Understanding Solid and Liquid Fuels

Aug 5, 2024

Lecture 1 - Module 2: Solid and Liquid Fuels

Introduction

  • Focus on understanding solid and liquid fuels.
  • Discuss the heating value, ultimate analysis, and proximate analysis of fuels.

Overview of Fuel Sources

  • Fossil Fuels: Coal, oil, and gas are primary energy sources today.
  • Biomass: Historically primary fuel, now considered non-conventional.
    • Used for space heating in many countries.
  • Issue with biomass: Lower energy content, making transportation and direct use economically infeasible.
    • Conversion to high-energy products necessary.

Classification of Fuels

  1. Solid Fuels:
    • Examples: Coal, coke, briquettes, charcoal, torrified biomass, biocoque, biochar.
    • Solid fuels primarily from fossil sources (coal, coke) and bio-based materials (briquettes, biochar).
  2. Liquid Fuels:
    • Examples: Gasoline, diesel, kerosene, fuel oil, coal tar, ethanol, biodiesel.
    • Includes both fossil and bio-based sources.
  3. Gaseous Fuels:
    • Examples: Natural gas, liquefied petroleum gas, biogas.
    • Derived from fossil sources and biomass.

Properties of Fuels

  • Variation in fuel properties due to different source materials and conversion technologies.
  • Importance of fuel characterization for reliable energy conversion and compatibility with equipment.
  • Characterization aspects:
    • Control of fuel quality and assessment of environmental impact.

Key Characteristics of Fuels

  1. Physical Properties:
    • Density, permeability, diffusivity, viscosity.
  2. Thermodynamic Properties:
    • Thermal conductivity, heating value, specific heat, ignition temperature.
  3. Composition:
    • Ultimate analysis, proximate analysis, structural composition (cellulose, hemicellulose, lignin).
    • Biological materials also include carbohydrates, proteins, and lipids.

Tools for Fuel Characterization

  • Atomic Ratios: H/C, O/C, and N/C ratios.
  • Lignocellulosic Composition: Helps rank biomass fuels.
  • Ternary Diagrams: Visual representation of carbon, hydrogen, and oxygen proportions.

Detailed Discussion on Solid Fuels

  • Historical importance of biomass for heating and food.
  • Broader applications of solid fuels in industry and energy generation.
  • Types of solid fuels:
    • Biomass: Wood, agricultural waste, etc.
    • Fossil Fuels: Peat, coal, oil shale.
    • Upgraded Forms: Coke, briquettes from coal dust.

Characteristics of Solid Fuels

  • Physical Properties: Specific gravity, porosity, grindability.
  • Thermodynamic Properties: Thermal conductivity, heating value.
  • Chemical Characteristics: Ultimate analysis, proximate analysis, chemical structure.

Density Measurement

  • Three types: True density, apparent density, and bulk density.
  • Equations:
    • True density = mass/solid volume (excluding pore volume).
    • Apparent density = mass/apparent volume (including internal pores).
    • Bulk density = mass/bulk volume (total volume of particles).

Thermal Conductivity

  • Ability to conduct heat; influenced by composition, moisture, density, and temperature.

Heating Value

  • Higher Heating Value (HHV): Heat released when fuel combusted and products returned to 25°C.
  • Lower Heating Value (LHV): Heat released minus latent heat of vaporization of water.
  • Calculation of heating values based on moisture and ash content.

Specific Heat and Heat of Combustion

  • Specific Heat: Energy required to raise temperature.
  • Heat of Combustion: Heat released during combustion; can be calculated from heat of formation values.

Ultimate and Proximate Analysis

  • Ultimate Analysis: Quantitative estimation of C, H, N, S, O.
  • Proximate Analysis: Includes fixed carbon, volatile matter, ash, and moisture.
  • Comparison of ultimate analysis for different fuels, including ratios influencing heating value.

Environmental Considerations

  • Sulfur in fuel can lead to SO2 emissions; removal necessary before combustion.
  • Use of flue gas desulfurization units to scrub sulfur dioxide.

Classification and Ranking of Fuels

  • Higher carbon content generally indicates higher heating value.
  • Use of atomic ratios (H/C, O/C) for fuel ranking.
  • Ternary diagrams help visualize fuel composition and conversion processes.

Conclusion

  • Importance of understanding properties of solid and liquid fuels for energy generation.
  • Next lecture will cover proximate analysis and structural composition of fuels.