Lanthanides in coal combustion fly ash

Transcription

1 2013 World of Coal Ash (WOCA) Conference - April 22-25, 2013 in Lexington, KY Lanthanides in coal combustion fly ash Jim Hower Shifeng Dai Vladimir Seredin Irena Kostova Luis Silva

2 Outline Previous studies Kentucky Chinese anthracite New directions Low-rank coals Various Ohio Valley power plants

3 Kentucky: Dean coal study sites Mine in Dean coal bed (correlative of Fire Clay coal), Knox County, KY Coal mined for two weeks prior to utility burn Power plant is 220-MW wall-fired utility unit in southeastern Kentucky Utility burned coal for several days CAER sampled at plant following several days of burning, giving us some confidence that coal and CCB s represented mined coal Mardon and Hower, 2004, I.J. Coal Geology, v. 59, p, 153.

4 Study sites Kentucky Power plant location (Pulaski Co.) Mine location (Knox Co.) Previous Fire Clay study area

5 Previous studies of Fire Clay coal Studies of Fire Clay coal bed in eastern Kentucky have emphasized geochemical and mineralogical aspects of coal with respect to volcanic ash fall deposit within coal Trends of REE and Zr proved to be the most important in demonstrating link between tonstein and coal geochemistry (Hower et al., 1999, Int. J. Coal Geology 39, ) Compare to example of Fire Clay correlative at mine and as delivered to power station (Mardon & Hower, 2004, Int. J. Coal Geology 59, )

6 Comparative Geochemistry with other major Eastern Kentucky coals (all values ppm, ash basis) Coal La Ce Nd Y Zr Coalburg Fire Clay Pond Creek Clintwood

7 Illitic clay Tonstein Fire Clay tonstein

8 Mineralogical clues for volcanic origin of tonstein: Beta quartz (left) Sanidine (below left) Zircon (REE site) (below)

9 Rare earth elements in Fire Clay coal and tonstein: REE-rich Ca-phosphate in kaolinite (left and lower left) Ce- & La-rich Ca-phosphate (below)

10 Tonstein Chemically dominated by SiO 2 and Al 2 O 3 with low K 2 O - reflection of kaolinite dominance Zr can be high, up to 1830 ppm - generally higher concentration than in coal lithotypes Y + sum REE is in ppm range

11 n n n Coal separated from tonstein by illitic clay has 500 ppm Zr (ash basis) Always higher in Zr than tonstein - up to 4540 ppm (ash basis) in lithotype where thin ash layers noted Underlying Coal kaolinite

12 Underlying Coal n Y + sum REE ranges from ppm n (ash basis) - in sample with 4198 ppm, each element in La to Sm range has at least 3x concentration of any other lithotype n Next higher concentrations generally in lithotypes immediately above tonstein

13 100 cm 0 Bench 1/6 2/6 3/6 4/6 5/6 6/6 Ash S Spy Hg Dean coal study Coal sampled in six Benches - Sampled from same pit where coal was mined - High S and Hg coal only found at top of coal bed Coal is high volatile A bituminous

14 Dean coal: Trace element comparison Y+REE Hg Whole coal Bench 1/6 (top) Bench 2/ Bottom 4 benches Feed coal Pulverizer reject

15 REE Geochemistry Use of chondrite-normalized plots offers another means of comparing mine benches, delivered coal, and coal at power plant Corrections after Korolev (

16 Reject Whole coal Upper benches Feed & Delivered coal Lower benches Dean coal at mine + delivered, feed, and reject coal

17 Dean coal: REE Geochemistry Delivered and feed coal REE distribution falls between whole channel sample and lower benches Supports premise that delivered and feed coals are biased towards low-s/low-hg lower benches

18 REE in Dean coal-derived fly ash Location in plant La Ce LREE HREE Y+REE LREE/HREE Feed coal Mech 1 st row Mech 2 nd row ESP 1 st row ESP 2 nd row ESP 3 rd row Bottom ash Note decrease in LREE/HREE from Mechanical collection rows through to 3 rd ESP row

19 REE in Chinese anthracitederived fly ash Samples from two power plants 4 units at Diandong in East Yunnan 2 units at Anwen Silva et al., Applied investigation on the interaction of hazardous elements binding on ultrafine and nanoparticles in Chinese anthracite-derived fly ash. The Science of the Total Environment 419, Additional samples from Junger plant previously unpublished

20 REE in Chinese anthracitederived fly ash Plant La Ce LREE HREE Y+REE LREE/HREE Diandong Diandong Diandong Diandong Anwen Anwen Similar LREE/HREE between rows of same plant; Different LREE/HREE between plants

21 REE in Chinese anthracitederived fly ash: Jungar plant Location in plant La Ce LREE HREE Y+REE LREE/HREE Feed coal Economizer Fly ash Bottom ash

22 REE in Chinese anthracite-derived fly ash: Jungar plant sized economizer fly ash Particle size La Ce LREE HREE Y+REE LREE/HREE >120 mesh x 160 mesh x 300 mesh x 360 mesh x 500 mesh <500mesh Progressive increase in Y+REE with decrease in particle size LREE/HREE passes through minimum in middle of size range

23 REE in Bulgarian lignite-derived fly ash Plant Row La Ce LREE HREE Y+REE LREE/HREE Republika Republika Republika Bobov Dol Bobov Dol Bobov Dol

24 LREE/HREE decreases with decrease in flue gas T LREE/HREE similar to Diandong fly ash (discussed above) Less than Chinese anthracite-derived ashes and Mardon & Hower s (2004) hvab ash Two plants have similar Y+REE REE in Bulgarian lignite-derived fly ash

25 Republika Republika fly ash REEs are similar to each other Lower than Kentucky plant H burning medium-s high volatile A bituminous coal { Kentucky REE in Bulgarian Republika & Kentucky plant H fly ash

26 REE in Kentucky bituminousderived fly ash Plant Row La Ce LREE HREE Y+REE LREE/HREE I I I H H H H R R R R R P P P

27 Dilution by pet coke passing through to fly ash Fly ash derived from 70 coal:30 pet coke burn has low Y+REE All lower than tonstein-influenced fly ash studied by Hower & Mardon (2004) Variation in Y+REE between power plants REE in Kentucky fly ash

28 Further investigation of wider range of feed coals, plant designs, & ash collection systems will be conducted Element partitioning responsible for LREE/HREE not understood Kentucky Plant H, burning high-s Illinois Basin coal, deviates from trend Decrease in LREE/HREE from hotter to cooler rows is general trend REE distributions in fly ash: conclusions from this study

29 Questions?

30

31

32 Dean study: Problems Tonstein not present in seam section, complicating interpretation of geochemistry Coal is at mapped location & elevation of Dean coal bed Whole-coal geochemistry from mine section does not match delivered coal Specifically, high-s/high-hg component in whole coal from mine is not as evident in delivered coal

33 100 cm 0 Bench 1/6 2/6 3/6 4/6 5/6 6/6 Ash S Spy Hg Coal sampled in six Benches - Sampled from same pit where coal was mined - High S and Hg coal only found at top of coal bed Coal is high volatile A bituminous

34 Dean study: Problems Tonstein not present in seam section, complicating interpretation of geochemistry Coal is at mapped location & elevation of Dean coal bed Whole-coal geochemistry from mine section does not match delivered coal Specifically, high-s/high-hg component in whole coal from mine is not as evident in delivered coal

35 Dean study: Possibilities Coal shipped was from different part of mine than coal sampled at face Sampling at mine followed mining and delivery Company practiced selective mining, isolating and not shipping higher-s coal Geochemistry offers means to demonstrate what part of coal was shipped