Yongqiang Feng

Effect of lipid-free microalgal biomass and waste glycerol on growth and lipid production of Scenedesmus obliquus: Innovative waste recycling for extraordinary lipid production

In the present work, a novel approach of using growth medium with different substitutions of lipid-free algal hydrolysate (LFAH, 0, 5, 10 and 15%) and/or waste glycerol (WG, 0, 5, 10 and 20 g L-1) for enhanced biodiesel production from Scenedesmus obliquus was studied. Combination of different concentrations of WG with 15% LFAH showed the maximum significant biomass productivity, which represented 27.4, 30.5 and 28.9% over the control at combined 5, 10 and 20 g L-1 WG, respectively. The combinations of different LFAH with 20 g L-1 WG showed the maximum significant lipid accumulation, where lipid productivity showed its maximum significant value of 59.66 mg L-1 d-1 using LFAH15-WG10. In addition, LFAH15-WG10 significantly enhanced total FAMEs yield by 21.2% over the control. Moreover, it reduced polyunsaturated fatty acids (PUFAs) ratio from 52.1% to 47.8% of total FAMEs, and increased monounsaturated fatty acids (MUFAs) ratio from 26.6% to 31.3% of total FAMEs.

Entropy and Entransy Dissipation Analysis of a Basic Organic Rankine Cycles (ORCs) to Recover Low-Grade Waste Heat Using Mixture Working Fluids

Mixture working fluids can reduce effectively energy loss at heat sources and heat sinks, and therefore enhance the organic Rankine cycle (ORC) performance. The entropy and entransy dissipation analyses of a basic ORC system to recover low-grade waste heat using three mixture working fluids (R245fa/R227ea, R245fa/R152a and R245fa/pentane) have been investigated in this study. The basic ORC includes four components: an expander, a condenser, a pump and an evaporator. The heat source temperature is 120 °C while the condenser temperature is 20 °C. The effects of four operating parameters (evaporator outlet temperature, condenser temperature, pinch point temperature difference, degree of superheat), as well as the mass fraction, on entransy dissipation and entropy generation were examined. Results demonstrated that the entransy dissipation is insensitive to the mass fraction of R245fa. The entropy generation distributions at the evaporator for R245/pentane, R245fa/R152a and R245fa/R227ea are in ranges of 66–74%, 68–80% and 66–75%, respectively, with the corresponding entropy generation at the condenser ranges of 13–21%, 4–17% and 11–21%, respectively, while those at the expander for R245/pentane, R245fa/R152a and R245fa/R227ea are approaching 13%, 15% and 14%, respectively. The optimal mass fraction of R245fa for the minimum entropy generation is 0.6 using R245fa/R152a.

Comparative Study of Combustion Properties of Two Seaweeds in a Batch Fluidized Bed

ABSTRACT In the present study, combustion of two seaweeds, Enteromorpha clathrate and Sargassum natans, was carried out in a bench-scale fluidized bed. According to the shrinking core model, combustion of E. clathrate particles resulted in dehydration and release of volatile components first, followed by char combustion. While combustion of S. natans particles resulted in scraps formation due to the rapid release of large amounts of volatiles, followed by expansion and fragmentation. The cross sections of E. clathrate particles and the cokes collected after different combustion durations were analyzed with a scanning electron microscope. Some micro-pores were generated with a rougher surface after being burned for 30 s. When combustion continued for 3 min, a cotton wool-like structure was obtained due to complete release of volatiles. After 4 min of burning, internal surface of the ash particle became cohesive, due to partial melting of ash particles. In addition, the released gases were studied during the combustion process. Results showed that SO2, NOx, and other gases emitted spontaneously as soon as seaweed particles were fed into the fluidized bed, indicating that both pyrolysis and oxidation reactions rapidly take place within the seaweed particles. In general, the heat transfer rate was accelerated by increasing bed temperature and led to an earlier release of volatile components with shortened burnout time. Moreover, increasing air velocity and raising the bed height also enhanced, to some extent, the combustion and shortened the burnout time.