GB2567168A

GB2567168A - Nozzle and method

Info

Publication number: GB2567168A
Application number: GB1716185.2A
Authority: GB
Inventors: Magni Simone; Soo Choi Yun; Kyoo Ko Chan
Original assignee: Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2017-10-04
Filing date: 2017-10-04
Publication date: 2019-04-10
Also published as: TW201922353A; SG11202003132PA; GB201716185D0; EP3692770B1; CN111149437B; KR20200062218A; WO2019069066A1; CN111149437A; TWI796368B; EP3692770A1

Abstract

A nozzle 50 is used to convey a plasma stream 90 from a plasma generator to a reaction chamber 70, and the nozzle has a conduit extending between an inlet arranged to receive the plasma stream, an outlet arranged to fluid couple with the reaction chamber, and an aperture to deliver water from a water dispenser 55 to the conduit for mixing with the plasma stream. In operation, the plasma-forming gas stream is introduced between a cathode 30 and an anode 40 which are electrically charged and undergo a DC arc discharge to generate the plasma stream. The plasma stream flows through a tubular conduit of the anode and exits towards the nozzle inlet. The arrangement may be used to treat an effluent gas stream 100, and the combined plasma stream and effluent gas stream travel through the nozzle towards the reaction chamber, and water is dispensed by the water dispenser for mixing. The water dispensed by the water dispenser generates hydrogen and oxygen radicals which also enter the reaction chamber where abatement of compounds within the effluent gas stream occurs. The hydrogen and oxygen radicals help improve the destruction rate efficiency of the abatement apparatus.

Description

FIELD OF THE INVENTION

The present invention relates to a nozzle for conveying a plasma stream and a method.

BACKGROUND

Thermal plasma torches 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 fluorinated or perfluorinated compounds (PFCs) and other compounds exist in the effluent gas stream pumped from the process tool. These compounds 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.

One approach to remove the PFCs and other compounds from the effluent gas stream is to use a radiant burner as described, for example, in EP1773474. However, when fuel gases normally used for abatement by combustion are undesirable or not readily available, it is also known to use a plasma torch abatement device.

Plasmas for abatement devices can be formed in a variety of ways. Microwave plasma abatement devices can be connected to the exhaust of several process chambers. Each device requires its own microwave generator, which can add considerable cost to a system. Plasma torch abatement devices are advantageous over microwave plasma abatement devices in terms of scalability and in dealing with powder (present in the effluent stream or generated by the abatement reactions). In fact, with regard to microwave plasmas, if powder is present it can modify the dielectric characteristic of the reaction tube and render ineffective the microwave injection that sustains the discharge. The plasma generated by the plasma abatement device is used to destroy or abate unwanted compounds within the effluent gas stream.

Although these apparatus exist for processing the effluent gas stream, they each have their own shortcomings. Accordingly, it is desired to provide an improved technique for processing and effluent gas stream.

SUMMARY

According to a first aspect, there is provided a nozzle for conveying a plasma stream from a plasma generator to a reaction chamber, the nozzle comprising: a conduit extending between an inlet arranged to receive the plasma stream and an outlet arranged to fluid couple with the reaction chamber, the conduit being defined by a wall having at least one aperture therein, the aperture being arranged to deliver water into the conduit for mixing with the plasma stream when transiting therethrough.

The first aspect recognises that the destruction rate efficiency when trying to remove compounds from an effluent gas stream may be sub-optimal. In particular, existing abatement apparatus employ a DC-arc plasma torch coupled with an inlet assembly, a restriction, a mixing (Venturi) cone and a reaction tube where the abatement reaction takes place. PFC abatement is mainly achieved by injecting compressed dried air (CDA) as a reagent before the Venturi cone. Here the reagent mix with PFC gases and the N2 plasma plume before entering the “hot” reaction area, which exists after the cone and is delimited by a reaction tube (which may be made by ceramic cement but can be of other materials such as metal). In the reaction area, O2 reacts with the PFC gases before the gas temperature is reduced with a N2 flow in the DeNOx section and by water sprays in the quench. As an example, two chemical reactions that can take place in the case of CF4 abatement are: 2CF4 + O2 2COF2 + 2F2 (dominant reaction) and CF4 + O2 CO2 + 2F2. Similarly, in the case of SF6 abatement SOF2, SO2F2 can be formed in larger amounts than more soluble by-products SO2, F2, HF.

-3While this “dry” abatement has its inherent benefits such as no wasted energy into converting H2O into plasma phase and very low NOx (mainly generated if N2 radicals comes in contact with water) the lack of H2 as reagent can present some weaknesses. Chiefly, by-products like COF2, SOF2 and SO2F2can be scrubbed with difficulty by fresh water and can be still present after the abatement at high concentrations and beyond acceptable levels. With regards to plasma torch scrubbers, F2 and CI2 molecules can be broken down in the reaction section but due to lack of H2 radicals they can only be dealt with further downstream in the wet quench section where sprayed water can be employed to reduce the temperature of the gas exiting from the reaction section. This is a major difference with burners where H2 radicals from CH4 allow easy conversion of CI2 I FI2 to HCII HF. In some abatement apparatus, CI2 abatement has been especially proven to be very dependent on the conditions upstream of the quench. Simple addition of H2 is proved to be effective for CF4 but flammable reagents are discouraged as “non-fuel” abatement solutions. Water vapour is instead a viable solution for SF6.

Hence, the first aspect also recognises that the presence of hydrogen concurrently with/instead of oxygen radicals can improve destruction rate efficiency of some compounds and greatly reduced the formation of noxious, hardly-soluble by-products. However, the introduction of such hydrogen radicals from a source gas like H2, CH4, C3H8 etc. can be problematic, particularly when it is desired to minimise the presence of combustible compounds outside the abatement apparatus and the cost of operation of the equipment.

Accordingly, a nozzle such as a plasma stream nozzle is provided. The nozzle may convey or transport a plasma stream or jet between a plasma generator and a reaction chamber. The nozzle may comprise a conduit. The conduit may extend between or have an inlet and an outlet. The inlet may receive the plasma stream. The outlet may fluidly couple with the reaction chamber. The conduit may have a wall which may surround or circumscribe the plasma stream as it is conveyed or passes through the nozzle between the inlet and the outlet. The

-4wall may define one or more apertures, openings or nozzles. Those apertures may deliver water into the conduit which mixes with the plasma stream being conveyed. In this way, water is introduced into the plasma stream within the nozzle, which generates both hydrogen and oxygen radicals that help improve the destruction rate efficiency of the abatement apparatus. This provides for a particularly safe and convenient way to improve the destruction rate efficiency since no combustible materials are required to be supplied to the nozzle to generate those radicals.

In one embodiment, the aperture is orientated to deliver the water radially into the conduit. Delivering the water into the plasma stream in a direction having a radial component helps it to penetrate into and mix with the plasma stream. That is to say that the water enters the conduit and/or the plasma stream in a direction with at least a radial component with respect to the conduit and/or the plasma stream.

In one embodiment, the aperture is orientated to deliver the water tangentially into the conduit. Delivering the water into the plasma stream in a direction having a tangential component helps to maintain stable flow of the plasma stream within the nozzle by introducing a rotational component, improving the mixing ofthe effluent gas with the injected water reagent. That is to say that the water enters the conduit and/or the plasma stream in a direction with at least a tangential component with respect to the conduit and/or the plasma stream.

In one embodiment, the aperture is orientated to deliver the water axially into the conduit. Delivering the water into the plasma stream in a direction having an axial component helps to maintain the stability of flow of the plasma stream through the conduit. This configuration is particularly useful when large flows of water reagent are required for the abatement. That is to say that the water enters the conduit and/or the plasma stream in a direction with at least an axial component with respect to the conduit and/or the plasma stream.

-5ln one embodiment, the nozzle comprises a plurality of the apertures. This helps to provide for a uniform distribution and/or an increased volume of water and subsequent radicals throughout the plasma stream.

In one embodiment, the plurality of the apertures are positioned circumferentially around the conduit.

In one embodiment, the plurality of the apertures are fluidly coupled with a gallery concentrically surrounding the conduit, the gallery being arranged to receive the water for delivery to the plurality of the apertures. The provision of a gallery is a convenient arrangement for delivery of water from a single source to multiple apertures.

In one embodiment, the gallery comprises an inlet for receiving the water.

In one embodiment, the nozzle is thermally conductive for heating the water. Accordingly, the nozzle itself may help pre-heat the water and may even vaporize it prior to delivery within the conduit in order to reduce the cooling effect on the plasma stream.

In one embodiment, the nozzle is arranged to be heated by direct exposure to the plasma stream.

In one embodiment, the conduit comprises a restriction operable to generate turbulent flow to mix the water with the plasma stream. Generating turbulent flow with a restriction or discontinuity in or on the wall of the conduit helps to mix the water with the plasma stream.

In one embodiment, the water comprises at least one of water droplets and water vapour.

-6ln one embodiment, the nozzle comprises an aerosol device operable to generate the water droplets.

In one embodiment, the nozzle comprises a control device operable to control delivery of water to the aerosol device.

In one embodiment, the inlet is arranged to receive the plasma stream together with an effluent stream.

In one embodiment, the nozzle comprises the plasma generator positioned upstream of the inlet.

In one embodiment, the plasma generator comprises a DC-arc, a microwave or an inductively-coupled discharge apparatus, which creates the plasma stream, plume or plasma jet.

In one embodiment, the nozzle comprises a process inlet arranged to deliver the effluent stream to the inlet.

In one embodiment, the nozzle comprises the reaction chamber positioned downstream of the outlet.

According to a second aspect, there is provided a method comprising: conveying a plasma stream from a plasma generator to a reaction chamber using a nozzle, the nozzle comprising a conduit extending between an inlet arranged to receive the plasma stream and an outlet arranged to fluid couple with the reaction chamber, the conduit being defined by a wall having at least one aperture therein; and delivering water through an aperture in a wall which defines the conduit for mixing with the plasma stream.

In one embodiment, the method comprises orientating the aperture to deliver the water radially into the conduit.

ln one embodiment, the method comprises orientating the aperture to deliver the water tangentially into the conduit.

In one embodiment, the method comprises orientating the aperture to deliver the water axially into the conduit.

In one embodiment, the method comprises providing a plurality of the apertures.

In one embodiment, the method comprises positioning the plurality of the apertures circumferentially around the conduit.

In one embodiment, the method comprises fluidly coupling the plurality of the apertures with a gallery concentrically surrounding the conduit and receiving the water using the gallery for delivery to the plurality of the apertures.

In one embodiment, the method comprises receiving the water at an inlet of the gallery.

In one embodiment, the nozzle is thermally conductive and the method comprises heating the water with the nozzle.

In one embodiment, the method comprises heating the nozzle by direct exposure to the plasma stream.

In one embodiment, the method comprises generating turbulent flow to mix the water with the plasma stream using a restriction within the conduit.

-8ln one embodiment, the method comprises generating the water droplets with an aerosol device.

In one embodiment, the method comprises controlling delivery of water to the aerosol device.

In one embodiment, the method comprises receiving the plasma stream together with an effluent stream at the inlet.

In one embodiment, the method comprises positioning the plasma generator upstream of the inlet.

In one embodiment, the method comprises delivering the effluent stream a process inlet for delivery to the inlet.

In one embodiment, the method comprises positioning the reaction chamber downstream of the outlet.

According to a third aspect, there is provided an abatement apparatus comprising the nozzle of the first aspect.

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.

-9Where 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 a plasma abatement apparatus according to one embodiment; Figures 2a to 2c illustrate nozzles according to embodiments;

Figure 3 illustrates a summarized change of state of the water reagent; and Figure 4 illustrates an aerosol device according to one embodiment.

DESCRIPTION OF THE EMBODIMENTS

Before discussing the embodiments in any more detail, first an overview will be provided. Embodiments provide a technique for the safe generation of hydrogen and/or oxygen radicals to improve the destruction rate efficiency of a plasma abatement apparatus. Water is introduced into a nozzle which provides the plasma stream to the reaction chamber in order to generate those radicals. The water may be injected or forced into the conduit of the nozzle carrying the plasma stream and/or drawn in by a Venturi effect due to a pressure difference between the water and plasma stream flowing through the conduit. The nozzle itself typically pre-heats the water prior to being delivered to the nozzle conduit which both assists in nozzle cooling and in minimizing cooling ofthe plasma stream by the water. Different arrangements for dispensing the water into the conduit are envisaged, to help with mixing of the water with the plasma stream and effluent gas stream, while retaining stability of that stream and an adequate plasma temperature profile, when required. The provision of water in the plasma stream causes hydrogen and oxygen radicals to be generated which helps improve the destruction rate efficiency of the abatement apparatus.

- 10General Arrangement - Abatement Apparatus

Figure 1 illustrates a plasma abatement apparatus, generally 10, according to one embodiment. The plasma abatement apparatus has a plasma torch 20 comprising a cathode 30 and an anode 40. The anode 40 comprises an annular structure which defines a tubular void, with the cathode 30 being coaxially aligned with an elongate axis of that tubular void.

A nozzle 50 is coaxially aligned with the plasma torch 20, located further along the elongate axis, away from the anode 40. The nozzle 50 also comprises an annular structure defining a tubular conduit extending along the elongate axis. The nozzle comprises a water dispenser 55 arranged to convey water for delivery into the tubular conduit.

The nozzle 50 is received within a concentrically-surrounding casing 60 which defines a reaction chamber 70. The casing 60 is cooled by a water jacket 80.

In operation, a plasma-forming gas stream 80 is introduced between the cathode 30 and the anode 40 which are electrically charged and undergo a DC arc discharge to generate a plasma stream 90 which flows in a direction of flow A which is aligned with the elongate axis. The plasma stream 90 flows through the tubular conduit of the anode 40 and exits towards the nozzle 50. An effluent gas stream 100, typically together with a compressed dried airstream 110, enters the tubular conduit of the nozzle 50. As the combined plasma stream 90, effluent gas stream 100 and compressed dried air stream 110 travel through the nozzle 50 towards the reaction chamber 70, water is dispensed by the water dispenser

55. The water dispensed by the water dispenser 55 generates hydrogen and oxygen radicals which also enter the reaction chamber 70 where abatement of compounds within the effluent gas stream 100 occurs.

Radial Nozzle

Figure 2a illustrates a nozzle, 50A, according to one embodiment. In this embodiment, an upstream inlet 51A has a bevelled edge which defines a conical structure into which the combined plasma stream 90, effluent gas stream 100 and compressed dried air stream 110 can be optionally received. The tubular inner wall 52A extends from the inlet 51A to an outlet 53A. Four apertures 54A are positioned circumferentially around the inner wall 52A at a position along the elongate axis. The apertures 54A, in this example, are uniformly distributed around the inner wall 52A, spaced 90 degrees apart. The apertures 54A are orientated to deliver water radially into the tubular conduit for mixing with the combined plasma stream 90, effluent gas stream 100 and compressed dried air stream 110.

Although not illustrated to improve clarity, a gallery 55A is provided which communicates with each aperture 54A in order to convey water to each aperture 54A.

In this embodiment, the nozzle 50A is thermally conductive and so pre-heats the water prior to being dispensed through the apertures 54A.

In operation, the combined plasma stream 90 and effluent gas stream 100 mix with the dispensed water and exit the outlet 53A and enter the reaction chamber 70. Compressed dried air 110 can be added upstream to this mix, depending on the species present in the effluent gas stream to abate.

Axial Nozzle

Figure 2b illustrates a nozzle 50B, according to one embodiment. The arrangement of this nozzle 50B is identical to the arrangement described above with the exception that the apertures 54B are instead orientated to deliver the water in the elongate axial direction. In this embodiment, there are 12 apertures 54B, each located circumferentially. In this embodiment, the water is dispensed downstream of a discontinuity 56B, which causes turbulence to promote mixing between the water and the combined plasma stream 90, effluent gas stream 100 and compressed dried air stream 110. This embodiment is particularly suitable for treating effluent gas streams requiring high flows of water as a reagent.

- 12Although not illustrated to improve clarity, a gallery 55B is provided which communicates with each aperture 54B in order to convey water to each aperture 54B.

Tangential Nozzle

Figure 2c illustrates a nozzle, generally 50C, according to one embodiment. The arrangement of this nozzle 50C is identical to the arrangement described above with the exception that the apertures 54C are instead orientated to deliver the water in a tangential axial direction. In this embodiment, there are four apertures 54C, each located circumferentially. This embodiment is particularly suited to enhancing the mixing of the effluent gas stream with the water as a reagent.

Although not illustrated to improve clarity, a gallery 55C is provided which communicates with each aperture 54C in order to convey water to each aperture 54C.

It will be appreciated that intermediate arrangements of apertures are also possible, which introduce water into the tubular conduit with a radial and/or tangential and/or axial component. Also, the water may be introduced at one or more different locations along the elongate axis of the tubular conduit, either with or without a discontinuity. Also, the location and number of apertures may be adjusted to suit individual requirements. Furthermore, different apertures of the plurality of apertures may be orientated in different directions.

Embodiments provide a technique to inject water as a reagent in a thermal plasma abatement system. The water is vaporized by the plasma hot temperature in the vicinity of the injection nozzles featured by the speciallydesigned mixing cone (Venturi). This technique aims at delivering the “right” amount of water and at the “most appropriate” point of the abatement reaction zone in order to minimize both NOx emissions and concurrently improve abatement efficiency. This method can tackle chemical by-products originating

- 13from PFC abatement as well as improving abatement performances of halogens such as F2 and CI2 currently achieved by plasma abatement systems. The vaporization is achieved without employing an expensive evaporator or other complex, gold plated solutions. Embodiments utilise different nozzle positions and different devices to feed the liquid water to them.

Embodiments aim to solve the by-products reductions and improve halogen DRE performances. Table 1 reports some experimental evidence for the case of SF6 by-products. SOF2, SO2F2and SO2 have a known toxicity and a tabulated concentration, considered to be of Immediate Danger to Life and Health (IDLH). The experimental data shows below-IDLH emissions of SF6 by-products (SO2F2, SOF2, SO2) if H2O is used instead of CDA.

kVA	SF6in	Reagent	pump purge	Qout	%	SF6 Out	HF	SO2F2	S0F2	SO2	NOx
Power	[slm]		Qin [slm]	[slm]	DRE	PPm	PPm	PPm	PPm	PPm	mg/min
CDA injection
10.61	0.5	CDA=2slm	150	271	94.5%	103	BDL	732	202	15	3.1.E+01
Water Injection
10.41	0.5	H2O= 1.1 g/min	150	271	96.5%	66	0.3	BDL	2	4	1.6.E+02

Table 1

Table 2 shows some experimental data in the case of CI2 abatement. If H2O is used instead of CDA, a lower plasma power can be used to treat CI2 below IDLH concentrations.

kVA	CI2 in	Reagent	pump purge	Qout	%	CI2	NOx
Power	[slm]		Qin [slm]	[slm]	DRE	PPm	mg/min
CDA injection
13.33	1.0	CDA=3slm	90	189	99.998%	<5	2.2.E+02
Water Injection
8.64	1.0	H2O= 1.2 g/min	90	179	99.930%	<5	2.2.E+02

Table 2

Also, it is advantageous to avoid the evaporator /steam generator where possible to reduce complexity and capital cost. Some embodiments therefore use the hot temperature at which the nozzle 50 is running to convert liquid water into water

- 14vapour. The primary function of the nozzle 50 is to mix the effluent gas with the hot plasma stream, jet or plume 90. If the nozzle 50 is made of corrosion resistant metal alloys (such as but not limited to stainless steel, hastelloy, monel etc.), it can be thermally-conductive. In this way, the nozzle 50 can be watercooled on its outer edge (hence preserving its gas and water seals), while it can still experience high temperatures on its inner ring, which is in contact with the hot plasma stream or plume 90. In embodiments, the steam generated around the annular chamber due to the plasma proximity is expelled by small nozzles and eventually converted into plasma radicals inside the reaction section in order to form compounds with the effluent gas which are easier to water-scrub.

Figure 3 illustrates a summarized change of state of the water reagent.

The liquid water can be fed in different ways. A needle valve can be used with a rotameter or ultrasonic flowmeter to measure the flow. Also envisaged is the use of a liquid mass flow controller (MFC) or a syringe pump. A bubbler coupled with a needle valve and a flow-measurement device is a further alternative.

Figure 4 illustrates an aerosol device (which is similar to a bubbler) according to one embodiment which comprises an immersed semi-permeable membrane 120 in a shaft 130 where some water flows and generates water droplets for delivery to the nozzles. The purge gas can be nitrogen or CDA and allows the fine control of the amount of water fed to the annular chamber. This arrangement is particular useful when CDA has to be used concurrently with H2O to abate flammables such as chemical vapour deposition (CVD) precursors. The water exerts a pressure onto the membrane and creates some droplets in a small nitrogen flow stream; not shown the needle valve that allows to control water pressure and hence the amount of water passed into the aerosol.

In embodiments, the annular chamber feeds the nozzles and which are positioned to provide the injection just after the plasma super-sonic expansion of the plasma stream, jet or plume 90. One advantage of embodiments is that H2O

- 15can immediately convert F2/CI2 radicals originating from PFCs, BCI3, S1F4 and/or SiCI4 in the effluent stream to HF/HCI rather than leaving their treatment further downstream in the wet stages.

Embodiments are particularly suited to semiconductor etch markets where PFC gases and halogens have to be abated. In this case a small amount of reagent water is required and the nozzles can be directed in the radial direction, perpendicularly to the flare. The same concept can be utilized to abate effluent gases originating in clean steps typical of CVD process. In this case large amounts of F2 are generated by NF3 used in remote plasma cleaning and have to be dealt with a plasma abatement apparatus. Finally, FPD etch processes employ larger amount of halogens/PFCs than semiconductor etch. In these cases a larger amount of reagent water may be required and this can be injected in a parallel direction to the plasma plume and into its external “tails”, avoiding excessive quenching of the plasma itself. This region is still chemically active for abatement reactions to take place. Other variations comprise the use of different devices to inject liquid as described above.

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.

- 16REFERENCE SIGNS

plasma abatement apparatus	10
plasma torch	20
cathode	30
anode	40
nozzle	50; 50A; 50B; 50C
inlet	51 A;
inner wall	52A;
outlet	53A;
aperture	54A; 54B; 54C
water dispenser/gallery	55; 55A; 55B; 55C
discontinuity	56B
casing	60
reaction chamber	70
plasma forming gas stream	80
plasma stream/jet/plume	90
effluent gas stream	100
compressed dried air stream	110
membrane	120
shaft	130
direction of flow	A

Claims

1. A nozzle for conveying a plasma stream from a plasma generator to a reaction chamber, said nozzle comprising:

a conduit extending between an inlet arranged to receive said plasma stream and an outlet arranged to fluid couple with said reaction chamber, said conduit being defined by a wall having at least one aperture therein, said aperture being arranged to deliver water into said conduit for mixing with said plasma stream when transiting therethrough.

2. The nozzle of claim 1, wherein said aperture is orientated to deliver said water radially into said conduit.

3. The nozzle of claim 1 or 2, wherein said aperture is orientated to deliver said water tangentially into said conduit.

4. The nozzle of any preceding claim, wherein said aperture is orientated to deliver said water axially into said conduit.

5. The nozzle of any preceding claim, comprising a plurality of said apertures.

6. The nozzle of claim 5, wherein said plurality of said apertures are positioned circumferentially around said conduit.

7. The nozzle of claim 5 or 6, wherein said plurality of said apertures are fluidly coupled with a gallery concentrically surrounding said conduit, said gallery being arranged to receive said water for delivery to said plurality of said apertures.

8. The nozzle of claim 7, wherein said gallery comprises an inlet for receiving said water.

9. The nozzle of any preceding claim, wherein said nozzle is thermally conductive for heating said water.

10. The nozzle of any preceding claim, wherein said conduit comprises a restriction operable to generate turbulent flow to mix said water with said plasma stream.

11. The nozzle of any preceding claim, wherein said water comprises at least one of water droplets and water vapour.

12. The nozzle of claim 11, comprising an aerosol device operable to generate said water droplets.

13. The nozzle of claim 12, comprising a control device operable to control delivery of water to said aerosol device.

14. The nozzle of any preceding claim, wherein said inlet is arranged to receive said plasma stream together with an effluent stream.

15. The nozzle of any preceding claim, comprising said plasma generator positioned upstream of said inlet.

16. The nozzle of any preceding claim, comprising a process inlet arranged to deliver said effluent stream to said inlet.

17. The nozzle of any preceding claim, comprising said reaction chamber positioned downstream of said outlet.

18. A plasma abatement apparatus comprising the nozzle as claimed in any proceeding claim.

19. A method comprising:

conveying a plasma stream from a plasma generator to a reaction chamber using a nozzle, said nozzle comprising a conduit extending between an inlet arranged to receive said plasma stream and an outlet arranged to fluid couple with said reaction chamber, said conduit being defined by a wall having at least one aperture therein; and delivering water through an aperture in a wall which defines said conduit for mixing with said plasma stream.

20. The method of claim 19, comprising orientating said aperture to deliver said water radially into said conduit.

21. The method of claim 19 or 20, comprising orientating said aperture to deliver said water tangentially into said conduit.

22. The method of any one of claims 19 to 21, comprising orientating said aperture to deliver said water axially into said conduit.

23. The method of any one of claims 19 to 22, comprising a plurality of said apertures.

24. The method of claim 23, comprising positioning said plurality of said apertures circumferentially around said conduit.

25. The method of claim 23 or 24, comprising fluidly coupling said plurality of said apertures with a gallery concentrically surrounding said conduit and receiving said water using said gallery for delivery to said plurality of said apertures.

26. The method of any one of claims 19 to 25, comprising receiving said water at an inlet of said gallery.

27. The method of any one of claims 19 to 26, wherein said nozzle is thermally conductive and said method comprising heating said water with said nozzle.

28. The method of any one of claims 19 to 27, comprising generating turbulent flow to mix said water with said plasma stream using a restriction within said conduit.

29. The method of any one of claims 19 to 28, wherein said water comprises at least one of water droplets and water vapour.

30. The method of any one of claims 19 to 29, comprising generating said water droplets with an aerosol device.

31. The method of claim 30, comprising controlling delivery of water to said aerosol device.

32. The method of any one of claims 19 to 31, comprising receiving said plasma stream together with an effluent stream at said inlet.

33. The method of any one of claims 19 to 32, comprising positioning said plasma generator upstream of said inlet.

34. The method of any one of claims 19 to 33, comprising delivering said effluent stream to a process inlet for delivery to said inlet.

35. The method of any one of claims 19 to 34, comprising positioning said reaction chamber downstream of said outlet.