I N D U S T R Y

Government Service — Davison Style New plant extracts AEC thorium from government monazite, returns rare earth salts to GSA Stock

APPROPRIATE CEREMONIES attended by officials from the Atomic Energy Commission, Bureau of Mines, and other government agencies, marked the opening of Davison Chemicals $2 mil­lion rare earth processing plant at Curtis Bay, Md. The new plant, de­signed to produce thoria and rare earth salts from monazite sand, has a daily capacity of 15 to 25 tons of crude ore.

Operating under AEC contract, the new plant uses as raw material mona­zite sand from General Services Ad­ministration stockpile. The process is essentially a separation and refining op­eration designed to do two things:

• Supply AEC with a stock of tho­rium compounds in preparation for the expected emergence of the thorium breeder as the most popular reactor type.

• Upgrade the government rare earth stockpile by returning to GSA a concen­trated, purified mixed rare earth double salt in insoluble form to permit outdoor storage.

Since Davison Chemical and its

affiliate Rare Earths, Inc., are respon­sible for the government-owned raw materials and government-owned prod­ucts, elaborate precautions have been taken in the new plant to keep the ac­counting straight and to guard against loss. Elaborate automatic sampling systems take continuous samples of the incoming ore and finished products. There are no floor drains in the plant, so that there will be no loss in the event of spillovers. All effluent streams discharge to a common sump, and pol­ishing filters are installed in individual lines to remove the last traces of solid material.

• The Process: Classical. At pres­ent Davison is not revealing the details of the process, other than to say it involves large-scale application of classical principles of rare earth chem­istry. Heart of the process is the sepa­ration of the thorium fraction from the rare earths and gangue by solution in hot sulfuric acid. The thorium stream is refined in a process utilizing hydro­fluoric acid, and the resulting product, thoria, is dried in a drum dryer.

F. C. Nicholson, Davison vice president, explains process details of monazite processing plant to John E. Crawford, Bureau of Mines, Paul Sweeney, ODM, Charles W. Tully and R. L Faulkner, AEC, and Frank D. Lamb, Bureau of Mines

View of reactor kettles at new mona­zite processing plant of Davison Chemi­cal and Rare Earths at Curtis Bay, Md.

On the other side of the process, the insoluble gangue is removed from the rare earth fraction, and the last traces of valuable materials are removed be­fore the gangue is discarded. The rare earth fraction is purified, and the mixed rare earths are precipitated as the double sulfates by the addition of so­dium sulfate. The resulting product is dried in an oil fired rotary drum dryer.

The process fits in well with other operations conducted at Davison's Cur­tis Bay plant. All the sulfuric acid used comes from Davison's contact acid plant located next door. Since the rare earths in monazite occur princi­pally as the phosphates, considerable quantities of phosphoric acid are gen­erated in the purification. Spent acid from the process, a mixture of sulfuric and phosphoric, is piped to Davison's superphosphate operation.

• Process Advantages. In addition to the advantage of integrated opera­tion, other advantages claimed for this process are:

• Ores of variable composition can he processed without difficulty, including low grade ore.

• The rare earth salts produced are extremely low in phosphates, an ad­vantage in subsequent processing.

• The thorium product has a high concentration of thorium with very lit­tle rare earth contamination.

• Minimum quantities of process raw materials are required.

In designing the rare earth process­ing plant, the layout of equipment has been made as flexible as possible. When the AEC contract expires at the end of 1957, the plant could be con­verted with little difficulty to the pro­duction of individual rare earth salts.

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