U.S. patent application number 14/806387 was filed with the patent office on 2016-02-11 for enhanced methods for solvent deasphalting of hydrocarbons.
The applicant listed for this patent is MEG ENERGY CORP.. Invention is credited to TOM CORSCADDEN, GREG DIDUCH, DAMIEN HOCKING, JIM KEARNS, DARIUS REMESAT.
Application Number | 20160040079 14/806387 |
Document ID | / |
Family ID | 48128703 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160040079 |
Kind Code |
A1 |
CORSCADDEN; TOM ; et
al. |
February 11, 2016 |
ENHANCED METHODS FOR SOLVENT DEASPHALTING OF HYDROCARBONS
Abstract
Improvements to open-art Solvent Deasphalting (SDA) processes
have been developed to reduce capital and operating costs for
processing hydrocarbon streams are provided whereby open art SDA
scheme is modified to include appropriately placed mixing-enabled
precipitators (MEP's) to reduce solvent use requirements in an
asphaltene separation step and to increase overall reliability for
SDA processes, particularly suitable for Canadian Bitumen. When
integrated with a mild thermal cracker, the improved SDA
configuration further improves crude yield to be pipeline-ready
without additional diluent and for use to debottleneck existing
facilities such as residue hydrocrackers and coking units.
Inventors: |
CORSCADDEN; TOM; (Calgary,
CA) ; DIDUCH; GREG; (Calgary, CA) ; HOCKING;
DAMIEN; (Calgary, CA) ; REMESAT; DARIUS;
(Calgary, CA) ; KEARNS; JIM; (Calgary,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MEG ENERGY CORP. |
Calgary |
|
CA |
|
|
Family ID: |
48128703 |
Appl. No.: |
14/806387 |
Filed: |
July 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13566493 |
Aug 3, 2012 |
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14806387 |
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61548915 |
Oct 19, 2011 |
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Current U.S.
Class: |
422/187 ;
196/14.52 |
Current CPC
Class: |
C10G 21/003 20130101;
C10G 2300/44 20130101; C10G 55/04 20130101; C10G 9/00 20130101;
C10G 2300/206 20130101; C10G 2300/4056 20130101 |
International
Class: |
C10G 21/00 20060101
C10G021/00; C10G 55/04 20060101 C10G055/04 |
Claims
1. A Mixing Enabled Precipitator (MEP) supporting a continuous
process to completely and rapidly mix a heavy hydrocarbon stream
with a light hydrocarbon stream for enhanced mass transfer to
accelerate precipitation of solid asphaltenes by changing the
solubility characteristics of asphaltene particles from the heavy
hydrocarbon stream in a resulting blended stream for downstream
separation.
2. The device of claim 1 where the precipitation is nearly
instantaneous with the mixing.
3. The device of claim 1 which enhances mass transfer by
disentangling hydrocarbon chains.
4. The device of claim 1 which changes the characteristics of
asphaltene molecules by cleaving side chains of included Canadian
bitumen molecules producing additional viable hydrocarbon
product.
5. The device of claim 1 which enhances mass transfer by intimately
mixing two different fluids with comparative viscosity difference
of at least 100,000:1.
6. The device of claim 1 where solids precipitated in the MEP and
transported out of the device are in the 10 .mu.m to 900 .mu.m
range.
7. The device of claim 1 with a shear number in the range of
3-40.
8. A Mixing Enabled Precipitator (MEP) placed upstream of a
secondary asphaltene extractor supporting a continuous process to
completely and rapidly mix a heavy hydrocarbon stream with a light
hydrocarbon stream for enhanced mass transfer to accelerate
precipitation of solid asphaltenes by changing the solubility
characteristics of asphaltene particles from the heavy hydrocarbon
stream in the resulting blended stream for downstream
separation.
9. The device of claim 8 where the precipitation is nearly
instantaneous with the mixing.
10. The device of claim 8 which enhances mass transfer by
disentangling hydrocarbon chains.
11. The device of claim 8 which changes the characteristics of
asphaltene molecule by cleaving side chains of Canadian bitumen
molecules it processes, producing additional viable hydrocarbon
product.
12. The device of claim 8 which enhances mass transfer by
intimately mixing two different fluids with comparative viscosity
differences of at least 100,000:1.
13. The device of claim 8 where solids precipitated in the MEP and
transported out of the device are in the 10 .mu.m to 900 .mu.m
range.
14. The device of claim 8 with a shear number is in the range of
3-40
15. A Mixing Enabled Precipitator (MEP) placed upstream of a mild
thermal cracker to improve the performance of the thermal cracker
and increase the yield of bitumen processing supporting a
continuous process to completely and rapidly mix a heavy
hydrocarbon stream with a light hydrocarbon stream for enhanced
mass transfer to accelerate precipitation of solid asphaltenes by
changing the solubility characteristics of the asphaltene particles
in the blended stream from the heavy hydrocarbon stream for
downstream separation.
16. The device of claim 15 which provides a homogenized fluid
feedstock with untangled asphaltene molecules to improve uniform
heat flux for all molecules.
17. The device of claim 15 which changes the characteristics of the
asphaltene molecule by cleaving side chains of Canadian bitumen
molecules producing additional viable hydrocarbon product.
18. The device of claim 15 where the shear number is in the range
of 1-30.
19-35. (canceled)
36. The device of claim 1 where the mixing-enable precipitator can
be a mixer, or a pump/mixer combination, generating both pressure
for the process and mixing the liquids into a homogenized
fluid.
37. The device of claim 36 that can accommodate solids, in the
range of 10 .mu.m to 900 .mu.m, flowing through it.
38. The device of claim 36 that has shear numbers in the range of
3-40 developing sufficient turbulence for instantaneous mixing.
39. The device of claim 36 where at least 1 rotor/stator generator
is used.
40. The device of claim 1 where the MEP and asphalt separator are
combined into one operating unit (MEP plus asphaltene separator)
for precipitating and separating the precipitated asphaltenes
creating a deasphalted oil/solvent mixture and a dry solid
asphaltene product.
41. The device of claim 40 where the MEP and the asphalt separator
are close coupled.
42. The device of claim 40 where the MEP and the asphalt separator
are separated by a pipe of at least a fraction of an inch to a
length suitable in a commercial operating unit.
Description
[0001] This application claims the benefit of U.S. provisional
patent application No. 61/548,915 filed Oct. 19, 2011.
FIELD OF THE INVENTION
[0002] This invention has to do with improving produced bitumen,
focusing on (but not limited to) Canadian bitumen, by a novel
post-production process improving deasphalting in particular.
DESCRIPTION OF PRIOR ART
Prior Art SDA Schemes
[0003] Solvent Deasphalting ("SDA") is a process employed in oil
refineries to extract valuable components from residual oil from a
prior operation. The extracted components can be further processed
in refineries where they are cracked and converted into valuable
lighter fractions, such as gasoline and diesel. Suitable residual
oil feedstocks which can be used in solvent deasphalting processes
include, for example, atmospheric tower bottoms, vacuum tower
bottoms, crude oil, topped crude oils, coal oil extract, shale
oils, and oils recovered from oil sands.
[0004] Solvent Deasphalting processes are well known and described,
with many in the open-art, for instance, in Smith's U.S. Pat. No.
2,850,431, Van Pool's U.S. Pat. No. 3,318,804, King et al's U.S.
Pat. No. 3,516,928, Somekh et al's U.S. Pat. No. 3,714,033, Kosseim
et al's U.S. Pat. No. 3,714,034, Yan's U.S. Pat. No. 3,968,023,
Beavon's U.S. Pat. No. 4,017,383, Bushnell et al's U.S. Pat. No.
4,125,458, and Vidueira et al's U.S. Pat. No. 4,260,476 all of
which would benefit from further energy saving and performance
enhancing features that could reduce solvent to oil ratio and/or
improve recovery of desired hydrocarbon products.
Treatment of SDA Generated Asphaltene-Rich Streams in the Prior
Art
[0005] In U.S. Pat. No. 4,421,639 a SDA process uses a 2.sup.nd
asphalt extractor to concentrate asphaltene material (and recover
more deasphalted oil). A concentrated asphalt stream with added
solvent is sent through a heater which raises the stream's
temperature to 425.degree. F. at 18 psia, and is then sent to a
flash drum and steam stripper to separate solvent (in this case
propane) from the asphalt stream. Asphalt product in liquid form is
pumped to storage. This arrangement only works if the asphalt rich
stream is liquid at these conditions. It is burdened by plugging if
any appreciable solid asphaltenes are present as in asphaltene-rich
streams like bitumen, and the process has a high solvent
requirement.
[0006] In U.S. Pat. No. 3,847,751, concentrated asphaltenes
produced from an SDA unit are mixed with solvent and transported as
a liquid solution into a spray dryer. The spray nozzle design and
pressure drop in the dryer determines the size of liquid droplets
that are formed. The smaller the light hydrocarbon (solvent)
droplet, the faster it will flash completely to vapour. The smaller
the heavy hydrocarbon (asphaltene) particle the more surface area
per volume/mass available for heat transfer by radiation and
conduction to cool the heavy droplets. The goal in the dryer is to
produce dry, non-sticky solid asphaltene particles. Cold gas is
added to the bottom of the spray dryer to enhance cooling by
additional convective and conductive heat transfer as well as
increasing droplet residence time by slowing droplet descent rate
(via upward cooling gas flow) in order to reduce the size of the
vessel (which tend to be extremely large). This arrangement is not
feasible if the asphaltene particles that have settled out in the
extractor are in a solid form in the solvent at the process
operating temperature. Solid particles plug the spray drier nozzle
limiting reliability and thus viability of this scheme in solid
asphaltene rich streams.
[0007] In U.S. Pat. No. 4,278,529, a process for separating a
solvent from a bituminous material by pressure reduction without
carry-over of bituminous material is disclosed. A feedstock in a
fluid-like phase comprising bituminous material and solvent
undergoes a pressure reduction process by passage through a
pressure reduction valve and is then introduced into a steam
stripper. The pressure reduction process vaporizes part of the
solvent and also disperses a mist of fine bituminous particles in
the solvent. The remaining asphaltene remains wet and sticky and
has not enough solvent left to keep the heavy bituminous phase
(with many solids) fluid.
[0008] U.S. Pat. No. 4,572,781 discloses a SDA process for
separating substantially dry asphaltenes of high softening point
(temperature) from heavy hydrocarbon material using a centrifugal
decanter to separate a liquid phase from a highly concentrated
slurry of solid asphaltenes. This process is designed to handle a
rich asphaltene stream that has solid particles but is a highly
costly process since the separation of the solids is done through a
solid/liquid separation with additional solvent needed to make the
material flow to the decanter. The solid material is still
relatively wet once separated and needs a further drying step to
recover solvent as a vapour. The recovered solvent vapour then
needs to be condensed for re-use, which is another high energy step
adding complexity.
[0009] In U.S. Pat. No. 7,597,794, a dispersion solvent is
introduced into am asphalt stream after separation by solvent
extraction and the resulting asphalt solution undergoes rapid
change in a gas-solid separator and is dispersed into solid
particles and solvent vapor, resulting in low temperature
separation of asphalt and solvent with adjustable size of the
asphalt particles. The challenge with flash/spray driers such as
disclosed here using liquid solvent as a transport media is the
propensity for the asphaltenes generated in the integrated process
to remain wetted before, during and after a flash drying phase. In
addition, with this integrated process, the asphaltene continues to
liquefy at elevated temperatures. Wetted asphaltene sticks to
surfaces and fouls and plugs process equipment. The reduced
reliability inherent in this approach makes such operations costly
for heavy crudes with high asphaltenic content.
[0010] In U.S. Pat. No. 7,964,090 a method for upgrading heavy
asphaltenic crudes using SDA and gasification is disclosed. A
stream to a gasifier is generated by mixing hydrocarbons comprising
one or more asphaltenes and one or more non-asphaltenes with a
solvent, wherein the ratio of solvent to hydrocarbon is from about
2:1 to about 10:1. The resulting asphaltene rich stream is
transferred out of the SDA to a gasifier as a liquid. The large
quantities of solvent used in transport are consumed in the
gasifier and downgraded in value to a fuel gas equivalent. Since
the asphaltenes tend to be liquid, using a solvent to transport the
material in the quantities stated is feasible. For a solid
asphaltene, this method would require 10-20 times more solvent for
transport and the high quantity of expensive solvent would be
consumed in the process and its value reduced.
[0011] In U.S. Pat. No. 4,572,781, a process for separating
substantially dry asphaltenes from heavy hydrocarbon material using
solvents is disclosed. Two stages of liquid extraction (decanters)
to produce a DAO product followed by screw conveyance of asphaltene
slurry, and two stages of solid-vapour separation in a spray drier
and separator to generate dry asphaltenes form the scope of the
patent. The patent is instructive and educational in that the
concept of generating a dry asphaltene byproduct is feasible in the
DAO production process. However, the process is burdened by the
many required process steps to get both the DAO product and the dry
asphaltene product. In addition, the operating conditions required
to generate the solid asphaltenes in the decanting step do not work
for Canadian bitumen. At conditions sited in the patent,
(<150.degree. C.), Canadian bitumen, whether thermally converted
or separated in an upstream fractionator, will not flow and will
plug the system. In an alternate embodiment, U.S. Pat. No. '781
replaces the spray drier with an evaporator and adds
water/surfactant to the process to assist in separating the
solvent. No savings in processing steps are made and an additional
material is added increasing the complexity of operation.
SDA Schemes in Refining and Upgrading in the Prior Art
[0012] In U.S. Pat. No. 7,749,378, a ROSE (Residual Oil
Supercritical Extraction) SDA process is applied to an atmospheric
residue or vacuum bottoms residue stream within a refinery or
Upgrader. The separated asphaltene-rich stream from the ROSE SDA
unit is a liquid solution which is very sticky and requires extreme
operating conditions (high temperatures) and added solvent to
facilitate feedstock flow through the process equipment which is
very intensive and expensive. This process does not put the solid
asphaltenes through a mild thermal cracking process, and thus does
not convert the asphaltenes from a sticky to a crunchy texture, and
relies primarily on excess solvent to transport the asphaltene
stream in a diluted form.
[0013] The targeted embodiment of the ROSE SDA process disclosed
requires at least a 4:1 solvent to oil (residue) ratio (by mass)
and operating temperatures of the extractor in the range of
300-400.degree. F. In practice, the temperature must be even higher
or the solvent flow must be increased in order to keep the
asphaltene-rich stream from plugging the process. In this set up, a
large portion of the original feedstock is downgraded from crude
and sent to a low conversion (i.e. coker, gasification) or low
value operation (asphalt plant) reducing the overall economic yield
of the crude (in addition to the relatively high process intensity
of the operation).
The Desirability of Integrated Hydrocarbon Cracking and SDA
Schemes
[0014] Processes have been disclosed to convert and/or condition
heavy hydrocarbon streams (for instance Oil Sands bitumen) into
pipeline transportable and refinery acceptable crude. Of note,
thermal cracking, catalytic cracking, solvent deasphalting and
combinations of all three (for example, visbreaking and solvent
deasphalting) have been proposed to convert bitumen to improve its
characteristics for transport and use as a refinery feedstock.
[0015] The benefits of the invention disclosed below may be
understood in the context of the operation of the thermal cracking
unit noted in U.S. Pat. No. 7,976,695 and an example generated by
integrating operation of that ('695) thermal cracker with an SDA in
U.S. patent application Ser. No. 13/037185.
[0016] Figure A shows the arrangement of two types of asphaltene
molecules. These molecules are complex with long side chains
exhibiting the high molecular weight of the bitumen hydrocarbon
molecules and the great tendency to coke as noted by high MCR
(micro-carbon residue) numbers.
[0017] In addition, these long side chains readily entangle with
other similar molecules to make large unmanageable sticky clumps.
Adding direct, intense, instantaneous heat to these sticky clumps
generates substantial quantities of coke and light gases. Rapid
cooling creates condensation reactions generating differently
configured complex asphaltenes with long side chains that are just
as difficult to deal with further downstream in the processing,
##STR00001##
[0018] A controlled mild thermal cracker creates a
thermally-affected asphaltene that cleaves the long side chains of
the bitumen molecules in such a fashion that retains the molecules'
core structure, which resembles an inert coke particle. The resins,
which normally solubilize the asphaltenes, are also thermally
affected, resulting in a reduction of asphaltene solubility,
enabling precipitation. Once precipitated, the particles of these
modified asphaltenes remain solid at elevated temperatures. The
cleaved side chains when separated become primarily light
hydrocarbon liquid molecules which when captured may increase the
overall economic yield of pipeline ready crude.
[0019] In U.S. Pat. No. 4,454,023 a process for the treatment of
heavy viscous hydrocarbon oil is disclosed, the process comprising
the steps of: visbreaking the oil; fractionating the visbroken oil;
solvent deasphalting the non-distilled portion of the visbroken oil
in a two-stage deasphalting process to produce separate asphaltene,
resin, and deasphalted oil fractions; mixing the deasphalted oil
fractions ("DAO") with the visbroken distillates; and recycling and
combining resins from the deasphalting step with the feedstock
initially delivered to the visbreaker. The U.S. Pat. No. 4,454,023
patent provides a means for upgrading lighter hydrocarbons (API
gravity>15) than Canadian Bitumen but is burdened if used with
Canadian Bitumen by the misapplication of thermal cracking that
will over-crack and coke the hydrocarbon stream, as well as by the
complexity and cost of an additional solvent extraction stage to
separate the resin fraction from the DAO. Recycling part of the
resin stream is required to produce a product which meets pipeline
transportation specifications and increases the operating costs and
complexity and process intensity of the operation.
[0020] Typical thermal crackers, like visbreakers, do not
appreciably improve the characteristics of the complex Canadian
Bitumen asphaltene molecules. At elevated temperatures, the
asphaltene molecules will become liquid and are highly sticky.
[0021] When these typical visbreakers are integrated with SDA
processes, the solvent in the liquid phase from the SDA process is
typically used to transport these separated asphaltenes, as a
slurry to the byproduct processing operation (gasification, spray
drier, or asphalt plant).
[0022] In U.S. Patent application 2007/0125686, a process is
disclosed where a heavy hydrocarbon stream is first separated into
various fractions via distillation with the heavy component sent to
a mild thermal cracker (visbreaker). The remaining heavy liquid
from the mild thermal cracker is solvent deasphalted in an open art
SDA unit. The asphaltenes separated from the SDA are used as feed
to a gasifier. The resulting deasphalted oil is blended with the
condensed mild thermal cracker vapour to form a blended product.
Standard visbreaking faces the challenges of early coke generation
without impacting the characteristics of the asphaltenes. The
asphaltenes are mixed with the SDA solvent and sent to a gasifier
as a liquid slurry. The high-cost solvent is consumed in the
gasifier, increasing the capital and operating cost of the entire
operation while also increasing the carbon footprint of the process
and the process intensity.
Static Mixers and Primary Bitumen Processing in the Prior Art
[0023] Refining industry practice uses static mixers to mix two
streams, typically a light hydrocarbon stream and a heavy
hydrocarbon stream. Static mixers are useful when the two streams
have similar viscosities and the flow regime is in the turbulent
region. When viscosities of the streams differ by factors of
greater than 1000, static mixers do a poor job of mixing the
streams. In addition, for processes with a stream or streams having
a high propensity to foul, such as a modified-asphaltene stream,
static mixers create a flow restriction point, added surface area
and irregular wall features exposed to the stream, and increase the
probability of fouling.
[0024] Static mixers have been used to attempt to mix solvent and
crude to enhance a deasphalting process in an asphalt extractor.
However, due to the large viscosity differences between the heavy
crude and solvent (well over a factor of 1000 difference), a static
mixer in this application does not provide any noticeable
benefit.
Rotary Shear Mixing Devices in Crude Refining/Oil Sands Upgrading
Processes in the Prior Art
[0025] High shear mixers have been considered in crude refining
applications to improve the flow properties of the crude. In US
Patent Application 2011/0028573, a shear mixer is used to attempt
to increase the API gravity of a crude oil, by introducing the
crude oil to a light gas within a high shear mixing device. The
high shear forces essentially "entrain" the gas into the crude.
After a nominal settling time, the gas will liberate from the crude
especially under warmer temperatures, thus impacting RVP (Reid
vapour pressure) on the crude thereby limiting the benefit of this
application of shear mixing in crude refining and with a resulting
increase in a two-phase fluid which is unsuitable for pipeline
transport and pumping. This application though does demonstrate the
ability to thoroughly mix two different phases of material with
dissimilar relative densities (and viscosities).
[0026] In the Canadian Oil Sands, vessels with rotating disks have
been used in studies to determine the dissolution rate of bitumen
into organic solvents. R. Ulrich et al (Application of the Rotating
Disk Method to the Study of Bitumen Dissolution into Organic
Solvents, Canadian Journal of Chemical Engineering, Volume 69,
August 1991) discovered that as the degree of shear increased from
the rotating disk the less sensitive the bitumen dissolution was to
solvent type. This learning has been applied to open-art commercial
SDA units by Foster Wheeler (U.S. Pat. No. 4,088,540) in their
commercial asphalt extractors, however, the moving mechanical
device is a reliability concern especially when dealing with a
precipitated solid asphaltene from Canadian Bitumen. Their
objective is to produce light liquid and a heavy liquid hydrocarbon
product streams by mixing. The precipitated asphaltenes easily foul
the rotating disks in the Foster Wheeler process within the
extractor vessel.
DESCRIPTION OF DRAWINGS
[0027] FIG. 1 depicts an illustrative SDA process with a Mixing
Enabled Precipitator (MEP) included to improve solvent deasphalting
with an inertial separator to enhance solid asphaltene segregation,
according to one or more embodiments described.
[0028] FIG. 2 depicts a further SDA enhancement on FIG. 1 with a
secondary MEP and asphalt extractor arrangement illustrated to
improve solvent deasphalting, according to one or more embodiments
described.
[0029] FIG. 3 depicts an illustrative application of an integrated
mild thermal cracking and improved solvent deasphalting process
similar to FIG. 2, according to one or more embodiments
described.
[0030] FIG. 4 depicts an illustrative application of an integrated
mild thermal cracking and improved solvent deasphalting process
with appropriately placed shear mixing devices within an existing
upgrader or refinery with a vacuum and/or coking unit according to
one or more embodiments described.
[0031] FIG. 5 depicts a specific illustrative application from FIG.
4 of an integrated mild thermal cracking and improved solvent
deasphalting process with appropriately placed shear mixing devices
fed a vacuum bottoms stream from an existing upgrader or refinery
with the various products from the integrated cracker/improved SDA
sent to hydrocracking, residual hydrocracking and gasification
units according to one or more embodiments described.
[0032] FIG. 6 depicts a process intensification of a specific
illustrative arrangement for a MEP with a receiving vessel
(asphaltene separator) to separate the precipitated solid
asphaltenes and the DAO/solvent mixture.
SUMMARY OF THE INVENTION
[0033] It is to be understood that other aspects of the present
invention will become readily apparent to those skilled in the art
from the following detailed description, wherein various
embodiments of the invention are shown and described by way of
illustration. As will be realized, the invention is capable for
other and different embodiments and its several details are capable
of modification in various other respects, all without departing
from the spirit and scope of the present invention. Accordingly the
drawings and detailed description are to be regarded as
illustrative in nature and not as restrictive.
[0034] A Mixing Enabled Precipitator (MEP) in one embodiment
supports a continuous process to completely and rapidly mix two
different viscosity fluids with the magnitude of viscosity
difference being at least 100,000. The MEP of an embodiment
provides enhanced mass transfer to accelerate precipitation of
solid asphaltenes by changing the solubility characteristics of the
asphaltene particles in the blended stream from the heavy
hydrocarbon stream for downstream separation.
[0035] The MEP in an embodiment provides nearly instantaneous
precipitation with the mixing and enhances mass transfer by
disentangling hydrocarbon chains. The device may change the
characteristics of the asphaltene molecule by cleaving side chains
of Canadian bitumen molecules and producing additional viable
hydrocarbon product. The solids precipitated in an embodiment of
the MEP and transported out of the device may be in the 10 .mu.m to
900 .mu.m range. The MEP may operate in a preferred embodiment,
optimally in the shear number range of 3 to 40.
[0036] An open art SDA scheme may be modified in another embodiment
to include appropriately placed mixing-enabled precipitators
(MEP's) to reduce solvent use requirements in an asphaltene
separation step and increase overall reliability for SDA processes,
particularly suitable for Canadian Bitumen. When integrated with a
mild thermal cracker, an improved SDA configuration of this
embodiment may further improve crude yield for oil producers
looking to produce pipeline-ready crude without the additional
diluent and for refiners/upgraders wishing to debottleneck existing
facilities such as residue hydrocrackers and coking units.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0037] The detailed description set forth below in connection with
the appended drawings is intended as a description of various
embodiments of the present invention and is not intended to
represent the only embodiments contemplated by the inventor. The
detailed description includes specific details for the purpose of
providing a comprehensive understanding of the present invention.
However, it will be apparent to those skilled in the art that the
present invention may be practiced without these specific
details.
[0038] FIG. 1 is a process flow diagram depicting an improved SDA
process, using an open-art SDA process with addition of a Mixing
Enable Precipitator (MEP) 30, applied to a heavy hydrocarbon (ex.
Canadian Bitumen) stream 5 to effect mixing with a solvent to
create a blended hydrocarbon suitable as refinery and pipeline feed
from various combinations of product streams 82, 100 and 102.
Stream 5 is typically heated in an exchanger 20, prior to entering
the MEP 30, creating ideal feed conditions in stream 21 where
appropriate. The well-mixed outlet stream 31, essentially in
equilibrium, is ready for asphaltene separation in unit 40, an
asphaltene extractor and/or separator.
[0039] Fresh solvent make-up is added in a stream, 1, and recycled
solvent from the process through other streams 101 and 122. The
mixed stream 14 is heated to an appropriate temperature
(275-400.degree. F. range) and sent through a MEP 30. With such
large differences in viscosity between the asphaltene-rich stream
and the solvent (light hydrocarbons like butane through to
heptane), static mixers have proven not to provide adequate mixing
and thus additional solvent is required to force mixing in the
absence of MEP or active mixing devices. However, after a certain
point of adding more solvent, the two liquids (solvent and
asphaltene-rich stream) will exhibit stratification in the
transport piping thus limiting any premixing of the liquids in the
piping prior to the asphalt extractor/separator. Theoretically, the
open area of a static mixer can be reduced to improve mixing, but
in practice, plugging of the reduced open area mixer results when
dealing with the asphaltene-rich stream.
Rapid/Complete (Ex. High Shear) Mixing and Primary Bitumen
Processing
[0040] Nothing in the prior art of primary heavy crude (ex.
Canadian Bitumen) processing involves the use of rapid/complete
(ex. high shear) mixing directly upstream of a solvent deasphalting
unit. In addition, precipitation of asphaltenes directly to the
solid form has be avoided by prior designs as being an undesirable
result. Application of rapid/complete mixing in the petroleum
industry has heretofore focused on the initial extraction of
bitumen from the sand, and on processing oils ands tailings (a
reclamation process stream as noted in the following patents, U.S.
Pat. No. 7,758,746, U.S. Pat. No. 7,867,385, U.S. Pat. No.
7,585,407 among others).
[0041] A MEP 30, has been applied by the Applicants to a pilot
plant in the service of deasphalting to improve the mixing of the
two involved highly different viscosity liquid (asphaltene-rich and
light hydrocarbon solvent) to promote solids precipitation.
[0042] This novel application of rapid/complete mixing can provide
the following benefits, which it is thought to arise through
either/both: [0043] 1. Creating intimate contact between solvent
and oil resulting in: [0044] a. Reduced S/O ratio to meet same
yield/quality of products reducing operating costs. [0045] b.
Reduce equipment size by reducing residence time to meet the same
yield/quality of products at a constant S/O ratio. [0046] c. Remove
need for any mass transfer and/or mixing internals within the
asphalt extractor thus improving reliability economically for the
entire process--creating a simple clarifier or asphaltene
separator. [0047] d. Reduced solvent losses. [0048] e. Promote
rapid precipitation of asphaltene solids [0049] 2. Increased forces
(ex, shear forces) acting on the long-chained, entangled asphaltene
molecules, to firstly untangle and separate these molecules and
secondly, in theory to break any weak bonds/attractions (polar)
that might otherwise hold resins/asphaltenes together to create
"larger" asphaltene structures. This may: [0050] a. Increase liquid
DAO/resin yield by better separating the asphaltenes from the
DAO/resin creating a solubility change between DAO and asphaltenes.
[0051] b. Increase potential to remove metals that may be held in
these larger molecules with minimal/no attraction. [0052] c.
Enhance rapid precipitation of asphaltene solids.
[0053] A MEP successfully deals with the challenge of intimately
mixing a high viscosity stream (i.e. bitumen) and a low viscosity
stream (i.e. low MW hydrocarbon like butane, pentane, hexane or
heptane or a mixture) of solvent. The rapid/complete mixing
produces a standardized and relatively homogenous mixture of
ingredients that do not otherwise naturally mix as intimately or
thoroughly. It is thought that high shear (turbulence) acts to keep
the solubility driving force high for mass transfer: As turbulence
increases, mass transfer improves, and complete mixing is
approached. With the achievement of instantaneous mixing, the
desired rapid precipitation of asphaltenes from the bitumen and
light solvent results.
[0054] As an example of accomplishing the desired mix, MEP's can be
applied to generate rapid/complete mixing to promote the necessary
turbulence. There are a variety of methods to generate shear force.
Below is an example of a preferred embodiment of a high shear
mixing device with provision for handling solid precipitation
within the device. The device may utilize a rotor and a stationary
stator typically operating at considerably high rotational speeds
to produce high rotor tip speeds. Multiple rotors and stators with
varying degrees of shear generation can be applied. The
differential speed between the rotor and the stator imparts
extremely high shear and turbulent energy in the gap between the
rotor and stator. Therefore, rotor tip speed is an important factor
when predicting the amount of shear input into the mixing of the
two streams. Rotor tip speed, a function of rotor diameter and
rotational speed, can be represented by equation (1)
V = .pi. Dn ( i n m s ) ( 1 ) ##EQU00001##
[0055] where D is the diameter of the rotor in metres, and n is the
rotational speed of the rotor in rpm. Equation 1 indicates the
relation of the rotor size and the rate at which it rotates. Rotor
tip speed is in [units]. If multiple rotor blades are deployed,
this measure is the sum of tip speed of all blades.
[0056] Additionally, the gap distance between the rotor and the
stator will contribute to the amount of shear. The equation that is
used for calculating the shear in the gap between rotor and stator
is noted in (2):
S r = V g ( s - 1 ) ( 2 ) ##EQU00002##
[0057] where S.sub.r is the shear rate, and g is the gap between
the rotor and stator in metres. The shear rate is typically used to
describe the performance of a high shear mixer. Where multiple
rotor tips (blades) are involved, this fact is already considered
in the calculation of V (tip speed) in equation 1.
[0058] Another important factor is the shear frequency, f.sub.8, or
the number of occurrences that rotor and stator openings mesh.
The shear frequency considers the shear mixer geometry and is given
by Equation (3):
f s = N r N s n 60 ( s - 1 ) ( 3 ) ##EQU00003##
where N.sub.r represents the number of rotor blades and N.sub.s
represents the number of stator openings.
[0059] An empirically useful shear calculation provides the shear
number (S) which is a relation of the shear frequency and shear
rate (a direct function of tip speed). Equation (4) shows the
method of devising a dimensionless Shear number which provides a
means for comparing shear effects of two (or more) mixing
devices.
S = s r f s ( 4 ) ##EQU00004##
[0060] On that basis, it has been determined that shear numbers in
the range of 3-40 may be best suited in this application to
successfully accomplish the desired instantaneous intimate mixing
of asphaltene-rich material and solvent to allow for fast
precipitation of solid asphaltenes. In a preferred embodiment,
optimal shear numbers are in the 8-14 range. Shear numbers above 50
probably provide a diminishing return on shear generated and
benefit obtained (i.e. costs of providing force to the fluid).
Those increased shear rates are not commensurate to suitable
incremental disentanglement or mixing effects.
[0061] When considering rotor-stator designs, there may be multiple
stators and rotors, and the shear number must be applied for each
rotor in each row.
[0062] The MEP needs to generate high shear forces to promote
instantaneous and rapid mixing (mass transfer which accelerates
asphaltene precipitation) of the two hydrocarbon streams to create
the precipitated solid asphaltenes while allowing for continuous
transport of the resulting solid/liquid mixture within the
device.
[0063] The mixing portion of the MEP (typically one or more sets of
rotors and stators) must accommodate the precipitation/generation
and presence of a large quantity of asphaltene solids within the
device. The MEP design must balance the requirement for high shear
forces to promote asphaltene precipitation with sufficient opening
within the device to allow solids to travel through and out of the
device. The exit of the MEP must have a chamber to accept solids
generated/precipitated within the device and accommodation or
provide pressure differentials which push material in the MEP out
to a transport pipe or a settling vessel (asphaltene separator).
The chamber can be open or equipped with a volute and/or impeller
to promote transport of the solid/liquid mixture out of the
MEP.
[0064] In a preferred embodiment, the MEP would be able to pass
solid particles that range in size from 10 .mu.m up to 900 .mu.m
and are suspended in a liquid mixture.
[0065] A primary benefit of placing a MEP upstream of a standard
asphalt extractor with process internals is that the intimate
mixing from the MEP removes the necessity of having static or
moving mixing internals within the asphalt extractor. The
precipitated solid asphaltenes are highly fouling and thus
provisions to remove any restrictions in the system are desirable
and reduce process intensity. A simple asphaltene separator can be
used instead of an extractor.
[0066] Another primary benefit of the rapid/complete MEP device in
this application is a reduced S/0 ratio over that of a static mixer
by at least 30%. This results in smaller separator equipment and
less operating cost (i.e. circulating solvent liquid and
recovery/make-up facilities) to produce the same yield/quality of
products from static mixing. The increased force applied by the
rapid/complete MEP device on any remaining co-mingled long and
medium chained portions of the asphaltenes may also assist in the
solvent being even more intimately mixed with asphaltenes to
promote rapid and effective precipitation of asphaltene out of
solution. Even after factoring in the added (relatively low) power
requirements for the rapid/complete MEP mixing, there is
significant savings through the lower solvent to oil ratios
achieved, and reduced process intensity.
[0067] At these low solvent to oil ratios, after processing in
asphaltene extractor/separator 40, the asphaltenes are considered
essentially oil-free and can be removed from the asphaltene
extractor/separator 40 and transported as stream 42 via fluidized
gas (similar to conventional transport of coke and coal in other
industrial settings) to an inertial separator 60, for separation of
solids from any entrained liquid and transport gas to create a dry
solid that is easily stored and transported for further
processing.
[0068] The transfer line, stream 42, is heated to vaporize as much
solvent as possible while still keeping the asphaltenes in a solid
state, within a range of transport temperatures which is readily
found by adjustment in operating but is within a range of
150-300.degree. C. This may depend on the input feedstock and the
solvent used.
[0069] Additional solvent, as used in the prior art, does not have
to be added/wasted as a transportation media in this process.
Approximately 4-10 times the solvent needed for the SDA would be
needed to transport the solid asphaltenes without plugging in a
conventional system.
[0070] Also, instead of a device like a spray drier that requires a
restriction (nozzle) which will readily plug to promote solid/gas
separation an inertial separator 60 with a large open area, and
geometry conducive to solid separation from gas and continuous
solid flow is provided.
[0071] The gas stream 4 is injected at the bottoms outlet of column
4 to promote the flow of the solids. Solvent in stream 3 is added
to the extractor to improve DAO extraction. The gas in stream 42
ends up in the inertial separator 60 along with any entrained
solvent. The vapour stream 62 from the inertial separator is cooled
in exchanger 110, with an outlet stream 111, and separated in a
flash drum 120. The recovered liquid solvent stream 122 is mixed
with stream 1 for reuse in the process. Stream 121, the fluidized
gas is separated and reused. The dry solids, stream 61, are removed
from unit 60 and sent to a dry storage asphaltene unit 130.
[0072] As in other SDA processes, the extracted DAO from unit 40 is
processed further to separate solvent from DAO. Stream 41 has
solvent added from stream 2 if necessary and is heated to reduce
the solubility of the DAO in the solvent to begin the separation
phase. Heater 90, or if a resin product is desired, heater 70, are
used to heat stream 41 to create a warmer DAO rich stream 91 or 71
depending on whether a resin extractor 80 is present.
[0073] Supercritical conditions can be used to separate the solvent
from the DAO in unit 100, which typically comprises a solvent
extraction column and a low pressure stripper.
[0074] Stream 102 is a highly concentrated DAO stream, while stream
101 is solvent that is recycled in the process. If a resin product
is desired, the resin extractor 80 complete with an extractor
column and a low pressure stripper may be employed. Stream 41 is
heated and enters the resin extractor 80 creating a resin rich
stream 82 and a DAO/solvent rich stream 81 to be processed in the
solvent extraction unit 100.
[0075] In another aspect, FIG. 2 demonstrates another placement of
the MEP to improve DAO extraction, when a secondary asphaltene
extractor/settler, unit 50, is used in the SDA process. This second
MEP produces the same types of benefits as placing a MEP in front
of the primary extractor. Essentially, a MEP can advantageously be
coupled with any extraction column designed to separate asphaltenes
from DAO, and can be classified in this invention as a asphaltene
separator or precipitator/separator.
[0076] The secondary asphaltene extractor 50 is employed to
increase overall recovery of product hydrocarbon from the process
and ensure all oil is removed from stream 42 prior to being sent to
the inertial separator 60. In addition, unit 50 reduces overall
solvent circulation rates.
[0077] Instead of sending stream 42, directly to the secondary
asphaltene extractor, it is in this case sent to a MEP 230 to
provide enhanced mixing of the asphaltene to allow the solvent to
be intimately and rapidly mixed with the asphaltene. This
thoroughly mixed stream 231 is sent to the secondary asphaltene
extractor 50.
[0078] Conventionally, and in common current practice, additional
solvent extraction is performed on the primary deasphalted oil in
the form of a resin extractor 80 to provide a separate deasphalted
heavy oil stream 82. This feature is included in the process of
this invention as well. As an improvement, the additional solvent
extraction step on the asphaltene-rich stream by extractor 50 uses
standard liquid-liquid extraction with the same solvent used in the
primary extractor 40, and has a MEP 230 included in the design. The
placement of this MEP 230 and standard liquid-liquid column
arrangement on the asphaltene-rich stream is new and is beneficial,
since the solvent to oil ratio can be further decreased within this
column to 5:1 (from 10 to 20:1 typically) to increase the recovery
of deasphalted oil with the overall solvent use reduced.
[0079] Solvent in stream 3 is added to the asphaltene-rich stream
41 to a very high solvent to oil ratio and is cooled further to
enhance asphaltene precipitation and thus oil recovery within
column 50.
[0080] The deasphalted oil stream 51 is sent to the resin extractor
80 to be further refined for product blending.
[0081] The bottoms stream from the secondary asphaltene extractor
column 50, like the bottoms of column 40, is concentrated
asphaltene and becomes stream 52 and is sent via gas in stream 4 to
the inertial separator 60 for solids separation, drying and
storage.
[0082] It is to be noted that the invention can embody either or
both MEP mixing devices at either or both locations.
[0083] Overall solvent use to achieve high hydrocarbon recovery
using the combination of the rapid/complete mixing device 230, and
the secondary asphaltene column 50, is about 15-30% less than when
using a static mixer in the process. The result is a significant
reduction in energy consumption compared to a state of the prior
art 3-stage extraction process. This high performance solvent
extraction scheme, including the MEP 230 and column 50 can be
applied to an existing open-art solvent extraction scheme in
operation to further increase crude yield and/or reduce operating
costs by reducing total solvent circulation. In another aspect, the
new scheme can be used as an improvement to designs in heavy oil
recovery that would normally use prior art solvent
deasphalting.
[0084] As in FIG. 1, the deasphalted oil in stream 41 is mixed with
a similar solvent, if necessary, and the temperature is raised by
heat exchanger 70 to precipitate out any resins and remaining
entrained asphaltenes in unit 80 the resin extractor. The bottoms
from the resin extractor are blended with the final product, while
stream 81 is further heated in exchanger 90, and sent to solvent
recovery 120. The solvent recovery unit 120 is typically run as a
supercritical extractor to reduce operating costs, with a stripper
provided on the deasphalted oil to reduce solvent losses to below
1%. The recovered solvent stream 101 is recycled to the front of
the process for re-use, while stream 102 is blended with streams 12
(FIGS. 3 to 5) and 82 (FIGS. 1 to 5) for use as product.
[0085] An advantageous application of the enhanced SDA scheme noted
in both FIGS. 1 and 2 is the integration of this SDA configuration
with a conventional mild thermal cracker of the prior art which is
illustrated in FIG. 3. A preferred embodiment is integrating the
thermal cracker in U.S. Pat. No. 7,976,695 with the MEP/separator
configuration in this invention. A light hydrocarbon stream 12, a
heavy DAO and asphaltene stream 13, and an offgas stream 11 are
generated from the unit 10 reactor. Stream 13 is mixed with solvent
to begin the asphaltene separation step as stream 14.
[0086] Through pilot testing of the concept, it was demonstrated
that the thermally-affected asphaltenes recombined together to
create higher molecular weight asphaltenes. The asphaltene
molecules range in size from Sum to 500 um, are thermally stable,
remain a solid at elevated temperatures, can be physically compared
to inert coke particles and are readily separated from the oil in
the presence of a modest amount of solvent. The application of the
MEP 30 and/or 230 may act to untangle any asphaltene particles
physically combined to allow for easier solvent separation.
[0087] The impact of unit 10 and 30 on stream 13 is the need for a
very simple separation in the asphalt extractor (asphaltene
separator now) 40. The amount of solvent required in stream 1 to
mix with stream 13 is far less than what is required in industrial
applications for bitumen (8-9:1 by mass), approximately in the
2-4:1 solvent to oil ratio range. The solvent may be C4-C9, or an
appropriate mixture. The extractor creates a deasphalted oil stream
41 and an increasingly concentrated solid, stable and non-sticky
asphaltene-rich stream 42.
[0088] As noted in table 1, this integrated process provides higher
yields than other traditionally arranged upgrading processes. Along
with this product benefit, the capital cost reductions from using
an inertial separator 60, and the operating cost savings from the
generated thermally affected asphaltenes by reactor 10, the MEP's
30 and/or 230, and secondary asphaltene extraction column 50, make
this a valuable tool to increase refiners' and upgraders' long-term
profits and sustainability.
TABLE-US-00001 TABLE 1 Product yield comparison Volume % Mass %
Coking 80-84 78-80 Standard reactor/solvent 86 80-82 extraction
process FIG. 3 process >89 84-86
[0089] In addition to applications of this invention in new
greenfield plant design opportunities, FIG. 4 shows an illustrative
application of the integrated controlled thermal cracker and
improved SDA with MEPs. The proposed integrated process, reactor
10, and improved SDA with appropriately placed MEPs (30 and/or 230
as necessary), and asphaltene recovery, items 40-230, can be placed
upstream of a refiner's/upgrader's coking unit. The benefit to a
refiner/upgrader is the ability to debottleneck existing vacuum and
coking facilities and accept more heavy crude to the unit. More
barrels processed on existing equipment equates to larger profits
and economic returns for similar capital costs. In addition, with a
higher quality material being sent to the coking unit 300, the
operating severity can be decreased, increasing the life of the
coker by increasing the cycle time for the coker (from 12 to 24
hours), and producing less gas and coke and more high value
product. Capital costs to replace equipment can be delayed and an
increased yield can be realized (approx. 2-3%). Solid asphaltenes
captured in the SDA have a readily available disposition, stream
302, the existing coke gathering and transport systems, making the
addition of the proposed integrated process more cost effective and
highly profitable. Process intensity may be decreased.
[0090] As well, and by example, stream 5 can be the bottoms streams
from an atmospheric column, vacuum column, or a catalytic cracking
unit, generally referred to as unit 200 in FIG. 4. The integrated
cracker and SDA process produces a DAO stream 102, that can be
further processed into a transportation fuels stream 401 in a
hydrocracking and hydrotreating complex unit 400. The integrated
cracker and SDA process with MEP also can produce a resin quality
stream 82 that can be sent to a coking, FCC (fluidized catalytic
cracking) and/or an asphalt plant for further processing into
finished products. Solid asphaltenes generated as stream 61 can
either be mixed with coke generated in unit 300 or sent off-site
for further processing (energy generation and/or sequestration). In
addition, the offgas stream 301 from the coking unit can be sent to
unit 400 for further processing to deal with any olefins generated
for use in the final product.
[0091] As yet another example, FIG. 5 shows a specific embodiment
for a new design or revamp opportunity for a refinery and/or
upgrader. Unit 200 is a vacuum unit and the bottoms stream 5 is
sent to the integrated cracker/SDA process units 10, 20, 30, 40-230
with appropriately placed MEPs 30 and/or 230. The DAO stream 102,
is sent to the hydrocracking and hydrotreating unit 400, along with
stream 205 from the vacuum unit. A resin stream 82 is produced from
units 40-230 and sent to a residue hydrocracking unit 500. With
less asphaltenes, that are highly exothermic when reacted, sent to
unit 500, the residue hydrocracker can run at higher conversion
rates producing more material as final transportation fuel product.
A high converted oil stream 501 is generated from unit 500. The
solid asphaltene stream 61 from units 40-230 can be mixed with
stream 502, the bottoms of unit 500, and sent to the gasification
unit 600 for hydrogen generation.
[0092] As in FIG. 4, the benefits of adding the integrated unit in
FIG. 5 can include: [0093] 1. Maximum yield of incoming crude to
plant [0094] 2. Debottlenecking, if existing, or reduction of
coking unit size [0095] 3. Debottlenecking, if existing, or
reduction of residue hydrocracking size [0096] 4. Debottlenecking,
if existing, or reduction of gasification unit size [0097] 5.
Overall carbon footprint reduced for process facility. [0098] 6.
Process intensity decreases (gains in overall efficiencies and
economics)
[0099] The integrated process in FIG. 3 can also can help sweet,
low complexity (hydro-skimming) refiners accept heavier, cheaper
crudes which are more readily available, and thus reposition
refining assets to capture more value by accepting a broader range
of feedstock. The integrated process of this invention can be
placed at the front of the refinery to provide the initial
conditioning of the heavier crude.
[0100] FIG. 6--illustrates a preferred arrangement for the MEP
(40a) and the asphalt separator (40b). The two units are considered
one operation within the dotted lines with 40a and 40b typically
separated by a relatively short transport pipe. The complete and
intimate mixing in the MEP provides desired precipitation of the
solid asphaltene particles resulting in stream 41 which is a two
phase solid/liquid mixture. The downward discharge from the MEP,
taking advantage of Stokes' Law, enters a clarifying vessel 40b to
allow settling of downward flowing asphaltenes. The MEP (40a) and
separator (40b) can be closely coupled or separated by an
appropriate distance based on processing and plot plan
requirements. In a preferred embodiment, 40a and 40b are classified
as one unit with the MEP discharging directly into a settling
vessel which can be referred to as a clarifier or asphaltene
separator.
[0101] Within the separator (40b), an asphaltene washing zone can
be created by injecting solvent into the bottom portion of the
vessel as indicated by stream 3. The solvent/DAO mixture leaves via
stream 43 with solid asphaltenes leaving via stream 42. The merging
of the two units may greatly increase the reliability of the entire
process by reducing the amount of transport piping that could foul
or plug. In addition, this simplified arrangement reduces the size
of the overall equipment (lower capital cost) and reduces the
overall solvent usage (lower operating cost), providing reduced
process complexity.
[0102] As a further opportunity for process intensification, the
MEP can be a high-shear mixing pump that includes pressure
generation while performing rapid/complete mixing. The need for
separate pump devices may be removed if a high-shear mixing pump
MEP is located in an appropriate spot in the process, thereby
potentially reducing capital cost and further simplifying the
process.
[0103] The mixing-enabled precipitation can be used in other
industries from stream lab analysis to any process involving
asphaltene processing (i.e. asphalt plant operation).
DEFINITIONS
[0104] The following terms are used in this document with the
following meanings. This section is meant to aid in clarifying the
applicant's intended meaning.
[0105] A slurry is, in general, a thick suspension of solids in a
liquid.
[0106] In chemistry, a suspension is a heterogeneous fluid
containing solid particles that are sufficiently large for
sedimentation. Suspensions are classified on the basis of the
dispersed phase and the dispersion medium, where the former is
essentially solid while the latter may either be a solid, a liquid,
or a gas.
[0107] In chemistry, a solution is a homogeneous mixture composed
of only one phase. In such a mixture, a solute is dissolved in
another substance, known as a solvent.
[0108] An emulsion is a mixture of small globules of one liquid
into a second liquid with which the first will not dissolve.
[0109] Precipitation is the process of separating a substance from
a solution as a solid
[0110] Pneumatics is a branch of technology, which deals with the
study and application of use of pressurized fluids to effect
mechanical motion.
[0111] Process intensification is the replacement or combination of
separate operating units into one unit improving the overall
performance of the process. Similarly, process intensity expresses
a relative concept for comparing a combination of complexity,
capital intensity and operational expense factors for processes or
facilities.
[0112] Canadian Bitumen is a form of petroleum that exists in the
semi-solid or solid phase in natural deposits. Bitumen is a thick,
sticky form of crude oil, having a viscosity greater than 10,000
centipoises under reservoir conditions, an API gravity of less than
10.degree. API and typically contains over 15 wt % asphaltenes.
* * * * *