WO2019037315A1

WO2019037315A1 - Method for quickly finding lowest melting point of quaternary molten salt system

Info

Publication number: WO2019037315A1
Application number: PCT/CN2017/112219
Authority: WO
Inventors: 曾智勇; 曾帆; 崔小敏
Original assignee: 深圳市爱能森科技有限公司
Priority date: 2017-08-21
Filing date: 2017-11-22
Publication date: 2019-02-28
Also published as: CN109425630A

Abstract

A method for quickly finding the lowest melting point of a quaternary molten salt system, comprising: 1) drawing a composition diagram of the quaternary molten salt system; 2) selecting a face I that represents a ternary molten salt system, and measuring the melting points at 3 vertexes of face I, at least 1 point on each side, and at least 1 point inside face I; 3) using the melting points above as data points, and using a software to draw an isothermal curve; 4) in low melting point composition regions, performing tests in the same way, narrowing the prediction range until the lowest melting point a is found; 5) then obtaining triangle II on the regular tetrahedron, repeating the operation above to obtain the lowest melting point b of the triangle II; 6) repeating step 5) at least one time to obtain at least one lowest melting point; and 7) using the lowest melting points above as data points, using the software to draw an isothermal curve, predicting the variation of the melting point of the quaternary molten salt system with the composition, so as to obtain the lowest melting point of the quaternary molten salt system. The method can quickly find the lowest melting point of a quaternary molten salt system.

Description

Method for quickly searching for the lowest melting point of quaternary molten salt system

Technical field

The present disclosure belongs to the technical field of melting point measurement of a quaternary molten salt system, and relates to a method for finding the lowest melting point of a quaternary molten salt system, for example, a method for quickly finding the lowest melting point of a quaternary molten salt system.

Background technique

At present, in the field of industrial energy storage and solar high-temperature heat utilization, the molten salt salt system for heat transfer and heat storage medium is the main body, and the binary molten salt KNO ₃ -NaNO ₃ system has a high melting point, but it is easy to cause the pipeline. The blockage affects system safety, so the development of low-melting molten salt has become very urgent. The quaternary molten salt system has received more and more attention because of its low melting point and good high temperature stability.

At present, the only reliable way to find the lowest melting point of the system is to draw a phase diagram of the molten salt system. The molten salt phase diagram shows the phase relationship of the molten salt system in the equilibrium state. It is an important basis for studying the thermodynamic properties such as the melting point transformation point, solubility, heat capacity, and even the molten salt structure. In practical applications, it is also the storage of hot molten salt. The basic basis for selection. At present, the following problems mainly exist in the process of drawing the ternary molten salt phase diagram:

1. The quaternary molten salt system is more complicated than the binary system and the ternary system, and the process of finding the lowest melting point is more complicated.

2. Looking for the melting point of the multi-molten salt system, it is necessary to test a large amount of molten salt formula, the process is slow, and there is no preliminary work to predict the corresponding minimum melting point formula, and the molten salt formula screening is very blind.

3. The method of calculating the melting point by calculating the molten salt phase diagram is not reliable, and it is still necessary to rely on experimental data to verify the calculation method.

Summary of the invention

The following is a summary of the subject matter described in detail in this disclosure. This Summary is not intended to limit the scope of the claims.

It is an object of the present disclosure to provide a method for finding the lowest melting point of a quaternary molten salt system, and more particularly to a method for rapidly finding the lowest melting point of a quaternary molten salt system. The method of the present disclosure can reduce the ineffective experimental workload by quickly selecting the experimental point selection and combining the software program to simulate the isothermal curve, and quickly find the lowest melting point of the quaternary molten salt; and, for the quaternary melting of the eutectic point The salt system can also be used to find the eutectic point reduction range, that is, to quickly reduce the eutectic point to the lowest melting point range, thereby facilitating the rapid search for the eutectic point.

To achieve the above objectives, the present disclosure adopts the following technical solutions:

A method for finding the lowest melting point of a quaternary molten salt system, especially a method for quickly finding the lowest melting point of a quaternary molten salt system, comprising the following steps:

(1) Draw a component map of the quaternary molten salt system, the composition diagram is recorded as regular tetrahedron ABCD (the specific name is not limited), then the four vertices represent 4 pure substances, respectively, and the faces of 4 triangles respectively represent 4 kinds of ternary molten salt, the points inside the regular tetrahedron represent quaternary mixed molten salt;

(2) Measuring one of the faces of the four triangles representing the ternary molten salt system, measuring the melting points at the three vertices of the face I, the melting point at at least one point on each side, and the face I a melting point at least 1 point inside;

(3) Taking the melting point temperature measured in the step (2) as a data point, and using the software to draw an isothermal curve, thereby predicting the variation of the melting point of the ternary molten salt system represented by the surface I with the composition;

(4) In the low melting component region, the data is measured in the same manner as described in steps (2) and (3) to further narrow the prediction range, and finally find the lowest melting point a of the ternary molten salt system represented by the surface I. ;

(5) continue to connect 3 points on the regular tetrahedron to obtain the triangle II, repeat the operations of steps (2)-(4) to obtain the lowest melting point b of the ternary molten salt system represented by the triangle II;

(6) repeating at least one step (5) to obtain at least one triangle and at least one lowest melting point;

(7) Using the lowest melting point a, the lowest melting point b, and the temperature of at least one lowest melting point obtained in step (6) as data points, the isothermal curve is drawn by software to predict the melting point of the quaternary molten salt system with the composition. Regularity, and then the lowest melting point of the quaternary molten salt system.

The following is a preferred technical solution of the method of the present disclosure, but is not intended to limit the present disclosure, and the following preferred technical solutions are adopted to better achieve the beneficial effects claimed in the present disclosure.

Preferably, the quaternary molten salt system comprises NaNO ₃ -KNO ₃ -LiNO ₃ -Ca(NO ₃ ) ₂ nitrate molten salt system, NaNO ₃ -KNO ₃ -NaNO ₂ -Ca(NO ₃ ) ₂ nitrate molten salt system or NaNO _3- KNO ₃ -Mg(NO ₃ ) ₂ -Ca(NO ₃ ) ₂ nitrate molten salt system, NaCl-KCl-CaCl ₂ -MgCl ₂ chloride molten salt system or N _a2 SO ₄ -K ₂ SO ₄ -Al ₂ (SO ₄ ) Any of _{3 -} MgSO ₄ sulfuric acid molten salt systems. However, it is not limited to the above-described quaternary molten salt system, and other quaternary molten salt systems commonly used in the art can also be used in the present disclosure.

Preferably, step (2) measures the melting point at at least 2 points on each side, and this at least 2 points equally divides the side on which it is located into 3 or more parts.

As a preferred technical solution of the method of the present disclosure, among all the points measured in the step (2), the intervals of adjacent points are equal. In order to achieve this effect, the following scheme can be adopted: the three sides are equally divided into the same number of parts, the aliquots are made as parallel lines of three sides and intersect, and the three vertices obtained on the three sides The aliquots and the intersections inside the triangle satisfy that "the intervals of adjacent points are equal".

Preferably, step (2) measures the melting point at at least 4 points on each side, and the at least 4 points equally divide the sides on which they are located by 5 or more.

Preferably, step (2) measures the melting point at at least 6 points inside the face I.

Preferably, step (2) measures the melting point at three vertices; the melting point at 4 points on each side, and the sides on each side are equally divided into 5 parts; and the inside of the triangle is measured at 6 o'clock. Melting point, the 6 points are the intersections inside the plane I obtained by parallel lines of three sides of the triangle which are the plane I of each side at 4 points.

Herein, the method of drawing the isothermal curve by using the software in the steps (3) and (7) is not limited, and for example, it may be, but not limited to, drawing the isothermal curve by Matlab interpolation.

Preferably, the low-melting component region of the step (4) is found by comparing the height of the melting point measured in the step (2), and the region where the three melting points have the lowest melting point is the low-melting component region. .

As a preferred technical solution of the method of the present disclosure, the triangle II of the step (5) is parallel to the surface I of the step (2).

Preferably, step (6) repeats step (5) three times to obtain three lowest melting points, denoted as the lowest melting point c, the lowest melting point d and the lowest melting point e;

Preferably, the step (7) is: taking the temperature of the lowest melting point a, the lowest melting point b, the lowest melting point c, the lowest melting point d and the lowest melting point e as data points, and using the software to draw an isothermal curve, thereby predicting the quaternary molten salt The melting point of the system varies with the composition, and the lowest melting point of the quaternary molten salt system is obtained.

As a preferred technical solution of the method of the present disclosure, the triangle II of the step (5) is parallel to the surface I, and the step (5) is repeated four times to obtain a triangle III, a triangle IV, a triangle V and a triangle VI; and, a triangle II, a triangle III, Triangle IV, Triangle V, and Triangle VI equally divide the vertex of the regular tetrahedral vertices to plane I. For example, the regular tetrahedron represents the ABCD quaternary molten salt system, and the triangle ABC represents the ABC ternary molten salt system. The content of the component D in the triangle ABC is 0, and the triangle II, the triangle III, and the triangle IV parallel to the triangle ABC. , triangle V, due to the parallel relationship, the content of D in the above several triangles is constant. Preferably, the content of the triangle II, the triangle III, the triangle IV, and the triangle V may be sequentially changed in the same order, for example, the content of D is 20%, 40%, 60%, and 80%, respectively. However, it is not limited to a change in the equivalence, and for example, it may be 10%, 20%, 30%, and 50%, respectively.

It should be noted that when the content of D in the plane parallel to the plane ABC is a fixed value x%, the other A, The maximum content of the B and C components is (1-x)%.

As a preferred technical solution of the method of the present disclosure, the method further comprises measuring the temperature of the unmeasured point near the low melting component region to verify the accuracy of the inferred temperature value, and if the inferred temperature value is different from the measured actual value, Then correct to the actual value.

Preferably, the method further comprises measuring the temperature of the unmeasured point near the low temperature line in the isothermal curve to verify the accuracy of the inferred temperature value, and if the inferred temperature value is different from the measured actual value, the correction is the actual value.

As a further preferred technical solution of the method of the present disclosure, the method comprises the following steps:

(1) Drawing the composition diagram of the quaternary molten salt system, the composition diagram is recorded as regular tetrahedron ABCD, the four vertices of the regular tetrahedron represent 4 kinds of pure substances, and the faces of 4 triangles respectively represent 4 kinds of three a molten salt system, the dots inside the regular tetrahedron represent a quaternary mixed molten salt;

(2) Measure the melting point at the three vertices of the face ABC; the melting point at 4 points on each side, and divide the side where the edge is equal to 5 at 4 points on each side; and measure 6 points inside the face ABC The melting point at the point where the 6 points are the intersections of the three sides of the side ABC on the sides of each side of the face ABC;

(3) using the melting point temperature measured in the step (2) as a data point, and using the software to draw an isothermal curve, thereby predicting the variation of the melting point of the ternary molten salt system represented by the surface ABC with the composition;

(4) In the low melting component region, the data is measured in the same manner as described in steps (2) and (3) to further narrow the prediction range, and finally find the lowest melting point a of the ternary molten salt system represented by the surface ABC. ;

(5) Continue to connect 3 points on the regular tetrahedron to obtain the surface A'B'C' parallel to the surface ABC. Repeat the steps (2)-(4) to obtain the ternary melting represented by the triangle A'B'C'. The lowest melting point of the salt system b;

(6) Repeating step (5) four times to obtain four faces parallel to the face ABC, and four lowest melting points (the lowest melting point c, the lowest melting point d, the lowest melting point e, and the lowest melting point f) respectively located in the four faces. ;

The surface A'B'C' and the four faces obtained in the step (6) respectively correspond to the content of D being 20%, 40%, 50%, 60% and 80%;

(7) Taking the temperature of the lowest melting point a, the lowest melting point b, the lowest melting point c, the lowest melting point d, the lowest melting point e, and the lowest melting point f as data points, the isothermal curve is drawn by software, thereby predicting the melting point of the quaternary molten salt system. The variation of the composition, and thus the lowest melting point of the quaternary molten salt system.

The theoretical basis on which the method of the present disclosure is based is that for a quaternary molten salt system, no sudden rise or a drop in melting point occurs in adjacent regions.

Compared with the prior art, the present disclosure has the following beneficial effects:

(1) The present disclosure can determine the low melting point component area by reasonable selection of experimental formula points, and simulate the isothermal curve by software program, which can reduce the invalid experimental workload and quickly find the lowest melting point of the quaternary molten salt system.

(2) In practical applications, it is not necessary to select the molten salt of the lowest melting point, and the cost and other issues are also considered. It is important to select the optimum ratio of used components. A quaternary molten salt phase diagram can be made by the method of the present disclosure, and can also be used to evaluate changes in cost and melting point caused by changes in component content, thereby facilitating selection of an optimum practical component ratio.

(3) In the phase diagrams herein, the melting points of some of the points are known, and the melting points obtained by the method of the present disclosure are substantially identical to the known data, which also illustrates the reliability of the disclosed method.

(4) The present disclosure combines experimental verification with reasonable prediction to improve the reliability of the experiment.

(5) The method of the present disclosure can not only predict the lowest melting point of the composite molten salt system, but also quickly find the lowest melting point of the quaternary molten salt system, and for the quaternary molten salt system in which the eutectic point exists, it is also possible to find a total The narrowing of the crystal point, that is, the eutectic point is quickly reduced to the lowest melting point, thereby facilitating rapid Look for eutectic points.

DRAWINGS

Figure 1 is a compositional diagram of the quaternary molten salt system of Example 1;

2 is a composition diagram of a ternary molten salt system represented by the surface ABC of Example 1, wherein the marked points are test recipe points, that is, test points;

Figure 3 is a compositional diagram of the system represented by the face A'B'C' of Example 1, in which the marked points are the experimental formulation points, i.e., the points tested.

Detailed ways

The technical solutions of the present disclosure will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

This embodiment provides a method for quickly finding the lowest melting point of a quaternary molten salt system, comprising the following steps:

(1) Plot the composition of the quaternary molten salt system (component A - component B - component C - component D) (see Figure 1), the component chart is recorded as regular tetrahedron ABCD, positive tetrahedron The four vertices of the body represent four kinds of pure substances (ie, substance A, substance B, substance C and substance D), and the faces of the four triangles represent four kinds of ternary molten salt systems (ie, ABD ternary molten salt system, ACD). Ternary molten salt system, BCD ternary molten salt system, ABC ternary molten salt system);

(2) The melting point at the three vertices of the measuring surface ABC (which represents the composition diagram of the ternary molten salt system see Fig. 2), the melting point at 4 points on each side (the four points will be where they are located) The sides are divided into 5 parts), and the melting points at 6 points inside the surface ABC (the 6 points are obtained by intersecting the parallel lines of the three sides of the face ABC on each side of the face ABC);

(4) Measuring the number in the same manner as described in steps (2) and (3) in the low melting component region According to, in order to further narrow the prediction range, the lowest melting point a of the ternary molten salt system represented by ABC is finally found;

(5) Continue to connect 3 points on the regular tetrahedron ABCD to obtain the face A'B'C' parallel to the face ABC, and repeat the operations of steps (2)-(4) to obtain the ternary represented by the triangle A'B'C'. The lowest melting point b of the molten salt system;

Example 2

(1) Plot the composition of the quaternary molten salt system (component A - component B - component C - component D), which is recorded as regular tetrahedron ABCD, 4 vertices of regular tetrahedron Representing 4 kinds of pure substances (ie, substance A, substance B, substance C and substance D), the four triangular faces represent four kinds of ternary molten salt systems (ie, ABD ternary molten salt system, ACD ternary molten salt system). , BCD ternary molten salt system, ABC ternary molten salt system);

(2) The melting point at the three vertices of the measuring surface BCD, the melting point at 4 points on each side (the four points divide the edge of the four points into five), and the six points inside the surface BCD Melting point (these six points are obtained by intersecting the parallel lines of the three sides of the face BCD on the side of each side of the BCD);

(3) Taking the melting point temperature measured in step (2) as the data point, using the software to draw the isothermal curve, thereby predicting the variation of the melting point of the ternary molten salt system with the composition, and further drawing the surface BCD. Representative ternary molten salt phase diagram;

(4) A region in which the melting point temperature measured by the comparison step (2) is measured, and the three points at which the melting point temperature is the lowest is determined as a low melting component region, and in the low melting component region, the step (2) and Step (3) the same method, test the data to further narrow the prediction range until the lowest melting point a of the ternary molten salt system is finally found;

(5) Continue to connect 3 points on the regular tetrahedron ABCD to obtain the face B'C'D' parallel to the face BCD, and repeat the operations of steps (2)-(4) to obtain the ternary represented by the triangle B'C'D'. The lowest melting point b of the molten salt system;

(6) repeating step (5) three times to obtain three faces parallel to the face BCD, and three lowest melting points (the lowest melting point c, the lowest melting point d, and the lowest melting point e) respectively located in the three faces;

The surface B'C'D' and the three faces obtained in the step (6) correspond to A content of 20%, 40%, 60% and 80%, respectively;

(7) Taking the temperature of the lowest melting point a, the lowest melting point b, the lowest melting point c, the lowest melting point d, and the lowest melting point e as data points, the isothermal curve is drawn by software to predict the melting point of the quaternary molten salt system with the composition. Regularity, and then the lowest melting point of the quaternary molten salt system.

Example 3

The other test methods and conditions are the same as in the first embodiment except that the faces A'B'C' and the four faces obtained in the step (6) correspond to the contents of D being 10%, 20%, 30%, 50%, and 70%, respectively. .

In the embodiments of the present disclosure, some of the other positions at the marked points can be obtained from the molten salt of the Hitec system, and the obtained melting point temperature is substantially consistent with the results detected by the method of the present disclosure, and verified. The reliability of the disclosed method.

Comparative example 1

The phase diagram of quaternary molten salt (Ca(NO ₃ ) ₂ -NaNO ₃ -NaNO ₂ -KNO ₃ ) was drawn by conventional methods. When the conventional phase diagram was used for testing by conventional methods, the choice of formula was blind and selected in some intervals. The experimental points are too dense, resulting in unnecessary testing, and led to a little interval gap, no experimental points, resulting in experimental unreliability.

Comparing Examples 1-3 and Comparative Example 1, it can be seen that the method of the present disclosure can effectively reduce the ineffective experimental workload, select the experimental points to determine the low-melting component region, and simulate the isothermal temperature in combination with the software program. Curve, you can quickly find the lowest melting point of the quaternary molten salt.

The Applicant claims that the present invention is described by the above-described embodiments, but the present invention is not limited to the above detailed methods, that is, it does not mean that the invention must be implemented by the above detailed methods. It should be apparent to those skilled in the art that any modifications of the present disclosure, equivalent substitutions of the various materials of the present disclosure, and the addition of the auxiliary components, the selection of the specific manners, and the like, are all within the scope of the present invention.

Claims

A method for finding the lowest melting point of a quaternary molten salt system, comprising the steps of:

(1) Drawing the composition diagram of the quaternary molten salt system, the composition diagram is recorded as regular tetrahedron ABCD, the four vertices of the regular tetrahedron represent 4 kinds of pure substances, and the faces of 4 triangles respectively represent 4 kinds of three a molten salt system, the dots inside the regular tetrahedron represent a quaternary mixed molten salt;

(2) Measuring one of the faces of the four triangles representing the ternary molten salt system, measuring the melting points at the three vertices of the face I, the melting point at at least one point on each side, and the face I a melting point at least 1 point inside;

(3) Taking the melting point temperature measured in the step (2) as a data point, and using the software to draw an isothermal curve, thereby predicting the variation of the melting point of the ternary molten salt system represented by the surface I with the composition;

(4) In the low melting component region, the data is measured in the same manner as described in steps (2) and (3) to further narrow the prediction range until the lowest melting point of the ternary molten salt system represented by face I is finally found. a;

(5) continue to connect 3 points on the regular tetrahedron to obtain the triangle II, repeat the operations of steps (2)-(4) to obtain the lowest melting point b of the ternary molten salt system represented by the triangle II;

(6) repeating at least one step (5) to obtain at least one triangle and at least one lowest melting point;

(7) Using the lowest melting point a, the lowest melting point b, and the temperature of at least one lowest melting point obtained in step (6) as data points, the isothermal curve is drawn by software to predict the melting point of the quaternary molten salt system with the composition. Regularity, and then the lowest melting point of the quaternary molten salt system.
The method according to claim 1, wherein said quaternary molten salt system comprises NaNO 3 -KNO 3 -LiNO 3 -Ca(NO 3 ) 2 nitrate molten salt system, NaNO 3 -KNO 3 -NaNO 2 -Ca ( NO 3 ) 2 nitrate molten salt system or NaNO 3 -KNO 3 -Mg(NO 3 ) 2 -Ca(NO 3 ) 2 nitrate molten salt system, NaCl-KCl-CaCl 2 -MgCl 2 chloride molten salt system or Na 2 Any one of SO 4 -K 2 SO 4 -Al 2 (SO 4 ) 3 -MgSO 4 sulfuric acid molten salt systems.
The method according to claim 1 or 2, wherein the step (2) measures the melting point at at least 2 points on each side, and the at least 2 points equally divides the side on which it is located by 3 or more.
The method according to any one of claims 1 to 3, wherein among all the points measured in the step (2), the intervals of the adjacent points are equal.
The method according to any one of claims 1 to 3, wherein step (2) measures a melting point at at least 4 points on each side, and the at least 4 points equally divides the side on which it is located by 5 or more Multiple copies.
A method according to any one of claims 1 to 3, wherein step (2) measures the melting point at at least 6 points inside the face I.
The method according to any one of claims 1 to 6, wherein the step (2) measures the melting points at the three vertices; the melting point at four points on each side, and the four sides on each side equalize the side on which they are located Divided into 5 parts; and measured the melting point at the inner 6 points, which is the intersection point inside the surface I obtained by the parallel lines of the three sides of the triangle which are 4 points on each side.
The method according to any one of claims 1 to 7, wherein the method of drawing an isothermal curve by software according to steps (3) and (7) comprises: drawing an isothermal curve by Matlab interpolation.
The method according to any one of claims 1 to 8, wherein the low melting point component region of the step (4) is found by comparing the level of the melting point temperature measured by the step (2) and the lowest melting point temperature. The area where the dots are connected is a low melting component region.
The method according to any one of claims 1 to 9, wherein the triangle II of the step (5) is parallel to the plane I of the step (2).
The method according to any one of claims 1 to 10, wherein the step (6) is repeated three times in the step (5) to obtain three lowest melting points, which are referred to as the lowest melting point c, the lowest melting point d and the lowest melting point e.
The method according to any one of claims 1 to 11, wherein said step (7) is: The temperature of the low melting point a, the lowest melting point b, the lowest melting point c, the lowest melting point d and the lowest melting point e is used as a data point, and the isothermal curve is drawn by software, thereby predicting the variation of the melting point of the quaternary molten salt system with the composition, thereby obtaining The lowest melting point of the quaternary molten salt system.
The method according to any one of claims 1 to 12, wherein the triangle II of the step (5) is parallel to the plane I, and the step (5) is repeated four times to obtain a triangle III, a triangle IV, a triangle V and a triangle VI;

Also, the triangle II, the triangle III, the triangle IV, the triangle V, and the triangle VI equally divide the vertex of the regular tetrahedral vertices to the plane I.
A method according to any one of claims 10 to 13, further comprising measuring the temperature of the unmeasured point near the low melting component region to verify the accuracy of the inferred temperature value, if the inferred temperature value is different from the measured actual value, Then correct to the actual value;
The method of claim 14 further comprising measuring the temperature of the unmeasured point near the low temperature line in the isothermal curve to verify the accuracy of the inferred temperature value, and if the inferred temperature value is different from the measured actual value, the correction is actual value.