Abstract:
A radiant burner and method are disclosed. The radiant burner is for treating an effluent gas stream from a manufacturing process tool and comprises: a combustion chamber having a porous sleeve through which combustion materials pass for combustion proximate to a combustion surface of the porous sleeve; at least one effluent nozzle for ejecting the effluent gas stream into the combustion chamber; and a perforated liner proximate to the combustion surface. Providing a perforated liner controls the combustion materials passing into the combustion chamber to treat the effluent gas stream and also provides a surface onto which residual combustion deposits may be received. Accordingly, the liner can both improve the efficiency of the treatment of the effluent gas stream and can act as a sacrificial surface which may be replaced or cleaned either in accordance with a maintenance regime or when the performance of the radiant burner reduces.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a Section 371 National Stage Application of International Application No. PCT/GB2013/051907, filed Jul. 17, 2013, which is incorporated by reference in its entirety and published as WO 2014/016566 A2 on Jan. 30, 2014 and which claims priority of British Application No. 1213306.2, filed Jul. 26, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a radiant burner and method. 
       BACKGROUND 
       [0003]    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 and their release into the environment is undesirable because they are known to have relatively high greenhouse activity. 
         [0004]    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. A fuel gas is 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. 
         [0005]    As the surface areas of the semiconductors being produced increases, the flow rate of the effluent gas also increases. 
         [0006]    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. 
         [0007]    The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
       SUMMARY 
       [0008]    According to a first aspect, there is provided a radiant burner for treating an effluent gas stream from a manufacturing process tool, the radiant burner comprising: a combustion chamber having a porous sleeve through which combustion materials pass for combustion proximate to a combustion surface of the porous sleeve; at least one effluent nozzle for ejecting the effluent gas stream into the combustion chamber; and a perforated liner proximate to the combustion surface. 
         [0009]    The first aspect recognizes that a problem with the increasing flow rates is that greater quantities of effluent gas need to be processed. One approach would be to increase the size of the radiant burner. However, the first aspect recognizes that a problem with this approach is that the combustion mechanisms within the radiant burner are complex and simply increasing the size of the radiant burner to match the increased flow rate of the effluent gas can lead to reduced performance of the radiant burner. Also, even if it were possible to produce a larger radiant burner with adequate performance, it is not straightforward to integrate such a larger radiant burner with existing processing equipment at the manufacturing site. Another approach would be to add further radiant burners to increase the processing capacity. However, the first aspect also recognises that a problem with this approach is that it is not straightforward to integrate such further radiant burners with existing processing equipment at the manufacturing site. The first aspect further recognizes that whilst it is possible to increase the flow rate of the effluent gas through a radiant burner, this can lead to increased combustion residues or deposits on the radiant burner caused by the non-PFC compounds, which significantly impair its performance over time. 
         [0010]    Accordingly, a gas abatement apparatus or radiant burner is provided. The radiant burner may treat an effluent gas stream from a manufacturing process tool. The radiant burner may comprise a combustion chamber. The combustion chamber may have a porous or permeable sleeve through which combustion materials pass. The combustion materials may combust proximate to, near to or adjacent a combustion surface of the porous sleeve. One or more effluent nozzles may be provided which eject the effluent gas stream into the combustion chamber. A perforated, porous or punched liner may be provided proximate to, near to or adjacent the combustion surface. Providing a perforated liner controls the combustion materials passing into the combustion chamber to treat the effluent gas stream and also provides a surface onto which residual combustion deposits may be received. Accordingly, the liner can both improve the efficiency of the treatment of the effluent gas stream and can act as a sacrificial surface which may be replaced or cleaned either in accordance with a maintenance regime or when the performance of the radiant burner reduces. Such replacement or cleaning of the liner saves having to replace the porous sleeve or other components of the combustion chamber which cannot readily be removed or cleaned. This enables the radiant burner to operate at higher flow rates and avoids needing to increase the size of the radiant burner or needing to add further radiant burners. 
         [0011]    In one embodiment, the perforated liner is accommodated within the combustion chamber. Accordingly, the liner may be located within the combustion chamber itself to receive the combustion residues and protect other components of the combustion chamber. 
         [0012]    In one embodiment, the combustion materials combust in a combustion zone proximate to the combustion surface of the porous sleeve to produce combustion products and the perforated liner is located adjacent the combustion zone. Accordingly, the liner may be located adjacent, near or proximate to the combustion zone where the combustion products are generated. The exact position of the liner may vary depending on the characteristics of the combustion zone. In embodiments, the combustion products comprise, for example, oxygen. 
         [0013]    In one embodiment, the perforated liner extends at least partially along an axial length of the combustion chamber. Accordingly, the liner may extend along the axial length of all or a part of the combustion chamber. 
         [0014]    In one embodiment, the perforated liner is perforated with a plurality of holes. Providing holes or apertures enables the combustion products to pass from the combustion zone into the combustion chamber to mix and treat the effluent gas stream. It will be appreciated that the exact placement of the holes or apertures will affect or control the flow of the combustion products into the combustion chamber. 
         [0015]    In one embodiment, the perforated liner comprises an expandable mesh-like structure. Providing an expandable structure provides both perforations for the products to pass from the combustion zone into the combustion chamber whilst enabling the liner to flex to enable deposits to be removed. 
         [0016]    In one embodiment, the radiant burner comprises an actuator operable to retain the expandable mesh-like structure in a retained position within the combustion chamber and to displace at least one end of the expandable mesh-like structure to an expanded position. This enables the structure to be held in a desired position within the combustion chamber whilst expanding the structure causes deposits on the structure to be removed. 
         [0017]    In one embodiment, the expandable mesh-like structure has a first axial length when in the retained position and second axial length when in the expanded position, wherein the second axial length is greater than the first axial length. Accordingly, a simple longitudinal extension of the structure causes flexing of the perforations and dislodges deposits. 
         [0018]    In one embodiment, the expandable mesh-like structure has an axial length matching that of the combustion chamber when in the retained position and greater than that of the combustion chamber when in the expanded position. It will be appreciated that many embodiments include a water curtain structure adjacent the outlet of the combustion chamber into which the structure may be extended. 
         [0019]    In one embodiment, the expandable mesh-like structure comprises a coil spring having spacers arranged to space apart adjacent turns when in the retained position. It will be appreciated that other structures are possible such as a honeycomb arrangement or woven sock, but providing a coil spring arrangement is particularly beneficial for providing a self-supporting structure which maintains its outer dimensions during axial expansion. 
         [0020]    In one embodiment, the coil spring is formed from one of a cylindrical and a planar substrate. 
         [0021]    In one embodiment, the spacers comprise at least one of projections from a surface of the coil spring; an annular ring, a ferrule and a wound coil surrounding a surface of the coil spring; and a pleated coil spring having adjacent turns interspaced between adjacent turns of the coil spring. The provision of these spacers controls the spacing between adjacent turns of the spring when in the retained position. 
         [0022]    In one embodiment, dimensions and locations of the coil spring and spacers are selected to provide a selected hole density of the perforated liner. By controlling the size of the coil spring and of the spacers, and by controlling the location of the spacers on the coil spring, the size of the holes or perforations can be controlled when in the retained position. 
         [0023]    In one embodiment, a density of the holes of the perforated liner changes along the axial length. Accordingly, the density, concentration or quantity per unit surface area of the perforations, or the ratio of aperture surface area to non-aperture surface area of the liner may vary along the axial length of the liner. This variation in the size and density of holes or apertures in the liner helps to vary the rate of flow, concentration or amount of combustion products within different parts of the combustion chamber. Varying the flow rate, concentration or amounts of combustion products within the combustion chamber can help to improve the efficiency of the effluent treatment process by providing the right amounts of combustion products at the right locations. 
         [0024]    In one embodiment, the combustion chamber has a nozzle end proximate to the at least one effluent nozzle and an exhaust end axially distal from the at least one effluent nozzle, the density of the holes of the perforated liner decreases towards the exhaust end. Accordingly, the density or concentration of apertures in the liner may decrease along the axial length of the liner. That is to say that the amount of aperture surface area of the liner is higher towards the effluent nozzles than it is the exhaust end. This helps to increase the amount of combustion products near where the effluent gas enters the combustion chamber and decreases the amount of combustion products near the exhaust end where the quantity of untreated effluent gas is reduced. 
         [0025]    In one embodiment, the combustion chamber has an exhaust zone extending axially proximate to the exhaust end, the density of the holes of the perforated liner increases towards the exhaust zone. Accordingly, a region of the liner near the exhaust end may have an increased or high concentration of aperture surface area in order to increase the concentration of combustion products near the exhaust end where the treatment of the effluent gas is least effective. 
         [0026]    In one embodiment, the combustion chamber has a nozzle zone extending axially proximate to the nozzle end, the density of the holes of the perforated liner decreases towards the nozzle zone. Accordingly, a region of the liner near the nozzle end may have a decreased or low concentration of aperture surface area in order to decrease the concentration of combustion products in a region where combustion residues or deposits cause particular performance degradation or where cleaning such residues or deposits is difficult. 
         [0027]    In one embodiment, the perforated liner is unperforated proximate to the nozzle zone. 
         [0028]    In one embodiment, the radiant burner comprises a plurality of the nozzles positioned circumferentially around the combustion chamber and the density of the holes of the perforated liner increases circumferentially proximate to the plurality of the nozzles. Accordingly, the amount of aperture surface area of the liner may increase near the nozzles in order to deliver more combustion products in the vicinity of the effluent gas stream being ejected from the nozzles. This helps to ensure that the combustion products are concentrated in the regions where they are most needed to react with the effluent gas stream. 
         [0029]    In one embodiment, the radiant burner comprises at least one spray nozzle for ejection of a cleaning fluid onto a cleaning zone of the perforated liner, the density of the holes of the perforated liner decreases towards the cleaning zone. Accordingly, cleaning fluids may be sprayed from the nozzle onto the liner. The density of holes in the region where the cleaning fluid impacts the liner may be decreased or even no holes are provided at all in order to prevent the cleaning fluid from passing through the liner and contacting the porous sleeve or other potentially damageable components of the radiant burner. 
         [0030]    In one embodiment, the perforated liner comprises one of a mesh, a wire screen, a perforated sheet and a louvered sheet. 
         [0031]    In one embodiment, the louvers of the louvered sheet are orientated to direct the combustion products within the combustion chamber. It will be appreciated that the louvers provide both a mechanism for directing the flow of the combustion products to specified regions within the combustion chamber, whilst also providing an effective bather to prevent cleaning fluid from passing through the liner. 
         [0032]    In one embodiment, louvers of the louvered sheet are orientated to receive on a major surface the cleaning fluid from the at least one spray nozzle. Hence, it will be appreciated that the use of louvers enables perforations to be provided within the cleaning zone. It will be appreciated that that a louver is typically a long, thin, planar member; the major surface would be one of the large (typically ‘upper’ or ‘lower’) surfaces of the louver as opposed to a minor surface which would in effect be its edges. 
         [0033]    In one embodiment, the perforated liner is axially displaceable between an accommodated position where the perforated liner is accommodated within the combustion chamber and an unaccommodated position where the perforated liner protrudes from the combustion chamber. Accordingly, the liner may be movable within the combustion chamber to protrude from the combustion chamber to facilitate cleaning. It will be appreciated that such displacement may be provided in addition to or instead of providing the spray nozzle. 
         [0034]    In one embodiment, the perforated liner fully extends from the combustion chamber in the unaccommodated position. Fully removing of the liner from the combustion chamber further helps to aid its cleaning or replacement. 
         [0035]    In one embodiment, the radiant burner comprises a cleaning tank for holding a cleaning fluid and wherein the perforated liner extends into the cleaning tank in the unaccommodated position Immersing the liner within the cleaning tank helps to remove the combustion residues and clean the liner. 
         [0036]    In one embodiment, the radiant burner comprises means for agitating the perforated liner in the cleaning tank. It will be appreciated that agitating further helps to clean the liner. 
         [0037]    In one embodiment, the perforated liner comprises an aperture for receiving an associated one of the effluent nozzles, displacement of the perforated liner causing movement of the aperture with respect to the associated one of the effluent nozzles to dislodge any effluent treatment deposit located on an outer surface thereof. Accordingly, the act of displacing the liner may facilitate the removal of combustion deposits or residues that may have been deposited on the nozzles, which may in time otherwise reduce the performance of these nozzles. 
         [0038]    In one embodiment, the perforated liner is metallic. Providing a metallic liner enables increased mechanical and thermal shock stress to be applied when performing the cleaning compared to that which would be possible when trying to clean the porous sleeve or other components of the combustion chamber. 
         [0039]    In one embodiment, the perforated liner comprises nickel. 
         [0040]    In one embodiment, the combustion zone and the perforated liner are cylindrical. 
         [0041]    According to a second aspect, there is provided a method of treating an effluent gas stream from a manufacturing process tool, the method comprising the steps of: passing combustion materials through a porous sleeve of a combustion chamber for combustion proximate to a combustion surface of the porous sleeve; ejecting the effluent gas stream from at least one effluent nozzle into the combustion chamber; and providing a perforated liner proximate to the combustion surface. 
         [0042]    In one embodiment, the perforated liner is accommodated within the combustion chamber. 
         [0043]    In one embodiment, the combustion materials combust in a combustion zone proximate to the combustion surface of the porous sleeve to produce combustion products and the perforated liner is located adjacent the combustion zone. 
         [0044]    In one embodiment, the perforated liner extends at least partially along an axial length of the combustion chamber. 
         [0045]    In one embodiment, the perforated liner is perforated with a plurality of holes. 
         [0046]    In one embodiment, the perforated liner comprises an expandable mesh-like structure. 
         [0047]    In one embodiment, the method comprises retaining the expandable mesh-like structure in a retained position within the combustion chamber and displacing at least one end of the expandable mesh-like structure to an expanded position. 
         [0048]    In one embodiment, the expandable mesh-like structure has a first axial length when in the retained position and second axial length when in the expanded position, wherein the second axial length is greater than the first axial length. 
         [0049]    In one embodiment, the expandable mesh-like structure has an axial length matching that of the combustion chamber when in the retained position and greater than that of the combustion chamber when in the expanded position. 
         [0050]    In one embodiment, the expandable mesh-like structure comprises a coil spring having spacers arranged to space apart adjacent turns when in the retained position. 
         [0051]    In one embodiment, the coil spring is formed from one of a cylindrical and a planar substrate. 
         [0052]    In one embodiment, the spacers comprise at least one of projections from a surface of the coil spring; an annular ring, a ferrule and a wound coil surrounding a surface of the coil spring; and a pleated coil spring having adjacent turns interspaced between adjacent turns of the coil spring. 
         [0053]    In one embodiment, the method comprises selecting dimensions and locations of the coil spring and spacers to provide a selected hole density of the perforated liner. 
         [0054]    In one embodiment, a density of the holes of the perforated liner changes along the axial length. 
         [0055]    In one embodiment, the combustion chamber has a nozzle end proximate to the at least one effluent nozzle and an exhaust end axially distal from the at least one effluent nozzle, the density of the holes of the perforated liner decreases towards the exhaust end. 
         [0056]    In one embodiment, the combustion chamber has an exhaust zone extending axially proximate to the exhaust end, the density of the holes of the perforated liner increases towards the exhaust zone. 
         [0057]    In one embodiment, the combustion chamber has a nozzle zone extending axially proximate to the nozzle end, the density of the holes of the perforated liner decreases towards the nozzle zone. 
         [0058]    In one embodiment, the perforated liner is unperforated proximate to the nozzle zone. 
         [0059]    In one embodiment, the step of ejecting comprises ejecting from a plurality of the nozzles positioned circumferentially around the combustion chamber and wherein the density of the holes of the perforated liner increases circumferentially proximate to the plurality of the nozzles. 
         [0060]    In one embodiment, the method comprises the step of ejecting a cleaning fluid from at least one spray nozzle for onto a cleaning zone of the perforated liner and wherein the density of the holes of the perforated liner decreases towards the cleaning zone. 
         [0061]    In one embodiment, the perforated liner comprises one of a mesh, a wire screen, a perforated sheet and a louvered sheet. 
         [0062]    In one embodiment, the louvers of the louvered sheet are orientated to direct the combustion products within the combustion chamber. 
         [0063]    In one embodiment, the louvers of the louvered sheet are orientated to receive on a major surface the cleaning fluid from the at least one spray nozzle. 
         [0064]    In one embodiment, the method comprises the step of axially displacing the perforated liner between an accommodated position where the perforated liner is accommodated within the combustion chamber and an unaccommodated position where the perforated liner protrudes from the combustion chamber. 
         [0065]    In one embodiment, the perforated liner fully extends from the combustion chamber in the unaccommodated position. 
         [0066]    In one embodiment, the step of axially extending comprises extending the perforated liner into a cleaning tank holding a cleaning fluid. 
         [0067]    In one embodiment, the method comprises the step of agitating the perforated liner in the cleaning tank. 
         [0068]    In one embodiment, the perforated liner comprises an aperture for receiving an associated one of the effluent nozzles and the method comprises the step of displacing the perforated liner to cause movement of the aperture with respect to the associated one of the effluent nozzles to dislodge any effluent treatment deposit located on an outer surface thereof. 
         [0069]    In one embodiment, the perforated liner is metallic. 
         [0070]    In one embodiment, the perforated liner comprises nickel. 
         [0071]    In one embodiment, the combustion chamber and the perforated liner are cylindrical. 
         [0072]    According to a third aspect, there is provided a perforated liner for a radiant burner for treating an effluent gas stream from a manufacturing process tool, the radiant burner comprising a combustion chamber having a porous sleeve through which combustion materials pass for combustion proximate to a combustion surface of the porous sleeve; at least one effluent nozzle for ejecting the effluent gas stream into the combustion chamber, the perforated liner being shaped and configured for placement proximate to the combustion surface. 
         [0073]    In one embodiment, the perforated liner is shaped and configured for accommodation within the combustion chamber. 
         [0074]    In one embodiment, the combustion materials combust in a combustion zone proximate to the combustion surface of the porous sleeve to produce combustion products and the perforated liner is shaped and configured for location adjacent the combustion zone. 
         [0075]    In one embodiment, the perforated liner is dimensioned to extend at least partially along an axial length of the combustion chamber. 
         [0076]    In one embodiment, the perforated liner is perforated with a plurality of holes. 
         [0077]    In one embodiment, the perforated liner comprises an expandable mesh-like structure. 
         [0078]    In one embodiment, the expandable mesh-like structure has a first axial length when in a retained position and second axial length when in an expanded position, wherein the second axial length is greater than the first axial length. 
         [0079]    In one embodiment, the expandable mesh-like structure has an axial length matching that of the combustion chamber when in the retained position and greater than that of the combustion chamber when in the expanded position. 
         [0080]    In one embodiment, the expandable mesh-like structure comprises a coil spring having spacers arranged to space apart adjacent turns when in the retained position. 
         [0081]    In one embodiment, the coil spring is formed from one of a cylindrical and a planar substrate. 
         [0082]    In one embodiment, the spacers comprise at least one of projections from a surface of the coil spring; an annular ring, a ferrule and a wound coil surrounding a surface of the coil spring; and a pleated coil spring having adjacent turns interspaced between adjacent turns of the coil spring. 
         [0083]    In one embodiment, dimensions and locations of the coil spring and spacers are selected to provide a selected hole density of the perforated liner. 
         [0084]    In one embodiment, a density of the holes changes along the axial length. 
         [0085]    In one embodiment, the density of the holes decreases towards an exhaust end. 
         [0086]    In one embodiment, the density of the holes increases towards an exhaust zone. 
         [0087]    In one embodiment, the density of the holes of the perforated liner decreases towards a nozzle zone. 
         [0088]    In one embodiment, the perforated liner is unperforated proximate to the nozzle zone. 
         [0089]    In one embodiment, the density of the holes of the perforated liner increases circumferentially proximate a plurality of nozzle regions. 
         [0090]    In one embodiment, the density of the holes of the perforated liner decreases towards a cleaning zone. 
         [0091]    In one embodiment, the perforated liner comprises one of a mesh, a wire screen, a perforated sheet and a louvered sheet. 
         [0092]    In one embodiment, the louvers are orientated to direct the combustion products within the combustion chamber. 
         [0093]    In one embodiment, the louvers are orientated to receive on a major surface the cleaning fluid from the at least one spray nozzle. 
         [0094]    In one embodiment, the liner comprises an aperture for receiving an associated effluent nozzle. 
         [0095]    In one embodiment, the perforated liner is metallic. 
         [0096]    In one embodiment, the perforated liner comprises nickel. 
         [0097]    In one embodiment, the perforated liner is cylindrical. 
         [0098]    According to a fourth aspect, there is provided a radiant burner perforated liner for treating an effluent gas stream from a manufacturing process tool, the radiant burner comprising a combustion chamber having a porous sleeve through which combustion materials pass for combustion proximate to a combustion surface of the porous sleeve; at least one effluent nozzle for ejecting the effluent gas stream into the combustion chamber, the perforated liner being shaped and configured for placement proximate to the combustion surface. 
         [0099]    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. 
         [0100]    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. 
         [0101]    The Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detail Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0102]    Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which: 
           [0103]      FIG. 1  illustrates a radiant burner according to one embodiment; 
           [0104]      FIG. 2  is an enlarged view of the interface between a liner and nozzle shown in  FIG. 1 ; 
           [0105]      FIGS. 3 to 5  illustrate regions of differing perforation density according to embodiments; 
           [0106]      FIGS. 6 and 7  illustrate displacement of the liner according to one embodiment; 
           [0107]      FIGS. 8 and 9  illustrates a radiant burner according to one embodiment; 
           [0108]      FIGS. 10A to 10C  illustrate a structure which is coiled to provide the turns of a coil spring according to embodiments; 
           [0109]      FIG. 11  illustrates side view of a portion of turns of a coil spring according to one embodiment; and 
           [0110]      FIG. 12  illustrates a structure which is coiled to provide the turns of a coil spring according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
     Overview 
       [0111]    Before discussing the embodiments in any more detail, first an overview will be provided. As mentioned above, the conditions within the combustion chamber of a radiant burner may be such that combustion residues deposit on surfaces within the combustion chamber due to changes in flow rate of effluent gases into the combustion chamber. These residues affect the performance of the combustion chamber typically by preventing flow of the combustion materials through a burner element and by blocking nozzles providing the effluent gas stream. In addition, the residues can potentially affect the chemistry of the combustion within the combustion chamber. 
         [0112]    Providing a perforated or porous liner within the combustion chamber protects the burner element and/or nozzles from such combustion deposits since the combustion residues deposit on the liner, which can be cleaned more conveniently and in any of a variety of different ways than is possible for the burner element or the nozzles. For example, the liner may be mechanically cleaned using a scraper, by spraying water onto the liner or by expanding the liner to change the shape of the perforations and dislodge the deposits. Such cleaning would typically not be possible or would damage the burner element. This cleaning may be performed in-situ or by removing the liner from the combustion chamber. Again, this is something that is not easy to do with the burner element or the nozzles. This approach makes it easier and faster to clean the radiant burner. 
         [0113]    Also, the mechanical arrangement of the liner may be configured to adjust the combustion properties of the combustion chamber. For example, the perforations or apertures within the liner may be sized and distributed to affect the concentration and flow of the combustion gases within the combustion chamber. Also, the size and location of the perforations may be configured to prevent or reduce the likelihood of any cleaning material being used to clean the liner from contacting and potentially damaging the combustion element. 
         [0114]    Hence, it can be seen that the arrangement of a liner helps to improve the performance of the radiant burner. 
       Radiant Burner—General Configuration and Operation 
       [0115]      FIG. 1  illustrates a radiant burner, generally  8  according to one embodiment. The radiant burner  8  treats an effluent gas stream pumped from a manufacturing process tool such as a semiconductor or flat panel display process tool typically by means of a vacuum pumping system. The effluent stream is received at inlets  10 . The effluent stream is conveyed from the inlet  10  to a nozzle  12  which injects the effluent stream into a cylindrical combustion chamber  14 . In this embodiment, the radiant burner  8  comprises four inlets  10  arranged circumferentially, each conveying an effluent stream pumped from a respective tool by a respective vacuum pumping system. Alternatively, the effluent stream from a single processed tool may be split into a plurality of streams, each one of which is conveyed to a respective inlet  10 . Each nozzle  12  is located within a respective bore  16  formed in a ceramic top plate  18  which defines an upper or inlet surface of the combustion chamber  14 . 
         [0116]    The combustion chamber  14  has sidewalls defined by an exit surface  21  of a foraminous burner element  20  such as that described in EP 0 694 735. The burner element  20  is cylindrical and is retained within a cylindrical outer shell  24 . A plenum volume  22  is defined between an entry surface  23  of the burner element  20  and the cylindrical outer shell  24 . A mixture of fuel gas, such as natural gas or a hydrocarbon, and air is introduced into the plenum volume  22  via one or more inlet nozzles [not shown]. The mixture of fuel gas and air passes from the entry surface  23  of the burner element  20  to the exit surface  21  of the burner element  20  for combustion within the combustion chamber  14 . 
         [0117]    The ratio of the mixture of fuel gas and air is varied to vary the temperature within the combustion chamber  14  to that which is appropriate for the effluent gas stream to be treated. Also, the rate at which the mixture of fuel gas and air is introduced into the plenum volume  22  is adjusted so that the mixture will burn without visible flame at the exit surface  21  of the burner element  20 . The exhaust  15  of the combustion chamber  40  is open to enable the combustion products to be output from the radiant burner  8 . 
         [0118]    Accordingly, it can be seen that the effluent gas received through the inlets  10  and provided by the nozzles  12  to the combustion chamber  14  is combusted within the combustion chamber  14  which is heated by the mixture of fuel gas and air which combusts near the exit surface  21  of the burner element  20 . Such combustion causes heating of the chamber  14  and provides combustion products, such as oxygen, typically within a range of 7.5% to 10.5% depending on the air/fuel mixture [CH 4 , C 3 H 8 , C4H 10 ], provided to the combustion chamber  14 . This heat and the combustion products react with the effluent gas stream within the combustion chamber  14  to clean the effluent gas stream. For example, SiH 4  and NH 3  may be provided within the effluent gas stream, which reacts with O 2  within the combustion chamber  14  to generate SiO 2 , N 2 , H 2 O, NO x . Similarly, N 2 , CH 4 , C 2 F 6  may be provided within the effluent gas stream, which reacts with O 2  within the combustion chamber  14  to generate CO 2 , HF, H 2 O. 
       Perforated Liner—Fixed Arrangement 
       [0119]    Provided within the combustion chamber  14  is a liner  40 . In this embodiment, the liner  40  is cylindrical and it is received within the combustion chamber  14  adjacent the exit surface  21  of the burner elements  20 . The combustion of the mixture of fuel gas and air occurs within a combustion zone  25  adjacent the exit surface  21  of the burner element  20 . In this embodiment, the outer surface  44  of the liner  40  is positioned adjacent the combustion zone  25  so that combustion products pass through perforations of the liner  40  and enter the combustion chamber  14 . However, it will be appreciated that the exact location of the liner  40  with respect to the exit surface  21  of the burner element  20  and the combustion zone  25  may be varied to vary the conditions within the combustion chamber  14 . 
         [0120]    The liner  40  is perforated to enable the combustion products to pass from the combustion zone  25  into the combustion chamber  14 . The size and distribution of these perforations are selected to facilitate the distribution and flow of combustion products from the combustion zone  25  into the combustion chamber  14 , as will be described in more detail below. Also, the size and distribution of the perforations can be varied to protect the burner elements  20  from damage during cleaning of the liner  40 . It will be appreciated that the perforations can be provided in a variety of different ways; for example, the liner  40  may be punched or rolled to create apertures at the correct locations or may even be louvered. 
         [0121]    In this embodiment, the liner  40  is formed of two parts; namely a cylindrical section and a top plate section. The cylindrical section and the top plate section  46  are affixed. The top plate  46  has a radially outer circumferential flange which is clamped between an upper section  60  and a lower section  62  of the radiant burner  8 . This retains the liner  40  in place within the combustion chamber  14 . 
       Spray Nozzle 
       [0122]    In order to clean the fixed liner, a further bore  30  in the ceramic top plate  18  is provided through which a spray nozzle  32  extends at the inlet end of the combustion chamber  14 . The spray nozzle  32  is supplied with a cleaning fluid, such as water, from an accumulator which operates to dispense a selected or fixed amount of fluid, such as water, from the spray nozzle  32  at a selected pressure. The geometry of the spray nozzle  32  defines a spray pattern for the cleaning fluid. In this example, a 120° ejection nozzle is provided which directs the fluid in a 120° cone having an angular tolerance which causes cleaning fluids to impact on an impact zone  34  of the liner  40 . 
         [0123]    The mechanical impact, vaporisation and/or thermal shock of the cleaning fluid contacting the inner surface of the hot liner  40  causes combustion residues deposited on the liner  40  to become detached. 
       Nozzle Cleaning 
       [0124]    As can be seen in more detail in  FIG. 2 , the top plate  46  comprises apertures, each of which receives a respective nozzle  12 . The apertures are defined by upstanding edges  48  of the top plate which may be toleranced to provide an interference fit with an outer surface  13  of the nozzles  12 . The presence of the upstanding edges  48  of the top plate  46  enables any combustion residues deposited on the outer surface  13  of the nozzles  12  to be scraped off when the liner  40  is removed from the combustion chamber  14 . 
         [0125]    In the embodiment shown in  FIG. 1 , removal of the liner  40  is achieved by separating the upper section  60  and lower section  62  of the radiant burner  8 . However, in embodiments described in more detail below, the liner  40  may be displaced from the combustion chamber  14  without separating the upper section  60  and lower section  62 . 
       Perforated Liner—Displaceable Arrangement 
       [0126]      FIG. 6  illustrates a displaceable arrangement according to one embodiment where the spray nozzle  32  is omitted. In order to clean the liner  14 , it is displaced from the exhaust  15  of the combustion chamber  14  for cleaning. Typically, the liner  40  is displaced into a water bath  90 . Immersing the liner  40  in the water bath causes a mechanical impact, vaporisation and/or thermal shock which dislodges combustion residues. The liner  40  may then be agitated within the water bath or the water bath itself may be agitated to facilitate cleaning. 
         [0127]    In particular, the perforated liner  42  is retained by a fixing  80  coupled with an actuator  82  which is shown in the accommodated or retracted position. Coupled with the cylindrical outer shell  24  is a lower chamber, generally  92 . The lower chamber  92  provides for cooling of the processed effluent gases exiting the combustion chamber  14 . The processed effluent gases enter a cylindrical tube  83 , flow through an aperture  85  and out of an outlet  88 . The cylindrical tube  83  has a water curtain which flows in the direction A and is fed by a water curtain feed  84 . A cooling spray  86  is directed towards the aperture  85  the water curtain. The cooling spray  86  helps to cool the processed effluent gases and to trap particulate material. The water bath  90  is maintained at the lower portion of the container  92 . 
         [0128]      FIG. 7  shows the perforated liner  42  in the unaccommodated or protruding position. The perforated liner  42  is displaced by the actuator  82  into the water bath  90 . The immersion of the perforated liner  42  within the water bath  90  causes residues deposits to be removed. Reciprocating the actuator  82  helps to agitate the liner  42  within the water bath  90 . The actuator  82  may be retracted to displaced the perforated liner  42  and accommodate this back within the combustion chamber  14 . Displacement of the perforated liner  42  helps to remove any residue deposits on the nozzles  12 . 
         [0129]    It will be appreciated that for such an arrangement, the circumferential flange  50  is omitted and the liner  40  is instead retained within the combustion chamber  14  by the fixing  80  and actuator  82 . The displacement mechanism can then return the liner  40  to the accommodated position as shown in  FIG. 1 . 
         [0130]    The displacement of the liner  40  causes combustion residue on the outer surface  13  of the nozzles  12  to be removed. 
         [0131]    In both the fixed and displaceable arrangements, a mechanical scrapper may be inserted which contacts with the inner surface  42  of the liner  40  and provides mechanical cleaning. Alternatively, or additionally, the mechanical scraper may be located in the water bath  90  and may engage the liner  40  during displacement of the liner  40  to the unaccommodated position. 
       Perforated Liner—Expandable Mesh Arrangement 
       [0132]      FIGS. 8 and 9  illustrate a radiant burner according to one embodiment. This embodiment incorporates all the features of the embodiments mentioned above and below, but this embodiment omits the provision of the spray nozzle  32  and the actuator  82 . Instead, as will become clear from the description below, a modified actuator  82 A is provided which operates to expand a liner  42 A in order to remove deposits. However, it will be appreciated that further embodiments may also include the spray nozzle  32  to eject cleaning fluid onto the liner  42 A and/or the actuator  82  to displace the liner  42 A in a similar manner to that mentioned above. 
         [0133]    In this embodiment, the liner  42 A is cylindrical and it is received within the combustion chamber  14  adjacent the exit surface of the burner elements. The combustion of the mixture of fuel gas and air occurs within a combustion zone adjacent the exit surface of the burner element. In this embodiment, the outer surface of the liner  42 A is positioned adjacent the combustion zone so that combustion products pass through perforations of the liner  42 A and enter the combustion chamber  14 A. However, it will be appreciated that the exact location of the liner  42 A with respect to the exit surface of the burner element and the combustion zone may be varied to vary the conditions within the combustion chamber  14 A. 
         [0134]    The liner  42 A is an expandable mesh which is perforated to enable the combustion products to pass from the combustion zone into the combustion chamber  14 A. The size and distribution of these perforations is selected to facilitate the distribution and flow of combustion products from the combustion zone into the combustion chamber  14 A, as will be described in more detail below. Also, the size and distribution of the perforations can be varied to protect the burner elements from damage during cleaning of the liner  42 A for those embodiments which incorporate the spray nozzle. It will be appreciated that the perforations can be provided in a variety of different ways; for example, the liner  42 A may be formed from a coil spring as will be explained in more detail below or may even be a woven sock. 
         [0135]    In this embodiment, the liner  42 A is formed of two parts; namely a cylindrical section and a top plate section. The cylindrical section and the top plate section are affixed. The top plate has a radially outer circumferential flange which is clamped between an upper section and a lower section of the radiant burner. This retains the liner  42 A in place within the combustion chamber  14 A. 
         [0136]    In an alternative embodiment, where the liner  42 A is also displaced from the exhaust of the combustion chamber  14 A for cleaning in the manner described above, the liner  42 A is retained by a fixing coupled with the actuator  82  in addition to the modified actuator  82 A. This enables the liner  42 A to be both expanded as well as immersed and/or manually scraped as mentioned above. 
         [0137]    The modified actuator  82 A is coupled with the end  42 B opposing the top plate section. When it is desired to remove deposits from the liner  42 A, the modified actuator  82 A actuates to extend the length of the liner  42 Aa in the direction B shown in  FIG. 9 . The top plate section retains the liner  42 A in place as the end  42 B is displaced. The modified actuator  82 A is connected with the end  42 B using an annular ring. The extension of the liner  42  causes the perforations of the liner  42 A to extend and flex, thus dislodging any deposits. Once the liner  42 A has been extended by the required amount, the modified actuator  82 A reverses the expansion and restores the liner  42 A back to its retained position, as shown in  FIG. 8 . 
         [0138]    Typically, the expansion will seek to expand the size of the perforations by around a half and will require the axial length of the liner  42 A to be extended by typically between one third and two thirds of its axial length in the retained position. 
         [0139]    An advantage of this arrangement is that through a simple mechanical displacement, deposits can be dislodged. This displacement can be performed relatively quickly compared to the displacement technique shown in  FIG. 7  and has a reduced effect on the conditions within the combustion chamber  14 A compared to any of the techniques mentioned above. 
         [0140]    As mentioned above, one embodiment the liner  42 A comprises a coil spring.  FIGS. 10A to 10C  illustrate the structure which is coiled to provide the turns of such a coil spring. A substrate  100 A;  100 B is provided. The substrate may be cylindrical, having a generally circular cross-section or may be planar, having a generally rectilinear cross-section. 
         [0141]    Spacers  102 A;  102 B;  102 C are provided either surrounding or protruding from the substrate  100 A;  100 B. In particular, the spacer  102 A comprises a smaller-diameter substrate (such as a wire) wound around the outside of the substrate  100  A;  100  B. The spacer  102 B comprises projections which extend from the surface of the substrate  100 A;  100 B. The Spacer  102 C comprises an annular ring or a ferrule provided on the outer surface of the substrate  100 A;  100 B. 
         [0142]    The diameter of the substrate  100 A;  100 B, is denoted by the distance D. The distance between one outer surface of the substrate  100 A;  100 B and an outer surface of the spacer  102 A;  102 B;  102 C is denoted by the distance d. The length of the spacers  102 A;  102 B;  102 C is denoted by the distance l. The distance between adjacent spacers is denoted by the distance L. The distances d, D, l and L determine the size and geometry of the perforations  104  when the liner  42 A is in the retained position, as shown in  FIG. 11 . Typically, the distance D will be around 1.5 to 2 mm, whilst the distance d will be typically around 2 to 2.5 mm Typically, the distances l and L are selected in order to avoid spacers on adjacent turns of the coil spring from contacting. However, it will also be appreciated that it is possible to adjust these so that they to contact, if required. 
         [0143]    Also, it will be appreciated that by varying the distances d, D, l and L, along the length of the substrate, it is possible to vary the density of perforations within the liner  42 A when in the retained position, as will be described in more detail below. 
         [0144]      FIG. 12  illustrates an alternative coil ring structure according to one embodiment. In this embodiment, the substrate  100 A;  100 B is provided. However, rather than providing spacers which surround the substrate  100 A;  100  B, instead, a separate spacer structure  102  D is provided which is itself formed into a coil spring and turns of that coil spring are interleaved between adjacent turns of the substrate  100 A;  100 B. In particular, the spacer  102  C comprises a pleated substrate which undulates with a reciprocating, sinusoidal or sawtooth profile, which is then wound into a coil spring. The spacing provided by the undulations provides the perforations when in the retained position. 
       Liner Perforations—Combustion Product General Flow Control 
       [0145]    In order to control the introduction of combustion products from the combustion zone  25  into the combustion chamber  14 , the size and distribution of perforations is varied as shown in  FIG. 3 . To improve clarity, the cylindrical portion is shown as a rectangular net. 
         [0146]    As can be seen, in a region  70  which is adjacent the ceramic top plate  18 , no or a lower density of perforations is provided. Optionally, in a region  74  which is adjacent the exhaust  15  of the combustion chamber  14 , a higher density of perforations is provided. In a region  72  between the regions  70  and  74 , the density of perforations changes from a higher density of perforations towards the region  70  to a lower density of perforations towards the region  74 . 
         [0147]    Providing a higher density of perforations in the region  72  close to the nozzles  12  helps to increase the distribution of combustion products in the region where the effluent gas stream combusts within the combustion chamber  14 . Generally reducing the density of perforations towards the outlet  15  reduces the amount of combustion products as the amount of untreated effluent gas stream reduces. 
         [0148]    Providing the region  74  with a high density of perforations also increases the density of combustion products in the vicinity of the outlet  15  where combustion is likely to be less efficient. Reducing the density of perforations in the region  70  helps to decrease the distribution of combustion products in the region where the effluent gas stream undergoes little combustion within the combustion chamber  14 . 
       Liner Perforations—Combustion Product Flow—Nozzle Optimisation 
       [0149]    In order to control the introduction of combustion products from the combustion zone  25  into the combustion chamber  14 , the size and distribution of perforations is varied as shown in  FIG. 4 . To improve clarity, the cylindrical portion is shown as a rectangular net. 
         [0150]    In the embodiment shown in  FIG. 1 , there are provided four nozzles  12  equally spaced circumferentially. The relative positions of those nozzles  12  are indicated schematically in  FIG. 4 . In order to concentrate the presence of combustion products in the vicinity of each of those nozzles  12 , the density of perforations in the regions  12   a  is increased compared to the density of perforations in the regions  12   b.    
         [0151]    It will be appreciated that depending on the particular number and configuration of the nozzles  12 , the precise location of the regions  12   a  and  12   b  will vary to match. 
       Liner Perforations—Spray Protection 
       [0152]    In order to prevent damage to the burner element  20 , the size and distribution of perforations is varied as shown in  FIG. 5 . To improve clarity, the cylindrical portion is shown as a rectangular net. 
         [0153]    As can be seen, a region  34  of no or a low density of perforations is provided. This prevents or reduces the likelihood of any cleaning fluid ejected from the spray nozzle from passing through the liner  40  and contacting and causing damage to the burner element  20 . 
         [0154]    It will be appreciated that in embodiments utilising louvers rather than perforations, the presence of the zone  34  is not required. 
       Liner Perforations—Density Combinations 
       [0155]    In order to provide combustion product control and spray protection, the densities shown in  FIGS. 3 ,  4  and/or  5  may be combined to arrive at an appropriate density profile for the perforated liner. In particular, the zones  70  and  74  may, for example, be omitted. 
         [0156]    As mentioned above, the processing of effluent gases such as silane, chloro-silanes and organo-silane produces solid by-products such as SiO 2  and Si 3 N 4 . These tend to deposit on surfaces within the radiant burner. The rate of deposit is sufficient that, typically, turbulent flame burners are instead used for processing of such gases which are typically produced during photovoltaic solar and flat panel display processes. 
         [0157]    In embodiments, a perforated screen is interposed between the burner element and the combustion chamber. For example, a 6 inch diameter screen is mounted within a 7 inch diameter burner element. The burner is fired in a conventional way, with the perforated screen forming a gas purged radiant boundary to the combustion chamber. The screen may be capped with a metallic plate which is perforated to allow for various head fixtures to protrude, for example a pilot burner, process nozzles, thermocouple, etc. This provides for a sacrificial surface, covering the areas ordinarily prone to deposition, but made of substantially more robust material than the base parts [which are currently ceramic fibre for the head insulation and composite metal fibre/ceramic fibre for the burner elements]. Providing a perforated screen provides surfaces that can be cleaned. In one embodiment, the parts are cleaned by impacting water droplets from a high pressure spray nozzle. In another embodiment, the liner is mounted on an actuator, allowing it to be translated out of the burner and dipped into a tank of water immediately below the burner. 
         [0158]    The screen may be a simple perforated sheet which is rolled and welded, or may be punched with louvers such that the combustion bi-products are directed downwards, but any water spray or steam [if admitted through the top of the combustion chamber] is prevented from coming into contact with the surface of the burner. Alternatively, a knitted wire braided wire screen may be employed. 
         [0159]    The liner needs to be able to withstand the high temperature oxidizing conditions of the combustion chamber and also to withstand the high thermal shock of cleaning events. Accordingly, the liner may include inconnel 600 or similar alloys. Alternatively, mild steel may be used with a heavy high phosphorus electrode-less nickel plating. When heated to braising temperatures in a vacuum furnace [800° c. 250° c.] the nickel coating flows into the surface of the mild steel and the phosphorus is subsequently burned out, leaving a non-porous coating of essentially pure nickel which has a melting point of approximately 1440° c. and a coating melting point of 800° c. to 1200° c., depending on phosphorus content. 
         [0160]    As mentioned above, embodiments provide for the combustive abatement of process gases such as silane chloro-silanes and organo-silanes produces solid by-products such as SiO2, Si3N4. These tend to deposit on surfaces within the abatement system, for example on the head ceramic, and burner liner of radiant burners. 
         [0161]    Despite offering the best abatement performance (in terms of fuel use per litre of gas treated to a defined destruction or removal efficiency level) such burners have been superseded by inferior turbulent flame burners for the harshest photovoltaic solar and flat panel display processes. However, embodiments provide an arrangement that provides for the abatement of such processes, combining the efficiency and performance of the radiant burner with the mean time between service of a simpler turbulent flame device. 
         [0162]    In one embodiment, a perforated screen is interposed between the radiant burner and the combustion chamber. For example a 6″ diameter screen is mounted in a 7″ diameter burner. The burner is fired in the conventional way, with the perforated screen forming a gas purged radiant boundary to the combustion chamber. The screen may be capped with a metallic plate perforated to allow for the various head fixtures to protrude—for example pilot burner, process nozzles, thermocouple, etc. This provides for a sacrificial surface, covering the areas ordinarily prone to deposition, but made of a substantially more robust material than the base parts (currently ceramic fibre for the head insulation and composite metal fibre/ceramic fibre for the burner liner) 
         [0163]    In another embodiment, the screen is an expanding screen rolled from wire, with spacers along the wire to keep the turns of the wire at a mutual separation which defines the openness of the screen. To clean the screen, it is expanded by translating the lower end of the screen downwards (the upper end requires to be fixed.) The screen may be similar to a cross filter but the spacing of the wire would require to be say 1 mm on a wire of a similar size. This method is particularly applicable to a concentric burner, where the water spray/steam clean method is impractical. 
         [0164]    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. 
         [0165]    Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.