2. Estimation and Selection of Air for a Fuel P M V Subbarao Professor Mechanical Engineering Department A Criteria for Sizing of Furnace & Furnace Accessories.

3. Chemical Models for Real Fuels Wood Peat Lignite Sub-bituminours

4. Production of Useful Fuels from Crude

5. Boiling range, and molecule size for typical refinery BOILING RANGE # CARBON ATOMS Refinery Gas <25 o C3 Gasoline 40-150 o C 4-10 Naptha 150-200 o C 10-12 Kerosene 200-300 o C 12-16 Diesel Fuel 300-400 o C 16-25 Residual Oil >400 o C >25

6. Generation of Fuel Model Practical fuels are complex mixtures of compounds. Some useful for generation of heat & some are useless. Some are threat to environment. Proximate Analysis & Ultimate Analysis. Proximate analysis - to determine the moisture, ash, volatiles matter and fixed carbon National Capital Power Station Dadri Equilibrated Basis SampleMOIS.ASHV.M.FC UHV (%) K.CaI/Kg. Wash Coal7.133.725.034.23270 Raw Coal6.435.225.832.63159

7. Commercial Use of Proximate Analysis The Energy content -- CFRI Formulae -- Low Moisture Coal(M < 2% ) -- CV (Kcal/kg) = 71.7 FC + 75.6 (VM-0.1 A) - 60 M High Moisture Coal(M > 2%) -- CV(kcal.kg) = 85.6 {100 - (1.1A+M)} - 60 M Where, M, A, FC and VM denote moister, ash, fixed carbon and Volatile mater (all in percent), respectively.

8. Ultimate Analysis Ultimate or elementary analysis - to determine the elemental composition of the fuel Ultimate Analysis: On Air Dried Basis Wash Coal % Gross Calorific Value4370 Carbon Content51.28 Hydrogen Content3.18 Oxygen Content9.72 Nitrogen Content0.45 Sulfur Content0.30 Ash Content35.07 Raw Coal Gross Calorific Value4250 Carbon Content51.00 Hydrogen Content3.14 Oxygen Content8.20 Nitrogen Content0.35 Sulfur Content0.35 Ash Content36.96

9. Ultimate Analysis: On Air Dried Basis Raw Coal Gross Calorific Value3884 Carbon Content42.6 Moisture Content6.0 Hydrogen Content3.3 Oxygen Content11.5 Nitrogen Content0.7 Content0.35 Ash Content35.7

10. Fuel Model

11. Ash Model

13. Fuel Model Ultimate Analysis of fuel: Gravimetric Percentage of carbon : x --- Number of moles, X = x/12 Percentage of combustible hydrogen : y --- Number of atomic moles, Y = y/1 Percentage of combustible oxygen: k --- Number of atomic moles, K = k/16 Percentage of sulfur: z – Number of atomic moles, Z = z/32 Equivalent chemical formula : C X H Y S Z O K Equivalent Molecular weight : 100 kgs.

15. Ideal Combustion Ideal combustion C X H Y S Z O K + 4.673 (X+Y/4+Z-K/2) AIR → P CO 2 +Q H 2 O + R N 2 + G SO 2 Ideal Air- Fuel Ratio:

16. Second law limit on possibility of extent of reaction Reactants Products At any time a reactor contains a combination of reactants and products. A reaction is said to be complete when the entropy of an adiabatic furnace reaches its maximum value. The value of maximum entropy will vary with the pressure and temperature of the reaction. A reaction system and parameters of reaction should be designed such the the maximum entropy is obtained when the reaction is almost complete (>98%).

17. Mathematical Model for Completion of Reaction For every fuel, a designer should know all possible reactants !!! Some products will influence the efficiency of reaction. Few other may not influence the efficiency of reaction but severely affect the environment. The optimal parameters for efficient reaction may not be optimal for safe reaction !!

18. Generalized Theory of Extent of Reaction Possible Extent of Reaction Entropy of Universe P 1,T 1 P 2,T 2 P 3,T 3

19. Model Testing for Determination of important species Air Flow Rate Fuel Flow Rate Water Flow Rate Flue gas Analysis

20. Results of Model Testing. For a given fuel and required steam conditions. Optimum air flow rate. Optimum fuel flow rate. Optimum steam flow rate. Optimum combustion configuration!!! Realization of MATt  Theory Mixing: Fuel preparation systems. Air: Draught systems. T : Preheating of fuel. t : Dimensions of combustion chamber.  : Turbulence generation systems.