Pyrolysis of autoclaving waste

Abstract

Consulta en la Biblioteca ETSI Industriales (9078)

[EN] The project concerns the waste from an autoclaving process. The waste autoclave was inserted in a static bed batch reactor. In the reactor was conducted pyrolysis of waste. The waste was burned in absence of oxygen at four different temperatures 400, 500, 600 and 700 ºC. The hold time at each temperature was one hour. The pyrolysis process was carried out under nitrogen atmosphere, and the heating rate was 5ºC /min. The pyrolysis products were char, oil and gas. The products were analysed in detail by a different methods in order to determine their elemental composition and calorific value. Char analyse consist of determinate surface area, porosity, elemental analysis and proximate analyse. The char and activated carbons surface area and porosity were determinate using the method BET. This device operates by measuring the quantity of nitrogen adsorbed onto or desorbed from solid sample at different equilibrium vapour pressure. Char surface area and micropore structure was highest at 700ºC, however the highest gross calorific value of char was 5622.42 kcal/kg at 400ºC. The elemental analysis was carried out using elemental analyser. The humidity, volatile matter and ashes decreased with temperature, however when increase temperature more than 500ºC or 550ºC the carbon mass obtained is insignificant; hence the maximum percentage of mass of char obtained was 50.53% at 400ºC. Liquid yield was increased with temperature and was obtained a total of 43.75% of mass at 700ºC. Fourier Transform Infra_red Spectroscopy was used to oil analyse. Infrared testing allows us to get a picture of oil¿s health and also whether any contaminants are present such as fuel or coolant. Liquid contents were manly oxygenated compounds and polars compounds (alcohols, esters, ethers, ketones, acids, phenols, aldehydes) at 400ºC due to when increased temperature these molecules are transformed in complex molecules and dangerous such as PAH¿s. Pyrolysis gases collected at regular intervals are analysed off line by gas chromatography. Hydrocarbons gases were analysed using a gas chromatography with a flame ionisation detector. Carbon dioxide, hydrogen, nitrogen, carbon monoxide and oxygen were analysed with a thermal conductivity detector. The gases contents mainly were CO2 which decreased with temperature and CO, CH4 and hydrocarbons increased with temperature and the major calorific value was 12MJ/m3 at 700ºC. Finally the results were analysed with the purpose to determine if pyrolysis products could be used in process as energy recovery, liquid fuel, carbon or activated carbon.