Oxyfuel Calciner with Segmented Preheating for Cement CO2 Capture
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Solution Overview
Problem
The production of cement clinker results in significant CO2 emissions, and existing methods to reduce these emissions either increase fuel energy requirements or face challenges with high-temperature dust handling and recarbonation effects.
Innovation Solution
A method and plant design that preheat cement raw meal in separate calciner and kiln preheaters, using an oxyfuel process in an entrained flow reactor calciner with recirculated exhaust gases, followed by post-combustion CO2 separation utilizing waste heat for energy efficiency and effective CO2 capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oxyfuel firing is used in the calciner to generate CO2-rich exhaust gas, then CO2 separation efficiency is improved, but fuel energy requirement increases significantly
Solution Approach 1:
The preheating process is segmented into two separate preheaters: a calciner preheater using calciner exhaust gas and a kiln preheater using kiln exhaust gas. This segmentation allows the oxyfuel calciner to operate independently, generating CO2-rich exhaust gas for efficient separation without requiring excessive fuel energy, as each preheater utilizes its own exhaust gas source.
Solution Approach 2:
The system changes the chemical composition parameter of the combustion air by using oxygen-enriched air (30-50 vol% O2) instead of normal air in the oxyfuel calciner. This parameter change enables CO2-rich exhaust gas generation for efficient separation while the dual preheater configuration manages the energy balance to prevent excessive fuel consumption.
2Use of energy by moving object
If flue gas is cooled for recirculation to maintain low fuel energy requirement, then fuel energy consumption is reduced, but recarbonation effects increase
Solution Approach 1:
The exhaust gas recirculation is segmented into separate streams: calciner exhaust gas is recirculated to the calciner and kiln exhaust gas is recirculated to the kiln. This segmentation prevents CO2-rich calciner exhaust gas from contacting cooled raw meal in the kiln, thereby minimizing recarbonation effects while maintaining fuel energy efficiency through appropriate flue gas cooling and recirculation.
3Loss of energy
If high dust loads are handled in heat exchangers at high temperatures, then heat recovery efficiency is improved, but operational reliability decreases due to dust adhesion
Solution Approach 1:
Each preheater is designed with local quality optimization: the calciner preheater handles high-temperature, high-dust calciner exhaust gas with appropriate heat exchange surfaces, while the kiln preheater handles kiln exhaust gas separately. This localized design allows each heat exchanger to be optimized for its specific operating conditions, maintaining heat recovery efficiency while managing dust adhesion challenges through appropriate material selection and design for each location.
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
Achieves greater CO2 separation without significantly increasing fuel requirements, while minimizing recarbonation effects and operational complexities, and utilizing waste heat for efficient CO2 capture and processing.
Implementation Method 1
part of the cement raw meal is preheated in a calciner preheater (2) and the other part of the cement raw meal is preheated in a kiln preheater (3)
Implementation Method 2
the calcinator preheater is operated with calcinator exhaust gases from the calcinator and the kiln preheater is operated with kiln exhaust gases from the kiln
Implementation Method 3
the precalcined cement raw meal in a kiln is fired
Implementation Method 4
an entrained flow reactor being used as the calciner, with part of the calcinator exhaust gas being recirculated to the calciner
Implementation Method 5
the kiln exhaust gas is subjected to a post-combustion CO2 separation
Implementation Method 6
utilizing waste heat for energy efficiency and effective CO2 capture
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method and a system for producing cement clinker from raw cement mixture, wherein - one part of the raw cement mixture is preheated in a calciner preheater, and the other part of the raw cement mixture is preheated in an oven preheater, - the preheated raw cement mixture is pre-calcined in a calciner which is operated according to the oxyfuel method, - the pre-calcined raw cement mixture is fired in an oven, - the fired raw cement mixture is cooled in a cooler, - the calciner preheater is operated using exhaust gases of the calciner, - the oven preheater is operated using exhaust gases of the oven, - an entrained flow reactor is used as the calciner, a part of the calciner exhaust gas being recirculated to the calciner after being used in the calciner preheater, and - the oven exhaust gas undergoes a post-combustion CO2 separation.