JPH0127769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a desiccant in a gas dehumidifier for obtaining dry gas by removing moisture from gas.

In general, inert gas for filling the holds of tankers is produced by almost complete combustion of fuel, and in order to remove moisture from the resulting gas, it is cooled with a refrigerator, dehumidified, and then desiccant such as silica gel or activated alumina is added. The water is circulated through a large-capacity dehumidifying tower filled with water to dry it to a low dew point. After this desiccant is used for a certain period of time, it becomes saturated with moisture and loses its dehumidifying ability, so it needs to be regenerated. Conventionally, this regeneration method involves drawing air for regeneration from the atmosphere using a blower, heating it with an electric heater, etc., and feeding it into the dehumidification tower, heating the desiccant and evaporating the water. After the desiccant is discharged outside, the heater is turned off and the desiccant is cooled by the air. However, in this method, the desiccant is only cooled to about 40 to 50 degrees Celsius, so if you switch the inert gas inflow tower and start drying the gas by flowing the inert gas into the regenerated dehumidification tower, the initial stage of tower switching will be reduced. In our case, the desiccant has a relatively high temperature, so its adsorption capacity is poor, and the dew point of the dry gas flowing out of the dehumidifying tower is high (for example, the dew point of -50°C before switching the tower becomes -10°C). It continues for a while and is not good.

The present invention solves the above-mentioned conventional drawbacks and provides a method for regenerating desiccant in a gas dehumidifier in which the dew point of the drying gas does not fluctuate widely even at the beginning of tower switching.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG.

In the figure, 1 is a dehumidifier for inert gas dehumidification.
Reference numerals 2 and 3 are dehumidification towers that form the main part, and the casing is filled with a desiccant such as silica gel, activated alumina, or synthetic zeolite. 4 is a gas inlet connected to the inert gas production device, 5 is a dry gas outlet connected to the use side, 6 to 21 are automatic opening/closing valves, 22 is a blower for blowing air, 23 is an electric heater, and 24 is a seawater This is a cooler used as cooling water. Also, 25 is the air intake port 26 used when heating the desiccant, and 27 is the dry gas outlet 5.
A purge pipe line 28 connecting the section and the suction port side of the blower 22 is a surplus gas discharge port used during purging.

Next, a method for regenerating the desiccant using the dehumidifying device 1 having the above configuration will be explained. The drawing shows the dehumidification of inert gas in the dehumidification tower 2 and the regeneration of the desiccant in the dehumidification tower 3, and the double line diagram indicates the distribution route of the inert gas.
The solid arrow indicates the direction of gas flow during heating of the desiccant.
The dashed line and the chain arrow indicate the direction of gas flow during cooling of the desiccant, respectively. First, inert gas, which is the gas to be dried, is produced by almost completely burning heavy oil, etc. in a combustion device (not shown), and the resulting gas is heated in a shower-type cooler using seawater, etc.
After cooling to about 40℃, further cooled to about 5℃ by refrigerator.
The sample is cooled down to a temperature of 100 mL, cooled and dehumidified, and then supplied to the dehumidifier 1. This low-temperature inert gas flows into the dehumidifying tower 2 from the gas inlet 4 via the on-off valve 10, is highly dehumidified to a dew point of about -50°C, passes through the on-off valve 8, flows out from the dry gas outlet 5, and is used as dry inert gas. Ru. On the other hand, in order to regenerate the saturated desiccant in the dehumidification tower 3, first the on-off valves 20, 16, 7, 13, 1
4 and operate the blower 22, and open the air intake port 2.
The air taken in from 5 is heated to approximately 190℃ by heater 23.
The heated air is passed through the dehumidifying tower 3 to evaporate the moisture in the desiccant. This moisture is discharged into the atmosphere from the discharge port 26 through the on-off valves 13 and 14 together with the heated air. During this heating process, if the humidity of the air from the air intake port 25 is high, close the on-off valves 14 and 20 and open the valve 21.
If the air flowing through the dehumidification tower 3 is cooled and dehumidified by the cooler 24, heated by the heater 23, and then circulated to the dehumidification tower 3, moisture removal is promoted by the low-humidity high-temperature air. After heating the desiccant for a predetermined period of time (3 hours as shown in FIG. 2 in this embodiment), the on-off valves 14, 16, 20, and 21 are closed, and the on-off valves 15 and 18 are opened. , air that has been cooled and dehumidified to about 40°C by the cooler 24 is opened and closed by valves 18 and 1
3 and flows into the dehumidifying tower 3, where the desiccant is primarily cooled. The air flowing out of the dehumidification tower 3 is returned to the cooler 24 through the on-off valves 7 and 15, where it is cooled, dehumidified, and circulated as shown by the broken line arrows in the figure. During this primary cooling (in this example, 2 hours and 15 minutes after the start of cooling), the on-off valves 17 and 19 are opened, and a part of the dry gas that has flowed out of the dehumidification tower 2 is circulated through the purge pipe 27 for cooling. into the system,
The air in the dehumidification tower 3 is gradually replaced with inert gas, and the excess air and inert gas mixture is discharged into the atmosphere from the excess gas discharge port 28. After performing this gas purge for a predetermined period of time (15 minutes in this embodiment), the on-off valves 7 and 13 are closed to stop the blower 22, and the on-off valves 9 and 11 are opened to allow some of the inert gas ( for example 50%)
The gas flowing through the dehumidifying tower 3 is made to join the dry gas flowing out of the dehumidifying tower 2 via the on-off valve 9, and is supplied to the user side. Since the inert gas from the gas inlet 4 has been cooled down to about 5° C. by cooling and dehumidifying by the refrigerator as described above, the desiccant in the dehumidifying tower 3 is efficiently secondary cooled by this low-temperature inert gas. Furthermore, the dew point of the dry gas from the gas outlet 5 rises somewhat due to the merging of the gases that have passed through the dehumidifying tower 3, but since the dew point of the gas flowing out of the dehumidifying tower 2 is sufficiently low at -50°C, the dew point remains at 5 to 10°C.
It only increases in degree. Note that the distribution ratio of inert gas to the dehumidifying towers 2 and 3 is appropriately determined based on the cooling time, the allowable dew point of the drying gas, etc. After performing the above secondary cooling for a predetermined period of time (30 minutes in this example), the tower is switched by operating each on-off valve to flow the entire amount of inert gas into the dehumidification tower 3 for dehumidification. The desiccant in No. 2 is regenerated in the same manner as above. Thereafter, tower switching is performed in the same manner. In the dehumidifying tower 3, where the desiccant was regenerated, the temperature of the desiccant has dropped to about 5°C due to the secondary cooling using the above-mentioned inert gas, so the dehumidifying capacity is sufficiently high, and even at the time of tower switching, the dew point remains low. −40℃
The dew point is reduced to -50℃ or less by cooling with inert gas.
Dry gas with little dew point fluctuation can be obtained continuously.

The present invention is not limited to the above embodiments, and the method of heating and primary cooling of the desiccant may be other than those described above, such as heating the desiccant with a heater built into a dehumidifying tower. The time allocation for heating, primary cooling, and secondary cooling of the desiccant may also be other than the above values.

Although the present invention has been described above in a case where it is applied to a dehumidifying device for dehumidifying inert gas for tankers, the present invention can also be applied to gas dehumidifying devices for other uses.

As explained above, according to the present invention, when the desiccant is heated and then cooled and regenerated in the gas dehumidifier that further dehumidifies the to-be-dried gas that has been cooled and dehumidified by the refrigerator, the desiccant is removed by air. After primary cooling, a part of the gas to be dried before flowing into the dehumidifying tower during dehumidification is flowed into the dehumidifying tower during regeneration, and the gas to be dried flowing out from the dehumidifying tower is dried by flowing out from the dehumidifying tower during dehumidification. Since it is made to join the gas, it is possible to make effective use of the low-temperature gas to be dried and lower the desiccant to a low temperature without using any special equipment. There is little variation in the dew point of the drying gas even at the beginning of column switching after completion of regeneration.

[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, and FIG. 2 is an operating diagram of the apparatus shown in FIG. 1...Dehumidification device, 2...Dehumidification tower, 3...Dehumidification tower, 4...Inert gas inlet, 5...Dry gas outlet, 8-11...Opening/closing valve, 22...Blower, 23
... Heater, 24 ... Cooler, 25 ... Air intake port, 26 ... Air discharge port, 27 ... Purge pipe line.

Claims (1)

[Scope of Claims] 1. A gas dehumidifier that further highly dehumidifies a gas to be dried that has been cooled and dehumidified by a refrigerator, which comprises one of a pair of dehumidifying towers that is alternately selected from a pair of dehumidifying towers filled with a desiccant inside. A gas dehumidifier that dehumidifies the gas to be dried in a dehumidifying tower and regenerates the desiccant by heating and cooling the desiccant in the other dehumidifying tower, characterized in that the desiccant is cooled by the following process. A method for regenerating desiccant in a gas dehumidifier. (a) Primary cooling process in which the desiccant is cooled by air cooled by a cooler. (b) A gas purge step in which, in the latter half of the primary cooling step, a part of the dry gas flowing out from the dehumidifying tower during dehumidification flows into the dehumidifying tower during regeneration, and the air in the dehumidifying tower is replaced with dry gas. (c) After the gas purging step, a part of the gas to be dried before flowing into the dehumidifying tower being dehumidified is caused to flow into the dehumidifying tower being regenerated, and the gas flowing out from the dehumidifying tower is transferred to the dehumidifying tower being dehumidified. A secondary cooling process in which the dry gas flowing out from the