US2219046A - Treatment of iron ores - Google Patents

Description

Patented Oct. 22, 1940 PATENT OFFICE TREATMENT OF IRON ORES Karl Koller and Zsigmond Galocsy, Budapest,

' Hungary Application April 19, 1938, Serial No. 202,92 Hungary May 12, 1934 4 Claims.

This is a continuation-in-part of our application Serial No. 20,654, filed May 9, 1935 for the treatment of iron ores.

Our invention relates to the smelting of iron 5 ores in the blast furnace and has for one of its objects to provide means whereby the thermal economy of the smelting process in general is improved and more especially the proportionof coke or charcoal required per unit of ore is considerably reduced, While blast furnace gases of high caloric effect are produced.

According to the "present invention we treat in a blast furnace ferriferous ores with a carbonaceous agent for the recovery of iron or iron alloys by introducing into the smelting zone of the furnace a hot mixture of those gases which result from the complete, combustion of a primary carbonaceous fuel with oxygen in the presence of steam; said combustion being carried through outside of, but close to the blast furnace and the mixture introduced into the furnace containing substantially the whole of the heat of combustion so as to possess, when entering the blast furnace, a temperature of at least 1300 C. The hot gas mixture introduced consists mainly of carbon dioxide, steam and free oxygen in such proportions with regard to the carbon content of the carbonaceous agent, with which the ores are treated in the furnace, that the carbon dioxide passes through the blast furnace substantially without being changed, i. e. without reacting with the carbon present. In this manner we succed in obtaining in a particularly favorable manner iron or 35 iron alloys such as ferromanganese or ferrosilicon (iron silicide) or the like.

In the practice of our invention a primary carbonaceous fuel is burnt with oxygen, or air enriched in oxygen, in a chamber outside of the blast furnace, but arranged close to it. If desired, the air or oxygen is preheated. The carbon dioxide thus produced is led into the blast furnace together with steam and an excess of oxygen at a temperature which is about equal to the temperature of the combustion by which the said products were formed. The constituentsof this mixture may react in the blast furnace according to the following equations:

The carbon mentioned in these equations is that of the carbonaceous agent, such as coke, which is introduced into the blast furnace in mixture with the ferriferous ores. 1

Reaction 1 is exothermic, while Reactions 2 and 3 are endothermic. However the heat developed in Reaction 1 would not by far he sufficient to furnish the heat required for melting the charge and for the reduction of the iron oxide and for compensating the heat consumed by the endothermic Reactions 2 and 3.- Additional heat must be supplied to the furnace in order to compensate for-this difierence of the heat quantities needed and produced. This additional heat is produced, according to the invention, by burning a primary fuel in a chamber outside of, but close to the blast furnace; the heat is supplied to the furnace in the products of that combustion.

Whether and to which extent the Reactions 2 and 3 proceed beside the Reaction 1, depends upon the quantity of oxygen introduced at the bottom part of the blast furnace, provided that a definite quantity of carbon is introduced into the blast furnace from above. For the quantities of H20 and CO2 which are converted according to Equations 2 and 3 will be the smaller, the more carbon is consumed in Reaction 1, i. e. the less carbon remains over for the Reactions 2 and 3. In the (theoretical imaginable) extreme case that the whole of the carbon content of the carbonaceous agent introduced in mixture with the ores were consumed by the Reaction 1-i. e. in the case that a quantity of oxygen is introduced into the furnace from below such as required for converting the whole carboncontent of said carbonaceous agent into CO-no carbon would be available for the Reactions 2 and 3, so that these two reactions could not proceed any longer. In this case the CO2 and H20 introduced withvthe combustion mixture would pass through the blast furnace without reacting with the other constituents present, while they would transfer to these constituents their sensible heat. On the contrary, in the other (theoretically imaginable) extreme case the whole of the CO3 and .H20 introduced from below will be converted according to Equations 2 and 3. innumerable practical possibilities exist between these two extremes. By regulating the composition of the gas mixture introduced from below one is thus enabled to adjustthe blast furnace process to the requirements of any special case in view of the specific ore to be treated, the highest temperature to be reached in the furnace, the composition of the blast furnace-gas desired andso on.

We found that it is particularly advantageous to'choose the excess of oxygen inproportion to the carbon content of the carbonaceous agent mixed with the ore so that apart from Reaction 5 1 only Reaction 2 proceeds in the blast furnace. while Reaction 3 is completely suppressed. This means that thewhole of the CO: passes through the blast furnace, without reacting with the-carbon present, and serves only as a heat carrier, while the whole of the H20, or part'thereof, is converted according to Reaction 2. Reaction 3 can besuppressed in this manner, since in practice Reaction 2 always precedes Reaction 3.

It is known that half a mol i. e about 11.2 15 m=., is required for the combustion of one mol carbon, 1. e. of about 12 kgs. C. to one mol CO. This quantity of O: is supplied by the mixture of combustion gases introduced into the blast furnace and consisting of 0:, H20 and C011 Whether the quantity of 02 required is supplied solely by the content of this mixture in free ongen or also by the combined oxygen of the H20 present or of that of the H20 and C02, depends only on the composition of this gas mixture. Therefore by adjusting the individual quanties of the components of the mixture entering the blast furnace or by adjusting the individual quantities of the substances introduced into the combustion chamber connected to the blast furnace, viz. of the quantities of the primary fuel, the oxygen and the steam in relation to the carbon of the secondary fuel charged into the blast furnace from above, we may control the operation in such manner that for the combustion of the secondary fuel in the blast furnace there are used, of the constituents of the introduced gas mixture, only the free oxygen and the whole or part of the oxygen combined in the form of steam, while the carbon dioxide does 40 not participate inthe combustion.

As to the temporal course of the reaction which takes place in the blast furnace, first the carbon is burnt to C0, while the decomposition of the H20 follows subsequently, since the heat 45 consumption of this endothermic reaction is smaller than that .of the decomposition of the CO1.

Thus when practicing our invention, we charge a blast furnace with a mixture of a carbonaceous 5o agent such as coke with ferriferous ores, which may also contain other metal compounds such as compounds of manganese or silicon, if iron alloys shall be produced, and we simultaneously burn in a separate chamber, arranged close to the blast 55 furnace, a primary carbonaceous fuel with oxygen in the presence of steam and introduce the gas mixture, obtained in this combustion and having a temperature of at least 1300 (2., into the blast furnace. from below. We choose the proportion of the substances participating in said combustion, i. e. the proportions of the carbon of the primary fuel, oxygen and steam in such a manner in relation to the carbon of the carbonaceous' agent mixed with the ores, that the mixture of combustion gases obtained consists mainly of carbon dioxide, steam and free oxygen and contains these substances in such proportions that the mixture passes through the blast 7o furnace substantially without any change of the carbon dioxide contained therein. The combustion in the chamber outside of the blast furnace may be carried out with oxygen, such as commerical oxygen, or with air enriched in oxygen, 5 and this oxygen or air may be preheated before being introduced into the chamber. The pri mary fuel burnt therein may be gaseous or liquid or solid and may be of an inferior quality such as cannot be employed as the carbonaceous agent charged into the furnace in mixture with the We produce the mixture of combustion gases by the complete combustion of someprimary fuel with oxygen of any degree of purity or air containing a high percentage of oxygen, either cold or preheated, in a primary combustion chamber structuraliy combined with "the blast furnace. According to the percentage of moisture or hydrogen in the primary fuel a corresponding percentage of steam may be added to it.

The primary fuel maybe of any physical kind or condition. We may use any fuel of inferior value such as coal dust, sawdust, green lignites, peat and the like. We may further use liquid fuel such as oil or tar, and wemay'use gases including producer gas, blast furnace gas. The secondary fuel may coal, coke, wood, charcoal and the like.

The advantages obtained by proceeding as above described are the following:

1. Reduction of cake or charcoal consumption-Part of the coke or the charcoal is replaced by a materially cheaper primary fuel, since a considerable part of the heat required in the process is supplied by the heat content of the hot gas mixture introduced into the blast furnace and obtained by the combustion of the cheap primary fuel carried out outside of the blast furnace.

2. Production of more favorable conditions of reaction-The primary products of combustion are formed for the greater part not in the blast furnace proper, but outside of the furnace, and

furnace gases of reduction (carbon monoxide and hydrogen) are formed which promote indirect reduction, whereby the ratio of direct to indirect reduction is shifted in a favorable manner towards indirect reduction. In this respect the hydrogen formed in the blast furnace by the decomposition of the steam exerts a particularly favorable action inasmuch as it forms one of the best reducing agents. The carbon dioxide forming part of the mixture of combustion gases supplied merely serves as a heat carrier and does not participate in the reactions, so that no heat is consumed for the decomposition of carbon dioxide which is a strongly endothermic reaction. The carbon dioxide, in consequence of its high specific heat, is, moreover, an excellent heat carrier. The heat balance of the blast furnace is therefore very favorable. Furthermore, since the primary fuel is burnt with oxygen or with air containing a high percentage of oxygen, the hitherto unavoidable inert nitrogen is done away with partly or altogether.

3. Production of a blast furnace gas of high value, the composition of which can be regulated. The heating value of the blast furnace gases is considerably increased, since they contain a comparatively high percentage of carbon monoxide and hydrogen and little or no nitrogen. The composition of the gases can be regulated according to requirements by varying the percentage of oxygen and/or steam and/or carbon dioxide in the gas mixture introduced into the furnace, so

that the waste gases can also be utilized for the further treatment of the iron (for instance for heating Martin-furnaces without admixing any additions) and for synthetic processes of the chemical industry.

4. Increased capacity of the blast furnace- Since little or no nitrogen is introduced into the furnace, the volume of the gas introduced into it is diminished and we can therefore use for a predetermined output a blast furnace of considerably smaller dimensions. 0n the other hand we are enabled to obtain a considerably greater output than in any existing blast furnace. For the charge requires only from two to three hours to pass through the blast furnace in accordance with the present invention, in comparison withfrom seven to ten hours hitherto attained with rapidly operating blast furnaces.

5. Increase of the thermal efficiency of the blast jurnace.The air heaters required in the normal operation of the furnace, such as the Cowper heater etc., may be dispensed with and consequently and owing to the smaller dimensions of the furnace the losses by radiation are greatly reduced. Since the quantity-of waste gases produced is smaller, the heat losses by the palpable heat of the waste gases is diminished also. The

waste gases may further be utilized for any de.-,

nace with the charging hopper shown in two different positions.

Fig. 2 is a cross-section on the line 11-11 and Fig. 3 a cross-section on the line III-III in Fig. 1.

Referring to the drawing l is a blast furnace of'normal design, which is charged in a well known manner from above with ore, additions and coke or charcoal, 2, 2 are burners evenly distributed around the bottom part of the furnace and 3, 3 are nozzles leading from the burners to and into the furnace, 4 are pipes for introducing into the burners oxygen or air containing a high percentage of oxygen, which may be saturated with steam, while 5 are pipes for introducing gaseous fuel such as for instance producer gas or the waste gases resulting in the operation of the furnace itself. This gas is burnt the shaft of the furnace.

If a fresh charge shall be introduced into the furnace, the charging hopper is lowered until it rests on the upper shoulders of the ribs 1. In this position the charge slides along the conical surface of the charging hopper into the annular space l0 surrounding the pipe 5, since this pipe itself is covered by the charging hopper. Thus the charge slides down through the space III, while the gases move upwardly through the pipe 8, where they do not meet any resistance, andescape through the exhaust pipe II in the direction of the arrow. As shown in Fig. 1 by the dotted arrow, the gases can be withdrawn even with the charging hopper in its lower position between the ribs I. The arrangement of the pipe 6 forces the gases introduced through the nozzles 3 to flow upwardly somewhat nearer to the middle axis of the oven. We found that without such an arrangement the gases intend to rise near the circumference of the furnace so that a dead space forms in the center'of the furnace.

In the furnace the carbon of the coke contained in the charge is burnt with the oxygen introduced, forming carbon monoxide; the steam introduced is wholly or partly decomposed, while the carbon dioxide passes through the furnace without any change. The main proportion of the carbon monoxide and hydrogen thus formed effects indirect reduction of the ore, while the remainder escapes, through pipe H, together with waste gases and increases their heating value.

Obviously the primary combustion chamber should be designed in accordance with the requirements and corresponding to the.primary fuel used in each individual case.

The ores such as for instance ferriferous bauxites may also be introduced into the furnace in agglomerated form as briquettes containing the ore together with carbon and/or additions.

We have for instance treated a bauxite ore according to the following example, the quantities being calculated on 1000 kgs. pig iron.

There were introduced into the blast furnace from above Kgs. Crude bauxite 1555 Coke serving as secondary fuel 1945 Scrap iron 780 Quicklime 800 and from below (in the form of a mixture of combustion gases) Industrial oxygen m. 2160 Blast furnace gases serving as primary fuel m. 1385 Steam kgs. 180

These raw materials and fuels were composed as follows:

Bauxite Coke Coke ashes Quicklime 45. 35% A1203 82.54% c 41. 89% em, 96. 0% 050 20. 05% F8203 0.97% S 32. 33% 203 0.9% MgO 2. 26% SiO 0.50% O 14. 39% F0203 0.3% SiOz 1. 25% TiOq 0.50% H 5. 63% CaO 0. 4% F6203 1.00% CaO 0. 92% N O 29% MgO 2. 4% C0 14. 54% roast- 9. 67% ashes 0 49% P205 ing losses 14. 75% E10 4. 90% E20 2 44% SO Caloric effect: 6700 thermal units Industrial oxygen Blast furnace gases 02 See below 14% N:

' The products obtained were the following:

The constitution of these products was the following:

I Pig iron Per cent Fe 94.45 C 3.21 Si 1.98 S 0.32 P 0.04

slay cement.

Per cent A1303 43.69 Hydraulic modulus: CaO 44.20 Ca+! 0 8 S102 6.63 m =--.=0.89 T102 Alz03+Sl0g FeO 1.75 M80 0.44 CaSO4 0.45 CaS 1.73

Blast .fumace gases Per cent CO: 22.00 Caloric effect: 2008 CO 49.78 thermal units per cu Ha 19.4 bic metre. Na 8.57 0; 0.14 ms 0.11

disclosed in the foregoing specification, without departing from the invention or sacrificing the advantages thereof.

We claim:

1. The process of treating in a blast furnace a mixture of ferriferous ores with a carbonaceous agent for "the recovery of iron or iron alloys, which comprises introducing into the smelting zone of the furnace a mixture of the combustion gases which result from the complete combustion, occurring outside of, but close to the blast furnace, of a primary carbonaceous fuel with oxygen in the presence of steam, which mixture, containing substantially the whole of the heat of combustion, has a temperature of at least 1300 C. and consists mainly of carbon dioxide, steam and free oxygen, the composition of said mixture of combustion gases being so chosen with regard to the carbon content of said carbonaceous agent that the carbon dioxide passes through the blast furnace substantially without being ,changed.

2. The process of treating in a blast furnace a mixture of ferriferous ores with a carbonaceous agent for the recovery of iron or iron alloys, which comprises introducing into the smelting zone of the furnace a mixture of the combustion gases which result from the complete combus tion, occurring outside of, but close to the blast furnace, of a primary carbonaceous fuel with air enriched in oxygen in the presence of steam, which mixture, containing substantially the whole of the heat ofcombustion, has a temperature of at least 1300 C.-and consists mainly of carbon dioxide, steam and free oxygen, the composition of said mixture of combustion gases being so chosen with regard to the carbon content of said carbonaceous agent that the dioxide passes through the blast furnace substantially without being changed.

3. The process of treating in a blast furnace a mixture of ferriferous ores with a carbonaceous agent for the recovery of iron or iron alloys, which comprises introducing into the smelting zone of the furnace a mixture of the combustion gases which result from the complete combustion, occurring outside of, but close to the blast furnace, of a primary carbonaceous fuel with preheated oxygen in the presence of steam, which mixture, containing substantially the whole of the heat of combustion, has a temperature of at least 1300 C. and consists mainly of carbon dioxide, steam and free oxygen, the composition of said mixture of combustion gases being so chosen with regard to the carbon content of said carbonaceous agent that the carbon dioxide passes through the blast furnace substantially without being changed.

4. The process'of treating in a blast furnace a mixture of ferriferous ores with a carbonaceous agent for the recovery of iron or iron alloys, which comprises introducing into the smelting zone of the furnace a mixture of the combustion gases which result from the complete combustion, occurring outside of, but close to the blast furnace, of a primary carbonaceous fuel with preheated air enriched in oxygen in the presence of steam, which mixture, containing substantially the whole of the heat of combustion,

- has a temperature of at least 1300 C. and consists mainly of carbon dioxide, steam and free oxygen, the composition of said mixture of combustion gases being so chosen with regard to the carbon content of said carbonaceous agent that the carbon dioxide passes through the blast furnace substantially without being changed.

KARL KOLLER. ZSIGMOND GALoosY.

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