Coal analysis indicates 75% by mass of C, 17% H, 2% S, and the rest are non-combustible ashes. The coal burns at a rate of 5000 kg/h, and the air feed rate to the burner is 50 kmol/min. All ashes and 6% of the carbon in the fuel leave the furnace as molten slag; the remaining carbon exits with the flue gas in the form of CO and CO2; the hydrogen in the coal is oxidized to water, and the sulfur exits as SO2. The selectivity of CO2 production relative to CO is 10:1. (a) Calculate the percentage of excess air supplied to the reactor. Write the chemical reactions and use atomic species balances to perform the calculations. Answer: 19.8% (b) Calculate the molar fractions of the gaseous pollutants — CO and SO2 — in the flue gas. Answer: 8.3×10^{-3} mol CO/mol; 9.6×10^{-4} mol SO2/mol (c) The emitted sulfur dioxide is already a danger in itself but becomes more harmful to the environment as a precursor to acid rain. Under the catalytic action of sunlight, sulfur dioxide is oxidized to sulfur trioxide (SO2 + 1/2 O2 → SO3), which in turn combines with water vapor to form sulfuric acid (SO3 + H2O → H2SO4), which returns to Earth as rain. Acid rain formed in this manner causes extensive damage to forests, fields, and lakes in many parts of the world. For the furnace described above, calculate the rate of sulfuric acid formation (kg/h) if all emitted SO2 were converted as indicated. Answer: 304 kg H2SO4/h
Coal analysis indicates 75% by mass of C, 17% H, 2% S, and the rest are non-combustible ashes. The coal burns at a rate of 5000 kg/h, and the air feed rate to the burner is 50 kmol/min. All ashes and 6% of the carbon in the fuel leave the furnace as molten slag; the remaining carbon exits with the flue gas in the form of CO and CO2; the hydrogen in the coal is oxidized to water, and the sulfur exits as SO2. The selectivity of CO2 production relative to CO is 10:1.
(a) Calculate the percentage of excess air supplied to the reactor. Write the chemical reactions and use atomic species balances to perform the calculations. Answer: 19.8%
(b) Calculate the molar fractions of the gaseous pollutants — CO and SO2 — in the flue gas. Answer: 8.3×10^{-3} mol CO/mol; 9.6×10^{-4} mol SO2/mol
(c) The emitted sulfur dioxide is already a danger in itself but becomes more harmful to the environment as a precursor to acid rain. Under the catalytic action of sunlight, sulfur dioxide is oxidized to sulfur trioxide (SO2 + 1/2 O2 → SO3), which in turn combines with water vapor to form sulfuric acid (SO3 + H2O → H2SO4), which returns to Earth as rain. Acid rain formed in this manner causes extensive damage to forests, fields, and lakes in many parts of the world. For the furnace described above, calculate the rate of sulfuric acid formation (kg/h) if all emitted SO2 were converted as indicated. Answer: 304 kg H2SO4/h
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