Firing Installation Combustion Management with Internal Recirculation
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Solution Overview
Problem
Existing combustion management methods in firing installations fail to achieve optimal burn-out of solid fuels while minimizing nitrogen oxide formation and maintaining stable operation with low excess air coefficients.
Innovation Solution
The method involves adjusting stoichiometric to substoichiometric reaction conditions in the primary combustion area, using internal and external recirculation gases, and introducing turbulence gases like steam or inert gases to extend dwell time of waste gases at high temperatures, along with controlling air ratios to achieve efficient gasification and burn-out, and utilizing a hybrid grate system for gasification and burn-out processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If stoichiometric to highly substoichiometric reaction conditions are adjusted in the primary combustion area, then syngas heating value is increased, but complete combustion and nitrogen oxide control become difficult
Solution Approach 1:
The combustion chamber is divided into a primary combustion area with substoichiometric conditions for syngas production and a downstream burn-out area for complete combustion. This spatial segmentation allows both high syngas heating value (up to 4000 kJ/Nm³) and stable operation to be achieved simultaneously by optimizing each zone independently.
Solution Approach 2:
The internal recirculation gas is supplied downstream of the primary combustion area to enable burn-out of the syngas after it has been generated. This preliminary formation of high-value syngas followed by controlled burn-out allows the system to maintain both high energy content and combustion stability.
2Object-generated harmful factors
If internal recirculation gas is supplied to burn-out waste gases, then nitrogen oxide formation is reduced, but dwell time and temperature maintenance become challenging
Solution Approach 1:
A turbulence gas (steam or inert gas) is introduced as an intermediary substance between the primary combustion area and the internal recirculation gas supply. This turbulence gas extends the dwell time of waste gases at temperatures above 850°C for at least 2 seconds, providing sufficient time for burn-out while the internal recirculation gas suppresses nitrogen oxide formation through reduced oxygen availability.
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 results in optimal burn-out of waste gases with minimal nitrogen oxide formation, stable operation, and high syngas heating values, allowing for efficient fuel conversion and cinder burn-out with excess air coefficients between 1.1 and 1.5, thereby optimizing combustion management.
Implementation Method 1
internal recirculation gas is supplied in a burn-out area that lies downstream of the primary combustion area referred to the flow direction
Implementation Method 2
supplying a turbulence gas downstream of the primary combustion area referred to the flow direction in order to generate turbulence
Implementation Method 3
admix external recirculation gas, which has passed through a steam generator and, if applicable, a waste gas cleaning system, to the internal recirculation gas
Implementation Method 4
a primary combustion gas quantity is conveyed through the fuel into a primary combustion area
Implementation Method 5
stoichiometric to highly substoichiometric reaction conditions with λ=1 to λ=0.5 are adjusted in the primary combustion area
Data Source
AI summary
In a method for the combustion management in firing installations, in which a primary combustion gas quantity is conveyed through the fuel into a primary combustion area, part of the waste gas flow is extracted in the rear grate area and returned to the combustion process in the form of internal recirculation gas. In this case, no secondary combustion air is supplied between the grate and the supply of the internal recirculation gas. A firing installation for carrying out this method features nozzles above the firing grate such that no air supply is arranged between the firing grate and the nozzles.