Abstract: A wet phosphoric acid production process comprising the attack on phosphate rock by sulfuric acid and phosphoric acid utilizing a vacuum cooling and a recirculation of the reaction slurry. The flow rates of the materials within the system are maintained at a level, relative to the rate of withdrawal of the slurry from the system, of between 300% and 4000% for the cyclic flow, between 2000% and 4000% for the vacuum cooling flow and between 500% and 2200% for the local agitation flow. Control of the flow rates according to factors including the rock analysis allows maximization of the yield of H.sub.3 PO.sub.4.

Abstract: Electrostatic separation of aqueous and particulate matter from a primarily organic impurities phase which forms at the organic/aqueous interface in a liquid-liquid extraction process.

Abstract: Aqueous phosphoric acid, e.g., a slurry of the acid produced by the "wet" process, is contacted with steam under organic volatile-removing conditions to remove volatile organic material. A "wet process" aspect of the process involves contacting crude phosphoric acid produced by the wet process at a temperature, preferably not greater than 100.degree. C., while binding bindable solid impurities present and controlling the density of the acid to avoid deleterously affecting the processing character of the acid. In a first facet of this aspect, humic-extracting extractants are employed to remove humics, and in a second facet, heavy metal-extracting extractants are employed to recover heavy metals, from the acid.

Abstract: Sodium sulfate is purged from a sulfur dioxide removal system involving contact of a sulfur dioxide-containing gas with a solution containing sodium sulfite to absorb sulfur dioxide from the gas. The spent absorbing solution is regenerated by desorbing sulfur dioxide and recycled for further use. To avoid an unduly large build-up of sulfate in the system, at least a portion of the absorbing-desorbing medium, e.g. spent absorbing solution, containing sodium sulfate and a relatively large amount of sodium bisulfite is treated to reduce the amount of water in the medium so that there is precipitated therefrom up to about 10 weight percent undissolved solids containing sodium sulfate in greater concentration than would otherwise be obtained in the absorption-desorption cycle. The insolubles containing sodium sulfate are removed from the liquid, and the liquid can be returned to the sulfur dioxide removal system.

Abstract: Sodium sulfate is purged from a sulfur dioxide removal system involving contact of a sulfur dioxide-containing gas with a solution containing sodium sulfite to absorb sulfur dioxide from the gas. The spent absorbing solution is regenerated by desorbing sulfur dioxide, and recycled for further use. To avoid an unduly large build-up of sulfate in the system, a portion of the absorbing-desorbing medium, e.g., spent absorbing solution, containing sodium sulfate, a relatively large amount of sodium bisulfite, and generally a minor amount of sodium sulfite, is treated to precipitate solids containing sodium sulfate in a concentration which is greater on a dry basis than would otherwise be obtained in the absorption-desorption cycle. The concentration of sodium sulfate in the precipitated solids is increased by providing a portion of the precipitated sodium sulfate-containing solids, e.g. about 25 to 75 weight percent, in solution in the absorbing-desorbing medium treated for sulfate removal.

Abstract: There is disclosed a process for obtaining purer sodium sulfate from a mixture of solids containing sodium sulfate and sodium sulfite. The process involves contacting an aqueous slurry of the sulfate-sulfite mixture with a sulfur dioxide-containing gas under conditions which solubilize a significant amount of the sulfite as sodium bisulfite dissolved in the liquid aqueous phase. The remaining solid phase contains sodium sulfate of greater purity than in the mixture treated with sulfur dioxide. The mixture of sodium sulfate and sodium sulfite which is purified by the process may be obtained advantageously as a purge material from a process for removing sulfur dioxide from a gas stream.

Abstract: Sodium sulfate is purged from a sulfur dioxide removal system involving contact of a sulfur dioxide-containing gas with a solution containing sodium sulfite to absorb sulfur dioxide from the gas. The spent absorbing solution is regenerated by desorbing sulfur dioxide and recycled for further use. To avoid an unduly large build-up of sulfate in the system, at least a portion of the absorbing-desorbing medium containing sodium sulfate and a relatively large amount of sodium bisulfite, e.g. spent absorbing solution, is contacted with a treating gas containing at least a small amount of sulfur dioxide while reducing the amount of water in the medium so that a slurry is obtained having up to about 10, or even up to about 20, weight percent precipitated solids containing sodium sulfate in greater concentration than would otherwise be obtained in the absorption-desorption cycle. Preferably, the sulfur dioxide-containing treating gas is unsaturated with respect to water.

Abstract: Sodium thiosulfate is purged from a sulfur dioxide removal system involving contact of a sulfur dioxide-containing gas with a solution containing sodium sulfite to absorb sulfur dioxide from the gas. A portion of the liquid from a desorption zone containing a minor amount of sodium thiosulfate and a relatively large amount of sodium bisulfite, is treated to reduce the amount of water in the medium so that solids are precipitated from the liquid phase. The insolubles containing sodium sulfites are removed from the liquid. The liquid separated from the solids can be discarded and thereby purge thiosulfate more selectively with respect to other sodium salts. Also, the sodium values of the sodium thiosulfate-containing purge liquid can be recovered in active form by chemical reduction, and, preferably, carbonation. A sodium sulfate purge material from the absorption-desorption system can also be subjected to the chemical reduction system for further recovery of active sodium values.

Abstract: There is disclosed a process for reducing the loss of sodium values in a system for removing sulfur dioxide from a gas by the use of an absorption-desorption cycle employing aqueous sodium sulfite as the essential absorption solution. Sodium sulfate and/or sodium thiosulfate build-up in the system is avoided and the loss of sodium values reduced by subjecting sodium sulfate and/or sodium thiosulfate-containing material to chemical reduction to form a product containing a substantial amount of sodium carbonate. Preferably, the reduced product is subjected to carbonation followed by reaction of the bicarbonate and bisulfide components of the mixture to give a resulting liquid which is more suitable for use in the absorption-desorption process. By-product gases can be incinerated to produce sulfur dioxide-containing gases which can be charged to the sulfur dioxide absorption zone.

Abstract: Wet process phosphoric acid is made by grinding phosphate rock as a slurry in water, and digesting the ground rock slurry with sulfuric acid which has been diluted by spent calcium sulfate wash water before being combined with the ground slurry.

Abstract: Metal, e.g. sodium sulfate, is separated from metal, e.g. sodium sulfite, in a solution, for instance a solution used in a system involving contact of sulfur dioxide-containing gases with the sodium sulfite solution as an absorbing solution to recover sulfur dioxide wherein the absorbing solution is regenerated after contact with the gas and recycled for further use. A portion of the absorbing solution is purged to avoid the unduly large build-up of sodium sulfate in it. The purge stream is contacted with sulfur dioxide to reduce the amount of sodium sulfite therein to relatively soluble sodium bisulfite, and the relatively insoluble sodium sulfate is recovered therefrom as undissolved solids. The liquid separated from the sodium sulfate, which is rich in sodium bisulfite, is returned to the absorbing solution. In a preferred aspect, the purge stream is withdrawn from the absorbing solution subsequent to contact with the sulfur dioxide-containing gases and before regeneration.