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The performance of selective catalyst reduction systems highly depends on the degree of mixing between NH 3 and NO x and the flow uniformity of velocity and concentration, which are sensitive to several parameters such as the installment of gate leafs, a hybrid grid, a straightener, and the ammonia injection method. In this work, computational fluid dynamics was applied to investigate these parameters in heat recovery steam generators. Performance of gate leafs and a new type of hybrid grid was considered. Analyses showed that gate leafs significantly improved the uniformity of velocity distribution and that the new type of hybrid grid improved the uniformity of concentration distribution. The velocity relative standard deviation decreased from 19.6% to 5.4%, and the concentration relative standard deviation decreased from 70% to 12.7%. Experiments also qualitatively confirmed the reliability of simulation results. Moreover, the hybrid grid was optimized with different structures. Results indicated that a 30° crossed angle could obtain a better mixing between NH 3 and NO x with a slight decrease in pressure. In addition, an optimal injection method of the ammonia injection grid was designed, and it was helpful in conducting the field operation. The relationship between the thickness of the straightener and the incident angle at the entrance of catalyst layer was discussed., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

[Display omitted] • The performance and mechanism of CO 2 capture by amine blended solvents were reviewed. • The technology of simultaneous removal of CO 2 /NOx/SO 2 by ammonia was discussed. • The industrial challenges during CO 2 capture were summarized. • The specific directions have been proposed for the future development. Absorption/regeneration systems based on chemical solutions are considered a more appropriate option for post-combustion CO 2 capture, with amine solvents being the most commonly utilized. First, this paper provides a systematic review of the mechanisms and performance of CO 2 capture by blended solvents of amine–amine, amine-organic solutions, amine-inorganic solutions, and amine-ionic liquids. Furthermore, some process modifications that can reduce energy consumption and amine degradation during CO 2 capture are discussed. As a promising and challenging absorbent, aqueous ammonia shows potential for simultaneous removal of CO 2 /NOx/SO 2 , producing valuable byproducts like ammonium sulphate and ammonium nitrate fertilizers. Therefore, the current development of ammonia scrubbing techniques for CO 2 capture and simultaneous removal of CO 2 /NOx/SO 2 is subsequently reviewed in terms of reaction mechanisms, process modifications, and application challenges. Finally, specific directions have been proposed for the future development of amine and aqueous ammonia scrubbing techniques, which are expected to provide meaningful guidance for CO 2 capture by chemical absorption. [ABSTRACT FROM AUTHOR]

Highlights: [•] MnO x –CeO2–ZrO2/γ-Al2O3 catalyst showed high SCR activity at low temperature. [•] MnO x –CeO2–ZrO2/γ-Al2O3 catalyst was well-behaved in the presence of SO2 and H2O. [•] NO and NH3 could be adsorbed on the catalyst in different forms. [•] The SCR reaction route followed both of the E–R mechanism and L–H mechanism. [Copyright &y& Elsevier]

Abstract: Currently, selective catalytic reduction (SCR) of NO x with NH3 has been widely applied to reduce the emission of nitrogen oxides from mobile and stationary sources. But the detailed SCR reaction mechanism is still controversial and lacks the related comparative study of molecule modeling. The SCR reaction belongs to the gas–solid multiphase reaction, in which the adsorption of NH3 and NO by the catalysts plays an important role. In the present study, the adsorption properties of NH3 and NO on both the dry and partially hydroxylated γ-Al2O3 (110) surfaces supported CuO were revealed using the density-function theory (DFT) calculations. The results showed that NH3 could be adsorbed strongly on the dry (110) surface in the form of coordinated NH3 and NH4 +. Some of the coordinated NH3 could then undergo H-abstraction and form the –NH2 species. NO could be adsorbed weakly on the dry surface, and could also be adsorbed as bidentate nitrates or bridged nitrites. However, the adsorption activation of NH3 and NO on the partially hydroxylated surface was much weaker. The results of the DFT calculations are in good agreement with the experimental results and provided detailed clues to understand the adsorption mechanism of NH3 and NO on the CuO/γ-Al2O3 catalysts. [Copyright &y& Elsevier]