Fuels and Combustion Concepts
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Fuels and Combustion Concepts

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Questions and Answers

What percentage of the composition of compressed natural gas (CNG) is methane (CH4)?

  • 10.0%
  • 1.0%
  • 88.5% (correct)
  • 80.5%

    • What is one important property of compressed natural gas (CNG) compared to petrol?

  • CNG is liquid at room temperature.
  • CNG has a lower ignition point than petrol.
  • CNG burns completely with no CO and SOX emissions. (correct)
  • CNG can store more energy in a smaller volume.

    • Which of the following is NOT a use of compressed natural gas (CNG)?

  • Source of carbon black and hydrogen gas
  • Substitute fuel for petrol and diesel
  • Industrial and domestic fuel
  • Main component in liquid propane gas (LPG) (correct)

    • Why is monoethanolamine used in the processing of remaining gas?

    <p>To separate H2S from the gas</p> Signup and view all the answers

    What is the calorific value of compressed natural gas (CNG)?

    <p>13000 kcal/m3</p> Signup and view all the answers

    What happens to the extra liquid if a large part of the vapors gets condensed on a bubble tray?

    <p>It flows down to higher temperature lower trays and evaporates.</p> Signup and view all the answers

    Which of the following fractions is specifically mentioned as being obtained from a refinery?

    <p>Kerosene</p> Signup and view all the answers

    What is the purpose of the cracking process in petroleum refinement?

    <p>To break down higher hydrocarbon molecules into smaller ones.</p> Signup and view all the answers

    Which property of ethyl alcohol contributes to reducing polutant emissions when used as power alcohol?

    <p>Presence of oxygen atoms</p> Signup and view all the answers

    Why is straight run petrol considered a lower quality petrol?

    <p>It has a lower octane number.</p> Signup and view all the answers

    What is the typical octane number of petrol as mentioned?

    <p>65</p> Signup and view all the answers

    What is the effect of blending ethyl alcohol with petrol?

    <p>It enhances the octane number.</p> Signup and view all the answers

    Which of the following is a disadvantage of using ethyl alcohol in engines?

    <p>Lower calorific value (C.V.)</p> Signup and view all the answers

    What does the process of combustion typically produce when a fuel containing carbon is burned?

    <p>Heat and carbon dioxide</p> Signup and view all the answers

    Why is the Gross Calorific Value (G.C.V.) considered to be of only theoretical importance?

    <p>It assumes that all combustion products are cooled to a certain temperature.</p> Signup and view all the answers

    Which component of a fuel is primarily responsible for the production of water vapor during combustion?

    <p>Hydrogen</p> Signup and view all the answers

    What is the main difference between Gross Calorific Value (G.C.V.) and Net Calorific Value (N.C.V.)?

    <p>N.C.V. accounts for heat loss due to water vapor, while G.C.V. does not.</p> Signup and view all the answers

    What is the significance of calorific values for fuels?

    <p>They help in comparing the energy output from different fuels.</p> Signup and view all the answers

    What is the steady rise in temperature (t2 – t1) when the incoming and outgoing water temperatures are 20°C and 33°C, respectively?

    <p>13°C</p> Signup and view all the answers

    Which of the following fuels are primarily considered fossil fuels?

    <p>Coal and natural gas</p> Signup and view all the answers

    During the proximate analysis of coal, what is the purpose of heating the coal sample at 110°C for 1 hour?

    <p>To escape moisture present in the coal</p> Signup and view all the answers

    What does the volatile matter percentage indicate in the proximate analysis of coal?

    <p>Thermal degradation of coal molecules</p> Signup and view all the answers

    What happens to the heat produced during combustion when water vapor is formed?

    <p>A portion of the heat is absorbed by the water vapor for evaporation.</p> Signup and view all the answers

    What is the next step after the initial weight of the coal sample is measured in proximate analysis?

    <p>Cooling in a desiccator and weighing again</p> Signup and view all the answers

    When calculating calorific values, what is important to note about the measurement conditions?

    <p>They must be conducted under standard temperature and pressure (STP).</p> Signup and view all the answers

    What happens to coal molecules at a temperature of 925°C during the volatile matter analysis?

    <p>They undergo thermal degradation</p> Signup and view all the answers

    What is the weight of steam condensed if 250 gm of steam is produced during combustion?

    <p>0.25 kg</p> Signup and view all the answers

    Which of the following is NOT part of the proximate analysis in coal analysis?

    <p>Sulfur content</p> Signup and view all the answers

    What is the weight of water circulated in Boy's gas calorimeter experiment?

    <p>25 kg</p> Signup and view all the answers

    What is the weight of carbon dioxide formed when 1 gram of coal sample was burnt in oxygen?

    <p>3.157 gm</p> Signup and view all the answers

    How much weight of water vapor is absorbed by CaCl2 when 0.20 gm of coal is burnt?

    <p>0.08 gm</p> Signup and view all the answers

    What was the percentage of hydrogen found in the coal sample based on the analysis provided?

    <p>5.6%</p> Signup and view all the answers

    In the analysis of 2.4 gm of coal, what indicates the efficiency of the combustion process?

    <p>Weight of residue after the first heating</p> Signup and view all the answers

    During the combustion of 0.5 gm of coal, what represents the successful capture of CO2 in the U-tube?

    <p>0.90 gm</p> Signup and view all the answers

    What is the main component formed from the anaerobic decay of debris from plants and animals?

    <p>Petroleum</p> Signup and view all the answers

    How does the weight of the residue change after heating coal in a silica crucible?

    <p>It decreases over time</p> Signup and view all the answers

    What was the increase in weight of KOH U-tube when a coal sample was burnt?

    <p>0.90 gm</p> Signup and view all the answers

    Study Notes

    Fuels and Combustion

    • Fuel: A substance that produces heat when burned.
    • Combustion: A chemical reaction between a fuel and an oxidant, usually oxygen, releasing heat and light.
    • Chemical Fuels: Fossil fuels (coal, crude oil, natural gas), wood, vegetable oils that produce heat when burned.
    • Calorific Value: The amount of heat produced by the complete combustion of a specific amount of fuel.
    • Gross Calorific Value (GCV): The total heat released by the complete combustion of a fuel, including the latent heat of vaporization of water in the combustion products.

    Types of Calorific Value

    • Net Calorific Value (NCV): The heat released by combustion of 1 unit mass of fuel after deducting the heat taken away by water vapor.
    • Measuring Calorific Value: Commonly done using a Bomb Calorimeter, measuring the temperature change of a known amount of water when the fuel burns.

    Coal

    • Formation: Coal is formed over millions of years from decomposed plant matter subjected to heat and pressure.
    • Types of Coal Analysis:
      • Proximate Analysis: This determines the percentages of: moisture, volatile matter, ash, and fixed carbon.
      • Ultimate Analysis: This determines the percentages of the elements present in coal: carbon, hydrogen, oxygen, nitrogen, sulfur, and ash.

    Petroleum or Crude Oil

    • Formation: Petroleum is formed over millions of years from the anaerobic decay of organic matter (plants and animals) under high temperature and pressure.
    • Fractionation: The process of separating crude oil into different components (fractions) based on their boiling points:
      • Petroleum Refining: The process involves fractional distillation of crude oil, separating the components based on their boiling points. There are several fractions obtained:
        • Petroleum Gas: Used as fuel & for making plastics
        • Petroleum Ether: Solvent
        • Gasoline: Used as fuel for cars
        • Kerosene: Used as fuel for stoves and lamps
        • Diesel Fuel: Used as fuel for trucks and buses
        • Lubricating Oil: Used to reduce friction in engines
        • Paraffin Wax: Used in candles and for waterproofing materials
        • Asphalt: Used for paving roads

    Cracking

    • Cracking: Breaking down larger hydrocarbon molecules into smaller molecules by heat or catalysts.
    • Purpose: To increase the yield of lighter, more useful products like gasoline from the heavier fractions of crude oil.

    Power Alcohol

    • Definition: Ethyl alcohol, a biofuel, used as a fuel in internal combustion engines.
    • Preparation: Ethanol is produced by fermentation of starchy materials (e.g., corn, sugarcane) through a series of steps:
      • Starch conversion to glucose: Starch is hydrolyzed to glucose using enzymes or acids.
      • Glucose fermentation: Glucose is fermented by yeast to produce ethanol and carbon dioxide.

    Advantages of Power Alcohol

    • High Octane Number: Boosts the octane rating of petrol, reducing engine knocking.
    • Water Absorption: Absorbs water, preventing it from affecting engine performance.
    • Reduced Pollution: Lowers emissions of carbon monoxide, hydrocarbons, and particulates.

    Compressed Natural Gas (CNG)

    • Composition: Predominantly methane (88.5%), with other hydrocarbons and hydrogen.
    • Extraction: CNG is extracted from natural gas, which is composed mostly of methane.
    • Properties:
      • Higher Ignition Point: Safer than liquid fuels.
      • Better Mixing: Mixes more readily with air for efficient combustion.
      • Low Emissions: Burns cleanly, producing minimal pollutants.

    Uses of CNG

    • Alternative Fuel: Used in cars, buses, and auto-rickshaws, especially in urban areas.
    • Industrial Fuel: Used in various industries.
    • Domestic Fuel: Can be used for cooking and heating.

    Liquefied Petroleum Gas (LPG)

    • Composition: Primarily propane and butane, along with small amounts of pentane and hexane.
    • Properties:
      • High Calorific Value: Produces a significant amount of heat per unit volume.
      • Odorization: A sulfur-containing compound is added to impart a distinctive odor, enabling detection of leaks.
      • Clean Burning: Burns with a clean, blue flame, minimizing pollutants.

    Uses of LPG

    • Domestic Fuel: Used for cooking and heating in homes.
    • Industrial Fuel: Used in various industrial applications.
    • Motor Fuel: Can be used as a fuel for vehicles with modifications.

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    Description

    Test your knowledge on fuels and combustion with this quiz. Cover essential definitions, types of calorific value, and the process of measuring calorific values. Perfect for anyone studying chemistry or energy resources.

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