Fmc Corporation

Peter H Zeh

Richard E Hall

Paul L Hensler

Richard A Mohr

Sushil K Bhalla

Barry Schwartz

Gary E Wolfe

Bert D McMunn

Chris C Dick

Frederic B Jueneman

Frederick J Kelso

Bert Douglas Mcmunn

Chris Charles Dick

A fast-dissolving, non-caking, food grade sodium tripolyphosphate is produced by spraying into a spray dryer an aqueous sodium orthophosphate feed liquor having an Na.sub.2 O:P.sub.2 O.sub.5 ratio of from about 1.60 to about 1.67 containing potassium hydroxide or a soluble potassium salt in amounts to yield about 0.4% to 0.8% by weight potassium in the final product, heating the feed to at least 440.degree. C. to form sodium tripolyphosphate, cooling the sodium tripolyphosphate and adding to it at least about 1% by weight moisture.

Fast-dissolving, non-caking, food grade sodium tripolyphosphate

Phosphoric acid is treated to remove and/or tie up heavy metals and antimony to enable the acid to be used in electrical semiconductor applications by reacting the acid with hydrogen sulfide and with hydrogen peroxide in separate treating steps. The hydrogen sulfide precipitates metal sulfides which are separated from the acid, and the hydrogen peroxide oxidizes dissolved antimony so that it is tied up and does not post-precipitate in the acid after removal of the metal sulfides.

Process for purifying phosphoric acid for electrical semiconductor use

The concentration of Phase II sodium tripolyphosphate in the sodium tripolyphosphate produced by spray drying a feed liquor comprising sodium orthophosphate, sodium pyrophosphate or mixture thereof, is increased to at least 90% by weight of sodium tripolyphosphate product, by seeding the feed liquor with Phase II material. Phase II yield is further increased by introducing with the feed liquor, in addition to the Phase II seed material, a minor amount of sodium sulfate. Hydrolysis of the Phase II seed is minimized by concentrating the Phase II seed in feed liquor in a separate feed tank at a lower temperature than the main feed line. Dispersing the Phase II seed in water, a dilute soda ash solution or an inert organic liquid and then injecting the dispersion into the feed liquor into the spray dryer promotes good contact between the seed and feed.

Production of Phase II sodium tripolyphosphate

Manufacturing dry, free-flowing crystalline sodium carbonate peroxide by passing a gas stream at a temperature between 70.degree. and 150.degree. C into a drying zone containing moist sodium carbonate peroxide while maintaining the exit gas stream temperature between 50.degree. and 130.degree. C until the sodium carbonate contains between 0.05% and 0.5% by weight moisture, immediately passing the dried material into a cooling zone where the sodium carbonate peroxide temperature is lowered to between 0.degree. and 40.degree. C, and removing a dry, free-flowing, crystalline sodium carbonate peroxide product containing between 0.001% and 0.20% by weight moisture.

Process for drying sodium carbonate peroxide

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Fremont, CA, United States of America

Peter H Zeh