Novel Fluidized Bed Reactor for Integrated NO_x Adsorption−Reduction with Hydrocarbons

Abstract

In order to avoid the negative impact of excessive oxygen in the combustion flue gases on the selectivity of most hydrocarbon selective catalytic reduction (HC-SCR) catalysts, an integrated NO(x) adsorption-reduction process has been proposed in this study for the treatment of flue gases under lean burn conditions by decoupling the adsorption and reduction into two different zones. The hypothesis has been validated in a novel internal circulating fluidized bed (ICFB) reactor using Fe/ZSM-5 as the catalyst and propylene as the reducing agent. Effects of propylene to the NO(x) molar ratio, flue gas oxygen concentration, and gas velocity on NO(x) conversion were studied using simulated flue gases. The results showed that increasing the ratio of HC:NO improved the reduction performance of Fe/ZSM-5 in the ICFB reactor. NO(x) conversion decreased with an increasing flue gas flow velocity in the annulus U(A) but increased with an increasing reductant gas flow velocity in the draft tube U(D). The NO(x) adsorption ratio decreased with increasing U(A). In most cases, NO(x) conversion was higher than the adsorption ratio due to the relatively poor adsorption performance of the catalyst. Fe/ZSM-5 showed a promising reduction performance and a strong inhibiting ability on the negative impact of excessive O2 in the ICFB reactor, proving that such an ICFB reactor possessed the ability to overcome the negative impact of excessive O2 in the flue gas using Fe/ZSM-5 as the deNO(x) catalyst.

NOx adsorption and reduction with C3H6 over Fe/zeolite catalysts: Effect of catalyst support

“…To overcome this problem, an internal circulating fluidized bed (ICFB) reactor with integrated NO x adsorption-reduction has been proposed to mitigate the negative impact of excess O 2 in the flue gas [11,12]. The SCR catalysts with good adsorption capacity and reduction of NO x are important for ICFB reactor.…”

Catalytic Performance of NO Reduction by CO over Activated Semicoke Supported Fe/Co Catalysts

“…However, reactor design is a possible way to overcome the oxygen inhibition effect. For example, in the internal circulating fluidized bed (i-CFB) proposed by Yang and Bi, − NO x adsorption and reduction were set into two different zones by separating the gas streams of flue gas and reducing gas. Thus, reducing gas will not get in touch with oxygen in the flue gas and the negative effect of oxygen could be avoided.…”

Catalytic NOx Reduction in a Novel i-CFB Reactor: I. Kinetics Development and Modeling of Reduction Zone

“…The configuration of the fluidized bed and details of the experiment were shown in a previous work. 7 The data will later be used for the evaluation of fluidized bed reactor model. The experimental conditions of both the fixed and fluidized beds were summarized in Table 1.…”

“…As a technology under development, selective catalyst reduction by hydrocarbon (HC-SCR), which uses hydrocarbons as the reducing agent, shows satisfactory performance in deNO x reactions, 2 although the conversion efficiency is significantly affected by the oxygen concentration present in the flue gases. 3−6 To avoid the negative impact of excess O 2 and other poisoning components in the flue gas, Yang and Bi 7 proposed a new integrated NO x adsorption-reduction process, where the NO x adsorption and reduction are carried out in two separate zones of the reactor. The flue gas is passed into the adsorption zone where NO x is absorbed by the catalyst.…”

“…To avoid the negative impact of excess O 2 and other poisoning components in the flue gas, Yang and Bi proposed a new integrated NO x adsorption-reduction process, where the NO x adsorption and reduction are carried out in two separate zones of the reactor. The flue gas is passed into the adsorption zone where NO x is absorbed by the catalyst.…”