Use of Low-Volatile Solid Fuels in a 100 kW Chemical-Looping Combustor

Abstract

Carbon capture and storage (CCS) can be used to mitigate climate change. Chemical-looping combustion (CLC) is an innovative carbon-capture technology with potential to drastically reduce the capture cost. In CLC, oxygen is transported from combustion air to fuel by means of metal-oxide particles, called oxygen carrier. This work presents findings from a 100 kW CLC reactor system, which is designed as interconnected fluidized beds. The 100 kW unit was operated with ilmenite as the oxygen carrier. Swedish wood char and Mexican petcoke, both having low volatile content, were used as fuel. High gas conversion was achieved with both fuels. The carbon capture efficiency was high with wood char, but not as high with petcoke. The duration of operation was 34.5 h with fuel, of which the majority, 31 h, was achieved with wood char. Oxygen demand was strongly correlated with the solids inventory in the fuel reactor, as has been observed in previous works. Using wood char as fuel, gas conversion was 90−95.3%, except during high fuel power, and carbon capture efficiency was 93−97%, except during high fuel power. The gas conversion should be compared to what has previously been observed in the 100 kW unit, where the highest gas conversion was 84%, using a bituminous coal. Furthermore, comparatively high solid fuel conversion was seen in many tests with wood charthe highest value was 89%. Using petcoke as fuel, high gas conversion was achieved even when employing very high fuel power, 148 kW. The highest gas conversion for petcoke was 89%. The carbon capture efficiency was, however, much lower than what has been observed with pulverized coal and wood char. In summary, this study shows that important improvements can be achieved regarding gas conversion in the 100 kW unit by using low-volatile fuels.

Characterization of ilmenite used as oxygen carrier in a 100 kW chemical-looping combustor for solid fuels

“…Operational results from the 100 kW unit using ilmenite as oxygen carrier and wood char as fuel can be found in [27]. In this work, the gas conversion was 89-95%, and the carbon capture efficiency was 93-97% at a fuel power of 67 kW.…”

Comprehensive study of Mn–Fe–Al oxygen-carriers for chemical-looping with oxygen uncoupling (CLOU)

“…(Lyngfelt and Thunman, 2005;Ryu et al, 2004;Abad et al, 2006;Adanez et al, 2006;Johansson et al, 2006;de Diego et al, 2007;Linderholm et al, 2008). Development of the use of solid fuels in CLC involves experimental work in laboratory batch reactor (Mattisson et al, 2009b;Leion et al, 2007;Scott et al, 2006;Brown et al, 2010;Eyring et al, 2011;Azimi et al, 2011) and circulating systems (Berguerand and Lyngfelt, 2008;Shen et al, 2009a;Cuadrat et al, 2011;AdanezRubio et al, 2011;Linderholm et al, 2014;Markström et al, 2013). Further, the use of biomass with CLC holds great promise, as CCS with biofuels would mean negative emissions of carbon dioxide to the atmosphere (Shen et al, 2009b;Azar et al, 2010).…”

Oxygen carriers for chemical-looping combustion

“…• A 10-kW unit for solid fuels at Chalmers (Berguerand & Lyngfelt, 2008a,b;Berguerand & Lyngfelt, 2009a,b;Cuadrat, Linderholm, et al, 2011;Linderholm, Lyngfelt, Cuadrat, & Jerndal, 2012) • A 140-kW unit at Vienna University of Technology Kolbitsch et al, 2009c;Pr€ oll, Mayer, et al, 2009) • A 0.3-kW unit at Chalmers (Moldenhauer et al, 2012;Rydén et al, 2010) • A 10-kW unit at University of Stuttgart (Bidwe et al, 2011) • A 0.5e1.5 kW unit for solid fuels at CSIC (Cuadrat et al, 2011a,b;Cuadrat et al, 2012a,b;Mendiara, Izquierdo, et al, 2014) • A 100-kW unit for solid fuels at Chalmers (Linderholm, Schmitz, Knutsson, K€ allén, & Lyngfelt, 2014 (Moldenhauer, Rydén, Mattisson, Younes, & Lyngfelt, 2014) In addition, a 1-MW chemical-looping pilot has been built and operated with ilmenite in partial CLC mode (Str€ ohle, Orth, & Epple, 2014), i.e. with support of air to maintain fuel-reactor temperature.…”