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Energy from Waste, Lecture 09, Fuel Technology2, (Week 11).pptx

  1.  Solid waste are non-liquid, non-soluble materials ranging from municipal garbage to industrial waste which contain complex and hazardous substances.  Population growth, Increasing urbanization, Industrialization, and standard of living have contributed to rise in both the amount and variety of waste generated in most countries.  The technology of recovering energy from solid waste will play a significant role in mitigating issues relating to waste and will also result in reduction of overall quantity of waste.
  2. Solid waste?  Any material that we discard, that is not liquid or gas, is solid waste.  Municipal Solid Waste: solid waste from home and offices.  Industrial Solid Waste: solid waste produced from mines, Agriculture, and industries.
  3. Sources and Types of Solid Waste Sources of solid waste in a community are:  Residential  Commercial  Institutional  Construction  Municipal services  Treatment plant sites  Industrial  Agricultural
  4. Sources and Types of Solid Waste
  5. Sources and Types of Solid Waste
  6. Sources and Types of Solid Waste
  7. Waste as a renewable source of Energy  The enormous increase in the quantity of waste materials generated by human activity and their potential harmful effects on the general environment and public health, have led to an increasing awareness about an urgent need to adopt scientific methods for safe disposal of wastes.
  8. Waste Conversion Technology  Technologies used to convert solid waste into useful products, chemicals and fuels are referred as conversion technology.
  9.  Various technologies are available for realizing the potential of waste as an energy source, ranging from very simple systems for disposing of dry waste to more complex technologies capable of dealing with large amounts of industrial waste.  There are three main pathways for conversion of organic waste material to energy – thermo chemical, biochemical and physicochemical
  10. Thermo chemical Conversion  It is characterized by higher temperatures and faster conversion rates.  Best suited for lower moisture feedstock.  Thermochemical routes can convert the entire organic (carbon) portion of suitable feedstock to energy.  Inorganic fraction (ash) of a feedstock does not contribute to the energy products but may increase nutrient loading in wastewater treatment and disposal facilities.
  11. Thermo chemical Conversion It includes the following;  Incineration  Gasification  Pyrolysis
  12. Waste Incineration The incineration technology is the controlled combustion of waste with the recovery of heat to produce steam which in turn produces power through steam turbines. • Volume and weight reduced. • Incineration can be done at generation site . • Air discharges can be controlled and small disposal area required.
  13. Gasification  Partial oxidation process, pure oxygen, oxygen enriched air, hydrogen, or steam.  Produces electricity, fuels (methane, hydrogen, ethanol, synthetic diesel), and chemical products.  Temperature > 700oC.  More flexible than incineration, more technologically complex than incineration or pyrolysis, more public acceptance.
  14. Pyrolysis  Thermal degradation of carbonaceous materials.  Lower temperature than gasification (400 – 700oC)  Absence or limited amount of oxygen.  Products are pyrolitic oils and gas, solid char.  Distribution of products depends on temperature  Pyrolysis oil is used for (after appropriate posttreatment) liquid fuels, chemicals, adhesives, and other products.  A number of processes directly combust pyrolysis gases, oils, and char.
  15. Biochemical Conversion It includes the following;  Anaerobic digestion (occurs in controlled reactors or digesters and also in a less controlled environment in landfills)  Anaerobic fermentation (for example, the conversion of sugars from cellulose to ethanol). Biochemical conversion proceeds at lower temperatures and lower reaction rates than other conversion processes.
  16. Physicochemical Conversion It includes the following;  Transesterification (biodiesel production)  Physical and chemical synthesis of products from feedstock  The combustible fraction of the waste is converted into high- energy fuel pellets which may be used in steam generation.  Fuel pellets have several distinct advantages over coal and wood because it is cleaner, free from incombustibles, has lower ash and moisture contents, is of uniform size, cost- effective, and ecofriendly.
  17. Advantages  Majority of waste that goes into landfills can be reused.  Always a reliable source of fuel as people will always have waste.  The fuel is obtained cheaply.
  18. Disadvantages  Public is not convinced that Waste to Energy facilities are clean and free of harmful chemicals.  Waste to Energy facilities are expensive to construct.  Air Pollution from combustion process.  Possibility of toxic ash as a byproduct and it may leach into groundwater and make it impure.
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