Assembly for disributing and cooling particulate material

Abstract: A fluid-cooled jacket (14) formed by a plurality of panels (16,18,20,22) surrounding and cooling the inlet portion of an air-swept distributor (10), a component of a fluidized bed reactor system. Each panel contains inlet and outlet tubes, inlet (24) and outlet (40) headers, and a heat exchange portion (28) partitioned to direct the fluid flow through the heat exchange portion. The heat dissipated from the reactor is extracted to prevent the temperature of the entire distributor and the fuel from rising, which allows the use of fuels having a lower temperature softening point.

Description: This invention relates to a fluid-cooled jacket and, more particularly, to a fluid-cooled jacket for an air-swept distributor for particulate solid materials. Fluidized bed reactors, such as combusters, steam generators, and gasifiers are well known. In these arrangements, air is passed through a bed of particulate materials, including a fossil fuel such as coal and an adsorbent for the sulphur generated as a result of the combustion of the coal, to fluidize the bed and to promote the combustion of the fuel at a relatively low temperature. When the heat produced by the fluidized bed is utilized to convert water to steam, such as in a steam generator, the fluidized bed system offers an attractive combination of high heat release, high sulphur adsorption, low nitrogen oxide emissions, and fuel flexibility. The particulate fossil fuel combusted in these fluidized bed reactors is supplied to the reactor by a distributor which transports the particulate fuel from the fuel supply to the fluidized bed reactor. The particular design of the distributor controls the flow characteristics of the fuel. Utilization of fluidized bed reactors has increased with their ability to combust lower heating value fuels, which often have a relatively higher moisture level and a lower temperature softening point. The higher moisture level in the fuel causes increased adhesiveness, which makes these fuels difficult to transport. Therefore, air-swept distributors have been utilized, since they provide efficient, low-cost, low-maintenance transportation of these relatively high moisture-level fuels. However, when the temperature of the air-swept distributor causes the fuel to be heated above its softening point, the adhesive qualities of the fuel are dramatically increased, which severely curtails fuel transportation through the distributor. Also, if the air-swept distributor is heated to such a high temperature that the fuel will stick and then burn in the distributor, the distributor would be damaged. GB-269 937 shows a fuel feed device for a furnace with the inlet cooled by a cooling passage which is integrally formed in the inlet. US 3 019 618 shows a conveying trough provided with a separate cooling jacket. It is therefore an object of the present invention to provide a fluid-cooled jacket for cooling an air-swept distributor. According to the invention there is provided an assembly for distributing and cooling particulate material, the assembly comprising a distributor for distributing particulate material, and a jacket comprising a plurality of hollow panels surrounding and positioned in heat exchange relation with a portion of the distributor for removing heat from the distributor, characterised in that the heat exchange portion of each of the panels comprises a plurality of partitions disposed within the panel and defining a plurality of discrete channels aligned along the longitudinal axis of the distributor for receiving a cooling fluid, an inlet header registering with all of the channels for passing the fluid simultaneously through the channels in a single, common direction opposite to the flow of the particulate material through the distributor and an outlet header registering with all of the channels for receiving the fluid from the channels and directing the fluid from the panel, whereby the panels can be operated independently of each other. In such an assembly a fluid-cooled jacket cools the internal faces of an air-swept distributor. That jacket can utilize a variety of fluids, including water, steam, or a combination thereof, to cool the internal faces of an air-swept distributor. As a result a fluid-cooled jacket reduces the internal face temperature of the distributor to such a level that the distributor can accommodate low temperature-softening point fuels without the occurrence of sticking or burning, and so there is an increase in the number of fuels available for use in the above-mentioned fluidized bed reactors. In one embodiment of the present invention a fluid-cooled jacket encompasses the exterior surface area of the inlet portion of the air-swept distributor for a fluidized bed reactor. This fluid-cooled jacket consists of four rectangularly-shaped panels arranged so as to surround the rectangularly-shaped distributor. The fluid is passed independently through each of the four panels to cool the distributor. Each panel has a fluid inlet tube, an inlet header, a heat exchange portion, an outlet header, and a fluid outlet tube. By cooling the inlet portion of the distributor, the entire distributor will remain relatively cool and eliminate the above problems. The invention will now be described, by way of example, with reference to the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a cross-sectional side view of the fluid-cooled jacket used in an assembly according to the present invention; and FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1. Referring to FIGS. 1 and 2 of the drawings, the reference numeral 10 refers, in general, to a distributor which includes a top plate 10a, a bottom plate 10b, and two side plates 10c and 10d. The distributor 10 transports fuel from a fuel supply (not shown) to the furnace section of a fluidized bed reactor, with a portion of a wall of the furnace section being referred to by the reference numeral 12. The fluid-cooled jacket of the present invention is shown in general by the reference number 14 and surrounds a portion of the distributor 10. FIG. 2 illustrates a top panel 16, a bottom panel 18, and two side panels 20 and 22 which together constitute the fluid-cooled jacket 14. The panels 16, 18, 20, and 22 extend over the top plate 10a, the bottom plate 10b, and the side plates 10c and 10d, respectively, and thus surround the lower end portion of the distributor 10 as viewed in Fig. 1. The top panel 16 is hollow and includes an inlet header 24 to which an inlet tube 26 is connected. The inlet header 24 extends the full width of the top plate 10a and is integrated with, and in fluid communication with, a heat exchange portion 28, which also extends the full width of top plate 10a. Relative to the distributor 10, the heat exchange portion 28 includes an inner plate 30 resting on the outer surface of the top plate 10a, a spaced outer plate 32, and two spaced side plates 34 and 36, which plates are connected in any known manner to form a hollow structure. The heat exchange portion 28 is divided by a plurality of evenly spaced parallel partitions 38, which are oriented to extend from the inner plate 30 to the outer plate 32 and along the longitudinal axis of the distributor 10 to channel the fluid flow through the heat exchange portion 28. The heat exchange portion 28 abuts and is connected to the distributor 10 in any known manner and is integrated with, and in fluid communication with, an outlet header 40 (FIG. 1). The inlet header 24 and the outlet header 40 are the same width as heat exchange portion 28 but do not have any partitions. The outlet header 40 is connected to, and in fluid communication with, an outlet tube 42. The panels 18, 20, and 22 are configured and constructed in the same manner as top panel 16, relative to the distributor 10 (FIG. 2). As a result, the panels 18, 20, and 22 will not be discussed further. In operation, a cooling fluid, such as water, steam, or a combination thereof, enters the top panel 16 through the inlet tube 26 and passes into the inlet header 24 before passing into the heat exchange portion 28. The fluid is then channeled along the longitudinal axis of the distributor 10 through the heat exchange portion 28 by the partitions 38. The fluid then passes into the outlet header 40 and exits through outlet tube 42. The panels 18, 20, and 22 function in the same manner as the top panel 16, as described above and each panel functions independently of the others. As a result of the foregoing, the fluid-cooled jacket of the present invention reduces the internal face temperature of the distributor, which allows the distributor to accommodate low temperature softening-point fuels without the fuel sticking or burning. The cooling of the distributor allows the use of a wide variety of fuels in the fluidized bed reactor. The fluid-cooled jacket of the present invention can be varied in several respects. For example, the size of the panels, the volume, direction, and velocity of the fluid flow, the number, orientation, and type of partitions, the type of fluid used to cool the distributor, and the portion of the distributor encompassed by the jacket can be varied. Also the present invention is not limited to use in connection with a distributor of fuel material to a reactor but rather can be used in connection with distributors of other particulate solid materials.

Claims: An assembly for distributing and cooling particulate material, the assembly comprising a distributor (10) for distributing particulate material, and a jacket (14) comprising a plurality of hollow panels (16,18,20,22) surrounding and positioned in heat exchange relation with a portion of the distributor (10) for removing heat from the distributor, characterised in that the heat exchange portion of each of the panels (16,18,20,22) comprises a plurality of partitions (38) disposed within the panel and defining a plurality of discrete channels (39) aligned along the longitudinal axis of the distributor (10) for receiving a cooling fluid, an inlet header (24) registering with all of the channels (39) for passing the fluid simultaneously through the channels (39) in a single, common direction opposite to the flow of the particulate material through the distributor (10) and an outlet header (40) registering with all of the channels (39) for receiving the fluid from the channels (39) and directing the fluid from the panel, whereby the panels (16,18,20,22) can be operated independently of each other. An assembly as claimed in Claim 1 in which the distributor (10) has a rectangular cross-section defined by four walls (10a,10b,10c,10d), and a respective panel (16,18,20,22) is mounted on each of these walls (10a,10b,10c,10d). An assembly as claimed in Claim 1 or Claim 2 in which the partitions (38) are evenly spaced, parallel, and oriented along the longitudinal axis of the distributor (10). An assembly as claimed in any preceding claim in which the distributor (10) distributes particulate fossil fuel to a reactor and one end of the panels (16,18,20,22) is located adjacent to the reactor and the other end is in a spaced relation to the one end.

Inventors: GARCIA-MALLOL JUAN ANTONIO, GARCIA-MALLOL, JUAN ANTONIO
Applicants: FOSTER WHEELER ENERGY CORP, FOSTER WHEELER ENERGY CORPORATION
Application year: 1993
Main classification: F23K3
IPC codes: F23C10, B01J4, B01J19, F23K3, B01J8