SAND BENEFICIATION PROCESS DESCRIPIION

CHAPTER-2

SAND BENEFICIATION PROCESS DESCRIPTION

2.1 GENERAL

Silica (quartz) sand is used in glass manufacture. Quartz comprises '50-65% of the mix used to. make glass. The high purity of

dune sand makes it especially useful in glass manufacturing. The

quality of sand used for glass making is highly restrictive.

Specifications for glass sands generally require a specific range of

grain sizes which produce even melting. Chemically, the sands must

be over 98% pure silica and contain practically no impurities,

especially metallic oxides. As little as 0.001% metallic oxides will

impart colour to glass. Most glass companies prefer to have nearly

pure silica sand (99.5% or greater purity) to which they will add their

own desired special ingredients. This is particularly true in the case

of optical glass, which has very high silica and very low metal oxide

content.

2.1.1 SILICA SAND MINING

The activity of mining and quarrying covers underground and

surface mines, quarries and wells involving extraction of minerals and

also all the supplemental activities such as dressing and benefaction

of ores, crushing, screening, washing, cleaning, grading, milling,

floatation, melting and other preparations carried out at the mine site

which are needed to render the material marketable,

The mining activities in the country are governed by the Mineral

Conservation Development Rules (MCDR) 1988. Every license holder

of mining, lease shall take all possible precautions for protection of

environment and control of pollution while conducting prospecting,

mining, beneficiation or metallurgical operations in the area. Specific

provisions for proper removal and utilization of top soil, storage of over

burden and waste rocks, reclamation and rehabilitation of lands,

precautions against air pollution, noise and ground vibrations,

restoration of flora, discharge of toxic liquid, control of surface

subsidence have been provided under the MCDR. The Indian Bureau

of Mines collects the statistics on all these aspects under the above

rules.

2.1.2 SAND BENEFICIATION

,'

After the ore containing the desired material has been brought

to the surface, it is generally necessary to separate the wanted from

the unwanted constituents, and to create a more uniformly sized

material for subsequent processing. Such operations, collectively

referred to as beneficiation, are often carried out near the extraction

point, to minimize transport of low-value materials.

Beneficiation processes primarily directed towards resizing

include:

Milling (crushing, grinding)

Sizing (screening, centrifugation)

Consolidation (sintering, palletizing, brique'tting)

Beneficiation processes carried out with the object of removing

impurities or concentrating desired material include:

Wet processes

o Washing

o Leaching

o Flotation

o Dissolution or solvent extraction, followed by crystallization

or precipitation

o Filtration

o Electrowinning

o Ion exchange

Thermal processes

o Calcining

o Roasting

o Autoclaving

o Drying

Magnetic and electrostatic separation

The sand beneficiation process followed at the plant site near

Tada, under study, consists of the five distinguished steps:

Removal of trash/weeds or lumps (> 3 mm size) by scalping

vibrating screens.

Removal of over size (> 630 p) and under size (< 100 11 size)

sands by the principle of hindered settlement with water jets.

Attrition and washing with water to separate fines and clay

which is adhered to the sand particles.

Heavy mineral separation through the principle of density

separation from the sand in the spirals. Heavy minerals having

a specific gravity of greater than 2.6 will get separated from

sand having a specific gravity of 2.6.

Dewatering of the treated sand in a vibrating screen down to

15% moisture.

2.2 LOCATIOI AND ACCESSIBILITY OF THE INDUSTRY

The glass manufacturing industry of M / s . Saint Gobain India

Ltd., has the following components:

1. Silica Sand Minors: Silica sand is available in the mines

of Chintavaram, Ballavolu, Momidi, Yeruru and

Vellapalem situated at a distance of about 26 km from Gudur town, in Nellore district of Andhra Pradesh state.

2. Sand beneficiation plant: Sand beneficiation plant is

located at Karuru village in Tada Industrial Area (TIA) of

Nellore district of Andhra Pradesh state.

3. Float glasa factory: Float glass manufacturing unit, "the

Float" is located at Sriperumbudur town in Chengai-Anna

district of Tamil Nadu state, which is situated at a

distance of 60 km west-south west of Chennai.

The present study is concentrated on the application of EIA over

the sand mining area near Gudur and the sand beneficiation plant

situated near Tada.

2.2.1 Silica Sand Mines

Silica sand is available in the mines of Chintavaram, Ballavolu,

Momidi, Yeruru and Vellapalem situated about 26 krn from Gudur.

Gudur is on the Kolkata-Chennai National Highway No. 5

approximately 70 km from the sand beneficiation plant site at Tada

and 135 km from Chennai. The location map of the silica sand mines

is shown in Fig. 2.1.

lJ' ANDHRA PRADESH

Fig. 2.1 .loeation of Silica b d Mine8

9

2.2.2 Sand Beneficiation Plant

The sand beneficiation plant site is located at K a r u r u village,

Tada Industrial Area set up by Andhra Pradesh Industrial

Infrastructure Corporation (APIIC). The Industrial Development

Area (IDA) falls under Nellore district of Andhra Pradesh and is

actually located in the border of Nellore and Chittoor districts. Tada

Industrial Area (TIA) is located 5 krn south of Tada town and

approximately 60 krn from Chennai, adjacent to National Highway

No. 5 connecting C henna. and Kolkata.

The site is located approximately 70 krn from sand mining area

and 115 krn from float glass factory at Sriperumbudur, Tamil Nadu.

The sand beneficiation plant is 10 m above Mean Sea Level ( MSL ).

Total rainfall in the area is 1260 mm per annum, of which 770 mm

occurs during peak monsoon i,e., during October to December

months. The wind speed at Tada is considered same as in Chennai

which is 50 m/s as per IS 875. Tada comes under zone I1 for earth

quakes with a seismic coefficient of 0.02 as per IS 1893- 1984.

The area of the plant site is having non-uniform silty sand of l m

thickness on top followed by clayey sand. The location map of the

sand beneficiation plant is shown in Fig. 2.2.

2.3 DETAILS OF PLANT LAYOUT

The details of plant layout are shown in Fig. 2.3.

fig. 2.2 h t i o n Map of the Sand kneflciatbn Piant

11

Fig, 2.3 Details of Sand Beneficiation Plant Layout

The details of various units of the sand bencficiation plant are

shown in Table 2.1.

Table 2.1 Units of the Sand Beneficiation Plant

UNIT 1 .LAND AND SITE DEVELOPMENT Land Gate Compound Wall and Fencing Security Post (RCC) Partitions for site office Roads, RCC (Dump Hopper Area Roads with Asphalting

Roads with WBM Storm water drains 2. BUILDING / CIVIL WORKS .

Plant Building (Inclusive of Maintenance Area & Worker Amenities)

HT Yard Civil Works Dump Hopper Shed Dump Hopper tunnel (Truck unloading area) Shed for Scalping Screen Office block with toilets Toilet Block - Truck Drivers 2 Wheeler Parking Shed Car Parking Shed Instrumentation Room Including A/c LT Control Room DG & Compressor Room Oil storage yard - HSD- 20 k L Maintenance Shed - For Material Handling Equipment Weigh Bridge Control Room Equipment Foundations 3. SAND STORAGE AREA a) Civil Works Storage yard - treated sand (3700 MT) RCC Partition Walls for Treated Sand

RCC Partition Walls for Raw Sand Pad

Storage pad(WBM) - Raw Sand

PARTICULAR8

215 m x 321 m (17 Acres) 6 m x 2 m H t . 1080 m (Site 32 1 m x 2 15 m) 4 m x 3 m x 3 m ( H t . )

2500 Sq m 500m x 6m Wide % 300m x 1Om Wide 500 m x 6 m Wide 1500 m x 1 m x 0.6m (Ht.)

21 m x 25 m including mezzanines 1 5 m x 1 5 m x 6 m H t 1 5 m x 8 m 15x 1 5 m - 10mHt 15 m Long Tunnel, 5m Ht., 5m Wide 9 x 6 m - 5 m H t . 10 m x 10 m 3 m Ht. 5 m x 4 m x 3 m H t . 3 m x 1 0 m x 3 m H t . 4 m x 1 0 m x 3 m H t . 5 m x 5 m x 3 . 5 ~ 1 7.5 m x 9 m x 3.5 m 9 x 9 m - 5 m H t . _ 2 0 m x 1Sm -- - - - 15 m x 15 m x 5 m Ht.

5 m x Z m x 3 m 4 % af Equipment Cost

2 5 m x 4 0 m x 15mHt. Wall 20 m x 8 m Ht. x 0.3 m thick, 4 + 1 Nos. Wall30mx8mHt.xO.3m thick, 6 Nos. 110 m x 30 m, 12500 Tons

' Silos - Sand with Stairs & Bin Activator b) Equipment

-Treated Sand Inlet conveyor + Tripper . Incl Conveyor to Raw Sand Yard + Tripper 4. WATER RECOVERY Underground Storage Sump - Fresh water Sand basin (Excavation Only)

Pump House - Sand Basin Over Head Tank (Recycled Water) Water Tank, office block - (Sintek) . Thickner - Civil Structure Thickner mechanism / Flocculent Sys. Pump House (WRP - Below OHT - 1)

, Under Ground Sump (Recycled water) Under Ground Sump (Sump of Feed Pump to Thickner) Bore wells Incl. Pump B piping 5. PLANT AND MACHINERY Front End Loader Tipper Hydraulic Truck Unloader Dump Hoppers - RCC / Steel Vibrator feeders Weigh Belt Feeders Belt Weigher - Raw Sand Belt Weigher - Treated Sand Inclined Conveyor to silo Diverter chute at silo top - Motorised Conveyor feeder to Sump box Scalping Screen Conveyor to Screen Vats (Pump - Sumps) Slurry Pump for Unisizer Pump for Unishr upward Current (Water) Slurry Pump, HC - 1 Slurry Pump, To Flotation Cell Slurry Pump, HC-2 Feed

200 T

50 TPH 100 TPH (10 m, 165 m)

7 m x 7 m x 3 m, 150 k L 3000 CUM x 2 Nos. (30 m x 65 m x 1.5 m Ht.) 4 m x 3 r n x 4 m H t . 100 k L, 15 m Head 5 k L, 15 m Head 13mDIAx4mSWD

D i a 6 m x 3 m H t . 400 k L 40 k L

6"

FEL, 1.7 CUM 10 T

20 Tons 100 TPH 75 TPH 75 TPH 50 TPH 75 TPH

75 TPH 75 TPH x 3 mm opening 75 TPH

200 CMH : 1 + 1 Stand by 100 CMH 200 CMH : 1 + 1 Stand by 200 CMH : 1 + 1 Stand by 200 CMI-I : 1 + 1 Stand by

Slurry Pump, Primary Spiral Feed Slurry Pump, Cleaner Spiral Slurry Pump Thickner feed Pump, SB - UGS - 2 (Water) Pump, TKR - SB (Slurry) Clarified watcr pump to OHT - 1 Fresh water pump to Office Block OHT - 2 Fresh water pump - to Plant Bldg. OHT - 3 Sand Pile Drainage Slurry Pump Makeup water Pump to OHT - 1 Hydrocyclone

100 CMH : 1 + 1 Stand by 100 CMH : 1 + 1 Stand by 400 CMH : 1 + 1 Stand by 30 CMH 30 CMH 400 CMH 5 CMH 5 CMH 15 CMH 30 CMH 200 CMH

Drying pad with piping Dewatering Screen 25 TPH

2.4 RAW MATE- AND PRODUCTS

Silica sand is the basic raw material which is beneficiated and

sized between 100 p to 630 p, to obtain pure silica sand. A s the silica

sand is likely to be supplied from different sources with varying

qualities (impurities and sizes) the characteristics of the raw silica

sand from the various locations of the mines, may likely vary.

.

Dewatering Screen Coarse Rejects Conveyor Vibrating Feeder for DH - 3,4 Flotation Equipment Floating Cells Conditioners - Auto Float Blower Compressor Reagent Mixer, Tanks % Pumps Slurry Pump to HC - 3 6. ELECTRICALS DG sets 380 kVA x 2 No. SEB Cost - For 1 1 kV power Construction Power Plant Instrumentation 86 Controls

7. VALVES AND PIPING

8. UTILITlES AND OTHERS HSD Storage - pumps & piping Maintenance Equip B Facilities Laboratory Equip. 86 Facilities . X-Ray analyzer Weigh Bridge including civil works Lifting Gates for Truck entry

Office Equipment Industrial cabinets for workers Compressor Fire Extinguishers Air Ventilation system / DC System

On an average raw silica sand characteristics required is

presented in Table 2.2

2

50 TPH 25 TPH 75 TPH

5 Cell

Housed within the plant Housed within the plant Provided 200 CMH

Located within the plant

Major equipment8

Within the plant

20 KL Full fledged Already set up at Bangalore Available - 1 No. 30 T Hydraulic with common Power Pack

100 CFM, 7 KSC

Table 2.2 Characterhtics of raw sand

The raw silica sand is transported from the mines near Gudur

SiOz A h 0 3 Fez03 Ti02

NazO + K2O CaO + MgO

Loss on ignition Moisture

i

to the sand beneficiation plant near Tada. It is then subjected to

96 1.5 0.2 0.2 1 .o 0.2 0.2

15% maximurn

beneficiation at the plant. The product in the form of treated sand is

obtained. The characteristics of the treated sand fmm the plant are

such that the product is good for the manufacturer of high quality

glass. The characteristics of treated sand are shown in Table 2.3.

Table 2.3 Characteristics of treated sand

Components I Value (YO) 1. Chemical

SiO2 A1203 Fez03 Ti02

NazO + K2O CaO + MgO

< 98 < 1.5 (max. variability * 6.5% of absolute)

< 0.07 (wax. variability f 10.0% of absolute) < 0.1 < 0.1 < 0.1 < 0.2

The % of moisture < 4 2. Grain size distribution (%)

> 630 microns < 100 microns

Nil < 3%

3. Heavy minerals Total quantity < 0.05%

The quantity of raw materials required, products and

by-products obtained from the plant are presented in Table 2.4.

Table 2.4 Quantities of raw materials, products and by-products

2.5 SAND BENEFICIATION PROCESS

&No. 1.

2.

3. 4. 5. 6. 7.

Sand beneficiation process at the plant near Tada, involves

various stages, as given below:

Sand mining: Silica sand is mined at Chintavaram, Ballavolu,

Yeruru, Momidi and Vellapalem situated about 26 km from Gudur by

open stripping. The quantity of sand mined is about 1200 MT/day.

Material Raw,sand Rejects large size (> 3 mm 86 vegetation) Sand rejects > 630 p Sand rejects < 100 p Mineral matter Clay particles Product (treated sand)

Transportation: The mined sand is transported to Tada by trucks

having capacity of 9 to 16 tonnes. About 30 trucks are used for

transporting of the sand to the sand beneficiation plant at Tada.

Quantity (MT/ hour) 80

0.2

15 1.8 2.4 0.6 60

Receiving and Storage: .Sand is received through dump hoppers and

is sent to storage yard through tripper conveyor.

Sand feeding to process: The sand is fed through front end loader to

dump hopper from where the sand will be taken to scalping screen.

Scalping: Trash/weed or lumps bigger than 3 mm size are removed

by scalping screen.

Controlled silos: Screened sand is fed to control silos for feeding

uniformly at a rate of 75 to 80 tonnes/hour to sand beneficiation

plant. Two silos of 200 tonnes each are provided. This storage of

400 tonnes, will cater for nearly 5 hours of plant operation.

Sand Benefichation: The sand beneficiation process mainly

consists of

i) Over size removal

ii) Attrition of washing

iii) Heavy mineral separation and

iv) Dewatering and quality check

Over she removal: For the purpose of removing over size, unisizer is

used which works on the principle of hindered settlement. Water jets

acting from below, whose velocity can be adjusted, is used to separate

the sand into two fractions. The fraction greater than 630 j . ~ will settle

in the unisizer and discharged from below and the undersize less than

630 1 will overflow. This is achieved by setting the upward water

current in the controller of the unisizer. The under flow from the

unisizer having particle size greater than 630 p will be dewatered in a

dewatering screen and stored on a open pad for ,natural drying. The

overflow containing less than 630 p sand particles is fed into a vat and

pumped to a hydrocyclone for dewatering.

Attrition and washing: The sand slurry from the underflow of the

hydrocyclcone is fed into an Attritor wherein the clay adhering to the

sand particles will be separated. The attrited sand is pumped to a

hydrocyclone for the removal of clay and fines less than 100 y size.

Heavy mineral separation: The underflow of the hydrocyclone is fed

into the distribution box of the Rougher Spirals for removal of heavy

minerals. This works on the principle of density separation. Heavy

minerals having a specific gravity of greater than 2.6 will get separated

from sand having a specific gravity of 2.6. The good material is

collected in a vat and this slurry is again fed into Cleaner Spirals ibr

further separation of heavy minerals.

Dewatering: The good product from the spiral is fed into a vat, water

is added in the required quantity, and pumped through a slurry pump

to a hydrocyclone. Here the level of moisture is reduced to 25%. The

underflow from hydrocyclone is further dewatered in a Vibrating

Dewatering Screen down to 15% moisture.

Natural drying and storage of products. The treated sand coming

out of the processed plant at 60 tonnes/hour is dewatered using

dewatering screen to reduce moisture to less than 15% and is

conveyed and stored in a product storage shed.

Treated sand handling: The dried sand after inspection and

clearance is loaded on to trucks for dispatch for float plant at

Sriperambudur .

The schematic manufacturing process flow diagram is presented

in Fig. 2.4.

Fig. 2.4 Schematic Flow Diagram of Sand Beneficiation Process

2.6 MATrCRUL AND WATER BALANCES

Material balance: The material balance in the sand beneficiation

process is presented in Fig. 2.5.

Raw sand (80.0 TPH) Sand rejects (0.2 TPH) (> 3 mm)

uni-b Sand rejects (15 TPH) (> 630 pm)

Hydrocyclone ---+ Sand rejects (0.6 TPH) (< 100 pm)

Hydrocyclone ----+ Sand rejects (1.2 TPH) (100 pm) 1 63.0 TPH

Rougher Spiral Sand rejects (1.2 TPH)

I Cleaner Spiral Sand rejects (1.2 TPH)

Sand rejects (0.6 TPH)

Treated sand

Fig. 2.5 Mass balance of Materials

Water Balance: The water balance in the sand beneficiation process

is presented in Fig. 2.6.

4 -1 ~nisizcr 4 d , hour aih reject rand -I 59.5 m3bow I

m3/ hour with rcjcc sand +

120.6 m3hour 140.7 m3 I how

Hydrocyclone 121.1 m3 I hour with reject rand

m31 hour with reject sand -4

! hour with reejct rand -r

127.8 m3 hour - 1 0 9 3 m 3 a w

*.~m31h,r 2.5 m31 hour

reject sand

k 2 m3 ! hour cvaporrtron loas W 401.9m3/hourw . -.. 4

'E *12.9 rn3/ hour Fresh water

Fig. 2.6 Mass balance of Water

2.7 RAW WATER USAGE

The plant presently requires water to an extent of 200 m3/day

as make u p water. This amount of water is required for various losses

of water a t various locations in the sand beneficiation process. The expected loss of water at various locations is shown in Table 2.5.

Table 2.5 Expected loss of water at various location8

The water requirement for the entire sand beneficiation process

is 410.3 m3/hour. The total recycled water from the beneficiation

process works out to 401.9 m3/hour. The total loss of water at

various locations amounts to 12.9 m3/ hour.

. S.No.

1.

2.

3.

4.

5.

Therefore, the quantity of make up water required is

12.9 m3/hour or 200 m3/day, considering 16 working hours/day.

This quantity of water is extracted from the bore well located at the

plant site and is fed into the sand beneficiation process as fresh water.

2.8 LAND

Location

Loss in sand basin with clay

Evaporation losses

Water loss in dewatering screen

Net loss of water .

Make up water quantity required

The sand beneficiation plant is spread on area of 22.5 acres of

land. The land utilization is presented in the Table 2.6.

?

Quantity (m3fhour)

2.5

2.0

8.4

12.9

200 m3 /day

Table 2.6 Land utilization of the plant site

The plant presently employed 90 persons on regular basis. Out

of these 6 Nos are officers, 17 Nos are technical people and others are semi skilled persons.

2.10 ELECTRICAL POWER

Area provided In acres

2.24 5.54 4.48 2.50 7.74 22.50

&No.

1. 2. 3. 4. 5.

C

The power requirement for the existing sand beneficiation plant

for average running load is 694 kW with a contracted demand of

500 kVA and transformer rating 1000 kVA. The connected load to the

plant is 1004 kW.

Category

Plant and buildings Storage area Green belt Roads and paths Space available for future expansion

Total

Based on the critical load required to run the process plant

2 Nos of D.G. sets of 380 kVA were provided.

2.11 CAPITAL

The total capital investment for the industry is Rs. 1680 lakh.

Out of this, Rs.175 lakh was invested on land and site development,

Rs.337 lakh on building and civil works, Rs.1108 lakh on plant and

machinery, and Rs.60 lakh was invested on pollution control and

treatment facilities which comprise dust collection systems and

effluent treatment plant.