JPS6019732A - Distillation of 1,2-dichloroethane - Google Patents

Abstract

PURPOSE:To distill the titled compound containing high-boiling substances in good heat efficiency, by recovering heat energy having a gas of the titled compound recovered from the top of a column for high-boiling substances by a compressor under specific conditions, using it as heat source for specific reboilers. CONSTITUTION:In distilling 1,2-dichloroethane (EDC) containing high-boiling substances by distillation process for low-boiling substances, distillation process for high-boiling substances, and heat recovery process for a gas recovered from the top of the column for high-boiling substances, the pressure of the top of the column 305 for high-boiling substances is kept at >=0.5kg/cm<2>G, a EDC gas recovered from the top of the column is pressurized from suction pressure to >=0.5kg/cm<2> by the compressor 307 and heated from suction temperature to a temperature >=10 deg.C higher than it, and it is used as a heat source for the reboilers 314, 309, etc. of at least two columns selected from the column 305 for high-boiling substances, the column 303 for low-boiling substances, a dehydration column, EDC recovery column, and a column for vinyl chloride, etc. so that heat efficiency of EDC distillation process is extremely improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for distilling 1.2 dichloroethane (hereinafter referred to as EDC). In more detail, the thermal energy of the EDC gas recovered from the top of the column during distillation with high boiling point groups (including high boiling point substances) is fully utilized, and the overall thermal efficiency of the EDC distillation process is maintained. Improved E
This relates to a DC distillation method.

Conventionally, the method for distilling KDC has been carried out in the manner shown in FIG. That is, in FIG. 1, crude EDC containing low boiling point substances and high boiling point substances is passed through conduits 101 and 102 from a dehydration tower and a vinyl chloride tower to a low boiling point group 103.
The low boiling point material is then separated by distillation. In addition, the bottoms of column 103 containing high-boilers are fed via conduit 105 to high-boilers group 106 for distillation. tower 103
The thermal energy required for this is supplied 712 from the 11 boiler 104. 'f1! The effluent is collected through conduit 107 and fed to the E1)C cracking furnace. Bottom liquid H: While being circulated through conduit 108', it is reheated in boiler 109, rises completely within the column, and is distilled again.

1, l, 2) High boiling point substances such as 11 glolethane and 1,1,2.2 tetrachloroethane' (i-EDC containing 5 to 20 moles; n1 bottoms, conduit 110'
N is supplied to the EDC recovery tower via the . In addition, most of the E I) C gas discharged from the top of the column 106 and having a pressure in the range of less than 0-5 Kg/cIIG is cooled and condensed in the condenser Ill, and then transferred to the gas-liquid separation tank 112. The condensed liquid ♂ is separated into non-condensed gas, and the #ll liquid-liquid pump 11
3 and refluxed to the top of the column IC) 6.

I) C gas containing hydrogen chloride and water that is not condensed in condenser 111 is sent to vent condenser 1.
The condensed gas is extracted from the conduit 115 and the non-condensed gas is extracted from the conduit 116.

By the way, in this conventional method, the capacitor 111
However, the disadvantage was that thermal energy was lost or not utilized effectively.

The present inventors previously invented and patented a distillation method for El C, including a heat recovery method using the flow sheet shown in FIG. However, this method requires large equipment costs for the compressor for the EDC gas discharged from the top of the column and the boiler condenser for the distillation column, and furthermore, the energy consumption of the compressor increases. The heat recovery rate is not satisfactory because the thermal energy of the C gas is greater than the required thermal energy in the reboiler condenser. In addition, since the condensation temperature of the compressed EDC sludge in the reboiler condenser becomes low, it is difficult to recover and utilize the sensible heat energy (thermal energy from the condensation temperature to the top temperature of the high boiling point column) of the condensed EDC. This had some drawbacks, and it was necessary to improve it further.

The present inventors have developed an EDC with high thermal efficiency that eliminates all of the above drawbacks.
The present invention was arrived at as a result of intensive research in search of a distillation method.

In other words, the present invention provides a high boiling point distillation process, a high boiling point distillation process, and a heat recovery process for gas recovered from the top of a high boiling point column. In the distillation method, the top pressure of the high boiler column is 0-5 Kg/crl.
E f) C gas that is distilled under pressure greater than l G and recovered from the top of the column? The compressor further increases the pressure and temperature by 0.5 Kf/cII or more and 10°C or more from the suction pressure and temperature, and passes this through the high-boiling point column, low-boiling point column, dehydration column, EDC recovery column and ground vinyl column. At least two towers selected from the group consisting of:
(1) A method for distilling EDC with the following features is provided.

In the present invention, the top pressure of the high boiler column is 0.59/c
It is good if it is higher than r/lG, but usually 0.5 to 1.5 KI? / crl G will be adopted.

Also, the compression of E 13 C gas by a compressor is Q, 5K
q/crl or higher, but usually in order to completely suppress the increase in the energy required for boosting the pressure and the equipment cost required for installing the compressor C], 5 to 2. OKf/c/l is adopted.

According to the present invention, the total amount of heat can be recovered as a heat source for a distillation column plus one boiler of a vinyl chloride monomer plant including a high boiler column, with an energy of about 8 times the thermal energy loss in the overhead condenser of a high boiler column. However, if you reduce the pressure loss in the distillation column or increase the heat transfer area of the boiler condenser, the compression energy 1
It can also be set to 1 or less.

Furthermore, even when compared to the case where the heat recovery method of the flow sheet shown in Fig. 2 is applied to the high boiling point column, the total energy required for the compressor can be reduced to 1/2, and the equipment cost can be reduced. Significant reductions are possible.

Furthermore, the operating pressure of the high boiler column? In order to raise the temperature of the distillate, that is, the temperature of the purified EDC and the bottom EDC, the increased thermal energy is effectively recovered in the EDC cracking furnace and the EDC recovery tower, which are the respective supply destinations. .

In addition, since the condensation temperature of El)C on the outside of the reboiler tube is high, the tf process can be made even more advantageous by recovering the thermal energy from the condensation temperature to the column temperature of the high boiler column. It is possible. For example, it is also possible to reduce the steam requirements of the high boiler column by exchanging heat with the dehydration column bottoms and low boiler bottoms. Yet another example is that the generated steam can be increased by heat exchange with heated water supplied to a steam generator for removing reaction heat in the oxychlorination reaction zone.

As described above, the present invention is an industrially extremely advantageous method that enables a significant reduction in the energy consumption of a vinyl chloride monomer plant, a significant reduction in equipment costs, and ease of operation.

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

Comparative example 1 It is operated according to the flow sheet shown in FIG.

Crude El)C45' containing 0.7 mol% of low-boiling substances and 0.5 mol% of high-boiling substances, 2 tons/h, heat transfer area 3
It was supplied through conduits 101 and 102 to a low boiler column 103 equipped with all 000 thermosiphon reboilers 104 and having 85 sieve trays, and a total of 5.9 tons/hour of steam was supplied to boiler 104 for distillation. A high boiler column 106 with 51 sieve trays is connected from the bottom of the column via a conduit 105', and the pressure at the top of the column is 0.05 Kg/cr.
ftG, steam was distilled by supplying 10.3 tons/hour of steam to the reboiler 109 having a heat transfer area of 600-n11.

73.4 tons of EDC gas at 85℃ discharged from the top of the tower
Time is supplied to condenser 111 via conduit 117, of which 72.8 tons/hour of E1) C gas is condensed and refluxed by pump 113. The heat of condensation at this time is 5.64 x 10' at calZ. . On the other hand, non-condensed EDC gas (
1.6 tons/hour is fed via conduit 118 to a vent condenser 114, cooled and then withdrawn.

On the other hand, 3.8 tons/hour of bottoms at 95° C. containing 5 moles of high-boiling substances are fed via conduit 110 to the E DC recovery column.

8 extracted from the upper part of the column 106 via the conduit 107
The purified KDC in liquid form at 5°C contained 0.5 mol% of low-boiling substances and 0.01 mol% of high-boiling substances. In this distillation method, the amount of steam supplied to columns 103 and 106 was 16.2 tons/hour.

Comparative example 2 It is operated according to the flow sheet shown in FIG.

Crude EDC, which has the same composition, temperature, and flow rate as the bottoms of the low boiler column of Comparative Example 1, is transferred to Comparative Example 1 through 201 conduits.
It is fed to the same distillation stage of the high boiler column 202 having the same structure as , and distilled at a column top pressure of 0.05 Kg/cr/l G.

73.4 tons of EDC gas at 85℃ discharged from the top of the tower
At that time, the turbo compressor 203 was 1.4.1 Kf/iG.

The pressure and temperature are increased to 131° C., of which 71.3 tons/hour is supplied via a conduit 204 to the outside of the tube of a thermosiphon reboiler 205 having a heat transfer area of 1000 mm. The supplied EDC gas is circulated through conduit 206 9
Bottom liquid of column 202 at 5°C and 5.55 x 10'Kc
The heat exchanged during al7 is condensed and supplied to a gas-liquid separation tank 208 via a conduit 207.

On the other hand, excess thermal energy to maintain the full pressure in the column 202 is cooled and removed in a condenser 210.7 As a result, it is supplied to a condenser 210 via a conduit 209, and after being condensed, it is sent to a gas-liquid separation tank 208 via a conduit 211. The EDC supplied was 1.5 tons/hour.

E containing all trace amounts of hydrogen chloride and water from the separation tank 208
l) 11.6 tons/hour of C gas is supplied via conduit 215 to condenser 216, cooled, and then discharged.

Liquid E at 13.5°C stored in 2081 separation tanks
The DC is cooled to 85° C. in heat exchanger 212 and then refluxed to the top of column 202 via conduit 214′ by pump 213. On the other hand, 3.8 tons/hour of bottoms having the same composition and temperature as in Comparative Example 1 was supplied to I (DC recovery tower) via conduit 217.

Liquid purified EDC at 85° C. withdrawn via conduit 218 from the same distillation stage as column 106 of Comparative Example 1 in column 202
is 0.5 mol of low boiling point substance and 11.01 mol of high boiling point substance
It was contained in mol%'.

The power required for the compressor 203 in this operation is 91 OKWH
/ It was time.

EXAMPLE One embodiment of the present invention operates according to the flow sheet of Figure @3.

Crude EDC4 with the same composition, temperature, and flow rate as Comparative Example 1
5.2 tons/hour is passed through conduit 3 to low boiler column 303 of the same structure.
(Supplied from sources 11 and 302 and distilled under the same conditions.

The bottoms of the low boiling point column 303 are supplied via a conduit 304 to a high boiling point column 305 having the same structure as in Comparative Example 1, and the top pressure of the column is 1.
．． Distilled under the condition of 0 Kg/iG.

73.4 tons/hour of E at 106°C discharged from the top of the tower
DC gas is supplied to turbo compressor 307 via conduit 306; 2. l Ky/cr/lG, i Compressed to 30°C. The turbo compressor was driven by an electric motor at approximately 3600 revolutions per minute.

Of the compressed EDC gas, 42.4 tons/hour is in conduit 30.
8, it is supplied to the outside of the tube of the thermosiphon reboiler 309 for a low-boiling point bath with a heat transfer area of 370 d, and heat is exchanged with the 95° C. bottom liquid circulating inside the tube through the conduit: (10'?). , and is condensed at a temperature of 123°C and supplied to the gas-liquid separation tank 312 via the conduit 311.The amount of heat exchanged in this case is 3.14 x 1 (1'K (41117 hours),
This corresponds to the 5.9 tons/hour of steam required for distillation in the low boiler column 103 in Comparative Example 1.

In addition, the remaining compressed E I) 31.0 tons/hour of C gas is transferred via a conduit 313 to a tube tube of a thermosiphon reboiler 314 for a tube boiler with a heat transfer area of 10 (10 deg).
1, which is supplied to the side and circulated throughout the inside of the tube via the conduit 315.
It exchanges heat with the bottom liquid at 15° C., condenses at a temperature of 123° C., and is supplied to a gas-liquid separation tank 317 via a conduit 316. The amount of heat exchanged in this case is 2.29 x 10'Kcal/
hour, which corresponds to 4.4 tons/hour of steam. The boiler 3186 with a heat transfer surface of $300 m' was supplied with steam at a rate of 6.5 tons/hour. this is:(,
It corresponds to a heat amount of 4X 10'Kcal/hour.

EDC gas containing trace amounts of hydrogen chloride and water is discharged from the separation tanks 312 and 317 at 0.3 tons/hour each through a total of 319 pipes.

Liquid E I) C at 123°C stored in separation tanks 312 and 317 is heated to 106°C in heat exchangers 320 and 321.
The high boilers are cooled to 100% and refluxed via conduit 324 to the top of high boiler column 305 by pumps 322 and 323.

From the bottom of the high boiler column 305, 3.8 tons/hour of bottoms having the same composition as in Comparative Example 1 and a temperature of 115° C. is supplied to the EDC recovery column through 325 conduits.

4 0.5 obtained from the 48th distillation stage from the bottom of the column
At the time of sifting, liquid purified EDC at 106°C has no low boiling point substances.
．． 5 molti and high boiling substances 0. It contains 1 mol% O and is fed to the EDC cracking furnace via a 326 gold conduit.

The power required for the compressor 307 in this operation was 500KWH/
It was time. In addition, the pressure in the high boiler column 305 was increased from Comparative Examples 1 and 2 to 1-OKg/clL G,
The amount of heat required for EDC decomposition and EDC recovery tower is: (, I
111'Kcal decreased at 7 o'clock. This is steam 0
．． This corresponds to 6 tons/hour.

[Brief explanation of drawings]

1 and 2 are flow sheets showing a method for distilling 1.2 dichloroethane as a comparative example, and FIG. 3 is a flow sheet showing an embodiment of the present invention. In Figures 1, 2 and 3, each symbol has the following meaning?
show. 103...Low-boiling point column 104...Thermosiphon reboiler for low-boiling point bath] 06... High-boiling point column 109... High-boiling point column Bath thermosiphon reboiler 111...Condenser 202...High boiler column 203...Turbo compressor 205...Thermosiphon reboiler 20
8... Gas-liquid separation tank 210... Condenser 212... Heat exchanger 303... Low boiling point group 305... High boiling point substance Group 307... Turbo compressor 309... Thermosiphon reboiler for low boiling point bath 312... Gas-liquid separation tank 3゛4°°°゛°4°°°゛°High boiling -e-t! 7.
Type 1-7"12 Boiler 317... Gas-liquid separation tank 318... Reboiler 320.321... Heat exchanger patent applicant Toyo Ichida Kogyo Co., Ltd. No. 2 Figure ff

Claims (3)

[Claims] (1) In the distillation method for 1,2 dichloroethane containing high-boiling substances, which consists of a low-boiling point distillation step, a high-boiling point distillation step, and a heat recovery step of the gas recovered from the top of the high-boiling point group, high-boiling point substances Base tower top pressure total 0.5Ky/ail G
1 and 2 distilled under the above pressure and recovered from the top of the column.
Add dichloroethane gas to the compressor, and further reduce the suction pressure and temperature by 0.5. Kg/cr! 1 or more, the pressure and temperature are increased by 10°C or more, and this r high-boiling point group, low-boiling point group, dehydration tower, 1,
A method for distilling 1,2-dichloroethane, characterized in that at least two columns selected from the group consisting of a 2-dichloroethane recovery column and a vinyl chloride column are used as a heat source for a boiler. (2) Adjust the tower top pressure of high boiling point groups to 0.5 to 1.5 kg/
1 of claim (1) distilled with ff1G
．． Distillation method of 2-diglolethane. (3) 1,2 dichloroethane according to claim (1) or (2), whose pressure is further increased by 0.5 to 2.0 Kg/Clft from the suction pressure using a 1.2 dichloroethane gas compressor. Distillation method.