Multi-Shaft Kiln Decarbonation with Buffer and Oxygen Enrichment
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Solution Overview
Problem
The lime industry faces challenges in reducing CO2 emissions during the decarbonation process, particularly due to the intermittent nature of flue gas flow and low CO2 concentration in conventional lime kilns, which complicates the implementation of CO2 capture technologies like amine scrubbers, leading to increased energy consumption and production costs.
Innovation Solution
A multi-shaft vertical kiln process that uses oxygen-enriched combustion air to maintain a continuous exhaust gas flow, with a buffer system for storing and pressurizing the exhaust gas to enhance CO2 concentration, allowing for efficient CO2 capture and purification, and minimizing energy consumption by recycling and cooling the exhaust gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional single-shaft or parallel-flow regenerative kilns are used, then decarbonation process can be carried out, but the flue gas flow is intermittent and CO2 concentration is low (15-20 vol %), which complicates CO2 capture implementation
Solution Approach 1:
The system divides the flue gas handling into separate functional segments: a buffer vessel for continuous gas supply, a compressor for pressure control, and an amine scrubbing unit for CO2 capture. This segmentation allows each component to operate optimally and independently, resolving the contradiction between low CO2 concentration and capture system complexity.
Solution Approach 2:
A buffer vessel acts as an intermediary between the intermittent flue gas source and the continuous CO2 capture process. It stores exhaust gas and provides continuous flow to the amine scrubbing unit, enabling efficient CO2 capture despite the intermittent nature of kiln operation and low CO2 concentration in the raw flue gas.
2Quantity of substance
If amine scrubbers are implemented for CO2 capture from conventional kilns, then CO2 can be captured, but energy consumption increases due to intermittent gas flow and low CO2 concentration
Solution Approach 1:
The buffer vessel ensures continuous gas flow to the amine scrubbing unit, eliminating the intermittent operation that causes energy inefficiency. The compressor maintains steady pressure, and the continuous flow allows the amine solution to consistently absorb CO2 at optimal rates, significantly reducing energy consumption compared to intermittent capture from conventional kilns.
Solution Approach 2:
The system changes the pressure parameter by using a compressor to pressurize the exhaust gas before it enters the buffer vessel and amine scrubbing unit. This pressure increase improves CO2 solubility in the amine solution and enhances mass transfer efficiency, thereby improving CO2 capture efficiency while reducing the energy required for the absorption process.
3Productivity
If multi-shaft vertical kiln with oxygen-enriched combustion air is used, then continuous exhaust gas flow is achieved with high CO2 concentration, but device complexity increases
Solution Approach 1:
The system uses oxygen-enriched air (up to 95% O2) instead of conventional air for combustion in the multi-shaft vertical kiln. This accelerated oxidation produces exhaust gas with very high CO2 concentration (up to 95 vol %), enabling high-throughput decarbonation while the subsequent buffer and compression system manages the complexity of handling this concentrated gas stream.
4Quantity of substance
If CO2 concentration is increased through oxygen-enriched air, then CO2 capture efficiency improves, but energy consumption for oxygen enrichment and gas pressurization increases
Solution Approach 1:
The system changes the pressure parameter by compressing the exhaust gas to 5-50 bar before CO2 capture. This pressurization increases CO2 solubility in the amine solution and enhances mass transfer efficiency, allowing efficient CO2 capture at higher concentrations while managing the energy input required for compression through optimized system design.
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 enables high-throughput decarbonation with a high decarbonation grade, producing a CO2-rich stream suitable for sequestration or utilization while reducing energy consumption and production costs by maintaining continuous gas flow and optimizing CO2 capture efficiency.
Implementation Method 1
a buffer system for storing and pressurizing the exhaust gas to enhance CO2 concentration
Implementation Method 2
recycling and cooling the exhaust gas
Implementation Method 3
heated to a temperature above 910° C. in order to cause its calcination into quicklime (calcium oxide) and carbon dioxide
Implementation Method 4
heat is produced through the direct firing of a fuel
Data Source
AI summary
The present disclosure relates to a decarbonation process of carbonated materials, in particular limestone and dolomitic limestone, with CO2 recovery in a multi-shaft vertical kiln (MSVK) comprising a first and a second shaft with preheating, heating and cooling zones and a cross-over channel between each shaft. The method includes alternately heating carbonated materials by a combustion of at least one fuel with at least one comburent, up to a temperature range in which carbon dioxide of the carbonated materials is released, the combustion of the fuel and the decarbonation generating an exhaust gas. Decarbonated materials are cooled in the cooling zones with one or more cooling streams. The process further includes extracting the exhaust gas from the multi-shaft vertical kiln and feeding a buffer with the extracted exhaust gas.