WO2017186769A1

WO2017186769A1 - Method and facility for wet desulphurisation of the exhaust fumes of an engine of a sea ship

Info

Publication number: WO2017186769A1
Application number: PCT/EP2017/059879
Authority: WO
Inventors: Bernard Siret; Frank Tabaries
Original assignee: Lab Sa
Priority date: 2016-04-27
Filing date: 2017-04-26
Publication date: 2017-11-02
Also published as: FR3050654B1; CN109069985A; FR3050654A1; KR102343017B1; KR20180135953A; CN109069985B

Abstract

According to this method, the fumes to be desulphurised (1) are conveyed into a scrubber (100) via a vertical chimney (200) that opens at the bottom (101) of the scrubber, substantially in the centre of same. The fumes flow upwards inside the scrubber so as to be brought into contact with first (3) and second (4) scrubbing liquids intended to capture the sulphur dioxide contained in the fumes. In order for the velocity profile of said fumes to be as flat as possible inside the scrubber, they meet successively therein: - a rotation device (400) that is traversed by the fumes (1), rotating them inside the scrubber (100), - a protection device (300) that protects the downstream outlet (201) of the chimney against the entry of liquid while maintaining the flow of fumes, - a spraying device (500), that sprays the first scrubbing liquid (3), in the form of at least one pair of liquid curtains, from a central region of the scrubber (100), through which a central geometric axis (Z100) of the scrubber passes, to the peripheral wall (102) of the scrubber, the liquid curtains of the or each pair being sprayed, from the spraying device, on either side of a same horizontal plane (H) associated with said pair, then - a distribution device (600) that distributes the second scrubbing liquid (4) in the form of a rain falling downwards in a free space (V100) of the scrubber, which extends from the spraying device to the distribution device and inside which the fumes flow freely, said distribution device comprising at least one stage of distributors (601) that are located at a same height, being distributed over the cross-section of the scrubber associated with said height, and that respectively distribute a corresponding fraction of the rain.

Description

Process and installation for wet desulfurization of fumes

engine exhaust from a marine vessel

The present invention relates to a method and a plant for the wet desulfurization of the exhaust fumes of an engine of a marine vessel.

Marine vessels, whether ships or other vessels, primarily use fuel oil as fuel for diesel engines propelling them. This fuel contains up to 5% by weight of sulfur, most often between 0.5 and 3.5% by weight. During the combustion process in the engines, this sulfur is converted into sulfur dioxide (S0 ₂ ). Therefore, the exhaust fumes from these engines are acidic.

Current maritime regulations require, in certain areas, to limit the discharge of ships by the stack to an equivalent of 0.1% sulfur by weight in the fuel oil. In practice, the discharge limit value depends on the navigation zone: near the coast or in a port, sulfur dioxide emissions must be lower than in the open sea. It should be noted that even at the port, a passenger liner The cruise must continue to run its engines to provide on-board power, and potentially, emits sulfur dioxide. To comply with the regulations, it is therefore necessary for the ship to incorporate means to reduce sulfur dioxide emissions from its fumes before discharging them into the atmosphere. Several solutions are possible.

The sulfur content of the fuel used can first be reduced, or even liquefied gas can be used, which immediately leads to a reduction of sulfur dioxide emissions. However, very low sulfur fuel oil or liquefied gas is expensive, so this approach is not economical.

Another approach is to use a wet scrubber, in which is dispersed a neutralization reagent such as sodium hydroxide. However, the quantities of soda to be expected are important, since the flow of sulfur dioxide to be treated can reach 500 kg per hour and per washer for very large steamers. In addition to the price of soda, it must be planned for storage and take into account its very caustic and therefore dangerous nature.

Also, exhaust smoke is more often operated with seawater. This technique, which is implemented by scrubbers using the natural alkalinity of seawater to neutralize sulfur dioxide, is known and controlled, especially for power plants located on the seafront. In practice, two technologies exist. A first technology is based on the implementation of scrubbers using a lining. This lining is either made of rings or internals, introduced loose in the tower of the washer, or provided with a structured character, that is to say that the lining has a pattern repeating structurally in space. In terms of transfer efficiency, i.e., the ability to capture sulfur dioxide back to the volume used in the scrubber, these packings are very good. However, two limitations are to be considered. On the one hand, the pressure drop induced by the packings can be important: in the case where the washers must be placed downstream of a diesel engine, it forces to use a fan to overcome this loss of load, which costs energy and an extra investment. On the other hand, the fumes from a diesel engine are very hot and, despite the presence of a quenching device, it is necessary to provide the case where, following a malfunction, very hot and uncooled fumes, for example at more than 200 ° C, enter the scrubber. Since a by-pass is not always possible, the washer and its lining must be able to withstand dry running at the very least, and therefore their constituents withstand temperatures above 200 ° C. This makes it necessary to select, for the washer and its lining, temperature-dependent materials. This being so, in the case of shipboard washers, the marine environment, which is rich in chloride, which is acidic and which is reducing, is highly corrosive so that the cost of the packing is substantially affected.

The second technology using seawater to reduce the sulfur oxides contained in fumes, is widely used in power plants that produce energy on land: the second technology is to use empty scrubbers, in which the water sea is scattered. This dispersion can be carried out either in the form of drops falling in the central region of the scrubber, as shown very schematically in FIG. 1, or in the form of a liquid film, as taught in FR 1 231 173 and as shown very schematically on FIG. Figure 2.

In the known situation of FIG. 1, fumes to be desulfurized F are introduced into the bottom of a scrubber V via a chimney C centered on the bottom of the scrubber. In the central region of the head of the scrubber V, nozzles D dispense a washing liquid L, designed to capture the sulfur dioxide present in the flue gases F, in the form of drops falling downwards, countercurrently flowing F flue gases. up inside the scrubber.

In the known situation of FIG. 2, fumes to be desulphurized F are also introduced into the bottom of a scrubber V via a chimney C centered on the bottom of the scrubber. In the center of the scrubber V, a sprayer P projects a washing liquid, intended to capture the sulfur dioxide present in the flue gases F, in the form of a web, from the region of a central geometric axis ZV of the scrubber V towards the peripheral wall of this washer. The solutions of Figures 1 and 2 both have advantages. They are simple and, to the extent that the washer V is empty and flue F flowing freely, the pressure drop is low, compared to a solution using a lining internal scrubber. In addition, they are economical, although, insofar as the transfer capacity is less than for a washer using a lining, the height of the washer V will be greater. Finally, since the washer V is essentially empty, there is no need to worry about the constituents of the packing, in particular their resistance to corrosion and temperature, as well as their fouling. However, the weakness of the pressure drop, which is an important advantage from the operating point of view, makes problematic the distribution of flue gases F inside the scrubber V. In fact, in the case of the installation of FIG. any instability, whether due to the movements of the vessel, a small distortion in the distribution of the washing liquid, for example due to the clogging of some of the nozzles D, or even to instabilities in the sense of chaos theory will cause the fumes to be treated F to concentrate on one side of the scrubber V while the washing liquid is discharged from the opposite side of the scrubber, as shown schematically in FIG. 1: the flue gases F then present, at inside the scrubber V, an asymmetrical speed profile and unbalanced, which is not necessarily stable over time, a pendulum effect may indeed occur for example at the discretion of the external movements of the scrubber. As for the case of the installation of FIG. 2, the fumes to be purified F go, by transfer of the amount of movement of the washing liquid towards these fumes F, gradually to deviate from the central axis ZV, concentrating against the peripheral wall of the washer V as shown schematically in Figure 2: the smoke velocity profile F then undergoes a distortion that makes it inhomogeneous. In both cases, despite the central introduction of the flue gases F at the bottom of the scrubber V, the heterogeneity of the flue velocity profile F, inside the scrubber V, is such that the ratio of liquid to gas is that is, the ratio of the amount of washing liquid to the amount of smoke present at a given location inside the scrubber V is inhomogeneous within the scrubber, resulting in a significant loss of efficiency for the desulfurization of the scrubbers. F. fumes

In the context of the problem detailed so far, US 2016/0016109 proposes a method and an installation for desulphurizing the exhaust fumes of a marine engine, which can be considered as the closest to the process and the installation presently claimed. In US 2016/0016109, the exhaust fumes emitted by a marine engine are admitted, via a vertical stack, into a scrubber inside which these fumes circulate upwards. Inside the scrubber, the fumes, coming out of the chimney, successively meet a first deflection member which protects the opening of the chimney against the introduction of liquid, first injectors of water for injecting water downwards, second injectors of water for injecting water upwards, a constriction member at which the passage section is strangled, a second deflector, third injectors of water to inject water down, and a demister. The first, second and third injectors are all of the same type. The constriction member separates the inside of the scrubber into two chambers, namely a lower chamber in which are arranged the first deflection member and the first and second injectors, and an upper chamber, in which are arranged the second deflection member. , the third injectors and the mist eliminator. Even if the constriction member tends to have the fumes coming out of the lower chamber refocused when entering the upper chamber, the circulation of fumes in each of the two chambers is subject to the risk of instability mentioned above because of the fact that that the first, second and third injectors are all positioned on the central geometric axis of the washer: the water injected by these first, second and third injectors tends to deport the flow of fumes against the peripheral wall of the washer. In addition, the presence of the constriction member necessarily induces a significant loss of pressure and requires the recovery, by dedicated extraction arrangements, the water that has been injected into the upper chamber and which accumulates at the level of the organ of constriction. The desulfurization efficiency is thereby impaired.

In another area than the desulphurisation of exhaust fumes,

No. 4,375,976 proposes a method and a plant for dedusting a gas flow, in particular an air flow. The gas stream to be de-dusted is first sent to a cyclone separator at the top of which the gas stream is recentered and channeled vertically in a tube opening at the base of a scrubber. Inside this scrubber, the gaseous flow circulates upwards, successively meeting a protective cone, a water spray, a water spray nozzle and a filter. The protective cone, the sprayer and the nozzle are aligned with the central geometric axis of the scrubber. The sprayer produces a spray, which by nature has a low water density, similar to a mist, and is sprayed horizontally from the central axis of the scrubber: this spray is intended to moisten the solid particles present in the ascending gas flow. The sprayer also projects a conical water projection, facing up, to keep the bottom of the filter wet. The dispensing nozzle, in turn, produces a conical projection of water, facing downwards and intended to moisten the solid particles present in the gas stream. This installation seems satisfactory for trapping solid particles carried by the gas flow, but does not is not interested in desulphurizing exhaust fumes, which moreover is emitted by the engine of a marine vessel.

The object of the present invention is to provide an arrangement of a scrubber, which aims to overcome the disadvantages mentioned above to desulfurize exhaust fumes, based on a clever and inexpensive implementation.

To this end, the subject of the invention is a process for the wet desulfurization of exhaust fumes from an engine of a marine vessel, as defined in claim 1.

The invention also relates to a wet desulphurization installation of the exhaust fumes of an engine of a marine vessel, as defined in claim 8.

Thanks to the invention, the fumes to be desulphurated, which pass through the scrubber from bottom to top, have a speed profile that is as flat as possible, thus ensuring very efficient desulphurization of these fumes by the first and second wash liquids dispersed in the scrubber. washer. In addition, the implementation of the invention remains economical, relying on facilities that individually are simple to install and operate.

Additional advantageous features of the method and the installation according to the invention are specified in the other claims.

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:

FIGS. 1 and 2 are diagrammatic views of desulphurization installations which belong to the prior art and which have been described above;

FIG. 3 is a diagrammatic view of a desulfurization installation according to the invention, implementing a desulfurization process according to the invention;

FIG. 4 is an elevational view of an embodiment of a device belonging to the installation of FIG. 3;

- Figure 5 is an elevational view along the arrow V of Figure 4;

FIG. 6 is a view similar to FIG. 4, illustrating an alternative embodiment of the device of FIG. 4;

- Figure 7 is an elevational view along arrow VII of Figure 6;

FIG. 8 is a detailed perspective view of another device belonging to the installation of FIG. 3; and

FIG. 9 is a schematic section along the line IX-IX of FIG.

FIG. 3 shows an installation for desulfurizing exhaust fumes 1 from a diesel engine propelling a marine vessel on which is embedded this installation. The fumes 1 contain sulfur oxides, in particular sulfur dioxide (SO ₂ ).

At the level of the installation of FIG. 3, the fumes 1, which come from the exhaust outlet of the aforementioned engine and which may have undergone prior denitrification, are introduced into a desulphurization washer 100 by a fireplace 200.

As shown schematically in Figure 3, the washer 100 is generally in the form of a tower which, in use, extends in length vertically. At its base, the scrubber 100 has a bottom 101 from which a peripheral wall 102 of the scrubber is raised, ending in a top 103. The peripheral wall 102 of the scrubber 100 defines a central geometric axis Z100 which, when the scrubber 100 is in use, extends vertically.

Note that the washer 100 is empty, in the sense that it lacks an internal lining, such as rings or internals mentioned in the introductory part of this document.

The chimney 200, which is made for example in the form of a sheath or a similar duct, is arranged below the scrubber 100 and extends substantially vertically so as to open into the bottom 101 of the scrubber 100. The downstream end of the chimney 200 passes through the constituent wall of the bottom 101 centrally on the central axis Z100 of the scrubber 100, so that the downstream outlet 201 of the chimney 200, which connects the rest of the chimney to the bottom 101 of the scrubber 100, is substantially coaxial with the peripheral wall 102 of the scrubber. In use, the exhaust fumes are admitted by the chimney 200 into the bottom 101 of the scrubber 100, and then, once inside this scrubber, they circulate, from the bottom 101 of the latter, upwards, until at its summit 103 from where they are evacuated, in the form of purified fumes.

This admission of the fumes 1 by the vertical stack 200 is advantageous for the installation of FIG. 3, embarked on a ship, since this arrangement takes up less space than a lateral introduction of the fumes into a washer, such a lateral introduction being common for washing columns of power plants on land.

To give an order of magnitude, and without this being of a nature to limit the invention, the flue gas flow rate 1 is for example between 50 000 and 200 000 Nm ³ / h and the diameter of the inside of the peripheral wall 102 of the washer 100 is for example between 3 and 6 m.

According to one of the characteristics of the invention, the washer 100 is internally equipped, at a lower part of its peripheral wall 102, with a protection 300 whose function is to protect the outlet 201 of the chimney 200 against the introduction of liquid inside the chimney, while allowing the fumes 1 out of the chimney. In other words, the protection device 300 prevents any liquid falling or dripping from the region directly above the outlet 201 to enter the chimney 200 by gravity while allowing the fumes 1 coming out of this chimney to bypass the protection device for Spread inside the scrubber 100. The protective device 300 is of paramount importance, in the sense that, for safety reasons, a liquid introduction into the chimney 200, with a possible rise of liquid towards the diesel engine. where fumes 1 escape, can not be tolerated.

In practice, various embodiments can be envisaged for the protection device 300. Fairly open embodiments are preferred, so as to limit the pressure drop at the level of the protection device 300. For this purpose, an embodiment of the device protection device 300, which is illustrated in Figures 4 and 5, consists of a Chinese hat 301, that is to say a cone, which has a half-angle at the apex of at least 60 ° and which, in the installation of FIG. 3, is substantially centered on the Z100 axis of the scrubber 100. A more elaborate embodiment, which, compared to the Chinese hat 301, limits the flue 1 to be folded towards the peripheral wall 102 of the 100, is shown in FIGS. 6 and 7: the protective device 300 then consists of an assembly 302 comprising a top cone 302.1 and two coaxial and superposed conical trunks 302.2 and 302.3, which are coaxially surmounted by the top cone 302.1, the cone members 302.1, 302.2 and 302.3 all having a top half-angle of at least 60 °, all being substantially centered on the Z100 axis of the washer 100 within the installation of FIG. 3. Of course, in a variant that is not shown, the number of cone trunks 302.2 and 302.3 can be reduced to one or, on the contrary, be greater than two.

According to one characteristic of the invention, the washer 100 is internally equipped, at the lower part of its peripheral wall 102, with a rotation device 400 which is designed to be traversed by the fumes 1 coming out of the chimney 200, so as to rotate these fumes inside the scrubber 100 before they meet the protection device 300. The rotation device 400 is for example placed in the outlet 201 of the chimney 200, as Diagrammatically shown in Figure 3. Alternatively, the rotation device 400 caps the outlet 201 or is arranged a little downstream of this outlet 201.

In practice, the embodiment of the rotation device 400 is not limiting of the invention. For example, and as indicated schematically on the 3, the rotation device 400 comprises smoke deflection vanes 401, which are fixedly arranged within the rotational device 400, being carried, if necessary, by a central core 402, and which , in the installation of Figure 3, are distributed substantially uniformly about the central axis Z100 of the washer 100. These deflection vanes 401 are advantageously provided in six to ten copies. Figure 8 shows in more detail a corresponding embodiment of this rotating device 400. As a variant not shown, the rotating device 400 may be similar to those employed at the input of cyclonic separators. Whatever its embodiment, the rotating device 400 has the effect of imparting a swirling movement to the fumes 1 flowing through this device, by preventing the fumes 1 from concentrating inside the washer 100, on one side of this washer at the expense of the diametrically opposed side as in Figure 1.

According to another characteristic of the invention, the washer 100 is internally equipped, at a current portion of its peripheral wall 102, with a spraying device 500 which makes it possible to spray a washing liquid 3, in the form of sails. of liquid, from substantially the central axis Z100 to the peripheral wall 102 of the scrubber 100. Because the spray device 500 is not punctual, or consists of several separate spray elements as detailed below, the sails 3 are sprayed by this spray device 500 from an area which is not strictly limited to the central axis Z100 of the scrubber 100, but from a central region of the scrubber 100, through which this Z100 axis passes, if appropriate which is centered on the latter. As shown in FIG. 3, each veil of the liquid 3, projected by the spraying device 500, extends from the spraying device 500 to the peripheral wall 102 of the scrubber 100, so that each veil covers, in projection according to Z100 axis, the entire cross section of the washer 100, of course outside the spray device 500 itself. In addition, also as shown in FIG. 3, the sails of the liquid 3 are associated in pairs, being noted that one or more of these pairs are possible: the two sails of each pair are projected from the spray device 500, on either side of the same horizontal geometric plane H, thus forming with the axis Z100 an angle which is strictly less than 90 °. According to a practical embodiment, but not limiting, the two webs of each pair are substantially symmetrical with respect to the horizontal plane H associated with this pair, which amounts to saying that these two webs form with the axis Z100 an angle of the same value, noted a in Figure 3. According to an advantageous optional dimensioning, the value a is advantageously between 50 ° and 70 °. In any case, when the installation of Figure 3 is in operation, the fumes 1, which, after having encountered the protective device 300, circulate upward inside the scrubber 100, pass through the lower sail then the sail from the top of the or each pair of sails of the liquid 3, projected by the spraying device 500, and this over the entire cross section the washer, that is to say, both in the vicinity of the spraying device 500 and near the peripheral wall 102 of the washer and between this device and this wall. In this way, all the flue gas stream F coming from the protection device 300 passes through the two webs of the or each pair of webs of the liquid 3, thus making it possible to capture the sulfur oxides contained in these fumes by transfer of these oxides. of sulfur in the washing liquid 3.

The spray device 500 is thus used to provide a large amount of the washing liquid 3, without generating a lot of pressure drop. The spraying device 500 thus operates the quenching of the flue gases 1, that is to say the reduction of their temperature between the flue gas inlet temperature 1 in the scrubber 100, typically between 150 ° C. and 450 ° C. and a final temperature of thermodynamic equilibrium, typically between 20 ° C and 70 ° C, the value of this final temperature depending on the initial temperature and the water content of the fumes 1. Moreover, in the common part of the scrubber 100 where the spraying device 500 is located, the liquid-to-gas ratio has a high value which makes it possible to rapidly capture the sulfur oxides, in particular the sulfur dioxide, where their concentration is the highest.

To further increase the desulfurization efficiency, several pairs of webs of the liquid 3 may be projected by the spraying device 500, being associated with respective horizontal planes H at different heights, as shown in FIG. 3: providing that the bottom web of each pair intersects the top web of the pair, located just above it, before these webs reach the peripheral wall 102 of the scrubber 100, a complementary atomization of the liquid 3 becomes produced to meet these sails, which creates an extra transfer surface between the liquid 3 and the fumes 1.

In practice, the embodiment of the spraying device 500 is not limiting of the invention, this spraying device 500 being, in any case, arranged above the protection device 300. By way of example, as envisaged schematically in FIG. 3, the spraying device 500 comprises one or more sprayers 501 which belong to a known technology in itself: each pair of sails of the liquid 3 is projected by one of the sprayers 501, each of they being located in the aforementioned central zone of the scrubber 100, or even located substantially on the central axis Z100 of the scrubber, and these sprayers 501 being staggered along this axis Z100. Alternatively, it is conceivable that several 501 sprayers are located substantially in the same horizontal plane and at a distance from each other, of course while all remaining in the aforementioned central region of the washer 100: for example, such sprayers are provided in triplicate, respectively arranged at the vertices a geometric triangle substantially horizontal. Of course, this variant can be combined with the staging of the sprayers 501, previously envisaged: in this case, each stage includes several sprayers 501, arranged for example in a triangle or other. In any case, the number of spray stage (s) of the spray device 500 and the number of sprayer (s) 501 per spray stage depends on the purification rate to be ensured, as well as on the concentration of sulfur fumes 1, the number of stage (s) being for example between 1 and 12 and the number of sprayer (s) per stage being for example between 1 and 3.

In relation to the order of magnitude mentioned above, the flow of the washing liquid 3 sprayed at each pair of sails, in other words projected by each sprayer 501, is for example between 30 and 200 m ³ / h.

According to another characteristic of the invention, the washer 100 is internally equipped, at an upper part of its peripheral wall 102, with a dispensing device 600, which is placed above the spraying device 500 and which allows a washing liquid 4 to be dispensed in the form of rain falling downwards in a free volume V100 formed inside the peripheral wall 102 of the scrubber 100, from the spraying device 500 to the dispensing device 600 In this free volume V100, the fumes 1, which, after having passed through the webs of the liquid 3, freely circulate upwards inside the washer 100, countercurrently encounter the rain formed by the washing liquid 4, which carries out a complementary purification of these fumes by capturing in the liquid 4 of the sulfur oxides still present in the fumes.

The embodiment of the dispensing device 600 is not limiting of the invention. By way of example, as indicated diagrammatically in FIG. 3, this dispensing device 600 comprises distributors 601 which are known per se and which are, for example, spray nozzles, distribution manifolds, projection heads, etc. Where appropriate, also as shown in FIG. 3, these distributors 601 are distributed over one or more, for example four, preferably two, stages succeeding one another vertically. In all cases, at each of these stages, the distributors 601 of this stage, which are thus all located substantially at the same height, in other words at the same level along the axis Z100, and whose number is for example between 5 and 30, are distributed over the cross section of the washer associated with this height: in this way, and providing that each distributor 601 of each floor distributes a fraction of the rain of the liquid 4, the rain of the liquid 4 obtained below the distribution device 600 falls over the entire cross section of the free volume V100, even if the distribution of the distributors 601 of each floor is not rigorously homogeneous.

In relation to the order of magnitude mentioned above, the flow of the washing liquid 4 distributed by each stage of the dispensing device 600 is about 200 m ³ / h.

Of course, the values and orders of magnitude given heretofore are not limiting of the invention. Depending on the size of the desulphurization plant, these values are adjusted, possibly much larger or much smaller than those previously given.

The respective compositions of the washing liquids 3 and 4 are not limiting of the invention. Each of these liquids 3 and 4 preferably comprises seawater, optionally added with an alkaline reagent. This being the case, one and / or the other of the washing liquids 3 and 4 may consist of a suspension of limestone, lime or a sodium solution. Moreover, according to a first operating possibility, the respective compositions of the washing liquids 3 and 4 are the same. According to an alternative operating possibility, the composition of the washing liquid 4 is not the same as that of the washing liquid 3: in particular, the washing liquid 4 is for example composed of fresh sea water, with or without addition of an alkaline reagent, while the washing liquid 3 may be a recirculated liquid, in particular partially depleted seawater. In any case, it is understood that the total quantity of the washing liquors 3 and 4, which are respectively projected by the spraying device 500 and dispersed by the dispensing device 600, depends on the flow, for example in kg / h, of sulfur oxides in fumes 1.

According to an optional and advantageous feature of the invention, the scrubber 100 is internally equipped with a stripper 700 which, in a manner known per se, makes it possible to retain the droplets of liquid which, in the absence of this stripper, would be trained to the outside of the scrubber 100, in the purified fumes 2. The stripper 700 is located above the dispensing device 600, so, in use, to be traversed by the fumes 1 which, after having met the dispensing device 600 circulate upward inside the scrubber 100.

The embodiment of the flyer 700 is not limiting of the invention. For example, the mist separator 700 consists of a herringbone basket.

The installation of Figure 3 is particularly effective for desulphurizing fumes

1 thanks to the stabilization of the flow of these fumes inside the scrubber 100, under the combined effect of the washing liquid webs 3, projected by the spraying device 500, and the rain of the washing liquid 4, distributed by the dispensing device 600, in conjunction with both the vertical centered introduction of the fumes 1 in the bottom 101 of the washer by the chimney 200 and the rotation of these fumes inside the washer by the rotation device 400. Indeed, the profile of the speed of fumes 1, which is necessarily very inhomogeneous just downstream of the protective device 300, is progressively and rapidly re-homogenized under the combined action of the spraying device 500 and the dispensing device 600. In addition, the rotation of the fumes 1, by the device of rotating 400, especially prohibits any oscillation instability flue 1 between two diametrically opposite zones of the washer 100.

It will be understood that the contact between the fumes 1 and the washing liquid 3 is of a different type from that of the contact between the fumes 1 and the washing liquid 4, because the liquid 3 is projected under form of sails while the liquid 4 is distributed in the form of rain. This differentiation of the type of contacting is beneficial for the desulfurization efficiency and advantageously allows to project, by the spraying device 500, a liquid flow 3 much larger than the flow of the liquid 4 distributed by the dispensing device 600 the flow of the liquid 3 can thus be 1, 5 times, or even twice as large as the flow of the liquid 4. In this way, the desulphurization is operated with more liquid 3 than liquid 4, which makes it possible to on the one hand, to limit the flow of liquid 4 which has the greatest impact on the pressure drop inside the washer 100, and, on the other hand, to increase the flow of liquid 3 which operates on the fumes at the beginning of their circulation in the scrubber, that is to say where a high value of the liquid to gas ratio is desired to treat the high concentrations of sulfur dioxide in the flue gas.

As an optional and advantageous arrangement, the dispensing device 600 is designed in such a way that the distribution density of the washing liquid 4 is less important in the center of the scrubber than in the periphery of this scrubber. In practice, this arrangement is based on a dedicated choice and / or arrangement of the distributors 601 of the distribution device 601: the term "dedicated choice" means that the distributors 600 are not necessarily all identical, and the term "dedicated arrangement" refers to the fact that that the location of the distributors 601 is not necessarily homogeneous. In other words, the type and number of distributors 601 per square meter may be variable over the cross section of the scrubber 100.

To better understand this aspect, Figure 9 shows the fictitious distribution of a cross section of the washer 100, at its free volume V100, in two parts, namely a central portion S100.1, crossed by the central axis Z100 of the washer, and a peripheral portion S100.2 running around the central portion S100.1, the areas respective of the central portion S100.1 and the peripheral portion S100.2 being equal to one another: the distribution density of the washing liquid 4 on the central portion S100.1, that is to say the flow of the washing liquid 4 which is distributed by the dispensing device 600 in this central part S100.1 and which is brought back to the area of this central part S100.1, for example expressed in m ³ / m ² / h , is at most 0.9 times the distribution density of the washing liquid 4 on the peripheral portion S100.2, that is to say the flow of the washing liquid 4 which is distributed by the dispensing device 600 in this peripheral part S100.2 and which is brought back to the area of this peripheral part S100.2, expressed in the same unit.

More drops of rain of the washing liquid 4 thus fall in the portion of the volume V100, whose section corresponds to the peripheral portion S100.2, than in the rest of the volume V100, that is to say that in the portion of this volume whose section corresponds to the central part S100.1. The liquid 4 distributed in the portion of the volume V100 associated with the peripheral portion S100.2 thus creates a greater friction with respect to the fumes 1 flowing upwards in this portion of the volume V100, forcing a rebalancing vis-à-vis of the remainder of the volume V100 and thus compensating, at least partially, the effect on the fumes 1 of the spraying device 500 and the protection device 300.

In practice, depending on the operating speed of the installation, that is to say according to the flow of fumes 1, their composition and their temperature, it is possible to adjust, manually or automatically, the amounts of the washing liquid 4 distributed respectively on the central part S100.1 and on the peripheral part S100.2.

Thus, an overall profile is restored for the liquid-to-gas ratio inside the scrubber 100, which is more favorable for flue gas desulfurization 1.

Example:

The invention has been tested with the following specificities.

The installation of FIG. 3 processes 105,000 Nm ³ / h of exhaust fumes 1, admitted by the chimney 2 into the bottom 101 of the scrubber 100 at a temperature of 390 ° C. The washer 100 has, at its peripheral wall 102, an inside diameter of 3200 mm and a total height of about 10 m. The chimney 200 has an inside diameter of 1800 mm. The rotation device 400 comprises eight deflection vanes 401. The protection device 300 is in the form of the Chinese hat 301 of FIGS. 4 and 5. Four step sprayers 501 each project 80 m ³ / h of the liquid 3. A single distributor stage 601 distributes 200 m ³ / h of the washing liquid 4. The stripper 700 is herringbone.

The implementation of this example makes it possible to note the rapid homogenization of the smoke velocity profile 1 inside the scrubber 100, this profile being very inhomogeneous just downstream of the protection device 300 while it is substantially flat at free volume level V100.

Claims

1. - Process for the wet desulfurization of exhaust fumes from an engine of a marine vessel,

in which fumes to be desulphurized (1) are admitted into a scrubber (100) by a vertical chimney (200) which opens substantially centrally into the bottom (101) of the scrubber,

and wherein the flue gases (1) flow upwardly within the scrubber (100) to be contacted with first (3) and second (4) scrubbing liquids for sensing the sulfur dioxide contained in the scrubber (100). the fumes, which fumes meet in the washer successively:

- a rotation device (400), which is traversed by the fumes (1) by rotating them inside the washer (100),

- a protection device (300), which protects the downstream outlet (201) of the chimney (200) against the introduction of liquid while maintaining the flow of fumes (1),

- a spraying device (500), which projects the first washing liquid (3), in the form of at least one pair of liquid webs, from a central region of the scrubber (100) through which a central geometric axis passes (Z100) of the scrubber, to the peripheral wall (102) of the scrubber, the liquid webs of the or each pair being projected from the spraying device, on either side of the same horizontal plane (H ) associated with this pair, then

- a dispensing device (600), which distributes the second washing liquid (4) in the form of downward falling rain in a free volume (V100) of the scrubber (100), which extends from the spraying device (500) to the dispensing device (600) and wherein the fumes circulate freely, which distribution device comprises at least one stage of distributors (601), which are located at the same height, being distributed over the cross section of the washer associated with this height, and which respectively distribute a corresponding fraction of the rain.

2. - A process according to claim 1, wherein the flow of the first washing liquid (3), projected by the spraying device (500), is at least 1.5 times greater than the flow of the second washing liquid ( 4), distributed by the dispensing device (600).

3. A method according to one of claims 1 or 2, wherein, the cross section of the washer (100) below the dispensing device (600) being constituted a central portion (S100.1) and a peripheral portion (S100.2) having the same area, the distribution density of the second washing liquid (4) on said central portion, i.e. to say that the flow of the second washing liquid which is distributed by the dispensing device (600) in said central portion and which is brought back to the area of said central portion, is at most 0.9 times the distribution density of the second liquid washing on said peripheral portion, that is to say the flow of the second washing liquid which is distributed by the dispensing device in said peripheral portion and which is brought back to the area of said peripheral portion.

4. A process according to any one of the preceding claims, wherein at least two pairs of liquid webs are projected by the spraying device (500), being associated with respective horizontal planes (H) which are located at different heights, so that the two sails of liquid, which belong respectively to a first pair and a second pair above the first pair and which are respectively projected above the horizontal plane associated with the first pair and projected below the horizontal plane associated with the second pair, intersect each other.

5. - Process according to any one of the preceding claims, wherein each of the two webs of liquid of the or each pair projected by the spraying device (500) forms with the central axis (Z100) of the washer (100) a angle (a) between 50 ° and 70 °.

6. A process according to any one of the preceding claims, wherein the first and second wash liquids (3, 4) comprise, or even consist of, seawater.

7. A process according to any one of the preceding claims, wherein the respective compositions of the first (3) and second (4) wash liquors are not the same.

8. - Wet desulfurization plant for exhaust fumes from an engine of a marine vessel,

which installation includes:

- a washer (100) in the bottom (101) which opens substantially a vertical chimney (200) for flue gas (1) into the scrubber, - a rotation device (400), which is adapted to be traversed by fumes (1) out of the chimney (200) so as to rotate these fumes inside the scrubber (100),

- a protection device (300), which is adapted to protect the downstream outlet (201) of the chimney (200) against the introduction of liquid while allowing fumes (1) to flow out of the chimney,

- a spraying device (500), which is adapted to project a first washing liquid (3), in the form of at least one pair of liquid webs, from a central region of the scrubber (100), through which passes a central geometric axis (Z100) of the scrubber, up to the peripheral wall (102) of the scrubber, the liquid webs of the or each pair being projected from the spraying device on either side of the same plane horizontal (H) associated with this pair, and

a dispensing device (600), which is adapted to dispense a second washing liquid (4) in the form of downward falling rain into a free volume (V100) of the scrubber (100), which extends from spray device (500) to the dispensing device (600) and in which the flue gases (1) flow freely, which dispensing device comprises at least one distributor stage (601), which are located at the same height, being distributed on the cross section of the washer associated with this height, and which respectively distribute a corresponding fraction of the rain,

the rotating device (400), the protective device (300), the spraying device (500) and the dispensing device (600) being arranged inside the scrubber (100) so that fumes to desulphurize (1), exiting the stack (200) and flowing upwardly into the scrubber to be contacted with the first and second scrubbing liquids (3, 4) which are intended to capture the dioxide of sulfur contained in these fumes, successively meet the rotation device, the protective device, the spraying device and the dispensing device.

9. - Installation according to claim 8, wherein the spraying device (500) comprises a single sprayer (501), which is located in said central zone of the scrubber (100) and which is adapted to spray the first washing liquid ( 3) as a single pair of liquid sails.

10. - Installation according to claim 8, wherein the spraying device (500) comprises several sprayers (501), which are each adapted to project the first washing liquid (3) in the form of a pair of sails of liquid and which are all located in said central zone of the scrubber (100), at least some of these sprays being:

arranged staggered along the central axis (Z100) of the scrubber (100) so that the two webs of liquid, which are respectively projected, by a first of the sprayers, above the horizontal plane (H) associated with the pair of this first sprayer, and projected, by a second sprayer located above the first sprayer, below the horizontal plane associated with the pair of this second sprayer, intersect, and / or

- arranged substantially in the same horizontal plane and at a distance from each other.

1 1. - Installation according to any one of claims 8 to 10, wherein the rotation device (400) comprises vanes (401) flue deflection (1), which are fixedly distributed around the central axis (Z100 ) of the washer (100) and which are in particular provided in six to ten copies.

12. - Installation according to any one of claims 8 to 11, wherein the dispensing device (600) comprises several stages of distributors (601), these stages being located at different respective heights.

13. - Installation according to any one of claims 8 to 12, wherein the protective device (300) consists of a Chinese hat (301), that is to say a cone having a half angle at the summit of at least 60 °.

14.- Installation according to any one of claims 8 to 12, wherein the protection device (300) comprises a conical top (302.1) and one or more conical truncated cones (302.2, 302.3), which is or are coaxially surmounted by the top cone (302.1), the top cone and the at least one truncated cone all having a top half-angle of at least 60 °.

15.- Installation according to any one of claims 8 to 14, wherein the installation further comprises a stripper (700) which is arranged inside the scrubber (100) so as to be traversed by the fumes (1). ) after they have encountered the dispensing device (600).