Abstract:
A spray dryer disperser  24, 26, 28, 30  is described for use in a spray dryer absorption (SDA) system  18  for flue gas FG impurity reduction. As such, the spray dryer disperser  24, 26, 28, 30  disperses absorbent liquid or reagent slurry droplets into contact with a hot flue gas FG stream containing gaseous impurities to produce a flue gas FG stream of reduced impurity content and dry powder end products EP. The spray dryer disperser  24, 26, 28, 30  is useful in larger capacity SDA vessels  22  of approximately 12 to 22 meters in diameter or larger, to avoid disperser  24, 26, 28, 30  shroud  34   a  scale deposits, to avoid reagent slurry spray cloud suppression, to avoid vessel  22  wall  22   b  scale deposits and to achieve increased droplet rotational momentum for increased droplet flue gas FG penetration for efficient impurity reduction.

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to a spray dryer disperser for use in a spray dryer absorption (SDA) system for contacting a hot flue gas stream containing gaseous impurities with an absorbent material to produce a flue gas stream of reduced impurity content and dry powder products. More specifically, the present disclosure relates to a relatively high rotational momentum disperser for use in a relatively larger capacity SDA vessel of approximately 12 to approximately 22 meters or larger in diameter, that avoids disperser shroud deposits, avoids spray cloud suppression, avoids vessel wall deposits and achieves extended droplet penetration for required impurity removal efficiency with reduced absorbent material consumption. 
     BACKGROUND OF THE DISCLOSURE 
     Combustion of fuel, particularly carbonaceous materials such as fossil fuels and waste, results in hot flue gas streams that contain impurities, such as mercury (Hg), sulfur oxides (SOx), nitrogen oxides (NOx), and particulates, such as fly ash, which must be removed or reduced to a more acceptable level prior to release of the flue gas to the environment. In response to regulations in place in many jurisdictions, numerous processes and equipment systems have been developed to remove or reduce impurity levels and/or particulates in flue gas. 
     Typical methods of reducing flue gas particulates, Hg, NOx, and SOx impurities from steam generating boilers powered by fuel combustion is through the use of flue gas treatment equipment. Such equipment includes electrostatic precipitators (ESP), fabric filter bag houses, selective catalytic reduction (SCR) systems, wet flue gas desulfurization (WFGD) systems and/or dry flue gas desulfurization (DFGD) systems. 
     In some flue gas stream processing systems, removal of acidic components, such as SOx, is facilitated through the use of a DFGD system, wherein a reagent slurry or solution is dispersed in the flue gas stream to react with the SOx present therein. Current DFGD systems utilize spray dryer absorber vessels equipped with an atomizer system that receives a reagent slurry, typically in combination with a dilution liquid, and disperses it within the vessel for contact with the flue gas. Upon contact, the reagent slurry reacts with the impurities to produce dry powder products and a flue gas stream of reduced impurity content. 
     U.S. Pat. No. 4,226,603 discloses an atomizing device arranged centrally in an atomizing chamber. A processing gas is supplied around the atomizing device through a conical guide duct communicating with a horizontal spiral duct through an annular mouth. Processing gas distribution is adjusted by deflection of the gas stream from the spiral duct into the conical guide duct by means of two separate sets of stationary guide vanes arranged relatively close to and overlaying each other in the mouth. A damper is arranged along the mouth to control the ratio of the portions of the gas stream conducted into each of the two vane sets. 
     U.S. Pat. No. 4,481,171 discloses a spray reactor for flue gas desulfurization equipped with an atomizing disc to spray an alkaline reagent into the flue gas. Concentric inner and outer annular passages around the atomizing disc convey the flue gas. The outer passage flow is controlled by a series of dampers adapted to maintain a relatively constant flow velocity in the inner passage in response to turndown of the load. 
     U.S. Pat. No. 4,519,990 discloses an atomizer located in an upper portion of a chamber for introducing a finely dispersed spray of aqueous medium, and a gas injection means for receiving a major portion of a hot gas stream for introduction circumferentially about the atomizer. An essential feature of the apparatus is that a minor portion of the hot gas stream is introduced into the chamber in a direction counter to the direction of swirl of the major portion of the hot gas stream passing downwardly through the chamber from about the atomizer. 
     U.S. Pat. No. 4,560,543 discloses an absorption chamber in which a stream of waste gas is injected downwards from an upper part thereof with an aqueous liquid containing an absorbent atomized into the gas stream. The water content of the aqueous liquid is adjusted depending on the drying capacity of the downward gas stream so the drying of the atomized liquid produces a particulate material having a moisture content of at least 3 percent by weight, to at least 10 percent by weight. A second gas stream is introduced upwards from a bottom part of the absorption chamber at a rate sufficient for fluidizing the moist particulate material within the absorption chamber. 
     U.S. Pat. No. 4,571,311 discloses a process gas treatment chamber with a pair of concentric, inner and outer annular gas inlet ducts surrounding a liquid spray apparatus. Partition means divide a spiral supply duct into independent inner and outer sub-ducts which define separate inner and outer flow passages connected respectively to the inner and outer annular gas inlet ducts. Damper means are provided in the inlet to the outer sub-duct to selectively control the flow of process gas there through as a means of maintaining the velocity of the flow of process gas through the inner flow passage at a minimum acceptable velocity. 
     U.S. Pat. No. 4,619,404 discloses a gas distribution arrangement with a helical inlet duct through an annular orificial slit for processing gas introduction into a space between two coaxial guide walls. Guide vanes are provided in the orificial slit to impart a change of direction to the flow of processing gas. Each guide vane is a spatial body with differently extending, vertical limitation surfaces which between adjacent vanes delimit ducts whose sectional area as measured transversely of the flow direction of the processing gas through the individual duct is substantially of the same size over the extent of the duct. The vertical height of the guide vanes may decrease along their radial extent inwards in the orificial slit, and their vertical limitation surfaces may form an acute angle at the radially innermost ends of the guide vanes. 
     Delivery of a reagent slurry or solution to an atomizer system such as one or more of those described above, in combination with a dilution liquid, typically results in scale buildup. Scale buildup causes plant or system shut downs for necessary cleaning and/or maintenance. Plant or system shut downs, as well as the related cleaning and maintenance of the system and/or plant, is time consuming and costly. 
     Further, in the case of larger capacity SDA vessels of approximately 12 to approximately 22 meters or larger in diameter, which are desirable to reduce capital expenditures and reduce equipment footprint requirements, scale buildup is even a greater issue. Current dispersers do not allow slurry droplets to penetrate the flue gas sufficiently under higher volume flue gas stream flow as characteristic through the larger capacity SDA vessels. The higher volume flue gas stream thereby readily suppresses downwardly the droplet spray cloud within the SDA vessel. Droplet spray cloud suppression in turn causes poor contact between the reagent slurry and flue gas, resulting in low SO x  removal efficiency. Attempts to address low SO x  removal efficiency by using an increased number of dispersers within the larger capacity SDA vessels of approximately 12 to approximately 22 meters or larger in diameter, results in additional problems. Such additional problems include intense droplet impactions on vessel walls and significant scale buildup thereon with associated high reagent consumption and cost. Accordingly, an efficient and economical disperser for use in larger capacity SDA vessels of approximately 12 to approximately 22 meters or larger in diameter, that avoids disperser shroud deposits, avoids spray cloud suppression, avoids vessel wall deposits and achieves extended droplet penetration through the flue gas for required impurity removal efficiency with reduced absorbent material consumption is needed. 
     SUMMARY OF THE DISCLOSURE 
     A relatively high rotational momentum disperser is disclosed herein operable for efficient atomized slurry distribution across a relatively larger capacity spray dryer absorption (SDA) vessel of approximately 12 to approximately 22 meters or larger in diameter, while avoiding disperser shroud deposits, avoiding spray cloud suppression, avoiding vessel wall deposits and achieving extended droplet penetration through the flue gas for required impurity removal efficiency with reduced absorbent material consumption. 
     The subject SDA system equipped with a relatively larger capacity SDA vessel of approximately 12 to approximately 22 meters or larger in diameter is operative for efficiently removing gaseous pollutants from a hot flue gas stream. The subject SDA system comprises a SDA vessel of approximately 12 to approximately 22 meters or larger in diameter defining an interior chamber with one or more relatively high rotational momentum dispersers of approximately 4 to approximately 5 meters in diameter mounted at a roof of the interior chamber. Each such relatively high rotational momentum disperser is operative for dispersing a portion of the hot flue gas to be treated around a respective atomizer. Each atomizer is operative for atomizing and dispersing an absorption liquid, such as a reagent slurry, within the interior chamber for contact with, reaction with, and absorption of gaseous pollutants from the hot flue gas. 
     The subject relatively high rotational momentum disperser for use in a relatively larger capacity SDA vessel of approximately 12 to approximately 22 meters or larger in diameter, includes three annular channels formed concentrically around a central atomizer. The three annular channels include an inner channel, a middle channel and an outer channel. The inner channel is approximately 10 centimeters to approximately 20 centimeters in width, or approximately 15 centimeters in width extending around and adjacent to a central atomizer. The inner channel provides a constant flow area meaning that the width of the inner channel is slightly larger at the outlet bottom than at the inlet top. Optionally, the inner channel may include a vane pack comprising a plurality of approximately 8 to approximately 12 rotational vanes. Each vane in the vane pack is of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical. In using the subject disperser, hot flue gas flowing through the inner channel is imparted a relatively strong downward rotational flow to deflect the direction of dispersal of atomized slurry droplets radially downwardly to avoid slurry deposits or build-up on the disperser shroud. Around and immediately adjacent to the inner channel is a middle channel. 
     The middle channel houses a vane pack comprising a plurality of approximately 20 to approximately 30, or approximately 25 rotational vanes. Each vane in the vane pack is of a like angle of approximately 35 degrees to approximately 45 degrees, or approximately 40 degrees from vertical. The middle channel is sized to provide approximately 65 to approximately 80 percent of the total flow area of the disperser. As such, each the inner channel and the outer channel is sized to provide approximately 7 to approximately 15 percent of the total flow area of the disperser. In using the subject disperser, hot flue gas flowing through the angled rotating vanes of the middle channel is imparted a relatively strong rotational movement that extends penetration of the slurry droplets into a greater proportion of the hot flue gas flowing from the disperser throughout the interior chamber. The rotational movement imparted to flue gas flowing through the middle channel is of the same clockwise or counter clockwise direction as that imparted to the flue gas by the inner channel should an optional vane pack be utilized there as well. Around and immediately adjacent to the middle channel, with an outer wall defined by the disperser housing, is the outer channel. 
     The outer channel is approximately 10 centimeters to approximately 18 centimeters in width, or approximately 13 centimeters to approximately 15 centimeters in width. In using the subject disperser, hot flue gas flowing through the outer channel is imparted a relatively strong downward flow that deflects the direction of slurry droplet dispersal from radial to axial relative to the rotational axis of the atomizer. This deflection of direction of slurry droplet dispersal avoids slurry droplets from impacting the interior chamber walls thus reducing or avoiding deposit formation thereon. 
     In summary, the subject SDA system for flue gas impurity reduction comprises a vessel defining an interior chamber of approximately 12 to Approximately 22 meters or larger in diameter. One or more dispersers are arranged in a roof of the interior chamber with an atomizer for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across the interior chamber, centered therein and surrounded by a flow directing device. The flow directing device comprises three annular channels formed concentrically around the atomizer for a flow of flue gas therethrough. Of the three annular channels, the inner channel without vanes, or optionally with a vane pack comprising a plurality of approximately 8 to approximately 12 rotational vanes of like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud. The middle channel comprises a plurality of rotational vanes angled approximately 35 degrees to approximately 55 degrees from vertical to increase droplet rotational momentum and droplet penetration through the flue gas stream, and the outer channel reduces scale formation on interior chamber walls. The absorption liquid or reagent slurry droplets dispersed by the atomizer absorb flue gas impurities and dry to form a powder end product collected in the interior chamber. 
     The subject disperser for an interior chamber defined by a spray dryer absorption vessel, is approximately 4 meters or larger in diameter and comprises an atomizer for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across the interior chamber. The atomizer is centered within the disperser and surrounded by a flow directing device. The flow directing device surrounding the atomizer comprises three annular channels for a flow of flue gas therethrough. Of the three annular channels, the inner channel without vanes, or optionally with a vane pack comprising a plurality of approximately 8 to approximately 12 rotational vanes of like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud. The middle channel comprises a plurality of rotational vanes angled approximately 35 degrees to approximately 55 degrees from vertical to increase droplet rotational momentum for efficient flue gas penetration and flue gas impurity reduction. The outer channel reduces scale formation on interior chamber walls. The absorption liquid or reagent slurry droplets atomized and dispersed by the atomizer absorb flue gas impurities and dry to form a powder end product collected in the interior chamber. 
     A method of using the subject spray dryer absorption system for flue gas impurity reduction comprises providing a vessel defining an interior chamber of approximately 12 to approximately 22 meters or larger in diameter and arranging one or more dispersers of approximately 4 meters or larger in diameter in a roof of the interior chamber. An atomizer for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across the interior chamber is centered within the disperser and surrounded by a flow directing device. The flow directing device comprises three annular channels formed concentrically around the atomizer for a flow of flue gas therethrough. Of the three annular channels, the inner channel without vanes, or optionally with a vane pack comprising a plurality of approximately 8 to approximately 12 rotational vanes of like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud. The middle channel comprises a plurality of rotational vanes angled approximately 35 degrees to approximately 55 degrees from vertical to increase droplet rotational momentum and flue gas penetration, and the outer channel reduces scale formation on interior chamber walls. Droplets atomized and dispersed by the atomizer absorb impurities from the flue gas for flue gas impurity reduction. Also, the absorption liquid or reagent slurry droplets dry to form a powder end product collected in the interior chamber. 
     A method of using the subject disperser for flue gas impurity reduction comprises providing a vessel defining an interior chamber of approximately 12 to approximately 22 meters or larger in diameter, and arranging one or more dispersers of approximately 4 meters or larger in diameter in a roof of the interior chamber. An atomizer for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across the interior chamber is centered within the disperser, and surrounded by a flow directing device. The flow directing device comprises three annular channels formed concentrically around the atomizer for a flow of flue gas therethrough. Of the three annular channels, the inner channel without vanes, or optionally with a vane pack comprising a plurality of approximately 8 to approximately 12 rotational vanes of like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud. The middle channel comprises a plurality of rotational vanes angled approximately 35 degrees to approximately 55 degrees from vertical to increase droplet rotational momentum and flue gas penetration, and the outer channel reduces scale formation on interior chamber walls. Droplets atomized and dispersed by the atomizer absorb impurities from the flue gas for flue gas impurity reduction. Additionally, the droplets dry to form a powder end product collected in the interior chamber. 
     A method of making the subject spray dryer absorption system for flue gas impurity reduction comprises providing a vessel defining an interior chamber of approximately 12 to approximately 22 meters or larger in diameter, and arranging one or more dispersers approximately 4 meters or larger in diameter in a roof of the interior chamber. An atomizer for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across the interior chamber, is centered within the disperser and surrounded by a flow directing device. The flow directing device comprises three annular channels formed concentrically around the atomizer for a flow of flue gas therethrough. Of the three annular channels, the inner channel without vanes, or optionally with a vane pack comprising a plurality of approximately 8 to approximately 12 rotational vanes of like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud. The middle channel comprises a plurality of rotational vanes angled approximately 35 degrees to approximately 55 degrees from vertical to increase droplet rotational momentum and flue gas penetration, and the outer channel reduces scale formation on interior chamber walls. Droplets atomized and dispersed by the atomizer absorb impurities from the flue gas for flue gas impurity reduction and dry to form a powder end product collected in the interior chamber. 
     A method of making the subject disperser for flue gas impurity reduction comprises centering an atomizer for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across an interior chamber defined by a vessel of approximately 12 to approximately 22 meters or larger in diameter, and surrounding the atomizer with a flow directing device. The flow directing device comprises three annular channels formed concentrically around the atomizer for a flow of flue gas therethrough. Of the three annular channels, the inner channel without vanes, or optionally with a vane pack comprising a plurality of approximately 8 to approximately 12 rotational vanes of like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud. The middle channel comprises a plurality of rotational vanes angled approximately 35 degrees to approximately 55 degrees from vertical to increase droplet rotational momentum and flue gas penetration, and the outer channel reduces scale formation on interior chamber walls. Droplets atomized and dispersed by the atomizer absorb impurities from the flue gas for flue gas impurity reduction and dry to form a powder end product collected in the interior chamber. 
     Additional features and advantages of the subject disclosure will be readily apparent from the following description in which a preferred embodiment has been set forth in detail in conjunction with accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject disclosure will now be described in more detail with reference to the appended drawings in which: 
         FIG. 1  is a schematic side view of a power plant; 
         FIG. 2  is a schematic side perspective view of a disperser of  FIG. 1  in accordance with one embodiment of the present invention; and 
         FIG. 3  is a schematic side cross-sectional view taken along line  3 - 3  of a disperser of  FIG. 2  in accordance with the embodiment of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic side view illustrating a power plant  10 . The power plant  10  comprises a boiler  12  in which a fuel F, such as coal or oil, is combusted. The combustion of the fuel generates a hot process gas in the form of a flue gas FG. Sulphur species contained in the coal or oil produce upon combustion sulphur dioxide, which forms part of the flue gas FG. The flue gas FG flows from the boiler  12  to a fluidly connected electrostatic precipitator  14  via a duct  16 . The electrostatic precipitator  14 , an example of which is described in U.S. Pat. No. 4,502,872, the teachings of which incorporated herein by reference, serves to remove dust particles from the flue gas FG. 
     Flue gas FG, from which most of the dust particles have been removed, then flows to a fluidly connected spray dryer absorber (SDA) system  18  via a fluidly connected duct  20 . The SDA system  18  comprises a relatively larger capacity SDA vessel  22  of approximately 12 to approximately 22 meters or larger in diameter. SDA vessel  22  defines interior chamber  22   a . One or more dispersers,  24 ,  26 ,  28 ,  30  of approximately 4 to approximately 5 meters in diameter are mounted at a roof  32  of the interior chamber  22   a . Each disperser  24 ,  26 ,  28 ,  30  comprises an atomizer  34 . The atomizers  34  could be of the so-called rotary atomizer type, in which a wheel spinning at a high velocity is operative for atomizing an absorption liquid or a reagent slurry. In this regard, reference may be had by way of exemplification and not limitation, to the rotary atomizer described in U.S. Pat. No. 4,755,366, the teachings of which incorporated herein by reference. A further alternative is to utilize as atomizers  34  atomizing nozzles which atomize an absorption liquid or reagent slurry supplied thereto under pressure. 
     Each disperser  24 ,  26 ,  28 ,  30  also comprises a flow directing device  36 ,  38 ,  40 ,  42 . A dividing duct  44  supplies each of the fluidly connected dispersers  24 ,  26 ,  28 ,  30  with a portion of the flue gas FG from fluidly connected duct  20 . Each of the flow directing devices  36 ,  38 ,  40 ,  42  is operative for imparting the respective portion of flue gas FG flowing therethrough with movement, described in greater detail below, around atomizers  34  of the respective dispersers  24 ,  26 ,  28 ,  30 . 
     A supply source or tank  46  supplies each fluidly connected atomizer  34  with a flow of an absorption liquid or reagent slurry via fluidly connected distributing pipe  48 . Such absorption liquid or reagent slurry comprises, for example, a limestone slurry with a dilution liquid of, for example, water. 
     The action of the respective dispersers  24 ,  26 ,  28 ,  30  result in the mixing of flue gas FG with the absorption liquid or reagent slurry within interior chamber  22   a . The result is that the absorption liquid or reagent slurry absorbs gaseous pollutants, such as sulphur dioxide, SO 2 , from the flue gas FG. At the same time the absorption liquid or reagent slurry absorbs the gaseous pollutants, the absorption liquid or reagent slurry is dried by the hot flue gas FG, producing a dry end product EP. The dry end product EP is collected at the bottom  50  of the interior chamber  22   a . The dry end product EP is removed for disposal via a pipe  52  fluidly connected to interior chamber  22   a . Flue gas FG, from which most of the gaseous pollutants have been removed, flows out of the SDA system  18  via a fluidly connected duct  54 . As such, flue gas FG flows through duct  54 , to a second filter  56 , which may, for example, be an electrostatic precipitator. As alternative option, the second filter  56  may be a bag house or any other suitable filtering device. The second filter  56  removes most of the remaining dust particles, and any dried residues of the absorption liquid or reagent slurry entrained in the flue gas FG. A cleaned flue gas CG may then be released into the environment via a clean gas duct  58  fluidly connected to second filter  56 . 
       FIGS. 2 and 3  illustrate the subject disperser  26  in more detail. The subject relatively high rotational momentum disperser  26  for use in a relatively larger capacity SDA vessel  22  of approximately 12 to approximately 22 meters or larger in diameter, includes three annular channels  60 ,  62   64  formed concentrically around a central atomizer  34 . The three annular channels  60 ,  62 ,  64  include an inner channel  60 , a middle channel  62  and an outer channel  64 . The inner channel  60  extending around and adjacent to a central atomizer  34  is approximately 10 centimeters to approximately 20 centimeters in width Wi, or approximately 15 centimeters in width Wi measuring from central atomizer  34  to first wall  66 . Optionally, the inner channel  60  may include a vane pack  60   a  comprising a plurality of approximately 8 to approximately 12 rotational vanes  60   b . Each vane  60   b  in the vane pack  60   a  is of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical. In using the subject disperser  26 , hot flue gas FG flowing through the disperser  26  and inner channel  60  of flow directing device  38  is imparted a relatively strong downward rotational flow to deflect the dispersal direction of atomized liquid or slurry droplets radially downwardly and outwardly to avoid liquid or slurry deposits on the disperser shroud  34   a . Around and immediately adjacent to the inner channel  60  is a middle channel  62 . 
     The middle channel  62  extending around and adjacent to inner channel  60  is sized to provide approximately 65 to approximately 80 percent of the total flow area of the disperser  26 . As such, each the inner channel  60  and the outer channel  64  is sized to provide approximately 7 to approximately 15 percent of the total flow area of the disperser  26 . The middle channel  62  extends around and adjacent to inner channel  60  and is approximately 20 centimeters to approximately 40 centimeters in width Wm, or approximately 30 centimeters in width Wm measuring from first wall  66  to second wall  72 . Middle channel  62  houses a vane pack  70  comprising a plurality of approximately 10 to approximately 40 or approximately 20 to approximately 30 rotational vanes  70   a . Each vane  70   a  in the vane pack  70  is of a like angle of approximately 35 degrees to approximately 55 degrees, or approximately 40 to approximately 50 degrees, or approximately 45 degrees, from vertical. In using the subject disperser  26 , hot flue gas FG flowing through angled rotating vanes  70   a  of the middle channel  62  is imparted a relatively strong rotational movement that extends penetration of the liquid or slurry droplets into a greater proportion of the hot flue gas FG flowing from the disperser  26  throughout the interior chamber  22   a . The rotational movement imparted to flue gas FG flowing through middle channel  62  is of the same clockwise CW or counter clockwise CCW direction as that imparted to the flue gas FG by the inner channel  60 . In using the subject disperser  26 , hot flue gas FG flowing through the disperser  26  and the middle channel  62  of flow directing device  38  is deflected by angled rotating vanes  70   a  housed within middle channel  62  and thereby imparted a relatively strong rotational movement. In the case of disperser  26 , this rotational movement is clockwise CW as illustrated by curved arrows in  FIG. 2 . However, as understandable to those skilled in the art, counter clockwise rotational movement could just as easily be imparted if desired by reversing the angle of vanes  70   a . As such, the relatively strong rotational movement imparted to the hot flue gas FG by the relatively largely angled rotating vanes  70   a  increases the rotational momentum of and extends the penetration of the liquid or slurry droplets into a greater proportion of the hot flue gas FG flowing from disperser  26  throughout the interior chamber  22   a . Around and immediately adjacent to the middle channel  62  is an outer channel  64 . 
     Outer channel  64  is approximately 10 centimeters to approximately 20 centimeters in width Wo, or approximately 15 centimeters in width Wo measuring from second wall  72  to disperser housing  68 . In using the subject disperser  26 , hot flue gas FG flowing through the disperser  26  and the outer channel  64  of flow directing device  38  is imparted a relatively strong downward flow that deflects the direction of liquid or slurry droplet dispersal from radial to axial relative to the rotational axis of the atomizer  34 . This axial downward velocity is approximately 18 m/s or greater. This direction deflection of liquid or slurry droplet dispersal avoids liquid or slurry droplets from impacting walls  22   b  of interior chamber  22   a  thus reducing or avoiding deposit formation thereon. 
     In summary, the subject SDA system  18  for flue gas FG impurity reduction comprises a vessel  22  defining an interior chamber  22   a  of approximately 12 to approximately 22 meters or larger in diameter. One or more dispersers  24 ,  26 ,  28 ,  30  are arranged in a roof  32  of the interior chamber  22   a  with an atomizer  34  for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across interior chamber  22   a , centered therein and surrounded by a flow directing device  36 ,  38 ,  40 ,  42 . The flow directing device  36 ,  38 ,  40 ,  42  comprises three annular channels  60 ,  62 ,  64  formed concentrically around the atomizer  34  for a flow of flue gas FG therethrough. Of the three annular channels  60 ,  62 ,  64 , an inner channel  60  without or optionally with a vane pack  60   a  comprising a plurality of approximately 8 to approximately 12 rotational vanes  60   b  of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud  34   a . A middle channel  62  comprising a plurality of rotational vanes  70   a  angled approximately 35 degrees to approximately 55 degrees, or approximately 40 degrees to approximately 50 degrees, or approximately 45 degrees from vertical increase droplet rotational momentum and droplet penetration through the flue gas FG stream. An outer channel  64  reduces scale formation on interior chamber  22   a  walls  22   b . The absorption liquid or reagent slurry droplets dispersed by the atomizer  34  absorb flue gas FG impurities and dry to form a powder end product EP collected in the interior chamber  22   a.    
     The subject disperser  24 ,  26 ,  28 ,  30  for a spray dryer absorption vessel  22  defining an interior chamber  22   a  of approximately 12 to approximately 22 meters or larger in diameter comprises an atomizer  34  for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across interior chamber  22   a , centered within the disperser  24 ,  26 ,  28 ,  30  and surrounded by a flow directing device  36 ,  38 ,  40 ,  42 . The flow directing device  36 ,  38 ,  40 ,  42  surrounding the atomizer  34  comprises three annular channels  60 ,  62 ,  64  for a flow of flue gas FG therethrough. Of the three annular channels  60 ,  62 ,  64 , an inner channel  60  without or optionally with a vane pack  60   a  comprising a plurality of approximately 8 to approximately 12 rotational vanes  60   b  of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud  34   a . A middle channel  62  comprises a plurality of rotational vanes  70   a  angled approximately 35 degrees to approximately 55 degrees, or approximately 40 degrees to approximately 50 degrees, or approximately 45 degrees from vertical to increase droplet rotational momentum for efficient flue gas FG penetration for flue gas FG impurity reduction. An outer channel  64  reduces scale formation on interior chamber  22   a  walls  22   b . The absorption liquid or reagent slurry droplets atomized and dispersed by the atomizer  34  absorb flue gas FG impurities and dry to form a powder end product EP collected in the interior chamber  22   a.    
     A method of using the subject spray dryer absorption system  18  for flue gas FG impurity reduction comprises providing a vessel  22  defining an interior chamber  22   a  of approximately 12 to approximately 22 meters or larger in diameter and arranging one or more dispersers  24 ,  26 ,  28 ,  30  in a roof  32  of the interior chamber  22   a . An atomizer  34  for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across interior chamber  22   a , is centered within the disperser  24 ,  26 ,  28 ,  30 . Surrounding the atomizer  34  is a flow directing device  36 ,  38 ,  40 ,  42  comprising three annular channels  60 ,  62 ,  64  formed concentrically around the atomizer  34  for a flow of flue gas FG therethrough. Of the three annular channels  60 ,  62 ,  64 , an inner channel  60  without or optionally with a vane pack  60   a  comprising a plurality of approximately 8 to approximately 12 rotational vanes  60   b  of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud  34   a . A middle channel  62  comprises a plurality of rotational vanes  70   a  angled approximately 35 degrees to approximately 55 degrees, or approximately 40 degrees to approximately 50 degrees, or approximately 45 degrees from vertical to increase droplet rotational momentum and flue gas FG penetration. An outer channel  64  reduces scale formation on interior chamber  22   a  walls  22   b . Droplets atomized and dispersed by the atomizer  34  absorb impurities from the flue gas FG for flue gas FG impurity reduction. Also, the absorption liquid or reagent slurry droplets dry to form a powder end product EP collected in the interior chamber  22   a.    
     A method of using the subject disperser  24 ,  26 ,  28 ,  30  for flue gas FG impurity reduction comprises providing a vessel  22  defining an interior chamber  22   a  of approximately 12 to approximately 22 meters or larger in diameter, arranging one or more dispersers  24 ,  26 ,  28 ,  30  in a roof  32  of the interior chamber  22   a , and centering an atomizer  34  for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across the interior chamber  22   a . The atomizer  34  centered within the disperser  24 ,  26 ,  28 ,  30 , is surrounded by a flow directing device  36 ,  38 ,  40 ,  42  comprising three annular channels  60 ,  62 ,  64  formed concentrically around the atomizer  34  for a flow of flue gas FG therethrough. Of the three annular channels  60 ,  62 ,  64 , an inner channel  60  without or optionally with a vane pack  60   a  comprising a plurality of approximately 8 to approximately 12 rotational vanes  60   b  of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud  34   a . A middle channel  62  comprises a plurality of rotational vanes  70   a  angled approximately 35 degrees to approximately 55 degrees, or approximately 40 degrees to approximately 50 degrees, or approximately 45 degrees from vertical to increase droplet rotational momentum and flue gas FG penetration. An outer channel  64  reduces scale formation on interior chamber  22   a  walls  22   b . Droplets atomized and dispersed by the atomizer  34  absorb impurities from the flue gas FG for flue gas FG impurity reduction. Additionally, the droplets dry to form a powder end product EP collected in the interior chamber  22   a.    
     A method of making the subject spray dryer absorption system  18  for flue gas FG impurity reduction comprises providing a vessel  22  defining an interior chamber  22   a  of approximately 12 to approximately 22 meters or larger in diameter, arranging one or more dispersers  24 ,  26 ,  28 ,  30  in a roof  32  of the interior chamber  22   a , and centering an atomizer  34  for atomization and dispersal of absorption liquid or a reagent slurry droplets therefrom across the interior chamber  22   a . Within the disperser  24 ,  26 ,  28 ,  30 , and surrounding the atomizer  34  is a flow directing device  36 ,  38 ,  40 ,  42  comprising three annular channels  60 ,  62 ,  64  formed concentrically around the atomizer  34  for a flow of flue gas FG therethrough. Of the three annular channels  60 ,  62 ,  64 , an inner channel  60  without or optionally with a vane pack  60   a  comprising a plurality of approximately 8 to approximately 12 rotational vanes  60   b  of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud  34   a . A middle channel  62  comprises a plurality of rotational vanes  70   a  angled approximately 35 degrees to approximately 55 degrees, or approximately 40 degrees to approximately 50 degrees, or approximately 45 degrees from vertical to increase droplet rotational momentum and flue gas FG penetration. An outer channel  64  reduces scale formation on interior chamber  22   a  walls  22   b . Droplets atomized and dispersed by the atomizer  34  absorb impurities from the flue gas FG for flue gas FG impurity reduction and dry to form a powder end product EP collected in the interior chamber  22   a.    
     A method of making a disperser  24 ,  26 ,  28 ,  30  for flue gas FG impurity reduction comprises centering an atomizer  34  for atomization and dispersal of absorption liquid or reagent slurry droplets therefrom across an interior chamber  22   a  defined by a vessel  22  of approximately 12 to approximately 22 meters or larger in diameter, and surrounding the atomizer  34  with a flow directing device  36 ,  38 ,  40 ,  42 . Flow directing device  36 ,  38 ,  40 ,  42  comprises three annular channels  60 ,  62 ,  64  formed concentrically around the atomizer  34  for a flow of flue gas FG therethrough. Of the three annular channels  60 ,  62 ,  64 , an inner channel  60  without or optionally with a vane pack  60   a  comprising a plurality of approximately 8 to approximately 12 rotational vanes  60   b  of a like angle of approximately 25 to approximately 35 degrees, or approximately 30 degrees from vertical, reduces scale formation on the disperser shroud  34   a . A middle channel  62  comprises a plurality of rotational vanes  70   a  angled approximately 35 degrees to approximately 55 degrees, or approximately 40 degrees to approximately 50 degrees, or approximately 45 degrees from vertical to increase droplet rotational momentum and flue gas FG penetration. An outer channel  64  reduces scale formation on interior chamber  22   a  walls  22   b . Droplets atomized and dispersed by the atomizer  34  absorb impurities from the flue gas FG for flue gas FG impurity reduction and dry to form a powder end product EP collected in the interior chamber  22   a.    
     While the subject disclosure has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, many modifications may be made to adapt a particular situation or material to the subject teachings without departing from the essential scope thereof. Therefore, the particular embodiment disclosed as the best mode contemplated is not intended to be limiting, but rather to include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.