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9.72. A bituminous coal is burned with air in a boiler furnace. The coal is fed at a rate of 40,000 kg/h and has an ultimate analysis of 76 wt% C, 5% H, 8% O, negligible amounts of N and S, and 11% noncombustible ash (see Problem 9.58), and a higher heating value of 25,700 kJ/kg. Air enters a preheater at 30°C and 1 atm with a relative humidity of 30%, exchanges heat with the hot flue gas leaving the furnace, and enters the furnace at temperature T„(°C). The flue gas contains 7.71 mole% CO2 and 1.29 mole% CO on a dry basis, and the balance is a mixture of O2, N2, and H2O. It emerges from the furnace at 260°C and is cooled to 150°C in the preheater. Noncombustible residue (slag) leaves the furnace at 450°C and has a heat capacity of 0.97 kJ/(kg-°C). Steam H2O(1) Flue gas Flue gas 260°C PREHEATER 150°C 40,000 kg coal/h Air 25°C FURNACE Air 30°C T("C) Slag 450°C (a) Prove that the air-to-fuel ratio is 16.1 standard cubic meters/kg coal and that the flue gas contains 4.6% H2O by volume. (b) Calculate the rate of cooling required to cool the flue gas from 260°C to 150°C and the temperature to which the air is preheated. (Note: A trial-and-error calculation is required.) (c) If 60% of the heat transferred from the furnace (-Q) goes into producing saturated steam at 30 bar from liquid boiler feedwater at 50°C, at what rate (kg/h) is steam generated?

9.72. A bituminous coal is burned with air in a boiler furnace. The coal is fed at a rate of 40,000 kg/h and has an ultimate analysis of 76 wt% C, 5% H, 8% O, negligible amounts of N and S, and 11% noncombustible ash (see Problem 9.58), and a higher heating value of 25,700 kJ/kg. Air enters a preheater at 30°C and 1 atm with a relative humidity of 30%, exchanges heat with the hot flue gas leaving the furnace, and enters the furnace at temperature T„(°C). The flue gas contains 7.71 mole% CO2 and 1.29 mole% CO on a dry basis, and the balance is a mixture of O2, N2, and H2O. It emerges from the furnace at 260°C and is cooled to 150°C in the preheater. Noncombustible residue (slag) leaves the furnace at 450°C and has a heat capacity of 0.97 kJ/(kg-°C). Steam H2O(1) Flue gas Flue gas 260°C PREHEATER 150°C 40,000 kg coal/h Air 25°C FURNACE Air 30°C T("C) Slag 450°C (a) Prove that the air-to-fuel ratio is 16.1 standard cubic meters/kg coal and that the flue gas contains 4.6% H2O by volume. (b) Calculate the rate of cooling required to cool the flue gas from 260°C to 150°C and the temperature to which the air is preheated. (Note: A trial-and-error calculation is required.) (c) If 60% of the heat transferred from the furnace (-Q) goes into producing saturated steam at 30 bar from liquid boiler feedwater at 50°C, at what rate (kg/h) is steam generated?

Introduction to Chemical Engineering Thermodynamics
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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9.72. A bituminous coal is burned with air in a boiler furnace. The coal is fed at a rate of 40,000 kg/h and has an ultimate analysis of 76 wt% C, 5% H, 8% O, negligible amounts of N and S, and 11% noncombustible ash (see Problem 9.58), and a higher heating value of 25,700 kJ/kg. Air enters a preheater at 30°C and 1 atm with a relative humidity of 30%, exchanges heat with the hot flue gas leaving the furnace, and enters the furnace at temperature T„(°C). The flue gas contains 7.71 mole% CO2 and 1.29 mole% CO on a dry basis, and the balance is a mixture of O2, N2, and H2O. It emerges from the furnace at 260°C and is cooled to 150°C in the preheater. Noncombustible residue (slag) leaves the furnace at 450°C and has a heat capacity of 0.97 kJ/(kg-°C). Steam H2O(1) Flue gas Flue gas 260°C PREHEATER 150°C 40,000 kg coal/h Air 25°C FURNACE Air 30°C T("C) Slag 450°C (a) Prove that the air-to-fuel ratio is 16.1 standard cubic meters/kg coal and that the flue gas contains 4.6% H2O by volume. (b) Calculate the rate of cooling required to cool the flue gas from 260°C to 150°C and the temperature to which the air is preheated. (Note: A trial-and-error calculation is required.) (c) If 60% of the heat transferred from the furnace (-Q) goes into producing saturated steam at 30 bar from liquid boiler feedwater at 50°C, at what rate (kg/h) is steam generated?
Transcribed Image Text:9.72. A bituminous coal is burned with air in a boiler furnace. The coal is fed at a rate of 40,000 kg/h and has an ultimate analysis of 76 wt% C, 5% H, 8% O, negligible amounts of N and S, and 11% noncombustible ash (see Problem 9.58), and a higher heating value of 25,700 kJ/kg. Air enters a preheater at 30°C and 1 atm with a relative humidity of 30%, exchanges heat with the hot flue gas leaving the furnace, and enters the furnace at temperature T„(°C). The flue gas contains 7.71 mole% CO2 and 1.29 mole% CO on a dry basis, and the balance is a mixture of O2, N2, and H2O. It emerges from the furnace at 260°C and is cooled to 150°C in the preheater. Noncombustible residue (slag) leaves the furnace at 450°C and has a heat capacity of 0.97 kJ/(kg-°C). Steam H2O(1) Flue gas Flue gas 260°C PREHEATER 150°C 40,000 kg coal/h Air 25°C FURNACE Air 30°C T("C) Slag 450°C (a) Prove that the air-to-fuel ratio is 16.1 standard cubic meters/kg coal and that the flue gas contains 4.6% H2O by volume. (b) Calculate the rate of cooling required to cool the flue gas from 260°C to 150°C and the temperature to which the air is preheated. (Note: A trial-and-error calculation is required.) (c) If 60% of the heat transferred from the furnace (-Q) goes into producing saturated steam at 30 bar from liquid boiler feedwater at 50°C, at what rate (kg/h) is steam generated?
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