This document discusses thermal processing techniques for solid waste management, specifically focusing on combustion or incineration. It provides details on the combustion process and types of incinerators. Mass fired, RDF fired, and fluidized bed incinerators are described. Key factors for incineration efficiency like combustibility, temperature, turbulence, and residence time are summarized. Common problems in incinerator operations such as excessive emissions, smoke leakage, and incomplete burning are also outlined.

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
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17CE413
SOLID AND HAZARDOUS
WASTE MANAGEMENT
2.11 – Fundamentals of
thermal processing

2. 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

3. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 3
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4. 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.
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5. 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.
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6. 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.
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7. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar
Combustion or Incineration Systems
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8. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar
Combustion or Incineration Systems
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9. 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.
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10. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 10
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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.
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12. 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.
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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.
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15. 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.
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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.
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17. 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.
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18. 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.
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19. 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.
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20. 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.
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21. 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.
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22. 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.
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23. 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.
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24. 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.
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25. 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.
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26. 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.
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27. 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.
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28. 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.
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29. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 29
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30. 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.
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31. 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.
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32. 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.
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33. 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.

34. SHWM – Module 2 – MUNICIPAL OF SOLID WASTES HANDLING AND MANAGEMENT  Mr.M.R.Ezhilkumar 34
End of this topic