Studies of acidification of raffinate in Kuhni column, to increase the yield in the phosphoric acid purification process

• Grant number: 98/08122-6
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Start date: November 01, 1998
• End date: April 30, 1999
• Field of knowledge: Engineering - Chemical Engineering - Chemical Process Industries
• Principal Investigator: Roberto Corrêa de Cerqueira César
• Grantee: Roberto Corrêa de Cerqueira César
• Company: Fosbrasil S/A

Abstract

The objective of this process is to increase the efficiency of the liquid-liquid extraction in flux process for the purification of phosphoric acid, which has been successfully used for the last 13 years by Fosbrasil, which is the only Brazilian company to have mastered this cutting edge technology, possessing in its premises a pilot plant where it has already carried out various tests with raw materials, improving and implementing changes in the purification process. The purification process, via extraction, is divided into three stages: extraction, cleaning and re-extraction. In the first stage, the extraction of the acid H3 PO4 occurs to the degree of that used as a fertilizer (aqueous phase) with a cooled solution of isopropyl ether/ tri-butyl phosphate (organic phase). The residue produced from this phase is called raffinate, which is rich in compounds of phosphate not available for extraction, generally metallic phosphates of Mg2 +, Fe3 + and Al3 +, deriving from the phosphate mineral. The process is now looking to improve on the extraction process operations of the pilot plant with a reactor and a Kuhni column, where the acidification using sulfuric acid from the raffinate occurs, followed by extraction with the solvent of phosphoric acid. The acidification with the stronger acid frees the phosphates in the raffinate, increasing the yield of the process. In the extraction process, the phosphates must present themselves in the form H3 PO4 in order for the transfer from the aqueous phase to the organic solvent phase to occur. With increased efficiency in the process, it will be possible to reduce the cost of the final product. (AU)