CRP Processing Technologies & Equipment 1 — Questions and Answers
Question 1: What is the primary function of an eddy current separator in a MRF?
- To repel and separate non-ferrous metals (primarily aluminum) from the conveyor stream using a rapidly alternating magnetic field (Correct answer)
- To separate ferrous metals using a permanent magnet
- To sort plastics by resin type using electrical conductivity
- To remove glass fines from mixed recyclables
Correct answer: To repel and separate non-ferrous metals (primarily aluminum) from the conveyor stream using a rapidly alternating magnetic field
An eddy current separator creates a rapidly alternating magnetic field that induces repulsion in non-ferrous metals like aluminum, ejecting them away from non-metallic materials.
Question 2: Which MRF equipment uses near-infrared (NIR) technology to identify and sort materials?
- Optical sorter (Correct answer)
- Trommel screen
- Ballistic separator
- Negative-sort air classifier
Correct answer: Optical sorter
Optical sorters use NIR spectroscopy to identify polymer resin types and paper grades by their unique light absorption signatures, then use air jets to divert target materials.
Question 3: What is a 'trommel screen' used for at the front end of a MRF sorting line?
- Screening out small fines, broken glass, and contaminants that would interfere with downstream sorting equipment (Correct answer)
- Separating plastics from paper using rotation speed
- Baling sorted commodity streams for shipment
- Detecting ferrous metals before the magnetic separator
Correct answer: Screening out small fines, broken glass, and contaminants that would interfere with downstream sorting equipment
Trommel screens rotate a drum with holes that allow small materials (fines, broken glass, dirt) to fall through, cleaning the stream before it reaches optical sorters and other sensitive equipment.
Question 4: What is the purpose of a 'ballistic separator' in a single-stream MRF?
- To separate 2D flat materials (paper/cardboard) from 3D containers using spinning paddles that throw lighter flat items up and roll heavier containers down (Correct answer)
- To detect and remove metallic contaminants using ballistic impact sensors
- To compact materials at high speed before baling
- To screen out oversized items at the receiving tipping floor
Correct answer: To separate 2D flat materials (paper/cardboard) from 3D containers using spinning paddles that throw lighter flat items up and roll heavier containers down
Ballistic separators use rotating elliptical paddles that propel flat 2D materials (like paper) up a screen while 3D containers roll down and off, separating these two major stream components.
Question 5: Which MRF processing problem is most directly caused by 'tanglers' such as plastic bags, hoses, and wire?
- Wrapping around rotating equipment shafts and screens, causing jams and requiring costly manual cleaning downtime (Correct answer)
- Contaminating paper bales and reducing their market value
- Blocking NIR sensors and reducing optical sorter accuracy
- Increasing the weight of residue sent to disposal
Correct answer: Wrapping around rotating equipment shafts and screens, causing jams and requiring costly manual cleaning downtime
Flexible film and wire tanglers wrap around the shafts and paddles of screens, balers, and conveyors, causing frequent jams that require workers to shut down and manually cut material free.
Question 6: What is the 'residue rate' at a MRF, and why is it a key performance indicator?
- The percentage of incoming material that cannot be recycled and is sent to disposal, indicating overall sorting efficiency (Correct answer)
- The percentage of sorted bales rejected by end-markets due to contamination
- The proportion of recycling program revenue lost to market price drops
- The fraction of truck loads that arrive over the weight limit
Correct answer: The percentage of incoming material that cannot be recycled and is sent to disposal, indicating overall sorting efficiency
Residue rate measures what percent of total incoming material ends up as landfill-bound waste after sorting, directly reflecting the MRF's efficiency and the cleanliness of the incoming stream.
CRP Processing Technologies & Equipment 1
What is the primary function of an eddy current separator in a MRF?