Method for cleaning wax filter pipe of Fischer-Tropsch reactor

Abstract

The invention provides a method for cleaning a wax filter tube of a Fischer-Tropsch reactor. The cleaning method comprises the following steps: S1) carrying out first cleaning on a wax filter pipe to be cleaned by using an alkaline cleaning agent to obtain a first wax filter pipe; s2) performing secondary cleaning on the first wax filter pipe by using an acidic cleaning agent to obtain a second wax filter pipe; and S3) performing third cleaning on the second wax filter pipe to obtain the cleaned wax filter pipe. The wax filter tube cleaning device can solve the problem of short service life of a wax filter tube in the prior art and is suitable for the field of wax filter tube cleaning.

Description

Technical Field

[0001] The invention relates to the field of wax filter tube cleaning, and in particular to a method for cleaning a wax filter tube of a Fischer-Tropsch reactor. Background Art

[0002] The Fischer-Tropsch synthesis process is one of the indirect coal liquefaction technologies and the core of coal-to-liquids technology. First, coal reacts with water vapor at high temperature to generate synthesis gas (a mixture of CO and H2), and then the synthesis gas is heterogeneously hydrogenated under a solid catalyst and appropriate reaction conditions to generate a mixture of hydrocarbons of different chain lengths (C1 to C100) and oxygen-containing compounds. In the slurry bed reactor of Fischer-Tropsch synthesis, the high molecular weight liquid wax product generated has a high boiling point. It is liquid under conventional Fischer-Tropsch synthesis operating conditions and is difficult to vaporize and discharge, so it will accumulate in the reaction liquid. In order to maintain the normal operation and safe operation of the slurry bed reactor, the heavy wax product needs to be discharged from the inside of the reactor in an intermittent or continuous operation mode.

[0003] Due to the special reaction medium and conditions of the slurry bed reactor, the discharged liquid wax will inevitably contain fine solid catalyst particles. In order to reduce the catalyst loss in the system and ensure that the liquid wax product enters the next step for further processing, a filter tube is required to separate the catalyst from the liquid wax, that is, after the mixed liquid enters the filter tube, the liquid wax passes through the filter screen and the catalyst is intercepted by the filter screen.

[0004] After the wax filter tube has been running for a period of time, catalyst powder, wax polycondensates (i.e. heavy wax or oil coke), corrosion products, etc. tend to be deposited on the outer surface and internal aperture of the filter tube, thereby blocking the filter screen channel, causing the filter tube's filtering capacity to decrease, affecting the stable operation of the device. The filter tube is expensive to manufacture, and if it is directly replaced after being blocked, it will increase the company's operating costs. Therefore, the ideal solution is to reuse the filter tube by cleaning it.

[0005] The traditional cleaning methods of Fischer-Tropsch wax filter tubes are mainly divided into two categories: mechanical method and chemical method. Among them, mechanical methods (such as manual knocking, grinding, sandblasting, etc.) can only remove the dirt on the surface of the filter element of the filter tube, and cannot effectively remove the dirt inside the filter element. The chemical method is currently the most widely used method in industry, but the traditional cleaning formula cannot effectively remove the blockage of the filter element, and it is easy to damage the filter element body in the wax filter tube, and even cause harm to the environment and operators. In patent application CN107236605A, the wax filter tube is treated with a passivator and then cleaned, but the passivator has complex components and a cumbersome preparation process, and the cleaning method only focuses on the emulsification of organic matter and colloid, and the dispersion reaction is completed by loosening the pollutants and then rinsing and peeling. There is a lack of cleaning agent components that can react with Fischer-Tropsch catalyst components such as iron and silicon and corresponding cleaning steps, the cleaning effect is limited, and it is difficult to remove the catalyst blockage of the filter element.

[0006] Therefore, the prior art lacks a method for effectively cleaning the dirt inside and outside the wax filter tube, which shortens the service life of the wax filter tube and is not conducive to the development of the Fischer-Tropsch synthesis process. Summary of the invention

[0007] The main purpose of the present invention is to provide a method for cleaning a wax filter tube of a Fischer-Tropsch reactor, so as to solve the problem of short service life of the wax filter tube in the prior art.

[0008] In order to achieve the above-mentioned purpose, according to the first aspect of the present invention, a method for cleaning a wax filter tube of a Fischer-Tropsch reactor is provided, and the cleaning method comprises: S1) performing a first cleaning on the wax filter tube to be cleaned using an alkaline cleaning agent to obtain a first wax filter tube; S2) performing a second cleaning on the first wax filter tube using an acidic cleaning agent to obtain a second wax filter tube; S3) performing a third cleaning on the second wax filter tube to obtain a cleaned wax filter tube.

[0009] Furthermore, the alkaline cleaning agent includes an alkali, a surfactant, a chelating agent and an auxiliary agent; preferably, the alkali includes sodium hydroxide and / or potassium hydroxide; preferably, the surfactant includes fatty polyoxyethylene ether and / or triethanolamine; preferably, the chelating agent includes sodium salt of ethylenediaminetetraacetic acid and / or sodium citrate; preferably, the auxiliary agent includes sodium carbonate and / or sodium thiosulfate.

[0010] Furthermore, the alkaline cleaning agent comprises, by weight: 3-8 parts of alkali, 0.5-2 parts of surfactant, 0.5-3 parts of chelating agent and 0.1-1 parts of auxiliary agent.

[0011] Furthermore, the time of the first cleaning is 2-6 hours; preferably, the temperature of the first cleaning is 50-80° C.; preferably, the pH of the alkaline cleaning agent is 12.5-13.5.

[0012] Further, the acid cleaning agent includes organic acid, inorganic acid and pickling corrosion inhibitor;

[0013] Preferably, the organic acid includes oxalic acid and / or citric acid; preferably, the inorganic acid includes one or more of hydrochloric acid, nitric acid, hydrofluoric acid or hydrogen fluoride; preferably, the pickling corrosion inhibitor includes Lan-826.

[0014] Furthermore, the acid cleaning agent includes, by weight, 3-8 parts of organic acid, 1-3 parts of inorganic acid and 0.1-1 parts of pickling corrosion inhibitor.

[0015] Furthermore, the second cleaning time is 3-6 hours; preferably, the second cleaning temperature is 35-55° C.; preferably, the pH of the acidic cleaning agent is 1.5-3.

[0016] Furthermore, before the first cleaning is performed, the wax filter tube to be cleaned is pre-cleaned; preferably, the pre-cleaning includes steam blowing.

[0017] Further, the third cleaning includes ultrasonic cleaning in water.

[0018] Furthermore, the frequency of ultrasonic cleaning is 25-45 KHz; preferably, the time of ultrasonic cleaning is 1-3 hours.

[0019] By applying the technical solution of the present invention, the wax filter tube to be cleaned is cleaned for the first and second cleanings in sequence using an alkaline cleaning agent and an acidic cleaning agent, which can remove the residual dirt of wax, catalyst and metal oxide on the surface and inside of the wax filter tube. Finally, by the third cleaning, the wax filter tube mesh and the residual dirt hanging on the wall are removed, and the cleaning is completed. The wax filter tube cleaning method of the present application can effectively clean the dirt on the surface and inside of the wax filter tube, which is conducive to the reuse of the wax filter tube and avoids the residual dirt from affecting the progress of the Fischer-Tropsch synthesis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application 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 drawings:

[0021] Figure 1 The figure shows the appearance of the wax filter tube after cleaning in Example 1 of the present invention.

[0022] Figure 2 The figure shows the appearance of the wax filter tube after cleaning in Comparative Example 1 of the present invention.

[0023] Figure 3 The figure shows the appearance of the wax filter tube after cleaning in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0025] As mentioned in the background technology, it is difficult for the traditional cleaning method of the Fischer-Tropsch wax filter tube to effectively clean the surface dirt and internal dirt at the same time, which affects the reuse of the wax filter tube and shortens its service life. Therefore, in this application, the inventor attempts to develop a wax filter tube cleaning method that can effectively clean the surface and internal dirt of the wax filter tube, and based on this, a series of protection schemes of this application are proposed.

[0026] In a first typical embodiment of the present application, a method for cleaning a wax filter tube of a Fischer-Tropsch reactor is provided, the cleaning method comprising: S1) performing a first cleaning on the wax filter tube to be cleaned using an alkaline cleaning agent to obtain a first wax filter tube; S2) performing a second cleaning on the first wax filter tube using an acidic cleaning agent to obtain a second wax filter tube; S3) performing a third cleaning on the second wax filter tube to obtain a cleaned wax filter tube.

[0027] In the Fischer-Tropsch synthesis process, the use of the wax filter tube for a period of time is easy to accumulate substances such as catalyst powder, wax polycondensate (i.e. heavy wax or oil coke) and corrosion products in the tube wall and pores. These sediments will block the filter channel, resulting in reduced filtration efficiency, thereby affecting the stable operation of the entire device. According to the analysis of the previous stage of this application, the pollutants in the above-mentioned wax filter tube are inorganic and organic composite substances, the inorganic substances are mainly Fischer-Tropsch catalyst powder and some corrosion products, and the organic substances are mainly copolymers of wax, among which there are more inorganic substances. These components react with each other and slowly deposit when passing through the filter element to form mixed dirt. Since these filter tubes are expensive, if they are replaced once they are blocked, the operating cost of the enterprise will be increased. Therefore, the service life of these wax filter tubes will be restored by cleaning, which is the most effective way to reduce production costs. However, in the current cleaning method, it is difficult to effectively clean the surface and interior of the complex dirt in the wax filter tube in the Fischer-Tropsch synthesis process, which affects the service life of the wax filter tube.

[0028] In the present application, the wax filter tube to be cleaned is first cleaned with an alkaline cleaning agent, and the components in the alkaline cleaning agent react with the wax on the surface of the wax filter tube, and can be removed by simple rinsing after the reaction is completed; the wax of the wax filter tube is removed after the first cleaning, and the acidic cleaning agent can more fully react with the residual dirt on the surface and inside of the wax filter tube, and a second cleaning is performed, which can further remove catalyst dirt and metal oxide type dirt; through the first cleaning and the second cleaning, the heavy wax, catalyst and metal oxide type residual dirt on the surface and inside of the wax filter tube have been removed, making it easier to remove the dirt deposited in the aperture channel of the wax filter tube by the third cleaning.

[0029] The wax filter tube cleaning method of the present application can effectively clean the surface and interior of the wax filter tube in the Fischer-Tropsch synthesis process to remove heavy wax and catalyst dirt, and will not affect the Fischer-Tropsch synthesis when used next time, which is beneficial to extend the service life of the wax filter tube and reduce the production cost of the Fischer-Tropsch synthesis process. Compared with cleaning with an acidic detergent first and then an alkaline detergent, the cleaning sequence of the present application is more in line with the clear distribution of dirt on the wax filter tube of the Fischer-Tropsch synthesis reactor. If acid washing is performed first and then alkaline washing is performed, the acidic cleaning liquid first contacts the surface of the filter tube during acid washing, and hardly reacts with the wax, and can only peel off some wax when removing part of the catalyst; although the wax on the outer surface of the filter tube can be obviously removed during the subsequent alkaline washing, it cannot react with the catalyst with blocked internal pores, and the inside of the filter tube is still in a "blocked" state, and the cleaning effect is poor, and the requirements for reuse cannot be met, and the service life of the wax filter tube is shortened.

[0030] In a preferred embodiment, the alkaline cleaning agent includes an alkali, a surfactant, a chelating agent and an auxiliary agent; preferably, the alkali includes sodium hydroxide and / or potassium hydroxide, more preferably sodium hydroxide; preferably, the surfactant includes fatty polyoxyethylene ether and / or triethanolamine; preferably, the chelating agent includes sodium salt of ethylenediaminetetraacetic acid and / or sodium citrate; preferably, the auxiliary agent includes sodium carbonate and / or sodium thiosulfate.

[0031] In a preferred embodiment, the alkaline cleaning agent includes, by mass, 3-8 parts of alkali (including but not limited to 3, 4, 5, 6, 7 or 8 parts), 0.5-2 parts of surfactant (including but not limited to 0.5, 1, 1.5 or 2 parts), 0.5-3 parts of chelating agent (including but not limited to 0.5, 1, 1.5, 2, 2.5 or 3 parts) and 0.1-1 parts of auxiliary agent (including but not limited to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 part).

[0032] The alkaline cleaning agent of the present application contains a surfactant, which reduces the surface tension of the wax filter tube and improves the overall wetting and penetration properties and emulsification, dissolution, and dispersing solubilization properties of the alkaline cleaning agent, thereby enhancing the penetration and dissolving power of the alkaline cleaning agent to achieve the purpose of quickly removing wax scale. The role of the chelating agent is to react with the surfactant to chelate and improve the decontamination ability and stability of the surfactant. The role of the auxiliary agent is to improve the cleaning effect of stubborn pollutants on the surface of the filter tube. The present application controls the number of components in the alkaline cleaning agent within the above range, which is conducive to the synergistic effect of each component, fully reacts with the waxy dirt on the wax filter tube, and improves the efficiency of the first cleaning.

[0033] In a preferred embodiment, the time of the first cleaning is 2-6 hours, including but not limited to 2, 3, 4, 5, 6 hours; preferably, the temperature of the first cleaning is 50-80°C, including but not limited to 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C; preferably, the pH of the alkaline cleaning agent is 12.5-13.5, more preferably 13.

[0034] The present application controls the time, temperature and pH of the first cleaning within the above range, which is conducive to the synergistic effect of each component, fully reacting, emulsifying and decomposing the wax dirt in the wax filter tube, and improving the efficiency of the first cleaning. After the first cleaning is completed, the wax dirt in the wax filter tube can be removed by simple rinsing, which is conducive to the subsequent second cleaning and promotes the improvement of the overall cleaning effect.

[0035] In a preferred embodiment, the acid cleaning agent includes an organic acid, an inorganic acid and a pickling corrosion inhibitor; preferably, the organic acid includes oxalic acid and / or citric acid; preferably, the inorganic acid includes one or more of hydrochloric acid, nitric acid, hydrofluoric acid or hydrogen fluoride; preferably, the pickling corrosion inhibitor includes Lan-826.

[0036] The acidic cleaning agent in the present application has a good dissolving ability for catalyst and metal oxide type dirt on the surface of the wax filter tube, wherein the organic acid component is used to react with iron substances, and the inorganic acid mainly reacts with silicon substances, and both can fully react with the above-mentioned dirt and remove it.

[0037] In a preferred embodiment, the acid cleaning agent includes, by mass, 3-8 parts of organic acid (including but not limited to 3, 4, 5, 6, 7 or 8 parts), 1-3 parts of inorganic acid (including but not limited to 1, 1.5, 2, 2.5 or 3 parts) and 0.1-1 parts of pickling corrosion inhibitor (including but not limited to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 part).

[0038] The acid cleaning agent of the present application is a weakly acidic cleaning agent, and the number of its components is controlled within the above-mentioned range. It can effectively clean the wax filter tube without causing corrosion to the wax filter tube, which is beneficial to extending the life of the wax filter tube.

[0039] In a preferred embodiment, the second cleaning time is 3-6 hours, including but not limited to 3, 4, 5 or 6 hours; preferably, the second cleaning temperature is 25-55°C, including but not limited to 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or 55°C; preferably, the pH of the acidic cleaning agent is 1.5-3, more preferably 2.

[0040] The second cleaning time, temperature and pH are controlled within the above ranges to promote the acidic cleaning agent to fully react and dissolve with the catalyst dirt and metal oxide dirt in the wax filter tube, so that the acid corrosion inhibitor can play a role and avoid corrosion of the wax filter tube. After the second cleaning, a simple rinse can remove the catalyst dirt and metal oxide dirt on the surface and inside of the wax filter tube, which is conducive to the subsequent third cleaning and promotes the final cleaning effect.

[0041] In a preferred embodiment, before the first cleaning, the wax filter tube to be cleaned is pre-cleaned; preferably, the physical cleaning includes steam blowing.

[0042] The purpose of physical cleaning is to first remove the loose dirt on the surface of the wax filter tube, so that the alkaline cleaning agent in the subsequent first cleaning can fully react with the waxy dirt in the wax filter tube, improve the cleaning effect of the first cleaning, and facilitate the subsequent second and third cleanings.

[0043] In a preferred embodiment, the third cleaning includes ultrasonic cleaning in water.

[0044] In a preferred embodiment, the frequency of ultrasonic cleaning is 25-45KHz, including but not limited to 25, 30, 35, 40 or 45KHz; preferably, the time of ultrasonic cleaning is 1-3 hours, including but not limited to 1, 2 or 3 hours.

[0045] The purpose of the third cleaning is to remove some dirt in the mesh of the wax filter tube and on the wall after the first cleaning and the second cleaning, which is beneficial to improve the final cleaning effect.

[0046] The alkaline cleaning agent and the acidic cleaning agent provided by the present invention are mild and do not corrode the wax filter tube, are both composed of conventional reagents, and the waste water after cleaning is easy to dispose of. In addition, the cleaning method of the present application has a simple process and is easy to operate, and can efficiently remove various organic and inorganic pollutants on the Fischer-Tropsch wax filter tube, realize the recycling of the wax filter tube, extend the service life of the wax filter tube, reduce the operating cost of the device, and is conducive to the development of the Fischer-Tropsch synthesis process.

[0047] Unless otherwise specified, the reagents in the examples of this application are conventional commercially available products.

[0048] The beneficial effects of the present application will be further explained in detail below in conjunction with specific embodiments.

[0049] Example 1

[0050] The wax filter tube scale sample in the wax Fischer-Tropsch synthesis was taken for ignition weight loss experiment. Calculation showed that the wax filter tube lost about 35.5% of its weight after ignition at 550°C for 2 hours, indicating that the organic component content in the scale sample was about 35.5%, and the inorganic component was about 64.5%.

[0051] X-ray fluorescence analysis (XRF) was performed to further determine the main components of the inorganic matter. The results of the X-ray fluorescence analysis are shown in Table 1.

[0052] Table 1

[0053] <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> <![CDATA[Al2O3]]> MnO CaO <![CDATA[K2O]]> <![CDATA[SO3]]> other Components (wt%) 67.1 20.6 3.3 3.1 2.2 1.9 1.2 0.6

[0054] It can be seen from Table 1 that the inorganic components of the wax filter tube are mainly Fe2O3 and SiO2, which are basically consistent with the catalyst components.

[0055] Analysis of the burning test and XRF test results shows that the pollutants are inorganic / organic composite substances. The inorganic substances are mainly Fischer-Tropsch catalyst powder and some corrosion products, and the organic substances are mainly wax copolymers, with more inorganic substances. When these components pass through the filter element, they react with each other and slowly deposit to form mixed dirt.

[0056] The wax filter tube of the Fischer-Tropsch synthesis described above is divided into multiple sections for cleaning. The wax filter tubes cleaned in the embodiments of the present application are all from this wax filter tube.

[0057] The method for cleaning one section of the wax filter tube in this embodiment is as follows.

[0058] 1. Physical cleaning (pre-cleaning)

[0059] Use high-temperature steam to blow the filter tube surface, use low-pressure steam with a pressure of 0.5MPa to clean, the temperature is 150℃, blow for 30min, and then rinse to remove the soft dirt on the surface of the wax filter tube.

[0060] 2. Alkaline washing (first cleaning)

[0061] Alkaline cleaning agent ratio: 7 parts of sodium hydroxide, 1.5 parts of surfactant, 1 part of chelating agent, 0.2 parts of auxiliary agent, the balance is water, pH = 13.

[0062] The alkaline cleaning time is 5 hours, the cleaning temperature is 70°C, and rinsing is performed after completion.

[0063] 3. Pickling (second cleaning)

[0064] Acid cleaning agent formula: 7 parts of citric acid, 2 parts of ammonium bifluoride, 0.5 parts of pickling corrosion inhibitor, the balance is water, pH = 2.

[0065] The pickling time is 5 hours, and the pickling temperature is controlled below 40°C.

[0066] 4. Ultrasonic cleaning (third cleaning)

[0067] After the above cleaning is completed, the second wax filter tube is subjected to ultrasonic vibration (a non-standard cleaning tank customized by Jinan Songpu Automation Company) to remove some dirt in the mesh of the filter tube and on the wall. The ultrasonic frequency is 30KHz and the ultrasonic time is 1.5 hours.

[0068] Rinse and dry:

[0069] After the ultrasonic treatment, rinse and dry naturally. The appearance of the wax filter tube after cleaning is as follows Figure 1 shown.

[0070] Example 2

[0071] The difference between this embodiment and embodiment 1 is that the alkaline cleaning agent is composed of 5 parts of sodium hydroxide, 1 part of surfactant, 1.5 parts of chelating agent, 0.5 parts of auxiliary agent, and the balance is water.

[0072] Example 3

[0073] The difference between this embodiment and embodiment 1 is that the ratio of the acid cleaning agent is 5 parts of oxalic acid, 1 part of ammonium bifluoride, 0.2 parts of pickling corrosion inhibitor, and the balance is water.

[0074] Example 4

[0075] The only difference between this embodiment and embodiment 1 is that the alkali washing time is 2 hours and the washing temperature is 50°C.

[0076] Example 5

[0077] The difference between this embodiment and embodiment 1 is that the alkali washing time is 6 hours and the washing temperature is 80°C.

[0078] Example 6

[0079] The difference between this embodiment and embodiment 1 is that the alkali washing time is 2 hours and the washing temperature is 30°C.

[0080] Comparative Example 1

[0081] One section of the wax filter tube in the Fischer-Tropsch synthesis industry consistent with Example 1 is cleaned, and the specific method is as follows:

[0082] 1. Physical cleaning (pre-cleaning)

[0083] The pre-cleaning method is consistent with that of Example 1.

[0084] 2. Pickling (i.e., the second cleaning of Example 1)

[0085] The acid cleaning agent formulation and cleaning conditions of the second cleaning are consistent with those of Example 1.

[0086] 3. Alkali washing (i.e. the first washing of Example 1)

[0087] The alkaline cleaning agent formulation and cleaning conditions of the first cleaning are consistent with those of Example 1.

[0088] 4. Ultrasonic cleaning (third cleaning)

[0089] The conditions are consistent with those of the third cleaning in Example 1.

[0090] Rinse and dry

[0091] After the ultrasonic treatment, rinse and dry naturally. The appearance of the wax filter tube after cleaning is as follows Figure 2 shown.

[0092] When the wax filter tube is first acid-washed and then alkaline-washed, the cleaning effect is not good, the bright metallic color is not visible on the surface, and the bubbling volume is small during the bubbling test, and the bubbling is not uniform. This is because most of the Fischer-Tropsch granular catalyst is blocked in the internal pores of the filter tube, and the wax wraps a small part of the catalyst and adheres to the surface. During acid washing, the acidic cleaning liquid first contacts the surface of the filter tube and hardly reacts with the wax. It can only peel off some wax while removing part of the catalyst. Although the wax on the outer surface of the filter tube can be obviously removed during the subsequent alkaline washing, it cannot react with the catalyst that is blocked in the internal pores. The inside of the filter tube is still in a "blocked" state, and the bubbling effect is poor.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 is that a different acid cleaning agent is used in the pickling process. The formula is 7 parts of citric acid, 2 parts of hydrochloric acid, 1 part of hydrofluoric acid, 0.5 parts of pickling corrosion inhibitor, and the balance is water. The pH is 1, the pickling time is 5 hours, the pickling temperature is controlled at 40°C, and the pickling is carried out. The remaining steps are consistent with Example 1.

[0095] The appearance of the wax filter tube after cleaning in this comparative example is as follows Figure 3 shown.

[0096] This scheme has a good effect on removing pollutants from the filter tube, but the appearance is yellowish after cleaning. The bubbling volume is large and uniform during bubbling detection. In addition, the corrosion rate during strong acid and low pH pickling is significantly higher than that during weak acid cleaning. The research results show that although this scheme can achieve a good cleaning effect, it has a great damage to the filter tube material itself. After repeated cleaning, it will have an adverse effect on the interception accuracy, material strength and other properties of the filter tube, and may even cause harm to production equipment and operators.

[0097] Test Example 1

[0098] The cleaned wax filter tubes of the above-mentioned embodiments and comparative examples were subjected to bubbling test, hardness test and corrosion rate test.

[0099] The specific operation of the bubbling test is as follows: inject fresh water into the test tank, the amount of water can submerge the entire filter tube, and then inject clean compressed air into the filter tube from the injection port. Visually observe the bubbling situation, and the cleaning is qualified when the bubbling amount is large, the bubbling is basically uniform, and there is no splashing water line. The results are shown in Table 2.

[0100] Table 2

[0101] Bubble volume Bubble size Splash water line Example 1 big Uniform none Example 2 big Uniform none Example 3 big Uniform none Example 4 big Uniform none Example 5 big Uniform none Example 6 Smaller Basically uniform none Comparative Example 1 Smaller Uneven have Comparative Example 2 big Uniform none

[0102] The hardness of the same position of the filter tube was tested before and after cleaning (using a Leeb hardness tester model HL-600 to quickly test the hardness). The results are shown in Table 3. The hardness of the test point before cleaning was 381N / mm 2 The cleaning method of the present application does not significantly affect the material structure during the cleaning process of the wax filter tube. The low hardness before cleaning is due to the filter tube being covered with softer dirt. After cleaning, the dirt is removed, so the hardness increases slightly.

[0103] Table 3

[0104] <![CDATA[Hardness (N / mm 2 )]]> Example 1 392 Example 2 390 Example 3 389 Example 4 384 Example 5 387 Example 6 382 Comparative Example 1 383 Comparative Example 2 391

[0105] Detect the corrosion rate of the filter tube during the chemical cleaning process (use the fast corrosion measuring instrument 9000PLUS to detect the corrosion rate, the weight change per unit area per unit time, unit g / m- 2 ·h-1), and analyze the corrosion of the cleaning agent on the material. The results are shown in Table 4. The test found that the corrosion rate after the final cleaning was <0.6g / m- 2 ·h-1, to meet the requirement of stainless steel corrosion resistance <1.0g / m- 2 The national standard of h-1 ensures that the entire cleaning process does not cause damage to the filter tube itself.

[0106] Table 4

[0107] <![CDATA[Corrosion rate (g / m -2 ·h -1 )]]> Example 1 0.51 Example 2 0.49 Example 3 0.47 Example 4 0.43 Example 5 0.41 Example 6 0.37 Comparative Example 1 0.54 Comparative Example 2 0.77

[0108] It can be seen from the test results of the above-mentioned embodiments and comparative examples that the cleaning method of the present application can be used to achieve efficient cleaning of the fouled Fischer-Tropsch wax filter tube, and the cleaning process does not cause damage to the material itself.

[0109] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: the wax filter tube in the Fischer-Tropsch synthesis process is cleaned by the cleaning method of the present application, which can effectively elute wax dirt, catalyst dirt, metal oxide dirt and other complex dirt on its surface and inside, and has little effect on hardness, and will not cause corrosion to the filter tube, which is beneficial to extend the life of such wax filter tube and promote the development of the Fischer-Tropsch synthesis process.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for cleaning a wax filter tube of a Fischer-Tropsch reactor, characterized in that: The cleaning method comprises: S1) performing a first cleaning on the wax filter tube to be cleaned using an alkaline cleaning agent to obtain a first wax filter tube; S2) performing a second cleaning on the first wax filter tube using an acidic cleaning agent to obtain a second wax filter tube; S3) performing a third cleaning on the second wax filter tube to obtain the cleaned wax filter tube.

2. The cleaning method according to claim 1, characterized in that: The alkaline cleaning agent comprises alkali, surfactant, chelating agent and auxiliary agent; Preferably, the base comprises sodium hydroxide and / or potassium hydroxide; Preferably, the surfactant comprises fatty polyoxyethylene ether and / or triethanolamine; Preferably, the chelating agent comprises sodium salt of ethylenediaminetetraacetic acid and / or sodium citrate; Preferably, the auxiliary agent comprises sodium carbonate and / or sodium thiosulfate.

3. The cleaning method according to claim 2, characterized in that: Calculated by weight, the alkaline cleaning agent comprises: 3-8 parts of the alkali, 0.5-2 parts of the surfactant, 0.5-3 parts of the chelating agent and 0.1-1 part of the auxiliary agent.

4. The cleaning method according to any one of claims 1 to 3, characterized in that: The first cleaning time is 2-6 hours; Preferably, the temperature of the first cleaning is 50-80°C; Preferably, the pH of the alkaline cleaning agent is 12.5-13.

5.

5. The cleaning method according to claim 1, characterized in that: The acid cleaning agent includes organic acid, inorganic acid and pickling corrosion inhibitor; Preferably, the organic acid comprises oxalic acid and / or citric acid; Preferably, the inorganic acid comprises one or more of hydrochloric acid, nitric acid, hydrofluoric acid or hydrogen fluoride; Preferably, the pickling corrosion inhibitor comprises Lan-826.

6. The cleaning method according to claim 5, characterized in that: In parts by mass, the acid cleaning agent includes 3-8 parts of the organic acid, 1-3 parts of the inorganic acid and 0.1-1 parts of the pickling corrosion inhibitor.

7. The cleaning method according to any one of claims 1, 5 or 6, characterized in that: The second cleaning time is 3-6 hours; Preferably, the temperature of the second cleaning is 35-55°C; Preferably, the pH of the acidic cleaning agent is 1.5-3.

8. The cleaning method according to claim 1, characterized in that: Before performing the first cleaning, pre-cleaning the wax filter tube to be cleaned; Preferably, the pre-cleaning comprises steam purging.

9. The cleaning method according to claim 1, characterized in that: The third cleaning includes ultrasonic cleaning in water.

10. The cleaning method according to claim 9, characterized in that: The frequency of the ultrasonic cleaning is 25-45KHz; Preferably, the ultrasonic cleaning time is 1-3 hours.

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