Current scenario of CNG vehicular pollution and their possible abatement technologies: an overview

Abstract

Compressed natural gas is an alternative green fuel for automobile industry. Recently, the Indian government is targeting to replace all the conventional fuel vehicles by compressed natural gas (CNG) automobiles due to its several merits. Still, the presence of a significant amount of CO, CH 4 , and NO x gases in the CNG vehicle exhaust are quiet a matter of concern. Thus, to control the emissions from CNG engines, the major advances are under development of and oxidation is one of them in catalytic converter. In literature, the catalysts such as noble and non-noble metals have been reported for separate oxidation of CO and CH 4.. Experimentally, it was found that non-noble metal catalysts are preferred due to its low cost, good thermal stability, and molding tractability. In literature, several articles have been published for CO and CH 4 oxidation but no review paper is still available. Thus, the present review provides a comprehensive overview of separate as well as simultaneous CO and CH 4 oxidation reactions for CNG vehicular emission control.

Assessment of Petrol and Natural Gas Vehicle Carbon Oxides Emissions in the Laboratory and On-Road Tests

“…Moreover, the CO emission (Figures 12 and 14) for petrol propulsion would temporarily reach higher values than with natural gas, amounting to approximately 0.3 g/s. Figures [15][16][17][18] show the changes in the cumulative emission values of the pollutants under study versus time. The values of cumulative CO2 emission in the entire on-road test, when the vehicle was fueled with petrol (Figure 15) and then natural gas (Figure 17), show a large difference in emission (approximately 2800 g).…”

“…Increased awareness of the threat posed by CO 2 emissions contributed to the introduction of regulations regarding its emissions from passenger vehicles. The European Union has set a greenhouse gas reduction target of 60% compared to 1990 levels [17]. Data from the European Environmental Agency (EEA) for 2015 [18] confirm that vehicles produced in 2014 achieved the target of 130 g/km CO 2 emissions, while the average emissions were 123.4 g/km.…”

“…The reduced proportion of carbon to hydrogen in the molecule of this fuel, with a high calorific value per unit of mass, allows the reduction in CO 2 emissions. Moreover, the research results presented in the literature show a reduction in the emission of other gaseous pollutants and solid particles in relation to fueling with petrol [42,43] or diesel oil [16,17]. However, when a vehicle is fueled with natural gas, NOx emissions can be significantly higher under heavy load conditions compared to petrol.…”

Recent Developments in Natural Gas Flaring Reduction and Reformation to Energy-Efficient Fuels: A Review

“…During the compression operation (usually multistage), the heavier components (C 5+ components) are condensed out. CNG can be trucked to the nearby gas processing plants, but so far, there are no major CNG projects in operation to utilize the stranded associated gas (methane) by using any seaborne transport …”

Catalyst Conversion Rates Measurement on Engine Fueled with Compressed Natural Gas (CNG) Using Different Operating Temperatures

“…Emissions of toxic compounds from the CNG-fueled engine (without after-treatment systems) and from the low-sulfur diesel vehicle fitted with DPF were lower than from the low-sulfur diesel vehicle fitted with OC. A comprehensive review of separate as well as simultaneous CO and CH4 oxidation reactions to control emissions from CNG vehicles is presented in [25]. PM emission is also a very important emission issue.…”