Magnesium oxide process, conventional

An improved magnesium oxide (MgO) flue gas desulfurization process and its comparative economics are described. Innovations made include the use of a spray dryer, a cyclic hotwater reheater, and a coal-fired fluidized-bed reactor for regeneration of the MgO absorbent. Several technical concerns with the proposed design are addressed, including fly ash and chloride buildup. The economic evaluation shows the process to have a capital investment of about seven percent less than that of a conventional MgO scrubbing process and a 40 percent smaller annual revenue requirement. Finally, a sensitivity analysis is shown relating annual revenue requirements to the byproduct sulfuric acid price credit. 

TVA s involvement with magnesium oxide (MgO) flue gas desulfurization (FGD) systems extends over a period of years and has been documented in a recent Environmental Protection Agency symposium paper (JO. The process described therein utilizes conventional MgO FGD technology and is similar in design to one being installed commercially by Philadelphia Electric Company. 

Conventional methods of preparation of magnesium oxide yield products that have large and varied grain sizes and fairly low surface areas. The most popular method of nanoparticle synthesis has been via sol-gel processing. Other liquid-phase methods involve the use of hydrothermal synthesis, which has yielded rod, tube, and needle-shaped morphologies (Ding et al., 2001). Klabunde (2001) has reviewed the various synthetic methods. 

Sulfate ion was incorporated on alumina and/or silica-alumina or transition metal oxide (iron oxide or zinc oxide) the catalysts were used in the oligomerization of oct-l-ene. The results showed that these sulfated catalysts had a higher activity and selectivity in the olefin oligomerization process, while the conventional catalysts such as cobalt sulfate or magnesium sulfate supported on alumina or silica-alumina exhibited lower activity in the same process. The oligomers had a sufficiently low degree of branching and were useful as a material for, e.g. phthalic acid plasticizer. 

Table 1 summarizes some microstructural and electrochemical properties of porous Si anode materials, as pertaining to the second approach mentioned above, collected from the literature published since 2005. Several synthesis methods have been identified for preparing the porous Si anode materials (column 1, Table 1). One of the two most adopted methods is known as the metal-assisted chemical etching (MACE denoted as E in Table 1). The fundamental principle of this method can be found in the handbook chapter Porous Silicon Formation by Metal Nanoparticle Assisted Etching. Figure 2 shows an example of the MACE-derived porous Si particle. The other most adopted method is magnesiothermic reduction (denoted as M in Table 1). In this method (see handbook chapter Porous Silicon Formation by Porous Silica Reduction ), porous Si oxide materials are reduced by magnesium vapor under high-temperature thermal treatment. The porous Si oxide precursors may be synthesized via the conventional sol-gel processes. Porous Si particles with unique pore structures, such as hollow interior and ordered mesoporosity, may be obtained from Si oxides having the same pore structures which are achieved by using proper templates.

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