Arthur D. Little, Inc.

Combustion Equipment Associates, Inc.

Ravindra M Nadkarni

Chakra J Santhanam

James R Valentine

August H Schutte

Herbert E Beningson

Thomas J Lamb

Richard W Hyde

Stephen A Reber

Robert M Beningson

Lee K Fox

William V Keary

Narayanankutty V Menon

Method and apparatus for removing heavy metals as sulfides from aqueous liquids. The aqueous liquid is introduced into a circulating liquid loop wherein there are established a mixing zone, a controlled precipitation initiating zone, a crystal growing zone and a crystal settling zone. The aqueous feed liquid containing H S dissolved therein and at a pH below that at which the sulfide is precipitated is mixed in the loop with a pH-adjusting liquid; and the degree of supersaturation with respect to the metal sulfide is maintained within the controlled precipitation initiating and crystal growing zones in the metastable condition so that the growth rate of the metal sulfide crystals remains greater than under uncontrolled conditions vis-a-vis the nucleation rate to effect the production of metal sulfide crystals of a character which makes it possible to separate them through clarification and filtration.

Apparatus for removing heavy metals from aqueous liquids

Method and apparatus for removing heavy metals as sulfides from aqueous liquids. The aqueous liquid is introduced into a circulating liquid loop wherein there are established a mixing zone, a controlled precipitation initiating zone, a crystal growing zone and a crystal settling zone. The aqueous feed liquid containing H.sub.2 S dissolved therein and at a pH below that at which the sulfide is precipitated is mixed in the loop with a pH-adjusting liquid; and the degree of supersaturation with respect to the metal sulfide is maintained within the controlled precipitation initiating and crystal growing zones in the metastable condition so that the growth rate of the metal sulfide crystals remains greater than under uncontrolled conditions vis-a-vis the nucleation rate to effect the production of metal sulfide crystals of a character which makes it possible to separate them through clarification and filtration.

Method for removing heavy metals from aqueous liquids

Process and apparatus for recovering a precious metal, either as pure metal or in alloyed form, from a bimetallic material in which the precious metal is mechanically bonded to a base material comprising at least one base metal, e.g., copper, brass or bronze. The base material is leached off with an ammoniacal solution of an ammonium salt, preferably ammonium carbonate, using a leaching liquid containing reactive oxygen. The base metal or metals are recovered as metal compounds by thermally decomposing the resulting pregnant leach liquor; and the ammonia and ammonium salt are reconstituted for recycling. The method and apparatus are particularly suited for recovering karat gold from filled gold scrap.

Process for recovering precious metals from bimetallic material

Process and apparatus for removing sulfur dioxide from gases such as stack gases. The gases are scrubbed with an alkali metal compound in an aqueous solution to form alkali metal sulfite/sulfate salts which are then reacted with barium sulfide to precipitate barium sulfite/sulfate and form alkali metal sulfide/bisulfide in solution. The alkali metal sulfide/bisulfide is oxidized to form elemental sulfur and regenerated wash liquid; and the barium sulfite/sulfate is reduced by roasting to form the barium sulfide required. In a preferable embodiment, coal is used as both the reductant and fuel in the roasting of the barium sulfite/sulfate and the stack gases from the roasting are scrubbed along with the primary stack gases. As an optional step a portion of the alkali metal sulfite salts may be oxidized to sulfate prior to reaction with barium sulfide.

Process and apparatus for removing sulfur from stack gases in the form

Apparatus for the disposal of solid wastes by converting the organic fraction of such wastes to a fuel or fuel supplement and by recovering one or more of the constituents of the inorganic fashion. A minimum amount of sterile land fill remains. No significant pollution problems are created. The apparatus comprises shredding means, primary separating means, magnetic separating means, fines separating means, acid applying means, drying/heating means, grinding means and means to separate the fine product fuel. The system can, if desired, be essentially self-contained in heat energy requirements.

Apparatus for disposal of solid wastes and recovery of fuel product

Process for producing fluid fuel from coal. Moisture-free coal in particulate form is slurried with a hydrogen-donor solvent and the heated slurry is charged into a drum wherein the pressure is so regulated as to maintain a portion of the solvent in liquid form. During extraction of the hydrocarbons from the coal, additional solvent is added to agitate the drum mass and keep it up to temperature. Subsequently, the pressure is released to vaporize the solvent and at least a portion of the hydrocarbons extracted. The temperature of the mass in the drum is then raised under conditions required to crack the hydrocarbons in the drum and to produce, after subsequent stripping, a solid coke residue. The hydrocarbon products are removed and fractionated into several cuts, one of which is hydrotreated to form the required hydrogen-donor solvent while other fractions can be hydrotreated or hydrocracked to produce a synthetic crude product. The heaviest fraction can be used to produce ash-free coke especially adapted for hydrogen manufacture. The process can be made self-sufficient in hydrogen and furnishes as a by-product a solid carbonaceous material with a useful heating value.

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Arlington, MA, United States of America

Ravindra M Nadkarni