U.S. patent application number 10/510441 was filed with the patent office on 2005-06-16 for support grid.
Invention is credited to Colman, Derek Alan, Hesketh, Trevor John, Reid, Allan Beattie.
Application Number | 20050126107 10/510441 |
Document ID | / |
Family ID | 9934735 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050126107 |
Kind Code |
A1 |
Colman, Derek Alan ; et
al. |
June 16, 2005 |
Support grid
Abstract
The present invention provides a support grid having the form of
a web of vertically disposed plates said web of plates comprising
(a) a network of strands of plate segments connected by junctions,
the said strands terminating only at the periphery of the grid, and
(b) one or more internal plate branches, each plate segment being
joined at one end to a junction with at least two other plate
segments and at the other end either being joined to a junction
with at least two other plate segments or terminating at or near C
the periphery of the grid, said internal branch comprising a plate
having a free end within the grid and being joined at one end
thereof to a segment or to another branch, characterised in that in
horizontal cross-section through the grid each segment has at least
two angular and/or curved portions which alternate in
direction.
Inventors: |
Colman, Derek Alan; (Fleet
Hampshire, GB) ; Hesketh, Trevor John; (Weybridge,
GB) ; Reid, Allan Beattie; (Southfields, GB) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Family ID: |
9934735 |
Appl. No.: |
10/510441 |
Filed: |
October 7, 2004 |
PCT Filed: |
April 1, 2003 |
PCT NO: |
PCT/GB03/01423 |
Current U.S.
Class: |
52/673 |
Current CPC
Class: |
B01J 8/008 20130101;
B01J 2208/00884 20130101 |
Class at
Publication: |
052/673 |
International
Class: |
E04C 002/42 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2002 |
GB |
0208458.0 |
Claims
1-10. (canceled)
11. A grid having the form of a web of vertically disposed plates
said web of plates comprising (a) a network of strands of plate
segments connected by junctions, the said strands terminating only
at the periphery of the grid, and (b) one or more internal plate
branches, each plate segment being joined at one end to a junction
with at least two other plate segments and at the other end either
being joined to a junction with at least two other plate segments
or terminating at or near the periphery of the grid, said internal
branch comprising a plate having a free end within the grid and
being joined at one end thereof to a segment or to another branch,
characterised in that in horizontal cross-section through the grid
each segment has at least two angular and/or curved portions which
alternate in direction.
12. A grid according to claim 11 wherein the alternation in
direction of the angular and/or curved portions may be of equal
magnitude or of differing magnitude.
13. A grid according to claim 11 wherein the grid is formed from
vertical plates wherein each vertical plate has a high resistance
to deformation in a direction parallel to its vertical plane and is
relatively easily deformed in the horizontal plane.
14. A grid according to claim 11 wherein the grid is free from a
solid boundary perimeter plate.
15. A grid according to claim 11 wherein the grid is formed from a
metal.
16. A grid having the form of a web of vertically disposed
interconnected plates or strips, said web having in horizontal
cross-section a repeating pattern, said pattern comprising one or
more series of unit cells, each cell having substantially polygonal
shape wherein each polygon contains at least 8 sides, at least two
internal angles above 180.degree. and at least four internal angles
below 180.degree..
17. A grid according to claim 16 wherein one or more linear or
branched internal projections can be provided on one or more sides
of a polygon and/or at the junction of two sides of a polygon,
wherein the said projections do not bridge any polygon.
18. A grid according to claim 16 wherein the grid is formed from
vertical plates wherein each vertical plate has a high resistance
to deformation in a direction parallel to its vertical plane and is
relatively easily deformed in the horizontal plane.
19. A grid according to claim 16 wherein the ratio of the height of
the web to the average thickness of the vertical plates forming the
web lies in the range 100:1 to 2:1.
20. A grid according to claim 16 wherein the defined geometry of
the unit cell dictates that the polygon has at least 8 sides, at
least two internal angles above 180.degree. and at least four
internal angles below 180.degree..
21. A grid according to claim 20 wherein the geometric shape of the
polygon can be superimposed on itself when rotated in the
horizontal plane through 90.degree., or through 180.degree. or
through 120.degree..
22. A grid according to claim 13 wherein the grid is free from a
solid boundary perimeter plate.
23. A grid according to claim 13 wherein the grid is formed from a
metal.
Description
[0001] The present invention relates to a grid suitable for
load-bearing applications. The invention particularly relates to a
grid suitable for supporting articles within an environment which
is subject to substantial thermal changes, for example, within a
reaction vessel used for exothermic chemical reactions, or within a
furnace. The present invention finds particular utility as a
support grid for catalyst briquettes, for example in chemical
processes involving catalytic oxidation, reduction or other
chemical conversion processes.
[0002] Support grids having a shape obtained by the notional
superimposition of two or more sets of vertically disposed parallel
plates or bars arranged mutually at an angle or angles to form a
mesh are well-known in the art. In particular, some prior art grids
comprise, for example, a web of vertically disposed plates wherein
the horizontal cross-section of the web shows a repeating pattern
of unit cells of, for example, square, rectangular or triangular
shape.
[0003] Such grids are normally satisfactory for many load-bearing
applications, but are prone to problems in circumstances where the
grid is subjected to substantial changes in temperature. In
particular, heating of rigid grids of this type can generate
powerful internal and external forces due to the thermal expansion
of the material (normally metal) from which they are
fabricated.
[0004] Internal expansive forces within the grid can occur when the
heating of the grid is rapid or uneven, and can result in
distortion of the grid in a vertical direction to give warping or
bowing of the support surface thereof. Such distortions can have an
adverse effect on the disposition of, for example, briquettes of
catalyst stacked thereon.
[0005] Powerful external expansive forces occur due to the overall
thermal expansion of the grid material on heating. Such forces can
cause damage to the grid itself, or to articles in contact with the
grid, for example, vessels or pipes containing the grid or elements
supporting the grid. One solution to avoid damage caused by the
external expansive forces of the grid is to provide gaps or spaces
designed to accommodate such expansive movement of the grid. For
example, in the case of circular grid resting on an annular spigot
situated in a vertical pipe of corresponding circular
cross-section, an annular gap is provided around the grid periphery
of the grid to accommodate the thermal expansion of the grid.
However, the provision of such gaps or spaces generates additional
problems, for example, they can allow undesirable passage of
materials (e.g. undesirable bypass of gases) or can become blocked
with solid material, e.g. decomposition products such as coke, or
materials derived from corrosion of the apparatus, or from the
catalyst material or the catalyst support itself. Blocking of these
spaces could prevent the intended ability of the grid to expand
within the holder.
[0006] It is an object of the present invention to provide an
improved load-bearing grid. It is a further object of the present
invention to provide a grid having improved performance in
environments subject to substantial thermal changes.
[0007] Accordingly the present invention provides in a first aspect
a grid having the form of a web of vertically disposed plates said
web of plates comprising (a) a network of strands of plate segments
connected by junctions, the said strands terminating only at the
periphery of the grid, and optionally (b) one or more internal
plate branches, each plate segment being joined at one end to a
junction with at least two other plate segments and at the other
end either being joined to a junction with at least two other plate
segments or terminating at or near the periphery of the grid, said
optional internal branch comprising a plate having a free end
within the grid and being joined at one end thereof to a segment or
to another branch, characterised in that in horizontal
cross-section through the grid each segment has at least two
angular and/or curved portions which alternate in direction.
[0008] The alternation in direction of the angular and/or curved
portions may be of equal magnitude or of differing magnitude. Thus,
for example, the segment may have a shape similar to the letter
"S", or a shape similar to the letter "Z", or combinations of
alternating shapes of this type. Thus for example, the segment may
comprise an angular portion having a first angle of, for example,
+5.degree. to +170.degree. and a second angle, not necessarily
equal to the first angle of, for example, -5.degree. to
-170.degree.; or the segment may comprise, for example, a curved
portion curving through a first angle of, for example, +5.degree.
to +175.degree. and a second angled portion having an angle in the
range, for example, of -5.degree. to -170.degree..
[0009] In a preferred second aspect the present invention provides
a grid having the form of a web of vertically disposed
interconnected plates or strips, said web having in horizontal
cross-section a repeating pattern, said pattern comprising one or
more series of unit cells, each cell having substantially polygonal
shape wherein each polygon contains at least 8 sides, at least two
internal angles above 180.degree. and at least four internal angles
below 180.degree., and, optionally, wherein one or more linear or
branched internal projections can be provided on one or more sides
of a polygon and/or at the junction of two sides of a polygon, with
the proviso that the said projections do not bridge any
polygon.
[0010] The web of the grid in both aspects of the present invention
is preferably formed from vertical plates, each of which, by virtue
of its height and horizontal width, has high resistance to
deformation or bending in a direction parallel to its vertical
plane, but, due to its relatively small thickness, is relatively
easily deformed or bent in the horizontal plane. Preferably the
ratio of the height of the web to the average thickness of the
vertical plates forming the web lies in the range 100:1 to 2:1 most
preferably in the range 30:1 to 5:1.
[0011] In the second aspect of the present invention the defined
geometry of the unit cell dictates that the polygon has at least 8
sides, at least two internal angles above 180.degree. and at least
four internal angles below 180.degree.. Thus regular polygons
having all internal angles equal are clearly excluded. However,
some regularity or symmetry to the polygonal shape is preferred. In
particular the following characteristics of the polygon are
preferred: (a) polygons have an even number of sides; (b) pairs of
sides, not necessarily adjacent sides, have equal length; (c) pairs
of angles, not necessarily adjacent angles, have equal size; (d)
the reflex angles (greater than 180.degree.) are separated from one
another by at least two other angles.
[0012] The reflex angles are preferably in the range 210.degree. to
330.degree. most preferably 240.degree. to 300.degree.. The number
of reflex angles in each polygon is preferably one for each four or
more sides. Thus for a polygon of eight or ten sides, the number of
reflex angles is preferably 2, for a polygon of twelve or fourteen
sides the number of reflex angles is preferably 3 and for a polygon
of 16, 18 or 20 sides the number of reflex angles is preferably
4.
[0013] It is preferred that the geometric shape of the polygon can
be superimposed on itself when rotated in the horizontal plane
through 90.degree., or through 180.degree. or through
120.degree..
[0014] The polygons can optionally contain defined internal
projections. Such projections can be provided primarily to reduce
the span of unsupported regions of the grid, and thus to improve
the distribution of the load across the grid. The projections, if
any, are preferably formed from plates or strip having similar
thickness and height to the rest of the web. Such optional
projections are positioned within the free space between one or
more of the polygons and each such projection projects only from
its single point of attachment to the polygon (i.e., no projection
may form a bridge across a polygon). The, or each, projection can
comprise, for example, a plate or strip having linear, curved, or
branched cross-section. The projection may bridge back upon itself
if desired, e.g. it can have a branch bearing an element of
circular or triangular cross section.
[0015] The polygonal cells can be arranged together to form a grid
having any suitable overall shape. For example square for a square
reactor section or circular for a circular reactor. The diameter of
the circle or edge of the square is preferably in the range 50 to
2000 mm and more preferably in the range 100 to 1000 mm.
[0016] The pattern of polygons formed by the cross-section through
the vertical web of plates or strips is carried through to the
upper surface of the grid, and hence forms the load-bearing surface
thereof. To increase the surface area of the material forming the
support surface, as has been specified above, additional plates or
strips are optionally provided which project into the polygonal
areas and partially in fill these.
[0017] In both the first and second aspects of the present
invention the grid preferably is free from a solid boundary
perimeter plate. Preferably the periphery is provided, in the first
aspect of the present invention, by free ends of the defined
segments. In the second aspect of the present invention, the
periphery is provided by the angular edges of the polygons or by
radially or outwardly directed vertical plates connected
thereto.
[0018] If desired the grid can be welded in position in a conduit
or pipe or can, for example, rest on protrusions on, or in recesses
in, such a conduit or pipe,
[0019] The material from which the web is formed can be any
suitably flexible structural material. Metals are preferred,
especially, for example, ductile cast iron, mild steel, stainless
steel, or other suitable metal alloy compatible with the
process.
[0020] The material from which the grid is formed can be coated or
surface-treated to provide, for example protective anti-corrosion
or anti-coking properties, or to provide a surface having reduced
self-catalytic activity. For example, the surface of a metal grid
can be alloyed or coated with metal, non-metal or chemical
compound. For example the surface can be with aluminised or
alonised, or, for example, coated with another metal, e.g. copper,
or with a thin layer of a ceramic.
[0021] The web can be manufactured by any suitable method, for
example, by moulding or casting processes, or by welding, brazing
or bolting suitable plates together, or by cutting the web from a
block or blocks of suitable material.
[0022] The support grid of the present invention finds a wide
variety of uses in many areas of industry, particularly in the
Chemical Industry in processes involving cyclical heating and
cooling.
[0023] The support grid of the present invention will be further
described with reference to the accompanying drawings wherein FIG.
1 is a plan view and FIG. 2 is a perspective view of a grid in
accordance with the first aspect of the present invention. FIG. 3
is a plan view of a grid in accordance with both the first and
second aspects of the present invention and FIG. 4 is a magnified
view of part of FIG. 3.
[0024] FIG. 1 of the drawings represents a horizontal cross-section
through the grid depicted in FIG. 2 (in perspective view). The
cross section is taken at a plane slightly over half the height of
the grid. The grid 1 comprises a network of steel strands, for
example X-J-W, Y-J-Z and X-J-Z. The grid exhibits considerable
rigidity to flexing or bowing in the bending in a vertical
direction due to the height of the steel plates which form the
strands. However, the steel plates are relatively thin in
horizontal cross-section, and hence exhibit flexibility along their
length. Each of the said strands terminates only at or near the
periphery of the grid represented by the dashed line X,Y,Z,W. The
strand X-Y-J comprises two plate segments X-J and J-Z which are
connected at junction J. Segment X-J has one end X at the periphery
of the grid, and the other end J at the junction of three other
segments W-J, Y-J and Z-J. Each of the segments has branches, for
example, segment X-J has single branches 2 having a free end 3 and
being joined to segment X-J at 4. Branch 5 has a free end 6, and is
joined to branch 7 at S. Each segment has two angular or curved
portions which alternate in direction, for example the segment J-Z
bends through about +90.degree. at M and then bends back in the
opposite direction through about -130.degree. at N. Cut-away
portions 9 at each corner permit the grid to be located on
protrusions located on the inside of a square-section conduit.
[0025] In use, the grid can, for example, be used for supporting
catalyst (not shown) in a conduit (not shown). When heat is applied
to the catalyst, or is generated by a catalytic reaction on the
catalyst, the grid undergoes thermal expansion. The strands X-J-Z
and Y-J-W expand lengthwise, but if the ends X, Y, Z, and W are
constrained from movement by the interior wall of the conduit, the
expansion is accommodated by virtue of the flexibility of the bends
at, for example M and N. It can be seen that an increase in the
length of strand X-J-Z will be accommodated by a reduction on the
angles, e.g. at M and N. It will be clearly apparent that the force
exerted on the conduit wall by the strands of the grid (which are
capable of accommodating the expansion by bending at the angled
segments) will be substantially less than the force which would
have been produced by a network of linear bars of similar
cross-section.
[0026] FIG. 3 shows a plan view of a larger-sized grid formed from
a number of units similar to the one depicted in FIGS. 1 and 2.
FIG. 4 is a magnified view of part of FIG. 3. The grid comprises a
network of strands, eg strand P-J1-J2-J3-Q, which comprises of four
plate segments P-J1, J1-J2, J2-J3 and J3-Q. Each strand terminates
only at the periphery of the grid, e.g. strand P-J1-J2-J3-Q
terminates at P and Q. Each strand, comprises plate segments, e.g.
segment J1-J2, having at least two angular or curved portions S, T
which curves/angles are oppositely disposed. The grid further
comprises one or more internal plate branches 10, 11 having free
ends 12, 13 and joined at their other ends 14, 15 to a plate
segment. It will be seen that the web in FIGS. 3 and 4 has a
repeating pattern comprising a series of unit cells having the
shape depicted by the polygon unit J1-J2-J5-J6 drawn in FIG. 4 in
solid line. The polygon J1-J2-J5-J6 has twelve sides, two reflex
angles of 270.degree. at R1, R2, two reflex angles of 225.degree.
at R3, R4, six right-angles at J1, S, J2, J5, R5, J6 and two angles
of 135.degree. at A1, A2. Addition of these angles provides a total
of 180.degree., which is correct for a twelve-sided polygon. During
thermal expansion, peripheral constraint of the grid, e.g. by the
wall of a pipe in which it may be contained, results in bending of
the strands at the angles/bends thereof with the result that the
overall expansive force to which the wall or pipe is subjected is
reduced compared with a rigid grid formed from linear bars or
plates.
[0027] FIGS. 5, 6 and 7 are provided to illustrate examples of
other patterns of polygons that can be used to provide grids in
accordance with the present invention.
[0028] FIG. 5, which is in accordance with the second aspect of the
present invention, shows diagrammatically in horizontal
cross-section a grid 20 having the form of a web of vertically
disposed interconnected plates or strips, said web having in
horizontal cross-section a repeating pattern, said pattern
comprising a series of unit cells, each cell having substantially
polygonal shape wherein each polygon contains 8 sides, e.g. sides
n.sup.1, n.sup.2, n.sup.3, n.sup.4, n.sup.5, n.sup.6, n.sup.7,
n.sup.8. The unit cell contains two internal angles above
180.degree. (1.sup.3 and 1.sup.4) and at least four internal angles
below 180.degree., i.e. four right angles and two angles (1.sup.1
and 1.sup.2). greater than 90.degree. but less than 180.degree.. No
branches are shown in this diagrammatic drawing. The unit cell in
this case is superimposable on itself when rotated through an angle
of 180.degree..
[0029] FIG. 6, which is in accordance with the second aspect of the
present invention, shows diagrammatically in horizontal
cross-section a grid 21 having the form of a web of vertically
disposed interconnected plates or strips, said web having in
horizontal cross-section a repeating pattern, said pattern
comprising a series of unit cells, each cell having substantially
polygonal shape wherein each polygon contains 12 sides, e.g. sides
m.sup.1, m.sup.2, m.sup.3, . . . m.sup.12. The unit cell contains
three internal angles above 180.degree. (p.sup.1, p.sup.2 and
p.sup.3) and nine equal internal angles q.sup.1, q.sup.2, etc.,
greater than 90.degree. but less than 180.degree.. No branches are
shown in this diagrammatic drawing. The unit cell in this case is
superimposable on itself when rotated through an angle of
120.degree..
[0030] FIG. 7, which is in accordance with both the first and the
second aspects of the present invention, shows diagrammatically in
horizontal cross-section a grid 22 having the form of a web of
vertically disposed interconnected plates or strips, said web
having in horizontal cross-section a repeating pattern, said
pattern comprising a series of unit cells, each cell having
substantially polygonal shape wherein each polygon contains 20
sides, e.g. sides r.sup.1, r.sup.2, r.sup.3, . . . r.sup.20). The
unit cell contains eight internal angles above 180.degree. (e.g.
s.sup.1, s.sup.2, s.sup.3), eight right-angles (e.g. t.sup.1,
t.sup.2) and four angles (e.g. u.sup.1, u.sup.2, etc,) between
90.degree. and 180.degree.. No branches are shown in this
diagrammatic drawing. The unit cell in this case is superimposable
on itself when rotated through an angle of 90.degree..
* * * * *