BF2RAbf2ra.org/csl/Grant 05 Orla Williams.pdf · Standard coal abrasion index test does not work...
Transcript of BF2RAbf2ra.org/csl/Grant 05 Orla Williams.pdf · Standard coal abrasion index test does not work...
2015 BF2RA Technical Session
On Biomass Milling for Power Generation
Presenter: Orla Williams, University of Nottingham
Co-Authors: Dr Carol Eastwick, Prof Ed Lester, Dr Donald Giddings, Prof
Ed Lester, Mr Stephen Lormor (EDF Energy plc)
Tuesday 6th October 2015
BF2RA
BF2RA
4 year EngD with BF2RA completed in September
2015
Part of the Efficient Fossil Energy Technologies
Centre at the University of Nottingham
Research theme: biomass milling in the power
generation sector
Academic supervision: Dr Carol Eastwick & Dr
Donald Giddings (University of Nottingham)
Industrial supervision: Stephen Lormor EDF Energy
Project Outline
BF2RA
How different woody, herbaceous, fruit and thermally
treated densified biomasses comminute in different mills
How mills impact densified biomass particle shape
factors
Suitability of standard coal grindability test for densified
biomass
Differences between grindability tests and classification
on mill product
Investigation of industrial operational issues associated
with biomass, such as mill choking and olive caking
Key Research Areas
BF2RA
Samples UsedMixed Wood Eucalyptus Sunflower Miscanthus
Olive Cake Steam Exploded Microwave La Loma Coal
BF2RA
Planetary Ball Mill
Laboratory scale Retsch PM100
planetary ball mill
High impact compression forces
100ml of sample milled at 300 RPM
for 3 minutes
BF2RA
Cutting Mill
Retsch SM300 cutting mill
Operated at speed of 1500
RPM, feed rate of
0.0025kg/s, screen size of 4mm
Continuous throughout mill fed
by vibrating bed feeder
Cutting mills use primarily shear
forces to reduce the particle
size of the material
BF2RA
Hardgrove Grindability Index
Hardgrove Grindability
Index (HGI) most widely
used grindability test for
coal for vertical spindle
mills
Test conducted according
to BS 1016-112:1995 [1]
Limited data for
grindability of densified
biomass
BF2RA
Bond Work Index
Test conducted on a Bond Work
Index testing mill
The Bond Work Index Wi expressesthe resistance of the material to
grinding to a specified product size
(kWh/ton) [2]
Study recently published in journal
Fuel “Investigation into the
applicability of Bond Work Index
(BWI) and Hardgrove Grindability
Index (HGI) tests for several
biomasses compared toColombian La Loma coal” [3]
BF2RA
Ring-Roller Mill
The Lopulco LM 1.6
laboratory scale ring-
roller mill
Continuous through put
mill with dynamic
classification
(separator)
No biomass
comminution literature
published for this type
of laboratory scale mill
BF2RA
Laboratory scale milling tests assess the grindability of a
material to a given size
Full scale mills use classifiers to select particles
Stokes number of a biomass particle should match that of an
equivalent coal particle in order to pass through the classifier
[4].
Stokes number is dependent on the sphericity and Reynolds
number of the particle
Possible for large biomass particles to have similar
aerodynamic properties to that of a much smaller coal
particle provided it has a sufficiently low sphericity
Particle Size and Shape
BF2RA
Camsizer® Digital Analysis
CAMSIZER P4
simultaneously
measures both
particle size and
shape
CAMSIZER P4 uses
Dynamic Image
Analysis principle
to detect each
particle and
record its size and
shape
BF2RA
Mixed Wood Pellets Particle Shape
Characteristic Pre-milledPlanetary
Ball Mill
Bond
Work
Index
Cutting MillRing-Roller
Mill
Particle Size d80
1373 µm 975 µm 787 µm 1105 µm 1201 µm
Sphericity Q50
0.347 0.381 0.387 0.384 0.403
Symmetry
Q50
0.821 0.769 0.766 0.796 0.764
Aspect Ratio
Q50
0.471 0.519 0.527 0.522 0.548
Circularity
Q50
0.502 0.427 0.465 0.509 0.433
BF2RA
Eucalyptus Pellets Particle Shape
Characteristic Pre-milledPlanetary
Ball Mill
Bond
Work
Index
Cutting MillRing-Roller
Mill
Particle Size d80
1215 µm 705 µm 751 µm 1171 µm 958 µm
Sphericity Q50
0.404 0.398 0.409 0.409 0.382
Symmetry
Q50
0.804 0.789 0.764 0.810 0.794
Aspect Ratio
Q50
0.552 0.540 0.554 0.555 0.520
Circularity
Q50
0.551 0.506 0.466 0.555 0.500
BF2RA
Miscanthus Pellets Particle Shape
Characteristic Pre-milledPlanetary
Ball Mill
Bond
Work
Index
Cutting MillRing-Roller
Mill
Particle Size d80
1251 µm 1181 µm 813 µm 1069 µm 1377 µm
Sphericity Q50
0.324 0.330 0.339 0.355 0.343
Symmetry
Q50
0.826 0.781 0.757 0.783 0.769
Aspect Ratio
Q50
0.437 0.446 0.460 0.482 0.464
Circularity
Q50
0.511 0.457 0.413 0.482 0.441
BF2RA
Sunflower Pellets Particle Shape
Characteristic Pre-milledPlanetary
Ball Mill
Bond
Work
Index
Cutting MillRing-Roller
Mill
Particle Size d80
1744 µm 1220 µm 757 µm 1145 µm 1523 µm
Sphericity Q50
0.347 0.384 0.418 0.397 0.382
Symmetry
Q50
0.831 0.782 0.745 0.803 0.793
Aspect Ratio
Q50
0.470 0.521 0.567 0.540 0.517
Circularity
Q50
0.571 0.479 0.452 0.530 0.496
BF2RA
Olive Cake Particle Shape
Characteristic Pre-milledPlanetary Ball
Mill
Bond Work
IndexCutting Mill
Particle Size d80
3660 µm 1553 µm 589 µm 1461 µm
Sphericity Q50
0.562 0.577 0.490 0.535
Symmetry
Q50
0.886 0.871 0.833 0.870
Aspect Ratio
Q50
0.708 0.714 0.645 0.685
Circularity
Q50
0.806 0.778 0.682 0.781
BF2RA
Steam Exploded Pellets Particle Shape
Characteristic Pre-milledPlanetary
Ball Mill
Bond
Work
Index
Cutting MillRing-Roller
Mill
Particle Size d80
1196 µm 466 µm 346 µm 1412 µm 521 µm
Sphericity Q50
0.428 0.454 0.455 0.464 0.445
Symmetry
Q50
0.840 0.785 0.770 0.846 0.823
Aspect Ratio
Q50
0.580 0.608 0.608 0.620 0.600
Circularity
Q50
0.645 0.522 0.506 0.690 0.630
BF2RA
Microwave Pellets Particle Shape
CharacteristicPlanetary Ball
Mill
Bond Work
IndexCutting Mill Ring-Roller Mill
Particle Size d80
285 µm 888 µm 1091 µm 538 µm
Sphericity Q50
0.464 0.385 0.414 0.403
Symmetry
Q50
0.763 0.827 0.836 0.819
Aspect Ratio
Q50
0.621 0.524 0.563 0.549
Circularity
Q50
0.520 0.605 0.651 0.597
BF2RA
La Loma Coal Particle Shape
Characteristic Planetary Ball Mill Bond Work Index Ring-Roller Mill
Particle Size d80
2723 µm 78 µm 402 µm
Sphericity Q50
0.503 0.506 0.403
Symmetry
Q50
0.862 0.796 0.804
Aspect Ratio
Q50
0.656 0.657 0.660
Circularity
Q50
0.579 0.628 0.636
BF2RA
Project Findings
Biomass Characterisation
Pre-milled biomass pellets are composed of similar particle sizedistributions, but show a large variance in particle shape
Standard coal abrasion index test does not work for biomass as itcaused the apparatus to catch fire
Standard Coal Grindability Test
HGI is a poor indicator of the grindability of biomass in a verticalspindle mill
Grindability tests which aim to analyse the grindability of biomassto 75µm are inappropriate – should be informed by classifiersettings
BWI can be used replicate mill choking
Biomass pellets should be composed of particles close to therequired size
BF2RA
Olive Caking
Olive caking phenomenon is associated with the pulp section of
the material
Sugar and moisture content of the pulp section are such that
when milled a glass transition step occurs which results in the
caking of the olive
Olive cake fines below 1mm should be sieved out and sent
directly to the burner and not comminuted
Ring-Roller Mill
Strong negative correlation was obtained between comminuted
particle size and shape for mill with separator
Biomass mill classifiers should be set to the Stokes number
requirements for coal rather than a blanket particle size for all
biomasses
Project Findings 2
BF2RA
The critical particle size for comminution through compression is key to
understanding milling behaviour in different mills.
By knowing a materials critical particle size and the target size of the specific
biomass based on the classifier settings for a mill, it will be possible to tell:
i. Whether or not a biomass pellet will break down easily within the mill
ii. If the biomass particles which compose the pellet will need extra
comminution to reach its required particle size for combustion
iii. If the biomass particles will struggle to reduce in size if comminution is
required due to their critical particle size being larger than the target
particle size for combustion
Milling had little impact on particle shape even when an order of magnitude
difference was seen in the particle size.
Particle shape is inherent to a pellet and is determined by the pre-densified
comminution processes.
Overall Project Findings
BF2RA
Follow on Engineering Doctorate currently under way with BF2RA which is
developing numerical models of biomass comminution based on the test results
Development of a new standard test to quantify the abrasiveness of biomass in
pneumatic conveying systems
New HGI test for biomass which incorporates larger volumes and targets s
Models to predict the required particle size for a classifier based on the physical
characteristics of the pre-milled particles to inform grindability test
Need to find the critical particle size for compressed fracture for biomass for all
types of biomasses, and compared to the particle size distributions of
disintegrated pellets
Ring-roller mill: energy consumption and particle size correlations should be
compared to those of the full scale Lopulco ring-roller mill at EDF West Burton
and the pilot scale ring-ball mill at Doosan [5] for standard materials
Future Work
BF2RA
Thank you for listening
The authors would like to thank the University of
Nottingham, the Biomass and Fossil Fuel
Research Alliance (BF2RA), and EDF Energy plc
for their support during this project.
Questions?
BF2RA
[1] The British Standards Institution, 1995. BS 1016-112: 1995 Methods for Analysis and testing of coal and coke — Part 112: Determination of Hardgrove grindability index of hard coal. Milton Keynes: BSI.
[2] Bond FC. The Third Theory of Comminution. Trans AIME 1952;193:484–94.
[3] Williams, O., Eastwick, C., Kingman, S., Giddings, D., Lormor, S., & Lester, E. (2015). Investigation into the applicability of Bond Work Index (BWI) and Hardgrove Grindability Index (HGI) tests for several biomasses compared to Colombian La Loma coal. Fuel.
[4] Mandø, M., Rosendahl, L., Yin, C., & Sørensen, H. (2010). Pulverized straw combustion in a low-NOx multifuel burner: Modeling the transition from coal to straw. Fuel, 89(10), 3051–3062
[5] Livingston, W. R., Horne, P. A., McGhee, B. F., Gibson, J. R., & Chakraborty, R. K. (1998). The Characteristics of Coal Blends -Milling Behaviour & Ash Fusion Temperatures
References