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Fundamentals of thermal processing - Municipal Solid Wastes

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Ezhilkumar, Professor (Asst), Sri Krishna College of Engineering and Technology, Coimbatore.
Ezhilkumar, Professor (Asst), Sri Krishna College of Engineering and Technology, Coimbatore.

Municipal Solid Wastes Handling and Management

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Prof. M.R.Ezhilkumar Assistant Professor Department of Civil Engineering Sri Krishna College of Engineering and Technology Coimbatore ezhilkumar@skcet.ac.in I only feel angry when I see waste. When I see people throwing away things we could use. – Mother Teresa 1 17CE413 SOLID AND HAZARDOUS WASTE MANAGEMENT 2.11 – Fundamentals of thermal processing
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 2 Learning Outcomes ☼ Combustion or Incineration ☼ Pyrolysis ☼ Gasification ☼ Pelletization 2.11 – Fundamentals of thermal processing
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 3 Video Session Click on the image to watch the video
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar  Thermal conversion of solid waste includes transformation of wastes into gaseous, liquid, and solid conversion products.  The process also generates energy due to burning of waste materials.  Thermal processing also results in waste volume reduction.  Combustion or Incineration, Pyrolysis, and Gasification are the techniques commonly employed for thermal conversions. 4 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Combustion or Incineration Systems 1. Combustion or incineration is a process based on thermal processing of solid waste by oxidation. 2. Various combustion gases e.g. N2, CO2, SO2, water vapors and non-combustible residues in the form of ash are obtained. 3. Energy can be recovered by heat exchange from the combustion gases. 4. The burning of solid wastes is usually accomplished in incinerators. 5. Different types of incinerators are Mass Fired, RDF Fired, Fluidized Bed type. 5 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Combustion or Incineration Systems 6. The Incinerator Institute of America (IIA) classified incinerable wastes into seven types. 7. The IIA also separates incinerators into nine classes according to their use and size. 6 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Combustion or Incineration Systems 7 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Combustion or Incineration Systems 8 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 1. Mass Fired Incineration 1. Mass fired combustion systems are designed to incinerate the MSW as collected without or with very little prior processing. 2. The energy produced by mass fired combustion system depends upon the composition of municipal solid waste. 9 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 10 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 2. RDF Based Incineration 1. In RDF fired combustion system, processed solid waste refuse derived fuel (RDF) is burnt. 2. Various components e.g. metals, glass and other non-combustible materials are removed to produce RDF. 3. Since RDF is more homogeneous the system is better controlled for combustion and more energy is recovered. 11 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 3. Fluidized Bed Incineration 1. A fluidized bed type combustion system includes a steel vertical cylinder, lined inside with refractory bricks, and has a sand bed. 2. Air nozzles called tuyeres are provided to inject air at high pressure. 3. Solid fuel (or RDF) is injected into the cylinder. 4. Auxiliary fuels such as natural gas or oils may be used initially to increase the temperature of the bed upto operational Ievel which is about 1450 to 1750 oF. 5. This system can also be used for burning of sewage sludge and other chemical wastes. 12 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 13 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Factors Affecting Efficiency of Incinerators The efficiency of incinerators is measured in terms of the unburnt organics or of the products of improper combustion escaping through the flue gas and the bottom ash. The important parameters in the design of an incineration system are waste Combustibility, temperature, turbulence, and residence time required for combustion. 14 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Combustibility 1. It is the ease with which the waste can be oxidized. 2. It is measured in terms of the calorific value or the heat produced during incineration. 3. In general, a value of about 2500 kcal/kg or greater is preferred for incineration. 4. This limit however increases as the excess air required for proper contact with the waste increases. 5. Waste with lower calorific value require addition of auxiliary fuel to maintain adequate temperature. 6. Wastes with high moislure content also require additional fuel. 15 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Temperature 1. Temperature in the incinerator is maintained such that all the components in the waste decompose to release the volatile fraction and to oxidize the fixed carbon fraction of wastes. 2. All contaminants such as pathogens, volatile hydrocarbons, smoke and gases (e.g. CO) should be completely oxidized. 16 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Turbulence 1. Proper mixing of air with the solid wastes is necessary for complete combustion. 2. Turbulence is therefore created by applying a high current of air in the form of swirling motion. 3. In rotary kiln type incinerators, the movement of kiln itself provides the mixing effect. 4. ln small static incinerators, raking is required at regular intervals for creating turbulence. 17 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Residence Time 1. Residence time is crucial in combustion processes to ensure complete oxidation of combustible matters. 2. It can be maintained by adjusting the frequency of ash removal. 3. ln some incinerators such as rotary kiln type, the speed of the kiln is adjusted to allow sufficient residence time for combustion. 18 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Problems associated with incinerator operations Some problems associated with the operation of incinerators include excessive stack emissions smoke leakage through charging door, excessive auxiliary fuel consumption, and incomplete burning of wastes. These problems can be minimized by a systematic operational approach and proper maintenance of incinerators. 19 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Excessive Stack Emissions 1. Excessive emission rates are caused due to variety of reasons e.g. excessive infiltration air, overcharging of waste, excessive negative draft in the primary chamber, low temperature in secondary chamber. 2. Proper maintenance of temperature in both primary and secondary chambers and controlled air infiltration can help reduce the emission rates. 20 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Black Smoke 1. Black smoke generally indicates the presence of unburnt carbon, as a result of incomplete combustion of waste materials. 2. This could be due to overcharging of waste or poor temperature conditions in the chambers or due to less amount of air available than is required for complete combustion. 3. Large quantities of highly combustible materials e.g. plastics, rubber in the waste may also generate excessive black smoke. 4. Generally such materials must constitute less than l0 percent of the total charge. 21 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar White Smoke 1. Aerosols present in the emission may result in white smoke. 2. Excess air entering the incinerator may cause micron sized particle to move out through the stack. 3. Proper air and temperature control in the chambers may reduce this problem. 4. White smoke is also formed due lo finely divided noncombustible minerals present in the waste stream. 5. Paper bags, pigments or other metallic oxides, and minerals such as calcium chloride also generate fine inorganic particulate forming white smoke. 22 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Leakage of smoke from Charging Door 1. Leakage of smoke through charging doors or orther openings in the combustion chamber is usually due to excessive air pressure inside the primary chamber. 2. Overcharging of wastes or excessive amount of highly volatile matters present in the waste stream also contribute to such problems. 23 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Excessive Auxiliary Fuel Consumption 1. Overcharging, excessive air infiltration, improper flame distribution are some of the reasons of excess consumption of auxiliary fuel. 2. Proper control of air and charging of waste in batches ( 10 to 15 % of the rated capacity) may help control this problem. 3. Damaged seals of charging doors may also result in heat loss and therefore, if needed, should be repaired or replaced. 24 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Incomplete burning and poor ash quality 1. This is due to overcharging of wastes, non-uniform air distribution along with other problems including partial blockage of primary burner, leakage of fuel etc. 2. Clogged air inlets obstruct air distribution inside the chamber resulting in incomplete combustion. 3. Proper maintenance of burners, air inlets etc. is required to control this problem. 25 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Pyrolysis  Pyrolysis is a chemical change due to partial combustion of solid wastes in the absence of oxygen.  It is also known as thermal decomposition where external source of heat is employed.  Pyrolysis is an endothermic process and requires heat from a, extremal source.  Therefore it is also termed as destructive distillation. 26 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Pyrolysis  It yields gaseous, liquid and solid fractions as follows: 1. Gas fraction includes hydrogen, methane, carbon monoxide and carbon dioxide. 2. Liquid fraction includes tar or oil stream containing acetic acld, acetone, and methanol. 3. Solid fraction includes char, consisting of carbon and other inert materials originally present in MSW. 27 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Pyrolysis 4. The proportion of gases, liquid, and char obtained depends upon the temperature at which pyrolysis is carried out. 5. As temperature increases, the amount of gaseous component increases while the quantity of liquid and char decreases. 6. The energy content of pyrolytic gases is about 26100 KJ/m3 and that of pyrolytic tar or oils is 23240 KJ/kg. 28 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 29 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Gasification 1. Gasification is a process in which partial combustion is carried out in the presence of oxygen but in lesser amount than that is stoichiometrically required for complete combustion. 2. The self-sustaining partial combustion is carried out to obtain combustible gases e.g. hydrogen and carbon monoxide, which are used as a fuel. 3. The energy content is in the range of 5.2 to 6.0 MJ/m3. 4. When the pure oxygen is used as oxidant instead of air, the energy content increases to about 12.9 to 13.9 MJ/m3. 30 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Gasification 5. Typically, composition of combustible gas, obtained from gasification process contains CO2 (10%), CO (20%), H2 (15%), and CH4 (2%) and some N2 and other trace gases. 31 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar Pelletization 1. Pelletization is a process of converting domestic solid waste into small pellets of size generally about 3 inches in length and 1 inch in dia. 2. The recyclable and non-combustaible fractions in MSW are separated out. 3. The remaning combustible material is dried and shredded. 4. Binding ingredients e.g. lime is mixed to the shredded material and fuel pellets are made. 5. These are also called refuse derived fuel (RFD). 6. The average RDF production rate is found to be 15-20 tons/ 100 tons of MSW. 32 Thermal Conversion
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 33 Assessment Time Review Question Identify the common problems associated with incinerators? Suggest suitable precautions to prevent them.
SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 34 End of this topic

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Fundamentals of thermal processing - Municipal Solid Wastes

  • 1. Prof. M.R.Ezhilkumar Assistant Professor Department of Civil Engineering Sri Krishna College of Engineering and Technology Coimbatore ezhilkumar@skcet.ac.in I only feel angry when I see waste. When I see people throwing away things we could use. – Mother Teresa 1 17CE413 SOLID AND HAZARDOUS WASTE MANAGEMENT 2.11 – Fundamentals of thermal processing
  • 2. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 2 Learning Outcomes ☼ Combustion or Incineration ☼ Pyrolysis ☼ Gasification ☼ Pelletization 2.11 – Fundamentals of thermal processing
  • 3. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 3 Video Session Click on the image to watch the video
  • 4. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar  Thermal conversion of solid waste includes transformation of wastes into gaseous, liquid, and solid conversion products.  The process also generates energy due to burning of waste materials.  Thermal processing also results in waste volume reduction.  Combustion or Incineration, Pyrolysis, and Gasification are the techniques commonly employed for thermal conversions. 4 Thermal Conversion
  • 5. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Combustion or Incineration Systems 1. Combustion or incineration is a process based on thermal processing of solid waste by oxidation. 2. Various combustion gases e.g. N2, CO2, SO2, water vapors and non-combustible residues in the form of ash are obtained. 3. Energy can be recovered by heat exchange from the combustion gases. 4. The burning of solid wastes is usually accomplished in incinerators. 5. Different types of incinerators are Mass Fired, RDF Fired, Fluidized Bed type. 5 Thermal Conversion
  • 6. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Combustion or Incineration Systems 6. The Incinerator Institute of America (IIA) classified incinerable wastes into seven types. 7. The IIA also separates incinerators into nine classes according to their use and size. 6 Thermal Conversion
  • 7. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Combustion or Incineration Systems 7 Thermal Conversion
  • 8. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Combustion or Incineration Systems 8 Thermal Conversion
  • 9. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 1. Mass Fired Incineration 1. Mass fired combustion systems are designed to incinerate the MSW as collected without or with very little prior processing. 2. The energy produced by mass fired combustion system depends upon the composition of municipal solid waste. 9 Thermal Conversion
  • 10. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 10 Thermal Conversion
  • 11. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 2. RDF Based Incineration 1. In RDF fired combustion system, processed solid waste refuse derived fuel (RDF) is burnt. 2. Various components e.g. metals, glass and other non-combustible materials are removed to produce RDF. 3. Since RDF is more homogeneous the system is better controlled for combustion and more energy is recovered. 11 Thermal Conversion
  • 12. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 3. Fluidized Bed Incineration 1. A fluidized bed type combustion system includes a steel vertical cylinder, lined inside with refractory bricks, and has a sand bed. 2. Air nozzles called tuyeres are provided to inject air at high pressure. 3. Solid fuel (or RDF) is injected into the cylinder. 4. Auxiliary fuels such as natural gas or oils may be used initially to increase the temperature of the bed upto operational Ievel which is about 1450 to 1750 oF. 5. This system can also be used for burning of sewage sludge and other chemical wastes. 12 Thermal Conversion
  • 13. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 13 Thermal Conversion
  • 14. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Factors Affecting Efficiency of Incinerators The efficiency of incinerators is measured in terms of the unburnt organics or of the products of improper combustion escaping through the flue gas and the bottom ash. The important parameters in the design of an incineration system are waste Combustibility, temperature, turbulence, and residence time required for combustion. 14 Thermal Conversion
  • 15. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Combustibility 1. It is the ease with which the waste can be oxidized. 2. It is measured in terms of the calorific value or the heat produced during incineration. 3. In general, a value of about 2500 kcal/kg or greater is preferred for incineration. 4. This limit however increases as the excess air required for proper contact with the waste increases. 5. Waste with lower calorific value require addition of auxiliary fuel to maintain adequate temperature. 6. Wastes with high moislure content also require additional fuel. 15 Thermal Conversion
  • 16. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Temperature 1. Temperature in the incinerator is maintained such that all the components in the waste decompose to release the volatile fraction and to oxidize the fixed carbon fraction of wastes. 2. All contaminants such as pathogens, volatile hydrocarbons, smoke and gases (e.g. CO) should be completely oxidized. 16 Thermal Conversion
  • 17. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Turbulence 1. Proper mixing of air with the solid wastes is necessary for complete combustion. 2. Turbulence is therefore created by applying a high current of air in the form of swirling motion. 3. In rotary kiln type incinerators, the movement of kiln itself provides the mixing effect. 4. ln small static incinerators, raking is required at regular intervals for creating turbulence. 17 Thermal Conversion
  • 18. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Residence Time 1. Residence time is crucial in combustion processes to ensure complete oxidation of combustible matters. 2. It can be maintained by adjusting the frequency of ash removal. 3. ln some incinerators such as rotary kiln type, the speed of the kiln is adjusted to allow sufficient residence time for combustion. 18 Thermal Conversion
  • 19. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Problems associated with incinerator operations Some problems associated with the operation of incinerators include excessive stack emissions smoke leakage through charging door, excessive auxiliary fuel consumption, and incomplete burning of wastes. These problems can be minimized by a systematic operational approach and proper maintenance of incinerators. 19 Thermal Conversion
  • 20. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Excessive Stack Emissions 1. Excessive emission rates are caused due to variety of reasons e.g. excessive infiltration air, overcharging of waste, excessive negative draft in the primary chamber, low temperature in secondary chamber. 2. Proper maintenance of temperature in both primary and secondary chambers and controlled air infiltration can help reduce the emission rates. 20 Thermal Conversion
  • 21. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Black Smoke 1. Black smoke generally indicates the presence of unburnt carbon, as a result of incomplete combustion of waste materials. 2. This could be due to overcharging of waste or poor temperature conditions in the chambers or due to less amount of air available than is required for complete combustion. 3. Large quantities of highly combustible materials e.g. plastics, rubber in the waste may also generate excessive black smoke. 4. Generally such materials must constitute less than l0 percent of the total charge. 21 Thermal Conversion
  • 22. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar White Smoke 1. Aerosols present in the emission may result in white smoke. 2. Excess air entering the incinerator may cause micron sized particle to move out through the stack. 3. Proper air and temperature control in the chambers may reduce this problem. 4. White smoke is also formed due lo finely divided noncombustible minerals present in the waste stream. 5. Paper bags, pigments or other metallic oxides, and minerals such as calcium chloride also generate fine inorganic particulate forming white smoke. 22 Thermal Conversion
  • 23. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Leakage of smoke from Charging Door 1. Leakage of smoke through charging doors or orther openings in the combustion chamber is usually due to excessive air pressure inside the primary chamber. 2. Overcharging of wastes or excessive amount of highly volatile matters present in the waste stream also contribute to such problems. 23 Thermal Conversion
  • 24. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Excessive Auxiliary Fuel Consumption 1. Overcharging, excessive air infiltration, improper flame distribution are some of the reasons of excess consumption of auxiliary fuel. 2. Proper control of air and charging of waste in batches ( 10 to 15 % of the rated capacity) may help control this problem. 3. Damaged seals of charging doors may also result in heat loss and therefore, if needed, should be repaired or replaced. 24 Thermal Conversion
  • 25. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Incomplete burning and poor ash quality 1. This is due to overcharging of wastes, non-uniform air distribution along with other problems including partial blockage of primary burner, leakage of fuel etc. 2. Clogged air inlets obstruct air distribution inside the chamber resulting in incomplete combustion. 3. Proper maintenance of burners, air inlets etc. is required to control this problem. 25 Thermal Conversion
  • 26. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Pyrolysis  Pyrolysis is a chemical change due to partial combustion of solid wastes in the absence of oxygen.  It is also known as thermal decomposition where external source of heat is employed.  Pyrolysis is an endothermic process and requires heat from a, extremal source.  Therefore it is also termed as destructive distillation. 26 Thermal Conversion
  • 27. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Pyrolysis  It yields gaseous, liquid and solid fractions as follows: 1. Gas fraction includes hydrogen, methane, carbon monoxide and carbon dioxide. 2. Liquid fraction includes tar or oil stream containing acetic acld, acetone, and methanol. 3. Solid fraction includes char, consisting of carbon and other inert materials originally present in MSW. 27 Thermal Conversion
  • 28. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Pyrolysis 4. The proportion of gases, liquid, and char obtained depends upon the temperature at which pyrolysis is carried out. 5. As temperature increases, the amount of gaseous component increases while the quantity of liquid and char decreases. 6. The energy content of pyrolytic gases is about 26100 KJ/m3 and that of pyrolytic tar or oils is 23240 KJ/kg. 28 Thermal Conversion
  • 29. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 29 Thermal Conversion
  • 30. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Gasification 1. Gasification is a process in which partial combustion is carried out in the presence of oxygen but in lesser amount than that is stoichiometrically required for complete combustion. 2. The self-sustaining partial combustion is carried out to obtain combustible gases e.g. hydrogen and carbon monoxide, which are used as a fuel. 3. The energy content is in the range of 5.2 to 6.0 MJ/m3. 4. When the pure oxygen is used as oxidant instead of air, the energy content increases to about 12.9 to 13.9 MJ/m3. 30 Thermal Conversion
  • 31. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Gasification 5. Typically, composition of combustible gas, obtained from gasification process contains CO2 (10%), CO (20%), H2 (15%), and CH4 (2%) and some N2 and other trace gases. 31 Thermal Conversion
  • 32. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar Pelletization 1. Pelletization is a process of converting domestic solid waste into small pellets of size generally about 3 inches in length and 1 inch in dia. 2. The recyclable and non-combustaible fractions in MSW are separated out. 3. The remaning combustible material is dried and shredded. 4. Binding ingredients e.g. lime is mixed to the shredded material and fuel pellets are made. 5. These are also called refuse derived fuel (RFD). 6. The average RDF production rate is found to be 15-20 tons/ 100 tons of MSW. 32 Thermal Conversion
  • 33. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 33 Assessment Time Review Question Identify the common problems associated with incinerators? Suggest suitable precautions to prevent them.
  • 34. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT ï‚— Mr.M.R.Ezhilkumar 34 End of this topic