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Microwave Energy Aided Mineral Comminution
Presented by: Ashish Kumar, Bala P Kamath, V V Ramarao (Speaker), D B Mohanty Central Research & Development Laboratory, Hindustan Zinc Limited
Introduction • •
Comminution in Mineral Beneficiation is an energy hungry process. About 50 % of the total energy is consumed during Comminution. Milling Measures to improve grindability of 43.6 % ore & attain energy savings were on trial since early 1900s;Thermally Assisted Liberation (T.A.L.) based on conventional heating was explored. Conventional T.A.L. was uneconomical on commercial scale. Recent researches in MICROWAVE & RF pioneered Microwave energy as an EFFECTIVE solution for Heating source.
Flotation & Filteration 32.3 %
Tailing disposal 10 %
Crushing 13.2 %
Others 0.9 %
Microwaves & Mineral Processing
Percy Le Baron Spancer – 1st to provide the idea of Heating by Microwaves in 1946.
Microwave energy is a form of Electro Magnetic Radiation having frequency between 3000 MHz to 3000 GHz. – Common applications of microwaves: communication; heating; – Frequency bands for microwave heating application in India is 2450±50MHz.
Ore constituents have different thermal & mechanical properties (thermal expansion coefficients, microwave absorption coefficients); Microwave irradiation Increased ore grindabilty
Differential heating of ore minerals
Developing stress
to create trans-granular & inter-granular cracks / micro-fractures
Absorption of microwave is Characteristic phenomenon of respective Mineral. For example, presence of sulphides, oxides and graphitic carbon enhances fracture formation.
Breakthrough concept for various industries that consume large amounts of energy including mineral processing, cement etc.
MICROWAVES
Applications of Microwave Variety of applications of microwave heat in several industries are in practice like: – – – – – – – – –
Drying of food items (Tea leaves, seeds, edible items) Hospital sanitation Sprouting Vulcanization of rubber Carbon reactivation Pressure leaching Roasting Sintering Rocks & Ore comminution
Background for Present Work •
Hindustan Zinc Limited is a Vedanta Group company;
•
CRDL is for HZL’s R&D;
•
Technology cell at CRDL has decided to adopt microwave energy use as a step change technology in its road map.
•
Work on Microwave aided comminution project started during 2005; benefits targeted are – Increased mill throughput – Reduced grinding energy through reduction in the ore work index.
COPPER SIIL KCM
VEDANTA M INIU M U / AL CO BAL CO MAL
ZIN
C& LE R& HZL AD CR D DL
Rampura Agucha Beneficiation Plant EXISTING RAMPURA AGUCHA – 6100 T.P.D. LEAD/ZINC CONCENTRATOR FLOWSHEET additional fine ore bin
Pri.Cyc.D20
R.O.M.
Primary Crusher
Sec.Cyc.D15
Fine Crush Plant 3 Rod Mills Fine Ore Bin Active 4,500T (Each)
Coarse Ore Stock Pile Active less than 9,000T
115
3 Ball Mills
110
7 Lead Roughers OK-16 10 Lead Scavengers OK-16
2 Zn. Conditioners
Pb Conditioner
2 Zinc Roughers 9 Zinc Scavengers OK-38
8 Zinc Roughers OK-38
140 139 153
177
181
178 Pb 3-Stage Cleaning
Zn 4-Stage Cleaning
Regrind Cyclones
151
148
D15
145
196 193 Pb Conc.Thickener
190
14 M Dia
Regrind Mill To Reclaim Water
187
162
Pb Stock Tank
224
222 To Reclaim Water
Zn Conc. Thickener 14 M Dia
249 252
Tailing Thickener 55 M Dia
7 Zn Filter Presses PF25
1 Pb Filter Press PF25
To Reclaim Water
288
16 M Dia Neutralization Tank
254
247 Zn Stock Tank
282 Zn Conc. Stock Pile TAILING DAM
Pb Conc. Stock Pile
Microwave Experimental Work Preparation of sample: 3 kg representative samples from plant rod mill feed were prepared mixing ore size fraction in the range –19 mm to + 2 mm in the same size proportion as in plant rod mill feed. (minus 2 mm size fraction discarded in accordance with previous observations) Grindability studies: Laboratory ball mill was used for wet grinding with 3 kg sample each time at a pulp density of 60% solids (by wt); ground material size distribution is known through wet sieving; Observations are: o Effect of microwave on particle size distribution under water quenched & unquenched conditions w.r.t. unexposed samples. o Effect of microwave on work index of ore. The relative work index of the ore was calculated using Berry & Bruce formula.
– –
Wi : work index kW.h/t; r and t refer for reference and test samples; P and F refer to 80% passing of the product and feed stream.
Experimental Work
….contd.
o Effect of microwave on the grinding time, which is directly proportional to the saving in grinding energy of the ore.
Simulation studies – Prediction of mill throughput increase for reduction in ore work index; o JKSimMet comminution software o Microwave irradiation (with quenching) at different time/intensity ranges for using different work index values. o Simulations predicted Throughput changes for same P-80 size;
(more finer size for same grinding) Average of cumulative wt% passing
94 92 y = -0.9646Ln(x) + 95.346
90
y = -0.8184Ln(x) + 91.935
88
y = -0.9906Ln(x) + 92.559
86 84 0
50
100
150
200
250
300
350
400
450
Sieve size (in mesh)
Blank
UQ AVG
Q AVG
Log. (UQ AVG)
Log. (Q AVG)
Log. (Blank)
Trend line (semi log) for average particle size distribution of R A Mine samples under water quenched, unquenched & unexposed conditions
60
(more grindability with more exposure)
% reduction in work index
50
40
30
20
10
0 0 Unexposed
10
20
30
40
50
60
70
Exp osure time (min)
% Reduction in work index
Effect of microwave exposure for different time intervals on work index of ore
% cumulative pass by 200 mesh
Microwave & Grinding Time
100 90 80 70 60 50 0
10
20
30
40
50
60
70
50
60
70
50
60
70
Time of grinding (min)
•
More finer fraction generated for irradiated & quenched fractions than non-irradiated (normal) fractions – 100 #, 150 # & 200 # (for same grinding time more finer product & for same product size reduced residence time)
Unexposed
Exposed
100 % cumulative pass by 150 mesh
Plot of % passing fraction at different particle sizes in ground product for different grinding times – Irradiated & quenched – Non-irradiated
90 80 70 60 50 0
10
20
30
40
Time of grinding (min) Unexposed
% cumulative pass by 100 mesh
•
Expos ed
100 90 80 70 60 50 0
10
20
30
40
Time of grinding (min) Unexposed
Exposed
10
% increase in plant throughput
8
6
4
2
0 10
20
30
40
% reduction in work index
Percent increase in plant throughput
Simulation studies to estimate the increased plant throughput rate with percent reduction in work index
50
Conclusion Lead-Zinc sulphide ore of R A Mine is responsive to microwave radiation. Water quenching immediately after microwave exposure causes substantial reduction in work index of the ore. Reduced work index results in reduction in grinding residence time that reflects grinding energy reduction. Increased grindability of ore causes increased plant throughput rate (predicted by simulation studies). Microwave energy has a potential role in commercial scale comminution and other mineral / metallurgical operations; Strong need for developing appropriate technology.
R.O.M. Fine Crush Plant
Crusher
Pri. Crusher
Coarse Ore Stock Pile
F O B
F O B
Microwave To Flotation Pri. Cyclone Sec. Cyclone Applicator Cavity Rod Mill Ball Mill
Typical Flow Sheet For Microwave Aided Ore Milling(Proposed )
Thank You !
Presented by: Ashish Kumar, Bala P Kamath, V V Ramarao (Speaker), D B Mohanty Central Research & Development Laboratory, Hindustan Zinc Limited
Introduction • •
Comminution in Mineral Beneficiation is an energy hungry process. About 50 % of the total energy is consumed during Comminution. Milling Measures to improve grindability of 43.6 % ore & attain energy savings were on trial since early 1900s;Thermally Assisted Liberation (T.A.L.) based on conventional heating was explored. Conventional T.A.L. was uneconomical on commercial scale. Recent researches in MICROWAVE & RF pioneered Microwave energy as an EFFECTIVE solution for Heating source.
Flotation & Filteration 32.3 %
Tailing disposal 10 %
Crushing 13.2 %
Others 0.9 %
Microwaves & Mineral Processing
Percy Le Baron Spancer – 1st to provide the idea of Heating by Microwaves in 1946.
Microwave energy is a form of Electro Magnetic Radiation having frequency between 3000 MHz to 3000 GHz. – Common applications of microwaves: communication; heating; – Frequency bands for microwave heating application in India is 2450±50MHz.
Ore constituents have different thermal & mechanical properties (thermal expansion coefficients, microwave absorption coefficients); Microwave irradiation Increased ore grindabilty
Differential heating of ore minerals
Developing stress
to create trans-granular & inter-granular cracks / micro-fractures
Absorption of microwave is Characteristic phenomenon of respective Mineral. For example, presence of sulphides, oxides and graphitic carbon enhances fracture formation.
Breakthrough concept for various industries that consume large amounts of energy including mineral processing, cement etc.
MICROWAVES
Applications of Microwave Variety of applications of microwave heat in several industries are in practice like: – – – – – – – – –
Drying of food items (Tea leaves, seeds, edible items) Hospital sanitation Sprouting Vulcanization of rubber Carbon reactivation Pressure leaching Roasting Sintering Rocks & Ore comminution
Background for Present Work •
Hindustan Zinc Limited is a Vedanta Group company;
•
CRDL is for HZL’s R&D;
•
Technology cell at CRDL has decided to adopt microwave energy use as a step change technology in its road map.
•
Work on Microwave aided comminution project started during 2005; benefits targeted are – Increased mill throughput – Reduced grinding energy through reduction in the ore work index.
COPPER SIIL KCM
VEDANTA M INIU M U / AL CO BAL CO MAL
ZIN
C& LE R& HZL AD CR D DL
Rampura Agucha Beneficiation Plant EXISTING RAMPURA AGUCHA – 6100 T.P.D. LEAD/ZINC CONCENTRATOR FLOWSHEET additional fine ore bin
Pri.Cyc.D20
R.O.M.
Primary Crusher
Sec.Cyc.D15
Fine Crush Plant 3 Rod Mills Fine Ore Bin Active 4,500T (Each)
Coarse Ore Stock Pile Active less than 9,000T
115
3 Ball Mills
110
7 Lead Roughers OK-16 10 Lead Scavengers OK-16
2 Zn. Conditioners
Pb Conditioner
2 Zinc Roughers 9 Zinc Scavengers OK-38
8 Zinc Roughers OK-38
140 139 153
177
181
178 Pb 3-Stage Cleaning
Zn 4-Stage Cleaning
Regrind Cyclones
151
148
D15
145
196 193 Pb Conc.Thickener
190
14 M Dia
Regrind Mill To Reclaim Water
187
162
Pb Stock Tank
224
222 To Reclaim Water
Zn Conc. Thickener 14 M Dia
249 252
Tailing Thickener 55 M Dia
7 Zn Filter Presses PF25
1 Pb Filter Press PF25
To Reclaim Water
288
16 M Dia Neutralization Tank
254
247 Zn Stock Tank
282 Zn Conc. Stock Pile TAILING DAM
Pb Conc. Stock Pile
Microwave Experimental Work Preparation of sample: 3 kg representative samples from plant rod mill feed were prepared mixing ore size fraction in the range –19 mm to + 2 mm in the same size proportion as in plant rod mill feed. (minus 2 mm size fraction discarded in accordance with previous observations) Grindability studies: Laboratory ball mill was used for wet grinding with 3 kg sample each time at a pulp density of 60% solids (by wt); ground material size distribution is known through wet sieving; Observations are: o Effect of microwave on particle size distribution under water quenched & unquenched conditions w.r.t. unexposed samples. o Effect of microwave on work index of ore. The relative work index of the ore was calculated using Berry & Bruce formula.
– –
Wi : work index kW.h/t; r and t refer for reference and test samples; P and F refer to 80% passing of the product and feed stream.
Experimental Work
….contd.
o Effect of microwave on the grinding time, which is directly proportional to the saving in grinding energy of the ore.
Simulation studies – Prediction of mill throughput increase for reduction in ore work index; o JKSimMet comminution software o Microwave irradiation (with quenching) at different time/intensity ranges for using different work index values. o Simulations predicted Throughput changes for same P-80 size;
(more finer size for same grinding) Average of cumulative wt% passing
94 92 y = -0.9646Ln(x) + 95.346
90
y = -0.8184Ln(x) + 91.935
88
y = -0.9906Ln(x) + 92.559
86 84 0
50
100
150
200
250
300
350
400
450
Sieve size (in mesh)
Blank
UQ AVG
Q AVG
Log. (UQ AVG)
Log. (Q AVG)
Log. (Blank)
Trend line (semi log) for average particle size distribution of R A Mine samples under water quenched, unquenched & unexposed conditions
60
(more grindability with more exposure)
% reduction in work index
50
40
30
20
10
0 0 Unexposed
10
20
30
40
50
60
70
Exp osure time (min)
% Reduction in work index
Effect of microwave exposure for different time intervals on work index of ore
% cumulative pass by 200 mesh
Microwave & Grinding Time
100 90 80 70 60 50 0
10
20
30
40
50
60
70
50
60
70
50
60
70
Time of grinding (min)
•
More finer fraction generated for irradiated & quenched fractions than non-irradiated (normal) fractions – 100 #, 150 # & 200 # (for same grinding time more finer product & for same product size reduced residence time)
Unexposed
Exposed
100 % cumulative pass by 150 mesh
Plot of % passing fraction at different particle sizes in ground product for different grinding times – Irradiated & quenched – Non-irradiated
90 80 70 60 50 0
10
20
30
40
Time of grinding (min) Unexposed
% cumulative pass by 100 mesh
•
Expos ed
100 90 80 70 60 50 0
10
20
30
40
Time of grinding (min) Unexposed
Exposed
10
% increase in plant throughput
8
6
4
2
0 10
20
30
40
% reduction in work index
Percent increase in plant throughput
Simulation studies to estimate the increased plant throughput rate with percent reduction in work index
50
Conclusion Lead-Zinc sulphide ore of R A Mine is responsive to microwave radiation. Water quenching immediately after microwave exposure causes substantial reduction in work index of the ore. Reduced work index results in reduction in grinding residence time that reflects grinding energy reduction. Increased grindability of ore causes increased plant throughput rate (predicted by simulation studies). Microwave energy has a potential role in commercial scale comminution and other mineral / metallurgical operations; Strong need for developing appropriate technology.
R.O.M. Fine Crush Plant
Crusher
Pri. Crusher
Coarse Ore Stock Pile
F O B
F O B
Microwave To Flotation Pri. Cyclone Sec. Cyclone Applicator Cavity Rod Mill Ball Mill
Typical Flow Sheet For Microwave Aided Ore Milling(Proposed )
Thank You !
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