U.S. patent application number 16/001445 was filed with the patent office on 2018-10-04 for integrated enhanced solvent deasphalting and coking process to produce petroleum green coke.
The applicant listed for this patent is Saudi Arabian Oil Company. Invention is credited to Omer Refa KOSEOGLU.
Application Number | 20180282640 16/001445 |
Document ID | / |
Family ID | 56609980 |
Filed Date | 2018-10-04 |
United States Patent
Application |
20180282640 |
Kind Code |
A1 |
KOSEOGLU; Omer Refa |
October 4, 2018 |
INTEGRATED ENHANCED SOLVENT DEASPHALTING AND COKING PROCESS TO
PRODUCE PETROLEUM GREEN COKE
Abstract
An integrated process is provided for producing deasphalted oil,
high quality petroleum green coke and liquid coker products. An
enhanced solvent deasphalting process is used to treat the
feedstock to reduce the level of asphaltenes, N, S and metal
contaminants and produce a deasphalted oil with reduced
contaminants. A coking process is integrated to produce liquid and
gas coking unit products, and petroleum green coke.
Inventors: |
KOSEOGLU; Omer Refa;
(Dhahran, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company |
Dhahran |
|
SA |
|
|
Family ID: |
56609980 |
Appl. No.: |
16/001445 |
Filed: |
June 6, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15220896 |
Jul 27, 2016 |
9994780 |
|
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16001445 |
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62197342 |
Jul 27, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 53/08 20130101;
C10B 55/00 20130101; C10G 55/04 20130101; C10G 2300/206 20130101;
C10G 9/005 20130101; C10G 25/00 20130101; C10G 25/12 20130101; C10G
29/20 20130101; C10G 2300/202 20130101; C10B 57/08 20130101 |
International
Class: |
C10G 55/04 20060101
C10G055/04; C10G 9/00 20060101 C10G009/00; C10G 53/08 20060101
C10G053/08; C10G 29/20 20060101 C10G029/20; C10G 25/12 20060101
C10G025/12; C10B 57/08 20060101 C10B057/08; C10B 55/00 20060101
C10B055/00; C10G 25/00 20060101 C10G025/00 |
Claims
1. An integrated process that operates within the battery limits of
a refinery for conversion of a heavy hydrocarbon feedstock
containing asphaltenes, sulfur-containing and nitrogen-containing
polynuclear aromatic molecules comprising: a. mixing the heavy
hydrocarbon feedstock, paraffinic solvent and an effective quantity
of solid adsorbent material at a temperature and pressure that are
below the critical pressure and temperature of the solvent to
promote solvent-flocculation of solid asphaltenes and for a time
sufficient to adsorb the sulfur-containing and nitrogen-containing
polynuclear aromatic molecules on the solid adsorbent material; b.
passing the heavy hydrocarbon feedstock, paraffinic solvent and
solid adsorbent material to a first separation vessel; c.
separating a solid phase comprising asphaltenes and solid adsorbent
material from a liquid phase comprising deasphalted oil and
paraffinic solvent; d. passing the solid phase to a filtration
vessel with an aromatic and/or polar solvent to desorb the adsorbed
contaminants and to recover regenerated solid adsorbent material;
e. passing the liquid phase to a second separation vessel to
separate deasphalted oil and paraffinic solvent, and optionally
recycling at least a portion of the separated paraffinic solvent to
step (a); f. passing deasphalted oil from the second separation
vessel to a coking unit; g. thermally cracking the deasphalted oil
in a coking unit to produce liquid and gas coking products; and h.
recovering petroleum green coke from the coking unit.
2. The process of claim 1 wherein the coke has bulk density in the
range 720-800 Kg/m.sup.3.
3. The process of claim 1 wherein the coke contains sulfur in the
range 1 to 2.5 W %.
4. The process of claim 1 wherein the coke contains nickel up to
200 ppmw.
5. The process of claim 1 wherein the coke contains vanadium up to
350 ppmw.
6. The process of claim 1 wherein the coke contains volatile
combustible material up to 0.5 W %.
7. The process of claim 1 wherein the deasphalted oil is heated in
a furnace of the coking unit to a temperature in the range of
480.degree. C. to 530.degree. C.
8. The process of claim 1 wherein the coker unit is a delayed coker
unit.
9. The process of claim 8, wherein the coker unit is configured
with two or more parallel drums and is operated in a swing mode,
and wherein the process is continuous.
10. The process of claim 1, wherein the petroleum green coke
recovered from the coker drum effective raw material for
calcination into anode grade coke (sponge) or electrode grade coke
(needle).
11. An integrated process that operates within the battery limits
of a refinery for conversion of a feedstock containing hydrocarbons
having a boiling point greater than 300.degree. C. that includes
solvent deasphalting and delayed coking, the process comprising: a.
introducing a heavy hydrocarbon feedstock containing asphaltenes
into a mixing vessel with a C.sub.3 to C.sub.7 paraffinic solvent
and a solid adsorbent material; b. mixing the heavy hydrocarbon
feedstock containing asphaltenes, paraffinic solvent and solid
adsorbent material in the mixing vessel at a temperature and
pressure that are below the critical pressure and temperature of
the solvent in order to solvent-flocculate solid asphaltenes
particles which include sulfur-containing and nitrogen-containing
polynuclear aromatic molecules; c. maintaining the heavy
hydrocarbon feedstock, solvent-flocculated asphaltenes, paraffinic
solvent, and adsorbent material in the mixing vessel for a time
sufficient to adsorb the sulfur-containing and nitrogen-containing
polynuclear aromatic molecules on the adsorbent material; d.
separating the solid phase comprising asphaltenes and adsorbent
material from the liquid phase comprising deasphalted oil and
paraffinic solvent; e. passing the solid phase comprising
asphaltenes and adsorbent material to a filtration vessel with an
aromatic or polar solvent to desorb the adsorbed sulfur-containing
and nitrogen-containing compounds and to recover the solid asphalt
phase and regenerated adsorbent material; f. passing the aromatic
or polar solvent mixture containing desorbed sulfur-containing and
nitrogen-containing polynuclear aromatic molecules to a
fractionator to recover the aromatic or polar solvent; g. passing
the liquid phase comprising deasphalted oil and paraffinic solvent
to a separation vessel to separate the deasphalted oil and
paraffinic solvent and recovering the solvent for recycling to the
mixing vessel; h. heating the deasphalted oil to delayed coking
temperatures in a coking unit furnace and passing the heated
deasphalted oil to a delayed coking drum; i. recovering a delayed
coking product stream from the delayed coking drum comprising
liquid and gas coking products; and j. recovering petroleum green
coke from the delayed coking drum.
12. The process of claim 11 wherein the coke has bulk density in
the range 720-800 Kg/m.sup.3.
13. The process of claim 11 wherein the coke contains sulfur in the
range 1 to 2.5 W %.
14. The process of claim 11 wherein the coke contains nickel up to
200 ppmw.
15. The process of claim 11 wherein the coke contains vanadium up
to 350 ppmw.
16. The process of claim 11 wherein the coke contains volatile
combustible material up to 0.5 W %.
17. The process of claim 11 wherein the deasphalted oil is heated
in a furnace of the coking unit to a temperature in the range of
480.degree. C. to 530.degree. C.
18. The process of claim 11 wherein the coker unit is a delayed
coker unit.
19. The process of claim 18, wherein the coker unit is configured
with two or more parallel drums and is operated in a swing mode,
and wherein the process is continuous.
20. The process of claim 11, wherein the petroleum green coke
recovered from the coker drum effective raw material for
calcination into anode grade coke (sponge) or electrode grade coke
(needle).
Description
RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 15/220,896 filed on Jul. 27, 2016, which
claims the benefit of priority of U.S. Provisional Patent
Application No. 62/197,342 filed Jul. 27, 2015, which are both
incorporated by reference herein.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to integrated enhanced solvent
deasphalting and delayed coking processes for production of liquid
and gas coking unit products, high quality petroleum green coke,
and asphalt.
Description of Related Art
[0003] Crude oils contain heteroatomic molecules, including
polyaromatic molecules, with heteroatomic constituents such as
sulfur, nitrogen, nickel, vanadium and others in quantities that
can adversely affect the refinery processing of the crude oil
fractions. Light crude oils or condensates have sulfur
concentrations as low as 0.01 percent by weight (W %). In contrast,
heavy crude oils and heavy petroleum fractions have sulfur
concentrations as high as 5-6 W %. Similarly, the nitrogen content
of crude oils can be in the range of 0.001-1.0 W %. These
impurities must be removed during refining to meet established
environmental regulations for the final products (for instance,
gasoline, diesel, fuel oil), or for the intermediate refining
streams that are to be processed for further upgrading, such as
isomerization reforming. Contaminants such as nitrogen, sulfur and
heavy metals are known to deactivate or poison catalysts.
[0004] In a typical refinery, crude oil is first fractionated in
the atmospheric distillation column to separate sour gas including
methane, ethane, propane, butanes and hydrogen sulfide, naphtha
(36-180.degree. C.), kerosene (180-240.degree. C.), gas oil
(240-370.degree. C.) and atmospheric residue, which are the
hydrocarbon fractions boiling above 370.degree. C. The atmospheric
residue from the atmospheric distillation column is either used as
fuel oil or sent to a vacuum distillation unit, depending upon the
configuration of the refinery. Principal products from the vacuum
distillation are vacuum gas oil, comprising hydrocarbons boiling in
the range 370-520.degree. C., and vacuum residue, comprising
hydrocarbons boiling above 520.degree. C.
[0005] Naphtha, kerosene and gas oil streams derived from crude
oils or other natural sources, such as shale oils, bitumens and tar
sands, are treated to remove the contaminants, such as sulfur, that
exceed the specification set for the end product(s). Hydrotreating
of these individual fractions is the most common refining
technology used to remove these contaminants. Vacuum gas oil is
processed in a hydrocracking unit to produce naphtha and diesel, or
in a fluid catalytic cracking (FCC) unit to produce mainly
gasoline, light cycle oil (LCO) and heavy cycle oil (HCO) as
by-products, the former being used as a blending component in
either the diesel pool or in fuel oil, the latter being sent
directly to the fuel oil pool.
[0006] Heavier fractions from the atmospheric and vacuum
distillation units can contain asphaltenes. Asphaltenes are solid
in nature and comprise polynuclear aromatics, smaller aromatics and
resin molecules. The chemical structures of asphaltenes are complex
and include polynuclear hydrocarbons having molecular weights up to
20,000 joined by alkyl chains. Asphaltenes also include nitrogen,
sulfur, oxygen and metals such as nickel and vanadium. They are
present in crude oils and heavy fractions in varying quantities.
Asphaltenes exist in small quantities in light crude oils, or not
at all in all condensates or lighter fractions. However, they are
present in relatively large quantities in heavy crude oils and
petroleum fractions. Asphaltenes have been defined as the component
of a heavy crude oil fraction that is precipitated by addition of a
low-boiling paraffin solvent, or paraffin naphtha, such as normal
pentane, and is soluble in carbon disulfide and benzene. In certain
methods their concentrations are defined as the amount of
asphaltenes precipitated by addition of an n-paraffin solvent to
the feedstock, for instance, as prescribed in the Institute of
Petroleum Method IP-143. The heavy fraction can contain asphaltenes
when it is derived from carbonaceous sources such as petroleum,
coal or oil shale. There is a close relationship between
asphaltenes, resins and high molecular weight polycyclic
hydrocarbons. Asphaltenes are hypothesized to be formed by the
oxidation of natural resins. The hydrogenation of asphaltic
compounds containing resins and asphaltenes produces heavy
hydrocarbon oils, that is, resins and asphaltenes are hydrogenated
into polycyclic aromatic or hydroaromatic hydrocarbons. They differ
from polycyclic aromatic hydrocarbons by the presence of oxygen and
sulfur in varied amounts.
[0007] Upon heating above about 300-400.degree. C., asphaltenes
generally do not melt but rather decompose, forming carbon and
volatile products. They react with sulfuric acid to form sulfonic
acids, as might be expected on the basis of the polyaromatic
structure of these components. Flocs and aggregates of asphaltenes
will result from the addition of non-polar solvents, for instance,
paraffinic solvents, to crude oil and other heavy hydrocarbon oil
feedstocks.
[0008] Therefore, it is clear that significant measures must be
taken during processing of crude oils and heavy fractions to deal
with asphaltenes. Failure to do so interferes with subsequent
refining operations.
[0009] There are several processing options for the heavy fractions
such as vacuum residue, including hydroprocessing, coking,
visbreaking, gasification and solvent deasphalting. In the solvent
deasphalting process, the asphalt fraction, for instance, having
6-8 W % hydrogen, is separated from the vacuum residue by contact
with a paraffinic solvent (for instance, C.sub.3-C.sub.7) at or
below the solvents' critical temperatures and pressures. The
deasphalted oil, for instance, having 9-11 W % hydrogen, is
characterized as a heavy hydrocarbon fraction that is free of
asphaltenes and is typically passed to other conversion units such
as a hydrocracking unit or a fluid catalytic cracking unit to
produce lighter, more valuable fractions.
[0010] Deasphalted oil contains a high concentration of
contaminants such as sulfur, nitrogen and carbon residue which is
an indicator of the coke forming properties of heavy hydrocarbons
and defined as micro-carbon residue (MCR), Conradson carbon residue
(CCR) or Ramsbottom carbon residue (RCR). MCR, RCR, CCR are
determined by ASTM Methods D-4530, D-524 and D-189, respectively.
In these tests, the residue remaining after a specified period of
evaporation and pyrolysis is expressed as a percentage of the
original sample. For example, deasphalted oil obtained from vacuum
residue of an Arabian crude oil contains 4.4 W % of sulfur, 2,700
ppmw of nitrogen, and 11 W % of MCR. In another example, a
deasphalted oil of Far East origin contains 0.14 W % sulfur, 2,500
ppmw of nitrogen, and 5.5 W % of CCR. These high levels of
contaminants, and particularly nitrogen, in the deasphalted oil
limit conversion in hydrocracking or FCC units. The adverse effects
of nitrogen and micro-carbon residue in FCC operations have been
reported to be as follows: 0.4-0.6 W % higher coke yield, 4-6 V %
less gasoline yield and 5-8 V % less conversion per 1000 ppmw of
nitrogen. (See Sok Yui et al., Oil and Gas Journal, Jan. 19, 1998.)
Similarly, coke yield is 0.33-0.6 W % more for each one W % of MCR
in the feedstock. In hydrocracking operations, the catalyst
deactivation is a function of the feedstock nitrogen and MCR
content. The catalyst deactivation is about 3-5.degree. C. per 1000
ppmw of nitrogen and 2-4.degree. C. for each one W % of MCR.
[0011] It has been established that organic nitrogen is the most
detrimental catalyst poison present in the hydrocarbon streams from
the sources identified above. Organic nitrogen compounds poison the
active catalytic sites resulting in catalyst deactivation, which in
turn reduces catalyst cycle process length, catalyst lifetime,
product yields, and product quality, and also increases the
severity of operating conditions and the associated cost of plant
construction and operations. Removing nitrogen, sulfur, metals and
other contaminants that poison catalysts will improve refining
operations and will have the advantage of permitting refiners to
process more and/or heavier feedstocks.
[0012] In coking processes, heavy feeds are thermally decomposed to
produce coke, gas and liquid product streams of varying boiling
ranges. Coke is generally treated as a low value by-product. It is
removed from the units and can be recovered for various uses
depending on its quality.
[0013] The use of heavy crude oils having high metals and sulfur
content as an initial feed is of interest due to its lower market
value. Traditional coking processes using these feeds produce coke
which has substantial sulfur and metal content. The goal of
minimizing air pollution is a further incentive for treating
residuum in a coking unit since the gases and liquids produced
contain sulfur in a form that can be relatively easily removed.
[0014] While individual and discrete solvent deasphalting and
coking operations are well developed and suitable for their
intended purposes, there remains a need for improved processes
using heavy feeds having asphaltenes, N, S and metal
contaminants.
SUMMARY OF THE INVENTION
[0015] An integrated system and process is provided for producing
liquid coker products, high quality petroleum green coke, and
asphalt. An enhanced solvent deasphalting process is used to treat
the feedstock to reduce the level of asphaltenes, N, S and metal
contaminants and produce a deasphalted oil with reduced
contaminants. A coking process is integrated so that the
deasphalted oil with reduced contaminants is the coking unit
feedstock, facilitating production coker liquid and gas fractions
and recovery of petroleum green coke.
[0016] In certain embodiments of the integrated process, which can
be carried out within refinery limits, use of the deasphalted oil
intermediate stream as feed to the coking unit enables recovery of
high quality petroleum coke that can be used as raw material to
produce low sulfur marketable grades of coke including anode grade
coke (sponge) and/or electrode grade coke (needle).
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention will be described in further detail below and
with reference to the attached drawings in which the same or
similar elements are referred to by the same number, and where:
[0018] FIG. 1 is a process flow diagram of one embodiment of an
integrated enhanced solvent deasphalting and coking process;
and
[0019] FIG. 2 is a process flow diagram of a second embodiment of
an integrated enhanced solvent deasphalting and coking process.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The process and system herein facilitates production of
coker liquid and gas fractions and petroleum green coke from heavy
crude oils or fractions having asphaltenes, metal and sulfur
content that typically has lower market value compared to light
crude oils or fractions. Enhanced solvent deasphalting processes,
such as those described in commonly owned U.S. Pat. No. 7,566,394,
which is incorporated by reference herein in its entirety, are used
to process the heavy crude oils or fractions. The deasphalted oil
is thermally cracked in a coking unit, such as a delayed coking
unit. In contrast to typical coking operations in which the coke is
low market value by-product, in the integrated process herein,
using as an initial feed heavy crude oils or fractions having
reduced asphaltenes, metal and sulfur content, petroleum green coke
recovered from the coker unit drums is low in sulfur and metals.
The recovered petroleum green coke can be used as high quality, low
sulfur and metal content fuel grade (shot) coke, and/or a raw
material for production of marketable grades of coke including
anode grade coke (sponge) and/or electrode grade coke (needle).
[0021] The deasphalted oil is thermally cracked in a coking unit,
such as a delayed coking unit. In contrast to typical coking
operations in which the coke is low market value by-product, in the
integrated process herein, high quality petroleum green coke
recovered from the coker unit drums is low in sulfur and metals.
The recovered high quality petroleum green coke can be used as high
quality, low sulfur and metal content fuel grade (shot) coke,
and/or a raw material for production of low sulfur and metal
content marketable grades of coke including anode grade coke
(sponge) and/or electrode grade coke (needle). Table 1 shows the
properties of these types of coke. In accordance with certain
embodiments of the process herein, calcination of the petroleum
green coke recovered from the coking drums produces sponge and/or
needle grade coke, for instance, suitable for use in the aluminum
and steel industries. Calcination occurs by thermal treatment to
remove moisture and reduce the volatile combustible matter.
TABLE-US-00001 TABLE 1 Fuel Calcined Calcined Property Units Coke
Sponge Coke Needle Coke Bulk Density Kg/m.sup.3 880 720-800 670-720
Sulfur W % (max) 3.5-7.5 1.0-3.5 0.2-0.5 Nitrogen ppmw (max) 6,000
-- 50 Nickel ppmw (max) 500 200 7 Vanadium ppmw 150 350 -- Volatile
W % (max) 12 0.5 0.5 Combustible Material Ash Content W % (max)
0.35 0.40 0.1 Moisture Content W % (max) 8-12 0.3 0.1 Hardgrove W %
35-70 60-100 -- Grindability Index (HGI) Coefficient of .degree. C.
-- -- 1-5 thermal expansion, E + 7
[0022] As used herein, "high quality petroleum green coke" refers
to petroleum green coke recovered from a coker unit that when
calcined, possesses the properties as in Table 1, and in certain
embodiments possessing the properties in Table 5 concerning
calcined sponge coke or calcined needle coke identified in Table
1.
[0023] As used herein, a process that operates "within the battery
limits of a refinery" refers to a process that operates with a
battery of unit operations along with their related utilities and
services, distinguished from a process whereby effluent from a unit
operation is collected, stored and/or transported to a separate
unit operations or battery of unit operations.
[0024] In one embodiment, of a process herein, which can be carried
out within the battery limits of a refinery and on a continuous or
semi-continuous basis, a heavy hydrocarbon feedstock is subjected
to enhanced solvent deasphalting in the presence of an effective
quantity of solid adsorbent material to adsorb sulfur-containing
compounds or nitrogen-containing polynuclear aromatic molecules
concurrently with solvent assisted removal of asphaltenes.
Contaminants are adsorbed and the solvent and deasphalted oil
fraction is removed as a separate stream from which the solvent is
recovered for recycling. The adsorbent having contaminants adsorbed
thereon and the asphalt bottoms are mixed with aromatic and/or
polar solvents to desorb the contaminants and washed as necessary
to clean the adsorbent, which can preferably be recovered and
recycled. The solvent-asphalt mixture is sent to a fractionator for
recovery and recycling of the aromatic or polar solvent. Bottoms
from the fractionator include the desorbed contaminants are further
processed as appropriate. The deasphalted oil having reduced
contaminants is thermally cracked in a coking unit, such as a
delayed coking unit, and coker liquid and gas products are
recovered, along with high quality petroleum green coke.
[0025] In another embodiment, a heavy hydrocarbon feedstock is
subjected to a first separation step in a solvent deasphalting
process to produce a primary deasphalted oil phase and discharge a
primary asphalt phase. An effective quantity of solid adsorbent
material mixed with the primary deasphalted oil phase, which
contains the deasphalted oil and paraffinic solvent.
Sulfur-containing and/or nitrogen-containing polynuclear aromatic
molecules in the deasphalted oil are adsorbed by the solid
adsorbent material. The paraffinic solvent is separated from the
deasphalted oil and adsorbent material, and the solvent is
recovered for recycling. A slurry containing the adsorbent having
contaminants adsorbed thereon and deasphalted oil is mixed with
aromatic and/or polar solvents to desorb the contaminants, and
washed as necessary to clean the adsorbent, which can preferably be
recovered and recycled. The deasphalted oil mixture is sent to a
fractionator for recovery and recycling of the aromatic and/or
polar solvents. The deasphalted oil having reduced contaminants is
thermally cracked in a coking unit, such as a delayed coking unit,
and coker liquid and gas products are recovered, along with high
quality petroleum green coke.
[0026] The solid adsorbent material can be selected from the group
consisting of clay (for instance, attapulgus clay), silica,
alumina, silica-alumina, titania-silica, activated carbon,
molecular sieves, fresh zeolitic catalyst materials, used zeolitic
catalyst materials, and combinations comprising one or more of the
foregoing. The material is provided in particulate form of suitable
dimension, such as granules, extrudates, tablets, spheres, or
pellets of a size in the range of 4-60 mesh. The quantity of the
solid adsorbent material used in the embodiments herein is about
0.1:1 to 20:1 W/W, and preferably about 1:1 to 10:1 W/W
(feed-to-adsorbent).
[0027] In the herein embodiments, the coking unit is integrated
with an enhanced solvent deasphalting process to produce coker
liquid and gas products and recover high quality petroleum green
coke suitable for production of marketable coke from the starting
heavy hydrocarbon feedstock. Advantageously, the integrated
processes herein facilitate recovery of such high quality petroleum
green coke since the feed to the delayed coking unit has desirable
qualities. In particular, the deasphalted oil stream in the present
process is characterized by a sulfur content of generally less than
about 3.5 wt %, in certain embodiments less than about 2.5 wt % and
in further embodiments less than about 1 wt %, and a metals content
of less than about 700 ppmw, in certain embodiments less than about
400 ppmw and in further embodiments less than about 100 ppmw. Use
of this feedstream results in a high quality petroleum coke product
that can be used as raw material to produce low sulfur marketable
grades of coke including anode grade coke (sponge) and/or electrode
grade coke (needle), in an efficient integrated process.
[0028] Coking is a carbon rejection process in which low-value
atmospheric or vacuum distillation bottoms are converted to lighter
products which in turn can be hydrotreated to produce
transportation fuels, such as gasoline and diesel. Conventionally,
coking of residuum from heavy high sulfur, or sour, crude oils is
carried out primarily as a means of utilizing such low value
hydrocarbon streams by converting part of the material to more
valuable liquid and gas products. Typical coking processes include
delayed coking and fluid coking.
[0029] In the delayed coking process, feedstock is typically
introduced into a lower portion of a coking feed fractionator where
one or more lighter materials are recovered as one or more top
fractions, and bottoms are passed to a coking furnace. In the
furnace bottoms from the fractionator and optionally heavy recycle
material are mixed and rapidly heated in a coking furnace to a
coking temperature, for instance, in the range of 480.degree. C. to
530.degree. C., and then fed to a coking drum. The hot mixed fresh
and recycle feedstream is maintained in the coke drum at coking
conditions of temperature and pressure where the feed decomposes or
cracks to form coke and volatile components.
[0030] Table 2 provides delayed coker operating conditions for
production of certain grades of petroleum green coke in the process
herein:
TABLE-US-00002 TABLE 2 Variable Unit Fuel Coke Sponge Coke Needle
Coke Temperature .degree. C. 488-500 496-510 496-510 Pressure
Kg/cm.sup.2 1 1.2-4.1 3.4-6.2 Recycle Ratio % 0-5 0-50 60-120
Coking time hours 9-18 24 36
[0031] The volatile components are recovered as vapor and
transferred to a coking product fractionator. One or more heavy
fractions of the coke drum vapors can be condensed, for instance
quenching or heat exchange. In certain embodiments the contact the
coke drum vapors are contacted with heavy gas oil in the coking
unit product fractionator, and heavy fractions form all or part of
a recycle oil stream having condensed coking unit product vapors
and heavy gas oil. In certain embodiments, heavy gas oil from the
coking feed fractionator is added to the flash zone of the
fractionator to condense the heaviest components from the coking
unit product vapors.
[0032] Coking units are typically configured with two parallel
drums and operated in a swing mode. When the coke drum is full of
coke, the feed is switched to another drum, and the full drum is
cooled. Liquid and gas streams from the coke drum are passed to a
coking product fractionator for recovery. Any hydrocarbon vapors
remaining in the coke drum are removed by steam injection. The coke
remaining in the drum is typically cooled with water and then
removed from the coke drum by conventional methods, for instance,
using hydraulic and/or mechanical techniques to remove green coke
from the drum walls for recovery.
[0033] Recovered petroleum green coke is suitable for production of
marketable coke, and in particular anode (sponge) grade coke
effective for use in the aluminum industry, or electrode (needle)
grade coke effective for use in the steel industry. In the delayed
coking production of high quality petroleum green coke, unconverted
pitch and volatile combustible matter content of the green coke
intermediate product subjected to calcination should be no more
than about 15 percent by weight, and preferably in the range of 6
to 12 percent by weight.
[0034] In certain embodiments, one or more catalysts and additives
can be added to the fresh feed and/or the fresh and recycle oil
mixture prior to heating the feedstream in the coking unit furnace.
The catalyst can promote cracking of the heavy hydrocarbon
compounds and promote formation of the more valuable liquids that
can be subjected to hydrotreating processes downstream to form
transportation fuels. The catalyst and any additive(s) remain in
the coking unit drum with the coke if they are solids, or are
present on a solid carrier. If the catalyst(s) and/or additive(s)
are soluble in the oil, they are carried with the vapors and remain
in the liquid products. Note that in the production of high quality
petroleum green coke, catalyst(s) and/or additive(s) which are
soluble in the oil can be favored in certain embodiments to
minimize contamination of the coke.
[0035] The feed to the embodiments of the enhanced solvent
deasphalting systems herein can be a heavy hydrocarbon stream such
as crude oils, bitumens, heavy oils, shale oils and refinery
streams that include atmospheric and vacuum residues, fluid
catalytic cracking slurry oils, coker bottoms, visbreaking bottoms
and coal liquefaction by-products and mixtures thereof having
asphaltenes, sulfur, nitrogen and polynuclear aromatic molecules,
for instance, that typically reduce the market value of the
material compared to similar streams having lesser quantities of
these constituents.
[0036] For the purpose of this simplified schematic illustrations
and description, the numerous valves, pumps, temperature sensors,
electronic controllers and the like that are customarily employed
in refinery operations and that are well known to those of ordinary
skill in the art are not shown.
[0037] Referring to FIG. 1, an embodiment of an integrated enhanced
solvent deasphalting and coking process and system is shown,
includes a mixing vessel 10, a first separation vessel 20, a
filtration vessel 30, a fractionator 40, a second separation vessel
50, a coking unit furnace 60, delayed coking drums 70a and 70b, and
a coking product fractionator 80.
[0038] In a process for producing high quality petroleum green coke
and coker liquid and gas products operation of a system according
to FIG. 1, a heavy hydrocarbon feedstream 2, a paraffinic solvent 4
and solid adsorbent slurry 6 having an effective quantity of solid
adsorbent material are introduced into the mixing vessel 10. Mixing
vessel 10 is equipped with suitable mixing means, for instance,
rotary stirring blades or paddles, which provide a gentle, but
thorough mixing of the contents.
[0039] The rate of agitation for a given vessel and mixture of
adsorbent, solvent and feedstock is selected so that there is
minimal, if any, attrition of the adsorbent granules or particles.
The mixing is continued for 30 to 150 minutes, the duration being
related to the components of the mixture.
[0040] The mixture of heavy oil 2, paraffinic solvent 4 and solid
adsorbent 6 is discharged through line 12 to a first separation
vessel 20 at a temperature and pressure that is below the critical
temperature and pressure of the solvent to separate the feed
mixture into an upper layer comprising light and less polar
fractions that are removed as stream 22 and bottoms comprising
asphaltenes and the solid adsorbent 24. A vertical flash drum can
be utilized for this separation step.
[0041] Conditions in the mixing vessel and first separation vessel
are maintained below the critical temperature and pressure of the
solvent. In certain embodiments the solvent selected for use in the
mixing vessel and first separation vessel in the enhanced solvent
deasphalting process herein is a C.sub.3 to C.sub.7 paraffinic
solvent. The following Table 3 provides critical temperature and
pressure data for C.sub.3 to C.sub.7 paraffinic solvents:
TABLE-US-00003 TABLE 3 Carbon Number Temperature, .degree. C.
Pressure, bar C.sub.3 97 42.5 C.sub.4 152 38.0 C.sub.5 197 34.0
C.sub.6 235 30.0 C.sub.7 267 27.5
[0042] The asphalt and adsorbent slurry 24 is mixed with an
aromatic and/or polar solvent stream 26 in a filtration vessel 30
to separate and clean the adsorbent material. The solvent stream 26
can include benzene, toluene, xylenes, tetrahydrofuran, methylene
chloride. Solvents can be selected based on their Hildebrand
solubility factors or on the basis of two-dimensional solubility
factors. The overall Hildebrand solubility parameter is a
well-known measure of polarity and has been tabulated for numerous
compounds. (See, for example, Journal of Paint Technology, Vol. 39,
No. 505, February 1967). The solvents can also be described by
two-dimensional solubility parameters, that is, the complexing
solubility parameter and the field force solubility parameter.
(See, for example, I. A. Wiehe, Ind. & Eng. Res., 34(1995),
661). The complexing solubility parameter component which describes
the hydrogen bonding and electron donor-acceptor interactions
measures the interaction energy that requires a specific
orientation between an atom of one molecule and a second atom of a
different molecule. The field force solubility parameter which
describes van der Waal's and dipole interactions measures the
interaction energy of the liquid that is not impacted by changes in
the orientation of the molecules.
[0043] In certain embodiments the polar solvent, or solvents, if
more than one is employed, used in filtration vessel 30 has an
overall solubility parameter greater than about 8.5 or a complexing
solubility parameter of greater than one and a field force
parameter value greater than 8. Examples of polar solvents meeting
the desired solubility parameter are toluene (8.91), benzene
(9.15), xylene (8.85), and tetrahydrofuran (9.52). Preferred polar
solvents for use in the practice of the invention are toluene and
tetrahydrofuran.
[0044] In certain embodiments, the adsorbent slurry and asphalt
mixture 24 is washed with two or more aliquots of the aromatic or
polar solvent 26 in the filtration vessel 30 in order to dissolve
and remove the adsorbed compounds. The clean solid adsorbent stream
38, is recovered and recycled to the mixing vessel 10, an asphalt
stream 36 is recovered, and spent adsorbent is discharged 34. A
solvent-asphalt mixture 32 is withdrawn from the filtering vessel
30 and sent to a fractionator 40 to separate the solvent from the
asphalt containing heavy polynuclear aromatic compounds which are
withdrawn as stream 42 for appropriate disposal. The clean aromatic
and/or polar solvent is recovered as stream 44 and recycled to
filtration vessel 30.
[0045] The recovered deasphalted oil and solvent stream from the
first separation vessel 22 is introduced into a second separation
vessel 50 maintained at an effective temperature and pressure to
separate solvent from the deasphalted oil, such as between the
solvent's boiling and critical temperature, under a pressure of
between one and three bars. The solvent stream 52 is recovered and
returned to the mixing vessel 10, in certain embodiments in a
continuous operation. The deasphalted oil stream 54 is discharged
from the bottom of the vessel 50.
[0046] In one example, analyses for sulfur using ASTM D5453,
nitrogen using ASTM D5291, and metals (nickel and vanadium) using
ASTM D3605 indicate that the oil has a greatly reduced level of
contaminants, that is, it contains no metals, and about 80 W % of
the nitrogen and 20-50 W % of the sulfur which were present in the
original feedstream have been removed.
[0047] A portion 55 (for instance, 10-100%) of the discharged
deasphalted oil stream 54 is processed a coking operation to
produce coker gas and liquid products and high quality petroleum
green coke. In certain embodiments, as shown in FIG. 1, a delayed
coking operation is used. The discharged deasphalted oil stream 55
is charged to a delayed coking furnace 60 where the contents are
rapidly heated to an effective coking temperature, such as the
range of about 480.degree. C. to 530.degree. C., and then fed to
delayed coking drum 70a or 70b. In certain embodiments, two or more
parallel coking drums 70a and 70b are provided and are operated in
swing mode, such that when one of the drums is filled with coke,
the deasphalted oil stream is transferred to the empty parallel
drum and coke, in certain embodiments anode grade coke, is
recovered from the filled drum 74. A liquid and gas delayed coker
product stream 72 is recovered from the coker drum 70a or 70b. Any
hydrocarbon vapors remaining in the coke drum can be removed by
steam injection.
[0048] The liquid and gas delayed coker product stream 72 is
introduced into a coking product stream fractionator where it is
fractionated to yield separate product streams that can include a
light gas stream 82, a coker naphtha stream 84, a light coker gas
oil stream 86 and a heavy coker gas oil stream 88. Optionally, all
or a portion of the heavy coker gas oil stream 88 is recycled to
the coking unit furnace 60.
[0049] The coke remaining in coker drum 70a or 70b is cooled, for
instance, water quenched, and removed from the coke drum as
recovered coke product 74. The coke can be removed by mechanical or
hydraulic operations. For instance, coke can be cut from the coke
drum with a high pressure water nozzle. According to the process
herein, the recovered coke is high quality petroleum green
coke.
[0050] Advantageously, the integrated process facilitates
production of high quality petroleum green coke from the coking
operation since the intermediate feed thereto, the
deasphalted/desulfurized oil stream, has desirable qualities, that
is, low content of asphaltenes and sulfur-containing and
nitrogen-containing polynuclear aromatics.
[0051] FIG. 2 depicts another embodiment of an integrated enhanced
solvent deasphalting and coking process and system. The system
includes a first separation vessel 120, a second separation vessel
150, a filtration vessel 130, a fractionator 140, a coking unit
furnace 160, delayed coking drums 170a and 170b, and a coking
product fractionator 180.
[0052] In a process for producing high quality petroleum green coke
and coker liquid and gas products operation of a system according
to FIG. 2, a heavy hydrocarbon feedstream 102 and a paraffinic
solvent 104 are introduced into a first separation zone 120 in
which asphalt is separated from the feedstream and discharged from
the first separation zone 120 as stream 124. Conditions in the
first separation vessel are maintained below the critical
temperature and pressure of the solvent. In certain embodiments the
solvent selected for use in the first separation vessel in the
enhanced solvent deasphalting process herein is a C.sub.3 to
C.sub.7 paraffinic solvent.
[0053] A combined deasphalted oil and solvent stream 122 is
discharged from the first separation zone 120 and mixed with an
effective quantity of solid adsorbent material 106.
[0054] The deasphalted oil, solvent, and solid adsorbent mixture is
passed to the second separation zone 150 where the mixture is
maintained at an effective temperature and pressure to separate
solvent from the deasphalted oil, such as between the solvent's
boiling and critical temperature, under a pressure of between one
and three bars. In addition, the mixture is maintained in the
second separation zone 150 for a time sufficient to adsorb on the
adsorbent material any remaining asphaltenes and/or
sulfur-containing polynuclear aromatic molecules and/or
nitrogen-containing polynuclear aromatic molecules. The solvent is
then separated and recovered from the deasphalted oil and adsorbent
material and recycled as stream 152 to the first separation zone
120.
[0055] A slurry 155 of deasphalted oil and adsorbent from the
second separation vessel 150 is mixed with an aromatic and/or polar
solvent stream 126 in a filtration vessel 130 to separate and clean
the adsorbent material. The solvent stream 126 can include benzene,
toluene, xylenes, tetrahydrofuran, methylene chloride. Solvents can
be selected based on their Hildebrand solubility factors or on the
basis of two-dimensional solubility factors as discussed above.
[0056] In certain embodiments, the deasphalted oil and adsorbent
mixture 155 is preferably washed with two or more aliquots of
aromatic or polar solvent 126 in the filtration vessel 130 in order
to dissolve and remove the adsorbed sulfur-containing and
nitrogen-containing compounds. The clean solid adsorbent stream
138, is recovered and recycled for mixing with the deasphalted oil
stream 122. Spent adsorbent material is discharged from the
filtration vessel as stream 134. The deasphalted oil and solvent
mixture 132 is passed from the filtration vessel 130 to the
fractionator 140 to separate the solvent from the asphalt
containing heavy polynuclear aromatic compounds which are withdrawn
as stream 142 for appropriate disposal. The clean aromatic and/or
polar solvent is recovered as stream 144 and recycled to filtration
vessel 130.
[0057] A portion 193 (for instance, 10-100%) discharged deasphalted
oil stream 192 is processed a coking operation to produce coker gas
and liquid products and high quality petroleum green coke. In
certain embodiments, as shown in FIG. 2, a delayed coking operation
is used. The discharged deasphalted oil stream 193 is charged to a
delayed coking furnace 160 where the contents are rapidly heated to
an effective coking temperature, such as the range of about
480.degree. C. to 530.degree. C., and then fed to delayed coking
drum 170a or 170b. In certain embodiments, two or more parallel
coking drums 170a and 170b are provided and are operated in swing
mode, such that when one of the drums is filled with coke, the
deasphalted oil stream is transferred to the empty parallel drum
and coke is recovered from the filled drum 174. A liquid and gas
delayed coker product stream 172 is recovered from the coker drum
170a or 170b. Any hydrocarbon vapors remaining in the coke drum can
be removed by steam injection.
[0058] The liquid and gas delayed coker product stream 172 is
introduced into a coking product stream fractionator where it is
fractionated to yield separate product streams that can include a
light gas stream 182, a coker naphtha stream 184, a light coker gas
oil stream 186 and a heavy coker gas oil stream 188. Optionally,
all or a portion of the heavy coker gas oil stream 188 is recycled
to the coking unit furnace 160.
[0059] The coke remaining in coker drum 170a or 170b is cooled, for
instance, water quenched, and removed from the coke drum as
recovered coke product 174. The coke can be removed by mechanical
or hydraulic operations. According to the process herein, the
recovered coke is high quality petroleum green coke.
[0060] By integrating an enhanced solvent deasphalting process with
a delayed coking process, the deasphalted oil feedstream to the
coking unit does not contain sulfur-containing and
nitrogen-containing polynuclear aromatic molecules, thereby
resulting in the production of high quality petroleum green coke.
Moreover, by recycling both solvents as well as the solid adsorbent
material, economic and environmental advantages are achieved. In
certain embodiments, when activated carbon is used as an adsorbent
in the solvent deasphalting unit before or after the desorption
step, it can be used as fuel, for instance, in associated power
plants.
[0061] Computer models can be used advantageously in evaluating
whether process modifications are technically feasible and
economically justifiable. The use of computer modeling is described
by J. F. Schabron and J. G. Speight in an article entitled "An
Evaluation of the Delayed-Coking Product Yield of Heavy Feedstocks
Using Asphaltenes Content and Carbon Residue", Oil & Gas
Science and Technology--Rev. IFP, Vol. 52 (1997), No. 1, pp. 73-85.
A coking process model commonly used in the industry was modified
to reflect the presence of light components and the corresponding
yields based on the mid-boiling temperatures of the respective
cuts. The model also included experimental data regarding the
characteristics of the feedstream. Three types of residual oils
were delayed coked at the same conditions to see the impact of
feedstock quality on the product yields and coke quality. The
properties of the feedstocks are summarized in Table 4. The
feedstream are subjected to delayed coking at a temperature of
496.degree. C. from the furnace outlet and at atmospheric
pressure.
TABLE-US-00004 TABLE 4 Arab Heavy Property Vacuum Residue DOA-SDA
DAO-ESDA API Gravity, .degree. 9 14.16 14.5 SG 1.007 0.971 0.969
Sulfur, W % 4.38 3.31 2.9 Nitrogen, W % 0.4833 0.0835 0.017 CCR, W
% 24.3 7.32 4.1 Nickel, ppmw 59 2 0.1 Vanadium, ppmw 182 8 0.1
[0062] DAO-SDA: Solvent deasphalted oil using conventional solvent
deasphalting technology
[0063] DAO-ESDA: Solvent deasphalted oil using enhanced solvent
deasphalting technology (with adsorbents)
[0064] The Arab heavy residue is the heaviest and dirties of the
oil tested and DAO-ESDA is the cleanest oil tested. The product
yields from the delayed coking operations are shown in Table 5.
TABLE-US-00005 TABLE 5 Arab Heavy Vacuum Residue DOA-SDA DAO-ESDA
Yields, W % Coke 38.9 11.7 6.6 Gas 11.3 8.9 8.4 Naphtha 19.6 13.8
12.7 Light Coker Gas Oil 17.3 36.9 37.8 Heavy Coker Gas Oil 12.9
28.7 34.6 Total 100.0 100.0 100.0
[0065] Arab heavy vacuum residue yielded the highest amount of coke
(38.9 W %) and a substantial drop 70 W % is observed when the
vacuum residue is deasphalted. When the vacuum residue is solvent
deasphalted with adsorbents, and the deasphalteed the coke yield
decreased further by 83 W % to 6.6 W %.
[0066] The sulfur and metals levels are also calculated for the
three feedstock and summarized in Table 6.
TABLE-US-00006 TABLE 6 Arab Heavy Vacuum Residue DOA-SDA DAO-ESDA
*Specification Sulfur, W% 7.5 4.5 3.2 1-3.5 Metals, ppmw 620 85 3
550 *Anode grade coke
[0067] As seen the deasphalted oil obtained from enhanced solvent
deasphalting unit, which utilizes adsorbent, produces high coke
meeting the anode grade coke specification.
[0068] Petroleum green coke recovered from a delayed coker unit is
subjected to calcination. In particular, samples of about 3 kg of
Petroleum green coke were calcined according to the following
heat-up program: Room Temperature to 200.degree. C. at 200.degree.
C./h heating rate; 200.degree. C. to 800.degree. C. at 30.degree.
C./h heating rate; 800.degree. C. to 1100.degree. C. at 50.degree.
C./h heating rate; Soaking Time at 1,100.degree. C.: 20 h.
[0069] Table 7 shows the properties of the samples of petroleum
green coke and Table 8 shows the properties of the calcium
samples.
TABLE-US-00007 TABLE 7 Sample Sample Property Method Unit Range 1 2
Water Content ISO % 6.0-15.0 0.0 0.0 11412 Volatile Matter ISO %
8.0-12.0 4.8 5.9 9406 Hardgrove ISO -- 60-100 41 50 Grindability
Index 5074 XRF Analysis ISO %/ 0.50-4.00 3.40 3.36 S V Ni Si Fe Al
Na Ca 12980 ppm 50-350 83 76 P 50-220 80 77 K Mg 20-250 71 45 Pb
50-400 92 154 50-250 71 45 20-120 44 27 20-120 18 13 1-20 2 1 5-15
0 0 10-30 13 11 1-5 0 0 Ash Content ISO 8005 % 0.10-0.30 0.08
0.08
TABLE-US-00008 TABLE 8 Property Method Unit Range Sample 1 Sample 2
Water Content ISO 11412 % 0.0-0.2 0.0 0.0 Volatile Matter ISO 9406
% 0.0-0.5 0.3 0.5 Hardgrove ISO 5074 -- -- 41 49 Grindability Index
Ash Content ISO 8005 % 0.10-0.30 0.04 0.07
[0070] The method and system of the present invention have been
described above and in the attached drawings; however,
modifications will be apparent to those of ordinary skill in the
art and the scope of protection for the invention is to be defined
by the claims that follow.
* * * * *