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Process for preparation of calcium thiosulfate liquid solution from lime, sulfur, and sulfur dioxide

a technology of calcium thiosulfate and liquid solution, which is applied in the field of process for the preparation of calcium thiosulfate, a plant nutrient solution, can solve the problems of not being able to remove all ammonia, lingering ammonia odor and/or contamination of calcium thiosulfate, and sulfur dioxide being toxic to vegetation, etc., to achieve high purity level, reduce undesirable formation, and reduce the effect of ammonia concentration

Active Publication Date: 2011-10-27
TESSENDERLO KERLEY INC
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  • Summary
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  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a process for producing calcium thiosulfate by reacting sulfur dioxide with sulfur and hydrated lime or with lime-sulfur or calcium polysulfide under specific conditions. The invention allows for the production of high concentration calcium thiosulfate solutions with low byproduct formation. The invention also provides apparatus for reacting sulfur dioxide with a slurry to prepare a calcium thiosulfate solution. The invention can use sulfur dioxide obtained from industrial operations as a byproduct, and a semi-continuous approach can be used for removing sulfur dioxide tail gas from chemical processing units, power generation industries, and mining industries.

Problems solved by technology

Although calcium thiosulfate has been known for many years and has many references in the literature, there are not many known commercial methods that employ inexpensive raw materials to produce high purity calcium thiosulfate with a low amount of byproducts and with solid residue of insoluble calcium salts which permit easy separation from the calcium thiosulfate product.
Further, not all the ammonia can be removed by this process, and as a result, the resulting calcium thiosulfate tends to have a lingering ammonia odor and / or contamination with ammonia or ammonium thiosulfate.
High yield is only obtained in the preparation of magnesium thiosulfate, and the preparation of calcium thiosulfate requires a difficult filtration of a slurry containing magnesium hydroxide.
The byproduct of this approach is a large amount of sodium chloride that also contaminates the resulting calcium thiosulfate.
The calcium thiosulfate product formed in this way is contaminated with sodium chloride, calcium chloride and sodium thiosulfate.
However, the '368 patent does not utilize sulfur dioxide.
However, sulfur dioxide may be toxic to vegetation in concentrations of about 2 to 3 ppm and corrosive to materials made of metal.

Method used

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  • Process for preparation of calcium thiosulfate liquid solution from lime, sulfur, and sulfur dioxide
  • Process for preparation of calcium thiosulfate liquid solution from lime, sulfur, and sulfur dioxide
  • Process for preparation of calcium thiosulfate liquid solution from lime, sulfur, and sulfur dioxide

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Experimental program
Comparison scheme
Effect test

experiment # 3

[0116]Experiment #3 was not completed due to the low recovery of calcium in step (i).

[0117]The inventors determined that the higher the CCa was in the lime-sulfur parent solution, the higher the CCa was in the calcium thiosulfate solution. This was true if CCaTs was less than about 27 wt %. The further increase of CCa in the lime-sulfur solution did not influence CCaTs, but resulted in the growth of the amount of solid.

[0118]The preferred temperature during the step (i) in which lime-sulfur is produced by reacting calcium hydroxide and sulfur is about 93° C. to about 99° C. (200° F.-210° F.) as described in U.S. Pat. No. 6,984,368.

[0119]The inventors determined that the duration of the step (i) appears to be dependent on molar ratio only (since temperature is not variable).

[0120]While using pure lime (99% or better) and pure sulfur with the optimal molar ratio of S:Ca(OH)2:H2O=(3.6-3.8):1:25.5, the endpoint of step (i) could be judged by the appearance of the solution. The endpoint ...

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Abstract

An efficient batch or semi-continuous method of production of relative high concentration, low byproduct-containing, calcium thiosulfate (CaS2O3) from lime, sulfur or calcium polysulfide, and sulfur dioxide under elevated reaction temperature conditions is described. The product is an emulsion of liquid calcium thiosulfate and solid byproducts. Under the conditions of the art, including the mole ratios of lime to sulfur, the temperature of the reaction process and the sulfur dioxide reaction conditions, including rate and duration, the byproducts are reduced to about 2% by weight.

Description

FIELD OF INVENTION[0001]The present invention is directed to a process for the preparation of calcium thiosulfate, a plant nutrient solution. Another aspect of the present invention is the removal of air pollutant sulfur dioxide from industrial plants producing it, to convert the sulfur dioxide to calcium thio sulfate.DESCRIPTION OF RELATED ART[0002]The thiosulfate ion, S2O32−, is a structural analogue of the SO42− ion in which one oxygen atom is replaced by one S atom. However, the two sulfur atoms in S2O3−2 are not equivalent. One of the S atoms is a sulfide-like sulfur atom that gives the thiosulfate its reducing properties and complexing abilities.[0003]Thiosulfates are used in leather tanning, paper and textile manufacturing, flue-gas desulfurization, cement additives, dechlorination, ozone and hydrogen peroxide quenching, coating stabilizers and so on.[0004]Due to these complex-forming abilities with metals, thiosulfate compounds have been used in commercial applications such ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C01B17/64
CPCC01B17/64C01P2006/60C01P2006/10
Inventor HOJJATIE, MICHAEL MASSOUDFEINSTEIN, YELENALOCKHART, CONSTANCE LYNN FRANK
Owner TESSENDERLO KERLEY INC
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