Turning raw municipal waste into refuse-derived fuel (RDF) takes a sequence of machines, each doing one job: meter the waste, open the bags, sort out inerts, screen out soil, shred to a uniform size and dry. This guide goes through a four-line front end proposed for a 1,200 tonne-per-day facility in Thailand and explains why each machine is there.
The challenge: wet, mixed waste
The waste analysis supplied for the project showed a feed that is difficult for fuel use:
- Food waste about 49%, plastic about 28%, wood and leaves about 7%, paper about 5%, leather about 6%, fabric about 2.5%.
- Non-combustibles such as glass, metal, concrete and hazardous items each under 2%.
- Moisture content of about 57% as received.
The supplier reserved the right to change design and price if actual waste differed significantly from this analysis. That is a sensible warning: front-end sizing depends on a waste audit.
The machines, in order
| Stage | Duty | Why |
|---|---|---|
| Drum feeder | 4 units, 15 t/h each | Meters waste evenly into the line |
| Bag opener | 4 units, 15 t/h, 98% opening success | Releases material trapped in plastic bags |
| Weighing scale | 15 t/h | Records waste processed |
| Hand sorting line | 4 lines | Picks out metal, glass and large items that damage equipment |
| Overhead magnet | Ferrite or neodymium; about 200 kg/h removed | Takes remaining ferrous metal for recycling |
| Trommel | 15 t/h, removes particles over 60 mm | Removes soil and fines, raising calorific value and cutting moisture |
| Shredder | 4 units, 10 t/h, to 50 mm | Gives uniform fuel size |
| Superheated steam dryer | 7.5 t/h per line | Reduces moisture to about 20% |
Why four lines at 15 t/h
1,200 tonnes a day is 50 t/h averaged over 24 hours. Four lines of 15 t/h give 60 t/h, a margin that allows for equipment running at about 80% availability. The shredders and dryers are sized to the lower flows that reach them after rejects are removed.
Where rejects go
Rejected material from the trommel is returned to the landfill from which the waste was excavated, since this was a landfill-mining project. Useful waste goes to storage.
Drying
The dryer is a rotating drum with direct-contact superheated steam from a boiler. Although incoming waste is 57% moisture, the material reaching the dryer is expected to be drier, because the trommel removes wet fines.
Control and safety
A central SCADA system in the control room runs the line, with emergency stops at each machine. Extra SCADA options were priced separately.
What to consider for your own project
- Do the waste audit. Moisture and plastic content decide dryer size and fuel value.
- Design for availability. Four parallel lines let you keep running when one stops.
- Protect the shredder. Manual sorting and magnets remove what would damage it.
- Plan rejects. Trommel and sorting rejects need a disposal route.
- Check the downstream need. RDF specification depends on the thermal plant that will use it.
For UK context see government waste statistics and the Environment Agency’s permitting guidance for waste treatment.
FAQ
What is RDF?
Refuse-derived fuel: processed waste with the non-combustible and wet fractions reduced, used as fuel.
Why dry to 20% moisture?
Water absorbs heat. Lower moisture raises the net energy available downstream.
Why hand sorting?
Machines miss large or hard objects that could damage downstream equipment.