A new WTE (Waste-to-Energy) power plant configuration combining municipal solid waste and gas turbines or landfill gas engines is proposed. The system has two objectives: increase the thermodynamic efficiency of the plant and avoid the corrosion in the MSW (Municipal Solid Waste) boiler caused by high tube metal temperatures. The difference between this concept and other existing configurations, such as the Zabalgarbi plant in Bilbao, Spain, is lower natural gas consumption, allowing an 80% waste contribution to the net energy exported or more. This high efficiency is achieved through four main steps: 1 . introducing condensing heat exchangers to capture low temperature heat from the boiler flue gases; the stack temperature can drop to 70°C; 2 . high steam temperatures in external superheaters using hot clean gases heated with duct burners; 3 . mixing the exhaust gases of a small gas turbine with hot air preheated in a specially designed heat exchangers. The resulting temperature of this gas mixture is almost the same as a standard gas turbine but with the flow similar to that of a large machine with a higher O 2 content; 4 . After the duct burner and heat exchangers, the oxygen content of the clean gas mixture is still high, nearly 18%, and the temperature is approximately 200°C. The gas is then used as combustion air to the MSW boiler such that all the energy stays in the system. The efficiency can be as high as 33% for the MSW part of the plant and 49% for the natural gas system. Since the natural gas consumption is almost ten times less than the existing designs, it can be replaced by landfill gas or gasified ethanol or biodiesel. Currently an 850 ton/day plant is being designed in Brazil in partnership with a large power company. Other advantages include, self generation of internal power and lower steam superheating temperatures in the MSW boiler. This concept can be used with any grate design.

Energy recovery from waste is an efficient way to reduce emissions of greenhouse gas and other gaseous, liquid and solid pollutants and thereby to contribute to a sustainable development. Waste fired power plants are an important part of the European waste management system, and the demands made to modern waste fired power plant are very focused on high electrical output. Lately, Babcock & Wilcox Vo̸lund (BWV) and the CHEC research centre at the Technical University of Demnark has developed a new technology and received a world patent. The basic idea is to improve the electrical efficiency by increasing the steam data. Especially, increasing the steam temperature without the risk of superheater corrosion. The new concept is fully integrated in the boiler and from the outside the waste fired power plant has the same layout as the classic waste fired power plant. The goal is to achieve an increase between 50 °C to 100 °C in the superheated steam temperature and a total increase of electrical efficiency up to 30% without any influence on the normal operation. This paper presents the basic ideas that provide a basis for the patent. The core of the technology is a combination of a new furnace design and a new control system. At the moment, test results from an operating plant support the principal idea. Furthermore, the concept will be studied in the numerical laboratory where CFD simulation will be used to evaluate the technology and to determine the potential process improvements. The final improvement of electricity production has to be determined in the coming test period on a full scale installation, which is currently being planned.

Montenay Inc. operates a municipal solid waste (MSW) incinerator plant located in Burnaby, British Columbia. The facility operates three essentially identical boilers that were designed to generate slightly superheated steam at 248°C (478°F) and 3,140 kPa (455 psig). The plant was originally sized to supply process steam for export to an adjacent industrial plant. The fraction of steam that was exported decreased in recent years to about 35% of the production with the remainder being condensed. This has caused Montenay Inc. to initiate a power generation project with the goal to improve the plants energy efficiency and generate additional revenues by purchasing and operating a steam turbine generator. A superheater upgrade was required to raise the final steam temperature to a level that was suitable for use in an efficient steam turbine-generator. Jansen Combustion and Boiler Technologies Inc. (JANSEN) was contracted to perform the process and design engineering for the required boiler modifications. The project work included defining target process conditions, deriving conceptual design options, sizing the new superheater, deciding on material selection, preparing equipment specifications, and supplying the fabrication and installation drawings. The boiler modifications has been implemented in all three units in spring 2003. Power production will start in early summer 2003.