Pretreatment pipeline cleaning method for oil product near-infrared analysis

Abstract

The invention discloses a pretreatment pipeline cleaning method for near-infrared analysis of oil products, and provides an improvement scheme aiming at the problems that a traditional cleaning method lacks an effective verification mechanism, the cleaning effect is not easy to judge, and incomplete cleaning is possibly caused. And after washing with the cleaning agent, carrying out multiple times of small-amount replacement cleaning on the oil product to be detected, continuously collecting a near infrared spectrogram, verifying the cleaning effect by adopting the standard deviation, and judging residues. The method helps an operator to objectively evaluate the cleaning effect and reasonably control the amount of displacement oil, and lays a foundation for the accuracy of oil property detection.

Description

Technical Field

[0001] The invention belongs to the field of near-infrared spectroscopy rapid detection of oil product properties in a refinery, and specifically is a technical method for cleaning a pipeline by replacing the oil product to be tested and judging the cleaning effect by the spectral standard deviation. Background Art

[0002] In the near-infrared spectroscopy detection process of oil products (such as crude oil, distillate oil, finished oil, etc.) in refining enterprises, pretreatment pipelines are often shared, resulting in the residue in the previous pipeline may affect the accuracy of the oil product property spectral detection results this time. Therefore, effective cleaning of the pipeline is very important. The traditional cleaning method is generally: first use high-purity acetone to circulate the acetone in the pipeline by pumping to fully clean the inner wall of the pipeline. Then, use dry air or nitrogen to purge the pipeline to accelerate the evaporation of acetone. After the acetone flushing and purge are completed, the sample oil to be tested is injected into the pipeline to replace the residual acetone or air. After the sample oil flows through the pipeline, it is discharged. The replacement process is usually repeated once or twice to achieve complete replacement.

[0003] However, in practice, traditional cleaning methods rely on human experience to select the number of replacements and the amount of replacement oil, and cannot provide an accurate verification mechanism to judge the cleaning effect. Too little replacement may not completely remove acetone and residual oil, resulting in detection errors, while too much replacement will be limited by the sample loading. In fact, for refining companies, the sample loading volume of the oil to be tested at one time generally does not exceed 150ml.

[0004] Therefore, how to design a pipeline cleaning method and provide an accurate verification mechanism to determine whether the residue in the pipeline has been completely removed. In this way, the operator can objectively evaluate the effect of pipeline cleaning, reasonably control the amount of replacement oil used, thereby improving the cleaning efficiency and ensuring the accuracy of subsequent testing. Summary of the invention

[0005] In view of the problems existing in the background technology, the present invention proposes a pretreatment pipeline cleaning method for near-infrared analysis of oil products. After flushing the pipeline with a cleaning agent, the pipeline is cleaned by replacing the oil to be tested with a small amount of oil for multiple times, and multiple near-infrared spectra are continuously collected. The standard deviation of the absorbance of the spectra is used to verify the cleaning effect and determine whether there is any residue in the pipeline. The method specifically includes the following steps:

[0006] 1) Use cleaning agent to flush the pretreatment pipeline for near infrared spectroscopy analysis of oil products;

[0007] 2) Use the oil product to be tested with a displacement amount of F to perform pipeline replacement cleaning;

[0008] 3) After the oil replacement is completed, let the discharged oil stand and wait for time T;

[0009] 4) After the oil product has been left to stand for a while, Q near-infrared spectra are collected continuously;

[0010] 5) Calculate the standard deviation of the absorbance deviation of each spectrum graph and the last spectrum graph at each frequency. The calculation formula is:

[0011]

[0012] Among them, S q is the standard deviation of the absorbance deviation between the qth spectrum and the last spectrum at each frequency, n is the number of samples at the spectral frequency, x q,j is the absorbance of the qth spectrum at frequency j, q = 1, 2, ... Q, μ q is the average value of the absorbance deviation between the qth spectrum and the last spectrum at each frequency, that is:

[0013]

[0014] 6) Compare the standard deviation S q Relationship with threshold ε, if S q ≥ε, go ​​to step 2, otherwise go to step 7;

[0015] 7) Cleaning is completed.

[0016] Preferably, acetone is used as a cleaning agent to dissolve and remove residues on the inner wall.

[0017] Preferably, after the cleaning agent is flushed through the pipeline, the pipeline is subsequently purged with dry air or nitrogen to accelerate its evaporation.

[0018] Preferably, the amount of oil F used for pipeline replacement cleaning satisfies 20ml≥F≥10ml.

[0019] Preferably, the waiting time T satisfies T≥30s.

[0020] Preferably, the number of spectra collected continuously, Q, satisfies Q≥10.

[0021] Preferably, the standard deviation threshold ε=2×10 -4 .

[0022] Beneficial effects:

[0023] The present invention discloses a pretreatment pipeline cleaning method for near-infrared analysis of oil products. The method proposes an improvement scheme to solve the problems that the current cleaning method lacks an effective verification mechanism, the cleaning effect is difficult to judge, and the cleaning may not be thorough. After flushing the pipeline with acetone, the oil to be tested is used for multiple small-scale replacement cleaning, and multiple near-infrared spectra are continuously collected. The cleaning effect is verified by the standard deviation of the spectra to determine whether there are any residues in the pipeline. The method enables operators to objectively evaluate the effect of pipeline cleaning, reasonably control the amount of replacement oil used, and lay the foundation for the accuracy of oil property detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 General flow chart of traditional cleaning method

[0025] Figure 2 This is a flow chart of a pretreatment pipeline cleaning method for near infrared analysis of oil products according to the present invention.

[0026] Figure 3 is the standard deviation of absorbance using the method of the present invention in the examples

[0027] Figure 4 Absorbance standard deviation after replacement and cleaning with 30 ml oil

[0028] Figure 5 The standard deviation of absorbance after replacement and cleaning with 100 ml of oil DETAILED DESCRIPTION

[0029] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0030] Taking the near-infrared rapid detection of crude oil properties of a certain refinery as an example, the company originally used traditional cleaning methods, and the implementation process was as follows: Figure 1 As shown, high-purity acetone is pumped through the pipeline to circulate and clean the inner wall of the pipeline. Next, the pipeline is purged with dry air, and finally the crude oil to be tested is injected into the pipeline to displace the residual acetone or air. However, this method has obvious defects: due to operating experience, different operators have different cleaning standards, and there is a lack of effective verification mechanism, which makes it impossible to accurately judge the cleaning effect of the pipeline, which may lead to incomplete cleaning and property detection errors. The method of cleaning the pipeline by multiple small amounts of crude oil replacement is now adopted, and multiple near-infrared spectra are continuously collected. The cleaning effect is verified by the standard deviation of the spectra. The implementation process is as follows Figure 2 shown.

[0031] The specific steps include:

[0032] 1) Use high-purity acetone (in other embodiments, solvent oil or petroleum ether can be used) as a cleaning agent, circulate it in the pipeline to dissolve and remove the residue on the inner wall, and then use dry air or nitrogen to purge the pipeline to accelerate its evaporation.

[0033] 2) Use 10 ml of the crude oil to be tested to perform replacement cleaning on the pipeline, and ensure that the crude oil can fully contact the inner wall of the pipeline.

[0034] 3) After the replacement of crude oil is completed, let the discharged crude oil stand and wait for 30 seconds.

[0035] 4) After the crude oil has been allowed to stand for a long time, 50 near-infrared spectra are collected continuously. Table 1 shows the absorbance measurement data of some spectra.

[0036] Table 1 Spectral absorbance measurement data

[0037]

[0038] 5) Calculate the standard deviation of the near-infrared spectrum absorbance of the spectrum. The core idea of ​​this step is to determine whether the cleaning is completed by detecting the repeatability index. Table 2 shows the standard deviation of the absorbance of some near-infrared spectra. The standard deviation is the standard deviation of the absorbance deviation of each spectrum graph and the last spectrum graph at each frequency, and its calculation formula is:

[0039]

[0040] Among them, S q is the standard deviation of the absorbance deviation between the qth spectrum and the last spectrum at each frequency, n is the number of samples at the spectral frequency, x q,j is the absorbance of the qth spectrum at frequency j, q = 1, 2, ... Q, μ q The average value of the absorbance deviation between the qth spectrum and the last spectrum at each frequency, that is:

[0041]

[0042] Table 2 Near infrared spectroscopy absorbance standard deviation

[0043]

[0044] 6) According to the calculated standard deviation, it is found to be higher than the threshold value ε = 2 × 10 -4 , indicating that the pipeline has not been cleaned, so it is necessary to repeat the replacement and spectrum collection process from step 2 to step 5.

[0045] 7) Table 3 shows the standard deviation of absorbance of some near-infrared spectra after the second replacement.

[0046] Table 3 Standard deviation of near infrared spectral absorbance after the second replacement

[0047]

[0048] According to the calculated standard deviation, it is found to be lower than the threshold ε = 2 × 10 -4 , indicating that the pipeline has been cleaned.

[0049] Figure 3 The solid line on the left represents the standard deviation of absorbance after the first discharge of 10 ml, and the dashed line on the right represents the standard deviation of absorbance after another discharge of 10 ml.

[0050] To compare the effectiveness of this method, Figure 4 and Figure 5 The comparison chart of the cleaning method of the present invention and other cleaning methods is given. The first time, 30 ml of oil was used for displacement cleaning, and 50 spectra were collected. Figure 4 is the standard deviation of absorbance after 30ml is discharged. It can be seen that the effect of using the replacement once did not meet the requirements. The second time, 100ml of oil was used for replacement and cleaning, and 50 spectra were collected. Figure 5 The standard deviation of absorbance after 100 ml is discharged. At this time, the standard deviation has reached the requirement, but please note that the amount used at this time is too large, and the sample volume is only 150 ml at a time, which will result in insufficient remaining oil for sample testing.

[0051] It can be seen that after adopting the multiple small-volume replacement method proposed in the present invention, the cleaning effect is significantly improved, and the cleaning effect of the pipeline and sample pool can be objectively evaluated, laying a foundation for the accuracy of oil property detection.

Claims

1. A pretreatment pipeline cleaning method for near infrared analysis of oil products, characterized in that: After flushing the pipeline with a cleaning agent, a small amount of the oil to be tested is used for replacement cleaning multiple times, and multiple near-infrared spectra are continuously collected. The standard deviation of the absorbance of the spectra is used to verify the cleaning effect and determine whether there are any residues in the pipeline. The specific steps include the following: 1) Use cleaning agent to flush the pretreatment pipeline for near infrared spectroscopy analysis of oil products; 2) Use the oil product to be tested with a displacement amount of F to perform pipeline replacement cleaning; 3) After the oil replacement is completed, let the discharged oil stand and wait for time T; 4) After the oil product has been left to stand for a while, Q near-infrared spectra are collected continuously; 5) Calculate the standard deviation of the absorbance deviation of each spectrum graph and the last spectrum graph at each frequency. The calculation formula is: Among them, S q is the standard deviation of the absorbance deviation between the qth spectrum and the last spectrum at each frequency, n is the number of samples at the spectral frequency, x q,j is the absorbance of the qth spectrum at frequency j, q = 1, 2, ... Q, μ q is the average value of the absorbance deviation between the qth spectrum and the last spectrum at each frequency, that is: 6) Compare the standard deviation S q Relationship with threshold ε, if S q ≥ε, go ​​to step 2, otherwise go to step 7; 7) Cleaning is completed.

2. A pretreatment pipeline cleaning method for near infrared analysis of oil products according to claim 1, characterized in that Use acetone as a cleaning agent to dissolve and remove residue from the inner walls.

3. A pretreatment pipeline cleaning method for near infrared analysis of oil products according to claim 1, characterized in that After the cleaning agent has flushed the pipeline, it is then purged with dry air or nitrogen to accelerate its evaporation.

4. A pretreatment pipeline cleaning method for near infrared analysis of oil products according to claim 1, characterized in that The amount of oil F used for pipeline replacement cleaning satisfies 20ml≥F≥10ml.

5. The method for cleaning a pretreatment pipeline for near infrared analysis of oil products according to claim 1, characterized in that Waiting time T, satisfying T ≥ 30s.

6. A pretreatment pipeline cleaning method for near infrared analysis of oil products according to claim 1, characterized in that The number of spectra collected continuously, Q, satisfies Q ≥ 10.

7. The method for cleaning a pretreatment pipeline for near infrared analysis of oil products according to claim 1, characterized in that Standard deviation threshold ε = 2 × 10 -4 .

Images