JPH01163286A - Hydrated calcium chloride-containing composition for accumulating and recovering heat due to phase change at about 20 degree and production thereof - Google Patents

Abstract

PURPOSE: To obtain the subject composition having most suitable latent heat and used in cattle stall and agricultural greenhouse by including calcium chloride (specified hydrate), ammonium chloride, potassium chloride, potassium nitrate and water.

CONSTITUTION: The composition contains (A) calcium chloride of which total moles of deficient water content based on the necessary water quantities to crystallize in the form of 6-hydrate is 1-12% (preferably 3-8%), (B) ammonium chloride, (C) potassium chloride, (D) potassium nitrate and/or ammonium nitrate and (E) water. The anhydrous calcium chloride to total moles components A-D converted as the anhydrous chloride is preferably regulated to 60-75 mol.%.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is suitable for use in a liquid-solid phase at a temperature of about 20° C., for example at home, in an industrial building, in a livestock farm or in an agricultural greenhouse. Compositions containing "moderately hydrated calcium chloride", ammonium chloride, potassium chloride, and ammonium nitrate and/or potassium nitrate to contemplate maximum heat accumulation and release by transformation. The compositions of the invention can also be used for temperature stabilization of industrial buildings. The composition of the invention, its method of preparation and its thermophysical properties are described below.

[Conventional technology]

Heat storage compositions made from calcium chloride hexahydrate have already been described for their applications, but the heat storage temperature and heat recovery temperature are too high for these applications. Thus French Patent No. 79/13296, US Pat. No. 4,273,390, European Patent Nos. 0019573 and 0063348 relate to heat storage compositions whose initial melting point is of the order of 27-28°C.

Belgian patents 902448 and 902449 further disclose the development of heat storage compositions whose melting points are approximately 23.5°C and 24.5°C, respectively.

The addition of diatomaceous earth is recommended in the above two patents. Said diatomaceous earth was first mentioned in said French patent 79/13296. The recommendation of the two patents is that diatomaceous earth protects against the danger of phase separation, which can lead to the formation of undesirable calcium chloride tetrahydrate.

It is also possible to lower the melting point of the above compositions by adding a slight excess of water. However, this method results in an increase in the melting range of the composition and, moreover, significantly reduces the amount of heat recovered.

Finally, French Patent No. 84/13329 discloses compositions containing calcium chloride hexahydrate, which contain as essential additives ammonium chloride and potassium nitrate or nitrite. This composition has an initial melting point of 20.
Although it is true that 4°C is exhibited, the latent heat of fusion/solidification consumption on the order of 135 J/g results in a melting point range of 17-21.5°C. In contrast, the latent heat of fusion/solidification of calcium chloride hexahydrate is on the order of 170 J/g.

[Disclosure of the invention]

Therefore, the present invention essentially uses calcium chloride and water as a base, and further contains ammonium chloride (N Ht CE'),
Potassium chloride (KC7'), ammonium nitrate (NH
4No. 3) and/or potassium nitrates (INOs), which compositions have an optimal latent heat and achieve heat storage and recovery at temperatures of the order of 20°C. .

The composition of the present invention is characterized in that the total molar amount of water to be deficient with respect to the amount of water required for crystallizing all of the calcium chloride in the form of hexahydrate is 1 to 12%, preferably 3 to 8%. %. The above components of the composition, along with diatomaceous earth optionally added as a stabilizer, account for more than 98% by weight of the composition, with the remaining approximately 2% being various impurities such as sodium chloride (which is generally calcium chloride) and a nucleating agent as an optional additional ingredient. The beneficial effect of water starvation is evidenced by the curves representing the change in specific heat under constant pressure (Cp) as a function of temperature and the change in enthalpy ΔH as a function of T. It is also proved by the synthetic curve. The curves are shown in Figure 1, which relates to the measurements of the compositions shown in Table 1 below.

1”21 (The calorimeter used for measurement is Setaram type.
SC1) 1 apparatus ), and the sample amount is 1
It is on the order of 60 ■, and the temperature rise rate is 3 per hour.
It is ℃. ) Sample S31 in the above table is a control for comparison and does not fall within the scope of the present invention.

In the Cp = f (T) curves, notice the difference in the appearance of the calorimeter signal before reaching the melting point identified by the intersection of the baseline and the "tangent to the first inflection point". Probably. This region (shaded region on the Cp=f(T) curve) is a region of less influence, but an increase in this region is related to water loss. It is indicated as "lag (initial part)".

The curve shows the change in enthalpy as a function of temperature as shown for the case of low water deficit obtained for calcium chloride pore hydrate. or in the presence of excess water, in which case the sudden increase in Cp at the melting point becomes a gradual increase (division).
This changes to S31 and 33 in Figure 1.
This is clearly demonstrated by a comparative experiment with 6. The essential importance in the present invention is that the change in enthalpy for a given temperature interval is considerably smaller in the presence of excess water.

Furthermore, the amount of heat corresponding to lag and ΔH1ag is considered to be proportional to the "relationship missing water expressed by the following relational expression": Δn/n = (nH2O-n theoretical value)/n theoretical value However, above In the formula, n theoretical value=6.

Another way to quantify the magnitude of lag in the above text is to relate ΔHlag to the total recovered heat measured over a temperature range of 15 to 24° C., for example. Under these conditions a quotient on the order of 15% was obtained for composition 336 and a quotient on the order of 40% for composition S31.

Therefore, reducing the size of the lag by reducing the amount of water required below the stoichiometric amount for calcium chloride hole hydrate is an original and important aspect of the present invention.

The amount of calcium chloride introduced into the composition according to the invention depends on the anhydrous components, namely Caα2, KCl, N84NO3
and/or) expressed as the mole percentage of anhydrous calcium chloride to the total number of moles of KNO3, this value is between 60 and 7
The value is expressed as , which can vary within a range of 5%.

FIG. 2 shows the total enthalpy values obtained (calculated at 15 DEG -24 DEG C.) and the associated enthalpy values corresponding to lag as a function of the amount of anhydrous calcium chloride described above.

EXAMPLES Representative examples of the present invention are shown in Tables 2 and 3 below, which are a summary of the results obtained in practice and also a summary of the corresponding practice conditions.

Table 2 Table 3 Calcium chloride used in the preparation of the compositions of the invention may be obtained from any source, but advantageously may be a commercial product, particularly of industrial grade; The composition of any hydrate must be well defined so that, in accordance with aspects of the present invention, the total amount of water present in the composition can be precisely controlled.

One advantage of using technical grade calcium chloride is that products of this grade generally contain sufficient amounts of impurities, such as, inter alia, strontium chloride, which advantageously achieves the crystal nucleation action of the calcium chloride pore hydrate. It is known to do so.

The apparent calorimetric signal Cp = f (T) can be more or less (combined). A feature of the compositions of the invention is that they have at most two well-separable peaks, These correspond to two phases with melting points close to each other, the relative importance of which can be varied as desired.

Figures 4.5.6 and 7 show some examples of Cp curves obtained with the present invention.

Figure 4 is a comparison diagram, where curve S00 is for the composition according to the already mentioned French patent No. 84/13329, curve S35 is for KC.
1' and NH, , (J, but containing neither NH4NO3 nor KNOs, respectively, these correspond to the other compositions namely 333, S34 and S2
Similar to No. 7, this is a composition in the presence of 3% depleted water. (&
The Il products S33, S34 and S27 have their NH4
N03 content is 0.06, 0.05 and 0, 1024 respectively
Same as composition S29 in Table 1 except that it is molar. ) The main point of the composition is that it has a eutectic character and a melting point of 19.6-20°C. Through repeated experiments of sequential melting and crystallization, the above melting point range is within the measurement accuracy limit (plus or minus 0.5°C).
) and that the composition is stable.

FIG. 5 represents the concave curves corresponding to compositions S53.355, S58 and S62, for which the missing water (moles) is 8%.
It is. (Compositions S53, S58 and S62 have NH, NO contents of 0.08, 0.12 and 0.0, respectively.
Same as composition S55 in Table 4 except that it is 16 moles. ) The curves confirm the existence of "eutectic with the same melting point" as the main phase. A precise analysis of the enthalpies associated with these respective peaks allows determining the influence of the relative proportions of each component NH4N0:+, K(J! and NH,CI!).

In the compositions of the invention, the initial ratio of the total number of moles of ammonium nitrate and/or potassium nitrate to the total number of moles of ammonium chloride and/or potassium chloride is 0.
It can vary within the range of 2 to 0.95.

Furthermore, the amount of potassium ions relative to the amount of ammonium ions can vary within the range of 0.3 to 1.2.

The curve of FIG. 6 shows a composition further comprising a high content of NH, (IJ!) and an initial ratio of (n KNO3/n NH<C1) of 0.20 to 0.35. The composition of these compositions is shown in Table 5, which relates to the use of 1 mol of anhydrous Caα2.

The first peak predominates to the greatest degree; furthermore, the corresponding melting point is well determined and is equal to 19.7°C (plus or minus 0.5°C), which was already seen from Fig. 4. That's true. The presence of KCl affects the width of the second peak [e.g. (n K(j/n
When KNOz) = 0.75, the melting end point is 21.5
°C, and in the absence of KCI' it is 22.8 °C]
.

The curves in Figure 7 (see also Table 5) are NH,CI'
This corresponds to cases where the content rate is low, and generally the missing water value is high (5% or more), (n KN (h/n
The value of NH4NO3) is 0.30 to 0.95. 8th
and Figure 9 are the corresponding enthalpy curves ΔH= g (
T), and the curves overlap. 0℃～30℃
Repeated experiments with sequential melting and crystallization confirmed the presence of slight slopes and highly reproducible plateaus.

Furthermore, similarities in experiments with additives based on NH4NO3 and KNO revealed the effect of NO3 ions. That is, regardless of whether NO ions are bonded to potassium ions and/or ammonium ions, the effect is achieved as long as the ratio is within the above range.

The invention is also directed to methods of making the compositions of the invention.

The process involves first preparing an aqueous solution of potassium chloride, ammonium chloride, and potassium nitrate and/or ammonium nitrate, to which is added the required amount of anhydrous or partially hydrated calcium chloride, provided that the required amount is added after the preparation. The solution is calculated to have the desired molar deficit of water and further includes optionally adding the required amount of diatomaceous earth and nucleating agent at the end of the manufacturing operation.

In a first step, the exact amount of water required to prepare the composition of the invention must be calculated as a function of the number of moles of Caα2 to be introduced into the composition. If you use CacI! ,
If is already partially hydrated, e.g. Cacl
! The amount of water already present in the calcium chloride should be taken into account when It's obvious.

Weigh each of the anhydrous salts necessary for producing this composition (taking into account the possibility of impurities in the case of industrial chemical-related salts),
Add the required amount of water according to the calculation method above and stir the mixture to dissolve all ingredients.

This operation is highly endothermic, with KC7', NH, α,
KNO3 and NH4N0. The heat of solution of is highly negative for all of the four compounds. After that, under constant stirring, CaCJ! Add the calculated amount of 2.XH,O (this operation is highly exothermic) and add any required amount of diatomaceous earth. The sequence of these operations must be closely monitored if the difficulties associated with dissolving anhydrous salts into calcium chloride permanents are to be avoided, as well as the risk of formation of calcium chloride tetrahydrate. must be done.

The viscosity of the mixture can be adjusted by varying the proportion of diatomaceous earth, which proportion does not exceed 12% by weight relative to the total composition. ? Samples for measurements by &N calorimeter are taken at 30-35° C. and subjected to standard treatments to adjust the thermophysical properties of the resulting solution.

The produced composition is then immediately packaged in an impermeable container suitable for the intended use, thus avoiding the risk of subsequent uncontrolled changes in the total water content of the composition.

[Brief explanation of the drawing]

FIG. 1 of the accompanying drawings shows compositions 329, S32, S36 of the invention and control composition S31 corresponding to the data in Table 1.
A curve representing the change in specific heat under constant pressure (Cp) as a function of temperature T and a curve representing the change in enthalpy ΔH as a function of temperature T are shown for . Regarding calcium chloride hexahydrate, in the case of excess water presence (S31), the rapid increase in Cp at the melting point temperature changes to a gradual increase. FIG. 2 shows the total enthalpy value and its associated enthalpy value corresponding to lag. FIG. 3 shows curves representing the change in specific heat for each composition S66, S67.369 corresponding to the examples of the invention (Table 3). Figure 4 shows the C9 curve of the compositions of the invention (S27, S33.534) compared to the control compositions (S00 and 535), in which the compositions have a eutectic character and 19.
It is found that it has a melting point of 6-20°C. FIG. 5 shows composition S53. of the present invention. S55, S58
, C9 curves for S62 are shown, and the curves prove the existence of a eutectic with the same melting point as the main phase. FIG. 6 corresponds to the data in Table 5 and shows a curve representing the influence of the presence of salts. Figure 7 corresponds to the data in Table 5 and shows NH, CI! shows a curve representing the influence of Figures 8 and 9 show the corresponding enthalpy curves ΔH=g
(T) is shown. Figure 2 Anhydrous (, acQ2% Figure 4 Temperature 0C Figure 5 Temperature ℃

Claims (6)

[Claims] (1) In a composition containing calcium chloride, ammonium chloride, potassium chloride, potassium nitrate and/or ammonium nitrate and water for heat storage and recovery by phase change at a temperature of about 20°C, all of the calcium chloride is A composition as described above, characterized in that the total molar amount of water lacking in relation to the amount of water required for crystallization in the form of the hexahydrate is from 1 to 12%, preferably from 3 to 8%. (2) The amount of calcium chloride, i.e., the "amount of anhydrous calcium chloride expressed in mol%" relative to the total number of moles of the initial anhydrous components, i.e., calcium chloride, ammonium chloride, potassium chloride, potassium nitrate, and/or ammonium nitrate, is 60
The composition of claim 1, wherein the composition is 75%. (3) The initial ratio of the total number of moles of ammonium nitrate and/or potassium nitrate introduced to the total number of moles of ammonium chloride and/or potassium chloride is 0.20 to 0.95.
The composition according to claim 1 or 2. (4) Any one of claims 1 to 3, wherein the amount of potassium ions relative to the amount of ammonium ions is 0.30 to 1.20.
Compositions as described in Section. 5. The composition of claim 1 further comprising at least one nucleating agent and a thickening agent such as diatomaceous earth in an amount up to 12% by weight of the composition. (6) In the method for producing the composition according to any one of claims 1 to 5, an aqueous solution of potassium chloride, ammonium chloride, and potassium nitrate and/or ammonium nitrate is first prepared, and then a necessary amount of anhydrous or partially hydrated calcium chloride, the required amount being calculated so that the solution after preparation has the desired molar deficit of water, and at the end of this manufacturing operation adding the required amount of diatomaceous earth. and a nucleating agent are optionally added.