JP2021037447A - Quench tower and gas cooling method - Google Patents

Abstract

To provide a quench tower and a gas cooling method, capable of preventing a solid component deposited by cooling from adhering to a solid packing in large quantities or suppressing occurrence of the phenomenon, and executing cooling of gas to be cooled stably over an extended period.SOLUTION: In a quench tower, which is a quench tower having a gas-liquid contact component inside, for cooling gas to be cooled supplied from a tower lower part by cooling water supplied from a tower upper part, the gas to be cooled is gas for depositing a solid component adhering to the gas-liquid contact component by being cooled, and a washing mechanism for supplying washing water to the gas-liquid contact component is provided.SELECTED DRAWING: Figure 1

Description

The present invention relates to a quench tower and a gas cooling method suitable for cooling a gas to be cooled containing impurities that precipitate solid components when cooled.

Conventionally, as a method for producing 1,3-butadiene (hereinafter, also simply referred to as “butadiene”), a fraction having 4 carbon atoms obtained by cracking naphtha (hereinafter, also referred to as “C4 fraction”). A method is adopted in which components other than butadiene are separated by distillation.
Butadiene is in increasing demand as a raw material for synthetic rubber, etc., but the supply of C4 fraction is decreasing due to the shift of ethylene production method from naphtha cracking method to ethane thermal decomposition method. Therefore, there is a demand for the production of butadiene using the C4 fraction as a raw material.

Therefore, as a method for producing butadiene, a method for separating butadiene from a product gas obtained by oxidatively dehydrogenating n-butene has attracted attention (see, for example, Patent Documents 1 to 4). This production method includes an oxidative dehydrogenation reaction step in which a raw material gas containing n-butene and a molecular oxygen-containing gas containing molecular oxygen (specifically, for example, air) is subjected to an oxidative dehydrogenation reaction. It has a cooling step of cooling the produced gas obtained by the step, and a produced gas separating step of separating butadiene from the produced gas cooled by this step.

Japanese Unexamined Patent Publication No. 2012-72086 Japanese Unexamined Patent Publication No. 2014-198707

However, in the above method for producing butadiene, reaction by-products such as carbonyl compounds such as acetaldehyde and methyl vinyl ketone and organic acids such as carboxylic acid are generated. Such reaction by-products are precipitated by, for example, quenching the product gas in the cooling step, and the solid component adheres to the solid packing in the quench column used. If the amount of this solid component adhered increases with time, a differential pressure is generated in the quench tower, which makes it impossible to continue the cooling step. Therefore, it is necessary to decompose the quench tower to remove the adhered solid component, and therefore, it is difficult to stably cool the produced gas for a long period of time.

The present invention has been made based on the above circumstances, and an object of the present invention is to prevent or suppress a large amount of solid components precipitated by cooling from adhering to the solid packing, and to be cooled gas. It is an object of the present invention to provide a quenching tower capable of stably performing cooling for a long period of time.
Another object of the present invention is to provide a gas cooling method capable of stably cooling a gas to be cooled for a long period of time.

The quench tower of the present invention is provided with a gas-liquid contact member inside, and the cooled gas supplied from the lower part of the tower is cooled by the cooling water supplied from the upper part of the tower.
The gas to be cooled precipitates a solid component adhering to the gas-liquid contact member when cooled.
It is characterized by having a cleaning mechanism for supplying cleaning water to the gas-liquid contact member.

In the quench tower of the present invention, a plurality of the gas-liquid contact members are arranged in the tower so as to be vertically overlapped with each other via a space, and the cleaning mechanism is attached to the gas-liquid contact member at the lowermost stage. It is preferable that the washing water is supplied from above.

Further, in the quench tower of the present invention, it is preferable that the cleaning mechanism has an injection head that injects cleaning water onto the gas-liquid contact member.

Further, in the quench tower of the present invention, it is preferable that the cleaning mechanism is driven when specified.

The gas cooling method of the present invention is a gas cooling method in which, in a quench tower provided with a gas-liquid contact member, the gas to be cooled supplied from the lower part of the tower is cooled by the cooling water supplied from the upper part of the tower.
The gas to be cooled precipitates a solid component adhering to the gas-liquid contact member when cooled.
It is characterized in that washing water is supplied to the gas-liquid contact member.

In the gas cooling method of the present invention, it is preferable to supply the gas-liquid contact member by spraying cleaning water.

According to the quench tower of the present invention, since the cleaning mechanism for supplying cleaning water to the gas-liquid contact member is provided, it is possible to prevent or suppress a large amount of solid components precipitated by cooling from adhering to the gas-liquid contact member. Therefore, the cooling of the gas to be cooled can be stably performed for a long period of time.
According to the gas cooling method of the present invention, since the cleaning water is supplied to the gas-liquid contact member, it is prevented or suppressed that a large amount of solid components precipitated by cooling adhere to the gas-liquid contact member, and as a result, Cooling of the gas to be cooled can be stably performed for a long period of time.

It is explanatory cross-sectional view which shows the outline of the structure in the example of the quench tower of this invention. It is a flow chart which shows an example of the specific method for producing butadiene using the quench tower of this invention.

Hereinafter, embodiments of the present invention will be described.

[Quench tower and gas cooling method]
FIG. 1 is an explanatory sectional view showing an outline of a configuration in an example of a quench tower of the present invention.
The quench tower 2 has a configuration in which the cooling water is brought into countercurrent contact with the gas to be cooled to quench the gas to be cooled, and is a cylindrical tower body 20 extending in the vertical direction and having both ends closed. Has.

A gas introduction port 25 for introducing the gas to be cooled into the inside of the tower main body 20 is provided at a position on the lower side of the peripheral wall portion 21 of the tower main body 20. Further, the tower top 22 of the tower body 20 is provided with a gas outlet 26 for leading out the gas to be cooled from the inside of the tower body 20. Further, the bottom 23 of the tower body 20 is provided with a cooling water outlet 27 for leading out the cooling water supplied from the cooling water supply mechanism 35, which will be described later.

A gas-liquid contact member 30 is provided in the tower body 20 at a position between the gas introduction port 25 and the gas outlet port 26. In the illustrated example, a plurality of gas-liquid contact members 30 are arranged so as to be vertically overlapped with each other via a space. A cooling water supply mechanism 35 for supplying cooling water for cooling the gas to be cooled is provided above the gas-liquid contact member 30 on the uppermost stage. Then, at a position above the gas-liquid contact member 30 in the lowermost stage, a cleaning mechanism 40 that cleans the gas-liquid contact member 30 by supplying cleaning water to the gas-liquid contact member 30 in the lowermost stage is provided. It is provided.

As the gas-liquid contact member 30, when the quench tower 2 is composed of a filling tower, an irregular filling can be used. Specific examples of irregular fillings include Raschig rings, pole rings, cascade mini rings, and the like. Further, when the quench tower 2 is composed of a shelf column, a shelf board is used as the gas-liquid contact member 30.

The cooling water supply mechanism 35 has a spray head 36 for spraying cooling water. The spray head 36 is arranged above the gas-liquid contact member 30 at the uppermost stage in the tower body 20 so as to face downward. Water or alkaline water can be used as the cooling water supplied from the cooling water supply mechanism 35. The temperature of the cooling water is appropriately determined according to the cooling temperature of the gas to be cooled, but is preferably 10 ° C. or higher and 90 ° C. or lower, more preferably 20 ° C. or higher and 70 ° C. or lower, and particularly preferably 20 ° C. It is 40 ° C. or lower. The amount of cooling water supplied from the spray head 36 is, for example, 1200 to 1500 L / min.

The cleaning mechanism 40 has an injection head 41 that supplies cleaning water to the gas-liquid contact member 30 at the bottom stage by injection. The injection head 41 is arranged above the gas-liquid contact member 30 at the lowermost stage in the tower body 20 so as to face downward.
As the injection head 41, it is preferable to use one in which the injected cleaning water forms a conical spray pattern. Further, the conical spray pattern ejected from the injection head 41 is a ratio (L / D) of the spray distance (height of the formed cone) L and the spray width (diameter of the bottom surface of the formed cone) D. Is preferably 2 or less, and more preferably 0.6 to 1.6.

As the cleaning water supplied from the cleaning mechanism 40, water or alkaline water can be used. The temperature of the washing water is not particularly limited, but is, for example, 5 to 30 ° C.
The amount of wash water supplied from the injection head 41 is, for example, 861 to 1076 L / min.
The amount of wash water supplied per unit area of the surface of the gas-liquid contact member 30 is, for example, 44 to 55 L / m ² .
The amount of cleaning water used for one cleaning treatment of the gas-liquid contact member 30 is, for example, 144 to 179L.

The cleaning mechanism 40 can be controlled to be driven at a designated time during the cooling process of the water to be cooled. For example, during the cooling process of the water to be cooled, the operation of driving and stopping the cleaning mechanism 40 is repeatedly performed every predetermined time, for example, 6 to 8 hours, that is, the driving of the cleaning mechanism 40 is intermittent. The cleaning mechanism 40 can be controlled so as to be performed.

In the quench tower 2 described above, the gas to be cooled is introduced into the inside of the tower main body 20 from the gas introduction port 25 and is led out from the gas outlet 26. As a result, the gas to be cooled is circulated from the lower part of the tower main body 20 to the upper part via the gas-liquid contact member 30 inside the tower main body 20. On the other hand, the cooling water by the cooling water supply mechanism 35 is sprayed downward from the spray head 36. As a result, the cooling water comes into countercurrent contact with the gas to be cooled that flows upward inside the tower body 20, and as a result, the gas to be cooled is rapidly cooled. The supplied cooling water is led out from the cooling water outlet 27 to the outside of the tower body 20.

In the above, when the gas to be cooled precipitates the solid component adhering to the gas-liquid contact member 30 by cooling, the deposited solid component adheres to the gas-liquid contact member 30 in the lowermost stage. When the cleaning mechanism 40 is driven during the cooling process of the gas to be cooled, the cleaning water is supplied from the injection head 41 to the gas-liquid contact member 30 in the lowermost stage, thereby supplying the lowermost stage. The solid component adhering to the gas-liquid contact member 30 is removed.

As described above, according to the quench tower 2 of the present invention, since the cleaning mechanism 40 for supplying the cleaning water to the gas-liquid contact member 30, a large amount of solid components precipitated by cooling adhere to the gas-liquid contact member 30. This can be prevented or suppressed, and therefore cooling of the gas to be cooled can be stably performed for a long period of time.

[Method for producing 1,3-butadiene]
INDUSTRIAL APPLICABILITY The present invention can be suitably used for a cooling step of a produced gas in a method for producing 1,3-butadiene by oxidative dehydrogenation reaction between a raw material gas containing n-butene and oxygen.
That is, according to the present invention, the produced gas containing 1,3-butadiene obtained by the oxidative dehydrogenation reaction between the raw material gas containing n-butene and oxygen is released from the lower part of the quench tower provided with the gas-liquid contact member. In a method for producing butadiene having a cooling step of cooling the produced gas by supplying cooling water from the upper part of the quench tower as well as supplying the gas.
It is possible to provide a method for producing butadiene, which comprises performing a cleaning treatment step of supplying cleaning water to a gas-liquid contact member in the quench tower.

This method for producing butadiene (1,3-butadiene) has the steps shown in (1) to (3) below, and by going through the steps (1) to (3) below, n -Butadiene is produced from a raw material gas containing butene.

(1) Obtained in the first step (2) first step of obtaining a product gas containing 1,3-butadiene by an oxidative dehydrogenation reaction between a raw material gas containing 1-butene and 2-butene and a molecular oxygen-containing gas. Second step of cooling the produced gas (3) By selectively absorbing the produced gas that has undergone the second step into an absorbing solvent, the produced gas is mixed with molecular oxygen and inert gases and other gases including 1,3-butadiene. Third step to separate into

FIG. 2 is a flow chart showing an example of a specific method for producing butadiene using the quench tower of the present invention. Hereinafter, a specific example of the above-mentioned method for producing butadiene will be described in detail with reference to FIG.
The butadiene production method of the example shown in FIG. 2 has the above steps (1) to (4), and is an absorption solvent that has absorbed other gases containing 1,3-butadiene obtained in the third step. It has a desolubilization step of solvent separation treatment and a circulation step of refluxing the molecular oxygen and the inert gas obtained in the third step to the first step, that is, feeding the reflux gas as a reflux gas. is there.
Further, in the butadiene production method of the example shown in FIG. 2, the absorption solvent used in the third step is circulated and used.

<First step>
In the first step, a product gas containing butadiene (1,3-butadiene) is obtained by oxidatively dehydrogenating the raw material gas and the molecular oxygen-containing gas in the presence of a metal oxide catalyst. In this first step, the oxidative dehydrogenation reaction between the raw material gas and the molecular oxygen-containing gas is carried out by the reactor 1 as shown in FIG. Here, the reactor 1 is a tower-like structure in which a gas inlet and a gas outlet are provided in the upper part and a catalyst layer (not shown) is formed by filling the inside with a metal oxide catalyst. is there. In the reactor 1, the pipe 100 and the pipe 112 are connected to the gas introduction port via the pipe 116, and the pipe 101 is connected to the gas outlet.

Specifically, the first step will be described in detail. The reactor 1 is connected to the raw material gas and the molecular oxygen-containing gas via the pipe 100 communicating with the pipe 116, and if necessary, the inert gas and water (water vapor). ) (Hereinafter, these are also collectively referred to as "new supply gas"). Before being introduced into the reactor 1, the new supply gas is heated to about 200 ° C. or higher and 400 ° C. or lower by a preheater (not shown) arranged between the reactor 1 and the pipe 100. Further, the reactor 1 is supplied with the new supply gas supplied through the pipe 100 and the reflux gas from the circulation step after being heated by the preheater via the pipe 112 communicating with the pipe 116. Will be done. That is, a mixed gas of the newly supplied gas and the reflux gas is supplied to the reactor 1 after being heated by the preheater. Here, the new supply gas and the reflux gas may be directly supplied to the reactor 1 from separate pipes, but are supplied in a mixed state from the common pipe 116 as shown in FIG. It is preferable to be done. By providing the common pipe 116, the mixed gas containing various components can be supplied to the reactor 1 in a state of being uniformly mixed in advance, so that the non-uniform mixed gas is partially contained in the reactor 1. It is possible to prevent the formation of explosive gas.
Then, in the reactor 1 to which the mixed gas is supplied, butadiene (1,3-butadiene) is generated by the oxidative dehydrogenation reaction between the raw material gas and the molecular oxygen-containing gas, and the produced gas containing the butadiene is obtained. Be done. The obtained generated gas flows out to the pipe 101 from the gas outlet of the reactor 1.

(Raw material gas)
As the raw material gas, a gaseous substance obtained by gasifying n-butene, which is a monoolefin having 4 carbon atoms, with a vaporizer (not shown) is used. This raw material gas is a flammable gas. In the present invention, "n-butene" means linear butene, and specifically, 1-butene, cis-2-butene and trans-2-butene are included in n-butene.
Further, the raw material gas may contain arbitrary impurities. Specific examples of this impurity include branched monoolefins such as i-butene and saturated hydrocarbons such as propane, n-butane and i-butane. Further, the raw material gas may contain 1,3-butadiene, which is a production target, as an impurity. The amount of impurities in the raw material gas is usually 60% by volume or less, preferably 40% by volume or less, more preferably 25% by volume or less, and particularly preferably 5% by volume or less in 100% by volume of the raw material gas. When the amount of impurities is excessive, the reaction rate tends to be slowed down or the amount of by-products tends to increase due to the decrease in the concentration of linear butene in the raw material gas.

As the raw material gas, for example, a fraction containing linear butene as a main component (raffinate 2) obtained by separating butadiene and i-butene from a C4 fraction (fraction having 4 carbon atoms) produced as a by-product of naphtha decomposition. ) And the butene fraction produced by the dehydrogenation reaction of n-butane or the oxidative dehydrogenation reaction can be used. Gases containing high-purity 1-butene, cis-2-butene and trans-2-butene, and mixtures thereof, obtained by dimerizing ethylene can also be used. Furthermore, fluid catalytic cracking (Fluid Catalytic), which decomposes the heavy oil fraction obtained when crude oil is distilled in an oil refining plant or the like using a powdery solid catalyst in a fluidized bed state, and converts it into hydrocarbons having a low boiling point. A gas containing a large amount of hydrocarbons having 4 carbon atoms obtained from Cracking) (hereinafter, may be abbreviated as “FCC-C4”) can be used as a raw material gas as it is, or from FCC-C4 to phosphorus or the like. It is also possible to use a raw material gas from which the impurities of the above have been removed.

(Molecular oxygen-containing gas)
The molecular oxygen-containing gas is usually a gas containing 10% by volume or more of _{molecular oxygen (O 2).} In this molecular oxygen-containing gas, the concentration of molecular oxygen is preferably 15% by volume or more, more preferably 20% by volume or more.
In addition, the molecular oxygen-containing gas includes molecular oxygen (N ₂ ), argon (Ar), neon (Ne), helium (He), carbon monoxide (CO), and carbon dioxide (CO ₂ ). And may contain any gas such as water (water vapor). The amount of any gas in the molecular oxygen-containing gas is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less when the arbitrary gas is molecular nitrogen. Yes, and when any gas is a gas other than molecular nitrogen, it is usually 10% by volume or less, preferably 1% by volume or less. If the amount of the arbitrary gas is excessive, the required amount of molecular oxygen may not coexist with the raw material gas in the reaction system (inside the reactor 1).
In the first step, air is mentioned as a preferable specific example of the molecular oxygen-containing gas.

(Inert gases)
The inert gases are preferably supplied to the reactor 1 together with the raw material gas and the molecular oxygen-containing gas.
By supplying the inert gas to the reactor 1, the concentration (relative concentration) of the raw material gas and the molecular oxygen is adjusted so that the mixed gas does not form a roar in the reactor 1. can do.
Examples of the inert gas include molecular nitrogen (N ₂ ), argon (Ar) and carbon dioxide (CO ₂ ). These can be used alone or in combination of two or more. Of these, molecular nitrogen is preferable from an economic point of view.

(Water (steam))
Water is preferably supplied to the reactor 1 together with the raw material gas and the molecular oxygen-containing gas.
By supplying water to the reactor 1, the raw material gas and the molecular oxygen are used so that the mixed gas does not form a roar in the reactor 1 as in the case of the above-mentioned inert gases. The concentration (relative concentration) can be adjusted.

(Mixed gas)
Since the mixed gas contains a flammable raw material gas and molecular oxygen, its composition is adjusted so that the concentration of the raw material gas does not fall within the explosive range.
Specifically, each gas constituting the mixed gas (specifically, a raw material gas, a molecular oxygen-containing gas (air), and an inert gas and water (water vapor) used as needed) is used. The gas of the reactor 1 is monitored by a flow meter (not shown) installed in a pipe (specifically, a pipe (not shown) communicating with the pipe 100 and a pipe 112) supplied to the reactor 1. Control the composition of the mixed gas at the inlet. For example, the composition of the new supply gas supplied to the reactor 1 via the pipe 100 is controlled according to the molecular oxygen concentration of the reflux gas supplied to the reactor 1 via the pipe 112.
In the present specification, the “explosion range” refers to a range in which the mixed gas has a composition that ignites in the presence of some ignition source. Here, it is known that when the concentration of flammable gas is lower than a certain value, it does not ignite even if an ignition source exists, and this concentration is called the lower explosive limit. The lower explosive limit is the lower limit of the explosion range. It is also known that when the concentration of flammable gas is higher than a certain value, it does not ignite even if an ignition source exists, and this concentration is called the explosive limit. The explosive limit is the upper limit of the explosive range. These values depend on the concentration of molecular oxygen. Generally, the lower the concentration of molecular oxygen, the closer the two values are, and when the concentration of molecular oxygen reaches a certain value, both values match. .. The concentration of molecular oxygen at this time is called the critical oxygen concentration. Thus, in the mixed gas, if the concentration of molecular oxygen is lower than the critical oxygen concentration, the mixed gas will not ignite regardless of the concentration of the raw material gas.

Specifically, in the mixed gas, the total concentration of 1-butene and 2-butene is 2% by volume or more and 30% by volume in 100% by volume of the mixed gas from the viewpoint of butadiene productivity and suppression of the burden on the metal oxide catalyst. It is preferably 5% by volume or less, more preferably 3% by volume or more and 25% by volume or less, and particularly preferably 5% by volume or more and 20% by volume or less. If the total concentration of 1-butene and 2-butene is too small, the productivity of butadiene may decrease. On the other hand, if the total concentration of 1-butene and 2-butene is excessive, the burden on the metal oxide catalyst may increase.

Further, in the mixed gas, the concentration (relative concentration) of the molecular oxygen with respect to the raw material gas is preferably 50 parts by volume or more and 170 parts by volume or less, more preferably 70 parts by volume or more, with respect to 100 parts by volume of the raw material gas. It is 160 parts by volume or less. When the concentration of molecular oxygen in the mixed gas deviates from the above range, it tends to be difficult to adjust the concentration of molecular oxygen in the gas outlet of the reactor 1 by adjusting the reaction temperature. If the concentration of molecular oxygen in the gas outlet of the reactor 1 cannot be controlled by the reaction temperature, it becomes impossible to suppress the decomposition of the target product and the occurrence of side reactions inside the reactor 1. There is a risk.

Further, in the mixed gas, the concentration (relative concentration) of molecular nitrogen with respect to the raw material gas is preferably 400 parts by volume or more and 1800 parts by volume or less, more preferably 500 parts by volume or more, with respect to 100 parts by volume of the raw material gas. It is 1700 parts by volume or less. The concentration (relative concentration) of water (water vapor) with respect to the raw material gas is preferably 0 parts by volume or more and 900 parts by volume or less, more preferably 80 parts by volume or more and 300 parts by volume with respect to 100 parts by volume of the raw material gas. It is as follows. When the concentration of molecular nitrogen or the concentration of water is excessive, in any case, as the value increases, the concentration of the raw material gas decreases, so that the production efficiency of butadiene tends to decrease. On the other hand, when the concentration of molecular nitrogen or the concentration of water is too low, in any case, the smaller the value, the more the concentration of the raw material gas falls within the explosive range, or the heat removal of the reaction system, which will be described later. Tends to be difficult.

(Metal oxide catalyst)
As the metal oxide catalyst, a composite oxide catalyst containing molybdenum and bismuth is used. As such a composite oxide catalyst, for example, one containing at least molybdenum (Mo), bismuth (Bi) and iron (Fe) can be used, and specific examples thereof include the following composition formula (1). Examples thereof include those containing a composite metal oxide represented by.

Composition formula (1):
Mo _a Bi _{b F c} X _d Y _e Z f O _g

In the above composition formula (1), X is at least one selected from the group consisting of Ni and Co. Y is at least one selected from the group consisting of Li, Na, K, Rb, Cs and Tl. Z is at least one selected from the group consisting of Mg, Ca, Ce, Zn, Cr, Sb, As, B, P and W. a, b, c, d, e, f and g each independently indicate the atomic ratio of each element, and when a is 12, b is 0.1 to 8 and c is 0.1 to 0.1. 20, d is 0 to 20, e is 0 to 4, f is 0 to 2, and g is the number of atoms of the oxygen element required to satisfy the valence of each of the above components. ..

The composite oxide catalyst containing the composite metal oxide represented by the above composition formula (1) has high activity and high selectivity in a method for producing butadiene using an oxidative dehydrogenation reaction, and further has a long life. Excellent stability.

The method for preparing the composite oxide catalyst is not particularly limited, and is an evaporative drying method, a spray-drying method, or oxidation using the raw material of each element related to the composite metal oxide constituting the composite oxide catalyst to be prepared. A known method such as a product mixing method can be adopted.
The raw material of each of the above elements is not particularly limited, and for example, oxides, nitrates, carbonates, ammonium salts, hydroxides, carboxylates, ammonium carboxylates, ammonium halides, and hydrogen acids of the constituent elements. , Alkoxide and the like.

Further, the composite oxide catalyst may be used by supporting it on an inert carrier. Examples of the carrier type include silica, alumina, and silicon carbide.

(Oxygen dehydrogenation reaction)
In the first step, when starting the oxidative dehydrogenation reaction, first, the supply of molecular oxygen-containing gas, inert gas and water (steam) to the reactor 1 is started, and the supply amounts thereof are adjusted. Therefore, the concentration of molecular oxygen at the gas inlet of the reactor 1 is adjusted to be equal to or less than the critical oxygen concentration, and then the supply of the raw material gas is started, and the concentration of the raw material gas at the gas inlet of the reactor 1 is adjusted. It is preferable to increase the supply amount of the raw material gas and the supply amount of the molecular oxygen-containing gas so as to exceed the explosive limit.
Further, when increasing the supply amount of the raw material gas and the molecular oxygen-containing gas, the supply amount of the mixed gas may be kept constant by reducing the supply amount of water (water vapor). By doing so, the gas residence time in the piping and the reactor 1 can be kept constant, and fluctuations in the pressure of the reactor 1 can be suppressed.

The pressure of the reactor 1 (specifically, the pressure at the gas inlet of the reactor 1), that is, the pressure in the first step is preferably 0.1 MPaG or more and 0.4 MPaG or less, more preferably 0.15 MPaG. It is 0.35 MPaG or less, and more preferably 0.2 MPaG or more and 0.3 MPaG or less.
By setting the pressure in the first step within the above range, the reaction efficiency in the oxidative dehydrogenation reaction is improved. When the pressure in the first step is too small, the reaction efficiency in the oxidative dehydrogenation reaction tends to decrease. On the other hand, when the pressure in the first step is excessive, the yield in the oxidative dehydrogenation reaction tends to decrease.

Further, oxide in the dehydrogenation reaction, the gas hourly space velocity obtained by the following equation (1) (GHSV) is preferably at 500h ^-1 or more 5000h ^-1 or less, more preferably 800h ^-1 or more 3000h ^-1 or less, and more preferably not more than 1000h ^-1 or 2500H ^-1.
By setting GHSV in the above range, the reaction efficiency in the oxidative dehydrogenation reaction can be further improved.

Formula (1):
GHSV [h ^-1 ] = atmospheric pressure equivalent gas flow rate [Nm ³ / h] ÷ catalyst layer volume [m ³ ]

In the above mathematical formula (1), the "catalyst layer volume" indicates the volume (apparent volume) of the entire catalyst layer including the voids.

Further, in the oxidative dehydrogenation reaction, the real volume gas spatiotemporal velocity (real volume GHSV) obtained by the following mathematical formula (2) ^{is preferably 500 h -1} or more and 2300 h ^-1 or less, more preferably 600 h ^-1. above 2000h ^-1 or less, and more preferably not more than 700 h ^-1 or more 1500h ^-1.
By setting the actual volume GHSV in the above range, the reaction efficiency in the oxidative dehydrogenation reaction can be further improved.

Formula (2):
Actual volume GHSV [h ^-1 ] = actual gas flow rate [m ³ / h] ÷ catalyst layer volume [m ³ ]

In the above formula (2), the "catalyst layer volume" indicates the volume (apparent volume) of the entire catalyst layer including the voids, as in the above formula (1).

Further, in the oxidative dehydrogenation reaction, since the oxidative dehydrogenation reaction is an exothermic reaction, the temperature of the reaction system rises, and a plurality of types of by-products can be produced. As by-products, unsaturated carbonyl compounds having 3 to 4 carbon atoms such as acrolein, acrylic acid, methacrolein, methacrolein, maleic acid, fumaric acid, maleic anhydride, methyl vinyl ketone, crotonaldehyde and crotonic acid are used. When it is produced and the concentration in the produced gas is increased, various harmful effects occur. Specifically, since the unsaturated carbonyl compound dissolves in an absorption solvent or the like that is circulated in the third step, impurities are accumulated in the absorption solvent or the like, and precipitation of deposits on each member is likely to be induced. ..

Therefore, in the oxidative dehydrogenation reaction, as a method for keeping the concentration of the unsaturated carbonyl compound within a certain range, a method of adjusting the reaction temperature of the oxidative dehydrogenation reaction can be mentioned. Further, by adjusting the reaction temperature, the concentration of molecular oxygen at the gas outlet of the reactor 1 can be kept within a certain range.
Specifically, the reaction temperature is preferably 300 ° C. or higher and 400 ° C. or lower, more preferably 320 ° C. or higher and lower than 380 ° C.
By setting the reaction temperature within the above range, caulking (precipitation of solid carbon) in the metal oxide catalyst can be suppressed, and the concentration of the unsaturated carbonyl compound in the produced gas can be kept within a certain range. It will be possible. Further, the concentration of molecular oxygen at the gas outlet of the reactor 1 can be kept within a certain range.
On the other hand, if the reaction temperature is too low, the conversion rate of n-butene may decrease. On the other hand, when the reaction temperature is excessive, the concentration of the unsaturated carbonyl compound becomes high, and impurities tend to accumulate in an absorbing solvent or the like, or caulking in a metal oxide catalyst tends to occur.

Here, as a preferable specific example of the method for adjusting the reaction temperature, the reactor 1 is appropriately cooled by, for example, removing heat with a heat medium (specifically, dibenzyltoluene, nitrite, etc.). A method of controlling the temperature of the catalyst layer to be constant can be mentioned.

(Produced gas)
The produced gas includes 1,3-butadiene, which is the target product of the oxidative dehydrogenation reaction between the raw material gas and the molecular oxygen-containing gas, as well as a reaction by-product, an unreacted raw material gas, and unreacted molecular oxygen. And gas for concentration adjustment etc. are included. Reaction by-products include carbonyl compounds and heterocyclic compounds. Here, the carbonyl compound includes ketones, aldehydes, and organic acids.
Ketones include methyl vinyl ketone, acetophenone, benzophenone, anthraquinone and fluorenone.
Examples of aldehydes include acetaldehyde, acrolein, methacrolein, crotonaldehyde, benzaldehyde and the like.
Examples of organic acids include maleic acid, fumaric acid, acrylic acid, phthalic acid, benzoic acid, crotonic acid, tetrahydrophthalic acid, isophthalic acid, terephthalic acid, methacrylic acid, phenol and the like.
Moreover, as a heterocyclic compound, furan and the like can be mentioned.

<Second step>
In the second step, the product gas obtained in the first step is cooled. In this second step, the cooling of the generated gas from the first step is performed by the quench tower 2 and the cooling heat exchanger 3 of the present invention.
Specifically, the generated gas from the first step, that is, the generated gas flowing out from the reactor 1, is sent to the quench tower 2 via the pipe 101, cooled in the quench tower 2, and then the pipe. It is supplied to the cooling heat exchanger 3 via 104, and is further cooled in the cooling heat exchanger 3. The gas produced from the first step cooled by the quench tower 2 and the cooling heat exchanger 3 in this way flows out from the cooling heat exchanger 3 to the pipe 105.
By going through this second step, the produced gas from the first step is purified. Specifically, a part of the by-products contained in the produced gas from the first step is removed.

(Quench Tower)
In the quench tower 2, the produced gas is rapidly cooled to a temperature of, for example, about 30 ° C. or higher and 90 ° C. or lower by bringing the cooling medium into countercurrent contact with the generated gas from the first step.
A pipe 101 whose one end is connected to the gas outlet of the reactor 1 is connected to the gas inlet of the quench tower 2, and a pipe 104 is connected to the gas outlet of the quench tower 2. Further, a pipe 102 is connected to an injection head (not shown) of a cooling water supply mechanism (not shown) in the quench tower 2, and a pipe 103 is connected to a cooling water outlet of the quench tower 2.

Further, in the quenching tower 2 in operation, the internal temperature is preferably 10 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower.

Further, the pressure of the quench tower 2 during operation (specifically, the pressure of the gas outlet of the quench tower 2), that is, the pressure of the second step is equal to or less than the pressure of the first step. It is preferable to have.
Specifically, the difference between the pressure in the second step and the pressure in the first step, that is, the value obtained by subtracting the pressure in the second step from the pressure in the first step is preferably 0 MPaG or more and 0.05 MPaG or less. , More preferably 0.01 MPaG or more and 0.04 MPaG or less.
By setting the pressure difference between the first step and the second step within the above range, the quenching tower 2 promotes the condensation and dissolution of the reaction by-products in the product gas produced from the first step in the cooling water. As a result, the concentration of reaction by-products in the product gas flowing out of the quench tower 2 can be further reduced.

Then, in the quench tower 2, a cleaning process of supplying cleaning water to the lowermost gas-liquid contact member (not shown) by spraying is intermittently performed by a cleaning mechanism (not shown).

(Cooling heat exchanger)
As the cooling heat exchanger 3, a heat exchanger 3 capable of cooling the generated gas flowing out from the quench tower 2 to room temperature (10 ° C. or higher and 30 ° C. or lower) is appropriately used.
In the example of this figure, the cooling heat exchanger 3 is connected to the gas inlet with a pipe 104 having one end connected to the gas outlet of the quench tower 2, and the gas outlet is connected to the pipe 105. ing.

Further, the pressure of the cooling heat exchanger 3 during operation (specifically, the pressure of the gas outlet of the cooling heat exchanger 3) is the pressure of the quench tower 2 during operation (gas outlet of the quench tower 2). Pressure) is preferably equal to.

In the cooling product gas flowing out from the cooling heat exchanger 3, that is, the product gas cooled by the second step, the concentration of molecular nitrogen is preferably 60% by volume or more and 94% by volume or less, more preferably. It is 70% by volume or more and 85% by volume or less. The concentration of butadiene is preferably 2% by volume or more and 15% by volume or less, more preferably 3% by volume or more and 10% by volume or less. The concentration of water (water vapor) is preferably 1% by volume or more and 30% by volume or less, and more preferably 1% by volume or more and 3% by volume or less. The concentration of ketones and aldehydes is preferably 0% by volume or more and 0.3% by volume, more preferably 0.05% by volume or more and 0.25% by volume or less.
When the concentration of each component in the produced gas cooled in the second step is within the above range, the efficiency of butadiene purification in the next and subsequent steps can be improved, and the side reaction occurring in the desolubilization step can be suppressed. As a result, the energy consumption in producing butadiene can be further reduced.

<Third step>
In the third step, the produced gas obtained through the second step is separated (coarse separation) into molecular oxygen and inert gases and other gases containing 1,3-butadiene by selective absorption into an absorbing solvent. To do. Here, the "other gas containing 1,3-butadiene" refers to at least butadiene and 1-butene and 2-butene (unreacted 1-butene and 2-butene) absorbed by the absorbing solvent. Indicates the gas contained.
In this third step, the separation of the produced gas through the second step is performed by the absorption tower 4 as shown in FIG. Here, the absorption tower 4 is provided with a gas introduction port for introducing the generated gas that has undergone the second step at the lower part, a solvent introduction port for introducing the absorption solvent at the upper part, and a gas at the bottom of the tower. A solvent outlet is provided to derive an absorption solvent that has absorbed (specifically, other gas containing 1,3-butadiene), and a gas that has not been absorbed by the absorption solvent (specifically, a gas that has not been absorbed by the absorption solvent) is provided at the top of the column. , Molecular oxygen and inert gases) are provided with a gas outlet. A pipe 105 having one end connected to the gas outlet of the heat exchanger 3 is connected to the gas inlet, a pipe 106 is connected to the solvent inlet, and a pipe 113 is connected to the solvent outlet. A pipe 107 is connected to the gas outlet.
More specifically, the third step will be described. The generated gas that has undergone the second step, that is, the generated gas that has flowed out of the heat exchanger 3, is sent to the absorption tower 4 via the pipe 105, and is absorbed in synchronization with the feed. The absorption solvent is supplied to the tower 4 via the pipe 106. In this way, the absorbing solvent is countercurrently contacted with the produced gas that has undergone the second step, and the other gas containing 1,3-butadiene in the produced gas that has undergone the second step is selectively absorbed by the absorbing solvent. The other gas containing 1,3-butadiene is roughly separated from the molecular oxygen and the inert gas. Then, the absorption solvent that absorbed the other gas containing 1,3-butadiene flows out from the absorption tower 4 to the pipe 113, while the molecular oxygen and the inert gas that were not absorbed by the absorption solvent are absorbed. It flows out from the tower 4 to the pipe 107.

In the operating absorption tower 4, the temperature inside the absorption tower 4 is not particularly limited, but as the temperature inside the absorption tower 4 increases, molecular oxygen and inert gases are less likely to be absorbed by the absorption solvent. On the other hand, as the temperature inside the absorption tower 4 decreases, the absorption efficiency of hydrocarbons such as butadiene (other gases containing 1,3-butadiene) into the absorption solvent increases, so that the productivity of butadiene increases. In consideration of the above, it is preferably 0 ° C. or higher and 60 ° C. or lower, and more preferably 10 ° C. or higher and 50 ° C. or lower.

Further, the pressure of the absorption tower 4 during operation (specifically, the pressure of the gas outlet of the absorption tower 4), that is, the pressure of the third step is equal to or less than the pressure of the second step. It is preferable to have.
Specifically, the difference between the pressure in the third step and the pressure in the second step, that is, the value obtained by subtracting the pressure in the third step from the pressure in the second step is preferably 0 MPaG or more and 0.05 MPaG or less. , More preferably 0.01 MPaG or more and 0.04 MPaG or less.
By setting the pressure difference between the second step and the third step within the above range, the absorption of butadiene (other gas containing 1,3-butadiene) into the absorption solvent in the absorption tower 4 can be promoted, and the absorption thereof can be promoted. As a result, the amount of the absorbing solvent used can be reduced, and the energy consumption can be reduced.

(Absorption solvent)
Examples of the absorption solvent include those containing an organic solvent as a main component. Here, "having an organic solvent as a main component" means that the content ratio of the organic solvent in the absorption solvent is 50% by mass or more.
Examples of the organic solvent constituting the absorption solvent include aromatic compounds such as toluene, xylene and benzene, amide compounds such as dimethylformamide and N-methyl-2-pyrrolidone, sulfur compounds such as dimethyl sulfoxide and sulfolane, acetonitrile and butyronitrile and the like. Nitrile compounds, ketone compounds such as cyclohexanone and acetophenone, and the like.

The amount of the absorbing solvent used (supplied amount) is not particularly limited, but is 10% by mass or more with respect to the total flow rate (mass flow rate) of butadiene, 1-butene and 2-butene in the produced gas that has undergone the second step. It is preferably 100 times by mass or less, and more preferably 17 times by mass or more and 35 times by mass or less.
By setting the amount of the absorbing solvent used in the above range, the absorption efficiency of other gases containing 1,3-butadiene can be improved.
On the other hand, when the amount of the absorbing solvent used is excessive, the amount of energy consumed for purification for circulating use of the absorbing solvent tends to increase. Further, when the amount of the absorbing solvent used is too small, the absorption efficiency of other gases containing 1,3-butadiene tends to decrease.

The temperature of the absorbing solvent (temperature at the solvent inlet) is preferably 0 ° C. or higher and 60 ° C. or lower, and more preferably 0 ° C. or higher and 40 ° C. or lower.
By setting the temperature of the absorption solvent in the above range, the absorption efficiency of other gases containing 1,3-butadiene can be further improved.

<Circulation process>
In the circulation step, the molecular oxygen and the inert gas obtained in the third step are fed to the first step as reflux gas. In this circulation step, the molecular oxygen and the inert gas from the third step are treated by the solvent recovery column 5 and the compressor 6.
Specifically, the molecular oxygen and the inert gas from the third step, that is, the molecular oxygen and the inert gas flowing out from the absorption tower 4, are sent to the solvent recovery tower 5 via the pipe 107. After the solvent is removed, the gas is fed to the compressor 6 via the pipe 110, and the pressure is adjusted if necessary. The molecular oxygen and the inert gas from the third step, which have been subjected to the solvent removal treatment and the pressure adjustment treatment in this manner, flow out from the compressor 6 toward the reaction tower 1 into the pipe 112.
In the example of this figure, the molecular oxygen and the inert gas discharged from the solvent recovery tower 5 are partly transferred to the pipe 110 in the process of flowing through the pipe 110. It is discarded via the communicating pipe 111. In this way, the supply amount of the reflux gas for the first step can be adjusted by providing the pipe 111 for discarding a part of the molecular oxygen and the inert gas flowing out from the solvent recovery tower 5. it can.

(Solvent recovery tower)
The solvent recovery tower 5 is configured to remove the molecular oxygen and the inert gas from the solvent by washing the molecular oxygen and the inert gas from the third step with water or a solvent. A gas introduction port for introducing molecular oxygen and inert gases from the third step is provided in the central portion of the solvent recovery tower 5. A cleaning liquid inlet for introducing water or solvent is provided in the upper part of the solvent recovery tower 5. A pipe 107 whose one end is connected to the gas outlet of the absorption tower 4 is connected to the gas introduction port, and a pipe 108 is connected to the cleaning liquid introduction port. Further, the solvent recovery tower 5 is provided at the top of the tower with a gas outlet for leading out molecular oxygen and inert gases washed with water or a solvent. Further, the bottom of the solvent recovery tower 5 is provided with a cleaning liquid outlet for leading out the water or solvent used for cleaning the molecular oxygen and the inert gas from the third step. A pipe 110 is connected to the gas outlet, and a pipe 109 is connected to the cleaning liquid outlet.

In the solvent recovery tower 5, the absorption solvent contained in the molecular oxygen and the inert gas from the third step is removed, and the removed absorption solvent is used for cleaning together with the water or solvent used for cleaning. It flows out from the liquid outlet to the pipe 109 and is collected through the pipe 109. Further, the molecular oxygen and the inert gas from the third step, which have been subjected to the solvent removal treatment, flow out to the pipe 110 from the gas outlet of the solvent recovery tower 5.

Further, in the solvent recovery tower 5 during operation, the temperature inside the solvent recovery tower 5 is not particularly limited, but is preferably 0 ° C. or higher and 80 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower. ..

(Compressor)
As the compressor 6, a compressor capable of boosting the molecular oxygen and the inert gas from the solvent recovery column 5 as necessary to obtain the pressure required in the first step is appropriately used.
In the example of this figure, the compressor 6 is connected to a gas inlet with a pipe 110 having one end connected to a gas outlet of the solvent recovery tower 5, and a pipe 112 is connected to the gas outlet. ..

In the compressor 6, when the pressure in the third step is less than the pressure in the first step, the pressure difference is increased according to the pressure difference between the third step and the first step.
When the boosting is performed in the compressor 6, the boosting is usually small, so that the electric energy consumption of the compressor remains small.

The concentration of molecular nitrogen in the molecular oxygen and the inert gas discharged from the compressor 6, that is, the reflux gas is preferably 87% by volume or more and 97% by volume or less, and more preferably 90% by volume or more and 95% by volume or more. It is less than or equal to the volume. The concentration of molecular oxygen is preferably 1% by volume or more and 6% by volume or less, more preferably 2% by volume or more and 5% by volume or less.

<Demelting process>
In the desolubilization step, the absorption solvent that has absorbed other gas containing 1,3-butadiene obtained in the third step is subjected to solvent separation treatment. That is, by separating the absorption solvent from the absorption solvent from the third step, a gas flow of another gas containing 1,3-butadiene, that is, a gas containing 1,3-butadiene is obtained. In this thawing step, as shown in FIG. 2, the thawing tower 7 separates the other gas containing 1,3-butadiene from the absorbing solvent.
Specifically, the absorption solvent from the third step, that is, the absorption solvent that has absorbed the other gas containing 1,3-butadiene that has flowed out from the absorption tower 4, is sent to the demelting tower 7 via the pipe 113. It is fed and solvent-separated. Then, in the demelting tower 7, the other gas containing 1,3-butadiene and the absorbing solvent are distilled and separated.

(Demelting tower)
The demelting tower 7 is configured to perform solvent separation treatment by distilling and separating the absorbing solvent from the third step. A solvent introduction port for introducing the absorption solvent from the third step is provided in the central portion of the demelting tower 7. Further, a gas outlet for deriving a gas containing 1,3-butadiene separated from the absorption solvent from the third step is provided at the top of the demelting column 7. The bottom of the demelting column 7 is provided with a solvent outlet for deriving the absorbing solvent separated from the absorbing solvent from the third step. A pipe 113 having one end connected to the solvent outlet of the absorption tower 4 is connected to the solvent introduction port, a pipe 115 is connected to the gas outlet, and a pipe 114 is connected to the solvent outlet. Has been done.

In the demelting tower 7, the gas containing 1,3-butadiene and the absorption solvent separated from the absorption solvent from the third step are piped from the gas outlet, respectively. It flows out to 115, and the absorbing solvent flows out from the solvent outlet to the pipe 114.

The pressure inside the demelting tower 7 is not particularly limited, but is preferably 0.03 MPaG or more and 1.0 MPaG or less, and more preferably 0.2 MPaG or more and 0.6 MPaG or less.

Further, in the thawing tower 7 in operation, the temperature of the bottom of the thawing tower 7 is preferably 80 ° C. or higher and 1900 ° C. or lower, and more preferably 100 ° C. or higher and 180 ° C. or lower.

According to such a method for producing 1,3-butadiene, the second stage of the quench tower 2 cools the generated gas by performing a cleaning process of supplying cleaning water to the lowermost gas-liquid contact member. Since the process can be carried out stably over a long period of time, 1,3-butadiene can be produced with high time efficiency.

Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

[Example 1]
According to the flow chart of FIG. 2, 1,3-butadiene is obtained from the raw material gas containing 1-butene and 2-butene by going through the following first step, second step, third step, desolubilization step and circulation step. , 500 hours continuously.
Further, as the raw material gas, a gas containing 1-butene and 2-butene and having a ratio of 2-butene to 87% by volume with respect to a total of 100% by volume of 1-butene and 2-butene was used.

(First step)
Reactor 1 (inner diameter 21.2 mm, outer diameter 25.4 mm) filled with a metal oxide catalyst so that the catalyst layer length is 4000 mm is filled with a volume ratio (1-butene and 2-butene / O ₂ / N _2). A mixed gas having a / H ₂ O) of 1 / 1.5 / 16.3 / 1.2 is ^{supplied at a GHSV of 2000 h -1} , and a raw material gas and molecular oxygen are supplied depending on the conditions of a reaction temperature of 320 to 350 ° C. A produced gas containing 1,3-butadiene was obtained by subjecting the contained gas to an oxidative dehydrogenation reaction. The pressure in this first step, that is, the pressure at the gas inlet of the reactor 1, was 0.1 MPaG. Here, the actual volume GHSV of the mixed gas was 2150 h ^-1 .
In this first step, as the metal oxide catalyst, an oxide represented by the composition formula Mo ₁₂ Bi ₅ Fe _0.5 Ni ₂ Co ₃ K _0.1 Cs _0.1 Sb _0.2 is added to spherical silica at a ratio of 20% of the total catalyst volume. The one supported by was used.
The mixed gas is a mixture of a raw material gas and a reflux gas (molecular oxygen and inert gases), and if necessary, air as a molecular oxygen-containing gas, molecular nitrogen as an inert gas, and the like. The composition is adjusted by further mixing water (steam).

(Second step)
As the quench tower 2, the one having the following specifications was used.
Overall length of tower body 20: 780 cm
Inner diameter of tower body 20: 15.24 cm
Gas-liquid contact member 30: Irregular filling (cascade mini ring)
Number of gas-liquid contact members 30: 5
Ratio (L / D) of spray distance L and spray width D by the injection head 41: 1.6

The generated gas flowing out of the reactor 1 was brought into countercurrent contact with the cooling water in the quench tower 2 to be rapidly cooled, cooled to 76 ° C., and then cooled to 30 ° C. in the cooling heat exchanger 3. The amount of cooling water supplied is 1 L / min. The pressure in the second step, that is, the pressure at the gas outlet of the quench tower 2, was 0.1 MPaG, and the pressure at the gas outlet of the cooling heat exchanger 3 was also 0.1 MPaG.
Then, in the quench tower 2, the cleaning mechanism was driven under the following conditions every 8 hours after the cooling treatment of the produced gas.
Amount of wash water supplied from the injection head 41: 0.002 L / min
Supply amount of wash water per unit area of the surface of the gas-liquid contact member 30: 55 L / m ²
Amount of cleaning water used for one cleaning treatment of the gas-liquid contact member 30: 1 L

(Third step)
The generated gas flowing out from the heat exchanger 3 (hereinafter, also referred to as “cooling generated gas”) is collected from the absorption tower 4 (outer diameter 152.4 mm, height 7800 mm, material SUS304) in which a regular filling is arranged. It was supplied from the lower gas inlet, and an absorption solvent containing 95% by mass or more of toluene was supplied at 10 ° C. from the upper solvent inlet of the absorption tower 4. The amount of the absorbing solvent supplied was 33 times by mass with respect to the total flow rate (mass flow rate) of butadiene, 1-butene and 2-butene in the cooling product gas. The pressure in this third step, that is, the pressure at the gas outlet of the absorption tower 4, was 0.1 MPaG.

(Circulation process)
The gas flowing out from the absorption tower 4 was washed with water or a solvent in the solvent recovery tower 5 to remove a small amount of the absorption solvent contained in the gas. The gas from which the absorbing solvent was removed in this manner flowed out from the solvent recovery tower 5, a part of the gas was discarded, and most of the remaining gas was sent to the compressor 6. Then, in the compressor 6, the gas from the solvent recovery tower 5 was boosted by the pressure adjusting process. The absorbing solvent was removed in this way, and the pressurized gas flowed out of the compressor 6 and returned to the reactor 1.

(Demelting process)
The liquid flowing out from the absorption tower 4 was supplied to the thawing tower 7, and the gas flowing out from the thawing tower main body was cooled by a condenser to obtain a gas containing 1,3-butadiene. In addition, an effluent, that is, an absorption solvent (hereinafter, also referred to as “circulation absorption solvent”), in which a part of the effluent from the main body of the demelting tower was heated in a reboiler was obtained. In this way, the gas containing 1,3-butadiene and the circulating absorption solvent were distilled and separated in the demelting tower 7.

[Comparative Example 1]
In the second step, 1,3-butadiene was added from the raw material gas containing 1-butene and 2-butene for 127.5 hours in the same manner as in Example 1 except that the cleaning mechanism of the quench tower 2 was not driven. Manufactured continuously.

When the gas-liquid contact member 30 at the bottom of the quench tower 2 was examined after the production of 1,3-butadiene was completed in Example 1 and Comparative Example 1, a small amount of solid components adhered in Example 1. On the other hand, in Comparative Example 1, it was confirmed that a large amount of solid components were attached.
Moreover, when the drainage from the quench tower 2 was examined, a large amount of solid components was observed in Example 1, and a small amount of solid components was observed in Comparative Example 1.
From the above, according to the first embodiment, it is prevented or suppressed that a large amount of solid components precipitated by cooling adhere to the gas-liquid contact member 30, and as a result, the cooling of the produced gas is stabilized for a long period of time. It is understood that it is possible to carry out.

1 Reactor 2 Quenching tower 3 Heat exchanger 4 Absorption tower 5 Solvent recovery tower 6 Compressor 7 Demelting tower 20 Tower body 21 Peripheral wall 22 Tower top 23 Tower bottom 25 Gas inlet 26 Gas outlet 27 Cooling water outlet 30 Gas-liquid contact member 35 Cooling water supply mechanism 36 Spray head 40 Cleaning mechanism 41 Injection head 100-116 Piping

Claims (6)

In a quench tower, which has a gas-liquid contact member inside and the gas to be cooled supplied from the lower part of the tower is cooled by the cooling water supplied from the upper part of the tower.
The gas to be cooled precipitates a solid component adhering to the gas-liquid contact member when cooled.
A quench tower characterized by having a cleaning mechanism for supplying cleaning water to the gas-liquid contact member. A plurality of the gas-liquid contact members are arranged in the tower so as to be vertically overlapped with each other via a space, and the cleaning mechanism supplies cleaning water to the lowermost gas-liquid contact member from above. The quench tower according to claim 1, wherein the quench tower is characterized in that. The quench tower according to claim 1 or 2, wherein the cleaning mechanism has an injection head that injects cleaning water onto the gas-liquid contact member. The quench tower according to any one of claims 1 to 3, wherein the cleaning mechanism is driven when specified. In a quench tower provided with a gas-liquid contact member, a gas cooling method in which the gas to be cooled supplied from the lower part of the tower is cooled by the cooling water supplied from the upper part of the tower.
The gas to be cooled precipitates a solid component adhering to the gas-liquid contact member when cooled.
A gas cooling method comprising supplying washing water to the gas-liquid contact member. The gas cooling method according to claim 5, wherein the gas-liquid contact member is supplied with washing water by spraying it.

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