1. Environmentally Sound Destruction of POP’s – Incineration Kåre Helge Karstensen

2. 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. Dedicated hazardous waste incinerator

4. 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 1,000oC and less than one second residence time, while other more complex organic halogens require more stringent conditions.
Slide 22 Thermal treatment
The slide shows some of the different thermal processing methods which are used for hazardous waste treatment. More details can be found in Chapter 6.5 Thermal treatment.
One of the most widely used thermal treatment for hazardous wastes is co-combustion in cement kilns.

5. US EPA Toxic Substances Control Act (TSCA) PCB Incineration Criteria
“...more complex organic halogens such as PCB requires 1200oC and 2 seconds residence time ”
A DRE of % is required by TSCA for the incineration of PCB’s

6. 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”.

7. Technology description
Hazardous waste is normally incinerated in two types of facilities: merchant plants who accept different types of waste for disposal; and 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.
The most common combustion technology in hazardous waste incineration is the rotary kiln. Facilities in the merchant sector range in size from 30,000 to 100,000 tons/year throughput. Dedicated hazardous waste incinerators use a variety of incineration, pyrolysis, and plasma treatment techniques.
Similar to the incineration of municipal solid waste, hazardous waste incineration offers the benefits of volume reduction and energy recovery.

8. Dedicated hazardous waste incinerator for treating liquid and gaseous chlorinated wastes at a chlorinated chemical manufacturing facility

9. Technology description
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 minutes.
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 ºC, effectively destroying any remaining organic compounds.

10. Rotary kiln incinerator
Slide 23 Examples of technology 1 Rotary kiln incinerator
Rotary kiln incinerators are extensively used because of their ability to handle a wide variety of hazardous wastes. The average plant capacity is 25,000-50,000 tonnes per year. Wastes can be in the form of solids, liquids or drummed wastes. Solid and drummed wastes are sometimes shredded before they are fed through the conveyer system. Pumpable sludge and liquids are injected through a nozzle. The kiln is operated at around 1200oC and the off-gas from the first chamber is then combusted (at around 1000oC) in the secondary chamber to reduce particulates and ensure complete destruction of hazardous components. From the secondary chamber the hot gases go to a waste heat boiler which produces steam. The slag’s long residence time of approximately 30 minutes is necessary because the temperature in the solid bed of the kiln is not uniform.
Wet or dry scrubbers are used to treat the flue gases, with any fluids from the gas scrubbing process themselves being treated. Sludge is sent for sedimentation and dewatering, and, in some countries, for additional processes such as activated carbon filtration. A 50,000 tonnes per year facility might generate around 10,000 tonnes of slag, 1,000 tonnes of fly ash and 150 tonnes of dewatered sludge per year. The disadvantages of rotary kiln furnaces include their high capital, operating and maintenance costs and the need for trained operators.

12. 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.

13. 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
Slide 13 Flue gases
The amount and type of pollutant in the emissions from thermal processes depend on the pollutants in the waste, the technology and the efficiency of its operation.
The current methods of incinerating wastes generate on average between 6 and 7 normal cubic metres of flue gas for every kilogramme of incinerated waste. This varies according to a number of elements, including the chemical composition of the wastes themselves.
Regulatory controls on emissions from incineration have been strengthened in recent years in most countries. For example, the legal thresholds in the European Union have been divided by more than 100 in 20 years, and the emission limit for dioxins is now 0.1ng TEQ/Nm3 (where TEQ represents an agreed toxic equivalent). These stricter regulations have required major changes in technology and operating practices, and greatly increased the costs of waste incineration.
Dust: To comply with the new limits a number of stages are required. This may include the use of electrostatic precipitators (which alternate high voltage discharges of ionising wires with earthed collection plates) as well as fabric filters which trap the dust.
Chlorine: It is necessary to neutralise the chlorine with calcium (usually in the form of lime) or sodium hydroxide in one of several alternative treatment systems: dry, semi-dry, semi-wet or wet scrubbing. The last is the most efficient but has higher equipment costs and leaves a larger liquid residue which (due to its low pH) needs to be neutralised before discharge.
Sulphur: a significant part of the sulphur is eliminated with chlorine but in order to comply with emissions limits it is probably necessary to add a washing stage with a higher pH than the first wash. This adds to the complexity of the total process because – like every other wet treatment – it imposes additional equipment needs and reagent conditions as well as leaving a liquid residue for treatment and disposal.

14. Example of flue gas cleaning technology
Slide 15 Example of flue gas cleaning technology
As has been stated, there are several technologies for flue gas cleaning, differing in the amount of water which is used. The slide shows the flow chart for a rotary kiln incinerator including the stages for flue gas cleaning technology which uses a wet scrubbing process.

15. Examples of APCD’s relevant to the prevention or reduction of unintentional POPs 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

16. Unintentional POPs formation can occur within the ESP at temperatures in the range of 200ºC to about 450ºC. Operating the ESP within this temperature range can lead to the formation of unintentional POPs in the combustion gases released from the stack.

17. Fabric filters are also referred to as baghouses or dust filters
Fabric filters are also referred to as baghouses or dust filters. These particulate matter control devices can effectively remove unintentional POPs that may be associated with particles and any vapors that adsorb to the particles in the exhaust gas stream.
Filters are usually 16 to 20 cm diameter bags, 10 m long, made from woven fiberglass material, and arranged in series. Fabric filters are sensitive to acids; therefore, they are usually operated in combination with spray dryer adsorption systems for upstream removal of acid gases.

18. Fabric filters (bag filters) are widely applied in waste incineration and have the added advantage, when coupled with semi-dry sorbent injection (spray drying), of providing additional filtration and reactive surface on the filter cake.
Pressure drop across fabric filters should be monitored to ensure filter cake is in place and bags are not leaking.
Fabric filters are subject to water damage and corrosion and are best suited for dry gas streams with upstream removal of acid gases. Some filter materials are more resistant to these effects.

19. Carbon Adsorption
Activated carbon is injected into the flue gas prior to the gas reaching the spray dryer-fabric filter/ESP combination. PCDD/PCDF (and mercury) are absorbed onto the activated carbon, which is then captured by the fabric filter or ESP. The carbon injection technology improves capture of the unintentional POPs in the combustion gases by an additional 75% and is commonly referred to as flue gas polishing. Many APCDs have been retrofitted to include carbon injection.

20. Spray dry scrubbing, also called spray dryer adsorption, removes both acid gas and particulate matter from the post-combustion gases.
The spray drying technology is often used in combination with ESPs and fabric filters. Spray drying reduces ESP inlet temperatures to create a cold-side ESP.

21. Selective Catalytic Reduction (SCR) is a secondary control measure primarily designed to reduce NOx emissions. The process also destroys unintentional POPs via catalytic oxidation. SCR is a catalytic process in which an air-ammonia mix is injected into the flue gas stream and passed over a mesh catalyst. The ammonia and NOx react to form water and N2.
SCR units are usually placed in the clean gas area after acid gas and particulate matter removal. Efficient operation of the SCR process requires maintenance of the catalyst between 130 and 400ºC. For this reason, SCR units are often placed after ESPs to avoid the need for reheating of the flue gases. Caution must be exercised in such placement to avoid additional unintentional POPs formation in the ESP.

22. Wastewater from incineration
Controls vary from country to country
Quantity:
influenced by gas scrubbing technology chosen i.e. wet, semi-dry, dry
Treatment:
in aerated lagoons / widely used / low cost / may not meet required standard
physico-chemical treatment may also be needed
Slide 16 Wastewater from incineration
The controls on wastewater vary from country to country.
The wastewater from flue gas cleaning is normally treated in a separate wastewater treatment plant.
Treatment of wastewater in aerated lagoons is a widely used and low cost option but this may not meet the required standard and physical-chemical treatment is generally needed prior to the biological stage. The less wastewater generated eg by use of dry or semi dry flue gas scrubbing techniques, the lower the facility’s equipment and operating costs.

23. 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.

24. Waste Inspection and Characterization

25. Proper Handling, Storage, and Pre-Treatment
Storage areas must be properly sealed with controlled drainage and weatherproofing. Fire detection and control systems for these areas should also be considered. Storage and handling areas should be designed to prevent contamination of environmental media and to facilitate clean up in the event of spills or leakage.
Odors can be minimized by using bunker air for the combustion process.

26. Proper Handling, Storage, and Pre-Treatment

27. Minimizing Storage Times
Minimizing the storage period will help prevent putrefaction and unwanted reactions, as well as the deterioration of containers and labeling.
Managing deliveries and communicating with suppliers will help ensure that reasonable storage times are not exceeded.

28. 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.

30. 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.

31. Circulating fluidised bed
Slide 24 Examples of technology 2 Fluidised bed combustion
Fluidised bed combustion is suitable for a variety of hazardous wastes, whether they are solid, liquid or gaseous. The technology enables the operator to control residence times and sustain stable temperatures, and it has good gas-to-solids contact characteristics. It operates at temperature ranging from 650 to 775oC. Highly persistent chlorinated hydrocarbons can be destroyed by this technology.
Types of fluidised bed incinerators shown on the slide:
Bubbling fluidised bed incinerator
Circulating fluidised bed incinerator

32. Incinerator Operating and Management Practices
Ensuring Good Combustion cont.
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.

33. Bubbling fluidised bed
Slide 24 Examples of technology 2 Fluidised bed combustion
Fluidised bed combustion is suitable for a variety of hazardous wastes, whether they are solid, liquid or gaseous. The technology enables the operator to control residence times and sustain stable temperatures, and it has good gas-to-solids contact characteristics. It operates at temperature ranging from 650 to 775oC. Highly persistent chlorinated hydrocarbons can be destroyed by this technology.
Types of fluidised bed incinerators shown on the slide:
Bubbling fluidised bed incinerator
Circulating fluidised bed incinerator

34. 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.

35. Operator Training
Regular training of personnel is essential for proper operation of waste incinerators

36. 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.

37. BAT - 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).

38. BAT - Hazardous Waste Incineration Techniques
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.

39. Condensation electrostatic precipitator

40. BAT – 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.

42. Destruction efficiency
DRE’s of greater than percent have been reported for treatment of wastes consisting of, containing or contaminated with POPs.

43. BAT - 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.
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.

44. Costs and Economic Considerations
The construction of large state-of -the-art incinerators requires major capital investment, often approaching hundreds of millions USD. Installations recover capital and operating costs through treatment fees and, in the case of waste-to-energy facilities, through the sale of steam or electricity to other industries and utilities.
The ability to fully recover the costs of construction and operation is dependent on a number of factors including: the relative cost of alternative disposal methods; the availability of sufficient waste within the local area; provisions for disposal of residues; and proper staffing, operation, and maintenance to maintain peak efficiency and minimize downtime.

45. Costs Related to site-specific and country-specific factors
High level of sophistication & control = high construction costs
Air pollution control costs = % of total
Slide 19 Costs
The high level of sophistication and control associated with thermal methods of waste treatment are reflected in the high costs of constructing such a plant.
Once built, treatment costs per tonne may not differ greatly from other technologies, but all costs are related to a number of site specific and country specific factors and cannot be estimated here.
The costs of air pollution control systems represent a substantial proportion of the cost of a new facility, and may be 30-40% of the total.
It is worth noting that the volume, weight and hazard of waste remaining for final disposal are greatly reduced, a valuable point when treatment or disposal capacity are limited. The recovery and sale of energy from the process also improves overall costs.

46. Capital and operating costs for an average 70,000 tpy HWI facility
Cost Structure
EUR
Planning/approval
3,000,000
Machine parts
16,000,000
Other components
14,000,000
Electrical works
10,000,000
Infrastructure works
6,000,000
Construction time
Total investment costs
54,000,000
Capital financing costs
5,000,000
Personnel
Maintenance
4,000,000
Administration
300,000
Operating resources/energy
1,300,000
Waste disposal
800,000
Other
Total operational costs
14,700,000
Per ton incineration costs (without revenues)

47. Costs and Economic Considerations
Country
Gate Fees in EUR/ton
MSW
Hazardous Waste
Belgium
56-130
Denmark
40-70
France
50-120
Germany
Italy
40-80
Netherlands
90-180
Sweden
20-50
Not available
United Kingdom
20-40

48. Throughput
Hazardous waste incinerators have a capacity from a few hundred tons to >100,000 tons per year

49. Dedicated incinerators are available in many countries
Availability
Dedicated incinerators are available in many countries

50. Hazardous waste incineration
are in principle capable to treat POP’s and POP’s waste in an environmentally sound way and can meet stringent ELV’s
are highly regulated
need skilled personnel
require high operating and safety standards
require high capital investment
have medium to high operating costs
Slide 3 Application of thermal treatment
Thermal treatment is suitable for wastes with a high carbon and hydrogen content ie organic wastes. Around 20% of industrial waste and 30% of domestic waste is typically incombustible. This includes ferrous and non-ferrous metals such as iron and aluminium.
In some cases the first stage of the combustion process is an evaporation stage, where the water is first removed for treatment, prior to the actual combustion.
Application of thermal processing of hazardous wastes is constrained by the costs, the need for skilled personnel and the requirements for high operating and safety standards. Safety precautions include a requirement for automatic shutdown of the plant when specified, vital parameters (such as required temperature) are not complied with.
For thermal treatment to be an acceptable and environmentally sound waste treatment process, properly designed, operated and controlled, the most important factors are good combustion control and effective flue gas cleaning. These in turn require high capital investment, comprehensive regulation, trained personnel and high operating standards. The complexity of the technology and its need for skilled operation and management result in moderate to high operating costs.