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Patent Abstract
The present invention involves the addition of a black water filter
to the outlet of the quench chamber of the gasification reactor.
The normal flow of water out of the gasification reactor is through
the side of the quench chamber, but in the present invention it
leaves out the bottom of the quench chamber into the black water
filter. In the black water filter, slag in the black water is allowed
to settle out. Soot water exits the top of the black water filter
and flows to downstream purification/processing units.
Patent Claims
What is claimed is:
1. A process comprising: removing water through an outlet means
on the bottom of a gasification reactor; introducing the water into
a filter, wherein solids in the black water are allowed to settle
to the bottom of the filter; and removing the water from filter
through the top of the filter.
2. The process of claim 1 wherein the water is removed from a quench
chamber of the gasification reactor.
3. The process of claim 1 wherein the solids are ash or slag generated
in the gasification reactor.
4. The process of claim 1 further comprising removing the solids
from the filter.
5. The process of claim 4, wherein the solids are removed after
the filter is isolated from the gasification reactor.
6. A process for removing solids from a filter comprising: stopping
the flow of feed to the filter, cooling the solids in the filter,
reducing the pressure inside the filter, and removing the solids
from the filter.
7. The process of claim 6, wherein the solids are cooled by running
high pressure water through the filter.
8. The process of claim 7 wherein the high pressure water is high
pressure grey water.
9. The process of claim 7 wherein the solids are cooled by the
high pressure water to at or below a temperature of about 165.degree.
C.
10. The process of claim 9 wherein after the solids are cooled
by the high pressure water to at or below a temperature of about
165.degree. C., the flow of the high pressure water is stopped,
and demineralized water is used to cool the solids in the filter.
11. The process of claim 10, wherein the solids are cooled by the
demineralized water to a temperature at or below about 70.degree.
C.
12. The process of claim 6 wherein the pressure inside the filter
is reduced to about zero bar gauge.
13. The process of claim 6 wherein low pressure nitrogen is introduced
into the filter while the solids are being removed from the filter.
14. The process of claim 6, wherein after the solids have been
removed from the filter, the filter is filled with water and pressurized
to a pressure near the operating pressure of the gasification reactor.
15. The process of claim 14 wherein the water used to pressurize
the filter is high pressure grey water.
16. The process of claim 14 wherein after the filter is pressurized
feed is allowed to flow into the filter.
Patent Description
BACKGROUND OF THE INVENTION
[0001] High pressure, high temperature gasification systems have
been used to partially oxidize hydrocarbonaceous fuels to recover
useful by-products or energy. The fuels can be admixed with water
to form an aqueous feedstock that is fed to the reaction zone of
a partial oxidation gasifier along with a oxygen containing gas
and a temperature moderator.
[0002] Mixing the feed with water may not be necessary, given the
composition and physical nature of the feedstock. Generally, solid
carbonaceous fuels will need to be liquefied with oil or water prior
to feeding to the gasifier. Liquid and gaseous hydrocarbonaceous
fuels may be suitable for direct feed to the gasifier, but can be
pretreated for removal of any impurities that might be present in
the feed.
[0003] The term liquid hydrocarbonaceous fuel as used herein to
describe various suitable feedstocks is intended to include pumpable
liquid hydrocarbon materials and pumpable liquid slurries of solid
carbonaceous materials, and mixtures thereof. In fact, any combustible
carbon-containing liquid organic material, or slurries thereof may
be included within the definition of the term "liquid hydrocarbonaceous."
For example, there are pumpable slurries of solid carbonaceous fuels,
liquid hydrocarbon fuel feedstocks, oxygenated hydrocarbonaceous
organic materials, and mixtures thereof. Gaseous hydrocarbonaceous
fuels may also be burned in the partial oxidation gasifier alone
or along with liquid hydrocarbonaceous fuel.
[0004] The partial oxidation reaction is preferably carried out
in a free-flow, unpacked non-catalytic gas generator, or gasifier
at a temperature within the range of about 700.degree. C. to about
2000.degree. C., preferably about 1200.degree. C. to about 1500.degree.
C. The gasifier operates at a pressure of about 2 to about 250 atmospheres,
preferably about 10 to about 150 atmospheres, and most preferably
about 20 to about 90 atmospheres. Under these conditions, about
95% to 99.99% of the hydrocarbonaceous feedstock can be converted
to a synthesis gas containing carbon monoxide and hydrogen, also
referred to as synthesis gas or syngas. Carbon dioxide and water
are either formed or consumed via water gas shift reaction [CO+H.sub.2OCO.sub.2+H.sub.2]
depending on the type of the moderator employed and operating conditions.
[0005] Water is further used as quench water to quench and cool
the syngas. In a typical gasification reactor, the effluent gas
passes out the bottom of the gasification reactor into a quench
chamber. The effluent gas is cooled by passing through a pool of
quench water. The quench water cools the syngas and scrubs particulate
matter from the syngas, and is further used to convey particulate
waste solids, such as ash and/or slag out of the gasifier. Generally,
ash and/or slag is allowed to accumulate in the bottom of the quench
chamber, and periodically that ash and/or slag is removed from the
quench chamber using a lockhopper system. The quench water is continuously
circulated in the quench chamber, being removed from the quench
chamber at an outlet port below the level of the quench water. The
syngas leaves the quench chamber through an outlet port above the
level of the quench water.
[0006] Referring to FIG. 1, a typical prior art gasification unit
is shown. Hydrocarbonaceous fuel, a temperature moderator, and an
oxygen containing gas are fed through lines 2, 4 and 6 to gasification
reactor 10 via feed injector 8. In the reaction section 12 of the
gasification reactor 10 the feed streams react to form syngas. The
syngas passes out the bottom of the reaction section 12 into a pool
of quench water 14 in the quench chamber 16 of the gasification
reactor 10. The pool of quench water 14 has a level 18 that is higher
than the inlet of the syngas. The syngas bubbles through the quench
water 14, and exits the quench chamber 16 through outlet port 26.
Fresh quench water is fed to the quench chamber 16 through inlet
port 20 into the quench ring 27, and is removed through outlet port
22. After being removed from the quench chamber 16, the quench water,
now referred to as soot water, is sent to a soot recovery unit for
separation of soot from the water. The recovered soot can either
be recycled as a soot-oil slurry after treatment in a traditional
naphtha extraction unit or rejected as a filter cake. Alternately,
a portion of the soot water stream can be recycled directly to the
gasification reactor 10 as a moderator stream. After being treated,
the recovered, water is usually recycled back to the quench chamber
of the gasifier. Ash and/or slag accumulates in the bottom of the
quench chamber 16, and is periodically removed by opening valve
24 and sending the ash and/or slag to a lockhopper system (not shown).
The mixture of ash and/or slag and water is commonly referred to
as black water.
[0007] When processing high ash content gasifier feedstocks, most
of the inorganic material in the feed is converted into a vitreous
slag. Although this slag is usually directly removed from the gasifier
after the syngas is quenched with process water, some slag does
build up on the walls of the gasifier reaction chamber 12 and accumulates
in the bottom of the quench chamber 14. The slag builds up in the
bottom of the gasification quench chamber often gets carried out
through the outlet port 22 and plugs the downstream equipment. The
material that accumulates on the walls of the gasifier reaction
chamber 12 remains inside the reaction chamber until the gasifier
is shutdown and exposed to air. Then the slag oxidizes and melts,
causing the slag to flow into the quench chamber, plugging the gasifier
dip tube 29 and outlet port 22.
[0008] The composition of the soot water discharged from the gasification
system is fairly complex. This water can contain chlorides, ammonium
salts, and other potentially environmentally harmful dissolved materials
such as sulfide and cyanide. The grey water is usually treated to
remove these compounds. Other compounds found in the slag, particularly
heavy metals such as Vanadium and Nickel, are more difficult to
remove. Excess slag accumulation in the soot water and downstream
soot water treatment units can cause serious operating problems
in the entire gasification unit operation. Because hard to treat
compounds, such as heavy metals, can build up in the soot water,
it would be desirable to develop a process that would greatly facilitate
the removal of slag from the soot water.
SUMMARY OF THE INVENTION
[0009] The present invention involves the addition of a black water
filter to the outlet of the quench chamber of the gasification reactor.
In the present invention black water leaves out the bottom of the
quench chamber into the black water filter. In the black water filter,
slag in the black water is allowed to settles out of the black water.
Soot water exits the top of the black water filter and flows to
downstream purification/processing units. During shutdown period,
the black water filter can also be used to collect the slag that
melts and flows into the gasifier reaction chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a common prior art gasification unit.
[0011] FIG. 2 shows a preferred embodiment of the present invention.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0012] The present invention involves the addition of a black water
filter to the outlet of the quench chamber of the gasification reactor.
The normal flow of water out of the gasification reactor is through
the side of the quench chamber, but in the present invention it
leaves out the bottom of the quench chamber into the black water
filter. In the black water filter, more of the slag in the black
water settles out. The soot water exits the top of the black water
filter and then flows to downstream purification/processing units.
[0013] Referring now to FIG. 2, one embodiment of the present invention
is shown. The quench chamber 16 of a gasifier is shown, but in contrast
to the prior art, the normal outlet of the quench water through
outlet port 22 is blocked by closing valve 36. The quench water
is instead removed through the bottom of the quench chamber through
line 27. The quench water, or black water, passes through valve
28 into black water filter 30. In black water filter 30, the ash
and/or slag is allowed to settle into the lower conical section
of the filter 30. The soot water leaves out the top of the black
water filter 30 through outlet port 32, passes through valve 34,
and joins with line 40 to be sent to the downstream soot water purification/processing
units. The black water filter 30 occasionally needs to be emptied
of slag, and this is accomplished by returning the quench chamber
to its normal operation. This is done by opening valve 36 and closing
valves 28 and 34, isolating the black water filter 30. Then valve
42 can be opened, allowing for the removal of the ash and/or slag.
[0014] FIG. 3 shows another embodiment of the present invention.
Black water is removed through line 102 from quench chamber 100,
and passes through valves 104 and 106 before entering black water
filter 110 through inlet port 108. In black water filter 110 the
ash and/or slag is allowed to settle into the lower portion of the
filter, while soot water leaves through outlet port 114, through
line 116 and valves 118 and 120, and then into line 122 where it
is sent to downstream purification/processing units. Valve 124 is
normally closed so that no black water can leave the quench chamber
100 through outlet port 126.
[0015] When it is time to dump the accumulated slag from the black
water filter, valve 124 is opened and valves 104 and 106 are closed.
This allows for the black water to leave the quench chamber 100
through outlet port 126, and then into line 122 where it is sent
directly to downstream purification/processing units, bypassing
the black water filter 110. High pressure grey water through 128
is introduced into the black water filter by opening valves 130
and 132. This assists in cooling the accumulated slag in the black
water filter. When the outlet temperature of the water leaving the
black water filter, measured at some point in line 116, reaches
a specified temperature, preferably 165.degree. C. or cooler, valve
130 is closed, shutting off the grey water flow to the black water
filter.
[0016] Valve 136 is then opened, allowing demineralized water to
flow through line 134 into the black water filter 110 to further
cool the slag. When the outlet temperature of the water leaving
the black water filter reaches a second specified temperature, preferably
about 70.degree. C. or cooler, valves 132 and 136 are closed, shutting
off the flow of the demineralized water to the black water filter.
Valves 118 and 120 are then closed, completely isolating black water
filter 110.
[0017] Valve 152 is then opened so as to depressure the black water
filter 110. When the pressure in the black water filter is reduced
to an acceptable level, preferably near about zero bar gauge, valve
152 is closed. Valve 112 is then opened so that the accumulated
slag in the black water filter can be dumped. Low pressure nitrogen
may be introduced through line 142 by opening valve 144, which helps
to sweep the accumulated slag out of the black water filter.
[0018] Once the black water filter 110 is empty, valves 112 and
144 are closed, and valves 140 and 148 are opened. This allows water
to flow through line 138 into the black water filter. Once water
is observed leaving the black water filter through line 150, valves
140 and 148 should be closed. High pressure grey water is then introduced
to the black water filter through line 128 by opening valves 130
and 132. Once the pressure in the black water filter is near the
operating pressure of the gasification reactor, valves 130 and 132
are closed. Finally, the black water filter can be placed back in
service by first opening valves 118 and 120, and then opening valves
104 and 106. Finally, valve 124 can be closed, forcing all the black
water out the bottom of the quench chamber 100 and into the black
water filter 110.
[0019] While the apparatus and methods of this invention have been
described in terms of preferred embodiments, it will be apparent
to those of skill in the art that variations may be applied to the
process described herein without departing from the concept and
scope of the invention. All such similar substitutes and modifications
apparent to those skilled in the art are deemed to be within the
scope and concept of the invention. In particular, it should be
noted that although the preferred embodiments were described as
a treatment for black water from a gasification reactor, the apparatus
and methods of this invention can be used for any type of solids
removal system for which this system may be useful. |