An evaluation of a new automated duplicate-sample Fischer Assay setup according to ISO/ASTM standards and analysis of the tar fraction
Journal of Analytical and Applied Pyrolysis
Coal Research Group, School of Chemical and Minerals Engineering, North West-University, Potchefstroom 2520, South Africa; Sasol Technology (Pty) Ltd, Box 1, Sasolburg 1947, South Africa
The ISO 647 standard describes a method for the pyrolysis of coal that quantitatively yields water, gas, tar and char, also known as a Fischer Assay. This method has several limitations i.e. The versatility of the method is limited by the thermal properties of aluminium (the retort material); the result is operator-dependent due to manual manipulation of the retort temperature using a gas generated flame. This study evaluates an alternative method (referred to as the automated Fischer Assay setup), which operates with a pre-programmed heating curve using two stainless steel retorts in an electrical oven. Comparison of the methods indicated a lower tar yield for the automated Fischer Assay method, whilst the water yield increased and the gas and char yields were within the same ranges. The automated Fischer Assay experiments were, however, more repeatable when compared to the standard ISO method. Simulated distillation (simdis) and size-exclusion chromatography (SEC-UV) analyses of the tar fractions found no significant differences between the tars from the two methods. Gas chromatography-mass spectrometry (GC-MS) found the tars of the automated Fischer Assay method to contain more alkyl-phenolic groups, with a decrease in the mixed compounds (compounds that exhibited both aromatic and aliphatic mass peaks in the mass spectra). It is concluded that the new method is more versatile with regard to the operating temperature control and the pre-programmed heat curve. Additionally, it provides an alternative means to generate a Fischer Assay that is not limited by the thermal properties of the retort material. It is noted, that the goal of the study was not to propose a replacement to the current ISO 647 Fischer Assay method, but to establish an automated system that can be used in pyrolysis research (qualitative and quantitative studies). Results showed that this method is adequate for qualitative and quantitative pyrolysis research and can be used as an alternative, less-biased method for ISO 647. © 2014 Elsevier B.V.
Automated systems; Gas chromatography-mass spectrometries (GC-MS); GC/MS; ISO 647; Operating temperature; Quantitative pyrolysis; Quantitative study; Simulated distillation; Coal tar; Distillation; Gas chromatography; Mass spectrometry; Pyrolysis; Size exclusion chromatography; Thermodynamic properties; Automation