Air-Cooled Injection Lance for NOx Reduction in Boilers
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Solution Overview
Problem
Existing injection lances for reducing NOx in boiler and furnace flue gases require costly temperature control systems to prevent corrosion, leading to high maintenance and operational inefficiencies due to the challenge of maintaining the correct temperature for effective reagent distribution.
Innovation Solution
An injection lance design featuring oblong separate injectors with a single spraying nozzle at each end, utilizing air as the first cooling means to cool the injectors and a surrounding pipe with air-cooling to maintain the correct temperature, enhancing NOx reduction and distribution with minimal maintenance requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-cooled injector lances are used to maintain wall temperature above 150°C to avoid corrosion, then corrosion resistance is improved, but system complexity and maintenance cost increase due to required heat exchangers, pumping modules, and temperature control equipment
Solution Approach 1:
The invention extracts and eliminates the complex temperature control system (heat exchangers, pumping modules, control equipment) from the injection lance design. Instead of actively controlling temperature, the system allows the lance walls to naturally maintain temperatures above 150°C through the exothermic chemical reactions and hot flue gas environment, thereby avoiding corrosion without the cumbersome temperature control apparatus.
Solution Approach 2:
The injection lance system utilizes the inherent thermal environment of the flue gas and exothermic chemical reactions to self-maintain the wall temperature above 150°C. The hot flue gas and chemical reactions provide the necessary heat automatically, eliminating the need for external cooling systems or active temperature control mechanisms.
2Reliability
If liquid reducing reagent is injected into the flue gas, then NOx reduction is achieved, but proper distribution and temperature control become challenging, requiring complex systems
Solution Approach 1:
The invention divides the injection system into multiple separate oblong injectors (at least two) with different lengths, each equipped with its own spraying nozzle. This segmentation allows each injector to be independently positioned and operated, facilitating better distribution of the liquid reducing reagent throughout the flue gas stream without requiring complex centralized control systems.
Solution Approach 2:
The injection system employs dynamic positioning and variable injection parameters. The multiple injectors with different lengths can be positioned at optimal locations, and the injection rate can be adjusted based on operating conditions, allowing the system to adapt to varying flue gas flow rates and temperature profiles for consistent NOx reduction performance.
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 design improves NOx reduction by creating turbulence and ensuring better mixing of the reagent with flue gas, while reducing maintenance and operational costs, and is more cost-efficient compared to existing systems.
Implementation Method 1
first cooling means to cool the injectors with air; second cooling means to cool the surrounding pipe with air
Implementation Method 2
each having a single spraying nozzle at the end thereof for spraying the liquid reducing agent
Implementation Method 3
The design improves NOx reduction by creating turbulence and ensuring better mixing of the reagent with flue gas
Data Source
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AI summary
The present application relates to an injection lance for injecting a liquid reducing reagent into a flue gas from the combustion of fuel in a combustion chamber of a boiler or furnace to reduce the amount of nitrogen oxides in the flue gas, wherein the injection lance comprises at least two oblong separate injectors having a different 10 length and each having a single spraying nozzle at the end thereof for spraying the liquid reducing agent, first cooling means to cool the injectors with air, an surrounding pipe coaxial with and disposed around the injectors and provided with at least one opening per injector spaced along its length and located in the vicinity of the respective spraying nozzles to allow the spraying nozzles to spray the liquid reducing 15 agent through the openings into the flue gas and second cooling means to cool the surrounding pipe with air.