An industrial plant needs 20,000 lbm of saturated steam at 280oF per hour for heating purposes and ten MW of electrical power. A small turbine system is to be designed to handle both of these needs. Steam is supplied to a turbine at 400 psia pressure from a boiler and expanded until 280oF saturated steam is obtained whereupon the steam needed for heating is extracted. The rest of the steam is expanded in a second turbine to a condenser pressure of 5 psia, where it is condensed, compressed to 400 psia and returned to the boiler. The heating steam returns as a liquid at 200oF and 1 atm pressure where it is compressed to 400 psia and returned to the boiler. Both turbines have an efficiency of 72% and both feed water pumps have an efficiency of 50%. The power from the turbines is used to drive the feed water pumps. (a) At what temperature must the steam be generated in the boiler to supply the 280oF saturated heating steam? (b) How much steam must the boiler supply? (c) If one pound of coal delivers 11,000 Btu of heat to the water in the boiler, how many pounds of coal are consumed per hour?
An industrial plant needs 20,000 lbm of saturated steam at 280oF per hour for heating purposes and ten MW of electrical power. A small turbine system is to be designed to handle both of these needs. Steam is supplied to a turbine at 400 psia pressure from a boiler and expanded until 280oF saturated steam is obtained whereupon the steam needed for heating is extracted. The rest of the steam is expanded in a second turbine to a condenser pressure of 5 psia, where it is condensed, compressed to 400 psia and returned to the boiler. The heating steam returns as a liquid at 200oF and 1 atm pressure where it is compressed to 400 psia and returned to the boiler. Both turbines have an efficiency of 72% and both feed water pumps have an efficiency of 50%. The power from the turbines is used to drive the feed water pumps.
(a) At what temperature must the steam be generated in the boiler to supply the 280oF saturated heating steam?
(b) How much steam must the boiler supply?
(c) If one pound of coal delivers 11,000 Btu of heat to the water in the boiler, how many pounds of coal are consumed per hour?
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