U.S. patent application number 14/103714 was filed with the patent office on 2015-06-11 for system and method for continuous slag handling with direct cooling.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is General Electric Company. Invention is credited to Whitney Tolbert Norris, Raymond Douglas Steele, Hsien-Chin William Yen.
Application Number | 20150159097 14/103714 |
Document ID | / |
Family ID | 53270524 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150159097 |
Kind Code |
A1 |
Yen; Hsien-Chin William ; et
al. |
June 11, 2015 |
SYSTEM AND METHOD FOR CONTINUOUS SLAG HANDLING WITH DIRECT
COOLING
Abstract
A system includes a quench chamber configured to continuously
receive a mixture of a gas and slag, and a downstream end portion
coupled to the quench chamber. The quench chamber includes a quench
sump configured to continuously separate the gas from the slag in
the mixture via a quench liquid. The downstream end portion is
configured to continuously convey a slag slurry to a
depressurization system. The downstream end portion includes a
cooling system configured to directly cool the slag slurry with a
cooling fluid, and the slag slurry includes the separated slag and
at least a portion of the cooling fluid
Inventors: |
Yen; Hsien-Chin William;
(Sugar Land, TX) ; Norris; Whitney Tolbert;
(Schenectady, NY) ; Steele; Raymond Douglas;
(Cypress, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
53270524 |
Appl. No.: |
14/103714 |
Filed: |
December 11, 2013 |
Current U.S.
Class: |
48/128 |
Current CPC
Class: |
C10J 3/485 20130101;
C10J 3/526 20130101; C10J 3/845 20130101 |
International
Class: |
C10J 3/84 20060101
C10J003/84 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH &
DEVELOPMENT
[0001] This invention was made with Government support under
contract number DE-FE0007859 awarded by the Department of Energy.
The Government has certain rights in the invention.
Claims
1. A system comprising: a quench chamber configured to continuously
receive a mixture of a gas and slag, wherein the quench chamber
comprises a quench sump configured to continuously separate the gas
from the slag in the mixture via a quench liquid; and a downstream
end portion coupled to the quench chamber, wherein the downstream
end portion is configured to continuously convey a slag slurry to a
depressurization system, the downstream end portion comprises a
cooling system configured to directly cool the slag slurry with a
cooling fluid, and the slag slurry comprises the separated slag and
at least a portion of the cooling fluid.
2. The system of claim 1, comprising one or more slag crushers
configured to receive the slag slurry.
3. The system of claim 2, wherein the cooling system is disposed at
least partially between a first slag crusher of the one or more
slag crushers and a second slag crusher of the one or more slag
crushers.
4. The system of claim 2, wherein the cooling system is disposed at
least partially upstream of the one or more slag crushers.
5. The system of claim 1, comprising a slag crusher coupled to the
downstream end portion.
6. The system of claim 1, comprising a reactor coupled to the
quench chamber, wherein the reactor is configured to react a
carbonaceous feedstock to generate the gas and the slag.
7. The system of claim 1, wherein the cooling system comprises one
or more nozzles configured to dispense the cooling fluid directly
into the slag slurry.
8. The system of claim 1, wherein the cooling system comprises a
plurality of nozzle sets configured to dispense the cooling fluid,
wherein each nozzle set comprises one or more nozzles, and each of
the one or more nozzles is configured to dispense the cooling fluid
at a different angle than another of the one or more nozzles of the
respective nozzle set, at a different axial position than another
of the one or more nozzles of the respective nozzle set, at a
different circumferential position than another of the one or more
nozzles of the respective nozzle set, or any combination
thereof.
9. The system of claim 1, wherein the cooling system is configured
to cool the slag to less than approximately 70 degrees C.
10. A system comprising: a gasifier configured to react a
carbonaceous feedstock into a mixture of a gas and slag, wherein
the gasifier comprises: a quench sump configured to continuously
separate the gas from the slag in the mixture via a quench liquid,
wherein the quench liquid is configured to flow through the quench
sump at a first flow rate; and a downstream end portion of the
gasifier comprises a cooling system, wherein the downstream end
portion is configured to continuously convey a slag slurry to a
depressurization system at a third flow rate approximately 15
percent or less of the first flow rate, the downstream end portion
is configured to add a cooling fluid at a second flow rate to cool
the slag slurry, and the slag slurry comprises the slag and the
cooling fluid; and a controller configured to control the second
flow rate.
11. The system of claim 10, comprising one or more slag crushers
configured to continuously receive the slag slurry.
12. The system of claim 10, comprising the depressurization system
coupled to the downstream end portion, wherein the depressurization
system comprises one or more orifice plates, one or more let down
valves, one or more expansion turbines, one or more centrifugal
pumps, or any combination thereof.
13. The system of claim 12, wherein the controller is configured to
control the second flow rate based at least in part on a desired
flow rate of the depressurization system.
14. The system of claim 10, wherein the cooling system is
configured to directly cool the slag slurry to reduce vaporization
of the slag slurry upon depressurization in the depressurization
system.
15. The system of claim 10, comprising a plurality of sensors
configured to provide feedback to the controller, wherein the
feedback comprises temperature data, pressure data, flow data, or
viscosity data, or any combination thereof.
16. The system of claim 10, wherein the slag comprises less than
approximately 5 percent of the quench liquid.
17. A method, comprising: separating slag from a gas, wherein a
temperature of the slag is greater than approximately 175 degrees
C.; dispensing a cooling fluid into a downstream end portion of a
gasifier, wherein the cooling fluid is configured to decrease the
temperature of the slag to less than approximately 70 degrees C.;
forming a cooled slag slurry from the slag and the cooling fluid;
and conveying the cooled slag slurry substantially continuously
through an exit of the downstream end portion.
18. The method of claim 17, wherein forming the cooled slag slurry
comprises crushing the slag into a plurality of particles with one
or more slag crushers.
19. The method of claim 18, wherein the cooling fluid is dispensed
upstream, downstream, or between the one or more slag crushers.
20. The method of claim 18, wherein separating the slag from the
gas comprises supplying a quench liquid at a first flow rate,
wherein the cooling fluid is dispensed at a second flow rate, and
the second flow rate is less than approximately 15 percent of the
first flow rate.
Description
BACKGROUND
[0002] The subject matter disclosed herein relates to a slag
handling system, and, more particularly, to a continuous slag
handling system.
[0003] An industrial process may utilize a slurry, or fluid mixture
of solid particles suspended in a liquid (e.g., water), to convey
the solid particles through the respective process. For example,
partial oxidation systems may partially oxidize carbon-containing
compounds in an oxygen-containing environment to generate various
products and by-products. For example, gasifiers may convert
carbonaceous materials into a useful mixture of carbon monoxide and
hydrogen, referred to as synthesis gas or syngas. In the case of an
ash-containing carbonaceous material, the resulting syngas may also
include less desirable components, such as heavy ash or molten
slag, which may be removed from the gasifier along with the useful
syngas produced. Accordingly, the molten slag byproduct produced in
the gasifier reactions may be directed into a gasifier quench
liquid in order to solidify the molten slag and to create a slurry.
Generally, this slurry is discharged from the gasifier at elevated
temperatures and high pressures. The slurry discharged from the
gasifier is depressurized to enable the disposal of, or the further
processing of, the slurry. Unfortunately, heat exchangers that
reduce the temperature of the slurry after discharge from the
gasifier may have complex flow paths, may have relatively large
foot prints, and/or may be susceptible to erosion or blockages due
to slag accumulation.
BRIEF DESCRIPTION
[0004] Certain embodiments commensurate in scope with the
originally claimed invention are summarized below. These
embodiments are not intended to limit the scope of the claimed
invention, but rather these embodiments are intended only to
provide a brief summary of possible forms of the invention. Indeed,
the invention may encompass a variety of forms that may be similar
to or different from the embodiments set forth below.
[0005] In a first embodiment, a system includes a quench chamber
configured to continuously receive a mixture of a gas and slag, and
a downstream end portion coupled to the quench chamber. The quench
chamber includes a quench sump configured to continuously separate
the gas from the slag in the mixture via a quench liquid. The
downstream end portion is configured to continuously convey a slag
slurry to a depressurization system. The downstream end portion
includes a cooling system configured to directly cool the slag
slurry with a cooling fluid, and the slag slurry includes the
separated slag and at least a portion of the cooling fluid.
[0006] In a second embodiment, a system includes a gasifier
configured to react a carbonaceous feedstock into a mixture of a
gas and slag. The gasifier includes a quench sump configured to
continuously separate the gas from the slag in the mixture via a
quench liquid, and the quench liquid is configured to flow through
the quench sump at a first flow rate. The gasifier also includes a
downstream end portion of the gasifier having a cooling system and
a controller. The downstream end portion is configured to
continuously convey a slag slurry to a depressurization system at a
third flow rate approximately 15 percent or less of the first flow
rate, the downstream end portion is configured to add a cooling
fluid at a second rate to cool the slag slurry, and the slag slurry
includes the slag and the cooling fluid.
[0007] In a third embodiment, a method includes separating slag
from a gas, dispensing a cooling fluid into a downstream end
portion of a gasifier, forming a cooled slag slurry from the slag
and the cooling fluid, and conveying the cooled slag slurry
substantially continuously through an exit of the downstream end
portion. The temperature of the slag is greater than approximately
175 degrees C., and the cooling fluid is configured to decrease the
temperature of the slag to less than approximately 70 degrees
C.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0009] FIG. 1 is a schematic diagram of an embodiment of a
continuous slag removal system;
[0010] FIG. 2 is a schematic diagram of an embodiment of a gasifier
having a direct cooling system;
[0011] FIG. 3 is a cross-section of an embodiment of the direct
cooling system, taken along line 3-3 of FIG. 2; and
[0012] FIG. 4 is a flowchart illustrating a process for
continuously handling the slurry in accordance with an
embodiment.
DETAILED DESCRIPTION
[0013] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, all features of an actual
implementation may not be described in the specification. It should
be appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0014] When introducing elements of various embodiments of the
present invention, the articles "a," "an," "the," and "said" are
intended to mean that there are one or more of the elements. The
terms "comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements.
[0015] Various industrial processes involve the handling of
slurries. A slurry may include particulate solids dispersed in a
fluid, such as water. In certain situations, the slurry is
transported from a first location, or vessel, to a second location.
The slurry may be depressurized and/or cooled during transport from
the first location to the second location. For example, the
reaction chamber of a partial oxidation system (e.g., a gasifier)
may receive a carbonaceous feedstock (e.g., a slurry of
carbonaceous particulate solids such as coal or biomass, a
pneumatically-conveyed stream of particulate solids, a liquid, a
gas, or any combination thereof) and an oxidant (e.g., high purity
oxygen). In some embodiments, the reaction chamber may receive
water (e.g., water spray or steam) to contribute to the slurry. The
partial oxidation of the feedstock, the oxidant, and in some cases,
the water, may produce a useful gaseous product and an ash or a
molten slag byproduct. For example, a gasifier may receive the
feedstock, the oxygen and the water to generate a synthetic gas, or
syngas, and a molten slag. In certain cases, the molten slag may
flow through the gasifier into a quench liquid, such as water, to
create a slag slurry. The slag slurry discharged from the gasifier
may be at a high gage pressure between approximately 1000 to 10,000
kilopascals (kPa). The slag slurry within the gasifier may be at a
temperature between approximately 80 to 250 degrees C., (e.g., 175
to 475 degrees F.), between approximately 100 to 225 degrees C.
(e.g., 212 to 440 degrees F.), or between approximately 150 to 200
degrees C. (e.g., 300 to 400 degrees F.) or more. Before the slag
slurry is further processed or disposed of, the slag slurry may be
depressurized to a lower pressure (e.g., atmospheric pressure).
Depressurization of the slag slurry at elevated temperatures may
cause vapor flash where at least a portion of the liquid (e.g.,
water) in the slag slurry evaporates. The disclosed embodiments
discussed below cool the slag slurry to a temperature that
substantially reduces the occurrence of vapor flash when the slag
slurry is depressurized. For example, the disclosed embodiments may
cool the slag slurry to a temperature less than approximately 70
degrees C. (e.g., 160 degrees F.). The slag slurry may be cooled
without a heat exchanger or cooler downstream of the gasifier. The
slag slurry is cooled upstream of the depressurization system by a
cooling fluid (e.g., water). The cooling fluid may be injected into
the slag slurry at a gage pressure greater than or approximately
equal to the gage pressure of the slag slurry.
[0016] The disclosed embodiments convey the slag slurry in a
continuous process, rather than a batch process. As may be
appreciated, a continuous process may occupy less vertical space
than a batch process (e.g., lock hopper) and may have lower costs
than a batch process. In some embodiments, a continuous process may
utilize less water than the batch process. Furthermore, as
discussed in detail below, embodiments of the continuous process
may increase control of the amount of water (e.g., cooling fluid)
in the slag slurry relative to the batch process. Thus, the
disclosed embodiments employ a depressurization system (e.g.,
liquid expansion system) to continuously remove the slag slurry and
reduce the pressure, while also consuming less space. In some
embodiments, the depressurization system generates power, such as
via an expansion turbine. Therefore, certain embodiments may be
referred to as slag slurry depressurizing systems, or more
generally as slag slurry handling systems.
[0017] With the foregoing in mind, FIG. 1 is a schematic diagram of
an embodiment of a continuous slag removal system 10. As shown in
FIG. 1, the continuous slag removal system 10 may include a partial
oxidation system, such as a gasifier 12, a slag slurry 14, a
depressurization system 16 (e.g., liquid expansion system, one or
more expansion turbines, one or more centrifugal pumps, one or more
reciprocating devices, one or more orifice plates, or one or more
let down valves), and a controller 18.
[0018] The partial oxidation system, or gasifier 12, may further
include a reaction chamber 20, a quench chamber 22, and a
downstream end portion 62. A protective barrier 24 may enclose the
reaction chamber 20, and may act as a physical barrier, a thermal
barrier, a chemical barrier, or any combination thereof. Examples
of materials that may be used for the protective barrier 24
include, but are not limited to, refractory materials, non-metallic
materials, ceramics, and oxides of chromium, aluminum, silicon,
magnesium, iron, titanium, zirconium, and calcium. In addition, the
materials used for the protective barrier 24 may be in the form of
bricks, a castable refractory material, coatings, a metal wall, or
any combination thereof. In general, the reaction chamber 20 may
provide a controlled environment for the partial oxidation chemical
reaction to take place. A partial oxidation chemical reaction can
occur when a fuel or a hydrocarbon is mixed in an exothermic
process with oxygen to produce a gaseous product and byproducts.
For example, a carbonaceous feedstock 26 may be introduced to the
reaction chamber 20 with oxygen 28 to produce an untreated syngas
30 and a molten slag 32. The carbonaceous feedstock 26 may include
materials such as biofuels or fossil fuels, and may be in the form
of a solid, a liquid, a gas, a slurry, or any combination thereof.
The oxygen 28 introduced to the reaction chamber 20 may be replaced
or supplemented with air or oxygen-enriched air. In certain
embodiments, an optional slag slurrying agent 34 may also be added
to the reaction chamber 20. The slag slurrying agent 34 may be used
to maintain the viscosity of the slag slurry 14 within a suitable
range and thus may aid in transporting the slag slurry 14 through
the continuous slag removal system 10. In yet other embodiments, an
optional moderator 36 (e.g., water or steam) may also be introduced
into the reaction chamber 20. The chemical reaction within the
reaction chamber 20 may be accomplished by subjecting the
carbonaceous feedstock 26 to steam and oxygen at elevated gage
pressures (e.g., from approximately 2000 to 10,000 kPa, or 3000 to
8500 kPa) and temperatures (e.g., approximately 1100 degrees C. to
1500 degrees C.) depending on the type of gasifier 12 utilized.
Under these conditions, and depending upon the composition of the
ash in the carbonaceous feedstock 26, the ash may be in the molten
state, which is referred to as molten ash, or molten slag 32.
[0019] The quench chamber 22 of the partial oxidation system, or
gasifier 12, may receive the untreated syngas 30 and the molten
slag 32 as it leaves the reaction chamber 20 through the bottom end
38 (or throat) of the protective barrier 24. The untreated syngas
30 and the molten slag 32 enter the quench chamber 22 at a high
pressure and a high temperature. In general, the quench chamber 22
may be used to reduce the temperature of the untreated syngas 30
and to disengage the molten slag 32 from the untreated syngas 30,
and the quench chamber 22 may be used to quench the molten slag 32
to at least partially solidify the molten slag 32. In certain
embodiments, a quench ring 40 arranged at the bottom end 38 of the
protective barrier 24 is configured to provide a quench liquid 42
(e.g. water) to the quench chamber 22. The quench liquid 42 may be
directed through a quench inlet 44 and into the quench ring 40
through a line 46. In general, the quench liquid 42 may flow
through the quench ring 40 and down the inner surface of a dip tube
47 into a quench chamber sump 48. The controller 18 may control the
flow rate of the quench liquid 42 through the quench inlet 44. For
example, the controller 18 may control the flow rate of the quench
liquid 42 to be between approximately 4,000 to 10,000 liters per
minute (LPM) (e.g., approximately 1,050 to 2,640 gallons per minute
(GPM)), approximately 5,000 to 9,000 LPM (e.g., approximately 1,320
to 2,375 GPM), or approximately 6,000 to 8,000 LPM (e.g.,
approximately 1,585 to 2,110 GPM).
[0020] The untreated syngas 30 and the molten slag 32 may also flow
through the bottom end 38 of the protective barrier 24, and along
the inner surface of the dip tube 47 into the quench chamber sump
48. As the untreated syngas 30 passes through the pool of quench
liquid 42 in the quench chamber sump 48, the molten slag 32 is
solidified and disengaged from the syngas, the syngas is cooled and
quenched, and the syngas subsequently exits the quench chamber 22
through a syngas outlet 50, as illustrated by arrow 52. Syngas 54
exits through the syngas outlet 50 for further processing in a gas
treatment system 56, where it may be further processed to remove
acidic gases, particulates, etc., to form a treated syngas.
Solidified slag 58 may accumulate at the bottom of the quench
chamber sump 48 and may be continuously removed from the gasifier
12 as the slag slurry 14. In certain embodiments, a portion of the
quench liquid 42 may also be continuously removed from the quench
chamber sump 48 for treatment through a quench outlet 60. For
example, particulates, soot, slag, and other matter may be removed
from the quench liquid 42 in a black water treatment system, and
the treated quench liquid 42 may be returned to the quench chamber
sump 48 through the quench inlet 44. In such embodiments, the
removed quench liquid 42 may have properties similar to the slag
slurry 14 and thus, may be transported and depressurized using a
liquid expansion system separate from or shared with the
depressurization system 16 for the slag slurry 14.
[0021] The slag slurry 14 may have various compositions of solids
suspended in the quench liquid 42, including, but not limited to,
fuels (e.g., coals), dry char, catalysts, plastics, chemicals,
minerals, and/or other products. The slag slurry 14 entering the
downstream end portion 62 of the gasifier 12 may have a high
pressure and a high temperature. For example, the gage pressure of
the slag slurry 14 may be between approximately 1000 to 10,000 kPa,
2000 to 9000 kPa, or 3000 to 8000 kPa, and the temperature of the
slag slurry 14 may be between approximately 150 to 350 degrees C.
(e.g., 300 to 660 degrees F.), 200 to 300 degrees C. (e.g., 390 to
570 degrees F.), or 225 to 275 degrees C. (e.g., 435 to 525 degrees
F.) or more. In some embodiments, the downstream end portion 62 is
narrower than the quench chamber 22.
[0022] A cooling system 64 controls a flow of a cooling fluid 66
into the downstream end portion 62 via one or more nozzles 68
(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more nozzles). In some
embodiments, the cooling system 64 includes a heat exchanger,
evaporation system, or refrigerant system to cool the cooling fluid
to between approximately 10 to 70 degrees C. The cooling fluid 66
may be at a high gage pressure of between approximately 1000 to
10,000 kPa, 2000 to 9000 kPa, or 3000 to 8000 kPa, and a flow rate
of the cooling fluid 66 may be between approximately 1 to 760 LPM
(e.g., 0.25 to 200 GPM), 100 to 475 LPM (e.g., 26 to 125 GPM), or
190 to 380 LPM (e.g., 50 to 100 GPM). The flow rate of the cooling
fluid 66 may be less than approximately 15 percent (e.g., 3 to 10
percent) of the flow rate of the quench liquid 42 into the quench
chamber 22. For example, the quench liquid 42 flow rate may be
approximately 7570 LPM, the cooling fluid 66 flow rate may be
approximately 300 LPM, the slag 58 may flow through the downstream
end portion 62 of the gasifier 12 with a flow rate of approximately
75 LPM, and the slag slurry 14 (e.g., the cooling fluid 66 and the
slag 58) may flow through the downstream end portion 62 with a flow
rate of approximately 375 LPM. The flow rate of the slag slurry 14
may be between approximately 2 to 15% of the flow rate of the
quench liquid 42 into the quench chamber 22. In some embodiments,
the temperature of the cooling fluid 66 may be between
approximately 10 to 60 degrees C. (e.g., 50 to 140 degrees F.), 20
to 50 degrees C. (e.g., 70 to 125 degrees F.), or 30 to 40 degrees
C. (e.g., 85 to 105 degrees F.). The cooling fluid 66 may include,
but is not limited to, gray water, boiler feed water, raw makeup
water, condensate, other water streams, or any combination
thereof.
[0023] The cooling system 64 dispenses the cooling fluid 66 into
the downstream end portion 62 to directly cool the slag slurry 14
that will be discharged from the gasifier 12. One or more streams
(e.g., jets) of the cooling fluid 66 interface with slag 58 in the
slag slurry 14, thereby decreasing the temperature of the slag
slurry 14. While the quench liquid 42 cools the syngas 30 and the
slag 32 that enters the quench chamber 22 from the reaction chamber
20, the cooling fluid 66 primarily cools the solidified slag 58 in
the slag slurry 14. The cooling system 64 may be integrated with
the downstream end portion 62 of the gasifier 12 and/or coupled
directly to the downstream end portion 62 of the gasifier 12. In
some embodiments, the nozzles 68 of the cooling system 64 may be
arranged among and/or upstream of one or more slag crushers 70 that
receive the slag slurry 14 from the downstream end portion 62.
[0024] As may be appreciated, certain designs of continuous slag
removal systems 10 may include a cooler 72 (e.g., heat exchanger)
for the slag slurry 14 and/or may dispense cold water 74 into the
slag slurry 14 between the gasifier 12 and a depressurization
system 16 (e.g., one or more let down devices). Presently
contemplated embodiments of the continuous slag removal system 10
may cool the slag slurry 14 to less than approximately 70 degrees
C. (e.g., approximately 160 degrees F.) without the cooler 72 or
cold water 74 injection shown in the dashed box 78 downstream of
the gasifier 12. Moreover, the cooling fluid 66 directly cools the
solidified slag 58 and the slag slurry 14 in the downstream end
portion 62 of the gasifier 12 rather than indirectly, such as when
the slag slurry 14 is cooled via a cooler 72 (e.g. heat exchanger)
downstream of the gasifier 12. The removal of the cooler 72 from
the continuous slag removal system 10 may reduce the height and/or
foot print of the continuous slag removal system 10. Furthermore,
the removal of the cooler 72 from the continuous slag removal
system 10 may reduce operational and/or installation costs. The
tubes of the cooler 72 may be susceptible to accumulation of slag
particulates that may restrict slag slurry flow, and/or the slag
slurry may wear or corrode tubes in the cooler 72.
[0025] The controller 18 may receive signals from various sensors
disposed throughout the continuous slag removal system 10. For
example, flow rate sensors 80 measure flow rates of the quench
liquid 42, the cooling fluid 66, and the slag slurry 14. One or
more pressure sensors 82 and/or temperature sensors 83 may provide
information regarding characteristics of the slag slurry 14,
operating conditions within the continuous slag removal system 10,
temperatures of the slag slurry 14, pressures of the slag slurry 14
at various sites, and so forth. In some embodiments, the controller
18 may receive additional sensor information about the slag slurry
14 as it exits the gasifier 12, such as, but not limited to,
viscosity, particle size, and so forth. Furthermore, the controller
18 may adjust operational conditions of the continuous slag removal
system 10 in response to received sensor information, as described
in detail below.
[0026] In certain embodiments, one or more slag crushers 70 coupled
to a slag crusher driver 84 (e.g., a steam turbine, the
depressurization system 16, a motor, or other source of power) may
optionally receive the slag slurry 14 before it is directed through
the depressurization system 16. The one or more slag crushers 70
may crush the solidified slag 58 in the slag slurry 14 in order to
attain a desired particle size distribution or a desired average
particle size of particles in the slag slurry 14. The one or more
slag crushers 70 may be arranged in one or more stages, and the one
or more slag crushers 70 may be arranged in series or in parallel
with one another. The one or more slag crushers 70 may include, but
are not limited to, rotary screw crushers and toothed rotor slag
crushers. Establishing an appropriate particle size distribution
may be useful for enabling the slag slurry 14 to flow, for
increasing the effectiveness of the cooling system 64, or for a
desired flow through the depressurization system 16, or any
combination thereof. Furthermore, the one or more slag crushers 70
may reduce the average particle size of the solids suspended in the
quench liquid 42 and cooling fluid 66 of the slag slurry 14 to an
appropriate range.
[0027] In certain embodiments, the one or more slag crushers 70 may
reduce the particle size such that the average particle size is
between approximately 0.5 to 26 mm (e.g., 0.02 to 1.0 inches), 2 to
8 mm (e.g., 0.08 to 0.31 inches), or 4 to 6 mm (0.16 to 0.24
inches. In one embodiment, the average particle size may be less
than 2, 3, 4, 5, or 6 mm. In certain embodiments, a single slag
crusher 70 may be sufficient to establish this average particle
size, and in other embodiments, two or more slag crushers 70 may
function together (e.g., in series and/or in parallel) to establish
this average particle size. For example, a first slag crusher may
provide a coarse crushing of the slag slurry 14, while a second
slag crusher may provide a finer crushing of the slag slurry 14. In
one embodiment, the controller 18 may control the slag crusher 70
by controlling the slag crusher motor 84. The controller 18 may
adjust the slag crusher motor 84 based on information received from
other sensors. In certain embodiments, a flow control valve 86 may
be disposed downstream of the slag crusher 70 to adjust the flow
rate of the slag slurry 14 flowing to the liquid expansion system
16. In one embodiment, the controller 18 may receive information
about the flow rate of the slag slurry 14 from a flow rate sensor
80. In response to the information received by the flow sensor 80,
the controller 18 may control the flow rate of the slag slurry 14
by adjusting the flow control valve 86. In other embodiments, the
controller 18 may adjust the flow rate of the slag slurry 14 based
on signals from other sensors 82, 83.
[0028] The slag slurry 14 may be fed into the depressurization
system 16 to decrease the pressure of the slag slurry 14. In some
embodiments, the depressurization system 16 is a turbomachine or
expansion machinery, such as, but not limited to, an expansion
turbine, a posimetric pump, a rotary screw pump, a modified
centrifugal pump, a reciprocating device, a restriction orifice, a
let down valve, or any combination thereof. A pressure sensor "P2"
82 may provide information on the pressure of the slag slurry 14
exiting the depressurization system 16. In some embodiments, the
depressurization system 16 (e.g., turbine) may generate power
(e.g., drive an electric generator) while depressurizing the slag
slurry 14 from the pressure at pressure sensor "P1" 82. For
example, the first gage pressure of the slag slurry 14, as measured
by the first pressure sensor "P1" 82, may be between approximately
1000 to 10,000 kPa, 2000 to 9000 kPa, or 3000 to 8000 kPa, or
approximately the high operating pressure of the gasifier 12. In
contrast, the second gage pressure of the slag slurry 14, as
indicated by the second pressure sensor "P2" 82, may be between
atmospheric pressure (0 kPa) to 100 kPa, 20 to 80 kPa, or 40 to 60
kPa. In certain embodiments, the second pressure is approximately
equal to atmospheric pressure. After exiting the depressurization
system 16, the slag slurry 14 may travel further downstream to a
slag processing system 88, such as for dewatering of the slag
slurry 14, before the slag slurry 14 is disposed of.
[0029] FIG. 2 illustrates an embodiment of the downstream end
portion 62 of the gasifier 12 and an embodiment of the cooling
system 64. The quenched and solidified slag 58 may settle from the
quench chamber 22 into the downstream end portion 62. Within the
downstream end portion 62, the solidified slag 58 forms the slag
slurry 14 with the quench liquid 42 and the cooling fluid 66. The
cooling system 64 may have one or more nozzle sets 100 (e.g., 1, 2,
3, 4, 5, 6, 7, 8, 9, 10 or more) to dispense the cooling fluid 66
(e.g., water) into the downstream end portion 62, and each nozzle
set 100 may have one or more nozzles 68 (e.g., 1, 2, 3, 4, 5, 6, 7,
8, 9, 10 or more). For example, a first nozzle set 102 may have 2
nozzles 68, and a second nozzle set 104 and a third nozzle set 106
may each have 4 nozzles 68.
[0030] FIG. 3 illustrates a cross-sectional view of an embodiment
of the first nozzle set 102, taken along line 3-3 of FIG. 2. The
nozzles 68 of each nozzle set 100 may extend through a wall 108 of
the downstream end portion 62 of the gasifier 12. Each of the
nozzles 68 may be oriented toward a center 110 of the downstream
end portion 62, in a first tangential direction 112, or a second
tangential direction 114, or any combination thereof. For example,
a first nozzle 116 may be oriented toward the center 110 and a
second nozzle 118 may be oriented in the first tangential direction
112. In some embodiments, one or more nozzles 68 of a nozzle set
100 may extend through the wall 108 to the center 110 and be
oriented towards the wall 108 in a radial direction 120 from the
center 110, to induce counter-clockwise swirl, and a third nozzle
116 may be oriented in the second tangential direction 114 to
induce clockwise swirl. Each of the one or more nozzles 68 may
dispense the cooling fluid 66 in a jet or stream that penetrate the
flow of the slag slurry 14, thereby enabling the cooling fluid 66
to directly interface and contact the slag 58 in the slag slurry
14. In some embodiments, one or more of the nozzles 68 may dispense
the cooling fluid 66 into the slag slurry 14 as a stream (e.g.,
jet) a sheet (e.g., vertical sheet, horizontal sheet, oblique
sheet), or a cone, or any combination thereof.
[0031] The one or more nozzle sets 100 depicted in FIGS. 2 and 3
may have various arrangements of the one or more nozzles 68. In
some embodiments, arrangements of the nozzles 68 in each nozzle set
100 may be rotationally symmetric about the center 110, thereby
enabling the cooling system 64 to cool the slag slurry 14 to a
substantially uniform temperature (e.g., less than approximately 50
to 95 degrees C., less than approximately 60 to 80 degrees C., or
less than approximately 70 degrees C.). For example, the second
nozzle 118 may be spaced by approximately 180.degree. from the
first nozzle 116, as illustrated in FIG. 3. As may be appreciated,
the term "approximately" as used herein to describe arrangement of
the nozzles 68 may be within 10.degree. or less. Other arrangements
of the one or more nozzle sets 100 may include, but are not limited
to, an arrangement with nozzles 68 spaced from one another by
approximately 90.degree. (e.g., the first nozzle 116, a third
nozzle 120, the second nozzle 118, a fourth nozzle 122) or by
approximately 60.degree. (e.g., the fourth nozzle 122, a fifth
nozzle 124, and a sixth nozzle 126), as illustrated in FIG. 3. In
some embodiments, multiple nozzle sets 100 may be arranged on the
wall 108 such that the nozzles 68 are circumferentially offset
about the center 110 to enable the nozzles 68 to dispense the
cooling fluid 66 to cool different portions of the slag slurry 14.
For example, the first nozzle set 102 may have four nozzles 68
spaced by approximately 90.degree. from each other starting at a
first point 128, and the second set 104 may have four nozzles 68
spaced by approximately 90.degree. from each other starting at a
second point 130.
[0032] Returning to FIG. 2, each nozzle set 100 dispenses (e.g.,
injects) the cooling fluid 66 (e.g., water) into the downstream end
portion 62. The cooling fluid 66 may be dispensed at a relatively
high gage pressure (e.g., between approximately 1000 to 10,000 kPa)
that is greater than or approximately equal (e.g., within 10
percent or less) to the gage pressure of the slag slurry 14,
thereby enabling the cooling fluid 66 to readily flow into the slag
slurry 14. In some embodiments, substantially all (e.g., greater
than 75 percent) of the cooling fluid 66 may cool the slag slurry
14 and flow through an exit 132 of the downstream end portion 62
rather than through the syngas outlet 50 or the quench liquid
outlet 60. Accordingly, the cooling fluid 66 primarily cools the
slag slurry 14 downstream of the quench chamber 22.
[0033] In some embodiments, the downstream end portion 62 may
include one or more slag crushers 70 to establish a desired average
particle size. As discussed above, a first slag crusher 134 may
provide a coarse crushing of the slag slurry 14, while a second
slag crusher 136 may provide a finer crushing of the slag slurry
14. Each slag crusher 70 may include one or more elements 138 for
breaking up the solidified slag 58 in the slag slurry 14, although
other types of slag crushers may be used alone or in combination
with slag crushers 70 having elements 138. Additionally, or in the
alternative to one or more slag crushers 70 in the downstream end
portion 62, some embodiments may include one or more slag crushers
70 downstream of the exit 132.
[0034] The one or more nozzle sets 100 may be arranged among the
one or more slag crushers 70 of the downstream end portion 62. In
some embodiments, a nozzle set 100 (e.g., the second nozzle set
104) is arranged between the first and the second slag crushers
134, 136. Additionally, or in the alternative, a nozzle set 100
(e.g., the first nozzle set 102) may be arranged upstream of the
slag crusher 70 and/or a nozzle set 100 (e.g., the third nozzle set
106) may be arranged downstream of the slag crusher 70. The cooling
system 64 may include one or more flow control valves and/or
manifolds to control the distribution of the cooling fluid to the
one or more nozzle sets 100. The cooling system 64 may
differentially control the flow of the cooling fluid 66 to each of
the nozzle sets 100. For example, the cooling system 64 may direct
more cooling fluid 66 to the second or third nozzle sets 104, 106
while directing less cooling fluid 66 to the first nozzle set 102.
In some embodiments, the cooling system 64 may differentially
control the flow of the cooling fluid 66 to each nozzle 68 of a
respective nozzle set 100. For example, the cooling system 64 may
direct more cooling fluid 66 to a nozzle 68 proximate to a warm
component of the continuous slag removal system 10 and less cooling
fluid 66 to a nozzle 68 proximate to a cooler external ambient
environment.
[0035] In some embodiments, the depressurization system 16 may
include one or more let down devices including, but not limited to,
one or more orifice plates 140, one or more let down valves 142,
one or more expansion turbines 144, or one or more reverse-acting
centrifugal pumps, or any combination thereof. The one or more let
down devices may depressurize the slag slurry 14 based at least in
part on the flow rate of the slag slurry 14 and/or the particle
size of the solidified slag 58 within the slag slurry 14. For
example, the one or more orifice plates 140 and/or the one or more
let down valves 142 may depressurize the slag slurry 14 a greater
amount when the slag slurry 14 flows at a first flow rate (e.g.,
approximately 380 LPM) than when the slag slurry 14 flows at a
decreased second flow rate (e.g., approximately 300 LPM).
Accordingly, the controller 18 may control the flow rate of the
slag slurry 14 to control the depressurization of the slag slurry
14. In some embodiments, the controller 18 may control the flow
rate of the slag slurry 14 via controlling the flow rate of the
cooling fluid 66 from the cooling system 64. For example,
increasing the cooling fluid 66 flow rate may increase the flow
rate of the slag slurry 14 and increase the pressure drop across
the depressurization system 16. Conversely, decreasing the cooling
fluid 66 flow rate may decrease the flow rate of the slag slurry 14
and decrease the pressure drop across the depressurization system
16. Controlling the flow rate of the cooling fluid 66 may enable
the controller 18 to exercise a fine control of the flow rate of
the slag slurry 14 to satisfy any minimum flow specifications of
the depressurization system 16 relative to control of the flow rate
of the quench liquid 42. For example, adjusting the flow rate of
the cooling fluid 66 by about 10 percent (e.g., from 380 LPM to 340
LPM) may affect the flow rate of the slag slurry 14 less than
adjusting the flow rate of the quench liquid 42 by about 10 percent
(e.g., from 7570 LPM to 6800 LPM). Additionally, or in the
alternative, the controller 18 may control the flow rate of the
slag slurry 14 directly via controlling a flow control valve
86.
[0036] Adjusting the flow rate of the slag slurry 14 via
controlling the flow rate of the cooling fluid 66 from the cooling
system 64 may enable the cooling system 64 to accommodate a flow
rate specification of the depressurization system 16 without adding
fluid between the downstream end portion 62 and the
depressurization system 16. In some embodiments, the controller 18
may control the flow rate of the slag slurry 14 and/or the flow
rate of the cooling fluid 66 based at least in part on feedback
from a pressure sensor 82 downstream of the depressurization system
16. The controller 18 may also control the flow rate of the slag
slurry 14 and/or the flow rate of the cooling fluid 66 based at
least in part on a temperature of the slag slurry 14. For example,
the controller 18 may control the flow rate of the slag slurry 14
and/or the cooling fluid 66 to cool the slag slurry to less than
approximately 50 to 95 degrees C., less than approximately 60 to 80
degrees C., or less than approximately 70 degrees C. As may be
appreciated, a processor 146 of the controller 18 may execute
instructions (e.g., code) stored in a memory 148 of the controller
18 to control the cooling fluid 66 flow rate and/or the slag slurry
14 flow rate. Accordingly, the cooling system 64 coupled to the
downstream end portion 62 may reduce the complexity of the flow
path of the slag slurry 14 from the gasifier 12 to the
depressurization system 16. Thus, the cooling fluid 66 may be
utilized to cool the slag slurry 14 and to control the flow rate of
the slag slurry 14 to sufficiently depressurize the slag slurry 14
without vapor flash.
[0037] FIG. 4 is a flowchart illustrating a process 180 for
continuously handling the slag slurry 14. In some embodiments, the
process 180 begins when carbonaceous fuel reacts (block 182) in the
gasifier 12. As described above, the carbonaceous fuel may react
with an oxidant and optionally additional water. Upon reaction
within the gasifier 12, the continuous slag removal system 10 adds
(block 184) a quench liquid to a quench chamber 22 in the gasifier
12 at a first flow rate, and quenches (block 186) the reacted
products, such as a gas product and a slag byproduct. The gasifier
12 then separates (block 188) the gas from the slag, and conveys
(block 190) the gas to the gas treatment system. As described
above, the continuous slag removal system 10 adds (block 192) the
cooling fluid to the downstream end portion 62 of the gasifier 12
at a second flow rate, thereby cooling (block 194) the slag and
forming (block 196) the slag slurry. The slag slurry may be cooled
to less than approximately 50 to 95 degrees C., less than
approximately 60 to 80 degrees C., or less than approximately 70
degrees C. In some embodiments, one or more slag crushers 70 may
crush the slag to form the slag slurry, which may include the slag,
a first portion of the cooling fluid, and a second portion of the
added quench liquid. In some embodiments, the second flow rate of
the cooling fluid may be between approximately 2 to 15 percent,
approximately 3 to 10 percent, or approximately 3 to 7 percent of
the first flow rate of the quench liquid. The continuous slag
removal system 10 conveys (block 198) the slag slurry at a third
flow rate to a depressurization system 16 that depressurizes (block
200) the slag slurry. The third flow rate is based at least in part
on the second flow rate. The continuous slag removal system 10 may
control the third flow rate to depressurize (block 200) the slag
slurry to a desired pressure, such as approximately atmospheric
pressure.
[0038] Technical effects of the invention include enabling a
continuous slag removal system without a cooler and/or water added
between a downstream end portion of a gasifier and a
depressurization system. A cooling system dispenses a high gage
pressure cooling fluid to cool the slag slurry in the downstream
end portion of the gasifier to less than approximately 50 to 95
degrees C. (e.g., 120 to 200 degrees F.), less than approximately
60 to 80 degrees C. (e.g., 140 to 175 degrees F.), or less than
approximately 70 degrees C. (e.g., 160 degrees F.), thereby
reducing the likelihood of vapor flash in the depressurization
system. In addition to cooling the slag slurry, the cooling fluid
may be used to control the flow rate of the slag slurry to the
depressurization system. The pressure drop across the
depressurization system may be based at least in part on the flow
rate of the slag slurry through the depressurization system.
Accordingly, controlling the slag slurry flow rate via control of
the cooling fluid flow rate may control the pressure drop across
the depressurization system.
[0039] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
* * * * *