JPS62155920A - Method for regenerating drying agent in gas dehumidifier - Google Patents

Abstract

PURPOSE:To obtain low-dew point dry gas in a simple equipment by providing both a subdehumidification tower and a by-pass duct thereof to a flow path of regeneration gas wherein gas to be dried is made to the gas for regeneration. CONSTITUTION:One part A of gas to be dried which is compressed by a compressor and introduced through a gas inlet 4 is branched in a proportional valve 5 and heated by a heater 15 via a branched duct 13, a three-way valve 18 and a by-pass pipe 17 and used to heat a drying agent of a dehumidification tower 3 via a flow path 14 of regeneration gas. In the latter period of the heating process, the three-way valve 18 is changed over and gas A is passed to the inside of a subdehumidification tower 16 and dehumidified by a subdrying agent and after heating it by the heater 15, it is passed through the tower 3 to desorb the adsorbed water of the drying agent in high degree. Then a four-way valve 8 is changed over and gas A of the duct 13 is passed through the tower 3 via the four-way valves 8, 9 to perform cooling of the drying agent. Since the gas A flowed out through the tower 3 is made to high temp. in the first stage of cooling, it is used to perform heating and regeneration of the tower 16 via a four-way valve 7 and the flow path 14. The gas A is descended in temp. and the sub-tower 16 is cooled by the processing of cooling of the tower 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for regenerating a desiccant in a gas dehumidifier that removes moisture from gas to obtain 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, the regenerating gas such as air is circulated through the dehumidifying tower using an electric heater or the like. A method of evaporating water was common, but it required energy for heating, which was not preferable in terms of energy conservation. Therefore, as an improvement plan for this, JP-A-55-1525
In No. 22, the desiccant is heated by using the thermal energy of the high-temperature drying gas to be dehumidified and using part or all of this supplementary drying gas as a regeneration gas,
A regeneration method has been proposed in which the dry gas is then cooled and used as a desiccant or cooling gas.

(Problem to be Solved by the Invention) However, although the method described in the above-mentioned publication is preferable in terms of energy saving, since the gas to be dried naturally contains water, there is a limit to how much water can be removed from the desiccant during regeneration. Therefore, in a gas dehumidifier using this regeneration method,
For example, it is difficult to obtain a drying gas with a dew point as low as -70°C, and it is difficult to obtain a drying gas with a dew point as low as -40°C.

This invention solves the above conventional problems and provides a method for regenerating a desiccant used in a gas dehumidifier that can obtain dry gas with a low dew point using a device with a simple configuration. It is something.

(Means for Solving the Problems) However, the desiccant regeneration method of the present invention dehumidifies the gas to be dried in one of the dehumidifying towers that is alternately selected from a pair of dehumidifying towers filled with a desiccant inside. In the desiccant regeneration method, the desiccant is regenerated by heating and cooling the desiccant using part or all of the gas to be dried as a regeneration gas in the other dehumidification tower. In the latter stage of the process, the regeneration gas is passed through a sub-dehumidifying tower filled with a sub-desiccant, heated, and flowed into the dehumidifying tower during regeneration, and in the cooling process of the desiccant, the dehumidification during regeneration is performed. A method for regenerating a desiccant in a gas dehumidifier, characterized in that the regeneration gas flowing out of the tower is passed through the sub-dehumidification tower, cooled, and then introduced into one of the dehumidification towers.

(Function) In the method for regenerating a desiccant in a gas dehumidifier of the present invention, in the latter stage of the process of heating the desiccant in the dehumidifying tower by the gas to be dried, the regeneration gas, which is the gas to be dried, is Since the regeneration gas is passed through the sub-dehumidifying tower, the regeneration gas is dehumidified by the sub-drying agent, and is further heated and circulated through the dehumidifying tower as a low-humidity, high-temperature dry gas. The desiccant, which has been heated to remove a considerable amount of moisture, is brought into contact with the desiccant, and the adsorbed moisture is further desorbed. In addition, in the subsequent cooling step of the desiccant using the gas to be dried (regeneration gas), the high temperature regeneration gas that has been heated by cooling the desiccant in the dehumidification tower,
The regeneration gas flows through the sub-dehumidifying tower to heat the sub-desiccant, and as the desiccant cools down, the temperature of the regeneration gas flowing out of the dehumidification tower decreases compared to the initial stage of cooling, and the regeneration gas with the lowered hot water level The secondary desiccant is also cooled by the circulation in the secondary dehumidification tower, and the regeneration of the secondary desiccant is completed. The desiccant in the dehumidifying tower, which has been regenerated by J:), has a high degree of adsorbed moisture, so in the subsequent dehumidification process for the gas to be dried, the gas is dehumidified to 4 degrees Celsius to reduce the dew point. (Example)
' □゛An embodiment of the present invention will be explained below with reference to FIG. □ In the cell, 1 is a dehumidifying device for air dehumidification, and 3 is a dehumidifying tower, which is the main part of the dehumidifying tower, and the casing is filled with a desiccant such as silica gel, activated alumina, or synthetic zeolite. Reference numeral 4 denotes a dry gas inlet, which is connected to a compressor and an air supply source (not shown) mainly consisting of a water-cooled cooler connected to its downstream stage.

5 is a proportional valve that divides a part of the gas to be dried, 6 J3 and 7 are four-way valves that are also adult switching valves for switching the dehumidifying liquid, 8
13 is a four-way valve that is a switching valve that performs 1.7 J inspection of heating and cooling during storage, 9 is an air cylinder that is a driver for driving the four-way valve, 10 is a water-cooled gas cooler, 11 1 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 line from the inlet side of the proportional valve 5 to the four-way valve 8, 14 is a regeneration gas flow path from the four-way valve 8 to the four-way valve 7, and 1"5 is an electric heater. 16 is a sub-conductor. In a dehumidification tower, silica gel, activated alumina,
It is filled with an auxiliary desiccant such as synthetic zeolite, and the filling amount may be about one-sixth of that of the dehumidifying tower 2 or 3. 17
18 is a three-way valve that is a switching valve for selectively switching between the bypass pipe 17 and the sub-dehumidifying tower 16; 19 is an air cylinder that is a driver for driving this three-way valve; Reference numeral 20 denotes a temperature sensor for detecting the temperature at the regenerated gas outlet of the dehumidifying tower, which is also provided in the dehumidifying tower 2, but its diagram is omitted. Reference numeral 21 denotes a switching control device which switches between the three-way valve 18 and the four-way valve white during dry period regeneration, and its operation will be described later. Further, 22 is a dry gas outlet that supplies dry air to the user side.

Next, a method of regenerating the desiccant using the gas dehumidifier 1 having the above configuration will be explained. The dehumidifying tower 2 dehumidifies the gas and the dehumidifying tower 3 regenerates the desiccant.
The tll line diagram shows the μm raw path. The solid arrows indicate the direction of gas flow while the desiccant is being heated, the dotted arrows indicate the direction of gas flow when dehumidifying the regeneration gas during heating, and the dashed arrows indicate the direction of gas flow when the desiccant is being cooled. Each shows the direction of gas flow.

First, the air, which is the gas to be dried, is heated to a high temperature by adiabatic compression in the compressor, and then cooled by the water cooler, and the air flows in from the gas to be dried as a saturated gas at about 40°C. , a part of it (referred to as gas Δ) is divided by the proportional valve 5 and flows into the branch pipe 13, and the other part passes through the four-way valve 6, enters the dehumidification tower 2, is dehumidified, and passes through the four-way valve 7 to be dried. It is supplied to the user side as dry air from the gas outlet [122]. On the other hand, the diverted gas A passes through the four-way valve 8 and the three-way valve 18,
It flows through the bypass pipe 17 and is heated to about 200°C by the heater 15.
The regenerating gas is heated to 100%, flows through the regeneration gas passage 14, flows into the dehumidifying tower 3 via the four-way valve 7, and heats the desiccant in a saturated state. Due to this heating, the moisture in the desiccant flows out of the dehumidification tower 3 as water vapor together with gas A, passes through a four-way valve 6.8, is cooled by the gas cooler 10, and is condensed.
The condensed water is separated and discharged to the outside from the drain trap 12, and the gas A from which the condensed water has been separated joins the gas from the drying gas population 4 at the outlet of the proportional valve 5, and is dehumidified by the dehumidification tower 2. Used as drying gas.

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

Next, after using this sub-dehumidification tower 16 for 30 minutes,
The four-way valve 8 is switched to the switching state shown by the broken line using the switching control device 21, and the gas A at about 40°C from the branch pipe 13 is allowed to flow into the dehumidification tower 3 via the west valves 8 and 6 to remove the desiccant. Perform cooling. The gas A that has flowed out of the dehumidification tower 3 has a high temperature of about 150°C in the early stage of cooling, and this 12 gases are passed through the four-way valve 7 and the regeneration gas flow path 14 (the heater 15 is turned off). Then, it flows through the sub-dehumidifying tower 16 to heat and regenerate the sub-dehumidifying material, passes through the three-way valve 18 and the west valve 8, is cooled by the gas cooler 10, and after the condensed water is separated by the drain separator 11, the proportional valve 5, It passes through a four-way valve 6 and enters a dehumidifying tower 2 for dehumidification.

As the desiccant in the dehumidifying tower 3 continues to cool, the temperature of the gas flowing out of the dehumidifying tower 3 approaches 40° C., and this gas A cools the sub-desiccant in the sub-dehumidifying tower 16.

In this way, the desiccant in the dehumidification tower 3 is cooled7. After heating and cooling the secondary desiccant in the secondary dehumidifying tower 16 for 60 minutes, the four-way valves 6 and 7 are switched to regenerate the desiccant in the dehumidifying tower 2 in the same manner as above, and the dehumidifying tower In step 3, the gas to be dried is dehumidified. During this dehumidification, the desiccant is immersed in drying gas with a low dew point (for example, -70 DEG C.) because the adsorbed moisture has been highly desorbed from the desiccant through the above regeneration process.

Apparatus with the above configuration (320 kg of activated alumina is used as a desiccant for each of dehumidifying towers 2 and 3, sub-dehumidifying tower 16
When the dehumidifying device 1 was operated using activated alumina as an auxiliary desiccant (50:9) and regenerating the desiccant by dividing the flow rate by 40% using the proportional valve 5 using the method described above, the inlet mixture was Moisture saturated air at 40°C 120°C
By dehumidifying the ONd/h, it was possible to obtain dry air with an outlet dew point of -70°C. On the other hand, according to the conventional regeneration method in which the sub-dehumidifying tower 16 is not provided and the gas to be dried is used as it is, only dry air with an outlet dew point of -40° C. can be obtained.

In the above embodiment, while the desiccant in the dehumidifying tower 3 is being heated, the recycled gas flowing out of the dehumidifying tower is detected, and the temperature is close to the completion of desiccant moisture desorption (110° C. in the above embodiment).
Since the sub-dehumidifying tower 16 is operated at the 115 point where the temperature becomes 115, it is possible to prevent the desiccant from being heated more than necessary when there is little adsorbed moisture due to fluctuations in the inlet gas dew point or temperature, etc. This has the advantage that it is preferable in terms of energy saving, since it is not necessary to conduct a large amount of electricity. Note that instead of this, the switching operation of the sub-dehumidifying tower 16 may be performed only based on time, such as operating the sub-dehumidifying tower 16 90 minutes after the start of heating the desiccant.

Although the above description has been made regarding a dehumidifying device for air drying, the present invention can also be applied to regenerating desiccant in dehumidifying devices for various gases to be dried other than 1 gas of air, such as N2 gas and 1-12 gas. This method can also be applied when the entire amount of the gas to be dried is used as a gas for regenerating the desiccant.

(Effects of the Invention) As explained above, according to the present invention, dry gas with a low dew point can be easily obtained using a device having a simple configuration in which a sub-dehumidification tower and its bypass pipe are provided in the regeneration gas flow path. I can do it.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an example of an apparatus for carrying out the method of the present invention. 1... Dehumidification device, 2... Dehumidification tower, 3... Dehumidification tower,
4... Gas inlet to be dried, 5... Proportional valve, 6... Four-way valve, 7... Four-way valve, 8... Four-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 pipe line, 18...
...Three-way valve, 22...Dry gas outlet.

Claims (1)

[Claims] Out of a pair of dehumidifying towers filled with a desiccant inside, one of the dehumidifying towers selected alternately dehumidifies the gas to be dried, and the other dehumidifying tower uses part or all of the gas to be dried as a regeneration gas. In a desiccant regeneration method in which the desiccant is heated and then cooled to regenerate the desiccant, the regeneration gas is passed through an auxiliary dehumidifying tower filled with an auxiliary desiccant in the latter half of the desiccant heating step. The desiccant is then heated and allowed to flow into the dehumidifying tower being regenerated, and in the step of cooling the desiccant, the regeneration gas that has flowed out of the dehumidifying tower being regenerated is passed through the sub-dehumidifying tower and then cooled to the one of the dehumidifying towers. A method for regenerating a desiccant in a gas dehumidifier, the method comprising causing the desiccant to flow into the gas dehumidifier.