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Limestone is widely used as a sorbent in fluidized bed combustors. The study of limestone attrition characteristics is significant for mass balance and desulfurization efficiency. The present study investigates the sulfation and attrition behavior of limestone in a bubbling fluidized bed reactor. The product distribution and development of the product layer are analyzed by scanning electron microscopy. The experimental results show the attrition rate dropped dramatically at the initial kinetic-controlled regime of the sulfation reaction. The observations show that the distribution of the product is not uniform but primarily concentrated on the external surface of the particle. Meanwhile, the thickness of the product layer at the initial stage of the sulfation reaction reaches 0.7 μm, which is larger than that predicted by previous investigators, and it results in a dramatic decrease in the attrition rate. As sulfation continues, the thickness of the product layer increases and reaches 1.6 μm at the diffusion-controlled regime of the reaction, whereas the attrition rate decays to a steady state. A random pore model is also used to analyze the development of the product layer thickness by counting in the whole reaction surface, but the results show a much smaller value as a result of the lack of consideration of the unreacted core, which verifies the early pore blockage in the initial stage observed in the present study.