JPS5950915B2 - Hot air circulation continuous dryer - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement of a hot air continuous dryer.

A conventional hot air continuous dryer is shown in FIG. 1 (longitudinal sectional view), and the dryer 1 has an inlet 3 for the material to be dried 81 and an outlet 19 for the material to be dried 82 as openings at both ends. It has a drying chamber 2 with a drying chamber 2, and circulated hot air is passed through an inlet 3. The exhaust fan 15 prevents the drying chamber from flowing out through the outlet 19.
The drying chamber 2 is maintained at a reduced pressure with respect to the outside air at the inlet 3 and outlet 19.

The circulating hot air 46 is blown into the drying chamber through the hot air circulation duct 17, and at this time, the outside air 32 entering the drying chamber through the outlet 19 mixes with the circulating hot air 46 to become circulating hot air 47.
It flows through the drying chamber 2, mixes with the solvent vapor of the coating film of the material to be dried 81 that evaporates from the material to be dried, becomes circulating hot air 48, advances to the circulation duct 6, and enters from the inlet 3 at this time. It mixes with outside air 31 and becomes circulating hot air 49.

The hot air 49 is preheated by a heat source 8 provided in the oxidation chamber 7, and then passes through the catalyst layer 9. At this time, the organic solvent in the hot air generates heat due to oxidation, the temperature of the hot air rises, and is sucked by the circulation fan 10. It is discharged as circulating hot air 41, and a portion is discharged outside the dryer by the exhaust fan 15 via the exhaust duct 11.

The remainder of the circulating hot air 41 is sent to the circulation duct 1 as circulating hot air 44.
6, it is heated by the heat source 18 as circulating hot air 45, and reaches the circulation duct 17.

The material to be dried 81 is circulated by hot air 47.4 while passing through the drying chamber 2.
8 and the heat dissipated from the inner wall of the drying chamber 2 heated by the circulating hot air 47 and 48, the dried material 82 is heated and dried, forming a coating film, and continuously exits the drying chamber 2 through the outlet 19. It is carried out and drying is completed.

In the above process, the speed at which the material to be dried 81 is brought in, the temperature and flow rate of the circulating hot air 47 are selected so that the drying conditions are optimal, and the flow rate of the outside air 31 is selected so that the conditions of the circulating hot air 47 are satisfied. The heating amount of the heat sources 8 and 18 is determined by the inflow amount of .32, and the flow rate of the circulating hot air 41 is determined by the circulation fan 10.
The volume of the exhaust duct 11 is adjusted by the exhaust fan 15.

In order to reduce the load on the heat sources 8 and 18 and the amount of heat required to operate the dryer, it is necessary to prevent the circulating hot air in the dryer from causing a gas explosion due to organic solvents or decomposition products generated from the material to be dried 81 during drying. It is necessary to reduce the total amount of outside air 31 and outside air 32 within a range that does not cause this, but the difference in temperature between the inflow temperature of these outside air 31 and 32 and the temperature of the exhaust duct 11 , it is inevitable that the amount of heat corresponding to the total inflow amount of these outside air 31 and 32 will be taken out of the dryer by the exhaust from the exhaust duct 11, and the inflow amount of outside air 31 and 32 must be adjusted independently. There is a drawback that it cannot be done.

In order to improve these drawbacks, the present invention preheats the main part of the air required for drying by exhaust air and forcibly supplies the air into the dryer, and also reduces the amount of air that flows into the drying chamber from the opening of the drying chamber. can be adjusted and limited.

As shown in the longitudinal sectional view of FIG. 2, the drying chamber 2 of the dryer 1 is
It has an opening 3 as an inlet for the material to be dried 81 and an opening 19 as an outlet for the material to be dried 82, and further, the opening 3 communicates with the outside air via a vacuum equalization box 4.

The circulating hot air 46 flows into the drying chamber 2 from the circulation duct 17,
At this time, it mixes with the outside air 32 flowing in from the opening 19 to become circulating hot air 47, which gives the amount of heat necessary for drying to the material to be dried 81 while moving in the drying chamber 2, and also generates heat from the material to be dried 81. It mixes with the decomposition products and solvent vapor to become circulating hot air 48, which mixes with outside air 31 flowing in from the opening 3 and flows into the circulation duct 6 to become circulating hot air 49, which is preheated by the heat source 8 provided in the oxidation chamber 7. After passing through the catalyst layer 9, at this time,
The organic matter in the hot air oxidizes and generates heat, raising the temperature of the hot air, which is sucked in by the circulation fan 10 and discharged as circulating hot air 41. A part of it passes through the exhaust duct 11 as exhaust air 42 and reaches the heat exchanger 13. In the heat exchanger 13, the incoming outside air 33 is heated by the air supply fan 12, and then becomes exhaust air 43, which is then discharged to the outside of the dryer by the exhaust fan 15 via the exhaust duct 14.

The remaining circulating hot air 44 of the circulating hot air 41 is combined with the preheated supply air 34 heated by the heat exchanger 13 to become circulating hot air 45,
It passes through the circulation duct 16, is heated by the heat source 18, flows into the circulation duct 17, and becomes circulating hot air 46.

Here, the outside air 33 supplied by the air supply fan 12
is the main part of the amount of air required to maintain the concentration of solvent vapor, etc. in the dryer below the lower explosive limit and to prevent overheating of the catalyst layer 9, and the remainder of the required air amount is the outside air 31 and 32. Adjust to allow more inflow.

With Kempo, compared to the conventional method, the amount of heat taken out from the dryer by exhaust air is reduced by the amount of heat exchanged for preheating the incoming outside air 33, and the amount of heat consumed for drying is saved. It is desirable to reduce the amount of inflow as much as possible.

Therefore, the temperature 64 of the circulating hot air 46 and the temperature 65 of the circulating hot air 47 are sensed, and the difference between these temperature differences 64-65 and a preset temperature difference Δ66 of the circulating hot air 46.47 is detected by the calculation circuit 66. Detected by (64-65)-△66-
A signal for increasing or decreasing the rotational speed of the motor of the exhaust fan 15 is sent from the comparison calculation circuit 66 so that the amount of exhaust gas 42 is adjusted by the exhaust fan 15.

On the other hand, since the amount and temperature 64 of the circulating hot air 46 are determined by the circulation fan 10 and the supply air fan 12, the temperature 65 can be adjusted by controlling the amount of the circulating hot air 42, and the temperature 64 can be adjusted by controlling the amount of the circulating hot air 42.
can be adjusted.

Next, the temperature 61 of the circulating hot air 48 and the temperature 62 of the circulating hot air 49 near the opening 3 are sensed, and the temperature difference 61 -
62 and the preset temperature difference △63 between these circulating hot air 48 and 49 is detected by the comparison calculation circuit 63.
1-62) The internal pressure of the vacuum equalization box 4 is adjusted by sending a signal from the comparison calculation circuit 63 to increase or decrease the rotation speed of the motor of the pressure reduction fan 5 of the vacuum pressure equalization box 4 so that -Δ63=0,
The inflow amount of outside air 31 can be controlled.

In this way, by setting the temperature differences △66 and △63 small within the adjustable limits, the respective inflow amounts of the outside air 32 and 31 into the dryer can be controlled to be small, and therefore, the total amount of them can be reduced. By controlling the amount of outside air 33 to be small, and increasing the ratio of the amount of outside air 33 to the amount of air required for drying,
The amount of heat recovered from the exhaust gas 42 and returned to the dryer can be increased, and the amount of heat consumed by the dryer can be reduced.

[Brief explanation of drawings]

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, 32... Outgoing outside air, 33... Outgoing air supplied, 34... Preheating supply air, 1...・Dryer body, 2... Drying chamber, 3... Opening (inlet), 4... Decompression equalization box, 5... Decompression fan, 6... Circulation duct, 7... Oxidation chamber, 8... Heat source, 9... Catalyst layer, 10... Circulation fan, 11 ...Exhaust duct, 12...Air supply fan, 13...Heat exchanger, 14...
Exhaust duct, 15...Exhaust fan, 16...
...Circulation duct, 17...Circulation duct, 18
...Heat source, 19..., ...Opening (exit)
, 41... Circulating hot air, 42... Exhaust hot air, 43... Exhaust, 44... Circulating hot air, 45... Circulating hot air, 46... Circulating hot air, 47... Circulating hot air, 48... Circulating hot air, 49... Circulating hot air, 61...4
8 temperature, 62...49 temperature, 63...
...Comparison calculation circuit, 64...46 temperature, 65
. . . Temperature of 47, 66 . . . Comparison calculation circuit, 81 . . . Material to be dried, 82 . . . Material to be dried.

Claims (1)

[Claims] 1 The drying chamber has openings at both ends used as the inlet and outlet of the material to be dried, and the drying chamber is kept at a lower pressure than the air pressure outside the openings during the hot air circulation drying process in which forced air supply and forced exhaust are performed. , so that the temperature difference between the temperature of the circulating hot air blown into the chamber near the opening with higher indoor pressure and the temperature after mixing with the outside air and the hot air flowing from the opening is made constant. The exhaust volume of the exhaust fan of the dryer is controlled, and a reduced pressure equalization box is provided at the opening with lower indoor pressure, and the temperature of the circulating hot air flowing near the opening and the temperature of the circulating hot air flowing from the pressure equalization box are controlled. The amount of outside air that flows into the dryer from the opening is controlled by controlling the exhaust volume of the pressure reducing fan that depressurizes the pressure equalization box so that the temperature difference between the outside air and the temperature after mixing the hot air is kept at a predetermined value. Continuous dryer with hot air circulation that can adjust the temperature.