The influence of K2CO3 and KCl on H2 formation during heat treatment of an acid-treated inertinite-rich bituminous coal–char

Thermogravimetric-mass spectrometry (TG-MS) studies were conducted in order to investigate the effect of potassium carbonate (K2CO3) and potassium chloride (KCl) on the conversion and hydrogen evolution of chars derived from acid-leached South African inertinite-rich bituminous coal. K2CO3 and KCl (0.5, 1, 3, 5 potassium ion mass percentages) were loaded to the acid-leached (demineralized) coal samples prior to charring. The resulting ‘doped’ coal–char samples were subjected to heat treatment in a CO2 atmosphere up to 1200 °C, and the thermogravimetric curves, as well as the temperature ranges of evolution of hydrogen, were investigated. The results obtained indicate that the temperatures at maximum rate of mass loss (from the DTG curves), as well as the temperatures at maximum rate of hydrogen (H2) evolution (from the MS curves) are lowered with increasing potassium salt loadings. The relative coal gasification reaction reactivity (1/Tmax) determined from the DTG curves increases with increasing potassium salt loading and increases more for K2CO3 than for KCl. The catalytic influence of K2CO3 on the CO2 gasification of the acid-treated coal sample was found to be greater than that of KCl at a loading of 5 % potassium ion mass percentag

Characterization of Reactor Ash Deposits from Pilot-Scale Pressurized Entrained-Flow Gasification of Woody Biomass

Pressurized entrained-flow gasification of renewable forest residues has the potential to produce high-quality syngas suitable for the synthesis of transport fuels and chemicals. The ash transformation behavior during gasification is critical to the overall production process and necessitates a level of understanding to implement appropriate control measures. Toward this end, ash deposits were collected from inside the reactor of a pilot-scale O-2-blown pressurized entrained-flow gasifier firing stem wood, bark, and pulp mill debarking residue (PMDR) in separate campaigns. These deposits were characterized with environmental scanning electron microscopy equipped with energy-dispersive X-ray spectrometry and X-ray diffractometry. The stem wood deposit contained high levels of calcium and was comparatively insubstantial. The bark and PMDR fuels contained contaminant sand and feldspar particles that were subsequently evident in each respective deposit. The bark deposit consisted of lightly sintered ash aggregates comprising presumably a silicate melt that enveloped particles of quartz and, to a lesser degree, feldspars. Discontinuous layers likely to be composed of alkaline-earth metal silicates were found upon the aggregate peripheries. The PMDR deposit consisted of a continuous slag that contained quartz and feldspar particles dispersed within a silicate melt. Significant levels of alkaline-earth and alkali metals constituted the silicate melts of both the bark and PMDR deposits. Overall, the results suggest that fuel contaminants (i.e., quartz and feldspars) play a significant role in the slag formation process during pressurized entrained-flow gasification of these woody biomasses.</p