IVA5/f-C R-/1Lt 107-

"

DOE/JPL/1060-76

(DE85000352)

LANGLEY RESEARCH CENTER

LIBRARY, NASA

HAMI'TOt'!, VIRGINIA

LIBRARY COpy

Jet Propulsion Laboratory

Pasadena, California

Work Performed Under Contract No. AM04-80AL13137

July 15, 1984

By

Y. S. Won

G. E. Voecks

J. H. McCrary

Technical Information Center

Office of Scientific and Technical Information

United States Department of Energy

EXPERIMENTAL AND THEORETICAL STUDY OF A SOLAR

THERMOCHEMICAL RECEIVER MODULE
DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the

United States Government. Neither the United States Government nor any agency

thereof, nor any of their employees, makes any warranty, express or implied, or

aSsumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents

that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process. or service by trade name, trademark, manufac·

tUfer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.

The views and opinions of authors expressed herein do not necessarily state or

reOect those of the United States Government or any agency thereof.

This report has been reproduced directly from the best available copy_

Available from the National Technical Information Service, U. S. Department of

Commerce, Springfield, Virginia 22161.

Price: Printed Copy A03

Microfiche AOl

Codes are used for pricing all publications. The code is determined by the number

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found in the current issues of the following publications, which are generally available in most iibraries: Energy Research Abstracts (ERA); Government Reports

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Pnnted in the United :c>tates of Arnenca

USDOE Office of SCienblK: and TechnK:allnformation

Oak Ridge, Tef11"1eSSee


5105-139

Solar Thermal Power Systems Project

Parabolic Dish Systems Development

DOE/JPLfl060-76

(jPL-PUB·84·53)

(DE85000352)

Distribution Category UC-62b

Experimental and Theoretical Study

of a Solar Thermochemical

Receiver Module

Y.S. Won

G.E. Voecks

J.H. McCrary, New Mexico State University

July 15, 1984

Prepared for

U.S. Department of Energy

Through an Agreement with

National Aeronautics and Space Administration

by

Jet Propulsion Laboratory

California Institute of Technology

Pasadena, California

JPL Publication 84-53

Ng5-1331't-~

ABSTRACT

A few years ago, a prototype test module of a solar thermochemical

receiver using an SOZ/S03 reaction system was designed, built, and tested

to establish a technical data base for future subsystem design efforts.

Emphasis was placed on experimental verification of the computer simulation to

establish a reliable design tool to predict the thermochemical performance of

the receiver with a reasonable degree of confidence. The computational

results were compared with experimental results obtained from the module

tested at New Mexico State University. Reasonable agreement was found over a

range of test conditions. It was concluded that the present design offers

satisfactory conversion performance and operational flexibility for the

construction of a complete reactor/receiver unit for use in a 10- to l5-kW

dish collector system.

iii
ACKNOWLEDGMENT

The work described herein was conducted by the Jet Propulsion

Laboratory, California Institute of Technology, for the U.S. Department of

Energy through an agreement with the National Aeronautics and Space

Administration (NASA Task RE-152, Amendment 327; DOE/ALO/NASA Interagency

Agreement No. DE-AM04-80AL13137).

iv
A

CI,e

HR,v

kf

kg

ks

m

Nu

Pf

Tf, Ts '

T •

w

QR

U

NOMENCLATURE

cross-sectional area of the tube, m2

catalyst surface area per unit bed volume, m2/m3

bulk concentration of reactant in the fluid stream,

kg-mole/m3

reactant concentration at the catalyst surface, kg-mole/m3

equilibrium concentration of reactant, kg-mole/m3

specific heat of fluid, J/kgOK

reactor tube diameter, m

catalytic particle diameter, m

mass flow rate per unit area, kg/s m2

convective heat transfer coefficient between catalyst and

fluid, W/m2oK

heat of reaction per unit bed volume, J/m3s

thermal conductivity of gas mixture, W/moK

mass transfer coefficient between fluid and catalyst,

kg-mole/m/s

reaction constant, kg-mole/m/s

mass flow rate, kg/s

viscosity, kg/m s

Nusselt number

fluid density, kg/m3

temperatures of fluid, catalyst surface, and tube wall,

respectively, °c

insulated wall temperature, 0c

solar radiant heat flux, W/m2

overall heat transfer coefficient between the heat-receiving

surface and fluid, W/moK

v

CONTENTS

I. INTRODUCTION • .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .... 1-1

II. TEST MODULE DESIGN .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .... 2-1

III. DESIGN ANALYSIS AND MODEL DEVELOPMENT. • • • • • • • • • • • • •• 3-1

IV.. EXPERIMENTAL...................................................... 4-1.

V. RESULTS AND DISCUSSION • • • • • • • • • • • • • • • • • • • • •• 5-1

VI. CONCLUSION........................................................ 6-1

VII. REFERENCES.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .... 7-1

Figures

3-1. Flowchart of CRAM••••••••••

4-1. Schematic of the Experimental Setup.

3-3

4-2

4-2. Thermocouple Map 4-3

5-1. Mass Flow Rate As a Function of Time

5-2. Temperature History at Thermocouple Locations 10, 11,

and 12 .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..

5-2

5-3

5-3.

5-4.

5-5.

5-6.

S02 Concentration in Product Gas As a Function of Time

Fluid Stream Temperature Profile for m= 1 gls

Fluid Stream Temperature Profile for m= 2 gls

Fluid Stream Temperature Profile for m= 3 gls

5-4

5-5

5-6

5-7

5-7. Extent of Reaction As a Function of Axial Distance from the

Reactor Inlet for IiI = 2 gls and Tmax = 9000 C •• ••••• 5-9

5-8. Comparison of S02 Concentrations at Reactor Exit

and Heat Exchanger Exit. • • •••••• 5-10

5-9. Surface Analysis for Inlet Catalyst Samples at a 20-keV

Energy Source.. .. .. .. .. .. .. .. .. .. .... ........ 5-12

vii
Table

5-10. Surface Analysis for Exit Catalyst Samples at a 20-keV

Energy Source. · · · · · · · · · 5-13

5-11. Surface Analysis for Inlet Catalyst Samples at a 40-keV

Energy Source. · · · · · · · · · . . . 5-14

5-12. Surface Analysis for Exit Catalyst Samples at a 40-keV

Energy Source. · . . . · · · · · · · · . . . . . . . . . 5-15

5-1. Comparison of Pressure Drop and Conversion. • • • • • • •• 5-8

viii
SECTION 1

INTRODUCTION

Use of reversible chemical reactions as a means of transporting and

storing solar thermal energy is a promising research and development area.

Various thermochemical systems have been suggested. These systems, each with

its own merits and shortcomings, were at various stages of development at the

time this work was performed.

Although the identification of the most prom1s1ng reaction system for a

specific application is important, it is equally important that the

techno-economic feasibility of the proposed system be assessed at an early

stage of development. In assessing a system, however, the parameters normally

used are primarily projections because little actual test information is

available at the present time. Overly optimistic assumptions or inadequate

treatment of potential systems problems may lead to erroneous conclusions and

result in a waste of time and effort. Generation of more realistic

performance data by fabricating and testing the actual hardware (scaled down

in size) is essential for effective planning of the overall development effort.

The intent of this study was (1) to demonstrate the concept's technical

feasibility by developing reliable design tools and identifying any outstanding

problems and (2) to generate reliable performance data required for an economic

feasibility study. The thermochemical system chosen for the present study is

one based on the catalyzed sulfur trioxide dissociation reaction

S02 + 02 (1)

initially proposed by Chubb (Refs. 1 and 2).

Technical feasibility primarily involves the determination of the

catalytic activity of a particular reactor design and catalyst, and the

reactor/catalyst material compatibility with reactants. As a first step

toward this effort, a small test module was designed and fabricated by the Jet

Propulsion Laboratory (JPL), and tested at New Mexico State University. This

module would conceivably be one element in a reactor/receiver that features a

stack of these double-tube coils, of which the innermost layers form a

heat-receiving cavity.

1-1

SECTION II

TEST MODULE DESIGN

The feasibility demonstration of the prototype metal reactor was to be

conducted in a solar environment with the Omnium-G collector installed at the

JPL Parabolic Dish Test Site in the Mojave Desert, California. Therefore, the

reactor capacity was based On the thermal power input obtainable by a

collector of the size comparable to Omnium-G (OG-7500), i.e., 12.5 kWt with

an 8-in. aperture at an insolation of 1.0 kW/m2• Assuming a receiver

efficiency of 80%, the thermal power input was estimated to be 10 kWt • From

a materials viewpoint, the maximum cavity wall temperature was limited to

900oC. Approximate sizing followed by detailed analysis, using a computer

program, produced a design encompassing a cavity, 12 in. in diameter and

20 in. long, formed by 20 circular reactor rings of I-in. stainless steel

tubing. Each reactor ring, packed with catalyst, was connected to a spiral

double-tube heat exchanger, having a total of 5 1/2 turns.

The reactor was made of one piece of I-in. diameter tubing, 38 in. long,

and formed into a 12-in. diameter circle. At 5-in. intervals on the tube

surface, orthogonal to the plane, 1/16-in. Swagelok fittings were welded for

instrumenting with thermocouples. Swagelok fittings (1/16 in.) were also

welded to the two right-angle Swagelok elbows on the out-of-plane surface for

thermocouple instrumentation. These elbows were also fitted with a stainless

steel wire mesh screen to retain the catalyst. The reactor was filled with

platinum catalyst deposited on spherical aluminum oxide substrate.

Thermocouples (K type, stainless steel sheath, 1/16-in. diameter, 18 in.

long) were inserted approximately 1/4 in. into the catalyst bed and tightened

into position for gas phase temperature monitoring at the inlet, outlet, and

incrementally along the reaction path. In addition, thermocouples were

attached to the outside wall of the reactor on the inside and outside of the

circle to monitor the heated wall temperature and the temperature differential

across the tube during operation.

The heat exchanger spiral was fabricated from tubing 5/8 in. and 1 in.

in diameter and 38 ft long. A stainless steel wire (1/8-in. diameter) was

wrapped around the smaller tubing and inserted together into the larger tubing

prior to winding them 5 1/2 turns. The tubing ends on the inside of the

spiral were positioned to match the reactor's I-in. Swagelok fittings. The

outside tubing was welded shut around the inside tube, and I-in. Swagelok

fittings were welded onto both ends to permit easy installation of the

reactor. The resulting configuration allowed the reactor to be easily

connected to the heat exchanger without disturbing either the catalyst or the

position of the heat exchanger.

During testing, t~e reactant flowed through the annular passage of the

spiral where it was preheated prior to entering one end of the reactor ring.

The product gases and unreacted reactant exited the other end of the reactor

after one pass and flowed through the inner tube of the double-tube heat

exchanger to the exit.

2-1

SECTION III

DESIGN ANALYSIS AND MODEL DEVELOPMENT

A performance simulation computer program has been developed for the

conceptual reactor designs currently being considered. The program, called

Chemical Receiver Analysis Method (CRAM), is designed for the analysis of a

single-layer reactor section and heat exchanger section, with the incoming

reactants in the annulus being heated by the exiting reaction products. The

reactor layer is either double-tube with the inside wall of the outer tube

coated with catalyst, or single-tube packed with catalyst.

For the purpose of confining the complexity of the problem to the degree

necessary for reasonable performance prediction, a one-dimensional,

steady-state analysis was made with a number of simplifying assumptions as

listed be low:

(1) No cosine effect of impinging radiant energy along the

semicircumference of the tube.

(2) Negligible axial conduction compared with radial conduction across

the tube.

(3) No end effect of the flow.

(4) Negligible radiative heat transfer in the case of packed bed

reactor.

(5) Reaction rate is first-order in relation to the concentration

difference between surface concentration and equilibrium.

In terms of an example of a packed bed reactor, assuming the conditions

listed above, the one-dimensional governing equations are as follows:!

(1) Energy Balance

2 (T - T ) = a

D

t

w f (2)

(3)

2 U (T - T ) - D

t

w f a (4)

lRefer to Nomenclature for definition of terms used in the equations.

3-1
(2) Species Balance

2 U (T' - T ) = °

D

t

w f

dC1 --- + k a (C - c ) dx g v 1 1,s °

(5)

( 6)

(7)

This set of simultaneous equations was solved numerically using a library

subroutine. The program versatility is provided by analyzing the heat

exchanger section and reactor section separately and by effecting most of the

calculations in subroutines rather than in the main program. The flow chart

of the program is shown in Figure 3-1. The program run begins by reading the

input data and assigning initial estimates to the temperature and

concentration profiles. The program then evaluates the temperature profile in

the heat exchanger section by solving the heat balance equations with

coefficients based on the assumed conditions. The temperature profile for the

reactor section is then determined based on the inlet stream temperature and

assumed concentration profile. Mass diffusion and reaction kinetics provide

the estimation of coefficients in species conservation equations. Newly

calculated values continuously improve the previous values until they finally

converge. Once the converged profiles of the reactor are obtainerl, the

interface conditions between the heat exchanger and the reactor are checked.

To control the stability of the convergence, a relaxation method was employed

using an appropriate relaxation factor.

Thermophysical properties of the gas mixture are estimated using the

properties of individual pure components and the mixing rule. The diffusion

coefficient of the reactant gas in the mixture is estimated using the Maxwell

concept and the Chapman-Enskog equation for the binary diffusion coefficient.

The convective heat transfer coefficient in the packed bed reactor was

estimated using the correlation presented by Leva (Ref. 3).

Nu 0.813 (Re)0.9 exp(-6D /D ) P t

D

for r!- < 0.35

t

( 8)

where Re = (DpG)/~.

Based on work by Reynolds (Ref. 4), the asymetrica1 heating of the

reactor tube wall was approximately accounted for by estimating an effective

convective heat transfer coefficient between the reactor wall and the bulk of

the fluid. For the reaction rate equation for 503 dissociation, the

Westinghouse data (Ref. 5) deduced by Rocket Research in terms of catalytic

surface area (Ref. 6) was used.

3-2
SET UP HEAT

BALANCE FOR

CONVERTER

(CNHEO)

INPUT

ASSIGN TEMPERATURE

AND CONCENTRATION

PROFILES

(SETUP)

SET UP HEAT

BALANCES FOR HEAT

EXCHANGER SECT!ON

(HEEQ)

SOLVE LINEAR

SIMULTANEOUS

EQUATIONS

(SOR)

CALCULATE NEW

CONCENTRATION

PROFILE

(CNREQ)

NO

L..._.:.::N~O:...:' CONCENTRATION

PROFILE?

(CHECK) YES TE MPERATURE

PROFILE?

(CHECK)

SOLVE LINEAR

SIMULTANEOUS

EQUATIONS

(SOR)

NO

PRINT

OUTPUT

(OUT)

Figure 3-1. Flowchart of CRAM

3-3

SECTION IV

EXPERIMENTAL

The test module designed and fabricated at JPL was tested at a solar

chemical receiver test facility belonging to the Physical Science Laboratory

of New Mexico State University. A detailed description of the facility is

found elsewhere (Ref. 7).

The facility features three major units: S03 storage and vapor supply

unit, testing unit, and effluent gas disposal unit. The S03 storage and

vapor supply unit consists of a temperature-controlled hot box containing a

55-gal liquid S03 drum, metering pump, and evaporator of the heated

pressure-vessel type with an electronic temperature controller. The testing

unit consists of the reactor, insulation, heated cavity, heating elements, and

gas analyzer. The gas disposal unit is of an agricultural scrubber type

described by Miyamoto, et al (Ref. 8). A schematic of the experimental test

setup is shown in Figure 4-1.

Prior to the dissociation test, the reactor module as well as connecting

plumbing was leak tested by pressurizing with nitrogen gas up to 60 psia; the

heat exchanger thermal performance was tested at a predetermined test condition. For the dissociation reaction, the test procedure followed three steps:

start-up, operation, and normal shutdown.

The liquid S03, maintained at a constant temperature, was pumped into

the electrically heated evaporator at a regulated flow rate. A magnetically

coupled gear pump constructed from stainless steel and Teflon was used. The

evaporator is a custom built, heated pressure-vessel type made of stainless

steel with a Z-liter capacity. The lid is removable and is equipped with a

Teflon seal. An electronic temperature controller maintained the liquid phase

temperature in the range of 50 to IOOaC. The vapor from evaporation is

carried through a l/Z-in. stainless steel tube, which is metered into the

converter/heat exchanger.

The pressures were measured by absolute pressure transducers, of which

analog voltage signals were recorded in the data logger. Temperatures were

measured by the sheathed chromel-alumel thermocouples positioned either

externally at the reactor wall or internally at the center of the flow

passages. The thermocouple sensors are connected directly to the .data logger,

which records the gas temperatures in degrees centigrade (OC). The thermocouple map is shown in Figure 4-Z.

The effluent gas leaving the reactor is carried directly to the

scrubber, with a fraction of the effluent gas flowing through the gas

analyzer. In addition to the effluent gas analysis, the local concentrations

of SOZ gas along the reactor bed were also meas~red in order to investigate

the reactivity of the catalyst used. Gas samples were tapped from the equally

spaced thermocouple ports along the reactor length. The SOZ analyzer is a

Dupont Model 400 ultraviolet-absorption, continuous-flow gas analyzer. This

instrument measures the volume fraction of S02 present in the sample gas.

4-1
GAS

0 0 ANALYZER

CO2 HEATING 0 0

0 OR COILS - 0

N 2 0 . 0 SCRUBBER 0 0

EVAPORATOR

P HEATER

HOT BOX r--- ---I TO SCRUBBER r-------- ---------,

I I I I

I S03

I I , I

I I 00000 I

I DRUM I PRESSURE I / I

.... I I RE LIEF I I

I L ____ __--J L_ _ ____ lYRNAC~_______J

N VALVE U P FLOW

METER

Figure 4-1. Schematic of the Experimental Setup
4 (PLUGGED) 14

6

x

18

X 12

X 8

X INTERNAL THERMOCOUPLE

o EXTERNAL THERMOCOUPLE

x

10

21

L-:.....---'

IN OUT

Figure 4-2. Thermocouple Map

4-3
Upon completion of the 803 conversion tests, the reactor/heat

exchanger was disassembled, and the catalyst was removed. Removal of the

catalyst was conducted in a controlled manner in order to permit its analysis

in reference to its location within the circular reactor. Samples from the

inlet and exit sections were analyzed using EDAX (energy dispersive analysis

by X-ray). Elemental analyses were conducted at two different energy levels,

20 keV and 40 keV, to examine the relative concentrations of the observed

elements at slightly different levels below the surface.

4-4
SECTION V

RESULTS AND DISCUSSION

A total of nine test runs, including heat exchanger tests with inert

gas, were made at varying flow rates and at maximum temperature. Each run

lasted about 90 minutes. At the inception of each of the runs, the system

reached steady state in 15 to 20 minutes, but the change of test condition

during normal operation was stabilized in a shorter time. Continuous system

operation was not possible because of the system fouling problem, which was

believed to be caused by the existence of stabilizer in feedstock S03' The

data measured during each test are the temperature, flow rate, pressure, and

S02 concentration as a function of time at particular locations of the

reactor and/or heat exchanger. A typical example showing the transient system

performance is shown in Figures 5-1 through 5-3, where plots of reactant flow

rate, three temperatures near the reactor exit end, and the product gas

composition are presented. Point-to-point variation in mass flow rate is real

and caused by the relatively large gas transit time between the mass flow

transducer and the mass flow control valve. It should be noted, however, that

when averaged over 10-minute periods, the mass flow is very stable, and these

short-term variations do not show up in the temperature and S03

concentration data. Reduction of raw data was made by calculating the average

quantities during the period of presumed steady state. Figures 5-4

through 5-6 show the fluid stream temperature profile along the reactor length

as compared with computed results at three different reactant flow rates and

at two or three different heat input levels. At a lower fluid flow rate, the

agreement is quite good except at thermocouple position 9 where an

exceptionally high temperature was measured. Three possible explanations for

this exist: (1) a malfunction of the thermocouple, (2) local overheating due

to, perhaps, damaged catalyst, and (3) plugging and redistribution of the gas

flow. The discrepancy is more pronounced in cases of higher flow rates as

shown in Figures 5-5 and 5-6.

Figure 5-5 is the result of a 2-g/s test at 304 kPa with a reactor

maximum temperature of 9000 C for one hour. At 30 minutes into the run,

thermocouples 12 and 13 rose sharply by over 1000C while thermocouple 9

again measured an abnormally high temperature. This abnormal temperature

behavior is attributed to the buildup of deposits of iron or sulfur compounds

within the reactor bed causing local heating due to reduced activity. This

speculation is further substantiated by the accompanying pressure drop

increase observed. Because the power input was controlled by watching the

maximum temperature, it is likely that the power input was maintained at an

inadvertently low level due to this false Tmax reading. Indeed, computed

results at lower power input agree closely with experimental results.

Figure 5-6 is the result of a 3-g/s test at 304 kPa input pressure and

8000 C for 30 minutes followed by 9000C for 30 minutes. Difficulties were

encountered during the test; the pressure regulator overheated and the data

logger failed to record the outputs from thermocouples 8, 9, 11, and 12. A

similar trend of overheating toward the end of reactor bed is observed.

5-1
3.00 r::l;-::----....,'r------,Ir-----rl------rl------rl----,-I---.--j---r-I -----,

+

2.50 -

+

+

+

+

+ MASS FLOW

-

E

Ol

2.00 -

+ +

+

++

+ ++ + + + + + + +

+ + ++ +*+++ + + +-N+ + + +++ + + + + + + ++ - + + ++ ++ + + + + ++ ++ + + + + ++ +

+ + ++ +++ + + + + + + ++

+

I.n

I

...,

~. 1.50- ...J

u..

'"'"

1.00 -

0.50 -

8

f mdt =10.66 kg

o

(mdt

= rIi = 2.019 gm/s

-

-

-

+

o':----:-':1,..,-----"'::-:-1----=-'1,..,-----"'::-:-1----:-'1.,..-----:--1:-:- ' __-::-,Ic:-::-__..".-I:-:- I_----,~ o 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00

TIME, min x 10

Figure 5-1. Mass Flow Rate As a Function of Time
12.00 r-----,----,-------,----r------,-------.----r-----,----

10.00

4.00 5.00 6.00 7.00 8.00 9.00

TIME, min x 10

1.00 2.00 3.00

8.00

N 0

)(

U0

u.;

"" 6.00 ::> lJ' lI < w W

0-""

::2:

w

I4.00

+ THERMOCOUPLE 10

x THERMOCOUPLE 11

2.00 (!) THERMOCOUPLE 12

Figure 5-2. Temperature History at Thermocouple Locations 10, II, and 12
5.00 ,.------r---,-----,----,----,---r-----r----r---,

+

a

+

x 3.00 N ++

"" 0

I Vl

... "g0 +

u.' ::!'

:J

...J 2.00 + 0

>

+

+

+

+

++. +++++++++-+++++--++++1111+1+1111111+11 III J II H:I 1I IIIIII+.

+ ++++ +

+

+

1.00

4.00

o +

o 1.00 2.00 3.00 4.00 5.00

TIME, min x 10

6.00 7.00 8.00 9.00

Figure 5-3. 802 Concentration in Product Gas As a Function of Time
900 r--,--,---,--,--,--,..---r--o-----,----,--,--r--,---,-----,---,

2 Q ~230 Jim Is

800

u

0

w· 6.

::>

""

Q 167 J/m2/s I-

.... «

I

.... ""

W

Q..

:E

w

I500

14

15

INLET END

16 25

OUTLET END

Figure 5-4. Fluid Stream Temperature Profile for m= 1 gls
900

2 Q =460 Jim Is

800

0

0

2

u Q =377 Jim Is

0

w'

:::>

'".... lJ1 <

I

a> '"

w

0..

:::E

w 600 ....

500

13

25

OUTLET END

7 8 9 10 11 12

16 17 19 20 22 23

18 21 24

THERMOCOUPLE LOCATION ALONG THE REACTOR BED

6

14

15

INLET END

4001--_..l...-_..l...-_...l-_...l-_...l-_...L_--L_......L_--L_-L_-L_-L_--.l._--.l._---I_---I

5

Figure 5-5. Fluid Stream Temperature Profile for m= 2 g/s
900

'"I

....

U

a

2 Q =502 Jim Is

o

13 25

OUTLET END

12 23

24

THERMOCOUPLE LOCATION ALONG THE REACTOR BED

400 ':-_-"--_...I.-_-'--_-:':-_----l.__'--_"'-_-'-_...I.-_--::-':-_---'-_---I__'--_-"--_...I.-_--'

5 14 6 16 7 17 8 19 9 20 10 22 11

15 18 21

INLET END

Figure 5-6. Fluid Stream Temperature Profile for rn = 3 g/s
A summary comparison of pressure drop and extent of reaction is shown in

Table 5-1. Conversions range from 23 to 33% of 502 mole fraction at a

maximum wall temperature of 8000 C, and 37 to 40% at a maximum wall

temperature of 9000 C.

Figure 5-7 is a plot of the experimentally measured extent of reaction

compared with calculated results and equilibrium composition at the catalyst

surface temperature. The reactant 503 enters the converter at a 5-deg

angle, and product gases leave at a 355-deg angle. Due to the approximate

90-minute time limit of each run, measurements could be made at only two

different angle positions and at the heat exchanger exit. Therefore, extreme

care was taken to keep the reaction run conditions constant at an inlet

pressure of 304 kPa, a mass flow rate of 2 gIs, and a maximum temperature of

9000 C.

One of the key issues in the test program was to determine the potential

catalytic effect of bare 316 stainless steel tube on the oxidation of 802'

the reverse reaction. This test was made by alternately tapping the gas

samples from reactor exit and heat exchanger exit and analyzing them.

Figure 5-8 shows the result at two different power input levels. As is shown

in the figure, no appreciable difference in concentration across a 30-ft-long

316 stainless steel tube is observed in the higher temperature range. throughout the test, the pressure drop kept increasing as the reaction runs were

repeated, but a partial restoration of the flow passage could be made by

simply shaking the reactor.

Table 5-1. Comparison of Pressure Drop and Conversion

Conversion,

802 Vol %

~n

~. m, gls Tw,max' °c ~P, psi Experimental Computed

1 1.0 800 2.0 + 1.0 33.0 29.5

900 2.1 + 0.5 40.5 42.5

2 2.0 800

900 3.5 + 0.5 39.0 41.5

3 3.0 800 5.5 + 0.5 24.0 22.5

900 6.5 + 1.0 37.0 37.5

4 2.0 800 7.5 + 1.0 23.0

900 8.5 + 0.5 37.5

5-8
o

EXPERIMENTAL

COMPUTED RESULT

EQUILIBRIUM

o

"

'"

' .... ............-

--

--------------------------- 0.2

1.0 r--;:=-r--r----;r----.----.----.--.----,-----,-----,---,--,---,---,--....--,

0.4

0.8

0.6

z

o

>=

u

«

'"

LL

C")

o

Vl

13 25

OUTLET END

12 23

24

11 22

OL-_!..-_.1-_-'--_-'--_..l-_...l-_...l-_...l-_--l-_-l...._-L_-L._--l_--L_--L_--l

5 6 7 8 9 10

14 16 17 19 20

15 18 21

INLET END THERMOCOUPLE LOCATION ALONG THE REACTOR BED

Figure 5-7. Extent of Reaction As a Function of Axial Distance

from the Reactor inlet for m= 2 g/s and T = 9000 C

max
7.20 .-----'1---'1---'1----.-1---.,-1---.,-1---.,-1---.,-1----,

6.00 f4.80 f0

X

N

0

VI

"if. 3.60 -

'"

I ~- 0 :::)

...J

0

>

2.40 -

+

I

U

>-

LU

J: u....

LU

:I: I

U

>-

LU

J: I

LU

J: LU

J:

LU

J:

+

+

+

-

-

-

-

+ PERCENTAGE 502

HE HEAT EXCHANGER

TC THERMOCOUPLE

+

1.20 -

+

o +

o

1

1.00

1

2.00

I

3.00

1

4.00

1

5.00

1

6.00

1

7.00

+

+

+ - +

++++

1

8.00 9.00

TIME, min x 10

Figure 5-8. Comparison of 502 Concentrations at Reactor Exit

and Heat Exchanger Exit
The EDAX analysis results with a 20-keV source are shown in Figures 5-9

and 5-10 for the inlet and exit catalyst samples, respectively. Because all

the catalyst was prepared uniformly with a 1 wt. % platinum loading on the

surface, platinum was used as a comparative standard. The platinum/sulfur

peak height ratio is nearly 1/2 in the inlet catalyst sample, while the same

ratio is approximately 1/3 in the exit catalyst sample. This indicates that

the sulfur content on the surface increases from the inlet to the exit. At

the higher beam energy (40 keV) the corresponding ratio found for the inlet

sample is 2/3 (Figure 5-11), while for the exit sample the ratio is 1/1

(Figure 5-12). In relative terms, the sulfur has migrated into the catalyst

to a lesser extent at the exit section of the bed than at the inlet. However,

the penetration of the iron, which originated at the reactor wall, is greater

in the exit than in the inlet samples as portrayed by the platinum/iron ratios

of 1/1 (at 20 keV) and 2.5/1 (at 40 keV) in the exit sample and of 3/1 and 4/1

in the inlet sample. Detection of chromium in these samples also illustrates

the collection of wall material on the catalyst surface.

Large flakes of oxidized stainless steel from the walls of the reactor

were found in the catalyst bed, most notably in the center one-third section.

In the exit one-third of the reactor, fine material was observed packed in the

catalyst spheres along with the wall scale. This material was believed to

have contributed to the speculated gas flow restrictions and channelings.

5-11
RANGE = 20.46 keV

VERTICAL = 5000 COUNTS

DISPLACEMENT = 1

INTEGRAL 0 = 132141

Preset= 100s

Elapsed= 100s ........ , , .. ................. .

........................................................... . ......................................... . ................................................................................... . ......................................... . .................................................. . ................. . .................................................. . ......................................................................................................................................................... .

::::::::::::::::::::::::::::::::::: S:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ................................... . . ...................................... . ...................................... . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ............... . ..................................... . ..................................... . ..................................... . .... .. .................. ............. . " . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ..................................... . ...................................... . ..................................... . ..................................... .

:::::::::::::::::::::::::::::::::Pt

.................................. "

:::::::::::::::::::::}11 :::::~ :

:::::::.

:::::::::::::::::::::::: .:::::.

;:;::;;;Cr :::;:;:;::~ ::::: :::::::::::::::::::::::~ i;;.J ••••• $ ....b .••• r

". ..

.........................................................................................................................

........... .. .........................................................................................................................

............................................................................................ . .........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

. . . . .. . , . , . .................... . . . .........................................................................................................................

t: ::::::::::::::::: :::::::::::::::::::: :: ::: ::::::: :::: ::: ::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::: ........................................................................................................................

........................................................................................................................

.......... . .......... . .......... .

..; jP'd'U:j:: jjj:: j: jj::: j:::j: j::::j: j:C·~' j: j:::::::: j:r

l

" j:: jj::::::::::::::::: jj: j: jH::::i::::::i,:p't':::: j:: '01-1' iI'" .._,~'" "r·· _',.;' .. ~:..:.:.:.:: , , oe..:.;.,:,::::" _4ii9i. r..c~. --..,.- "'-N i ·················;;,ip"····~ .............::

HI. 100 -.

Figure 5-9. Surface Analysis for Inlet Catalyst Samples

at a 20-keV Energy Source
RANGE = 20,46 keV

VERTICAL = 5000 COUNTS

DISPLACEMENT = 1

INTEGRAL 0 = 140228

Preset= JOOs

Elapsed=IOOs .................................................................................................................................................................

................................................................................................................................................................

................................................................................................................................................................

................................................................................................................................................................

.............................................................. . .............................................................. . .............................................................. . .............................................................. . .............................................................. .

..............................................................................................................................................................

~~~ ~~ ~~~ ~~ ~~ ~~ ~~ ~~ ~~ ~'s: ~~~~ ~~ ~~~ ~~ ~~~ ~~ ~~ ~:~ ~:: ~~: :~~:::~:::~::~~:: :~:::::::::::: :::::::::::::~::::~:::: ~::::: ::: ~:: ~::~ :~::::~:: ..................................... . ..................................... . ..................................... . ..................................... . ..................................... .

'"

I

......

'"

............... . ............................ " . .....................................

.....................................

.....................................

..................................... .....................................

.....................................

.....................................

........................... . .....................................

.....................................

................. . .....................................

.....................................

.....................................

.....................................

:::::::::::::::::::::::::::::::::::::- .....................................

.....................................

.....................................

....................... . .........................................................................................................................

....................... . .........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

....................... . :::: :: ::: :: ::::: :::: :::::::::: :::: ::::: :: ::::::::: ::: :::: :::: ::: :::: ::::::: :::: :::: ::: ::::::::: :: ::: :::: ::: :::: ::: : :~ :: :: .........................................................................................................................

....................... . .........................................................................................................................

.........................................................................................................................

....................... . .........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... ..................................... . ..................................... . ..................................... . ..................................... . ............... . ..................................... . ..................................... . ..................................... . ..................................... . :::::::::::::::::::::::::::::::::Pt :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::Fe:::::::::::::::::::::::::::::::::::::::::::::::::::::::

:::::::::::::::::::::::::::::::::. . :::::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::....::::::::: :::: ::::::::::::::::::::::::::::::::::::: ::::: ::: : :: : : :: :: : : : :: : :: : : : : : : : : :: : : :: I : : : : : : : : : : : : :: ::: : :: : : : :: :: : : : :: : : : : : : : : : : : : : : : : : :: : : : : : : : : :: : : : : : : : :: :: : : : : : : : : : : :: : : : : : : : ::: : : :: ::: : : : : : ::: : :: : : ::: : :

::: ::: ::::::::::::::::::::::::: :: ..................................

..................................

..................................

:::::::::::::::::::::::::::: :::::. .................................

............. . ........ .. .. .... ·.. ·Cr t"I 1.... :::::::: ::::::::::M~~

........................

...... ·· ......·........·1-- ::;";.,,. 'N"'" ..... -

..............................................................

-::::::::::::

............................................................. ::::::: :::::::::::::::::::::::::::::::::::::: :::. . . . . ............................................................

::~ d

l

·:::::::::::::::::::::::::::::::::::::::::::::::::::

•;::~ ~::::::::::::::::::::::::::::::::Cr ::::::::::: - ",,",",;,"" ui...." dill III l ~. r

w.;,;..~"

.........................................................

.........................................................

.........................................................

. . . . . . ': :::: ::::::: ::: :::: :: :::::::: :::: ::: :: :: ::::::: :: ::::::; : . . . . . . t::::::Fe:::::::::::::::::::::::::::::::::::::::::::::

~:~::: ... --i,;: ::.:::::::::::::::::::::::::::::::::-.;.:::::: - , F -.::

10.100 -.

Figure 5-10. Surface Analysis for Exit Catalyst Samples

at a 20-keV Energy Source
RANGE = 40.92 keV

VERTICAL = 10,000 COUNTS

DISPLACEMENT = 1

INTEGRAL 0 = 227742

Preset= Off

Elapsed= 100s .................................. " " . ..................................................................................................... . ................................................................................................................................................................

..................................................................................................... . ..................................................................................................... . ..................................................................................................... . ..................................................................................................... . ................................................................................................................................................................

................................................................................................................................................................

............................................................................................................................................... . ................................................................................................................................................................

................................................................................................................................................................

................................................................................................................................................................

~~~~~~~ ~~~ ~~ ~~~ ~~{ ~~ ~:~ ~:~ ~~ ~~: ~:: ~~:~:~:~::: ~:: ::::::~ :;:;:: ~:::::: :::::::::::;:::::: ~::::::::::::: ~:::::: ::: :;~:::: ~;::::::::::;:::::::::::::::

..............................................................................................................................................................

~~~~ ~~~~:~ ~~: :~~~ ::; ~~~ ~~ :~~ ~~~ ~~ ~:~ ~~:~: ~:~: ~:: ~:: ~: ~~::: ~: ~:::: ::~::~ ~: ~~::: ~~: ~: ~::::::: ~:::::::~ ~~: ~:~ ~: ~:::::::::~: ~~ ~~::::: ~:: ................... . ................... . ................... .. ................... . ................... . ................... .. ................... . ................... . ................... . ................... . ................... . ................... . ................... .

..............................................................................................................................................................

H~H: H~ ~::p t ::::~: H:::HHH:H:::::::::::::::::H::::::::::::::::::::::HH:: H:H:::HH::H::::::::H ~:::: H:::::::::::H: ~::::H::~:n:::: ................... . ................... . ................... . .................. . . .................. . . .................. . . ................. . . ................. . . ................. . . ................. . . ................. . . ................. . .

HHiiA:tH ............. .:iiHiHiiiiiHT:Tiii:iHiiiiiHi:i:iiiiiiiiHptiiiHiiHiHiiHHiHi:i::::iHHiii:iiHiiiiiiHi::HiH:iiHi:iiTiiiiiiii:~i . ............. . -. ............................. ........................................................................... . ............. . .. ............... . . ................ . .

iii iiiiiiiii: iiI' ~:~ii iiiiiil~j iii!~:; jiilTftiiilf~~ lI~:t iiliii' jiiiiIi ii:jtiiiIIi~ii ~:~ i!ii iiiIIiiiii~ ii:liIIii:iiiii!iiii:iiiiililiii iii:i:i .............. '1................ I""'" ~~ , ::::::0 . . ............ rI' ~~ __ _ .. ,;;:::~...;,;,;,;::::::::::::::::::::::::::::::::::::::::::::::::::::: :::~ _. 11. ..........,.................:: ..•

• - 0.000 20.200 -.

Figure 5-11. Surface Analysis for Inlet Catalyst Samples

at a 40-keV Energy Source
RANGE = 40.92 keV

VERTICAL = 10,000 COUNTS

DISPLACEMENT = 1

INTEGRAL°= 232268

Preset= Off

Elapsed= 100s

20.200 -.

............................................................................................................. ................................................................................................................................................................

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

................................................................................................................................................................

................................................................................................................................................................

................................................................................................................................................................

........................................................................................................................................................... ..... ................................................................................................................................................................

........................................................................................................................................................... ..... ................................................................................................................................................................

................................................................................................................................................................

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

.# •••••••••• # # .

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

................................................................................................................................................................

................................................................................................................................................................

................................................................................................................................................................

........................................................................................................................................... . ................................................................................................................................................................

........................................................................................................................................................... . .............................................................. . ................................................................ . .............................................................. . .............................................................. . ................................................................................................................................................................

................................................................................................................................................................

................................................................................................................................................................

. .. .. . .. ..... .. .. .... ., , .

~~~~~~ ~~~~ ~~~ ~~ ~~ ~S;~ ~~ ~;~;~ ~~~~;~ ~~ ~~ ~~~~;; ;~~~ ~~~; ~~ ~~ ~~ ~~; ~;; ~;~ ~~ ~~ ~~ ~~; ~~ ~~; ~~ ~~ ~; ~~~~ ~~ ~~ ~;~ ~~~ ~~; ~~ ~~~ ~~~:

j:n n:n::ptHt::::T::::ji:n: ~:: HiH:H::n:Hj: n:nnH:n nH::::::::::::::: j:::Hj::nn: j:n:::: ~:: H::::::n:::::nn:::H:::::::n::: .................. . . .................. . .................. . .................. . .

HH:::HH ................. .::nn:n::H::HiH::::::nHHn~:~:HnHpt:::j:n:::nH:::nnn::::::::::::n:::::::::::::ijHH::::::::::::::H:~:H: . ................. . . ................. . . ................. . . ................. . . ................. . . ................. . . ................. . . ................. . .

i ii i i i i i ; ; ; i i iiF' iiii iii ii i i. ; ;i ; i=lt ;;i ii i i;i ;;i;;:i:;i;ii;:ii;ii;;;;i;i;;i;i;i;;iiii;ii::i;i;iii

::: :::::: ::::~::: :::::: :::: ::::::::::::::::::: '1":::::::::::::::: ::: :::: :::::::.'~::::::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

~~~jH: :~f~:1: it ~:~:: ::::ii:ii::i j~~i~:j::! li: ~f~:i j:!:::i::i:1 ~i ii::i:i!t ~::::::::::::::::::::::i ::::::::::::::i: :~::::::::: ::::::::::::::::::::

:::::: :::: ::' io" ·1'.:,;;,;ie~"''''Y+= I ~.-...~-.;,;;,;.;;,. \::::::: :~~c ~~:~: ~::: ~:: ~: ~: ~: ~::~ i~: <i;:: ::;~; ~::~::: : :~- •...." ,..If' ol'ttt.-,JI{BI,M' t .... : :

.- 0.000

Figure 5-12. Surface Analysis for Exit Catalyst Samples

at a 40-keV Energy Source

SECTION VI

CONCLUSION

The receiver design presented herein assures a nominal lO-kWt conversion

capacity and demonstrates the off-design operation flexibility to successfully

accommodate the incident radiant energy density profile that the inner wall of

the cavity is to be subjected when operating as part of a dish collector

system. The developed computer simulation program predicts reasonably well

the actual performance and can be used for future design optimization and for

techno-economic studies. The catalytic effect of stainless steel tube for the

S02!02 recombination reaction appears to be negligible. At a maximum

temperature of about 900oC, the extended use of reactors made of stainless

steel (316) appears limited. For long-term reliable operation, units

constructed using ceramic material should eventually be developed.

6-1

SECTION VII

REFERENCES

1. Chubb, T.A., "Analysis of Gas Dissociation Solar Thermal Power System,"

Solar Energy, Vol. 17, p. 129, 1975.

2. Chubb, T.A., Nemecek, J.J., and Simmons, D.E., "Application of Chemical

Engineering to Large Scale Solar Energy," Solar Energy, Vol. 20,

p. 219, 1978.

3. Leva, M., "Packed-Tube Heat Transfer," I & EC, Vol. 42, p. 2498, 1950.

4. Reynolds, W.C., "Heat Transfer to Fully Developed Laminar Flow in a

Circular Tube with Arbitrary Circumferential Heat Flux," J. Heat

Transf., Vol. 110, May 1960.

5. Farbman, G.H., and Koump, V., Hydrogen Generation Process, Final Report,

Advanced Energy Systems Division, Westinghouse Electric Corp., June 1977.

6. Li, C.H., and Schmidt, E.W., "Heat and Mass Transfer Analysis of a

Chemical Converter/Heat Exchanger for the S02/S03 Distributed Solar

Energy Collection System," Presented at 1979 International Congress of

ISES, Atlanta, Georgia, May 28 to June 1, 1979.

7. McCrary, J.H., Evaluation of Metallic Converters, Test Plan, March 1980.

8. Miyamoto, S., Warrick, A.W., and Bohn, H.L., "Land Disposal of Waste

Gas," J. Environmental Quality, Vol. 3, p. 49, 1974.

7-1


DOE/]PL/I060-76 EXPERIMENTAL AND THEORETICAL STUDY OF A SOLAR THERMOCHEMICAL RECEIVER MODULE DOE