2. The Project
• Collect and analyze data on Geldart’s
type A cohesive particles.
• Determine radial flux profiles and
overall entrainment in the CFB for
various:
gas velocities
particle diameters (monodisperse only)
bed weights (8 kg this summer)
Circulating
Fluidized Bed
(CFB)
3. Methods for Measuring Flux
1. Shadowgraphy Analysis
The camera takes two pictures very rapidly. The software
then uses the two frames to determine the each particle’s
instantaneous velocity.
Using the recorded
velocities, we can
determine the flux
through that radial
position in the column
4. Methods for Measuring Flux (cont.)
2. Local Flux Probe
This probe can be inserted through the
column wall, and be used to measure
local flux at a radial position in the
column.
3. Total Entrainment
Measurement
The butterfly valves in the
standpipe allow us to measure the
total entrainment through our CFB.
3
2
5. Particle Loss from Gas Outlet
We observed a large number of particles shooting out
the gas outlet of our CFB.
This indicated that the system was not circulating
properly, and particles were constantly being lost
while the bed was in use.
This means the bed weight was changing, and would
lead to invalid entrainment measurements.
6. Solution
First, we examined the whole CFB for
gas leaks using snoop, and made sure
it was airtight.
We realized it could be a problem with
the cyclones.
Eventually got the bed to recirulate
properly using only one group B
cyclone.
Group A
Group B
7. The switch of cyclones
resulted in much more
efficient entrainment.
Allowed us to run at a
higher gas velocity
• streamers became
present.
8. Standpipe Buildup
The working cyclone circulated particles effectively, but particles began to
buildup in the standpipe
WHY?
Hypothesis: the particle size resulted in tighter packing in the standpipe. The
standpipe/column connection was horizontal → Pressure drop from standpipe
to column base was not large enough to recirculate particles.
Solution: Vacuum out particles and redistribute into column
10. Flux Probe
GOAL:
• To obtain data that offered a correlation between gas
velocity, particle size, and height/radial position in the
column to local flux measurements.
• Compare to Shadowgraphy analysis data at various
heights and radial postions.
11. ● In order to obtain valid results we
needed to determine necessary gas
flow rates in and out of the probe to
ensure equal stream velocities into and
out of the probe.
HOWEVER…
● Unable to control gas flow rate in/out of
the probe with any sort of precision.
controllable
valve
12. • When we opened the valve an
appropriate amount, no
significant mass of particles
could be measured…
HOWEVER
• When we took the valve off to
let air flow freely, we observed
this
WHY?
• Hypothesis: Particle size
particles tend to follow gas
stream if some gas went
around the probe inlet, so did
the particles
13. Shadowgraphy Analysis
The camera itself was a challenge to take crisp, in-focus
pictures with.
When we did get nice pictures the software had difficulty
analyzing them accurately.
18. Flux calculations from Shadowgraphy
Analysis
We were able to get a couple decent image/analysis
pairings -> computed a flux value:
• Values depend on velocity, initial position, chosen time
lapse (dt).
19. Determining an appropriate time lapse:
● Find average velocity of particles (2 ways)
● Using avg vertical velocity, determine time needed (dt) for a
particle at the bottom of the frame to reach the threshold/mid
level height.
○ We used dt = .229 seconds
20. Effect of Time Lapse (dt)
*Yh = 5.525 (midline)
*If statements determine
positive and negative flux
based on particles crossing
Yh
