The present invention is applied to an exhaust system provided with a three-way catalyst and a NOx catalyst which are provided in an exhaust passage of an engine and to which sulfur components in exhaust adhere and release the attached sulfur components by rich components in exhaust, and NOx sensors provided downstream of the catalysts. The NOx sensor is a limiting current type sensor. It is determined whether a sulfur release state is present in which a sulfur component is released from the three-way catalyst and the NOx catalyst. When it is determined that it is in the state of sulfur release, reaction suppression processing for suppressing the reaction between oxygen and sulfur components in the pump cell electrodes and the monitor cell electrodes of the NOx sensors is performed.

The present invention relates to a compressed natural gas combustion and exhaust system comprising: (i) a natural gas combustion engine and (ii) an exhaust treatment system comprising an intake for receiving an exhaust gas from the combustion engine and a catalyst article arranged to receive and treat the exhaust gas, wherein the catalyst article comprises: a substrate having at least first and second coatings, the first coating comprising a palladium-containing alumina and/or a base-metal containing alumina and the second coating comprising a palladium-containing zeolite, wherein the first coating is arranged to contact the exhaust gas before the second coating; and, wherein the system is configured to selectively operate in: (a) a lean first mode in which sulphur is trapped on the first coating; and (b) a rich second mode whereby sulphur is released from the first coating. The present invention further relates to a method.

A control device of an exhaust sensor comprises a cell temperature detecting part detecting a temperature of the electrochemical cell, a heater control part controlling the heater so that a temperature of the electrochemical cell becomes the target temperature, and a judging part judging whether a water repellency of the protective layer is falling. The judging part judges that the water repellency of the protective layer is falling if a condition for judging abnormality is satisfied. The condition for judging abnormality includes a temperature of the electrochemical cell detected by the cell temperature detecting part falling from the target temperature and a speed of fall of the temperature being faster than a speed of fall of the temperature of the electrochemical cell when the heater is turned off.

A sulfur oxide detection system includes an element part which includes a sensor cell and a diffusion regulating layer. The sensor cell includes a solid electrolyte layer, a first electrode arranged, and a second electrode. The sulfur oxide detection system also includes a voltage application circuit configured to apply a voltage to the sensor cell so that a potential of the second electrode becomes higher than a potential of the first electrode, and a current detection circuit configured to detect a current flowing between the first electrode and the second electrode. The sulfur oxide detection system further includes a controller coupled with the voltage application circuit and the current detection circuit, and configured to estimate a sulfur oxide concentration in a gas to which the first electrode is exposed by way of the diffusion layer.

An aftertreatment system comprises a SCR system including a catalyst formulated to decompose constituents of an exhaust gas passing therethrough. A filter is positioned upstream of the SCR system. The filter comprises a sulfur suppressing compound formulated to reduce an amount of SOx gases included in the exhaust gas flowing through the aftertreatment system. In particular embodiments, the filter comprises a filter housing and a filter element positioned within the filter housing. The filter element comprises the sulfur suppressing compound.

A gas analyzer via which exhaust gas to be analyzed is conducted untreated through a first measurement chamber and, after treatment in an oxidation device, through a second measurement chamber, wherein ozone is produced from oxygen to thereby convert nitrogen monoxide into nitrogen dioxide, where the gas analyzer has a first light emitting diode and a second light emitting diode, light of both diodes is conducted through the first measurement chamber onto a first detector, light of the first light emitting diode is partly conducted through the second measurement chamber onto a second detector via a beam splitter arrangement, based on the first detector signal, the nitrogen dioxide concentration of the untreated gas is also measured, based on the second detector signal, the nitrogen dioxide concentration of the treated exhaust gas is measured, and the nitrogen oxide concentration of the exhaust gas is additionally determined from measured nitrogen dioxide concentrations.

Methods and systems are provided for an exhaust system. In one example, a method may include determining presence of a zone flow based on a comparison of a first exhaust sensor and a second exhaust sensor. The presence or absence of the zone flow may determine a rate at which an air-fuel ratio is adjusted.

A SOx concentration acquiring apparatus of an internal combustion engine of the invention acquires sensor currents as SOx concentration currents after a sensor voltage reaches an oxygen decreasing voltage in a reoxidation voltage decreasing control, acquires the sensor current as a base current when the sensor voltage is equal to or lower than the oxygen decreasing voltage in the reoxidation voltage decreasing control, acquires an integration value of differences between the base current and each of the SOx concentration currents, and acquires a SOx concentration of an exhaust gas discharged from an internal combustion engine on the basis of the integration value.

Methods and systems are provided for an exhaust system. In one example, a method may include determining presence of a zone flow based on a comparison of a first exhaust sensor and a second exhaust sensor. The presence or absence of the zone flow may determine a rate at which an air-fuel ratio is adjusted.

The present invention is applied to an exhaust system provided with a three-way catalyst and a NOx catalyst which are provided in an exhaust passage of an engine and to which sulfur components in exhaust adhere and release the attached sulfur components by rich components in exhaust, and NOx sensors provided downstream of the catalysts. The NOx sensor is a limiting current type sensor. It is determined whether a sulfur release state is present in which a sulfur component is released from the three-way catalyst and the NOx catalyst. When it is determined that it is in the state of sulfur release, reaction suppression processing for suppressing the reaction between oxygen and sulfur components in the pump cell electrodes and the monitor cell electrodes of the NOx sensors is performed.