dimensioning explosives energy in the blast - ken

WealthUnearthed

Dimensioning explosives energy in the blast30th October 2014

What is an explosive?

Anthracite

Subbituminous

Lignite

Bituminous

Take 1kg of Coal and Explosive

Which produces more energy?

Coal produces more energy!

Approximately 6.5 x more

Coal 20 to 30MJ/kg

vs.

Anfex 3.8MJ/kg

So why don’t we use coal as an explosive?

Time

Coal burns slowly!

Coal needs additional elements- Explosives has its own oxygen

Air (Oxygen)

Combustion products from coal

Some 6.25kg of these elements required per 1kg of coal for combustion to occur

Carbon

CO2

Hydrogen

H2O

Sulphur

SO2

Oxygen

Nitrogen

NOx

Ash

An explosive produces:

A rapid reaction

Shock wave

Expansion of gases

Shock wave and rapid expansion of gases

4 x 100 kg SAN mortar

Traditional Energy conversion

www.photron.com

Fragmentation energy -> Shock

www.photron.com

Heave -> Gas

www.photron.com

Density of rock mass

High density rocks do not deform easily and require high explosive energy to fragment

But – hard rock is easy to blast

Low density rocks deform easily and require distributed low explosive energy to fragment

But – soft rock is difficult to blast

How’s this delivered?- Emulsion (Shock)

How’s this delivered?- Anfex® (Heave)

2250225022502250

2500250025002500

2750275027502750

3000300030003000

3250325032503250

3500350035003500

Det

onat

ion

Velo

city

Det

onat

ion

Velo

city

Det

onat

ion

Velo

city

Det

onat

ion

Velo

city

(m/s

)(m

/s)

(m/s

)(m

/s)

0000 2222 4444 6666 8888

% Moisture% Moisture% Moisture% Moisture

No water resistanceRapid drop off in performance

Breaking effect: How is the energy delivered?

Required:

Fragmentation, movement

Unwanted:

Damage, vibration, flyrock, fumes, sensitivity.

What form of energy is required at mine?Useful energies = fragmentation, heave

Reduce wasted energy, fuel, wear & tear

load, haul, crush, mill

Want as little as possible

Fragmentation optimisation- Powder factor

Derive drilling patterns?

Drill & Blast cost

30

19

115

REE PF K A = X 6

10.8-

50

Kuz - Ram fragmentation

Fragmentation – Cost control- Energy

Compare energy cost?

Bang per buck

30

19

115

REE PF K A = X 6

10.8-

50

Kuz - Ram fragmentation

Do our customers understand our product catalogue in terms of energy?

S

S100 Eco

75

S120 Eco

75

S130 Eco

100

S135 Eco

100

Effect of different strength ratings- Ideal detonation

For the SAME emulsion chemical formulation ...

CAUTION: Different companies have different measures

Criterion 20MPa 20MPa 100MPa Heat of

Reaction

ANFO

Density

0.8 0.82 0.8 0.8

REE 99 98 112 82

How are we supposed to compareBang per buck?

Another way to look at energy is:- Non Ideal Detonation

How well is the product mixed?

Incomplete Reaction

Dependent on Confinement

Ideal assumes no rock movement

Curved Shock Front

Dependent on Diameter

How does this affect the detonation?

Detonation becomes less ideal in smaller diameters

Detonation pressure is reduced

Velocity of detonation decreases

HSBM – The Blast Modelling Tool

Rock movement vs. timing (muckpile heave)

Mixing for grade control

Blast Modelling Outputs – Getting it right

Mineral re

covery

% Retained

New design methodology- Fragmentation for Mineral recovery?

Fragment Size

Fines OversizeMid Range0

Haulage

% Retained

New design methodology- Or fragmentation for Load & Haul?

Fragment Size

Fines OversizeMid Range0

Energy of AEL Bulk Explosives – 100MPa

Pump < 165 mm Augur > 165 mm

Emulsion +AN prill AN Prill + Fuel Oil + Emulsion

Overburden (Hard - Soft Rock)Quarrying (Hard Rock)

Low VODHigh VOD

Explosives selection to meet rock structure and strength properties

Fractures

Strength

High VODHigh density-S235

Quarry Academy

Explosives Selection is meeting the rock structure and strength properties

Fractures

Strength

Explosives selection to meet rock structure and strength properties

Fractures

Strength

Quarry Academy

Medium VODHigh density- S100

Low VODLow density-S257

Explosives Selection to meet rock structure and strength properties

Fractures

Strength

Explosives Selection to meet throw and fragmentation requirements

Fragmentation requirement

Throw requirement

Low VODMed-High density

Explosives Selection to meet blast design in cast blasting

Fragmentation requirement

Throw requirement

Fragmentation requirement

Throw requirement

Low VODLow density

Explosives Selection to meet removal of cap

Fragmentation requirement

Throw requirement

Achieving the best blast performance,

necessitates the replacement of guess by

understanding, brute force by finesse and

laxity by care and precision

- T.N Hagan, 1997 ISEE

Confidence, Courage and CareBlast Performance

Dimensioning explosives energy in the blast30th October 2014

Questions?