Interaction of Potassium and Calcium in the Catalytic Gasification of Biosolids and Switchgrass

Abstract

9Catalytic gasification is a method of converting biosolids, the solids created during wastewater 10 treatment, into a valuable gaseous stream. One of the challenges with this process is that the 11 components in the ash of the biosolids can interact with the gasification catalyst(s) -in 12 particular, calcium and potassium. In this study, the behaviors of different combinations of 13 switchgrass (the source of potassium), biosolids, ash-free carbon black, and mixtures of each 14 feed with added calcium and/or potassium were observed with a thermogravimetric analysis unit. 15The results were consistent with calcium preferentially reacting with components in the ash, 16preventing the deactivation of potassium. Any additional calcium available may form bimetallic 17

Effect of calcium and barium on potassium-catalyzed gasification of ash-free carbon black

“…Wang et al proposed that a bimetallic carbonate compound formed during gasification when both potassium and calcium salts are present [54]. In our previous study [26], XRD analysis of the remaining ash after CO2 gasification at 850 °C of carbon black with added KOH and Ca(OH)2 did not provide evidence for this bimetallic compound. There was, however, evidence of calcium preferentially reacting with aluminum and silicon to form aluminosilicate compounds, to allow the potassium to remain in a catalytically active form.…”

“…Metallic species in the feed materials, including calcium and potassium, can be used as intrinsic gasification catalysts [10][11][12][13][14]. Calcium can be found in feeds such as biosolids/sewage sludge [15][16][17][18], coal [19][20][21][22], and biomass [10,23,24], while potassium is found in biomass with an order of magnitude higher abundance than typically found in coal [23,25] or biosolids [26,27]. Biomass has been co-gasified with coal to increase the reaction rate by introducing more potassium [27][28][29][30][31][32].…”

Bed material as a catalyst for char gasification: The case of ash-coated olivine activated by K and S addition

“…In fact, the chemical deactivation of K-catalysts occurs when K reacts with Si/Al to form non-volatile silicates or aluminosilicates [31]. Ca has been found to prevent the chemical deactivation of K by preventing its reaction with Si/Al, thereby ensuring that K is available in a mobile form [32,33].…”

Current state and future prospects for liquid biofuels in Canada

“…In addition, various new feedstocks are being explored. The University of Calgary in collaboration with McGill University are looking at catalytic gasification of biosolids (Arnold et al, 2017) while University of Saskatchewan and York University are looking at gasification of horse manure, fruit wastes, and agro-food residues using supercritical water gasification (Nanda et al, 2016). Supercritical gasification is another area that is receiving attention at the academic level in Canada at several institutions, including the University of Saskatchewan (Kang et al, 2016) and University of Western Ontario (Behnia et al, 2016), as the use of supercritical water increases diffusion coefficients and reaction rates in the gasifier.…”