Tube-in-Tube Lance System for NOx Reduction
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Solution Overview
Problem
Existing lance systems for NOx reduction in large power plants face challenges in mixing reducing agents uniformly across large combustion chamber cross-sections and maintaining the optimal temperature window, leading to inefficiencies and potential corrosion damage from liquid droplets reaching heating surfaces.
Innovation Solution
A lance system with a tube-in-tube design, featuring an inner tube placed inside an outer tube, with strategically arranged outlet openings to ensure uniform mixing and evaporation of reducing agents before injection, preventing liquid droplets from reaching heating surfaces and optimizing NOx reduction in the desired temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If reducing agents are injected into large combustion chambers using conventional lances, then NOx reduction is achieved, but uniform distribution and mixing across large cross-sections is difficult
Solution Approach 1:
The lance is divided into multiple sections with numerous outlet openings distributed along its length. This segmentation allows the reducing agent to be injected at multiple locations simultaneously, improving uniform distribution across the large combustion chamber cross-section while maintaining effective NOx reduction.
2Ease of manufacture
If lances are installed within the area of heating surfaces to simplify structural design, then ease of installation is improved, but liquid droplets may reach heating surfaces and cause corrosion damage
Solution Approach 1:
The lance design ensures complete evaporation of the reducing agent before it reaches the heating surfaces. By positioning outlet openings and utilizing the hot flue gas environment, the liquid reducing agent is fully vaporized in advance, eliminating liquid droplet contact with heating surfaces and preventing corrosion while maintaining structural simplicity.
Solution Approach 2:
The reducing agent undergoes phase transition from liquid to gas within the lance structure. The hot flue gas provides the necessary heat for complete evaporation before the reducing agent exits the lance, ensuring only gaseous reducing agent contacts the heating surfaces and prevents corrosion.
3Productivity
If reducing agents are injected as liquid to achieve effective NOx reduction, then reaction effectiveness is improved, but liquid droplets reaching heating surfaces cause corrosion
Solution Approach 1:
The lance is designed to complete the phase transition of the reducing agent from liquid to gas before it reaches the heating surfaces. The hot flue gas environment within the combustion chamber provides the necessary heat for complete evaporation, ensuring that only gaseous reducing agent contacts the heating surfaces while maintaining effective NOx reduction.
Solution Approach 2:
Complete evaporation of the reducing agent is achieved as a preliminary action before the reducing agent exits the lace. The outlet openings and internal lance geometry are designed to ensure充分的 vaporization time and heat transfer, eliminating liquid droplets before they can cause corrosion damage.
4Manufacturing precision
If multiple outlet openings are arranged along the lance to improve distribution, then uniform mixing is improved, but device complexity increases
Solution Approach 1:
The lance is segmented into multiple sections with outlet openings distributed along its length. This segmentation approach achieves uniform mixing by injecting the reducing agent at multiple locations, while the modular segmented structure actually simplifies manufacturing compared to a single complex nozzle, as each section can be independently fabricated and assembled.
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
The lance system achieves uniform distribution and evaporation of reducing agents, enhancing NOx reduction efficiency while preventing corrosion and maintaining system integrity by ensuring all reducing agents are injected in a gaseous form, thus improving the effectiveness and longevity of the NOx reduction process.
Implementation Method 1
whereby the reducing agent is completely evaporated in the space between the inner and outer tubes
Implementation Method 2
is mixed in the space with separately supplied additional gaseous oxidizing agent
Implementation Method 3
supplying a gaseous oxidizing agent into the space between the inner and outer tubes
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a lance system (9) for introducing reducing agents into a boiler (1) for the selective non-catalytic reduction of nitrogen oxides in combustion gases, comprising an inner section designed to be arranged inside the boiler (1) and an outer section designed to be arranged outside the boiler (1), the lance system (9) having an inner tube (16) and an outer tube (17), and at least along the inner section of the lance system (9) the inner tube (16) is arranged inside the outer tube (17), thereby forming a space (22) between the outer wall of the inner tube (16) and the inner wall of the outer tube (17), wherein, according to the invention, a plurality of first outlet openings (18) are arranged in the circumferential wall of the inner tube (16) along the inner tube, and a plurality of second outlet openings (19) are arranged in the circumferential wall of the outer tube (17) along the outer tube (17).The first outlet openings (18) of the inner tube (16) open into the space (22), the interior (23) of the inner tube (16) is in fluid communication with the space (22) via the first outlet openings (18) of the inner tube (16), and the space (22) is in fluid communication with the outside via the second outlet openings (19) of the outer tube (17). The invention further relates to a boiler comprising at least one lance system according to the invention and a method for reducing the concentration of nitrogen oxides in a combustion gas.