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Technical Cement Forum / High fuel consumption

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asim 06/01/2011 04:08:16

High fuel consumption

Dear All,

Here is some data to study, Actually we have high consumption of coal, although the GCV of raw coal is reasonably good but NCV of the same coal remarkably low. what are the reasons. ?

ASIM

Grinded Coal Results

Loca & South African Coal(imported)

Ratio (1 : 1)

Analysis of blended coal

Moisture, % 2.11

Residue on 90 µm sieve, % 10.64

Ash, % 19.17

Volatile Matter, % 22.75

Sulfur, % 1.34

GCV, Kcal/kg 5903

NCV, Kcal/kg 5778

South African Coal

Analysis pure South African coal

Moisture, % 2.08

Residue on 90 µm sieve, % 9.60

Ash, % 14.93

Volatile Matter, % 27.81

Sulfur, % 0.60

GCV, Kcal/kg 6206

NCV, Kcal/kg 6035

Local coal analysis

Moisture, % 10.5

Ash, % 17.06

Volatile Matter, % 12.3

Sulfur, % 2.0

GCV, Kcal/kg 6523

NCV, Kcal/kg 6275

Engr.Amin 06/01/2011 06:23:37

The difference between GCV and NCV looks ok as the South African coal haveing about 4 to 5 % hydrogen. SO i feel there is no big differnce. e.g if coal having 4.5 % hydrogen then the heat taken by water for steam is ~ 236 Kcal/Kg, if South African coal of you specs (GCV=6206 Kcal/Kg) is taken for calculation purpose of NCV than deduct 236Kcal/Kg from GCV. The resultant NCV will be come 5970Kcal/Kg instead of your value of NCV 6035Kcal/Kg. Therefore i would suggest you to first find the exact %age of hydrogen in coal.

Regards,

Bhaskar Agate 12/01/2011 10:04:49

Net on wet values (kcal./ kg.) for the coals appears to be ok.Coal consumption in terms of kg.cal./kg.clinker is important; if the losses in the system have gone up then coal consumption figure could be considered higher.

Ted Krapkat 14/01/2011 04:53:11

Hello Asim,

The Ash content and energy values for the 1:1 blend do not match a 1:1 weighted average of the SA coal and local coal.

Are all the data you quoted above for fine coal (as fired), or are some of the data referring to raw coal?

Fine coal generally contains 3-5% of raw meal dust from the top cyclones which increases the "as fired" ash content while also proportionately decreasing the "as fired" NCV and GCV values.

Regards,

Ted.

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