Abstract:
An apparatus and method for mixing and distributing solid material in which the material is continuously introduced into a vessel and a pressurized gas is introduced into the lower portion of the vessel at a velocity sufficient to pass upwardly through the material in the vessel to promote mixing of the material. A plurality of outlets are disposed in an angularly spaced relation along the vessel for permitting the material to continuously discharge to a plurality of selected locations. The excess gas in the vessel is removed, cleaned and introduced back into the vessel.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a mixing and distributing apparatus and method, and more particularly to such an apparatus and method in which one or more materials are mixed in a vessel and distributed from the vessel. 
     The use of fluidized beds has long been recognized as an attractive way of generating heat. In these type of arrangements, a particulate material, including a mixture of fuel material, such as coal, and an adsorbent material for the sulfur released as a result of the combustion of the fuel material, are disposed on a grate or grate-like plate. Air is passed through the bed to fluidize the material so that the bed behaves as a boiling liquid which promotes the combustion of the fuel. 
     Additional fuel and adsorbent material must be continuously supplied to the bed through a plurality of overbed or inbed feeders disposed at spaced locations along the walls of the vessel housing of the fluidized bed. Since in many arrangements a plurality of material inlets are provided through two or more walls of the vessel, it becomes difficult from a materials handling standpoint to receive the fuel materials and the adsorbent materials from separate sources, mix them and uniformly distribute them to the selected locations along the walls of the vessel. 
     In order to promote the mixing and improve the handling capability of the material it has been suggested to pass a stream of air through the materials. However, since the air discharged with the mixed solids is only a relatively small percentage of the air flow required to insure proper mixing, a considerable amount of excess air is present in the system which must be removed to insure proper operation. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an apparatus in which solid particulate material is received from separate sources, is mixed and is discharged in a precise and uniform manner. 
     It is a further object of the present invention to provide an apparatus of the above type in which a stream of air is passed through a bed of the materials to be mixed to insure a uniform mixture of the material before it is discharged. 
     It is a still further object of the present invention to provide an apparatus of the above type in which the excess air in the system is removed, cleaned, and injected back into the bed of material. 
     Toward the fulfillment of these and other objects, a vessel is provided for supporting a bed of particulate material and for receiving additional material. Pressurized air is introduced into the vessel at a velocity sufficient to pass through the material in the vessel and cause spouting to induce a flow of the material within the vessel to promote mixing. The excess air is removed from the vessel, cleaned and reinjected back into the bed. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiment in accordance with the present invention when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a schematic view of the system of the present invention; 
     FIG. 2 is a front elevational view, partially in section, of the mixing and distributing apparatus of the system of FIG. 1. 
     FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 2; 
     FIG. 4 is a vertical cross-sectional view taken along the line 4--4 of FIG. 3; 
     FIG. 5 is a view similar to FIG. 4 but depicting an alternate embodiment of the apparatus of the present invention; and 
     FIG. 6 is a horizontal cross-sectional view taken along the line 6--6 of FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring specifically to FIGS. 1 and 2 of the drawings, the reference numeral 10 refers in general to an elongated cylindrical vessel having an upper inlet 12 which is adapted to receive particulate material from one or more sources (not shown). The particulate material can, for the purpose of example, be a source of crushed coal for a fluidized bed and a source of limestone for adsorbing the sulfur formed as a result of combustion of the coal. 
     The lower end portion of the vessel 10 is formed into a conically shaped hopper 14 which has an inlet 16 registering with its apex for receiving a pressurized gas, such as air, from an external source, which air passes upwardly through the vessel in a manner to be described in detail later. 
     Four equiangularly spaced outlet pipes 18 (two of which are shown in FIG. 1) extend at an acute angle with respect to a horizonal plane from a point within the vessel 10, through the vessel wall and to a point externally of the vessel. 
     The material from the source or sources mentioned above is introduced into the upper inlet 12 of the vessel 10 and flows downwardly through the vessel by gravity before accumulating in the vessel. Air is introduced into the inlet 16 and passes through the hopper 14, and upwardly through the material accumulating in the vessel 10. The velocity and flow of the air are regulated so that &#34;spouting&#34; occurs, i.e., a portion of the materials from the bed in the vessel will be discharged upwardly from the upper surface of the bed. As will be described later, this induces a circulation of materials in the bed and an improved mixing of same. 
     The considerable amount of excess air rising upwardly in the vessel 10 from the bed of particulate material exits through an opening formed in the upper portion of the vessel 10 and into an outlet line 20. A recirculating blower 22 is provided which operates to drain the air from the upper portion of the bed vessel through the line 20 and into a solid separating device 24 of any conventional design, such as a cyclone separator. The separating device 24 operates in a conventional manner to remove a great majority of the solid bed particles from the air, which solids are passed vertically downwardly through a line 26 containing a rotary valve 28 to a reinjection nozzle 30. The output of the blower 22 is connected, via a line 32, to the inlet side of the reinjecting nozzle 30 which operates to entrain the solid particles passing from the valve 28 and introduce them, via a line 34, to the inlet 16 of the vessel 10. The rotary valve 28 functions as a seal to prevent backflow of air from the high pressure side of the blower 22 to the low pressure zone in the separating device 24. 
     The air outlet of the separating device 24 is connected, via a line 36, to a second-stage separating device 38 which also can be in the form of a cyclone separator. Although not shown in the drawings, it is understood that the solids outlet from the separating device 38 can be discharged to another vessel or the like. 
     The air outlet from the separating device 38 is connected, via a line 40, back to the inlet side of the recirculation blower 22 for injection back into the system. Thus, the suction from the blower 22 draws the air from the vessel 10, through the separators 24 and 38 and to the blower 22. A heat exchanger 42 can be provided in the line 40 to cool the recycled air passing through the latter line, especially if the heat removed with the air-solids mixture from the vessel 10 is not sufficient to compensate for the heat added by the recirculation blower 22 without excessive temperature buildup in the bed in the vessel 10. 
     FIGS. 2-4 depict the specifics of the vessel 10 in more detail. More particularly, it is noted that four outlet pipes 18 extend from the vessel and are covered by a refractory material 44. As better shown in FIG. 4, a filler plug 46 is provided in the vessel immediately above the hopper portion 14 and has a central bore 48 through which the air from the inlet 16 passes, which bore widens out into a substantially conical shaped opening 50 which receives the material flowing downwardly in the vessel. As a result of this flow of the air through the material, a central zone, shown in general by the reference numeral 60 is formed which is concentric with the axis of the vessel 10 and in which the concentration of the particles is low and the general movement of the particles is upward. An annular zone 62 is also formed which extends around the central zone 60 and in which the concentration of the particles is high and the general movement is downward. The central zone 60 is continually supplied with particles from the annular zone 62 in the vicinity of the opening 50 which particles are thus transported to the upper part of the bed by means of the pressurized air and then fall back down into the annular zone 62 and repeat the cycle. As a result, a thorough mixing of the particles within the bed is achieved. 
     During movement of the particles in the annular zone 62 downwardly, a portion will enter the upper end of the discharge pipe 18 and be transported, by gravity, through the entire length of the pipes to areas external of the vessel 10. In the present embodiment in which four such pipes 18 are provided, it can be appreciated that a precise distribution of the mixed particles into four separate locations is thus achieved. In the case of a fluidized bed discussed above, a ducting system, or the like, can be provided to connect the outlet ends of the pipes 18 to the feeders associated with the walls of the vessel housing the fluidized bed. 
     Of course, the supply of new particulate material to the inlet 12 of the vessel 10 is regulated according to the discharge from the pipes 18 so that a continuous replenishing of the particle material in the vessel 10 is achieved. 
     Of course, the excess air (usually in excess of 90% of the air discharged from the pipes 18) passes upwardly into the upper portion of the vessel and out through the line 20 for treatment and recirculation by the separating device 24, the blower 22, etc., as described above. 
     An alternative embodiment of the vessel 10 is depicted in FIGS. 5 and 6 and includes identical components of the latter vessel which are given the same reference numerals, with the particulate material being omitted from the drawings in the interest of clarity. In this embodiment, the filler plug 46 of the previous embodiment is omitted and four equiangularly spaced inlet pipes 64 are provided which extend through the wall of the hopper portion 14 of the vessel and at an angle to the horizontal. The pipes 64 receive the particulate material from one or more sources as in the previous embodiment and feed the material into the lower portion of the hopper 14 immediately above the air inlet 16. 
     A central zone and an annular zone are thus formed and the flow pattern of the material in the vessel is the same as discussed in connection with the previous embodiment. 
     Four vertically extending, angularly spaced, discharge pipes 66 extend from a point inside the vessel 10, and through the inclined walls of the hopper 14 for discharging the particulate material to four separate external locations in a manner similar to that in connection with the embodiments of FIGS. 2-4. Of course, the vessel of the embodiment of FIGS. 5 and 6 can be used with the recirculating, separating and reinjecting apparatus depicted in FIG. 1. 
     It is thus seen that, as a result of the foregoing, a precise mixing and distribution of the particulate material from one or more sources to a plurality of discharge points is achieved in a relatively simple and efficient manner while the excess air from the vessel is used in an efficient manner. 
     It is noted that several variations may be made in the foregoing. For example, if the vessel 10 is operated at, or near, atmospheric pressure, the recycled air line 40 (FIG. 1) and the heat exchanger 42 can be omitted, and the air leaving the second-stage separating device 38 can be discharged to atmosphere and the blower 22 can take suction from the atmosphere. 
     As will be apparent to those skilled in the art, various changes and modifications may be made to the apparatus of the present invention without departing from the spirit and scope of the present invention as recited in the appended claims and their legal equivalent.