Abstract:
A sorbent activation plate having a first surface, a second surface opposite the first surface, a plurality of reliefs in the first surface, and a plurality of protrusions on the second surface. The sorbent activation plate is structured to attach to a boiler tube such that the plurality of protrusions contact the boiler tube and offset the second surface from the boiler tube.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    This invention is generally in the field of emission control devices. More particularly, the present invention is directed to a device and method of activating sorbent using sorbent activation plates placed in the flue gas flow path. 
         [0004]    Sorbents are widely used in power generation systems such as coal-burning power plants to neutralize or capture various combustion by-products. Examples of such sorbents include activated carbon, silica, calcium hydroxide, and sodium bicarbonate. The selection of a sorbent for a particular application is dictated by the type of by-product which is to be captured or eliminated. For example, activated carbon is often used to capture mercury. Calcium hydroxide and sodium bicarbonate are often used to neutralize sulfur dioxide and/or NOx emissions. 
         [0005]    Conventionally, sorbents are injected into the combustor or into the flue gas flow path downstream of the combustor. The sorbent is then allowed to mix and/or react with the combustion by-products before the combustion by-products are exhausted to the atmosphere. The sorbent is typically reclaimed from the exhaust flow by filtration or other separation process. 
         [0006]    Sorbent utilization increases operating costs both because of the cost of providing the sorbent and the costs of separating and/or disposing the sorbent from the flue gas flow path. As such, it would be desirable to provide a device and method to improve the efficiency of sorbent utilization. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    In one aspect, the present invention comprises a sorbent activation plate. The sorbent activation plate has a first surface, a second surface opposite the first surface, a plurality of reliefs in the first surface, and a plurality of protrusions on the second surface. The sorbent activation plate is structured to attach to a boiler tube such that the plurality of protrusions contact the boiler tube and offset the second surface from the boiler tube. 
         [0008]    In another aspect, the present invention comprises a system for improving sorbent effectiveness comprising a boiler tube and a sorbent activation plate attached to the boiler tube. The sorbent activation plate comprises a body having a first surface facing the boiler tube, a second surface facing away from the boiler tube, and a plurality of reliefs in the second surface. 
         [0009]    In yet another aspect, the present invention comprises a system for improving sorbent effectiveness comprising a housing providing a flow path for a flue gas, and a sorbent activation plate provided in the housing. The sorbent activation plate comprises a body having a first surface and a plurality of reliefs or channels in the first surface. The sorbent activation plate is attached within the housing such that the first surface lies in the flow path of the flue gas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view, illustrating a sorbent activation plate. 
           [0011]      FIG. 2  is a side view, illustrating a sorbent activation plate attached to a boiler tube in accordance with an embodiment of this invention. 
           [0012]      FIG. 3  is a plan view, illustrating sorbent activation plates employed in a boiler in accordance with an embodiment of this invention. 
           [0013]      FIG. 4  is a perspective view, illustrating a sorbent activation plate in accordance with an embodiment of this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Sorbent effectiveness—a sorbent&#39;s ability to adsorb or react with a component to be separated from a flue gas—is primarily dictated by the adsorption or reaction kinetics of the component and the sorbent. Residence time, temperature, pressure, and component and sorbent concentrations are among the many factors affecting the amount of the component that can be removed from the flue gas by a specific amount of a particular type of sorbent. 
         [0015]    In one aspect, the present invention comprises a sorbent activation plate which improves the residence time and/or temperature conditions under which the sorbent and component combine, react or adsorb. 
         [0016]    One embodiment of the present invention is illustrated in  FIG. 1 . The sorbent activation plate  10  includes a body  11  with an outer surface  12  and an inner surface  16 . The outer surface  12  may be generally formed into the shape of an exterior cylindrical surface. The inner surface  12  may be generally formed into the shape of an interior cylindrical surface. The width of body  11  between the outer surface  12  and the interior surface  16  may be uniform throughout the sorbent activation plate  10 . The outer surface  12  may have a plurality of reliefs  14  formed therein. Each of the reliefs  14  may be formed to have a corresponding protrusion  18  on the inner surface  16  opposite the relief. 
         [0017]    Although embodiments of the sorbent activation plate  10  may be made of various materials and manufactured according to various methods, it is preferred for the sorbent activation plate  10  to be manufactured of materials capable of withstanding flue gas temperatures. For example, the sorbent activation plate  10  may be made of various materials including but not limited to stainless steel, aluminum, or ceramic. 
         [0018]    In some embodiments, the reliefs  14  may be formed in the shape of concave dimples as illustrated in  FIG. 1 . The protrusions  18  may be formed in the shape of convex bumps. The body  11  of these embodiments may be formed by various manufacturing processes including, but not limited to, casting, molding, extrusion and/or stamping processes. 
         [0019]    In another aspect, the present invention comprises a system for improving the effectiveness a sorbent. In one embodiment, the sorbent activation plate  10  is attached to a boiler tube  20  as illustrated in  FIG. 2 . The sorbent activation plate  10  is attached to the boiler tube  20  with an attachment clip  22  such that the outer surface  12  of the sorbent activation plate  10  is exposed to the flue gas flow path. The protrusions  18  may be configured to act as stand-offs, separating the cylindrical portion of the inner surface  16  from the boiler tube  20 . The sorbent activation plate  10  may be fastened to the attachment clip by welding or with the use of a fastener. 
         [0020]    In some embodiments, a plurality of sorbent activation plates  10  are attached at multiple locations in a boiler housing  26  as illustrated in  FIG. 3 . In the embodiment of  FIG. 3 , the boiler housing  26  has an entrance boiler tube  20  and an exit boiler tube  24 . The boiler tubes  20  and  24  carry fluids which are heated in the boiler housing  26  by the flow of hot flue gases, illustrated as arrows in  FIG. 3 . In some embodiments, the sorbent activation plates  10  are attached to the boiler tube  20  at a plurality of locations. 
         [0021]    Because the protrusions  18  separate the inner surface  16  of from the boiler tube  20 , the sorbent activation plate  10  is able to operate at higher temperatures than the boiler tube  20 . Also, the reliefs  12  may be positioned to face the flow path of the flue gas so that injected sorbent collects or is deposited on the sorbent activation plate  10 . This increases the average residence time in which the sorbent particles are present in the boiler housing  26 , and, thus, increases the time the sorbent particles are exposed to the flue gas. In embodiments in which the sorbent activation plates  10  are attached to the boiler tubes  20  and/or  24 , collection of the sorbent particles on the boiler tubes  20  and  24  is also reduced. 
         [0022]    Because the boiler tubes  20  and  24  carry a fluid that is cooler than the flue gases, the sorbent particles are normally cooled when they contact the boiler tubes  20  and  24 . In most cases, this cooling reduces the effectiveness of the sorbent and can lead to build up of the sorbent on the boiler tubes. As such, it should be appreciated that the attachment of the sorbent activation plates  10  to the boiler tubes  20  may generally result in increased average sorbent residence times and increased average sorbent temperatures. Both of these features increase sorbent effectiveness and allow for less sorbent utilization. 
         [0023]    It should be appreciated that many different designs may be employed for the sorbent activation plates. Another embodiment is illustrated in  FIG. 4 . In this embodiment, a sorbent activation plate  28  includes a surface  30  which faces the flue gas flow and a plurality of channels  32  which allow the flue gases to pass therethrough. Similar to the embodiment of  FIG. 1 , sorbent particles are deposited on surface  30  when the flue gas flows through channels  32 . Sorbent activation plate  28  may be placed in various locations along the flue gas flow path. For example, multiple sorbent activation plates  28  may be placed at the inlet of a boiler or at various locations in the boiler housing  26  of  FIG. 3 . 
         [0024]    The sorbent activation plate  28  may be manufactured of various materials. In some embodiments, the sorbent activation plate  28  comprises expanded metal, grating, or any other surface structured to allow a sorbent in the flue gas to deposit thereon. 
         [0025]    Modifications and variations of the devices and systems described herein will be obvious to those skilled in the art from the foregoing detailed description. Such modifications and variations are intended to come within the scope of the appended claims.