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%.

Hydrocarbon (HC) traps are disclosed. The HC trap may include a first zeolite material having an average pore diameter of at least 5.0 angstroms and configured to trap hydrocarbons from an exhaust stream and to release at least a portion of the trapped hydrocarbons at a temperature of at least 225° C. The HC trap may also include a second zeolite material having an average pore diameter of less than 5.0 angstroms or larger than 7.0 angstroms. One or both of the zeolite materials may include metal ions, such as transition, Group 1A, or platinum group metals. The HC trap may include two or more discrete layers of zeolite materials or the two or more zeolite materials may be mixed. The multiple zeolite HC trap may form coke molecules having a relatively low combustion temperature, such as below 500° C.

A provision of assemblies and methods for treating an exhaust gas from an internal combustion engine. The treatment method comprises at least two catalyst stages. The exhaust gas is directed to a first stage catalyst. After the first stage catalyst, the exhaust is passed to an inter-catalyst stage comprising an exhaust cooling process and an oxygen enrichment process. Next, the exhaust is passed to a second stage catalyst for reducing carbon monoxide, ammonia and hydrocarbon concentration in the exhaust gas, before exiting via an outlet.

In a broad form the present invention relates to a method for oxidation of a species comprising sulfur in an oxidation state below +4, such as H.sub.2S, CS.sub.2, COS and S.sub.8 vapor, to SO.sub.2 said method comprising the step of contacting the gas and an oxidant with a catalytically active material consisting of one or more elements taken from the group consisting of V, W, Ce, Mo, Fe, Ca, Mg, Si, Ti and Al in elemental, oxide, carbide or sulfide form, optionally with the presence of other elements in a concentration below 1 wt %, at a temperature between 180° C. and 290° C., 330° C., 360° C. or 450° C., with the associated benefit of such a temperature being highly energy effective, and the benefit of said elements having a low tendency to form sulfates under the conditions, with the related benefit of an increased stability of the catalytically active material. The other elements present may be catalytically active noble metals or impurities in the listed materials.

An after-treatment system includes, in series along an exhaust gas flow direction through the after-treatment system: a diesel oxidation catalyst (DOC), a diesel exhaust fluid (DEF) delivery device, a soot-reducing device and a selective catalytic reduction (SCR) catalyst.

A process for the oxidation of hydrogen sulfide to sulfur trioxide with subsequent sulfur trioxide removal comprises oxidizing hydrogen sulfide to sulfur trioxide in at least one catalyst-containing reactor and feeding the effluent from the last reactor to a candle filter unit for SO.sub.3 removal, where it is mixed with an injected alkaline sorbent slurry or powder to form an alkali sulfate and a hot clean gas. Preferably the oxidation is done in two reactors, the first oxidizing H.sub.2S to SO.sub.2 over a monolith type catalyst and the second oxidizing SO.sub.2 to SO.sub.3 over a VK type catalyst.

An aftertreatment system comprises a SCR system, a first filter, and a second filter disposed downstream of the first filter and a bypass conduit providing a flow path bypassing the second filter. A valve is operatively coupled to the bypass conduit and is moveable between a closed position in which the exhaust gas flows through the second filter, and an open position in which at least a portion of the exhaust gas flows through the bypass conduit. A controller is operatively coupled to the valve configured to adjust the valve based on a first filtration efficiency of the first filter to cause the exhaust gas expelled into the environment from the aftertreatment to have a particulate matter count meeting particulate matter emission standards.

An exhaust system assembly including a catalyst housing, a catalyst core, and a swirler tube positioned inside the catalyst housing. The swirler tube has a plurality of openings that permit radial exhaust flow into an inner volume of the swirler tube from the catalyst housing. One end of the swirler tube has blades that extend inward and include oblique surfaces arranged at oblique angles relative to a centerline axis of the swirler tube. These blades induce a vortex in the exhaust gases exiting the first swirler tube end. The swirler tube is arranged inside the catalyst housing such that a sequential flow path is created where the exhaust gases flowing through the catalyst housing must first pass through the openings in the swirler tube and then by the blades at the first swirler tube end.

In an EHC, a ratio of a heat capacity of the second catalyst body with respect to a heat capacity of the first catalyst body is made within a range of 0.67-1.5. A ratio of an amount of coat of an OSC material in the second catalyst body with respect to an amount of coat of an OSC material in the first catalyst body is made larger than the ratio of the heat capacity of the second catalyst body with respect to the heat capacity of the first catalyst body. A ratio of an amount of support of a noble metal in the second catalyst body with respect to an amount of support of a noble metal in the first catalyst body is made smaller than the ratio of the heat capacity of the second catalyst body with respect to the heat capacity of the first catalyst body.

An after-treatment system includes, in series along an exhaust gas flow direction through the after-treatment system: a diesel oxidation catalyst (DOC) or a passive NOx adsorber (PNA), a diesel exhaust fluid (DEF) delivery device, a soot-reducing device and a selective catalytic reduction (SCR) catalyst, which may also include an additional PNA.