Sample Problem Petrochem

Sample Problem:

1. An automobile uses an unleaded gasoline with an octane of 85. Air is supplied 30% in excess such that the molar ratio of CO2 to CO is 5:2 and H2 to CO is 1:1 in the exhaust gas. Calculate the Orsat Analysis of the exhaust gas. The of iso-octane is 0.6918 and n-heptane is 0.684 g/ml. Note: the octane number of gasoline is the % volume in an iso-octane (C8H18), n- heptane(C7H16) mixture with the same knocking tendency as the fuel. 2. A gasoline is supplied to an automobile engine with an analysis of 90% C and 10% H ad burned with 30% excess air, If the process does complete combustion, Calculate a. Orsat Analysis b. Volume of the flue gas leaving at 900oF (on dry basis) 3. A high speed diesel engine burns diesel fuel to give an exhaust gas analyzing 7.14% CO2, 4.28%CO, 8.24% O2 and 80.34% N2. Calculate the cetane number of the fuel fired. Density of cetane is 0.7751 and methyl naphthalene is 1.025 g/ml. Note: Cetane number are used to indicate the quality of a diesel fuel oil for compression ignition engines. It is defined as the % volume of cetane (C16H34) in a cetane-methyl naphthalene (C11H10) mixture that has the same performance as the fuel. 4. A ternary blend of gasoline (Octane no. = 90), alcohol (75% ethanol,25% methanol) and benzole (75% benzene, 15% toluene and 10% xylene) is burned completely in 35% excess O2. Analysis of the blend shows 70% gasoline, 15% benzole and 15% alcohol. Calculate the complete analysis of the exhaust gas. Calculate the complete analysis of the exhaust gas. 5. An alcogas mixture made up of 85% gasoline (Octane no. 95) and 15% ethanol (90% purity) is used as fuel for an engine in the presence of 17.05 m3 air/kg alcogas supplied essentially dry at 30 oC and 740 mmHg 80% of the C burns to CO2, the rest to CO; molal ratio of the H2 to CO is 1:2. Calculate: a. Orsat analysis of the exhaust gas b. % excess air

An automobile uses an unleaded gasoline with an octane of 85. Air is supplied 30% in excess such that the molar ratio of CO2 to CO is 5:2 and H2 to CO is 1:1 in the exhaust gas. Calculate the Orsat Analysis of the exhaust gas. The of iso-octane is 0.6918 and n-heptane is 0.684 g/ml. Note: the octane number of gasoline is the % volume in an iso-octane (C8H18), n- heptane(C7H16) mixture with the same knocking tendency as the fuel.

30% x’s Air

Given:

Exhaust gas

Gasoline Required: Orsat Analysis of the exhaust gas Solution:

Assume the composition of the gasoline can be expressed as an octane-heptane mixture Volume 85 15

C8H18 C7H16 Total

Density 0.6918 0.684

Wt. 58.80 10.26 69.06

% Wt. 85.14 14.86 100

Basis: 100 kg of gasoline

C8H18 C7H16

Wt. 85.14 14.86

MW 114 100

Mole 0.7468 0.1486

O2 theo = 7.01 mol C

2

O2 supplied = 10.97 mol O2(1.30) = 14.26 mol O2 N2from air= 14.26 mol O2 CO2 produced = 7.01 mol CO produced = 7.01 mol C

At C 5.97 1.04 7.01

= 53.64 mol N2 2

At H 13.44 2.38 15.82

H2= CO= 2.01 mol H2 Free O2= (0.30)(10.97) +1+1 = 5.29 mol H2

CO2 CO H2 O2 N2

Mol 5.01 2.01 2.01 5.29 53.64 67.94

% mol 7.37 2.95 2.95 7.79 78.94 100

A gasoline is supplied to an automobile engine with an analysis of 90% C and 10% H ad burned with 30% excess air, If the process does complete combustion, Calculate a. Orsat Analysis b. Volume of the flue gas leaving at 900oF (on dry basis)