Recent developments on sewage sludge pyrolysis and its kinetics: Resources recovery, thermogravimetric platforms, and innovative prospects

Thermogravimetric analyzer was applied to analyze 22 solid materials and their mixtures at a heating rate of 10 K min−1 under nitrogen atmosphere. A grey-relation-based method for thermogravimetric (TG) data analysis was proposed, which introduced a mass loss vector (MLV) as numeric form of TG curves and calculated grey relations between MLVs of different materials as criterion. The method was applied to TG data, exemplifying its applications in classification of some solid wastes, simulation of biomass based on three compositions and interaction analysis of two materials. The results indicated that paper category could be represented by cellulose below 673 K while textile category could be represented by cellulose and polyethylene terephthalate (PET). 12 kinds of biomass could be simulated with all relation values larger than 0.92 between experimental and calculated data. Influences of interaction between PVC, paper and poplar wood were quantitatively analyzed, which showed less influence between paper and poplar than PVC and poplar.

A grey-relation-based method (GRM) for thermogravimetric (TG) data analysis

Bio-oil from microalgae pyrolysis has excellent potential to be developed as a renewable, sustainable, and environmentally friendly energy fuel. Using pyrolysis technology to use the solid waste from microalgae extraction of spirulina platensis as an energy source is a solution for pollution due to biomass extraction. The solid residue is known as Spirulina Platensis Residue (SPR). SPR pyrolysis will produce liquid fuel (bio-oil), gas, and biochar. This paper discusses the study of the pyrolysis kinetics of SPR with Thermogravimetric analysis (TGA) by flowing nitrogen, the settlement method using Kissinger - Akahira - Sunose (KAS) and Flynn -Wall - Ozawa (FWO). The samples were heated at a temperature ranging from 30°C to 1000°C with three different heating levels, namely 10, 30, and 50°C/min yang injected 20 mL/min Nitrogen (N2). The results obtained from the thermal decomposition process show three main stages, namely dehydration, active and passive pyrolysis. The activation energy (Ea) and the pre-exponential factor (A) obtained by the KAS method were around 42.241 kJ/mol, 51.290 kJ/mol, 54.556 kJ/mol, and 61.604 kJ/mol with conversion of 0.2%, 0.3%, 0.4%, while the estimation of activation energy from FWO 48.963 kJ/mol, 58.107 kJ/mol, 61.498 kJ/mol, and 68.457 kJ/mol with conversion of 0.2%, 0.3%, 0.4%, and 0.5% respectively. the kinetic parameter can be described by using this method. The experimental results show that the kinetic parameters obtained from the two methods are slightly different. However, the KAS and FWO methods are quite efficient in explaining the mechanism of the degradation reaction.

https://doi.org/10.1088/1755-1315/963/1/012010

Thermogravimetric analysis kinetic study of Spirulina platensis residue pyrolysis

Waste-to-energy technology is an alternative way to reduce fossil fuels and to secure energy resources. This technology can be readily applied to our real society because non-recyclable but combustible wastes are generated every day and the technology is already available and mature as shown in many facilities for waste incineration. However, this technology incurs environmental and human health concerns due to toxic metals in wastes, which have not been effectively managed because metal- and waste-related risk assessment is too time- and resource-consuming for field facilities. Thus, this study suggests a practical methodology to effectively screen toxic combustible wastes and to identify priority metals to be targeted for pollution prevention; and carries out a case study to demonstrate the methodology. The methodology is based on the assessment of toxicity potentials (for instance, cancer, non-cancer, and eco-toxicity potentials) from metals in combustible wastes on a per-energy basis. The toxicity potential is quantified by using (i) the metal contents and lower heating value (LHV) of a combustible waste and (ii) the characterization factors accounting for the fate, exposure, and effect of metals. A case study is performed by applying the methodology to waste cable coating, waste engine oil, waste paint, refuse-derived fuel (RDF), refuse plastic fuel (RPF), waste medium-density fiberboard (MDF), and wastewater sludge. The case study results showed that the cable coating, engine oil, brown paint, RDF, and wastewater sludge had relatively high toxicity potentials, and their priority metals were lead (Pb), zinc, and copper. This study can be used for waste-to-energy facilities to practically screen toxic waste fuels and to determine post-treatment processes that can effectively remove priority metals.

A Practical Methodology for Waste-to-Energy Facilities to Screen Toxic Combustible Wastes and Priority Metals

Study on the co-combustion process and mercury emission characteristics of sewage sludge-coal slime coupled fuel

This research studied the characteristics of dried sewage sludge using TGA to co-fire dried sewage sludge with coal in power plants. The sewage sludges that were discharged from Daejeon, Korea were dried and examined fundamental properties to use them as a fuel. Also, the properties of bituminous coal and wood pellet, which are used in domestic coal power plants, were analyzed and compared with them of sewage sludges and non-isothermal analyses of dried sewage sludges were performed at the heating rates of 5, 10, 20, and 30C /min using TG analyzer to investigate the basic combustion characteristics. As a results of these TGA/DTG analyses, sewage sludges showed its primary peak at the temperature of 250–500 °C, which overlapped with main peak of wood and secondary peak at around 500–600 °C, which overlapped with main peak of coals. Also for the interpretation by Friedman method, the activation energies in the section of highest weight loss were 525.16 kJ/mole for dried digested sewage sludge, 544.88 kJ/mole for dried excess sewage sludge, 203.86 kJ/mole for wood pellet and 146.4585 kJ/mole for bituminous coal. The reaction orders for dried digested excess sewage sludge, dried excess sewage sludge, wood pellet and bituminous coal were 28.775, 24.319, 18.398 and 9.1005, respectively, and the frequency factors were 5.89 
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 1028, 1.65 
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 1024,, 9.59 
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 1016 and 1.77 
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 108 for each, respectively.

Hyuk Im

Papers

Characterization of dried sewage sludge for co-firing in coal power plant by using thermal gravimetric analysis