Gas scrubbing process with direct removal of the used scrubbing fluid into a further processing stage

Abstract

This invention relates to equipment for scrubbing a first substance comprising of a gas, using a second substance comprising of a scrubbing fluid. More specifically, the invention relates to a simple, effective and very compact means for the rapid removal of the used scrubbing fluid directly into equipment where it is desirable for the used scrubbing fluid to have a stable and uniform velocity as it enters that equipment. In addition, the invention relates to situations where this existing or similar gas scrubbing technology is being used for other types of mass or energy transfer purposes.

Description

[0001] GAS SCRUBBING PROCESS WITH DIRECT REMOVAL OF THE USED SCRUBBING FLUID INTO A FURTHER PROCESSING STAGE

[0002] TECHNICAL FIELD

[0003] In the following document, the term “scrubbing” should be understood as including the transfer of components (including energy) from the scrubbing fluid into the gas as well as or in addition to the transfer of components from the gas into the scrubbing fluid.

[0004] This invention relates to equipment for scrubbing a first substance comprising of a gas, using a second substance comprising of a scrubbing fluid. More specifically, the invention relates to a simple, effective and very compact means for the rapid removal of the used scrubbing fluid directly into equipment where it is desirable for the used scrubbing fluid to have a stable and uniform velocity as it enters that equipment.

[0005] BACKGROUND ART

[0006] The removal of gaseous components and / or particulates and / or droplets from a gas stream, using a scrubbing fluid, is well known, and is often carried out by means of a wet scrubbing process. Similar equipment can be used for transferring components from the scrubbing fluid into the gas stream.

[0007] Within South African Patent PCT / ZA 2003 / 000160 (WO 2004 / 039492 A2) technology is described which enables a wet scrubbing process to achieve dust removal efficiencies from a gas stream of above 90% for 0.5 micron sized dust particles. This patent describes equipment comprising of a static, co-current contacting device having a plurality of stages defining a flow path, with a flow profile and a flow direction for the gas and the scrubbing fluid from an inlet end of the flow path towards an outlet end of the flow path; at least some of the stages being shaped to define a substantially curved flow path having an effective centre of curvature located to one side of the flow path, and wherein each adjacent stage has an effective centre of curvature on an opposite side of the flow path, the flow path characterised in being provided with an edge formation between at least two adjacent stages so as to enhance a launch of the scrubbing fluid on an outside of the curved flow path of the adjacent stage that immediately precedes the respective edge formation from that edge formation with a trajectory towards an opposite wall of the flow path, wherein the opposite wall of the flow path is positioned, orientated and shaped to create a landing area that would intersect the flight path of the scrubbing fluid at an angle of incidence of less than 35 degrees and to then smoothly continue towards a next stage or towards the outlet end of the flow path.

[0008] Computational fluid dynamic (CFD) modelling indicated that for designs that were capable of achieving dust removal efficiencies of above 90% for 0.5 micron sized dust particles, essentially all of the 20 micron droplets of scrubbing fluid and all the larger droplets of scrubbing fluid were able to reach the landing area that is nearest to the outlet end of the flow path (the last landing area). This CFD modelling also indicated that within the range of droplet sizes that were created at the edge formation within the scrubbing unit that is nearest to the outlet end of the flow path (the last edge formation), all the 20 micron droplets together with all the smaller droplets accounted for less than 1 % by weight of the droplets that were created. This meant that considerably more than 99% of the scrubbing fluid would arrive at the last landing area and would be incorporated into a film of scrubbing fluid that would then continue to flow along that side of the flow profile towards an outlet end of the flow path.

[0009] The CFD modelling also indicated that similar proportions of used scrubbing fluid would arrive at an equivalent landing area when operating with less, even considerably less, intense scrubbing conditions and when operating with equipment that had one, two or more edge formations.

[0010] This meant that effectively all the used scrubbing fluid could conveniently be removed from the scrubbed gases by locating an offtake arrangement or slot further on from the last landing area and within the same wall of the flow path as the last landing area.

[0011] Further, the CFD modelling showed that immediately downstream of the last landing area, the flowing film of used scrubbing fluid had a reasonably stable and uniform velocity in the direction towards the outlet end of the flow path and that any transverse velocity components resulting from the landing processes of the droplets were rapidly attenuated. As expected, the effects of viscous drag within the film caused the velocity of the film to be progressively reduced as the film progressed towards the outlet end of the flow path. However, at the same time, turbulent eddies within the scrubbed gases progressively caused the velocity of the film to become considerably more variable and for progressively increasing transverse velocity components to develop within the flowing film.

[0012] These instabilities within the flowing film of used scrubbing fluid would have a relatively minor effect on the performance of the sort of additional equipment that is shown in Figure 1 for immediately contacting the used scrubbing fluid with a gas, e.g. for removing dissolved CO2 from the used scrubbing fluid. However, these instabilities would have a profound effect on the benefits that could be achieved by counter current multi-stage contacting of the used scrubbing fluid with a gas within the sort of equipment that is shown in Figure 2.

[0013] The CFD modelling showed that providing the offtake for the used scrubbing fluid did not significantly disturb the flow within the scrubbed gases, then virtually all the velocity energy within the scrubbed gases could be converted into pressure energy thereby saving up to around 25% of the pressure drop across a gas scrubbing process that included launching the scrubbing fluid from three successive edge formations. With fewer scrubbing stages, the percentage of the pressure drop that could be saved would be greater.

[0014] It was therefore apparent that if it is desirable within any subsequent processing of the used scrubbing fluid for the velocity of the fluid to be stable and uniform, it would be necessary to protect the film from the effects of turbulent eddies within the scrubbed gases. However, at the same time, the eddy protection measures should not affect the maximum recovery of velocity energy into pressure energy. Unfortunately, inserting a flow control surface close to the fluid film at a location that was close to the end of the last droplet landing area created a substantial intensification of the effect of turbulence within the scrubbed gases on the uniformity of the velocity of the fluid film. It also increased the magnitude of the transverse velocity components that were introduced into the fluid film. This intensification was particularly apparent within the entry region of the space that was created between the fluid film and the flow control surface. As the distance between the flow control surface and the fluid film was increased, the intensity of the intensification was reduced. Similarly, as the start location for the flow control surface was moved away from the last landing area, the intensity of the intensification was reduced.

[0015] Also, tapering the space between the fluid film and the flow control surface so as to progressively slow the gas velocity as the film approached the offtake slot was found to be beneficial. Similarly, extending the distance between the last landing area and the offtake slot created a more uniform velocity within the fluid film. However, as this distance was increased, the velocity of the fluid film was reduced, causing the droplet size that would be created within the subsequent gas contacting process to increase. The increased droplet size created a reduced droplet surface area per unit volume of fluid and a reduced mass transfer coefficient per unit of droplet surface area.

[0016] Eventually, an arrangement similar to that which is shown within Figure 3 appeared to represent a reasonably optimum arrangement for enabling the used scrubbing water to be contacted by a gas within a counter current multi-stage contacting arrangement. However, in relation to achieving good control over the droplet flight paths within a counter current multi-stage gas contacting process for the used scrubbing fluid, the Figure 4 arrangement, without a flow control surface was found to be better. But this Figure 4 arrangement created a turbulent zone within the scrubbed gases which significantly reduced the efficiency of the subsequent velocity recovery into pressure.

[0017] Introducing the surface (50) into the gas flow, as shown in Figure 5, prevented the turbulent zone from forming and at the same time, enabled a much lower gas velocity to be achieved within the region immediately adjacent to the fluid offtake slot than was possible within the Figure 4 arrangement. Turbulence intensification issues at the landing area end of surface (50) were an issue until the flow area at A in Figure 6 was made to be approximately 80% of the flow area at C whilst at the same time the flow areas at B and D were kept approximately equal; and whilst the flow area at C was kept between approximately 60% and 120% of the flow area at D. Surprisingly, it was only whilst keeping flow areas at B and D approximately the same, and whilst increasing the velocity at A above a value that was 10% higher than the velocity at C that a rapid decline began to occur within the turbulence intensification within the area immediately following C.

[0018] OBJECT OF THE INVENTION

[0019] It is accordingly a first object of the present invention to create a simple, effective and compact offtake for a flowing film of used scrubbing fluid that has been formed from droplets that have been created by an edge formation and then received at an associated landing area both of which have been shaped, positioned and orientated with respect to each other in a manner that is similar to that which is described within South African Patent PCT / ZA 2003 / 000160 (WO 2004 / 039492 A2); wherein the fluid film, once formed, is sufficiently protected from the effects of turbulent eddies within the scrubbed gases for it to be suitable for inputting directly into the type of equipment shown within Figure 2 or into other processing equipment where it is desirable for the velocity of the fluid film to be stable and uniform.

[0020] In addition, it is a further objective of the present invention to achieve this protection and removal of the used scrubbing fluid without causing disturbances to the gas flow that would be large enough to prevent the available velocity energy that is within the scrubbed gases from being converted efficiently into pressure energy.

[0021] DISCLOSURE OF THE INVENTION

[0022] According to a first aspect of the invention there is provided equipment for scrubbing a first substance comprising of a gas, with a second substance comprising of a scrubbing fluid: wherein, after the first substance has been scrubbed and whilst not creating disturbances within the flow of the first substance that are large enough to prevent the available velocity energy that is within the first substance from being converted efficiently into pressure energy, the second substance is removed as a flowing film of fluid the velocity of which is stable and uniform; the equipment comprising of a static, co-current contacting device having a plurality of stages defining a flow path, with a flow profile and a flow direction for the first and the second substances from an inlet end (1) of the flow path towards an outlet end (18) of the flow path; at least some of the stages being shaped to define a substantially curved flow path having an effective centre of curvature located to one side of the flow path, and wherein each adjacent stage has an effective centre of curvature on an opposite side of the flow path, the flow path characterised in being provided with an edge formation (5) between at least two adjacent stages so as to enhance a launch of the second substance on an outside of the curved flow path (4) of the adjacent stage that immediately precedes the respective edge formation from that edge formation with a trajectory and an ongoing flight path (6) towards an opposite wall (2) of the flow path, wherein the opposite wall (7) of the flow path immediately downstream of the edge formation is positioned, shaped and orientated to intersect the flight path of the second substance within a landing area at an angle of incidence of less than 35 degrees and to then smoothly continue towards a next stage or towards the outlet end (18) of the flow path; wherein, a flow control surface (50) is inserted into the flow path immediately following the edge formation (51 ) which is nearest to the outlet end of the flow path; wherein, a leading edge (52) of the flow control surface (50) is positioned just clear of the flight path of the second substance that is launched from edge formation (51 ) at a distance C from the landing area and a distance D from wall (53) of the flow path that is opposite to the landing area; wherein, the flow control surface (50) creates a smooth passageway between it and wall (53), and a trailing edge (54) of the flow control surface (50) is a distance A from ongoing surfaces (55) of the flow path, and a distance B from the wall (53); wherein the flow area at A is between 70% and 90% of the flow area at C; wherein the flow area at C is between 50% and 120% of the flow area at D, and the flow area at B is approximately equal to the flow area at D; wherein, downstream of the landing area (56) that is nearest to the outlet end of the flow path and within a same wall as this landing area an offtake slot (58) is located; wherein, a wall (57) between the offtake slot (58) and the landing area (56) is shaped, positioned and orientated to create a progressively expanding flow path for the first substance between the flow control surface (50) and the wall (57) and also to convey a flowing film of the second substance that emanates from landing area (56) into and through the offtake slot (58); wherein, downstream of the offtake slot (58), surfaces (55) progressively narrow the flow path between the surfaces (55) and the flow control surface (50) prior to this portion of the flow path reaching the trailing edge (54) of the flow control surface and joining the smooth flow passage that is between the flow control surface (50) and the wall (53), thereby allowing all the first substance to combine and to continue towards a first outlet at the outlet end (18) of the flow path.

[0023] The flow path may have a flow profile that is configured and dimensioned such that all of the second substance that is able to reach the landing area that is downstream of an edge formation does so before the second substance that accumulates on that side of the flow path reaches a next edge formation or the offtake slot.

[0024] The flow path may have a flow profile that is configured and dimensioned such that, by the angle of the lead up to an edge formation and by the positioning, dimensioning and orientation of the opposite wall that is immediately downstream of that edge formation, the second substance, when reaching the opposite wall, arrives at an angle of approach which is less than 35 degrees. According to a second aspect of the invention there is provided a method for scrubbing a first substance comprising of a gas, with a second substance comprising of a scrubbing fluid; wherein, after the first substance has been scrubbed and whilst not creating disturbances within the flow of the first substance that are large enough to prevent the available velocity energy that is within the first substance from being converted efficiently into pressure energy, the second substance is removed as a flowing film of fluid, the velocity of which is stable and uniform; the method including the steps of transporting the first substance and the second substance through a plurality of stages, at least some of the stages being shaped to define a substantially curved flow path having an effective centre of curvature located to one side of the flow path, and wherein each adjacent stage has an effective centre of curvature on an opposite side of the flow path, wherein as the first substance and the second substance progress past an edge formation (5) that is located between adjacent stages within the equipment, the second substance on an outside of the curved flow path (4) of the adjacent stage that immediately precedes an edge formation is launched from that edge formation with a trajectory and an ongoing flight path (6) towards an opposite wall of the flow path (2), where the shape, position and orientation of the surface of the opposite wall of the flow path (7) immediately downstream of the edge formation enables the second substance to be received within a landing area with an angle of incidence of less than 35 degrees and then routes the resultant film of the second substance towards a next stage or towards the outlet end (18) of the flow path; wherein, a flow control surface (50) with its leading edge just clear of the flight path of the second substance that is launched from the edge formation (51 ) that is nearest to the outlet end of the flow path is arranged such that the flow area for the first substance as it enters a first space between the flow control surface (50) and the droplet landing area (56) is between 50% and 120% of the flow area for the first substance as it enters a smooth passageway that is formed between the flow control surface (50) and wall (53) of the flow path and which is opposite to the landing area; wherein, the flow control surface (50) is further arranged such that the flow area for the first substance as it enters the smooth passageway is approximately the same as the flow area for the first substance as it leaves the smooth passageway and such that the flow area for the first substance as it enters the first space is between 100% and 130% of the flow area for the first substance as it leaves the first space between a trailing edge (54) of the flow control surface (50) and ongoing surfaces (55) of the flow path that is within the first space; wherein the flow area for the first substance within the first space is progressively increased as the first substance progresses towards offtake slot (58) for the second substance and is then progressively decreased before it leaves the first space to combine with the first substance that is leaving the smooth passageway; wherein, a wall (57) between offtake slot (58) and the landing area (56) conveys a flowing film of the second substance that emanates from the landing area (56) directly into and through the offtake (58); wherein, the first substance is able to combine and to continue towards a first outlet at the outlet end (18) of the flow path.

[0025] BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

[0026] The invention will now further be described, by way of example only, with reference to the accompanying diagrams wherein:

[0027] Figure 1 is a sectioned view of example equipment within which the used scrubbing fluid is exposed to a single stage of contacting with a gas. In this example, the used scrubbing fluid is derived from a single scrubbing stage. However, this single stage of contacting with a gas could be applied to a used scrubbing fluid that is derived from more than one scrubbing stage;

[0028] Figure 2 is a sectioned view of example equipment with arrows indicating the direction of gas and fluid droplet flow and within which a curtain of droplets is exposed to multiple stages of contact with a gas and where between each contacting stage the gas is conveyed via side channels into an earlier contacting stage with respect to the flow direction of the droplets;

[0029] Figure 3 is a sectioned view of equipment with arrows indicating the direction of gas and fluid droplet flow and where gas contacting equipment of the type shown in Figure 2 has been substituted into the type of equipment that is shown in Figure 1 and where flow control surfaces have been introduced to limit the effects of turbulent eddies within the scrubbed gases on the uniformity of the flow of the film of used scrubbing fluid as it approaches the offtake slot into the gas contacting portion;

[0030] Figure 4 is the same as Figure 3 except that the flow control surfaces that were introduced to limit the effects of turbulent eddies within the scrubbed gases have been removed;

[0031] Figure 5 is a sectioned view of the invention showing equipment that is similar to that which is shown in Figure 4 and where an additional flow control surface (50) has been introduced; and

[0032] Figure 6 is an enlargement of the upper half of Figure 5 and shows the locations where the flow areas at A, B, C and D are determined.

[0033] It should be noted that whilst Figures 3, 4, 5 and 6 show arrangements within which the used scrubbing fluid is derived from only one scrubbing stage, the used scrubbing fluid can be derived from one or more scrubbing stages.

[0034] The presently disclosed subject matter will now be described more fully hereinafter with reference to the accompanying Examples, in which representative embodiments are shown. The presently disclosed subject matter can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments to those skilled in the art. SPECIFIC EMBODIMENT OF THE INVENTION

[0035] A preferred embodiment of the invention will now be described by means of a nonlimiting example only and with reference to the various aspects of the invention and the accompanying Figures 1 to 6.

[0036] Figure 1 shows the shape of a typical flow path for a single contact gas contacting arrangement for used scrubbing fluid that has been derived from a single scrubbing stage.

[0037] Within Figure 1 , arrow 1 points to the inlet end of the flow path. Arrows 2 and 4 point to the side walls of the flow path. These walls may be the sides of a rectangular or approximately rectangular flow path, or they may be the inner and outer walls of an annular flow path. For optimum scrubbing performance within an annular flow path, the flow profile needs to remain the same all the way around the annulus. For optimum scrubbing performance for a rectangular or approximately rectangular flow path, the flow profile needs to remain the same throughout the width of the flow path.

[0038] The preferred location for the addition of the scrubbing fluid would be to uniformly distribute it along the whole of the length of the side wall (4), preferably at the entry (3). A combination of friction between the incoming gas and the scrubbing fluid as it flows over the side wall (4) and the feed velocity of the scrubbing fluid should be used to achieve an approach velocity for the scrubbing fluid towards the edge formation (5) that will produce the size of droplets that would be suitable for the quality of scrubbing that is required.

[0039] The necessary means for accelerating the gas that is to be scrubbed to a velocity that would be suitable for the quality of scrubbing that is required and for delivering it to the inlet end of the flow path would be obvious to a skilled practitioner and are therefore not shown here. For similar reasons, the means for delivering the scrubbing fluid to the inlet end of the flow path have not been shown.

[0040] Arrow 5 points to the edge formation within the scrubbing portion of this example arrangement and arrow 6 points to the likely range of flight paths for the majority of the droplets that would be launched from this edge formation.

[0041] Arrow 7 points to the landing area in this example arrangement.

[0042] Arrow 8 points to the offtake slot through which the film of used scrubbing fluid that emanates from the landing area (7) can be intercepted and allowed to flow smoothly along a connecting surface (9) to an edge formation (10) from which the used scrubbing fluid is launched into a gas contacting chamber (12).

[0043] Arrow 11 points to the outlet connection for the used contacting gas which, within this example arrangement, is into the flow of scrubbed gases. Outlet connections to different locations would also be possible. The necessary pressure control arrangements that will be needed to ensure that only / mostly used scrubbing fluid enters through the offtake slot (8) will be familiar to an experienced practitioner.

[0044] Therefore, a suitable example arrangement is not shown here.

[0045] Arrow 13 points to the curtain of droplets that will be produced from the edge formation (10).

[0046] Arrow 14 points to a preferred, but not essential offtake position for the used and contacted scrubbing fluid. Preferably, a fluid level should be maintained within the collection area for the scrubbing fluid to absorb the velocity energy from the droplets and thereby reduce the erosion that would otherwise occur on the walls of the contacting chamber within this area.

[0047] Arrow 15 points to an alternative outlet for the used and contacted scrubbing fluid. Preferably, outlet (14) should be used for normal operations and outlet (15) should only be used for sludge removal as and when needed or for drain down purposes.

[0048] Arrow 16 points to the inlet for the contacting gas. The exact location for this inlet may be arranged to suit the individual circumstances, but preferably, this inlet should be positioned such that the contacting gas has to follow a generally counter current route towards the gas outlet relative to the flight path of the droplets. Also, ideally, the contacting gas should be arranged to cross the flight path of the scrubbing fluid droplets. The necessary feed, pressure and flow control arrangements for controlling the amount of and the pressure of the contacting gas that is supplied will be familiar to an experienced practitioner. Therefore, a suitable example is not shown here.

[0049] Arrow 17 points to the preferred area where the start of a diverging section for converting velocity energy into pressure energy should be located.

[0050] Arrow 18 points to the connection to the ongoing arrangements for routing the scrubbed gases to where they need to be sent.

[0051] Within Figure 2, arrows 10, 11 , 13, 14 and 16 point to the locations in this Figure which are equivalent to the respective locations within Figure 1 .

[0052] Arrow 21 points to a film of fluid that has been arranged to flow along a surface (22) towards an edge formation (10). Similar comments to those that were made in respect of locations (3), (4) and (5) in relation to Figure 1 would also apply here.

[0053] Figure 3 shows a sectioned view of an example arrangement by which Figure 2 type equipment can be introduced into a Figure 1 arrangement.

[0054] Arrows 5, 6, 7, 8, 10, 11 , 13, 14, 16 and 18 point to the locations in this Figure which are equivalent to the respective locations within Figure 1.

[0055] Arrow 31 points to a flow control surface the purpose of which is to provide a smooth flow passage for the scrubbed gases prior to the start of a shallow angle diverging section for recovering the velocity energy within the gases back into pressure energy.

[0056] Arrow 32 points to the leading edge of the flow control surface (31 ) and arrow 33 points to a shallow angle diverging section within which the gases that accompany the fluid film as the film passes between the end (32) and the wall (35) are slowed down so as to reduce the intensity of the turbulent eddies that will be present within that gas.

[0057] Arrow 34 points to a converging section within which those gases within the channel (33) that do not accompany the fluid film through the offtake slot (8) are accelerated again to a velocity that is similar to the gas velocity in the main flow of scrubbed gases.

[0058] Figure 4 is a copy of the Figure 3 arrangement, except that the items associated with arrows 31 to 34 have been removed.

[0059] In Figure 5 an additional flow control surface (50) has been added to the Figure 4 arrangement. This surface has an inlet end (52) and an outlet end (54).

[0060] Arrow 51 points to the edge formation that is nearest to the outlet end of the flow path within the gas scrubbing portion of the equipment and which within Figure 1 was referred to as item (1 ) and arrow 56 points to the droplet landing area that is nearest to the outlet end of the flow path and which within Figure 1 was referred to as item (7). Arrows 53 and 57 point to the side walls of the flow path and arrow 55 points to an ongoing surface that follows on from the offtake slot (58) towards the wall (59) of the flow path.

[0061] Arrow 58 points to the offtake slot that within Figure 1 was referred to as item (8).

[0062] Within the Figure 5 arrangement, the gas outlet (11 ) has been relocated to a suitable location within the surface (55). This was necessitated because of the much greater reduction in gas velocity and hence pressure increase that could be achieved within the region immediately surrounding the offtake slot (58) relative to what could be achieved within the Figure 3 and Figure 4 arrangements. Achieving a sufficient flow control over the flow of gas through outlet (11 ) required very tight tolerances on the size of outlet (11 ) if it remained within the Figure 4 location. However, locating it at an appropriate point along the gas re-acceleration route meant that outlet (11 ) could be much wider with much relaxed tolerance limits.

[0063] In Figure 6, the arrows point to the same locations as in Figure 5.

[0064] The many means for connecting the used and contacted scrubbing fluid to appropriate arrangements for its onward transmission to where it needs to be sent are well established and should be well known to an experienced practitioner. Therefore, a suitable example is not shown here. Similarly, the means that can be used to convert some or most of the velocity energy that will be present within the scrubbed gases back into pressure energy and for ducting the scrubbed gas to wherever it needs to be sent are also well established and should be well known to an experienced practitioner. Therefore, a suitable example is not shown here.

[0065] It will be appreciated that many variations in detail are possible without departing from the scope or spirit of the invention as claimed in the claims hereinafter, such as the application of the method and equipment to other off-gases and dust emissions.

Claims

CLAIMSIn the following claims, the term “scrubbing” should be understood as including the transfer of components (including energy) from the scrubbing fluid into the gas as well as or in addition to the transfer of components from the gas into the scrubbing fluid.

1. Equipment for scrubbing a first substance comprising of a gas, with a second substance comprising of a scrubbing fluid: wherein, after the first substance has been scrubbed and whilst not creating disturbances within the flow of the first substance that are large enough to prevent the available velocity energy that is within the first substance from being converted efficiently into pressure energy, the second substance is removed as a flowing film of fluid the velocity of which is stable and uniform; the equipment comprising:- a static, co-current contacting device having a plurality of stages defining a flow path, with a flow profile and a flow direction for the first and the second substances from an inlet end (1 ) of the flow path towards an outlet end (18) of the flow path;- at least some of the stages being shaped to define a substantially curved flow path having an effective centre of curvature located to one side of the flow path, and wherein each adjacent stage has an effective centre of curvature on an opposite side of the flow path;- the flow path characterised in being provided with an edge formation (5) between at least two adjacent stages so as to enhance a launch of the second substance on an outside of the curved flow path (4) of the adjacent stage that immediately precedes the respective edge formation(5) from that edge formation with a trajectory and an ongoing flight path towards an opposite wall (2) of the flow path; and wherein the opposite wall of the flow path (7) immediately downstream of the edge formation is positioned, shaped and orientated to intersect the flight path of the second substance within a landing area at an angle of incidence of less than 35 degrees and to then smoothly continue towards a next stage or towards the outlet end (18) of the flow path; wherein, a flow control surface(50) is inserted into the flow path immediately following the edge formation(51 ) which is nearest to the outlet end (18) of the flow path; wherein, a leading edge (52) of the flow control surface (50) is positioned just clear of the flight path of the second substance that is launched from edge formation (51 ) at a distance C from the landing area and a distance D from wall (53) of the flow path that is opposite to the landing area; wherein, the flow control surface (50) creates a smooth passageway between it and wall (53), and a trailing edge (54) of the flow control surface (50) is a distance A from ongoing surfaces (55) of the flow path, and a distance B from the wall (53); wherein the flow area at A is between 70% and 90% of the flow area at C; wherein the flow area at C is between 50% and 120% of the flow area at D, and the flow area at B is approximately equal to the flow area at D; wherein, downstream of the landing area (56) that is nearest to the outlet end of the flow path and within a same wall as this landing area an offtake slot (58) is located; wherein, a wall (57) between the offtake slot (58) and the landing area (56) is shaped, positioned and orientated to create a progressively expanding flow path for the first substance between the flow control surface (50) and the wall (57) and also to convey a flowing film of the second substance that emanates from landingarea (56) into and through the offtake slot (58); wherein, downstream of the offtake slot (58), surfaces (55) progressively narrow the flow path between the surfaces (55) and the flow control surface (50) prior to this portion of the flow path reaching the trailing edge (54) of the flow control surface and joining the smooth flow passage that is between the flow control surface (50) and the wall (53), thereby allowing all the first substance to combine and to continue towards a first outlet at the outlet end (18) of the flow path.

2. Equipment as claimed in claim 1 wherein the flow path has a flow profile that is configured and dimensioned such that all of the second substance that is able to reach the landing area that is nearest to the outlet end of the flow path does so before the second substance that accumulates on that side of the flow path reaches the offtake slot.

3. A method for scrubbing a first substance comprising of a gas, using a second substance comprising of a scrubbing fluid; wherein, after the first substance has been scrubbed and whilst not creating disturbances within the flow of the first substance that are large enough to prevent the available velocity energy that is within the first substance from being converted efficiently into pressure energy, the second substance is removed as a flowing film of fluid the velocity of which is stable and uniform; the method including: transporting the first substance and the second substance through a plurality of stages, at least some of the stages being shaped to define a substantially curved flow path having an effective centre of curvaturelocated to one side of the flow path, and wherein each adjacent stage has an effective centre of curvature on an opposite side of the flow path; wherein as the first substance and the second substance progress past an edge formation (5) that is located between adjacent stages within the equipment, the second substance on an outside of the curved flow path(4) of the adjacent stage that immediately precedes an edge formation(5) is launched from that edge formation with a trajectory and an ongoing flight path (6) towards an opposite wall (2) of the flow path; where the shape, position and orientation of the surface of the opposite wall (7) of the flow path immediately downstream of an edge formation (5) enables the second substance to be received within a landing area (7) with an angle of incidence of less than 35 degrees and then routes the resultant film of the second substance towards a next stage or towards the outlet end (18) of the flow path; wherein, a flow control surface (50) with its leading edge just clear of the flight path of the second substance that is launched from the edge formation (51 ) that is nearest to the outlet end of the flow path is arranged such that the flow area for the first substance as it enters a first space between the flow control surface (50) and the droplet landing area (56) is between 50% and 120% of the flow area for the first substance as it enters a smooth passageway that is formed between the flow control surface (50) and wall (53) of the flow path and which is opposite to the landing area; wherein, the flow control surface (50) is further arranged such that the flow area for the first substance as it enters the smooth passageway isapproximately the same as the flow area for the first substance as it leaves the smooth passageway and such that the flow area for the first substance as it enters the first space is between 100% and 130% of the flow area for the first substance as it leaves the first space between a trailing edge (54) of the flow control surface (50) and ongoing surfaces(55) of the flow path that is within the first space; wherein the flow area for the first substance within the first space is progressively increased as the first substance progresses towards offtake slot (58) for the second substance and is then progressively decreased before it leaves the first space to combine with the first substance that is leaving the smooth passageway; wherein, a wall (57) between offtake slot (58) and the landing area (56) conveys a flowing film of the second substance that emanates from the landing area (56) directly into and through the offtake (58); and - wherein all the first substance is allowed to combine and to continue towards a first outlet at the outlet end (18) of the flow path.

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