CN1089015C - Rotary-disc extracting tower provided with interstage rotary baffle plate - Google Patents

Abstract

The invention relates to a rotating disk extraction tower equipped with interstage rotating baffles. The extraction tower includes a tower body, a fixed ring, a rotating shaft, a rotating disk and a rotating baffle. The rotating baffle is placed between the two turntables and fixed on the rotating shaft. It is on the same plane as the fixed ring. The ratio of the diameter of the rotating baffle to the diameter of the turntable is: 1-0.8:1; Small holes arranged in concentric circles, the diameter of the small holes is 10-30mm, and the opening rate on the rotating baffle is 40-60%. According to the measurement results of the velocity field, adding sieve baffles can effectively suppress the axial backmixing between the stages, and at the same time, the mixing intensity in the stage increases, which is beneficial to the mass transfer between the two phases in the rotary column.

Description

A kind of rotating disk extraction tower equipped with interstage rotating baffles

The invention relates to a turntable extraction tower equipped with rotating baffles between stages, belonging to the field of chemical separation equipment.

The large rotating disk extraction tower is an important chemical mass transfer equipment, which is widely used in the fields of chemical industry, petroleum and environmental protection. Rotating Disk Extraction Column (RDC) has the advantages of simple structure, large processing capacity and small investment. Therefore, since its appearance in the 1950s, it has been widely used in the petroleum and chemical industries. The main factors affecting the mass transfer of the rotating disk extraction column are the residual fraction of the dispersed phase and axial backmixing. During the industrial scale-up of the rotary disk extraction column, 75-90% of the column height is used to compensate for the reduction of the mass transfer driving force caused by the axial back-mixing due to the axial back-mixing. Axial backmixing in the continuous phase in extraction columns is believed to be caused by one or more of the following factors: 1) eddy diffusion due to fluid and fluid agitation; 2) radial velocity distribution; 3) Entrainment of the continuous phase in the wake of the dispersed phase droplet; 4) Vortex induced by the flow of the dispersed phase droplet. However, the research on the specific factors, sources, influence degree and influence area of backmixing is still insufficient. In addition, for the rotating disk extraction tower, due to channel flow and short circuit, the non-ideal continuous phase distribution on the extraction tower cross-section; the dispersed phase produces pre-mixing due to the rising flow rate of the droplet with the size of the droplet, as well as droplet breakup and liquid Coalescence between droplets is a factor that produces non-ideal flow in a rotating disk column. The mass transfer characteristics of the rotating disk extraction tower have been quite extensive and in-depth, including the prediction of the droplet diameter, the correlation of the mass transfer coefficient, the droplet breakup, the characteristic velocity of the droplet, the sliding velocity correlation, the size of the diameter of the rotating disk column on the mass transfer impact etc. However, it is quite difficult to study the non-ideal factors of rotating disk extraction towers, especially industrial scale rotating disk extraction towers. Known empirical correlations for determining axial backmixing are limited to fixed rotating disk column geometries, and experimental data for large column diameters are rather scarce.

Computational Fluid Dynamics (CFD) is a fast-growing frontier subject, and its application in the aerospace and automobile industries has achieved great success. The application in the chemical industry is also developing rapidly. Weiss et al. theoretically calculated the flow field in the turntable tower (150 mm in diameter) by computational fluid dynamics, and studied the flow pattern of the fluid flow in the tower. They point out that models based on the momentum equation can provide useful tools for the design and operation of extraction columns. Bart et al. conducted an in-depth study on the flow of single-phase and two-phase fluids in the rotating disk extraction tower. They pointed out that sufficient radial momentum transfer is a sufficient condition to ensure efficient utilization of the device volume during mass transfer. If the geometric structure of the equipment cannot guarantee this radial momentum transfer, it is impossible to increase the rotational speed of the turntable column to achieve sufficient mass transfer and separation requirements, especially for large-diameter turntable columns. In the case of laminar boundary layer flow, the radial momentum transfer of the disk is achieved by releasing free liquid jets outward from the edge of the disk. According to the boundary layer theory, the maximum flow velocity on the jet axis decreases at a rate of X ^-1/3 in the case of laminar flow (X is the axial distance to be set up). In the turbulent state, it decreases at a speed of X ^-1/2 . If this velocity is small compared with the flow velocity of the liquid continuous phase, the fluid flowing towards the column wall by the centrifugal force of the turntable will not reach the column wall. The radial momentum transfer in the turbulent regime is generated by eddy currents on the edge of the turntable. In the large-diameter extraction tower, this laminar flow and turbulent flow mechanism will lose its effectiveness, and the effective tangential movement of the fluid will be broken. In this case, back mixing will occur, and the effective use volume of the column will be reduced.

The purpose of the present invention is to design a rotating disk extraction tower equipped with interstage rotating baffles, change the structure of the prior art, eliminate the interstage back-mixing in the rotating disk tower, and ensure that the mass transfer is improved under the premise that the flux is basically unchanged. efficiency.

The rotating disc extraction tower equipped with interstage rotating baffles designed by the present invention includes a tower body, a fixed ring, a rotating shaft, a rotating disc and rotating baffles. The rotating baffle is placed between the two turntables and fixed on the rotating shaft. It is on the same plane as the fixed ring. The ratio of the diameter of the rotating baffle to the diameter of the turntable is: 1-0.8:1; The small holes arranged in concentric circles have a diameter of 10-30mm, and the opening rate on the rotating baffle is 40-60%.

Using the rotating disk extraction tower designed by the present invention equipped with inter-stage rotating baffles, from the measurement results of the velocity field, the axial back-mixing between the stages can be effectively suppressed after adding the sieve baffles, and the mixing intensity in the same stage The increase is beneficial to the mass transfer between the two phases in the rotary column.

Description of drawings:

Fig. 1 is the structure schematic diagram of the rotating disk extraction column that the design of the present invention is equipped with interstage rotating baffles.

Figure 2 is a comparison of the mass transfer efficiency before and after adding rotating baffles to the extraction tower of the rotary table tower.

Below in conjunction with accompanying drawing, introduce the content of the present invention in detail.

In Fig. 1, 1 is a tower body, 2 is a fixed ring, 3 is a rotating disk, 4 is a rotating shaft, 5 is a rotating baffle, and 6 is an aperture on the rotating baffle.

As shown in FIG. 1 , the rotating disk extraction tower with interstage rotating baffles designed by the present invention includes a tower body 1 , a fixed ring 2 , a rotating shaft 4 , a rotating disk 3 and a rotating baffle 5 . The rotating baffle 5 is placed between the two turntables 3 and fixed on the rotating shaft 4, and is on the same plane as the fixed ring 2. The ratio of the diameter of the rotating baffle 5 to the diameter of the turntable 3 is: 1-0.8:1. Example is 1:1. The rotating baffle is provided with small holes 6 arranged in concentric circles, the diameter of which is 10-30mm, and the opening ratio on the rotating baffle is 40-60%.

The present invention will now be described. The sieve type rotating baffle plate in the present invention will be installed on the plane of the fixed ring of the rotary extraction tower. The rotating baffle can be composed of two semicircular baffles, which are stuck on the rotating shaft of the rotary extraction tower during installation. It can also be a whole, inserted from one end of the shaft during installation. The diameter of the baffle is 80-100% of the diameter of the turntable. There are round holes on the baffle, the diameter of which is 10-30mm, depending on the specific process, the opening rate is 40-60%.

The working principle of the present invention is: the transfer between the two phases in the turntable tower depends on the rotation of the turntable 3 between the two fixed rings 2 to cause the fluids to mix and exchange mass. However, mass exchange also occurs at the top and bottom of the fixed ring plane between the two turntables, that is, interstage backmixing or axial backmixing, which affects the mass transfer efficiency of the turntable column. After the rotating baffle 5 is added to the plane of the fixed ring, the mass transfer (axial back-mixing) above and below the plane can be effectively suppressed, so that the mass transfer efficiency of the turntable tower is greatly improved.

The effects of the present invention are illustrated below with examples.

On the basis of flow field measurement and computational fluid dynamics simulation, a mass transfer experiment was carried out in a rotating disk extraction column with a column diameter of 100mm. In the experiment, the n-butanol-succinic acid-water system was selected for experimental research. This is a typical low interfacial tension system and one of the three standard systems recommended by the European Federation of Chemical Engineers for extraction studies. In the experiment, n-butanol was used as the continuous phase, water was used as the dispersed phase, and succinic acid was used as the solute. Among them, water is deionized water treated by electrodialyzer, n-butanol is a chemically pure reagent produced by Beijing Chemical Plant, and succinic acid is an analytically pure reagent produced by Beijing Qiuxian Chemical Plant. The body of the turntable tower used in the experiment is made of hard glass, and the fixed ring and turntable are made of stainless steel. The turntable is mounted on a stainless steel shaft with a diameter of 15 mm. The physical property data of the experimental system are listed in Table 1, and some structural parameters of the tower are shown in Table 2.

Table 1 Physical property data of the experimental system physical properties ρ _c (kg/m ³ ) _ρd (kg/m ³ ) μ _c (cP) μ _d cP σ(mN/m) D _c (μm ² /s) D _d (μm ² /s) no solute 846.0 985.6 3.364 1.426 1.75 With solute 876.2 1000.0 3.925 1.610 0.75 229 584

Table 2 Structural parameters of the turntable tower Tower height(mm) Tower diameter(mm) Fixing ring diameter(mm) Turntable diameter(mm) Compartment height (mm) 1000 100 80 60 30

The comparison of the mass transfer efficiency of the modified rotary column and the conventional rotary column under various operating conditions is plotted in Fig. 2 . The results of mass transfer experiments show that the mass transfer efficiency of the improved rotating disk tower installed with baffles can be increased by 20-40% on average if the organic phase is used as the dispersed phase, and it can be increased by 15-30% on average if the aqueous phase is used as the dispersed phase. The invention has the advantages that no modification is needed on the existing rotary disk extraction tower, the modification is simple and has no influence on the process operation, the investment cost of the modification is low, and the economic benefit is considerable.

Claims (1)

1. A rotating disk extraction tower equipped with interstage rotating baffles, the extraction tower includes a tower body, a fixed ring, a rotating shaft, and a rotating disk, and is characterized in that it also includes a rotating baffle; the rotating baffle is placed between the two rotating disks between, and fixed on the rotating shaft, in the same plane as the fixed ring, the ratio of the diameter of the rotating baffle to the diameter of the turntable is: 1~0.8:1; the rotating baffle has small holes arranged in concentric circles, small The hole diameter is 10-30 mm, and the opening rate on the rotating baffle is 40-60%.

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