Note: Descriptions are shown in the official language in which they were submitted.
~32~2
SLAG REMOVAL SYSTEM FOR A
SOLID FUELS GASIFICATION REACTOR
This invention concerns the gasification
of solid carbonaceous materials such as coke, coal,
or lignite. More particularly, thls invention con-
cerns discharging slag and/or heav~ ash from a
S solid fuels gaslfication reactor.
As presently well-known in the art, solid
fuels such as coke, coal or lignite can be ground
to a fine particulate size and mixed with oll or
water to form the feed stream for a gasification
reactor which is designed to make a useful syn-
thetic gas product. When this type of process is
carried out, a large ~uantity of molten slag that
requires disposal is formed in the reactor. Typ-
ically, the waste slag or heavy ash generaged in a
solid fuels gasification process consists of sol-
idified inorganic matter and a small amount of
unreacted car~on. Generally, this slag is dis-
charged from the bottom of the reactor an an
elevated temperature and pressure in the form of
a water slurry. The slurry being discharged may
.
29,309A-F -1-
.:
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be at a temperature as high as between 150 and
350F (65 ~nd 177C) and at a pressure as high as
between lO~ and 500 pounds per s~uare inch (690
to 3450 kPa). Prior art apparatus and methods
generally include crushing the slag to reduce the
size of the slag particles, using lockhoppers to
reduce the pressure, and flashing the water from
the slag in order to further lower the temperature
and pressure of the slurry being discharged.
In general, the present invention pro-
vides an improved apparatus and process for the
continuous, uninterrupted removal of a slag/water
slurry from a pressurized solid fuels gasification
reactor, the apparatus comprising: at least one
pressurized crusher for reducing the particle size
of the slag solids, said crusher being connected
to the slag discharge end of the reactor, and a
depressurizing system which includes a conduit
through which the slag/water slurry continuously
flows, said conduit being connected to the discharge
end of the crusher, and at least one restriction
element to restrict the continuous kinetic fluid flow
of the slag/water slurry through the conduit, said
restriction element being disposed within the conduit
and having an opening, the diameter of which is less
than that of the conduit, said element causing a
reduction in the pressure of the slurry at the dis-
charge end of the depressurizing system to a level
substantially below the pressure of the reactor.
The final discharge pressure of the slurry
may be essentially atmospheric or either higher or
29,309A-F -2-
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lower than atmospheric if the slurry is transferred
to other apparatus. The present apparatus may also
include additional crushers and flow restriction
elements in a series configuration to further
reduce the particle size of the slag and pressure
drop from the reactor. The flow restriction
elements provide a restric-tion to the fluid flow
of the slurry in the passageway transportiny the
slurry from the reactor, thereby causing a pres
sure drop accross the element under continuous
kinetic fluid flow conditions.
The present process for discharging a
slag/water slurry from a coal gasification reactor
includes: first comminuting or crushing the slag
solids in the slurry discharged from the reactor
to reduce the particle size thereof, said slurry
being discharged from the reactor at a pressure sub-
stantially equal to the reactor pressure; and passing
the slurry through a depressurizing system which
includes a conduit through which the slurry flows
continuously and at least one restriction element
to restrict the continuous kinetic fluid flow of the
slurry and therehy reduce the pressure of the slurry
at the discharge end of the depressuring system to
a level substantially below that of the pressure of
the reactor said restriction element being disposed
wi`thin the conduit and having an opening the diameter
of which is less than that of the conduit. The process
may also include additional steps of comminuting or
crushing the solids in the slurry, and restricting
the fluid flow of the slurry, to further reduce
the size of the slag and lower the exit pressure of
the slurry from the depressurizing system. The
29,309A-F -3-
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present method further provides for injecting and
mixing water with the slurry at a controlled rate
of flow after the slag solids have been comminuted,
thereby cooling the slurry and providing for variable
flow and pressure control of the slurry through the
depressurizing system of the reactor.
The present system provides for the
continuous flow removal of slag from a pressurized
gasification reactor with a reduced risk of plug-
ging as compared to intermittent removal providedby the known lockhopper systems. These and other
aspects of the present invention will be apparent
to those skilled in the art from the more detailed
description which follows.
lS The advantages of the present invention
are even more apparent when taken in conjunction
with the accompanying drawings in which like charac-
ters of reference designate corresponding material
and parts throughout the several views thereof, in
which: ~
Figure 1 is a schematic representation
illustrating a slag removal system in a solid
fuels gasification process constructed according
to the principles of the present inventon;
Figure 2 is a cross-sectional view of a
specific restriction element of the depressurizing
system made according to the present invention;
29,309A-F -4-
-- ~32S~S~
Figure 3 is a cross-sectional veiw of
ano-ther restriction element of the depressurizing
syst~m made according to the present invention;
and
Figure 4 is a cross-sectional view of still
another restriction element of the depressuri~ing
system made according to the present invention.
The following description illustrates
the manner in which the principles of the present
invention are applied, but such description is not
to be construed as limiting the scope of the inven-
tion.
More specifically, a slag removal apparatus
10 is illustrated by Figure 1 for communuting, cooling,
and depressurizing the slag/water slurry from the
bottom of a coal-gasification reactor 1. The waste
discharge from reactor 1 comprises a solid residue
which can be characterized as either a solidified
inorganic residue or heavy ash. The slag dis-
charge is combined with water in reactor 1 to forma slurry. The reactor 1 is operated under conditions
of temperature, pressure, and concentrations generally
well-known and practiced in the art for converting
coke, lignite, or coal into gaseous fuel. The tem-
perature at the discharge end of the reactor 1 isbetween 150 and 350F (65 and 177C) and the pres-
sure is between 100 and 500 pounds per square inch
(690 and 3450 kPa). Preferably, the reactor 1 is
operated continuously; and the comminution, cooling,
and depressurization of the reactor slag/water
slurry are carried out as a con-tinuous process.
29,309A-F 5-
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The slag/water slurry is discharged
from the reactor 1 through a first conduit 2
to a primary crusher 3. The crusher 3 is pro-
vided with a housing capable of withstanding
the full pressure at the discharge end of the
reactor 1. The conduit 2 and crusher 3 are con-
nected together by flanges 4.
The partially comminuted slag from the
primary crusher 3 is discharged to a secondary
crusher 3a, where the slag is further comminuted.
The crusher 3a is also provided with a housing
which, like the housing for the primary crusher
3, is capable of withstanding the full operating
pressure at the discharge end of the reactor 1.
Crushers 3 and 3a are connected together
by flanges 4a.
The comminuted slag is then discharged
as a slurry from the secondary crusher 3a to a
second conduit 5. The conduit 5 is connected to
the crusher 3a by flanges 4b and 4c. Flow through
the conduit 5 may be controlled by a first valve
5a. Downstream of the valve 5a, water is intro-
duced into conduit 5 from conduit 6 through valve
6a. The slag/water slurry then passes through a
series of restriction elements 7 in the conduit
5. Valves 5a and 6a regulate and control the flow
rate of the water and of the slag/water slurry.
As the stream continuously flows through conduit
5, there is a drop in pressure caused by the
resistance to flow imposed by each restriction
element 7. The slurry stream may then be discharged
29,309A-F -6-
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from the last restriction element 7 at substantially
atmospheric pressure.
The addition of water through conduit 6
and the providion of the restriction elements 7
in conduit 5 beneficially elminate the necessity
for flashing the water from the slurry to reduce
the temperature and pressure of the slurry stream
after it exits from the depressurizing system.
Moreover, the use of the valve 6a to control the
flow rate of the water added to the slag stream
overcomes the need for providing a downstream
valve in conduit 5 to control the slurry flow
rate. Since the rate of mechanical wear in
such a valve would be much higher due to the
abrasive characteristics of the slurry as compared
to thQ wear caused only by water, this method of
injecting water into the slurry to provide flow
control is highly beneficial, economical, and
advantageous. The introduction of water into
conduit 5 also provides both a positive safety and
most beneficial means of pxeventing plugging of
conduit 5 with the slag.
A preferered restriction element 20
of a modified design which has been successfully
useed in conduit 5 is shown in Figure 2. As shown
in Figure 2, element 20 is similar to the reduced
diameter pipe element 7 shown in Figure 1, in that
element 20 includes a wear-resistant plate 8 through
which a reduced diameter orifice 8a is provided for
29,309A-F -7-
-8- ~32~
restricting the flow of the slag/water slurry.
The plate is held in position b~ flanges 4d in con~
duit 5. The plate 8 may also be formed as a lami-
nated structure in which the up-stream layer is a
highly abrasion-resistant material such as silicon
caxbide, tungsten carbide, alumina, or wear-
resistant metal or ceramic material. Although
not shown, an abrasion-resistant liner for conduit
5 may also be provided if the conduit is not directly
formed of an abrasion resistan-t material.
Two additional restriction elements 30
and 40 which have been successfully used in conduit
5 are shown in Figures 3 and 4. Figure 3 illustrates
a restriction element 30 which includes a frustra-
-conical support 9 which is held in place by flanges
4e in conduit 5, and which in turn holds a wear-
resistant cone-shaped liner 9a with an orifice 9b
in place to receive the slag/water slurry. Con-
duit 5 on both sides of element 30 also has a
wear-resistant liner insert 11. Figure 4 illus-
trates still another useful restriction element
40 which includes a restriction plug 12 with an
orifice 12a held in place by a wear-resistant liner
insert 13 in conduit 5. The restriction elemen-t
40 is further held in place by an obstruction, not
shown, in a down-stream flange of conduit 5. Plug
12 is beneficially molded in one piece from a hard
abrasion-resistant ceramic material such as alumina.
The restricted opening or orifices of
all the above restriction elements may be formed with
any desired cross-sectional shape. For example,
29,309A-F -8-
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an ori~ice having a round, oval, square, -triangular
or rectangular shape may be used successfully in
conduit 5. The most beneficial shape is a round
cross-section with the orifice having a relative
diameter of ten to thirty percent of the diameter
of the conduit in which it is disposed. The siæe
of orifices of different shapes should be selected
to provide about the same relative orifice to conduit
size ratio. The materials of construction for the
slag removal apparatus 10 may be selected from known
materials that will stand up under the temperatures
and pressures previously noted, with the preferred
material being carbon steel. Also in areas where
severe mechanical wear is expected from the slag/
water slurry, the high wear-resistant materials
noted above should be used.
The primary and secondary crushers 3 and
3a are beneficially rotary crushers which include
rotor plates and breaker pIates, not shown. Such
crushers are well-known in the art~ Preferably,
the slag is comminuted in the primary crusher 3 to
a maximum dimension of about two and one-half
inches (63~5 mm), and in the secondary crusher
3a to a dimension of between one-eight of an
inch and one inch (3.2 and 25 mm).
The present combination of slag crushers,
restriction elements and means for introducting
water at or down-stream from the crushers provides
a continuous, reliable, controllable apparatus for
removal of slag from a solid fuels gasification
reactor which has a far less tendency to be plugged
by slag than other known slag removal systems.
29,309A-F -9-
~32~
While certain representative embodiments
and de-tails have been shown for the purpose of
illustrating the present invention, it will be
apparent to those ~killed in the art that various
changes and modifications can be made therein
without departing fr~m spirit and scope of the
invention.
29,309A-F -10-
