An advanced thermal recycling system (or an ATR system) is an advancement of existing energy-from-waste (EfW) technology. An ATR system transforms municipal solid waste (MSW) into electricity or steam for district heating or industrial customers. The combustion bottom ash and the combustion fly ash, along with the air pollution control system fly ash, are treated to produce products that can be beneficially reused. Specifically, ATR systems consist of the following:
Solid waste combustion, boiler and combustion control system, energy recovery and air pollution control equipment; Combustion bottom ash and fly ash treatment systems that produce commercially reusable products and An optional pre-processing system to recover recyclable materials contained in the MSW delivered to the facility before the MSW enters the thermal processing area of the facility.
Application in Germany
As a result of the growing need to manage waste throughout greater Hamburg, the first commercially operating ATR facility – the Müllverwertung Rugenberger Damm (MVR) in Hamburg, Germany – was commissioned in 1999. The German Green Party has endorsed the specific features of the MVR facility in its "Concept 2020" initiative to cease all landfilling of waste by 2020 as an essential part of an integrated waste management system achieving the highest standards in the EfW industry. No landfilling of unprocessed waste has been allowed in Germany since 2005.
Description
Quality control occurs at the inception of the process. Overhead refuse cranes, which hold approximately 5 tons [?] each, mix the waste in the bunker to create a homogeneous mixture. This is important for the bottom ash byproduct's good combustion and low carbon content. These cranes then deliver the mixed waste into the feeding hopper, which leads down onto highly engineered stoker grates, controlling the rate at which rubbish travels through the boiler. The intense heat ignites the trash as it moves along the forward feeding grates until only the byproduct bottom ash remains at the end of the grate. Each combustion line feeds a boiler that operates above 1,560 °F (850 °C) for 2 seconds. The temperature in the combustion zone is measured through acoustic monitoring.
Careful monitoring of the combustion process guarantees the complete burning of the combustible material in an environmentally safe manner. A highly sophisticated computer controls the temperature, the grate speed, the amount of air used, and all other aspects of the process that enable complete combustion and minimization of emissions.
Maintaining the furnace's high temperature is essential to rid the waste and the resulting combustion gases of complex organic compounds such as dioxin/furans. To prevent the reformulation of pollutants, fly ash is separated from the flue gas downstream of the superheaters to reduce the fly ash content, which could act as a catalyst in the critical reformulation temperature range of 600 to 400 °F (316 to 204 °C). At the exit of the boiler, the flue gas has been cooled down to a level of 340 °F (171 °C).
We are converting waste heat to electricity. As the waste is combusted, heat is released in the boiler. This heat produces high-pressure, high-temperature, superheated steam, which generates electrical energy when passed through a turbine generator. The electricity is fed into the public power grid or sold directly to a customer. The steam can also be exported now for district heating or industrial processes.
Air pollution control. Each unit has an independent air pollution control system. Flue gas cleaning begins in the boiler, where nitrogen oxides are reduced by injecting ammonia water into the combustion chamber. Lightly loaded absorbents (activated carbon from the second bag house) are injected into the flue gas downstream of the first bag house to separate any contaminants that have reformed (such as organic compounds like dioxins and furans), any condensed heavy metals, salts, and other gaseous pollutants, as well as residue fly ash.