Direct Reducing-Agent Injection for Exhaust Gas NOx Removal
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Solution Overview
Problem
The existing SCR systems for removing nitrogen oxides (NOx) from exhaust gas streams in combustion systems are costly, complex, and require significant space due to the need for vaporization systems, injection grids, and blowers, which also face challenges in achieving uniform distribution of reducing agents across the exhaust gas stream.
Innovation Solution
A direct reducing agent injection system that injects liquid reducing agent into the exhaust gas stream with turbulence, allowing vaporization within the stream, and uses injectors with adjustable nozzles to optimize distribution, reducing the need for separate vaporization and distribution systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional SCR system with separate vaporization systems, injection grids, and blowers is used, then NOx removal is achieved, but system complexity and cost increase significantly
Solution Approach 1:
The patent combines the vaporization system, injection grid, and blower into a single integrated reducing agent injection assembly. The liquid reducing agent is injected directly into the exhaust gas stream where it vaporizes and distributes without requiring separate vaporization chambers or complex injection grids, thereby simplifying the overall system while maintaining NOx removal efficiency.
Solution Approach 2:
The reducing agent injection assembly performs multiple functions simultaneously: it injects liquid reducing agent, vaporizes it through direct contact with hot exhaust gas, distributes it across the exhaust stream, and delivers it to the catalyst bed. This multi-functional design eliminates the need for separate dedicated components for each function, reducing system complexity.
2Reliability
If a conventional SCR system with extensive vaporization and distribution systems is used, then reducing agent distribution is achieved, but the space required increases
Solution Approach 1:
The patent merges the vaporization and distribution functions into a compact injection assembly that fits within or near the catalyst bed structure. By eliminating separate vaporization chambers and extensive distribution piping, the overall system footprint is dramatically reduced while still achieving uniform reducing agent distribution across the exhaust gas stream.
Solution Approach 2:
The system uses the hot exhaust gas itself to vaporize the liquid reducing agent, eliminating the need for external heaters or vaporization chambers. The exhaust gas provides both the heat for vaporization and the flow medium for distribution, reducing the space required for dedicated vaporization and distribution infrastructure.
3Ease of manufacture
If liquid reducing agent is injected directly into turbulent exhaust gas stream, then vaporization and distribution occur naturally, but precise control of injection timing and location becomes challenging
Solution Approach 1:
The patent incorporates sensors and control systems that monitor the exhaust gas flow conditions, temperature, and reducing agent injection rates. This feedback enables real-time adjustment of injection timing and quantity to optimize vaporization and distribution effectiveness, maintaining precise control despite the simplified direct injection approach.
Solution Approach 2:
The injection system is designed to dynamically adapt to varying exhaust gas flow conditions. The injection rate and timing are adjusted in response to changing flow velocities and turbulence levels, ensuring consistent reducing agent distribution across different operating conditions without requiring complex predetermined control schedules.
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 approach enhances the uniformity of reducing agent distribution, improves NOx removal efficiency, and reduces system complexity and cost by integrating vaporization and distribution within the exhaust gas stream, while maintaining compliance with emission regulations.
Implementation Method 1
injecting a reducing agent into the exhaust gas stream at a point of injection wherein the exhaust gas stream is flowing with a flow turbulence at or after the point of injection causing the reducing agent to be distributed within the exhaust gas stream
Implementation Method 2
the exhaust gas stream is flowing with a flow turbulence at or after the point of injection causing the reducing agent to be distributed within the exhaust gas stream
Implementation Method 3
passing the exhaust gas stream through an expansion zone in the duct system to a reduced velocity; passing the exhaust gas stream at the reduced velocity through a catalyst bed wherein the catalyst enables a reaction between the vaporized reducing agent and the at least one type of nitrogen oxide
Data Source
AI summary
The present invention is directed towards an apparatus and method for the removal of one or more nitrogen oxides (NOx) from an exhaust gas stream of a combustion systems (for example exhaust gas from a gas turbine). In particular, a reducing agent is directly injected into a selected location in a duct system for the exhaust gas (for example at the inlet duct).