Catalytic effect of representative calcium salts on the steam gasification of a Shengli lignite

Effects of Water-Soluble Sodium Compounds on the Microstructure and Combustion Performance of Shengli Lignite

“…In addition, the absorption peak at 1607 cm –1 for both SL + and SL + -NaCl, which is attributed to the asymmetric stretching vibration of −COO, shifted to 1576 cm –1 for SL + - Na 2 CO 3 and SL + -NaOH, and the symmetric stretching vibration absorption peak of −COO appeared at 1383 cm –1 . The relatively strong asymmetric stretching vibrations in the wavenumber range of 1610–1550 cm –1 and the relatively weak symmetric stretching vibrations near 1400 cm –1 confirm the presence of carboxylate. , Owing to the interactions between the complex oxygen-containing functional groups in low-rank coal, the tensile vibrations of the C–O bond formed by the delocalization of the C–O and CO bands in the carboxyl structure are not obvious. − In addition, the Na + of Na 2 CO 3 and NaOH may convert the −COO on the surface of SL + into a resonance configuration; consequently, the absorption peaks near 1570 and 1400 cm –1 correspond to the asymmetric and symmetric stretching vibrations of the “–COONa” configuration, respectively. These results demonstrate that the Na + in NaCl solution will not interact with the carboxyl functional groups in the coal, whereas those in Na 2 CO 3 and NaOH can react with these to form a “–COONa” structure.…”

Analysis of Coal Gasification Reactivity, Kinetics, and Mechanism with Iron-Based Catalyst from Coal Liquefaction

“…It is a fact that the more the active sites are consumed first, 24 the more the deactivation and the volatilization of the catalyst with the gasification process. 30 Besides, the E a values of HMC and HMDC3 were pretty close, and it was speculated that the E a values of HMDC1 or HMDC2 were also close to that of HMC. It indicated that there were no significant changes for the active sites of char prepared from dry mixing with the catalyst, whereas the E a of char prepared from wet impregnation had a much lower E a value than that of raw coal char.…”

“…Moreover, E a increased with the conversion for all samples, especially for HMWC2, indicating that the gasification reactivity decreased gradually. It is a fact that the more the active sites are consumed first, the more the deactivation and the volatilization of the catalyst with the gasification process . Besides, the E a values of HMC and HMDC3 were pretty close, and it was speculated that the E a values of HMDC1 or HMDC2 were also close to that of HMC.…”

Potassium-Induced Phenomena and Their Effects on the Intrinsic Reactivity of Biomass-Derived Char during Steam Gasification

“…During gasification, char undergoes structural changes, such as generation of new pores, enlargement and coalescence of existing ones, particle fragmentation, ,, etc., all of which influence the specific surface area, porosity, and pore size distribution ,, and affect the accessibility of the oxidizing agents to the inner particle during the char conversion. , When it comes to minerals, alkali and alkaline earth metals (AAEMs) are of importance. − ,,, For biomass-based feedstocks, among the inherent AAEM species, potassium (K) is of greatest interest , followed by calcium (Ca), which is typically found as a carbonate or an oxide. − The importance of potassium lies in the fact that it enhances the gasification rate by forming active potassium-oxygen complexes. − The role of Ca is however unclear with literature reporting (a) enhancement of pore structure development for coal chars during gasification , and (b) inhibition of potassium deactivation ,, and hence gasification rate promotion, especially in the presence of steam, plausibly due to the formation of Ca-K active compounds. , Nevertheless, the catalytic activity of Ca is manifested at early stages of char conversion ( X < 0.4), whereas K enhances the reaction rate at the later stages, − with K being indisputably more active toward char gasification than Ca. , Other elements influencing the catalytic char gasification reactivity are iron (Fe), sodium (Na), and magnesium (Mg), but their role in the overall conversion is limited because of their low abundance and reduced (or even inhibiting) activity compared to potassium. , …”