Moisture is almost always an unwelcome contaminant in shipments of recyclables, and at least one equipment company is considering how removing moisture from auto shredder residue (ASR) may add value to that byproduct in later stages.
In a session of the Institute of Scrap Recycling Industries Inc. (ISRI) 2015 Convention & Exposition, held in April in Vancouver, British Columbia, Dick Reeves and Ron Fruit of General Kinematics Inc. (GK), Crystal Lake, Illinois, described their findings when it comes to seeking the optimal moisture content for ASR.
Reeves said GK is still working with auto shredding plant operators to answer the question, “Why dry ASR?” Even if no additional metals or plastic recovery stages are taken, Reeves said one of the answers is to reduce the weight of the ASR and bring down the hauling costs to take the byproduct to its disposal site.
When it comes to conveying, screening and separating ASR to recover more metal or potentially separate plastics by resin, Reeves said GK is undertaking trials to determine how a drier ASR stream may be easier to work with.
In the drying process, Reeves said there are “temperature limitations,” as some plastics can begin to melt at 500 degrees Fahrenheit. ASR that “bone dry” may not be desirable, as it can be dusty and potentially flammable. GK has found a range of 8-to-15-percent moisture represents “a happy medium,” said Reeves.
Methods being used to dry ASR include:
- pile management, or simply letting water seep out from ASR as it is stored in piles;
- rotary dryers, which can dry ASR faster, although it can also entail emissions control costs; and
- fluid bed dryers, a “little more complicated” method, according to Reeves, that allows air to pass through material to dry it out and also allows plant operators to monitor the moisture level.
Fruit showed video clips of GK fluid bed dryers at work and said they can effectively reduce ASR moisture levels from 30 percent to as low as 2 percent, though he said “the best level seemed to be about 10 percent.”
Fruit said for ASR generators interested in producing an engineered fuel pellet from their material, reaching a consistently low moisture level “would be a major step forward.” He added, “I think as time moves forward you’re going to see significantly more interest in this.”
The ISRI 2015 Convention & Exposition was at the Vancouver Convention Centre April 21-25.