Jan. 28, 1958 F. B. SELLERS 2,821,471 ' PROCESS Fon REDUCTION of IRON Om Filed Dec
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Jan. 28, 1958 F. B. SELLERS 2,821,471 ' PROCESS Fon REDUCTION oF IRON om Filed Dec. y.19.,1956 Uittittd . Stattt Ptttttt O 1. i 2 ing carbon monoxide and hydrogen are produced .which are subjected to the water-gas shift reaction wherein the 2,821,471 carbon monoxide is reacted with steam to produce addi tional hydrogen and carbon dioxide. The carbon dioxide PROCESS FOR REDUCTION OF IRON ORE may then be removed, for example, by absorption in mono Frederick Burton Sellers, Tarrytown, N. Y., assignor to ethanolamine, to provide a gas of high hydrogen concen Texaco Development Corporation, New York, N. Y., tration. The combined process of Water gas shift conver a corporation of Delaware sion and hydrogen ore reduction described herein may employ carbon monoxide-containing gases produced by Application December 19, 1956, Serial No. 629,255 l0 other means as well as those referred to above. How 9 Claims. (Cl. 75-26) ever, the combined process of this invention is particu larly well adapted for the use of carbon monoxide-hydro gen mixtures produced by the partial combustion of car bonaceous fuels with oxygen. p This invention relates to a method for the reduction of 15 In the well-known water-gas shift conversion process, iron ore. More particularly, it is directed to a process carbon monoxide is reacted with steam at a temperature for the reduction of iron ore in the presence of hydrogen produced by the Water gas shift conversion of car between about 600° F. and 1000° F. at a pressure from atmospheric to about 650 p. s. i. g. in the presence of an bon monoxide-containing gases. Advantageously, carbon iron oxide catalyst. The catalyst is usually prepared monoxide-containing gases are generated by the partial 20 from highly purified iron oxide with lesser quantities vof combustion of a carbonaceous fuel. In the process of the oxides of magnesium, potassium, sodium, aluminum this invention, at least a part of the raw ore to be reduced and chromium to produce a catalyst of long life, sustained is passed first to a water gas shift conversion step to pro activity, and high strength. In the vprocess of my inven vide catalyst therein and is thereafter passed to a hydro tion, iron ore is employed in place of the expensive con gen reduction step. 25 ventional catalysts. Since the iron ore can be added and The great bulk of iron ore reduction is effected in the withdrawn continuously or as necessary, the maintenance well-known blast furnace operation wherein carbon and of catalyst activity over a long period is unimportant. carbon monoxide are employed as reducing agents at ele Similarly, materials which would otherwise tend to poison vated temperatures. Blast furnace operation is limited 30 the catalyst are continuously removed with the ore. to the use of high quality coke in order to provide the Crushing strength of the ore is unimportant when the -ore necessary structural strength to support the weight of ore, is employed in a fluidized bed. v coke, and limestone in the blast furnace charge and to In the process of this invention, it is preferred to gen provide passageways within the mass for the reducing gases erate a mixture of carbon monoxide and hydrogen by the and molten iron and slag. Additionally blast furnace 35 partial combustion of carbonaceous or hydrocarbon fuels, operation is restricted to the use of limited high quality for example coal, fuel oil or gaseous hydrocarbons. In ores which are available in lump form of high strength and this operation, the fuel is reacted with an oxygen-contain iron content. For example, ores such as taconite are un ing gas, preferably oxygen. Commercially pure oxygen suitable as mined and must be processed to reduce the is readily obtained by the rectification of air. vLiquid hy high silica content, and the line particles of beneficiated drocarbons and solid fuels are ordinarily gasitìed with taconite must be formed into hard balls before inclusion 40 in blast furnace feed. v added steam to control the temperature Within the desired range. The steam further serves to generate hydrogen The Soderfors process has been developed on a limited in the reaction. The generation of carbon monoxide and scale as permitted by the availability of cheap electric hydrogen by this process is carried out at a temperature power. The Soderfors process effects reduction of iron 45 within the range of about l800° F. to about 3200° F. ore at a temperature of about 1800” F. with a carbon preferably within the range of 2200 to 2800° F. In gen monoxide-rich gas which is normally produced by the eral, from about one-half to about three volumes of hy reaction of carbon dioxide-containing off-gas with an elec drogen are generated for each volume of carbon monoxide trically heated bed of coke. The Soderfors process, like produced. the blast furnace, is not adapted to the reduction of iron 50 The crude hydrogen and carbon monoxide-containing orefines because of the necessity of the ore supporting gas from the partial oxidation zone is passed with steam itself -in the shaft-like vertical vessel employed therein. to a water-gas shift reactor containing a catalyst consist The _disadvantages of the Soderfors process are as follows: ing of iron ore particles. The temperature of the water First, high quality ore is required; second, the output is gas shift conversion zone is maintained within the range low because of the slow rate of reduction; and third, use 55 of about 600 to l000° F. Advantageously, the iron ore of electrical heating in the production of reducing »gas particles are maintained in a ñuidized bed in the shift necessitates the availability of cheap electric power. ` reactor and oreis continuously added and withdrawn to The continuous reduction of iron ore to metallic iron maintain high catalytic activity.` Between about 90 and with'hydrogen in a ñuid bed‘has now been developed and 95% of the carbon monoxide in the inlet gas stream is is `described in detail inthe co-pending application of 60 reacted with the steam to produce carbon dioxide and Du Bois Eastman, Serial No. 379,861 filed September 14, additional hydrogen according to the following equation: 1,953.. _ Typically, in‘ the ñuidized reduction of iron ore, the ore is sized into particles suitable for fluidization, and is contacted in a ñuidized bed with a hydrogen-containing Effluent from the water gas shift reaction is scrubbed gas at a temperature-between about 700 and 16_00° F. at 65 a pressure between 50 and 650 p. s. i. g. or higher. It will with a solvent to remove carbon dioxide. The resultant be 'realized'that suitable operating conditions will vary gas stream comprising hydrogen and preferably contain depending upon the characteristics of the ore employed. ing at least 90% hydrogen is supplied to the recycle sys tem of the ore reducer as make-up for the hydrogencon 4 _Many methods have been developed for‘the generation sumed in the reduction. _ of hydrogen'jincludi'ng the water-gas process, steam-hy 70 drocarbon reforming, and the partial combustion 'of car The reduction step of vthe process of this invention is eiîectedv in a Huid bed operation to maintain isothermal bonaceous fuels. In these processes, mixttir’esïcompris conditions inthe reaction? bed thereby-¿facilitatingïïntróé 2,821,471 3 4 duction'of the required endothermic seat of reaction. 2500 microns, and accordingly an average particle size The reduction is effected at a temper-ature within the within this range is preferred. range of about 700 to 1600° F. to maintain an adequate When sulfur-containing carbonaceous fuels are em reaction rate and avoid sintering or aggregation of the ployed, for the generation of gas by partial oxidation, the iron ore particles which would lead to deñuidization of gases produced contain a corresponding amount of hydro the fiuid bed. A preferable temperature range selected gen sulfide. Ordinarily gas containing large quantities of from within the foregoing range will depend upon the hydrogen sulfide would rapidly deactivate shift conver particular ore selected. For example, a maximum tem sion catalyst. However, since the catalyst in the process perature limitation of 1200° F. or lower may be imposed of my invention is continuously replenished, the poison by the tendency of certain ores, for example, a magnetite 10 ing effect is inconsequential. The hydrogen sulfide re type ore such as taconite, to agglomerate and cause de acts with the iron ore catalyst in the shift conversion zone fiuidization of the fluidized bed. Magnetite type ores may to form iron sulfide and the effluent hydrogen-containing be reduced rapidly at relatively low temperatures and gas is reduced in sulfur by a corresponding amount. 90 percent reduction may be effected in from about 20 to Advantageously, a part of the hydrogen-containing gas of 40 minutes at 1000° F. On the other hand, hematite type reduced sulfur content may be withdrawn for other uses iron ores exhibit increased rates of reduction up to tem which require a hydrogen stream of low sulfur content. peratures as high as about 1600° F. without deñuidiza The presence of iron sulfide in the ore from the shift tion. Some hematite type ores may be ninety percent conversion zone does not interfere with subsequent re reduced in as little as ten minutes at a temperature of duction to metallic iron but does release hydrogen sulfide about 1400” F. Preferablc temperature ranges are about 20 into the recycle hydrogen stream. The hydrogen sulfide 700 to 17.00° F. for magnetite type ores and about 1200 content of the recycle stream may be maintained at a to about l600° F.