Method and device for measuring and correcting the water saturation content of coal-based hydrocarbon fuel oil

Abstract

The present application belongs to the technical field of saturated water detection, and relates to a coal-based hydrocarbon fuel oil saturated water content measurement correction method and device, the measurement correction method comprising: 1) determining the water activity of each temperature node corresponding saturated fuel oil sample at normal temperature; and detecting the water content corresponding to each temperature node saturated fuel oil sample by using Karl Fisher Coulomb method; 2) correcting the saturation degree calculation formula of the saturated fuel oil sample by using the measurement results of step 1), and determining the correction coefficients A, B and C values; 3) cooling the saturated fuel oil sample, real-time monitoring the temperature and the corresponding water activity in the cooling process, and substituting into the corrected formula, and calculating the saturated water content in the saturated fuel oil at low temperature. The coal-based hydrocarbon fuel oil saturated water content measurement correction method provided by the present application corrects the saturation degree calculation formula, thereby improving the measurement accuracy of trace saturated water at low temperature.

Description

Technical Field

[0001] This invention belongs to the field of saturated water detection technology, and relates to a method and apparatus for measuring and correcting the saturated water content of coal-based hydrocarbon fuel oil, which is used to accurately measure the saturated water content in coal-based hydrocarbon fuel oil at low temperatures. Background Technology

[0002] During the refining, storage, transportation, refueling, and use of coal-based hydrocarbon fuels, a small amount of water inevitably mixes into the fuel due to various internal and external influencing factors. Especially when aircraft fly at high altitudes and in low temperatures, the low temperature can cause trace amounts of water in the fuel to condense into ice. Water in fuel oil can exist in three forms: dissolved water, suspended water, and free water. When coal-based hydrocarbon fuel is exposed to air, it absorbs moisture from the air and the surrounding environment until a moisture balance is reached. Undissolved water in the fuel system, i.e., suspended and free water, can contaminate the aircraft fuel system, reduce fuel performance, and when the temperature is below its freezing point, water crystallization may occur, causing blockages in critical components of the aircraft fuel system such as pipes, heat exchangers, and filters. This can obstruct fuel flow to the engine, leading to insufficient fuel supply. Furthermore, as the temperature of the coal-based hydrocarbon fuel decreases further, the dissolved water continues to precipitate and freeze, leading to even more serious safety hazards.

[0003] Patent application CN106338490A discloses an infrared light sensor for detecting water concentration, which has a small detection error caused by changes in external temperature and humidity. However, this method is expensive, the equipment is complex to use and maintain, and it requires a high level of technical expertise from the operators. Patent application CN103033437A discloses a measuring instrument for determining water content by gravimetric method. The method is simple and the equipment cost is low. However, this method has low measurement accuracy, takes a long time to measure, and the equipment is large and inconvenient to carry.

[0004] The Karl Fischer titrator determines trace water based on Faraday's law of electrolysis, calculating the water content in the sample. Methods include Karl Fischer volumetric titration and Karl Fischer coulometric titration. The coulometric method offers high accuracy and is primarily used to measure the dissolved and undissolved total water content in fuels. However, because Karl Fischer titrators can only be used in environments ranging from 2°C to 50°C, at lower temperatures, below 0°C, or even -40°C, they can detect undissolved frozen water, introducing significant errors in the detection of dissolved water content and leading to inaccurate measurement results. Summary of the Invention

[0005] To address the technical problems of large errors and inaccurate measurement results in dissolved water measurement at low temperatures, this invention provides a method and apparatus for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil. This invention utilizes a combination of an oil moisture detector and the Karl Fischer coulomb method to correct the coefficients of the saturation calculation formula, thereby improving the measurement accuracy of saturated water content in fuel oil at low temperatures.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for measuring saturated water content includes the following steps:

[0008] 1) Determine the water content of saturated fuel oil samples at room temperature

[0009] The prepared saturated fuel sample was heated, and the temperature and water activity of the saturated fuel sample were monitored in real time during the heating process. The water activity values ​​at the temperature nodes of 20℃, 25℃, 30℃, 35℃ and 40℃ were recorded respectively. The water content of the saturated fuel sample at each temperature node was detected by Karl Fischer coulometric method.

[0010] 2) From the water content values ​​corresponding to the saturated fuel samples at each temperature node, take the water activity corresponding to three temperature nodes with a temperature difference of 10℃, and correct the saturation calculation formula (1) of the saturated fuel samples to determine the correction coefficients A, B and C.

[0011]

[0012] ppm x =ppm / aw (2)

[0013] in:

[0014] ppm x Saturation level in ppm;

[0015] aw represents water activity;

[0016] T is the Kelvin temperature;

[0017] ppm refers to the saturated water content of coal-based hydrocarbon fuel oil;

[0018] 3) Cool the prepared saturated fuel sample from 20℃ to -40℃, monitor the temperature and corresponding water activity in real time during the cooling process, record the real-time monitoring data, and substitute it into the modified formula (1) in step 2) to obtain the ppm of the saturated fuel sample at low temperature. x Substituting this into formula (2), we obtain the saturated water content (ppm) in saturated fuel at low temperature.

[0019] Further specifying, in step 1), the heating rate is approximately 2–3 °C / min.

[0020] Further specifying that, during the heating process in step 1), the saturated fuel sample is stirred.

[0021] Further specifying that when correcting the saturation calculation formula (1) in step 2), the average value of 3 to 5 measurements at each temperature node is taken.

[0022] Further specifying, in step 3), the cooling rate is approximately 0.5–1.5 °C / min.

[0023] Further specifying, step 3) uses a 5°C gradient for cooling.

[0024] Furthermore, in steps 1) and 3), an oil moisture analyzer is used to monitor temperature and water activity in real time.

[0025] Further specifying, in steps 1) and 3), the preparation process of the saturated fuel oil sample is as follows: at a temperature of 27±1℃, water is atomized and continuously circulated to mix with fuel oil, and undissolved water in the fuel oil is removed to obtain a saturated fuel oil sample.

[0026] Further specified, the atomization rate is 0.25–0.39 mL / min.

[0027] An apparatus for implementing a method for measuring and correcting the saturated water content of coal-based hydrocarbon fuel oil includes a saturated fuel oil water distribution unit, a high and low temperature test chamber, an oil moisture detector, a Karl Fischer titrator, a data correction unit, and a water content calculation unit.

[0028] The saturated fuel water mixing unit is used to prepare saturated fuel samples and atomize the saturated fuel samples.

[0029] The high and low temperature test chamber is used to heat up and cool down the prepared saturated fuel sample;

[0030] The oil moisture detector is used to monitor the temperature and water activity of a saturated fuel sample during heating and cooling in real time; it is used to transmit the monitoring data during heating to the data correction unit and the monitoring data during cooling to the water content calculation unit.

[0031] The Karl Fischer titrator is used to monitor the water content at different temperatures during the heating process of the saturated fuel sample in real time and transmit the data to the data correction unit.

[0032] The data correction unit is used to receive the temperature, water activity and corresponding water content of the saturated fuel sample during the heating process, correct the saturation calculation formula according to the received data, and transmit the corrected saturation calculation formula to the water content calculation unit.

[0033] The water content calculation unit is used to calculate the saturated water content in saturated fuel at low temperature based on the temperature, water activity, and corrected saturation calculation formula received during the cooling process.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. This invention uses an oil moisture analyzer and the Karl Fischer coulometric method at room temperature to correct and calibrate the coefficients of the saturation calculation formula in the oil moisture analyzer, thereby accurately determining the water content in the coal-based hydrocarbon fuel sample at a low temperature of -40℃. This method has high reliability and accuracy.

[0036] 2. The optimized method of the present invention effectively solves the problems of high cost, inconvenience of use and insufficient accuracy in the measurement of trace water in coal-based hydrocarbon fuels. It is more accurate and convenient for measuring and monitoring the saturated water content of coal-based hydrocarbon fuels at low temperatures, and the measurement speed is fast and efficient. Attached Figure Description

[0037] Figure 1 This is a simplified diagram of the entire measurement method of the present invention;

[0038] Figure 2 This is a schematic diagram of the measuring device of the present invention;

[0039] Figure 3 This is a simplified diagram of the saturated fuel water distribution unit of the present invention;

[0040] Figure 4 This is a schematic diagram illustrating the deviation in the determination of saturated water content in Example 1;

[0041] Figure 5 This is the fitted curve for the determination of saturated water content in Example 1;

[0042] Figure 6 This is a schematic diagram illustrating the deviation in the determination of saturated water content in Example 2;

[0043] Figure 7 This is the fitted curve for the determination of saturated water content in Example 2;

[0044] Figure 8 This is a schematic diagram illustrating the deviation in the determination of saturated water content in Example 3;

[0045] Figure 9 This is the fitted curve for the determination of saturated water content in Example 3;

[0046] Figure 10This is a schematic diagram illustrating the deviation in the determination of saturated water content in Comparative Example 1.

[0047] Figure 11 The fitting curve for the determination of saturated water content in Comparative Example 1;

[0048] Figure 12 This is a schematic diagram illustrating the deviation in the determination of saturated water content in Comparative Example 2.

[0049] Figure 13 The fitting curve for the determination of saturated water content in Comparative Example 2;

[0050] Figure 14 This is a schematic diagram illustrating the deviation in the determination of saturated water content in Comparative Example 3.

[0051] Figure 15 The fitting curve for the determination of saturated water content in Comparative Example 3;

[0052] in:

[0053] 1—Oil storage tank; 2—Water distribution tank; 3—Micro-mesh atomizer; 4—Temperature sensor; 5—Static mixer; 6—Oil moisture detector; 7—Sampling port; 8—Heat exchanger; 9—Water separator; 10—Gear oil pump. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of specific examples, and further explained.

[0055] See Figure 1 The present invention provides a method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil, comprising the following steps.

[0056] 1) Determine the water content of saturated fuel oil samples at room temperature

[0057] The prepared saturated fuel sample was heated, and the temperature and water activity of the saturated fuel sample were monitored in real time during the heating process. The water activity values ​​at temperature nodes of 20℃, 25℃, 30℃, 35℃ and 40℃ were recorded respectively. The water content of the saturated fuel sample at each temperature node was detected by Karl Fischer coulomb method.

[0058] Specifically, a saturated fuel oil sample is placed in a beaker into a high and low temperature test chamber, with the fuel oil filling 1 / 2 to 2 / 3 of the beaker's volume. The oil moisture analyzer is fixed in the upper middle part of the fuel oil sample. The initial temperature is set to 20℃, and then the temperature is increased to 40℃ in increments of 5℃, with a heating rate of approximately 2 to 3℃ / min. At each temperature point, the mixture is stirred for 3 to 5 minutes. After standing for 20 to 30 minutes, the readings from the oil moisture analyzer are recorded. Simultaneously, a 10ml syringe is used to sample the water content of the coal-based hydrocarbon fuel using the Karl Fischer coulometric method. The same method is used to operate at different temperatures.

[0059] 2) From the water content values ​​corresponding to the saturated fuel samples at each temperature node, take the water activity corresponding to three temperature nodes with a temperature difference of 10℃, and correct the saturation calculation formula (1) of the saturated fuel samples to determine the correction coefficients A, B and C.

[0060]

[0061] ppm x =ppm / aw (2)

[0062] in:

[0063] ppm x Saturation level in ppm;

[0064] aw represents water activity;

[0065] T is the Kelvin temperature;

[0066] ppm refers to the saturated water content of coal-based hydrocarbon fuel oil.

[0067] Specifically, in step 1), the water content of coal-based hydrocarbon fuel is determined by the Karl Fischer coulometric method. The water activity of the coal-based hydrocarbon fuel is measured at three temperatures with a difference of at least 10°C using an oil moisture analyzer. Measurements are taken 3-5 times at each temperature point, and the average is calculated. The corresponding correction coefficients A, B, and C are calculated from the water content and water activity using formulas. The absolute values ​​are multiplied by 100 and stored in the oil moisture analyzer. In other words, three temperature points with a difference of 10°C are selected, along with the water content of the coal-based hydrocarbon fuel measured by the Karl Fischer coulometric method at these three temperature points, and the water activity corresponding to these three temperature points in the oil moisture analyzer. These values ​​are substituted into formulas (1) and (2) respectively to establish three equations concerning the correction coefficients A, B, and C. The correction coefficients A, B, and C are then solved to complete the correction of the ppm saturation calculation formula.

[0068] 3) Cool the prepared saturated fuel sample from 20℃ to -40℃, monitor the temperature and corresponding water activity in real time during the cooling process, record the real-time monitoring data, and substitute it into the modified formula (1) in step 2) to obtain the ppm of the saturated fuel sample at low temperature. x Substituting this into formula (2), we obtain the saturated water content (ppm) in saturated fuel at low temperature.

[0069] Specifically, a prepared saturated fuel sample is placed in a beaker, filling the beaker to 1 / 2 to 2 / 3 of its volume. The beaker is then placed in a high and low temperature test chamber for cooling. Since the oil moisture analyzer is mainly used to test the dissolved water in the fuel, it is fixed at the point where the oil sample is immersed to monitor its value in real time. The initial fuel temperature is set to 20°C, and then the temperature is lowered to -40°C at a rate of 5°C / min, with a cooling rate of approximately 0.5 to 1.5°C / min, to obtain the accurate low-temperature saturated water content.

[0070] In steps 1) and 3) of this invention, the preparation process of the saturated fuel oil sample is as follows: at a temperature of 27±1℃, water is atomized and continuously circulated to mix with fuel oil, and undissolved water in the fuel oil is removed to obtain the saturated fuel oil sample.

[0071] When preparing saturated fuel, the saturated fuel is atomized at a rate of 0.25–0.39 mL / min.

[0072] Atomization was achieved using an atomizer, with particles smaller than 5 μm accounting for 55.49–67.97% of the atomizer. (See [link to relevant documentation]). Figure 2 The present invention also provides a saturated water content measuring device, including a saturated fuel water distribution unit, a high and low temperature test chamber, an oil moisture detector 6, a Karl Fischer titrator, a data correction unit and a water content calculation unit.

[0073] The saturated fuel water mixing unit is used to prepare saturated fuel samples and atomize them.

[0074] High and low temperature test chambers are used to heat up and cool down prepared saturated fuel samples.

[0075] The oil moisture analyzer 6 is used to monitor the temperature and water activity of saturated fuel samples during the heating process and the temperature and water activity of saturated fuel samples during the cooling process in real time; it is used to transmit the monitoring data during the heating process to the data correction unit and the monitoring data during the cooling process to the water content calculation unit.

[0076] The Karl Fischer titrator is used to monitor the water content at different temperatures during the heating process of a saturated fuel sample in real time and transmit the data to the data correction unit.

[0077] The data correction unit is used to receive the temperature, water activity and corresponding water content of the saturated fuel sample during the heating process, correct the saturation calculation formula according to the received data, and transmit the corrected saturation calculation formula to the water content calculation unit.

[0078] The water content calculation unit is used to calculate the saturated water content in saturated fuel at low temperatures based on the temperature, water activity, and corrected saturation calculation formula received during the cooling process.

[0079] For details, see Figure 3 The saturated fuel water distribution unit includes an oil storage tank 1, a water distribution tank 2, a micro-mesh atomizer 3, a temperature sensor 4, a static mixer 5, an oil moisture detector 6, a sampling port 7, a heat exchanger 8, a water separator 9, and a gear oil pump 10.

[0080] Coal-based hydrocarbon fuel oil is circulated and mixed with water through a saturated fuel oil water distribution unit. The fuel oil to be mixed with water is placed in the oil storage tank 1 and connected in sequence through pipelines to the micro-mesh atomizer 3, temperature sensor 4, static mixer 5, oil moisture detector 6, sampling port 7, heat exchanger 8, water separator 9, and gear oil pump 10, finally returning to the oil storage tank 1 to form a circulation pipeline. During water mixing, the gear oil pump 10 starts working, first pumping water from the water distribution tank 2 into the fuel pipeline through the micro-mesh atomizer 3 according to the calculated water injection volume, and then mixing it with the coal-based hydrocarbon fuel oil in the static mixer 5. During the mixing process, the temperature of the saturated fuel oil water distribution system pipeline is controlled at 27±1℃ through the heat exchanger 8. The ambient temperature of the water distribution environment is monitored by the temperature sensor 4. The water separator 9 is used to absorb undissolved water in the coal-based hydrocarbon fuel. The water-absorbing material is a high-molecular-weight water-absorbing resin. The water distribution process is cyclical, and the water activity value of the fuel oil and water mixture is monitored in real time by the oil moisture detector 6 until the index requirements of saturated fuel oil are met. It is generally believed that adding 1 ml of water to every 1 L of fuel oil is sufficient for saturation. After the water distribution is completed, the saturated fuel oil is taken out from the sampling port 7.

[0081] The measurement method protected by this invention will be described in detail through several examples.

[0082] Example 1

[0083] The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil in this embodiment includes the following steps.

[0084] (1) Take a sample of fuel oil prepared by the coal-based hydrocarbon fuel saturated fuel oil water distribution system, put the sample into a beaker and place it in a high and low temperature test chamber. Set the test chamber temperature to 20℃. After the temperature is constant for 20 minutes, insert the oil water detector into the upper part of the fuel oil to monitor the temperature and water activity of the fuel oil sample in real time and record it. After the temperature is constant, take 3g of the sample from the upper part of the beaker for Karl Fischer titration experiment. Repeat the measurement three times and take the average value to obtain the saturated water content value at this temperature. Increase the temperature of the test chamber every 2℃ as a detection point until 40℃. Repeat the same steps. After the temperature is constant, record the temperature and water activity of the fuel oil sample, and take 3g of the sample from the upper part of the beaker for Karl Fischer titration experiment. Repeat the measurement three times and take the average value to obtain the saturated water content value at each temperature.

[0085] (2) Take three sets of data with a temperature difference of 10℃, namely 20℃, 30℃ and 40℃ (see Table 1) to correct the coefficients of the oil moisture detector. By using the temperature, water activity and water content measured by Karl Fischer, the saturation calculation formula is corrected using the water activity and water content measured by Karl Fischer, and the correction coefficients A, B and C are determined.

[0086]

[0087] ppm x =ppm / aw (2)

[0088] in:

[0089] ppm x Saturation level in ppm;

[0090] aw represents water activity;

[0091] T is the Kelvin temperature;

[0092] ppm refers to the saturated water content of coal-based hydrocarbon fuel oil;

[0093] Finally, the values ​​of A, B, and C are calculated, and their absolute values ​​are multiplied by 100 and stored in a register, as shown in the table below.

[0094] Table 1. Water activity values ​​at three temperatures in Example 1

[0095] T / ℃ T / K water activity aw ppm saturation 20 293.06 0.6194 29.06 30 303.16 0.3823 47.08 40 313.16 0.2415 74.53

[0096] We get A = 461991.21, B = -6787.01, and C = 19.45.

[0097] (3) Next, the saturated water content below 20℃ was measured.

[0098] The temperature in the high and low temperature test chamber was changed, and the temperature was continuously lowered at 2.5℃ intervals until -40℃. The water activity value corresponding to any temperature at the low temperature was measured and substituted into the corrected formula (1) to calculate the ppm value. x Then, substitute the values ​​into formula (2) to calculate the saturated water content of the coal-based hydrocarbon fuel oil at this low temperature. The results are shown in [reference]. Figure 4 and Figure 5 .

[0099] from Figure 4 and Figure 5 It can be seen that the modified saturation calculation formula can accurately measure the saturated water content of coal-based hydrocarbon fuels at low temperatures. The measurement deviation using the modified saturation calculation formula is about 1 ppm, which is highly accurate. Since the water absorption characteristics of coal-based hydrocarbon fuels show an exponential trend with increasing temperature, the saturated water content fitting curve at low temperatures has a good relationship.

[0100] Example 2

[0101] The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil in this embodiment includes the following steps.

[0102] (1) Take a sample of fuel oil prepared by the coal-based hydrocarbon fuel saturated fuel oil water distribution system, put the sample into a beaker and place it in a high and low temperature test chamber. Set the test chamber temperature to 20℃. After the temperature is constant for 20 minutes, insert the oil water detector into the upper part of the fuel oil to monitor the temperature and water activity of the fuel oil sample in real time and record it. After the temperature is constant, take 4g of the sample from the upper part of the beaker for Karl Fischer titration experiment. Repeat the measurement three times and take the average value to obtain the saturated water content value at this temperature. Increase the temperature of the test chamber every 5℃ as a detection point until 40℃. Repeat the same steps. After the temperature is constant, record the temperature and water activity of the fuel oil sample, and take 4g of the sample from the upper part of the beaker for Karl Fischer titration experiment. Repeat the measurement three times and take the average value to obtain the saturated water content value at this temperature.

[0103] Three sets of data with temperature differences of 10℃ (i.e., 20℃, 30℃, and 40℃ respectively) (see Table 2) were used to correct the coefficients of the oil moisture detector. The saturation calculation formula was corrected by using temperature, water activity, and water content measured by Karl Fischer, and the correction coefficients A, B, and C were determined.

[0104]

[0105] ppm x =ppm / aw (2)

[0106] in:

[0107] ppm x Saturation level in ppm;

[0108] aw represents water activity;

[0109] T is the Kelvin temperature;

[0110] ppm refers to the saturated water content of coal-based hydrocarbon fuel oil;

[0111] Finally, the values ​​of A, B, and C are calculated, and their absolute values ​​are multiplied by 100 and stored in a register, as shown in the table below.

[0112] Table 2. Water activity values ​​at three temperatures in Example 2

[0113] T / ℃ T / K water activity aw ppm saturation 20 293.16 0.6163 29.21 30 303.16 0.3902 46.13 40 313.16 0.2399 75.03

[0114] We get A = 2218344, B = -18412.34, and C = 38.67.

[0115] (3) Next, the saturated water content below 20℃ was measured.

[0116] The temperature in the high and low temperature test chamber was changed, and the temperature was continuously reduced to -40℃ at 5℃ intervals. The water activity value corresponding to any temperature at the low temperature was measured and substituted into the corrected formula (1) to calculate the ppm value. x Then, substitute the values ​​into formula (2) to calculate the saturated water content of the coal-based hydrocarbon fuel oil at this low temperature. The results are shown in [reference]. Figure 6 and Figure 7 .

[0117] from Figure 6 and Figure 7 As can be seen, the same conclusion as in Example 1 is that the modified saturation calculation formula can accurately measure the saturated water content of coal-based hydrocarbon fuels at low temperatures. The measurement deviation using the modified formula is about 1 ppm, which is highly accurate, and the fitting curve relationship of the saturated water content at low temperatures is good.

[0118] Example 3

[0119] The method for measuring and correcting the saturated water content of coal-based hydrocarbon fuel oil provided in this embodiment includes the following steps.

[0120] (1) Take a sample of fuel oil prepared by the coal-based hydrocarbon fuel saturated fuel oil water distribution system, put the sample into a beaker and place it in a high and low temperature test chamber. Set the test chamber temperature to 20℃. After the temperature is constant for 30 minutes, insert the oil water detector into the upper part of the fuel oil to monitor the temperature and water activity of the fuel oil sample in real time and record it. After the temperature is constant, take 2g of the sample from the upper part of the beaker for Karl Fischer titration experiment. Repeat the measurement three times and take the average value to obtain the saturated water content value at this temperature. Increase the temperature of the test chamber every 5℃ as a detection point until 40℃. Repeat the same steps. After the temperature is constant, record the temperature and water activity of the fuel oil sample, and take 2g of the sample from the upper part of the beaker for Karl Fischer titration experiment. Repeat the measurement three times and take the average value to obtain the saturated water content value at this temperature.

[0121] (2) Take three sets of data with a temperature difference of 10℃, namely 20℃, 30℃ and 40℃ respectively (see Table 3) to correct the coefficient of the oil moisture detector. Correct the saturation calculation formula by temperature, water activity and water content measured by Karl Fischer, and determine the correction coefficients A, B and C.

[0122]

[0123] ppm x =ppm / aw (2)

[0124] in:

[0125] ppm x Saturation level in ppm;

[0126] aw represents water activity;

[0127] T is the Kelvin temperature;

[0128] ppm refers to the saturated water content of coal-based hydrocarbon fuel oil.

[0129] Finally, the values ​​of A, B, and C are calculated, and their absolute values ​​are multiplied by 100 and stored in a register, as shown in the table below.

[0130] Table 3. Water activity values ​​at three temperatures in Example 3

[0131]

[0132]

[0133] We get A = 552787.8, B = -7346.91, and C = 20.3.

[0134] (3) Next, the saturated water content below 20℃ was measured.

[0135] The temperature in the high and low temperature test chamber was changed, and the temperature was continuously reduced to -40℃ at 5℃ intervals. The water activity value corresponding to any temperature at the low temperature was measured and substituted into the corrected formula (1) to calculate the ppm value. x Then, substitute the values ​​into formula (2) to calculate the saturated water content of the coal-based hydrocarbon fuel oil at this low temperature. The results are shown in [reference]. Figure 8 and Figure 9 .

[0136] from Figure 8 and Figure 9 As can be seen, the conclusions of the above embodiments are the same. The modified saturation calculation formula can accurately measure the saturated water content of coal-based hydrocarbon fuels at low temperatures. The measurement deviation using the modified formula is about 1 ppm, which is highly accurate. Furthermore, the fitting curve relationship of the saturated water content at low temperatures is good.

[0137] Comparative Example 1

[0138] This comparative method for measuring the saturated water content of fuel oil includes the following steps.

[0139] Take a sample of fuel oil produced by a coal-based hydrocarbon fuel saturated fuel oil water distribution system, put the sample into a beaker and place it in a high and low temperature test chamber. The temperature range of the test chamber is -40 to 40℃, with a test point every 5℃. After the temperature is constant, take 4g of the sample from the top of the beaker and perform Karl Fischer volumetric method to determine the saturated water content. Repeat the measurement three times and take the average value to obtain the saturated water content value at this temperature.

[0140] Using a WKT-C21 Karl Fischer moisture analyzer with volumetric titration as the analytical principle, the accuracy is ±10 ppm. The obtained saturated water content values ​​for coal-based hydrocarbon fuels showed significant fluctuations at each temperature point, primarily due to the insufficient precision of the Karl Fischer volumetric method. Furthermore, the use of visual estimation to read reagent consumption on the Karl Fischer moisture analyzer also resulted in considerable measurement error. The determination and fitting curve of saturated water content in coal-based hydrocarbon fuels at -40℃ to 40℃ are shown below. Figure 10 and Figure 11 As shown.

[0141] from Figure 10 and Figure 11 It can be seen that the maximum deviation of the Karl Fischer volumetric titration method for measuring the saturated water content of coal-based hydrocarbon fuels is ±8ppm, which is a large error for the detection of trace water, and the data distribution in the fitting curve is irregular.

[0142] Comparative Example 2

[0143] This comparative method for measuring the saturated water content of fuel oil includes the following steps.

[0144] Take a sample of fuel oil produced by a coal-based hydrocarbon fuel saturated fuel oil water distribution system, put the sample into a beaker and place it in a high and low temperature test chamber. The temperature range of the test chamber is -40 to 40℃. First, raise the temperature to 40℃ and then continuously lower it. After each temperature is constant, take 3g of the sample from the top of the beaker and perform a Karl Fischer coulometric titration experiment. Repeat the measurement three times and take the average value to obtain the saturated water content value at that temperature.

[0145] The Karl Fischer moisture titrator is primarily used to measure the water content of total water, therefore the measured water content may be too high. Furthermore, due to the significant temperature difference between the low-temperature conditions and the ambient temperature, even rapid injection into the reaction vessel after sampling will cause a temperature rise, introducing further errors. Therefore, the Karl Fischer titration method is inaccurate for determining the saturated water content at low temperatures. The determination and fitting curve of saturated water content in coal-based hydrocarbon fuels at -40℃ to 40℃ are shown below. Figure 12 and Figure 13 As shown.

[0146] from Figure 12 and Figure 13 It can be seen that the Karl Fischer coulometric titration method has a large measurement deviation at low temperatures, which is almost a straight line. Therefore, it cannot meet the requirements for determining the saturated water content of coal-based hydrocarbon fuels at low temperatures.

[0147] Comparative Example 3

[0148] This comparative method for measuring the saturated water content of fuel oil includes the following steps.

[0149] Take a sample of fuel oil produced by a coal-based hydrocarbon fuel saturated fuel oil water distribution system, put the sample into a beaker and place it in a high and low temperature test chamber. The temperature range of the test chamber is -40 to 40℃. First, raise the temperature to 40℃ and then continuously lower it. Record the data every 5℃. Read the data 3 times at each temperature point ±0.1℃ and take the average to obtain the saturated water content value at that temperature.

[0150] While oil moisture analyzers offer high accuracy and strong feedback, they are significantly affected by the type of oil. Without oil type calibration, the measured water content values ​​for coal-based hydrocarbon fuels are inaccurate and cannot represent the saturated water content of coal-based hydrocarbon fuels. The determination and fitting curves for the saturated water content of coal-based hydrocarbon fuels at -40℃ to 40℃ are shown below. Figure 14 and Figure 15 As shown.

[0151] from Figure 14 and Figure 15 It can be seen that without modifying the saturation calculation formula in the oil moisture analyzer, the test results do not match the theoretical experimental values, resulting in large errors and low accuracy. Therefore, when measuring trace water, the saturation calculation formula in the oil moisture analyzer cannot be used directly. This invention, by performing a secondary correction on the saturation calculation formula, achieves a better overlap between the actual test values ​​and the theoretical experimental values, resulting in higher measurement accuracy.

[0152] The above are several preferred measurement methods provided by the present invention. By modifying the saturation calculation formula through the measurement methods of the present invention, the content of saturated trace water in fuel can be measured at low temperatures with small error and high accuracy.

Claims

1. A method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil, characterized in that, Includes the following steps: 1) Determination of water content in saturated fuel oil samples at room temperature The prepared saturated fuel sample was heated, and the temperature and water activity of the saturated fuel sample were monitored in real time during the heating process. The water activity at temperature nodes of 20℃, 25℃, 30℃, 35℃ and 40℃ was recorded respectively. The water content of the saturated fuel sample at each temperature node was detected by Karl Fischer coulometric method. 2) From the water content values ​​corresponding to the saturated fuel samples at each temperature node, take the water activity corresponding to three temperature nodes with a temperature difference of 10℃, and correct the saturation calculation formula (1) of the saturated fuel sample to determine the correction coefficients A, B and C. （1） （2） in: ppm x for ppm Saturation; aw Water activity; T is the Kelvin temperature; ppm This refers to the saturated water content of coal-based hydrocarbon fuel oil; 3) Cool the prepared saturated fuel sample from 20℃ to -40℃, monitor the temperature and corresponding water activity during the cooling process in real time, record the real-time monitoring data, and substitute it into the modified formula (1) in step 2) to obtain the saturated fuel sample at low temperature. ppm x Substituting this into formula (2), we can obtain the saturated water content in saturated fuel oil at low temperatures. ppm .

2. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 1, characterized in that, In step 1), the heating rate is 2~3℃ / min.

3. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 1, characterized in that, During the heating process in step 1), the saturated fuel sample is stirred.

4. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 1, characterized in that, When correcting the saturation calculation formula (1) in step 2), the average value of 3 to 5 measurements at each temperature node is taken.

5. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 1, characterized in that, In step 3), the cooling rate is 0.5~1.5℃ / min.

6. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 1, characterized in that, In step 3), a cooling gradient of 5°C is used.

7. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 1, characterized in that, In both steps 1) and 3), an oil moisture analyzer is used to monitor temperature and water activity in real time.

8. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 1, characterized in that, In steps 1) and 3), the preparation process of the saturated fuel oil sample is as follows: at a temperature of 27±1℃, water is atomized and continuously mixed with fuel oil to remove undissolved water from the fuel oil, thereby obtaining a saturated fuel oil sample.

9. The method for correcting the measurement of saturated water content in coal-based hydrocarbon fuel oil according to claim 8, characterized in that, The atomization rate is 0.25~0.39 mL / min.

10. An apparatus for implementing the method for measuring and correcting the saturated water content of coal-based hydrocarbon fuel oil as described in claim 9, characterized in that, It includes a saturated fuel water distribution unit, a high and low temperature test chamber, an oil moisture detector (6), a Karl Fischer titrator, a data correction unit, and a water content calculation unit; The saturated fuel water mixing unit is used to prepare saturated fuel samples and atomize the saturated fuel samples. The high and low temperature test chamber is used to heat up and cool down the prepared saturated fuel sample; The oil moisture detector (6) is used to monitor the temperature and water activity of the saturated fuel sample during the heating process and the temperature and water activity of the saturated fuel sample during the cooling process in real time; it is used to transmit the monitoring data during the heating process to the data correction unit and the monitoring data during the cooling process to the water content calculation unit. The Karl Fischer titrator is used to monitor the water content at different temperatures during the heating process of the saturated fuel sample in real time and transmit the data to the data correction unit. The data correction unit is used to receive the temperature, water activity and corresponding water content of the saturated fuel sample during the heating process, correct the saturation calculation formula according to the received data, and transmit the corrected saturation calculation formula to the water content calculation unit. The water content calculation unit is used to calculate the saturated water content in saturated fuel at low temperature based on the temperature, water activity, and corrected saturation calculation formula received during the cooling process.

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