Note: Descriptions are shown in the official language in which they were submitted.
Description
Title of Invention: ELECTRIC POWER PLANT AND METHOD FOR OPERATING
ELECTRIC POWER PLANT
Technical Field
[0001] The present invention relates to a technology of combusting heavy
hydrocarbons,
which are produced as by-products during a process of refining crude oil in a
refinery, as a fuel
in a power plant for recovering heat and motive power to recover metal from
the heavy
hydrocarbons.
Background Art
[0002] Crude oil produced from an oil field includes metal components such as
nickel and
vanadium, in addition to hydrocarbons and sulfur components.
Many of such metal
components are locally present in heavy hydrocarbons, and the metal components
become
inhibitory substances during a process of refining heavy hydrocarbons with use
of a catalyst.
Hence, heavy hydrocarbons containing these metals are combusted in a utility
facility (for
example, power plant) in a refinery, and heat and motive power are recovered.
There have
been made efforts to recover these metals from combustion soot recovered from
a combustion
exhaust gas (for example, Patent Literature 1).
[0003] However, because of a low combustion efficiency of heavy hydrocarbons,
the
combustion soot thereof includes a large amount of uncombusted carbons. Thus,
there is a
need for a process of combusting and removing uncombusted carbons with use of
a combustion
furnace such as a rotary kiln before recovery of metal. Due to establishment
of a facility
necessitated by such pretreatment, temperature control in the combustion
furnace for avoiding
vanadium corrosion, consumption of additives, and the like, recovery of metal
from combustion
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soot of heavy hydrocarbons is a metal recovery method disadvantageous in terms
of cost.
Citation List
Patent Literature
[0004] [PTL 1] 2003-275616 A
Summary of Invention
Technical Problem
[0005] The present technology provides a technology that facilitates metal
recovery for
combustion soot generated by combustion of heavy hydrocarbons.
Solution to Problem
[0006] According to the present invention, there is provided a power plant for
generating
power with use of water steam obtained by combustion of fuel oil, or
generating both of steam
and power by combustion of fuel oil, containing:
a raw-material concentration unit configured to supply heavy hydrocarbons
having
been subjected to a concentration process of vanadium and nickel contained in
vacuum residual
oil obtained by vacuum distillation of atmospheric residual oil obtained by
atmospheric
distillation of crude oil, or supply the vacuum residual oil as heavy
hydrocarbons, for use as a
raw material of the fuel oil;
an emulsion-fuel manufacturing unit configured to mix the heavy hydrocarbons
supplied from the raw-material concentration unit with water and an
emulsifier, to obtain
emulsion fuel oil that is the fuel oil in which the heavy hydrocarbons are
dispersed in water;
a power generation unit configured to drive a power generator to generate
power with
use of energy obtained by combustion of the emulsion fuel oil;
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a boiler unit configured to generate water steam with use of energy obtained
by
combustion of the emulsion fuel oil; and
an exhaust-gas treatment unit containing a dust collector configured to
collect
combustion soot contained in an exhaust gas discharged after combustion of the
emulsion fuel
oil,
wherein the raw-material concentration unit is configured to supply the heavy
hydrocarbons containing the nickel and the vanadium at such a concentration
that a content
ratio of a sum of nickel and vanadium in the combustion soot collected by the
dust collector is
equal to or more than 25 mass%.
[0007] The power plant may have the following characteristics.
(a) The raw-material concentration unit is configured to supply the heavy
hydrocarbons
containing the vanadium at such a concentration that a content ratio of
vanadium in the
combustion soot collected by the dust collector is equal to or more than 10
mass%.
(b) The heavy hydrocarbons having been subjected to the concentration process
are extraction
residual oil provided after a solvent de-asphalting process of the vacuum
residual oil, or
pyrolysis residual oil provided after a pyrolysis process of the vacuum
residual oil.
(c) The boiler unit is configured to combust the emulsion fuel oil to generate
water steam, and
the power generation unit is configured to drive the power generator with a
steam turbine
configured to operate with use of the water steam generated by the boiler
unit.
(d) The power generation unit includes an internal combustion engine
configured to combust
the emulsion fuel oil to drive the power generator, and the boiler unit is an
exhaust-heat
recovery boiler configured to recover heat from the exhaust gas discharged
from the internal
combustion engine to obtain water steam. In this case, the power plant further
includes a
steam turbine configured to operate with use of the water steam obtained by
the exhaust-heat
boiler, and drive a second power generator to generate power, wherein the
second power
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generator is different from a first power generator that is the power
generator configured to be
driven by the internal combustion engine.
[0008] Further, according to the present invention, there is provided a power-
plant operation
method for generating power with use of steam obtained by combustion of fuel
oil, or generates
both of steam and power by combustion of fuel oil, including:
a step of generating power by driving a power generator with use of energy
obtained
by combustion of emulsion fuel oil that is the fuel oil in which heavy
hydrocarbons having been
subjected to a concentration process of vanadium and nickel contained in
vacuum residual oil
obtained by vacuum distillation of atmospheric residual oil obtained by
atmospheric distillation
of crude oil, or heavy hydrocarbons that are the vacuum residual oil, are
mixed with water and
an emulsifier, and the heavy hydrocarbons are dispersed in water;
a step of generating water steam with use of energy obtained by combustion of
the
emulsion fuel oil; and
a step of collecting combustion soot contained in an exhaust gas discharged
after
combustion of the emulsion fuel oil,
wherein the heavy hydrocarbons serving as a raw material of the emulsion fuel
oil
include the nickel and the vanadium at such a concentration that a content
ratio of a sum of
nickel and vanadium in the collected combustion soot is equal to or more than
25 mass%.
Advantageous Effects of Invention
[0009] According to this technology, in combusting fuel oil to generate water
steam and
power, emulsion fuel oil in which heavy hydrocarbons are dispersed in water
with use of an
emulsifier is used. This can enhance the combustion efficiency of the fuel
oil. As a result,
combustion soot in which the content of uncombusted carbons is significantly
reduced and
nickel and vanadium are contained at a high concentration can be obtained.
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Brief Description of Drawings
[0010] FIG. 1 is a configuration diagram for illustrating a power plant
according to an
embodiment.
FIG. 2 is a configuration diagram for illustrating an exhaust-gas treatment
unit
provided in the power plant.
FIG. 3 is a diagram for illustrating comparison between a composition of
combustion
soot of conventional heavy oil and a composition of combustion soot of
emulsion fuel oil.
FIG. 4 is an explanatory diagram for illustrating a process concerning
recovery of
metal components from combustion soot.
FIG. 5 is a configuration diagram for illustrating a power plant according to
another
embodiment.
Description of Embodiments
[0011] FIG. 1 is a schematic diagram for illustrating a configuration example
of a power plant
according to this embodiment. The power plant of this embodiment employs
emulsion fuel
oil in which heavy hydrocarbons in fine particle sizes are dispersed in water,
as a fuel for
generating water steam and electricity. This forms a configuration that can
enhance the
combustion efficiency and facilitate recovery of nickel and vanadium
(hereinafter also simply
referred to as "metal components") included in combustion soot. The power
plant of this
embodiment, one provided in a refinery for refining crude oil is shown as an
example.
[0012] The power plant illustrated in FIG. 1 includes: a raw-material
concentration unit 12
configured to supply heavy hydrocarbons; an emulsion-fuel manufacturing unit
13 configured
to manufacture emulsion fuel oil with use of the heavy hydrocarbons as a raw
material; devices
configured to combust the emulsion fuel to generate water steam and power (for
example, a
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boiler unit 21 and a steam turbine 22); and an exhaust-gas treatment unit 3
configured to treat
a combustion exhaust gas of the emulsion fuel.
[0013] The raw-material concentration unit 12 is supplied with vacuum residual
oil obtained
by atmospheric distillation and vacuum distillation of crude oil. Examples of
crude oil having
a high content of metal components include aromatic conventional crude oil
produced in the
Middle East or the like (for example, Arabian heavy, Kuwaiti crude oil, and
Iranian crude oil),
Mexican or Russian heavy crude oil, Canada's oil sands, Venezuelan extra heavy
crude oil, and
the like.
FIG. 1 briefly shows an atmospheric distillation column that performs
atmospheric
distillation of crude oil and a vacuum distillation column that performs
vacuum distillation of
atmospheric residual oil distilling from the bottom of the atmospheric
distillation column,
together as a distillation unit 11. Vacuum residual oil distills from the
bottom of the vacuum
distillation column and is supplied to the raw-material concentration unit 12
via, for example,
an intermediate tank (not shown).
[0014] The raw-material concentration unit 12 may be configured so as to
supply the vacuum
residual oil supplied from the distillation unit 11, to the emulsion-fuel
manufacturing unit 13
after performing a process of concentrating metal components included in the
vacuum residual
oil.
Alternatively, the raw-material concentration unit 12 may be
configured so as to directly
supply the vacuum residual oil supplied from the distillation unit 11, to the
emulsion-fuel
manufacturing unit 13.
[0015] Examples of the concentration process of metal components include a
solvent de-
asphalting process (SDA process) performed by a solvent de-asphalting (SDA)
plant 121 and a
pyrolysis process performed by a pyrolysis plant 122.
The SDA plant 121 brings butane (C4) or pentane (C5) serving as a solvent into
contact
with the vacuum residual oil to extract light fractions, pulverizes heavy
fractions that are left
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un-extracted as SDA pitch (extraction residual oil) or mixes heavy fractions
with a small
amount of light oil for adjustment of the viscosity, and supplies the heavy
fractions to the
emulsion-fuel manufacturing unit 13, as heavy hydrocarbons serving as a raw
material of the
emulsion fuel. Most of metal components contained in crude oil are locally
present in vacuum
residual oil.
Heavy hydrocarbons containing the metal components are difficult to
be
extracted into a solvent, and hence most of the heavy hydrocarbons are left in
SDA pitch.
Thus, the metal components are concentrated in SDA pitch by the SDA process.
[0016] The pyrolysis plant 122 heats the vacuum residual oil to about 400 C to
500 C to crack
the vacuum residual oil, then performs distillation separation into light
fractions and heavy
fractions, and supplies pyrolysis pitch (pyrolysis residual oil) formed of the
heavy fractions to
the emulsion-fuel manufacturing unit 13 as heavy hydrocarbons serving as a raw
material of
the emulsion fuel. As a specific configuration of the pyrolysis plant 122, a
case that employs
a process that does not involve a catalyst, such as a vis-breaking process,
can be exemplified.
Almost all of the metal components are contained on the heavy-fraction side
also after pyrolysis
of the vacuum residual oil, and hence the metal components are concentrated in
pyrolysis pitch
by a pyrolysis process.
Note that the concentration process of metal components is not limited to the
above-
mentioned examples such as a SDA process and a pyrolysis process.
Any other kind of
process that can increase the concentration of the metal components as
compared to that of the
vacuum residual oil distilling from the distillation unit 11 may be used.
[0017] Further, for crude oil having a high content of metal components in
vacuum residual
oil, such as Canada's oil sands and Venezuelan extra heavy crude oil, the
vacuum residual oil
may be directly supplied as heavy hydrocarbons serving as a raw material of
the emulsion fuel.
In this case, the vacuum distillation column in the distillation unit 11, and
a pump and a
transportation pipe that deliver vacuum residual oil are devices forming the
raw-material
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concentration unit 12.
[0018] FIG. 1 shows an example of the raw-material concentration unit 12 in
which the SDA
plant 121 and the pyrolysis plant 122 that perform the concentration process
of metal
components in vacuum residual oil, and the transportation pipe that directly
transports vacuum
residual oil are provided in parallel between the distillation unit 11 and the
emulsion-fuel
manufacturing unit 13. This is a diagram drawn for convenience in describing a
configuration
example of the raw-material concentration unit 12. Actually, there can be
exemplified a case
in which either of the SDA plant 121 and the pyrolysis plant 122 is provided,
a case in which
either of the plants 121 and 122 and the transportation pipe for vacuum
residual oil are provided
in parallel, and a case in which the plant and the pipe are provided in
tandem.
Further, on condition that it is possible to achieve a state in which metal
components
in a specified amount or more described later are contained in combustion
soot, vacuum residual
oil subjected to the concentration process may be mixed with atmospheric
residual oil or lighter
fractions.
[0019] The emulsion-fuel manufacturing unit 13 performs a process of mixing
heavy
hydrocarbons in which vacuum residual oil has been subjected to the
concentration process of
metal components or heavy hydrocarbons in which vacuum residual oil is
directly used, with
water and an emulsifier, to manufacture the emulsion fuel oil.
The manufacturing method of the emulsion fuel oil is not limited to any
particular
method, and publicly known methods can be used. In one example, the
temperature of heavy
hydrocarbons supplied from the raw-material concentration unit 12 is increased
to reduce the
viscosity to about 100 cSt. After that, the heavy hydrocarbons, water, and an
emulsifier are
added to a stir tank in which a stir blade is placed and the emulsion fuel oil
is manufactured,
and the micronized heavy hydrocarbons are dispersed in water that is a
continuous phase.
Thus, the emulsion fuel oil that is stably storable and pumpable at a normal
temperature is
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prepared. In a case in which the temperature of the heavy hydrocarbons during
supply thereof
to the stir tank is increased to about 200 C to 250 C to reduce the viscosity
of the heavy
hydrocarbons, the operations are performed at a high pressure in order to
suppress water
evaporation, and an emulsifier that is not thermally affected is selected.
[0020] Water containing the heavy hydrocarbons and the emulsifier is added to
the stir tank
in which dynamic stirring is performed by the stir blade or an in-line in
which static stirring is
performed. Thus, high shear force acts on the heavy hydrocarbons, and fine oil
droplets
having a size of about 10 gm on average are formed. At that time, by the
action of the
emulsifier, the emulsion fuel in which fine oil droplets are dispersed in
water that is a
continuous phase is obtained. The emulsifier used for manufacture of the
emulsion fuel is not
limited to any particular kind. A case in which an emulsifier that can stably
keep oil droplets
emulsified for about several days to several months is selected can be
exemplified. Regarding
the content ratio of water to the entirety of the emulsion fuel, a case in
which the content ratio
is set to, for example, 30 vol% in a range of from 25 vol% to 40 vol% can be
exemplified.
Note that, as water that is a continuous phase, drainage that is generated by
a corrugated plate
interceptor (CPI) oil separator or the like in the refinery and includes water-
soluble organic
components or the like can be used, but there is a limitation to a ph value
depending on the kind
of the emulsifier or a limitation to a chloride concentration depending on the
specification of a
combustion facility at a subsequent stage. For example, for heavy hydrocarbons
having a high
softening point, such as SDA pitch formed of C5 (pentane), in making the
emulsion fuel by
dispersion of heavy hydrocarbons at a normal temperature, solid heavy
hydrocarbons having
been pulverized may be used as the heavy hydrocarbons, to manufacture the
emulsion fuel.
The emulsion fuel is successively drawn out of the stir tank and stored in,
for example,
a storage tank (not shown) at a normal temperature.
[0021] The power plant of this embodiment combusts the emulsion fuel
manufactured by the
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method described above, to generate water steam and power.
FIG. 1 exemplifies a
configuration in which the steam turbine 22 caused to operate by water steam
generated by the
boiler unit 21 drives a power generator 221 to generate power.
The boiler unit 21 is configured to heat boiler water with heat obtained by
combustion
of the emulsion fuel, to generate water steam (step of generating water
steam). The boiler unit
21 is only required to include a combustion nozzle 211 capable of combusting
the emulsion
fuel, and other configuration may be the same as those of an ordinary heavy-
oil-fired boiler.
[0022] The emulsion fuel stored in the storage tank is supplied to the
combustion nozzle 211
placed in the boiler unit 21 by a pump (not shown). From the combustion nozzle
211,
atomized liquid droplets are sprayed to flames generated by combustion of the
emulsion fuel in
a heating furnace of the boiler unit 21. When the sprayed liquid droplets are
exposed to high
temperature, the moisture evaporates abruptly and micro-explosion occurs,
which further
micronizes the liquid droplets. Consequently, a contact area between the
further micronized
heavy hydrocarbons and high-temperature air is increased, and thus formation
of uncombusted
carbons can be suppressed, which enables efficient combustion of the heavy
hydrocarbons.
[0023] Also in a conventional vacuum-residual-oil-fired boiler, vacuum
residual oil is sprayed
into a combustion furnace with use of a large amount of atomization steam. An
amount of
surplus air to be required is larger than that of the emulsion fuel. Further,
heat sources of a
tracing pipe (that consumes energy of steam or electricity) for reducing the
viscosity to about
500 cSt to deliver the vacuum residual oil to the conventional boiler unit via
a pump, a heater
(that consumes energy such as steam or electricity) for keeping the storage
tank warm, and a
heater for reducing the viscosity to about 20 cSt to 30 cSt so that the vacuum
residual oil can
be sprayed well with a combustion nozzle, consume fuels as necessary. In
contrast, the
emulsion fuel containing water can save electricity, steam, and fuel, and thus
a thermal
efficiency not lower than that of vacuum residual oil conventionally used as a
fuel, can be
CA 03192468 2023- 3- 10
achieved.
A combustion exhaust gas of the emulsion fuel is subjected to an exhaust gas
treatment
in the exhaust-gas treatment unit 3 described later, and then is released to
the atmosphere via a
stack 4.
[0024] The water steam generated in the boiler unit 21 is delivered to the
steam turbine 22,
and the power generator 221 is driven by rotation of the steam turbine 22, to
generate power
(step of generating power). This manner of power generation is similar to that
of an ordinary
steam-turbine power generator. The water steam is condensed in a steam
condenser 222
provided on an outlet side of the steam turbine 22, is subjected to
predetermined boiler-water
treatment, and is supplied again to the boiler unit 21. Alternatively, the
steam at the outlet of
the steam turbine 22 is directly supplied to the refinery, as a utility.
[0025] The steam turbine 22, the power generator 221, and the steam condenser
222 form a
power generation unit of the power plant according to this embodiment. The
water steam is
generated by combustion of the emulsion fuel, and hence the power generation
unit is
configured to drive the power generator 221 to generate power with use of
energy obtained by
combustion of the emulsion fuel oil.
[0026] Next, a configuration of the exhaust-gas treatment unit 3 is described
with reference
to FIG. 2. The exhaust-gas treatment unit 3 removes environmental pollutants
contained in an
exhaust gas generated by combustion of the emulsion fuel in the boiler unit
21. The exhaust-
gas treatment unit 3 illustrated in FIG. 2 includes: a flue gas
denitrification unit 31 configured
to remove nitrogen oxide contained in an exhaust gas; an electric dust
collector 32 configured
to remove combustion soot; and a flue gas desulfurization unit 33 configured
to remove sulfur
oxide.
The flue gas denitrification unit 31 illustrated in FIG. 2 is an example
employing an
ammonia selective catalytic reduction method in which ammonia is sprayed into
an exhaust gas
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and then is brought into contact with a reducing catalyst to decompose
nitrogen oxide into
nitrogen and water. Note that the emulsion fuel has a lower flame temperature
and a lower
oxygen concentration than those of the conventional vacuum residual oil when
combusted, and
hence a generation amount of nitrogen oxide (thermal N0x) is reduced. For the
same reasons
as described above, a ratio at which sulfur oxide (sulfur dioxide) is
converted into sulfur trioxide
is reduced, and a generation amount of ammonium sulfate that is a compound of
sulfur oxide
and ammonia is reduced. This reduces the operations of the electric dust
collector.
[0027] The electric dust collector 32 electrifies combustion soot contained in
the exhaust gas
having been subjected to flue gas denitrification, by discharge, and
thereafter causes the
combustion soot to adhere and deposit onto a dust collecting electrode (step
of collecting
combustion soot). After that, the combustion soot is removed off the dust
collecting electrode
by hammering or by supply of cleaning water, and is discharged toward a
hopper. In a case
in which the conventional vacuum residual oil is combusted, combustion soot
adhering to the
electric dust collector is mainly composed of uncombusted coke and ammonium
sulfate. On
the other hand, in a case in which the emulsion fuel is combusted, an adhesion
amount of those
substances is significantly reduced. Note that the method of collecting
combustion soot is not
limited to electric dust collection, and dust collection may be performed with
use of, for
example, a bag filter.
The flue gas desulfurization unit 33, in the case of, for example, a wet type,
sprays
limestone in a slurry form to the exhaust gas having been subjected to dust
collection, to cause
the limestone and sulfur oxide (oxygen disulfide) to react with each other,
and recovers plaster
(CaS03Ø5H20, CaSO4.2H20). In order to further remove remaining sulfur oxide
(oxygen
trisulfide), removal is performed by a wet electric dust collector in some
cases.
In the exhaust-gas treatment unit 3, an exhaust gas is subjected to the above-
mentioned
series of exhaust gas treatment and then is released to the atmosphere through
the stack 4.
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[0028] In the exhaust-gas treatment unit 3 having the configuration described
above, the
combustion soot collected by the electric dust collector 32 includes metal
components of nickel
and vanadium. Meanwhile, as described above, an exhaust gas in which the
combustion soot
has been collected is generated by combustion of the emulsion fuel.
[0029] FIG. 3 shows an outline of change in composition of the combustion soot
in a case in
which heavy oil (vacuum residual oil) corresponding to the conventional fuel
is combusted and
a case in which the emulsion fuel is combusted. In the case in which heavy oil
is directly
combusted, carbons (uncombusted carbons) account for 70 mass% (wt%) to 80
mass% (wt%)
of the combustion soot. Further, 10 wt% to 20 wt% of the combustion soot
corresponds to
ammonium sulfate generated by reaction between ammonia supplied during flue
gas
denitrification and sulfur oxide. Then, the content of metal components such
as nickel and
vanadium is so low as not to reach 10 wt% of the combustion soot.
[0030] As described above, in order to recover metal components from
combustion soot
containing a large amount of carbons, as shown in a process flow on the left
side of FIG. 4, it
is required to perform pretreatment of combusting and removing uncombusted
carbons with
use of a transportation cost, an additional combustion facility, a fuel, and
an additive before
recovering metal components. Such pretreatment involves an additional cost,
and hence
causes reduction of a commercial value of combustion soot as a commodity
product serving as
a supply source of nickel and vanadium. Thus, in business dealings of
combustion soot
generated in a power station and the like, payment of a cost for treatment to
a treatment
undertaker who treats the combustion soot occurs in many cases even in a case
in which metal
components are to be recovered from the combustion soot.
[0031] In this regard, the power plant according to this embodiment combusts
the emulsion
fuel in which heavy hydrocarbons supplied from the raw-material concentration
unit 12 are
dispersed in water, to obtain water steam and power. The applicant of this
application has
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grasped that the combustion soot of the emulsion fuel can reduce the content
of carbons by 90%
or more in comparison with that of the conventional fuel.
[0032] Further, as described above, the emulsion fuel can reduce the amount of
surplus air
required for combustion, to lower the concentration of surplus oxygen, and has
a flame
temperature lower than that of the conventional fuel, to generate a smaller
amount of nitrogen
oxide than that generated by combustion of heavy oil. For those reasons, the
amount of
ammonia supplied in the flue gas denitrification unit 31 can be reduced.
Moreover, reduction
of the supply amount of ammonia can significantly reduce a generation amount
of ammonium
sulfate as compared to that associated with the conventional fuel.
[0033] By significantly reducing the content of carbons as described above, as
illustrated in a
process flow on the right side of FIG. 4, the conventionally-required
pretreatment in which
carbons are combusted and removed can be omitted. Further, even in a case in
which it is
required to combust and remove carbons, a carbon combusting time and a cost
for treatment
can be reduced, and hence the pretreatment can be simplified.
[0034] Moreover, by reducing the content of ammonium sulfate in the combustion
soot, a
burden on treatment of removing sulfur components in the recovery process of
metal
components can also be reduced.
Furthermore, through reduction of the contents of carbons and ammonium sulfate
that
are unnecessary components, the total weight of combustion soot containing the
same amount
of metal components can significantly be reduced. As a result, this can also
contribute to, for
example, reduction of a transportation cost of combustion soot discharged from
the power plant.
[0035] For a composition of the combustion soot that can produce the above-
mentioned
effects, the content ratio of the sum of nickel and vanadium in the combustion
soot collected
by the electric dust collector 32 is preferably equal to or more than 25 wt%,
and more preferably
equal to or more than 50 wt%. Further, when focus is given to vanadium alone,
the content
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ratio of vanadium in the combustion soot is preferably equal to or more than
10 wt% and more
preferably equal to or more than 20 wt%.
[0036] Note that it is not essentially required that the above-mentioned
content ratio be
achieved at all times during operation of the power plant. For example, as
long as the average
for each treatment lot subjected to metal recovery achieves the above-
mentioned content ratio,
it is not forbidden that the content ratio of nickel and vanadium occasionally
becomes lower
than the above-mentioned value during operation of the power plant.
[0037] The content ratio of nickel and vanadium is adjusted in the raw-
material concentration
unit 12. In a case in which the concentration process of metal components is
performed, the
content ratio of nickel and vanadium in combustion soot can be increased by,
for example,
selection of crude oil, selection of the kind of the vacuum residual oil
supplied to the SDA plant
121 and the pyrolysis plant 122 and the kind of the solvent in the SDA plant
121, a reaction
temperature in the pyrolysis plant 122, a recovery method of pyrolysis pitch
after pyrolysis, and
the like.
Further, in a case in which vacuum residual oil is directly used as heavy
hydrocarbons,
the content ratio of nickel and vanadium is adjusted by, for example,
selection of crude oil and
a cut temperature for separating the vacuum residual oil and lighter fractions
from each other.
[0038] In each of the above-mentioned adjustment methods, the total amount of
nickel and
vanadium is determined by the fact that the crude oil supplied to the SDA
plant 121 and the
pyrolysis plant 122 is aromatic and heavy. In this regard, the heavier the
vacuum residual oil
directly supplied to the emulsion-fuel manufacturing unit 13 is, or the
heavier the SDA pitch
and the pyrolysis pitch provided after the concentration process in the SDA
plant 121 and the
pyrolysis plant 122 are, the higher the content ratio of nickel and vanadium
in combustion soot
can be. The content ratio of nickel and vanadium can be increased also by
increase of
combustibility with use of the emulsion fuel or the like.
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[0039] According to the findings described above, through setting of specific
gravities
indicating a degree of heaviness of heavy components of the crude oil, the
vacuum residual oil,
the SDA pitch, and the pyrolysis pitch, a kind of vacuum residual oil having a
desired specific
gravity, and operating conditions of the distillation unit 11, the SDA plant
121, and the pyrolysis
plant 122 for obtaining various kinds of pitch, and the like, as operating
variables, it is possible
to increase the content ratio of nickel and vanadium in combustion soot.
Relationships
between those operation variables and the content ratio can be grasped based
on preliminary
experiments in an experimental furnace, operation records in the power plant,
and the like.
Based on the thus grasped relationships between the respective operating
variables and
the content ratio of nickel and vanadium in combustion soot, the crude oil is
selected and the
operation of the power plant is regulated so that the content ratio exceeds
the above-mentioned
value.
[0040] According to this embodiment, the following effects can be obtained. In
combusting
fuel oil to generate water steam and power, the emulsion fuel oil in which
heavy hydrocarbons
are dispersed in water with use of an emulsifier is used. This can enhance the
combustion
efficiency of the fuel oil. As a result, combustion soot in which the content
of uncombusted
carbons is significantly reduced and nickel and vanadium are contained at a
high concentration
can be obtained.
Further, pretreatment of combusting and removing carbons for recovering metal
contained in the combustion soot can be omitted, or the implementation steps
thereof can be
significantly reduced.
[0041] Here, with reference to FIG. 1, there has been described the embodiment
in which the
power plant is provided with the boiler unit 21 that directly combusts the
emulsion fuel to
generate steam, and the power generation unit that causes the steam turbine 22
to operate with
use of the steam and drives the power generator 221 to generate power.
However, the
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configurations of the boiler unit and the power generation unit forming the
power plant are not
limited to the examples described above.
[0042] For example, FIG. 5 shows an example in which the power generation unit
includes;
a diesel engine 23 that is an internal combustion engine configured to combust
the emulsion
fuel to operate; and a power generator (first power generator) 231 configured
to be driven by
the diesel engine 23 to generate power. Also in a case in which the emulsion
fuel is directly
combusted in the internal combustion engine, it can be understood that the
power generator 231
is driven to generate power with use of energy obtained by combustion of the
emulsion fuel oil.
Note that, in FIG. 5, the same components as those described with reference to
FIG. 1
are denoted by the same reference symbols as those illustrated in FIG. 1.
[0043] An exhaust gas generated by combustion of the emulsion fuel in the
above-mentioned
diesel engine 23 is subjected to heat recovery in which steam is generated in
an exhaust-heat
boiler 24 corresponding to the boiler unit. The exhaust-heat boiler 24 is
regarded as having a
function of generating water steam with use of heat obtained by combustion of
the emulsion
fuel oil, or heat obtained by complete combustion of unreacted hydrocarbons
and surplus
oxygen in the diesel engine 23 through additional combustion of the emulsion
fuel.
Further, the exhaust gas having been subjected to heat recovery in the exhaust-
heat
boiler 24 is discharged to the outside through the above-mentioned exhaust-gas
treatment unit
3 and the stack 4. This example is similar to the example described with
reference to FIG. 1
and FIG. 2 in that combustion soot is electrically collected by the electric
dust collector 32 in
the exhaust-gas treatment unit 3.
[0044] Meanwhile, the steam generated in the exhaust-heat boiler 24 is
directly used and
supplied to the refinery, as a utility. Alternatively, the steam is delivered
to a steam turbine
25 so as to rotate the steam turbine 25 and drive a power generator (second
power generator)
251, and thus power is generated (step of generating power by driving a second
power
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generator). The water steam is condensed in a steam condenser 252 provided on
an outlet side
of the steam turbine 25, and is subjected to predetermined boiler-water
treatment, to be supplied
again to the exhaust-heat boiler 24. Alternatively, the steam at the outlet of
the steam turbine
25 is directly supplied to the refinery, as a utility.
[0045] Also the steam turbine 25, the power generator 251, and the steam
condenser 252 form
the power generation unit of the power plant illustrated in FIG. 5. Then, the
water steam
supplied to the steam turbine 25 is generated with use of exhaust heat of an
exhaust gas
generated by combustion of the emulsion fuel, and hence also this power
generation unit drives
the power generator 251 to generate power with use of energy obtained by
combustion of the
emulsion fuel oil. With use of the emulsion fuel in a complex power plant as a
whole, it is
possible to achieve higher power generation and a higher energy efficiency.
[0046] Further, in this case, it is not essentially required that the power
plant include the raw-
material concentration unit 12 and the emulsion-fuel manufacturing unit 13 in
the same site as
exemplified in FIG. 1 and FIG. 5. The power generation unit and the boiler
unit may be
provided in a place remote from the refinery containing the raw-material
concentration unit 12
and the emulsion-fuel manufacturing unit 13. In this case, the emulsion fuel
manufactured in
the emulsion-fuel manufacturing unit 13 is transported by a tanker or a
pipeline with the use of
an emulsifier or the like appropriate for securing long-term stability at a
normal temperature,
and is stored in a storage tank provided on the power-plant side that is a
consumer. After that,
the emulsion fuel is used for generating water steam and power, and then
combustion soot is
collected.
Reference Signs List
[0047] 12 raw-material concentration unit
13 emulsion-fuel manufacturing unit
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21 boiler unit
22 steam turbine
221 power generator
3 exhaust-gas treatment unit
32 electric dust collector
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