JPS6197002A - Distillation method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a distillation method for separating and refining a feedstock consisting of a plurality of components having different boiling points by distillation.

[Conventional technology]

In conventional distillation methods, uncontrolled conditions are set in consideration of the physical properties of the raw materials to be processed and the quality of the products or intermediates to be extracted, and steam or other fuel is usually used as the heat source for the reboiler. There is.

The type of reboiler used is a thermosiphon type, falling film type, kettle type, etc., and the heating source, steam or other fuel, is either by-product from the plant or purchased from outside. It is covered.

By the way, distilled steam discharged from a distillation tower is usually condensed by cooling it with a water-cooled condenser, an air-cooled condenser, or a boiler.
In some cases, distilled steam is directly compressed to increase its enthalpy, and this is used as a heat source for a distillation column.

[Problem that the invention seeks to solve]

However, in conventional distillation methods, it cannot be said that the retained heat of the distilled steam is sufficiently recovered, and most of the heat is dissipated into the cooling water or air.

It is also possible to recover the heat retained by this bubbling steam in a boiler, but depending on the physical properties of the raw material being handled, it may be necessary to pressurize the unreported tower, or it may be necessary to switch the heat source of the reboiler from steam to another fuel, etc. There are problems such as an increase in equipment costs and an increase in the number of equipment such as pressure vessels that require legal inspection.

Furthermore, in the method of compressing and utilizing bubbling steam,
Due to the balance of equipment costs, it is generally difficult to apply this method to anything other than non-registered towers with a large reflux ratio from an economical standpoint.

[Means and effects for solving the problem] The present invention was devised in view of this point of view, and it is possible to identify the characteristics such as temperature and pressure of the bubbling steam from the unreported tower and to solve the problem. The present invention provides a distillation method that can effectively utilize retained heat.

That is, the present invention provides a first column equipped with a reboiler at the bottom of the column.
A side reboiler is installed in the recovery section of the non-reporting tower, and this side reboiler has a second non-reporting tower that distills the bottom liquid of the first non-reporting tower as a heat source, and a second non-reporting tower that distills the bottom liquid of the first non-reporting tower. This is a distillation method in which bubbled steam from the second non-reporting column obtained by operating at a pressure equal to or higher than the above is charged.

Distillation methods include a method in which the feedstock supplied to the unreported tower is cut in order of boiling point starting from the heavy part, a method in which the feedstock is cut in order of boiling point starting from the heavy part, or a method in which the feedstock is cut in order from the heavy part in order of boiling point. There are methods of organically combining heavy components and cutting them economically, and the method of the present invention can be applied to any of these methods.

Further, the distillation apparatus to which the present invention is applied includes a plurality of non-reporting towers, and the bottom liquid extracted from the bottom of the first non-reporting tower in the previous stage is transferred to the second non-reporting tower in the subsequent stage. Any type of distillation device may be used as long as it has a configuration for charging and distilling, even if it is a two-stage distillation device equipped with two non-reporting towers, or a multi-stage distillation device equipped with three or more non-reporting towers. Good too. Furthermore, there are no particular restrictions on the type of unregistered column used in the distillation apparatus to which the present invention is applied, and conventionally known types such as plate column type and packed column type can be adopted. .

In the present invention, the recovery section of the non-reported tower refers to the area between the bottom of the non-reported tower where the heating reboiler is installed and the charging position where the feedstock is charged into the non-reported tower; A side reboiler will be provided. If the side reboiler is installed at a location above the charging position rather than at the recovery section of the non-reported tower, the non-reported efficiency will decrease. Furthermore, the position where the side reboiler is installed is such that an appropriate temperature difference can be maintained between the internal temperature of the first non-reporting tower and the temperature of the bubbling steam of the second non-reporting tower. It is best to consider and confirm the load and temperature distribution of liquid or steam at each stage in the unreported tower, and set the most effective position within the above range.

From this point of view, the location of the side reboiler to be installed in the first non-reporting tower is the recovery section of the non-reporting tower, and is an economical position in terms of the design of the installed side reboiler.
It varies depending on the raw material supply conditions, the operating conditions of the non-report tower, the characteristics of the non-report tower, etc., but for example, when using a thermosiphon reboiler, the distance between the tube side and the shell side is 10
A position where a temperature difference of ~25°C can be achieved, or, when a kettle type reboiler is used, a position where a temperature difference of 10 to 20°C can be achieved is desirable. Generally, in order to effectively utilize the heat supplied from this side reboiler and to ensure separation performance in the first non-reporting tower, the recovery section of the first non-reporting tower is It is preferable that it be the head.

In addition, in the present invention, if it is not possible to maintain an appropriate temperature difference between each part of the first non-reported tower and the steam pumped out of the second non-reported tower, the operating pressure of the first non-reported tower Or, by controlling the operating pressure of the second non-reporting tower, the bubbling vapor of the second non-reporting tower and the first
The temperature is controlled to maintain an appropriate temperature difference between each part of the tower. This temperature control method includes a method of operating the first non-reporting tower under reduced pressure;
A method of filling the inside of the first non-reporting tower with trays or packing material with a low differential pressure to lower the internal pressure differential and, ultimately, the temperature inside the tower, and further pressurizing the second non-reporting tower to produce distilled steam. There are methods of increasing the temperature level of the distillation column, and by implementing these methods alone or in combination, an appropriate temperature difference can be created between each part of the first distillation column and the surface steam of the second distillation column. Try to take it. Preferably, the first distillation column is operated at reduced pressure, and the second distillation column is operated at or near normal pressure.

Note that the second distillation column charged to the side reboiler of the first distillation column
The surface steam of the distillation column may be steam bubbling out from the side cut, but preferably it is top surface steam bubbling out from the top of the column.

By the way, the main disturbance factors for the first distillation column are ■
Changes in the reflux temperature of the first distillation column, ■Changes in the withdrawal steam flow in the second distillation column, ■Changes in the operating pressure in the first and second distillation columns, ■Changes in the composition of the feedstock, ■Changes in the feedstock Temperature changes, etc. can be mentioned, but regarding the disturbance factors ■ to ■, the reflux liquid temperature is maintained constant by adjusting the cooling source of the reflux liquid, the internal reflux port is constantly suppressed, and the surface steam m This can be dealt with by minimizing changes in Further, the disturbance factors (1) and (2) can be dealt with by analyzing the composition of the raw material or measuring the temperature, and controlling the internal temperature of the column by performing feedforward control or feedback control based on this analysis.

When using an air fin cooler as a cooling method for the reflux liquid, either the louver opening that adjusts the amount of air and the reflux liquid temperature are automatically adjusted, or the reflux liquid temperature is detected and the air fin cooler's drive motor is operated. It is preferable to control the rotational speed by a ball change method or a VVVF (variable resistance variable frequency control) method, etc., and adjust the reflux liquid cooling source according to the scale of the facility.

Furthermore, in the present invention, when a multi-stage distillation apparatus is used, for example, three distillation columns, i.e., a first, second and third distillation column, to carry out unreported feedstock, the second distillation column is operated under pressurized conditions. By doing so, it is possible to create a temperature difference between the first distillation column and the first distillation column, and there is no need to use other means such as a pump when transferring the bottom liquid of the second distillation column to the third distillation column. Further energy savings can be achieved.

Furthermore, heat exchange is performed between the bottom liquid of the third distillation column and the bottom liquid of the first distillation column, and heat is exchanged between the feedstock charged to the first distillation column at the side reboiler outlet of the first distillation column. By replacing them, further energy savings can be achieved.

〔Example〕

Hereinafter, the non-notification method of the present invention will be specifically explained based on the embodiments shown in the accompanying drawings.

Figure 1 shows benzene, toluene and xylene (BTX)
This is a flow sheet of a two-stage distillation apparatus for separating and refining raw material oil mainly composed of.

In this flow sheet, a side reboiler (3) is installed in the first distillation column (1) three stages below the supply stage to which the charging line (2) for supplying feedstock oil is connected, and a side reboiler (3) is installed inside the first distillation column (1). The column is packed with regular packing in order to lower the differential pressure within the column, that is, the temperature inside the column, and to reduce the reflux ratio.

The raw oil heated to 110-120℃ is transferred to the charging line (2
) is charged into the first distillation 1 (1) and heated under reduced pressure conditions.

The bottom liquid of the first distillation column (1) is circulated through the line (4) to the bottom reboiler (5).
) and then transferred to the first distillation column (1) again from the line (6).
It's like going back inside.

This bottom reboiler (5) is used to compensate for the lack of heat during startup and normal operation.
10 is supplied with steam of 9/cti·G.

Further, the top vapor mainly composed of benzene obtained from the top of the first distillation column (1) has a temperature of 60 to 70°C, and is extracted from the line (7) and sent to the condenser (8). 40～
It is cooled to 50°C and charged into the flow tank (9), a part of which is refluxed to the upper part of the first distillation column (1) from the line (10), and the other part is refluxed to the line (10). (11) is extracted from the system as light oil.The heavy fraction is handled through the upper line (12) of the first distillation column.

In addition, a part of the bottom liquid extracted from the bottom of the first distillation column (1) is transferred from the line (13) to the second distillation column (14).
) and blackened under slightly pressurized conditions.

A part of the bottom liquid of this second distillation column (14) is circulated from the line (15) to the bottom reboiler (16),
It is heated to ~160°C and returns to the second distillation column (14) from the line (17), while the other part is heated to the line (18).
) is extracted from the system. In addition, the above-mentioned tower bottom reboiler (
16) is supplied with steam of 10Kg/ai.G.

The toluene-based top steam extracted from the top of the second distillation column (14) has a temperature of 110 to 120°C, and
19), the first via the three-way valve (20) and the line (21)
It is supplied to the side reboiler (3) of the distillation column (1) as its heat source.

The top steam of the second distillation column (14) after heat exchanged in the side reboiler (3) is sent from the line (23) to the condenser (22), cooled to 40-50°C, and refluxed. It is charged into a tank (24), and part of it is circulated to the upper part of the M2 distillation column (14) through a line (25), and the other part is extracted from the system through a line (26).

Here, during steady operation of the 1M sluice tower (1), the line (19) to the three-way valve (20) is
, condenser (22), reflux ff1 (24), line (25
) By switching the three-way valve (20), the top production steam that has been circulated to the upper part of the second distillation column (14) is transferred to the line (19), the three-way valve (20), and the line (21).
, side reboiler (3), line (23), condenser (22), reflux tank (24), line (25), and line (26), and part of the line (
25) to the upper part of the second distillation column (14), and the other part is extracted from the system through a line (26).

In this first steam M column (1), part of the liquid and/or steam in the column is extracted and sent to the side reboiler (3) through the line (21), and circulated to the side reboiler (3). It is heated to 80 to 90° C. by heat exchange with the top produced steam of the second distillation column (14), and is circulated again into the first silent distillation column (1) through the line (28).

In addition, the vent of the first distillation column (1) is led from the line (29) to the pressure reducing device, and the temperature balance of the uncontrolled system is maintained within an appropriate range, that is, 400 to 500 m+) 1 g ab.
The second distillation column (14) is heated to normal pressure or slightly pressurized by introducing an inert gas such as nitrogen to 1.0 to 1.31°C.
cs/cjabs, and the second distillation column (
14) The temperature of the reflux liquid flowing from the reflux 1 (24) to this second distillation column (14) is detected and the flow and temperature of the column top production steam are automatically adjusted.

In the Kuroshio equipment of this example, the 10Kg/ci/G steam conventionally used in the bottom reboiler (5) can be reduced from 97/H to 5T/H, thereby reducing the reboiler steam pressure from the conventional one. 10Ky/1i-
It was found that the level could be lowered from Q system to 2KI/cd-G system low pressure steam.

(Effect of the invention) According to the present invention, the amount of heat held by the surface steam of the second unreported tower can be effectively used as a heating source for the first unreported tower. The amount of heat required can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing a non-reporting method according to an example of the implementation of the present invention. (1)...First non-reporting tower (3)...Side reboiler (5) (16 )・−・Bottom reboiler (14)・・・・
・Second unregistered tower patent applicant: Agent for Nippon Steel Chemical Co., Ltd.
Patent Attorney Masaru Naruse Daido 1
Patent attorney Satohiro Nakamura! 111v
lI F1 1. First Distillation Memo 3: Buoy μ ° Snail ° Iller 5, + 6: Engineering various acupoint ° Iller 14: 纂 2 NO STEAM, RESULTS ANSWER PROCEDURE NEM SUBJECT (Showa 59) Manabu Shiga, Director General of the Japan Patent Office, November 2010, 1, Indication of the case, Patent Application No. 218296 of 1982, 2, Method of non-notification of the title of the invention, 3, Relationship with the amendment person case Patent applicant address: Chuo, Tokyo Ward Ginza 5-13-16 Name (6
64) Nippon Steel Chemical Co., Ltd. 4, Agent 105 Telephone 03 (433) 442
0 Address: Building 5, Shin 113-8-8, Minato-ku, Tokyo
Floor 6: No increase in the number of inventions due to the amendment 7: Contents of the amendment in the [Detailed Description of the Invention] section of the specification subject to the amendment ” will be amended as follows. If the temperature is above r, depending on the steam and liquid loads in the tower, the operating conditions of the tower often lack stability, and unreported performance may deteriorate. ” (2) “Separation performance in the first non-notification tower” stated on page 6, line 7 of Akira [1] is amended as follows. ``Maintain stable operating conditions in the first steam WI@ and separation performance (3) ``Slightly pressurize'' described in the last line of page 10 of the Mei I document shall be corrected as follows. . "Normal pressure or slightly pressurized" (4) "40-5
0°C" is corrected as follows. "40-90℃" or more

Claims (2)

[Claims] (1) A side reboiler is provided in the recovery section of the first distillation column equipped with a reboiler at the bottom of the column, and this side reboiler has a second distillation column as a heat source for distilling the bottom liquid of the first distillation column. A distillation method characterized by charging the distilled steam from a second distillation column obtained by operating the column at a pressure equal to or higher than the operating pressure of the first distillation column. (2) The distillation method according to claim 1, wherein the temperature of distilled steam from the second distillation column is controlled by adjusting the operating pressure, and the temperature is controlled and the steam is charged into the side reboiler of the first distillation column.