A heavy duty truck includes a diesel engine that generates an exhaust gas flow and an exhaust after-treatment system for treatment of the exhaust gas flow. The exhaust after-treatment system includes at least one temperature sensor at an underbody SCR system within the exhaust after-treatment system and a DEF injector upstream of a close-coupled SCR system within the exhaust after-treatment system. The DEF injector is operated to inject DEF into the exhaust gas flow at a rate that varies as a function of a temperature measured by the temperature sensor.

An exhaust system for a diesel engine is provided. The exhaust system includes a component body with a surface, and a surface treatment disposed on some of the surface or all of the surface. The surface treatment is disposed so as to receive Diesel Exhaust Fluid (DEF) injected into the exhaust system during operation of the diesel engine. The surface treatment facilitates increased heat transfer to the received DEF to promote water evaporation and urea thermolysis of the received DEF.

A catalytic converter includes at least one heating element that is configured to disrupt the direction of flow of exhaust gases which contain harmful toxic gases and pollutants and aid in removing and/or reducing said toxic gases and pollutants.

A catalyst converter includes: a substrate (1) having a cell structure formed of a center area (1A) having the highest cell density, a peripheral area (1C) having the lowest cell density, and an intermediate area (1B) having the cell density between that of the center area and that of the peripheral area; a first catalyst layer formed in the center area (1A); a second catalyst layer formed in the intermediate area (1B); and a third catalyst layer formed in the peripheral area (1C). A length in a longitudinal direction of the second catalyst layer is longer than that of the first catalyst layer. A length in the longitudinal direction of the third catalyst layer is longer than that of the second catalyst layer. A ratio of the length in the longitudinal direction of the first catalyst layer to the length of the substrate is 65% or more.

In an exhaust gas purification system provided with a denitration catalyst layer, a reducing agent oxidation catalyst layer is installed together; a reducing agent and air are supplied into the reducing agent oxidation catalyst layer at the time of catalyst regeneration of the denitration catalyst layer; a high-temperature oxidation reaction gas is produced by a reaction heat generated by an oxidation reaction of the reducing agent and the air in this reducing agent oxidation catalyst layer; and this high-temperature oxidation reaction gas is introduced into the denitration catalyst layer to heat the denitration catalyst, thereby recovering a denitration performance of the catalyst.

A plasma selective catalytic reduction (SCR) system according to an exemplary embodiment of the present invention includes: an exhaust pipe connected to an engine to communicate exhaust gas; a plasma burner installed in a first bypass line connected to the exhaust pipe, and configured to supply fuel to discharged plasma and form flame; a urea solution injector installed in the first bypass line at a rear side of the plasma burner, and configured to inject a urea solution to exhaust gas heated by the flame and generate ammonia; and an SCR catalyst installed in the exhaust pipe at a rear side of the urea solution injector, and configured to reduce a nitrogen oxide included in the exhaust gas with the ammonia.

The honeycomb structure includes a honeycomb structure body made of a zeolite material containing at least a coarse particle zeolite having a large average particle diameter (coarse zeolite particles). A fine particle zeolite having an average particle diameter smaller than that of the coarse particle zeolite (fine zeolite particles), and an inorganic bonding material, the coarse particle zeolite (the coarse zeolite particles) is a chabazite type zeolite in which an average particle diameter of primary particles is 2 μm or more and 6 μm or less, and in the fine particle zeolite (the fine zeolite particles), an average particle diameter of primary particles is 0.02 μm or more and smaller than 2 μm, and in the zeolite material which is comprised the honeycomb structure body, a ratio of a volume of pores having pore diameters of 0.02 to 0.15 μm to a volume of all pores is 42% or less.

A honeycomb structure includes: a honeycomb structure body including a plurality of cells; and a plugging portion to alternately plug open end parts of the plurality of cells on one side as an inflow side of the exhaust gas and open end parts on the other side as an outflow side of the exhaust gas. The partition wall is loaded, on the side of the outflow cells, with an oxidation catalyst made of a transition metal oxide to oxidize NO gas or an oxidation catalyst made of a transition metal oxide loaded at CeO.sub.2 to oxidize NO gas. The partition wall has porosity of 70% or less, the oxidation catalyst has a particle diameter of more than 1 μm and less than 50.0 μm, and the loading amount of the oxidation catalyst is 5.0 g/L or more and 50 g/L or less.

A reducing agent injection device includes a honeycomb structure and a urea spraying device spraying a urea water solution in mist form. In addition, the reducing agent injection device includes a carrier gas inlet that introduces carrier gas f between the urea spraying device and the honeycomb structure. The exhaust gas treatment method of the present invention supplies the urea water solution from the urea spraying device into the cells from the first end face of the honeycomb structure body to generate the ammonia, while introducing the carrier gas f from the carrier gas inlet, and injecting the ammonia to the outside to treat exhaust gas containing NO.sub.X.

A reducing agent injection device includes a honeycomb structure and a urea spraying device spraying a urea water solution in mist form. A pair of electrode members is formed in the honeycomb structure. The honeycomb structure of the reducing agent injection device, the hydraulic diameter HD, defined as HD=4×S/C, when the area of the cross section of one of the cells in the cross section perpendicular to the cell extending direction is S, and the peripheral length of the cross section of one of the cells is C, is 0.8 to 2.0 mm. Also, the open frontal area OFA of the honeycomb structure in the cross section perpendicular to the cell extending direction is 45 to 80%.