressure equalization box, 5...Pressure fan, 6...Hot air circulation duct, 7... ... Oxidation chamber, 8 ... Heat source,
9... Catalyst layer, 10... Hot air circulation fan, 11... Exhaust duct, 12... Air supply fan, 13... Heat Exchanger, 14...
・Exhaust duct, 15...Exhaust fan, 16...
... Circulation duct, 17 ... Hot air circulation duct, 18 ... Heat source, 19 ... Outlet opening, 41 ... Circulation hot air, 42. ·····exhaust,
43... Exhaust, 44... Circulating hot air, 4
5... Circulating hot air, 46... Circulating hot air,
47... Circulating hot air, 48... Circulating hot air, 49... Circulating hot air, 61... Temperature of 48, 62... Temperature of 49 Temperature, 63...
Comparison calculation circuit, 64...46 temperature, 65...
...47 temperature, 66...comparison calculation circuit,
81... Material to be dried, 82... Material to be dried.

Claims (1)

[Claims] 1. In a hot air circulation continuous drying chamber that has openings at both ends of the drying chamber that are used as the inlet and outlet of the material to be dried, and that performs forced exhaust, the internal pressure of the drying chamber at the opening on the side where the circulating hot air flows is controlled. The temperature of the hot air blown near the opening is maintained higher than the outside pressure of the dryer, a pressure equalization chamber is provided between the opening and the outside air, and the internal pressure of the pressure equalization chamber is maintained higher than the internal pressure of the drying chamber. , the pressure fan in the pressure equalization chamber is controlled to adjust the internal pressure of the pressure equalization chamber so that the temperature difference between the air flowing into the drying chamber from the pressure equalization chamber and the temperature after mixing of the hot air is constant; In the other opening, the internal pressure of the drying chamber near the opening is maintained lower than the atmospheric pressure outside the opening, and the temperature of the circulating hot air flowing into the opening;
By controlling the exhaust fan of the dryer and adjusting the interior of the drying chamber so that the temperature difference between the hot air, the air flowing in through the opening, and the temperature after mixing is kept constant, the hot air is directed outside through the opening. A hot air circulation type continuous dryer that prevents leakage and allows the amount of air flowing into the dryer from the opening to be adjusted.