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Report submitted to the 36-month SOLHYCARB Meeting

DLR, Cologne, Germany17-18 March, 2009

Recent improvements in the starting procedure of STMS tests

at WIS and some corresponding test results.

Abraham Kogan

The kinematic viscocity of Methane at room temperature is too low for the

establishment of a stable confined tornado flow configuration. The correct starting

procedure of a STMS test is by maintaining a whirling flow of a neutral gas (N2, He

or Ar) inside the reaction chamber for a short warm-up period. The whirling Methane

stream can be admitted into the reaction chamber only when the inside surface of the

chamber wall has attained a minimum predetermined temperature.

Up until recently the WIS SR10 reactor was equipped with a two-way entry valve

through which it was possible to introduce in sequence a transient warming-up flow

F′1(N2) and then the permanent flow F1(CH4) through the same annular entry port,situated just below the quartz window as shown in Fig 1. The zirconia insulation

temperature in the vicinity of the reactor aperture was obviously high enough to

sustain the high rate of decomposition of Methane passing through the aperture into

the lower part of the reaction chamber.

By visual observation of the gas flow inside the reaction chamber during high

temperature tests with the SR10 kW reactor equipped with the increased window

diameter, we became aware of the danger of window destruction due to slight

oscillation in the confined Tornado flow pattern, see, e.g., the heavy Pyrocarbon

deposit formed on the periphery of the reactor aperture on the side facing the reactor

quartz window, illustrated in figure 2.

By increasing the diameter of the reactor window and by removing the window plane

from the reactor aperture plane, the interior of the reaction chamber became divided

into two distinct parts: an upper part, the area between the aperture and window

planes and the main body of the reaction chamber, between the aperture plane and the

exit port.

In order to avoid this danger, we decided to eliminate the two-way entry valve and to

use the annular entry port situated above the aperture plane for the introduction of

whirling flow F′1(N2) and to install an additional annular entry below the aperture for

the introduction of whirling flow F1(CH4). The inside contour of the reaction chamber was designed in line with the following CFD simulation results.



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Fig. 1 An early configuration of the upgraded SR10 WIS Reactor. The reactor quartzwindow was increased and moved 28mm by translation from the reactor aperture

plane towards the ø 155cm Secondary Concentrator.

Fig. 2 Formation of a heavy deposit of Pyrocarbon on the periphery of the reactor

aperture caused by splitting of Methane during its flow along the surrounding heated

Zirconia plate.

Fig. 3 shows contours of stream function inside the reaction chamber obtained by

CFD simulation with an improved reactor axial cross section [1]. The following four

gas flows were postulated:

F2(He) = 2 L/M

F′1(N2) = 26.3 L/M; whirling, horizontal deviation from radial direction θ = 55°

F1(CH4) = 20 L/M; whirling, horizontal deviation from radial direction, θ = 55°

F3,2(N2) = 1 L/M; blowing stream

The whirling flow F′1(N2) splits upon entry into the reaction chamber into two uneven

parts. The smaller part joins the Helium stream to form the gas curtain adjacent to the

reactor window. The larger part of stream F′1 follows line bcd towards the forced

separation point d . It continues almost undisturbed towards the axis of symmetry

where it joins the tornado funnel stream. The hefty funnel stream generates by friction

the large annular vortex stream dijkl. The ascending branch of the annular vortex



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stream kl collides with the whirling Methane stream entering at point f and entrains it

along the wall fed to join the tornado funnel.

A slight blowing stream F3,2(N2) = 1 L/M enters the reaction chamber at point g just

out of the influence of the annular whirling stream. It flows along the peripheral

boundary gh of the chamber performing a slight blowing and cooling action along

wall gh.

Fig. 3 Contours of Stream Function 1

Fig. 4 Contours of Stream Function 2Fig. 4 shows contours of stream function of a similar flow configuration in which the

slight stream F3,2 (N2) = 1 L/M was replaced by an enlarged stream of Nitrogen, 20

L/M.



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We observe that the large increase in the flowrate of the blowing stream F3,2 did not

modify most of the characteristics of the previous flow, except for providing

enhanced cooling and blowing along peripheral wall gh. Flow separation at point d ,

formation of the large annular vortex and entrainment of the Methane flow F1(CH4)

towards the aperture plane, which coincides with the secondary focal plane, thehottest region in the reactor cavity, were not much perturbed.

The updated design of the STMS reactor is illustrated in Fig. 5. In this design part of

the zirconia structure at the exit end of the reactor is replaced by a 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 a tertiary 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

Pyrocarbon deposit.

Fig. 5: Axial cross section of the WIS 10 kW prototype reactor



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Sequence of operations when starting a STMS test (Fig. 5).

1. The cooling water flow F(CW), the external cooling air flow F(CA) and the two

Nitrogen flows F(N2) (for boundary layer blowing and for quenching of products)

are started.

2. The secondary flow F2(He) is started.3. The confined tornado flow configuration is established in the reaction chamber by

starting the whirling flow F1'(N2).

4. Concentrated solar radiation is admitted to the reactor window.

5. When the reactor wall reaches a local predetermined temperature the whirling flow

of Methane F1(CH4) is started. It enters the reaction chamber along a horizontal

circle, somewhat below the aperture plane. It is intercepted by the ascending

branch of the large annular vortex that was generated by flow detachment at point

d (see Figs 3,4) which entrains it towards the aperture, i.e., towards the hottest spot

in the chamber.

6. When a steady state and steady flow is reached, the whirling N2 flow F1'(N2) may

be reduced appreciably.7. The Carbon Black–Nitrogen suspension F(N2-CB) is admitted into the reaction

chamber, pointing also towards the hottest region inside the chamber.

First STMS test with the present version of the WIS SR10 reactor

A first STMS test with the WIS SR10 version illustrated in Fig. 5 was performed on

Jan. 22, 2009.

During 11:07≤ t ≤ 12:15 insolation was 913 ≥ I ≥ 893 w/m2.

In order to prevent influence of a Taylor flow instability we used a 50% N2-50% He by volume gas mixture for the neutral gas mixture flows F′1 and F2.

During the starting warm-up period (t =11:12-11:25) the neutral gas flow F′1 + F2 =

30L/M was heated by concentrated radiation submitted to the reactor through the

60cm x 70cm wicket. The maximum temperature inside the reaction chamber reached

977°C.

At t =11:27 the concentrated radiation was admitted to the reactor through the 100%

open North window.

At t = 11:33 the maximum reactor temperature reached near the aperture plane was

1748°C. At this time we started seeding the reaction chamber with CB.

At 11:40 a flow F1(CH4) = 2 L/M was started into the reaction chamber.

During t =11:50 – 12:09 the Methane flow into the reaction chamber was increased to

F1(CH4) = 4 L/M.

The GC analysis indicated a 100% extent of reaction.



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Table 2. Temperatures during experiment

PARAMETER

TIME

UNIT

11:07 11:12 11.15 11:20 11:25 11:27 11:33 11:40 11:50 11:57 12:05 12:09 12:15

TC-B1

near aperture, N°C 831 946 977 1748 1735 1680 1677 1675 1677

TC-B′1

Below aperture,N°C 242 325 618 756 840 860 875 886

TC-B′2 °C 835 934 960 1450 1446 1470 1430 1500 1454

TC-B3 °C 346 480 544 841 859 943 939 966 970

T pyrometer °C 122 126 264 265 330 322 330 322

I (Insolation) W/m2 906 913 911 912 904 911 906 885 884 893

F′1(N2+He)

50/50% by volSLM 25 24 24 24 24 24 25 25 25

F2(N2+He)

50/50% by volSLM 5 5 5 5 5 5 5 5 5

F1(CH4) SLM 0 0 0 0 0 2 4.2 4 4 4

Ffluidizer (N2) SLM 0 0 0 0 8 9 9 9 9 9

Freject (N2) SLM 0 0 0 0 8 8 9.3 9 8.8 8.8

F3,2 SLM 20

R a d i a t i o n a d m i t t e d t h r o u g h 6 0 c m x 7 0 c m w i c k e t

20 20 20 R

a d i a t i o n a d m i t t e d t h r o u g h 1 0 0 % o p e n N o r t h w

i n d o w

20 20 20 20 S h a

d o w

o f S o l a r T o w e r r e a c h e s H e l i o s t a t H 2 0

4 – T e s t

d i s c o n t i n u e d



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Fig. 6. A Gas Chromatogram obtained during STMS test of Jan. 22, 2009, at 11:58

(Instrument time: Summertime +1)

The second STMS test with the WIS SR10 reactor version illustrated in Fig.5 was performed on Feb. 16, 2009. The original aperture diameter of 65mm was increased to

75mm. The test started at insolation I = 951w/m2. In order to operate at high reactor

temperature, a mixture of N2 and He 50%-50% by volume was used again as

secondary gas, to alleviate any Taylor flow instability.



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PARAMETER TIME

UNIT

11:04 11:15 11:23 11:25 11:26 11:29 11:31 11:35 11:45 12:00 12:05 12:11 12:24

12:25

To

12:35

TC-C1 N

near aperture, N°C 892 1650 1790 1800 1700 1630 1700

TC-C′1 N

Below aperture,N°C 774 1302 1418 1430 1390 1370 1340

downto

570

TC-B′2 °C 15 895 1345 1410 1400 1420 1350 1330

TC-B3 °C 18 803 1007 1030 1025 1030 1080 1173

TCdeflector1 °C 16 16 16 16.5 18.5 16.7 17 18

TCdeflector2 °C 15 18 20 23 24 28 30 24

T pyr.housing °C 16 17 19 18.5 19 20 20 20

T pyrometer °C 15 123 18 310 310 310 308 305

T product1 °C 101 209 253 323 334 385 430 448

T product2 °C 16 25 30 31 32 35 40

TCfilter °C 15 25 30 29 28 25 25

I (Insolation) W/m2 936 951 959 934 930 940 950

F1(CH4) SLM 19 19 0

F2 SLM 1.2 2 2 2 2 2 2

F2(CH4) SLM 0 6 6 14 19 19

Ffluidizer (N2) SLM 0.1 5 8.2 8.5 8.8 0

Freject (N2) SLM 8.6 8.7 9.2 9.5 0

F3,2 (N2) SLM 20 20 20 20 24 20

F′1(N2+He)

50/50% by volSLM

R a d i a t i o

n a d m i t t e d t h r o u g h 6 0 c m x 7 0 c m w i c k e t

0

R a d i a t i o n a d m i t t e d t h r o u g h 1 0 0 % o p e n N o r t h w i n d o w

0 24 24 24 20

F 1

( N 2 ) s t o p p e d

24 C l o s e M e t h a n e ;

T o r n a d o

d i s a p p e a r s ;

C l o s e a p e r t u r e w i n d o w



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-The Feb. 16, 2009 test endured almost an hour. During 20 minutes after start of CB

seeding, the flow of Methane to the reactor was increased gradually up to F1=20

L/M. Then it was kept constant at 19 L/M for half an hour, up to the end of the test.

-The tornado whirling flow was observed visually through a small plane reflecting

mirror during the whole test duration. It appeared steady.

-The Tornado initial “driving force”, the F′1(N

2+He)=24 L/M flow was maintained

constant throughout the test duration.

-The GC recordings indicate approximately 100% extent of reaction.

-Seventeen minutes before the end of the test the CB seeding was discontinued. The

tornado effect continued unaffected.

-The maximum temperature of 1600-1800°C was recorded by a C-type thermocouple

just below the aperture plane. About 2cm below that location the reactor inner wall

temperature was about 1400°C, while near the exit port the wall temperature was

below 1200°C.



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Figures 6,7 and 8 are various SEM magnifications of parts of a CB cluster collected

from the product filter after the test of Feb. 16, 2009.

Fig. 6

Fig. 7

Fig. 8



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The additional 11 pictures are TEM magnifications of two additional CB samples

collected from the product filter after the same test.

Figure 9 is a slight magnification TEM picture of four adjacent clusters of CB

particles. The object at the extreme left at the base of the uppermost cluster is a

Fulerene surrounded by four small Fulerenes in different stages of their evolution.

Details of this group are shown in Figures 10-14. The big central unit servesapparently as catalyst in the formation of the smaller four units.

Fig. 9 TEM of four clusters of CB particles

Fig. 10 Fig. 11



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Fig. 12 Fig. 13

Fig. 14

Figure 15 is apparently a spot of formation of nano-tubes that could be building

blocks in the formation of nearby Fulerenes, as suggested by the Figures 16-19

following.

Fig. 15



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Fig. 16 Fig. 17

Fig.18 Fig. 19

REFERENCE

[1] A. Kogan, et al A non-polluting solar chemical process for production of

Hydrogen and Carbon Black by solar thermal Methane splitting. 49th Israel Annual

Conference on Aerospace Sciences, Israel, March 4-5, 2009.

report 36 month meeting

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