For the waste disposal of urban areas and major cities at the North American market place rather large scale energy from waste (EfW) plants are needed. This implies a mechanical input of approx. 40 Mg/h [39.36 tn l./h] and thermal input by waste per unit of 110 MW [375.3 MBTU/h] and more. There are basic design criteria that feature large scale EfW plants: - Layout of boiler with horizontal or vertical orientation of convective part. - Top or bottom suspension of boiler. - Flexible design of stoker regarding large throughput figures and heating values of waste with water or air cooled grate bars. - Design and geometry of combustion furnace in order to optimize the flow pattern. - Optimization of boiler steel structure: integrated steel structure for boiler and boiler house enclosure. - Optimization of corrosion protection and maintainability of large scale boilers: cladding versus refractory lining. - Maintenance aspects of the boiler. The paper gives information on the pros and cons regarding the design features with special focus on optimized solutions for large scale EfW plants. For the core component of the combustion system — the grate — Fisia Babcock Environment (FBE) is using forward moving grates as well as roller grates. The moving grate in STEINMÜLLER design, which is used in the great majority of all our plants, has specific characteristics for providing uniform combustion and optimal burnout. The automatic combustion rate control system is the key component in the combustion process in order to receive good burn out quality in slag and flue gas as well as constant steam production and oxygen content of flue gas. This paper includes a detailed report on a modern control system with focus on a simple and efficient control structure. Besides these measures regarding the combustion process, this paper also reports about the respective aspects and concepts for the flue gas cleaning systems. In this field the FBE CIRCUSORB ® process was presented in previous papers and is now compared with a multistage wet flue gas cleaning system. The latter is relevant in case of very low emission requirements.

This paper is based on data compiled in the course of developing, for InterAmerican Development Bank (IDB), a WTE Guidebook for managers and policymakers in the Latin America and Caribbean region. As part of this work, a list was compiled of nearly all plants in the world that thermally treat nearly 200 million tons of municipal solid wastes (MSW) and produce electricity and heat. An estimated 200 WTE facilities were built, during the first decade of the 21st century, mostly in Europe and Asia. The great majority of these plants use the grate combustion of as-received MSW and produce electricity. The dominance of the grate combustion technology is apparently due to simplicity of operation, high plant availability (>90%), and facility for training personnel at existing plants. Novel gasification processes have been implemented mostly in Japan but a compilation of all Japanese WTE facilities showed that 84% of Japan’s MSW is treated in grate combustion plants. Several small-scale WTE plants (<5 tons/hour) are operating in Europe and Japan and are based both on grate combustion and in implementing WTE projects. This paper is based on the sections of the WTE Guidebook that discuss the current use of WTE technology around the world. Since the beginning of history, humans have generated solid wastes and disposed them in makeshift waste dumps or set them on fire. After the industrial revolution, near the end of the 18 th century, the amount of goods used and then discarded by people increased so much that it was necessary for cities to provide landfills and incinerators for disposing wastes. The management of urban, or municipal, solid wastes (MSW) became problematic since the middle of the 20 th century when the consumption of goods, and the corresponding generation of MSW, increased by an order of magnitude. In response, the most advanced countries developed various means and technologies for dealing with solid wastes. These range from reducing wastes by designing products and packaging, to gasification technologies. Lists of several European plants are presented that co-combust medical wastes (average of 1.8% of the total feedstock) and wastewater plant residue (average of 2% of the feedstock).

Rapid economic development and also population growth of urban centers in developing island nations have resulted in the generation of large amounts of MSW that in the past were dumped at uninhabited areas indiscriminately. Also, islands have very limited space for new, sanitary landfills. This study examines islands where WTE has been implemented successfully (Bermuda, Martinique, St. Barth) and several others (Jamaica, Mauritius, Rhodes) where WTE has been considered and is in various stages of implementation. The study showed that the per capita generation of MSW increases as GDP per capita increases. Also, it is usually recommended that the waste management system be improved one step at a time, that is, to go from dumps to sanitary landfills, to waste to energy; it is interesting to note that the three islands examined in this study went directly from dumps to WTE. This phenomenon can be partly attributed to the scarcity of land for new landfills, but may also be due to the desire to develop a local and renewable energy source.

The size of combustion generated particles ranges from a few nanometers up to 1 micron, whereas the size of naturally occurring PM such as pollens, plant fragments, and sea salt is generally larger than 1 micron. Particles generated by photochemical processes in the atmosphere are generally smaller than 1 micron. Ultrafine particles (UFP), also called “nanoparticles”, are <0.1 micron and in recent yearshave attracted attention due to potential adverse health effects associated with them. The contribution of UFP to the total PM mass is very small. However, they dominate the total number of particles in urban aerosols. Their sources are both mobile and stationary combustion sources and also gas-to-particle conversions. In coal and waste combustion systems, UFP are hypothesized to be generated mainly by nucleation of metal vapors. Coal naturally contains a vast range of inorganic elements among which are heavy metals. Sources of heavy metals in MSW include batteries, electronic devices, light bulbs, house dust and paint chips, food containers, used motor oils, plastics, yard wastes and some papers. The input of these metals into WTE facilities can be controlled by better source-separation of metal-containing materials. In 2007 almost 50% of the approximately 4.16 billion MWh generated in the United States was produced by coal power plants whereas only 0.3% was generated by the WTE industry. A preliminary study has shown that in terms of contribution to UHF in the atmosphere, MSW combustion has a minor effect in comparison to coal-fired power plants in the U.S. This paper will report on the results of this investigation.

The maximum environmental benefits from a new Energy from Waste (EFW) facility may require locating the new plant close to both the source of the waste and the potential energy customers. This paper will present design features that were incorporated into several new EFW facilities to allow them to be located directly into urban environments while minimizing their impact on the community and often improving the quality of life for the surrounding communities. Locating the EFW facility directly into an urban community: • Minimizes the cost and the environmental impact of waste transport. • Allows electrical power to be generated at the point of consumption. • Provides thermal energy for district heating and cooling. • Reduces the dependence on imported fossil fuel for electrical generation and for heating / cooling. • Provides secure and well paying jobs for members of the community. • Reduces the carbon foot print of the community. • An EFW plant typically leads to higher recycling rate, both pre and post combustion. Some of the specific measures that have been considered for EFW plants in urban environment have included architectural enhancements, more stringent noise and odor control, significant reduction or even elimination of visible plumes. The two case studies included in this paper will be the new Isse´ane EFW plant in Paris and the recently awarded Riverside EFW plant in London.

The Olmsted County Waste-to-Energy Facility (WTE) is in the process of expanding the facility capacity. The original facility began commercial operation in 1987 and consists of two 100 tpd units, equipped with Riley boilers and Takuma grates. The plant was built during the construction boom for WTE plants in the U.S. At that time there were some industry leading technologies, and also were many other players in the field offering European, Japanese, as well as U.S. technologies for the combustion of MSW. The industry has changed since those exciting times when nearly every city and urban county in the country would at least consider WTE. Years of industry stagnation caused by a number of events and trends resulted in the merger, bankruptcy, or pull out of WTE engineering firms in the U.S. market. Today there are only a handful of technologies used and an even smaller fraternity of private operating companies. Many private and publicly operated WTE facilities continue to operate successfully and recently several are in various stages of facility expansion or new plant development. Olmsted County started this process three years ago laying the groundwork for a facility expansion to double its capacity. Currently, the County is in the engineering phase of the expansion and expects to begin construction in 2007. The engineering effort includes consideration of commercially available combustion technologies and procurement of this equipment. This paper looks briefly at the historical availability of grate and boiler technologies and the findings of the County’s assessment of technologies available in the U.S. market.

Waste to energy is only one way of handling waste, material recovery is another aspect of sustainable waste management. This is actually nothing new and has always been part of the operation of WTE (Waste to Energy) plants in Hamburg. In descriptions of the first waste incineration plant in Hamburg, which started operation in 1896, it was stated that “the fly ash” collected in the ash chambers was used as filler material for the insulation of ceiling cavities. Its use in the sandwich walls of money safes was expressly recommended by the members of the urban refuse collection authority. Another lucrative trade was the sorting of scrap iron. It was separated from the incineration slag with magnets. The slag itself was said to be as sterile as lava, as hard as glass, as useful as bricks, and it was a profitable side product of waste incineration. The crushed incinerator slag was evidently so much in demand in road construction and as an aggregate in concrete production that demand could often not be met in the building season, even though it was stored through the winter, [1,2,3].

Essex County Resource Recovery Facility (one of American Ref-Fuel Company’s six operating plants) has processing MSW capacity of approximately 2700 TPD and about 60% of this waste comes from NY City. Therefore, availability of the Essex plant boilers is very important not only for the company’s financial performance, it is also critical for the overall garbage disposal situation in the NYC Metropolitan area. One of the main factors affecting plant availability is boiler unscheduled downtime. The most recent data show that approximately 85% of Essex boilers unscheduled downtime is caused by tube failures, the majority of which occur in the superheater tubes. These tube failures are almost exclusively caused by fireside tube metal wastage driven by complicated mechanisms of corrosion in combination with local erosion. The corrosion is caused by chloride salts in the slag that deposits on the boiler tubes, coupled with high temperatures of flue gas going through the boiler. Corrosion rates are known to be very sensitive to flue gas temperature, tube metal temperature, heat flux, flow distribution. Erosion is typically caused by high velocities and flyash particle loading and trajectories. Extensive research revealed that in addition to this typical to WTE boiler corrosion/erosion mechanism, Essex boiler superheater tubes experienced a unique problem, resulting in tube overheating, accelerated wastage, and ultimate failure. In order to address this problem a modification plan was developed, which comprised several redesign options. A specially developed Three-dimensional Computational Fluid Dynamics (3-D CFD) model was utilized for comprehensive technical evaluation of the considered design options and for predicted performance simulations of the selected design at different operating conditions. The economical analysis, conducted in conjunction with the superheater redesign, provided financial justification for this project. The project has been recently executed, and field data collection is still in progress. Some preliminary data analyses have been performed. They have shown that the boiler performance after superheater modification is very close to the predicted target simulated by the CFD model. The plant and the company are already measuring financial benefits as a result of this project, the initial phase of which is presented in this paper.

The U.S. generates about 370 million short tons of Municipal Solid Waste (MSW) each year. In 2002, an average of 26.9% of this material was either recycled or composted. Of the remainder, an estimated 242 million short tons were disposed of in landfills and about 29 million short tons were combusted in Waste to Energy (WTE) facilities to produce electricity and scrap metal. Effective management of MSW is becoming increasingly challenging, especially in densely populated regions, such as New York City, where there is little or no landfill capacity and the tipping fees have doubled and tripled in recent years. There is also a growing appreciation of the environmental implications of landfills. Even with modern landfill construction, impacts remain from the need for transfer stations to handle putrescible wastes, their transport to distant landfills, and finally landfill gas emissions and potential aqueous run-off. Environmental impacts of concern associated with disposal in WTEs include air emissions of metals, dioxins and greenhouse gases. In the U.S., there is also a strong negative public perception of WTE facilities. Decisions about waste management should be influenced by a consideration of the overall, quantified life-cycle environmental impacts of different options. In this paper we therefore develop a methodology to assess these impacts for landfilling and WTE waste management options. Specifically we attempt to compare these two options for New York City, a large urban area.