JPH0659380B2 - Method for regenerating desiccant in gas dehumidifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for regenerating a desiccant in a gas dehumidifier for removing water in a gas to obtain a dry gas.

(Prior Art) When regenerating a desiccant such as silica gel or activated alumina saturated with water by dehumidifying gas in a conventional dehumidifying tower, a regeneration gas such as air is heated by an electric heater or the like and then circulated in the dehumidifying tower. Although the method of evaporating water is generally used, it requires energy for heating and is not preferable in terms of energy saving. Therefore, as an improvement plan, this is disclosed in JP-A-55-1525.
In No. 22, the heat energy of the high-temperature dried gas to be dehumidified is used to heat the desiccant by using part or all of this dried gas as a regeneration gas,
Then, a regeneration method has been proposed in which the gas to be dried is cooled and used as a gas for cooling the desiccant.

(Problems to be Solved by the Invention) However, according to the method described in the above publication, it is preferable in terms of energy saving, but since the gas to be dried naturally contains water, there is a limit to the removal of water from the desiccant at the time of regeneration. Therefore, in the gas dehumidifier by this regeneration method,
For example, it is difficult to obtain a dry gas having a low dew point of about −70 ° C., and at most, only an outdoor dry gas of about −40 ° C. can be obtained.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a method for regenerating a desiccant in a gas dehumidifying device capable of obtaining a dry gas having a low dew point with a device having a simple structure.

(Means for Solving the Problems) The method for regenerating a desiccant according to the present invention, however, dehumidifies the gas to be dried in one of the dehumidifying towers alternately selected from the pair of dehumidifying towers filled with the desiccant inside. In a method for regenerating a desiccant, the desiccant is heated by cooling a desiccant by using a part or all of the gas to be dried as a regeneration gas in the other dehumidifying tower, and a heating step of the desiccant. 90 minutes have passed since the start of the heating of the desiccant, or the temperature of the regeneration gas flowing out of the dehumidifying tower during regeneration is 110.
After the temperature exceeds ℃, the regeneration gas is circulated through a sub-dehumidifying tower filled with a sub-drying agent and then heated to flow into the dehumidifying tower during regeneration. A method for regenerating a desiccant in a gas dehumidifying apparatus, characterized in that a regeneration gas flowing out of a dehumidifying tower is circulated in the sub dehumidifying tower, cooled, and then allowed to flow into one of the dehumidifying towers.

In the heating step of the desiccant in the present invention, 90 minutes after the start of heating the desiccant, or when the temperature of the regeneration gas flowing out of the dehumidifying tower during regeneration exceeds 110 ° C., the regeneration gas is subsequently dehumidified. After the tower is circulated, it is heated and allowed to flow into the dehumidifying tower during regeneration. Under the above conditions, the heating time of the desiccant is generally set to 90 minutes.
Since the adsorbed moisture is removed to a considerable extent by heating for a minute, the moisture desorption process time by the regeneration gas that has passed through the sub dehumidification tower that follows is shortened to reduce the capacity of the sub dehumidification tower and the sub desiccant. This is because the playback time of can be shortened. Under the above conditions, the temperature of the regenerating gas is set to 110 ° C. because it exceeds the evaporation temperature of water (100 ° C.).
This is because when the regeneration gas outlet temperature reaches 0 ° C., the desorption of the moisture of the desiccant is almost completed, and by switching to the use of the sub-dehumidification tower at this time, it is possible to prevent unnecessary heating of the desiccant. (Operation) In the method for regenerating a desiccant in the gas dehumidifying apparatus of the present invention, in the step of heating the desiccant in the dehumidifying tower by the gas to be dried, 90 minutes have elapsed from the start of heating the desiccant, or the dehumidifying tower during regeneration. When the temperature of the regenerating gas flowing out of the tank exceeds 110 ° C., the regenerating gas, which is the gas to be dried, is circulated through the sub dehumidifying tower filled with the sub desiccant, so that the regenerating gas is dehumidified by the sub desiccant. It is further heated and circulates in the dehumidifying tower as a low-humidity high-temperature dry gas, and comes into contact with the desiccant that has already been heated by the high-temperature dry gas in the dehumidifying tower to remove moisture to a considerable extent. , Its sucking More highly desorb moisture. At this time, the regeneration gas flow to the sub-dehumidification tower is performed at a regeneration gas temperature of 110 even before 90 minutes have passed since the start of heating the desiccant.
When the temperature exceeds ℃, since it is started, it is possible to prevent the desiccant from being heated more than necessary when the adsorbed water content is small due to fluctuations in the inlet gas dew point or the temperature during dehumidification. Further, in the subsequent cooling step of the desiccant with the gas to be dried (regeneration gas), the high-temperature regeneration gas that has been heated by cooling the desiccant in the dehumidifying tower flows through the sub-dehumidifying tower. The temperature of the regeneration gas flowing out of the dehumidifying tower due to the progress of cooling of the desiccant due to the heating of the sub-desiccating agent is lower than that at the initial stage of cooling, and the temperature of the regeneration gas flowing through the sub-dehumidifying tower is sub-dried. The agent is also cooled, and the regeneration of the auxiliary desiccant is over. In the desiccant in the dehumidification tower that has completed the regeneration in this way, since the adsorbed moisture is highly desorbed, the gas is highly dehumidified in the subsequent dehumidification step of the gas to be dried,
A dry gas with a low dew point is obtained.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.

In the figure, 1 is a dehumidifying device for dehumidifying air, and 2 and 3 are dehumidifying towers, which are the main components of the dehumidifying device. The casing is filled with a desiccant such as silica gel, activated alumina, or synthetic zeolite. A dry gas inlet 4 is connected to an air supply source (not shown) mainly composed of a compressor and a water-cooled cooler connected to the subsequent stage. 5 is a proportional valve for dividing a part of the gas to be dried, 6 and 7 are four-way valves which are switching valves for switching the dehumidifying tower, 8 is a four-way valve which is a switching valve for switching between heating and cooling during regeneration, Reference numeral 9 is an air cylinder which is a driving machine for driving this four-way valve, 10 is a water-cooled gas cooler, 11 is a drain separator, 12 is a drain trap, and the gas outlet of the drain separator 11 is connected to the outlet side of the proportional valve 5. . Further, 13 is a branch pipe from the inlet side of the proportional valve 5 to the four-way valve 8, 14 is a regeneration gas flow passage from the four-way valve 8 to the four-way valve 7, and 15 is an electrothermal heater. Reference numeral 16 is a sub-dehumidification tower, which contains silica gel, activated alumina,
The auxiliary desiccant such as synthetic zeolite is filled, and the filling amount may be about one sixth of the dehumidifying tower 2 or 3. 17
Is a bypass pipe line of the auxiliary dehumidification tower 16, 18 is a three-way valve which is a switching valve for selectively switching between the bypass pipe line 17 and the auxiliary dehumidification tower 16, 19 is an air cylinder which is a driving machine for driving the three-way valve, 20 Is a temperature detector for detecting the temperature of the regeneration gas outlet of the dehumidifying tower, which is also provided in the dehumidifying tower 2, but is not shown. A switching control device 21 switches the three-way valve 18 and the four-way valve 8 when the desiccant is regenerated, and its operation is as described later. Reference numeral 22 is a dry gas outlet for supplying dry air to the use side.

Next, a method of regenerating the desiccant by using the gas dehumidifying device 1 having the above configuration will be described. The drawing shows a state in which dehumidification of the gas is performed in the dehumidification tower 2 and regeneration of the desiccant is performed in the dehumidification tower 3, the double-lined portion indicates the dehumidification route, and the single-lined portion indicates the regeneration route. The solid line arrow indicates the gas flow direction during heating of the desiccant, the dotted line arrow indicates the gas flow direction when dehumidifying the regeneration gas during this heating, and the dashed line arrow indicates the cooling direction of the desiccant. The respective gas flow directions are shown.

First, the air to be dried is heated to a high temperature by adiabatic compression by a compressor and then cooled by a water-cooled cooler.
As a gas in a saturated state at ℃, it flows in from the dry gas inlet 4, a part of it (referred to as gas A) is branched by the proportional valve 5 and flows into the branch pipe line 13, and the other is dehumidified via the four-way valve 6. It is dehumidified by the tower 2 and passes through the four-way valve 7 and the dry gas outlet
2 is supplied to the use side as dry air. On the other hand, the divided gas A flows through the four-way valve 8 and the three-way valve 18 through the bypass line 17, is heated to about 200 ° C. by the heater 15 and flows through the regeneration gas flow path 14, and passes through the four-way valve 7 and the dehumidification tower. Three
And heat the desiccant in a saturated state. Due to this heating, the moisture in the desiccant flows out from the dehumidifying tower 3 together with the gas A as steam, is cooled by the gas cooler 10 through the four-way valves 6 and 8 and condensed, and the condensed water is separated by the drain separator 11 and the drain trap 12 is drawn. The gas A discharged from the outside to the condensed water is merged with the gas from the dry gas inlet 4 at the outlet of the proportional valve 5, dehumidified by the dehumidifying tower 2, and used as a dry gas.

When the heating of the desiccant in the dehumidifying tower 3 progresses, and one and a half hours have elapsed after the start of heating, or when the temperature detected by the temperature detector 20 exceeds 110 ° C., the switching control device 21 outputs an output signal and the three sides The valve 18 is switched to the switching state shown by the dotted line. As a result, the gas A flows through the sub dehumidification tower 16, is dehumidified by the sub desiccant and heated by the heater 15, and then the dehumidification tower 3
Since it circulates inside, the adsorbed moisture of the desiccant in the dehumidifying tower is desorbed to a higher degree.

Next, if this sub-dehumidification tower 16 is used for 30 minutes,
The four-way valve 8 is switched to the switching state shown by the broken line by the switching control device 21, and the gas A at about 40 ° C. from the branch pipe 13 is made to flow into the dehumidifying tower 3 via the four-way valves 8 and 6 to cool the desiccant. Do it. The gas A flowing out from the dehumidification tower 3 has a high temperature of about 150 ° C. at the initial stage of cooling, and this gas A passes through the four-way valve 7 and the regeneration gas flow path 14 (the heater 15 is electrically disconnected). After flowing through the auxiliary dehumidifying tower 16 to heat and regenerate the auxiliary dehumidifying material, the gas is cooled by the gas cooler 10 via the three-way valve 18 and the four-way valve 8, and the condensed water is separated by the drain separator 11, and then the proportional valve 5, four-way valve. It is dehumidified by the dehumidifying tower 2 via the valve 6. As the cooling of the desiccant in the dehumidifying tower 3 progresses, the temperature of the gas A flowing out of the dehumidifying tower 3 approaches 40 ° C., and the gas A cools the sub desiccant in the sub dehumidifying tower 16.

After the desiccant in the dehumidifying tower 3 is cooled and the auxiliary desiccant in the sub-dehumidifying tower 16 is heated and cooled for 60 minutes, the four-way valves 6 and 7 are switched to dry the dehumidifying tower 2. The agent is regenerated in the same manner as described above, and the gas to be dried is dehumidified in the dehumidification tower 3. At the time of this dehumidification, since the adsorbed water content of the desiccant is highly desorbed by the regeneration step, a dry gas having a low dew point (for example, -70 ° C) is obtained.

Using the apparatus having the above configuration (however, 320 kg of activated alumina is used as the desiccant of the dehumidifying towers 2 and 3, respectively, and 50 kg of activated alumina is used as the auxiliary desiccant of the sub-dehumidifying tower 16), the flow rate is 40% by the proportional valve 5 by the above method. When the dehumidifying device 1 was operated while regenerating the desiccant by controlling the amount of water, 1200 Nm ³ of moisture-saturated air having an inlet temperature of 40 ° C.
By dehumidifying h, it was possible to obtain dry air having an outlet dew point of −70 ° C. On the other hand, according to the conventional regeneration method in which the gas to be dried is used as it is without providing the auxiliary dehumidification tower 16,
Only dry air with an outlet dew point of -40 ° C was obtained.

As described above, while the desiccant in the dehumidifying tower 3 is being heated, the temperature of the regeneration gas flowing out of the dehumidifying tower is detected, and when the temperature reaches a temperature close to the completion of desorption of the desiccant moisture (110 ° C.), sub-dehumidification is performed. Since the tower 16 is operated, it is possible to prevent the desiccant from being heated more than necessary when the adsorbed water content is small due to the fluctuation of the inlet gas dew point or the temperature, and the heater 15 does not need to be additionally energized. It has an advantage that it is preferable in terms of energy saving. Instead of this,
The switching operation of the auxiliary dehumidifying tower 16 may be performed only by the time such as operating the auxiliary dehumidifying tower 16 at 90 minutes after the start of heating the desiccant.

Although the dehumidifying device for air drying has been described above, the present invention is also applicable to the regeneration of a desiccant in a dehumidifying device for various dry gases other than air such as N ₂ gas and H ₂ gas. It can also be applied when the entire amount of gas is used as the gas for regenerating the desiccant.

(Effects of the Invention) As described above, according to the present invention, a dry gas having a low dew point can be easily obtained by a device having a simple structure in which a sub-dehumidifying tower and its bypass pipeline are provided in a regeneration gas flow path. it can.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an apparatus for carrying out the method of the present invention. 1 ... Dehumidifying device, 2 ... Dehumidifying tower, 3 ... Dehumidifying tower, 4 ...
Dry gas inlet, 5 ... Proportional valve, 6 ... Four-way valve, 7 ...
4-way valve, 8 ... 4-way valve, 10 ... Gas cooler, 11 ...
Drain separator, 13 ... Branch pipe line, 14 ... Regeneration gas flow path, 15 ... Heater, 16 ... Sub-dehumidification tower, 17 ...
Bypass line, 18 ... 3-way valve, 22 ... Dry gas outlet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-143818 (JP, A) JP 51-19096 (JP, Y2)

Claims (1)

[Claims] 1. A dehumidifying tower, which is alternately selected from a pair of dehumidifying towers having a desiccant filled therein, dehumidifies the gas to be dried, and the other dehumidifying tower removes part or all of the gas to be dried. In a method for regenerating a desiccant by heating the desiccant as a regeneration gas and then cooling the same to regenerate the desiccant, in the heating step of the desiccant, 90 minutes have elapsed from the start of heating the desiccant, or during the regeneration. When the temperature of the regenerating gas flowing out of the dehumidifying tower exceeds 110 ° C., the regenerating gas is circulated through the sub dehumidifying tower filled with the sub desiccant and then heated to flow into the dehumidifying tower during regeneration. In the cooling step of the desiccant, in the gas dehumidifying device, the regeneration gas flowing out of the dehumidifying tower during regeneration is circulated through the sub dehumidifying tower and then cooled to flow into the one dehumidifying tower. Regeneration of desiccant Law.