Concept explainers
The estimated temperature of the combustion products.
Answer to Problem 82P
The estimated temperature of the combustion products is
Explanation of Solution
Express the total mass of the coal when the ash is substituted.
Here, mass of ash is
Express the mass fraction of carbon.
Here, mass of carbon is
Express the mass fraction of hydrogen.
Here, mass of hydrogen is
Express the mass fraction of oxygen.
Here, mass of oxygen is
Express the mass fraction of nitrogen.
Here, mass of nitrogen is
Express the mass fraction of sulphur.
Here, mass of sulphur is
Express the number of moles of carbon.
Here, molar mass of carbon is
Express the number of moles of hydrogen.
Here, molar mass of hydrogen is
Express the number of moles of oxygen.
Here, molar mass of oxygen is
Express the number of moles of nitrogen.
Here, molar mass of nitrogen is
Express the number of moles of sulphur.
Here, molar mass of sulphur is
Express the total number of moles.
Express the mole fraction of carbon.
Express the mole fraction of hydrogen.
Express the mole fraction of oxygen.
Express the mole fraction of nitrogen.
Express the mole fraction of sulphur.
Apply energy balance under steady flow conditions on the combustion chamber.
Here, number of moles of products is
Conclusion:
Refer Table A-1, “molar mass, gas constant, and the critical point properties”, and write the molar masses.
Here, molar mass of air is
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Express the combustion equation.
Perform the species balancing:
Carbon balance:
Hydrogen balance:
Sulphur balance:
Oxygen balance:
Nitrogen balance:
Substitute
Refer Equation (XX), and write the number of moles of products and reactants.
Refer Appendix Table A-18, A-19, A-20 and A-23 and write the property table for products and reactants as in Table (1).
Substance |
|
|
|
0 | 8682 | 11,171 | |
0 | 8669 | 11,640 | |
9904 | |||
9364 |
Substitute the values form Table (I) into Equation (XVIII) to get,
Perform trial and error method to balance the Equation (XXI).
Iteration I:
Take
Iteration II:
Take
Perform the interpolation method to obtain the adiabatic flame temperature of the product gases.
Write the formula of interpolation method of two variables.
Here, the variables denote by x and y is enthalpy and estimated temperature respectively
Show the adiabatic flame temperature corresponding to enthalpy as in Table (1).
Enthalpy |
Estimated temperature |
1980 | |
2000 |
Substitute
Thus, the estimated temperature of the combustion product gases is,
Here, estimated temperature of the combustion product gases is
Hence, the estimated temperature of the combustion products is
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Chapter 15 Solutions
Thermodynamics: An Engineering Approach
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