Evaluation of the fuel potential of sewage sludge mixtures with beech sawdust and lignite

Abstract

Sewage sludge (SS) from municipal wastewater treatment has drawn serious attention of scientists around the world in the attempt to find feasible disposal methods. Therefore, in this work, a solution for valorisation of SS as solid fuel is proposed based on an advanced compositional investigation of SS versus conventional solid fuels, namely, lignite (L) and beech sawdust (BS). A characterisation in terms of proximate analysis and ultimate analysis was performed for the studied materials, both to SS, L, and BS as single fuel and to bi-component mixture formulas of SS and L/BS, in variable proportions of 30:70, 50:50, and 70:30. SS:BS based blends had higher hydrogen (from 4.43 wt. % to 5.14 wt. %) and carbon (from 30.76 wt. % to 40.12 wt. %) contents than the SS:L mixtures, very close to the one for BS (5.5 wt. % for hydrogen and 44.00 wt. % for carbon), indicating a more efficient release of energy during combustion. The combustion behaviour of SS and its blends with L and BS was also studied by thermogravimetric analysis (DSC-TGA) by heating the samples from ambient temperature up to 1100 °C at a rate of 20 °C/min under a nitrogen inert atmosphere. Analysis showed differences among SS, L, and BS, and the improvements were observed in the SS combustion profile after the addition of L or BS. The best potential as an alternative fuel was showed by the blends SS+L in a proportion of 30%:70% and SS+BS as a 30%:70% mixture. Additional information regarding the environmental risk induced by SS was obtained through the determination of the content of dioxines, furans, and carcinogenic polycyclic aromatic hydrocarbons of dried sewage sludge and the calculation of the toxicity equivalent factor. The values were within acceptable limits, and therefore, the proposed solution for valorization of waste sewage sludge offers a feasible way to reduce the anthropogenic impact and to enhance the durable development of the society.

1H-NMR Profiling and Carbon Isotope Discrimination as Tools for the Comparative Assessment of Walnut (Juglans regia L.) Cultivars with Various Geographical and Genetic Origins—A Preliminary Study

“…The elemental composition (C/H/N) of the walnut, oil, and residue was determined in triplicate using a Flash2000 Thermo (Thermo Fisher Scientific, Leicestershire, UK) with a TCD detector (Thermo Fisher Scientific, UK) [33]. Analysis conditions: Chromatographic columns—(i) molecular sieve 5A for separating flue gases after combustion, gas type CO, and (ii) PoraPLOT Q (30 cm, 20 μm, 65 °C) for separating flue gases after combustion, gas type NO 2 , CO 2 , H 2 O, SO 2, furnace temperature: 950 °C, TCD detector: 1000 mA, measuring time—12 min, sample mass 2.5 mg.…”

From Plastic to Fuel - New Challenges

“…In a previous study [16] we have shown data related with the pyrolysis processes of catalysts directly mixed with plastic wastes. Upon completion of this processes, the catalysts cannot be recovered; they became part of the viscous mass of the residue/wax at the end of the pyrolysis experiments.…”

“…As a further step in our research related to the disposal by valorisation of specific wastes [15,16], this study aimed to investigate the thermochemical effect, the basis of a pyrolysis process, applied to several types of polymeric materials, the polyethylene (PE -HDPE and LDPE), polypropylene (PP) and polystyrene (PS), responsible for more than 90% of plastic products and wastes in Romania. Thus, we assessed the pyrolysis of plastics both in the absence and presence of a mesoporous silica material, trying to obtain feasible data for designing and implementing a sustainable process for recycling of plastic waste.…”

An Alternative for Valorization of Wastes as Energy Source

“…Sulfur level of Slag and BW do not highlight problems, since is below that of fossil fuels, except in MBM samples which recorded values 20 times higher than lignite. MBM is an animal waste naturally containing amino acids such as methionine, cystine and cysteine, explaining thus the high sulfur level (S > 8 %wt).As for oxygen and hydrogen, the levels are high, corresponding to potential alternative fuels, andis comparable to those found in the literature (Magdziarzand Wilk, 2013;Ylmaz et al, 2018;Constantinescu et al, 2018), which also led to significant calorific values (HHV), of 3730 kcal/kg for MBM, to4813 kcal/kg for BW, significantly higher than of lignite, ~ 2086 kcal/kg.…”

“…The mixtures followed three compositional proportions, of (%, wt) 25:50:25, 50:25:25 and 25:25:50, thus to cover a varied range of data that will offer information (Table 4) on the durability of the proposed fuel solution. As for other energetic solid waste blends (Constantinescu et al, 2017;Ylmaz et al, 2018;Constantinescu et al, 2018), the proposed tri-component solid energy sorts mainly based on waste materials, reveals a positive evolution, both in terms of high energy levels and decrease of elementary components (S, N, and C) with potential environmental negative impact. The multicompound-based waste solid fuels, namely MBM+Lignite+Slag and MBM+BW+Lignite, registered high energy values, of 2162 to 2791 kcal/kg and from 3412 to 3982 kcal/kg, respectively.…”