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New Waste Furnace in Norway

by H Rosvold, AITOS, Norway

Introduction

After four years testing the prototype, the first full-scale AITOS energy recycling plant for waste materials (plastics, paper, wood) is now running. The plant's low emissions of SO2, HCl, CO and NO2, combined with high energy utilisation, satisfy the EU's proposed demands in the year 2000 by a wide margin.

The AITOS energy recycling plant has a thermal output of 6 MW. It is located at Ranheim, a residential and industrial area just outside Trondheim. The refuse-derived fuel is delivered by the municipal waste handling department and the Peterson Linerboard Ranheim papermill. All the recycled thermal energy is returned to the adjoining paper mill in the form of steam. This concept has several positive effects on the environment. The local conditions at Ranheim are in no way unique, and domestic and international markets have shown great interest in the new energy recycling technology.

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The AITOS plant at Ranheim

AITOS was founded in 1995 to develop and produce plants based on the new technology. The company received grants and support from the Norwegian Water Resources and Energy Administration, the Norwegian Ministry of the Environment, the Norwegian Industrial and District Development Fund and private investors. The oven process is patented and is ready to be released on the market.

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The Principle

The oven has two combustion chambers which lie one above the other (see figure). All waste fed into the lower, primary combustion chamber is continously monitored and checked for certain variables moisture and carbon content, among others. The control is automated and this data is recorded continously while the chamber is being filled with waste. A control unit summarises and co-ordinates the data with the temperature of the oven. As waste is fed into the lower chamber, the oven temperature is optimised in relation to the waste being fed in. Waste containing heavy metals will not result in large emissions to air because of the moderate temperature in the primary chamber.

Heavy metals are separated out along with the ashes and transferred into a separate container. The remainder of the waste is incinerated and all flue gases go into the upper, secondary chamber where the combustion is completed. Here, the thermal energy is transferred to a boiler which produces steam. After passing the boiler, the flue gas is at a temperature of 150 C. The cooled flue gas is cleansed of impurities by adding lime and active carbon. The flue gas is then led into a chalk collecting filter, and can then be released to the atmosphere.

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Schematic of the recycling plant

Clean & Efficient

By co-operation with local industry, in this case the papermill company Peterson Linerboard Ranheim and the municipal waste handling department, the establishment of this plant has resulted in a number of benefits:

  • about a 30% reduction in fuelling costs and CO2 emissions for Peterson Linerboard;
  • the papermill no longer has to pay a landfill charge on the reject delivered to the plant;
  • the service life of the local landfill is increased by 10 to 15 years;
  • methane gas emissions from the municipal landfill are reduced;
  • waste which otherwise would have been broken down at the landfill can now be energy-recycled.

Since it is possible to build profitable plants with output from 3 MW, the threshold for establishment is much lower than for larger, more conventional plants.

More conventional plants have often been reliant on long pipelines to achieve high energy utilisation. The AITOS plant can be built quickly, near the potential user of energy and the fuel can be taken either directly from the manufacturer of the fuel or from temporary storage. This minimises both loss of energy and pipeline investment costs. If the need for energy changes geographically, the plant can be disassembled and moved elsewhere.

The table shows the energy recycling plant's emission data, together with the Norwegian and EU proposed emission demands in the year 2000.

More and more built-up areas in Norway are experiencing problems related to waste handling. Amounts of waste are rising, landfills are being closed down and the responsibility for the handling of waste is decentralised. Many existing landfills also have problems with capacity.

The AITOS energy recycling plant does not take up much space, and this is a definite advantage. In Ranheim the plant is situated close to a residential area, and the size of the plant means that it does not disfigure the surroundings. Low noise levels and proven low emissions have meant that the local residents have not objected to the establishment of the plant.

Components

Expected EU target

(mg/Nm3)

Expected Norwegian target
(mg/Nm3)

AITOS plant - measured emissions
(mg/Nm3)

SO2

50

10

0-2

HCI

10

10

0.2-0.4

CO

50

50

1-3

NO2

200

80

60-100

Dust/particles

10

10

0-2

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Table 1: The plant's emissions data, Norwegian regulations and the Eu's proposed emissions demands in the year 2000

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Economics

To establish the plant at Ranheim has cost roughly NOK 50 million (where NOK is the Norwegian krone). How profitable the plant becomes will, of course, depend on the alternative energy prices:
ie electricity and oil. Based on realistic price prognoses for competitive sources of energy the plant is profitable. The value of the recycled energy is around NOK 10,000 per installed kW.

Operating the plant continuously will produce 48 GWh annually. This means a cost of about NOK 1 per produced kWh. The plant requires a total of 17,000 tonnes of
refuse-derived fuel to produce this output.

When the plant in Ranheim was built, the Norwegian Department of the Environment demanded that there would be 100% energy recycling. This requirement has been fulfilled.

For more information contact the CADDET Norwegian National Team in Rud.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to
Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.