Note: Descriptions are shown in the official language in which they were submitted.
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COOLED TUBES ARRANGED TO FORM IMPACT TYPE PARTICLE SEPARATORS
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates, in general, to the field of circulating
fluidized bed (CFB) boilers
and, in particular, to improved impact type particle separator constructions
comprised of fluid-cooled
tubes.
CFB boiler systems are known and used in the production of steam for
industrial processes
and/or electric power generation. See, for example, U. S. Patent Nos.
5,799,593, 4,992,085, and
4,891,052 to Belin et al.; 5,809,940 to James et al.; 5,378,253 and 5,435,820
to Daum et al.; and
5,343,830 to Alexander et al. In CFB reactors, 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 impact type particle separators.
The impact type particle
separators are placed in staggered arrays to present a path which may be
navigated by the gas stream,
but not the entrained particles. The collected solids are returned to the
bottom of the reactor. One CFB
boiler arrangement uses a plurality of impact type particle separators (or
concave impingement
members or U-beams) at the furnace exit to separate particles from the flue
gas. While these
separators can have a variety of configurations, they are commonly referred to
as U-beams because
they most often have a U-shaped configuration in cross-section.
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When applied to a CFB boiler, a plurality of such impact type particle
separators are
supported within the furnace enclosure and extend vertically in at least two
rows across the
furnace exit opening, with collected particles falling unobstructed and
unchanneled underneath
the collecting members along the rear enclosure wall. The gap between each
adjacent pair of U-
beams in one row is aligned with a U-beam in a preceding or following row of U-
beams to
present a tortuous path for the flue gas/solids to.navigate. The U-beams in
each row collect and
remove particles from the flow of flue gas/solids, while the flue gas stream
continues to flow
around and through the U-beam array.
These types of collection elements are generally relatively long in comparison
to their
width and depth. The shape of the collection elements is usually dictated by
two considerations:
namely, the collection efficiency of the U-beams themselves and the ability of
the U-beams to
be self-supporting. When these elemerits are used, they are generally placed
at the furnace exit
and not cooled. Their placement at the furnace outlet is to protect the
downstream heating
surfaces from erosion by solid particles. Thus, the U-beams are exposed to the
high temperatures
of the flowing stream of flue gas/solids, and the materials used for the U-
beams must be
sufficiently temperature resistant to provide adequate support and resistance
to damage.
Long, self-supporting stainless steel plate channels have been successfully
used in CFB
boilers for the primary solids collector, but the "creep" strength of the
commercially available
and suitable alloys limits the length of the collection elements. By breaking
up the long
collection channel into short segments, the required strength of each short
segment is much less
than for the long channel due to the series of intermittent supports and the
small amount of
weight of any individual segment or element.
Methods of making collection elements which are cooled or supported off a
cooled
structure have usually included collection plates welded to water cooled
support tubes. See U.S.
Pat. Nos. 5,378,253 and 5,435,820 to Daum et al. However, welding to the
cooling tubes
increases the opportunity for tube leaks to occur at the welds.
In addition, under this known design structure, the collection element is
cooled
asymmetrically due to the proximity of the cooled tube or tubes to only some
portion of the
shaped collection channel segment or element. Thus, the plate forming the
collection elements
will tend to distort due to the differeritial expansion of the cooler arf:as
in comparison to the
hotter portions of the collection elements.
In addition, it is necessary to protect the tubes themselves from erosion
caused by the
impacting solids entrained within the solid/gas flow. This protection requires
the use of tube
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shields made of stainless steel or ceramic which must be used along the entire
height of the
collector, which adds further cost.
,SUMMARY OF THE INVENTION
The present invention comprises various arrangements of fluid-cooled tubes
which are
used to form impact type particle separators, commonly in a U-shape, but which
can also be
formed into W-, E-, V- or other shapes. Such impact type particle separators
find particular use
in circulating fluidized bed (CFB) boilers or reactors.
Accordingly, one aspect of the present invention is drawn to an apparatus for
separating
solids from flue gas in a circulating fluidized bed (CFB) boiler. In one
embodiment, the
apparatus comprises a plurality of vertical, impact type particle separators
located within the
CFB. The impact type particle separators are adjacently positioned and
horizontally spaced from
one another in a plurality of staggered rows. Each impact type particle
separator includes a
plurality of vertical cooling tubes for ccinveying a cooling medium
therethrough. A plurality of
slip fit elements having apertures which accept and surround the cooling tubes
are provided, the
plurality of slip fit elements cooperatir-g with one another to form a
collecting channel along a
length of the cooling tubes formed by side walls and a back wall. The side
walls and back wall
have a plurality of separate vertically aligned segments extending
longitudinally along the height
of the impact type particle separator, each vertically aligned segment being
connected at its ends
to an adjacent segment.
Another aspect of the present invention is drawn to an apparatus for
separating solids
from flue gas in a circulating fluidized bed (CFB) boiler. In this embodiment,
the apparatus
comprises a plurality of vertical, impact type particle separators located
within the CFB. The
impact type particle separators are acijacently positioned and horizontally
spaced from one
another in at least two staggered rows. Each impact type particle separator
includes a plurality
of vertical cooling tubes for conveying a cooling medium therethrough. The
plurality of cooling
tubes forming an individual impact type particle separator are attached or
connected to one
another by intermediate tube alignment plate or bar welded at least inter-
mittently inbetween and
along the adjacent cooling tubes to form a unitary structure. A plurality of
pin studs may be
welded to the tubes, and then covered with a coating of refractory. Other
erosion resistant
mechanisms, such as tiles, metal or ceramic spray coatings, metal or ceramic
castings, weld
overlay, and shields, may be employed.
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The various features of novelty which characterize the invention are pointed
out with
particularity in the claims annexed to and forming a part of this disclosure.
For a better
understanding of the invention, its operating advantages and specific benefits
attained by its uses,
reference is made to the accompanying drawings and descriptive matter in which
a preferred
embodiment of the invention is illustrated.
BRIEF DESCRIPTION OF THE DRA WINGS
In the drawings:
Fig. 1 is a schematic view of a known CFB boiler design employing an impact
type particle separator system;
Fig. 2 is a sectional plan view of the in-furnace group of U-beams in Fig. 1,
viewed in the direction of arrows 2-2;
Fig. 3 is a top view of a first embodiment of an individual U-beam impact type
particle separator according to the present invention;
Fig. 4 is a right side view of the U-beam impact type particle separator of
Fig.
3, viewed in the direction of arrows 4-4;
Fig. 5 is a rear view of the U-beam impact type particle separator of Fig. 3,
viewed in the direction of arrows 5-5;
Fig. 6 is a top view of' a second embodiment of an individual U-beam impact
type particle separator according to the present invention;
Fig. 7 is a left side view of the U-beam impact type particle separator of
Fig. 6,
viewed in the direction of arrows 7-7;
Fig. 8 is a rear view of the U-beam impact type particle separator of Fig. 6,
viewed in the direction of arrows 8-8;
Fig. 9 is a right side view of the U-beam impact type particle separator of
Fig.
6, viewed in the direction of arrows 9-9;
Fig. 10 is a top view of a third embodiment of an individual U-beam impact
type
particle separator according to the present invention;
Fig. 11 is a left side view of the U-bearn impact type particle separator of
Fig. 10,
viewed in the direction of arrows 11-11;
Fig. 12 is a rear view of the U-beam impact type particle separator of Fig.
10,
viewed in the direction of arrows 12-12;
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Fig. 13 is a right side view of the U-beam impact type particle separator of
Fig.
10, viewed in the direction of arrows 13-13;
Fig. 14 is a side view of another embodiment of a U-be;am impact type particle
separator apparatus according to the present invention;
Fig. 15 is a sectional view of an individual U-beam impact type particle
separator
of Fig. 14, viewed in the direction of arrows 1545;
Fig. 16 is a side view of'the lower portion of Fig. 14;
Fig. 17 is a sectional view of the lower portion of the U-beam impact type
particle separator apparatus of Fig. 16, viewed in the direction of arrows
17-17;
Fig. 18 is a side view of' an alternate embodiment of the lower portion of the
U-
beam impact type particle separator apparatus of Fig. 14;
Fig. 19 is a side view of' an alternate embodiment of the upper portion of the
U-
beam impact type particle separator apparatus of Fig. 14;
Fig. 20 is a sectional plan view of an impact type particle separator
apparatus
illustrating a staggered arrangement of V-shaped collecting elements;
Fig. 21 is a side view of an alternative embodiment of the present invention
employing a chevron collecting element;
Fig. 22 is a sectional plan view of the chevron collecting element
configuration
of Fig. 21, viewed in the direction of arrows 22-22;
Fig. 23 is a sectional view of an individual chevron collecting element of the
type
illustrated in Figs. 21 and 22;
Fig. 24 is a sectional view of a deflecting plate which may be employed in the
chevron collecting element configuration of Figs. 21 and 22, viewed in
the direction of arrows 24-24;
Fig. 25 is a schematic sectional view of an individual U-beam impact type
particle separator wherein the cooled tubes comprise omega tubes
according to the present invention;
Fig. 26A is a sectional view of an individual omega tube of the type used in
the
embodiment of Fig. 25;
Fig. 26B is a sectional view of an alternate way to implement omega tubes in
the
embodiment of Fig. 25 using conventional tubes and membrane bars;
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Fig. 27 is a sectional view of two interlocking slip fit castings which may be
provided over the cooled tubes forming an indiviclual U-beam impact type
particle separator to improve erosion resistance according to the present
invention;
Fig. 28 is a sectional view of an individual U-beam impact type particle
separator
wherein the cooled tubes are provided with protective castings attached
thereto to improve erosion resistance according to the present invention;
Fig. 29 is a sectional view of a portion of an individual U-beam impact type
particle separator wherein the cooled tubes are provided with bolt-on
protective castings to improve erosion resistance according to the present
invention;
Fig. 30 is a side view of the portion of the individual U-beam impact type
particle
separator of Fig. 29, viewed in the direction of arrows 30-30 in Fig. 29;
Fig. 31 is a sectional plan view of an alternative embodiment of a staggered
array
of chevron collecting elements according to the present invention;
Fig. 32 is a sectional view of an individual chevron collecting element of the
type
illustrated in Fig. 31, provided with erosion resistant refractory according
to the present invention;
Fig. 33 is a sectional view of an individual chevron collecting element of the
type
illustrated in Fig. 31, provided with an encircling stainless steel casing to
improve erosion resistance according to the present invention;
Fig. 34 is a sectional view of an individual chevron collecting element of the
type
illustrated in Fig. 31, wherein the cooled tubes are surrounded by cast
metal to improve erosion resistance according to the present invention;
Fig. 35 is a top view of an alternative embodiment of an individual U-beam
impact type particle separator comprised of rectangular tubing for
conveying the cooling fluid according to the present invention;
Fig. 36A is a perspective view of a lower portion of an individual U-beam
impact
type particle separator according to the present invention wherein the
lower ends of adjacent cooling tubes are fluidically connected to one
another to form 180 bends;
Fig. 36B is a perspective view of a lower portion of an individual U-beam
impact
type particle separator according to the present invention wherein the
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lower ends of cooling tubes forming opposite sides of the U-beam are
fluidically connected to one another to form 180 bends;
Fig. 37 is a perspective view of a lower portion of an individual U-beam
impact
type particle separator according to the preserit invention wherein the
lower ends of the cooling tubes are fluidically connected to a common
manifold located proximate above a floor of a gas path;
Fig. 38 is a side view of a lower portion of an individual U-beam impact type
particle separator according to the present invention wherein the lower
ends of the cooling tubes are fluidically connected to a common manifold
located proximate below a floor of a gas path; and
Fig. 39 is a perspective view of yet another alternative embodiment of an
individual U-beam impact type particle separator according to the present
invention wherein a lower portion of each of the cooling tubes is provided
with a reduced diameter portion to prevent erosion of the lower portion.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As used herein, the term CFB boiler will be used to refer to CFB reactors or
combustors
wherein a combustion process takes place. While the present invention is
directed particularly
to boilers or steam generators which employ CFB combustors as the means by
which the heat
is produced, it is understood that the present invention can readily be
employed in a different
kind of CFB reactor. For example, the invention could be applied in a reactor
that is employed
for chemical reactions other than a combustion process, or where a gas/solids
mixture from a
combustion process occurring elsewhere is provided to the reactor for further
processing, or
where the reactor merely provides an enclosure wherein particles or solids are
entrained in a gas
that is not necessarily a byproduct of a combustion process. Similarly, the
term U-beam is used
in the following discussion for the sake of convenience, and is meant to refer
broadly to any type
of concave impingement members or impact type particle separators used to
collect and remove
particles from a particle laden flue gas. Particularly, the impact type
particle separators are non-
planar; they may be U-shaped, V-shaped, E-shaped, W-shaped, or any other shape
as long as they
have a concave or cupped surface which is presented to the oncoming flow of
flue gas and
entrained particles which will enable the members to collect and remove
particles from the flue
gas.
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Referring now to the drawings, in which like reference numerals are used to
refer to the
same or functionally similar elements throughout the several drawings, Fig. 1
shows a furnace,
generally designated 10, containing circulating fluidized bed 12, exhaust flue
14, and particulate
return 16. Combustion of fuels occurs in circulating fluidized bed 12,
generating hot waste or
flue gases which are laden with particulate matter. The hot gases rise through
furnace 10 to
exhaust flue 14, from where the gases pass across and/or through several heat
transfer surfaces
(such as superheater, reheater or econoinizer) 17 and cleaning stages before
being conveyed to
the atmosphere (not shown).
Rows of staggered, impact type particle separators 20 are oriented in the
upper part of
fizrnace 10, and are generally supported from furnace roof 26. A first group
of particle separators
22 is referred to as the in-furnace U-beams 22, while a second group of
particle separators 24 is
provided and located downstream of the furnace exit which is schematically
represented by the
clotted vertical line in Fig. 1 shown in between groups 22 and 24. Particulate
matter entrained
in flue gas strikes impact type particle separator 20, becomes separated and
free-falls directly
back into the circulating fluidized bed 12, where further combustion or
reaction of the recycled
particulate can occur. Generally, the impact type particle separators 20 are
nonplanar and
preferably U-shaped in cross-section, but they may be V-shaped, E-shaped, W-
shaped or of some
similar concave or cupped configuration.
Fig. 2 is a sectional plan view of'the in-fumace U-beams 22 forming the in-
furnace group
22 of U-beams 20, and illustrates how the rows of U-beams 20 are staggered
with respect to one
another in adjacent rows. At the bottom of each U-beam 20 in the in-furnace
group 22 there is
typically a plate forming a pan or baffle 23 whose purpose is to prevent the
flue gases and
entrained particles from bypassing the U-beams 20.
Referring now to Figs. 3, 4 and 5, there is illustrated a first embodiment of
the U-beam
impact type particle separator 20 according to the present invention. Each U-
beam 20 is
comprised of cooling tubes 30 which may be cooled by water, steam, a mixture
thereof, or some
other suitable cooling medium. The cooling tubes 30, and thus the U-beams of
which they form
a part, are arranged vertically like the known U-beams 20 illustrateci in Fig.
1, and may be
supported from the roof 26 of the furnace 10. 'rhe cooling tubes 30 forming an
individual U-
beam 20 are arranged next to one another; as illustrated in Fig. 3, four
cooling tubes 30 may be
used to form an individual U-beam, one at each corner thereof. The cooling
tubes 30 are
1:ypically I" outside diameter (OD) but other tube diameters may of course be
used.
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As illustrated in Figs. 3, 4 and 5, each U-beam 20 further comprises a
plurality of slip fit
elements 50 having apertures 52 therein in a portion 57 (which may be an
enlarged portion as
shown to surround the cooling tube 30 receive(I therein) and which accept each
of the cooling
tubes 30 forming an individual U-beam 20. The slip fit elements 50 thus
surround each cooling
tube 30 and, by being stacked one upon the other along the vertical height of
the U-beams 20,
form a collection channe160. Each slip fit element 50 forming the U-beam 20
includes two side
walls 54 and a back wall 56. As illustrated in Figs. 4 and 5, each of the side
walls 54 and the
back wall 56 are comprised of a plurality of vertically aligned segments 70
extending in between
the portions 57 containing the apertures 52 suIxounding the cooling tubes 30.
The vertically
aligned segments 70 of the plurality of slip fit elements 50 are located along
the length of the
vertically extending cooling tubes 30 and combine with one another to form the
collection
channel 60 of the U-beam 20.
Shiplap joints 80 or other siniilar type connections are provided between
vertically
aligned segments 70. The shiplap joint 80 configuration at the top and bottom
of each vertically
aligned segment 70 prevents gas and solids from leaking between segments 70
and allows for
short term and long tenn expansion and contraction of segment dimensions in
the vertical
direction.
The cooling tubes 30 thus provide a cooled support as well as alignment and
cooling of
aligned segments 70. Cooling tubes 30 further provide a unique symmetrical
temperature
distribution along each aligned segment 70 without distortion of the element
shape which would
normally be the case whenever an asymmetrical temperature distribution occurs
due to
asymmetrical cooling of segment 70.
Each slip fit element 50 may be comprised of alloy metal, ceramic or other
materials
having high heat resistance. In the embodiment of Figs. 3, 4 and 5, each of
the slip fit elements
50 comprise a single unitary piece which includes the two side walls 54 and
back wall 56, and
which slips over cooling tubes 30. 'I'he single unitary piece may be a
casting, or an extrusion.
However, it will be appreciated that other constructions may be employed for
the slip fit
elements.
Referring now to Figs. 6, 7, 8 and 9, in another embodiment, each of the side
walls 54 and
back wall 56 are separate, slip fit elerr.ients; thus three separate slip fit
elements are required to
form an individual level or cross-section portion of the U-beam 20. The end
portions 57 and
their apertures 52 of each of side walls 54 and back wall 56 overlap at
shiplap joint 80.
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Referring now to Figs. 10, 11, 12 and 13, in a still further embodiment, the
side walls 54
and the back wall 56 may be formed from two elements 59 having an L-shaped
cross-section.
'The ends of the L-shaped elements 59 overlap at the back wall 56 by shiplap
joint 80.
As illustrated in the embodiments of Figs. 6 and 10, additional cooling tubes
30 may be
used, as compared to the four cooling tubes shown in Fig. 3, to form, support
and cool the
collection channel elements. Such a co:nstruction may also be used if larger
size U-beams 20 are
desired, or if different cooling tubes 30 are desired. By this means lower
heat resistance of the
material forming the slip fit element 50 may be used, while preserving the
unique symmetrical
temperature distribution along the vertical height of each U-beam 20.
While the aforementioned U.S. Pat. Nos. 5,378,253 and 5,435,820 to Daum et al.
disclose
cooled collection elements, the designs illustrated therein do not address
significant practical
difficulties which prevent them from being utilized in the majority of
commercial applications.
As shown in the'253 and'820 patents, each separator element is comprised of
only four cooled
tubes per separator with welded me:mbrane bar extending betweeri the tubes to
form the
collecting portion. This severely limits the ability to apply such designs for
two reasons. First,
it has been determined that the membrane bar temperature oxidation limit
limits the maximum
width of the membrane bar when the separator elements are operated at the
temperatures
experienced in a CFB. Since the membrane bar is cooled by the tubes to which
it is attached, the
maximum membrane bar temperature occurs midway between tubes connected by the
membrane,
and the temperature at that location must be held to acceptable levels below
the oxidation
temperature limit for the material forming the membrane bar. While this aspect
could be
addressed by using an alloy bar having a higher oxidation temperature limit,
or even using
stainless steel tubes and membrane bar, it will be appreciated that this
approach is cost
prohibitive and, in fact, may still not provide the designer with much of an
increase in maximum
membrane bar width. Second, and as a result of being limited in the rnaximum
membrane bar
width, the actual size of the individual collecting elements may be restricted
from that necessary
for efficient and cost effective collection performance.
In contrast, the following embodiments of present invention employ at least
three or more
cooling tubes 126 per side of each of the individual separator elements 120,
along with a
corresponding number of cooling tubes 126 forming the rear of each of the
elements 120. The
size of the separator elements 120 is thus not limited by peak membrane
temperatures and the
separator elements 120 can be designed as large as desired. This is important
because the use
of larger size separator elements 120 er.iables longer separators to be used,
since the greater cross-
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section within an individual separator element 120 enables a greater solids
quantity to remain
"within" the cross-section before the collected solids "spill out" due to
overfilling on the
downward movement of the solids to the bottom of the separator element 120. In
other words,
the separator element 120 has a longer effective portion. The use of larger
size separator
elements 120 means that fewer will be required/used, allowing the CFB boiler
to be narrower
(since the furnace depth can be greater for a given furnace plan cross-
sectional area) which
reduces cost.
Figs. 14 through 24 illustrate another embodiment of a U-beam impact type
particle
separator apparatus according to the present invention, generally referred to
as 100, and which
is particularly suited for application in CFB boilers. Again, the term U-beam
is used for the sake
of convenience, and is meant to refer broadly to any type of concave
iinpingement members or
impact type particle separators used to collect and remove particles frorri a
particle laden flue gas.
Particularly, the impact type particle separators are non-planar; they may be
U-shaped, V-shaped,
E-shaped, W-shaped, or any other shape as long as they have a concave or
cupped surface which
is presented to the oncoming flow of' flue gas and entrained particles which
will enable the
members to collect and remove particles from the flue gas.
The particle separator apparatus 100 is comprised of a plurality of vertically
extending,
staggered collection U-beam elements 120, arranged in at least two rows, an
upstream row 122
and a downstream row 124. The apparatus 100 may be used as the group of in-
furnace U-beams
22, or as external U-beams 24. The U-beams 120 are comprised of a plurality of
cooled tubes
126 which convey a cooling medium, such as water, steam, a mixture thereof or
some other
suitable cooling fluid therethrough. The cooling fluid is conveyed into and
out of the U-beams
120 via an arrangement of upper and lower piping, headers and manifolds
located at upper 128
and lower 130 portions of the apparatus 100. As will be more fully described
later, the particular
arrangement of such piping, headers and manifolds for the U-beams 120 forms an
important
aspect of the present invention.
Turning now to Fig. 15, there is shown a sectional view of an individual U-
beam impact
type particle separator element 120 of Fig. 14. A plurality of cooling tubes
126 are provided,
arranged with respect to one another so as to form the general outline of the
collection element,
in this case a U-beam collection element. In this case, a total of twelve
cooling tubes 126 are
employed, but more or fewer tubes 126 may be used, depending upon the size of
the U-beam
desired, fluid cooling and pressure drop considerations, etc. Each cooling
tube 126 in a U-beam
120 is provided with a plurality of studs 132 welded to the tubes 126 along
its length and around
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its circumference to permit refractory 134 to be applied to the U-beam 120.
Individual tubes 126
fonning a given U-beam are also connected to one another by intermediate tube
alignment plate
or bar (for example, membrane bar 136) welded at least intermittently
inbetween and along the
adjacent cooling tubes to maintain the U-beam 120 as a unitary, fixed
structure. The membrane
bar 136, as well as the studs 132, conduct heat from the refractory 134 to the
cooling tubes 126
where it is conducted away by the internally flowing cooling medium, typically
water and/or
steam. The refractory 134 may be factory installed on the U-beams 120 to
reduce costs and
ensure uniformity of application or it may be field-installed.
Fig. 16 illustrates a side view of the lower portion of Fig. 14; more
particularly a first
embodiment of the piping, header and nianifold arrangement which can be used
to supply cooling
fluid to or from the U-beams 120. Lower ends of the cooling tubes 126 are
fluidically connected
to a plurality of vertical manifolds 138 which, in turn, are fluidically
connected to a header 140.
Again, this can be an arrangement of an inlet header 140 and associated inlet
manifolds 138, or
an outlet header 140 and outlet manifolds 138. In the arrangement illustrated
in Fig. 16, both
rows 122, 124 of U-beams 120 are part. of the same module; that is, they are
fed from the same
manifold 138. The size of the CFB and allowable shipping limitations will
determine the number
of individual U-beams 120 which can be shop assembled and shipped to the field
for erection.
Inlet or outlet piping 144 would be applied and routed as required.
With reference to Figs. 16 and 1.7, another aspect of the present invention
comprises the
use of a cooling tube 126 bent in suitable fashion to form a pan or baffle 142
at a lower end of
the U-beam which helps to prevent gas and entrained particles from bypassing
around the lower
end 130 of the U-beams 120. The fluid cooled pan 142 is also provideli with
pin studs 132 and
coated with refractory 134. If desired, a conventional pan or baffle 23 may be
employed on the
lower ends of the U-beams 120 according to the present invention.
Fig. 18 illustrates a side view of an alternate embodiment of the lower
portion of the U-
'beam impact type particle separator apparatus of Fig. 14; in particular, an
arrangement where the
front 122 and rear 124 rows of U-beams 120 are fluidically connected to an
individual manifold
138 for each row. The concepts mentioned before concerning the possibility of
the lower portion
130 being the inlet or the outlet for the cooling medium flowing in the U-
beams 120 still apply.
Fig. 19 illustrates a side view of the upper portion 128 of the alternate
embodiment
-illustrated in Fig. 18. Here, individual inlet or outlet manifolds 138, orie
for each row 122, 124
of U-beams 120 would be provided, connected to suitable inlet or outlet piping
144 as shown.
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Fig. 20 is a sectional plan view of an impact type particle separator
apparatus according
to the invention illustrating a staggered arrangement of V-shaped collecting
elements. Again,
each cooling tube 126 is provided with a plurality of studs 132 welded to the
tubes 126 along its
length and around its circumference to permit refractory 134 to be applied to
the collecting
element 120. Individual tubes 126 fonning a given collecting element 120 are
also connected
to one another by membrane bar 136 welded at least intermittently between the
tubes 126 to
maintain it as a fixed structure. The membrane bar 136, as well as the studs
132, conduct heat
from the refractory 134 to the cooling tubes 126 where it is conducteci away
by the internally
flowing cooling medium, typically water and/or steam. The refractory 134 may
be factory
installed to reduce costs and ensure unifonnity of application, or it may be
field-installed.
Figs. 21 through 24 illustrate an embodiment of the present invention which
employs an
arrangement of what is generally referred to as chevron collecting eleinents
150. The cooling
tubes 126 are again provided with a plurality of pin studs 132 welded to the
tubes 126 along their
length and around their circumference to permit refractory 134 to be applied
to the chevron
collecting elements 150. Individual tubes 126 forming a given chevron
collecting element 150
are also connected to one another by membrane bar 136 welded at least
intermittently between
the tubes 126 to maintain it as a fixed sti-ucture. The membrane bar 136, as
well as the studs 132,
conduct heat from the refractory 134 to the cooling tubes 126 where it is
conducted away by the
internally flowing cooling medium, typically water and/or steam. The
refractory 134 may be
factory installed to reduce costs and ensure uniformity of application, or it
may be field-installed.
The chevron collecting elements 150 may optionally be provided with one or
more deflecting
plates 152 at intervals along the vertical height of the chevron collecting
element 150. The
deflecting plates 152 are intended to direct collected solids particles back
into the chevron
collecting element 150. It is attached preferably by welding to a first
portion 154 of the chevron
collecting element 150 which extends substantially parallel to the flow of
flue gas and solids
particles when in service, such as in a CFB boiler, and a second portion 156
which is connected
to and which extends at an angle 0 with respect to the first portion 154.
Angle 6 is typically
approximately 30 , but this may be varied from approximately 10 to
approximately 90 to suit
a particular application.
While the second portion 156 illustrated in Figs. 22 and 23 is shown as being
planar, the
present invention is not so limited and the second portion 156 may
alternatively be arcuate or
segmented and bent at an angle as illustrated at A and B in Fig. 23 by the
broken lines.
., ., CA 02383170 2002-04-23
CASE 6111
-14-
Fig. 23 illustrates individual V-shaped chevron collecting elements 150. Those
collecting
elements 150 in line with one another (vvith respect to a predominant
direction of the flue gas and
solids particles through these elements 150) can be connected at ends of the
first portions 154
thereof as shown at C, or they can be separate from one another.
The present invention also involves various constructions to improve erosion
resistance
of the cooled U-beam impact type particle separators disclosed herein. In Fig.
25, the cooling
tubes forming an individual U-beam 120 comprise what are referred to as omega
tubes 160
welded together as illustrated at 164 to form the desired U-beam configuration
in cross-section.
In the embodiment shown, the dimensions of the omega tube could be 1-3/8" by
1" with a
minimum wall thickness of 3/16". Wliile such omega tubes 160 are known to
those skilled in
the art, heretofore it has not been known to employ same in such U-beam impact
type particle
separators. As shown in Fig. 26A, each omega tube is provided with a flow
passage 161, and
ends 166 provided with beveled portions to facilitate welding 164 to adjacent
omega tubes.
Omega tubes may effectively be implemented using conventional tubes 126 and
membrane bars
137 welded to the tube crowns as shomm in Fig. 26B.
Fig. 27 illustrates an arrangement of two slip on castings 170 having
apertures 162 which
would receive and encircle the cooling tubes 126. The slip on castings 170
have male portions
172 and female portions 174 to facilitate alignment of adjacent castings.
These castings 170
would typically be made of low alloy metal material, but they might be
surfaced with "309" alloy
1Eor improved erosion resistance.
Fig. 28 illustrates an arrangement of protective castings 180 which would be
welded to
the cooling tubes 126, preferably via plug welding as illustrated at 184. The
castings 180 would
have a 1/4" overface except at the leading edge, where the casting 182 would
be provided with
a%Z" overface. As shown, the back portions of each type of casting would be
curved to mate with
the outside diameter of the cooled tube to which it would be attached.
Figs. 29 and 30 illustrate an arrangement of protective castings 190 which are
intended
to bolt 194 onto the U-beam impact type particle separators 120, preferably
through the
membrane 136 or intermediate metal tube alignment plates holding tubes 126
adjacent to one
another. Apertures 192 in the castings 190 would be provided. In either case,
it is preferred that
the castings clear the membrane or the intermediate tube alignment plates. If
desired, the bolts
194 could be replaced by studs welded to either side of the membrane or the
intermediate tube
alignment plates. Castings at the leading edge (not shown) would preferably be
plug welded as
described earlier.
CA 02383170 2005-10-26
- 15-
Figs. 31 and 32 - 34 illustrate an alternative embodiment of a staggered array
of chevron
collecting elements according to the present invention, and various ways to
provide improved
resistance for this embodiment. Again, a staggered array of impact type
particle separator elements is
provided, this time aligned banks of cooled tubes 126 connected together as
before (intermediate tube
alignment plates or membrane 136). At regular intervals, fms 200 are welded to
the cooled tubes 126
to provide a tortuous path to the incoming flue gas/solids flow. The cooled
tubes may be provided
with erosion resistant refractory (Fig. 32); an encircling stainless steel
shield 202 (Fig. 33) (with
expansion slots if needed); or they may be surrounded by cast metal or weld
overlay 204 (Fig. 34).
Fig. 35 illustrates yet still another embodiment of an individual U-beam
impact type particle
separator 120, this one comprised of rectangular tubing 210 for conveying the
cooling fluid according
to the present invention. The individual tubing elements 210 would be welded
together at 212 as
shown. Preferably, the rectangular tubing 210 might be made of carbon steel
(SA-178 Gr. C), so long
as the cooling fluid being conveyed therethrough maintains the metal
temperature below the creep
range (greater than 700 F) for carbon steel.
Figs. 36A, 36B, 37 and 38 illustrate particular construction details of the
lower ends of the
individual U-beam impact type particle separators 120 according to the present
invention. For the sake
of clarity, no erosion protection for either the cooling tubes 126 or any
manifold 138 is shown, it
being understood that such erosion protection would of course be provided in
actual practice. As
disclosed in U.S. Patent No. 6,095,095 to Alexander et al., CFB constructions
are known in which at
least two rows of external U-beams may be located within an exhaust gas flue
14 downstream of the
furnace exit with collected particles being returned along a floor 220 (Figs.
36 A, 36B, 37 and 38 of
the present invention). The sides 222, 224 and a rear portion 226 of the U-
beams 120 are again
comprised of cooling tubes 126.
The lower ends 228 of the cooling tubes 126 may be fluidically connected in
various ways.
For example, as illustrated in Figs. 36A, 36B, 37 and 38 the lower ends 228 of
the cooling tubes 126
extend proximate to the floor 220 located immediately below the staggered rows
of impact type
particle separators. The floor 220 forms the gas path 14 of the CFB boiler 10.
In some cases, as
illustrated in Fig. 36A, the lower ends of adjacent cooling tubes 126 (such as
those forming one or the
other side 222, 224, or the rear portion 226) forming the impact type particle
separators 120 are
fluidically connected to one another to form 180 bends. Alternatively, as
illustrated in Fig. 36B, the
lower ends 228 of the cooling tubes 126 forming opposite sides 222,
CA 02383170 2005-10-26
-16-
224 of the impact type particle separators 120 are fluidically connected to
one another to form 180
bends. These arrangements are relatively simple in construction but it will be
appreciated that they
render the cooled impact type particle separators 120 undrainable.
As illustrated in Fig. 37, the lower ends 228 of the cooling tubes 126 forming
an individual
impact type particle separator 120 are fluidically connected to a common
manifold 138 located
proximate to the floor 220 of the gas path 14, in this case above the floor
220, while Fig. 38 illustrates
an embodiment wherein the manifold 138 is located beneath the floor 220. It is
understood that the
common manifold could actually be partially or completely embedded in the
floor 220. While more
elaborate, this design allows the separators 120 to be drainable, and the
mixing of the cooling fluid
from each of the cooling tubes may provide other benefits such as the
elimination of temperature
imbalances due to uneven heat absorption by individual cooling tubes 126.
Further, the design
illustrated in Fig. 38 allows for better accessability of any welds of the
cooling tubes 126 to the
manifold 138, if required.
Finally, Fig. 39 is a perspective view of yet another alternative embodiment
of an individual
U-beam impact type particle separator 120 according to the present invention
wherein a lower portion
228 of each of the cooling tubes 126 is provided with a reduced diameter
portion 250 to prevent
erosion of the lower portion 228. This embodiment employs a variation of the
concepts employed in
U.S. Patent No. 6,044,805 to Walker et al. entitled Wall Protection from
Downward Flowing Solids,
and in published PCT application WO 00168615. In those publications, a reduced
diameter portion is
employed to eliminate the discontinuity normally present at interfaces on wall
enclosures and division
wall structures. However, as shown in Fig. 39, the lower portion 228 of each
of the cooling tubes 126
is provided with a reduced diameter portion or zone 250 to prevent erosion of
the lower portion 228 of
the U-beams 120. To accomplish this change, the outside diameter of each tube
126 is swaged down
as at 260 to a reduced diameter. As required, and disclosed in the
aforementioned U.S. 6,044,805 and
WO 00/68615 publications, a shaped refractory tile 270 is provided at the
transition 250 and the
discontinuity normally present where erosion resistant refractory would be
applied is eliminated.
Below the reduced diameter portion 250 there may also be provided erosion
resistant refractory 134
down to the end of each U-beam 120.
It will thus be seen that each U-beam impact type particle separator element
may be
comprised of cooling tubes which are attached to each other to keep the tubes
in position with respect
to one another. In some embodiments the tubes are attached or connected to one
another
-,CA 02383170 2002-04-23
CASE 6111
-17-
by intermediate tube alignment plate or bar welded at least intermittently
inbetween and along
the adjacent cooling tubes to form a unitary structure. Deflecting plates
intended to direct
collected solids particles back into a separator element, similar to the plate
152 in Fig. 24, may
be used with any embodiment of an individual U-beam impact type particle
separator. In all
embodiments it is necessary to protect the cooling tubes of the impact type
particle separator
elements from erosion and corrosion. Various means may be used to protect the
tubes from
erosion; in some cases, slip fit castings are employed over the cooling tubes,
in others materials
such as ceramics or refractory, are attached to the tubes for erosion
protection. As described
above and illustrated in the Figures forming a part of this disclosure, in
some embodiments of
the invention, the associated inlet and outlet routing and connections which
convey the fluid to
and from the tubes is considered to be an important feature of the invention.
In some cases, the
inlet and outlet connections determine the degree of modularity by which the
impact type particle
separator elements can be produced, thereby speeding field installation and
reducing costs. In
other cases, certain portions of such connections actually form and perform
the functions of pans
or baffles used in connection with such U-beams to prevent gas bypassing
around the ends of the
impact type particle separator elemerits. It will be understood, of course,
that conventional
uncooled metal pans or baffles may be employed with any of the aforernentioned
configurations
of the present invention.
While specific embodiments of the invention have been shown and described in
detail
to illustrate the application of the principles of the invention, those
skilled in the art will
appreciate that changes may be made in the form of the invention covered by
the following
claims without departing from such principles. For example, the present
invention may be
applied to new construction involving circulating fluidized bed reactors or
combustors, or to the
replacement, repair or modification of existing circulating fluidized bed
reactors or combustors.
In some embodiments of the invention, certain features of the invention may
sometimes be used
to advantage without a corresponding use of the other features. Accordingly,
all such changes
and embodiments properly fall within the scope of the following claiins.
