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EA-6010-16

Dist. Category UC-90C

MATERIALS RESEARCH FOR CLEAN UTILIZATION OF COAL

QUARTERLY PROGRESS REPORT

April - June 1978

Samuel J. Schneider

Project Manager

Center for Materials Science

National Bureau of Standards

Washington, D. C. 20234

PREPARED FOR THE UNITED STATES

DEPARTMENT OF ENERGY

Under Contract No. EA-77-A-01-6010

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

States Government. Neither the United States 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 any information,

apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights."

TABLE OF CONTENTS

PAGE

X. OBJECTIVE AND SCOPE OF WORK 1

II. SUMMARY OF PROGRESS TO DATE 1

Articles Published and Talks Presented 4

III. DETAILED DESCRIPTION OF TECHNICAL PROGRESS 5

1. Metal Corrosion , 5

a. Slow Strain Rate Test 5

b. Pre-Cracked Fracture Test 14

2. Ceramic Deformation, Fracture and Erosion. ... 16

3. Chemical Degradation 27

a. Reactions and Transformations 27

b. Slag Characterization 35

c. Vaporization and Chemical Transport 41

4. Failure Prevention 44

a. Failure Information Center 44

b. Materials Properties Data Center 47

I. OBJECTIVE AND SCOPE OF WORK

Coal Gasification processes require the handling and containment of

corrosive gases and liquids at high temperature and pressures, and also

the handling of flowing coal particles in this environment. These severe environments cause materials failures which inhibit successful and longtime operation of the gasification systems. The project entails investigations on the wear, corrosion, chemical degradation, fracture, and

deformation processes which lead to the breakdown of metals and ceramics

currently being utilized in pilot plants. Studies will also be carried

out on new candidate materials considered for improved performance.

Special emphasis will be devoted to the development of test methods,

especially short-time procedures, to evaluate the durability of materials

in the gasification environments. These methods will focus on wear,

impact erosion, stress corrosion, strength, deformation, slow crack

growth and chemical degradation. A system has been initiated to abstract

and compile all significant operating incidents from coal conversion plants

as well as materials property and performance information important to the

design and operation of these plants. This program will provide a central

information center where problems of common interest can be identified

and analyzed to avoid unnecessary failures and lead to the selection of

improved materials for coal conversion and utilization. Active consultation to DOE and associated contractors will be provided as requested.

II. SUMMARY OF PROGRESS TO DATE

Brief Summary

1. Metal Corrosion

a. Constant Strain-Rate Test

The wedge-loaded DCB specimens exposed in the Synthane plant in the

liquid phase scrubber surge tank were further evaluated by splitting

them apart and measuring the crack length. Type 310 SS, Type 309 SS

,

and nickel alloy 800 showed no crack growth during the test. Type 304

SS, Type 446 SS, and nickel alloy 671 showed only very minimal crack

growth (175ym to 775ym) . Low carbon steel (AISI 1015-20) exhibited a crack growth of 2.63 cm. Coating the Type 310 SS tensile specimens

with nickel or copper increased the ductility (elongation and reduction

in area) of Type 310 SS as compared to a smooth or glass-beaded Type 310

SS specimen when tested at 600 °C in helium at a strain rate of 10 -6 /s.

The results of testing Type 310 SS in air at 600 °C at a strain rate of

10

-6 /s show that the ductility (elongation and reduction in area) are very similar to results obtained when tested in argon, helium, or simulated

coal conversion gases. Several Type 309 SS specimens, which are similar

in composition to Type 310 SS except for lower nickel and chromium contents

and higher silicon content, were tested at 600 °C (in argon, helium, and

simulated coal conversion gas) at strain rates of 10 6 /s and lower and

were found to be much more ductile than Type 310 SS when tested under the same conditions. No cracking was observed in any of the Type 309 SS

specimens tested.

1
Some limited testing of alloys will be done, but the preparation of the

final summary report on the test method will take precedence during the

next quarter.

b. Pre-Cracked Fracture Tests

Development and analysis of the tension loaded double cantilever beam

stress corrosion specimen has continued. Experimental tests to verify

the analysis and to test for the susceptibility to cracking were initiated.

2. Ceramic Deformation, Fracture and Erosion

Construction and assembly of the high-pressure, high-temperature mechanical

loader was completed this quarter with the installation and checkout of the

pressure balancing system. In addition, the elevated temperature properties

of two low-alumina refractory concretes both before and after hydrothermal

exposure were investigated. Mineral phase changes were monitored by x-ray

diffraction techniques at room temperature after the hot flexural strength

determination

.

Final evaluation of the high-pressure, high- temperature mechanical loader

will be undertaken. This evaluation mainly involves establishing the

operating characteristics of the pressure-balancing system and the load

application system in the presence of an applied pressure. Exposure

studies will begin for a high and a low-alumina refractory concrete in a 60% H 2 O - 40% H2 environment.

3. Chemical Degradation

a. Reactions and Transformations

Energy dispersive powder diffraction patterns obtained in three series

of experiments with an unfired bar of high-alumina neat cement heated

in steam have been interpreted. Initially, the specimen consisted of

CA and a-A with small amounts of CAHi 0 , C 2 AH 8 , C 3 AH 6 , and AH. Of the

reactions observed, the hydration of a-A to form AH, and the subsequent

dissociation of AH at higher temperatures are amoung the most important.

These reactions, which are believed to have an important effect on the

strength of high alumina castable refractories have been observed in

real time by the in situ x-ray diffraction method, and the progress of

the reactions has been plotted.

During the next quarter NBS refractory A-56 with mullite aggregate, as well as the bonding matrix of A-56, are to be tested in steam. Additional work on specimens of neat cement is also planned.

b. Slag Characterization

The vertical temperature profile of the molten slag was determined in

steam. A uniform temperature profile was found in the central portion

2
of the crucible, and it was concluded that this is where the actual

temperature must be measured.

It is planned to construct a new drag cup assembly allowing direct

temperature measurement of the molten slag.

c. Vaporization and Chemical Transport

Evidence of non-equilibrium chemical reaction effects has been noted

for systems involving H 2 O as a gaseous reactant and either sodium calcium

silicate or sodium sulfate molten substrate. The new capillary probe

sampling device has been calibrated and shown to faithfully sample

equilibrium vaporization systems.

Results obtained to date will be checked, and extended where necessary,

for presentation and publication at the 10th Materials Research Symposium

on Characterization of High Temperature Vapors.

4. Failure Prevention

a. Failure Information Center

Thirty-two additional reports of operating experiences and failure

analysis reports were entered into the Center's data base. Over two

hundred information items were transmitted to plant operators and

fossil energy contractors. Additional progress was made in completing

the detailed report covering the performance of materials and components

used in the Conoco lignite gasification pilot plant. The Center's data

base is being revised in format and content to aid in future information

dissemination.

b. Materials Properties Data Center

The regular activities of the Data Center have gained momentum with the

submission to DoE of the first Data Summaries of contractor's research

projects, the delivery of ordered computer-terminal equipment, increasing activity with respect to learning about the equipment capabilities,

the choice of a Data Base Management System and more intensive study of

data base design with respect to the chosen system, and the arrangement

to test the Management System with respect to the services of two vendors

of the system.

3
Articles Published and Talks Presented

"X-ray Powder Diffraction Measurements in Reactive Atmospheres at

1000 °C and 7 Mpa," F. A. Mauer and C. R. Robbins. Accepted for

publication in Advances in X-ray Analysis , Vol. 22.

"Hot Strength and Fracture Toughness of an Anorthite-Bonded Refractory,"

J. M. Bukowski, May 6-11, 1978, American Ceramic Society Meeting - Refractories Properties and Testing, Detroit, Michigan.

"Erosion of Castable Refractories," S. M. Wiederhorn, 14th Annual

Symposium on Refractories, April 1978, St. Louis, Mo.

4
III. DETAILED DESCRIPTION OF TECHNICAL PROGRESS

i. Metal Corrosion

a. Slow Strain Rate Test (G. M. Ugiansky and C. E. Johnson, 561.00)

Progress : The wedge-loaded DCB specimens exposed in the Synthane plant

in the liquid phase scrubber surge tank (mentioned previously in the

March 1978 Quarterly Report) were further evaluated by splitting

them apart and measuring the crack length. These specimens had been

exposed for a combined time of 2046 hours (592 hours operating time

and 1454 hours standby time) at an average operating temperature

of 196°C (385°F) and a pressure of 600 psig. Type 310 SS , Type 309 SS,

304 SS, Type 446 SS, and nickel alloy 671 showed only very minimal

crack growth (175jim to 775ym) . Low carbon steel (AISI 1015-20)

exhibited a crack growth of 2.63 cm. Although the test temperature

may not have been high enough to have had a detrimental effect on

the stainless steel specimens, it was high enough to cause some

stress relief of the specimens; thus, reducing the initial load on

the specimen.

In the laboratory slow strain rate testing, several Type 310 SS

specimens were run in air and in an inert atmosphere of helium at

600°C and a strain rate of 10~6/s (Table 1) . Several different surface

preparations of the Type 310 SS specimens were investigated from the point

of view of keeping the environment away from the specimen so that a base line (that is, properties without environmental interaction)

could be determined. On one of the Type 310 SS specimens the reduced

section was glass-beaded to alter the surface structure to see if

this would affect the surface cracking previously seen in Type 310 SS

under the same test conditions. The glass-beaded Type 310 SS specimen fractured in a brittle manner (Table I) with many secondary

cracks - much like the previously tested smooth tensile specimens

of 310 SS . Another Type 310 SS specimen was plated with a 62.5ym

layer of nickel to see if this would act as a barrier layer to

prevent any environmental interaction with the specimen. This speci- men failed with slightly higher ductility (Table I) than the glassbeaded specimen but several cracks were apparent through the nickel

layer (Fig. 1) . Another Type 310 SS specimen was plated with lOOym

of copper to see if this layer would act as a getter for oxygen thus

preventing any environmental interaction with the specimen. This

specimen was less susceptible to cracking (had higher ductility)

than both the glass-beaded and nickel plated specimens (Table I)

Only a few cracks were visible through the copper layer (Fig. 1)

.

The differences in ductility of the glass beaded, nickel plated,

and copper plated 310 SS specimens are apparent from the stressstrain curves in Fig. 2. Even though there is still some cracking in the Type 310 SS specimens, the plating of nickel and copper

has greatly increased the ductility of these specimens. It is not

5
known at this time as to whether the plated coatings have acted

as complete barriers to prevent any interaction of the environment

and the Type 310 SS material since there is still a possibility

of diffusion through the coatings. With the coatings the ductility

of Type 310 SS has increased when tested in helium, which may

contain a low partial pressure of O 2 and/or H2O, at 600°C at a strain

rate of 10“®/s. (He manufacture specifications indicates 0,1-0, 5%

O 2 and 2-250 ppm H2 O contents.)

Another Type 310 SS specimen was tested in air at 600°C at a strain

rate of 10“6/s. The results are shown in Table 1. The elongation

and reduction in area results for the Type 310 SS tested in air at

600°C are similar to the results obtained for the same alloy tested in

helium, in the oxidizing/sulfidizing simulated coal conversion gas,

and in the oxidizing/sulfidizing/carburizing simulated coal con- version gas. It appears that if oxygen does play a part in the cracking of Type 310 SS when tested at 600°C at a strain rate of 10”^/s

then only a minimum amount is necessary and any larger amount does

not have any further detrimental effect.

Several Type 309 SS specimens were tested at 600°C in different

environments and strain rates (Table I) . Type 309 SS is similar

in composition to Type 310 SS except for lower nickel and chromium

contents and higher silicon content (Table 2) . The results of testing

Type 309 SS In argon at a strain rate of 10~^/s are shown In Table 1

and Fig. 3. The Type 309 SS specimen remained ductile with no cracking; whereas. Type 310 SS cracked* and was less ductile when tested

under the same conditions. A Type 309 SS specimen tested in

helium at 600°C at a strain rate of 10”^/s had even higher ductility

(elongation and reduction in area) than the 309 SS specimen tested

in argon (Table 1) . A comparison of stress-strain curves of Type

309 SS and Type 310 SS tested in helium at 600°C and at a strain

rate of 10“^/s is shown in Fig, 4. Type 309 SS remained ductile even when tested at a slower strain rate of 5 X 10”^/s at 600°C in helium

(Table 1) . No cracking was apparent in the Type 309 SS specimen

tested at this slower strain rate of 5 X 10~^/s. Type 309 SS also

remained ductile with no cracking when tested in the oxidizing/

sulf idizing/carburizing simulated coal gasification environment

(Table 1) . The microstructure of the Type 309 SS was found to

contain some ferrite which could contribute to the higher ductility

than was seen in the Type 310 SS where no ferrite was found. The

higher silicon content and greater chromium to nickel ratio in the

Type 309 SS, as compared to Type 310 SS, could promote the formation

of the ferrite. The existence of ferrite could account for sigma

phase formation except that the test temperature of 600°C does not seem to be great enough for sigma formation. In summary, the slow

strain rate test indicates that the Type 309 SS performs better than

the Type 310 SS. Since Type 309 SS has all of the necessary properties of

Type 310 SS for coal conversion application but appears to be less susceptible

*See January-March 1978 Quarterly Report,

6
to stress cracking, these results may be of great signficance. Their

implications should be looked into further.

Plans ; Some limited testing of alloys will be done, but the preparation of the final report will take precedence.

7
Slow Strain Rate Test Results

TABLE 1

Tensile Strength Elongation Reduction

Specimen Test Environment MPa (psi

)

% in Area, %

Glass-beaded 310 SS Helium 343 (51,200) 12.5 19.2

Nickel plated 310 SS Helium 327 (47,400) 22.6 31.2

Copper plated 310 SS Helium 301 (43,600) 27.6 33.9

310 SS Air - - 17.1 26.0

#1 309 SS Tank Argon 323 (46,800) 31.2 57.1

#2 309 SS Helium 334 (48,400) 37.7 69.2

#3 309 SS* Helium - - 34.3 62.1

#4 309 SS 0-S-C

+

- - 36.5 62.7

*Tested at a strain

_7

rate of 5 x 10 /s •

^O-S-C : oxidizing-sulfidi zing-carburizing simulated coal gasification environment

8
Alloy Composition, Wt%

TABLE 2

309 SS 310 SS

Carbon 0 . 07% 0.08%

Manganese 1.74 1.76

Phosphorus 0.018 0.027

Sulfur 0.013 0.021

Silicon 0.70 0.48

Nickel 13.22 19.66

Chromium 22.96 24.83

Molybdenum 0.08 0.10

Copper 0.07 0.17

Iron Bal Bal

9
Fig. 1. Photographs of fractured 310 SS specimens tested

in helium at 600 C at a strain rate of l0-6 /s. (A)

Nickel plated to a thickness of 62.5ym. (B) Copper

plated to a thickness of lOOpm. Magnification: 4X.

10
310

55

600 QCHELIUM

li

Stress-strain

curves

of

Type

310

SS

specimens

tested

at

strain

rate

of

l0

-6

/s.
Fig. 3. Photograph of fractured 309 SS specimen tested

in argon at 600°C at a strain rate of l0“6 /s.

Magnification: 5X.

12
600

Q

C

-

HELIUM

]

9

9* 4.

4i

9*E

E

9*C

C

9*X

X

9*B

Z

rl

l U

z

H

CE

O'

h

m

m

a

a s a a

»a a «a a

* * w w

<1 Lf cz) W >

a a a a a a

iA a tfl a i/i N N H H

^5S3d±5

13

Fig.

4.

Comparison

stress-strain

curves

of

Types

309

SS

and

310

SS

tested

at

a

strain

rate

of

lO“^/s.
b. Pre-Cracked Fracture Test (J. H. Smith, 562)

Progress : Additional analysis of the tension loaded double cantilever-beam

specimen was completed. Stress analysis programs were developed that are suitable for calculating the change in stress intensity with temperature,

(K /K ) , for a wide range of specimen materials, specimen configurations,

specimen sizes, and initial stress intensity (K ) . These stress analysis

programs were used to extend the analysis shown in reference (1) to

several candidate test materials which included 304, 310, 347 stainless

steels, and Inconel 800. This analysis showed that the initial stress

intensity level (K ) can be varied over a sufficiently wide range, (up

to 100 ksi /in) for typical specimen, and that the ratio (K /K ) can be

maintained equal to 1.0 up to approximately 600°C when the size and

material in the specimen grips are properly chosen. In all cases, type

18-8 stainless steel is the optimum material for the loading fixture

because it has a high coefficient of thermal expansion.

Optimization of the tension-loaded double cantilever beam specimen included

a sensitivity analysis to determine what effect small changes in loading

fixture length (L ) , initial stress-intensity level (K ) , and coefficients

of expansion (a) has on the variation of the ratio ,K^ with temperature.

K

o These analyses show that when the initial loading fixture length (L ) is

chosen so that is independent of temperature, that changes of as much

<r>

K

as 10% in L do not change — more than 2%. Variations in the coefficients

F K

o of expansion of the specimen, loading grips, or loading fixtures of less

than 10% (the maximum expected variation for a given material) do not cause more than 2% variation in (K /K ) . The ratio (K /K ) is quite sensitive to To To the initial stress intensity value (K ) and require that the length of the

loading fixture (L ) , be adjusted as the initial stress intensity (K ) is

varied. F °

Experimental tests to verify the analysis of the tension loaded double

cantilever beam specimen were initiated. To verify the analysis of the

specimen, the variation of the load-line displacement, V, and modulus

of elasticity with temperature must be determined. This verification can

be easily carried out with a metal having a low modulus of elasticity, a large change of modulus with temperature (dE/dT) , and a large initial

load-line displacement (V ) . Therefore, the initial verification tests

can best be carried out using an aluminum specimen to verify the stress

analysis. Subsequent tests will be carried out at higher temperatures

with Ni-Cr alloys.

14
Initial tests were planned to use pre-cracked fracture mechanics specimens

to conduct cracking tests in severe environments. These initial tests

will include testing 304 and 347 type stainless steels in a chloride

environment at temperatures to 600°C. Subsequent tests will include in

addition type 310 stainless steel and will be conducted in a sulfidizing/

oxidizing environment.

Plans ;

1. Additional specimen development will complete the analysis of other

test specimens and the sensitivity analysis. Elastic and creep strains

will be included in the analysis.

2. The experimental verification of the stress analysis will be conducted.

3. Initial tests of a series of stainless steel alloys will be conducted.

Reference 1: Quarterly Report, Jan. 1 - March 31, 1978, p. 12 "Materials

for Clean Utilization of Coal," EA 6010-15.

15
2. Ceramic Deformation, Fracture, and Erosion (E. R. Fuller, Jr., S. M.

Wiederhorn, J. M. Bukowski,

C. R. Robbins, and D. E.

Roberts, 562.00)

Progress : Construction and assembly of the high- temperature , highpressure mechanical loader was completed this quarter. This equipment

is capable of mechanical property measurements at elevated temperatures

and elevated pressures in the presence of simulated coal gasification

environments. It remains, however, to establish and to optimize the

operating characteristics of a pressure-balancing subsystem, and to

determine the operational characteristics of the system as a whole.

The final phase of construction, completed this quarter, was the assembly

and installation of the electronic pressure-balancing unit. This unit

is required to minimize the pressure differential between the inner

environmental chamber and the outer pressure vessel. The unit senses

the pressure differential between the two chambers and, depending on the

sign of pressure differential, controls two motor-driven metering valves.

One of these valves admits a pressurizing gas into the outer pressure

vessel to increase its pressure with respect to the inner chamber,

whereas the other valve vents the containing gas from the outer pressure

vessel to reduce its pressure.

Satisfactory operation of this pressure-balancing system has been established using two lengths of pressure tubing to simulate the two pressure

chambers. (The tubing is actually the inlet plumbing to each of the two

pressure chambers.) Although no attempt was made to optimize the

controlling characteristics for this simplified test system, results were very encouraging. For an applied pressure of approximately 0.7 MPa

(100 psi) , the controllability was +0.007 MPa (+1 psi) . Upon increasing

the operating pressure to approximately 4 MPa (600 psi) , a 1% controllability was maintained, i.e., +0.04 MPa (+6 psi). We expect that the

increased volume of the actual vessels will somewhat dampen the response

and minimize this pressure differential even further.

In addition to the above-mentioned equipment construction, a study was undertaken this quarter to examine the elevated temperature properties

of two low-alumina refractory concretes after they had been exposed to a hydrothermal environment. The two laboratory refractory concrete com- positions were composed of a calcined kaolin aggregate and either a high-purity or medium-purity calcium aluminate cement. The refractory

concrete formulated with the high-purity and medium-purity cements are denoted A56 and A50, respectively, as they contain approximately 56 and

50 weight percent alumina. The cement to aggregate ratio (0.33) as well

as the particle size distribution of the aggregate was the same for both

refractories. The chemical composition of the two refractory concretes

is given in Table 1.

16
Table 1 - Chemical Composition of Laboratory-Prepared Low-Alumina

Refractory Concretes

A56 A50

Alumina (AI 2 O 3 ) 55.6% 50.4%

Lime (CaO) 4.5% 8.4%

Silica (Si(>2 ) 37.0% 38.4%

Iron Oxide (Fe 2

C> 3 ) 0 . 8 % 1 . 1 %

Soda (Na20 ) 0 . 2 % 0 . 1 %

Others and Loss on Ignition 1.9% 1 . 6 %

100 . 0 % 100 . 0 %

Refractory concrete batches of 2000 grams were dry-mixed in a paddle

mixer of 5 liter capacity until a homogeneous mixture was obtained.

Water was added slowly to obtain the required workability for casting as determined by the "ball -in-hand" technique. The casting water used was

11.0 and 12.5 percent for the A56 and A50 compositions, respectively.

Flexural strength bars (75 x 15 x 7.5 mm) were cast in gang molds coated with

a silicone releasing agent. A combination of vibrating and tamping was

used in placing the concrete in the molds. Immediately after casting,

the molds were placed in a +95 percent relative humidity environment at

a temperature of 22 to 25 °C for 24 hours. The specimens were then

removed from the molds, and dried for 48 hours at 110 °C.

Samples treated hydrothermally were placed in a pressure vessel and

heated to a temperature of 310°C in a saturated vapor environment of

H 2 O. After 65 hours, the temperature was increased to 610°C. Above the

saturation temperature of 342 °C during this heat-up, the steam was vented from the system to maintain the vapor pressure at 15.0 MPa (2180

psi) . After exposure to temperature and pressure for 160 hours, the

refractory concrete specimens were cooled to 500°C, where the hydrothermal environment was slowly vented to atmospheric pressure. During this

venting the temperature decrease was typically 20 to 50°C. The specimens were then allowed to cool to room temperature.

The hot strength of the refractory concretes both before and after

hydrothermal treatment was determined in four-point flexure on a universal

testing machine. A constant crosshead displacement rate of 5xl0 -2

millimeters per minute was used throughout this study. All specimens

were heated to the test temperature at approximately 5°C per minute. The

specimens remained at the test temperature for 15 hours before measuring

the high-temperature flexural strength.

The data for the hot strength, or hot modulus of rupture (MOR) , are presented

in Figures 1 and 2 for the A56 and the A50 refractory concretes, respectively.

Similar to our studies at room temperature, these low-alumina refractory

concretes exhibited a hot flexural strength after hydrothermal exposure

that was 2 to 3 times greater than normally cured refractory specimens.

The A56 refractory composition, which contains the high-purity calcium

17
aluminate cement, had the highest overall strength both before and after

hydrothermal treatment. However, the largest relative increase in hot

strength due to hydrothermal exposure was seen in the A50 refractory

concrete at 1310°C.

The fractured surfaces of the refractory concretes before and after

hydrothermal treatment are distinctly different. In the normally cured

concretes, crack propagation and fracture occurred predominantly in the

cement matrix, circumventing the aggregate grains. In the hydrothermally

treated concretes, transgranular fracture of the aggregates was observed

as the crack propagated through the refractory specimen. This indicates

that the hydrothermal treatment has dramatically increased the strength

of the cementing matrix as well as the cement-to-aggregate bond.

The erosion resistance of these refractory concretes was determined both

at room temperature and at 1000°C. Particle speeds of 57 and 94 meters per

second were used for these measurements. The abrading particles were

100 mesh silicon carbide particles and the impingement direction was normal to the surface being eroded. For each experiment, the erosion

rate was determined from the total weight loss per unit weight of abrasive.

A description of the erosion apparatus is given in Reference 1.

Initial results on the erosion resistance of the two low-alumina refractories

are presented in Figure 3. Since each point represents only one specimen,

the results indicate qualitative behavior requiring further quantitative

confirmation. In all cases, the erosion rate of the normally cured lowalumina refractory (triangles) appears to be 2 to 3 times greater than

similar specimens that were treated hydrothermally (squares) . Filled and

open symbols are used to denote the room temperature and 1000°C data,

respectively.

Observation of the specimen surface after particle impingement provides

a possible explanation for the differences in erosion rate. Erosion of

the normally cured refractory occurs predominantly in the cementing

matrix, as the cement is considerably weaker and more friable than the

calcined kaolin aggregate. As the cement is removed, the aggregates are left standing in relief above the surface of the refractory, producing a channelling pattern of erosion. The protruding aggregate particles are bonded to the surface only by residual cement, and once this cement is

removed, these particles also detach from the surface of the refractory.

A slight rounding of the protruding calcined kaolin aggregate indicates

that these particles are also being eroded by the silicon carbide, but

at a much slower rate than the cement. The degree of channeling in the

normally cured refractory concretes was greater in the A50 composition.

In fact, the A56 composition exhibited hardly any channelling erosion in

the 1000°C experiment.

18
The hydrothermal ly treated refractories did not exhibit this channeling

phenomenum. Rather, the cementing matrix and the calcined kaolin

aggregate appear to be eroded at approximately the same rate. This

observation is in agreement with the strength data. Both indicate that

the cementing matrix and the matrix-to-aggregate bond have become com- parable in strength, and in erosion resistance, to that of the aggregate

material

.

Mineral phase changes were monitored by x-ray diffraction techniques at room temperature after the hot flexural strength determination. The

results are tabulated in Tables 2 and 3. In general, hydrothermal

exposure increases the reactivity of the free silica contained in the

low-alumina refractory concretes. This free silica reacts with the

calcium aluminate phases in the cement at approximately 300°C to form a hexagonal anorthite phase [CAS 2 (H)]*. The hexagonal anorthite phase

forms a strong, continuous structure of small crystallites that permeate

the refractory matrix, and accounts for its high strength. At a temperature of approximately 1000°C in air, the hexagonal anorthite phase

begins to transform to the more common triclinic form of anorthite

[CAS 2 (T) ]

.

Room temperature x-ray analysis of hot MOR specimens shows

that this transformation has gone to completion in 15 hours at 1210°C.

The mineral phases present at 1210°C, and above, in both the normally

and hydrothermal ly cured refractories, are the same. This suggests that

a controlling factor in the observed improvement in mechanical properties

at elevated temperatures is not so much the phase assemblage, but rather,

the path taken to produce the given phase assemblage.

Plans : In the next quarter, final evaluation of the apparatus for

mechanical property testing at elevated temperatures and pressures will

be undertaken. The controlling characteristics of the pressure-balancing

unit will be established, and then optimized, as a function of operating

pressure. Operation of the load application system will then be established in the presence of an applied pressure. To prevent condensation

of steam in the lower region of the environmental chamber, a small

heater will be installed around the lower loading bellows. The temperature profile will then be determined as a function of applied pressure

to provide a temperature calibration for the system. Upon completion of

these checkout procedures, the system will be operational and studies

will begin on refractory concretes under hydrothermal conditions.

Cement Chemistry Notation: C=CaO , A=Al 203 , S=Si02

19
Determination of the high-temperature mechanical properties of two lowalumina (+50%) refractory concretes after hydrothermal exposure will be

completed. Exposure studies will begin for a high and low-alumina

refractory concrete in a 60% H 2 O - 40% H2 environment. Room temperature

mechanical properties subsequent to exposure will be determined for both

refractories. X-ray diffraction analysis and scanning electron microscopy (S E M ) will be used to monitor mineralogical and microstructural

changes that have occurred from exposure.

20
Table

2

-

Mineral

Phases

in

the

A50

low-alumina

refractory

as

determined

by

Room-Temperature

X-Ray

Diffraction

Analysis.

The

symbol

X

denotes

the

presence

of

the

designated

phase,

whereas

the

symbol

t

denotes

only

a

trace

quantity.

<

i3

CM O

X

X X

S

X X X X

<

u

XXX

CM

c

n

6

X X

CM

cn<U

X X X X X X X

cn<

CM O

X X X X X

cn X X X X X X X X X X nc

3

CM cn X X X X X X X X X

o o

CM 4-1

o2

o

in<

<up

3

-P

(0P

<D

i*

0) EhEO

s

<1> P

3

-P3

P

0J u u u u 0 & O u u u

o o o o p E o o o 0 O O o O T) <u O o O O

i—

1

i—

1

rH rH IP Eh rH r-H r-H rH CD o CN ro X CD o CN ro

rH rH rH E rH r-H rH oa

cn

CM CM

cn cn < < u u

21

Cristobalite
Table 3-

Mineral

Phases

in

the

A56

low-alumina

refractory

as

determined

by

Room

Temperature

X~Ray

Diffraction

Analysis.

The

symbol X

denotes

the

presence

of

the

designated

phase,

whereas

the

symbol t

denotes

only a

trace

quantity. <ia

XXXX

X

XXXXX

00 Xu

X

co

<Cu

CM <u

CM co<o

CM CO<u

CO<

CM CJO

CO

CM CO

XX

XX

XXX

XXXXXX

X

XXX

XX

XXXX

XX

X

X

X

X

XX

X

X

<L)O rH

-P •r4 ITj *H c c

rH •H 0

CD 0) 03 r-H O'

in

u 22 o id 3 3 O •H X

4J 4->

V Cm 0-

m id cn

U

X

u in •rH 1—1

CD 0) >H II II id 0, o & u a e U u u u u E u u u u -—- G <u o o o o TJ CL) o 0 o o II Eh X 0 Eh O O O O Ln Eh O O O O — —

2 r—1 i—l

rH rH SC i—1 i—1

rH rH .—

CM CM E CD o (N CO E CD o CM CO o CO CO vD 0 r—1

rH *—1

CD 0 rH rH rH

—

< <C

m

Q

m

O CO

O

U < 06 < 06 * +

T3c

idI g o o

4-4 4-4

22
(

°F)

1130

1310

1490

1670

1850

2030

2210

2390

(psi)

(*?£W) ggbuajgs leanxaij goH

23

Figure

1.

Hot

flexural

strength

of

a

low-alumina

(56%)

refractory

concrete

both

before

and

after

hydrothermal

exposure.
1130

1310

1490

1670

1850

2030

2210

2390

(psi)

(eaw) q^6uaaq.s iPjnxau qon

24

Figure

2.

Hot

flexural

strength

of

a

low-alumina

(50%)

refractory

concrete

both

before

and

after

hydrothermal

exposure.
o m o in O

CN r—I i—

I

U)s

T3

<1) <D0«

C/l 3

o

•H

4-> U

fO cu

(aATsejrqv go 6x/6) ag^n uoTSOjg

25

Figure

3.

Erosion

rate

of

low-alumina

refractory

concretes

both

before

and

after

hydrothermal

treatment.

3. Chemical Degradation of Ceramics

a. Reactions and Transformations (F. A. Mauer and C. R. Robbins, 565)

Progress : Three series of experiments were carried out using an unfired

bar of high alumina neat cement (specimen #5) in a steam atmosphere.

The specimen consisted initially of CA and a-A (major phases) with small

amounts of CAHiq, ^AHg, C 3AH6' an<3 AH 3. Study of this cement provides

information on the chemical response of the bonding matrix of a high

purity castable refractory to the steam in a gasification reactor environment. Phase assemblages were identified by visual inspection with

the aid of standard reference patterns previously prepared, and by

computer assisted analysis. A slight loss of pressure with time was detected early in the experimental sequence. Work was continued,

however, because useful new information was being obtained even though

the experimental conditions were somewhat different from those intended.

In the first series of experiments the sample was heated over a temperature range of 25-350 °C at pressures from ambient to 522 psig* for a total of 8 days. Results are summarized in Table 1. Hydration of CA

was slight after 23 hrs. at 52 °C, but proceeded rapidly during the next

1.5 hours at 92 °C. After 2 additional hours at 93 °C, C 3 AH0 was readily

identifiable and the amount of CA was greatly diminished. X-ray evidence

indicates that CA hydrates much more readily than the aluminas present.

After 3 hrs. at 150 °C, 60 psig all compounds in the assemblage C 3 AH5 , a-A, and AH were well crystallized. The amount of AH continued to

increase through experiment 15 at 300 °C and 522 psig but, insufficient

H2 O was present to hydrate all the a-A. At 241 °C and 308 psig, the

C 3 AH0 phase was decreasing and a small amount of C 4A 3 H 3 may have been

present. At 300 °C and 480 psig, C 4 A3 H 3 , a-A and AH were the major

phases. With an increase in temperature to 350 °C and a decrease in

pressure to 350 psig, there was a marked decrease of bonding phase AH

over a period of 5 hours.

A table of x-ray data is not given for the second group of experiments.

The starting phase assemblage was C 4 A 3 H 3 , a-A, and AH. The bonding

phase C 4 A 3 H 3 was observed to be dissociating after 14 hours at 42 °C

with the accompanying formation of bonding phase C 3 AH0

. After 3 hours

at 93 °C , C 3 AH0 was the major phase and C4 A 3 H 3 was present in only trace

amounts. After 3 hours at 252 °C and 475 psig C 4A 3 H 3 had reformed

from dissociating C 3 AH0 , which is unstable in this temperature-pressure

region. Further dissociation and reformation of these hydrated calcium

aluminates was observed as temperature and pressure were varied.

k

In SI units, 1 MPa = 145 psia.

27
Experimental results for the third series of experiments are summarized

in Table 2. At the start of the experiment the bar was composed of

C4 A 3 H 3 , a-A, and AH. At 103 °C after 20 hours of exposure the C 4A 3 H 3 had completely dissociated to form C 3 AH0

. In experiment 40 the test bar was composed of C 3 AH0 , a-A, and AH, all well crystallized. Hydration of

a-A was monitored by in situ x-ray diffraction as the temperature and

pressure were gradually increased to 247 °C and 442 psig in experiment

number 47. The amount of AH increased noticeably at 207 °C, 240 psig

(experiment 45). At 235 °C and 410 psig (experiment 46) bonding phase

C 3 AH0 was being replaced by bonding phase C 4 A3 H 3 , and bonding phase AH

continued to form. At 247 °C and 442 psig (experiment 47) the specimen

was essentially fully hydrated and the equilibrium phase assemblage was

C4A3 H 3 , AH and a small amount of a-A. This assemblage was obtained to

354 °C, 715 psig (experiment 53)

,

at which point AH was observed to have

started to dissociate. Dissociation of AH continued as the temperature

was slowly increased. At 448 °C, 520 psig (experiment 57) the rate of

dissociation increased. Even at 550 °C, 542 psig (experiment 61) AH was present in the test bar as a minor phase. This temperature is roughly

200 °C above the "equilibrium" dissociation temperature commonly reported

in the literature.

Hydration of the a-A of neat cement to form AH (boehmite) , followed by

dissociation of the latter as temperature is increased is illustrated by

this series of experiments. Because of the dramatic loss of strength

associated with the dissociation of the strong bonding phase, AH+,

the ability of the in situ x-ray method to observe the reaction in real

time is of special interest. A series of four patterns showing the

dissociation of AH are reproduced in Figure 1. The over-all change is

shown in a difference plot (Figure 2) in which the negative peaks corres- pond to the AH phase consumed in the reaction, while the positive peaks

show the increase in a-A, a reaction product.

Physical properties such as strength and erosion rate, which are affected

by the presence of AH, can be expected to follow trends somewhat parallel

to the formation or dissociation of this phase. For example, the flexural strength of the test bar used in this experiment (and, by analogy,

a high purity refractory) might be expected to approach a maximum value

at or near 354 °C and 715 psig under the conditions of this test. At

higher temperatures, the strength should gradually decline as AH dissociates with slowly rising temperatures as shown in Figure 3. In this

figure the intensity of an AH peak at channel 610 (solid line) and an a-A peak at channel 492 (dashed line) have been plotted for experiments

47 through 62 to show the trend in the relative amounts of these two

phases.

-j* E. R. Fuller, Jr. , C. R. Robbins, and A. Loeb, Quarterly Progress

Report FE 1749-6, December 1975.

28
Rapid heating of a test bar (or refractory) would result in the superheating of AH followed by abrupt dissociation of the compound over a short temperature interval.

Plans : Twenty-five patterns obtained in a test of NBS refractory A-56

with mullite aggregate are now being analyzed. Test bars of a composition approximating that of the bonding matrix of A-56 have been prepared,

and will be tested in steam. Work on both of these materials will be

continued during the next quarter, along with additional work on specimens of neat cement.

29
TABLE 1

IN

SITU

X-RAY

ANALYSIS

OF

UNFIRED

HIGH

ALUMINA

NEAT

CEMENT

SPECIMEN

*5

IN

STEAM P rH

rH

03 O' P

o> c inp

C P •H >1 •H 0 E P O' P in c c O c 0 u 03 p •H 0 •H P 0 <D 0 E p rH in W c u c rH 05

<v •H

U •h cr* CO

X a) 0) QJ 0 e a» E c X < P O

03 T3 •H < O 03 U CO to 0) P P P co X < X 03 TJ P x < U < <1> in in in < TJ P a> a> <D to to to

Vi «* CD - O in in in

XX

O in js in in id 03 03 03 < «C <

V) CD qj in Q) <1> TJ .cx

X CO CO CO

n

X in -h in in

a

a cu 0 U o

sz < 03

C 03 03 <

co £ -H

X

X

U P P P U a e Q. a, 0 0 O

XX

X

X

u •ro r~i •0

X < < < < 0 P 'O p p O' 03 03 0J <

CO 0 0 O

C E E E

03

X •r-» >. •0 •rn *H < < < < £ < 03 rH 03 OJ £ < O' < < <C 1 1 1 eg E P B E C 1 c 1 l 1 0 O O C5 U SZ O C5 -H C5 O P P P P P P O < < O' < < uh E

•*. *. - «• 1 1 *H 1 1 - P CO CO CO CO O 0 0 rH O O tO to O to to 0 0 O O O O to X X X X

in

X

X P X

X P P P P P P X CO CO CO CO

•»

X «» *. - < < < < P P p P P P < < < < < < < < < < < CO CO X CO •H •H •H H H •rH CO -3- J- J- J- U u u u O CJ U U < U U T3 T3 *0 TJ 'O U O u U U s u m s:

E-* ~

atD O' m -h

CO in a 3 &

30

Insufficient H2O

to

Hydrate

remaining
39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

59

61

TABLE 2 IN SITU X-RAY ANALYSIS OF UNFIRED HIGH ALUMINA NEAT CEMENT SPECIMEN # 5

TEMPERATURE PRESSURE TIME X-RAY ANALYSIS AND REMARKS

(°C) (psig)

(hr)

78 1 C 4A 3 H 3 , a-A, AH major phases

103 20 C 3 AH6 , a-A, AH major phases

115 4 ditto

117 17 ditto

164 92 3 ditto

208 240 5 ditto

207 240 15 C 3AH6 , a-A, AH major phases: AH increasing

235 410 6 C 4A 3 H 3 , C 3 AH6 , a-A, AH major phases:

C 3AH6 decreasing, C 4A 3 H 3 , AH increasing

247 442 6 C 4A 3 H 3 , AH major phases, a-A minor phase

274 675 18 ditto

300 880 3.5 ditto

323 950 3 ditto

325 718 16 ditto

340 730 1 ditto

354 715 5 C4A 3 H 3 , AH, major phases, a-A minor phases

a-A increasing, AH decreasing

375 540 21 C 4A3 H 3 , a-A, AH major phases:

a-A increasing, AH decreasing

400 520 4 ditto

428 522 0.5 ditto

448 520 1.3 ditto

525 535 1.3 ditto

550 532 1 C 4 A 3 H 3 , a-A major phases, AH minor phase

650 570 1 C 4A 3 H 3 , a-A

1 MPa =145 psia

31
CHANNEL

Figure 1. A series of four EDXD patterns showing the dissociation

of AH (boehmite) and the formation of additional a-A in

the temperature range 247° to 650°C.

32
UJzz

CTXo

03 X 0) 0

-P

p -P 3

Cn -P 35 3P

03

G

•Hj

-c e w a)

03

a

a,

m

03P

a)>

*H

4-1 •PWo < a •a

<13 -G <P

P>

O

-P P 03

C 0 i—1 0

r- 03 o •P *p A -C 4-3

4-3 in 3 c P p c a - -P

03

p 03

G

C

4-)

a 0 03

4-1

G •P

O

a

O 03 4-1

G

CP P > U 0

-P •r-j 3 O 1 *P P 03

in 03 P 03 Cm 0 O'1 -C

<D P4 03 03 -P e C rG G 0 -P G P o 0) •H

03 -C

C

4-> 03 •H 0)

4-3 in in a 03 33 3

O,

X • 03 0)

—

a

U £j P 0 O

4-3 c O in

G • 0 •p in c •P 4-3 1—1

lO o 0 a 03 o 03 3

cn

O .G 33

03

G P 03 -P 0 o 03 in P G -G o 3 a

0)O •G 0 P 3* a X

G

03 rp CN in 0

44 rp •H

44 03 0) in 4-1 •H P O'* x O

33 0)G 03 3 3 > 03 -G 03 03 < 0 P -P a P

<N

03P3

Cn -P

CP

33
mvz

0831

800

1

803

S1ND00

13N

fiH & ft

Figure 3. A plot of the intensities of an AH peak at channel 610 (solid

line) and an a-A peak at channel 492 (dashed line) for experiments 47 through 62. The trends in the relative amounts of

these two phases are shown.

34
b. Slag Characterization (W.S. Brower, J.L. Waring, C.A. Harding, and

D.H. Blackburn, 565)

Progress: Previously it was reported that preliminary data appeared

to indicate that the viscosity of a silicate melt increased with

increasing steam pressure. Since no appreciable compositional

deviations had apparently taken place in the slag, subsequent attempts

were made to obtain more reliable data.

In the design used to gather the data which was reported previously,

the temperature of the melt in the rotating crucible could not be

measured directly and therefore was related to the temperature of

the platinum heater.

An attempt was made to rectify this deficiency and thereby gain the

precision of temperature measurement which is necessary to reproduce

the data. A rotating thermocouple (Figure 1) was inserted through

the rotating shaft and was allowed to touch the bottom of the melt

crucible. This modification necessitated a complete redesign and

change of the melt crucible and the entire driving mechanism.

To accurately measure viscosity, the vertical temperature gradients

which exist in the melt must be established. This data is of particular

importance in a pressure system where the ravages of steam cooling

drastically effect the surface temperature of the melt.

In the first experiment, a vertical profile analysis, a thermocouple

shielded with platinum was inserted into the melt at various depths.

The temperatures at the different depths were recorded at a constant

55 psi and compared simultaneously with those of the platinum resistance

heater and the bottom outside of the melt crucible. The results of

this experiment are given in Figure 2. The data are plotted T°C vs

A time in minutes - of the platinum heater (curve 1) , of the vertical

thermocouple probe (curve 2) , of the bottom thermocouple (curve 3)

.

In addition the depth of the vertical probe is shown as a superimposed

upper ordinate. The values shown on curves 1 and 3 remain relatively

constant. The values shown on curve 2 are at a maximum in temperature

at about 1" depth (vertical midpoint of melt) with cooling at the top

and bottom surfaces. From this profile it can be concluded that the

bob must be placed at the approximate vertical center of the crucible

and that a thermocouple placed at any other place in the melt will

not reflect a representative melt temperature.

In the second experiment the vertical thermocouple probe was placed

at 1" in the melt and the melt temperature was related to the platinum

heater thermocouple and to the bottom thermocouple. The results are given in Table 1.

35
From Table 1 several things are immediately apparent. The difference

between the temperature at the center of the melt and the bottom of

the crucible (last column) is significantly large and relatively

constant over the range of temperatures. Secondly, when the heater

is operating at 1445°C and 60 psi, only 1201°C was achieved in the

melt.

Using the information obtained in experiments one and two the viscosity

(experiment 3) of the same slag as used previously was redetermined

and the results are given in Table 2. The summation of these data

(curve E) and how they are related to the previous data are shown in

Figure 3. The new viscosity data, curve E, might have been expected

to approximate closely curve B, but does not. When the temperature

of the platinum heaters and of the bottom thermocouple in experiment 2 (Table 1) are compared with the values found in experiment 2 (Table 2) a great variation is found to exist between bottom thermocouple

temperatures for the same platinum heater temperature. This apparent

non-reproducibility of temperatures from experiment to experiment

casts doubt on the validity of the viscosity measurement.

To reconcile this situation, an attempt was made to determine if

something had changed radically in the experimental set up. Experiment

4, a duplication of experiment 2, was completed and the results are given in Table 3. The results of experiment 4 essentially duplicate

those of experiment 2. The significant difference between experiments

3 and 2,4 is that in the calibration experiments (2,4) the thermocouple

does not stir the melt with the vigor that the platinum bob does

during viscosity measurements. The stirring action should cause a more uniform heat transfer to the bottom of the melt crucible and it

follows that the temperatures observed while using the bob should

more closely approximate the true temperature of the melt. However,

these temperatures are not the true melt temperatures because of the

steam cooling of the bottom surface.

Plans : Experiment 4 will be duplicated with a probe thermocouple with

stirring fins to determine the effects of stirring on the heat transfer

of the bottom thermocouple. A new suspension will be designed employing

a thermocouple which is part of the bob for direct temperature measurement of the slag while measuring viscosity.

36
Table 1 Calibration of Me^-t at 61 psi Steam.

\ Time

Platinum Heater

Thermocouple

Thermocouple

Immersed

in Melt

Thermocouple

Touching Bottom

of Melt Crucible Difference*

min °C °C °C °C

80 1302 1046 909 137

120 1377 1121 988 133

180 1434 1190 1068 122

240 1445 1201 1080 121

*Thermocouple temperature immersed in melt minus thermocouple

touching bottom of melt crucible.

Table 2. Redetermination of Viscosity of Synthetic Slag* at 57 psi.

Platinum Heater Thermocouple Touching

Thermocouple Bottom of Melt log n

°C

1024 2.09

1059 1.89

1115 1.74

wt %

42

3

25

5

5

15

5

Table 3. Recalibration of Melt at 63 psi Steam.

Thermocouple Thermocouple

Platinum Heater Immersed Touching Bottom

A Time Thermocouple in Melt of Melt Crucible Difference

min °C °C °C °C

80 1301 1042 921 121

120 1377 1113 990 123

180 1436 1167 1055 112

37

1305

1377

1434

Composition

SiO

A1 63

MgO

N*,0

k,6
Figure 1. Rotating thermocouple assembly.

38
1400

+

o.25

I

I

-

0.50

3, *ajn)vu9du»i

IQ

Figure

2.

Vertical

temperature

profile

of

melt

crucible.
<c

o

CM

oo

ooo

04 CM

(saSjLOd) I SODS LA 60 [ A r\

Figure

3.

Log

viscosity

vs

temperature

for

slag.
c Vaporization and Chemical Transport (j. Hastie and D. Bonnell, 561)

Progress: In the previous Quarterly report we presented experimental data,

in the form of a mass spectrum, for an alkali silicate vaporization

experiment. A thermodynamic calculation for the vaporization of this

system has now been made using the JANAF (1971) Thermochemical Tables

data base. The results indicated the presence of Na, NaOH and NaCl

in the vapor phase. This contrasts with the experimental data where only

Na was definitely identified. Similar thermodynamic calculations indicate

that Na 2 S 04 should vaporize as NaOH in the presence of H 2 O vapor. Using

the capillary probe sampler we monitored this possible effect at

temperatures of 1000-1200°C and an H 2 O partial pressure of 28 torr in 1 atm*

of N 2 . No NaOH vapor was seen, with Na and SO 2 being the main vapor

species. To test whether the absence of NaOH vapor species may be due

to NaOH being dissolved at very low activity in the Na 2 S 04 melt, we carried

out a separate series of vapor transport measurements over a NaS04 + 6wt%

NaOH substrate. At 1000°C large amounts of NaOH and Na were found in the

vapor, indicating a high activity for NaOH in this system. Hence the

H 2O + Na 2 S04 reaction seems to be kinetically hindered, and is not the

result of a strong interaction between NaOH and Na 2 S04 in the liquid.

This result also probably explains the nonobservation of NaOH and NaCl

vapor during the alkali silicate vaporization experiment.

A rather startling, but not yet repeated, effect was noted during the

Na2 S 04 + NaOH vaporization experiment. The presence of NaOH seemed to

markedly increase the loss of Na 2 S04 but not as SO 2 , Na or Na*S04 . Perhaps

a new as yet unidentified molecule is formed in the presence of NaOH.

Also during this study the capillary probe plugged as the result of apparent

Pt transport.

In order to verify that the observed lack of activity of H 2 O with Na

bearing liquids is a chemical kinetic phenomenon and not a sampling probe

perturbation of the data the following test was made. We should recall

from our earlier studies that the conical type of sampling probe did not

perturb equilibrium processes. However the capillary probe used for the

most recent experiments had not been tested for its ability to sample

equilibrium systems without perturbation. A critical test of sampling

fidelity is provided by measurements of the vapor phase dimerization process

2NaCl = (NaCl) 2

as was done earlier for the original conical probes. Using the capillary

probe we obtained vapor pressure data for the species NaCl and (NaCl )

2

from which the apparent equilibrium constant for the above reaction was determined. Data were obtained over a temperature interval of 1100-1500K

and an NaCl partial pressure range of 10 3 - 10

1

atm in 0.5 atm N 2 carrier

gas. The results shown in Fig. 1 are in good agreement with the JANAF

Thermochemical Tables data for an equilibrium process. Hence the sampling

probe does not perturb the system and the observed non-equilibrium effects

for H 2 O reactions are inherently chemical kinetic.

r l atm = 101,325 Pa

1 Torr =/ l01,325 \Pa

\ 760 /

41
Plans : In the following Quarter we plan to present a paper on the new

transpiration mass spectrometric technique, and its application to high

temperature - high pressure vapor transport measurement, at the 10th

Materials Research Symposium on Characterization of High Temperature

Vapors (NBS Sept 18-22, 1978). As this will be the first formal

presentation and publication of the technique, our efforts during the

next Quarter will emphasize demonstration of the method using the well

defined calibration systems of NaaSOi* and NaCl. The merits of various

types of sampling nozzles and the applicable range of temperature and

pressure will be investigated during the period.

Following completion of this evaluation and publication activity work

will resume on the slag-type mixtures using the capillary sampling probe

system. The new vacuum system designed for vertical sampling of greater

than atmospheric pressure systems should also be ready for laboratory

installation during this period.

42
I

£00 IH

00I

300 1

300 sa

C < Wld >d>

43

Figure

1:

Plot

of

equilibrium

constant

for

the

vapor

phase

process:

2NaCl -

(NaCl

)2

asa

function

of

temperature

using a

capillary

probe;

heavy

line —

JANAF

Thermochemical

Tables

data;

thin

line —

least

squares

fit

of

data

points.
4. Failure Prevention

a. Failure Information Center (R. C. Dobbyn and W. A. Willard, 562)

ProgressDuring the quarter the Failure Information Center received

32 reports of operational experiences and components and materials

failures in coal conversion pilot plants and process development units.

This number includes several diagnostic failure analyses from Argonne

National Laboratories and Oak Ridge National Laboratories. To date, the

percent contribution of information items received from different coal

conversion processes is shown in Table 1.

These reports have been classified and evaluated for technical com- pleteness and accuracy and discrepancies have been resolved. Detailed

abstracts of this information have been entered into the Center's com- puterized data bank. A recent update of the frequency of failure modes,

which analyzes all information in the system, is shown in Table 2.

The Information Center continued to aid Battelle-Columbus in their

preparation of the DOE Materials and Components Newsletter feature on failure experiences. Weekly updates of all abstracts are furnished to

Battelle together with complete hard copy of certain reports when re- quested. During the quarter, the Center furnished 20 updated summaries

and 42 complete reports.

The Information Center also handled 19 other requests for information

during the quarter. In response to these inquiries, copies of 203

abstracts, hard copy and draft reports were transmitted. In addition, 8

visitors to the Center were briefed on its scope, operation and future

plans

.

During this quarter major emphasis continued to be placed on completing

the final report covering the performance of materials and components at

the Conoco lignite gasification pilot plant - the CO Acceptor Process.

The draft report is now approximately seventy percent complete; delivery

of the report to DOE and Conoco for review is now scheduled for mid - August.

PlansPlans for the next quarter include completion of the final

report covering the CO^ Acceptor Process pilot plant and a similar, but

less detailed, report covering the operating experiences to date at the

IGT Hygas pilot plant.

In addition, liaison with the remaining gasification and liquefaction

pilot plants and process development units - those not yet visited —will

continue

.

The format of failure data entries is being revised to facilitate

information exchange and further, in-depth analysis of common problems.

These analyses will become the subject of future reports issued periodically and supplied to DOE for distribution. Submittal of candidate

topics and report outlines for DOE concurrence is also planned during

the next quarter.

44
TABLE 1

COAL CONVERSION PROCESSES

NO OF ITEMS PERCENT

17 3.86

1 0.22

37 8.40

7 1.59

17 3.86

1 0.22

54 12.27

2 0.45

12 2.72

2 0.45

3 0.68

57 12.95

1 0.22

11 2.50

19 4.31

24 5.45

2 0.45

22 5.00

6 1.36

111 25.22

4 0.90

30 6.81

440 = TOTAL NUMBER OF ITEMS IN FILE

PROCESS

BIGAS

BIOMASS

BMI

CARBONATE

CLEAN COKE

COED

CO2 CPC

CRESAP

EXXON

GFERC

HYGAS

LERC

LIGNITE

MERC

MISC.

PERC

SRC

SRC-W

SYNTHANE

SYNTHOIL

WESTINGHOUSE

45
NUMBER

OF

REPORTED

INCIDENTS

OF

FAILURES

IN

COAL

CONVERSION

PLANTS

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46

FAILURES

FROM

TEMPERATURE

/PRESSURE

EXCURSIONS.
b. Materials Properties Data Center (H. M. Ondik and T. A. Hahn, 565,

and I. J. Feinberg, 562)

Progress : The two computer terminals and the two acoustic couplers

described in previous reports, have been delivered, but the telephone

lines necessary for communication with a central computer have not yet

been installed. Even though the terminals are not connected to a large

computer, there are useful operations which may be performed, providing

experience with the equipment and aiding in the data design. The "intelligent" terminal with cathode-ray tube display is particularly useful.

Because this terminal has a small core storage memory it is possible to use it as a very small computer. As a result, the staff of the center

has had opportunity to gain some familiarity with the detailed capability

of the terminal with respect to its graphics handling capacity.

More equipment for the computer-terminal facility is now on order. A

hard-copy unit, compatible with the "intelligent" terminal, will enable

the operator to obtain a high-quality copy of material from the cathoderay tube. Copies of graphs produced by the terminal and displayed on the tube will be available very simply with this copier.

A decision has been made as to the computer Data Base Management System

(DBMS) to be used. The system of choice has the necessary system flexibility, an appropriate data storage structure including an inverted

file system, an ad hoc query language necessary for ready searching, and

suitably large storage capacity for the projected contents of the data

bank. The DBMS is available from several GSA-approved commercial vendors.

Investigation and comparison of the services provided by these vendors

is in progress. Arrangements have been made for short-term (the remainder of the fiscal year) use of the chosen DBMS through the services of

two different vendors. Benchmark testing will be performed by building

a small portion of the Data Base, storing the data on the computer,

manipulating it, and searching it. These operations will test the

system controls provided by the two vendors, and also compare the costs

incurred during use of the two vendors' systems. The appropriate documents are being prepared for the justifications to obtain the various

approvals required for contracting with a vendor.

Members of the staff have taken a one week course on the chosen DBMS,

learning how data should be structured to make the best use of the

capabilities of the system. Since each DBMS has its own special features, and complicated restrictions, it is necessary to have detailed

instruction in its use. The chosen system, because of its large capability and flexibility, especially requires this special study and

instruction so that it may be used efficiently. Inefficient use can drastically affect the computer expenditures.

47
The design features of the data bank are being planned. The arrangement

of the data must take into account the varied types of information to be

stored and the estimated order and frequency of requests for information.

The optimum structure of the file for ready search capability must

provide for the use of the fastest, therefore least expensive, search

patterns compatible with flexibility, having as many items being searchable as possible for reasonable use. Major search elements will, of

course, include the material names or designations and the properties.

Searches must be possible on various combinations of these elements.

The conditions under which the properties were studied must be retrievable along with the property data and should probably also be a searchable item as well. Many other items which must be appropriately entered

for retrieval with the property data such as brief summaries of the test

procedures, references, etc., must be considered carefully as possible

candidates for keying as search catagories. Since search items are carried in storage as inverted files and therefore, add to computer

storage costs, the question of optimum use of the DBMS and its storage

and query capabilities is an important one to answer carefully.

The first reports summarizing DOE contractors' reports have been submitted to DOE for approval of style, format, and content. These reports

have gone through several revisions and are now considered to be in a form which can form the nucleus of the input to the data bank. The

summaries condense the results of many reports into a concise form.

Further reports now in progress will be completed when DOE approval of

the first two is given.

Plans ; The regular operations of the Center will continue with the

handling and summarizing of the contractors' reports, the design of the

structure of the data base, further study of the DBMS with respect to

making optimum use of it, and also further study of the use of the

computer terminal equipment as it arrives. The investigation of suitable vendors of the DBMS will continue so as to choose one as soon as possible

.

48