Simplot Phosphoric Acid Purification Process

The Research and Development Department of the J. R. Simplot Company has successfully developed a membrane based system for the purification of wet process phosphoric acid after four years of intensive research. A first-of-a-kind, 30,000 t/y solution purification plant using this technology successfully started up in 1996 to produce high quality, fertigation (drip) grade phosphoric acid.

Process Advantages

• A high value added product is manufactured from wet process phosphoric acid.
• No solvents are used in the process.
• Commercially proven.
• Only by-product is a raffinate acid stream.
• Low capital and operating costs.
• Produces a technical grade acid.
• Available through a licensing agreement with KEMWorks Technology.
• Process is flexible - high levels of product quality can be met through multiple stages of membrane filtration.
• Simple, easy to operate process.

Process Description

In the Simplot phosphoric acid purification process, a high quality purified phosphoric acid is produced from wet process phosphoric acid using a proprietary membrane based process. This process is novel and unique, and unlike other purification processes is not based on solvent extraction.

The phosphoric acid feed stock to this process is either 30%, 42% P2O5 or higher strengths wet process phosphoric acid. This feed acid is cooled and, if necessary, reacted with a suitable calcium source such as finely ground phosphate rock or lime to reduce sulfate levels to less than 0.25%. The acid is then filtered to remove gypsum and other suspended solids.

The clean phosphoric acid filtrate is pressurized and fed to an ultrafiltration system to remove the suspended solids by cross-flow membrane filtration. Approximately 95% of the feed acid is recovered as an ultrafiltration permeate. This ultraclean, solids free permeate is pressurized using centrifugal or positive displacement pumps and filtered using proprietary membranes that remove 99+% of all metallic constituents.

Following the phosphoric acid purification step, the purified produce acid is concentrated in a forced circulation evaporator to 50 to 54% P2O5. The raffinate acid, that contains all the removed impurities, may be concentrated by evaporation. The raffinate, containing all the rejected impurities, is utilized in the production of single or triple superphosphate, 16-20-0, or mono-ammonium phosphate (MAP).

* 42% or, alternatively, 30% P2O5 feed acid may be used as feed stock to process.
** Product quality produced with a two-stage membrane purification process using phosphoric acid produced from Idaho uncalcined rock.

Raw Materials, Utilities, etc.