Question

Blast furnace gas in a steel mill is available at 25°C to be burned for the generation of steam. The composition of this gas is as follows on a volumetric basis:

CH4: 0.1, H2:2.4, Co: 25.3, CO2:14.4, N2:56.4, H2o:1.4

Find the HHV (kJ/m3) of this gas at 25°C and ambient pressure.

Answer 1

Blast furnace gas in a steel mill is available at 25°C to be burned for the generation of steam. The composition of this gas is as follows on a volumetric basis:

CH4: 0.1, H2:2.4, Co: 25.3, CO2:14.4, N2:56.4, H2o:1.4

Find the HHV (kJ/m3) of this gas at 25°C and ambient pressure.

Of the six components in the gas mixture, only the first 3 contribute to the heating value. These are, per kmol of mixture:

0.024 H2 , 0.001 CH4 , 0.253 CO

For these components,

0.024 H2 + 0.001 CH4 + 0.253 CO + 0.1305 O2 → 0.026 H2 O + 0.234 CO2

the contributions to reactants and products cancel. For the lower HV(water as vapor) at 250°C

hRP = 0.026(-241 826 + 7742) + 0.234(-393 522 + 9348)

- 0.024(0 + 6558) - 0.001(-74 873 + 2.254 × 16.04(250-25))

- 0.233(-110 527 + 6625) – 0.1305(0 + 6810)

= -72 573 kJ kmol /fuel

v 0 = RTo/Po = 8.3145 × 523.2/100 = 43.5015 m63 /kmol

LHV = +72 573 / 43.5015 = 1668 kJ/m^3