JPS6210076A - Method of recovering ethylene oxide - Google Patents

Abstract

PURPOSE:To use effectively energy and to recover EO, by subjecting the bottom solution of EO desorption tower to flash treatment, compressing a gaseous phase part, using the part as a heat source for the EO desorption tower, subjecting a liquid phase part to heat exchange with the bottom solution of an EO absorption column and generating steam by the use of a heat pump. CONSTITUTION:The bottom solution of the ethylene oxide(EO) absorption tower 2 is heated 5, an inert gas is separated 7, fed to the top part of the EO desorption tower 10 and EO is stripped and recovered 11. Part of the bottom solution containing substantially no EO is fed from the bottom of the desorption tower 10 to the flash tank 41 to generate low-pressure steam, the steam is compressed 43 to high pressure, the pressure at the bottom of the desorption tower 10, introduced to the gaseous phase part at the bottom of the desorption tower, used as part of its heat source, the rest of the solution of the tank 41 is fed to the heat exchanger 5, subjected to heat exchange with the bottom solution of the EO absorption tower, sent to the refrigerant evaporator 51, cooled 18 and used as the absorption solution of the absorption tower 2. The refrigerant evaporated in the evaporator 51 is compressed, sent to the refrigerant condenser 55 and fluid in the outside is provided with heat and steam is generated 60.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for recovering ethylene oxide obtained by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst. For more details,
The reaction product gas containing ethylene oxide obtained by catalytic gas-phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is guided to an ethylene oxide absorption tower and absorbed into an absorption liquid to recover ethylene oxide, and then the ethylene oxide-containing absorption tower The liquid is sent to an ethylene oxide stripping tower and heated to diffuse ethylene oxide from the top of the ethylene oxide stripping tower to release ethylene oxide.A part of the liquid extracted from the bottom of the tower is led to an ethylene oxide absorption tower and recycled as an absorption liquid.
This invention relates to an ethylene oxide recovery method that reduces the heating energy of a collapsed tower and further recovers the thermal energy of the liquid extracted from the bottom of the ethylene oxide stripping tower.

(Prior art) In the process of recovering ethylene oxide, the reaction product gas is absorbed into an absorption liquid mainly composed of water and recovered as an ethylene oxide aqueous solution, and the ethylene oxide is diffused from this aqueous solution to obtain ethylene oxide.Ethylene oxide is generally The reaction product gas containing ethylene oxide produced by catalytic gas-phase oxidation of ethylene and molecular oxygen-containing gas over a silver catalyst is led to an ethylene oxide absorption tower, and an absorption liquid mainly composed of water is recovered. The solution is recovered as an ethylene oxide aqueous solution through countercurrent contact, and then sent to an ethylene oxide stripping tower, and the bottom of the ethylene oxide stripping tower is heated with heating steam to diffuse ethylene oxide from the aqueous solution, and the solution is extracted from the bottom of the ethylene oxide stripping tower and substantially contains ethylene oxide. The remaining aqueous solution is recycled as an absorption liquid, and the ethylene oxide, water, carbon dioxide, and inert gases (nitrogen, argon, methane, ethane,
) and other low-boiling point impurities such as formaldehyde, and high-boiling point impurities such as acetaldehyde and acetic acid, are purified through a dehydration process, a light fraction separation process, and a small fraction separation process to produce ethylene oxide'! You can make one.

(Problems to be Solved by the Invention) However, such a method for recovering ethylene oxide has the problem of consuming a large amount of heating steam in the ethylene oxide stripping tower, and the recovery of the thermal energy of the liquid discharged from the ethylene oxide stripping tower. There was a problem that a large amount of heat was not sufficient and was discarded outside the system. In the conventional method, the bottom liquid of the ethylene oxide stripping tower at 100 to 130°C is heat exchanged with the bottom liquid of the ethylene oxide absorption tower, and after recovering the amount of heat, it is cooled and used as the absorption liquid of the ethylene oxide absorption tower. As a result of research into energy conservation in these ethylene oxide recovery processes, the present invention was completed by focusing on the effective use of energy in the ethylene oxide stripping column bottom liquid.

(Means for solving the problem) A reaction product gas containing ethylene oxide produced by catalytic gas-phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is introduced into an ethylene oxide absorption tower and exchanged with the absorption liquid. A part of the gas from the top of the ethylene oxide absorption tower is circulated to the ethylene oxidation reaction process, and the bottom liquid of the ethylene oxide absorption tower containing ethylene oxide is supplied to the ethylene oxide stripping tower, where ethylene oxide is diffused from the top of the ethylene oxide stripping tower. The liquid extracted from the bottom of the ethylene oxide stripping tower is sent to the ethylene oxide absorption tower and recycled as an absorption liquid, and the remainder is sent to the by-product ethylene glycol concentrating tower to concentrate the ethylene glycol contained in the liquid. The liquid extracted is flash-treated and separated into a gas phase and a liquid phase. The gas phase is compressed and introduced into an ethylene oxide stripping tower, and the liquid phase is exchanged with the ethylene oxide absorption tower bottom liquid and heat in a heat exchanger. After the exchange, a heat pump is used to recover the thermal energy of the absorption liquid to generate water vapor, and the absorption liquid cooled by the heat pump is further cooled in the cold 1413, and then used as the absorption liquid for the ethylene oxide absorption tower. The present invention relates to a characteristic method for recovering ethylene oxide. In the present invention, the temperature of the absorption liquid supplied to the ethylene oxide absorption tower is 5 to 40°C, preferably 10°C.
-35°C, and the composition of the absorption liquid is as follows: pH is 5-12, preferably 6-11, ethylene glycol concentration is 1-40% by weight, preferably 5-30% by weight, and antifoaming agent concentration is 0. l
The amount of residual water is controlled within the range of ppm or more, preferably 1 to 1 ooppm. In order to keep the ethylene glycol concentration in the absorption liquid constant, a part of the absorption liquid that circulates between the ethylene oxide absorption tower and the ethylene oxide stripping tower is extracted from the bottom of the ethylene oxide stripping tower and sent to the by-product ethylene glycol concentration tower. will be introduced and controlled. It is preferable to adjust the pH by adding a compound that dissolves in the absorption liquid, such as a hydroxide or carbonate of an alkali metal such as potassium or sodium. Specifically, the additive is potassium hydroxide or Sodium hydroxide is preferred.

Any antifoaming agent can be used as long as it is inert to ethylene oxide, by-product ethylene glycol, etc. and has an antifoaming effect on the absorption liquid.A typical example is a water-soluble silicone emulsion. It is effective because it has excellent dispersibility in liquids, dilution stability, and thermal stability.

The operating conditions of the ethylene oxide absorption tower are such that the ethylene oxide concentration in the reaction product gas is 0.5 to 5% by volume, preferably 1.0 to 4% by volume, and the operating pressure of the ethylene oxide absorption tower is 2 to 40 KO/%. tyiG, preferably 1
0 to 30 K (J/cd G"C).

The operating conditions of the ethylene oxide stripping tower are such that the top pressure of the ethylene oxide stripping tower is 0 to 1 kg/cIIiG, preferably 0.
．． 3-0.6 kq/cIIiG1 ethylene oxide stripping tower top temperature 85-110°C, ethylene oxide stripping tower bottom temperature 100-130°C, ethylene oxide stripping tower bottom ethylene oxide concentration is 1101) p or less, preferably 0.5
ppm or less.

A feature of the present invention is that the reaction product gas containing ethylene oxide produced by contact vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is introduced into an ethylene oxide absorption tower and brought into countercurrent contact with an absorption liquid. A part of the gas from the top of the ethylene oxide absorption tower is circulated to the ethylene oxidation reaction process, and the ethylene oxide absorption tower bottom liquid containing ethylene oxide is supplied to the ethylene oxide stripping tower to diffuse ethylene oxide from the top of the ethylene oxide stripping tower. The liquid extracted from the ethylene oxide absorption tower undergoes heat exchange with the bottom liquid of the ethylene oxide absorption tower in a heat exchanger, and then is cooled in a cooler and sent to the ethylene oxide absorption tower for circulation and use as an absorption liquid.The remainder is used as the ethylene glycol contained in the liquid. In the process of sending the by-product ethylene glycol to the concentrating column for concentrating it, the thermal energy possessed by the liquid extracted from the bottom of the ethylene oxide stripping column is recovered, and the recovered thermal energy is used effectively.

As a means for this purpose, the liquid discharged from the bottom of the ethylene oxide stripping tower is introduced into a flash tank operated at normal pressure or slightly reduced pressure to generate low-pressure steam. This generation of water vapor is endothermic and has the effect of lowering the temperature of the solution. The generated water vapor is pressurized by an electrically driven centrifugal compressor, screw compressor, or reciprocating compressor and is supplied to the gas phase at the bottom of the ethylene oxide stripping tower, where it becomes part of the heating source of the ethylene oxide stripping tower and is used to dissipate ethylene oxide. To have a reduction in water vapor in the heating source of the tower. Furthermore, the remaining liquid that has generated low-pressure steam is heat exchanged with the liquid from the bottom of the ethylene oxide absorption tower in a heat exchanger, and the heat is recovered. Then, the ethylene oxide dispersion tower bottom liquid that exits the heat exchanger still has usable thermal energy, so it is recovered by a heat pump and used as a heating source in the ethylene oxide purification process, especially in the ethylene oxide rectification column. It is possible to reduce the amount of heating steam used in the rectification column.

The refrigerant used as the working fluid of the heat pump used in the present invention is used in circulation by repeating the evaporation line in the heat pump process, so in addition to its thermodynamic properties, the refrigerant is thermally and chemically stable. In terms of safety and handling, it is required that the material be odorless, non-toxic, and non-explosive. Refrigerants that can be used in the present invention include R-11 and R-1.
2, fluorinated hydrocarbons such as R-22, R-113, and R-114, and hydrocarbons such as propane and pentane, but considering the heat pump operating temperature conditions, R-
12, R-114 is the most suitable.

The operating conditions for the heat pump of the present invention are such that the ethylene oxide stripping column bottom liquid, which comes out from the bottom of the ethylene oxide stripping column and which does not substantially contain ethylene oxide and whose heat is recovered by the ethylene oxide absorption column bottom liquid and the heat exchanger, is 50 to 60°C.
The refrigerant enters the refrigerant evaporator at a temperature of be done.

The refrigerant evaporated in the evaporator by the ethylene oxide stripping tower bottom liquid is compressed by a centrifugal, screw, or reciprocating compressor to a pressure at which the saturation temperature of the refrigerant is 80 to 100°C. The pressurized refrigerant is given heat to the outside by the following two methods, and is then sent to the refrigerant evaporator by a pump and used for circulation.

(1) A refrigerant vapor is directly sent to a boiler, such as an ethylene oxide rectification tower (bottom temperature: 50 to 70°C), to condense it and give the heat of condensation to the bottom liquid of the rectification tower.

■ Send refrigerant vapor to the refrigerant liner to cool it! The refrigerant is condensed by imparting latent heat of condensation to the fluid in the condenser, such as water.

A fluid, for example water, which has been given heat by this refrigerant, is heated to a temperature 5 to 10 degrees Celsius lower than the temperature of the refrigerant, and low-pressure steam is generated by flashing, which can be used.

On the other hand, the ethylene oxide absorption tower bottom liquid undergoes heat exchange with the remaining liquid that generated low-pressure steam, and after separating light gas in a flash tank, the ethylene oxide stripping tower In
The ethylene oxide is supplied to the reactor and dissipated. In the present invention, what is emitted from the ethylene oxide stripping tower is mostly ethylene oxide and water, and the receiving portion is carbon dioxide and trace amounts of oxygen, ethylene, and inert gases (nitrogen,
It is an emissive product consisting of low-boiling point impurities such as argon, methane, ethane) and formaldehyde, and high-boiling point impurities such as acetaldehyde and acetic acid.

In order to describe the present invention in more detail, the present invention will be explained based on FIG.

In Figure 1, the reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is passed through a conduit (1) to an ethylene oxide absorption tower in the form of a packed column or tray column. (2), and from (24) to the upper part of the ethylene oxide absorption tower (2). An absorbing liquid consisting of alli = 1 to 50 ppm and the balance being water is introduced and brought into countercurrent contact with the reaction product gas to absorb ethylene oxide in the reaction product gas into the absorbing liquid. Here, 99% by weight or more of ethylene oxide in the reaction product gas is recovered. Ethylene, oxygen, carbon dioxide, and inert gases (nitrogen, argon, methane,
Gases such as ethane), aldehydes, and acidic substances are transported through the conduit (3
) to the carbon dioxide absorption step and/or oxidation reaction step.

In the ethylene oxide absorption process, in addition to ethylene oxide, ethylene, oxygen, carbon dioxide, and inert gases (nitrogen,
low-boiling impurities such as argon, methane, ethane) and formaldehyde generated in the ethylene oxidation reaction process;
A substantial amount of high boiling point impurities such as acetaldehyde and acetic acid are also absorbed at the same time.

The bottom liquid of the ethylene oxide absorption tower (2) is transferred to a conduit (4),
It is sent to a heat exchanger (5) and exchanged with the bottom liquid for ethylene oxide dispersion to raise the temperature to 70 to 110°C, and through a conduit (6),
Send to gas-liquid separation tank (7) and partially remove ethylene oxide,
Light fractions of the inert gas containing water are separated by conduit <8). The remaining absorption liquid after flushing the light gas is passed through the conduit (9) at a pressure of 0.1 to 1.0 KO/rmG.
Ethylene oxide stripping tower (10
), and supply a heating medium such as steam or Dowsum (heat medium product of Dow Co., USA) through the conduit (13) to the heater (12) of the ethylene oxide stripping tower (10), or directly into the ethylene oxide stripping tower. Ethylene oxide is dissipated by introducing water vapor into the bottom of the tank and heating it. At a temperature of 100 to 130, the temperature is substantially free of ethylene oxide from the bottom of the ethylene oxide stripping tower (10).
A portion of the ethylene oxide stripping tower bottom liquid at ℃ is transferred to the conduit (14).
and through the conduit (16) to the flash tank (41)
The pressure relief pressure at normal pressure or slightly reduced pressure is lowered to generate low-pressure steam, which lowers the temperature of the solution. The low-pressure vapor generated in the flash tank (41) is sent to the compressor (43) through the conduit (42), compressed to a pressure slightly higher than the bottom pressure of the ethylene oxide stripping tower (10), and then transferred to the ethylene oxide absorption tower through the conduit (44). The remaining liquid flushed in the flash tank (41) is introduced into the heat exchanger (5) through the conduit (45) and exchanged heat with the bottom liquid of the ethylene oxide absorption column. The absorption liquid leaving the heat exchanger (5) passes through the refrigerant evaporator (51) of the heat pump, and then passes through the cooler (1).
8), water from conduit (21), potassium hydroxide aqueous solution from conduit (22), and antifoaming agent (from conduit (23)).
water-soluble silicone emulsion) and conduit (24).
The ethylene oxide can be introduced into the ethylene oxide absorption tower (2) through the ethylene oxide absorption tower (2).

On the other hand, the remaining absorption liquid extracted from the bottom of the ethylene oxide stripping tower (10) through the conduit (14) is transferred to the conduit (15).
) can be sent to the by-product ethylene glycol concentration tower.

The refrigerant is evaporated by exchanging heat with the bottom liquid of the ethylene oxide stripping tower in the refrigerant evaporator (51), and is sent to the compressor (53) through the conduit (52) and compressed, and then passed through the conduit (54) to the refrigerant condenser (55). ), which gives heat to the external fluid and condenses it. The condensed refrigerant is sent to the refrigerant evaporator (51) again through the conduit (56).

Water vapor can be recovered through the conduit (60) by circulating water supplied through the conduit (62) through the refrigerant condenser (55), through the conduit (57), the conduit (58), and the tank (59).

This recovered steam can be effectively used as a heating source in the ethylene oxide manufacturing process. In particular, this steam can be used in an ethylene oxide rectification column.

In order to briefly describe the present invention in detail, a conventionally known method will be explained based on FIG. 2.

In Figure 2, the reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is passed through a conduit (1) to an ethylene oxide absorption tower in the form of a packed column or tray column. (2), the absorption liquid is introduced into the upper part of the ethylene oxide absorption tower (2) through the conduit (24), and is brought into countercurrent contact with the reaction product gas, so that ethylene oxide with a concentration of 99% or more in the reaction product gas is The ethylene that was not absorbed was recovered from the top of the ethylene oxide absorption tower (2), lS! Gases such as hydrogen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane), aldehydes, acidic substances, etc. are recycled to the carbon dioxide absorption stage and/or the oxidation reaction stage through the conduit (3). In this absorption process, in addition to ethylene oxide, ethylene, oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane, etc.), low-boiling point impurities such as formaldehyde generated in the ethylene oxidation reaction process, and high-boiling point impurities such as acetaldehyde and acetic acid are used. A substantial amount of impurities are also absorbed at the same time. The bottom liquid of the ethylene oxide absorption tower (2) is sent to the heat exchanger (5) through the conduit (4), and is heated to exchange with the ethylene oxide stripping bottom liquid to raise the temperature to 70-110°C. The inert gas is sent to a separation tank (7) and separated by a conduit (8). The absorption liquid partially containing ethylene oxide and water is supplied through a conduit (9) to the upper part of an ethylene oxide stripping tower (10) with a top pressure of 0.1 to 1.0 KO/cnGS and a temperature of 85 to 100°C. 10) from the heater (12) using a heating medium such as steam or Dow Sam (a product of Dow Company), or by a heating method that directly introduces steam into the lower part of the ethylene oxide stripping tower (10). A portion of the ethylene oxide stripping tower bottom liquid at a temperature of 110 to 130° C. which substantially does not contain ethylene oxide is released from the bottom of the ethylene oxide stripping tower (10) to the conduit (14) and the conduit (14). (16) to exchange heat with the feed liquid of the ethylene oxide stripping tower (10) in the heat exchanger (5), and further cooled by the cooler (18), and then to adjust the ethylene glycol degree in the absorption liquid. Fresh water is introduced through conduit (21>) and an aqueous potassium hydroxide solution is added through conduit (22) to adjust the D I-1 in the absorption liquid and to adjust the antifoam formulation in the absorption liquid. An antifoaming agent can be introduced through the conduit (23).The by-product ethylene glycol is produced in the absorption liquid by the hydrolysis reaction of ethylene oxide and water during the oxidation step of oxidizing ethylene with molecular oxygen and the ethylene oxide diffusion step. and ethylene oxide tIi to prevent an increase in low-boiling impurities such as formaldehyde and high-boiling impurities such as acetaldehyde J3 and acetic acid.
Conduits (14) and (15) from the bottom of the defeated tower (10)
The bottom liquid of the ethylene oxide stripping tower (10) is extracted through the ethylene oxide stripping tower (10) and sent to the concentration step.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the scope of the present invention is not limited only by this example.

Example 1 In Figure 1, the reaction product gas containing ethylene oxide produced by catalytic gas phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is passed through the conduit (1) to absorb ethylene oxide in a tray column format. Supplied to the lower part of the tower (2),
From the conduit (24) to the upper part of the ethylene oxide absorption R11 (2), temperature 29.6 ° C., pH = 6, ethylene glycol concentration = 9.0% by weight, antifoaming agent (water-soluble silicone emulsion) concentration = 3 ppm, and the remainder. An absorption liquid consisting of water was introduced and brought into countercurrent contact with the reaction product gas to cause ethylene oxide in the reaction product gas to be absorbed by the absorption liquid. At this point, more than 99% by weight of ethylene oxide in the reaction product gas was recovered. Unabsorbed ethylene, oxygen, carbon dioxide, and inert gas (
Gases such as nitrogen, argon, methane, ethane), aldehydes, acidic substances, etc. were circulated through the conduit (3) to the carbon dioxide absorption step and the oxidation reaction step.

The bottom liquid of the ethylene oxide absorption tower (2) is passed through a conduit (4),
Heat exchanger (5) and conduit (6) allow 11 tanks of gas and liquid (
7), and a light component gas of an inert gas containing a portion of ethylene oxide and water was separated by a conduit (8). The remaining absorption liquid after flushing the light gas is supplied to the upper part of the ethylene oxide stripping tower (10) through the conduit (9),
Steam is supplied to the heater (12) of the ethylene oxide stripping tower (10) through the conduit (13) for heating, and the ethylene oxide stripping tower bottom liquid, which does not substantially contain ethylene oxide, is supplied from the bottom of the ethylene oxide stripping tower (10) through the conduit (
14), and a portion of it was supplied to the flash tank (41) through the conduit (16), where the pressure was lowered to normal pressure or slightly reduced pressure to generate low-pressure steam.

The low pressure steam generated in the flash tank (41) is transferred to the conduit (
42) to compression II (43) and the bottom pressure of the ethylene oxide stripping tower (10) is 0.5 k G/ci.
It was compressed to a pressure slightly higher than G and sent to the gas phase at the bottom of the ethylene oxide stripping tower (10) through the conduit (44). The remaining liquid flushed in the flash tank (41) was introduced into the heat exchanger (5) through the conduit (45) and was heat exchanged with the ethylene oxide absorption tower bottom liquid. The absorption liquid leaving the heat exchanger (5) is transferred to the refrigerant evaporator (5) of the heat pump.
After passing through 1), the conduit (21) is passed through the cooler (18).
Water, an aqueous potassium hydroxide solution through the conduit (22), and an antifoaming agent (water-soluble silicone emulsion) through the conduit (23) were added, and the mixture was introduced into the ethylene oxide absorption tower (2) through the conduit (24).

On the other hand, the remaining absorption liquid discharged from the bottom of the ethylene oxide stripping tower (10) through the conduit (14) is transferred to the conduit (14).
5) to the by-product ethylene glycol concentration column.

The refrigerant is evaporated by exchanging heat with the bottom liquid of the ethylene oxide stripping tower in the refrigerant evaporator (51), and is sent to the compressor (53) through the conduit (52) and compressed, and then passed through the conduit (54) to the refrigerant condenser (55). ), which gives heat to the external fluid and condenses it. The condensed refrigerant was sent to the refrigerant evaporator (51) again through the conduit (56).

Water vapor was recovered by the conduit fJ (60) by circulating water supplied from the conduit (62) to the refrigerant condenser (55), the conduit (57), the conduit (58), and the tank (59).

Table 1 shows the conditions for continuous operation of this PROHIS.

Comparison Example 1 In Figure 2, the reaction product gas containing ethylene oxide produced by catalytic gas-phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is passed through the conduit (1) to absorb ethylene oxide in a tray column format. Supplied to the lower part of the tower (2),
The absorption liquid was introduced into the upper part of the ethylene oxide absorption tower (2) from the conduit (24), and the temperature was 29.6°C, pH = 6, ethylene glycol concentration = 9.0%, and antifoaming agent (water-soluble silicone emulsion). ) An absorption liquid having a concentration of 3 ppm and the remainder being water was introduced and brought into countercurrent contact with the reaction product gas to cause the ethylene oxide in the reaction product gas to be absorbed by the absorption liquid. Gases such as ethylene, oxygen, carbon dioxide, inert gases (nitrogen, argon, methane, ethane), aldehydes, acidic substances, etc. that are not absorbed from the top of the ethylene oxide absorption tower (2) are transferred to carbon dioxide gas through the conduit (3). It was recycled to the absorption step and/or the oxidation reaction step. The bottom liquid of the ethylene oxide absorption tower (2) is passed through a conduit (4), a heat exchanger (5),
The conduit (6) sends the inert gas to the gas-liquid separation tank (7), and the inert gas containing some ethylene oxide and water is sent to the conduit (8).
Separated by After flushing the light valve gas, the remaining absorption liquid is passed through the conduit (9) to the ethylene oxide stripping tower (
10). Ethylene oxide stripping tower (1
Steam is supplied to the heater (12) of 0) through the conduit (13) to heat it, and the ethylene oxide stripping tower bottom liquid, which is substantially free of ethylene oxide, is extracted from the bottom of the ethylene oxide stripping tower (10) through the conduit (14). , a part of which passes through the conduit (16), the heat exchanger (5) and the cooler (18), and the water from the conduit (21), the conduit (2).
2), an aqueous potassium hydroxide solution and an antifoaming agent (water-soluble silicone emulsion) were added through a conduit (23), and the mixture was supplied to the top of the ethylene oxide absorption column through a conduit (24).

On the other hand, the remaining absorption liquid extracted from the bottom of the ethylene oxide stripping tower (10) through the conduit (14) is transferred to the conduit (15).
) was sent to the by-product ethylene glycol concentration column. Table 2 summarizes the operating conditions for this process.

(Effects of the Invention) According to the method of the present invention, the vapor generated when flashing the ethylene oxide stripping column bottom liquid is separated from the flash drum and compressed by the compression means to a pressure slightly higher than the pressure at the bottom of the ethylene oxide stripping column. By introducing it into the bottom of the stripping tower, it is possible to significantly reduce the amount of heating heat trapped in the ethylene oxide flirll tower. In addition, by recovering heat from the ethylene oxide stripping column bottom liquid using a compression heat pump and using the heat as part of the heat source of the ethylene oxide rectification column, energy conservation of the ethylene oxide rectification column can be achieved at the same time. Furthermore, by carrying out this method, the effect of reducing the thermal load of the cooling water for cooling the absorption liquid sent to the ethylene oxide absorption tower is exhibited.

[Brief explanation of drawings]

FIG. 1 is an example showing a preferred specific example of the ethylene oxide recovery method of the present invention. FIG. 2 is an example showing a known ethylene oxide recovery method related to the present invention. (2) Ethylene oxide absorption tower (5) Heat exchanger (7) Gas-liquid separation tank (10) Ethylene oxide stripping tower (12) Heater (18) Cooler (41) Flash tank (43) Compressor (51) Heat pump refrigerant Evaporator (53) Heat pump refrigerant compressor (55) Heat pump refrigerant condenser (59) Heat pump flash tank patent applicant Nippon Shokubai Chemical Co., Ltd. Figure-1 Figure-2

Claims (1)

[Claims] (1) A reaction product gas containing ethylene oxide produced by contact vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst is introduced into an ethylene oxide absorption tower, brought into countercurrent contact with the absorption liquid, and the ethylene oxide absorption tower A part of the gas from the top is circulated to the ethylene oxidation reaction process, and the ethylene oxide absorption tower bottom liquid containing ethylene oxide is supplied to the ethylene oxide stripping tower, ethylene oxide is diffused from the top of the ethylene oxide stripping tower, and the liquid is extracted from the bottom of the ethylene oxide stripping tower. is led to the ethylene oxide absorption tower and recycled as an absorption liquid, and the remainder is sent to the by-product ethylene glycol concentration tower to concentrate the ethylene glycol contained in the liquid. In the process, the liquid extracted from the bottom of the ethylene oxide stripping tower is flashed, The gas phase is separated into a gas phase and a liquid phase, and the gas phase is compressed and introduced into the ethylene oxide stripping tower.The liquid phase exchanges heat with the bottom liquid of the ethylene oxide absorption tower in a heat exchanger, and then is absorbed using a heat pump. A method for recovering ethylene oxide, which comprises recovering the thermal energy of the liquid to generate water vapor, cooling the absorption liquid by a heat pump, further cooling it in a cooler, and then using it as the absorption liquid for an ethylene oxide absorption tower.