Circulating fluidized bed reactor with plural furnace outlets

Details Circulating fluidized bed reactor with plural furnace outlets Circulating fluidized bed reactor with plural furnace outlets

1998-05-29

2000-05-09

Lazarus, Ira S.

Furnaces

Refuse incinerator

Refuse suspended in or supported by a fluid medium

110204, 110216, 122 4D, 55443, 55464, F23G 500, F23G 700, F23J 300

Patent

active

060588586

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates, in general, to circulating fluidized bed (CFB) reactors or combustors having an internal impact-type primary particle separator which provides for the internal return of all primary collected solids to a bottom portion of the reactor or combustor for subsequent recirculation without external and internal recycle conduits. In particular, it relates to an improved CFB reactor or combustor design wherein the CFB reactor enclosure or furnace is provided with plural furnace outlets. This construction permits increased furnace depths and reduced furnace widths, resulting in a compact, low-cost design particularly suitable for new construction or for replacement of existing fossil-fueled steam generator capacity, whether or not such existing capacity is of the CFB type.


BACKGROUND OF THE INVENTION

Throughout the several drawings forming a part of this disclosure, like numerals represent the same or functionally similar elements. FIGS. 1 and 2 are schematics of known CFB boiler systems used in the production of steam for industrial process requirements and/or electric power generation. Referring to FIG. 1, fuel and sorbent are supplied to a bottom portion of a furnace 1 contained within enclosure walls 2, which are normally fluid cooled tubes. Air 3 for combustion and fluidization is provided to a windbox 4 and enters the furnace 1 through apertures in a distribution plate 5. Flue gas and entrained particles/solids 6 flow upwardly through the furnace 1, releasing heat to the enclosure walls 2. In most designs, additional air is supplied to the furnace 1 via overfire air supply ducts 7.
The system of FIG. 1 provides two stages of particle separation: in-furnace impact-type particle separators or U-beams 13 and external impact-type particle separators or U-beams 14. Since the particular designs of such U-beams configurations and their functions have been previously disclosed (see, for example, U.S. Pat. Nos. 4,992,085 and 4,891,052 to Belin, et al. and U.S. Pat. No. 5,343,830 to Alexander et al., all assigned to The Babcock & Wilcox Company), and they will not be discussed in further detail. Suffice it to say that the in-furnace U-beams return their collected particles directly into the furnace 1, while the external U-beams return their collected particles into the furnace via the particle storage hopper 11 and L-valve 12, collectively referred to as a particle return system 15. An aeration port 16 supplies air for controlling the flow rate of solids or particles through the L-valve 12.
The flue gas and solids 6 pass into a convection pass 17 which contains convection heating surface 18. The convection heating surface 18 can be evaporating, economizer, or superheater as required.
Although not shown in connection with the FIG. 1 system, an air heater would also be provided downstream of the convection pass 17 to extract further heat from the flue gas and solids 6. A multiclone dust collector (also not shown) would also be supplied to recycle solids back to a lower portion of the furnace enclosure.
In CFB reactors, the reacting and non-reacting solids are entrained within the reactor enclosure by the upward gas flow which carries solids to the exit at the upper portion of the reactor where the solids are separated by the internal and/or external particle separators. The collected solids are returned to the bottom of the reactor commonly by means of internal or external conduits. In the system of FIG. 1, the L-valve 12 is a pressure seal device that is needed as a part of the return conduit due to the high pressure differential between the bottom of the reactor and the particle separator outlet. The primary separator at the reactor exit collects most of the circulating solids (typically from 95% to 99.5%). In many cases an additional (secondary) particle separator and associated recycle means are used to minimize the loss of circulating solids due to inefficiency of the primary separator.
The internal impact-type particle separators are comprised of a plurality

REFERENCES:
patent: 4599952 (1986-07-01), Meier
patent: 4761131 (1988-08-01), Abdulally
patent: 4891052 (1990-01-01), Belin et al.
patent: 4992085 (1991-02-01), Belin et al.
patent: 5215042 (1993-06-01), Beisswenger et al.
patent: 5343830 (1994-09-01), Alexander et al.
patent: 5370084 (1994-12-01), Skowyra et al.
patent: 5759495 (1998-06-01), Hyppanen
Belin et al., "Repowering of Ukrainian Power Plants with CFB Boilers", PowerGen Americas '95 Conference in Anaheim, CA, pp 1-18, Dec. 1995.

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