A detection method for the thermal stability of organic heat carriers in solar thermal power generation

Abstract

The present invention relates to the technical field of organic heat carrier detection, and specifically relates to a method for detecting the thermal stability of organic heat carriers for solar thermal power generation. The present invention only needs to measure the change in the chemical composition purity of the organic heat carrier before and after heating, and calculate the deterioration rate of the product based on the change in the purity of the chemical composition therein. The result can be obtained only by one test, and the process is simple, with short time, low cost and good repeatability.

Description

Technical Field

[0001] The present invention relates to the technical field of organic heat carrier detection, and more particularly to a method for detecting the thermal stability of organic heat carriers for solar thermal power generation. Background Art

[0002] Thermal stability is the most important quality performance of organic heat carriers, and its quality directly affects the efficiency (economic efficiency) and operation safety of solar thermal power generation. When the organic heat carrier deteriorates severely, it will not only affect the system load and reduce the power generation, but also more easily cause safety accidents such as pipe explosion and fire. Organic heat carriers are a general term for organic substances used as heat transfer media. The organic heat carriers for solar thermal power generation are mainly diphenyl-diphenyl ether organic heat carrier products, and their thermal stability is often determined by the existing method GB23800. This method heats the organic heat carrier at a specified temperature, and evaluates the thermal stability of the organic heat carrier by measuring the deterioration rate of the organic heat carrier. The deterioration rate is the sum of the mass fractions of high-boiling substances, low-boiling substances, gas-phase decomposition products and non-evaporable products. The unused organic heat carrier can be sealed in a glass ampoule placed in a metal protection tube, or added to a steel tester and sealed. The metal protection tube or steel tester containing the glass ampoule is heated at the specified test temperature for the specified time. Open the glass ampoule or steel tester, and use the gas chromatography method SH / T 0558-1993 to measure the mass fractions of high-boiling substances and low-boiling substances, and use a bulb distiller to measure the content of non-evaporable products. Compare the test results before and after heating the organic heat carrier, and calculate the final deterioration rate content by correction and summation according to the formula. This method requires instruments such as a heating furnace, a gas chromatograph, a simulated distillation software, and a bulb distiller, with a high cost; and it is necessary to complete four tests of high-boiling substances, low-boiling substances, gas-phase decomposition products and non-evaporable products to obtain the results, with a complex process, many steps and a long time. When the gas-phase decomposition products and non-evaporable products are less than 0.5%, they are all ignored, which affects the result accuracy and the result repeatability is poor. Summary of the Invention

[0003] In view of this, the present invention provides a method for detecting the thermal stability of organic heat carriers for solar thermal power generation, which has a simple, fast and good repeatability process.

[0004] The technical solution of the present invention is as follows:

[0005] The present invention provides a method for detecting the thermal stability of organic heat carriers for solar thermal power generation, comprising the following steps:

[0006] (1) Detect the purity of the organic heat carrier;

[0007] (2) Heat the organic heat carrier within the upper limit range of the use temperature, and detect the purity of the organic heat carrier after heating;

[0008] (3) Fit the relationship between the difference in the purity of the organic heat carrier before and after heating and the thermal stability deterioration rate. According to the above relationship and the purity of the organic heat carrier sample before and after heating, calculate the thermal stability deterioration rate result at this temperature.

[0009] As an implementation manner, the organic heat carrier is diphenyl - diphenyl ether.

[0010] Preferably, the relationship formula between the difference in the purity of diphenyl - diphenyl ether before and after heating and the thermal stability deterioration rate is y = 0.0096x 3 - 0.0584x 2 + 3.2582x, where x is the difference in the purity of diphenyl - diphenyl ether before and after heating, and y is the thermal stability deterioration rate of diphenyl - diphenyl ether at this temperature.

[0011] As an implementation manner, the organic heat carrier is separated and analyzed by gas chromatography to calculate the purity of the organic heat carrier.

[0012] As an implementation manner, dissolve the diphenyl - diphenyl ether organic heat carrier in a solvent, and separate and analyze it by gas chromatography. The analysis result is calculated by the corrected peak area normalization method to obtain the percentage content of diphenyl and diphenyl ether, which is the purity of the diphenyl - diphenyl ether organic heat carrier.

[0013] Preferably, the solvent is carbon disulfide or acetone.

[0014] Preferably, the gas chromatography uses a quartz capillary chromatographic column of 5% diphenyl - 95% dimethylsiloxane copolymer, and the specification of the chromatographic column is

[0015] Preferably, the gas chromatograph has an SSI injection port and an FID detector.

[0016] Preferably, the heating temperature is 370 - 450 °C.

[0017] Preferably, the heating time is not less than 1000 h.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] The present invention only needs to use gas chromatography to measure the chemical composition of the product after heating, and calculate the deterioration rate of the product based on the percentage content of the chemical composition therein. Only one test is required to obtain the result, and the process is simple and has good repeatability.

[0020] The method of the present invention only needs to be equipped with a heating furnace and a gas chromatograph to complete the detection, and the cost is lower. This method only requires one person, and the instrument automatically runs for about 1.5 hours to complete, with a short time and high analysis efficiency. Description of the Drawings

[0021] Figure 1 is the gas chromatogram of biphenyl - diphenyl ether;

[0022] Figure 2 is the gas chromatogram of the in - use biphenyl - diphenyl ether;

[0023] Figure 3 is the correlation relationship diagram of the deterioration rate of the organic heat carrier in the present invention and the comparative example. Detailed implementation mode

[0024] The present invention conducts qualitative and quantitative analysis of the detailed composition of in - use organic heat carrier samples with different deterioration degrees, thermal stability deterioration rate analysis, summarizes the correlation relationship between the organic heat carrier and the deterioration rate of the in - use organic heat carrier and the chemical composition, deduces the basis for calculating its thermal stability deterioration rate from the chemical composition information, and finally establishes a rapid analysis method for the thermal stability of the organic heat carrier in solar thermal power generation.

[0025] The method for detecting the thermal stability of the organic heat carrier for solar thermal power generation in the present invention includes the following steps:

[0026] (1) Detect the purity of the organic heat carrier;

[0027] (2) Heat the organic heat carrier within the upper limit range of the use temperature and detect the purity of the organic heat carrier after heating;

[0028] (3) Fit the relationship between the difference in the purity of the organic heat carrier before and after heating and the thermal stability deterioration rate, and calculate the thermal stability deterioration rate result at this temperature according to the above relationship and the purity of the organic heat carrier samples before and after heating.

[0029] As an implementation mode, the organic heat carrier of the present invention is biphenyl - diphenyl ether, which is the most typical organic heat carrier for solar thermal power generation. In the present invention, as a preferred embodiment, the relationship formula between the difference in the purity of biphenyl - diphenyl ether before and after heating and the thermal stability deterioration rate is y = 0.0096x 3 - 0.0584x 2 + 3.2582x, where x is the difference in the purity of biphenyl - diphenyl ether before and after heating, and y is the thermal stability deterioration rate of biphenyl - diphenyl ether at this temperature.

[0030] As an implementation mode, the chemical composition and component analysis of the organic heat carrier of the present invention are preferably separated and analyzed by gas chromatography to calculate the purity of the organic heat carrier. Those skilled in the art can select other suitable determination methods according to the specific components of the organic heat carrier.

[0031] Taking diphenyl - diphenyl ether as an example, the specific purity determination method includes: dissolving the diphenyl - diphenyl ether organic heat carrier in a solvent, separating and analyzing it by gas chromatography, and calculating the percentage content of diphenyl and diphenyl ether by the corrected peak area normalization method for the analysis result, which is the purity of the diphenyl - diphenyl ether organic heat carrier.

[0032] Preferably, the solvent is carbon disulfide or acetone. Preferably, the mass fraction of the organic heat carrier in the solvent is 8% - 12%.

[0033] The gas chromatography method of the present invention can be detected by using a commercially available gas chromatograph. Preferably, the gas chromatograph has an SSI (split / splitless) injection port and an FID (hydrogen flame ionization) detector.

[0034] Preferably, the gas chromatography uses a quartz capillary chromatographic column of 5% diphenyl - 95% dimethylsiloxane copolymer, and the specification of the chromatographic column is or a capillary chromatographic column that can meet the separation requirements.

[0035] The gas chromatograph adopted by the present invention is selected to be able to achieve a resolution R of diphenyl and diphenyl ether ≥ 1.5, and the injection volume and the sensitivity of the instrument should be controlled within the linear response range of the diphenyl ether component.

[0036] The present invention has no special limitation on the heating temperature and time, and those skilled in the art can set the heating temperature and time according to actual needs. The basic principle is that the heating temperature is within the upper limit range of the use temperature of the organic heat carrier. Preferably, the heating temperature is 370 - 450 °C, and more preferably 390 - 400 °C. Preferably, the heating time is not less than 1000 h, and more preferably 1000 - 1200 h.

[0037] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] The experimental methods used in the following examples are all conventional methods unless otherwise specified.

[0039] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0040] All experimental results in the following examples are the average values of the results of three experiments.

[0041] Example 1

[0042] Select at least 40 groups of in-use biphenyl-diphenyl ether samples. Take about 0.5 ml of the samples, dilute them with carbon disulfide solvent, and then perform separation and analysis by gas chromatography. The analysis results are obtained by the corrected peak area normalization method to get the biphenyl content and diphenyl ether content before heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity before heating.

[0043] After heating the biphenyl-diphenyl ether organic heat carrier sample at 400 °C for 1000 h, use the same method to obtain the biphenyl content and diphenyl ether content after heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity after heating.

[0044] Calculate the change in purity of biphenyl-diphenyl ether before and after heating. Use the method of GB / T 23800-2009 to determine the thermal stability deterioration rate of each group of biphenyl-diphenyl ether samples.

[0045] According to the correlation between the change in purity of biphenyl-diphenyl ether before and after heating and the thermal stability deterioration rate, fit the calculation formula as follows:

[0046] y = 0.0096x 3 - 0.0584x 2 + 3.2582x

[0047] Among them, x is the difference in the purity of the organic heat carrier before and after heating, and y is the thermal stability deterioration rate at this temperature. The deterioration rate can be calculated from the change in purity of the sample before and after heating.

[0048] Example 2

[0049] Select in-use biphenyl-diphenyl ether samples. Take about 0.5 ml of the samples, dilute them with carbon disulfide solvent, and then perform separation and analysis by gas chromatography. The analysis results are obtained by the corrected peak area normalization method to get the biphenyl content and diphenyl ether content before heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity before heating.

[0050] Heat the above in-use biphenyl-diphenyl ether organic heat carrier sample at 400 °C for 1200 h, use the same method to obtain the biphenyl content and diphenyl ether content after heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity after heating.

[0051] Calculate the change in purity of in-use biphenyl-diphenyl ether before and after heating. According to the formula y = 0.0096x 3 - 0.0584x 2 + 3.2582x Calculate the result of the thermal stability deterioration rate at this temperature, where x is the difference in the purity of biphenyl-diphenyl ether before and after heating, and y is the thermal stability deterioration rate at this temperature.

[0052] Example 3

[0053] Select the used biphenyl-diphenyl ether sample. Take about 0.5 ml of the sample, dilute it with carbon disulfide solvent, and then perform separation and analysis by gas chromatography. The analysis results are obtained by the corrected peak area normalization method to get the biphenyl content and diphenyl ether content before heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity before heating.

[0054] Heat the above-mentioned used biphenyl-diphenyl ether organic heat carrier sample at 405 °C for 1000 h. Use the same method to obtain the biphenyl content and diphenyl ether content after heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity after heating.

[0055] Calculate the change in purity of the used biphenyl-diphenyl ether before and after heating. According to the formula y = 0.0096x 3 - 0.0584x 2 + 3.2582x to calculate the result of the thermal stability deterioration rate at this temperature, where x is the difference in the purity of biphenyl-diphenyl ether before and after heating, and y is the thermal stability deterioration rate at this temperature.

[0056] Example 4

[0057] Select the used biphenyl-diphenyl ether sample. Take about 0.5 ml of the sample, dilute it with carbon disulfide solvent, and then perform separation and analysis by gas chromatography. The analysis results are obtained by the corrected peak area normalization method to get the biphenyl content and diphenyl ether content before heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity before heating.

[0058] Heat the above-mentioned used biphenyl-diphenyl ether organic heat carrier sample at 395 °C for 1000 h. Use the same method to obtain the biphenyl content and diphenyl ether content after heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity after heating.

[0059] Calculate the change in purity of the used biphenyl-diphenyl ether before and after heating. According to the formula y = 0.0096x 3 - 0.0584x 2 + 3.2582x to calculate the result of the thermal stability deterioration rate at this temperature, where x is the difference in the purity of biphenyl-diphenyl ether before and after heating, and y is the thermal stability deterioration rate at this temperature.

[0060] Example 5

[0061] Select the used biphenyl-diphenyl ether sample. Take about 0.5 ml of the sample, dilute it with acetone solvent, and then perform separation and analysis by gas chromatography. The analysis results are obtained by the corrected peak area normalization method to get the biphenyl content and diphenyl ether content before heating, and calculate the mass percentage content of biphenyl and diphenyl ether, which is the purity before heating.

[0062] Heat the above-mentioned used biphenyl-diphenyl ether organic heat carrier sample at 385°C for 1400 h. Using the same method, obtain the biphenyl content and diphenyl ether content after heating, and calculate the mass percentage of biphenyl and diphenyl ether, which is the purity after heating.

[0063] Calculate the change in purity of the used biphenyl-diphenyl ether before and after heating. According to the formula y = 0.0096x 3 - 0.0584x 2 + 3.2582x, calculate the result of the thermal stability deterioration rate at this temperature, where x is the difference in purity of biphenyl-diphenyl ether before and after heating, and y is the thermal stability deterioration rate at this temperature.

[0064] Example 6

[0065] Select a used biphenyl-diphenyl ether sample, take about 0.5 ml of the sample, dilute it with acetone solvent, and perform separation and analysis by gas chromatography. The analysis result is obtained by the corrected peak area normalization method to obtain the biphenyl content and diphenyl ether content before heating, and calculate the mass percentage of biphenyl and diphenyl ether, which is the purity before heating.

[0066] Heat the above-mentioned used biphenyl-diphenyl ether organic heat carrier sample at 395°C for 1500 h. Using the same method, obtain the biphenyl content and diphenyl ether content after heating, and calculate the mass percentage of biphenyl and diphenyl ether, which is the purity after heating.

[0067] Calculate the change in purity of the used biphenyl-diphenyl ether before and after heating. According to the formula y = 0.0096x 3 - 0.0584x 2 + 3.2582x, calculate the result of the thermal stability deterioration rate at this temperature, where x is the difference in purity of biphenyl-diphenyl ether before and after heating, and y is the thermal stability deterioration rate at this temperature.

[0068] Comparative example

[0069] Determine the thermal stability deterioration rate of the biphenyl-diphenyl ether organic heat carrier samples in Examples 2 - 6 using the method of GB / T 23800 - 2009.

[0070] The sample deterioration rate (mass fraction) Z (%) is calculated according to the following formula:

[0071] Z = G + N + H + U

[0072] In the formula:

[0073] G - Content of gas-phase decomposition products of the sample (mass fraction), %;

[0074] N - Content of low-boiling substances of the sample after correction (mass fraction), %;

[0075] H—Mass fraction of high-boiling substances in the corrected sample, %;

[0076] U—Mass fraction of non-evaporable products in the sample, %.

[0077] Among them, the content of gas-phase decomposition products G (wt%) and the content of non-evaporable substances U (wt%) less than 0.5 are negligible;

[0078] N = N'×(100 - G - U) / 100;

[0079] H = H'×(100 - G - U) / 100;

[0080] N' is the uncorrected low-boiling substance content (mass fraction) (%), and H' is the uncorrected high-boiling substance content (mass fraction) (%).

[0081] Table 2 Comparison of thermal stability deterioration rates measured by different methods in Examples 2-6

[0082]

[0083] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting the thermal stability of an organic heat carrier for solar thermal power generation, characterized in that, Comprising the following steps: Detecting the purity of the organic heat carrier; Heating the organic heat carrier within the upper limit range of the service temperature, the heating time being not less than 1000 h, and detecting the purity of the organic heat carrier after heating; Fitting the relationship between the difference in the purity of the organic heat carrier before and after heating and the thermal stability deterioration rate, and calculating the thermal stability deterioration rate result at this temperature according to the above relationship and the purity of the organic heat carrier samples before and after heating; The organic heat carrier is diphenyl-diphenyl ether; The relationship formula between the difference in the purity of biphenyl-diphenyl ether before and after heating and the thermal stability deterioration rate is y = 0.0096x 3 - 0.0584x 2 + 3.2582x, where x is the difference in the purity of biphenyl-diphenyl ether before and after heating, and y is the thermal stability deterioration rate of biphenyl-diphenyl ether at this temperature.

2. The method according to claim 1, characterized in that The organic heat carrier is separated and analyzed by gas chromatography to calculate the purity of the organic heat carrier.

3. The method according to claim 2, wherein Dissolving the diphenyl-diphenyl ether organic heat carrier in a solvent, separating and analyzing by gas chromatography, and calculating the percentage contents of diphenyl and diphenyl ether by the corrected peak area normalization method for the analysis result, which is the purity of the diphenyl-diphenyl ether organic heat carrier.

4. The method according to claim 3, wherein The solvent is carbon disulfide or acetone.

5. The method according to claim 3, characterized in that, The gas chromatography uses a quartz capillary chromatographic column of 5% diphenyl-95% dimethylsiloxane copolymer, and the specifications of the chromatographic column are ø0.25 mm×30 m×0.25 μm.

6. The method according to claim 3, wherein The gas chromatograph used in the gas chromatography has an SSI injection port and an FID detector.

7. The method according to claim 1, wherein The heating temperature is 370 - 450 °C.

Images