Flue Gas Desulfurization: Physicochemical and Biotechnological Approaches

Various flue gas desulfurization processes —physicochemical, biological, and chemobiological—for the reduction of emission of SO₂ with recovery of an economic by-product have been reviewed. The physicochemical processes have been categorized as “once-through” and “regenerable.” The prominent once-through technologies include wet and dry scrubbing. The wet scrubbing technologies include wet limestone, lime-inhibited oxidation, limestone forced oxidation, and magnesium-enhanced lime and sodium scrubbing. The dry scrubbing constitutes lime spray drying, furnace sorbent injection, economizer sorbent injection, duct sorbent injection, HYPAS sorbent injection, and circulating fluidized bed treatment process. The regenerable wet and dry processes include the Wellman Lord's process, citrate process, sodium carbonate eutectic process, magnesium oxide process, amine process, aqueous ammonia process, Berglau Forchung's process, and Shell's process. Besides these, the recently developed technologies such as the COBRA process, the OSCAR process, and the emerging biotechnological and chemo-biological processes are also discussed. A detailed outline of the chemistry, the advantages and disadvantages, and the future research and development needs for each of these commercially viable processes is also discussed.

KEY WORDS:

• biological
• chemobiological
• elemental sulfur
• physicochemical
• sulfate-reducing bacteria
• Thiobacillus sp.