EP3147565B1 - Device for partially or totally removing a smoke plume, installation for discharging smoke to the atmosphere comprising such a device, and corresponding marine vessel - Google Patents

Description

The present invention relates to an installation for discharging fumes to the atmosphere, comprising a plume suppression device. It also relates to a marine vessel comprising such an installation.

Installations burning fossil fuels, whether for fuel combustion in an engine, or coal or fuel oil in power plants, emit fumes containing water vapor and, generally, pollutants such as oxides of sulfur resulting from the presence of sulfur in the burned fuels. The mere presence of water vapor at concentrations much higher than that in the atmosphere means that, when the combustion fumes, which are hot and charged with moisture, encounter a cold air mass, condensation occurs. occurs, forming a cloud of condensed water vapor, which shows a plume visible above the outlet of the conduit, typically a chimney, through which the fumes are released into the atmosphere. The figure 1 illustrates this situation, the fumes to be rejected, the exhaust duct of these fumes and the plume being respectively referenced F, C and P on the figure 1 .

The formation of such a plume is in certain circumstances inadmissible so that measures must be taken to remove at least partially or totally this plume.

It is known to those skilled in the art that to reduce or eliminate a plume of water vapor, it is sufficient to raise the temperature of the fumes sufficiently so that, when they are mixed with the cold air of the atmosphere, the plume is reduced or not formed. This rise in temperature can be done either with burners or heat exchangers, which directly heat the fumes to be rejected, or by mixing between these fumes and a gas, for example air, expected hotter than the fumes. It is also possible to remove fumes from the water by condensation, prior to the discharge of these fumes. In practice, when the temperature rise of the fumes to be rejected is moderate and / or the humidity of these fumes remains high, the plume at the exit of the evacuation pipe remains, but appears taken off in the sense that there is a empty space of condensation, between the outlet mouth of the duct C and the condensation cloud forming the plume P, as illustrated in FIG. figure 2 . In contrast, on the figure 1 , the plume P is formed immediately above the outlet mouth of the exhaust pipe C, the fumes to reject F being substantially wet and very little or not heated. On the other hand, figure 3 shows a situation of complete suppression of the plume, obtained by a greater increase of temperature or by a premixing of the fumes F with a lot of dry and hot air: the plume never appears.

WO 2012/100074 proposes to heat combustion fumes using residual heat. In practice, the complete suppression of the plume requires a significant energy expenditure when the fumes contain more than 15% of water or the ambient air is very cold. This document therefore reduces the plume, as in the figure 2 rather than delete it completely as in the figure 3 . For its part, US 8,721,771 describes a condensation system, to remove fumes from water by condensation. However, particularly in the case of on-board installations, for example aboard a ship having a diesel engine, such a system is not convenient and it is often preferred or even almost obliged to heat the fumes by mixing.

EP 0 040 166 , US 4,149,453 and DE 21 23 220 propose to arrange a plenum around an intermediate portion of a flue gas duct: this plenum communicates with the interior of the duct through openings through the wall of the aforementioned part of this duct. By sending up the hot air at overpressure to the plenum base, this hot air is evenly distributed in the plenum, and then enters the duct, via the openings, in the form of respective jets which are directed towards the center of the plenum. leads. By the effect of pressure, these jets of hot air tend to converge the fumes towards the center of the duct, while mixing completely with the fumes to raise the temperature. These solutions therefore require a substantial source of hot air and is relatively bulky, which is difficult to exploit on board a ship.

US 3,566,768 and EP 2,609,995 propose, for their part, to also arrange a plenum around a flue gas duct, but by placing this plenum around the upper outlet of this duct. The plenum does not communicate with the interior of the duct, but its upper end opens on the outside so that by sending up hot air at overpressure at the base of the plenum, this hot air comes out of the plenum through its upper end, forming, only above the duct, a stream of hot gas belting the jet of fumes exiting the duct. These solutions are particularly bulky, need to be implanted at the outlet of the duct and are efficient from the point of view of the plume overpressure only subject to having a considerable source of hot air to stabilize, above the upper outlet of the duct, the aforementioned hot gas vein vis-à-vis the jet of fumes exiting the duct and, where appropriate, vis-à-vis the wind of the surrounding atmosphere.

DE 22 38 790 also proposes to provide a plenum between a flue and an external pipe, with several specificities. First, hot air is introduced at the base of the plenum tangentially and thus rotates around the base of the flue gas duct, before flowing upwards along the duct whose height is provided equal to between three and five times the diameter of the external tubing. Then, as in US 3,566,768 and EP 2,609,995 , the plenum of DE 22 38 790 does not communicate with the inside of the flue gas duct: at the upper outlet of the plenum, the hot air exits the plenum above the duct, through a horizontal annular passage. Finally, the external pipe extends well above the upper outlet of the flue gas duct, so that, inside the upper part of the outer pipe, the hot air exiting the plenum via the annular passage and the fumes exiting the evacuation pipe mix together under the effect of the turbulence of these fumes so that the resulting gas mixture has a high homogeneous temperature and, hence, dries out, before this mixture exits the atmosphere. atmosphere, via the upper outlet of the external tubing. Thus, this installation, seeks to mix the fumes to evacuate with hot air before their release to the atmosphere.

More generally, the fundamental mechanisms and the thermodynamics of the plumes are well known and are for example explained in the article " How to suppress the emission of plume over a humid cooling tower " by JF LAVRARD, Modern Technology, January 1976.

The document EP 0 040 166 mentioned above is considered to be the closest state of the art.

The object of the present invention is to provide a device for removing the plume at least partially or totally, under economic and practical conditions.

For this purpose, the subject of the invention is an installation for discharging fumes into the atmosphere, as defined in claim 1.

One of the basic ideas of the invention is to seek to delay as far as possible the contact between the fumes to be rejected and the cold air of the atmosphere. To do this, the invention proposes that a hot gas, that is to say a gas, for example air, which is hotter than the fumes to be rejected, is channeled by a dedicated duct around the duct evacuation of fumes into the atmosphere, so that the hot gas rotates around the conduit, more precisely around a portion of the latter having a substantially circular profile. In addition, via dedicated openings that cross the conduit discharge at its portion surrounded by the sheath, the hot gas passes from the internal volume of the sheath inside the conduit: providing that these openings are distributed around the circular profile portion of the conduit and that the total sum of their passage section is between 0.05 and 0.4 times the passage section of the aforementioned part of the duct, the hot gas enters the duct partially retaining its rotating kinematic, but inside the duct , which forms, directly against the inner face of the duct, a peripheral gas stream which is hot compared to a central cold vein through which the central longitudinal axis of the duct passes. Thus, the rotating movement of the hot gas in the sheath causes this hot gas to not radially enter the duct, but with a tangential component which maintains the rotating effect inside the duct and stabilizes the duct layer. hot gas thus created against the inner face of the duct downstream of the openings. In practice, it is understood that the central vein is composed almost exclusively or exclusively of the fumes to be rejected while the peripheral vein consists of a mixture between the fumes and the hot gas distributed by the sheath, the portion of the hot gas in this mixing is significant, even majority, or almost exclusive. Of course, between the hot peripheral vein and the cold central vein, a vein consisting of a mixture between the fumes and the hot gas is present, a temperature gradient being established in this intermediate vein. Although the three aforementioned veins are not physically separated from each other, the hot peripheral vein creates, as it were, a gaseous shielding which delays the moment of contact between the fumes to be rejected, predominantly maintained inside this shielding gaseous in the central vein, and the cold air of the external atmosphere. This shielding increases all the empty space of plume between the outlet mouth of the duct and the zone of appearance of the plume, as on the figure 2 , or even avoids the visible appearance of a plume, as on the figure 3 . It is understood that the device and the installation according to the invention do not seek to achieve a homogeneous mixture between the fumes to be rejected and the hot gas in order to raise the common temperature of this mixture, but, on the contrary, stratify the temperature profile of the gaseous flow flowing in the discharge duct downstream of the duct, this gaseous flow having inhomogeneous temperatures, densities and viscosities in the sense that the peripheral vein, resembling an external gaseous sheath, protects the vein central, similar to an internal gas core, to delay the contact between the latter and the air of the atmosphere, the contact being located well beyond the outlet mouth of the conduit. Thus, the device and the installation according to the invention are particularly compact, the whole device being light and compact, and they allow to partially or completely remove the plume of fumes from efficient and inexpensive way, including using as little hot gas as possible.

Additional features of the installation according to the invention are specified in claims 2 to 11.

The invention also relates to a marine vessel, as defined in claim 12.

• les figures 1 à 3 sont des schémas illustrant trois situations différentes pour un panache de fumées, entre une situation sans contrôle du panache, montrée à la figure 1, et une situation de suppression complète du panache, montrée à la figure 3, en passant par une situation de suppression partielle du panache, montrée à la figure 2 ;
• la figure 4 est une vue en perspective d'une installation conforme à l'invention ;
• la figure 5 est une section selon le plan V de la figure 4 ;
• la figure 6 est une coupe selon la ligne VI-VI de la figure 5 ; et
• les figures 7 et 8 sont des vues respectivement similaires aux figures 4 et 6, illustrant le fonctionnement de l'installation.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings in which:

• the Figures 1 to 3 are diagrams illustrating three different situations for a plume of smoke, between a situation without control of the plume, shown in figure 1 , and a situation of complete suppression of the plume, shown at figure 3 , passing through a situation of partial suppression of the plume, shown at figure 2 ;
• the figure 4 is a perspective view of an installation according to the invention;
• the figure 5 is a section according to plan V of the figure 4 ;
• the figure 6 is a section along the line VI-VI of the figure 5 ; and
• the figures 7 and 8 are respectively similar views to figures 4 and 6 , illustrating the operation of the installation.

On the Figures 4 to 6 there is shown a plume suppression device 10 associated with a flue gas exhaust duct 20.

The conduit 20 is centered on a longitudinal axis X-X, the device 10 being located at an axial level of the conduit 20, between the inlet mouth of the latter, not shown, and its outlet mouth 21 to the atmosphere. In practice, the location, along the axis XX, of the level of the duct 20 where the device 10 is located is irrelevant, the device 10 may also be located near the inlet mouth near the outlet mouth 21, or at an intermediate height between these mouths.

In a manner not shown in the figures, the inlet mouth of the duct 20, through which fumes to be discharged into the atmosphere penetrate inside the duct 20, is, upstream of the duct, connected to the outlet of a duct. equipment producing fumes to be discharged, for example at the outlet of a desulphurization washer to which are sent the exhaust gas of a propulsion engine of a marine vessel. In practice, the X-X axis of the duct 20 extends, in use, substantially vertically, the fumes circulating in the duct between its inlet mouth and outlet mouth 21 being vertically upward. The duct 20 thus typically constitutes a chimney.

In the exemplary embodiment considered in the figures, the duct 20 has a transverse profile, that is to say a profile in a plane perpendicular to the axis XX, which is both circular, both internally and externally. , and constant over the entire height axial of the duct. Thus, at the axial level of the duct 20 where the device 10 is located, the duct 20 includes an axial portion 22 with a circular transverse profile. As a variant not shown, the transverse profile of the duct 20, outside the aforementioned part 22, may have other geometries and / or not be constant in the direction of the axis XX.

For reasons that will appear later, the portion 22 of the conduit 20 is provided with through openings 23 which are visible on the Figures 5 and 6 . Each of these openings 23 connects the inner and outer faces of the portion 22 of the conduit 20 to one another. As is clearly visible on the figure 5 the openings 23 are distributed, preferably uniformly, all around the part 22. According to an advantageous characteristic of the invention, between six and twenty-four, preferably between eight and twelve, openings 23 are provided.

According to a preferred embodiment, which is implemented in the example considered in the figures, each of the openings 23 has a rectangular passage section. As a variant not shown, other geometric shapes are possible for the passage sections of the openings 23. In all cases, according to one characteristic of the invention, the ratio between, on the one hand, the total sum of the sections respective passage openings 23 and, secondly, the passage section of the portion 22 of the conduit 20, in other words the circular internal section of this portion 22 worth π times the square of its internal radius, is between 0, 05 and 0.4.

The device 10 comprises a sheath 11 which, as is clearly visible on the Figures 4 to 6 , is designed to completely surround the portion 22 of the conduit 20. The internal volume V11 of the sheath 11 is thus wound externally around the portion 22 of the conduit 20, covering all the openings 23.

This sheath 11 is provided with a mouth 12 input into its internal volume V11, as clearly visible on the figures 4 and 5 according to an advantageous characteristic of the invention, the passage section of this inlet mouth 12 is between 0.05 and 0.4 times the passage section of the portion 22 of the conduit 20.

According to a preferred embodiment, which is implemented in the embodiment considered here, the internal volume V11 of the sheath 11 forms a spiral wound around the portion 22 of the duct 20, the internal volume V11 narrowing gradually to as one moves away from his entry mouth 12, as clearly visible on the figure 5 . In other words, the internal volume V11 preferably winds in a spiral or snail around the portion 22 of the conduit 20, its section being reduced as the winding of the sheath 11 around the conduit 20 from its mouth. In this way, a certain similarity exists between this preferred form of the invention and what is done for the inputs of the cyclonic separators. This being so, instead of being shaped in a spiral, the internal volume V11 of the sheath 11 may, as a variant, not shown, be annular, with a substantially constant section around the duct 20.

Advantageously, especially for economic and practical reasons, in particular for weight reduction, the device 10 and / or the conduit 20 are made mainly, or even entirely, of a resin that withstands a temperature of at most 250 ° C.

In practice, the device 10 and the conduit 20 may form an integral assembly in one piece or the device 10 may be attached to a pre-existing chimney which then constitutes the conduit 20 as long as the openings 23 can be made in a part circular profile of this chimney, at the axial level of which the device 10 will be arranged.

The use of the device 10 and the conduit 20 will now be described with regard to figures 7 and 8 .

F discharges, typically combustion fumes loaded with moisture and having for example a temperature between 20 ° C and 65 ° C, flow vertically and upwardly in the conduit 20, from its inlet mouth to its mouth 21, as indicated by the arrows associated with the reference F on the figures 7 and 8 .

At the same time, a gas G, preferably air, feeds the inlet mouth 12 of the sheath 11. This gas G is hot, in the sense that it has a temperature strictly greater than that of the fumes F, the temperature difference between the gas G and the fumes F being several tens of degrees, for example between 45 ° C and 125 ° C. In practice, this hot gas G feeds the sheath 11 via ad hoc supply means, especially designed to send to the inlet mouth 12 of the heated air at a temperature between 80 ° C and 250 ° C, preferably between 100 ° C and 150 ° C.

Inside the internal volume V11, the hot gas G is channeled by the sheath 11 so as to turn around the portion 22 of the conduit 20. It is understood that the hot gas G flowing in the device 10 has a rotary movement relative to flue F circulating in the conduit 20, this rotating movement being oriented in a single direction of rotation about the axis XX. Part of this rotating kinematic component of the hot gas G is retained when the hot gas passes from the internal volume V11 of the sheath 11 inside the conduit 20 via the openings 23: the hot gas G enters the conduit 20 with a component tangential to the axis XX and, inside the conduit 20, the hot gas G thus forms, mixing only marginally or almost is zero with the fumes F, a peripheral gas stream V1 constituting an annular sheath which is centered on the axis XX and which covers the inner face of the conduit 20 downstream of the portion 22, as shown in FIGS. figures 7 and 8 . The spiral shape advantageously allows a substantially constant speed to be maintained in the internal volume V11 of the sheath 11 as the hot gas G escapes inside the duct 20 through the openings 23.

The flue gas F from the upstream side of the part 22 is, at the level of the part 22 and then downstream of the latter, forced towards the middle of the duct 20, forming a central gas stream V2 in which the mixture with the hot gas G is only marginal or even substantially non-existent. As illustrated schematically on figures 7 and 8 , an intermediate gas stream V3 is formed radially between the peripheral vein V1 and the central stream V2, by substantial mixing between the fumes F and the hot gas G. Because of their respective compositions in fumes F and hot gas G, the veins V1, V2 and V3 have different respective temperatures: the peripheral vein V1 is much hotter than the central vein V2, the vein V3 having, for its part, a temperature gradient between the high temperature of the vein V1 and the low temperature vein V2. In other words, downstream of the part 22, an inhomogeneous temperature profile is naturally established in the duct 20. The part of the gas stream located near the inner face of the duct 20 is hotter than the part of the duct. flow, located in the center of the duct. This inhomogeneous temperature profile is maintained from the portion 22 of the conduit 20 to its outlet mouth 21 and, by conservation of the momentum, the thermal shielding of the central vein V2 through the peripheral vein V1 is extended to the outside the conduit 20, beyond the outlet mouth 21, delaying or even avoiding the appearance of a plume.

On the figures 7 and 8 the aforementioned veins V1, V2 and V3 are schematized by different gray levels, being separated by dashed lines: this illustration is of course symbolic in the sense that, in practice, the veins V1, V2 and V3 are not materially separated from each other. However, this illustration makes it possible to clearly understand the stratification of the gaseous flow in the conduit 20 downstream of the device 10, being noted that, as clearly visible on the figure 7 this stratification results, in section planes perpendicular to the axis XX, by concentric circular profiles at the interface between the veins V1 and V3 and at the interface between the veins V3 and V2.

Furthermore, an additional advantage provided by the invention is that the hot gas G distributed by the sheath 11 contributes to increasing the ejection speed at the outlet of the conduit 20, thus facilitating the dispersion of the fumes. Indeed, by the sheathing of fumes F through the peripheral vein V1 resulting from the passage of hot gas inside the conduit 20 through the openings 23, the effective passage section that can occupy the fumes F downstream of the portion 22 is decreased compared to the upstream of this part 22: as the fumes F no longer occupy, alone, the entire passage section of the conduit 20, they acquire a higher speed and, after being out of the conduit 20, disperse more easily.

Example:

The device 10 and the conduit 20 are used to limit the plume of fumes emitted by the propulsion diesel engine of a ship. The fumes to reject F have a flow rate of 125,000 Nm ³ / h and a temperature of 20 to 50 ° C, being saturated with moisture at this temperature. The hot gas G is air having a flow rate of 20,000 Nm ³ / h and a temperature of between 100 and 120 ° C.

The conduit 20 is made of a temperature-resistant resin and has an internal diameter of 1800 mm. Its passage section is thus 2.54 m ² .

The sheath 11 is made of a resin resistant to temperature. This sheath has a spiral shape, as on the figure 5 . The passage section of its inlet mouth 12 is 0.78 m ² .

Eleven rectangular openings 23, 125 mm by 300 mm each, are provided in the portion 22 of the conduit 20. The cumulative total of the respective passage sections of these openings 23 is equal to 0.41 m ² .

Claims (12)

1. Installation for discharging fumes into the atmosphere, comprising:

   - a pipe (20) for discharging fumes (F) towards the atmosphere, which includes a portion (22) having a substantially circular transverse profile and being provided with traversing openings (23) which are distributed all around said portion and the total sum of the sections of passage of which is between 0.05 and 0.4 times the section of passage of said portion, and

   - a device (10) for suppression, partial or even total, of a wreath of fumes (F), the device comprising a casing (11) for distributing a hot gas (G) which is adapted to surround in its entirety said portion (22) of the pipe (20) so that hot gas (G) entering the internal volume (V11) of the casing is channelled by the casing in order:

   - to turn around said portion (22) of the pipe (20) by circulating within the casing according to a turning movement relative to the fumes circulating in the pipe, and

   - to pass inside the pipe via the openings (23) of said portion of the pipe so that the hot gas which thus passes to the inside of the pipe via the openings retains a portion of said turning movement and forms a peripheral gaseous stream (V1), which covers the inner face of the pipe downstream of said portion of the pipe and inside which the fumes form a central gaseous stream (V2).
2. Installation according to claim 1, characterised in that the internal volume (V1) of the casing (11) forms a spiral coiled around said portion (22) of the pipe (20), by narrowing in the turning direction of circulation of the hot gas (G) within the casing around said portion of the pipe.
3. Installation according to any of the preceding claims, characterised in that the casing (11) is provided with a mouth (12) for inlet of the hot gas (G) into its internal volume (V11), this inlet mouth having a section of passage which is between 0.05 and 0.4 times the section of passage of said portion (22) of the pipe (20).
4. Installation according to any of the preceding claims, characterised in that between six and twenty-four openings (23) are provided in said portion (22) of the pipe (20).
5. Installation according to claim 4, characterised in that between eight and twelve openings (23) are provided in said portion (22) of the pipe (20).
6. Installation according to any of the preceding claims, characterised in that each of the openings (23) has a rectangular section of passage.
7. Installation according to any of the preceding claims, characterised in that the casing (11) is formed from a resin which is resistant to a temperature of at most 250°C.
8. Installation according to any of the preceding claims, characterised in that the pipe (20) is formed from a resin which is resistant to a temperature of at most 250°C.
9. Installation according to any of the preceding claims, characterised in that the installation comprises furthermore means for supplying the casing (11), adapted in order to supply the casing with air heated to a temperature between 80°C and 250°C.
10. Installation according to claim 9, characterised in that the supply means are adapted in order to supply the casing (11) with air heated to a temperature between 100°C and 150°C.
11. Installation according to claim 9 or claim 10, characterised in that the supply means are designed in order to heat the air supplying the casing (11) to a temperature strictly greater than that of the fumes (F), the deviation in temperature between the air and the fumes being between 45°C and 125°C.
12. Marine vessel, comprising:

    - a propulsion engine,

    - a desulphurisation scrubber to which the exhaust gases from the propulsion engine are sent, and

    - an installation according to any of the preceding claims which discharges to the atmosphere the fumes (F) exiting the desulphurisation scrubber.

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