Experimental Investigation On Co-Pyrolysis And Kinetic Modeling Of Waste Plastic And Biomass Blend For Bio-Fuel Application

Abstract

Pyrolysis of plastic waste is the best way to manage the waste while producing biofuels which can be improved to replace diesel. However, plastic thermal pyrolysis has certain limitations, such as the high decomposition temperature. Co-pyrolytic techniques have received much attention to provide an alternative way to dispose and convert plastic and lignocellulosic biomass waste into high-value added products. In this work, pine sawdust (SD) co-pyrolysis with polypropylene (PP) and polystyrene (PS) was investigated, which resulted in a decrease in the decomposition temperature. The main objectives of this study are to build knowledge on the co-pyrolysis of mixed biomass and plastic waste using two model fitting (Criado and Coats–Redfern) methods. Co-pyrolysis behavior of pine sawdust, waste plastics, and their blends was characterized using thermogravimetric analyzer (TGA). The data obtained from TGA reveals the decomposition behavior of materials involved and their synergistic effect. This has been done for each of the plastics, biomass, and their blends. Seven different co-pyrolysis tests were conducted using (TGA) at a heating rate of 200C/min for different binary and ternary mixed compositions of polypropylene (PP), polystyrene (PS), and pine saw dust (SD) were conducted. The Master plot of the Criado model was used to determine the most suitable reaction mechanism. Then, the Coats-Redfern model was used to efficiently obtain the kinetic parameters (Ea and A0), and the values of the activation energy (Ea) and pre-exponential factor (A0) of waste plastics (PP and PS) and pine sawdust (SD) decomposition were found to be 111.4,110.46 and 48.78kJ/mol respectively. The activation energy of the plastic decomposition reaction was reduced to 99.35kJ/mol when plastics were mixed with sawdust. Simulation of plastic and biomass co-pyrolysis process was modelled with the aid of Aspen HYSYS V10 to estimate the bio-fuel yields from PS, PP and SD. Aspen HYSYS simulator was used to develop the steady state model and to simulate the co-pyrolysis process with the above mentioned plastic and biomass blends. PengRobinson thermodynamics model was employed as a fluid package of this simulation. The process converts waste to fuel as a two stage process in an Aspen HYSYS Simulation Environment involving i) A conversion of plastics and biomass wastes into Vapor-Liquid Fraction (VLF) with small quantity of char residue using conversion reactor (Pyrolytic Reactor) and ii) Separation of produced Vapor-Liquid Fraction to pyro gases and liquid fuel with the help of a Cooler. The synergistic effect on the co-pyrolysis of plastic and biomass blends is reported. Compared to pure polymer samples, the maximum decomposition temperature of the mixture is also reduced from 4640C to 4500C. The Aspen HYSYS result shows that bio-oil was the main product from pyrolysis at 4500C of the mixture. The final products of the simulation are 82.29% bio-oil, 2.747% of gas, and, 14.96% char. It also showed that mixing the plastic and biomass waste has a positive synergy on the quality and quantity of the produced bio-oil. The water content of the bio-oil decreased from 26.87% to 13.27% when the ratio of plastic increased in the mixture. The char content decreased from 35% to 14.96%. The developed simulation model can be a bench mark for scale-up studies and will give an aspiration to the researchers for understanding the actual product ranges.