Selection of Desulfurizer and Control of Reaction Products on Flue-Gas Desulfurization Using Chemical-Looping Technology

Abstract

Chemical-looping technology (CLT) can achieve energy efficiency and reduce the environmental pollution and is usually conducted on a fixed-bed reactor. In this paper, the thermodynamic simulations for flue-gas desulfurization (FGD) systems with CLT are carried out using HSC Chemistry software to choose a suitable desulfurizer, control the type and quantities of reaction products, and collect sulfur-containing byproducts with high economic value. The Ellingham diagrams are developed to relate the Gibbs free energy of the relevant reactions to the temperature. The fixing-sulfur potential; the reaction degree with CO 2 , H 2 O, and CO; and the acceleration effect of removing NO x of different metal oxides in 100 to 300 °C are estimated. Compared comprehensively, Mn-based oxides have distinct advantages for flue-gas desulfurization using CLT. Based on calculation results, both low reaction temperatures (T < 400 °C) and sufficient H 2 (m H 2 /m MnSO 4 > 4) can effectively prevent the loss of sulfur element. In the regeneration of Mn 3 O 4 , if pure O 2 is replaced by diluent air or a low level of oxygen, the formation of trace amounts of MnSO 4 can be inhibited. This paper provides ample theoretical basis for Mn-based oxides as active components of desulfurizer and collecting pure SO 2 from flue gas through chemical-looping technology.

Chemical Looping Combustion of Coal in China: Comprehensive Progress, Remaining Challenges, and Potential Opportunities

“…During the past 30 years, the chemical looping strategy has witnessed a rapid development in not only combustion processes but also gasification, , reforming, − calcium looping, − hydrogen production, − air separation, − desulfurization, − dechlorination, − selective oxidation, − ammonia synthesis, − etc. As a result of the merits of in situ product separation and cascade energy utilization, chemical looping is anticipated to continually find its extensive applications in many other chemical engineering processes …”

Reaction Characteristic Investigation of the Combined Template-Method-Made CaSO4–Mn3O4 Mixed Oxygen Carrier with Lignite

“…The apparent related equation was listed in eq , in which CaMn 2 O 4 was reported to own inferior reactivity, even for the reaction with CO, and, thus, was kept stable throughout the reaction of the YN lignite with the prepared OC mixed pair as a result of intensification of the CaMn 2 O 4 crystal structure by Ca 2+ involved. Meanwhile, besides CaMn 2 O 4 , direct decomposition of formed Mn 2 O 3 would also occur with O 2 emitted, as shown in eq , which promoted the combustion of the YN residual char during its reaction with the prepared mixed OC, similar to the combustion of the coal char by O 2 emitted with Mn 2 O 3 in the oxygen uncoupling process, as shown in eq . Thus, the higher maximal reaction rate was reached, as shown in Figure d, and simultaneously, the residual carbon fraction left after the YN lignite reaction with the prepared mixed OC was much lower, as seen in Table by EDX analysis. For MnSO 4 identified after the YN coal reaction with the prepared mixed OC shown in Figure c, it was easy to form via capture of SO 2 emitted in eqs – by reduced MnO in the presence of O 2 , as shown in eq . Of course, a little formed MnSO 4 was possible to further reduce to MnS with the reducing gases emitted from YN coal, such as CO, which was shown in eq . However, as indicated in Figure b, under the high concentration of CO 2 locally produced, such a reaction pathway was not preferred and MnS formed from this pathway was insignificant in Figure c. In addition to direct reduction of formed MnSO 4 , as presented above, MnS was more likely to be formed by another pathway as follows.…”

“…For MnSO 4 identified after the YN coal reaction with the prepared mixed OC shown in Figure 4c, it was easy to form via capture of SO 2 emitted in eqs 1−3 by reduced MnO in the presence of O 2 , 53 as shown in eq 9.…”