KOTA STONE SLURRY PROBLEM AND POSSIBLE SOLUTIONS- A. Hussain

India has largest reserves of dimensional stones in the world and this makes suo-moto largest producer of dimensional stones in the world. We have a wide spectrum of dimensional stones including Granites. Marbles of different colours and textures, Sand stone, Lime stone, Slates and Quartzites spreaded all over country. In today’s reference India alone share about 32 percent of world’s total dimensional stone output, with total annual production of combined range exceeding 185 million tones per year. Rajasthan is leading producer of dimensional stones contributing about 90 percent of country’s total Marble, Sandstone and Kota stone production. The estimated reserves of important dimensional stones in Rajasthan are given in table – A.

Table – A

Estimated Reserves of Dimensional Stone in Rajasthan (Million Tonnes)Marbles 1100 Million TonnesCeranites 1128 million tonesSand Stones 900 million tonesFlaggy Lime Stones 1800 million tonesSlates 50 million tones

A simple and most generalized chemical composition of important dimensional stones is given in table –B

Table – BChemical composition of Marble, Granites and Limestone

Chemical composition

Marble (Percentage)

Granite (Percentage)

Limestone (Percentage)

Lime 28-32 1-4 38-42Magnesia 20-25 0.5-1 4-6Ferrons and Fernic oxides

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Mining and polishing of dimensional stones generate a large quantity of waste and fine dust, which creates a serious environmental problem. According to international Journal of Engineering sciences and research teachnology the mining and processing activities of marble in Rajasthan alone is produching about 50,00,000 Mt of marble slurry in a year out of 1.5 to 2.0 million tones of total waste generated out of marble mining in the state. The waste slurry contains about 40,00,000 Mt of water and rest 10,00,000 Mt of calcareous line particles. This volume of gigantic slurry is released from 1000 gang shaws and thousands of stone cutters operating in the state marble producing zones. This marble waste is indestructible and harmful to common man, animals and vegetation creating aesthetic problems. This is a major threat to environment.

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India has over 85,600 million tones of calcareous stones (marble and other lime stone based stones) and the annual production of all dimensional stones is over 185 million tones and Indian stone cutting and polishing industry produce around 17.8 million tones of solid calcareous waste per annum. The accumulated waste is of the order of 250 million tonnes. Apart from the entire calcareous stones, in this paper we want to focus on Kota stone mining and processing problems in specific, thought Kota stone is part of overall calcareous stones spectrum and face similar environmental problems. Table – C provides chemical composition of all the Indian calcareous stones (Dimensional stones)

Table – CChemical compesition of Indian calcareous stonesIngradient Percentage by weight

Marble Limestone GraniteCalcium oxide 35-40 38-42 1-3Silica 3-25 15-18 73-76Alumina and Ferrous oxide

9.12-11-76 1.02-1.53 18.78-21.12

Potassium and sodium oxide

0.06-1.12 0.35-0.62 5.12-7.15

Magnesium oxide 2-3 13.14-15.32 0.04-0.09Loi 38-43 32-34 <0.5

Kota stone as is better known in building stone terminology, is basically a calcareous sedimentary rock available in a number of colours (blue, green, brown, grey etc) and textures. The stone deposits are well stratified and split easily all along the well formed weak plans facilitating smooth and well textured homogenous stone panels in various thickness.

Kota and Jhalawar districts of Rajasthan and neighbouring Madhya Paredsh district of Neemach have 1800 million tones of this splittable dimensional stone reserves and a typical chemical analysis of this type of stone is given in Table – D

Table – DChemical composition of Kota Stone

Calcium oxide 37.30%Magnesium oxide 4.13%Sodium oxide 1.21%Postssium oxide 0.40%Aluminium Trioxide 1.37%Ferrous oxide 0.86%Titanium oxide 0.05%Silica 24.90%Loi 31.94%

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Generation of Stone Waste:In specific to stone powder generation, there are two types of powder wastes coming out of Kota stone mining ie-

1. Quarrying or sawing from the insitu stone mining sites and 2. Cutting and polishing wastes from polishing industries.

During processing of the stone, different size cuts are made in the insitu stone benches, facilitating tiles or slabes of various sizes and thicknesses (usually 2 to 4 cms thick) using diamond blades. A constant stream of water is thrown over the blades, while cutting is in progress to cool the blades and to remove the dust produced during cutting operation. The waste water from this operation is in a considerable large quantity and highly alkaline in nature.

(Fig. 1 : Kota stone mining in progress)

Quantity of slurry generation:The blades thickness of the cutting drums used in stone mining is about 5 mm and the longitudinal cuts are made at an intervate of 60 cms all along the productive benches. The slabes are further cut and dressed into 20mm thick slabes, and therefore out of every 25mm thick slabes production, 5 mms are converted into powder while cutting the stone to make slabes. This powder flows alongwith water as slurry.

To find the quantity of fine powder generation vis-à-vis the stone slabes production a number of tests were conducted. The slurry coming out of the operation, was channeled into a two compartment rock chamber, where the overflow of the first chamber was allowed to collect in the second chamber for recycling. The stone dust was trapped into first chamber as a white cake. Once the first chamber was filled up with the stone polish recycling was stopped and the dry-polish cake was loaded into tippers with the help of JCB machine, and weighment made at the weighbridge. A relationship was envoled between the weight of the collected dust and stone output, results are given in Table – E

(Fig. 2 : Waste dumps in Kota stone Mines)

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Table – E

(Results of stone output and waste generated in the form of dry dust)

S.No. Stones Quarried in MT Weight of Dry Dust generated MT Percentage1. 328 MT 50 15.242. 287 MT 40 13.933. 362 MT 55 15.194. 285 MT 40 14.005. 318 MT 50 15.72

Thus, normally 15% of the total weight of limestone produced is converted into fine powder slurry containing 35 to 45 percent of water content.

YEARLY QUNTUM OF KOTA STONE POLISH GENERATION AND ITS DISPOSALPresent level of Kota stone production is about 80 lakh Mt per annum, and consequent to its mining and processing a fine dust waste to the tune of 12 lakh MT is generated every year, out of which about 4 to 5 lakh MT of dust is disposed in the mined out areas, and rest all the waste is discharged into convenient places, including near by water streams, agricultural lands, govt. pasture lands, forest land ,road sides etc.

Disposal of this type of dust is affecting 5 to 10 hectors of prime land every year. So far, a considerable land has already been permanently damaged due to this activity

(Fig. 3 – Stone dust on agricultural land)

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ENVIRONMENTAL HARARD OF STONE DUST

Some of the ill effects of stone dust wastes are given as under –

1. The stone waste is indestructible 2. Dumping grounds gives repulsive dirty looks3. Land fertility of agricultural land is totally impaired 4. Loss of valuable top soil due to blanketing with dust 5. Contamination of rivers, nallas and other surface water bodies6. Slurry affects productivity of land due to decreased porosity water absorption and

percolation7. Slurry dumped areas can not support vegetation8. The fine particles of slurry gets entrenched into land capillaries and block ground

acquifers recharging.9. Drains and nallas are chocked due to setteling of fine dust and adjoining

agricultural fields are flooded with rain water, making crops losses.10. Dust nuisance11. Fine particles of slurry (size less than 363 micron) becomes air borne and causes

air pollution12. public out-cry against the dust nuisance

(Fig. 4: Washed out powder dust)

PROPERTIES OF STONE WASTE (POWDER)Some of the important physical properties of stone powder waste material are given in Table – F

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Table F(Physical properties of Kota stone dust)

Specific gravity 2.58-2.65Bulk Density 1568-1743 kg/m3

Water absorption 2-4 percentMax partical size 0.2 mmFineness Module 3900-4123 cm2/gmColour White

Kota stone it self is a soft stone having hardness between 3-4 (Moh scale) with density varying from 2.20 to 2.85 gms/cc and having compressive strength between 1800-2100 kg/cm2. It has low prosity and good weather resistant charactersistics.

APPLICATION POTENTIALITIES

Considering its harmfull impacts a number of exercises have been carried out by various organizations including Private Mine/Factory Owners Associations, to explore gainfull uses of stone dust. Some of the areas identified for potential uses are given as under-

1. Cement manufacturing2. Filler material in paper making3. Paints and poly propylene4. Soda production5. Blast furnace flux6. Acid neritralizer for industrial effluents 7. Agricultural soil amendment specialy to offset soil acidity8. Flue gas desulphuration in electric power generation stations9. Lime manufacturing10. Resin conglomerates for florring11. Wall coatings in buildings12. Chemical applications13. Cosmetics and pharmaceuticals14. Filler in concrete15. Paving material

Recycle and use of Kota stone dust in cement plants is still a research based issues. High silica is a point of consideration apart from logistical complexities. Experiments have shown that it is a good substitute for some of the material items used in road construction but public works departments as well other construction agencies have not shown much interest, mainly because of transportation cost considerations.In chemical segment, quality gypsum can be made from the slurry, but process cost in comparison to natural available gypsum is forbidding. Brick samples with cast size 230x125x75 mms were casted manually by mixing cement in various ratios and putting into moulding frames for a specified time intervals. The resultant bricks have shown compressive strength up to 30 to 50 kg/cm2. Hosever, the

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cost of processing is still an hindrance. We have tried mixture of Dust with white cement in various ratios, giving beautiful white tiles, but cost is an impairment.

SCIENTIFIC DISPOSALAs earlier said that lime stone slurry is a processing waste of Kota stone mining and dressing industry and its huge quantity to the tune of 15 percent of total production is dumped on empty lands, agricultural fields, pasture lands, rivers beds and road sides creating a number of serious environmental problems. The problem has to be tackled in two critical alternatives i.e. firstly by finding and using a compatible engineering utilization and second by adopting a scientific disposal.

Fig – 5: Slurry dumped into Nalla.

The scientific disposal can be practicised with a little enforcement of discipline in waste disposal system, and some of the recommendations are as under-1. The processing facilities are situated is a close area

designated as Kota stone extractive zone. This zone covers a part of Kota and Jhalawar districts. There are a number of working and abandoned quarries located in this zone. State mining and geology department should take initiative and fix some old workings in this zone and direct all the processing units to dump their slurry waste into these old workings, Processing Industries owned by the mine owners should be forced to dump the waste slurry into their own waste dump yards or re-use for reclamation programmes.

2. Stone processing units operating near Kota town should be given a specified land refill area, and should not be allowed to dump their waste slurry in all possible ways and means.

3. The slurry generated in the mining process should be channelized into two inter connected chambers. Where, the sediments settle into first chamber and clean water over flows into adjoining chamber, from there it can be recycled for cutting operations. The collected sediments in first chamber can be removed from time to time with the help of a JCB and tipper combination and dumped into waste dumps.

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Fig. 6: Water recycling

This will not only save water for recycling, this will also help in the reduction of water demand by re-utilization of water and also help in disposing slurry and lowering down the damage to eco-system.

Conclusion:

Kota stone slurry waste is indestructible and harmful to common man, animals and vegetation, creating aesthetic problems. This is a major threat to environment and efforts should be made to find viable engineering applications at the earliest. Till then, scientific disposal of the waste should be given top priority.

A. Hussain

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