Degradação Térmica da Casca de Arroz e Utilização do Carvão Obtido no Processo para Polimento de Águas Cinzas

Abstract

The objective of this research was to obtain through the thermochemical process of pyrolysis of rice husk produced in Tocantins active carbon aiming adsorption of pollutants in gray-waters. The biomass was characterized by immediate and instrumental analysis (Elemental Analysis, Lignin, Cellulose, Hemocellulose, Scanning Electron Microscopy – SEM, Infrared Spectrometry and Thermogravimetric Analysis). The pyrolytic plant in laboratory scale had a stainless steel fixed bed reactor heated by two parts furnace using water steam heated as carrier gas. In the Thermochemical pyrolysis process, it was studied the following parameters: reaction temperature (360 to 640oC) and heating rate (23 to 37oC/min). The obtained carbon was characterized using Immediate Analysis, pH, Thermogravimetric Analysis and Scanning Electron Microscopy – SEM. The bio-oil produced in the process was characterized using density analysis, pH and gas chromatigraphywith mass spectrometry – CG-MS. The maximum output of the carbon was around 68,99% obtained under the temperature of 360oC and heating rate of 30oC/min. The produced carbon presented low humidity 4,35%), high range of volatile components (51,17%) and high range of ashes (37,63%), with heterogeneous structures, revealing in its micro-graphics cavities and holes of irregular shapes, indicating the use of the material as absorber. The bio-oil has acidic pH and density that varies from 0,915 to 1,53 g/mL. Several chemical compounds were found in the pyrolytic liquid (aliphatic hydrocarbons, aromatic hydrocarbons, aliphatics having oxygen, aromatics having oxygen, nitrogen compounds, polycyclic hydrocarbons, sulfur and compounds of boron), related to the biomass characteristics. The carbon of this research proced to be efficient for the removal of methylene blue solution in concentration of 2mg/L and flow ratio of 5mL/min resulting a curve of extended rupturing. During the tests of flocculation the aluminum sulphate was the most efficient coagulant in the removal of gray-waters turbidity. The polishing of gray-waters using carbon produced by thermochemical pyrolysis process of the rice husk proved to be efficient to remove settlable solids, volatile solids, turbidity, total coliforms, DQO and alkalinity in rates over 90% and other parameters (soluble orthophosphate, total solids, residual chloride and ammonia) rate over 50%.