Abstract:
A sample probe includes a sample probe tip filter and a deflector disposed in relation to the sample probe tip filter, where the deflector is operable to deflect particles in a gas stream away from the sample probe tip filter.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to gas stream sampling and, in particular, to reducing the number of particulates from entering a sample probe at the sampling location of a gas stream. 
         [0002]    Fly ash is one of several pollutant particulate residues generated in the combustion of coal or other fossil fuels by, e.g., boilers or furnaces. Fly ash is generally captured from the chimneys of coal-fired power plants. In the past, fly ash was generally released into the atmosphere, but pollution control equipment mandated in recent decades now requires that the fly ash be captured instead of being released into the environment. In the U.S., the fly ash is now generally collected and stored at the power plant. Depending upon the source and makeup of the coal being burned, the components of the fly ash produced vary considerably, but fly ash typically includes substantial amounts of silicon dioxide (SiO 2 ) (both amorphous and crystalline) and calcium oxide (CaO). Fly ash is commonly used to supplement cement in concrete production, where it can bring both technological and economic benefits, and is increasingly finding use in the synthesis of geopolymers and zeolites. 
         [0003]    However, when sampling a gas stream, for example, in a combustion furnace or boiler operating at relatively high temperatures (e.g., 900° F.-1500° F.), it is generally difficult to continuously separate on-line or in-situ the relatively hot fly ash from the sampling flue gas such that primarily the flue gas is sensed. Removal of fly ash in a relatively substantial amount from the gas sampling stream at or near the sample probe or sensor is needed for typical sampling applications. Failure to reduce the amount of fly ash leads to: 1) ash accumulation within the sampling probe, which may lead to plugging of the probe; and 2) ash accumulation on the analyzer&#39;s sensors, which may reduce or impair the sensing ability and accuracy and also the lifetime of the sensors. 
         [0004]    There exist many techniques to remove fly ash from hot flue gas sampling streams. A common technique is to use a sampling conditioning system to cool down the temperature of the sample flue gas. The separation of fly ash from the sample flue gas stream is then performed via a filtering device such as a fabric filter, cyclone, or other filtering device system. This approach turns out to be cumbersome and expensive due to the additional parts needed. In addition, this type of system usually requires relatively high maintenance due to ash disposal requirements from the filtering system. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    According to one aspect of the invention, a sample probe includes a sample probe tip filter, and a deflector disposed in relation to the sample probe tip filter, where the deflector is operable to deflect particles in a gas stream away from the sample probe tip filter. 
         [0006]    According to another aspect of the invention, a sample probe for sampling flue gas in a gas sampling stream includes a sample probe filter having a tip portion located at one end of the sample probe filter, the tip portion of the sample probe filter being operable to sample the flue gas in the gas sampling stream. The sample probe also includes a deflector disposed in relation to the sample probe filter, the deflector having a length that at least substantially covers the sample probe filter. 
         [0007]    According to yet another aspect of the invention, an extension of a sample probe includes a deflector that connects to a support sleeve pipe, the deflector having a length that extends beyond an end of the support sleeve pipe. 
         [0008]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0010]      FIG. 1  illustrates an embodiment of a sample probe inserted in a flue gas stream; 
           [0011]      FIGS. 2-5  are various side, top, perspective and end views, respectively, that together illustrate a sample probe with a deflector in accordance with an embodiment of the invention; and 
           [0012]      FIG. 6  illustrates a sample probe with a deflector in accordance with another embodiment of the invention. 
       
    
    
       [0013]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    In  FIG. 1  is an embodiment of a sample probe filter  10  inserted in a relatively hot flue gas stream  14  within, e.g., a furnace or boiler. The high temperature flue gas (e.g., 900° F. to 1500° F.) may travel downward as indicated by the lines with arrowheads  18  in  FIG. 1 , and contact the sample probe filter  10  typically at a ninety-degree angle as shown, but may contact the filter  10  at other angles as well. Also, the flue gas may travel in any other direction, such as horizontally through a corresponding horizontally oriented flue gas path. The hot flue gas typically contains undesirable (e.g., pollutant) particulate matter such as fly ash. The flue gas enters the sample probe filter  10  due to a vacuum pressure created by a vacuum system associated with the gas analyzer equipment  22 . The analyzer sample probe  26  also comprises at least one pipe section  30 . The sample probe filter  10  is disposed within the pipe section  30  and a tip portion of the sample probe filter  10  is located at the end of the pipe section  30 , with the pipe section  30  and probe tip filter  10  protruding into the flue gas stream  14 . The pipe section  30  and probe tip filter  10  may be inserted within a support sleeve pipe  34 , which supports the sample probe pipe section(s)  30 . If more than one pipe section  30  is utilized, these sections  30  may be connected together to form one contiguous pipe section  30 . The support sleeve pipe  34  is utilized to avoid bending of relatively long sample probes  26  (e.g., 3-20 feet) inside the furnace. The sample probe tip filter  10  may extend beyond the support sleeve pipe  34  by, e.g., a few inches to collect flue gas  14  from the combustion furnace. The flue gas  14  enters through the probe tip filter  10 , flows through the sample probe pipe section(s)  30  as indicated by the line with the arrowhead  38  in  FIG. 1 , and through the sensors within the analyzer  22 . The sampled flue gas is then released back into the hot combustion furnace gas stream  14  via a gas pathway indicated by the line with the arrowhead  42  in  FIG. 1  and defined between the support sleeve pipe  34  and the sample probe pipe section(s)  30 . 
         [0015]    In  FIGS. 2-5  taken together is a sample probe tip filter  50  with a deflector  54 , which reduces the amount of fly ash particulates that impinge on the probe tip filter  50  according to an embodiment of the invention. In this embodiment, the deflector  54  may comprise a heavy gauge metal or other suitable material in the form of a shield having any number of suitable forms and shapes. For example, the deflector  54  may comprise an inverted “V”-shaped angled shield as illustrated in  FIG. 5 . However, the shape of the deflector may be round, flat or some other suitable shape, as desired. The deflector  54  may, in an embodiment, be added on top of and at the end of, and thus connected to, the support sleeve pipe  58  (see the side and perspective views of  FIGS. 2 and 4 , respectively). However, other embodiments may omit the support sleeve pipe  58 , and the deflector  54  may be connected to other items, such as the analyzer  22  using appropriate means. If the support sleeve pipe  58  is included, the deflector  54  need not necessarily be connected to the support sleeve pipe  58  or may be indirectly connected to the support sleeve pipe  58  through other means. If connected to the support sleeve pipe  58 , the deflector  54  may be an extension of the support sleeve pipe  58 . The deflector  54  may be attached to the support sleeve pipe  58  via metal rods, a metal piece or by other suitable mechanical support devices  62  (see the side and end views of  FIGS. 2 and 5 , respectively). The length of the deflector  54  may, in an embodiment, be such that it substantially covers the sample probe tip filter  50 , regardless of whether or not the deflector  54  is connected to the support sleeve pipe  58 . The deflector  54  may be set at an elevation of, e.g., a few inches above the sample probe tip filter  50 . In this configuration, the deflector  54  is disposed upstream of the sample probe tip filter  50  in the hot flue gas stream  14  ( FIG. 1 ). 
         [0016]    The purposes of the deflector  54  are to: 1) deflect (and, thus, reduce) a substantial amount of the fly ash particulates from directly entering into and accumulating onto the sample probe tip filter  50  (e.g., so that primarily the hot flue gas enters the sample probe tip filter  50  and ultimately the analyzer  22  for sampling thereby); and 2) prevent the high velocity flue gas from directly contacting the sample probe tip filter  50 , which could damage the filter  50  over time. Typically the deflector  54  will deflect the relatively larger fly ash particles from entering the sample probe tip filter  50  and only allow the relatively smaller fly ash particulates along with the flue gas to enter the sample probe tip filter  50 . 
         [0017]    The design of the sample probe tip filter  50  may vary between applications, but in one embodiment the filter  50  may comprise a fabric filter inserted inside one or more concentric pipes  64  with open slots  66  along the lengths of the concentric pipes  64  ( FIG. 2 ). In the alternative, the support sleeve pipe  58  may be extended to some distance over the sample probe tip filter  50  and thus have the open slots  66  or other holes or perforations formed therein. In embodiments, the sample probe tip filter openings  66  may begin at approximately six to ten inches (or any other suitable distance greater than or less than 6-10 inches) past the end of the support sleeve pipe  58 . The openings  66  help to avoid any analyzer exhaust sample gas from the support sleeve pipe  58  or the concentric pipes  64  from recirculating back to and into the sample probe tip filter  50 . The analyzer exhaust sample gas may undesirably affect the accuracy of the sampling of the flue gas if the exhaust sample gas were to recirculate back into the analyzer  22 , and the distance from the beginning of the openings  66  from the end of the support sleeve pipe  58  may be chosen as needed to avoid any such undesirable recirculation. 
         [0018]    In  FIG. 6  is another embodiment of a sample probe tip filter  70  with a deflector  74  utilized again to reduce the amount of fly ash that impinges on the probe tip filter  70 . This embodiment is somewhat similar to the previous embodiment of  FIGS. 2-5 , but instead of using a separate deflector  54 , the support sleeve pipe  78  is extended by an additional half-pipe section support sleeve length  74 . The half pipe section deflector  74  may be considered an extension of the support sleeve pipe  78 , and its length may, in an embodiment, be such that it substantially covers the sample probe tip filter  70  extending from the support sleeve pipe  78 . As with the embodiment of  FIGS. 2-5 , in the embodiment of  FIG. 6  the half pipe section deflector  74  is disposed upstream of the sample probe tip filter  70  in the flue gas stream  14  ( FIG. 1 ). 
         [0019]    The purposes of the half pipe section support sleeve deflector  74  are similar to those of the deflector  54  of the embodiment of  FIGS. 2-5 ; that is, to: 1) deflect (and, thus, reduce) a substantial amount of the fly ash particulates from directly entering into and accumulating onto the sample probe tip filter  70  (e.g., so that primarily the hot flue gas enters the sample probe tip filter  70  and ultimately the analyzer  22  for sampling thereby); and 2) prevent high velocity flue gas from directly contacting the sample probe tip filter  70 , which could damage the filter  70  over time. The support sleeve  74  does not need to be a half pipe. Instead, the support sleeve may comprise some other portion of a completely enclosed pipe (e.g., a one-third section, a one-quarter section, or any other angled amount less than a full 360 degree circumferential pipe section. Alternatively, if the support sleeve pipe  78  is something other than of cylindrical shape (e.g., a square opening), then the support sleeve  74  may be a portion of that other shape or even a different shape. The design of the sample probe tip filter  70  may vary between applications, but in one embodiment may comprise a fabric filter inserted inside one or more concentric pipes with openings in the form of open slots, perforations, etc. located along the length of the concentric pipes, similar to the embodiment shown in  FIG. 2 . As with the embodiment of  FIGS. 2-5 , in the embodiment of  FIG. 6  the sample probe tip filter slot openings may begin at approximately six inches (or some other suitable distance) past the end of the support sleeve pipe  78  to avoid any analyzer exhaust sample gas from the support sleeve pipe  78  to recirculate into the sample probe tip filter  70 . Also, the half pipe support sleeve deflector  74  may have one or more openings formed therein for similar reasons. 
         [0020]    Embodiments of the invention reduce the amount of hot temperature fly ash from entering into the sampling flue gas analyzer system. This allows for in-situ separation of fly ash from sample flue gas streams in hot temperature furnaces with little or no maintenance required. Embodiments of the present invention may be used to continuously sample flue gas in a hot furnace that carries high loads of fly ash or dust particulates, such as coal fired boiler units, cement kilns or other plants with relatively high particulate loads in their furnace. 
         [0021]    Embodiments of the invention comprise filtering concepts that meet the following criteria: 1) reduce the amount of fly ash particulates that enter into the flue gas analyzer sampling system by segregating a substantial amount of the fly ash particulates from the gas sampling stream; 2) protect the sample probe tip filter from any damage that may be caused by high velocity of flue gases, proximity of soot blowers or other damaging devices, by diverting the hot flue gases away from direct contact with the sample probe filter tip; and 3) applies to hot temperature gases in the range of about 900° F. to about 1500° F. This allows embodiments of the invention to perform in-situ hot flue gas sampling in hot combustion furnaces or boilers with relatively high loads of particulates such as fly ash, thereby allowing the flue gas analyzer to be used in a broader range of environmentally harsh dust conditions. 
         [0022]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.