Concentric NOx Injection Conduit for Fluidized Bed Combustion
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Solution Overview
Problem
Existing fluidized bed combustion systems face inefficiencies in reducing NOx emissions due to inadequate reactant distribution and mixing within the exhaust gas stream, leading to excessive reactant usage and system degradation from high temperatures and particulates.
Innovation Solution
A NOx reducing system with a concentric conduit design, where reactants are injected downstream of the vortex finder in the outlet duct, utilizing a plurality of supply lines with ports on the downstream surface to ensure uniform distribution and resistance to temperature and particulate-induced degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactant is injected into the furnace or at various locations across the inlet duct, then the reactant can reach the NOx-containing exhaust gases, but the reactant mixes too much with particulate materials and insufficient mixing with exhaust gases occurs
Solution Approach 1:
The injection system is segmented into multiple injection ports distributed along the outlet duct, allowing reactant to be introduced at multiple locations rather than at a single point. This segmentation enables better distribution of reactant throughout the exhaust gas stream while minimizing premature mixing with particulate materials.
Solution Approach 2:
The injection ports are arranged in a longitudinal dimension along the outlet duct, transitioning from point injection to distributed linear injection. This dimensional arrangement allows the reactant to be introduced at multiple positions along the flow path, improving mixing with exhaust gases while maintaining separation from particulate-rich zones.
2Reliability
If reactant is injected into the solids separator or at the top of the vortex finder, then the reactant can be introduced into the exhaust gas stream, but insufficient distribution and residence time occur
Solution Approach 1:
The reactant is injected into the outlet duct downstream of the vortex finder, where the exhaust gases are already in motion and ready for mixing. This preliminary positioning ensures that the reactant enters the stream at an optimal location where immediate mixing can occur without requiring excessive residence time in separate chambers.
Solution Approach 2:
Multiple injection ports are distributed along the outlet duct to segment the injection process into multiple simultaneous introduction points. This segmentation increases the effective surface area for reactant introduction and enhances distribution throughout the exhaust gas stream, compensating for the reduced residence time available downstream of the vortex finder.
3Reliability
If injection ports or lances are used to introduce reactant, then reactant can be discharged into the exhaust gas stream, but high temperature and clogging of ports occur
Solution Approach 1:
The injection ports are strategically positioned on the downstream surface of the outlet duct, where the local temperature is lower and particulate concentration is reduced compared to the furnace or separator regions. This local quality selection minimizes thermal degradation and clogging while maintaining effective reactant injection capability.
Solution Approach 2:
The injection ports are designed as simple, replaceable components that can be easily replaced if clogged or degraded. This approach accepts that the ports may experience some degradation from heat and particulates, but allows for economical replacement rather than requiring complex protection systems.
4Reliability
If excessive amounts of reactant are added to ensure sufficient mixing, then NOx reduction effectiveness improves, but new pollution problems and increased cost occur
Solution Approach 1:
The system optimizes the reactant injection rate and distribution parameters to achieve the minimum effective concentration required for NOx reduction. By carefully controlling the quantity and timing of reactant introduction through multiple ports, the system achieves sufficient mixing and reduction effectiveness without excessive reactant addition that would cause ammonia slip or other pollution issues.
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 design enhances reactant distribution and mixing with NOx-containing exhaust gases, reducing NOx emissions and ammonia slip, while maintaining system integrity and extending the life cycle of components by minimizing clogging and corrosion.
Implementation Method 1
a reactant such as urea or ammonia is injected into the combustion system to react with the NO x , fouling nitrogen ('N 2 ') and water ('H 2 O')
Implementation Method 2
enhances reactant distribution and mixing with NOx-containing exhaust gases
Data Source
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AI summary
Disclosed herein is a NOx reducing system comprising a first inner conduit in fluid communication with a reactant source; and a first outer conduit comprising an open end for receiving the first inner conduit and a closed end; the first outer conduit comprising a port for discharging reactant from the reactant source into an exhaust gas stream. Also disclosed herein is a NOx reducing system comprising a conduit comprising a closed end and an open end that is in fluid communication with a reactant source; the conduit comprising a port for discharging reactant from the reactant source into an exhaust gas stream; the port being located on a downstream surface of the first outer conduit.