• Energy Research

AbstractThe downstream processing of biocrudes obtained from direct biomass pyrolysis poses significant challenges due to stability issues, necessitating costly upgrading for further coprocessing with refinery feeds. This study examines the impact of torrefaction pretreatment on pyrolysis product distribution and biocrude composition using sawdust (SD) and groundnut shell (GS) feeds. Torrefaction was conducted at varying temperatures (200, 250 and 300°C) for 30 min under different reactor conditions. Increasing the severity of torrefaction resulted in decreased biocrude yields with reduced water content and gas formation, particularly evident with GS. A torrefaction temperature of 250°C and 30 min of pretreatment yielded higher phenolics and hydrocarbons. This increase in phenolics can be attributed to lignin enrichment during torrefaction, which, in the presence of a catalyst, undergoes deoxygenation leading to hydrocarbon formation. The influence of feed particle size, whether in powder or pellet form, on biocrude yield and composition was found to be minimal. Catalytic pyrolysis of SD using molecular sieve catalysts yielded the highest hydrocarbon (42%) and aromatic content (44%) at catalyst to biomass ratios of 1:1 and 2:3. The combination of torrefaction and pyrolysis was shown to enhance the quality of biocrude by increasing its hydrocarbon content, but at the expense of lower liquid yields. Experimental observations were supported by statistical analysis tools such as principal component analysis, which assessed pyrolysis product yields and composition.

The purpose of this work was to establish the pyrolysis kinetics of agricultural biomass residues (mustard husk (MH), cotton stalk (CS), and groundnut shell (GNS)) using thermogravimetric analysis (TGA). TGA is carried out at different heating rates (5, 10, 30, and 50 K/min) under inert conditions in the temperature range of 303–1173 K. The iso-conversional methods of Friedman, Kissinger-Akahira-Sunose, and Flynn-Wall-Ozawa were used to estimate the activation energy of the decomposition process. The Criado method, Coats-Redfern Method, and Direct Differential methods were used to model the kinetics, with the latter two methods providing a closer fit with the experimental data. The kinetics of thermal degradation were separately studied for three temperature zones represented as drying, active, and passive zones. The results of Coats-Redfern and Direct Differential methods showed that (i) the nth-order reaction model is applicable for all the samples with order of reaction in the active zone being around ~ 2.0–3.0, ~ 2.5–3.0, and ~ 3.0 for MH, CS, and GNS, respectively, and (ii) the D-3 model is applicable for all the samples in the passive zone.

AbstractSolid state decomposition studies of Low and High Density Polyethylene (LDPE and HDPE) have been carried out in the present work. Thermo‐gravimetric analysis (TGA) is utilized to determine the degradation kinetics for pure plastic samples at different heating rates. The distribution of activation energy values and rates estimated using various Iso‐conversional methods have been selected on basis of correlation coefficients. For LDPE, isoconversional method of Friedman and for HDPE Flynn Wall Ozawa methods are used to estimate the distribution of activation energies having their mean values as 256.5 and 257.2 kJ/mol respectively. The inputs from Isoconversional methods are used to determine decomposition behavior with Criado method. Model based studies performed with Criado method identifies the solid‐state degradation follows contracting volume‐sphere (R3) model based on lower statistical parameter values. The identified decomposition model is validated by Coats Redfern method which also results in lower statistical parameter values. This is further validated through a best fit of extent of reaction profile against temperature, substantiating the solid‐state decomposition model followed by given plastic fractions.

Abstract Global economic development and continuous rise in the standard of living has led to resource depletion and increased per capita waste generation and, thus waste management issue becomes crucial. Sustainable development and circular economy require prominent technology for reducing the pace of resource depletion while producing alternatives to meet future energy demands. Municipal Solid Waste (MSW) is a potential source of interest for the recovery of either secondary raw material or to produce energy. At present, most of the MSW in waste treatment plants is converted into recyclable fractions called Refuse Derived Fuel (RDF) through the process of Mechanical Biological Treatment (MBT) with the aim of reducing environmental concerns and increasing its value. The focus of this review is to evaluate the importance of a thermo-chemical process for conversion of RDF into fuel and value-added products as well as evaluating applicability of this process in waste management sector and solid waste treatment. However, due to heterogeneous nature of RDF, investigation of co-pyrolysis behavior of RDF components as well as reaction mechanisms in both catalytic and non-catalytic reactions has been conducted. It has been observed that a high H/C, low O/C ratio and lower biomass content in RDF feed produces better quality products and decreases the dioxins emission during pyrolysis. Interactions of free radicals produced from polymer components with biomass greatly affect the product distribution. Chemicals derived out of RDF pyrolysis have been discussed and effect of various catalysts in enhancing oil yield and quality has been summarized. Catalytic pyrolysis with the use of P, Ni, Co, and Mo modified zeolite catalyst improves the quality of oil, and also the activity and catalyst lifetime. Different reactor technologies available for solid waste valorization have also been analyzed.

Catalytic co-pyrolysis of two different refinery oily sludge (ROS) samples was conducted to facilitate resource recovery. Non-catalytic pyrolysis in temperatures ranging from 500 to 600°C was performed to determine high oil yields. Higher temperatures enhanced the oil yields up to ~ 24 wt%, while char formation remained unchanged (~ 45%) for S1. Conversely, S2 exhibited a notably lower oil yield (~ 4 wt%) than S1. Pyrolysis oil of S1 consisted of phenolics (~ 50% at 600 °C) whereas hydrocarbons were predominant in S2 oil (~ 80% at 600 °C). Catalytic pyrolysis of S1 did not exhibit a substantial impact on oil yields but the oil composition varied significantly. High hydrocarbons, phenolics, and aromatics were obtained with molecular sieve (MS), metal slag, and ZSM-5, respectively. Catalytic co-pyrolysis of S2 with sawdust (SD) in the presence of MS enhanced the oil yield, and the resulting oil consisted of high hydrocarbons (~ 54%) and aromatics (~ 44%).