dust control in room and pillar

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DUST CONTROL IN ROOM AND PILLARCOAL MINING USING IMPROVED

SCRUBBERS AND IMPROVED SPRAYCONFIGURATIONS

Y. P. Chugh1, A. S. Patwardhan2,1, H. G. Gurley1 & R. C.Carty3

1Department of Mining and Mineral Resources Engineering

Southern Illinois University at Carbondale

2Rio Tinto Minerals, Boron Operations

3Illinois Clean Coal Institute, Carterville, IL

Mine Ventilation Symposium - 2008

Reno, NV



ACKNOWLEDGEMENTS

Illinois Department of Commerce and

Economic Opportunity

Illinois Clean Coal Institute

Illinois Mining Companies

Joy Mining Machinery

Spray Systems Inc.Mine Safety and Health Administration

NIOSH

Coal Research Center, SIUC



OUTLINE

Background

Sources and distribution of dust around a CM

Sampling and Data Analysis methods

Modified Scrubbers & Improved Spray

Systems

Conclusions



BACKGROUND

Increased productivity (2.5 to 4.0 tons/man-

hour over past decade) – higher dust

Further productivity gains needed for reducing

production cost

Productivity gains may be dust constrained

Potential tightening of regulations – Allowable

dust exposure reduction from 2 to 1 mg/m3 willresult in only 37% mining units remaining in

compliance

Health and safety of workforce



Ram Car

BOOM

SCRUBBER

MAIN BODY

FLIGHT CHAIN CONVEYOR BOOM

SCRUBBER

MAIN BODY

FLIGHT CHAIN CONVEYOR

Loading

Scrubber

Exhaust

Cutting

at Face

Escaping

from sides

Escaping

from sides

Roll-

back

Intake

Ram Car

BOOM

SCRUBBER

MAIN BODY

FLIGHT CH

AIN CONVEYOR BOOM

SCRUBBER

MAIN BODY


Loading

Scrubber

Exhaust

Cutting

at Face

Escaping

from sides

Escaping

from sides

Roll-

back

Intake

Sources of Dust around a CM

Trimming

Roof

Gathering

Arms

Scrubber

Exhaust


BOOM

MAIN BODY

Roll-

back

Loading Trimming

Roof

Gathering

Arms

Scrubber

Exhaust


BOOM

MAIN BODY

Roll-

back

Loading

PLAN VIEW

ELEVATION VIEW



Conceptual

Dust Profiles

DustConc.

(mg/m3)

Distance (m) 0

F A C E

Plan View

0Distance (feet)

% Respirable

Total Dust Conc.

A

A

FACE

Plan View

% Respirable DustTotal Dust Conc.

B0

Roof Level

Floor LevelB

H ei gh t

f r om f l o or

• Highest concentration at the face.

• Respirable dust fraction increases

away from face as coarse dust settles.

• Respirable dust fraction highest at

roof level due to cutting of rock and

coal.

• Therefore, scrubber suction inlets

should be located close to roof level.



CFD ModelingCFD modeling of a CM in Room-and-Pillar Entry.

Aerodynamic conditions in the face area provide

invaluable insights into analyzing the problem of

occupational dust exposures.

Though modeling requires refinement, it is clear

that improvements in line-curtain management

practices are necessary to reduce dust exposures

to occupations and to dilute methane

concentrations.



Model 3 (Mid-Plane)

ExperimentallyValidated Airflows

Recirculation Zone – Ram Car OperatorBreathing Zone

Miner OperatorLocation VerySensitive

Very Low AirVelocities at Face

Tight Line Curtain



Model 8 (Mid-Plane)

Ample room forMiner Operator tostay in Fresh Air

15-ft AdvanceTight LC



Dust Sampling



SamplingLayout

Ram Car In

Ram Car Out

41’

Intake Air

Curtains

10’-40’

Return Air

~30’

1

2

3

4

Straight Cut - Deep

19’



Dust Data Transformations

Dust Concentrations Corrected for

Intake Dust Concentration

Line Curtain Airflow

LOXC Airflow Production

Cut Dimensions

Delays

Data Screening

+/- 2 SD Outliers

Post-Hoc comparisons between cut types



Develop an Innovative SpraySystem For Continuous Miners

Proven principles:

Have multiple check points when you are fighting

a large, smart army.

Surround the enemy to efficiently use

resources and minimize enemy escape at each

check point.

Utilize different tactics to deal with enemy left

at each check point.



Modify Spray Configuration arounda Miner - Principles

Control the dust as close to the generation

point as possible.

“Cutting face”, “In the pan”, “at conveyor

discharge” and “Scrubber inlets” must be

emphasized.



Unmodified Scrubber

UnmodifiedHorizontal Spray

Only Screen (30

Layer)



Modified ScrubberSprays

First 10-layerfilter

Sprays

Second 10-layerfilter



Expanded Metal Screen Coverson Suction Inlets

Left Side Suction

Right Side Suction

Expanded metal screens keep out the

coarsest coal particles being sucked

into the scrubber

Side suctions improve suction of

respirable dust concentrated at higher

levels into the scrubber.



Key Concepts Utilized for SpraySystem Design

Prevent dust generation, and minimizegenerated dust from becoming airborne byincreasing water at the cutting bits, andcutting face, with appropriate spatialdistribution of sprays.Wet and surround the airborne dust to allowthe scrubber to capture it.Further wet the airborne dust escaping thescrubber inlets area before it enters the areabehind the miner and the last open crosscut.Maximize the residence time in the face areato improve wetting of coal dust.

Detailed spray system discussion curtailed due to

Intellectual Property reasons.



Mining Conditions During Sampling(Rounds I-III)

Sprays Cut Sampled

Mining Height

(inches) Cut Rock (inches)

Conventional 11 96.96 23.45

Modified 14 96.93 24.35

Very Comparable Conditions



Summarized Results (Graphical)

0

2

4

6

8

10

12

14

M i n e r

O p e r a t o r

M i n e r

O p e r a t o r

M i n e r

O p e r a t o r

I m m e d i a t e

R e t u r n

I m m e d i a t e

R e t u r n

I m m e d i a t e

R e t u r n

R e t u r n

R e t u r n

R e t u r n

Round I Round II Round III Round I Round II Round III Round I Round II Round IIITesting Round - Sampling Location

D u s t C o n c e n t r a t i o n ( m g / m ^ 3 )

Conventional Sprays

Modified Sprays



Realized Improvements in DustControl

H0:Conventional= Modified

p-value

Difference(mg/m3) at90%

confidence

Percentagereduction at90%

confidenceMinerOperator

0.003 1.461 33.6%

Immediate

Return

0.01 0.831 26.9%

Return 0.52 - -

High variance in standard spray sampling and very high diluting LOXC air

flow makes confidence level determination difficult.

R lt t A th Mi



Results at Another Mine(Round IV)

ConventionalHt - 74.6”, Roof – 10.4”, Floor – 7.3”

ModifiedHt - 72.6”, Roof – 11.6”, Floor – 6.6”

Average SD No. Average SD No. Reduction

MinerOperator

1.42 1.59 15 1.20 1.38 6 15%

ImmediateReturn

3.48 1.99 15 2.25 2.30 4 35%

Return* 4.96 2.15 15 3.62 1.18 6 27%

* Statistically Significant Difference @ 0.10 significance

R lt t A th Mi



Results at Another Mine(Round V)

ConventionalHt – 79.7”, Roof – 2.1”, Floor – 10.5”

ModifiedHt – 77.1”, Roof – 4.1”, Floor – 7.3”

Average SD No. Average SD No. Reduction

MinerOperator

1.000 0.959 18 0.379 0.505 12 62%

ImmediateReturn

0.798 0.477 18 0.493 0.368 13 38%

Return* 1.664 1.105 16 1.344 1.126 13 19%

* Statistically Significant Difference @ 0.10 significance



Summary Results

0

20

40

60

80

100

Round I Round II Round III Round IV Round V

P e r c e n t D u s t R e d u c t i o

n

Testing Round

Miner Operator Haulage Operator Return



Summary

Approximately 25-40% reduction in dust hasbeen documented using the modified sprayand scrubber systems.

These improvements have been statisticallyvalidated.

Higher improvements would have beenpossible if higher water pressures (120+ psi)were available.

Results may improve even further if improvedface ventilation practices are followed.



THANK YOU !

dust control in room and pillar

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