Municipal Solid Waste (MSW) Pre Treatment
The solid waste mechanical sorting and selected - MSW production plants - can make part of an integrated system for the disposal of MSW. The company produce:
- MSW to be fed to WtE plant;
- An organic stabilized fraction, to be used for soil reclamation
- Ferrous materials, to be inserted in the secondary raw material circuit;
- Solid rejects, to be disposed of in landfills.
The waste mechanical sorting section consists of more lines operating in parallel. Each of them includes the following stages:
- Preliminary shredding: Each line provides, as a first treatment, MSW size reduction and bag tearing through a low speed rotary shredding machine.
- Primary screening: After shredding, waste dimensional classification is carried out in a primary rotary drum sieve, with 120 mm screen hole size. In the primary screening section the material is separated into two streams: primary tailing and primary fine fraction.
- Primary tailing treatment: The primary tailing, consisting mainly of non−putrescible materials, having quite high heat value, is discharged by gravity from the terminal end of the primary screen.
- Secondary screening: The primary fine fraction undergoes a secondary screening in a rotary drum sieve, identical to the primary one, but with a smaller screen hole size (60 mm). In the secondary screening section, the primary fine fraction is separated into two streams: secondary tailing and secondary fine fraction.
- Ballistic classification of the secondary tailing: The secondary tailing, consisting of materials sized between 60 and 120 mm, includes a remarkable quantity of materials having high heat value. However, it is not suitable to be sent to combustion as it is, since it still contains organic materials and solid aggregates. It therefore undergoes further processing, for separating those materials. A ballistic classifier is provided for this purpose.
- Aerobic biomass stabilization: The secondary fine fraction and the screened material out of the ballistic classifier are stored in windrows in a covered yard. The residence time there is almost 28 days.
- Selected MSW packing section: Selected MSW, consisting of the primary tailings and the light fraction separated in the ballistic clarifier, is conveyed to the packing section, where it can be directly loaded on trucks by means of a loading press, or it can be packed in 1−1,2 m3 bales, wrapped into polyethylene sheet for long−period storage.