Patent Application
20130276904
Probes can be used to collect sample fluid streams from main fluid streams. For example, probes can be used to collect sample fluid streams from stack emissions, such as wet stack emissions. Wet stacks are stacks containing main flows of emissions that are saturated with water vapor and have liquid water droplets that can vary from micro droplets typical of fogs (micrometers in diameter) to macro droplets typical of rain (millimeters in diameter). These droplets can contain a large fraction of particulate matter (PM) and metals associated with health effects. It can be difficult to collect a representative sample of these droplets for analysis on a continuous basis. Currently, continuous emission monitor systems (CEMS) use large diameter probes to reduce deviations from isokinetic sampling, avoid heating sampling probes to minimize dried salt plugs, use steam and compressed air “blow back” to prevent probe build up and plugging, or other similar techniques to allow continuous operations.
Current probes can be ineffective in transporting a representative total stack aerosol sample to a CEMS. The description herein is directed to tools and techniques for probe apparatuses for collecting and transporting sample fluid streams. For example, a sample fluid stream may be redirected in a redirection area, and a flowing gas sheet may be directed into the redirection area. Such a gas sheet may provide one or more of various benefits, such as redirecting the flow while reducing impact of the flow with conduit walls, mixing the flow to promote drying, breaking up large droplets in the flow to promote drying, etc. Additionally, a conduit downstream of a probe nozzle may define a reverse taper (where the conduit is wider downstream), a lip for collecting droplets that have collected on conduit walls, and/or re-entraining gas directed at collected droplets. Such features can aid in decreasing impaction of droplets on the conduit walls and/or re-entraining collected droplets into the sample fluid stream. As another example, focusing gas may focus the sample fluid stream away from the walls of the conduit. Such focusing gas may be at different temperatures for different sections of the conduit. For example, the focusing gas may be a lower temperature near the probe inlet (which may decrease overheating of the probe nozzle, which could cause increased evaporation of droplets on the nozzle), and may be at a higher temperature to act as drying gas farther downstream. Such tools and techniques and/or others discussed below may be used alone or in combination.
This Summary is provided to introduce a selection of concepts in a simplified form. The concepts are further described below in the Detailed 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 to limit the scope of the claimed subject matter. Similarly, the invention is not limited to implementations that address the particular techniques, tools, environments, disadvantages, or advantages discussed in the Background, the Detailed Description, or the attached drawings.
The description and drawings may refer to the same or similar features in different drawings with the same reference numbers.
The probe features discussed herein include many new features that may be used alone or in combination. For example, the probe apparatus can use high velocity gas to redirect the flow of stack gas, particles and liquid droplets from the original direction of the stack gas to a direction towards the containment walls where the aerosol can be sampled or analyzed. For example, the high velocity gas can be in the form of a gas sheet, which can have a width that is at least ten times, at least fifty times, at least one-hundred times, at least five-hundred times, or at least one-thousand times a thickness of the gas sheet at an outlet of a gas knife. Other features can relate to reducing impaction of aerosol components in the sample fluid stream on conduit walls, encouraging re-entrainment of liquid deposited on walls of the inlet nozzle, etc. The various aspects of such features will now be discussed with reference to
Referring to
The nozzle (120) can have a nozzle inlet (122) defined by a leading edge of the nozzle (120). The nozzle inlet (122) can be centrally located within the shroud (110). The nozzle inlet (122) can have a diameter that is substantially smaller than an inner diameter of an entrance to the shroud (110) (e.g., from 0.1 to 0.4 times the diameter of the shroud (110)). For example, the nozzle inlet may have a diameter of about three-fourths of an inch and the shroud may have an inner diameter of about three inches. The nozzle can have an outer surface (124) that can slope outward downstream of the inlet (122). An inner surface (126) of the nozzle (120) can extend downstream from the nozzle inlet (122). The inner surface (126) can have a constant diameter for some length (e.g., for between 1/16 inch to ¼ inch, or ⅛ inch), and can end in a lip (128). From the lip (128), the inner surface (126) can form a reverse taper (130). The reverse taper (130) can extend outward at any of various different angles, such as an angle less than ninety degrees and/or an angle greater than ninety degrees.
A main conduit (140) can extend back from the nozzle inlet (122), defining a stream area (142) where the sample fluid stream is to flow, as will be discussed more below. The main conduit (140) can include the nozzle (120) and the other conduit components discussed below (e.g., the outer non-porous and inner porous conduit components).
A downstream portion of the nozzle (120) can fit over at least a portion of a first outer non-porous conduit component (150) or can otherwise be secured to the non-porous conduit component (150). The first outer non-porous conduit component (150) can surround a first inner porous conduit component (152) to form a first annular gas chamber (154) between the components (150). A focusing gas source (156) can be connected in fluid communication with the first gas chamber (154). The first outer non-porous conduit component (150) can be sealed to the first inner porous conduit component (152). This seal may not be an entirely gas-tight seal, but it can be sealed sufficiently to force focusing gas to pass through the first inner porous conduit component (152). The focusing gas source (156) can provide focusing gas that is at a temperature at or below the temperature of the main fluid stream entering the nozzle (120).
Downstream of the nozzle area (102), the stream area (142) can continue and the main conduit (140) can include a second outer non-porous conduit component (160) surrounding a second inner porous conduit component (162) to form a second annular gas chamber (164) between the second outer non-porous conduit component (160) and the second inner porous conduit component (162). A drying gas source (170) can be connected in fluid communication with the second gas chamber (164). The second outer non-porous conduit component (160) can be sealed to the first inner porous conduit component (162). This seal may not be an entirely gas-tight seal, but it can be sealed sufficiently to force focusing gas to pass through the first inner porous conduit component (162). The focusing gas source (156) can provide focusing gas that is also heated to act as drying gas. Accordingly, the drying gas can be at a temperature that is above the temperature of the main fluid stream entering the nozzle (120). The second gas chamber (164) can extend along the redirection area (104) and along the transport area (106), providing drying gas through the second inner porous conduit component (162). The second gas chamber (164) may be interrupted by a joint in the main conduit (140), so that there is also a third gas chamber (166) that can also supply drying gas. There may also be additional gas chambers to supply drying gas and/or unheated focusing gas downstream of the third gas chamber (166), leading to a materials monitoring apparatus (180) shown schematically in
Additionally, the probe apparatus (100) can include a gas knife (200) that can be connected to a pressurized gas source (210). The gas knife (200) can define a gap that acts as an outlet (220) through which the pressurized gas can be forced to form a high velocity sheet of flowing gas. The outlet (220) may be curved so that the gas sheet is also curved. For example, the outlet (220) can form a concave curve from the perspective of the nozzle (120). Accordingly, the curve of the outlet (220) may match the curve of the conduit (140) distal from the nozzle (120) in
Various different materials and/or manufacturing methods may be used in the components of the probe apparatus (100). For example, the components may be made of corrosive-resistant metals such as stainless steel, titanium, or aluminum. Additionally, lightweight metals such as aluminum may be coated with corrosive-resistant coatings. The inner porous conduit components (152 and 162) may be sintered material such as sintered stainless steel.
Operation of the probe apparatus (100) will now be discussed with reference to a flowchart illustrated in
The sample fluid stream (230) can travel into the nozzle (120) in a first direction. Some droplets (240) from the main fluid stream (232) that are not in the sample fluid stream (230) may collect on the outer surface (124) of the nozzle (120). Other droplets (242) in the sample fluid stream (230) may impact and collect on the inner surface (126) of the nozzle (120). Such droplets (242) can be forced farther into the nozzle (120) by the flow of the sample fluid stream (230). These droplets (242) can be re-entrained (315) in the sample fluid stream (230). For example, the droplets (242) may collect on the lip (128) that is upstream of at least a portion of the reverse taper (130). A re-entraining gas flow (250) (e.g., part of a flow of focusing gas (252) from the first gas chamber (154)) can be directed along a flow path to the droplets (242), such as by flowing along the lip (128) and carrying the droplets (242) back into the sample fluid stream (230).
The focusing gas (252) passing through the first inner porous conduit component (152) can also be directed into the sample fluid stream (230) from multiple different sides (e.g., from all around the sample fluid stream (230) so that the focusing gas (252) surrounds the sample fluid stream (230)) to focus (320) the sample fluid stream into a central area away from the surrounding walls of the first inner porous conduit component (152). This focusing (320) can reduce impaction of droplets and/or dry particles from the sample fluid stream (230) from impacting walls of the main conduit (140). Additionally, the reverse taper (130) brings the walls of the main conduit (140) out and away from the sample fluid stream (230), which can also reduce impaction of droplets and/or dry particles from the sample fluid stream (230) on walls of the main conduit (140).
The sample fluid stream (230) can be redirected (325) in the redirection area (104) from the first sample fluid stream direction to a second sample fluid stream direction. A flowing gas sheet (260) can be directed (330) into the sample fluid stream (230) in the redirection area (104), such as through the gas knife (200). The gas sheet (260) can be traveling in a sheet direction that is different from the first sample fluid stream direction. The gas sheet (260) can redirect at least a portion of the sample fluid stream (230) in the redirection area (104). The gas sheet (260) may also break liquid droplets in the sample fluid stream (230), which can promote drying of such droplets. Additionally, the gas sheet (260) can mix a central portion of the sample fluid stream (230) (which can be cooler and wetter than the rest of the sample fluid stream (230)) with other portions of the sample fluid stream (230). This may also promote drying of the overall sample fluid stream (230).
The gas sheet (260) can be wider than the sample fluid stream (230). Also, the gas sheet (260) may be curved and have a high velocity. For example, a velocity of the gas sheet (260) may be greater than a velocity of the sample fluid stream (230). For example, the main fluid stream (232) may be flowing with a velocity of about twenty to about sixty miles per hour, and this velocity may be cut in half in the shroud (110) before the sample fluid stream (230) enters the nozzle inlet (122). The gas sheet (260) may have a velocity that is from fifty to two-hundred miles per hour, such as from one-hundred mile per hour to one-hundred and fifty miles per hour. The source of gas for the gas sheet (260) can be heated so that the gas sheet may be at an elevated temperature, such as a temperature above two-hundred and twelve degrees Fahrenheit, such as 250 degrees Fahrenheit.
The sample fluid stream can be transported (335) from the redirection area (104), such as to the materials monitoring apparatus (180). As noted above, the sample fluid stream (230) can be focused, such as using focusing gas (252). The focusing gas (252) in a first section (e.g., the nozzle area (102)) can be a lower temperature than focusing gas in a second section (e.g., the redirection area (104) and/or the transport area (106)) downstream of the first section. For example, the focusing gas in the second section can be drying gas (270), which can be supplied through the second gas chamber (164) and possibly through subsequent gas chambers (e.g., the third gas chamber (166)). This drying gas (270) can focus the sample fluid stream (230) in the redirection area (104) and/or the transport area (106). The drying gas (270) may be heated to an elevated temperature similar to the temperature of the gas sheet (260). Such high temperatures can heat the sample fluid stream (230) and promote drying of droplets in the sample fluid stream (230). The gases discussed above may be air and/or one or more other gases.
The subject matter defined in the appended claims is not necessarily limited to the benefits described herein. A particular implementation of the invention may provide all, some, or none of the benefits described herein. Although operations for the various techniques are described herein in a particular, sequential order for the sake of presentation, it should be understood that this manner of description encompasses rearrangements in the order of operations, unless a particular ordering is required. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Techniques described herein with reference to flowcharts may be used with one or more of the systems described herein and/or with one or more other systems. Moreover, for the sake of simplicity, flowcharts may not show the various ways in which particular techniques can be used in conjunction with other techniques.
While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
