Although thermogravimetric analysis (TGA) is a widely accepted technique for assessing coal combustion, conflicting trends have often been reported when relating apparent TGA reactivities to pulverized fuel (PF) burner conditions. Therefore, this paper compares the reactivity of chars generated in a drop tube furnace (DTF) to those from TGA. The implications of devolatilization temperature, heating rate and residence time are considered. For the smaller particle size ranges of the bituminous coal investigated (ATC), optimized devolatilization procedures were used to generate corresponding TGA burnout rates between the two char types. However, with fractions of >75 μm, the DTF chars showed an increased burnout propensity when moving from combustion regime II to combustion regime III. Scanning electron microscope (SEM) images and internal surface areas indicate that this is because of incompatible char morphologies. Thus, while chars produced under the conditions of TGA pyrolysis strongly resemble raw coal and display an undeveloped pore network; the DTF chars are highly porous, extensively swollen and possess considerably larger internal surface areas. Subsequently, char burnout variability was quantified, with the reactivity distribution for the DTF samples found to be up to an order of magnitude more significant than for the TGA chars. This is attributed to a fluctuating devolatilization environment on the DTF. Finally, a TGA study observed a robust particle size based compensation effect for the TGA chars, with the relative reaction rates and activation energies demonstrating the presence of internal diffusion control. However this phenomenon was partly alleviated for the DTF chars, since their higher porosities reduce mass transfer restrictions. Moreover, it should be realized that DTF char fractions of <38 μm, including those required to ensure true intrinsic control under the investigated burnout conditions, cannot be produced directly. This is because of bridging and sloughing in the DTF's screw-feeder. Instead, such samples must be created by grinding larger particles, which destroys the char's existing porosity.

There is a notable lack of published data concerning sodium cocoyl isethionate (SCI) despite widespread application in the personal care industry. A specific homologue, sodium lauroyl isethionate (SLI) was therefore synthesized, purified by recrystallization and then subjected to a detailed physicochemical examination. Purity of 98% was achieved via repeat recrystallization in methanol. A turbidimetric solubility analysis was then executed to identify both its crystallizability and metastable zone width as a function of temperature. Thermogravimetric analysis yielded decomposition onsets of 330°C for the purified SLI. A dynamic vapor sorption study also demonstrated reversibility in the 2.3% mass gained, when exposed to sustained humidity of 87%. Surface tension measurements of purified SLI yielded a critical micellar concentration (CMC) of 5.4 mM and a plateau surface tension of 38 mN/m at 20°C. Both values were lower than the previously reported values for SLI in water, thus indicating the performance benefits of purified isethionates in personal care formulations. The single step synthesis was chlorine-, catalyst-and solvent-free, thus improving process efficiency, safety and throughput over existing SLI syntheses. The succeeding physicochemical analysis crucially provides a much needed insight into the purification, properties and performance of isethionate ester surfactants; all of which is strongly applicable to their commercial manufacture from biorenewable sources.

Opportunities exist for effective coal combustion additives that can reduce the carbon content of pulverized fuel ash (PFA) to below 6%, thereby making it saleable for filler/building material applications without the need for postcombustion treatment. However, with only limited combustion data currently available for the multitude of potential additives, catalytic performance under pulverized fuel (PF) boiler conditions has received relatively little attention. For the first time, this paper therefore compares the reactivity of catalyzed bituminous coal chars from thermogravimetric analysis (TGA) with those generated by devolatilization in a drop tube furnace (DTF). The principal aim was to explore the fundamental chemistry behind the chosen additives' relative reactivities. Accordingly, all eight of the investigated additives increased the TGA burnout rate of the TGA and DTF chars, with most of the catalysts demonstrating consistent reactivity levels across chars from both devolatilization methods. Copper(I) chloride, silver chloride, and copper nitrate were thus identified as the most successful additives tested, but it proved difficult to establish a definitive reactivity ranking. This was largely due to the use of physical mixtures for catalyst dispersion, the relatively narrow selection of additives examined, and the inherent variability of the DTF chars. Nevertheless, one crucial exception to normal additive behavior was discovered, with copper(I) chloride perceptibly deactivating during devolatilization in the DTF, even though it remained the most effective catalyst tested. As a prolonged burnout at over 1000 °C was required to replicate this deactivation effect on the TGA, the phenomenon could not be detected by typical testing procedures. Subsequently, a comprehensive TGA study showed no obvious relationship between the catalyst-induced reductions in the reaction's apparent activation energy and the samples' recorded burnout rates. Although copper(I) chloride did generate a diffusion controlled reaction regime at a lower temperature than the other additives. Furthermore, only the thermally labile iron(III) chloride appeared capable of exerting a catalytic effect under mass transfer controlled combustion regimes, signifying that the physical state of the catalyst could be an important factor during PF combustion.

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Even though alkali and alkaline earth metal compounds are well-known catalysts for the combustion of coal, there has been no significant investigation into the importance of the anion across a broad selection of salts. The results described here compare the burnout of bituminous coal samples containing 21 Group I and II compounds on a thermogravimetric analyzer, thereby furnishing a wide-ranging systematic evaluation of anion effects for the first time. A variety of acetates, bicarbonates, carbonates, chlorides, hydroxides, nitrates, and sulfates were studied. Testing was also extended to a drop tube furnace (DTF), so that individual combustion additives could be assessed under conditions more similar to those found in a pulverized fuel (PF) boiler. All of the catalysts were subsequently found to increase the rate of TGA char combustion, but establishing definitive carbon burnout improvements proved to be more difficult on the DTF. This was probably due to a combination of the experimental variability associated with this setup, poor additive-coal contact, and the intrinsic volatility of the tested salts, particularly sodium carbonate's removal at high temperatures and the loss of calcium nitrate in an oxidizing environment. Despite these uncertainties, the attained DTF reactivity ranking was quite similar to that of thermogravimetric analysis (TGA). The alkali chlorides were identified as the most active additives, with their higher melting points possibly enhancing both their retention and the catalyst−coal contact achieved during devolatilization. However, the burnout improvements associated with the other Group I salts appeared to be limited by the propensity of the cations to interact with the coal matrix, while the activities of the less effective Group II compounds seemed to be restricted by their higher ionization energies and different bonding.