Exhaust Gas After-Treatment Device with Segmented Thermal Reactor
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Solution Overview
Problem
Existing exhaust gas after-treatment devices struggle to effectively integrate regenerative thermal oxidation and selective catalytic reduction in a single system due to differing temperature requirements for each process.
Innovation Solution
An exhaust gas after-treatment device with a mixing device for adding a reducing agent between the inlet and thermal reactor, featuring at least one second reaction zone for catalytic reaction, which can also act as a heat accumulator, and includes a bypass line to manage temperature and prevent overheating, allowing for simultaneous thermal oxidation and catalytic reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If regenerative thermal oxidation is implemented in a thermal reactor, then unburned hydrocarbons and carbon monoxide are effectively oxidized, but the temperature becomes too high for selective catalytic reduction
Solution Approach 1:
The exhaust gas flow is divided into two separate reaction zones: a first reaction zone for regenerative thermal oxidation and a second reaction zone for selective catalytic reduction. This segmentation allows each zone to operate at its optimal temperature independently, resolving the contradiction between high temperature oxidation and low temperature catalytic reduction
Solution Approach 2:
Different regions of the exhaust gas after-treatment device are assigned different temperature characteristics. The first reaction zone maintains high temperature (400-530°C) for thermal oxidation, while the second reaction zone maintains lower temperature (350-500°C) for catalytic reduction, allowing each process to operate under its optimal local conditions
2Productivity
If selective catalytic reduction is implemented for nitrogen oxide reduction, then ammonia reacts with nitrogen oxides to form molecular nitrogen, but the temperature must be kept below 500°C which conflicts with thermal oxidation requirements
Solution Approach 1:
The exhaust gas flow is divided into two separate reaction zones: a first reaction zone for regenerative thermal oxidation and a second reaction zone for selective catalytic reduction. This segmentation allows each zone to operate at its optimal temperature independently, resolving the contradiction between high temperature oxidation and low temperature catalytic reduction
Solution Approach 2:
Different regions of the exhaust gas after-treatment device are assigned different temperature characteristics. The first reaction zone maintains high temperature (400-530°C) for thermal oxidation, while the second reaction zone maintains lower temperature (350-500°C) for catalytic reduction, allowing each process to operate under its optimal local conditions
3Device complexity
If a single exhaust gas after-treatment device is used for both thermal oxidation and catalytic reduction, then device complexity is reduced, but temperature management becomes difficult
Solution Approach 1:
The exhaust gas after-treatment device is segmented into distinct reaction zones with different temperature characteristics, allowing both thermal oxidation and catalytic reduction to be implemented in a single device while maintaining independent temperature management for each process
Solution Approach 2:
The system employs dynamic temperature management where the exhaust gas flow is alternately directed through different reaction zones, and heating facilities are selectively activated to maintain optimal temperatures for each catalytic process under varying operating conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables efficient simultaneous operation of regenerative thermal oxidation and selective catalytic reduction, optimizing temperature management and preventing damage to catalysts, thereby enhancing the overall exhaust gas treatment process.
Implementation Method 1
the exhaust gas flows at a temperature of about 400 to 530° C. from the motor through a change over mechanism into a first storage volume, where it is heated to about 700-850° C.
Implementation Method 2
In the reaction chamber, the exhaust gas reacts with the available oxygen, where carbon monoxide and unburned hydrocarbons are oxidized to carbon dioxide and water.
Implementation Method 3
When passing through the second storage volume, the exhaust gas again releases heat and attains the changeover mechanism at a temperature of 430 to 560° C.
Implementation Method 4
the exhaust gas flow is initially admixed with a reduction agent, which is usually an aqueous urea solution. The urea dissociates to ammonia in the hot exhaust gas flow. In a catalytic reaction zone suitable for the SCR, the ammonia reacts together with the nitrogen oxides present in the exhaust gas flow
Implementation Method 5
The urea dissociates to ammonia in the hot exhaust gas flow
Implementation Method 6
In a catalytic reaction zone suitable for the SCR, the ammonia reacts together with the nitrogen oxides present in the exhaust gas flow over several reaction paths to form molecular nitrogen and water.
Data Source
AI summary
Embodiments relate to an exhaust gas after-treatment device with an exhaust line having an inlet for discharging the exhaust gas and a thermal reactor, which is arranged in the exhaust line and has a first, thermal reaction zone for the exhaust gas flow, where a mixing device is provided for admixing a reducing agent to the exhaust gas flow in the exhaust line, which is arranged between the inlet and the thermal reactor and where the thermal reactor has at least one second reaction zone for a catalytic reaction in the exhaust gas flow with the involvement of the reducing agent.