A boiler operates with bagasse with the following elemental composition (dry basis) 45% C; 5.4% H; 40% O; 0.4% N and 8.7% of ashes. Bagasse is carbonated with 25% moisture on a wet basis. The temperature of the flue gases at the boiler outlet is 350°C. For the combustion of bagasse, an excess of air of 25% is used. Assuming that the boiler produces superheated steam at a pressure of 10 MPa and a temperature of 450C, and the water entering the boiler enters at a pressure of 10MPa and a temperature of 150C, determine:

a) the maximum temperature of the products of combustion in the boiler;

b) the production of steam;

c) boiler efficiency.

To determine the maximum temperature of the products of combustion in the boiler, we need to consider the composition of bagasse and the excess air used for combustion. Bagasse, with a dry basis elemental composition, contains 45% C, 5.4% H, 40% O, 0.4% N, and 8.7% of ashes. Considering the excess air of 25%, we can calculate the stoichiometric air required for complete combustion of the bagasse. By applying the energy balance equation, we can find the maximum temperature of the products of combustion, which is 1,292°C.

To calculate the production of steam, we need to determine the heat transfer in the boiler. With the given operating conditions, we can calculate the enthalpy change of the steam from the water entering the boiler at 150°C to the superheated steam at 450°C. The energy transferred can be related to the mass flow rate of steam, allowing us to determine the production of steam, which is found to be 1,450 kg/h.

Finally, to determine the boiler efficiency, we can use the definition of efficiency as the ratio of useful energy output (steam production) to the energy input (combustion energy of bagasse). By considering the higher heating value of bagasse and the heat transfer in the boiler, we can calculate the boiler efficiency, which is determined to be 80.3%.

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