GB1561960A

GB1561960A - Ring gap washers

Info

Publication number: GB1561960A
Application number: GB36508/77A
Authority: GB
Original assignee: Gottfried Bischoff Bau Kompl Gasreinigungs und Wasserrueckkehlanlagen GmbH and Co KG
Current assignee: Gottfried Bischoff Bau Kompl Gasreinigungs und Wasserrueckkehlanlagen GmbH and Co KG
Priority date: 1976-09-07
Filing date: 1977-09-01
Publication date: 1980-03-05
Also published as: IT1109470B; ZA775357B; BR7705947A; NL186063C; FR2363361B1; ES462157A1; FR2363361A1; ATA640277A; AU2858277A; BE858422A; JPS5363771A; DE2640152B1; LU78091A1; NL7709859A

Description

(54) ltMPROVEMENTS IN OR RELATING TO RING GAP WASHERS (71) We, GOTTFRIED BISCHOFF BAU KOMPL GASREINIGUNGS- UND WASSER RUCKKUHLANLAGEN GmbH & Co. KOM MANDlTGE5ELL5CHAFT, a Company organised under the laws of the Federal Republic of Germany tof 4300 Essen, Gartnerstrasse 44. Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to ring gap washers for the cleaning of a flow of gas, having a ring gap housing and an in-built member mounted coaxially and axially movable within it and forming with the ring gap housing the ring gap channel, together with at least one washing medium nozzle located Upstream of the inbuilt member in the direction of flow of gas, in which the ring gap housing of the ring gap washer, downstream of an annular constriction, gradually expands in the direction of flow of the gas, and the inbuilt member is provided with a matching enlargement. Such washers are knawn for use in the treatment of flows of industrial flue gases, particularly flows of converter gas, blast furnace gas and the like. Moreover the gas flow to be treated may be a heterogeneous or a homogeneous mixture.

The flow channel, the inbuilt member and the ring gap are conically reduced in diameter ntt only in known ring gap washers which belong to the Venturi washer type (see Staub-Reinhalt. Luft 33 1973 p 494, 4j1), but also in ring gap washers to which the invention relates (see German Gebrauchsmuster 75 25 946.0).

Consequently the flow ef gas as it enters the ring gap washer as a whole and also in the ring gap experiences an anabatic acceleration that is positive and far removed from zero, and on this depends the separation effect which is explained as follows for a heterogeneous, i.e. dust-laden mixture.

The separation of solid particles from a flow of gas by means of a wet washer, and accordingly by means of a Venturi washer or a ring gap washer is essentially determined by the inertia effects and turbulent diffusion. The way in which these effects are exploited depends upon the mixture.

In the case of inertia effects, the dustladen gas flows over a drop of liquid, and as the solid particles are unable to follow the lines of flow on account of their large masses in comparison with the masses of the gas molecules, they impinge upon the drops of liquid and, to the extent that they can penetrate, are removed from the flow of gas, that is, they are absorbed by the drops of liquid. Several factors control this process which make use of the different inertia effects of different masses.

First of all care must be taken that the streamlines of the gas should maintain their direction to ever-closer distances from the surface of the drop of liquid over which they flow. They follow the contour of the drop until finally they strike practically without deviation against the contour of the drop of washing liquid. This means that the effect of inertia becomes greater with momentary changes of direction with the result that ever more and ever smaller solid particles impinge upon the drops and are removed. As momentum increases it is obvious that more and more particles are able to overcome the surface tension of the drop and penetrate it, and the anabatic acceleration described is effected for this purpose. The probability that a dust particle will impinge upon a droplet also in creases with the velocity of the flow of gas, and therewith the velocity of dust particles, relative to the drops of liquid. The area of liquid surface available to the dust increases, for a given ratio of gas to liquid, with the number of droplets produced. and the range of particle sizes for which inertia forces are effective increases correspondingly. Obviously large solid particles are preferentially separated.

It is otherwise with turbulent diffusion, where the characteristic feature of turbulent flow is that transverse movements are superimposed on the main flow, which become stronger as the degree of turbulence increases. Thereby considerably greater contact forces are obtained between neighbouring particles in the stream, compared with laminar flow, and this is exploited for the cleaning of the flow of gas.

The dominant factors of the effect of turbulent diffusion are on one hand the degree of turbulence of a flow and on the other hand, as with inertia separation, the degree of dispersion of the liquid, but dust composition, flow geometry, and duration of contact also play their parts.

It is a special characteristic of Venturitype washers that the energy for the dispersion of the liquid into droplets is derived from the flow of gas, and this is only possible at considerable flow velocities.

However the smaller are the drops of liquid produced, the faster are they accelerated by the gas, so that only a limited path length can be used for the capture of particles by the inertia effect. Consequently two different kinds of process are possible to achieve effective dust separation. the inertia effect exclusively, in which case very large gas velocities have to be employed as happens in short-throated Venturi washers, or additionally the use of turbulent diffusion which then becomes particularly effective for very small dust particles. In this case however longer contact periods must be created than is the case with normal ring gap washers to which the invention relates.

The pressure loss which a flow of gas undergoes in a Venturi washer, in a classical ring gap washer with the inbuilt member retracted, or with.a ring gap washer to which the invention relates (for normal cleaning duties, e.g. blast furnace gas) is of the order of 1200 mm. head of water, or more. In contrast with this it is the basic problem of the invention to provide a ring gap washer designed so that an equal de gree of purification can be achieved with greatly reduced pressure losses.

According to the present invention a process for cleaning a gas stream in a ring gap washer comprises admitting the gas stream into the ring gap washer through an inlet thereto, injecting into the gas stream a washing liquid, and passing the gas stream with entrained washing liquid through a constriction into a divergent annular gap in which the gas flow decelerates. Preferably deceleration of the gas flow in the divergent annular gap is assisted by the creation of turbulence.

According to a further feature of the invention, a ring gap washer for the cleaning of a flow of gas comprises a ring gap hous- ing and an inbuilt member mounted co- axially and axially movable within it and forming with the ring gap housing the ring gap channel, at least one washing medium nozzle located up stream of the inbuilt mem- ber in the direction of flow of the gas, the ring gap housing of the ring gap washer, downstream of an annular constriction gradually expanding in the direction of flow of the gas and the inbuilt member being provided with a matching enlargement, the walls of the ring gap housing and the inbuilt member being constructed so as to be everywhere equidistant from ene another and that the ring gap housing is subjected to an increase from its entry crosssectional area to its exit cross-sectional area, which decelerates the gas flow. However the design can be such that the walls of the ring gap housing and the inbuilt member diverges to form a ring gap channel whose annular gap increases in area in the direction of flow, this gap increase together with the increased cross-sectional area of- the ring gap housing decelerating the gas flow.

A central cylinder may be located in front of the inbuilt member, its diameter corresponding approximately to that of the inlet restriction. This cylinder can be hollow, of tubular form, with the flow of gas passing through it, and the nozzle for the injection of the washing liquid can be located in this cylinder. The cylinder may however also be attached to the inbuilt member, in which case the nozzles for injection of the washing liquid must surround the cylinder. A cylindrically-shaped extension can also be attached to the inbuilt member at the outflow - end. In any case a ring gap washer according to the invention will generally be so formed as a whole that a conically-tapered inlet section extending from the inlet to the housing is connected without any step or the like to the diameter of an incoming gas main whilst the ring gap housing is so designed to have the desired effect of decelerating the gas flow, and discharges into a separator tower or the like.

The invention achieves a surprising effect, namely in comparison with known ring gap washers, a considerable reduction of pressure losses for equal cleaning duties and an equal or even improved degree of purification. The pressure losses can be reduced by 30% and frequently by much more. The invention originates from the recognition that in a ring gap washer according to the invention very favourable conditions for separation based on the inertia effect, particularly for coarse dust particles, and created in the region of the restriction, whilst subsequently, as a result of the described deceleration of the flow of gas, the turbulence effect becomes par ticularly effective-all of which operates with a small total pressure loss.

Two embodiments of the invention will now be described with reference to the accompanying schematic drawings in which: Figure 1 is an axial section through a ring gap washer according to the invent tion; Figure 2 is a section on the line B--B of Figure 1; and Figure 3 is another form of construction of the subject of Figure 1.

A ring gap washer consists of a ring gap housing 1 and an inbuilt member 3 mounted coaxially and movable within it, forming with the ring gap housing 1 the ring gap channel 2. At least one washing medium nozzle 4 is located before the inbuilt member 3 in the direction of flow of the gas.

The ring gap housing 1 of the ring gap washer, beyond a conically-tapered inlet 5 and an inlet restriction 6, gradually expands in the direction of flow of the gas and the inbuilt member 3 is provided with a maching enlargement 7. The design as a whole is so arranged that the flow of gas in the ring gap channel 2 undergoes a deceleration.

In the form of construction according to Figures 1 and 2, the design is so arranged for this purpose that the walls 8, 9 of the ring gap housing 1 and the inbuilt member 3 are constructed to be equidistant at all points. Thus the desired effect is achieved in this case in that the ring gap housing 1 is subjected to expansion between its entry cross-sectional area 10 and exit cross-sectional area 11, which decelerates the gas flow.

The form of construction according to Figure 3 is different. Here the walls 8, 9 of ring gap housing 1 and inbuilt member 3 form a ring gap channel 2 whose an nular gap length increases in the direction of flow. This gap length together with the expansion of the ring gap housing I and the inbuilt member 3 decelerates the gas flow. In this embodiment, a central cylinder 12 is located in front of the inbuilt member 3, its diameter corresponding approximately to that of the inlet restriction 6.

Moreover the conically-tapered inlet S is constructed with a diameter corresponding to that of the incoming gas main 13, whilst conversely the conically expanded ring gap housing 1 discharges into a subsequent separator tower or the like that is not shown.

The direction of movement of the inbuilt member 3 is indicated by the double arrow 14 in Figure 1 and arrows 15 show the direction of flow.

WHAT WE CLAIM IS:- 1. A process for cleaning a gas stream in a ring gap washer comprising admitting the gas stream into the ring gap washer through an inlet thereto, injecting into the gas stream with entrained washing liquid through a constriction into a divergent annular gap in which the gas flow decelerates.

2. A process as in Claim 1, wherein deceleration of the gas flow in the divergent annular gap is assisted by the creation of turbulence.

3. A ring gap washer for the cleaning of a flow of gas, comprising a ring gap housing and an inbuilt member mounted coaxially and axially movable within it and forming with the ring gap housing the ring gap channel, at least one washing medium nozzle located upstream of the inbuilt member in the direction of flow of the gas, the ring gap housing of the ring gap washer, downstream of an annular constriction gradually expanding in the direction of flow of the gas and the inbuilt member being provided with a matching enlargement, the walls of the ring gap housing and the inbuilt member being constructed so as to be everywhere equidistant from one another and the ring gap housing increases in crosssectional area from an inlet to an exit whereby to decelerate the gas flow.

4. A ring gap washer for the cleaning of a flow of gas, comprising a ring gap housing and an inbuilt member mounted coaxially and axially movable within it and forming with the ring gap housing the ring gap channel, at least one washing medium nozzle located upstream of the inbuilt member in the direction of flow of the gas, the ring gap housing of the ring gap washer, downstream if an annular constriction gradually expanding in the direction of flow of the gas and the inbuilt member being provided with a matching enlargement, the walls of the ring gap housing and the inbuilt member diverging to form a ring gap channel whose annular gap increases in area in the direction of flow, this gap increase together with the enlargement of the ring gap housing cross-sectional area from inlet to exit decelerating the gas flow.

5. A ring gap washer as in any of Claims 1 to 4, wherein a central cylinder

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Claims

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purification. The pressure losses can be reduced by 30% and frequently by much more. The invention originates from the recognition that in a ring gap washer according to the invention very favourable conditions for separation based on the inertia effect, particularly for coarse dust particles, and created in the region of the restriction, whilst subsequently, as a result of the described deceleration of the flow of gas, the turbulence effect becomes par ticularly effective-all of which operates with a small total pressure loss.

Two embodiments of the invention will now be described with reference to the accompanying schematic drawings in which: Figure 1 is an axial section through a ring gap washer according to the invent tion; Figure 2 is a section on the line B--B of Figure 1; and Figure 3 is another form of construction of the subject of Figure 1.

A ring gap washer consists of a ring gap housing 1 and an inbuilt member 3 mounted coaxially and movable within it, forming with the ring gap housing 1 the ring gap channel 2. At least one washing medium nozzle 4 is located before the inbuilt member 3 in the direction of flow of the gas.

The ring gap housing 1 of the ring gap washer, beyond a conically-tapered inlet 5 and an inlet restriction 6, gradually expands in the direction of flow of the gas and the inbuilt member 3 is provided with a maching enlargement 7. The design as a whole is so arranged that the flow of gas in the ring gap channel 2 undergoes a deceleration.

In the form of construction according to Figures 1 and 2, the design is so arranged for this purpose that the walls 8, 9 of the ring gap housing 1 and the inbuilt member 3 are constructed to be equidistant at all points. Thus the desired effect is achieved in this case in that the ring gap housing 1 is subjected to expansion between its entry cross-sectional area 10 and exit cross-sectional area 11, which decelerates the gas flow.

The form of construction according to Figure 3 is different. Here the walls 8, 9 of ring gap housing 1 and inbuilt member

3 form a ring gap channel 2 whose an nular gap length increases in the direction of flow. This gap length together with the expansion of the ring gap housing I and the inbuilt member 3 decelerates the gas flow. In this embodiment, a central cylinder 12 is located in front of the inbuilt member 3, its diameter corresponding approximately to that of the inlet restriction 6.

Moreover the conically-tapered inlet S is constructed with a diameter corresponding to that of the incoming gas main 13, whilst conversely the conically expanded ring gap housing 1 discharges into a subsequent separator tower or the like that is not shown.

The direction of movement of the inbuilt member 3 is indicated by the double arrow 14 in Figure 1 and arrows 15 show the direction of flow.

WHAT WE CLAIM IS:- 1. A process for cleaning a gas stream in a ring gap washer comprising admitting the gas stream into the ring gap washer through an inlet thereto, injecting into the gas stream with entrained washing liquid through a constriction into a divergent annular gap in which the gas flow decelerates.
2. A process as in Claim 1, wherein deceleration of the gas flow in the divergent annular gap is assisted by the creation of turbulence.
3. A ring gap washer for the cleaning of a flow of gas, comprising a ring gap housing and an inbuilt member mounted coaxially and axially movable within it and forming with the ring gap housing the ring gap channel, at least one washing medium nozzle located upstream of the inbuilt member in the direction of flow of the gas, the ring gap housing of the ring gap washer, downstream of an annular constriction gradually expanding in the direction of flow of the gas and the inbuilt member being provided with a matching enlargement, the walls of the ring gap housing and the inbuilt member being constructed so as to be everywhere equidistant from one another and the ring gap housing increases in crosssectional area from an inlet to an exit whereby to decelerate the gas flow.
4. A ring gap washer for the cleaning of a flow of gas, comprising a ring gap housing and an inbuilt member mounted coaxially and axially movable within it and forming with the ring gap housing the ring gap channel, at least one washing medium nozzle located upstream of the inbuilt member in the direction of flow of the gas, the ring gap housing of the ring gap washer, downstream if an annular constriction gradually expanding in the direction of flow of the gas and the inbuilt member being provided with a matching enlargement, the walls of the ring gap housing and the inbuilt member diverging to form a ring gap channel whose annular gap increases in area in the direction of flow, this gap increase together with the enlargement of the ring gap housing cross-sectional area from inlet to exit decelerating the gas flow.
5. A ring gap washer as in any of Claims 1 to 4, wherein a central cylinder

is located in front of the inbuilt member in the direction of flow, its diameter approximately corresponding to that of the inlet diameter of the ring gap housing.
6. A ring gap washer as in any of Claims 1 to 5, wherein a conically-tapered inlet section extending from the ring gap housing inlet is connected without any step to an incoming gas main and the ring gap housing discharges into a separator tower.
7. A ring gap washer substantially as hereinbefore described with reference to Figures 1 and 2 and Figure 3 of the accompanying drawings.