Development and validation of a two phase CFD model for tubular biodiesel reactors

The use of biodiesel as an alternative to diesel has gained increasing momentum over the past 15 years. To meet this growing demand there is a need to optimise the transesterification reactor at the heart of the biodiesel production system. Assessing the performance of innovative reactors is difficult due to the liquid–liquid reaction mixture that is affected by mass transfer, reaction kinetics and component solubility. This paper presents a Computational Fluid Dynamic model of a tubular reactor developed in ANSYS CFX that can be used to predict the onset of mixing via turbulent flow. In developing the model an analysis of the reaction mixture is provided before the presentation of experimental data, which includes flow visualisation results and temperature dependant viscosity and density data for each phase. The detailed data and model development procedure represents an advancement in the modelling of the two phase transesterification reaction used in biodiesel production

Life cycle analysis of milking of microalgae for renewable hydrocarbon production

Botryococcus braunii is a unique microalga which can repeatedly produce the hydrocarbons after their non-destructive extraction - the process called milking. Botryococcus braunii hydrocarbons can be converted to high-quality fuel or used as other high-value products. In this study, we conduct the life cycle analysis of the milking process for renewable hydrocarbon production focusing on the GHG emissions, the fossil energy consumption, the freshwater consumption and the land use of the process. The total-CO2 emissions and the GHG emissions over 100-year time span for production of B. braunii hydrocarbons were estimated to be -0.39 kg CO2-eq/kg hydrocarbons and -0.90 kg CO2-eq/kg hydrocarbons, respectively. The fossil energy ratio of the process was found to be 1.04 MJ produced/MJ fossil energy consumed. The fresh water consumption of the process and the land use were estimated to be 1802 kg/kg hydrocarbons and 0.85m2/kg of hydrocarbons, respectively

Life cycle analysis of milking of microalgae for renewable hydrocarbon production

Botryococcus braunii is a unique microalga which can repeatedly produce the hydrocarbons after their non-destructive extraction - the process called milking. Botryococcus braunii hydrocarbons can be converted to high-quality fuel or used as other high-value products. In this study, we conduct the life cycle analysis of the milking process for renewable hydrocarbon production focusing on the GHG emissions, the fossil energy consumption, the freshwater consumption and the land use of the process. The total-CO2 emissions and the GHG emissions over 100-year time span for production of B. braunii hydrocarbons were estimated to be -0.39 kg CO2-eq/kg hydrocarbons and -0.90 kg CO2-eq/kg hydrocarbons, respectively. The fossil energy ratio of the process was found to be 1.04 MJ produced/MJ fossil energy consumed. The fresh water consumption of the process and the land use were estimated to be 1802 kg/kg hydrocarbons and 0.85m2/kg of hydrocarbons, respectively

A multi-category decision support framework for the Tennessee Eastman problem

The paper investigates the feasibility of developing a classification framework, based on support vector machines, with the correct properties to act as a decision support system for an industrial process plant, such as the Tennessee Eastman process. The system would provide support to the technicians who monitor plants by signalling the occurrence of abnormal plant measurements marking the onset of a fault condition. To be practical such a system must meet strict standards, in terms of low detection latency, a very low rate of false positive detection and high classification accuracy. Experiments were conducted on examples generated by a simulation of the Tennessee Eastman process and these were preprocessed and classified using a support vector machine. Experiments also considered the efficacy of preprocessing observations using Fisher Discriminant Analysis and a strategy for combining the decisions from a bank of classifiers to improve accuracy when dealing with multiple fault categories

Facile fabrication of perovskite-incorporated hierarchically mesoporous/macroporous silica for efficient photoassisted-Fenton degradation of dye

LaFeO3-doped hierarchically mesoporous/macroporous silica (LFO/MMS) was prepared for the first time by impregnation method and then calcination. The sample was characterized in detail, suggesting the successful incorporation of LFO into MMS which was consisting of mesopores and macropores. The high surface area, accessible pores as well as low band gap energy supported its high performance towards efficient photoassisted-Fenton degradation of dye under visible light irradiation. Rhodamine B (RhB), which has been widely used as one of typical synthetic dyes in textile industry, was selected as the dye model. It was found that the incorporation of LFO into the MMS support induced a significant enhancement in the visible-light photo-Fenton catalytic performance, as compared with pure LFO. The degradation rate using LFO/MMS under the conditions (temperature = 25 °C, catalyst dosage = 1 g L−1, initial dye concentration = 10 mg L−1, initial H2O2 concentration = 10 mM and initial pH = 6) was 95.6% after 90-min exposure to the visible light. This was 7% and 19.8% greater than that of LFO and MMS, respectively. In particular, the pseudo-first-order reaction rate constant for LFO/MMS was 0.0367 min−1, which was approximately 2 times higher than that for pure LFO (0.0215 min−1). The newly developed catalyst, LFO/MMS, showed a good stability for recycle and reuse, which is crucial for its potential use in industrial application

Heterogeneous photo-Fenton degradation of organics using highly efficient Cu-doped LaFeO 3 under visible light

Cu-doped LaFeO3 was prepared by a facile hydrothermal reaction and evaluated as highly efficient photo-Fenton-like catalyst under visible light for organic degradation. The use of LFO-15Cu (LaFe0.85Cu0.15O3), which possessed favourable physicochemical characteristics, could achieve almost complete decolourisation of cation and anion dyes within 60 min visible light irradiation. The mechanism study by ESR spectroscopy confirmed LFO-15Cu could activate H2O2 under visible light to generate many more hydroxyl radicals than LFO (LaFeO3). LFO-15Cu was proven with excellent stability and reusability; and in turn showed great potential for use in continuous photo-Fenton-like degradation of organic in water under visible light

New safety evaluation methodology; A gold mining application

Several safety assessment methods have been used to evaluate and improve safety in the process industries. Different methods have various approaches and may consider safety from different aspects and at different levels of the process design. Some methods may evaluate chemical and physical safety in the processes while some other methods analyse the failure risk associated with the processes. According to the importance of both aspects of safety, a method that can evaluate them concurrently and intervene in the early design phases would be of great importance. This paper presents a method with mentioned ability which is developed based on the inherent safety assessment and probabilistic risk analysis methods. This method is implemented on an industrial case using the Petri net modelling and safety assessment tool introduced by the authors in their previous work

Development of an optimal biogas system design model for Sub-Saharan Africa with case studies from Kenya and Cameroon

The optimal biogas system design model (OBSDM) described in this paper is intended to be used as a decision-making tool to increase awareness of the potential of biogas technology for different applications in Sub-Saharan Africa (SSA). The decision-making tool identifies the most suitable biodigester design based on user defined inputs, including energy and fertiliser requirements; feedstock (type, amount, and rate of supply); water supply; land use (area, soil type, ground water level); climate (temperature and rainfall); construction materials available locally; and the priorities (based on sustainability criteria) of the intended biogas user. The output of the model provides a recommended design with estimates of the expected costs, energy and fertiliser production, and links to contact biodigester suppliers. In order to test the model, data from household surveys conducted in rural regions of Kenya and Cameroon were used as inputs to the model. An innovative fixed dome biodigester design, which uses stabilised soil blocks instead of bricks, was identified as optimal for both Kenyan and Cameroonian rural households. The expected performance of the optimal biogas system design from the model output was consistent with survey data on existing biogas systems in the region

Sustainable conversion of light to algal biomass and electricity: A net energy return analysis

A substantial interest is growing in the cultivation of microalgae as a source of biofuel production, considering their relatively high lipid content, fast growth rates, use of alternative water sources, and growth on non-arable land. This paper conducts an energy life cycle analysis for a novel hypothetical hybrid energy system where the electricity required for microalgae cultivation is generated from semi-transparent PV panels to energise paddle wheels and light emitting diodes installed on raceway ponds. The combined system configuration allows for a full utilisation of the solar spectrum, while enhancing the photosynthetic productivity of microalgae cultivation and reducing the evaporation from raceway ponds. The findings of study for a hypothetical system installed in Western Australia show that the amount of land use substantially decreases by 43%, the productivity of microalgae cultivation increases by 75%, while the net energy return of the system remains significantly higher than one, in comparison with a microalgae cultivation system energised by grid electricity. Among a range of variables affecting the energy performance of the proposed system, the primary energy demand for PV panels and conversion efficiency of LEDs exert the highest impact on energy life cycle of the syste

Effects of different light spectra on the growth, productivity and photosynthesis of two acclimated strains of Nannochloropsis sp.

Light (quantity and quality) is the main growth-limiting factor of photoautotrophic microalgae. The integration of selective permeable photovoltaic filters above microalgae cultivation systems has been proposed previously to improve both production efficiencies and economics. In order to optimize such system, we evaluated the growth and photosynthesis of two spectrally acclimated strains of Nannochloropsis sp. (MUR 266 and MUR 267) grown semi-continuously under different light spectra in this study. No significant differences in biomass productivity were observed between cultures acclimated under full blue (BL, 400-525 nm) and narrow blue (LEDB, 430-490 nm) light when compared to the positive control of white light (WL, 400-700 nm), while lower values were recorded under red (RL, 600-700 nm) and pink light (PL, 400-525, 600-700 nm) for both species. When compared to WL, the photosynthetic performance (Fq′/Fm′, αETR, ETRmax) of both species was higher under both BL and LEDB except for the Fq′/Fm′ of MUR 267 under LEDB. Chlorophyll a content was highest in cultures acclimated to RL while values tended higher under LEDB, RL and PL for MUR 267. Total lipid yield of both MUR 266 and MUR 267 was higher under BL and PL than WL. Based on the results of this study, theoretical modelling of the proposed photovoltaic-microalgae system indicate approximately 150-210 W m−2 of electricity could be potentially generated if only blue wavelengths (BL and LEDB) are selectively filtered from sunlight while converting the remaining unused spectrum of sunlight into electricity