JPH0627593B2 - Adsorption type heat pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention has a net-like structure having macropores having an apparent density of 0.1 to 0.8 g / cm ³ , a porosity of 50 to 90% and an average diameter of 1 to 500 μm. The present invention relates to an adsorption heat pump in a cooling mode and a heating mode in which an adsorption tower filled with structured activated carbon as an adsorbent and an evaporator and a condenser containing a working medium are connected to each other. It can be widely applied to the effective use of energy in the field or in high temperature fields such as hot water supply, heating, heating, and heat storage.

(Prior art and its problems) Adsorbent chemical heat pumps that use solid adsorbents
There is no need to use a power source such as a compressor, and it has the advantage that thermal energy at a relatively low temperature can be used as drive energy, and heat pumps using various adsorbents such as silica gel, activated alumina, zeolite, activated carbon have been investigated. ing.

Adsorption characteristics of these absorbents are determined in combination with various working media, and suitability as an adsorbent for heat pumps is evaluated.For example, in the zeolite-water system, a large pumping temperature difference can be taken, but regeneration is possible. , It is difficult to remove,
It has a drawback that the regeneration temperature must be increased to make a large difference in the regeneration temperature, and activated alumina also has a drawback similar to zeolite.

Further, the silica gel-water system can be regenerated by a relatively low heat source of 100 ° C. or lower, but has a drawback that a large difference in adsorption / desorption amount cannot be obtained.

By the way, the conventional activated carbon, when using water as the working medium,
When the relative pressure P / Ps (P: partial vapor pressure of water vapor, Ps: saturated vapor pressure of water) is around 0.5 to 0.6, the adsorption amount changes greatly, and the operating pressure is set over a large change in the adsorption amount. By taking on both sides, adsorption and desorption can be easily performed,
It is known to have an advantage that a large difference in adsorption / desorption amount can be obtained. On the other hand, however, since the operating pressure is large at a relative pressure of around 0.5 to 0.6, there is a serious drawback that the pumping temperature difference is small, which is a major obstacle to practical use.

Further, the above various solid adsorbents are usually used as powders or granules, so that the pressure loss is large, the movement of the substance to be adsorbed is not rapid, and the deviation of the adsorption amount distribution in the adsorption tower easily occurs. In addition to uneven filling of the adsorbent in the tower,
It is not preferable because the temperature is non-uniform and the heat transfer rate varies depending on the location in the adsorption tower.

The present inventor has completed the present invention as a result of earnest research to improve the above-mentioned drawbacks of the conventional adsorption heat pump.

(Means for Solving Problems) The present invention provides a reticulated structure activated carbon having an apparent density of 0.1 to 0.8 g / cm ³ , a porosity of 50 to 90% by weight, and macropores having an average diameter of 1 to 500 μm. It is an adsorption heat pump in a cooling mode and a heating mode in which an adsorption tower filled as an adsorbent is connected to an evaporator and a condenser containing a working medium.

The network structure activated carbon of the present invention has the following excellent features as compared with the conventional powdered activated carbon or granular activated carbon.

That is, the adsorption / desorption rate is extremely fast as compared with the granular activated carbon, and the adsorption / desorption can be completed in a short time. Since the packed state of the adsorbent in the packed tower is uniform and the air permeability is good, there is little variation in the adsorption amount distribution in the packed tower, and therefore the uneven temperature distribution is reduced, and the heat of adsorption and adsorption tower are removed. It is suitable for rapidly raising and lowering the temperature.

Further, the network activated carbon of the present invention has extremely fine pores with a maximum value of the distribution of the pore radius (r) of the micropores r <8Å or less by selecting the activation method, and has a specific surface area. The activated carbon can be about 500 to 1000 m ² / g.

The micropores of the invention are pores having a pore radius r ≦ 20Å, and the macropores are pores having a pore radius r> 100Å.

Now, the synthetic resin composite porous body as a precursor for producing the reticulated structure activated carbon used in the adsorption heat pump of the present invention is described in, for example, JP-B-58-54082 and JP-A-57-58.
It can be produced by the method disclosed in JP-A-51109, JP-A-57-11809 or the like, or any other known method. The polyvinyl alcohol resin and the phenol resin or melamine resin are reacted with the pore-forming material to complete the reaction. After that, the pore forming material may be removed.

The synthetic resin composite porous body has a maximum value of the distribution of the pore radius (r) r <
It becomes 8 Å, and the amount of water adsorbed in the region where the relative pressure is low can be made large reticulated structure activated carbon.

The limited activation condition is activation at a temperature of about 700 ° C. or lower in an oxidizing atmosphere such as a steam atmosphere or an air atmosphere. For example, in a steam atmosphere
Temperature range of 500-700 ℃, 250-500 in air atmosphere
An activation temperature of about 0 ° C is suitable. If the activation temperature is too high, the pore size of activated carbon after activation becomes too large, and the amount of adsorbed water in the region of low relative pressure is significantly reduced, which is not preferable.

Usually, the pore volume and pore size distribution of an adsorbent having fine pores such as activated carbon and silica gel are obtained from the adsorption isotherm of nitrogen gas, ethane gas, butane gas and the like. Most commonly, by using nitrogen gas as the adsorption gas and helium gas as the carrier gas, cooling to liquid nitrogen temperature and determining the relationship between the adsorption amount of nitrogen gas in the pores of the adsorbent and the nitrogen partial pressure An adsorption isotherm is obtained.

As a method for obtaining the pore volume and the pore radius from the adsorption isotherm, the Kelvin equation based on capillary condensation is proposed, and the analysis based on this equation is generally performed.

P, saturated vapor pressure P _O when the adsorbed gas condenses in the pores, saturated vapor pressure γ of the adsorbed gas under normal conditions, surface tension V, one molecular volume R of liquid nitrogen, gas constant T, absolute temperature r _K , Kelvin radius of pores The Kelvin radius of pores needs to be corrected for adsorption other than capillary condensation.For example, there is a method to correct only the adsorption amount of the monolayer in Higuchi, or a correction method using the Halsey equation. It is often used. Strictly speaking, the applicable range of the Kelvin formula based on capillary condensation is said to be about 20 Å to 300 Å as the pore radius, but a strict pore radius measurement method to replace the Kelvin formula has not yet been established, and the pore radius is 20 Å or less. In the domain of, the analysis applying the Kelvin equation is often used. The analysis of the pore radius and the pore diameter distribution in the present invention is an application of the Kelvin equation together with its commonly used correction method.

Now, FIG. 1 shows the results of adsorption isotherms of commercially available granular activated carbon and the network activated carbon of the present invention to water. Although FIG. 1 shows the measurement results at 20 ° C., almost the same adsorption isotherm was obtained by the measurement at 50 ° C. and 70 ° C.

Conventionally, activated carbon, unlike silica gel and zeolite, is a non-polar substance, so as shown in FIG. 1A, low relative pressure (P
/ Ps 0.5 or less), it is known that the amount of adsorbed water is extremely small. However, the inventors of the present invention have found that the maximum value of the distribution of the pore radius (r) is r <8Å as a result of diligent examination of the composition of the activated carbon having a network structure and the activation conditions.
As shown in (3), the present invention has found an extremely suitable activated carbon as a heat pump adsorbent having a large water adsorption amount under a low relative pressure.

As the working medium of the adsorption heat pump, in addition to water, alcohols such as methanol, ethanol, butanol, cyclohexanol and benzyl alcohol, ammonia, acetone or aromatic hydrocarbons such as benzene, toluene and xylene can be used. . Among these working media, water has the largest latent heat of vaporization of about 10 Kcal / mol, and is most preferred as the working medium in the temperature range of 0 ° C to 100 ° C. In the low temperature range of 0 ° C. or lower, lower alcohols such as methanol and ethanol are suitable as the working medium, and in the high temperature range of 100 ° C. or higher, high boiling point hydrocarbons such as cyclohexanol, benzyl alcohol and xylene are suitable. The adsorption heat pump has an advantage that it can use a low temperature heat source of relatively low temperature of 50 to 100 ° C. and that it can regenerate and store heat of the adsorbent at the same time by utilizing solar heat and the like. Water is the most suitable working medium for the cool heat pump. Therefore, a case where water is used as the working medium will be described below as an embodiment.

(Effects of the Invention) FIGS. 2 (1) and 2 (2) are schematic views of the adsorption heat pump in the cooling mode and the temperature rising mode using the network structure activated carbon of the present invention.

In the cooling mode shown in FIG. 2 (1), first, the evaporator and the adsorption tower are connected to each other so that the working medium is evaporated from the evaporator and adsorbed by the adsorbent until a predetermined adsorption amount is reached. At this time, the temperature of the evaporator is lowered by the evaporation of the working medium, and the water having the ambient temperature Ta can be lowered to Tcold through the heat exchanger. When the adsorption amount of the working medium reaches the specified amount, switch the valve, connect the adsorption tower and the condenser, and set the heat source temperature to the adsorption tower.
Hot water of Ts is flowed to raise the temperature, the working medium is desorbed and condensed in the condenser. When the desorption is completed, the valve is switched to return to the first adsorption process again.

In the case of the temperature raising mode shown in Fig. 2 (2), first, the evaporator and the adsorption tower are connected, and the working medium is adsorbed to the adsorbent while flowing hot water of the heat source temperature Ts to both, and adsorption by the adsorption heat is performed. The temperature of the tower is taken out by heat exchange and the temperature of the hot water can be raised from the heat source temperature Ts to T _hot . After the adsorption amount in the adsorption tower reaches a predetermined amount, the valve is switched and the working medium is desorbed from the adsorbent and condensed in the condenser at the temperature Ta. After the adsorption is completed, the valve is switched to return to the adsorption process.

FIG. 3 shows a relative pressure P / Ps (P, steam partial pressure, Ps, saturated steam of water) showing an equilibrium relationship between the working medium and the adsorbent when water is used as the working medium in the adsorption heat pump of the present invention. The pressure) -temperature diagram is shown.

When water is used as the working medium in the reticulated structure activated carbon of the present invention, the relative pressure P / Ps = 0.05 to 0 on the low pressure side (desorption side) of the operating pressure range from the adsorption isotherm of FIG. 1B. .25,
The pressure can be selected from about 0.25 to 0.50 on the high pressure side (adsorption side), and preferably the relative pressure P / P on the low pressure side (desorption side).
s = 0.05 to 0.20, relative pressure P / Ps on the high pressure side =
It can be set to about 0.25 to 0.40.

For example, when cooling water at 20 ° C, the high pressure side (adsorption side)
Assuming the relative pressure at P / Ps = 0.30, the temperature can theoretically be reduced to 2 ° C if the loss due to heat exchange is neglected from the equilibrium relationship between points in Fig. 3, and the cooling width Is 18 ° C. However, in the case of the conventional activated carbon, the adsorption isotherm shown in FIG. For example, the relative pressure on the high pressure side (adsorption side) is P
When /Ps=0.60 is set, the theoretically attainable temperature is 12 ° C. and the cooling temperature range is 8 ° C. due to the equilibrium relationship between points in FIG. 3, and the cooling effect of the heat pump of the present invention is extremely large. I understand. Similarly, even in the heating mode, if the operating pressure on the adsorption side is set to P / Ps = 0.30 using the activated carbon of the present invention, theoretically possible pumping temperature ignoring heat transfer loss. 2 with hot water at 60 ℃
It is possible to raise the temperature to 8 ° C (Fig. 3 ~), that is, to 88 ° C. Using conventional activated carbon, the operating pressure is P / Ps on the adsorption side.
This is significantly higher than 12 ° C. (= 0.60) (see FIG. 3).

The adsorption-type heat pump of the present invention, which uses the network structure activated carbon as an adsorbent, can have a large cooling temperature range and a large heating temperature range as described above, and can significantly improve energy efficiency.

Further, the network structure activated carbon of the present invention has an extremely high adsorption / desorption rate and can complete adsorption / desorption in a short time. In addition, the packed state in the packed tower is uniform and the air permeability is good, there is little variation in the adsorption amount distribution in the packed tower, uneven temperature rise is less likely to occur, the adsorption heat is taken out, and the adsorption tower rises. The temperature can be quickly lowered.

Furthermore, in the adsorption heat pump of the present invention, since the regeneration temperature of the network structure activated carbon that is the adsorbent can be performed at a relatively low temperature level of 60 to 90 ° C, it can be regenerated by utilizing solar heat energy, In that case, it is also possible to use the network structure activated carbon as a heat storage material and use the accumulated heat for heating or a hot water supply system.

Hereinafter, a specific description will be given with reference to examples.

Example 1 After dissolving 5 kg of polyvinyl alcohol having a degree of polymerization of 1700 and a degree of saponification of 88% in hot water, 3.2 kg of potato starch was added and heated to gelatinize. A water-soluble resol resin having a solid content concentration of 60% by weight (BRL-2, a product of Showa Highpolymer Co., Ltd.) was added to the solution.
854) Add 17 kg and stir well, then 37%
9 kg of formalin and 3.5 kg of 30% by weight oxalic acid were added and uniformly mixed, and water was added to adjust the liquid volume, and the total liquid volume was set to 100. This mixed solution has an inner diameter of 120φ x 700 mm
It was cast in a L mold, reacted at 60 ° C. for 24 hours, and then washed to obtain a PVA / phenolic synthetic resin composite porous body.

The synthetic resin composite porous body was placed in an electric furnace, heated to 650 ° C. at a heating rate of 30 ° C./hr, and activated in a steam atmosphere for 5 hours to obtain a reticulated structure activated carbon. The network activated carbon has an apparent density ρ = 0.21 g / cm ³ , a porosity of 87%, an average diameter of macropores of 100 μm and a pore radius of micropores.
The maximum of the distribution of (r) was r <8Å.

FIG. 1B shows the measurement result of the adsorption isotherm of water at 20 ° C. by the above-mentioned network activated carbon. The adsorption isotherms at 50 ° C. and 70 ° C. were also almost the same as those at 20 ° C. when the horizontal axis was arranged by relative pressure P / Ps.

An experiment was conducted to obtain cold heat by the heat pump shown in FIG. 2 using the above-mentioned network structured activated carbon.

The operating condition of the experiment is that the water adsorption amount of the network structure activated carbon in the adsorption tower is 0.05 g / g during desorption and 0.20 during adsorption.
It was set to be g / g. The corresponding operating pressure range is relative pressure P / Ps = 0.12-0.30. The temperature of water used for cooling is Ta = 20 ° C.

First, water at 20 ° C. was flown into the evaporator, the valve was opened, and the water vaporized from the evaporator was adsorbed by the activated carbon having a network structure in the adsorption tower. By this operation, the water temperature at 20 ° C was lowered to 6 ° C.
From the equilibrium relationship in Fig. 4, theoretically, the temperature range up to 2 ℃ is 18
Although it is possible to lower the temperature by ℃, in this experiment, the temperature decreased by 14 ℃ due to heat transfer loss. After adsorbing for 40 minutes, the valve was switched to connect the adsorption tower and the condenser, and hot water was flowed to the adsorption tower to desorb from the adsorbent and condense it in the condenser. The temperature Ts ₁ of hot water required for desorption is 59 ° C. according to the equilibrium relationship of FIG. 4, but in this experiment, desorption was performed for 40 minutes by flowing hot water of 65 ° C. in consideration of heat transfer loss. From the results of this example, FIG.
It was possible to cool water at 20 ° C. to 6 ° C. by using a network structure activated carbon that exhibits an adsorption isotherm of water as shown in FIG.

[Comparative example]

Commercially available granular activated carbon (particle size 10-32 mesh, specific surface area 1,
The adsorption isotherm of water having a density of 080 m ² / g and a packing density of 0.45 g / cm ³ was as shown in FIG. 1A. Using this granular activated carbon, an experiment was conducted in the same manner as in Example 1 to obtain cold water using a heat pump. The amount of adsorption was set to 0.05 g / g during desorption and 0.20 g / g during adsorption as in Example 1. The corresponding operating pressure range is P / Ps = 0.42-0.6
It was 1.

The equilibrium relationship of adsorption and desorption operation with this commercially available granular activated carbon is described in
Shown in the figure. As can be seen from FIG. 5, the temperature range that can theoretically be lowered is 7.5 ° C., and warm water at 20 ° C. can be lowered to 12.5 ° C., but actually it could be lowered only to 16 ° C. The adsorption operation was performed for 40 minutes, after which the adsorption tower and the condenser were connected, and desorption was performed with warm water at 65 ° C. for 20 minutes.

From these results, it was found that the temperature range of cooling can be widened by using the network structure activated carbon of the present invention.

Example 2 Using the same reticulated activated carbon as in Example 1, a heat pump temperature rising experiment was conducted. The evaporator and the adsorption tower were heated with hot water having a heat source temperature (Ts2) of 62 ° C., and the water evaporated from the evaporator was adsorbed by the activated carbon having a network structure. The operating conditions are the same as in Example 1, and the adsorption amount is 0.05 (P / Ps = 0.12) to 0.20.
It was set to g / g (P / Ps = 0.30).

The adsorption equilibrium relationship under the conditions of this example is shown in FIG.
The heat source temperature of 62 ° C. can theoretically be raised to 90 ° C. by 28 ° C., but in the present example, it was possible to raise 13 ° C. from 62 ° C. to 75 ° C. by the adsorption time of 40 minutes. . Desorption was carried out by connecting an adsorption tower and a condenser and passing water at 18 ° C. through the condenser for 40 minutes.

[Comparative Example 2] In the same manner as in Example 2, using the commercially available granular activity used in Comparative Example 1, a temperature rising experiment by a heat pump was performed. The operating range of the heat pump is the same as in the case of Comparative Example 1, and the adsorption amount is 0.05 (P / Ps = 0.42) to 0.20 (P / Ps =
0.61) and the heat source temperature was 62 ° C.

From the equilibrium relationship shown in FIG. 5, the theoretically attainable temperature of the heat pump using the commercial granular activated carbon as the adsorbent is 71.
The temperature range is 5 ° C and the temperature range in which the temperature can be raised is as small as 9.5 ° C. In this experiment, adsorption was carried out for 40 minutes, and the temperature of the hot water actually obtained was 66 ° C. The desorption was performed by connecting the adsorption tower and the condenser and passing water at 18 ° C. through the condenser for 20 minutes.

[Brief description of drawings]

FIG. 1 is an adsorption isotherm diagram for water of commercially available granular activated carbon and reticulated activated carbon according to the present invention, and FIG. 2 is an adsorption heat pump in cooling mode and heating mode using the reticulated activated carbon according to the present invention. Schematic and FIG. 3 are relative pressures (P / Ps) representing the equilibrium relationship between the working medium and the adsorbent when water is used as the working medium in the adsorption heat pump of the present invention.
-Temperature diagram, Fig. 4 is an equilibrium relation diagram of the reticulated activated carbon-water heat pump according to the present invention, and Fig. 5 is an equilibrium relation diagram of the commercial granular activated carbon-water heat pump.

Claims (3)

[Claims] 1. An adsorption tower filled with as an adsorbent a network structure activated carbon having an apparent density of 0.1 to 0.8 g / cm ³ , a porosity of 50 to 90% and an average diameter of 1 to 500 μm. Adsorption heat pump in cooling mode and heating mode, which is formed by connecting an evaporator and a condenser containing a medium. 2. The network activated carbon has a micropore radius (r) of micropores.
Adsorption pump according to claim (1), wherein the maximum value of the distribution of r is less than 8 Å 3. The claim (1), wherein the working medium is water.
Heat pump of paragraph (2)