Augmenting NO _x reduction in diesel exhaust by combined plasma/ozone injection technique: a laboratory investigation

Abstract

With the advent of non-thermal plasma technique for diesel exhaust treatment attention is being focused on reducing oxides of nitrogen (NO x) both from stationary as well as automobile sources. In this work, an attempt has been made to enhance NO x reduction only by utilising a plasma/ozone injection approach without resorting to additional treatments based on catalysts/adsorbents. It was observed that cascading ozone injection with discharge plasma enhances the reduction of NO x as high as 95% for the specific energy of 123 J/l. In the long run, this plasma-only based approach may be beneficial or a possible alternative for catalyst/adsorbent based NO x treatments. The results have been discussed and a comparative analysis has been made with respect to individual plasma and ozone injection treatment.

High Reduction Efficiencies of Adsorbed NOx in Pilot-Scale Aftertreatment Using Nonthermal Plasma in Marine Diesel-Engine Exhaust Gas

“…The engine operation was stopped once during each process. Figure 7 shows the time-dependent NO x emissions before and after the gas passes through the aftertreatment for cycles [16][17][18][19] represent the transition of the adsorbent from the unsteady state to the steady state. The engine load is set as 75% for all adsorption processes and 50% for all desorption processes, considering the exhaust-gas temperatures for the adsorption and desorption of NO x .…”

“…The desorption of NO x is enhanced in cycle 19. Figure 8 shows the time-dependent temperature of the adsorbent pellets in cycles [16][17][18][19]. At the beginning of each adsorption process, the adsorbent temperature is high because of residual heat from the previous desorption process.…”

“…Consequently, the appropriate temperatures are achieved for both the adsorption and desorption processes. Table 4 shows the resulting adsorbed, desorbed, reduced, and treated amounts of NO x in cycles [16][17][18][19], as well as the gaseous flow rates and energy efficiencies in aftertreatment. The adsorbed mass of NO x , W a , ranges from 855 to 1651 g(NO 2 ).…”

“…In the desorption process of cycle 19, the NO x concentrations upstream and downstream of the NTP generator are 5610 and 1620 ppm, respectively. Figure 9 shows the relationship between the mass of desorbed NO x and the reduction energy efficiency in the NTP treatment in the desorption processes of cycles [16][17][18][19]. The data for the desorption processes of cycles 5-12 of the previous experiments [2] are also shown.…”

“…However, SCR requires a high temperature of 300 • C for catalyst activation, and there are issues regarding the production of nanoparticles, leakage of harmful ammonia, use of harmful heavy-metal SCR catalysts, and storage of the urea solution. Additionally, NO x reduction technologies using NTP without a catalyst have been investigated [17,18].…”