Reductant distributor for lean NOx trap
AssigneeGeneral Motors Corporation
InventorShi-Wai Cheng
Life of this patent
Estimating the term…
Abstract
A lean NOx trap operating in a lean NOx exhaust stream is progressively regenerated, sector to sector, for efficient operation of the trap and conservation of reducing gas used in the regeneration. A reductant gas distributor is inserted in the exhaust upstream of the trap. Reductant gas is carried into the exhaust duct through a conduit portion and the reductant gas stream diverged and directed through a distributor into selected cells of the trap. The NOx in the selected cells is reduced to N2 while lean NOx exhaust continues to flow through the remainder of the trap. By relative movement of the reductant gas distributor and the trap, the entire trap is progressively and continually regenerated while still preforming as a NOx trap.
Claims18
A reductant distributor for placement in a stream of lean NOx exhaust flowing through a lean NOx trap, the NOx trap having an inlet face comprising openings of longitudinal cells for through-flow of lean NOx exhaust, the cells having cell walls carrying absorbent material for trapping NOx from lean NOx exhaust and for releasing NOx in the presence of a reducing atmosphere for trapped NOx;
- the reductant distributor comprising:
- a reductant gas conduit, a reductant gas distributor with an outlet, and a mechanism for progressive positioning of the outlet of the reductant gas distributor at portions of the inlet face of the lean NOx trap;
- the reductant gas conduit having an inlet for receiving reductant gas under gas flow pressure and transporting it to the reductant gas distributor, the reductant gas distributor having an inlet for reductant gas from the reductant gas conduit and a distributor outlet shaped to release the reductant gas at a predetermined sector portion of the inlet face of the lean NOx trap while deflecting the lean NOx exhaust stream to other portions of the inlet face, and the positioning mechanism being operative for progressive relative movement between the distributor outlet and sector portions of the inlet face of the lean NOx trap for reduction of trapped NOx in a sector while lean NOx exhaust is flowing through cells of the trap not receiving reductant gas from the distributor.
A method of regenerating a lean NOx trap through which lean NOx exhaust is flowing, the NOx trap having an inlet face comprising openings of longitudinal cells for through-flow of lean NOx exhaust, the cells having cell walls carrying absorbent material for trapping NOx from lean NOx exhaust and for releasing NOx in the presence of a reducing atmosphere for trapped NOx, the method comprising:
- selectively directing a stream of reducing gas through a portion of the inlet face cell openings while diverting the flow of lean NOx exhaust through the remainder of the inlet face cell openings, the flow of reducing gas being continued to reduce and remove trapped NOx from the cell walls exposed to the reductant gas flow in the selected portion.
A reductant distributor for placement in a stream of lean NOx exhaust flowing through a lean NOx trap, the NOx trap having an inlet face comprising openings of longitudinal cells for through-flow of lean NOx exhaust, the cells having cell walls carrying absorbent material for trapping NOx from lean NOx exhaust and for releasing NOx in the presence of a reducing atmosphere for trapped NOx;
- the reductant distributor comprising:
- a reductant gas conduit, a reductant gas distributor with an outlet, and a mechanism for progressive positioning of the outlet of the reductant gas distributor at portions of the inlet face of the lean NOx trap;
- the reductant gas conduit having an inlet for receiving reductant gas under gas flow pressure and transporting it to the reductant gas distributor;
- the reductant gas distributor having an inlet for reductant gas from the reductant gas conduit, a distributor outlet shaped to release the reductant gas at a predetermined sector portion of the inlet face of the lean NOx trap while deflecting the lean NOx exhaust stream to other portions of the inlet face, an inlet for lean exhaust gas, and an oxidation catalyst for oxidation of a portion of the reductant gas to increase the temperature of gas released at the inlet face;
- and
- the positioning mechanism being operative for progressive relative movement between the distributor outlet and sector portions of the inlet face of the lean NOx trap for reduction of trapped NOx in a sector while lean NOx exhaust is flowing through cells of the trap not receiving reductant gas from the distributor.
Dependencies are inferred from the claim text.