Method for cleaning titanium tetrachloride preheater

Abstract

The invention relates to the technical field of cleaning agents, in particular to a method for cleaning a titanium tetrachloride preheater. According to the method for cleaning the titanium tetrachloride preheater, provided by the invention, the titanium tetrachloride preheater is regularly cleaned by adopting dry ice. Dry ice cleaning is a physical process, a cleaning medium is solid carbon dioxide and does not chemically react with equipment materials (such as Inconel 601 alloy) and residual titanium tetrachloride, the problem that corrosive hydrogen chloride gas is generated by traditional water washing is completely eradicated, and an equipment body is protected. Efficient and lossless cleaning of the titanium tetrachloride preheater can be achieved, and the titanium dioxide quality problem caused by falling of a carbon scale layer of the titanium tetrachloride preheater is thoroughly solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cleaning agents, in particular to a method for cleaning a titanium tetrachloride preheater. BACKGROUND

[0002] In the oxidation process of chlorination titanium dioxide production enterprises, the titanium tetrachloride preheater is the core equipment of the process, which preheats the fine titanium tetrachloride to the process control temperature by the high-temperature gas provided by burning toluene, and is the main energy supply of the oxidation process. In the preheating process, about 30 ppm of organic dissolved substances in fine titanium tetrachloride will adhere to the inner wall of the high-temperature preheater pipeline and gradually carbonize to form a layer of firm carbon scale. This carbon scale will fall off at irregular times and quantities during production, enter the oxidation reactor with the material, and finally mix in the titanium dioxide product in the form of black carbon particles. Since carbon particles cannot be separated by subsequent processes, it seriously affects the whiteness, brightness and other key indicators of titanium dioxide products, and this problem has become a common technical problem that has plagued all chlorination titanium dioxide production enterprises and affected the stability of product quality.

[0003] To solve this problem, various cleaning schemes have been explored in the industry. At present, most enterprises use water assisted with cleaning agents for flushing, but this method has inherent defects: ① The residual medium on the inner wall of the preheater is titanium tetrachloride, and water will react violently with it to generate highly corrosive hydrogen chloride gas, causing serious corrosion to the inner wall of the preheater (usually Inconel 601 and other high-value alloys), shortening the service life of the equipment; ② After water washing, thorough drying must be carried out to remove all moisture, and the drying process is time-consuming and long, which seriously affects the continuity and efficiency of production; ③ The scouring force of water flow is limited, and the cleaning effect on the carbonized hard scale is not good, making it difficult to completely remove.

[0004] In order to further improve the cleaning effect, more advanced chemical cleaning schemes (such as disclosed in Chinese patent CN115044415A) have appeared in the prior art. This scheme uses a special cleaning agent composed of phosphoric acid, surfactant, corrosion inhibitor, etc., and carries out cleaning through steps such as circulating flushing, solid-liquid separation and subsequent gas blowing and drying. Although this method improves the cleaning ability of carbon scale to some extent, it still cannot get rid of the fundamental category of "wet cleaning", and the process is complex, requiring matching mixing, heating, separation and drying devices, and the system is large and the operation is complicated. More importantly, it cannot completely avoid the potential chronic corrosion risk of chemical reagents to the equipment, and the drying process after cleaning still causes production interruption and affects the overall efficiency.

[0005] Therefore, it is of great significance to develop a cleaning method that can fundamentally avoid corrosion, does not require drying and is efficient and thorough, for improving the quality and production efficiency of titanium dioxide products. SUMMARY

[0006] In view of this, the present invention proposes a method for cleaning a titanium tetrachloride preheater, which achieves efficient and non-destructive cleaning of the titanium tetrachloride preheater and completely solves the titanium dioxide quality problem caused by the shedding of carbon scale layer from the titanium tetrachloride preheater.

[0007] The method for cleaning a titanium tetrachloride preheater proposed in this invention uses dry ice to clean the titanium tetrachloride preheater.

[0008] In some embodiments, the cleaning process is carried out in a closed system, which includes at least a dry ice cleaner and a dust collector connected in communication, with a titanium tetrachloride preheater configured between the dry ice cleaner and the dust collector.

[0009] In some embodiments, the method includes the following steps: stopping production and draining the titanium tetrachloride from the titanium tetrachloride preheater; connecting the titanium tetrachloride preheater to a cleaning circuit consisting of a dry ice cleaner and a dust collector; and turning on the dry ice cleaner to spray dry ice into the titanium tetrachloride preheater for cleaning.

[0010] In some embodiments, the process inlet valve and outlet valve of the titanium tetrachloride preheater are closed before the dry ice cleaning machine is turned on.

[0011] In some embodiments, after cleaning is completed, the cleaning effect of the titanium tetrachloride preheater is tested; if the test is qualified, the titanium tetrachloride preheater is reconnected to the production process loop and production is resumed.

[0012] In some embodiments, detection is achieved by checking the discharged gas for carbon particles using white lint-free gauze at the inlet of the dust collector.

[0013] In some embodiments, dry ice is sprayed in the form of particles.

[0014] In some embodiments, the dry ice jet flow rate of the dry ice cleaner is 2000 kg / h to 5000 kg / h.

[0015] In some embodiments, the duration of a single dry ice cleaning cycle is 30 to 60 minutes.

[0016] In some embodiments, the dust collector is a bag filter or an electrostatic precipitator.

[0017] The beneficial effects of this invention are as follows: The method for cleaning titanium tetrachloride preheaters proposed in this invention uses dry ice for periodic cleaning. Dry ice cleaning is a physical process, and the cleaning medium is solid carbon dioxide, which does not chemically react with the equipment material (such as Inconel 601 alloy) or residual titanium tetrachloride, completely eliminating the problem of corrosive hydrogen chloride gas generated by traditional water washing, thus protecting the equipment itself. Compared with high-pressure water jet cleaning, dry ice cleaning has a gentle impact kinetic energy and will not cause erosion, thinning, or damage to the inner wall of the precision preheater coil, achieving truly non-destructive cleaning. Moreover, the dry ice instantly sublimates into gaseous carbon dioxide after impact, eliminating the need for drying the expected heat after rinsing, preventing the generation of corrosive hydrogen chloride gas, and leaving no secondary residues. This avoids the risk of contamination of subsequent production due to cleaning agent residue or moisture introduction. It is time-efficient, low-cost, and does not damage the equipment, truly achieving efficient and non-destructive cleaning of titanium tetrachloride preheaters. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram illustrating the cooperation between the closed system and the titanium tetrachloride preheater in a method for cleaning a titanium tetrachloride preheater according to an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Dry ice cleaning machine; 2. Titanium tetrachloride preheater; 3. Dust collector. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0022] The technical problem this invention aims to solve is to provide a method for cleaning titanium tetrachloride preheaters, achieving efficient and non-destructive cleaning and completely resolving titanium dioxide quality issues caused by carbon scale shedding from the preheaters. To address this problem, the method proposed in this invention uses dry ice for periodic cleaning of the titanium tetrachloride preheater. Dry ice cleaning is a physical process; the cleaning medium is solid carbon dioxide, which does not chemically react with the equipment material (such as Inconel 601 alloy) or residual titanium tetrachloride, completely eliminating the problem of corrosive hydrogen chloride gas generated by traditional water washing and protecting the equipment itself. Compared to high-pressure water jet cleaning, dry ice cleaning has a gentler impact kinetic energy, preventing erosion, thinning, or damage to the delicate inner walls of the preheater coils, achieving truly non-destructive cleaning. Furthermore, the dry ice instantly sublimates into gaseous carbon dioxide after impact, leaving no secondary residues and avoiding the risk of contamination to subsequent production caused by cleaning agent residue or moisture introduction.

[0023] In some embodiments, the cleaning process is carried out in a closed system, such as Figure 1 As shown, the closed system includes at least a connected dry ice cleaner 1 and a dust collector 3, with a titanium tetrachloride preheater 2 positioned between the dry ice cleaner 1 and the dust collector 3. This closed system effectively isolates the carbon scale dust shed during the cleaning process from the external environment. The dry ice cleaner 1 injects dry ice for cleaning, while the dust collector 3 simultaneously and instantly extracts and collects the carbon scale particles flushed out of the titanium tetrachloride preheater 2 and some of the sublimated carbon dioxide gas, thus completely preventing the escape of carbon scale dust from the operating space. This not only ensures the occupational health and safety of on-site personnel and prevents environmental pollution, but also avoids the risk of contamination to other equipment and product purity caused by secondary dust settling, ensuring the cleanliness and efficiency of the cleaning operation.

[0024] In some embodiments, the method for cleaning the titanium tetrachloride preheater includes the following steps: stopping production and draining the titanium tetrachloride from the titanium tetrachloride preheater 2; connecting the titanium tetrachloride preheater 2 to a cleaning circuit consisting of a dry ice cleaner 1 and a dust collector 3; and turning on the dry ice cleaner 1 to spray dry ice into the titanium tetrachloride preheater 2 for cleaning. First, "stopping production and draining the titanium tetrachloride" fundamentally cuts off the supply of hazardous materials, creating a safe and clean operating environment for subsequent physical cleaning and avoiding the risk of uncontrollable reactions between titanium tetrachloride and any medium. Next, "connecting the preheater to a dedicated cleaning circuit" enables a rapid conversion of system function, temporarily reconfiguring the titanium tetrachloride preheater into an independent, closed cleaning unit, ensuring that the flow path of the dry ice is precisely guided and effectively collected. Finally, "starting the dry ice cleaner 1 for spraying" is the core cleaning action initiated on this safe and dedicated platform. This allows the low-temperature embrittlement and impact peeling effect of dry ice to act precisely and efficiently on the carbon scale on the inner wall of the titanium tetrachloride preheater 2. This achieves the ultimate goal of efficient cleaning while ensuring absolute non-destruction and minimizing the overall downtime.

[0025] In some embodiments, before starting the dry ice cleaning machine 1, the inlet and outlet valves of the titanium tetrachloride preheater 2 are closed. By closing the inlet and outlet valves, the titanium tetrachloride preheater 2 to be cleaned is physically isolated from the entire active, continuous production system, effectively preventing any possibility of titanium tetrachloride material accidentally flowing into the cleaning area, and fundamentally eliminating the risk of hazardous chemical leakage or cross-reaction with the cleaning medium.

[0026] In some embodiments, after cleaning, the cleaning effect of the titanium tetrachloride preheater 2 is tested; if the test is qualified, the titanium tetrachloride preheater 2 is reconnected to the production process loop and production is resumed. By directly testing the cleaning effect (such as using white lint-free gauze to verify whether carbon particles have been completely removed), an objective and verifiable acceptance standard is established for the cleaning process, ensuring that each cleaning effectively meets the quality requirement of eliminating carbon contamination, thereby providing a prerequisite guarantee for the subsequent production of high-whiteness, high-purity titanium dioxide products.

[0027] In some embodiments, detection is achieved by using white lint-free gauze at the inlet of the dust collector 3 to check whether the discharged gas contains carbon particles. This method can transform invisible trace carbon particles distributed in the gas into obvious evidence that is visible to the naked eye, thereby providing an immediate and objective criterion for the cleaning effect.

[0028] In some embodiments, dry ice is sprayed in particle form, and through its low-temperature embrittlement effect and physical impact effect, it peels off the carbon deposits on the inner wall of the preheater. Specifically, the extremely low temperature (approximately -78.5°C) of the dry ice causes the carbon deposits to shrink and generate microcracks, significantly weakening the adhesion between the deposits and the metal substrate; simultaneously, the high-speed sprayed dry ice particles directly impact the embrittled deposits with kinetic energy, completely breaking them off like miniature scrapers. This synergistic physical effect of "embrittlement followed by rinsing" not only thoroughly removes stubborn carbon deposits but also completely avoids the corrosion risks of chemical cleaning agents or the mechanical damage that high-pressure water jets may cause to the equipment body. Thus, while ensuring cleaning effectiveness, it truly achieves long-term safe maintenance of precision preheater equipment.

[0029] In some embodiments, the dry ice jet flow rate of the dry ice cleaner 1 is 2000 kg / h to 5000 kg / h. This flow rate range ensures that sufficient dry ice particles act on the inner wall of the preheater per unit time, which can both create an effective low-temperature embrittlement environment to cause the carbon scale to shrink and crack, and provide sufficient physical impact kinetic energy to completely remove the scale layer.

[0030] In some embodiments, the duration of a single cleaning cycle of the dry ice cleaner 1 is 30 to 60 minutes. This duration ensures that the low-temperature embrittlement and impact peeling effects of the dry ice have sufficient time to fully act on the entire inner wall of the preheater pipes, systematically removing various types of carbon deposits, from loose to stubborn, and eliminating localized residues caused by insufficient cleaning time.

[0031] In some embodiments, the dust collector 3 is a bag filter or an electrostatic precipitator. The bag filter has high capture efficiency for micron-sized particles due to its physical filtration characteristics, while the electrostatic precipitator uses electric field force to efficiently adsorb submicron-sized suspended particles. The choice of the two dust collectors can specifically capture and separate ultrafine carbon particle dust washed out from the preheater.

[0032] Example 1 A method for cleaning a titanium tetrachloride preheater, employing a cleaning system consisting of a dry ice cleaner, a titanium tetrachloride preheater, and a bag filter, specifically includes the following steps: (1) Stop the oxidation process and completely drain the remaining titanium tetrachloride in the titanium tetrachloride preheater; (2) Close the inlet and outlet valves of the titanium tetrachloride preheater to completely isolate it from the production system; (3) Open the pipe valves connecting the dry ice cleaner and the bag filter, and connect the preheater to the closed cleaning circuit; (4) Start the dry ice cleaning machine and spray dry ice particles into the preheater at a flow rate of 2000 kg / h for 60 minutes. (5) After cleaning, use white lint-free gauze to check the exhaust gas at the dust collector inlet; (6) After observing and confirming that there are no black carbon particles on the gauze, the cleaning effect is deemed to be qualified, and the dry ice cleaning machine is then turned off. (7) Close the pipeline valves of the dry ice cleaner and the bag filter in sequence; (8) Reopen the inlet and outlet valves of the titanium tetrachloride preheater and reconnect it to the production system to restore normal production of the oxidation process.

[0033] Example 2 A method for cleaning a titanium tetrachloride preheater, employing a cleaning system consisting of a dry ice cleaner, a titanium tetrachloride preheater, and an electrostatic precipitator, specifically includes the following steps: (1) Stop the oxidation process and completely drain the remaining titanium tetrachloride in the titanium tetrachloride preheater; (2) Close the inlet and outlet valves of the titanium tetrachloride preheater to completely isolate it from the production system; (3) Open the pipe valves connecting the dry ice cleaner and the electrostatic precipitator, and connect the preheater to the closed cleaning circuit; (4) Start the dry ice cleaning machine and spray dry ice particles into the preheater at a flow rate of 5000 kg / h for 30 minutes. (5) After cleaning, use white lint-free gauze to check the exhaust gas at the dust collector inlet; (6) After observing and confirming that there are no black carbon particles on the gauze, the cleaning effect is deemed to be qualified, and the dry ice cleaning machine is then turned off. (7) Close the pipeline valves of the dry ice cleaner and the electrostatic precipitator in sequence; (8) Reopen the inlet and outlet valves of the titanium tetrachloride preheater and reconnect it to the production system to restore normal production of the oxidation process.

[0034] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0035] It should be understood that, provided it is technically feasible, the technical features listed above for different embodiments can be combined with each other to form other embodiments within the scope of this invention.

[0036] In this application, the use of antonymous conjunctions is intended to include the conjunction itself. The use of definite or indefinite articles is not intended to indicate cardinality. Specifically, references to “the” object or to “a” and “one” objects are intended to indicate one of a plurality of such objects. Furthermore, the conjunction “or” may be used to convey simultaneous features rather than mutually exclusive schemes. In other words, the conjunction “or” should be understood as including “and / or”. The term “including” is inclusive and has the same scope as “contains”.

[0037] The above embodiments are possible examples of implementations of the present invention and are provided only to enable those skilled in the art to clearly understand the principles of the present invention. Those skilled in the art should understand that the above discussion of any embodiment is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of the present invention (including the claims) is limited to these examples. Under the overall concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined with each other to produce many other variations of different aspects of the embodiments of the present invention as described above. For the sake of brevity, these variations are not provided in the specific embodiments. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of the present invention should be included within the scope of protection claimed by the present invention.

Claims

1. A method for cleaning a titanium tetrachloride preheater (2), characterized in that, The titanium tetrachloride preheater (2) was cleaned using dry ice.

2. The method according to claim 1, characterized in that, The cleaning process is carried out in a closed system, which includes at least a dry ice cleaner (1) and a dust collector (3) connected together, with the titanium tetrachloride preheater (2) disposed between the dry ice cleaner (1) and the dust collector (3).

3. The method according to claim 2, characterized in that, The method includes the following steps: Stop production and drain the titanium tetrachloride from the titanium tetrachloride preheater (2); The titanium tetrachloride preheater (2) is connected to the cleaning circuit consisting of a dry ice cleaner (1) and a dust collector (3); Turn on the dry ice cleaner (1) and spray dry ice into the titanium tetrachloride preheater (2) for cleaning.

4. The method according to claim 3, characterized in that, Before starting the dry ice cleaning machine (1), close the production process inlet valve and outlet valve of the titanium tetrachloride preheater (2).

5. The method according to claim 3, characterized in that, After cleaning, the cleaning effect of the titanium tetrachloride preheater (2) is tested; after passing the test, the titanium tetrachloride preheater (2) is reconnected to the production process loop and production is resumed.

6. The method according to claim 5, characterized in that, The detection is achieved by using white lint-free gauze at the inlet of the dust collector (3) to check whether the discharged gas contains carbon particles.

7. The method according to claim 1, characterized in that, The dry ice is sprayed in the form of particles.

8. The method according to claim 2, characterized in that, The dry ice spray flow rate of the dry ice cleaning machine (1) is 2000 kg / h to 5000 kg / h.

9. The method according to claim 2, characterized in that, The duration of a single cleaning cycle of the dry ice cleaning machine (1) is 30 to 60 minutes.

10. The method according to claim 2, characterized in that, The dust collector (3) is a bag filter or an electrostatic precipitator.

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