Marcelo Godinho

Nanofibrillated cellulose from tobacco industry wastes.

Tobacco stems waste underwent steam explosion pulping for nanofibrillated cellulose (NFC) production. In order to obtain NFC hydrogels, the pulp obtained by steam explosion was bleached and refined in a grinder employing specific energy of up to 5067kWh/t. Eucalyptus kraft pulp was processed under the same conditions to produce NFC hydrogels, later used in order to compare with NFC hydrogels from tobacco stems waste. According to statistical analysis, the optimum tobacco stems pulping condition was obtained with a severity index of log3.0 and active alkali of 16.25%. These conditions allowed obtaining a bleached pulp with Schopper Riegler degree of 46. Electronic microscopy with field emission showed a higher presence of nanofibers in the tobacco stems pulp than in commercial eucalyptus kraft pulp, both after refining. Thermal analysis indicated that tobacco stems pulp degrade at lower temperatures than eucalyptus kraft pulp. FTIR analysis did not indicate chemical bonding differences between the two pulps.

Formation of PCDD and PCDF in the thermal treatment of footwear leather wastes

The leather waste generated by the footwear industry is considered dangerous due to the presence of trivalent chromium, derived from the salt utilized to tan hides. In Brazil, the majority of this waste is disposed on landfills and only about 3% are recycled. The thermal treatment is an alternative method for purification of such residues. By using this technique it is possible to generate energy and recover the chromium present in the ash for the production of basic chromium sulfate (tanning industry), high carbon ferrochromium or carbon-free ferrochromium (steel industry). In the last 10 years, the gasification and combustion of footwear leather waste have been intensively studied at the Federal University of Rio Grande do Sul. The research experiment for characterization of the emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) were carried out in a semi-pilot unit (350 kW(th)). From new investments the thermal capacity of the unit will increase to 600 kW(th). The unit will produce power from the heat generated in the combustion. The experimental results indicated that during the thermal treatment of footwear leather wastes, the formation mechanism of PCDD/F is the de novo synthesis. Most of PCDD/F were found in the particulate phase (>95%). A kinetic model was used for discussion of the achieved experimental results. The model is based in the carbon gasification, PCDD/F formation, desorption and degradation. From the conclusions obtained in this work will be possible minimize the PCDD/F formation in process of combustion of footwear leather wastes.

Aluminothermic reduction of Cr2O3 contained in the ash of thermally treated leather waste

In this study the viability of utilising ashes with high chromium oxide content, obtained by thermal treatment of footwear leather waste, in the production of low-carbon ferrochromium alloy (Fe-Cr-LC) by aluminothermic reduction was investigated. The following key-factors were selected for process modelling: the quantity of aluminium (Al) employed in the reaction, the iron amount added, the iron compound (Fe and/or Fe2O3) used, and the chromic acid addition. The process was investigated using a 24 full factorial design where the percentage of Cr2O3 reduced was used as the response. Variance analysis was employed to determine the significant effects and to validate the obtained model. The model was useful for finding the optimal operating conditions, including the maximisation of chromium conversion and the gross margin. Both resulted in similar process conditions, with 76.8±12.3% of chromium being reduced to the metallic phase, and 1.65±0.52 USD (kg ash)-1 as the gross margin. The qualities of some alloys obtained were investigated by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy analysis (SEM/EDS). The results showed that the main problem for these alloys in a standard specification was the P and S content, suggesting that a pre-treatment is required.

Critical analysis of non-isothermal kinetics of poultry litter pyrolysis

Poultry litter is a waste from poultry industry that has been used for bioenergy generation and has high potential as feedstock for thermochemical processes, as pyrolysis. Kinetic parameters of poultry litter pyrolysis are paramount for techno-economic analysis of commercial scale processes. Scientific community has shown concern about the suitable application of different methods (model-free/model-fitting) for the determination of kinetic parameters. The application of an unsuitable method may lead to unreliable kinetic parameters. In this study, the performance of model-free methods for the determination of the kinetic parameters of poultry litter pyrolysis was evaluated. The characterization was performed through thermogravimetric analysis. Were applied the methods of Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa and Vyazovkin. The model-free methods were not adequate to describe the kinetics of poultry litter pyrolysis throughout the whole reaction. Therefore, a model-based (five pseudo-components model) method was applied to obtain the kinetic parameters of poultry litter pyrolysis. Such model provided an adequate fit to the experimental data.

Adsorption of leather dyes on activated carbon from leather shaving wastes: kinetics, equilibrium and thermodynamics studies

ABSTRACT In this work, the adsorption of Acid Black 210 (AB210) and Acid Red 357 (AR357) onto activated carbon prepared from leather shaving wastes (ACLW) was investigated. The activated carbon presented a surface area of 800.4 m²/g with an average pore size of 1.27 nm. The kinetic study showed that the adsorption of both dyes followed the Elovich kinetic model while the AB210 and AR357 isotherm data were well described by the Langmuir and BET models, respectively. Furthermore, the Boyd plot revealed that the adsorption of the leather dyes on activated carbon was mainly governed by film diffusion. The pH had a strong influence on the adsorption, and the higher amounts of dye adsorbed were obtained at pH 2. The obtained activated carbon exhibited a high monolayer adsorption capacity of 573.9 and 204.4 mg/g for AB210 and AR357, respectively. Its high capacity is mainly attributed to its basicity (0.17 mmol/g) and high surface area. Desorption efficiency of the spent activated carbon was found to be 54.3% and 43.0% for AB210 and AR357, respectively. The spontaneity of the process was demonstrated by the negative values of the Gibbs free energy change.

CARACTERÍSTICAS DO RESÍDUO DO TRITURADOR DE SUCATAS (RTS) DE UMA SIDERÚRGICA BRASILEIRA

Daniele Perondi Danielle Restelatto Christian Manera Andrezza Piroli Tonello Marcelo Godinho Antônio Cezar Faria Vilela Resumo Diferentes resíduos são gerados pelas indústrias siderúrgicas, dentre eles o resíduo dos trituradores de sucatas (RTS). O RTS gerado pelas siderúrgicas brasileiras se difere dos demais países devido aos materiais que são alimentados no triturador. Assim, o objetivo deste trabalho foi avaliar as características do RTS gerado por uma siderúrgica brasileira. As seguintes técnicas foram utilizadas: identificação e quantificação dos principais constituintes, análise termogravimétrica, imediata, elementar, poder calorífico superior e teor de cloro e metais. Os principais polímeros presentes no RTS foram o poliestireno e o polietileno. A partir dos resultados de análise imediata, elementar e de poder calorífico superior do RTS, verificou-se uma elevada quantidade de matéria volátil (76,22% ± 6,90). Os altos teores de carbono (72,92%) e hidrogênio (9,86%), foram atribuídos à elevada quantidade de polímeros e borrachas presentes no resíduo. O teor de enxofre (0,21%) pode ser atribuído a presença de borracha no resíduo, enquanto o teor de cloro (1,33% ± 0,13) pode ser atribuído a presença do PVC no resíduo. O poder calorífico superior do RTS foi de 30,01 ± 1,22 MJ/kg, de forma que uma avaliação termoquímica mostra-se como uma técnica atrativa para a sua destinação final. Palavras-chave: Resíduo do triturador de sucata; Siderúrgica brasileira; Técnicas de caracterização.

Characteristics of Pyrolysis Products from Waste Tyres and Spent Foundry Sand Co-Pyrolysis

The products obtained through thermal conversion of tyres can represent a solution for its disposal which has been considered an environmental problem. In the foundry industry two types of sand are generated: core sand (CS) and green sand (GS); CS is classified as hazardous waste. In this paper two kinds of industrial wastes were approached, in order to propose a solution through co-pyrolysis. The experiments were performed in a bubbling fluidized bed reactor. The oil, fuel gas and char obtained were characterized. The main components present in the oil were naphthalene and anthracene. Char morphology was assessed by Scanning Electron Microscopy, confirming the resin absence on its surface. Isothermal adsorption and desorption indicated that the char obtained from tyre pyrolysis with lower particles has higher superficial area (higher than 200 m2·g−1). The main compounds identified in fuel gas were hydrogen, carbon monoxide, carbon dioxide and hydrocarbons up to 5 carbons.