| 摘要 |
A multi-stage SCR system including a front reductant injecting device, a front mixer, a front SCR catalyst, a back reductant injecting device, a back mixer, a back SCR catalyst, and a DCU. The front and back reductant injecting devices receives reductant from an air-driven pump, which includes a liquid supply tank, a pressure tank, and solenoids control valves. Under pressure provided by a compress air source, reductant is pressed into the front and back reductant injecting devices from the air-driven pump. The front and back reductant devices also have flow-back paths fluidly connected to a reductant tank. And in purging or maintenance heating, the flow-back paths can be energized open. In the multi-stage SCR system, a DOC can be further positioned in between the two SCR devices for increasing the deNOx efficiency in the back SCR catalyst, so that the system is less sensitive to catalyst aging. |
| 主权项 |
1. An exhaust gas after-treatment apparatus for an internal combustion engine, comprising:
a first selective catalytic reduction device; a first reductant injecting device positioned upstream from said first selective catalytic reduction device; a second selective catalytic reduction device located downstream from said first selective catalytic reduction device; a second reductant injecting device, which is fluidly connected to said first reductant injecting device, positioned in between said first selective catalytic reduction device and said second selective catalytic reduction device; a mixing device positioned in between said second reductant injecting device and said second catalytic reduction device for creating a uniform exhaust gas; a reductant delivery module including a pressure outlet port fluidly connected to said first reductant injecting device and said second reductant injecting device, and a first reductant-flow control valve for allowing and shutting off a reductant flow passing therethrough fluidly coupling said first reductant injecting device to a reductant tank; and a dosing control unit configured to control said first reductant injecting device to deliver a first dosing quantity of reductant in response to a first dosing rate command, and control said second reductant injecting device to deliver a second dosing quantity of reductant in response to a second dosing rate command. |
