It is shown in lecture 31 that

(4)

(5)

By equation 3 4 5 and noting

(6)

The eq. 6 is in terms of kj /kg mole of product iron.

Eq. 6 is a simplified approach. It considers heat demand for hot metal only. In reality one has to consider heat demand for slag formation, decomposition of limestone, heat of mixing etc.The heat demand terms can be added simply on the left hand side of the equation 6

Left hand side of eq. 6 is heat demand (D) which is a variable; variable because it may vary from furnace to furnace type of charge etc. Thus equation 6 is

.

D= heat demand of the process /kg mole of iron produced.

Illustration of the concept

The  in top gas leaving a hematite changed BF is The carbon supply rate (incluing C in PI 5Wt.%) is 500 kg /ton of product iron. What is the enthalpy supply to the furnace (kj/kg mole of pnduct ) assuming blast and top gas leave at

Enthalpy supply










Enthalpy supply = 525200kj/g mole.