WO2018015713A1

WO2018015713A1 - Inlet mixing assembly and method

Info

Publication number: WO2018015713A1
Application number: PCT/GB2017/052001
Authority: WO
Inventors: Ian David BENZEVAL; Andrew Seeley; Mark Richard O'NEILL
Original assignee: Edwards Limited
Priority date: 2016-07-18
Filing date: 2017-07-07
Publication date: 2018-01-25
Also published as: GB201612400D0; GB2552321A; TW201809549A

Abstract

An inlet mixing assembly for an abatement apparatus and a method are disclosed. The inlet mixing assembly (100) for an abatement apparatus comprises: an inlet portion (20) configured to receive an effluent stream to be treated; a throat portion (3) fluidly coupled with the inlet portion; an outlet portion (30) fluidly coupled with the throat portion; and a first secondary gas aperture (12A) and a second secondary gas aperture (13A), each positioned proximate the throat portion and configured to deliver, respectively, a first secondary gas stream and a second secondary gas stream for mixing with the effluent stream to generate a mixed gas stream, the outlet portion being configured to deliver the mixed gas stream to a treatment chamber of the abatement apparatus. In this way, the mixing of the first secondary gas stream and the second secondary gas stream with the effluent gas stream occurs in the vicinity of the throat portion, which improves the pre-mixing of the secondary gas streams with the effluent gas stream prior to delivery of the mixed gas stream to the treatment chamber of the abatement apparatus, which improves the destruction rate efficiency of the abatement apparatus.

Description

INLET MIXING ASSEMBLY AND METHOD

FIELD OF THE INVENTION

The present invention relates to an inlet assembly for an abatement apparatus and a method.

BACKGROUND

Abatement apparatus, such as radiant burners are known and are typically used for treating an effluent gas stream from a manufacturing process tool used in, for example, the semiconductor or flat panel display manufacturing industry. During such manufacturing, residual perfluorinated compounds (PFCs) and other compounds exist in the effluent gas stream pumped from the process tool. PFCs are difficult to remove from the effluent gas stream and their release into the environment is undesirable because they are known to have relatively high greenhouse activity.

Known radiant burners use combustion to remove the PFCs and other compounds from the effluent gas stream. Typically, the effluent gas stream is a nitrogen stream containing PFCs and other compounds. Secondary gases such as fuel gas and oxygen are mixed with the effluent gas stream and that gas stream mixture is conveyed into a combustion chamber that is laterally surrounded by the exit surface of a foraminous gas burner. Fuel gas and air are simultaneously supplied to the foraminous burner to affect flameless combustion at the exit surface, with the amount of air passing through the foraminous burner being sufficient to consume not only the fuel gas supplied to the burner, but also all the combustibles in the gas stream mixture injected into the combustion chamber.

The range of compounds present in the effluent gas stream and the flow characteristics of that effluent gas stream can vary from process tool to process tool, and so the range of fuel gas and air, together with other gases or fluids that need to be introduced into the radiant burner will also vary. Although techniques exist for processing the effluent gas stream, they each have their own shortcomings. Accordingly, it is desired to provide an improved technique for processing an effluent gas stream.

SUMMARY

According to a first aspect, there is provided an inlet assembly for an abatement apparatus, comprising: an inlet portion configured to receive an effluent stream to be treated; a throat portion fluidly coupled with the inlet portion; an outlet portion fluidly coupled with the throat portion; and a first secondary gas aperture and a second secondary gas aperture, each positioned proximate the throat portion and configured to deliver, respectively, a first secondary gas stream and a second secondary gas stream for mixing with the effluent stream to generate a mixed gas stream, the outlet portion being configured to deliver the mixed gas stream to a treatment chamber of the abatement apparatus.

The first aspect recognises that in order to obtain a good destruction rate efficiency (DRE) of compounds in an effluent gas stream, high temperatures and/or good mixing are required within an abatement apparatus. The first aspect also recognises that although secondary gas streams may be introduced into an effluent gas stream in order to improve destruction rate efficiency, the destruction rate efficiency may still be less than is possible. In particular, the first aspect recognises that the destruction rate efficiency may be less than is possible due to insufficient pre-mixing of the secondary gas streams with the effluent gas stream prior to introduction into the abatement apparatus. Accordingly, an inlet assembly may be provided. The inlet assembly may be an abatement apparatus inlet assembly. The inlet assembly may comprise an inlet portion or section which is configured, adapted or dimensioned to receive an effluent gas stream which is to be treated by an abatement apparatus. The inlet assembly may also comprise a throat portion, section or restriction. The throat portion may be fluidly coupled with or connected to the inlet portion. The inlet assembly may also comprise an outlet portion or section. The outlet portion may be fluidly coupled with or connected to the throat portion. The inlet assembly may also comprise a first secondary gas aperture or inlet. The inlet assembly may also comprise a second secondary gas aperture or inlet. Both the first secondary gas aperture and the second secondary gas aperture may be positioned proximate or in the vicinity of the throat portion. The first secondary gas aperture may be configured or positioned to deliver a first secondary gas stream for mixing with the effluent gas stream. The second secondary gas aperture may be configured or positioned to deliver a second secondary gas stream for mixing with the effluent gas stream. The effluent gas stream mixed with the first secondary gas stream and the second secondary gas stream may comprise a mixed gas stream. The outlet portion may be configured, adapted or dimensioned to deliver the mixed gas stream to a treatment chamber of the abatement apparatus. In this way, the mixing of the first secondary gas stream and the second secondary gas stream with the effluent gas stream occurs in the vicinity of the throat portion, which improves the pre-mixing of the secondary gas streams with the effluent gas stream prior to delivery of the mixed gas stream to the treatment chamber of the abatement apparatus, which improves the destruction rate efficiency of the abatement apparatus. In one embodiment, at least one of the first secondary gas aperture and the second secondary gas aperture are positioned within the inlet portion proximate the throat portion. Accordingly, one or more of the apertures may be located within the inlet portion, proximate, near to or adjacent to the throat portion in order to deliver one or more of the secondary gas streams for mixing with the effluent gas stream in the vicinity of the throat portion.

In one embodiment, at least one of the first secondary gas aperture and the second secondary gas aperture are positioned within the outlet portion proximate the throat portion. Accordingly, one or more of the apertures may be located within the outlet portion, proximate, near to or adjacent to the throat portion in order to deliver one or more of the secondary gas streams for mixing with the effluent gas stream in the vicinity of the throat portion. In one embodiment, at least one of the first secondary gas aperture and the second secondary gas aperture are positioned within the throat portion.

Accordingly, one or more of the secondary gas apertures may be positioned or located within the throat portion in order that one or more secondary gas streams may be mixed with the effluent gas stream in the vicinity of the throat portion.

In one embodiment, both the first secondary gas aperture and the second secondary gas aperture are positioned within the throat portion. Accordingly, both of the gas apertures may be positioned or located within the throat portion in order to mix both of the secondary gases with the effluent gas stream in the vicinity of the throat portion.

In one embodiment, at least one of the first secondary gas aperture and the second secondary gas aperture are positioned within the throat portion proximate the inlet portion. Accordingly, one or more of the secondary gas apertures may be positioned or located within the throat portion proximate, near to or adjacent to the inlet portion. This helps to ensure that at least one of the secondary gas streams are delivered to a low-pressure location in the effluent gas stream in order to facilitate the delivery of the secondary gas streams and to improve mixing.

In one embodiment, at least one of the first secondary gas aperture and the second secondary gas aperture are positioned within the throat portion proximate the outlet portion. Accordingly, one or more of the secondary gas apertures may be positioned or located within the throat portion proximate, near to or adjacent to the outlet portion. This helps to ensure that at least one of the secondary gas streams are delivered to a low-pressure location in the effluent gas stream in order to facilitate the delivery of the secondary gas streams and to improve mixing. In one embodiment, one of the first secondary gas aperture and the second secondary gas aperture are positioned within the throat portion proximate the inlet portion and another of the first secondary gas aperture and the second secondary gas aperture are positioned within the throat portion proximate the outlet portion. Accordingly, one of the secondary gas apertures may be positioned or located within the throat portion proximate, near to or adjacent to the inlet portion and another of the secondary gas apertures may be positioned or located within the throat portion proximate, near to or adjacent to the outlet portion. This helps to ensure that both secondary gas streams are delivered to a low-pressure location in the effluent gas stream in order to facilitate the delivery of the secondary gas streams and to improve mixing.

In one embodiment, both the first secondary gas aperture and the second secondary gas aperture are positioned within the throat portion proximate the inlet portion. Accordingly, both of the secondary gas apertures may be

positioned or located within the throat portion proximate, near to or adjacent to the inlet portion. This helps to ensure that at the secondary gas streams are delivered to a low-pressure location in the effluent gas stream in order to facilitate the delivery of the secondary gas streams and to improve mixing.

In one embodiment, the assembly comprises a plurality of the first secondary gas apertures and a plurality of the second secondary gas apertures. Accordingly, more than one of the gas apertures may be provided in order to improve delivery and distribution of the secondary gases and improve mixing.

In one embodiment, the plurality of the first secondary gas apertures and the plurality of the second secondary gas apertures are positioned circumferentially.

In one embodiment, the plurality of the first secondary gas apertures and the plurality of the second secondary gas apertures are circumferentially positioned alternately. Again, this helps improve the mixing of the secondary gas streams with the effluent gas stream. In one embodiment, the plurality of the first secondary gas apertures and the plurality of the second secondary gas apertures are circumferentially positioned alternately around the throat portion.

In one embodiment, the assembly comprises a first coupling configured to receive the first secondary gas stream and a first gallery fluidly coupled with the first coupling and the first secondary gas apertures. The first gallery provides a convenient structure to distribute the first secondary gas stream to each of the first secondary gas apertures.

In one embodiment, the assembly comprises a second coupling configured to receive the second secondary gas stream and a second gallery fluidly coupled with the second coupling and the second secondary gas apertures. The second gallery provides a convenient structure to distribute the second secondary gas stream to each of the second secondary gas apertures.

In one embodiment, the first secondary gas apertures and the second secondary gas apertures are orientated to convey the first secondary gas stream and the second secondary gas stream in a direction transverse to a direction of flow of the effluent gas stream. Hence, the secondary gas streams are delivered to intercept the effluent gas stream to improve mixing.

In one embodiment, the first coupling is offset from the second coupling in a direction of an elongate axis of the inlet assembly. This makes for easier mechanical coupling to the assembly.

In one embodiment, the first coupling is offset radially from the second coupling about the elongate axis of the inlet assembly. This makes for easier mechanical coupling to the assembly. In one embodiment, a cross-sectional area of the inlet portion reduces towards the throat portion. Hence, the inlet portion comprises a converging, restricting or tapering conical conduit. In one embodiment, the inlet portion tapers towards the throat portion.

In one embodiment, the inlet portion has a taper angle of 1 ^Q to 60^Q and preferably around 25^Q. In one embodiment, a cross-sectional area of the throat portion is constant.

In one embodiment, a cross-sectional area of the outlet portion increases away from the throat portion. Hence, the outlet portion comprises a diverging, increasing or tapering conical conduit.

In one embodiment, the outlet portion tapers away from the throat portion.

In one embodiment, the outlet portion has a taper angle of 1 ^Q to 60^Q and preferably around 3^Q.

In one embodiment, the inlet portion has an inlet aperture configured to receive the effluent stream and the outlet portion has an outlet aperture configured to deliver the mixed gas stream, and wherein a cross sectional area of the throat portion is smaller than both the inlet aperture and the outlet aperture.

According to a second aspect, there is provided a method, comprising: receiving an effluent stream to be treated at an inlet portion fluidly coupled with a throat portion, which is fluidly coupled with an outlet portion; and generating a mixed gas stream by delivering a first secondary gas stream with a first secondary gas aperture and a second secondary gas stream with a second secondary gas aperture, each positioned proximate the throat portion; and delivering the mixed gas stream from the outlet portion to a treatment chamber of the abatement apparatus.

In one embodiment, the method comprises positioning at least one of the first secondary gas aperture and the second secondary gas aperture within the inlet portion proximate the throat portion.

In one embodiment, the method comprises positioning at least one of the first secondary gas aperture and the second secondary gas aperture within the outlet portion proximate the throat portion.

In one embodiment, the method comprises positioning at least one of the first secondary gas aperture and the second secondary gas aperture within the throat portion.

In one embodiment, the method comprises positioning both the first secondary gas aperture and the second secondary gas aperture within the throat portion.

In one embodiment, the method comprises positioning at least one of the first secondary gas aperture and the second secondary gas aperture within the throat portion proximate the inlet portion.

In one embodiment, the method comprises positioning at least one of the first secondary gas aperture and the second secondary gas aperture within the throat portion proximate the outlet portion.

In one embodiment, the method comprises positioning one of the first secondary gas aperture and the second secondary gas aperture within the throat portion proximate the inlet portion and another of the first secondary gas aperture and the second secondary gas aperture within the throat portion proximate the outlet portion. In one embodiment, the method comprises positioning both the first secondary gas aperture and the second secondary gas aperture within the throat portion proximate the inlet portion. In one embodiment, the method comprises a plurality of the first secondary gas apertures and a plurality of the second secondary gas apertures.

In one embodiment, the method comprises positioning the plurality of the first secondary gas apertures and the plurality of the second secondary gas apertures circumferentially.

In one embodiment, the method comprises alternately positioning the plurality of the first secondary gas apertures and the plurality of the second secondary gas apertures circumferentially.

In one embodiment, the method comprises alternately positioning the plurality of the first secondary gas apertures and the plurality of the second secondary gas apertures circumferentially around the throat portion. In one embodiment, the method comprises receiving the first secondary gas stream at a first coupling and conveying the first secondary gas stream from the first coupling to the first secondary gas apertures via a first gallery.

In one embodiment, the method comprises receiving the second secondary gas stream at a second coupling and conveying the second secondary gas stream from the second coupling to the second secondary gas apertures via a second gallery.

In one embodiment, the method comprises orientating the first secondary gas apertures and the second secondary gas apertures to convey the first secondary gas stream and the second secondary gas stream in a direction transverse to a direction of flow of the effluent stream. ln one embodiment, the method comprises offsetting the first coupling from the second coupling in a direction of an elongate axis of the inlet assembly. In one embodiment, the method comprises radially offsetting the first coupling from the second coupling about the elongate axis of the inlet assembly.

In one embodiment, the method comprises reducing a cross-sectional area of the inlet portion towards the throat portion.

In one embodiment, the method comprises tapering the inlet portion towards the throat portion.

In one embodiment, the inlet portion has a taper angle of 1 ^Q to 60^Q and preferably around 25^Q.

In one embodiment, a cross-sectional area of the throat portion is constant.

In one embodiment, the method comprises increasing a cross-sectional area of the outlet portion away from the throat portion.

In one embodiment, the method comprises tapering the outlet portion away from the throat portion. In one embodiment, the outlet portion has a taper angle of 1 ^Q to 60^Q and preferably around 3^Q.

In one embodiment, the method comprises receiving the effluent stream at an inlet aperture of the inlet portion and delivering the mixed gas stream from an outlet aperture of the outlet portion and wherein a cross sectional area of the throat portion is smaller than both the inlet aperture and the outlet aperture. According to a third aspect, there is provided an inlet assembly or method substantially as hereinbefore described with reference to the accompanying drawings. Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims. Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

Figure 1 illustrates an inlet assembly according to one embodiment;

Figure 2 is an end-on view of the inlet assembly;

Figure 3 is a sectional view through the plane shown in Figure 2;

Figure 4 is another sectional view on the plane shown in Figure 2; and

Figure 5 illustrates the geometry and simulated pressure levels within the inlet assembly.

DESCRIPTION OF THE EMBODIMENTS

Overview

Before discussing the embodiments in any more detail, first an overview will be provided. Embodiments provide an inlet assembly for mixing two or more secondary gases with an effluent gas stream. Typically, the secondary gases need to be well-mixed with each other and with the effluent stream to improve the abatement performance of an abatement apparatus. Also, typically, it is desirable to prevent the secondary gases (which may comprise an oxidant and a fuel) from being pre-mixed in order to reduce the risk of combustion prior to delivery to the abatement apparatus.

The inlet assembly has a throat portion positioned between an inlet portion and an outlet portion. Secondary gas apertures are provided proximate or near to the throat portion and deliver the secondary gas streams to mix with the effluent stream in the region of the throat portion. This provides for effective mixing of the secondary gas streams with each other and with the effluent gas stream.

Reductions in pressure typically occur at the transitions between the inlet portion and the throat portion and between the outlet portion and the throat portion.

Delivering the secondary gas streams to either or both of those low-pressure regions helps to facilitate the delivery of the secondary gases for mixing with the effluent gas stream. The mixed gas stream is then delivered to the abatement apparatus. This arrangement leads to increases in the destruction rate efficiency of the abatement apparatus due to improved mixing of the secondary gas streams with the effluent gas stream.

Inlet Assembly - General Arrangement

Figure 1 is a view of an inlet assembly, generally 1 00, according to one embodiment. Figure 2 is an end-on view of the inlet assembly 1 00. Figure 3 is a sectional view through the plane shown in Figure 2. Figure 4 is a sectional view on the plane shown in Figure 2.

As can be seen in Figure 1 , but best illustrated in Figure 4, the inlet assembly 1 00 comprises an elongate, generally-cylindrical tube 1 . The tube 1 extends from an inlet aperture 20 to an outlet aperture 30. The inlet aperture 20 receives an effluent gas stream to be treated from upstream processing equipment (not shown). The outlet aperture 30 delivers the effluent gas stream mixed with secondary gases to an abatement apparatus (not shown). Accordingly, the effluent gas stream flows in the direction shown by the arrows, from the inlet aperture 20 to the outlet aperture 30. Inner Structure

The tube 1 defines three main regions: an inlet section 2, a throat section 3 and an outlet section 4. The inlet section 2 converges from the inlet aperture 20 to the throat section 3. That is to say that the generally-circular cross-sectional area of the inlet section 2 reduces from the inlet aperture 20 to the throat section 3 in the direction of flow of the effluent gas stream. In this embodiment, the generally- circular cross-sectional area of the throat section 3 is constant in the direction of flow of the effluent gas stream from the inlet section 2 to the outlet section 4. The outlet section 4 diverges from the throat section 3 to the outlet aperture 30. That is to say that the generally-circular cross-sectional area of the outlet section 4 increases in the direction of flow of the effluent gas stream from the throat section 3 to the outlet aperture 30. In other words: the inlet section 2 is a conical, converging section with a fixed taper angle and extends from the inlet aperture 20 to the throat section 3; the throat section 3 is a restricting cylindrical section which extends from the inlet section 2 to the outlet section 4; and the outlet section 4 is a conical, diverging section with a fixed taper angle and extends from the throat section 3 to the outlet aperture 30.

As can best be seen in Figures 3 and 4, apertures 12A and 13A extend

circumferentially around the surface of the throat section 3 to deliver the secondary gas streams in the vicinity of the interface between the inlet section 2 and the throat section 3. In order to facilitate uniform delivery and mixing of the secondary gas streams, the secondary gas apertures 12A, 13A extend

circumferentially around the inner surface of the throat section 3.

Secondary Gas Couplings

To enable a first secondary gas stream to be delivered, a first secondary coupling 12 is provided which couples with a source of the first secondary gas stream and extends to a first gallery 6, which feed first conduits 7, which terminate at the secondary gas apertures 12A. In this embodiment, the first conduits 7 extend radially, orthogonal to the direction of flow of the effluent gas stream. However, it will be appreciated that the first conduits 7 may extend radially at an angle other than orthogonal to the direction of flow of the effluent stream, if required.

To enable a second secondary gas stream to be delivered, a second secondary coupling 1 3 is provided which couples with a source of the second secondary gas stream and extends to a second gallery 8, which feed second conduits 9, which terminate at the secondary gas apertures 13A. In this embodiment, the second conduits 9 extend radially, angled to the direction of flow of the effluent gas stream. However, it will be appreciated that the second conduits 9 may extend radially orthogonal to the direction of flow of the effluent stream, if required.

As can be seen in Figures 1 to 4, the first gallery 6 and second gallery 8 are formed by recesses turned onto the surface of the conduit 1 and enclosed by annular sleeves 1 0 and 1 1 , respectively.

Longitudinally offsetting the first gallery 6 and the second gallery 8 prevents the secondary gases from pre-mixing prior to delivery into the effluent gas stream and facilitates a simple mechanical coupling arrangement for the first secondary gas coupling 1 2 and the second secondary gas coupling 1 3, which are both longitudinally and rotationally offset from each other.

Operation

In operation, an effluent gas stream from a processing tool is provided via the inlet aperture 20. The effluent gas stream accelerates as it travels through the converging inlet section 2 and passes into the throat section 3.

Figure 5 is a computational fluid dynamics model showing the change in pressure of the effluent gas stream as it flows through the conduit 1 based on the geometry shown. As can be seen, regions 3A, 3B of low pressure occur within the effluent gas stream as it flows through the throat section 3. Hence, as the effluent gas stream enters the throat section 3, the effluent gas stream pressure reduces, which helps draw the secondary gas streams from the secondary gas apertures 1 2A, 1 3A. Mixing of the effluent gas stream with the secondary gas streams occurs as the mixed gas stream travels through the throat section 3 and as it expands along the diverging outlet section 4. The mixed gas stream then exits through the outlet aperture 30 and is delivered to the abatement apparatus. It will be appreciated that although in this embodiment the secondary gases are delivered to the region 3A, they could equally have either or both been delivered to the region 3B.

Modelling

As mentioned above, to obtain good DRE of CF4, high temperatures are required. Existing inlet assemblies typically consists of (per inlet assembly (nozzle)):

· 50 SLM nitrogen with the process gases (effluent gas stream)

approximately 1 %;

^• 1 8-20 SLM oxygen via a side inlet upstream of the treatment chamber;

^• 9 SLM methane via a lance in the middle of the inlet assembly, approximately 5 cm before the tip;

· 2.5 SLM methane in an annulus around the inlet assembly;

^• 25 SLM CDA in an annulus around the methane annulus (this provides the additional oxygen to get into a slightly lean mix).

Initial modelling of that existing assembly has shown that these annuli do not provide a perfect mixture of fuel, oxidant and process prior to ignition. Therefore, the inlet assembly of embodiments is arranged to allow this quantity of methane and oxygen to be thoroughly pre-mixed into a process stream prior to the nozzle that feeds into the burner. 2D Simulations to Identify Maximum Pressure Drop

Initially some 2D axisymmetric simulations were performed, varying the convergent and divergent angles to identify the best combination, with the best being that which produces the greatest at-wall pressure drop. The angles were varied from 3 ° to 25 ° (from the axis of the tube).

The maximum pressure drops recorded on the surface of the throat at varying convergent and divergent wall angles are as follows: ponvergent Angle

Divergent

le

The data shows the following overall trends: as the divergent angle decreases, the pressure drop increases. Conversely, as the convergent angle increases, the pressure drop increases. Put together, to obtain a high at-wall pressure drop in the throat, a highly angled inlet and a significantly more gentle outlet is required. In all instances the peak pressure drop was observed in the throat immediately after the convergence, thus the side inlets should be placed as far towards the inlet end of the throat as possible.

Accordingly, embodiments provide a device for introducing both a fuel and an oxidant into a process stream. The device is a mixer that allows the introduction of two different gases into a main process stream in the throat of the device. Typically these will be a fuel and an oxidant, thus allowing a fully pre-mixed gas to be introduced into a reaction chamber.

Current ways of introducing additional fuel into a process stream via co-axial nozzles and lances do not result in good mixing. Ideally, the fuel and oxidant should be thoroughly mixed with the process stream prior to ignition to achieve higher local temperatures to improve breakdown of polyfluorocarbons. This arrangement mixes two separate gases into an existing third stream

simultaneously. In one embodiment, the device comprises a converging inlet section with an angle of 25° to the long axis, feeding into a cylindrical throat of 20.0 mm length and 14.0 mm diameter. This then feeds a divergent conical section with an angle of 4° to the long axis. Within the throat, on a radial plane 3.0 mm from the entrance of the throat, are centred eight holes equally spaced around the circumference. Alternate holes are fed by two different annular galleries. Each gallery therefore has four holes, at 90° intervals, between it and the throat. The two sets of holes are 45 " separate from each other, resulting in the

aforementioned eight holes. The first gallery is in the same plane as the holes into the throat, with the four holes between it and the throat being radial. The gallery is 7.75 mm from the throat and has a rectangular cross-section of 10.0 mm (axial direction) x 2.5 mm (radial direction). These four holes are each 3.0 mm in diameter. The outer surface of this gallery is closed by a metal sleeve, which is welded in place, and fed by an inlet pipe. The second gallery is the same radial distance from the throat, but is positioned on the convergent side of the first gallery. The four holes between it and the throat are therefore at a 40° angle to the long axis and are thus approximately 1 1 mm long. The cross-section of the gallery is similar to the first gallery, but has a chamfered upstream edge to allow the four holes to be drilled. These four holes are each 3.0 mm in diameter. The outer surface of this gallery is formed by a second metal sleeve and is fed by a second inlet pipe. The bulk gas is fed into the device via the converging inlet and exits via the diverging section. Secondary gases are simultaneously fed into the throat via the feed pipes. The effect of the divergent section after the introduction of these two additional gases is to ensure good mixing. Improved mixing of the oxidant and fuel into the process stream has the potential to improve the DRE and reduce fuel consumption. Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

REFERENCE SIGNS tube 1 inlet section 2 throat section 3 outlet section 4

1 st gallery 6

1 st conduits 7

2nd gallery 8

2nd conduits 9

1 st annular sleeve 10

2nd annular sleeve 1 1

1 st secondary gas coupling 12

2nd secondary gas coupling 13 secondary gas aperture 12A, 13A inlet aperture 20 outlet aperture 30 inlet assembly 100

Claims

1 . An inlet assembly for an abatement apparatus, comprising: an inlet portion configured to receive an effluent stream to be treated; a throat portion fluidly coupled with said inlet portion;

an outlet portion fluidly coupled with said throat portion; and

a first secondary gas aperture and a second secondary gas aperture, each positioned proximate said throat portion and configured to deliver, respectively, a first secondary gas stream and a second secondary gas stream for mixing with said effluent stream to generate a mixed gas stream, said outlet portion being configured to deliver said mixed gas stream to a treatment chamber of said abatement apparatus.

2. The inlet assembly of claim 1 , wherein at least one of said first secondary gas aperture and said second secondary gas aperture are positioned within said inlet portion proximate said throat portion.

3. The inlet assembly of claim 1 or 2, wherein at least one of said first

secondary gas aperture and said second secondary gas aperture are positioned within said outlet portion proximate said throat portion.

4. The inlet assembly of any preceding claim, wherein at least one of said first secondary gas aperture and said second secondary gas aperture are positioned within said throat portion.

5. The inlet assembly of any preceding claim, wherein both said first

secondary gas aperture and said second secondary gas aperture are positioned within said throat portion.

6. The inlet assembly of any preceding claim, wherein at least one of said first secondary gas aperture and said second secondary gas aperture are positioned within said throat portion proximate said inlet portion.

7. The inlet assembly of any preceding claim, wherein at least one of said first secondary gas aperture and said second secondary gas aperture are positioned within said throat portion proximate said outlet portion.

The inlet assembly of any preceding claim, wherein one of said first secondary gas aperture and said second secondary gas aperture are positioned within said throat portion proximate said inlet portion and another of said first secondary gas aperture and said second secondary gas aperture are positioned within said throat portion proximate said outlet portion.

The inlet assembly of any preceding claim, wherein both said first secondary gas aperture and said second secondary gas aperture are positioned within said throat portion proximate said inlet portion.

The inlet assembly of any preceding claim, comprising a plurality of said first secondary gas apertures and a plurality of said second secondary gas apertures.

1 1 . The inlet assembly of claim 10, wherein said plurality of said first

secondary gas apertures and said plurality of said second secondary gas apertures are circumferentially positioned.

1 2. The inlet assembly of claim 10 or 1 1 , wherein said plurality of said first secondary gas apertures and said plurality of said second secondary gas apertures are circumferentially positioned alternately.

The inlet assembly of any one of claims 1 0 to 1 2, wherein said plurality of said first secondary gas apertures and said plurality of said second secondary gas apertures are circumferentially positioned alternately around said throat portion.

The inlet assembly of any preceding claim, comprising a first coupling configured to receive said first secondary gas stream and a first gallery fluidly coupled with said first coupling and said first secondary gas apertures.

The inlet assembly of any preceding claim, comprising a second coupling configured to receive said second secondary gas stream and a second gallery fluidly coupled with said second coupling and said second secondary gas apertures.

1 6. The inlet assembly of any preceding claim, wherein said first secondary gas apertures and said second secondary gas apertures are orientated to convey said first secondary gas stream and said second secondary gas stream in a direction transverse to a direction of flow of said effluent stream.

1 7. The inlet assembly of any one of claims 14 to 1 6, wherein said first

coupling is offset from said second coupling in a direction of an elongate axis of said inlet assembly.

18. The inlet assembly of any one of claims 15 to 17, wherein said first coupling is offset radially from said second coupling about said elongate axis of said inlet assembly.

19. The inlet assembly of any preceding claim, wherein a cross-sectional area of said inlet portion reduces towards said throat portion.

20. The inlet assembly of any preceding claim, wherein said inlet portion

tapers towards said throat portion.

21 . The inlet assembly of any preceding claim, wherein said inlet portion has a taper angle of 1 ^Q to 60^Q and preferably around 25^Q.

22. The inlet assembly of any preceding claim, wherein a cross-sectional area of said throat portion is constant.

23. The inlet assembly of any preceding claim, wherein a cross-sectional area of said outlet portion increases away from said throat portion.

24. The inlet assembly of any preceding claim, wherein said outlet portion tapers away from said throat portion.

25. The inlet assembly of any preceding claim, wherein said outlet portion has a taper angle of 1 ^Q to 60^Q and preferably around 3^Q.

26. The inlet assembly of any preceding claim, wherein said inlet portion has an inlet aperture configured to receive said effluent stream and said outlet portion has an outlet aperture configured to deliver said mixed gas stream, and wherein a cross sectional area of said throat portion is smaller than both said inlet aperture and said outlet aperture.

27. A method, comprising: receiving an effluent stream to be treated at an inlet portion fluidly coupled with a throat portion, which is fluidly coupled with an outlet portion;

generating a mixed gas stream by delivering a first secondary gas stream with a first secondary gas aperture and a second secondary gas stream with a second secondary gas aperture, each positioned proximate said throat portion; and

delivering said mixed gas stream from said outlet portion to a treatment chamber of said abatement apparatus.

28. An inlet assembly or method substantially as hereinbefore described with reference to the accompanying drawings.