Calciner with Segmented NOx Reduction Zone
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Solution Overview
Problem
Existing cement clinker manufacturing systems face challenges in achieving both high combustion efficiency with fuels of low volatile content and low NOx emission levels, as current designs either compromise on NOx reduction or fuel efficiency when using such fuels.
Innovation Solution
The system introduces kiln exhaust gases and fuel into the upper end of the calciner, with preheated air and raw meal fed under the exhaust gas/fuel zone, allowing the raw meal to flow down the calciner wall, creating a NOx reduction zone where tertiary air enhances combustion temperature and efficiency, and preheated raw meal is introduced to promote further NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the calciner is designed for using fuels with low volatile content, then combustion efficiency is improved, but NOx emission levels increase
Solution Approach 1:
The calciner is divided into two distinct zones: an upper combustion zone for efficient fuel burning and a lower NOx reduction zone for reducing nitrogen oxide emissions. This segmentation allows each zone to optimize its specific function without compromising the other.
Solution Approach 2:
A reducing zone is introduced as an intermediary between the combustion zone and the exhaust system. This zone uses injected fuel to create reducing conditions that convert NOx into nitrogen, thereby mediating the harmful effect of NOx emissions while maintaining combustion efficiency.
2Object-generated harmful factors
If a reducing zone is added to reduce NOx emissions, then NOx emission levels decrease, but the system complexity increases
Solution Approach 1:
The NOx reduction function is merged into the existing calciner structure by utilizing the lower portion of the calciner body as the reducing zone. This integration approach reduces system complexity compared to adding a completely separate reduction device.
Solution Approach 2:
The calciner structure serves multiple functions: the upper portion handles combustion while the lower portion handles NOx reduction. This multi-functionality eliminates the need for separate dedicated reduction equipment, thereby reducing overall system complexity.
3Object-generated harmful factors
If preheated raw meal is introduced into the reducing zone, then NOx reduction is enhanced, but combustion temperature decreases
Solution Approach 1:
Preheated raw meal is introduced specifically into the lower reducing zone rather than the upper combustion zone. This localized introduction ensures that the cooling effect occurs only in the region where temperature reduction is desirable for NOx reduction, while the combustion zone maintains its high temperature for efficient fuel burning.
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 configuration achieves a significant reduction in NOx emissions and high fuel burnout, maintaining a high combustion temperature even with fuels of low volatile content, thereby reducing NOx formation and minimizing wall coatings.
Implementation Method 1
combustion of fuel by reacting with NOx contained in the exhaust gases from the kiln, thereby reducing the NOx content
Implementation Method 2
preheated air from the clinker cooler and preheated raw meal from the preheater are subsequently fed to the calciner
Implementation Method 3
exhaust gases from the kiln are introduced at the bottom of the combustion chamber, thereby causing the gases to flow upwards through the combustion chamber and the subsequent calciner
Data Source
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AI summary
A system for reducing NOx emission levels during the manufacture of cement clinker having a calciner unit with the following features: an upper portion; a lower portion; a NOx reduction zone in the lower portion; a tertiary air inlet in the upper portion for introducing tertiary air into the upper portion; a main calciner meal inlet located above the NOx reduction zone for introducing a main calciner meal portion into the upper portion; a first cooling calciner meal inlet located in the NOx reduction zone for introducing a first cooling calciner meal portion into a periphery of the NOx reduction zone; and a fuel inlet located in or below the NOx reduction zone for introducing fuel into the reduction zone.