Allied Chemical Corporation

Philip F Seeling

Samuel L Bean

James William Swaine, Jr

Robert Joel Hoffman

William W Low

Robert Joel Hoffmann

Calcium nitrate with low nitrate content is prepared by reacting in a series of absorption reactors lime slurry and nitrogen oxide gases. The lime slurry flows serially through the series of absorption reactors with a major portion being recycled to the inlet of a Venturi absorber in each reactor. Nitrogen oxide gases flow cocurrently with the slurry from each reactor to the following Venturi inlet and are contacted by recycle slurry in each Venturi with a molar ratio of calcium hydroxide to nitrogen oxides of at least about 20. Slurry from the last reactor with a calcium nitrite content of below about 22 weight percent and a calcium hydroxide content of at least about 2 weight percent may be freed of unreacted calcium hydroxide, for example by treatment with NO.sub.x gases, and then concentrated to the desired product concentration. The exit gases may be scrubbed with incoming lime slurry after passing through a holdup vessel which increases the ratio of NO.sub.2 to NO.

Manufacture of calcium nitrite solutions with low nitrate content

Anhydrous sodium sulfite is made by a process involving introducing substantially anhydrous sodium carbonate concurrently with impurities-containing mother liquor from which sodium metabisulfite crystals have been crystallized and sulfur dioxide-containing gas into a saturated solution of sodium sulfite maintained at pH of between about 6.5 and about 7.6 at temperature above about 35.degree. C. to form a slurry of anhydrous sodium sulfite crystals, and withdrawing the crystals from the slurry. The process is initiated using a concentrated sodium sulfite solution containing less than about 3 ppm of dissolved iron.

Production of sodium sulfite utilizing mother liquor from the sodium

Improvement in the method for making a sulfur dioxide-containing gas stream of low elemental sulfur content by contacting a stream of oxygen-containing gas with elemental sulfur maintained above its auto-ignition temperature to generate a gas stream containing sulfur dioxide and gaseous elemental sulfur, followed by contacting this gas stream with liquid elemental sulfur maintained below its auto-ignition temperature, which improvement involves subsequently scrubbing the gas stream in a confined area with water or an aqueous medium, preferably containing small amounts of ammonia, under conditions of turbulent flow to obtain a sulfur dioxide-containing gas stream substantially free of oxygen and sulfur trioxide and containing less than about 0.0002 lb. of sulfur per cubic foot of gas, measured at standard conditions.

Method for making sulfur dioxide-containing gas stream

Anhydrous sodium sulfite is made by a process involving introducing substantially anhydrous sodium carbonate concurrently with sulfur dioxide-containing gas into a saturated solution of sodium sulfite maintained at pH of between about 6.5 and about 7.6 at temperature above about 35.degree. C. to form a slurry of anhydrous sodium sulfite crystals, and withdrawing the crystals from the slurry. The process is initiated using a concentrated sodium sulfite solution containing less than about 3 ppm of dissolved iron.

Growing community of inventors

North Syracuse, NY, United States of America

Philip F Seeling