WO1997012685A1

WO1997012685A1 - Spraying device for solid-laden liquids, particularly abrasive liquids

Info

Publication number: WO1997012685A1
Application number: PCT/FR1996/001538
Authority: WO
Inventors: Daniel Bontoux
Original assignee: Lab S.A.
Priority date: 1995-10-03
Filing date: 1996-10-02
Publication date: 1997-04-10
Also published as: FR2739306A1; FR2739306B1

Abstract

Spraying device for solid-laden liquids, particularly of the abrasive type, wherein the liquid to be sprayed, introduced tangentially into an annular groove (1) from which it overflows on one side only in order to form a hollow cone of fine droplets, comes in contact, when overflowing, with a circular cross-section movable member (2) held loose about an axis (3) along which it may be displaced rotationally and translationally in a limited way, said liquid causing the rotation of the movable member, characterized in that, when inactivated, the movable member (2) is in contact with the central portion (6) of the annular groove (1) so as to leave free a substantially annular passage for the liquid between the overflow surfaces (10 and 8) and the periphery of said member (2), and in that, due to the clearance of that member (2) rotationally actuated by the liquid, the contact between the liquid and said member causes a spraying effect and the generation of very fine droplets.

Description

SPRAYER FOR LOADED LIQUIDS, ESPECIALLY ABRASIVE

PATENT AREA

The present invention relates to a sprayer specially adapted for liquids containing a suspension of solid particles which can be abrasive.

STATE OF THE ART

Spraying liquids is a significant problem for many industrial applications. Among these, mention may be made: cooling of hot gases, conditioning of gases, purification of smoke. It is known that a particularly effective process for ensuring the spraying of liquids in the form of very fine droplets consists of injection. simultaneous gas under pressure and the liquid to be sprayed with a sprayer. However, this solution does not lend itself well to the use of liquids loaded with solids, the risks of clogging being considerable.

It is also known that an effective method in the case of liquids loaded with heavy particles consists in injecting the liquid tangentially into an annular groove inside which it rotates at high speed and from which it tangentially escapes in the form of 'one or more tablecloths. French Patent No. 2,304,409 describes such a device. However, in this case a very fine spray is not obtained, the speed of the liquid not being able to be very high in the presence of abrasive liquid.

Document EP-A-0 010 925 (IRRITECH) shows a sprayer of the aforementioned type in which there is provided in the outlet orifice a movable member capable of ensuring by rotation the deflection of the liquid and the improvement of the spraying . However, it should be noted that this improvement has the aim and effect of suppressing the production of very fine droplets in order to limit losses by evaporation. 0r the present invention is part of industrial applications in which it is advantageous to generate very fine droplets suitable for evaporating water spray. SUMMARY DESCRIPTION OF THE INVENTION

The present invention aims to remedy these drawbacks.

For this purpose, in a sprayer in which the liquid is fed tangentially into the inner part of a shallow groove inside which it is rotated and overflows from this groove on one side, there is provided a movable member with circular section maintained loosely around a fixed axis to come into contact with the liquid overflowing from the throat and thus promote the formation of fine droplets.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is a cross section (along I-I of Figure 2) of the sprayer object of the invention.

Figure 2 is a top view with partial section (along II-II of Figure 1). Figures 3 and 4 illustrate the tests carried out with a sprayer according to the invention.

In FIG. 1, the sprayer shown comprises a hollow annular body open on one of its faces. The edge (8) of the opening has a conical profile flared towards the outside. The interior space is hollowed out by a groove (1) with a transverse profile in the form of a spiral, its depth going thus decreasing from the point of supply of the liquid to a deflector (7), that is to say after a slightly smaller angle. 360 °. This groove (1) is connected to the conical edge (8) by a substantially toroidal curved surface (10) of internal diameter Di. The deepest part of this groove (1) is connected to a supply chamber (9) provided with a junction flange (12).

The other face of the sprayer is formed by the central part (6) of the annular page (1), this central part (6) being preferably raised relative to the mean plane of the groove (1). On this central part (6) is welded an axis (3) on which is fixed, for example by a nut and lock nut system (5), a large disc-shaped washer (4) whose center coincides with the axis of the conical edge (8) and the surface of which is parallel to the plane of the central part (6), its diameter being slightly less than the diameter Di. Between this washer (4) and the central part (6) is mounted a member mobile of revolution (2), hollowed out with a cylindrical internal recess of diameter significantly greater than that of the axis (3 ⁾ , preferably at least 1.7 times this diameter. The outer surface of revolution is preferably conical, being more flared on the side of the washer (4). Advantageously, this movable member (2) has a low height compared to its average diameter, preferably less than 1.9 times this diameter. The operation is as follows: things are arranged so that at rest the underside of the member (2) is in contact with the central part (6), providing a free annular space between the overflow surfaces (10 and 8) and the periphery of said member (2). The liquid arriving under pressure through the chamber (9) is introduced tangentially into the groove (1) at the place where it is the deepest and is rotated in the latter. As the liquid angularly advances, the depth of the throat decreases, so that the liquid is gradually and uniformly ejected towards the curved surface (10) where it comes into contact with the movable member (2) which by following the game it has on the axis (3) enters into rotation, which has the effect of breaking the cohesion of the liquid and thus generating a set of very fine droplets ready to be ejected. The liquid thus divided escapes through the edge (8) in the form of a very open cone directed towards the outside by defining a hollow cone of very fine droplets of said liquid.

The function of the deflector (7) is not only to complete the ejection, but above all to force the elimination of any solid particles that may be present which could tend to accumulate at the bottom of the throat in the absence of said deflector. Since the sprayer does not have a very narrowed part, we are in a situation where we are, by design, safe from clogging.

The deflector (7) has in its preferred embodiment, a triangular profile. The movable member (2) advantageously has a taper angle of 5 to 15 degrees and it touches the liquid overflowing from the groove (1) in the part of the curved surface where the speed of this Liqui¬ is very high.

To demonstrate the advantages of the sprayer according to the invention, two series of experiments were carried out. The scheme of the experiments is described in Figure 3 where we can see the sprayer (b) mounted in the center of a tank (g) whose diameter is 4 m. The water (e) is circulated using a pump (c) which supplies the sprayer (b). Which projects a veil of droplets (a). The temperature of water is measured at several points including (d). The performances have been compared with those of a "conventional" sprayer, obtained by operating the sprayer according to the invention without its movable member (2).

The first experiment aimed to establish, all other things being equal, that the droplet size distribution is finer. To do this, the liquid flow rate which reaches a defined distance d was measured using a container (f) cut from a slot of dimensions w = 20 mm by h = 150 mm, which container is moved in a movement. of revolution around the sprayer (b). The water used for these experiments was supplied at a relative pressure of 331 kPa. The main data are summarized in the table below:

It has been verified that the height of the slit used for the measurement is sufficient to intercept the entire veil. The decrease in the quantity of water reaching the wall is explained by the fact that much finer drops are generated by the sprayer according to the invention and that these fine drops, comparatively more aerodynamically braked than the large ones, cannot reach the wall and are evaporated en route. This phenomenon of increased evaporation has been observed in subsequent tests.

In a second series of tests carried out to evaluate the performance in terms of mass transfer, the temperature profile and the quantity of total water evaporated at the end of tests obtained by spraying water were measured. hot in a room containing Air as shown in Figure 3. The water temperature is about 40 degrees for each test. The main results are given in the following table: day of test Type of sprayer Duration of test quantity of evaporator riser day 1 with 12 mm moving part 0.10 m ³

day 1 without moving part 12 mm 0.03 m ³

day 2 with movable organ 30 mm 0.08 m ³

day 2 without organ 30 mm 0.04 m ³ mobile

For each of the tests, it can therefore be seen that the quantity of water evaporated is at least two to three times greater with the invention described. In Absolute, the differences observed from one trial to another (day 1 vs day 2) are to be taken into account variations in the air humidity conditions. FIG. 4 shows the curve of evolution of the temperature as a function of time for the two configurations (curve (a) without movable member and curve (b) with movable member). The faster decrease in temperature obtained with the invention, the final temperature level as well as the previous observations clearly establish the superiority of the sprayer according to the invention.

Claims

1. Sprayer for loaded liquids, in particular of an abrasive nature, of the kind in which the liquid to be sprayed, tangentially introduced into an annular groove (1) from which it overflows on one side to form a hollow cone of fine droplets, comes, when it overflows, into contact with a movable member (2) of circular section, loosely held around an axis (3) Along which it can move in rotation and in translation in a limited way, Said Liquid causing the mobile member to rotate, characterized in that at rest, the mobile member (2) is in contact with the central part (6) of the annular groove (1), so that a substantially annular passage is left free to the liquid between the overflow surfaces (10 and 8) and the periphery of said member (2), and that as a result of the play available to this member (1) then rotated by The Liquid, The contact between The liquid and this organ causes an effect of e spraying and generation of very fine droplets.

2. Sprayer according to any one of claims 1 and 2, characterized in that the movable member (2) has a conical external profile at a reduced angle.

3. Sprayer according to claim 1, characterized in that the height of the movable member (2) is reduced relative to its diameter.

4. Sprayer according to any one of claims 1, 2 or 3, characterized in that the movable member (2) has a diameter at least 1.7 times equal to the diameter of the axis (3) around which it is mounted.