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Join Date: May 2009
Location: Mumbai
Posts: 73

Coal GCV

09/06/2017 8:33 AM

Dear Sir(s)

Boiler Capacity : 20 TPH

Avg Steam Generation : 250 TPD

Coal used : Indonetia Coal

Feed Water Temp : 65 deg C

I am confused with ADB and ARB method for GCV testing.

Actually my problem is that, we purchase coal of 5400 Kcal/kg based on ADB which contains about 37% moisture and 7-10% ash.

In monsoon situation is worst, moisture level comes upto 52%

While testing same coal with ARB method , we got GCV ranging 3500-4000 only

With this type of coal I am not getting S/F ratio more than 4

Management considers GCV based on ADB but actually we are using coal on ARB basis.

So, I wanted to confirm , generally which norms followed by industry for GCV , ADB or ARB

Pls help me with this regards.

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Guru
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#2

Re: Coal GCV

09/06/2017 1:38 PM

You need to use the dry weight basis GCV of said coal, instead of paying for the water content. You do not seem to have control over this asset, due to weather exposure.

I can assure you the moisture content contributes nothing to the heating value of the fuel, but it does suck heat out of the burn to remove it as fed to the boiler.

Do you have fuel pre-heating equipment?

I feel for you, in sorting this out. I have heard of situations where the coal is paid for by the tonnage based on the lower heating value. My personal opinion of this practice is a dim one, since the numbers are all over the board, depending on the water content.

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Guru
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#3

Re: Coal GCV

09/07/2017 1:35 AM

It depends how your purchasing department buys your coal, how they evaluate its price, how you analyze it, and how your boiler burns it.

The GCV (Gross Calorific Value) for high moisture content coal, peat, lignite, etc., can be determined on either the ARB (As Received Basis) or the ADB (Air Dried Basis). The ADB should always be higher since the moisture that has been absorbed during shipping and handling is removed prior to testing, while the ARB includes that water that doesn't contribute to the heating value of the fuel as mined.

Which would you rather pay for, a ton of coal that is 50% or 20% water? The price depends upon the contract specs, while you're stuck with the poorer performance and process retuning necessary that comes with varying moisture content.

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Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
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#4
In reply to #3

Re: Coal GCV

09/07/2017 9:33 AM

Thanks for saying precisely, and clearly what I was stumbling over.

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