CN111170824A

CN111170824A - Rectification process for isobutane separation

Info

Publication number: CN111170824A
Application number: CN202010029470.6A
Authority: CN
Inventors: 唐超; 鲁妙霞
Original assignee: Anhui Shihua Engineering Technology Co ltd
Current assignee: Anhui Shihua Engineering Technology Co ltd
Priority date: 2020-01-13
Filing date: 2020-01-13
Publication date: 2020-05-19

Abstract

The invention relates to a rectification process for separating isobutane, which comprises the steps of taking a mixture of normal butane, isobutane and components above C5 as raw materials, feeding the raw materials into a rectification tower, and separating light components and heavy components in the tower; the tower top gas is compressed by a compressor and heated, and then exchanges heat with the circulating material at the bottom of the tower through a heat exchanger, and then the tower top gas passes through a water cooler, wherein one part of the tower top gas returns to the tower top to be used as cold reflux, and the other part of the tower top gas is directly extracted. According to the characteristic that the COP value of the isobutane material is high, the medium on the top of the tower has a large amount of heat in the form of external mechanical work, so that a heat source is provided for the bottom of the tower, and the aim of cooling the tower is fulfilled. Compared with the prior art, the method cancels the cooling load at the top of the tower and the heating load at the bottom of the tower, saves a large amount of cooling water at the top of the tower and medium-pressure steam at the bottom of the tower in the process, reduces energy consumption, and achieves the purposes of energy conservation and environmental protection.

Description

Rectification process for isobutane separation

Technical Field

The invention relates to the technical field of chemical industry, energy conservation and environmental protection, in particular to a rectification process for isobutane separation

Background

In chemical production processes, the mixture system needs to be separated in order to achieve a substance of a certain purity. However, chemical separation, especially physical systems with relatively close boiling points, requires huge energy consumption for multi-stage rectification, and the separation is achieved by means of repeated evaporation and condensation. Therefore, energy conservation and environmental protection become key points and difficulties in the chemical rectification process.

In the chemical production, an aromatization device, an MTBE device and a methyl ethyl ketone device react to generate byproducts of n-butane, isobutane and components above C5, and in the prior art, a rectification process for separating the isobutane from the byproducts is shown in figure 1: the by-product from the aromatization unit (stream F1), the by-product from the MTBE unit (stream F2), and the by-product from the methyl ethyl ketone unit (stream F3) enter the rectifying tower 7 from the 24 th, 26 th, and 48 th trays, respectively. Light components in the tower face upwards and heavy components face downwards, heavy components which are not completely separated move downwards again through tower top reflux and tower tray reflux of each layer (sequentially pass through the top condenser 1, the reflux tank 2 and the reflux pump 3 and return to the rectifying tower 7), and light components which are not completely separated move upwards again through the tower bottom reboiler 6, so that the purposes of separation and purification are achieved. And a large amount of circulating cold water is adopted at the tower top, a part of products are discharged from the device after being cooled, and most of products return to the fractionating tower as reflux. The product purity was controlled by extensive cold reflux with a mass reflux ratio of about 7. Part of the bottom product is taken out of the device as the product, and in addition, a large amount of the product is evaporated by a reboiler at the bottom of the tower and returns to the rectifying tower 7. The prior rectification technology needs to heat and purify isobutane in a bottom product by a large amount of medium-pressure steam. Therefore, the energy consumption is very large.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to: the process improvement of the rectification technology in the isobutane separation process is provided, the consumption of cold and hot public works required in the rectification process is optimized, the energy consumption is reduced, and the process is energy-saving and environment-friendly.

In order to achieve the above purpose, the invention provides the following technical scheme:

a rectification process for separating isobutane comprises the steps of taking a mixture of normal butane, isobutane and components above C5 as raw materials, feeding the raw materials into a rectification tower, and separating light components and heavy components in the tower; the tower top gas is compressed by a compressor and heated, and then exchanges heat with the circulating material at the bottom of the tower through a heat exchanger, and then the tower top gas passes through a water cooler, wherein one part of the tower top gas returns to the tower top to be used as cold reflux, and the other part of the tower top gas is directly extracted.

Preferably, the mixture of n-butane, isobutane and components above C5 is derived from a byproduct F1 of an aromatization unit, a byproduct F2 of a methyl ethyl ketone unit and a byproduct F3 of an MTBE unit.

Preferably, the by-product F1 of the aromatization device is a mixture of n-butane and isobutane, and is used as the first feed of the rectification and enters a rectification tower from a 24 th tray.

Preferably, the byproduct F2 of the MTBE plant is a mixture of n-butane, isobutane, C5, which enters the rectification column from tray 26 as the second feed for this rectification.

Preferably, the by-product F3 of the methyl ethyl ketone device is a mixture of n-butane and isobutane, and the mixture is used as a third feed of the rectification and enters the rectification tower from the 48 th tray.

Preferably, the process parameters of the rectification column are as follows: the overhead temperature was 51 ℃ and the operating pressure was 0.6 MPag; the column bottom temperature was 65 ℃, the operating pressure was 0.65MPag, and the operating reflux ratio was 7.

The invention has the beneficial effects that:

according to the characteristic that the COP value of the isobutane material is high, the medium on the top of the tower has a large amount of heat in the form of external mechanical work, so that a heat source is provided for the bottom of the tower, and the aim of cooling the tower is fulfilled. Mechanical/electrical energy of higher quality is used as energy input to convert it into heat. Compared with the prior art, the method cancels the cooling load at the top of the tower and the heating load at the bottom of the tower, saves a large amount of cooling water at the top of the tower and medium-pressure steam at the bottom of the tower in the process, reduces energy consumption, and achieves the purposes of energy conservation and environmental protection.

Drawings

FIG. 1 is a flow chart of a rectification process in isobutane separation in the prior art;

FIG. 2 is a process flow diagram of the present invention;

in the reference signs

1-top condenser, 2-reflux tank, 3-reflux pump, 4-intermediate condenser I, 5-intermediate condenser II, 6-reboiler, 7-rectifying tower, 8-compressor, 9-heat exchanger, and 10-water cooler.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

And (3) carrying out rectification purification on isobutane on a normal butane-isobutane system after the arylation device, the methyl ethyl ketone device and the MTBE device, wherein the scale of feeding gas is 31466kg/h, the isobutane content is about 79.49 wt%, the normal butane content is about 14.36 wt%, and other components above C4 are about 6.15 wt%. The purity of the separated isobutane is more than 98 wt%.

The distillation process for separating isobutane specifically comprises the following steps:

the aromatization unit by-product F1(F1 is normal butane and isobutane, and the temperature of F1 is 60 ℃) is used as the first feed of the rectification, and enters the rectification tower 7 from the 24 th tray.

The by-product F2 of MTBE unit (F2 is n-butane, isobutane and components above C5, F2 temperature is 101 deg.C) is used as the second feeding material of said rectification, and is fed into the rectification tower 7 from 26 th tray.

The by-product F3 of methyl ethyl ketone device (F3 is normal butane and isobutane, and the temperature of F3 is 25 ℃) is used as the third feeding material of the rectification and enters the rectification tower 7 from the 48 th tray.

Light and heavy components are separated in the tower; the gas at the top of the tower is compressed by a compressor 8 to be heated, then passes through a heat exchanger 9 to exchange heat with the product returned from the bottom of the tower, then passes through a water cooler 10, one part of the gas at the top of the tower returns to the top of the tower to move downwards again, and the other part of the gas is directly extracted.

Wherein, the technological parameters of the rectifying tower 7 are as follows: the overhead temperature was 51 ℃ and the operating pressure was 0.6 MPag; the column bottom temperature was 65 ℃, the operating pressure was 0.65MPag, and the operating reflux ratio was 7.

The results show that the energy consumption is reduced from 68.162 gJ/ton to 45.87 gJ/ton and 32.7% compared with the conventional rectification method.

Claims

1. A rectification process for isobutane separation is characterized in that: the method comprises the following steps of (1) taking a mixture of n-butane, isobutane and components above C5 as raw materials, feeding the raw materials into a rectifying tower, and separating light components from heavy components in the tower; the tower top gas is compressed by a compressor and heated, and then exchanges heat with the circulating material at the bottom of the tower through a heat exchanger, and then the tower top gas passes through a water cooler, wherein one part of the tower top gas returns to the tower top to be used as cold reflux, and the other part of the tower top gas is directly extracted.

2. The process according to claim 1, wherein the distillation process comprises the following steps: the mixture of the normal butane, the isobutane and the components with the carbon number of more than 5 is derived from a byproduct F1 of an aromatization device, a byproduct F2 of a methyl ethyl ketone device and a byproduct F3 of an MTBE device.

3. The process according to claim 1, wherein the distillation process comprises the following steps: the by-product F1 of the aromatization device is a mixture of normal butane and isobutane, and is used as the first feed of the rectification and enters a rectification tower from a 24 th tray.

4. The process according to claim 1, wherein the distillation process comprises the following steps: the byproduct F2 of the MTBE unit is a mixture of n-butane, isobutane and C5, and enters a rectifying tower from a 26 th tray as a second feeding material of the rectification.

5. The process according to claim 1, wherein the distillation process comprises the following steps: the by-product F3 of the methyl ethyl ketone device is a mixture of n-butane and isobutane, and is used as a third feed of the rectification and enters the rectification tower from a 48 th tray.

6. The process according to claim 1, wherein the distillation process comprises the following steps: the technological parameters of the rectifying tower are as follows: the overhead temperature was 51 ℃ and the operating pressure was 0.6 MPag; the column bottom temperature was 65 ℃, the operating pressure was 0.65MPag, and the operating reflux ratio was 7.