Continuous Micro-Sorting of Complex Waste Plastics Particle Mixtures Via Liquid-Fluidized Bed Classification (LFBC) for Waste Minimization and RecyclingEPA Grant Number: R826731
Title: Continuous Micro-Sorting of Complex Waste Plastics Particle Mixtures Via Liquid-Fluidized Bed Classification (LFBC) for Waste Minimization and Recycling
Investigators: Calo, Joseph M.
Institution: Brown University
EPA Project Officer: Hahn, Intaek
Project Period: February 1, 1999 through March 31, 2002 (Extended to August 31, 2003)
Project Amount: $265,000
RFA: Technology for a Sustainable Environment (1999) RFA Text | Recipients Lists
Research Category: Sustainability , Pollution Prevention/Sustainable Development
A fundamental investigation is proposed to provide a technical basis for the development of a novel, liquid-fluidized bed classification (LFBC) technology for the continuous separation of complex waste plastic mixtures for in-process recycling and waste minimization. Although a number of processes have been developed or proposed for the separation of waste plastics from manufacturing operations, none are completely satisfactory in terms of economics and performance. LFBC has a number of distinct advantages over most of these processes: (1) It can be used to separate a number of plastic particle types simultaneously in the same device. All other density-based techniques like flotation, centrifugation, air classification, hydroclones, etc., can only separate "lights" from "heavies" (i.e., two fractions), at best. (2) Only unmodified water is required for both "heavier-than-water" plastics ("upflow fluidization) and "lighter-than-water" plastics ("downflow" fluidization). Therefore, no density-modification of the fluidizing medium is necessary, which obviates the need for separation and recovery of modifying agents. Only water is needed to effect the separation of all plastic types; and water is already in ample use in chopping, grinding, and washing operations of plastic particles. (3) Due to the inherent physicochemical property differences between different plastic types, selective particle size/density modification can be performed in conjunction with LFBC to enhance separations, and/or to perform separations between different particle types with similar densities which are not possible using other conventional density-based separation processes. Finally, LFBC is completely compatible with most other separation/identification methods, such that it can be used in conjunction with other technology to improve the overall process economics.
An experimental research program is presented which has been formulated to address the key technical issues that must be understood/solved in order to optimize the performance of LFBC systems and allow for their development. This involves fundamental hydrodynamic studies, including measurements of dispersion coefficients and separation performance as a function of such critical parameters as particle size, aspect ratio, and column loading, which are not available in the literature for irregularly shaped particles. The experimental focus of the proposed work is a pilot-scale column will be constructed to obtain the requisite data using in-situ image analysis techniques. The column will also be fitted with the capability to program cyclic step changes in the temperature of the fluidizing water to cause preferential modification of the size/density of selected plastic particles by type to improve separation. These data will be used to develop a predictive numerical model of system performance for particular applications of interest.
The resultant data and the model will provide the basis for the design and detailed economic analysis of these systems for commercialization. An industrial partner is already identified. In addition, the Center for Environmental Industry and Technology of the USEPA, Region I (J. Cabot, Director), has indicated an interest in working with us to promote this promising technology commercially.
Estimated Improvement in Risk Management:
Successful completion of this project will provide the basis for a new, low-cost, environmentally benign technology for waste minimization.