Relining efficiency and liner design for improved plant performance

Liners in grinding mills not only protect the mill shell from the aggressive environment inside the mill, but they also play a significant role in the efficiency of grinding. The design of mill liners dictates the charge trajectory and hence the grinding efficiency. The common approach in designing liners is designing for a longer life. However, this approach does not necessarily consider optimum performance over the liner life. It has been observed in many operations that mills under-perform over a significant portion of the liner life (10–25% of the liner life at the beginning and often 5–10% at the end). This paper extends the method proposed by Toor (2013) and Toor et al. (2013) to design liners for performance through investigating the effect of relining efficiency using such an approach in an industrial case.As indicated in the Toor et al. (2013) study, relining efficiency affects the benefits that can be realised by designing liners for efficiency. Russell Mineral Equipment’s Mill Reline Director (MRD) analyses the relining process and provides an accurate estimation of relining time for a given scenario. In this study, five different relining scenarios were simulated and compared against the reference reline (i.e. current liner design) to accurately estimate the time required for relining. This is the first study to demonstrate that incorporating relining constraints in the liner design can be used to inform liner design characteristics of a proper design that meets the requirements of an efficient relining practice.JKSimMet simulation for the industrial case predicts a liner which has same lifter face angle as the current liner design with reduced lifter height from 300 mm to 210 mm, could increase the plant throughput by 8% on average while producing a product with same P80 as the current liner. Considering relining time predictions by MRD for the proposed liner, this study predicts a 3.7% increase on average in throughput per annum. Although the proposed strategy will increase the cost of liners plus relining by 31.5% (i.e. A$ 548,000), the increase in plant throughput is estimated to yield A$ 20.1 M of additional revenue based on data for 12 months to 30 June 2014 from the plant quarterly report.     

Performance analysis and temperature gradient of solid oxide fuel cell stacks operated with bio-oil sorption-enhanced steam reforming

A high temperature gradient within a solid oxide fuel cell (SOFC) stack is considered a major challenge in SOFC operations. This study investigates the effects of the key parameters on SOFC system efficiency and temperature gradient within a SOFC stack. A 40-cell SOFC stack integrated with a bio-oil sorption-enhanced steam reformer is simulated using MATLAB and DETCHEM. When the air-to-fuel ratio and steam-to-fuel ratio increase, the stack average temperature and temperature gradient decrease. However, a decrease in the stack temperature steadily reduces the system efficiency owing to the tradeoff between the stack performance and thermal balance between heat recovered and consumed by the system. With an increase in the bio-oil flow rate, the system efficiency decreases because of the lower resident time for the electrochemical reaction. This is not, however, beneficial to the maximum temperature gradient. To minimize the temperature gradient of the SOFC stack, a decrease in the bio-oil flow rate is the most effective way. The maximum temperature gradient can be reduced to 14.6 K cm⁻¹ with the stack and system efficiency of 76.58 and 65.18%, respectively, when the SOFC system is operated at an air-to-fuel ratio of 8, steam-to-fuel ratio of 6, and bio-oil flow rate of 0.0041 mol s⁻¹.     

Robust proton exchange membrane for vanadium redox flow batteries reinforced by silica-encapsulated nanocellulose

High ion selectivity and mechanical strength are critical properties for proton exchange membranes in vanadium redox flow batteries. In this work, a novel sulfonated poly(ether sulfone) hybrid membrane reinforced by core-shell structured nanocellulose (CNC-SPES) is prepared to obtain a robust and high-performance proton exchange membrane for vanadium redox flow batteries. Membrane morphology, proton conductivity, vanadium permeability and tensile strength are investigated. Single cell tests at a range of 40–140 mA cm⁻² are carried out. The performance of the sulfonated poly(ether sulfone) membrane reinforced by pristine nanocellulose (NC-SPES) and Nafion® 212 membranes are also studied for comparison. The results show that, with the incorporation of silica-encapsulated nanocellulose, the membrane exhibits outstanding mechanical strength of 54.5 MPa and high energy efficiency above 82% at 100 mA cm⁻², which is stable during 200 charge-discharge cycles.     

Study of haze emission efficiency based on new co-opetition data envelopment analysis

As haze intensifies in China, controlling haze emission has become the country's top priority for environmental protection. Because haze moves across different regions, it is necessary to develop a data envelopment analysis (DEA) model underpinned by both competition and cooperation to evaluate the haze emission efficiency in different provinces. This study innovatively adopts the spatial econometrics to construct the co-opetition matrices of Chinese provinces, then builds the co-opetition DEA model to evaluate the haze emission efficiency of them, and finally uses the haze data of 2015 as an example to assess the applicability of the model. The results of the study include the following: First, compared with the traditional CCR (A. Charnes & W. W. Cooper & E. Rhodes) model, this study constructs the co-opetition DEA cross-efficiency model that integrates haze's feature of cross-border moving; thus, it is more in line with the reality of haze emission and movement. Second, compared with the efficiency value gained from the CCR model, the haze emission efficiency values for Tianjin and Guangdong, two decision-making units, register greater variance when using the DEA model. The reason might lie in that they have a different spatial transportation relationship with their surrounding provinces. Third, the haze emission efficiency of provinces, according to the evaluation based on the co-opetition DEA method, varies greatly: Those with high efficiency are mostly inland provinces with slow economic growth and adverse climatic conditions, whereas many of the provinces with low efficiency are located in the relatively prosperous East China. The specific co-opetition DEA model constructed in this study enriches the research on the DEA model, which can be applied to the emission efficiency evaluation of similar pollutants around the world and can contribute empirical support to the haze reducing efforts of the government with its empirical results.     

Improved error performance for generalised spatial modulation with enhanced spectral efficiency

The existing analytical average bit error rate (ABER) expression of conventional generalised spatial modulation (CGSM) does not agree well with the Monte Carlo simulation results in the low signal‐to‐noise ratio (SNR) region. Hence, the first contribution of this paper is to derive a new and easy way to evaluate analytical ABER expression that improves the validation of the simulation results at low SNRs. Secondly, a novel system termed CGSM with enhanced spectral efficiency (CGSM‐ESE) is presented. This system is realised by applying a rotation angle to one of the two active transmit antennas. As a result, the overall spectral efficiency is increased by 1 bit/s/Hz when compared with the equivalent CGSM system. In order to validate the simulation results of CGSM‐ESE, the third contribution is to derive an analytical ABER expression. Finally, to improve the ABER performance of CGSM‐ESE, three link adaptation algorithms are developed. By assuming full knowledge of the channel at the receiver, the proposed algorithms select a subset of channel gain vector (CGV) pairs based on the Euclidean distance between all CGV pairs, CGV splitting, CGV amplitudes, or a combination of these.     

Electroactive polythiophene/polystyrene bottlebrushes as morphology compatibilizers in photovoltaic systems

Poly(3‐thiophene ethanol) (P3ThEt)‐graft‐polystyrene (PSt) bottlebrushes were synthesized and applied in active layers of poly(3‐hexylthiophene) (P3HT):phenyl‐C71‐butyric acid methyl ester (PC71BM) solar cells as morphology compatibilizers. In the presence of 15 wt% of P3ThEt‐graft‐PSt bottlebrush compatibilizers, the P3HT crystallite dimensions (D₍₁₀₀₎ = 45.67 nm and D₍₀₂₀₎ = 30.12 nm) and R_mean (38.96 nm) of PCBM clusters were the largest and the layer spacings were all the smallest (d₍₁₀₀₎ = 1.054 nm, d₍₀₂₀₎ = 0.301 nm and d_(PCBM) = 0.406 nm). These dimensional properties led to better hole (1.9 × 10^?3 cm² V^?1 s^?1) and electron (1.2 × 10^?2 cm² V^?1 s^?1) mobilities. The content of bottlebrushes was optimized at 15 wt%, and thereby the best photovoltaic results including the maximum cell efficiency of 5.37% were obtained for this turning point (12.75 mA cm^?2, 61%, 0.69 V). On exceeding the optimum weight percentage, all photovoltaic parameters decreased markedly and reached even less than that of pristine devices (1.92% versus 2.24%). After an optimum weight percentage of compatibilizers, further enhancement in bottlebrush content in active layers saturated and finally oversaturated the system and, consequently, the cell parameters significantly decreased. Accumulation of bottlebrushes in interfaces and donor/acceptor phases ruined the system function even with large and packed P3HT crystallites and PC71BM clusters. © 2019 Society of Chemical Industry     

Stability enhancement of garlic essential oil using new opopanax gum/gelatin nanofibres

Opopanax gum/gelatin nanofibre was produced by the electrospinning method, and the efficiency of this new technique for encapsulation of garlic essential oil was investigated. Fourier-transform infrared spectroscopy results showed the physical and weak interactions between opopanax gum and gelatin, as well as the improvement of their thermal stability in the nanofibres structure. Incorporating 10% garlic essential oil based on biopolymer weight in nanofibres was considered the best percentage. The results confirmed the presence of garlic essential oil in the nanofibres and the improvement of its thermal stability by entrapment to the nanofibre structure. The data of analysis of the stability of garlic essential oil in the forms of free and encapsulated conditions showed that its stability increased at 25 °C from 20 days to more than 60 days. It indicated the efficiency of opopanax gum/gelatin nanofibres as an applicable coating material for stability enhancement of essential oils.     

Modeling and parameter optimization for the design of vibrating screens

In this paper, we simulated the complex particle flow-behavior and screening efficiency on a linear vibrating screen using the Discrete Element Method (DEM). The simulations were validated with data from an adjustable experimental prototype screen. Then the novel application of non-linear regression modeling based on Support Vector Machines (SVMs) is used for mapping the sample space of operating parameters and vibrating screen configuration. Lastly, parameter optimization is implemented using Particle Swarm Optimization (PSO) algorithm. The primary findings proved that the SVM-based nonparametric model is not only feasible, but also highly adaptive to the parameter optimization that requires large-scale iterative computation. The non-parametric model established using the integration of DEM and SVM, combined with PSO algorithm in subsequent parameter optimization offered insights to the design and manufacture of vibrating screens.     

Yeast and enzymatic hydrolysis in converting Chlorella biomass into hydrogen gas by Rhodobacter sp. and Rhodopseudomonas palustris

Enhanced hydrogen evolution was pursued in this work. Rhodobacter sp. (Rb) and Rhodopseudomonas palustris (Rp), single or mixed were used to extract hydrogen molecules from Chlorella fusca biomass. To elevate their fermentable contents, Chlorella was grown at nitrogen and/or phosphorus deprivation. Besides, cellulase and/or macerozyme, Triton X100 or sonicated yeast were applied for further biohydrogen fermentation. Utilizing hydrolysates of mineral deprived Chlorella cultures, Rb exhibited relatively higher cumulative hydrogen (4200 ml L^?1) than Rp (2500 ml L^?1) while mixed cultures attained significantly higher levels (4700 ml L^?1). Triton or enzymes significantly enhanced hydrogen evolution, with more effectiveness of macerozyme than cellulase. A novel use of sonicated yeast, as enzymes pool, induced the highest significant collective H₂ (up to 47 times that of microalgal supernatant). Sonicated yeast induced a remarkable hydrolysis of algae, as inferred from increased reducing sugars. However, hydrogen evolution efficiency exhibited poor proportionality with reducing sugars, indicating fermentation of other metabolites.