JPH0824558A - Medical air dryer adopting pressure fluctuation adsorption method - Google Patents

Abstract

PURPOSE:To prevent the composition of dry air from being changed even if the used quantity of the dry air is sharply changed by determining the quantity of an adsorbent so that the quantity of an average adsorptive material adsorbed by the adsorbent may be smaller than that of the average adsorptive material in air introduced into the inlet end of an adsorptive cylinder within a operation cycle time. CONSTITUTION:Adsorptive cylinders 22, 24 are filled with alumina in the lower bed and with A type zeolite thereon. Compressed air is introduced from an air introducing port 10 to remove dust contained in the air by a filter 12, and is introduced toward the adsorptive cylinder 22 through a solenoid valve 14. At this time, the adsorptive cylinder 22 is in a pressure adsorptive process, and almost all the moisture contained in the introduced air is adsorbed onto alumina and zeolite in the adsorptive cylinder, and the dried air having little moisture reaches a filter 32 from the outlet end of the other end of the adsorptive cylinder through a solenoid valve 28 because the solenoid valve 28 is opened. Further, fine dust is removed by a filter 32, and the air is discharged from a dry air outlet 38 through a pressure control valve 34.

Description

Detailed Description of the Invention

[0001]

[Industrial field of use] In medical facilities such as hospitals, used as a drive source or ventilation air for a ventilator, or as a drive source air for a therapeutic instrument, or a drive source for a ventilator alone. The present invention relates to improvement of a medical air dryer for drying air used as air for breathing and breathing.

[0002]

2. Description of the Related Art The main uses of compressed air for medical use in medical facilities such as hospitals are as follows. Air for the drive source of the ventilator and for breathing. Air for the drive source of therapeutic instruments used in dentistry and surgery.

A compressor is usually used as a means for obtaining these compressed air. When atmospheric air at room temperature is compressed by this compressor (about 7 × 10 ⁵ Pa), it is heated to about 50 to 70 ° C. due to the heat of compression. Therefore, after that, a water-cooled or air-cooled after-cooler including a drain separator (hereinafter, also simply referred to as “after-cooler”) is used to cool to about 25 ° C. or less, and a part of the water content in the compressed air is cooled. Is separated and removed, and the compressed air is supplied to the required place through a pipe.

However, if only a portion of the water contained in the compressed air is separated and removed by the aftercooler, the compressed air for medical use has the following problems. The above-mentioned aftercooler is used to separate and remove a part of this moisture, and the temperature after cooling the compressed air is 25 ° C.
In this case, the dew point temperature is about 25 ° C. in the pipe pressurized to about 4 × 10 ⁵ Pa. In Japan, the temperature of most areas may fall below this temperature, so that condensed water condensed in this pipe will accumulate. If this condensate enters the ventilator, it can damage the expensive ventilator or even reach the patient's respiratory system. If this condensed water stays in the pipe, bacteria such as bacteria may grow. Further, if water is accumulated in the pipe, rust may be generated in the pipe, and if the pipe is copper, patina which is a toxic substance may be generated.

Therefore, it is necessary to additionally install an air dryer in the middle of the aftercooler and the pipe. Conventionally,
This air dryer was mainly a refrigeration type, but in this refrigeration type air dryer, the cooling temperature of the refrigerator is set to 0 ° C or higher (for example, about 4 ° C) to prevent freezing. Therefore, the dew point temperature under pressure is about 4 ° C,
The dew point temperature of the air discharged from this air dryer is about -20 ° C in terms of atmospheric pressure, but the dewpoint temperature in the pressurized pipe as described above is around 4 ° C, which means that in winter There are many areas where the ambient outside air temperature is 4 ° C. or lower, and in such a case, dew condensation water may accumulate in the pipe. In addition, since once accumulated water cannot be easily removed, the above-mentioned problems 1 and 2 still remain.

In order to solve this problem, the present invention provides an air dryer by a pressure fluctuation adsorption method, instead of the above-mentioned refrigeration type air dryer. This is a method in which compressed air is introduced under pressure into an adsorption cylinder filled with an adsorbent to remove moisture by adsorbing moisture to this adsorbent to obtain dry air. The pressure is reduced to atmospheric pressure or lower, and further, a part of the dry air is reversely flowed in as a purge gas countercurrently from the outlet end of another adsorption cylinder,
The dry air is continuously produced by alternately performing the depressurization desorption process of desorbing and regenerating water from the adsorbent and the pressurized adsorption process of introducing compressed air again, which has the following advantages. .

When an air dryer of the pressure fluctuation adsorption method is used and silica gel or activated alumina is used as the adsorbent, the dew point temperature of the dry air to be discharged can be reduced to about -40 ° C or lower. In addition, if a moisture absorbent such as silica gel or activated alumina is also used as the adsorbent together with the zeolite, the dew point temperature of the dry air to be discharged can be reduced to about −40 ° C. or lower, and further, CO, CO ₂ , NOx can be obtained. , SO
It is also possible to remove so-called impure gases, such as χ, which are present in the atmosphere in trace amounts.

[0008]

This zeolite can be used in an air dryer by the pressure fluctuation adsorption method, but the oxygen concentrator of the pressure fluctuation adsorption method for separating and concentrating oxygen gas in the air by exactly the same principle. It is well known that it can also be used as. Zeolite has a property that water molecules are most strongly adsorbed in the crystal structure of the molecules, then nitrogen gas and impure gas molecules are strongly adsorbed, and oxygen molecules are adsorbed to some extent. And, since the amount of adsorption increases as the pressure increases, it decreases as the pressure decreases.
The method of pressure fluctuation adsorption method (hereinafter referred to as "pressure fluctuation adsorption method") , Also referred to as PSA method), and since the air dryer also treats water as a gas called water vapor, it should have a structure similar to that of the oxygen concentrator described above. Can be done.

Zeolites used as adsorbents include
The size of the crystal lattice and its pores differ depending on how the cation (cation) is added. For example, there are types such as 4A, 5A, and 13X, and the performance as a molecular sieve is different. Water molecules exhibit strong adsorption to adsorbents of any of these sizes. This 4A type adsorbent does not adsorb nitrogen gas or oxygen gas, but 5A type and 13X type also adsorbs nitrogen gas well, and among them, 13X type is known to have superior adsorption ability. ing.

In order to adsorb and remove only water as an air dryer by the PSA method, the 4A type adsorbent described above may be used. However, since the 4A type adsorbent has small pores, it is temporarily adsorbed. There is a problem that it is difficult for the water molecules to be desorbed. To separate oxygen from air, 5A type or 13X type (preferably 13X type) zeolite is used.

When this 13X type zeolite is used as an adsorbent, it can be used as an air dryer because it has a strong water adsorption capacity. Since the pores are large, it is easy to desorb the once adsorbed gas, and when this is used in the separation device by the PSA method, the adsorbent packed in the adsorption column has a portion where the strongly adsorbing gas is sufficiently adsorbed The boundary surface with the non-adsorbed portion is also called a mass transfer zone, or MTZ. The thickness of this MTZ in the traveling direction of the source gas is smaller than that of other 4A type and 5A type. Since it is small and can be sharpened, the amount of the adsorbent may be correspondingly small, and the shape of the adsorption cylinder can be made smaller.

As an adsorbent, zeolite 5A type or 13
Use the gas separation device by the PSA method when using the X type, either as an air dryer for separating water in the air or as an oxygen concentrator, depending on the control method of the PSA method. Can be done. This means that if the control conditions and other conditions change, the composition of the air (mainly nitrogen, oxygen, argon, etc.), which is a necessary function of the air dryer, changes, and the function as an oxygen concentrator can be expressed. It shows that it is possible.

On the other hand, the dry air in a medical facility is used not only as the air for the drive source of the artificial respirator or the therapeutic instrument as described above, but also as the inhaled gas of the artificial respirator. Usually, these are mixed and used, so that the composition of the dry air must be equal to the composition of the air in the atmosphere and kept constant.

On the other hand, the amount of dry air used in a medical facility greatly changes depending on the condition of use of the medical facility over time and other conditions. It is an object of the present invention to provide an air dryer according to the PSA method which does not change the composition of the dry air even when the amount of the dry air used changes drastically.

[0015]

[Means for Solving the Problems] The amount of moisture (humidity) contained in the air is, for example, an air temperature of 30 ° C. and a relative humidity of 100.
%, 35 g in 1 m ^{3 of} air, the weight of 1 mol of water (H ₂ O) is 18 g, and its water vapor is 22.4 liters at 0 ° C. atmospheric pressure. 4.
This corresponds to a gas concentration of 6% (volume ratio, the same applies hereinafter). On the other hand, the composition of air is 78% nitrogen gas, 21% oxygen gas,
Argon gas is 0.9% or the like.

The relationship between the amount of adsorbent used when 78% of nitrogen gas is adsorbed and removed by the adsorbent to separate the oxygen gas and the amount of air sent as a raw material gas is as follows. It is necessary that the volume of nitrogen gas in the air fed into the adsorption column within the same operation cycle time as this raw material gas is smaller than the total adsorption capacity of nitrogen gas per operation cycle time.

On the other hand, when used as an air dryer,
The following relationships are required. That is, the amount of water in the air sent to this adsorption cylinder within the same operation cycle time is smaller than the total adsorption capacity per one operation cycle time for adsorbing the moisture of the adsorbent filled in the adsorption cylinder. is necessary. This means that, as can be seen from the gas concentrations described above regarding the composition of air, the amount of the adsorbent with respect to the constant amount of air sent to the adsorption column is larger when nitrogen is adsorbed and removed, and water is adsorbed and removed. It was found that the number of cases was less and was 17: 1.

On the contrary, regarding the adsorbent packed in the adsorption column having a constant capacity, the ratio of the amount of air sent into the adsorption column in the air dryer to the oxygen concentrator is 1:17.

As the adsorbent, in addition to the above-mentioned zeolite, there is a molecular sieve charcoal which activates activated carbon and has a molecular sieve function, and it has an ability to adsorb oxygen gas earlier than nitrogen gas. Also using the time difference, PSA
It is known that a nitrogen concentrator by the method can be constructed.

This molecular sieve charcoal also has a strong water adsorption capacity and can be constructed as an air dryer like the above zeolite. That is, by changing the control method, it is possible to use an apparatus configured with the same mechanism as a nitrogen gas concentrator or an air dryer.

In the above case, since the molecular sieving charcoal is adsorbed mainly to oxygen gas, as in the above example, the concentration of oxygen gas is 21%, and the gas concentration is 4.6% in terms of water vapor. Ratio of about 4.6: 1. When using a molecular sieve charcoal as an adsorbent used when constructing an air dryer by the PSA method, water is a strongly adsorbing substance. Also,
When used in a nitrogen concentrator with this configuration, the water is a strongly adsorbing substance as described above, but the oxygen gas is controlled to be a medium adsorbing substance.

Next, when using zeolite 5A type or 13X type so as to have the function of an oxygen concentrator,
Although water is a strongly adsorptive substance, nitrogen gas is controlled so as to be a medium adsorbent.

For the purpose of the PSA air dryer,
When considering water as a strongly adsorptive substance, when these adsorbents filled in the adsorption column are compared with the water in the air under pressure, the above-mentioned nitrogen gas or oxygen gas that is an intermediate adsorbent substance The amount of nitrogen gas or oxygen gas, which is the medium adsorbent contained in the air sent into the adsorption column within the same operation cycle time, is more than the total capacity capable of adsorbing the same within one operation cycle time. When the amount is large, the medium-adsorptive substance flows out (also referred to as breakthrough) to the outlet end of the adsorption column, so that water is adsorbed and removed, but the composition of the main components is It has substantially the same composition as the air sent to the adsorption column.

During a decompression / desorption process in which a part of the dried air is desorbed by the adsorption column during the pressure adsorption step, the adsorption column is decompressed to atmospheric pressure or below to desorb the adsorbent. Although it is regenerated, at the time of this vacuum desorption process, a part of the dried air is used as a purge gas so as to flow countercurrently from the outlet end of the adsorption cylinder, so that the inside of the adsorption cylinder is also filled with dry air. Will be done.

When the above-mentioned pressure process, which is the next cycle process, is moved from this state, moist air enters from the inlet end of the adsorption cylinder and the outlet end of the adsorption cylinder at the other end. Therefore, as described above, the dry air filled in the adsorption cylinder in the immediately preceding desorption / regeneration / purging step and the air newly supplied from the inlet end are discharged together with the dry air. The composition of the discharged air is almost the same as that of the air supplied to the inlet end of the adsorption cylinder except that it is dry.

This is because when zeolite is used as the adsorbent, it functions as an oxygen concentrator and the composition of the air discharged from the outlet end of the adsorption column changes. As described above, the amount of air sent into the apparatus by the PSA method functioning as an air dryer is 17
This is the case when it becomes less than one-third.

When an air dryer is constructed by using molecular sieve charcoal as an adsorbent, the air dryer functions as a nitrogen concentrator and the composition of the air discharged from the outlet end of the adsorption cylinder as described above. Similarly, when the amount of air sent is less than 1 / 4.6.

By controlling the feed air amount so as not to fall below the feed air amount in each of these examples, the amount of adsorbent used is also introduced into the adsorption column during the adsorption cycle. The amount of the adsorbent adsorbing the medium-adsorbing substance is smaller than that of the adsorbent. It is possible to leave the composition of (oxygen) unchanged.

As described above, as a method of satisfying the function as an air dryer using an adsorbent, in the case of an air dryer using zeolite as an adsorbent, the amount of dried air to be discharged and used is Regardless, the amount of air that is supplied as a purge gas countercurrently to another adsorption cylinder is at least 6% or more, preferably 15% of the processing air amount of the adsorption cylinder.
It is possible to make it less than.

When the number of adsorption cylinders is one, the present invention can be carried out by using a buffer tank for storing dry air.

[0031]

EXAMPLES Examples of the present invention will be described below with reference to the drawings.
The invention is not limited to this example. FIG.
FIG. 3 is a system diagram in which electrical control of an air dryer according to the present invention is omitted. The principle and examples of the PSA air dryer will be described with reference to this system diagram.

Alumina was placed in the lower layers of the adsorption cylinders 22 and 24, and 5A type zeolite was filled thereover, compressed air was introduced from the air inlet 10, and dust contained in the air was removed by the filter 12. Adsorption cylinder 22 via solenoid valve 14
Will be introduced to. At this time, the adsorption column 22 is in the pressure adsorption step, and almost all the water contained in the introduced air is adsorbed by the alumina and zeolite in the adsorption column and is discharged from the outlet end at the other end of the adsorption column. Since the solenoid valve 28 is opened, dry air having a low water content reaches the filter 32 through this. Further fine particles are removed by the filter 32, and the dust is discharged from the dry air outlet 38 through the pressure adjusting valve 34.

At this time, a portion of the dried air flows from the outlet end 44 of the adsorption cylinder 22 to the outlet end 46 of the adsorption cylinder 24 through the orifice 26 as a purge gas in the adsorption cylinder 24 in a countercurrent direction, and this adsorption cylinder The adsorbent filled in 24 promotes desorption of water and the like adsorbed in the pressure adsorption step,
Since the electromagnetic valve 20 is opened from the inlet end 50 of the adsorption cylinder 24, the electromagnetic valve 20 passes through this and is discharged to the atmosphere from the silencer 36.

The adsorption cylinder 24 is decompressed to a position where the pressure is equal to the atmosphere by opening the solenoid valve 20. After a certain amount of air is introduced into the adsorption cylinder 22, the solenoid valves 14, 20, 28
Is closed and the solenoid valves 16, 18, 30 are opened, the introduction of compressed air from the adsorption cylinder 22 to the adsorption cylinder 24 is switched, and the solenoid valve 16 connected to the adsorption cylinder 22 is opened. Since it passes through this, it is discharged to the atmosphere from the silencer 36, and this time the dry air produced in the adsorption cylinder 24 flows backward through the orifice 26 and flows into the adsorption cylinder 22 as purge gas, and flows countercurrently in the adsorption cylinder 22. To promote desorption and regeneration of the adsorbent.

Dry air is produced by alternately performing the pressure adsorption step and the depressurization desorption step in this way. As described above, the switching operation cycle time and the flow rate of the introduced air with respect to the amount of the adsorbent are specified. This makes it possible to configure an air dryer by the PSA method that removes only water without changing the composition of the main components such as nitrogen gas and oxygen gas in the air introduced from the air inlet.

FIG. 2 is a system diagram in which electrical control of an air dryer according to another embodiment is omitted. Basically, it is almost the same as the above-mentioned embodiment, except that the check valves 40 and 42 are used instead of the solenoid valves 28 and 30, and the pressurized air is supplied to the outlet ends 44 and 46 of the adsorption cylinder. From the filter 32 to the filter 32 in only one direction, the control sequence can be simplified because it has the same effect as controlling by opening solenoid valves 28 and 30 for a certain period of time.

Also, with the same structure as this air dryer,
By specifying the switching operation cycle time of the PSA side and the flow rate of the introduced air with respect to the amount of the adsorbent, it is possible to have a function as an oxygen concentrator. In this case, the oxygen concentrator is intended to positively change the composition of oxygen and nitrogen in the air.

In the configuration of this oxygen concentrator, the water contained in the air is adsorbed by the alumina in the adsorption column, the nitrogen gas is adsorbed by the zeolite, and the oxygen-enriched gas having less water than the outlet end of the adsorption column. Is obtained. (For example, oxygen gas concentration 95%, nitrogen gas concentration 0.1%) Note that desorption of moisture or nitrogen gas adsorbed by alumina or zeolite, flow of purge gas, or the operation and operation of each solenoid valve is the same as the air drying described above. It is the same as in the case of vessels.

[0039]

The present invention has the following excellent effects by carrying out the present invention. The atmospheric pressure converted dew point temperature of the refrigeration type air dryer is about -2.
Although it is 0 ° C., the dew point temperature can be reduced to about −40 ° C. or lower by using the air dryer according to the present invention by the PSA method. Since the composition of the air introduced into the air inlet and the composition of the dry air discharged from the dry air outlet are almost the same except that the air is dried by removing water, it can be used as the intake air. .

[Brief description of drawings]

FIG. 1 is a system diagram in which electrical control of an air dryer according to the present invention is omitted.

FIG. 2 is a system diagram in which electrical control of an air dryer according to another embodiment is omitted.

[Explanation of symbols]

 10 air inlet 12 filter 14-20 solenoid valve 22-24 adsorption cylinder 26 orifice 28-30 solenoid valve 32 filter 34 pressure regulating valve 36 silencer 38 dry air outlet 40-42 check valve 44-46 outlet end 48-50 inlet end

Claims (6)

[Claims] 1. An adsorbent in which water is a strongly adsorbing substance, nitrogen gas is a medium adsorbing substance, and oxygen gas is a weakly adsorbing substance, or water is a strongly adsorbing substance and oxygen gas is medium adsorbing substance. Among the adsorbents that are organic substances and nitrogen gas is a weakly adsorbent substance, have an adsorption column filled with any adsorbent,
Compressed air is supplied under pressure to the inlet end of the adsorption cylinder, the strongly adsorbent substance in the compressed air is adsorbed by the adsorbent, and dry air is obtained from the outlet end of the other end of the adsorption cylinder. Process,
During the desorption process in which the adsorption column is depressurized to atmospheric pressure or below atmospheric pressure to desorb the strongly adsorbing substance or the like adsorbed by the adsorbent in the adsorption step, to the outlet end of the adsorption column during the depressurized desorption step, A desorption process is carried out in which the dry air is caused to flow countercurrently as a purge gas from the adsorption cylinder in the adsorption process or from the buffer tank that stores the dried air obtained in the adsorption process. In a medical air dryer by a pressure fluctuation adsorption method in which the steps and are alternately repeated at a constant operation cycle time, the amount of the medium adsorbent substance in the air introduced into the inlet end of the adsorption cylinder within the operation cycle time. The air dryer for medical use according to the pressure fluctuation adsorption method, wherein the amount of the adsorbent is determined so that the amount of the adsorbent adsorbing the medium adsorbent is smaller than that of the adsorbent. 2. An adsorbent in which water is a strongly adsorbing substance and nitrogen gas is a medium adsorbing substance and oxygen gas is a weakly adsorbing substance, or water is a strongly adsorbing substance and oxygen gas is medium adsorbing substance. Of the adsorbents that are organic substances and nitrogen gas is a weakly adsorbent material, have an adsorption cylinder filled with one of the adsorbents,
Compressed air is supplied under pressure to the inlet end of the adsorption cylinder, the strongly adsorbent substance in the compressed air is adsorbed by the adsorbent, and dry air is obtained from the outlet end of the other end of the adsorption cylinder. Process,
During the desorption process in which the adsorption column is depressurized to atmospheric pressure or below atmospheric pressure to desorb the strongly adsorbing substance or the like adsorbed by the adsorbent in the adsorption step, to the outlet end of the adsorption column during the depressurized desorption step, A desorption process is carried out in which the dry air is caused to flow countercurrently as a purge gas from the adsorption cylinder in the adsorption process or from the buffer tank that stores the dried air obtained in the adsorption process. In a medical air dryer by a pressure fluctuation adsorption method in which the steps and the steps are alternately repeated at a constant operation cycle time, the adsorbent is in the above-mentioned adsorbent during the pressure adsorption step within the operation cycle time. The amount of air to be introduced or the amount of air to be introduced so that the amount of the medium adsorbent in the air introduced to the inlet end of the adsorption cylinder becomes larger than the amount to adsorb the adsorbent. Medical air dryer according to the pressure swing adsorption method is characterized in that configured to control the force and operation cycle times and the like. 3. An adsorbent in which water is a strong adsorbent and nitrogen gas is a medium adsorbent and oxygen gas is a weak adsorbent, or water is a strongly adsorbent and oxygen gas is medium adsorbent. Of the adsorbents that are organic substances and nitrogen gas is a weakly adsorbent material, have an adsorption cylinder filled with one of the adsorbents,
Compressed air is supplied under pressure to the inlet end of the adsorption cylinder, the strongly adsorbent substance in the compressed air is adsorbed by the adsorbent, and dry air is obtained from the outlet end of the other end of the adsorption cylinder. Process,
During the desorption process in which the adsorption column is depressurized to atmospheric pressure or below atmospheric pressure to desorb the strongly adsorbing substance or the like adsorbed by the adsorbent in the adsorption step, to the outlet end of the adsorption column during the depressurized desorption step, A desorption process is carried out in which the dry air is caused to flow countercurrently as a purge gas from the adsorption cylinder in the adsorption process or from the buffer tank that stores the dried air obtained in the adsorption process. In a medical air dryer by a pressure fluctuation adsorption method in which the steps and the steps are alternately repeated at a constant operation cycle time, the adsorbent is in the above-mentioned adsorbent during the pressure adsorption step within the operation cycle time. Similarly, the amount of adsorbable substance adsorbed is such that the amount of medium adsorbent substance in the air introduced to the inlet end of the adsorption cylinder within this operation cycle time is 17 times or more. of Alternatively medical air dryer according to the pressure swing adsorption method is characterized in that configured to control the pressure and operation cycle times and the like. 4. The adsorbent is 5A type zeolite or 13X type zeolite, wherein:
The medical air dryer according to any one of claims 2 and 3. 5. The medical air dryer according to claim 1, wherein the adsorbent is molecular sieve charcoal. 6. The medical air dryer according to claim 1, wherein the adsorption cylinder is filled with a hygroscopic agent together with an adsorbent.