Method for removing hydrocarbon-based deposits

Abstract

This method for removing hydrocarbon-based deposits adhered to a device is characterized by removing the hydrocarbon-based deposits adhered to the device by means of steam to which a cleaning liquid is added.

Description

Method for Removing Hydrocarbon Deposits

[0001] The present invention relates to a method for removing hydrocarbon deposits adhering to equipment in a petroleum refining or petrochemical plant. Here, a petroleum refining or petrochemical plant also refers to a plant whose raw materials are not only fossil resources but also components derived from biomass such as plants or waste plastics.

[0002] In a petroleum refining or petrochemical plant, a process fluid such as crude oil is heated in a heat exchanger or a heating furnace and then sent to a distillation column for distillation operation. Alternatively, when the process fluid such as crude oil is sent to a reaction column and receives a heat history on the inner surface of a heat exchanger or a heating furnace, dirt such as asphaltene and sludge polymer adheres.

[0003] As a specific example of cleaning a stopped petroleum refining plant, there is a method of extracting a heat exchanger bundle and performing high-pressure water washing. While dirt can be reliably removed by this method, since it takes time for the extraction, transportation, high-pressure water washing, and restoration work of the heat exchanger bundle, the regular repair period is prolonged. Also, since high-pressure water washing is mainly performed by humans, there is unevenness in the finish depending on the skill level.

[0004] Patent Document 1 describes a method for removing hydrocarbon deposits by circulating light oil, water, and a chemical agent through a heat exchanger in a petroleum refining plant. However, in this method, skilled workers are required for the work, and the number of constructors is limited. Also, it is necessary to construct a temporary circulation system capable of circulating a predetermined amount of cleaning liquid. In addition, depending on the equipment, there may not be a piping system arrangement that can ensure the required flow rate.

[0005] Japanese Unexamined Patent Application Publication No. 2019 - 168162

[0006] The present invention provides a method for removing hydrocarbon deposits adhering to equipment such as a heat exchanger, and aims to shorten the process for removing hydrocarbon deposits, eliminate the need for operations such as extracting and transporting heavy objects such as bundles, and shorten the overall construction period of the cleaning process.

[0007] The gist of the present invention is as follows.

[0008] [1] A method for removing hydrocarbon deposits attached to equipment, characterized in that the hydrocarbon deposits attached to the equipment are removed with steam to which a cleaning solution is added.

[0009] [2] The cleaning solution comprises a solvent and / or a surfactant, and is a method for removing hydrocarbon deposits according to [1].

[0010] [3] The cleaning solution further comprises a fraction equivalent to light oil, the method for removing hydrocarbon deposits according to [2].

[0011] [4] The cleaning solution is a mixture of a solvent and a surfactant. [1] Method for removing hydrocarbon deposits.

[0012] [5] The cleaning solution is a mixture of a solvent, a surfactant, and a fraction equivalent to diesel fuel. [1] Method for removing hydrocarbon deposits.

[0013] [6] A method for removing hydrocarbon deposits according to any one of [2] to [5], wherein the solvent is at least one of alcohol, polyethylene glycol, glycol ether, tetralin, N-methylpyrrolidone, methyl ethyl ketone, tetrahydrofuran, heavy aromatic solvent, alkylbenzene, and oleic acid.

[0014] [7] A method for removing hydrocarbon deposits from the equipment having hydrocarbon deposits inside, wherein the equipment has hydrocarbon deposits inside by circulating steam with a cleaning solution added inside the equipment.

[0015] [8] The method for removing hydrocarbon deposits according to [7], wherein the cleaning solution is supplied to the inside of the device in an amount of 1 to 50% by volume of the internal volume.

[0016] [9] The cleaning solution contains a fraction equivalent to light oil, and the cleaning solution is supplied to the inside of the unit in an amount of 1 to 50% by volume of the internal volume, in the manner of removing hydrocarbon deposits according to [7].

[0017] According to the present invention, hydrocarbon deposits in equipment such as heat exchangers can be efficiently removed using a cleaning solution containing chemicals and steam, thereby shortening the cleaning process. Furthermore, the work can be performed effectively even by inexperienced workers.

[0018] Furthermore, since there is no need to remove or transport the heat exchanger bundle, the work is also easier.

[0019] This is a flow diagram of a part of an oil refining plant. It is a configuration diagram showing an example of a hydrocarbon deposit removal mechanism.

[0020] The method for removing hydrocarbon deposits according to the present invention will be described in more detail below.

[0021] In the present invention's method for removing hydrocarbon deposits, hydrocarbon deposits on process equipment such as heat exchangers are removed using a cleaning solution containing a chemical and steam.

[0022] As mentioned above, in petroleum refining or petrochemical plants, various process fluids such as crude oil are heated in heat exchangers or furnaces before being sent to distillation columns for distillation. Alternatively, they are sent to reaction columns for catalytic reactions. On the internal surfaces of heat exchangers and furnaces, process fluids such as crude oil undergo thermal history, and contaminants such as asphaltenes and sludge polymers adhere to them. Similar contaminants also adhere to power generation facilities that heat and utilize fuels such as petroleum.

[0023] The present invention removes hydrocarbon deposits adhering to these process facilities. Examples of process facilities include heat exchangers, reactors, and distillation columns in petroleum refining or petrochemical plants, coal chemical plants, various factories, and power generation facilities.

[0024] Figure 1 is a flow chart showing the configuration of an atmospheric distillation unit in an oil refining plant.

[0025] In the petroleum refining plant shown in this example, crude oil is supplied to the heat exchanger 1 by pump 1a from a crude oil storage tank (not shown). This crude oil is heated to 110-140°C in the heat exchanger 1 and enters the desolter 2. In the desolter 2, water and inorganic components are removed, and the oil is heated to 150-180°C in the heat exchanger 3 before being sent to the pre-distillation column 4, where low-boiling point gases are separated. After that, the crude oil is sent to the heat exchanger 5 through piping 10. The crude oil is heated to 240-280°C in the heat exchanger 5 and sent to the heating furnace 6 through piping 20. The crude oil is heated to 350-380°C in the heating furnace 6 and then sent to the atmospheric distillation column 7. In the atmospheric distillation column 7, fractions separated by boiling point differences are sent as a heat source to the shell side of the heat exchanger 5 via pumps, such as pump 8. Valves 11 and 21 are provided in piping 10 and 20, as shown in Figure 2.

[0026] In this embodiment, two heat exchangers 5 are connected in series, but there may be one, three or more heat exchangers connected in series or parallel, or a combination thereof.

[0027] Figure 2 shows the mechanism for removing hydrocarbon deposits from the heat exchanger 5.

[0028] Pipe 12 is connected to pipe 10, and a valve 13 is provided in pipe 12.

[0029] Furthermore, one end of pipe 22 is connected to pipe 20, and the other end of pipe 22 is connected to a steam source 23.

[0030] A valve 24 is provided in the piping 22. A pressure gauge 25 is installed on the steam source 23 side of this valve 24.

[0031] A cleaning fluid injection line 27 is connected to the piping 22 on the steam source 23 side of the pressure gauge 25. This cleaning fluid injection line 27 is configured to inject cleaning fluid from the cleaning fluid tank 28 into the piping 22 via a valve 29, a pump 30, a flow meter 31, and a valve 32.

[0032] Of the piping 20, one end of a spare steam supply pipe 33 is connected to the heat exchanger 5 side of the connection point of pipe 22, and the other end of the pipe 33 is connected to the steam source 34. A valve 35 is provided on the pipe 33.

[0033] For steam sources 23 and 34, boilers from an oil refinery may be used, or temporary boilers may be used.

[0034] To remove hydrocarbon deposits, first, valves 11 and 21 provided in the crude oil introduction piping 10 to the heat exchanger 5 and the crude oil discharge piping 20 from the heat exchanger 5 are closed. To clean the heat exchanger 5, valve 35 is closed and valves 13, 24, 29, and 32 are opened. Then, steam is sent from the steam source 23 to the piping 22, and the pump 30 is operated to send the cleaning liquid from the cleaning liquid tank 28 to the piping 22. The steam pressure is preferably around 0.5 to 2.0 MPa. The steam temperature is preferably around 100 to 200°C. The steam from the steam source 23 may be in a gas-liquid mixed state containing condensed water formed from the condensed steam.

[0035] The steam and cleaning liquid mix in pipe 22 to form a multiphase flow. This multiphase flow is passed through pipe 20, heat exchangers 5, 5, and pipes 10, 12 in that order to remove hydrocarbon deposits from heat exchangers 5, 5. At least a portion of the steam in the multiphase flow condenses into a liquid. Cleaning wastewater containing hydrocarbon deposits flows out from pipe 12.

[0036] As described above, by circulating steam and cleaning solution for 4 to 24 hours, hydrocarbon deposits on the heat exchanger 5 and piping 10, 20, etc., are sufficiently removed. The circulation time may be extended depending on the number of heat exchangers 5 installed (for example, 48 hours if there are three heat exchangers).

[0037] After the cleaning is complete, the pump 30 is stopped, valves 13, 24, 29, and 32 are closed, then valves 11 and 21 are opened, and the operation of the petroleum refining plant is restarted.

[0038] According to the method of the present invention, the effects of U-value (overall heat transfer coefficient of the heat exchanger), differential pressure reduction, and flow rate recovery can be obtained much more quickly than with conventional cleaning methods.

[0039] Also, in small-scale regular repair work, conventionally, it took about 14 days to extract, transport, high-pressure water wash, and restore the bundles of heat exchanger groups. According to the method of the present invention, the extraction, transport, and restoration processes of the bundles are eliminated, and it is shortened to about 8 days.

[0040] As components included in the above cleaning liquid, solvents and surfactants can be mentioned. As the cleaning liquid, a mixed liquid of a solvent and a surfactant is preferable, and a mixed liquid of a solvent, a surfactant, and a fraction equivalent to light oil is also preferable.

[0041] When the cleaning liquid is a mixed liquid of a solvent and a surfactant, the proportion of the surfactant in the cleaning liquid is preferably 1 to 20 wt%, particularly about 3 to 10 wt%. When the cleaning liquid is a mixed liquid of a solvent, a surfactant, and a fraction equivalent to light oil, the proportion of the surfactant in the cleaning liquid is preferably 0.1 to 18 wt%, particularly about 0.5 to 8 wt%, and the proportion of the fraction equivalent to light oil is preferably 5 to 90 wt%, particularly about 30 to 60 wt%.

[0042] As the solvent, alcohol, polyethylene glycol, glycol ether, tetralin, N-methylpyrrolidone, methyl ethyl ketone, tetrahydrofuran, heavy aromatic solvent, alkylbenzene, oleic acid, etc. are suitable, and at least one of these is used.

[0043] As the surfactant, at least one of mainly nonionic surfactants, anionic surfactants, or cationic surfactants can be used.

[0044] As the nonionic surfactant, glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene-polyoxypropylene glycol, fatty acid polyethylene glycol, fatty acid polypropylene glycol, fatty acid polyoxyethylene sorbitan, fatty acid polyoxypropylene sorbitan, fatty acid alkanolamide, etc. are suitable.

[0045] As anionic surfactants, aliphatic monocarboxylate salts, aliphatic dicarboxylate salts, polyoxyethylene alkyl ether carboxylate salts, N-acyl sarcosine salts, N-acyl glutamate salts, dialkyl sulfosuccinate salts, alkane sulfonate salts, α-olefin sulfonate salts, naphthalene sulfonate-formaldehyde condensates, alkyl naphthalene sulfonate salts, alkyl benzene sulfonate salts, N-methyl-N-acyl taurine salts, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fatty oil sulfates, linear alkyl phosphates, branched alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, etc. are suitable.

[0046] As cationic surfactants, ethylenediamine, ethylenediamine salts, alkylamine salts, etc. are suitable. Examples of fractions equivalent to light oil include LCO (cracked light cycle oil), LGO (straight-run light cycle oil), etc.

[0047] The preferred addition amount of the cleaning liquid is as follows.

[0048] In the present invention, steam added with the cleaning liquid is supplied to the equipment. The addition ratio of the cleaning liquid to the steam is preferably 0.5 to 10 kg, particularly about 2 to 6 kg, of the cleaning liquid per 1 kg of steam.

[0049] When the cleaning liquid is a mixture of a solvent and a surfactant, the supply amount of the cleaning liquid with respect to the volume of the equipment (in the case of FIGS. 1 and 2, heat exchangers 5, 5) for removing hydrocarbon-based deposits is preferably 1 to 50%, and more preferably 5 to 15%, particularly 5 to 10% from the viewpoint of costs required for removal such as the amount of chemical solution used.

[0050] When the cleaning liquid is a mixture of a solvent, a surfactant, and a fraction equivalent to light oil, the fraction equivalent to light oil is preferably supplied at 1 to 50%, more preferably 5 to 15%, particularly 5 to 10% with respect to the volume of the equipment for removing hydrocarbon-based deposits.

[0051] As shown in FIG. 2, the cleaning liquid injection point is preferably the steam injection pipe 22 and utilizes the connection before and after the heat exchanger. As the pump 30, an existing pump or a temporary pump may be used.

[0052] The following describes an example of an experiment.

[0053] [Experimental Example 1] Hydrocarbon deposit cleaning test (without chemicals) <Experimental conditions> 5 g of hydrocarbon deposits (hereinafter referred to as sludge) collected from a crude oil preheating system was placed on a wire mesh. Then, 50 g (50 ml) of pure water was placed in a 100 ml glass beaker, and the wire mesh with the sludge was placed inside this glass beaker. At this time, the wire mesh was placed so that the bottom of the mesh was in slight contact with the water surface. The top of the beaker was closed with a lid. This glass beaker was placed on a hot plate and heated, and the water was kept boiling for 8 hours, and the weight of the sludge was measured before and after the test.

[0054] The sludge weight increase rate was measured using the following formula based on the sludge weight measurements taken before and after the test.

[0055] Sludge weight increase rate (%) = [(Sludge weight after test) - (Sludge weight before test)] / [Sludge weight before test] × 100

[0056] <Results and Discussion> The sludge did not dissolve in water, and the weight of the sludge increased to 172% of the initial weight after 4 hours and to 147% of the initial weight after 8 hours.

[0057] [Experimental Example 2] Hydrocarbon-based deposit cleaning test (using chemical solution) <Experimental conditions> The test was conducted under the same conditions as in Experimental Example 1, except that a mixture of 45 g of water and 5 g of chemical solution (0.05 g of polyethylene glycol, 4.0 g of heavy aromatic solvent, 0.3 g of surfactant and others) was used instead of 50 g of water. A nonionic surfactant was used as the surfactant. The volume of the space above the liquid surface of the mixture in the beaker was 50 ml. The volume of 5 g of the chemical solution was approximately 5 ml, which corresponds to approximately 10% of the volume of the space.

[0058] The sludge weight reduction rate was measured using the following formula based on the sludge weight measurements taken before and after the test.

[0059] Sludge weight reduction rate (%) = [(Sludge weight before test) - (Sludge weight after test)] / [Sludge weight before test] × 100

[0060] <Results and Discussion> The sludge weight reduction rate was 45% after 4 hours and 59% after 8 hours. This indicates that the sludge dissolves when exposed to vapor containing the chemical solution. However, a large amount of dissolved sludge adhered to the beaker wall after the test.

[0061] [Experimental Example 3] Hydrocarbon deposit cleaning test (no chemical solution (LCO only)) <Experimental conditions> The test was conducted under the same conditions as in Experimental Example 2, except that a mixture of 45g of water and 5g of LCO (cracked light diesel fuel) was used as the mixed solution.

[0062] <Results and Discussion> The sludge did not dissolve, and after 4 hours it was 145% of the initial weight, and after 8 hours it was 109% of the initial weight.

[0063] A comparison with Experimental Example 2 revealed that sludge does not dissolve when exposed to vapor containing a fraction equivalent to diesel fuel.

[0064] [Experimental Example 4] Hydrocarbon-based deposit cleaning test (using chemical solution) <Experimental conditions> The test was conducted under the same conditions as in Experimental Example 2, except that a mixture of 40.5 g of water, 5 g of chemical solution (0.05 g of polyethylene glycol, 4.0 g of heavy aromatic solvent, 0.3 g of surfactant, and others), and 4.5 g of LCO (decomposed light diesel fuel) was used as the mixed solution. The same heavy aromatic solvent and surfactant as in Experimental Example 2 were used. The volume of this 5 g chemical solution is approximately 5 ml.

[0065] <Results and Discussion> The sludge weight reduction rate was 67% after 4 hours and 78% after 8 hours.

[0066] A comparison with Example 2 revealed that using a solution containing LCO further improved the sludge solubility. Furthermore, the sludge adhesion to the beaker wall that occurred in Example 2 did not occur in this Experimental Example 4.

[0067] This application is based on Japanese Patent Application No. 2024-225531, filed on December 20, 2024, which is incorporated herein by reference in its entirety.

[0068] 1, 3, 5 Heat exchanger 2 Desolter 4 Pre-distillation column 6 Heating furnace 7 Atmospheric distillation column 23, 34 Steam source 25 Pressure gauge 28 Washing liquid tank 31 Flow meter

Claims

1. A method for removing hydrocarbon deposits attached to equipment, characterized in that the hydrocarbon deposits attached to the equipment are removed with steam to which a cleaning solution is added.

2. The method for removing hydrocarbon deposits according to claim 1, wherein the cleaning solution comprises a solvent and / or a surfactant.

3. The method for removing hydrocarbon deposits according to claim 2, wherein the cleaning solution further comprises a fraction equivalent to diesel fuel.

4. The method for removing hydrocarbon deposits according to claim 1, wherein the cleaning solution is a mixture of a solvent and a surfactant.

5. The method for removing hydrocarbon deposits according to claim 1, wherein the cleaning solution is a mixture of a solvent, a surfactant, and a fraction equivalent to diesel fuel.

6. A method for removing hydrocarbon deposits according to any one of claims 2 to 5, wherein the solvent is at least one of alcohol, polyethylene glycol, glycol ether, tetralin, N-methylpyrrolidone, methyl ethyl ketone, tetrahydrofuran, heavy aromatic solvent, alkylbenzene, and oleic acid.

7. The method for removing hydrocarbon deposits according to any one of claims 1 to 6, wherein the equipment has hydrocarbon deposits adhering to its interior, and the hydrocarbon deposits inside are removed by circulating steam with a cleaning solution added to the interior.

8. The method for removing hydrocarbon deposits according to claim 7, wherein the cleaning solution is supplied to the inside of the equipment in an amount of 1 to 50% by volume of the internal volume.

9. The cleaning solution contains a fraction equivalent to light oil, and the cleaning solution is supplied such that the fraction is supplied to the inside of the device in an amount of 1 to 50% by volume of the internal volume, according to claim 7, for the removal of hydrocarbon deposits.

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