JPS6035076A - Reversible phase transfer composition of calcium chloride hexahydrate and potassium chloride - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to reversible liquid/solid phase transition compositions. In particular, the present invention comprises calcium hydrate and potassium chloride, and
6 during repeated cycles of melting and crystallization, characterized in that it consists of a mixture of 46-52% by weight of aClO, 5-8% by weight of KClO, and the balance (up to 100% by weight) of water.
The present invention relates to a reversible liquid phase/solid phase transition composition that reduces the formation of CaC1°J ice crystals other than hydrates.

The heat of fusion of various hydrated salt compositions is used to develop phase change materials (P
CM) is well known in the literature. Dr. M. Cirkes' ASHRAE Journal of September
er, in 1974” 5OLARENERGY
The paper entitled ``5TORAGE'' evaluates the thermal, physical, and other properties of PCM based on economics, usability, corrosiveness, toxicity, and potential for large-scale equipment use. compounds and their eutectics, some of which undergo several phase transitions into substances with different crystal structures;
aC14” 4 HzO+2 HzO with CaC1,
e 6H,0 is also included.

When the salt CaC1,.6HzO is heated to a temperature above 33°C, it completely dissolves in the crystallization water. On cooling four different crystalline forms, namely CaC1z .6 HzO and CaCl2@4■t.

The production of three crystalline forms is possible. If any of the 4H20 crystal forms are formed, the heat of fusion is much less than 46 cat/t.

(Substantially pure CaCl2 @ 6 HzO is approximately 46
Approximately 30℃ from emitting or absorbing cal/t of heat
undergoes a liquid/solid phase transition. ) Although CaC1, is relatively inexpensive, its disadvantage is the formation of four different crystal forms.

Swedish Patent No. 410 for Suppression of Tetrahydrate Crystal Formation During Repeated Cycles of Melting and Crystallization in Hydrated CaCl, Systems
No. 004 is a technical grade CaC1, (road salt) henoCa(OH)t, 5r (NO3h and
The addition of one or more rC12e 6HzO compounds is proposed. However, this patent specifically describes the relative amounts of each impurity in the industrial edge-loaded salt, and states that KCI as an impurity component in the industrial salt has no effect on the tetrahydrate bioactivity in the hydrated Ca C1x phase transition composition. Nor does it acknowledge the fact that it favors reduction.

It is now highly desirable according to the present invention to add a certain amount of KCI to the hydrated CaCl2 in order to substantially reduce the formation of crystalline forms other than CaC1*.6H20, so that after melting and crystallization, the formation of crystalline forms other than the hexahydrate form is highly desirable. It has been found that CaC1z/KCI mixtures can be modified such that the precipitation of the crystalline form is substantially reduced to almost zero. Moreover, the hydrated CaCl2/KCI composition of the present invention further has the advantage of being substantially cheaper than other PCMs. Specifically, the hydrated CaCl2/KCI composition of the present invention is composed mainly of hydrated CILC1* and mixed with KCI. The present invention represents a significant improvement in the aim of developing inexpensive reversible liquid/solid phase transition compositions. KCI is a hydrated CaC other than CaCl2/6H20 during heat storage recovery during coagulation of the composition.
1 is present in the hydrated CaCl2 in an amount effective to reduce crystalline phase formation. The composition of the invention consists of a mixture of 1.46 to 52% by weight of CaCl, 0.5 to 8.0% by weight of KCl and the balance (in an amount of 100 qb by weight) of HzO. The substance is Ca1l! 47 to 51% by weight and KCI
A mixture of 2.3 to 6.0% by weight with the remainder (up to 100% by weight) HzO is preferred. The most preferred composition of the present invention is 48.0-48.5% by weight of 1g CaCl, 4.0-4.7% by weight of KCI, and the balance (100% by weight).
HzO in an amount up to 100 Hz.

Salt hydrates generally exhibit three types of phase transition properties: eutectic, non-eutectic and gyudon melting. The most desirable property is eutectic, which occurs when the solid phase change composition (ratio of salt to bound water) is the same as the liquid phase composition, in which case the hydration/dehydration process is considered to be the same as the melting and solidification process. semi-congruent mel
ting) occurs when a substance has two or more frozen forms with different solid compositions and melting points. Substances B are those that transform into other hydrated forms before either completely melting or solidifying, and have a wide range of melting points. Furthermore, there is a temporary loss of heat storage capacity. Calcium chloride hexahydrate is an example of Gyudon W4J type PCM.

Non-eutectic substance (■ncongruently mel
ting material) is clearly visible when melting.
Phase: Produces saturated solution and precipitation of insoluble anhydrous salts. If the precipitate settles to the bottom of the vessel, the anhydrous salt will not completely hydrate upon cooling and some heat storage capacity will be lost during each solidification-thaw cycle, as seen for example with sulfurized sodium decahydrate.
Non-eutectic melting is a more serious problem as it results in continued loss of storage heat capacity.

"Additive" also includes additive precursors that are harmless to the action of the PCMs of the present invention. In particular, additives as referred to herein are either anhydrous or hydrated compositions of inorganic salts or precursors that form salts when added to hydrated calcium chloride.

There may be impurities within 3.0 wt qIDv in the phase change composition as long as they are not detrimental to the operation of the hydrated CaClt/KCI system of the present invention.

Impurities include, for example, alkaline earth metals or alkali metal chlorides such as LiCL NaCl, MgCl*, or CaS
Other calcium salts such as 04 may also be used.

The thermal storage compositions of the present invention are conveniently packed into individual packaging materials for use with solar heating systems. Examples of suitable packaging materials for the heat storage compositions described above are water-impermeable films or foils made of plastic and metal laminates. For example, U.S. Pat.
, No. 003, No. 426, an independent gas-filling plastic foam has also been proposed, which allows PCM to be contained within the air cells of the foam structure. Other useful packaging materials include concrete, metal or plastic containers, tubing, and the like.

The following example demonstrates the effect of KCI on suppressing the formation of glacial products in the CaC1,.6&0/KC1 phase change composition of the present invention.

Example 1 An aqueous solution containing 1 g of CaC 47.4% by weight was stirred, the 8832 was cooled, and CaC1 snow/6H was added to the solution. A significant amount of 0 crystals was produced. When 8.3f of KC1 powder was added and dissolved and equilibrium was reached (at 27.85°C), a small amount of the liquid phase was analyzed to find 5% by weight of CJLC1247.05% and KC1.
It was found to be IO, 95% by weight.

CaCl 55% by weight aqueous solution and KCI powder were added stepwise, allowing the system to reach equilibrium after each addition.

CaC1z 55% by weight solution 607.9f and powder KCI
Equilibrate at 29.02°C with the addition of 4.4f, and the liquid phase sample contains 49.32% by weight of 1g of CaCl and 96% of KCI O.
% by weight. Optical microscopy showed only hexagonal CaCl, 6H20 in the suspended solid phase.
The equilibrium temperature after adding CI9-1.2f is 29.35℃,
The liquid phase is CaCl1t 49.29% by weight and KCl0.95
% by weight. Optical microcasting involves CaC in a suspended solid phase.
Only the triclinic crystal of l2.4H30 was shown.

Further, add CaC1 55 Chongkei Chi aqueous solution and powdered KCI to obtain a KCI:CaC1 weight ratio of 1:50 and H2
A composition having a molar ratio of O: Ca C1x of 6:1,
The equilibrium melting point of CaC1*4H*O is 32.1°C and Ca
Equilibrium melting point of C1*6H10 (externally inserted) 29.2°C
I found out. Therefore, the molten CaCl2@6&O of the above composition
If the sample is to be cooled, it must be cooled by 2.9°C in temperature. During this time, it is possible to crystallize CaC1g.4H 0 before solidification of CaC1*.6H20 begins.

Example 2 In the same manner as in Example 1, 932 t of a 1,46,0% by weight aqueous solution of CaC and 69 f of powder KC were converted into solid CILC.
Equilibrium at 25.859 with 1*.6HsO10-. liquid phase CaCl2
A 55 wt% aqueous solution of 0CaC1z containing 45.28 wt% and 2.46 wt% KCI and powdered KC1 were added stepwise to form solid CaC1t6) (20 slurry to 28 wt%
．． Equilibration was carried out at 13°C, resulting in a liquid containing 48.73 weight % of CaCl* and 2.64 weight % of KCI. Furthermore, by adding a 55% by weight aqueous solution of CaCl2,
C in a solution containing 98% by weight and 2.43% by weight of KCI.
aCl2114 Hz0 equilibrium slurry (28,70℃)
I got it.

Furthermore, add concentrated CaCl2 solution and KCI powder to make KCI: C
aC1! Weight ratio 1:20 and Hz0:CaCl2
CaC1,·4H20 for a composition with a molar ratio of 6:1
The equilibrium melting point of CaCl2.6H20 was 30.1°C and the equilibrium melting point of CaCl2.6H20 (extrapolated) was 28.1°C. Therefore upper Lr
- A molten CaC1z.6H20 sample of the composition must be cooled by 2.0° C. in temperature to solidify. Meanwhile, CaCl2 @ 6 Before H20 starts to solidify, CaCl2
Crystallization of II 4&0 is possible.

Example 3 CaC saturated with KCI in the same manner as Examples 1 and 2
l244.0 wt% aqueous solution 8892 as CaCl2*
6 T (equilibrated at 20 and 2452 °C. The liquid phase was 244.16 wt.% CaCl and 3.16 wt.
It contained.

An aqueous solution containing 1.53.7% by weight of CaCl and 2.6% by weight of KCI was added stepwise, and KCI powder was added occasionally to form a slurry of solid CaCl2.6B20 and KCI of 27.26% by weight.
CaCl 1°48.21% by weight and KCI 4.
Equilibrated with a solution containing 19% by weight. Furthermore, CaC1t5
3.7 wt% and KCI 2.6 wt% solution and KC
Add I powder to solid CaC1z @ 4 Hz0 and KC
CaC148,21 at 27.91℃
% by weight and equilibrated with a solution having 4.48% by weight of KCI.

Add #CaC1z/KCI solution and solid KCI to the east,
It was found that if the weight ratio of KCI:CaC1 is maintained at 1:10, KCI is completely dissolved when the molar ratio of HzO:CaC12 is less than about 59=1.
CaC1, molar ratio 6:1 and KCl:CaCl2 weight ratio 1:10. : The equilibrium melting point of 4H20 is 28.0°C, and the equilibrium melting point of crushed CaCl2.6H20 is 27.3°C.

A liquefied sample of CaC1,.6H20 of this composition only needs to be cooled within a range of 0.7°C for solidification, during which time CaC1z
・6H! It is possible to crystallize CaCl2.4H20 before the start of coagulation.

Comparative Example As in Examples 1.2 and 3, but with K
Adding no CI Ca(::l) was tested for aqueous samples.

When KCI is not included at a Hz0:CaCl2 molar ratio of 6:1, the equilibrium melting point of CaCl2.4&O is 32.8°C, and that of CaCl2.6H20 is 29.6°C. Therefore, the molten sample of CaCl2.6H20 needs to be cooled to a width of 3.2 DEG C. During this time, CJLC12.4H20 can be crystallized before the solidification of CaCl,.6H2013- begins.

Summary of actual 111-3 and comparative examples CaC1z-4
Example 1 for the equilibrium mA of hydrates and 6-water (lj)
The results of ~3 and Comparative Example are summarized in Table 1.

Table ■ Effect of potassium cyclide on calcium chloride hydrate phase Wa
0 32.8 29.6 3.2℃ 9.45chi 1:5
0 32.1 29.2 2.9℃ 7.58%1:2
0 30.1 28.1 2.0℃ 5.88chi 1:1
0 28.0 27.3 0.7℃ 1.86chia-H
z0: CaC11 molar ratio 6:1b...This is an example of the present invention, that is, a comparative example.

Table ■ also shows CaCl2 and 4H2 that can be produced by coagulation.
The theoretical maximum amount of 0 is shown. This is Examples 1 to 3
The peritectic composition determined by the experiment described in the Comparative Example was calculated using the "Leverage 14-Method". Surprisingly, KCI addition is C
It has been found that simply decreasing the temperature at which aC12.4H20 is produced also reduces the amount of conversion to tetrahydrate.

Furthermore, in the experiments in Examples 1.2 and 3 above, when CaCl2.4H20 crystals are present, concentrated CaC
Each addition of the 1z solution required a much longer time to reach temperature and composition equilibrium than in the case of the comparative example, which did not contain KCI. This indicates that the kinetics of CaC1z·4H20 production is slow.

Patent applicant: The Dow Chemical Corporation 15-

Claims (1)

[Claims] 1. Contains hydrated CaC1z and KCI, and contains CaCl
CaC1z other than hexahydrate during repeated cycles of melting and crystallization characterized in that it consists of a mixture of 246 to 52% by weight of KCI O, 5 to 8% by weight and the balance (up to 100% by weight) of water. Reversible liquid phase/solid phase transition composition 2 with reduced hydrate crystal formation, containing 47-51% by weight of CaC1z, 2.3-6.0% by weight of KCI, and the balance (10% by weight).
A composition according to claim 1, consisting of a mixture with water (up to 0% by weight). 3. CaC1z 48.0 to 48.5% by weight and KCl
KCI in the composition □4, as defined in claim 1 or 2, consisting of a mixture of 4.0 to 4.7% by weight and the balance (up to 100% by weight) of water of CaCl
The weight ratio of H2O to (:aCl) in the composition is 1:50 to 1:10, and the molar ratio of H2O to (:aCl) in the composition is 6:
1, and the temperature at which CaCl2@6H2O can start crystallization is within 3°C. 5. The composition according to any one of claims 1 to 4, wherein the upper component contains impurities in an amount of 3% by weight or less.