Thermokinetic Investigations of High Temperature Carbon Capture Using a Coal Fly Ash Doped Sorbent

Abstract

Carbon capture (CC) employing novel sorbents at high temperature is highly significant to address the serious concerns of global warming. In this work, thermodynamic and kinetic studies have been conducted on the carbonation using doped sorbents of CaO–MgO–CFA (coal fly ash). The thermodynamic estimations not only proved the feasibility and spontaneity of the reaction but also reinforced the positive role played by CFA in not only enhancing the CC but also reducing the regeneration temperatures. Regarding the kinetic studies, a model has been proposed for both the reaction and diffusion kinetic control regimes and has been validated with experimental data at optimal conditions. Various kinetic and Arrhenius parameters have been estimated and compared with the reported values. The rate constants at 650 °C and activation energies estimated for reaction and diffusion controlled regimes were 2.5 min−1, 23 kJ/mol and 0.8 min−1, 30 kJ/mol, respectively. Our values clearly indicate the enhanced rate achieved by doped sorbents along with thermal stability and also show that kinetics are strongly dependent on the nature of the sorbent along with process conditions.

Understanding Hysteresis in Carbon Dioxide Sorption in Porous Metal–Organic Frameworks

“…Capture and separation of CO 2 by physisorption involve weaker bonding energetics and can thus be applied to cyclic adsorption/desorption processes, with desorption induced by changes in pressure or by heating. Zeolites, − activated carbon, , metal–organic frameworks (MOFs), − zeolitic imidazolate frameworks (ZIFs), and covalent-organic frameworks materials (COFs) − are the most prominent solid adsorbents considered for CO 2 capture by physisorption. Many of these materials demonstrate one-step type I sorption isotherms with CO 2 indicating a typical Langmuir sorption mechanism.…”

Valorization of Coal Fly Ash as a Stabilizer for the Development of Ni/CaO-Based Bifunctional Material

“…In another study, efforts were made to enhance the CO 2 capture performance of FA-stabilized CaO-based sorbents using either FA pretreated by grinding, calcination, and alkaline solution leaching or mixing CaO, FA, and basic/acidic solutions . The results showed that CaO combined with FA under acidic conditions (50% acetic acid solution) presented an increased reactivity and achieved high CO 2 capture capacity, which was attributed to the formation of Ca 12 Al 14 O 33 and CaSiO 3 , as well as a better microstructure. , Sreenivasulu et al , employed various combinations of sorbents based on CaO, MgO, zeolites (H-β and H-ZSM 5), and Al 2 O 3 in the presence or absence of FA for evaluating the CO 2 capture performance. They found that 50%CaO–10%MgO–40%FA exhibited the highest capture capacity and cyclic stability of up to 15 cycles …”

Calcination Thermokinetics of Carbon Capture Using Coal Fly Ash Stabilized Sorbent

“…Increased CC capacity of sorbent has been reported with higher CO 2 partial pressures in feed gas mixture. − In our previous studies, the sorbent screening from more than 20 potential candidates has been done at two levels, and the sorbent CaO50MgO10FA-C40 was then selected as the best sorbent in powder form that gave the highest capture capacity of more than 11 mmol/g ads at the optimal conditions of temperature, time, gas flow rate, sorbent nature, morphology, and amount . The positive role played by CFA along with active sorbents of CaO and MgO (CaO50MgO10FA-C40) in enhancing the thermodynamic feasibility and carbon capture rate and capacity was reported by us in our earlier work …”