A comprehensive and overall simulation evaluation method for heat-oxidative stability of heat conducting oil

Abstract

The present application relates to the technical field of heat conducting oil performance detection, and particularly relates to a comprehensive and overall heat conducting oil thermal oxidation stability simulation evaluation method, which comprises the following steps: S1, contacting the heat conducting oil with a catalyst and performing a high-temperature heating test; S2, cooling the heat conducting oil and the catalyst to room temperature after the high-temperature heating test; S3, determining the thermal oxidation stability performance of the heat conducting oil, wherein the performance includes kinematic viscosity, viscosity index, color, acid value, sediment, flash point, self-ignition point and refractive index; and S4, comprehensively scoring the thermal oxidation stability performance of the heat conducting oil. The heat conducting oil thermal oxidation stability simulation evaluation method is objective, comprehensive and accurate, realizes the overall evaluation of the oil sample after the heat aging simulation test of the heat conducting oil, can effectively avoid the risk of subsequent application of the oil sample, and has great popularization and application value.

Description

Technical Field

[0001] This invention relates to the field of heat transfer oil performance testing technology, specifically to a comprehensive and complete method for simulating and evaluating the thermal oxidation stability of heat transfer oil. Background Technology

[0002] Currently, heat transfer technology, which involves comprehensive energy utilization, is rapidly advancing and developing. Ensuring efficient and stable heat transfer systems while achieving breakthroughs in energy conservation and carbon reduction has become a key focus for related industries. Since heat transfer oils are mostly used under high-temperature conditions, system maintenance is highly dependent on on-site operation and maintenance personnel. It is understood that most expansion tanks in current heat transfer oil systems lack nitrogen or liquid sealing, especially in some small and medium-sized systems. This leads to prolonged contact between the heat transfer oil and air at high temperatures, causing oxidation and deterioration, ultimately inducing a large amount of sediment. This affects the normal and stable operation of the system and reduces the overall heat transfer efficiency, potentially leading to accidents. Previous system tracking has revealed numerous similar problems in practical applications, resulting in abnormal system operation or reduced heat transfer oil lifespan, necessitating partial or complete replacement. In some cases, the need for thorough system cleaning has significantly increased costs. Considering the current situation, establishing a comprehensive, effective, and efficient method for assessing the thermal oxidation stability of heat transfer oils is essential. This method will play a better role in comprehensively evaluating the thermal oxidation performance of heat transfer oils and improving their overall performance.

[0003] Currently, the main test methods for evaluating the oxidizability of oil samples in the presence of air (oxygen) involve the rotating oxygen bomb method and the thermal oxidation stability of hydraulic oil. Among these, the evaluation method related to the aging of heat transfer oil is mainly the thermal oxidation stability test method, which is similar to that for hydraulic oil. The thermal oxidation stability test is performed according to Appendix C of GB 23971. A certain amount of sample is weighed into a test beaker, a steel rod is placed in it, and the sample is subjected to 72 hours at 175°C. The changes in kinematic viscosity, acid value, and amount of sediment before and after the test at 40°C are then evaluated.

[0004] Although the above test methods have certain operability, they also have many shortcomings. For example, Appendix C of GB23971 has the following shortcomings that need to be improved: (1) Not objective and comprehensive enough. For oil samples with good oxidation stability, there will generally be no sediment due to oxidation, but for oil samples with poor oxidation stability, there will be corresponding sediment due to oxidation. The amount and particle size of the sediment also vary greatly depending on the oil sample formulation. In Appendix C of GB 23971, the oil sample after the thermal oxidation stability test is filtered with quantitative filter paper. The quantitative filter paper is washed with solvent, dried and weighed to calculate the total amount of sediment. For smaller particles, they will generally pass through qualitative filter paper, thus completely ignoring the sediment of smaller particles. Although the final evaluation result meets the requirements, the oil sample in this state is prone to serious coking problems in actual use. (2) The test items are not comprehensive enough. Only the viscosity change, acid value change and sediment amount before and after the oil sample test are evaluated, without involving the evaluation of other items that change due to aging performance. (3) There is mutual influence between different samples in the test results, which leads to inaccurate evaluation results.

[0005] Therefore, the existing methods for evaluating the thermal oxidation stability of heat transfer oils cannot achieve a comprehensive, complete, and objective assessment of the aging performance of oil samples. There is an urgent need to establish a comprehensive and complete evaluation method for the thermal oxidation stability aging test of heat transfer oils. Summary of the Invention

[0006] In view of this, the present invention provides a method for simulating and evaluating the thermal oxidation stability of heat transfer oil, comprising the following steps:

[0007] S1. Contact the heat transfer oil and catalyst and conduct a high-temperature heating test;

[0008] S2. Cool the heat transfer oil and catalyst to room temperature after the high-temperature heating test;

[0009] S3. The thermal oxidation stability of the heat transfer oil is measured, and the properties are: kinematic viscosity, viscosity index, color, acid value, sediment, flash point, auto-ignition point and refractive index.

[0010] S4. A comprehensive score is given based on the thermal oxidation stability of the heat transfer oil.

[0011] The thermal oxidation stability simulation evaluation method for heat transfer oil of the present invention is objective, comprehensive, and accurate. Based on the thermal oxidation stability test method in Appendix C of GB 23971, the evaluation method of the present invention achieves a comprehensive evaluation of oil samples after thermal aging simulation tests by adding tests for viscosity index, color, refractive index, flash point, and autoignition point.

[0012] In the specific implementation process, the measurement methods for the above indicators can be adopted using existing technologies.

[0013] In a preferred embodiment of the present invention, the method for determining the comprehensive score is as follows:

[0014] (1) When the kinematic viscosity increases by ≤5%, the viscosity index decreases by ≤5, the color increases by ≤2, the acid value increases by ≤0.5mgKOH / g, the sludge content decreases by ≤5mg / 100g, the flash point decreases by ≤5℃, the auto-ignition point decreases by ≤5℃, and the refractive index changes by ≤5%, the comprehensive score is Grade I.

[0015] (2) When 5% < kinematic viscosity increase ≤ 15%, 5 < viscosity index decrease ≤ 10%, 2 < color increase ≤ 3%, 0.5 mg KOH / g < acid value increase ≤ 0.6 mg KOH / g, 5 mg / 100g < sludge ≤ 10 mg / 100g, 5℃ < flash point decrease ≤ 10℃, 5℃ < auto-ignition point decrease ≤ 10℃, and 5% < refractive index change ≤ 10%, the comprehensive score is Grade II;

[0016] (3) When 15% < kinematic viscosity increase ≤ 25%, 10 < viscosity index decrease ≤ 15%, No. 3 < color increase ≤ No. 4, 0.6 mg KOH / g < acid value increase ≤ 0.8 mg KOH / g, 10 mg / 100g < sludge ≤ 20 mg / 100g, 10℃ < flash point decrease ≤ 15℃, 10℃ < auto-ignition point decrease ≤ 15℃, and 10% < refractive index change ≤ 20%, the comprehensive score is Grade III;

[0017] (4) When 25% < kinematic viscosity increase ≤ 35%, 15 < viscosity index decrease ≤ 20%, No. 4 < color increase ≤ No. 5, 0.8 mg KOH / g < acid value increase ≤ 1.0 mg KOH / g, 20 mg / 100g < sludge ≤ 50 mg / 100g, 15℃ < flash point decrease ≤ 20℃, 15℃ < auto-ignition point decrease ≤ 20℃, and 20% < refractive index change ≤ 30%, the comprehensive score is IV level;

[0018] (5) When the kinematic viscosity increases by more than 35%, the viscosity index decreases by more than 20, the color increases by more than 5, the acid value increases by more than 1.0 mg KOH / g, the sludge content increases by more than 50 mg / 100g, the flash point decreases by more than 20℃, the auto-ignition point decreases by more than 20℃, and the refractive index changes by more than 30%, the comprehensive score is grade V.

[0019] As a preferred embodiment of the present invention, after step S2, the sample is filtered through a filter membrane with a pore size of 0.8 to 10 micrometers before proceeding to step S3.

[0020] Through extensive work verification, this invention has found that increasing the pore size of the filter membrane to 0.8–10 micrometers for effective filtration of fine particles can more objectively and realistically evaluate the differences in thermal oxidation stability of different oil samples, and can effectively avoid risks in the subsequent application of oil samples.

[0021] More preferably, after step S2, the sample is filtered through a filter membrane with a pore size of 7 to 9 micrometers before proceeding to step S3, with the most preferred filter membrane having a pore size of 8 micrometers.

[0022] As a preferred embodiment of the present invention, after step S2, the sample is first filtered through quantitative filter paper, and then filtered through a filter membrane with a pore size of 0.8 to 10 micrometers, and then step S3 is performed.

[0023] In a preferred embodiment of the present invention, the high-temperature heating test is conducted in a natural convection heating test chamber; the natural convection heating test chamber contains an oil sample container unit, which includes an oil sample container and a sample condensation device provided at the opening of the oil sample container.

[0024] The present invention further discovers that by setting a sample condensation device at the upper opening of a traditional oil sample container unit, the mutual influence between different oil samples can be minimized, resulting in more accurate evaluation results.

[0025] In a preferred embodiment of the present invention, a metal bath is used to control the temperature of the high-temperature heating test; preferably, the material of the metal bath is aluminum.

[0026] In a preferred embodiment of the present invention, the catalyst is steel and / or copper.

[0027] In the specific implementation process, steel rods and / or copper rods can be used as catalysts.

[0028] Placing copper and steel rods simultaneously as catalysts can further increase the rigor of the simulation test.

[0029] Preferably, the copper rod has the following parameters: T2Y copper, 99.90% copper content, 6.35 mm in diameter, and 76.20 mm in length; and / or, the steel rod has the following parameters: T10A steel, 1% carbon content, 6.35 mm in diameter, and 76.20 mm in length.

[0030] In a preferred embodiment of the present invention, in step S1, the amount of heat transfer oil added is 150-200g, preferably 160-180g.

[0031] In a preferred embodiment of the present invention, in step S1, the temperature of the high-temperature heating test is 150-200℃, preferably 160-180℃.

[0032] In a preferred embodiment of the present invention, in step S1, the high-temperature heating test lasts for 24-96 hours, preferably 60-80 hours.

[0033] Those skilled in the art can further combine the above-mentioned preferred solutions to obtain other preferred embodiments of the thermal oxidation stability simulation evaluation method for heat transfer oil in this invention.

[0034] The beneficial effects of this invention are as follows:

[0035] The thermal oxidation stability simulation evaluation method of the present invention is objective, comprehensive and accurate, and realizes a comprehensive evaluation of the oil sample after the thermal aging simulation test of the thermal oil. It can effectively avoid the risks in the subsequent application of the oil sample and has significant value for promotion and application. Attached Figure Description

[0036] Figure 1 A schematic diagram of the sample condensation device set up in the oil sample container unit of the natural convection heating test chamber.

[0037] Figure 2 This is a schematic diagram of a natural convection heating test chamber. Detailed Implementation

[0038] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0039] Unless otherwise specified, all methods used in the examples were conventional or performed according to techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents and instruments used without specified manufacturers were all conventional products that could be purchased from legitimate channels.

[0040] The following embodiments employ the following methods: Figure 2 The test was conducted in a natural convection heating chamber, which contains an oil sample container unit. The oil sample container unit includes a 300mL beaker and other components. Figure 1 The sample condensation device shown.

[0041] The natural convection heating test chamber uses a constant temperature aluminum test chamber to heat the oil sample being tested, ensuring the stability of the aging treatment temperature throughout the entire thermal aging test.

[0042] The measurement methods for each indicator in the following embodiments adopt conventional testing methods in the prior art.

[0043] Example 1

[0044] This embodiment utilizes the thermal oxidation stability simulation evaluation method for heat transfer oil of the present invention to test and compare the thermal oxidation stability of five heat transfer oil samples A, B, C, D, and E with different properties. The test samples are as follows:

[0045] Sample A: Composed of base oil containing a mixture of alkanes, cycloalkanes and some aromatics, and functional additives such as antioxidants and dispersants, with functional additives not exceeding 5% of the total amount;

[0046] Sample B: Composed of base oil containing a mixture of alkanes, cycloalkanes and some aromatics, and functional additives such as antioxidants and dispersants, with functional additives not exceeding 2% of the total amount;

[0047] Sample C: Composed of base oil containing a mixture of alkanes, cycloalkanes, etc., and functional additives such as antioxidants and dispersants, with functional additives not exceeding 5% of the total amount;

[0048] Sample D: Contains alkanes, cycloalkanes, and aromatic hydrocarbons with general structures;

[0049] Sample E: Composed of alkanes, cycloalkanes, aromatics with general structures, and functional additives such as antioxidants and dispersants, it exhibits excellent high-temperature resistance; it also contains aromatics with conjugated structures.

[0050] Based on the differences in intermolecular bond energies, the thermal oxidation stability of several oil samples can be inferred as follows: Oil Sample B > Oil Sample A > Oil Sample C > Oil Sample E > Oil Sample D.

[0051] The specific testing and evaluation methods include the following steps:

[0052] S1. Contact 150g of heat transfer oil with the catalyst and conduct a high-temperature heating test;

[0053] The catalyst uses steel rods and copper rods; the copper rods have the following parameters: T2Y copper, 99.90% copper content, 6.35mm diameter, and 76.20mm length; the steel rods have the following parameters: T10A steel, 1% carbon content, 6.35mm diameter, and 76.20mm length.

[0054] The high-temperature heating test was conducted at 150℃ for 96 hours.

[0055] S2. Cool the heat transfer oil and catalyst to room temperature after the high-temperature heating test;

[0056] S3. The thermal oxidation stability of the heat transfer oil is measured, and the properties are: kinematic viscosity, viscosity index, color, acid value, sediment, flash point, auto-ignition point and refractive index.

[0057] S4. A comprehensive score is given based on the thermal oxidation stability of the heat transfer oil.

[0058] The test results are shown in Table 1.

[0059] Table 1. Performance test results of the thermal oxidation stability of the heat transfer oil in Example 1.

[0060]

[0061]

[0062] As can be seen from the data in Table 1, the color of all five samples changed after the thermal stability test, with samples C, D, and E showing more significant changes. Sample B performed best in all aspects, which is consistent with the aforementioned conclusion.

[0063] Example 2

[0064] This embodiment utilizes the thermal oxidation stability simulation evaluation method of the present invention to test and compare the thermal oxidation stability of five thermal oil samples A, B, C, D, and E with different properties. The thermal oil samples are the same as in Example 1, except that the specific testing and evaluation method differs from that in Example 1: the high-temperature heating test temperature is 180°C and the time is 72 hours.

[0065] The test results are shown in Table 2.

[0066] Table 2. Performance test results of thermal oxidation stability of heat transfer oil in Example 2.

[0067]

[0068]

[0069] As can be seen from the data in Table 2, the color of all five samples changed after the thermal stability test, with samples C, D, and E showing more significant changes. Sample B performed best in all aspects, which is consistent with the aforementioned conclusion.

[0070] Example 3

[0071] This embodiment utilizes the thermal oxidation stability simulation evaluation method of the present invention to test and compare the thermal oxidation stability of five thermal oil samples A, B, C, D, and E with different properties. The thermal oil samples are the same as in Example 1, except that the specific testing and evaluation method differs from that in Example 1: the high-temperature heating test temperature is 200°C, and the time is 24 hours.

[0072] The test results are shown in Table 3.

[0073] Table 3. Performance test results of thermal oxidation stability of heat transfer oil in Example 3.

[0074]

[0075] As can be seen from the data in Table 3, the color of all five samples changed after the thermal stability test, with samples C, D and E showing more significant changes. Sample B performed best in all aspects, which is consistent with the aforementioned conclusion.

[0076] Example 4

[0077] This embodiment utilizes the thermal oxidation stability simulation evaluation method of the present invention to test and compare the thermal oxidation stability of five thermal oil samples A, B, C, D, and E with different properties. The thermal oil samples are the same as in Example 1, except that the specific testing and evaluation method differs from Example 1 in that the high-temperature heating test temperature is 175°C and the time is 48 hours. The test results are shown in Table 4.

[0078] Table 4. Performance test results of the thermal oxidation stability of the heat transfer oil in Example 4.

[0079]

[0080] As can be seen from the data in Table 4, the color of all five samples changed after the thermal stability test, with samples C, D, and E showing more significant changes. Sample B performed best in all aspects, which is consistent with the aforementioned conclusion.

[0081] Comparative Example

[0082] This comparative example provides a method for simulating and evaluating the thermal oxidation stability of heat transfer oils. The thermal oxidation stability of five heat transfer oil samples (A, B, C, D, and E) with different properties is tested and compared. The heat transfer oil samples are the same as in Example 1; the only difference in the specific testing and evaluation method is the absence of a condenser.

[0083] The test results are shown in Table 5.

[0084] Table 5. Performance test results of thermal oxidation stability of comparative heat transfer oils

[0085]

[0086] As can be seen from the data in Table 5, the results for flash point, auto-ignition point, and sediment differ from the aforementioned inferences, and the regularity is worse, indicating that there is a certain mutual influence between different samples.

[0087] In summary, the advantages of the determination method of this invention are that the objectivity of the test and the reliability of the data are greatly improved. During the thermal oxidation stability test, the influence between different oil samples is minimized. The determination method of this invention can provide a more objective and comprehensive evaluation of samples that produce fine particulate sediment. Furthermore, the determination method of this invention adds items such as oil sample viscosity index, refractive index, flash point, autoignition point, and color, making it more comprehensive, objective, and accurate than Appendix C of GB 23971.

[0088] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for simulating and evaluating the thermal oxidation stability of heat transfer oil, characterized in that, The steps include the following: S1. Contact the heat transfer oil and catalyst and conduct a high-temperature heating test; S2. Cool the heat transfer oil and catalyst to room temperature after the high-temperature heating test; S3. The thermal oxidation stability of the heat transfer oil is measured, and the properties are: kinematic viscosity, viscosity index, color, acid value, sediment, flash point, auto-ignition point and refractive index. S4. A comprehensive score is given based on the thermal oxidation stability of the heat transfer oil. After step S2 is completed, the sample is first filtered through quantitative filter paper, and then filtered through a filter membrane with a pore size of 0.8~10 micrometers, and then step S3 is performed. The high-temperature heating test is conducted in a natural convection heating test chamber; the natural convection heating test chamber contains an oil sample container unit, which includes an oil sample container and a sample condensation device installed at the opening of the oil sample container; The method for determining the comprehensive score is as follows: (1) When the kinematic viscosity increases by ≤5%, the viscosity index decreases by ≤5, the color increases by ≤2, the acid value increases by ≤0.5 mg KOH / g, the sludge decreases by ≤5 mg / 100g, the flash point decreases by ≤5℃, the auto-ignition point decreases by ≤5℃, and the refractive index changes by ≤5%, the comprehensive score is Grade I. (2) When 5% < kinematic viscosity increase ≤ 15%, 5 < viscosity index decrease ≤ 10%, 2 < color increase ≤ 3, 0.5 mgKOH / g < acid value increase ≤ 0.6 mg KOH / g, 5 mg / 100g < sludge ≤ 10 mg / 100g, 5℃ < flash point decrease ≤ 10℃, 5℃ < auto-ignition point decrease ≤ 10℃, and 5% < refractive index change ≤ 10%, the comprehensive score is Grade II; (3) When 15% < kinematic viscosity increase ≤ 25%, 10 < viscosity index decrease ≤ 15, No. 3 < color increase ≤ No. 4, 0.6 mg KOH / g < acid value increase ≤ 0.8 mg KOH / g, 10 mg / 100g < sludge ≤ 20 mg / 100g, 10℃ < flash point decrease ≤ 15℃, 10℃ < auto-ignition point decrease ≤ 15℃, and 10% < refractive index change ≤ 20%, the comprehensive score is Grade III; (4) When 25% < kinematic viscosity increase ≤ 35%, 15 < viscosity index decrease ≤ 20, No. 4 < color increase ≤ No. 5, 0.8 mg KOH / g < acid value increase ≤ 1.0 mg KOH / g, 20 mg / 100g < sludge ≤ 50 mg / 100g, 15℃ < flash point decrease ≤ 20℃, 15℃ < auto-ignition point decrease ≤ 20℃, and 20% < refractive index change ≤ 30%, the comprehensive score is IV level; (5) When the kinematic viscosity increases by more than 35%, the viscosity index decreases by more than 20, the color increases by more than 5, the acid value increases by more than 1.0 mgKOH / g, the sludge increases by more than 50 mg / 100g, the flash point decreases by more than 20℃, the auto-ignition point decreases by more than 20℃, and the refractive index changes by more than 30%, the comprehensive score is grade V.

2. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to claim 1, characterized in that, The temperature of the high-temperature heating test was controlled by using a metal bath.

3. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to claim 2, characterized in that, The material of the metal bath is aluminum.

4. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to any one of claims 1 to 3, characterized in that, The catalyst is steel and / or copper.

5. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to any one of claims 1 to 3, characterized in that, In step S1, the amount of heat transfer oil added is 150-200g.

6. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to claim 5, characterized in that, In step S1, the amount of heat transfer oil added is 160-180g.

7. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to any one of claims 1 to 3, characterized in that, In step S1, the temperature of the high-temperature heating test is 150-200℃.

8. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to claim 7, characterized in that, The temperature for the high-temperature heating test is 160-180℃.

9. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to any one of claims 1 to 3, characterized in that, In step S1, the high-temperature heating test lasts for 24-96 hours.

10. The method for simulating and evaluating the thermal oxidation stability of heat transfer oil according to claim 9, characterized in that, In step S1, the high-temperature heating test lasts for 60-80 hours.

Images