Description

Field of the invention

The invention relates to the fine dispersion of liquids in gas flows, in particular where the nature of the service makes retractability of the injection and dispersion device, without the need for interruption or depressurization of the gas flow, a desirable feature.

Description of the related art

Retractable injection devices are believed to be already applied in the art. These devices are straight tubes with an open end commonly known as 'quills'. Alternatively, a tube with a single spray nozzle at its end can serve as a retractable dispersion device but its capacity is limited by the single nozzle. The open ended 'quills' have no intrinsic dispersion capacity which depends mainly on the velocity of the gas flow. Devices with a single spray nozzle have little flexibility in their spray characteristics and have a confined capacity range.

For a given pressure and orifice size a finer dispersion can be realized when the liquid flow is rotating around the axis of the orifice while it flows towards the orifice. This configuration is a well established practice in the art. GB 1516421A, for instance, claims a spray head on a spray-can that imposes a swirling motion on the liquid to improve dispersion. US2006/0249598A1 claims a spray head for liquids consisting of a spray orifice over a spray chamber fed through non-radial channels. Injection devices for liquids with a plurality of dispersion orifices either consists of a tube with holes or a tube with a plurality of externally attached spray nozzles. The former device produces a relatively coarse dispersion; the latter device is not retractable from a pressurized system without depressurization or considerable leakage of gas.

US2001042797 describes a device for dispensing a curtain spray pattern of liquid through a tubular body having an open end and a closed end. The open end can be connected to a flexible hose or the like for supplying pressurized liquid to the tubular body which has a plurality of spaced openings along its length on one side. The openings can be in a single line or in a plurality of rows.

Essentially, this describes a perforated tube. No claims are made with regard to internal parts that improve the dispersion.

US 2004/0201142 describes a flanged tubular device for dispensing a steam ammonia gas mixture in a combustion flue gas stream which consists of an inner tube and an outer tube with orifices and a plurality of channels between the two. Being designed for dispensing gas, spray devices or swirl- inducing internal parts are not disclosed. The device is not designed to be retractable.

US005277250 describes a retractable injection device for a liquid in a liquid stream which consists of a tube that is closed at one end and is provided with a set of openings to dispense the liquid. Internal parts or a spray functionality are not disclosed.

Summary of the invention

When the purpose of injection of liquids into gas streams is to establish a physical or chemical interaction between the two phases a large interphase surface area between liquid and gas is beneficial in order to increase the physical or chemical reaction rate between the phases. This can only be achieved by establishing a fine dispersion of the liquid. A fine dispersion implies a small average droplet size which correlates with a large liquid surface area. Since the number of droplets for a given liquid volume increases with the third power of the reciprocal droplet diameter and the surface area of a droplet decreases with the second power of its diameter, there is an inverse correlation between average droplet size and total liquid surface area. Typically, small droplets are produced by high liquid shear stresses as may result from high flow velocities through small orifices. For any given mass flow rate finer dispersion is realized by a smaller orifice and a higher pressure. For any given mass flow rate at a given pressure a finer dispersion can be achieved by an increase of the number and a decrease of size of the orifices. The present invention relates to a retractable spray lance, or injection lance, for finely dispersing liquids in gas streams under pressure through a multitude of orifices in a smooth tube. Since the channels and swirl chambers of the dispersion nozzle are situated inside the tube this leaves the outside of the tube smooth and of uniform cross-section. The spray lance is retractable without depressurization or significant loss of gas due to its uniform cross-section which allows its retraction from the medium under pressure through a nozzle with a full bore valve and a gland which fits sufficiently tight around the lance to seal but allows longitudinal movement.

The injection lance of the present invention comprises a tube with a plurality of spray orifices , one or more inserts, preferably a plurality of inserts, with the function to guide the liquid stream to the spray orifices while forcing the liquid in a circular 'swirl chamber' into a swirling motion around the axis of the orifice on its path towards the orifice. The inserts typically fit tightly in the tube and may be slightly radially expanded after assembly by axial compression. The inserts consist of a central channel, one or more swirl chambers and one or more conduits between the central channel and each swirl chamber, preferably configured so that the direction of flow enhances the momentum of the liquid in the swirl chamber.

Preferably, the present swirl chambers are circular, more preferably the present swirl chambers have a circular shape in cross section, relative to an axis perpendicular to the central axis of the central channel. Accordingly, the present central channel preferably has a central axis which corresponds or is parallel to the central axis of tubular body.

In a preferred embodiment, the present conduits provide a tangential flow into the circular swirl chamber, by a tangential connection of the present conduit with the circular swirl chamber. By tangential connection of the conduit with the swirl chamber, the conduit provides a tangential flow of the liquid flowing from the central channel trough the conduit into the swirl chamber.

In a preferred embodiment, the present conduits extend in a direction parallel to the central axis of the central channel, and in a direction perpendicular to the central axis of central channel.

Preferably, the angle between the conduit and the central axis of the central channel is smaller than 90°, more preferably, the angle between the conduits and the central channel is within the range of 10° to 80°, more preferably 20° to 70°, most preferably between 25° or 30° to 60°.

The axis of each swirl chamber is approximately aligned with the axis of the corresponding orifice in the tube. To secure the alignment, the inserts have a longitudinal groove or ridge which fits in a matching ridge or groove in the tube. By variation of liquid pressure level, tube size, channel size, swirl chamber size and orifice size different spray types may be generated. Variation of the numbers, the sizes and the positions of orifices may be applied to change the spray pattern and capacity of the injection lance.

Description of the drawings

The various features of the invention may be more readily understood with reference to the accompanying drawings wherein numbers designate the structural elements shown, in conjunction with their function described in the detailed description.

Figure 1 shows a cross-sectional view of the length of the injection lance with a multitude of inserts.

Figure 2a shows a view of the cross-section of the tube and insert with grooves and ridges.

Figure 2b shows a side view of an insert with a swirl-chamber and channels.

Figure 3a-c show cross-sectional views of possible orifices (11). Description of the preferred embodiment

Referring to the drawings, figure 1 illustrates in a cross sectional view of the length of the injection lance having multiple orifices (11) and one or multiple inserts (20) with swirl chambers at locations that match the position of the orifices. The injection lance is comprised of two sections: a conduit section without orifices (15) and a dispersion section which is a tubular body (12) with a multitude of orifices (11) and one or more grooves (13) or ridges (14) or both for aligning the inserts (20). The two sections (12) and (15) can be machined from a single tube or be assembled from two separate components. The connection between the section (15) and the perforated tubular body (12) can be a screwed or welded connection. Optionally, an edge (17) that may support the first insert (20) is present. The other end of the tubular body (12) is closed with a cap or plug (16) that seals off the end of the tubular body and optionally can be tightened to compress and laterally expand the inserts (20). The distances and orientations of the orifices (15) are such that they match the distances and orientations of the axes of the swirl chambers (22) in the inserts (20) in the functional state. Optionally, the present injection lance is provided with an inner tube that is a conduit for the liquid to be dispersed and is closed at the end. Said tube runs through the channel

(21) with perforations that match the positions of the conduits (25).

The figure 2a shows a cross section of an insert (20) with a central channel (21), swirl chambers

(22) and conduits (25) between channel (21) and swirl chambers (22), which are configured in such a way that the liquid flow enters the swirl chambers tangentially. The figure also shows the ridges

(23) and grooves (24) which mate with grooves (13) and ridges (14) for proper alignment. There is significant freedom in choosing the orientation of the swirl chambers relative to the ridges which allows a large variation of spray configurations to be created to match the specific requirements of an application. Figure 2b illustrates a possible configuration of conduits (25) to obtain a tangential flow in the swirl chamber.

Since the tightness of the fit of the inserts (20) in the tubular body (12) is an important factor for the dispersion, the inserts should be made to narrow tolerances. Advantageously, and less costly than precise machining, the inserts (20) can be laterally expanded by longitudinal compression after they have been inserted in the tube, for instance by tightening of the threaded plug (16). In that case for insert (20), a material with a low elastic modulus is applied, for instance a plastic or an elastomer provided the material is suitable for the intended service conditions.

The figures 3 a,b,c illustrate some possible shapes of the orifices (11) . When the wall of the tubular body 12 is very thin, a straight hole can be applied; for a thicker wall a conical shape is preferred such as in figure 3 b, c, wherein the cross section of the orifice increases towards the surface of the tubular body.