Exhaust gas purifying system

A technology for exhaust purification and exhaust passage, which is used in exhaust devices, exhaust treatment, machines/engines, etc.

Inactive Publication Date: 2010-12-22
TOYOTA IND CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Therefore, if the exhaust purification system disclosed in the above document is applied to the conventional urea SCR system, then by using an electric heater to heat the oxidation catalyst to increase the NO 2 The molar ratio may not be able to ensure that the NO and NO contained in the exhaust gas flowing into the SCR catalyst 2 The molar ratio between becomes one to one, and it may not be able to ensure the maximum purification efficiency of the SCR catalyst

Method used

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Embodiment Construction

[0016] Refer to the following Figure 1 to Figure 3 An exhaust purification system according to a first preferred embodiment of the present invention will be described. Referring to the diagram showing the exhaust purification system according to the first preferred embodiment of the present invention figure 1 , used to oxidize part of the NO contained in the exhaust gas to form NO 2 An oxidation catalyst 3 is provided in an exhaust passage 2 through which exhaust gas discharged from a diesel engine 1 serving as an internal combustion engine flows. A diesel particulate filter (DPF) 4 for removing particulate matter (PM) contained in exhaust gas is provided downstream of the oxidation catalyst 3 . used by making the NO x Reacts with ammonia produced by hydrolysis of urea water to form nitrogen and water to reduce NO x A selective catalytic reduction (SCR) catalyst 5 is disposed downstream of the DPF 4 . An oxidation catalyst 6 for oxidizing unreacted or consumed ammonia re...

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Abstract

An exhaust gas purifying system includes an exhaust passage, an oxidation catalyst, a selective catalytic reduction catalyst, a urea water supply device, a first heating mechanism and a controller. The exhaust gas discharged from an internal combustion engine flows through the exhaust passage. The oxidation catalyst for oxidizing nitrogen monoxide contained in the exhaust gas to nitrogen dioxide is disposed in the exhaust passage. The selective catalytic reduction catalyst is disposed downstream of the oxidation catalyst. The urea water supply device supplies urea water into the exhaust passage at the upstream of the selective catalytic reduction catalyst. The first heating mechanism heats the oxidation catalyst. The controller controls the first heating mechanism to adjust the temperature of the oxidation catalyst such that molar ratio between nitrogen monoxide and nitrogen dioxide in the exhaust gas flowing into the selective catalytic reduction catalyst become one to one.

Description

technical field [0001] The present invention relates to an exhaust gas purification system, and more particularly to an exhaust gas purification system including a urea selective catalytic reduction (SCR) system for purifying exhaust gas from a diesel engine. Nitrogen oxides (NO x ) for purification. Background technique [0002] Urea SCR systems have been developed to reduce NO contained in exhaust gases from diesel engines x . In a urea SCR system, a catalyst called an SCR catalyst is used to pass NO x Purification is achieved by reacting with ammonia produced by hydrolysis of urea water. [0003] When nitric oxide (NO) and nitrogen dioxide (NO 2 ) when the molar ratio is one to one, the purification efficiency of the SCR catalyst is maximized. However, the content of NO in ordinary exhaust gas is usually greater than that of NO 2 content. In order to make NO and NO 2 The molar ratio between them is close to one to one, and the following measures have been impleme...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): F01N3/20
CPCY02T10/24F01N3/208F01N2610/02F01N2560/06F01N2240/16F01N3/021F01N3/106F01N2560/14Y02T10/12
Inventor 吉田浩二加藤祥文
Owner TOYOTA IND CORP
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