Refuse-derived fuel

Alternative fuels (RDF ) or secondary fuels are fuels derived from waste. With increasing economic and ecological importance of sustainability, their share of the commodity economy continues to grow.

This can both be solid, liquid or gaseous wastes that are treated in different treatment depth for the purposes in view.

The waste used for the production of alternative fuel can come from domestic, industrial or commercial. The treatment depth is dependent on the use of waste fuel and of different quality requirements of the thermal process. To date, neither the treatment nor the product replacement fuel are defined by law.

The processing steps of the high calorific fractions from industrial waste and household waste includes the preliminary sorting, the coarse crushing, the sieve classification, the air classification and the ferrous and non- ferrous separation. Additional processing steps for the production of secondary fuels are sensory sorting and drying processes. Significant fuel parameters are in addition to the emission-related parameters, the calorific value, ignition residue, chlorine content and the ash content. Be recovered EBS together with conventional fuels in the so-called co-incineration, especially in cement, lime, lignite and for the most part in industrial power plants ( calorific fraction ) as well as in waste incinerators or as the sole fuel in RDF power plants. The expediency of the use of alternative fuels should, in addition to sustainable use, are assessed by the comparison of the energy efficiency of energy and material recycling.

Distinction between

The term substitute fuel or alternative fuels include all non-fossil fuels. You can as municipal waste, are made from selectively obtained, production-specific (commercial ) waste as well as from non-specific mixtures of wastes.

This includes both liquid, paste as well as solid waste and biomass, which are processed for energy recovery / incineration, which are subjected to final and heating value used for energy recovery. These are, for example, calorific fractions from municipal waste, commercial waste, solvents, Ältöl, whole or shredded used tires and dried sewage sludge, rice husk, straw, or even animal meal.

As a " calorific fraction " of the separated from the waste mixture fraction is called, which then has a higher calorific value than the initial raw garbage. It is usually with a lower degree of conditioning ( local) won and transferred to private conditioners for postprocessing. This high-calorie fraction can also be recycled without further treatment in so-called substitute fuel power plants, the steam or gain power from it.

History and current status

Since about 40 years of waste mixtures of different origin by mechanical methods fuels produced. The term developed around 1980 " BRAM " (acronym for " fuel from waste " ) describes the first steps of a fuel production from undefined mixed waste, its origin and composition were completely unknown. However, the use of waste fuels at that time was less successful than it is today. The term BRAM is now no longer in use, but it is used in a report to the European Commission in 2003 as a German term for Refuse Derived Fuel ( RDF).

Today, the concepts of replacement, substitute or secondary fuel are common. With the introduction of these terms, the introduction of minimum quality requirements and a regulated quality assurance is connected. There were established quality communities like the Bundesgütegemeinschaft fuels eV ( BGS ). In the past, new machines techniques for crushing and sorting of waste have been developed. The quality control and quality assurance are made possible by advanced sorting techniques such as optimized eddy current separator for the separation of non-ferrous metals or new sensor-based sorting techniques.

At European level, there are efforts to standardize the quality requirements. To date, however, neither the treatment nor the product replacement fuel are defined by law. According to the EU Waste Framework Directive ( 2008/98/EC ), the energy recovery or the processing of waste into fuels no recycling represents the reuse and recycling has to EU Waste Framework Directive ( 2008/98/EC ) has priority over energy recovery, if it is the best option for environmental aspects. Only if the energy efficiency (energy output / energy input) is over 60 %, with newer systems (after December 31, 2008 approved ) over 65 %, is from incineration of waste according to 2008/98/EC, energy utilization, otherwise to a waste disposal.

It has not yet been clearly defined at EU level, at which stage substances not as waste, but as products are. A possible CEN standardization of alternative fuels currently would not change the status of the waste material. With a revision of the EU Waste Framework Directive, EU-wide criteria could be developed in the future, compliance with which the EBS material would misdeclared from a waste to a product.

Treatment intensity and quality requirements

The treatment intensity of the use of waste fuel and of different quality requirements of customers, specify an unambiguous specification of the abzunehmenden product dependent. Significant fuel parameters arise from the quality of the land used for alternative fuel production raw waste.

These are calorific value, ignition residue and chlorine content. Depending on the immissionsrechtlichen permits the system in which the fuel is recycled, minimum and maximum values ​​for heavy metal concentrations are defined and put different demands on the degree of Metallentfrachtung.

Also different demands are placed on the grain size: important here lumpiness, so limiting the piece size and bulk density. The type of storage and transport are dependent on the exploitation manner of the replacement fuel.

The assurance and testing the quality of a replacement fuel have an impact on the selection of the waste stream and the used raw waste and the process management of its preparation.

Treatment processes

The higher the quality required by the customers of the waste fuel, the more selective waste sorting used must be made. Already at the entrance control a minimum quality of raw waste must be ensured in order to minimize contamination and to obtain a high fuel efficiency.

The preparation of a waste mixture begins with the pre-sorting or Störstoffauslese. This is followed by coarse grinding and then the screen classification and the iron magnetic separation of magnetizable metals. To separate the high calorific fraction air classifier are used. This plastic films and paper are enriched, and collected surface and airworthy components in lightweight power.

In order to produce quality-assured substitute fuels, the actual secondary fuels, further treatment is necessary. For use in cement plants as a fine preparation is performed. It will be held sensory sorting by near-infrared spectroscopy ( NIR) and image recognition systems. Again comes a metal sorting to the application so that non-ferrous metals are deposited. By a sensor-based sorting chlorine carriers are removed. A downstream air separation away more impurities. By drying steps storage stability and calorific value increased.

Classification and standardization

In Germany there is the classification of secondary fuel qualities Label Quality Association for fuels and recycled wood eV ( BGS ). It is about the quality mark RAL- GZ 724 for secondary fuels from high-calorific waste, the quality mark RAL -GZ 727 for the determination of biogenic content in secondary fuels in accordance with RAL -GZ 724 and other solid waste fuels, and RAL -GZ 428 for recycling wood. The criteria for the quality of secondary fuels include, for example, the heating value, water - chlorine and sulfur contents.

In 2002, the standardization committee CEN TC 343 Solid Recovered Fuels (SRF ) was established. The standards should be treated first as a technical specification. Only then they should apply after a validation process as a European standard. Currently, there are many draft standards for the classification of Solid Recovered Fuels, ie fixed substitute fuels in the approval process. Just a few points, such as a provision to the density of pellets and briquettes, have already ratified. The individual standards due to come into force between 2010 and 2012.

In a report of the European Recovered Fuel Organisation ( 2005 ) Principles for Classification of Solid Recovered Fuels ( SRF) are summarized. The key features for the classification of the calorific value of the chlorine and mercury content were determined. The calorific value represents the economic value, chlorine, the technological limitations and the environmental mercury burden or emissions. After these three parameters, the SRF will be divided into 5 grades. After a resolution in 2004, the lowest grade shall comply with limits to be classified as SRF.

Recovery and consumer of alternative fuels

Be recovered EBS together with conventional fuels in the so-called co-incineration, especially in cement, lime and lignite power plants, mostly in industrial power plants ( calorific fraction ) as well as in waste incinerators or as the sole fuel in RDF power plants. EBS -use installations must at least meet the requirements of EU Directive correspond ( 2000/76/EC ) for incineration and co-incineration of waste. In Germany is the 17 th BImSchV for waste incineration and co-incineration.

For example, the material flows from selected specifically treated secondary fuels are used mainly in the cement plants due to the higher quality requirements by sophisticated processing technologies. With energy levels of approximately 15 % and above, the raw waste are as old tires, plastics, industrial and commercial waste as well as meat and bone meal and animal fats to substitute fuel reprocessing for use in the cement industry. With lower energy shares, inter alia, also waste oil, solvents, and municipal waste is used for the treatment.

Energy efficiency

In contrast to the thermal treatment is the recovery of energy from waste, the use of the waste, that is, the use of abfallbürtigen energy content more prominent. Plants using only waste burly fuel but must, unlike mitverbrennende systems, so that is done (usually secondary fuel ), have similar flue gas cleaning and elimination of the pollution potential. The energy recovery from waste can be assessed in terms of energy efficiency. With regard to the discussion on the appropriateness of the use of EBS comparison of the energy efficiency of energy and material recycling is relevant.

Both the chemical group with paper, paperboard, cardboard (PPK ) as well as some plastics recycling is usually a higher energy efficiency, as in the energetic. Thus, the accumulated energy consumption for the production of copy paper from pulp about 35 MJ / kg. With a cumulative energy demand for the production of copy paper from waste paper of about 15 MJ 20 MJ / kg can be saved in the recycling. In energy recovery, however, only about 10 MJ / kg can be saved at a high fuel efficiency of 76%.

In the production of polyethene polymer of secondary materials can be saved compared with the use of primary materials about 53 MJ / kg. The energy saving than EBS is, however, also assuming a high fuel utilization ratio only 32.7 MJ / kg. The energy recovery of waste paper and waste plastic is however useful if these are not suitable, for example due to contamination or Kleinteiligkeit for recycling. In terms of bio-waste has the highest energy efficiency is achieved when organic waste recycled as compost, while the straw, which can be replaced on arable land by the compost is used for energy recovery.