Note: Descriptions are shown in the official language in which they were submitted.
84312726
PLASMA GASIFICATION REACTOR
[0001] This is a divisional of Canadian Patent Application Serial No.
2751859, filed on
February 4, 2010.
FIELD OF THE INVENTION
[0001a] The invention relates to plasma gasification reactors with features
that can facilitate
processes such as syngas production particularly including reactor vessel top
section
configurations; reactor outlet port configurations; and/or reactor feed port
configurations, in
combination with other aspects of plasma gasification reactors and systems in
which they are used.
BACKGROUND
[0002] This background is presented to give a brief description of the
general context of
the invention.
[0003] Plasma gasification reactors (sometimes referred to as PGRs) are
known and used
for treatment of any of a wide range of materials including, for example,
scrap metal,
hazardous waste, other municipal or industrial waste and landfill material to
derive useful
material, e.g., metals, or to vitrify undesirable waste for easier
disposition. Interest in such
applications continues. (In the present description "plasma gasification
reactor" and "PGR"
are intended to refer to reactors of the same general type whether applied for
gasification or
vitrification, or both.)
[0004] Along with the above-mentioned uses, PGRs are also adaptable for
fuel reforming
or generating gasified reaction products that have applicability as fuels,
with or without
subsequent treatment.
[0005] PGRs and their various uses are described, for example, in
Industrial Plasma Torch
Systems, Westinghouse Plasma Corporation, Descriptive Bulletin 27-501,
published in or by
2005; a paper by Dighe in Proceedings of NAWTEC16, May 19-21, 2008, (Extended
Abstract
#NAWTEC16-1938) entitled "Plasma Gasification: A Proven Technology"; a paper
of
Willerton, Proceedings of the 276 Annual International Conference on Thermal
Treatment
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Technologies, May 12-16, 2008, sponsored by Air & Waste Management Association
entitled
"Plasma Gasification - Proven and Environmentally Responsible" (2008); a U.S.
patent
application of Dighe etal., 2008/0299019, published December 4, 2008, entitled
"System and
Process for Upgrading Heavy Hydrocarbons"; a U.S. patent application of Dighe
et al, Serial
No. 12/157,751, filed June 14, 2008, entitled "System and Process for
Reduction of
Greenhouse Gas and Conversion of Biomass".
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SUMMARY
[0006] This summary briefly characterizes some aspects of the
invention. Statements
made are intended to be generally informative although not as definitive as
the appended
claims.
[0007] In various aspects, this invention relates to reactor vessel
features and
combinations including reactor vessel geometries, outlet port (or exhaust
port) configurations,
and material feed port configurations also subject to independent utility.
[0008] The present invention is, in part, directed to a PGR
particularly, but not limited
to, one applied primarily as a gasifier capable of producing a synthesized gas
(or "syngas")
that may be useful as a fuel, that is characterized, in a vessel of a vertical
configuration, by
having a bottom section, a top section, and a roof over the top section with
certain geometric
and structural characteristics. In some disclosed embodiments the bottom
section, which may
be cylindrical, contains a carbonaceous bed into which one or more plasma
torches inject a
plasma gas to create an operating temperature of at least about 600 C (and
typically up to
about 2000 C), and the top section extends upward from the bottom section as a
conical wall,
substantially continuously without any large cylindrical or other configured
portions, to the
roof of the vessel, the conical wall being inversely oriented, i.e., its
narrowest cross-section
diameter being at the bottom where it is joined with the bottom section, and
is sometimes
referred to herein as having the form of a truncated inverse cone.
[0009] Although some previously disclosed PGR configurations have top
sections
that are enlarged between the lower end of the top section and the upper end
of the top
section, the presently disclosed embodiments of PGRs are not previously known.
[0010] Such example embodiments may further include in their overall
combination
innovative arrangements of one or more feed ports for introduction of feed
stock into the
reactor vessel that can contribute to more uniform distribution of material.
Such distributive
feed port configurations are also applicable to PGRs with other vessel
geometries.
[0011] Also, in further examples with the conical wall, there are one
or more outlet
ports each having a duct extending from the roof to the exterior of the vessel
and also
extending, by an intrusion, into the interior of the vessel. Such outlet ports
with intrusions
can also be applied in other locations and vessel geometries of PGRs.
[0012] These and other aspects of' PGRs can be selectively applied,
along with the
referred to conical wall, for any of the general purposes of PGRs,
particularly including, but
not limited to, that of producing a syngas useful for fuel applications after
exiting the vessel
through the outlet ports. Some disclosed examples take advantage of an
improved
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understanding of how reactor structural features can affect characteristics
such as gas flow and
residence time of reactants that can contribute to achieving more complete
reactions of
supplied materials for enhanced production of desired output products.
[0012a] According to one aspect of the present invention there is
provided a thermal
gasification reactor system comprising: a reactor vessel that has, in a
vertical arrangement, a
bottom section containing a bed of fragmented carbonaceous fuel material
supplied with
fluids subjected to a temperature sufficiently high to promote surface
reactions on the fuel
material comprising
C +1/2 02 ¨> CO,
C CO2 ¨> 2CO, and
C + H20 ¨>C0 + H2;
a reactor vessel top section, above the bottom section, and a roof above the
top section; the top
section being characterized by a substantially continuous inverse conical side
wall
configuration that extends from the bottom section of the roof; a lower
portion of the top
section having additional fluid inlets extending through the side wall; a feed
port arrangement
into an upper portion of the top section receiving feed material from one or
more supplies
external of the reactor comprising solids that descend to the lower portion of
the top section
forming a charge bed above the bottom section into which flow reaction
products from the
bottom section and, also, fluids from the additional fluid inlets through the
side wall with
resulting gasification of at least some of the feed material; and outlet ports
located to allow
exit from the top section of gaseous reaction products comprising a syngas
containing H2 and
CO.
[0013] The following description presents more aspects and
information about
example embodiments of the invention.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Fig. 1 is an elevation view, partly in section, of one example of
a plasma
gasification reactor in accordance with the invention;
[0015] Figs. 2 and 3 are outline elevation views of other example PGRs;
[0016] Fig. 4 is a plan view of the top roof of a PGR in accordance with an
example of the
invention;
[0017] Figs. 5-8 are partial and schematic views of feed port
arrangements that can be
applied in some examples of the invention; and
[0018] Fig. 9 is an outline schematic view of a PGR system in accordance
with an
example of the invention.
[0019] Fig. 1 illustrates an example PGR, such as for gasification of
carbonaceous and
non-carbonaceous feed material (e.g., a mixture of coal and biomass) to
produce a syngas,
slag and metals. "Syngas" is a term referring to "synthesis gas" generally
derived from a feed
material, including carbon material (e.g., coal) or hydrocarbon material
(e.g., biomass or
heavy oils), subjected to gasification with oxygen (e.g., from air) and water
(e.g., steam). The
resulting syngas typically contains hydrogen and carbon monoxide that can be
useful.
Additionally, depending on the solid and gaseous materials supplied,
quantities of vaporized
hydrocarbons may occur in the syngas. The syngas produced may be applied to
use as a fuel,
for example fueling a gas turbine, or further processed to form a liquid fuel,
e.g., ethanol, for
transportation purposes. A PGR such as that of Fig. 1 may also be applied to
purposes, such as
metal salvage, where gaseous products are exhausted with or without subsequent
treatment.
[0020] The reactor of Fig. 1, shown in full elevation in its left half
and vertically sectioned
in its right half, has a reactor vessel 10, generally of refractory-lined
steel (the lining not
being specifically shown in the drawing), whose prominent parts include a top
section 12, a
bottom section 14, and a roof 16. The top section 12 has its lower and upper
ends joined,
respectively, to the bottom section 14 and the roof 16 in a gas tight manner.
One aspect of
particular interest in the Fig. 1 embodiment is that the top section 12 has a
conical
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84312726
wall 18 from the bottom section 14 (smaller cross-section) to the roof 16
(larger cross-
section). The wall 18 has an angle (a, in Fig. 1) relative to the vertical
axis of the reactor
vessel 10 (e.g., an angle in the range of about 5 to about 25 ) over
substantially its entire
extent. This is one example of a configuration that can aid operational gas
flow (discussed
further below). However, useful configurations and benefit can also be
obtained if there are
minor variations, such as a wall like the wall 18 but having a variation in
its conical slope
anywhere along its extent to a larger angle relative to vertical as one
proceeds up the wall 18,
or to a lesser angle, by a change of no more than about 5 , or where the wall
includes, for
whatever reason, a minor portion, no more than about 10% to 20% of its total
length, of
variant or non-conical (such as cylindrical) form (where the use of up to
about 20% of the
total length in cylindrical form can be particularly useful for the location
of feed ports as will
he explained further in reference to Fig. 6.).
(0021] Figs. 2 and 3 illustrate embodiments in which a lower portion of
the top
section 12a has a conical wall portion 18a at a slightly different angle than
the conical wall
portion 18b of an upper portion of the top section 12b, as examples of other
suitable
innovative arrangements. In Fig. 2, the wall 18a of the lower portion 12a is
angled out more
than wall 18b of the upper portion 12. In Fig. 3, the variation is that wall
18b is angled out
more than wall 18a. Other aspects of Figs. 2 and 3 will be discussed below.
100221 Returning to Fig. 1, the bottom section 14 of the reactor vessel
10 example can
be of any convenient configuration and is generally cylindrical. It fits
directly with the
circular bottom of the top section 12, however with a minor conical transition
13 with a
greater angle than most of the wall 18. Thus, the top of the bottom section 14
and the bottom
of the top section 12, have like configurations or have a transition of minor
extent
therebetween.
[0023] It is generally convenient for the top section 12 and its
substantially conical
wall 18 to have a circular cross-section at horizontal levels over the
vertical extent of the
vessel. Another variation is where the lateral cross-section of the top
section 12 is not
circular; for example an oval cross-section with orthogonal lateral dimensions
having a ratio
in a range greater than 1 to 1, including those up to about 3 to 1, is
suitable. Any example
described may have a circular or non-circular cross-sectional configuration,
as well as the
other described aspects of PGRs.
[0024] To summarize the geometrical characteristics of a wall 18 as
shown in Fig. 1
and, also, as subject to some variations in other examples of PGRs:
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the wall 18, or at least about 80% to 90% of it, has a slope relative to the
vertical axis at an angle a that is between about 5 and about 25';
the wall angle a is either the same overall or is increasingly wider as one
proceeds up from the bottom section 14 to the roof 16 or, in examples in which
a becomes
less, i.e., there is a transition from a larger a to a smaller a as one
proceeds vertically up, any
such transition is no more than about 5 of angle and the upper part still has
an a greater than
zero;
the conical wall 18 can have either a circular cross-section (the most
typical case) or some other including an oval cross-section, such as up to a
ratio of about 3:1
in two orthogonal diameters; and
any parts of a side wall of a PGR top section 12, from a bottom section
14 to a roof 16 that do not meet any of the above criteria, e.g., a
cylindrical wall with zero
angle to vertical, is limited to no more than about 10% of the vertical height
of the top
section, except where a cylindrical wall portion is provided with one or more
lateral feed
ports it may occupy up to about 20% of the vertical height of the top section.
[0025] Even with such possible modifications, all of which are to be
considered
within the scope of the invention as a "conical top section" or "conical
wall", or "continuous
conical wall", whether or not the term "substantially", or the like,
accompanies them, the
conical wall 18 contrasts with prior PGR vessel configurations, e.g., those
with substantial (at
least about 25%) cylindrical portions or conical portions that are wider at
bottom than top.
10026] 'The upper section wall geometry referred to herein is the
geometry of the
interior surface of a wall such as wall 18 in Fig. 1. Typically, the outer
surface of a top
section wall is parallel with the inner surface but that is not essential to
meet the criteria of
interest.
[0027] Additional features of the bottom section 14 and their purposes
are as follows
for this typical example. The bottom section 14 contains a space for a
carbonaceous bed 20
(sometimes referred to as the carbon bed or the coke bed) that can be of
constituents such as
fragmented foundry coke, petroleum coke, or mixed coal and coke. By way of
further
example, the bed 20 can be of particles or fragments of the mentioned
constituents with
average cross-sectional dimensions of about 5-10 cm., or are otherwise sized
and shaped to
have ample reactive surface area while allowing flow through the bed 20 of
supplied
materials and reaction products, all generally in accordance with past PGR
practices.
[0028] The bottom section 14 has a wall 15 with one or more (typically
two to four)
nozzles, ports or tuyeres 22 (alternative terms) for location of a like number
of plasma torches
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24 (not shown in detail). The plasma ports 22 may be either at an angle to the
horizontal,
inclined downward, as shown, or otherwise, such as horizontal (which is also
the general case
for feed ports 28 and additional tuyeres 30 of the top section 12 discussed
below).
[0029] The bottom section 14 is also equipped with a number (one or
more; typically
one or two) of molten liquid outlets 26 for removal from the reactor of metal
and/or slag.
[0030] Returning now to further describe aspects of the top section
12, the conical
wall 18 is provided with a number (at least one; typically one to three) of
lateral (i.e., through
the wall 18) feed ports 28. Lateral feed ports 28 make it generally
unnecessary to have any
feed port through the roof 16 although that form is not excluded as either an
addition or an
alternative. The lateral feed ports 28 allow entry of feed material close to
the primary
reaction region of the reactor and can lessen the chance of unreacted feed
material being
blown out through outlet ports in or near the roof Subsequent description of
Figs. 5-8 below
includes discussion of ways of getting substantially uniform distribution of
material as well
as thoroughness of reactions. In accordance with one example, described
further in
connection with Fig. 8, a feed port is equipped with a distributive feed
mechanism to help get
more uniform distribution of feed material over the interior of the reactor's
top section.
[0031] Additionally, the top section 12 of Fig. 1 has a number of
tuyeres 30 (e.g., up
to about a dozen in each of two rows) for use as needed or desired in any
particular process
that is performed to supply additional, generally gaseous, material. The
tuyeres 30 are, in this
example, located through the conical wall 18 below the feed ports 28 and
proximate the
bottom section 14. The plasma ports 22 of the bottom section 14 are sometimes
referred to as
primary tuyeres while the tuyeres 30 of the top section 12 are sometimes
referred to as
secondary tuyeres (those in a row closest to the bottom section 14) and
tertiary tuyeres (in a
row above the second tuyeres).
[0032] The roof 16 covers the upper end of the conical wall 18 of the
top section 12.
The perimeter of the upper end of the wall 18 is sealed in a gas-tight
relation to the roof 16.
The roof 16 has a number, one or more, typically two to six, of outlet ports
32. The outlet
ports 32 constitute ducts for exit of gaseous products (e.g., syngas) from the
reactor vessel 10.
In some examples of a FOR of the invention, as in Fig. 1, outlet ports 32 are
only through the
roof 16 of the reactor vessel 10 and feed ports 28 are only through the
conical side wall 18.
[0033] In the example of Fig. 1, the outlet ports 32 extend directly
vertically through
the roof 16. Among alternative arrangements, roof outlet ports, of whatever
number, can be
arranged with their axes at an angle to the vertical; one example being to
have the axis of an
outlet port at an angle substantially the same as the angle of the wall 18 and
parallel with the
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wall 18. More generally, the axis of outlet ports through the roof may be at
any angle and in
some instances be other than as shown through the roof 16, such as laterally
through the
upper periphery of the wall 18 itself, such as in Fig. 3, while the roof of
the vessel has either
none or also has one or more outlets. Typically, a manway with a removable
cover is also
provided in the roof 16.
[0034] In some examples of interest, as in Fig. 1, the outlet ports
32 are located in the
roof 16 proximate the inner surface of the wall 18. In whatever configuration
of the outlet
ports is utilized, in terms of their number, size, location and angle, they
can be mere openings
through the roof (or wall) of the vessel 10, with suitable external ductwork,
or, as shown in
Fig. 1, the outlet ports 32 can be arranged with ducts 34 passing to the
exterior of the vessel
from a location inside of the vessel 10. The inner part of the ducts 34 is
referred to as an
intrusion or intruding port 36. The intrusions 36, in some examples as shown
in Fig. 1,
extend into the space proximate the inner side of the side wall 18 of the top
section 12.
t0035] Fig. 1 and the above description including various
modifications provide
examples of PGRs each utilizing a top section 12 with a substantially
continuous conical wall
18, as described, in contrast to prior known PGRs of comparable parts and
purposes that
have, in one or more sections above that which contains a carbonaceous bed, a
significant
part of cylindrical or other configuration.
[0036] Practitioners can utilize and take advantage of a
substantially continuous
conical wall 18 in PGRs of otherwise conventional configuration, for example,
with normal
gravity fed feed ports and outlet ports anywhere near the top of the vessel
and without an
intrusion, Also, a continuous conical wall 18 can be part of overall altered
PGR designs
including, for example, one or more feed ports having means for enhanced
distribution of
Iced material as well as one or more outlet ports having a duct with an
intrusion, as described
above.
100371 In Fig. 2, outlet ports 32 are shown through a roof 116. Here
the roof 116 is
domed shaped.
[0038] In Fig. 3, a variation is shown with outlet ports 132
extending laterally from an
extreme top portion 12c of the top section 18c that also, in this example, is
shown with a
cylindrical configuration of a minor extent that still keeps an overall
substantially conical
configuration for the wall 18. Alternatively, the conical shape of the wall 18
itself may
continue up and the lateral outlet ports 132 provided through it.
[0039] Fig. 3 can be an example of outlet ports 132 without an inner
intrusion,
although intrasions can suitably be used there as well. Figs. 2 and 3 for
simplicity do not
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illustrate feed ports except the top central feature 116a in the roof 116' of
Fig. 3 can represent
either a central gravity fed feed port or a manway. Feed ports and tuyeres in
the top section
and the entire bottom section of the reactors in Figs. 2 and 3 are omitted for
simplicity. They
may, for example, be configured substantially as described in connection with
Fig. 1 or the
other examples herein.
[0040] PGR outlet ports with intrusions, like outlet ports 32 having
duets 34 with
intrusions 36 of Fig. 1, are not limited to use in PGRs with a substantially
conical wall, such
as the wall 18. Favorable use of such outlet ports can be made with other side
wall
geometries, as well as in other locations than the specific examples shown.
[0041] The following is presented by way of further explanation and
example of
factors influencing the conical top section design configurations.
[0042] The arrangements disclosed have particular relevance in their
application to
vertically oriented, atmospheric gasifier vessels. These are gasifier vessels
for operation at or
near atmospheric pressure (i.e., operable in a range from slightly negative
pressure to slightly
positive pressure) that are subjected to flow of gases and gas borne solid
elements, with high
temperatures, throughout their operation. It can be important how reactor
configurations
affect the movement of gases and particles in a freeboard region 38 of the
reactor 10, as in
Fig. I.
[0043] The interior of the top section 12 can be considered to contain
two principal
regions. A gasification region 29 is the region at or proximate the tuyeres 30
in which
supplied material is (at least partially) gasified. (A water jacket 31 can be
used as desired to
moderate wall temperature.) The freeboard region 38 is the space in the top
section 12 above
the tuyeres 30 through which gasified materials ascend. Studies by
computational fluid
dynamics can model heat transfer and fluid flow for the gasifier vessel in the
freeboard region
38 to help achieve improved performance, Alternative designs can be evaluated
based on a
number of criteria such as the velocity flow field, the gas residence time
distribution and the
solids carryover to an outlet. Such studies can demonstrate how a benefit can
be attained by
having a conical expansion, as described above, for the wall 18. One
characteristic attainable
is that of minimizing the flow separation from the reactor wall and minimizing
low velocity
recirculation zones created as a result of the flow separation. It is of
incidental benefit to be
able in some cases to achieve lower cost for both the steel required for the
vessel and its
refractory lining by the relative simplicity of the conical wall 18.
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[0044] Regarding the velocity flow field, it is considered that the
reactor cross-
sectional velocity is better if it is more uniform as that leads to more
efficient use of the
reactor volume for the reactions performed.
[0045] The gas residence time distribution profile indicates the
average gas residence
time. A longer time is generally better for more consistent composition of
products at the
reactor outlets. Also, feed materials need a high enough temperature for a
sufficiently long
time for more thorough reaction, i.e., so an undesirable amount of unreacted
feed material
does not exit the reactor. This can be of particular importance with some
heavy materials
such as tar. A generally desirable characteristic is for the reactor to
perform substantially like
a plug flow reactor which means input solid materials descend mainly
vertically and output
gases ascend mainly vertically.
[0046] Consequently, the gas generated within the reactor should have
at least a
minimum residence time of sufficient length to achieve satisfactory
performance.
[0047] Based on the above considerations, it is the case that
performance of a reactor
in which there is a conical top section wall, such as wall 18, (including the
described minor
variations) is often better than one having a cylindrical or other
configuration for any more
significant portion of the top section 12.
[0048] in addition, whether used with a top section conical wall or
with a
conventional top section of some significant cylindricality, the configuration
of outlet ports
can make a significant difference in the carry-over velocity as well as the
residence time.
[0049] The solids carryover is mainly a function of the axial velocity
along the main
flow path apart from the solid physical properties. The average axial velocity
along the main
gas flow path to the outlets is termed the "carry-over velocity". It is
desirable to have the
carry-over velocity as low as possible to minimize the solids carryover.
[0050] Various outlet configurations have been evaluated. It is found
generally that
better flow and efficiency characteristics result if there are two or more
individual outlets,
e.g., at least four. By way of further example, six outlets, as shown in Fig.
4, can be one
effective arrangement. Here is shown a domed roof 116 of a reactor vessel with
six outlet
ports 32 uniformly arranged about, or near, the outer periphery of the roof
116, without any
more centrally disposed outlets. For combination with a circular top of a
conical wall 18, the
roof 116 can be circular. The outlet ports 32 may be circular in cross-
section, as shown, or
have some other cross-section. With any number of outlet ports 32 provided
through the roof
116, it is generally suitable to have them located proximate the periphery of
the roof 116.
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[00511 A PGR roof can be of various forms including, for example,
substantially
planar across the top of the top end of the conical wall 18 or, as shown by
roof 16 in Fig. 1,
projecting upwardly from the top of the wall 18, either with joined roof
portions, such as
portions 16a and 16b, that are individually planar, or a continuous bowed out
curved surface
as shown by roof 116 in Figs. 2 and 4.
[0052] The individual outlet ports 32, of whatever number or location,
can usefully
include in their ductwork an intrusion, similar to the intrusions 36 of Fig.
I. The intrusions
can, for example, extend about 0.5-1.0 m. from the roof into the vessel (i.e.,
from thc interior
surface of the root). These have been found, at least in some analyses, to
contribute to
stability of gas flow from the outlets.
[0053] The additional tuyeres 30 of Fig. 1 include a row of secondary
tuyeres and a
row of tertiary tuyeres. The secondary tuyeres typically number about twelve
in a row below,
nearer the coke bed 20, than a row of a similar (or larger) number of the
tertiary tuyeres. The
tuyeres 30 are used to admit materials, usually gaseous materials such as air
(or other oxygen
containing gas) and steam (or other water). Particulate solids can also be
introduced through
the tuyeres 30. Embodiments like Figs. 2 or 3 can have similarly arranged
additional tuyeres,
which are emitted from those figures for simplicity.
[0054] In some process operations it can be satisfactory for feed
material to be
supplied merely through an opening through the roof of a reactor but it can be
more generally
helpful to enhance the residence time of solids by only supplying feed
material through
lateral feed chutes such as feed port 28 through a side wall, such as 18. One
or more of such
feed chutes, with other wall arrangements, are included in prior examples of
PGRs. Further
innovations can include some means for more uniform distribution of feed
material into the
top section of the reactor as is more fully described in connection with Figs.
5-8. For
example, and without limitation, one may get reasonably uniform feed material
distribution if
a feed chute (even where just one is used) is angled down from the horizontal,
such as the
feed port 28 shown in Fig. 1. Also, in combination with such an angled chute
or
independently, it can help to have a distributive feed mechanism within a feed
chute.
Variations can include mechanisms that can be programmed or adjusted to vary
the force
applied to the feed material (to achieve variations in the distance it is
injected, for example, in
a radial inward direction) and/or to vary the angle or direction from the feed
chute that the
material is injected. Fig. 8 further illustrates this aspect.
[0055] The following supplemental information refers to some other
aspects of
embodiments the invention may take.
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[0056] Plasma torches
24 that may be applied in the plasma torch ports 22 in Fig. I
may be in accordance with prior practice such as that shown and described in
U.S. Patent
4,761,793 by Dighe et al.
[0057] PGRs to which
the inventive features are applicable can be of a wide range of
sizes. Just for example, and similar to some past practices, the total
vertical extent of a
reactor vessel may be about 10-12 in. and the bottom section, containing the
carbon bed, can
have a width of about 3-4 in. and a depth of about 1-4 m. The top section can
be such as to
expand from a bottom diameter like that of the bottom section (about 3-4 m.)
to a top
diameter, at the roof, of about 7-8 m. Other dimensional examples are given in
reference to
the description of Fig. 9.
[0058] Also by way of
example, it is found helpful in various applications to operate
so that feed material forms a charge bed on top of the carbon bed that extends
up past the
height of both of the rows of tuyeres 30 (such as by about 0.5 to 1.0 m.). In
regard to the
reactor geometry, it may also be noted that reactor vessel 10 can, as
examples, be configured
to have the secondary tuyeres located about 5-15% of the distance up from the
top of the
bottom section to the roof, the tertiary tnyeres about 10-30% of that distance
up from the top
of the bottom section, and the one or more lateral feed chutes at least about
40-60% of the
distance up.
[0059] Figs. 5-8
generally illustrate some means for distributive introduction of feed
material through ports into the top section 12 of a reactor vessel, such as
one having a conical
wall 18 although applicable to other configurations as well. It is recognized
that having feed
material relatively uniformly distributed within the reactor vessel is
favorable to unifonnity
of performance and completion of reaction processes. These are some of the
means that can
be employed that can result in a better distribution than a single gravity
feed port through a
lateral wall, such as, but not limited to, the conical wall 18. These are
means that also have
an advantage over merely dropping material through an opening in the roof,
which is a
generally workable practice but risks considerable blowing out of unreacted
material through
nearby outlet ports.
[0060] Fig. 5 is an
example with multiple (here two, typically two to four could be
, used) feed ports
128 through a wall 18 (just part of which is shown). The feed ports 128 can
be merely gravity fed without other distribution enhancements (which could be
additionally
provided if desired) and the different points of material introduction help to
distribute the
feed material. It is acknowledged that multiple lateral feed ports have been
previously
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disclosed in plasma rectors, such as in Dighe et al. U.S. patent 5,728,193 and
Do et al. U.S.
patent 5,987,792. Here it is a combination of multiple lateral feed ports 128
and a
substantially continuous conical wall 18 of the top section 12 of the reactor
that is being
disclosed. However, such multiple side entry points for feed material,
although generally
effective as well as simple to construct, are not the only means for
advantageous feed
distribution.
100611 Figs. 6, 7, and 8 illustrate other means for feed distribution.
These are means
for feed distribution applicable to use with even only one feed port, although
not limited
thereto.
[0062] In Fig. 6, feed material is supplied through a lateral feed
port 228 that has a
protrusion 229 (e.g., of refractory lined steel, which additionally may be
water cooled) that
extends into the vessel toward the vessel's center axis. The protrusion 229
can also be, for
example, angled down, such as at angle of about 60', below horizontal and have
an end from
which feed material falls nearer to the center axis of the vessel 10 than to
the side wall which
in this example is a substantially conical wall 218 which includes a
cylindrical section 218a
(of no more than about 20% of the top section's height). Feed material will
descend by
gravity to the central region of' the lower part of the reactor roughly along
the dashed line
trajectory shown. Such a feed port 228 and protrusion 229 through a side wall
can be applied
to other wall configurations as well.
[0063] Among the notable points about the particular example of Fig.
6, and referring
back to Fig. 1, are that a protrusion 229 can be chosen to extend any desired
distance into the
reactor vessel's top section 12 from the conical wall 18. It can extend
further toward the
center of the vessel where it is intended to form a more uniform charge bed or
where it is
intended to further minimize the impact of feed material on the inner surface
of the wall 18,
that typically has a layer of refractory material.
[0064] Furthermore, even with a very limited protrusion 229, or even
no protrusion of
the feed port beyond the wall 18 into the vessel, Fig. 6 shows an example of a
configuration
of the wall 218 that can help minimize wear on the inner wall surface below
the feed chute
228. In this embodiment, the wall 218 has outwardly extending, conical
portions 218b and
218c with the feed port 228 located on the cylindrical wall portion 218a
between portions
218b and 217c. The cylindrical wall portion 218a extends below the feed port
228 before it
meets the conical wall portion 218b. That means, in contrast to Fig. I,
material entering the
vessel from the feed port 228 does not immediately descend onto the inner
surface of a
conical wall. Here, in Fig. 6, the material from the feed port 228 generally
takes an arcurate
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path and scatters to some extent so the impact on an inner wall surface 218b
is minimized and
its wear is lessened.
[0065] Fig. 7 shows an alternative in which a feed port 328 is at
least proximate the
center of the roof 316 and has a protrusion 329, similar in form to protrusion
229 of Fig. 6 but
here extending vertically down well into the top section 12, i.e., so material
enters well below
the outlet ports 332, which is also the case in Fig. 6. Thus, the protrusion
329 can, although it
need not, extend at least a third of the way down through the top section 12
at or near the
center axis. Naturally a feed port protrusion, such as 229 or 329, requires
structural strength
and/or cooling adequate for its exposure to high temperature.
[0066] Fig. 7 shows an outline 360 of the approximate maximum extent
of any build
up of feed material on a charge bed in the reactor. Lines 322 and 330 in Fig.
7 are shown as
representative indications of the location of primary and additional tuyeres
of the example
reactors. The Fig. 7 embodiment can place feed material centrally on the
charge bed. Outlet
ports 332 with intrusions 336 are also shown in the example of Fig. 7.
[0067] Fig. 8 shows another means for feed distribution. A feed port
428 in a lateral
wall 18 is arranged with a distributive feed mechanism 450 that has feedstock
supplied to it
from a supply 452 and by mechanical force injects or throws the material into
the interior of
the vessel.
100681 The distributive feed mechanism 450 arranged in the combination
can be like
or similar to mechanisms heretofore applied for forced distribution of
materials in apparatus
applied in fields such as agriculture and mining. One such mechanism is that
commonly
referred to as a slinger conveyor, Other mechanisms can be used; for present
purposes a
distributive feed mechanism can be any that applies mechanical force to the
feed material.
An air blower is one other such apparatus but is best used where the feed
stock has a
substantial amount of matter that is roughly consistent in size and weight.
[0069] Fig. 8 additionally shows, as an option in combination with the
distributive
feed mechanism 450, a force and direction controller 454, that can do either
or both of two
things: the controller 454 can be arranged so the feed mechanism 450 applies
varying
magnitudes of force to feed material to provide, over time, even better
distribution than with
constant force. Also, the controller 454 can be arranged so the feed mechanism
450 applies
force at varying angles (e.g., by a range of movement of the mechanism 450),
either, or both,
= in a horizontal plane or vertically, for better distribution than if
material continuously enters
at the same angle. The particular mechanism 450 and controller 454 can be
adapted from
material handling equipment technology used in other contexts.
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[0070] The means disclosed in Figs. 6-8 are each shown applied to only
a single feed
port of the reactor vessel. That is generally satisfactory but other numbers
of such means, or
combinations of such means, could be employed. It should also be understood
that the
arrangements for feed ports with enhanced distribution of feed material as
shown in Figs. 6,
7, and 8 are not necessarily limited to use with a reactor having a top
section with a
substantially conical wall, although such a wall may be often preferred.
[0071] In the case of any of the feed ports described herein, they can
either be open to
admission of air along with feedstock, such as under normal atmospheric
conditions, or the
feed supply and feed ports can be restricted to limit air admission, which can
sometimes be
favorable for some reactions.
[0072] Fig. 9 shows an example of a system in accordance with the
invention, in
outline and schematic form, that includes a plasma gasification reactor vessel
510 in a form
as previously described, and subject to variations such as those previously
described.
[0073] Merely by way of further example, some examples of suitable,
approximate,
dimensions for some elements of the vessel 510 are given. Unless otherwise
made clear, the
dimensions given refer to internal dimensions only. The vessel 510 is not
shown with a wall
thickness but the wall could typically be in a range of about 0.3-0.6 m.,
including steel and
refractory material. A top section 512 of the vessel 510, within a conical
wall 518, can have
a cross-sectional diameter at a bottom level 512a (above a transition 513
between the bottom
section 514 and this top section 512) of about 3.5 to 4.5 m. and a cross-
sectional diameter at a
top level 512b of about 7 to 8 m., resulting in an angle a of about 12 . At a
level 512c,
proximate and slightly above some auxiliary tuyeres 530 (which may be in two
levels of
secondary and tertiary tuyeres as previously disclosed), the cross-sectional
diameter of the
vessel can be about 4 to 5 m, and this would bc the approximate diameter of
the top surface
of a charge bed 529 of feed stock fed into the vessel from a feed port 528,
subject to aft the
prior descriptions of examples of feed ports, which can be one or more in
number.
[0074] Fig. 9 does not intend to show a particular configuration for
the top surface of
the charge bed 529; it need not be level, although approximate levelness is
favorable, and it
typically is somewhat higher in one or more locations that are closer to
(e.g., directly under)
any gravity fed feed ports that the reactor has which do not have a
distributive feed
mechanism.
[0075] The overall height of the top section 512, from level 512a to
level 512b can be
about 11 to 13 in,; the charge bed 529 can have a height between the levels
512a and 512e of
about 2 to 3 m.
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[0076] The vessel 510 also has a bottom section 514. It can have a
cylindrical diameter of about
Ito 2 m. and a height of about 3 to 4 in. The bottom section 514 contains a
bed 520 (labeled C bed) of
carbonaceous material as described in connection with Fig. 1.
100771 The bottom section 520 is here shown with a plasma torch nozzle or
primary tuyere 522
for a plasma torch 524 injecting a plasma gas into the bed 520 that creates a
suitably high temperature
in the bed 520. As shown, the torch 524 is supplied with a torch gas,
conveniently air but other gases
and gas mixtures are suitable as well. The plasma torch in any of the
embodiments may have an
additional supply (not shown) of material such as steam, oil, or another
material reactive in the bed
520 with the torch gas. The additional material can be supplied to the 'nozzle
522 in front of the plasma
generating torch 524 or a region of the C bed 520 proximate the location of
the nozzle 522. Reference
is made to the above-mentioned U.S. patent number 4,761,793 for further
understanding of examples
of plasma torch nozzles that may be applied in systems such as that of Fig. 9
and which have a shroud
gas applied around the plasma plume of a torch.
[00781 The C bed 520 need not fill the bottom section 514 of the reactor
510 to the top of
section 514; the plasma torch 524 can extend part way within the top of
section 514.
100791 Fig. 9 also shows an outlet 526 for molten metals and slag 541
from the bottom of the
C bed 520.
[0080] The secondary and tertiary tuyeres 530 that supply the charge bed
529 in the gasification
region of the reactor are shown connected with a supply 531 (which is
representative of one or more
supplies of the same or different materials) that is shown, for example, as
introducing one or more
fluids such as air or steam into the charge bed 529.
[0081] The plasma torch 524 is formed of material fed into the vessel 510
from a feed port 528
that is shown in conical wall 518 and is merely representative of feed ports
as previously described.
The feed port 528 is supplied from a feedstock supply 539 supplying, for
example, coal or other
carbonaceous material, waste which could be municipal solid waste or
industrial waste, biomass,
which could be any wood or plant material harvested for the purposes of the
system or a byproduct of
other agricultural activity, or some combination of such materials.
[0082] Most of the feedstock descends to the plasma torch 524 but some
may react with rising
hot gases in the freeboard region 538 above the charge bed 529. Also, the
rising gases from the plasma
torch 524 can react further in the freeboard region 538.
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10083] Reactions performed in a system like that of Fig. 9 typically
include fuel
particle surface reactions and gas phase reactions. The fuel particle surface
reactions can
include a gasification. reaction. of
C +1/2 02 CO,
Boudouard reaction of
C + CO2 2CO,
and a water gas reaction of
C + H20 CO + H2.
The gas phase reactions can include a combustion reaction of
CO + Y2 02 -3 CO2,
a CO shift reaction of
= CO +H20 -4 CO2+112)
and a steam reforming reaction of
CH4+ H20 CO + 3112.
[0084] The total reactions result in a syngas formed in the
freeboard region 538,
particularly in the region above the entry point for material from the feed
port 528. The
syngas can have significant amounts of carbon monoxide and hydrogen, along
with nitrogen
from air supplied to the reactor. Lesser amounts of carbon dioxide and other
compounds can
occur in the syngas.
[0085] At the top of the top section 512 of vessel 510 is the roof
516 that has some
number of outlet ports 532 from which the syngas 540 exits for subsequent use
as fuel or
other disposition.
[0086] Along with the other dimensional examples given above, the
roof 516 covers =
the maximum width of the top section 512 and also has a raised center 516a
about Ito 2 m. above
the top level 512b of the top section 512 with sloping surfaces (at, for
example, about a 30
angle) therebetween in which the outlet ports 532 occur, near to the conical
wall 518. The
outlet ports 532 can, for example, have a diameter of about 1 to 1.5 an. with
each having an
intrusion 536 of about 0.5 to 1 m.
100871 By way of more particular example, a reactor vessel 510 can
have four plasma
torch ports 522 with plasma torches 524, twelve each of the secondary and
tertiary tuyeres
530 and six of the outlet ports 532, with the several elements each being
spaced around the
circular periphery of the reactor structure, along with one or more feed ports
528.
[0088] Accordingly, it can be seen how PGRs can be configured with
one or more
innovative features. Without limitation as to particular levels of
performance, it is believed
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. õ
that among the ways the innovations can be used are ways in which they
contribute to overall
efficiency in terms of thoroughness of reactions and yields of desirable
reaction products.
[00891 In some described examples, it is indicated the innovations
presented are
combined with some aspects of prior PGR practices. Any public knowledge of
prior
apparatus and practices can be drawn upon as needed to facilitate practice of
the innovations
presented.
100901 In the course of the description various embodiments are
presented, along with
some variations and modifications, all of which are to be taken as examples of
arrangements
but not the sole or exclusive arrangements, practitioners may employ that are
within the
scope of the claims.
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