Note: Descriptions are shown in the official language in which they were submitted.
S9~
This invention relates to an apparatus for re-
moving hydrogen sulF,hide and polysulphides ln liquid sulphur
sub~equent to production of liquid sulphur b~ the Claus
, process.
As is well known, liquid sulphur can be produced
in the Claus process by passing hydrogen sulphide (H2S)
through a combustion chamber where most o~ the hydrogen sul-
phide is burned to produce sulphur and in such a manner that
approximately one-third of the remaining volume of hydrogen
sulphide is converted into sulphur dioxide. A~ter cooling,
hydrogen sulphide and sulphur dioxide are passed through a
catalyst converter where the hydrogen sulphide and sulphur
dioxide react to form liquid sulphur and water.
Liquid sulphur prepared by this process often
; 15 contains liquid hydrogen polysulphides as impurities
2S (ga6) ~ (X-l)S (liquid~ 2SX (liquid)]. The
liquid polysulphides will 810wly decompose and evolve as
H2S gas over a period of time to create dange~ to equipment
and the health of employees. I~ the liquid sulphur ls
shipped without removing the impurities and they gradually
evolve as H2S during shipment, suf~iciently high levels of
hydrogen sulphide may be evolved and under certain con-
ditions an explo~ion might occur Similarly~ the escaping
gas evolved during shipment could endanger workmen when
the container is opened.
Previous attempts at reducing the hydrogen sulphide
content o~ liquid sulphur have usually lnvolved more com-
plicated proces~eæ, impractical for commerclal operations.
- For example, in United States Patent No. 3,364,655 a process
3Q i5 described in which llquid sulphur is degaæi~ied by
2. ~
...
!i"
"~f
, ,f,~;
~459~ :
atomizing liquid sulphur. By the process taught by this
patent ammonia is added and the temperature of the liquid
, sulphur cooled to approximately 125C. The liquid sulphur
then is atomized by passage through nozzles of approximately
7 mm. in diameter. While this system may be used on a small
sc~le, it would have inherent problems when practiced on ~.
the large commercial scale as contemplated by our invention.
Not only are the nozzles of small capacity and ~hus limiting
;~ production to a small scale but ~he necessity of adding ammonia
f. 10 introduces another ingredient which may react to form stable
l;~ ammonia polysulphide which would be a contaminant in the liquid
,~ sulphur, especially if the liquid sulphur is subsequently used
to manufacture sulphuric acid. The need to cool the liquid
sulphur requires additional cooling equipment, another
disadvantage. Finally, no mention is made in the prior art
of the hydrogen polysulphide problem and the need to remove
~, the same.
It is therefore an object of the invention to
~, .
provide a liquid sulphur gas scrubber apparatus which obviates
~; 20 the dangers of the shipment and storage of liquid sulphur
by removing substantially all the hydrogen sulphide and
dissolved hydrogen polysulphides in the liquid sulphur.
~,- Thus, in accordance with the present teachings,
a liquid sulphur gas scrubber apparatus is provided for
,~ removing hydrogen sulphide and polysulphides from liquid
;l sulphur disposed in an enclosed reservoir. An elongated
r; outer casing in communication with and extending vertically
, ~ .
' upwardly from the reservoir is provided and includes a gas
~,l discharge passage for venting gas externally of the casing.
,, 30 Liquid sulphur downflow passage means is provided disposed
within the casing and extending downwardly into the reservoir
includes a first plurality of spaced apart openings disposed ~`
l 3
i,,~ ,
,,
~ .~;)459t~18
in one side of the passage means and a second plurality of
spaced apart openings disposed on the opposite side and offset
with respect to the first plurality of openings. The casing
and the passage means defined therebetween at least within a
portion of the casing an annular gas venting passage
communicating with the openings for venting gas from the
passage means into the casing and externally of the casing
through the gas discharge passage. A plurality of vertically
spaced apart, downwardly canted baffle plates are provided
disposed in the passage means and extend inwardly thereinto
above each of the openings of the first and second plurallty
of openings in alternating ashion, each of the plates extend
into the passage means beyond the edge of the next lower
'; adjacent baffle plate so as to form a cascade downflow path
rom the liquid sulphur in the passage means. Means are
provided coupled to the reservoir and extending inwardly into
the passage means for supplying liquid sulphur from the
~ reservoir to the vertically uppermost of the baffle plates.
F~ The liquid sulphur downflow passage means is formed by an
elongated cylinder coaxially disposed within the outer casing
and in the portion of the casing disposed above the reservoir
by a plurality of vertically disposed plates disposed within
and spaced apart rom the casiny so as to define the annular
gas venting passage.
Other features and objects of the invention will
~,, become apparent in the ollowing description, claims, and in
the drawings in which:
Fig. 1 is a schematic flow diagram of one
embodiment of the process of this invention;
Fig. 2 is a cross-sectional view of one
~, embodiment of a gas scrubber apparatus constructed according
ii to the invention;
L
~: ~-4~
~ S9~3~
Fig. 3 is a cross-sectional view of another
embodiment of a gas scrubber apparatus constructed according
to the invention;
Fig. 4 is a cross-sectional view of the downflow
passage of the apparatus taken along section 4-4 of Fig. 3;
and
Fig. 5 is a perspective view of the downflow
passage of the apparatus of Fig. 3.
Referring now to the drawings, specifically -
Fig. 1, liquid sulphur at approximately 280F. and containing
hydrogen polysulphides is pumped from a Claus process pro-
~; duction facility 1 through appropriate piping to a large
$:
,~, .
~ .
~.~,; .
..
"11 ~ . ;
~` 20
,, ~ ,' ~.
, .
:
tY
~ ~4a~ -~
. ~ ~ .. . .
16~4598~
enclosed reservoir illustrated as storage tank 2. This
tank may b~ of any siæe and in one embodiment is a 13~000
long ton storage tank ln whlc~l the liquld sulphur is stored
at atmospheric pressure and 2800F. By the practice of this
invention the equilibrium between hydrogen polysulphide,
hydrogen sulphide and llquid sulphur is shifted and the
hydrogen polysulphides will decompose to for~ hydrogen sul-
phide and liquid sulphur as follo~s:
H2SX (li~uid~ H2S ~ (gas) ~ (X-l)S (liquid)
In order to provide agitation for removing the entrapped
hydrogen sulphide, a vertical gas scrubber apparatus 5 is
mounted with.in tank 2 in such a manner that it is communi-
cative with and extends ~rom the bottom of tank 2 vertically
upwardly through and beyond the top of tank 2 as shown in
Figs. 1 and 2. After the tank has been partially fllled,
the liquid sulphur stored in the tank ls continuously pumped
from the tank 2 by a liquid sulphur supply means illustrated
as pump 4 and supply pipe 16 to the top of the scrubber
~; apparatus 5 through pipe 16 where the liqùid sulphur is then
allowed to flow in cascade fashion over a series of staggered
internal baffle plates 8.
In the embodiment of the apparatus illustrated in
Fig. 2, a liqu~d sulphur downflow passage means is formed in
~ the upper portion o~ apparatus 5 above tank 2 by a pluralit~
,; 25 of vertically disposed plates 9 to which ba~fle plates 8 `
are attached. The baffle plates are downwardly canted and
overlap the innermost edge of the next lower adjacent baffle
~;~ plate, so as to provide a cascad0 downflow path for the :~
liquid sulphur. Openings 15 are provided in opposing sides
of the downflow passage formed by plates 9 in an of~set
. ` .
~ .
1045988
arrangemen-t and are com~unicati~e ~ith an annular,gaa venting
passage 14 def;ned b.y plates, ~ and an elongated outer ca4ing ~:
10 to w~i.ch t~e plate~ g are attached. The casing is communicative
with and extends upwardly ~rom tank 2 and includes a gas dis-
charge passage illustrated a~ vent and hood arrangement 7. Tank
vents 19 are provided ~or venting yas from tank 2 to the atmos-
phere. .~.
,, In the portion of the apparatus located within tank , .
2, the ba~fle plates 8 are composed of straight plates 2Q, one
l~ end o~ ~hich is cut in an arc to match the shape of casing lQ :~
:: and is attached directly.to the inner sides of the casing by any ~
~,~; conventional means. By designing the lo~er portion of the ~ .. '
.. apparatus in this manner, the.fIow area of the sulphur is
,.~
,; increased. These lower plates 2Q continue to the bottom of
apparatus 5 so that even when the sulphur in tank 2 is low .:
~ the incoming sulphur.is.not al.lowed to fall free for mo~eZ~.than
',~ one foot. This avoids static electrical charge buildup on the
~i sulphur and po~sible spark ignition re~ulking in fire oreexplosion. ~': ,.~-,'
~ ~ In the operation of the gas scrubber apparatus, .:.`
,'.1, 20, li~uid sulphur ~lows through.pipe 16 down the side of plates
9 on to the pitched ~a~fle plate~ a from one baffle plate . .~:
~, to the next in a zigzag flo~ do~n the do~n~.lo~ passage ~ormed
!: in apparatus 5. This cascade.down~low within the apparatu~ ~.
agitates the. li~uid, increa~es.the sur~ace area of the liquid
~: sulphur and ~acili~ates the.break down of the hydrogen poly~
,,; sulphides into H2S and liquid sulphur. T~e H2S gas then ':
escapes.~rom the sulphur, pa~e~ through'vent openings 6 pro~ided
: ,. ..~
$ . .in the lower portion of the casing w.ithin .t`ank ~ and coLlects .``~
,. in the upper portion of ~he tank 2. : '
~` 30 ,:. :
,~ ,~ -: -
1, ~ ,' ;:
/l i
' - 6 - ~
~(14L5~38
Gas i5 vented from the tank through vents 19. Gas escaping
,~ f`rom the liquid sulphur in thc upper portion of the apparatus
is vented by openings 15, pa~sage 14~ and vent and hood 7
externally of casing 10. After the liquid sulphur has passed -~
through the scrubber apparatus 5 ~t spreads out over the surface
of the liquid sulphur in the tank allowing more gaseous hy-
drogen sulphide to escape. Openings 21 are provided in casing
10 near the top of the tank to venk the hydrogen sulphide gas
from the tank into passage 14. After sufficient treatment~
the purified liquid sulphur in tank 2 is pumped from the
tank by pump 17 through the appropriate piplng 18 to tank
~`~ cars or other suitable containers for shipment to the ulti-
mate users.
Another alternative embodiment which can easily
~; 15 be adapted to this invention is to collect the escaping gas
at vents 7 and 19 and recycle the gaseous hydrogen sulphide
~ through the production facility 1 to convert, this gaseous ;
hydrogen sulphide into liquid sulphur.
The typical dimensions for the splash tower shown
d ~ ; 20 in Fig. 2 would be a tower of some 32' in height of which 5'
protrudes above the 'GOp of the storage tank. The lnterior
~ baf~'les could be approximatel~ 16" ln helght with a vertical
'~ separation of 12" between each baffle at the center point
of the tower. A typical slope for the hor-lzontal surface
25 o~ each baffle would be 1" per 11". -
Fig. 3 illustrates a further embodiment of the gas
~` scrubber apparatus in Which the liquid sulphur downflow
,~ . . .
passage means comprises an elongated cylinder 22 coaxially
disposed within casing 10. The cylinder terminates before
the vertically upper end of casing 10 so as to form a
;: ' '
'f,~ 7
~: :
,!
,
~)45511~8
chamber 23 at the uppe~ end thereof.
Openings 15 are provided in opposing sides of
cylinder 22 i.n an offset arrangement and are communicative
wlth the gas venting passage lL~ deflned between cylinder 22
and casing 10. The openings terminate in cylind~r 22 above
-the minimum sulphur leve} in tank 2, but addltional b~ffle
plates 15a are disposed below the openings ln cylinder 22,
one below and one above the minimum liquid sulphur level P ~ ?
the tank, to prevent free :~all of the sulphur for an excessive ~-
10 dlstance. Coupllng means, illustrated as a discontinuous ;~ ~ .
sleeve 24, couples cylirder 22 to the storage tank and the
reservoir of liquid sulphur to the downflow passage there- .
within. Each of baffle plates 8 ls also provided with liquid
.~ .. ..
sulphur down.~low diversion means, illustrated as rectangular :::
.~ 15 shaped plates 25, disposed in a staggered arrangement on the
upper surface thereof. The plates further agitate the liqu-ld
sulphur flowing over the baPfle plates and increase the sur-
face area thereof to ~acili-tate the release of gas. !~ ~
Chamber 23 conta.ins means for separating entrained :~ ;
.:
vapors from escaping gas, illustrated as demister pad 26.
Means for heating the demister pad, illustrated as steam
`~ coils 27, are also provided, and serve to remove condensed ; ~;
liquid sulphur collected on pad 26 and return it to the
re.ser~oir in tank 2. As in the previous embodiment of the
~ .
invention means for supplying liquid sulphur to the upper-
~ most baffle plate is provided and includes supply pipe 16
'l and a U-shaped baffle plate 28. Steam tracing and insulation ~.
i;~ is also pro~ided in casing 10.
, . : .
, In an illustrative embodiment of the gas scrubber
, ~ ..
; 30 apparatus shown in Figs~ 3 - 5, the cross-sectional area of
1: ~ '' - '. .
t,'. :
. .. .
,.. "~ . . ,- ,- . '.' , ,, .,,' ,' ` . ' ., , ' ' " .': . ' '
~ o~9~
casing lo with respect to the cross-sectional area of
~; cylinder 22 could ha~e a ratlo of approximately 3:1. Gas ~
discharge passage 7 would be approximately 2~ feet in length; ~:
cylinder 22 approxin~ately 36 feet long; and plates 25
approximately 3 inches in vertical height and 6 inches in
horizontal length, and spaced apart by a distance of approxi-
mately 6 inches. The operation of this ernbodiment of the
scrubber apparatus is substantially khe same as that illus-
trated in F~g. 2
In order to determine the effectiveness of this
.,
invention in reducing hydrogen sulphide and polysul.phide
in liquid sulphur, the following tests were conducted by
: :~
bubbling nitrogen through a weighed sample of sulphur, then
, ~
¦~ passing the nltrogen through an absorption train consisting `
of a magnesium perchlorate drier, then ~ollowed by passage
,
through an activated copper phosphate hydrogen sulphide
; absorber. When tested by this process the following example
illustra~es the ef~ectiveness of this invention in reducing
hydrogen polysulphide in liquid sulphur. Liquid sulphur -;~
samples taken from the 13,000 long ton storage tank prior -~
to treatment in the scrubber or splash tower, when analyzed `~
for equivalent hydrogen sulphide content according to the `~
process described above~ have been found to contain between ` `
170 ppm (parts per million) and 218 ppm. After aging ~or 4
day~ and one pass through the spla~h tower, the equivalent
hydrogen sulphide content of the liquid sulphur had been ~ :
~; . .,
reduced to between 46 and 39 ppm. By continuously passing
the liqu.id sulphur through the splash tower, the equivalent
P~ hydrogen sulphide content of the liquid sulphur can be
reduced even further.
,.~ .
~.~ 9' ;~"-' '
:~ .
~' '"'', ~,
A ~
~()4S9198
A~ a ~urther illustratlon o~ the ~ffectiveness
of our process, liquid sulphur which had been pretreated in
accordance with thls invention and~shipped in a sealed tank
car ~or a period O:r ~ days evolved hydrogen sulphide at the
rate of 1.88 cublc ~eet per long ton. Liquid sulphur which
had not been treated according to this invention but was
shipped directly from the production facility in a sealed
tank car for the same amount o~ time, evolved hydrogen sulphide
at the rate of 4.39 cubic feet per long ton. This marked
reduction in equivalent hydrogen sulphide was accomplished
by only one passage through the splash tower.
t~ While the illustrated embodiments o~ the invention
use a continuous circulation of the liquid sulphur during
storage, another alternative embodiment which we have found
most advantageous is to use two tanks. In one tank the
material is stored rOr a period of l to ~ days during which
time the hydrogen sulphlde slowly evolves and ls vented into
;-~ . ...
t ~ the atmosphere. After this storage period the liquid sulphur
is then pumped to a second tank which includes the described ~-
., .
gas scrubber apparatus. While the liquid sulphur is in this
aecond tank it is circulated through the splash tower for a
;~:. ; .
suffic~ent period o~ time to circulate all the material at
least twice. In this manner the hydrogen polysulphide content
can be simllarly reduced to su~f:Lclentl~ low levels to provide
j 25 ~or sa~e handling during storage and shipment. ;~
In the ~oregoing, the invention has been described
with reference to specific exemplary embodiments thereof. It
~l will be evident, however, that variations and modificakions
`~ may be made thereto by those skilled in the art without de-
parting from the spirit and scope Or the in~enkion.
:
~i~ 10. .. .
,., "
.~ .. ; . . . , , ~ : , . : .
