Selective Catalytic Reduction Applications Research Articles

Deactivation of a Fe-ZSM-5 catalyst during the selective catalytic reduction of NO by n-decane: An operando DRIFT study

The selective catalytic reduction (SCR) of NO by n-decane was investigated on a Fe-ZSM-5 prepared by the FeCl3 sublimation method. NO conversion profiles versus temperature were followed in both temperature programmed surface reaction (TPSR, 10°Cmin−1) and steady state experiments. A higher NO conversion with a maximum of ca. 80% at 400°C is observed in the course of the TPSR tests. This phenomenon has been attributed to strong adsorption of n-decane which protects the active sites against the poisoning. Indeed, in steady state experiments at 390°C the strong decrease of activity as a function of time on stream is due to the polymerisation of conjugated nitriles. This study indicates that long chain alkanes are not the most adequate reductants of NO for high temperature SCR applications. Moreover, due to an easier polymerization of conjugated nitriles on iron zeolites (stronger Fe Lewis sites), this type of catalyst seems less attractive than Cu-zeolite catalysts for the SCR of NO by hydrocarbons in this respect.

脱硝装置付き低速ディーゼル機関の運転動特性

In the 2-stroke diesel engine power plant, application of SCR (Selective Catalytic Reduction System) in between engine's cylinder exhaust gas outlet and the turbo-charger is one solution to get higher NOx reduction rate.In this case well know phenomena is unstable engine operation due to rather large heat mass of the SCR, specially during engine load up and down program.This paper shows that this phenomena is soluble by installing exhaust gas extract valve and adequate active valve control, also shows the outline of mathematical anlytic evaluation model and the test results on the actual power plant.

Study of catalytic reduction of NO x in exhaust gas from a diesel engine

We experimentally evaluate applying a deoxidizer-injected TiO 2–V 2O 5 catalyst reactor apparatus to reduce the concentration of NO x in the exhaust gas of a conventional diesel engine. In this application of selective catalytic reduction (SCR), the deoxidizer, i.e., a urea solution used as a reducing agent, is mixed with exhaust gas and the effects of reaction temperature, space/linear velocity, and the amount of urea solution on the NO x removal rate are considered. We found that (i) the catalytic material substantially reduces the NO x concentration at a catalyst bed temperature from 190°C to 440°C, (ii) the NO x removal rate is 95% at a reaction temperature of >400°C and space velocity of 22 500 h −1, (iii) the particulate matter (PM) contained in diesel exhaust probably causes a significant reduction in NO x removal, and (iv) the emission of N 2O during the denitration process is <15 ppm. Also discussed are the results of an urban driving test using a diesel-engine truck equipped with the presented apparatus, as well as needed improvements associated with practical application.

Is advanced SCR technology at a standstill? A provocation for the academic community and catalyst manufacturers

Despite extensive contributions to the literature since 1975 regarding selective catalytic reduction (SCR) catalysis with ammonia for NO x removal from combustion gases, there is still on-going, controversial discussion in academia concerning both catalytically active sites in the SCR mechanism and deactivation phenomena with regard to practical SCR applications. New developments such as SCR of NO x by hydrocarbons are still thwarted by problems relating to the development of suitable materials. Efforts to replace SCR technology by selective catalytic decomposition (SCD) for NO remain confused in both theory and experiment.

Pillared clays as superior catalysts for selective catalytic reduction of nitric oxide with ammonia

Five pillared clays (PILC) have been synthesized and tested for their activities in the selective catalytic reduction (SCR) of NO by NH 3 in the temperature range 250-450°C. They all showed considerable activities, in the decreasing order Cr 2 O 3 -PILC, Fe 2 O 3 -PILC, TiO 2 -PILC, ZrO 2 -PILC, and Al 2 O 3 -PILC. Cr 2 O 3 -PILC exhibited higher activities than a commercial (VTT) WO 3 -V 2 O 5 /TiO 2 catalyst, but its activity was severely decreased by SO 2 . Fe 2 O 3 -PILC showed activities comparable to that of V 2 O 5 /TiO 2 and was SO 2 resistant. Doping with cerium oxide significantly enhanced the activity; for Fe 2 O 3 -PILC, doping with 1.5-2% CeO 2 more than doubled its activity, and the resulting activity was significantly higher than that of the VTT commercial catalyst (both with and without SO 2 and H 2 O). The formed PILC catalyst will have a bimodal pore structure, with which a superior poison resistance has been demonstrated in SCR operation with a V 2 O 5 -based catalyst. Thus, the high activities and the potential poison resistance make pillared clays a promising new class of catalyst for SCR applications

Application of selective catalytic reduction (SCR) technology for NOx reduction from refinery combustion sources

AbstractSelective Catalytic Reduction (SCR) has been applied as a NOx abatement technique for stationary sources of nitrogen oxides (NOx) in Japan since the early 1970s. To date, there are over 100 SCR installations operating in Japan.During the 1980s, a number of SCR systems have been installed in the United States, primarily in California. Among these applications are fired heater, boiler, and gas turbine/heat recovery steam generator (HRSG) installation. These installations provide a basis to assess the state‐of‐the‐art for applying SCR to comply with refinery NOx emission limitations.

Sorbent and ammonia injection at economizer temperatures upstream of a economizer temperatures upstream of a high—temperature baghouse

AbstractThe current technology of choice—world–wide—for post–combustion NOx control is selective catalytic reduction (SCR) with ammonia. The application of SCR to coal–fired units has proven to be somewhat more difficult than its application to natural gas and oil–fired units due to SO2 poisoning of the catalyst, catalytic oxidation of SO2 to SO3, and erosion and fouling of the catalyst by fly ash [1]. These problems could be potentially diminished if SO2 and particulate removal systems were placed upstream of the SCR reactor. However, this is not easily accomplished since SCR systems operate best in the temperature range of 600°F–800°F (315°C–425°C). Several SCR installations in Europe employ conventional flue gas desulfurization (FGD) and particulate control upstream of flue gas reheat and SCR. However, the flue gas reheat typically imposes a 1%–2% energy penalty [2]. Several recent technical developments now offer a technology whereby these limitations of SCR for coal applications can be alleviated.These technical developments are in the areas of high temperature filtration, improved SCR catalysts, and advances in sorbent injection. These advances have been incorporated into a patented process known as the SOxNOxRox Box™ (SNRB) process. Briefly, this process consists of a “hot” baghouse employing woven ceramic fabric bags, a zeolite SCR catalyst incorporated into the baghouse, and the injection of either calcium–or sodium–based sorbent upstream of the baghouse (see Figure 1).This paper deals with the status and development of the SNRB process, including some results from recently completed pilot–plant tests performed under a contract with the Ohio Coal Development Office (OCDO).