Separation of Lighter Particles from Heavier Particles in Fluidized Bed for SE Hydrogen Production and CLC

Transcription

1 The 6 th High temperature Solid Looping Cycles Network Meeting September 1 th -2 th,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

2 Outline Introduction Experiments Simulation Results Conclusions

3 H 2 fraction (%) Introduction - sorption enhanced hydrogen production CH 4 + 2H 2 O = CO 2 + 4H 2 Catalyst CO 2 sorbent CH 4 + 2H 2 O H 2 Reactor CO 2 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)

4 Introduction - process >95% H 2 CO 2 Reformer CH 4 (g) + H 2 O(g)=CO(g)+3H 2 (g) CO(g) + H 2 O(g) =CO 2 (g) +H 2 (g) CO 2 (g) +CaO(s)=CaCO 3 (s) CaCO 3 CaO Regeneratror CaCO 3 (s) = CO 2 (g) +CaO(s) CH 4 + H 2 O Sorbent/catalyst is cycled Fuel + O 2 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;

5 Introduction - progress University of Leeds INCAR-CSIC (1)mobile CO 2 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);

6 Introduction objective of this presentation >95% H 2 CO 2 Reformer CH 4 (g) + H 2 O(g)=CO(g)+3H 2 (g) CO(g) + H 2 O(g) =CO 2 (g) +H 2 (g) CO 2 (g) +CaO(s)=CaCO 3 (s) CaCO 3 catalyst catalyst catalyst separator CaCO 3 Regeneratror CaCO 3 (s) = CO 2 (g) +CaO(s) CaO CH 4 + H 2 O Fuel + O 2 or heat Terminal velocity: u t 4 d ( ) g p s g 4 g [ ( [ ] 3 C 3 C 1/ 2 1/2 1/ 2 ] d ) p s g D g D (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;

7 Experiments - setups reformer Riser based catalyst separator

8 Experiments Materials ω: weight losing after burning at 800 o C particles d p (0.5) size ρ p u t ω (μm) (μm) (kg/m 3 ) (m/s) (%) Ilmenite Plastic beads Combustion method to determine the fraction of lighter particles c fraction of lighter particle m - m ' m ix m ix = m m ix pb ilm ilm

9 Results solid distribution along height Port ±1.6 kg/m 2 s 23.7±2.6 kg/m 2 s Port 5 Port 1 Below Port 5, ε s decreases dramatically with height ε s keeps almost constant above Port 5 lighter particles that were entrained up would not settle down below Port ±3.4 kg/m 2 s

10 Results lighter particle distribution along height Port ±1.6 kg/m 2 s 23.7±2.6 kg/m 2 s Port 5 fraction of lighter particles increases with increasing of riser height. 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/m 2 s

11 Separation efficiency Results - Separation efficiency = mass of lighter particles to reformer mass of lighter particles to separator reformer Separation efficiency increases linearly with u g. 2.5m/s is an appropriate operation gas velocity for separator. With u g =2.5m/s and G mix =12.2kg/m 2 s, separation can approach 99%. Lighter catalyst can be separated from sorbent mixture!!

12 Entrained fraction Results entrained fraction = total mass return back to reformer total mass go into separator reformer ~40% sorbent mixture will be entrained back to the reformer. Entrained fraction increases with gas velocity. Entrained fraction decreases with circulation rate.

13 Simulation Governing Equations (DEM) t g g t u g u 0 g g Gas Phase u u p τ F g g g g g sg g dv m F F F F dt i i drag collision gravitation saffm an lift Particles Parcel Concept The position of each parcel is determined by tracking a s ingle representative particle radius parcel radius (parcel) = m m ass parcel particle Geometry and BC

14 Simulation modified drag force model Particles Drag force is calculated based on multi-scale cluster model dv m F F F F dt i i drag collision gravitation saffm an lift

15 Results simulation be used to optimize separator Drag Law Soft Sphere 30% Gid Drag UDF k 1000 e BC v g m/s 2.5 Iteration Num N ite - 30 Volume fraction of ilmenite Volume fraction of plastic beads 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%)

16 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/m 2 s, 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.

17 Thank You! Acknowledgments: This work was supported by the National Natural Science Foundation of China ( , , ).