Denis Leocádio Teixeira

Resistance to forced airflow through layers of composting organic material

The objective of this study was to adjust equations to estimate the static pressure gradient of airflow through layers of organic residues submitted to two stages of biochemical degradation, and to evaluate the static pressure drop of airflow thought the material layer. Measurements of static pressure drop in the layers of sugarcane bagasse and coffee husks mixed with poultry litter on day 0 and after 30 days of composting were performed using a prototype with specific airflow rates ranging from 0.02 to 0.13 m(3) s(-1) m(-2). Static pressure gradient and specific airflow rate data were properly fit to the Shedd, Hukill & Ives and Ergun models, which may be used to predict the static pressure gradient of air to be blown through the organic residue layers. However, the Shedd model was that which best represented the phenomenon studied. The static pressure drop of airflow increased as a power of the material layer thickness and showed tendency for decreasing with the biochemical degradation time of the organic material.

Demanda de potência do ventilador para aeração de material em compostagem

This study aimed to adjust loss curves in static air pressure when forced into layers of organic material, with different thicknesses and two stages of biochemical degradation, to enable the calculation of the power demand of the ventilation system. The residues used to evaluate air pressure loss were poultry litter mixed with coffee cherry husk, mass ratio of 2.5:1, to obtain an initial C/N relation of 30:1. It was found that the loss in static pressure increased linearly with the thickness of the organic compound, and that there was an increase in static pressure loss with increased specific flow rate of air, which practically did not change by the biochemical degradation stage of the composting material. All models used (potential, logarithmic and quadratic) fit the experimental data in the range of specific air flow between 0.045 and 0.159 m 3 s -1 m -2 , and they may be used to predict the static pressure gradients in the organic compost. The power demanded by the ventilation system in layers of 1 m thickness was 1.16 W t -1 in the material before composting, and 2.38 W t -1 , after 60 days of composting. In layers of 2 m thickness, the demand was 17.70 and 21.65 W t -1 , respectively.This study aimed to adjust loss curves in static air pressure when forced into layers of organic material, with different thicknesses and two stages of biochemical degradation, to enable the calculation of the power demand of the ventilation system. The residues used to evaluate air pressure loss were poultry litter mixed with coffee cherry husk, mass ratio of 2.5:1, to obtain an initial C/N relation of 30:1. It was found that the loss in static pressure increased linearly with the thickness of the organic compound, and that there was an increase in static pressure loss with increased specific flow rate of air, which practically did not change by the biochemical degradation stage of the composting material. All models used (potential, logarithmic and quadratic) fit the experimental data in the range of specific air flow between 0.045 and 0.159 m3 s-1 m-2, and they may be used to predict the static pressure gradients in the organic compost. The power demanded by the ventilation system in layers of 1 m thickness was 1.16 W t-1 in the material before composting, and 2.38 W t-1, after 60 days of composting. In layers of 2 m thickness, the demand was 17.70 and 21.65 W t -1, respectively.

ALTERAÇÕES NAS CARACTERÍSTICAS FÍSICAS DO MATERIAL ORGÂNICO SUBMETIDO AO PROCESSO DE COMPOSTAGEM

This study aimed to evaluate the physical changes of organic material provided by the compost process for aerated static piles. The wastes used were from mixture of the bulking agent sugarcane bagasse and coffee straw with chicken litter, in order to obtain the initial C/N ratio of 25/1. The material using the aerated static piles system was composted, for 30 days, at which time it was observed the end of thermophilic phase. The composting process contributed to increase the dry bulk density of the material in approximately 12 and 13%, respectively for the mixture which the sugarcane bagasse and coffee straw were the bulking agents. The initial volume decreased 60% in the mixture which the bulking agent was sugarcane bagasse and 36% when used the coffee straw. The power demanded by the fan to overcome the air static pressure drop imposed by material layer, decrease with the composting process, due the higher granulation of the material.

CARACTERIZAÇÃO E EXTRAÇÃO DE CRÔMIO DE RESÍDUOS SÓLIDOS DA INDÚSTRIA DO COURO - DOI: 10.13083/1414-3984/reveng.v23n4p326-335

The increase in leather exportation in recent years has increased the generation of solid waste from leather industries in Brazil. Classified as Class I Residue, hazardous and presenting high contamination potential, correct disposal of these wastes in the environment is mandatory. Given the high content of nitrogen present in leather, there is growing interest for its utilization in agriculture, however to make this possible it is necessary to reduce the chromium content in the residue. Therefore, this study sought to characterize waste from the leather industry and develop a method for chromium extraction from it. Based on waste characterization, it was observed that waste from Wet Blue leather differs physically and chemically from finished leather strips, and although it presents a high nitrogen content (14 dag kg-1), for agricultural use most of the chromium must be extracted. The extraction method using a phosphoric acid solution resulted in 91.1% efficiency of Cr removal, where sequential extraction is a viable option both economically and environmentally.