Nilson Romeu Marcilio

Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather

Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept.

The influence of Chromium supplied by tanning and wet finishing processes on the formation of cr(vi) in leather

Chromium used in leather manufacturing can be oxidized from the trivalent to the hexavalent state, causing environmental concerns. In this study, the influence of Cr(III) from tanning, deacidification pH, fatliquors, chrome retanning and vegetable retanning on the formation of Cr(VI) in leather was analyzed by comparing natural and aged samples. In wet-blue leather, even after aging and in fatliquored leathers that did not suffer the aging process, the presence of Cr(VI) was always below the detection limit of 3 mg/kg. Considering the presence of Cr(VI), the supply of chromium during the retanning step had a more significant effect than during the tanning. In the fatliquoring process with sulfites, fish and synthetic fatliquor leather samples contained Cr(VI) when aged, and the highest concentration detected was 26.7 mg/kg. The evaluation of Cr(VI) formation led to recommendations for regulation in the leather industry.

Production of hydrogen in the reaction between aluminum and water in the presence of NaOH and KOH

The objective of this work is to investigate the production of hydrogen as an energy source by means of the reaction of aluminum with water. This reaction only occurs in the presence of NaOH and KOH, which behave as catalysts. The main advantages of using aluminum for indirect energy storage are: recyclability, non-toxicity and easiness to shape. Alkali concentrations varying from 1 to 3 mol.L-1 were applied to different metallic samples, either foil (0.02 mm thick) or plates (0.5 and 1 mm thick), and reaction temperatures between 295 and 345 K were tested. The results show that the reaction is strongly influenced by temperature, alkali concentration and metal shape. NaOH commonly promotes faster reactions and higher real yields than KOH.

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.

Modeling of Biomass Gasification Applied to a Combined Gasifier-Combustor Unit: Equilibrium and Kinetic Approaches

Abstract This study proposes an analysis of biomass gasification using two mathematical models: one equilibrium model and one kinetic model based on the level of details and input data. After validation with data from literature, the models were applied for analysis of a combined gasifier-combustor unit for processing of solid wastes (biomass) of footwear industries. The gas product predicted by the models was indirectly validated with experimental data. For this, the adiabatic flame temperature estimated from the gas product was confronted to experimental temperature of the combustor unit, showing the accuracy of each model. Sensitivity analyses of the models were carried out regarding to the feed air flow rate. The responses to parametric changes were observed in major output parameters: low heating value (LHV) of gas product, and cold gas efficiency, which are important measures to quantify the performance of the system.

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.

Dry Reforming of Methane over Mg-Co-Al Mixed-Oxides Catalysts: Effect of Mg Content and Reduction Conditions

Mg-Co-Al mixed oxides were synthesized by the precipitation method and evaluated for dry reforming of methane. The samples were characterized by thermal techniques (TGA/DTA, NH3-TPD, H2-TPR, and TPO), specific surface area, and X-ray diffraction (XRD). Activity runs were conducted at atmospheric pressure, temperatures between 400 and 550°C, a CH4/CO2 molar ratio of 1, and a space velocity of 6000 NmL CH4/g/h. The partial substitution of Co with Mg increased the surface area and thermal stability and changed the reducibility and acid-base properties of the samples. These modifications led to a higher activity for dry reforming of methane for the catalyst with Mg/Co = 0.5, primarily due to its enhanced thermal stability. However, its higher activity was followed by higher amounts of coke. The different activation procedures highlighted Co3O4 as the main active phase rather than the Co-mixed oxides. Therefore, milder activation temperatures are required to properly reduce the Co3O4 phase and avoid sintering.

Fluid Dynamics Simulation for Design of a Biomass Gasifier

Abstract The obtaining of alternative sources to generate energy has been a worldwide focus of research in the last years, mainly due to scarcity of fossil fuels in a close future. A very promising source to obtain combustion gases (especially methane and hydrogen) consists of gasification of biomass wastes generated by tanneries and footwear-leather industries. The Brazilian state of Rio Grande do Sul has a very privileged position concerning this industrial area, because it owns a large number of companies of these branches. The objective of this work is the design and simulation of a biomass gasification reactor, by using the technique of computational fluid dynamics. A commercial computational package of simulation, CFX 11.0, was the software employed for the development of this work. The gasification process may be carried out in two types of reactor configurations: fluidized and fixed bed. The present work has been developed upon fixed bed reactors in downdraft operation, considering four steps of gasification zones develop along the gasifier: drying, devolatilization, reduction, and combustion. The single and two-phase reactions were simulated coupled with the transport equations (momentum, mass, and energy) and the tracking of biomass particles. Several design configurations were tested in order to verify how they could influence the fluid flow and the temperature distributions inside the reacting chamber. Finally, one has been chosen a configuration that counterbalances project features, easiness, and operation costs. The remaining simulations have been run from this last configuration. The preliminary results show a good consistency with experimental data obtained previously from a pilot plant. Also, based on the results obtained with different scenarios, a new and modern pilot plant will be built. Forthcoming simulations will have the objective of optimizing and improving the operating conditions of the equipment.

Potassic zeolites from Brazilian coal ash for use as a fertilizer in agriculture

Brazilian coal has an ash content ranging from 30 to 50% by weight. Consequently, its use in coal-fired thermoelectric for power production generates a lot of waste. The construction sector is the largest consumer of coal ash, but it cannot absorb the entire amount generated. Thus, other applications for coal ash should be studied in aim to optimize the use of this industrial waste. This research had as focus to synthesize potassic zeolite from of the coal ash into on potassium fertilizer for the grown wheat plant. In this work, it was used a subbituminous coal from Mina do Leão (RS, Brazil) presenting 48.7% ash content on a dry basis. Concerning the synthesis of potassic zeolite, it was adopted the conventional method of hydrothermal treatment with potassium hydroxide. A schedule of experiments was conducted in order to define the optimum condition of zeolite synthesis that was then used an alkaline solution of 5M KOH with a reaction time of 24h at 150°C. According to this procedure, it was obtained a zeolite with a single crystalline phase, identified through X-ray diffraction as Merlinoite. Subsequently, it was performed a set of tests using potassic zeolite asa fertilizer for plants in a greenhouse. The synthesized potassic zeolite showed a good potential for its use as fertilizer in agriculture.

Design of nanocomposites with cobalt encapsulated in the zeolite micropores for selective synthesis of isoparaffins in Fischer–Tropsch reaction

A new strategy for the synthesis of metal–zeolite nanocomposite materials containing metal nanoparticles only in the zeolite pores is proposed. These materials were first prepared by zeolite impregnation with metal salts which resulted in metal species located both inside the zeolite pores and on the zeolite outer surface. Then, the metal oxide nanoparticles on the external zeolite surface were selectively extracted by larger heteropolyacid molecules which cannot enter the zeolite pores. The use of cobalt–zeolite nanocomposites with cobalt nanoparticles selectively encapsulated in the zeolite pores led to significantly higher selectivity to C5–C12 branched hydrocarbons in Fischer–Tropsch synthesis with the maximum ratio of isoparaffins to n-paraffins of 5.8.