JP3326697B2 - Absorption chiller / heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption chiller / heater,
In particular, the present invention relates to an absorption chiller / heater using pervaporation membrane separation in a regenerator.

[0002]

2. Description of the Related Art In an absorption chiller / heater, instead of a high-temperature regenerator that heats a dilute solution and separates a refrigerant and a solution by pool boiling, a pervaporation membrane separation that separates a refrigerant and a solution by a pervaporation membrane is adopted. Have been.

[0003] Pervaporation membrane separation means increasing the temperature of a solution flowing on the primary side (supply side) of the membrane and depressurizing the secondary side (permeate side) of the membrane to reduce the vapor pressure difference between components passing through the membrane. This is an operation of selectively permeating a more volatile component through the membrane by giving it, and collecting the vapor with a cold trap or the like to separate the liquid mixture. The mechanism of the vapor permeation through the membrane is that the vapor component that permeates on the primary side of the membrane dissolves in the membrane, diffuses through the membrane, and becomes vaporized because the secondary side of the membrane is depressurized. The pervaporation membrane separation involves a phase change of a liquid phase on the primary side and a gas phase on the secondary side across the membrane, so it is necessary to raise the temperature on the primary side to replenish latent heat.

A configuration of an absorption chiller / heater using a pervaporation membrane separation in a conventional regenerator will be described with reference to FIGS.

FIG. 4 is a flow diagram showing the structure of a conventional absorption chiller / heater.

FIG. 5 is an explanatory diagram showing flows of heated water and a medium in the membrane module in the regenerator of FIG.

In the following description, an example in which a LiBr aqueous solution is used as an absorbing liquid, water is used as a refrigerant, and water is used as a heating and cooling liquid, respectively, will be described in detail.

[0008] The regenerator 3 houses the membrane module 301,
The membrane module has an absorbing liquid inlet pipe 300, an outlet opening 311, a heated water inlet pipe 32, and an outlet pipe 30, respectively. The condenser 4 houses the cooling heat exchangers 40, respectively, and the regenerator 3 and the condenser 4 are connected by a steam passage 70. The LiBr aqueous solution flowing through the absorber 1 and the regenerator 3 has a system flowing through the heat exchanger 5.

Next, the operation of the above-described apparatus for obtaining cold heat will be described with reference to FIG. LiBr with a concentration of 55%
The aqueous solution (C) is introduced into the membrane module 301 of the regenerator 3 through the absorption liquid inlet pipe 300. As shown in FIG. 5, the absorbing liquid flows through the gap 35 formed between the heat transfer surface 33 and the hydrophobic porous material 500 inside the membrane module 301. On the other hand, the heated water (A) is introduced from the pipe 32 and
6 and the heat transfer surface 33, and the flow is opposed to the above-described absorbent. Therefore, the density 55
% LiBr aqueous solution is heated via the heat transfer surface by the heating water (B) and evaporates. The generated steam passes through the opening of the hydrophobic porous material 500, passes through the gap 38 formed with another hydrophobic porous material 500, and is introduced into the condenser 4 through the steam passage 70. By the above operation, the concentration is 60% (D)
The LiBr aqueous solution concentrated to the maximum accumulates at the bottom of the container of the regenerator 3 through the opening 311 and flows to the heat exchanger 5 through the absorbent outlet pipe 310.

Next, the LiBr aqueous solution concentrated to 60% is cooled by the heat exchanger 5 and introduced into the absorber 1 by the liquid tube 100. Since the LiBr aqueous solution whose concentration has decreased due to the absorption of water vapor and whose temperature has increased is cooled by lower-temperature cooling water, steam can be absorbed again. Therefore, the LiBr aqueous solution finally discharged from the opening 111 has a concentration of 55% and a temperature of 35 ° C. (F). This aqueous solution stays on the bottom surface of the absorber 1 and flows through the liquid pipe 110 through the pump 14.
0, introduced into the heat exchanger 5 through the liquid pipe 130, and introduced at 80 ° C.
Heat is taken from the 0% LiBr aqueous solution to increase the temperature, and the path is introduced to the regenerator 3 via the absorption liquid inlet pipe 300.

In the regenerator 3, the membrane module 30
1 will be described.

FIG. 7 is an explanatory diagram for explaining the concentration of the absorbing solution by the membrane module of the regenerator.

As shown in FIG. 7, the absorbing liquid 300 flowing through the gap 600 formed by the heat transfer surface 33 and the hydrophobic porous material 500 is transferred by the heated water 32 flowing opposite to the absorbing liquid. It is heated through the surface 33 to evaporate,
0 is transmitted through the opening of the hydrophobic porous material 500. The evaporating and concentrated absorbing liquid flows through the gap and is heated by the higher-temperature heating water, so that it is further evaporated and concentrated.

A material which does not allow the absorption liquid in the membrane module 301 of the regenerator 3 to pass through and allows only water vapor to pass therethrough is a hydrophobic porous material, and has a membrane shape, a tubular shape, and the like, and is made of polytetrafluoroethylene ( PTFE), polyethylene (P
E), polypropylene (PP), nylon, silicone,
Cellulose acetate and the like. A gap is formed between the film or tube formed of these materials and the heat transfer surface or heat transfer tube for heat exchange,
The absorbing liquid is caused to flow through the gap. Known examples of absorption chillers / heaters using membrane separation in a regenerator include JP-A-1-98866 and JP-A-61-272566.

[0015]

The prior art uses a hydrophobic porous membrane as a membrane material, which is based on the principle that water vapor permeates through the geometrical pores of the membrane. It is proportional to the water vapor pressure difference on both sides of the membrane according to Fick's law of diffusion. Therefore, in order to increase the permeation flux, it is sufficient to increase the water vapor pressure difference. However, it is necessary to increase the temperature of the regenerator, and the durability of the membrane material is reduced due to corrosion. Therefore, a need exists for a membrane material that increases the permeation flux without increasing the temperature of the regenerator. An object of the present invention is to provide a membrane having a high separation efficiency of a regenerator of an absorption chiller / heater. .

[0016]

An object of the present invention is to provide an evaporator for evaporating a liquid refrigerant and removing heat of evaporation from a low temperature medium to cool the evaporator.
An absorber that absorbs the refrigerant vapor vaporized by the evaporator into a concentrated solution to generate a dilute solution, and a dilute solution is introduced from the absorber to separate the refrigerant vapor and the concentrated solution into a concentrated solution for regeneration. An absorption cooling / cooling system comprising a regenerator, a condenser for condensing and liquefying the refrigerant vapor separated by the regenerator and supplying it to the evaporator, and an absorbent pump for pumping the concentrated solution regenerated by the regenerator to the absorber. In the water machine, it is achieved by the porous membrane being a hydrophobic porous membrane having a charged membrane formed thereon.

[0017]

The permeation flux due to pervaporation membrane separation is expressed by Fick's diffusion formula.

[0018]

(Equation 1)

According to the present invention, by forming a charged film on the hydrophobic porous film, ions in the vicinity of the charged film are eliminated (donane exclusion), and the LiBr concentration is apparently reduced, whereby the partial pressure of water is reduced. And the vapor pressure difference on both sides of the hydrophobic porous membrane increases. Even if the steam pressure difference which is the driving force for water vapor permeation as a regenerator is reduced, a high water vapor permeation flux can be obtained for the above reasons.

A charged membrane charged by the plasma polymerization method has a high water vapor permeation flux.

In the charged membrane negatively charged by the plasma polymerization method, the negative ions of the salt are eliminated in the pores thereof, and the partial pressure of water increases, so that the vapor pressure difference on both sides of the hydrophobic porous membrane increases. A permeate flux is obtained.

When a negatively charged film and a positively charged film are alternately laminated on the hydrophobic porous film, positive and negative ions such as Li + ion and Br ~ ion in LiBr water are eliminated from the film surface. However, since the partial pressure of water is increased and the vapor pressure difference on both sides of the hydrophobic porous membrane is increased, a higher water vapor permeation flux can be obtained.

A large permeation flux can be obtained by charging a polytetrafluoroethylene hydrophobic porous membrane by a plasma polymerization method.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The difference between the present embodiment and the prior art absorption chiller / heater shown in FIG. 4 lies in the membrane module built in the regenerator. This membrane module is formed by molding a material in which a charged film is formed on a hydrophobic porous film.

First, a process of forming a charged film on a hydrophobic porous film by the plasma polymerization method of this embodiment will be described.
A substrate is placed in a reaction vessel of a known plasma graft polymerization apparatus, and the pressure is reduced (2.7 Pa). After irradiation with low-temperature plasma to generate radicals, a 5% aqueous solution of acrylic acid in a monomer vessel (freezing under reduced pressure, The reaction vessel in which the molten oxygen was removed to remove dissolved oxygen) was brought into contact with the liquid phase under reduced pressure, and graft polymerization was carried out for 30 to 300 minutes in a constant height tank.

Table 1 below shows the conditions for plasma graft polymerization.

[0028]

[Table 1] Pressure (Pa) Electric power (W) Irradiation time (min) Graft time (min) 1 2.7 10 130 2 2.7 10 1 60 3 2.7 10 1 180 4 2.7 10 1 300 5 2.7 10 1 180 Base material No. 1-4 High density polyethylene porous membrane (HDP
E) (Tonen Chemical Co., Ltd., film thickness 25 μm, pore size 0.03 μm) 5 Hydrophobic polytetrafluoroethylene membrane (P
(TFE) (manufactured by Nitto Denko; film thickness: 80 μm, pore size: 0.2 μm) Table 2 shows the ion exchange capacity of the membrane subjected to plasma graft polymerization.

[0029]

[Table 2] Ion exchange capacity Ion exchange capacity (mol / kg dry Mem.) (Mol / m ³ wet Mem.) 1 0.113 0.550 2 0.116 0.541 3 0.128 0.570 4 0.130 0. 589 5 0.169 0.400 From the results shown in Table 2, it was found that the membrane subjected to plasma graft polymerization was a cation exchange membrane having a negative charge.

Next, the water vapor permeation characteristics of the above-mentioned plasma graft polymerized membrane and the conventional hydrophobic porous membrane were evaluated by a pervaporation method.

FIG. 1 is a table showing a relationship between a vapor pressure difference Δp and a permeation flux Q of a polyethylene porous membrane and a membrane obtained by plasma polymerization on the polyethylene porous membrane.

As shown in FIG. 1, a polyethylene porous membrane which is a conventional hydrophobic porous membrane and Comparing the plasma-polymerized membrane on the polyethylene porous membrane No. 3, the permeation flux Q of the plasma-polymerized membrane is higher.

FIG. 2 is a table showing the relationship between the permeate flux Q and the vapor pressure difference Δp of the polytetrafluoroethylene porous membrane and the membrane polymerized on the polytetrafluoroethylene porous membrane by plasma polymerization. As shown in FIG. 2, a polytetrafluoroethylene porous membrane which is a conventional hydrophobic porous membrane and Comparing the plasma-polymerized membrane on the polytetrafluoroethylene porous membrane of No. 5, the permeation flux Q of the plasma-polymerized membrane is high.

FIG. 3 is a table showing the relationship between the vapor pressure difference Δp of each ion exchange membrane and the permeation flux Q.

The membrane permeated by plasma polymerization on the porous polytetrafluoroethylene membrane shown in FIG. 2 has a higher permeation flux than the ion exchange membrane shown in FIG.

As shown in Table 2, the film subjected to the plasma graft polymerization has a negative charge, and this charge increases the permeation flux, and further reduces the negative charge on the film surface. Alternatively, the permeation flux is further increased by alternately forming positive charges obtained by plasma graft polymerization of vinylpyridine or a quaternary ammonium salt in addition to negative charges on the membrane surface.

As described above, according to this embodiment, if a membrane is used as a means for separating the refrigerant in the regenerator of the absorption chiller / heater, the regeneration side and the condensation side can be opposed to each other, and the area of the gas-liquid interface can be increased. This makes the regenerator more compact. By forming a charged membrane on a porous membrane as a separation membrane, it becomes possible to apparently lower the concentration of LiBr in the vicinity of the membrane, reduce the vapor pressure difference that is a driving force for permeation, and increase the permeation amount. This makes the regenerator / condenser more compact.
The temperature of the regenerator can be reduced.

[0038]

According to the present invention, by forming a charged membrane on a hydrophobic porous membrane, ions in the vicinity of the charged membrane are eliminated, thereby increasing the partial pressure of water and increasing the hydrophobic porous membrane. Since the steam pressure difference between both sides is large, a high steam permeation flux can be obtained with a small steam pressure difference as a regenerator.

[Brief description of the drawings]

FIG. 1 is a table showing the permeation flux of a conventional polyethylene porous membrane and a membrane obtained by plasma polymerization on the polyethylene porous membrane of the present invention.

FIG. 2 is a table showing the permeation flux of a conventional PTFE film and a film obtained by plasma polymerization on a PTFE film of the present invention.

FIG. 3 is a chart showing a permeation flux of each general ion exchange membrane.

FIG. 4 is a flow diagram showing a configuration of a conventional absorption chiller / heater.

FIG. 5 is an explanatory diagram showing flows of heated water and a medium in a membrane module in the regenerator of FIG.

FIG. 6 is an operation diagram in the system shown in FIG. 4;

FIG. 7 is an explanatory diagram illustrating concentration of an absorbing solution by a membrane module of the regenerator in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Absorber 2 Evaporator 3 Regenerator 4 Condenser 5 Heat exchanger 30 Heated water outlet pipe 32 Heated water inlet pipe 301 Membrane module 300 Absorbent liquid inlet pipe 310 Absorbent liquid outlet pipe 311 Outlet opening

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F25B 15/14 B01D 71/06 F25B 33/00

Claims (1)

(57) [Claims] An evaporator for evaporating a liquid refrigerant and removing heat of evaporation from a low-temperature medium to cool the evaporator; an absorber for absorbing a refrigerant vapor vaporized by the evaporator into a concentrated solution to generate a dilute solution; A regenerator that introduces a dilute solution from the vessel and separates and regenerates the refrigerant vapor and the concentrated solution by a porous membrane and regenerates the condenser, and condenses and liquefies the refrigerant vapor separated by the regenerator to supply the vapor to the evaporator; An absorption chiller / heater comprising an absorbent pump for pumping the concentrated solution regenerated by a regenerator to the absorber, wherein the porous membrane is a membrane formed by forming a charged membrane on a hydrophobic porous membrane. Absorption chiller / heater.