The hydrodynamics of the high-density bottom zone in a CFB riser analyzed by means of electrical capacitance tomography (ECT)

Local instantaneous temperature and time-averaged heat transfer coefficient in the bottom zone of a circulating fluidized bed

“…From the bed centre to the bed wall, k value increased slightly in the bottom zone, while it increased distinguishably near the wall in the upper dilute zone (Bai et al, 1996). Malcus et al (2000) also observed similar phenomenon in the local voidage fluctuation signals measured in the upper dilute zone. Figures 15 and 16 show logarithmic plots of the S(f) calculated from the temperature fluctuations shown in Figures 13 and 14, respectively.…”

“…Ma et al (1996) measured local instantaneous bed-to-wall heat transfer coefficient at only one position in the 'dense phase zone' of a CFB; Reddy and Nag (1998) measured local bed-to-wall heat transfer in the bottom zone of a circulating fluidized bed. Up to now, only some experimental studies on hydrodynamics in the bottom zones in CFBs are available in the literature (Svensson et al, 1993(Svensson et al, , 1996Werther and Wein, 1994;Bai et al, 1996;Zijerveld et al, 1996Zijerveld et al, , 1997Johnsson et al, 1999;Schlichthaerle and Werther, 1999;Wiesendorf et al, 1999;Sun et al, 1999;Malcus et al, 2000;Liu et al, 2001;Stern! e eus et al, 2000).…”

ECT studies of the choking phenomenon in a gas–solid circulating fluidized bed

“…Electrical capacitance tomography (ECT) is one of a handful of real-time tomography techniques and has been applied recently to three-phase flow imaging (Warsito and Fan, 2001a). ECT has also been applied to other solid flow systems, including standpipe flow, bubbling and turbulent fluidized beds, circulating fluidized beds, pneumatic conveying, and cyclone diplegs (Du et al, 2002(Du et al, , 2003Dyakowski et al, 1997Dyakowski et al, , 2000Wright, 2002a, 2002b;Malcus and Pugsley, 2001;Malcus et al, 2000;Smolders et al, 2001;Yang and Liu, 2000). The crux for the accurate application of the ECT or any other tomography techniques is the robustness of the image reconstruction technique used in resolving the "inverse" tomography imaging problem (Warsito and Fan, 2001b).…”

Validação Experimental De Simulações CFD De Um Leito Fluidizado Circulante Gás-Sólido Tipo Riser

“…Estudos anteriores (Malcus et al, 2000) têm verificado a dificuldade de se modelar um CFB, tendo em vista que diferentes estruturas geométricas do leito, condições operacionais e de material particulado podem produzir diferentes características hidrodinâmicas ao leito. Nas últimas décadas Gayfin et al (1997) e Sterneus et al (2000) realizaram estudos experimentais para investigar o comportamento hidrodinâmico do riser com base nos perfis radiais da concentração de gás, enquanto que Subramanya et al (2005) e Gupta et al (2003) simularam numericamente o efeito da atomização do gasóleo na região de alimentação para avaliar o desenpendo do riser.…”