Cold Model Study of a 1.5 MW_th Circulating Turbulent Fluidized Bed Fuel Reactor in Chemical Looping Combustion

Abstract

A circulating turbulent fluidized bed (CTFB) connected with a riser and an annular carbon stripper (CS) is proposed to be used as a fuel reactor (FR) in chemical looping combustion. The bottom section of the FR is operated under turbulent fluidization regime which can achieve enough solid residence time and enhance the mixing of oxygen carrier with solid fuel. A 1.5 MWth cold model of the FR was designed, constructed and tested in order to investigate the hydrodynamics of solid particles with different size. Three kinds of quartz sands with different particle sizes (d50=122 μm, 249 μm, and 392 μm) were used as bed materials to simulate the oxygen carrier.Continuous operation with reasonable pressure balance was achieved in the cold model. The effects of important variables including gas velocity, static bed height and 2 particle size on the gas-solid hydrodynamics of the FR were measured and discussed.It was found that the transition velocities from bubbling to turbulent fluidization for different particles of d50=122 μm, 249 μm, and 392 μm were measured to be 0.78 m/s, 0.95 m/s and 1.06 m/s respectively, indicating the transition velocity increased with increasing particle size. The solid fraction profile along reactor height and solid circulation rate were affected by gas velocity and static bed height. A modified correlation was proposed to predict the solid fraction of the annular CS dilute phase, and the predicted results agree well with the experimental data under wide range of operational conditions.

Solid Circulation Study in a 1.5 MWth Cold Flow Model of Chemical Looping Combustion

“…Then, turn off the fluidizing gas of the loop seal between FR and SR and measure the Gs,FR using the same method, as shown in equation ( 4). The results of the Gs,FR have been provided in previous work 32 . It should be noted that the value of the FR solid circulation rate in the literature 32 is calculated based on the sectional area of the annular CS, while the Gs,FR in this work is calculated based on the sectional area of the simplified riser, so the literature value needs to be converted.…”

“…The FR is composed of a turbulent fluidized bed (TFB), a FR riser, and an annular carbon stripper (CS), and the specific dimensions of the FR have been provided in a previous work. 32 An overflow port is located on the side of the TFB with a height of 1.25 m, an inner diameter of 0.15 m, and a downward opening. A LS is connected with the overflow port and a simplified AR riser.…”

“…The results for G s,FR have been provided in a previous work. 32 It should be noted that the value of the FR solid circulation rate in the literature 32 is calculated based on the sectional area of the annular CS, while the G s,FR in this work is calculated based on the sectional area of the SR, so the literature value needs to be converted.…”

“…The schematic diagram of the 1.5 MW th CLC cold flow model system is shown in Figure . The FR is composed of a turbulent fluidized bed (TFB), a FR riser, and an annular carbon stripper (CS), and the specific dimensions of the FR have been provided in a previous work . An overflow port is located on the side of the TFB with a height of 1.25 m, an inner diameter of 0.15 m, and a downward opening.…”

Fast versus turbulent fluidization of Geldart Group B particles

“…2 It is common in industrial fluidization because of advantages including vigorous gas-solid contact, favorable bed-tosurface heat transfer, high solid hold-up (typically 25-35% by volume), and limited axial gas mixing. 7 The turbulent fluidized bed continues to find innovative applications in sorbent regeneration, 10 carbon capture, 11,12 combustion, 13 and chemical synthesis, 14 with pursuit of the understanding of behaviors like heat transfer, 15 gas-solid flow [16][17][18] persisting. The fast fluidization regime is operated as a circulating fluidized bed due to the much higher entrainment rates.…”