Amax Incorporated

Other

The United States of America As Represented by the United States Energy

Mahesh C Jha

Willem P Duyvesteyn

Gustavo A Meyer

Marcy J Kramer

Malcolm T Hepworth

Guy W Lussiez

Gordon R Wicker

Deepak Malhotra

Premo Chiotti

Antonio E Blandon

William Carl Warneke

Robert L McCormick

Paul W Woessner

Frank J Smit

Gopalan Ramadorai

Coal is heated between about 95.degree. and 250.degree. C. to evaporate moisture, but not volatile hydrocarbons. The dried coal is heated to a temperature between about 400.degree. and 700.degree. C. to recover volatile hydrocarbons and to form char, the char is treated with hydrogen at a temperature between about 700.degree. and 1000.degree. C. to form methane, and the methane is decomposed to form pure carbon and hydrogen, which is recycled to treat the char.

Process for production of value-added coproducts from coal and other

A process is provided for forming activated carbon from coal in the particulate state. The coal is first dried at a temperature sufficiently high to effect removal of moisture therefrom but below the temperature at which contained volatile matter vaporizes. The dried coal is then heated to an elevated temperature in a substantially non-oxidizing atmosphere at substantially atmospheric pressure sufficient to volatilize and remove the contained volatile matter and produce a char thereof and the char thereafter subjected to hydrogenation at an elevated temperature and pressure for a time sufficient to form activated carbon characterized by a BET surface area of at least about 200 m.sup.2 /g and an iodine number of at least about 400.

Process for the manufacture of activated carbon from coal by mild

A method is provided for removing contaminating minerals from coal by true heavy-liquid media. The coal is comminuted to liberate a substantial portion of the minerals from the coal, the method comprising forming a slurry of the comminuted coal in a solution of smelter-grade sulfuric acid of specific gravity ranging from about 1.2 to 1.7, the specific gravity of the sulfuric acid solution selected being greater than that for the liberated coal but less than that of the contaminating mineral to be separated, thereby effecting substantial separation between the liberated coal and the contained minerals. The coal is removed from the solution and then washed to remove occluded acid therefrom.

Use of smelter-grade sulfuric acid as true heavy-liquid media in coal

Durable, porous sulfur sorbents useful in removing hydrogen sulfide from hot coal gas are prepared by water pelletizing a mixture of fine zinc oxide and fine iron oxide with inorganic and organic binders and small amounts of activators such as sodium carbonate and molybdenite; the pellets are dried and then indurated at a high temperature, e.g., 1800.degree. C., for a time sufficient to produce crush-resistant pellets.

Durable zinc ferrite sorbent pellets for hot coal gas desulfurization

Low-grade refractory gold ores, which may also contain silver and other metal values are treated by partial roasting of concentrate to remove controlled amounts of sulfur and carbon, then oxygen pressure leached to oxidize further amounts of sulfur and carbon and to dissolve base metals and a portion of any silver present, and the residue is then cyanided to dissolve gold and remaining silver which are then recovered.

Recovery of precious metals from refractory low-grade ores

A process is disclosed for the hydrometallurgical treatment of finely divided iron-containing steel plant dusts containing zinc, lead and such other metal values as calcium, manganese, silicon, magnesium, aluminum, cadmium, copper, and the like. The process is carried out by forming an aqueous slurry of the flue dust with a mixed lixiviant comprising HCl and H.sub.2 SO.sub.4, the amount of sulfate ion concentration being in excess of the chloride ion concentration and in stoichiometric excess of that required to sulfate substantially all of the lead and calcium present. The amount of chloride ion present as HCl should be sufficient to maintain the pH at about 1 to 4. The leaching is conducted at a temperature ranging from ambient to below the boiling point for a time at least sufficient to effect dissolution of at least zinc and other metal values and form a residue containing iron oxide, calcium sulfate and lead sulfate.

Mixed lixiviant for separate recovery of zinc and lead from

A process is provided for selectively recovering zinc from steel plant dust containing substantial amounts of iron. The process comprises atmospherically leaching the steel plant dust in a first stage wherein an amount of steel plant dust is mixed with an amount of acidic zinc sulfate solution to leach zinc therefrom, the leaching of the dust being such that the solution is controlled to a terminal pH ranging from about 2 to 3.5 and preferably from about 2.5 to 3.5, thereby limiting iron dissolution. The mixture is then subjected to a crude liquid/solid separation step whereby a thickened pulp is produced containing zinc and iron values and a separated liquid containing low iron and substantial amounts of zinc, the solution being sent to zinc recovery. Following separation, the thickened pulp, together with additional sulfuric acid or spent electrolyte, is subjected to high pressure leaching at a temperature at least sufficient to leach the remaining zinc values and provide an acid zinc sulfate solution thereof, while converting hydrated iron oxides into free settling hematite residue, the amount of additional sulfuric acid added to said thickened pulp being sufficient to obtain near quantitative dissolution of zinc without excessive iron dissolution.

Two-stage leaching process for steel plant dusts

A process is provided for recovering zinc from zinc residues containing iron, and lead. The residue is leached with hydrochloric acid to provide a pregnant liquor containing zinc, iron, and lead. The iron is selectively removed from the pregnant liquor and the zinc extracted from the liquor by an organic solvent extraction system. The zinc is subsequently stripped from the organic solvent using water or hydrochloric acid to provide a zinc chloride solution which is then fed to an electrowinning cell for the production of marketable electrolytic zinc.

Zinc recovery from steel plant dusts and other zinciferous materials

A process is provided for recovering fluorine from dilute hydrofluoric acid solutions, such as waste scrubber solution obtained in the treatment of phosphates. The dilute solution is used to react with oxidic titanium material to solubilize the contained titanium and subsequently form, in the presence of potassium ions, crystals of K.sub.2 TiF.sub.6 which are commercially useful as a grain-refining agent in the manufacture of aluminum alloys.

Production of potassium hexafluotitanates using dilute hydrofluoric acid

In the high-pressure sulfuric acid leaching of nickeliferous oxide and silicate ore, there is a tendency for the formation of scale on autoclave surfaces. The scale comprises oxides and sulfates of metals selected from the group consisting of aluminum, iron, silicon and magnesium. The scale is chemically removed by flushing the autoclave following completion of a leaching regime with a sulfuric acid solution containing about 20 to 100 gpl H.sub.2 SO.sub.4 at a temperature of about 150.degree. C. to 250.degree. C. and a pressure ranging from about 54 psig to 562 psig for a time sufficient to effect substantial removal of the scale.

Chemical dissolution of scale formed during pressure leaching of

A method for efficiently precipitating nickel sulfide from an acidic nickel sulfate solution having a pH between 1.5 and 4, containing about 1 to 40 gpl nickel, optionally containing cobalt, and containing sufficient inert soluble sulfate salt to buffer the solution during the precipitation of nickel sulfide at relatively low temperature and pressure.

Selective precipitation of nickel and cobalt sulfides from acidic

Uranium is separated from mixed oxides of thorium and uranium by a pyrometallurgical process in which the oxides are mixed with a molten chloride salt containing thorium tetrachloride and thorium metal which reduces the uranium oxide to uranium metal which can then be recovered from the molten salt. The process is particularly useful for the recovery of uranium from generally insoluble high-density sol-gel thoria-urania nuclear reactor fuel pellets.

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Arvada, CO, United States of America

Mahesh C Jha