incineration of hazardous wastes

1. INCINERATION OF HAZARDOUS WASTES
Dr. V.C. SRIVASTAVA
Department of Chemical Engineering, Indian Institute of Technology- Roorkee,
Roorkee-247667 (UA), India
Types of Waste
GENERAL: Office Waste, Domestic Waste
INFECTITIOUS: Hospital Waste, Research Lab, Waste
CHEMICAL: Pharmaceutical, Chemical, Pesticides, Refineries, etc.
Infectitious and chemical wastes are together termed as hazardous.
STRATEGY TO DECIDE INCINERATION
IS HAZARD DUE
TO HEAVY METALS?
N N
INCINERATION is a thermal treatment process in which combustion occurs at high temperature
in controlled environment for high combustion efficiency with minimum undesirable products
IINNCCIINNEERRAATTIIOONN
WASTE
WASTE
CONSTITUENTS
CONSTITUENTS
C
H
O
Cl
N
S
P
END
END
PRODUCTS
CO2
H2O
PRODUCTS
O2
HCl
N2
SOX
P2O5
Combustion Efficiency = % (CO2 / (CO +CO2))
START
CHECK WASTE
COMPOSITION
IS HAZARD DUE
TO RADIOACTIVITY ?
Y
CHECK ALTERNATE
TECHNOLOGY
ANY SPECIFIC
TOXIC MAT. ?
HEAT CONTENT
> 2500 KCal / kg ?
HEAT CONTENT
1500 - 2500 KCal / kg ?
INCINERATE INCINERATE
OR
USE AS FUEL
INCINERATE
WITH AUX.
FUEL
N
Y
Y Y Y
N
N

2. INCINERATION SYSTEM
WASTE
WASTE
PREPARATION
PREPARATION
WASTE
FEEDING ININCCININEERRAATTOORR
WASTE
FEEDING
ACID GAS
REMOVAL
ACID GAS
REMOVAL
GAS
GAS
COOLING
COOLING
ASH
ASH
DISPOSAL
DISPOSAL
PARTICULATE
REMOVAL
PARTICULATE
REMOVAL
DEMISTER &
DEMISTER &
STACK
STACK
RESIDUE
TREATMENT
RESIDUE
TREATMENT
WASTE
INCINERATOR INCINERATOR
WASTE HANDLING
AACCTTIIVVIITTYY MMEETTHHOODDSS / /E EQQUUIIPPMMEENNTT
Preparation
Conveying
Feeding
Screening /Shredding, Crushing, Blending,
Heating, Baling, Evaporation
Slat /Screw / Grab / Pneumatic Conveyors,
Hoists, Pumps, Blowers
Manual / Gravity /Ram / Screw Feeders,
burners, Injectors, Sludge lances
TECHNOLOGY DESCRIPTION
High temperature hazardous waste incinerators are available in a number of configurations and
principles. Typically a process for treatment involves heating to a temperature greater than
850°C or, if the chlorine content is above 1 %, greater than 1,100 °C, with a residence time
greater than 2 seconds, under conditions that assure appropriate mixing and subsequent
destruction.

3. Temperature & residence time: Combustion temperature and residence time needed for mixed
hazardous wastes cannot be readily calculated and are often determined empirically. Some
common solvents such as alcohols and toluene can easily be combusted at temperatures less than
1,000 oC and less than one second residence time, while other more complex organic halogens
require more stringent conditions.
US EPA Toxic Substances Control Act (TSCA) PCB Incineration Criteria: “...more complex
organic halogens such as PCB requires 1200 OC and 2 sec residence time ””
EU Directive 2000/76/EC on Incineration of Waste regulates Co-incineration of Hazardous
Waste in Cement Kilns: ““...if more than 1 % of halogenated organic substances, expressed as
chlorine, are incinerated, the temperature has to be raised to minimum 1100 °C during at least
two seconds””.
INFECTITIOUS WASTE INCINERATION
Infectitious Waste: Waste that can spread infection, generates in hospitals & medical
institutions, research establishments, animal/slaughter houses.
FIXED HEARTH INCINERATOR
Applicable For Wastes: Hospitals, Research Labs, Canteens, Hotels, Offices and banks,
Automobile / White Goods Industries, Chemical industries, Workshops
PRIMARY
CHAMBER
SECONDARY
CHAMBER
FEEDING
DOOR
DEASHING
DOOR
PRIMARY
BURNER
SEC.
BURNER
HEARTH
TO GAS
CLEANING
Two Stage Combustion
•Primary Combustion: –Decomposition Of All Combustibles, –Gasification / Partial
Combustion, –Burning Of Carbon
•Secondary Combustion: –Complete Combustion Of All Unburnts And Partially Burnt In Gas
Form, –Destruction Of Pathogens
Temperature Control: Primary 800±50 OC & Secondary 1050 ±50 OC, Through Individual
Burners In Both Chambers, Auto On/off Operation Of Burners For Fuel Efficiency
Residence Time - 1 Sec @ 1050±50 C in Secondary Chamber, Through Adequate Sizing,
Turbulence To Ensure Proper Mixing With Air
Chimney Height: Min 30 Meters, To Ensure Low Ground Level Concentration

4. CHEMICAL WASTE INCINERATION
CHEMICAL WASTE: By-product Gases And Vapors, Organic Liquid Streams, Aqueous
Waste Containing Dissolved Organics And Salts, Distillation Bottom Tars, Organic
Sludge And Semi-solids, Slurries And Sludge With High Moisture, Granular Solids, Filter
Cakes
SOURCES SOURCES O OFF C CHHEEMMIICCAALL W WAASSTTEE
Industries Manufacturing And Handling Variety Of
Chemicals Such As:
• Petrochemicals
• Pharmaceuticals
• Antibiotics, Bulk Drugs
• Oil Refineries, Srus
• Agro-chemicals, Pesticides
• Dyes, Dye-intermediates
• Organic Chemicals
• Speciality Chemicals
• Petrochemicals
• Pharmaceuticals
• Antibiotics, Bulk Drugs
• Oil Refineries, Srus
• Agro-chemicals, Pesticides
• Dyes, Dye-intermediates
• Organic Chemicals
• Speciality Chemicals
• Polymers, Plastics
• Pulping Mills
• Coke Ovens (By-product
• Polymers, Plastics
• Pulping Mills
• Coke Ovens (By-product
Recovery)
Recovery)
• Coating, Printing, And
• Coating, Printing, And
Laminating
Laminating
• Automobiles (Paint Shop)
• Automobiles (Paint Shop)
CHEMICAL WASTE INCINERATORS
STATIC: Liquid/Gaseous Injection, Fluid Bed Incinerator, Fixed Hearth
NON – STATIC: Rotary Kiln
LIQUID WASTE INCINERATORS
APPLICATIONS
Low melting distillation bottoms
Organic liquid waste
Waste Waters
Gaseous Waste
Chlorinated waste from PVC / ECH manufacturing
High fluorine containing waste.

5. M. S. SHELL
BURNER
ASSEMBLY
REFRACTORY
MANHOLE
FLUE GAS
OUTLET
MANHOLE
INJECTOR
LIQUID WASTE INCINERATORS
MERITS
1. No Secondary Combustion Chamber
2. Simple Construction
3. No Moving Parts
4. Suitable For Gaseous / Liquid Waste
5. Low Maintenance Required
6. Capable Of High Turndown.
7. Accepts Wide Range Of Liquid / Gaseous Waste.
DEMERITS
•For Only Atomizable Liquid Wastes.
•Not Suitable For Slurries With Large Size Solids.
FLUIDISED BED INCINERATORS
APPLICATIONS
Distillation Bottom Tars
2. Organic Liquid & Semi Solid Waste.
3. Sludge With High Moisture Content.
4. Organic Sludge.
5. Pharmaceutical Sludge
6. Aqueous Waste containing Sodium Sulfate & Sodium
Carbonate & Recovery
7. Granular, Powdery waste

6. MERITS
•Ability to handle heterogeneous waste.
• High efficiency due to
- Vigorous mixing in the bed
- High retention time
• Low NOx formation due to
- Lower operating temperature &
- Low excess air.
• In bed neutralization possible for removing acid gases
• Quick re-start due to heat stored in the bed.
• Absence of moving parts hence low maintenance.
• Flexibility to handle diverse fuels.
DE-MERITS
•Difficult To Remove Residual Materials From Bed.
•Requires Elaborate Waste Preparation For Bulk Solids.
•High Power Costs.
•Incineration Temperature Limited To 800 Deg C.
•Special Care For Feed Selection & Mixing Of Additives To Prevent Bed Damage.
ROTARY KILN INCINERATORS
•In Rotary kilns solid, sludge, containerized or pumpable waste is introduced at the upper end of
the inclined drum. Temperatures in the kiln usually range between 850 and 1300ºC. The slow
rotation of the drum allows a residence time of 30-90 minutes.

7. •The secondary combustion chamber following the kiln completes the oxidation of the
combustion gases. Liquid wastes and/or auxiliary fuels may be injected here along with
secondary air to maintain a minimum residence time of two seconds and temperatures in the
range of 900-1300ºC, effectively destroying any remaining organic compounds.
MERITS
•Suitable For All Kinds Of Wastes.
•Feed Capability For Drums & Bulk Containers.
•Can Be Operated At High Temperatures.
•Residence Time Adjusted By Varying Kiln Speed.
•Waste Feeding - Without Much Preparation
LIMITATIONS
•Expensive For Low Feed Rates.
•Subject To High Wear & Tear.
•Relatively Low Thermal Efficiency.
•Large Particulate Carry-over.
•Air leakage possible without good sealing
DEDICATED INCINERATORS
DEDICATED INCINERATORS that handle a particular waste stream.
An example of the latter might be a chemical manufacturing plant treating chlorinated wastes to
recover HCl.
Dedicated hazardous waste incinerators use a variety of incineration, pyrolysis, and plasma
treatment techniques.

8. incinerator for treating liquid and gaseous chlorinated wastes at a chlorinated chemical
manufacturing facility
Monitoring
In addition to carbon monoxide, oxygen in the flue gas, air flows and temperatures, pressure
drops, and pH in the flue gas can be routinely monitored at reasonable cost. While these
measurements represent reasonably good surrogates for the potential for unintentional POPs
formation and release, periodic measurement of PCDD/F’s in the flue gas will aid in ensuring
that releases are minimized and the incinerator is operating properly.
Maintaining Public Awareness and Communication
•Successful incineration projects have been characterized by: holding regular meetings with
concerned citizens; providing days for public visitation; posting release and operational data to
the Internet; and displaying real time data on operations and releases at the facility site.
General Combustion Techniques
Ensure design of furnace is appropriately matched to characteristics of the waste to be processed.
Maintain temperatures in the gas phase combustion zones in the optimal range for completing
oxidation of the waste.
Provide for sufficient residence time (e.g., 2 seconds) and turbulent mixing in the combustion
chamber(s) to complete incineration.
Pre-heat primary and secondary air to assist combustion.
Use continuous rather than batch processing wherever possible to minimize start-up and shut-down
releases.
Establish systems to monitor critical combustion parameters including grate speed and
temperature, pressure drop, and levels of CO, CO2, O2.
Provide for control interventions to adjust waste feed, grate speed, and temperature, volume, and
distribution of primary and secondary air.
Install automatic auxiliary burners to maintain optimal temperatures in the combustion
chamber(s).
Hazardous Waste Incineration Techniques

9. •Rotary kilns are well demonstrated for the incineration of hazardous waste and can accept
liquids and pastes as well as solids.
••Water-cooled kilns can be operated at higher temperatures and allow acceptance of wastes with
higher energy values.
••Waste consistency (and combustion) can be improved by shredding drums and other packaged
hazardous wastes.
••A feed equalization system e.g., screw conveyors that can crush and provide a constant amount
of solid hazardous waste to the furnace, will ensure smooth feeding.
Flue Gas Treatment
The type and order of treatment processes applied to the flue gases once they leave the
incineration chamber is important, both for optimal operation of the devices as well as for the
overall cost effectiveness of the installation. Waste incineration parameters that affect the
selection of techniques include: waste type, composition, and variability; type of combustion
process; flue gas flow and temperature; and the need for, and availability of, wastewater
treatment.
Formation and Release of Unintentional POPs
Emission testing has confirmed that composition of the waste, furnace design, temperatures in
the post-combustion zone, and the types of air pollution control devices (APCD) used to remove
pollutants from the flue gases are important factors in determining the extent of POPs formation
and release. Depending on the combination of these factors, POPs releases can vary over several
orders of magnitude per ton of waste incinerated.
Average 6 - 7 Nm3 of flue gas per kg waste
Specific collection/treatment for:
Dust - staged filters
Chlorine - neutralised by scrubbing with lime
Sulphur - washing stage
Dioxins - combustion control, activated carbon
Examples of APCD’s relevant to the prevention or reduction of unintentional releases
•Cyclones and multi-cyclones
•Electrostatic precipitators – wet, dry, or condensation
•Fabric filters – including catalytic bag filters
•Static Bed Filters
•Scrubbing systems - wet, spray dry, or ionization
•Selective catalytic reduction (SCR)
•Rapid Quenching Systems
•Carbon Adsorption
Wastewater from incineration
Controls vary from country to country
Quantity:
•influenced by gas scrubbing technology chosen i.e. wet, semi-dry, dry

10. •Treatment:
•in aerated lagoons / widely used / low cost / may not meet required standard
•physico-chemical treatment may also be needed
Best Environmental Practices for Waste Incineration
Well-maintained facilities, well-trained operators, a well-informed public, and constant attention
to the process are all important factors in minimizing the formation and release of the
unintentional POPs from the incineration of waste. In addition, effective waste management
strategies (e.g., waste minimization, source separation, and recycling), by altering the volume
and character of the incoming waste, can also significantly impact releases.
Establishing Quality Requirements for Waste Fed
Facilities must be able to accurately predict the heating value and other attributes of the waste
being combusted in order to ensure that the design parameters of the incinerator are being met.
Incinerator Operating and Management Practices
Ensuring Good Combustion
Optimal burn conditions involve:
•mixing of fuel and air to minimize the existence of long-lived, fuel rich pockets of combustion
products,
••attainment of sufficiently high temperatures in the presence of oxygen for the destruction of
hydrocarbon species, and
••prevention of quench zones or low temperature pathways that will allow partially reacted fuel
to exit the combustion chamber.
Proper management of time, temperature, and turbulence as well as oxygen (air flow), by means
of incinerator design and operation will help to ensure the above conditions. The recommended
residence time of waste in the primary furnace is 2 seconds. Temperatures at or above 850°C are
required for complete combustion in most technologies. Turbulence, through the mixing of fuel
and air, helps prevent cold spots in the burn chamber and the buildup of carbon which can reduce
combustion efficiency. Oxygen levels in the final combustion zone must be maintained above
those necessary for complete oxidation.
Residue Management Techniques
•Unlike bottom ash, APCD residuals including fly ash and scrubber sludges may contain
relatively high concentrations of heavy metals, organic pollutants (including PCDD/F), chlorides
and sulfides.
••Mixing fly ash and FGT residues with bottom ash should be avoided since this will limit the
subsequent use and disposal options for the bottom ash.
••Treatment techniques for these residues include:
–Cement solidification. Residues are mixed with mineral and hydraulic binders and additives to
reduce leaching potential. Product is landfilled.
–Vitrification . Residues are heated in electrical melting or blast furnaces to immobilize
pollutants of concern. Organics, including PCDD/F are typically destroyed in the process.
–Catalytic treatment of fabric filter dusts under conditions of low temperatures and lack of
oxygen;
–The application of plasma or similar high temperature technologies.

11. –•Fly ash and scrubber sludges are normally disposed of in landfills set aside for this purpose.
Some countries include ash content limits for PCDD/F in their incinerator standards. If the
content exceeds the limit, the ash must be re-incinerated.
CONTROLS AND SAFETIES
•Temp. control for constant efficiency
•Air control for adequate excess air
•Pressure control for balance draft
•pH control for scrubber performance
•Interlocks for safe operation & shutdown
Costs
•Related to site-specific and country-specific factors
•High level of sophistication & control = high construction costs
•Air pollution control costs = 30-40% of total
Scenario in Hazardous Waste Management in India
•Major issues in India
–30 million tons of waste generated apart from fly ash (2003 data)
•8 million tons of hazardous waste
•Key issues
–Lack of secure landfills and Treatment, storage and disposal facility
–Lack of incineration facilities
–Lack of waste handling and management systems
Hazardous waste disposal industry in the industry sector is worth about $200 million
Utilization of wastes in cement plants
•Waste utilisation in cement plants in India
–Almost nil – except fly ash and gypsum
•US/Japan and European Cement plants
–Use 80% of waste as fuel
–450 kg of waste is used as raw material for production of one ton of Cement production in
Japan
•Tremendous potential in India
–Waste utilization technology
–Waste processing equipment
•Key requirement
–Suitable legislation for waste processing in Cement industry
Indian cement plants can absorb 14 million tons of hazardous waste /year
CONCLUSIONS
Hazardous waste incineration
•Is in principle good strategy to treat hazardous waste in an environmentally sound way
•are highly regulated

12. •need skilled personnel
•require high operating and safety standards
•require high capital investment•have medium to high operating costs