Note: Descriptions are shown in the official language in which they were submitted.
~ ~ ~ 7~3 ~ ~
1 Eisenwerk-Gesellschaft mbH
Maximilianshutte
8458 Sul~bach-Rosenberg
Method and Apparatus for Continuous
Gasification, of Solid and/or Fluid
Carbon-Containing and/or Hydrocarbon-
Containing Substances in Molten Iron
in a Reaction Vessel
The invention relates to a method Eor the
continuous gasification of solid and/or fluid carbon-
containing and/or hydrocarbon-containing substances in
molten iron in a reaction vessel, means for carrying
out the method and the use of the gas obtained.
~here is already known a method in which coal
and oxygen or oxygen-containing gas are blown into
molten iron by means of lances in order to produce a
reaction gas substantially comprising Co and H2, (U.S.
Patent Specifications 3 526 478 and 3 533 739). Here
the carbon is introduced into the molten iron below its
surface in a finely divided ~orm through a water-cooled
lance which is introduced into the melt from above.
Simultaneously a second lance device is used to introduce
oxygen and steam into the melt, likewise below its
surface. Reference is made in greater detail later to
the main drawbacks of such lance arrangements.
Slag promoters, pre-ferably lime, limestone
and dolomite are added to the melt in the known methods
to produce a slag which will pick up sulphur. The slag r
takes up the sulphur present in the coal, resulting in
a largely sulphur-free gas having a composition of
about 70 to 80~ carbon monoxide and about 15 to 25%
hydrogen.
However this known method turns out in practice
to be almost impossible to use. There are two main
reasons for this.
.1. .
~ .
,: . .
~ 763~i~
1 First, the lances used for adding in the
reactive components below the surface of the melt,
including the necessary moving and controlling devices,
present a problem which has so far not been capable of
solution. A gasification process is naturally only
capable of being introduced on a larger scale and being
of interest on economic grounds if it can be carried
out reliably and on a continuous basis over a relatively
long period. Hitherto a molten iron reaction vessel of
the kind described has not been able to meet this
requirement.
Up to now it has been impossible to provide
lance axrangements for a gassing me-thod that will
operate over a period of several days without inter-
ruption. Whilst in the LD process oxygen is blown onto
the surface of the iron melt, in the introduction of
combustibles by gas it is necessary for the lance to be
immersed in the meltO Otherwise the carbon-containing
or hydrocarbon-containing substances would undergo
various reactions, for example cracking processes,
resulting in the unwanted production of soot. In high
capacity iron melt reaction vessels, which are desirable
on economic grounds, one must take into account a
relatively marked movement of the melt, and a gas space
of adequàte height must be provided above the surface
of the melt. For this reason it is necessary to provide
lances having a length of a few metres, which are
subjected to extremely high mechanical loads by the
marked movement of the melt ~the specific gravity of
the molten ~ron is substantially the same as that of
solid iron, and so the forces that act are very high).
Lances having a length of the order of metres canno-t
withstand such severe mechanical loads.
A further significant ~rawback of lances lies
ln that, with the lance immersed at the required depth,
the flow of gas emerging from the lance subjects to
extremely heavy wear those points in the refractory
lining of the vessel which it strikes.
1~76~
-
1 Because of the intensive movement in the melt
any refractory coating which may be provided` to protect
the lance is subjected to increased mechanical loads
and an increased attack by chemical reactions with the
slag and by erosion.
In lances which are intensively cooled, for
example those with water cooling, it is a serious
drawback that this extracts a great deal of heat from
the process itself.
The lances have to be introduced from above
through the thick layer of slag, which gives rise to
further problems, for example lumps of slag freezing
onto the lance.
Finally rapid replacement of the lances is
impossible without interrupting the process as it has
been found impractical to seal the vessel adequately
against the penetration of undesired quanities of air
when changing lances. Yet as soon as any unmonitored
quantities of air reach an iron melt reaction vessel
this not only has an adverse influence on the gas
composition but also gives rise to the danger of ex-
plosion.
Furthermore it is difficult to control the
overall slag position in the known method because
relatively large quantities of high sulphur content
slag have to be removed and replaced by additions of
lime. Quite apart from the undesired handling problem,
the resulting heat losses are also found to be ex-
tremely undesirable.
It is the aim of the invention to provide a
method an apparatus for allowing the continuous gasifi~
cation of solid and/or fluid carbon-containing and/or
hydrocarbon-containing substances in a molten iron
reaction vessel without interruption and with security
of operation over a long period of time.
~763S~
1 The invention is based on a recognition of
the fact that this problem can be solved in that the
eomponents of the reaction, namely on the one hand
carbon-eontaining and/or hydrocarbon-containing sub-
stances and on the other hand oxygen or oxygen-contalning
m~dia, are .introduced into the melt through nozzles
Which are mounted in the refractory lining of the
vessel below the surface of the molten iron.
Unexpeetedly it has been found that by the
introduction of nozzles which are mounted in the refractory
lining of the vessel below the level of the surface of
the melt, in contrast to the known lance devices,
trouble-free operation can be achieved over long periods
of time and particularly pure yases are obtained.
The subject of the invention is a method for
the continuous gasification, of solid and/or fluid
earbon-containing and/or hydrocarbon-containing subs-tances
in a bath of molten iron in a reaction vessel which is
characterised in that the components in the reaction,
on the one hand carbon-containing and/or hydrocarbon-
containing substances and on the other hand oxygen or
oxygen-eontaining media, are introduced into the melt
through one or more nozzles which are mounted in the
vessel in a refractory lining below the surface of the
melt and thereby wear away equally with the lining.
. ~
The subject of the invention is furthermore
appara~us for carrying out this method which is charac-
terised in that, in the refractory lining of a reaction
vessel for molten iron for the continuous gasification
of ~olid and/or fluid carbon-containing and/or hydrocarbon-
eontaining substances, one or more nozzles comprising
eoncentric tubes are arranged below the surface of the
melt.
Finally the subject of the invention is the
use of the gases produced in accordance with the method
as reduction gas for metallurgical purposes, in particular
for the reduction of iron ore.
.4.
:~L0763~0
l By ~he n~etho~; accorcling to the invention
continuous operation can be maintained wi~hout trouble
over significantly 1onger perlods oE time than was
possible with the known method. Furthermore there is
the advantage that gas-tiyht openings in the vessel,
which moreover need to permit a certain amount of
movement, are unnecessary and so, in addition to an
increase in the operational safety there is a reduction
in the danger of explosion through the introduction of
unwanted air.
By means of the method according to the
invention it is possible to obtain a gas which is
largely free of sulphur and has a composition of about
50 to 9S~ carbon monoxide and 5 to 50% hydrogen.
Usually the carbon monoxide content is between 60 and
80~ and the hydrogen content is between 15 and 40~.
The composition of the gas obtained naturally depends
on the carbon-containing and~or hydrocarbon-containing
substances that are introduced. When hydrocarbons are
used, the hydrogen content of the gas obtained is
higher than when orthodox kinds of coal are used.
Using ordinary carbon, the gas generally has a carbon r
monoxide content of 60 to 80~ and hydrogen content oE
15 to 25~. Using fuels which comprise substantially
only carbon, the hydrogen content can theoretically be
reduc~d close to 0. However, because of the protective
media of gaseous and/or liquid hydrocarbons or hydrocarbon-
containing media, the gas produced normally has 5% or
more or hydrogen.
In the method according to the invention the
starting material for the gassing may be carbon-containing
substances in the form of all kinds of coal, as well as
coke, which are normally available commercially.
Relatively pure kinds, of high energy, such as for
example anthracite and coke do however give fewer
problems in treatment as the proportion of slag-producing
residues is lower and so special measures with regard
to the heat balance in the reac~ion vessel are not
necessary. On account of the favourable material
~L~7~3~i~
1 costs, low-energy kinds of coal are also of substantial
signi~icance, for example brown coal, also distilled or
carbonised brown coal and bituminous kinds of coal,
which are chiefy known commercially under the name
"open-burning coal". The coal or carbon-containing
substances are preferably introduced in a finely divided
form.
Hydrocarbon-containing substances are of
substantial ~ignificance in this gassing process. The
distillation of petroleum products produces, in addition
to the easily sold light mobile fractions, also heavy
oils. The useful employment of this heavy oil fraction
is of decisive importance for the overall economy of
the entire mineral oil industry. At the present day
the heavy oil fractions are chiefly processed further
to make bitumen and asphalt or are cracked, by means of
special processes, to produce more volatile fractions.
~owever cracking processes require heavy investment and
this shifts the limits of what is economical. In
attempts to introduce the heavy oil fraction as a
startlng material for other chemical processes dif-
ficulties of a technical nature arise and have hitherto
caused the introduction of most methods on a significant
scale to fail. The origin of this is in the first
place the heavy soot formation in the gassing of heavy
heating oils. The formation of soot has hitherto only
been able to be countered by taking into account a
higher degree of oxidation of the reduction gases
produced from the heavy oil fractions. Furthermore it
gives rise to special problems in adequately de-sulphurising
the crude oil or the gas produced from it. However
adequate de-sulphurisation is necessary for the un-
restricted employment of these gases, if only to meet
the need to avoid polluting the environment.
By means of the method according to the
invention it is now possible to gasify, in large scale
technology, liquid hydrocarbons of varying viscosity,
right up to a pasty consistency, but in particular
heavy oil fractions, and thereby to produce a gas which
has in particular a low sulphur content and a minimum
degree of oxidation.
.6.
1~7~;36~
1 The hydrocarbons to be gasified are preferably
pre-heated in order to obtain trouble-free handling and
passage through the nozzles. This is of particular
advantage in the case of highly viscous heavy oil
fractions. Hydrocarbons of the consistency of a paste
are either pre-heated to such t~mperatures that they
-can be handled as fluids, or they are fed to the no2zles
through special handling devices.
The second component in the reac-tion is
preferably oxygen, in particular in commercially pure
~orm. In addition to oxygen itself, oxygen-containing
media, primarily air and hot blast, especially with
oxygen enrichment, can be taken into consideration.
The nozzles mounted in the refractory wall of
the iron ba~h reaction vessel below the surface of the
melt ma~ be provide~ in the floor and/or in the side
wall of the lining of the vessel.
.
The nozzles preferably comprise a number of
concentric tubes. For example one could use three,
four or more than four concentric tubes.
The nozzles which are arranged, according to
the invention in the refractory lining of the vessel
below the surface of the melt, are protected against
premature wear ahead of the refractory by arranging
that the oxygen and~or the oxygen-containing media are
surrounded by a protective medium of gaseous and/or
liquid hydrocarbon or hydrocarbon-containing medium.
As a protective medium consideration has been given for
example to methane, ethane, propane, various qualities
of oil, in particular light heating oil and methanol,
each either individually or in any desired mixtures.
It has been found particularly advantageous
to feed the reaction components to the bath below its
surface and if necessary a finely divided slag former,
at the same point i.e. in common through the same
nozzle. Alsc one could employ several such nozzles
~ 7.
360
1 through which the components in the reaction are introduced
in common, and in this case they all take an equal
share. The introduction of the components at the same
point has the advantage that, because oE the rapid
turbulence and mixing with the melt, one obtains rapid
dissolving of the carbon in the bath. For this reason
the grain size, for example, of the powdered carbon
that is blown in can ~e chosen to ~e larger than is
possiblQ where the components to the reaction are fed
in separately. A further advantage obtained by the
simultaneous introduction of the components lies in the
lowering of the temperature at the so called oxygen
focus, i.e. directly in front of the mouth of the
nozzle. This again leads to a reduction in the vapori-
zation of the iron.
Preferably the components to the reaction are
fed into the melt in the vessel through a nozzle,
through a number of passages, preferably annular, in
alternating and any desired sequence, and, looking from
the centre of the nozzle outwards, each passage through
which the oxygen is fed is surrounded by the protective
medium of hydrocarbon and/or hydrocarbon-containing
medium.
It is of further advantage to distribute the
gasifying substances and/or the oxygen or oxygen-
containing medium within a noæzle into a number of
streams so that on the one hand there is an intensive
reaction between the components and on the other hand
part of the carbon-containing and/or hydrocarbon-
containing substances serves to keep down the tem-
peratu~e at the focus. This can be achieved for example
by a nozzle made of several concentric tubesl in which
for example powdered coal i5 blown in through the
innermost, oxygen through an annular gap surrounding it
ànd carbon again through an outer gap. The stream of
oxygen is preferably surrounded in this arrangement
both on the inside and also on the outside by a hydro-
carbon-containing protective medium.
71~i36(~
-
1 It is possible furthermore to do without the
separate supply of 'nydrocarbon-containing protec7~ive
gas where hydrocarbon-containing media are employed as
a carrier gas for feeding in the powdered coal. The
same effect can be obtained by suspending the powdered
coal in a hydrocarbon-containlng liquid.
~ here hydrocarbon-corltaining substances are
being used for gasification one can likewise do without
the protective medium of gaseous and/or liquid hydro-
carbons or hydrocarbon-containing media.
Suitable feeding methods in the use oE hydro-
carbons for gasification are for example the following.
Through the inner tube of the nozzle one blows in heavy
oil, through the next annular space one blows in oxygen
and through the outer annular space one blows in liquid
or gaseous hydrocarbons. Where four concentric tubes
are used, one can blow in oxygen through the innermost
one, heavy oil through the next one, oxygen again
through the next and a protective medium comprising
liquid or gaseous hydrocarbon through the outermost
one.
In order to improve the interaction between
the components, which is of lnterest in particular in
large installations in which more than 10 tons of
combustible per hour are gasiEied, it is desirable to
enlarge the nozzle system in diameter and to make the
core of the nozzle in the form o a solid body. Then
all the components to the reaction are introduced into
the melt through concentric annular openings. In
practice it has been found to be advantageous for the
width of the annular openings to be a-t a maximum one
tenth of the diameter of the ring. In this way an
improvement is obtained in the turbulence and mixing
wlth the other components to the reaction. For example
in such a nozzle one can introduce heavy oil in the
innermost annular opening, oxygen in the next one, and
a liquid or gaseous protective medium in the outermost
one. Additional mixing can be achieved for examply by
~7636~
1 arranging that guide elements are incorporated in the
annular openings of the nozzle, preferably in those
which introduce the substance to be gasified, the guide
elements acting to give the emerging stream a twist.
The substances to be gasified and the oxygen
or the oxygen-containing medium could already be pre-
mixed before entry into the iron bath. On grounds of
safety this mixing should only take place near to the
molten iron, preferably only within the nozzle.
The components to the reaction could further-
more be introduced into the bath of :Lron thrcugh two or
more separate nozzles. Where a hydrocarbon is the
substance to be gasified, then where the introduction
ls separated in this way, it is unnecessary to use a
nozzle made up of several concentric tubes for the
hydrocarbon. On the contrary one can employ a noz~le
comprising a single tube. For the separate supply of
oxygen, on the other hand, it is necessary to use a
nozzle made up of at least two concentric tubes, so
that the stream of oxygen can be surrounded by the
protectlve medium.
The supply of the slag-forming agent through
the nozzles in the floor of an iron bath reaction
vessel to produce a de-sulphurising slag in the bath
can be achieved in various waysO For example the
slagging agent preferably chalk dust with or without
the addition of limestone or dolomite, can be added to
the stream of oxygen. Another way is to mix the finely
divided slag former with the finely divided coal or the
hydrocarbon before addition into the reaction vessel
and then to introduce this mixture into the vessel.
The desired continuous uniform gasification
over long periods can be adversely affected by dif~
ferences in concentration that can arise between the
~lag and the bath and possibly within the bath. These
diferences in concentration lead -to alterations in the
production of the gas and in its composition. These
.~.0, .
~L~763~;~
1 difficulties can be counteracted by adding the reackion
components in pulses. By the addition of the com-
ponents in pulses over brief periods one can very
rapidly return to normal operating conditions. In most
cases ten pressure pulses per minute are sufficient.
The frequency of the pressure pulses can however be
varied as desired. These can also be employed only ~or
predetermined periods of time. To improve the con~
version rate of the components to the reaction one can
also work all the time with a pulsating feed. In this
arrangement only a minimal basic pressure is present in
the medium in the supply nozzle, lying only slightl~
above the ferrostatic pressure plus the pressure
prevailing above the melt in the bath. The resulting
pressure of the medium is them altered periodically up
to a maximum of about five fold.
In continuous gasification it is important to
maintain the iron bath at the desired temperature.
Cooling of the bath has a very adverse effect on the
gasification and leads to the desired gasification no
. longer being achieved. This problem arises in particular
where one uses carbon-containing and/or hydrocarbon-
containing substancesi the conversion of which leads to
the gasification process no longer being exothermic.
On the other hand it is just this introduction of low- r
energy uels, for example low-energy kinds of coal such
as brown coal or low energy heavy oil fractions that is
of signi~icant economical importance on the grounds of
the low purchasing costs of these materials.
It would have been obvious, when using low
energy fuels, to supply the necessary additional energy
requirements from an external source, Eor example by
the arc heating ox induction heating which are common
in steel production. Furthermore an obvious and
advantageous possibility would be to burn part of the
gas produced and in this way to add the necessary
energy. However it has turned out that neither supple-
mentary heating arrangements nor the partial burning of
the gases achieves a worthwhile addition of energy to
~7636~
the bath. This i~ apparently attributable to the high
energy concentration in the bath.
Unexpectedly it has been recognised that this
problem can be solved in that, in contrast to the
above-mentioned possibilities of a all in the -tem-
perature of the bath, the temperature can be main-tained
by arranging that energy-rich materials are supplied to
the oxidation process in the bath itsel~O
With the use of kinds of coal which would
lead to cooling of the bath in their gasification it
is, for example, possible to modify this by preparation
and/or conversion in such a way that in the gasifying
process an excess of heat is achieved in the vessel
without the supply of extexnal energy.
One possibility lies in drying the coal of
low heat value and/or pre-heating it and then introducing
it into the reaction vessel.
A further possibility is to mix additional
carbon into low-energy coal. For example various high
energy coals, such as anthracite could be added. It
has also been found advantageous to use uncombined
carbon material such as coke.
(
It has been found particularly economical to
add into the bath additional quantities of carbon,
preferably in the form of cok~. For example the coke
can be introduced into the bath in powdered form together
with the substances to be gasified. It can also be fed
into the bath from above in the form of lumps. To
reduce the quantity of coke required it is preferable
to pre-heat it.
Furthermore it is possible to add continuously
lnto the bath materials of which the oxidation reaction
takes place under strongly exothermic conditionsO
Preferably one can employ for this purpose substances
which have a high heat of reaction and lead to oxidation
.12.
7636C~
products which have a favourable action on the composition
of the slag. For example aluminium or silicon could be
blown in, together with the substances to be yassed or
independently of them. For example by the addition of
10 gms of aluminium per kilogram of coal one can add
about 75 kilocals to the bath. Furthermore a particularly
suitable material is calcium carbide, which is converted
in the bath into carbon monc)xide and CaO. Caxbon
monoxide is the desired reactijn rroduct of the gasifi-
cation, whilst CaO represel~s tl.e material which isnormally employed for the de-sulphurising slag. The
introduction of calcium carbide thus introduces undesired
materials neither into the gas nor into the slagO
The addition of the above-mentioned or similar
caxriers can be carried out either by mixing them with
the substances of low heat value to be gasified or
separately therefrom.
In practice it has turned out to be very
advantageous, in the gassing of substances of low heat
value, to introduce a predetermined proportion of the
substances of high heat of reaction, for example aluminium,
silicon and/or calcium carbide, separately from the
normal supply of the reaction components to the bath,
in order to control the temperature of the bath. In
thls way it is possible to control the temperature of
the bath directly. As soon as the ternperature of the
melt threatens to fall the supply of the heat carrier
is increased and conversely Witl~ a rising bath tem-
peraturè it is restricted.
Cheap kinds of coal and mineral oil fractions
have hitherto only been open to economic employment
with difficulty, because of their high sulphur content.
In particular the sulphur content leads to increased
corrosion of the components of the installation which
come into contact with the sulphu~ and in particular
with its gaseous reaction products, as well as leading
to pollution of the environment by the sulphur-containing
waste gases. With the method according to the invention,
~13.
~6366~
1 however, there is provided th~ possibility of con-
vextinc; _.h ~ els in',.o va~uable products.
The sulphur in ~he Euel is ta]cen up, during
gasification in the reaction vessel, by a sulphur-
absorbing slag which floats on the molten ironO
A significant proportion of this sulphur
taken up by the slag can be removed by arranging that
the liquid sulphur-rich slag is transferred from the
iron bath in a liquid condition into a reaction vessel
and there is de-sulphurised by the introduction of
oxygen or oxygen-containing media with or without the
addition of an inert gas, and finally it is returned to
the iron bath in a liquid condition.
In this way it is possible to gasify, in an
~ron bath reaction vessel, substances of high sulphur
content, in an operationally reliable and economic
manner to produce a substan-tially sulphur free gasO
This furthermore avoids pollution of the environment by
a sulphurous gases. Ivioxeover this manner of operation
2Q has the advantage that by returning the slag to the
iron bath one avoids high heat losses. The de-~ulphurisation
in a reaction vessel which is completely separate in
gas space from the iron bath, advantageously takes
place by the introduction of oxygen below the level of
the surface of the slag. Preferably the oxygen is fed
through the floor and/or in the lower region of the
side wall of the vessel in order to keep the path of
the oxygen through the slag as large as possible and
thereby effect intensive de-sulphurisat10n. It has
been found that the removal of the sulphur from the
slag is helped if an inert gas is mixed in with the
oxygen or is simultaneously introduced below the level
of the surface of the slag separately from the oxygen.
~he nozzles for introducing oxygen or an oxygen~containing
medium and inert gas may for example be made up of two
concentric tubes, the oxygen being fed in through the
inner tube and the inert gas through the space around
it.
.14.
~763~
1 To de-sulphurise the slag air can be introduced
for example into the reaction vessel. The air can be
cold or may be pre-heated, according to the heat balance
of the processO For example the use of a blast furnace
hot blast with or without the addition of cold air has
been found effective.
It has been found a~vantageous to maintain
the temperatures in the iron bath and in the de-sulphurising
reaction vessel substantially equal. The temperature
in the iron bath reaction vessel can be controlled
within wide limits by the addition of materials which
react endothermically or exothermically. In the de-
sulphurising reaction vessel the temperature can be
controlled by the oxygen content in the gas mixture and
by its temperature and its quantity. In practice a
temperature in the molten iron bath and in the slag de-
sulphurising vessel of about 1350 to 1~50C has been
found advantageous. However this temperature range can
be exceeded by at least 100C in either direction. The
temperature can be varied according to the parameters
of the process and likewise it is possible for there to
be temperature differences between the iron bath and
the slag de-sulphurising ve-ssei~
The de~sulphurisat~on of the slag allows the
sulphur content of the slag in the iron bath to ~e kept
relatively low. This allows one to employ slags of low
basicity. Whereas normally one would employ a basici-ty
(CaO:SiO2) in the range between 1 and 3, this process
allows one also to obtain adequate de-sulphurisation
30 ` with basicities of, for exampie, 0.8 and below.
The low basicity of the slag in combination
with the components of the coal ash which generally
contains substantial quantities of alkalisl result in
low melting points for the de-sulphurising slag. This
again is an important requirement for the low operating
temperatures of the process according to the invention.
76366~
1 Furthermore the low basicity of the de-
sulphurising slag means that one needs only a low
addition of lime in order to maintain the desired slag
composition despite the continuous ~ddition of coal
ash. This is an advantage whlch has a favourable
efect on the heat balance of ~he method according to
the invention.
The composition of the de-sulphurised slag
which is fed back from the reaction vessel to de-
sulphurise the lron bath and of which one extracts apredetermined fraction from the processing circuit on
the way, allows this slag that is withdrawn to be used
in the manufacture of cement.
In the usual performance of the method according
to the invention the sulphur contents o~ the de-sulphurising
sla~ withdrawn from the iron bath reaction vessel lie
well below their sulphur saturation value. For example
one can operate with a sulphur content in the slag of
less than 1~. Whilst the de-sulphurising slags from
the bath may have sulphur contents of 1 to 3~, they are
however preferably de-sulphurised in the reaction
vessel to sulphur contents of 0.5 and 1%.
The low sulphur contents in the de-sulphurising
slags allow one to obtain extremely low sulphur conten-ts
in the gas that is produced. If very low sulphur
contents are obtained in the iron bath in the production
of gas, then for example the sulphur content in the
slag in the iron bath can be maintained at 10~ of the
saturation solubility.
The gas produced in de-sulphurisation i9 kept
separate from the pure product gases and because of its
high sulphur content it can easily be de-sulphurised or
otherwise employed, for example in the manufacture of
sulphur.
.16.
. . .
~C~7636~:)
The carbon content in the iron bath is preferably
maintained between about 1 and about ~. With this
manner of operation there is produced a gas of which
the carbon dioxide, water and methane contents are
extremely low. In particular cases a very high carbon
content in the bath of about 4% or a very low content
of about 0.05% carbon can be introduced.
Where low carbon contents are used the advantage
is obtained that the heat balance of the process is
partially balanced out by the partial combustion of the
carbon in the bath to CO2. On the other hand it causes
an increase in the CO2 content of the gas.
The gases formed by the process according to
the invention are particularly suitable for use in
metallurgy, for example for use in the blast furnace
process or preferably for the reduction of iron ore.
The use of reduction gases in the reduction
of iron ores has won increasing accceptance in recent
. times. Mainly the large spread of the various so
called "direct reduction processes" which serve mainly
to produce iron pellets or sponge iron has contributed
to this to a substantial extent. In addition, in the
reduction of ores in blast furnaces, a part of the coke
has experimentally been replaced by reduction gases.
In comparison with the production of reduction
gases in other ways, for example from natural gas, the
production according to the invention has significant
advantages. The main advantages lie in that cost]y
removal of undesired components from the resulting gas
ls eliminated and the gases emerge at such temperature
and pressure that it is possible to employ them directly
for metallurgical purposes in an optimum manner. This
last-mentioned point of view is of particular significance
on economical grounds. Of overriding significance,
however, is the combination of obtaining the necessary
purity of the gas and at the same -time obtaining the
desired temperature as well as the desired pressure.
.17.
~7~36~
1 In a gas of the desixed temperature and the desired
pressure but which contains impurities it would be
necessary first to cool i-t down, then to purify it and
then to heat it up again.
The reduction gas, comprising substantially
carbon monoxide and hydrogen, which if desired also
contains inert gases, can be passed on for immediate
employment in the metallurgical processes.
The iron bath reac-tion vessel is preferably
constructed so that it allows the introduction of the
kind of pressure the reduction gas is to have according
to its metallurgical use, for example for a reduction
proc~ss. Operz~ion of the reaction vessel at an elevated
pressure furthermore avoids the introduction of impurities
into the resulting gas through leakage points.
Where the gas is to be used for reducing iron
ores, the carbon dioxide and water contents should be
kept as low as possible as even small percentages o~
these components have an adverse eff~ct on the operational
eff~ciency in the gas reduction processes.
The process according to the invention allows
the production of extremely pure gas without any undesired
carbon dioxide and water impurities. The reduction gas
that is produced may contain only small quantities of
iron vapour which do not upset its employment in metalluryy,
preerably in the reduction of iron ore. The iron
vapour is deposited on the ore as the gas passes through
~t.
The reduction gases produced in the bath iron
reaction vessel generally have a temperature of about
1350 to 1450C as they leave the vessel. However the
process according to the invention is particularly
flexible on this point and allows the temperature to be
varied within wide limits, for example between 1250 and
1600C, for example in accordance with the heat supplied
by the substances to be gasified, by the admission of
.18.
~07~36~
Co2 and/or water vapour which are converted into carbon
dioxi~e and hydrogen in the reaction vessel, by pre-
heatiny of the oxygen-containing media or by the intxoduction
of materials whose oxidation reaction is strongly
exothermi~.
~ he gases supplied fol- direct use ln metallugical
processes can if nec~ssary b~ cooled down to the desired
temperature when this i~ lower than that at which -the
gases leave the reaction vessel. This cooling of the
gases can be done in heat exchangers in an orthodox
manner.
An advantageous way for controlled reduction
of the temperature of the reduction gases is to add
cold inert gases, for example nitrogen! as they leave
the reaction vessel. In particular where the reduction
gases are employed in blast furnaces the addition of
nitrogen has been found effective. The nitrogen is
often available as a cheap gas from the production of
oxygen in an iron works.
The addition of nitrogen as a ballast gas to
the reduction gas leaves the heat in the process unaffected.
Furthermore the addition of nitrogen largely suppresses
the tendency of the reduction gas, primarily when it is
one of high carbon monoxide content, to soot formation
by the so called Boudouard reaction.
Instead of adding nitrogen to the reduction
gas to obtain the right temperature for use, one can
add cooled reduction gas. For example the reduction
gas in some direct reduction processes leaves the
reduction equipment at low temperatures and can be
relieved of its carbon dioxide and hydrogen contents by
a simple chemical process without intermediate cooling.
The clean but cold reduction gas obtained in this way
can then be employed for adjusting the temperature of
the reduction gas coming from the iron bath reaction
vessel.
.19 .
1C 1763GO
1 The gases produced by the process according
to the invention could have equally well be employed
for other purposes.
A further possible use is as a heating gas,
for example in power stations.
Because of their purity the gases produced
are also suitable for various fields in the chemical
lndustry, for example as a synthesis gas for the production
of methanol or as a source of hydrogen for synthesis of
ammonia and in hydration,
The invention is further explained in the
~ollowing by referencè to some embodiments by way of
~xample and with reference to the drawings, in which:
Figure 1 is a vertical section through one
embodiment of an iron bath reaction vessel;
Figure 2 is a vertical section through a
nozzle made of four concentric tubes;
Figure 3 is a vertical section through a
nozzle made of three concentric tubes;
Figure 4 is a vertical section through a
nozzle which has only annular openings, some
with inserts, for supplying the reaction
components and media;
Figure 5 is a vertical section through a
nozzle having three annular openings and a
solid core, a strip-like helix being visible
in one annular opening as a guide element;
Figure 6 shows an embodiment of a nozzle in
which the components for the reaction are
already mixed before entering the bath:
Figure 7 is a vertical section t~rough a
further embodiment of an iron bath reaction
vessel; and
. ~ (~ ,
763~3
1 Fi~ure 8 is a horizontal section through the
vessel of Figure 7.
The iron bath reaction vessel illustrated in
Figure 1 comprises substantially a steel casing 1 with
a refractory lining 2. Within the vessel is the bath 3
of molten iron and above it the slag ~. The slag picks
up the ash residues and a substantial proportion of the
sulphur in the carbon-containing and hydrocarbon-
containing substances. The components for the reaction
10 are introduced into the bath 3 through one or more
nozzles 5 which are mounted in the refractory lining 2.
The slag-forming agents, preferably lim~ with or without
the addition of fluxing agents, are preferably likewise
fed into the metal bath through the nozzle. One normally
employs quicklime as a slagging agent. However, in
order to reduce the temperaturej in accordance with the
heat ~alue or energy content of the substances introduced,
th~ ~uicklime can be partially or wholly replaced by
limestone.
In the following description we refer mostly
to powdered coal as the substance to be gasiied.
However it will be understood that the coal dust could
be replaced by other substances to be gasified, for
example heavy oil.
The nozzles 5 in the refractory lining 2 wear
away uniformly in step with the refractory material and
are preferably made up of concentric tubes of circular
cross-section. However one could equally well employ
tubes of oval cross-section or right up to a rectangular
form. However, on grounds of economy normal tubes of
circular cross~section are preferred.
The nozzle shown in Figure 2 is made up of
four concentric tubes 6, 7, 8, 9. For example cold
dust is introduced into the bath through the innermost
tube 6 together with a carrier gas. Suitable carrier
gases are preferably inert gases, nitrogen, carbon
dioxide and steam. In this layout carbon dioxide and
~7~36~
1 steam can be simultaneously introduced for controlling
the temperature. Through the annular opening formed by
the tubes 7 and 8 oxygen or an oxygen-containing medium
is introduced. The two openinys between tubes 6 and 7
and between tubes 8.and 9 serve for the supply of
protective media for the nozzle. The protective medlum
is made up of gaseous and/or liquid hydrocarbons or
hydroca~bon-containing media. Alternatively oxygen can
be introduced through the innermost tube, heavy oil
through the next one, oxygen again through the next and
heavy oil again throuyh the outermost annular opening.
The dimensions of the openings can be chosen for example
so that the greater part of the oil is fed in through
the innermost tube, whilst the quantity of oil entering
through the outermost annular opening is significantly
smaller and serves primarily to protect the nozzle.
Also the outermost annular openiny can be used for
introducing a gaseous or liquid hydrocarbon as a protective
medium for the nozzle. The supply of the various
substances for media introduced can if necessary be
combined.
Figure 3 shows a nozzle having three passages 10,
11, 12. The passages in such a layout could be employed
in the following distribution for feeding the components
of the reaction and the media. Either the central
tube 10 carries oxygen, the annular-opening 11 carries
the protèctive medium and the outer annular opening 12
supplies the coal dust: alternatively the central
tube 10 and the outer opening 12 could carry the coal
in suspension in the hydrocarbon-containing protective
m~dium whilst oxygen flows through the annular opening 11.
Alternatively the substance to be gasified can pass
through the inner pipe 10, oxygen through the annular
opening 11 and a protective medium through thP outer
opening 12, this protective medium being natural gas,
to the extent of 5~ of the oxygen flow.
The embodiment of the nozzle shown in Figure 4
which is preferred for use when introducing large
quantit.ies of substance to be gasified, has a solid
~76~66~
1 core 13. At least some of the supply passages 14,
15, 16 contain inser~,ed elements. BasicaIly the openings 14,
15, 16 can be employed in the same sense as the passages 10,
11, 12 for in-troducing the components of the reaction.
In Figure 4 the opening 14 serves for the medium ta be
gasified. Spiral guide elements 17 are mounted in this
passage 14, impartin~ a sw:irl or twis-t to the flow of
substance. The oxygen enters through the opening 15.
The annular opening 16, split up into appro~imately
circular passages, serves to carry the protective
medium.
A further preferred embodiment of a nozzle is
shown in Figure 5. In this nozzle the supply of oxygen
is through the opening 40, the width of which is substantially
smaller than the diameter of the ring. For example
suitable nozzles have been found to have an inner
diametex of 10 cm and a radial width of about 3 mm. In
such nozzles the substance to be gasifiedt for example
heavy oil, is fed through the annular spaces 41 and 42.
Here again it is advantageous to make the quantity
delivered through the inner gap 42 larger than that in
the outer gap 41. It can also be of advantage to
deliver only a small quantity of a hydrocarbon-containing
compound through the outer gap 41 and to supply the
whole of the substance to be gasified through the inner
gap 42. In this form of nozzle it has furthermore been
found desirable to give the oxygen stream a marked
swirl by spiral guide elements 43 in the gap 40 used
for supplying the oxygen. This causes rapid mixing
between the oxygen, the substance to be gasified and
the molten iron bath and ensures calm blowing behaviour
in the bath. Furthermore by the use of this form of
nozzle the number of nozzles required can be substantially
reduced. For example, in comparison with about ten
simple concentric nozzles it has been found possible to
àchieve success with two such nozzles. The solid
helical body 43 can close off about a quarter of the
annular space 40O This partial closing-off of the
annular space assists the entry into the centre of the
bath of iron of the streams of reactive medium emerging
from the nozzle.
~7636~
- Figure 6 shows a particular form of nozzle.
Here the substances 19 to be gasified, for example coal
dust and oxygen 20 are already mixed together be~ore
entering the bath. The coal dust 19 and the oxygen 20
are first introduced separately through the steel
casing 1 of the reaction vessel and partially through
the refractory lini.ng 2 and at ~his point the components
of the reaction are mixed to~e-ther in the nozzle.
~he pressure in the space above the molten
iron in the bath can for example amount to about 5
atmospheres where the reduction gas is destined for use
in a blast furnace; it can for example be about 2
atmospheres where it is to be used for a direct reduction
process. The reduction gas is conducted directly to
the reduction process through a refractory-coated pipe
or, i necessary, indirectly with deliberate intermediate
cooling.
In Figure 7 there is shown an iron bath
reaction vessel provided with a de-sulphurising installation~
In the iron bath reaction vessel 21, which is like a
converter and which is partially filled with the carbon-
containing bath 22 of molten iron, oxygen or oxygen-
containing media an~ powdered li:.e are blown into the
bath 22. The de-sulphurising slag 24 flows through an
outlet passage 25 in which is lncorporated a settling
chamber 26 for separating out d-^ople-ts of iron, into
the reaction vessel 27 for de-sulphurising the slag.
The iron collected from the separa-ted-out droplets
flows through a passaye 28 back into the main reaction
vessel 21. The outlet passage 25 runs below the level
of the surface of the slag.
The settling chamber 26 in the slag outlet
passage 2S has the important function of giving the
opportunity for as complete as possible a separation of
the portions of iron carried from the bath in the slag
and which are present chiefly in the form of finally
divided droplets. It is important that there should be
as complete as possible seperation of iron from the
o2~
- ~ ~7~;~6a~
l slag before the slag passes into the slag-de-sulphurising
vessel 27 because any metal in the slag has an adverse
influence on the de-sulphurisation in the vessel 27.
Any metal particles present primarily upset the de-
sulphurisation of the slag in relation to the added
oxygen and thereby make it almost impossible to regulate
the de-sulphurisation process. Likewise the temperature
in the de-sulphurising vessel 27 cannot be controlled
within the d~sired limits if there is any transfer of
heat through combustion of the metal. The size o~ the
settling chamber 26 is made such that the slag spends
an adequate delayed period in this chamber, i.eO the
velocity of flow of the slag must be reduced significantly
in the chamber 26 compared to its flow rate in the
outlet passage 25. For greater speed o~ the coal
gasifying process and a consequent high slag throughput
the settling chamber 26 must be made greater than for
relatively slower processing. Normally there is a
ratio of at least 1:10 maintained between the cross-
sectional area of the passage 25 and that of the chamber 26.
O~ygen or oxygen-containing media are introduced
into the de-sulphurising vessel 27 through a nozzle 29
mounted in its floor and this oxygen oxidises the slag,
which leads to a substantial reduction in the sulphur
solubility and oxidation of the sulphur, which is then
removed from the system as sulphur dioxide.
By means of a gas lift 30 fed, for example,
with nitrogen, the slag is pushed back to the main
reaction vessel 21 through a passage 31 illustrated in
Figure 8.
In a particular embodiment of the gas lift 30
the nozzle 29 required for de-sulphurising the slag is
mounted in the floor lining of the vessel 27 in such a
way that it also fulfils the function of the gas lift
and makes the separately provided gas lift 30 unnecessary.
Also in Figure ~ can be seen the overflow 32
which is provided in the slag return passage 31 and
through which a proportion of the slag can be continuously
withdrawn from the circuitO
..
~C~763~
1 An embodiment of a reaction vessel by way of
example for producing 100,000 cubic metres of gas per
hour of the approximate composition of about 25~ hydrogen
and about 75~ carbon monoxide comprises an iron bath of
60 tons and a quantity of slag on top of 15 tons. The
~ree space in the newly lined reaction vessel amounts
to 80 cub~c metres. Two nozzles 5 are provided in the
floor of this vessel.
The nozzles are made up of four concentric
stainless steel tubes 6, 7, 8, 9 having a wall thickness
of 3 mm. The significant alloying elements of the
steel are 0.04~ C and 13% Cr. The tube 6 has an inside
diameter of 70 mm and feeds into the bath 3 with the
carrier gas 50,000 kilograms per hour of coal having a
maximum grain size of 0.5 mm. The annular space
formed between the tubes 7 and 8 has a width of 8 mm.
Through this are introduced 40,000 cubic metres per
hour of oxygen. The two spaces for protective media,
formed by the tubes 6 and 7 and by the tubes 8 and 9
have a width of 0.5 mm and through each gap there ~lows
2,000 cubic metres per hour of natural gas having a
composition of 90~ methane, 4~ CnHm, 3% carbon dioxide
and 3~ nitrogen. 20% of fine lime (CaO) are added to
the coal as a slagging agent. The second nozzle in the
floor is supplied with the same quantities of reaction
components and media.
Such a reaction vessel for the continuous
gasification of coal makes possible continuous trouble-
ree operation ovex a period of at least two months.
The reduction gases that are produced can for
example be used in an blast furnace as follows.
A blast furnace, for example with a daily
output of 5,000 tons of pig iron, is operated in conjunction
with the reaction vessel for producing the reduction
gases. Without the addition of reduction gas, the coke
consumption is 550 kilograms per ton of pig iron. The
.26.
1~76360
introduct~on of xed~ction ~a~ sayes. 2~0 k~lo~xams~ of
coke per ton and for thi~s purpose. altogeth.er l,OOQ tons of
coal are gas~ ed i`n the reaction ve.s.sel per day.
The reaction vessel used for this purpose has, in
its newly lined condition, an internal volume of about 30
cubic metres. For a relative].y large blast furnace, therefore,
only a relatively small additional apparatus is required for
producin~ reduction gas. The temperature of the bath of iron
is for example about 1450C. In determining the temperature
of use of the reduction gas in the blast furnace the opera-ting
data of the other blast furnace auxiliaries are taken into
account, for example the blast temperature. Normally the
reduction ~as is fed to the blast furnace at temperatures
b~t~een about 1000 and 1300C. For example the addition of
about 20~ by volume of nitrogen at ambient temperature (20 C)
achieves a reduction gas temperature of about 1100C. With
about 10% of nitrogen by volume and with conditions otherwise
the same the temperature of the reduction gas is around 1300C.
In the production of reduction gas for a dlrec-t
reduction process which operates at a pressure of about
atmospheres, the volume of the reaction vessel should be about
50% greater than that described above. The optimum reduction
gas temperature for the direct reduction process lies generally
between about 700 and 1000C. A desired temperature of about
~S0C can for example be obtained by adding in about 45% by
volume of nitrogen.
- 27 -
