Removal of SO₂ Using a Magnetically Fluidized Bed in the Semi‐Dry Flue Gas Desulfurization Process: Roles of Ferromagnetic Particles and Applied Magnetic Field in the Desulfurization Reaction

Abstract

A new semidry flue gas desulfurization (FGD) process is proposed. The process uses a magnetically fluidized bed (MFB) as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. A slurry of lime is continuously sprayed into the reactor by an atomizer fixed at the top of the bed. As a consequence, the desulfurization reaction and slurry drying take place simultaneously in a same reactor. Experiments with a laboratory‐scale apparatus were carried out to investigate the roles of the ferromagnetic particles and the magnetic field applied in the desulfurization reaction. The results show that when ferromagnetic particles are used as the fluidization material, both sulfite (SO32–) salts and sulfate (SO42–) salts are found in the desulfurization products. When quartz particles are used, only sulfite (SO32–) salts are found. This suggests that the Fe(III) ions and Fe(II) ions result from the ferromagnetic particles dissolving in the liquid phase. In addition, the ions act as catalysts in the oxidation of S(IV) to S(VI) and react with SO2 producing FeSO3 and Fe2(SO4)3 as the products. On the other hand, the level of the sulfate (SO42–) salts in the products increases with increasing intensity of applied field intensity, which suggests that the oxidation of S(IV) can be enhanced by the applied magnetic field. The oxidation of S(IV) can increase the solubility of SO2, and therefore, intensify the reaction between SO2 and Ca(OH)2, leading to an increased SO2 removal efficiency.

Magnetic Field Assisted Fluidization - A Unified Approach Part 7. Mass Transfer: Chemical reactors, basic studies and practical implementations thereof

“…Furthermore, variations in the field intensity affect remarkably the desulphurization efficiency 195 Brought to you by | University of Birmingham Authenticated Download Date | 6/13/15 5:09 PM Vol. Zhang and Gui (2008) decided that field affects mainly the reaction rather than on the bed structure; confirmed by analyses of the desulphurization products (compositions), namely: i) At Η = 0 , the CaSO$ dominates over the other composition. Nos.…”

“…Magnetically assisted trickle beds (MATB) with co-current gas-liquid flow are new devices in focus of researchers in the last 2 years Zhang and Gui, 2008;Li et al, 2007. These studies address directly overall mass transfer characteristics of the devices studied and information pertinent to bed hydrodynamics is scarce.…”

“…5.6a) revealed increase in bed efficiency with field increase from 100 up to 200 Gs. (Gui and Zang 2006;Zhang and Gui, 2008 ). to establish optimal conditions at // = 350Gauss.…”

“…Iron in the experiments of Gui and Zhang (2006) is a catalyst and the process chemistry considers falling lime slurry drops falling and consequent liquid dispersion on the particle surface (Zang and Gui, 2008 According to Zhang and Gui (2008) the efficiency of a ferromagnetic particles bed is about 14% higher than that of the quartz particles used as a controlling (comparative) particulate material (packing).The ferromagnetic phase acts as a catalyst and SO 2 sorbents which react in accordance with all consequent reactions listed above. Furthermore, variations in the field intensity affect remarkably the desulphurization efficiency 195 Brought to you by | University of Birmingham Authenticated Download Date | 6/13/15 5:09 PM Vol.…”

“…25. When the field reaches 400Oe(«32000^/m) CaSOj is only a small portion of the desulphurization product, iii) In general, the benefit of use of ferromagnetic particles (Zhang and Gui, 2008) is the possibility to oxidize S (IV) to S(Vl) in the liquid phase thus increasing the SO 2 solubility and capturing efficiency, iv) The increase in field intensity does not affect the bed structure but affects the oxidation of S(iy) . 1-2-3, 2009 Magnetic Field Assisted Fluidization A Unified Approach-Part 7 £502 = (l-QoiW C A>2-<»<f) xl()0% ( see Fi § ure 5 -6b) with almost linear relationships between 90Oe(*72QQA/m) and 2600<?(«20780Λ//η).…”