Operating method of distillation column and distillation system

Abstract

To provide a method for operating a distillation column that is compatible with various operations and saves energy.SOLUTION: A method of operating a distillation column and a distillation system comprises supplying at least one fraction distilled from the distillation column and / or a fraction corresponding to the one fraction to the distillation column in the distillation column that distills two or more fractions.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for operating a distillation column and a distillation system.

Background Art

[0002] In an oil refinery, depending on changes in the supply-demand balance of the market, a situation may occur where a specific fraction is surplus or deficient, and it becomes necessary to respond to various operations. For example, in a distillation column that distills a plurality of fractions including the specific fraction, when the specific fraction is surplus, it is considered to respond by using the specific fraction including the surplus in the conventional applications (products) (see, for example, Patent Document 1). In Patent Document 1, it is considered to satisfy various properties such as the ignition property and combustibility required for the product even when the mixing ratio of the cracked base oil in the product increases with an increase in the production of cracked base oil.

[0003] Further, as a method for dealing with the surplus of the fraction, there is also a method of reducing the surplus by adjusting the supply destination of the surplus or adjusting the operating rate in various towers such as a reaction tower and a distillation column. However, for example, in the operation of a distillation column, a minimum operating rate is usually determined in order to perform the desired distillation properly and stably. When the surplus of a specific fraction becomes significant, in order to eliminate this, the operating rate of the distillation column is reduced, approaching the minimum operating rate of the distillation column, or it may be necessary to operate at a lower operating rate. Therefore, it is expected that the change in the supply-demand balance cannot be dealt with only by adjusting the operating rate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, awareness of environmental issues has been steadily increasing, and one example of this is the strengthening of regulations by the International Maritime Organization (IMO). As part of measures to prevent air pollution, these regulations will drastically reduce the sulfur content in fuel oil for all ships from 3.5% by mass to 0.5% by mass or less starting in 2020. As a result, the supply and demand balance for heavy fuel oil, especially for ships, is expected to change significantly towards 2020, and a surplus of heavy fuel oil fractions with relatively high sulfur content is anticipated, particularly vacuum residual heavy fuel oil fractions such as vacuum residual oil fraction (VC), which mainly consists of vacuum residual oil fraction (VR) distilled from vacuum distillation columns (VACs). Since vacuum residual heavy fuel oil fraction (VC) is mainly distilled from vacuum distillation columns (VACs), if there is a surplus of vacuum residual heavy fuel oil fraction (VC), which mainly consists of vacuum residual oil fraction (VR), it will be necessary to operate the vacuum distillation columns (VACs) that distill off vacuum residual oil fraction (VR) at a lower operating rate. However, as mentioned above, from the perspective of ensuring a minimum utilization rate, there are limits to what can be achieved by simply reducing the utilization rate, and it is conceivable that this may not be sufficient in some cases.

[0006] Furthermore, refineries are required not only to adapt to diverse operational needs in response to changes in supply and demand, but also to conserve energy. In other words, refinery operations must balance adapting to diverse operational needs in response to changes in supply and demand with energy conservation.

[0007] Therefore, the present invention aims to provide a method for operating a distillation column and a distillation system that can accommodate diverse operating conditions and achieve energy savings. [Means for solving the problem]

[0008] The inventors of the present invention have conducted extensive research to solve the aforementioned problems and have found that they can be solved by the following invention. That is, the present invention provides a method for operating a distillation column and a distillation system having the following configuration.

[0009] 1. In a distillation column that distills two or more fractions, At least one fraction distilled from the distillation column and / or a fraction equivalent to the one fraction are supplied to the distillation column. How to operate a distillation column. 2. A method for operating the distillation column described in item 1 above, which reduces the amount of distillate of a fraction heavier than the first fraction. 3. A method for operating a distillation column according to 1 or 2 above, wherein a fraction corresponding to the aforementioned fraction is supplied, and the amount of the first fraction distilled is increased. 4. A method for operating a distillation column according to any one of 1 to 3 above, wherein the distillation column is a vacuum distillation column (VAC). 5. A method for operating a distillation column according to any one of items 1 to 4 above, wherein the first fraction is vacuum gas oil fraction (VGO). 6. A method for operating a distillation column according to any one of items 2 to 5 above, wherein the heavy fraction is the vacuum residue fraction (VR). 7. A distillation system comprising a distillation column for distilling two or more fractions, A distillation system having a line for supplying to the distillation column at least one fraction and / or a fraction equivalent to the one fraction distilled from the distillation column. 8. The distillation system according to item 7 above, wherein the distillation column is a vacuum distillation column (VAC). [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for operating a distillation column and a distillation system that can accommodate diverse operating conditions and achieve energy savings. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic process diagram relating to the operation method of the distillation column of the present invention. [Figure 2] This is a schematic process diagram relating to the operation method of the distillation column of the present invention. [Modes for carrying out the invention]

[0012] [Operation method of a distillation column] The method for operating a distillation column according to an embodiment of the present invention (hereinafter sometimes simply referred to as "this embodiment") is characterized in that, in a distillation column that distills two or more fractions, at least one fraction distilled from the distillation column and / or a fraction equivalent to the one fraction distilled from the distillation column are supplied to the distillation column. When changes in the supply and demand balance result in an excess distillation volume of fractions other than the first fraction mentioned above, attempting to address this by reducing the operating rate of the distillation column may not be sufficient, even if the operating rate falls below the minimum operating rate required to ensure proper distillation in the distillation column. To address this situation, according to this embodiment, by supplying the first fraction and / or a fraction equivalent to the first fraction to the distillation column, the apparent operating rate of the distillation column is improved, maintaining the minimum operating rate and ensuring stable operation of the distillation column while addressing the excess distillation volume of other fractions. Furthermore, since it is possible to address the issue simply by supplying the first fraction, etc., the consumption of excess energy can be suppressed, and since stable operation of the distillation column is ensured and excessive energy consumption is suppressed, energy savings can be achieved as a result.

[0013] The operating method of this embodiment is effective when the excess fraction (the "other fraction" mentioned above) is heavier than the first fraction. Since distilling heavier fractions consumes more energy than distilling lighter fractions, applying the operating method of this embodiment in such cases can reduce energy consumption. In other words, in the operating method of this embodiment, from the viewpoint of improving energy conservation, it is preferable to reduce the amount of distillate heavier fractions than the first fraction.

[0014] For example, a vacuum distillation column (VAC) will be described as an example. The vacuum distillation column (VAC) mainly distills a vacuum gas oil fraction (VGO) and a vacuum residue fraction (VR) which is a fraction heavier than the vacuum gas oil fraction (VGO) from the atmospheric residue fraction (RC) mainly distilled from the atmospheric distillation column (TOP). When the supply of the vacuum residue fraction (VR) becomes excessive due to changes in supply and demand balance, if it can be dealt with by reducing the operating rate of the distillation column, then it can be dealt with by reducing the operating rate. However, when it is below the minimum operating rate, by supplying the vacuum gas oil fraction (VGO) as one fraction to the vacuum distillation column (VAC), it is possible to reduce the distillation amount of the vacuum residue fraction (VR) which becomes another fraction without reducing the operating rate of the distillation column. In the present embodiment, in addition to one fraction, other fractions may be supplied to the distillation column. However, when the other fraction is a fraction heavier than the one fraction, from the perspective of energy conservation, it is preferable to supply only the one fraction.

[0015] In the present embodiment, not only one fraction but also a fraction corresponding to the one fraction may be supplied to the distillation column. Here, the "fraction corresponding to the one fraction" means a fraction whose 50% volume distillation temperature is in the range of ±20°C or less with respect to the 50% volume distillation temperature of the one fraction (or "a fraction whose 15°C density is in the range of ±10% or less with respect to the 15°C density of the one fraction"). Also, "the other fraction is a fraction heavier than the one fraction" means that "the 50% volume distillation temperature of the other fraction is a temperature higher than 20°C with respect to the 50% volume distillation temperature of the one fraction" (or "the 15°C density of the other fraction is a density more than 10% larger than the 15°C density of the one fraction"). In this specification, the 50% volume distillation temperature is the temperature measured by a vacuum distillation method conforming to ASTM D1160 in the case where the fraction is an atmospheric residue fraction (RC), a vacuum gas oil fraction (VGO), or a vacuum residue fraction (VR), and is the temperature measured by a distillation method conforming to ASTM D86 in the case of a cracked gas oil fraction (LCO). (In this specification, the 15°C density is a value measured in accordance with JIS K2259-1:2011 (Crude oil and petroleum products - Method for determining density - Part 1: Vibration method).)

[0016] The mode of supplying a fraction corresponding to a certain fraction to the distillation column is, for example, when three or more fractions are distilled from the distillation column, and when a certain fraction and the fraction corresponding to the certain fraction are distilled, the mode of supplying the fraction corresponding to the certain fraction, or the mode of supplying the fraction distilled from another distillation column or the like as the fraction corresponding to a certain fraction to the distillation column according to this embodiment is assumed. Thus, in this embodiment, the fraction supplied to the distillation column is not limited to the fraction distilled from the distillation column, and fractions distilled from other distillation columns or the like can be used. In any case, it is possible to improve the apparent operating rate of the distillation column, maintain the minimum operating rate, ensure stable operation of the distillation column, and respond to various operations due to changes in the supply-demand balance such as being able to respond to an excessive supply of the distillation amount of other fractions, and energy saving is also possible.

[0017] In this embodiment, at least one fraction distilled from the distillation column and / or the fraction corresponding to the certain fraction, that is, a certain fraction may be supplied to the distillation column alone or in combination of multiple types, or the fraction corresponding to a certain fraction may be supplied to the distillation column alone or in combination of multiple types, or a certain fraction and the fraction corresponding to a certain fraction may be supplied to the distillation column in combination. When supplying in combination of multiple types to the distillation column, if the mixture of multiple types of fractions combined is the fraction corresponding to the fraction at a certain position, even if one of the fractions is not the fraction corresponding to a certain fraction, it is acceptable.

[0018] Also, as the mode of supplying the fraction corresponding to a certain fraction in the method of this embodiment, for example, when the straight-run light gas oil fraction (LGO) is insufficient in the atmospheric distillation column (TOP), by supplying the cracked light gas oil fraction (LCO) distilled from the fluid catalytic cracking unit (FCC / RFCC) with similar properties (that is, equivalent to straight-run light gas oil (LGO)) to the atmospheric distillation column (TOP), the mode of increasing the distillation amount of the straight-run light gas oil fraction (LGO) can be cited. Also, according to the method of this embodiment, only the necessary fractions can be supplied, so the consumption of extra energy can be suppressed and energy saving is also possible.

[0019] In this embodiment, the operation method of the distillation column preferably uses a vacuum distillation column (VAC) and has one fraction as vacuum gas oil fraction (VGO), from the viewpoint of effectively utilizing the effect of being able to accommodate diverse operations and save energy. Furthermore, in this case, it is preferable that the fraction heavier than the first fraction is vacuum residual oil fraction (VR). As previously described, as regulations by the International Maritime Organization (IMO) become stricter, a surplus of heavy oil fraction is expected, and in order to reduce the amount of vacuum residual heavy oil fraction (VC) produced, it is expected that the amount of vacuum residual oil fraction (VR), which is mainly contained in it, will need to be reduced. Under these circumstances, according to the operation method of this embodiment, it is easy to set the first fraction as vacuum gas oil fraction (VGO) in the vacuum distillation column (VAC) and reduce the amount of vacuum residual oil fraction (VR), which is heavier than VGO, distilled.

[0020] Regarding the method of supplying a fraction to a distillation column, for example, using a vacuum distillation column (VAC) as an example, we will explain with reference to Figures 1 and 2 how to supply a vacuum gas oil fraction (VGO) as the first fraction. Figure 1 shows a method for constructing a new line (dashed line in the figure) that can supply vacuum light oil fraction (VGO) together with vacuum residual oil fraction (VR). In the embodiment shown in Figure 1, a portion of the existing line used to supply atmospheric residual fraction (RC) distilled from the atmospheric distillation column (TOP) to the vacuum residual heavy oil fraction tank (VC tank) is used. In this case, for example, instead of using the existing line used to supply atmospheric residual fraction (RC) to the vacuum residual heavy oil fraction tank (VC tank), a new line may be constructed that combines the vacuum light oil fraction (VGO) and vacuum residual oil fraction (VR) and then connects to the line that supplies the atmospheric residual fraction (RC) to the vacuum distillation column (VAC) (the line after the branch of atmospheric residual fraction (RC) to the vacuum distillation column (VAC)).

[0021] Furthermore, Figure 2 shows a method for constructing a new line (dashed line in the figure) to supply vacuum-reduced light oil fraction (VGO) to a vacuum distillation column (VAC) for recycling. In the embodiment shown in Figure 2, if it becomes necessary to supply vacuum residual oil fraction (VR) to a vacuum distillation column (VAC), the existing line used to supply atmospheric pressure residual oil fraction (RC) to the vacuum residual heavy oil fraction tank (VC tank) may be used, as explained with respect to Figure 1, or a new line for supplying to the vacuum distillation column (VAC) may be constructed. In the operating method of this embodiment, the method of supplying the above-mentioned fraction to the distillation column is merely an example and is not limited to this; any convenient method should be adopted depending on the situation.

[0022] When the distillation column is a vacuum distillation column (VAC), the operating conditions can vary depending on the properties of the fraction supplied to the vacuum distillation column (VAC) and the desired properties of the fraction distilled out, so it is not possible to generalize. However, the supply temperature to the distillation column is usually 360 to 410°C, preferably 370 to 400°C, and more preferably 375 to 390°C, and the top pressure of the distillation column is usually 2.5 to 4.0 kPa, preferably 3.0 to 3.5 kPa.

[0023] [Distillation column] The distillation column of this embodiment is a distillation column that distills two or more fractions, and is characterized by having a line that supplies at least one fraction distilled from the distillation column and / or a fraction equivalent to the first fraction to the distillation column.

[0024] As for the distillation column, any type commonly used for distilling two or more fractions can be used without particular restrictions, and a multi-stage distillation column is preferred. For example, a distillation column having multiple trays and packed beds for gas-liquid contact can be used. Examples of trays used for shelves include valve trays, bubble trays, and perforated plate trays. Examples of packing materials used for the packing layer include ring-type packing materials such as Raschig rings and pole rings, saddle-type packing materials such as bell saddles and interlock saddles, and various packing materials such as McMahon packing, Cannon packing, and Terralet.

[0025] The fractions distilled from the distillation column are as described in the operating method of the distillation column described above. Therefore, a typical example of a distillation column is a vacuum distillation column (VAC) that distills vacuum gas oil fraction (VGO) and vacuum residual oil fraction (VR).

[0026] The lines supplying at least one fraction distilled from the distillation column and / or a fraction equivalent to said one fraction to the distillation column (hereinafter sometimes simply referred to as "lines supplying to the distillation column") are also as described in the operating method of the distillation column described above. Specifically, as explained in Figures 1 and 2, for example, the lines that supply (return) the fraction distilled from the distillation column to the distillation column in Figures 1 and 2 correspond to the lines supplying to the distillation column. For example, in Figure 1, (i) The line branching off from the line of vacuum gas fraction (VGO) distilled from the vacuum distillation column (VAC) and joining the line of vacuum residual fraction (VR) distilled from the vacuum distillation column (VAC) (dashed line in the figure), (ii) From the line of vacuum residue fraction (VR) distilled from the vacuum distillation column (VAC) to the point where the vacuum gas fraction (VGO) line and the atmospheric residue fraction (RC) line described in (i) above merge, and (iii) The line from the confluence of the vacuum gas fraction (VGO) line and the vacuum residual fraction (VR) line to the vacuum distillation column (VAC) However, this corresponds to the "line that supplies to the distillation column."

[0027] Furthermore, in Figure 2, (iv) A line that branches off from the line of vacuum gas oil fraction (VGO) distilled from the vacuum distillation column (VAC) and supplies it to the vacuum distillation column (VAC) for recycling (dashed line in the diagram), Furthermore, if vacuum residue (VR) is also supplied to the vacuum distillation column (VAC), then, (v) The line from the vacuum residue fraction (VR) distilled from the vacuum distillation column (VAC) to the confluence point of the vacuum gas fraction (VGO) line and the atmospheric residue fraction (RC) line described in (i) above, and (vi) The line from the confluence point of (v) above to the vacuum distillation column (VAC) However, this corresponds to the "line that supplies to the distillation column."

[0028] In the distillation column of this embodiment, the "line supplying to the distillation column" may be a newly constructed line, for example, as shown in Figure 1(i) and Figure 2(iv), or it may be an existing line, as shown in Figure 1(ii) and (iii), and Figure 2(v) and (vi).

[0029] Each distillation line may be equipped with instruments such as flow meters and flow control valves. The installation of flow control valves allows for operation tailored to the specific conditions. Furthermore, the materials used to form the distillation column and the materials used in the supply lines to the distillation column may be appropriately determined according to the fractions supplied to and discharged from the distillation column and the operating conditions. [Examples]

[0030] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to these examples.

[0031] (Example 1) In Figure 1, a new line for vacuum gasoline fraction (VGO), indicated by the dashed line, was installed, and the vacuum distillation column (VAC) was operated under the following operating conditions. When the amount of atmospheric residue fraction (RC) distilled from the atmospheric distillation column (TOP) supplied to the vacuum distillation column (VAC) was set to 795 kL / D, the amount of vacuum light oil fraction (VGO), which is the first fraction distilled from the vacuum distillation column (VAC), supplied to the vacuum distillation column (VAC) was set to 337 kL / D, and the amount of vacuum residual oil fraction (VR), which is a heavier fraction than the first fraction distilled from the vacuum distillation column (VAC), supplied to the vacuum distillation column (VAC) was set to 298 kL / D, the total supply to the vacuum distillation column (VAC) was set to 1430 kL / D (operating rate: 37.5%), the amount of vacuum residual oil fraction (VR) distilled as a product from the vacuum distillation column (VAC) was 374 kL / D.

[0032] Vacuum Distillation Column (VAC) Operating Conditions Distillation column supply temperature: 376.0℃ Distillation column top pressure: 3.2 kPa Other information: When the atmospheric pressure residue fraction (RC) is processed, the proportions of each fraction obtained are 53% by volume for vacuum gasoline fraction (VGO) and 47% by volume for vacuum residual fraction (VR). Properties of atmospheric pressure residue fraction (RC); 50% by volume distillation temperature: 536℃, 15℃ Density: 0.961g / cm 3 , Sulfur content: 3.42% by mass Properties of vacuum gasoline fraction (VGO); 50% by volume distillation temperature: 445℃, 15℃ Density: 0.918g / cm 3 , Sulfur content: 2.33% by mass Properties of vacuum residue fraction (VR); 50% by volume distillation temperature: 659℃, 15℃ Density: 1.029g / cm 3 , Sulfur content: 4.86% by mass

[0033] (Comparative Example 1) Using the equipment from Example 1 before the new line was installed, the vacuum distillation column (VAC) was operated in the same manner as in Example 1, with a flow rate of atmospheric pressure residue fraction (RC) to 1430 kL / D (operating rate 37.5%). The amount of vacuum residue fraction (VR) distilled from the vacuum distillation column (VAC) was 672 kL / D.

[0034] From the above results, it was confirmed that, according to the operation method of the distillation column of this embodiment, it is possible to reduce the amount of vacuum residual oil fraction (VR) distilled from 672 kL / D to 374 kL / D, a reduction of 44%, even without reducing the operating rate of the vacuum distillation column (VAC) to below the minimum operating rate. [Explanation of symbols]

[0035] HGO: Heavy light oil fraction RC: Atmospheric pressure residue fraction VGO: Reduced-pressure light oil fraction VR: Vacuum Residual Oil Fraction VC tank: Reduced pressure residual heavy oil fraction tank RC tank: Atmospheric pressure residue fractionation tank

Claims

1. In a distillation column that distills two or more fractions, A method for operating a distillation column, comprising supplying to the distillation column at least one fraction and / or a fraction equivalent to the first fraction, and a fraction heavier than the first fraction, wherein the fraction equivalent to the first fraction has a 50% volume distillation temperature within ±20°C of the 50% volume distillation temperature of the first fraction, or a 15°C density within ±10% of the 15°C density of the first fraction, thereby reducing the amount of the fraction heavier than the first fraction distilled off.

2. A method for operating a distillation column according to claim 1, wherein a fraction corresponding to the aforementioned fraction is supplied, and the amount of the first fraction distilled out is increased.

3. The method for operating a distillation column according to claim 1 or 2, wherein the distillation column is a vacuum distillation column (VAC).

4. The method for operating a distillation column according to any one of claims 1 to 3, wherein the first fraction is vacuum gasoline fraction (VGO).

5. The method for operating a distillation column according to any one of claims 1 to 4, wherein the heavy fraction is the vacuum residue fraction (VR).

6. A distillation system comprising a distillation column for distilling two or more fractions, A distillation system having a line for supplying to the distillation column at least one fraction and / or a fraction equivalent to the first fraction, and a fraction heavier than the first fraction, wherein the fraction equivalent to the first fraction has a 50% volume distillation temperature within ±20°C of the 50% volume distillation temperature of the first fraction, or a 15°C density within ±10% of the 15°C density of the first fraction.

7. The distillation system according to claim 6, wherein the distillation column is a vacuum distillation column (VAC).

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