U.S. patent application number 12/754865 was filed with the patent office on 2010-07-29 for apparatus for upgrading heavy hydrocarbons using supercritical water.
This patent application is currently assigned to AIR PRODUCTS AND CHEMICALS, INC.. Invention is credited to Rodney John Allam.
Application Number | 20100189610 12/754865 |
Document ID | / |
Family ID | 40954128 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100189610 |
Kind Code |
A1 |
Allam; Rodney John |
July 29, 2010 |
Apparatus for Upgrading Heavy Hydrocarbons Using Supercritical
Water
Abstract
Heavy hydrocarbons are upgraded more efficiently to lighter,
more valuable, hydrocarbons with lower amounts of solid
carbonaceous by-products in supercritical water using two heating
stages, the first stage at a temperature up to about 775K and the
second stage at a temperature from about 870K to about 1075K. The
temperature is preferably raised from the first temperature to the
second temperature by internal combustion using oxygen.
Inventors: |
Allam; Rodney John;
(Chippenham, GB) |
Correspondence
Address: |
AIR PRODUCTS AND CHEMICALS, INC.;PATENT DEPARTMENT
7201 HAMILTON BOULEVARD
ALLENTOWN
PA
181951501
US
|
Assignee: |
AIR PRODUCTS AND CHEMICALS,
INC.
Allentown
PA
|
Family ID: |
40954128 |
Appl. No.: |
12/754865 |
Filed: |
April 6, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12033933 |
Feb 20, 2008 |
|
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12754865 |
|
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Current U.S.
Class: |
422/198 |
Current CPC
Class: |
B01J 2219/00006
20130101; Y02P 20/54 20151101; B01J 2219/00777 20130101; C10J 3/80
20130101; B01J 19/0053 20130101; Y02P 20/544 20151101; C10G 9/38
20130101; B01F 5/0604 20130101; B01J 3/008 20130101; C10J 2300/0989
20130101; C10J 2300/0979 20130101 |
Class at
Publication: |
422/198 |
International
Class: |
B01J 19/00 20060101
B01J019/00 |
Claims
1. A reactor system for converting heavy hydrocarbon feedstock into
conversion products comprising lower molecular weight hydrocarbon
compounds, said reactor system comprising: a source of SCW; a
mixing zone for mixing heavy hydrocarbon feedstock and SCW to form
a fluid reaction mixture at a first temperature up to about 775K; a
feeding system for feeding SCW from said source and feedstock into
said mixing zone; a heating system for heating said fluid reaction
mixture from said first temperature to a second temperature from
about 870K to about 1075K; a higher temperature reaction zone for
maintaining said fluid reaction mixture at said second temperature
for sufficient time to form a resultant fluid mixture containing
said conversion products, said reaction zone being in fluid flow
communication with said mixing zone; and an outlet system for
removing said resultant fluid mixture.
2. A reactor system according to claim 1 wherein said heating
system is for providing heat internally within the reactor
system.
3. A reactor system according to claim 1 wherein said heating
system comprises an oxygen inlet system for feeding
oxygen-containing gas into said fluid reaction mixture.
4. A reactor system according to claim 3 wherein said oxygen inlet
system comprises a device for creating turbulence in a flow of
fluid reaction mixture for facilitating mixing of oxygen with said
fluid reaction mixture.
5. A reactor system according to claim 4 wherein said device
comprises at least one umbrella, the or each umbrella having at
least one outlet to feed oxygen-containing gas from under the
umbrella towards the periphery thereof.
6. A reactor system according to claim 1 wherein said outlet system
comprises a separator for separating entrained solid material from
said resultant fluid mixture.
7. A reactor system according to claim 1 comprising internal
components made from a metal selected from the group consisting of
titanium and copper and alloys thereof.
8. A reactor system according to claim 1 comprising a plurality of
concentric shells in the mixing zone to increase fluid velocity for
a given residence time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional of application Ser. No. 12/033,933
filed on Feb. 20, 2008 which is incorporated herein by reference in
its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to upgrading low value, heavy
hydrocarbons, i.e. converting heavy hydrocarbons into more
valuable, lower molecular weight (or "lighter") hydrocarbons, using
supercritical water ("SCW").
[0003] Heavy hydrocarbons may be upgraded in partial oxidation
processes. "Partial oxidation" refers generally to the combustion
of a fuel using a sub-stoichiometric amount of oxygen ("O.sub.2")
to produce a "synthesis gas" (or "syngas") comprising carbon
monoxide and hydrogen. The synthesis gas (which also contains
methane and carbon dioxide) can then be converted into light
hydrocarbons in, for example, a Fisher-Tropsch process.
[0004] Broadly speaking, there are two types of partial oxidation
process, i.e. thermal partial oxidation ("TPOX") and catalytic
partial oxidation ("CPOX"). Current TPOX processes generally
require high temperatures, typically above 1600K, and high
pressures, typically from 40 to 70 bar, and efficiency is rather
low (e.g. 70% dry gas efficiency for a Texaco/GE quench gasifier
and 80% for a Shell dry feed gasifier). Accordingly, there is a
need to develop an alternative process to the current TPOX process
to improve the efficiency of upgrading heavy, low value,
hydrocarbons.
[0005] Molecular modeling studies carried out under the direction
of the Inventor predicted that partial oxidation of heavy
hydrocarbons in SCW with pure oxygen gas would be rapid at lower
temperatures, e.g. from 600K to 1000K, and pressures, e.g. 250 bar
to 350 bar. Importantly, these studies predicted the same spectrum
of products as produced in conventional TPOX reactions.
Unexpectedly, experimental studies revealed that, in contrast to
the results predicted by the molecular modeling studies, lower
molecular weight hydrocarbon compounds are produced directly from
reaction of heavy hydrocarbon feedstock in SCW.
[0006] SCW is already known to a certain extent for use in
processes to convert hydrocarbon compounds. For example, it has
been reported ("Pyrolysis of eicosane in supercritical water";
Vostrikov et al Russian Chemical Bulletin, Int Ed.; Vol. 50, No. 8,
pp. 1478-1480, August 2001) that eicosane can be converted into a
mixture of methane, carbon monoxide, carbon dioxide and hydrogen by
heating in SCW at 30 MPa (300 bar) and at a temperature from
450.degree. C. to 750.degree. C. (.about.723K to .about.1023K). It
has also been reported ("Naphthalene oxidation in supercritical
water"; Vostrikov et al; Russian Chemical Bulletin, Int. Ed.; Vol.
50, No. 8, pp. 1481-1484, August 2001) that naphthalene can be
converted into a mixture of benzene, toluene, methane, hydrogen,
soot and carbon oxides by heating in SCW at 30 MPa (300 bar) and at
temperature from 660.degree. C. to 750.degree. C. (.about.935K to
.about.1025K).
[0007] U.S. Pat. No. 4,421,631 (Ampaya et al; published in 1983)
discloses a process for upgrading a heavy hydrocarbon material,
e.g. a petroleum residual, using a molten salt, e.g. alkali metal
carbonate(s). Heat for the process is provided by combustion of
carbonaceous material, produced as a by product of the upgrading
process and entrained in the flow of molten salt, using oxygen.
[0008] Processes to upgrade low value, heavy hydrocarbons into more
valuable, lighter hydrocarbons using water under supercritical
conditions are also known.
[0009] U.S. Pat. No. 1,956,603 (White; published in 1934) discloses
"aquolysis" processes for converting heavy petroleum hydrocarbons
including tars, tarry oils and shale oil into liquids of lower
boiling points by heating the heavy hydrocarbons in the form of an
emulsion with water at a temperature from 900.degree. F. to
1300.degree. F. (.about.755K to .about.980K) and a pressure from
below 100 bar to above 1000 bar. It is disclosed that supercritical
pressures are preferred.
[0010] U.S. Pat. No. 3,989,618 (McCollum et al; published in 1976)
discloses a process for upgrading hydrocarbons including heavy
materials such as gas oil, residual oils, tar sands oil, oil shale
kerogen extracts and liquefied coal products by contacting the
hydrocarbons with a water-containing fluid at a temperature in the
range of 600.degree. F. to 900.degree. F. (.about.590K to
.about.755K) and, preferably, at about 705.degree. F. (647K) which
is the critical temperature of water. U.S. Pat. No. 3,989,618
exemplifies heating tar sands oil in water (1:3) at a temperature
of 752.degree. F. (.about.675K) and at a reaction pressure of 4350
psig (.about.300 bar) for 3 hours in an autoclave. The tar sands
oil was cracked to produce hydrogen, carbon dioxide and methane
gases (11.2 wt % total), light ends (75.2 wt %), heavy ends (8.6 wt
%) and a solid residue (5.0 wt %). U.S. Pat. No. 3,989,618 also
exemplifies semi-continuous flow processing of tar sands oil in
water (1:3) at 752.degree. F. (.about.675K) and 4100 psig
(.about.285 bar) in an externally-heated pipe reactor having a
reaction volume of about 6 milliliters.
[0011] U.S. Pat. No. 4,840,725 (Paspek; published in 1989)
discloses a process for converting heavy hydrocarbon oil feedstocks
to fuel range liquids. The process involves contacting the heavy
hydrocarbons with water (typically, 2:1 to 1:1) at a temperature
from 600.degree. F. to 875.degree. F. (.about.590K to .about.740K)
at a pressure preferably from 4000 psi to 6000 psi (.about.275 bar
to .about.415 bar). It is disclosed that reaction times are
generally short (from a few seconds up to about 6 hours) and that
the fuel range liquids produced have increased amounts of high
value aromatic carbons. U.S. Pat. No. 4,840,725 exemplifies
converting shale oil using a 400 ml vertical tube reactor operating
at 825.degree. F. (.about.715K) and 4900 psi (.about.340 bar). U.S.
Pat. No. 4,840,725 acknowledges that coke is produced as a by
product of the reaction of feedstock with SCW and indicates that
the reaction temperature should not exceed 875.degree. F.
(.about.740K) in order to minimize formation of this by
product.
[0012] U.S. Pat. No. 4,818,370 (Gregoli et al, published in 1989)
discloses processes for upgrading heavy hydrocarbons using brine
under supercritical conditions. It is disclosed that hydrocarbon
deposits may be upgraded in situ in subterranean reservoirs and
that heat for these processes may be provided by pumping oxygen
into the reservoir to combust a portion of the deposits.
Temperatures in the combustion zone are allowed to reach
.about.478K to .about.1030K at which point the combustion is
stopped to allow heat to soak through the reservoir and for the
upgrading reactions to occur.
[0013] US 2005/0040081 (Takahashi et al, published in 2005)
discloses a process for upgrading heavy hydrocarbon oil using SCW
at a temperature up to .about.725K to produce lighter hydrocarbons
which are combusted in a gas turbine to generate power. Any
unreacted hydrocarbon residue is combusted to produce heat which is
used, together with heat produced in the gas turbine, to heat water
for the process. Further heat for the cracking process is provided
externally using a heater. However, it is disclosed that the amount
of heat supplied externally may be reduced by reacting a portion of
the heavy hydrocarbon with an oxidant.
[0014] US 2007/0144941 (Hokari et ah, published in June 2007)
discloses a process for upgrading heavy hydrocarbon oil using SCW
in the presence of an oxidant, e.g. oxygen, to remove vanadium from
the heavy oil to ensure that vanadium is not present in the lighter
hydrocarbon products.
[0015] There is a need for new processes for upgrading heavy
hydrocarbon feedstock. New direct conversion processes should be
more efficient than existing processes, for example by increasing
the overall yield of the lighter hydrocarbons and by improving the
spectrum and distribution of hydrocarbons produced. In addition,
new processes should improve control of the formation of unwanted
solid carbonaceous by-products such as coke and soot.
BRIEF SUMMARY OF THE INVENTION
[0016] According to a first aspect of the present invention, there
is provided a process for converting heavy hydrocarbon feedstock
into conversion products comprising lower molecular weight
hydrocarbon compounds, said process comprising: [0017] mixing heavy
hydrocarbon feedstock and supercritical water ("SCW") to form a
fluid reaction mixture at a first temperature up to about 775K;
[0018] heating said fluid reaction mixture to a second temperature
from about 870K to about 1075K; [0019] maintaining said fluid
reaction mixture at said second temperature for sufficient time to
form a resultant fluid mixture containing said conversion
products.
[0020] In the context of the present invention, "heavy hydrocarbon
feedstock" is hydrocarbonaceous materials typically having an
initial boiling point ("IBP") of at least 300.degree. C.
(.about.575K), preferably at least 400.degree. C. (.about.675K),
and most preferably at least 500.degree. C. (.about.775K). The
feedstock is usually characterized by the presence of polycyclic
aromatic hydrocarbons such as asphaltenes. The feedstock may be
heavy residual by-products of oil refining or may be naturally
occurring materials. Examples of suitable heavy hydrocarbons for
use with the present invention include bitumen (or asphalt); pitch;
tar; tar sand oil; vacuum residue; shale oil; kerogen; and coal
tar. The invention has particular application to the conversion of
bitumen, pitch or tar.
[0021] "Lower molecular weight hydrocarbon compounds" are
hydrocarbon compounds having a lower molecular weight than the
heavy hydrocarbon feedstock. The lower molecular weight hydrocarbon
products have lower viscosities and lower boiling points than the
heavy hydrocarbon feedstock.
[0022] The lower molecular weight hydrocarbon compounds are
typically produced in three fractions, i.e. a gas fraction; a
liquid hydrocarbon fraction having a density less than water; and a
hydrocarbon fraction having a density greater than water. The gas
fraction usually comprises C.sub.1-C.sub.4 alkanes such as methane,
ethane and propane; and C.sub.2-C.sub.4 alkenes such as ethene and
propene. The gas fraction typically also includes hydrogen; carbon
monoxide; and carbon dioxide. The liquid hydrocarbon fraction
usually comprises a mixture of benzene; toluene; and xylenes
("BTX"). The denser hydrocarbon fraction usually comprises the
heavier, e.g. C.sub.8-C.sub.20 hydrocarbon fragments. Solid
carbonaceous materials such as coke, soot and/or carbon are also
produced.
[0023] "SCW" is water which is at a temperature and pressure
exceeding its critical temperature and critical pressure. The
critical temperature of water is the temperature above which water
cannot be liquefied by an increase in pressure, i.e. 374.degree. C.
(647K). The critical pressure of water is the pressure of water at
its critical temperature, i.e. 22.1 MPa (221 bar).
[0024] According to a second aspect of the present invention, there
is provided a reactor system for converting heavy hydrocarbon
feedstock into conversion products comprising lower molecular
weight hydrocarbon compounds, said reactor system comprising:
[0025] a source of SCW; [0026] a mixing zone for mixing heavy
hydrocarbon feedstock and SCW to form a fluid reaction mixture at a
first temperature up to about 775K; [0027] a feeding system for
feeding SCW from said source and feedstock into said mixing zone;
[0028] a heating system for heating said fluid reaction mixture
from said first temperature to a second temperature from about 870K
to about 1075K; [0029] a higher temperature reaction zone for
maintaining said fluid reaction mixture at said second temperature
for sufficient time to form a resultant fluid mixture containing
said conversion products, said reaction zone being in fluid flow
communication with said mixing zone; and [0030] an outlet system
for removing said resultant fluid mixture.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0031] FIG. 1 is a cross sectional representation of a first
embodiment of the reactor according to the present invention;
and
[0032] FIG. 2 is a schematic representation of an embodiment of the
process according to the present invention involving a second
embodiment of the reactor.
DETAILED DESCRIPTION OF THE INVENTION
[0033] The process of the present invention comprises mixing SCW
and, typically pre-heated, feedstock to form a fluid reaction
mixture at a first temperature up to about 775K. The fluid reaction
mixture is thought to be a single phase, homogeneous mixture. The
fluid reaction mixture is heated to a second temperature from about
870K to about 1075K and maintained at said second temperature for
sufficient time to produce a resultant fluid mixture containing
said lower molecular weight hydrocarbon compounds and, typically,
solid carbonaceous material. Solid carbonaceous material may have
been deposited on the surface of internal components of a reactor
in which the process takes place.
[0034] The feedstock is usually warmed to a suitable temperature to
reduce viscosity so that the feedstock can be pumped to the
required pressure. The Inventor has observed, however, that bitumen
cakes (i.e. viscosity actually increases due to polymerization) at
temperatures above about 725K. Thus, heavy hydrocarbon feedstock is
usually pre-heated to a temperature below the upper solidification
temperature of the feedstock. The upper solidification temperature
varies between different feedstocks and the temperature of the
pre-heated feedstock will depend on the behavior of the actual
feedstock used. However, feedstock is preferably at a temperature
of no more than 725K, e.g. from about 647K to about 725K. Such a
temperature is particularly suitable if the feedstock is
bitumen.
[0035] The temperature of the SCW is typically selected to ensure
that the temperature of the fluid reaction mixture is from about
650K to about 775K after the feedstock is mixed with the SCW.
Before mixing with the feedstock, the SCW is usually at a
temperature from about 650K to about 900K.
[0036] Provided that the pressure of the process is over the
critical pressure of water (about 22.1 MPa or 221 bar), the
pressure is not critical to the invention. The pressure may be up
to about 100 MPa (1000 bar), e.g. up to about 50 MPa (500 bar). The
pressure is preferably from about 25 MPa to about 40 MPa (250 bar
to 400 bar), e.g. about 30 MPa (300 bar), as such pressures ensure
the presence of supercritical conditions for the mixture of water
and hydrocarbons in the system.
[0037] The mass ratio of feedstock to water is typically from about
2:1 to about 1:10, usually from about 3:2 to about 1:6 and,
typically, from about 1:1 to 1:2.
[0038] Experimental investigations have determined that a preferred
value for the first temperature is typically from the supercritical
temperature of water, i.e. about 647K, to about 775K, and
preferably from about 650K to about 755K, e.g. about 675K to about
725K, and that the second temperature is preferably from about 925K
to about 1050K and more preferably from about 950K to about
1025K.
[0039] Without wishing to be bound by any particular theory, the
two operational ranges of temperature are chosen corresponding to
two possible mechanisms of reaction. The first temperature range is
typically about 647K to about 775K. In this range, the heavy
hydrocarbon feedstock forms primarily a single phase, homogenous
mixture with SCW with a minor amount of undissolved residue having
a high carbon to hydrogen ratio which also contains the ash and at
least the bulk of the inorganic content of the feed. Feedstock
molecules are understood to break down under these conditions to
produce lighter hydrocarbon fragments, having a higher hydrogen to
carbon ratio than the feedstock, and leaving a higher carbon to
hydrogen ratio fraction as a non-reactive insoluble residue. At the
first temperature, the water is acting as a solvent and as a heat
carrier but does not actually react with the feedstock itself.
[0040] Preliminary investigations regarding the first stage used
experiments involving injecting pre-heated tar (vacuum residue
having composition C.sub.1H.sub.1.43S.sub.0.015) into SCW within a
horizontal reactor with a constant wall temperature of about 690K
at a pressure of about 300 bar. The investigations revealed that
the tar dissolved in the SCW by diffusion alone until an
equilibrium point was reached in about 75 minutes. About 76% of the
total tar mass was recovered as useful lighter hydrocarbon products
in three distinct fractions, leaving about 24% as coke having a
carbon to hydrogen ratio of about 1:1.13. The three fractions
were:
(a) a gas fraction (29.9% of the total tar mass) having a
composition as follows: [0041] CH.sub.4 47.6% (molar); [0042]
C.sub.2H.sub.6 29%; [0043] C.sub.3H.sub.6 13.3%; [0044]
C.sub.2H.sub.6 3.4%; [0045] C.sub.3H.sub.8 6.0%; and [0046]
C.sub.3+ 0.7%, (b) a hydrocarbon fraction having a density less
than water (33.7% of the total tar mass) with about half of the
fraction having a boiling point of less than 373K; and (c) a
"heavy" hydrocarbon fraction having a density greater than water
(heating this fraction to 723K in a vacuum loses 22.7% of mass
evaporated; extraction with toluene left a final residue of 24% of
the total tar mass).
[0047] Analysis of the total liquid fraction [(b) plus (c)] showed
that the total mass fraction of hydrocarbon molecules, with carbon
atom numbers of 12 or less, was 36% while the total mass fraction
with a boiling temperature of less than 573K was 42%.
[0048] The Inventor observed that sulfur present in the tar is
released partly as H.sub.2S and partly as COS and a good deal is
retained in the residual coke. The degree of release of sulfur as
H.sub.2S and COS was seen to increase as the temperature was
raised. During a test at 300 bar in a horizontal reactor at 690K
for duration of 2 hours and with no mixing except diffusion, the
total mass proportion of sulfur in the tar feed released as
H.sub.2S was 27.3%. This proportion will be maintained for lower
residence times with increased mixing of the tar and supercritical
water.
[0049] Rapid mixing of the feedstock and the SCW is, however,
preferred. The time taken to reach mixing equilibrium is
drastically reduced by agitating the mixture by creating flow
turbulence. Flow turbulence may be created by a device such as a
static mixer or otherwise by an arrangement of concentric shells
defining a convoluted path or "multi-pass" arrangement. The use of
a high flow velocity also creates flow turbulence. The time
required to form the fluid reaction mixture can be reduced by
increasing the temperature of the solution up to about 775K
although it is important to bear in mind the upper solidification
temperature of the feedstock. The feedstock is preferably atomized,
e.g. using a suitable high intensity nozzle mixer, to increase
interfacial surface area between feedstock and SCW.
[0050] In preferred embodiments, the period of time over which the
feedstock is mixed with SCW is typically from about 1 second to
about 10 minutes. This period is preferably less than 5 minutes
and, more preferably, from about 5 seconds to about 60 seconds.
[0051] The second mechanism of reaction occurs in the range of the
second temperature, i.e. from about 870K to about 1075K. The
Inventor believes that, at the second temperature, water reacts
with hydrocarbon molecules in accordance with the following
equation:
(n+4)C+2nH.sub.2O--.fwdarw.4.fwdarw.CH.sub.n+nCO.sub.2
(where the feed C refers to carbon in high molecular weight
hydrocarbons) thereby hydrogenating feedstock fragments and
increasing the yield of lighter, more valuable, hydrocarbon
products and improving the distribution of products. The rate of
conversion is determined by the kinetics of essentially gas phase
reactions. The hydrogenation reactions are understood to be
substantially isothermal. At this stage, not only is SCW acting as
a solvent and a heat carrier, it is also acting as a
hydrogenator.
[0052] Once the temperature rise has occurred, it is necessary to
maintain the fluid reaction mixture at the second temperature for
sufficient time to allow not only the free-radical reactions but
also the hydrogenation reactions to occur, which leads to formation
of valuable products with higher hydrogen to carbon ratio than the
feedstock. The period of time over which the fluid reaction mixture
is maintained at the second temperature is typically from about 1
second to about 10 minutes. In preferred embodiments, this period
is less than 5 minutes and, preferably, from about 5 seconds to
about 60 seconds.
[0053] The period to form the fluid reaction mixture is, typically,
longer than the period at which the mixture is maintained at the
second temperature. Ultimately, the difference in the two periods
depends on the particular conversion in question. However, a ratio
of the periods from about 2:1 to about 4:1 may be appropriate.
[0054] The Inventor has observed that reaction temperatures between
the upper limit of the first temperature range and the lower limit
of the second temperature range (e.g. from about 775K to about
870K) unfortunately favor bitumen caking and formation of solid
carbonaceous material such as hard coke and fluffy carbon soot
rather than the formation of the desired conversion products.
Neither of these effects is desirable as they both lead to loss of
recovery and increased risk of blockage of the reactor and
associated apparatus, necessitating the reactor being taken
off-line for periodic cleaning. Therefore, in order to reduce the
number of times the reactor needs to be cleaned, the solution is
preferably heated from the first temperature to the second
temperature as fast as possible, i.e. in as short a time as
possible, to avoid undue formation of unwanted solid carbonaceous
deposits. In preferred embodiments, the fluid reaction mixture is
heated from the first temperature to the second temperature in no
more than 20 seconds, preferably in no more than 10 seconds, more
preferably in no more than 5 seconds and most preferably in less
than 1 second.
[0055] The soot and coke formation occurs by dehydrogenation of the
feedstock down to an approximate formula CH.sub.0.5. The
dissociation of water molecules has been shown to become
significant at a temperature of over 925K. It appears that above
this temperature the soot potential radicals are oxidized in
reactions such as:
2CH.sub.0.5+2H.sub.2O.fwdarw.2CO+2H.sub.2+H
[0056] Thus, one molecule of water should be required for each mol
of CH.sub.0.5 radical. It has also been found, experimentally, that
the rate of this reaction is greater than the rate of formation of
CH.sub.0.5 and free C radicals at these temperatures, so that the
soot suppression at above 925K takes place with less than an
overall 2:1 water ratio.
[0057] At least a portion of the heat required to increase the
temperature of the solution from the first temperature to the
second temperature may be provided externally, e.g. from a furnace
or by electrical heating elements. However, in preferred
embodiments, at least a portion and, preferably all, of the heat
required to heat the fluid reaction mixture from the first
temperature to the second temperature is provided internally.
[0058] The fluid reaction mixture will typically comprise
combustible components including hydrocarbonaceous components (e.g.
selected from feedstock and/or lower molecular weight hydrocarbon
compounds and fragments) and carbonaceous components (e.g. selected
from coke, soot and/or carbon). The addition of gaseous oxygen
(O.sub.2) to the fluid reaction mixture results in combustion of a
portion of these combustible components.
[0059] The portion of the combustible components that react with
oxygen to increase the temperature from the first temperature to
the second temperature usually equates to no more than 30 wt %,
preferably no more than 20 wt %, e.g. from about 10 wt % to about
20 wt % of the feedstock, particularly in embodiments in which the
feedstock is bitumen.
[0060] An oxygen-containing gas such as air may be introduced to
combust the portion of combustible components. However, an
oxygen-containing gas containing at least 50%, preferably at least
90%, and more preferably at least 95%, oxygen (with the remainder
being an inert carrier gas such as nitrogen) is typically used. The
use of "pure" oxygen, i.e. at least 99% oxygen, is preferred.
[0061] The oxygen-containing gas is preferably pre-heated to a
suitable temperature which is typically from about 550K to about
700K, preferably from about 600K to about 650K, e.g. about 625K.
The oxygen-containing gas will be introduced to the fluid reaction
mixture at the operating pressure of the process.
[0062] The temperature of the second stage of the reactor is
carefully controlled by the amount of oxygen-containing gas added
to the fluid reaction mixture. The amount of oxygen is a control
variable for the process and is defined by the heat balance. In
this connection, it is well within the ability of the skilled
person to calculate the required amounts of oxygen necessary to
control the temperature of the second stage as required based on
the mass flows rates of SCW and feedstock (hence, the composition
of the fluid reaction mixture), the required mixing temperature and
the temperature of the oxygen.
[0063] The upper and lower limits of the amount of oxygen used may
be defined empirically based on the highest and lowest hydrocarbon
to water mass ratios and the highest and lowest temperature rises
from the first temperature to the second temperature. For example,
an appropriate total amount of oxygen gas for a process converting
bitumen at a mass ratio with water of 1:1 to 1:2 with a temperature
rise from the first temperature to the second temperature from
about 95K to about 428K is typically about 15 wt % to about 60 wt
%. These figures may, of course, refer to the total amount of pure
oxygen or the total amount of oxygen fed as a component in an
oxygen-containing gas.
[0064] The Inventor has observed that the exothermic reaction
causes an extremely rapid temperature rise. The presence of water
moderates the temperature rise, and the very rapid reaction, which
typically takes place in well under 1 second, does not lead to any
significant soot formation.
[0065] An important feature of the stage of the process at the
second temperature is the hydrocracking reaction with hydrogen
derived from reaction between water molecules and the hydrocarbon
material. This reaction may be improved by feeding hydrogen gas to
the fluid reaction mixture at the second temperature to assist with
the hydrogenation of the hydrocarbon material.
[0066] The hydrogen gas may come from an external source.
Alternatively, the hydrogen could be produced by gasifying residual
hydrocarbon material or by partial oxidation of coke, e.g. coke
produced in the process. If the residual bitumen is gasified using
pure gaseous oxygen in a conventional gasifier with carbon dioxide
capture producing hydrogen which is then used to hydrogenate the
fluid reaction mixture, the nett coke production may be
dramatically reduced and both the yield and hydrogen to carbon
ratio of the product slate may be improved.
[0067] The process is carried out in a reactor system. A suitable
reactor system is a batch reactor such as an autoclave. However, in
preferred embodiments, the process is carried out in a continuous
flow reactor. The process preferably has a total residence time
within a continuous flow reactor from about 2 seconds to about 20
minutes, e.g. from about 5 seconds to about 10 minutes, preferably
about 10 seconds to about 5 minutes.
[0068] In embodiments where the reactor system has a mixing zone,
the residence time in the mixing zone may be from about 1 second to
10 minutes, e.g. from about 5 seconds to about 60 seconds and,
preferably about 30 seconds. In embodiments where the reactor
system has a higher temperature reaction zone, the residence time
in the reaction zone may be from about 1 second to about 10
minutes, e.g. from about 5 seconds to about 60 seconds and,
preferably about 30 seconds.
[0069] The reactor system will usually be operated in a
discontinuous or cyclic manner comprising an "on-line" phase (when
feedstock is fed to the reactor system and converted into the
conversion products), followed by an "off-line" phase in which only
SCW and an oxygen-containing gas enter the reactor system to burn
off solid carbonaceous deposits.
[0070] The reactor system typically operates in the "on-line" phase
until the extent of the deposition of solid carbonaceous material
is such that the reactor system needs to be cleaned. The period of
the "on-line" phase is highly variable and depends on several
factors such as the composition of the feedstock and the material
from which the internal components of the reactor (e.g. those
components in contact with the fluid reaction mixture) are made.
The period may be from as little as about 30 minutes to as much as
about 1 week or more.
[0071] The reactor system typically operates in the "off-line"
phase until the reactor system has been cleaned of the deposits of
solid carbonaceous material. The period of the "off-line" phase is
highly variable and depends on several factors such as the extent
of the deposition and the material of the internal components.
However, the "off-line" phase usually lasts from about 5 minutes to
about 1 hour.
[0072] The resultant fluid mixture may be supercritical or
subcritical due to the production of gaseous conversion products.
The resultant fluid mixture usually comprises particles of solid
material such as coke, soot and ash, entrained within the flow of
the fluid. These particles are preferably separated from the fluid.
A suitable separator is a hydrocyclone device, e.g. a Norway-type
entrainment separator, which may be located in the base of the
higher temperature reaction zone of the reactor system.
[0073] The resultant fluid mixture, typically with the solid
particles removed, is usually cooled to near ambient temperature
(such as from about 5.degree. C. to about 65.degree. C., e.g. about
20.degree. C. to about 55.degree. C. or about 35.degree. C. to
about 50.degree. C.) and the pressure reduced to allow liquid and
vapor phases to separate. The final pressure is usually chosen to
facilitate the optimum economics for separation of lower molecular
weight hydrocarbon compounds, hydrogen, methane, etc. from the
water phase. An appropriate final pressure may, for example, be
from about 10 bar to about 100 bar, perhaps about 40 bar to about
60 bar, e.g. about 50 bar.
[0074] The water phase is usually recycled back to the process,
typically with fresh make-up water.
[0075] Water, pressurized to the operating pressure of the process,
may be heated by indirect heat exchange against the resultant fluid
mixture or a fluid mixture derived therefrom, e.g. following
removal of the entrained solid materials, to produce the SCW.
However, the heat generated in the process is typically more than
enough to produce the SCW. Accordingly, the process may comprise a
steam heating cycle to provide heat balance in which water is
heated by indirect heat exchange against the resultant fluid
mixture, preferably following removal of said entrained solid
materials to produce steam. In these embodiments, at least a
portion of the excess heat is used to heat water at a pressure from
about 100 bar to about 200 bar, e.g. 150 bar, to produce
superheated steam at a temperature of about 750K to about 850K,
e.g. about 793K.
[0076] At least a portion of the steam may be used to pre-heat
feedstock by indirect heat exchange. In embodiments in which oxygen
is fed to the fluid reaction mixture to combust a portion of the
combustible components of said fluid reaction mixture, at least a
portion of the steam may be used to pre-heat an oxygen-containing
gas by indirect heat exchange. At least a portion of the steam may
be used to generate power in a steam turbine.
[0077] In preferred embodiments, a first portion of the steam is
used to pre-heat feedstock; a second portion of the steam is used
to pre-heat the oxygen-containing gas; and a third portion of the
steam is used to generate power is a steam turbine. The resultant
water streams may be combined and recycled to a condensate pump for
re-pressurization.
[0078] The hydrogenation process may be catalyzed using either a
homogeneous catalyst or a heterogeneous catalyst. Any suitable
conventional catalysts may be used, including nickel-based
catalysts. However, in preferred embodiments, the process is
uncatalyzed which is advantageous since there is no catalyst to
have to clean periodically or remove from the residual fluid
mixture. The Inventor notes that bitumen often contains nickel and
vanadium that may self-catalyze the hydrogenation reaction.
[0079] Limestone (CaCO.sub.3), sodium carbonate (Na.sub.2CO.sub.3),
or sodium hydroxide (NaOH) or mixtures thereof may be added to the
feedstock to facilitate desulfurization of the heavy hydrocarbon
feedstock.
[0080] The reactor system comprises: [0081] a source of SCW; [0082]
a mixing zone for mixing heavy hydrocarbon feedstock and SCW to
form a fluid reaction mixture at a first temperature up to about
775K; [0083] a feeding system for feeding SCW from said source and
feedstock into said mixing zone; [0084] a heating system for
heating said fluid reaction mixture from said first temperature to
a second temperature from about 870K to about 1075K; [0085] a
higher temperature reaction zone for maintaining said fluid
reaction mixture at said second temperature for sufficient time to
form a resultant fluid mixture containing said conversion products,
said reaction zone being in fluid flow communication with said
mixing zone; and [0086] an outlet system for removing said
resultant fluid mixture.
[0087] The reactor system typically comprises a source of
feedstock. In such embodiments, the feed system preferably feeds
feedstock from the feedstock source to the mixing zone.
[0088] A preferred continuous flow reactor is a tubular device with
a high length to diameter ratio. Such an aspect ratio reduces the
capital cost of the reactor as the reactor can have a thinner
reactor wall. In addition, such an aspect ratio not only increases
the length of the internal flow path and but also the fluid
velocities, thereby increasing fluid turbulence and promoting good
mixing. An example of a suitable reactor might be a pipe
reactor.
[0089] The feeding system preferably comprises an atomizer, such as
a high intensity atomizing nozzle, for atomizing said feedstock at
the point of mixing with the SCW. The use of an atomizer increases
the interfacial surface area of the feedstock thereby facilitating
formation of the fluid reaction mixture.
[0090] The reactor system usually comprises a device provided in
the mixing zone to create flow turbulence. The turbulence created
by such a device facilitates dissolution of the feedstock in the
SCW and decreases the necessary residence time of the mixture in
the mixing zone. The device may be a static mixer or a set of
internal concentric flow separation shells. For example, two
internal concentric shells would provide a "three pass" arrangement
and, with a constant area in each pass, would give three times the
flow velocity with the same residence time in a reactor of a given
volume. Such an arrangement reduces the wall temperature gradient
and increases turbulence in the mixing zone of the reactor
system.
[0091] The heating system may comprise an external heating system
such as a furnace or an electrical heater. However, in preferred
embodiments, the heating system is for providing heat internally
within the reactor system.
[0092] The rise in temperature from the first temperature to the
second temperature may be achieved by injecting an
oxygen-containing gas into the fluid reaction mixture. In these
embodiments, the heating system preferably comprises an oxygen
inlet system for feeding oxygen-containing gas into said fluid
reaction mixture.
[0093] The oxygen inlet system preferably provides a rapid, even
reaction of oxygen with the fluid reaction mixture. Such a reaction
may be achieved by the introduction of the oxygen-containing gas
into the fluid reaction mixture in either a single stage or in a
plurality of stages. Either way, the oxygen inlet system preferably
provides uniform injection of the oxygen-containing gas into the
fluid reaction mixture.
[0094] The oxygen inlet system preferably comprises a device for
creating turbulence in a flow of fluid reaction mixture for
facilitating mixing of oxygen with the fluid reaction mixture. In
some embodiments, the oxygen-containing gas may be introduced to
the fluid reaction mixture via an atomizing mixing nozzle. In other
embodiments, the oxygen-containing gas may be introduced to the
fluid reaction mixture from under the periphery of at least one
umbrella (where high fluid velocities and turbulences exist) or
stage-wise from under the peripheries of a plurality of umbrellas,
typically arranged in series.
[0095] The oxygen-containing gas may come from any suitable
location. For example, oxygen gas may be stored in a pressurized
storage vessel and fed, with compression and/or pre-heating as
required, to the oxygen inlet system of the reactor. Oxygen may be
stored in a cryogenic storage tank as liquid oxygen; pumped in a
LOX pump to the required pressure and heated in a suitable heat
exchanger to produce oxygen gas at the required temperature and
pressure which is then fed to the oxygen inlet system of the
reactor system. However, in preferred embodiments, oxygen is
produced on site in a cryogenic air distillation system, preferably
operating a pumped LOX cycle. The LOX may taken from the cryogenic
distillation system, pumped to the required pressure and heated to
produce oxygen gas at the required temperature which is them fed to
the oxygen inlet system of the reactor system.
[0096] The outlet system preferably comprises a separator for
separating entrained solid materials from the resultant fluid
mixture. A suitable separator is a hydrocyclone separator such as a
Norway-type entrainment separator. The separator may be located
outside the higher temperature reaction zone of the reactor system.
However, in a preferred embodiment, the separator is located within
the higher temperature reactor system, e.g. in the base
thereof.
[0097] The Inventor has observed that there is a large amount of
deposition of solid carbonaceous material in reactor systems having
internal components made from stainless steel and he has concluded
that the carbonaceous by-products are interacting with carbides in
the steel. Therefore, in preferred embodiments, the internal
components of the reactor system, i.e. those components in contact
with the fluid reaction mixture, are made from a metal selected
from the group consisting of titanium and copper and alloys
thereof.
[0098] In embodiments where all fluids in the product heat exchange
system are clean and free from solid particles, the heat exchangers
can be fabricated as diffusion bonded multichannel blocks. Suitable
heat exchangers would be those exchangers manufactured by Heatric
Ltd (Poole, Dorset, UK) which are capable of achieving the required
high temperature and pressure and can be fabricated in corrosion
resistant materials.
[0099] Provision is preferably made for oxygen dissolved in SCW at
temperatures above 700K to be pumped into both the mixing and
higher temperature reaction zones of the reactor so that any
deposits of coke and soot can be removed by oxidation to carbon
dioxide and water. In preferred embodiments, oxygen is added to the
SCW and then fed to the reactor.
[0100] Referring to FIG. 1, tubular reactor 110 comprises a mixing
zone 112 for dissolving heavy hydrocarbon feedstock in SCW to form
a fluid reaction mixture at a temperature from 650K to 775K and a
higher temperature reaction zone 114 for heating the fluid reaction
mixture at a temperature of 870K to 1075K for sufficient time to
produce the resultant fluid mixture. The reaction zone 114 is in
fluid flow communication with the mixing zone 112.
[0101] A stream 116 of pre-heated heavy hydrocarbon feedstock and a
stream 118 of SCW are combined in a feed system 120 and fed to the
mixing zone 112. The mixing zone 112 comprises a static mixer 122
which mixes the feedstock with the SCW to produce the fluid
reaction mixture which flows into the reaction zone 114 which
comprises an oxygen inlet system 124 for feeding a stream 126 of
oxygen into the fluid reaction mixture downstream of the mixing
zone 112. The oxygen inlet system 124 comprises a series of three
umbrellas 128, 130, 132 provided co-axially with the longitudinal
axis of the reactor 110. Oxygen is injected into the reactor from
under the umbrellas to combust a portion of the feedstock in the
fluid reaction mixture, thereby raising the temperature of the
fluid reaction mixture from the first temperature to the second
temperature. The umbrellas cause turbulence in the flow of fluid
reaction mixture through the second zone thereby facilitating
mixing of the oxygen with the mixture from under the annular
periphery of the umbrellas.
[0102] The reactor 110 has an outlet 134 for removing the resultant
fluid mixture as stream 136. Temperature sensors 138 and 140
monitor the temperature within the reactor in both the mixing and
higher temperature reaction zones.
[0103] Referring to FIG. 2, reactor 210 has a mixing zone 212 and a
higher temperature reaction zone 214. Feedstock, in this case
bitumen, is warmed to reduce its viscosity and produce a stream 216
of warmed bitumen. Stream 216 is pumped to 300 bar in pump 218 to
produce a stream 220 of pumped bitumen which is then pre-heated by
indirect heat exchange in heat exchanger 222 against a condensing
stream 224 of steam to produce a stream 226 of pressurized and
heated bitumen. The bitumen is heated to a temperature from about
650K to about 725K to avoid caking. The actual temperature of the
pre-heated bitumen depends in part on the upper solidification
temperature of the bitumen. Stream 226 is then fed to the reactor
210 via feed system 228.
[0104] A water stream 230, comprising a stream 232 of recycled
water and a stream 234 of make-up water, is pumped to 300 bar in
pump 236 to produce a stream 238 of pumped water. Stream 238 is
heated by indirect heat exchange in heat exchanger 240 to produce a
stream 242 of SCW at a temperature such that, when mixed with
stream 226 of heated bitumen to produce a fluid reaction mixture,
the fluid reaction mixture is at a first temperature from about
647K to about 775K.
[0105] Feed system 228 comprises a high intensity atomizing nozzle
(not shown) for atomizing the heated bitumen into the SCW to
facilitate dissolution of the bitumen in the water. The mass ratio
of bitumen to water is from about 1:1 to about 1:2.
[0106] The mixing zone 212 comprises two concentric shells defining
a "three pass" arrangement of sections to increase the fluid
velocity of the mixture through the mixing zone 212. The SCW and
bitumen mixture passes through the three concentric sections,
taking about 30 seconds which is sufficient time to allow the
initial reduction in bitumen viscosity and the initial cracking of
the complex molecular structure of the bitumen to take place. Most
of the bitumen forms a single homogeneous phase with the SCW (the
fluid reaction mixture) but a small fraction of a solid phase,
composed of ash and a residue having high carbon to hydrogen ratio,
is also formed.
[0107] The fluid reaction mixture leaves the mixing zone 212 via a
mixing nozzle 244 where a stream 246 of pre-heated oxygen gas is
introduced. In the exemplified embodiment, oxygen is separated from
air in a cryogenic air separation plant 248 operating a pumped
oxygen cycle producing a stream 250 of pressurized oxygen product
at the operating pressure of the reactor 210 (about 300 bar) which
is pre-heated to about 625K by indirect heat exchange in heat
exchanger 252 against a condensing stream 254 of steam at 150 bar
to produce the stream 246 of pre-heated oxygen gas.
[0108] The oxygen reacts rapidly, e.g. within 1 or 2 seconds, with
combustible components of the fluid reaction mixture and raises the
temperature of the solution to a second temperature from about 870K
to about 1075K, e.g. about 975K. The quantity of oxygen is derived
from the flow rates of the feedstock and the SCW and from the
required first temperature. In the present example, the quantity of
oxygen is about 30 wt % of that of the feedstock and the effect of
which is that about 17 wt % of the hydrocarbon content of the fluid
reaction mixture is combusted to raise the temperature. The oxygen
reacts with this portion of the hydrocarbon content which is
oxidized to carbon dioxide and water. The increase in temperature
of the fluid reaction mixture causes free radical reactions to take
place which allow water molecules to react with the feedstock
molecules causing cracking and hydrogenation of the fragments with
production of carbon dioxide. Residence time in the reaction zone
is about 10 seconds, producing the resultant fluid mixture. The
increase in temperature following oxygen injection will result in a
three fold reduction in fluid density.
[0109] There is no need to use internal baffles in the reaction
zone 214 of the reactor 210. Each zone will have approximately the
same volume and the same fluid velocity. As an example, a reactor
for 1 million tons (102000 tonnes) per year of bitumen with two
sections, each section having an effective length of 15 meters,
would have an internal diameter of about 1 meter.
[0110] The lower part of the reaction zone has an internal vortex
Norway-type entrainment separator 258 which can separate any solid
particles of coke, ash or carbon entrained with the resultant fluid
mixture. The solid particles are removed as stream 260 and then
further processed or disposed of. A stream 262 of resultant fluid
mixture (with solid particles removed) is cooled in a heat
exchanger 240 to produce a stream 264 at near ambient temperature,
e.g. from about 35.degree. C. to about 50.degree. C. Stream 264, a
two phase liquid/gas mixture, is reduced in pressure over valve 266
to produce a product stream 268 at about 50 bar which is then
separated in a phase separator system 270 into a gaseous stream 272
(predominantly methane and some C.sub.2 hydrocarbons, hydrogen and
carbon monoxide) and some liquid phases 274, 276 and 278, i.e.
hydrocarbons with a density lower than water (stream 274), water
(stream 276) and hydrocarbons with a density higher than water
(stream 278).
[0111] All these product streams can be treated in a conventional
component separation train 280. A typical separation might be a
methane stream 282; a fuel gas stream 284 which also contains all
the CO.sub.2 produced; a BTX (benzene/toluene/xylene) fraction 286;
and a light and heavy oil fraction 288.
[0112] The heat released by cooling the product stream 262 in heat
exchanger 240 is greater than that required for heating the 300 bar
water feed stream 238 and, therefore, the process includes a steam
heating cycle to provide heat balance. The excess heat is used to
heat a stream 290 of water at a pressure of 150 bar delivered from
a condensate pump 292 to produce a stream 294 of superheated steam
at about 793K. Stream 294 is divided into two streams, 296 and 298.
Stream 296 is used to generate power in a condensing steam turbine
300 and 302, producing recycle stream 304. Stream 298 is further
divided to produce streams 224 and 254 which are used respectively
to pre-heat the hydrocarbon feedstock in heat exchanger 222 and to
pre-heat the oxygen in heat exchanger 252, thereby producing
recycle streams 306 and 308. Recycle stream 304, 306 and 308 are
recycled to the condensate pump 292.
[0113] When any part of the reactor system becomes blocked by
deposits of solid coke or soot on internal surfaces, the deposits
are burned away using a flow of oxygen dissolved in SCW. In this
connection, the flow of stream 216 of bitumen feedstock is stopped
and hydrocarbon compounds are purged from the system by a flow of
SCW alone. Valve 310 is then opened and pre-heated oxygen gas is
mixed with the SCW feed stream 242 via stream 312. The oxygen/water
mixture burns off any coke or soot deposits and cleans the internal
components of the reactor. Excessive temperatures are prevented by
carefully controlling the amount of oxygen gas delivered to the
reactor.
EXAMPLE
[0114] The performance of a bitumen conversion process according to
the present invention using the laboratory scale reactor depicted
in FIG. 1 has been measured over six test runs with varying ratios
of water, bitumen and oxygen.
[0115] The reactor has an internal diameter of 28 mm, a higher
temperature reaction zone length of 170 mm, and a three stage
umbrella mixer and oxygen injection system. The laboratory reactor
was fitted with external heating elements to ensure stable
operation at the defined operating temperatures.
[0116] The feedstock considered was bitumen derived from oil vacuum
distillation with a bottom column temperature of 870K. The formula
of the bitumen used was C.sub.1H.sub.1.43S.sub.0.015.
[0117] The reaction conditions for each run and the identity and
proportions of the products are reproduced in Table 1.
TABLE-US-00001 TABLE 1 TEST 1 2 3 4 5 6 T.sub.M(K) wall 724 [~774]
714 [~764] 706 [~756] 690 [~740] 673 [~723] 702 [~752] [~fluid]
T.sub.R(K) wall 844 [~894] 826 [~876] 875 [~925] 879 [~929] 875
[~925] 963 [~1013] [~fluid] P (bar) 350 350 350 300 300 300 G.sub.W
(mg/s) 150 50 100 100 100 100 G.sub.T (mg/s) 27 28 84 114 54 97
G.sub.O2 (mg/s) 26 17 21 17 35 20 t.sub.M (s) 48 165 93 80 133 110
t.sub.R (s) 32 99 44 37 37 33 t.sub.H (s) 2.8 3.2 3.6 4.9 6.7 2.0
H.sub.2 (%) 0.02 0.08 0.23 0.07 0.31 0.30 CH.sub.4 (%) 5.9 12.0 29
26 28 35 C.sub.2H.sub.6 (%) 3.0 7.6 4.9 9.7 3.6 5.8 C.sub.6H.sub.6
(%) 7.1 15.9 23 22 25 24 C.sub.7H.sub.8 (%) 6.2 11.4 6.6 11.6 3.3
8.8 C.sub.8H.sub.10 (%) 3.6 9.0 1.54 3.3 0.45 2.8 C.sub.9H.sub.12
(%) 0.55 2.15 0.24 0.24 0.05 0.28 C.sub.10H.sub.14 (%) 0 0.51 0.03
0.24 0 0.13 C.sub.10H.sub.8 (%) 0.34 0.59 0.74 1.62 1.54 1.68 CO
(%) 4.1 2.3 2.3 0.9 4.9 3.1 CO.sub.2 (%) 50 28.4 17.6 3.4 33 4.4
(H.sub.2O).sub.f (%) 18 3 -25 6 -9 7.2 H.sub.2S (%) 0 0.54 1.07 2.7
2.0 1.84 C.sub.4H.sub.4S (%) 0 0 0.64 0.01 0.19 0.44
C.sub.5H.sub.5S (%) 0 0.52 0.27 0.17 0 0.53 .SIGMA. C.sub.xH.sub.y
(%) 51 16 10 9 9 6.9 R.sub.S (%) 13.6 5 6 5 9 1.6 Coke (%) 9.6 12.6
10.7 10.0 12.9 10.7 BTX (%) 16.9 36.3 31 36.6 29 35.6 "T.sub.M" is
temperature of the reactor wall in the mixing zone; "T.sub.R" is
the temperature of the reactor wall in the higher temperature
reaction zone; "P" is the pressure; "G.sub.W" is the flow rate for
water "G.sub.T" is the flowrate for the bitumen (tar); "G.sub.O2"
is the flowrate for oxygen; "t.sub.M" is the residence time in the
mixing section; "t.sub.R" is the residence time in the reaction
zone; and "t.sub.H" is the residence time in the outlet pipe;
[0118] It is important to note that the temperature of the fluid
inside the reactor is more than the temperature of the reactor wall
by approximately 50K. The approximate fluid temperatures are given
in parenthesis.
[0119] The mass percentage of combustion products is normalized to
the bitumen input decreased by the combusted bitumen. In addition,
the mass percentage of carbon monoxide and carbon dioxide shows
only the contained carbon quantity.
[0120] The difference in water mass flow at the reactor outlet
compared to the inlet is (H.sub.2O).sub.f. If this figure is
negative, more water molecules dissociate in the reactor than are
formed from bitumen combustion.
[0121] R.sub.s is a high boiling point oil fraction. The coke
residue has an approximate formula CH.sub.0.5.
[0122] The results clearly indicate that substantial quantities of
lighter, more valuable, hydrocarbon compounds such as methane;
ethane; benzene; toluene; and xylene may be produced efficiently,
in good yield and with reduced coke formation, directly from heavy,
low grade hydrocarbon feedstock such as bitumen using the two stage
heating process of the present invention with internal combustion
heating to raise the temperature between the two stages. The
results show that a significant degree of hydrogenation has
occurred due to dissociation of water molecules.
[0123] The results demonstrate that the maximum yield of valuable
products from bitumen conversion occurs at a temperature in the
range 925K to 1025K while the initial process of tar dissolution
occurs at a temperature of no more than 775K. It has also been
shown that conversion rates at 925K are rapid.
[0124] The process can be used to treat heavy hydrocarbon
feedstocks to produce a natural gas substitute; BTX; liquid oil
fractions; and a coke fraction. The capital and running costs are
typically far less than for an equivalent process involving
gasification and Fischer-Tropsch liquid hydrocarbon synthesis. In
addition, oxygen consumption is typically much lower (only about 30
wt %) than for a conventional high temperature gasification.
[0125] It will be appreciated that the invention is not restricted
to the details described above with reference to the preferred
embodiments but that numerous modifications and variations can be
made without departing from the spirit or scope of the invention as
defined in the following claims.
* * * * *