The 6th High temperature Solid Looping Cycles Network Meeting
September 1 th-2th,2015,Politecnico Di Milano
Separation of Lighter Particles from
Heavier Particles in Fluidized Bed for SE
Hydrogen Production and CLC
Sun Hongming, Li Zhenshan, Cai Ningsheng
The Department of Thermal Engineering, Tsinghua University
2015-09-02
Outline
 Introduction
 Experiments
 Simulation
 Results
 Conclusions
Introduction - sorption enhanced hydrogen production
CH4 + 2H2O = CO2 + 4H2
Catalyst
CO2 sorbent
H2
CH4 + 2H2O
Reactor
H2 fraction (%)
 CO2 can be removed in-situ by sorbents
 High purity of hydrogen can be produced
 No necessary for purification
 Heat from exothermic carbonation can be
directly used by the endothermic
reforming reaction
Reaction time (min)
Introduction - process
>95% H2
CO2
CaCO3
Reformer
CH4(g) + H2O(g)=CO(g)+3H2(g)
CO(g) + H2O(g) =CO2(g) +H2(g)
CO2 (g) +CaO(s)=CaCO3(s)
CH4 + H2O
Regeneratror
CaO
CaCO3(s) = CO2 (g) +CaO(s)
Sorbent/catalyst is cycled
Fuel + O2 or heat
（1）Two reactors are required in order to regenerate CaO;
（2）Reaction heat of carbonation: ~178kJ/mol; fluidized bed?
（3）Combustion is required in regenerator for providing heat;
（4）Catalyst degradation due to oxidation and sintering;
Introduction - progress
University of Leeds
INCAR-CSIC
（1）mobile CO2 adsorbent flowing through a stationary SMR
catalyst phase (university of Leeds);
（2）combing CaL with CLC into one particle(INCAR-CSIS);
（3）sorbent/catalyst bifunctional material (many groups);
Introduction – objective of this presentation
>95% H2
CO2
CaCO3
catalyst
Reformer
CH4(g) + H2O(g)=CO(g)+3H2(g)
CO(g) + H2O(g) =CO2(g) +H2(g)
CO2 (g) +CaO(s)=CaCO3(s)
CaCO3
catalyst
separator
Regeneratror
catalyst
CaCO3(s) = CO2 (g) +CaO(s)
CaO
CH4 + H2O
Terminal velocity: u t  [
Fuel + O2 or heat
4d p ( s   g )g
3 gC D
1/ 2
]
 (d p  s )
1/ 2
[
4g
3 gC D
1/ 2
]
（1）sorbent: bigger and heavier; catalyst: smaller and lighter;
（2）a catalyst separator between reformer and regenerator;
（3）fluidized bed, direct heat transfer for regenerator;
Experiments - setups
reformer
Riser based catalyst separator
Experiments – Materials
particles
dp(0.5)
(μm)
ω: weight losing after burning at 800oC
ρp
ut
(μm)
(kg/m3)
(m/s)
(%)
size
ω
Ilmenite
257
140-440
4260
5.65
1
Plastic beads
94
70-130
960
0.39
100
Combustion method to determine the
fraction of lighter particles
fraction of lighter particle
 m m ix - m m ix '

c pb = 
-  ilm 
m
m ix


 1 -  ilm 
Results – solid distribution along height
Port 11
12.2±1.6 kg/m2s
23.7±2.6 kg/m2s
 Below Port 5, εs decreases
dramatically with height
 εs keeps almost constant
above Port 5
 lighter particles that were
entrained up would not
settle down below Port 5
Port 5
Port 1
34.8±3.4 kg/m2s
Results – lighter particle distribution along height
Port 11
12.2±1.6 kg/m2s
23.7±2.6 kg/m2s
fraction of lighter particles
increases with increasing of
riser height.
Port 5
Port 1
heavier ilmenite particles settle
down to the bottom of the bed
and the lighter plastic beads are
entrained up
34.8±3.4 kg/m2s
Separation efficiency =
mass of lighter particles to separator
Separation efficiency
Results -
mass of lighter particles to reformer
 Separation efficiency increases linearly with ug.
 2.5m/s is an appropriate operation gas velocity for separator.
 With ug=2.5m/s and Gmix =12.2kg/m2s, separation can approach 99%.
 Lighter catalyst can be separated from sorbent mixture!!
reformer
entrained fraction =
total mass go into separator
Entrained fraction
Results –
total mass return back to reformer
 ~40% sorbent mixture will be entrained back to the reformer.
 Entrained fraction increases with gas velocity.
 Entrained fraction decreases with circulation rate.
reformer
Simulation
Governing Equations (DEM)
   g 
t
     g u g   0
   g u g 
t
mi
dv i
dt
Gas Phase
     g u g u g      p     τ g  Fsg   g g
 Fdrag  Fcollision  Fgravitation  Fsaffm an lift
Particles
Parcel Concept
 The position of each parcel is determined by tracking a s
ingle representative particle
ra d iu s  p a rc e l  
m a ss  p a rc e l 
 p a rtic le
 radius (parcel) = 0.002 m
Geometry and BC
Simulation – modified drag force model
Drag force is calculated based on
Particles
mi
dv i
dt
multi-scale cluster model
 Fdrag  Fcollision  Fgravitation  Fsaffm an lift
Results – simulation be used to optimize separator
Drag Law
Soft Sphere
Volume fraction
of ilmenite
Volume fraction
of plastic beads
30% Gid Drag UDF
k
1000
e
-
0.85
BC
vg
m/s
2.5
Iteration Num
Nite
-
30
 The ilmenite particles are concentrated
in the lower part of the bed
 The plastic beads are concentrated in
the upper part of the bed
 Mixture separation ratio: 54%
(Experimental result: 29.2%)
 Plas beads separation ratio: 86.7%
(Experimental result: 87%)
Conclusions
 A riser-based catalyst separator is proposed for the
sorption enhanced hydrogen production process.
 An appropriate gas velocity range for the separating
plastic beads from ilmenite particles is >2.5m/s.
 When the solid circulation rate is below 24kg/m2s, 10
~30wt% mixture can be entrained, separation
efficiency of plastic beads is higher than 95.4wt %
 The riser-based separator will be optimized.
 A hot setup will be built and operated to produce
continuously high purity of hydrogen.
Thank You !
Acknowledgments:
This work was supported by the National Natural Science
Foundation of China (51376105, 91434124, 51561125001).