JP2001289531A - Adsorbent for heat pump and heat pump system using the same - Google Patents

Abstract

(57) [Summary] An object of the present invention is to provide an adsorbent in which the heat of water adsorption in the water saturated adsorption region is larger than that of a conventionally known adsorbent in order to solve the problems of the prior art. And to provide a heat pump system using the same. A heat pump adsorbent is water adsorption heat moisture saturated adsorption region of the adsorbent is 1.2kcal / gH ₂ O or more, the heat pump adsorbent adsorbent made of a synthetic zeolite, the adsorbent MFI type A heat pump adsorbent comprising zeolite, and a heat pump system for heating using the adsorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorbent for a heat pump having a large heat of water adsorption in a water saturated adsorption region. The present invention also relates to a heat pump using an adsorbent, which has been difficult to realize with conventional natural or synthetic zeolites and other adsorbents. Heat pumps for heating can be used for many purposes, such as heating living and working spaces, producing hot water, keeping chemicals and preventing cooling.

[0002]

2. Description of the Related Art The idea of a heat pump using an adsorbent has been proposed for a long time. I. Tc
report by Hernev (Natural Zeol)
items, Pergamon Press, p. 479
-485, 1978 and Proceedings
of 5th International Zeol
Item Conference, Heyden, p.
788-794, 1980) have proposed a system that utilizes warm heat by the heat of water adsorption using natural zeolite, and uses cold heat by the latent heat of vaporization of water by water adsorption after dehydration by solar heat. Also, a report by Hiroshi Taota et al. (Solar Energy, vol. 8, No. 1, p. 28-3)
7 and vol. 8, no. 4, p13-22), studies on heat pump systems using synthetic zeolites of type A or X have been conducted. However,
None of these studies have been put to practical use.

In order to increase the efficiency of a heat pump using an adsorbent, it is premised that low-temperature regeneration or use of solar heat or low-temperature exhaust heat is used. This is because only an adsorbent having a small heat of adsorption at the time of re-adsorption was present.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an adsorbent in which the heat of water adsorption in the water saturated adsorption region is larger than that of a conventionally known adsorbent in order to solve the problems of the prior art. And to provide a heat pump system using the same.

[0005]

Means for Solving the Problems In order to solve the problems of the prior art, the present inventors have made intensive studies on the structure, composition, combination with the exchanged ion species of zeolite, and on the water adsorption characteristics. As a result, a zeolite having a large heat of adsorption in the moisture re-adsorption region after heating at a low temperature in the moisture saturated adsorption region, that is, in a moisture re-adsorption region was found, and it was found for the first time that this was applied to a heat pump system. .

[0006] The heat of adsorption of zeolite generally has a large initial heat of adsorption, regardless of the substance to be adsorbed, and gradually decreases as the amount of adsorption increases. The present inventors have found that, for some zeolites, the heat of adsorption, which has decreased with an increase in the amount of water adsorbed during the adsorption of water, increases again in the saturated adsorption region, and for the first time found that this is applied to a heat pump system. Invented the invention.

[0007] Zeolites are porous crystalline aluminosilicates of the general formula _{xM 2 / n O · Al 2} O 3 · ySiO 2 · zH 2 O ( where, n represents the valence of the cation M, x is 0 .8-1.
2, y is a number of 2 or more, and z is a number of 0 or more). Here, the cation M is bonded to compensate for the negative charge of the aluminosilicate skeleton. Generally, the cation M is an alkali metal, alkaline earth metal and / or organic cation, but can be easily exchanged for another metal cation.

[0008] In some cases, the ammonium type treated with mineral acids or ion-exchanged with an ammonium salt is heat-treated and used as the proton type. The skeletal structure of zeolite is a three-dimensional regularly bonded tetrahedron in which four oxygen atoms are coordinated around silicon and aluminum, sharing oxygen. Its crystal structure is characterized by an X-ray powder diffractogram, and many types are known. Zeolites have pores in the structure of about 3 to about 10 ° in size, and the pore size and pore structure are characterized by the type of zeolite.

The reason why the heat of water adsorption of the zeolite of the present invention becomes larger than that of other zeolites in the water saturated adsorption region is not yet sufficiently clear. Therefore, the type of zeolite used in the present invention is not particularly limited. In the measurement of the heat of moisture adsorption, any material having a heat of adsorption of 1.2 kcal / g H ₂ O or more in the moisture saturated adsorption region may be used. Further, the composition of the zeolite skeleton (SiO ₂ / A
(I ₂ O ₃ ratio), exchange cations, and exchange rates are not particularly limited. Since these zeolites generate a large amount of heat of adsorption, they are suitably used particularly as adsorbents for heat pump systems for heating.

The form of the adsorbent when these adsorbents are used in a heat pump system is not particularly limited. In the case of a small device, the fine crystal powder may be used as it is, or a method of applying an adsorbent slurry to the heat exchanger surface may be used. In a large-sized apparatus, since the amount of adsorbent charged is large, when the powder is charged, diffusion of water vapor is hindered, and it is difficult to efficiently adsorb moisture to all adsorbents.

Therefore, if a granulated adsorbent is used, the voids of the molded body serve as water vapor diffusion paths, so that moisture can be efficiently adsorbed and heat of adsorption can be recovered. Further, latent heat of evaporation due to sufficient water evaporation can be recovered. The shape of the granular compact is not particularly limited, and the shape and size are selected in consideration of the size and packing density of the container. The binder and the molding aid for molding are not particularly limited, but it is preferable to devise to increase the thermal conductivity in order to perform heat exchange efficiently.

The method for measuring the heat of adsorption of the adsorbent for a heat pump is not particularly limited, and may be obtained from a plurality of adsorption isotherms or may be directly measured using a calorimeter.

<Synthesis and Pretreatment of MFI-type Zeolite> Tetrapropylammonium hydroxide was added as a template agent to a sodium aluminosilicate gel slurry, and heated at 180 ° C. for 24 hours under autogenous pressure to obtain Si.
MFI-type zeolites with O ₂ / Al ₂ O ₃ ratio = 24.5 and 92 were synthesized. After washing and drying these zeolites,
The template was removed by baking at 00 ° C. Then one
Sodium ion exchange was performed using an N sodium chloride aqueous solution to prepare a Na ⁺ ion-exchanged MFI zeolite. The ion exchange rate was 99%, and the balance was H ⁺ ions.

[0014]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to these examples.

Example 1 SiO ₂ / Al ₂ O ₃ ratio = 24.
After the Na ⁺ ion-exchanged MFI type zeolite No. 5 was vacuum-heated at 400 ° C. for 6 hours, the amount of water adsorbed and the heat of adsorption were simultaneously measured by a thermal conductivity calorimeter connected to an adsorption amount measuring device. When the amount of water adsorbed is 7.0 wt%, the heat of adsorption is 0.
Although it was 93 kcal / g H ₂ O, the water adsorption amount was 8.
0 wt% and 9.0 wt% heat of adsorption when the were respectively 1.66 and 2.66kcal / gH ₂ O.

Example 2 A Na ⁺ ion-exchanged MFI type zeolite having a SiO ₂ / Al ₂ O ₃ ratio of 92 was heated in vacuum at 400 ° C. for 6 hours, and then heated with a thermal conductivity calorimeter connected to an adsorption amount measuring device. , The amount of water adsorbed and the heat of adsorption were measured simultaneously. The heat of adsorption is 0.8 when the amount of water adsorbed is 3.0 wt%.
Although it was 6 kcal / g H ₂ O, the water adsorption amount was 3.7.
The heats of adsorption at wt% and 4.3 wt% were 1.66 and 2.93 kcal / g H ₂ O, respectively.

<Comparative Example 1> Example of using NaA-type zeolite
The heat of moisture adsorption was measured in the same manner as in 1. The heat of adsorption when the water adsorption capacity is 15 wt% is 0.84 kcal / gH _2.
O. The saturated water adsorption capacity of this zeolite is 28
wt%.

<Comparative Example 2> The heat of water adsorption of a (Mg, Na) A type zeolite (magnesium ion exchange rate: 78%) obtained by subjecting NaA type zeolite to magnesium ion exchange was measured in the same manner as in Example 1. . Water adsorption capacity 20
The heat of adsorption at 0.8 wt% was 0.87 kcal / g H ₂ O.

<Comparative Example 3> Example of using NaX-type zeolite
The heat of moisture adsorption was measured in the same manner as in 1. The heat of adsorption when the water adsorption capacity is 25 wt% is 0.93 kcal / gH _2.
O.

Claims (4)

[Claims] 1. An adsorbent for a heat pump, wherein the adsorbent has a heat of water adsorption of 1.2 kcal / gH ₂ O or more in a water saturated adsorption region. 2. The method of claim 1, wherein the adsorbent comprises a synthetic zeolite.
The adsorbent for a heat pump according to the above. 3. The heat pump adsorbent according to claim 1, wherein the adsorbent comprises MFI type zeolite. 4. A heat pump system for heating using the adsorbent according to claim 1, 2 or 3.