Conceived in 1995 at Penn State, Plastofuel® is a densification process for converting dirty plastics into a clean burning fuel. The process accepts both rigid and film plastics and forces them through a heated die, melting the outer layer of plastic which locks in dirt, debris and small pieces of plastic. By melting only the outer one to two millimeters of plastic, energy is conserved, especially when compared with the standard pelleting process which requires the entire mass of plastic to be melted. The extruded material, called extrudate, is then cut with a hot knife to any length desired, melting and sealing the ends for durability. The fuel nuggets produced can be co-fired with coal or wood, or someday burned as the primary fuel described in the “Korean Combustion Technology & Eco Clean Burner” section.
The First Prototype
Shown in the next two photos is the first prototype machine operated by hydraulics. Notice dirty mulch film and drip irrigation tubing are hand fed into the hopper, where the red-colored hydraulic cylinder forces the material through the die (a pipe) that is heated with silver-colored electric band heaters. Note the extrudate peeking out of the die.
The first hand-operated prototype machine.
Hydraulics force plastic items through the heated die.
The Second Prototype
A second, more sophisticated Plastofuel® machine was designed as part of Matt Lawrence’s Ph.D. degree requirement, shown in the first photo. It uses an IQAN programmable logic controller to regulate the hydraulics which pre-compact items as large as nursery trays. Once densified to a specified limit, the hydraulics automatically force the plastic over a linear grid (sharp knives) and through a four-channel heated die. Hydraulically actuated hot knives cut the extrudate to any predetermined length, shown in the second photo below. In the third photo, without the cutoff knives in place the extrudate forms some shepherd’s crooks for the research team to use during Halloween dress-up, or maybe elsewhere, who knows.
Matt's linear grid type machine.
Densified materials exiting the four channel die are very dense.
Science or art?
Today’s Plastofuel® machine has been redesigned, since the linear grid system proved ineffective for high material throughputs, mainly due to bridging of material in the mouth of the four-channel dies. In today’s rejuvenated machine, the primary alteration has been to revert to an 80 mm diameter cyclindrical die, allowing more material throughput. In the photo shown, a single acting hydraulic cylinder is used; for a production model a double rod end hydraulic cylinder would be used. With double rod end cylinders, hydraulic system pressure surges are smoothed since one end is pushing while the other end is being loaded, and vice versa when the hydraulic flow is reversed. The larger diameter die helps with material feed, allowing shredded plastics to easily flow into the mouth of the die.
The newest prototype unit shown in 2010.
The 80 mm diameter extrudate holds together quite well.
Burning Plastofuel® with Coal
Making the fuel is one thing, burning it cleanly is another. In 2002, combustion tests were conducted in the combustion laboratory of Penn State’s Energy Institute. Plastic was blended 5 and 10 percent by calorific content with coal. Dirty mulch film and drip irrigation tape from three States were made into Plastofuel™. The Plastofuel™ was then sliced into small pieces (first photo), then burned with the coal in a stoker simulator (second photo). Air emissions and burn quality were closely monitored. Test results were encouraging. See the “Additional Information” section to view the test reports.
Plastofuel® was diced and blended with coal.
The stoker simulator shown with air emissions test equipment.