Physical and chemical characterization of acid tar waste from crude benzol refining

The physical and chemical composition of acid tar waste is important in assessing and developing technological processing options for their subsequent utilization. In the present investigation gas chromatography/mass spectrometry (GC/MS), fourier transform infrared (FTIR), inductively coupled plasma/atomic emission spectrometry (ICP/AES), scanning electron microscopy with energy dispersive Xray (SEM/EDX) were mainly used to characterize the acid tar waste from crude benzol refining. The acid tar waste had a moisture content within the range 7-11%, pH values < 2.5 at a Liquid Solid (L/S) ratio of 20. Chemical analysis indicated the presence calcium, phosphorus and iron at 56.3, 15.7 and 11.3 ppm respectively with trace concentrations of lead, zinc, manganese and chromium. Organic analysis of the aromatic fraction of the acid tar waste by GC-MS revealed a wide range of compounds, including polycyclic aromatic hydrocarbons, furans, phenols, thiophenes and biphenyls. FTIR analysis was used to complement GC-MS. These results may be useful in the design and development of technological processes that can utilize acid tar waste.Keywords: Acid tars; Analytical techniques; Hazardous waste; Hydrocarbon

Pyrolysis characteristics and kinetics of acid tar waste from crude benzol refining: A thermogravimetry-mass spectrometry analysis

Pyrolysis is an attractive thermochemical conversion technology that may be utilised as a safe disposal option for acid tar waste. The kinetics of acid tar pyrolysis were investigated using thermogravimetry coupled with mass spectrometry under a nitrogen atmosphere at different heating rates of 10, 15 and 20 K min(-1). The thermogravimetric analysis shows three major reaction peaks centred around 178 degrees C, 258 degrees C, and 336 degrees C corresponding to the successive degradation of water soluble lower molecular mass sulphonic acids, sulphonated high molecular mass hydrocarbons, and high molecular mass hydrocarbons. The kinetic parameters were evaluated using the iso-conversional Kissinger-Akahira-Sunose method. A variation in the activation energy with conversion revealed that the pyrolysis of the acid tar waste progresses through complex multi-step kinetics. Mass spectrometry results revealed a predominance of gases such as hydrogen, methane and carbon monoxide, implying that the pyrolysis of acid tar waste is potentially an energy source. Thus the pyrolysis of acid tar waste may present a viable option for its environmental treatment. There are however, some limitations imposed by the co-evolution of corrosive gaseous components for which appropriate considerations must be provided in both pyrolysis reactor design and selection of construction materials