Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR THE PRODUCTION OF SULPHUR IN GRANULAR FORM
The invention relates to a method for thè production
of sulphur in granular form, wherein heated sulphur, preferably
produced by the Clause - process, is divided by bead forming
means and cooled.
Various methods are known for the production of sulphur
in granular form or in bead form. In one known method, the sulphur
produced, e.g. by the Clause process, is directly deposited onto
a steel belt and is there subjected to laminar cooling. It has
been shown in such methods that an easily handled dry end product
is obtained which can be produced at flexible adjustments of the
production capacity at a high bulk weight. However, as it turned
outt the sulphur has the tendency to form dust.
In another known method, the granulation i5 effected
under water, wherein, though fast cooling is obtained, the end
product is wet, porous and fragile. These end products, therefore,
also had the tendency of forming dust due to their fragility. Fur-
ther disadvantage of this method is in water pollution and in
that t~e method allows only relatively small bulkweights.
A similar known method~spray cooling in prilling towers~
provides the advantages of very high capacity and of a small
dust portion, however, it still has the disadvantages that substan-
tial costs are required for investment, and that, furthermore,
transport losses occur. The environmental pollution by air
pollution caused by the prilling towers is likewise of importance.
It is also known to choose conventional bead forming
agents, by which the sulphur is formed into drops or beads. As
a disadvantage o same, it has been shown that the sulphur obtained
at a temperature between 140 and 150 in the Clause process is
a low viscosity and possesses a low surace tension, which~ in
turn, produces, on the bead formation with the conventional
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arrangements, very flat, fragile beads. Besides, the available
production capacity is lower.
It is an object of the present invention to provide
a technical way whereby sulphur can be successfully produced in
a simpler way and can be economically transferred into a bead
form without having to cope with the disadvantages of reduced
strength, a wet end product or a strong tendency to form dust.
The invention resides in that the sulphur is first
heated up to a temperature above 150C and thereupon is brought
into the form of drops and then solidified in at least two cool-
ing steps at dif~erent cooling temperatures, wherein at no part
of the cooling process a predetermined temperature difference
betwe~n the sulphur and the coolant is exceeded. It has been
shown that such a pxocess for the production of sulphur in granular
form does not give rise to the disadvantages referred to above.
Sulphur is usually obtained in the refinery at about 145C and
has a relatively low viscosity.
When sulphur is heated before the ~ormation of the
drops to a temperature above 150C, preferably between 159 and
163C, it has ~een shown that the drop formation is possible
without strong tendency o~ fibre pull, at higher temperatures the
sulphur cannot be transformed into drops due to its increased
viscosity. On lower temperatures, it has been shown that sulphur
is too thin and thus cannot ~e brought to a good bead formation.
By the cooling in a number of cooling steps, good ~ead sizes
and a strong end product are obtained. In so doing, a pr~determined
temperature di~ference between the sulphur and the coolant is
not to be exceeded. Thus, optimum cooling can be achieved since
undercooling and thus li~uid discharge is avoided.
It is very advantageous when the beaded sulphur is
solidified in three cooling steps. In 50 doing, it is to be
observed in each cooling step that the temperature difference
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between the sulphur and the coolant does not exceed the value
of at most 90C. P greater temperature difference would give
rise to a too fast cooling and would result in undesired pro-
perties associated with same.
In a more advantageous way, arrangements can be made that
the sulphur is delivered to a first cooling zone without any
coolant and then is conveyed to a cooling zone in which the cool-
ing is effected by coolant haviny the temperature of between
45 and 55 C and then is further conveyed to a cooling zone
wherein the coolant temperature is less than 20C. In the
first cooling section, the sulphur is cooled by the surrounding
air and is transformed, at a temperature still above 100,
into a cooling zone in which the cooling is effected by a cool-
ant whose temperature is between 45C and 55C. In the last
cooling step, the cooling then proceeds with less than 20C.
The passage through the thrPe cooling zones should take at
least the time period of 15 seconds. It is of advantage when
a rotary bead forming mold is used for the carrying out of
the method for the formation of beads, which is disposed above
a conveying belt which passes through cooling ~ones of different
temperatures. With such a rotary drop or bead forming mold,
the method can be effected in an economic way. The rotary
drop forming mold may comprise a cylindric container which is
surrounded by a second container rotatable relative to the
fixst container, wherein the first container is provided with
openings discharging in the direction towards the conveyor belt~
which openings are cyclically aligned with the openings in
the second container on the relative rotation of the containers.
The sulphur, heated up to a temperature above 150CJcan then
be placed into the inner container, relative to which an outer
container is rotated. When the openings of both containers
are flush, the hot sulphur is extruded from the opening in
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drop - shaped configuration and falls drop-wise onto the
belt disposed below. rrhe sulphur, however, can also be
brought within the container to the above mentioned temper-
ature if the inner container of the rotary drop-forming mold
is suitably heated. On the conveyor belt are then provided
different cooling zones wherein the region immediately follow-
ing that of the deposition of the sulphur does not require
any cooling. The sulphur cools itself and is then passed on
the belt into a second region in which the belt is sprayed
e.g. by water having the temperature of between 45 and 55C.
In a third section, the conveyor belt is sprayed with water
having the temperature of 17C, whereupon, after the passage
through the three regions, the solidified sulphur is produced
which can be easily released from the belt and, as it has
been shown, has a good abrasive resistance.
In the following, the method and the apparatus for
carrying out the method will be described in exemplary fashion
with refexence to ~he figures. The drawing shows:
Figure 1 - a diagrammatic representation of the method by
way of a block diagram;
Figure 2 - a device for the carrying out the invention; and
Figure 3 - a detailed representa~ion of the device according
to Figure ~.
In Figure 1, the individual method sections are readily
visible. As a starting step, sulphur is provided, such as
sulphur produced by the Claus~- method. Normally~ the sulphur
has the temperature between 140 and 150C and has a relatively
low viscosity. The sulphur is ~hen heated by means of a heating
device up to a temperatuxe of preferably between 159C and 163C.
Thus, the sulphur is polymerized and increases its viscosity
to a substantial degreeO The ~iscosity is still not so high as
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to give rise to the phenomenon of fibre pull during the drop
formation. It can thus be formed into drops which are then
cooled with a conveyor belt at different cooling zones, where-
by the sulphur solidifies. Within the cooling zones, the drops
are cooled at different cooling temperatures, preferably, in
the first cooling zone without the addition of a coolant. A.s
an end product, a solidified, bead-shaped sulphur is obtained
which possesses, as a dry end product, a high strength. On a
suitable drop forming, the end product also possesses the feature
of uniform grain size so that no transportation or handling
problems are encountered.
Figure 2 shows a device which is formed in a simple way
and can be very advantageously used for carrying out the
method as described above. Above a steel belt 1 is arranged
a rotary drop forming mold referred to in total with reference
numeral 5, to which is delivered sulphur, having suitable
te~.perature greater than 150C, preferably between 159 and
163C. The device for heating the sulphur to this temperature
is not shown.
The rotary mold 5 consists of an inner container 3
and a container 4 surrounding the former J wherein the outer
container 4 can be rotated by a drive device ll relative to
the inner container 3. Into the inner container 3 communicates
a feeding sleeve 6 and an outlet sleeve 7 as we~l as inlet
sleeves 8. By the feeding sleeve 6, a heating agent can be
produced for the double wall of the inner container 3, which
serves the purpose of obtaining the desired temperature above
160C. Over the inlet sleeve ~ r the liquid sulphur is brought
into the interior of the container 3. By the rotating of the
outer container 4 xelative to the inner container 3, the
sulphur is discharged in a way to be described later, onto the
belt l, which passes through cooling zones 12, 13 and 14 having
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different temperatures. Inside the cooling zone 12, the sulphur
is cooled without the input of a coolant and is then transformed
into a cooling zone 13, wherein water is sprayed by a spray
device onto an undersurface of the belt 1. The water temper-
ature in this region should be between 45 and 55C. Before the
end of the belt, one more cooling zone 14 is provided wherein
water having the temperature of about 20 is sprayed from under-
neath against the belt 1. As can be seen from the cross-sectional
view shown in Fig. 3 of the rotary drop forming mold, along
the line III - III of Fig. 2, the inner container 3 is provided
with openings 15 directed towards the belt 1 and dispo-
sed one behind the other. The openings 10 of the outer container
extend over its entire periphery, are cyclically aligned with
the openings 15 when the outer container 4 is rotated relative
to the inner container 3. By this cycl.ic shearing of the sulphur
flowing out of openings 15, drops are then formed which are
deposited onto the belt 1 and are finally cooled in the above
descrLbed way~
The use of such a rotary drop-forming mold for the
carrying out of the method allows a very economic production
of granular or bead-shapad sulphur, whereby a solid end pro-
duct is obtained having a high strength, a uniform particle
size and a reduced tendency to form dust, which until now could
be ohtained only at a substantially greater expense.
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