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Waste to Energy

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Submitted By srirambhat
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1. ABSTRACT
Alternative uses of waste for energy production becomes increasingly interesting both from a waste management perspective - to deal with increasing waste amounts while reducing the amount of waste deposited at landfills and from an energy system perspective to improve the flexibility of the energy system in order to increase the share of renewable energy and reduce greenhouse gas emissions. The object of analysis is waste which is not reused or recycled, but can be used for energy production. Different Waste-to-Energy technologies are analyzed through energy system analysis of the current Danish energy system with 13-14% renewable energy, as well as possible future Danish energy systems with 43% (2025) and 100% renewable energy (2050), respectively. The technologies include combustion, thermal gasification, anaerobic digestion, fermentation, and transesterification technologies producing electricity, heat, or transport fuel. In the USA, according to the US energy recovery council, there are 87 WTE plants producing 2,700 megawatts that results into 17 million of kwh per year which is enough to meet the needs for power for 2 million households. In the EU incineration is more popular. According to the confederation of European Waste to energy plants (CEWEP) the plants in Europe can supply annually about 13 million inhabitants with electricity and 12 million inhabitants with heat.
Waste to energy is produced mainly by biological material and thus the energy produced is mainly biomass energy along with all its pros and cons. In addition significant steps have been taken in recent years to make sure that the portion of non biological material incinerated is harmless to the environment. Therefore, waste to energy incineration is a great way to reduce our dependency on fossil fuel and in addition to reduce CO2 emissions and Land filling.

2. INTRODUCTION
Waste to energy is the production of heat and/or electricity mainly with the usage of garbage as a fuel or as their official term is Municipal Solid Waste (MSW). MSW includes all solid waste produced by households, apartment building, schools and commercial establishments that local authorities collect. Waste to energy is considered a type of energy recovery and there are two main methods: * incineration which is done via direct combustion of the waste and * Transformation of waste into combustible gaseous form (i.e. methane, ethanol) via thermal treatment without direct combustion (i.e. pyrolysis, gasification.)
The most popular method out of the two is incineration. Incineration is a quite controversial method as it often raises environmental concerns. This is because municipal solid waste contain a diverse mix of waste materials, some benign and some very toxic such as heavy metals, trace organics, such as dioxins and furans. As a result there is a debate on whether waste to energy can be considered biomass energy. Biomass is a renewable energy source that uses as fuel material of biological origin. Consequently, the production of biomass does not add into the co2 environmental concentration as its fuel can be replaced and recapture the emitted carbon dioxide used during its production i.e. in the case of burning wood or corn you can replant. Waste to energy on the other hand does not use exclusively biological material, even though the greatest portion of MSW is of biological origin, and thus opponents of it claim that is not a sustainable form of energy. The counterargument is that WTE is sustainable since people will continue to produce garbage of non-biological origin. In addition, regarding harmful emissions (dioxins etc), modern techniques applied to new WTE plants have minimized the amount released to acceptable levels. Finally, a large portion of the risk can be eliminated via thorough pre-sorting of MSW at plants sites to exclude toxic materials from being used as fuel thus reducing pollution emissions to a minimum. Hence, waste to energy can help in the reduction of Land filling since it reduces the volume of waste by 95%. In addition, as oppose to WTE, Land filling creates methane which is much more harmful to the environment since it contributes 20 to 25 times more to global warming than the CO2 emissions.

3. WASTE TO ENERGY TECHNOLOGY
Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of creating energy in the form of electricity or heat from the incineration of waste source. WtE is a form of energy recovery. Most WtE processes produce electricity directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels.
Wastes to Energy Incineration
Incineration, the combustion of organic material such as waste, with energy recovery is the most common Waste to Energy implementation. Incineration may also be implemented without energy and materials recovery, however this is increasingly being banned in OECD (Organisation for Economic Co-operation and Development) countries. Furthermore, all new Waste to Energy plants in OECD countries must meet strict emission standards. Hence, modern incineration plants are vastly different from the old types, some of which neither recovered energy nor materials. Modern incinerators reduce the volume of the original waste by 95-96 %, depending upon composition and degree of recovery of materials such as metals from the ash for recycling.
Concerns regarding the operation of incinerators include fine particulate, heavy metals; trace dioxin and acid gas emissions, even though these emissions are relatively low from modern incinerators. Other concerns include toxic fly ash and incinerator bottom ash (IBA) management. Discussions regarding waste resource ethics include the opinion that incinerators destroy valuable resources and the fear that they may reduce the incentives for recycling and waste minimization activities. Incinerators have electric efficiencies on the order of 14-28%. The rest of the energy can be utilized for e.g. district heating, but is otherwise lost as waste heat.
The method of using incineration to convert municipal solid waste (MSW) to energy is a relatively old method of waste-to-energy production. Incineration generally entails burning garbage to boil water which powers steam generators that make electric energy to be used in our homes and businesses. One serious problem associated with incinerating MSW to make electrical energy, is the pollutants that are put into the atmosphere when burning the garbage that power the generators. These pollutants are extremely acidic and have been reported to cause serious environmental damage by turning rain into acid rain. One way that this problem has been significantly reduced is through the use of lime scrubbers on smokestacks. The limestone mineral used in these scrubbers has a pH of approximately 8 which means it is a base. By passing the smoke through the lime scrubbers, any acids that may be in the smoke are neutralized which prevents the acid from reaching the atmosphere and hurting our environment. (Field) According to the New York Times, modern incineration plants are so clean that "many times more dioxin is now released from home fireplaces and backyard barbecues than from incineration."

WtE technologies other than incineration
There are a number of other new and emerging technologies that are able to produce energy from waste and other fuels without direct combustion. Many of these technologies have the potential to produce more electric power from the same amount of fuel than would be possible by direct combustion. This is mainly due to the separation of corrosive components (ash) from the converted fuel, thereby allowing higher combustion temperatures in e.g. boilers, gas turbines, internal combustion engines, fuel cells. Some are able to efficiently convert the energy into liquid or gaseous fuels:
Thermal technologies: * Gasification (produces combustible gas, hydrogen, synthetic fuels) * Thermal depolymerization (produces synthetic crude oil, which can be further refined) * Pyrolysis (produces combustible tar/biooil and chars) * Plasma arc gasification PGP or plasma gasification process (produces rich syngas including hydrogen and carbon monoxide usable for fuel cells or generating electricity to drive the plasma arch, usable vitrified silicate and metal ingots, salt and sulphur)
Non-thermal technologies: * Anaerobic digestion (Biogas rich in methane) * Fermentation production (examples are ethanol, lactic acid, hydrogen) * Mechanical biological treatment (MBT) * MBT + Anaerobic digestion * MBT to Refuse derived fuel

4. WASTE INCINERATION - AN EFFECTIVE WASTE MANAGEMENT PROCESS
Environment has great influence in the life of all the living things on this earth. When it comes to wastage and its treatment, one of the very oldest effective waste treatments is waste incineration. It is basically a process where the domestic and industry waste materials are burnt. In this process, the waste materials turn into ash, flue gas and heat. On the basis of the type of waste materials, the incineration can of various scales, such as: small scale, medium scale and large scale.
Though some people think that waste management or waste treatment is not a very big issue, but in reality it is a serious matter of concern. In waste incineration method, waste materials or organic substances are burnt which incorporate households, hazardous and also medical wastes equipments. As the method of incineration involves combustion, therefore it is also known as thermal treatment. These days, the incinerations help in saves energy from being wasted.

Moreover, the method of incineration has a lot of benefits over other types of waste treatment system. While treating the waste materials, such as clinical and hazardous materials, waste incineration has proved to be more effective in this regard. By using this waste treatment method, the harmful pollutant and pathogens can be burnt completely in high temperature. This method of waste treatment has become extremely popular in countries having scarcity of lands.

However, while gong for waste incineration, one should also keep in mind that this process can have some negative effectives on our health due to environmental pollution. Production of ashes, flue gases and other releases of incineration can also lead to some serious consequences on mankind as well as on our natural atmosphere. In incineration, the waste materials get reduced in its amount and also get transformed into ashes that consist of some of the most venomous substances like: dioxins and heavy metals. These substances are difficult to destroy. As we all know that waste materials can be of various kinds, therefore in order to manage various kinds of waste materials, various types of incinerator plants are designed, such as: moving grate, fixed grate, rotary-kiln, and fluidized bed. The best thing about the modern incinerators is that they have pollution mitigation equipment such as flue gas cleaning in them.

5. WASTE-TO-ENERGY PLANT
Waste-to-Energy Plant Operations
Incineration is a thermal treatment technology used to reduce the volume of waste requiring final disposal. Incineration can typically reduce the waste volume by over 90% and it is one of the widely used technologies for treating municipal solid waste prior to disposal at landfills. Most modern incineration plants incorporate heat recovery as well as power generation facilities to recover the heat energy in the waste. To ensure that the gas emissions meet the stringent standards imposed by regulatory bodies (e.g. EU Waste Incineration Directive) for public health and environmental protection, modern incineration plants adopt a number of advanced design and process controls as well as exhaust gas cleaning measures as illustrated by the flow chart below:

Combustion - Waste is continuously fed into the furnace by an overhead crane. The waste is combusted in the specially designed furnace at high temperature of > 850oC for more than 2 second with sufficient supply of air so as to ensure complete burning of the waste and to prevent the formation of dioxins and carbon monoxide. Boiler/ steam turbine - The heat from the combustion is used to generate steam in the boiler. The steam then drives the turbine which is coupled to the electricity generator. The excess heat generated can also be used for other purposes, e.g. heat for swimming pool.
Exhaust gas cleaning - The exhaust gas from the boiler is typically cleaned by the following advanced pollution control systems to ensure compliance with the stringent environmental standards: l Dry or Wet scrubbers – to spray lime powder or fine atomized slurry into the hot exhaust gas to neutralize and remove the polluted acidic gases (sulphur oxides, hydrogen chloride) l Activated Carbon Injection – to adsorb and remove any heavy metal and organic pollutants (e.g. dioxins) in the exhaust gas l Bag house filter - to filter and remove dust and fine particulates l Selective Non-Catalytic Reduction - to remove nitrogen oxides (which is a cause of urban smog) by reacting them with ammonia or urea. Ash residues handling - The ash residues from incineration generally include bottom ash from the furnace and fly ash from the exhaust gas cleaning units. The bottom ash is either reused as construction material or disposed of at landfills. Fly ash is typically stabilized and solidified by reagents (e.g. cement) and disposed of at dedicated landfill with continuous environmental monitoring. Ash melting that use the heat energy in the incinerator to melt the ash residues at a high temperature is a technology used in some place. The melted products are inert and contain no hazardous materials so that they may be re-used (e.g. as construction material). Comparatively ash melting is more expensive but it has the advantages of further volume reduction and fixation of any hazardous materials in the fly ash.

Environmental Preservation System Check - Air Quality * Daily round-the-clock monitoring and analysis of emissions from the Waste-to- Energy (WTE) plants as well as annual stack testing continuously confirm that all emissions are well within limits allowed by federal and state regulators. * To reduce mercury emissions, the County launched a cooperative program with local hospitals to begin using nonmercury batteries, resulting in the removal of nearly a ton of mercury a year from the waste stream. To divert button batteries, hundreds of businesses, schools, offices, and residential complexes began serving as drop-off sites. Within the two years of implementation, some 600,000 batteries and an estimated 153 pounds of mercury were removed from the waste stream. These programs, combined with both plants' state-of-the-art emissions control technology and the battery industry's changeover to nonmercury batteries, are helping to protect our environment.
System Check - Water Resources
Neither of the plants drains the County's precious water resources. About 80% of the water used at both plants is recycled from different sources. On a daily basis, each plant saves about one million gallons of water through recycling efforts.
At the North plant, wastewater is brought in from the County's North Regional Waste Water Treatment Plant, where it is reused for purposes such as cooling and landscaping. The South plant recycles water from the plant's ash monofill.

6. INDIA WASTE TO ENERGY
India – Waste Generation Scenario
Every year, about 55 million tonnes of municipal solid waste (MSW) and 38 billion liters of sewage are generated in the urban areas of India. In addition, large quantities of solid and liquid wastes are generated by industries. Waste generation in India is expected to increase rapidly in the future. As more people migrate to urban areas and as incomes increase, consumption levels are likely to rise, as are rates of waste generation. It is estimated that the amount of waste generated in India will increase at a per capita rate of approximately 1-1.33% annually. This has significant impacts on the amount of land that is and will be needed for disposal, economic costs of collecting and transporting waste, and the environmental consequences of increased MSW generation levels.
Types of Waste
Waste can be broadly classified into i. Urban Waste ii. Industrial Waste iii. Biomass Waste iv. Biomedical Waste
Urban waste includes Municipal Solid Waste, Sewage and Fecal Sludge, whereas industrial waste could be classified as Hazardous industrial waste and Non-hazardous industrial waste.
Why Waste to Energy is Important?
Most wastes that are generated, find their way into land and water bodies without proper treatment, causing severe water pollution. They also emit greenhouse gases like methane and carbon dioxide, and add to air pollution. Any organic waste from urban and rural areas and industries is a resource due to its ability to get degraded, resulting in energy generation.
The problems caused by solid and liquid wastes can be significantly mitigated through the adoption of environment-friendly waste-to-energy technologies that will allow treatment and processing of wastes before their disposal. These measures would reduce the quantity of wastes, generate a substantial quantity of energy from them, and greatly reduce environmental pollution. India’s growing energy deficit is making the government central and state governments become keen on alternative and renewable energy sources. Waste to energy is one of these, and it is garnering increasing attention from both the central and state governments.
While the Indian Government’s own figures would suggest that the cost of waste to energy is somewhat higher than other renewable sources, it is still an attractive option, as it serves a dual role of waste disposal and energy production.

India Waste to Energy Potential
India is the second largest nation in the world, with a population of 1.21 billion, accounting for nearly 18% of world’s human population, but it does not have enough resources or adequate systems in place to treat its solid wastes. Its urban population grew at a rate of 31.8% during the last decade to 377 million, which is greater than the entire population of US, the third largest country in the world according to population (3). India is facing a sharp contrast between its increasing urban population and available services and resources. Solid waste management (SWM) is one such service where India has an enormous gap to fill. Proper municipal solid waste (MSW) disposal systems to address the burgeoning amount of wastes are absent. The current SWM services are inefficient, incur heavy expenditure and are so low as to be a potential threat to the public health and environmental quality (4). Improper solid waste management deteriorates public health, causes environmental pollution, accelerates natural resources degradation, causes climate change and greatly impacts the quality of life of citizens The present citizens of India are living in times of unprecedented economic growth, rising aspirations, and rapidly changing lifestyles, which will raise the expectations on public health and quality of life. Remediation and recovery of misused resources will also be expected. These expectations when not met might result in a low quality of life for the citizens (See Section 4.6). Pollution of whether air, water or land results in long-term reduction of productivity leading to a deterioration of economic condition of a country. Therefore, controlling pollution to reduce risk of poor health, to protect the natural environment and to contribute to our quality of life is a key component of sustainable development (5).
The per capita waste generation rate in India has increased from 0.44 kg/day in 2001 to 0.5 kg/day in 2011, fuelled by changing lifestyles and increased purchasing power of urban Indians. Urban population growth and increase in per capita waste generation have resulted in a 50% increase in the waste generated by Indian cities within only a decade since 2001. There are 53 cities in India with a million plus population, which together generate 86,000 TPD (31.5 million tons per year) of MSW at a per capita waste generation rate of 500 grams/day. The total MSW generated in urban India is estimated to be 68.8 million tons per year (TPY) or 188,500 tons per day (TPD) of MSW. Such a steep increase in waste generation within a decade has severed the stress on all available natural, infrastructural and budgetary resources.
Big cities collect about 70 - 90% of MSW generated, whereas smaller cities and towns collect less than 50% of waste generated. More than 91% of the MSW collected formally is landfilled on open lands and dumps (6). It is estimated that about 2% of the uncollected wastes are burnt openly on the streets. About 10% of the collected MSW is openly burnt or is caught in landfill fires (5). Such open burning of MSW and landfill fires together releases 22,000 tons of pollutants into the lower atmosphere of Mumbai city every year (Figure 15). The pollutants include carbon monoxide (CO), carcinogenic hydro carbons (HC) (includes dioxins and furans), particulate matter (PM), nitrogen oxides (NOx) and sulfur dioxide (SO2) (5).
Most of the recyclable waste is collected by the informal recycling sector in India prior to and after formal collection by Urban Local Bodies (ULB). Amount of recyclables collected by informal sector prior to formal collection are generally not accounted. This report estimates that 21% of recyclables collected formally are separated by the formal sector at transfer stations and dumps. Even though this number does not include amount of recycling prior to formal collection, it compares fairly well with the best recycling percentages achieved around the world (See Section 5.1.1). Informal recycling system is lately receiving its due recognition world-wide for its role in waste management in developing nations. In India, government policy and non-governmental organizations (NGOs) are expected to organize the sector present in different regions, and to help integrating it into the overall formal system. ‘Plastic Waste Management and Handling Rules, 2011’ by the Ministry of Environment and Forests (MOEF) is a step ahead in this direction. These rules mandate ULBs to coordinate with all stake holders in solid waste management, which includes waste pickers.
MSW rules 2000 made by the Government of India to regulate the management and handling of municipal solid wastes (MSW) provide a framework for treatment and disposal of MSW. These rules were the result of a ‘Public Interest Litigation (PIL)’ in the Supreme Court of India (SC). The MSW rules 2002 and other documents published by the Government of India (GOI) recommend adoption of different technologies, which include biomethanation, gasification, pyrolysis, plasma gasification, refuse derived fuel (RDF), waste-to-energy combustion (WTE), sanitary landfills (SLF). However, the suitability of technologies to Indian conditions has not been sufficiently studied, especially with regard to the sustainable management of the entire MSW stream and reducing its environmental and health impacts.
MUNICIPAL SOLID WASTE (MSW):-
MSW is defined as any waste generated by household, commercial and/or institutional activities and is not hazardous (10). Depending upon the source, MSW is categorized into three types: Residential or household waste which arises from domestic areas from individual houses; commercial wastes and/or institutional wastes which arise from individually larger sources of MSW like hotels, office buildings, schools, etc.; municipal services wastes which arise from area sources like streets, parks, etc. MSW usually contains food wastes, paper, cardboard, plastics, textiles, glass, metals, wood, street sweepings, landscape and tree trimmings, general wastes from parks, beaches, and other recreational areas (11). Sometimes other household wastes like batteries and consumer electronics also get mixed up with MSW.

PER CAPITA MSW GENERATTION:-
The per capita waste generation rate is strongly correlated to the gross domestic product (GDP) of a country (Table 2). Per capita waste generation is the amount of waste generated by one person in one day in a country or region. The waste generation rate generally increases with increase in GDP. High income countries generate more waste per person compared to low income countries due to reasons discussed in further sections. The average per capita waste generation in India is 370 grams/day as compared to 2,200 grams in Denmark, 2,000 grams in US and 700 grams in China (12) (13) (14).

Waste generation rate in Indian cities ranges between 200 - 870 grams/day, depending upon the region’s lifestyle and the size of the city. The per capita waste generation is increasing by about 1.3% per year in India (7).

Cities in Western India were found to be generating the least amount of waste per person, only 440 grams/day, followed by East India (500 g/day), North India (520 g/day), and South India. Southern Indian cities generate 560 grams/day, the maximum waste generation per person. States with minimum and maximum per capita waste generation rates are Manipur (220 grams/day) and Goa (620 grams/day). Manipur is an Eastern state and Goa is Western and both are comparatively small states. Among bigger states, each person in Gujarat generates 395 g/day; followed by Orissa (400 g/day) and Madhya Pradesh (400 grams/day). Among states generating large amounts of MSW per person are Tamil Nadu (630 g/day), Jammu & Kashmir (600 g/day) and Andhra Pradesh (570 g/day). Among Union Territories, Andaman and Nicobar Islands generate the highest (870 grams/day) per capita, while Lakshadweep Islands (340 grams/day) generates the least per capita. Per capita waste generation in Delhi, the biggest Union Territory is 650 g/day.
The Census of India classifies cities and towns into 4 classes, Class 1, Class 2, Class 3, and Class 4, depending upon their population (Table 4). Most of the cities studied during this research fell under Class 1. For the purpose of this study, these Class 1 cities were further categorized as Metropolitan, Class A, Class B, etc, until Class H depending upon the population of these cities. This finer classification allowed the author to observe the change in waste generation closer. However, the waste generation rates did not vary significantly between Class A, B, C, D, E, F, G & H cities. They fell in a narrow range of 0.43-0.49 kg/person/day. They generated significantly less MSW per person compared to the six metropolitan cities (0.6 kg/day). The per capita waste generation values of Class 2, 3 and 4 towns calculated in this report are not expected to represent respective classes due to the extremely small data set available. Data for only 6 out of 345 Class 2 cities, 4 out of 947 Class 3 cities and 1 out of 1,167 class 4 towns was available. Despite the lack of data in Class 2, 3, and 4 towns, the 366 cities and towns represent 70% of India’s urban population and provide a fair estimation of the average per capita waste generation in Urban India (0.5 kg/day).

MSW GENERATION:-
Generation of MSW has an obvious relation to the population of the area or city, due to which bigger cities generate more waste. The metropolitan area of Kolkata generates the largest amount of MSW (11,520 TPD or 4.2 million TPY) among Indian cities.
Among the four geographical regions in India, Northern India generates the highest amount of MSW (40,500 TPD or 14.8 million TPY), 30% of all MSW generated in India; and Eastern India (23,500 TPD or 8.6 million TPY) generates the least, only 17% of MSW generated in India. Among states, Maharashtra (22,200 TPD or 8.1 million TPY), West Bengal (15,500 TPD or 5.7 million TPY), Uttar Pradesh (13,000 TPD or 4.75 million TPY), Tamil Nadu (12,000 TPD or 4.3 million TPY) Andhra Pradesh (11,500 TPD or 4.15 million TPY) generate the highest amount of MSW. Among Union Territories, Delhi (11,500 TPD or 4.2 million TPY) generates the highest and Chandigarh (486 TPD or 177,400 TPY) generates the second highest amount of waste.

7. CASE ON WASTE TO ENERGY
Case 1:-BIOMASS POWER PLANT
Biomass or organic fuels are some of the other fuels that can also be used for fuelling Gasification. This also reduces the risk of polluting the air that occurs with the burning of Coal. This is attributed to the high temperature conversion reaction that helps in the refinement of corrosive elements of ash, for instance, potassium and chloride, furthermore aiding in the production of clean gas fuel. It has also been observed that using these Biomass or organic fuels helps in keeping the calorific value of the fuel stable irrespective of the moisture content, content of ash or feedback stock.

Plasma Gasification Process (PGP) is a thermal process involving the application of intense heat to waste materials in a completely closed, controlled, and oxygen-starved environment. This process actually helps in the conversion of waste materials into a clean synthetic gas and heat that can be used to generate electricity. This process is considered to be far superior to incineration because no emissions are released into the atmosphere and the syngas produced is rich in energy and is also regarded as an efficient fuel for creating electricity with gas engines or gas turbinesThe PGP system possesses the ability to process any waste stream such as: MSW (Municipal Solid Waste), biomedical waste and spent potliner, paint sludge, drum reconditioning sludge, organic petrochemical sludge, illicit drugs, high metal content waste, coal and MSW incinerator ashes, paper mill reject waste, fluorescent light ballasts, asbestos containing material, explosives industry waste, rubber tires and industrial hazardous wastes including PCBs and concentrated insecticides. The units heat these fuels with about one-third of the oxygen necessary for complete combustion to produce a mixture of carbon dioxide and hydrogen, known as syngas. Biomass energy accounts for about 11% of the global primary energy supply, and it is estimated that about 2 billion people worldwide depend on biomass for their energy needs.Generation of electricity in the industrial plants is obtained by the Gasification of wood. Although any type of raw material can be used as a fuel but wood is the generally prescribed preference.There are primarily three products produced by PGP. The main product of the process is a synthetic gas produced when the volatile elements in the waste material are reduced to their base molecules. This gas is used for the generation of electricity by feeding it into the same type of gas engine that is used in the production of electricity from natural gas. |
The second product of the process is heat which produces steam. The steam is collected and fed into the electricity generation process to improve its efficiency.
The third and final product of the process is a glass-like reusable solid, also known as slag, produced when the non-volatile elements of the waste material gets decomposed. As hard and clean as glass, this solid has a variety of uses such as a road or building material additive. The solid does not react with other elements and leaches less than the glass from a common soda bottle
Case 2:- THERMAL TREATMENT OF HAZARDOUS INDUSTRIAL WASTES AND WASTE-TO-ENERGY SYSTEMS
Multi-purpose incinerator for processing solid and liquid wastes

Originally:
Disposal of wastes (treatment of wastes)
At present:
Waste processing (waste-to-energy systems) * Recovering heat (generating steam & electricity * Preheating purposes (reduced fuel demand) * Processing of residues (vitrification)

INCINERATION vs GASIFICATION – COMPARISON * Discussion of comparison :- in the case of gasification: * Generating gaseous products at the first stage outlet up to 10 times lower Þ aspects influencing operating and investment costs * Considerably lower consumption of auxiliary fuel (natural gas) autothermal regime * Reduced size of the afterburner chamber compared to that necessary for a comparable oxidation incineration plant * Lower specific volume of gas produced Þ reduction in size of flue gas heat utilization and off-gas cleaning systems Þ reduction of investment and operating costs of the flue gas blower * Lower production of steam (proportional to the volume of flue gas produced)

TECHNOLOGY SELECTION CONSIDERATIONS ON

“ EEE“ TECHNOLOGY
ENVIRONMENT ECONOMY ENERGY * CO2 Control Cost Control Energy Recovery * DXNs Control Profit High Efficiency * Emission Control Growth Utilization / Sale * Landfill Control
WTE systems = up-to-date technology + experience(know-how) + theoretical backgro

8. CONCLUSION 1 It has been shown how various aspects of a process and equipment design can contribute to improving economic and environmental design. 2 WTE systems provide us with clean, reliable and renewable energy. Waste-to-Energy technologies show good prospects:

1) Incineration for CHP of the main amount of waste (77% of total) with the highest possible electricity and heat efficiencies
2) Biogas production from the full potential of organic household waste and manure for production of CHP or transport fuel
3) Co-combustion of refuse derived fuel (RDF) with coal in new coal-fired power plants today and thermal gasification of RDF for CHP in the future when fully developed, if reduced CO2 emissions are not the main goal

9. REFERENCES 1 Community Energy Technologies, CANMET Energy Technology Centre-Ottawa, Natural Resources Canada, 1997. 2 Ciavaglia, L., "Personal communication," CANMET Energy Technology Centre-Ottawa, Natural Resources Canada, 2003. 3 www.jkcontrols.co.uk 4 McRae, S.G., Waste to Energy, Halstead Press, New York, NY, USA, 1988 5 Internet…...

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