Space velocity in catalytic converter

The emission durability depends on the quality of the catalyst coating and on the operating conditions such as temperature or levels of catalyst poisons in the exhaust gas. The catalytic converter design has to provide the required mechanical system durability.

Despite exposure to high temperatures and thermal shock, moisture and corrosive environments, as well as mechanical vibration Table 1 [] , they endure hundreds of thousands of kilometers. The final mechanical durability of the emission control system is a combination of the substrate durability, durability of packaging materials and packaging technology.

Since the diesel engine is more durable than its gasoline counterpart, the required life expectancy for diesel catalytic converters is also longer than that for gasoline converters. In situations where thermal losses from the converter are important, they have to be modeled during the converter design. Double walled designs with either air gaps or ceramic fiber insulation are commonly used on gasoline converters in the close-coupled location, which are optimized for cold start hydrocarbon performance.

Since diesel cold start emissions are much less critical, such designs have not been used for diesel converters. However, due to the low temperature of diesel exhaust gases, diesel converters should be placed close to the exhaust manifold or exhaust pipe insulation should be applied to assure satisfactory catalyst performance.

Hansel, K. Aykan, J. Event: Automotive Engineering Congress and Exposition. Related Topics: Exhaust emissions Catalytic converters Catalysts. Preview Document Add to Cart. Login to see discount. Most catalysts in all of the above applications use noble, platinum group metals as their active components. Following the success in mobile engine applications, catalyst technologies were introduced for stationary applications, for the control of volatile organic compounds VOC and NOx emissions.

The list of catalyst applications covers such emission sources as chemical plants, painting and coating processes, ovens, printing, dry cleaning, power generation, and, last but not least, stationary engines. Examples of catalyst technologies for stationary engines include non-selective catalytic reduction NSCR of NOx from rich burn natural gas engines and selective catalytic reduction SCR of NOx by ammonia from diesel engines. The wide acceptance and popularity of catalysts for emission control from internal combustion engines can be attributed to a number of advantages, as follows:.

Catalysts also have a number of disadvantages and potential issues, which need to be carefully observed when designing emission control systems.