Browsing by Author "Huang, Xiao"

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Catalytic supercritical water gasification of biomass waste using iron-doped alkaline earth catalysts
(Springer Nature Switzerland AG., 2022-05-18) Bakari, Ramadhani; Kivevele, Thomas; Huang, Xiao; Jande, Yusufu
The objective of this study is to optimise the process of supercritical water gasification of rice husk biomass utilising a low-cost catalyst made from alkaline-earth materials. The interactions between catalyst loading and Fe content on gasification yield were investigated using response surface methodology. The catalyst characterisation findings revealed that the catalysts’ predominant reactive site is on iron oxide, calcium ferrite, and calcium oxide. Under all the conditions tested, the manufactured catalyst was highly active in promoting char gasification, gas volume, and gasification efficiency whilst the tar yield was substantially elevated. The maximum gasification efficiency of 69.57%, gas yield of 402.8 mL/g biomass, char yield 24.68 wt%, and gravimetric tar yield of 57.5 mg/g were obtained under the catalytic conditions of 15% catalyst loading with 5%Fe/limestone, 492 °C, 120-min residence time, and 9.5 wt% feed concentrations. Thus, the manufactured catalyst showed a potential for optimising gasification outputs.
Simulation and optimisation of the pyrolysis of rice husk: Preliminary assessment for gasification applications
(Elsevier B.V., 2020-09) Bakari, Ramadhani; Kivevele, Thomas; Huang, Xiao; Jande, Yusufu
Thermochemical conversion of biomass into useful products is a promising route to harness biofuels. This process is clean, renewable and can reduce the use of fossil fuel. In this study, SuperPro Designer (SPD) software and response surface methodology (RSM) is used to simulate and optimize rice husk pyrolysis process. The SPD simulator was built to handle kinetics and stoichiometric reaction of lignocellulosic composition of rice husk into final products. The SPD simulation and RSM optimization were performed at a temperature ranging from 350 to 800 °C and residence time of 0.25−60 s. The simulated results were in agreement with product yield published in the literature at an average relative error of 6.8 %. The combined effect of temperature and residence time were analysed by using RSM and analysis of variance (ANOVA). A cubic model for bio-oil and quartic model for char and gas yield were proposed. The desirability function in Design-Expert showed that the optimum bio-oil yield (36.72 %) could be attained at a temperature 588 °C and a residence time 0.25 s while the optimum gas yield (73.25 %) could be achieved at a temperature 798.8 °C and a residence time 15.47 s. These findings therefore revealed that the energy content of the rice husk could be harnessed by pyrolysis/gasification to obtain substantial fuel products.
Sub- and Supercritical Water Gasification of Rice Husk: Parametric Optimization Using the I-Optimality Criterion.
(ACS Publications, 2021-05-18) Bakari, Ramadhani; Kivevele, Thomas; Huang, Xiao; Jande, Yusufu
In this study, rice husk biomass was gasified under sub- and supercritical water conditions in an autoclave reactor. The effect of temperature (350-500 °C), residence time (30-120 min), and feed concentration (3-10 wt %) was experimentally studied using the response surface methodology in relation to the yield of gasification products. The quadratic models have been suggested for both responses. Based on the models, the quantitative relationship between various operational conditions and the responses will reliably forecast the experimental outcomes. The findings revealed that higher temperatures, longer residence times, and lower feed concentrations favored high gas yields. The lowest tar yield obtained was 2.98 wt %, while the highest gasification efficiency and gas volume attained were 64.27% and 423 mL/g, respectively. The ANOVA test showed that the order of the effects of the factors on all responses except gravimetric tar yield follows temperature > feed concentration > residence time. The gravimetric tar yield followed a different trend: temperature > residence time > feed concentration. The results revealed that SCW gasification could provide an effective mechanism for transforming the energy content of RH into a substantial fuel product.