Incinerator ashes

In municipal waste incineration ash (also: domestic waste incineration slag HMV ash , MIBA) is, to recycled bottom ash (also: ash) generated by the incineration of household waste / municipal waste incineration sanlagen (MVA) is formed. This thermal treatment generates energy and reduces the amount of household waste by 75%.

In Germany, between 5 and 6 million tons of incineration ash are produced each year.

Recycled household waste incineration ash is one of the substitute building materials and is subject to the relevant structural and environmentally relevant regulations for the relevant areas of application.

Composition of bottom ash

The composition of bottom ash depends, among other things, on the composition of the waste, the type of combustion or the ash discharge. Based on the information from the LAGA , HMV grate ashes basically consist of grate shedding and grate diarrhea and are a mixture of:

Sintered combustion products (slag),
Scrap iron and other metals,
Glass and ceramic shards ,
other mineral ingredients as well
unburned residues (see LAGA M20, 2.2.1)

In order to determine which raw materials the bottom ash from a specific waste incineration plant contains, the companies commissioned with the processing test the composition on appropriate samples. This makes it possible to understand how well the processing works or how high the recovery and the efficiency of individual processes is.

Processing of the grate ash

Conventional processing

The processing of the bottom ash from household waste incineration is essentially carried out by classifying the mineral fraction and separating ferrous and non-ferrous metals (also: non-ferrous metals) as well as organic foreign components.

Air separators remove contaminants such as unburned items, including wood or paper . Ferrous metals are recovered at different sieve cuts using magnets (overbelt or drum magnets). Eddy current separators are used for the non-ferrous metals.

The process diagram (graphic 1) is an example of the production steps in a processing plant for incinerator ash. Basically, different aggregates are produced , depending on the later application.

After several months of storage, in which the corresponding chemical reactions take place, HMV ash meets the water management requirements for substitute building materials . Due to its structural properties, household waste incineration ash is a sustainable alternative to natural aggregates for the construction sector .

Increased recovery of non-ferrous metals

The metal recovery rate, especially of valuable non-ferrous metals, can be increased significantly by using additional technologies - especially in the area of non-ferrous fractions of 2 to 4 mm, which are often not recovered in a conventional plant. In general, bottom ash contains around 2% non-ferrous metals. 75 mass% of this is in the fraction range> 4 mm. The distribution of non-ferrous metals across the different fractions of bottom ash is shown in Figure 2.

Additional technologies are used to separate non-ferrous metals <4 mm from the ash. MERIT ^® technology is an example of this type of discharge . In a ballistic separation process, the disruptive mineral ash fine fraction 0-2 mm is separated from the fraction 0 to 4 mm by a directed air flow without removing the non-ferrous metals.

Improvement of the minerals through additional technologies

In order to be able to recycle domestic waste incineration ash in high quality, the material properties required for the corresponding application are improved. This includes increasing the quality of the structural properties as well as the environmentally relevant parameters. Optimal metal recovery is an important part of this improvement, as metals in the ash are undesirable for use in road construction or in concrete . Additional measures to increase the quality of the mineral ash content are also z. B. complex 3-D sieving techniques or hydromechanical cleaning - i.e. a washing system.

By using a washing system, the muddy portions of the ash are removed and the pollutant levels are reduced. Additional screening techniques improve the structural properties. This expands the range of areas of application for aggregates from incineration ash.

Main areas of application

Earthworks and road construction

The environmental compatibility of building materials made from mineral waste and intended to be recycled must be guaranteed. The Replacement Building Materials Ordinance for Germany as a whole is not yet in force. At the moment there are still state-specific regulations that must be observed. Examples of this are, for example, the Gem.RdErlasse of the federal state of North Rhine-Westphalia, as well as that of the LAGA M20 to which many federal states orient themselves.

What the regulations have in common is that a fundamental distinction is made between recycling inside and outside of water protection , mineral spring protection areas and floodplain areas and hydrogeologically sensitive areas. Within these areas, a more in-depth investigation of the geological and hydrogeological conditions is required, which is a very complex task for those involved in the construction. In comparison, the use outside of water protection, medicinal spring protection areas and floodplain areas and hydrogeologically sensitive areas is manageable, which enables a transparent and safe decision.

If you now take into account the environmental specifications as well as the structural engineering options, the safe and relevant areas of application in road and earthworks for Germany, as shown in Table 1.

concrete

In the Netherlands, treated incinerator ash is already being used as aggregate material in concrete , the basis being the relevant standards and corresponding national supplements (see Figure 3). In the Netherlands, HMV ash is produced in accordance with EU standards, the Dutch CUR aanbeveling 116 and BRL 2507. The CUR aanbeveling 116 stipulates for the Netherlands as follows:

Replacement of sand and gravel up to 20% by volume in reinforced concrete
Replacement of sand and gravel of up to 50% by volume in unreinforced concrete and concrete products
Use in strength classes from C 12/15 to C 30/37
Use in all exposure classes except XA2, XA3; for use in class XF, the proportion of HMV ash is limited to 20% by volume; the use of cements CEM III / B and CEM II / BV is mandatory for exposure classes XD and XS
Use permitted in all strength and exposure classes for unreinforced concrete and in concrete products
The conformity and suitability of is proven with CE and KOMO certificates.

Web links

Individual evidence

↑ ^a ^b Quality monitoring of mineral substances in road construction and earthworks. Ministerialblatt (MBl. NRW.) . Edition 2001, No. 78 , December 13, 2001, p. 1525–1534 (according to the Ministry of the Environment and Nature Conservation, Agriculture and Consumer Protection - VI A 3 - 32 - 40/45 - and the Ministry of Economy and Small Business, Energy and Transport IV - 3 - 953-26308 - IV - 8 - 1573-30052 - 9 October 2001).
↑ Requirements for quality monitoring and the use of household waste incineration ashes in road construction and earthworks. Ministerialblatt (MBl. NRW.) . Edition 2001, No. 77 , December 4, 2001, p. 1507–1524 (According to the Ministry of the Environment and Nature Conservation, Agriculture and Consumer Protection IV - 3 - 953-26308 - IV - 8 - 1573-30052 - and the Ministry of Economy and Small Business, Energy and Transport - VI A 3 - 32 - 40/45 - 9 October 2001).
↑ Requirements for the recycling of mineral residues / waste - technical rules . In: Länderarbeitsgemeinschaft Abfall (Ed.): Communication M20 (LAGA M20) . Status: November 6, 1997. Erich Schmidt Verlag, Neuburg 1998.
↑ Requirements for the recycling of mineral residues / waste - Technical rules - General part . In: Länderarbeitsgemeinschaft Abfall (Ed.): Communication M20 (LAGA M20) . Mainz November 2003 (revised November 6, 2003).

[:0-1] Quality monitoring of mineral substances in road construction and earthworks. Ministerialblatt (MBl. NRW.) . Edition 2001, No. 78 , December 13, 2001, p. 1525–1534 (according to the Ministry of the Environment and Nature Conservation, Agriculture and Consumer Protection - VI A 3 - 32 - 40/45 - and the Ministry of Economy and Small Business, Energy and Transport IV - 3 - 953-26308 - IV - 8 - 1573-30052 - 9 October 2001).

[2] Requirements for quality monitoring and the use of household waste incineration ashes in road construction and earthworks. Ministerialblatt (MBl. NRW.) . Edition 2001, No. 77 , December 4, 2001, p. 1507–1524 (According to the Ministry of the Environment and Nature Conservation, Agriculture and Consumer Protection IV - 3 - 953-26308 - IV - 8 - 1573-30052 - and the Ministry of Economy and Small Business, Energy and Transport - VI A 3 - 32 - 40/45 - 9 October 2001).

[3] Requirements for the recycling of mineral residues / waste - technical rules . In: Länderarbeitsgemeinschaft Abfall (Ed.): Communication M20 (LAGA M20) . Status: November 6, 1997. Erich Schmidt Verlag, Neuburg 1998.

[4] Requirements for the recycling of mineral residues / waste - Technical rules - General part . In: Länderarbeitsgemeinschaft Abfall (Ed.): Communication M20 (LAGA M20) . Mainz November 2003 (revised November 6, 2003).