The dominant technology for large Waste-to-Energy (WTE) facilities is combustion on a moving grate of “as-received” municipal solid wastes (MSW). However, there are circumstances where a low-capacity plant (<100,000 tons per year) is required. This study examines the technical, economic, and environmental aspects of some small-scale WTE technologies currently in operation. The Energos technology was developed in Norway, in order to provide relatively small communities with an economically efficient alternative to mass-burn incineration with equally low emissions to the atmosphere and flexibility in feedstock. All operating plants treat MSW plus additional streams of commercial or industrial wastes. Prior to thermal treatment, the materials are shredded in a high-torque, low-rpm shredder and ferrous metals are removed magnetically. The feedstock is partially oxidized on a moving grate in the gasification chamber where the fixed carbon is completely burnt off. The volatilized gases are fully combusted in a second chamber and the heat is transferred to a heat recovery system for steam generation. The Energos gasification technology is currently in operation at six plants in Norway, one in Germany, and one in the UK. As expected, the capital cost per ton of annual ton of capacity increases with decreasing plant capacity, while there is a linear relationship between energy recovery and capacity. Some other small-scale technologies are investigated in this study and will be reported at the NAWTEC meeting. Low capacity (<80,000 tons) WTE facilities require a relatively small footprint (1.5 to 2 acres; <1 hectare) and it is believed that these facilities can be built at a capital cost per ton that is as low, or lower, than that of large mass burn WTE facilities.

High-energy recovery combined with low emissions to air and water was targeted when Jo¨nko¨ping Energi planned their new Waste to Energy plant at Torsvik in Sweden. The plant is compliant with the new EU Industry Directive and the Waste Frame Directive R-formula, which defines energy recovery levels for recycle of energy. In total about 160 000 tons of municipal (40%) and commercial waste (60%) is annually converted into usable energy. The average heat value is 11,7 MJ/kg. The energy produced is a combination of electricity (14 MW e ) and heat (42–56 MW th , depending on electricity production). The heat is recovered both in a boiler and in a condenser. The flue gas condensing system is combined with a heat pump (10 MW th ) to optimize the heat recovery rate. The plant is designed to fulfill the requirements set by the Swedish authorities, which are more stringent than the EU emission requirements. Some examples of the plant emissions to air guarantees: dust 5, HCl 5, SO 2 20, HF1, Hg 0,03, Cd+Tl 0,05, other HM 0,5 all in mg/Nm 3 and dioxin 0,05 ng/Nm 3 . The flue gas cleaning upstream of the condenser consists of a combination of a semi-dry system and a wet scrubber. The gas cleaning system operating range goes from 60 000 up to 127 000 Nm3/h depending on load and fuel heat value. The semi-dry system is carrying out the major part of the gas cleaning and is sufficient to comply with the air regulations. However, in order to minimize the treatment of the condensate from the condenser the wet scrubber is installed after the semi-dry system and upstream the condenser. The blow down from the scrubber is reused within the plant. Thus the polishing scrubber secures minimal treatment of the condensate to comply with the local stringent limits, particular chlorides, before release to the recipient lake Munksjo¨n. Emissions to water were 2010 nitrogen 1,7 mg/l, Cl <3,6 mg/l, As 0,66 μg/l, Cd <0,07 μg/l, Cr <6 μg/l, Cu 0,8 μg/l, Hg <0,4 μg/l, Ni <0,66 μg/l, Pb<1,2 μg/l, Tl<1,3 μg/l, Zn<7,2 μg/l and PCDD/PCDF 0,0088 ng/l. In the wet scrubber acid stage residual HCl and excess ammonia from the SNCR system are removed. The latter compound is important to capture in order to prevent eutrophication. The combination of a semidry and a wet system enables an optimization of the flue gas cleaning with regard to the different operating situations, taking into account seasonal demand variations as well as fuel alterations. The concept has demonstrated very low emissions combined with low consumption of lime. The possibility to optimize the flue gas cleaning performance is a prerequisite for minimal condensate treatment and optimal energy recovery. The paper will describe the system and the operating experiences.

Covanta Energy, in cooperation with United Technologies Corporation (UTC), has evaluated, designed, and is in the process of installing an Organic Rankine Cycle (ORC) system at its Haverhill Energy from Waste (EfW) Facility to improve heat recovery and energy efficiency, and to generate more clean renewable energy. ORC systems have been applied in geothermal applications and some other industrial processes to recover low grade and waste energy to generate electricity. This paper describes the design and integration of the ORC system into the Haverhill EfW steam cycle, and the landfill gas engine system, which also operates at the facility. The anticipated energy efficiency improvements and increased net power output have been analyzed and simulated. The results show that the integration of the ORC system could lead to a potential increase in the net power output by as much as 305 kWe in the summer and by 210 kWe in normal weather. It is also anticipated that with the ORC system the facility has the potential to improve the overall plant energy efficiency, as well as save city water.

Babcock Power Environmental (BPE), a Babcock Power Inc. company, has developed a new, innovative, high-efficiency NO x reduction technology designed to greatly reduce the NO x emissions from waste to energy (WTE) boilers at relatively low cost. This “tail-end” system uses Selective Catalytic Reduction (SCR) to achieve the high reduction performance. Conventional SCR catalyst cannot be used in the traditional “high-dust” location, downstream of the economizer because constituents in the ash would poison the catalyst quickly, rendering it useless. Thus, the Regenerative Selective Catalytic Reduction (RSCR ® ) system is designed to operate at the end of the plant before the flue gas is discharged to the stack. The process utilizes a reactant (usually aqueous ammonia) to be added to the flue gas stream upstream of the RSCR to reduce NO x to harmless reaction products, N 2 and H 2 O. The RSCR combines the efficient heat recovery, temperature control, reactant mixing, and catalyst into a single unit and provides the maximum NO x reduction and heat recovery practical. The paper will describe the overall predicted performance of a typical WTE boiler plant using this new technology. The paper will also provide actual operating data on the RSCR, which has been retrofitted to four biomass-fired units.

The Algonquin Power Energy-From-Waste (APEFW) facility is located in the suburban Toronto, Ontario city of Brampton. It receives approximately 140,000 metric tonnes (154,000 tons) of MSW per year from the Region of Peel (Region) and approximately 10,000 metric tonnes (11,000 tons) per year of international airport waste from the area’s two international airports. The APEFW facility commenced initial operations in 1992 and included four, 91 tonne (100 ton) per day Consumat two stage incinerators with heat recovery boilers and a dual-train air pollution control (APC) system consisting of evaporative cooling towers, venturi reactors and fabric filter baghouses. The APEFW facility expanded its capacity in 2001 with the addition of a fifth 91 tonne (100 ton) per day modular incinerator and heat recovery boiler. One of the stipulations in the permitting process was that the entire expanded facility meet more stringent emission standards that included a significantly lower nitrogen oxides (NOx) emission rate. After a review of several available NOx control technologies, the APEFW facility chose to install a Selective Catalytic Reduction (SCR) system. While SCR systems are fairly common on EFW facilities in Europe, the APEFW facility is the only EFW facility in North America that currently operates with an SCR system and as such has gained valuable insight into the application and performance of this technology that is very relevant to the North American EFW industry. This paper discusses the operation and maintenance of the SCR system, compares pre- and post-SCR NOx emissions and presents capital and operating costs for the SCR including the cost per tonne of waste processed and the cost per tonne of NOx removed.

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.

In 2001, SEGHERS was awarded the contract for the design and construction of the furnace and heat recovery system of a new, 330 tons per day WtE-plant in Orebro¨, Sweden. A wide variety of municipal and industrial wastes (including electronic waste, demolition waste, car fluff, filters, plastic and rubber...) will be treated. The design point corresponds to an average heating value (HHV) of 13.1 MJ/kg (5600 Btu/Lb). The first part of the paper addresses the engineering and construction phase of the project, which took 15 months in total. Key decisions and design options, including the choice and characteristics of a partially water-cooled grate, the use of the cooling water heat (with implications on plant efficiency) and the design features resulting in a low-NOx WtE plant are discussed in detail. The second part of the paper focuses on the construction and commissioning of the plant. Finally, the plant performance is documented. The main results are compared with the guaranteed values and the differences are discussed. The performance of the water-cooled grate is compared to that of other WtE plants.

The City of Tampa’s solution to solving their waste disposal problems started almost 30 years ago. A conventional refractory lined incinerator equipped with a wet quench scrubber was constructed and operated by the City, starting in 1965. The old incinerator would often belch black soot and smoke and in 1979 was shutdown for environmental concerns. The City selected Waste Management Energy Systems, then a subsidiary of Waste Management Inc., to design, build, and operate for 20 years, a tried and proven waste combustor linked with a heat recovery boiler, electrostatic precipitator, and a turbine generator. This system was placed into operation in 1985 and the last two units were operated until July 2000 when compliance with the Clean Air Act required their retrofit. In 1996, the City assembled a Project Team consisting of consultants that specialized in various aspects of solid waste disposal including: permitting, design, operations, and construction oversight. After several years of design, procurement, and negotiations, Wheelabrator was selected as the successful vendor to design, construct, and operate the retrofitted facility. Construction began in April 1999 and went into commercial operation in January 2002.

During the last two decades, several research groups as well as consultants have been analysing the environmental impacts of incineration in comparison to other waste treatment options. Methods and models for describing these systems have been developed. Systems studies on local, regional and national level have been performed using a wide range of different modelling approaches. The aim of this paper is to describe the environmental performance of incineration with energy recovery in Europe in comparison with other options for waste treatment/recovery. This includes identifying key factors that largely affect the outcome from environmental systems studies where such comparisons are made. The paper focuses on mixed solid waste and on waste fractions where there has been a lot of controversy whether the material should be recycled, incinerated or treated biologically (e.g. paper, plastics, compostable material). The paper is based on a meta-study, where the above research field is mapped out in order to gather relevant systems studies made on local, regional and national levels in Europe. By thoroughly examining these studies, conclusions are drawn regarding the environmental performance of incineration with energy recovery and regarding key factors affecting the environmental results.