A novel systematic multi-objective optimization to achieve high-efficiency and low-emission waste polymeric foam gasification using response surface methodology and TOPSIS method

Gasification is one of the most important thermochemical processes to convert a solid fuel to energy carriers of a gaseous product called syngas. This process has been well addressed in the literature for biomass and several valuable researches have been performed on plastic waste gasification. However, it is the first effort for a systematic comprehensive investigation and multi-objective optimization of gasification process for waste polymeric foams using response surface methodology and TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) approach. Air and steam waste rigid polyurethane foam gasifications were modeled using coupled method of Gibbs minimization free energy and Lagrange method of undetermined multipliers, and then, validated. Effects of key features consisting gasification temperature and moisture content in both air and steam gasification types and equivalence ratio in air and steam to waste foam ratio in steam types were thoroughly studied on gas composition and energy and hydrogen efficiencies. Analysis of variance was employed for recognizing the most effective parameters on air and steam gasification performances. The results revealed that hydrogen and energy efficiencies of air gasification at multi-objective optimum conditions were 42.68 % and 89.58 %, respectively, and these values were 64.02 % and 96.52 % for steam gasification type. Air gasification of waste rigid polyurethane foam produced 3.13 g of CO2 emission at optimum state; however, its value was 10.02 g for steam gasification type. A multi-criteria decision analysis based on TOPSIS method was utilized for selecting the best gasification type in different scenarios and the findings indicated that air gasification had better performance compared to steam type due to its low emissions.