EP0676244A1 - Method and apparatus for spraying a liquid, especially a high viscosity liquid by using at least one auxiliary gas - Google Patents

Abstract

The atomiser head (1) has several primary conduits (11) whose atomising orifices (12) are regularly located around a circular crown. The different primary conduits are supplied with liquid from a single supply channel (4). Each primary conduit is associated with two secondary conduits (13,14) connected to a pressurised auxiliary gas supply. The gas is supplied from a single annular channel (9) concentric with the liquid supply channel. The auxiliary gas is injected laterally into the primary conduits in two longitudinally separated places, upstream of the atomising orifice and perpendicular plane to the primary conduit axis. The axes of the two secondary conduits make angles between zero and 90 degrees with the primary conduit axis. The primary and secondary conduits have a transverse dimension equal to 1mm <IMAGE>

Description

The present invention relates to a process for spraying a liquid, in particular a high viscosity liquid, using at least one auxiliary gas.

The method and the device according to the invention have been particularly studied for spraying fuels with a view to their combustion, but, obviously, they can be used for spraying liquids for other applications.

Reference will be made below, to locate the problem posed, to the combustion of products from the refining of crude oil, in particular of fuels, but the solution provided by the invention can be used to solve equivalent problems, as it will be explained later in this description.

The refining of crude oil currently produces heavy, increasingly viscous products from conversion units.

To obtain good combustion of these heavy products, it is necessary that they be sprayed into fine droplets, the diameter of which is quite small, of the order of 100 thousandths of a millimeter. It is estimated that, in order to obtain this droplet size, the viscosity of the product must be reduced to less than 20 mm² / s, at the spraying temperature. For products whose viscosity at 100 ° C is 4000 mm² / s, it is necessary to use spray temperatures from 200 ° C to 230 ° C, so as to reduce the viscosity of the product to approximately 20 mm² / s and to carry out a good spraying by the usual spraying means.

If we do not want to use too high temperatures, economically unattractive, we are forced to partially flow (dilute) the viscous heavy products with middle distillates, which the refining industry is in deficit, and therefore d '' increase production heavy fuels, the refining of which is surplus.

If we try to use the usual spraying processes at lower temperatures without fluxing the fuel, we are led to use this fuel at higher viscosities, but mechanical spraying then requires high pressures, of the order of 2.10 pascals, at 200 ° C, for a product with a viscosity of 400 mm² / s at 200 ° C, which, of course, is a drawback.

In its French patent application FR-A-2 662 377, the Applicant has already proposed to spray viscous fuels at viscosities higher than those generally used and therefore at lower temperatures, by developing, in the device for spray, a film of viscous fluid, which is then sprayed into fine droplets using two streams of gaseous fluids.

• d'un flux annulaire dudit liquide,
• d'un flux annulaire d'un gaz primaire,
• d'un flux annulaire d'un gaz secondaire, identique ou non au précédent,

et il consiste:

• a) à conduire le flux de liquide à l'intérieur dudit flux de gaz primaire dans le sens d'écoulement de celui-ci,
• b) à réaliser un film mince annulaire de liquide, en conduisant les flux coaxiaux de liquide et de gaz primaire sur la périphérie d'un anneau dont l'une des extrémités libres est conformée en forme d'arête,
• c) à pulvériser le liquide à l'extrémité de ladite arête par l'action combinée dudit flux de gaz primaire et du flux de gaz secondaire s'écoulant à l'intérieur de l'anneau dans le même sens que ledit flux de liquide et ledit flux de gaz primaire.

This prior process includes the implementation:

• an annular flow of said liquid,
• an annular flow of a primary gas,
• an annular flow of a secondary gas, identical or not to the previous one,

and it consists:

• a) directing the flow of liquid inside said flow of primary gas in the direction of flow thereof,
• b) producing an annular thin film of liquid, by conducting the coaxial flows of liquid and primary gas on the periphery of a ring of which one of the free ends is shaped as an edge,
• c) spraying the liquid at the end of said edge by the combined action of said primary gas flow and the secondary gas flow flowing inside the ring in the same direction as said liquid flow and said primary gas flow.

According to the aforementioned patent application, this process is characterized in that the ratio of the total mass of gas to the total liquid mass is less than 0.5. The speeds of the primary and secondary gas flows are sonic at the height of the edge.

In this patent application, there is also described a spraying device implementing this method and the use of this device and of this method for spraying liquid fuels, in particular heavy and viscous fuels, with a view to their combustion. The gases used can be air, water vapor, refinery gas, in the case of the combustion of fuel oil, or water vapor, in the case of a prior spraying of said fuel. fuel.

By continuing its work on this type of process and device, the Applicant then established that a simple and easy-to-implement means for obtaining a homogeneous distribution of the liquid droplets, without altering the quality of the dispersion produced by these devices with annular layer of liquid, consists in placing at least one obstacle across a part of the layer of liquid, this obstacle having the effect of tearing this layer locally and creating a discontinuity therein, which modifies the trajectory of the droplets.

This technique was the subject of his French patent application FR-A-2 692 502.

However, such spraying methods and devices with the formation of a prefilm have the drawback that the annular space used to produce the annular flow of liquid usually has, perpendicular to the direction of movement of the liquid, a reduced dimension, most of the time much less than 1 mm, which leads to serious risks of clogging by particles suspended in the liquid.

To be able to eliminate or limit these risks of blockage, it is preferable that the annular spaces in which both the liquid and the auxiliary gases circulate have a minimum transverse dimension at least equal to one millimeter.

With such a choice of dimensions, the Applicant has established that it is no longer possible to use injectors with the formation of a prefilm, but systems using conduits, both for the circulation of the liquid to be sprayed and for the passage of the auxiliary gas (es), the use of conduits facilitating the production of the injector.

The object of the invention is therefore to propose a method and a device for spraying a liquid, in particular a high viscosity liquid, using at least one auxiliary gas, in which the risks of clogging of the conduits are reduced.

To this end, the subject of the invention is a process for spraying a liquid, in particular a high viscosity liquid, using at least one auxiliary gas, in which the liquid circulates in a plurality of first conduits each provided with a spray orifice, characterized in that the auxiliary gas is injected under pressure into the first conduit by at least two second lateral conduits opening into at least two separate locations, upstream of the spray orifice.

The auxiliary gas may advantageously be nitrogen, water vapor, air or a combustible gas.

The invention also relates to a device for spraying a liquid, in particular a high viscosity liquid, using at least one auxiliary gas under pressure, this device comprising a plurality of first conduits, supplied with liquid to be sprayed, these conduits each comprising a spray orifice, this device being characterized in that each first conduit is associated with at least two second conduits connected to a source of auxiliary gas under pressure, these two second conduits opening laterally into the first leads into two separate locations.

The second conduits may converge on the same point on the axis of each first conduit or be connected to the latter at offset locations.

Preferably, the axes of the two second conduits will make with the axis of the first conduit equal angles, between 0 and 90 °.

As indicated above, in order to limit the risks of plugging, the first and second conduits will have a transverse dimension preferably at least equal to 1 mm.

As will be seen below, in the description of two embodiments of the invention, the device according to the invention will advantageously include a head comprising a plurality of first conduits, the spraying orifices of which are regularly distributed over the head of the device according to a circular crown or according to two coaxial circular crowns.

Preferably, the various first conduits of the device will be supplied with liquid to be sprayed from a single first supply line, while the various second conduits will be supplied with pressurized gas from a single second supply line , for example with annular section and concentric with the first pipe. Of course, we can also use two separate pipes.

• La figure 1 est une vue en coupe axiale d'une première forme de réalisation du dispositif, suivant la ligne I-I de la figure 2 ;
• La figure 2 est une vue de bout du dispositif suivant la flèche F de la figure 1 ;
• La figure 3 est une vue de détail illustrant un exemple de raccordement des premiers et seconds conduits du dispositif ;
• Les figures 4 et 5 sont des vues analogues à celles des figures 1 et 2 d'une seconde forme de réalisation d'un dispositif conforme à l'invention.

In the detailed description of these embodiments of the device according to the invention which follows, reference will be made to the accompanying drawings, in which:

• Figure 1 is an axial sectional view of a first embodiment of the device, along line II of Figure 2;
• Figure 2 is an end view of the device along arrow F of Figure 1;
• Figure 3 is a detail view illustrating an example of connection of the first and second conduits of the device;
• Figures 4 and 5 are views similar to those of Figures 1 and 2 of a second embodiment of a device according to the invention.

We will first refer to Figures 1 to 3.

The device shown comprises a spray head 1, made integral with a cylindrical pipe 2 by a collar 3, screwed onto the pipe 2. In the pipe 2, coaxial therewith, is disposed a pipe 4 for supplying liquid at high viscosity to be sprayed, while the pressurized auxiliary gas used for spraying circulates in the space 5 separating the pipes 2 and 4.

For the sake of simplification, the head 1 has been shown made in one piece. It is obvious that, for machining reasons, it must be in several pieces. This machining is naturally within the reach of those skilled in the art.

In the part of the head 1 in contact with the tube 2 are provided, parallel to the axis of the pipe 4, on the one hand, conduits 9, communicating with the space 5 and consequently supplied with auxiliary gas, on the other hand, conduits 10, which communicate with the pipe 4 for supplying the liquid to be sprayed.

The conduits 10 communicate at their other end, via a toric chamber 10 ′, with conduits 11, inclined relative to the axis of the head and opening out of the latter according to orifices 12 for spraying the liquid supplying these conduits 11.

In the conduits 11, in the immediate vicinity of the orifices 12, two conduits 13 and 14 open laterally, supplied with auxiliary gas from the conduits 9. The conduits 13 communicate with the conduits 9, via an O-ring chamber 9 ' while the conduits 14 are connected to an axial conduit 15, communicating by conduits 16, inclined relative to the axis, with the conduits 9.

The liquid therefore borrows successively the tube 4, the conduits 10 and the conduits 11, while the auxiliary gas circulates successively in the annular space 5, the conduits 7 and 9, then through the conduits 13 or through the conduits 16, 15 and 14.

As can be seen in FIG. 3, the conduits 13 and 14 will form with the conduit 11 angles α avec and α₂ between 0 and 90 °. The angles α₁ and α₂ may be equal and of the order of 45 °. Conduits 13 and 14 can converge in direction of the same point on the axis of the conduit 11 or, as shown, connect to the latter in offset locations.

Figures 4 and 5 illustrate another embodiment of the device according to the invention. In these figures, the members already described are designated by the same reference numbers as in Figures 1 to 3.

In this embodiment, the spray orifices of the conduits 11 are not distributed regularly in a single circular ring on the head of the device, but in two coaxial rings, the orifices 12, four in number in the case of the device shown, being offset angularly 45 ° relative to the orifices 12 '. The orifices 12 'are associated with conduits 11', 13 'and 14', arranged in a similar manner to the conduits 11, 13 and 14 and which have the same function.

The diameters and dimensions of the conduits 11, 13 and 14 can be different from those of their counterparts 11 ', 13' and 14 ', as can the angles formed by the axes of the injection orifices with the axis of the device.

The following examples illustrate applications of the devices described above for spraying a liquid with a high viscosity, namely oil.

EXAMPLE 1

• nombre de conduits 11 et d'orifices 12 de pulvérisation : 6,
• diamètre des conduits 11 : 1,7 mm,
• diamètre des conduits 13 et 14 : 1,7 mm,
• angles α ₁ et α₂ : 45°,
• décalage entre les points de raccordement au conduit 11 des conduits 13 et 14 : 0,
• distance de ces points de raccordement à l'orifice 12 : 2 mm.

The device used is of the type shown in Figures 1 to 3. It has the following characteristics:

• number of ducts 11 and spray orifices 12: 6,
• diameter of the ducts 11: 1.7 mm,
• diameter of ducts 13 and 14: 1.7 mm,
• angles α ₁ and α₂: 45 °,
• offset between the connection points to the conduit 11 of the conduits 13 and 14: 0,
• distance from these connection points to port 12: 2 mm.

The test conditions are as follows:

Oil

• oil flow: 33 kg / h, per spray orifice,
• oil pressure: 9.5. 10 pascals,
• oil viscosity: 200 mm² / s at 20 ° c.
• auxiliary fluid: nitrogen,
• auxiliary fluid pressure: 6.5. 10 pascals,
• mass rate of nitrogen relative to oil: 30% by mass.

With this liquid with high viscosity and under the conditions indicated above, the average JUMP diameter of the droplets leaving the device is 35 microns, 90% of the droplets having a diameter of less than 120 microns and 99% of them having a diameter less than 290 microns.

EXAMPLE 2

• nombre de conduits 11 et 11' et d'orifices 12 et 12' de pulvérisation : 8,
• diamètre des conduits 11 : 1,7 mm
• diamètre des conduits 13 et 14 : 1,7 mm,
• angles α₁ et α₂ : 45°,
• décalage entre les points de raccordement au conduit 11 des conduits 13 et 14 : 0,
• distance de ces points de raccordement à l'orifice 12 : 2 mm,
• angle γ des conduits 12 par rapport à l'axe de l'injecteur : 30°,
• diamètre des conduits 11' : 2,0 mm
• diamètre des conduits 13' et 14': 2,0 mm
• angles α₁ ,α₂ : 45°,
• décalage entre les points de raccordement aux conduits 11' des conduits 13' et 14' : 0,
• distance de ces points de raccordement à l'orifice 12' : 2 mm,
• angle δ des conduits 12' par rapport à l'axe de l'injecteur : 20°.

The device used is of the type shown in Figures 3 and 4. It has the following characteristics:

• number of ducts 11 and 11 'and of spray ports 12 and 12': 8,
• diameter of ducts 11: 1.7 mm
• diameter of ducts 13 and 14: 1.7 mm,
• angles α₁ and α₂: 45 °,
• offset between the connection points to the conduit 11 of the conduits 13 and 14: 0,
• distance from these connection points to port 12: 2 mm,
• angle γ of the conduits 12 relative to the axis of the injector: 30 °,
• 11 'duct diameter: 2.0 mm
• diameter of the 13 'and 14' ducts: 2.0 mm
• angles α₁, α₂: 45 °,
• offset between the connection points to the ducts 11 'of the ducts 13' and 14 ': 0,
• distance from these connection points to the orifice 12 ': 2 mm,
• angle δ of the conduits 12 'with respect to the axis of the injector: 20 °.

The test conditions are as follows:

Oil

• oil flow:
  • * 33kg / h per port 12,
  • * 45kg / h per 12 'orifice,
• oil pressure: 9.5. 10⁵ pascals,
• oil viscosity: 200. 10⁻⁶ m² / s (200 mm² / s) at 20 ° C,
• auxiliary fluid: nitrogen,
• auxiliary fluid pressure; 6.5. 10⁵ pascals,
• mass rate of nitrogen relative to oil: 30% by mass.

Under such conditions, the average diameter of the droplets leaving the device is again 35 microns, 90% of the droplets having a diameter less than 120 microns and 99% of them having a diameter less than 290 microns.

These tests demonstrate the effectiveness of the process and of the device according to the invention, when applied to the spraying of liquids with high viscosity, such as those used as fuels.

Claims (13)

Method for spraying a liquid, in particular a high viscosity liquid, using at least one auxiliary gas, in which the liquid circulates in a plurality of first conduits (11) each provided with an orifice spray (12), characterized in that the auxiliary gas is injected under pressure into the first conduit (11) by at least two second lateral conduits (13,14) opening into at least two separate locations, upstream of the orifice of spray. Device for spraying a liquid, in particular a high viscosity liquid, using at least one auxiliary gas under pressure, this device comprising a plurality of first conduits (11), supplied with liquid to be sprayed, these first conduits each comprising a spray orifice (12), this device being characterized in that at each first conduit (11) are associated with at least two second conduits (13,14) connected to a source of pressurized auxiliary gas, these two second conduits (13,14) opening laterally into the first conduit (12) at at least two separate locations. Device according to claim 2, characterized in that the two second conduits (13,14) open into the first conduit (11) at locations arranged substantially in the same plane perpendicular to the axis of the first conduit (11). Device according to claim 2, characterized in that the two second conduits (13,14) open into the first conduit (11) at two locations offset longitudinally. Device according to claim 2, characterized in that the axes of the conduits (11), (13) and (14) are substantially in the same plane. Device according to any one of Claims 2 to 5, characterized in that the axes of the two second conduits (13,14) make angles (α₁, α₂) between 0 and 90 with the axis of the first conduit (11) ° Device according to any one of claims 2 to 6, characterized in that the second conduits (13) and (14) have a transverse dimension substantially equal to or greater than the transverse dimension of the first conduits (11). Device according to one of claims 2 to 7, characterized in that the first duct (11) and the second ducts (13,14) have a transverse dimension at least equal to 1 mm. Device according to one of Claims 2 to 8, characterized in that it comprises a head (1) comprising a plurality of first conduits (11), the spraying orifices of which (12) are regularly arranged in a circular ring. Device according to any one of claims 2 to 8, characterized in that it comprises a head (1) comprising at least two sets of first conduits (11) and (11 ') whose transverse dimensions are possibly different and whose spray orifices (12) and (12 ') are regularly arranged in at least two coaxial circular rings. Device according to one of claims 2 to 10, characterized in that the various first conduits (11) are supplied with liquid to be sprayed from a single supply line (4), while the second conduits (13, 14) are supplied with pressurized auxiliary gas from a single pipe (9). Device according to claim 11, characterized in that the pipes (4, 9), respectively for supplying liquid and auxiliary gas are concentric, the auxiliary gas circulating in the space with an annular section separating the two pipes. Device according to claim 11, characterized in that the pipes (4, 9), respectively for supplying liquid and auxiliary gas are distinct and separate.

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