Note: Descriptions are shown in the official language in which they were submitted.
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- 1 - C-I-L 633B
Converter
This invention relates to converters of the kind used to
convert sulphur dioxide gas to sulphur trioxide gas. Such
converters are usually used in the manufacture of sulphuric
acid.
Converters presently used to convert sulphur dioxide
gas to sulphur trioxide gas are normally large cylindrical
vessels containing a number of granular catalyst beds. Each
~' 10 catalyst bed occupies the complete cross-section of the
; vessel and the beds are disposed one above the other. The
process gas passes through the catalyst beds in sequence and
is cooled between beds both to recover the heat generated in
each bed and to assist in the kinetics and equilibrium of
the reaction. Each bed is separated from the others by a
division plate.
The converters used'in the indu~try suffer from a number
of serious disadvantages. Among these disadvantages are the
. following.
The outer shell of the converter is normally fabricated
,~ from carbon steel, typically sprayed with aluminum to resist
; high temperature oxidation. Because the highest temperatures
are generated in the first catalyst bed, it is necessary to
place the first catalyst bed at the top of the converter
25 tower. When the first bed is so located, the very hot shell
around the first bed is not required to support any load
above the first bed and therefore is less likely to rupture.
Since the metal of the shell around the first bed is heated
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to a temperature at whic~ it is weakened and frequently
bulges, location of the ~irst bed at the top of the converter
has important structural bene~its However most of the dirt
5 in the gas entering the converter is caught by the first
- catalyst bed, since the catalyst is sticky and tends to
remove dirt~ Since dirt accumulation will block a bed, the
first catalyst bed must be cleaned more often than the others.
Locating the first bed at the top of the converter, usually
10 many feet in the air, requires scaffolding for the clean-out
. process and renders the clean-out difficult.
In addition, should the first bed collapse due to the
: high temperatures within it, a circumstance which occasionally
occurs, the contents of the first bed will be dropped onto the
15 bed beneath it, tending to cause a series of collapses within
the converter tower. It would therefore be preferable, if
possible, to place the first bed at the bottom of the
converter,
A further disadvantage of present converter design is
20 that the beds themselves are often supported on a series of
cast-iron plates, generally of equilateral triangular form,
supported from the base of the converter by numerous cast-
iron pillars, Subse~uent beds and division plates are
supported from the level benea~h them. The ~orest o~ cast~
iron plates and pill~rs results in extremely high erection
costs and compl.icates maintenance and clean-out of the beds.
In addition, because cast-iron division plates cannot be
welded, they are normally sealed to the shell by packing
asbestos rope between the division plates and the shell and
also between the division plates themselves. Since sulphur
dioxide rich gases in the converter are generally at a higher
pressure than sulphur dioxide lean gases, leakage of sulphur
: dioxide rich gases tended to occur past the converter beds,
reducing the conversion efficiency and increasing pollution.
As an alternative to the pillar and triangular plate
structure, some converters have been fabricated employing
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- 3 - C-I-L 63
cast-iron or mild steel plates supported on beams between a
central core tube and the outer shell. Where cast-iron has
been used, the previously described leakage problems have
5 occurred If steel division plates are used, they can be
welded, but because they sag in use, the welds break. They
car. then be rewelded and usually will not break again, having
formed themselves, but this requires costly extra welding
and involves considerable down time for the converter.
Another factor involved in converter design is that,
since catalyst must be loaded and unloaded from the beds, and
gas must be introduced above and removed below the beds,
spaces must be allowed above and below eac'.l bed. The height
of such spaces is generally governed in practice by the need
15 to allow free movement of people inside the spaces (to load
and unload catalyst and for maintenance purposes). Such
: height is frequently less than the diameter of the gas inlet
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; and exit ducts used~ Therefore, such ducts are often modified
into an eliptical or rectangular form for entry into the
. 20 converter, a costly arrangemen~ Even with this arrangement,
considerable difficulty is encountered in obtaininy good gas
: distribution within the converter. The high local gas
~ velocities which commonly occur can disturb the catalyst bec1
: physically, resultiny in poor performance, re~u.iring that the
catalyst be covered with a top layer of protective stones.
The stones add undesirable weight and interfere with cleaning
the catalyst
A further disadvantage of converters commonly used is
that they are supported on I-beams and are permitted to move
back and forth across the beams in order to accommodate their
expansion. Because of this the exact radial posltion of the
converter has an uncertainty of several lnches. This creates
severe stresses in the piping connected to the converter.
A still further disadvantage of converters now used is
that the gas exiting from the first catalyst bed is at a very
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high tem~eratu~e (typically oyer 600C) ! SO that the exit
pipe from the first bed requires a bellows therein. The
bellows causes maintenance difficulties and in addition
occupies a great deal of space, so that a 30 foot diameter
: - converter may require a 50 foot diameter space to cope wi-th
: its attendant input and exit piping~
The present invention involves a number of aspects, each
of which deals with one or more of the above identified
disadvantages. In one aspect the invention provides a
converter having an exterior shell of stainless steel, an
interior core tube of stainless steel extending vertically
within said shell and being concentric thereunder, a plural-
itY of annular catalyst beds within said shell and located
one above the other, means supporting said beds from said
shell and from said core tube, means for conducting sulphur
: dioxide gas from a source of such gas into the lowermost of
said beds so that said lowermost bed is the first catalyst
bed, and means for conducting gas from said lowermost bed in
succession through the remaining catalyst beds
. In another aspect the invention provides a converter
having:
(a) an exterior shell,
(b) a plurality of vertically spaced catalyst beds within
said shell, one of said catalyst beds being a first
catalyst bed to receive sulphur dioxide containing gas
: from a source of said gas,
~c) means aefining a plenum around said first bed,
~d) means defining with said plenum a space above said first
. 30 bed,
~e) said plenum having a gas inlet opening therein for
receiving said gas, and a circumferential outlet
opening into said space, said outlet opening being
located above said inlet opening and said plenum and
35 said inlet and outlet openings being arranged for gas
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entering said inlet opening to change its direction
sharply to pass through said plenum toward said outlet
opening and then again to change direction sharply to
:. 5 pass through said outlet opening, whereby to tend to ..
remove particulates entrained in the gas entering said
. - inlet opening.
In another aspect the invention provides a converter
having:
(a) a shell,
(b) an interior core tube extending vertically within said
;~ shell and being concentric therewith,
; (c) a plurality of annular catalyst beds within said shell
and located one below the other,
(d) a plurality of support plates one supporting each of
: said beds from said shell and from said core tube,
(e) axial heat exchange means within said core tube for
conducting hot gas axially from one of said beds to a
second of said beds,-
(f) said heat exchange means including means f~r conducting
cooled gas past said hot gas to cool said hot gas and
to warm said cooled gas, and for directlng such warmed
cool gas into a thixd one of said beds,
(g) a plurali:ty of divis:ion plates one between each adjacent
pair of said beds and separating said beds,
(h) sald sllpport plates and division plates being preformed
in essentially the configuration of a trough-shaped
toroidal section encircling said core tube, to reduce
sagging of said support plates and division plates in
: 30 use.
In another aspect the invention provides a converter
having an exterior shell, at least two catalyst beds within
said shell, one above the other, each catalyst bed having a
support plate for said catalyst thereof, a division plate
between said beds, said support and division plates extending
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to and being sealingly secured to said shell, said division
plate and said support plate of said one bed defining a space
therebetween, said shell having an opening therein below said
5 support plate of said one bed for flow of gas between said
space and the exterior of said converter, the diameter of
said opening being greater than the height of said space, said
division plate having a slot therein, the periphery of said
slot meeting the edges of said opening, and a transition plate
10 extending between the periphery of said slot and the periphery
of that part of said opening located below said transition
plate.
Further objects and advantages of the invention will
appear from the following description, taken together with the
15 accompanying drawings in which:
Fig. 1 is a perspective view, partly cut away, of a
converter according to the present invention;
Fig. 2 is a perspective view of a portion of the
catalyst support structure of the Fig. 1 converter;
Fig. 3 is a view in vertical section of the converter
of Fig. l;
Fig. 4 is a perspective view of a portion of a catalyst
support plate of the ~ig. 1 converter,
Fig. 5 i5 a vertical sectional view of a portion of the
25 catalyst support system o~ the Fig. 1 converter;
Fig. 6 is a view similar to that of FigO 3 but showing
a modification of the Fig. 1 converter; and
Fig. 7 is a view similar to that of Fig. 3 but showing
a still further modification of the Fig. 1 converter.
Reference is first made to Figs. 1 and 3, which show a
converter generally identified at 10 and having a shell 12.
The shell 12 may t~pically be 30 to 40 feet in diameter, and
40 to 50 feet in height, and is made of a tough material which
maintains substantial strength at the maximum temperatures
35 occurring in the convert~r (about 600C). Stainless steel is
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preferred, but other suitable materials may also be used, such
as titanium or titanium alloys. Where stainless steel is
used in a tower of the dimensions mentioned, the thickness of
the stainless steel may typically be between 3/16 and 1/4
inch. It is found that with the design to be described, a
stainless steel shell even of this small thickness will not
',~ bulge, although it is common for a one inch thick carbon
- steel shell to bulge severely. In the description of the
preferred embodiment, the use of stainless steel will be
described.
Located within the shell 12 are four catalyst beds
14-1, 14-2, 14-3, and 14-4, through each of which the process
gas is passed. Each catalyst bed 14-1 to 14-4 is annular in
form, being located between the outer shell 12 and an inner
core tube 16 formed from stainless steel.
Each catalyst bed 14-1 to 14-4 is supported on a
stainless steel annular support plate 18-1 to 1~3 4 respect-
ively. The support plates 18-1 to 18-4 have holes 19 therein
(also shown in Fig. 2) to permit gas to pass therethrough and
are preformed into a concave configuration as viewed from
above (to be described in more detail presently), to prevent
excessive sagging when they are loaded and subjected to
heat. The support plates 18-1 to 18-4 are we:Ldecl around
their inner peripherles to the inner core tube 16 and (except
for plate 18-1) are welded around their outer peripherles to
the outer shell 12.
The catalyst beds are separated by division plates 20,
22, 24, also of stainless steel. The upper two division
plates 20, 22 are also preformed into a concave shape as
viewed from above to eliminate excessive later sagging. The
; shape will be seen to be that of a trough-shaped toroidal
section. The upper division plate 20 is welded at its ou-ter
and inner peripheries to the shell 12 and the core tube 16
respectively. The middle division plate 22 is welded around
- ~ - C-I-L 633B
its outer periphery to the outer shell 12 and is welded at
its inner periphery to a cold gas distributing duct 26 (to be
described) supported by spaced posts 28 (Fig. 1) on a radially
outwardly projecting ring 30 welded from the core tube 16.
The division plate 24 between beds 14-1 and 14-4 is also
welded around its outer and inner peripheries to the shell
12 and core tube 16 respectively but is domed upwardly
instead of downwardly. The upward doming also prevents
excessi~e sagging in use.
The side of the first bed 14-1 is bounded by a stainless
steel side plate 32, which slopes downwardly and inwardly
from the division plate 24 in the shape of an inverted
truncated cone, The first bed support plate 18-1 is welded
around its outer periphery to the side plate 32. A downwardly
domed bottom plate 34 is welded around its outer and inner
peripheries to the bottom of the side plate 32 and to the
` core tube 16 respectively. Encircling the lower portion of
the side plate 32 is a second side plate 36, also defining an
inverted truncated cone. The upper periphery of the second
- side plate 36 is welded to the shell 12. The lower periphery
of plate 36 is welded to an upwardly and inwardly sloping
annular connecting plate 38 which is in turn welded to s.ide
plate 32. The she].l 12, side plates 32 and 36, and connecting
plate 38 together form an annular chamber 40 which encircles
the first bed 14-1.
Gas 42 containing sulphur dioxide to be converted
enters the first bed 14-1 via a large duct 44 which passes
through the outer shell 12 and opens at 46 into the annular
chamber 40. The inlet gas flows around the chamber 40 and
turns upwardly, as indicated by the arrows 48, and then flows
radially inwardly through circumferentially spaced holes 50
located in side plate 32 above the first bed 14-1. The gas
then passes downwardly through the first bed 14-1, sweeps
beneath the first bed, and then flows into the core tube 16
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; - 9 - C-I-L 633B
via circumferentially spaced holes 52 in the csre tube.
~ The lower portion of the co~e tube 16 contains a plenum
; 54 defined by a circular flat tube sheet 56 and a verkical
annular support plate 58 which extends between a central base
portion 60 and the tube sheet 56. A second annular support
plate 62 in the shape of an inverted truncated cone extends
between the base portion 60 and tube sheet 56 to help support
the tube sheet. The plate 62 contains a row of circumferen-
tially spaced holes 64 for gas to pass therethrough.
Gas from the plenum 54 travels upwardly through a
; series of heat exchanger tubes 66 ~of which there are a
number of rings, only two rings being shown) to the top of
the converter tower. During its passage through the tubes
66, the gas in tubes 66 is cooled by counter-currént flowing
gas indicated by arrows 68, as will be described. The cooled
gas leaving the heat exchanger tubes 66 fans out under the
~: dome-shaped converter roof 70 and enters the second converter
bed 14~2. After passiny through bed 14-2, where additional
conversion occurs, the gas leaves the converter via exit
openins 72 in the outer shell 12.
In a conventional application of the converter, the gas
leaviny via exit opening 72 is cooled and then directed to
an intermediate absorber (not shown) where sulphur trioxide
is absorbed. The cooled gas from the intermediate absorber,
still containing SO2 to be converted, then re~enters the
converter 10 via entry opening 74 at the top of the converter.
The re-entering gas is indicated by arrows 76.
The cooled gas flowing through opening 74 passes down-
wardly through a reduced diameter upper portion 16a of thecore tube 16. Portion 16a of the core tube is welded to an
annular upper tube sheet 78 which in turn is welded at its
periphery to the upper edge of the core tube 16. Tube sheet
78 retains the upper ends of the tubes 66. As shown, portion
16a of the core tube contains a bellows 80 to accommodate
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the dif'ferential expansion of the hot roof 70 of the shell 12
and the cooler upper portion 16a.
After the gas leaves the reduced diameter portion 16a
of the core tube, it is directed by disc and donut baffles
82, 84 respecti~ely, past the heat exchange tubes 66, to
rewarm the cooled gas from the intermediate absorber and to
cool the gas passing from the first bed 14-1 to the second
bed 14-2. The disc baffles 82 are fastened to an internal
axial by-pass tube 86 which extends from just below the top
of upper core tube portion 16a downwardly to approximately
the level of the fourth bed 14-4. Struts 88 support the by-
pass tube 86 at its top from the upper core tube portion 16a.
A by-pass valve 90 is fitted within the top of the by-pass
tube 86, to allow some cooled gas from the intermediate
absorber to by-pass most of the length of the heat exchange
tubes 66, to reduce the extent of cooling of the gas flowing
from the first bed 14-1 to the second bed 14-2, The by-pass
, is provided because the heat exchanger is usually made
, , 20 oversize so that it will have sufficient capacity even when
' it becomes dirty after long use.
The donut baffles 84 are mounted on a heat exchanger
shell 92 located within the core tube 16 and concentric
therewith. The shell 92 is suspended from the upper tube
sheet 78 ancl terminates at the bottorn donut ba~fle 84, well
above the bottom tube sheet 56.
After the gas indicated by arrows 94 has passed the
, last donut baffle 84, it flows,upwardly as indicated by
arrow,s 96, through the narrow annular space 98 between the
~ 30 shell 92 and the core tube 16. This gas then enters the
,'' space above the third bed 14-3, via a row of circumferentially
'~ spaced holes 100 in the core tube 16.
~- The process yas after passing through the third bed 14-3
then flows as indicated by arrows 102 into the space above
,'~ 35 the fourth bed 14-4, via a narrow gap 104 between the
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: - 11 - C-I-L 63
distributing duct 26 and the core tube 16. Only slight
cooling is required after the gas passes through the third
bed 14-3, and this cooling is typically provided by a cold
air quench which is supplied from the distributing duct 26
via a conduit 1060
The gas after passing through the fourth bed 14-4
finally leaves the converter via an exit opening 108 in the
shell 12, and is then directed to the final absorber (not
shown).
It will be seen that the diameter of exit opening 108 is
greater than the height Dl of the space between the fourth
bed support plate 18-4 and the division plate 24 beneath this
support plate. This difference in size is accommodated by
providing a curved slot 110 (Fig. 1) in the division plate 24
- where the division plate 24 meets the borders of opening 108.
The outer edges of the slot 110 meet the borders of the
opening 108 at points 112 (only one point 112 is shown), and
extend inwardly sufficiently so that the area of the slot 110
is preferably at least as great as the area of that; part of
exit opening 108 located below the division plate 24. A
transition plate 114, of curved coniguration, extends
between the edges of the slot 112 and the periphery 116 of
that part of exit opening 108 .located below the division
plate 24. The transition plate 114 allows smooth, relatively
unrestricted flow of gas from the narrow space below the bed
. 14-4 into the exit opening 108.
As shown, the same structure is provided for exit
opening 72 from bed 14-2, i.e. a slot 118 is formed in
division plate 20, and a transition plate 120 extends between
: slot 118 and the portion 122 of the periphery of opening 72
located below the division plate 20.
Access openings to the spaces above and below the beds
14-1 to 14-4 are provided by cylindrical tubes 124 (Fig. 1)
welded from and projecting from the exterior shell 12 and
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- 12 - C-I-L 633B
having closed ends 126. When access is needed to the interior
of the converter, the ends of the projecting tubes 124 are
simply cut off with a torch, to allow maintenance personnel
to enter. After maintenance has been completed, the closures
126 are re-welded onto the tubes 124.
The central base portion 60 of the converter is formed
of refractory concrete or fire brick, which in turn rests on
a concrete footing 128 supported on piles 130~ Horizontal
10 stainless steel rings 132, 134 are welded to the bottoms of
core tube 16 and support plate 58 respectively to form T-
shaped fittings which support core tube 16 and support plate
58 on the central base portion 60. The rings 132, 134 are
free to slide on the central base portion 60, to allow for
. .
expansion.
The outer shell 12 is separately supported on a stainless
steel ring 136 welded to the bottom of the shell 12 and tied
by bolts 138 to a separate concrete foundation 140. Found-
ation 140 is supported on piles 142. Because shell 12 is
tied at its bottom to the foundation 140, the position of the
`~ bottom of the shell 12 is fixed and is always determined.
The top part of the shell will expand radially outwardly in
use, the bottom part actiny as a hinge about which this
expansion occurs.
The area between the qundation 140 and central base
portion 60 is filled with crushed stone 144, which helps to
insulate the hot lower portion of the converter from the
ground below. Heat pipes 146, having finned heat sinks 148,
~;~ extend through the gravel and through the footing 128 to
remove excess heat to atmosphere.
' The structure described has a number of sianificant
advantages. Firstly, since the first catalyst bed 14-1
(which requires the most maintenance) is located at the
bottom of the converter rather than at the top, the mainten-
; 35 ance of this bed is greatly simplified.
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Secondly, because the gas entering the first bed 14-1
is forced to make two.abrupt changes in direction befor it
; can pass through the holes 50, particles of dirt carried with
the gas tend to drop into the bottom of the annular chamber
;. 40, reducing the contamination of the first bed 14-1.
. Thirdly, because the outer periphery of the first bed
14-1 is located against the side plate 32, rather than against
the shell 12, less heat from the first bed 14-1 (which is the
10 hottest of all the beds) is transferred to the outer shell 12,
reducing heat related weakening of the outer shell. The hot
- gases below the first bed 14-1 are also prevented by the side
plate 32 from contacting the load bearing shell 12. Heat
losses are also reduced by this arrangement~
Fourthly, gas enters the first bed 14-1 from a plenum
chamber 40 extending around the entire periphery of the first
bed, so that the local velocity of gas entering the first bed
is much lower than would be the case if the gas entered the
first bed directly from a duct. Therefore, little or no
protection of the top of the first catalyst bed by means of a
. layer of stones is required.
Fifthly, because the hot gases from the first bed 1~-1
are directed upwardly to the second bed 14-2 via an .interior
axial heat exchanger, the usual complex bellows system used
: 2S to conduct the hot gases fram the first bed out of the
converter has been eliminated. In addition, the upwardly
moving gases from the first bed, after leaving heat exchanger
tubes 66, impinge on and fan out under the domed roof 70 of
.. the converter, thereby also reducing the local velocity of
; 30 the gas entering the second bed 14-2. Thus the catalyst in
- bed 14-2 is also less likely to be physically disturbed by
the gas and requires little or no protection by a layer of
.. stones.
Sixthly, the preformed division plates 20, 22, 24 and
the bottom plate 34 allow a tight seal between stages of the
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- 14 - C-I-L 633B
con~erter while greatly reducing the likelihood of broken
welds caused by sagging of the plates in useO This reduces
the likelihood that SO2 containing gas will by-pass beds of
the converter,
Seventhly, the transition plates 114, 120, together with
the slots 110, 118 in the division plates 24, 20, permit the
use of large diameter exit ducts without the need for complex
horn-shaped ducting between the exit ducts and the converter.
This not only reduces the cost of the structure but also
considerably reduces the plant space required, since the horn-
shaped ducting occupies substantial space.
Although the division plates 20, 22, 24 and the bottom
plate 34 ideally have a true double curvature form, i.e. the
form of a surface of revolution lin other words the form of
i a trough-shaped toroidal section), this form is in fact
~; - difficult to fabricate in large sizes. Therefore if desired
the plates 20, 22, 24, 34 may be made in single curvature
form, i.e. as a series of segments like an umbrella, as shown
in Fig. 4. In Fig. ~, the individual segments of a portion
of division plate 20 are indicated at 150, each segment
having the forms of a surface o~ revolution. The segments 150
are welded together along their edges 152 to form a down~
;- war~ly domed umbrella-shaped division plate 20.
In use, and as the division plate ~0 heats, the form
shown in Fig. 4 will sag to approximately a true double curv-
; ature form, without creating strains which would rupture
metal or break the welds either between the segments or
between the segments and the shell and core tube.
The catalyst support system is shown in detail in Figs.
2 and 5. As shown, the catalyst support plate 18-1 (which is
typical of all the catalyst support plates) includes a
- number of holes 153 of considerable size, e.g. two inch
diameter, spaced on six inch centres. The plate 18-1 supports
a layer of stainless steel expanded metal 154. The expanded
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` - 15 - C~I-L 633B
metal 154 is very coarse, and may typically be formed from
stainless steel sheets of thickness about .14 inches. After
forming into expanded metal, the sheet is of thickness about
3/8 inch, with diamonds 156 of dimension about three inches
by one inch, and with ligaments 158 about .14 inches square.
The expanded metal 154 supports a second and less coarse
layer of stainless steel expanded metal 160, typically formed
from 18 gauge material, of ligament thickness about .1 inch
square and with openings of diamonds 162 of size about .75
inch by .25 inch.
The upper layer of expanded metal 160 carries a layer of
stones 164 which prevent the catalyst pieces 166 from
contacting the stainless steel, since the catalyst tends to
flux or melt into the openings of any metal which it contacts.
If the mesh 160 is made of material with which the catalyst
will not flux, then the stones 164 can be eliminated.
The coarse expanded metal mesh 154 is about 70% voidage;
the fine expanded metal mesh 160 is about 60% voidage, the
stones 164 are about 50% voidage, while the catalyst 14~1 is
; about 36~ voidage for solid cylindrical pieces 166 of catalyst
and slightly higher for tubular pieces of catalyst. The mesh
154 permits gases 1Owing through the catalyst 14~1 ancl stones
164 to flow with a mlnimum of back pressure as indicated by
arrows 168 in Fig. 5, into the holes 153 in the support plate
18-1.
Reference is next made to Fig. 6,which shows an ~mbodiment
similar to that of Figs. 1 to 5, and where primed reference
numerals indicate parts corresponding to those of Figs. 1 to
5. The major difference in Fig. 6 embodiment is that there
. . .
: is no internal axial heat exchanger. Instead, gas from the
first bed 14-1' leaves the space below the first bed support
plate 18-1' via an exit duct 170, and is cooled outside the
converter. The cooled gas is then brought back into the
converter via a top opening 172 in an outer tube 174 encircling
- 16 - C-I-L 633B
the upper core tube por*ion~l6a'~ Tube 174 is closed at its
top to define an annuIar space 176 which opens do~nwardly
into the space above the second bed 14-2l, The cooled gas
entering opening 172 flows through the annular space 176 and
then through the second bed 14-2. The gas then leaves the
space below the second bed, via opening 72', and is directed
to the intermediate absorber (not shown). The gas from the
intermediate absorber is returned to the converter directly
~;10 into the core tube upper portion 16a', as indicated by arrow
178. The gas flows into core tube 16' and is distributed
,;through holes 100' into the space above bed 14-3. A barrier
180 in tube 16' prevents the gas from travelling much below
the holes 100'.
In the Fig. 6 embodiment the distributing duct 26' is
located at the wall of the outer shell 12', and the cold air
quench is supplied directly via conduit 106' into the duct
26'.
` Reference is next made to Fig. 7, where double primed
reference numerals indicate parts corresponding to those of
... .
Figs. 1 to 5. Fig. 7 shows a converter for use where the
sulphur dioxide is obtained from a metallurgical plant rather
: than ~rom a sulphur burning plant as was assumed ko be the
case in the previous embodirnents. When the sulphur dioxide
contalning supply gas is obtained from a metalluryical plant,
the gas will have been cleaned prior to entry into the
converter and will be much cooler than the gas from a sulphur
burning furnace. Therefore the supply gas nsw enters the
converter at the upper opening 74" and then travels downwardly
; 30 through the heat exchanger, where it cools the gas in tubes
66" from the first bed 14-1" and is in turn warmed prior to
its entry into the first bed.
After the supply gas, indicated by arrows 182, has passed
the last donut baffle 84", it enters the space above the first
bed 14-1" via a series of circumferentially spaced holes 184
- 17 - C-I-L 633B
in the core tube 16". The plenum 54 has been eliminated but
the side plate 32" still prevents the first bed and the hot
gases beneath it from contacting the shell 12".
The remainder of the FigO 7 system is the same as that
of Figs. 1 to 5, except that the gas from the intermediate
absorber (not shown) now enters the third bed 14-3" via an
inlet opening 186 in the side of the shell 16". To reduce
local gas velocities, a second division plate 188 is provided,
spaced below division plate 20" to define a plenum 189
therebetween. The gas from opening 186 passes through a set
of circumferentially spaced openings 190 in a circular plate
192 extending between division plates 20", 188. The gas then
passes through rows of circumferentially spaced openings 194
and into the space above bed 14-3".
Since opening 186 extends above division plate 20" and
below division plate 188, slots 196, 198 respectively have
been cut in these plates, and transition plates 200, 202 have
been welded in these slots as previously described.
.
, .
~ .
.
.
.
