Note: Descriptions are shown in the official language in which they were submitted.
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Pyrolysis of bitumen in a reactor containing grinding
bodies
This invention relates to a method suitable for the
thermal decomposition of bitumen in a reactor that is
heated from the outside and contains grinding bodies.
In particular, the reactor is able to process into
synthetic crude oil bitumen that has been extracted from
oil-containing sand.
Bitumen, when extracted from oil sand, is in the form
of a semifluid viscous complex mixture of compounds of
high molecular weight. The economical refining of bitumen
presupposes its conversion to a synthetic crude oil that,
being readily transportable, is largely free from
contaminants.
At this stage in the process, the constituents of the
bitumen should already have been converted into high-grade
hydrocarbon compounds, in particular aromatic compounds.
The conversion of bitumen has to date been accomplished
by coking processes (delayed coking, fluid coking,
flexicoking - see e.g. Heavy Oil Processing Handbook 1982).
Such processes involve either discontinuous treatment
or necessitate the employment of costly aggregates for the
purpose of producing fluidized beds.
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The object of the invention is to develop a continuous
process employing simple and inexpensive aggregates.
According to one aspect of the invention there is
provided a process of pyrolyzing bitumen which comprises:
preheating the bitumen to over 80 C and continuously spraying
the bitumen onto an inner wall of a heated rotating reactor
containing separate grinding bodies freely movable within the
reactor and/or onto the grinding bodies themselves, heating
the bitumen in the reactor to pyrolysis temperature so that it
is broken down into pyrolysis gas and pyrolyzed coke,
continuously removing the pyrolysis gas from the reactor and
continuously removing pyrolyzed coke particles produced when
the pyrolyzed coke is deposited on the inner wall and/or
grinding bodies and is ground away and removed, at least from
the inner wall, by the grinding bodies that move during
rotation of the reactor.
According to another aspect of the invention there is
provided apparatus suitable for carrying out the above
process, comprising a reactor in the form of a generally
horizontal cylinder rotatable about its longitudinal axis and
containing separate grinding bodies freely movable within the
reactor, said cylinder having one or more nozzles for spraying
preheated bitumen therein and apertures over a portion of its
length that feed into a hollow ring which seals and surrounds
the cylinder, from which hollow ring extend a gas removal
member and a coke removal member.
The process according to the invention takes place inside
a rotating cylindrical reactor that contains grinding bodies.
At the start of and during the operation, the equipment is
rendered inert by waste gases produced when the reactor is
heated. The pressure inside the reactor is maintained at a
level slightly above atmospheric in order to prevent the
incursion of oxygen into the reactor.
Preheated bitumen is sprayed into the reactor and, given
a suitable pyrolysis temperature, is pyrolyzed inside the
reactor and especially on the heated inner walls thereof.
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In a preferred embodiment employing multiple jet
nozzles arranged more or less along the cylinder axis, the
preheated bitumen is sprayed in a virtually radial fashion
onto the walls that have been cleansed of pyrolysis
products by the grinding bodies, such spraying being
directed at a point on the reactor circumference that
exhibits, due to the disposition of the burners, the
highest temperature and that during operation remains free
of grinding bodies.
Solid pyrolysis products (pyrolyzed coke) and gaseous
pyrolysis products (pyrolysis gas) are produced during the
pyrolysis (coking) process. The pyrolysis gas is a mixture
of hydrocarbon compounds that differ in composition and
boiling points.
The relative motion occuring between the reactor and
the grinding bodies, which is preferably caused by the
reactor's rotation about its essentially horizontal
cylinder axis, causes the inner walls of the reactor to be
largely free of solid pyrolysis products. Coke particles
deposited either on the inner walls or on the grinding
bodies, are thus rubbed off.
Such an arrangement permits the now finely ground
pyrolyzed coke to precipitate and, without being further
ground, to be fed to a furnace with a high specific energy
output. The pulverized pyrolyzed coke is continuously
removed from the reactor.
A further advantage of the proposed process is that,
on the inner walls of the reactor that have been largely
(cleansed) of pyrolyzed coke, a consistently suitable heat
transition and a defined inner wall temperature suitable
for pyrolysis are maintained.
The reactor is heated by burners that are fed
preferably with low-boiling constituents of the pyrolysis
gases and that heat the reactor from the outside.
A plurality of burners are preferably disposed more or
less linearly assuming a battery-like configuration along
the longitudinal axis of the reactor, each of which heats
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the portion of the circumference present in its vicinity
at any given moment.
Reactor output can be increased if several such burner
batteries are arranged in series around the circumference,
since the inner wall, freed of grinding balls, can be
utilized as a spraying surface for the pyrolysis of the
bitumen.
The pyrolytic process can take place at a temperature
lying between 300 and 900C. In a preferred embodiment
of the process according to the invention, the temperature
of the inner wall in the zone of the spraying surface lies
between 700 and 750C, which permits an optimal yield of
aromatic compounds. The average temperature of a metal
conversion system employing grinding bodies lies prefer-
ably between 650 and 700C.
The grinding bodies can be maintained at a temperature
below that of the inner wall, for example through a
suitable choice of the quantity and temperature of the
sprayed-in bitumen and thus advantageously facilitate the
processing of the pyrolyzed coke.
The proposed process may, in accordance with another
embodiment, be carried out inside a reactor having one or
more separating walls, whereby the various reactor parts
are maintained at different temperatures in order to
create different reaction zones. In a special embodiment
involving a two stage process, the temperature of-the
reactor inner wall in the first reaction zone lies between
460 and 500C, while in the second reaction zone, the
temperature of the reactor wall lies between 700 and
750C. In this case, the bitumen is sprayed onto the
grinding bodies located in the first reaction zone,
whereby a quantity of low-boiling hydrocarbon escapes.
The viscous mass that initially sets on the grinding bodies
is, through the rotation of the reactor, transported into
the second, hotter reaction zone, in which a cracking
process occurs, whereby further gaseous pyrolysis products
are released and pyrolyzed coke remains, which is removed.
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The circulation of the grinding bodies, which in this case
are composed preferably of metal, can be facilitated by
the installation inside the reactor of suitable structures.
An embodiment involving a single or multi-stage process
with improved output can be developed if a middle chamber
is fitted with devices to expel the pyrolyzed coke and if
both frontal sides of the reactor are fitted with nozzles
suitable for expelling the bitumen. In this case, the
outer chambers may, in order to facilitate an alternating
process, be operated in alternating fashion, at high and
low temperatures. Such an arrangement is especially suit-
able in the case of certain types of bitumen which results
in the creation of solid pyrolysis products that assume
a highly viscous form and can be cracked only at high
temperatures.
The material constituting the jacket of the reactor
should consist of one or more layers of a heat-and-
oxidation resistant steel, consisting preferably, in the
case of a special embodiment, of NiCr 15Fe + Si(3%).
A wear lining of steel or a refractory, but not thermal
insulating material, can be installed inside the reactor.
The grinding bodies may consist of metallic material,
e.g. heat-resistant steel in the form of balls, ceramic
material, ceramic material combined with a catalyst, or
hardened limestone, the rubbed off portions of which
combine with solid pyrolysis products and during the
combustion of the latter act as a desulfurant.
The overall volume of the grinding bodies inside a
reactor should not exceed 10% of the inner space of the
reactor. The speed at which the reactor rotates should
ideally not exceed 70% of the critical rotation speed.
A simplified preferred embodiment of an apparatus
suitable for the execution of the process according to the
invention is depicted in the drawings, wherein
Fig. 1 shows a vertical longitudinal section through a
reactor, and
Fig. 2 shows a vertical cross section corresponding to
II-II in Fig. 1.
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Apertures 5 are distributed over the circumference and
part of the length of a cylindrical reactor 1 having an
outer jacket surface 2, an inner jacket surface 22, two
outer curved frontal surfaces 3, 4, inner curved surfaces
43, 44 and inner plane frontal surfaces 23, 24. Such
apertures 5 are covered by a hollow, cylindrical ring 6
that is supported gas tight upon the outer wall 2 of the
reactor on surfaces 7 that face such outer wall.
The ring 6 does not rotate with the reactor 1 about
its longitudinal axis. Attached to ring 6 are a gas vent
8 in the shape of a frustum of a cone and a similarly
frustum-shaped coke delivery member 9 for the removal of
the pyrolyzed coke. The pyrolyzed coke is extracted
through a water basin 10 which serves to prevent the out-
flow of pyrolysis gas from the reactor and the incursion
of air into the reactor . A rod-shaped lance 11 is
attached to the frontal surface 43 of reactor 1 in the
longitudinal axis of the reactor 1. Rod-shaped lance 11
is sealed, by means of seal 45, against the inner curved
frontal surface 43. The exit end of rod-shaped lance 11
forms a nozzle 25. Rod-shaped lance 11, through which
fluid bitumen, preheated to at least 80C, flows, is
enveloped by insulation 20 and can also be kept heated by
hot water. The rotational axis of reactor 1, which is
borne in bearings 27, runs more or less horizontally.
The rotational drive for reactor 1 and the heating
burners, are not shown in Fig. 2. The inner space of
reactor 1 is divided by a perforated division wall 12 into
two chanbers, whereby in the first chamber 13, the bitumen
is decomposed and the deposited pyrolyzed coke is ground
away by grinding bodies 15, of which only a number are
illustrated, removed from the inner wall 22, while in the
second chamber 14 only the removal of gas and coke occurs,
although the coke can be additionally treated by the
addition of e.g. limestone. Disposed underneath chamber
13 are at least the burners 32 shown in Fig. 2. An inert
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gas such as waste gas can be introduced prior to
processing through feed pipe 17 for example at the coke
removal device 9 into reactor 1. Inert gas can also be
fed during processing through pipe 17 into the reactor 1
for the purpose of maintaining a slight over pressure
inside the reactor and thus to preclude the entry of air.
Fig. 2 shows the cross section through a rotating
reactor 1 that has spherical grinding bodies 15, which are
carried in the direction of rotation along the inner wall
22 up to a certain height 30, whereupon they either roll
or fall back over the mass of processing balls. At nozz le
25 which is disposed more or less centrally in the frontal
surface 43, fluidized bitumen is sprayed e.g. in a
plurality of jets streams over a spraying sector 29 on the
inner wall 22. Even such spraying sector 29 features the
highest surface temperature from 700 to 750C on the
circumference of the inner wall, since the burners 32 are
directed at the corresponding point on the outer wall 2.
Spray sector 29 and burner 32 are located, advantageously,
in the first lower quarter of the reactor, considered from
the direction of turn 30. Ideally, the burners 32 in the
illustrated example are disposed such that their flames
are directly downwards and the flames 33 are aimed virtu-
ally tangentially to the reactor wall 2, thus permitting
the escaping gases 34 to flow around and heat-a large
portion of the reactor circumference. The bitumen is
broken down more or less within the spray sector 29,
whereby heat is drawn from the wall, so that the adjacent
circumference portion, in which the grinding bodies 15 are
located and where the grinding bodies themselves feature a
lower temperature, which is however sufficient for the
treatment of the pyrolyzed coke and its removal from the
inner wall.
The solid pyrolysis products are preferably fired in
the pyrolysis operation in order to produce electricity or
in an extraction operation to produce hot water to aid in
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extracting bitumen from oilsands. The gaseous pyrolysis
products are condensed, whereby the low-boiling fractions
are separated out and used to feed the burner.
The fluid pyrolysis products condensed out of the
pyrolysis gas can be further processed as a synthetic
crude oil economically produced according to the proposed
method.
