NL1043367B1 - Retractable injection lance for finely dispersing liquids in gas streams - Google Patents

Abstract

An injection lance for dispersing liquids into gas streams at over- or under pressure through a plurality of spray nozzles which are placed inside a smooth tube of sufficient length for the application. The 5 spray orifices in the spray nozzles are designed to preserve the shape and dimensions of the tube. The spray nozzles typically fit inside the tube and the spray orifice is aligned with the outer surface of the tube through an elevated section that fits in the holes in the tube. The lance is retractable due to its uniform cross-section, which allows its retraction from the medium through a nozzie with a full bore valve and a gland without significant leakage. 10 1043367

Description

Retractable injection lance for finely dispersing liquids in gas streams The invention relates to the fine dispersion of liquids in gas flows as may be applied in the process industries, in particular where the nature of the service makes retractability of the dispersion device for inspection or maintenance a desirable feature, while avoiding the need for interruption and depressurization of the gas flow.

Retractable dispersion devices are already applied in the art.

These devices are normally straight round tubes that can be inserted into and withdrawn from process equipment at low or medium pressure through a nozzle with a full bore valve and a gland which can be tightened sufficiently around the tube to seal but still allow longitudinal movement.

When these devices have an open end they are commonly known as ‘quills’. Likewise, a tube with a single spray nozzle at its end can serve as a retractable dispersion device but its flow capacity is limited by the single nozzle.

The open ended ‘quills’ have no intrinsic dispersion capacity; dispersion depends on the velocity of the gas flow.

A device with a single spray nozzle has little flexibility in its spray pattern and has a limited capacity range.

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 since it increases the physical interaction or chemical reaction rate between the phases.

A large interphase area can be achieved by generating a fine dispersion of the liquid.

A fine dispersion implies a small average droplet size, which correlates with a large liquid surface area.

Typically, small droplets are produced by high liquid shear as would result from high flow velocities through small orifices.

For any given mass flow rate, a finer dispersion is realized by a smaller orifice and a higher flow velocity.

Therefore, for any required mass flow rate at a given pressure a finer dispersion can be achieved by a larger number of smaller orifices.

For any given flow rate and orifice size a finer dispersion can be realized when the liquid flow is rotating around the axis of the orifice in a swirl chamber while it accelerates towards the spray orifice.

This configuration is a well-established practice in the art.

In the current state of the art, injection devices for liquids with a plurality of dispersion orifices often comprise a tube with holes, for instance, US 005277250A, 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.

The present invention is a round, smooth and hence retractable spray lance for finely dispersing liquids in gas streams under pressure through a multitude of orifices in an externally 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 due to its uniform cross- section insertable and retractable from a pressurized system through a gland and full-bore valve without depressurization or significant loss of gas.

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 axis of each swirl chamber is approximately aligned with the axis of the corresponding orifice in the tube. This arrangement is problematic because it requires very precise longitudinal positioning of the inserts in a long tube as well as angular positioning, which makes the device vulnerable and poorly maintainable in a process industry environment. US 2017/0087567A1 claims a shower head for domestic use comprising a spout apparatus for discharging hot or cold water with a reciprocal motion through a plurality of oscillation-inducing chambers rather than swirl-chambers. As a shower head, no claims are made regarding shape of the conduit, its retractability, the fineness of dispersion, the alignment of said chambers with the orifices inthe tube or the ease of assembly and disassembly for maintenance purposes.

DE 10 2006 046 568 A1 claims a spraying device for spraying a suspension on a hot forging in which the spray nozzles are holes in an inner tube which are covered by a radiation shield comprising of an outer tube that can be moved by rotation or translation to uncover the orifices.

The present invention is a significant improvement on previous art due to its ease of assembly and its robustness. It comprises of a long tube with a plurality of large holes. In each hole an internal part is fitted, which comprises of a spray orifice, a swirl chamber, a flow-rotation generator between the liquid supply and the swirl chamber. The internal part is secured in its correct position by its circular contour which has the same outer radius as the inner radius of the tube. The outer contour of the internal part has an elevated section, which section fits in the hole in the tube and aligns with the outer radius of the tube.

The opening in the tube and the matching elevated section is preferably round but can have any shape to suit its purpose. The elevated section protrudes sufficiently to align with the outer surface of the tube to maintain a cylindrical outer surface and ensure retractability through a gland with no risk of significant leakage. By variation of liquid pressure level, tube size, channel size, swirl chamber size and orifice size and shape different spray types may be generated. Variation of the numbers, the sizes and the positions of orifices may be applied on a single spray lance to change the spray pattern and capacity of the injection lance in case that is advantageous for its purpose.

The preferred configuration has a single spray orifice per insert but insert/orifice ratios other than one are possible.

The present invention is also a significant improvement on NL1040268 because the spray orifice is an integral element of the insert. This eliminates the need to secure the radial alignment of swirl chamber and orifice by guiding elements such as grooves and ridges as claimed in NL1040268, and the longitudinal alignment by very precise dimensioning and positioning of the internal parts. In addition, since the spray orifice is the part of the nozzle where flow velocities are highest, wear and erosion will occur there first. By making the spray orifice an integral part of the insert, it is more convenient and less expensive to replace a worn part. Finally, when the spray orifice is part of the insert, a suitable material can be selected, either integrally or as a separate component of the insert. If the orifice is part of the tube, as in NL1040268, the material and thickness of commercially available tubes will, for practical reasons, determine the material and dimensions of the spray orifice.

40 To keep the inserts in place before and during operation clamping or locking the insert is preferred.

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 schematically the assembly of the tube with a plurality of inserts. Figures 2 show (a) a longitudinal and (b) a transverse cross-section of the tube and an internal part. Figures 3 show two modifications of the swirl generating device: (a) tangential channels or (b) a helical vane. Figures 4 show two ways to secure the inserts in the tube: (4a) with an internal C-spring, (4b) with a filling piece.

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 inserts (20) with spray orifices (26). The outer tube of the injection lance is comprised of two sections: a conduit section without orifices (10) and a dispersion section which is a tubular body (11) with a plurality of holes (12). The two sections (10) and (11) can be machined from a single tube or can be assembled from separate components. The end of the tubular body (11) comprises a cap or plug (13) that seals off the end of the tubular body.

The figure 2 shows a transverse cross section of an insert (20) in the tubular body (11). The insert leaves free passage for the liquid through a central channel (21) and feeds a swirl chamber (22) through rotational flow generators (25 or 27) between the channel (21) and the swirl chambers (22). The rotational flow can be generated as shown in figure 3a through channels (25) that enter the swirl chamber (22) tangentially to establish a rotational momentum in the liquid flow, or, as shown in figure 3b by one or more helical vanes (27) in the passage between the channel (21) and the swirl chamber.

Figure 2a shows how the outer surface of the internal part (20) has an elevated section (24), which section fits precisely in the hole (12) in the tubular body. The hole (12) and the matching elevated section (24) are preferably circular but can have any shape to suit its purpose. The elevated section (24) is preferably curved to align with the outer surface of the tubular body in order to maintain a cylindrical outer surface which benefits reducing leakage during the retraction under pressure.

Figure 4a shows how the position of the insert (20) is secured in the tubular body (11). Optionally, a C- spring (29) is placed in the insert (20) to ensure a tight fit. Alternatively, the insert (20) is secured by a filling piece (28) that complements the gap in the insert (20) as shown in figure 4b.

Claims (7)

Claims 1) Device for finely atomizing a liquid in a space under positive or negative gas pressure by means of a tube (11) with a plurality of holes (12) in the wall, characterized in that the tube (11) is provided with one of a plurality of internal parts (20) provided with a supply channel for the liquid to be atomized {21} connected to a swirl chamber (22) by means of channels generating a rotating flow in said swirl chamber and a central spray orifice (26) so formed that the rotating flow in the narrowing vortex chambers accelerates towards the central opening (26), which causes a fine atomization of the liquid upon exit, characterized in that on the outer surface of said internal parts (20) around the outflow openings (26) there is a raised section (24) that fits into one of the holes (12) in the tube, such that the outer cylindrical surface of the assembly remains largely intact. 2. Device for fine nebulizing a liquid as described in claim 1) characterized in that the rotary flow of the liquid in the whirl chamber is generated by channels (25) which intersect the whirl chamber at an angle to the radial. 3) Device for fine atomizing a liquid as described in claim 1) characterized in that the rotary flow of the liquid in the whirl chamber is generated by one or more vanes (27) placed between the supply channel (21) and the swirl chamber (22). 4) device for fine atomizing a liquid as described in claim 1) characterized in that the internal parts (20), after being placed in position in the tube (11), are pressed and fixed by means of a spring, such that a good fit of the the internal parts in the tube are effected. Device for fine atomizing a liquid as described in claim 1), characterized in that the internal parts (20), after being placed in position in the tube (11), are pressed and fixed by means of a filling piece. A device for fine atomizing a liquid as described in claim 1) characterized in that the internal parts (20) are composed of several components, possibly made of different materials. 7) Device for fine nebulizing a liquid as described in claim 1) characterized in that each of the internal parts (20) is resilient in such a way that it can be slid into or out of the tube (12) in a compressed state and into expanded condition is fixed in its correct position.