Background and Planning
The decision to construct this power plant was made in May 2005; and since summer 2007, the Combined Heat and Power Plant has been supplying the company Pfanni, manufacturer of potato-based instant products, with process steam and electrical power by means of a co-generation system.
By utilising around 95 000 tonnes of refuse-derived fuel, the plant supplies 200 000 tonnes of steam and more than 12 GWh electricity to Pfanni each year. This means that all of the factory’s electricity demand is met and excess electricity is fed into the national grid. This type of energy utilisation not only makes economic sense, but also provides a considerable contribution towards environmental conservation: by using this concept, CO2 emissions for the Pfanni manufacturing process have been reduced by 10 000 t/a.
Combined Heat and Power Plant Process
Refuse-derived fuel is unloaded and stored in a silo from where it is transported by crane into the furnace for combustion in a moving grate incinerator. The combustion process generates steam, which is then used in an extraction-turbine to produce power. The extraction-turbine also provides process heat that is used for the Pfanni-plant and its processes.
The process heat is fed into steam-to-steam heat exchangers, ensuring that the steam systems of the CHP plant and the Pfanni plant are kept separate. The pure steam generated for Pfanni is used to carry out processes including peeling, boiling, cooking and drying.
Slag, fly ash and flue gases arise as waste products of the combustion process and need to be dealt with. Fly ash and flue gas are treated within a three-stage flue gas cleaning system: including a semi-wet absorption process, a roller-ball-reactor and a filter unit. During the first purification stage, the flue gas is treated in a spray-dryer using lime as an adsorbent. In the second treatment stage, activated carbon and lime are used to scrub the already treated flue gas stream. Flue gas cleaning efficiency is further improved by the use of a dust recycling loop, leading from the bag filter back to the flue gas duct behind the spray dryer unit. Finally, a bag filter is used as the third stage before the cleaned flue gas is released to the atmosphere. Annually, approximately 5 600 tonnes of filter residue are produced and 20 000 tonnes of slag arise at the bottom of the incinerator.
General Manager of Nehlsen Heizkraftwerk GmbH & Co. KG
Karl-Heinz Plepla, Phone +49 39954 246211