CN1785495A - Bubbling tower reactor having damping internal construction member - Google Patents

Abstract

In the bubble column reactor with damping internal components disclosed by the invention, the damping internal components coaxial with the tower body are installed in the reaction zone above the gas distributor of the bubble column. Since the damping internal member exerts a certain resistance to the flow of the fluid, it can effectively suppress the excessively fast flow velocity in the central area, making the radial distribution of the velocity more uniform. At the same time, by damping the interference of internal components to the flow field, local turbulence is promoted, the gas-liquid mass transfer rate is increased, and the process is strengthened.

Description

Bubble column reactor with damped internals

technical field

The invention relates to a gas-liquid bubble column reactor or a gas-liquid-solid three-phase bubble column reactor, especially a bubble column reactor with a damping inner member, which is used in various chemical production processes Phase reaction or gas absorption operation.

Background technique

Bubble column reactors are widely used in many fields such as chemical industry, energy, environment, biochemistry, etc., for mass transfer and reaction operations of gas-liquid two-phase or gas-liquid-solid three-phase, such as oxidation, hydrogenation, carbonylation, halogenation, fermentation , Absorption and other processes. Industrial bubble column reactors are becoming larger and larger. An important problem in the enlargement of the bubble column is the inhomogeneous distribution of the fluid axial velocity in the radial direction: in the central area of the column, the gas-liquid two-phase flows upward, and the flow rate is relatively high; in the area close to the column wall, the gas-liquid Downward flow, lower velocity. The gas holdup in the central area is high, and the gas holdup in the near wall area is low. At the same time, the two-phase velocity in the center of the tower also increases with the increase of the diameter of the tower. Thus, when the bubble column is scaled up, especially at high gas velocities, the flow velocity distribution and gas holdup distribution will become more inhomogeneous. The computer simulation results show that for a large bubble column with a diameter of 6m, when the superficial gas velocity is 0.3m, the center liquid velocity may reach 4-5m/s, and the gas velocity is even higher. This may cause the gas to short-circuit from the center of the tower, causing poor gas-liquid contact and making it difficult to scale up. For some oxidation reactions, the short circuit of the gas will also increase the oxygen concentration of the tail gas, which will bring safety hazards. Most of the bubble column internals proposed in the current literature and used in industry are for the consideration of improving the gas-liquid mixing state, such as draft tubes, multi-layer partitions, stirring paddles, etc. Obstruction internals to improve the radial distribution of gas-liquid velocity are reported.

Contents of the invention

The object of the present invention is to provide a bubble column reactor with damping internal components which can suppress uneven gas-liquid flow velocity in the bubble column, prevent gas short circuit, enhance mass transfer, and be easily scaled up.

The bubble column reactor with damping internal components of the present invention mainly includes a tower body and a gas distributor, and is characterized in that a damping internal component that hinders fluid movement is installed in the reaction zone above the gas distributor, and the damping internal component and the tower body coaxial line.

As for the damping internal components set up, it only needs to satisfy: 1) It has a certain damping area perpendicular to the fluid flow direction; 2) It has a certain flow area to allow the fluid to pass through; 3) There is a certain form of distribution of the damping area in the radial direction. In the area, the damping area density is higher, and the damping area density in the peripheral area is smaller. This is because the fluid velocity in the central area is high, and more damping area is needed to suppress the flow velocity, while the fluid velocity in the peripheral area is relatively small, so too much damping area is not needed. Therefore, the damping inner member proposed by the present invention has the characteristics of being dense in the center and sparse in the periphery.

In principle, the ratio of the outer maximum diameter or radial length of the damping internal member to the diameter of the bubble column reactor can take any value between 0 and 1 (0 is the center position, 1 is the wall position). However, if the diameter or length of the damping inner member is too small, the range of action is limited, and it is difficult to effectively suppress the flow velocity in the central area; and if the diameter of the damping inner member is too large, it is unnecessary, because the flow velocity outside the central area is small, and no need to suppress. According to the flow velocity distribution measurement, the suitable ratio of the peripheral diameter or radial length of the damping internal member to the diameter of the bubble column reactor is 0.1-1.0, and the preferred diameter ratio is 0.2-0.6.

The damping inner member includes multiple damping units, and the number or installation density of the damping units is determined according to the damping requirements for the flow velocity distribution: if there are too few damping units, the requirements for effectively suppressing the central flow velocity cannot be met, and if there are too many damping units, the The flow rate may be over-inhibited, forming a new uneven distribution, and even forming a flow dead zone in the central area. The present invention uses the concept of damping area density to determine the installation density of the damping unit. The damping area density is defined as the damping area of the damping internal components in the unit volume of the reactor, and its calculation formula is: damping area of all damping internal components / total volume of the reactor. According to a large number of flow measurements and hydrodynamic calculation experiments, the present invention provides a suitable damping area density of 0.05-5.0m ² /m ³ , and a preferred damping area density of 0.20-2.0m ² /m ³ . Once the value of the damping area density has been determined, the size and number of damping elements required can be calculated.

In the present invention, a damping internal member is installed in the center of the reaction area of the bubble column, that is, the area below the liquid level of the reactor and above the gas distributor, which exerts a certain hindering effect on the flow of the fluid, and can effectively suppress the excessively fast flow rate in the central area. , making the radial distribution of velocity more uniform. At the same time, by damping the interference of internal components to the flow field, local turbulence is promoted, the gas-liquid mass transfer rate is increased, and the process is strengthened. The present invention is applicable to any form of gas-liquid or gas-liquid-solid bubble column reactor, such as a bubble column reactor with an expansion section at the top, and a rectification section, a gas absorption section, and a particle and liquid foam separation section at the top. For the bubble column reactor, any improvement to other parts of the reactor will not affect the scope of application of the present invention.

Description of drawings

Fig. 1 is the bubble column reactor schematic diagram of band damping internal member of the present invention;

Fig. 2 is a schematic diagram of a radial structure damping plate;

Fig. 3 is a schematic diagram of annular ring damping plates connected by concentric circles;

Fig. 4 is a schematic diagram of a mesh damping sheet;

Fig. 5 is a schematic diagram of damping fins with staggered fin structure;

Fig. 6 is liquid axial velocity distribution diagram, and among the figure abscissa R is dimensionless radial coordinate, is defined as radial coordinate/bubble column radius, and R=0 is center position, and R=1 is wall surface position; Ordinate is The measured axial velocity of the liquid. A positive value of the velocity indicates upward flow, and a negative value indicates downward flow.

Detailed ways

Referring to Fig. 1, a bubble column reactor with damping internals, including a tower body 1 and a gas distributor 3, is characterized in that a damping internal member 2 that hinders fluid movement is installed in the reaction zone above the gas distributor, and the damping internals Component 2 is coaxial with the tower body. In the specific example shown in the figure, the damping member 2 is composed of a vertical rod whose bottom end is fixed on the bottom of the bubble column or on the gas distributor and a plurality of damping units. A plurality of damping units are perpendicular to the vertical rod and installed on the vertical rod at intervals along the axial direction. The damping unit acts as a hindrance to the fluid flow, and its shape can be in various forms, for example, it can be a radial structural sheet (Figure 2), or an annular ring connected by concentric circles (Figure 3), or the center area has a greater damping than the periphery Circular mesh with area damping (Fig. 4), or staggered fin-type structure (Fig. 5).

The damping inner member 2 can be installed in various ways, for example, each damping unit or combination of damping units can be tensioned radially with multiple wires or thin rods, and suspended and fixed on the wall of the bubble column.

Example 1

In the axial central area of the bubble column reactor with a diameter of 500 mm and a height of 4000 mm, a damping member is fixed by a central vertical rod in the reaction area above the gas distributor and below the liquid level of the bubble tower. The damping member has 14 As shown in Figure 2, the radial damping unit has a diameter of 250mm, the distance between adjacent damping units is 200mm, the lowermost damping unit is 200mm away from the gas distributor, and the uppermost damping unit is flush with the liquid level. The damping area density is 0.35m ² /m ³ .

The experiment was carried out in an air-water system, the liquid level height after bubbling was 3000mm, and the superficial gas velocity was 0.62m/s. At the midpoint between the two damping units at a distance of 2250mm from the distributor, measure the axial velocity at different radial positions, and then compare the radial distribution of the fluid velocity without the damping inner member and after installing the damping inner member. The results are shown in Figure 6.

The flow velocity distribution of the empty tower reactor is uneven, and the liquid velocity in the central area is as high as 1.2m/s. After adding the damping inner member, the position where the maximum flow velocity appears moves outward, and the maximum value also drops to 0.88m/s, indicating that adding the damping inner The member then effectively suppresses excessively high fluid flow rates in the central region.

Example 2

The experimental conditions were the same as in Example 1. The gas-liquid mass transfer rate was measured by chemical absorption method, and then the gas-liquid mass transfer coefficient k _l α was compared with that without damping internals and with damping internals installed. The results are shown in Table 1.

The gas-liquid mass transfer coefficient of the empty tower reactor is 0.41. After adding the damping internal member described in Example 1, the mass transfer coefficient increases to 0.49, and the mass transfer rate increases by 20%. It shows that the disturbance of the damping internal member to the flow field strengthens the fluid turbulence and significantly increases the mass transfer rate.

Table 1 Empty column and gas-liquid mass transfer coefficients of bubble column measured with different internal member sizes Experimental conditions No damping member Example 2 Comparative example 3 Comparative example 4 Mass transfer coefficient k _l α(l/s) 0.41 0.49 0.43 0.55

Comparative example 1

In the flow rate measurement experiment, the number of damping units in the reactor is doubled, the distance between adjacent damping units is reduced to 100mm, and the damping area of the damping internal member contained in the reactor per unit volume, that is, the damping area density is 0.7m ² /m ³ , other conditions are identical with embodiment 1. The measurement results are also shown in FIG. 6 . It can be seen that although the flow velocity in the central area is greatly reduced after adding the damping inner member, the flow velocity is excessively suppressed, especially near the central axis, almost forming a dead zone. It shows that the damping area density of the damping inner member in this example is too large. Of course, if the unit structure of the inner member is improved and the damping area is appropriately reduced at the central position, a damping member with such an area density is also desirable.

Comparative example 2

In the flow velocity measurement experiment, the number of damping units in the reactor was doubled, the distance between adjacent damping units was increased to 400mm, the damping area density was 0.18m ² /m ³ , and other conditions were the same as in Example 1. The measurement results are also shown in FIG. 6 . It can be seen that, because the damping area density of the damping internal member is too small, the liquid flow velocity distribution is close to the distribution in the case of an empty tower, indicating that the number of damping units is too small, the damping area density is not enough, and the flow velocity in the central area has not been effectively suppressed .

Comparative example 3

In the gas-liquid mass transfer experiment, the diameter of the damping unit was reduced from 250mm to 120mm, the damping area density was reduced from 0.35m ² /m ³ to 0.18m ² /m ³ , and other conditions were the same as in Example 1. The measured gas-liquid mass transfer coefficient k _l α values are also listed in Table 1. It can be seen that due to the small diameter of the damping inner member, the influence on fluid turbulence is limited, and the mass transfer coefficient does not change significantly.

Comparative example 4

In the gas-liquid mass transfer experiment, the diameter of the damping unit was increased from 250mm to 480mm, the damping area density was increased from 0.35m ² /m ³ to 0.65m ² /m ³ , and other conditions were the same as in Example 1. The measured gas-liquid mass transfer coefficient k _l α values are also listed in Table 1. It can be seen that the mass transfer coefficient can be improved to a certain extent by using the damping inner member whose diameter is close to the tower diameter, but the magnitude has been reduced. For example, the mass transfer rate can be increased by 20% if the damping internal member with a diameter of 250mm is used, but the mass transfer rate can only be increased by 10% if the damping internal member with a diameter of 480mm is used.

The above example shows that the addition of damping internals can not only effectively suppress the excessive flow velocity in the central part of the bubble column, but also significantly increase the gas-liquid mass transfer rate. It is not difficult to infer from the above examples that the radial distribution of the damping area can meet certain requirements by adopting more complex-shaped internal components, and a more uniform velocity distribution in the central area can also be obtained, so we will not list them one by one. Any improvement to the shape of the damping internal member falls within the scope of the present invention and will not change the technical features of the present invention.

Claims (8)

1. A bubble column reactor with damping internals, mainly comprising a tower body (1) and a gas distributor (3), characterized in that the damping internals ( 2), the damping internal member (2) is coaxial with the tower body. 2. The bubble column reactor with damping internals according to claim 1, characterized in that the damping internals (2) are made up of a vertical rod fixed at the center of the tower body axis and a plurality of damping units, and a plurality of damping The units are mounted on the pole vertically and spaced apart from each other in the axial direction. 3. The bubble column reactor with damping internals according to claim 2, characterized in that said damping unit is a radial structure sheet, or an annular ring connected by concentric circles, or the central area damping is greater than Circular mesh for damping in the peripheral area, or staggered fins. 4. The bubble column reactor with damping internals according to claim 1 or 2, characterized in that the damping area of the damping internals (2) has a greater damping area density in the radial central area than in the peripheral area. 5. The bubble column reactor with damping internals according to claim 1 or 2, characterized in that the ratio of the maximum diameter or radial length of the damping internals (2) to the diameter of the reactor is 0.1 to 1.0. 6. The bubble column reactor with damping internals according to claim 1 or 2, characterized in that the ratio of the maximum diameter or radial length of the damping internals (2) to the diameter of the reactor is 0.2 to 0.6. 7. The bubble column reactor with damping internals according to claim 1 or 2, characterized in that the damping area of the damping internals included in the unit reactor volume is 0.05-5.0m ² /m ³ . 8. The bubble column reactor with damping internals according to claim 1 or 2, characterized in that the damping area of the damping internals included in the unit reactor volume is 0.20-2.0m ² /m ³ .

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