Patent Publication Number: US-2019170376-A1

Title: Gas humidity regulating method and regulator

Description:
TECHNICAL FIELD 
     The present invention relates to a gas humidity regulating method and a regulator that control water content in the air, that is, humidity in, for example, a hospital, a nursing home, an office, a sports facility, a food factory, and a pharmaceutical factory. 
     BACKGROUND ART 
     Such a regulator is known as a liquid-desiccant air conditioner where a liquid desiccant (drying agent) is used. The liquid-desiccant air conditioner is combined with a heat pump so as to separate latent heat and sensible heat, and can construct an energy-saving air conditioning system. 
     For example, a wet desiccant apparatus is disclosed in Patent Literature 1. The wet desiccant apparatus includes a dehumidifying unit that allows water content absorption into a liquid desiccant (absorbent); a recycling unit that releases water content in the liquid desiccant; a dehumidifying unit pump that transports an absorbent from the dehumidifying unit to the recycling unit; a recycling unit pump that transports the absorbent in the reverse direction; and a pump controller that drives the pumps under predetermined conditions. 
     Specifically, the dehumidifying unit includes a case and a structure provided with a fin or the like in the case. An inlet port for feeding air subjected to treatment is provided in the lower part of the case while an outlet port for discharging dehumidified air subjected to treatment is provided in the upper part of the case. While the liquid desiccant is poured to the structure, air subjected to treatment from the inlet port is brought into contact with the liquid desiccant to absorb water content from the air subjected to treatment into the liquid desiccant. The dehumidified air subjected to treatment is discharged from the outlet port. 
     The recycling unit has the same configuration as the dehumidifying unit. While the liquid desiccant having absorbed water content from the dehumidifying unit is poured to the structure, air to be recycled from the inlet port is brought into contact with the liquid desiccant to remove water content from the liquid desiccant into the air, and then the moisturized air is discharged from the outlet port. 
     CITATION LIST 
     Patent Literature 
     
         
         [Patent Literature 1] Japanese Patent Laid-Open No. 2010-54136 
       
    
     SUMMARY OF INVENTION 
     Technical Problems 
     In the wet desiccant apparatus having a related-art configuration according to Patent Literature 1, the liquid desiccant in the dehumidifying unit is raised in temperature by heat generated when water content in air subjected to treatment is absorbed into the liquid desiccant. Thus, the saturation vapor pressure of the liquid desiccant increases in the case so as to suppress water content absorption into the liquid desiccant. This may reduce humidity-control efficiency. 
     In addition, when the liquid desiccant having absorbed water content is poured to the structure, the temperature of the liquid desiccant decreases in the recycling unit so as to suppress movement of water content from the liquid desiccant into air to be recycled. This may reduce humidity-control efficiency. 
     An object of the present invention is to provide a gas humidity regulating method and a regulator that can regulate a temperature during humidity control and improve humidity-control efficiency. 
     Solution to Problems 
     In order to attain the object, in a gas humidity regulating method of the present invention, a gas-liquid contact part having a heat exchanging pipe is provided in a gas-liquid contact case having an inlet port for feeding gas subjected to treatment and an outlet port for discharging treated gas, a first medium serving as a liquid desiccant is caused to flow onto the gas-liquid contact part, and a second medium for regulating a temperature is passed through the heat exchanging pipe. In this state, gas subjected to treatment is fed from the inlet port into the gas-liquid contact case, a gas-liquid contact is made by the first medium on the gas-liquid contact part so as to absorb water content into the first medium from the gas subjected to treatment, and then the treated gas is discharged from the outlet port. 
     Thus, gas subjected to treatment and the first medium make a gas-liquid contact on the gas-liquid contact part and water content in gas subjected to treatment is absorbed into the first medium serving as a liquid desiccant. At this point, the second medium is passed through a heat exchanging pipe constituting the gas-liquid contact part so as to regulate the temperature of the first medium on the gas-liquid contact part. This can accelerate dehumidification or humidification so as to increase humidity-control efficiency. 
     Advantageous Effect of Invention 
     According to a gas humidity regulating method according to the present invention, a temperature can be regulated during humidity control, thereby improving humidity-control efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory drawing schematically showing an air humidity regulator including a dehumidifier and a humidifier according to an embodiment. 
         FIG. 2( a )  is a front view showing a gas-liquid contact structure on a gas-liquid contact part for the dehumidifier or the humidifier, and  FIG. 2( b )  is an explanatory drawing schematically showing the gas-liquid contact structure. 
         FIG. 3( a )  is a perspective view showing the gas-liquid contact structure in the dehumidifier or the humidifier, and  FIG. 3( b )  is a perspective view showing the gas-liquid contact structure on a gas-liquid contact part of the related art. 
         FIG. 4  is a graph showing the relationship between a flow rate and an absolute humidity of a first medium in examples or a comparative example. 
       The x-axis in  FIG. 4  shows the flow rate of a first medium (in “kg/m 2 ·s”). The y-axis in  FIG. 4  shows the absolute humidity of a first medium (in “g/kg”).
 
The meaning of the dots in  FIG. 4  represent the results obtained for the solution of each example as follows:
 
       Example 1: ⊚; Example 2: Δ; Example 3: ⋄; 
       Example 4: □; Example 5: x; Example 6: *; 
       Example 7: +; Comparative Example 1: ∘. 
         FIG. 5  is a graph showing the relationship between a viscosity and a saturation vapor pressure of the first medium in the examples and the comparative example. 
       The x-axis in  FIG. 5  shows the viscosity of a first medium (in “mPa·s”). The y-axis in  FIG. 5  shows the saturation vapor pressure of a first medium (in “kPa”).
 
The meaning of the dots in  FIG. 5  represent the results obtained for the solution of each example as follows:
 
       Example 1: ⊚; Example 2: Δ; Example 3: ⋄; 
       Example 4: □; Example 5: x; Example 6: *; 
       Example 7: +; Comparative Example 1: ∘. 
         FIG. 6  is a graph showing the relationship between a flow rate and an absolute humidity of the first medium in the examples or the comparative example. 
       The x-axis in  FIG. 6  shows the flow rate of a first medium (in “kg/m 2 ·s”). The y-axis in  FIG. 6  shows the absolute humidity of a first medium (in “g/kg”).
 
The meaning of the dots in  FIG. 6  represent the results obtained for the solution of each example as follows:
 
Examples 1 to 4 (mean value): ⊚; Comparative Example 1: ∘.
 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     An embodiment of the present invention will be specifically described below in accordance with the accompanying drawings. 
       FIG. 1  is a schematic diagram showing a gas humidity regulator  10  according to the present embodiment. The regulator  10  includes a dehumidifier  11  and a humidifier  12  that are connected to each other. The dehumidifier  11  and the humidifier  12  have identical basic configurations. The dehumidifier  11  will be first discussed below. 
     As shown in  FIG. 1 , an inlet port  14  for feeding air as gas subjected to treatment is formed on a side wall  13   a  of a gas-liquid contact case  13  that constitutes the gas humidity regulator  10 , and an outlet port  15  for discharging treated air is formed on an upper wall  13   b  of the gas-liquid contact case  13 . 
     As shown in  FIGS. 2( a ) and 2( b ) , the gas-liquid contact case  13  contains a meandering heat exchanging pipe  17  with a fin  16  provided on the surface of the heat exchanging pipe  17 . The heat exchanging pipe  17  constitutes a dehumidifying unit serving as a gas-liquid contact part  18 . The heat exchanging pipe  17  and the fin  16  are made of metals such as aluminum, stainless steel or alloys and can improve a heat exchanging function. 
     As shown in  FIG. 3( a ) , for example, the heat exchanging pipe  17  includes meandering pipes  19  that are horizontally arranged in parallel in five rows, the pipe  19  vertically extending so as to meander at regular intervals. As shown in  FIG. 3( b ) , the gas-liquid contact part  18  for gas-liquid contact of the related art has paper contact members  51  that are disposed at regular intervals. The gas-liquid contact part  18  is configured such that an absorbent flows along the surfaces of the contact members  51 . 
     As shown in  FIG. 1 , a sprinkling pipe  21  having a plurality of discharge ports  20  at the bottom of the sprinkling pipe  21  is disposed above the heat exchanging pipe  17 . A receiving pan  23  for receiving a first medium  22  is disposed below the heat exchanging pipe  17 . A mixed solution of water and a solution mainly composed of an ionic liquid serving as the first medium  22  is sprayed from the discharge ports  20  of the sprinkling pipe  21  to the fin  16  and the heat exchanging pipe  17 , so that the first medium  22  is deposited and stays on the surface of the heat exchanging pipe and an excess of the first medium  22  is collected in the receiving pan  23 . 
     Moreover, a flowmeter  32  and a thermometer  33  are connected to the inlet port of the heat exchanging pipe  17  while the thermometer  33  is connected to the outlet port of the heat exchanging pipe  17 . This configuration allows measurements of the flow rate and temperature of a second medium  24 . 
     The first medium  22  sprayed from the sprinkling pipe  21  preferably has a flow rate of 0.5 to 10 kg/m 2 ·s. If the flow rate of the first medium  22  is lower than 0.5 kg/m 2 ·s, only a small amount of water content is absorbed into the first medium  22  from the air, disadvantageously leading to a poor dehumidifying function. If the flow rate of the first medium  22  is higher than 10 kg/m 2 ·s, the flow rate is so excessive that water content in the air is hard to absorb any more. Thus, an improvement of the dehumidifying function is not expected and the first medium  22  may be wasted. 
     In the dehumidifier  11 , air fed from the inlet port  14  comes into contact with the fin  16  and the first medium  22  on the surface of the heat exchanging pipe  17 , the air comes into contact with the flowing first medium  22 , water content in the air is absorbed by an ionic liquid in the first medium  22 , and then the dehumidified air is discharged from the outlet port  15 . 
     A solution mainly composed of an ionic liquid is preferably used as a liquid desiccant. A preferably used ionic liquid with high water absorbency and noncorrosive properties to metals is expressed by a chemical formula C + A −  where C +  is 1,3-dialkylimidazolium cation and A −  is acid anion. As an alkyl group, an alkyl group containing 1 to 4 carbon atoms is preferable and a methyl group or an ethyl group is more preferable. Preferable acid anion is sulfonate anion, phosphate anion, or carboxylate anion. 
     The 1,3-dialkylimidazolium cation is expressed by the following chemical formula (1): 
     
       
         
         
             
             
         
       
     
     where R 1  and R 2  are alkyl groups containing 1 to 4 carbon atoms. 
     Specifically, the ionic liquid is selected from 1,3-dimethylimidazolium acetate (anion is CH 3 COO − ), 1,3-dimethylimidazolium methylsulfonate (anion is SO 3 H − ), 1-ethyl-3-methyl imidazolium diethylphosphate [anion is (C 2 H 5 ) 2 PO 3   − ], 1,3-dimethylimidazolium propionate (anion is C 2 H 5 COO − ). Most preferably, the ionic liquid is 1-ethyl-3-methyl imidazolium diethylphosphate [anion is (C 2 H 5 ) 2 PO 3   − ]. When the ionic liquid is selected from 1,3-dimethylimidazolium acetate (anion is CH 3 COO − ), 1,3-dimethylimidazolium methylsulfonate (anion is SO 3 H − ), 1-ethyl-3-methyl imidazolium diethylphosphate [anion is (C 2 H 5 ) 2 PO 3   − ], 1,3-dimethylimidazolium propionate (anion is C 2 H 5 COO − ), it is preferred to carry out humidification at 40° C. to 90° C., in particular 50° C. to 80° C., even more preferably 45° C. to 70° C., even more preferably 50° C. to 60° C., and most preferably 55° C. 
     The solution mainly composed of ionic liquid contains media such as water and other components. The amount of ionic liquid contained in the solution is preferably 60 to 99, preferably 60 to 90, or alternatively 70 to 99 mass %. If not stated differently, “mass %” give the percentage of a certain substance (for example, ionic liquid) with respect to the weight of the complete solution. 
     The ionic liquid satisfactorily functions as a liquid desiccant with proper viscosity and thus the first medium  22  is used as a mixed solution of water and a solution mainly composed of the ionic liquid. The ionic liquid in the first medium  22  preferably has a concentration of 60 to 90, preferably 70 to 80, mass %. If the concentration of the ionic liquid falls below 60 mass %, the concentration of the ionic liquid is extremely low in the mixed solution, so that the water absorbency of the ionic liquid disadvantageously decreases. If the concentration of the ionic liquid exceeds 90 mass %, the viscosity of the mixed solution excessively increases, resulting in poor contact between the air and the ionic liquid so as to deteriorate water absorbency. 
     When the concentration of the ionic liquid is 80 mass %, the first medium  22  preferably has a low saturation vapor pressure at 35° C. For example, a saturation vapor pressure of 1.9 kPa or less is preferable. However, ionic liquid having a low saturation vapor pressure is likely to become unstable and thus it is desirable to selectively use kinds of ionic liquid. If the saturation vapor pressure of the first medium  22  exceeds 1.9 kPa, water absorbency disadvantageously decreases due to vapor-liquid equilibrium. 
     The first medium  22  preferably has a viscosity of 13 to 21 mPa·s. If the viscosity of the first medium  22  is lower than 13 mPa·s, the first medium  22  has a high saturation vapor pressure, disadvantageously reducing water absorbency. If the viscosity of the first medium  22  is higher than 21 mPa·s, the first medium  22  decreases in flowability and deteriorates gas-liquid contact between the air and the first medium  22 , reducing water absorbency. 
     In the heat exchanging pipe  17 , the second medium  24  flows and exchanges heat with the surface of the heat exchanging pipe  17  and the first medium  22  on the surface of the fin  16  (mainly by cooling). This adjusts the temperature of the first medium  22  so as to regulate water absorbency. The second medium  24  may be water, hydrofluorocarbon (HFC), or hydrofluoroolefin (HFO). Water is the most preferable in view of heat exchanging capability and ease of handling. 
     The temperature of the second medium  24  is preferably equal to or lower than that of the first medium  22 . At this point, the water absorbency of the first medium  22  is increased on the gas-liquid contact part  18 , thereby improving dehumidification efficiency. 
     A container  25  is placed below the receiving pan  23 . The first medium  22  collected in the receiving pan  23  is stored and accumulated in the container  25 . One end of a first connecting pipe  26  is connected to the bottom of the container  25 . 
     The humidifier  12  will be discussed below. The basic configuration of the humidifier  12  is identical to that of the dehumidifier  11 . Thus, the same parts are indicated by the same reference symbols and the explanation thereof is omitted. 
     The first connecting pipe  26  connected to the container  25  of the dehumidifier  11  is connected to a sprinkling pipe  21  of the humidifier  12  via a valve  31  through a heat exchanger  27  provided between the dehumidifier  11  and the humidifier  12 . A heat exchanging pipe  17  in the humidifier  12  constitutes a humidifying unit serving as a gas-liquid contact part  18 . One end of a second connecting pipe  28  is connected to the bottom of a container  25  in the humidifier  12 . The second connecting pipe  28  is connected to the sprinkling pipe  21  of the dehumidifier  11  via the valve  31  through the heat exchanger  27 . Moreover, the flowmeter  32  and the thermometer  33  are connected to the first connecting pipe  26  and the second connecting pipe  28  so as to measure a flow rate and a temperature of the first medium  22 . 
     The temperature of the second medium  24  is preferably equal to or higher than that of the first medium  22 . At this point, water release from the first medium  22  is increased on the gas-liquid contact part  18 , thereby improving humidification efficiency. 
     In the humidifier  12 , air fed from an inlet port  14  comes into contact with the first medium  22  on the surface of the heat exchanging pipe  17  and droplets of the flowing first medium  22 , water content in the first medium  22  is released into the air, and then the humidified air is discharged from an outlet port  15 . 
     The effects of the air humidity regulator  10  and the regulating method according to the present embodiment will be described below. 
     As shown in  FIG. 1 , in dehumidification of humid air, the first medium  22  containing an ionic liquid is sprayed from the discharge ports  20  of the sprinkling pipe  21  in the dehumidifier  11  to the fin  16  and the heat exchanging pipe  17  that serve as the gas-liquid contact part  18 . In this state, humid air is blown to the gas-liquid contact part  18  from the inlet port  14  of the gas-liquid contact case  13 . 
     At this point, the air comes into contact with droplets of the first medium  22  and the first medium  22  deposited on the surface of the heat exchanging pipe  17 , causing gas-liquid contact. Since the first medium  22  contains the ionic liquid having high water absorbency, water content in the air is absorbed into the ionic liquid on the gas-liquid contact part  18  so as to reduce a water content in the air, achieving dehumidification. 
     Additionally, the second medium  24  passes through the heat exchanging pipe  17  on the gas-liquid contact part  18 . This exchanges heat between the second medium  24  and the first medium  22  on the surface of the heat exchanging pipe  17 . Specifically, the first medium  22  on the surface of the heat exchanging pipe  17  is cooled and water content absorption from the air into the ionic liquid is accelerated. This can also suppress a temperature increase caused by heat generated in water content absorption into the ionic liquid. Thus, the air can be quickly dehumidified with a high rate of dehumidification. 
     The effects of the specifically discussed embodiment will be described below. 
     (1) In the air humidity regulating method of the present embodiment, the first medium  22  is caused to flow onto the heat exchanging pipe  17  of the gas-liquid contact part  18  in the dehumidifier  11 ; meanwhile, the second medium  24  is passed through the heat exchanging pipe  17 . In this state, air is fed into the gas-liquid contact case  13  from the inlet port  14  and gas-liquid contact is made by the first medium  22  on the gas-liquid contact part  18  so as to absorb water content from the air into the first medium  22 . After that, the treated air is discharged from the outlet port  15 . 
     Thus, the air and the first medium  22  make a gas-liquid contact on the gas-liquid contact part  18  and water content in the air is absorbed into the first medium  22  serving as a liquid desiccant. In this case, the second medium  24  passes through the heat exchanging pipe  17  constituting the gas-liquid contact part  18  and thus the temperature of the first medium  22  can be regulated on the gas-liquid contact part  18 , thereby accelerating dehumidification. 
     In the humidifier  12 , the first medium  22  of the dehumidifier  11  is fed into the sprinkling pipe  21  from the first connecting pipe  26  and then is sprayed to the gas-liquid contact part  18 . At this point, air fed into the gas-liquid contact case  13  makes a gas-liquid contact with the first medium  22  and then water content in the first medium  22  is released into the air. Also in this case, the second medium  24  is passed through the heat exchanging pipe  17  and thus the temperature of the first medium  22  can be regulated on the gas-liquid contact part  18 , thereby accelerating humidification. 
     This can efficiently dehumidify indoor air in summer and efficiently humidify indoor air in winter. Thus, the air humidity regulating method of the present embodiment can regulate a temperature during humidity control, thereby improving humidity-control efficiency. 
     (2) The first medium  22  is a mixed solution of water and a solution mainly composed of an ionic liquid. Thus, the viscosity of the ionic liquid serving as a liquid desiccant can be adjusted so as to improve gas-liquid contact. This can effectively exert the water absorbency of the ionic liquid, thereby improving humidity-control efficiency.
 
(3) The ionic liquid is expressed by the chemical formula C + A −  where C +  is 1,3-dialkylimidazolium cation and A −  is acid anion. In this way, a proper design selection of an ion pair facilitates ionization. This can improve the water absorbency of the first medium  22  and prevent corrosiveness to metals.
 
(4) The alkyl group of the 1,3-dialkylimidazolium cation is preferably a methyl group or an ethyl group. Acid anion is carboxylate anion, sulfonate anion, or phosphate anion. These ionic liquids particularly have high water absorbency, thereby contributing to improvement of humidity-control efficiency.
 
(5) The ionic liquid in the first medium  22  preferably has a concentration of 60 to 90 mass %, preferably 70 to 80 mass %. In this case, the viscosity of the ionic liquid can be set in a proper range, thereby properly exerting water absorbency based on the ionic liquid.
 
(6) When the ionic liquid has a concentration of 80 mass % and preferably 20 mass % water, the first medium  22  has a saturation vapor pressure of 1.9 kPa or less, preferably 1.8 kPa or less, more preferably 1.2 kPa or less, even more preferably 1.0 kPa or less, and a viscosity of 13 to 21, preferably 14 to 16, mPa·s at 35° C. Thus, the first medium  22  has a proper saturation vapor pressure and a proper viscosity on the gas-liquid contact part  18 , thereby effectively exerting the water absorbency of the ionic liquid.
 
(7) The first medium  22  has a flow rate of 0.5 to 3 kg/m 2 ·s, preferably 0.5 to 1.0 kg/m 2 ·s. This can improve contact efficiency between the first medium  22  and the air on the gas-liquid contact part  18 , thereby obtaining high humidity-control efficiency.
 
(8) In the regulator  10  used for the air humidity regulating method, the heat exchanging pipe  17  serving as the gas-liquid contact part  18  is disposed in a meandering manner in the gas-liquid contact case  13  that includes the inlet port  14  for feeding air and the outlet port  15  for discharging treated air. The sprinkling pipe  21  that sprays the first medium  22  to the heat exchanging pipe  17  is provided above the heat exchanging pipe  17  and the second medium  24  is passed through the heat exchanging pipe  17 .
 
     Thus, on the gas-liquid contact part  18 , a gas-liquid contact is made between the air and the first medium  22 . At this point, the second medium  24  regulates the temperature of the first medium  22 , thereby improving humidity-control efficiency. 
     (9) The regulator  10  includes the dehumidifier  11  and the humidifier  12  in a pair. The first connecting pipe  26  is provided to guide the first medium  22 , which is collected in the container  25  of the dehumidifier  11 , to the sprinkling pipe  21  of the humidifier  12 . The second connecting pipe  28  is provided to guide the first medium  22 , which is collected in the container  25  of the humidifier  12 , to the sprinkling pipe  21  of the dehumidifier  11 . 
     This can simultaneously improve dehumidification efficiency in the dehumidifier  11  and humidification efficiency in the humidifier  12 , thereby increasing energy efficiency in the dehumidifier  11  and the humidifier  12 . 
     (10) The heat exchanging pipe  17  and the fin  16  are made of metals, preferably aluminum, stainless steel or alloys, even more preferably aluminum or stainless steel, most preferable is aluminum. Thus, heat is efficiently exchanged on the gas-liquid contact part  18 , thereby improving water absorbency. 
     EXAMPLES 
     The embodiment will be more specifically described below in accordance with examples and a comparative example. The values of the parameters cited herein were measured and can be reproduced by the following respective methods: 
     “Absolute humidity” refers to the total mass of water vapor (in g) per a given mass of dry air (in kg). It can be measured by methods known to the skilled person, for example ISO/TR 18931:2001 (en).
 
“Saturation vapor pressures” were determined by the method described in: OECD Guidelines for the Testing of Chemicals (1981): Test No. 104, items 14-19 “Static Method”, adopted Mar. 23, 2006.
 
“Flow rate” of solutions were determined with a Coriolis flow meter known to the skilled person.
 
“Viscosity” used herein refers to dynamic viscosity. The measurements of dynamic viscosity were performed at the indicated temperature (for example at 35° C.) by DIN EN ISO 3104 (“multirange capillary”). All the viscosity values given in this specification mean to be those obtained when this method is used.
 
Density measurements were carried out with DIN 51757, process 4 (“Biegeschwinger-Verf.”=“bending vibrator method”).
 
     Examples 1 to 7 and Comparative Example 1 
     In examples 1 to 7, the air humidity regulating method was tested using the air humidity regulator  10  in  FIG. 1  under the following conditions: 
     [First Medium  22 ] 
     Example 1: A mixed solution of 80 mass % 1,3-dimethylimidazolium acetate and 20 mass % water, a saturation vapor pressure of 1.0 kPa at 35° C., and a viscosity of 14 mPa·s at 35° C. 
     Example 2: A mixed solution of 80 mass % 1,3-dimethylimidazolium methylsulfonate and 20 mass % water, a saturation vapor pressure of 1.9 kPa at 35° C., and a viscosity of 13 mPa·s at 35° C. 
     Example 3: A mixed solution of 80 mass % 1-ethyl-3-methyl-imidazolium diethylphosphate and 20 mass % water, a saturation vapor pressure of 1.8 kPa at 35° C., and a viscosity of 21 mPa·s at 35° C. 
     Example 4: A mixed solution of 80 mass % 1,3-dimethylimidazolium propionate and 20 mass % water, a saturation vapor pressure of 1.2 kPa at 35° C., and a viscosity of 16 mPa·s at 35° C. 
     Example 5: A mixed solution of 80 mass % 1-ethyl-3-methyl-imidazolium tetrafluoroborate and 20 mass % water, a saturation vapor pressure of 3.5 kPa at 35° C., and a viscosity of 4 mPa·s at 35° C. 
     Example 6: A mixed solution of 80 mass % 1-ethyl-3-methyl-imidazolium nitrate and 20 mass % water, a saturation vapor pressure of 2.8 kPa at 35° C., and a viscosity of 21 mPa·s at 35° C. 
     Example 7: A mixed solution of a 80 mass % mixture of 1,3-dimethylimidazolium chloride and lithium chloride (a mass ratio of 5 to 1) and 20 mass % water, a saturation vapor pressure of 1.9 kPa at 35° C., and a viscosity of 52 mPa·s at 35° C. 
     Comparative example 1: Lithium chloride as an absorbent (an aqueous solution of 33 mass % at 35° C.), a saturation vapor pressure of 1.8 kPa at 35° C., and a viscosity of 4 mPa·s at 35° C. 
     [Dehumidifier  11 ] 
     Air as gas subjected to treatment: A temperature of 34° C., an absolute humidity of 19.5 g/kg, and a flow rate of 216 m 3 /h [In  FIG. 3( a ) , L=0.1 m, H=0.4 m, and a flow rate of 1.5 m/s were determined and thus 0.1×0.4×1.5×3600=216 m 3 /h was obtained.] 
     First medium  22 : A temperature of 17° C.
 
Second medium  24 : A temperature of 17° C., a flow rate of 6 L/min
 
     [Humidifier  12 ] 
     Air as gas subjected to treatment: A temperature of 34° C., an absolute humidity of 19.5 g/kg, and a flow rate of 216 m 3 /h (as in the case of the dehumidifier  11 ) 
     First medium  22 : A temperature of 50° C.
 
Second medium  24 : A temperature of 50° C. and a flow rate of 2.5 L/min
 
     The flow rate of the first medium  22  was changed and an absolute humidity was measured in the air serving as treated gas.  FIG. 4  shows the measurement results. 
     In comparative example 1, an air humidity regulating method was tested using a plate heat exchanger and a gas-liquid contactor according to the related art.  FIG. 4  shows the test results. 
     According to the results of  FIG. 4 , in examples 1 to 4, the absolute humidity of treated air was reduced to a target humidity or less, that is, 13 g/kg or less when the first medium  22  had a flow rate of 0.5 to 3 kg/m 2 ·s, particularly a low flow rate of 0.5 to 1.0 kg/m 2 ·s. Since L=0.1 m and W=0.2 m were determined in  FIG. 3( a ) , the passage cross-sectional area of the first medium  22  was 0.02 m 2 . The flow rate was calculated by dividing the flow velocity (kg/s) of the first medium  22  by the passage cross-sectional area of the first medium  22 . 
     In examples 5 to 7, the absolute humidity was reduced to 13 to 15 g/kg when the first medium  22  had a flow rate of 0.5 to 3 kg/m 2 ·s. 
     In comparative example 1, treated air had a high absolute humidity of 14 to 18 g/kg and the absolute humidity did not decrease to 13 g/kg or less when an absorbent had a low flow rate of 2 kg/m 2 ·s or less. This is because the paper contact member  51  serving as the gas-liquid contact part  18  did not suppress a temperature increase, precluding heat exchange. Moreover, a desiccant in comparative example 1 was highly corrosive to metals and thus the metallic fin  16  or the metallic heat exchanging pipe  17  was unusable. 
     [Relationship Between the Viscosity of the First Medium and a Saturation Vapor Pressure] 
     The viscosity and saturation vapor pressure of the first medium  22  or the absorbent used in examples 1 to 7 and comparative example 1 were measured according to the methods mentioned above.  FIG. 5  shows the measurement results. 
     As shown in  FIG. 5 , the first medium  22  in examples 1 to 4 had a low saturation vapor pressure with a relatively high viscosity. The first medium  22  in examples 5 to 7 had a relatively high saturation vapor pressure with a low viscosity or a high viscosity. The absorbent in comparative example 1 had a low saturation vapor pressure with a low viscosity. 
     [Test on the Concentration of an Ionic Liquid in the First Medium  22 ] 
     An air humidity regulating method was tested as in examples 1 to 4 while the concentration of the ionic liquid in the first medium  22  used in examples 1 to 4 was changed by 5 mass % from 50 mass % to 95 mass % and the first medium  22  had a flow rate of 2 kg/m 2 ·s. Table 1 shows the test results where Good (indicated by “o”) represents an absolute humidity not higher than 13 g/kg, Not Good (indicated by “x”) represents an absolute humidity not lower than 13 g/kg, and Untested (indicated by “-”) represents an untested state with a high viscosity. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Concentration of ionic liquid in first medium (in “mass %”) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 50 
                 55 
                 60 
                 65 
                 70 
                 75 
                 80 
                 85 
                 90 
                 95 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
               
               
                 Example 2 
                 x 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
               
               
                 Example 3 
                 x 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 — 
               
               
                 Example 4 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 — 
               
               
                   
               
            
           
         
       
     
     As shown in the test results of Table 1, the ionic liquid in the first medium  22  preferably has a concentration of 60 to 90 mass %. 
     [Humidification Test on the Humidifier  12 ] 
     As in a dehumidification test on the dehumidifier  11  in examples 1 to 4, a humidification test was conducted under the conditions of the humidifier  12 . Moreover, the relationship between a flow rate and an absolute humidity of the first medium  22  was determined. The test results are shown in  FIG. 6 . 
       FIG. 6  shows the mean value of absolute humidity in examples 1 to 4. A humidification test was similarly conducted in comparative example 1. The test results are shown in  FIG. 6 . 
     As shown in  FIG. 6 , when the first medium  22  had a low flow rate in the humidification test, an absolute humidity was higher in examples 1 to 4 than in comparative example 1. 
     [The Influence of a Temperature During Humidification by the Humidifier  12 ] 
     In examples 1 to 4, a humidification test was conducted while the first medium  22  had a flow rate of 2 kg/m 2 ·s and the temperature of the first medium  22  was changed from 30 to 90° C. Table 2 shows the test results where Good (indicated by “∘”) represents an absolute humidity not lower than 22 g/kg and Not Good (indicated by “x”) represents an absolute humidity lower than 22 g/kg. 
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Temperature during humidification of first medium (° C.) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 30 
                 35 
                 40 
                 45 
                 50 
                 55 
                 60 
                 70 
                 80 
                 90 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
               
               
                 Example 2 
                 x 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
               
               
                 Example 3 
                 x 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
               
               
                 Example 4 
                 x 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
                 ∘ 
               
               
                   
               
            
           
         
       
     
     As shown in Table 2, proper humidification was obtained at a temperature of 40 to 90° C. during humidification. 
     The embodiment may be changed in a concrete form as follows: 
     The first connecting pipe  26  or the second connecting pipe  28  that allows the passage of the first medium  22  may be provided with a heat exchanger for heat exchange with the 15 second medium  24 , accelerating the temperature regulation of the first medium  22  through heat exchange with the second medium  24 . 
     The discharge ports  20  of the sprinkling pipe  21  may be varied in opening diameter so as to regulate the droplet size of the first medium  22  flowing from the discharge ports  20 . 
     The container  25  in the gas-liquid contact case  13  may be omitted and the first medium  22  may be collected in the lower part of the gas-liquid contact case  13 . In this case, one end of the first connecting pipe  26  or the second connecting pipe  28  is connected to the gas-liquid contact case  13 . 
     REFERENCE SIGNS LIST 
     
         
           10  regulator 
           11  dehumidifier 
           12  humidifier 
           13  gas-liquid contact case 
           13   a  side wall of gas liquid contact case 
           13   b  upper wall of gas liquid contact case 
           14  inlet port 
           15  outlet port 
           16  fin 
           17  heat exchanging pipe 
           18  gas-liquid contact part 
           19  pipe 
           20  discharge port 
           21  sprinkling pipe 
           22  first medium 
           23  receiving pan 
           24  second medium 
           25  container 
           26  first connecting pipe 
           27  heat exchanger 
           28  second connecting pipe 
           31  valve 
           32  flowmeter 
           33  thermometer 
           51  paper contact members