2. Dr. Shivendra Singh Assistant Professor NET-JRF, PhD (IIT Indore) 1 Engineering Chemistry Fuels

3. 1.To acquire knowledge of different types of fuels and about calorific value. 2.To acquire required knowledge about Bomb calorimeter. Objectives Outcomes Students will gain the basic knowledge of fuels. They can understand the basic properties of fuels and measurement of calorific values.

4. 1.Introduction- Importance of fuels in industry 2.Classification of fuels 3.Comparison of solid, liquid & gaseous fuels 4.Properties/Characteristics of fuels 5.Calorific value of a fuel 6.Determination of calorific value by Bomb Calorimeter Outlines

5. Fuels: Most widely-used sources of energy in the world today. Most fuels are natural substances such as petro fuel, diesel, and natural gas, which are either extracted straight from the earth or produced by refining substances such as petroleum. The energy produced by burning fuel has many applications; 1.Powering vehicles, ships & airplanes 2.Providing electricity for homes and industries. Some common fuels are; Wood, Coal, Petroleum, Kerosene, Diesel, Natural gases Definition (Fuel): Any combustible substance which during combustion gives large amount of industrially or domestically useful heat. Introduction

6. A.On the basis of their occurrence: 1)Natural / Primary Fuels: Found in nature. Eg Wood, Coal, Petroleum, Natural gas etc. 2)Artificial / Secondary Fuel: Prepared artificially generally from primary fuels. Eg. Petrol, Coal gas, kerosene etc. B. On the basis of physical state of aggregation: 1)Solid: Eg Wood, Coal etc. 2)Liquid: Eg. Petrol, kerosene etc. 3)Gas: Eg. Natural gas, coal gas, bio gas, water gas etc. Classification

7. SNFuel CharacteristicsSolid FuelLiquid FuelGaseous Fuel 1CostCheapCostly than solidsCostly 2StorageEasyIn a closed containerLeak proof container 3Risk of fire hazardsLeastGreaterVery high 4Combustion rateSlowQuickVery rapid 5Combustion controlNot easyControlledPossible by controlling air supply 6AshAlways producedNo issue 7SmokeProducedIf high carbon; then produced Not produced 8W/W calorific valueLeastHigherHighest 9Thermal efficiencyLeastHigherHighest Advantages Easy to transportHigh CV, burn without dustBurn without any smoke, clean in use Moderate ignition temp Easy to transportHigh CV Classification

8. 1.High calorific value 2.Moderate ignition temperature 3.Low moisture content 4.Low non-combustible matter content 5.Moderate rate of combustion 6.Harmless combustion products 7.Low cost 8.Easy to transport 9.Low storage cost 10.Controllable combustion 11.Uniform size 12.Fuel should burn in air with efficiency without much smoke Characteristics of good fuel

9. 1.High calorific value: “Total quantity of heat liberated from combustion of a unit mass (or volume) of the fuel in air or oxygen.” 2.Moderate ignition temperature: “Lowest temperature to which the fuel must be pre-heated so that it starts burning smoothly.” Moderate ignition temp is ideal. 3.Low moisture content: Moisture reduces its heating value. Low moisture is ideal. 4.Low non-combustible matter content: Ash or clinker after combustion. Low is preferred. 5.Moderate rate of combustion: “Moderate ideal”. Characteristics of good fuel

10. 6. Harmless combustion products: Not pollute the atmosphere. 7. Low cost: 8. Easy to transport: 9. Low storage cost: 10. Controllable combustion: 11. Uniform size: “Combustion is regular”. 12. Fuel should burn in air with efficiency without much smoke. Characteristics of good fuel

11. Calorific Value of a fuel: “The total quantity of heat liberated from the combustion of a unit mass (or unit volume) of the fuel in air or oxygen”. Units of heat: 1.Calorie: Amount of heat required to increase the temp of 1 gm of water through 1 °C. 2.Kilocalorie (Kilogram centigrade units): (METRIC SYSTEM) 1 Kg of water through 1°C. (1KCal = 1,000 Cal) 3.British Thermal Unit (BTU): (ENGLISH SYSTEM) Amount of heat required to increase the temp of 1 pound of water through 1 °F. (1 BTU = 252 Cal = 0.252 Kcal) 4.Centigrade Heat Unit (CHU): Amount of heat required to increase the temp of 1 pound of water through 1 °C. (1KCal = 3.968 BTU = 2.2 CHU) Calorific value and Units

12. Higher or Gross Calorific Value (HCV): Hydrogen is found to be present in almost all fuels and when the calorific value of hydrogen-containing fuel is determined experimentally, the hydrogen is converted into steam. If the products of combustion are condensed to the room temperature, the latent heat of condensation of steam also gets included in the measured heat, which is then called “higher or gross calorific value”. Definition of HCV: “The total amount of heat liberated, when unit mass (or unit volume) of the fuel has been burnt completely and the products of combustion are cooled to room temperature” Calorific value and Units

13. Lower or Net Calorific Value (LCV): In actual use of any fuel, the water vapors and moisture escape as such along with hot combustion gases. Since they are not condensed. Hence a lesser amount of heat is available. LCV = HCV – Latent heat of water vapors Since 1 parts by mass of hydrogen produces 9 parts by mass water Hence, LCV = HCV – mass of hydrogen x 9 x Latent heat of steam (The latent heat of steam is 587 Kcal/Kg or 1,060 BTU/lb of water vapors formed at room temperature) LCV: “The net heat produced, when unit mass or unit volume of the fuel is burnt completely and the combustion products are allowed to escape.” H 2 + ½ O 2 -----  H 2 O 2 gm18 gm 1 gm9 gm Calorific value and Units

14. For Solid or Liquid Fuel: Calorie/gram Kcal/Kg BTU/lb Relations: 1 Kcal/Kg = 1.8 x BTU/lb 1 Kcal/m 3 = 0.1077 x BTU/Ft 3 1 BTU/Ft 3 = 9.3 Kcal/m 3 For Gaseous Fuels: Kcal/Cubic meter (Kcal/m 3 ) BTU/Cubic Feet (BTU/ft 3 ) Ib is an abbreviation of the latin word “libra” means “balance or scales” Calorific value and Units

15. 1. By Bomb Calorimeter: For solid and liquid fuels. 2. By Boy’s Gas Calorimeter 3. By Junker’s Gas Calorimeter By Bomb Calorimeter 1.Principle: A known mass of fuel is burnt and the quantity of heat produced is absorbed in water & measured. Then the quantity of heat produced by burning a unit mass of the fuel is calculated. 2.Construction: 3.Working: 4.Calculations: 5.Correction: Determination of calorific value

16. 2. Construction: Bomb calorimeter

17. 3. Working: 1.Weighed amount of the fuel in a crucible. Crucible is supported over the ring. 2.A fine Mg wire, touching the fuel sample is then stretched across the electrodes. 3.The Bomb lid is tightly screwed and Bomb filled with oxygen to 25-30 atmospheric pressure. 4.The Bomb is then lowered into copper calorimeter, containing a known mass of water. 5.The initial temperature of water is noted. The electrodes are then connected to 6 Volt battery and circuit is then completed. 6.The sample burns and heat is liberated which is transformed to water. 7.Now Calorific value can be calculated; Bomb calorimeter

18. 4. Calculations: Let x = mass of gms of fuel sample taken in crucible; W = Mass of water in the calorimeter (in gms) w = water equivalent in gms of calorimeter, stirrer, thermometer etc (= weight of apparatus x specific heat = W’ x S) T1 = initial temp of water in calorimeter T2 = final temp of water in calorimeter L = Higher (gross) calorific value of fuel in cal/gm Hence Heat liberated by burning of fuel = x L Cal And heat absorbed by water = W x S x (T2-T1) And heat absorbed by apparatus = W’ x S x (T2-T1) = w(T2-T1) Bomb calorimeter

19. Hence total heat absorbed by water, apparatus etc. = [W x 1 x (T2-T1) + w x 1 x (T2-T1)] = [(W+w) x 1(T2-T1) Cal Since specific heat of water = 1 cal/gm °C & 1 cal=4.186 J xL = (W+w) (T2-T1) Or HCV of fuel (L) = (W+w) (T2-T1)/x cal/gm Bomb calorimeter

20. Let H = % of hydrogen in the fuel Then gms of hydrogen present in 1 gm fuel = 1 x H/100 Since hydrogen is converted into steam, H 2 + ½ O 2 -----------  H 2 O 2 gm18 gm 1 gm9 gm So, weight of water produced from 1 gm H 2 = 9 gm Weight of water produced from H/100 H 2 (or 1 gm fuel) = 9 x H/100 = 0.09 H gm Moreover, Latent heat of steam = 587 cal/gm Hence, Heat taken by water in forming steam (or Latent heat of water vapors formed) = 0.09 H x 587 cal Hence, LCV = (HCV – 0.09 H x 587) cal/gm Bomb calorimeter

21. Summary 1.Introduction- Importance of fuels in industry 2.Classification of fuels 3.Comparison of solid, liquid & gaseous fuels 4.Properties/Characteristics of fuels 5.Calorific value of a fuel 6.Determination of calorific value by Bomb Calorimeter

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