Asphalt Recovery from Used Roofing Shingles

Over eleven million tons of asphalt roofing shingles are discarded in the United States annually, and there is interest in separating asphalt from the other components of the shingles. Separations based upon dissolving asphalt in solvents and upon mechanical agitation in non-solvents at elevated temperatures were investigated. Agitation in boiling water and boiling propylene glycol was not effective in separating asphalt from other components, and produced suspensions of particles that were difficult to separate from the liquid. Asphalt solubility in five common organic solvents was tested, and toluene was selected by qualitative observation of the solutions and consideration of potential process hazards of tetrahydrofuran. Experiments were performed to quantify mass transfer in the solution process. Samples were taken as 1-6 g samples of shingles were stirred with 75-150 mL of toluene for 10-40 minutes.  A colorimeter was used to determine the asphalt concentration. Stir rate, shingle particle size and type were also varied during testing. Analysis is ongoing, and the results will be applied in a preliminary process design for a large-scale process.