ABSORPTION TYPE AIR DRYING SYSTEM AND METHOD OF PERFORMING HEATING REGENERATION OF THE SAME

Abstract

This invention relates to an absorption type air drying system which can maximize energy efficiency, and to a method of controlling the same. This absorption type air drying system includes first and second adsorption towers, first diverter valves provided below the first and second adsorption towers to change the direction of transport of dehumidification air and regeneration air and including first to fourth on-off valves, second diverter valves provided above the adsorption towers to change the direction of transport of dehumidification air and regeneration air and including fifth to eighth on-off valves, and regeneration diverter valves connected to the first and second diverter valves to circulate the regeneration air and including ninth and tenth on-off valves which are opened upon heating regeneration, and eleventh and twelfth on-off valves which are opened upon cooling regeneration.

Description

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an air drying system for dehumidifying air and a method of performing heating regeneration of the same, and more particularly to an absorption type air drying system which consumes less energy and so has increased energy efficiency, and to a method of performing heating regeneration of the same.

2. Description of the Related Art

Typically, air drying systems for dehumidifying air have been widely utilized in a variety of automation facilities requiring dry air, semiconductor manufacturing processes, production lines of chemical processes that cause chemical reactions upon contact with moisture, etc.

Such air drying systems are classified into a cooling type air drying system for dehumidifying air by decreasing the temperature of compressed air using a chiller compressor and then condensing the moisture contained in the compressed air, and an absorption type air drying system for dehumidifying air by adsorbing moisture from wet air using an adsorbent (or a dehumidifier, or a desiccant).

In particular, the absorption type air drying system includes a pair of adsorption towers or dehumidification tanks having an adsorbent, diverter valves for changing the direction of compressed air so that dehumidification and regeneration are alternately carried out in the pair of adsorption towers or dehumidification tanks, and a controller including an electronic valve for controlling the operation of the diverter valves and a timer.

Such a conventional absorption type air drying system is problematic because it requires a large space to be mounted in, and the manufacturing cost and the mounting cost are high, and maintenance expenses are also high.

Meanwhile, the absorption type air drying system should be able to efficiently supply the wet air compressed by the compressor to the dehumidification tank in order to increase the efficiency with which air is dried and the regeneration efficiency of the adsorbent, and also heated air required upon regeneration should be fed in a more effective manner. Furthermore, the absorption type air drying system should drastically reduce the consumption of energy so as to be cheap to maintain.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind the problems encountered in the related art and an object of the present invention is to provide an absorption type air drying system, in which first and second diverter valves and regeneration diverter valves are operated at predetermined temporal intervals, so that upon switching adsorption towers, a dew point is prevented from being searched for and an ultra-low dew point may be maintained, thus maximizing energy efficiency.

Another object of the present invention is to provide a method of performing heating regeneration of an absorption type air drying system using compression heat, in which upon regeneration of the air drying system, the internal temperature of the adsorption tower is detected so that the operation of a heater can be appropriately controlled, thereby remarkably reducing energy consumption.

A further object of the present invention is to provide an absorption type air drying system, in which wet air compressed by a compressor is efficiently supplied to a dehumidification tank and regeneration air necessary for regeneration may be effectively fed, thus drastically increasing the drying efficiency of the air and the regeneration efficiency of the adsorbent.

Still a further object of the present invention is to provide an absorption type air drying system, in which the consumption of energy is considerably reduced, so that maintenance of the system can be cheaply conducted.

In order to accomplish the above objects, an aspect of the present invention provides an absorption type air drying system, comprising first and second adsorption towers, first diverter valves provided below the first and second adsorption towers so as to change a direction of transport of dehumidification air and regeneration air which are fed into or discharged from the first and second adsorption towers, second diverter valves provided above the first and second adsorption towers so as to change the direction of transport of dehumidification air and regeneration air which are fed into or discharged from the first and second adsorption towers, and regeneration diverter valves connected to the first and second diverter valves so as to circulate the regeneration air, wherein the first diverter valves include first and second on-off valves for feeding the dehumidification air into the first and second adsorption towers, and third and fourth on-off valves for circulating air regenerated in the first and second adsorption towers, the second diverter valves include fifth and sixth on-off valves for discharging air dehumidified in the first and second adsorption towers to outside, and seventh and eighth on-off valves for feeding the regeneration air into the first and second adsorption towers, and the regeneration diverter valves include ninth and tenth on-off valves which are opened upon heating regeneration, and eleventh and twelfth on-off valves which are opened upon cooling regeneration.

In this aspect, the first to twelfth on-off valves may have a two-way valve structure.

In this aspect, the first adsorption tower performs a dehumidification process, and the second adsorption tower performs a regeneration process.

In this aspect, the first adsorption tower performs a regeneration process, and the second adsorption tower performs a dehumidification process.

A further aspect of the present invention provides a method of performing heating regeneration of an absorption type air drying system comprising a compressor for compressing external wet air, first and second adsorption towers, first diverter valves provided below the first and second adsorption towers to change a direction of transport of dehumidification air and regeneration air, second diverter valves provided above the first and second adsorption towers to change the direction of transport of dehumidification air and regeneration air, regeneration diverter valves connected to the first and second diverter valves to circulate the regeneration air to the first and second adsorption towers, a heater provided on a pipe communicating with upper portions of the first and second adsorption towers, and a controller, the method comprising 1) circulating the regeneration air to either of the first and second adsorption towers by the regeneration diverter valves, 2) selectively operating the heater depending on an internal temperature of the first or second adsorption tower, and 3) passing the regeneration air through the first or second adsorption tower to perform heating regeneration of the first or second adsorption tower, wherein the selectively operating the heater in 2) comprises 2-1) detecting the internal temperature of the first or second adsorption tower wherein the regeneration process is performed, 2-2) determining whether the detected temperature corresponds to a temperature of compression heat of the compressor, and 2-3) operating the heater when the internal temperature of the first or second adsorption tower corresponds to the temperature of compression heat of the compressor, so that the regeneration air is heated to a regeneration temperature.

In this aspect, in 2-1), the temperature of a lower portion of the first or second adsorption tower may be detected by means of a temperature sensor.

In 2-2), the temperature of compression heat of the compressor may be 90˜150° C.

In 2-3), the regeneration temperature may be 170˜250° C.

Still a further aspect of the present invention provides an absorption type air drying system, comprising a dehumidification tank including a first dehumidification bed, a second dehumidification bed and a third dehumidification bed, which are partitioned by at least one barrier; a compressor for compressing external wet air; a cooler for cooling the wet air discharged from the compressor; a wet air supplier provided downstream of the cooler so as to supply the wet air to the dehumidification tank; a wet air chamber connected above the dehumidification tank via a pipe; a dry air chamber connected below the dehumidification tank via a pipe; a cold compressed air regeneration chamber connected between the dehumidification tank and the wet air chamber via a pipe; a hot compressed air regeneration chamber connected between the dehumidification tank and the dry air chamber via a pipe; a dehumidification line connected between the compressor and the wet air chamber; a hot compressed air regeneration line, which is divided from the dehumidification line provided between the compressor and the cooler and is connected to the hot compressed air regeneration chamber; a cold compressed air regeneration line, which is divided from a dehumidification line provided between the cooler and the wet air supplier and is connected to the cold compressed air regeneration chamber; first and second diverter valves respectively provided on the hot compressed air regeneration line and the cold compressed air regeneration line so as to change flow of regeneration air; a connection pipe connected between the first and second diverter valves; and a separator communicating with the connection pipe and including an air outlet for discharging air connected to the wet air supplier via a circulation pipe, wherein a plurality of inlet pipes extends from the wet air chamber, and the plurality of inlet pipes is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of upper air control valves, the cold compressed air regeneration chamber is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of communication pipes, the plurality of upper air control valves is provided between the inlet pipes and the communication pipes, and the upper air control valves have a three-way valve structure with first, second and third ports, and the first and second ports are provided to communicate with the communication pipes and the third ports are provided to communicate with the inlet pipes, a plurality of outlet pipes extends from the dry air chamber, and the plurality of outlet pipes is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of lower air control valves, the hot compressed air regeneration chamber is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of communication pipes, and the plurality of lower air control valves is provided between the outlet pipes and the communication pipes, and the lower air control valves have a three-way valve structure with first, second and third ports, and the first and second ports are provided to communicate with the communication pipes and the third ports are provided to communicate with the outlet pipes.

In this aspect, the wet air supplier may include an ejector having a nozzle, and the nozzle of the ejector may be connected to the circulation pipe of the separator.

In this aspect, the wet air supplier may include a flow control valve, and the circulation pipe of the separator may be connected downstream of the flow control valve of the dehumidification line.

In this aspect, the hot compressed air regeneration line may be provided with a heater.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features and further advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view showing an absorption type air drying system according to a first embodiment of the present invention;

FIG. 2 is a flow diagram showing a dehumidification process using the absorption type air drying system of FIG. 1;

FIG. 3 is a flow diagram showing a heating regeneration process of the absorption type air drying system of FIG. 1;

FIG. 4 is a flow diagram showing a cooling regeneration process of the absorption type air drying system of FIG. 1;

FIG. 5 is a schematic view showing an absorption type air drying system according to a second embodiment of the present invention;

FIGS. 6 and 7 are flowcharts showing a heating regeneration process of the absorption type air drying system of FIG. 5;

FIG. 8 is a schematic view showing an absorption type air drying system according to a third embodiment of the present invention;

FIG. 9 is a flow diagram showing dehumidification and heating regeneration processes of the absorption type air drying system of the present invention;

FIG. 10 is a flow diagram showing dehumidification and cooling regeneration processes of the absorption type air drying system of the present invention; and

FIGS. 11 and 12 are modifications of FIG. 8.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, a detailed description will be given of preferred embodiments of the present invention with reference to the appended drawings.

FIG. 1 is a schematic view showing an absorption type air drying system according to a first embodiment of the present invention. Referring to FIG. 1, respective elements of the present invention are described below.

According to the present invention, the absorption type air drying system is a dehumidification system using waste heat and includes a pair of adsorption towers 10, namely, first and second adsorption towers 112, 114 which are of the same shape and structure and dehumidify wet air so as to produce dry air. The first and second adsorption towers 112, 114 are provided in the form of a hermetically sealed cylinder of a predetermined length, and are filled with an adsorbent, and include inlets and outlets at tops and bottoms thereof so that the adsorbent can be replaced. Also, a stainless steel-made screen mesh for preventing the loss of the adsorbent and an air distributor for appropriately distributing the flow of air (dehumidification air and regeneration air) are provided at the upper and lower portions of the adsorption towers 112, 114. Examples of the adsorbent charged in the adsorption towers 112, 114 include activated alumina, silica gel, alumina silica gel, molecular sieves, etc.

A compressor 120 is disposed at the forefront of the absorption type air drying system according to the present invention so as to compress external wet air to a predetermined pressure (about 7.0 kg/cm²). Typical examples of such a compressor include a screw type compressor or a turbo type compressor. In particular, a screw type compressor generates compression heat having a temperature of about 150° C. upon compression, and a turbo type compressor generates compression heat having a temperature of about 120° C., and the wet air compressed by the compressor 120 has a temperature of about 90˜150° C.

A first branch point 130 is provided at the outlet side of the compressor 120 so that the compressed wet air is divided into dehumidification air and regeneration air, and the amount of the regeneration air thus divided may be about 30˜40% of the total amount of air (wet air).

A first cooler 140 is provided on a pipe for transporting the dehumidification air divided at the first branch point 130 so as to cool the dehumidification air, whereby the dehumidification air at high temperature and high pressure is cooled to about 40° C. or less.

A first separator 150 is provided at the outlet side of the first cooler 140 so as to separate moisture from the dehumidification air cooled by the first cooler 140, and typically includes for example a cyclone type separator or a demister type separator.

A pretreatment filter 160 is used to further remove impurities (moisture or oil and dust) which were not removed by the first separator 150, and the removed impurities are discharged to the outside via an auto-drain. The pretreatment filter 160 automatically opens a bypass valve in order to prevent pressure at the outlet from decreasing due to the generation of excessive differential pressure in the adsorption towers 110 and the improper operation of a variety of valves, so that pressure at the outlet is maintained uniform.

A second branch point 170 is used to further divide the dehumidification air from which impurities including moisture were removed by the first separator 150 and the pretreatment filter 160, into dehumidification air and regeneration air, and the amount of the regeneration air thus divided may be about 30˜40% of the amount of the dehumidification air from which impurities were removed by the pretreatment filter 160. As such, the ratio of the dehumidification air and the regeneration air, which are divided at the second branch point 170, may be adjusted by means of a flow control valve 180 which will be described below.

The flow control valve 180 is installed on one side of the second branch point 170, namely, on a pipe for transporting the dehumidification air, to adjust the ratio of the dehumidification air and the regeneration air, which are divided at the second branch point 170. In order to maintain the amount of the regeneration air used to regenerate the adsorbent at a constant level, the ratio of dehumidification air to regeneration air is adjusted. When pressure at the inlet side of the flow control valve 180 is increased, the amount of regeneration air may decrease. In contrast, when pressure at the inlet side thereof is decreased, the amount of regeneration air may increase.

Regeneration diverter valves 190 are used to circulate the regeneration air divided at the first branch point 130 and the regeneration air divided at the second branch point 170 so as to regenerate the adsorbent, and include four on-off valves 192, 194, 196, 198 on the circulation line of the regeneration air, and the opening and closing thereof are controlled to achieve heating regeneration or cooling regeneration of the adsorbent. For the sake of description, the four on-off valves of the regeneration diverter valves 190 are referred to as ninth, tenth, eleventh and twelfth on-off valves 192, 194, 196, 198.

A heater 210 is provided on the circulation line of the regeneration air so as to heat the regeneration air that is transported to the first or second adsorption towers 112, 114, and may include a typical electric heater. As such, because the regeneration air that is transported to the heater 210 is regeneration air at high temperature (about 120˜150° C.) divided at the first branch point 130, not a lot of energy is consumed to heat it up to about 200° C. In brief, the regeneration air may be heated to a desired temperature even by a small amount of energy, so that energy consumption is low. Hence, a heater 210 having small capacity may be used for the present invention.

The temperature of the regeneration air heated by the heater 210 may vary depending on the kind of the adsorbent. For example, regeneration air of about 185˜205° C. is required to perform heating regeneration of activated alumina, and regeneration air of about 120˜150° C. is required to perform heating regeneration of silica gel, and regeneration air of about 210˜230° C. is required to perform heating regeneration of molecular sieves.

A second cooler 220 and a second water separator 230 are provided on the regeneration line of the regeneration diverter valves 190, and the second cooler 220 functions to cool the regeneration air passed through the first or second adsorption tower 112, 114 to a temperature of about 40° C. or less as in the first cooler 140.

The function of the second separator 230, which is provided at the outlet side of the second cooler 220, is to separate moisture from the regeneration air cooled by the second cooler 220, and the second separator 230 may include a cyclone type separator or a demister type separator, as in the first separator 150.

Also, a summing point 250 is positioned downstream of the flow control valve 180 and the second water separator 230 which cross each other, and the dehumidification air passed through the flow control valve 180 and the regeneration air passed through the second separator 230 are combined at the summing point 250.

First diverter valves 260 are connected to the circulation line of the regeneration air below the first and second adsorption towers 112, 114 so as to change the direction of transport of the dehumidification air and the regeneration air which are fed into or discharged from the first and second adsorption towers 112, 114. Also, second diverter valves 270 are connected to the circulation line of the regeneration air above the first and second adsorption towers 112, 114 so as to change the direction of transport of the dehumidification air and the regeneration air which are fed into or discharged from the first and second adsorption towers 112, 114.

The first and second diverter valves 260, 270 include four on-off valves 262, 264, 266, 268 and 272, 274, 276, 278, respectively. By controlling the opening and closing thereof, the transport of the dehumidification air and the regeneration air is selectively regulated, so that the first and second adsorption towers 112, 114 may alternately undergo dehumidification and regeneration. For the sake of description, the four on-off valves of the first diverter valves 260 are referred to as first, second, third, and fourth on-off valves 262, 264, 266, 268, and the four on-off valves of the second diverter valves 270 are referred to as fifth, sixth, seventh, and eighth on-off valves 272, 274, 276, 278.

The dry air dehumidified by the first and second diverter valves 260, 270 is treated with a post-treatment filter 280 to further remove impurities (moisture or oil and dust) therefrom before being discharged to a variety of use places, so that a variety of systems that use dry air are prevented from being damaged. As in the pretreatment filter 160, the post-treatment filter 280 automatically opens a bypass valve in order to prevent pressure at the outlet from decreasing due to the generation of excessive differential pressure in the adsorption towers 110 and the improper operation of a variety of valves, so that pressure at the outlet is maintained constant.

A dew point controller 290 includes a temperature controller 292 which is provided on the circulation line of the regeneration air extending under the first and second adsorption towers 112, 114 so as to detect the temperature of the circulating regeneration air and control the temperature using a block valve, the block valve 294 which is opened and closed by the temperature controller 292 to circulate and block the regeneration air, and a dew point gauge 296 installed on one side of a pipe extending on the first and second adsorption towers 112, 114.

Below is a description of the dehumidification and regeneration (heating and cooling) processes of the absorption type air drying system thus configured to prevent the dew point from being searched for and retain the ultra-low dew point upon switching the adsorption towers. As such, the dehumidification and regeneration procedures are simultaneously performed in the pair of adsorption towers 112, 114, provided that in the present embodiment, the dehumidification process is carried out in the first adsorption tower 112 and the regeneration process is conducted in the second adsorption tower 114.

Referring to FIG. 2, the dehumidification process is as follows.

The external wet air is compressed to high temperature (about 120˜150° C.) and high pressure (about 7.0 kg/cm²) by the compressor 120, and then divided into dehumidification air and regeneration air at the first branch point 130. As such, the amount of the regeneration air which was divided at the first branch point 130 may be about 30˜40% of the amount of the air discharged from the compressor 120.

Then, the dehumidification air divided at the first branch point 130 is cooled to about 40° C. by means of the cooler 140, and moisture generated upon cooling is removed therefrom by the first separator 150. Impurities which were not yet removed by the first separator 150 are then removed by the pretreatment filter 160.

The dehumidification air from which moisture was removed by the pretreatment filter 160 is further divided into dehumidification air and regeneration air at the second branch point 170. The amount of the regeneration air thus divided may be about 30˜40% of the amount of the dehumidification air from which impurities were removed by the pretreatment filter 160.

The dehumidification air divided at the second branch point 170 is fed into the first adsorption tower 12 via the flow control valve 180 and the first diverter valves. In order to feed the dehumidification air into the first adsorption tower 112, among the first diverter valves 260, the first and fourth on-off valves 262, 268 should be opened and the second and third on-off valves 264, 266 should be closed.

The dehumidification air fed into the first adsorption tower 112 comes into contact with the adsorbent therein and is thus completely dehumidified and converted into dry air, which is then discharged to a variety of use places. In order to discharge the completely dehumidified dry air to a variety of use places, among the second diverter valves 270, the fifth and eighth on-off valves 272, 278 should be opened and the sixth and seventh on-off valves 274, 276 should be closed.

With reference to FIG. 3, the heating regeneration process is as follows.

The regeneration air (the amount of which is about 30˜40% of the amount of the air discharged from the compressor) divided at the first branch point 130 is heated to 200° C. while passing through the heater 210 provided on the regeneration circulation pipe, and then fed into the second adsorption tower 114 via the ninth on-off valve 192. As such, in order to prevent the regeneration air from flowing into the first adsorption tower 112, among the second diverter valves 270, the fifth and eighth on-off valves 272, 278 should be opened and the sixth and seventh on-off valves 274, 276 should be closed. Also, the eleventh and twelfth on-off valves 196, 198 of the regeneration diverter valves 190 should be in a state of being closed. This is to prevent the regeneration air from being directly transported to the second cooler 220 without going through the second adsorption tower 114 or the regeneration air passed through the second adsorption tower 114 from being directly transported to the second branch point 170.

The regeneration air fed into the second adsorption tower 114 desorbs moisture from the adsorbent charged therein, and is then transported to the second cooler 220 via the fourth on-off valve 268 and the tenth on-off valve 194. Subsequently, the air thus transported is cooled to about 40° C. in the second cooler 220, treated to remove impurities containing moisture therefrom in the second separator 230, and then combined with the dehumidification air at the summing point 250, after which the resulting air is fed into the first adsorption tower 112. As such, because the second and third on-off valves 264, 266 of the first diverter valves 260 should be in a state of being closed, the regeneration air discharged from the second adsorption tower 114 is not fed into the first adsorption tower 112.

Referring to FIG. 4, the cooling regeneration process is described below.

The regeneration air (the amount of which is about 30˜40% of the amount of the dehumidification air from which impurities were removed by the pretreatment filter 160) divided at the first branch point 170 is fed into the second adsorption tower 114 via the eleventh on-off valve 196 and the fourth on-off valve 268. As such, in order to prevent the regeneration air from being fed into the first adsorption tower 112, among the first diverter valves 260, the first and fourth on-off valves 262, 268 should be opened and the second and third on-off valves 264, 266 should be closed. Furthermore, the ninth and tenth on-off valves 192, 194 of the regeneration diverter valves 190 should be in a state of being closed. This is to prevent the regeneration air from being transported to the second cooler 220 without going through the second adsorption tower 114 or the regeneration air passed through the second adsorption tower 114 from being transported to the heater 210.

The regeneration air fed into the second adsorption tower 114 desorbs moisture from the adsorbent charged therein, and is then transported to the second cooler 220 via the eighth on-off valve 278 and the twelfth on-off valve 198. This air is cooled to about 40° C. in the second cooler 220, treated in the second separator 230 to remove impurities containing moisture, and then combined with the dehumidification air at the summing point 250, after which the resulting air is fed into the first adsorption tower 112. As such, because the second and third on-off valves 264, 266 of the first diverter valve 260 are in a state of being closed, the regeneration air discharged from the second adsorption tower 114 is not fed into the first adsorption tower 112.

The method of controlling the absorption type air drying system will now be described while referring to FIG. 1. The method of controlling the absorption type air drying system is a method of controlling the switching of the adsorption towers in which the direction of wet air that is fed into respective adsorption towers 112, 114 is changed so that dehumidification and regeneration which were respectively carried out in the pair of adsorption towers 112, 114 are alternately performed at predetermined temporal intervals.

Typically, when the second diverter valves 270 and the regeneration diverter valves 190 are simultaneously opened upon switching the adsorption towers, hot wet air fed via the ninth on-off valve 192 among the regeneration diverter valves 190 is combined with the dry air discharged from the first or second adsorption tower 112, 114, thus reducing dryness. Also as mentioned above, in the case where hot wet air is introduced, the dew point may vary (about 15˜30° C.), undesirably lowering energy efficiency.

To solve such problems, the method of controlling the absorption type air drying system according to the present invention is as follows.

When an adsorption tower switching signal is applied in a state of the dehumidification process in the first adsorption tower 112 and the regeneration process in the second adsorption tower 114 being conducted, the third, fourth, seventh and eighth on-off valves 266, 268, 276, 278 are closed, so that the hot wet air is prevented from flowing into the first and second adsorption towers 112, 114.

After a lapse of a first predetermined period of time, the first and fifth on-off valves 262, 272 are closed and the second and sixth on-off valves 264, 274 are opened so that external air is introduced into the second adsorption tower 114. Also, after a lapse of a second predetermined of time, the ninth and tenth on-off valves 192, 194 or the eleventh and twelfth on-off valves 196, 198 are opened and closed so as to circulate the regeneration air.

Finally after a lapse of a third predetermined period of time, the third and seventh on-off valves 266, 276 are opened and the fourth and eighth on-off valves 268, 278 are closed, so that the regeneration air is fed only into the first adsorption tower 112.

When the regeneration process is conducted in the first adsorption tower 112 and the dehumidification process is carried out in the second adsorption tower 114 in this way, the switching of the adsorption towers is completed.

Also when the adsorption tower switching signal is applied in the aforementioned state, namely, a state of the regeneration process in the first adsorption tower 112 and the dehumidification process in the second adsorption tower 114 being carried out, the third, fourth, seventh and eighth on-off valves 266, 268, 276, 278 are closed, so that the hot wet air is prevented from flowing into the first and second adsorption towers 112, 114.

After a lapse of the first predetermined period of time, the second and sixth on-off valves 264, 274 are closed and the first and fifth on-off valves 262, 272 are opened so that external air is introduced into the first adsorption tower 112. After a lapse of the second predetermined period of time, the ninth and tenth on-off vales 192, 194 or the eleventh and twelfth on-off valves 196, 198 are opened and closed, whereby the regeneration air is circulated.

Finally after a lapse of the third predetermined period of time, the fourth and eighth on-off valves 268, 278 are opened and the third and seventh on-off valves 266, 276 are closed, so that the regeneration air is fed only into the second adsorption tower 112.

When the dehumidification process is conducted in the first adsorption tower 112 and the regeneration process is performed in the second adsorption tower 114 in this way, the switching of the adsorption towers is completed.

Herein, whether the ninth and tenth or the eleventh and twelfth on-off valves 192, 194 or 196, 198 are opened or closed is determined depending on the type of regeneration process. For example, in the case of the heating regeneration process, the ninth and tenth on-off valves 192, 194 may be opened and the eleventh and twelfth on-off valves 196, 198 may be closed. Also, in the case of the cooling regeneration process, the ninth and tenth on-off valves 192, 194 may be closed and the eleventh and twelfth on-off valves 196, 198 may be opened.

The first predetermined period of time is 2˜4 seconds, the second predetermined period of time is 4˜6 seconds and the third predetermined period of time is 9˜11 seconds, but the present invention is not necessarily limited and these periods of time may vary depending on conditions.

When the adsorption towers are switched as mentioned above, the hot wet air is prevented from being combined with the dry air, so that the attempt to determine the dew point due to changes in dew point is prevented and the ultra-low dew point (about −100° C.) may be maintained, thus maximizing the energy efficiency.

FIG. 5 schematically shows an absorption type air drying system according to a second embodiment of the present invention.

As shown in FIG. 5, the absorption type air drying system according to the second embodiment of the present invention further includes a discharge member 240 in addition to the elements of the absorption type air drying system of FIGS. 1 to 4. Thus, a description of the elements other than the discharge member 240 is omitted with reference to FIGS. 1 to 4.

The discharge member 240 is provided at the outlet side of the second separator 230, so that the regeneration air is discharged from the second separator 230 to the outside. The discharge member 240 includes a pair of on-off valves 242, 244 having different discharge amounts, and a muffler 246 disposed at the outlet side of the above on-off valves, in which the pair of on-off valves 242, 244 are connected in parallel.

As mentioned above, the discharge member 240 is used to selectively operate the absorption type air drying system in purge mode or non purge mode depending on the amount of dry air to be produced. Specifically, in the case where the amount of air (dry air) to be produced is small, the discharge member 240 is opened and thus the regeneration air is discharged from the second separator 230 to the outside, whereby the system is operated in purge mode. In contrast, in the case where the amount of air (dry air) to be produced is large, the discharge member 240 is closed and thus the regeneration air discharged from the second separator 230 is combined with the dehumidification air at the summing point 250, whereby the system is operated in non purge mode.

Thus, superior energy efficiency may be always obtained regardless of the amount of air (dry air) to be produced. Moreover, the discharge member may be applied to initial, medium or final operation stages in which different amounts of air are compressed by the compressor. In particular, in the case where the pair of on-off valves 242, 244 having different discharge amounts, which are connected in parallel, are used, the amount of the regeneration air discharged to the outside may be finely adjusted, and thus the energy efficiency may be prevented from decreasing when the operating mode (purge mode or non purge mode) is changed.

The dehumidification process and the regeneration (heating and cooling) process of the absorption type air drying system of FIG. 5 are described below. As such, dehumidification and regeneration are simultaneously carried out in respective adsorption towers 112, 114, provided that the dehumidification process is performed in the first adsorption tower 112 and the regeneration process is conducted in the second adsorption tower 114.

First, the dehumidification process is described below.

The external wet air is compressed to high temperature (about 90˜150° C.) and high pressure (about 7.0 kg/cm²) by means of the compressor 120, and then divided into dehumidification air and regeneration air at the first branch point 130, after which the dehumidification air divided at the first branch point 130 passes through the first cooler 140, the pretreatment filter 160, and the first water separator 150 and is then further divided into dehumidification air and regeneration air at the second branch point 170.

The dehumidification air divided at the second branch point 170 is transported to the first diverter valves 260 via the flow control valve 180, and among the first diverter valves 260 the first and fourth on-off valves 262, 268 are opened and the second and third on-off valves 264, 266 are closed, so that the dehumidification air is fed into the first adsorption tower 112.

The dehumidification air fed into the first adsorption tower 112 comes into contact with the adsorbent therein and thus is made into completely dehumidified dry air, which is then emitted to a variety of use places. As such, among the second diverter valves 270 the first and fourth on-off valves 272, 278 are closed and the second and third on-off valves 274, 276 are opened, thus discharging the dehumidification air to the outside.

The heating regeneration process is described below.

The regeneration air (the amount thereof is about 30˜40% of the amount of the air discharged from the compressor) separated at the first branch point 130 is heated to 170˜250° C. while passing through the heater 210 provided on the regeneration line of the regeneration diverter valves 190, and is then fed into the second adsorption tower 114 via the first on-off valve 192 among the regeneration diverter valves 190. As in the dehumidification process, among the second diverter valves 270 the first and fourth on-off valves 272, 278 are closed and the second and third on-off valves 274, 276 are opened, and the third and fourth on-off valves 196, 198 of the regeneration diverter valves 190 are closed.

The regeneration air fed into the second adsorption tower 114 desorbs moisture from the adsorbent charged therein, and is then transported to the second cooler 220 via the fourth on-off valve 268 among the first diverter valves 260 and the second on-off valve 194 among the regeneration diverter valves 190, so that it is cooled to about 40° C. by the second cooler 220, after which impurities containing moisture are removed therefrom by the second water separator 230.

In the case where the absorption type air drying system of FIG. 2 is operated in purge mode, the regeneration air from which impurities containing moisture were removed by the second water separator 230 is discharged to the outside via the discharge member 240. Whereas, in the case where it is operated in non purge mode, such regeneration air is combined with the dehumidification air at the summing point 250 and the resulting air may be fed into the first adsorption tower 112.

The cooling regeneration process is described below.

The regeneration air (the amount thereof is about 30˜40% of the amount of the dehumidification air from which impurities were removed by the pretreatment filter 160) separated at the first branch point 170 is fed into the second adsorption tower 114 via the third on-off valve 196 among the regeneration diverter valves 190 and the fourth on-off valve 268 among the first diverter valves 260. As in the dehumidification process, among the first diverter valves 260 the first and fourth on-off valves 262, 268 are opened and the second and third on-off valves 264, 266 are closed, and the first and second on-off valves 192, 194 of the regeneration diverter valves 190 are closed.

The regeneration air fed into the second adsorption tower 114 desorbs moisture from the adsorbent charged therein, and is then transported to the second cooler 220 via the second on-off valve 278 among the second diverter valves 270 and the fourth on-off valve 198 among the regeneration diverter valves 190, so that it is cooled to about 40° C. by the second cooler 220, after which impurities containing moisture are removed therefrom by the second water separator 230.

In the case where the absorption type air drying system is operated in purge mode, the regeneration air from which impurities containing moisture were removed by the second water separator 230 is discharged to the outside via the discharge member 240. Whereas, in the case where it is operated in non purge mode, such regeneration air is combined with the dehumidification air at the summing point 250 and the resulting air may be fed into the first adsorption tower 112.

FIGS. 6 and 7 show the process of controlling the heating regeneration of the absorption type air drying system of FIG. 5.

As shown in FIGS. 6 and 7, the method of controlling the heating regeneration of the absorption type air drying system of FIG. 5 includes circulating the regeneration air to either of the first and second adsorption towers 112, 114 (S1), selectively operating the heater 210 depending on the internal temperature of the first or second adsorption tower 112, 114 (S2), and passing the regeneration air through the first or second adsorption tower 112, 114, thus achieving heating regeneration of the first or second adsorption tower.

The wet air compressed by the compressor 120 is heated to about 90˜150° C. by compression heat of the compressor 120 and then discharged, and the wet air thus heated is divided into regeneration air at the first branch point 130, after which the regeneration air thus divided is circulated to either of the first and second adsorption towers 112, 114 via the regeneration diverter valves 190 (S1). As such, the function of the heater 210 is to heat the regeneration air that was heated to about 90˜150° C. to a regeneration temperature of about 170˜250° C., and the regeneration air having an appropriate regeneration temperature is passed from the upper portion of the adsorption tower 112, 114 to the lower portion thereof, thereby appropriately regenerating the inside of the adsorption towers 112, 114.

On the other hand, in the method of controlling the heating regeneration of the absorption type air drying system according to the second embodiment, when the heater 210 is continuously operated during the heating regeneration process, energy may be increasingly wasted, undesirably increasing the total cost of operation.

For this reason, the internal temperature of the adsorption tower 112, 114 is appropriately detected (S2-1). When the internal temperature of the adsorption tower 112, 114 thus detected corresponds to the temperature (about 90˜150° C.) of compression heat of the compressor 120 (S2-2), the heater 210 is selectively operated, so that the regeneration air is heated to the regeneration temperature of about 170˜250° C. (S2-3).

In particular, the temperature of the lower portion of the adsorption tower 112, 114 may be detected by the temperature sensor, thereby more exactly controlling the regeneration temperature of the regeneration air.

As the heater 210 is selectively operated depending on the internal temperature of the adsorption tower 112, 114, the regeneration air having an appropriate regeneration temperature (about 170˜250° C.) may be passed through the adsorption tower 112, 114, whereby the adsorption towers may undergo heating regeneration (S3).

FIG. 8 shows an absorption type air drying system according to a third embodiment of the present invention.

As shown in FIG. 8, the absorption type air drying system according to the third embodiment includes a dehumidification tank 10 wherein two or more dehumidification beds 10a, 10b, 10c are partitioned by one or more barriers 10d, a compressor 11 for compressing external wet air, a cooler 12 for cooling the wet air discharged from the compressor 11, a wet air supplier 40 for supplying the cooled wet air to the dehumidification tank 10, a wet air chamber 16 disposed above the dehumidification tank 10, a dry air chamber 17 disposed below the dehumidification tank 10, a hot compressed air regeneration chamber 18 disposed between the dry air chamber 17 and the dehumidification tank 10, and a cold compressed air regeneration chamber 19 disposed between the wet air chamber 16 and the dehumidification tank 10.

The dehumidification tank 10 is a hermetically sealed pressure vessel, in which the internal space is partitioned by one or more barriers 10d to thus form two or more dehumidification beds 10a, 10b, 10c. The barriers 10d are made of a material able to avoid thermal contact between the dehumidification beds 10a, 10b, 10c. An adsorbent is charged in the dehumidification beds 10a, 10b, 10c, and an inlet and an outlet necessary to replace the adsorbent are respectively formed at the top and the bottom of each of the dehumidification beds 10a, 10b, 10c.

The adsorbent may be any one or a mixture of two or more selected from among activated alumina, silica gel, alumina silica gel, molecular sieves, and synthetic silica gel. Particularly useful in the present invention is a synthetic silica gel. The synthetic silica gel is advantageous because it may be efficiently regenerated at a comparatively low temperature of about 130° C.

The compressor 11 is used to compress the external wet air to a predetermined pressure (about 7.0 kg/cm²), and typically includes a screw type compressor or a turbo type compressor. The screw oil free type compressor generates compression heat having a temperature of about 150° C. upon compression, and the turbo type compressor generates compression heat having a temperature of about 140° C. or higher upon compression. In the present invention, the wet air is preheated by multi-stage compression heat at about 140˜150° C. by the compressor 11, and the wet air thus compressed becomes hot compressed air having a temperature of about 140˜150° C. When the hot compressed air is used to regenerate the adsorbent, an additional heat source is not required thus exhibiting superior energy saving effects and obviating the need to use a heat source such as fossil fuel to thereby suppress the generation of CO₂ and so on.

A dehumidification line 13 for delivering the wet air is connected at the outlet of the compressor 11, and a first branch point 11a is positioned downstream of the compressor 11. A hot compressed air regeneration line 13a is divided at the first branch point 11a of the dehumidification line 13, and the hot compressed air regeneration line 13a is connected to the hot compressed air regeneration chamber 18. Part of the wet air compressed by the compressor 11 is divided via the hot compressed air regeneration line 13a.

Alternatively, as shown in FIG. 11 according to a modification of the above embodiment, a heater 27 may be provided on the hot compressed air regeneration line 13a. If the temperature of the hot compressed air is lower than a set level (e.g. about 140˜150° C.), the heater 27 may be selectively operated so as to efficiently perform the heating regeneration process using the hot compressed air.

A cooler 12 is disposed downstream of the compressor 11, and the wet air at high temperature and high pressure may be cooled to about 40° C. or less by the cooler 12.

A wet air supplier 40 for supplying the wet air to the dehumidification tank 10 is provided downstream of the cooler 12. The wet air supplier 40 is configured such that the wet air compressed and cooled by the compressor 11 and the cooler is very efficiently transported to the dehumidification tank 10.

As shown in FIGS. 8 and 11, the wet air supplier 40 includes an ejector 41 having a nozzle. While the wet air passes through the nozzle, the flow rate thereof becomes fast, thus increasing the transport efficiency of wet air. Connected to the nozzle of the ejector 41 is an air outlet of a separator 23 via the circulation pipe 23a. When the wet air discharged from the compressor 11 passes through the nozzle, negative pressure is formed in the inner space of the nozzle because of the Bernoulli's principle, and accordingly the wet air discharged from the air outlet of the separator 23 is combined via the nozzle and then transported to the dehumidification tank 10. In this way, the transport efficiency of wet air is increased by the ejector 41 thus increasing the yield of dry air.

In addition, as shown in FIG. 12, the wet air supplier 40 may include a flow control valve 42. The flow control valve appropriately controls the flow rate of the wet air discharged from the compressor 11 so as to supply it to the dehumidification tank 10. The air outlet of a separator 23 is connected downstream of the flow control valve 42 of the dehumidification line 13 via a circulation pipe 23a, and the circulation pipe 23a is provided with an orifice 43 that is connected with a differential pressure transformer (FT) and a flow indication controller (FIC). The wet air after regeneration passing through the orifice 43 may be combined with the dehumidification line 13 by means of the differential pressure transformer (FT) and the flow indication controller (FIC).

Also, a second branch point 12a is positioned between the cooler 12 and the wet air supplier 40, and a cold compressed air regeneration line 13b is divided at the second branch point 12a of the dehumidification line 13, and a cold compressed air regeneration chamber 19 is connected downstream of the cold compressed air regeneration line 13b. Part of the wet air cooled by the cooler 12 may be divided via the cold compressed air regeneration line 13b.

The hot compressed air regeneration line 13a and the cold compressed air regeneration line 13b are respectively provided with first and second diverter valves 21, 22, and the first and second diverter valves 21, 22 each have a three-way valve structure for simply changing the flow of the regeneration air. The first diverter valve 21 has first to third ports 21a, 21b, 21c, and the first and second ports 21a, 21b of the first diverter valve 21 are provided to communicate with the hot compressed air regeneration line 13a, and the second diverter valve 22 has first to third ports 22a, 22b, 22c and the first and second ports 22a, 22b of the second diverter valve 22 are provided to communicate with the cold compressed air regeneration line 13b. A connection pipe 24 is disposed between the third port 21c of the first diverter valve 21 and the third port 22c of the second diverter valve 22. A branch pipe 24a is divided at one side of the connection pipe 24, and the separator 23 is connected to the branch pipe 24a. The separator 23 includes a cooler, an air outlet for discharging wet air, and a moisture outlet. The separator 23 is configured such that the regeneration air is cooled by the cooler to condense moisture, and the condensed moisture is separated and discharged via the moisture outlet, and the wet air is discharged via the air outlet. A circulation pipe 23a extends from the air outlet of the separator 23, and communicates with the nozzle of the ejector 15.

The wet air chamber 16 is disposed above the dehumidification tank 10, and is connected downstream of the dehumidification line 13. A plurality of inlet pipes 16a, 16b, 16c extends from the wet air chamber 16, and the respective inlet pipes 16a, 16b, 16c are connected to communicate with the dehumidification beds 10a, 10b, 10c of the dehumidification tank 10 via a plurality of upper air control valves 31, 32, 33. The cold compressed air regeneration chamber 19 is connected to communicate with the dehumidification beds 10a, 10b, 10c of the dehumidification tank 10 via a plurality of communication pipes 19a, 19b, 19c. Furthermore, the plurality of upper air control valves 31, 32, 33 are disposed between the inlet pipes 16a, 16b, 16c and the communication pipes 19a, 19b, 19c, and the upper air control valves 31, 32, 33 have a three-way valve structure having first, second and third ports 31a, 31b, 31c; 32a, 32b, 32c; 33a, 33b, 33c. The first and second ports 31a, 31b; 32a, 32b; 33a, 33b are provided to communicate with the communication pipes 19a, 19b, 19c, and the third ports 31c, 32c, 33c are provided to communicate with the inlet pipes 16a, 16b, 16c.

A dry air chamber 17 is disposed below the dehumidification tank 10. A plurality of outlet pipes 17a, 17b, 17c extends from the dry air chamber 17, and the plurality of outlet pipes 17a, 17b, 17c is connected to communicate with the dehumidification beds 10a, 10b, 10c of the dehumidification tank 10 via a plurality of lower air control valves 34, 35, 36. Furthermore, a hot compressed air regeneration chamber 18 is connected to communicate with the dehumidification beds 10a, 10b, 10c of the dehumidification tank 10 via a plurality of communication pipes 18a, 18b, 18c. Also the plurality of lower air control valves 34, 35, 36 is provided between the outlet pipes 17a, 17b, 17c and the communication pipes 18a, 18b, 18c, and the lower air control valves 34, 35, 36 have a three-way valve structure having first, second and third ports 34a, 34b, 34c; 35a, 35b, 35c; 36a, 36b, 36c, respectively, and the first and second ports 34a, 34b; 35a, 35b; 36a, 36b are provided to communicate with the communication pipes 19a, 19b, 19c, and the third ports 34c, 35c, 36c are provided to communicate with the outlet pipes 17a, 17b, 17c.

With reference to FIGS. 9 and 10, the dehumidification and regeneration (heating and cooling) processes of the absorption type air drying system according to the third embodiment are described below. In the present embodiment, the plurality of dehumidification beds 10a, 10b, 10c includes a first dehumidification bed 10a, a second dehumidification bed 10b, and a third dehumidification bed 10c, and thus the plurality of inlet pipes 16a, 16b, 16c designates first to third inlet pipes 16a, 16b, 16c, and the plurality of outlet pipes 17a, 17b, 17c designates first to third outlet pipes 17a, 17b, 17c, and the plurality of air control valves 31, 32, 33, 34, 35, 36 designates first to sixth air control valves 31, 32, 33, 34, 35, 36.

First, the case where a dehumidification process is performed in the first and second dehumidification beds 10a, 10b and a regeneration process is carried out in the third dehumidification bed 10c will be assumed.

The wet air compressed by the compressor 11 is transported to the wet air chamber 16 via the dehumidification line 13, and the wet air of the wet air chamber 16 is supplied to the first and second dehumidification beds 10a, 10b by opening the second and third ports 31b, 31c; 32b, 32c of the first and second air control valves 31, 32. The wet air comes into contact with the adsorbent in the first and second dehumidification beds 10a, 10b and is thus dehumidified, thus obtaining dry air. The dry air thus obtained is collected to the dry air chamber 17 via the first and second outlet pipes 17a, 17b by opening the first and third ports 34a, 34c; 35a, 35c of the fourth and fifth air control valves 34, 35, and is then discharged to a variety of use places.

Also the heating regeneration process of the third dehumidification bed 10c is shown in FIG. 9. In the heating regeneration process, the first port 22a of the second diverter valve 22 is closed, and the other ports 22b, 22c are opened. Furthermore, the third port 21c of the first diverter valve 21 is closed and the other ports 21a, 21b are opened. Thereby, part of the hot wet air divided at the first branch point 11a is transported to the hot compressed air regeneration chamber 18 via the hot compressed air regeneration line 13a.

Part of the wet air at high pressure and high pressure compressed by the compressor 11 (that is, hot compressed air) is divided at the first branch point 11a of the dehumidification line 13 and then transported to the hot compressed air regeneration line 13a. The hot compressed air transported via the hot compressed air regeneration line 13a is delivered into the hot compressed air regeneration chamber 18. When the first and second ports 36a, 36b of the sixth air control valve 36 are opened, the hot compressed air in the hot compressed air regeneration chamber 18 is moved from the lower portion of the third dehumidification bed 10c to the upper portion thereof so that the moisture adsorbed to the adsorbent is removed. When the first and second ports 33a, 33b of the third air control valve 33 are opened, the hot compressed air having removed moisture is fed into the cold compressed air regeneration chamber 19, transported to the cold compressed air regeneration line 13b, and then delivered to the connection pipe 24 via the second diverter valve 22 of the cold compressed air regeneration line 13b. The hot compressed air passed through the connection pipe 24 is fed to the separator 23 via the branch pipe 24a, and the separator 23 cools the hot compressed air so that the condensed moisture is separated and discharged. The regeneration air which was cooled and from which moisture was separated by the separator is sucked via the nozzle of the ejector 41 and then combined with the dehumidification line 13.

Then the cooling regeneration process of the third dehumidification bed 10c is shown in FIG. 10. In the cooling regeneration process, the first port 21a of the first diverter valve 21 is closed, and the other ports 21b, 21c are opened. Furthermore, the third port 22c of the second diverter valve is closed, and the other ports 22a, 22b are opened. Thereby, part of the cold wet air divided at the second branch point 12a is transported to the cold compressed air regeneration chamber 19 via the cold compressed air regeneration line 13b.

Part of the wet air cooled by the cooler 12 (that is, cold compressed air) is divided at the second branch point 12a, and is then transported to the cold compressed air regeneration line 13b. The cold compressed air delivered via the cold compressed air regeneration line 13b is transported into the cold compressed air regeneration chamber 19. When the first and second ports 33a, 33b of the third air control valve 33 are opened, the cold compressed air in the cold compressed air regeneration chamber 19 is moved from the upper portion of the third dehumidification bed 10c to the lower portion thereof, so that the adsorbent is cooled to a proper temperature. When the first and second ports 36a, 36c of the sixth air control valve 36 are opened, the cold compressed air the cooling of which has completed is fed into the hot compressed air regeneration chamber 19, transported to the hot compressed air regeneration line 13a, and then delivered to the connection pipe 24 via the first diverter valve 21 of the hot compressed air regeneration line 13a. The cold compressed air passed through the connection pipe 24 is fed to the separator 23 via the branch pipe 24a, and the separator 23 cools the cold compressed air so that the condensed moisture is separated and discharged. The regeneration air which was cooled and from which moisture was separated by the separator 23 is sucked via the nozzle of the ejector 41 and is then combined with the dehumidification line 13.

According to the third embodiment, the total of period of time required to perform heating regeneration and cooling regeneration in the third dehumidification bed 10c is about 30 minutes, and simultaneously the dehumidification process is efficiently carried out in the first and second dehumidification beds 10a, 10b, thus shortening the regeneration time and increasing the drying efficiency of the wet air at least two fold.

In particular, the hot compressed air and the cold compressed air, which are used for heating regeneration and cooling regeneration, are effectively sucked via the ejector of the wet air supplier 40, combined with the dehumidification line 13 and then transported to the dehumidification tank 10, thereby increasing the transport efficiency of the wet air and drastically increasing the yield of the dry air.

As described hereinbefore, the present invention provides an absorption type air drying system and a method of controlling the same. According to the present invention, first and second diverter valves and regeneration diverter valves are operated at predetermined temporal intervals, so that upon switching adsorption towers, a dew point is prevented from being searched for and a ultra-low dew point (about −100° C.) may be maintained, thus maximizing energy efficiency. A heater only has to be operated when the internal temperature of the adsorption tower where a heating regeneration process is performed corresponds to the temperature of compression heat of the compressor, thereby drastically reducing energy consumption.

Also, the temperature of regeneration air is precisely and exactly controlled, thus remarkably increasing the heating regeneration efficiency, and the wet air compressed by the compressor is efficiently supplied to a dehumidification tank and the regeneration air necessary for regeneration is effectively fed, thus considerably increasing the drying efficiency of the air and the regeneration efficiency of the adsorbent.

Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. An absorption type air drying system, comprising:

first and second adsorption towers;

first diverter valves provided below the first and second adsorption towers so as to change a direction of transport of dehumidification air and regeneration air which are fed into or discharged from the first and second adsorption towers;

second diverter valves provided above the first and second adsorption towers so as to change the direction of transport of dehumidification air and regeneration air which are fed into or discharged from the first and second adsorption towers; and

regeneration diverter valves connected to the first and second diverter valves so as to circulate the regeneration air,

wherein the first diverter valves include first and second on-off valves for feeding the dehumidification air into the first and second adsorption towers, and third and fourth on-off valves for circulating air regenerated in the first and second adsorption towers,

the second diverter valves include fifth and sixth on-off valves for discharging air dehumidified in the first and second adsorption towers to outside, and seventh and eighth on-off valves for feeding the regeneration air into the first and second adsorption towers, and

the regeneration diverter valves include ninth and tenth on-off valves which are opened upon heating regeneration, and eleventh and twelfth on-off valves which are opened upon cooling regeneration.

2. The absorption type air drying system of claim 1, wherein the first to twelfth on-off valves have a two-way valve structure.

3. The absorption type air drying system of claim 1, wherein the first adsorption tower performs a dehumidification process, and the second adsorption tower performs a regeneration process.

4. The absorption type air drying system of claim 1, wherein the first adsorption tower performs a regeneration process, and the second adsorption tower performs a dehumidification process.

5. A method of performing heating regeneration of an absorption type air drying system comprising a compressor for compressing external wet air, first and second adsorption towers, first diverter valves provided below the first and second adsorption towers to change a direction of transport of dehumidification air and regeneration air, second diverter valves provided above the first and second adsorption towers to change the direction of transport of dehumidification air and regeneration air, regeneration diverter valves connected to the first and second diverter valves to circulate the regeneration air to the first and second adsorption towers, a heater provided on a pipe communicating with upper portions of the first and second adsorption towers, and a controller, the method comprising:

1) circulating the regeneration air to either of the first and second adsorption towers by the regeneration diverter valves;

2) selectively operating the heater depending on an internal temperature of the first or second adsorption tower; and

3) passing the regeneration air through the first or second adsorption tower to perform heating regeneration of the first or second adsorption tower,

wherein the selectively operating the heater in 2) comprises:

2-1) detecting the internal temperature of the first or second adsorption tower wherein the regeneration process is performed;

2-2) determining whether the detected temperature corresponds to a temperature of compression heat of the compressor; and

2-3) operating the heater when the internal temperature of the first or second adsorption tower corresponds to the temperature of compression heat of the compressor, so that the regeneration air is heated to a regeneration temperature.

6. The method of claim 5, wherein in 2-1), the temperature of a lower portion of the first or second adsorption tower is detected by means of a temperature sensor.

7. The method of claim 6, wherein in 2-2), the temperature of compression heat of the compressor is 90˜150° C.

8. The method of claim 6, wherein in 2-3), the regeneration temperature is 170˜250° C.

9. An absorption type air drying system, comprising:

a dehumidification tank including a first dehumidification bed, a second dehumidification bed and a third dehumidification bed, which are partitioned by at least one barrier;

a compressor for compressing external wet air;

a cooler for cooling the wet air discharged from the compressor;

a wet air supplier provided downstream of the cooler so as to supply the wet air to the dehumidification tank;

a wet air chamber connected above the dehumidification tank via a pipe;

a dry air chamber connected below the dehumidification tank via a pipe;

a cold compressed air regeneration chamber connected between the dehumidification tank and the wet air chamber via a pipe;

a hot compressed air regeneration chamber connected between the dehumidification tank and the dry air chamber via a pipe;

a dehumidification line connected between the compressor and the wet air chamber;

a hot compressed air regeneration line, which is divided from the dehumidification line provided between the compressor and the cooler and is connected to the hot compressed air regeneration chamber;

a cold compressed air regeneration line, which is divided from a dehumidification line provided between the cooler and the wet air supplier and is connected to the cold compressed air regeneration chamber;

first and second diverter valves respectively provided on the hot compressed air regeneration line and the cold compressed air regeneration line so as to change flow of regeneration air;

a connection pipe connected between the first and second diverter valves; and

a separator communicating with the connection pipe and including an air outlet for discharging air connected to the wet air supplier via a circulation pipe,

wherein a plurality of inlet pipes extends from the wet air chamber, and the plurality of inlet pipes is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of upper air control valves,

the cold compressed air regeneration chamber is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of communication pipes,

the plurality of upper air control valves is provided between the inlet pipes and the communication pipes, and the upper air control valves have a three-way valve structure with first, second and third ports, and the first and second ports are provided to communicate with the communication pipes and the third ports are provided to communicate with the inlet pipes,

a plurality of outlet pipes extends from the dry air chamber, and the plurality of outlet pipes is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of lower air control valves,

the hot compressed air regeneration chamber is connected to communicate with the first to third dehumidification beds of the dehumidification tank via a plurality of communication pipes, and

the plurality of lower air control valves is provided between the outlet pipes and the communication pipes, and the lower air control valves have a three-way valve structure with first, second and third ports, and the first and second ports are provided to communicate with the communication pipes and the third ports are provided to communicate with the outlet pipes.

10. The absorption type air drying system of claim 9, wherein the wet air supplier includes an ejector having a nozzle, and the nozzle of the ejector is connected to the circulation pipe of the separator.

11. The absorption type air drying system of claim 9, wherein the wet air supplier includes a flow control valve, and the circulation pipe of the separator is connected downstream of the flow control valve of the dehumidification line.

12. The absorption type air drying system of claim 9, wherein the hot compressed air regeneration line is provided with a heater.