scholarly journals Increasing Gas–Solids Mass Transfer in Fluidized Beds by Application of Confined Fluidization—A Feasibility Study

2019 ◽  
Vol 9 (4) ◽  
pp. 634 ◽  
Author(s):  
Jesper Aronsson ◽  
David Pallarès ◽  
Magnus Rydén ◽  
Anders Lyngfelt
Keyword(s):  
Mass Transfer ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Cross Flow ◽  
Active Role ◽  
High Density ◽  
Low Density ◽  
Olivine Sand ◽  
Bed Material ◽  
Utility Scale

Fluidized bed applications where the bed material plays an active role in chemical reactions, e.g. chemical looping combustion, have seen an increase in interest over the past decade. When these processes are to be scaled up to industrial or utility scale mass transfer between the gas and solids phases can become a limitation for conversion. Confined fluidized beds were conceptualized for other purposes in the 1960’s but are yet to be applied to these recent technologies. Here it is investigated if they can prove useful to increase mass transfer but also if they are feasible from other perspectives such as pressure drop increase and solids throughflow. Four spherical packing solids, 6.35–25.4 mm in diameter at two different densities, were tested. For mass transfer experiments the fluidizing air was humidified and the water adsorption rate onto silica gel particles acting as fluidizing solids was measured. Olivine sand was used in further experiments measuring segregation of solids and packing, and maximum vertical crossflow of solids. It was found that mass transfer increased by a factor of 1.9–3.8 with packing solids as compared to a non-packed reference. With high-density packing, fluidizing solids voidage inside the packing was found to be up to 58% higher than in a conventional fluidized bed. Low density packing material favoured its flotsam segregation and with it higher fluidization velocities yield better mixing between packing and fluidizing solids. Maximum vertical cross-flow was found to be significantly higher with low density packing that fluidized, than with stationary high-density packing. Conclusively, the prospect of using confined fluidized beds for improving mass transfer looks promising from both performance and practical standpoints.

Liquid-wall mass transfer in three phase fluidized beds with cross-flow of electrolyte

2008 ◽  
Vol 135 (3) ◽  
pp. 224-231 ◽  
Author(s):  
K.V. Ramesh ◽  
G.M.J. Raju ◽  
C. Bhaskara Sarma ◽  
R.V. Subba Raju
Keyword(s):  
Mass Transfer ◽  
Fluidized Beds ◽  
Cross Flow ◽  
Three Phase ◽  
Liquid Wall ◽  
Wall Mass

Particle Motion in the Vicinity of the Wall of Circulating Fluidized Beds

2012 ◽  
Vol 614-615 ◽  
pp. 3-7
Author(s):  
Jian Hui Liu ◽  
Shuan Shi Fan ◽  
Dong Lai Xie
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Particle Motion ◽  
Fluidized Beds ◽  
High Density ◽  
Circulating Fluidized Beds ◽  
Low Density ◽  
Transfer Coefficients ◽  
Tube Heat Exchanger ◽  
Operation Conditions

High-density circulating fluidized beds (CFB) differ in several respects from low-density CFB systems. In high-density CFB risers, solids move upward throughout the entire riser cross-section, and the net downflow of particles at the wall, a commonly observed feature of fast fluidized beds, is absent. Hence there exists a transition regime from the low density to high density CFB where the net particle motion in the vicinity of the wall is changing from downwards to upwards. This was confirmed by experiments carried in a dual-loop high-density CFB facility with concentric-tube heat exchanger installed in the riser. Local suspension-to-wall heat transfer coefficient and suspension temperature distribution below and above the heat exchange section were measured. Experimental results elucidated that particles move both upwards and downwards in the vicinity of the wall for the operation conditions studied. This alternation of direction leads to higher heat transfer coefficients at both ends of the heat exchange.

scholarly journals Mass Transfer Enhancement in GLS Fluidized Beds using Nanomaterials

2019 ◽  
Vol 8 (3) ◽  
pp. 5763-5766
Keyword(s):  
Mass Transfer ◽  
Benzoic Acid ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Physical Property ◽  
Gas Velocity ◽  
Three Phase ◽  
Unique Physical Property

Nanomaterial has unique physical property which made it important for many applications and that is why the use of nanomaterials rapidly increasing in the field of science and engineering.1 . This work focuses on mass transfer of solids into liquid in three phase fluidized beds in presence of nanomaterial. This include the study of effect of gas velocity, time and different concentration of nanomaterials on mass transfer coefficient in stagnant liquid column in three phase fluidized bed system. To measure coefficient of the mass transfer, known quantity of solid pellets ie benzoic acid and known amount of nanomaterial fraction ie Arachitol nano were charged in the test column of three phase fluidized bed system. At the beginning of each run, test section was partially filled with water which prevent breakage of particles. The experiments were conducted by sequentially varying gas velocity for different volumes of nanomaterial and measuring the rate of mass transfer by collecting samples directly from the outlet ports at the top subsequently analysed by volumetric titration method. The results show enhancement in mass transfer coefficient by addition of nanomaterials. Arachitol nano has been taken in different volumes ie 3ml, 7ml, 10ml and 20ml in (GLS) gas ,liquid and solid fluidized bed with air, water and benzoic acid pellets as three phases respectively in the system. The presence of nanomaterial increases the solid liquid mass transfer coefficient value with increasing fraction of nanomaterial, increasing gas velocity and increasing time although experimental run has been taken only for one hour.

Fluidization of Geldart Type-D Particles in a Swirling Fluidized Bed

2011 ◽  
Vol 110-116 ◽  
pp. 3720-3727 ◽  
Author(s):  
Mohd Faizal Mohideen ◽  
Suzairin Md Seri ◽  
Vijay Raj Raghavan
Keyword(s):  
Particle Size ◽  
Pressure Drop ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Superficial Velocity ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Type D ◽  
Minimum Fluidization ◽  
Bed Material

Geldart Type-D particles are often associated with poor fluidization characteristics due to their large sizes and higher densities. This paper reports the hydrodynamics of various Geldart Type-D particles when fluidized in a swirling fluidized bed (SFB). Four different sizes of particles ranging from 3.85 mm to 9.84 mm with respective densities ranging from 840 kg/m3 to 1200 kg/m3 were used as bed material to study the effect of various bed weights (500 gram to 2000 gram) and centre bodies (cone and cylinder) for superficial velocities up to 6 m/s. The performance of the SFB was assessed in terms of pressure drop values, minimum fluidization velocity, Umf and fluidization quality by physical observation on regimes of operation. The swirling fluidized bed showed excellent capability in fluidizing Geldart Type-D particles in contrast to the conventional fluidized beds. The bed pressure drop of increased with superficial velocity after minimum fluidization as a result of increasing centrifugal bed weight. It was also found that the particle size and centre body strongly influence the bed hydrodynamics.

Sign in / Sign up

Export Citation Format

Share Document