JP3481538B2 - Absorption liquid regeneration system and absorption heat pump using the same - 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 liquid regeneration system for an absorption heat pump using a working medium that also evaporates the absorption liquid when the absorption liquid is regenerated, and an absorption heat pump using the same.

[0002]

2. Description of the Related Art In recent years, in addition to an increase in the amount of electric power used in the summer due to the spread of air conditioners, the demand for air-conditioning due to the office automation of office buildings has increased, and the tight supply and demand of electric power in the summer has become a serious problem. In particular, during the peak power usage in August, about 40% of the power usage is due to cooling, and this ratio is expected to remain unchanged even if the total power usage increases in the future. In order to solve such a problem, it is said that it is effective to use an absorption heat pump (refrigerator) that consumes less power as a home air conditioner or an office air conditioner. Further, an absorption heat pump capable of driving a heat source is effective for effective utilization of industrial waste heat and cogeneration by hybridizing energy equipment.

From these viewpoints, an absorption heat pump using lithium bromide aqueous solution as an absorption solution and water as a refrigerant has been developed and put on the market in many cases. An absorption heat pump using ammonia-water as a working refrigerant has also been proposed. Furthermore, JP-A-9-296966
As disclosed in Japanese Patent Laid-Open No. 9-104862, a hydrocarbon or HFC is used as a refrigerant and an absorption heat pump is operated by using a vinyl ether compound as an absorbing liquid. In addition, trifluoroethanol (TFE:
(HFC, which is a refrigerant of a compression heat pump, in which hydrogen in the HFC is replaced with hydroxyl group OH), and one that uses a high boiling point polar solvent, dimethyl imidazolidone (DMI), to operate the absorption heat pump are proposed. Has been done.

However, in a conventional absorption heat pump using an aqueous lithium bromide solution as an absorption solution and water as a refrigerant, water has a vapor pressure of several meters at the operating temperature of the heat pump.
Low mHg, difficult to remove non-condensable gas, lithium bromide is corrosive and requires regular maintenance, difficult to miniaturize, difficult to air cool, etc. There are some things to consider. Also,
Since the coolant water (pure water) freezes, the heat pump cannot be operated in winter and the heating operation efficiency is not good.

Further, an absorption heat pump using ammonia as a drivable refrigerant and water as an absorption liquid has also been proposed, but the toxicity of ammonia is strong, there is no suitable inhibitor for avoiding corrosion, and the working pressure is high. There is a problem that needs to be considered, such as the fact that it is difficult to double-use because it is high.

Water is a very good refrigerant in terms of global warming and toxicity, but it is not corrosive at high temperatures and the refrigerant water freezes so that it cannot be operated in the winter and heating operation is performed. Not efficient. In order to popularize absorption heat pumps, it is desirable that they do not require maintenance and that they have a low global warming potential.

Hydrocarbons such as dimethyl ether have a large energy density per unit volume, a low viscosity, and a low global warming potential as a candidate for a refrigerant for an absorption heat pump that satisfies the above conditions. Wo
rking Fluids '98 (B. Adamson, M. AIRAH, Australi
a, 'Dimethyl Ether as an R-12 Replacement', Natu
ral Working, Fluids '98, IIR-Gustav Lorentzen Con
ference, pp. 569-575 (1998)). The toxicity of this dimethyl ether has not been reported, and it is currently used in Japan as a pressurized medium in spray pipes such as insecticides.

When these refrigerants are used as working refrigerants for absorption heat pumps, bleeding is not required and the energy density per unit volume can be increased, which facilitates miniaturization and has a low global warming potential. Load is reduced. Furthermore, problems such as corrosion and toxicity at high temperatures can be solved.

In addition, even if the flow rate of the absorbing liquid and the flow rate of the vapor are changed, an absorption heat pump that secures a stable gas-liquid contact area and maintains the rectification effect (for example, Japanese Patent Laid-Open No. 10-30).
No. 859), a rectifier for an absorption heat pump (for example, Japanese Patent Laid-Open No. 9-26230), which is intended to be miniaturized.

[0010]

In the absorption heat pump, the absorption liquid absorbs the refrigerant to keep the pressure inside the vessel low to evaporate the refrigerant, thereby enabling cooling. In order to continuously perform this absorption and evaporation, it is necessary to separate the absorbing liquid and the refrigerant (regenerate the absorbing liquid) on the other hand. In the conventional absorption heat pump using water-lithium bromide aqueous solution, since the difference in boiling point between the refrigerant and the absorption liquid is large, the lithium bromide dissolved in the absorption liquid during regeneration (concentration) of the absorption liquid does not evaporate, It could be played in a relatively easy way.

However, in order to miniaturize the equipment, the concentration concentration range can be widened and troubles such as crystallization can be prevented,
Absorption liquid whose boiling point difference with the refrigerant is not so large, for example,
When an ether type natural refrigerant having a relatively low boiling point is used as the refrigerant and a hydrocarbon such as ester or aromatic is used as the absorbing liquid, not only the refrigerant but also the absorbing liquid is vaporized when the absorbing liquid is regenerated. With such a combination, the conventional regenerator cannot cope with it, and it has been necessary to newly develop a compact regenerator, that is, a distiller having a good performance of separating the refrigerant and the absorbing liquid.

In such a distiller, the absorbing liquid evaporates in the same manner as the refrigerant. Therefore, when the refrigerant is regenerated at a high concentration, it is necessary to recirculate the condensed and liquefied refrigerant once again in the distiller. Become. Thus, in order to effectively exchange heat and mass between the reflux and the vapor generated in the still,
Fill the top in the still in the still. Similarly, the absorption liquid flowing in from the middle part of the distiller flows down the lower filling material located below the upper filling material, and when flowing down, the absorption liquid evaporates in the heating part at the bottom of the distilling equipment. Exchanging the heat substance with the vapor.

As described above, heat and mass exchange of vapor and liquid in the distiller is routinely performed in a chemical plant, but in an absorption heat pump, the amount of refrigerant flowing back and the amount of refrigerant flowing into the distiller flow. Due to the fact that there is a difference of several tens of times with the amount of absorbed liquid, and the height of the distiller is limited because it is installed inside or on the side of a building or house, the technology of the chemical plant is applied as it is. It is not possible.

For example, based on the absorption liquid having a large inflow amount,
If coarse packing is selected as the packing material to be packed, the height of the packing area of the packing material becomes high at the portion where the reflux of the refrigerant having a small amount flows down. Also, if a fine packing is selected according to the portion where the reflux of the refrigerant with a small amount of flow down flows, the flow of the vapor is obstructed in the part of the absorbing liquid with a large amount of flow down, and the performance of the distiller deteriorates. I will end up.

An object of the present invention is to provide an absorption liquid regeneration system for an absorption heat pump which can regenerate a working medium in which the absorption liquid evaporates with high efficiency. Another object of the present invention is to provide an absorption heat pump that can be easily installed in a building, a house, etc. by reducing the height of the system by using a regeneration system that regenerates a working medium with high efficiency. is there.

[0016]

In order to achieve the above-mentioned object, the constitution of the invention of the absorption liquid regenerating system according to the present invention comprises a distiller for regenerating the absorption liquid having a large boiling point difference with the refrigerant, and Installed above the distiller to condense the refrigerant
Refrigerant condensing section and provided below the distiller to absorb the absorption
And a reboiler that heats the liquid to generate steam, before
The refrigerant condensed and liquefied in the refrigerant condensing section is stored in the distiller.
Generated by the absorption liquid heater while flowing down and refluxing
And the steam to raise the in the distiller, in the reproduction system of the absorbent using a working medium also evaporates absorbing liquid during regeneration of the absorbent, and a top of the distiller, on this
The upper part of the distiller is divided into a lower part and a lower part.
And the absorption liquid inlet between the lower formed, filled the absorbing solution inlet port from a fine filling on top, wherein the lower the absorption liquid inlet port, generally from the porosity of the top of the packing Three
It is to fill a coarse packing with double porosity .

[0017]

[0018]

[0019]

[0020]

In order to achieve the above object, the constitution of the invention of the absorption heat pump according to the present invention has a difference in boiling point from that of the refrigerant.
Distiller to play no greater absorption liquid, <br/> condenser for condensing the refrigerant, absorbing liquid pressure that by heating the absorption liquid to generate steam
Equipped with a heater and absorber , condensed in the refrigerant condensing part and liquefied
When the generated refrigerant is flowed down in the distiller and refluxed,
The vapor generated in the absorption liquid heater in the distiller
As it rises, the absorbent also evaporates during regeneration of the absorbent
In the absorption heat pump Ru using the working medium, before
Install the distiller into the upper part and the lower part below this upper part.
An absorbent inlet is provided between the upper and lower parts of the distiller, a fine packing is filled above the absorbent inlet , and an upper portion is installed below the absorbent inlet. of
It is intended to pack the coarse filler having a generally three times the void ratio than the porosity of the filler.

[0022]

[0023]

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cycle flow diagram of an absorption heat pump according to the present invention, which uses a regeneration system for regenerating an absorption liquid from a working medium in which the absorption liquid evaporates when the absorption liquid is regenerated. Absorption heat pump is a distiller 1
01, condenser 102, evaporator 104, refrigerant expansion valve 10
3, refrigerant heat exchanger 105, absorber 106, absorption liquid pump 107, absorption liquid heat exchanger 108, absorption liquid pressure regulating valve 109,
And piping 110, 111, 112, 11 connecting them
3, 114, 115, absorption liquid heater 116, condenser cooling water pipe 117, and cold water pipe 118.

Refrigerant vapor 110 generated from the still 101
Is condensed in the condenser 102 by exchanging heat with the condenser cooling water 117. The condensed and liquefied refrigerant is the refrigerant heat exchanger 105.
Through the refrigerant expansion valve 103 to flow into the evaporator 104, and into the reflux 111 and return to the distiller 101 again. The refrigerant flowing into the evaporator 104 exchanges heat with cold water via the heat transfer surface of the cold water pipe 118, evaporates while removing heat from the cold water, and then flows into the absorber 106 in a vapor state.

On the other hand, the absorbing solution 115 flowing out from the distiller 101 via the pipe 115 is cooled by itself while heating the absorbing liquid returning from the absorber 106 via the solution heat exchanger 108. It flows into the absorber 106, is cooled by the absorber cooling water 119, and absorbs the refrigerant vapor. The absorbing solution is heated by the absorbing solution heat exchanger 108 via the absorbing solution pump 107, flows into the distiller 101 again, and is heated by the distiller heating medium 116 to be concentrated. The above is the cycle flow of the absorption heat pump.

FIG. 2 is a diagram showing the relationship between the boiling point concentration (dew point temperature) of the mixed liquid and the absorption liquid mass concentration. This figure shows the relationship between the boiling point temperature (K) and the mass concentration of the low boiling point component of the mixed solution calculated using the gas-liquid equilibrium estimation method. A method for obtaining the inlet and outlet concentrations will be described.

Since the physical property measurement data at the time of mixing the refrigerant and the absorbing liquid do not exist for all combinations, it is necessary to discuss the gas-liquid equilibrium in the state close to the critical point for evaluation. For this reason, it is proposed by J. Gmehling et al. (J.
Gmehling, 'From UNIFAC to Modified UNIFAC to PARK
with the help of DDB ', Fluid Phase Equilibria, 107,
pp1-29 (1995)) The one using the equation of state was used.

In the figure, the mass concentration of the absorbing liquid and the boiling point temperature are shown for the conditions of the evaporator with the vapor pressure of the low boiling point component of 5 ° C. and the condition of the condenser with the vapor pressure of the low boiling point component of 40 ° C. Show the relationship. From the figure, under the evaporator conditions (solid line),
It can be understood that when the temperature of the absorbing liquid is 40 ° C. at which cooling is possible, it can be diluted to the absorbing liquid mass concentration X _A. Similarly, under the condensing condition (broken line), the temperature of the absorbing liquid is distiller 101.
It can be understood that when the temperature is 100 ° C., at which the heating can be performed at 100 ° C., it is possible to concentrate to the absorption liquid mass concentration X _G. At this time, the concentration range of the absorption liquid is about 3% to 10%, though it varies depending on the combination of working refrigerants. In the figure, X _A represents the absorption liquid mass concentration (wt%) in the absorber, and X _G represents the absorption liquid mass concentration (wt%) in the distiller.

Next, the energy loss when the distiller 101 is regenerated will be described. FIG. 3 is a diagram showing the relationship between the required reflux amount and the required theoretical plate number for obtaining a refrigerant of constant purity. When the boiling point difference between the refrigerant and the absorbing liquid is not large, in order to regenerate the refrigerant at a high concentration, it is necessary to recirculate the condensed and liquefied refrigerant once again in the distiller 101. The larger the reflux, the larger the amount of heat required for regeneration, and the smaller the reflux ratio, the larger the number of theoretical plates required and the higher the height of distiller 101. Further, if the reflux is insufficient, the refrigerant does not evaporate sufficiently in the evaporator 104, and the coefficient of performance (COP) of the absorption heat pump decreases.

FIG. 4 is a diagram of the liquid-phase molar concentration and the vapor-phase molar concentration in the distiller, and the necessary minimum reflux ratio when the distiller is made sufficiently large can be obtained by drawing from the diagram.

That is, a perpendicular line is drawn on the X = Y line from the refrigerant molar concentration X _A of the absorbing liquid flowing into the distiller 101, and from this point, −q / (1−q) [q (Molar liquid fraction
of feed) is calculated from equation 1. ] The intersection of the straight line (q line: a raw material supply line or a rectification diagram auxiliary line for two components) and the vapor-liquid equilibrium line is the intersection of the concentration operation line and the recovery operation line. If the Y coordinate of this point is Y _A , the minimum reflux ratio is
Can be obtained by Here, Q _R inflow refrigerant 1
Amount of heat (kJ / mol) to make mol a saturated vapor, Δ
H _R represents the latent heat of vaporization of the refrigerant (kJ / mol).

[0033]

## EQU1 ## q = Q _R / ΔH _R

[0034]

[Number 2] (R / D) min = X D -Y A / Y A -X a reflux ratio determined in this manner, varies depending on the combination of working refrigerant, the order of about 0.1 0.9 Next to
The amount of reflux is about 1/10 to 9/10 of the amount flowing out to the evaporator 104.

Therefore, the ratio of the amount of the absorption liquid flowing into the distiller 101 and the amount of reflux is as follows.

For example, assuming that the amount of absorbing liquid flowing into the distiller 101 is 1 kg / s, the inflowing mass concentration of the inflowing absorbing liquid is 80 wt%, and the outflowing mass concentration is 85 wt%, the refrigerant generation amount at that time is 0.059 kg. / S, and assuming that the reflux ratio at this time is 0.5, the reflux rate is 0.0295 kg /
s. This corresponds to about 1/34 of the amount of absorbed liquid inflow.

In general, the thickness of a liquid film having a free surface is proportional to one third or more of the flow rate. Therefore, comparing the liquid film thicknesses at this time, it is one-third of 34. Approximately twice as much. Therefore, in order to allow the liquid film to flow down while having a free surface, the liquid film lower part of the lower part of the absorbing liquid inflow part is 3 times lower than the lower part of the liquid film lower part of the absorbing liquid inflow part.
About twice as much clearance is required.

FIG. 5 is a detailed vertical sectional view of an embodiment of the distiller. The distiller of this embodiment is constructed based on the above knowledge.

A distiller 1 is divided into a distiller lower part 2 and a distiller upper part 3 located thereabove. Reference numeral 4 denotes an absorption liquid heater, which is attached below the lower part 2 of the still. 5
Is a refrigerant condensing part, which is a part for condensing the refrigerant, and is located above the distiller upper part 3. Reference numeral 6 denotes an absorbent inlet, which is located between the lower part 2 of the still and the upper part 3 of the still. Reference numeral 7 denotes an absorbent outlet, which is attached to the liquid reservoir of the absorbent 8 of the absorbent heater 4. Reference numeral 9 denotes a refrigerant outlet, and an end portion located inside the still 1 is expanded to form a receiving port 9a. 10 is a packing, which is packed in the upper part 3 of the still, and in this embodiment, a regularly knitted wire mesh is used. Similarly, 11 is the packing, which is the bottom 2 of the still.
In this embodiment, granular Raschig rings are used. The particle size and length of this packing 11 are selected so that the packing 11 has a coarser mesh than the packing 10. That is, the fineness of the packing 10 is selected to be approximately one-third of that of the packing 11 based on the above knowledge. Along with this, the porosity of the filling material 11 is
Is larger than the porosity of (approximately 3 times). Reference numeral 12 denotes a cooling medium, which flows in the pipe inside the refrigerant condensing section 5.

In the above structure, when the absorbing liquid 9 flows into the still 1 through the absorbing liquid inlet 6, the absorbing liquid 9 is absorbed in the lower portion 2 of the still.
While flowing down between the filling materials 11 of FIG. Here, the absorbing liquid 8 is heated by the heat medium, and the vapor 12 containing a relatively large amount of the refrigerant is generated. Thereby, the absorbing liquid 8 is concentrated, and the concentrated absorbing liquid flows out from the absorbing liquid outlet 7.

On the other hand, the vapor 13 containing a relatively large amount of refrigerant still contains a large amount of absorbing liquid. The vapor 13 exchanges heat and mass with the absorbing liquid flowing down between the fillings 11 and gradually rises between the fillings 10 while gradually reducing the concentration of the absorbing liquid. At this time, the vapor 13 is the reflux 14 of the condensed refrigerant and the filler 1.
The heat and mass are exchanged between 0, and further, the temperature rises while increasing the purity of the refrigerant, and the heat is exchanged with the cooling medium 12 flowing into the refrigerant condensing section 5, and becomes the liquid refrigerant 15. A part of the refrigerant 15 recirculates into the distiller 1 again 14 and the rest flows out from the refrigerant outlet port 8.

In this embodiment, in order to improve the performance of the distiller 1, two packings 10 and 11 are individually selected at the upper part 3 and the lower part 2 of the absorbing liquid inlet 6 in the distiller 1 to absorb and A fine packing 16 is used above the liquid inflow portion 6, and a coarse packing 1 is used below the absorbing liquid inlet 6.
1 is packed. By using the fine packing 10 in the upper part 3 of the absorption liquid inlet 6 to the distiller 1, the amount of the reflux 14 is extremely smaller than the amount of the absorption liquid flowing in from the absorption liquid inlet 6. Even so, it is possible to efficiently exchange the heat substance with the vapor in the still 1.

Therefore, the height of the distiller 1 can be reduced, and the height of the absorption heat pump using the distiller 1 is also reduced. Therefore, the interior of the building or the house or the side thereof can be easily installed, and the installation height can be increased. Even if there are restrictions on the size, it becomes easier to comply with the installation restrictions.

Further, by using the coarse packing 11 in the lower portion 2 below the absorption liquid inlet 6, the absorption liquid having a large amount of flow-down obstructs the upward flow of the vapor 13 generated in the absorption liquid heater 4. Without doing so, the performance of the distiller 1 can be prevented from deteriorating.

FIG. 6 is a detailed vertical sectional view of another embodiment of the distiller. The same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. Above the absorption liquid inlet 6 to the distiller 1, there is a granular fine packing (for example, Raschig ring) 16
The lower portion 2 below the absorbent inlet 6 is filled with a filler 11 having coarser mesh than the filler 16 (also Raschig ring). Packing material 1 in the upper part 3 from the absorption liquid inlet 6 to the still 1
The fineness of the mesh 6 is 6
Approximately one third of one. A filling support 18 supports the filling 16.

With the above-mentioned structure, even if the amount of the reflux 14 is extremely smaller than the amount 9 of inflow of the absorbing liquid, the heat substance can be efficiently exchanged with the vapor in the still 1, and the height of the still 1 can be increased. It can be lowered, and the same effect as in the above embodiment can be obtained.

FIG. 7 is a detailed vertical sectional view of still another embodiment of the distiller. The same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In the lower part 2 of the absorbing liquid inlet 6, the cross-sectional area of the distiller 1 in the part where the packing 11 is packed is made larger than the cross-sectional area of the part where the packing 11 is packed in the upper part 3,
The same material is used as the filling material 11. That is, even if the same filling material 11 is used for the lower part 2 and the upper part 3, the heat mass exchange capacity per unit height is increased by increasing the cross-sectional area on the lower part side, and the distiller 1 of the lower part 2 is The same heat and mass exchange is performed as when the height is increased, and the same effect as that of the above-described embodiment can be obtained.

[0048]

As described above, according to the present invention,
It is possible to provide an absorption liquid regeneration system of an absorption heat pump capable of highly efficiently regenerating a working medium in which an absorption liquid evaporates, as in the case of using a natural refrigerant having a low global environmental load as the refrigerant.

Further, according to the present invention, by using the regeneration system for regenerating the working medium with high efficiency, the height of the system can be reduced, and the absorption heat pump which can be easily installed inside a building or a house is provided. can do.

[Brief description of drawings]

FIG. 1 is a cycle flow diagram of an absorption heat pump according to the present invention.

FIG. 2 is a diagram showing a relationship between a boiling point concentration (dew point temperature) of a mixed liquid and an absorption liquid mass concentration.

FIG. 3 is a diagram showing a relationship between a required reflux amount and a required theoretical plate number for obtaining a constant-purity refrigerant.

FIG. 4 is a diagram of a liquid phase molar concentration and a vapor phase molar concentration in a still.

FIG. 5 is a detailed vertical sectional view of an embodiment of the still.

FIG. 6 is a detailed vertical sectional view of another embodiment of the still.

FIG. 7 is a detailed vertical sectional view of still another embodiment of the still.

[Explanation of symbols]

1: Distiller 2, 17: Distiller lower part 3: Distiller upper part 4: Absorption liquid heater 5: Refrigerant condensing part 6: Absorbing liquid inlet 7: Absorbing liquid outlet 8: Absorbing liquid 9: Refrigerant outlet, 9a : Receptacles 10, 11, 16: Packing 12: Cooling medium 13: Steam 14: Reflux 15: Liquid medium 16, 18, 20: Packing 17: Irregular packing 19: Packing support 101: Distiller 102: Condenser 103: Refrigerant expansion valve 104: Evaporator 105: Refrigerant heat exchanger 106: Absorber 107: Absorbing liquid pump 108: Absorbing liquid heat exchanger 109: Absorbing liquid pressure regulating valve 110, 111, 112, 113, 114, 115 : Pipe 116: Absorption liquid heater 117: Condenser cooling water pipe 118: Cold water pipe

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F25B 33/00 F25B 15/00

Claims (2)

(57) [Claims] 1. A distiller that regenerates an absorbing liquid having a large boiling point difference with the refrigerant, and a distiller installed above the distiller to cool the refrigerant.
A refrigerant condensing unit for condensing and provided below the distiller
An absorption liquid heater that heats the absorption liquid to generate vapor, and the refrigerant condensed and liquefied in the refrigerant condensing unit is
The distiller is allowed to flow down to reflux and the absorption liquid is added.
As the steam generated in the heater rises in the distiller
Then, in the absorption liquid regeneration system using a working medium that also evaporates the absorption liquid at the time of regeneration of the absorption liquid, the distiller is provided in an upper part and a lower part located below the upper part.
Is divided into, the liquid absorbent inlet between the top and bottom of the distiller provided, packed fine filling of eyes on top than this absorbing solution inlet port, at the bottom than the absorbing solution inlet port, said Top filling
The absorbent regeneration system is characterized in that it is filled with a coarse filler having a porosity about three times as large as that of No. 2. A distiller for regenerating an absorbing liquid having a large boiling point difference with the refrigerant, a condenser for condensing the refrigerant, and the absorbing liquid.
It is equipped with an absorption liquid heater and an absorber that generate steam by heating, and the refrigerant that is condensed and liquefied in the refrigerant condensing part is distilled.
The absorption liquid heater is caused to flow down and reflux in the container.
So that the steam generated in
In the absorption heat pump using a working medium that also evaporates the absorption liquid when the absorption liquid is regenerated , the distiller is provided at an upper part and a lower part located below the upper part.
Is divided into, the liquid absorbent inlet between the top and bottom of the distiller provided, packed fine filling of eyes on top than this absorbing solution inlet port, at the bottom than the absorbing solution inlet port, said Top filling
Absorbing heat pump for absorbing liquid, characterized in that it is filled with a coarse filler having a porosity about 3 times higher than that of the above.