FR2740990A1 - MULTI-STAGE SPOKE COLUMN, WITH PERFORATED PLATES - Google Patents

Abstract

The present invention relates to a multistage bubble column, comprising three or more perforated plates (3) placed in contact with the column inner wall (6), which have perforations distributed non-uniformly. The ratio of the total void area of each perforated plate to the cross-sectional area of the cell column is 15% or less, and which has a good mixing or reaction efficiency.

Description

The present invention relates to a multiple sparging column

  floors. More particularly, it relates to a multistage bubbling column in which perforated plates having non-uniformly distributed perforations are arranged therein.

  A multistage bubbling column is a device comprising a cellular column incorporating perforated plates in the lower part of which a gas is supplied, and a liquid, or a liquid and a solid, are applied in a parallel flow. lele or countercurrent, so as to mix continuously in a system with several gas-liquid or gas-liquid-solid phases. For example, in Figure 6.1 (C) on page 264 and page 266 of "Industrial Reaction Device" (published February 25, 1984, Baifukan), a multi-stage cell column is described having perforated plates forming several stages incorporated in a cell column which is used for an olefin oxidation reaction in the liquid phase where a secondary reaction occurs successively, or for a continuous microbial reaction operation. The perforated plates incorporated into the usual multi-stage cell column were plates in which the perforations were uniformly distributed over the entire perforated plate, as shown in Figure 6.

  However, the usual multi-stage cell column into which perforated plates are incorporated having uniformly distributed perforations has the disadvantage that a back-mixing (for example a liquid, or the liquid and a solid of the upper stage, flows backwards from the perforations of the perforated plate towards the lower stage

  laughing, thus mixing the fluid of the upper stage with that of the lower stage) is likely to exist between each stage of the gas-liquid or gas-liquid-solid multiphase system and therefore the yield of 5 reaction is not good. The present inventors have intensively studied the solution to the above problem and the possibility of providing a multistage bubbling column with good reaction yield. As a result, it has been found that when the perforations of the perforated plate are distributed in a non-uniform manner and that the ratio of the total area of voids to the cross-sectional area of the cell column, for each perforated plate , is less than or equal to 15%, back mixing is prevented and the yield of the mixture and the yield of the reaction are remarkably improved.

  A subject of the present invention is thus a multi-stage bubbling column comprising three or more of three perforated plates arranged inside thereof, in which each perforated plate has perforations distributed in a non-uniform manner and is placed in contact with the inner wall of the column and the ratio of the total void area of each perforated plate to the cross-sectional area of the cell column is 15% or less. The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: - Figure 1 is a schematic view in longitudinal section showing a multi-stage bubbling column, - Figure 2 is a top view showing a first embodiment of a perforated plate

  used in the multistage bubbling column of the present invention, - Figure 3 is a top view showing another embodiment of a perforated plate used in the multistage bubbling column of the present invention , - Figure 4 is a top view showing yet another embodiment of a perforated plate used in the multistage bubbling column of the present invention, - Figure 5 is a top view showing as a further embodiment of a perforated plate used in the multistage bubbling column according to the present invention, - Figure 6 is a top view showing a perforated plate used in a conventional bubbling column in several stages, FIG. 7 is a top view showing again an additional embodiment of perforated plate used in the bubbling column Sev- eral stages of the present invention.

  In these figures, the reference numeral 1 indicates the gas inlet, the reference numeral 2 indicates the liquid entry, the reference numeral 3 indicates a perforated plate, the reference numeral 4 indicates an exit of liquid phase, the reference numeral 5 indicates a gas phase output, and reference numeral 6 indicates a multi-stage bubbling 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 can also be a two-phase gas-liquid system comprising two or more two liquids and at least one gas, and it can also be a

  three gas-liquid-solid phases consisting of one or more gases, one or more liquids and one or more solids. In the present invention, it is not imperative that the distances between the respective perforated plates are the same. When the gas and liquid are fed in a parallel flow in a successive reaction such as a liquid phase oxidation reaction of the olefin, the distance between the respective perforated plates at the bottom of the cell column can be relatively large and, on the other hand, the distance between the respective perforated plates at the top of the cell column can 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 be the same. For example, circular perforations and square perforations, which have different diameters, can exist simultaneously. The diameter (average diameter) of the perforations is normally about 0.5 to 40 mm.

  The ratio of the total void area of each perforated plate to the cross-sectional area of the cell column is 15% at most, preferably 10% at most, especially 5% at most, depending on the reaction yield. It is necessary that the perforated plate be placed in contact with the interior wall of the column. Thus it is necessary that the internal diameter of the column wall and the diameter of the perforated plate are practically the same and that at the same time the perforations of each perforated plate are distributed in a non-uniform manner. The term "non-uniformly distributed" indicates that the persons

  holes exist on the entire perforated plate but irregularly, or that the perforations are distributed uniformly but not over the entire perforated plate. 5 As a perforated plate satisfying the first condition, for example, there is a perforated plate as shown in FIG. 4. As a perforated plate satisfying the second condition, for example, there are perforated plates as shown - 10 felt in Figures 2, 3, 5 and 7.

  These perforated plates can be produced, for example, by drilling or punching perforations or closing a part of the holes of an already ready perforated plate in which perforations are distributed uniformly, using bolts and nuts.

  When the perforations are partially present at the peripheral part of the disc, as shown in FIG. 2, the perforated plate is preferably produced in such a way that the area ratio between the area where the perforations are partially present and the cross-sectional area of the cell column is between 35 and 90%. When the perforations are partially present at the central part of the disc, as shown in FIGS. 3 or 5, the perforated plate is preferably produced so that the area ratio between the area where the perforations are partially present and the cross-sectional area of the cell column is between 10 and 65%.

  In order to produce the perforated plate in which the perforations are irregularly present over the entire perforated plate, as shown in FIG. 4, several perforations are formed by cutting out a set of plates having a

  adapted shape (for example elliptical or square) and then these plates can be arranged in the disc in which the plate having the adapted shape has been cut.

  As shown in FIG. 7, in the perforated plate, the perforations of which are arranged in fan-shaped zones, it is preferably made in such a way that the surface ratio between the zone where the perforations are partially present and the cross-sectional area of the cell column is about 50%. In the multistage bubbling column according to the present invention, perforated plates having the same or a different void distribution or a different void distribution can be used in combination.

  Examples of a preferred embodiment of a multistage bubbling column according to the present invention include those in which some or all of the positions of the perforations of adjacent perforated plates are different when incorporating perforated plates having perforations distributed in a non-uniform manner. Consequently, when adjacent perforated plates having the same void distribution are used, it is preferred to incorporate the perforated plates by shifting them at an angle to each other. Examples of particularly preferred embodiments include those in which adjacent perforated plates having different void distributions are used such that some or all of the perforations of the adjacent perforated plates are different.

  As an embodiment using perforated plates having different void distributions, there is for example a multi-stage bubbling column in which perforated plates of which

  the perforations are present only in the central part of the cell column are used as upper and lower perforated plates of three perforated plates, which are adjacent to each other, and a perforated plate whose perforations are present only in the peripheral part of the cell column is used as a central perforated plate, thus making it possible that the gas phase having passed through the lower perforated plate causes a deflected flow at the peri part - spherical of the cell column during the passage through the central perforated plate and the deviated flow of this gaseous phase causes a deviated flow at the level of the central part of the cell column during the passage through the plate perforated upper. As a variant, perforated plates whose perforations are present only in the peripheral part of the cell column are used as upper and lower perforated plates and a perforated plate 20 whose perforations are present only in the central part of the cell column is used as a central perforated plate, so that it is possible that the gas phase having passed through the

  lower perforated plate causes a deviated flow at the central part of the cell column when passing through the central perforated plate and the deviated flow of this gas phase causes a deviated flow at the peripheral part of the cell column when passing through the upper perforated plate 30. In this case, a particularly preferred column is a multi-stage bubbling column in which a combination of the perforated plates shown in FIGS. 2 and 3 is used (or FIG.

  5) so that all the positions of the perforations of two adjacent perforated plates are different. As another embodiment using a combination of perforated plates having different void distributions, there is for example a multi-stage bubbling column in which three types of perforated plates are incorporated as shown in Figures 2, 3 and 4. Specific examples thereof include those in which the perforated plates of Figures 2, 3 and 4 are used respectively as the central top and bottom plates of three perforated plates which are adjacent to each other. 'to each other, and those in which the perforated plates of Figures 3, 4 and 2 are used respectively as upper central and lower plates.

  On the other hand, as an embodiment using a combination of perforated plates having the same void distribution, for example, there may be mentioned a multi-stage bubbling column in which the perforated plates indicated in Figure 7 are used. - seated with adjacent plates turned around 45,

  so that the positions of the perforations of the perforated plates of the upper part and / or of the lower part and those of the perforated plate of the central part do not overlap each other, thus making it possible that the gas phase having passed through the perforated plate situated at the level of the lower part is offset by 45 to cause a deflected flow during the passage through the perforated plate situated at the level of the central part and the deflected flow from this gaseous phase again shifts by 45, causing a deviated flow when passing through the perforated plate of the upper part. When the system containing the gas and the liquid or the liquid and the solid are mixed or reacted

  smells continuously using the multistage bubbling column according to the present invention, the gas supply speed is normally 0.3 to 30 cm / second and the liquid supply speed is 0.02 to i cm / second in the case of a parallel flow (empty column speed in both cases).

  When the reaction or mixing is carried out using the multistage bubbling column according to the present invention, it is preferred to adjust the linear speed of the gas through the holes in the perforated plates below 4 m / second, in particular below 3.5 m / second. When the hole diameters of all the perforated plates and the total void areas of all the perforated plates are the same, in a similar manner, it is preferable to adjust the linear speed of the gas phase and of the liquid phase to inside the column of cells to satisfy the following expressions:

  ReLd / ReGd> 0.1 20 in which ReLd is wLd-d-oL / TL, and ReGd is wGd d-oG / nG. In this expression, ReLd and ReGd are the Reynolds numbers of the liquid phase and of the gas phase respectively in the perforations of a perforated plate, wLd is the linear velocity of the liquid phase passing through the perforations of a perforated plate, wGd is the linear velocity of the gas phase in the perforations of a perforated plate, d is the hole diameter of a perforated plate, aL is the density of the liquid phase, aG is the density of the gas phase , IL is the viscosity of the liquid phase and nG is the viscosity of the gas phase.

  The thickness of the perforated plate may be a thickness sufficient to obtain sufficient resistance of the multistage bubbling column, and

  the distance between the perforated plates is normally about 200 to 5000 mm. The material of the perforated plate is suitably selected depending on the type of reaction material for which the multistage bubbling column according to the present invention is intended, and a corrosion resistant material is normally used.

  Examples of the reaction to which the multistage bubbling column according to the present invention is applied include reactions between gas and liquid in a two-phase gas-liquid system, such as oxidation with olefin air (e.g. reaction to produce ethylene oxide or acetaldehyde from ethylene, etc.), air oxidation of an aldehyde (e.g. reaction to produce acetic acid from acetaldehyde, etc.), air oxidation of aromatic hydrocarbons (eg oxidation reaction of xylene, cumene, etc.), alkylation of phenols (by example butylation reaction of a phenol, etc.) and wet oxidation of waste water, and reactions of a gas-liquid-solid multiphase system using gas, liquid and solid, such as coal liquefaction reactions (e.g. reaction for additional hydrocracking of liquefied oil 25 ob held by decomposition of carbon, using a solid catalyst, etc.), olefin polymerization reaction (eg reaction to obtain polyethylene using a low pressure process, etc.), reaction d oxidation of cyclohexane to cyclohexanone, reaction of hydrogenation of hydrocarbons (eg reaction of production of cyclohexane from benzene, etc.) and waste water treatment reaction.

  The following examples illustrate the present invention in more detail. 35 Example 1

  A multi-stage bubbling column (diameter: 0 1 m, each distance between perforated plates: 509 mm) shown in Figure 1 was provided with perforated plates shown in Figure 2, and air and the water has been sent continuously from the gas inlet and the liquid inlet arranged at the bottom of the column so that the surface speed in a column thereof becomes 2.12 cm / second and 0.0637 cm / second, respectively. At the same time, 27% aqueous sodium hydroxide was continuously sent from the central part of the side wall of the second stage (area separated by the second and the third perforated plate from the bottom) . Samples were taken over time from sampling taps, which are opposite to the sodium hydroxide supply inlet, arranged at the central parts of the side wall of the first stage (area separated by the first and second perforated plate from the bottom) and second stage, respectively, and the concentration of sodium hydroxide was measured. The reflux ratio a after the sodium hydroxide concentration reached a stable state was calculated according to the following equation and the resulting backward flow ratio a is shown in Table i (a indicates the makes it more difficult to induce back mixing when its 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]

  12 Table 1 Sample n Ex. Ex. 1 Ex. 2 Ex. 2 Ex. 2 Ex. 2 Comp. 1 diameter of 10 10 10 10 10 10 empty, mmn Opening% * 1 1.0 1.0 1.0 1.0 1.0 1.0 plate Part Fig. 6 Fig. 2 Fig. 3 Fig. 4 Fig. 3 Fig. 5 per- most drilled bottom * 2 Part Fig. 6 Fig. 2 Fig. 3 Fig. 4 Fig. 2 Fig. 2 central part Fig. 6 Fig. 2 Fig. 3 Fig. 4 Fig. 3 Fig. 5 highest, highest

  Ratio a of 0.87 0.57 0.41 0.38 0.17 0.15 reflux * 1: Ratio of the total area of voids to the cross-sectional area of the cell column. * 2: The distribution of the perforations of each perforated plate is as shown in each figure, and three perforated plates which are adjacent to each other in Examples 1 to 3 are arranged so that the positions of all the perforations of the holes be the same. The perforated plate of Figure 6 10 has a distance between centers of perforations (pitch) of 26 mmn. Examples 2 to 5 and Comparative Example 1 In the same manner as that described in Example 1 except that the perforated plate shown in Table 1 was changed, tests were carried out. In all of Examples 1 to 5, no gas buffer formation was observed. Even if the air supply speed has been changed to

  3.2 cm / second (surface velocity in a column), no air buffering was observed. When the distance between the perforated plates is the same and when the number of stages of the cell column is 5, the number of stages in an ideal system where no back-mixing occurs, and where complete mixing is carried out at level of each stage was determined by each reflux ratio c obtained in Comparative Example 1, Example 1 and Example 2. As a result, this was 2.4 in the case of 'a usual cell column in which the perforated plate of Figure 6 is incorporated. It was 2.8 in the case

  of a cell column of the present invention in which the perforated plate of Figure 2 is incorporated. It was 3.1 in the case of a cell column of the present invention in which the perforated plate of Figure 3 is incorporated. As this appears, the multistage bubbling column according to the present invention, for example cellular columns 20 used in Examples 1 and 2, is greater than the level of the number of stages in the ideal system (in in other words, the yield of the mixture) of approximately 20 or 30% relative to the usual cell column used in Comparative Example 1). With regard to another multistage bubbling column according to the present invention, for example a cellular column in which the perforated plate of FIG. 5 is incorporated as a perforated plate of the lowest or highest part, as shown in Example 5, and where the perforated plate of Figure 2 is incorporated as the perforated plate of the central portion, the reflux ratio a is remarkably small compared to the usual cell column. In the same manner as described above, the number of stages in the ideal system was determined and the result was

  that this is 4.1. Consequently, it appears that the cell column of this Example is remarkably higher in number of stages. The multistage bubbling column according to the present invention is superior to the reaction yield level compared to a usual multistage cellular column.

  Therefore, when using the multistage bubbling column according to the present invention, it is possible to effectively carry out desulfurization using an exhaust gas containing sulfur oxides such as SO3 (e.g. flue gases, etc.) as gas and to feed an aqueous solution of sodium hydroxide dissolved as liquid in the flow against the current with respect to the exhaust gas. In addition, a corresponding hydroperoxide can be efficiently obtained by using air as the gas and by feeding an aqueous solution of sodium hydroxide and isopropylbenzene (or isopropyltoluene) as liquid in the flow parallel to the air, and reacting them between about 100 and 2,150 C under a pressure of about 3 kg / cm. Therefore, phenol (or cresols) can be produced by cleavage of the hydroperoxide in an industrially advantageous manner.

Claims (6)

  1. Multi-stage bubbling column comprising three or more perforated plates incorporated therein, characterized in that each perforated plate (3) has perforations distributed in a non-uniform manner and is placed in contact with the interior wall of the column and the ratio of the total void area of each perforated plate to the cross-sectional area of the cell column is 15% or less.   2. Multi-stage bubbling column according to claim 1, characterized in that adjacent perforated plates are different as regards their distribution of perforations.   3. Multi-stage bubbling column according to claim 1, characterized in that adjacent perforated plates have the same perforation distribution. 4. Multi-stage bubbling column according to any one of claims 1 to 3, characterized in that some or all of the positions of the perforations of adjacent perforated plates are different.   5. Multi-stage bubbling column according to any one of claims 1 to 4, characterized in that the ratio of the total surface area of the voids of each perforated plate to the cross-sectional area of the cell column, is 5% or less.   6. Multi-stage bubbling column according to any one of claims 1 to 5, characterized in that the distances between adjacent perforated plates are equal.