Method for evaluating corrosion inhibition performance of tower top corrosion inhibitor of crude oil distillation device

Abstract

The invention belongs to a method for evaluating the corrosion inhibition performance of an injection agent, and particularly discloses a method for evaluating the corrosion inhibition performance of a tower top corrosion inhibitor of a crude oil distillation device, which comprises the following steps: firstly, preparing a corrosion medium solution and pretreating a sample, carrying out a blank experiment and a corrosion inhibition test on the sample to be tested, and treating the tested sample; the uniform corrosion rate, the corrosion inhibition efficiency and the pitting corrosion rate are measured by obtaining the sample quality after a blank experiment and a corrosion inhibition test, the pitting corrosion on the surface of the sample is observed, the site working condition of a refinery enterprise is met, and the slow release efficiency and the pitting corrosion rate of the corrosion inhibitor can be objectively evaluated; the method effectively distinguishes the performance of the corrosion inhibitor at the top of the crude oil distillation device, can solve the problem that the existing evaluation method is inaccurate, checks the use admission of the corrosion inhibitor of a refinery enterprise, reduces the corrosion leakage risk of the device, and improves the economic benefit of the enterprise.

Description

Technical Field

[0001] The invention belongs to a method for evaluating the corrosion inhibition performance of an injection agent, and in particular relates to a method for evaluating the corrosion inhibition performance of a corrosion inhibitor at the top of a crude oil distillation unit. Background Art

[0002] The top corrosion of crude oil distillation unit is mainly caused by the corrosion of HCl+H2S+H2O system. The unplanned shutdown caused by corrosion failure of the unit often causes economic losses of millions or even tens of millions. At present, the corrosion control measures adopted by the top system are mainly to inject corrosion inhibitors, neutralizers and water. Adding corrosion inhibitors can protect metals from corrosion; adding neutralizers and water can reduce the acidity of the corrosive solution, thereby reducing the corrosiveness of the environmental medium.

[0003] In addition to testing the physical and chemical properties of the corrosion inhibitor before injection, its corrosion inhibition efficiency also needs to be evaluated to meet the product use requirements. Since 2008, 1g / L HCl+1g / L H2S aqueous solution has been used as the corrosion medium, and concentrated ammonia water has been used to adjust the pH value. The corrosion inhibition performance of the top corrosion inhibitor of the crude oil distillation unit has been evaluated at 98°C. However, the evaluation results in the past decade have proved that this evaluation method is relatively harsh, and the release efficiency of the corrosion inhibitors used on the market almost all do not meet the standards. In 2017, the evaluation method for the corrosion inhibition performance of the top corrosion inhibitor was revised, using 1g / L HCl solution as the corrosion medium and evaluating it at 85°C. However, the evaluation method system is simple, and the temperature is relatively low, which is quite different from the actual working conditions. The evaluation results show that the release rate of the slow-release agent used can meet the product use requirements, but the local corrosion is serious. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for evaluating the corrosion inhibition performance of a top corrosion inhibitor in a crude oil distillation unit, so as to solve the problem that the existing corrosion inhibition performance evaluation method of the corrosion inhibitor is quite different from the actual working conditions, and the evaluation results show that the local corrosion of the slow-release agent used is still serious.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for evaluating the corrosion inhibition performance of a corrosion inhibitor at the top of a crude oil distillation unit, comprising:

[0007] preparing a corrosive medium solution to obtain a corrosive medium solution;

[0008] Pre-treat the samples to obtain the sample quality of the sample to be tested and the sample quality before the test;

[0009] The corrosion inhibition performance evaluation test of the corrosion inhibitor is to conduct a blank test and a corrosion inhibition test respectively using the prepared corrosive medium solution and the pretreated test sample;

[0010] Sample processing after the test to obtain the sample mass after the blank test and the sample mass after the corrosion inhibition test;

[0011] The measurement results were calculated and analyzed, the pitting corrosion on the sample surface was observed, and the uniform corrosion rate, corrosion inhibition efficiency and pitting corrosion rate were measured through the sample mass after the blank test and the sample mass after the corrosion inhibition test.

[0012] Furthermore, the specific process of preparing the corrosive medium solution is as follows:

[0013] Mix the HCl solution and the H2S solution, add the on-site neutralizer to adjust the pH value to 6.5-7.0, and then obtain the corrosive medium solution. Place the corrosive medium solution in a 1L five-necked bottle.

[0014] Furthermore, the concentration of the HCl is 1 g / L, and the concentration of the H2S solution is 1 g / L.

[0015] Furthermore, the specific process of pre-treating the sample is as follows:

[0016] After wiping off the oil stain on the sample with gauze or rough paper, polish it step by step to 800 mesh, measure the sample size and record it;

[0017] Place the surface treated sample in a vessel filled with petroleum ether with a boiling range of 60℃ to 90℃, remove dirt from the sample surface with absorbent cotton, wash it twice in succession and soak it in anhydrous ethanol for 5 minutes, take out the sample, wipe it dry with gauze and blow it dry with cold air to obtain the sample to be tested, then put it in a dryer to dry for 30 minutes and weigh it to obtain the sample mass before the test.

[0018] Furthermore, the specific process of the corrosion inhibitor corrosion inhibition performance evaluation test is as follows:

[0019] Carry out a blank experiment, place the prepared corrosive medium solution in a constant temperature oil bath at 98±2℃, and when the temperature of the corrosive medium solution stabilizes at 98±2℃, put in the test sample, and the test time is 6h;

[0020] In the corrosion inhibition test, after adding 100 ppm of the corrosion inhibitor to be tested into the corrosive medium solution, the five-necked bottle is placed in a constant temperature oil bath at 98±2°C and the test sample is placed in it. The test time is 6 hours.

[0021] Furthermore, the specific process of sample processing after the test is as follows:

[0022] After the test, take out the sample and observe it, record the surface corrosion and adhesion of corrosion products, then immediately rinse it with clean water, wipe it dry with filter paper, and take photos;

[0023] The tested sample was placed in acetone, and the oil on the surface of the sample was removed with absorbent cotton. Then, the sample was immersed in anhydrous ethanol for 5 minutes for further degreasing and dehydration; the sample was immersed in a 0.5wt.% hexamethylenetetramine cleaning solution for 5 minutes; the sample was taken out from the cleaning solution, and the residual acid on the surface was washed off with deionized water. Then, the sample was immediately immersed in a 60g / L sodium hydroxide solution for 30s, and then rinsed with deionized water, and then immersed in anhydrous ethanol for 5 minutes; the sample was taken out and placed on filter paper, dried with cold air, and placed in a dryer. After being placed for 1 hour, it was weighed to obtain the mass of the sample after the blank test and the mass of the sample after the corrosion inhibition test.

[0024] Furthermore, the observation of pitting on the sample surface is specifically as follows: using a 10x microscope to observe whether there is pitting on the sample surface; if pitting exists, the microscope is magnified to 100x, the number of pitting per unit area on the sample surface is recorded, and the deepest pitting depth is measured with a pitting depth meter.

[0025] Furthermore, the uniform corrosion rate is calculated according to the following formula:

[0026]

[0027] Where: r corr is the uniform corrosion rate, mm / year; m is the mass of the sample before the test, g; m t is the mass of the sample after the corrosion inhibition test, g; S1 is the total area of ​​the sample, cm 2 ; ρ is the density of the sample material, g / cm 3 ; t is the test time, h.

[0028] Furthermore, the corrosion inhibition efficiency is calculated according to the following formula:

[0029]

[0030] Where: η1 is the corrosion inhibition efficiency, %; Δm0 is the mass loss of the sample in the blank test, g; Δm1 is the mass loss of the sample in the corrosion inhibition test, g;

[0031] Δm0=m-m0

[0032] Δm1=mm t

[0033] Where m0 is the mass of the sample after the blank test, g.

[0034] Further, the pitting rate is calculated according to the following formula:

[0035]

[0036] Where: r tis the pitting rate, mm / year; h t is the deepest pitting depth on the surface of the sample after the test, mm; t is the test time, h.

[0037] The present invention has at least the following beneficial effects:

[0038] The evaluation method of the present invention first prepares a corrosive medium solution and pre-treats a sample, performs a blank test and a corrosion inhibition test on the test sample, treats the sample after the test, measures the uniform corrosion rate, the corrosion inhibition efficiency and the pitting rate by obtaining the sample quality after the blank test and the corrosion inhibition test, and observes the pitting corrosion on the sample surface. The method not only meets the on-site working conditions of the refinery enterprise, but also can objectively evaluate the slow-release efficiency and the pitting rate of the corrosion inhibitor, effectively distinguish the advantages and disadvantages of the performance of the corrosion inhibitor at the top of the crude oil distillation unit, can solve the problem of inaccuracy of the existing evaluation method, control the use access of the corrosion inhibitor of the refinery enterprise, reduce the risk of corrosion leakage of the device and improve the economic benefits of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0040] Figure 1 It is a schematic diagram of sample specifications;

[0041] Figure 2 This is the macroscopic morphology of the sample after evaluation using the 2008 evaluation method;

[0042] Figure 3 This is the macroscopic morphology of the sample after evaluation using the 2017 evaluation method;

[0043] Figure 4 The macroscopic morphology of the sample after evaluation by the evaluation method of the present invention;

[0044] Figure 5 This is the pitting morphology of the sample evaluated using the 2017 evaluation method. DETAILED DESCRIPTION

[0045] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0046] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0047] A method for evaluating the corrosion inhibition performance of a crude oil distillation unit top corrosion inhibitor comprises the following steps:

[0048] S1: preparing a corrosive medium solution to obtain a corrosive medium solution;

[0049] The corrosive medium solution includes: a mixed aqueous solution of HCl solution, H2S solution and a neutralizer;

[0050] The specific process for preparing the corrosive medium solution is as follows: HCl solution and H2S solution are mixed, and after mixing, a neutralizer for on-site use is added for adjustment, and the pH value is adjusted to 6.5-7.0 to obtain a corrosive medium solution, and the corrosive medium solution is placed in a 1L five-necked bottle; wherein the concentration of HCl is 1g / L, and the concentration of the H2S solution is 1g / L.

[0051] The neutralizer used on site is the neutralizer used by each enterprise. Because different refining and chemical enterprises use different types of neutralizers, the neutralizer used by the enterprise is added during the evaluation.

[0052] S2: Pre-treat the sample to obtain the sample to be tested and the sample mass before the test;

[0053] The specific process of pre-treatment of the sample is as follows: wipe off the oil stain on the sample with gauze or rough paper, grind it step by step to 800 mesh, measure the sample size and record it; the sample material is 20# carbon steel, the specifications are as follows Figure 1 shown.

[0054] Place the surface treated sample in a vessel filled with petroleum ether (analytical grade) with a boiling range of 60℃ to 90℃, remove dirt from the sample surface with absorbent cotton, wash it twice in succession and soak it in anhydrous ethanol for 5 minutes, take out the sample, wipe it dry with gauze and then blow it dry with cold air to obtain the sample to be tested, then put it in a dryer and dry it for 30 minutes and weigh it (accurate to 0.0001g) to obtain the sample mass before the test.

[0055] S3: Corrosion inhibition performance evaluation test of corrosion inhibitor, blank test and corrosion inhibition test are carried out respectively by using the prepared corrosive medium solution and the pretreated test sample;

[0056] The specific process of corrosion inhibitor corrosion performance evaluation test is as follows:

[0057] At room temperature, a blank experiment was conducted. The corrosive medium solution prepared in step S1 was placed in a constant temperature oil bath at 98±2°C. When the temperature of the corrosive medium solution stabilized at 98±2°C, the test sample was placed in the bath. The test time was 6 hours.

[0058] In the corrosion inhibition test, after adding 100ppm of the corrosion inhibitor to be tested into the corrosive medium solution, the five-necked bottle is placed in a constant temperature oil bath at 98±2℃, and the sample to be tested is placed in it. The test time is 6h. The corrosion inhibitor to be tested is the corrosion inhibitor used in the top tower system of the refinery distillation unit, with a concentration of 1μg / g-1000μg / g. The corrosion inhibitor to be tested refers to the effect evaluation of the corrosion inhibitor used in the refinery. The corrosion inhibitors used in each refinery are also different, some are imidazolines, and some are organic amines.

[0059] S4: Sample processing after testing;

[0060] The specific process of sample treatment after the test is as follows: take out the sample after the test and observe it, record the surface corrosion and adhesion of corrosion products, immediately rinse it with clean water and wipe it dry with filter paper, and then take pictures.

[0061] Put the tested sample into acetone, remove the oil on the surface of the sample with absorbent cotton, and then soak it in anhydrous ethanol for 5 minutes for further degreasing and dehydration. Then soak it in a 0.5wt.% hexamethylenetetramine (urotropine) acid cleaning solution for 5 minutes to remove corrosion products. Take out the sample from the cleaning solution, rinse the residual acid on the surface with deionized water, and immediately immerse the sample in a 60g / L sodium hydroxide solution for 30s, then rinse with deionized water, and then soak it in anhydrous ethanol for 5 minutes. Take out the sample and place it on filter paper. After drying with cold air, place it in a dryer and weigh it after 1 hour to obtain the mass of the sample after the blank test and the mass of the sample after the corrosion inhibition test.

[0062] S5: Calculation and analysis of measurement results.

[0063] The calculation and analysis of the measurement results specifically include: observation of pitting corrosion on the sample surface, determination of uniform corrosion rate, determination of corrosion inhibition efficiency and determination of pitting corrosion rate.

[0064] (1) Observation of pitting on the sample surface: Use a 10x microscope to observe whether there is pitting on the sample surface. If there is pitting, magnify the microscope to 100x, record the number of pitting per unit area on the sample surface, and use a pitting depth meter to measure the deepest pitting depth.

[0065] (2) The uniform corrosion rate is calculated according to the following formula:

[0066]

[0067] Where: r corris the uniform corrosion rate, mm / year; m is the mass of the sample before the test, g; m t is the mass of the sample after the corrosion inhibition test, g; S1 is the total area of ​​the sample, cm 2 ; ρ is the density of the sample material, g / cm 3 ; t is the test time, h.

[0068] (3) The corrosion inhibition efficiency η1 is calculated according to the following formula:

[0069]

[0070] Where: η1 is the corrosion inhibition efficiency, %; Δm0 is the mass loss of the sample in the blank test, g; Δm1 is the mass loss of the sample in the corrosion inhibition test, g;

[0071] Δm0=m-m0

[0072] Δm1=mm t

[0073] Where m0 is the mass of the sample after the blank test, g.

[0074] (4) Pitting rate r t The determination is calculated according to the following formula:

[0075]

[0076] Where: r t is the pitting rate, mm / year; h t is the deepest pitting depth on the surface of the sample after the test, mm; t is the test time, h.

[0077] To ensure the accuracy of the evaluation test, three parallel samples are taken for each group of tests, and the arithmetic mean of the measurement results is taken as the measurement result. The relative deviation of the parallel measurement results should not exceed ±10%.

[0078] Three methods were used to evaluate and compare the corrosion inhibition performance of an oil-soluble corrosion inhibitor in a refinery. The sample material was 20# carbon steel and the amount of corrosion inhibitor added was 100ppm. The specific implementation conditions of the three methods were:

[0079] Example 1

[0080] The corrosion inhibition performance of an oil-soluble corrosion inhibitor of a refinery was evaluated using the 2008 evaluation method: 1g / L HCl+1g / L H2S aqueous solution was used as the corrosive medium, and concentrated ammonia was used to adjust the pH value to 6.0-7.0. The samples were tested at 98±2℃ for 6h and then taken out for corrosion inhibition performance evaluation; the sample material was 20# carbon steel, and the amount of corrosion inhibitor added was 100ppm.

[0081] Example 2

[0082] The corrosion inhibition performance of an oil-soluble corrosion inhibitor of a refinery was evaluated using the 2017 evaluation method: 1g / L HCl solution was used as the corrosive medium, and the samples were tested at 85±2℃ for 6h before being taken out for corrosion inhibition performance evaluation; the sample material was 20# carbon steel, and the amount of corrosion inhibitor added was 100ppm.

[0083] Example 3

[0084] The corrosion inhibition performance of an oil-soluble corrosion inhibitor of a refinery was evaluated by using the evaluation method of the present invention: 1g / L HCl+1g / L H2S aqueous solution was used as the corrosive medium, and the pH value was adjusted to 6.5-7.0 by using a neutralizer on site. The samples were tested at 98±2℃ for 6h and then taken out for corrosion inhibition performance evaluation. The sample material was 20# carbon steel, and the amount of corrosion inhibitor added was 100ppm.

[0085] The evaluation results of Example 1 to Example 3 are shown in Table 1, and the macroscopic morphology of the samples after evaluation is shown in Figure 2-Figure 4 .

[0086] Table 1 Evaluation results of different implementation methods

[0087] Evaluation Method Average corrosion rate (mm / year) Corrosion inhibition efficiency (%) Pitting rate (mm / year) Example 1 3.140 -140％ No obvious pitting Example 2 0.886 94.4％ 36 Example 3 0.839 58.4％ No obvious pitting

[0088] Figure 5 This is the pitting morphology of the sample evaluated using the 2017 evaluation method.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor, characterized in that: include: preparing a corrosive medium solution to obtain a corrosive medium solution; Pre-treat the samples to obtain the sample quality of the sample to be tested and the sample quality before the test; The corrosion inhibition performance evaluation test of the corrosion inhibitor is to conduct a blank test and a corrosion inhibition test respectively using the prepared corrosive medium solution and the pretreated test sample; Sample processing after the test to obtain the sample mass after the blank test and the sample mass after the corrosion inhibition test; The measurement results were calculated and analyzed, the pitting corrosion on the sample surface was observed, and the uniform corrosion rate, corrosion inhibition efficiency and pitting corrosion rate were measured through the sample mass after the blank test and the sample mass after the corrosion inhibition test.

2. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The specific process of preparing the corrosive medium solution is as follows: Mix the HCl solution and the H2S solution, add the on-site neutralizer to adjust the pH value to 6.5-7.0, and then obtain the corrosive medium solution. Place the corrosive medium solution in a 1L five-necked bottle.

3. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 2, characterized in that: The concentration of the HCl solution is 1 g / L, and the concentration of the H2S solution is 1 g / L.

4. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The specific process of pre-treating the sample is as follows: After wiping off the oil stain on the sample with gauze or rough paper, polish it step by step to 800 mesh, measure the sample size and record it; Place the surface treated sample in a vessel filled with petroleum ether with a boiling range of 60℃ to 90℃, remove dirt from the sample surface with absorbent cotton, wash it twice in succession and soak it in anhydrous ethanol for 5 minutes, take out the sample, wipe it dry with gauze and blow it dry with cold air to obtain the sample to be tested, then put it in a dryer to dry for 30 minutes and weigh it to obtain the sample mass before the test.

5. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The specific process of the corrosion inhibitor corrosion inhibition performance evaluation test is as follows: Carry out a blank experiment, place the prepared corrosive medium solution in a constant temperature oil bath at 98±2℃, and when the temperature of the corrosive medium solution stabilizes at 98±2℃, put in the test sample, and the test time is 6h; In the corrosion inhibition test, after adding 100 ppm of the corrosion inhibitor to be tested into the corrosive medium solution, the five-necked bottle is placed in a constant temperature oil bath at 98±2°C and the test sample is placed in it. The test time is 6 hours.

6. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The specific process of sample processing after the test is as follows: After the test, take out the sample and observe it, record the surface corrosion and adhesion of corrosion products, then immediately rinse it with clean water, wipe it dry with filter paper, and take photos; The tested sample was placed in acetone, and the oil on the surface of the sample was removed with absorbent cotton. Then, the sample was immersed in anhydrous ethanol for 5 minutes for further degreasing and dehydration; the sample was immersed in a 0.5wt.% hexamethylenetetramine cleaning solution for 5 minutes; the sample was taken out from the cleaning solution, and the residual acid on the surface was washed off with deionized water. Then, the sample was immediately immersed in a 60g / L sodium hydroxide solution for 30s, and then rinsed with deionized water, and then immersed in anhydrous ethanol for 5 minutes; the sample was taken out and placed on filter paper, dried with cold air, and placed in a dryer. After being placed for 1 hour, it was weighed to obtain the mass of the sample after the blank test and the mass of the sample after the corrosion inhibition test.

7. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The pitting observation on the sample surface is specifically as follows: using a 10x microscope to observe whether there is pitting on the sample surface; if pitting exists, the microscope is magnified to 100x, the number of pitting per unit area on the sample surface is recorded, and the deepest pitting depth is measured with a pitting depth meter.

8. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The uniform corrosion rate is calculated according to the following formula: Where: r corr is the uniform corrosion rate, mm / year; m is the mass of the sample before the test, g; m t is the mass of the sample after the corrosion inhibition test, g; S1 is the total area of ​​the sample, cm 2 ; ρ is the density of the sample material, g / cm 3 ; t is the test time, h.

9. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The corrosion inhibition efficiency is calculated according to the following formula: Where: η1 is the corrosion inhibition efficiency, %; Δm0 is the mass loss of the sample in the blank test, g; Δm1 is the mass loss of the sample in the corrosion inhibition test, g; Δm0=m-m0 Δm1=m-m t Where m0 is the mass of the sample after the blank test, g.

10. The method for evaluating the corrosion inhibition performance of a crude oil distillation unit overhead corrosion inhibitor according to claim 1, characterized in that: The pitting rate determination is calculated according to the following formula: Where: r t is the pitting rate, mm / year; h t is the deepest pitting depth on the surface of the sample after the test, mm; t is the test time, h.

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