US1858274A - Process for reducing oxide ores - Google Patents

Description

Patented May 17, 1932 UNITED STATES PATENT OFFICE LYU'IQWIG KERN, FERNANDO C. KERN, AND FREDERICK E. KERN, OF WEBSTER GROVES,

' KISSOURI z PROCESS FOR REDUCING OXIDE ORES Io Drawing.

This invention relates to the reduction of oxide ores, particularly those of iron, and to the recovery of certain by-products produced in the process.

Briefly stated, the process comprises mixing finely crushed ore with finely-divided coal, or other carbonaceous material high in volatiles, plastici'zing and preferably briquetting the mixture, subjecting the plasticized mass 'or briquett'es to destructive distillation in a closed retort with recovery of volatile matter, and thereafter pulverizing the distilled briquettes and separating the metal therefrom; all as more particularly hereinafter described and claimed.

In conventional or known processes of reducing iron ores, alternate layers of ore, fuel and flux, usually limestone or dolomite, are charged to a blast furnace and blown with aircto produce the required heat and gases of combustion and to reduce the ore to a metallic state. In such known processes coke is employed as the fuel, and consequently, it must possess special properties, such as, for example, a content of sulfur and phosphorus. Further, only relatively highgrade ores may be treated by such processes, i. e., the ore must not contain more than 60 to 65% of substances other than the metal to be recovered and must be extremely low in sulfur and phosphorus content.

One object of our invention is to provide a process for the reduction of iron and other metals from their ores, which is applicable to thetreatment of ores higher in sulfur and phosphorus content than those whidh may be treated by conventional processes heretofore utilized.

Another object of our invention is to pro.- vide a process by which coals or similar carbonaceous materials high in volatile, sulfur and phosphorus content may be employed successfully in-the reduction of oxide ores.

Another object is to provide a process of the class described, which does not require the use of-fluxes. r

A further object of our invention is the recovery .of volatile by-products produced during the reduction process and also the recovery of a by-product in the form of coke.

1929. Serial No. 357,831.

A further object of our invention, when the conditioning agents used are either hydrochloric acid, chlorine, chlorides, or other chlorine carrying compounds, is the recovery of certain volatile chlorides in the distillates and their reuse in the system, thereby engendering production economy.

In' accordance with our invention oxide ore is ground fine, preferably to an extent that Wlll pass through a 50 to 100 mesh screen, and mixed with raw bituminous coal or other solid bituminous or carbonaceous material, preferably ground to a fineness sufiicient to pass through a 100 to 200 mesh screen, the coal or other carbonaceous material being preferably of high volatile content and in suflicient quantity to provide an excess of carbon after the volatiles have been removed. The mixture of ore and coal is now formed into a plastic mass by Wetting with water or other reagents. Preferably,

the mixture is moistened with hydrochloric acid of from 10 to 20 Baum, the purpose of the hydrochloric acid being to produce plasticity in the coal and ore mixture and also to react with the sulfur content of the ore and coal, with the resultant reduction and/or artial elimination of sulfur in the form of volatile compounds. In place of hydrochloricacid there may be employed other acids, chlo-' rine, hypochlorites, salts-especially chlorides, acid salts, or mixtures of salts and acidsespeci'ally chlorides wet with hydrochloric acid, to bring about reactions with sulfur and phosphorus and o impart sufficient plasticity to the mixture. Also in the treatment of ores or mixtures high in phosphorus there may be employed bases, basic .salts or mixtures of bases and salts to likesimilar homogenizing apparatus, and fur ther treated, as hereinafter set forth. Themass is preferably molded into bricks or briquettes or other shaped objects by means of a suitable briquetting machine, such as is 600 C. to drive off the volatiles, which are recovered by condensation in a known manner. The products thus recovered are light and middle oils and also some heavier fractions, and the non-condensible gas thus formed is a high calorific coal gas containing some carbon monoxide, carbon dioxide and nitrogen compounds, which may be recovered and utilized. Upon completion of the distillation the temperature'is raised sufficiently to allow the residual carbon or coke to react with the remaining oxygen in the oxide ore to form carbon monoxide and/ or carbon dioxide and reduce the ore. If the temperatures are maintined at or above 900 C., the chief gas eliminated will be carbon monoxide, which may be collected and utilized for heating purposes. In this heating process further nitrogen compounds are given off, chiefly in the form of ammonium chloride. Other volatile chlorides are' also evolved. These chlorides are preferably recovered and used as conditioning agents for the plasticizing operation. On account of the temperatures maintained and the' intimate contact of the carbonaceous and bituminous matter with the finely-divided mineral matter of the mix,

these carbonaceous and bituminous materials are so decomposed as to leave a peculiarly reactive carbon residue known as active carbon to distinguish it from the less reactive form commonly found in ordinary coke.

Throu h expulsion of the liquid and gaseous products from the coal, and on account of the intimate contact of the coal and the oxide ore engendered by the homogenizing or its close contact with the ore, efi'ectively reduces the latter to the metallic state by breaking down the combination of metal and oxy-' gen. When sulfur-containing coals are employed, such as the Illinois bituminous coals, the sulfur reacts also with the chlorine liberated from the chlorides introduced as such or formed through the reaction of the hydrochloric acid, chlorine, etc., with the basic substances or impurities present in the gangue material, as well as in the ore, and the sulfur is thus removed as volatile compounds,

largely in the form of hydrogen sulfide and sulfur chlorides.

The residue of the distillation or carbonization now comprises, in briquette form, a

mixture of desulfurized and devolatilized 9 coke and reduced metal free of sulfur and phosphorus, and containing silicious, calcareous and aluminous constituents of both the ore and coal which have not been volatilized as chlorides. To recover the reduced metal the briquettes are crushed and pulverized and the metal separated by known mechanical methods.

The material separated from the reduced metal constitutes a commercially valuable byproduct, the recovery of which brings about a considerable savings in the reduction process above described. This material consists mainly of a mixture composed of de-volatilized or carbonized coal or coke, and more or less gangue material. This mixture of coke and gangue material may be used as a fuel for steam boilers or other furnaces, or for making water gas. It is of special value in the manufacture of water gas, as the gangue material consists essentially of silica, which acts as a catalyst in water gas reactions. Where the gauge material associated with the coke is present only in negligible quantities, the coke may also be used as a domestic fuel. On the other hand, if the gauge material is present in such quantities as to make the use of the coke prohibitive for certain purposes, the mixture may be subjected to air flotation, or to wet flotation to separate the gangue material from the carbon. The resultant product of such treatment is a comparatively pure carbon of high calorific value, low in ash and volatile, and is an excellent sulfur-free steam coke having the property of igniting rapidly and at low combustion temperatures. It may be advantageously used for heat, light and power purposes, or for preparing activated carbon.

In order that the details of our invention may be better understood, a specific example of the process will be described, although it is to be understood that the invention is not limited to the particular material treated or to the specific conditions of operation set forth.

Soft red hematite ore containing approximately 44% iron, 17% silica, 1% sulfur and 3.7% alumina is ground together with a high volatile bituminous coal containing volatile matter and 3% sulfur, the proportion being by weight of ore to 40% by weight of coal. The mixture is wetted in wet pans with 10 Baum hydrochloric acid, sufiicient in amount to react as described and to produce a plastic mass, and the mixture formed into briquettes. The briquettes are then dried and distilled at temperatures below 600 C. for about five hours, after which the temperature is raised to between 900 and 1,000 0., the tem erature being maintained until evolution 0 carbon monoxide ceases. The condensable volatile matter from the low temperature treatment and the gaseous materials from the subsequent heating are removed, collected and utilized as above set forth. The residue resulting from the heat treatment is cooled, finely ground and passed over a magnetic separator of known construction for separation of the metallic iron. The iron thus obtained is of'suflicient purity to be used directly in an electric furnace for the production of steel or for other purposes. The residual material remaining after the removal of the iron may be utilized directly as fuel or in the production of water gas, or as above described.

From the foregoing it will be seen that we have devised a novel process for reducin oxide ores, especially iron oxides, in whic commercially valuable by-products are recovered in the form of oils, gases and solid fuel. Also by virtue of the procedure above described,- it is possible to treat, according to' our process, ores of lower metal content and of higher sulfur and phosphorus con-. tent than commercially possibile by processes now utilized. Further, in place of a coke free of volatiles, sulfur, and phosphorus,

such as heretofore employed, we may use inour process coals and carbonaceous materials ,high in volatiles, sulfur, and phosphorus.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. The process of reducing oxide ores, which comprises forming a mixture of comminuted ore, comminuted solid distillable carbonaceous material, and a chlorine containing material plasticizing the mixture, forming the lastic mixture into briquettes, heating the riquettes out of contact with air sufficiently to distil the volatiles and to reduce the ore to the metallic state, and recovering the metal from the solid residue.

2. The process of reducing oxide ores, which comprises mixing the ore with a solid bituminous or carbonaceous material, wetting the mixture with chlorine-containing agents adapted to react with the impurities present in the carbonaceous substance and oxide ore, molding and pressing the mass to form briquettes, heating to dry said briquettes and thereafter subjecting said briquettes to heat out of contact with air, at a temperature sufiiciently high to volatilize chlorides formed as Well as at least part of the hydrocarbons obtainable from the coal collecting the products of volatilization, raising the temperature sufliciently to reduce the ore to its metallic state, and recovering the metal from the solid residue of carbonization.

3. The process of reducing oxide ores, which comprises mixing the ore with solid distillable carbonaceous material, wetting the mlxture with a reagent adapted to react upon sulfur and whereby said sulfur and phosphorous are substantially eliminated from the mixture, forming the mixture into briquettes, heating the bnquettes out of contact with air to a distillation temperature to remove volatile matter, raising the temperature sufiiciently to reduce the ore to the metallic, state, and'recovering the metal from the solid residue.

4. The process of'recovering metalsfrom their oxide ores which, comprisesmixing the ore with solid distillable carbonaceous'material, wetting the mixture with a reagent adapted to produce chlorine on heating, forming the mixture into briquettes, subjecting the-briquettes to destructive distillation in a-closed retort, raising the temperature sufficiently to reduce the ore to the metallic state, and separating the metal from the solid residue.

5. The combined process of separating metals from their oxide ores and recovering volatiles from distillable carbonaceous material, which comprises mixing the ore with the distillable carbonaceous material, wetting the mixture with hydrochloric acid, forming the mixture into briquettes, subjecting the briquettes to Idffitructive distillation in a closed retort, re oving and collecting the resultant vapors, raising the temperature sufiicientlg to reduce the ore to the me tallic state, an separating the metal from the resultant residue.

6. The process of recovering iron from its oxide ores, which comprises formin a mixture of the ore, bituminous coal, an a chlorine-containing material, forming the mixture in a plastic mass, heating the mass in a closed chamber sufliciently to expel vapors and gases and to reduce the iron oxide to metallic iron, and separating the iron from the solid residue.

7. The process of recovering iron from its oxide ores, which comprises mixing theore with bituminous coal, wetting the mixture with a reagent adapted to produce chlorides on heating, forming the mixture into briquettes, destructively distilling the briquettes and recovering the resultant vola-- tiles, raising the temperature sufliciently to reduce the iron oxides to metallic iron, and separating the iron from the solid residue.

8. The process of recovering iron from its oxide ores, which comprises mixing the ore with bituminous coal, plasticizing, the mixture by means of hydrochloric acid and forming the plastice mass into briquettes,-

heating the briquettes sufficiently to reduce the iron oxides to metallic iron, and separating the iron from the solid residue.

phosphorous upon heating, I

9. The process which comprises mixing comminuted iron oxide with comminuted bituminouscoal, wetting the mixture with hydrochloric acid forming the mixture into briquettes, destructively distilling the briquettes in a closed retort, removing and condensing the resultant vapors, further heating the briquettes sufliciently to reduce the iron oxides to metallic iron and collecting the resultant gases, pulverizing the briquettes, and se arating the same into metallic. iron and co e.

10. The process of reducing oxide ores containing phosphorus, which comprises mixing the ore with solid distillable, carbonaceous material, Wetting the mixture with a reagent adapted to convert the phosphorous into compounds of phosphorus, forming the mixture into briquettes, heating the briquettes sufficiently to drive ofi volatiles and to reduce the ore to the metallic state, and separating the metal from the briquettes.

11. The process of reducing iron ore containing phosphorus, which comprises mixing the ore with bituminous coal, plasticizing the mixture by means of a reagent adapted to convert the phosphorus into compounds of phosphorus, forming the plastic mass into briquettes, destructively distilling the briquettes and recovering the resultant volatiles, raising the temperature sufliciently to reduce the iron oxides to metallic iron, pulverizing the briquettes, and separating the iron therefrom.

12. The process as described, which comprises the steps consisting of comminuting an oxide ore and bituminous coal to a fine state of division, mixing same and adding to a chlorine carrier, homogenizing the three components to form a cohesive and plastic mass, having a close contact, increasing the' contact by pressing the mass to form shapes of desired size, heating said shapes to evaporate water present, increasing the temperature to drive ofi from said mass the chlorides formed by the co-action of the chlorine carrier and the basic salt-forming impurities present, and to likewise drive 011' a substantial amount of condensable and non-condensable hydrocarbons, likewise hydrogen,

carbon monoxide, etc., from the mixture, re-

covering said condensable and non-condensable products of volatilization, exposin the ore-coal compound to heat, sufficiently to bring about the conversion of the oxide ore into its metallic state and the coal into coke, and separating the reduced ore and coke obtained.

13. The process of reducing oxide ores which comprises mixing comminuted ore with comminuted distillable carbonaceous material, plasticizing and homogenizing the mixture with a chlorine-containing agent, forming the plastic mixture into briquettes, distilling the briquettes to remove the volatiles therefrom, and heating the'distilled briquettes to reduce the ore to the metallic state.

14. The process of reducing oxide ores which comprises forming a plastic mixture of comminuted ore, oomminuted distillable material, and a chlorine-containing reagent, forming the plastic mixture into briquettes, distilling the briquettes to remove the volatiles therefrom, and heating the distilled briquettes to reduce the ore to the metallic state.

15. The process of reducing oxide ores Y