Note: Descriptions are shown in the official language in which they were submitted.
6597
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CRUDE OIL CRACKING USING
P~RTIAL COMBUSTION GASES
This invention relates to a process for the
cracking of crude oil using partial combustion gases
wherein superheated steam, crude oil and oxygen are
injected into a partial combustion zone at one or more
points.
It is known in the prior art that crude oil
and other hydrocarbon fractions may be thermally cracked
by mixing superheated steam and the oil together and allow-
ing the pyrolysis to proceed adiabatically. These pro-
cesses allow crude and heavy hydrocarbon fractions, whichwould foul conventional tubes, to be cracked and have the
advantage that the steam diluent and heat carrler may be
readily condensed from the products and a savings is
thereby made as only the product gases need to be com-
pressed for separation. Among the disadvantages of theseprocesses are expense associated with the generation of
the superheated steam in the 1699C to 2000C range gen-
erally required. Also among the by-products formed in
the cracking process are heavy aromatic liquids and coke
which foul reactors and heat exchangers and which contain
18,442B-F -1- ~
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high quantities of sulfur and metals whlch must be dis-
posed of. Some of the problems associated with the gen-
eration of superheated steam have apparently been solved
by using a hydrogen burner to generate high temperature
gases, but the yields that may be obtained in this manner
are still low and the by-products still remain a problem.
Other processes for pyrolysis of heavy hydro-
carbons involve the use of a partial or complete combus-
tion burner, where the crude oil or fraction thereof to
be cracked is sprayed into the hot gases from the burner.
These processes avoid some of the problems associated with
the generation of high temperature steam and (when partial
combustion is used) also produce hydrogen gas which lowers
the heat required for cracking, increases ethylene yield,
and aromatics yield, and reduces coke formation.
The main disadvantage of these processes is
that large ~uantities of non-condensible gases (especi-
ally carbon monoxide) are produced, which must be com-
pressed to be removed. This involves a considerable cost
for large compressors and large size separation equipment.
In U.S. Patent 4,134,824, issued to Kamm et al.,
January 16, 1979, a process is disclosed in which crude oil
is first distilled to separate asphaltic components. The
distillate is then cracked using partial combustion gases
from a methane burner to generate ethylene, with recycling
of the asphaltic components to the burner. This process
uses a high fuel to oxidant ratio, and does not generate
H2 ln situ.
18,442B-F -2-
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It has been discovered that when a partial
combustion burner is used to generate hydrogen, carbon
monoxide, carbon dioxide, and water, and superheated or
shift steam is injected into the burner or combustion
gases, the superheated steam is additionally heated to
a higher temperature and much of the CO produced in the
burner is reacted with the steam by the shift reaction
to produce greater quantities of CO2 and H2. This has
the advantage that the benefits of hydrogen in the crack-
ing process are realized while most of the CO, which isdifficult to remove, is converted to CO2 which can be
readily scrubbed from the product gases with conventional
acid gas absorbents such as caustic solutions of alkanol-
amine solutions.
When crude oil or crude oil fractions are
injected into this hydrogen-enriched gaseous mixture, the
yield of the desired olefins and aromatics is increased
over the use of superheated steam alone while the forma-
tion of coke or coke deposits is virtually eliminated.
The use of this invention reduces the volume of off-gases
to be processed as compared to the use of partial combus-
tion cracking alone.
Additionally, it has been found that if the
heavy oils which are generated in the processes are used
as fuel for the partial combustion burner, any sulfur
compounds contained therein are converted mainly to hydro-
gen sulfide, and a smaller amount to carbonyl sulfide
which may be scrubbed out using known techniques. This
has the unique advantage that it allows a waste stream of
residual oils, which may not be suitable for burning in
18,442B-F -3-
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air because of restrictions on sulfur emissions, to be
used as some or all of the total fuel required to operate
the process.
The present invention is a process for the
cracking of crude oils or high boiling fractlons thereof
to obtain a mixture of lower hydrocarbons with a high
proportion of ethylene characterized by:
(l) partially burning a carbonaceous fuel
with an oxidizing gas and process steam in a par-
tial combustion zone to form a mixture of hot com-
bustion gases having an average temperature in the
range from 1200C to 2200C and containing more
than 5 volume percent carbon monoxide;
(2) injecting superheated steam into said
combustion gases in a shift reaction zone having
an average temperature in the range from 1200C
to 1800C react with said carbon monoxide to form
a gaseous mixture containing more than 5 volume
percent hydrogen and carbon dioxide;
~3) injecting said crude oils or fractions
thereof into said steam~hydrogen mixture in a crack-
ing zone having an average temperature in the range
of from 600C to 1500C under time and temperature
conditions which crack the crude oils or fractions
thereof into gaseous products and favor the forma-
tion of ethylene; and
(4) quenching the gaseous products with a
hydrocarbon quench oil.
Another aspect of the invention is a method
for the partial combustion cracking of crude oil or high
boiling crude oil fractions whereby a heavy recycle oil
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is recovered by quenching the gaseous products from the
cracking step and this heavy recycle oil is recycled for
use as a quench oil and/or use as a fuel or fuel supple-
ment.
The present invention is illustrated by the
drawing which is a schematic diagram showing the associ-
ation of the reactor 10, the burner assembly 12, and the
quench apparatus 14 together with the separation equip-
ment 44.
In the drawing, a reactor assembly 10 is shown
which has three zones comprising the partial combustion
zone 11, a shift reaction zone 13 and a cracking zone 15,
respectively. The reactor assembly is conventional and
is illustrated by U.S. Patent 2,698,830, issued to Jenny,
15 January 4, 1955.
A burner 12 is fed with oxygen or oxygen-
-enriched air through conduit 18. A hydrocarbon fuel
and steam are supplied to the burner through conduit 20
and a steam inlet conduit 22, respectively. The process
or saturated steam used in conduit 22 preferably has a
pressure of from about 50 to 250 pounds per square inch
(3.53-17.7 kg/cm2) and a temperature of about 150C to
210C. This steam is used to mix and atomize the hydro-
carbon feed in the burner 12.
Conduit 34 supplies superheated steam to the
reactor 10 and/or the burner 12. This superheated steam
generally has a pressure of from about 5 to 50 psig (0.35-
-3.53 kg/cmZ) and a temperature of about 700C to 1100C.
The superheated steam is supplied from a conventional
18,442B-F -5-
~6S97
-6-
superheater (not shown). The flow of superheated steam
is controlled by valves 26, 28, 30 and 32, associated
with conduit 24.
Conduit 16 supplies crude oil or high boiling
crude oil fractions, i.e., residuums to the cracking zone
15 in the reactor 10. The crude oil is stored in a sup-
ply tank (now shown) and is heated by preheater (not
shown) to a temperature of about 30C to 260C, depend-
ing upon the crude oil, to a flowable viscosity for use.
Cracked hydrocarbons from the reactor 10 are
then quenched with a quench oil in quench apparatus 14.
The quench apparatus can be of any well-known type, but
a falling film quench apparatus is preferred. Hydrocar-
bon gases are removed through conduit 38 and tars and
heavy oils are removed through conduit 40 and fed to the
burner 12 by a conduit (not shown).
outlet conduit 42 is provided to recycle quench
oil back to the fuel conduit 20. The flow of the quench
oil to the fuel conduit 20 is controlled and/or regulated
by valve 43. Thus, if or when a surplus of quench oil is
generated during the process, it can be used as fuel to
make the process partially or wholly self-sustaining.
Hydrocarbon gases leave the quench apparatus
14 through conduit 38 and enter into the separation appa-
ratus 44 which consists of conventional fractionators orcondensors, as shown in U.S. Patent 2,698,830, previously
identified. The desired lower hydrocarbon gases such as
ethylene and propylene, are removed by conduit 52.
18,442B-F -6-
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Light oils from the separation apparatus 44
are pumped by a pump (not shown) through conduit 47 where
they diverge through conduits 36 and 48 to supply quench
oil to the quench apparatus 14 and the fuel conduit 20,
respectively. The flow of the light oils is controlled
by valves 46 and 50. Valve 50 controls the flow back to
the quench apparatus 14 and valve 46 controls the flow
to the fuel conduit 20.
The temperature of the partial combustion
zone is controlled so as to have an average temperature
in the range from 1200C to 2200C and preferably from
1600C to 2000C. The average temperature in the shift
reaction zone is in the range from 1200C to 1800C and
preferably 1300C to 1600C. The average temperature in
the cracking reaction zone is in the range from 600C to
1500C and preferably 700C to 1100C. The foregoing
: average temperatures represent the estimated average tem-
peratures of the top and the bottom of each of the respec-
tive zones. Since there are no known temperature probes
which can be inserted to directly read these temperatures,
due to the high temperatures and high erosion, the same
information can be restated by indicating the outlet tem-
peratures which are measured on the outside of the respec-
tive zones. Thus, for the partial combustion zone the
outlet temperature is preferably at least 1700C. In the
shift reaction zone the outlet temperature is preferably
at least 1100C and the cracking reactor zone has a pre-
ferred outlet temperature of at least 600C.
In the partial combustion zone, care should
be exercised to insure that the average temperature is
not lower than 1200C since the rate of combustion is too
18,442B-F -7-
659
--8--
slow and inefficient, which results in more carbon and
methane formation. Further, the upper limit should not
be exceeded since the high temperatures will damage the
refractory linings of the reactor.
In the shift reaction zone, the average tem-
perature should be kept above 1200C since below that tem-
perature there is no significant shift reaction rate, i.e.,
conversion of CO and H2O to ~2 and CO2. The upper temper-
ature range is limited by the fact that it represents the
highest temperature that is known to be obtained under the
conditions of this invention.
In the cracking zone, the average temperature
should be kept above 600C since there is no significant
cracking below this temperature. Above 1500C it has
been found that very short residence times are required
and that more acetylene and less ethylene are produced.
The hot combustion gases resulting from the
partial combustion contain more than 5 volume percent C0
and preferably in the range of 6 to 60 volume percent.
The gaseous shift mixture contains more than
5 volume percent H2 and preferably in the range of 6 to
70 volume percent.
The actual composition of these combustion
gases can vary considerably depending upon (1) the type
of fuel being used, (2) the relative amount of oxidizer
to fuel, and (3) the amount of moderating steam used to
protect the refractory lining of the reactor. This flex-
ibility of composition allows the maximum or optimum con-
ditions for each case to be developed on an individual
18,442B-F -8-
597
g
basis. For instance, if a heavy oil or residue is being
crac~ed there will probably be enough excess (quench oil)
heavy cracked oil produced to operate the burner, thus
usually a considerable quantity of CO would be present
in the burner gas. But, if a relatively low molecular
weight paraffinic feedstock is being cracked, not enough
heavy cracked oil may be produced to sustain the burner,
so that some of the light gas (H2+CH4) produced from the
pyrolysis is used in the burner, which results in more
hydrogen and less C0 being present.
For the invention to function it is only
necessary that the minlmum conditions be met, and the
preferred range or values will vary depending upon the
factors listed above.
The weight ratio of oxygen to fuel used in
the burner in the process of this invention for partial
combustion is greater than about 1.2:1. The upper limit
should not exceed about 2.9:1. This upper limit will
vary somewhat depending upon the carbon-hydrogen ratio
of the fuel.
The weight ratio of process steam to fuel is
normally in the range from about 0.5:1 to 10:1. The use
of this ratio is not critical since the process steam is
used primarily to control the temperature in the combus-
tion zone, and the above ratios are dependent upon thequantity of oxygen used.
The weight ratio of superheated steam used to
burner fuel is in the range from about 2.0:1 to 8.0:1. It
-has been found that the use of a ratio below this weight
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ratio results in a poor shift reaction since too little
superheated steam ls present, whereas the use of a ratio
above this weight ratio will cool the cracking reaction
and slow down the desired shift reaction.
The crude oil or fractions thereof is sprayed
or injected into the cracking zone at a ratio from about
0.5 to 8.0 parts by weight of oil per part by weight of
fuel and preferably 1.5 to 6.0 parts by weight of oil per
part by weight of fuel to give a residence time from about
10 0.01 to l.0 seconds in the reactor and preferably 0.05 to
0.5 seconds.
The oxidizing gas used in the partial combus-
tion zone can be pure oxygen, or air enriched with oxygen.
The fuel which is burned in the partial com-
bustion zone can be any one of the known fuel oils,
cracked oils, or a mixture of fuel oils and cracked oils,
natural gas, or cracked gases.
The pressure range for the reactor during
combustion is in the range from 0-200 psig (0-14.1 kg/cm2)
20 and preferably in the range from 5-65 psig (0.35-4.59
kg/cm2 ) .
The invention is illustrated by the following
examples:
Example 1
Using the apparatus disclosed in the drawing
and the process of the present invention, the following
reactants were processed under the given conditions:
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S97
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Fuel:
30 API Domestic Crude 100 lb/hr (45.3 kg/hr)
Oxidant:
Oxygen 184 lb/hr (83.5 kg/hr)
5 Process steam
(200C) to burner: 180 lb/hr (81.6 kg/hr)
Shift steam: 549 lb/hr (248 kg/hr)
Cracking stock:
30 API Domestic CrudP 223 lb/hr (101 kg/hr)
Conditions:
Reactor Pressure 11.1 psig (0.78 kg/cm2)
Temperature Partial
Combustion Zone 1910C
Shift Steam Inlet Temp. 905C
Shift Steam Inlet Into top of Shift Zone
Temperature of
Shift Zone Outlet 1210C
Temperature of
Cracking Reactor Outlet 696C
Reactor Volume 1.64 ft3 (46.4 1)
Residence Time 0.15 seconds
The following yields in pounds (kg) were
obtained per 100 pounds (45.3 kg) of cracking stock.
18,442B-F -11-
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H23.1 (1.4) C3H41.1 (0.50)
C05.7 (2.58) C3H68.8 (3.98)
CH414.1 (6.40) C4 5.0 (2.27)
C23 0 (1.36) c5 3.8 (1.72)
5 H2S0.2 (0.09) Benzene8.3 (3.76)
C2H21.9 (0.86) Toluene4.5 (2.04)
C2H424.8 (11.3) c6+*20.5 (9.31)
C2H61.6 (0.73)
*C + includes all carbon compounds of C6 or greater
e~cept benzene and toluene.
Example 2
Using the same apparatus as in Example 1 and
the process of the present invention, the following reac-
tants were reacted in a continuous manner:
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Based on 100 lb
(45.3 kg/hr)
fuel/hr
Fuel:
~eavy recycle oil
or quench oil from
Example 1 100 lb/hr (45.3 kg/hr)
Oxidant:
Oxygen 188 lb/hr (85.3 kg/hr)
10 Process steam
(200C) to burner: 240 lb/hr (108 kg/hr)
shift steam: 311 lb/hr (141 kg/hr)
Cracking stock:
30 API Domestic Crude 220 lb/hr (99.8 kg/hr)
15 Conditions:
Reactor Pressure 6.1 psig (0.42 kg/cm2)
Temperature Partial
Combustion Zone 1903C
Shift Steam Inlet Temp. 870C
Shift Steam Inlet Into top of Shift Zone
Temperature of
Shift Zone Outlet 1163C
Temperature of
Cracking Reactor Outlet 697C
Reactor Volume 1.64 ft3 (46.4 1)
Residence Time 0.21 seconds
The following yields in pounds (kg) were
obtained per 100 pounds (45.3 kg) of cracking stock.
18,442B-F -13-
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H21.3 (0 59) C3H40 9 (0.41)
CO3.9 (1.76) C3H67.3 (3.31)
CH411.3 (5.12~ c46.2 (2.81)
C25.2 (2.36) c51.9 (0.86)
5 H2S0.2 (0.09) Benzene7.2 (3.26)
C2H22.5 (1.13) Toluene5.2 (2.36)
C2H420.7 (9.38) c6+*25.0 (11.3)
C2H61.4 (0.64)
*C6+ includes all carbon compounds of C6 or greater
except benzene and toluene.
Control - Total Combustion with Superheated Steam
49 Pounds (22 kg) of fuel oil were burned per
hour with 145 pounds (65.8 kg~ of oxygen per hour which
resulted in essentially complete combustion of the fuel
15 oil to CO2 and H2O. Additionally, 306 pounds (139 kg) of
200C process steam was added to the burner to maintain
the temperature below 1900C. The resulting gaseous mix-
ture was combined with 300 pounds (136 kg) of steam per
hour which had been superheated to 870C to yield a gas-
eous heat carrier containing in volume percentages 0.6 H2;
0.3 CO; 8.9 CO2; and 90.2 H2O at a temperature of 1460C.
Into this gaseous heat carrier, 158 pounds
(71.8 kg) per hour of vacuum gas oil (650F-1050F (343C-
-566C) boiling range) was sprayed using 75 pounds (34.0
kg) of 200C process steam per hour for atomization. The
yield of products are shown in Table I.
18,442B-F -14-
6597
-15-
Exam~le 3
82 Pounds (37.2 kg) per hour of fuel oll were
burned with 163 pounds (74.0 kg) of oxygen per hour. Addi-
tionally, 255 pounds (116 kg) per hour of 200C process
steam was added to maintain the flame temperature below
1900C. This mixture was deficient in oxygen and resulted
in the partial combustion of the fuel. The gaseous mix-
ture contained substantial portions of C0 and H2 in addi-
tion to CO2 and H20. The volume percentages in the gas-
10 eous mixture were 12.5 H2; 12.5 C0; 11.2 C02; and 63.4
H20 .
The resulting gaseous mixture was combinedwith 300 pounds (136 kg) per hour of steam which had
been superheated to 870C. At these conditions with a
residence time sufficient to achieve e~uilibrium, 30
percent of the C0 present was converted to C02 with a
corresponding increase in ~2 content.
The resulting gaseous heat carrier had a tem-
perature of 1460C and consisted of (volume percentages)
20 9.8 H2; 5.3 CO; 8.9 CO2; and 75.9 H2O.
Into this gaseous heat carrier 158 pounds
(71.8 kg) per hour of vacuum gas oil was sprayed using
75 pounds (34.0 kg) per hour of process steam (200C).
The yields of products are shown in Table I. It is to
be noted that the yield of ethylene is increased about
28 percent over the control and thus the injection of
superheated steam into the partial combustion gases is
highly effective to lncrease the yield of ethylene.
A detailed comparison of Example 3 and the
control is shown in Table II.
18,442B-F -15-
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TABLE I
Yields in pounds (kg) per
100 pounds (45.3 kg) of feedstock
Control Example 3
~2 1.7 (0.77) 1.0 (0.45)
CO S.0 ~2.27) 3.0 (1.36)
CH4 10.3 (4.68) 13.7 (6.20)
C2 0.2 (0.09) 2.4 (1.09)
H2S 0.7 (0.32) 1.1 (0.50)
10 C2H2 2.7 (1.22) 2.7 (1.22)
C2H420.9 (9.48) 26.8 (12.2)
C2H6 1.0 (0.45) 1.1 (0.50)
C3H4 0.8 (0.36) 0.9 (0.41)
C3H6 4.3 (1.95) 5.8 (2.63)
15 C4 3.0 (1.36) 4.0 (1.82)
C5 1.2 (0.54) 1.3 (0.59)
Benzene7.5 (3.40) 8.0 (3.62)
Toluene4.7 (2.13) 3.0 (1.36)
c6+ 39.6 (17.5) 29.3 (13-3
18,442B-F -16-
597
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TABLE II
Control Example 3
Fuel, lb/hr (kg) 49 (22.0) 82 (37.2)
Oxygen, lb/hr (kg) 145 (65.8) 163 (74.0)
200C Steam,
lb/hr (kg/hr) 306 (139.0) 255 (116.0)
Combustion
Temp. C1900 1900
870C Steam,
lb/hr (kg/hr) 300 (136.0) 300 (136.0)
Total lb
Carrier Gas (kg)800 (362.0) 800 (362.0)
Temp. of Carrier
Gas, C 1460 1460
Feedstock,
lb/hr (kg)158 (71.8)158 (71.8)
Products, lb~hr~ kg)
H 2.7 (1.22) 9.6 (4.35)
C~ 8.7 (3.94) 44.4 (22.0)
20 CO161.2 (73.0) 181.0 (82.2)
CH216.3 (7.39) 21.7 (9.84)
C2~24.2 (1.90) 4.1 (1.86)
C H33.0 (15.0) 42.3 (19.2)
c2H41.5 (0.68) 1.8 (0.81)
25 C3H41.3 (0.59) 1.4 (0.63)
C H6.8 (3.08) 9.1 (4.11)
c3+683.1 (37.6) 73.8 (33.4)
H40638.1 (289) 567.0 (257)
H2S1.1 (0.50) 1.7 (0.77)
18,442B-F -17-
