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Патент USA US3043661

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July 10, 1962
K. F. PIETZSCH
3,043,651
CATALYTIC CONVERTER
Filed April 29, 1957
INVENTOR.
M 5*.’ PW
BY jyaiean'“ 0W
M,
United States Patent 0 f ice
1
3,043,651
CATALYTIC CONVERTER
Kurt F. Pietzsch, 3248 Pinehurst Ave., Pittsburgh 16, Pa.
Filed Apr. 29, 1957, Ser. No. 655,832
4 Claims. (Cl. 23-1)
This invention relates to method of and apparatus for
carrying out exothermic reactions by vapor phase catalytic
oxidation of organic compounds to produce phthalic an
hydride, maleic anhydride and/or other products.
It is a primary object of this invention to provide an
improved catalytic converter for passing vapor air mix
tures through tubes containing granular catalyst in which
the temperature regulation is effected by a large volume
3,043,651
Patented July 10, 1962
2
of inert granules 15 of substantially the thickness of tube
sheet 3 is placed in each tube and rests. upon screen seg
ments 14. The catalyst material 16 is placed on top of
the granules 15 to form the catalyst bed. A layer 17
of inert granules is placed on top of the catalyst 16, as
shown.
The space within the shell '1 below the tube sheet 2
outside the catalyst tubes 4 contains the cooling liquid
or converter bath designated A which, for example, may
consist of a mixture of molten nitrates and nitrites of
sodium and potassium, having a melting point of between
140° and 150° C. Other mixtures like molten metal may
also be used as the coolant. It is of prime importance
to the successful operation of the tube converter to em
ploy a large volume coolant circulation at substantially
uniform velocity in both horizontal and vertical directions,
tubes with the continuous addition of relatively small
which is maintained at suitable temperature by addition
amounts of cooled coolant and the removal of like
of a comparable small amount of coolant that has been
amounts of hot cooling liquid.
cooled, for example, 100° or 150° C. outside of the con
It is a further object of this invention to provide a
catalytic converter capable of close temperature control 20 verter. The external coolant supply means and internal
ba?le arrangement for circulating the coolant consists of
in large capacity production units in which units the re
the following:
action is completed and in which the desired product is
A draft tube 18 is mounted at the vertical center line
safely obtained without the addition of excess air for
of
the converter having a propeller 19 for circulating the
maintaining the organic vapor air mixture entering the
coolant upward. A horizontal baffle 20 extends radially
converter below its lower explosive limit.
from draft tube 18 to form a horizontal ?ow pass for the
Another object of the invention is the provision of a
coolant with tube sheet 3 as shown by the directional
tubular catalytic converter in which the arrangement of
arrows. A cylindrical wall or vertical ?ow ba?le 21 at
the catalyst tubes, the tube sheets, the bath impelling and
the outer edge of baffle‘ 20 forms, with the shell, the
bathe means, the height or level of the bath and the inlet
and outlet provide maximum output or production ca 30 outer vertical pass for the coolant circulation. A cylinder
or draft tube 22 of smaller diameter than cylinder 21
pacity while maintaining a desirable low temperature
is mounted concentric with draft tube 18 above horizontal
gradient.
baf?e 20. Cylinder 22 forms the vertical middle pass
These and other objects of the invention will become
with ba?le 21 and with draft tube 18 the inner vertical
more apparent from a consideration of the accompany
ing drawing constituting a part hereof in which like ref 35 pass.
The propeller 19 is driven by a motor driven gear re
erence characters designate like parts and in which:
duction mechanism 23 supported on bracket 24 and
FIGURE 1 is a vertical section, partially in elevation,
plate 25 at the top of the converter. Plate 25 is secured
of a tubular catalytic converter embodying the principles
bath circulation or coolant on the outside of the catalyst
of this invention;
FIGURE 2, a top plan view of a screen section taken
along the line 2-—2, FIGURE 1; and
FIGURE 3, a top plan view of a portion of a tube sheet
to short tube 26 welded to tube sheet 2. from which it ex
tends upward through cover 6 to which it is connected
by ?ange 27. A propeller shaft 28 extends downward
from drive 2'3 through sleeve 29 in which it is journalled
by bearing v30. Sleeve 29 is supported by sleeve 31 of
larger diameter that is secured to plate 25-. Spacing col
showing an improved arrangement of the tube perfora
tions taken along the line 3-—3, FIGURE 1.
In the drawing the numeral 1 designates a cylindrical 45 lars 32 and 33 close off a space between sleeves 2.9 and
shell having an upper and lower tube sheet 2 and 3, re
spectively, for receiving catalyst tubes 4, the ends of which
are welded into the tube sheets in the conventional man
ner. As shown in FIGURE '3, the perforations 2a and
31 forming a ?uid chamber which communicates at the
top with conduit '34 leading through plate 25 to a source
of cooled coolant. The bottom of the chamber is pro
vided with radial pipes 35 closed at their ends having
3a for the tubes 4 are spaced in a manner novel to obtain 50 openings 36 of selected number and size through which
the cooled coolant flows to mix with the circulating
a practically even radial flow of the coolant. To this end
bath A.
the centers of the outer tubes are arranged on a circle
The cooled coolant ?owing past propeller shaft hear
concentric with the converter shell 1, then the next row
ing 30 keeps the temperature of the bearing below the
on a smaller circle vwith tubes staggered. Following this
temperature of the circulating bath A inside the converter.
pattern with an ever decreasing number of tubes in the 55
Where the temperature of the coolant A is maintained at
tube center circles as shown in the drawing, the spacing
450° C. or higher, the corrosive action of the coolant may
between the tubes permits the coolant to flow in a radial
require stainless steel construction. Cooling the bearq
direction at a substantially constant velocity. The tubes
ing as described permits the use of non-stainless bearing
are not shown on the left side of FIGURE 1 to better
60 materials. If the cooled coolant is not employed to cool
illustrate the baffle arrangement.
the propeller shaft bearing it may be fed into the circulat
A converter head 5 having a top cover or end wall 6
ing bath while passing through the center space of the
forms an inlet compartment with the upper tube sheet 2
converter in any suitable manner other than described as
having an inlet pipe 7. A bottom converter head 8 is
for example by a pipe extending through the bottom of
provided with an end wall 9 which forms an outlet com 65 tube sheet 3 at the center thereof, the only requirement.
being that the cooled coolant is completely diffused before
partment with the lower tube sheet 3 having an outlet
leaving the draft tube so that no cold spots may occur in
pipe 10. A safety flange 11 on cover 6 secures a rup
ture diaphram 12 and a vent 13. Segment shaped screen
any of the catalyst tubes.
An amount of coolant equal to that delivered to the
sections 14 are arranged in overlapping relation to close
the lower ends of the catalyst tubes 4. The screen sec 70 converter by conduit 34 is removed from the bath A in
the following manner.
tions overlap slightly on the straight radial edges to as
The top of the converter shell 1 is provided with an
sure complete coverage of the ends of the tubes. A layer
‘3,043,651
3
'4
.
expansion joint 37 thatextends below the upper edge 38
of the shell forming a large circular ‘weir for the coolant
over?ow as shown. A discharge pipe 39 extends inside
per minute coolant addition.
Although the invention has been described in connec
the converter and passes further down to the outside.
The operation of the above-described converter is
anhydride, it will be apparent that the converter may be
brie?y as follows:
circulating coolant would require less than 600 gallons
tion with the production of phthalic anhydride and maleic
.
applied in producing other products by vapor phase cat
alytic oxidation of organic compounds.
For example, to produce phthalic anhydride from naph
thalene, napthalene Vapors mixed with compressed air
enter the converter through inlet pipe 7 into the inlet
I claim:
1. In a converter for carrying out exothermic reactions
by vapor phase catalysis in the form of an outer shell
compartment above tube sheet 2 at a temperature of about
150° C., then pass downward into tubes 4 where initial
having a pair of tube sheets mounted in vertically spaced
preheating takes place, which is enhanced by the pres
relation to form a chamber therebetween for circulating
ence of the inert granules 17. The vapors and compressed
air then pass through the catalyst bed 16 in which the
naphthalene reacts with part of the oxygen of the air
cooling ?uid and having catalyst tubes mounted between
said tube sheets and communicating at their ends with
inlet and outlet passages outside of said chamber in which
forming phthalic anhydride and some by-products. The
the chamber between said tube sheets has inlet and out
maximum temperature in the catalyst is in the neighbor
let passages for the continuous ?ow of a cooling liquid
hood of 500° C. The formed vapors and gases pass
with means for causing said cooling liquid to circulate be
through the lower inert granule layer 15, through screen
tween said tube sheets and for controlling the rate of ?ow
section 14 into the outlet compartment below tube sheet 20 thereof and in which a central draft tube is placed verti
3 through outlet pipe 10 to gas cooling and phthalic an
cally in the center of the converter with its top disposed a
hydride condensing equipment.
distance from the upper tube sheet to provide adequate
To maintain suitable working temperature conditions,
space for a coolant being propelled upward in said draft
the propeller drive 23 is energized and propeller 19 moves
tube to discharge radially into the spaces between the sur
the coolant upward in draft tube 18, hence downward in
rounding catalyst tubes, the said chamber having an out
the inner pass around the lower edge of draft tube 22 up
wardly extending horizontal baffle at the lower end of the
ward in the middle pass over the edge of ba?ie 21 and
central draft tube terminating at its outer periphery in an
downward in the outer pass and back through the hori
outer draft tube, which is a large diameter vertical draft
zontal pass below ba?le 20 to the draft tube 18, as shown
tube that extends upward concentrically with the central
by the arrows in FIGURE 1 of the drawing.
draft tube terminating at its upper end at a distance from
The bath circulating on the outside of the catalyst
the upper tube sheet essentially the same as the distance
tubes absorbs the heat created by catalytic reaction in
of the top of the central draft tube from the same tube
side the tubes, which is in large converters, over 10 mil
sheet, the space above said horizontal ba?le being open
lion B.t.u. and to avoid a temperaure rise of more than
and an intermediate draft tube placed concentrically be
about 10 degrees C., a large volume of coolant has to be
tween the central draft tube and outer draft tube extend
circulated.
ing upward forming a ?ow barrier and with its lower end
The tube and ba?ie arrangement shown in FIGURE 1
terminating at adequate distance from said horizontal
permits fast flow of the coolant with minimum ?ow re
battle to cause the coolant discharging from the top of
sistance. Low ?ow resistance is necessary for maintain
the central draft tube to pass through the spaces between
ing the liquid level below the underside of the tube sheet
the catalyst tubes in the section above said horizontal
2, as shown, to avoid contact with‘ the tube sheet and
ba?le in a sinuous path on its Way to an outer ?ow pas
raising the temperature of the tube sheet to that of the
sage, the combination with a propeller within said cen
coolant and the liquid level must not vary more than a.
tral draft tube, mounted on a shaft, axially centered in
few inches. As shown, the surface of the bath or coolant
said central draft tube and supported on top of the con
is higher in the center of the converter than near the
verter, of a sleeve in said central draft tube coaxial with
shell. For example, at the center it may be 8 inches be
said propeller shaft having radial arms at the lower end
low the upper tube sheet 2, while at the shell or outer edge
thereof, said sleeve being provided with a partition to
of the converter it maybe 12 inches below the tube sheet.
form a ?ow chamber communicatiing with an inlet pas
Flow resistance is also reduced to a minimum by spacing
sage for receiving a cooled cooling ?uid, and said arms
the tubes in the manner shown in FIGURE 3 of the draw
having perforations for the escape of said ?uid into the
ing, as heretofore explained. By thus arranging the tubes
mixing chamber formed by the top section of the central
and by the arrangement of the battles as shown, the ve
draft tube above said propeller, said radial arms disposed
locity of the coolant ?owing vertically through the passes
closely above the propeller being located in said cen
and horizontally through the narrow spaces between the
tral draft tube at adequate distance from the top of the
tubes is substantially the same throughout the converter. 55 central draft tube to obtain turbulent mixing of the cooled
By maintaining the liquid level higher on the inside of
coolant with the circulating coolant in the mixing cham
draft tube 22 over the level on the outer side, as shown at
A, the coolant moves from the one side of draft tube 22
around its lower edge to the other side, as shown by the
arrows.
The hot coolant, leaving the converter through pipe 39
is being cooled down, say 100 to 150 degrees C. and is
pumped back in amounts controlled by the temperature
of the bath in the converter. To illustrate, the coolant ‘
quantities being circulated by the propeller and the quan
titles for cooling added through pipe 34, the production of
maleic anhydride in a unit into which 3000 lbs. per hour
of benzene vapors are fed, is assumed. In producing
ber to uniformly cool the cooling liquid discharging from
the top of said mixing chamber into the spaces between
60
the catalyst tubes, said propeller shaft being journalled by
a bearing disposed within said radial arms which bearing
is maintained at a safe operating temperature by the cool
ant passing through the?ow chamber of the propeller
shaft supporting sleeve into the mixing chamber, and
65 means for withdrawing some of the cooling liquid from
the top of said circulating chamber at the same rate as the
amount of cooling liquid delivered through said inlet
passage.
2. Apparatus as set forth in claim 1 in which the sleeve
maleic anhydride, catalytically, the exotherm is extremely
high and over 30 million Btu. would have to be removed 70 in the central draft tube is blocked off to constitute a ?ow
by the coolant. Circulating about 12,000 gallons per
chamber, having an inlet connection with a source of
minute by the propeller, the temperature of the coolant
cooled coolant outside of the converter.
circulating around the catalyst tubes is, within about 6
3. Apparatus as set forth in claim 1 in which the cooled
degrees C., the same throughout the converter. Adding
coolant, cooledsdown about 100 degrees C., or more, the
cooling ?uid is continuously delivered and added to the
liquid in the circulating chamber from a source outside
3,043,661
5
substantially below the temperature of the cooling liquid
in said chamber, and cooling; liquid is continuously with~
References Cited in the ?le of this patent
UNITED STATES PATENTS
drawn from said last named chamber in the same amount
as the cooled coolant added to the liquid in said cham
her.
4. In the method of maintaining substantially uniform
cooling throughout the reaction zone of a converter in
which heat liberating catalytic reaction takes place be
tween substances in the vapor phase in catalyst tubes at
constant elevated temperatures, the steps which consist
of continuously passing a large volume of cooling liquid
of predetermined temperature from the axial center of the
converter into the spaces between the catalyst tubes and
cooling the circulating cooling liquid by continuously de
livering into the circulating stream of cooling liquid con
trolled amounts of the same cooling liquid at temperatures
substantially below the temperature of the circulating
6
cooling liquid while constantly removing a like amount of
the circulating cooling liquid from the converter.
of said chamber in controlled amounts at temperatures
15
964,936
1,627,450
1,812,341
1,905,719
1,909,358
1,917,718
1,936,610
2,042,632
2,198,555
Pownall _____________ __ July 19,
Otis _________________ __ May 3,
Iaeger ______________ __ June 30,
Jaeger ______________ __ Apr. 25,
Jaeger _______________ __ May 16,
Iewett _______________ __ July 11,
1910
1927
1931
1933
1933
1933
Thomas _____________ __ Nov. 28, 1933
Reynolds _____________ .. June 2, 1936
Wilson ______________ __ Apr. 23, 1940
FOREIGN PATENTS
963,913
France ______________ __ Ian. 18, 1950
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