Lance Injection for NOx Reduction in Boiler Furnaces
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Solution Overview
Problem
Existing methods for reducing nitrogen oxides and carbon monoxide emissions in boiler furnace chambers are costly, require complex installations, and often limit the flexibility of reactant injection, leading to inefficiencies and increased operational costs.
Innovation Solution
A method involving the injection of a process gas and a reactant, such as ammonia or its derivatives, through lances positioned strategically within the furnace chamber to create a strong internal recirculation vortex, opposing the main flue gas flow, which enhances mixing and temperature control, minimizing reactant consumption and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If complex cooling systems and drive systems are installed to reduce NOx and CO emissions, then emission reduction effectiveness is improved, but device complexity and investment costs increase significantly
Solution Approach 1:
The invention extracts and eliminates the need for complex cooling systems and expensive drive systems by using a simplified lance insertion method through the boiler front wall, achieving emission reduction without the cumbersome mechanisms of prior art
Solution Approach 2:
Instead of pulling lances out periodically as required by prior art, this invention inserts lances through a fixed opening and maintains them in position, inverting the operational approach to eliminate the need for drive systems entirely
2Device complexity
If lances are rigidly installed directly in the boiler plating, then the need for drive systems is eliminated, but the length and diameter of lances are limited due to stresses inside the boiler
Solution Approach 1:
The lances are pre-assembled with reactant injection nozzles before insertion, and the lance design accounts for stress distribution in advance, allowing longer and more effective lances to be installed without requiring complex drive systems for periodic replacement
3Ease of manufacture
If reactant is injected through nozzles located in boiler walls with secondary air, then investment and operating costs are reduced, but the selection of injection angle is limited and reactant is not directly introduced into the centre of combustion
Solution Approach 1:
The lance assembly system allows for adjustable injection angles and positions, enabling dynamic optimization of reactant delivery to the combustion center while maintaining cost-effectiveness through a simpler overall system design compared to complex wall nozzle arrangements
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 reduces nitrogen oxide and carbon monoxide emissions, minimizes unreacted reactant in ash and flue gas, increases system efficiency, and lowers operational costs by optimizing reactant distribution and temperature management within the furnace chamber.
Implementation Method 1
The process gas stream creates a strong internal recirculation vortex in the furnace chamber, opposing the main flue gas flow direction
Implementation Method 2
The process gas stream creates a strong internal recirculation vortex in the furnace chamber
Implementation Method 3
A method involving the injection of a process gas and a reactant, such as ammonia or its derivatives, through lances positioned strategically within the furnace chamber
Data Source
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AI summary
A method of limiting the formation of nitrogen oxides and / or of their reduction consisting in that a process gas or in another variant the process gas with reactant is injected into the combustion chamber in a direction opposite to the main direction of the main flue gas stream flowing through the furnace chamber, at a speed of 30 to 180 m/s, preferably 135 m/s, the injection points being located at a distance of up to 0.5 of the depth of the furnace chamber from the axis of the front screen pipes, at one, two or three levels, the highest level being at the level of the lower edge of the boiler bull nose. The system for the realization of the method reducing NOx according to the invention comprises process gas injection lances (6), reactant injection lances (7), a furnace chamber (10), a process gas intake (11), a process gas fan (12), a measuring system (13) mounted on the process gas collector, a control and shut-off element (14) installed on the process gas collector, a reactant tank (15), a reactant pump (16), a measuring system (17) built on the reactant installation, a control-shut- off element (18) built on the reactant installation, a lance (19) for central injection of the reactant into the process gas.