Note: Descriptions are shown in the official language in which they were submitted.
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BACKGRO'JI~'D OF ~HE INVEI~TION
The present ~nvention relates to a process and racility
for upgradin~ heavy hydrocar~on2ceous materials, and more
particularly, a proce~s and facility lor upgrading heavy crude
oils generally characterized ~y high speci1ic gravities, high
pour points, high viscosities and high contents of sulfur,
metals, water, salt and conradson carbon ~or making coke
suita~le for metallurgical purposes.
In the typical delayed coking process, residual oil is
heated ~y exchanging heat with liquid products from the process
and is fed into a fractionating tower wherein light end products
producedin the process or present in the residual oil are
separated by distillation. The residual oil is then pumped
from the base o~ the fractionating tower through a tubular
furnace under pressure where it is heated to the required
temperature and discharged into the bottom of the coke drum.
The first stages of thermal`decomposition reduce this residual
oil to volatile products and a very heavy tar or pitch which
further decomposes to yield solid coke particles. The vapors
formed during the decomposition produce pores and channels in
the coke and pitch mass through which the incoming residual oil
from the furnace must pass. The incoming oil and decomposition
vapors serve to a~ltate and maintain the coke mass and residual
oil mixture at relatively uniform temperature. This decomposition
process is continued until the` coke drum is filled ~ith a mass
of coke with a small amount of pItch. The vapors ~ormed
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leave the top of the coke drum and are returned to the
fractionatinc tower where they a.e l`ractionated into the
desired petroleum cuts. After the coke drum is filled with a
mixture of coke particles and some tar, residual vapors are
removed, and the coke is removed from .he drum hy hydraulic
or mechanical means. This green delayed ~etroleum coke has
particular crystalline and chemical properties which make it
especially suitable for making carbon anodes for the aluminum
industry, but the green coke must be calcined or carbonized
by further treatment to produce a finished calcined coke product.
~ ue to the characteristics of the heavy crude oils of the
type set forth above they cannot be processed economically by
conventional processing. In addition to their low auality these
crude oils are extremely temperature sensitive and decompose
at relatively low temperatures. The processin~ and treatment
of these crude oils at conventional conditions and in typical
refining processes results in higher operating costs and the
production of products which are predominantly of little value.
Naturally, it is highly desirable to provide a process
and facility for upgrading heavy crude oils so as to allow for
the economic production of valuable petroleum products. The
process and facility of the present inve~tion should allow for
the economic production of coke suitable for metallurgical purposes.
Accordingly, it is a principal object of the present
invention to provide a process and facility for upgrading heavy
crude oils.
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In particular the present invention seeks to provide a
process and facillty for upgrading heavy crude oils for use
in the production of metallurgical coke.
The invention further seeks to provide a process and
facility for upgrading heavy crude oils wherein a hydro-
carbon diluent is employed to facilitate control of temperature
and residence time thereby prohibiting premature decomposition.
Still further the invention seeks to provide a process
and facility for upgrading heavy crude oils wherein the crude
oil is carefully fractionated to maximize liquid yields
during the coking step.
In accordance with one aspect of the invention there is
provided a process for upgrading heavy crude oils for making
coke suitable for metallurgical purposes which includes the
steps of (a) mixing a diluent with incoming heavy crude oil
SO dS to form a mixture of crude oil and diluent; (b) sub-
jecting the mixture of crude oil and diluent to distillation
whereby gas hydrocarbon products, an overhead liquid hydro-
carbon product and a residuum are produced; (c) subjecting
the overhead liquid hydrocarbon product to further treatment
whereby naphtha and off gases are separated out as overhead
products and a narrow boiling point diluent is produced;
(d) recycling the narrow boiling point diluent; and (e)
mixing the narrow boiling point diluent with said incorning
heavy crude oil.
In accordance with another aspect of the invention there
is provided a facility or apparatus for upgrading heavy crude
oils for making coke suitable for metallurgical purposes
including (a) means for mixing a diluent with incoming heavy
crude oil so as to form a mixture of crude oil and diluent;
(b) a distillation unit downstream of the means for mixing
the diluent with incoming heavy crude for distilling the
mixture into gas hydrocarbon products, an overhead liquid
hydrocarbon product and a residuum product; (c) splitter means
downstream of the distillation unit to further treat said
overhead liquid hydrocarbon product so as to obtain a narrow
boiling point diluent; and (d) recirculating mears for
recirculating the narrow boiling point diluent to the means
for mixing the narrow boiling point diluent with the incoming
heavy crude oil.
The present invention relateS to a process and facility
for upgrading heavy hydrocarbonaceous materials9 and more
particularly a process and facility for upgrading heavy crude
oils for making coke suitable for metallurgical purposes. The
crude oils found in Orinoco Oil Belt of Venezuela are generally
characterized by high gravities (close to that of water); high
pour points (solid at ambient temperatures); high viscosities;
high metals, sulfur, water, salt and conradson carbon contents.
In addition, the crude oils are extremely temperature sensitive,
that is they easily decompose at low temperatures. The process
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and facility of` the present invention allows for the economic
production of petroleum products of upgraded -value such as
LPG, gasoline, kerosene~ jet fuel, diesel oil and gas oils.
The process and facility employs the use of a hydrocarbon
diluent with a closely controlled boiling range to facilitate
transport, dehydration and desalting of the crude oil. Further,
the diluent facilitates close control of temperatures and
residence times thus avoiding premature decomposition and
therewith degradation of coker yields. The process and facility
also uses a coker fractionator and coker heater design intended
to better control the quantity and quality of the coker recycle
s-tream to minimize gas- and coke formation and improve the
density of the produced coke. The process and facility utilizes
a careful fractionation of the crude oil for front end control
to ma~imize liquid yields in the coking step.
BRIEF DESCRIPTION OF THE DRAWING
The Figure is a schematic flow diagram illustrating the
p:rocess and facility of the present invention.
DETAILED DESCRIPTION
The f`acility 10 and process of the present invention as
shown in the drawing depicts the various stages of a delayed
coke pilot plant including the facility for upgrading heavy crude
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oil feedstocks. A typical heavy crude oil feedstock ~rom the
Orinoco Oil Belt has the ~ollowing composition and properties:
TABLE I
.
Gravity API 8.o (1,0l4 Kg/ms)
Sulfur, % wt 3.71
Mercaptans, wt ppm hlil
Pour Point, F 80
Nitrogen, % wt 0.60
Water and Sediments, % Vol 6.4
Salt Content as NaCl, Lbs/1000 BBls. 500
Conradson Carbong % wt 13.8
H2S, wt ppm 37
Neutrali~a-~ion Number, mgr KOH/gr 3.95
MNI, % wt 13.54
Asphaltenes, % wt 7.95
UOP K Factor 11.3
Viscosities:
XV at 180F, cst 118LI
KV at 140F, cst 7558
KV at 122F, cst 19229
Metals Content:
Iron, wt ppm 19
Vanadium, wt ppm 396
Nickel, wt ppm 78
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Most of the oils fall within the following composition and
properties:
TABLE II
Gravity, APl 6 ~ 12
Viscosities:
KV at 180F, cst 400 - 2500
KV at 140F, cst Z000 - 20000
KV at 122F, cst 5 - 4
Metals Content:
Iron, wt ppm 15 - 25
Vanadium~ wt ppm 3O - 5~
Nickel, wt ppm 60 - 120
Asphaltenes, % wt 6 - 12
Salt Content as NaCls Lbs/1000 BBls. 35 - 1000
Pour Point, F 50 - 9Q
Sulfur, % wt 3.5 - 4.5
Water and Sediments~ % Vol 0.2 - 10
The crude feedstock is supplied to the facility shown in
the Figure via line 12. Tne heavy crude oil is mixed with a
diluent at the productlon well and later at the facility the
crude is mixed with additional diluent delivered to line 12 by
way of primary llne 14~ recycled diluent line 15 and line 18.
The use of the diluent is critIcal for a number of reasons.
Firstly, the diluent lowers the viscosity and pour point of the
crude so that it is not solid at room temperature thereby
facilitating transport of the crude. Secondly, the diluent aids
in controlling the temperatures and residence times in the
facility thereby avoiding premature decompos~tion and
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there~ith degradation of coker yields~ The diluent should be
mixed ~ith t.he crude oil in an amount of fro~ about 10 to about
50 percent volume. In accordance with the present invention,
the diluent should be a narro~ ~oiling hydrocarbon diluent
having suitable solubility characteristics so as to avoid
separationO The composition and properties of the diluent
should fall ~ithin the following ranges:
TABLE III
Gravity, API 20 65
Viscosities:
KV at 100F, cst 0.5 - 10.5
KV at 210F, cst 0.1 ~ 3
Distillation ASTM ~-86 (F)
IBP 150 - 410
50% Vol 200 - 610
EP 250 _ 800
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A diluent having the following composition and properties is
preferred:
TA~LE IV
Gravity, API 35, Ll
Sulfur 9 ~ wt o.48
Pour Point~ F -25
Water and Sedimentsg ~ Vol 0.02
Conradson Carbon, ~ wt 0.05
KV at 100F, cst 3.35
KV at 122F, cst 2.78
Distillation ASTM D-86 (F)
IBP 360
50~ Vol 496
EP 642
The incom:lng feedstock from line 12, which is mixed with
dlluent from line 18, :Ls fed to a desalting statlon 20 comprising
in series a dehydrator 22 and a first and second stage desalter
24 and 26, respectively. The water content of the crude oil
is reduced ln dehydrator 22 down to about 1.0 volume percent
and the salt content is reduced in the dehydrator to about 150 PTB,
and in the desalters 24 and 26 down to about 5 PTB. The
temperature in the desalting station 20 should not exceed 275F.
The desalted crude oil flows from desalter 26 to ~ired
heater 28 where the crude is preheated to its desired
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crude tower feed :Lnlet temperature and from there to an
atmospheric pressure oil distillation unit 30 where it is
separated into gases, liquid products and atmospheric residuum.
The atmospheric distillation unit 30 is designed for several
modes of operation.
In one operation~ 500F plus residuum is produced and is
drawn off and fed via line 32 to combination tower 34 for use
as coker feed. The 500F minus overhead is drawn off through
line 36 to splitter tower 38. The off gases from the atmospheric
distillation unit 30 are removed through line 40 and passed to
a gas scrubber of' conventional design. The gas oil products
from atmospheric distillation unit 30 are drawn off through
line 42. The 500F minus overhead is fed to splitter tower 3
where naph-tha and off gases are separated out as overhead
products and drawn off through lines 44 and 46, respectively.
The splitter tower bottom product is a narrow boiling
400F-500F liquid having properties and composition suitable
for use as the diluent. The splitter bottom product is drawn
off through line 16 and is recycled and mixed with the crude
oil feedstock entering dehydrator 22.
In another mode of operation of atmospheric distillation
unit 30, the unit will again produce a 500F minus overhead
product which is drawn off and fed to splitter tower 38 via
line 36. A 500F to 70~F gas oil is produced and removed
through line 42. The atmospheric residuum is a 700F plus
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product which is drawn off through line 32 to line 48 where it
is fed to gas fired heater 50 where the atmospheric residuum
ls heated to its desired temperature and from there to vacuum
distillation unit 52 for further processing. The atmospheric
residuum is vacuum distilled in distillation unit 52 to produce
a vaporized gas oil product which is drawn off through line 54
which may be recovered separately or combined with gas oil from
the atmospheric unit 30. The vent ~ases from the vacuum
distillation unit 52 are removed through line 56 and combined
with the o~f gases from the atmospheric unit 30. The vacuum
distillation unit is designed to produce from the atmospheric
residue 900F plus vacuum residuum which is drawn off through
line 58 and .fed to combination to~er 34 for use as coker feed
via line 32.
The reduced crude coker feed from either o.f the above
modes o~ operAtion is fed via line 32 to combination tower 34.
Combination tower 34 comprises a heat transfer portion and a
~ractionator portion. The coker fresh feed ~rom the atmospheric
residuum or vacuum residuum flows via line 32 to the bottom
section of combination tower 34 where it is heated by direct
contact with coker effluent and fractionated to produce a
reduced coker feed mixed with recycle. Coker ~eedstock is
wlthdrawn from the bottom portion of combination tower 34 via
line 60 and flows to coker heater 62 where the feedstock is
heated to the desired temperature of about 920F. The coker
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feedstock is heated as it passes through coker heater 62 and
is fed via line 64 to one of several delayed coking drums,
either coke drum 66 or coke drum 68, where the hydrocarbon
feedstock decomposes leaving a mass of green coke. The coke
drum vapor containing coker products and recycle is drawn
off through line 70 and flows to the fractionation portion of
combination tower 34. The recycle is condensed and mixed with
the fresh feed in the bottom section of tower 34 while the
coker products are fractionated lnto off gas, coker naphtha,
coker distillate and coker gas. The above fractionated coker
products are drawn off via lines 72, 74, 76 and 78, respectively.
The unit is designed to operate normally with a recycle ratio
of 0.1. However, if necessary the recycle ratio may be
increased to 1.0 with a small reduction in fresh feed.
After sufficient coke is deposited in one coke drum, for
example coke drum 66, the flow of the coker heater feedstock
is switched to another coke drum 68 which has been preheated.
The coke in coke drum 68 is then removed. The coke bed in the
full drum is steam stripped and then cooled by water quenching.
After draining of the water, the top and bottom heads of the
drum are removed. The coke is then removed by hydraulic
cutting and collected in a coke pit. Coke cutting water
drained from the coke pit is collected through sluiceway and
is pumped to storage tank for reuse. The empty drum is then
reheated, steam purged and pressure tested. It is then reheated
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wlth superheated steam to about 70F and ready to receive the
coking heater ef~luent again.
The coker liquid products may be further processed by
hydrogenation to produce final products such as LPG, gasoline,
kerosene, ~et fuel, diesel oils and gas oils.
It is to be understood that the invention is not limited
to the illustrations described and shown herein, which are
deemed to be merely illustrative of the best mode~ of carrying
out the invention, and which are susceptible of modification
of form, size, arrangement of parts and details of operation.
The inventlon rather is intended to encompass all such
modifications which are within its spirit and scope as defined
by the claims.
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