Increasing the efficiency of municipal solid waste energy by investigating the effect of die temperature and retention time on the produced pellets: A case study of Kahrizak, Iran

Abstract

In order to optimize waste production and address the global energy crisis, the conversion of waste into energy has become a necessary practice. This study aimed to investigate fuel pellet production from unused waste at the Kahrizak Waste Center in Tehran, Iran. Pellets were produced in the laboratory as single pellets, and the impacts of two variables including die temperature (90 °C and 110 °C) and retention time (5 s and 20 s) on density, toughness, water resistance time, density change, proximate analysis, calorific value, and energy consumption producing single pellets were evaluated. The appearance of pellets indicated that higher temperatures have more effect on pellet coherence than retention time. The solid waste was shredded to fluff, and the fluff waste bulk density and heating value were measured at 30.3 kg/m³ and 12 MJ/kg, respectively. By converting fluff to pellets, the density and heating value were increased. The highest density and heating value was for pellets made at 110 °C and 5 s, and they were 883.70 kg/m³ and 29.01 MJ/kg, respectively. Additionally, retention time was the main factor influencing the total amount of energy consumption. Pellets produced at high temperatures and retention times had higher toughness up to 1696.29 J/m³ . A longer retention time in the die reduced the rate of density changes.‎ In conclusion, considering the ‎‎characteristics of the pellets and the ‎amount of energy consumed, fuel pellets produced at 110 °C ‎and 5 s were the best option ‎‎for converting unused waste into a high-value pellet in the Kahrizak waste ‎center‎‎.