Materials balance calculation procedure in coke making

In coke making coal of certain composition is carbonized in a by-product coke oven. As a result of carbonization, products and by-product are produced. Main product is coke, whereas by-products are coke oven gas and tar.

Basis of calculation: one may take 1 kg coal, 100kg coal or 1000kg coal.
Amount of coke is determined by ash balance, namely if W kg is amount of coke then ash balance is
   
  

 is the amount of ash in coal,  and  are amounts of ash in coke and tar respectively. By knowing weight of tar, W can be calculated.

Amount of coke oven gas can be calculated by carbon balance:

 


Heat balance:

For heat balance calculations, reverence temperature of 298K is normally selected.
Heat balance at steady state is

 

In coke –making heat input is the calorific value of coal and calorific value of coke- oven gas calorific value of coal and of any other solid fuel can be determined by Dulong formula:

 

 

GCV is gross calorific value and NCV is the net calorific value.
Heat output consists of

1. Sensible heat in coke:

It can determined by  in Kcal or kj, where X is mass of coke, Cp is specific heat of coke and  is temperature of coke discharged from coke oven.  is 0.359 . 

a) Sensible heat in coke oven gas: it may be calculated by  in kcal or kj, where  is specific heat of coke oven gas. Its value may be taken as .

b) CV of coke and tar can be calculated by Dulong formula.

c)  CV of coke-oven gas is the summation of heat of combustion values of all combustible components in coke-oven gas s illustrated on lecture2.

Heat balance calculations disclose

a) Distribution of heat energy in products and by-products.

b) Sensible heat available in products and by-products.

c) Heat losses can be determined from difference between heat output and heat input values.

 
Conclusions:

In this lecture a brief description of blast furnace ironmaking is given so that one to can proceed to perform material and heat balance. Coke is an integral part of blast furnace ironmaking. Material and heat balance is discussed in lecture 27.