Ship Exhaust Purification Device Urea Injector Mixing
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Solution Overview
Problem
The existing exhaust gas purification devices for ships face challenges in ensuring adequate diffusion of urea water in the exhaust gas, leading to inefficient NOx reduction and potential urea precipitation, and the configuration with a bypass path can result in decreased denitrification performance due to reverse flow into the NOx catalyst.
Innovation Solution
The device incorporates multiple reducing agent injectors with injection ports aligned to overlap with the edges of mixing fins in the exhaust mixer, ensuring uniform distribution of the reducing agent along the exhaust pipe, and a selective catalytic reduction system with a honeycomb structure NOx catalyst, allowing for efficient mixing and denitrification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the urea water nozzle is positioned close to the exhaust mixer, then the device size is reduced, but the urea water is not adequately diffused causing local concentration and temperature drop leading to urea precipitation
Solution Approach 1:
The urea water nozzle is divided into multiple nozzle units arranged circumferentially around the exhaust pipe. Each nozzle unit has multiple injection ports that spray urea water in different directions, segmenting the single injection point into multiple distributed points. This segmentation enables adequate diffusion of urea water even at short distances from the exhaust mixer, preventing local concentration while maintaining compact device size.
2Stability of the object's composition
If a longer exhaust pipe is employed to achieve adequate distance between the urea water nozzle and exhaust mixer, then the urea water diffuses adequately, but the device size is increased
Solution Approach 1:
Instead of increasing the axial distance (one-dimensional solution) between the nozzle and exhaust mixer, the invention transitions to a radial arrangement where multiple nozzle units are positioned circumferentially around the exhaust pipe. This dimensional change allows urea water to be injected from multiple radial directions simultaneously, achieving adequate diffusion without increasing the axial length of the device.
3Adaptability or versatility
If the bypass path is disposed in the purification casing, then the exhaust gas can be diverted outside emission control areas, but the exhaust gas may reversely flow into the NOx catalyst decreasing denitrification performance
Solution Approach 1:
The exhaust gas purification device is extracted from the purification casing and positioned in the exhaust pipe upstream of the purification casing. By separating the injection and mixing functions from the purification casing, the device enables bypass operation without causing reverse flow into the NOx catalyst, as the injection occurs before the exhaust gas enters the purification casing where the catalyst is located.
4Productivity
If multiple reducing agent injectors are used with injection ports aligned to overlap mixing fins, then the mixing efficiency is enhanced and temperature drops are reduced, but the device complexity is increased
Solution Approach 1:
Multiple nozzle units are merged into a single integrated component that is fitted onto the exhaust pipe. The nozzle units, injection ports, and support structures are combined into one assembly that can be installed as a single unit. This merging approach enhances mixing efficiency through multiple injection points while avoiding the complexity of installing and coordinating multiple separate injector systems.
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 enhances the mixing efficiency of the reducing agent with exhaust gas, reduces temperature drops, and maintains the performance of the NOx catalyst by preventing reverse flow, thereby increasing the overall reduction efficiency and extending the catalyst's service life.
Implementation Method 1
the urea water is thermally decomposed upon heated by an exhaust gas and hydrolyzed, so that ammonia is produced
Implementation Method 2
the urea water is thermally decomposed upon heated by an exhaust gas and hydrolyzed, so that ammonia is produced
Implementation Method 3
Ammonia acts on NOx as a reducing agent, and consequently NOx is decomposed into nitrogen and water, which are harmless
Implementation Method 4
an exhaust mixer for mixing the exhaust gas and the reducing agent
Data Source
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AI summary
An object of this invention is to provide an exhaust gas purification device with which a decrease in reduction (denitrification) efficiency can be reduced. An exhaust gas purification device of this invention for a ship 1 includes: a reducing agent injector 61 of a reducing agent supply device supplying a reducing agent to an exhaust gas passing through an exhaust pipe of an engine 21 to be mounted in the ship; an exhaust mixer 62 mixing the exhaust gas and the reducing agent in a location downstream of the reducing agent injector 61 in an exhaust gas traveling direction; and selective catalytic reduction devices 34, 35 facilitating reduction of NOx in the exhaust gas of the engine 21 in a location downstream of the exhaust mixer 62 in the exhaust gas traveling direction. Multiple reducing agent injectors 61 are provided, and respectively have injection ports arranged at equal intervals along a circumferential direction of the exhaust pipe.