Multi-section tandem type gas-liquid parallel flow bubbling reactor

Abstract

The invention relates to a multi-section type gas-liquid parallel flow upward bubble tower reactor, aims to solve the problems of flooding and too short retention time of liquid phase reactants caused by gas-liquid countercurrent contact, and can be suitable for slow gas-liquid reaction easy to foam. A two-layer barrel structure is adopted, wherein an outer barrel is a liquid channel and is provided with a plurality of downcomers; the inner cylinder is a bubbling reactor and is used for gas-liquid reaction. In order to improve the reaction efficiency and prevent liquid phase backmixing, the whole tower body is divided into a plurality of sections, and the adjacent sections are separated by partition plates. And liquid overflowing from the upper-section inner cylinder flows into the lower section through the downcomer, and then flows into the space of the inner cylinder through the side wall of the bottom of the inner cylinder arranged at the lower section to carry out bubbling reaction. And gas passes through the outer cylinder from the outside of the outer cylinder through a plurality of parallel pipelines and is introduced into each section of reactor from the side wall of the bottom of the inner cylinder. The invention provides a method for connecting all sections of bubble towers in the same tower body in series, the problems of liquid phase back-mixing and fluid foaming are effectively solved by utilizing the method, the liquid phase can obtain high conversion rate, and the operation can be carried out under a wide gas / liquid flow rate ratio range.

Description

Technical Field

[0001] The present invention relates to a bubble column reactor, in particular to a bubble column with multiple sections connected in series. Background Art

[0002] The liquid in the bubbling reactor is a continuous phase and the gas is a dispersed phase. It has the advantages of no moving parts, simple structure, large heat capacity, good heat transfer performance, easy temperature control and high safety. However, when the apparent gas velocity is large, the reactor flow pattern will enter the turbulent zone by uniform bubbling flow, and the gas will gather toward the center of the tower, so a low-density zone appears in the center of the tower, and a parabolic velocity distribution appears in the liquid in the tower, that is, the liquid in the center of the tower flows upward, and the near-wall area flows downward, causing the circulation of the liquid in the tower. Although the liquid phase circulation in the bubbling tower is conducive to heat transfer and mass transfer, the back mixing is serious. Back mixing is unfavorable for reactions with series steps, not only affecting the selectivity of the reaction, but also affecting the conversion rate. For example, in the invention patent CN 103819380 A, in order to reduce the back mixing of the reaction mixture, multiple bubbling tower reactors are connected in series to form a plug flow reactor with a very large aspect ratio, so as to eliminate the impact of back mixing on the reaction, improve the contact time of the gas-liquid phase reaction, and improve the conversion rate of the reaction. Industrial cyclohexane catalytic oxidation reaction also adopts a multi-stage series connection to limit the residence time of the oxidation product and avoid deep oxidation of the reaction product, thereby improving the selectivity and yield of the target product. The series reaction characteristics include not only hydrocarbon oxidation, but also selective hydrogenation, Fischer-Tropsch synthesis and other systems.

[0003] In order to improve the flow state of the bubbling reactor, the commonly used solution is to install multiple baffles or sieve plates in the tower. For example, CN2422041Y adopts a full-section bubbling sieve plate tray to form an orderly arranged bubble flow in the synthesis tower, which promotes the liquid phase to flow upward and effectively overcomes the longitudinal back mixing. CN 102580630 A proposes a bubbling tower reactor for strengthening acetylene dimerization, in which a circular, rectangular or polygonal baffle is connected to the inner wall of the bubbling tower, and the angle formed by the lower surface of the baffle and the tower wall is 30 to 120 degrees to reduce the back mixing of acetylene gas. The function of the baffle is usually to force the fluid to flow along the baffle route to avoid short circuit. The sieve plate can effectively redistribute the liquid flow in the tower and eliminate the velocity distribution. However, at high temperature and high pressure or when a solid catalyst is present, the sieve plate will have many problems such as sintering, blocking, bending deformation due to heat, and difficulty in cleaning, which seriously affect the reaction.

[0004] In summary, there are currently two measures to limit the back-mixing of the liquid phase in the bubble tower: one is to connect multiple bubble towers in series, and the other is to add multiple sieve plates in the same bubble tower for segmentation. The former method requires a large investment, the equipment is relatively scattered, and the operating cost and management cost are high. In addition, once the liquid foams, it will affect the flow of liquid between the bubble towers. The latter method cannot fundamentally prevent the back-mixing of the liquid, because the liquid will flow in the opposite direction through the sieve plate under the action of gravity. In addition, the holes on the sieve plate will promote the generation of bubbles, which is not suitable for the gas-liquid reaction of the foaming system.

[0005] The present invention is as follows:

[0006] The present invention relates to a novel gas-liquid bubbling reactor which is required to limit liquid phase backmixing in order to obtain a high conversion rate of liquid phase reactants. A plurality of inner cylinders are arranged in the same tower body to form a multi-stage bubbling tower. These bubbling towers are distributed in each tower section, separated by tower plates, and are not interconnected. A plurality of downcomers are arranged in the annular gap area between the inner and outer cylinders, and the liquid in the upper tower section can be led to the next tower section, so that the bubbling towers in each section are connected in series.

[0007] In the present invention, the liquid is fed from the top of the tower at one time, and the gas is fed from the side of the tower in stages. The liquid first enters the top first stage bubbling tower for gas-liquid reaction, and passes through the following stages in sequence, realizing the series connection of multiple stages of bubbling towers, and completely eliminating the back mixing of materials between the upper and lower bubbling towers. In order to prevent the liquid from foaming, the gas and liquid are introduced tangentially from the bottom side wall of the tower, which is different from the method of feeding upward from the tower bottom distributor used in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a structural diagram of a bubble tower with a porous plate structure;

[0009] Explanation of symbols:

[0010] 1 reactor outer cylinder; 2 pre-distributor; 3 porous distributor; 4 partition; 5 downcomer; 6 inner cylinder (bubble tower); 7 gas main pipe; 8 gas branch pipe; 9 liquid inlet pipe.

[0011] Figure 2 It is the change of conversion rate of harmful substances in wastewater with air flow rate. DETAILED DESCRIPTION

[0012] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0013] Example 1

[0014] The core components of the multi-stage gas-liquid bubbling reactor of this embodiment include: an outer cylinder 1 of the tower body, an inner cylinder 6 on the partition 4, a downcomer 5, etc. Figure 1As shown, the liquid flows into the reactor from the top of the outer cylinder 1, first passes through the pre-distributor 2 to slow down the liquid flow rate and pre-distribute it, and then passes through the porous distributor 3 to further evenly distribute it to reach the first layer of partitions. The liquid on the partition then flows into the cylinder tangentially from the bottom side of the inner cylinder 6 through the downcomer 5 and the liquid inlet pipe 9. The gas also flows into the cylinder tangentially from the bottom side of the inner cylinder 6 through the gas main pipe 7 and the gas branch pipe 8. With the continuous inflow of liquid, the liquid level of the first section of the inner cylinder 6 will continue to rise, and the first section of the bubbling reaction will be carried out. After the liquid overflows, it will flow into the next section of the bubbling tower through the downcomer 5 together with the gas, and finally leave the reactor.

[0015] Example 2

[0016] In this example, enzymes are used as homogeneous catalysts to treat industrial wastewater using air oxidation, so that harmful substances in the wastewater are degraded into harmless compounds.

[0017] The fixed wastewater flow rate in the experiment is 0.16m 3 / h, the concentration of harmful substances is about 10mol / m 3 , adjust the air flow rate to carry out gas-liquid bubbling reaction. In order to study the effect of gas-liquid mass transfer area and liquid residence time on the reaction, a three-stage series bubbling bed was used for the experiment. The bed height was 0.40m and 0.6m respectively, and the total volume of the bubbling bed was 0.35m 3 and 0.52m 3 , the liquid phase residence time was 2.2h and 3.3h respectively. The change of the conversion rate of harmful substances at the reactor outlet with the gas flow rate was measured as follows Figure 2 It can be seen that increasing the gas flow rate and increasing the volume of the bubble tower are both beneficial to improving the conversion rate, but the conversion rate increases slowly when the gas flow rate is large.

[0018] When the air flow rate is small, the oxygen supply cannot meet the reaction needs, so the conversion rate of harmful substances is low. After increasing the gas volume, the conversion rate increases significantly. After continuing to increase the gas volume, the conversion rate increases slowly. This is because the solubility of oxygen is very low, and the excess air has little effect on the increase of oxygen concentration in the reaction liquid.

[0019] The reactor volume has a great influence on the reaction conversion rate, which is mainly due to the change in the liquid phase reaction time. When the reactor volume is small, even if the gas volume is large, it is impossible to achieve a high conversion rate.

Claims

1. A gas-liquid reactor for achieving a high conversion rate requiring a long reaction time, characterized in that: The reactor consists of an outer cylinder and a plurality of segmented inner cylinders.

2. The outer cylinder according to claim 1, characterized in that: Its interior is divided into several sections by partitions, and each section contains an inner tube.

3. The inner cylinder according to claim 1, characterized in that: The bottom of the cylinder is the outer cylinder partition, which is installed between two adjacent layers of partitions. The top is open and the height is lower than the upper partition. It is the place where the gas-liquid reaction occurs.

4. The separator according to claim 2, characterized in that A plurality of liquid drop holes are evenly arranged along the circumference in the annular gap between the outer cylinder and the inner cylinder.

5. The downcomer according to claim 4, characterized in that: The outlet of the hole is connected to a downcomer of the same diameter, and the downcomer extends to the bottom of the next tower section.

6. The downcomer according to claim 5, characterized in that: Its outlet end is tangentially connected to the bottom of the inner cylinder in the same tower section through a short pipe.

7. The gas-liquid reactor according to claim 1, characterized in that: Liquid reactants are added through the top of the reactor, and gaseous reactants are added through multiple parallel inlet pipe side lines.

8. The side line air intake pipe according to claim 7, characterized in that: Its starting point is the gas main pipeline, its end point is the bottom of the inner cylinder, and its outlet end is tangentially connected to the inner cylinder.

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