JP2002031480A - Method and apparatus for sealing type drying - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a method at a low cost, because a sealing type drying method for not exhausting an offensive gas generated from a material to be dried during drying into the atmosphere is expensive. SOLUTION: The method for sealing type drying comprises the steps of drying the material to be dried in a drying chamber, in a sealing system by a dry air heated by a burning furnace or the like, thereafter raising the drying temperature, while repeating heating of the drying air and drying of the material, repeating the heating of the drying air, the drying of the material and cooling and dehumidifying of the drying air with an ambient temperature air or water as a cold source in the sealing system at a stage, in which the temperature of the drying air after the material is dried reaches a temperature capable of cooling to dehumidify the ambient temperature air or the water as the cold source, and the relative humidity of the drying air becomes sufficiently high and dries the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to drying of articles. Specifically, when the gas generated from the material to be dried due to drying cannot be released to the outside air from the viewpoint of pollution, such as offensive odor, or when the product quality is improved by circulating through the system without releasing it to the outside air When collecting volatile gas generated together with moisture, when it is not preferable to introduce outside air pollution and changes in relative humidity into the drying system, it is desirable to perform drying in a closed state, and The present invention relates to drying of an object to be dried when the drying temperature of the object to be dried may be a high temperature level that can be used as a cooling source for cooling and dehumidifying the outside air temperature.

[0002]

2. Description of the Related Art Generally, when drying an object, outside air is heated and introduced into a drying chamber containing the object to be dried, and the object to be dried is dried and released into the outside air. I have. However, in order to improve energy efficiency, the entire amount is not released and is repeatedly used within the range that can be recycled. If it is desired to dry the product at a low temperature, the air for drying is cooled and dehumidified by the evaporator using a refrigerator, and the air is dried by heating the air in the condenser to obtain the appropriate temperature and humidity. In this case, the drying is performed in a sealed state, which is shielded from the outside air.

[0003]

When it is desired to dry in a closed drying system, for example, when it is not preferable to release gas generated during drying of the material to be dried to the outside air, the latter refrigerator is now used. Although the cooling and dehumidifying method to be used is employed, the cost of this method is higher than that of the heating and drying method. Therefore, a low-cost closed drying method is desired.
The present invention seeks to realize a low cost closed drying method.

[0004]

Means for Solving the Problems Drying air whose temperature is higher than the outside air temperature and whose relative humidity is high is heated by combustion heat or waste heat, and the object to be dried is dried with the drying air. The dehumidified air is cooled and dehumidified using air or water at the outside temperature as a cold heat source repeatedly in a closed system. Above "drying air where the temperature is higher than the outside temperature and the relative humidity is high"
Can be obtained by repeatedly drying an object to be dried with heated air, and heating the air whose temperature after drying has decreased and humidity has increased to dry the object to be dried. Alternatively, it can be obtained by adding steam generated by a steam generator to the drying air.

[0005] A combustion furnace or waste heat recovery furnace for heating the drying air, a drying chamber for drying the object to be dried with the heated air, and air having increased humidity by drying the object to be dried at room temperature. A closed-type drying device is manufactured, which mainly includes a cooling device that cools and dehumidifies the atmosphere or water using a cold heat source.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The relationship between the temperature of air containing moisture, the absolute humidity, the relative humidity, the stored energy of air, and the like is represented by a psychrometric chart shown in FIG. According to the figure,
When air at a temperature of 20 ° C. and a relative humidity of 100% (position a in FIG. 3) is heated to the position b in FIG. 3 and sent to the drying chamber, moisture is increased by drying the material to be dried, and the temperature is reduced. It comes down from the drying chamber (position c in FIG. 3).
This air is heated again to d in FIG. 3 and is sent to the drying chamber to dry the object to be dried. Similarly, the water content is increased, and the temperature is lowered to go to e in FIG. As described above, since the moisture of the drying air increases each time the object to be dried is dried in the drying chamber, the relative humidity is higher than before at the same temperature.

When the object to be dried is dried to reheat the drying air whose temperature has decreased and the humidity has increased, the temperature is initially increased so as to be higher than the previous time. The heating is adjusted so that the temperature does not rise above a predetermined temperature (f, 70 ° C. in FIG. 3).
h, j, etc.). This is to prevent the equipment inside the drying chamber from deteriorating due to excessively high temperature and humidity, and furthermore due to the bad gas, etc., and to prevent the quality of the material to be dried from lowering when the temperature becomes higher than the appropriate temperature. is there. The humidity of the drying air after drying the material to be dried does not rise sufficiently,
If the drying capacity is still high, a part or all of the drying air is sent to the drying chamber by bypassing the heating heat exchanger until the humidity rises sufficiently.

When the absolute humidity becomes high to some extent (position k in FIG. 3), the amount of heating is adjusted so as to reach a temperature suitable for drying the material to be dried (position l in FIG. 3). The air is sent to the drying chamber, and the air coming out of the drying chamber (FIG. 3)
(Position m in FIG. 3) after cooling and dehumidification (position o in FIG. 3 via n), and then heated to the position l in FIG. 3 and sent to the drying chamber, whereafter l, m, n, o, l Enter into the regular operation that is repeated. The material to be dried evaporates a large amount of water in the beginning, and its latent temperature is low, although the temperature of the drying air is high, but the temperature of the drying air is low. The temperature of the drying air may be initially higher than the optimum drying temperature, but care must be taken not to exceed the optimum drying temperature if the product temperature approaches the optimum drying temperature of the material to be dried.

[0009] The lower the humidity of the drying air, the faster the drying speed of the material to be dried. (Points b, e and f in FIG.
If the moisture transfer in the object to be dried is slow, inconveniences such as drying of the surface quickly may occur. In such a case, the humidity of the drying air is increased by separately supplying steam. In addition, by repeating the "heating of air for drying" and "drying of the material to be dried" many times, it is not necessary to bring it to a steady operation under high humidity. It is also possible to shift to the operation state. In the cooling, dehumidifying and drying method using a refrigerator, it is common that a part of the drying air is passed through a circuit for cooling, dehumidifying and then heating, and most of the drying air is simply passed through a circulation circuit. Recruitment is possible.

[0010]

FIG. 1 is a front view of a sludge drying apparatus according to the present invention. The drying chamber 1 is sealed by a container 2, in which net conveyors 31 to 34 move in the front-back direction. FIG. 2 is a side view of the sludge. The formed sludge is dropped from the sludge inlet 4 to the left end of the net conveyor 31, comes to the right end while being dried by the drying air, and is dropped to the net conveyor 32. Hereinafter, similarly, it moves while being dried by the net conveyors 32 to 34, and finally drops from the left end of the net conveyor 34 to the carry-out device 5 and is sent out of the drying chamber.

The drying air whose temperature has decreased and the humidity has increased by drying the sludge exits from the suction port 6 of the drying chamber, is cooled and dehumidified by the heat exchanger 7 for cooling and dehumidification, and is then heated to the heat exchanger 8 for heating. The sludge on the net conveyor is dried while descending into the drying chamber through the drying chamber outlet 11. The cooling heat source of the cooling and dehumidifying heat exchanger 7 is a cooling tower 9.
And the heat source of the heat exchanger for heating is steam sent from the boiler 10. When drying sludge, the sludge generates aggressive gas, and various devices in the drying room are often deteriorated by the aggressive gas. To suppress this, the cooling tower 9 is used to dry the sludge at the lowest possible temperature. Is preferred.

If there is no fear of deterioration of various devices in the drying chamber, the drying temperature may be increased and an air-to-air heat exchanger may be used. That is, the upper limit of the drying temperature is further increased,
If the absolute humidity is increased by performing “drying of the object to be dried” and “heating the drying air” many times (or by supplying steam), for example, the positions of p, q, r, and s in FIG. Steady operation in the vicinity can be performed. The higher the drying temperature,
The saturation curve of the wet psychrometric chart (curve at 100% relative humidity) becomes almost vertical, and a large amount of water can be condensed and dehumidified by a slight temperature change. In this embodiment, the drying air enters the drying chamber from above and exits from below. This is not rational, economical, and has been improved, but has been described in a conventional manner that is easy to understand because it is not directly related to the present invention.

[0013]

According to the present invention, the following effects can be obtained by applying the present invention to the objects to be dried which need to adopt the closed-type drying method and which can be used at a high drying temperature. 1. By increasing the drying temperature, the drying speed is increased, the amount of drying per hour is increased, and the productivity of the equipment is increased. 2. Since a refrigerator is not used for cooling for dehumidification, capital investment and operating costs are reduced. 3. Since no chlorofluorocarbon is used, the effect of environmental measures is great.

[Brief description of the drawings]

FIG. 1 is a front view of a sludge drying device according to the present invention.

FIG. 2 is a lateral view of the sludge drying device.

FIG. 3 is a psychrometric chart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drying room 2 Airtight container 31-34 Net conveyor 4 Sludge input device 5 Dry sludge discharge device 6 Drying room suction port 7 Heat exchanger for cooling and dehumidification (water to air) 8 Heat exchanger for heating (steam to air) 9 Cooling tower 10 Boiler 11 Drying room outlet

Claims (4)

[Claims] An air having a high humidity after drying, wherein drying air having a higher temperature than the outside air temperature and a high relative humidity is heated by combustion heat or waste heat, and the object to be dried is dried by the drying air. A closed drying method in which cooling and dehumidification are repeatedly performed using air or water at the outside temperature as a cold heat source. 2. The method of drying an object to be dried with heated air and repeatedly drying the object to be dried by heating the air whose temperature after drying has decreased and the humidity has increased, so that “the temperature is higher than the outside air temperature”. The closed drying method according to claim 1, wherein "drying air having a high relative humidity" is obtained. 3. The method according to claim 1, wherein "water for drying having a higher temperature than the outside air temperature and a higher relative humidity" is obtained by adding water vapor generated by the water vapor generator to the air for drying. The closed drying method described. 4. A combustion furnace or waste heat recovery furnace for heating the drying air, a drying chamber for drying the object to be dried with the heated air, and air having increased humidity by drying the object to be dried. A hermetically-sealed drying device whose main component is a cooling device that cools and dehumidifies using ambient air or water as a cold heat source.