Heterogeneous Ammonia Storage Model for NH₃–SCR Modeling

Abstract

Single-and dual-site ammonia storage models are initially developed and calibrated from ammonia TPD experiments. The dual-site model gives better agreement with the experimental measurements, but neither of these models is able to adequately represent the observed ammonia storage trends over a wide range of temperatures. An alternative heterogeneous single-site model considering the heterogeneity of ammonia storage sites is proposed that more accurately predicts ammonia storage in the temperature window of 150 °C−400 °C. When the heterogeneous storage site model is combined with kinetics for NH 3 and NO oxidation for simulating standard SCR, the NH 3 and DeNO x trends as well as the NH 3 inventories during reaction conditions reported for lab reactor studies are replicated.

Development of a Nonequilibrium Multisite Kinetic Model for NH3-SCR of NOx on CHA Cu-SAPO-34: Impact of Active Site Configurations and Locations

“…The desorption peak is accordingly represented by both S1 and S2 sites, where the NH 3 coverage dynamic, Figure A, indicates the complete desorption of NH 3 from these sites above 500 °C. The S2 desorption dynamic centred around 360 °C is in accordance with the desorption from bridged Brønsted acid sites. − The tuned activation energies for both sites: and , respectively, are in agreement with those reported in the literature for Cu-CHA catalysts using same kind of estimation. , …”

“…However, some assumptions are also made, for example, total storage capacity and redox reactions can take place on the same single active site, which allows faster simulation, as reported by De-La-Torre et al, for steady state SCR process investigations or, as reported by Supriyanto et al, for hydrothermal aging modeling. Nevertheless, for NH 3 adsorption and desorption dynamic at high and low temperatures, at least two sites are generally adopted for better representation. ,, For instance, three sites were employed to model NH 3 storage capacity on Fe-zeolite catalysts, as reported by Skarlis et al, accurately representing the different NH 3 -temperature-programmed desorption (TPD) profiles of weak and strong acidic and nonacidic sites. Olsson et al used also three active sites to simulate the SCR behavior of Cu-CHA and storage capacity.…”

Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

“…The exhaust line was not equipped with a clean-up catalyst (CUC) to oxidise excessive ammonia, and therefore, sudden release of NH 3 was noted with the gas-temperature increase. The NH 3 storage capacity of an SCR catalyst is inversely proportional to its temperature, and therefore, the greater the temperature the less NH 3 can be stored inside the catalyst [20][21][22]. The NH 3 concentration measured downstream of the SCR was greater for the gaseous urea system for both α = 0.8 and α = 1.0.…”

Predictor and optimizer system on selective catalytic reduction of NO in activated carbons based on experiment and computational intelligence technique

“…Among them, NH 3 -SCR using ammonia is a mature and reliable technology and kinds of composite metals are widely used as catalysts for NH 3 -SCR reactions. Gao (Gao et al, 2013) summarized NH 3 -SCR catalyzed by Cu-SSZ-13.Gong (Gong et al, 2016) used Cu-chabazite as NH 3 -SCR adsorption and desorption catalyst, and an alternative ammonia storage model was developed by considering the heterogeneity of ammonia storage sites. Kamasamudram et al (2010) introduced a new class of SCR catalysts based on Cu-exchanged or Fe-exchanged zeolites and provided a comprehensive overview of multiple catalytic functions using select data from various catalysts.…”