presentation technion 2009

7/30/2019 Presentation Technion 2009

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A NON-POLLUTING SOLAR CHEMICAL

PROCESS FOR PRODUCTION OFHYDROGEN AND CARBON BLACK BY

SOLAR THERMAL METHANE

SPLITTINGA. Kogana , M. Koganb, S. Barak, M. Epstein, A. Segal, R. Rubin,

Y. Yeheskel, D. Lieberman, R. Arielic, Y. Hlopovitzd

a. Department of Aerospace Engineering, Technion IIT, Israel

Visiting Scientist at Solar Research Facilities Unit, Weizmann Institute of Science.b. Solar Research Facilities Unit, Weizmann Institute of Science, Rehovot, Israel

c. Department of Aerospace Engineering, Technion IIT, Israel

d. Department of Computer Science, Technion IIT, Israel

49th Israel Annual Conference on Aerospace Sciences

Tel Aviv - March 4, 2009


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HYDROGEN IS THE CHOICEFUEL OF THE 21ST CENTURY

ITS COMBUSTION IN AIR RELEASESGREAT QUANTITIES OF ENERGY PER

UNIT MASS.

ITS COMBUSTION PRODUCT IS ONLYWATER.

IT IS A NON-POLLUTING FUEL ANDTHEREFORE ITS USE ISENVIRONMENTALLY ACCEPTABLE.


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HYDROGEN PRODUCTION BYMETHANE-STEAM REFORMING

CH4+H2O CO+3H2

PRODUCTION OF 1 TON H2 IS ASSOCIATED WITHCONSUMPTION OF 2.6 TON CH4 AND DUMPING OF 7.15 TON

CO2 TO THE ENVIRONMENT.

THE PRESENT GLOBAL H2 DEMAND IS ABOUT 50106 TON.

THE CONCOMITANT CO2 PRODUCTION AMOUNTS TO MORETHAN 350106 TON.

800C

30 atm

CO+H2O CO2+H2400C


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2gr42HCCH C1500

HYDROGEN PRODUCTION

BY METHANE SPLITTING


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Three problems must be solved during thedevelopment of a Solar Thermal Methane

Splitting reactor based on direct heating of CH4

1. PROTECTION OF THE REACTOR WINDOWFROM CONTACT WITH SOLID CARBONPARTICLES GENERATED BY THE STMSREACTION.

2. PREVENTION OF PYROCARBON DEPOSITIONON THE REACTOR WALLS.

3. DEVELOPMENT OF ADEQUATE MEANS TOENABLE EFFICIENT ABSORPTION OFCONCENTRATED RADIATION BY METHANE,WHICH IS A TRANSPARENT GAS.


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Fig. 1. REACTOR MODEL M2B-CPC ASSEMBLY

Impeller-like disc

Insulation

Auxiliary stream inMain stream in

First annularpassage

Second annularpassage

Window

Exit port


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7Fig. 2. IMPELLER RING INSTALLED IN FLANGE GROOVE


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Smoke charged radial auxiliary flow 2 L/M

Fig. 3. CONSECUTIVE STAGES IN THE EVOLUTION OF ATORNADO FLOW PATTERN IN A REACTION CHAMBER


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Fig. 5. FLOW OF A REAL LOW-VISCOSITY FLUID PAST

A CIRCULAR CYLINDER


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Fig 6. SMOKE FLOW VISUALIZATIONOF AN UNSTABLE TORNADO

FLOW CONFIGURATION

Fig. 7. SMOKE FLOW VISUALIZATION

OF A DEGENERATED TORNADO

FLOW CONFIGURATION


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It has been shown by a room temperature experiment that this

flow configuration remains stable in our laboratory-scale

reactor model when operated at a gas flow rate of up to 20 L/Mcorresponding to a minimum Ekman number

5

max

min104.3

swirlVD

E

Under actual conditions of operation of a STMS plant, say at

T=2000 K, the kinematic viscosity of Methane goes up by a

factor of 25, as compared to its value at room temperature. This

indicates the potential for upscaling the reactor for industrial use.

The small laboratory reactor mentioned above could be operated

at 2000 K with a maximum gas flowrate close to 500 L/M, with the

quartz window protected by the confined tornado flow effect


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Fig. 9. THE QUARTZ INSERT TUBEBECAME CLOGGED WITH CARBON

Fig. 8. CROSS SECTION OFREACTOR M4-3, USED DURINGTEST CH4-9


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A sequence of such tests was performed

with the same reactor at similar insulation,

but with the quartz insert tube replaced by a

zirconia tube and then by a copper tube of a

similar geometry.In all these cases the testsended due to heavy clogging of the inserts

with carbon, while the rest of the reactor

walls were free of Pyrocarbon deposition.

Fig. 10 CROSS SECTIONOF REACTOR M4-5, USEDDURING TEST CH4-11

The insert tube was then replaced by a longcopper tube that reached down to the bottom

of the quenching chamber. The tube was

cooled strongly by water sprays. In this case

there was no carbon deposition inside the

reactor.The test lasted for half an hour and was

terminated because of a cloud in the sky.


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Next we studied some gas dynamics methods to facilitate evacuation of

particles from the reaction chamber [5].

By rebuilding of the Fig. 8 reactor by assembling the three components (a),

(b) and (c) shown in Fig. 11 and by installing an additional annular plenum

chamber (Fig. 12), it became possible to apply radial blowing along thebase of the reaction chamber.

Fig. 11. COMPONENTS OF

REACTOR D2

Fig. 12. AXIAL CROSS SECTIONOF REACTOR D2


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The exit port section from the chamber was rounded by insertion of

flared metal inserts (Fig. 13).

Fig. 14 illustrates the reduction of powder sedimentation at the reactor cavity

bottom by activation of the tertiary flow during a test at room temperature.

Fig. 14. REDUCTION OF POWDER SEDIMENTATION TEST# 204

(A) F3=0; (B) F3=3 SLM.

Fig. 13


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FIG. 15. COMPONENTS OF

REACTOR D3FIG. 16. AXIAL CROSS SECTION

OF REACTOR D3


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4. Some technical problems connected with the replacement of the smallsecondary concentrator by the 155 cm paraboloid mirror.

At this stage we acquired a 155 cm secondary concentrator (SC) to replace

the old 63 cm SC, in order to upgrade our solar power input to 10 kW. The

reactor window had to be increased and moved from the reactor aperture in

order to prevent its overheating (Fig. 18).

Fig. 18. ENLARGED WINDOW Fig. 19. TWO SS FLANGES REPLACED

BY ZIRCONIA INSULATION BOARD

Window

Aperture

plane


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Fig. 21. Contours of Stream function

F2 (He) 2 L/M

F1 (N2) = 26.3 L/M; =55

F1(CH4) = 20 L/M; =55

T4 = 1300 K

F3,2(N2) = 20 L/M


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The updated design of the STMS

reactor is illustrated in Fig. 22. In this

design part of the zirconia structure at

the exit end of the reactor is replaced bya shaped cylinder made of copper (a).

The temperature of the external

surfaces of shaped cylinder (a) is kept

down by out-of-contact water cooling.

The inner surface (b) of the zirconia

insulation is partly cooled by blowing atertiary stream of gas F(N2) at room

temperature in a direction tangential to

surface (b). The blowing stream

entrains any solid particles in gas

suspension in region (b) and thus

prevents the formation of a Pyrocarbondeposit.

F(N2)

Boundary layerblowing

F(N2-CB)

F1(CH4)

F1(N2)

F2(He)

F1(CA)

F(CW)

Shaped coppercylinder,water-cooled

Window

Aperturedd

Fig.22. AXIAL CROSS SECTION

OF THE WIS 10 Kw REACTOR

b

a


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TEM magnifications of two additional CB samples collected from

the product filter after the same test.


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A spot of formation of nano-tubes that

could be building blocks in the

formation of nearby Fulerenes


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CONCLUDING REMARKAS MENTIONED ABOVE, THE CONFINED

TORNADO FLOW CONFIGURATION COULD BEAPPLIED WITH THE WIS REACTOR DESIGNWITH A MAXIMUM FLOW RATE OF SWIRLINGGAS UP TO 510 L/M.

SUCH AN ENLARGED STMS INSTALLATIONWILL HAVE TO BE POWERED BY SOME 80 KWCONCENTRATED SOLAR RADIATION.TO DO THIS ONE WOULD HAVE TO USE A

CLUSTER OF AT LEAST 8 WIS HELIOSTATSCOUPLED WITH A NON-IMAGINGCONCENTRATOR, SUCH AS A COMPOUNDPARABOLIC CONCENTRATOR.

presentation technion 2009

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