Shredding of RDF, TDF and SRF

July 19, 2021 News

Energy recovery via RDF shredder machine in a power plant producing from refuse-derived fuels is prevalent in 1990. Tons of waste dormant in landfills are not reusable or recyclable but can be a great source of fuel because they contain a high caloric value. Similar to RDF shredder machine, TDF shredding and SRF shredding use two shaft shredders to downsize the waste. In the end, they are all convertible to energy in an alternative fuel production plant.

Understand the Difference of MSW/RDF/TDF/SRF

MSW: Abbreviation of municipal solid waste, commonly collected from post-consumer and commercial waste.
RDF: Abbreviation of refuse-derived fuel, which is similar to SRF but more generic.
TDF: Abbreviation of tire-derived fuel. It mainly consists of end-of-life tires.
SRF: Solid recovered fuel (SRF) is a high-quality alternative to fossil fuel and is produced from mainly commercial waste including paper, woods, textiles, and plastics.

Fuel Type	Lower heating value (kJ/kg)	LHV (Kcal/kg)	Max Moisture (%)
MSW	5,000 – 10,000	1,200 – 2,400	60%
RDF from MSW/Old landfill	6,600 – 10,000	1,600 – 2,600	55
RDF type 2 & 3	6,600 – 12,500	1,600 – 3,000	50
RDF from Industrial Waste	12,000 – 20,900	3,000 – 5,000	40
SRF	16,700 – 25,000	4,000 – 6,000	25

From the table, SRF features the highest heating value and MSW scores the lowest, due to the moisture content. RDF from MSW and RDF type 2 and 3 are similar in heating value. RDF from industrial waste is the second highest among all.

As a conclusion, RDF (refused-derived fuel) and SRF (solid recovered fuel) are the products from MSW (municipal solid waste). Industrial waste is an excellent ingredient for making RDF.

A massive primary shredder

Treatment of MSW

It is not advised to burn MSW, since it often contains a high level of moisture which hinders its efficiency in a kiln and boiler. A series of mechanical treatment is essential to produce high quality RDF. The major 4 factors are water content, toxins, size, and caloric value.

A preshredder is needed to debale and scramble to the waste. Next, the stream materials go to a series of shredding machines to achieve a proper size. Why size matters? Because a kiln can burn smaller particles at a high efficiency.

RDF Classification	Description
RDF 1: MSW	Municipal solid waste which has been removed the non-combustible material but remains physical properties as a discarded form.
RDF 2: Coarse RDF	Remove the non-combustible material, then MSW is processed by shredding or grinding to a coarse size.
RDF 3: Fluff RDF	Remove the non-combustible material, then MSW processed to a particle size such that 95%wt. passed through a 2-inch sieving.
RDF 4: Dust RDF	Only combustible material that is processed into a powdered form.
RDF 5: Densified RDF	Combustible material that is compressed its density into pellets, cubettes, briquettes. The average density is minimum of around 600 kg/m3.
SRF	Considered to be a more refined fuel with a low moisture content and an energy content around two-thirds that of coal. It can also be used in cement kilns and other industrial processes.

TDF shredder machine and SRF shredder machine are the first steps to downsize the waste, before making pellets. Often, the size reduction process takes 2 steps shredding: primary shredding (to get 60-100mm) and secondary shredding (to get below 40mm).

TDF Shredder machine

Wiscon RDF shredder machine bring you 9 advantages:

1. Integred rotor: ensure the cutting clearance between the moving knife and the fixed knife. Knife gap adjustment structure, can quickly and easily adjust the cutting gap between the movable knife and the fixed knife, to ensure the best cutting state, to ensure the crushing effect and save energy.
2. hydraulic driven service door: can be convenient and fast manual replacement of screen, through the replacement of different mesh screen can be controlled by different size of the discharge material.
3. Bearing has four seals, adapting to the complex working conditions.
4. Automatic lubrication system to ensure bearing lubrication and bearing life.
5. Built-in hydraulic swing arm: fast speed, high efficiency, intelligent variable speed, variable pressure, and spindle load linkage control, to avoid spindle jam.
6. Long-life rotary knife: can be used four times to change the surface, saving the cost of replacing knives.
7. Excellent blade material: a variety of heat treatment to ensure wear resistance and good impact toughness.
8. Shock absorption design: slow down the reducer and the whole machine vibration and impact.
9. Multiple self-protection functions such as motor temperature monitoring, motor bearing temperature monitoring, spindle bearing temperature monitoring, etc. to adapt to the harsh working conditions.

Another point to bear is the dust collection of in-house shredding. Bad circulation of air with too much dust can induce an explosion and air pollution.

In short, the treatment of refined waste involves Sorting – Primary shredding – Metal removal – Air Swifter – Secondary shredding – Briquetting.