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NOx emissions in compression-ignition engines can be reduced, either through the application of engine-internal methods, i.e., making sure that as little NOx as possible is produced as a result of the mixture combustion processes, or through the use of catalytic converters designed to reduce nitrogen oxides, including NH3-SCR or HC-SCR converters. Converters using ammonia offer high conversion rates, but they tend to be problematic in terms of their operation. For this reason, converters using hydrocarbons for the purpose of NOx reduction have been gaining in popularity. An Ag/Al2O3-SiO2 converter is an example of such a catalytic converter. This paper describes the process of preparing such a converter and characterises the porosity and acidity of its surface. The dispersion of silver was assessed based on oxygen absorption tests on crystallites of sliver and based on TEM images of crystallites of silver. The conversion of NO2, NO and propane was assessed depending on the temperature. Additionally, NO2, NO and propane conversion was assessed at 500 °C, depending on the admixture of a reducer, and propane selectivity in the process of reduction of NO to N2 was calculated. The test results indicate that the developed converter can be considered the basis for further research into the development of this compression-ignition engine exhaust after-treatment technology. [ABSTRACT FROM AUTHOR]

It is known that biogas without prior purification to biomethane is a commonly used fuel only for the stationary internal combustion engines but not for vehicle engines. The current study evaluates the use of biogas without its prior upgrading to biomethane as fuel for tractor engines. The following tests were carried out: biochemical methane potential tests, dynamometer engine tests, and field tests with the use of a tractor. The average methane content in biogas obtained from vegetable wastes exceeded 60%. The tests performed on the engine dynamometer showed that the engine powered by dual fuel worked stably when diesel was replaced by 40% biogas (containing 50% of CO2) or 30% methane. Dual fuel supplying of the engine caused an increase in the concentration of hydrocarbons and carbon monoxide in the exhaust gases and a decrease or no effect in the concentration of particulate matter and nitrogen oxides. It did not significantly affect the dynamics of the vehicle and its useful properties. Biogas that contains a maximum of 50% CO2 and from which H2S, moisture, and siloxanes have been largely removed, is suitable as a fuel for tractors. Such biogas can be obtained in biogas plants from different substrates, e.g., vegetable or agriculture wastes as well as biodegradable municipal wastes. [ABSTRACT FROM AUTHOR]