Papers by Keyword: NO_x Reduction

Abstract: This study investigates numerically the NOx reduction by SNCR in a CO boiler. The combustion and fluid flow in the FPC CO boiler is examined with emphasis on the influence of the injection position of reducing agent on NOx reduction. Simulation results indicate that NOx is formed mainly in the high temperature region near the boiler inlet where the mixing caused by swirler is strong. Among the reducing agent injection positions investigated, the boiler inlet has the best NOx reduction efficiency, while 0.5m behind the boiler inlet is the worst. When reducing agent is injected from the boiler inlet, a NOx reduction efficiency of 51% is achieved if default amount of reducing agent is injected. When reducing agent is injected from 3.6m behind the boiler inlet, the NOx reduction efficiency is 14% for default amount of reducing agent. The injection position of reducing agent has a siginificant influence on the NOx reduction efficiency. Better injection positions for NOx reduction should be where reducing agent can pass through a region where temperature is suitable for the SNCR reaction or residence time of reducing agent in the SNCR reaction region can be longer, e.g., the boiler inlet or the downstream region of the oxidizer lower portion where recirculation exists.

Abstract: The performance of Pd/TiO₂/Al₂O₃ catalyst for the NO_x reduction in the CO-rich conditions of simulated post Euro-IV diesel emissions at low temperature was investigated in this paper. The addition of a small amount of H₂ resulted in a visible synergetic effect. And the total amount of mixed reductant also improved the NO_x convertion. The catalyst showed NO_x conversions exceed 40% at 100~250°C when the reductant amount is 8,000 ppm with the H₂/CO ratio of 1:3, where water vapor is absence. Even though water vapor had a negative influence, 25~33% of NO_x can be decomposed using this catalyst, which is meaningful considering that it is used in a passive system.

Abstract: This paper presents the effect of inserting swirler outlet orifice plate of different sizes at the exit plane of the radial air swirler in liquid fuel burner system. Tests were carried out with three different orifice plates with area ratios (orifice area to swirler exit area ratio) between 0.7 and 1.0 using 280 mm inside diameter combustor of 1000 mm length. Several tests were conducted using the commercial diesel as fuel. The fuel was injected at the back plate of the 45^o vane angle swirler outlet using a central fuel injector with a single fuel nozzle pointing axially outwards. The aim of the insertion of orifice plates is to create the swirler pressure loss at the swirler outlet phase in order to maximise the swirler outlet shear layer turbulence to assist the fuel/air mixing. In the present work, the orifice plate with smaller area ratios exhibited very low NO_X emissions for the whole operating equivalence ratios. The NO_X reduction of more than 20 percent is achieved for orifice with 0.7 area ratio compared to 1.0 area ratio. Other emission such as carbon monoxide is increased with the decrease in the orifice area ratios. The results from this experiment show that good combustion is achieved by using smallest area ratios of orifice plate.

Abstract: The performance of various noble metal based catalysts for the NO_x reduction in the CO-rich conditions of simulated post Euro-IV diesel emissions at low temperature was investigated in this paper. Pd loaded catalyst showed higher catalytic activity than Ir or Rh loaded catalysts. Titania, as one of the support material, clearly promoted the deNO_x process due to the synergy with alumina and Palladium. The TiO₂ loading was optimized subsequently. As a result, Pd/TiO₂/Al₂O₃ catalyst with Pd loading of 2.0 wt.% and TiO₂ loading of 10 wt.% showed the NO_x conversions of 25~46% in the temperature range of 200~250°C.

Abstract: This paper presents anexperimental study on reduction of NO_x emission of a turbochargedengine fuelled with DME by means of EGR. Effects of EGR rate on engineefficiency and emission behavior was evaluated. The results show that the EGRcould be used as an effective way to reduce NO_x emission. NO_x isreduced almost linearly with increase of EGR rate. At low load condition, theNO_x emission is reduced by 80% with 40% EGR rate without any economypenalty. At high load condition, the same substantial reduction of NO_x couldbe achieved with only 20% EGR rate. While the HC and CO emissions are increasedwith increase of EGR rate. However, it is worth noting that EGR had a negativeeffect on fuel consumption at high load. Low EGR ratio should be taken at highengine load condition.

Abstract: To meet stringent exhaust emission norms worldwide, various exhaust pre-treatment and post-treatment techniques have been employed in modern engines. Using antioxidant additives in biodiesel fuels is a promising and effective NO_x reduction technology. Non-edible jatropha oil based methyl ester was produced and blended with conventional diesel. Five fuel samples (Diesel, JB5, JB5DPPD0.15%, JB15 and JB15DPPD0.15%) were tested for their use as substitute fuel for a radiator-cooled four cylinder diesel engine. Experiment results show that DPPD antioxidant additive could be reduced NO_x emission significantly with slight penalty on engine performance as well as CO and HC emission. However, when compared to diesel combustion the emissions of HC and CO were found nearly same or below. By addition of 0.15% (m) DPPD additive in JB5 and JB15 reduction of NO_x emission were 12.68% and 13.36 % compared to biodiesel blends without additive at full throttle position. As conclusion, JB5 and JB15 with addition of 0.15% (m) can be used in four cylinder diesel engine to reduce NO_x and consequently overcome the barrier to market expansion of biodiesel fuels.

Abstract: A series of coke samples with loading alkali and alkaline earth metals were prepared by the impregnation method, the NOx emission were investigated in a silica fixed bed reactor in the combustion process of raw coke and coke modified by Na, K, Ca and Mg. The results show that Na, K, Ca and Mg play in-situ catalytic effects on the NOx reduction reactions. When the loading amount of Na2CO3 is 2.0%, the NOx reduction ratio was around 17.4%, when the loading of K2CO3 is 2.0%, the amount of NOx emission is reduced by 26.5%. When the loading of CaCl2 is 2.0%, the amount of NOx emission is reduced by 22.3%. When the loading of MgCl2 is 2.0%, the NOx reduction ratio is about 10.9%.

Abstract: Abstract. With the global environment worsening and the consciousness of protecting environment strengthening, the limitation of noxious gas from diesel engines is becoming more and more strictly. Selective catalytic reduction (SCR) aftertreatment system has been applied to reduce Nitrogen Oxides (NOx) as a key technology. The urea solution injected into the tailpipe decomposes to ammonia, which will react with NOx on the surface of SCR catalyst. The main purpose of this paper is to study the effect of different concentrations of NO, NO2 and NH3 on the reactions taking place with SCR catalyst by simulation. Based on mass transfer equations and chemical kinetics the simulation results predict the concentrations of NO, NO2 and NH3 accurately. The mass conservation equations of species are solved by the software MATLAB. Some regulations can be revealed to improve the NOx conversion efficiency and reduced the NH3 slip.

Abstract: The catalytic and electrical properties of an electrochemical NOx reduction system were investigated. A power above 3.5W/cm2 reduced more than 60% of NOx to N2 over the (La,Sr)CoO3-α/Ce0.9Gd0.1O1.95/Pt laminated system in a temperature range of 450°C to 650°C. O2- transportation removed the oxygen around the cathode layer through the Ce0.9Gd0.1O1.95 electrolyte layer, then NO was able to decompose to N2 at the cathode. This ceria-based system exhibited stable NOx reduction with respect to electrical power, regardless of operating temperature.