JPS60115535A - Distillation of 1,2-dichloroethane - Google Patents

Abstract

PURPOSE:To utilize the thermal energy of 1,2-dichloroethane recovered from the top of a distillation column, and to improve the thermal efficiency remarkably, by carrying out the distillation of 1,2-dichloroethane containing high-boiling components with a distillation column under a specific pressure. CONSTITUTION:1,2-Dichloroethane (abbreviated as EDC) containing high-boiling components is distilled with a high-boiling component distillation column. The distillation is carried out keeping the column top pressure of the high-boiling component to >=0.7kg/cm<2>G, preferably 0.7-2.0kg/cm<2>G, and using the EDC (heated at about 100-120 deg.C) recovered from the column top as the heat source of the reboiler of the following processes, i.e. dehydration column, vinyl chloride distillation column and hydrogen chloride distillation column, without additional compression process. Especially, the EDC is used preferably as the heat source of the intermediate reboiler of the vinyl chloride distillation column or the hydrogen chloride distillation column at a stage having a column temperature of 60-110 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for distilling 1,2-dichloroethane (hereinafter referred to as EDC!).

More specifically, when FiDC containing high boiling point substances is distilled in a high boiling point column, the thermal energy of the EDC residue recovered from the top of the column is effectively utilized, and the thermal efficiency of the EDC distillation process is significantly improved. The present invention relates to a method for distilling BDc.

Here, the definitions of each group in this specification are as follows.

(1) Dehydration tower A distillation tower for removing water in crude EDC produced in the ethylene oxychlorination step and/or direct chlorination step.

(2) Low boiling point column Removes low boiling point substances such as crude EDC from which water has been removed by the dehydration tower and undecomposed gDc obtained from the KDO decomposition process, chloroform, ethyl chloride, and 1,1-dichloroethane. distillation column.

(3) High boiling point column 11, 2-) From EDC containing high boiling point substances such as lychloroethane and t1.2.2-tetrachloroethane, ED
G! A column that distills f#.

(4) 1.2-dichloroethane recovery column A column for distilling and recovering EDC from the bottoms of the high-boiling point column.

(5) Hydrogen chloride group]! A column for distilling and recovering hydrogen chloride from a mixture of hydrogen chloride, vinyl chloride, and undecomposed FiDO produced in the iDo decomposition process.

(6) Vinyl chloride tower A tower that recovers hydrogen chloride from the hydrogen chloride group and then separates vinyl chloride monomer by distillation.

In the past, distillation of EDC and production of vinyl chloride monomer in a chlorination and vinyl monomer production plant were normally carried out in the manner shown in FIG. .

That is, in FIG. 2, the crude KDC containing water, low boiling point substances and high boiling point substances produced in the oxychlorination process and the double chlorination process is first passed through the conduit (22
1), it is supplied to a dehydration tower (201), and water is removed from the top of the tower.

Next, the bottom liquid of this column (201) is supplied to the low boiler column (202) via the conduit (22'2), and P
Undecomposed F and DC are supplied from the DC decomposition furnace (207) to the vinyl chloride column (205) via a conduit (232), and low boiling point substances such as chloroform and ethyl chloride are distilled off from the top of the column.

The bottom liquid of the column (202) is IDC containing high boilers and is fed via conduit (223) to the high boilers column (203).

The distillate is collected as purified KDC through a conduit (224) and supplied to the next step, the EDC cracking furnace.

Most of the EDO gas discharged from the shell of the tower (205) is water-cooled and condensed in the condenser (215), then stored in the F, DC accumulator (215), and then passed through the conduit (227). It is then refluxed again to the top of the column (205).

EDC gas containing trace amounts of hydrogen chloride and water that is not condensed in the condenser (213) is stored in the vent condenser (21
4), it is cooled and taken out.

The bottom liquid is 1,1.2-) dichloroethane and 1
．． 1.2.2-Teton A pipe containing high boiling substances such as chloroethane is fed to the KDO recovery column (204) via conduit (22B)i.

In the column (204), KDC is distilled and recovered from the top of the column, high-boiling substances are concentrated from the bottom of the column, and extracted through a conduit (229).

On the other hand, FiDO purified in column 1 (203) is
It is supplied to a decomposition furnace (207) and decomposed into vinyl chloride%/mer and hydrogen chloride. This vinyl chloride 7mer 1 hydrogen chloride and water NEDc are passed through a conduit (2so),
Hydrogen chloride is supplied to the hydrogen chloride group (206), recovered from the top of the column, and then supplied to the vinyl chloride column (205) via a conduit (151).

After the vinyl chloride monomer is distilled and recovered from the top of the column (205), the undivided 8 yen EDC is transferred from the bottom of the column to the conduit (232).
is recycled to the tower (202) via.

In the above process, each distillation column boiler (210
), (211), (212), (216).

Steam is usually used as the heating source for (217) and (218). Among them, the amount of heat (steam) used in the high boiling point column (203) and glue boiler (212) is the largest, and therefore the heat lost in the condenser (213 in Figure 2 for the high boiling point column) is also high boiling point. It has the most towers.

In such cases, methods of utilizing the thermal energy of the tower JJi E D C gas include a method of heating hot water or generating and recovering steam using an absorption heat pump, and a method of using the tower top EDO gas further to a compressor, etc. Pressurize with
There are methods to use it as a heating source for reboilers, etc.

However, absorption heat pumps usually have a heat recovery rate of about 5
It is not a good idea because the compression method uses a compressor, which requires electric power for compression.

The present inventors have arrived at the present invention as a result of intensive research in order to recover the heat that was conventionally lost in the high-boiling point column and create a thermally efficient 'EDC distillation method.

That is, the present invention involves distilling KDO containing high-boiling substances in a high-boiling column, and adjusting the top pressure of the high-boiling column to α7 ky.
E is distilled under surface pressure and recovered from the top of the column.
Dehydration tower, low boiler tower, FiDC without further pressurizing DC gas! This is a method for distilling 1,2-dichloroethane by using at least one glue boiler selected from the group consisting of a recovery column, a vinyl chloride column, and a hydrogen chloride column as a heat source.

In the present invention, if the top pressure of the high boiler column is increased too much,
It is known that the bottom temperature of the column increases, which tends to promote thermal decomposition of EDc or high-boiling substances contained in EDc and scaling of the column or reboiler. However, as a result of testing the equipment under these pressurized operating conditions, the authors found that the top pressure was 0.7~z, o kg/Cnta.
It has been confirmed that within this range, the above problem does not occur and stable operation continues.

The pressure at the top of the high boiler column is set at 0.7 to 2. Orcg7td
When the temperature is set to ta, the temperature at the top of the column is usually 100 to 120°C.

For this reason, this tower top EDC gas usually has a tower bottom temperature of 90~90°C.
A dehydration tower operated at around 100°C.

It goes without saying that it can be used as a heating source for a reboiler at the bottom of a low-boiling point column or a FiDQ recovery column, and can also be used as another heating source if the usage requirements are met.

In addition, vinyl chloride towers are usually operated at a top temperature of 0 to 50°C and a bottom temperature of 110 to 160°C, but in such cases, the top BDO gas of the high boiling point tower according to the present invention has a temperature level of 0 to 50°C. Because of its low temperature, it cannot be used as a heating source for the reboiler at the bottom of the column.

Even in such a case, the middle part of the vinyl chloride tower, where the temperature level is low, i.e., the internal temperature of the tower is 60 to 110°C.
If an intermediate reboiler is installed in the section, the tower JJ4EDC
Gas can be used as a heat source, reducing the heat load on the glue boiler at the bottom of the tower.

The application of such intermediate reboilers is hydrogen chloride towers.

This is also possible for other towers.

By being used as a heating source as described above, ED
The C gas is condensed and refluxed to the top of the high boiler column as a reflux liquid. Furthermore, it is most practical to condense the amount that cannot be used in a conventional water condenser.

For example, the heat obtained by the present invention can be used in dehydration towers, low boiler towers, EDC! There is usually a surplus even when used in recovery towers, vinyl chloride towers, and hydrogen chloride fuel boilers. Therefore, when using only one of these columns, the remaining top gas of the high boiling point column may be condensed with water as described above.

In the present invention, the EDc gas at the top of the high boiling point column is not further pressurized using a compressor, so it cannot be used as a heating source for the high boiling point column itself. This is effective for the city under price system conditions where the price of steam is high and the ratio of steam to electricity is small.

As described above, the present invention utilizes the thermal energy of the EDO gas at the top of the high-boiling point column as a heating source for each boiler, thereby reducing steam quenching in a vinyl chloride monomer plant.
It is an extremely advantageous method from an industrial perspective as it allows for a significantly lower amount of raw material 'f'.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 An embodiment of the present invention operates according to 70-C) of FIG.

Crude EDC&8 containing water, low boiling point substances, and high boiling point substances
tons/hour was fed through a conduit (121) to a dehydration tower (101) equipped with a thermosiphon reboiler (110), and water was distilled off from the top of the tower. The crude BDO at the bottom of the column and the undecomposed KDC from the EDC decomposition step are each transferred to a conduit (12
2).

(152) to the low boilers column (102) equipped with a thermosiphon reboiler (111) at 7.01.77
) K was supplied, and low-boiling substances were separated by distillation from the top of the column.

The bottom liquid was supplied via a conduit (125) to a high boiler column (103) equipped with a thermositic, on-type reboiler (1i2), where EDc was purified by distillation. EDc containing boiling point substances is transferred from the bottom of the column to the conduit (128) at 04 tons/hour.
is extracted to an EDO recovery tower (104) equipped with a thermosiphon-only boiler (116), where 'F2DC is recovered.

Further, from the top of the tower, purified EDc is j5 'tM (1
24) through E D 00111'N furnace (107) [
It was then decomposed into vinyl chloride and hydrogen.

This mixture of vinyl chloride, hydrogen chloride, and undecomposed EDc is passed through a conduit (130) to a hydrogen chloride group (106), after which hydrogen chloride is recovered, it is introduced into a vinyl chloride column (105) (g(1)
s1), and the chloride and nil monomers are distilled and recovered from the top of the column.The undecomposed KDc at the bottom of the column is 3.2 tons/
At that time, it was recycle to the tower (102) via the lead J'f (132). Here, the high boiling point column has a top pressure of 1.5
It is operated under a pressurized condition of kg7 deG, and the temperature discharged from the top of the column is 115°C, 10 hours: 0 EDC! The gas is passed through conduits (133), (135), and (137) to the dehydration tower reboiler (110) as a heating source, respectively.
3.5 tons/hour to the low-boiling column reboiler (111), 0.3 tons/hour to the Do recovery column reboiler (116), and to the vinyl chloride column via conduit (139). (105) P-C intermediate reboiler (119
) was supplied at a rate of 1.7 tons/hour, and each distillation was performed. The steam used in the bottom reboiler (ff7) of the tower (105) at this time was [13 T/hour].

In addition, the remaining 2.7 tons/hour of EDO gas at the top of the tower is transferred to conductor 6 (1
25) and was cooled and condensed in a condenser (113), and uncondensed gas (0.2)77 hours was extracted through a conduit (126) and treated in a vent condenser (114). The condensed liquid in the condenser and the EDC gas used as a heating source for each reboiler are passed through 4 tubes (111
).

(134), (156), (13B), and (140), was received in the EDc accumulator (115), and was refluxed as a reflux liquid to the column (1O3) via conduit (127).

Due to further pressurization, the bottoms whose temperature rose to 125°C was supplied to the EDO recovery tower (104), and the purified EDO liquid from the top of the tower was supplied to the BDO decomposition furnace (107) at a temperature of 115°C.

Under these conditions, the steam consumption of the high boiler boiler (112) was 1.7 tons/hour.

The above is the embodiment of the present invention (110).

The steam usage h1 in (111), (112), (116), and (117) is 1.7 in the high boiler reboiler.
0.3 tons/hour and vinyl chloride column reboiler (117)
The total amount was 2.0 T/hour (tons/hour).

Comparative Example The conventional method is operated according to the flow sheet shown in FIG.

Examples and composition, temperature expansion, fluidity 1. Crude EDC in the same condition as both
is supplied to the dehydration tower (201) with the same structure via a dehydration column (22M), and undecomposed EDC is supplied to the low boiler tower (201).
2) via conduit (2?) 2), except for the high boiler column (206)'jI: 6 columns were operated under the same conditions as in the example.

Here, the high boiler column is operated at a column top pressure of 0.1 kg/crπG, and the 85°C EDC gas discharged from the column top is supplied to a condenser (213) via a conduit (225) and condensed. The resulting EDO was stored in an EDC accumulator (215) and refluxed via a conduit (227). Further, the exhaust condensed EDO gas was supplied to the vent condenser (214) via 4WC226) and extracted after being cooled.

In all of the above distillation methods, steam is used as the heating source for the beam boiler, and the reboiler (2JO)
, (211), (212).

The amount of steam used in (216) and (217) is (
0.2 ton/hour of (210), 0.5 ton/hour of (211)
hour, (212) 1.5 tons/hour.

The Q of (216) was 1 ton/hour, and that of (217) was 1.7 tons/hour, and the total was 2.9) 77 hours. As is clear from the above, by implementing the present invention, the reboiler (
110), (111), (112).

Steam f saved in (116), (117)
d: is 0.9 tons/hour, which means that a significant energy saving in the vinyl chloride field has been achieved.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an embodiment of the present invention. FIG. 2 is a flow sheet showing a conventional KDO distillation method as a comparative example. In FIG. 1 and FIG. 2, each symbol indicates the following content. 101.201: Dehydration tower 102.202: Low boiler group 103.203: High boiler group 104.204: BDC recovery tower 105.205: Vinyl chloride A/tower 106.206: Hydrogen chloride group 107 207: Kl) O decomposition furnace 110.210; low boiler group in dehydration tower reboiler 111.21 reboiler 112.212: high boiler group 1 11! + 215: Condenser 114.214: Vent condenser/zer 115 215: BDC! Accumulator 116,
216:EDC! Recovery tower reboiler 117.217 Vinyl dichloride tower ' 118.218: Hydrogen chloride group 1 119: Vinyl chloride tower intermediate reboiler Patent applicant Tohun Soda Kogyo Co., Ltd.

Claims (3)

[Claims] (1) When 1,2-dichloroethane containing high-boiling substances is distilled in a high-boiling column, the top pressure of the high-boiling column is set to 0.
The 1,2-dichloroethane gas recovered from the top of the tower after being distilled under a pressure of 7 &g/c#rG or higher is transferred to a dehydration tower, a low boiler tower, and 1,2-dichloroethane without further pressurization. A method for distilling 1,2-dichloroethane, characterized in that it is used as a heat source for at least one glue boiler selected from the group consisting of a recovery column, a vinyl chloride column, and a hydrogen chloride column. (2) The top pressure of the high boiling point column is 0.7 to 2.0 k.
The method according to claim 1, wherein the distillation is carried out in the range of g/ct. (3) The 1,2-dichloroethane gas recovered from the top of the high-boiling point column has an internal temperature of 60 to 110°C in the all-vinyl chloride column or hydrogen chloride column (used as a heat source for the D-stage Ω intermediate reboiler). %n'l・a The method according to claim (1).