ENVIRONMENTAL IMPACT OF THERMAL

POWER PLANTS

DR.M. H. FULEKAR

PROFESSOR &DEANSchool of Environment and Sustainable Development

&

DIRECTOR

Central University of Gujarat, Gandhinagar

Thermal Power Stations

At present, about 55% percent of total electric power produced in India is obtained from thermal power stations, most of which use Coal as a fuel

Trends in Coal Consumption for Power GenerationIndia Coal Production Year wise(1980-2011)

India Coal Consumption Year wise (1980-2011)

The present coal consumption in Thermal power stations results in adding an estimated 12.21 million tonnes of Fly Ash into the environment a year, of which a third goes into the air rest is

Characteristics of Fly ash

Analysis of Indian Coals on Air-dried Basis

Analysis of Indian Coals on Air-dried Basis

Continued ->

Chemical Composition of Indian Coal Ash

Continued ->

Chemical Composition of Indian Coal Ash

Composition of Coal and Fly Ash in ppm

Classification of Trace Elements present in Fly Ash into Three categories

• Melt Becoming Fly Ash or Slag- Al, Ba, Ca, Ce, Co, Eu, Fe, Hf, K, La, Mn, Pb, Sc, Sm, Sr, Ta, Th, Ti

Class I: Elements that form melt instead of volatilizing in

a combust ion zone

• Condense or absorb on the Fly Ash as flue gas cools leading to depletion of slag and concentration of Fly Ash- As, Ce, Cu, Ca, Pb, Sb, Se, Zn

Class II: Elements that are volatilized on combustion

• Hg, Se, Cl, Br

• Cr, Sc, Na, Ni, U, V are intermediate in behavior and placed between classes I and II

Class III: Elements that remain completely in gas

phase

Concentration of Heavy Metals in sized Fractions of Fly Ash

Heavy Metal Concentration in Pulverized Coal and Corresponding Fly Ash Used as Thermal Power Stations (Average Metal Concentration µg/g )

Fly Ash Disposal

Dry Disposal of Fly Ash on Open GroundsWet Disposal of Fly Ash into Ash

Pond/River

Air Pollution by Fly Ash

Air pollution from Coal-fired Power Plants is caused by the burning of Coal Inhalation of smaller particles as well as larger particles pose a major health hazards . Presence of Fly Ash particles causes serious environmental contamination

Fly Ash pollution at the Coal-fired Power Stations is found within the house, and particles which are spewed out of the chimneys can be carried by winds for several miles, leaving in its wake a thin carpet of black particles on roads, trees, houses, agricultural lands, water systems and even foodstuff

On combustion of Coal many of the naturally occurring trace elements (present in coal) get enriched in the fly ash, which in turn get deposited around the industry upto several tens of kilometers distance

Trace Elements Concentration of Typical Indian Coal and Fly Ash Samples (4)

Trace Element Concentration

Elemental Concentration in Fly Ash

*The table demonstrates that 83% Chromium; 84% Magnesium; 50% Nickel; 35% lead retained in Fly Ash and rest of the quantity (unaccounted) of these metals is possibly released in the atmosphere

Effect of Fly Ash Water System

Location of Sampling Stations in Ash-Effluent Drainage System

Case Study: Ash Effluents Along Stream Bed Flow To Jamuna River

Release of Trace Elements in Ash Effluents along Stream Bed Flow to Jamuna River

Key

A) Effect on River

B) Effect of Fly Ash on Pond

•Ash Effluent is allowed into impounding lagoons or ponds, where the dissolved and suspended material carried by the effluent from the settling basin creates Environmental impact of Fly Ash Disposal

•Sluicing precipitated Fly Ash to the settling basin will contribute additional factors which may promote environmental stress and also pose potential toxicity to biota in the drainage system

Location of Sampling Stations in Ash Effluent Disposal Basin

River and Sea Pollution Due to Fly Ash Effluent Disposal

Outlet reaching the river

Effluent drainage pipes Ash laden water

River water Contamination

River Contamination

Sea Contamination

Leachability and Solubility

The Movement of Toxic Elements through the Geo-cycle and their Availability to

Microorganisms and other plants and animals

Soil Contamination by Fly AshChemical Composition of Fly Ash and Soil

Chemical Composition of Fly Ash and Soil

Continued ->

Physicochemical Characteristics of Fly Ash Leachetes

Heavy Metal Concentrations in Fly Ash Leachetes at Various Concentrations

Rhizofiltration Of Heavy Metals (Cd, Pb and Zn) FROM Fly Ash Leachates Using Water Hyacinth (Eichhornia crassipes)

CASE

STUDY

Concentration of Cd, Pb and Zn (μg g-1dry wt) accumulated in the roots and shoots for 30 days upon exposure fly ash leachates

Concentration of Cd, Pb & Zn after 0th, 1st, 7th, 14th, 21st &30th day of expt

Heavy Metal Concentrations (mg/L) in various percentages of Fly Ash Leachetes

Variation in Heavy Metal Concentrations (mg/L) in various percentages of Fly Ash

Leachetes

Cd, Pb and Zn accumulation in the dry biomass of roots and shoots of Eichornia

plants

Removal % of heavy metal (Cd, Pb, and Zn) from 10%, 20% and 40% fly ash leachates after 0th, 1st, 7th, 14th, 21st and 30th day of treatment

Name Formula Percentage

Silica SiO2 62

Alumina Al2O3 26

Iron oxide Fe2O3 63

Calcium oxide CaO 1.13

Magnesium oxide MgO 0.49

Sodium oxide NaO2 0.28

Potassium dioxide KO2 1.28

Titanium dioxide TiO2 1.80

Phosphate Pento-oxide P2O5 0.40

Sulphate SO4 0.36

Rhizofiltration of Heavy Metals from Coal Ash Leachate

Table 1: Chemical Composition of Fly-Ash

Case Study:

Element Concentration in ppm Element Concentration in ppm

Coal Fly - ash Coal Fly - ash

Na 300 1300 Se 22.9 106

K 2075 18275 Zn 540 2027

La 47.6 238 Fe 20890 106670

Ce 30.2 145 Ta 1.5 5.1

Hg 11.0 48 Co 33.4 128

Pb 1.8 8.1 Eu 1.0 5.6

Th 5.3 25 Sn 0.065 2.29

Cr 62.8 404 Au 0.14 0.69

Hl 7.1 32.6

Table 2: Trace Elements Concentrations of Typical Indian

Coal and Fly-Ash Samples

Coal Ash

Concentration

pH DO TDS E.C. Sulphate

(g/L)

Phosphate

(g/L)

Ammonia

(mg/L)

Alkalinty

(mg/L)Initial readings

0% 8.05 4.5 0.2 0.33 6 13.2 1 0.48

5% 11.5 4.9 0.39 0.6 6 14 42 0.48

10% 12 4.6 1.162 1.768 11 13 40 0.48

20% 11.5 3.1 1.51 2.23 10 10.8 38 0.48

30% 10.57 2.9 2.14 3.25 9.6 14.4 31 0.48

40% 10.85 2.5 2.92 4.45 12 9.8 24 0.48

First week

0% 8.07 4.5 0.22 0.36 5 12 1 0.48

5% 8.03 2.8 0.665 1.012 6 13 45 1.6

10% 7.87 2.7 1.108 1.682 6.2 10 43 1.6

20% 8.04 2.3 2.2 3.35 7.2 9.9 39 0.88

30% 7.7 2 3.45 5.25 15 9.3 35 0.88

40% 7.09 1.5 3.63 5.53 18.8 8 29 0.56

Second week

0% 8.1 4.9 0.18 0.4 5.2 13.8 1.2 0.48

5% 8.12 4.7 1.06 1.62 6.2 13.1 40 0.88

10% 7.94 4.5 1.38 2.12 9.2 10.9 42 0.88

20% 8.02 4 2.48 3.78 7.2 9.7 40 1.12

30% 8 3.2 3.53 5.39 15 9.9 30 0.88

40% 8.68 3.1 4.02 6.12 18 8.5 25 0.72

Third week

0% 8.06 3 0.23 0.5 6.4 34.2 1 0.47

5% 8.57 4.9 1.25 2.04 16 27.2 49 0.8

10% 8.67 4.7 1.9 2.88 9.6 26.6 45 0.88

20% 8.42 4.4 3.67 5.56 9.6 24 43 1.04

30% 8.39 4.3 4.68 7.3 16.8 24 39 0.72

40% 8.68 4.2 6.5 10.03 19.2 25 29 0.96

Fourth week

0% 8.06 3 0.26 0.65 6.8 17.4 1.6 0.46

5% 8.05 3.7 0.646 0.981 7.2 17.4 62 0.72

10% 7.18 3.8 1.76 2.69 11.2 16 58 0.56

20% 8.11 4.6 1.909 2.89 16.8 12 46 0.56

30% 7.6 4.9 2.58 3.92 18.2 15.2 44 0.56

40% 7.9 5.1 2.74 4.16 19.6 11.8 33 0.72

Table 3: Parameters 0f Coal Ash Leachate at various Concentrations of

Coal Ash and Different Time Intervals

Coal ash percentage Zn

(ppm)

Cr

(ppm)

Cu

(ppm)

Water hyacinth

0 3.23 - -

5 3.76 - 0.31

10 2.76 - 0.3

20 3.3 - 0.25

30 3.29 - 0.32

40 6.25 0.25 0.3

Duckweed

0 3.22 - -

5 4.53 0.25 0.3

10 4.14 0.25 0.27

20 3.56 0.25 0.35

30 4.34 0.25 0.61

40 10.65 0.28 0.25

Pistia

0 8.6 - 0.37

5 16.33 0.25 0.5

10 9.83 0.26 0.52

20 11.34 0.26 0.3

30 7.58 0.53 0.4

Table 4: Results of Uptake of Heavy Metals by Aquatic Plants

Bioaccumulation

Fig: Zn, Cr, Cd accumulation in the dry biomass of plants A (Water hyacinth), B (Duck weed)

and C (Pistia) cultivated in hydroponics media containing different coal ash percentage

8.6

16.33

9.8311.34

7.58

11.89

0.25 0.26 0.26 0.53 0.280.37 0.5 0.52 0.3 0.4 0.47

0

5

10

15

20

0% 5% 10% 20% 30% 40%

(Co

nce

ntr

atio

n in

pp

m)

(Coal Ash Percentage)

C (Pistia)Zn Cr Cu

3.22

4.53 4.143.56

4.34

10.65

0.25 0.25 0.25 0.25 0.280.3 0.27 0.35 0.61 0.25

0

2

4

6

8

10

12

0% 5% 10% 20% 30% 40%

(Co

nce

ntr

atio

n in

pp

m)

(Coal Ash Percentage)

B (Duck weed) Zn Cr Cu

3.233.76

2.763.3 3.29

6.25

0.250.31 0.3 0.25 0.32 0…

0

1

2

3

4

5

6

7

0% 5% 10% 20% 30% 40%

(Co

nce

ntr

atio

n in

pp

m)

(Coal Ash Percenrage)

A (Water hyacinth)Zn Cr Cu

Fly Ash Utilization

Coal fly ash management poses a serious environmental problem for India and requires a mission-mode approach

Considerable research and development work have been undertaken across the country towards confidence building and developing suitable technologies for disposal and utilization in construction industries

As a result, fly ash utilization in the country has increased from 1 million tonneper year to more than 45 million tonne/year during 2005

Utilization of Fly Ash

Fly Ash Bricks/ Blocks

Cellular Concrete Products

Light Weight Aggregates

Concrete and Mortar

Cement Making

Asbestos Products Manufacturing

Road Construction

Embarkment/ Land Development

Controlled Low Strength fill

material (CLSM)

Use in Agriculture

Mine Filling

Manufacture of Fertilizer