Caracterização, processamento e aproveitamento energético de um lodo grafítico de uma estação de tratamento de efluentes de forjaria

Content Provider	Semantic Scholar
Author	Thiesen, Renan Fernando Tresoldi
Copyright Year	2018
Abstract	Forging is a steel transformation operation in which it is processed in presses under high temperatures, in order to give the steel the desired shape and structure. For the process to run properly, the use of a lubricant is necessary. The lubricants used in this process are mostly composed of an emulsion of graphite in oil or water. After the process, the lubricant is eliminated, generating an effluent composed predominantly of graphite particles in suspension and whose treatment generates a graphite-rich sludge. In a forging in the state of Rio Grande do Sul, the oil-based graphite lubricant was replaced by a water-based lubricant, which altered the characteristics of the effluent and of the sludge associated with its treatment. In this context, the objective of this work was to study the sludge generated by the treatment of the graphitic effluent. The granulometric distribution of the particles that compose the sludge was determined by laser diffraction analysis performed in samples of the raw effluent. Samples of the graphitic sludge were collected after dehydration in a filter press and subjected to the following analyzes: X-ray diffractometry, proximate analysis, calorific value, elemental analysis, specific gravity, surface area, thermogravimetric analysis and solubilization and leaching tests, according to NBR 10004. Samples of charcoal, Brazilian coal, petroleum coke and anthracite also underwent proximate, elemental and thermogravimetric analysis for comparison purposes. Tests were performed simulating an additional stage of dehydration in drying beds, as well as tests of compaction of the sludge with different levels of water content. Graphitic sludge straight from filter press had an average water content of 51,44% and an apparent density of 1,31 g/cm3. After drying and comminution, the real density measured via pycnometry was 0,41 g/cm3. The graphitic sludge had the following average values: a higher calorific value of 24,9 MJ/kg, fixed carbon content of 61,71%, volatile matter of 19,55% and ash content of 18,74% (values on dry basis). The crystalline phase of the sludge is composed mainly of graphite, associated with oxides of iron and silicon. The carbon, hydrogen, nitrogen, sulfur and oxygen contents in the sludge are, respectively, 73,24%, 1,61%, 0,32%, 0,50% and 6,67%. The predominant metallic elements are iron and aluminum, with concentrations of 4,7 and 0,9%. The mean diameter of the sludge particles is 7,1 μm and their morphology resembles that of flake graphite particles. Drying bed dewatering allowed an average decrease of 49% in the sludge mass over a period of 6 to 10 days. Sludge compaction at 60 MPa promoted an average reduction of 342% in sludge volume. The results show that these additional sludge processing steps can greatly reduce the costs associated with the sludge transport and disposal. The characterization of the sludge proved that it is predominantly composed of graphite particles and that it has good potential for energy recovery. Key-words: graphite, sludge, forging, energy recover, solid waste.
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Alternate Webpage(s)	https://www.lume.ufrgs.br/bitstream/handle/10183/189880/001089401.pdf?isAllowed=y&sequence=1
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article