PlV

PE—H-49-9

Dist. Category UC-90C

£ Ir l^ooJi

MATERIALS RESEARCH FOR CLEAN UTILIZATION OF COAL

QUARTERLY PROGRESS REPORT

October 1976

Samuel J. Schneider

Project Manager

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

PREPARED FOR THE UNITED STATES

ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION

Under Contract No. 14-32-0001-1749

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

United States Government. Neither the United States nor the United

States ERDA, nor any of their employees, nor any of their contractors,

subcontractor, 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."
Schneider, S. J. , Materials research for clean

utilization of coal. Quarterly progress

report October 1976, Energy Research and

Development Administration FE-380O-9 , 32 pages (Available from the Rational

Technical Information Services, Springfield,

VA 1976).

313

/l/£Si/? 7& //(, y
TABLE OF CONTENTS

PAGE

I. OBJECTIVE AND SCOPE OF WORK 1

II. SUMMARY OF PROGRESS TO DATE 1

III. DETAILED DESCRIPTION OF TECHNICAL PROGRESS 2

1. Metal Corrosion 2

a. Constant Strain-Rate Test 2

b. Pre-Cracked Fracture Test 13

c. Erosive Wear 13

2. Ceramic Deformation, Fracture and Erosion 20

3. Chemical Degradation 24

a. Reactions and Transformations 24

b. Slag Characterization. 25

c. Vaporization and Chemical Transport 25

4. Failure Prevention 26

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 long-time operation of the gasification systems. This

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 of refractories. A system has been initiated to abstract

and compile all significant operating incidents from coal conversion

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 ERDA and

associated contractors will be provided as requested.

II. SUMMARY OF PROGRESS TO DATE

The summary of progress is contained in the individual task progress and

plans - Section III.

1
III. DETAILED DESCRIPTION OF TECHNICAL PROGRESS

1. Metal Corrosion

a. Constant Strain-Rate Test (G.M. Ugiansky and C.E. Johnson, 312.04)

Progress : To further elucidate the relationship between sensitization of 310 stainless steel (SS) and the susceptibility to

intergranular embrittlement at elevated temperatures, tests were

carried out on 310 S stainless steel (a low carbon 310 SS which

is designed to resist sensitization). The 310 S stainless steel

was tested at 1000°F at a strain rate of 1 • 10 ^ s-1 in a vacuum

(726 mm Hg) . The reduced section of the specimen still showed

some cracking, but the elongation and reduction in area were twice

as great as for the 310 SS. Some necking could be detected. This was evidence that the lower carbon content in the alloy lowers the

susceptibility to intergranular embrittlement but does not prevent

it. The use of 310 S stainless steel in place of Type 310 SS also

slows the rate of sensitization but does not prevent it (1). Type

347 stainless steel (similar to 304 SS but stabilized with niobium

and tantalum) was tested at 1000°F at a strain rate of 1 • 10 ° s"l. The resultant fractures were ductile with a large reduction

in area (66%), but the elongation was low (16%). No cracking was apparent in the reduced section of the specimens. The tests of

this alloy showed that intergranular embrittlement can be prevented

by using stabilized alloys. These tests also further illustrate

that reduction in area is probably a better indicator than elongation for measuring susceptibility to stress corrosion cracking

(SCC), especially when comparing different alloys. Fig. 1 shows

the fractures of 347, 310 S, and 310 SS when tested at 1000°F in

a vacuum (726 mm Hg) at a strain rate of 8.4 • 10 ^ s”l.

Type 310 SS was also tested at temperatures of 1500°F and 1900°F.

These temperatures were chosen to look at the effect of sensitization

on intergranular embrittlement as a function of test temperature.

The sensitization temperature range is 800-1650°F. With tests

already completed at 1000°F (in the middle of the sensitization

range), the 1500°F tests would give information near the top of

the range, and the 1900°F tests would give results for testing

well above the sensitization range. These tests were run at a constant strain rate of 1 • 10 ^ s“^ in air because the present test

chambers were not designed for these high temperatures. At 1500°F,

the ultimate tensile strength was only 25 KSI versus 60 KSI when tested at 1000°F. The elongation was 11% which is a lower value than

any obtained for tests on 310 SS at 1000°F. The reduction in area was 14.5%, which is a lower value than any obtained for that parameter for any tests on 310 SS at 1000°F.

The 1900°F test still resulted in a fracture that seemed to be brittle.

The reduction in area was only 21% which compares to 18% for 310 SS

2
when tested at 1000°F. The elongation was 41% which was probably

due to the high ductility of the' non-embrittled portions of the

specimen. The ultimate tensile strength was only 11 KSI when tested

at the slow strain rate of 1 • 10 ^ s“l.

The series of tests that were requested by Dr. T.B. Cox, the project

monitor, to be run on 310, 310 S, 347 SS, and Incoloy 800 in wet

^S at 1000°F over a range of strain rates have been completed

except for one specimen of each alloy at the very slow strain rate

of 1 • 10"7 s"1

.

The resulting parameters measured for 310 stainless steel when

tested in wet H^S at 1000°F are tabulated in Table 1.

Table 1. Properties of 310 stainless

in wet I^sC^and f^O/l^S^)

steel tested

at 1000°F.

Strain Rate, s

^ Gas UTS, KSI Elongation, % Reduction in Area

1.3 • io“* 2 82 33.8 63.2

7.8 • 10

5

1 73 32.9 55.9

5.5 * 10

6

2 76 33.4 62.8

7.2 • 10

6

101

2 68.5 22.5 33.1

3.9 1 70 22.9 25.4

3.6 • 10

6

2 69 23.7 30.2

1.1 10

7 1 68 17.2 18.4

8.4 • 10

-7

2 68 18.7 17.5

wet I^S = l^S saturated with water vapor at room temperature.

2l^O/l^S = H

2 S plus steam.

The plot of percent reduction in area versus strain rate for 310 SS

(Fig. 2) shows that as the strain rate decreases, the reduction in area decreases from 63% to 17%. The difference between the

environments of wet I^O/I^S is that the wet I^S signifies the water

vapor saturated I^S at room temperature, whereas, the I^Q/I^S is a steam and H^S gas mixture. These two corrosive environments do not seem to have any effect on the lowering of the properties of

310 SS since the equivalent reduction in properties can be obtained

when the specimens are tested in helium, argon, or vacuum.* When the

*None of the environments used was O 2 or H2O free as seen by the

oxide films of various thicknesses that was always present after

testing.

3
I

request was made to test these different alloys over a range of

strain rates at 1000°F, the decision to use the wet H 2 S environment

was made.

The 310 S stainless steel (lower in carbon content, 0.25% max.

for 310 compared to 0.08% max. for 310 S) was tested in wet H S

at 1000 °F and was found to behave quite differently than 310 when

tested over the same range of strain rates. The measured properties

are tabulated in Table 2.

Table 2. Properties of 310 S stainless steel

tested in wet at 1000°F

train Rate, s

^ UTS, KSI Elongation, % Reduction in

1.3 • 10 -4 71.5 33.6 63.0

3.7 • 10"5 71.6 34.5 62.6

7.3 • 10'6 69.0 35.9 62.3

8.4 • 10“ 7 63.1 34.8 50.1

The plot of percent reduction in area versus strain rate (Fig. 3)

shows that the reduction in area remains constant at around 63% until

the slow strain rate of approximately 1 * 10 S“1 is reached when the

reduction in area begins to decrease somewhat. A test at the very slow

strain rate of 1 • 10“ 7 s“l should indicate whether the decrease is

significant and if the percent reduction in area decreases to a value

comparable to that obtained with 310 stainless steel. This curve

shows how the low carbon content in 310 S retards the process of

intergranular embrittlement but does not prevent it after a long

period of time at temperature, as is also the case for sensitization (1)

The measured properties of the stabilized 347 stainless steel that

were tested in wet H2

S over a range of strain rates at 1000°F are tabulated in Table 3.

Table 3. Properties of 347 stainless steel

tested in wet H^S at 1000°F

Strain, Rate, s

^ UTS, KSI Elongation, % Reduction in Area, %

1.3 • 10"4 78.8 17.4 62.0

3.7 • 10"5 78.1 15.5 63.1

7.3 • 10“6 71.6 15.1 64.3

8.4 ‘ 10“7 75.6 14.5 55.4

8.4 • 10" 7 75.4 17.1 61.4

4
The curve of percent reduction in area versus strain rate (Fig. 4) shows

that the percent reduction in area remains constant for 347 SS over

the range of strain rates tested.

The results of Incoloy 800 tested in wet H2

S over a range of strain

rates are tabulated in Table 4.

Table 4. Properties of Incoloy 800 tested in

wet H

2S at 1000°F

Strain Rate, s

^ UTS, KSI Elongation, % Reduction in Area, %

1.3 * 10"4 — 32.8 68.8

3.7 * 10-5 — 33.5 65.3

7.3 • 10

"6 — 34.2 55.2

8.4 * 10" 7 — 32.0 49.9

The curve in Fig. 5 shows the decrease of reduction in area from

69% to 50% as the strain rate decreases from lO-1^ to approximately

10"6 S ~1 for the Incoloy 800.

In order to change the testing apparatus to be able to handle the

gas mixtures being used at Battelle Labs, and Argonne National Lab., some design work had to be done. Contacts with Wright and Peterson

of Battelle and Nateson of Argonne were made to discuss their methods

of getting water into their systems. We made the decision to use steam and ordered a small steam generator.

Commercial gas suppliers were contacted to determine the availability

of gas mixtures. Mixtures of CO, CO 2 , and H2 in specific proportions

can be obtained but not with H 2

S or water.

Several problems arose during the quarter. A failure of a printed

circuit board in the data gathering facility delayed the starts of the

310 S, 347, and In 800 tests. A sensing element failure in the

data gathering facility resulted in loss of UTS data for all In 800 tests.

A DC-differential transformer failed on one of the test machines, thus

preventing strain measurements on that specimen during the test run. The Inconel 671 rod was received, but none of the material was suitable for machining the needed 23 inch long specimens. The material was

sent back to the supplier to be straightened.

5
Plans : Types 310, 310 S, 347 stainless steel, and Incoloy 800 will

be tested at the very slow strain rate of 1 • 10 7 s” 1 in wet H2 S at

1000°F. Inconel 671 will be tested over the range of strain rates

at 1000°F in wet H2 S after the alloy rods have been straightened.

During the time before the gas mixing apparatus is completed and

installed, the possible mechanisms of intergranular embrittlement

of 310 SS will be investigated.

The mechanism of failure of the 310 SS will be investigated by

testing this steel in vacuum or a reducing atmosphere with more

precautions taken to remove all oxygen and water. These tests

will be run to determine whether or not the susceptibility of

310 SS is actually environment insensitive. Since an oxide film

was always present and the cracks seem to initiate at the surface,

it is believed that the embrittlement may be due to oxidation of

the chromium depleted grain boundary region or possibly due to

hydrogen attack.

6
References

1. Heat Treating of Stainless Steels, Source Book on Stainless Steels — ASM Engineering Bookshelf (1976), p. 163.

7
Fig. 1. Fractures of 347, 310S, and 310 stainless steels from left to

right, respectively. Tests conducted in vacuum (726 mm Hg) at

1000°F at a strain rate of 8.4 • 10"? s"-*-. 2.5x

8
9

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Tests

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b. Pre-Cracked Fracture Test (J. H. Smith, 312.01)

Work is not scheduled to begin until 1977.

c. Erosive Wear (A. W. Ruff, L. K. Ives, J. Young, 312.03)

Progress : Tests were conducted in the flame-erosion apparatus to determine the angular dependence of erosion of 310 stainless steel

at 25°C and 975°C. As in previous work, SiC abrasive particles of 100 mesh size were employed as the eroding media. Particles were

supplied at a rate to yield a flux of approximately 0.04 %/crn^s. In some tests, a flux as high as 0.08 g/cm2s was used, however, this did not produce an appreciable change in relative erosion rate. Tests at 25°C were conducted in air while those at 975°C were

carried out in a combustion gas atmosphere produced by burning

an air, oxygen and propane mixture. An excess amount of oxygen

above that needed for complete combustion of the propane was supplied to yield a relatively strongly oxidizing atmosphere. An analysis of the gas composition under the specific conditions of these tests was not obtained. However, based on previous results under similar conditions, a composition of about 65% N 2 , 10%02, 10%C02 and 15% H2O would be expected. The particle velocity at both 25°C and 975°C was maintained at approximately 34 m/s.

Figure 1 shows a sample with the protective metal shield that is used to prevent erosion of the otherwise exposed top edge. The sample is clamped in a ceramic holder specifically designed for elevated temperature tests but also used at 25°C. A cylindrical

heat shield (not shown) was employed to reduce the temperature gradient

along the exposed specimen face to about 20°C at 975°C. It was indicated in an earlier monthly report, as a result of some pre- liminary data, that this heat shield might disturb the flow of particles and thereby affect the erosion rate. A number of tests have now been conducted at 25°C with and without the heat shield in place. The results indicate that the erosion rate is not affected by

the heat shield. Results of angular dependence tests at 25°C and 975°C are plotted

in Fig. 2. Each point in Fig. 2 represents the accumulated average

of a number of tests of approximately one hour duration on a single

sample. At 25°C, a rather broad maximum occurs at 15-30° followed by

a minimum at 90° (particle stream normal to the surface). This behavior is typical of ductile materials in general. A substantial

departure from this behavior is indicated at 975°C. The maximum

now occurs at 90° while only an inflection is apparent at 20°-30°. This angular dependence might be attributed to the fact that a relatively

thick oxide layer exists on the specimen surface at 975°C under oxidizing conditions. Studies described in the last quarterly report

(April - June 1976) indicated that the impacting particles probably

did not penetrate this layer at a velocity of 34 m/s. Thus, the eroding

13
material should be treated as an oxide rather than a metal. At

sufficiently low temperatures, such oxide materials fail by a brittle

fracture mechanism and exhibit a characteristically different angular

dependence then ductile metals. Namely, a maximum in erosion rate

occurs at 90° with a decreasing rate at lower angles. The shape of the curve in Fig. 2 obtained at 975°C suggests the superposition of ductile

and brittle characteristics. However, it is difficult to rationalize

a brittle oxide behavior at 975°C. Indeed, the topography of impact

craters at 90° (April - July 1976 quarterly report) suggests a ductile

mode of formation. Furthermore, the work of Wiederhorn e_t al. (See

previous quarterly reports) on refractory materials has shown that,

while these materials exhibit brittle erosion behavior at 25°C, their

angular erosion dependence is that of a ductile material at 1000°C.

The nature of the corroded-eroded sample surfaces and the mechanisms

by which erosion occurs is undoubtedly quite complex under the con- ditions of these tests. There is some indication that the erosion

rate gradually decreased with exposure time at 975°C. Erosion loss

is plotted against test number for different angles at 25°C in

Fig. 3 and 975°C in Fig. 4. For a given angle, each test (approximately 1 hr.) represents exposure of the sample surface to the same quantity of abrasive. At 25°C, Fig. 3 suggests that the erosion rate was nearly constant with test number; possibly, a slight increase

is indicated. In Fig. 4, continued exposure at 975°C appears to

result in a decrease in erosion rate at all angles except 30°. It is

thought that part of the protection shield was worn away in the latter

case. At other angles, the decrease may be due to a gradual change

in the nature of the exposed surface due to corrosion related effects.

That is, a steady state or balanced condition between oxidation and

erosion effects may not have been attained. It should be noted in

these tests that both the particle flux and gas flow, in a direction

normal to the specimen surface, decrease with decreasing angle of

attack. Thus at 15°, the particle flux in a direction normal to the

specimen surface is approximately one-quarter of that at 90°. Recognizing that the process under consideration is one of combined

erosion and corrosion, the direct comparison of results plotted in

Fig. 2 may not be valid. Additional tests at different particle

velocities and fluxes should lead to clarification of this question.

Results of previous tests have shown that the abrasive flow rate in

the Roberts Jet Abrader was not critical in determining the relative

erosion rate (specimen wt. loss/wt. abrasive) of a particular specimen

as long as the flow rate was known and could be maintained. A series

of erosion tests were recently made at nozzle pressure drops of 1/4,

1/2 and 1 psig (which are proportional to the abrasive flow rate)

to further determine the flow rate sensitivity. The data

14
shown below were obtained using different pressure reducing valves

(PRV) on the gas supply tank. Specimens of 304 stainless steel and

50ym A^O^ abrasive were used with the usual eroding conditions

(40 psig propellent gas, nozzle at 45°, 1 cm distance, for 2 min.)

and 5 runs in each condition.

PRV Nozzle Pressure Av. Wt. Loss Deviation

No. Drop (psig) (mg) (mg)

1 1/4 2.2 1.2

1 1/2 3.9 0.3

1 3/4 3.5 0.6

2 1/4 2.6 0.2

2 1/2 1.9 0.2

2 1 3.8 0.4

2 1/4 1.4 0.7

2 1/2 1.9 0.2

Investigation into the cause of the larger deviations in erosion

values revealed that PRV//1 was not returning to the same pressure

each time the eroder gas line valve was activated. This resulted

in a changed nozzle pressure and an erroneous signal to the

electronic flow controller on the system. This caused a greater

change in abrasive flow than would otherwise occur with a slight

change in propellent gas pressure. To correct this source of flow

variation a second pressure transducer has been connected to the

gas line ahead of the abrasive chamber. The circuit of the abrasive

flow controller has been modified to integrate the signal from

this second transducer, compensating for main line pressure changes

and maintaining the abrasive flow more constant.

Specimens installed in the Morgantown Energy Research Center (MERC)

experimental gasifier system in March 1976 (see January - March 1976

quarterly report) were retrieved on September 17, 1976. A preliminary examination of the specimens revealed that a significant

erosion loss had occurred in at least one case. Additional effects

resulting from the deposit of soot, tar and from corrosion were also

observed. Changes that occurred in the specimens are currently being

analyzed in detail. The data will be reported and an evaluation

of the results given in a future report.

Plans : This task has been terminated as of the current reporting

period, however, a report on the above activities will be provided

when the data is available.

15
Fig. 1. 310 stainless steel erosion test specimen with protective

shield in place.

16
Angle of^ Attack

Fig. 2. Angular dependence results on erosion of 310 stainless steel

at 25°C and 975°C.
Fig. 3. Trend of erosion rate with test number at 25°C.

18
Erosion

(mg/g)

310 Stainless Steel

Fig. 4. Trend of erosion rate with test number at 975°C.

II 19
2. Ceramic Deformation, Fracture, and Erosion (E. R. Fuller, S. M.

Wiederhorn, J. M.

Bukowski, C. R. Robbins,

and D. E. Roberts, 313.05)

Progress

:

The majority of the effort in the past quarter has been in

the design and construction of the three pressure vessel systems,

described in the last quarterly progress report. Additional experiments, however, have been performed which examine: the mechanical

behavior of a calcined kaolin, calcium aluminate castable after exposure

to environments of C0 2 and steam; the erosion of a phosphate bonded

tabular alumina castable; the microstructural morphology of various

hydrated calcium aluminate phases; and the dehydration behavior of the

calcium aluminate phase, 4 CaO. 3Al 2 O 3

. 3 H2 O.

Three pressure vessel systems are being developed: to extend the

temperature-pressure regime of our previous studies; to allow the

introduction of additional environmental components of coal gasification

systems; and to permit in situ mechanical property testing. Two of

these systems will be used for exposure testing with subsequent mechanical property characterization of exposed specimens and the other

system will be used for mechanical property testing under coal gasification conditions. The basic design has been completed for the system in

which in situ mechanical property testing can be conducted. All major

components have been ordered and construction of the outer pressure

shell is nearly completed. Welds in this vessel are presently being

radiographically inspected, after which the vessel will be hydrostatically

tested. A commercial pressure vessel unit for the exposure testing has

arrived and been installed. This unit with its two separate pressure

vessel systems will extend the temperature range of the exposure studies

to 960^;C (1760%F) and will allow accurate measurement of gaseous pressure.

"Check out" of this unit is still in progress. A steam injection system

is being installed on the other system for exposure testing. If operation

proves to be satisfactory, a similar steam injection system will be used

on the apparatus for in situ mechanical property testing.

A laboratory refractory composition has been prepared from calcined

kaolin aggregate and calcium-aluminate cement to produce a castable

refractory of approximately 56% alumina, 37% silica, and 4.5% lime.

Specimens, prepared from this mixture and fired according to standard

practice, have been exposed to environments of C0 2 and CC> 2 /steam at

610° C (1130°,F) and 1,000 psig total pressure. The results of these

experiments are tabulated in Table 2.1. X-ray diffraction analysis

shows an enhanced crystallization of anorthite (CaO. AI 2 O 3

. 2Si0 2 ) after

exposure to the C02 /steam environment. An example of the cement phase

morphology, developed by exposure to this environment, is shown in Fig.

2.1. The strengthened structure appears to be related to the interwoven

platelet structure of the anorthite crystallites.

20
Table 2.1 Properties of a calcined kaolin, calcium-aluminate castable after

exposure to environments' of CO2 and steam at 610°C (1130°F)

and 1,000 psig total pressure.

Exposure Flexural Mineral

Environment time strength phases

As fired

,

1,300 + 350 psi cristobalite , mullite,

no exposure a-alumina, Ca0 . 2Al 2 03 , Ca0 .Al 2 03 , anorthite.

CO 9 65 hrs 1,200 + 220 psi cristobalite, mullite.

a-alumina, Ca0 . 2Al2 03

Ca0 .Al 2 03 , anorthite.

50% C02 20 hrs 2,170 + 330 psi cristobalite, mullite

and a-alumina, anorthite,

50% H2 0 165 hrs 2,180 + 440 psi CaC03 (tr), tridymite(tr)

Fig. 2.1. Microstructure of the cementing phase of a calcined kaolin,

calcium-aluminate castable after exposure to an environment

of 500 psig C02 and 500 psig H 2 0 at 610°C (1130°F)

21
Erosion data on a phosphate bonded refractory have been collected at room temperature and at 1000°C. The behavior of this refractory at

both temperatures is very similar to that observed for the high purity

aluminum oxide refractory. Erosion occurs primarily by wear of the

cement phase of the refractory so that surface channels develop as the wear process proceeds. As in the case of the high purity alumina

refractory, the wear rate can be expressed as a power function of the

particle velocity, the wear rate increasing as (particle velocity) 2 * 3

. The exponent of approximately 2.3 was slightly less than an exponent

of 2.8 determined for the high purity aluminum oxide castable. At

1000 °C, the erosion rate was about a factor of three less than that

measured at 25 °C, agreeing with earlier data on the high alumina

castable. A comparison of the two types of refractories indicates a somewhat lower rate of erosion for the phosphate bonded refractory,

the phosphate bonded refractory being approximately three times as resistant to erosion. This conclusion, however, must be tempered by

the fact that erosion studies on the high alumina refractory were con- ducted on compositions that had been made with relatively large amounts

of water. Since the erosion resistance of the refractory depends

on the amount of water used in its formation, it may be possible to

increase the erosion resistance of the high alumina refractory by

decreasing the amount of water used inthe original mix for this refractory.

The microstructural morphology of various hydrated calcium-aluminate

phases have been examined by Professor C. H. Kim, a visiting scientist

at NBS , using scanning electron microscopy. His observations shows

that when a high alumina, calcium-aluminate castable refractory has been

treated hydrothermally to form the hydrate 4CaO.3Al2O3.6H2O, the binding

matrix microstructure is loosely connected (see Fig. 2 . 2 ) and consequently is probably a major contributing factor in the loss of structural

integrity observed in this refractory. In contrast, before this hydrate

is formed the integrity of the cementing microstructure is maintained by

an interwoven platelet structure of either 3CaO.Al2O3.6H2O or boehmite

(A 10 . 0H) (See Fig. 2 . 3 ) .

Since coal gasification systems operate at temperatures higher than those

used in our previous hydrothermal studies, the integrity of refractory

liners might not depend as much on the formation of 4CaO.3Al2O3.3H2O as on the dissociation of this compound. Although a number of laboratories

have reported the dehydration products as 12Ca0.7Al203 and CaO.Al203 - both in air and under hydrothermal conditions - little attention has

been given to. the compound 4Ca0.3Al203, a cubic compound first observed

in 1943 and later confirmed by single crystal structure analysis. In

anticipation of exposure studies to 960 °C ( 1760 °F) , a preliminary

examination of the dehydration of 4CaO.3Al2O3.3H2O in air was initiated.

The formation of 4Ca0.3Al203 has been observed both in calcium-aluminate

cement powders and in bar specimens of a high alumina, calcium-aluminate

castable after heat treatment at 650 °C in air. Subsequent attempts to

rehydrate this cubic compound under ambient conditions in 100% relative

humidity resulted in the formation of predominantly CaCOj, and gibbsite

[A1 . ()H)

3

]

.

22
Fig. 2.3. Microstructure of a high-alumina, calcium-aluminate castable

after exposure to steam at 210°C and 276 psi pressure. The

after-exposure flexural strength is 2,230 + 50 psi.

Fig. 2.2. Microstructure of a high-alumina, calcium-aluminate castable

after exposure to steam at 375°C and approximately 3,200 psi

pressure. The after-exposure flexural strength is 430 + 90

psi.

23
Plans: Construction of the outer pressure shell for the in situ

mechanical properties testing apparatus will be completed and this

vessel will be proof-tested and installed. Design of the internal

components of this apparatus will be completed and their construction

begun. The hydrothermal research unit will be "checked-out" on both

high and low alumina calcium-aluminate castables in a steam environment,

thus extending our previous hydrothermal results to 910°C (1670°F)

.

Exposure test in C0 2 and steam environment will then be continued.

Erosion measurements will be conducted on the phosphate bonded refractory

to complete the characterization of its wear behavior as a function of

temperature. Work will then begin on a calcined kaolin refractory.

3. Chemical Degradation

a. Reactions and Transformations (F. Mauer and C. R. Robbins, 313.06)

Progress : Design of the pressure vessel for x-ray diffraction measurements has been completed and submitted to the NBS Instrument Shops

Division. Material for construction of the pressure vessel has been

ordered and construction will begin shortly. The internal heater and

specimen mount are to be constructed in the laboratory. A mock-up of

the heater has been built and tested. A power input of 150 watts is

required to reach a temperature 700 °C above ambient. With the walls of

the vessel operating at 300 °C (to prevent condensation) this same power

input is expected to heat the specimen to 1000 °C. The boron carbide

disks for the x-ray windows have been received. They will have to be

ground and polished in the instrument shop to provide a finished surface

for the gaskets.

Samples of a-quartz, cristobalite , C 3 A, CA, CA2 , AH(Boehmite) , a-Al 2 0 3 , CAg

,

C 12A7 , C 3AH 6 , and CAS 2 have been obtained for use in preparing standard xray patterns so that these phases can be recognized. Patterns have been

prepared with a conventional x-ray diffractometer using copper radiation.

Patterns for the first six listed above have also been prepared by the

energy dispersive powder diffraction method that will be used for in

s itu studies of samples exposed to simulated coal gasification environments. Data from the conventional x-ray patterns are now being transformed so that the corresponding features of the energy dispersive x-ray

diffraction patterns (EDXD) can be identified and labled. The labled

EDXD patterns will serve as working standards.

Plans : The pressure vessel and ancillary equipment for introducing

atmospheres and measuring temperature and pressure will be assembled and

checked out during the next quarter. In situ x-ray diffraction measurements are expected to begin by January 1, 1977, according to our original

schedule

.

*The following abbreviations are used:

C = CaO

A = A1 2 0 3 S = Si0 2 H = H2 0

24
b. Slag Characterization (W.S. Brower, J.L. Waring, 313.03 and

D.H. Blackburn, 313.02)

Progress : Analyses of several Montana Rosebud coal ash samples have

been obtained from various sources. The initial synthetic slag

composition chosen was based on the high calcium content analyses,

which are representative of the initial Bigas feel stock. The normalized

composition is as follows:

Si0

2 42.10 wt%

A1

20

3

19.50

Fe

20

3

7.11

CaO 24.48

Na

20 0.21

k

2o 0.10

MgO 5 . 50

Ti0

2 0.90

This composition has been prepared for the initial ambient pressure

viscosity determinations. Delivery of the gear motor for rotation of

the slag container has not been made at this date. As this constitutes

the main part of the apparatus, pre-calibration of the bob and cup

assembly have not been started.

Plans : The viscosity of the selected slag composition will be determined

at ambient pressure as a function of temperature. Calibration of the

viscosity apparatus will be completed when the portions of the system

that have been ordered arrive.

c. Vaporization and Chemical Transport (J. Hastie and D. Bonnell, 313.01)

Progress

:

During this reporting period a platinum tube was acquired

for fabrication of several high temperature/high pressure reactors. * The first of several planned reactor-types has been constructed. This

reactor utilizes a well established free jet expansion and skimmer

arrangement for conversion of the high temperature/high pressure gas to

a molecular beam suitable for mass spectrometric analysis.

Plans

:

The free jet expansion reactor will be tested and calibrated

using an inert gas medium followed by a reactive gas mixture containing

NaCl. The calibration procedure will involve monitoring the mass spectral ion intensities for the NaCl and (NaCl )

2

species as a function

of temperature and total pressure. Comparison of these data with those

derived from the JANAF Thermochemical Tables will determine the reliability of the sampling technique for future studies of coal gas mixtures

where the literature thermochemical data are incomplete.

25
4. Failure Avoidance Prograip (J. H. Smith, 312.01)

Progress

To date approximately 350 items have been received concerning

pilot plant operating discrepancies, component failures, quarterly reports

from pilot plants, etc. These items have been reviewed and after

eliminating duplicates and extraneous items a total of 300 pertinent

reports have been abstracted, classified and typed into the CCA Model 204

computerized Data Base Management System. Information has been received

from the following pilot plants and PDUS : Battelle, Carbonate, COED,

C0 2 , CPC, HYGAS, LERC, Lignite, MERC, SRC (Ft. Lewis), SRC (Wilsonville)

,

Synthane and Westinghouse

.

Detailed computer programs have been written for the CCA Model 204 computer

program which will be used to conduct failure mode analyses to identify

critical operating problem areas. Failure reports in the computer can now be sorted by process, material, failure category, component category,

any combination of the preceding or all of the preceding. The program

will produce an output in the form of a table (Table 1) or as abstracts

(Table 2) . The program will also make the task of summarizing failure

incidences much easier (Table 3)

.

Two regular meetings of the ERDA - Performance Assurance System Steering

Committee were participated in as a regular committee member to make this

group aware of the present Failure Avoidance Program. A paper on the

Failure Avoidance Program was presented at the first annual ERDA-EPRI-AGA

Conference on Materials for Coal Conversion and Utilization held in

Germantown, Maryland September 30 - October 1, 1976. Information for

the ERDA Newsletter was furnished to Battelle resulting in three failure

experiences being reported in the August newsletter. In addition, a series of seven failure reports has been submitted to Battelle for

inclusion in future issues of the newsletter. We will be sending Battelle

a weekly updating on new material received on failure problems. The Data

Center has received many requests for further information based on articles

in the April, 1976 ERDA Newsletter. These have come from manufacturers,

universities, failure analysis laboratories and consulting engineers.

Plans

The information gathering phase of this task will continue as more information is received on a continuing basis from the pilot plants.

In addition, detailed follow-up of certain information already received

will be initiated. Additional visits to operating pilot plants will be

made to collect additional information.

The information evaluation and processing phase of this program will

continue and be enlarged. The operation of the automated data storage

system will be enlarged and refined for easier and more efficient use. The information presently in the data base will be used to conduct failure

mode analyses to identify critical operating problem areas.

The information dissemination phase of this program will continue and

will be developed to include more direct contact with users. At present,

several inquiries a month are answered from plant operations and design

personnel. Plans have also been initiated to include summary results of

this program in the bimonthly ERDA-Materials and Components Newsletter.

26
Additional information dissemination will take place through the Fossil

Energy - Performances Assurance Systems that is currently under

development. Close liaison with this program is being maintained.

USCOMM-NBS 27
Table 1

IS 6

IS 6

? 'SEARCH. CRITERIA

FAILURE CATEGORY = EROSION AND COMPONENT CATEGORY = PIPING OR PUMPS

??KEY

PROCESS

I . N

.

PROCESS MATERIAL FAILURE COMPONENT

£5 CO£ 3 04 S.S.

316 S.S.

, CARBON STEEL

STEEL CORROSION PIPING

PUMPS

VALVES

290 CO£ UNKNOWN EROSION

EQUIP. MALF.

OVERHEATING PIPING

Id HYGAS CARBON STEEL

A 1 05

A 53

A£43 EROSION PIPING

4£ HYGAS STELLITE

INCOLOY 800

CAST STEEL

STEEL

3 04 S.S.

446 3 . S

.

CORROSION

EROSION PUMPS

VALVES

• PIPING

* 51 HYGAS STELLITE EROSION . PIPING

£1 0 HYGAS INCOLOY 300 EROSION P I P I NG

BELLOWS

£ 06 HYGAS CARBON STEEL

STEEL CORROSION

EROSION PIPING

COOLING EU

3 0

1

LERC EROSION

DESIGN PIPING

VALVES

£34 LIGNITE UNKNOWN see CORROSION

EROSION P I P I NG

PREHEATER

HEAT EXCHA

THERMOWELL

31 SRC SEVERAL EROSION

DESIGN PUMPS
Table 2

IS 3

IS S

??SEARCh! CRITERIA

FAILURE CATEGORY = EROSION AND COMPONENT CATEGORY = PIPING OR PUMPS

??KEY

PROCESS

I. IS. PROCESS MATERIAL FAILURE

S10 HYGAS INCOLOY 800 EROSION

TELECON ? 5-- 5 ''76 ? FROM S. GREENBERG » ANL? TO E. ORCHARD? JGT

EXPANSION JOINT-GASIFIER TRANSFER LINE.

ABSTRACT

COAl PRODUCT—MET AL REACTION PRODUCTS ARE FOUND GENERALLY ON BOTH 1 SIDES OF

THE BELLOUS AND IN ALL AREAS. IT SEEMS UNLIKELY THAT CORROSION IS THE MAIN

CAUSE OF BELLOWS PERFORATIONS.

CURRENT VIEWS ARE THAT THE PITS ARE DUE TO EROSION? AT LEAST IN THE

CASE OF INTERNAL SURFACE PITS. PITTING WAS PRECEDED BY LOCALIZED FAILURE DF

THE LINER TUBE ALLOWING PART I CAL IMPINGEMENT ON THE INTERIOR BELLOWS SURFACE.

AFTER PERFORATION OF THE BELLOWS THE STRUCTURE OF THE TRANSFER LINE ASSEMBLE

ALLOWED PARTICLE IMPINGEMENT ON THE EXTERIOR SURFACE OF THF BELLOWS.

IT IS IMPORTANT TO EXAMINE THE REMAINDER DR THE BELLOWS AND ESPECIALLY

THE LINER TUBE.

SEE I.N. 186? 194? £36? £74? £85? 886 FOR FURTHER INFORMATION.

I.N. PROCESS MATERIAL FAILURE

301 LERC EROSION

REPORT? 8/1 0/76? FROM A. WEST « SANDI A LABS? TO H . FRANKEL? ERDA

REVIEW OF MATERIALS PROBLEMS AT LERC IN- SITU GASIFICATION FACILITY

ABSTRACT

1 . PIPE ELBOW EROSION: ELBOWS SHOWED SIGNS OF IMPACT BY LARGE' SIZED PARTICULATE

THAT EXIT THE PRODUCTION WELL NEAR THE END OF A BURN. THIS CAN BE DRASTICALLY

REDUCED BY USE OF APPROPRIATE BAFFLING OR USE OF CYCLONES TD PREVENT

PARTICULATES FROM LEAVING THE WELL.

3. CHILL RING EROSION: RESULTS FROM RING PROTRUDING INTO THE FLOW PATH OF

EXITING GAS--W PARTICULATES. CHILL RINGS ARE USED FOR ALIGNMENT DUPING MANUAL

FIELD WELDING OF PIPES. THE USE DF AUTOMATED WELDING PROCEDURES WITH

APPROPRIATE ALIGNMENT FIXTURES SHOULD ELIMINATE THE NEED FOR CHILL RINGS.

3. VALVES: THE PRIMARY PROBLEM AT LERC HAS BEEN THE GUMMING UP OP JAMMING

QP BDTH BALL AND GATE VALVES DUE TO HARDENING OF COAL TAR IN THE VALVE SEATS

4. STACK COLLAPSE: THE STACK FOR BURNING OFF GASES COLLAPSED DUE TO POOR DESIGN

COMPONENT

PIPING

COMPONENT

PIPING

29
Table 3

FREQUENCY OF FAILURE TOE

Cause of

Incident

No, of

Items

1

C02 Hygas SRC Synthane

i Others

Undetermined 20 5 7 3 —L 5

Sulfidation 18 19 8 |

!

Erosion 17 1 4 6 5 1

Corrosion 78 "

Pitting 4 2 2

Dusting 3 3

Carb. 3 6 2

General 63 28 18 4 ii 2

Design Defect 11

General 7 3 3 i

Thermal 4 2 2

Stresses •

SCC - CL 15

r~ 5 2 3

Fabrication 7 2

Welding 5 1 2 i

. . - 1

Quality Control 3 ‘i 1 i 2

30