Combined solvent extraction and stripping for removal and isolation of ammonia from sour waters

Simultaneous stripping and solvent extraction offer the possibility of removing and isolating ammonia from sour waters with less steam consumption. Liquid cation exchangers were found to be effective for extraction of ammonia under those conditions. Among the liquid cation exchangers considered, di-2-ethylhexyl phosphoric acid (D2EHPA) appeared to have the most favorable pro perties. Addition of modifiers to diluents for D2EHPA profoundly affects a number of important solvent properties and affords an avenue toward solvent improvement. Acid modifiers, such as alcohols, phenols, and carboxylic acids, solvate the D2EHPA-ammoni,um ion pair and thereby increase the degree of extraction of ammonia, reduce aqueous-solubility losses of D2EHPA, improve phase-separation properties, and decrease the volatility of ammonia upon solvent regeneration. Basic amine modifiers complex with D2EHPA, and thereby decrease the degree of ammonia extraction, reduce aqueous-solubility losses of D2EHPA, and increase the volatility of ammonia upon sol vent regeneration. These effects have been demonstrated and interpreted through complexation models. Preliminary cost analyses indicate that the dominant factors are steam costs for solvent regeneration and costs of replacing extractant lost by aqueous solubility.