Coal and Water

Dastgir:

 what is the water holding capacity of different coals and how it depend on various characters of coal.

 

By the word water holding capacity i will assume you mean surface moisture (In contrast to inherent/bonded moisture) and by coal i would assume bituminous coal

This basically depends on

1) Humidity/environment of Air/gas sorrounding the coal particles (or lump coal)

2) Nature/Rank of coal

When the partial pressure of air is equal to vapour pressure of surface moisture of coal the water holding capacity of coal seizes,(Bit technical ain't it?) let me try to explain...

When the RH of Air is high (let say hypothetical number 60%RH) and coal has less surface moisture (say 4% by weight), as air is not saturated (which is saturated at 100% RH ) the water holding capacity of coal will be reduced by the mass transfer of water to air and say 3.2% by weightof surface moisture remains and if the  RH of Air is 40%(more hungry) the coal water holding capacity will come down to say 2.7% as air demands more water (Now this kind of conditions you will find typically in dry seasons/places when humidity of air is low).....In simple terms coal will hold more moisture in rainy seasons and low in summer

Analogy of this would be.....

Imagine a cup with a 100 ml of water in it and add 10gm sugar to it may be it will dissolve in it immediately. Add 50gm more to it, may be it this too will dissolve again the process will continue till a saturation point is reached when no more sugar is dissolved in water, what ever is added remains undissolved . (water would be coal and sugar would be water in our case)

According to Rank/nature of coal water content decreases as following

Peat - Lignite - Bituminous - Anthracite

Basic chemistry behind the screen ???? May be the age factor i guess?

Er.Hussaini

sir,

the explanation is very much correct.As the coal surface moisture (not rain drinched coal) depends upon the humidity .

Dear Hussaini,

Even being bituminous in nature, and having piled for several month at the same site, Indonesian and south african coal differ in their surface moisture content by about 10 %.

Both are used for cement industry in india exhaustively.

This is the context whereto i am much interested

Regards,

Gulam Dastgir.