GB2307191A

GB2307191A - A multistage bubble column with plates having non-uniformly distributed perforations

Info

Publication number: GB2307191A
Application number: GB9623644A
Authority: GB
Inventors: Korekazu Ueyama; Takanori Ito; Nobuhiro Kawara; Hideo Narahara; Susumu Tsukada
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 1995-11-15
Filing date: 1996-11-13
Publication date: 1997-05-21
Anticipated expiration: 2016-11-13
Also published as: DE19647126A1; GB2307191B; JPH09136029A; GB9623644D0; JP3214320B2; FR2740990B1; FR2740990A1

Description

2307191 MULTISTAGE BUBBLE COLUMN WITH PERFORATED PLATES is The present

invention relates to a multistage bubble column. More particularly, it relates to a multistage bubble column wherein perforated plates having non-uniformly distributed perforations are incorporated inside.

The multi-stage bubble column is a device comprising a cell column having perforated plates incorporated inside, in which gas is fed into the lower part and a liquid, or a liquid and a solid, is supplied in parallel or counter flow, thereby providing continuous mixing in a gas-liquid-solid multiphase system.

For example, in Fig. 6.1 (C) of page 264 and page 266 of "Industrial Reaction Device" (published on February 25, 1984, Baifukan), there is described that a multistage cell column having multistage perforated plates incorporated in a cell column is used for a liquid phase oxidizing reaction of olefin where secondary reactions successively occur or for a continuous operation of a microbial reaction. Perforated plates incorporated in a conventional multistage cell column were those wherein perforations are uniformally distributed over the whole perforated plate, as shown in Fig. 6 of the accompanying drawings.

However, the conventional multistage cell column wherein perforated plates having uniformally distributed perforations are incorporated had a problem that back-mixing (e.g. a liquid or the liquid and a solid of the upper stage flow backward from perforations of the perforated plate to the lower stage, thereby.

is mixing a fluid of the upper stage with that of the lower stage) is liable to arise between each stace of the gas-liquid or gas-liquid-solid multiphase system and, therefore, reaction efficiency is not good.

The present inventors have intensively studied in order to solve the above problems and to provide a multistage bubble column having good reaction ef f iciency. As a result, it has been f ound that, when the perforations of the perforated plate are ununiformly distributed and the ratio of the whole pore area to the cell column section area of each perforated plate is not more than 15 %, the back mixing is inhibited and the mixing ef f iciency and reaction efficiency are remarkably improved. Thus, the present invention has been accomplished.

That is, the present invention provides a multistage bubble column having three or more perforated plates incorporated therein, wherein each perforated plate has nonuniformly distributed perforations and is placed in contact with a column inside wall and the ratio of the total pore area to the cell column sectional area of each perforated plate is 15% or less.

The present invention is further described hereinafter by way of example and with reference to the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional view illustrating a multistage bubble column.

Fig. 2 is a top view illustrating one embodiment of a perforated plate used in the multistage bubble column of the present invention.

Fig. 3 is a top view illustrating another embodiment of a perforated plate used in the multistage bubble column of the present invention.

Fig. 4 is a top view illustrating still another embodiment of a perforated plate used in the multistage bubble column of the present invention.

Fig. 5 is a top view illustrating a further embodiment of a perforated plate used in the multistage bubble column of the present invention.

Fig. 6 is a top view illustrating a perforated plate used in a conventional multistage bubble column.

Fig. 7 is a top view illustrating a still further embodiment of a perforated plate used in the multistage bubble column of thfpresent invention.

Explanation of Symbols 1: Gas inlet 2: Liquid inlet 3: Perforated plate 4: Liquid phase outlet 5: Gas phase outlet 6: Multistage bubble column The gas-liquid or gas-liquid-solid multiphase system to which the cell column of the present invention is applied is a system containing at least one liquid or at least one liquid and at least one solid, but it may also be a gas-liquid two phase system comprising two or more liquids and at least one gas, and it may also be a gas-liquid-solid three phase system comprising one or more gases, one or more liquids and one or more solids.

In the present invention, it is not necessarily required that the distances between the respective perforated plates are the same. When the gas and liquid are fed in parallel flow in a successive reaction such as liquid phase oxidizing reaction of olefin, the distance between the respective perforated plates at the cell column lower part may be relatively large and, on the other hand, the distance between the respective perforated plates at the cell column upper part inay be relatively small. However, it is normally preferred that the distances between the respective perforated plates are the same.

It is not necessarily required that the diameter and shape.

of all the perforations are the same. For examples circular perforations and square perforations, which differ in diameter, mav be simultaneously present. A diameter (average diameter) of the Derforations is normally about from 0.5 to 40 mm.

A ratio of the total pore area of each perforated plate to a cell column sectional area is 15% at most, preferably 10% at most, particularly 5% at most, in view of the reaction ef f iciency. it is necess ary that the perforated plate is placed in contact with the column inside wall. That is, it is required that the inner diameter of the column wall and the diameter of the perforated plate are almost the same and, at the same time, the perforations of each perforated plate are non-uniformly distributed. The term "non- uniformly distributed" means that the perforations are present over the whole perforated plate but irregularly or that the perforations are uniformly distributed but not over the whole perforated plate.

AS the perforated plate satisfying the former condition, for example, there is a perforated plate shown in Fig. 4. As the perforated plate satisfying the latter condition, for example. there are perforated plates shown in Pigs 24,.3, 5 and 7.

These perforated plates can be produced, for example, by drilling or punching perforations or closing a part of holes of a ready-made perforated plate wherein perforations are uniformly distributed, using bolts and nuts.

When the perforations are partially present at the peripheral part of the circle as shown in Fig. 2, the perforated plate is preferably produced so that a ratio of the region where the perforations are partially present to the sectional area of the cell column is in the range of from 35 to 90%. When the perforations are partially present at the centre part of the circle as shown in Fig. 3 or 5, the perforated plate is preferably produced so that a ratio of the region where the perforations are partially present to the sectional area of the cell column is in the range from 10 to 65%.

In order to produce a perforated plate with perforations irregularly present over the whole perforated plate as shown in Fig. 4, several perforations are formed by cutting of f a lot of plates having a suitable shape (e.g. elliptic or square) and then these plates may be fit in the circle wherein the plate having the suitable shape was cut off.

As shown in Fig. 7, in the perforated plate whose perf orations are arranged in fan-shaped areas, it is preferably produced so that a ratio of the region where the perforations are partially present to the sectional area of the cell column is about 50%.

In the multistage bubble column of the present invention, the perforated plates having the same or different pore distribution may be used in combination.

Examples of the preferred embodiment of the multistage bubble column of the present invention include those wherein some or all positions of perforations of adjacent perforated plates are different when incorporating perforated plates having non-uniformly distributed perforations. Accordingly, when using adjacent perforated plates having the same pore distribution, it is preferred to incorporate the perforated plates by shifting them by an angle to each other. Examples of the particularly preferred embodiment include those wherein adjacent perforated plates having different pore distributions are used so that some or all perforations of adjacent perforated plates are different.

As the embodiment using the perforated plates having the different pore distributions, for example, there is a multistage bubble column wherein perforated plates whose perforations are present only at the center part of the cell column are used as the upper and lower of three perforated plates, which are adjacent each other, and a perforated plate whose perforations are present only at the peripheral part of the cell column is used as the centre perforated plate, thereby making it possible that the gas phase passed through the perforated plate of the lower part causes a deviated flow at the peripheral part of the cell column on passing through the centre perforated plate and the deviated flow of this gas phase causes a deviated flow at the centre part of the cell column on passing through the upper perforated plate. Alternatively, perforated plates whose perforations are present only at the peripheral part of the cell column are used as the upper and lower perforated plates and a perforated plate whose perforations are present only at the centre part of the cell column is used as the centre perforated plate, thereby making it possible that the gas phase passed through the perforated plate at the lower part causes a deviated flow at the center part of the cell column on passing through the perforated plate at the center part and the deviated flow of this gas phase causes a deviated flow at the peripheral part of the cell column on passing through the perforated plate of the upper part.

In this case, a particularly preferred one is a multistage bubble column wherein a combination of the perforated plates as shown in Fig. 2 and Fig. 3 (or Fig. 5) is used so that all positions of perforations of two adjacent perforated plates are different.

As another embodiment using a combination of the perforated plates having different pore distributions, for example, there J s a multistage bubble column wherein three kinds of the perforated plates as shown in Pigs 2, 3 and 4 are incorporated. Specific examples thereof include those wherein the perforated plates of Fig. 2, 3 and 4 are respectively used as the upper, center and lower of three pore plates which are adjacent each other, and those wherein the perforated plates of Fig. 3, 4 and 2 are respectively used as the upper, centre and lower plates.

on the other hand, as the embodiment using a combination of the perforated plates having the same pore distribution, for example, there is a multistage bubble column wherein the perforated plates shown in Fig. 7 are used with adjacent plates relatively rotated by about 45 degrees. Thus the positions of perforations of the perforated plates of the upper part andlor lower part and those of the perforated plate of the centre part do not overlap each other, thereby making it possible that the gas phase passed through the perforated plate at the lower part shifts by 45 degrees to cause a deviated flow on passing through the perforated plate at the centre part and the deviated flow of this gas phase shifts again by 45 degrees to cause a deviated flow on passing through the perforated plate of the upper part.

When the system containing the gas and liquid or liquid and solid are continuously mixed or reacted using the multistage bubble column of the present invention, a feeding velocity of the gas is no rmally from 0.3 to 30 cm/second and a feeding velocity of the liquid is from 0. 02 to 1 em/second in case of the parallelflow (superficial velocity in a column in both cases).

When the reaction or mixing is carried out using the multistage bubble column of the present invention, it is preferred to adjust a linear gas velocity through the holes of perforated plated plates to less than 4 m/second, particularly less than 3.5 mlsecond. When the pore diameters of all perforated plates are the same and the total pore areas of all the plates are the same, similarly, it is more preferred to adjust the linear velocity of the gas phase and liquid phase within the cell column so as to satisfy the following expression:

ReLd/ReGd > 0.1 wherein ReLd is wLd. d. a L/ 77 L, and ReGd is wGd - d - a G/77 G.

In the expression, ReLd and ReGd are Reynolds numbers of the liquid phase and the gas phase respectively in perforations of a perforated plate, wLd is the linear velocity of the liquid phase passing through perforations of a perforated plate, wGd is a linear velocity of a gas phase in perforations of a perforated plate, d is a pore diameter of a Derf orated plate, a L is a density of a liquid phase, a G is a density of a gas phase, 77 L is a viscosity of a liquid phase and 77 G is a viscosity of a gas phase.

A thickness of the perforated plate may be a thickness enough to obtain a sufficient strength of the multistage bubble column, and a distance between the perforated plates is normally about from 200 to 5000 mm.

A material of the perforated plateis appropriately selected according to the kind of the reaction material to which the multistage bubble column of the present invention is applied, and a corrosion-resistant material is normally used.

Examples of the reaction to which the multistage bubble column of the present invention is applied include reactions of the gas-liquid twophase system between the gas and liquid, such as air oxidation of olef in (e.g. reaction for producing ethylene oxide or acetaldehyde from ethylene, etc.), air oxidation of aldehyde (e.g. reaction for producing acetic acid from acetaldehyde, etc.), air oxidation of aromatic hydrocarbon (e.g. oxidation reaction of xylene, cumene,. etc.),, alkylation of phenols (e.g. butylation reaction of phenol, etc.) and wet oxidation of waste water; and reactions of the gas- liquid-solid multiphase system using the gas, liquid and solid, such as liauefication reaction of coal (e.g. reaction for further hydrocracking a liquefied oil obtained by decomposing the coal, using a solid catalyst, etc.), polymerization reaction of olef in (e.g. reaction for obtaining polyethylene using a low-pressure process. etc.), reaction of oxidizing cyclohexane intc cyclohexanone, hydrogenation reaction of hydrocarbon (e. g. reaction for producing cyclohexane from benzene, etc.) and reaction for waste water disposal treatment.

The following Examples further illustrate the present invention in detail.

Example 1

A multistage bubble column (diameter: lm 05, each distance between perforated plates: 509 mm) shown in Fig. 1 was arranged with perforated plates shown in Fig. 2, and air and water were continuously fed from a gas inlet and a licTuid inlet provided at the lower part of the column so that a superficial velocity of them became 2.12 cm/second and 0.0637 cm/second, respectively. At the same time, aqueous 27% sodium hydroxide was continuously fed from - 10 the side wall center part of the second stage (region partitioned by the second and third perforated plates from the bottom) Samples were taken with time from sampling taps, which are opposite to the feeding inlet f or sodium hydroxide, provided at the side wall center parts of the first stage (region partitioned by the first and second perforated plates from the bottom) and second stage, respectively, and the concentration of sodium hydroxide was measured. A back-f low ratio a after the concentration of sodium hydroxide reached a steady state was calculated according to the following equation and the resulting back flow ratio a is shown in Table 1 (a indicates the fact that it becomes more dif f icult to cause the back mixing as the value becomes smaller).

a = [Concentration of sodium hydroxide of the first stage]/[ concentration of sodium hydroxide of the second stage concentration of sodium hydroxide of the first stage] <Table l> sample No. Compar- Example Example Example Example Example ative 1 2 3 4 5 Example

1 Pore diameter, =m 10 10 io 10 10 10 Opening % 1 1.0 1.0 1.0 1 o WO 1.0 1.0 Perfore Under- rig. 6 Fig. 2 Fig. 3 Fig. 4 rig. 3 Fig. 5 ted most plate part Canter rig. 6 Fig. 2 Fig. 3 Fig. 4 Fig. 2 Fig. 2 2 part UpperFig. 6 Fig. 2 Fig. 3 rig. 4 Fig. 3 Fig. 5 most part Back flow ratio 0.87 F 0.41 0.38 0.17 0.15 a 1: Ratio of whole pore area to cell column sectional area 2: The distribution of perforations of each perforated plate is as described in each figure, and three perforated plates which are adjacent each other in Examples 1 to 3 are arranged so that the positions of all perforations of holes are the same. The perforated plate of Fig. 6 has a center distance of perforations (pitch) of 26 mm.

ExamDles 2 to 5 and Comparative Example 1 Tests were carried out, according to the same manner as that described in Example 1 except for changing to the perforated plate shown in Table 1. In all Examples 1 to 5, no formation of gas cushion was observed. Even if the feeding velocity of air was changed to 3.2 cm/second (superficial velocity in a column), no formation of gas cushion was observed.

When the distance between the perforated plates is the same and the number of the stages of the cell column is 5, the number of the stages in an ideal system where no back mixing arises and a complete mixing is conducted at each stage was determined by each back f low ratio a obtained in Comparative Example 1, Example 1 and Example 2. As a result, it was 2.4 in case of a conventional cell column wherein the perforated plate of Fig. 6 is incorporated. it was 2.8 in case of the cell column of the present invention wherein the perforated plate of Fig. 2 is incorporated. it was 3.1 in case of the cell column of the present invention wherein the perforated plate of Fig. 3 is incorporated. As is apparent from this fact, the multistage bubble column of the present invention, e.g. cell columns used in Examples 1 and 2, is superior in number of the stages in the ideal system (in other words, mixing efficiency) by about 20 or 30% to the conventional cell column used in Comparative Example 1. Regarding another multistage bubble column of the present invention, e.g. cell column wherein the perforated plate of Fig. 5 is incorporated as the perforated plate of the lowermost or upphrmost part, as is shown in Example 5, and the perforated plate of rig. 2 is incorporated as the perforated plate of the center part, the back flow ratio a is remarkably small in comparison with the conventional cell column. According to the same manner as that described above, the number of the stages in the ideal system was determined. As a result, it was 4.1. Therefore, it is apparent that the cell column of this Example is remarkably superior in number of the stages.

The multistage bubble column of the present invention is suDerior in reaction efficiency to a conventional multistage cell column.

Accordingly, when using the multistage bubble column of the present invention, it is possible to efficiently conduct desulf urization by using a waste gas containing sulf ur oxides such as S03 (e.g. flue gas, etc.) as the gas and feeding an aqueous dilute sodium hydroxide solution as the liquid in the counter-crrent flow to the waste gas. Purthermore, a corresponding hydroperoxide can be efficiently obtained by using air as the gas and f eeding an aqueous sodium hydroxide solution and isopropylbenzene (or isopropyltoluene) as the liquid in the

Claims

CLAIMS is 1. A multistage bubble column having three or more perforated

plates incorporated therein, wherein each perforated plate has non-uniformly distributed perforations and is placed in contact with a column inside wall and the ratio of total pore area of each perforated plate to the cell column sectional area is 15% at most.
2. A multistage bubble column according to claim 1, wherein adjacent perforated plates differ in their distribution of perforations.
3. A multistage bubble column according to claim 1, wherein adjacent perforated plates have the same distribution of perforations.
4. A multistage bubble column according to any one of claims 1 to 3, wherein some or all of positions of perforations of adjacent perforated plates are different.
5. A multistage bubble column according to any one of claims 1 to 4, wherein the ratio of the total whole pore area of each perforated plate to the cell column sectional area is 5% at most.
6. A multistage bubble column according to any one of claims 1 to 5, wherein the distances between adjacent perforated plates are the same.
7. A multistage bubble column constructed and arranged to operate substantially as hereinbefore described with reference to Figures 1 to 5 and 7 to the accompanying drawings.