Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to an apparatus for the
gasification of powdered coal by partial combustion
with oxygen or a gas containing oxygen, consisting
of a vertical reactor provided with inlets for coal,
oxygen or a gas containing oxygen and with outlets
for product gas and ash. Besides oxygen also steam
; can be added.
In this context coal is taken to comprise a great
variety of free-carbon-containing fuels such as anthracite,
bituminous coal, brown coal, lignite, soot, coke. Gasification
of coal as envisaged here yields a gas containing carbon
monoxide and hydrogen. This gas can serve as a fuel,
whether or not after removal of undesirable componen~s
such as sulphur-containing compounds, soot, ash particles.
In general, gases can easily be freed from such contaminants,
which makes this route attractive for the preparation
of a gaseous fuel, because solid coal is much more
difficult to purify. Gases containing carbon monoxide
and hydrogen are also important base materials for
chemical syntheses such as the preparation of ammonia
and hydrocarbons.
In gasification the ash content of coal presents
a problem, because without special precautions it may
accumulate in undesirable places in the reactor and
tubes. The ash content varies strongly with the sort
of ash and also depends on whether or not the coal
has been pretreated. Now, the invention provides an
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apparatus which allows continuous gasification without
the ash content of the coal presenting problems.
The invention therefore relates to an apparatus
for the gasification of powdered coal by partial combustion
with oxygen or a gas containing oxygen, consisting
of a vertical reactor provided with inlets for coal,
oxygen or a gas containing oxygen and with outlets
for product gas and ash, while to the bottom of the
reactor, via a constriction, a section is connected
~for the supply of the gases required for gasification,
which supply section consists of a chamber with, in ^;
a central position and opening opposite the constriction,
a set of coaxial tubes for the supply of coal and for
at least part of the required gases, which set of tubes
protrudes through the bottom of the chamber, which
chamber is provided with an inlet for water for maintaining
an amount of water with free surface around the set ~ ~;
of coaxial tubes, and which chamber is provided with
an outlet for solid slag particles, the outlet for
product gas being located in the upper part of the
reactor.
When the apparatus is in operation, the flame
and reaction zones are situated completely inside the
reactor. The mixture of powdered coal and gas emerging
from the coaxial tubes moves upwards through the centre
of the constriction in the form of a jet and ignites
immediately after it has entered the reactor. In the
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reactor hot gas is recirculated, which leads to flame
stabilisation. The temperature prevailing throughout
the reactor is so high that the ash is liquid and descends
along the walls of the reactor in the form of liquid ~ -
slag. The recirculating gases promote the downward flow
of slagO It is important that the bottom of the reactor
and the wall of the constriction are at a very high
temperature. This is caused by recirculating gas that
still tends to descend through the constriction and
is then entrained in the opposite direction by the
aforementioned jet. Moreover, thermal radiation emanating
from the flame supplies heat to the constriction. At
this critical point of the reactor, where otherwise
the slag would accumulate, it remains in the liquid
form because o~ the high temperature. The liquid slag
falls down from the edge of the constriction and reaches
the water in the chamber. The slag then solidi~ies
and can leave the chamber through a suitable outlet.
This may be a pressure lock. The heat that is released
~0 converts water into steam, which is entrained with
the jet into the reactor. Should the gasification
be carried out with steam addition, which can be supplied
through the set of tubes, this amount of steam is to
be taken into account. The pressure in the chamber
is equal to that in the reactor, so that the steam
formed can be used immediately. The apparatus is suitable ~ !
for gasification at any desired pressure. The set
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of tubes for the supply of powdered coal and oxygen
(or air) is considerably cooled by the surrounding
water. This is an elegant solution to the frequently
arising problem of superheating of the metal supply
tubes as a result of flame radiation. With the apparatus
according to the invention this problem would be particularly
prominent, because the diameter of the constriction
is chosen not too small, for the purpose of facilitating
the discharge of slag. The diameter of the constriction
is preferably 3-10 times the diameter of the outer
tube of the set of tubes.
If required, some inlets for oxygen may be spaced
at regular intervals over the side wall of the chamber
in the vicinity of the constriction. Via these inlets,
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for example, 5% of the total quantity of oxygen can
be fed in the reactor. The small proportion of the
recirculating gas mentioned earlier, which descends
through the constriction is ignited by this oxygen,
which contributes to maintaining the wall of the constriction
at the desired high temperature.
The ohamber may contain, below the water surface,
an inclined surface, with the outlet for solid slag
partlcles being located near the lowest point. This
inclined surface may be the bottom of the chamber.
This leads to a better rundown of the solid particles.
With a view to enlarging the capacity, it is furthermore
possible to give at least the constriction an elongated
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horizontal cross-section, more than one set of tubes
being arranged side by side opposite the constriction.
If required, the horizontal cross-sections of the reactor
and the chamber may also have an elongated form.
The invention will now be elucidated with reference
to two figures giving cross-sections of apparatus according
the invention.
Fig. 1 shows constriction 1 located between reactor
2 and supply section 3. Chamber 4 is provided with ;
a set of tubes 5 consisting of an inner tube 6 and
a coaxial outer tube 7. Arrow 8 indicates that powdered
coal is supplied through inner tube 6 together with
part of the oxygen required for the partial combustion.
This may be pure oxygen, air or air enriched in oxygen.
Arrow 9 indicates the supply of oxygen and steam, if
any. The mixture of coal powder, oxygen and steam,
if any, emerging from the tubes enters via constriction
1 reactor 2 in the form of a jet and ignites. The dashed
arrows 10 indicate that a small part of the hot gas
formed, while recirculating, leaves the reactor 1 and
reaches a point beyond the constriction. If desired,
this gas has been ignited with oxygen 11 which has
entered chamber 4 via inlets 12 in the side wall. By
supplying water, indicated by arrow 13, a certain amount
of water is maintained in chamber 4. Liquid slag flows
down from the edge of constriction 1, indicated by
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arrows 14, and falls into the water. Slag that has
solidified is withdrawn at the bottom, as indicated
by arrow 15, Released steam is entrained to the reactor
with the jet emerging from tubes 5. In this example
the diameter of constriction 1 is four times the diameter
of the outer tube 7. The bottom 16 of chamber 4 is
an inclined surface.
Figure 2 shows a top view of a cross-section of ; -
a constriction with an elongated form. The wall of
the constriction is indicated by 17. This cross-section
also shows the top sides of three sets of tubes. These
lie in one line, which is centrally situated in respect
of the diameter of the width of the constriction.
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