A series of perhalocarbons are proposed as candidate heat exchange fluids for service in thermochemical cycles for hydrogen production that involve direct contact of the fluid with sulfuric acid and vaporization of the acid. The required chemical and physical criteria of the liquids are described and the results of some preliminary high temperature test data are presented

Lawson, D. D.

Petersen, G. R.

English

NASA Technical Reports Server

  
 
 
N O T I C E 
 
THIS DOCUMENT HAS BEEN REPRODUCED FROM 
MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT 
CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED 
IN THE INTEREST OF MAKING AVAILABLE AS MUCH 
INFORMATION AS POSSIBLE 
https://ntrs.nasa.gov/search.jsp?R=19800006101 2020-03-21T20:38:08+00:00Z
JPL PUBLICATION 79'-81
Potential beat Exchange Fluidssg	 for use in Sulfuric Acid Vaporizers
D.U. Lawson
G.R. Petersen
(N AS A-CR- 16 2 5 4 8) POTENTIAL HEAT LXCHANGE 	 180-14358
FLUIDS FOR USE iN SULFURIC ACID VAPORIZERS
(Jet Propulsion Lab.) 16 p RC A02/MF A01
CSCL 20D	 Unclas
G3/34 46430
October 1, 1979
i'
r
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
'	 a
e
JPL PUBLICATION 79-81
Potential Heat Exchange Fluids
for use in Sulfuric Acid Vaporizers
D.D. Lawson
G.R. Petersen
October 1, 1979
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
%- -A,
Prepared 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.
This report was prepared as an ac,.,)tint of work sponsored by the United States
Government. Neither the United Jtatcs nor the United States Department of
Energy, nor any of their employees, nor any of their contractors, subcontractors,
or their employees, makes any warranty, express or implied, or assumes any legal
liability or responsibility for the accuracy, completeness or usefulness of ally
information, apparatus, product or process disclosed, or represents that its use
would not infringe privately owned rights.
ii
yaF
r wgw-P ,—% , — ,
i
ABSTRACT
A series of liquids have been screened as candidate heat exchange
fluids for service in thermochemical cycles for hydrogen production
that involve direct contact of the fluid with sulfuric acid and vapor-
ization of the acid. The required chemical and physical criteria of
the liquids are described and the results of some preliminary high
temperature test data are presented.
,.
4
TECHNICAL REPORT STANDARD TITLE PAGE
1. Report No
-JPL pub. 79-81 2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle 5. Report Date
POTENTIAL HEAT EXCHANGE FLUIDS FOR USE IN SULFURIC October 1, 1979
6. Performing Organization CodeACID VAPORIZERS
7. Author(s)	 D. D. Lawson, G. R. Peterson 8. Performing Organization Report No.
9. Performing Organization Name and Address 10. Work Unit No.
JET PROPULSION LABORATORY
11. Contract or Grant No.Californ 4x Institute of Technology
4800 Oak Grove Drive NAS 7-100
13. Type of Report and Period CoveredPasadena, California 91103
JPL Publication
12. Sponsoring Agency Name and Address
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Washington, D.C. 20546 14. Sponsoring Agency Code
15. Supplementary Notes 	 prepared by JPL for the U.S. Department of Energy
through an agreement with NASA (ET-78-I-01-3112)
16. Abstract	 ~
A series of liquids have been screened as candidate heat exchange
fluids for service in thermochemical cycles for hydrogen production that invo'l.ve
direct contact of the fluid with sulfuric acid and vaporization of the acid. 	 The
required chemical and physical criteria of the liquids are described and the results
of some preliminary high temperature test data are pre-ented.
17.	 Key bVords	 (Selected by Author(s)) 18.	 Distribution Statement
Chemical Engineering
Energy Production Unclassified - Unlimited
Physical Chemistry
19.	 Security	 Classif.	 (of this	 report)
Unclassified
20.	 Security Classif.
	 (of this page)
Unclassified
21.	 No. of Pages
15
22.	 Price
CONTENTS
I. INTRODUCTION	 . . . . . . . . . . .	 . . . . . . . . . . 1-1
II. SELECTION OF MATERIALS . . . . . . . . . . 	 . . . . . . . 2-1
III. EXPERIMENTAL . . . . . . . . . . . . . . . . . . . . . . . . 3-1
IV. DISCUSSION .	 . . . . . . . . . . . . . . . . . .	 . . 4-1
REFERENCES . . . . . . . . . . . .	 . . . . . . . . . . . . . . . 5-1
TABLES
3-1 SUMMARY OF CHEMICAL AND PHYSICAL PROPERTIES OF CANDIDATE HEAT
TRANSFER LIQUIDS . . . . . . 	 . . . . . . . . . . . . . . . 3-3
3-2 CHARACTERISTIC RESULTS OF HIGH TEMPERATURE CONTACT BETWEEN
CONCENTRATED H 2SO4 AND SELECTED FLUOROCARBONS . . . . . . . 3-4
v
SECTION I
INTRODUCTION
In a number of thermochemical cycles under active investigation
for hydrogen production, the oxygen release step is the thermal decom-
position of sulfuric acid (H2SO4):*
2H2SO4
	
	A 	 2SO2 + 0 2 + 2H20	 (1)
ti$30°C
It has been suggested that direct fluid contact heat exchange with
H2SO4 would have energy saving benefits over a conventional heat ex-
changer in the vapoization of H 2SO4 at ti330°C before the high tempera-
ture cracking or decomposition step at ti830°C (Reference 1).
Direct contact heat exchange occurs when two immiscible fluids at
different temperatures are mixed. When one of the two fluids undergoes
a change of phase, extremely high heat transfer rates result (References
2 and 3). In this preliminary work, the physical and chemical require-
ments of liquids in contact with H 2SO4 have been examined at tempera-
tures up to the boiling point of the acid. Some candidate materials
are proposed for high temperature seat transfer by direct fluid contact.
*The thermochemical cycles are General Atomic/Sulfur-iodine Cycle,
Westinghouse/Hybrid Sulfur Cycle, and Euratom/Mark 13 Hybrid Sulfur
Bromine Cycle.
1-1
i
fSECTION II
SELECTION OF MATERIALS
Liquids used for heat exchange in contact with H 2SO4 must meet
the following criteria:
1. Liquids must be chemically stable to concentrated sulfuric
acid in the temperature range of 300 to 400°C for the required
service periods.
2. Liquids must have very low miscibility with sulfuric acid at
use temperatures.
3. Liquids must have low vapor pressure at use temperature to
prevent loss by vaporization.
It is also desirable that they should be liquid at room tempera-
ture and not be high :i.a cost.
Since the contact is being made with hot concentrated sulfuric
acid, most organics are not suitable because of reactivity with the
acid. Thus, because of the inertness of fluorine substituted organic
materials, they were selected for evaluation. Under very strong
acidic conditions, aliphatic fluorocarbons should be stable because
of the very high heats of formation of the carbon-fluorine bond.
However, previous experience has indicated that other fluorinated
compounds may be suitable, so perfluoro(propylene oxide) polymers,
tertiary butyl amine and a chloro-trifluoro alkane were tested.
2-1
J3:
SECTION III
EXPERIMENTAL
All compounds tested are perhalocarbons and a brief summary of
their known physical and chemical properties is given in Table 1. All
the thL, rmal testing (except for several early runs) was done in fused
quartz vessels because of the attack of concentrated sulfuric acid at
high temperatures on Pyrex glass, and lack of thermal stress in quartz.
Two types of thermal testing were conducted:
1. Refluxing sulfuric acid and the liquid —as carried out in a
quartz cyclinder about 6 cm in diameter and about 20 cm in
height, closed with a 100 ml Pyrex beaker. Any evolution of
hydrogen fluoride was detected by etching of the beaker. Th
reflux apparatus with beaker in place is shown in the follow-
ing figure:
3-1
2. Otte material, Fomblin U, was rested in a sealed tube. To a
quartz tube of 1.25 cm I.D. (2mm thick walls) and 15 cm
length was added 0.4 ml of Fomblin U and 0.4 ml of concentrated
H2s04 . The tube was then sealed and heated in a muffle fur-
nace for 6 hours at 370° to 400°C.
Only Fomblin U was tested in this manner because of concern
the tube might break due to high vapor pressure of the compound or
decomposition products. Table II gives a summary of the test results.
The Fomblin liquids appear to be the most promising. Fomblin U was
given the most rigorous treatment and infrared spectral analysis
showed no detectable structural alterations, although evolution of
hydrogen fluoride was detected.
In order to evaluate miscibility, Fomblin U tested in the re-
fluxing quartz cyclinder experiment was analyzed for sulfuric acid
content by titration. It was found that the sample contained less
than 0.1 mg acid per ml of Fomblin. The acid was most likely present
as a suspension in the Fomblin, because when a drop of this material
was placed on moistened pH paper, the acidity color change appeared
as small isolated spots.
All infrared spectra were obtained with a Perkin-Elmer Infracord
Model 137 using sodium chloride cells.
3-2
m
ro
t7'
a
v
4-t
m
H
v
x
v
sd
ro
ro
ro
0
m
v
v
a
0^
4
P4
s^
U
4
P4
ro
ro
cdU
v
U
w
0
T
s^
tt7
r-i
iM
41
r-I
ro
H
00
a "^
U ^: A b
q
7 A N tGny
u
.--i
cd
t^
.^ uro u 4-1
a
o
.cU
ca 41 O U
x
o U
V '^
 r G
G G
U
G 11 ri^
o°  ro
xz rr,^ r w Hr^r, ,°H
4J ^4 ..
A Q) U
4.J 0
	
^	
a)^.	 00
	
^4 4.J
	
u1
	
0roro
	 ^	 '^
Loa •^
: 
x o a
ro^4^
	 m Li-4 "c
w
V)U) 0 C `'
^
4J
sd	 CJ
4	
Li
^;	 ^
E Ln
cn
^;
p
o
a.1
R1
U
C
O
a; o v 0 c^ c^ v v
w in o u Mo o 1 m o uor^ n v v
.d	 1-1 to .Dr-1 r^ rnrl
 
p
N -4	 co Q 'Ly 4J
N
o
U ,n
I
v v
u
3 U v o
v ri r,
H o 0
o m o a o o q o G o
.c o r--+ ^4 v O. ^4n
o
o v a
o
" v
v
a
o 41,a 0' v a: vC o ro w^ w o ro -4	 Cl, vw
914 a u ;>,
a xw	 o w  o a	 0
.d
.0
N v ^
o o ao 0
^z -ao p w a o
^4
v v
o
^-4 ur^ v
cz
G
U)
.,j
ro
wi
a
.r{
1.1
cJ
41 r^1
G
o 4-+
H
co
tf1
t
3-3
IC
Table 3-2. Characteristic Fesults of High Temperature Contact Between
Concentrated H2 so4 and Selected Fluorocarbons*
Hours of Differences
Max Temp. high temp in iR Spectra Evidence of
Fluorocarbon attained 112SO4 before and HF Cotmnents,
(Tradename) (°C) coma t after Evolution + notes
1. 93 Yes; CH and Yes V.	 viscousFluorolube 285 -300
('.=U stretches at room temp.
found waxy after
ref lux
2. Mediflour 189 93 No change Yc:, All	 di:+-
tillud	 alter
93 hr^, of
reflux
3. Freon E-4 200 90 No change No All	 dis-
tilled	 after
90	 lira.
4. Flutes PP7 190 240 No change No All dis-
Wlad after
240	 1tr:,.
5. Fomblin L 310 96 No change Yes
6. Fomblin U 317 96 No change Yes
7. Fomblin U	 400	 6	 No Change	 Yes	 Carried out
in sealed
quartz tube.
(see experi-
ntenta 1 Bee-
tlon)
+ Etchinp, of pyrex covers or reflux column observed.
* All mixtures (1-6) contained equal aliquots (10-15 ml) of concentrated Ii, ) SO4 and
the fluorocarbon. Mixtures 2-4 could not be pushed beyond these temperature
plateaus. Temperature was measured by suspending a 360°C thermometer into the
fluid Just obcwe the hott0411 of the vessel.
3-4
SECTION IV
DISCUSSION
This preliminary study indicates that it is possible to have
stable liquids in the temperature range at which concentrated sulfuric
acid is a vapor. The most promising candidate materials are the
perfluoropropyl.ene oxide polymer.; with a degree of polymerization (DP)
of %10 to 50. It is desirable to have the DP in the high range be-
cause the vapor pressure of the material will decrease as the DP is
increased, resulting in higher operating temperatures.
Immiscibility is important, since it minimizes the transport of
H2SO4
 by the heat exchange fluid to the system heat source. Because
the solubility parameters of these fluids are low, the solubility in
acid should be very slight. (The solubility parameter of H2 SO4 at
298K is 18.0.)
The experiments showed very little acid was present in Fomblin U
at room temperature, but there was concern that mutual solubility may
increase at higher temperatures. Although the difference in solubility
parameters is high and therefore immiscibility is expected, a more
quantitative estimate of the degree of mutual solubility at the operat-
ing temperature can 'b p obtained from the following approximate relation-
ship (Reference 4).
1/ 2 (Vl + V2 ) (61 - 6 2 ) 2 > 2 RT when V1:V2
which indicates that mutual solubility will be low if the expression
on the left is greater than 2 RT. At T= 603°, the boiling point of
H2SO4 , 2 RT is 2395, and Vl , V2 , 5 1 and 62 are approximately 50,
4-1
2550, 15.5 and 5.0, respectively, (where the subscript one refers to
H? SO4
 and two to Fomblin U). Using these values in the above relation-
ships gives:
1.4 x 105 > 2395
or a ratio of 58 to 1, which indicates that Fomblin U and sulfuric acid
should be immiscible at the operating temperature.
The possible problem areas of the fluorocarbon fluids are:
1. The commercial polymer liquid materials are not pure com-
pounds and tend to evolve hydrogen fluoride during the First
hour_ or so on contact with sulfuric acid at these temperatures
(Reference 5). A pretreatment with sulfuric acid may elimi-
nate this problem.
2. Highly fluorinated fluids may react violently with metals
such as aluminum and magnesium and their alloys under condi-
tions where fresh active metal surfaces are created. There-
fore, the system should be designed to avoid this condition
and to ivoid corrosive contamination of sulfuric acid.
3. The perfluoroethers are decomposed by halogenated Lewis acids
such as AM 39 SbF5 , and CoF5 , but are stable to oxygen or
ozone. Therefore any use in other thermochemical cycles
besides service with sulfuric acid should be evaluated with
this in mind.
Since these tests were carried out with relatively pure materials,
in contact with only quartz or pyrex, potential contamination with any
other materials might have an adverse affect on stability or reacti-
vity of sulfuric acid and heat transfer fluid.
4
I
4-2
ti
The Fomblin compounds tested were only two of a series. It is
likely that the other Fomblins will. exhibit similar characteristics
and are also worthy of some further consideration.
4-3
i1
REFERENCES
1. Private communications from Dr. Armando Broggi, EURATOM, ISPRA
(Varese) Italy, on August 1978 and March 1976.
2. Sideman, S., and Shabak, H., Can. J. of Chem. Eng., June 1954.
3. Sideman, S., "Direct Contact Heat Transfer Between Immiscible
Liquids; Advances in Chemical Engineering;" Academic Press,
New York, N.Y., Vol. 6, pp. 207-268, 1966.
4. Hildebrand, 11. H. and Scott, R. L., The Solubility of Non-
Electrolytes; 3rd Edition, Reinhold, New York, p. 253, 1952.
5. Literature on the Montecatini-Edison FOMBLIN fluorinated fluids
may be obtained from PCR Inc., P.O. Box 1466, Gainesville, FL
32602.
5-1


Potential heat exchange fluids for use in sulfuric acid vaporizers

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server