Research Projects

Growing concern over climate change has revived interest on devising mitigation techniques for CO₂. Existing techniques primarily include cryogenic distillation, adsorption, scrubbing, absorption, and membrane separation which incur huge energy penalty (~ 20-30 % of the power plant output) in cooling the flue/fuel gas prior to the treatment. An emerging technique is high temperature CO₂ capture using CaO based sorbent that treats incipient gas at high temperatures ∼650−950°C in pre & post-combustion operations. Though techno-economically in terms of uptake capacity, it suffers from sintering-induced agglomeration that reduces its performance under repeated carbonation and calcination cycles. The drawback has attracted extensive research towards modifying the sorbent with (i) inert, dopants, binders and promoters; (ii) thermal pre-treatment and steam hydration; and (iii) use of several synthesis techniques. This proposal aims at infusing fly ash with CaO-MgO sorbent so as to enhance and stabilize the uptake capacity under repeated cycles. The advantage is two-fold: firstly, fly ash contains refractory materials such as SiO₂, Al₂O₃, Fe₂O₃ and TiO₂, which serve as dispersant at high temperature, forming intermediate phases: larnite (Ca₂SiO₄), mayenite (Ca₁₂Al₁₄O₃₃) and CaTiO₃ that seclude the CaO grains, thereby inhibiting sintering; secondly, use of fly ash serves as utilization route for disposal of fly ash, which poses a serious issue in thermal power plants in India. For upscale of hot CO₂ capture to industrial level, the modified sorbents need to be evaluated for detailed kinetics, thermodynamics and finally examined inside reactor for breakthrough characteristics.