Mechanical impurity analysis method for natural gas-to-ethylene glycol auxiliary material lubricating oil

Abstract

The invention discloses a mechanical impurity analysis method for natural gas-to-ethylene glycol auxiliary material lubricating oil. The method comprises the following steps: mixing to-be-detected lubricating oil and petroleum ether according to a certain ratio to form a sample solution; weighing quantitative filter paper for testing; keeping the weight of the quantitative filter paper constant; putting quantitative filter paper with constant weight into the glass funnel, heating and filtering the sample solution through a heating sleeve, and exhausting air in a suction flask through a mechanical impurity tester to form a certain negative pressure; pouring the sample solution into a glass funnel with quantitative filter paper for filtering; the quantitative filter paper is repeatedly washed with petroleum ether until no oil spots are left; weighing the quantitative filter paper with the impurities again; during the test, the solvent is corrected through a blank test; and taking an arithmetic mean value of two repeatedly measured results as a test result. The problems of poor safety and high test cost during lubricating oil mechanical impurity analysis can be effectively avoided, the accuracy of analysis data is ensured, and the physical and psychological health of staff is protected.

Description

Technical Field

[0001] The invention relates to the technical field of analysis and detection of mechanical impurities in lubricating oil of auxiliary materials for producing ethylene glycol from natural gas, and in particular to a method for analyzing mechanical impurities in lubricating oil of auxiliary materials for producing ethylene glycol from natural gas. Background Art

[0002] Ethylene glycol is an important chemical raw material, mainly used to make polyester, terylene, polyester resin, desiccant, plasticizer, surfactant, synthetic fiber, cosmetics and explosives, and used as a solvent for dyes, inks, etc., to prepare engine antifreeze, gas dehydrating agent, to make resins, and can also be used as a wetting agent for cellophane, fiber, leather, and adhesives. It can produce synthetic resin PET, fiber-grade PET, i.e. polyester fiber, and bottle-grade PET for making mineral water bottles, etc. It can also produce alkyd resin, glyoxal, etc., and is also used as an antifreeze. In addition to being used as an antifreeze for automobiles, it is also used for the transportation of industrial cold, generally called a coolant, and can also be used as a condensing agent like water.

[0003] Among them, the mechanical impurities in lubricating oil with ethylene glycol made from natural gas as an auxiliary material will increase the wear of engine parts and clog the oil filter. According to the current standard analysis method, the oil is first poured into the filter paper for filtration (sometimes combined with negative pressure suction filtration). After all the oil has basically dripped from the filter paper, toluene is poured into the filter paper to clean the residual oil and dilute it before dripping again. After multiple toluene washings of the filter paper, the residual oil on the filter paper is finally minimized, thereby achieving the accuracy of the analysis of the impurity content. However, since the flow-producing oil on the filter paper needs to be rinsed many times and the density and fluidity of the oil are poor, the test process takes a long time, which will inevitably cause some oils to be in contact with air for a long time and cause performance changes. Moreover, the length of time in the test process not only affects the test efficiency, but also affects the accuracy of the test results. The reagent used is toluene, which is very harmful to the analyst's body, and the procurement cycle is long, the process is cumbersome, and the price is expensive. Therefore, it is necessary to find a safer method with shorter test operation time to analyze the mechanical impurities of lubricating oil, so as to ensure that the lubricating oil with ethylene glycol made from natural gas as an auxiliary material has the problem of difficulty in reducing the accuracy error in the mechanical impurity analysis. Summary of the invention

[0004] In order to solve certain technical problems existing in the prior art, the purpose of this application is to provide a method for analyzing mechanical impurities in lubricating oil, an auxiliary material for producing ethylene glycol from natural gas, which can effectively avoid the problems of poor safety and high testing costs during the analysis of mechanical impurities in lubricating oil, thereby ensuring the accuracy of the analysis data and protecting the physical and mental health of employees.

[0005] In order to solve the above existing technical problems, this application adopts the following technical solutions:

[0006] A method for analyzing mechanical impurities in lubricating oil, an auxiliary material for natural gas to ethylene glycol, characterized in that the apparatus involved in the analysis method includes a suction filtration bottle, a mechanical impurity measuring instrument, a sampling bottle, a weighing bottle, a glass funnel, a washing bottle, a glass rod, a dryer, an analytical balance, petroleum ether, anhydrous ethanol and quantitative filter paper, and the steps of the analysis method include:

[0007] S1. Put the lubricating oil to be tested and petroleum ether into a sampling bottle in a certain proportion and shake until they are evenly mixed to form a sample solution;

[0008] S2. Place the quantitative filter paper for the test in a clean and dry open weighing bottle and weigh it using an analytical balance;

[0009] S3, drying the open weighing bottle with the quantitative filter paper in step S2 at a certain temperature, then covering the bottle cap and cooling it in a dryer for more than 30 minutes and weighing it again, weighing it to within 0.0002g, and finally repeating the drying and weighing 1 to 3 times until the difference between the two weighings does not exceed 0.0004g;

[0010] S4, placing the suction flask on the mechanical impurity analyzer, and connecting it to the suction interface of the suction flask through the suction pipe, placing the glass funnel in the heating jacket on the mechanical impurity analyzer and adjusting the height so that the bottom extends into the suction flask, and the mouth of the suction flask is sealed by the rubber stopper under the heating jacket;

[0011] S5, placing a constant weight quantitative filter paper in the glass funnel, heating the filtered sample solution with a heating jacket, and then evacuating the suction flask with a mechanical impurity analyzer to form a certain negative pressure;

[0012] S6. The sample solution is guided along the glass rod to a glass funnel with a quantitative filter paper for heating and drips into the suction filtration bottle in the shape of water drops after passing through the quantitative filter paper. The residual liquid in the sampling bottle is washed at least in sequence with petroleum ether and then poured into the glass funnel with the quantitative filter paper;

[0013] S7, petroleum ether flows along the glass rod into a glass funnel with quantitative filter paper; the residue on the quantitative filter paper is repeatedly rinsed with petroleum ether until no oil spots are left;

[0014] S8. After the filtration is completed, the quantitative filter paper with impurities is rinsed with a washing bottle containing anhydrous ethanol until no trace of the sample remains on the quantitative filter paper and the filtered solvent is completely transparent or colorless;

[0015] S9, after rinsing, put the quantitative filter paper with impurities into the corresponding weighing bottle before filtration and repeat the weighing in step S3;

[0016] S10. During the test, the solvent is corrected through a blank test; the arithmetic mean of the two repeated test results is taken as the test result.

[0017] Preferably, the analytical calculation formula of the test results is:

[0018]

[0019] Where:

[0020] m1----The mass of the filter paper and weighing bottle, in g;

[0021] m2----The mass of the filter paper and weighing bottle with impurities, in g;

[0022] m3----The mass of the filter paper and weighing bottle before the blank test filtration, in g;

[0023] m4----The mass of the filter paper and weighing bottle after the blank test filtration, in g;

[0024] m----The mass of the sample, in g.

[0025] Preferably, the quantitative filter paper has a conical structure, and the liquid level of the sample solution in the quantitative filter paper does not exceed 3 / 4 of the volume of the quantitative filter paper.

[0026] The quantitative filter paper has a conical structure, which enables it to better fit the inner wall of the glass funnel, and the liquid level of the sample solution in the quantitative filter paper does not exceed 3 / 4 of the volume of the quantitative filter paper, which can prevent the sample solution from dripping onto the side wall of the glass funnel due to operational errors, thereby affecting the final test results.

[0027] Preferably, the ratio of the lubricating oil to be tested and petroleum ether in the sampling bottle in step S1 is 10:3-5.

[0028] The ratio of the lubricating oil to be tested and petroleum ether is generally 10:3-5. After adding a certain amount of petroleum ether to dilute the lubricating oil to be tested, the sample solution can pass through the quantitative filter paper more quickly, avoiding the phenomenon of the sample solution being retained on the quantitative filter paper for a long time, and it is no longer necessary to add the dilution solution when the lubricating oil to be tested is in the quantitative filter paper and cannot pass through. Among them, when the proportion of petroleum ether exceeds half of the lubricating oil to be tested, it is easy to cause waste of petroleum ether and a long dripping time of the solution. When its proportion is less than 1 / 3, the dripping efficiency of the lubricating oil to be tested cannot be controlled to the maximum value due to insufficient dilution, and the test time cannot be significantly shortened. Therefore, the amount of petroleum ether added generally exceeds 1 / 3 and does not exceed 1 / 2 of the amount of the lubricating oil to be tested.

[0029] Preferably, the heating temperature of the heating jacket is 45-50°C, and the temperature of the sample solution after being heated by the heating jacket is between 40°C and 45°C.

[0030] At present, when heating lubricating oil, the heating temperature is generally 40°C. Since the oil agent takes a long time to pass through the quantitative filter paper, the heating temperature cannot be increased. Although the temperature is low, the overall test power is higher, the working environment is poor, and the oil agent is in a long-term heating state, which has a great impact on environmental hygiene. Therefore, after the sample solution is diluted in advance, its efficiency of passing through the quantitative filter paper is accelerated, and the heating temperature of the heating jacket can be set to 45-50°C. The temperature of the sample solution after heating by the heating jacket is between 40°C and 45°C. The heating speed of the sample solution is increased by increasing the temperature, so that the filtering effect of the oil agent can be better guaranteed, so that the sample solution stays on the quantitative filter paper for a shorter time, and the smell emitted during the heating process is less, the environmental hygiene is significantly improved, and the impact on the health of the operator is smaller.

[0031] Preferably, the negative pressure formed by the suction bottle through the mechanical impurity analyzer is 0.004-0.006 MPa.

[0032] Due to the high concentration of the oil, its fluidity is poor. If the negative pressure is not increased, although the diluted sample solution can also pass through the quantitative filter paper, the dripping speed is relatively slow, which makes the entire test process long and difficult to control the flow rate. By forming a negative pressure on the suction bottle, it is convenient to accelerate the dripping of the sample solution, so that the sample solution can achieve the maximum efficiency in the dripping efficiency within the controllable range, and effectively increase the fluidity of the sample solution. At the same time, the negative pressure required for direct dripping of the lubricating oil is generally about 0.008mpa, the dripping efficiency is not high and the efficiency is uncontrollable. After the negative pressure increases, it is easy to cause local damage to the bottom of the quantitative filter paper. Compared with the direct negative pressure dripping of the lubricating oil, the negative pressure required for the diluted sample solution is only 0.004~0.006mpa, which is smaller and more efficient during the experiment.

[0033] Preferably, in step S3, the drying temperature of the open weighing bottle with the quantitative filter paper is 115°±2°, and the drying time is 30 to 45 minutes.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. When analyzing mechanical impurities in lubricating oils with ethylene glycol made from natural gas as auxiliary materials, compared with the standard method, in the first step, the lubricating oil to be tested and petroleum ether are directly placed in a sampling bottle in a certain proportion and shaken until they are evenly mixed to form a sample solution. This can prevent the lubricating oil to be tested in the sample solution from being retained for a long time due to poor fluidity after being poured into the quantitative filter paper, effectively improving the stability of the lubricating oil to be tested passing through the quantitative filter paper;

[0036] 2. The sample solution poured into the quantitative filter paper can be heated by the heating jacket on the mechanical impurity analyzer and sucked by the suction bottle under negative pressure at the same time, thereby further improving the filtration efficiency of the oil in the sample solution, so that it can pass through the quantitative filter paper in the shortest time without causing errors in the filtration effect, effectively avoiding the generation of uncontrollable errors caused by the sample solution being retained in the quantitative filter paper for a long time;

[0037] 3. Using petroleum ether instead of toluene not only solves the problem of toxicity and harm, but also solves the problem that the current test method is difficult to popularize. By replacing the diluent and combining it with the combination of negative pressure + heating, the experiment of mechanical impurities in lubricating oil can be more popularized, the experimental operation time is shorter and safer, and the final analysis results in a smaller accuracy error. DETAILED DESCRIPTION

[0038] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0039] In the description of the present application, it should be understood that the terms "up", "down", "left", "right", etc., indicating directions or positional relationships are based on directions or positional relationships and are only used to facilitate the description of the present application and simplify the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present application.

[0040] The terms "first", "second", etc. in this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0041] Embodiment 1:

[0042] A method for analyzing mechanical impurities in lubricating oil, an auxiliary material of natural gas to ethylene glycol, the apparatus involved in the analysis method includes a suction filtration bottle, a mechanical impurity measuring instrument, a sampling bottle, a weighing bottle, a glass funnel, a washing bottle, a glass rod, a dryer, an analytical balance, petroleum ether, anhydrous ethanol and quantitative filter paper, and the steps of the analysis method include:

[0043] S1. Put the lubricating oil to be tested and petroleum ether in a ratio of 10:3-5 into a sampling bottle and shake until the mixture is evenly mixed to form a sample solution;

[0044] S2. Place the quantitative filter paper for the test in a clean and dry open weighing bottle and weigh it using an analytical balance;

[0045] S3, drying the open weighing bottle with quantitative filter paper in step S2 at a drying temperature of 115°±2° for 30-45 min, then covering the bottle cap and cooling it in a dryer for more than 30 min and weighing it again, weighing it to within 0.0002 g, and finally repeating the drying and weighing 1-3 times until the difference between the two weighings does not exceed 0.0004 g;

[0046] S4, placing the suction flask on the mechanical impurity analyzer, and connecting it to the suction interface of the suction flask through the suction pipe, placing the glass funnel in the heating jacket on the mechanical impurity analyzer and adjusting the height so that the bottom extends into the suction flask, and the mouth of the suction flask is sealed by the rubber stopper under the heating jacket;

[0047] S5. Place the constant weight quantitative filter paper in the glass funnel, heat and filter the sample solution through the heating jacket, and then evacuate the suction flask through the mechanical impurity analyzer to form a certain negative pressure; the quantitative filter paper is a conical structure, and the liquid level of the sample solution in the quantitative filter paper does not exceed 3 / 4 of the volume of the quantitative filter paper; the heating temperature of the heating jacket is 45-50°C, and the temperature of the sample solution after being heated by the heating jacket is between 40°C and 45°C; the negative pressure formed by the suction flask through the mechanical impurity analyzer is 0.004-0.006 MPa;

[0048] S6. The sample solution is guided along the glass rod to a glass funnel with a quantitative filter paper for heating and drips into the suction filtration bottle in the shape of water drops after passing through the quantitative filter paper. The residual liquid in the sampling bottle is washed at least in sequence with petroleum ether and then poured into the glass funnel with the quantitative filter paper;

[0049] S7, petroleum ether flows along the glass rod into a glass funnel with quantitative filter paper; the residue on the quantitative filter paper is repeatedly rinsed with petroleum ether until no oil spots are left;

[0050] S8. After the filtration is completed, the quantitative filter paper with impurities is rinsed with a washing bottle containing anhydrous ethanol until no trace of the sample remains on the quantitative filter paper and the filtered solvent is completely transparent or colorless;

[0051] S9, after rinsing, put the quantitative filter paper with impurities into the corresponding weighing bottle before filtration and repeat the weighing in step S3;

[0052] S10. During the test, the solvent is corrected through a blank test; the arithmetic mean of the two repeated test results is taken as the test result.

[0053] When conducting mechanical impurity analysis on lubricating oil with ethylene glycol made from natural gas as auxiliary material, compared with the standard method, in the first step, the lubricating oil to be tested and petroleum ether are directly put into the sampling bottle in a certain proportion and shaken until they are evenly mixed to form a sample solution. This can prevent the lubricating oil to be tested in the sample solution from being retained for a long time due to poor fluidity after being poured into the quantitative filter paper, effectively improving the stability of the lubricating oil to be tested passing through the quantitative filter paper, and the sample solution poured into the quantitative filter paper can be heated by the heating jacket on the mechanical impurity analyzer and sucked by negative pressure by the suction bottle at the same time, thereby further The filtration efficiency of the oil in the sample solution is improved, so that it can pass through the quantitative filter paper in the shortest time without causing errors in the filtration effect, and effectively avoids the generation of uncontrollable errors caused by the sample solution being retained in the quantitative filter paper for a long time. The use of petroleum ether instead of toluene as the diluent for the oil not only solves the problem of toxicity and harm, but also solves the problem that the current test method is difficult to popularize. By replacing the diluent and combining it with the combination of negative pressure + heating, the experiment of mechanical impurities in lubricating oil can be more popularized, the experimental operation time is shorter and the safety is higher, and the accuracy error obtained in the final analysis is smaller.

[0054] Further improvement is that the analysis and calculation formula of the test results is:

[0055]

[0056] Where:

[0057] m1----The mass of the filter paper and weighing bottle, in g;

[0058] m2----The mass of the filter paper and weighing bottle with impurities, in g;

[0059] m3----The mass of the filter paper and weighing bottle before the blank test filtration, in g;

[0060] m4----The mass of the filter paper and weighing bottle after the blank test filtration, in g;

[0061] m----The mass of the sample, in g.

[0062] Comparative Example 1:

[0063] The existing method for analyzing mechanical impurities in lubricating oil, an auxiliary material of natural gas to ethylene glycol, comprises the following steps:

[0064] S1. Put the lubricating oil to be tested into a sampling bottle and shake it until it is evenly mixed to form a sample solution;

[0065] S2. Place the quantitative filter paper for the test in a clean and dry open weighing bottle and weigh it using an analytical balance;

[0066] S3, drying the open weighing bottle with the quantitative filter paper in step S2 at a drying temperature of 105-110°C for 30 minutes, then covering the bottle cap and cooling it in a dryer for more than 30 minutes and weighing it again, weighing it to within 0.0002g, and finally repeating the drying and weighing at least 3 times until the difference between the two weighings does not exceed 0.0004g;

[0067] S4, placing the suction filtration flask on an electric heater and heating it to 40 degrees, and connecting it to the distillation flask interface through an extractor equipped with a condenser;

[0068] S5. Place the quantitative filter paper with constant weight in the extractor, and heat and filter the sample solution by setting the heating jacket to 40 degrees. The quantitative filter paper has a conical structure, and the liquid level of the sample solution in the quantitative filter paper does not exceed 3 / 4 of the volume of the quantitative filter paper.

[0069] S6. Toluene is boiled by heating, and the vapor causes the sample solution to flow along the reflux pipe into the extractor with quantitative filter paper for heating and drip into the distillation flask in the form of water drops. The filter paper in the extractor is rinsed with toluene until there are no oil spots and the filtered solvent is completely transparent or colorless.

[0070] S7, after rinsing, put the quantitative filter paper with impurities into the corresponding weighing bottle before filtration and repeat the weighing in step S3;

[0071] S8. During the test, the solvent is corrected through a blank test; the arithmetic mean of the two repeated measurements is taken as the test result.

[0072] Taking the test of 250 ml of 46# turbine oil as an example, the number of repeated drying and weighing in Example 1 is generally 2 times, while that in Comparative Example 1 is 3 times. The results of the tests using two different methods are shown in Tables 1 to 4:

[0073] Table 1

[0074]

[0075] Table 2

[0076]

[0077] Table 3

[0078]

[0079] Table 4

[0080]

[0081] Table 1 is a comparison table of the results of mechanical impurities in 46# turbine oil detected by using petroleum ether and toluene as solvents. It can be seen from Table 1 that after 6 tests, the largest mass fraction deviation was 0.0008, and the accuracy test fully met the requirements of the test results, indicating that petroleum ether can completely replace toluene as a solvent for the detection of mechanical impurities in 46# turbine oil, and it is safer.

[0082] Table 2 is a comparison of the constant weight time of an open weighing bottle with quantitative filter paper before and after the improvement of drying. The present invention uses the temperature required by the standard and the temperature after the improvement method to carry out the test. The results show that while ensuring the detection accuracy, the analysis time required by the new method is shorter, and there is sufficient time to carry out the test during working hours in the morning or afternoon. For the test personnel, the time required is shorter, and more types and quantities of oils can be tested every working day.

[0083] Table 3 is a comparison of the analysis time required after the heating jacket temperature is improved. It can be seen from Table 3 that the time for 46# turbine oil to pass through the quantitative filter paper is significantly improved, thereby effectively shortening the manual operation time, making the manual operation easier and less labor-intensive, and making it easier to promote and popularize.

[0084] Table 4 shows the time consumption after the vacuum pressure is improved. It can be seen from Table 4 that the time required for pressure is shorter.

[0085] The above-mentioned implementation modes are only preferred implementation modes of the present application and cannot be used to limit the scope of protection of the present application. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present application shall fall within the scope of protection required by the present application.

Claims

1. A method for analyzing mechanical impurities in lubricating oil, an auxiliary material for natural gas to ethylene glycol, characterized in that: The apparatus involved in the analysis method include a suction filtration bottle, a mechanical impurity measuring instrument, a sampling bottle, a weighing bottle, a glass funnel, a washing bottle, a glass rod, a dryer, an analytical balance, petroleum ether, anhydrous ethanol and quantitative filter paper. The steps of the analysis method include: S1. Put the lubricating oil to be tested and petroleum ether into a sampling bottle in a certain proportion and shake until they are evenly mixed to form a sample solution; S2. Place the quantitative filter paper for the test in a clean and dry open weighing bottle and weigh it using an analytical balance; S3, drying the open weighing bottle with the quantitative filter paper in step S2 at a certain temperature, then covering the bottle cap and cooling it in a dryer for more than 30 minutes and weighing it again, weighing it to within 0.0002g, and finally repeating the drying and weighing 1 to 3 times until the difference between the two weighings does not exceed 0.0004g; S4, placing the suction flask on the mechanical impurity analyzer, and connecting it to the suction interface of the suction flask through the suction pipe, placing the glass funnel in the heating jacket on the mechanical impurity analyzer and adjusting the height so that the bottom extends into the suction flask, and the mouth of the suction flask is sealed by the rubber stopper under the heating jacket; S5, placing a constant weight quantitative filter paper in the glass funnel, heating the filtered sample solution with a heating jacket, and then evacuating the suction flask with a mechanical impurity analyzer to form a certain negative pressure; S6. The sample solution is guided along the glass rod to a glass funnel with a quantitative filter paper for heating and drips into the suction filtration bottle in the shape of water drops after passing through the quantitative filter paper. The residual liquid in the sampling bottle is washed at least in sequence with petroleum ether and then poured into the glass funnel with the quantitative filter paper; S7, petroleum ether flows along the glass rod into a glass funnel with quantitative filter paper; the residue on the quantitative filter paper is repeatedly rinsed with petroleum ether until no oil spots are left; S8. After the filtration is completed, the quantitative filter paper with impurities is rinsed with a washing bottle containing anhydrous ethanol until no trace of the sample remains on the quantitative filter paper and the filtered solvent is completely transparent or colorless; S9, after rinsing, put the quantitative filter paper with impurities into the corresponding weighing bottle before filtration and repeat the weighing in step S3; S10. During the test, the solvent is corrected through a blank test; the arithmetic mean of the two repeated test results is taken as the test result.

2. The method for analyzing mechanical impurities of lubricating oil of auxiliary materials for natural gas to ethylene glycol according to claim 1, characterized in that: The analytical calculation formula for the test results is: Where: m1----The mass of the filter paper and weighing bottle, in g; m2----The mass of the filter paper and weighing bottle with impurities, in g; m3----The mass of the filter paper and weighing bottle before the blank test filtration, in g; m4----The mass of the filter paper and weighing bottle after the blank test filtration, in g; m----The mass of the sample, in g.

3. The method for analyzing mechanical impurities of lubricating oil of auxiliary materials for natural gas to ethylene glycol according to claim 1, characterized in that: Preferably, the quantitative filter paper has a conical structure, and the liquid level of the sample solution in the quantitative filter paper does not exceed 3 / 4 of the volume of the quantitative filter paper.

4. Preferably, the ratio of the lubricating oil to be tested and petroleum ether in the sampling bottle in step S1 is 10:3-5.

5. Preferably, the heating temperature of the heating jacket is 45-50°C, and the temperature of the sample solution after being heated by the heating jacket is between 40°C and 45°C.

6. Preferably, the negative pressure formed by the suction bottle through the mechanical impurity analyzer is 0.004-0.006 MPa.

7. Preferably, in step S3, the drying temperature of the open weighing bottle with the quantitative filter paper is 115°±2°, and the drying time is 30 to 45 minutes.

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