Absorbent tank for exhaust gas abatement system

Abstract

The invention provides a dry absorbent tank for an exhaust gas abatement system. The canister includes a hollow chamber configured to hold a particulate absorbing medium. The chamber has a cross-sectional area defined by a longitudinally extending wall, and the chamber has a gas inlet at a first end and a gas outlet at a second end. A cross-sectional area of the chamber varies between the first end and the second end. The cross-sectional area of the chamber increases from the gas inlet to a maximum cross-sectional area.

Description

Technical Field

[0001] The present invention relates to a dry absorbent canister, an exhaust gas abatement system including a dry absorbent canister, and a method of abatement an exhaust gas flow. Background Art

[0002] In some industries, exhaust abatement systems may be used to treat exhaust gases from process equipment. Such treatment may include removing toxic and / or environmentally harmful substances present in the exhaust gases to render them harmless before they are released into the atmosphere.

[0003] A "dry absorbent tank" is one example of a component that may form part of a gas abatement system. Figure 1 A cross-sectional view of a typical dry absorbent tank (1) of the prior art is shown. The tank (1) comprises a hollow chamber (3) defined by a cylindrical wall (2). The chamber (3) is filled with a chemically active absorption medium, such as basic copper (II) carbonate. The tank (1) comprises an inlet (4) arranged at a first end, which is fluidly coupled to an outlet of a semiconductor processing device (not shown). The tank (1) also comprises an outlet (5) arranged at a second end.

[0004] During operation, exhaust gas from a semiconductor manufacturing process enters the canister (1) through the inlet port (4) and passes through the chamber (3), passing through the absorption medium. Harmful compounds (such as hydrogen chloride) in the exhaust gas passing through the chamber (3) react with the absorption medium to form, for example, inert inorganic salts. Over time, the absorption medium becomes deactivated and is no longer able to react with the exhaust gas, and the canister (1) must be replaced.

[0005] The life of the tank (1) is limited by the rate of deactivation of the absorption medium contained therein. It is therefore desirable to improve the efficiency of the abatement process in order to increase the life of the tank (1) before replacement is required.

[0006] The present invention is directed to at least partially addressing these and other problems associated with prior art tanks. Summary of the invention

[0007] In one aspect, the present invention provides a dry absorbent canister for an exhaust gas abatement system. The canister includes a hollow chamber configured to hold a particulate absorbent medium. The chamber has a cross-sectional area defined by longitudinally extending walls and has a gas inlet at a first end and a gas outlet at a second end. The cross-sectional area of ​​the chamber varies between the first end and the second end, and the cross-sectional area of ​​the chamber increases from the gas inlet to a maximum cross-sectional area.

[0008] Preferably, the dry absorbent tank or tanks may be used in, or form part of, an exhaust abatement system for a semiconductor manufacturing process.

[0009] Typically, the dry absorbent tank may include a particulate absorption medium held within a chamber. Typically, the particulate absorption medium may be solid particles or pellets. The particulate absorption medium may contain a non-volatile inorganic salt, such as copper (II) chloride. Typically, when in use, the particulate absorption medium may be stacked within the chamber so that the particulate absorption medium is substantially fixed therein. The skilled person will appreciate that there may be gaps between the absorption medium particles to allow exhaust gas to flow therebetween. Preferably, each particle of the absorption medium may have a minimum size of from about 1 mm to about 10 mm, preferably from about 2 mm to about 8 mm. For example, each particle of the absorption medium may be roughly cylindrical and have a diameter of from about 2 mm to about 8 mm.

[0010] In an embodiment, the gas inlet may be connectable to a source of gas to be treated. For example, the gas to be treated may include hydrogen chloride.

[0011] In an embodiment, the gas outlet may be connectable to a device for removing the treated gas. For example, the gas outlet may be connectable to an extractor for removing the treated gas.

[0012] The screen plate may be located within the tank. The screen plate may be configured to retain the particulate absorption medium within the chamber. The screen plate may be disposed proximate to a gas inlet or a gas outlet. The screen plate may be configured to allow the exhaust gas to flow substantially unimpeded. The screen plate may include a mesh, wherein the holes in the mesh may be smaller than a minimum size of the absorption medium to prevent the absorption medium from passing through the screen plate.

[0013] The canister may include an inlet port, wherein the inlet port is fluidly coupled to a gas inlet of the chamber. Additionally, the canister may include an outlet port, wherein the outlet port is fluidly coupled to a gas outlet of the chamber. In use, the inlet port of the canister may be fluidly coupled to an exhaust port of a process tool. The process tool may be a tool used in a semiconductor manufacturing process. The outlet port of the canister may be coupled to another component of an exhaust abatement system. Alternatively, the outlet port may be directly open to the atmosphere.

[0014] The longitudinally extending wall of the chamber may be the outer wall of the tank. The wall may extend longitudinally generally between the first end and the second end of the chamber. The wall may be continuous, or it may be connected by welding and / or fastening. Typically, the chamber may have a generally circular cross-section. The diameter of the chamber may vary. In an embodiment, the chamber may have a maximum diameter of about 600 mm or less, for example 560 mm. The thickness of the longitudinally extending wall may vary.

[0015] The inventors of the present invention have made a comparison between the dry absorbent tank (i.e. Figure 1The extent of utilization of particulate absorption media within a tank (shown in Figure 1) was investigated. When examining the spent tank, only about 35% by weight of the absorption media within the tank was deactivated. Thus, about 65% by weight of the particulate absorption media within the tank was unused but still useful. Furthermore, it was noted that the deactivated absorption media was not evenly distributed throughout the chamber, but was found to be present in specific areas of the tank chamber.

[0016] Figure 2 A graph showing the utilization of the absorption medium as a function of the fraction of the column (i.e. chamber) length for a prior art tank (1) is shown. The column length is the distance from the inlet to the outlet, e.g. Figure 1 . It is found that the particulate absorption media near the inlet has a significantly higher utilization than the particulate absorption media near the outlet. This indicates that the absorption media does not react uniformly throughout the tank, with most of the reaction between the exhaust gas and the absorption media occurring near the inlet. When the exhaust gas passes through the absorption media near the outlet, most of the abatement reaction has already occurred, and therefore the rate of absorption media deactivation is significantly reduced.

[0017] Therefore, even when most of the absorption medium near the chamber outlet remains substantially unreacted, the time before replacing the prior art tank can be determined by the utilization of the absorption medium near the chamber inlet. Since all of the absorption medium in the chamber is disposed of before refilling, unused absorption medium may be wasted.

[0018] The inventors also studied the cross-sectional utilization of the absorption medium in the tank. Figure 3 , which shows "dead zones" (6, 7) found at the corners of a cylindrical tank (1) of the prior art. In these dead zones (6, 7), the utilization of the absorption medium is significantly lower than the utilization of the absorption medium in the rest of the tank. In particular, the dead zone (6) exists in the corner near the inlet (4), and the dead zone (7) exists in the corner near the outlet (5). Figure 3 is a two-dimensional schematic representation of the location of the dead zones (6, 7) within the container (1), but those skilled in the art will appreciate that this represents the three-dimensional location of the dead zones.

[0019] Without wishing to be bound by theory, in prior art tanks, the uneven utilization of the absorption medium along the length of the chamber may be due to a decrease in the concentration of reactants in the exhaust gas as the exhaust gas travels along the length of the chamber. This may be accompanied by a decrease in the local temperature of the exhaust gas along the length of the tank. In prior art tanks, the longitudinal residence time of the exhaust gas along the tank is essentially uniform, so the decrease in the concentration of reactants causes a decrease in the utilization of the absorption medium along the length of the chamber. In addition, the presence of dead zones may be due to uneven radial residence time of the exhaust gas within the chamber. The residence time of the exhaust gas toward the central axis of the chamber may be longer than that near the walls.

[0020] In the tank according to the present invention, the cross-sectional area of ​​the chamber varies between the first end and the second end, and the cross-sectional area increases from the gas inlet to the maximum cross-sectional area. Advantageously, the inventors have found that by providing a non-uniform cross-sectional area between the first end and the second end, the uniformity of the utilization of the absorption medium in the entire chamber can be improved. Without wishing to be bound by theory, the larger the cross-sectional area of ​​the chamber, the longer the residence time of the exhaust gas on the absorption medium in this region, and vice versa. The non-uniform residence time of the exhaust gas can compensate for the concentration reduction of the reactants along the length of the chamber. Therefore, the present invention can improve the uniformity of the utilization of the absorption medium in the chamber. In addition, the time between services can be increased.

[0021] In embodiments, the cross-sectional area of ​​the chamber may vary substantially monotonically, e.g., increase or decrease, between the first end and the second end of the chamber. Typically, the chamber may taper substantially along the entire length of the chamber. In other words, in embodiments, the chamber may not include two or more fractional segments having substantially continuous diameters.

[0022] The cross-sectional area of ​​the chamber may be defined by the inwardly facing surface of the longitudinally extending wall.

[0023] The flow path of the exhaust gas may be from a gas inlet to a gas outlet. Typically, the gas inlet and / or the gas outlet may be aligned on the central axis of the chamber. Preferably, the gas inlet and the gas outlet coincide with the central axis of the chamber. Advantageously, this may allow a greater proportion of the absorption medium to be directly in the flow path of the exhaust gas during operation. Aligning the gas inlet and / or the gas outlet with the central axis of the chamber and varying the cross-sectional area of ​​the chamber between the first end and the second end may reduce the likelihood of dead zones.

[0024] In an embodiment, the maximum cross-sectional area may be located at or adjacent to the second end of the chamber. In prior art cylindrical tanks, the utilization of the absorption medium at the second end of the chamber (i.e., near the outlet) is reduced compared to the utilization of the absorption medium at the first end of the chamber. Therefore, providing the maximum cross-sectional area of ​​the chamber at or adjacent to the second end of the chamber may increase the residence time of the exhaust gas at the second end of the chamber relative to the residence time at the first end of the chamber during use.

[0025] Typically, the cross-sectional area of ​​the chamber decreases between the maximum cross-sectional area and the gas inlet. Preferably, the portion of the chamber between the gas inlet and the maximum cross-sectional area may be substantially frustoconical. For the purposes of the present invention, frustoconical is defined as the shape of a non-planar portion of a frustum of a cone. The axial length of the frustoconical portion may be the same as the axial length of the chamber, or it may be less than the axial length of the chamber.

[0026] Advantageously, this arrangement reduces the likelihood of dead zones forming in the corners near the gas inlet, as found in prior art cylindrical tanks (see Figure 3 ). Furthermore, in use, the chamber cross-sectional area which decreases towards the inlet can reduce the residence time of the exhaust gas towards the gas inlet and thereby improve the uniformity of the absorption medium utilization throughout the chamber.

[0027] Typically, the cross-sectional area of ​​the chamber decreases towards the inlet. Preferably, the substantially frustoconical portion of the chamber may extend to the gas inlet. Preferably, the cross-sectional area of ​​the frustoconical portion of the chamber may be substantially equal to the cross-sectional area of ​​the gas inlet where the frustoconical portion of the chamber meets the gas inlet. Advantageously, this may substantially avoid a dead zone near the gas inlet and may reduce the residence time of the exhaust gas near the gas inlet.

[0028] Typically, the central axis of the chamber and the central axis of the frustoconical portion of the chamber may be coaxial. Advantageously, this may improve the symmetry of the chamber, which may improve the uniformity of absorption medium utilization throughout the dry absorbent tank.

[0029] As described above, the inventors have discovered that non-uniform reaction of the absorption medium occurs in conventional cylindrical tanks of the prior art, where most of the reaction between the exhaust gas and the absorption medium occurs near the inlet. Therefore, in embodiments, the cross-sectional area of ​​the chamber can be configured such that the degree of utilization of the absorption medium is substantially constant along the length of the chamber.

[0030] In embodiments, due to the improvements described herein, the utilization of the absorption medium as a function of the fraction of the column length of the tank can be consistently not less than about 20%, preferably 40%, more preferably not less than 60%, for example not less than 70% between the inlet and outlet. Figure 2 The percentage usage at each of the ten fractions of the column length between the inlet and the outlet shown is a minimum of 20%, preferably not less than 40%, more preferably not less than 60%, for example not less than 70%.

[0031] In other words, the cross-sectional area of ​​the chamber may vary along its length, such as increase or decrease, in substantial proportion to the change in absorbent medium utilization over the length of a theoretical cylindrical chamber having substantially similar length and substantially similar maximum diameter.

[0032] For example, the cross-sectional area of ​​the chamber may be increased to a maximum cross-sectional area corresponding to the fraction of the theoretical cylindrical chamber over the length of the theoretical cylindrical chamber that has the lowest or near lowest absorption medium utilization.

[0033] Thus, the chamber may be constructed, in particular the cross-sectional area of ​​the chamber may be arranged to substantially compensate for the loss of absorption medium utilization over the length of a corresponding theoretical cylindrical chamber having substantially the same length and substantially the same maximum diameter.

[0034] For example, if a theoretical cylindrical chamber having substantially the same length and maximum diameter and holding an equal amount of absorptive medium has a first fraction that is approximately 10% of the distance over the length of the chamber and approximately 80% of the utilization by weight and a second fraction that is approximately 80% of the distance over the length of the chamber and approximately 10% of the utilization by weight, then the cross-sectional area of ​​the chamber can be increased proportionally between the corresponding fractions of the column length, for example by approximately 70%, to compensate for the (original) reduction in utilization.

[0035] Those skilled in the art will appreciate that different process gases and / or different absorption media may require different changes in chamber cross-sectional area to achieve the same effect.

[0036] Typically, the cross-sectional area of ​​the chamber may decrease, ie taper, between the maximum cross-sectional area and the gas outlet.Preferably, the portion of the chamber between the maximum cross-sectional area and the gas outlet may be substantially frusto-conical.

[0037] Advantageously, this can reduce the likelihood of dead zones forming near the corners of the gas outlet, as found in prior art cylindrical tanks (see Figure 3 ). Preferably, the frustoconical portion may meet the gas outlet. Preferably, the minimum cross-sectional area of ​​the frustoconical portion may be substantially equal to the cross-sectional area of ​​the gas outlet where the frustoconical portion meets the gas outlet.

[0038] Preferably, the chamber may be at least partially defined by a frustoconical portion near the gas inlet, wherein the cross-sectional area of ​​the frustoconical portion decreases towards the gas inlet. The chamber may be defined by another frustoconical portion near the gas outlet, wherein the cross-sectional area of ​​the frustoconical portion decreases towards the gas outlet. Most preferably, the chamber and therefore the longitudinally extending walls may define a conical double frustum. Alternatively, the chamber and therefore the longitudinally extending walls may define a triangle, square, pentagon, hexagon, octagon or other double frustum. In an embodiment, the frustoconical portions may be adjacent to each other. In other words, the chamber may be completely defined by a frustoconical portion near the gas inlet and a frustoconical portion near the gas outlet.

[0039] Preferably, in such an embodiment, the axial length of the frustoconical portion near the gas inlet may be greater than the axial length of the frustoconical portion near the gas outlet. More preferably, the axial length of the frustoconical portion near the gas inlet may be at least half of the axial length of the chamber. Advantageously, this may further reduce the formation of dead zones and may increase the residence time of the exhaust gas toward the gas outlet. This arrangement may further improve the uniformity of the absorption medium consumption throughout the chamber.

[0040] Those skilled in the art will appreciate that the uniformity of the improvement in absorption medium consumption throughout the chamber depends on many factors, including, for example, the relative axial lengths and dimensions of the frustoconical portions proximate the gas inlet and gas outlet, respectively, the composition of the exhaust gas being treated, and the absorption medium selected.

[0041] In another aspect, the present invention provides a dry absorbent canister for an exhaust gas abatement system. The canister includes a hollow chamber configured to hold a particulate absorbent medium. The chamber is defined by a wall and has a gas inlet and a gas outlet. The chamber is configured to allow fluid to flow from the gas inlet to the gas outlet while holding the particulate absorbent medium. The chamber also includes a shield configured to shield at least a portion of the gas outlet from the gas inlet.

[0042] The dry absorbent tank may preferably be used in, or form part of, an exhaust gas abatement system for a semiconductor manufacturing process. The skilled person will appreciate that the particulate absorbent medium may be as defined in any other aspect or embodiment.

[0043] The canister may include an inlet port, wherein the inlet port is fluidly coupled to a gas inlet of the chamber. Additionally, the canister may include an outlet port, wherein the outlet port is fluidly coupled to a gas outlet of the chamber. In use, the inlet port of the canister may be fluidly coupled to an exhaust port of a process tool. The process tool may be a tool used in a semiconductor manufacturing process. The outlet port of the canister may be coupled to another component of an exhaust abatement system. Alternatively, the outlet port may be directly open to the atmosphere.

[0044] The wall defining the chamber may preferably be the outer wall of the can, preferably the wall may be a longitudinally extending wall. Typically, the wall may comprise sheet metal, which is shaped to define the chamber of the can. The chamber defined by the wall may be substantially cylindrical. Alternatively, the wall may have another shape, such as a frustoconical shape or a conical double frustum.

[0045] The shield is configured to shield at least a portion of the gas outlet from the gas inlet. Preferably, the shield can be configured to shield the entire gas outlet from the gas inlet. The term "shielding" can be defined as the shield being positioned between the gas inlet and the gas outlet so that there is no direct linear path for gas flow between the gas inlet and the gas outlet or parts thereof. The shield can be configured to divert the direction of the exhaust gas flow in use. Therefore, the gas flowing therebetween must flow around the shield.

[0046] Advantageously, the shield's diversion of the exhaust gas flow can increase the residence time of the exhaust gas in the chamber because the shield prevents the exhaust gas from taking the most direct route between the gas inlet and the gas outlet. In addition, the shield can improve the uniformity of the residence time of the exhaust gas throughout the chamber and / or can improve the uniformity of the utilization of the absorption medium.

[0047] For the avoidance of doubt, arrangements of any embodiment of this aspect may be combined with any embodiment of the previous aspect.

[0048] Typically, the gas inlet, gas outlet and shielding member can be arranged along the central axis of the chamber. Advantageously, such arrangement of the gas inlet, gas outlet and shielding member can improve the uniformity of the utilization rate of the absorption medium in the chamber.

[0049] Preferably, the shield is in the form of at least one spiral thread, which is configured to guide the exhaust gas flow from the gas inlet to the gas outlet. The spiral thread can be positioned in the chamber. The spiral thread or each spiral thread can extend around a thread axis. The thread axis can be substantially coaxial with the central axis of the chamber. The spiral thread can extend to the wall defining the chamber. The absorption medium can be arranged in a volume defined by each turn of the spiral thread. In an embodiment, the spiral thread can be arranged essentially as an Archimedean spiral, i.e. an arithmetic spiral.

[0050] Preferably, the or each helical thread may extend along at least half of the axial length of the chamber, more preferably at least 75% of the axial length of the chamber, most preferably substantially the entire axial length of the chamber.

[0051] Preferably, the helical thread may be a single start, double start or quad start helical thread. In embodiments comprising a multi-start helical thread (ie more than a single start helical thread), the chamber may have a plurality of gas inlets, each gas inlet being arranged to direct exhaust gas from a different starting point along the helical thread.

[0052] Preferably, the gas inlet may be arranged near the start of the helical thread. Preferably, the gas outlet may be arranged near the end of the helical thread. In use, the exhaust gas flow may enter the chamber via the gas inlet. The or each helical thread may define a spiral flow path for the exhaust gas through the chamber from the gas inlet to the gas outlet. By directing the exhaust gas through the chamber along the spiral flow path, dead zones may be reduced.

[0053] Advantageously, the helical flight may allow for greater uniformity of residence time of the exhaust gas throughout the chamber. The helical flight may direct the gas flow through the chamber such that the flow path is longer than the direct distance between the inlet and outlet.

[0054] In some embodiments, the or each helical thread may extend from a central rod. Preferably, the rod is coaxial with the central axis of the chamber. Advantageously, the rod may support the or each helical thread. Additionally or alternatively, the or each helical thread may extend to a wall of the chamber. Preferably, the rod and the helical thread are integral in structure.

[0055] Typically, the pitch of the or each spiral thread may vary along its axial length. Preferably, the pitch of the or each spiral thread may increase between the gas inlet and the gas outlet. The pitch of the spiral thread may be defined as the axial distance of the thread axis along a single turn (i.e. 360° turn) of the spiral thread. Preferably, the spiral thread includes at least one full turn (i.e. 360 turns) within the axial length of the chamber, more preferably from about 2 to about 10 full turns. Generally, the greater the pitch of the spiral thread, the longer the residence time of the exhaust gas in the area, and vice versa. Therefore, increasing the pitch of the spiral thread towards the gas outlet can increase the residence time of the exhaust gas through previously underutilized areas of the chamber. This can advantageously improve the uniformity of the utilization of the absorption medium.

[0056] In another aspect, the present invention provides a dry absorbent canister for an exhaust gas abatement system. The canister includes a main chamber having an inlet and an outlet. The main chamber contains a secondary chamber configured to hold a particulate absorbent medium. The secondary chamber includes a plurality of inlet apertures configured to convey an exhaust gas flow from the canister inlet into the secondary chamber and a plurality of outlet apertures configured to convey an exhaust gas flow from the secondary chamber to the canister outlet.

[0057] In use, the plurality of inlet orifices may disperse the exhaust gas flow throughout the sub-chamber. The plurality of outlet orifices may provide a plurality of locations for the exhaust gas flow to exit the sub-chamber. Advantageously, the arrangement of the present invention improves the dispersion of the exhaust gas flow within the sub-chamber and thereby improves the uniformity of the utilization of the particle absorbing medium within the sub-chamber.

[0058] The dry absorbent tank may be preferably used in an exhaust gas abatement system for a semiconductor manufacturing process.The particulate absorption medium may be as defined in any other aspect or embodiment.

[0059] The inlet of the main chamber may be connected to an inlet conduit of the tank. Alternatively, the inlet of the main chamber may be an inlet port of the tank. The inlet of the main chamber may be fluidly coupled to an exhaust port of a process tool, preferably via an inlet conduit of the tank. The process tool may be a tool used in a semiconductor manufacturing process. The outlet of the main chamber may be connected to an outlet conduit of the tank. The outlet of the main chamber may be fluidly coupled to another component of the abatement equipment, preferably via an outlet conduit. Alternatively, the outlet of the main chamber may be directly open to the atmosphere.

[0060] The secondary chamber may include from about 2 to about 40 inlet openings, preferably from about 2 to about 8 inlet openings, such as 4 inlet openings. The inlet openings may be generally circular, rectangular, elliptical or other shapes. The inlet openings may be substantially evenly spaced. Preferably, there may be from about 1 to about 40 outlet openings. The outlet openings may be generally circular, rectangular, elliptical or other shapes.

[0061] The dry absorbent tank may further include a screen. The screen may be located within the tank and may be configured to retain the particulate absorption medium within the secondary chamber. The screen may be disposed proximate to the tank inlet or the tank outlet. The screen may be configured to allow the exhaust gas to flow substantially unimpeded. The screen may include a mesh, wherein the holes in the mesh may be smaller than the minimum size of the absorption medium. Advantageously, such a configuration may prevent the absorption medium from passing through the screen.

[0062] For the avoidance of doubt, in embodiments including a sieve plate, the sieve plate may not define an inlet opening and / or an outlet opening of the sub-chamber. The function of the sieve plate may be to maintain the positioning of the particulate absorbing medium within the sub-chamber while allowing the exhaust gas to flow into / out of the sub-chamber substantially unimpeded by the sieve plate. In contrast, multiple inlet openings may be configured to disperse the exhaust gas flow throughout the sub-chamber. The multiple outlet openings may be configured to provide multiple locations for the exhaust gas flow to leave the sub-chamber. Advantageously, this arrangement of the inlet opening and the outlet opening may improve the dispersion of the exhaust gas flow within the sub-chamber.

[0063] Preferably, the secondary chamber may be substantially annular. The secondary chamber may be defined by a substantially tubular inner wall arranged within a substantially tubular outer wall. Preferably, the inlet orifice may be in the form of a perforation in either the substantially tubular inner wall or the substantially tubular outer wall. Additionally or alternatively, the outlet orifice may be in the form of a perforation in the other of the substantially tubular inner wall or the substantially tubular outer wall.

[0064] Preferably, there may be from about 2 to about 40 access openings, for example 4 access openings. The access openings may be generally circular, rectangular, oval or other shaped perforations. The access openings may be substantially evenly spaced on the generally tubular inner wall or the generally tubular outer wall. The access openings may be substantially evenly distributed on the generally tubular inner wall or the generally tubular outer wall.

[0065] Preferably, there may be from about 1 to about 40 egress openings, such as 4 egress openings. The egress openings may be generally circular, rectangular, oval or other shaped perforations. The egress openings may be substantially evenly distributed on the generally tubular inner wall or the generally tubular outer wall.

[0066] Preferably, the inlet aperture may be in the form of a perforation in the generally tubular inner wall and the outlet aperture may be in the form of a perforation in the generally tubular outer wall.

[0067] The generally tubular inner wall may surround and be substantially parallel to the generally tubular outer wall. The particulate absorbing medium may be retained within the sub-chamber such that the exhaust gas flow entering via the inlet orifice may pass through and / or through the absorbing medium as it travels to the outlet orifice. Preferably, the particulate absorbing medium may be retained between the generally tubular inner wall and the generally tubular outer wall. Preferably, the size of the particulate absorbing medium, the inlet orifice and the outlet orifice may be selected such that the particulate absorbing medium cannot exit the sub-chamber via the inlet orifice and / or the outlet orifice.

[0068] In use, the exhaust gas may flow substantially radially inwardly or substantially radially outwardly between the inlet and outlet apertures. Advantageously, such arrangement and positioning of the inlet and outlet apertures may improve the dissipation of the exhaust gas through the secondary chamber and thereby improve the uniformity of the absorption medium utilization throughout the secondary chamber.

[0069] Preferably, the substantially annular secondary chamber may be a substantially rectangular annular surface. The substantially tubular inner wall and the substantially tubular outer wall may be substantially parallel to the central axis of the substantially rectangular annular surface. Preferably, the substantially annular secondary chamber has an axial length that is at least twice its maximum radius. The axial length may be measured along the central axis of the secondary chamber.

[0070] Preferably, the outer wall of the secondary chamber may be surrounded by a plenum configured to direct the exhaust flow from the secondary chamber to the tank outlet or from the inlet to the secondary chamber. In such an embodiment, the outer wall of the secondary chamber may provide a shield as described in the previous aspects. Advantageously, the plenum may collect substantially all of the airflow leaving the secondary chamber and direct it to the tank outlet, or direct all of the airflow from the inlet to the secondary chamber.

[0071] In another aspect, the present invention provides an exhaust abatement system. The exhaust abatement system includes a dry absorbent tank according to any of the foregoing aspects or embodiments disposed therein. The dry absorbent tank includes a particulate absorbent medium within a chamber. An inlet of the dry absorbent tank is configured to be in fluid communication with an exhaust gas flow from a process tool. The particulate absorbent medium may be defined as defined elsewhere herein.

[0072] Typically, the process tool to which the exhaust abatement system is connected may be a process tool used for semiconductor manufacturing. For example, the exhaust abatement system may be connected to a Trias semiconductor process tool produced by Tokyo Electron Co., Ltd. (RTM).

[0073] The exhaust gas abatement system may be the iAreca manufactured by Edwards Limited.

[0074] Typically, the exhaust abatement system may include at least two dry absorbent canisters according to any of the foregoing aspects or embodiments disposed therein. At least one canister may be in communication with an exhaust port of a process tool, and at least one canister is not in fluid communication with an exhaust stream of the process tool.

[0075] Advantageously, having two dry absorbent canisters within the system allows canisters to be swapped out immediately when the absorbent medium in the canister in fluid communication with the exhaust stream is spent. This can reduce machine downtime and allow the system to operate while the spent absorbent medium is removed from the canister and replaced with fresh absorbent medium before the canister is nested back into the system.

[0076] Preferably, the at least two dry absorbent tanks may be embodiments as described herein, wherein at least a portion of the chamber is frustoconical. Preferably, the two dry absorbent tanks may be substantially identical. More preferably, the tank that is not in fluid communication with the exhaust gas stream may be inverted relative to the tank that is in fluid communication with the exhaust gas stream. Due to the frustoconical wall portion, this may allow the tank to be nested within the system and occupy less space. This may be beneficial because the size of the system is limited, and reducing the space occupied by the tank may provide more space for other components of the exhaust gas abatement system.

[0077] In another aspect, the present invention provides a method of abatement of an exhaust gas flow from a process tool. The method comprises the steps of providing an exhaust gas abatement system according to the foregoing aspects, and directing the exhaust gas flow through an inlet of a dry absorbent tank.

[0078] The advantages associated with this method are as described in relation to the previous aspects or embodiments.

[0079] For the avoidance of doubt, all aspects and embodiments described above may be combined mutatis mutandis. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Preferred features of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0081] Figure 1 A cross-sectional view of a typical dry absorbent tank (1) of the prior art is shown.

[0082] Figure 2 A graph showing the utilization of absorption medium as a function of fraction of column length for a prior art tank is shown.

[0083] Figure 3 A cross-sectional view of a typical prior art dry absorbent tank (1) is shown, indicating the "dead zone" of low absorption medium activity.

[0084] Figure 4-9 A cross-sectional view of a dry absorbent tank according to an embodiment of the present invention is shown.

[0085] Fig.10 A cross-sectional view of an exhaust abatement system according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0086] Figure 4 A cross-sectional view of a dry absorbent tank (8) according to an embodiment of the present invention is shown. The tank (8) includes a hollow chamber (9) configured to hold a particulate absorption medium (not shown). The tank (8) has an inlet conduit (10). The inlet conduit includes an annular flange extending radially outward for coupling the tank to another component when in use. The chamber (9) has a gas inlet (11) at a first end. The gas inlet (11) is directly connected to the inlet conduit (10). The tank (8) also includes an outlet conduit (12). The outlet conduit (12) includes an annular flange extending radially outward for coupling the tank to another component when in use. The chamber (9) also has a gas outlet (13) at a second end opposite to the gas inlet (11). The gas outlet (13) is directly connected to the outlet conduit (12). The gas inlet (11) and the gas outlet (13) are aligned with the central axis of the chamber (A).

[0087] The chamber is defined by a longitudinally extending wall (14). The cross-sectional area of ​​the chamber (9) measured perpendicular to the central axis of the chamber (A) varies between the first end and the second end. The cross-sectional area of ​​the chamber (9) is defined by the longitudinally extending wall (14). Specifically, in this embodiment, the cross-sectional area of ​​the chamber (9) increases from the first end to the second end. The maximum cross-sectional area of ​​the chamber (9) is at the second end adjacent to the gas outlet (13). The cross-sectional area of ​​the chamber (9) has a tapered decrease between the second end and the gas inlet (11).

[0088] The wall (14) defining the chamber (9) is frustoconical in shape. The central axis of the frustoconical wall (14) is coaxial with the central axis of the chamber (A). The diameter, and thus the cross-sectional area, of the frustoconical wall (14) varies between the inlet (10) and the outlet (11) of the chamber (9). The cross-sectional area increases from a cross-sectional area (D1) near the inlet to a cross-sectional area (D2) near the outlet. The rate of increase in cross-sectional area between the gas inlet (11) and the gas outlet (13) is substantially continuous.

[0089] In use, a waste gas stream (not shown) enters the chamber (9) through the gas inlet (11). The waste gas stream passes through and / or between the absorption medium, reacting therewith. The waste gas stream then leaves the chamber (9) through the gas outlet (13). The increased cross-sectional area of ​​the chamber (9) between the first end and the second end can reduce the residence time of the waste gas stream towards the first end of the chamber (9) relative to the residence time of the waste gas stream towards the second end of the chamber (9). Advantageously, this can improve the uniformity of the absorption medium utilization throughout the chamber (9).

[0090] Figures 4 to 8 Including some matching features, the same figure numbers will be used for these features and the description will not be repeated.

[0091] Figure 5 A cross-sectional view of a dry absorbent tank (15) according to an alternative embodiment of the present invention is shown. The chamber (17) of the illustrated embodiment is a double frustum of a cone. The longitudinally extending wall (16) defining the chamber (17) includes a first frustum of a cone portion (18) adjacent to the gas inlet (11). The cross-sectional area of ​​the chamber (17) measured perpendicular to the central axis (A) varies between a first end and a second end. The cross-sectional area of ​​the first frustum of a cone portion (18) decreases from a maximum cross-sectional area to a cross-sectional area adjacent to the gas inlet (11).

[0092] The longitudinally extending wall (16) defining the chamber (17) further comprises a second frustoconical portion (19) proximate the gas outlet (13). The cross-sectional area of ​​the second frustoconical portion (19) decreases from a maximum cross-sectional area towards the gas outlet (13). In this embodiment, the maximum cross-sectional area of ​​the chamber (17) is substantially equidistant from the gas inlet (11) and the gas outlet (13).

[0093] Advantageously, this embodiment can reduce the possibility of "dead zones" near the gas inlet (11) and the gas outlet (13), such as Figure 3 The prior art tank shown is identified.

[0094] Figure 6A cross-sectional view of a dry absorbent tank (20) according to an alternative embodiment of the present invention is shown. The chamber (22) of this illustrated embodiment is a double frustum of a cone. Similar to Figure 5 In the illustrated embodiment, the longitudinally extending wall (21) defining the chamber (22) includes a first frustoconical portion (23) proximate the gas inlet (13) and a second frustoconical portion (24) proximate the gas outlet (13). The cross-sectional area of ​​the first frustoconical portion (23) decreases from the maximum cross-sectional area toward the gas inlet (11). The cross-sectional area of ​​the second frustoconical portion (24) decreases from the maximum cross-sectional area toward the gas outlet (13).

[0095] The axial length of the first frustoconical portion (23) is greater than half the axial length of the chamber (22). In fact, in this embodiment, the axial length of the first frustoconical portion (23) is approximately 80% of the axial length of the chamber (22). Therefore, the maximum cross-sectional area of ​​the chamber (22) is closer to the gas outlet (13) than to the gas inlet (11). This embodiment can be advantageous because the arrangement of the first and second frustoconical portions (23, 24) can increase the residence time of the exhaust gas towards the gas outlet (13), and thereby can improve the uniformity of the residence time of the exhaust gas in the entire chamber (22). In addition, this embodiment can reduce the possibility of dead zones.

[0096] Figure 7 A cross-sectional view of a dry absorbent tank (25) according to an alternative embodiment of the present invention is shown. The tank (25) includes a hollow chamber (26) configured to hold a particulate absorbent medium (not shown). The chamber (26) has a gas inlet (27) and a gas outlet (28). The chamber (26) is defined by a wall (29). The chamber (26) is substantially cylindrical in shape and has a central axis (B).

[0097] The chamber (26) also includes a shield configured to shield at least a portion of the outlet (28) from the inlet (27). The shield includes a helical thread (30) housed within the chamber (26). The helical thread (30) is configured to direct an exhaust gas flow (not shown) from the gas inlet (27) through the chamber (26) to the gas outlet (28) when the tank (25) is in use. The thread axis of the helical thread (30) is coaxial with the central axis (B) of the chamber (26). The helical thread (30) is directly connected to the wall (29). A particulate absorption medium (not shown) is arranged between each turn of the helical thread (30). In this embodiment, the helical thread (30) is a single-start helical thread. In this embodiment, the pitch of the helical thread (30) is substantially consistent along the length of the helical thread (30), although it will be appreciated by those skilled in the art that it may also vary.

[0098] The gas inlet (27) is arranged approximately perpendicular to the central axis (B) of the chamber (26). The gas inlet (27) is arranged near the starting point of the spiral thread (30). The gas outlet (28) is approximately parallel to the central axis (B) of the chamber (26), but not coaxial therewith. The gas outlet (28) is arranged near the end point of the spiral thread (30). Therefore, in use, the exhaust gas flow can enter the chamber (26) via the gas inlet (27) and be immediately guided into the flow path defined by the spiral thread (30). The exhaust gas flow can then be guided by the spiral thread (30) along the spiral flow path through the chamber (26) to the gas outlet (28). By guiding the exhaust gas through the chamber (26) along the spiral flow path, the possibility of dead zones can be reduced.

[0099] Figure 8 The diagram shows a cross-sectional view of a dry absorbent tank (31) according to an alternative embodiment of the present invention. The tank (31) has a plurality of Figure 6 The common features of the embodiments of the present invention will not be described in detail and the same figure marks will be used for them.

[0100] The tank (31) further comprises a shielding member configured to shield at least a portion of the gas outlet (13) from the gas inlet (11). The shielding member comprises a helical thread (32) housed within the chamber (22). The helical thread (32) is configured to direct an exhaust gas flow (not shown) from the gas inlet (11) through the chamber (22) to the gas outlet (13) when the tank (31) is in use. The thread axis of the helical thread (32) is coaxial with the central axis (A) of the chamber (22). The helical thread (32) is directly connected to the wall (21) defining the chamber (22). The particulate absorption medium is arranged between each turn of the helical thread (32).

[0101] The pitch of the helical thread (32) varies along its length. The pitch of the helical thread (32) increases between the gas inlet (11) and the gas outlet (13) of the chamber (22). The increase in the pitch of the helical thread (32) can correspond to a longer residence time of the exhaust gas in the area with a larger pitch. Therefore, the increase in the pitch of the helical thread (32) toward the gas outlet (13) can increase the residence time of the exhaust gas toward the gas outlet (13). The pitch of the helical thread (32) and the diameter and length of the first and second frustoconical portions (23, 24) of the chamber (22) have been selected so that they can provide improved uniformity of absorption medium utilization. This arrangement can substantially avoid dead zones within the chamber (22).

[0102] Fig. 9A cross-sectional view of a dry absorbent tank (33) according to an alternative embodiment of the present invention is illustrated. The tank (33) includes a main chamber (34) having an inlet (35) and an outlet (36). The main chamber (34) contains a secondary chamber (37) configured to hold a particulate absorbent medium (not shown).

[0103] The secondary chamber (37) includes a plurality of inlet apertures (38) configured to convey the exhaust gas flow from the inlet (35) into the secondary chamber (37). The secondary chamber (37) also includes a plurality of outlet apertures (39) configured to convey the exhaust gas flow from the secondary chamber (37) to the outlet (36).

[0104] The secondary chamber (37) is generally annular. The secondary chamber (37) is generally a rectangular annular surface. The secondary chamber (37) is defined by a generally tubular inner wall (40) disposed within a generally tubular outer wall (41). A plurality of inlet orifices (38) are in the form of perforations in the generally tubular inner wall (40). A plurality of outlet orifices (39) are in the form of perforations in the generally tubular outer wall (41).

[0105] The inlet (36) may be arranged to be in fluid communication with an outlet of a process tool (not shown) in use. In use, exhaust gas may flow substantially radially outwardly through the secondary chamber (37) between the inlet orifice (38) and the outlet orifice (39). Advantageously, such arrangement and positioning of the inlet orifice (38) and the outlet orifice (39) may improve the uniformity of absorption medium utilization compared to prior art tanks.

[0106] The generally tubular outer wall (41) of the secondary chamber (37) is surrounded by a plenum (42). The plenum (42) is configured to convey the exhaust gas flow from the secondary chamber (37) to the canister outlet (36). The exhaust gas flow exits the plenum (42) at the end of the canister (33) opposite the inlet (35).

[0107] Fig.10 A pair of dry absorbent tanks (43, 44) are shown in a nested arrangement according to the present invention. The first tank (43) and the second tank (44) are substantially identical and can be arranged according to Figure 6 Or the embodiment of 8.

[0108] The inlet port (45) of the first tank (43) is in fluid communication with an exhaust port of a process tool (not shown). Exhaust gas is configured to flow through the first tank (43) and exit through the outlet port (46). The second tank (44) is not in fluid communication with an exhaust port of the process tool.

[0109] Each of the first and second tanks (43, 44) has a chamber with a frustoconical portion. Thus, in the arrangement shown, the second tank (44) can be inverted relative to the first tank (43), thereby allowing the tanks (43, 44) to be nested very closely. This can advantageously reduce the space required to arrange the tanks (43, 44) within the housing of the exhaust gas abatement system (not shown). In addition, when the absorption medium in the first tank (43) is used up and spent, the first tank (43) can be removed and the second tank (44) can be inverted and arranged in its place. This can allow the exhaust gas flow to be treated while the absorption medium in the first tank (43) is replaced.

[0110] For the avoidance of doubt, features of any aspect or embodiment described herein may be combined mutatis mutandis. It will be appreciated that various modifications may be made to the illustrated embodiments without departing from the spirit and scope of the invention as defined by the appended claims as interpreted in accordance with the patent statutes.

[0111] Reference numerals

[0112] 1. Tank (Prior Art)

[0113] 2. Wall (Existing Technology)

[0114] 3. Chamber (Prior Art)

[0115] 4. Inlet port (prior art)

[0116] 5. Exit port (prior art)

[0117] 6. Dead Zone (Existing Technology)

[0118] 7. Dead Zone (Existing Technology)

[0119] 8. Cans

[0120] 9. Chamber

[0121] 10. Entry Port

[0122] 11. Gas inlet

[0123] 12. Export Port

[0124] 13. Gas outlet

[0125] 14.Wall

[0126] 15. Cans

[0127] 16.Wall

[0128] 17. Chamber

[0129] 18. Frustoconical section

[0130] 19. Truncated cone section

[0131] 20. Cans

[0132] 21.Wall

[0133] 22. Chamber

[0134] 23. Frustoconical section

[0135] 24. Frustoconical section

[0136] 25. Cans

[0137] 26. Chamber

[0138] 27. Gas inlet

[0139] 28. Gas outlet

[0140] 29.Wall

[0141] 30. Helical thread

[0142] 31.Cans

[0143] 32. Helical thread

[0144] 33.Cans

[0145] 34. Main chamber

[0146] 35. Entrance

[0147] 36. Export

[0148] 37. Secondary chamber

[0149] 38. Enter the orifice

[0150] 39. Exit opening

[0151] 40. Roughly tubular inner wall

[0152] 41. Roughly tubular outer wall

[0153] 42. Gas collecting chamber

[0154] 43.Cans

[0155] 44.Cans

[0156] 45. Entry Port

[0157] 46.Export Port

Claims

1. A dry absorbent canister for an exhaust gas abatement system, the canister comprising a hollow chamber configured to hold a particulate absorbent medium; The chamber has a cross-sectional area defined by longitudinally extending walls, and the chamber has a gas inlet at a first end and a gas outlet at a second end; in, The cross-sectional area of ​​the chamber varies between the first end and the second end, and wherein the cross-sectional area of ​​the chamber increases from the inlet to a maximum cross-sectional area.

2. The dry absorbent tank according to claim 1, wherein: The largest cross-sectional area of ​​the chamber is located at or adjacent to the second end of the chamber.

3. The dry absorbent tank according to claim 1 or 2, wherein: The cross-sectional area of ​​the chamber decreases between the maximum cross-sectional area and the inlet, preferably wherein the section of the chamber between the inlet and the maximum cross-sectional area is substantially frusto-conical.

4. A dry absorbent tank according to any preceding claim, wherein: The cross-sectional area of ​​the chamber decreases between the maximum cross-sectional area and the outlet, preferably wherein the portion of the chamber between the maximum cross-sectional area and the outlet is substantially frustoconical; optionally wherein, when dependent on claim 3, the chamber is substantially entirely defined by a frustoconical portion proximate the gas inlet and a frustoconical portion proximate the gas outlet.

5. A dry absorbent canister for an exhaust gas abatement system, the canister comprising a hollow chamber configured to hold a particulate absorbent medium; The chamber is defined by a wall and has a gas inlet and a gas outlet; The chamber is configured to allow fluid to flow from the gas inlet to the gas outlet while retaining a particulate absorbent medium, wherein: The chamber also includes a shield configured to shield at least a portion of the gas outlet from the gas inlet.

6. The dry absorbent tank according to claim 5, wherein: The gas inlet, gas outlet and shield are all arranged along the central axis of the chamber.

7. The dry absorbent tank according to claim 5 or 6, wherein: The shield includes at least one helical thread configured to direct exhaust gas flow from the gas inlet to the gas outlet.

8. The dry absorbent tank according to claim 7, wherein: The or each helical thread extends about a thread axis, wherein the thread axis is substantially coaxial with a central axis of the chamber.

9. The dry absorbent tank according to claim 7 or 8, wherein: The pitch of the or each helical thread varies along its length, preferably wherein the pitch of the or each helical thread increases between the gas inlet and the gas outlet.

10. A dry absorbent canister for an exhaust gas abatement system, the canister comprising a main chamber having an inlet and an outlet and containing a secondary chamber configured to hold a particulate absorbent medium; in, The secondary chamber includes a plurality of inlet apertures configured to deliver exhaust flow from a canister inlet into the secondary chamber and a plurality of outlet apertures configured to deliver exhaust flow from the secondary chamber to the canister outlet.

11. The dry absorbent tank of claim 10, comprising from about 2 to about 40 inlet openings, preferably from about 2 to about 8 inlet openings.

12. The dry absorbent tank according to any one of claims 10 to 11, wherein: The secondary chamber is generally annular, preferably defined by a generally tubular inner wall arranged within a generally tubular outer wall, preferably wherein the entry orifice is in the form of a perforation in either the generally tubular inner wall or the generally tubular outer wall, and / or wherein the exit orifice is in the form of a perforation in the other of the generally tubular inner wall or the generally tubular outer wall.

13. The dry absorbent tank according to claim 12, wherein: The outer wall of the secondary chamber is surrounded by a plenum configured to convey an exhaust gas flow between the secondary chamber and a canister outlet or inlet.

14. An exhaust gas abatement system comprising: a dry absorbent tank according to any preceding claim disposed therein; Wherein the dry absorbent tank comprises a particulate absorbent media within the chamber, and wherein an inlet of the dry absorbent tank is configured to be in fluid communication with a waste gas stream from a process tool.

15. A method of abatement of an exhaust gas flow from a process tool comprising the steps of: An exhaust abatement system according to claim 14 is provided, and an inlet for directing exhaust gas flow through the dry absorbent tank.

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