Fuels and Combustion
- What is a fuel and what are the characteristics of a good fuel? In one line A fuel is a carbon-containing substance that burns in air (oxygen) and releases a large amount of heat that can be used economic... 1
- What is calorific value, and how are gross and net calorific values different? In one line Calorific value is the total quantity of heat liberated when a unit mass (or unit volume) of a fuel is burnt completely in air o... 1
- How does Boys' gas calorimeter measure the calorific value of a gaseous fuel? In one line A known volume of gas is burnt at a steady rate, and its heat is absorbed by water flowing through cooling tubes; from the water... 1
- How is the calorific value of a solid fuel determined using a bomb calorimeter? In one line A known mass of fuel is burnt in excess oxygen inside a sealed steel "bomb" placed in a known mass of water, and the rise in wat... 1
- How do you calculate the calorific value of coal using Dulong's formula? In one line Dulong's formula estimates the higher calorific value of a fuel from its percentages of carbon, hydrogen, oxygen and sulphur (fr... 1
- What is proximate analysis of coal and why do moisture, volatile matter, ash and fixed carbon matter? In one line Proximate analysis finds the percentages of moisture, volatile matter, ash and fixed carbon in coal by simple weighing and heati... 1
- How do you calculate the minimum weight of oxygen and air needed to burn 1 kg of coal? In one line Using balanced combustion equations, find the oxygen needed by C, H and S, subtract the oxygen already present in the fuel, and... 1
- What is ultimate analysis of coal and how are carbon, hydrogen, nitrogen, sulphur and oxygen found? In one line Ultimate analysis determines the elemental composition of coal (C, H, N, S, ash and O by difference) and is used for calorific v... 1
- How do you find the volume of air at STP needed to burn coal, including excess air? In one line Convert the minimum mass of oxygen into moles, multiply by 22.4 to get its volume at STP, then divide by 0.21 because air contai... 1
- A sample of coal has the following composition C = 84 %, O = 8.4 %, H = 5.5 %, S = 1.5%, N = 0.6 %, Calculate the higher and lower calorific values of coal. Given: C = 84%, H = 5.5%, O = 8.4%, S = 1.5%, N = 0.6% (N does not contribute to the heat). Dulong's formula (C, H, O, S in %): HCV = 1/100[... 1
- What are advantages of gaseous fuels over solid and liquid fuels? They can be carried easily through pipelines to the point of use, so there is no handling or storage labour. They mix intimately with air, s... 1
- 1 gm. of coal sample was used for determination of nitrogen. The ammonia evolved was passed into 50ml of 0.1 N H2SO4, the excess acid required 42 ml. of 0.1N NaOH for neutralization Calculate % of N. Given: W = 1 g; acid taken = 50 mL of 0.1 N H₂SO₄; excess acid = 42 mL of 0.1 N NaOH. Volume of 0.1 N acid used by NH₃ = 50 − 42 = 8 mL. %N... 1
- Explain the determination of sulphur present in coal sample and write its significance. Principle: the sulphur in coal is converted to sulphate and weighed as BaSO₄. Procedure A known mass (W g) of coal is burnt in a bomb calori... 1
- Define calorific value and write the significance of proximate analysis of coal. Calorific value is the total quantity of heat liberated when a unit mass (or unit volume) of a fuel is burnt completely in air or oxygen. Un... 1
- How is the percentage of sulphur determined in a solid fuel? Principle: the sulphur in the solid fuel is converted to sulphate, precipitated as BaSO₄ and weighed. A known mass (W g) of the fuel is burn... 1
- Calculate the gross and net calorific value of coal having the following compositions. Carbon=85%, hydrogen=8%, sulphur=1%, nitrogen=2%, ash=4%, and the latent heat of steam is 587 cal/gm. Given: C = 85%, H = 8%, S = 1%, N = 2%, ash = 4%. Total = 85 + 8 + 1 + 2 + 4 = 100%, so O = 0%. Latent heat of steam = 587 cal/g = 587 kcal/... 1
- 1.0 g of coal sample was digested (Kjeldahl method). The liberated ammonia was absorbed in 25 ml of N/10 H2SO4. To neutralise excess acid, 15 ml of 0.1 N NaOH was required. Determine the % nitrogen in the given sample of coal. Kjeldahl method: coal is digested with conc. H₂SO₄ + K₂SO₄ (with a CuSO₄ catalyst), which converts N to (NH₄)₂SO₄. Heating with NaOH liberat... 1
- 0.5 gm. of coal sample was burnt in Bomb calorimeter produced 0.06 gm. of BaSO4. calculate percentage of sulphur Given: mass of coal W = 0.5 g; mass of BaSO₄ = 0.06 g. Principle: S → SO₄²⁻ → BaSO₄. Since BaSO₄ = 233 and S = 32, 233 g of BaSO₄ contains 3... 1
- Explain with neat suitable diagram determination of Carbon and hydrogen by ultimate analysis Principle: a known mass of coal is burnt completely in a current of dry, CO₂-free oxygen. Its carbon becomes CO₂ and its hydrogen becomes H₂... 1
- A sample of coal has the following composition C = 80 %, O = 8%, H = 6 %, S = 1.5%, N = 1 %, Calculate the higher and lower calorific values of coal. Given: C = 80%, H = 6%, O = 8%, S = 1.5%, N = 1% (N does not contribute to the heat). Dulong's formula (C, H, O, S in %): HCV = 1/100[8080 C... 1
- What are the characteristics of good fuel? A good fuel should: Have a high calorific value, so it gives more heat per unit mass. Have a moderate ignition temperature. If it is too low... 1