CA1181238A - Method of gas production - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Gas is produced in a ferrous bath reactor containing an iron melt by feeding solid or liquid carbonaceous fuel (e.g.
coal) into the reactor and blowing an oxygen-containing gas from nozzles onto the surface of the melt to gasify the fuel. The gas is collected in a space through which the gas from the nozzles is blown. In traversing the gas space, the gas from the nozzles causes partial combustion of the generated gas so that the combustion gases are transported to the melt surface whereby the combustion heat is transmitted to the melt.

Description

This invention relates to a method of gas produc-tion in a ferrous bath reactor vessel containing a bath of molten iron to which solid or liquid carbonaceous fuels are fed whilst a gas iet consisting at least partly of oxygen is blown onto the top surface of the melt so that the fuels are gasified and collected in the gas space above the mel-t whence they are remo-~ed.

The continuous gasification of coal or other carbonaceous fuels in a reactor containing a bath of molten iron or steel covered by a layer slag to form a gas consisting essen-tially of C0 and H2 has been known for a long time. According to the method described in German OS 29 52 434 oxygen is blown onto -the top surface of the melt by means of a blasting lance arranged above the melt surface, thus generating a high-tempera-ture blasting zone. A jet of a solid, carbon-containing powder -together with a propellant gas is then directed at this high ternperature blasting zone.

Another method is described in German AS 25 20 8c83, according to which coal, or a carbonaceous fuel, is injected into the ferrous melt at a point situa-ted below -the mel-t surface.
A gas jet which consis-ts at leas-t par-tly of oxygen is also injected into -the melt beneath the surface thereof, -the jet being sheathed by hydrocarbons -to pro-tec-t the ~ssocia-ted nozzles .

Finally, German PS 25 20 868 describes a known process in 23~3 which high-energy-content coal, free carbon, aluminium, silicon,calcium carbide, or mixtures of these, are additionally fed into the ferrous bath, potentially indepenclently of the coal which is to be gasified in -the reactor. This feeds additional heat into the coal-gasifica-tion process.

A disadvantage of these known ~ethods is that low grade fuels, particularly those types of coal which have a low calorific value, could hitherto not be gasified in a cost-effective manner because an additional supply of high-energy fuels is needed with fuels of this type in order to maintain the temperature of the ferrous bath. Additionally, with these known methods it is not possible to use cheap, directly available oxidising gases, such as air.

An object of th0 present invention is therefore to minimise or overcome the disadvantages of the previously known methods and to provide a method which allows a combustible gas -to be produced in a cost effective manner from carbon and/or hydrocarbon-containing fuels of lower energy grades, the fuels beingsupplieclin solicl, pow~ered or licluicl form to a ferrous bath reactor with -the assistance of cheap o~iclising gases in s~lch a manner as to clispense with -the need for an additional supply of high~energy-content fuels for -thermal balance compensation in -the gasification process.

Accordingly, the invention resides in a me-thod of gas produc-tion in a ferro~ls ba-th reactor containinga ba-th of 23l3 molten iron, comprising the steps of feeding a carbon-containing ~uel in solid or liquicd form into the reac-tor, and blowing a jet consisting at least par-tly of o~ygen onto -the top surface of the mel-t, so that the fuel is gasified, collected in a gas space above the melt and removed therefrom, wherein -the gas je-t is blown -through -the gas space, sucks in -the already-produced gases, partially burns them and -transports them to the melt surface so that the heat generated by the combustion of the produced gases is transmitted to the ferrous melt.

In such an arrangement the gas traverses the gas collector space above the melt sur~ace over a dis-tance o~ maximum possible length. Due to the jet effect of the gas stream which is blown into the reactor, the gas whichhas already been produced by gasification of the fuels in the melt and is present in the gas space is sucked in-to the jet stream ancl carriecl along wi-th i-t. This kind of effect can also be observed with, for e~ample, a wa-ter jet pump. Since -the gas jet which is blown onto the surface of -the melt contains o~ygen, a por-tion o-~ the alreacly producecl combustible gases in the gas space is burnt ancl the resu:lting heat is fed into -the mel-t because the gas jet clirec-ts the hot comb~ls-tion products -towards -the me:Lt surface so that the hot combustion produc-ts coMe into contact -therewith and can -tr~nsmi-t their heat to t~e mel-t.

The me-~hod according to this inverltion of blowlng a jet 3lZ38 stream of a gas which has an o~idising effect (i.e~ ox~gen, air or the like) a-t the surface of the melt affords a sub-stantial improvement in the thermal balance of a ferrous bath reactor.

The method according -to -the inven-tion also allows the use of air for thè gas je-t. It is therefore no longer necessary to use technically pure oxygen, as in conventional processes. Air is generally very cheaply available and can be compressed to the required operative p~essure by simple means. It is particularly recommended to pre-hea-t the air in order to avoid heat being extracted from the gasification process for the preliminary heating up of the injected air. In practice, a pre-heating temperature of 300 to L~oO C has been found to be suitable. Up -to this temperature level it is possible to use conventional pipelines and valve means and the cos-ts of thermal insu-lation in the s~lpply system are acceptable.

~lowever, i-t is also possible -to use pure oxygen as -the gas je-t. This has particular advantases when working with fuels having very low hea-ting power. Thus, the percentage of oxygen in the gas je~ is determinecl by considera-t:ions of cost and by -the quali-ty of the fuels in cluestion .

Preferably, the fuels, in solid or liquid form, are injec-ted into the melt a-t a position below the mel-t surface~ The

2~8 fuels are injected by means of propellan;t gases such as, for example, air, nitrogen, carbon monoxide, ancl inert gas or the like. However, it is equally possible to feecl the fuel into the reactor above -the mel-t surface.

The oxygen in the gas stream which is directed through the gas space an~ onto the surface of the melt is specifically intended for the combus-tion of a portion of the gases which are produc.ed from the fuel. The supply o-f oxygen for the actual gasification process as such, on the o-ther hand, is preferably made through nozzles arrangecl beneath the melt surface. These nozzles may for example consist of several concsntric pipes, and a hydrocarbon may besupplied for nozzle protection in a known manner.

The proportional amoun-t of oxygen fed ~eneath the melt surface relative to -the proportional amount of oxygen contained in the gas je-t which is directecl at the surface of -the melt may be varied within very wide llml-ts. ~or e.~ample, 80 % of the total amoun-t of oxygen may be fecl from above -through the gas jet ancl only 20 % lnjec-ted beneath the melt surface, or conversely, 80 % of the -total amount of o~ygen supplied to -the .ferrous bath reac-tor rnay be lnjectecl benea-th -the surface of -the melt and on].y 20 %
adderl from above ln the form of the gaseous jet s-tream.

However, lt has been found -that in orcler -to obtain the aclvarltages of the i.nvention in respec-t of -t:hermal econorny at leas-t 10 % of the tot.al amount of oxygen fe~ in-to the 23~

reactor snould be blown as a gas jet onto the melt surface in the reac-tor vessel. This percentage may be increased up to 100%, and it has been found, surprisingly, that this oxygen in the gas je-t also serves -to oxidise -the fuel in -the ferrous melt. In normal operation of a ferrous-bath-reactor approxima-tely ~0 to 90% of the -to-tal amoun-t of oxygen would be supplied through the gas je-t. For reasons of economy alone the amount of oxygen which is fed into the melt from above will be chosen tobe ~shigh as possi~ae, because this fraction of the total oxygen supply is generally injected at a lower pressure than that which is required for oxygen injec-tion through the nozzles situated beneath the melt surface.

Preferably, several gas jets are directed at the melt surface.
The gas je-ts are arranged -to enter the reactor vessel at a large dis-tance from the top surface of -the bath and to impinge approximately in the central area of the bath surface. :[t is impor-tant -that -the gas jets should cover a sufficiently long dis-tance in the gas space above the mel-t.
~ormally a minimum distance of abou-t 2 m should be maintained between -the gas jet nozzles and the surface of the ferrous bath. The nozzles are mounted in the refrac-tory lining in the upper region of the reactor vessel. Particularly in -the case of air injec-tion, each nozzle may consist of a simple pipe, or else, for example for injec-tion of pure o~ygen, of two concentric pipes. ln the lat-ter case the o~ygen flows through the inner pipe and, for nozzle protection, small 2~8 amo-unts (0.1 to 5% relative to the oxidising gas) of nitrogen, carbon monoxide, an iner-t gas, a hydrocarbon or the like, are injectecl through the annular gap between the concentric pipes.

Accorcling -to a preferrecl embodime-nt of the me-thod accorcling to this invention, a gas, which i3 largely sulphur-free, is produced from sulphur-con-taining fuels in the ferrous-bath-reactor for subsequent combustion in boiler- and heating plant, for exarnple for elec-tric power generation. The sulphur is removed in the reactor by a slag which contains CaO. The necessary slag-formers, in particular CaO, are delivered, preferably in powder form, with the oxygen-containing gases which are injected into the melt below the surface thereof.
It is also possible to admi~ the slag-formers with the fuels, or to inject CaO spparately with the aid of a propel.lant gas. The resulting slag, including -the enriched content of -fuel ash co.n-tained therein, may be d:rawn off batchwise from the reactor, or it may be des-llph~.lrised in molten concli-tion for improved thermal economy accord:ing to Germcln Pa-tent 25 20 58l~, ancl large:ly returnecl in mol-ten conditio:n -to -the reactor.

For e.~ample, by app:Lication of the me-thod according to this invention, depending on the -type o e fuel fed into -the reactor, gases have been produced of the follor,~ing composi-tion. For the gasification of 1 -t coke con-taining about lO~o ash and 1% sulphur, approximately 2~00 m3 of air which llad been preheated-to atemperature of300C wasinjected in-to-the ferrous 2;~

meltbeneath themelt surfacéand at-the same time 2 400 m3 ofair which had been preheatedto thesame tempera-turewas blown on-to the -top surface of the melt. The ferrous mel-t hacl a tempera-ture of approximately 1400 C and a carbon content of about 2~ou For each -tonne of coke 5 500 m3 of gas were obtained, consisting of approximately 25% CO, appro~ima-tely 6% C02, approxima-tely 69% N2 and approximately 0.002% sulphur, at a temperature of 1400 C. The gas con-tained a clust frac-tion of about 2 g/m3 and could be fired directly in a boilex plant.

The gasification of a long-flame gas coal containing 78% C, 5% H, 7% O, 5% ash, produced a gas of the following composi-tion: 19.0% CO, 4.8% H2, 4.6% C02, 66.5% N2.

A lol~-energy, dried lignite product with 64.o ,~ by weigh-t C, 4.9% by weight H, 23.6% by weight 0, 5.9% by weight ash, 0.4% by weight sulphur and a heating value H of 5600 kcal, which was gasified wi-th air at 300 C in the ferrous-ba-th-reactor in accordance with -the method of this inventiorl, prodtlcecl a gas con-taining 21.~ vol% CO, 6.2 vol.%H2, 5.~
vol.% COz, 6.2 vol.% H2o,60.7 -~rol.% N2, 20 ppm sulptltlr and a heating value of 806 kcal/m . I~or clesulphuri~ation approximate:Ly 9 kg CaO / t coal were fed in-to the ferroas bath-reac-tor.

The application of oxygen in accorclance with this inven-tio is always found to be advan-tageous where -the demand for a high-energy content gas wi-th low N2 content ls of primary importance or where particularly low energy f~l~l grades are 23~1 -- 10 _ used for gas production in the ferrous bath reactor.
~hether pure oxygen, or oxygen-carrying gases, and in the latter case, which such gases, are used for gasification in the reac-tor clepends primarily on economic considera-tions and on the envisaged fur-ther application o~ -the produced gAses. According -to the method of -this inven-tion there are no method-technology problems encountered in the gasification process and i.n -the compensa-tion of energy requirements in -this process due to the partial combustion of the produced gas in the gas collecting space of the reactor and the application of different oxygen-beari~g media.

According to a further, particularly advantageous modi.fication of the invention substances which contain iron, in bonded or -free form, such as, for example iron ore, are added to the melt in the reactor vessel for the purpose of simul-taneously producing molten iron (pig iron) and a gas.
Accordingly, with -this modifica-tion of the inven-tion, the heat generated by the par-tial pos~t-combus-tion of the gas which is produced in -the ferrous mel-t reac-tor is utllised, a-t leas-t partially, for recluction of the iron-con-taining substances, particularly iro:n ore. Thus, in this rnodification, besides the carbon-con-taining solid or liquid fuels as ~ell as oxygen and slag-forming materials, further ma-terials which contain iron at least partially in oxicle form, such as for example iro:n ore, are added to the ferrous melt in the reac-tor vessel. An impor-tant economic a.dvan-tage of -this modification of the method according -to the presen-t invention z~

resides in -the fact that ore is direetly reduced at lo~
teehnical expense and ou-tlay by a relatively small quantity of eoal and at the same time a gas is generated whieh has many potential applieations. In one example o-f this rnodifieation, to produee one tonne of iron by reduetion of iron ore, approxirrlately 1.1 t of eoal (eomposition appro~i-mately 78% C, 5% H2, 3% H20, 5~0 ash, 5% 2' 1% S, ealorifie outpu-t value Hu = 7.500 kcal/m3) are required. The simultaneously produced gas is suitable for incLustrial use and has approximately -the following eomposition: 57% C0, 1~% C02, 14% H~ % ~I20, with a heating value Hu of about 2.100 kcal/m3. The method aeeording to this modifieation thus enables the eeonomie optimisation of the produetion of iron in eombination with gas produetion in a ferrous bath reaetor. By way of eontrast, if the method of said one example is repeated but without the feedba.ek of energy from the partial post eombustion of the gases whieh are produeed in the ferrous melt, aeeording -to this invention, approx:i-mately 3 t of the same kind o-f eoal are needed to produee 1 t of iron from the ore. The produeer gas woulcl then `have the followi.ng composi-tion: 70% C0, 1% C02, 27% H2, 1% H20, with a hea-ting value ~u of abou-t 2.700 kcal/m3.

0-ther known multi-stage methods for -the reduc-tion of iron ore and the procluction o:f molten iron, for e~arnple according to German OS 24 01 909, have -the clrawback -tha-t the gas ~hich is p:roducecL in s-uch a process, clue to i-ts :I.ow heating value, ean be usecL only for minor heatlng functions without incurring the cost penalty of adding high-energy gases.
With -this process approximately 650 kg of coal are needed to produce one tonne of iron and -the gas which is produced comprises approxima-tely ~1% C0, 30% C02, 18% H20, 10% H2, with a hea-ting value of 1.100 kcal/m3.

In this modi~ication of the present inven-tion, -the ore may be fed into -the ferrous mel-t directly through bottom nozzles or also from above by blowing it at the surface of the melt.
In a preferred embodiment, the ore is at least partly added jointly with -the o~ygen which is blown at the mclt surface.
In this case the pulverised ore is already pre-heated and pre-reduced in the gas atmosphere which improves -the thermal efficiency of the process. To further improve this effect it may be advisable to provide the blasting nozzle with maans for e~panding -the jet containing the ore particles, for example by imparting a spin to the je-t as it leaves -the nozzle.

Bes:icLes ores of VariO~LS qua:Lities, pellets and briquettes of incomp:Lete:Ly reducecl ore are founcl-to be particularly sui-table chQrge materials containing iron a-t least par-t]y in an oxicle form.

The IDethod ~ccording -to the present invention may be advan-tageously applied in all situations ~rhich allow the produced gases to be used as fuel ~as in the :immediate ~icinity, for ins-tance as a s~lbstitu-te for natural gas.

The partially burnt gas which is produced in the process accorcling -to the invention has approximately the same flame temperature as natural gas, mainly due to its rela-tively high CO-conten-t, so tha-t i-t can be substi-tu-ted for natural gas wi-thou-t major conversion of f~rnaces and their burner devices.

The following example describes the application of the method according -to this invention to a converter--type reactor vessel containing 60 t of ferrous melt. The base of the converter is provided with ten nozzles having an un-obstructed diame-ter of 28 mm. Through two of these nozzles pulverised coal dus-t is injected at the rate of 350 kg/min, the propellant gas being either nitrogen, carbon dioxide or even reduction gas from the converter i-tself. Oxygen is injected -toge-ther wi-th iron ore -through three nozzles whilst the remaining five nozzles are used for injec-ting oxygen partially charged with slag-formers such as for example lime.
A further nozzle is providecl in the upper co~:ical par-t of the conver-ter through which appro~:ima-tely 50% O:e -the total o~ygen reqlliremen-t is directecl a-t the top of the me1t. Using coal of the above specifiecl composition and an ore con-taining 85% ~`e203, 20 -t of iron wi-th a carbon con-tent of abou-t 3 is produced per hour. The o~ygen requirement for the gasification of one tonne of coal simul-taneously Witll the smelting of 1.~-~50 kg ore amo~mts to 580 m3. The process produces a carbon- or fuel gas having the above specified analysis (about 57% CO, 11t% C02, llt% H2, lLt% H20) and a 2~8 heating value Hu of approximately 2.100 ~cal/m3.

I-t is also wi,-th:in -the scope cf this in.vention -to design the reactor vessel in such a shape -that it may simultaneously serve as a conver-ter so that steel can be directly produced in the same vessel. To this end the carbon con-tent of abou-t 2 to 3%, which exists during normal operation of the ferrous melt reactor, is lowered to a'bout 0.05% prior to each tapping operation whereafter about 20 t of the melt is tapped from the converter. A melt of approximàtely 50 t is then left in the conver-ter and is subsequently slo-wly re-carbonised -to the desired carbon content of 2 to 3% in the course of con-tinued simultaneous blasting of o~ygen and coal with a small e~cess of the latter. When working in this manner it has been found to be advisable to remove the slag from the melt before the carbon of the mel-t has fully returned to i-ts original value, i.e. appro~ima-tely when the residual carbon content in the melt is be-tween 0.5 an,d 2%~
The subsequently newly formed fresh slag which .Ls in 'balance w,ith the tapped steel me:l.t then remains in -the conver-ter.

The me-thod accorcLing -to thi.s i.nvention is he:reinaf-ter more particularly descri'becl with reference to ~.n embocliment and with -the aid of the accompanying draw:irlg which represents ~ longitucllnal sec-tion through a ferrous ba-th reactor.

P~eferring -to -the drawing, a conver-ter-shaped reac-tor vessel 20, which is sealed in gas-tish-t manner, is filled to abou-t hal:f of its capacity wi-th a ferrous melt 21, -the surface of the melt 22 extending approximately hal-fway up the height of the vessel 20. A nozzle 23 is provicled in the base of the reactor vessel for the injection of finely-subdivicded coal 2~. Also arrangecl in -the base of the rcac-tor vessel 20 is ~n oxygen injection nozzle 25 -thro~lgh which oxygen is injected into the melt 21 separately from the nozzle 23. In practice this oxygen nozzle 25 will be surrounded by an ~nnular gap for the injection o~ hydrocarbons or the like for nozzle protection.

In the upper region of -the converter two nozzles 26 and 27 extend through the walls of the reactor vessel 20. They are supplied with air 28 and form jets 29 which are directed approximately at the central region of the melt surface 22. The outlet orifices of the jet nozzles 26 and 27 are situated approximately 2 m above -the melt surface 22.

The gas jets 29 travel -through the gas space 30 above -the rnelt surface 22 and by -their je-t ac-tion suck in ancl cLrag alon~ a portion of the gases 31 a:lreacly genera-tecl by gasifica-tion of -the fuel coal '~4. /~ fraction of these gases 3:l is burn-t by the oxygen content in the gas je-ts 29.
The combus-tion hea-t is transmi-ttecl throug:h the mel-t surface 22 -to -the ferrous rnel-t 21.

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of gas production in a ferrous bath reactor containing a bath of molten iron, comprising the steps of feeding a carbon-containing fuel in solid or liquid form into the reactor, and blowing a gas jet consisting at least partly of oxygen onto the top surface of said melt, so that the fuel is gasified, collected in a gas space above the melt and removed therefrom, wherein the gas jet is blown through the gas space onto the surface of the melt and, in traversing the gas space, sucks in the already-produced gases, partially burns them and transports them to the melt surface so that the heat generated by the combustion of the produced gases is transmitted to the ferrous melt.

2. A method as claimed in claim 1, wherein the gas jet which is directed at the melt surface is technically pure oxygen.

3. A method according to claim 1, wherein the gas jet which is blown through the gas space at the melt surface is air.

4. A method as claimed in claim 1 wherein, additionally to the gas jet which is blown through the gas space at the surface of the melt a gas which consists at least partly of oxygen is injected into the ferrous melt below the melt surface.

5. A method as claimed in claim 4, wherein the amount of oxygen blown onto the melt surface comprises at least 10% of the total quantity of oxygen fed into the ferrous bath reactor.

6. A method as claimed in claim 4 or 5, wherein the gas which is injected below the melt surface is pre-heated.

7. A method as claimed in any one of claims 1 to 3, wherein the gas jet which is directed through the gas space at the melt is pre-heated.

8. A method as claimed in any one of claims 1 to 3, wherein the fuel is injected into the ferrous melt beneath the melt surface.

9. A method as claimed in any one of claims 1 to 3, wherein the length of the trajectory of the gas jet in the gas space is greater than 2 metres.

10. A method according to claim 1, wherein,simultaneously with the production of gas, molten iron is produced in the ferrous bath reactor from a substance which contains iron at least partially in an oxide form.

11. A method according to claim 10, wherein to provide the substance containing iron at least partially in an oxide form, partially pre-reduced ore is fed into the ferrous-bath-reactor.

12. A method according to claim 10, wherein the substance containing iron at least partially in an oxide form is blown at the top of the melt together with the oxidising gas.

13. A method according to any one of claims 10 to 12, wherein the carbon-containing iron produced is refined into steel in the reactor vessel.