Circulating fluidized bed apparatus

Abstract

The invention relates to a circulating fluidized bed apparatus, comprising a combustion chamber (CC) with at least one outlet port (OP) at its upper end (UE) to transfer a mixture of gas and solids from said combustion chamber (CC) into at least one subsequent separator (SP) and from there at least partially back into the combustor chamber, wherein the combustion chamber (CC) is ring-shaped, comprising an inner wall (IW) and an outer wall (OW), arranged at a distance to each other in a radial direction of the combustion chamber (CC), and at least two intermediate walls (SW), which extend between the inner wall (IW) and the outer wall (OW) and in spaced relationship in a circumferential direction of the combustion chamber (CC), thereby subdividing the combustion chamber (CC) into a corresponding number of sections (CO), arranged adjacent to each other in the circumferential direction of the combustion chamber (CC).

Claims

1. A circulating fluidized bed apparatus, comprising a) a combustion chamber (CC) providing a bottom (GB), which is gas-permeable, at its lower end (LE), to allow development of a fluidized bed (FB) of particulate material above said bottom (GB), and at least one outlet port (OP) at its upper end (UE) to transfer a mixture of gas and solids from said combustion chamber (CC) via said outlet port (OP) into at least one subsequent separator (SP), wherein the separator (SP) is designed b) to allow at least part of said solids, separated from the gas, to pass on to at least one return duct (RD) and from there back into the combustion chamber (CC) or to pass on to at least one solids heat exchanger (SHE) and from there via corresponding recirculation means (RM) back into the combustion chamber (CC), or both, and c) to allow at least part of the gas, separated from the solids, to pass on to at least one subsequent treatment unit for said gas, wherein d) the combustion chamber (CC) is ring-shaped, comprising an inner wall (IW) and an outer wall (OW), arranged at a distance to each other in a radial direction of the combustion chamber (CC), and at least two intermediate walls (SW), which extend between the inner wall (IW) and the outer wall (OW) and in spaced relationship in a circumferential direction of the combustion chamber (CC), thereby subdividing the combustion chamber (CC) into a corresponding number of sections (CO), arranged adjacent to each other in the circumferential direction of the combustion chamber (CC).

2. The circulating fluidized bed apparatus of claim 1, wherein each section (CO) of the ring-shaped combustion chamber (CC) stands in fluidic communication with the at least one outlet port (OP), through which the mixture of solids and gas is transferred into the at least one subsequent separator (SP), which is arranged inside the ring-shaped combustion chamber (CC).

3. The circulating fluidized bed apparatus of claim 1, wherein at least two outlet ports (OP) of different sections (CO) of the combustion chamber (CC) merge into one common separator (SP), which is arranged inside the ring-shaped combustion chamber (CC).

4. The circulating fluidized bed apparatus of claim 1, wherein each intermediate wall (SW) covers at least 30% of a plane which extends between corresponding adjacent sections (CO).

5. The circulating fluidized bed apparatus of claim 1, wherein the number of sections (CO) equals or is an even multiple of the number of separators (SP).

6. The circulating fluidized bed apparatus of claim 1, wherein the inner wall (IW) and the outer wall (OW) of at least one section (CO) of the ring-shaped combustion chamber (CC) are planar.

7. The circulating fluidized bed apparatus of claim 1, wherein the inner wall (IW) and the outer wall (OW) of at least one section (CO) of the ring-shaped combustion chamber (CC) extend parallel to each other.

8. The circulating fluidized bed apparatus of claim 1, wherein the inner wall (IW) or the outer wall (OW) of the combustion chamber (CC), or both, are shaped as a circle, an oval, a triangle, a rectangle, a pentagon, a hexagon, a heptagon or an octagon.

9. The circulating fluidized bed apparatus of claim 1, wherein adjacent sections (CO) share a common intermediate wall (SW).

10. The circulating fluidized bed apparatus of claim 1, wherein the gas permeable bottoms (GB) of adjacent sections (CO) of the ring-shaped combustion chamber (CC) extend continuously over these adjacent sections (CO).

11. The circulating fluidized bed apparatus of claim 1 with the at least one solids heat exchanger (SHE) being equipped with more than one recirculation means (RM) for the solids, wherein different recirculation means (RM) merge into different sections (CO) of the ring-shaped combustion chamber (CC).

12. The circulating fluidized bed apparatus of claim 1, wherein the at least one solids heat exchanger (SHE) has a common wall (IW, CW) with an adjacent section (CO) of the ring-shaped combustion chamber (CC).

13. The circulating fluidized bed apparatus of claim 1, wherein the number of sections (CO) equals or is an even multiple of the number of solids heat exchangers (SHE).

14. The circulating fluidized bed apparatus of claim 1, comprising one common solids heat exchanger (SHE), wherein the recirculation means (RM) of the common solids heat exchanger (SHE) merge into at least two sections (CO) of the ring-shaped combustion chamber (CC).

15. The circulating fluidized bed apparatus of claim 1, wherein at least one of the inner wall (IW), the outer wall (OW) or the intermediate walls (SW) of the combustion chamber (CC) is designed to allow a fluid or a steam to flow through.

Description

(1) The invention will now be described with respect to various embodiments, schematically illustrated in the attached drawing and representing in

(2) FIG. 1: a vertical cross-section of a circulating fluidized bed apparatus (CFBA)

(3) FIG. 2: a top view onto said CFBA of FIG. 1,

(4) FIG. 3: a view from below onto a second embodiment of a CFBA

(5) FIG. 4: a top view of a CFBA in a third embodiment

(6) FIG. 5: a view from below onto a fourth embodiment of a CFBA

(7) FIG. 6: a view according to FIG. 2 of a fifth embodiment of a CFBA

(8) In the Figures functionally corresponding components are identified by the same numerals, independent on the respective embodiment.

(9) FIGS. 1, 2 represent a circulating fluidizing bed apparatus, comprising a ring-shaped combustion chamber CC, which is subdivided into four discrete sections CO, arranged adjacent to each other in a peripheral/circumferential direction (FIG. 2: Arrow P) of said ring-shaped combustion chamber CC.

(10) Each section CO is largely independent in functional terms and comprises an inner wall IW, an outer wall OW and side walls SW in between, a gas permeable bottom GB at its lower end LE and an outlet port OP at its upper end UE. All said inner walls IW and outer walls OW of sections CO represent one quarter of a circle-line. The four outer walls OW and the four inner walls IW form concentric circles.

(11) Air is fed through said gas permeable (grate-like) bottom GB and symbolized by arrows A to establish a circulating fluidized bed of particulate material above said bottom. While the inlet port for a fuel material into the combustion chamber CC is represented by arrow JO, the fluidized bed is symbolized by FB.

(12) A typical working temperature in the lower part of each section CO is about 800 C., while an overpressure of approximately 100 mbar prevails in the fluidized bed FB.

(13) The gas-/solids-stream flowing upwardly in each of said sections CO exits each section CO at approximately the same or a slightly higher temperature and under substantially ambient pressure via corresponding openings (outlet ports) OP.

(14) As may best be seen from FIG. 2 inner walls IW and outer walls OW of all four sections follow each other to form two concentric circles, while the outlet ports OP are arranged in such a way as to give the gas-/solids-stream a substantially tangential direction (arrows G) in FIGS. 1, 2.

(15) Said inner walls IW of the four sections CO, which are made of tube-like walls with fins in between, wherein the tubes are water-cooled tubes, represent an upper part of an outer wall of a separator (cyclone) SP, arranged within a cylindrical space CP defined by said inner walls IW.

(16) While the lower part LP of the cyclone SP tapers in a conventional way, return ducts RD extend from the lower part LP of the separator SP to allow solids, collected within the lower part LP of the separator SP, to be fed into the lower end LE of the combustion chamber CC. In this embodiment there are four return ducts RD, each of which bridges one of said four sections CO and the common separator SP. To overrule any pressure differences between the sections CO and the separator SP, a syphon SY is arranged at each return duct RD.

(17) The same is true with respect to feeding pipes FP with intermediate syphons SY, through which another part of the solids, collected in the separator SP, is transported into corresponding solids heat exchangers SHE.

(18) In the embodiment represented in FIGS. 1, 2 four solid heat exchangers SHE are provided, one after the other in the circumferential direction (arrow P) of the ring-shaped combustor chamber CC. Insofar the four heat exchangers SHE, through which the solids flow on their way back into the combustor's sections CO, again display a circular ring-shape, which ring-shape extends concentrically to the ring-shape of the four combuster sections CO. This allows to use the inner walls IW of the four sections CO as outer walls of the four heat exchangers SHE and to use side walls SW between adjacent heat exchangers SHE as common walls between two heat exchangers SHE. For this purpose the side walls SW of the sections CO have been extended at their inner ends according to the embodiment displayed.

(19) While the construction of each of said heat exchangers SHE may be of the conventional type, recirculation means RM are provided at each of said heat exchangers SHE to allow a recirculation (return) of the solids into the respective section CO and the fluidized bed FB respectively. These recirculation means RM, schematically represented by corresponding arrows in FIG. 1, are wall openings, but can also be designed as ducts or the like.

(20) A gas duct GD extends from an upper part of the separator SP and leads to (non displayed) subsequent treatment units for the gas, which was previously separated from the solids within the separator SP.

(21) The embodiment according to FIG. 3 differs from that of FIG. 1, 2 by the following features:

(22) The ring-shaped combustion chamber CC is subdivided into eight sections CO, each with planar inner and outer walls IW, OW, extending parallel to each other to give each section a rhomboid-like horizontal cross-section, wherein sidewalls SW extend between the corresponding corner-sections of said inner walls IW and outer walls OW. The outer geometry of the combustion chamber CC follows an octagon.

(23) The separator SP has an octagonal outer shape and its outer walls are arranged at a short distance to the inner walls IW of said sections CO.

(24) Each section CO has one outlet port OP at its upper end UE, which outlet port OP again is arranged in a way to allow the gas-/solids-stream, deriving from a section CO and entering the separator SP, to flow more or less tangential, i.e. more or less parallel to an adjacent wall AW of the separator SP. Only two of eight outlet ports OP and subsequent walls AW are illustrated in FIG. 3.

(25) Instead of a multiplicity of solids heat exchangers SHE the embodiment of FIG. 3 has just one common heat exchanger SHE below said separator SP. Insofar the number of feeding pipes FP may be less than the number of sections CO and may be even down to one single feeding pipe FP. The heat exchanger SHE is box shaped (four walls and right angles between adjacent walls) but may have any other shape.

(26) The number of recirculation means RM, in this embodiments designed as ducts, by which the solids, which have passed the solids heat exchanger SHE, are fed back into the combustor, corresponds to the number of sections CO (here: eight) to allow one recirculation means RM to enter each section CO.

(27) FIG. 3 again displays the arrangement of adjacent sections CO one after the other to give an overall ring-shaped combustion chamber CC, wherein each section CO with its rhomboid horizontal cross-section represents an autarkic combustion chamber of high structural integrity because of its small size and angled walls, allowing to set different thermodynamic conditions in different sections.

(28) The same is true with respect to the embodiment according to FIG. 4, which differs from that of FIG. 3 in particular by the following:

(29) While the outer profile (in a horizontal cross-section) of the embodiment of FIG. 4 is again octagonal, the number of sections has been reduced from eight to four by deleting every second sidewall SW.

(30) Correspondingly the number of outlet ports OP has been reduced to four, although each section CO may have more than one outlet port OP.

(31) The CFBA of FIG. 4 operates with one common separator SP, which differs from that of FIG. 3 insofar as it has a circular horizontal cross-section, wherein the upper part of said separator SP partially touches the inner walls IW of said four sections CO.

(32) At its lower part return ducts to the combustion chamber CC are fitted, while part of the solids is extracted directly from the separator SP without returning them into any of the sections CO. In this embodiment no heat exchanger(s) being provided.

(33) The embodiment of FIG. 5 displays a rectangular combustion chamber CC with four sections CO, one next to the other, each with a rhombic horizontal cross-section and insofar with sidewalls SW extending between corresponding corners C-C of said outer walls OW and inner walls IW of adjacent sections CO.

(34) Two cylindrical separators SP are arranged side by side inside the ring-shaped combustion chamber CC.

(35) Beneath each of said separators SP a corresponding solids heat exchanger SHE of a square inner and outer profile is arranged.

(36) Outlet ports of two adjacent sections CO merge into one separator SP, while the outlet ports of the other two sections lead into the second separator SP. Return ducts RD between the lower part LP of each separator SP and adjacent sections CO allow the solids to be returned into the combustion space and fluidized bed FB respectively.

(37) Feeding pipes FP are arranged between each of said two separators SP and a corresponding solids heat exchanger SHE. The solids, having passed the solids heat exchangers SP, are then returned into the two sections CO via recirculation ducts (arrows RM).

(38) In the embodiment of FIG. 5 each of said solids heat exchangers SHE has a square horizontal cross-section and is arranged at a distance to the inner walls IW of adjacent sections CO.

(39) FIG. 6 represents an embodiment similar to that of FIG. 1, 2 with the proviso that the intermediate (side) walls SW do not extend over the full vertical height H and full horizontal width W of the sections CO, but at a distance to the bottom grate (gas permeable bottom GB) and with a distance to the inner wall IW. This allows to extend one common permeable bottom GB over more than one section (compartment) CO, while at the same time at least part of the solids/gas mixture may pass from one section CO into the adjacent one through that gap between inner wall IW and side wall SW. Both height and width of the side walls SW are dimensioned such that the side walls SW cover about 70% of the maximum (virtual) plane between adjacent sections CO. All inner and outer walls IW, OW and all side walls are water cooled walls made of steel tubes, through which water flows, and steel fins between adjacent steel tubes.

(40) Features of the embodiments displayed may be combined arbitrarily, if technically useful and not explicitly excluded.