JPH05146604A - Distillation tower - Google Patents

Abstract

PURPOSE:To provide a distillation tower capable of enhancing the gain of a middle fraction by raising distillation temp. while holding the stability of drawing-out. CONSTITUTION:A cylindrical weir part 17 is vertically provided to a tower bottom part 1 and the through-holes 18 allowing the inside and outside of the weir part 17 to communicate with each other are provided to the side wall of the weir part 17 to constitute a distillation tower 10. A high temp. heavy component 14 passes through the weir part 17 to become possible to rapidly reach a bottom surface 12A and can be cooled in the outside before it is deteriorated by heat. Since the inside and outside of the weir part 17 are allowed to communicate with each other by the through holes 18, the stagnation part of the heavy component 14 expands outwardly and the cross-sectional area thereof is increased and control holding a liquid level to a constant height level is stabilized and volume possible to stagnate is increased to extend the total stagnation time of the heavy component 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distillation column used in a petroleum refining plant, a chemical plant or the like, and more particularly to a distillation column having an improved structure in the bottom of the distillation column.

[0002]

BACKGROUND ART Conventionally, by distilling crude oil, various petroleum products such as heavy oil, light oil, white oil, gasoline and the like have been produced, and a distillation column has been used for these production. In a general distillation column, the heavy component of crude oil is retained at the bottom of the distillation column, and the heavy component is extracted from an outlet provided at the bottom of the column bottom. In order to obtain the stability of extracting this heavy component, bubbles and the like contained in the bottom liquid are separated,
It is necessary to prevent it from reaching the outlet at the bottom of the tower,
For this reason, the liquid level of the crude oil is made sufficiently high, and control is performed to keep the liquid level of the crude oil constant.

On the other hand, since the demand for heavy oil has decreased in recent years, the need for medium-grade oil is relatively higher than that for heavy oil, and it is desired to be able to obtain more middle distillates during the petroleum refining process. There is. Therefore, a distillation column improved so that the distillation temperature can be raised to improve the yield of the middle distillate has been proposed (JP-A-60-61002).

In such a distillation column, when the distillation temperature is raised, the heavy components retained in the column bottom of the distillation column may be deteriorated by heat. Therefore, as shown in FIG. 2, it is retained in the column bottom 30. A cooling device 32 that cools the heavy component 31 is installed outside, and a quench line 33 that cools the heavy component 31 while recirculating between the column bottom 30 and the cooling device 32 including the cooling device 32 is configured. ing. Then, the column bottom 30 has a reduced inner diameter by reducing the inner cross-sectional area, thereby ensuring the height of the liquid level and increasing the volume of the heavy components 31 retained inside the column bottom 30. It is possible to reduce the residence time by shortening it, and to extract the hot heavy component 31 from the column bottom 30 with the pump 34 and cool it with the cooling device 32 before it deteriorates due to heat. Min 31 keeps away from heat.

[0005]

By the way, in the distillation column as described above, in order to reduce the flat cross-sectional area by narrowing the diameter of the column bottom portion 30, the fluctuation of the feed amount of the feed oil and the withdrawal amount of the heavy component 31 are fluctuated. As a result, the liquid level of the heavy component 31 fluctuates greatly, and it is difficult to control the liquid level height to be constant. Therefore, while the yield of the middle distillate can be improved, the liquid surface level tends to be unstable, and there is a problem in the stability of extraction.

An object of the present invention is to provide a distillation column which can raise the distillation temperature while maintaining the stability of extraction and improve the yield of middle distillates.

[0007]

DISCLOSURE OF THE INVENTION According to the present invention, a tubular weir is erected at the bottom of a tower, and a side wall of this weir is provided with a communicating portion for communicating the inside and the outside of the distilling. It constitutes the tower.

Here, it is preferable to adopt a so-called "plunge" type distillation column in which the diameter of the bottom of the column is not narrowed as the target distillation column. Further, as the communicating portion of the weir portion, a hole and a slit penetrating the side wall, a structure in which a part of the side wall is formed of a mesh member, or the like can be adopted. And the communication part,
It is set according to the viscosity of the liquid, and it is difficult for the liquid flowing downward in the weir portion to pass, and
It is desirable that the liquid flowing in the horizontal direction easily pass through due to the difference in liquid level between the inside and outside of the weir portion, and it is desirable to appropriately set the shape, form, opening area, and the like. Further, as the distillation column, it is desirable that a quench line or the like for cooling the liquid staying at the bottom of the column is installed externally, and as the quench line, the liquid inside the dam portion is extracted and cooled, and the cooled liquid is again used for the dam portion. It is preferable to return to the outer bottom of the column for recirculation.

[0009]

In the present invention, the high-temperature heavy components falling from the upper part of the distillation column quickly reach the bottom of the distillation column through the inside of the tubular weir, and during this time, the temperature of the low temperature rapidly increases. Since it is cooled by oil, it does not deteriorate.

Further, since the outer side and the inner side of the weir section are communicated by the communicating section, even if the liquid is retained in the outer side and the inner side of the weir section at the bottom of the tower, it is possible to collectively control the liquid level.
Therefore, for example, if a quench line or the like for extracting the liquid inside the weir and cooling it and returning the cooled liquid to the outside of the weir inside the tower bottom to recirculate the liquid is installed externally, A liquid that stays at a low temperature allows an increase in the flat cross-sectional area. Due to this increase in the flat cross-sectional area, the fluctuation amount of the liquid surface level due to the fluctuation of the liquid replenishment amount and the withdrawal amount becomes small, and the control for maintaining the liquid surface level at a constant height level becomes stable. To be done.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a column bottom 11 of a distillation column 10 for petroleum refining according to the present embodiment. The distillation column 10 has a cylindrical outer cylinder formed with substantially the same diameter over the entire height direction. 12
It is of a so-called "plunge" type, which has a bottom surface 12A with a spherical concave inside.

The outer cylinder 12 of the distillation column 10 is provided with an oil supply pipe 13 for supplying crude oil to the inside of the distillation column 10 on a side wall of a middle portion in the height direction, and serves as a column bottom 11 of the outer cylinder 12. A liquid level indicator 15A for displaying the liquid level of the heavy component 14 retained therein and a liquid level controller 15B for controlling the liquid level are installed on the side wall of the portion.

Inside the column bottom 11, there is provided a funnel-shaped guide 16 for collecting the heavy components 14 falling from the upper part of the distillation column 10 at the center of the column bottom 11. Below the guide portion 16, a cylindrical weir portion 17 is provided upright.
The plane position of is coaxial with the outer cylinder 12 so that the heavy component 14 collected by the guide portion 16 flows into the inside.

The side wall of the weir portion 17 is provided with a large number of through holes 18 which are communication portions that communicate the inside and outside of the side wall from the upper end to the position down to the dimension H1.

The size and shape of the through hole 18 are set according to the viscosity of the heavy component 14. That is, the through holes 18 are difficult for the heavy component 14 flowing downward in the weir portion 17 to pass through, and the heavy component 14 flowing in the horizontal direction due to the liquid level difference between the inside and the outside of the weir portion 17 do not pass. It is formed in an easy shape and size. Specifically, through holes
18 is a round hole having a diameter of 5 to 100 φ, preferably 10 to 30 φ.

At the lower end of the weir portion 17, several drain holes 19 are provided in order to introduce all the heavy components 14 on the outer side of the weir portion 17 into the inner portion.
A non-hole portion 17A having no hole is provided between the drain hole 19 and the through hole 18 by penetrating the side wall of the hole 17.

On the bottom surface 12A of the outer cylinder 12, the heavy component 14 in the weir 17 is extracted and cooled, and the cooled liquid is returned to the outside of the weir 17 in the column bottom 11 to collect the heavy component 14. A quench line 20 for recirculation is connected. Quench line
20 is a pump 21 for withdrawing the heavy component 14 from the tower bottom 11, a heat exchanger 22 for cooling the withdrawn heavy component 14, and a flow control valve.
23A, a liquid level control valve 23B, and a quench ring 26 formed in a hollow donut shape.

The pump 21 conveys a liquid having a high viscosity. The suction port of pump 21 is on the bottom 12
It is connected to the lowest position of A so that the heavy component 14 in the weir 17 can be extracted. The discharge port of the pump 21 is connected to the inlet of the heat exchanger 22 by a pipe 24B.

The heat exchanger 22 includes a heavy component 14 flowing in from the inlet.
Is cooled with cooling water flowing inside. A branch pipe 25 is connected to the outlet of the heat exchanger 22.

The branch pipe 25 is a branch pipe 25 that branches in two directions.
It has A and 24B. One branch pipe 25A of the pipe 25
Is connected to a quench ring 26 provided inside the tower bottom 11 via a flow control valve 23A. The other branch pipe 25B of the pipe 25 is connected to an outlet for the heavy components 14 via a liquid level control valve 23B.

The flow rate adjusting valve 23A is for adjusting the flow rate of the quench return, and is set so as to operate in the opening direction when the cooling efficiency is desired to be increased, and in the closing direction when the cooling efficiency may be low. There is. The operation of the flow rate adjusting valve 23A enhances the cooling efficiency by increasing the circulation amount, and does not affect the height of the liquid surface. Liquid level control valve 23B
The valve opening is adjusted by a control signal transmitted from the liquid level controller 15B according to the height position of the liquid level of the heavy component 14. The valve opening degree of the liquid level control valve 23B is set so that it operates in the closing direction when the height of the liquid level becomes low and operates in the opening direction when it becomes high.

The quench ring 26 is for returning the heavy components 14 cooled in the quench line 20 back into the column bottom portion 11 and outside the non-perforated portion 17A of the weir portion 17 having no through hole 18 or drain hole 19. Is installed so as to make a full circle, and innumerable discharge holes are formed on the outer periphery of the weir 17 so that the heavy components 14 are evenly discharged.

The inclination angle θ of the guide portion 16 is 1 to 45.
The angle is set to 0 °, preferably 3 to 10 °. The height dimension H1 of the portion of the weir portion 17 in which the through hole 18 is formed is such that H1 / H2 is 1/10 to 4/5, preferably 1 / the height dimension H2 of the entire weir portion 17.
It is set to be 5 to 3/5. Also, the through hole 18
Is 4 to 72 per round of the cylindrical weir 17, preferably
It is desirable to provide 12 to 36 pieces at equal intervals.

Next, the flow of the heavy component 14 of this embodiment will be described. First, the high-temperature heavy component 14 falling from the upper part of the distillation column 10 is collected by the guide part 16 in the plane center part of the column bottom part 11 and injected into the weir part 17. This heavy component 14 passes through the inside of the weir 17 and, in a short time, the bottom 12A of the tower bottom 11.
To reach. The heavy component 14 that has reached the bottom surface 12A is immediately sent to the heat exchanger 22 by the pump 21 and is cooled before being deteriorated. The cooled heavy fraction 14 is divided into two directions, a quench ring 26 and a heavy fraction collection outlet, by a pipe 25, and the respective amounts are stored in the column bottom 11 by a liquid level controller 15B and a liquid level control valve 23B. It is adjusted according to the liquid level of the heavy component 14 of.
The heavy component 14 sent to the quench ring 26 is returned to the inside of the tower bottom 11 and stays outside the weir 17. This makes it possible to
The staying portion of 14 is expanded to the outside and its flat cross-sectional area is expanded, and the staying amount of the heavy component 14 is increased. The heavy component 14 staying outside of the weir portion 17 flows into the weir portion 17 through the through hole 18 after the liquid level inside the weir portion 17 is lowered, and then is sent to the quench line 20 again. Therefore, the heavy component 14 is recirculated between the quench line 20 and the column bottom 11. Due to this recirculation, the heavy component 14 is stably extracted from the outlet through the quench line 20 by extending the residence time.

According to the above-mentioned embodiment, the following effects can be obtained. That is, the guide portion 16 and the weir portion 17 are provided inside the tower bottom portion 11 so that the falling heavy component 14 can quickly reach the bottom surface 12A of the tower bottom portion 11.
Even if 14 becomes high temperature, it becomes possible to cool the quench line 20 before it deteriorates, and deterioration of the heavy component 14 can be prevented in advance. Therefore, the yield of the middle distillate of crude oil can be improved by raising the distillation temperature.

Further, a through hole 18 is provided in the weir portion 17 to communicate the inside and outside of the weir portion 17, the cooled heavy component 14 is returned to the outer side of the weir portion 17, and a flat cross-sectional area of the retaining portion of the heavy component 14 is obtained. In addition to increasing the retention amount and recirculating the heavy component 14, it is possible to easily maintain the liquid surface level at a constant height level and the weir part.
Since the total retention time of the heavy component 14 can be further lengthened by retaining it outside the heavy component 17, the stability of the extraction of the heavy component 14 can be improved.

It should be noted that the present invention is not limited to the above-mentioned one embodiment, but includes the following modifications and the like. That is, the communication portion is not limited to the round hole, and may be, for example, a slit-shaped member or a net-shaped member.

Further, the weir is not limited to a non-perforated portion having no hole, and for example, a through hole may be provided over the entire side wall, and the specific form of the communicating portion of the weir is appropriately implemented. Just set it.

Further, the present invention is not limited to a "sendo" type distillation column, but may be, for example, a distillation column whose bottom is narrowed and narrowed. Further, the present invention is not limited to a petroleum distillation column but for alcohol. It may be a distillation column or the like, and may be applied to various distillation columns for chemical plants.

[0030]

As described above, according to the present invention, the yield of middle distillates can be improved while maintaining the stability of extraction.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a main part of an embodiment of the present invention.

FIG. 2 is a view similar to FIG. 1 showing a conventional example.

[Explanation of symbols]

 10 Distillation tower 11 Tower bottom 17 Weir 18 Through hole as a communication part

Claims (1)

[Claims] 1. A distillation column characterized in that a tubular weir is erected on the bottom of the tower, and a side wall of the weir is provided with a communicating portion that communicates the inside and the outside of the weir.