Aqueous Absorbents for Stack-Gas Desulfurization by Absorption/Stripping. Final Report

摘要

Several alternative aqueous absorbents were experimentally evaluated for use in absorption/stripping processes for flue gas desulfurization. The pH behavior of citrate, basic aluminum sulfate, ethylenediamine, and adipate buffers was measured and modeled. SO sub 2 vapor pressure was measured at 25 to 168 exp 0 C over solutions with sodium citrate, glyoxylic acid, and basic aluminum sulfate. Solution stability at 100 to 180 exp 0 C was studied with sodium citrate. The rate of SO sub 2 reaction with glyoxylic acid was deduced from measurements of the reverse reaction. Sodium citrate is not an attractive absorbent. With absorption of 3000 ppM SO sub 2 at 55 exp 0 C the actual steam requirements would be about 41 kg/kg SO sub 2 . Disproportionation and other side-reactions in sodium citrate buffer can be avoided by operating below 130 exp 0 C. Glyoxylic acid is also an unattractive alternative because rate data indicate that liquid holdup requirements and mass transfer requirements in the absorber would be prohibitive. Basic aluminum sulfate may be attractive if used in absorption below 45 exp 0 C. Solubility of basic aluminum salts limits operation to a pH less than 3.5. (ERA citation 08:045995)