Simultaneous SO{sub 2}/NO separation from flue gas using HFCLM. Final report

Abstract

Abatement technologies for oxides of sulfur and nitrogen present in flue and stack gases from coal fired boilers are becoming increasingly important. Scrubbing the gases with an aqueous limestone slurry to remove SO{sub 2} is a widely used treatment process. These scrubbing solutions are, however, not very effective in removing NO. In addition, the process is expensive and produces large volumes of sludge. The liquid membrane from a 0.01 M aqueous solution of Fe{sup 2+}EDTA has been found to have a very high selectivity for NO over N{sub 2}. Thus, SO{sub 2}/NO{sub x} can be removed simultaneously using an aqueous Fe 3{sup 3+}EDTA solution in a hollow fiber contained liquid membrane (HFCLM) permeator with hydrophobic fibers. The HFCLM configuration has addressed previous concerns about liquid membrane stability for an application such as this. In this project, a flow apparatus was constructed that will allow simultaneous SO{sub 2}/NO removal and recovery using two hollow fiber modules in series. Flowing the liquid membrane on the shell-side of the modules it is hypothesized will enhance the performance over that of HFCLMs without loss of stability. From the work completed in this exploratory project, it was concluded that to move the current state-of-the-art for this promising technology toward commercialization will require progress in the following areas: (1) sensitivity of the performance of the system to temperature changes, (2) validation of a mass transfer model to be used in scale-up calculations, (3) data on alternative flow schemes, and (4) overall process economics calculations.