The calcination kinetics and pore structure evolution of limestone in simultaneous calcination/sulfation was studied by a self-designed constant-temperature thermogravimetric reactor. Sulfation reaction took place to form CaSO4 simultaneously with limestone calcination as long as SO2 gas was present. The presence of SO2 reduced calcination rate of limestone. Compared to pure calcination

simultaneous calcination/sulfation had slower increase in specific surface area and specific pore volume

which both distribution curves were lower

and these two parameters of small pores with 2-8 nm in diameters decreased with time in the final calcination stage. A mechanism was proposed to describe pore microstructure evolution during simultaneous calcination and sulfation

that is

because limestone calcination occurs from surface to inner core

small amount of CaSO4 was formed on CaO surface with few plugged pores and CaSO4 had little effect on calcination rate and pore structure in initial reaction stage (0-75 s)

continuous increase of CaSO4 thickness and coverage enlarged both volume of closed pore and CO2 diffusion resistance but declined calcination rate in the middle calcination stage (75-225 s)

and further accumulation of CaSO4 accelerated plugging on pores especially smaller ones in the final stage (225-300 s). Calculation of volume of closed pores showed that pore plugging started in initial and middle calcination stages and intensified rapidly in final reaction stage

which validated the proposed mechanism.