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CLOSE THIS BOOKSmall-Scale Production of Portland Cement (HABITAT, 1993, 92 p.)
APPENDIX III. CASE STUDY: PERFORMANCE OF A TYPICAL OPERATING VSK-BASED CEMENT PLANT
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VIEW THE DOCUMENTAppendix III-A. Data on quality of raw materials, fuel, clinker and cement, and performance of unit operations

Small-Scale Production of Portland Cement (HABITAT, 1993, 92 p.)

APPENDIX III. CASE STUDY: PERFORMANCE OF A TYPICAL OPERATING VSK-BASED CEMENT PLANT

This is a small-scale cement plant in the central part of India. Based on CRI-MVSK technology, this plant was set up and commissioned in 1987 and has been operating continuously since then. Its performance is monitored on a regular basis in the manner described in chapter XII, and the feedback on the proforma as given in annex I is received regularly. The plant has a capacity of 100 tpd, comprised of two VSK kilns of 50 tpd each.

For a typical month, the total production was found to be 2766 tons. This corresponded to a capacity utilization of 90 per cent. The details of the quality of raw materials and fuel, and clinker and cement quality, as well as the performance of the various unit operations, are shown in appendix III-A. The plant uses cement-grade limestone from its captive mines, and clay from a nearby deposit, both conforming to the requirements for the process as recommended. Coke-breeze, with a calorific value of about 4000 kcal/kg, is used as fuel. The typical raw-mix proportions are 79 per cent limestone, 9 per cent clay, and 12 per cent coke-breeze as fuel which form nodules. No additives are required.

In a vertical-shaft kiln, if the burning of nodules is not thorough and uniform, the resulting clinker may be dusty and contain unburnt clinker and also cause a higher percentage of free-lime. The actual raw meal as fed to the plant is maintained close to the designed raw mix and moduli values are controlled within a desirable range. As a result, the clinker produced is well burnt and the free-lime is restricted to 1.96 per cent in clinker and 2.72 per cent in cement; nearly 99 per cent of clinker is found to be well burnt, indicating a thorough and uniform burning process in the plant.

On the basis of installed capacity, the availability of the kiln was ensured in the particular month. Kiln down-time was mainly due to power cuts and process stoppages. Preventive maintenance was carried out at the time of power cuts. The capacity utilization, therefore, for the month was of the order of 90 per cent which is considered to be good. The specific heat consumption was 760 kcal/kg of clinker and the specific electric power consumption was 115 kWh/ton of cement. The cost of production of cement was reported to be Rs 1360 (about $US45) per ton.

Appendix III-A. Data on quality of raw materials, fuel, clinker and cement, and performance of unit operations

Quality of raw materials and fuel:

Item

Chemical analysis and constituents (percentage)


CaO

SiO2

Fe2O3

Al2O3

MgO

LOI

Ash

Volatile matter

Limestone

48.14

7.80

1.62

2.45

0.60

38.85

-

-

Clay

7.38

46.59

12.01

15.56

1.19

15.41

-

-

Additive - I




Nil





Additive - II




Nil





Fuel

Coke-breeze

(specify type)

2.44

18.54

4.27

7.56

0.50

65.12

34.88

7.12

Raw-mix proportion (percentage)

Limestone

Clay

Additive - 1

Additive - II

Fuel

79.0

9.0

Nil

Nil

12.0

Quality of clinker

Burnt

(percentage):

98.93

Unburnt

(percentage):

0.65

Dust

(percentage):

0.42

Litre weight

-g/l:

1180

Chemical analysis (percentage)


Designed raw meal

Actual raw meal

Clinker

Cement

CaO

38.89

38.62

64.82

60.42

SiO2

12.57

12.49

21.32

21.58

Al2O3

4.25

4.06

6.42

6.21

Fe2O3

2.87

2.84

4.37

4.07

LOI

39.92

39.98

0.85

2.42

MgO

0.64

0.70

1.18

1.21

SO3

-

-

0.21

2.04

I.R

-

-

0.81

1.98

Free CaO

-

-

1.96

2.72

Moduli values





SM

1.77

1.81

1.97

1.91

AM

1.48

1.43

1.47

1.52

LSF

0.92

0.92

0.92

0.91

LC

-

-

30.46


Physical analysis of cement


Fineness (in blaines) cm2/g:

3592

Setting time (minutes)



Initial:

60


Final:

135

Soundness



Le Chatlier expansion (mm):

0.3


Autoclave expansion (percentage):

0.21

Compressive strength (kg/cm2) of standard cement: mortar, at



3 days

290


7 days

380


28 days

506

Output for the month

Equipment

Rated capacity (tph)

Running time (hrs)

Output (tons)

Crusher

15

371.00

3 568.82

Raw mill

12

385.50

4 517.50

MVSK - I

2.08

487.58

1 345.72

II

2.08

511.50

1 420.28

III

-

-

-

Cement mill

7.50

418.00

2 875.82

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