CFD simulation of solids residence time distribution for scaling up gas‐solid bubbling fluidized bed reactors based on the modified structure‐based drag model

Abstract

Solids residence time distribution (RTD), which reflects the degree of solids mixing in bubbling fluidized bed (BFB), has become an essential parameter for the evaluation of reactor performances. In this paper, a modified structure‐based drag model was established to investigate the effect of the bed size and the correlation of bubble dimension on the gas‐solids hydrodynamics and solids RTD in three different scales of BFB. The result obtained from the modified structure‐based drag model shows better agreement with the experimental values and it can be used to predict the RTD properly. The deviation of flow field will cause a large difference in the RTD prediction. An accurate flow field is a prerequisite for calculating the RTD. For the cases of Geldart B particles, the Darton correlation is the best choice for low gas velocities. When scaling up a BFB, the RTD calculated by the modified structure‐based drag model is reduced in comparison with the experimental value, which is related to the increase of the bed size and the excessive estimation of the bubble size. On the other hand, the lack of consideration for the friction on both front and back walls in 2D simulation may lead to the over‐prediction of particle velocity and result in the deviation between calculated and experimental RTD value.

Special issue in honour of Professor Jamal Chaouki

“…99, issue 12) with 12 papers as Part II. [17][18][19][20][21][22][23][24][25][26][27][28] The special issue and special section cover experiments, modelling and simulation of multiphase reactors, pyrolysis and gasification, mineral processing, and applied catalysis.We would like to take this opportunity to thank all the contributors, reviewers, Dr. João B. P. Soares, and Kyra Van Den Bos, who, as the Managing Editor for this special issue, led the support team, which includes Tiffany Noel, Production Editor, and Lisa Olsen, Editorial Coordinator, in the publishing process. Above all, on behalf of all the contributors, we would like to take this opportunity to express our gratitude to Dr. Chaouki for his decades of dedication to teaching, mentoring, research, and community services in Canada, Morocco, and worldwide, and wish him and his well-respected family all the best in the future.…”

“…99, issue 12) with 12 papers as Part II. [17][18][19][20][21][22][23][24][25][26][27][28] The special issue and special section cover experiments, modelling and simulation of multiphase reactors, pyrolysis and gasification, mineral processing, and applied catalysis.…”

Review of Research Related to Fluid Cokers

“…The distribution of the formation-to-stripper time, i.e., the time required for an agglomerate to travel from its formation zone, at the tip of the spray jet, to the stripper zone, depends upon agglomerate properties, bed hydrodynamics, and the location of the spray jet . Larger and wetter agglomerates are more likely to cause issues with fouling and liquid losses, because they travel faster than bed particles ,, and take longer to dry. , There is a wide distribution of the formation-to-stripper time for agglomerates of the same size and liquid content, with a ratio of over 30 between the longest and shortest times; this indicates strong backmixing, which is to be expected given a Peclet number of around 0.2. , Backmixing is, however, far from perfect, and agglomerates formed at the top spray bank take about 20 times longer to reach the stripper than agglomerates formed at the lowest bank; this can be attributed to the combination of the longer vertical distance and the increase with the height of the superficial gas velocity . Eliminating the lowest spray bank and redistributing its liquid to the upper banks can double or triple the formation-to-stripper time of the most problematic, fastest agglomerates …”

“…41,46 There is a wide distribution of the formation-to-stripper time for agglomerates of the same size and liquid content, with a ratio of over 30 between the longest and shortest times; 20 this indicates strong backmixing, which is to be expected given a Peclet number of around 0.2. 220,221 Backmixing is, however, far from perfect, and agglomerates formed at the top spray bank take about 20 times longer to reach the stripper than agglomerates formed at the lowest bank; 20 this can be attributed to the combination of the longer vertical distance and the increase with the height of the superficial gas velocity. 222 Eliminating the lowest spray bank and redistributing its liquid to the upper banks can double or triple the formation-to-stripper time of the most problematic, fastest agglomerates.…”