microtrace llc - nasdaqmedia.graytvinc.com/documents/tdec+report.pdf · particle atlas, volume v,...

Microtrace

790 Fletcher Drive, Suite 106 ● Elgin, IL 60123-4755 ● 847.742.9909 ● Fax: 847.742.2160 www.microtrace.com

microscopy ● microchemistry ● forensic consulting LLC

®

16 October 2019

Mr. Robert Wilkinson

CCR Techical Manager

TDEC

312 Rosa Parks Avenue

Nashville, TN 37243

RE: MT19-0298

Dear Mr. Wilkinson,

We have completed our analysis of six environmental samples, which were submitted to our

laboratory for the identification of coal ash. The results of our analysis were reported to you by

telephone on Thursday 10 October 2019. This report describes our analytical methods,

documents our results, and discusses the conclusions we have drawn from them.

Sample(s)

The following samples were received in our laboratory on 25 September 2019:

Sample 1: TDEC-BRF-001 (Figure 1)






Task

Analyze the six samples for coal ash by SEM and PLM

Analytical Methods and Results

Preliminary Examination

The samples were documented, on receipt, in their original packaging. Because the quantities of

samples 2-6 were quite small, they were first examined in their original packaging with the

unaided eye and then by stereomicroscopy to locate the material and to devise methods for their

recovery. The isolated samples from each plastic bag as well as the bottle and swab are

illustrated in Figures 7-12. Examination under the stereomicroscope indicated that the majority

MT19-0298

Microtrace

LLC

of the samples appeared to consist of a mineral rich soil composed primarily clay and clay coated

fine sand and coarse silt. Based on this observation, representative samples of the six samples

were prepared as slides for petrographic microscopy.

Microscopical Examination of the Samples to Search for and Identify Coal Ash

Microscope slides were prepared from the six samples and examined for coal ash using the

methods described in the Particle Atlas1. The slides were searched by polarized light microcopy

using a petrographic microscope. The particles comprising the specimens were identified on the

basis of their microscopic morphology and optical crystallographic properties. The identity of

particles originating from combustion properties was confirmed by isolating examples of the

tentatively identified particle types from the slide preparations and washing them free of the

refractive index liquids. These combustion particles were then mounted on a polished beryllium

plate2 for examination and analysis by SEM-EDS

3 to more carefully examine their morphology

at high magnification and determine their elemental compositions.

The analytical results obtained from each sample are described below. All of the samples are

otherwise similar with respect to their major composition, with the exception of -BRF 006,

which consists in large part of particles of white paint film and plant matter with a few of the

reddish-brown soil clumps. Sample -BRF-001 is the only one found to contain coal ash.

Therefore, its composition is described in detail below to put the amount of combustion products

identified into quantitative perspective.

Analytical Results

TDEC-BRF-001. The general appearance of this dust is illustrated in Figures 13 and 14. It a

reddish-brown soil composed almost entirely of mineral grains, primarily quartz and feldspars,

coated with an oxidized iron stained clay. Figure 15 shows a round, colorless, glassy sphere

among the mineral grains in a selected field of view. Two glassy spheres from another area of

the preparation are illustrated in Figure 16. These particles are one of the most characteristic

features of high efficiency coal-fired utility boilers. They show evidence of their time-

temperature history as the carbon of the coal burns away, leaving only the silicates originally

trapped in the coal, which melt to spheres. The bubbles inside are trapped escaping combustion

gases.

Figures 17 and 19 are SEM micrographs of glassy flyash spheres isolated from the microscope

slide preparations. Figures 18 and 20 are EDS spectra that provide the elemental composition of

these two particles. Note that, as expected, they are alumino-silicates composed primarily of

aluminum (Al), silicon (Si) and oxygen (O). The potassium (K) and sodium (Na) indicate the

feldspar silicates trapped in the coal from which they originated were of a type known as alkali

1 Palenik, S.J., Microscopical Examination of Air Pollutants in McCrone, W.C., Delly, J.G. and Palenik, S.J, The

Particle Atlas, Volume V, Ann Arbor Science Publishers (1973-1979), pp. 1362-1368 2 The low atomic number of the polished beryllium metal (Z=4) provides an essentially zero background for EDS.

3 Scanning electron microscopy – energy dispersive x-ray spectroscopy

of 46

MT19-0298

Microtrace

LLC

feldspars. The exact elemental composition of coals can be used4 to compare coal ash from

different sources.

Other characteristics of combustion products are carbonaceous soots and chars. Because of the

high efficiency of coal fired utility boilers, soot is typically rare in their effluent. Chars, which

however in this case, are unburned coal may be present based on the efficiency of the unit (the

more efficient the boiler, the less char that remains in the ash). This sample contains

carbonaceous chars. Charred carbonaceous matter is black, opaque and brittle. Figure 21 shows

a black opaque particle; however, this particular particles is not brittle, but elastomeric, and is a

particle of black rubber produced by tire wear and not related to combustion.

Black, opaque, round, ferro-magnetic particles are also present, although rare, in this sample.

These spheres are composed of magnetite (Fe3O4) and are produced in much the same way as the

glassy flyash spheres, but do not result from feldspars and other silicates but from iron sulfides,

which is where most of the sulfur is locked up in coal. Figure 22 shows one of these rare spheres

in this sample.

Figures 23 and 24 show examples of another type of carbonaceous char called cenospheres.

Cenospheres can be found in coal ash but are more characteristic of oil-fired boilers. Examples

of the appearance of carbonaceous cenospheres from this sample were also examined by SEM-

EDS and examples of several are shown in Figures 25, 27, 29 and 31. Their accompanying EDS

spectra are illustrated in Figures 26, 28, 30 and 32. Note the lacey structure of the cenospheres

themselves. This characteristic structure is caused by vapor produced by the burning fuel

forming “blow-holes” as it liquifies and decomposes inside the particle as it is burning.

Examination of these EDS spectra show, as expected, that the particles consist almost entirely of

carbon (C). Note that the small peaks contain the elements as the glassy flyash spheres, with the

exception of sulfur (S), because in the char it has not yet burned off.

Figures 33-34 show another carbonaceous particle type that was observed in this sample. These

particles are black, opaque and rounded to egg shaped. When crushed the particle is brittle and

breaks into small, greenish pieces as illustrated in Figure 35. The interior emits green

fluorescence, when excited by blue light, as depicted in Figure 36. Additional particles of this

type were also isolated and prepared for SEM-EDS analysis. Figures 37 and 39 show two

examples of these particles as they appear in the SEM. Figures 38 and 40, respectively, show

their EDS spectra. Note that although they are carbonaceous, they also contain a relatively high

silicate (silicon and oxygen) content. The presence of phosphorous (P) and nitrogen (short

unmarked peak between the carbon and oxygen in Figures 38 and 40) is somewhat interesting

since neither of these elements is typically associated with fossil fuels. They are, however, often

found in the ash of plants. These particles are present in trace amounts. We do not recognize the

source of these black, ovular particles and have not encountered them in samples of power plant

flyash. However, the best way to determine if they could originate from the coal ash from the

power plant that is suspected to be the source of the coal ash traces in this sample would be to

microscopically examine samples of that ash from that power plant.

4 By means of a more highly refined application of the same general method to compare coal or combustion

products to known coal and coal ash to help establish their sources.

of 46

MT19-0298

Microtrace

LLC

An example of another carbonaceous particle type found in -BRF-001 is illustrated in Figure 41.

Particles with this morphology are typical of oil soot. A few of these particles were located but

they are rare.

TDEC-BRF-002-006. No glassy flyash spheres or carbonaceous char that could be associated

with coal were detected in any of the remaining samples. Sample -BRF-005 contained a few rare

oil soot spheres and some particles of wood char. The black and brown colors on one of the

paint chips comprising -BRF-006 are not soot but dark matter from an inner layer of the multi-

layer paint that shows through to the surface and stands out against the white paint by contrast.

Summary and Conclusions

Sample TDCE-BRF-001 was the only sample showing detectable levels of glassy spheres and

carbonaceous char that could be associated with coal ash. The quantities of coal ash detected

were too low to quantitate. They are present only in trace amounts in this sample when

considered either by number of weight percentage. The other five samples showed no detectable

amounts of coal ash. Most of all of the samples consist of a red-brown soil composed primarily

minerals and a small amount of humic matter. Sample TDEC-BRF-006 consists primarily of

pieces of paint, plant matter, and a small amount of the red-brown soil (of the type that

constitutes the majority of the other samples).

One type of oval-shaped carbonaceous particle (observed in TDCE-BRF-001) could not be

associated with a particular source.

In summary, sample TDCE-BRF-001 contains traces of coal ash. No coal ash was detected in

the other five samples, which are composed almost entirely of a soil containing very little

organic matter.

of 46

MT19-0298

This report shall not be reproduced except in full, without written approval of Microtrace. Analyses performed at Microtrace are accredited under ISO/IEC 17025.

See certificate #5106.01 issued by the A2LA accrediting body.

Microtrace

LLC

If you have any questions concerning this report, or if we may be of further assistance, please do

not hesitate to contact either of us directly. It is our policy to retain samples for 30 days after

completion of our report, at which time they will be discarded. If you would prefer to have the

samples archived or returned, please contact us to make these arrangements before then. Thank

you for consulting Microtrace.

Sincerely,

Skip Palenik

Senior Research Microscopist

of 46

Microtrace LLC

MT19-0298

Figure 1. Sample BRF-001, as received.

of 46

Microtrace LLC

MT19-0298


of 46

Microtrace LLC

MT19-0298

Figure 7. The contents of sample –BRF-001 after transfer to a small petri dish.

of 46

Microtrace LLC

MT19-0298


of 46

Microtrace LLC

MT19-0298

Figure 12. The contents of sample –BRF-006 after transfer to a small petri dish. The yellow arrows depict the two larger particles of paint film.

of 46

Microtrace LLC

MT19-0298

Figure 13. A representative field of view of –BRF-001 showing the relatively bimodal size distribution of the particles comprising this sample.

Note that the fine particles are almost all crystals of silicates (quartz & feldspars). The larger particles are primarily crystals of minerals also.

Some of these are single crystals (e.g., the quartz grain at the upper right of the figure) while others are either single large mineral grains or

agglomerates of small grains coated with ferruginous (i.e., iron stained) clays. Transmitted plane polarized light.

of 46

Microtrace LLC

MT19-0298

Figure 14. Same as Figure 8 but between crossed polars, which demonstrates that the majority of the crystals are anisotropic with low order

interference colors. Mounted in 1.660 index of refraction liquid.

of 46

Microtrace LLC

MT19-0298

Figure 15. A typical glassy flyash sphere among the mineral grains comprising the majority of –BRF-001. Transmitted plane polarized light.

Mounting in 1.660 index of refraction liquid.

of 46

Microtrace LLC

MT19-0298

Figure 16. Two colorless glassy coal flyash spheres in –BRF-001. Transmitted plane polarized light. Mounting in 1.660 index of refraction liquid.

of 46

Microtrace LLC

MT19-0298

Figure 17. Backscatter electron (BSE) image of Particle F1 as it appears in the SEM. The inserted image shows the combustion product particles

isolated from sample –BRF-001 after they were removed from the microscope slides and washed prior to mounting on the beryllium plate for SEM-

EDS analysis.

of 46

Microtrace LLC

MT19-0298

Figure 18. EDS spectrum of glassy flyash sphere Particle F1.

of 46

Microtrace LLC

MT19-0298

Figure 19. Backscatter electron (BSE) image of Particle F2 as it appears in the SEM. Note the hollow sphere-within-a-sphere structure quite often

observed in glassy flyash spheres from coal fired utility boilers and some high efficiency municipal incinerators.

of 46

Microtrace LLC

MT19-0298

Figure 20. EDS spectrum of Particle F2.

of 46

Microtrace LLC

MT19-0298

Figure 21. Black particle of abraded tire rubber from sample –BRF-001.

of 46

Microtrace LLC

MT19-0298

Figure 22. Magnetite sphere from –BRF-001 as it appears by reflected darkfield illumination among the particles of mineral soil.

of 46

Microtrace LLC

MT19-0298

Figure 23. Black carbonaceous cenosphere fragment in –BRF-001. Transmitted plane polarized light.

of 46

Microtrace LLC

MT19-0298

Figure 24. Black carbonaceous cenosphere fragment in –BRF-001. Transmitted plane polarized light.

of 46

Microtrace LLC

MT19-0298

Figure 25. Backscatter electron (BSE) image of Particle B3 as it appears in the SEM.

of 46

Microtrace LLC

MT19-0298

Figure 26. EDS spectrum of Particle B3.

of 46

Microtrace LLC

MT19-0298

Figure 27. Backscatter electron (BSE) image of Particle A2 as it appears in the SEM. Inset shows the particle after isolation from the microscope

slide.

of 46

Microtrace LLC

MT19-0298

Figure 28. EDS spectrum of Particle A2.

of 46

Microtrace LLC

MT19-0298

Figure 29. Backscatter electron (BSE) image of Particle A3 as it appears in the SEM. Inset shows the particle after isolation from the microscope

slide.

of 46

Microtrace LLC

MT19-0298

Figure 30. EDS spectrum of Particle A3.

of 46

Microtrace LLC

MT19-0298

Figure 31. Backscatter electron (BSE) image of Particle B1 as it appears in the SEM. Inset shows the particle after isolation from the microscope

slide.

of 46

Microtrace LLC

MT19-0298

Figure 32. EDS spectrum of Particle B1.

of 46

Microtrace LLC

MT19-0298

Figure 33. Carbonaceous oval shaped particle of unknown combustion product. Transmitted plane polarized light. Mounted in 1.660 liquid.

of 46

Microtrace LLC

MT19-0298

Figure 34. Same particle illustrated in Figure 33 by reflected light.

of 46

Microtrace LLC

MT19-0298

Figure 35. The same particle illustrated in Figures 33 and 34 after crushing. Transmitted plane polarized light. Mounted in 1.660 index of

refraction liquid.

of 46

Microtrace LLC

MT19-0298

Figure 36. A portion of the crushed interior of the black particle shown in Figures 33-35 as it appears in the same preparation by blue light

excitation under a fluorescence microscope.

of 46

Microtrace LLC

MT19-0298

Figure 37. Backscatter electron (BE) image of Particle D1 as it appears in the SEM. Inset shows the particle after isolation from the microscope

slide.

of 46

Microtrace LLC

MT19-0298

Figure 38. EDS spectrum of Particle D1.

of 46

Microtrace LLC

MT19-0298

Figure 39. Backscatter electron (BSE) image of Particle D3 as it appears in the SEM. Inset shows the particle after isolation from the microscope

slide.

of 46

Microtrace LLC

MT19-0298

Figure 40. EDS spectrum of Particle D3.

of 46

Microtrace LLC

MT19-0298

Figure 41. Carbonaceous particle of the type usually associated with oil soot. Note the smoothed surface and the “blow holes” that pock mark its

surface.

of 46

microtrace llc - nasdaqmedia.graytvinc.com/documents/tdec+report.pdf · particle atlas, volume v,...

Documents