RU2461406C2 - Mass exchange contact device for interaction of fluid and gas - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to mass exchangers to be used in oil processing, petrochemical, chemical and food industries. Proposed device comprises zigzag-shape webs making through vertical zigzag fluid and gas passages and vertical rods tightly fitting in bend edges of zigzag web. Vertical partitioning plates are arranged staggered behind vertical rods in said vertical zigzag passages. Said webs feature H/A ratio equal to 1.2-3.25 where H is distance between webs equal to 35-75 m, while A is bend edge radius not exceeding 3 mm.

EFFECT: higher efficiency of mass exchange.

2 cl, 3 dwg, 1 tbl

Description

The invention relates to the construction of mass transfer contact devices and can be used in the processes of countercurrent interaction of gas (vapor) and liquid, mass transfer in gas-liquid systems in the oil refining, petrochemical, oil, chemical and food industries.

Known mass transfer apparatus, consisting of zigzag partitions forming a zigzag channel, and vertical contact grids installed between them. The main disadvantage of this apparatus is its low efficiency at high fluid loads (over 150 m ³ / m ² h), which is explained by the appearance of transverse fluid waves on zigzag partitions, leading to a violation of the uniform distribution of the contacting phases over the apparatus cross section. The emergence of transverse waves occurs due to the free flow of fluid along the edges of the bend of zigzag partitions (AS No. 394068).

The noted drawback is partially eliminated in the device with a water seal. In this apparatus, at the contact stage, due to the presence of a drainage partition, a fixed level of liquid that is not excited by the gas flow is maintained, which contributes to its uniform distribution along the edges of the bend of zigzag partitions (AS No. 243572).

However, the disadvantage of this apparatus is its low gas load at high irrigation densities, since the presence of a water seal significantly reduces the free section of the apparatus.

Known block structured nozzles for heat and mass transfer apparatus, including vertically arranged corrugated metal expanded metal sheets (PM No. 14014).

The closest invention adopted for the prototype (AS 1327897), where at the point of contact of the wavy zigzag septum and the string, the fluid flow is divided into two equal parts, the liquid in the form of a film flows down the septum and the string, thus the strings act as contact distribution devices. Gas is fed down the apparatus, is in contact with the surface of the liquid without disturbing its film motion. The execution of the wavy partitions is necessary to wet the inner surface of the partition. Thus, the phase contact surface cannot be larger than the nozzle surface introduced into the apparatus volume.

The aim of the invention is to increase the intensity of mass transfer in an apparatus operating with a high irrigation density (from 50 to 300 m ³ / m ² h) by creating dynamic free fluid films behind each vertical string, which in this invention are called rods 2 (Fig. 1) , since they can have different (round, tear-shaped) sections, with simultaneous sectioning of channels formed by zigzag partitions 1, vertical sectioning plates to eliminate wave formation in the cross section of the apparatus and face Hydatius local irregularities. At high densities of irrigation along the vertical of the column filled with a mass transfer nozzle, uneven flow of liquid may occur, namely, the ablation of most of the liquid to one or another wall of the column, which leads to a decrease in the gas-liquid contact surface and to a deterioration in the quantitative characteristics of mass transfer. To prevent wave formation, to uniformly fill the zigzag channels and to preserve the free surface of the liquid, regular vertical sectioning plates 3 are installed behind each rod throughout the nozzle volume. An illustration of the effect of vertical sectioning plates on the uniformity of flow distribution is shown in FIG. 2.

The specified goal is achieved due to the following design features:

- zigzag partitions 1 are performed with a ratio of N / A = 1.2 ÷ 3.25, where H is the distance between the bending edge of the zigzag partition (height of the contact chamber), A is (35-75 mm) the distance between adjacent zigzag partitions (width of the contact cameras);

- the radius of the edge of the bend of the zigzag partitions is not more than 3 mm, so that the fluid flow is disrupted from the sharp edge;

- perpendicular to the edges of the bend, adjacent to them by any known method, fasten the rods 2 of either round or tear-shaped section;

- in the channels formed by adjacent zigzag partitions 1, vertical sectioning plates 3 are installed in a checkerboard pattern (length of the contact chamber);

As a result of theoretical and experimental studies, it was found that when the above design parameters are fulfilled, hydrodynamic conditions are created that allow the interaction of gas and liquid at irrigation densities of 50-300 m ³ \ m ² h, and at each contact step behind each rod 2, the flowing liquid forms free dynamic parallel vibrating films 4, separated by gas, which reach the opposite zigzag septum, mix with other free films, then the liquid flows to the underlying contact stage, where the process is repeated (figure 3).

The gas, rising countercurrent from below, passes between the free films and, passing between the rods 2, dissects the liquid, contributing to uniform irrigation with the liquid of each rod. Thus, in contrast to the prototype in the proposed apparatus, the contact surface of the phases is significantly larger than the surface of the wetted contact elements (Table 1)

Table 1
The specific contact surface of the phases of the mass transfer contact devices (MCU) ON 1.2 1.6 2.0 2.4 3.0 According to the prototype 70.9 66 63.5 62.2 61 Proposed MCU 121 116 113.5 112.2 111

The cross-sectional shape and diameter of the rods 2, the step between the rods, the distance between the vertical sectioning plates depend on the properties of the processed fluid and the flow characteristics of gas and liquid. Such a mass transfer contact device is most appropriate to use in the processes of countercurrent interaction of gas and liquid, when the technology requires high irrigation densities (50-300 m ³ / m ² h).

The table shows that when the claimed design parameters are met, the technical result of the invention is the doubling of the contact surface of the phases due to the formation of free dynamic liquid films, and the surface increase is achieved without increasing the specific volume of the contact devices, and, therefore, the mass transfer between the liquid and gas is almost doubled . It was not possible to achieve such irrigation densities, in combination with the phase contact surface, in analog devices and in the prototype.

When the H / A ratio is less than 1.2, the irrigation density and the limiting gas velocity decrease, and the dynamic film formation mode becomes unstable. An increase in the N / A ratio in excess of 3.25 leads to a sharp decrease in the mass transfer efficiency in the apparatus due to a reduction in the number of gas and liquid contacts per unit height of the nozzle and a decrease in the gas-liquid contact surface with a slight increase in its productivity.

Sectioning of the zigzag partitions 1 with vertical sectioning plates 3 prevents the free flow of fluid along the edges of the bend of the zigzag partitions, which significantly reduces wave formation in the cross section of the apparatus. To eliminate local irregularities in the density of irrigation in the cross section of the apparatus and improve mixing of the liquid, vertical sectioning plates in adjacent zigzag partitions forming a through vertical channel are staggered. This arrangement of the sectioning plates 3 allows the liquid to be redistributed over the cross section of the apparatus, which ultimately leads to an increase in the overall efficiency of the device (Fig. 2).

The set of distinctive features of the claimed device gives it new properties, due to which the achievement of the technical result is ensured, namely:

- an increase in the intensity of the mass transfer process at high irrigation densities;

- increase in irrigation density up to 300 m ³ / m ² h;

The invention is illustrated by drawings, where in Fig.1 shows the design of the mass transfer apparatus, and Fig.2 is a diagram of the movement of the fluid flow in a zigzag channel with vertical sectioning plates, Fig.3 shows the behavior of the liquid during countercurrent movement with gas.

The mass transfer apparatus includes a housing for the reagent inlet and outlet (not shown), and a mass transfer contact device, which is the subject of the invention, which consists of zigzag partitions 1, rods 2, vertical sectioning plates 3. The partitions form a through zigzag channel for the passage of liquid and gas. The rods 2 fit snugly against the partitions 1 at the points of bending of the latter and contribute to the directional breakdown of the liquid with the formation of free dynamic parallel vibrating films in the form of a sail 4, as shown in Fig.3. The vertical sectioning plates 3, having the shape of isosceles triangles, are attached to the zigzag partitions 1 with two equal sides, while the zigzag channel is partitioned into sections bounded by the zigzag partition 1, near the rods 2 and two adjacent vertical sectioning plates 3. The staggered arrangement of the plates on opposite zigzag sections 1 eliminates the formation within the same zigzag channel of several autonomous through channels from top to bottom, so how each overlying section communicates with two underlying (figure 2).

The device operates as follows:

- the liquid is supplied to the upper part of the apparatus and, with the help of a distribution device, enters into each through zigzag channel, in which it flows along the zigzag partitions 1. At the junction of the zigzag partitions 1 with the rods 2, the liquid envelopes the rod at the indicated irrigation densities and forms under the influence of the gas coming from below the so-called “sails” 4 or two-sided free-falling vibrating films that have a mass-transfer surface independent of the area of contact devices and repeatedly exceeding it (FIG. 3);

- gas enters the lower part of the apparatus, rises through the through zigzag channels upward, supporting free-falling films and finally tearing them into drops and jets. Drops of liquid are thrown to the opposite zigzag partitions 1 and flow to the underlying contact stage, where the formation of “sails” and the interaction of the liquid and gas are repeated.

The installation of vertical sectioning plates in the proposed apparatus gives the following technical result: at high densities of irrigation, free-flowing liquid does not have free flow along the entire length of the bending edge of the partition 1 in the transverse direction, which prevents the flow of liquid into one of the edges and gas leakage. Within one section bounded by adjacent vertical sectioning plates 3, the superposition of the primary and reflected from the vertical sectioning plates 3 waves equalizes the liquid level. The staggered arrangement of vertical sectioning plates in the channel allows the liquid 5 to flow from one section to two adjacent ones and, in the case of an uneven supply of liquid by the distribution device, be redistributed (Fig. 2) and irrigate the entire cross section of the device evenly. At the same time, the possibility of the formation of autonomous gas and liquid flows in the apparatus cross section is eliminated, and their interaction efficiency is increased, i.e. mass transfer rate.

Thus, a mass transfer contact device for the interaction of liquid and gas, containing zigzag partitions forming through vertical zigzag channels for the passage of liquid and gas, and vertical rods that are tightly adjacent to the edges of the bend of zigzag partitions, in which vertical sectional zigzag partitions are secured in a checkerboard pattern plates, while the zigzag partitions are made with the ratio N / A = 1.2 ÷ 3.25, where H is the distance between the edges of the flexible and a zigzag partition, A is the distance between the zigzag partitions in the range from 35 to 75 mm, and the radius of the edge of the bend of the zigzag partitions is not more than 3 mm, can be used with irrigation densities of liquid of 50-300 m ³ / m ² h, and the phase contact surface and, therefore, the intensity of mass transfer doubles.

Claims (2)

1. Mass transfer contact device for the interaction of liquid and gas, containing zigzag partitions, forming through vertical zigzag channels for the passage of liquid and gas, and vertical rods that are closely adjacent to the edges of the bend of the zigzag partitions, characterized in that when the irrigation densities of the liquid are 50-300 m ³ / m ² h for vertical rods in vertical zigzag channels for the passage of liquid and gas on opposite zigzag partitions staggered vertically sectional plates, while the zigzag partitions are made with the ratio N / A = 1.2 ÷ 3.25, where H is the distance between the edges of the bend of the zigzag partition, A is the distance between the zigzag partitions in the range of 35-75 mm, and the radius of the edge of the bend zigzag partitions is not more than 3 mm. 2. The device according to claim 1, characterized in that the rods are made in the form of a round or tear-shaped section.

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