Exhaust Gas Purification Apparatus with DOC-DPF Integration
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Solution Overview
Problem
Conventional exhaust gas purification systems for diesel engines face challenges with energy efficiency, catalyst usage, and system complexity, particularly in passive regeneration and NOx conversion, due to the need for expensive precious metal catalysts and low thermal stability of certain catalysts, leading to decreased engine efficiency and operational instability.
Innovation Solution
An exhaust gas purification apparatus comprising a DOC unit for converting NOx to NO2, a composite DPF unit with a SCR layer supported by titanium dioxide-zirconia compounds, and a circulation line for enhanced NO2 conversion without a heat source, using rare earth element-vanadate compounds and transition metal oxides, which reduces catalyst usage and enables passive regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If precious metal catalysts (Pt, Pd) are used to convert NO to NO2 for passive regeneration, then the conversion rate improves, but the cost and catalyst amount increase significantly
Solution Approach 1:
The patent replaces expensive precious metal catalysts (Pt, Pd) with base metal catalysts such as Cu, Zn, or Mn-based catalysts. These base metal catalysts are significantly cheaper and can be used in smaller quantities while still achieving effective NO to NO2 conversion for passive DPF regeneration.
Solution Approach 2:
The patent optimizes catalyst parameters including metal composition ratios, support material properties, and catalyst preparation methods to enhance the activity and stability of base metal catalysts, enabling them to replace precious metals without sacrificing conversion performance.
2Device complexity
If metal oxide-based catalysts and V2O5-WO3/TiO2-based catalysts are used in SCR, then the system is simpler, but the NOx removal activity and hydrothermal stability at 500°C or higher are very low
Solution Approach 1:
The patent develops composite catalyst systems combining base metals (Cu, Zn, Mn) with specific support materials and promoters to create catalysts that maintain high NOx removal activity and hydrothermal stability at temperatures of 500°C and above, overcoming the limitations of simple metal oxide catalysts.
Solution Approach 2:
The patent creates catalysts with spatially varying properties, including core-shell structures or gradient compositions, where different regions of the catalyst perform different functions - some regions optimized for NOx conversion while others provide thermal stability and resistance to degradation.
3Object-affected harmful factors
If a DOC-DPF-SCR unit process system is used, then exhaust gas purification is achieved, but the back pressure increases and engine efficiency decreases
Solution Approach 1:
The patent integrates the DOC and DPF functions into a single combined unit, eliminating the need for separate DOC and DPF components. This merging reduces the total number of parts, decreases back pressure, and improves engine efficiency while maintaining effective exhaust gas purification capabilities.
Solution Approach 2:
The combined DOC-DPF unit performs multiple functions simultaneously - oxidation of CO and hydrocarbons, conversion of NO to NO2, and trapping of particulate matter - all within a single integrated component, reducing system complexity and pressure losses.
4Productivity
If a DOC unit is added to convert NOx to NO2, then passive regeneration capability improves, but the system complexity and catalyst usage increase
Solution Approach 1:
The patent combines the DOC functionality (NO to NO2 conversion) with the DPF functionality (PM trapping) into a single integrated unit. This eliminates the need for a separate DOC unit, reduces system complexity, and maintains effective passive regeneration capability.
Solution Approach 2:
The integrated unit performs multiple functions - oxidation catalysis, NO2 generation, and particulate filtration - all within a single component, providing universal exhaust treatment capabilities without increasing system complexity.
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 solution achieves excellent energy efficiency, economic feasibility, and compact design by enhancing NO2 conversion rates, reducing catalyst amounts, and improving pollutant processing efficiency in diesel exhaust gas, while maintaining catalytic activity at high temperatures.
Implementation Method 1
a DOC unit configured to convert NOx contained in exhaust gas input through a gas inlet into NO2
Implementation Method 2
a composite DPF unit which is connected to a rear end of the DOC unit via an input line, and removes harmful components including PM and NOx
Data Source
AI summary
The present invention relates to an exhaust gas purification apparatus and an exhaust gas purification method using the same. According to a specific embodiment, the exhaust gas purification apparatus comprises: a diesel oxidation catalyst (DOC) unit for converting nitrogen oxides (NOx), contained in an exhaust gas introduced therein through a gas inlet portion, into nitrogen dioxide (NO2); a composite diesel particulate filter (DPF) unit connected to the rear end of the DOC unit through an inflow line and removing harmful components including particulate substances and nitrogen oxides from the exhaust gas discharged from the DOC unit and introduced therein; and a circulation line disposed in the inflow line so as to introduce the exhaust gas discharged from the DOC unit into the gas inlet portion.