Limestone Attrition and Product Layer Development during Fluidized Bed Sulfation

Abstract

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.

Quantitative Structure–Activity Relationship of Nanowire Adsorption to SO2 Revealed by In Situ TEM Technique

“…19 On the basis of the solid−gas reaction, ZnO nanomaterials have been widely applied for capturing SO 2 from atmospheric air. 24 However, the SO 2 adsorption/sensing performance of ZnO nanomaterials has mainly been investigated through trial and error by using professional apparatuses such as fluidized beds, 25,26 but this approach is time-consuming and labor intensive. Note that the performance is mainly determined by the material structure (including size and morphology), thus a quantitative structure− activity relationship (QSAR) plays an essential role in the design, synthesis and highly efficient evaluation of SO 2adsorbing materials.…”

Modeling of the axial distributions of volatile species in a circulating fluidized bed boiler

“…denotes the mass fraction of particles in (i, j, k) group, and the sum of mass fraction of all group particles in each cell (including ash and lime) should be equal to one. The determination of Kaf of ash particles and lime particles was introduced in our previous studies (Ke et al, 2019, Li et al, 2020.…”

“…in our previous study, and the critical attrition sizes for ash particles, dcriA, A and dcriF, A, are set to be 90 μm and 20 μm, respectively. For lime particles, the attrition rate constant is determined based on the study of Li et al (2020). The FLPSD, dcriA, L and dcriF, L are from the experimental results of In this paper, the effects of feeding coal size and furnace temperature on the axial distributions of volatile species is discussed.…”

Virtual Special Issue of 2019 International Symposium on Clean Energy and Advanced Carbon Materials (CEAM-2019)

“…Rahman et al 4 studied the kinetics and mechanism of the catalytic oxidation of nitric oxide in coal combustion flue gas over the Co-doped Mn−Ti oxide catalyst. Li et al 5 conducted systematic research on limestone attrition and product layer development during fluidized-bed sulfation. Li et al 6 studied the influence of the slag−crucible interaction on coal ash fusion behavior at high temperatures.…”