Gaseous ethanol CH3CH2OH also expressed as C2H5OH is burned

Gaseous ethanol (CH_3CH_2OH, also expressed as C_2H_5OH) is burned with 150% of theoretical air at standard conditions. During the combustion process 90% of the Carbon in the fuel is converted to CO_2 and 10% is converted to CO. Determine the rate of heat transfer from the combustion in kJ/s for the combustion of 3 kg/h of fuel when the reactants and products are at 25 degree C and 1 atm.

Solution

Molar mass M_ethanol = 46

Mole Numbers N = m/M = m_ethanol/M_ethanol = (3/3600)/(46)= 0.00002 kmol/s

C₂H₅OH + 1.5 x 3 (O + 3.76 N₂ ) + -------- 2 CO₂ + 3 H₂O + 1.5 O₂ + 16.9 N₂

Substance

hf

o

kJ/kmol

h298 K

kJ/kmol

h1400 K

kJ/kmol

C2H5OH

-277,690

--- ---

--- ---

CH4

-74,850

--- ---

--- ---

O2

0

8682

45,648

N2

0

8669

43,605

H2O

-241,820

9904

53,351

H2O

-285,830

--- ---

--- ---

CO2

-393,520

9364

65,271

Q = 2 ( -393520+65271-9364)+3(-241820+53351-9904)+16.92(0+43605-8669)-1(277690)-0-0-

= -664426 -595119 + 569107- 277690

= + 2106342 kj/mol

Q = N Q = +2106342 x 0.00002 = -42.12 kJ/s

Q 90 % = + 37.91 kj/s

Substance	hf o kJ/kmol	h298 K kJ/kmol	h1400 K kJ/kmol
C2H5OH	-277,690	--- ---	--- ---
CH4	-74,850	--- ---	--- ---
O2	0	8682	45,648
N2	0	8669	43,605
H2O	-241,820	9904	53,351
H2O	-285,830	--- ---	--- ---
CO2	-393,520	9364	65,271