GB2070967A

GB2070967A - Gas-liquid contactor

Info

Publication number: GB2070967A
Application number: GB8106813A
Authority: GB
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1980-03-11
Filing date: 1981-03-04
Publication date: 1981-09-16
Also published as: DE3110173A1; GB2070967B; DE3110173C2

Abstract

The gas-liquid contactor, e.g. a reactor or a spray-drier for slurries is of the kind having a contactor body 1 with its axis directed substantially vertically, a throat 2 formed in the lower or upper part of the body and having an inside diameter smaller than that of the body, a cyclone provided below or above the throat and larger in inside diameter than the throat, and a nozzle shaft 4 held substantially vertically in the throat or cyclone. The nozzle may direct liquid upward, as shown, or downwardly. The invention is characterised in that a plurality of flow-velocity-control vanes 5 are mounted on the nozzle shaft; if appropriate, these vanes may each be formed with a plurality of perforations. It has been found that, by use of such vanes, there is an improved distribution of the axial and spiral velocity components in the vicinity of the throat compared with conventional apparatus, with a consequent improvement in mixing of the gas and liquid fed therethrough. <IMAGE>

Description

SPECIFICATION Gas-liquid contactors This invention relates to improvements in gasliquid contactors in general, including the apparatus in which a gas and a liquid are subjected to a contact reaction and the units in which a liquid is dried, or evaporated, by a hot gas.

The term "liquid" as used herein means any slurry as well as liquid to be handled.

Among conventional gas-liquid contactors is the one typically shown in Fig. 1. This contactor is of the upward gas flow type and comprises a cyclone c into which a gas to be treated or hot air for drying use a is tangentially introduced and is imparted with a spiral motion, a throat dformed by converging the upper part of the cyclone, a contactor body e fabricated above the throat by diverging the upper part of the throat, and a nozzle f extended vertically through the bottom of the cyclone up to the center of the throat d.

Another conventional contactor is of the downward gas flow type as shown in Fig. 2.

This comprises a cyclone c into which a gas to be treated or hot air for drying use a is tangentially introduced and is imparted with a spiral motion, a throat dformed by converging the lower part of the cyclone, a contactor body e fabricated below the throat by diverging the lower part of the throat, and a nozzle f extended vertically through the top of the cyclone down to the center of the throat d.

In these existing contactors the manner in which the gas to be treated or the hot air for drying use a introduced into the vessel mixes with the reactant chemical or the material to be dried b will influence, to a considerable extent, the reaction rate or drying efficiency to be achieved. In the case where the chemical or the material to be dried b is a slurry or liquid, its mixing with the gas will have a material effect also upon the adhesion of the resultant or evaporation residue to the inner all surfaces of the contactor.

To be more specific, mixing of gases in a contactor is dictated, as indicated in Figs. 1 and 2, by the velocity in the direction Z around the nozzle f(i.e., the velocity axially of the contactor, hereinafter called the "axial velocity") and by the velocity in the direction cp (velocity circumferentially of the contactor, hereinafter called the "spiral velocity").

With conventional gas-liquid contactors, however, these flow velocity components cannot be freely adjusted but are empirically held to predetermined values individually by modifying the contactor dimensions and nozzle position.

An object of the invention is to provide a gas-liquid contactor in which the flow velocity components are controllable as desired and the gas flow and the chemical or material to be dried are maintained in an optimumly mixed state to achieve a high rate of reaction or drying efficiency.

According to the invention, there is provided a gas-liquid contactor which has a contactor body with the axis directed substantially vertically, a throat formed in the lower or upper part of the body and having an inside diameter smaller than that of the body, a cyclone provided below or above the throat and larger in inside diameter than the throat, and a nozzle shaft held substantially vertically in the throat or cyclone, which is characterised in that a plurality of flow-velocity-control vanes are attached to the nozzle shaft.

Since the flow-velocity-control vanes are mounted on the nozzle shaft in accordance with the invention, the axial and spiral velocities of the gas to be treated or the hot air for drying use can be freely set to desired values by suitably altering the size, shape, and number of the vanes. The mixing conditions of the gas to be treated or the hot air and the chemical or the material to be dried that is issued out of the nozzle can be freely adjusted, and uniform mixing is produced within the contactor.

The above and other objects and features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which: Figures 1 and 2 are vertically sectional side views of two different gas-liquid contactors of conventional designs; Figure 3 is vertically sectional side view of a gas-liquid contactor embodying the invention; Figure 4 is a transverse sectional view taken on the line IV-IV of Fig. 3; Figure 5 is a vertically sectional side view of another embodiment of the invention; Figure 6 is a transverse sectional view taken on the line VI-VI of Fig. 5; Figure 7 is a vertically sectional view of still another embodiment of the invention; Figure 8 is a transverse sectional view taken on the line VIII-VIII of Fig. 7;;'and Figures 9 through 12 are characteristic curves representing the distributions of axial and spiral velocities in the contactors of the prior art and of the invention.

The invention will now be described in detail with reference to the drawings showing embodiments thereof. Figs. 3 and 4 illustrate an embodiment of the upward gas flow type.

The numeral 1 indicates a cylindrical contactor body with the axis directed substantially vertically. The body 1 is converged at a lower part to a truncated conical shape, forming a throat 2 of a venturi. The throat 2 is followed by a downwardly expanding or divergent section in the form of an inverted truncated cone.

This cone combines with a cylindrical bottom part to constitute a cyclone 3. A nozzle 4 is extended vertically through the bottom of the cyclone, upwardly along the central axis, to open in the center of the throat 2.

Near the upper end of the nozzle 4, there are flow-velocity-control vanes 5 integrally mounted at intervals of 60 deg. circumferentially so as to extend radially outward from the central axis of the nozzle. The cyclone 3 is provided with a tangential inlet 7.

Since the embodiment of Figs. 3 and 4 is constructed in the manner described, a stream of gas to be treated or hot air for drying use 8 enters the cyclone 3 tangentially at the inlet 7 and flows spirally upward while maintaining the tangential velocity around the axis of the contactor. The magnitude of this vortex flow is reduced above the throat 2 due to the presence of the vanes 5, or by virtue of the drag corresponding to the overall surface area of the vanes. Thus, the vortex flow can be reduced by a suitable amount above the throat by means of the vanes 5, without decreasing the original magnitude of the vortex flow in the cyclone 3.

Past the throat 2, the gas is mixed for reaction with a spray liquid chemical 10 or dries a material 10 sprayed to be dried, coming out of the nozzle 4 which is supplied with the liquid chemical or wet material, while the gas is being reduced in the magnitude of its vortex flow and is subjected to a flowvelocity-control action of its axial flow by the vanes 5. Following this, the gas leaves the contactor at the outlet 12 as treated or used gas 11.

In the embodiment of Figs. 3 and 4, as will be explained later, the axial and spiral velocities of the gas can be uniformly distributed by means of the vanes 5 attached to the nozzle 4.

Figs. 5 and 6 show another embodiment of the invention, in which each of the flowvelocity-control vanes 5 of the preceding embodiment is formed with a plurality of perforations 6 of suitable size and shape.

In this embodiment of Figs. 5 and 6, the magnitude of the vortex flow of the treated gas 8 that has entered the cyclone 3 tangentially at the inlet 7 and is flowing spirally upward decreases in the smaller-diameter portion of the throat 2 because of the drag corresponding to the overall surface area of the vanes 5 and the size and shape of the perforations 6. Thus, it is again possible to reduce the vortex flow by a suitable amount above the throat, on account of the overall surface area and the perforations 6 of the vanes 5 located above the cyclone.

Like the counterparts of the first embodiment. the vanes 5 of this embodiment act to control the velocity components of the upward gas flow and, in addition, the plurality of perforations 6 formed in the vanes 5 permit the latter to uniformalize the static pressures in the sectional spaces partitioned by the vanes, thus achieving an even greater flowregulating effect than the previous ones. Figs. 7 and 8 show an embodiment of the downward gas flow type. The numeral 101 designates a cylindrical contactor body with the axis directed substantially vertically. The upper part of the contactor body 101 is converged to the form of a truncated cone, forming a throat 102. Above the throat 102 is formed a cyclone 103 by a section up wardly diverged to the form of an inverted truncated cone and a cylindrical head.From above the cyclone 103 extends a nozzle 104 vertically downwardly along the central axis of the cyclone. so that its opening is located in the center of the throat 102.

A total of six flow-velocity-control vanes 105 are integrally mounted on a portion of the nozzle 104 near its lower end. They are spaced 60 deg. apart from one another cir cumferentially and extend radially outwardly from the central axis of the nozzle 104. Each of the vanes 105 is formed with a plurality of perforations 106 of suitable size and shape.

The numeral 107 represents an inlet to the cyclone 103, 11 2 an outlet of the contactor, 11 3 a hopper. and 114 a valve.

It should be obvious to those skilled in the art that the vanes 105 with the perforations 106 may, of course, be replaced by unperfor ated vanes as used in the embodiment illus trated in Figs. 3 and 4.

In the embodiment of the foregoing con struction depicted in Figs. 7 and 8, a stream of gas to be treated or hot air for drying use 108 enters the cyclone 103 tangentially at the inlet 107 and flows spirally downward while maintaining the tangential velocity around the axis of the contactor. The magni tude of this vortex flow is reduced beneath the throat 102 by virtue of the drag corre sponding to the overall surface area of the vanes 105 and the perforations 106. Thus, the vortex flow can be reduced by a suitable amount beneath the throat by means of the overall surface area of the vanes 105 and the perforations 106, without decreasing the orig inal magnitude of the vortex flow in the cyclone 103.

The vanes 105 act to regulate the down ward gas flow and, moreover, the plurality of perforations 106 formed in the vanes 105 permit the latter to uniformalize the static pressures in the sectoral spaces partitioned by the vanes.

Then, past the throat 102, the gas is mixed for reaction with a spray liquid chemical 110 or dries a material 110 sprayed to be dried, being issued from the nozzle 104 which is supplied with the liquid chemical or wet mate rial, while the gas is being reduced in the magnitude of its vortex flow and subjected to a flow-velocity-control action of its axial flow by the vanes 105. After this, the gas leaves the contactor at the outlet 112 as treated or used gas 111. The solids that have resulted from the reaction or drying are collected by the hopper 11 3 at the bottom of the contactor body 101 and are taken out of the apparatus by turning the valve 114 open.

In the embodiment shown, the axial and spiral velocities of the gas can be made uniform in distribution by means of the vanes 105 attached to the nozzle 104.

Now, the results of experiments we conducted to ascertain the advantageous effects of the present invention will be explained in connection with Figs. 9 and 10. Fig. 9 illustrates distributions of axial gas velocity components diametrally (along the chain line IX-IX of Fig. 4) of the cross section at the outlet of the throat 2 of the arrangements shown in Figs. 3 through 6. Fig. 10 shows distributions of spiral velocity components circumferentially of the region half the radius of the above cross section of the throat. In the both figures the curves L connecting circles represent the results of tests with the conventional vaneless apparatus; the curves M connecting crosses represent those with the embodiment of Figs. 3 and 4 having unperforated vanes 5; and the curves N connecting triangles represent those with the embodiment of Figs. 5 and 6 having vanes 5 with perforations 6.

As will be understood from these test results, the conventional apparatus free of vanes 5 involves an asymmetrical distribution of the axial velocity component as indicated by the curve L in Fig. 9, even producing a negative velocity (back flow) in and around the center of the throat. The spiral velocity, too, gives an extremely asymmetrical pattern as in Fig. 10.

In the embodiment of the invention equipped with unperforated vanes 5, as indicated by the curves M, the both axial and spiral velocity components are distributed almost symmetrically relative to the axis, with no axial back flow at all. Further, in the embodiment having vanes 5 with perforations 6, the axial velocity pattern is very close to axial symmetry and the distribution of the spiral velocity component is even closer to uniformity, as the curves N indicate, because the static pressures in the spaces defined by the vanes 5 are equalized by the perforations 6.

In the both embodiments of the invention the increased proportion of the velocity component in the axial direction and uniformalized axial and spiral velocity patterns positively keep the reaction product or dried matter from sticking to the inner wall surfaces of the contactor. By the way, in Fig. 10 symbol (+) is positive direction, and symbol (~) is negative direction.

Figs. 11 and 12 represent the results of experiments conducted in exactly the same way with the embodiment of the downward gas flow type shown in Figs. 7 and 8 and also with another embodiment having the same vanes 105 but without the perforations 106.

It will be seen from these figures that quite the same effects as with the units of the upward gas flow type are achieved. The curves L', M', and N' correspond, respectively, to the curves L, M, and N in Figs. 9 and 10.

Although the flow-velocity-control vanes 5 and 105 of the embodiments so far described are formed parallelly along planes extending through the central axes of the nozzles 4 and '104, pitched or helically shaped ones may be employed instead. Such a modification will make the correlative adjustments of the axial and spiral gas velocities easier.

Also, while the flow-velocity-control vanes of the embodiments are all fixed, they may be replaced by vanes which turn freely, either very lightly or with a certain rotational resistance.

Claims

1. A gas-liquid contactor having a contactor body with an axis directed substantially vertically, a throat formed in the lower or upper part of the body and having an inside diameter smaller than that of said body, a cyclone provided below or above the throat and larger in inside diameter than said throat, and a nozzle shaft located substantially vertically in said throat or said cyclone, characterised in that a plurality of flow-velocity-control vanes are mounted on said nozzle shaft.

2. A gas-liquid contactor according to Claim 1, characterized in that each of said flow-velocity-control vanes is formed with a plurality of perforations.

3. A gas-liquid contactor according to Claim 1 of Claim 2, characterized in that said flow-velocity-control vanes are non-rotationally fixed to said nozzle shaft.

4. A gas-liquid contactor, constructed, arranged and adapted to operate substantially as hereinbefore described, and as shown in Figs. 3 and 4, or 5 and 6 taken in conjunction with Figs. 9 and 10, or Figs. 7 and 8 taken in conjunction with Figs. 11 and 12.