High temperature corrosion is a major operating problem because it results in unscheduled shutdowns in Waste-to-Energy (WTE) plants and accounts for a significant fraction of the total operating cost of WTE plants. Due to the heterogeneous nature of municipal solid waste (MSW) fuel and the presence of aggressive elements such as sulfur and chlorine, WTE plants have higher corrosion rates than coal-fired power plants which operate at higher temperature. To reduce corrosion rates while maximizing the heat recovery efficiency has long been a critical task for WTE operators. Past researchers focused on high temperature corrosion mechanisms and have identified important factors which affect the corrosion rate [1–4]. Also, there have been many laboratory tests seeking to classify the effects of these corrosion factors. However, many tests were performed under isothermal conditions where temperatures of flue gas and metal surface were the same and did not incorporate the synergistic effect of the thermal gradient between environment (flue gas) and metal surface. This paper presents a corrosion resistance test using an apparatus that can maintain a well controlled thermal gradient between the environment and the surface of the metals tested for corrosion resistance. Two commercial substrates (steels SA213-T11 and NSSER-4) were tested under different corrosive environments. The post-test investigation consisted of mass loss measurement of tested coupons, observation of cross-sectional morphology by scanning electron microscopy (SEM), and elemental analysis of corrosion products by energy dispersive spectrometry (EDS). The stainless steel NSSER-4 showed good corrosion resistance within the metal temperature range of 500 °C to 630 °C. The alloy steel SA213-T11 had an acceptable corrosion resistance at metal temperatures up to 540 °C, and the performance decreased dramatically at higher temperatures.

The Waste-To-Energy Research and Technology Council (WTERT) was co-founded in May 2002 by the Earth Engineering Center of Columbia University (EEC) and Integrated Waste Services Association (IWSA). Its mission is to direct academic research on various aspects of energy and materials recovery from municipal and other solid wastes and disseminate the findings of its research to professionals and the public. WTERT is a non-profit organization that relies heavily on faculty and graduate students who are studying various aspects of integrated waste management and waste-to-energy. The main products of WTERT research are the theses, technical publications and presentations made during the year. In all there were 14 publications, 22 presentations, and 12 posters presented by WTERT faculty and graduate students at different technical meetings and public forums. This report presents the highlights of the WTERT activities since NAWTEC 14.

The Miami-Dade 3,000 tpd Refused-Derived Fuel (RDF) facility is located in Miami-Dade County, FL and is operated by Montenay Power, a Veolia Environmental Services Company. A team composed of plant staff and outside experts underwent a thorough equipment-by-equipment review of the Air Pollution Control (APC) system and identified a series of low cost design and operational improvements to the lime slakers, the spray dryers and the baghouses. These improvements were implemented over the course of several months and resulted in a drop in lime consumption, in the economy of one and a half air compressor units, and in reduced APC related plant downtime and maintenance costs. This paper describes several key improvement projects (including the upgrade of the spray nozzles, the change in slaking water quality and the fly ash fluidization project), detailing the initial problem, the chosen solution, the difficulties encountered during implementation and the achieved benefits.

The proportional composition of cellulose, hemicellulose, lignin and minerals in a biomass plays a significant role in the proportion of pyrolysis products (bio-oil, char, and gases). Traditionally, the composition of biomass is chemically determined, which is a time consuming process. This paper presents the results of a preliminary investigation of a method using thermo-gravimetric analysis for predicting the fraction of cellulose and lignin in lignin-cellulose mixtures. The concept is based on a newly developed theory of Pyrolytic Unit Thermographs (PUT). The Pyrolytic Unit Thermograph (PUT) is a thermograph showing rate of change of biomass weight with respect to temperature for a unit weight loss. These PUTs were used as input for two predictive mathematical procedures that minimize noise to predict the fractional composition in unknown lignin-cellulose mixtures. The first model used linear correlations between cellulose/lignin content and peak decomposition rate while the second method used a system of linear equations. Results showed that both models predicted the composition of lignin-cellulose mixture within 7 to 18% of measured value. The promising results of this preliminary study will certainly motivate further refinement of this method through advanced research.

This investigation has been initiated to characterize the thermal decomposition of waste tires with Thermo-Gravimetric Analysis (TGA) in various atmospheres ranging in oxygen content; 100% N 2 , 7%, 21% (air) and 30% O 2 . Chemical analysis focusing on light hydrocarbons, substituted aromatics, and polycyclic aromatic hydrocarbon has been done qualitatively and quantitatively to understand the mechanism of thermal degradation of scrap tires and hazardous air pollutants such as PAH. The release of chemicals from scrap tires has been determined experimentally using Gas Chromatography/Mass Spectroscopy (GC/MS) coupled to TGA unit. The identities and absolute concentrations of over 50 major and minor species have been established. Significant volatile organic carbons (VOC) including substituted aromatics and PAH were observed between 300°C and 500°C. In addition, significant black carbon residual was observed in most environments except air and oxygen enhanced atmospheres and suggested not only the potential recovery of black carbon out of feedstock, but also the possibility of combined thermal treatment between combustion and gasification. These measurements supply information on the identities and levels of hazardous air pollutants, and provide useful new data for the development and validation of detailed reaction mechanisms describing their origin and fate. Finally, while high contents of VOC show significant potential to be utilized as an unconventional solid fuel, they also tend to generate hazardous pollutants.

Experts believe that Legionella may be present in 25% of cooling towers at any time, even with normal water treatment programs in place. This could pose a risk to employees and others working near cooling towers, and it could pose a risk to neighboring facilities such as schools, hospitals, public facilities, other businesses, or residential communities. The goal is to reduce the risk of Legionella , more specifically Legionella pnuemophila , which is the bacterium that causes a potentially fatal pneumonia known as Legionenaires’ Disease or legionellosis. Reducing the risk of Legionella requires more than water treatment alone, it requires a strategic plan based on recommended industry best practices that considers the mechanical, operational, and chemical control of cooling water systems. Implementing a corporate wide policy for Legionella risk reduction is challenging for waste-to-energy facility cooling towers. While a corporate policy for managing the risk due to Legionella is prudent, application of such a policy should not be wholly applied across all facilities or plant locations because not all water systems are equal or operated the same. Implementation starts with a plan that involves a multidisciplinary team including third party consultation and expertise. The first step of the Legionella risk reduction strategy is to evaluate current equipment and practices at each plant through a risk assessment process. The second step is to prepare a written Management Plan based on the risk assessment that clearly details risk reduction practices. The third step is to implement the management plan and monitor the system to ensure practices remain effective. And finally, all documentation should be periodically reviewed and adjustments made as necessary. This presentation will describe a process for implementing a corporate Legionella risk reduction policy, and it will highlight some of the major experiences learned.

Part of the WTERT effort to increase the amount of metals recovered by the U.S. Waste-to-Energy industry was a survey to determine the type of equipment used for metal recovery and the quantities of ferrous and non-ferrous metals recovered, and the distribution in percent between front- and back-end recovered metals. A questionnaire was sent to the headquarters of the three major WTE companies and fifty three WTE plants responded with data for the year 2004. As mass burn and RDF plants were examined separately, a comparison of metal recovery by means of these two technologies was possible. The ways to recover metals in the U.S. WTE industry range from only manual separation of large objects at the tipping floor at mass burn facilities, to front-end recovery at RDF plants, to metal separation from the ash at the back-end of the WTE process or at a regional metal recovery facility. Accordingly, the amounts of metals recovered range from very little to over 40.000 tons per year. Comparison of the collected with estimated averages of ferrous (5%) and non-ferrous (0.7%) metals in U.S. MSW, indicated that 48% of ferrous and 9% of non-ferrous metal input are recovered at these 53 WTE facilities every year. The remainder is landfilled and represents a revenue loss that may be as high as $160 millions per year, including the payment of tipping fees for landfilling metals. Mass burn facilities recover an average of 43% of the ferrous and 5% of the non-ferrous metals, while RDF plants recover 71% of ferrous and 30% of non-ferrous of the assumed metal input. However, the metal input in some WTEs may differ from the U.S. average because of effective metal recycling practice in the community. Analysis of the front- and back-end recovery at mass burn and RDF plants shows that the former recover only 1% of the ferrous metal at the front-end and 99% from the bottom ash. In comparison, RDF plants recover 88% of the ferrous metal at the front-end and only 12% after combustion. Mass burn plants recover 94% of the non-ferrous metal at the back end. It is interesting to note that RDF plants also recover most of their non-ferrous metals (98% of the total) at the back-end. Our analysis shows that there is room for increasing metal recovery of both ferrous and non-ferrous metals at selected mass burn facilities that presently recover less than 10% of the input ferrous metals. Non-ferrous metal recovery is very low for mass-burn and low for RDF plants. Since the value of WTE metals has increased appreciably recently, due to increased consumption in China, it is a good time to consider plant modifications that will help increase metal recovery. Some of the most likely WTEs for implementing such modifications have been identified and discussions are under way for effecting plant retrofits at some facilities. A current objective is to obtain similar data from the nearly 30 facilities that were not included in the first part of this survey. We are also trying to determine how metal recycling practice in the communities that supply various WTE facilities correlates with the metal recoveries attained by these facilities.

As awareness regarding the potential threat of climate change has grown in the US, many local governments and businesses are being asked to consider the climate implications of their actions. In addition, many leaders, including solid waste managers, who are not yet pressured from the outside, consider it prudent to account for their greenhouse gas (GHG) emissions and consider it a proactive measure to assess climate risks and opportunities and to show commitment to progress. Sources of GHG emissions in the solid waste management process include: waste transport vehicles, composting facilities, processing equipment, landfills, and waste-to-energy facilities. Over the past 25 years, the levels of GHG emissions have been reduced through technological advancements in waste-to-energy, environmental regulations such as the Clean Air Act, landfill gas capture and control, and the promotion of recycling and reuse. There are many opportunities for solid waste managers to further reduce their GHG emissions levels, including promotion of waste-to-energy facilities as part of a low-carbon solid waste management plan. Waste-to-energy may also, in the future, offer potential revenue from the sale of renewable energy credits and carbon credits in emerging emissions trading programs.