U.S. patent application number 13/640847 was filed with the patent office on 2013-04-04 for method for the hydroconversion of oil feedstocks using slurry technology, allowing the recovery of metals from the catalyst and the feedstock, comprising an extraction step.
This patent application is currently assigned to IFP ENERGIES NOUVELLES. The applicant listed for this patent is Jean-Philippe Heraud, Frederic Morel, Alain Quignard. Invention is credited to Jean-Philippe Heraud, Frederic Morel, Alain Quignard.
Application Number | 20130081976 13/640847 |
Document ID | / |
Family ID | 43034134 |
Filed Date | 2013-04-04 |
United States Patent
Application |
20130081976 |
Kind Code |
A1 |
Heraud; Jean-Philippe ; et
al. |
April 4, 2013 |
METHOD FOR THE HYDROCONVERSION OF OIL FEEDSTOCKS USING SLURRY
TECHNOLOGY, ALLOWING THE RECOVERY OF METALS FROM THE CATALYST AND
THE FEEDSTOCK, COMPRISING AN EXTRACTION STEP
Abstract
A process for the hydroconversion of heavy oil feedstocks
comprises a step for hydroconversion of the feedstock in at least
one reactor containing a catalyst in slurry mode used to recover
metals from the residual unconverted fraction, especially those
used as catalysts. The process comprises a hydroconversion step, a
gas/liquid separation step, at least one liquid/liquid extraction
step, a combustion step, a metals extraction step and a step for
the preparation of catalytic solutions which are recycled to the
hydroconversion step.
Inventors: |
Heraud; Jean-Philippe;
(Saint Pierre de Chandieu, FR) ; Morel; Frederic;
(Chatou, FR) ; Quignard; Alain; (Roussillon,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Heraud; Jean-Philippe
Morel; Frederic
Quignard; Alain |
Saint Pierre de Chandieu
Chatou
Roussillon |
|
FR
FR
FR |
|
|
Assignee: |
IFP ENERGIES NOUVELLES
Rueil Malmaison Cedex
FR
|
Family ID: |
43034134 |
Appl. No.: |
13/640847 |
Filed: |
March 22, 2011 |
PCT Filed: |
March 22, 2011 |
PCT NO: |
PCT/FR11/00159 |
371 Date: |
December 18, 2012 |
Current U.S.
Class: |
208/49 ;
208/96 |
Current CPC
Class: |
C10G 2300/1074 20130101;
C10G 2300/44 20130101; C10G 2300/202 20130101; C10G 49/12 20130101;
C10G 2300/701 20130101; C10G 2300/1077 20130101; C10G 2300/206
20130101; C10G 67/0454 20130101; Y02P 10/214 20151101; C10G
2300/205 20130101; C22B 7/009 20130101; C10G 67/04 20130101; B01J
23/883 20130101; Y02P 10/20 20151101; C10G 2300/301 20130101 |
Class at
Publication: |
208/49 ;
208/96 |
International
Class: |
C10G 67/04 20060101
C10G067/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2010 |
FR |
1001560 |
Claims
1. A process for the hydroconversion of heavy oil feedstocks
containing metals, comprising: a) a step for hydroconversion of the
feedstock in at least one reactor containing a catalyst in the form
of a slurry containing at least one metal, and optionally a solid
additive; b) a step for separation of the hydroconversion effluent
without decompression into a fraction termed the light fraction
containing compounds boiling at 500.degree. C. at most and into a
residual fraction; b') an optional step for fractionation,
comprising vacuum separation of said residual fraction as obtained
in step b) to obtain a vacuum residue which is concentrated in
metals; c) a step for liquid/liquid extraction of said residual
fraction as obtained in step b) and/or said vacuum residue as
obtained in step b') at a temperature in the range 50.degree. C. to
350.degree. C. using an aromatic and/or naphtheno-aromatic and/or
polar solvent in order to obtain an extract which is concentrated
in metals and a raffinate; d) a step for combustion of said extract
at a temperature in the range 200.degree. C. to 700.degree. C. in
order to obtain ash which is concentrated in metals; e) a step for
extraction of metals from the ash obtained in the combustion step;
f) a step for preparing metallic solution(s) containing at least
the metal of the catalyst which is/are recycled as the catalyst to
the hydroconversion step.
2. A process according to claim 1, in which the liquid/liquid
extraction step is carried out at a temperature in the range
150.degree. C. to 350.degree. C.
3. A process according to one of the preceding claims claim 1, in
which the liquid/liquid extraction step is carried out with a
solvent/feedstock ratio of 0.5/1 to 20/1, preferably 1/1 to
5/1.
4. A process according to claim 1, in which the raffinate from the
liquid/liquid extraction step undergoes a second liquid/liquid
extraction step at a temperature in the range 50.degree. C. to
300.degree. C. using a paraffinic solvent.
5. A process according to claim 1, in which the second
liquid/liquid extraction step is carried out with a
solvent/feedstock ratio of 1/1 to 10/1, preferably 2/1 to 7/1, and
at a temperature in the range 50.degree. C. to 300.degree. C.,
preferably in the range 120.degree. C. to 250.degree. C.
6. A process according to claim 1, in which said "light" fraction
from the step for separation without decompression undergoes at
least one hydrotreatment and/or hydrocracking step.
7. A process according to claim 1, in which said residual fraction
from the step for separation without decompression is fractionated
by vacuum distillation into at least a vacuum distillate and a
vacuum residue, at least a portion and preferably all of said
vacuum residue being sent to the liquid/liquid extraction step, at
least a portion and preferably all of said vacuum distillate
undergoing at least one hydrotreatment and/or hydrocracking
step.
8. A process according to claim 1, in which the combustion step is
operated at a pressure of -0.1 to 1 MPa, preferably -0.1 to 0.5 MPa
and at a temperature of 200.degree. C. to 700.degree. C.,
preferably 400.degree. C. to 550.degree. C. in the presence of
air.
9. A process according to claim 1, in which the step for extraction
of the metals comprises leaching using at least one acidic and/or
basic solution.
10. A process according to claim 1, in which the heavy oil
feedstock is a hydrocarbon feedstock containing at least 50% by
weight of product distilling above 250.degree. C. and at least 25%
by weight distilling above 350.degree. C., and contains at least 50
ppm by weight of metals, at least 0.5% by weight of sulphur and at
least 1% by weight of asphaltenes (heptane asphaltenes).
11. A process according to claim 1, in which the heavy oil
feedstock is selected from oil residues, crude oils, topped crudes,
deasphalted oils, deasphalted asphalts, oil conversion process
derivatives, bituminous sands or their derivative, oil shale or
their derivatives, or mixtures of such feedstocks.
12. A process according to claim 1, in which the hydroconversion
step is operated at a pressure of 2 to 35 MPa, preferably 10 to 25
MPa, a partial pressure of hydrogen of 2 to 35 MPa, preferably 10
to 25 MPa, a temperature in the range 300.degree. C. to 500.degree.
C., preferably 420.degree. C. to 480.degree. C. and a contact time
of 0.1 h to 10 h, preferably 0.5 h to 5 h.
13. A process according to claim 1, in which the slurry catalyst is
a sulphurized catalyst containing at least one element selected
from the group formed by Mo, Fe, Ni, W, Co, V and Ru.
14. A process according to claim 1, in which the additive is
selected from the group formed by mineral oxides, spent supported
catalysts containing at least one element from group VIII and/or at
least one element from group VIB, carbonaceous solids with a low
hydrogen content or mixtures of said additives, said additive
having a particle size of less than 1 mm
Description
[0001] The invention relates to a process for the hydroconversion
of heavy oil feedstocks into lighter products, which can be
upcycled as fuels and/or raw materials for petrochemicals. More
particularly, the invention relates to a process for the
hydroconversion of heavy oil feedstocks comprising a step for
hydroconversion of the feedstock in at least one reactor containing
a catalyst in slurry mode used to recover metals from the residual
unconverted fraction, especially those used as catalysts, in order
to re-use them as catalytic solutions and recycle them upstream of
the slurry conversion process. The process comprises a
hydroconversion step, a gas/liquid separation step, at least one
liquid/liquid extraction step, a combustion step, a metals
extraction step and a step for the preparation of catalytic
solutions which are recycled to the hydroconversion step.
[0002] The conversion of heavy oil feedstocks into liquid products
may be carried out by heat treatments or by hydrogenation
treatments, also known as hydroconversion. Current research is
primarily orientated towards hydroconversion, because heat
treatments generally produce mediocre quality products and a
quantity of coke which is not negligible.
[0003] The hydroconversion of heavy feedstocks comprises conversion
of the feedstock in the presence of hydrogen and of a catalyst.
Depending on the feedstock, commercial processes use a fixed bed
technique, an ebullated bed technique or a slurry technique.
[0004] Fixed bed or ebullated bed hydroconversion of heavy
feedstocks is carried out using supported catalysts comprising one
or more transition metals (Mo, W, Ni, Co, Ru) on silica/alumina or
equivalent type supports.
[0005] In order to convert heavy feedstocks that are particularly
charged with heteroatoms, metals and asphaltenes, fixed bed
techniques are generally limited, since the contaminants cause
rapid deactivation of the catalyst, thereby necessitating too high
a frequency of renewal of the catalytic bed; this is too expensive.
Ebullated bed processes were developed in order to be able to treat
this type of feedstock. However, the degree of conversion in
ebullated bed techniques is generally limited to levels below 80%
because of the catalytic system employed and the design of the
unit.
[0006] Hydroconversion techniques operating with slurry technology
provide an attractive solution to the disadvantages encountered
when using a fixed bed or ebullated bed. Slurry technology can be
used to process heavy feedstocks which are heavily contaminated
with metals, asphaltenes and heteroatoms, while having degrees of
conversion generally of more than 85%.
[0007] Techniques for the slurry hydroconversion of residues use a
catalyst dispersed in the form of very small particles less than 1
mm in size, preferably a few tens of microns or fewer (generally
0.001 to 100 .mu.m). Because of the small size of the catalysts,
the hydrogenation reactions are facilitated by a uniform
distribution throughout the reaction zone and coke formation is
greatly reduced. The catalysts or their precursors are injected
into the inlet to the reactors with the feedstock to be converted.
The catalysts pass through the reactors with the feedstocks and the
products during conversion, then they are entrained with the
reaction products out of the reactors. Following separation, they
are found in the heavy residual fraction such as the unconverted
vacuum residue. Catalysts used in slurry mode are generally
sulphurized catalysts preferably containing at least one element
selected from the group formed by Mo, Fe, Ni, W, Co, V and/or Ru.
Generally, molybdenum and tungsten have far more satisfactory
performances than nickel, cobalt or ruthenium and even more so than
vanadium and iron (N Panariti et al, Applied Catalysis A: General
204 (2000), 203-213).
[0008] Commercial techniques for the hydroconversion of heavy
feedstocks in slurry mode are known. Examples which may be cited
are the EST technique licensed by ENI, the VRSH technique licensed
by Chevron-Lummus-Global, HDH and HDHPLUS techniques licensed by
Intevep, the SRC-Uniflex technique licensed by UOP, the (HC)3
technique licensed by Headwaters, etc.
[0009] Although the small size of slurry catalysts means that very
high conversions can be obtained, this size proves to be
problematic as regards the separation and recovery of the catalyst
or catalysts after the hydroconversion reaction. After separation,
the catalysts are to be found in the heavy residual fraction such
as the unconverted vacuum residue. In some processes, a portion of
the vacuum residue containing the unconverted fraction and the
catalysts is recycled directly to the hydroconversion reactor to
increase the conversion yield. However, those recycled catalysts
generally have no activity or very reduced activity compared with
that of a fresh catalyst. In addition, the vacuum residue is
traditionally used as a fuel for the production of heat,
electricity and ash. This ash contains metals and is generally
dumped. In this case, then, the metals are not recovered.
[0010] In addition, the deactivation of catalysts necessitates
regular replacement, thereby creating a demand for fresh catalysts.
The treated heavy feedstocks contain a high concentration of
metals, essentially vanadium and nickel. Those metals are largely
eliminated from the feedstock since they are deposited on the
catalysts during the reaction. They are carried away by the
particles of catalysts leaving the reactor. Similarly, catalyst
deactivation is accentuated by the formation of coke deriving in
particular from the high concentration of asphaltenes contained in
such feedstocks.
[0011] Continuous renewal of the finely dispersed catalytic phase
in the reaction zone means that, in contact with hydrogen dissolved
in the liquid phase, the injected heavy feedstock can be
hydrogenated and hydrotreated. In order to ensure a high degree of
conversion and maximum hydrotreatment of the feedstock, the
quantity of catalytic solution to be injected is rather large,
meaning that industrial scale operating costs are high. Thus,
slurry hydroconversion processes generally consume a large quantity
of catalysts, in particular molybdenum, which is the most active
but also the most expensive catalyst. The costs of fresh catalysts,
separating catalysts and recovering metals have a major impact on
the cost-effectiveness of such processes. Selective recovery of
molybdenum and recycling it as a catalyst are two indispensable
elements in the industrial exploitation of slurry processes. This
recovery is also accompanied by recovering other metals such as
nickel (that injected and that recovered in the feedstock) and
vanadium recovered in the feedstock, the contents of which are
comparable with that of molybdenum and which can be re-sold for
metallurgical applications.
[0012] Apart from these economic aspects, the recovery of metals is
also required for environmental reasons. In fact, the ash from
combustion of the residual fraction has been classified in many
states as dangerous waste, since the metals contained in the dumped
ash pose a danger for ground water.
[0013] Thus, there is a genuine need for recovering and recycling
metals from catalysts and the heavy feedstock of a slurry
hydroconversion process.
PRIOR ART
[0014] Processes for recovering metals from slurry processes are
known in the art.
[0015] Thus, patent application US2008/0156700 describes a process
for the separation of catalysts in the form of ultrafine particles
from a slurry hydroconversion process comprising a step for
precipitation or flocculation of a heavy fraction including
metallic portions using heptane type solvents, a step for
separation of the heavy fraction from the light fraction by
centrifuging and a step for cokefaction between 350.degree. C. and
550.degree. C. in an inert atmosphere in order to obtain coke
containing the catalyst. That coke may undergo a step for
extraction of metals.
[0016] U.S. Pat. No. 4,592,827 describes a process for the slurry
hydroconversion of heavy feedstocks in the presence of a soluble
metallic compound and water comprising, after the hydroconversion
reaction, a separation step, a step for deasphalting the vacuum
residue fraction using C5 to C8 hydrocarbons and a step for
gasification of the asphaltenes, producing hydrogen and ash
containing the catalyst. That catalyst then undergoes metal
extraction steps; the metals are recycled to the process.
[0017] U.S. Pat. No. 4,548,700 describes a slurry hydroconversion
process for heavy feedstocks comprising, after the hydroconversion
reaction, a step for separating the gaseous fraction, a
distillation step, washing the atmospheric residue (650.degree.
F..sup.+=343.degree. C..sup.+) with toluene at atmospheric pressure
and ambient temperature and a step for solid fraction combustion or
gasification at temperatures in the range 427-1093.degree. C.
(800-2000.degree. F.) to obtain ash containing metals. The metals V
and Mo are recovered by an oxalic acid extraction step then
recycled to the process.
[0018] U.S. Pat. No. 6,511,937 describes a slurry hydroconversion
process for heavy feedstocks comprising, after the hydroconversion
reaction, a step for separation in a high pressure, low temperature
separator to separate a very light fraction, a step for
deasphalting the whole of the residual fraction using paraffinic C3
to C5 solvents at ambient temperature, a coking step
(427-649.degree. C., no air) and/or a combustion step below
649.degree. C., to produce ash containing the catalyst. That
catalyst may then undergo metals extraction steps and be recycled
to the process.
SUBJECT MATTER OF THE INVENTION
[0019] The characteristic of slurry processes is that the catalyst
is finely divided and not supported on a mineral phase; this
renders recovery of the metals much more complex than with the
traditionally employed supported refining catalysts. The issue in
the industrial development of hydroconversion processes using
slurry technology is the necessity of recovering and recycling the
metals of the catalysts.
[0020] The present invention aims to improve processes for the
hydroconversion of heavy feedstocks using known slurry technology
by allowing a residual unconverted fraction derived from the slurry
conversion to be re-used, this fraction having a high concentration
of metals and heteroelements, and also includes the recovery of
said metals in said unconverted fraction and the production of
catalytic precursors in order to recycle them upstream of the
slurry mode conversion process. The process comprises a
hydroconversion step, a gas/liquid separation step, a liquid/liquid
extraction step, a combustion step, a metals extraction step and a
step for the preparation of catalytic solution(s) which is/are
recycled to the hydroconversion step.
[0021] The research work carried out by the Applicant on the
hydroconversion of heavy feedstocks has led to the discovery that
surprisingly, this process, comprising a separation used to
maximize the light fraction from the hydroconversion reactor and
minimize the residual fraction coupled with a liquid/liquid
extraction step using aromatic and/or naphtheno-aromatic solvents
and/or polar solvents at high temperature and a step for moderate
combustion avoiding the sublimation of the metals, can be used to
carry out the extraction of metals contained in the ash such that
very good degrees of recovery of metals that can be recycled to the
process are possible. In fact, the critical steps in this recovery
are firstly, the concentration of metals on the carbonaceous matrix
(via extraction), then the formation of a mineral phase (via the
moderate combustion) containing the metallic elements from the
catalyst (Mo and Ni), but also from the feedstock (Ni, V and Fe)
lacking in carbon.
[0022] One advantage of the process of the invention is the re-use
of a residual unconverted fraction which is highly concentrated in
metals and heteroelements, enabling the recovery of said metals and
the production of catalytic precursors in order to recycle them
upstream of the conversion process in slurry mode.
[0023] Another advantage is the optimization of the hydroconversion
step by gas/liquid separation following the hydroconversion,
carried out under operating conditions close to those of the
reactor and allowing effective separation, in a single step, of a
light fraction comprising future fuel bases (gases, naphtha, light
gas oil, or even heavy gas oil) from the residual unconverted
fraction containing solids such as metals. The light fraction yield
is thus maximized at the same time as the unconverted residual
fraction is minimized, its reduced quantity thereby facilitating
the subsequent concentration of metals. Maintaining the operating
conditions during separation also results in economic integration
of a subsequent treatment for hydrotreatment and/or hydrocracking
for the light fraction without the need for supplemental
compressors.
[0024] A further advantage is liquid/liquid extraction, using
aromatic and/or naphtheno-aromatic and/or polar solvents, of the
unconverted metal-containing fraction at high temperatures,
allowing efficient extraction of insoluble compounds (and thus
concentration of the metals)
[0025] A further advantage of the process is combustion at moderate
temperature in order to separate the organic phase from the
inorganic phase containing the metals in order to facilitate
subsequent extraction of the metals from the inorganic phase while
avoiding vaporization and/or sublimation (and thus loss) of metals
during combustion.
[0026] The process of the invention can thus be used to optimize
the conversion of heavy feedstocks into fuel bases while allowing
the recovery of metals with very good levels of recovery.
DETAILED DESCRIPTION
[0027] The invention concerns a process for the hydroconversion of
heavy oil feedstocks in slurry mode in order to enable the recovery
and recycling of metals in the residual unconverted fraction, in
particular those used as catalysts.
[0028] More particularly, the invention concerns a process for the
hydroconversion of heavy oil feedstocks containing metals,
comprising:
[0029] a) a step for hydroconversion of the feedstock in at least
one reactor containing a catalyst in the form of a slurry
containing at least one metal, and optionally a solid additive;
[0030] b) a step for separation of the hydroconversion effluent
without decompression into a fraction termed the light fraction
containing compounds boiling at 500.degree. C. at most and into a
residual fraction;
[0031] b') an optional step for fractionation, comprising vacuum
separation of said residual fraction as obtained in step b) to
obtain a vacuum residue which is concentrated in metals;
[0032] c) a step for liquid/liquid extraction of said residual
fraction as obtained in step b) and/or said vacuum residue as
obtained in step b') at a temperature in the range 50.degree. C. to
350.degree. C. using an aromatic and/or naphtheno-aromatic and/or
polar solvent in order to obtain an extract which is concentrated
in metals and a raffinate;
[0033] d) a step for combustion of said extract at a temperature in
the range 200.degree. C. to 700.degree. C. in order to obtain ash
which is concentrated in metals;
[0034] e) a step for extraction of metals from the ash obtained in
the combustion step;
[0035] f) a step for preparing metallic solution(s) containing at
least the metal of the catalyst which is/are recycled as the
catalyst to the hydroconversion step.
Hydroconversion
[0036] The process of the invention comprises a step for
hydroconversion of the feedstock in at least one reactor containing
a slurry catalyst and optionally a solid additive.
[0037] The term "hydroconversion" means hydrogenation,
hydrotreatment, hydrodesulphurization, hydrodenitrogenation,
hydrodemetallization and hydrocracking reactions.
[0038] The heavy feedstocks concerned are oil hydrocarbon
feedstocks such as oil residues, crude oils, topped crude oils,
deasphalted oils, asphalts or deasphalted tars, oil conversion
process derivatives (such as: HCO, FCC slurry, heavy GO/coking VGO,
residue from visbreaking or a similar thermal process, etc),
bituminous sands or their derivatives, oil shale or their
derivatives, or mixtures of such feedstocks. More generally, the
term "heavy feedstock" as used here encompasses hydrocarbon
feedstocks containing at least 50% by weight of product distilling
above 250.degree. C. and at least 25% by weight distilling above
350.degree. C.
[0039] The heavy feedstocks used in accordance with the invention
contain metals, essentially V and/or Ni, generally in amounts of at
least 50 ppm by weight and usually 100-2000 ppm by weight, at least
0.5% by weight of sulphur, and at least 1% by weight of asphaltenes
(heptane asphaltenes), usually more than 2% by weight or even more
than 5% by weight; quantities of 25% by weight or more of
asphaltenes may be obtained; they also contain condensed aromatic
structures that may contain heteroelements which are refractory to
conversion.
[0040] Preferably, the heavy feedstocks concerned are
non-conventional oils of the heavy crude type (.degree. API in the
range 18 to 25 and a viscosity in the range 10 to 100 cP),
extra-heavy crudes (.degree. API in the range 7 to 20 and a
viscosity in the range 100 to 10000 cP) and bituminous sands
(.degree. API in the range 7 to 12 and a viscosity of less than
10000 cP) present in large quantities in the Athabasca region of
Canada and the Orinoco in Venezuela, where reserves are
respectively estimated at 1700 Gb and 1300 Gb. These
non-conventional oils are also characterized by large quantities of
vacuum residue, asphaltenes and heteroelements (sulphur, nitrogen,
oxygen, vanadium, nickel, etc), which necessitate specific steps
for transformation into commercial gasoline, gas oil or heavy fuel
type product.
[0041] The heavy feedstock is mixed with a stream of hydrogen and a
catalyst which is as dispersed as possible in order to obtain a
hydrogenating activity which is also as uniformly distributed as
possible in the hydroconversion reaction zone. Preferably, a solid
additive favouring the hydrodynamics of the reactor is also added.
This mixture supplies the catalytic slurry hydroconversion section.
This section is constituted by a preheating furnace for the
feedstock and hydrogen and by a reaction section constituted by one
or more reactors disposed in series and/or in parallel, depending
on the capacity required. In the case of reactors in series, one or
more separators may be present on the overhead effluent from each
of the reactors. In the reaction section, the hydrogen may supply a
single, some or all of the reactors, in equal or different
proportions. In the reaction section, the catalyst may supply a
single, some or all of the reactors, in equal or different
proportions. The catalyst is maintained in suspension in the
reactor, moves from bottom to top of the reactor with the gas and
the feedstock and is evacuated with the effluent. Preferably, at
least one (preferably all) of the reactors is provided with an
internal recirculating pump.
[0042] The operating conditions of the catalytic slurry
hydroconversion section are in general a pressure of 2 to 35 MPa,
preferably 10 to 25 MPa, a partial pressure of hydrogen of 2 to 35
MPa, preferably 10 to 25 MPa, a temperature in the range
300.degree. C. to 500.degree. C., preferably 420.degree. C. to
480.degree. C., and a contact time of 0.1 h to 10 h with a
preferred duration of 0.5 h to 5 h.
[0043] These operating conditions, coupled with the catalytic
activity, can be used to obtain conversions per pass of 500.degree.
C..sup.+ vacuum residue that may be from 20% to 95%, preferably 70%
to 95%. The degree of conversion mentioned above is defined as
being the fraction by weight of organic compounds with a boiling
point of more than 500.degree. C. at the inlet to the reaction
section minus the fraction by weight of organic compounds with a
boiling point of more than 500.degree. C. at the outlet from the
reaction section, this being divided by the fraction by weight of
organic compounds with a boiling point of more than 500.degree. C.
at the inlet to the reaction section.
[0044] The slurry catalyst is in the dispersed form in the reaction
medium. It may be formed in situ, but it is preferable to prepare
it outside the reactor and in general to inject it continuously
with the feedstock. The catalyst promotes hydrogenation of the
radicals obtained from thermal cracking and reduces the formation
of coke. When coke is formed, it is evacuated by the catalyst.
[0045] The slurry catalyst is a sulphurized catalyst, preferably
containing at least one element selected from the group formed by
Mo, Fe, Ni, W, Co, V, Ru. These catalysts are generally
monometallic or bimetallic (by combining, for example, an element
from non-noble group VIIIB (Co, Ni, Fe) and an element from group
VIB (Mo, W). Preferably, NiMo, Mo or Fe catalysts are used. The
catalysts used may be powders of heterogeneous solids (such as
natural minerals, iron sulphate, etc), water-soluble dispersed
catalysts such as phosphomolybdic acid, ammonium molybdate, or a
mixture of Mo or Ni oxide with aqueous ammonia. Preferably, the
catalysts used are obtained from precursors which are soluble in an
organic phase (oil-soluble dispersed catalysts). The precursors are
organometallic compounds such as Mo, Co, Fe or Ni naphthenates or
such as multi-carbonyl compounds of these metals, for example Mo or
Ni 2-ethyl hexanoates,
[0046] Mo or Ni acetylacetonates, Mo or W salts of C.sub.7-C.sub.12
fatty acids, etc. They may be used in the presence of a surfactant
to improve dispersion of the metals when the catalyst is
bimetallic. The catalysts are in the form of dispersed particles,
which may or may not be colloidal depending on the nature of the
catalyst. Such precursors and catalysts that may be used in the
process of the invention have been extensively described in the
literature.
[0047] In general, the catalysts are prepared before being injected
into the feedstock. The preparation process is adapted as a
function of the state of the precursor and its nature. In all
cases, the precursor is sulphurized (ex situ or in situ) to
disperse the catalyst in the feedstock. For the preferred case of
oil-soluble catalysts, in a typical process, the precursor is mixed
with an oil feedstock (which may be a portion of the feedstock to
be treated, an external feedstock, a recycled feedstock, etc), the
mixture is optionally dried at least in part, and is then or is
simultaneously sulphurized by adding a sulphur-containing compound
(preferably H.sub.2S) and heated. The preparations of these
catalysts have been described in the prior art.
[0048] Preferred solid additives are mineral oxides such as
alumina, silica, mixed Al/Si oxides, spent supported catalysts (for
example on alumina and/or silica) containing at least one element
from group VIII (such as Ni, Co) and/or at least one element from
group VIB (such as Mo, W). Examples which may be cited are the
catalysts described in application US2008/177124. Carbonaceous
solids with a low hydrogen content (for example 4% hydrogen), which
have optionally been pre-treated, may also be used. It is also
possible to use mixtures of such additives. Their preferred
particle size is less than 1 mm The quantity of optional solid
additive present at the inlet to the reaction zone of the slurry
hydroconversion process is in the range 0 to 10% by weight,
preferably in the range 1% to 3% by weight, and the quantity of
catalytic solutions is in the range 0 to 10% by weight, preferably
in the range 0 to 1% by weight.
[0049] Known processes for the hydroconversion of heavy feedstocks
using slurry technology are EST and ENI operating at temperatures
of the order of 400-420.degree. C., at pressures of 10-16 MPa with
a particular catalyst (molybdenite); (HC)3 from Headwaters,
operating at temperatures of the order of 400-450.degree. C., at
pressures of 10-15 MPa with Fe pentacarbonyl or Mo 2-ethyl
hexanoate, the catalyst being dispersed in the form of colloidal
particles; HDH and HDHPLUS licensed by Intevep/PDVSA, operating at
temperatures of the order of 420-480.degree. C., at pressures of
7-20 MPa, using a dispersed metallic catalyst; CASH from Chevron
using a Mo or W sulphurized catalyst prepared by an aqueous method;
SRC-Uniflex from UOP, operating at temperatures of the order of
430-480.degree. C., at pressures of 10-15 MPa; VCC developed by
Veba and belonging to BP, operated at temperatures of the order of
400-480.degree. C., at pressures of 15-30 MPa, using an iron-based
catalyst; and Microcat from Exxonmobil, etc.
[0050] All of these slurry processes can be used in the process of
the invention.
Separation
[0051] All of the effluent from the hydroconversion step is
directed towards a separation section, generally in a high pressure
high temperature (HPHT) separator, which can be used to separate a
converted fraction in the gaseous state, termed the light fraction,
and an unconverted liquid fraction containing solids, termed the
residual fraction. This separation section is preferably
implemented under operating conditions close to those of the
reactor, which are in general a pressure of 2 to 35 MPa with a
preferred pressure of 10 to 25 MPa, a partial pressure of hydrogen
of 2 to 35 MPa, preferably 10 to 25 MPa, and a temperature in the
range 300.degree. C. to 500.degree. C., preferably 380.degree. C.
to 460.degree. C. The residence time for the effluent in this
separation section is 0.5 to 60 minutes, preferably 1 to 5 minutes.
The light fraction primarily contains compounds boiling at
300.degree. C. at most, or even at 400.degree. C. or 500.degree. C.
at most; they correspond to compounds present in the gases,
naphtha, light gas oil or even heavy gas oil. It should be pointed
out that the cut contains these compounds in the vast majority, as
separation is not accomplished at a precise cut point, but is
moreover a flash separation. If cut point terms have to be
employed, it could be said that it was in the range 200.degree. C.
to 400.degree. C. or even 450.degree. C.
[0052] Upgrading of the light fraction does not form part of the
subject matter of the present invention and these methods are well
known to the skilled person. The light fraction obtained after
separation may undergo at least one hydrotreatment and/or
hydrocracking step, the aim being to bring the various cuts to
specification (sulphur content, smoke point, cetane index,
aromatics content, etc). The light fraction may also be mixed with
another feedstock before being directed to a hydrotreatment and/or
hydrocracking section. An external cut generally originating from
another process in the refinery or possibly from outside the
refinery may be brought in before hydrotreatment and/or
hydrocracking; advantageously, the external cut is, for example,
VGO from fractionating crude oil (straight run VGO), VGO from
conversion, an LCO (light cycle oil) or a HCO (heavy cycle oil),
from FCC.
[0053] In general, the hydrotreatment and/or hydrocracking after
hydroconversion may be carried out in a conventional manner via a
standard intermediate separation section (with decompression)
using, after the high pressure high temperature separator, for
example, a high pressure low temperature separator and/or
atmospheric distillation and/or vacuum distillation. Preferably,
the hydrotreatment and/or hydrocracking section is directly
integrated with the hydroconversion section without intermediate
decompression. In this case, the light fraction is sent directly to
the hydrotreatment and/or hydrocracking section without
supplemental separation steps and without decompression. This last
embodiment can be used to optimize the pressure and temperature
conditions, avoid the use of additional compressors and thus
minimize supplemental equipment costs.
[0054] The residual fraction obtained from the separation (for
example via the HPHT separator) and containing metals and a
fraction of solid particles used as a possible additive and/or
formed during the reaction, may be directed to a fractionation
step. This fractionation is optional and comprises a vacuum
separation, for example one or more flash vessels and/or, as is
preferable, a vacuum distillation, that can be used to concentrate
a vacuum residue which is rich in metals at the bottom of the
vessels or the column and to recover one or more effluents overhead
of the column Preferably, the residual fraction from the separation
step without decompression is fractionated by vacuum distillation
into at least one vacuum distillate fraction and a vacuum residue
fraction, at least a portion, preferably all, of said vacuum
residue fraction being sent to the liquid-liquid extraction step,
at least a portion, preferably all, of said vacuum distillate
fraction preferably undergoing at least one hydrotreatment and/or
hydrocracking step.
[0055] A small part of the liquid effluent or effluents from the
vacuum distillate fraction produced is/are normally directed
towards the slurry hydroconversion unit where they can be recycled
directly to the reaction zone, or they may be used in the
preparation of catalytic precursors before injection into the
feedstock. Another part of the effluent or effluents is directed to
the hydrotreatment and/or hydrocracking section, optionally as a
mixture with other feedstocks such as, for example, the light
fraction obtained from the HPHT separator or a vacuum distillate
originating from another unit, in equal or different proportions as
a function of the quality of the products obtained. The aim of the
vacuum distillation is to increase the yield of liquid effluents
for a subsequent treatment by hydrotreatment and/or hydrocracking
and thus to increase the yield of fuel bases. At the same time, the
quantity of residual fraction containing the metals is reduced,
thereby facilitating concentration of the metals.
Liquid-Liquid Extraction
[0056] The residual fraction from the separation without
decompression (for example via the HPHT separator, for example)
and/or the vacuum residue fraction from the vacuum separation (for
example withdrawn from the bottom of the vacuum distillation stage)
are then directed towards a liquid/liquid type extraction step.
This step is aimed at concentrating the metals in the effluent to
be treated subsequently by combustion, thereby reducing its
quantity, and of maximizing the yield of liquid effluent for the
treatment by hydrotreatment and/or hydrocracking.
[0057] Extraction is carried out at high temperature using an
aromatic and/or naphtheno-aromatic and/or polar type solvent, mixed
or not mixed in equal or different proportions, said solvents
preferably having high boiling points. The liquid/liquid extraction
may be carried out in a mixer-settler or in an extraction column
This extraction is distinguished from the deasphalting known in the
prior art by the use of aromatic and/or naphtheno-aromatic and/or
polar solvents, allowing better separation of insoluble compounds
(containing the metals) compared with paraffinic solvents and also
by a higher extraction temperature, since it is necessary in order
to maintain the fraction in the liquid phase.
[0058] The extraction step may be carried out in one step or, as is
preferable, in two steps.
[0059] In a one-step liquid/liquid extraction implementation, the
operating conditions are generally a solvent/feedstock ratio of
0.5/1 to 20/1, preferably 1/1 to 5/1, and a temperature profile in
the range 50.degree. C. to 350.degree. C., preferably in the range
150.degree. C. to 300.degree. C. The solvent used in the case of a
one-step extraction is preferably aromatic and/or
naphtheno-aromatic and/or polar. Toluene, xylene, a BTX mixture,
phenol, cresols or their methyl derivatives, or a mixture of these
solvents may be used as the aromatic solvent, or a di-aromatic
solvent such as alpha-methyl naphthalene, and also aromatics-rich
cuts such as LCO, HCO, aromatic extracts or GO or heavy GO cuts,
mixed or otherwise in equal or different proportions. It may come
directly from the process or from any other refining process, such
as fluidized bed catalytic cracking (LCO/HCO type solvent) or units
for the extraction of aromatics from lubricant base production
lines. Tetralin, indane, indene or a mixture of these solvents may
be used as the naphtheno-aromatic solvent, as well as GO or heavy
GO cuts from the process or any other refining process, mixed or
otherwise in equal or different proportions. Furfural, NMP
(N-methyl-2-pyrrolidone), sulpholane, DMF (dimethylformamide),
quinoline, THF (tetrahydrofuran) or a mixture of these solvents in
equal or different proportions may be used as the polar
solvent.
[0060] The solvent which is selected must have a sufficiently high
boiling point in order to be able to fluidize the residual fraction
obtained from the HPHT separator and/or the vacuum residue without
vaporizing it, the residual fraction and/or the vacuum residue
typically being transported at temperatures in the range
200.degree. C. to 300.degree. C. After contacting the solvent with
the residual fraction and/or the vacuum residue, two phases are
formed, the extract being constituted by the portions of the
residue which are not soluble in the solvent (and concentrated in
metals) and the raffinate being constituted by solvent and the
soluble portions of the residue. The solvent is separated by
distillation of the soluble parts and recycled internally to the
liquid/liquid extraction process; management of the solvent is
known to the skilled person.
[0061] At least a portion of the soluble fraction after solvent
distillation, preferably all of it, is advantageously mixed with
the heavy feedstock hydrocarbon upstream of the slurry
hydroconversion section. A smaller portion may also be mixed with
the light fraction from the HPHT separator for subsequent treatment
by hydrotreatment and/or hydrocracking.
[0062] In the two step liquid/liquid extraction implementation, a
first extraction step is carried out with an aromatic and/or
naphtheno-aromatic and/or polar type solvent, followed by a second
extraction step with a paraffinic type solvent. In the case of
two-step liquid/liquid extraction, the first extraction step is
strictly identical to that described above for one-step extraction.
After contact of the aromatic and/or naphtheno-aromatic and/or
polar solvent with the residual fraction and/or the vacuum residue,
two phases are formed, the extract being constituted by the
portions of the residue that are not soluble in the solvent (and
which is concentrated in metals) and the raffinate being
constituted by solvent and the soluble portions of the residue.
After distillation of the solvent, this soluble phase is sent to
the liquid-liquid extraction step. This extraction is carried out
by a paraffin-type solvent such as propane, butane, pentane,
hexane, heptane, light naphtha from the process (after the
hydrotreatment and/or hydrocracking treatment, for example) or any
other refining process, mixed or otherwise in equal or different
proportions. The operating conditions are in general a
solvent/feedstock ratio of 1/1 to 10/1, preferably 2/1 to 7/1, and
a temperature profile in the range 50.degree. C. to 300.degree. C.,
preferably in the range 120.degree. C. to 250.degree. C., depending
on the solvent under consideration. After contact with the
paraffinic solvent, two phases are formed. The extract is
constituted by portions of the residue which are not soluble in the
solvent, containing highly polar resins and asphaltenes, and the
raffinate contains the soluble portions containing very few or no
asphaltenes. Because of its low concentration of asphaltene, after
separation of the solvent, at least a portion of the raffinate,
preferably all of it, can be mixed with the light fraction from the
HPHT separator for a hydrotreatment and/or hydrocracking
treatment.
[0063] At least a portion of the fraction, preferably all of the
extract containing the highly polar resins and asphaltenes, is
preferably recycled upstream of the slurry hydroconversion
section.
[0064] Because different solvents are used, the two-step
liquid/liquid extraction can thus be used to separate the raffinate
obtained from the first extraction step into a fraction containing
fewer asphaltenes which is thus suitable for direct hydrotreatment
and/or hydrocracking (thus to optimization of the process as
regards the fuel base yield) and into a fraction containing more
asphaltenes, preferably necessitating recycling to the slurry
reactor.
Combustion
[0065] The extract from the one-step liquid-liquid extraction or
from the first step of the two-step extraction step is highly
concentrated in metals. This extract is directed towards a moderate
temperature combustion step. Before being able to recover the
metals by conventional metal extraction methods, a preliminary step
is necessary in order to separate the organic phase from the
inorganic phase containing the metals. Hence, the aim of the
combustion step is to obtain ash containing metals that is easily
recoverable in the subsequent metal recovery units by burning the
organic phase or carbon phase of the extract at a temperature and
pressure which limits vaporization and/or sublimation of metals, in
particular that of molybdenum (sublimation temperature
approximately 700.degree. C. for MoO.sub.3). Hence, the step for
reduction of the organic phase consists of a moderate temperature
combustion in order to concentrate the metals, without substantial
loss by vaporization and/or sublimation into fumes, in a mineral
phase which may contain a proportion of organic phase of 0 to 100%
by weight, preferably 0 to 40% by weight. The general operating
conditions for this combustion are a pressure of -0.1 to 1 MPa,
preferably -0.1 to 0.5 MPa, and a temperature of 200.degree. C. to
700.degree. C., preferably 400.degree. C. to 550.degree. C.
Combustion is carried out in the presence of air.
[0066] The gaseous effluent from combustion requires purification
steps in order to reduce emissions of sulphur-containing and
nitrogen-containing compounds into the atmosphere. Processes which
are conventionally used by the skilled person in the field of air
treatment are employed under the operating conditions necessary to
satisfy regulations which are in force in states where such a
treatment of a hydrocarbon feedstock is carried out.
[0067] The solid from combustion is a mineral phase containing all
or almost all of the metallic elements contained in the extract, in
the form of ash.
[0068] The recovery of metals from the direct treatment of the
extract from the liquid/liquid extraction by a metals extraction
method as described below without combustion is insufficient.
Recovery of Metals
[0069] The ash from combustion is sent to a metals extraction step
in which the metals are separated from each other in one or more
sub step(s). This recovery of metals is necessary, as the catalytic
activity with simply recycling the ash to the hydroconversion step
is very weak.
[0070] In general, the metals extraction step can be used to obtain
a plurality of effluents, each effluent containing a specific
metal, for example Mo, Ni or V, generally in the form of a salt or
oxide. Each effluent containing a metal of the catalyst is directed
to a step for preparing an aqueous or organic solution based on a
metal identical to the catalyst or to its precursor, used in the
hydroconversion step. The effluent containing a metal from the
feedstock which cannot be re-used as a catalyst (for example
vanadium) can be re-used outside the process.
[0071] The operating conditions, fluids and/or extraction methods
used for the various metals are considered to be known to the
skilled person and already in industrial use as described, for
example, in Marafi et al, Resources, Conservation and Recycling 53
(2008), 1-26, U.S. Pat. No. 4,432,949, U.S. Pat. No. 4,514,369,
U.S. Pat. No. 4,544,533, U.S. Pat. No. 4,670,229 or US2007/0025899.
The various routes to extraction of metals that are known in
general include leaching by acidic and/or basic solutions, by
ammonium or ammonium salts, by bio-leaching with microorganisms, by
low temperature heat treatment (roasting), by sodium or potassium
salts, by chlorination or by recovering metals electrolytically.
Leaching with acids may be carried out using inorganic acids (HCl,
H.sub.2SO.sub.4, HNO.sub.3) or organic acids (oxalic acid, lactic
acid, citric acid, glycolic acid, phthalic acid, malonic acid,
succinic acid, salicylic acid, tartaric acid, etc). In general, for
basic leaching, ammonia, ammonium salts, sodium hydroxide or
Na.sub.2CO.sub.3 is used. In both cases, oxidizing agents
(H.sub.2O.sub.2, Fe(NO.sub.3).sub.3, Al(NO.sub.3).sub.3, etc) may
be present to facilitate extraction. Once the metals are in
solution, they may be isolated by selective precipitation (at
different pHs and/or with different agents) and/or by extraction
agents (oximes, beta-diketone, etc).
[0072] Preferably, the step for extraction of metals of the
invention comprises leaching with at least one acidic and/or basic
solution.
Preparation of Catalytic Solution(s)
[0073] The metals recovered after the extraction step are generally
in the form of a salt or oxide. The preparation of the catalytic
solutions in order to produce organic or aqueous solutions is known
to the skilled person and has been described in the hydroconversion
section. The preparation of the catalytic solutions primarily
involves the metals molybdenum and nickel; vanadium is generally
upcycled outside the process as vanadium pentoxide, or in
combination with iron to produce ferrovanadium.
[0074] The degree of recovery of metals re-used as a catalyst for
the slurry hydroconversion process or for the vanadium is at least
50% by weight, preferably at least 65% by weight and more generally
70% by weight.
DESCRIPTION OF FIGURES
[0075] The following figures present advantageous embodiments of
the invention. The unit and the process of the invention will
essentially be described. The operating conditions described above
will not be reiterated.
[0076] FIG. 1 shows a process for the hydroconversion of heavy oil
feedstocks integrating a slurry technique without metals
recovery;
[0077] FIG. 2 describes a process for the hydroconversion of heavy
oil feedstocks in accordance with the invention, integrating a
one-step liquid/liquid extraction;
[0078] FIG. 3 describes a process for the hydroconversion of heavy
oil feedstocks in accordance with the invention, integrating a
two-step liquid/liquid extraction.
[0079] In FIG. 1, the feedstock 1 supplies the catalytic slurry
hydroconversion section A. This catalytic slurry hydroconversion
section is constituted by a preheating furnace for the feedstock 1
and hydrogen 2 and a reaction section constituted by one or more
reactors disposed in series and/or in parallel, depending on the
capacity required. The catalyst 4 or its precursor is also
injected, as well as the optional additive 3. The catalyst 4 is
held in suspension in the reactor, moves from bottom to top of the
reactor with the feedstock, and is evacuated with the effluent. The
effluent 5 obtained from the hydroconversion is directed to a high
pressure high temperature separation section B which can be used to
separate a converted fraction in the gaseous state 6, termed the
light fraction, and a residual unconverted liquid/solid fraction 8.
The light fraction 6 may be directed to a hydrotreatment and/or
hydrocracking section C. An external cut 7, generally from another
process in the refinery or possibly from outside the refinery, may
be supplied before the hydrotreatment and/or hydrocracking. The
residual unconverted fraction 8 containing the catalyst and a
fraction of the solid particles used as an optional additive and/or
formed during the reaction is directed to a fractionation step D.
The fractionation step D is preferably a vacuum distillation that
can be used to concentrate the vacuum residue 10, which is rich in
metals, at the bottom of the column and to recover one or more
effluents 9 from the head of the column In this layout for re-using
a heavy feedstock by a traditional slurry hydroconversion process,
the vacuum residue 10 which is rich in metals is re-used as a fuel
with a very high viscosity or as a solid fuel after pelletization,
for example to produce heat and electricity on site or offsite or
as a cement-works fuel. A priori, the metals are not recovered. A
small portion of the effluent or effluents 9 thus produced is/are
normally directed via the line 24 to the slurry hydroconversion
unit A where they can be recycled directly to the reaction zone, or
they may be used in the preparation of catalytic precursors before
injection into the feedstock 1; another part may be sent to the
hydrotreatment and/or hydrocracking unit C via the line 25 as a
mixture with the effluents 6 and/or 7 in equal or different
proportions as a function of the quality of the products
obtained.
[0080] In FIG. 2, the steps (and references) for the
hydroconversion, HPHT separation, hydrotreatment and/or
hydrocracking and vacuum distillation are identical to FIG. 1. The
vacuum residue 10 withdrawn from the bottom of the vacuum
distillation D is directed to a liquid/liquid type extraction step
E to concentrate the effluent 10. This extraction step E is carried
out in one step and employs a solvent 11 of the aromatic and/or
naphtheno-aromatic and/or polar type. The raffinate 12 leaving the
extraction unit after evaporation of the solvent is preferably
mixed, via the line 27, with the hydrocarbon feedstock 1 upstream
of the slurry hydroconversion section A, or mixed via the line 28
with the effluent 6 and/or 7 upstream of the hydrotreatment and/or
hydrocracking section C. The extract 13, which is highly
concentrated in metals, is directed to a step for reduction of the
organic phase by moderate temperature combustion F in order to
concentrate the metals substantially without notable loss by
vaporization and/or sublimation into fumes. The gaseous effluent
from combustion 14 requires purification steps (not shown) in order
to reduce the emissions of sulphur-containing and
nitrogen-containing compounds into the atmosphere. The product 15
from the combustion F is a mineral phase containing all or nearly
all of the metallic elements contained in the extract 13 in the
form of ash. The product 15 described below is sent to a step for
the extraction of metals G in which the metals are separated from
each other in one or more sub step(s). The effluent 16 from the
extraction G is composed of a molybdenum type metal in the form of
a salt or oxide. This effluent 16 is then directed to a step H for
the preparation of an organic or aqueous solution based on
molybdenum 18 identical to the catalyst 4 or to its precursor
recycled in part or in its entirety to the slurry hydroconversion
step A via the line 40. The effluent 17 from the extraction G is
composed of a nickel type metal in the form of a salt or oxide.
This effluent 17 is then directed to a step I for the preparation
of an organic or aqueous solution based on nickel 19 identical to
the catalyst 4 or to its precursor recycled in part or in its
entirety to the slurry hydroconversion step A via the line 41. The
effluent 20 from the extraction G is composed of a vanadium type
metal in the form of a salt or oxide. This effluent 20 may be
upcycled, for example as vanadium pentoxide, or in combination with
iron, to produce ferrovanadium.
[0081] In FIG. 3, the steps (and references) for the
hydroconversion, HPHT separation, hydrotreatment and/or
hydrocracking and vacuum distillation are identical to FIG. 1. The
vacuum residue 10 withdrawn from the bottom of the vacuum
distillation D is directed to a liquid-liquid type extraction step
E1 to concentrate the vacuum residue 10. In this implementation,
the extraction step is carried out in two steps, E1 and E2. The
first step E1 is carried out using a solvent 11, which is
preferably aromatic and/or naphtheno-aromatic and/or polar. The
raffinate 12 is sent to the second liquid-liquid extraction E2.
Step E2 is carried out using a paraffinic type solvent 21. The
raffinate 22 leaving the second extraction step, which contains no
asphaltenes, may then be mixed with the effluent 6 and/or 7 via the
line 30 upstream of the hydrotreatment and/or hydrocracking section
C, while the extract 23 containing very polar resins and
asphaltenes is recycled via the line 32 to the slurry
hydroconversion section A, as a mixture with the feedstock 1. The
extract 13 from the first liquid-liquid extraction step E1, with a
high concentration of metals, is directed to a step for reduction
of the organic phase by low temperature combustion F in order to
concentrate the metals substantially, without substantial loss by
vaporization and/or sublimation into fumes. The gaseous effluent 14
from the combustion necessitates purification steps in order to
reduce the emission of sulphur-containing and nitrogen-containing
compounds into the atmosphere (not shown). The product 15 from
combustion F is a mineral phase containing all or nearly all of the
metallic elements contained in the extract 13, in the form of ash.
The product 15 described below is sent to a metals extraction step
G in which the metals are separated from each other into one or
more sub step(s). The effluent 16 from the extraction G is composed
of a molybdenum type metal in the form of a salt or oxide. This
effluent 16 is then directed towards a step H for the preparation
of an organic or aqueous solution based on molybdenum 18 identical
to the catalyst 4 or to its precursor recycled in its entirety or
in part to the slurry hydroconversion step A via the line 40. The
effluent 17 from extraction G is composed of a nickel type metal in
the form of a salt or oxide. This effluent 17 is then directed to a
step I for the preparation of an organic or aqueous solution based
on nickel 19 identical to the catalyst 4 or to its precursor
recycled in part or completely to the slurry hydroconversion step A
via the line 41. The effluent 20 from the extraction G is composed
of a vanadium type metal in the salt or oxide form.
[0082] In the preferred case of a slurry hydroconversion using a
catalyst based on molybdenum and nickel, the hydroconversion
employs a finely dispersed nickel and molybdenum type catalyst in
respective concentrations of 160 ppm by weight and 600 ppm by
weight under hydrogen pressure. Assuming that the industrial unit
has a capacity of 50000 barrels per day and a 90% per annum usage,
the quantity of nickel and molybdenum consumed per annum is thus
0.4 and 1.6 t/year respectively. Assuming the price of nickel is 25
k $/t and of molybdenum is 60 k $/t, representative of the average
prices observed on the metals market over the last 5 years, the
operating cost is 100 million dollars per annum.
[0083] The process of the invention can be used to upgrade a large
fraction of the metals nickel and molybdenum present in the
unconverted fraction of the effluent from slurry hydroconversion.
The degree of recovery of metals re-used as a catalyst for the
slurry hydroconversion process is at least 50% by weight,
preferably at least 65% by weight, and more generally 70% by
weight. This recycling of metals can thus be employed to reduce the
operating cost of 100 million dollars per annum to 30 million
dollars per annum. This therefore saves 70 million dollars per
annum, which can initially be used to offset the additional
investment for recovery of these metals. Furthermore, vanadium
present in the heavy feedstock in an amount of 400 ppm by weight
may be upcycled as ferrovanadium. Assuming a level of recovery of
at least 50% by weight, preferably at least 65% by weight, and more
generally 70% by weight, assuming an average observed cost of 40 k
$/t on the metals market over the last 5 years, sales of vanadium
can be estimated at 12 million dollars per annum. These sales can
also initially be used to offset the supplemental investment
required for recovery of these metals.
[0084] Recovering these metals in the residual unconverted fraction
can be used to reduce the overall quantity of nickel and molybdenum
used and to thereby reduce the environmental impact of the slurry
hydroconversion process. Assuming a recovery of 70% by weight of
metals present at the inlet to the reaction zone, the quantity of
makeup catalyst is reduced to 0.1 t/year for nickel and 0.5 t/year
for molybdenum, as opposed to 0.4 t/year and 1.6 t/year.
* * * * *