Process for the Extracting Oxygen and Iron from Iron Oxide-Containing Ores
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Michigan Technological University Digital Commons @ Michigan Tech Michigan Tech Patents Vice President for Research Office 3-5-1991 Process for the extracting oxygen and iron from iron oxide- containing ores Surendra K. Kawatra Timothy C. Eisele Michigan Technological University, [email protected] Follow this and additional works at: https://digitalcommons.mtu.edu/patents Part of the Chemical Engineering Commons Recommended Citation Kawatra, Surendra K. and Eisele, Timothy C., "Process for the extracting oxygen and iron from iron oxide- containing ores" (1991). Michigan Tech Patents. 60. https://digitalcommons.mtu.edu/patents/60 Follow this and additional works at: https://digitalcommons.mtu.edu/patents Part of the Chemical Engineering Commons United States Patent [19] [i i] Patent Number: 4,997,533 Kawatra et al. [45] Date of Patent: Mar. 5, 1991 [54] PROCESS FOR THE EXTRACTING OXYGEN Assistant Examiner—Kathryn Gorgos AND IRON FROM IRON Attorney, Agent, or Firm—Michael, Best & Friedrich OXIDE-CONTAINING ORES [57] ABSTRACT [75] Inventors: Surendra K. Kawatra; Timothy C. Oxygen and metallic iron are produced from an iron Eisele, both of Houghton, Mich. oxide-containing mineral, such as ilmenite, by extract [73] Assignee: Board of Control of Michigan ing iron from the mineral with hydrochloric acid, sepa Technological University, Houghton, rating solid residue from the resulting solution and dry Mich. ing same, electrolyzing the separated, iron chloride- [21] Appl. No.: 389,955 containing solution to produce electrolytic iron and chlorine gas, combining the chlorine gas with water [22] Filed: Aug. 7, 1989 recovered from the drying and/or iron chloride-con [51] Int. C1.5...................................................C25C 1/06 taining solution electrolysis steps of regenerate hydro [52] U.S. a ......................................... 204/113; 204/128; chloric acid and recycling the hydrochloric acid to the 204/129 extraction step. In an alternate embodiment, the chlo [58] Field of Search ............... 204/128, 129, 242, 112, rine gas is reacted with recovered water in the presence 204/113; 423/481, 486, 488, 487 of a catalyst to produce hydrochloric acid which is recycled to the extraction step, thereby eliminating the [56] References Cited need for water electrolysis and a separate hydrochloric U.S. PATENT DOCUMENTS acid regeneration step. In another alternate embodi 1.420.128 5/1919 Moxham . ment, electrolysis of the iron chloride-containing solu 1.420.129 5/1919 Moxham . tion is operated to produce oxygen instead of chlorine 2,441,856 5/1948 Turner et al............................ 23/202 gas at the anode and hydrochloric acid is generated 3,410,770 11/1968 Buechler ............................. 204/129 concurrently with plating of iron at the cathode. This 3,529,931 9/1970 M oklebust............................... 23/154 hydrochloric acid is recycled to the extraction step, 4,060,464 10/1977 Fahlstrom et al.................... 204/113 thereby eliminating the need for water electrolysis and 4,180,555 12/1979 Bamberger et al.................. 423/481 a separate hydrochloric acid regeneration step. 4,230,542 10/1980 Traini et al............................. 204/93 Primary Examiner—John F. Niebling 11 Claims, 1 Drawing Sheet U.S. Patent Mar. 5,1991 Sheet 1 of 1 4,997,533 4 , 997,533 1 2 separated solution to a level suitable for electrolysis, (e) PROCESS FOR THE EXTRACTING OXYGEN AND electrolyzing the reduced and pH-adjusted solution IRON FROM IRON OXIDE-CONTAINING ORES under conditions which produce chlorine gas and me tallic iron, (f) condensing water vapors recovered from BACKGROUND OF THE INVENTION 5 one or both of the drying and electrolysis steps, (g) This invention relates to processes for extracting electrolyzing the condensed water to produce elemen oxygen and metallic iron from iron oxide-containing tal oxygen and hydrogen, and (h) combining the chlo ores such as ilmenite and, more particularly, to such rine gas from the first electrolysis step with the hydro processes which can be used at lunar or other space gen from the second electrolysis step and water to form station installations. 10 hydrochloric acid and (i) recycling the hydrochloric Many prior techniques for extracting oxygen and acid to step (a). metallic iron from lunar rocks, such as hydrogen reduc In one embodiment, steps (g) through (i) are replaced tion or carbothermal reduction of ilmenite or electro with the steps of (j) reacting the chlorine gas from the winning of molten silicates, require temperatures in first electrolysis step with a condensed water in the excess of 900° C. Such techniques are not practical for 15 presence of a catalyst to produce hydrochloric acid and many applications because they require refractory ma oxygen and (k) recycling the hydrochloric acid to step terials and heavy insulation which results in high con (a). struction costs for full scale installations and operational In another embodiment, the first electrolysis is car costs are quite high, particularly energy costs. Also, the ried out under conditions to produce metallic iron and only useful material directly produced by the hydrogen 20 oxygen, the concentration and pH of the solution under reduction of ilmenite is gaseous oxygen. going electrolysis is maintained within predetermined U.S. Pat. No. to Turner et al, U.S. Pat. No. 2,441,856 ranges by controlling the amount of water and hydro discloses a cyclical process for producing titanium diox gen chloride vapor evaporated from the solution and ide from ilmenite. However, that process is designed water and hydrogen chloride vapors recovered from 25 primarily for recovering titanium dioxide pigments and the first electrolysis step are recycled to step (a). does not produce oxygen. U.S. Pat. No. 1,420,128to Moxham, U.S. Pat. No. BRIEF DESCRIPTION OF THE DRAWING 1,420,129 to Moxham and U.S. Pat. No. to Fahlstrom et The single FIGURE is a flow diagram of a process al, U.S. Pat. No. 4,060,464 disclose processes for ex embodying the invention. tracting iron from iron-bearing ores and recovering iron 30 by electrolysis. U.S. Pat. No. 3,529,931 to Moklebust DETAILED DESCRIPTION discloses a process for regenerating hydrochloric acid The process of the invention can be used with a vari from an iron chloride solution derived from leaching a ety of iron oxide-containing minerals, particularly tita titaniferous ore, such as ilmenite. U.S. Pat. No. to Traini et al, U.S. Pat. No. 4,230,542 discloses an electrolytic 35 niferous ores. It is particularly adaptable for use with process for treating a hydrochloric acid ilmenite leach ilmenite, an ore found on the moon and other potential solution to reduce ferric ions to ferrous ions. sites for space stations, and will be described in connec tion with that application. SUMMARY OF THE INVENTION Referring to the flow diagram, it can be seen that the A principal object of this invention is to provide a 40 process Produces primarily three end products: oxygen, low-temperature, low-pressure process for producing electrolytic iron and a titanium dioxide-rich solid waste elemental oxygen and metallic iron in usable form from product. In addition, under some conditions, a sludge an iron oxide-containing mineral, particularly ilmenite. containing salts such as calcium chloride, may be pro Another object of the invention is to provide such a duced during the first electrolysis step. This sludge process in which the reagents used for extraction are 45 contains the bulk of the chlorine values lost from the regenerated, thereby reducing the quantity of materials process. consumed by the process. The initial step in the process is extraction of ilmenite A further object of the invention is to provide such a with hydrochloric acid. During start up, finely divided process which can be operated with relatively low volt ilmenite ore is treated with fresh, concentrated hydro age DC power capable of being conveniently generated 50 chloric acid to dissolve the iron in the ilmenite. As by solar cells, nuclear reactors and the like. described in more detail below, while the process is A still further object of the invention is to provide being carried out, water and hydrochloric acid, hydro such a process which is practical for use at a lunar base gen chloride vapors and mixtures thereof are recycled or other space station installation. from various points in the process as the primary source Other objects, aspects and advantages of the inven 55 of the extractant and fresh hydrochloric acid is added to tion will become apparent to those skilled in the art make up for losses. upon reviewing the following detailed description, the The amount of hydrochloric acid used preferably is drawing and the appended claims. sufficient to substantially dissolve all the hydrochloric The invention provides a process for recovering oxy acid-soluble iron in the ilmenite. The amount of hydro gen and metallic iron from an iron oxide-containing 60 chloric acid used most preferably is in excess of that mineral, such as ilmenite, including the stes of (a) con theoretically required to dissolve all the hydrochloric tacting the mineral in finely divided form with water acid-soluble iron. After start up, the concentration of and hydrochloric acid, hydrogen chloride or mixtures the hydrochloric acid used in the extraction step prefer thereof to dissolve hydrochloric acid-soluble iron in the ably should be at least about 10% for an efficient opera material, (b) separating the insoluble, solid residue from 65 tion. the resulting solution, (c) drying the separated solid The extraction can be carried out in any suitable residue, (d) reducing ferric chloride in the separated manner, such as under a reflux or a countercurrent solution to ferrous chloride and adjusting the pH of the treatment. It preferably is carried out at an elevated 4 , 997,533 3 4 temperature greater than about 30° C. in order to obtain trolysis.