CFD simulations of particulate two-phase and three-phase flows

This dissertation describes computational fluid dynamics (CFD) simulations of gas-solid flow in a riser and gas-liquid-solid flow in a slurry bubble column reactor. Three computer codes were used. The commercial code, Fluent, was used to simulate the dilute flow of 530 μm in the IIT riser. The remaining simulations were performed using computer codes developed earlier at IIT.; A liquid-solid fluidized bed with a central jet, was modeled using IIT's computer code. The experimental apparatus and the data are described in this dissertation based on the work of Mr. Youliang Guo. In this dissertation the viscosity computed by Mr. Guo was used as an input to the computer code. For a converged solution, the granular temperature was highest in the jet, as expected for developed flow. The computed and the measured bed expansions agreed with each other with an error of about 10%. The average experimental turbulent intensity was 0.43, compared with a limiting theoretical value of 0.44. The CFD computation produced a value of 0.73.; The code developed by Wu was used to improve methanol production in a slurry bubble column reactor. The heat exchangers were rearranged to produce two stages, with a higher solid catalyst concentration in the upper stage. This rearrangement yielded a higher methanol production, due to increased activity in the upper stage. This simulation shows the potential of improving reactor design using CFD.; Riser simulations for challenge 2 problem were submitted for presentation at the Tenth International Fluidization Conference in China. From PSRI data received after the conference, we learned that the pressure drops in the riser for flow of FCC particles were in good agreement with the PSRI data. The flux profiles however, in agreement with most contestants, showed an asymmetry not seen in the PSRI experiment.; A by-product of the challenge problem 2 simulation was the computation of maximum carrying capacity or choking in the PSRI riser. An analytical approximate formula for the maximum carrying capacity based on the results obtained earlier, was used to compute choking for a wide range of data available in the literature. The key variable in the theory is the concept of the pseudo-sonic velocity of the particles. This sonic velocity was estimated based on measurements done at IIT over the last decade.