Crude oil floating roof storage tank emission reduction device and method

Abstract

The invention discloses a crude oil floating roof storage tank emission reduction device and method, the device is used for emission reduction of VOCs, and the device at least comprises a storage tank inner wall coating which is an oleophobic and hydrophobic coating and is coated on the inner wall of a storage tank and the corresponding position where a floating disc moves up and down; the circulating pipe is arranged above the edge of the floating disc and is fixedly connected with the floating disc; flowing oleophylic and hydrophilic cleaning liquid is arranged in the circulating pipe; during large breath, in the process that the circulating pipe moves along with the floating disc, the cleaning liquid makes contact with the oleophobic and hydrophobic coating, and crude oil hanging on the wall is removed. And the circulating pipe can also be communicated with an exhaust port of a breather valve at the top of the tank and is used for absorbing VOCs gas discharged by the small breath through oleophylic and hydrophilic cleaning liquid in the small breath process. By arranging the circulating pipe capable of moving along with the floating disc and the oleophobic and hydrophobic coating at the corresponding position of the inner wall of the storage tank, crude oil hanging on the wall can be effectively removed in the large respiration process, and meanwhile abrasion of the inner wall of the storage tank can be effectively reduced. The exhaust port of the breather valve at the top of the tank is connected with the circulating pipe, so that the problem of exhaust emission in the small breathing process can be solved.

Description

Technical Field

[0001] This invention relates to the field of petrochemical environmental waste gas treatment technology, and in particular to a device and method for reducing volatile organic compounds from crude oil floating roof storage tanks. Background Technology

[0002] Crude oil storage tanks in the petrochemical industry are generally large floating roof tanks. Their tops consist of a floating roof that can move up and down. The edges of the floating roof and the inner wall of the tank are typically sealed with an elastic sealing device to prevent oil and gas from escaping. Simultaneously, a wax scraper removes the crude oil adhering to the inner wall of the tank. Although the distance between the floating roof and the liquid surface in a floating roof tank is very small, effectively reducing the gas phase space inside the tank compared to a fixed roof tank, the phenomenon of "large breathing" still exists. "Large breathing" in floating roof tanks refers to the phenomenon where, as oil is released from the tank, some oil adheres to the inner wall as the liquid level and the floating roof descend, evaporating VOCs and forming fugitive emissions. When the crude oil tank wall is heavily corroded, wall-adhesion losses can account for up to 78% of the total emissions from the crude oil tank. Therefore, addressing wall-adhesion losses is a major way to reduce VOC emissions from crude oil storage tanks. When the storage tank is in a relatively static state and no crude oil receiving or dispatching operations are being carried out, a "small breathing" phenomenon will occur. Especially in environments with large temperature differences between day and night, solar radiation during the day causes the temperature of the crude oil in the storage tank to rise, and the gas space above the oil surface expands accordingly, accelerating the evaporation of oil and causing the pressure inside the tank to rise. Once the pressure exceeds the allowable value set by the breather valve, some of the oil-rich vapor will be released into the atmosphere, forming an unorganized emission.

[0003] The existing emission reduction methods for crude oil floating roof tanks have the following problems: (1) During the large breathing process, the wax scraper cannot completely remove the crude oil adhering to the wall. The residual wax causes VOCs to volatilize and leads to the waste of oil resources; (2) The long-term wear of the inner wall of the tank and the wax scraper makes it very easy to rust, which reduces the service life of the tank; (3) The sealing and venting of large floating roof crude oil tanks is a difficult problem. The fugitive emissions formed by the large and small breathing of the tank need to be treated at the back end, which makes the investment and operating costs of the back end treatment high; (4) Most of the fugitive emissions from the small breathing are directly discharged into the atmosphere, causing certain pollution.

[0004] For example, Chinese patent application CN114435784A discloses a method and apparatus for reducing VOC emissions from storage tanks. This apparatus mainly includes a storage tank, a floating roof, an annular enclosed chamber, a spray system, and an oil and gas collection system. The floating roof moves up and down during tank operation, collecting VOCs generated during operation into the annular enclosed chamber. The spray system is located within the annular enclosed chamber and is activated when the floating roof moves up and down to absorb oil and gas and clean the tank walls. This solution can solve the problem of VOC emissions from crude oil inside the tank and crude oil adhering to the tank walls, avoiding pollution and losses caused by crude oil evaporation and adhesion. However, the effect of this solution in removing crude oil adhering to the walls is not significant; thorough cleaning requires a large amount of cleaning agent, and downstream VOCs waste gas treatment facilities are still necessary. Furthermore, this solution does not consider the waste gas emissions during periods of slight breathing.

[0005] Therefore, there is an urgent need for a device and method to reduce volatile organic compounds (VOCs) from floating roof crude oil storage tanks. This device and method can not only solve the problem of crude oil adhering to the tank wall at the source during large-scale breathing and reduce wear on the inner wall of the tank, but also solve the problem of exhaust gas emissions during small-scale breathing.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a crude oil floating roof storage tank emission reduction device and method. By using a circulating pipe that moves with the floating roof and an oleophobic and hydrophobic coating at the corresponding position on the inner wall of the storage tank, crude oil adhering to the wall can be effectively removed during the large breathing process, while effectively reducing wear on the inner wall of the storage tank.

[0008] Another objective of this invention is to provide an emission reduction device and method for crude oil floating roof storage tanks, which can solve the problem of exhaust gas emission during small breathing processes by connecting the exhaust port of the tank top breather valve to the circulation pipe.

[0009] To achieve the above objectives, according to a first aspect of the present invention, the present invention provides an emission reduction device for crude oil floating roof storage tanks for VOCs emission reduction, comprising at least: an inner wall coating of the storage tank, which is an oleophobic and hydrophobic coating and is applied to the inner wall of the storage tank and at corresponding positions where the floating roof moves up and down; a circulation pipe disposed above the edge of the floating roof and fixedly connected to the floating roof; a flowing oleophilic and hydrophilic cleaning fluid disposed within the circulation pipe; during large breathing, as the circulation pipe moves with the floating roof, the cleaning fluid contacts the oleophobic and hydrophobic coating and removes the crude oil adhering to the wall.

[0010] Furthermore, in the above technical solution, the circulation pipe can be a pipe-groove structure, with the opening side of the pipe-groove tightly attached to the inner wall coating of the storage tank, forming a closed circulation space. When the floating plate moves up and down to perform large breathing, the oleophilic and hydrophilic cleaning liquid in the circulation pipe washes away the oleophobic and hydrophobic coating.

[0011] Furthermore, in the above technical solution, a dynamic seal is provided at the interface between the circulation pipe and the coating on the inner wall of the storage tank. The dynamic seal is preferably a mechanical spring seal.

[0012] Furthermore, in the above technical solution, the oleophobic and hydrophobic coating may include a double or multi-layer coating of primer and topcoat; the primer may be an adhesive layer, and the topcoat is preferably a super-hydrophobic coating material.

[0013] Furthermore, in the above technical solution, the circulation pipe can be connected to the exhaust port of the breather valve on the top of the tank, and is used to absorb the VOCs gas discharged during the small breathing process through the oleophilic and hydrophilic cleaning liquid.

[0014] Furthermore, in the above technical solution, a one-way valve can be installed between the circulation pipe and the exhaust port of the breather valve on the top of the tank to prevent the cleaning fluid from flowing into the tank.

[0015] Furthermore, in the above technical solution, the circulation pipe can be connected to the inlet and outlet pipes of the cleaning fluid; the cleaning fluid is pumped into the inlet pipe by a liquid pump, flows in the circulation pipe, and then flows out from the outlet pipe.

[0016] Furthermore, in the above technical solution, the crude oil floating roof tank can be an external floating roof tank or an internal floating roof tank; the upper surface of the floating roof is preferably inclined to collect rainwater and / or cleaning fluid that may leak.

[0017] Furthermore, in the above technical solution, a floating roof seal is provided at the annular edge of the floating roof; the circulation pipe can be set above the floating roof seal.

[0018] According to a second aspect of the present invention, the present invention provides a method for reducing emissions from a crude oil floating roof tank, comprising the following steps: A. Coating the inner wall of the tank with an oleophobic and hydrophobic coating and installing a circulation pipe, fixing the circulation pipe to the upper surface of the floating roof and ensuring that the open side of the circulation pipe is sealed tightly against the oleophobic and hydrophobic coating; B. When the tank is undergoing large breathing and the floating roof is descending, pumping an oleophilic and hydrophilic cleaning fluid into the circulation pipe, simultaneously flushing and absorbing the residual crude oil adhering to the oleophobic and hydrophobic coating; C. The cleaning fluid after absorbing the crude oil adhering to the coating flows out from the circulation pipe.

[0019] Furthermore, in the above technical solution, the method may also include: D. When the storage tank is breathing slightly, the VOCs gas in the tank is discharged into the circulation pipe through the exhaust port of the breather valve and absorbed by the cleaning liquid.

[0020] Furthermore, in the above technical solution, the flow rate of the cleaning fluid during large-scale breathing is preferably controlled at 10m. 3 The flow rate of the cleaning fluid should be approximately 0.5 m / h during periods of light breathing. 3 / h or so.

[0021] Furthermore, in the above technical solution, the coating method in step A can be spraying, brushing, or roller coating; preferably, when spraying is used, a two-step spraying method can be used to spray the primer and topcoat sequentially.

[0022] Furthermore, in the above technical solution, the topcoat can be a coating material with oleophobic and hydrophobic properties, preferably a superhydrophobic coating material prepared from FAS-17 modified silica nanoparticles; the primer can be an adhesive, preferably an E-44 / PTFE mixture.

[0023] Furthermore, in the above technical solution, the surfactant component of the oleophilic and hydrophilic cleaning solution in step B is preferably dodecyl dimethyl benzyl ammonium chloride or sodium dodecyl diphenyl ether disulfonate, etc.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) This invention, by applying an oleophobic and hydrophobic coating to the inner wall of the storage tank, minimizes the loss of crude oil and VOC pollution caused by oil adhering to the tank wall during the tank's large-scale breathing and floating roof descent process. Through the installation of a circulation pipe and the presence of a flowing oleophilic and hydrophilic cleaning fluid within the pipe, a small amount of crude oil adhering to the tank wall (i.e., the inner wall above the floating roof after descent) can be dynamically flushed away during the large-scale breathing process. The oleophobic and hydrophobic coating of this invention effectively prevents crude oil adhering to the tank wall and the resulting VOCs during the downward movement of the floating roof during large-scale breathing. The extremely small amount of residual oil and wax can be further removed by the circulating oleophilic and hydrophilic cleaning fluid. Experiments have shown that the combined design of the coating and the circulating flushing effectively removes almost all of the oil adhering to the tank wall.

[0026] 2) The groove structure with an opening on one side of the circulating pipe in this invention can better enable the cleaning fluid to fully contact and flush and absorb the small amount of crude oil adhering to the coating; the dynamic seal between the circulating pipe and the inner wall of the storage tank is preferably a mechanical spring seal, which can not only prevent the leakage of cleaning fluid to the maximum extent, but also ensure that the sliding friction between the circulating pipe and the inner wall of the storage tank is effectively reduced during the movement of the circulating pipe.

[0027] 3) The oleophobic and hydrophobic coating of the present invention has the characteristics of oleophobicity, hydrophobicity, wear resistance, corrosion resistance and adhesion to the inner wall of the storage tank. It is composed of a "coating + adhesive" structure, which is conducive to better absorption and removal of crude oil adhering to the wall during cleaning fluid flushing, and can also effectively protect the inner wall of the storage tank.

[0028] 4) This invention can not only remove the crude oil adhering to the inner wall of the floating roof tank during the large breathing process, but also absorb the VOCs emitted from the breathing valve through the cleaning fluid in the circulation pipe during the small breathing process of the tank, thus ultimately achieving VOCs emission reduction at the source of the floating roof tank.

[0029] 5) This invention has the advantages of simple structure and low energy consumption. It can effectively reduce the fugitive emissions of VOCs during the large and small breathing processes of floating roof tanks. At the same time, it eliminates the need for the oil and gas recovery system and deep VOCs waste gas treatment device commonly used in existing tanks, which greatly reduces the treatment cost of VOCs waste gas generated by the large and small breathing processes of floating roof tanks. In addition, it can also eliminate the need for the wax scraper widely used on the edge of the floating roof of external floating roof tanks, which effectively reduces the wear of the wax scraper on the inner wall of the tank during the up and down floating process of the floating roof, reduces the resulting corrosion, and extends the service life of the tank.

[0030] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0031] Figure 1 This is a cross-sectional structural schematic diagram of the crude oil floating roof storage tank of the present invention.

[0032] Figure 2 This is a top view of the crude oil floating roof storage tank of the present invention.

[0033] Figure 3 This is a side cross-sectional view of the crude oil floating roof tank emission reduction device of the present invention.

[0034] Figure 4 This is a cross-sectional view of another side of the crude oil floating roof tank emission reduction device of the present invention (showing the elastic mechanical seal of the circulation pipe and the fixed column of the circulation pipe).

[0035] Explanation of key figure labels:

[0036] 100-Storage tank, 101-Floating roof, 102-Floating roof edge seal, 103-Rainwater collector, 104-Breath valve;

[0037] 1-Oleophobic and hydrophobic coating, 2-Circulation pipe, 20-Circulation pipe dynamic seal, 20A-Mechanical spring seal, 21-Cleaning fluid inlet pipe, 22-Cleaning fluid outlet pipe, 23-Gas guide pipe, 24-One-way valve, 25-Fixed column. Detailed Implementation

[0038] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0039] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0040] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0041] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0042] like Figures 1 to 4 As shown, this invention provides an emission reduction device for crude oil floating roof storage tanks, used for VOCs emission reduction, comprising at least an inner wall coating 1 and a circulation pipe 2. The inner wall coating 1 is an oleophobic and hydrophobic coating applied to the inner wall of the storage tank 100 and at corresponding positions where the floating roof moves up and down (it can be applied to the entire inner wall area or within the travel range of the floating roof). The circulation pipe 2 is positioned above the edge of the floating roof 101 and fixedly connected to it; a flowing oleophilic and hydrophilic cleaning fluid is provided within the circulation pipe 2; during large-scale breathing, the circulation pipe 2 moves with the floating roof (mainly referring to the downward movement of the floating roof), and the cleaning fluid contacts the oleophobic and hydrophobic coating to remove the crude oil adhering to the wall.

[0043] The above-mentioned technical solution of the present invention, by setting an oleophobic and hydrophobic coating on the inner wall of the storage tank, can minimize the amount of crude oil adhering to the wall during the large-scale breathing and floating roof descent process of the storage tank (using the coating of the present invention, only a very small amount of crude oil adheres to the wall). Adhered crude oil will form wax, and if not treated, this exposed wax will cause loss of crude oil in the storage tank and generate VOCs that pollute the atmosphere. Through the setting of the circulation pipe and the presence of a flowing oleophilic and hydrophilic cleaning fluid inside the pipe, the small amount of crude oil already exposed to the wall can be dynamically flushed away during the large-scale breathing process of the storage tank. The oleophobic and hydrophobic coating of the present invention can effectively prevent crude oil from adhering to the wall during the downward movement of the floating roof during the large-scale breathing of the floating roof storage tank, as well as the resulting VOCs. The very small amount of residual wax can be further removed by the circulating oleophilic and hydrophilic cleaning fluid. Experiments have shown that the combined design of the coating and the circulation flushing allows for almost complete removal of the crude oil adhering to the wall.

[0044] Further as Figure 3 As shown, the circulation pipe 2 has a tube-groove structure, with the open side of the tube-groove tightly attached to the inner wall coating of the storage tank 100, forming a closed circulation space. When the floating roof moves up and down to perform large breathing, the oleophilic and hydrophilic cleaning fluid in the circulation pipe washes away the oleophobic and hydrophobic coating. The tube-groove structure with one open side allows the cleaning fluid to better contact with and wash away the small amount of crude oil adhering to the coating. A dynamic seal 20 is provided at the junction of the circulation pipe 2 and the inner wall coating 1 of the storage tank (reference). Figure 3 The dynamic seal is preferably a mechanical spring seal 20A (reference). Figure 4 The circulating pipe 2 of this invention can be fixed to the upper surface of the floating roof 101 by a fixed column 25, and can move up and down with the floating roof 101. Therefore, during the process of the cleaning fluid rinsing the coating on the inner wall of the storage tank, the circulating pipe 2 can slide on the coating 1 on the inner wall of the storage tank. Through the dynamic sealing design, leakage of the cleaning fluid can be prevented to the greatest extent. Reference Figure 4 The dynamic seal 20 here is preferably a spring mechanical seal 20A with good corrosion resistance. This structure is mainly composed of an elastic sealing gasket, a spring, and a spring column.

[0045] The oleophobic and hydrophobic coating of the present invention comprises a double or multi-layer coating of a primer and a topcoat. The primer serves as an adhesive layer, and the topcoat can be a super-hydrophobic coating material. Specifically, this oleophobic and hydrophobic coating simultaneously possesses oleophobicity, hydrophobicity, abrasion resistance, corrosion resistance, and the ability to adhere to the inner wall of a storage tank without easily peeling off. It consists of a "coating + adhesive" structure. The coating, serving as the topcoat, can be any coating material possessing oleophobic and hydrophobic properties, preferably a super-hydrophobic coating material prepared from FAS-17 modified silica nanoparticles. The adhesive, serving as the primer, provides adhesion and can be any adhesive available in the prior art, preferably an E-44 / PTFE blend material with excellent adhesive strength and chemical stability.

[0046] Further as Figure 1 ,2 As shown, the circulation pipe 2 connects the cleaning fluid inlet pipe 21 and the outlet pipe 22; the cleaning fluid is pumped into the inlet pipe 21 by a liquid pump (not shown in the figure), and flows in the circulation pipe 2. During the large breathing process, it washes the coating 1 on the inner wall of the tank and absorbs a small amount of crude oil adhering to the wall before flowing out from the outlet pipe 22. The crude oil floating roof tank 100 of the present invention can be an external floating roof tank or an internal floating roof tank; the upper surface of the floating plate 101 is inclined and can be used to collect rainwater and / or cleaning fluid that may leak (see...). Figure 1 , 2 The rainwater collector 103 is located in the center. A floating roof seal 102 is provided at the annular edge of the floating roof 101; the circulation pipe 2 is located above the floating roof seal 102 (see reference). Figure 3 ).

[0047] Further as Figure 3 As shown, preferably but not limitingly, the circulation pipe 2 is connected to the exhaust port of the tank top breather valve 104, used to absorb the VOCs gas discharged during the small breathing process using an oleophilic and hydrophilic cleaning liquid. A one-way valve 24 is provided between the circulation pipe 2 and the exhaust port of the tank top breather valve to prevent the cleaning liquid from flowing into the tank. During the small breathing process, the breather valve opens after reaching the tank gas pressure threshold, and the exhaust gas is discharged from the exhaust port of the breather valve, and then enters the circulation pipe 2 through the one-way valve 24 and the gas guide pipe 23 to be absorbed by the cleaning liquid. This invention absorbs the small breathing gas discharged from the breather valve 104 of the storage tank through the circulation cleaning liquid, and finally enters the sewage tank for centralized treatment with the cleaning liquid. It can not only thoroughly remove the crude oil adhering to the wall during the large breathing process, reducing crude oil loss and VOCs volatilization, but also effectively absorb the small breathing gas, ultimately achieving source VOCs emission reduction of crude oil floating roof storage tanks.

[0048] The floating roof edge seal 102 of this invention can employ conventional primary or secondary seals. Due to the vertical movement of the floating roof 101, an annular space exists between the floating roof and the inner wall of the floating roof tank. This space can be protected by a sealing device to prevent pollution, fire, and degradation of oil quality caused by oil and gas leaks. Common sealing devices include mechanical seals, elastic filler seals, and lip seals. All three of these sealing methods are primary seals. To further reduce oil and gas loss, a secondary seal can be added on top of the primary seal. Common secondary seal structures include roller skeleton seals.

[0049] The present invention also provides a method for reducing emissions from crude oil floating roof storage tanks, comprising the following steps:

[0050] Step S101: Apply an oleophobic and hydrophobic coating to the inner wall of the storage tank and install a circulation pipe. Fix the circulation pipe to the upper surface of the floating roof, ensuring that the open side of the circulation pipe is tightly sealed against the oleophobic and hydrophobic coating. The coating can be applied by spraying, brushing, or roller coating; spraying is preferred, and a two-step spraying method can be used to apply a primer and a topcoat sequentially. The topcoat is an oleophobic and hydrophobic coating material, preferably a super-hydrophobic coating material prepared from FAS-17 modified silica nanoparticles; the primer is an adhesive, preferably an E-44 / PTFE mixture.

[0051] In step S102, when the storage tank is undergoing large-scale breathing and the floating roof 101 descends, an oleophilic-hydrophilic cleaning fluid is pumped into the circulation pipe 2. Simultaneously, the cleaning fluid flows, flushing and absorbing the residual crude oil adhering to the oleophobic-hydrophilic coating. The surfactant component of the oleophilic-hydrophilic cleaning fluid is preferably dodecyl dimethyl benzyl ammonium chloride or sodium dodecyl diphenyl ether disulfonate, etc. The flow rate of the cleaning fluid during large-scale breathing is preferably controlled at 10 m / s. 3 / h or so.

[0052] In step S103, the cleaning fluid after absorbing the crude oil adhering to the wall flows out from the circulation pipe.

[0053] Step S104, this is the preferred step, where during the small-scale breathing of the storage tank, the VOCs gas inside the tank is discharged into the circulation pipe 2 through the exhaust port of the breather valve 104, and is thus absorbed by the cleaning fluid. The flow rate of the cleaning fluid during the small-scale breathing is preferably controlled at 0.5 m / s. 3 / h or so.

[0054] The method of the present invention, based on the existing floating roof tank, sprays an oleophobic and hydrophobic coating on the inner wall of the tank. When the tank's discharge floating roof moves downward (i.e., during the large breathing process of the tank), the coating surface hardly adheres to crude oil, effectively reducing the amount of crude oil adhering to the inner wall of the floating roof tank during the large breathing process. The low-volatility oleophilic and hydrophilic cleaning agent circulating at the edge of the floating roof further cleans the very small amount of crude oil remaining on the tank wall. During the small breathing process of the tank, it absorbs VOCs emitted from the breathing valve, ultimately achieving VOCs emission reduction at the source of the floating roof tank.

[0055] The device and method of this invention have advantages such as simple structure and low energy consumption, which can effectively reduce the fugitive emissions of VOCs during the large and small breathing processes of floating roof tanks. At the same time, it eliminates the need for the oil and gas recovery system and deep VOCs waste gas treatment device commonly used in existing tanks, greatly reducing the treatment cost of VOCs waste gas generated by the large and small breathing processes of floating roof tanks. In addition, it can also eliminate the need for the wax scraper widely used on the edge of the floating roof of external floating roof tanks, effectively reducing the wear of the wax scraper on the inner wall of the tank during the up and down floating process, reducing the resulting corrosion, and extending the service life of the tank.

[0056] Example 1

[0057] First, an oleophobic and hydrophobic coating was constructed on the inner wall of the external floating roof tank 100. The preparation process involved first dispersing epoxy resin E-44 in an acetone solution with ultrasonic assistance, then adding PTFE and ultrasonically treating for 1 hour. A curing agent was added before use to obtain the E-44 / PTFE adhesive. A certain amount of SiO2 was dispersed in an ethanol solution, ammonia was added, and the mixture was stirred for a certain time. Then, appropriate amounts of crosslinking agent and fluorinating agent were added and stirred for a certain time. The mixture was then centrifuged and washed with ethanol and acetone. Finally, acetone was added to prepare an F-SiO2 (fluorinated silica nanoparticles) suspension. A two-step spraying method was used: first, the E-44 / PTFE adhesive was sprayed as a primer onto the inner wall of the external floating roof tank; then, a certain amount of the F-SiO2 suspension was sprayed as a second coat onto the primer. After curing at ambient temperature for 24 hours, a coating with good oleophobic and hydrophobic properties was finally obtained.

[0058] When the storage tank undergoes large-scale breathing, circulation cleaning / absorption begins, with the flow rate of the oleophilic and hydrophilic cleaning agent set to 10m³. 3 / h. The test was conducted under constant temperature conditions of 26℃, during which the storage tank experienced almost no small breathing.

[0059] After 100 large breathing cycle simulation tests of the external floating roof tank, no obvious residual oil and wax was found on the inner wall coating surface of the floating roof tank. Gas sampling analysis of the gas phase space at the top of the tank showed that the VOCs emission was reduced by more than 96% compared with conventional external floating roof tanks.

[0060] Example 2

[0061] The experiment was essentially the same as Example 1, except that the storage tank did not undergo feeding or discharging operations (i.e., no large-scale breathing), the ambient temperature fluctuated continuously between 15 and 30°C, and the cleaning fluid in the circulation pipe flowed at a rate of 0.5 m³ / min. 3 Flowing at a rate of / h.

[0062] After a 100-hour small-scale breathing simulation test of the external floating roof tank, it was found that as the temperature rose, the tank top breathing valve opened multiple times, and the discharged gas entered the circulation pipe, was absorbed by the cleaning agent, and was eventually discharged; no VOCs were detected in the gas collected from the tank top.

[0063] Example 3

[0064] The experiment was essentially the same as Example 1, except that during the large-scale breathing of the storage tank and the descent of the floating roof, the ambient temperature continuously changed between 15 and 30°C (with several small-scale breathings occurring during this period), while circulating cleaning / absorption was performed simultaneously. The cleaning agent in the circulating pipe was at a rate of 10m...3 Flowing at a rate of / h.

[0065] After 100 large breathing cycle simulation tests of the external floating roof tank, no obvious residual oil and wax was found on the inner wall coating surface of the floating roof tank. Gas sampling analysis of the gas phase space at the top of the tank showed that the VOCs emission was reduced by more than 96% compared with conventional external floating roof tanks.

[0066] Comparative Example 1

[0067] Same as Example 1, except that the flow rate of the oleophilic and hydrophilic cleaning agent is set to 5 m / s. 3 / h.

[0068] After 100 cycles of large breathing cycle simulation test of the external floating roof tank, no obvious residual oil and wax was found on the inner wall coating surface of the floating roof tank. Gas sampling analysis of the gas phase space at the top of the tank showed that the VOCs emission was reduced by more than 92% compared with conventional external floating roof tanks.

[0069] Comparative Example 2

[0070] Similar to Example 1, but without the need for recirculation cleaning and the absence of oleophilic and hydrophilic cleaning agents in the recirculation pipe. After 100 simulated large-scale breathing cycles of the floating roof tank, it was found that as the number of cycles increased, the area of ​​the extremely small amount of oil and wax residue adhering to the wall in the initial stage of the test gradually expanded. Gas sampling and analysis of the gas phase space at the top of the tank after the final simulation test showed that the VOCs emission concentration increased by more than 1100% compared to Example 1. This is because the small amount of oil and wax adhering to the wall in the initial stage of the test replaced the surface of the oleophobic and hydrophobic coating, making it easier for crude oil to adhere to the wall after contact with crude oil. This vicious cycle resulted in an increasing amount of crude oil adhering to the wall, significantly affecting the source reduction effect of the floating roof tank.

[0071] Comparative Example 3

[0072] Similar to Example 2, except that the outlet of the breathing valve is not connected to the circulation pipe, and the breathing gas is directly discharged into the atmosphere.

[0073] After a 100-hour simulation test of the small breathing of the external floating roof tank, it was found that as the temperature rose, the breathing valve on the top of the tank opened multiple times, and VOCs were detected in the gas collected from the top of the tank.

[0074] Comparative Example 4

[0075] Similar to Example 1, the difference is that the oleophobic and hydrophobic coating sprayed on the inner wall of the external floating roof tank is only sprayed with topcoat and not primer. Due to the lack of the adhesive effect of primer, after three large breathing cycle simulation tests of the floating roof tank, the coating began to peel off in a large area, and its function of preventing crude oil from sticking to the wall was basically ineffective.

[0076] Comparative Example 5

[0077] Similar to Example 1, but with the difference that a wax scraper was added between the edge of the floating roof and the inner wall of the tank. After 100 simulated large-scale breathing cycles of the floating roof tank, wear was found on some of the coating surfaces. During the descent of the floating roof, oil and wax began to adhere to the worn areas, and the cleaning effect decreased. At this point, gas sampling and analysis were performed on the gas phase space at the top of the tank. The test results showed that, compared with Example 1, the VOCs emission concentration increased by more than 800%.

[0078] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A crude oil floating roof storage tank emission reduction device, characterized in that, VOCs emission reduction includes: The inner wall coating of the storage tank is an oleophobic and hydrophobic coating applied to the inner wall of the storage tank and the corresponding positions where the floating roof moves up and down; A circulation pipe is disposed above the edge of the floating roof and fixedly connected to the floating roof; the circulation pipe contains a flowing oleophilic and hydrophilic cleaning fluid; during large breathing, as the circulation pipe moves with the floating roof, the cleaning fluid comes into contact with the oleophobic and hydrophobic coating and removes the crude oil adhering to the wall.

2. The crude oil floating roof storage tank emission reduction device according to claim 1, characterized in that, The circulation pipe has a tube-groove structure, with the opening side of the tube-groove tightly attached to the inner wall coating of the storage tank, forming a closed circulation space. When the floating plate moves up and down to perform large breathing, the oleophilic and hydrophilic cleaning liquid in the circulation pipe washes away the oleophobic and hydrophobic coating.

3. The crude oil floating roof storage tank emission reduction device according to claim 1, characterized in that, A dynamic seal is provided at the junction of the circulation pipe and the inner wall coating of the storage tank.

4. The crude oil floating roof storage tank emission reduction device according to claim 3, characterized in that, The dynamic seal is a mechanical spring seal.

5. The crude oil floating roof storage tank emission reduction device according to claim 1, characterized in that, The oleophobic and hydrophobic coating comprises a double or multi-layer coating of primer and topcoat; the primer is an adhesive layer, and the topcoat uses a super oleophobic and hydrophobic coating material.

6. The crude oil floating roof storage tank emission reduction device according to claim 1, characterized in that, The circulation pipe is connected to the exhaust port of the breather valve on the top of the tank, and is used to absorb the VOCs gas discharged during the small breathing process through the oleophilic and hydrophilic cleaning liquid.

7. The crude oil floating roof storage tank emission reduction device according to claim 6, characterized in that, A one-way valve is installed between the circulation pipe and the exhaust port of the breather valve on the top of the tank to prevent the cleaning fluid from flowing into the tank.

8. The crude oil floating roof storage tank emission reduction device according to claim 1, characterized in that, The circulation pipe connects the inlet and outlet pipes of the cleaning fluid; the cleaning fluid is pumped into the inlet pipe by a liquid pump, flows in the circulation pipe, and then flows out from the outlet pipe.

9. The crude oil floating roof storage tank emission reduction device according to claim 1, characterized in that, The crude oil floating roof tank is either an external floating roof tank or an internal floating roof tank; the upper surface of the floating roof is inclined to collect rainwater and / or leaked cleaning fluid.

10. The crude oil floating roof storage tank emission reduction device according to claim 9, characterized in that, The floating roof is provided with a floating roof seal at its annular edge; the circulation pipe is located above the floating roof seal.

11. A method for reducing emissions from crude oil floating roof storage tanks, characterized in that, Includes the following steps: A. Coat the inner wall of the storage tank with an oleophobic and hydrophobic coating and install a circulation pipe. Fix the circulation pipe to the upper surface of the floating roof and ensure that the open side of the circulation pipe is sealed tightly against the oleophobic and hydrophobic coating. B. When the storage tank is breathing and the floating roof is descending, the oleophilic and hydrophilic cleaning fluid is pumped into the circulation pipe. While the cleaning fluid is flowing, the residual crude oil adhering to the wall on the oleophobic and hydrophobic coating is flushed and absorbed. C. The cleaning fluid after absorbing the crude oil adhering to the wall flows out from the circulation pipe.

12. The method for reducing emissions from crude oil floating roof storage tanks according to claim 11, characterized in that, The method further includes: D. During the small-scale breathing of the storage tank, the VOCs gas inside the tank is discharged into the circulation pipe through the exhaust port of the breather valve and absorbed by the cleaning liquid.

13. The method for reducing emissions from crude oil floating roof storage tanks according to claim 12, characterized in that, The flow rate of the cleaning fluid during the large breathing process is controlled at 10 m. 3 / h; the flow rate of the cleaning fluid during the small breathing is controlled at 0.5m. 3 / h.

14. The method for reducing emissions from crude oil floating roof storage tanks according to claim 11, characterized in that, In step A, the coating is applied by spraying, brushing, or roller coating. When spraying is used, a two-step spraying method is used to spray the primer and topcoat sequentially.

15. The method for reducing emissions from crude oil floating roof storage tanks according to claim 14, characterized in that, The topcoat is an oleophobic and hydrophobic coating material, which is a super-hydrophobic coating material prepared from FAS-17 modified silica nanoparticles; the primer is an adhesive, which is an E-44 / PTFE mixture.

16. The method for reducing emissions from crude oil floating roof storage tanks according to claim 11, characterized in that, The surfactant component of the oleophilic and hydrophilic cleaning solution in step B is dodecyl dimethyl benzyl ammonium chloride or sodium dodecyl diphenyl ether disulfonate.

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