Chapter 10: Material Balance with Chemical Reaction (Solution)
Problem 10.1: A synthesis gas analyzing 6.0 % CO2, 0.5 % O2, 40.0 % CO, 50 % H2, and the rest N2 is burned with 50 % excess air. What is the composition of the flue gas?
Problem 10.2: A gas mixture consisting of 80 % ethane and 20 % oxygen is burned in an engine with 200 % excess air. 80 % of the ethane goes to CO2, 10 % to CO and 10 % remains unburned. Calculate the composition of the exhaust gases on (a) a wet basis and (b) a dry basis.
Problem 10.3: Pure propane is burned with as much quantities of air as is required to limit the carbon dioxide content in the flue gas to 8 %. How much excess air is to be supplied?
Problem 10.4: One kilomole of methane is completely burnt to form CO2 and water vapor using 10 % excess air than that required for complete combustion. The resulting gas mixture is treated to remove all the water content. (a) What will be the volume of dry gas leaving the burner at 110.3 kPa and 275 K? (b) How many kilograms of water are removed from the products of combustion?
Problem 10.5: Pure methane is completely burned with air. The gas leaving the burner which contains no oxygen is passed through a cooler where some of the water is removed by condensation. The mole fraction of nitrogen in the gas leaving the cooler was 0.8335. Calculate the following: (a) The analysis of the gas leaving the cooler (b) Water condensed in kg per kmol of methane burned (c) The partial pressure of water in the gas leaving the cooler at 325 K and 1.5 bar.
Problem 10.6: A mixture of ethane (C2H6) and ethene (C2H4) occupies 40 L at 1 atm and 400 K. The mixture reacts completely with 130 g of O2 to produce CO2 and H2O. Assuming ideal gas behavior, calculate the mole fractions of C2H4 and C2H6 in the mixture.
Problem 10.7: Pure methane is completely burned with air. The outlet gases from the burner which contains no oxygen, are passed through a cooler, where some of the water is removed by condensation. The gases leaving the cooler have a nitrogen mole fraction of 0.75. Calculate the following: (a) The analysis of the gases leaving the cooler (b) The mass of water condensed per one kilogram of methane burned (c) The average molecular weight of the gases leaving the cooler.
Problem 10.8: Calculate the flue gas analysis on a dry basis for the following furnace operation. The fuel contains 85 % carbon and the rest hydrogen on a weight basis. 40 % excess air is used. It is found that all H2 is converted to H2O and 95 % carbon to carbon dioxide and the rest to carbon monoxide.
Problem 10.9: Producer gas has the following composition by volume: carbon monoxide = 25.0 % carbon dioxide = 4.0 %, oxygen = 3.0 %, and nitrogen = 68.0 %. (a) Determine the volume of the gas at 1 bar and 290 K per kg of carbon. (b) 100 m3 of the gas at 1 bar and 290 K is to be burned with 20 % excess air than that is theoretically required for complete combustion. What volume of air is required at 1 bar and 290 K? (c) For the conditions in part (b), what would be the composition of the gas after complete combustion?
Problem 10.10: A producer gas contains 28 % CO, 3.5 % CO2, 0.5 % O2, and 68 % N2. 100 kg of this gas is burned with 20 % excess air. If the combustion is only 90 % complete, determine the following: (a) The composition of the flue gas and (b) The weight of the gaseous products.
Problem 10.11: A gas mixture analyzing 6 % pentane, 10 % butane, 15 % propane, 10 % ethane, 55 % methane, and 4 % nitrogen by volume is burned at a rate of 100 m3 per hour at 350 kPa and 300 K with 12 % excess air. Air is supplied at 100 kPa and 300 K. It is found that the flue gas which leaves at 105 kPa and 800 K contains CO2 and CO in the mole ratio 18:1. Determine the following: (a) The rate of air supply (m3 per hour) (b) The Orsat analysis of flue gas (c) The flue gas produced (m3 per hour).
Problem 10.12: A fuel oil analyzing 85 % (weight) C and 15 % (weight) H is oxidized with 50 % excess air. For the oxidation of 100 kg of oil, calculate the following: (a) The air requirement in kilograms (b) The composition of the flue gas (c) The average molecular weight of the flue gas.
Problem 10.13: A fuel gas on a dry basis contains 80 % methane, 6 % ethane, 4 % propane, 2 % oxygen, and 8 % nitrogen. The fuel saturated with water vapor at 300 K and 101.3 kPa and measuring 100 m3 is burned with 50 % excess air supplied at 305 K and 101.3 kPa with a relative saturation of 60 %. The vapor pressure of water is given by the Antoine equation:
\ln P^S=16.26205-\frac{3799.887}{T-46.854}where P is in kPa and temperature is in K. Calculate the following: (a) The analysis of the gas leaving the combustion chamber (b) The volume of the gas (in m3) leaving the furnace at 550 K and 101.3 kPa assuming complete combustion (c) The dew point of the flue gas.
Problem 10.14: A liquid fuel analyzing 88 % (weight) C and 12 % (weight) H2 when burned with excess air gives a flue gas of the following composition on a dry basis: CO2 3.5% and N2 = 83.0 %. Calculate the following: (a) The percent excess air used (b) The volume of dry flue gases at STP per 100 kg of the fuel burned.
Problem 10.15: The Orsat analysis of the flue gas produced by the combustion of a hydrocarbon fuel shows 10.2 % CO2, 1.0 % CO, 8.4 % O2, and 80.4 % N2. What is the atomic ratio of H to C in the fuel?
Problem 10.16: The Orsat analysis of the flue gas resulting from the combustion of a pure hydrocarbon fuel oil is found to be: CO2 = 14.6 %, CO = 2.0 %, O2 = 2.8 %, N2 = 80.6 %. Calculate the composition of the fuel in weight percent.
Problem 10.17: A hydrocarbon fuel is burned with dry air. The combustion gases leave the furnace at 750 K and 100 kPa. The flue gas analysis shows CO2 = 12.0 %, CO =1.0 %, O2 = 4.0 % and N2 = 83 %. What is the dew point of the stack gas? The vapor pressure of water is given by the Antoine equation:
\ln P^S=16.26205-\frac{3799.887}{T-46.854}where P is in kPa and temperature is in K.
Problem 10.18: Pure propane is burnt in excess of air to give the following analysis of combustion products in volume percent: CO2 = 5.0, CO = 3.5, H2O = 11.4, O2 = 7.0, N2 = 73.1. Calculate the percent of excess air used.
Problem 10.19: The Orsat analysis of flue gas produced by the combustion of pure methane in excess of dry air is 8.17 % CO2, 0.96 % CO, 5.04 % O2, and 85.83 % N2. Calculate the percent excess air used for combustion.
Problem 10.20: The Orsat analysis of a flue gas produced by the combustion of a pure hydrocarbon fuel with an excess of dry air is found to be 8.5 % CO2, 1.0 % CO, 5.0 % O2, and 85.5 % N2. Calculate (a) the percent excess air used for combustion and (b) the weight ratio of C : H in the fuel.
Problem 10.21: A gas containing only CH4 and N2 is burned with air yielding a flue gas that has an Orsat analysis of CO2 = 8.7 %, CO = 1.0 %, O2 = 2.0 %, and N2 = 88.3 %. Calculate the following: (a) The percent composition of the fuel and (b) The percent excess air used.
Problem 10.22: The exhaust gases from a diesel engine using a high-grade fuel oil show 9.76 % CO2, 8.18 % O2, and the rest N2. Calculate the following: (a) The H/C weight ratio in the fuel (b) The amount of dry air supplied per kilogram of fuel burnt (c) The total amount of exhaust gases in kilograms per kilogram of fuel burnt.
Problem 10.23: A solid fuel has the following analysis: H = 5.0 %, S = 4.0 %, C = 65 %, O= 10 % and inerts 16 %. The fuel is burned with 20 % excess air. If only 80 % of the carbon burned gets converted to CO2, 15 % is converted to CO and 5 % is left behind as soot, determine the composition of the combustion gases.
Problem 10.24: The flue gas produced by the combustion of pure carbon with excess air contains N2 and O2 in the ratio 7.18:1 by mole and CO2 and CO in the ratio 2:1, what is the percent excess air used? No other compounds are present in the flue gas.
Problem 10.25: Coal containing 80 % carbon and 6 % ash by weight when burned leaves a cinder that contains 90 % ash and 10 % carbon. If 100 kg of coal is charged, calculate the following: (a) The weight of cinder produced (b) The percent fuel value wasted.
Problem 10.26: The combustible matter in a certain sample of coal is found to be 80 % C and 20 % H by weight. 50 kg of coal is burned with 1000 kg of air. The Orsat analysis of the combustion gas showed CO2 to CO in the ratio 3:2. Determine (a) the percent excess air and (b) the total moles of flue gas produced.
Problem 10.27: When coal containing 74 % C, 14.9 % H, and 11.1 % ash is burned, it gives a flue gas containing 12.5 % CO2, 1.0 % CO, 1.5 % O2, and 85 % N2 on a dry basis. Determine the following: (a) The mass of coal fired in kilograms per kilomole of dry flue gas (b) The percent excess air used (c) The amount of air supplied in kilograms per kg of coal burned.
Problem 10.28: A gaseous fuel made up of methane and ethane is burned with enriched air containing 50 % oxygen and 50 % nitrogen. The flue gas analysis on a dry basis is 25 % CO2, 15 % O2, and 60 % N2. Determine the following: (a) The mole percent of methane in the fuel (b) The moles of air used per mole of fuel.
Problem 10.29: A fuel gas consisting entirely of methane and ethane is burned with air to yield a flue gas whose Orsat analysis is 8.68 % CO2, 6.44 % O2, and 84.88 % N2. Calculate the following: (a) The analysis of the fuel in mole percent (b) The percent excess air.
Problem 10.30: A furnace is fired with natural gas consisting of 95 % methane and 5 % nitrogen. The flue gas analysis shows 9.1 % CO2, 0.2 % CO, 4.6 % O2, 86.1 % N2. Calculate the percentage of excess air supplied.
Problem 10.31: A pure hydrocarbon gas is burned with air and the Orsat analysis of the flue gas gave the following results: initial volume = 100 mL, volume after caustic absorption = 92.6 mL, volume after pyrogallol absorption = 87.1 mL, volume after cuprous chloride absorption = 83.4 mL. On the basis of this analysis, determine the following: (a) The percent excess air (b) The atomic ratio of carbon to hydrogen in the fuel (c) The volume of dry flue gas (in m3) at STP formed per kg fuel burned.
Problem 10.32: A relatively pure saturated hydrocarbon gas is burnt with air in a small furnace. The Orsat analysis of the sample of flue gas gives the following data:
Initial volume of the sample = 100 mL, volume after caustic absorption = 93.21 mL, volume after pyrogallol absorption = 85.74 mL, volume after cuprous chloride absorption = 83.48 mL. Determine the following: (a) The percent excess air (b) The atomic ratio H/C in the fuel and the molecular formula of the fuel (c) The volume (in cubic meters) at STP of flue gas produced by the combustion of one kg of fuel.
Problem 10.33: A furnace is supplied with a gaseous mixture of ethanol, acetic acid, and nitrogen containing 15 % nitrogen by volume at 400 K and 90 kPa. It is burned in excess of air and the flue gas contains 12.5 % CO2, 1.7 % CO, 3.2 % O2, and 82.6 % N2. The flue gas leaves the furnace at 550 K and 100 kPa. Calculate the following: (a) The percent excess air (b) The percentage of ethanol in the fuel by volume (c) The moles of air per mole of fuel used (d) The volume of flue gas in cubic meters per 100 m3 of fuel burned.
Problem 10.34: A producer gas analyzing 2.0 % CO2, 30.0 % CO, 2.0 % O2, 8.00 % H2, and 58.0 % N2 is burned with 20 % excess air. Due to an air leak, the flue gas gets diluted and the Orsat analysis (with water as the confining fluid) of the diluted flue gas is found to be 10.71 % CO2, 3.57 % CO, 7.99 % O2, and 77.73 % N2. Calculate the following: (a) The moles of air leaked into the flue gas per 100 kg fuel burned (b) The analysis of the dry flue gas before dilution.
Problem 10.35: The flue gas leaving two boilers, one using natural gas analyzing 96 % methane and 4 % CO2 and the other using hydrocarbon oil containing C and H in the mole ratio 1:0.9 has the following analysis: CO2 = 10.0 %, O2 = 4.5 % and N2 = 85.5 %. What percent of the total carbon burned comes from natural gas?
Problem 10.36: One hundred kg per hour of a pure hydrocarbon gas CnH2n+2 at 295 K is burnt in a furnace. The flue gas produced analyzed 9.57 % CO2, 6.38 % O2, and the rest nitrogen. The flue gas leaves the furnace at 700 K and 100 kPa. Calculate the following: (a) The atomic ratio H/C, and from this the formula of the fuel (b) The volumetric ratio of flue gas to fuel gas (c) The amount of flue gas produced in cubic meters per minute.
Problem 10.37: A fuel gas is made up of 20 % propane and 80 % CnH2n+2, where n is a whole number. It is burned with an oxygen-enriched air stream containing 50 % oxygen and 50 % nitrogen. The flue gas analyzed 29.72 % CO2, 3.49 % CO, 7.17 % O2 and 59.62 % N2. Determine the following: (a) The percent excess air used (b) The empirical formula of CnH2n+2 (c) The rate of air supplied in m3/h at 400 K and 350 kPa if the fuel is burned at a rate of 1000 cubic meters per hour at 300 K and 110 kPa (d) The moisture carried by the flue gas in kg/h.
Problem 10.38: The Orsat analysis of the flue gas from an oil-fired furnace is CO2: 8 %, CO: 3.0 %, O2: 4 %, and N2: 85 %. An analysis indicates that the oil contains 78 % by weight carbon, the remainder being combustible hydrogen and moisture. Air enters at 300 K and 1.013 bar. Assume the air to be dry. Calculate the following: (a) The percentage of excess air used (b) The carbon-hydrogen weight ratio of fuel oil (c) The volume of air used per kg of oil fired (d) The mass of moisture (kilograms) in the flue gas per kg of oil fired.
Problem 10.39: A furnace is burning fuel oil having the following analysis on a weight basis: 85.0 % C, 14.0 % H, and 1.0 % S. Dry air is used for combustion and is supplied in 20 % excess. 10 percent of the carbon burns to CO and S is converted completely to SO2. It has come to light that there is an air leak at some point in the base of the stack. The air is at 300 K and 100 kPa with 70% relative saturation. The Orsat analysis of the stack gases above this point indicates the concentration of CO2 and SO2 together as 8 %. What percent of the stack gas is air leaked into it? The vapor pressure of water at 300 K is 3.56 kPa.
Problem 10.40: Coal having the following analysis on a dry basis and containing 3.9 % moisture on a dry basis is burned with excess air.
C = 83.05 %, H = 4.45 %, O = 3.36 %, N = 1.08 %, S = 0.70 % and ash = 7.36 %. Air used contains 0.0048 kg of water vapor per kg of dry air. The Orsat analysis of the combustion gases gave the following results: CO2 + SO2 = 15.4 %, CO = 0.0, O2 = 4.0 %, and N2 = 80.6 %. The refuse analyzed 14.0 % unburned ash-free coal and the rest ash. Check the consistency of the given data and calculate the percent excess air used.
Problem 10.41: Coal having the following analysis on a dry basis and containing 3.9 % moisture is burned with excess air.
C = 65.4 %, H = 5.3 %, O= 18.5 %, N = 1.1 %, S = 0.60 % and ash = 9.1 %.
The Orsat analysis of the combustion gases gave the following result: CO2 + SO2 13.0 %, CO = 0.76, O2 6.17 %, H2 = 0.87 % and N2 = 79.2 %. Determine the following: (a) The mass of coal fired per 100 kmol of dry flue gas analyzed. (b) The ratio of the moles of total combustion gases to the moles of dry air supplied (c) The total moles of water vapor in the stack gas per 100 kg of coal if the air is dry (d) The percent excess air.
Problem 10.42: A furnace is fired with coal analyzing 70 % carbon, 5 % hydrogen, 12 % combined moisture, 5 % free moisture, and 8 % ash. The relative saturation of air with water vapor is 60 % at 295 K and 101.3 kPa. The combustion of coal is complete and the refuse contains no combustible matter. The flue gas leaves at 875 K and 100 kPa and has the following analysis on a dry basis: CO2 = 9 %, CO = 2 %, O2 = 7 % and N2 82 %. The vapor pressure of water at 295 K is 2.64 kPa. Calculate the following: (a) The percent excess air (b) The volume of flue gas (m3) formed per kg of coal (c) The volume of air (m3) supplied per kg of coal.
Problem 10.43: Hydrogen-free coke containing 85 % (weight) carbon and the rest inert materials are burned in a furnace. It is found that during combustion, 5 % of the coke charged is lost unburned. The flue gas analysis shows 15.0 % CO2, 2.0 % CO, 4.5 % O2 and 78.5 % N2. The flue gas leaves the furnace at 500 K and 100 kPa. Calculate the following: (a) The percent excess air assuming complete combustion of coke. (b) The weight of air supplied per kg of coke charged (c) The volume of flue gas per kg of coke charged (d) The composition of the refuse from the furnace.
Problem 10.44: 100 kg/h of coal containing 75.0 % C, 4.4 % H, 8.5 % O, 1.2 % S, 1.4 % N, and 9.5 % ash is burnt with 20 % excess air which contains 0.01 kg of water per kg of dry air. During combustion, 90 % of the carbon is burnt to CO2 and the rest to CO; and all sulphur is oxidized to SO2. The refuse produced is dry and contains only ash. Calculate the following: (a) Wet air supplied in kg/h (b) Wet furnace gas in kmol/h (c) Analysis of wet furnace gas.
Problem 10.45: One hundred kilograms of coal having the analysis 70 % C, 5 % H, 1.0 % N, 9.0 % O, 2 % moisture, and 13.0 % ash is contacted with 75 kg of steam in a producer gas plant. Dry air is also supplied to the unit. The producer gas analyzed 13.11 % CO2, 16.38 % CO, 4.37 % CH4, 18.08 % H2 and 48.06 % N2. The producer gas mixed with undecomposed steam leaves the gas producer. Tar formed in the unit is found to be 10 % of the weight of coal charged and contained 10 % (weight) hydrogen and the rest carbon. The refuse contains 8 % C, and the rest is ash. Calculate the following: (a) The amount of dry air supplied, in kilomoles (b) The percentage of steam fed to the gas producer that is undecomposed (c) The volume of wet producer gas (in m3) obtained at STP.
Problem 10.46: Producer gas is obtained by burning coke in a restricted supply of air so that more CO is produced than CO2. A producer gas having the CO:CO2 mole ratio of 5:1 is to be prepared from the coke containing 75 % carbon and 25 % ash. The solid residue after combustion contains 5 % unburned carbon. Calculate the following: (a) The moles of gas produced per 1000 kg of coke burnt (b) The moles of air supplied per 1000 kg of coke burnt (c) The percentage of carbon lost in the ash.
Problem 10.47: The ultimate analysis of coal is 78 % carbon, 6 % hydrogen, 7 % oxygen, 3 % sulfur, 2 % nitrogen, and 4 % ash. The proximate analysis is 65 % FC, 4 % moisture, 27 % VM, and 4 % ash. Calculate the masses of the combined water and net hydrogen in the coal.
Problem 10.48: During a test on a coal-fired steam generator, the following data were obtained: Ultimate analysis of coal: carbon 80.5 %, hydrogen 4.6 %, oxygen 5.0 %, nitrogen 1.1 %, sulfur 1.5 %, and ash 7.3 %. Data on the refuse from the ash pit: ash content 96 % and carbon 4 %. Orsat analysis of flue gas: CO2 16.4 %, O2 2.3 %, CO 0.4 % and N2 80.9 %. Calculate the following: (a) The weight of dry gaseous products formed per 100 kg of coal fired (b) The percent excess air supplied for the combustion.
Problem 10.49: Coal containing 72 % carbon, 15 % ash, and the remainder being net hydrogen and moisture is completely burnt in dry air. The Orsat analysis of the flue gas is 9 % CO2, 4 % CO, 8 % O2, and the rest N2. Calculate the following: (a) The net hydrogen content in the fuel (b) The percent excess air used (c) The volume of wet flue gas per kg of coal at STP.
Problem 10.50: Coal with the following ultimate analysis is burned in the boiler: carbon 66 %, hydrogen 4 %, nitrogen 1 %, combined water 6 %, free water 4 %, and ash 19 %. The refuse drawn from the ash pit contains 12.6 % carbon and the rest ash. The flue gas analysis gives CO2 11.51 %, O2 7.64 %, CO 0.09 % and N2 80.76 %. The humidity of dry air is 0.012 kg/kg dry air. For 100 kg of coal fired, determine the following: (a) The percent excess air supplied (b) The mass of wet air supplied (c) The weight of moisture in gaseous products (d) The volume of total flue gases at STP.
Problem 10.51: A furnace is fired with coal having the following proximate analysis: 2.9 % moisture, 33.8 % volatile matter, 53.1 % fixed carbon, and the rest ash. Only incomplete data are available for the ultimate analysis of coal. These are 1.1 % sulfur and 73.8 % carbon. The dry refuse from the furnace was analyzed as 3.1 % volatile matter, 18.0 % fixed carbon, and 78.9 % ash. The Orsat analysis of the flue gas is CO2 12.1 %, CO = 0.2 %, O2 7.2 % and N2 = 80.5 %. Air enters the furnace at 293 K with 60 % humidity at 101.3 kPa. For 100 kg of coal charged, determine the following: (a) The total carbon content in the refuse (b) The weight of dry flue gases (c) The volume of wet air admitted (d) The available hydrogen in the coal (e) The complete ultimate analysis of coal.
Problem 10.52: A furnace is fired with coal of the following analysis: carbon 60 %, hydrogen 14 %, oxygen 16 %, ash 10 %, and negligible nitrogen and sulfur. The proximate analysis is 40 % FC, 41 % VM, 9 % moisture, and 10 % ash. The refuse has the following analysis: 40 % FC, and 60 % ash. It is dry. 1200 m3 of air at 100 kPa, 295 K with a partial pressure of water of 1350 Pa is supplied per 100 kg of coal. The total pressure of the wet flue gas is 100 kPa. The ratio of mol CO2 to mol CO in the flue gas is 4:1. Determine the following: (a) The percent excess air (b) Orsat analysis of flue gas (c) Partial pressure of water vapor in the hot wet flue gas.
Problem 10.53: The analysis of a gas entering the secondary converter in a contact sulphuric acid plant is 5 % SO2, 15 % O2, and 80 % N2. The gas leaving the converter contains 1.06 % SO2 on an SO3-free basis. Calculate the percentage of SO2 converted.
Problem 10.54: Pure sulfur is burned with excess air to give sulfur trioxide. Due to incomplete oxidation, some sulfur dioxide is also formed. The analysis of the burner gases showed 8.2 % SO3, 0.91 % SO2, 8.65 % O2, and 82.24 % N2. Determine the following: (a) The percent excess air supplied (b) The volume of burner gases at 1.2 bar and 600 K per kg of sulfur burned (c) The volume of air supplied at 1.013 bar and 288 K per kg of sulfur burned.
Problem 10.55: The gases leaving a sulfur burner have the following analysis: 9.8 % SO2, 8.5 % O2, and 81.7 % N2. The gas is sent to a converter where SO2 is converted to SO3. The gas leaving the converter is found to contain 0.5 % SO2, 4.44 % O2, and the rest nitrogen. What percent of the SO2 entering the converter is oxidized to SO3?
Problem 10.56: In the manufacture of sulphuric acid from elemental sulfur, the sulfur is fed to the burner where it is burned with 100 % excess air to produce sulfur dioxide. The conversion of sulfur to sulfur dioxide is only 90 %. The hot combustion gases from the burner are taken to a converter where SO2 is converted to SO3. This conversion is 95 % complete. Calculate the following: (a) The amount of air supplied to the burner per 100 kg of sulfur burned (b) The composition of the burner gas (c) The composition of the converter gas.
Problem 10.57: Iron pyrites (FeS2) is burnt with air 100 % in excess of that required to oxidize all iron to Fe2O3 and all sulfur to sulfur dioxide. Calculate the composition of the exit gases, if 80 % of sulfur is oxidized to sulfur dioxide and the rest to sulfur trioxide. All iron is oxidized to Fe2O3.
Problem 10.58: The analysis of a gas entering the secondary converter of a contact sulphuric acid plant is 4 % SO2, 13 % O2, and 83 % N2. In the converter, SO2 is oxidized to SO3. The gases leaving the converter contain 0.45 % SO2 on an SO3-free basis. Calculate the percent conversion of SO2.
Problem 10.59: The Orsat analysis of gas leaving a pyrites burner shows 10 % SO2 and 5 % O2 and the rest N2. What percent of the sulfur burned is oxidized to SO3?
Problem 10.60: In the combustion of iron pyrites containing 85 % FeS2 and 15 % gangue, some FeS2 is lost in the cinder unburned. If the cinder carries 1.5 % sulfur as FeS2, how many kilograms of FeS2 are lost in the cinder per 100 kg of pyrites charged?
Problem 10.61: In the combustion of iron pyrites containing 85 % FeS2 and 15 % gangue, a portion of the SO3 formed during the combustion gets adsorbed in the cinder. If the cinder carries 1.5 % sulfur as SO3, what mass of SO3 is adsorbed by the cinder per 100 kg of pyrites charged?
Problem 10.62: The combustion of iron pyrites containing 90 % FeS2 and 10 % gangue is found to produce a burner gas having the Orsat analysis of 10 % SO2 and 5 % O2 and the rest nitrogen. Determine the volume of gas (in m3) leaving the burner at 101.3 kPa and 300 K per 100 kg of pyrites charged.
Problem 10.63: A mixture of pyrites and zinc sulfide ore is burned in a burner. The mixture contains 75 % pyrites and 25 % zinc sulfide ore. The pyrites yield 90 % FeS2 and the rest gangue. The zinc sulfide ore contains 70 % ZnS and the rest inerts. A sample of cinder yields 4.0 % S. 70 % of the sulfur in the cinder is in the form of SO3 absorbed in it, and the rest is unoxidized FeS2. Based on 100 kg of mixed charge, calculate the following: (a) The amount of cinder formed and its analysis (b) The percentage of the sulfur left in the cinder based on the total sulfur charged.
Problem 10.64: In the manufacture of sulphuric acid by the chamber process, iron pyrites having the composition of 75 % FeS2 and 25 % gangue are burned at 773 K using air. The reaction is
4FeS_2+11O_2\rightarrow2Fe_2O_3+8SO_2The gases leaving the burner contain 9.3 % SO2, 8.95 % O2, and 81.75 % N2. For 100 kg of pyrites charged, calculate the following: (a) The volume of air (in m3) supplied at 300 K and 100 kPa (b) The percent excess air used (c) The volume of gas (in m3) leaving the burner at 773 K and 100 kPa.
Problem 10.65: In a contact sulphuric acid plant, pyrites are burned in dry air to produce a gas analyzing 10 % SO2 and 7 % O2. The cinder carries 2 % by weight sulfur as SO3. The burner gas at a rate of 2000 m3/h at 365 K and 100 kPa is fed to an absorber to absorb the entire SO3 present in it. 70 % H2SO4 is used for the absorption at a rate of 25 kg/h and produces 90 % H2SO4. Determine the percentage of FeS2 in the pyrites charged.
Problem 10.66: One hundred kilograms of pyrites containing 32 % S are mixed with 10 kg of pure sulfur and is burned in excess air. A part of sulfur is converted to SO3 and the remaining part to SO2. But the sulfur trioxide in the combustion gases will not be detected in the Orsat analysis. The Orsat showed 13.5 % SO2, 3.0 % O2, and 83.5 % N2. Assuming that the entire SO3 in the combustion gases comes from the oxidation of pure sulfur, what is the fraction of the sulfur charged that is converted to SO3?
Problem 10.67: Impure FeS2 is burned to give a burner gas containing 8.0 % SO2, 10.2 % O2, and 81.8 % N2.
FeS_2+\frac{15}4O_2\rightarrow\frac12Fe_2O_3+2SO_3 FeS_2+\frac{11}4O_2\rightarrow\frac12Fe_2O_3+2SO_2 Fe_2O_3+3SO_3\rightarrow Fe_2(SO_4)_3The pyrites contain 48 % (weight) sulfur and the cinder contains 2 % (weight) sulfur as Fe2(SO4)3 and no FeS2. For a basis of 100 kg of pyrites burned, calculate the following: (a) The weight of cinder (b) The moles of burner gas constituents (c) The percentage excess air based on conversion to SO3 (d) The percentage conversion of S to SO3.
Problem 10.68: A mixture of pure sulfur and pyrites analyzing 85 % FeS2 and 15 % gangue is burnt in a standard pyrites burner. The burner gas contains 10 % SO2, 7 % O2, and 83 % N2 on a SO3-free basis and contains 1 mole of SO3 per 100 moles of SO3-free burner gas. The cinder contains 2 % S as SO3. Calculate the percentage of FeS2 in the charge.
Problem 10.69: In the contact process for the manufacture of H2SO4, SO3 is obtained by burning iron pyrites (FeS2) in air. The air supplied is 40 % in excess of that required for the complete conversion of all S to SO3. However, in the burner, only 40 % of the sulfur is converted to sulfur trioxide and the remainder is converted to SO2. Iron is oxidized to Fe2O3. Of the pyrites charged, 15 % is lost by falling through a grate. The burner gas is taken to a converter, where 95 % of SO2 present is converted to SO3. For a basis of 100 kg pyrites charged, calculate the following: (a) The weight of air supplied, kg (b) The burner gas analysis, wt% (c) The total weight of SO3 produced in kilograms (d) The converter gas analysis, vol% (e) The weight of cinder in kilograms.
Problem 10.70: In the contact process for the manufacture of sulphuric acid, iron pyrites (FeS2) are burned with air so that iron is oxidized as Fe2O3 which leaves with the cinder and S is oxidized to its oxides. It is found that in the burner 40 % of sulphur is converted to SO3 and the rest to SO2. The latter is further oxidized to SO3 in the catalytic converter. This conversion may be assumed to be 96 % complete. About 10 % of the pyrites charged is lost unburned and leaves with the cinder. The air supplied to the burner is 40 % in excess of that required for the conversion of all S to SO3. (a) How many kilograms of air are supplied per kg of pyrites charged? (b) What is the percent composition on a weight basis of the gases leaving the burner? (c) What mass of SO3 is obtained per 100 kg of pyrites charge? (d) What is the degree of conversion of S in the charge to SO3?
Problem 10.71: Dry pyrites containing 48 % sulfur is burned in a sulphuric acid plant. The cinder carries 2 % sulphur as SO3. The burner gas analysis shows 8.25 % SO2, 7.85 % O2, and the rest N2. The burner gas is passed through a converter where SO2 is oxidized to SO3. The converter gas is admitted into an absorber to absorb the SO3 in 70 % H2SO4. The gas leaving the absorber is free of SO3 and contains 1.09 % SO2, 4.73 % O2, and 94.18 % N2, and the acid produced is 100 % H2SO4. No secondary air supply is used in the converter. For 100 kg of pyrites charged, determine the following: (a) Moles of SO2 in the burner gas (b) Mole percent of SO3 in the converter gas (c) The amount of 100% acid produced in the absorber.
Problem 10.72: Sulphuric acid can be produced as a by-product in the manufacture of zinc from sulfide ores. The ore analyses 65 % ZnS and 35 % inert impurities by weight. The ore is burned in a furnace and the resulting SO2 is converted to SO3 in a catalytic reactor. The SO3 is then absorbed by water to give sulphuric acid, the final product being 2 % water and 98 % H2SO4 by weight. A total of 99 % of sulfur in the ore is recovered in the acid. The chemical reactions are:
ZnS+1.5O_2\rightarrow ZnO+SO_2 SO_2+0.5O_2\rightarrow SO_3 SO_3+H_2O\rightarrow H_2SO_4Compute (a) The quantity of the product sulphuric acid produced in a zinc plant that processes 2 x 105 kg/day of ore and (b) The quantity of water required per day.
Problem 10.73: In a sulphuric acid plant, 100 kg/h of dry pyrites containing 90 % FeS2 and 10 % inert material is burned with dry air in the burner. Only 85 % of FeS2 is oxidized. In the burner, 90 % of the sulfur burnt is oxidized to SO2 and the balance to SO3. Dry air supplied is 50 % in excess of that required for the complete conversion of S to SO3. Burner gas is fed to a converter where 95 % of the SO2 is converted to SO3 using the oxygen present in the burner gas. All the SO3 produced is absorbed in 70 % H2SO4 fed at a rate of 100 kg/h in an absorption tower. No SO3 is adsorbed on the cinder. Determine the following: (a) The percentage of sulfur in cinder (b) The amount of sulphuric acid produced in kg/h (c) The concentration of the acid product (d) The amount of gas leaving the absorber in kg/h (e) The composition of the gas leaving the absorber.
Problem 10.74: A limestone analyses 92.9 % CaCO3, 5.4 % MgCO3, and 1.7 % insolubles. (a) How many kilograms of CaO can be made from 1000 kg of this limestone? (b) How many kilograms of CO2 can be recovered per kg of limestone? (c) How many kilograms of limestone are needed to make 1000 kg of lime?
Problem 10.75: Carbon dioxide is produced by treating limestone with sulphuric acid. The analysis of the residue leaving the process showed 9.0 % CaSO4, 5.5 % MgSO4, 1.0 % H2SO4, 0.5 % inerts and 0.1 % CO2 and 83.9 % water. The limestone charged contains calcium carbonate, magnesium carbonate, and inert insoluble matter. The CO2 and water vapor produced are removed. Determine the following: (a) The percent composition of the limestone used (b) The percent excess acid used (c) The quantity of CO2 recovered per 100 kg of limestone charged.
Problem 10.76: The calcination of limestone can be represented by the following reactions:
CaCO_3\rightarrow CaO+CO_2 MgCO_3\rightarrow MgO+CO_2In a certain operation, 100 kg of limestone containing only calcium and magnesium carbonates and no inert materials is calcined producing 30 m3 of CO2 at 348.32 K and atmospheric pressure. What is the composition of the limestone in weight percent?
Problem 10.77: Carbon dioxide is produced by treating limestone ore with 15.0 % sulphuric acid. 1000 kg of ore consisting of CaCO3, MgCO3, and inert materials is mixed with an excess of acid:
CaCO_3+H_2SO_4\rightarrow CaSO_4+CO_2+H_2O MgCO_3+H_2SO_4\rightarrow MgSO_4+CO_2+H_2OThe liquid product containing 6.37 % MgSO4, 1.25 % H2SO4, and the rest water is treated with pure CaCO3 to neutralize the free acid. The solid residue consisting of CaSO4 and inerts is separated from the liquid by filtration. If the filter cake analyzed 1 kg of inert per 20 kg of CaSO4, determine the following: (a) The composition of the limestone used (b) The moles of CO2 produced (c) The weight of CaCO3 required to neutralize the excess acid (d) The percent excess of acid used.
Problem 10.78: A lime furnace burns 100 kg of coal containing 80 % C, 5 % H, 2 % N, 1.0 % S and 12 % ash and limestone containing 82.0 % CaCO3, 7.0 % MgCO3 and 11.0 % inert material with excess air. The average stack gas analysis is 14.42 % CO2, 6.03 % O2, and 79.55 % N2. CO2 percentage includes SO2 also. Calculate the following: (a) The percent excess air used for combustion (b) The fuel ratio on a weight basis (c) The amount of limestone supplied, in kilograms (d) The amount of total lime produced, in kilograms.
Problem 10.79: In the manufacture of phosphorus, calcium phosphate is mixed with sand and charcoal, and heated in an electric furnace. The silica used is 15 % in excess of that theoretically required to convert all the phosphorus to silicate. Charcoal used is 50 % in excess of that required to combine with oxygen in the phosphorus pentoxide to form carbon monoxide. It is observed that the conversion to silicate is 85 % complete and the reduction of the oxide to phosphorus is only 70 % complete. Determine the following: (a) The ratio in which phosphate, sand, and charcoal are mixed before they are sent to the furnace (b) The quantity of phosphorus produced per 100 kg of the above mixture.
Problem 10.80: The off-gases from the phosphate reduction furnace analyses 8.0 % P4, 85.0 % CO, and 7.0 % N2 on a mole basis. This gas is burned with air under such conditions that the phosphorus is selectively oxidized. The oxides of phosphorus (P4O6 and P4O10) present in the flue gas are precipitated by cooling and separated. After separation, the gases analyzed 0.8 % CO2, 23.0 % CO, 68.0 % N2 and 8.2 % O2. Calculate the following: (a) The percent of CO entering the burner that is converted to CO2 (b) The percent of P4 that is oxidized to P4O10.
Problem 10.81: Phosphorus is produced by reacting calcium phosphate with silica and carbon in an electric furnace:
Ca_2(PO_4)_2+3SiO_2\rightarrow3CaSiO_3+P_2O_5 2P_2O_5+5C\rightarrow4P+5CO_2Calcium silicate forms a liquid slag, whereas phosphorus passes off as vapor along with CO2 and is condensed. Phosphate rock containing 80 % Ca3(PO4)2 and the rest inert impurities is charged with 25 % excess silica and 50 % excess carbon. The first reaction is 80 % complete, whereas the second is 90 % complete. Calculate the following on a basis of per 1000 kg of the rock charged to the furnace: (a) The weight of phosphorus produced (b) The weight of calcium silicate produced (c) The percent recovery of phosphorus.
Problem 10.82: One hundred kilograms of fluorspar containing 75 % by weight CaF2 and 25 % inert materials is treated with concentrated sulphuric acid to produce hydrofluoric acid (HF).
CaF_2+H_2SO_4\rightarrow CaSO_4+2HFPure sulphuric acid is used in 30 percent excess of that theoretically required. 95 % of the hydrofluoric acid produced in the reaction chamber leaves as gas while the remaining 5 % leaves with the solid residue which consists of CaSO4 produced in the reaction, the unreacted sulphuric acid, and the inert materials. (a) Determine the amount of solid residue formed (b) Express the concentration in weight percent.
Problem 10.83: Copper is extracted from its ore having the following analysis: CuS = 10 %, FeS2 = 30 %, inerts = 60 %. The ore is first crushed and subjected to flotation during which 70 % of the inert materials are eliminated. The resulting concentrate has the following analysis: CuS = 16 %, FeS2 = 48 %, and inerts = 36 %. This is then roasted where the following reactions occur:
2CuS+\frac52O_2\rightarrow Cu_2O+2SO_2 2FeS_2+\frac{11}22O_2\rightarrow Fe_2O_3+4SO_2The Cu2O is then reduced to metallic copper. If 1000 kg of copper ore is originally charged, how many kilograms of the metal can be obtained if there is 3 % loss during the reduction of the oxide to the metal?
Problem 10.84: For producing 1000 kg of pig iron of composition 94 % Fe, 5 % C, and 1 % Si, iron ore containing 89.6 % Fe2O3 and the rest SiO2 is reduced in a blast furnace using 1000 kg of coke containing 90 % C and 10 % SiO2. The flux used contains 94 % CaCO3, 3 % MgCO3, and 3 % SiO2. If it is desired that the slag contains 40 % (CaO + MgO), how much flux is required for producing 1000 kg of pig iron? Assume that no iron is present in the slag.
Problem 10.85: Powdered bauxite is reacted with dilute sulphuric acid to produce aluminum sulfate. In a typical operation, 1000 kg of bauxite containing 50 % Al2O3 is treated with 1700 kg of 75 % sulphuric acid. The reacted mass is filtered to remove solid residue. The filtrate is concentrated to crystallize 2000 kg of Al2(SO4)3·9H2O. Calculate the following: (a) The percent excess reactant used (b) The degree of completion of the reaction (c) The weight and composition of solid residue produced.
Problem 10.86: Synthesis gas consists of nitrogen and hydrogen in the ratio 1:3. It is prepared by mixing air with pure hydrogen. Oxygen is removed as water formed in the reaction between hydrogen and oxygen. For treating 100 moles of air containing 21 % oxygen, 78 % nitrogen, and 1 % argon, determine (a) moles of hydrogen added (b) weight of water condensed in kg.
Problem 10.87: A plant produces 600 tons/day of ammonia. Nitrogen and hydrogen in the mole ratio 1:4 is sent to the converter. The gases leaving the converter contain these gases in the ratio 1:4.25. Calculate the volume of gases measured at 773 K and 100 kPa that is admitted to the reactor per day.
Problem 10.88: In the fixation of nitrogen by the arc process, air is passed through an electric arc. Some of the nitrogen is oxidized to NO which on cooling is oxidized to NO2. Of the NO2 formed, 66 % will get associated to N2O4 at 300 K. The gases are then passed into absorption towers where HNO3 is formed by the following reaction:
H_2O+3NO_2\rightarrow NO+2HNO_3The NO liberated in this reaction will be reoxidized in part and form more nitric acid. In the operation of such a plant, it is found possible to produce gases from the arc furnace in which the nitric oxide is 2 % by volume while hot. The gases are cooled to 300 K at a pressure of 1.013 bar before being sent to the absorber. Calculate the following: (a) The complete analysis by volume of the hot gases leaving the furnace assuming that the air entering the furnace was of average composition (b) The partial pressures of NO2 and N2O4 in the gases entering the absorption tower (c) The weight of HNO3 formed by 1000 m3 of gas entering the absorption system if the conversion to HNO3 of the combined N2 in the furnace gases is 85 % complete.
Problem 10.89: HNO3 is produced by treating NaNO3 with 95 % H2SO4. The resulting nitre cake contains 34 % H2SO4 and 1.5 % H2O. 2 % of the HNO3 formed remains in the cake. The reaction is complete. Calculate the following: (a) The weight of nitre cake per 100 kg of NaNO3 (b) The composition of nitre cake (c) The weight of aqueous H2SO4 used (d) The weight of HNO3 and H2O distilled from the nitre cake for 100 kg of NaNO3.
Problem 10.90: Urea is produced synthetically by reacting ammonia and carbon dioxide to form ammonium carbamate which is then decomposed to urea and water:
2NH_3+CO_2\rightarrow NH_2COONH_4 NH_2COONH_4\rightarrow NH_2CONH_2+H_2OThe conversion of ammonia is only 60 %. If 1000 kg of urea is to be produced, determine the following: (a) The volume of ammonia fed at STP and (b) The amount of water produced.
Problem 10.91: In the nitric acid manufacture 100 m3/h of ammonia at 300 K and 101.3 kPa is mixed with air and passed over a catalyst in a converter and the following reaction takes place:
4NH_3+5O_2\rightarrow6H_2O+4NOThe gases are then passed into an oxidizing tower where the oxidation is completed according to the following reaction:
2NO+O_2\rightarrow2NO_2The gases from the oxidizing tower are passed into a cooling tower where NO2 is absorbed in 150 kg/h of water and forms nitric acid as per reaction:
3NO_2+H_2O\rightarrow2HNO_3+NOThe overall reaction in the process is given by
NH_3+2O_2\rightarrow HNO_3+H_2OThe oxygen present in the air supplied is 20 % in excess of that required for the complete oxidation of the ammonia to nitric acid and water. Assume that (1) the degree of completion of the reaction in the converter is 85 % and no other decompositions take place, (2) 90 % of the nitric oxide entering the oxidizing tower is oxidized to nitrogen peroxide, and (3) the cooling tower exit gas contains no water vapor and all NO2 is absorbed in water. Calculate the following: (a) The amount of air to be used at 300 K, 101.3 kPa in m3/h (b) The moles of gases leaving the converter and its composition (c) The moles of gases leaving the oxidizer and its composition (d) The amount in kg/h and concentration by weight percent of nitric acid produced.
Problem 10.92: Hydrochloric acid is oxidized to chlorine by air in the presence of a catalyst. Air is supplied 30 % in excess of the theoretical requirement and the oxidation of the acid is 60 % complete. Calculate the following: (a) The ratio of acid to air on a weight basis (b) The composition of the gases leaving the reactor on a weight basis.
Problem 10.93: Chlorine is produced by the oxidation of hydrogen chloride gas with air
4HCl+O_2\rightarrow2Cl_2+2H_2OThe reaction is carried out at 1.2×105 N/m2 and 400 K. 50 percent excess air is used and the reaction is only 80 percent complete. Calculate (a) The volume of air admitted per 100 m3 of HCl if both air and HCl enter the reactor at 1.0 bar and 290 K (b) The volume of gases leaving the reactor per 100 m3 of HCl entering (c) The weight of chlorine produced per 100 m3 of HCl entering (d) The percent composition by volume of the exit gas on a dry basis.
Problem 10.94: In the Deacon process for the manufacture of chlorine, a dry mixture of hydrochloric acid and air is passed over a heated catalyst. Acid is oxidized in the presence of air, which is supplied 20 % in excess of that theoretically required:
4HCl+O_2\rightarrow2H_2O+2Cl_2Calculate the following for the oxidation of 1 kg of acid: (a) The amount of air supplied, in kilograms (b) If 60 % conversion is achieved, the composition of the product gases expressed in weight percent (c) The dew point of the exit gas stream which is at a pressure of 100 kPa and temperature of 450 K
The vapor pressure of water is given by the Antoine equation:
where pressure is in kPa and temperature is in K.
Problem 10.95: Carbon tetrachloride is made by chlorination of carbon disulfide in the following two steps:
CS_2+3Cl_2\rightarrow CCl_4+S_2Cl_2 CS_2+2S_2Cl_2\rightarrow CCl_4+6SThe reactants are admitted in stoichiometric ratio. Determine the mass of carbon tetrachloride and sulfur produced from 1000 kg of sulfide if (a) The conversion in both reactions are 100% (b) The yield is 85% in the first reaction and 90% in the second reaction.
Problem 10.96: Catalytic vapor-phase chlorination of CS2 gives carbon tetrachloride:
CS_2+3Cl_2\rightarrow CCl_4+S_2Cl_2The products leaving the converter analysed 26.0 % CCl4, 26.0 % S2Cl2, 17.5 % CS2, and 30.5 % Cl2. Determine the following: (a) The excess reactant and the percent excess (b) The percent conversion (c) The quantity of CCl4 obtained (in kilograms) per 100 kg of chlorine admitted.
Problem 10.97: Ethylene dichloride is manufactured by the oxychlorination of ethylene:
2C_2H_4+4HCl+O_2\rightarrow2C_2H_4Cl_2+2H_2OThough ethylene and air are supplied respectively 5 % and 10 % in excess over those required for the complete conversion of hydrogen chloride, the conversion attained is found to be only 90 %. For 500 kmol of HCl supplied, calculate the following: (a) The moles of the reactant and products (b) The mass of the reactants and products (c) The composition of the reactant stream in weight percent (d) The composition of the product stream in weight percent.
Problem 10.98: Monochloroacetic acid (MCA) is produced at a rate of 5000 kg/h by chlorination of glacial acetic acid with gaseous chlorine.
CH_3COOH+Cl_2\rightarrow CH_2ClCOOH+HClChlorine is supplied at a rate of 4500 kg/h. It is found that 300 kg/h of dichloroacetic acid (DCA) also is formed according to
CH_2ClCOOH+Cl_2\rightarrow CHCl_2COOH+HClAcetic acid is supplied in excess to minimize DCA production. Determine the conversion and yield of MCA.
Problem 10.99: Hydrochloric acid is made by the action of NaCl with H2SO4. The following reactions occur in series:
NaCl+H_2SO_4\rightarrow NaHSO_4+HCl NaHSO_4+NaCl\rightarrow Na_2SO_4+HClOne thousand kilograms of pure NaCl is treated with aqueous sulphuric acid solution of strength 75 % H2SO4. The solid cake obtained analyzed 91.5 % Na2SO4, 4.8 % NaHSO4, 2.0 % NaCl, 1.3 % H2O, and 0.4 % HCl. Determine the following: (a) The degree of completion of the first reaction (b) The degree of completion of the conversion to Na2SO4 (c) The quantity of acid added (d) The quantity of cake obtained (e) The weight of gases if the gases driven off are HCl and water vapor.
Problem 10.100: For purification of silicon from the metallurgical grade to the semiconductor grade, 100 kg of the metal is reacted with hydrogen chloride gas at 573 K. From several polychlorinated silanes that are formed in the reaction, trichlorosilane (HSiCl3), which is a liquid at room temperature, is separated by fractional distillation. Determine the quantity of pure trichlorosilane separated in the distillation unit if the gases leaving analyzed 21.0 % H2SiCl2, 14.0 % SiCl4, and 65 % H2.
Problem 10.101: Coal is hydrogenated in a fluidized bed reactor in the presence of air and steam at 675 K in order to produce gaseous hydrocarbon fuels. 2000 kg per hour of coal containing 10 % inert material by weight is charged into the reactor from the top, and air and steam are admitted from the bottom at a rate of 25000 kg/h and 3500 kg/h respectively. Assuming the complete conversion of coal, determine the flow rate of exit gases in kg/h.
Problem 10.102: An organic ester of formula C19H36O2 is to be hydrogenated at a rate of 100 kg/h to yield C19H38O2. The hydrogen required for the plant, which runs continuously, is available as 50 L cylinders in which the gas is contained at 70 bar and 300 K. How many cylinders should the company order per week?
Problem 10.103: Formaldehyde is made by the oxidation of methanol with air. The analysis of the exit gas from the reactor shows 63.1 % N2, 13.4 % O2, 5.9 % H2O, 12.3 % CH3OH, 4.1 % HCHO and 1.2 % HCOOH. Calculate the following: (a) The conversion per pass (b) The ratio of air to methanol in the feed.
Problem 10.104: In a propylene plant, 100 kg/h of pure propane is fed to a catalytic reactor where it is converted to a gas containing 25 % propylene, 45 % propane, and 30 % hydrogen by volume. This reactor gas is separated in a separator unit into three streams: (1) light gas containing 1.2 % propane, 0.8 % propylene and all hydrogen formed in the reactor, (2) desired product containing 99 % propylene and 1 % propane, and (3) bottom product containing 2 % propylene and 98 % propane. All the bottom product is returned back to the reactor. Calculate the following: (a) The amount of product obtained in kg/h (b) The amount of propane recycled, kg/h (c) The amount of propane in light gas, kg/h.
Problem 10.105: Formaldehyde is produced by the gas phase oxidation of methanol with air over a catalyst
CH_3OH+\frac12O_2\rightarrow HCHO+H_2O100 m3 of methanol vapor at 1.013×105 N/m2 and 550 K is to be treated. If 10 % excess air is supplied and the reaction is only 80 % complete, calculate the following: (a) The composition of the product gas (b) The volume of product gases at 1.5×105 N/m2 and 800 K.
Problem 10.106: Ethylene oxide is produced by burning ethylene gas with air in the presence of a catalyst. In the reaction, a substantial portion of ethylene is converted to ethylene oxide, a small fraction is completely oxidized to CO2, and water and some gases remain unconverted. The ethylene oxide in the product gas is recovered by absorption. The Orsat analysis of the gases leaving the absorber is: 8.77 % CO2, 4.38 % O2, and 4.38 % ethylene. Calculate the percent of the ethylene fed to the reactor that is converted to the oxide.
Problem 10.107: Ethylene glycol (CH2OH)2 is produced by air oxidation of ethylene to ethylene oxide and subsequent absorption of the oxide in water.
C_2H_4+\frac12O_2\rightarrow C_2H_4O C_2H_4O+H_2O\rightarrow(CH_2OH)_2A portion of the ethylene is oxidized to CO2:
C_2H_4+3O_2\rightarrow2CO_2+2H_2O100 kmol of a gas mixture containing 10 % ethylene and 90 % air is fed to the oxidizer. The gases leaving the reactor are absorbed in water fed at the rate of 10 moles per 100 moles of the original gas mixture. The off-gases leaving the absorber gave the following analysis on a dry basis: C2H4 2.31 %, CO2 6.94 %, and the rest oxygen and nitrogen. The gases leave the absorber at 101.325 kPa saturated with water vapor at 306 K. (The vapor pressure of water at 306 K is 5 kPa.) Determine the following: (a) The moles of ethylene glycol produced (b) The percent conversion of ethylene to glycol (c) The moles of dry gases leaving the absorber (d) The weight percent of ethylene glycol in the glycol water solution.
Problem 10.108: Acetylene is produced industrially by reacting calcium carbide and water:
CaC_2+H_2O\rightarrow CaO+C_2H_2Calcium carbide containing 8 % inert impurities is reacted with water so that the reaction goes to completion. For producing 1000 kg of acetylene, calculate the following: (a) The weight of impure carbide needed (b) The weight of solid residue after the reaction (c) The weight ratio of acetylene to water vapor if the acetylene produced is saturated with water vapor at 306 K and 101.3 kPa. The vapor pressure of water at 306 K is 5 kPa.
Problem 10.109: Ethanol is produced by the hydration of ethylene:
C_2H_4+H_2O\rightarrow C_2H_5OHSome of the product is converted to ethyl ether by the side reaction
2C_2H_5OH\rightarrow(C_2H_5)_2O+H_2OThe feed to the reactor contains 25 % C2H4, 65 % H2O, and the balance inert materials on a mole basis. An ethylene conversion of 10 % and ethanol yield of 90 % is achieved. Compute the composition of the reactor output stream.
Problem 10.110: A pilot plant reactor was charged with 50 kg of naphthalene and 200 kg (98 % by weight) of sulphuric acid. The reaction was carried out for 3 hours at 430 K. The reaction goes to completion:
C_10H_8+H_2SO_4\rightarrow C_10H_7(SO_3H)+H_2O C_10H_8+2H_2SO_4\rightarrow C_10H_6(SO_3H)_2+2H_2OThe product distribution by weight was found to be 18 % monosulphonate and 82 % disulphonate of naphthalene. Calculate (a) The quantities of monosulphonate and disulphonate products (b) The complete analysis of the product