Lecture20 Exercises on heat recovery

# 486kgmolwiththefollowingcomposition co 005832 kg mol

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Unformatted text preview: he furnace at the process temperature, i.e. 1600K. Basis of calculation is 298K and 1 kg coal By carbon balance, the amount of POC is 0.486 kg mol with the following composition CO 0.05832 kg mol HO 0.0243 kg mol O N 0.034 kg mol 0.3694 kg mol Heat to POC can now be calculated by using Cp values. The calculated value of heat to POC is 22063kJ. GAH/kg of coal 27900 Fuel consumption in kg/hr 22063 5837 kJ 1500 x 3600 / 5837 925kg/hr Suppose the combustion air is preheated with the heat recovered from the POC in a heat exchanger which is having 50% relative efficiency. Calculate the fuel consumption First we have to find amount of air. In this problem note that composition of coal is not completely given. Amount of air has to be calculated from the amount of POC: Nitrogen in POC is nitrogen from air Oxygen from air 0.3694 kg mole 0.0982 kg mole Sensible heat in preheated air relative efficiency x sensible heat in air at 1600K 0.5 x 0.3694 x 41620 0.0982 x 43710 9833 kJ GAH 27900 9833 22063 15670 kJ One notes that GAH increases with the addition of sensible heat in air. Fuel consumption 344 kg/hr Fuel saving = 580 kg/hr; if the furnace operates for 20 hrs/day then coal saving is 11140 kg/day. Carbon saving is 8127 kg/day. This saving means that now less carbon will be disch...
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## This note was uploaded on 10/23/2012 for the course ME 076 taught by Professor Ukkushwaha during the Spring '12 term at E. Kentucky.

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