A boiler furnace releases 10000.000kJ of heat for each kg of fuel burned and produces dry saturated steam at 10000.000kPa from feed water at 190.000 degrees Celsius. How many kg of steam will be produced for each kg of fuel burned if the boiler had an efficiency of 69%.
ANS = kg steam/ kg of fuel
To calculate the amount of steam produced per kilogram of fuel burned, we need to consider the efficiency of the boiler.
The efficiency of a boiler is defined as the ratio of useful output energy to the input energy. In this case, the useful output energy is the heat released by the furnace, which is 10000.000 kJ per kilogram of fuel burned.
The input energy is the energy available in the fuel, and we need to account for the energy lost during the combustion process. The efficiency of the boiler is given as 69%, which means that only 69% of the energy available in the fuel is converted into useful output energy.
So, the input energy is calculated as follows:
Input energy = 10000.000 kJ / 0.69
Now, we need to convert the heat energy into the amount of steam produced. To do this, we use the concept of enthalpy of vaporization (ΔHv) for water.
The enthalpy of vaporization is the amount of energy required to convert one kilogram of water at the saturation point to steam at the same temperature and pressure. For water at 10000.000 kPa and 190.000 degrees Celsius, the enthalpy of vaporization is approximately 2257 kJ/kg.
So, for each kilogram of fuel burned, the amount of steam produced is calculated as:
Steam produced = Input energy / enthalpy of vaporization
Substituting the values, we get:
Steam produced = (10000.000 kJ / 0.69) / 2257 kJ/kg
Now, we can calculate the value using a calculator:
Steam produced = 10000.000 / 0.69 / 2257
Steam produced ≈ 5.369 kg of steam per kilogram of fuel burned
Therefore, approximately 5.369 kg of steam will be produced for each kilogram of fuel burned if the boiler has an efficiency of 69%.