Potassium-based sorbents from fly ash for high-temperature CO₂ capture.

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Investigating novel sorbent materials for efficient high-temperature carbon dioxide (CO2) capture is crucial for climate change mitigation.
• Coal fly ash, a readily available industrial byproduct, presents a potential source for developing cost-effective CO2 sorbents.

Purpose of the Study:

• To synthesize and evaluate potassium-fly ash (K-FA) sorbents for high-temperature CO2 capture.
• To assess the impact of incorporating lithium carbonate (Li2CO3) and calcium hydroxide (Ca(OH)2) on the CO2 sorption performance of K-FA materials.
• To investigate the stability and reusability of the developed sorbents over multiple capture-regeneration cycles.

Main Methods:

• Synthesis of K-FA sorbents using coal fly ash, silica, and aluminum.
• Addition of Li2CO3 (10 wt%) and Ca(OH)2 to the synthesized K-FA materials.
• High-temperature CO2 sorption experiments conducted at 700 °C, with kinetic analysis of sorption and desorption rates.
• Cyclic performance evaluation over 10 sorption-desorption cycles.

Main Results:

• K-FA sorbents demonstrated CO2 uptake capacity, with K-FA 1:1 achieving 1.45 mmol CO2/g at 700 °C.
• The addition of 10 wt% Li2CO3 significantly enhanced CO2 sorption to 2.38 mmol CO2/g at 700 °C within 5 minutes, comparable to existing Li-FA sorbents.
• Li2CO3 incorporation accelerated both sorption and desorption kinetics, attributed to the formation of a K-Li eutectic phase promoting diffusion.
• K-FA materials exhibited stable CO2 uptake and reaction rates over 10 cycles, indicating good cyclic performance.

Conclusions:

• K-FA sorbents, particularly when modified with Li2CO3, are effective for high-temperature CO2 capture.
• The enhanced performance is linked to the formation of a K-Li eutectic phase, improving CO2 diffusion and reaction kinetics.
• These findings suggest K-FA materials as a promising and potentially cost-effective option for industrial CO2 capture applications.