CA1076360A - Method and apparatus for continuous gasification, of solid and/or fluid carbon-containing and/or hydro-carbon-containing substances in molten iron in a reaction vessel - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The invention relates to a method for 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. Previously lances used to introduce reactive ingredients have had to have been introduced from above and through the thick layer of slag. As well, they have had to have been replaced frequently because of chemically and mechanically induced breakages.
In the present invention the reactants are introduced from below the surface of the melt through nozzles mounted in the refractory lining of the vessel. As well, because there are no lances being continuously replaced, gas-tight vessels may be used and relatively pure gases may be collected from the vessel's interior.

Description

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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.

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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.

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-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.

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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.
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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.

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:~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.

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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.
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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.

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.

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-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, .

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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.

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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.

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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.

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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.

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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.

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~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.

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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.

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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.

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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.

Claims (21)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Method for continuous gasification of solid and/or liquid carbon-containing and/or hydrocarbon-containing substances in a molten iron reaction vessel, characterized in the the components for the reaction, on the one hand carbon-containing and/or hydrocarbon-containing substances and on the other hand oxygen and oxygen-containing media, are fed into the bath of iron through one or more nozzles arranged in the refractory lining of the vessel below the surface level of the bath, so that the oxygen and/or the oxygen-containing media are surrounded by a protective medium of gaseous and/or liquid hydrocarbon medium or hydrocarbon-containing medium whereby the nozzles are protected against premature wear ahead of the refractory lining.

2. Method according to claim 1 characterized in that the reaction components are on the one hand coal and/or heavy oil and on the other hand oxygen.

3. Method according to claim 1 or 2 characterized in that the components of the reaction are fed together in common through one or more nozzles.

4. Method according to claim 1 or 2 characterized in that the components of the reaction are fed separately into the bath through two or more nozzles.

5. Method according to claim 1 or 2 characterized in that the components of the reaction are fed into the bath in alternating sequence as desired through a nozzle, through respective passages, the arrangement being such that looking from the centre of the nozzle, the annular space that carries the oxygen is surrounded by hydrocarbons and/or media containing hydrocarbons.

6. Method according to claim 1 or 2 characterized in that the substances to be gasified are fed into the iron bath reaction vessel together with gaseous and/or liquid hydrocarbons or hydrocarbon-containing media.

7. Method according to claim 1 or 2 characterized in that the substances to be gasified are mixed with oxygen or oxygen-containing media before passing into the bath.

8. Method according to claim 1 or 2 characterized in that there is imparted to the flows of the components for the reaction, a twist, with which the components leave the nozzle and enter the bath.

9. Method according to claim 1 or 2 characterized in that the components of the reaction are introduced into the bath continuously or pulsating over periods of selected lengths.

10. Method according to claim 1 or 2 characterized in that slagging agents are fed into the bath in a mixture with the substances to be gasified.

11. Method according to claim 1 or 2 characterized in that when employing substances to be gasified which, on gasification in the reaction vessel would cause a cooling of the bath, they are modified by preparation and/or conversion in such a wall that in the gasification process in the vessel an excess of heat is achieved without the supply of external energy.

12. Method according to claim 1 or 2 characterized in that the substances to be gasified of low heat value have added to them fractions of energy-rich coal and/or uncombined carbon material such as coke.

13. Method according to claim 1 or 2 characterized in that the substances to be gasified having low heat value are dried

Claim 13 continued...

and/or pre-heated and then fed to the reaction vessel.

14. Method according to claim 1 or 2 characterized in that the substances to be gasified having low heat value have added to them aluminium, silicon, or calcium carbide individually or in any desired mixtures.

15. Method according to claim 1 or 2 characterized in that to increase and/or to control the temperature of the bath there is added to it, independently of the substances to be gasified, energy-rich coal, uncombined carbon material, aluminium, silicon or calcium carbide individually or in any desired mixture.

16. Method according to claim 1 or 2 characterized in that the reaction vessel is operated at an elevated pressure and the gasification takes place at a temperature between about 1350 and 1450°C.

17. Method according to claim 1 or 2 characterized in that the reduction gas produced is cooled by the introduction of inert gas after leaving the reaction vessel.

18. Method according to claim 1 or 2 characterized in that the sulphur-rich slay is transferred in a liquid condition from the main reaction vessel into a separate reaction vessel and is there de-sulphurized by the introduction of oxygen or oxygen-containing media with or without the addition of inert gas, and finally returned in a liquid condition to the main reaction vessel.

19. Method according to claim 1 or 2 characterized in that the sulphur content of the de-sulphurizing slay in the main reaction vessel is kept well below the sulphur saturation value.

20. Method according to claim 1 or 2 characterized in that the sulphur content of the slag in the main reaction vessel is kept at about 1 to 3%.

21. Method according to claim 1 or 2 characterized in that the temperature of the slag in the de-sulphurizing vessel is about 1350 to 1450°C.