text: Overhead refuse cranes are used to hold approximately 5 tons of garbage each. The waste is then mixed in the bunker to create a homogeneous mixture to ensure that the bottom ash byproduct has good combustion and low carbon content. These cranes then deliver the mixed waste into the feeding hopper, which leads down onto stoker grates. These grates control the rate at which the waste travels through the boiler. The 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 two seconds. The temperature in the combustion zone is measured through acoustic monitoring. A 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 dioxins and 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 . At the exit of the boiler, the flue gas is cooled down to a level of .
  As the waste is combusted, heat is released in the boiler. This heat produces high-pressure, high-temperature 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 directly for use in district heating or industrial processes.
  Each unit has an independent air pollution control system. Flue gas cleaning begins in the boiler, where oxides of nitrogen 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), any condensed heavy metals, salts and other gaseous contaminants, as well as residue fly ash.
  The first baghouse makes it possible to produce reusable by-products such as hydrochloric acid and gypsum from the consecutive air pollution control process steps. Acid gases are removed from the flue gases by passing through a two-stage scrubber to remove acid components, especially halogen compounds such as hydrochloric acid and hydrofluoric acid. A counter-flow neutral scrubber follows, using a lime slurry to remove sulphur oxides. The pollutant gases are either dissolved in water droplets (acids) or bound as calcium salts and thereby removed from the flue gas. A second baghouse acts as a polishing filter to capture any remaining aerosols, organic compounds and heavy metals, which thereby are reduced to levels usually below detection.
  Following combustion, the material left consists of the non-combustible components of the waste and the inert materials produced during combustion. This is known as bottom ash. The bottom ash is washed to eliminate soluble salts. Iron scrap and non-ferrous metals such as aluminium, copper and brass are separated and sold in secondary metals markets. The bottom ash is then screened, crushed and sold for use as a construction material.
  Gypsum is created when the oxides of sulphur (SO2 and SO3) are separated by the single stage scrubber. It is purified, then sold to the construction industry.
  The acid scrubbing process in the flue gas treatment system also produces a raw hydrochloric acid (HCl) with a concentration of 10%-12%. The acid is distilled (rectified) to yield commercial-grade (30% concentration) hydrochloric acid.
  Fly ash, separated in the boiler and baghouses and constituting up to 5% by weight of the combusted MSW, is treated to recover metals and minerals for reuse, resulting in an overall ATR process landfill diversion rate of approximately 98.5%.