Reduction characteristics of NOX emissions by optimal urea injection rate in a LPG steam boiler with urea-SCR reactor
The aim of this study is to develop the urea-SCR reactor aftertreatment system for reducing NOX emissions in a LPG steam boiler. The urea-SCR system utilizes ammonia converted from 17% aqueous urea solution injected in front of the SCR catalyst as a reducing agent for reducing NOX emissions. In this study, NOX emissions and exhaust gas temperatures according to boiler load were measured and compared with before and after urea injection in a LPG steam boiler with urea-SCR reactor. Also, the equivalence ratio, urea injection rate, ammonia slip and NOX conversion rate relative to boiler load were investigated. The equivalence ratio is different by changing the fuel consumption rate or intake air rate. In this experiment, the average equivalence ratio is calculated by changing only fuel consumption rate while the intake air rate is constantly fixed at 25,957.11 cm3/sec. The average equivalence ratios are 1.38, 1.11, 0.81 and 0.57 when boiler loads are 100, 80, 60 and 40%. In this experiment, NOX conversion rates are calculated by 89, 85, 77 and 79% in cases of the boiler loads of 100, 80, 60 and 40%. NOX conversion rate is raised with increasing urea injection rate, and NH3 slip is boosted at the same time. Consequently, the optimal urea injection rate for the respective boiler load should be determined by considering NOX conversion rate and NH3 slip simultaneously. In this study, the urea flow rates of 230, 235, 233 and 231 mg/min are injected at the boiler loads of 100, 80, 60 and 40%, and the final NH3 slips are measured by 8.48, 5.58, 11.97 and 11.34 ppm at the same conditions.
A study on performance and smoke emission characteristics by blending low purity methanol in a DI diesel engine with the EGR rates of 0, 12.8 and 16.5%
The purpose of this study is to investigate experimentally the effect of low purity methanol (LPM) on performance and smoke emission characteristics by using a four-cycle, four-cylinder, water-cooled, direct injection diesel engine with EGR system. The experiments are performed by the change of engine load in the engine load ranges of 25 to 100% with an interval of 25% under the constant engine speed of 2000 rpm. The LPM in the fuel blends contained 24.88% water by volume. The blended fuel ratios of diesel oil to LPM are maintained at 100/0, 95/5, 90/10 and 85/15% on the volume basis. In this paper, EGR rates are varied in three conditions of 0, 12.8 and 16.5%. The result shows that the brake power of a blended fuel with 15% LPM is reduced more 11.1% than that of the neat diesel oil at the full load with the EGR rate of 16.5%. At this condition, also, the brake specific fuel consumption (BSFC) is increased by 3.2%, the exhaust gas temperature is decreased by 10.7%, the smoke opacity is decreased by 18.7% and the brake thermal efficiency is increased by 7.3%. The sharp reduction of smoke opacity for a blended fuel with the LPM content of 15% at the full load without EGR system is observed by 68.4% compared with that of the neat diesel oil due to the high oxygen content of LPM.
A conceptual model for soot formation in pyrolysis of aromatic hydrocarbons
Abstract Soot formation in toluene-argon mixtures has been investigated behind reflected shock waves by monitoring attenuation of a laser beam in both the visible (632.8nm) and the infrared (3.39 μm) regions of the spectrum. The experiments were carried out at nearly constant total carbon atom concentration over temperature and pressure ranges of approximately 1500–2300K and 0.03–0.3 MPa, respectively. The experimental data indicate that there is a strong pressure effect on soot formation at lower pressures. The bell-shaped dependence of soot conversion on temperature shifts toward higher temperatures with decreasing pressure. The observed phenomenon can not be rationalized within Graham's model. A new conceptual model for soot formation is proposed that not only explains the current results but also unifies the various experimental facts which previously had been considered to be contradictory. The ratio of induction times for soot appearance in the visible and infrared regions was observed to be approximately constant over a wide temperature range, which is also in harmony with the proposed model.