Method for cleaning a wax filter tube of a fischer-tropsch reactor

Abstract

The application provides a cleaning method of a wax filtering tube of a Fischer-Tropsch reactor. The cleaning method comprises the following steps: S1) performing first cleaning on the wax filtering tube to be cleaned by using an alkaline cleaning agent to obtain a first wax filtering tube; S2) performing second cleaning on the first wax filtering tube by using an acidic cleaning agent to obtain a second wax filtering tube; and S3) performing third cleaning on the second wax filtering tube to obtain a cleaned wax filtering tube. The method can solve the problem of short service life of the wax filtering tube in the prior art and is suitable for the field of wax filtering tube cleaning.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wax filter pipe cleaning, in particular to a cleaning method for wax filter pipe of a Fischer-Tropsch reactor. BACKGROUND

[0002] Fischer-Tropsch synthesis process is one of the indirect coal liquefaction technologies, and is the core of coal-to-oil technology. First, coal reacts with steam at high temperature to generate synthesis gas (a mixture of CO and H2), and then the synthesis gas is hydrogenated under appropriate reaction conditions to generate a mixture of hydrocarbons (C1-C100) and oxygen-containing compounds of different chain lengths. In the slurry bed reactor of Fischer-Tropsch synthesis, the high molecular weight liquid wax product has a high boiling point and is difficult to vaporize and discharge under conventional Fischer-Tropsch synthesis operating conditions, so it accumulates 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 manner.

[0003] Due to the special reaction medium and conditions of the slurry bed reactor, fine solid catalyst particles will inevitably be brought out with the liquid wax. In order to reduce the catalyst loss of the system and at the same time to ensure that the liquid wax product can continue to be processed in the next process, a filter pipe needs to be used to separate the catalyst from the liquid wax, that is, after the mixed liquid enters the filter pipe, the liquid wax passes through the filter screen and the catalyst is intercepted by the filter screen.

[0004] After the wax filter pipe has been in operation for a period of time, catalyst powder, condensates of wax (i.e. heavy wax or oil coke), corrosion products, etc. are easily deposited on the outer surface and internal apertures of the filter pipe, thereby blocking the filter screen channels, causing the filtration capacity of the filter pipe to decrease, and affecting the stable operation of the device. The filter pipe is relatively expensive, and if it is directly replaced after being contaminated, the operating cost of the enterprise will increase, so the ideal solution is to achieve reuse of the filter pipe through cleaning.

[0005] The traditional cleaning methods for Fischer-Tropsch wax filter pipes mainly include mechanical methods and chemical methods. Among them, the mechanical methods (such as manual scraping, grinding, sand blasting, etc.) can only remove the dirt on the surface of the filter core, and cannot effectively remove the dirt inside the filter core. The chemical method is the most widely used method in industry at present, but the traditional cleaning formula cannot effectively remove the blockage of the filter core, and is easy to cause damage to the filter core body in the wax filter pipe, and even cause harm to the environment and the operating personnel. In patent application CN107236605A, a passivation agent is used to treat the wax filter pipe before cleaning, but the composition of the passivation agent is complex, the preparation process is complicated, and the cleaning method only focuses on the emulsification and dispersion reaction of organic matter and gum, and the cleaning is completed by loosening and washing off the pollutants after stripping. There is a lack of cleaning agent components that can react with Fischer-Tropsch catalyst components such as iron and silicon, and the corresponding cleaning steps, and the cleaning effect is limited, and it is difficult to remove the catalyst blockage of the filter core.

[0006] Therefore, there is a lack of a method capable of effectively cleaning the dirt inside and outside the wax filter tube, so that the service life of the wax filter tube is shortened, which is not conducive to the development of the Fischer-Tropsch synthesis process. SUMMARY

[0007] The main purpose of the present application is to provide a cleaning method for 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 a first aspect of the present application, a cleaning method for a wax filter tube of a Fischer-Tropsch reactor is provided, which comprises: S1) performing first cleaning on the wax filter tube to be cleaned by using an alkaline cleaning agent to obtain a first wax filter tube; S2) performing second cleaning on the first wax filter tube by using an acidic cleaning agent to obtain a second wax filter tube; and S3) performing third cleaning on the second wax filter tube to obtain a cleaned wax filter tube.

[0009] Further, the alkaline cleaning agent comprises a base, a surfactant, a chelating agent and an auxiliary agent; preferably, the base comprises sodium hydroxide and / or potassium hydroxide; preferably, the surfactant comprises a fatty base polyoxyethylene ether and / or triethanolamine; preferably, the chelating agent comprises sodium ethylenediaminetetraacetate and / or sodium citrate; and preferably, the auxiliary agent comprises sodium carbonate and / or sodium thiosulfate.

[0010] Further, the alkaline cleaning agent comprises 3-8 parts of the base, 0.5-2 parts of the surfactant, 0.5-3 parts of the chelating agent and 0.1-1 part of the auxiliary agent by mass fraction.

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

[0012] Further, the acidic cleaning agent comprises an organic acid, an inorganic acid and an acid pickling corrosion inhibitor.

[0013] 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; and preferably, the acid pickling corrosion inhibitor comprises Lan-826.

[0014] Further, the acidic cleaning agent comprises 3-8 parts of the organic acid, 1-3 parts of the inorganic acid and 0.1-1 part of the acid pickling corrosion inhibitor by mass fraction.

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

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

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

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

[0019] By using the technical scheme of the present application, the wax filter pipe to be cleaned is sequentially subjected to first cleaning and second cleaning by using alkaline cleaning agent and acidic cleaning agent, which can remove the residual dirt of wax, catalyst and metal oxide on the surface and inside of the wax filter pipe, and finally, the third cleaning is performed to remove the dirt remaining on the mesh of the wax filter pipe and the wall, thereby completing the cleaning. By using the wax filter pipe cleaning method of the present application, the dirt on the surface and inside of the wax filter pipe can be effectively removed, which is beneficial to the reuse of the wax filter pipe and avoids the influence of the residual dirt on the Fischer-Tropsch synthesis process. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of the present application, are intended to provide further understanding of the present application and are incorporated herein for a purpose of explanations of the present application and are not intended as improper limitations to the present application. In the drawings:

[0021] Figure 1 The appearance of the wax filter pipe after cleaning in Example 1 of the present application is shown.

[0022] Figure 2 The appearance of the wax filter pipe after cleaning in Comparative Example 1 of the present application is shown.

[0023] Figure 3 The appearance of the wax filter pipe after cleaning in Comparative Example 2 of the present application is shown. DETAILED DESCRIPTION

[0024] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0025] As mentioned in the background, the conventional cleaning method of the Fischer-Tropsch wax filter pipe cannot effectively clean the surface dirt and the internal dirt at the same time, which affects the reuse of the wax filter pipe and shortens the service life. Therefore, the inventors have tried to develop a wax filter pipe cleaning method which can effectively clean the surface dirt and the internal dirt of the wax filter pipe, and based on this, a series of protection schemes of the present application are proposed.

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

[0027] In the Fischer-Tropsch synthesis process, after the wax filter tube is used for a period of time, catalyst powder, wax condensates (i.e. heavy wax or oil coke) and corrosion products and the like are easily accumulated in the wall and the channel of the tube, which will block the filter screen channel, reduce the filtering efficiency, and further affect the stable operation of the entire device. Through the previous analysis of the present application, the above-mentioned contaminants in the wax filter tube are inorganic and organic composite substances, the inorganic substances are mainly Fischer-Tropsch catalyst powder and part of corrosion products, and the organic substances are mainly wax condensates, wherein the inorganic substances are more. These components react with each other and slowly deposit when passing through the filter core, forming mixed dirt. Since these filter tubes are relatively expensive, if they are replaced once they are blocked, the operating cost of the enterprise will be increased, therefore, cleaning is the optimal way to extend the service life of these wax filter tubes and reduce production costs. However, in the current cleaning method, it is difficult to effectively clean the surface and the inside of the dirt with complex components 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 by using an alkaline cleaning agent, the components in the alkaline cleaning agent react with the wax on the surface of the wax filter tube, and the reaction is removed by simple flushing after the reaction is completed; after the wax in the wax filter tube is removed by the first cleaning, the acidic cleaning agent can more fully react with the dirt remaining on the surface and the inside of the wax filter tube, and the second cleaning can further remove the catalyst dirt and the metal oxide type dirt; through the first cleaning and the second cleaning, the heavy wax, the catalyst and the metal oxide type residual dirt on the surface and the inside of the wax filter tube are all removed, so that the third cleaning is more easy to remove the dirt deposited in the pore channel of the wax filter tube.

[0029] The cleaning method of the wax filter pipe of the application can effectively clean the surface and interior of the wax filter pipe in the Fischer-Tropsch synthesis process to remove heavy wax and catalyst dirt, and does not affect the Fischer-Tropsch synthesis when used next time, which is conducive to prolonging the service life of the wax filter pipe and reducing the production cost of the Fischer-Tropsch synthesis process. Compared with cleaning first by using an acidic cleaning agent and then by using an alkaline cleaning agent, the cleaning sequence of the application is more in line with the clear distribution of dirt on the wax filter pipe of the Fischer-Tropsch synthesis reactor. If the acid cleaning is performed first and then the alkali cleaning, the acidic cleaning liquid first contacts the surface of the filter pipe and hardly reacts with the wax, and only some wax can be peeled off when part of the catalyst is removed; although the wax on the outer surface of the filter pipe can be obviously removed during the subsequent alkali cleaning, the catalyst cannot react with the catalyst that blocks the interior aperture, the interior of the filter pipe is still in a "blocked" state, the cleaning effect is poor, and the service life of the wax filter pipe is shortened.

[0030] In a preferred embodiment, the alkaline cleaning agent comprises a base, a surfactant, a chelating agent and an auxiliary agent; preferably, the base comprises sodium hydroxide and / or potassium hydroxide, more preferably sodium hydroxide; preferably, the surfactant comprises a fatty base polyoxyethylene ether and / or triethanolamine; preferably, the chelating agent comprises sodium ethylenediaminetetraacetate and / or sodium citrate; preferably, the auxiliary agent comprises sodium carbonate and / or sodium thiosulfate.

[0031] In a preferred embodiment, the alkaline cleaning agent comprises, in terms of mass fraction: 3-8 parts of a base (including but not limited to 3, 4, 5, 6, 7 or 8 parts), 0.5-2 parts of a surfactant (including but not limited to 0.5, 1, 1.5 or 2 parts), 0.5-3 parts of a chelating agent (including but not limited to 0.5, 1, 1.5, 2, 2.5 or 3 parts) and 0.1-1 part of an 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 application contains a surfactant, which can reduce the surface tension of the wax filter pipe, improve the overall wetting penetration performance and emulsification, dissolution, dispersion and solubilization performance of the alkaline cleaning agent, thereby enhancing the penetration and dissolution of the alkaline cleaning agent to achieve the purpose of quickly removing wax dirt. The chelating agent can react with the surfactant to improve the dirt removal capacity and stability of the surfactant. The auxiliary agent can improve the cleaning effect on stubborn contaminants on the surface of the filter pipe. The application controls the fraction of each component in the alkaline cleaning agent within the above range, which is conducive to the synergistic effect of each component, fully reacts with the wax dirt of the wax filter pipe, and improves the efficiency of the first cleaning.

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

[0034] By controlling the time, temperature and pH of the first cleaning in the above range, the present application is beneficial for the components to work synergistically, fully react with, emulsify and decompose the waxy dirt of the wax filter tube, and improve the efficiency of the first cleaning. After the first cleaning is completed, the waxy dirt in the wax filter tube can be removed by simple flushing, which is beneficial for the subsequent second cleaning and promotes the improvement of the overall cleaning effect.

[0035] In a preferred embodiment, the acidic cleaning agent includes organic acid, inorganic acid and pickling 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 inhibitor includes Lan-826.

[0036] The acidic cleaning agent in the present application has good dissolving capacity for the 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-based substances, and the inorganic acid mainly reacts with silicon-based substances, both of which can fully react with the above-mentioned dirt and remove it.

[0037] In a preferred embodiment, the acidic cleaning agent includes 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 part of pickling 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) by mass fraction.

[0038] The acidic cleaning agent of the present application is a weakly acidic cleaning agent, and by controlling the component fraction in the above range, it can effectively clean the wax filter tube without causing corrosion to the wax filter tube, which is beneficial for prolonging the service 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℃, including but not limited to 25℃, 30℃, 35℃, 40℃, 45℃, 50℃ or 55℃; 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 in the above range, the acidic cleaning agent is fully reacted with and dissolved in the catalyst dirt and metal oxide type dirt in the wax filter pipe, the acid corrosion inhibitor plays a role, corrosion of the wax filter pipe is avoided, and simple flushing after the second cleaning can remove the catalyst dirt and metal oxide type dirt on the surface and inside of the wax filter pipe, which is beneficial to subsequent third cleaning and promotes the final cleaning effect.

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

[0042] The purpose of the physical cleaning is to remove loose dirt on the surface of the wax filter pipe, so that the alkaline cleaning agent can fully react with the wax dirt in the wax filter pipe in the subsequent first cleaning, the cleaning effect of the first cleaning is improved, and the subsequent second cleaning and third cleaning are facilitated.

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

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

[0045] The purpose of the above third cleaning is to remove part of the dirt in the mesh of the wax filter pipe and the remaining wall-hanging dirt after the first cleaning and the second cleaning, which is beneficial to improving the final cleaning effect.

[0046] The alkaline cleaning agent and the acidic cleaning agent provided by the application have mild performance and do not corrode the wax filter pipe, are both composed of conventional reagents, and the wastewater after cleaning is easy to dispose. The cleaning method of the application has a simple process and is easy to operate, can efficiently remove various types of organic and inorganic pollutants on the plugged Fischer-Tropsch wax filter pipe, realizes recycling of the wax filter pipe, prolongs the service life of the wax filter pipe, reduces the operation cost of the device, and is beneficial to development of the Fischer-Tropsch synthesis process.

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

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

[0049] Embodiment 1

[0050] The scale sample on the wax filter pipe in the Fischer-Tropsch synthesis was taken to carry out a loss on ignition experiment, and calculation showed that the loss on ignition of the wax filter pipe was about 35.5% after ignition at 550 DEG C for 2 hours, indicating that the content of the organic component in the scale sample was about 35.5%, and the content of the inorganic component was about 64.5%.

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

[0052] Table 1

[0053] Fe2O3 SiO2 Al2O3 MnO CaO K2O SO3 Other Component (wt%) 67.1 20.6 3.3 3.1 2.2 1.9 1.2 0.6

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

[0055] According to the results of the burning experiment and the XRF experiment, the pollutant is an inorganic / organic composite substance, the inorganic matter is mainly the Fischer-Tropsch catalyst powder and part of the corrosion products, the organic matter is mainly the copolymer of wax, and there is more inorganic matter. These components react with each other and slowly deposit when passing through the filter element, forming mixed dirt.

[0056] The Fischer-Tropsch synthesized wax filter tube described above is divided into multiple sections for cleaning, and the wax filter tube cleaned in the present embodiment is from the wax filter tube.

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

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

[0059] High-temperature steam is used to blow the surface of the filter tube, and low-pressure steam with a pressure of 0.5 MPa is used for cleaning, the temperature is 150°C, and the blowing time is 30 min, then rinsing, to remove the relatively soft dirt on the surface of the wax filter tube.

[0060] 2. Alkaline cleaning (first cleaning)

[0061] The alkaline cleaning agent is composed of 7 parts of sodium hydroxide, 1.5 parts of surfactant, 1 part of chelating agent, 0.2 parts of auxiliary agent, and the rest is water, with pH = 13.

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

[0063] 3. Acid cleaning (second cleaning)

[0064] The acid cleaning agent is composed of 7 parts of citric acid, 2 parts of ammonium hydrogen fluoride, and 0.5 parts of acid cleaning corrosion inhibitor, and the rest is water, with pH = 2.

[0065] The acid cleaning time is 5 hours, and the acid cleaning temperature is controlled to be lower than 40°C,

[0066] 4. Ultrasonic cleaning (third cleaning)

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

[0068] Rinse and dry:

[0069] After the ultrasonic treatment, rinse and air dry. The appearance of the cleaned wax filter tube is shown in Figure 1

[0070] Example 2

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

[0072] Example 3

[0073] The difference between this example and Example 1 is only that the acidic cleaning agent is composed of 5 parts of oxalic acid, 1 part of ammonium hydrogen fluoride, and 0.2 parts of pickling corrosion inhibitor, with the balance being water.

[0074] Example 4

[0075] The difference between this example and Example 1 is only that the alkaline cleaning time is 2 hours, and the cleaning temperature is 50°C.

[0076] Example 5

[0077] The difference between this example and Example 1 is only that the alkaline cleaning time is 6 hours, and the cleaning temperature is 80°C.

[0078] Example 6

[0079] The difference between this example and Example 1 is only that the alkaline cleaning time is 2 hours, and the cleaning 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. Acid pickling (i.e., the second cleaning of Example 1)

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

[0086] 3. Alkaline cleaning (i.e., the first cleaning of Example 1)

[0087] ​The first cleaning was conducted in accordance with the alkaline cleaning agent formulation and cleaning conditions of Example 1.

[0088] 4. Ultrasonic cleaning (third cleaning)

[0089] The third cleaning was conducted in accordance with the conditions of Example 1.

[0090] Rinse and dry

[0091] After the ultrasonic treatment, rinse and air dry, the appearance of the cleaned wax filter tube is as shown in Figure 2

[0092] When the wax filter tube is first cleaned with acid and then cleaned with alkali, the cleaning effect is poor, the appearance is not bright and metallic, and the amount of bubbling is small and the bubbling is not uniform during the bubbling test. This is because most of the Fischer-Tropsch particulate catalyst is blocked in the internal pore diameter of the filter tube, and a small amount of catalyst is attached to the surface wrapped in wax. During acid cleaning, the acid cleaning solution first contacts the surface of the filter tube and hardly reacts with the wax, only removing part of the catalyst and peeling off some wax; during subsequent alkali cleaning, the wax on the outer surface of the filter tube can be removed, but the catalyst blocked in the internal pore diameter cannot react, and the internal pore diameter of the filter tube is still in a "blocked" state, resulting in poor bubbling effect.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 is only that a different acid cleaning agent is used during acid cleaning, the formulation is citric acid 7 parts, hydrochloric acid 2 parts, hydrofluoric acid 1 part, acid cleaning inhibitor 0.5 parts, the balance is water, pH = 1, acid cleaning time is 5 hours, acid cleaning temperature is controlled at 40°C, and the rest of the steps are the same as Example 1.

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

[0096] This scheme has good effect on removing contaminants from the filter tube, but the appearance after cleaning is yellow, the amount of bubbling is large and the bubbling is uniform during the bubbling test, and it is found that the corrosion rate during strong acid low pH acid cleaning is significantly higher than that during weak acid cleaning. The research results show that although this scheme can achieve good cleaning effect, it causes great damage to the filter tube material itself, and repeated cleaning will have adverse effects on the interception precision and material strength of the filter tube, and even cause harm to the production device and operating personnel.

[0097] Test Example 1

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

[0099] ​​The bubble detection test is specifically operated as follows: fresh water is injected into the detection tank, and the water amount can immerse the whole filter pipe, then clean compressed air is injected into the filter pipe from the sample inlet position. The bubble amount is observed, and the cleaning is qualified when the bubble amount is large, the bubbles are basically uniform, and there is no water line splashing, and the results are shown in Table 2.

[0100] Table 2

[0101] Amount of Bubbles Size of Bubbles Splash Line Example 1 Large Uniform None Example 2 Large Uniform None Example 3 Large Uniform None Example 4 Large Uniform None Example 5 Large Uniform None Example 6 Smaller Substantially Uniform None Comparative Example 1 Smaller Non-Uniform Yes Comparative Example 2 Large Uniform None

[0102] The hardness of the same position of the filter pipe before and after cleaning is detected (the hardness is rapidly detected by using a Leed hardness tester with a model number of HL-600), and the results are shown in Table 3. The hardness of the detection point before cleaning is 381 N / mm 2 , and the cleaning method of the present application does not obviously affect the material structure during the cleaning process of the wax filter pipe. The hardness is slightly low before cleaning because the filter pipe is covered by soft dirt, and the hardness is slightly increased after the dirt is removed.

[0103] Table 3

[0104] 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] The corrosion rate of the filter pipe during the chemical cleaning process is detected (the corrosion rate is detected by using a rapid corrosion measuring instrument 9000 PLUS, the weight change per unit area per unit time, unit g / m- 2 ·h-1), and the corrosion of the material by the cleaning agent is analyzed, and the results are shown in Table 4. It is found that the corrosion rate is less than 0.6 g / m- 2 ·h-1 after the final cleaning, which meets the national standard that the corrosion of stainless steel needs to be less than 1.0 g / m- 2 ·h-1, and it is ensured that the filter pipe itself is not damaged during the whole cleaning process.

[0106] Table 4

[0107] 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 known from the detection results of the above examples and comparative examples that the cleaning method of the present application can realize efficient cleaning of the blocked Fischer-Tropsch wax filter pipe, and the cleaning process does not damage the material itself.

[0109] From the above description, it can be seen that the above examples of the present application achieve the following technical effects: the cleaning method of the present application is used to clean the wax filter pipe in the Fischer-Tropsch synthesis process, which can effectively wash off the wax dirt, catalyst dirt and metal oxide dirt and other complex dirt on the surface and inside of the filter pipe, has little effect on the hardness, does not cause corrosion of the filter pipe, is beneficial to prolonging the service life of the wax filter pipe, and promotes the development of the Fischer-Tropsch synthesis process.

[0110] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

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; Wherein, the alkaline cleaning agent comprises alkali, surfactant, chelating agent and auxiliary agent; The acidic cleaning agent includes organic acid, inorganic acid and pickling corrosion inhibitor; Before performing the first cleaning, pre-cleaning the wax filter tube to be cleaned; The pre-cleaning includes steam purging; The third cleaning includes ultrasonic cleaning in water.

2. The cleaning method according to claim 1, wherein The base includes sodium hydroxide and / or potassium hydroxide.

3. The cleaning method according to claim 1, wherein The surfactant includes fatty polyoxyethylene ether and / or triethanolamine.

4. The cleaning method according to claim 1, wherein The chelating agent includes ethylenediaminetetraacetic acid sodium salt and / or sodium citrate.

5. The cleaning method according to claim 1, wherein The auxiliary agent includes sodium carbonate and / or sodium thiosulfate.

6. The cleaning method according to claim 1, wherein Calculated by mass, the alkaline cleaning agent includes: 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.

7. The cleaning method according to claim 1, wherein The first cleaning time is 2-6 hours.

8. The cleaning method according to claim 7, wherein: The temperature of the first cleaning is 50-80°C.

9. The cleaning method according to claim 1, wherein The pH of the alkaline cleaning agent is 12.5-13.

5.

10. The cleaning method according to claim 1, wherein The organic acid includes oxalic acid and / or citric acid.

11. The cleaning method according to claim 1, wherein The inorganic acid includes one or more of hydrochloric acid, nitric acid, hydrofluoric acid or hydrogen fluoride.

12. The cleaning method according to claim 1, wherein The pickling corrosion inhibitor includes Lan-826.

13. The cleaning method according to claim 1, wherein In parts by mass, the acidic cleaning agent includes 3-8 parts of the organic acid, 1-3 parts of the inorganic acid and 0.1-1 part of the pickling corrosion inhibitor.

14. The cleaning method according to claim 1, wherein The second cleaning time is 3-6 hours.

15. The cleaning method according to claim 14, characterized in that: The temperature of the second cleaning is 35-55°C.

16. The cleaning method according to claim 1, wherein The pH of the acidic cleaning agent is 1.5-3.

17. The cleaning method according to claim 1, wherein The frequency of the ultrasonic cleaning is 25-45KHz.

18. The cleaning method according to claim 1, wherein The ultrasonic cleaning time is 1-3 hours.

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