9 posts
TimePosted 11/02/2011 02:27:13
djmariano says

Ash absorption by clinker

Dear experts:

Good day!

I am interested in calculation the Percentage ash absorbed by clinker (% absorbed by wt per kg of cliker) during the calcination process with these following data:

(1)Specific heat requirement (e.g 880 Kcal/kgclk).

(2)Percentage fuel split by heat (eg 90%coal 10%RDF)

(3)Heating value of the fuels( 6500 Kcal/kgcoal, 4200 Kcal/kgrdf )

I have an initial an initial estimation below but I do not know if it is correct.

I would also like to know what does Percentage calcined addition means?

I will appreciate any reponse, thanks in advance 






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Ted Krapkat
536 posts
TimePosted 11/02/2011 05:37:25

Re: Ash absorption by clinker

Hello djmariano,

You would also need to know the individual ash contents of the two fuels. eg

Specific heat consumption = 880 kcal/kg clk

90% coal : 10% RDF

Heat value of coal = 6500 kcal/kg

Heat value of RDF = 4200 kcal/kg

Therefore the combined fuel would have a heat value of  (6500 * 0.9 + 4200 * 0.10) which equals 6270 kcal/kg fuel.

Since you require the Specific Heat Consumption to be 880 kcal/kg clinker,  the amount of combined fuel that will produce 1 kg of clinker under those conditions is;- 880 / 6270 = 0.14035 kg fuel

At this point we need the ash content of the combined fuel. For now, Let's call it Y.

The amount of ash in one kg of clinker would be;-  (0.14035 * Y/100) / 1

Therefore the amount of ash in 100kg clinker (or the percentage ash by weight) would be;-  0.14035 * Y

If the %ash in the coal was say C and the %ash in the RDF was R then the total ash in the combined fuel (Y) would be;-  C * 0.90 + R * 0.10

So the % of ash absorbed in the clinker would be;-  0.14035 * (C * 0.90 + R * 0.10)


I hope this helps,





9 posts
TimePosted 11/02/2011 07:20:45
djmariano says

Re: Ash absorption by clinker

Thanks Ted for your reply, I forgot to mention the individual ash content of each fuel I used.

I have a follow-up question.

Supposed I have the following given:

uLST: 1.2 Kglimestone/kgclk (unignited) = iLST: 0.7 kglimestone/kgclk (ignited)

uCLY: 0.3 kgclay/kgclk (unignited)           = iCLY: 0.12 kgclay/kgclk (ignited)

uPYR:  0.1 kgpyrite/kgclk (unignited)       = iPYR: 0.03 kgpyrite/kgclk (ignited)

                                                                         iASHc  0.1 kgcoal/kgclk (ignited)

                                                                         iASHr   0.05 kgrdf/kgclk (ignited) 

uPl = Unit Price of unignited limestone/kg

uPc = Unit Price of unignited Clay/kg 

uPp = Unit Price of unignited Pyrite/kg

uPcl = Unit Price of unignited coal/kg

uPr = Unit Price of unignited RDF/kg

I am to calculate the rawmaterial cost per kg of clinker as part of my constraint. My equation is as follows:

COST RWM/kg clk =  SUM(% wt of material * unit price) + SUM(%wt of ash * unit price)


(1) Do I need to use the unIgnited data or just use the ignited?

(2) Is the second term of my equation correct? Do I need to consider the ash as part of my rawmaterial cost?

(3) To follow-up my previous question about the fuel, what will be my fuel cost? since I have a given 90%coal:10% RDF by heat not by mass?

I will appreciate any response, thank again in advance 


Ted Krapkat
536 posts
TimePosted 16/02/2011 04:22:03

Re: Ash absorption by clinker

Hello DJ,

Question 1: I think it would be best to use the unignited raw material data because that way you can express the cost of raw materials in a manner that makes intuitive sense. ie $/kg as delivered to the raw mill.

Question 2: Although the ash in the fuel reports directly to the clinker, fuels are generally costed separately to the raw materials because we are paying for the energy content of the fuel rather than the contribution of the ash to the raw material. In which case you don't need the second term in your cost equation.

Question 3: The fuel cost/kg clinker will be based on the quantity of each fuel required to satisfy your Specific Heat Consumption criteria of 880 kcal/kg clk. The ratio of 90:10 relates to both heat and mass since the units are in kcal/kg and we are relating all our calculations back to 1kg of clinker.

For example, we previously calculated that to provide 880 kcal/kg clinker we would need 0.14035kg of combined fuel, This would be composed of (0.14035 * 0.9)kg coal and (0.14035 * 0.1) kg of RDF or;- 0.12632kg of coal and 0.01404kg RDF.

We can confirm that this combination would produce the 880kcal of energy we require by a simple back calculation. eg (0.12632 * 6500) + (0.01404 * 4200) = 880kcal

So finally, using the data you have provided;-

The total cost of fuel/kg clinker would be = (cost of 0.12632kg coal + cost of 0.01404kg RDF)

The total cost of raw materials/kg clinker would be = (cost of 1.2kg Limestone + cost of 0.3kg clay + cost of 0.1kg pyrite)