presentation technion 2009
TRANSCRIPT
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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.