ProblemSet1

1. Pure ethane is burned completely in 20% excess air. Air is supplied at 25⁰C, 740 torr and is substantially dry. Calculate: a) Orsat analysis of the products of combustion b) Kg dry air supplied/kg of fuel gas c) Cubic meters of air/ kg ethane d) Cubic meters of the products of combustion measured at 400⁰C, 100 kPa /kg ethane e) Partial pressure of water in the products of combustion

2. Pure methane is burned with 40% excess air and 25% of its carbon content is converted to CO the rest to CO2. 90% of its hydrogen burns to water, the rest remains as unburned H 2. Air supplied is at 23⁰C, 758 mm Hg with 80% RH. Calculate: a) Orsat analysis of the combustion products b) m3 of air supplied per kg methane c) m3 of combustion products at 350⁰C and normal barometric pressure per kg methane.

3. When a mixture of liquid hydrocarbons (C and H only) are burned in a test engine, the exhaust gas is found to contain 10% CO2 on a dry basis. It is also found that the exhaust gas contains no oxygen or hydrogen (on the dry basis). Careful measurement indicates 173 ft 3 of air of 80F and 740 mmHg absolute enter the engine for every pound of fuel used. Calculate the mass ratio of H to C in the fuel.

4. A medium Btu gas analyzes 6.4% CO 2, 0.1% O2, 39% CO, 51.8% H2, 0.6% CH4, and 2.1% N2. It enters the combustion chamber at 90F and a pressure of 35 inHg. It is burned with 40% excess air (dry) at 70F and the atmospheric pressure of 29.4 inHg, but 10% of the CO remains unburned. How many cubic feet of air are supplied per cubic foot of entering gas?

5. The majority of semiconductor chips used in the microelectronics industry are made of silicon doped with trace amounts of materials to enhance conductivity. The silicon initially must contain less than 20 ppm of impurities. Silicon rods are grown by the following chemical deposition reaction of trichlorosilane with hydrogen: HSiCl3 + H2  3HCl + Si Assuming that the ideal gas law applies, what volume of hydrogen at 1000C and 1 atm must be reacted to increase the diameter of a rod 1 m long from 1 cm to 10 cm? The density of solid silicon is 2.33 g/cm3

6. An industrial fuel gas consists of 40% CO and 60% CH 4; 121 ft3/min of the gas, measured at 500 psia and 90F, is completely burned with 25% excess air that enters at 70F and 770 mmHg. The resultant gases leave the furnace at 570F and 770 mmHg. Compute the composition and number of cubic feet per minute of the hot gases leaving the furnace.

7. Carbon dioxide dissociates at high temperatures according to the following equation: 2CO2   2CO + O2 At 3000C and 1 atm CO2 is 40% dissociated. If 5 L of CO2 at 20C and 1 atm is heated to 3000C at constant pressure, what volume of the gas will result?

8. In attest on an oil-fired boiler, it is not possible to measure the amount of oil burned, but the air used is determined by inserting a venturi meter in the air line. It is found that 5000 ft 3/min of air at 80F and 10 psig is used. The dry gas analyzes 10.7% CO 2, 0.55% CO, 4.75% O2, and 84.0% N2. If the oil is assumed to be all hydrocarbon, calculate the gallons per hour of oil burned. The specific gravity of the oil is 0.94.

9. A gas has the following composition: CO 2 (10%), CH4 (40%) and C2H4 (50%). It is desired to distribute 33.6 lb of thid gas per cylinder. Cylinders are to be designed so that the maximum pressure will not exceed 2400 psig when the temperature is 180F. Calculate the volume of the cylinder required by Kay’s method.

10. A gaseous mixture consisting of 50 mol% H 2 and 50mol% acetaldehyde (C2H4O) is initially contained in a rigid vessel at a total pressure of 760 mmHg abs. The formation of ethanol occurs according to: C2H4O + H2  C2H6O After a time it was noted that the total pressure in the rigid vessel had dropped to 700 mmHg abs. Calculate the degree of completion of the reaction using the following assumptions: (1) all reactants and products are in the gaseous state; and (2) the vessel and its contents were at the same temperature when the two pressured were measured.

11. A blast furnace gas analyzing 27% CO, 12% CO 2, 2% H2, 5% CH4, and 54% N2 at 25C and 98 kPa and saturated with water vapor is burned in 15% excess air. Air is supplied at 30C, 762 torr and also saturated with water. 90% of the total carbon in the fuel is converted to CO 2, the rest to CO. Molar ratio of H2 to CO is 1:4 in the stack gas which leaves at 200C and 750 torr. Calculate: a) Orsat analysis of the stack gas b) air-fuel ratio by volume c) Moles stack gas/mole fuel

12. Coal Gas at 15C, 760 torrs and saturated with water vapor is burned in a furnace. Air with 60% RH is supplied at the rate of 5.7 m3/ m3 coal gas and enters at the same temperature and pressure as the coal gas. The coal gas analyzes 1.4% CO 2, 2.7% C2H2, 0.7%O2, 5.8% CO, 53.2%H2, 29.6% CH4, and 6.6% N2. The molar ratio of CO2 to CO in the stack gas is 10:1. All the H2 in the fuel is burned to water. The stack gas leaves at 400C and 100 kPa. Calculate: a) % excess air b) Orsat Analysis of the stack gas c) m3 stack gas/m3 of coal gas d) Dew Point of the stack gas

13. A pure saturated hydrocarbon is burnt with excess air. Orsat analysis of the stack gas shows 7.9%, 1.18% CO, 0.24% H2, 5.25% O2, and 85.93% N2. Air is substantially dry. The stack gases leave at 750 mm Hg pressure. Calculate: a) % excess air b) kg air/kg fuel c) Formula of the hydrocarbon d) Dew point of the stack gas

14. Blue Water Gas is obtained by passing steam over red hot carbon enriched coal (coke). The gas is called "Blue" water gas because of its blue flame, a characteristic of the combustion of CO. A typical composition shows 4.7% CO2, 41% CO, 49% H2, 0.8% CH4 and 4.5%N2. If blue water gas at 25C, 745 torrs and 90% RH is burned in wet air, 30% in excess, supplied at the same conditions as BWG with 85% RH, calculate: (a) Orsat analysis of the stack gas if the molar ratio of CO 2 to CO 1:8; H2 to CO is 1:4 (b) m3 air/m3 BWG (c) m3 stack gas(100 kPa; 300C)/100 moles dry BWG

15. A pure saturated hydrocarbon is burned in excess air. Air is supplied at the rate of 284.14 m3/kgmol of the hydrocarbon. Air enters at 30C, 1 atm and saturated with water vapor. Partial orsat analysis of the stack gas shows 8.68% CO 2 and 1.3% CO. Calculate: a) % excess air b) Formula of the hydrocarbon c) Complete orsat analysis of the stack gas