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Lecture20 Exercises on heat recovery

# Drawenergyflowdiagramineachofthefollowingcasesalso a

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Unformatted text preview: f air preheater is being considered. It is estimated that the proposed preheater would recover one half of the sensible heat in the flue gases and would return to the furnace. Draw energy flow diagram in each of the following cases also a) If the daily process requirements and daily heat loss are kept same, what percent saving in fuel could be achieved by the preheater installation? What would be the new heat balance (in percent) ? b) If the daily fuel consumption and daily heat loss are kept same, what percent increase could be made in heat furnished to the process as a result of the preheater installation? What would be the new heat balance (in percent) ? Assignment 1a) Consider combustion of fuel oil with air to heat the furnace to a temperature at ToC. Fuel oil analyses 84% C, 5% H, 2% S, and 9% incombustibles. Gross calorific value of fuel oil is 9500 kcal/kg. Determine GAH in each case when the furnace temperature T is a) 727oC, b) 827oC, c) 927oC and d) 1127oC. Assume complete combustion with the theoretical amount of air 1b) Repeat calculations for problem 1 when the excess air is 20% and 50% than theoretical one. 2) The heat requirement of a process is 1.5 x 103 kW. The furnace is fired with coal which has 70% C. The NCV of coal is 27900 kJ/kg. The process is carried out at 1600K. Products of combustion analyse 76% N2, 7 % O2, 5% H2O and 12 %CO2. Calculate fuel consumption A heat balance for a continuous metallurgical process gives the following data: Heat input % of total Combustion of fuel 100 Heat output % of total 25 Process requirements Sensible heat in flue gases 50 Heat loss 25 The installation of air preheater is being considered. It is estimated that the proposed preheater would recover one half of the sensible heat in the flue gases and would return to the furnace. Draw energy flow diagram in each of the following cases also a) If the daily process requirements and daily heat loss are kept same, what percent saving in fuel could be achieved by the preheater installation? What would be the new heat balance (in percent) ? b) If the daily fuel consumption and daily heat loss are kept same, what percent increase could be made in heat furnished to the process as a result of the preheater installation? What would be the new heat balance (in percent) ?...
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