Jiangning Wu

Effect of ozone pretreatment on hydrogen production from barley straw

Application of ozone technology to lignocellulosic biohydrogen production was explored with a barley straw. Ozone pretreatment effectively degraded the straw lignin and increased reducing sugar yield. A simultaneous enzyme hydrolysis and dark fermentation experiment was conducted using a mixed anaerobic consortium together with saccharification enzymes. Both untreated and ozonated samples produced hydrogen. Compared to the untreated group, hydrogen produced by the groups ozonated for 15, 30, 45 and 90 min increased 99%, 133%, 166% and 94%, respectively. Some inhibitory effect on hydrogen production was observed with the samples ozonated for 90 min, and the inhibition was on the fermentative microorganisms, not the saccharification enzymes. These results demonstrate that production of biohydrogen from barley straw, a lignocellulosic biomass, can be significantly enhanced by ozone pretreatment.

Novel Ozonation Technique to Delignify Wheat Straw for Biofuel Production

Production of ethanol from lignocellulosic biomass is a promising alternative source of energy because this world is in need of a low cost, renewable and sustainable green energy source. Canada is among the top ten producers of wheat in the world with a capability of producing around 37.52 million tons of wheat straw per year. Hence, wheat straw could be a potential source of energy. Ozone was supposed to break down physical and chemical structure of lignin and hence make cellulose present in wheat straw more accessible for a conversion reaction. However, it was observed in our experimental work that without pretreatment of wheat straw, ozone did not produce the expected effects in the reaction with wheat straw. In spite of conducting the experiments under vigorous conditions only 13 % of lignin removal was achieved. The proposed technique, which is a strategic use of water and ozone, has overcome the problem of slow reaction of ozone with wheat straw. Through this technique, around 90% acid insoluble lignin (AIL) removal was achieved by controlling parameters such as reaction time, flow rate of ozone-oxygen feed stream, ozone concentration in ozone-oxygen feed stream, water contents and particle size. The maximum AIL (90%) was obtained at flow rates of 4L/min, 2L/min and 1L/min at reaction times 90, 120 and 180 minutes, respectively, with 2% wt ozone concentration in ozone-oxygen stream. Other factors supported maximum lignin removal were water contents at 3 times of the dry weight of wheat straw and at 0.5 mm particle size of wheat straw. It was also noted that excessive ozonation caused repolymerization of lignin by-products. The obtained results demonstrated that ozonation of wheat straw using the proposed technique was practical, easy to manage for the removal of lignin and it may be considered as an alternative method for delignification of biomass in production of biofuel.

Laminar mixing of non-Newtonian fluids in static mixers: process intensification perspective

Abstract Static mixers are widely used in various industrial applications to intensify the laminar mixing of non-Newtonian fluids. Non-Newtonian fluids can be categorized into (1) time-independent, (2) time-dependent, and (3) viscoelastic fluids. Computational fluid dynamics studies on the laminar mixing of viscoelastic fluids are very limited due to the complexity in incorporating the multiple relaxation times and the associated stress tensor into the constitutive equations. This review paper provides recommendations for future research studies while summarizing the key research contributions in the field of non-Newtonian fluid mixing using static mixers. This review discusses the different experimental techniques employed such as electrical resistance tomography, magnetic resonance imaging, planar laser-induced fluorescence, and positron emission particle tracking. A comprehensive overview of the mixing fundamentals, fluid chaos, numerical characterization of fluid stretching, development of pressure drop correlations, and derivations of generalized Reynolds number is also provided in this review paper.

A computational study of multiple surface-directed phase separation in polymer blends under a temperature gradient

The surface-directed phase separation (SDPS) phenomena of a model binary polymer blend quenched into the unstable region of its binary symmetric upper critical solution temperature phase diagram is numerically investigated using a mathematical model composed of the nonlinear Cahn–Hilliard (CH) theory for phase separation along with the Flory–Huggins–de Gennes (FHdG) free energy functional. The SDPS occurs in a square domain with a linear temperature gradient along the horizontal direction and with all sides having short range surface potential h 1. The effects of different quench depth, diffusion coefficient, surface potential, and temperature gradient were studied numerically. The numerical results indicate that there is a simultaneous competition between the four surfaces in attracting the preferred polymer. The side with a higher surface potential would win the competition against the side with a lower surface attraction in the case of a uniform quench. The numerical results also indicated a later transition time for higher values of h 1. As surface potential increased, the transition time from complete wetting to partial wetting occurred at a later time on the surface. The impact of different temperature gradient ΔT*/Δx* values on the surface enrichment rate with fixed temperature at one surface and higher temperature at the opposite surface was studied for the first time within a multiple surface potential set up. The results showed that higher values of ΔT*/Δx* increased the growth rate of the preferred polymer on the surface adding to the thickness of the wetting layer. The transition time from complete wetting to partial wetting occurred slightly later at the lower temperature side.