US1601015A - Method for producing pig iron or steel in blast furnaces - Google Patents

Description

mmms

Sept. 28 1926.

J. G. AARTS METHOD FOR PRODUCING PIG IRON OR STEEL IN BLAST FURNACES 2 Sheets-Sheet 1 Sept. 28 1926. 1,601,015 J. G. AARTS METHOD FOR PRODUCING PIG IRON OR STEEL IN BLAST FURNACES V Filed March 29. 1924 2 Sheets-Sheet 2 u Tr 72, IMF

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JACOBUS GERARDUSAARTS, OF DONGEN, NETHERLANDS, ASSIGNOR TO AARTS-EISEN -AKTIENGESELLSCHAFT, F LUZERN, SWITZERLAND.

METHOD FOR PRODUCING PIG IRON OR STEEL IN BLAST FURNACES.

Application filed March 29, 1924, Serial No. 702,954, and in Germany May 8, 1923.

My invention relates to an improved take place in presence of excessive quantities method of treating iron ores and ferriferous of carbon acting toreduce again directl waste in a blast-furnace in order to produce the formed carbon-dioxid or carbonic aci pig-iron or steel. the more so as the average temperature in a 55 a Theblast-furnace process hitherto accomblast-furnace is above 1000 C., so that carplished is objectionable for several reasons bonic-acid will decompose. or disadvantages. As coke and iron-ore are The object of my invention is to remedy supplied to the furnace in successive alterall of the hereinbefore mentioned disadvannate layers, the two materials cannot mix cages of the old art. 60 thoroughly and even in the bottom part of I am aware that electrical blast-furnaces the furnace they mix only very imperfectly. have been suggested heretofore, which are Further the ore is owing to its pieced or provided with a short supplying tube or conlumpy shape mainly not affected by the cardui-t mounted inthe mouth to depend therein bon monoxide-gas (CO) except externally, so that the fuel may be fed in through said 65 that is to say, by contact with its outer faces tube, while the ore is supplied separately only, and this is particularly prejudicial in from the fuel in the annular space surroundcase of hot agglomerated and fritted mateing said tube. Obviously as far as the tube rials as always present in blast-furnaces even or conduit goes, the two materials will deintemperature zones at 1200 to 1300 C. scend in the furnace separately for the pur- 7 As a result of this incomplete reduction the pose and with the result of producing in the oxides in the ores, that have not been reupper portion of the furnace a coking 0pduced, go into the slag which is formed in eration at a low temperature. In contradisthe bottom-zone of the furnace. Ore howtinction thereto the essential and novel feaever, thus slagged or fritted,'cannot be readtures of my invention are as follows. 7 ily reduced, so that the reduction must be I supply the ore and the fuel, with or mainly accomplished in the slag. This also without the required additions, to separate refers to objectionable constituents, such as spaces in the furnace, said spaces going sulphur, arsenic and so on. The iron must down as far as the boshes. The gases arisbe recovered from these compounds which ing from the boshes act to reduce in a dry 3 partly are hardly reducible, by the aid of way the ores mainly without primary c'oal dissolved carbon. being present, whilst the fuel is subjected Considering this, the blast-furnace procto fractional distillation and coked. The ess as hitherto carried out involves, that the ores and'the fuel having-thus undergone an main portion of the reducing operation is introductory or partial reduction each of its 35 accomplished in a very restricted space and own, thereafter meet on the hearth where under unfavourable circumstances, especially the final or complete reduction of the ore, 1nin the molten mass where quite a multitude eluding manganese, siliconand so on, takes of reactions take place which do not start place, the metallic iron and the slag are from metallic iron but from iron oxid and melted and at the same time the Hon is car- 4 which occur while the reagents are in a buretted.

liquid state. It will be seen that in my improved meth- Due to the stated unfavourable circ umod tlie reduction of the ore and the coking stances the quality of the produced pig-iron of the fuel to a large extent or malnly are is deficient; but a still more objectionable brought aboutin an operation separate from 4 particularity of the old process resides in the melting operation, so that the process is the excessive consumption of coal or coke, carried out under circumstances whichare since the principal reaction starts from solid especially advantageous for obtaining apure carbon with the intermediate formation of roduct of better quality. The amount of carbon-monoxide and iron-carbide. uel supplied at the top of the furnace may 50 A further drawback of the .old process be a multiple less, with relationto each ton, lies in the fact that all of the reductions than the weight ofthe ore whereby a considerable saving in fuel is realized. If desired or required the impurities, such as sulphur and arsenic, present in the charge may be hydrogenized and volatilized, with the aid of the hydrogen produced in the process, in the middle andlower part of the ore column and in absence of any coal, so that such impurities are prevented from going into the iron.

In the accompanying drawing wherein an approved embodiment of the invention is illustrated:

Fig. 1 shows a. vertical sectionthrough the complete furnace,

Fig. 2 is a vertical section through the furnace with means for feeding the fuel and the ore and conveying means for causing the ore to travel through the furnace.

Fig. 3 shows several crosssections through the furnace namely along lines A-A, BB, CC, DD of Fig. 2,

Fig. 4 is a diagrammatic longitudinal section through thefurnace showing the tem-" peratures for the zones at the various heights of the furnace.

'Coaxially to the vertical axis of the furnace is an inner shaft or chamber 6 within a larger shaft or chamber a of annular.

shape, the former receiving the fuel and the latter being supplied with the ore, both with the required additions. The interior of the furnace thus comprises four zones I, II, III and IV, I being the melting zone, II being the coke generator, III being the ore shaft and IV being the fuel shaft. The raw fuel, with additions if required, is fed at the top of the vessel 0, Figure 2, and the ore with additions, if required, is fed into the surroundingfunnel d, and the supplied fuel and ore are conveyed from the funnel c and the funnel (Z to the fuel shaft and the ore shaft respectively through descending tubes f and '9 provided with suitable closures.

Obviously the blast-furnace may, if desired, comprise a plurality of such reducing and coking chambers independently of each other. The ore chamber III may be equipped, wholly or partially, with mechanically working conveying devices, such as ro-- tary scoops or shovels for continuously transporting the ore from one story ,to the next lower story in counter-current to the gasesrising in wavy lines.

In the chamber IV the fuel gradually descends and in doing so it is subjected to fractional distillation and cokedby the heat of the rising gases, as will be described here inafter more in detail. The ore and its additions, if any required, are supplied at the top of the reducing chamberIII and gradually moved downwards in said chamber. During this gradual downward movement the ore is wholly or mainly reduced just in accordance with its particular nature.

In order to retain the descending ores within the reduction zone as long as possible and to bring them in constant and most intimate contact with the ascending gases, the reduction room is equipped with stories of staggered or overlapping relationship, so that the gases are compelled to move in permanent counter-current with respect to the descending ores, the arrangement being such that the so-called dry reduction of the ores and the expulsion of certain objectionable impurities will be ensured thereby.

The reduced and purified ores travel from the lower end of the ore shaft having a bottom k for supporting the weight of the ore through the openings Z of said bottom into the chamber II in order to meet and be mixed with the coked fuel descending from the fuel shaft IV. In said chamber II the reduction of the ores is completed, the iron and slag melted and the iron carburetted, as far as such is required. The hearth is provided, as usually, with a slag, hole m, a tapping hole a and air-blast nozzles 0.

The ore on having been wholly or mainly reduced in the dry reduction chamber III at a temperature below 1000 0., mixes, still finely comminuted, with the coke in the shaft or chamber II and is completely reduced to ferrite, carburetted and melted down in the latter. The reduction of the metallic oxids on the one side and the reduction of the impurities, on the other hand, therefore, occur separately and under different physicalconditions, that is to say, the former in a dry wayand the latter in a melted" state, it being noticeable that the principal impurities such as sulphur and arsenic, have been previously removed from the ore in a dry way in the chamber or shaft IIIas will be hereinafter described more in detail. F 7

It is advisable to inject steam through the radially arranged or. distributed pipes 7) into the lower part of the fuel shaft or chamber IV, which part is heated above 1100 C. The steam rises within the chamber IV together with the carbon-monoxid gases ascending from the hearth II and produces on meeting the-incandescent fuel water-gas. Instead of steam or together therewith, if required or advisable in the particular conditions of the case, wastegases containing carbonic acid and discharged from the ore shaft or chamber III through the openings 9 may be introduced into the fuel shaft IV at the bottom thereof for the purpose of reducing the carbonic acid contained therein and to regenerate the said waste-gas. P

Further it will be advisable to introduce the gas discharged from the shaft IV through the openings r after separation from its valuable constituents, into the shaft III- partly be employed for the reduction of the ore, but they have a temperature of between 1400 and 1500 (l, which is too high for the ores, since the latter would be fritted and the slag melted thereby. It, therefore, is necessary to reduce the temperature of the gases and for this purpose I utilize in my improved method mixed gas issued from the coking chamber and purified, which does not contain any by-products.

In this manner I alse realize the importantadvantage of having a gas rich in hydrogen and oversaturated with carbon in the reduction chamber. Hydrogen combines with sulphur, arsenic and the like and the gaseous compounds thus formed are carried awaywith the gas current. Moreover the hydrogen greatly assists in the reducing process and just in this point my improved method is essentially distinguished from the customary blast-furnace method, for-hydro-, gen is the most efficient reducing agent I known in the art.

'As the reduction of the ores is of great importance and a characteristic feature of my new method, I deem it necessary to explain in detail the single operations thereof.

The hot carbon-monoxid gases rising from the lower part of the furnace are mixed with the cool gases derived from the by-product, recovery for the reasons hereinbefore mentioned, whereby, as above explained, a practically carbonic acid-free gas rich in hydrogen and oversaturated with carbon will be obtained, which comes in contact with the already reduced ores at a temperature of 950 C. The hydrogen which, as is known, acts as a reducing agent even at low temperatures, did already create metallic iron in the upper zones of the reduction shaft. Upon meeting a gas rich in carbon-monoxid and containing hydrocarbon this gas will act as a catalyzer and the catalyzing action will be very eflicient owing to the enormous constantly increasing and varying surface of the gas. Amorphous carbon precipitates upon the metallic iron, and, as such carbon forms at a low temperature, it is evidently carbon of highest activity and of carburetting property. The thus formed iron-carbid-Fe C. is a still more active or eflicient reducing agent and adapted to reduce, together with the said a-carbon present, the iron and oxygen compounds still existing below the metallic surface of the ore. In this way carbonic acid respectively carbon-monoxid forms, while the 11011 carbid is reduced to metallic iron, which in turn acts as a catalyzer and again receives active carbon. This circuit action continues until the ore particles are completely reduced. As the ore advances to, the higher temperature-zones, theless active'fl-carbon forms at temperatures above 600 C. acting to carburet the iron preliminarily and to protect the same from subsequent melting with the slag.

My improved blast-furnace method may be divided into four separate elements according to the four zones I to IV of the furnace (see Figure 4) (1) The lower hearth.-In the lowerhearth the molten mass or bath consisting of iron and slag is intended to be brought to a temperature of about 1500 C. and maintained at such temperature, until the mass is discharged by tapping. Over and above the bath theoxidizing zone of thehot vent prevails which, however, cannot .exert an oxidizing action to any noticeable degree on ac,- count of the great speed of the dropping metal. i

- (2) The upper-hearth.-In this part of the furnace the following operations shall gas.

(3) The reduction 07zambe1".In this part of the furnace the following operations are to occur, viz:

(a) The dry reduction of the ore with the aid of the described gas mixture at a temperature not above 950 C.

(b) The hydrogenization of the impurities of the ore, in particular of sulphur and arsenic, as above described.

The reduction chamber, if constructed to be of annular shape, is further designed with a view to avoid any losses of heat from the coking chamber through radiation;

(4) The coking okam'ber.In this part of the furnace the following operations take place, viz: a

(a) The fractional distillation of the fuel at a temperature gradually rising from the tamperature of the atmosphere up to 1300 (b) ,In the lower part of the shaft, where the temperature is between 1100and 1300 (I, the production of water-gas and the reduction of the temperature to the limit suitable for a satisfactory coking process.

(0) In case that conditions allow, the regeneration of a part of the gas discharged from the shaft and introduced atthe bottom of the coal shaft, oriof foreign gases of the kind, either alone or, together with the production of water-gas at temperatures of 1100 to 1300 C.

In this regard it is to be noted that the distillation of the coal takes place endothermically i. e. in a heat consuming manner,

ment are saved;

(2) Saving of losses of heat arising from reheating and drying the coke in the blastfurnace;

(3) Saving of losses arising from cool-' ing, loading, piling, transporting and charging the coke;

(4) Saving of cost for transporting or conveying materials from the coke oven to the furnace,

\ (5) Avoiding deterioration of quality of the coke at the pressing, loading, transporting and charging operations;

(6) The coal to be coked is heated, without any expense and without'combustion of gas by the large amount of the available hot gases, so that the gases otherwise required for heating the coke oven are available for other purposes; moreover they bring about an absolutely ideal-distillation by preserving all of the distillates, no matter whether obtained at high or at low temperatures, and preventing their premature liquefaction or decomposition; in this way the out put is greatly increased, as regards both quantity and value thereof, a fact which further assists in lowering the price of the coke going into the furnace and of the iron produced.

(7 The method is restricted to the recoveryfrom the waste-gases of the coking chamber of ammonia andof those hydrocarbons, which when cooled are liquid and to the desulphuration of said hydrocarbons, if required. In this way a gas is obtained which is practically free from carbonic acid, poorer than normally in nitrogen, rich in hydrogen and over-saturated with carbon. A gas of this sort is a most etficient reducing agent for iron ores and a most efficient carburetting means for metallic iron, but it has never been used or available in the art as hitherto practiced.

For hydrogen is a reducing agent which is not only by far more efiicient than car bon-monoxid, but also active at lower temperatures as compared with thelatter, and further hydrogen acts to combine with 'very objectionable impurities, such as sulphur and arsenic, forming gaseous compounds therewith, which are easily removed, sothat iron of greater purity and higher value will be obtained.

Moreover owing to the enrichment with carbon monoxid and hydrocarbon an over saturation with carbon is obtained so that active, amorphous carbon may be formed in abundance which will act to greatly promote the reduction of the ironoxygen-compounds even at low temperature;

(8) The coke need not be of a certain high quality, since it has not to support the heavy weight of the ore and additions. Consequently the coke is not subject to crushing and rubbing, so that also coal of lessvalue may be employed in the furnace;

(9) In order to ensure a ready, quick and thorough reduction of the ores at low temperature, the ores must be finely comminuted. Considering this, there now is a possibility of utilizing ores on stock, which at the present state of the art, cannot be used for the purpose on account of their pulverulent state, or which otherwise must be previously briqueted in order to be in a treatable state, which, however, involves considerable extra costs;

(10) By causing the just mentioned rich and cold waste or by-product gases to mix with that portion of the carbon-monoxid containing gases coming from the upper hearth, which is intended to flow through the reduction chamber and which is of a detrimentally high temperature involving the danger of the ore particles getting coated with a layer of fritted or molten slag impermeable to the gas, a considerable reduction of the temperature is ensured, which will remove such danger. Apart from that the reduction of the ore particles commences, owing to the presence of reducing agents, which are even active at low temperature, in the upper stories of the reduction chamber and immediately thereafter the carburation of the produced metallic iron begins.

(11) Not only the costs of the unnecessary coking plant are fully saved but also the costs to be invested inerectin the blastfurnace are considerably reduced. In furnaces of the kind hitherto constructed enormous quantities of the very voluminous coke must slowly move down from the top to the bottom of the furnace, before the coke is in the required state of combustion, for the reason that the coke is charged together with the ore in alternate layers and cannot advance except in dependence upon the speed of the movement of the ore..

In my improved method, however, the deseending movements of the two materials are independent of each other and the fuel is free to move down at a greater speed. Consequently the portion of the furnace required for the reception of the fuel is comparatively small, which involves a considerable reduction of the costs to be invested in the construction of the furnace.

(12) All of the aforementioned savings in fuel involve further reduction of the room required for the fuel, and particularly an enormous reduction of the cost of production of the iron.

From the foregoing, it is believed, that the advantages and novel features of my invention will be readily understood and, therefore, further detail description is deemed unnecessary.

It will be evident, however, that my invention may be varied and adapted in many ways, according to the several requirements desired, or most suitable under the different circumstances.

l/Vhat I claim is: 1. A method of producing iron in a blas furnace, consisting in feeding the ore in some cases with additions downwardly through the blast furnace in an ore shaft and out of contact with solid fuel,-feeding the ber, passing steam into the lower portion of the fuel chamber, supplying gas from the upper part of the fuel chamber to the lower portion of the "ore shaft for reducing the grains of ore to iron sponge, and bringing the reduced ore into contact with the coke produced in the fuel chamber in the bosh of the furnace so as to melt down the iron and simultaneously carburize it.

2. A method of producing iron as claimed in claim 1, characterized by the featurethat the temperature of the gases servingforf carrying out the reduction process is fixed by mixing the cooled gas derived from the fuel shaft with the hot gases which rise from the melting zone of the furnace.

3. A method of producing iron as claimed in claim 1, characterized by the feature that simultaneously with the steam, a portion of the gases which pass out of'the' reduction shaft is introduced into the fuel shaft.

In testimony whereof I aflix my signature.

J AGOBUS GERARDUS TS.

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