Method of controlling NOx purification system, and NOx purification system
AssigneeIsuzu Motors Limited
InventorTetsuya Fujita
Life of this patent
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Abstract
Method to reduce NOx contained in an exhaust gas by including an oxidation catalyst device and a selective reduction type NOx catalyst device, which are arranged in this order from an upstream side, and a NOx purification system. Whether a volume of NO2 adsorbed in the oxidation catalyst device increases or decreases is estimated, and a flow rate of exhaust gas which bypasses the oxidation catalyst device on a basis of the increase or decrease in the estimated volume of adsorbed NO2 is controlled. This avoids incorrect supply of ammonia.
Claims10
A NOx purification system configured to reduce NOx contained in an exhaust gas, the system including:
- an oxidation catalyst device, a first valve, and a selective reduction type NOx catalyst device which are arranged in order from an upstream side of an exhaust gas passage, the first valve to supply an ammonia-based solution to the exhaust gas passage;
- a bypass passage branching from the exhaust gas passage at an upstream side of the oxidation catalyst device and joining together with the exhaust gas passage at an upstream side of the first valve;
- at least one second valve to control a flow rate of the exhaust gas which flows through the bypass passage, and
- a controller configured to calculate volumes of NOx respectively in stages before and after the oxidation catalyst device,
- estimate whether a volume of NO2 adsorbed in the oxidation catalyst device increases or decreases on a basis of the calculated volumes of NOx,
- control a flow rate of the exhaust gas which passes the oxidation catalyst device and a flow rate of the exhaust which passes the bypass passage on a basis of the increase or decrease in the estimated volume of adsorbed NO2, and
- control an amount of the ammonia-based solution to be supplied by the first valve.
A method of controlling a NOx purification system configured to reduce NOx contained in an exhaust gas, the system including:
- an oxidation catalyst device, a first valve, and a selective reduction type NOx catalyst device which are arranged in order from an upstream side of an exhaust gas passage, the first valve to supply an ammonia-based solution to the exhaust gas passage;
- a bypass passage branching from the exhaust gas passage at an upstream side of the oxidation catalyst device and joining together with the exhaust gas passage at an upstream side of the first valve;
- at least one second valve to control a flow rate of the exhaust gas which flows through the bypass passage, and
- a controller,
- the method comprising utilizing the controller to perform the following steps:
- calculating volumes of NOx respectively in stages before and after the oxidation catalyst device,
- estimating whether a volume of NO2adsorbed in the oxidation catalyst device increases or decreases on a basis of the calculated volumes of NOx,
- controlling a flow rate of the exhaust gas which passes the oxidation catalyst device and a flow rate of the exhaust which passes the bypass passage on a basis of the increase or decrease in the estimated volume of adsorbed NO2, and
- controlling an amount of the ammonia-based solution to be supplied by the first valve.
Dependencies are inferred from the claim text.