CN2910344Y - Bubbling tower oxidizing apparatus for production of aromatic carboxyl acid - Google Patents

Abstract

The utility model discloses a bubbling tower oxidizing apparatus for production of aromatic carboxyl acid, which comprises a straight canister type bubbling tower even from up to down, the top of the tower is rectification segment, while the down segment is a three-phase reaction segment. An air distributor is installed on the downside of the three-phase reaction segment. The canister of the three-phase reaction segment has a feeding pipe, and the bottom of the tower has a stuff-out pipe. A tail gas pipe and a condensation liquid reflux pipe are arranged on the top of the tower. A damp inner member is arranged in the three-phase reaction segment to hinder the liquid movement, and is in the same axis line with the tower. The utility model adopts the damp inner member to hinder the liquid movement, therefore restricting effectively the over fast velocity in the central area, making the radial of the velocity well-distributed, increasing the gas and liquid medium velocity, and favorable for enlarging and strengthening the bubbling tower reactor.

Description

Bubble column oxidation unit for the production of aromatic carboxylic acids

technical field

The utility model relates to a bubble tower oxidation device for the production of aromatic carboxylic acids, in particular to a device for air liquid-phase catalytic oxidation of alkyl aromatic hydrocarbons in the production process.

Background technique

Polybasic aromatic carboxylic acid is the important raw material of producing polyester (PET) fiber and resin, mainly adopts alkyl aromatic hydrocarbon air oxidation method to produce at present, and this method dissolves raw material alkyl aromatic hydrocarbon in containing catalyst cobalt acetate, manganese acetate, hydrogen bromide ( Or tetrabromoethane) in the acetic acid solvent, pass into air or enriched oxygen to carry out oxidation, generate solid product aromatic carboxylic acid. The typical reaction temperature is 120-225°C, the pressure is 0.1-2MPa, and the residence time is 40-120min. The reaction heat is removed by solvent evaporation, and the steam is condensed and returned to the reactor. The resulting slurry is then subjected to subsequent separation and refining processes to obtain high Pure aromatic carboxylic acid product.

The oxidation reactor is the core device for the production of high-purity aromatic carboxylic acid (such as purified terephthalic acid). Currently, there are two types of oxidation reactors: stirred tank and bubble column. The bubble column reactor is a straight cylindrical bubble column with uniform up and down. The upper part of the tower is a rectification section, and the lower part is a three-phase reaction section. A gas distributor is installed below the three-phase reaction section. The three-phase reaction section cylinder There is a feed pipe on the top, a discharge pipe at the bottom of the tower, and a tail gas pipe and a condensate return pipe on the top of the tower. Arranging a rectification tower above the oxidation reactor to separate the solvent acetic acid and water can directly use the reaction heat for rectification and separation, which is beneficial to energy saving. Therefore, some patents have proposed the measures of combining the reactor and the rectifying column, such as patent JP14098/1979 and ZL94103145.4, and patent ZL2003101078895 further proposes to use a bubble column reactor with a gas separation section to produce terephthalic di formic acid. However, the industrial bubble column reactors are becoming larger and larger, and the above-mentioned reactors will encounter certain difficulties when they are scaled up. 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. In this way, when the bubble column is enlarged, especially at high gas velocity (this is the case for the oxidation reaction of alkylaromatics), 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 the oxidation reaction of alkylaromatics, the short circuit of the gas will also cause the increase of the oxygen concentration of the tail gas, which will bring safety hazards.

Contents of the invention

The purpose of the utility model is to provide a bubble tower oxidation device for the production of aromatic carboxylic acids which can suppress uneven gas-liquid flow velocity in the bubble tower, prevent gas short circuit, enhance mass transfer, and be easily scaled up.

The bubble tower oxidation device for the production of aromatic carboxylic acids of the utility model comprises a vertically uniform straight cylinder bubble tower, the upper part of the tower is a rectification section, the lower part is a three-phase reaction section, and the three-phase reaction section is below the three-phase reaction section. A gas distributor is installed, there is a feed pipe on the barrel of the three-phase reaction section, a discharge pipe at the bottom of the tower, an exhaust pipe and a condensate return pipe on the top of the tower, and it is characterized in that it is installed in the three-phase reaction section to hinder fluid movement. The damping internal member is coaxial with the tower body.

The utility model installs damping internal components in the reaction section of the bubble tower reactor, that is, in the bubbling area below the liquid level of the reactor and above the gas distributor to hinder the fluid flow. 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 utility model 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 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 utility model adopts 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 the calculation formula is: damping area of all damping internal components / containing internal components the total volume of the reactor. According to a large number of flow measurements and hydrodynamic calculation tests, the utility model 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.

Because the utility model is equipped with a damping internal member in the center of the reaction area of the bubble tower, it exerts a certain hindering effect on the flow of the fluid, which can effectively restrain the excessively fast flow velocity in the central area and make 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 of drawings

Fig. 1 is a schematic diagram of a bubble column reactor of the present invention; among the figures: 1 is a three-phase reaction section, 2 is a damping internal member, 3 is a gas distributor, 4 is a rectification section, 6 is a return pipe, and 7 is a tail Air pipe, 8 is the raw material feed pipe, 9 is the slurry discharge pipe;

Fig. 2 is a schematic diagram of a radial internal component unit;

Fig. 3 is a schematic diagram of the internal member unit of the annular ring;

Fig. 4 is a schematic diagram of a reticular internal member unit;

Fig. 5 is a schematic diagram of a staggered fin-type internal member unit;

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, the bubble column oxidation device for the production of aromatic carboxylic acids includes a vertical bubble column uniform up and down, the upper part of the tower is a rectification section 4 composed of multi-layer trays or packing, and the lower part is a three-phase In the reaction section 1, a gas distributor 3 is installed below the three-phase reaction section 1. There is a feed pipe 8 on the barrel of the three-phase reaction section, a discharge pipe 9 at the bottom of the tower, and a tail gas pipe 7 and a condensate pipe on the top of the tower. The return pipe 6 is characterized in that a damping inner member 2 that hinders fluid movement is installed in the three-phase reaction section, and the damping inner member 2 is coaxial with the tower body. In the specific example shown, 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 internal member 2 can be installed in various ways, for example, each damping unit or combination of damping units can be tensioned radially with multiple metal wires or thin rods, suspended and fixed on the wall surface of the three-phase reaction section of the bubble tower superior.

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 bubble column gas-liquid mass transfer coefficient measured when different internal member sizes are used

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 tower oxidation device for producing aromatic carboxylic acids, including a vertically uniform straight bubble tower. The upper part of the tower is a rectification section (4), and the lower part is a three-phase reaction section (1). A gas distributor (3) is installed below the reaction section (1), a feed pipe (8) is provided on the barrel of the three-phase reaction section, a discharge pipe (9) is provided at the bottom of the tower, and a tail gas pipe (7) is provided at the top of the tower And the condensate return pipe (6), which is characterized in that a damping internal member (2) that hinders fluid movement is installed in the three-phase reaction section, and the damping internal member (2) is coaxial with the tower body. 2. The bubble tower oxidation device according to claim 1, characterized in that the damping internal member (2) is composed of a vertical rod fixed at the center of the tower body axis and a plurality of damping units, and the plurality of damping units are perpendicular to the vertical rod and Installed on the vertical pole at intervals from each other along the axial direction. 3. The bubble tower oxidation device according to claim 2, characterized in that said damping unit is a radial structural sheet, or an annular ring connected by concentric circles, or a circular shape in which the central area damping is greater than the peripheral area damping net, or staggered fins. 4. The bubble column oxidation device according to claim 1 or 2, characterized in that the damping area density of the damping inner member (2) in the radial central area is greater than the damping area density in the peripheral area. 5. The bubble column oxidation device according to claim 1 or 2, characterized in that the ratio of the maximum diameter or radial length of the damping internal member (2) to the diameter of the reactor is 0.1-1.0. 6. The bubble column oxidation device according to claim 1 or 2, characterized in that the ratio of the maximum diameter or radial length of the damping internal member (2) to the diameter of the reactor is 0.2-0.6. 7. The bubble column oxidation device according to claim 1 or 2, characterized in that the damping area of the damping internal member included in the unit volume of the reactor is 0.05-5.0m ² /m ³ . 8. The bubble column oxidation device according to claim 1 or 2, characterized in that the damping area of the damping internal member included in the unit volume of the reactor is 0.20-2.0m ² /m ³ .

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