Energy from Waste

Energy from Waste – clean and safe

Waste to Energy or Energy from Waste is the thermal recovery of waste for the generation of electric or thermal energy. Steinmüller Babcock Environment played a decisive role in developing and shaping this technology. We enable the use of the energy contained in waste and thus contribute significantly to reducing the impact on the environment. By using waste, climate-damaging fossil fuels such as natural gas, crude oil and coal are replaced cleanly. In addition, the waste output volume is reduced drastically, in modern incineration plants by approx. 90%. Depending on the composition of the waste, and depending on the degree of combustion, up to 30% energy efficiency can be reached in generating electric energy. The combined heat and power concept can be used to increase efficiency. In such cases, for example, thermal energy is extracted from the district heating network, and the overall efficiency of the plant can be increased to more than 80%. 

Energy from Waste solves several problems at once:

  • Reduction in waste by 90%  
  • Generation of electric and thermal energy from the energy contained in waste
  • Replacement of fossil fuels, thus reduction in CO2 emissions
  • Treatment of the waste, so that the residual slag can be disposed of in landfills without hazard
  • Recovery of materials contained in waste by means of slag treatment

The waste incineration process in a typical EfW plant 

The delivered waste is stored in a waste bunker (1) and homogenised by the waste crane. The crane then transports the mixed waste to the feeding hopper (2). From here the waste is sent to the feeder (3), which feeds the material into the incineration grate in accordance with the requirements of the combustion control.

The waste burns on the grate (4), which consists of rows of adjacent grate bars. The grate bars overlap, arranged one behind the other. Every second row moves forwards and backwards alternately, which moves the waste and later also the slag to the end of the grate. There, the slag is thrown into the deslagger (5).

The deslagger (5) is partially filled with water, creating an air lock between the atmosphere and combustion. The slag falling from the grate cools in the water and is extracted by the ram-type slag extractor to a conveyor, which transports the slag to the slag bunker (6).

By means of a video camera, the plant operator observes the “waste fire” (7). The air required for combustion (primary air) is fed in a regulated manner from below through the grate. In order to achieve a good burn-out of the flue gases, additional air (secondary air) is injected above the firing system. Then, in the boiler, the hot flue gases are cooled to the desired temperature at boiler outlet.

The heat of the flue gases is used to heat feed water in the heating surfaces of the economiser (10). This water is added to the drum (11), which feeds the evaporator that is operated in natural circulation. In the walls of the radiation passes (evaporator) (8), a water-steam mixture occurs, which is separated in the drum (11) into water and steam. The steam is then fed to the superheater heating surfaces (9). Once heated to the intended temperature, the steam goes to the turbine (12).

In the turbine (12), the superheated steam expands and then condenses, for example in an air-cooled condenser. The turbine and the coupled generator use the energy released during expansion to generate electricity, which is fed into the public network. The condensed water is fed into the feed water container (13) and pumped from there back to the boiler. Alternatively, some of the energy can also be fed into a local or district heating network, or used as process steam (combined heat and power).

In the spray absorber (14), water and milk of lime are injected into the flue gas coming from the boiler. The evaporation of the water leads to cooling. This allows optimal reaction conditions for adsorption of acidic pollutant gases in particular. After the flue gas cooling, recirculates (reaction products separated in the fabric filter), fresh dry absorbent and hearth furnace coke are injected into the entrained flow reactor (15).

The harmful substances that are still contained in the flue gas react chemically, or are absorbed in the subsequent fabric filter (16) by the solid materials discharged there on the filter hoses, and then removed from the flue gas together with the fly ash. Many thousands of filter hoses act as a filter medium, ensuring that the filtered flue gas meets all statutory requirements safely. Most of the reaction products are recirculated to the duct upstream the fabric filter. The recirculates can be moistened in order to optimise the efficiency of the input material. A partial flow is continuously discharged and conveyed to silos (17) for disposal.

The induced draft fan (18) generates the necessary negative pressure in the firing system and draws the flue gases through the boiler and the flue gas cleaning. The negative pressure prevents any pollutants from escaping outside. 

The cleaned flue gases are emitted into the atmosphere via the stack (19). To increase the degree of effectiveness even further, waste incineration plants often use condensation heat exchangers. This means that the clean, pure water vapour is visible as a white, dissipating plume at the output of the stack – a sign of optimal energy use.

Steinmüller Babcock Environment GmbH

Fabrikstraße 1

D-51643 Gummersbach, Germany

+49 (0) 2261 85 - 0

+49 (0) 2261 85 - 2999