Understanding coal thermoplasticity using high range molecular spectrometry (MALDI): the link between coal structure, pyrolysis and fluidity in blended coals during heating

摘要

This study investigated the use of Laser Desorption/Ionisation time of flight mass spectrometry (LDI-TOF-MS) as a tool for measuring molecular weight changes occurring during the development of thermoplasticity in a suite of industrial coking coals. The study indicates that the technique provides novel and new coal characterisation options for coking coals, whereby · Peak molecular weight and MALDI signal intensity in raw coal and semi-cokes was related to coal rank and fluid properties; providing a molecular basis for characterising coals · Solvent extractable "fluid phase" compounds are ranked on MALDI signal intensity, peak molecular weight, number of compounds of MALDI identified molecular groups and low boiling point volatiles by TGA; and · The Plastic Layer in simulated coke oven heated samples was found to correspond with the highest MALDI signal intensity across coal/plastic layer/semi coke regions. It was found that this value did not correspond with trends in standard fluidity measurements. This indicated that fluid properties in a coke oven may differ to those determined in a Geiseler fluidity test. Differences in the ratio of Low and High range molecules (below and above 2000Da) at this maximum fluidity point and the raw coal showed no clear trend and may be a coal specific process.