Techno-economic feasibility and flowsheet synthesis of scrap tire plastic waste liquefaction

A techno-economic feasibility study was undertaken to assess the viability of co-liquefying scrap tires and post-consumer plastic wastes into liquid t ransportation fuels. First, a generalized process flowsheet was synthesized . Next, material and energy balances as well as process simulations were de veloped. Finally, a profitability analysis was completed for all process sc enarios investigated. Two different base case scenarios were considered: (1 ) the melting/depolymerization of waste plastics and the pyrolysis of scrap tires and (2) the pyrolysis of both waste plastics and scrap tires. For th e techno-economic assessment, waste plastic and scrap tire feed rates of 20 0 and 100 tons per day respectively were assumed. Costs for individual piec es of equipment were either rigorously calculated or scaled down from liter ature sources. In addition to the two base case scenarios, two separate mod ules were also considered: (1) the melting/depolymerization and upgrading o f waste plastics alone and (2) the pyrolysis and upgrading of scrap tires a lone. The economies of scale for these two modules were also analyzed. The results for both base case scenarios indicate that a 15% rate of return on investment (ROI) can be achieved if a waste plastic tipping fee of $35-$45 per ton can be secured. Furthermore, the economic analysis of the two modul es reveals that tire pyrolysis has an ROI of 18% while the ROI of plastic m elting/depolymerization is much lower. This result is expected since the po tential tips and revenues from scrap tires is greater than those from waste plastics. Due to economy of scale, the process economics for both modules is considerably improved as capacity is increased. Thus, these results affi rm that the co-liquefaction of waste plastics and scrap tires as well as th e liquefaction of scrap tires alone is both technically and economically fe asible.