Inclined rotating fixed bed reactors as a new reactor ...

Hans-Ulrich Härting | Institute of Fluid Dynamics | www.hzdr.de

Inclined rotating fixed bed reactors as a new

reactor concept for process intensification

Hans-Ulrich Härting & Markus Schubert

Member of the Helmholtz Association


Outline

Process Intensification: Periodic operation of trickle bed reactors

The inclined rotating fixed bed reactor

Alternative reactor concept

Experimental setup

Experimental studies

Tomographic imaging and flow regime maps

Gas-liquid mass transfer experiments for reactor evaluation

Conclusions & Outlook

Member of the Helmholtz Association Page 5


Process Intensification: Trickle bed reactors

V. V. Ranade, R. V. Vhaudhari, P. R. Gunjal: Trickle Bed Reactors; Elsevier, Amsterdam, The Netherlands, 2011

Process Pressure

in Mpa

Temperature

in K

Ethanol oxidation on Pd/Al 2 343 – 373

Hydrodesulfurization on Mo-Ni 2 – 8 593 – 653

Fischer-Tropsch reaction on Co/TiO2 1 – 5 450 – 650

Gas-liquid-solid reactor for heterogeneous catalysis

Commonly gas and liquid (“trickling”) cocurrent downflow over

a fixed-bed of randomly packed catalyst particles

Disadvantages: liquid maldistribution, formation of hot spots,

poor radial heat transfer, low gas mass transfer rate

Initial liquid distribution crucial for reactor performance



Process Intensification: Periodic operation of TBR

Time

Liq

uid

flo

w r

ate

P. M. Haure et al.; AIChE Journal 35, 1989, pp. 1437

J. G. Boelhouwer et al.; Chem. Eng. Sci., 57, 2002, pp. 4876

Enhanced liquid distribution

Dampening of hot spots

Additional degrees of

freedom for reactor control



Process Intensification: Explanation of periodic operation

M. Schubert et al.; Chem. Ing. Tech. 78, 2006, pp. 1023

G

G

G

G

Stationary operation:

„Steady“ liquid film and wetting

efficiency at catalyst surface

Periodic operation:

Forced perturbation of liquid film and

wetting efficiency at catalyst surface

M. E. Trivizadakis et al.; Chem. Eng. Sci. 61, 2006, pp. 7684

G

G

Time

Liq

uid

flo

w r

ate



Process Intensification: Deficiencies of peridodic operation

Dampening of pulse intensity with

reactor length

Interference with upstream and

downstream facilities in plant

increase in capex

Higher demands on process

measurement and control

increase in capex and opex

Higher demands on models for

design and simulation

J. G. Boelhouwer et al.; Chem. Eng. Sci., 57, 2002, pp. 3387



Outline




Experimental setup








α

Liquid

Gas

Idea:

Periodic operation with constant feed rates

Reactor inclination forces gas-liquid seggregation

Superimposed rotation induces periodic wetting of fixed bed

Fixed bed tightened inside of reactor by screens

Transformation of temporal-periodic operation into spatial-

periodic operation

Benefits:

Initial uniform liquid distribution irrelevant

Introduction of periodicity over whole length of reactor

Enhanced mass transfer for gas phase

Two further degrees of freedom for flow control

Quasi-stationary flow regimes more simple to describe

H.-U. Härting, M. Schubert; Chem. Ing Tech. 84, 2012, p. 1250

Saturation

1.0

0.0 Time



The inclined rotating fixed bed reactor: Design features

Inclinable inner

frame with rollers

and hollow shaft

actuator

γ-ray CT-system

(“CompaCT“) on

rotary stage

Tubular reactor

(DI = 102 mm

L = 1210 mm)

with rotary unions

and intermediate

flanges

L x H x D ≈ 2.5 m x 3 m x 1 m



Experimental setup: Tomographic imaging - CompaCT

A. Bieberle, H. Nehring, R. Berger, M. Arlit, H.-U. Härting, M. Schubert, U. Hampel; Rev. Sci. Instrum. 84, 2013, 033106

modular signal processing boards

base plate with integrated

cooling circuit centrifugal pump

Detector

collimator

isotopic source

collimator

hollow shaft

rotary actuator

gamma-ray detector arc

112 detectors, LYSO, A = 4x2 mm2

Isotopic source: 137Cs with A = 1.1 GBq, E = 662 keV

Integrated convective cooling circuit

Aperture ≈ Object-Ø : max. 150 mm



The inclined rotating fixed-bed reactor: In real life

Experimental setup CompaCT at work



Outline




Experimental setup







Experimental studies: A short reminder on tomographic imaging

Acquisition of count rates for each detector d at

different angular position p

Two reference scans and scan of actual flow

experiment

Reconstruction of cross-sectional attenuation

coefficients by algebraic reconstruction technique

Calculation of βL,dyn = effective volume of flow

void volume

Projections

De

tecto

rs

βL,dyn



Experimental studies: Validation of CompaCT

A. Bieberle, H.-U. Härting, M. Schubert, U. Hampel; Proc. Eng., 2013, accepted

Mean systematic underestimation

of liquid saturation of about 2 %

No significant influence of rotational

speed on measured saturation

Aptitude of CompaCT for rotating reactor



Experimental studies: Identified flow regimes

Stratified flow

Stratified-sickle flow

Annular flow

Disperse flow

Comparison: Trickle flow Dynamic

liquid

saturation



Experimental studies: Flow regime map I

Deionate - air - 4 mm glass beads: ρ = 998 kg/m3 / η = 1 mPa*s / σ = 72.5 mN/m

H.-U. Härting, A. Bieberle, M. Schubert, U. Hampel; Proc. Eng., 2013, accepted



Experimental studies: Flow regime map II

Cumene - air - 4 mm glass beads: ρ = 862 kg/m3 / η = 0.8 mPa*s / σ = 28.2 mN/m

Rotational speed in rpm

Inclin

ation

an

gle

in

°

uL = 0.01 m/s & uG = 0.05 m/s

Stratified flow

Stratif ied-

sickle

flow

Annular flow

20 60 40 0 10 50 30

30

90

60

45

75

15

Dynamic

liquid

saturation



Experimental studies: Flow regime maps – comparison

Cumene - air - 4 mm glass beads lowered density and surface tension

No disperse flow for cumene

Stratified-sickle flow less pronounced

Density in kg/m3 Viscosity in mPa*s Surface tension in mN/m

Deionized (DI) water 998 1 72.5

DI-water with

surfactant

996 1 55.5



Experimental studies: Gas-liquid mass transfer – method

M. Wiezorek; diploma thesis, TU Dresden, 2012

L G

Vin

Vout

z2

V2-(

Vin+

Vout)

L+G

Vin

Vout

z1

V1-(

Vin+

Vout)

L G

L+G

“Developed flow“:

Goto & Smith 1975, Luo & Ghiaasiaan 1997

(𝑘𝐿𝑎)𝑧1𝐴𝑧1 = 𝑘𝐿𝑎𝑑𝑉𝑉𝑖𝑛

+ 𝑘𝐿𝑎𝑑𝑉𝑉𝑜𝑢𝑡

+ 𝑘𝐿𝑎𝑑𝑉𝑉1−(𝑉𝑖𝑛+𝑉𝑜𝑢𝑡)

(𝑘𝐿𝑎)𝑧2𝐴𝑧2 = 𝑘𝐿𝑎𝑑𝑉𝑉𝑖𝑛

+ 𝑘𝐿𝑎𝑑𝑉𝑉𝑜𝑢𝑡

+ 𝑘𝐿𝑎𝑑𝑉𝑉2−(𝑉𝑖𝑛+𝑉𝑜𝑢𝑡)

Desorption of oxygen from deionate with pure nitrogen

Measurement with amperometric oxygen probes

Inlet and outlet effects considered, no dispersion

0 = −𝑣𝜕𝑐

𝜕𝑧− 𝑘𝐿𝑎 𝑐 𝑘𝐿𝑎 =

𝑉 𝐿𝐴𝐿

𝑙𝑛𝑐𝑖𝑛𝑐𝑜𝑢𝑡

O2 balance:



Experimental studies: Gas-liquid mass transfer – results (I)

vG = 0.01 m/s and n = 10 rpm vG = 0.01 m/s and n = 60 rpm

TBR outperforms rotating reactor for lower rotational speed and vice versa

Mass transfer in rotating reactor decreases with increasing inclination for 10 rpm

Mass transfer in rotating reactor reaches maximum between 30° and 60° for 60 rpm



Experimental studies: Gas-liquid mass transfer – results (II)

vG = 0.01 m/s and α = 15°

Better liquid distribution rather through higher liquid velocity than through rotation

Pronounced influence of liquid velocity

Negligible influence of rotational speed

vL = 0.01 m/s and n = 10 rpm

vL = 0.01 m/s and n = 40 rpm

vL = 0.03 m/s and n = 10 rpm

vL = 0.03 m/s and n = 40 rpm



Experimental studies: Gas-liquid mass transfer – results (III)

vG = 0.01 m/s and α = 60°

Better liquid distribution through higher rotational velocity for lower liquid flow rate

Pronounced influence of liquid velocity as well as of rotational speed

vL = 0.01 m/s and n = 10 rpm

vL = 0.01 m/s and n = 40 rpm vL = 0.03 m/s and n = 40 rpm

vL = 0.03 m/s and n = 10 rpm



Experimental studies: Gas-liquid mass transfer – comparison

vG = 0.01 m/s and α = 60°

Gas-liquid mass transfer in new reactor concept depends strongly on liquid flow rate

Influence of rotational velocity increases with increasing inclination

vG = 0.01 m/s and α = 15°



Summary and outlook

Conclusions:

Proof of concept for controlling flow regimes by additional degrees of freedom

Successful application of a new, highly integrated gammy-ray tomograph

Identification of flow regimes for various systems and generation of flow regime maps

Future work:

Investigation of reactive behaviour about to start

Hydrogenation of AMS to cumene

Investigation of residence time distribution, radial and

axial dispersion via WLAN wire-mesh sensors

Implementation of 1-D reactor model with formulation

of adapted closure formulations for drag forces



Acknowledgements

Funding by German Research Foundation (DFG), grant no. SCHU 2412/2-1

Department FWDF: gamma-ray CT, construction, installation

Student research assistants

Questions?

[email protected]

Inclined rotating fixed bed reactors as a new reactor ...

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